Irstea Motive - lisc:publications

Journal Articles (164)

@author@
Impact of farming systems on agricultural landscapes and biodiversity: From plot to farm and landscape scales
European Journal of Agronomy, 2017
abs doi web bib

Green-way policies in agricultural landscapes focus on ecological continuity between semi-natural elements (hedgerows, permanent grasslands, woods) and landscape heterogeneity. These policies suggest annual crops and temporary grasslands exhibit a negative or neutral impact on biodiversity. However, recent studies indicated the spatial continuities between different crops (spring vs. winter) showed positive impacts on biodiversity. These landscape patterns were directly related to farmers' decisions regarding the crops cultivated and where the crops were distributed spatially on the farm. The aim of the present study was to evaluate the impacts of different livestock farming system management types on crop patterns and associated biodiversity (carabid beetles) in agricultural landscapes. We combined empirical analyses of farmers' decision making and ecological data to develop a modeling framework simulating crop allocation and abundance of two different carabid beetle species groups (maize and woody species). Modeling included field, farm, and landscape levels. We simulated different scenarios, where two livestock farming systems, swine and dairy, were combined in different proportions (i.e. number of swine vs. dairy farms) in two agricultural landscapes with varied hedgerow densities. Simulations showed maize carabid species abundance was higher in swine production landscapes due to more frequent spatial continuities between spring and winter crops. In contrast, woody carabid species were more abundant in mixed landscapes (dairy and swine) under high crop diversity. For a given combination of livestock farming systems, simulated landscapes were highly variable in crop acreages and spatial continuities between crops. Our results emphasized the need to manage landscape at a collective level, where crop allocation decisions create more interfaces without modifying livestock farming system combinations.
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@article{PUB00057126, title = {Impact of farming systems on agricultural landscapes and biodiversity: From plot to farm and landscape scales}, journal = {European Journal of Agronomy}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00057126}, doi = {http://dx.doi.org/10.1016/j.eja.2017.07.014}, year = {2017}, affiliation = {}, abstract = {Green-way policies in agricultural landscapes focus on ecological continuity between semi-natural elements (hedgerows, permanent grasslands, woods) and landscape heterogeneity. These policies suggest annual crops and temporary grasslands exhibit a negative or neutral impact on biodiversity. However, recent studies indicated the spatial continuities between different crops (spring vs. winter) showed positive impacts on biodiversity. These landscape patterns were directly related to farmers' decisions regarding the crops cultivated and where the crops were distributed spatially on the farm. The aim of the present study was to evaluate the impacts of different livestock farming system management types on crop patterns and associated biodiversity (carabid beetles) in agricultural landscapes. We combined empirical analyses of farmers' decision making and ecological data to develop a modeling framework simulating crop allocation and abundance of two different carabid beetle species groups (maize and woody species). Modeling included field, farm, and landscape levels. We simulated different scenarios, where two livestock farming systems, swine and dairy, were combined in different proportions (i.e. number of swine vs. dairy farms) in two agricultural landscapes with varied hedgerow densities. Simulations showed maize carabid species abundance was higher in swine production landscapes due to more frequent spatial continuities between spring and winter crops. In contrast, woody carabid species were more abundant in mixed landscapes (dairy and swine) under high crop diversity. For a given combination of livestock farming systems, simulated landscapes were highly variable in crop acreages and spatial continuities between crops. Our results emphasized the need to manage landscape at a collective level, where crop allocation decisions create more interfaces without modifying livestock farming system combinations. }, }
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S. Billiard, C. Smadi
The interplay of two mutations in a population of varying size: A stochastic eco-evolutionary model for clonal interference
Stochastic Processes and their Applications 127 (3), 2017
abs doi web bib

Clonal interference, competition between multiple beneficial mutations, has a major role in adaptation of asexual populations. We provide a simple stochastic model of clonal interference taking into account a wide variety of competitive interactions. The population evolves as a three-type birth-and-death process with type dependent competitions. This allows us to relax the classical assumption of transitivity between mutations, and to predict genetic patterns, such as coexistence of several mutants or emergence of Rock-Paper-Scissors cycles, which were not explained by existing models. In addition, we call into questions some classical preconceived ideas about fixation time and fixation probability of competing mutations.
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@article{PUB00052012, author = {Billiard, S. and Smadi, C.}, title = {The interplay of two mutations in a population of varying size: A stochastic eco-evolutionary model for clonal interference}, journal = {Stochastic Processes and their Applications}, volume = {127}, number = {3}, pages = {701-718}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00052012 / https://www.scopus.com/inward/record.uri?eid=2-s2.0-84996790718&doi=10.1016%2fj.spa.2016.06.024&partnerID=40&md5=55f34c97e35524f246fdd6b888e000ad}, doi = {http://dx.doi.org/10.1016/j.spa.2016.06.024}, year = {2017}, affiliation = {UNIVERSITE LILLE UMR CNRS ECO-ECO-PALEO LILLE FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {Clonal interference, competition between multiple beneficial mutations, has a major role in adaptation of asexual populations. We provide a simple stochastic model of clonal interference taking into account a wide variety of competitive interactions. The population evolves as a three-type birth-and-death process with type dependent competitions. This allows us to relax the classical assumption of transitivity between mutations, and to predict genetic patterns, such as coexistence of several mutants or emergence of Rock-Paper-Scissors cycles, which were not explained by existing models. In addition, we call into questions some classical preconceived ideas about fixation time and fixation probability of competing mutations. }, }
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R. Brink-Spalink, C. Smadi
Genealogies of two linked neutral loci after a selective sweep in a large population of stochastically varying size
Advances in Applied Probability 49 (1), 2017
abs doi web bib

We study the impact of a hard selective sweep on the genealogy of partially linked neutral loci in the vicinity of the positively selected allele. We consider a sexual population of stochastically varying size and, focusing on two neighboring loci, derive an approximate formula for the neutral genealogy of a sample of individuals taken at the end of the sweep. Individuals are characterized by ecological parameters depending on their genetic type, and governing their growth rate and interactions with other individuals (competition). As a consequence, the 'fitness' of an individual depends on the population state and is not an intrinsic characteristic of individuals. We provide a deep insight into the dynamics of the mutant and wild-type populations during the different stages of a selective sweep.
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@article{PUB00056693, author = {Brink-Spalink, R. and Smadi, C.}, title = {Genealogies of two linked neutral loci after a selective sweep in a large population of stochastically varying size}, journal = {Advances in Applied Probability}, volume = {49}, number = {1}, pages = {279-326}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00056693 / https://www.scopus.com/inward/record.uri?eid=2-s2.0-85015880663&doi=10.1017%2fapr.2016.88&partnerID=40&md5=afc6e22bd5c0de018e31f1abdd8ba85a}, doi = {http://dx.doi.org/10.1017/apr.2016.88}, year = {2017}, affiliation = {INSTITUTE FOR MATHEMATICAL STOCHASTICS GOTTINGEN DEU ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {We study the impact of a hard selective sweep on the genealogy of partially linked neutral loci in the vicinity of the positively selected allele. We consider a sexual population of stochastically varying size and, focusing on two neighboring loci, derive an approximate formula for the neutral genealogy of a sample of individuals taken at the end of the sweep. Individuals are characterized by ecological parameters depending on their genetic type, and governing their growth rate and interactions with other individuals (competition). As a consequence, the 'fitness' of an individual depends on the population state and is not an intrinsic characteristic of individuals. We provide a deep insight into the dynamics of the mutant and wild-type populations during the different stages of a selective sweep. }, }
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G. Carvalho, C. Guilhen, D. Balestrino, C. Forestier, J.D. Mathias
Relating switching rates between normal and persister cells to substrate and antibiotic concentrations: a mathematical modelling approach supported by experiments
Microbial Biotechnology 10 (6), 2017
abs doi web bib

We developed and compared two mathematical models of variable phenotypic switching rates between normal and persister cells that depend on substrate concentration and antibiotic presence. They could be used to simulate the formation of persisters in environments with concentration gradients such as biofilms. Our models are extensions of a previous model of the dynamics of normal and persistent cell populations developed by Balaban et al. (2004, Science 305: 1622). We calibrated the models’ parameters with experimental killing curves obtained after ciprofloxacin treatment of samples regularly harvested from planktonic batch cultures of Klebsiella pneumoniae. Our switching models accurately reproduced the dynamics of normal and persistent populations in planktonic batch cultures and under antibiotic treatment. Results showed that the models are valid for a large range of substrate concentrations and for zero or high doses of antibiotics.
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@article{PUB00056700, author = {Carvalho, G. and Guilhen, C. and Balestrino, D. and Forestier, C. and Mathias, J.D.}, title = {Relating switching rates between normal and persister cells to substrate and antibiotic concentrations: a mathematical modelling approach supported by experiments}, journal = {Microbial Biotechnology}, volume = {10}, number = {6}, pages = {1616-1627}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00056700 / https://www.scopus.com/inward/record.uri?eid=2-s2.0-85032338497&doi=10.1111%2f1751-7915.12739&partnerID=40&md5=6ffe0f94cf3d7707b368afb922eabf6d}, doi = {http://dx.doi.org/10.1111/1751-7915.12739}, year = {2017}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; LMGE UMR 6023 CNRS UNIVERSITE CLERMONT AUVERGNE CLERMONT FERRAND FRA ; LMGE UMR 6023 CNRS UNIVERSITE CLERMONT AUVERGNE CLERMONT FERRAND FRA ; LMGE UMR 6023 CNRS UNIVERSITE CLERMONT AUVERGNE CLERMONT FERRAND FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {We developed and compared two mathematical models of variable phenotypic switching rates between normal and persister cells that depend on substrate concentration and antibiotic presence. They could be used to simulate the formation of persisters in environments with concentration gradients such as biofilms. Our models are extensions of a previous model of the dynamics of normal and persistent cell populations developed by Balaban et al. (2004, Science 305: 1622). We calibrated the models’ parameters with experimental killing curves obtained after ciprofloxacin treatment of samples regularly harvested from planktonic batch cultures of Klebsiella pneumoniae. Our switching models accurately reproduced the dynamics of normal and persistent populations in planktonic batch cultures and under antibiotic treatment. Results showed that the models are valid for a large range of substrate concentrations and for zero or high doses of antibiotics.}, }
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C. Coron, M. Costa, H. Leman, C. Smadi
A stochastic model for speciation by mating preferences
Journal of Mathematical Biology, 2017
abs doi web bib

Mechanisms leading to speciation are a major focus in evolutionary biology. In this paper, we present and study a stochastic model of population where individuals, with type a or A, are equivalent from ecological, demographical and spatial points of view, and differ only by their mating preference: two individuals with the same genotype have a higher probability to mate and produce a viable offspring. The population is subdivided in several patches and individuals may migrate between them. We show that mating preferences by themselves, even if they are very small, are enough to entail reproductive isolation between patches, and we provide the time needed for this isolation to occur as a function of the carrying capacity. Our results rely on a fine study of the stochastic process and of its deterministic limit in large population, which is given by a system of coupled nonlinear differential equations. Besides, we propose several generalisations of our model, and prove that our findings are robust for those generalisations.
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@article{PUB00056701, author = {Coron, C. and Costa, M. and Leman, H. and Smadi, C.}, title = {A stochastic model for speciation by mating preferences}, journal = {Journal of Mathematical Biology}, pages = {1-43}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00056701 / https://www.scopus.com/inward/record.uri?eid=2-s2.0-85029502054&doi=10.1007%2fs00285-017-1175-9&partnerID=40&md5=9ae4dd568f9eaebc8ead8bd86bce8304}, doi = {http://dx.doi.org/10.1007/s00285-017-1175-9}, year = {2017}, affiliation = {LABORATOIRE DE MATHEMATIQUES UNIVERSITE PARIS SACLAY FRA ; INSTITUT DE MATHEMATIQUES TOULOUSE FRA ; CIMAT GUANAJUATO MEX ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {Mechanisms leading to speciation are a major focus in evolutionary biology. In this paper, we present and study a stochastic model of population where individuals, with type a or A, are equivalent from ecological, demographical and spatial points of view, and differ only by their mating preference: two individuals with the same genotype have a higher probability to mate and produce a viable offspring. The population is subdivided in several patches and individuals may migrate between them. We show that mating preferences by themselves, even if they are very small, are enough to entail reproductive isolation between patches, and we provide the time needed for this isolation to occur as a function of the carrying capacity. Our results rely on a fine study of the stochastic process and of its deterministic limit in large population, which is given by a system of coupled nonlinear differential equations. Besides, we propose several generalisations of our model, and prove that our findings are robust for those generalisations. }, }
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T. Ercan, N.C. Onat, O. Tatari, J.D. Mathias
Public transportation adoption requires a paradigm shift in urban development structure
Journal of Cleaner Production 142, Elsevier Ltd, 2017
abs doi web bib

Urban passenger transportation in the U.S. has been heavily dependent on car modes, mainly due to prevailing trends in urban development. However, transportation mode choice studies are currently limited to micro-level and regional-level boundaries, lacking of presenting a complete picture of the issues and the root causes associated with urban passenger transportation choices in the U.S. To this end, further analysis from a system perspective is required to investigate the interdependencies among system parameters more thoroughly, thus revealing the underlying mechanisms contributing or causing the low public transportation use in the U.S. Hence, system dynamics modeling approach is utilized to capture complex causal relationships among the critical system parameters affecting public transportation ridership in the U.S. as well as to identify possible policy areas to improve public transportation ridership rates. Considering the high degree of uncertainties inherent to the problem, multivariate sensitivity analysis is utilized to explore the effectiveness of existing and possible policy implications up to the year 2050 in the terms of their potential to increase transit ridership and locating critical parameters that influences the most on mode choice and emission rates. Transportation mode choice behavior is projected to change slightly and reach up to a maximum of 7.25% of public transportation ridership until 2050. Analysis results reveal that the effects of trip length and rate are by far the most influential factors. Both parameters are 99% sensitive compared to all other factors including the effects of fuel tax policies, federal funds for public transportation, use of alternative green bus technologies, increasing private vehicle occupancy rates, etc. on negative environmental, economic, and social impacts of transportation. This finding highlights how important urban structures are to secure the future of public transportation in the U.S. as the existing urban structures and the shared-idea in the minds of the society about how urban transportation should be (the prevailing paradigm) are the root causes of excessive trip generation and increasing average trip lengths. Thus a paradigm-shift, a radical change in the shared-idea in the minds of the society about existing urban structures, is needed. © 2016 Elsevier Ltd
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@article{PUB00051991, author = {Ercan, T. and Onat, N.C. and Tatari, O. and Mathias, J.D.}, title = {Public transportation adoption requires a paradigm shift in urban development structure}, journal = {Journal of Cleaner Production}, volume = {142}, publisher = {Elsevier Ltd}, pages = {1789-1799}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00051991 / https://www.scopus.com/inward/record.uri?eid=2-s2.0-85006802362&doi=10.1016%2fj.jclepro.2016.11.109&partnerID=40&md5=fb0090309fd3e698c2ee16db5c378d52}, doi = {http://dx.doi.org/10.1016/j.jclepro.2016.11.109}, year = {2017}, affiliation = {UNIVERSITY OF CENTRAL FLORIDA ORLANDO USA ; ISTANBUL SEHIR UNIVERSITY TUR ; UNIVERSITY OF CENTRAL FLORIDA ORLANDO USA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {Urban passenger transportation in the U.S. has been heavily dependent on car modes, mainly due to prevailing trends in urban development. However, transportation mode choice studies are currently limited to micro-level and regional-level boundaries, lacking of presenting a complete picture of the issues and the root causes associated with urban passenger transportation choices in the U.S. To this end, further analysis from a system perspective is required to investigate the interdependencies among system parameters more thoroughly, thus revealing the underlying mechanisms contributing or causing the low public transportation use in the U.S. Hence, system dynamics modeling approach is utilized to capture complex causal relationships among the critical system parameters affecting public transportation ridership in the U.S. as well as to identify possible policy areas to improve public transportation ridership rates. Considering the high degree of uncertainties inherent to the problem, multivariate sensitivity analysis is utilized to explore the effectiveness of existing and possible policy implications up to the year 2050 in the terms of their potential to increase transit ridership and locating critical parameters that influences the most on mode choice and emission rates. Transportation mode choice behavior is projected to change slightly and reach up to a maximum of 7.25% of public transportation ridership until 2050. Analysis results reveal that the effects of trip length and rate are by far the most influential factors. Both parameters are 99% sensitive compared to all other factors including the effects of fuel tax policies, federal funds for public transportation, use of alternative green bus technologies, increasing private vehicle occupancy rates, etc. on negative environmental, economic, and social impacts of transportation. This finding highlights how important urban structures are to secure the future of public transportation in the U.S. as the existing urban structures and the shared-idea in the minds of the society about how urban transportation should be (the prevailing paradigm) are the root causes of excessive trip generation and increasing average trip lengths. Thus a paradigm-shift, a radical change in the shared-idea in the minds of the society about existing urban structures, is needed. © 2016 Elsevier Ltd}, }
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A. Flache, M. Mäs, T. Feliciani, E. Chattoe-Brown, G. Deffuant, S. Huet, J. Lorenz
Models of social influence: towards the next frontiers
JASSS-The Journal of Artificial Societies and Social Simulation 20 (4(2)), 2017
abs doi web bib

In 1997, Robert Axelrod wondered in a highly influential paper "If people tend to become more alike in their beliefs, attitudes, and behavior when they interact, why do not all such differences eventually disappear?" Axelrod’s question highlighted an ongoing quest for formal theoretical answers joined by researchers from a wide range of disciplines. Numerous models have been developed to understand why and under what conditions diversity in beliefs, attitudes and behavior can co-exist with the fact that very often in interactions, social influence reduces differences between people. Reviewing three prominent approaches, we discuss the theoretical ingredients that researchers added to classic models of social influence as well as their implications. Then, we propose two main frontiers for future research. First, there is urgent need for more theoretical work comparing, relating and integrating alternative models. Second, the field suffers from a strong imbalance between a proliferation of theoretical studies and a dearth of empirical work. More empirical work is needed testing and underpinning micro-level assumptions about social influence as well as macro-level predictions. In conclusion, we discuss major roadblocks that need to be overcome to achieve progress on each frontier. We also propose that a new generation of empirically-based computational social influence models can make unique contributions for understanding key societal challenges, like the possible effects of social media on societal polarization.
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@article{PUB00055530, author = {Flache, A. and Mäs, M. and Feliciani, T. and Chattoe-Brown, E. and Deffuant, G. and Huet, S. and Lorenz, J.}, title = {Models of social influence: towards the next frontiers }, journal = {JASSS-The Journal of Artificial Societies and Social Simulation}, volume = {20}, number = {4(2)}, pages = {31}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00055530 / http://jasss.soc.surrey.ac.uk/20/4/2.html}, doi = {http://dx.doi.org/10.18564/jasss.3521}, year = {2017}, affiliation = {UNIVERSITY OF GRONINGEN ICS NLD ; UNIVERSITY OF GRONINGEN ICS NLD ; UNIVERSITY OF GRONINGEN ICS NLD ; UNIVERSITY OF LEICESTER GBR ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; JACOBS UNIVERSITY BREMEN DEU}, abstract = {In 1997, Robert Axelrod wondered in a highly influential paper "If people tend to become more alike in their beliefs, attitudes, and behavior when they interact, why do not all such differences eventually disappear?" Axelrod’s question highlighted an ongoing quest for formal theoretical answers joined by researchers from a wide range of disciplines. Numerous models have been developed to understand why and under what conditions diversity in beliefs, attitudes and behavior can co-exist with the fact that very often in interactions, social influence reduces differences between people. Reviewing three prominent approaches, we discuss the theoretical ingredients that researchers added to classic models of social influence as well as their implications. Then, we propose two main frontiers for future research. First, there is urgent need for more theoretical work comparing, relating and integrating alternative models. Second, the field suffers from a strong imbalance between a proliferation of theoretical studies and a dearth of empirical work. More empirical work is needed testing and underpinning micro-level assumptions about social influence as well as macro-level predictions. In conclusion, we discuss major roadblocks that need to be overcome to achieve progress on each frontier. We also propose that a new generation of empirically-based computational social influence models can make unique contributions for understanding key societal challenges, like the possible effects of social media on societal polarization.}, }
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I. Haidar, I. Alvarez, A.C. Prévot
Mathematical modeling of an urban pigeon population subject to local management strategies
Mathematical Biosciences 288, 2017
abs doi web bib

This paper addresses the issue of managing urban pigeon population using some possible actions that make it reach a density target with respect to socio-ecological constraints. A mathematical model describing the dynamic of this population is introduced. This model incorporates the effect of some regulatory actions on the dynamic of this population. We use mathematical viability theory, which provides a framework to study compatibility between dynamics and state constraints. The viability study shows when and how it is possible to regulate the pigeon population with respect to the constraints.
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@article{PUB00055493, author = {Haidar, I. and Alvarez, I. and Prévot, A.C.}, title = {Mathematical modeling of an urban pigeon population subject to local management strategies}, title = {Modélisation d'une population de pigeons urbains soumise à des stratégies de gestion locale}, journal = {Mathematical Biosciences}, volume = {288}, pages = {71-83}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00055493 / https://hal.archives-ouvertes.fr/hal-01319753}, doi = {http://dx.doi.org/10.1016/j.mbs.2017.03.002}, year = {2017}, affiliation = {UPMC IMJ-PRG ; IRSTEA CLERMONT FERRAND UR LISC FRA ; MNHN CESCO}, abstract = {This paper addresses the issue of managing urban pigeon population using some possible actions that make it reach a density target with respect to socio-ecological constraints. A mathematical model describing the dynamic of this population is introduced. This model incorporates the effect of some regulatory actions on the dynamic of this population. We use mathematical viability theory, which provides a framework to study compatibility between dynamics and state constraints. The viability study shows when and how it is possible to regulate the pigeon population with respect to the constraints.}, }
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F. Jabot, J. Pottier
Macroecology of seed banks: The role of biogeography, environmental stochasticity and sampling
Global Ecology and Biogeography 26 (11), 2017
abs doi web bib

The study of seed banks has been mainly conducted at local scales, thereby hampering our general understanding of the assembly processes of these biodiversity reservoirs. Here, we aim to document worldwide macroecological patterns of seed bank diversity and of their similarity with aboveground vegetation. Our second aim is to investigate the likely drivers of these macroecological patterns and to lay the foundation of a metacommunity theory of seed banks. Location: Worldwide. Time period: 1989'2005. Major taxa studied: Plants. Methods: We compiled a worldwide dataset of 130 seed banks located in grasslands. We assessed the likely drivers of seed bank diversity and similarity with aboveground vegetation, using structural equation modelling. We then developed a time-averaged neutral model of coupled seed bank'vegetation (S-V) dynamics that includes the effect of environmental stochasticity, and we compared its predictions with empirical findings. Results: We found evidence for two weak latitudinal gradients in seed bank diversity and S-V similarity, with larger species richness and smaller similarity closer to the tropics. We then showed that seed bank richness and S-V similarity are correlated with the following four distinct drivers: local environmental variability, plant regional diversity, seed bank density and sampling area. Finally, we showed that the predictions of the time-averaged neutral model are remarkably in accord with empirical observations. Main conclusions: Our results lay the foundations of a metacommunity theory for seed banks. They challenge the standard view that seed banks are principally structured by environmental variability, by highlighting the additional key roles of dispersal and stochastic sampling on seed bank diversity patterns.
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@article{PUB00056695, author = {Jabot, F. and Pottier, J.}, title = {Macroecology of seed banks: The role of biogeography, environmental stochasticity and sampling}, journal = {Global Ecology and Biogeography}, volume = {26}, number = {11}, pages = {1247-1257}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00056695 / https://www.scopus.com/inward/record.uri?eid=2-s2.0-85030452501&doi=10.1111%2fgeb.12631&partnerID=40&md5=03f07487877aeb9a1a7865f4182b6ff4}, doi = {http://dx.doi.org/10.1111/geb.12631}, year = {2017}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; INRA CLERMONT FERRAND FRA}, abstract = {The study of seed banks has been mainly conducted at local scales, thereby hampering our general understanding of the assembly processes of these biodiversity reservoirs. Here, we aim to document worldwide macroecological patterns of seed bank diversity and of their similarity with aboveground vegetation. Our second aim is to investigate the likely drivers of these macroecological patterns and to lay the foundation of a metacommunity theory of seed banks. Location: Worldwide. Time period: 1989'2005. Major taxa studied: Plants. Methods: We compiled a worldwide dataset of 130 seed banks located in grasslands. We assessed the likely drivers of seed bank diversity and similarity with aboveground vegetation, using structural equation modelling. We then developed a time-averaged neutral model of coupled seed bank'vegetation (S-V) dynamics that includes the effect of environmental stochasticity, and we compared its predictions with empirical findings. Results: We found evidence for two weak latitudinal gradients in seed bank diversity and S-V similarity, with larger species richness and smaller similarity closer to the tropics. We then showed that seed bank richness and S-V similarity are correlated with the following four distinct drivers: local environmental variability, plant regional diversity, seed bank density and sampling area. Finally, we showed that the predictions of the time-averaged neutral model are remarkably in accord with empirical observations. Main conclusions: Our results lay the foundations of a metacommunity theory for seed banks. They challenge the standard view that seed banks are principally structured by environmental variability, by highlighting the additional key roles of dispersal and stochastic sampling on seed bank diversity patterns. }, }
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F. Jabot, C. Giraldo, S. Lefebvre
Are food web structures well represented in isotopic spaces?
Functional Ecology 31 (10), 2017
abs doi web bib

Isotopic analyses are increasingly used to assess the structure of food webs and a series of isotopic functional indices have been proposed in the last decade to characterize this structure. These indices are based on the foundational assumption that proximity in the isotopic space informs on trophic similarity between species. While it has been recognized for long that this simplifying assumption should be used with caution, no formal evaluation of its domain of validity has been performed to date. We here simulate a large number (15 000) of food webs with varying characteristics to assess (i) whether isotopic distance is a good proxy of trophi c dissimilarity; (ii) whether isotopic functional indices are good proxies of troph ic functional properties; and (iii) how the quality of these two proxies depend on various spec ies and food web properties. We ﬁrst demonstrate that isot opic distance is moderately correlated with trophic similarity in simulated food webs. We ﬁnd, however, that two isotopic community metrics investigated (Rao’s index of functional divergence and nearest neighbour distance index of functional originality) are good indicators of community trophic struc ture, especially in food webs with large connectance, and when predators have low levels of diet specialization. We also ﬁnd that isot opic func tional indices are decreasingly reliable as they aim at characterizing more subtle functional patterns (such as standard deviation of nearest neighbour distance, an index of between species variation in originality). Taken together, our resul ts suggest that the reliability of the isotopic mapping of consumers decreases with their number of potential prey species, but increases with their number of realized prey species. Conse quently, isotopic reliability decreases in species-rich food webs with low connectance, large vertical diversity and large incidence of omnivory. Our study highlights that researchers should not hope to grasp subtle patterns of food web structure based solely on widely used isotopic indices. They should instead envisage mobilizing such isotopic information in combination with complementary data types.
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@article{PUB00056690, author = {Jabot, F. and Giraldo, C. and Lefebvre, S.}, title = {Are food web structures well represented in isotopic spaces?}, journal = {Functional Ecology}, volume = {31}, number = {10}, pages = {1975-1984}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00056690 / https://www.scopus.com/inward/record.uri?eid=2-s2.0-85020215657&doi=10.1111%2f1365-2435.12895&partnerID=40&md5=40a78515f7f26d7440325d5d43b22cae}, doi = {http://dx.doi.org/10.1111/1365-2435.12895}, year = {2017}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; GDR CNRS GRET LMGE AUBIERE FRA ; GDR CNRS GRET LMGE AUBIERE FRA}, abstract = {Isotopic analyses are increasingly used to assess the structure of food webs and a series of isotopic functional indices have been proposed in the last decade to characterize this structure. These indices are based on the foundational assumption that proximity in the isotopic space informs on trophic similarity between species. While it has been recognized for long that this simplifying assumption should be used with caution, no formal evaluation of its domain of validity has been performed to date. We here simulate a large number (15 000) of food webs with varying characteristics to assess (i) whether isotopic distance is a good proxy of trophi c dissimilarity; (ii) whether isotopic functional indices are good proxies of troph ic functional properties; and (iii) how the quality of these two proxies depend on various spec ies and food web properties. We ﬁrst demonstrate that isot opic distance is moderately correlated with trophic similarity in simulated food webs. We ﬁnd, however, that two isotopic community metrics investigated (Rao’s index of functional divergence and nearest neighbour distance index of functional originality) are good indicators of community trophic struc ture, especially in food webs with large connectance, and when predators have low levels of diet specialization. We also ﬁnd that isot opic func tional indices are decreasingly reliable as they aim at characterizing more subtle functional patterns (such as standard deviation of nearest neighbour distance, an index of between species variation in originality). Taken together, our resul ts suggest that the reliability of the isotopic mapping of consumers decreases with their number of potential prey species, but increases with their number of realized prey species. Conse quently, isotopic reliability decreases in species-rich food webs with low connectance, large vertical diversity and large incidence of omnivory. Our study highlights that researchers should not hope to grasp subtle patterns of food web structure based solely on widely used isotopic indices. They should instead envisage mobilizing such isotopic information in combination with complementary data types.}, }
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C.T. Kone, J.D. Mathias, G. De Sousa
Adaptive management of energy consumption, reliability and delay of wireless sensor node: Application to IEEE 802.15.4 wireless sensor node
PLoS One 12 (2), 2017
abs doi web bib

Designing a Wireless Sensor Network (WSN) to achieve a high Quality of Service (QoS) (network performance and durability) is a challenging problem. We address it by focusing on the performance of the 802.15.4 communication protocol because the IEEE 802.15.4 Standard is actually considered as one of the reference technologies in WSNs. In this paper, we propose to control the sustainable use of resources (i.e., energy consumption, reliability and timely packet transmission) of a wireless sensor node equipped with photovoltaic cells by an adaptive tuning not only of the MAC (Medium Access Control) parameters but also of the sampling frequency of the node. To do this, we use one of the existing control approaches, namely the viability theory, which aims to preserve the functions and the controls of a dynamic system in a set of desirable states. So, an analytical model, describing the evolution over time of nodal resources, is derived and used by a viability algorithm for the adaptive tuning of the IEEE 802.15.4 MAC protocol. The simulation analysis shows that our solution allows ensuring indefinitely, in the absence of hardware failure, the operations (lifetime duration, reliability and timely packet transmission) of an 802.15.4 WSN and one can temporarily increase the sampling frequency of the node beyond the regular sampling one. This latter brings advantages for agricultural and environmental applications such as precision agriculture, flood or fire prevention. Main results show that our current approach enable to send more information when critical events occur without the node runs out of energy. Finally, we argue that our approach is generic and can be applied to other types of WSN.
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@article{PUB00056192, author = {Kone, C.T. and Mathias, J.D. and De Sousa, G.}, title = {Adaptive management of energy consumption, reliability and delay of wireless sensor node: Application to IEEE 802.15.4 wireless sensor node}, title = {Gestion adaptative de la consommation d'énergie, de la fiabilité et des délais de transmission d'un capteur sans fil : application à un capteur sans fil IEEE utilisant le protocole 802.15.4}, journal = {PLoS One}, volume = {12}, number = {2}, pages = {28}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00056192 / http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0172336}, doi = {http://dx.doi.org/https://doi.org/10.1371/journal.pone.0172336}, year = {2017}, affiliation = {ESATIC ABIDJAN DRIT CIV ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR TSCF FRA}, abstract = {Designing a Wireless Sensor Network (WSN) to achieve a high Quality of Service (QoS) (network performance and durability) is a challenging problem. We address it by focusing on the performance of the 802.15.4 communication protocol because the IEEE 802.15.4 Standard is actually considered as one of the reference technologies in WSNs. In this paper, we propose to control the sustainable use of resources (i.e., energy consumption, reliability and timely packet transmission) of a wireless sensor node equipped with photovoltaic cells by an adaptive tuning not only of the MAC (Medium Access Control) parameters but also of the sampling frequency of the node. To do this, we use one of the existing control approaches, namely the viability theory, which aims to preserve the functions and the controls of a dynamic system in a set of desirable states. So, an analytical model, describing the evolution over time of nodal resources, is derived and used by a viability algorithm for the adaptive tuning of the IEEE 802.15.4 MAC protocol. The simulation analysis shows that our solution allows ensuring indefinitely, in the absence of hardware failure, the operations (lifetime duration, reliability and timely packet transmission) of an 802.15.4 WSN and one can temporarily increase the sampling frequency of the node beyond the regular sampling one. This latter brings advantages for agricultural and environmental applications such as precision agriculture, flood or fire prevention. Main results show that our current approach enable to send more information when critical events occur without the node runs out of energy. Finally, we argue that our approach is generic and can be applied to other types of WSN.}, }
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E. Lalechère, F. Jabot, F. Archaux, G. Deffuant
Non-equilibrium plant metapopulation dynamics challenge the concept of ancient/recent forest species
Ecological Modelling 366, 2017
abs doi web bib

Previous analyses of the regional distribution of forest plants have revealed that some species have a biased distribution towards either ancient or recent forest patches. It has been therefore proposed to classify forest plant species according to their affinity for ancient or recent patches. In this contribution, we aimed at providing a dynamical perspective on this static concept of ancient/recent forest species. We developed an inference method to estimate the metapopulation dynamics of forest plants based on landscape history and static (and incomplete) biodiversity data accounting for false absence records. We assessed the power of this novel inference method using simulated metapopulation and landscape dynamics. We finally applied this method to occupancy data of 174 and 121 forest species in two networks of 9208 and 9201 forest patches respectively. These patch networks are located in two French regions, with corresponding landscape historical data based on two forest maps conceived in 1840 and 2000. Our analyses revealed that i) the inference method enables to satisfactorily infer three parameters of the metapopulation model: the rates of colonization, extinction and decay of colonization with distance; ii) this three parameter metapopulation model is sufficient to reproduce the occurrence spatial structure of 72% and 61% of the investigated species in the two regions; iii) forest plant species are distributed along a spectrum of turn-over speed, in which small (large) colonization capacity are associated with small (large) propensity to extinction; iv) species position along this spectrum can be partially predicted from plant functional traits; and v) species metapopulation dynamics are driven by the interaction between landscape and species intrinsic properties, suggesting that ancient/recent forest species lists are unlikely to be easily extrapolated to novel landscapes.
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@article{PUB00056665, author = {Lalechère, E. and Jabot, F. and Archaux, F. and Deffuant, G.}, title = {Non-equilibrium plant metapopulation dynamics challenge the concept of ancient/recent forest species}, journal = {Ecological Modelling}, volume = {366}, pages = {48-57}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00056665}, doi = {http://dx.doi.org/10.1016/j.ecolmodel.2017.10.008}, year = {2017}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA NOGENT SUR VERNISSON UR EFNO FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {Previous analyses of the regional distribution of forest plants have revealed that some species have a biased distribution towards either ancient or recent forest patches. It has been therefore proposed to classify forest plant species according to their affinity for ancient or recent patches. In this contribution, we aimed at providing a dynamical perspective on this static concept of ancient/recent forest species. We developed an inference method to estimate the metapopulation dynamics of forest plants based on landscape history and static (and incomplete) biodiversity data accounting for false absence records. We assessed the power of this novel inference method using simulated metapopulation and landscape dynamics. We finally applied this method to occupancy data of 174 and 121 forest species in two networks of 9208 and 9201 forest patches respectively. These patch networks are located in two French regions, with corresponding landscape historical data based on two forest maps conceived in 1840 and 2000. Our analyses revealed that i) the inference method enables to satisfactorily infer three parameters of the metapopulation model: the rates of colonization, extinction and decay of colonization with distance; ii) this three parameter metapopulation model is sufficient to reproduce the occurrence spatial structure of 72% and 61% of the investigated species in the two regions; iii) forest plant species are distributed along a spectrum of turn-over speed, in which small (large) colonization capacity are associated with small (large) propensity to extinction; iv) species position along this spectrum can be partially predicted from plant functional traits; and v) species metapopulation dynamics are driven by the interaction between landscape and species intrinsic properties, suggesting that ancient/recent forest species lists are unlikely to be easily extrapolated to novel landscapes.}, }
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J.D. Mathias, S. J. Lade, V. Galaz
Multi-level policies and adaptive social networks. A conceptual modeling study for maintaining a polycentric governance system
International Journal of the Commons 11 (1), 2017
abs doi web bib

Information and collaboration patterns embedded in social networks play key roles in multilevel and polycentric modes of governance. However, modeling the dynamics of such social networks in multilevel settings has been seldom addressed in the literature. Here we use an adaptive social network model to elaborate the interplay between a central and a local government in order to maintain a polycentric governance. More specifically, our analysis explores in what ways specific policy choices made by a central agent affect the features of an emerging social network composed of local organizations and local users. Using two types of stylized policies, adaptive co-management and adaptive one-level management, we focus on the benefits of multi-level adaptive cooperation for network management. Our analysis uses viability theory to explore and to quantify the ability of these policies to achieve specific network properties. Viability theory gives the family of policies that enables maintaining the polycentric governance unlike optimal control that gives a unique blueprint. We found that the viability of the policies can change dramatically depending on the goals and features of the social network. For some social networks, we also found a very large difference between the viability of the adaptive one-level management and adaptive co-management policies. However, results also show that adaptive co-management doesn't always provide benefits. Hence, we argue that applying viability theory to governance networks can help policy design by analyzing the trade-off between the costs of adaptive co-management and the benefits associated with its ability to maintain desirable social network properties in a polycentric governance framework.
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@article{PUB00056696, author = {Mathias, J.D. and Lade, S. J. and Galaz, V.}, title = {Multi-level policies and adaptive social networks. A conceptual modeling study for maintaining a polycentric governance system}, journal = {International Journal of the Commons}, volume = {11}, number = {1}, pages = {220-247}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00056696 / https://www.scopus.com/inward/record.uri?eid=2-s2.0-85013995884&doi=10.18352%2fijc.695&partnerID=40&md5=00bb6c78428526251cc4c398df0532e2}, doi = {http://dx.doi.org/10.18352/ijc.695}, year = {2017}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; STOCKHOLM UNIVERSITY SWE ; STOCKHOLM UNIVERSITY SWE}, abstract = {Information and collaboration patterns embedded in social networks play key roles in multilevel and polycentric modes of governance. However, modeling the dynamics of such social networks in multilevel settings has been seldom addressed in the literature. Here we use an adaptive social network model to elaborate the interplay between a central and a local government in order to maintain a polycentric governance. More specifically, our analysis explores in what ways specific policy choices made by a central agent affect the features of an emerging social network composed of local organizations and local users. Using two types of stylized policies, adaptive co-management and adaptive one-level management, we focus on the benefits of multi-level adaptive cooperation for network management. Our analysis uses viability theory to explore and to quantify the ability of these policies to achieve specific network properties. Viability theory gives the family of policies that enables maintaining the polycentric governance unlike optimal control that gives a unique blueprint. We found that the viability of the policies can change dramatically depending on the goals and features of the social network. For some social networks, we also found a very large difference between the viability of the adaptive one-level management and adaptive co-management policies. However, results also show that adaptive co-management doesn't always provide benefits. Hence, we argue that applying viability theory to governance networks can help policy design by analyzing the trade-off between the costs of adaptive co-management and the benefits associated with its ability to maintain desirable social network properties in a polycentric governance framework. }, }
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J.D. Mathias, J.M. Anderies, M.A. Janssen
On our rapidly shrinking capacity to comply with the planetary boundaries on climate change
Scientific Reports 7, 2017
abs doi web bib

The planetary boundary framework constitutes an opportunity for decision makers to define climate policy through the lens of adaptive governance. Here, we use the DICE model to analyze the set of adaptive climate policies that comply with the two planetary boundaries related to climate change: (1) staying below a CO 2 concentration of 550 ppm until 2100 and (2) returning to 350 ppm in 2100. Our results enable decision makers to assess the following milestones: (1) a minimum of 33% reduction of CO 2 emissions by 2055 in order to stay below 550 ppm by 2100 (this milestone goes up to 46% in the case of delayed policies); and (2) carbon neutrality and the effective implementation of innovative geoengineering technologies (10% negative emissions) before 2060 in order to return to 350 ppm in 2100, under the assumption of getting out of the baseline scenario without delay. Finally, we emphasize the need to use adaptive path-based approach instead of single point target for climate policy design.
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@article{PUB00056699, author = {Mathias, J.D. and Anderies, J.M. and Janssen, M.A.}, title = {On our rapidly shrinking capacity to comply with the planetary boundaries on climate change}, journal = {Scientific Reports}, volume = {7}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00056699 / https://www.scopus.com/inward/record.uri?eid=2-s2.0-85011664816&doi=10.1038%2fsrep42061&partnerID=40&md5=386e9839d0e3a2351a143910495c3f97}, doi = {http://dx.doi.org/10.1038/srep42061}, year = {2017}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; SCHOOL OF SUSTAINABILITY ARIZONA STAT UNIVERSITY TEMPE USA ; SCHOOL OF SUSTAINABILITY ARIZONA STAT UNIVERSITY TEMPE USA}, abstract = {The planetary boundary framework constitutes an opportunity for decision makers to define climate policy through the lens of adaptive governance. Here, we use the DICE model to analyze the set of adaptive climate policies that comply with the two planetary boundaries related to climate change: (1) staying below a CO 2 concentration of 550 ppm until 2100 and (2) returning to 350 ppm in 2100. Our results enable decision makers to assess the following milestones: (1) a minimum of 33% reduction of CO 2 emissions by 2055 in order to stay below 550 ppm by 2100 (this milestone goes up to 46% in the case of delayed policies); and (2) carbon neutrality and the effective implementation of innovative geoengineering technologies (10% negative emissions) before 2060 in order to return to 350 ppm in 2100, under the assumption of getting out of the baseline scenario without delay. Finally, we emphasize the need to use adaptive path-based approach instead of single point target for climate policy design. }, }
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J.D. Mathias, S. Huet, G. Deffuant
An energy-like indicator to assess opinion resilience
Physica A-Statistical Mechanics and its Applications 473, 2017
abs doi web bib

Using the bounded-confidence model, with fixed uncertainties and extremists, we investigate how resilient the moderate mean opinion of a population is to the arrival in it of a new group of agents, when the energy of the opinion of this group extremeness × group size) is varied. We say moderate mean opinion is resilient when, even though it may become temporarily more extreme after the arrival of the new agents, it later recovers its moderate value. We show that such resilience is displayed up to a threshold value of the equivalent energy of the group. We also show that when the agent-based model spontaneously converges to a single extreme, then this energy threshold is nill.
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@article{PUB00052559, author = {Mathias, J.D. and Huet, S. and Deffuant, G.}, title = {An energy-like indicator to assess opinion resilience}, title = {Un indicateur type énergie pour évaluer la résilience d'une opinion}, journal = {Physica A-Statistical Mechanics and its Applications}, volume = {473}, pages = {501-510}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00052559}, doi = {http://dx.doi.org/10.1016/j.physa.2016.12.035}, year = {2017}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {Using the bounded-confidence model, with fixed uncertainties and extremists, we investigate how resilient the moderate mean opinion of a population is to the arrival in it of a new group of agents, when the energy of the opinion of this group extremeness × group size) is varied. We say moderate mean opinion is resilient when, even though it may become temporarily more extreme after the arrival of the new agents, it later recovers its moderate value. We show that such resilience is displayed up to a threshold value of the equivalent energy of the group. We also show that when the agent-based model spontaneously converges to a single extreme, then this energy threshold is nill.}, }
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J. Pottier, F. Jabot
Non-destructive biomass estimation of herbaceous plant individuals: A transferable method between contrasted environments
Ecological Indicators 72, 2017
abs doi web bib

Monitoring plant growth at the individual level in arrays of environmental conditions is key to understanding plant functioning with strong implications for ecophysiology, population biology and community ecology. This requires non-destructive methods for repeated estimates of individual plant biomass in time. Although allometric equations have been widely used for trees and shrubs, there is currently no general approach for herbaceous species that can be applied across habitats, plant architecture, life stage and leading to transferable equations between contrasted environments. Here we propose a method based on three biometric measurements of the minimum volume occupied by aboveground plant organs. A total of 36 equations were fitted and compared for twelve species of temperate grasslands, corresponding to various volume shapes, scaling functions (linear or power) and including (or not) a life stage effect. The accuracy of the selected equations was compared to similar attempts reported in the literature. We further assessed the across-site transferability of the best allometric equations. The goodness-of-fit of the best equations selected for each species was high (
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@article{PUB00056697, author = {Pottier, J. and Jabot, F.}, title = {Non-destructive biomass estimation of herbaceous plant individuals: A transferable method between contrasted environments}, journal = {Ecological Indicators}, volume = {72}, pages = {769-776}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00056697 / https://www.scopus.com/inward/record.uri?eid=2-s2.0-84987880979&doi=10.1016%2fj.ecolind.2016.08.030&partnerID=40&md5=78ff286a72d59c8a5c75358f69e62e0b}, doi = {http://dx.doi.org/10.1016/j.ecolind.2016.08.030}, year = {2017}, affiliation = {INRA CLERMONT FERRAND FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {Monitoring plant growth at the individual level in arrays of environmental conditions is key to understanding plant functioning with strong implications for ecophysiology, population biology and community ecology. This requires non-destructive methods for repeated estimates of individual plant biomass in time. Although allometric equations have been widely used for trees and shrubs, there is currently no general approach for herbaceous species that can be applied across habitats, plant architecture, life stage and leading to transferable equations between contrasted environments. Here we propose a method based on three biometric measurements of the minimum volume occupied by aboveground plant organs. A total of 36 equations were fitted and compared for twelve species of temperate grasslands, corresponding to various volume shapes, scaling functions (linear or power) and including (or not) a life stage effect. The accuracy of the selected equations was compared to similar attempts reported in the literature. We further assessed the across-site transferability of the best allometric equations. The goodness-of-fit of the best equations selected for each species was high (}, }
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R. Rouveure, T. Tourrette, M. Jaud, P. Faure, M.O. Monod
Design of lightweight airborne MMW radar for DEM generation. Simulation results
Robotics and Autonomous Systems 96, 2017
abs doi web bib

There is a growing need for lightweight airborne platforms that could provide precise information about the environment (topography, presence of obstacles, etc.) filling the data gap between aerial/satellite remote sensing and terrestrial systems. A major limitation of classical sensors such as vision or laser is that they are ineffective in degraded visual conditions. Millimeter-wave radar provides an alternative solution to overcome the shortcomings of optical solutions, because in the microwave range, data can be acquired independently of atmospheric conditions and time of the day. The intended application of a new radar sensor is the construction of digital elevation models of the overflown environments. As the design of new radar sensors for light airborne platforms is subject to specific technological constraints, a simulator of airborne radar surveys is developed. The objective of the simulator is to help the designer in defining the main parameters of the future airborne radar, and in developing radar signal processing algorithms.
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@article{PUB00057125, author = {Rouveure, R. and Tourrette, T. and Jaud, M. and Faure, P. and Monod, M.O.}, title = {Design of lightweight airborne MMW radar for DEM generation. Simulation results}, title = {Conception de radar MMW aéroporté léger pour la génération DEM. Résultats de la simulation}, journal = {Robotics and Autonomous Systems}, volume = {96}, pages = {26-40}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00057125}, doi = {http://dx.doi.org/10.1016/j.robot.2017.07.002}, year = {2017}, affiliation = {IRSTEA CLERMONT FERRAND UR TSCF FRA ; IRSTEA CLERMONT FERRAND UR TSCF FRA ; IUEM PLOUZANE FRA ; IRSTEA CLERMONT FERRAND UR TSCF FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {There is a growing need for lightweight airborne platforms that could provide precise information about the environment (topography, presence of obstacles, etc.) filling the data gap between aerial/satellite remote sensing and terrestrial systems. A major limitation of classical sensors such as vision or laser is that they are ineffective in degraded visual conditions. Millimeter-wave radar provides an alternative solution to overcome the shortcomings of optical solutions, because in the microwave range, data can be acquired independently of atmospheric conditions and time of the day. The intended application of a new radar sensor is the construction of digital elevation models of the overflown environments. As the design of new radar sensors for light airborne platforms is subject to specific technological constraints, a simulator of airborne radar surveys is developed. The objective of the simulator is to help the designer in defining the main parameters of the future airborne radar, and in developing radar signal processing algorithms.}, }
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R. Rouveure, P. Faure, M.O. Monod
Description and experimental results of a panoramic K-Band radar dedicated to perception in mobile robotics applications
Journal of Field Robotics, 2017
abs doi web bib

Robust environmental perception is a crucial parameter for the development of autonomous ground vehicle applications, especially in the field of agricultural robotics which is one of the priorities for the Horizon 2020 robotics funding (EU funding program for research and innovation). Because of uncontrolled and changing environmental conditions in outdoor and natural environments, data from optical sensors classically used in mobile robotics can be compromised and unusable. In such situations, microwave radar can provide an alternative and complementary solution for perception tasks. The aim of this paper is to present PELICAN radar, a microwave radar specifically designed for mobile robotics applications, including obstacle detection, mapping, and situational awareness in general. PELICAN radar provides each second a view over 360 of the sur- rounding environment, from 5 m up to 100 m. A description of the technological solutions adopted for the development of PELICAN radar (hardware and software) is presented. Results obtained in various outdoor and open environments, including urban and natural areas, are also described. Sets of PELICAN radar data are made available online for researchers interested in processing this type of data.
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@article{PUB00057123, author = {Rouveure, R. and Faure, P. and Monod, M.O.}, title = {Description and experimental results of a panoramic K-Band radar dedicated to perception in mobile robotics applications}, journal = {Journal of Field Robotics}, pages = {1-27}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00057123 / raphael.rouveure@irstea.fr}, doi = {http://dx.doi.org/10.1002/rob.21770}, year = {2017}, affiliation = {IRSTEA CLERMONT FERRAND UR TSCF FRA ; IRSTEA CLERMONT FERRAND UR TSCF FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {Robust environmental perception is a crucial parameter for the development of autonomous ground vehicle applications, especially in the field of agricultural robotics which is one of the priorities for the Horizon 2020 robotics funding (EU funding program for research and innovation). Because of uncontrolled and changing environmental conditions in outdoor and natural environments, data from optical sensors classically used in mobile robotics can be compromised and unusable. In such situations, microwave radar can provide an alternative and complementary solution for perception tasks. The aim of this paper is to present PELICAN radar, a microwave radar specifically designed for mobile robotics applications, including obstacle detection, mapping, and situational awareness in general. PELICAN radar provides each second a view over 360 of the sur- rounding environment, from 5 m up to 100 m. A description of the technological solutions adopted for the development of PELICAN radar (hardware and software) is presented. Results obtained in various outdoor and open environments, including urban and natural areas, are also described. Sets of PELICAN radar data are made available online for researchers interested in processing this type of data.}, }
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C. Smadi
The effect of recurrent mutations on genetic diversity in a large population of varying size
Acta Applicandae Mathematicae 149 (1), 2017
abs doi web bib

Recurrent mutations are a common phenomenon in population genetics. They may be at the origin of the fixation of a new genotype, if they give a phenotypic advantage to the carriers of the new mutation. In this paper, we are interested in the genetic signature left by a selective sweep induced by recurrent mutations at a given locus from an allele A to an allele a, depending on the mutation frequency. We distinguish three possible scales for the mutation probability per reproductive event, which entail distinct genetic signatures. Besides, we study the hydrodynamic limit of the A- and a-population size dynamics when mutations are frequent, and find non trivial equilibria leading to several possible patterns of polymorphism.
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@article{PUB00056692, author = {Smadi, C.}, title = {The effect of recurrent mutations on genetic diversity in a large population of varying size}, journal = {Acta Applicandae Mathematicae}, volume = {149}, number = {1}, pages = {11-51}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00056692 / https://www.scopus.com/inward/record.uri?eid=2-s2.0-85001090517&doi=10.1007%2fs10440-016-0086-x&partnerID=40&md5=e89de33047cc2f507143734a138d7a30}, doi = {http://dx.doi.org/10.1007/s10440-016-0086-x}, year = {2017}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {Recurrent mutations are a common phenomenon in population genetics. They may be at the origin of the fixation of a new genotype, if they give a phenotypic advantage to the carriers of the new mutation. In this paper, we are interested in the genetic signature left by a selective sweep induced by recurrent mutations at a given locus from an allele A to an allele a, depending on the mutation frequency. We distinguish three possible scales for the mutation probability per reproductive event, which entail distinct genetic signatures. Besides, we study the hydrodynamic limit of the A- and a-population size dynamics when mutations are frequent, and find non trivial equilibria leading to several possible patterns of polymorphism. }, }
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A. Brias, J.D. Mathias, G. Deffuant
Accelerating viability kernel computation with CUDA architecture: application to bycatch fishery management
Computational Management Science 13 (3), 2016
abs doi web bib

Computing a viability kernel consumes time and memory resources which increase exponentially with the dimension of the problem. This curse of dimensionality strongly limits the applicability of this approach, otherwise promising. We report here an attempt to tackle this problem with Graphics Processing Units (GPU). We design and implement a version of the viability kernel algorithm suitable for General Purpose GPU (GPGPU) computing using Nvidia's architecture, CUDA (Computing Unified Device Architecture). Different parts of the algorithm are parallelized on the GPU device and we test the algorithm on a dynamical system of theoretical population growth. We study computing time gains as a function of the number of dimensions and the accuracy of the grid covering the state space. The speed factor reaches up to 20 with the GPU version compared to the Central Processing Unit (CPU) version, making the approach more applicable to problems in 4 to 7 dimensions. We use the GPU version of the algorithm to compute viability kernel of bycatch fishery management problems up to 6 dimensions.
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@article{PUB00046149, author = {Brias, A. and Mathias, J.D. and Deffuant, G.}, title = {Accelerating viability kernel computation with CUDA architecture: application to bycatch fishery management}, title = {Accélérer le calcul de noyau de viabilité avec l'architecture CUDA : application à la gestion de pêcherie avec prises accessoires}, journal = {Computational Management Science}, volume = {13}, number = {3}, pages = {371-391}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00046149}, doi = {http://dx.doi.org/10.1007/s10287-015-0246-x}, year = {2016}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {Computing a viability kernel consumes time and memory resources which increase exponentially with the dimension of the problem. This curse of dimensionality strongly limits the applicability of this approach, otherwise promising. We report here an attempt to tackle this problem with Graphics Processing Units (GPU). We design and implement a version of the viability kernel algorithm suitable for General Purpose GPU (GPGPU) computing using Nvidia's architecture, CUDA (Computing Unified Device Architecture). Different parts of the algorithm are parallelized on the GPU device and we test the algorithm on a dynamical system of theoretical population growth. We study computing time gains as a function of the number of dimensions and the accuracy of the grid covering the state space. The speed factor reaches up to 20 with the GPU version compared to the Central Processing Unit (CPU) version, making the approach more applicable to problems in 4 to 7 dimensions. We use the GPU version of the algorithm to compute viability kernel of bycatch fishery management problems up to 6 dimensions.}, }
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A. Brias, J.D. Mathias, G. Deffuant
Computing the reliability kernel of a time-variant system: Application to a corroded beam
IFAC-PapersOnLine 49 (12), Elsevier B.V., 2016
abs doi web bib

Time-variant reliability analysis aims at assessing the probability of failure of a time-variant system within a given time horizon. We illustrate in this paper the computation of the reliability kernel which is the set of initial states for which the probability of failure remains under a threshold within the considered time horizon. This paper supposes that the time-variant system is discrete in time and space with given probabilities of transition between space states. We use a recursive relation for computing the cumulative probability of failure of the system, linking the probability of failure at time t with the probability of being at a given state x (for all possible states) at time t ' 1. Applying this relation, it is possible to compute the probability of failure at any starting point in the state space and hence to derive the reliability kernel. The computation of this kernel gives informations about the system which can be further helpful in reliable design. The approach is illustrated on an example of a steel beam under corrosion.
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@article{PUB00052001, author = {Brias, A. and Mathias, J.D. and Deffuant, G.}, title = {Computing the reliability kernel of a time-variant system: Application to a corroded beam}, journal = {IFAC-PapersOnLine}, volume = {49}, number = {12}, publisher = {Elsevier B.V.}, pages = {151-155}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00052001 / https://www.scopus.com/inward/record.uri?eid=2-s2.0-84992416427&doi=10.1016%2fj.ifacol.2016.07.566&partnerID=40&md5=89386a26531d31d5dc20942aebf7b71f}, doi = {http://dx.doi.org/10.1016/j.ifacol.2016.07.566}, year = {2016}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {Time-variant reliability analysis aims at assessing the probability of failure of a time-variant system within a given time horizon. We illustrate in this paper the computation of the reliability kernel which is the set of initial states for which the probability of failure remains under a threshold within the considered time horizon. This paper supposes that the time-variant system is discrete in time and space with given probabilities of transition between space states. We use a recursive relation for computing the cumulative probability of failure of the system, linking the probability of failure at time t with the probability of being at a given state x (for all possible states) at time t ' 1. Applying this relation, it is possible to compute the probability of failure at any starting point in the state space and hence to derive the reliability kernel. The computation of this kernel gives informations about the system which can be further helpful in reliable design. The approach is illustrated on an example of a steel beam under corrosion.}, }
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F. Jabot, T. Lohier
Non-random correlation of species dynamics in tropical tree communities
Oikos 125 (12), Blackwell Publishing Ltd, 2016
abs doi web bib

The importance of environmental stochasticity for tropical tree dynamics has been recently stressed by several studies. This has spurred the development of a 'time-averaged neutral model' of community dynamics by Kalyuzhny and colleagues that extends the neutral model by incorporating environmental stochasticity. We here show that this framework can be used to assess the presence of non-random correlations between species dynamics. Indeed, the time-averaged neutral model makes the simplifying assumption that species responses to environmental variation are uncorrelated. We therefore propose to use this model as a null hypothesis against which observed community dynamics can be compared. This study makes five contributions. First, we describe a novel time-averaged neutral model of community dynamics that is close to, but more flexible than the one previously proposed by Kalyuzhny and colleagues. Second, we develop an inference method based on approximate Bayesian computation (ABC) and demonstrate the identifiability of the model parameters from community time series data. Third, we develop a test of the significance of environmental stochasticity, and a method to quantify its contribution to population variance. Fourth, we develop a test of non-random correlation between species dynamics. Fifth, we apply these developments to three datasets of tropical tree dynamics. We evidence both a strong contribution of environmental stochasticity to population variance in the three datasets, and a non-random correlation of species dynamics in one of them. We finally discuss the implications of these results for the modelling of tropical tree community dynamics.
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@article{PUB00051993, author = {Jabot, F. and Lohier, T.}, title = {Non-random correlation of species dynamics in tropical tree communities}, journal = {Oikos}, volume = {125}, number = {12}, publisher = {Blackwell Publishing Ltd}, pages = {1733-1742}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00051993 / https://www.scopus.com/inward/record.uri?eid=2-s2.0-84963500373&doi=10.1111%2foik.03103&partnerID=40&md5=8cc161ed3099d78c0b13e1c78d6b578e}, doi = {http://dx.doi.org/10.1111/oik.03103}, year = {2016}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {The importance of environmental stochasticity for tropical tree dynamics has been recently stressed by several studies. This has spurred the development of a 'time-averaged neutral model' of community dynamics by Kalyuzhny and colleagues that extends the neutral model by incorporating environmental stochasticity. We here show that this framework can be used to assess the presence of non-random correlations between species dynamics. Indeed, the time-averaged neutral model makes the simplifying assumption that species responses to environmental variation are uncorrelated. We therefore propose to use this model as a null hypothesis against which observed community dynamics can be compared. This study makes five contributions. First, we describe a novel time-averaged neutral model of community dynamics that is close to, but more flexible than the one previously proposed by Kalyuzhny and colleagues. Second, we develop an inference method based on approximate Bayesian computation (ABC) and demonstrate the identifiability of the model parameters from community time series data. Third, we develop a test of the significance of environmental stochasticity, and a method to quantify its contribution to population variance. Fourth, we develop a test of non-random correlation between species dynamics. Fifth, we apply these developments to three datasets of tropical tree dynamics. We evidence both a strong contribution of environmental stochasticity to population variance in the three datasets, and a non-random correlation of species dynamics in one of them. We finally discuss the implications of these results for the modelling of tropical tree community dynamics. }, }
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Y. Kubota, B. Kusumoto, T. Shiono, W. Ulrich, F. Jabot
Non-neutrality in forest communities: Evolutionary and ecological determinants of tree species abundance distributions
Oikos 125 (2), 2016
abs doi web bib

The unified neutral theory of biodiversity and biogeography provides a promising framework that can be used to integrate stochastic and ecological processes operating in ecological communities. Based on a mechanistic non-neutral model that incorporates density-dependent mortality, we evaluated the deviation from a neutral pattern in tree species abundance distributions and explored the signatures of historical and ecological processes that have shaped forest biomes. We compiled a dataset documenting species abundance distributions in 1168 plots encompassing 16 973 tree species across tropical, temperate, and boreal forests. We tested whether deviations from neutrality of species abundance distributions vary with climatic and historical conditions, and whether these patterns differ among regions. Non-neutrality in species abundance distributions was ubiquitous in tropical, temperate, and boreal forests, and regional differences in patterns of non-neutrality were significant between biomes. Species abundance evenness/unevenness caused by negative density-dependent or abiotic filtering effects had no clear macro-scale climatic drivers, although temperature was non-linearly correlated with species abundance unevenness on a global scale. These findings were not significantly biased by heterogeneity of plot data (the differences of plot area, measurement size, species richness, and the number of individuals sampled). Therefore, our results suggest that environmental filtering is not universally increasing from warm tropical to cold boreal forests, but might affect differently tree species assembly between and within biomes. Ecological processes generating particularly dominant species in local communities might be idiosyncratic or region-specific and may be associated with geography and climate. Our study illustrates that stochastic dynamical models enable the analysis of the interplay of historical and ecological processes that influence community assemblies and the dynamics of biodiversity.
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@article{PUB00051999, author = {Kubota, Y. and Kusumoto, B. and Shiono, T. and Ulrich, W. and Jabot, F.}, title = {Non-neutrality in forest communities: Evolutionary and ecological determinants of tree species abundance distributions}, journal = {Oikos}, volume = {125}, number = {2}, pages = {237-244}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00051999 / https://www.scopus.com/inward/record.uri?eid=2-s2.0-84956580904&doi=10.1111%2foik.02232&partnerID=40&md5=31a41a9762298c024de2f98c93c301ad}, doi = {http://dx.doi.org/10.1111/oik.02232}, year = {2016}, affiliation = {FACULTY OF SCIENCE UNIVERSITY OF THE RYUKYUS OKINAWA JPN ; FACULTY OF SCIENCE UNIVERSITY OF THE RYUKYUS OKINAWA JPN ; FACULTY OF SCIENCE UNIVERSITY OF THE RYUKYUS OKINAWA JPN ; NICOLAUS COPERNICUS UNIVERSITY TORUN POL ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {The unified neutral theory of biodiversity and biogeography provides a promising framework that can be used to integrate stochastic and ecological processes operating in ecological communities. Based on a mechanistic non-neutral model that incorporates density-dependent mortality, we evaluated the deviation from a neutral pattern in tree species abundance distributions and explored the signatures of historical and ecological processes that have shaped forest biomes. We compiled a dataset documenting species abundance distributions in 1168 plots encompassing 16 973 tree species across tropical, temperate, and boreal forests. We tested whether deviations from neutrality of species abundance distributions vary with climatic and historical conditions, and whether these patterns differ among regions. Non-neutrality in species abundance distributions was ubiquitous in tropical, temperate, and boreal forests, and regional differences in patterns of non-neutrality were significant between biomes. Species abundance evenness/unevenness caused by negative density-dependent or abiotic filtering effects had no clear macro-scale climatic drivers, although temperature was non-linearly correlated with species abundance unevenness on a global scale. These findings were not significantly biased by heterogeneity of plot data (the differences of plot area, measurement size, species richness, and the number of individuals sampled). Therefore, our results suggest that environmental filtering is not universally increasing from warm tropical to cold boreal forests, but might affect differently tree species assembly between and within biomes. Ecological processes generating particularly dominant species in local communities might be idiosyncratic or region-specific and may be associated with geography and climate. Our study illustrates that stochastic dynamical models enable the analysis of the interplay of historical and ecological processes that influence community assemblies and the dynamics of biodiversity. }, }
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T. Lohier, F. Jabot, A. Weigelt, B. Schmid, G. Deffuant
Predicting stochastic community dynamics in grasslands under the assumption of competitive symmetry
Journal of Theoretical Biology 399, 2016
abs doi web bib

Community dynamics is influenced by multiple ecological processes such as environmental spatiotemporal variation, competition between individuals and demographic stochasticity. Quantifying the respective influence of these various processes and making predictions on community dynamics require the use of a dynamical framework encompassing these various components. We here demonstrate how to adapt the framework of stochastic community dynamics to the peculiarities of herbaceous communities, by using a short temporal resolution adapted to the time scale of competition between herbaceous plants, and by taking into account the seasonal drops in plant aerial biomass following winter, harvesting or consumption by herbivores. We develop a hybrid inference method for this novel modelling framework that both uses numerical simulations and likelihood computations. Applying this methodology to empirical data from the Jena biodiversity experiment, we find that environmental stochasticity has a larger effect on community dynamics than demographic stochasticity, and that both effects are generally smaller than observation errors at the plot scale. We further evidence that plant intrinsic growth rates and carrying capacities are moderately predictable from plant vegetative height, specific leaf area and leaf dry matter content. We do not find any trade-off between demographical components, since species with larger intrinsic growth rates tend to also have lower demographic and environmental variances. Finally, we find that our model is able to make relatively good predictions of multi-specific community dynamics based on the assumption of competitive symmetry
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@article{PUB00048174, author = {Lohier, T. and Jabot, F. and Weigelt, A. and Schmid, B. and Deffuant, G.}, title = {Predicting stochastic community dynamics in grasslands under the assumption of competitive symmetry}, journal = {Journal of Theoretical Biology}, volume = {399}, pages = {53-61}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00048174}, doi = {http://dx.doi.org/10.1016/j.jtbi.2016.03.043}, year = {2016}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; UNIVERSITAT LEIPZIG DEU ; UNIVERSITY OF ZURICH CHE ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {Community dynamics is influenced by multiple ecological processes such as environmental spatiotemporal variation, competition between individuals and demographic stochasticity. Quantifying the respective influence of these various processes and making predictions on community dynamics require the use of a dynamical framework encompassing these various components. We here demonstrate how to adapt the framework of stochastic community dynamics to the peculiarities of herbaceous communities, by using a short temporal resolution adapted to the time scale of competition between herbaceous plants, and by taking into account the seasonal drops in plant aerial biomass following winter, harvesting or consumption by herbivores. We develop a hybrid inference method for this novel modelling framework that both uses numerical simulations and likelihood computations. Applying this methodology to empirical data from the Jena biodiversity experiment, we find that environmental stochasticity has a larger effect on community dynamics than demographic stochasticity, and that both effects are generally smaller than observation errors at the plot scale. We further evidence that plant intrinsic growth rates and carrying capacities are moderately predictable from plant vegetative height, specific leaf area and leaf dry matter content. We do not find any trade-off between demographical components, since species with larger intrinsic growth rates tend to also have lower demographic and environmental variances. Finally, we find that our model is able to make relatively good predictions of multi-specific community dynamics based on the assumption of competitive symmetry}, }
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J.D. Mathias, S. Huet, G. Deffuant
Bounded confidence model with fixed uncertainties and extremists: The opinions can keep fluctuating indefinitely
JASSS-The Journal of Artificial Societies and Social Simulation 19 (1), 2016
abs doi web bib

The bounded confidence model and its variants applied to moderate and extremist agents exhibit three types of attractors: central clusters, double extreme and single extreme clusters. These attractors are observed when the models include a dynamics on the uncertainties tending to decrease the moderate uncertainties when interacting with extremists. We show here that a new stationary state appears when the uncertainties are fixed, for large uncertainties of the moderates. In this stationary state, the opinions of moderate agents keep fluctuating without clustering, altogether forming a stable density which shape changes significantly when the parameters vary.
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@article{PUB00046748, author = {Mathias, J.D. and Huet, S. and Deffuant, G.}, title = {Bounded confidence model with fixed uncertainties and extremists: The opinions can keep fluctuating indefinitely}, journal = {JASSS-The Journal of Artificial Societies and Social Simulation}, volume = {19}, number = {1}, pages = {15}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00046748 / http://jasss.soc.surrey.ac.uk/19/1/6.html}, doi = {http://dx.doi.org/10.18564/jasss.2967}, year = {2016}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {The bounded confidence model and its variants applied to moderate and extremist agents exhibit three types of attractors: central clusters, double extreme and single extreme clusters. These attractors are observed when the models include a dynamics on the uncertainties tending to decrease the moderate uncertainties when interacting with extremists. We show here that a new stationary state appears when the uncertainties are fixed, for large uncertainties of the moderates. In this stationary state, the opinions of moderate agents keep fluctuating without clustering, altogether forming a stable density which shape changes significantly when the parameters vary.}, }
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S. Palau, J.C. Pardo, C. Smadi
Asymptotic behaviour of exponential functionals of Lévy processes with applications to random processes in random environment
ALEA-Latin American Journal of Probability and Mathematical Statistics 13, 2016
web bib

@article{PUB00052862, author = {Palau, S. and Pardo, J.C. and Smadi, C.}, title = {Asymptotic behaviour of exponential functionals of Lévy processes with applications to random processes in random environment}, journal = {ALEA-Latin American Journal of Probability and Mathematical Statistics}, volume = {13}, pages = {1235-1258}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00052862}, year = {2016}, affiliation = {- ; - ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {}, }
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A Sagouis, F. Jabot, C. Argillier
Taxonomic versus functional diversity metrics: how do fish communities respond to anthropogenic stressors in reservoirs?
Ecology of Freshwater Fish, 2016
abs doi web bib

Biological indicators are frequently used to assess the effects of anthropogenic stressors on freshwater ecosystems. The structure of fish communities and their response to stressors have been commonly described by taxonomic richness, diversity and evenness. More recently, functional structure of communities has also been suggested to be a reliable indicator of disturbance. This article aimed at testing whether taxonomic and functional diversity metrics can provide comparable or complementary information on the response of fish communities to eutrophication and abundance of non-native species in reservoirs. Comparison of the responses of taxonomic and functional diversities to biogeography, habitat and stressors was made in 112 French reservoirs. Widely observed effects of biogeographic and habitat variables on taxonomic and functional diversities were identified. Taxonomic and functional richness metrics notably increased with lake area and temperature respectively. Taxonomic diversity metrics did not respond to any stressor, while all functional diversity metrics were found to be impacted by non-native species. Eutrophication was further found to decrease the impact of non-native species on two functional diversity metrics: evenness and divergence. Our study therefore reveals that functional metrics are more sensitive than taxonomic metrics to anthropogenic stressors in the studied reservoirs. Still, the multiple linear regressions tested had overall low explanatory power. Further refinements will thus be needed to use this type of metrics in an impact assessment scheme.
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@article{PUB00050919, author = {Sagouis, A and Jabot, F. and Argillier, C.}, title = {Taxonomic versus functional diversity metrics: how do fish communities respond to anthropogenic stressors in reservoirs?}, title = {Métrique de diversité taxonomique versus fonctionelle : comment répondent les communautés de poissons aux pressions anthropiques dans les retenues? }, journal = {Ecology of Freshwater Fish}, pages = {15}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00050919}, doi = {http://dx.doi.org/10.1111/eff.12306}, year = {2016}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA AIX EN PROVENCE UR RECOVER }, abstract = {Biological indicators are frequently used to assess the effects of anthropogenic stressors on freshwater ecosystems. The structure of fish communities and their response to stressors have been commonly described by taxonomic richness, diversity and evenness. More recently, functional structure of communities has also been suggested to be a reliable indicator of disturbance. This article aimed at testing whether taxonomic and functional diversity metrics can provide comparable or complementary information on the response of fish communities to eutrophication and abundance of non-native species in reservoirs. Comparison of the responses of taxonomic and functional diversities to biogeography, habitat and stressors was made in 112 French reservoirs. Widely observed effects of biogeographic and habitat variables on taxonomic and functional diversities were identified. Taxonomic and functional richness metrics notably increased with lake area and temperature respectively. Taxonomic diversity metrics did not respond to any stressor, while all functional diversity metrics were found to be impacted by non-native species. Eutrophication was further found to decrease the impact of non-native species on two functional diversity metrics: evenness and divergence. Our study therefore reveals that functional metrics are more sensitive than taxonomic metrics to anthropogenic stressors in the studied reservoirs. Still, the multiple linear regressions tested had overall low explanatory power. Further refinements will thus be needed to use this type of metrics in an impact assessment scheme.}, }
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C. Smadi, V.A. Vatutin
Reduced two-type decomposable critical branching processes with possibly infinite variance
Markov Processes and Related Fields 22, 2016
web bib

@article{PUB00052863, author = {Smadi, C. and Vatutin, V.A.}, title = {Reduced two-type decomposable critical branching processes with possibly infinite variance}, journal = {Markov Processes and Related Fields}, volume = {22}, pages = {311-358}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00052863}, year = {2016}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; STEKLOV MATHEMATICAL INSTITUTE MOSCOW RUS}, abstract = {}, }
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W. Ulrich, F. Jabot, N.J. Gotelli
Competitive interactions change the pattern of species co-occurrences under neutral dispersal
Oikos 126 (1), 2016
abs doi web bib

Non-random patterns of species segregation and aggregation within ecological communities are often interpreted as evidence for interspecific interactions. However, it is unclear whether theoretical models can predict such patterns and how environmental factors may modify the effects of species interactions on species co-occurrence. Here we extend a spatially explicit neutral model by including competitive effects on birth and death probabilities to assess whether competition alone is able to produce non-random patterns of species co-occurrence. We show that transitive and intransitive competitive hierarchies alone (in the absence of environmental heterogeneity) are indeed able to generate non-random patterns with commonly used metrics and null models. Moreover, even weak levels of intransitive competition can increase local species richness. However, there is no simple rule or consistent directional change towards aggregation or segregation caused by competitive interactions. Instead, the spatial pattern depends on both the type of species interaction and the strength of dispersal. We conclude that co-occurrence analysis alone may not able to identify the underlying processes that generate the patterns
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@article{PUB00051254, author = {Ulrich, W. and Jabot, F. and Gotelli, N.J.}, title = {Competitive interactions change the pattern of species co-occurrences under neutral dispersal }, journal = {Oikos}, volume = {126}, number = {1}, pages = {91-100}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00051254}, doi = {http://dx.doi.org/10.1111/oik.03392}, year = {2016}, affiliation = {NICOLAUS COPERNICUS UNIVERSITY CHAIR OF ECOLOGY AND BIOGEOGRAPHY TORUN POL ; IRSTEA CLERMONT FERRAND UR LISC FRA ; UNIVERSITY OF VERMONT BURLINGTON USA}, abstract = {Non-random patterns of species segregation and aggregation within ecological communities are often interpreted as evidence for interspecific interactions. However, it is unclear whether theoretical models can predict such patterns and how environmental factors may modify the effects of species interactions on species co-occurrence. Here we extend a spatially explicit neutral model by including competitive effects on birth and death probabilities to assess whether competition alone is able to produce non-random patterns of species co-occurrence. We show that transitive and intransitive competitive hierarchies alone (in the absence of environmental heterogeneity) are indeed able to generate non-random patterns with commonly used metrics and null models. Moreover, even weak levels of intransitive competition can increase local species richness. However, there is no simple rule or consistent directional change towards aggregation or segregation caused by competitive interactions. Instead, the spatial pattern depends on both the type of species interaction and the strength of dispersal. We conclude that co-occurrence analysis alone may not able to identify the underlying processes that generate the patterns}, }
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R. Vander Vorste, R. Corti, A. Sagouis, T. Datry
Invertebrate communities in gravel-bed, braided rivers are highly resilient to flow intermittence
Freshwater Science 35 (1), 2016
abs doi web bib

In naturally disturbed systems, harsh environmental conditions act as filters on the regional species pool, restricting the number of taxa able to form a local community to those with traits promoting resistance or resilience. Thus, communities in highly disturbed ecosystems may be less sensitive to a given disturbance than those in less disturbed ecosystems. We explored this idea by examining the response of aquatic invertebrate communities to flow intermittence in gravel-bed, braided rivers (BRs). Flow intermittence is considered a major driver of communities in rivers, but its influence on communities in BRs, which are recognized as naturally highly disturbed environments, is relatively unexplored. We used a multisite Before-After–Control- Impact (BACI) design to quantify the effects of drying events of different durations (moderate: 2–3 wk, severe:1–3 mo) on invertebrate communities in 8 BRs in southeastern France. As predicted, no effects of flow intermittence were detected 1 to 4 mo after flow resumption on taxonomic richness, composition, or functional diversity of communities facing moderate drying events. Communities subjected to severe drying events were similar to those in perennial reaches as few as 19 d after flow resumption. Moreover, communities showed functional redundancy and no loss of functional diversity after drying events. These results differ from those of studies in other river systems, where persistent effects of flow intermittence on communities generally have been found, and highlight the need for cross-system comparisons that explore the effects of drying on communities. Identifying the processes (e.g., niche selection, cotolerance) and habitat features (e.g., hyporheic zone refugia) that promote community resilience in BRs will advance our understanding of how anthropogenic stressors and climate change may affect communities in freshwater ecosystems.
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@article{PUB00044708, author = {Vander Vorste, R. and Corti, R. and Sagouis, A. and Datry, T.}, title = {Invertebrate communities in gravel-bed, braided rivers are highly resilient to flow intermittence}, title = {Les communautés d'invertébrés à lit de gravier, rivières tressés sont très résistants à l'écoulement intermittence}, journal = {Freshwater Science}, volume = {35}, number = {1}, pages = {164-177}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00044708}, doi = {http://dx.doi.org/10.1086/683274}, year = {2016}, affiliation = {IRSTEA LYON UR MALY FRA ; LEIBNIZ INSTITUTE OF FRESHWATER ECOLOGY AND INLAND FISHERIES BERLIN DEU ; IRSTEA AIX EN PROVENCE UR HYAX FRA ; IRSTEA LYON UR MALY FRA}, abstract = {In naturally disturbed systems, harsh environmental conditions act as filters on the regional species pool, restricting the number of taxa able to form a local community to those with traits promoting resistance or resilience. Thus, communities in highly disturbed ecosystems may be less sensitive to a given disturbance than those in less disturbed ecosystems. We explored this idea by examining the response of aquatic invertebrate communities to flow intermittence in gravel-bed, braided rivers (BRs). Flow intermittence is considered a major driver of communities in rivers, but its influence on communities in BRs, which are recognized as naturally highly disturbed environments, is relatively unexplored. We used a multisite Before-After–Control- Impact (BACI) design to quantify the effects of drying events of different durations (moderate: 2–3 wk, severe:1–3 mo) on invertebrate communities in 8 BRs in southeastern France. As predicted, no effects of flow intermittence were detected 1 to 4 mo after flow resumption on taxonomic richness, composition, or functional diversity of communities facing moderate drying events. Communities subjected to severe drying events were similar to those in perennial reaches as few as 19 d after flow resumption. Moreover, communities showed functional redundancy and no loss of functional diversity after drying events. These results differ from those of studies in other river systems, where persistent effects of flow intermittence on communities generally have been found, and highlight the need for cross-system comparisons that explore the effects of drying on communities. Identifying the processes (e.g., niche selection, cotolerance) and habitat features (e.g., hyporheic zone refugia) that promote community resilience in BRs will advance our understanding of how anthropogenic stressors and climate change may affect communities in freshwater ecosystems.}, }
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Wei W., P. Larrey lassalle, T. Faure, N. Dumoulin, P. Roux, J.D. Mathias
Using the reliability theory for assessing the decision confidence probability for comparative Life Cycle Assessments
Environmental Science & Technology 50 (5), 2016
doi web bib

@article{PUB00046749, author = {Wei W. and Larrey lassalle, P. and Faure, T. and Dumoulin, N. and Roux, P. and Mathias, J.D.}, title = {Using the reliability theory for assessing the decision confidence probability for comparative Life Cycle Assessments}, journal = {Environmental Science & Technology}, volume = {50}, number = {5}, pages = {2272-2280}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00046749}, doi = {http://dx.doi.org/10.1021/acs.est.5b03683}, year = {2016}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA MONTPELLIER UMR ITAP FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA MONTPELLIER UMR ITAP FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {}, }
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B. Courbaud, V. Lafond, G. Lagarrigues, G. Vieilledent, T. Cordonnier, F. Jabot, F. de Coligny
Applying ecological model evaludation: Lessons learned with the forest dynamics model Samsara2
Ecological Modelling 314, 2015
abs doi web bib

Ecological models are increasingly used as decision-making tools and their reliability is becoming a key issue. At the same time, the sophistication of techniques for model development and analysis has given rise to a relative compartmentalization of model building and evaluation tasks. Several guidelines invite ecological modelers to follow an organized sequence of development and analysis steps and have coined the term "evaludation" for this process. The objective of this paper is to assess the feasibility and the value of a structured evaludation process, based on the working example of the Samsara2 model, a spatially explicit individual-based forest dynamics model. We implemented the six steps of model design, process level calibration, qualitative evaluation, quantitative evaluation, global sensitivity analysis, and partial recalibration using approximate Bayesian computing. We then evaluated how the evaludation process revealed model strengths and weaknesses, specified the model's conditions of use, clarified how the model works, and provided insights into forest ecosystem functioning. Finally, the efficiency/cost ratio of the process and future improvements are discussed.
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@article{PUB00047597, author = {Courbaud, B. and Lafond, V. and Lagarrigues, G. and Vieilledent, G. and Cordonnier, T. and Jabot, F. and de Coligny, F.}, title = {Applying ecological model evaludation: Lessons learned with the forest dynamics model Samsara2}, journal = {Ecological Modelling}, volume = {314}, pages = {1-14}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00047597}, doi = {http://dx.doi.org/10.1016/j.ecolmodel.2015.06.039}, year = {2015}, affiliation = {IRSTEA GRENOBLE UR EMGR FRA ; IRSTEA GRENOBLE UR EMGR FRA ; IRSTEA GRENOBLE UR EMGR FRA ; CIRAD MONTPELLIER FRA ; IRSTEA GRENOBLE UR EMGR FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; INRA UMR AMAP MONTPELLIER FRA}, abstract = {Ecological models are increasingly used as decision-making tools and their reliability is becoming a key issue. At the same time, the sophistication of techniques for model development and analysis has given rise to a relative compartmentalization of model building and evaluation tasks. Several guidelines invite ecological modelers to follow an organized sequence of development and analysis steps and have coined the term "evaludation" for this process. The objective of this paper is to assess the feasibility and the value of a structured evaludation process, based on the working example of the Samsara2 model, a spatially explicit individual-based forest dynamics model. We implemented the six steps of model design, process level calibration, qualitative evaluation, quantitative evaluation, global sensitivity analysis, and partial recalibration using approximate Bayesian computing. We then evaluated how the evaludation process revealed model strengths and weaknesses, specified the model's conditions of use, clarified how the model works, and provided insights into forest ecosystem functioning. Finally, the efficiency/cost ratio of the process and future improvements are discussed.}, }
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G. Deffuant, A. Banos, D. Chavalarias, C. Bertelle, N. Brodu, P. Jensen, A. Lesne, J.P. Müller, E. Perrier, F. Varenne
Visions de la complexité. Le démon de Laplace dans tous ses états
Natures Sciences Sociétés 23 (1), 2015
abs doi web bib

Nous distinguons trois visions de la complexité afin de clarifier les contours de la recherche dans ce domaine. Nous utilisons le démon de Laplace comme référence pour présenter ces visions. La vision 1 brise le rêve du démon de Laplace en identifiant des systèmes particuliers qui lui résistent en mathématiques, physique et informatique. La vision 2 propose une nouvelle version du rêve de Laplace fondée sur la disponibilité récente de grandes quantités de données et de nouvelles technologies de programmation, de stockage et de calcul. La vision 3 met le démon face au défi de simuler la subjectivité et ses effets collectifs.
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@article{PUB00044234, author = {Deffuant, G. and Banos, A. and Chavalarias, D. and Bertelle, C. and Brodu, N. and Jensen, P. and Lesne, A. and Müller, J.P. and Perrier, E. and Varenne, F.}, title = {Visions de la complexité. Le démon de Laplace dans tous ses états}, title = {Visions of complexity. New challenges for revisited Laplace’s demon}, journal = {Natures Sciences Sociétés}, volume = {23}, number = {1}, pages = {42-53}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00044234}, doi = {http://dx.doi.org/10.1051/nss/2015007}, year = {2015}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; UNIVERSITE PARIS 1 UMR 8594 GEOGRAPHIE-CITES FRA ; CNRS UMR 8557 CENTRE D'ANALYSES ET DE MATHEMATIQUES SOCIALES PARIS FRA ; UNIVERSITE DU HAVRE FRA ; INRIA BORDEAUX FRA ; CNRS UMR 5672 LABORATOIRE DE PHYSIQUE LYON FRA ; CNRS UMR 7600 LABORATOIRE DE PHYSIQUE THEORIQUE DE LA MATIERE CONDENSEE PARIS FRA ; CIRAD MONTPELLIER FRA ; IRD UMI BONDY FRA ; UNIVERSITE DE ROUEN UMR 8598 FRA}, abstract = {Nous distinguons trois visions de la complexité afin de clarifier les contours de la recherche dans ce domaine. Nous utilisons le démon de Laplace comme référence pour présenter ces visions. La vision 1 brise le rêve du démon de Laplace en identifiant des systèmes particuliers qui lui résistent en mathématiques, physique et informatique. La vision 2 propose une nouvelle version du rêve de Laplace fondée sur la disponibilité récente de grandes quantités de données et de nouvelles technologies de programmation, de stockage et de calcul. La vision 3 met le démon face au défi de simuler la subjectivité et ses effets collectifs.}, }
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F. Jabot
Why preferring parametric forecasting to nonparametric methods?
Journal of Theoretical Biology 372, 2015
abs doi web bib

A recent series of papers by Charles T. Perretti and collaborators have shown that nonparametric forecasting methods can outperform parametric methods in noisy nonlinear systems. Such a situation can arise because of two main reasons: the instability of parametric inference procedures in chaotic systems which can lead to biased parameter estimates, and the discrepancy between the real system dynamics and the modeled one, a problem that Perretti and collaborators call "the true model myth". Should ecologists go on using the demanding parametric machinery when trying to forecast the dynamics of complex ecosystems? Or should they rely on the elegant nonparametric approach that appears so promising? It will be here argued that ecological forecasting based on parametric models presents two key comparative advantages over nonparametric approaches. First, the likelihood of parametric forecasting failure can be diagnosed thanks to simple Bayesian model checking procedures. Second, when parametric forecasting is diagnosed to be reliable, forecasting uncertainty can be estimated on virtual data generated with the fitted to data parametric model. In contrast, nonparametric techniques provide forecasts with unknown reliability. This argumentation is illustrated with the simple theta-logistic model that was previously used by Perretti and collaborators to make their point. It should convince ecologists to stick to standard parametric approaches, until methods have been developed to assess the reliability of nonparametric forecasting.
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@article{PUB00044367, author = {Jabot, F.}, title = {Why preferring parametric forecasting to nonparametric methods?}, journal = {Journal of Theoretical Biology}, volume = {372}, pages = {205-210}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00044367}, doi = {http://dx.doi.org/10.1016/j.jtbi.2014.07.038}, year = {2015}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {A recent series of papers by Charles T. Perretti and collaborators have shown that nonparametric forecasting methods can outperform parametric methods in noisy nonlinear systems. Such a situation can arise because of two main reasons: the instability of parametric inference procedures in chaotic systems which can lead to biased parameter estimates, and the discrepancy between the real system dynamics and the modeled one, a problem that Perretti and collaborators call "the true model myth". Should ecologists go on using the demanding parametric machinery when trying to forecast the dynamics of complex ecosystems? Or should they rely on the elegant nonparametric approach that appears so promising? It will be here argued that ecological forecasting based on parametric models presents two key comparative advantages over nonparametric approaches. First, the likelihood of parametric forecasting failure can be diagnosed thanks to simple Bayesian model checking procedures. Second, when parametric forecasting is diagnosed to be reliable, forecasting uncertainty can be estimated on virtual data generated with the fitted to data parametric model. In contrast, nonparametric techniques provide forecasts with unknown reliability. This argumentation is illustrated with the simple theta-logistic model that was previously used by Perretti and collaborators to make their point. It should convince ecologists to stick to standard parametric approaches, until methods have been developed to assess the reliability of nonparametric forecasting.}, }
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C.T. Kone, G. De Sousa, Mathias J.D.
Energy-network performance trade-off in a slotted IEEE 802.15.4 network with acknowledged uplink transmissions
International Journal of Sensor Networks 17 (4), 2015
abs doi web bib

This paper provides an analysis of the performance of wireless sensor network (WSN) under the beacon-enabled slotted CSMA/CA of IEEE 802.15.4 Standard in non-saturation mode with acknowledged uplink and limited buffers. The performance metrics of a node considered are: Reliability, average throughput per node, average packet delay and average energy consumption. An analytical model of energy is derived and used to analyse the average consumption of node. This model takes into account energy dissipation of the radio unit and also of the processing and the sensor units. All these performance metrics are evaluated with different parameters such as medium access control (MAC) parameters, network density and offer load per node in order to observe their influence and adjust them if necessary to obtain good performance.
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@article{PUB00045852, author = {Kone, C.T. and De Sousa, G. and Mathias J.D.}, title = {Energy-network performance trade-off in a slotted IEEE 802.15.4 network with acknowledged uplink transmissions}, title = {Compromis en termes de performances énergétiques pour un réseau sans fil en IEEE 802.15.4 avec créneaux dédiés à des transmissions acquittées}, journal = {International Journal of Sensor Networks}, volume = {17}, number = {4}, pages = {263-277}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00045852 / http://www.inderscience.com/info/inarticle.php?artid=69581}, doi = {http://dx.doi.org/10.1504/IJSNET.2015.069581}, year = {2015}, affiliation = {ESATIC ECOLE SUPERIEURE AFRICAINE DES TIC ABIDJAN CIV ; IRSTEA CLERMONT FERRAND UR TSCF FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {This paper provides an analysis of the performance of wireless sensor network (WSN) under the beacon-enabled slotted CSMA/CA of IEEE 802.15.4 Standard in non-saturation mode with acknowledged uplink and limited buffers. The performance metrics of a node considered are: Reliability, average throughput per node, average packet delay and average energy consumption. An analytical model of energy is derived and used to analyse the average consumption of node. This model takes into account energy dissipation of the radio unit and also of the processing and the sensor units. All these performance metrics are evaluated with different parameters such as medium access control (MAC) parameters, network density and offer load per node in order to observe their influence and adjust them if necessary to obtain good performance.}, }
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G. Lagarrigues, F. Jabot, V. Lafond, B. Courbaud
Approximate Bayesian Computation to recalibrate individual-based models with population data: illustration with a forest simulation model.
Ecological Modelling 306, 2015
abs web bib

Ecology makes an increasing use of complex simulation models. As more processes and model parameters are added, a comprehensive model calibration with process-level data becomes costly and predictions of such complex models are therefore often restricted to local applications. In this context, inverse modelling techniques enable to calibrate models with data of the same type than model outputs (thereafter called population data for the sake of clarity, although other data types can be used according to model outputs), which are usually simpler to collect and more readily available. This study aims at demonstrating how such data can be used to improve ecological models, by recalibrating the most influential parameters of a complex model in a Bayesian framework, and at providing general guidelines for potential users of this approach. We used the individual-based and spatially explicit forest dynamics simulation model Samsara2 as a case study. Considering the results of an initial calibration and of a sensitivity analysis as prerequisites, we assessed whether we could use approximate Bayesian computation (ABC) to recalibrate a subset of parameters on historical management data collected in forests with various ecological conditions. We propose guidelines to answer three questions that potential users of the approach will encounter: (1) How many and which parameters are we able to recalibrate accurately with such low-informative data? (2) How many ABC simulations are required to obtain a reasonable convergence of the parameter posterior estimates? (3) What is the variability of model predictions following the recalibration? In our case study, we found that two parameters by species could be recalibrated with forest management data and that a relatively low number of simulations (20,000) was sufficient. We finally pointed out that the variability of model predictions was largely due to model stochasticity, and much less to ABC recalibration and initial calibration uncertainties. Combining direct process-level calibration to ABC recalibration of the most influential parameters opens the door to interesting modelling improvements, such as the calibration of forest dynamics along environmental gradients. This general approach should thus help improve both accuracy and generality of model-based ecological predictions.
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@article{PUB00044368, author = {Lagarrigues, G. and Jabot, F. and Lafond, V. and Courbaud, B.}, title = {Approximate Bayesian Computation to recalibrate individual-based models with population data: illustration with a forest simulation model.}, journal = {Ecological Modelling}, volume = {306}, pages = {278-286}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00044368}, year = {2015}, affiliation = {IRSTEA GRENOBLE UR EMGR FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA GRENOBLE UR EMGR FRA ; IRSTEA GRENOBLE UR EMGR FRA}, abstract = {Ecology makes an increasing use of complex simulation models. As more processes and model parameters are added, a comprehensive model calibration with process-level data becomes costly and predictions of such complex models are therefore often restricted to local applications. In this context, inverse modelling techniques enable to calibrate models with data of the same type than model outputs (thereafter called population data for the sake of clarity, although other data types can be used according to model outputs), which are usually simpler to collect and more readily available. This study aims at demonstrating how such data can be used to improve ecological models, by recalibrating the most influential parameters of a complex model in a Bayesian framework, and at providing general guidelines for potential users of this approach. We used the individual-based and spatially explicit forest dynamics simulation model Samsara2 as a case study. Considering the results of an initial calibration and of a sensitivity analysis as prerequisites, we assessed whether we could use approximate Bayesian computation (ABC) to recalibrate a subset of parameters on historical management data collected in forests with various ecological conditions. We propose guidelines to answer three questions that potential users of the approach will encounter: (1) How many and which parameters are we able to recalibrate accurately with such low-informative data? (2) How many ABC simulations are required to obtain a reasonable convergence of the parameter posterior estimates? (3) What is the variability of model predictions following the recalibration? In our case study, we found that two parameters by species could be recalibrated with forest management data and that a relatively low number of simulations (20,000) was sufficient. We finally pointed out that the variability of model predictions was largely due to model stochasticity, and much less to ABC recalibration and initial calibration uncertainties. Combining direct process-level calibration to ABC recalibration of the most influential parameters opens the door to interesting modelling improvements, such as the calibration of forest dynamics along environmental gradients. This general approach should thus help improve both accuracy and generality of model-based ecological predictions.}, }
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J.D. Mathias, B. Bonté, T. Cordonnier, F. De Morogues
Using the viability theory to assess the flexibility of forest managers under ecological intensification
Environmental Management 56 (5), 2015
abs doi web bib

Greater demand for wood material has converged with greater demand for biodiversity conservation to make balancing forest ecosystem services a key societal issue. Forest managers, owners, or policymakers need new approaches and methods to evaluate their ability to adapt to this dual objective. We analyze the ability of forest owners to define sustainable forest management options based on viability theory and a new flexibility index. This new indicator gauges the adaptive capacity of forest owners based on the number of sustainable actions available to them at a given time. Here we study a public forest owner who regulates harvest intensity and frequency in order to meet demand for timber wood at forest scale and to meet a biodiversity recommendation via a minimum permanently maintained volume of deadwood per hectare at stand scale. Dynamical systems theory was used to model uneven-aged forest dynamics-including deadwood dynamics-and the dynamics of timber wood demand and tree removals. Uneven-aged silver fir forest management in the "Quatre Montagnes region" (Vercors, France) is used as an illustrative example. The results explain situations where a joint increase in wood production and deadwood retention does not reduce the flexibility index more than increasing either one dimension alone, thus opening up ecological intensification options. To conclude, we discuss the value of the new flexibility index for addressing environmental management and ecological intensification issues.
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@article{PUB00046742, author = {Mathias, J.D. and Bonté, B. and Cordonnier, T. and De Morogues, F.}, title = {Using the viability theory to assess the flexibility of forest managers under ecological intensification}, journal = {Environmental Management}, volume = {56}, number = {5}, pages = {1170-1183}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00046742}, doi = {http://dx.doi.org/10.1007/s00267-015-0555-4}, year = {2015}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA MONTPELLIER UMR G-EAU FRA ; IRSTEA GRENOBLE UR EMGR FRA ; FCBA GRENOBLE FRA}, abstract = {Greater demand for wood material has converged with greater demand for biodiversity conservation to make balancing forest ecosystem services a key societal issue. Forest managers, owners, or policymakers need new approaches and methods to evaluate their ability to adapt to this dual objective. We analyze the ability of forest owners to define sustainable forest management options based on viability theory and a new flexibility index. This new indicator gauges the adaptive capacity of forest owners based on the number of sustainable actions available to them at a given time. Here we study a public forest owner who regulates harvest intensity and frequency in order to meet demand for timber wood at forest scale and to meet a biodiversity recommendation via a minimum permanently maintained volume of deadwood per hectare at stand scale. Dynamical systems theory was used to model uneven-aged forest dynamics-including deadwood dynamics-and the dynamics of timber wood demand and tree removals. Uneven-aged silver fir forest management in the "Quatre Montagnes region" (Vercors, France) is used as an illustrative example. The results explain situations where a joint increase in wood production and deadwood retention does not reduce the flexibility index more than increasing either one dimension alone, thus opening up ecological intensification options. To conclude, we discuss the value of the new flexibility index for addressing environmental management and ecological intensification issues.}, }
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J.D. Mathias, A. Alzina, M. Grédiac, P. Michaud, P. Roux, H. De Baynast, C. Delattre, N. Dumoulin, T. Faure, P. Larrey Lassalle, N. Mati Baouche, F. Pennec, S. Sun, N. Tessier Doyen, E. Toussaint, W. Wei
Upcycling sunflower stems as natural fibers for biocomposite applications
Bioresources 10 (4), 2015
abs web bib

One of the big global, environmental, and socioeconomic challenges of today is to make a transition from fossil fuels to biomass as a sustainable supply of renewable raw materials for industry. Growing public awareness of the negative environmental effects of petrochemical-based products adds to the need for alternative production chains, especially in materials science. One option lies in the value-added upcycling of agricultural by-products, which are increasingly being used for biocomposite materials in transport and building sector applications. Here, sunflower by-product (obtained by grinding the stems) is considered as a source of natural fibers for engineered biocomposite material. Recent results are shown for the main mechanical properties of sunflower-based biocomposites and the socioeconomic impact of their use. This paper demonstrates that sunflower stem makes a good candidate feedstock for material applications. This is due not only to its physical and chemical properties, but also to its socioeconomic and environmental rationales.
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@article{PUB00046747, author = {Mathias, J.D. and Alzina, A. and Grédiac, M. and Michaud, P. and Roux, P. and De Baynast, H. and Delattre, C. and Dumoulin, N. and Faure, T. and Larrey Lassalle, P. and Mati Baouche, N. and Pennec, F. and Sun, S. and Tessier Doyen, N. and Toussaint, E. and Wei, W.}, title = {Upcycling sunflower stems as natural fibers for biocomposite applications}, journal = {Bioresources}, volume = {10}, number = {4}, pages = {8076-8088}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00046747}, year = {2015}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; UNIVERSITE DE LIMOGES LABORATOIRE GEMH LIMOGES FRA ; UNIVERSITE DE CLERMONT FERRAND I INSTITUT PASCAL FRA ; UNIVERSITE DE CLERMONT FERRAND I INSTITUT PASCAL FRA ; IRSTEA MONTPELLIER UMR ITAP FRA ; UNIVERSITE DE CLERMONT FERRAND I INSTITUT PASCAL FRA ; UNIVERSITE DE CLERMONT FERRAND I INSTITUT PASCAL FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA MONTPELLIER UMR ITAP FRA ; UNIVERSITE DE CLERMONT FERRAND I INSTITUT PASCAL FRA ; UNIVERSITE DE LIMOGES LABORATOIRE GEMH LIMOGES FRA ; UNIVERSITE DE CLERMONT FERRAND I INSTITUT PASCAL FRA ; UNIVERSITE DE LIMOGES LABORATOIRE GEMH LIMOGES FRA ; UNIVERSITE DE CLERMONT FERRAND I INSTITUT PASCAL FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {One of the big global, environmental, and socioeconomic challenges of today is to make a transition from fossil fuels to biomass as a sustainable supply of renewable raw materials for industry. Growing public awareness of the negative environmental effects of petrochemical-based products adds to the need for alternative production chains, especially in materials science. One option lies in the value-added upcycling of agricultural by-products, which are increasingly being used for biocomposite materials in transport and building sector applications. Here, sunflower by-product (obtained by grinding the stems) is considered as a source of natural fibers for engineered biocomposite material. Recent results are shown for the main mechanical properties of sunflower-based biocomposites and the socioeconomic impact of their use. This paper demonstrates that sunflower stem makes a good candidate feedstock for material applications. This is due not only to its physical and chemical properties, but also to its socioeconomic and environmental rationales.}, }
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N. Mouquet, Y. Lagadeuc, V. Devictor, L. Doyen, A. Duputié, D. Eveillard, D. Faure, E. Garnier, O. Gimenez, P. Huneman, Jabot F., P. Jarne, D. Joly, R. Julliard, S. Kéfi, G.J. Kergoat, S. Lavorel, L. Le Gall, L. Meslin, S. Morand, X. Morin, H. Morlon, G. Pinay, R. Pradel, F.M. Schurr, W. Thuiller, M. Loreau
Predictive ecology in a changing world: Review
Journal of Applied Ecology 52 (5), 2015
abs doi web bib

1-In a rapidly changing world, ecology has the potential to move from empirical and conceptual stages to application to management issues. It is now possible to make large-scale predictions up to continental or global scales, ranging from the future distribution of biological diversity to changes in ecosystem functioning and services. With these recent developments, ecology has a historical opportunity to become a major actor in the development of a sustainable human society. With this opportunity, however, also comes an important responsibility in developing appropriate predictive models, correctly interpreting their outcomes, and communicating their limitations. There is also a danger that predictions grow faster than our understanding of ecological systems, resulting in a gap between scientists who provide the predictions and stakeholders who use them (conservation biologists, environmental managers, journalists, policy makers). 2-Here we use the context provided by the current surge of ecological predictions on the future of biodiversity to clarify what prediction means, and to pinpoint the challenges that need to be addressed in order to improve predictive ecological models and the way they are understood and used. 3-Synthesis and applications: Ecologists face several challenges to ensure the healthy development of an operational predictive ecological science: (i) clarity on the distinction between explanatory and anticipatory predictions; (ii) developing new theories at the interface between explanatory and anticipatory predictions; (iii) open data to test and validate predictions; (iv) making predictions operational; and (v) developing a genuine ethics of prediction.
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@article{PUB00044371, author = {Mouquet, N. and Lagadeuc, Y. and Devictor, V. and Doyen, L. and Duputié, A. and Eveillard, D. and Faure, D. and Garnier, E. and Gimenez, O. and Huneman, P. and Jabot F. and Jarne, P. and Joly, D. and Julliard, R. and Kéfi, S. and Kergoat, G.J. and Lavorel, S. and Le Gall, L. and Meslin, L. and Morand, S. and Morin, X. and Morlon, H. and Pinay, G. and Pradel, R. and Schurr, F.M. and Thuiller, W. and Loreau, M.}, title = {Predictive ecology in a changing world: Review}, journal = {Journal of Applied Ecology}, volume = {52}, number = {5}, pages = {1293-1310}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00044371}, doi = {http://dx.doi.org/10.1111/1365-2664.12482}, year = {2015}, affiliation = {UNIVERSITE DE MONTPELLIER 2 FRA ; UNIVERSITE DE RENNES 1 FRA ; UNIVERSITE DE MONTPELLIER 2 FRA ; UNIVERSITE DE BORDEAUX FRA ; UNIVERSITE DE LILLE 1 ; UNIVERSITE DE NANTES FRA ; INSTITUT DES SCIENCES VEGETALES GIF SUR YVETTE FRA ; UNIVERSITE DE MONTPELLIER FRA ; UNIVERSITE DE MONTPELLIER FRA ; UNIVERSITE DE PARIS 1 FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; UNIVERSITE DE MONTPELLIER FRA ; CNRS PARIS FRA+ ; UNIVERSITE PIERRE ET MARIE CURIE UMR 7204 PARIS FRA ; UNIVERSITE DE MONTPELLIER FRA ; CENTRE DE DE BIOLOGIE POUR LA GESTION DES POPULATIONS MONTPELLIER FRA ; UNIVERSITE JOSEPH FOURIER GRENOBLE FRA ; MUSEUM NATIONAL D'HISTOIRE NATURELLE PARIS FRA ; UNIVERSITE DE MONTPELLIER 2 FRA ; UNIVERSITE DE MONTPELLIER 2 FRA ; UNIVERSITE DE MONTPELLIER FRA ; ECOLE NORMALE SUPERIEURE PARIS FRA ; UNIVERSITE DE RENNES 1 FRA ; UNIVERSITE DE MONTPELLIER FRA ; UNIVERSITE DE MONTPELLIER 2 FRA ; UNIVERSITE JOSEPH FOURIER GRENOBLE FRA ; CNRS MOULIS FRA}, abstract = {1-In a rapidly changing world, ecology has the potential to move from empirical and conceptual stages to application to management issues. It is now possible to make large-scale predictions up to continental or global scales, ranging from the future distribution of biological diversity to changes in ecosystem functioning and services. With these recent developments, ecology has a historical opportunity to become a major actor in the development of a sustainable human society. With this opportunity, however, also comes an important responsibility in developing appropriate predictive models, correctly interpreting their outcomes, and communicating their limitations. There is also a danger that predictions grow faster than our understanding of ecological systems, resulting in a gap between scientists who provide the predictions and stakeholders who use them (conservation biologists, environmental managers, journalists, policy makers). 2-Here we use the context provided by the current surge of ecological predictions on the future of biodiversity to clarify what prediction means, and to pinpoint the challenges that need to be addressed in order to improve predictive ecological models and the way they are understood and used. 3-Synthesis and applications: Ecologists face several challenges to ensure the healthy development of an operational predictive ecological science: (i) clarity on the distinction between explanatory and anticipatory predictions; (ii) developing new theories at the interface between explanatory and anticipatory predictions; (iii) open data to test and validate predictions; (iv) making predictions operational; and (v) developing a genuine ethics of prediction. }, }
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X. Qiao, F. Jabot, Z. Tang, M. Jiang, J. Fang
A latitudinal gradient in tree community assembly processes evidenced in forests of China
Global Ecology and Biogeography 24 (3), 2015
abs doi web bib

Aim :Most studies on latitudinal gradients of biodiversity have focused on gradients of species richness. Here we aim to test whether, on top of these strong diversity gradients, processes of community assembly vary along a latitudinal gradient of more than 33°. Location :China, latitude 18.67–51.86°N. Methods : We used species abundance distribution (SAD) data collected in 32 forest tree plots, and fitted a non-neutral model of community assembly to these SADs. We then calculated the fitted deviation from neutrality, delta, and looked for correlations between delta and geographical and environmental data. Results : The fitted parameter delta was positive in most plots, and was furthermore positively correlated with latitude and negatively with temperature, indicating a less even abundance distribution and a likely increase in the strength of environmental filtering in regions further from the tropics and with decreasing temperatures. These results imply that on top of reducing the species richness, cold temperature may impact community assembly processes by strengthening local environmental filtering. Main conclusions : Our results suggest a latitudinal gradient in tree community assembly process in Chinese forests, in which deviations from neutrality increase with latitude, probably because of an increase in environmental harshness.
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@article{PUB00044369, author = {Qiao, X. and Jabot, F. and Tang, Z. and Jiang, M. and Fang, J.}, title = {A latitudinal gradient in tree community assembly processes evidenced in forests of China}, journal = {Global Ecology and Biogeography}, volume = {24}, number = {3}, pages = {314-323}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00044369}, doi = {http://dx.doi.org/10.1111/geb.12778}, year = {2015}, affiliation = {PEKING UNIVERSITY BEIJING CHN ; IRSTEA CLERMONT FERRAND UR LISC FRA ; PEKING UNIVERSITY BEIJING CHN ; WUHAN BOTANICAL GARDEN WUHAN CHN ; PEKING UNIVERSITY BEIJING CHN}, abstract = {Aim :Most studies on latitudinal gradients of biodiversity have focused on gradients of species richness. Here we aim to test whether, on top of these strong diversity gradients, processes of community assembly vary along a latitudinal gradient of more than 33°. Location :China, latitude 18.67–51.86°N. Methods : We used species abundance distribution (SAD) data collected in 32 forest tree plots, and fitted a non-neutral model of community assembly to these SADs. We then calculated the fitted deviation from neutrality, delta, and looked for correlations between delta and geographical and environmental data. Results : The fitted parameter delta was positive in most plots, and was furthermore positively correlated with latitude and negatively with temperature, indicating a less even abundance distribution and a likely increase in the strength of environmental filtering in regions further from the tropics and with decreasing temperatures. These results imply that on top of reducing the species richness, cold temperature may impact community assembly processes by strengthening local environmental filtering. Main conclusions : Our results suggest a latitudinal gradient in tree community assembly process in Chinese forests, in which deviations from neutrality increase with latitude, probably because of an increase in environmental harshness.}, }
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T. Rougier, G. Lassalle, H. Drouineau, N. Dumoulin, T. Faure, G. Deffuant, E. Rochard, P. Lambert
The Combined Use of Correlative and Mechanistic Species Distribution Models Benefits Low Conservation Status Species
PLoS One 10 (10), 2015
abs doi web bib

Species can respond to climate change by tracking appropriate environmental conditions in space, resulting in a range shift. Species Distribution Models (SDMs) can help forecast such range shift responses. For few species, both correlative and mechanistic SDMs were built, but allis shad (Alosa alosa), an endangered anadromous fish species, is one of them. The main purpose of this study was to provide a framework for joint analyses of correlative and mechanistic SDMs projections in order to strengthen conservation measures for species of conservation concern. Guidelines for joint representation and subsequent interpretation of models outputs were defined and applied. The present joint analysis was based on the novel mechanistic model GR3D (Global Repositioning Dynamics of Diadromous fish Distribution) which was parameterized on allis shad and then used to predict its future distribution along the European Atlantic coast under different climate change scenarios (RCP 4.5 and RCP 8.5). We then used a correlative SDM for this species to forecast its distribution across the same geographic area and under the same climate change scenarios. First, projections from correlative and mechanistic models provided congruent trends in probability of habitat suitability and population dynamics. This agreement was preferentially interpreted as referring to the species vulnerability to climate change. Climate change could not be accordingly listed as a major threat for allis shad. The congruence in predicted range limits between SDMs projections was the next point of interest. The difference, when noticed, required to deepen our understanding of the niche modelled by each approach. In this respect, the relative position of the northern range limit between the two methods strongly suggested here that a key biological process related to intraspecific variability was potentially lacking in the mechanistic SDM. Based on our knowledge, we hypothesized that local adaptations to cold temperatures deserved more attention in terms of modelling, but further in conservation planning as well.
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@article{PUB00045248, author = {Rougier, T. and Lassalle, G. and Drouineau, H. and Dumoulin, N. and Faure, T. and Deffuant, G. and Rochard, E. and Lambert, P.}, title = {The Combined Use of Correlative and Mechanistic Species Distribution Models Benefits Low Conservation Status Species}, title = {L'utilisation conjointe de modèles de distribution d'espèces mécanistes et corrélatifs bénéficie aux espèces menacées}, journal = {PLoS One}, volume = {10}, number = {10}, pages = {21}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00045248}, doi = {http://dx.doi.org/10.1371/journal.pone.0139194}, year = {2015}, affiliation = {IRSTEA BORDEAUX UR EABX FRA ; IRSTEA BORDEAUX UR EABX FRA ; IRSTEA BORDEAUX UR EABX FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA BORDEAUX UR EABX FRA ; IRSTEA BORDEAUX UR EABX FRA}, abstract = {Species can respond to climate change by tracking appropriate environmental conditions in space, resulting in a range shift. Species Distribution Models (SDMs) can help forecast such range shift responses. For few species, both correlative and mechanistic SDMs were built, but allis shad (Alosa alosa), an endangered anadromous fish species, is one of them. The main purpose of this study was to provide a framework for joint analyses of correlative and mechanistic SDMs projections in order to strengthen conservation measures for species of conservation concern. Guidelines for joint representation and subsequent interpretation of models outputs were defined and applied. The present joint analysis was based on the novel mechanistic model GR3D (Global Repositioning Dynamics of Diadromous fish Distribution) which was parameterized on allis shad and then used to predict its future distribution along the European Atlantic coast under different climate change scenarios (RCP 4.5 and RCP 8.5). We then used a correlative SDM for this species to forecast its distribution across the same geographic area and under the same climate change scenarios. First, projections from correlative and mechanistic models provided congruent trends in probability of habitat suitability and population dynamics. This agreement was preferentially interpreted as referring to the species vulnerability to climate change. Climate change could not be accordingly listed as a major threat for allis shad. The congruence in predicted range limits between SDMs projections was the next point of interest. The difference, when noticed, required to deepen our understanding of the niche modelled by each approach. In this respect, the relative position of the northern range limit between the two methods strongly suggested here that a key biological process related to intraspecific variability was potentially lacking in the mechanistic SDM. Based on our knowledge, we hypothesized that local adaptations to cold temperatures deserved more attention in terms of modelling, but further in conservation planning as well.}, }
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C. Rougé, J.D. Mathias, G. Deffuant
Vulnerability: from the conceptual to the operational using a dynamical system perspective
Environmental Modelling & Software 73, 2015
doi web bib

@article{PUB00045375, author = {Rougé, C. and Mathias, J.D. and Deffuant, G.}, title = {Vulnerability: from the conceptual to the operational using a dynamical system perspective}, journal = {Environmental Modelling & Software}, volume = {73}, pages = {218-230}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00045375}, doi = {http://dx.doi.org/10.1016/j.envsoft.2015.07.018}, year = {2015}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {}, }
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J.B. Rouquier, I. Alvarez, R. Reuillon, P.H. Wuillemin
A kd-tree algorithm to discover the boundary of a black box hypervolume
Annals of Mathematics and Artificial Intelligence 75 (3), 2015
abs doi web bib

n the framework of Decision Support Systems, mathematical viability theory can be used to classify the states and the trajectories of a dynamical system evolving in a set of desirable states. Since obtaining this viability theory output is a complex and computationally intensive task, we propose in this article to consider a compact representation of this set and its approximations using kd-trees. Given a subset of $R^n$ of non null measure, defined through a black box function (an oracle), and assuming some regularity properties on this set, we build a kd-tree based data structure representing this set, which can be used as an input to the viability algorithm. This data structure has a complexity close to gaining one dimension, both in terms of space and in number of calls to the oracle, compared to the exhaustive computation on a regular grid. This data structure produces a characteristic function (i.e. a function that can be used in lieu of the oracle), allows to measure the volume of the set, and to compute the distance to the boundary of the set for any point. It offers distance guarantee between the points of the original set and its kd-tree approximation.
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@article{PUB00046791, author = {Rouquier, J.B. and Alvarez, I. and Reuillon, R. and Wuillemin, P.H.}, title = {A kd-tree algorithm to discover the boundary of a black box hypervolume}, title = {Un algorithme basé sur les kd-tree pour découvrir la frontière d'un hypervolume boîte-noire}, journal = {Annals of Mathematics and Artificial Intelligence}, volume = {75}, number = {3}, pages = {335-350}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00046791}, doi = {http://dx.doi.org/10.1007/s10472-015-9456-8}, year = {2015}, affiliation = {INSTITUT DES SYSTEMES COMPLEXES PARIS FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; INSTITUT DES SYSTEMES COMPLEXES PARIS FRA ; UNIVERSITE DE PARIS VI UMR 7606 LIP6 LABORATOIRE D'INFORMATIQUE DE PARIS FRA}, abstract = {n the framework of Decision Support Systems, mathematical viability theory can be used to classify the states and the trajectories of a dynamical system evolving in a set of desirable states. Since obtaining this viability theory output is a complex and computationally intensive task, we propose in this article to consider a compact representation of this set and its approximations using kd-trees. Given a subset of $R^n$ of non null measure, defined through a black box function (an oracle), and assuming some regularity properties on this set, we build a kd-tree based data structure representing this set, which can be used as an input to the viability algorithm. This data structure has a complexity close to gaining one dimension, both in terms of space and in number of calls to the oracle, compared to the exhaustive computation on a regular grid. This data structure produces a characteristic function (i.e. a function that can be used in lieu of the oracle), allows to measure the volume of the set, and to compute the distance to the boundary of the set for any point. It offers distance guarantee between the points of the original set and its kd-tree approximation.}, }
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S. Sun, M. Grédiac, E. Toussaint, J.D. Mathias, N. Mati Baouche
Applying a full-field measurement technique to characterize the mechanical response of a sunflower-based biocomposite
Experimental Mechanics 55 (5), 2015
abs web bib

This work is part of a project aimed at developing a new biocomposite material that can be used for thermal insulation purposes. This material is mainly composed of sunflower stem chips. A chitosan-based biomatrix is used as binder between them. We focus here only on the mechanical response of this biocomposite. The goal is to investigate experimentally the link between its macroscopic response and phenomena which occur at the scale of the constituents, namely the bark and pith chips. The grid method, which is one of the full-field measurement systems employed in experimental mechanics to measure displacement and strain fields, is employed because of the very heterogeneous nature of this material. This heterogeneity is not only due to the contrast in rigidity between bark and pith, but also to the presence of voids within the material. These voids, as well as the presence of pith, lead us to develop and employ a specific marking procedure for the specimen surface under investigation. Two values for the mass percent fraction of chitosan are investigated, to observe the influence of this parameter on the global stiffness of the material and on local phenomena that occur in its bulk. The full-field measurement technique employed here leads us to detect and quantify significant heterogeneities in the strain fields, which are closely related to the material heterogeneities themselves.
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@article{PUB00046740, author = {Sun, S. and Grédiac, M. and Toussaint, E. and Mathias, J.D. and Mati Baouche, N.}, title = {Applying a full-field measurement technique to characterize the mechanical response of a sunflower-based biocomposite}, journal = {Experimental Mechanics}, volume = {55}, number = {5}, pages = {917-934}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00046740}, year = {2015}, affiliation = {UNIVERSITE DE CLERMONT FERRAND I INSTITUT PASCAL FRA ; UNIVERSITE DE CLERMONT FERRAND I INSTITUT PASCAL FRA ; UNIVERSITE DE CLERMONT FERRAND I INSTITUT PASCAL FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; UNIVERSITE DE CLERMONT FERRAND I INSTITUT PASCAL FRA}, abstract = {This work is part of a project aimed at developing a new biocomposite material that can be used for thermal insulation purposes. This material is mainly composed of sunflower stem chips. A chitosan-based biomatrix is used as binder between them. We focus here only on the mechanical response of this biocomposite. The goal is to investigate experimentally the link between its macroscopic response and phenomena which occur at the scale of the constituents, namely the bark and pith chips. The grid method, which is one of the full-field measurement systems employed in experimental mechanics to measure displacement and strain fields, is employed because of the very heterogeneous nature of this material. This heterogeneity is not only due to the contrast in rigidity between bark and pith, but also to the presence of voids within the material. These voids, as well as the presence of pith, lead us to develop and employ a specific marking procedure for the specimen surface under investigation. Two values for the mass percent fraction of chitosan are investigated, to observe the influence of this parameter on the global stiffness of the material and on local phenomena that occur in its bulk. The full-field measurement technique employed here leads us to detect and quantify significant heterogeneities in the strain fields, which are closely related to the material heterogeneities themselves.}, }
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W. Wei, P. Larrey Lassalle, T. Faure, N. Dumoulin, P. Roux, J.D. Mathias
How to conduct a proper sensitivity analysis in life cycle assessment: Taking into account correlations within LCI data and interactions within the LCA calculation model
Environmental Science & Technology 49 (1), 2015
abs doi web bib

Sensitivity analysis (SA) is a significant tool for studying the robustness of results and their sensitivity to uncertainty factors in life cycle assessment (LCA). It highlights the most important set of model parameters to determine whether data quality needs to be improved, and to enhance interpretation of results. Interactions within the LCA calculation model and correlations within Life Cycle Inventory (LCI) input parameters are two main issues among the LCA calculation process. Here we propose a methodology for conducting a proper SA which takes into account the effects of these two issues. This study first presents the SA in an uncorrelated case, comparing local and independent global sensitivity analysis. Independent global sensitivity analysis aims to analyze the variability of results because of the variation of input parameters over the whole domain of uncertainty, together with interactions among input parameters. We then apply a dependent global sensitivity approach that makes minor modifications to traditional Sobol indices to address the correlation issue. Finally, we propose some guidelines for choosing the appropriate SA method depending on the characteristics of the model and the goals of the study. Our results clearly show that the choice of sensitivity methods should be made according to the magnitude of uncertainty and the degree of correlation.
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@article{PUB00046736, author = {Wei, W. and Larrey Lassalle, P. and Faure, T. and Dumoulin, N. and Roux, P. and Mathias, J.D.}, title = {How to conduct a proper sensitivity analysis in life cycle assessment: Taking into account correlations within LCI data and interactions within the LCA calculation model}, journal = {Environmental Science & Technology}, volume = {49}, number = {1}, pages = {377-385}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00046736}, doi = {http://dx.doi.org/10.1021/es502128k}, year = {2015}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA MONTPELLIER UMR ITAP FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA MONTPELLIER UMR ITAP FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {Sensitivity analysis (SA) is a significant tool for studying the robustness of results and their sensitivity to uncertainty factors in life cycle assessment (LCA). It highlights the most important set of model parameters to determine whether data quality needs to be improved, and to enhance interpretation of results. Interactions within the LCA calculation model and correlations within Life Cycle Inventory (LCI) input parameters are two main issues among the LCA calculation process. Here we propose a methodology for conducting a proper SA which takes into account the effects of these two issues. This study first presents the SA in an uncorrelated case, comparing local and independent global sensitivity analysis. Independent global sensitivity analysis aims to analyze the variability of results because of the variation of input parameters over the whole domain of uncertainty, together with interactions among input parameters. We then apply a dependent global sensitivity approach that makes minor modifications to traditional Sobol indices to address the correlation issue. Finally, we propose some guidelines for choosing the appropriate SA method depending on the characteristics of the model and the goals of the study. Our results clearly show that the choice of sensitivity methods should be made according to the magnitude of uncertainty and the degree of correlation.}, }
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A. Bridier, R. Briandet, T. Bouchez, F. Jabot
A model-based approach to detect interspecific interactions during biofilm development
Biofouling 30 (7), 2014
abs web bib

A model-based approach was developed to detect interspecific interactions during biofilm development. This approach relied on the comparison of experimental data with a simple null model of biofilm growth dynamics where individual species grew independently of one another, except that they competed for space. Such a model was directly parameterized with a 4D confocal image series of biofilms and then used as a null model to detect interspecific interactions between pairs of bacterial species. This approach was tested in two bispecific competitive trials. In the first trial, the progressive exclusion of Pseudomonas fluorescens by Pseudomonas putida appeared to be due solely to the different intrinsic growth rates of the two strains. In contrast, modelling results suggested the presence of interference competition between Pseudomonas aeruginosa and P. putida in mixed biofilms. The authors’ approach enables the detection of ecologically relevant interactions which constitute a prerequisite to building a comprehensive view of the dynamics and functioning of spatially structured bacterial communities.
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@article{PUB00041730, author = {Bridier, A. and Briandet, R. and Bouchez, T. and Jabot, F.}, title = {A model-based approach to detect interspecific interactions during biofilm development}, title = {Une approche de modélisation pour détecter les interactions interspecifiques pendant le développement d'un biofilm}, journal = {Biofouling}, volume = {30}, number = {7}, pages = {761-771}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00041730}, year = {2014}, affiliation = {IRSTEA ANTONY UR HBAN FRA ; INRA AGROPARISTECH UMR 1319 MICALIS JOUY EN JOSAS FRA ; IRSTEA ANTONY UR HBAN FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {A model-based approach was developed to detect interspecific interactions during biofilm development. This approach relied on the comparison of experimental data with a simple null model of biofilm growth dynamics where individual species grew independently of one another, except that they competed for space. Such a model was directly parameterized with a 4D confocal image series of biofilms and then used as a null model to detect interspecific interactions between pairs of bacterial species. This approach was tested in two bispecific competitive trials. In the first trial, the progressive exclusion of Pseudomonas fluorescens by Pseudomonas putida appeared to be due solely to the different intrinsic growth rates of the two strains. In contrast, modelling results suggested the presence of interference competition between Pseudomonas aeruginosa and P. putida in mixed biofilms. The authors’ approach enables the detection of ecologically relevant interactions which constitute a prerequisite to building a comprehensive view of the dynamics and functioning of spatially structured bacterial communities.}, }
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M. Lenormand, S. Huet, F. Gargiulo
Generating French virtual commuting networks at the municipality level
Journal of Transport and Land Use, 2014
abs doi web bib

We aim to generate virtual commuting networks in the rural regions of France in order to study the dynamics of their municipalities. Since it will be necessary to model small commuting flows between municipalities with a few hundred or thousand inhabitants, we have opted for the stochastic model presented by Gargiulo et al. (2012). This model reproduces various possible complete networks using an iterative process, stochastically selecting a workplace in the region for each commuter living in the municipality of a region. The choice is made considering the job offers in each municipality of the region and the distance to all of the possible destinations. This paper will present methods for adapting and implementing this model to generate commuting networks between municipalities for regions in France. We address three different issues: How can we generate a reliable virtual commuting network for a region that is highly dependent on other regions for the satisfaction of its residents demands for employment? What about a convenient deterrence function? How can we calibrate the model when detailed data is not available? Our solution proposes an extended job search geographical base for commuters living in the municipalities; we compare two different deterrence functions and we show that the parameter is a constant for network linking municipalities in France.
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@article{PUB00040106, author = {Lenormand, M. and Huet, S. and Gargiulo, F.}, title = {Generating French virtual commuting networks at the municipality level}, title = {Générer les réseaux de navettage français au niveau municipalité}, journal = {Journal of Transport and Land Use}, pages = {13}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00040106 / https://www.jtlu.org/index.php/jtlu/article/view/360}, doi = {http://dx.doi.org/http://dx.doi.org/10.5198/jtlu.v7i1.360}, year = {2014}, affiliation = {IFISC MAJORCA ESP ; IRSTEA CLERMONT FERRAND UR LISC FRA ; UNIVERSITE DE NAMUR NAXYS BEL}, abstract = {We aim to generate virtual commuting networks in the rural regions of France in order to study the dynamics of their municipalities. Since it will be necessary to model small commuting flows between municipalities with a few hundred or thousand inhabitants, we have opted for the stochastic model presented by Gargiulo et al. (2012). This model reproduces various possible complete networks using an iterative process, stochastically selecting a workplace in the region for each commuter living in the municipality of a region. The choice is made considering the job offers in each municipality of the region and the distance to all of the possible destinations. This paper will present methods for adapting and implementing this model to generate commuting networks between municipalities for regions in France. We address three different issues: How can we generate a reliable virtual commuting network for a region that is highly dependent on other regions for the satisfaction of its residents demands for employment? What about a convenient deterrence function? How can we calibrate the model when detailed data is not available? Our solution proposes an extended job search geographical base for commuters living in the municipalities; we compare two different deterrence functions and we show that the parameter is a constant for network linking municipalities in France.}, }
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T. Lohier, F. Jabot, D. Meziane, B. Shipley, P.B. Reich, G. Deffuant
Explaining ontogenetic shifts in root-shoot scaling with transient dynamics
Annals of Botany 114, 2014
abs doi web bib

Simple models of herbaceous plant growth based on optimal partitioning theory predict, at steady state, an isometric relationship between shoot and root biomass during plant ontogeny: i.e. a constant root-shoot ratio. This prediction has received mixed empirical support, suggesting either that optimal partitioning is too coarse an assumption to model plant biomass allocation, or that additional processes need to be modelled to account for empirical findings within the optimal partitioning framework. Here we use simulations to test two potential explanations for observed non-isometric relationships, namely root senescence and transient growth dynamics. We build a simple plant growth model based on optimal partitioning theory combined with empirically measured plant functional traits. We assess its ability to reproduce various experimental plant growth patterns, namely relative growth rate, root weight ratio and root nitrogen content. We then test whether this realistically parameterized minimal model can reproduce empirically observed non-isometric relationships during plant ontogeny, and whether additional model ingredients may produce non-isometric trajectories. We finally compare our model predictions regarding the transient dynamics of allometric relationships with experimental findings. We find that our simple model based on optimal partitioning theory is able to accurately reproduce overall plant growth patterns, but fails at explaining non-isometric growth trajectories. Among the additional model ingredients tested, only transient dynamics produces non-isometric growth trajectories. The role of transient dynamics in the shape of root-shoot relationships is further supported by our re-analysis of a plant growth experiment. Our model with the inclusion of transient dynamics enables to reconcile theoretical predictions based on optimal partitioning with empirically measured ontogenetic root-shoot allometries.
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@article{PUB00043298, author = {Lohier, T. and Jabot, F. and Meziane, D. and Shipley, B. and Reich, P.B. and Deffuant, G.}, title = {Explaining ontogenetic shifts in root-shoot scaling with transient dynamics}, title = {Le rôle des dynamiques transitoires dans les changements ontogénétiques du root-shoot ratio}, journal = {Annals of Botany}, volume = {114}, pages = {513-524}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00043298 / www.aob.oxfordjournals.org}, doi = {http://dx.doi.org/10.1093/aob/mcu128}, year = {2014}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; UNIVERSITE SIDI MOHAMED BEN ABDELLAH FES MAR ; UNIVERSITE DE SHERBROOKE CAN ; UNIVERSITE DE SHERBROOKE CAN ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {Simple models of herbaceous plant growth based on optimal partitioning theory predict, at steady state, an isometric relationship between shoot and root biomass during plant ontogeny: i.e. a constant root-shoot ratio. This prediction has received mixed empirical support, suggesting either that optimal partitioning is too coarse an assumption to model plant biomass allocation, or that additional processes need to be modelled to account for empirical findings within the optimal partitioning framework. Here we use simulations to test two potential explanations for observed non-isometric relationships, namely root senescence and transient growth dynamics. We build a simple plant growth model based on optimal partitioning theory combined with empirically measured plant functional traits. We assess its ability to reproduce various experimental plant growth patterns, namely relative growth rate, root weight ratio and root nitrogen content. We then test whether this realistically parameterized minimal model can reproduce empirically observed non-isometric relationships during plant ontogeny, and whether additional model ingredients may produce non-isometric trajectories. We finally compare our model predictions regarding the transient dynamics of allometric relationships with experimental findings. We find that our simple model based on optimal partitioning theory is able to accurately reproduce overall plant growth patterns, but fails at explaining non-isometric growth trajectories. Among the additional model ingredients tested, only transient dynamics produces non-isometric growth trajectories. The role of transient dynamics in the shape of root-shoot relationships is further supported by our re-analysis of a plant growth experiment. Our model with the inclusion of transient dynamics enables to reconcile theoretical predictions based on optimal partitioning with empirically measured ontogenetic root-shoot allometries.}, }
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S. Martin, I. Alvarez, J.D. Kant
Micro/macro viability analysis of individual-based models: Investigation into the viability of a stylized agricultural cooperative
Complexity 21 (2), 2014
abs doi web bib

The mathematical viability theory proposes methods and tools to study at a global level how controlled dynamical systems can be confined in a desirable subset of the state space. Multilevel viability problems are rarely studied since they induce combinatorial explosion (the set of N agents each evolving in a p-dimensional state space, can evolve in a Np dimensional state space). In this article, we propose an original approach which consists in solving first local viability problems and then studying the real viability of the combination of the local strategies, by simulation where necessary. In this article, we consider as multilevel viability problem a stylized agricultural cooperative which has to keep a minimum of members. Members have an economical constraint and some members have a simple model of the functioning of the cooperative and make assumptions on other members' behavior, especially proviable agents which are concerned about their own viability. In this framework, the model assumptions allow us to solve the local viability problem at the agent level. At the cooperative level, considering mixture of agents, simulation results indicate if and when including proviable agents increases the viability of the whole cooperative.
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@article{PUB00044373, author = {Martin, S. and Alvarez, I. and Kant, J.D.}, title = {Micro/macro viability analysis of individual-based models: Investigation into the viability of a stylized agricultural cooperative}, title = {Analyse de viabilité micro/macro de modèles individus-centrés : étude de la viabilité d'un modèle stylisé de coopérative}, journal = {Complexity}, volume = {21}, number = {2}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00044373 / http://onlinelibrary.wiley.com/doi/10.1002/cplx.21604/full}, doi = {http://dx.doi.org/10.1002/cplx.21604}, year = {2014}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; UNIVERSITE PARIS MARIE CURIE LIP6 FRA}, abstract = {The mathematical viability theory proposes methods and tools to study at a global level how controlled dynamical systems can be confined in a desirable subset of the state space. Multilevel viability problems are rarely studied since they induce combinatorial explosion (the set of N agents each evolving in a p-dimensional state space, can evolve in a Np dimensional state space). In this article, we propose an original approach which consists in solving first local viability problems and then studying the real viability of the combination of the local strategies, by simulation where necessary. In this article, we consider as multilevel viability problem a stylized agricultural cooperative which has to keep a minimum of members. Members have an economical constraint and some members have a simple model of the functioning of the cooperative and make assumptions on other members' behavior, especially proviable agents which are concerned about their own viability. In this framework, the model assumptions allow us to solve the local viability problem at the agent level. At the cooperative level, considering mixture of agents, simulation results indicate if and when including proviable agents increases the viability of the whole cooperative.}, }
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S. Mesmoudi, I. Alvarez, S. Martin, R. Reuillon, M. Sicard, N. Perrot
Coupling geometric analysis and viability theory for system exploration: Application to a living food system
Journal of Process Control 24 (12), 2014
abs doi web bib

This paper addresses the issue of studying a food complex system in a reverse engineering manner with the aim of identifying the set of all possible actions that makes it reach a quality target with respect to manufacturing constraints. Once the set of actions is identified, several criteria can be considered to identify interesting trajectories and control policies. A viability approach, coupling the viability theory and a geometric approach of robustness, is proposed to study complex dynamical systems. It can be implemented for several types of systems, from linear to non linear or hybrid systems. The proposed framework was adapted to a living food system: a ripening model of Camembert cheese to identify the set of states and actions (capture basin) from which it is possible to reach a predefined quality target. Within the set of viable trajectories, particular trajectories that improve the Camembert cheese ripening process are identified using the proposed approach. The results are applied at a pilot scale and are discussed in this paper.
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@article{PUB00043300, author = {Mesmoudi, S. and Alvarez, I. and Martin, S. and Reuillon, R. and Sicard, M. and Perrot, N.}, title = {Coupling geometric analysis and viability theory for system exploration: Application to a living food system}, title = {Coupler l'analyse géométrique et la théorie de la viabilité pour explorer les dynamiques des systèmes : application à un système alimentaire}, journal = {Journal of Process Control}, volume = {24}, number = {12}, pages = {18-28}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00043300 / http://www.sciencedirect.com/science/article/pii/S0959152414002522}, doi = {http://dx.doi.org/10.1016/j.jprocont.2014.09.013}, year = {2014}, affiliation = {ISCPIF LIP6 PARIS FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; ISCPIF PARIS FRA ; INRA UMR 782 GMPA AGROPARISTECH THIVERVAL GRIGNON FRA ; INRA UMR 782 GMPA AGROPARISTECH THIVERVAL GRIGNON FRA}, abstract = {This paper addresses the issue of studying a food complex system in a reverse engineering manner with the aim of identifying the set of all possible actions that makes it reach a quality target with respect to manufacturing constraints. Once the set of actions is identified, several criteria can be considered to identify interesting trajectories and control policies. A viability approach, coupling the viability theory and a geometric approach of robustness, is proposed to study complex dynamical systems. It can be implemented for several types of systems, from linear to non linear or hybrid systems. The proposed framework was adapted to a living food system: a ripening model of Camembert cheese to identify the set of states and actions (capture basin) from which it is possible to reach a predefined quality target. Within the set of viable trajectories, particular trajectories that improve the Camembert cheese ripening process are identified using the proposed approach. The results are applied at a pilot scale and are discussed in this paper.}, }
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T. Rougier, H. Drouineau, N. Dumoulin, T. Faure, G. Deffuant, E. Rochard, P. Lambert
The GR3D model, a tool to explore the Global Repositioning Dynamicsof Diadromous fish Distribution
Ecological Modelling 283, 2014
abs doi web bib

Within the context of ongoing environmental changes, the life history of diadromous fish represents areal potential for exploring and colonizing new environments due to high potential dispersal abilities. Theuse of dynamic approaches to assess how these species will respond to climate change is a challenging issue and mechanistic models able to incorporate biological and evolutionary processes are a promising tool. To this end we developed an individual-based model, called GR3D (Global Repositioning Dynamicsfor Diadromous fish Distribution), combining climatic requirements and population dynamics with an explicit dispersal process to evaluate potential evolution of their distribution area in the context of climatic change. This paper describes thoroughly the model structure and presents an exploratory test casewhere the repositioning of a virtual allis shad (Alosa alosa L.) population between two river catchments under a scenario of temperature increase was assessed. The global sensitivity analysis showed that land-scape structure and parameters related to sea lifespan and to survival at sea were crucial to determine the success of colonization. These results were consistent with the ecology of this species. The integration of climatic factors directly into the processes and the explicit dispersal process make GR3D an original and relevant tool to assess the repositioning dynamics and persistence of diadromous fish facing climate change.
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@article{PUB00041011, author = {Rougier, T. and Drouineau, H. and Dumoulin, N. and Faure, T. and Deffuant, G. and Rochard, E. and Lambert, P.}, title = {The GR3D model, a tool to explore the Global Repositioning Dynamicsof Diadromous fish Distribution}, journal = {Ecological Modelling}, volume = {283}, pages = {31-44}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00041011}, doi = {http://dx.doi.org/10.1016/j.ecolmodel.2014.03.019}, year = {2014}, affiliation = {IRSTEA BORDEAUX UR EABX FRA ; IRSTEA BORDEAUX UR EABX FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA BORDEAUX UR EABX FRA ; IRSTEA BORDEAUX UR EABX FRA}, abstract = {Within the context of ongoing environmental changes, the life history of diadromous fish represents areal potential for exploring and colonizing new environments due to high potential dispersal abilities. Theuse of dynamic approaches to assess how these species will respond to climate change is a challenging issue and mechanistic models able to incorporate biological and evolutionary processes are a promising tool. To this end we developed an individual-based model, called GR3D (Global Repositioning Dynamicsfor Diadromous fish Distribution), combining climatic requirements and population dynamics with an explicit dispersal process to evaluate potential evolution of their distribution area in the context of climatic change. This paper describes thoroughly the model structure and presents an exploratory test casewhere the repositioning of a virtual allis shad (Alosa alosa L.) population between two river catchments under a scenario of temperature increase was assessed. The global sensitivity analysis showed that land-scape structure and parameters related to sea lifespan and to survival at sea were crucial to determine the success of colonization. These results were consistent with the ecology of this species. The integration of climatic factors directly into the processes and the explicit dispersal process make GR3D an original and relevant tool to assess the repositioning dynamics and persistence of diadromous fish facing climate change.}, }
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C. Rougé, X. Cai
Crossing-scale hydrological impacts of urbanization and climate variability in the Greater Chicago Area
Journal of Hydrology 517, 2014
abs doi web bib

This paper uses past hydrological records in Northeastern Illinois to disentangle the combined effects of urban development and climatic variability at different spatial scales in the Greater Chicago Area. A step increase in annual precipitation occurred in Northeastern Illinois during 1965–1972 according to climate records. Urbanization has occurred as a gradual process over the entire Greater Chicago Area, both before and after the abrupt annual precipitation increase. The analysis of streamflow trends at each gaging station is supplemented by the comparison of the evolution of streamflow indicators in a group of urban and agricultural watersheds, thanks to an original use of the Mann–Whitney test. Results suggest that urban expansion in the Greater Chicago Area has led to widespread increases in a wide variety of streamflow metrics, with the exceptions being spring flows and some of the peak flow indicators. The increases detected in small (<100 km2) urban watersheds are mitigated in large (>200 km2) ones, over which the changes in streamflow are relatively homogeneous. While the impacts of land-use change are identified across a wide range of flow indicators and spatial scales, there are indications that some of these effects are mitigated or made negligible by other factors. For example, while impervious surfaces are found to increase flooding, stormwater management facilities, an adaptation to increased flooding, mitigate their impacts at a wide range of scales. While impervious surfaces are known to reduce infiltration and baseflow, a low flow increase was triggered by water withdrawals from Lake Michigan, as a response to a rising water demand which made on-site groundwater extraction unsustainable. Our analysis thus highlights the impacts of adaptive planning and management of water resources on urban hydrology.
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@article{PUB00041770, author = {Rougé, C. and Cai, X.}, title = {Crossing-scale hydrological impacts of urbanization and climate variability in the Greater Chicago Area}, journal = {Journal of Hydrology}, volume = {517}, pages = {13-27}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00041770}, doi = {http://dx.doi.org/10.1016/j.jhydrol.2014.05.005}, year = {2014}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; UNIVERSITY OF ILLINOIS VEN-TE CHOW HYDROSYSTEMS LABORATORY URBANA CHAMPAIGN USA}, abstract = {This paper uses past hydrological records in Northeastern Illinois to disentangle the combined effects of urban development and climatic variability at different spatial scales in the Greater Chicago Area. A step increase in annual precipitation occurred in Northeastern Illinois during 1965–1972 according to climate records. Urbanization has occurred as a gradual process over the entire Greater Chicago Area, both before and after the abrupt annual precipitation increase. The analysis of streamflow trends at each gaging station is supplemented by the comparison of the evolution of streamflow indicators in a group of urban and agricultural watersheds, thanks to an original use of the Mann–Whitney test. Results suggest that urban expansion in the Greater Chicago Area has led to widespread increases in a wide variety of streamflow metrics, with the exceptions being spring flows and some of the peak flow indicators. The increases detected in small (<100 km2) urban watersheds are mitigated in large (>200 km2) ones, over which the changes in streamflow are relatively homogeneous. While the impacts of land-use change are identified across a wide range of flow indicators and spatial scales, there are indications that some of these effects are mitigated or made negligible by other factors. For example, while impervious surfaces are found to increase flooding, stormwater management facilities, an adaptation to increased flooding, mitigate their impacts at a wide range of scales. While impervious surfaces are known to reduce infiltration and baseflow, a low flow increase was triggered by water withdrawals from Lake Michigan, as a response to a rising water demand which made on-site groundwater extraction unsustainable. Our analysis thus highlights the impacts of adaptive planning and management of water resources on urban hydrology.}, }
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C. Rougé, J.D. Mathias, G. Deffuant
Relevance of control theory to design and maintenance problems in time-variant reliability: The case of stochastic viability
Reliability Engineering & System Safety 132, 2014
abs doi web bib

The goal of this paper is twofold: (1) to show that time-variant reliability and a branch of control theory called stochastic viability address similar problems with different points of view, and (2) to demonstrate the relevance of concepts and methods from stochastic viability in reliability problems. On the one hand, reliability aims at evaluating the probability of failure of a system subjected to uncertainty and stochasticity. On the other hand, viability aims at maintaining a controlled dynamical system within a survival set. When the dynamical system is stochastic, this work shows that a viability problem belongs to a specific class of design and maintenance problems in time-variant reliability. Dynamic programming, which is used for solving Markovian stochastic viability problems, then yields the set of design states for which there exists a maintenance strategy which guarantees reliability with a confidence level beta for a given period of time T. Besides, it leads to a straightforward computation of the date of the first outcrossing, informing on when the system is most likely to fail. We illustrate this approach with a simple example of population dynamics, including a case where load increases with time.
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@article{PUB00041946, author = {Rougé, C. and Mathias, J.D. and Deffuant, G.}, title = {Relevance of control theory to design and maintenance problems in time-variant reliability: The case of stochastic viability}, title = {Pertinence de la théorie du contrôle pour les problèmes de maintenance de fiabilité dans le temps: le cas de viabilité stochastique}, journal = {Reliability Engineering & System Safety}, volume = {132}, pages = {250-260}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00041946 / http://www.sciencedirect.com/science/article/pii/S0951832014001926}, doi = {http://dx.doi.org/10.1016/j.ress.2014.07.025}, year = {2014}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {The goal of this paper is twofold: (1) to show that time-variant reliability and a branch of control theory called stochastic viability address similar problems with different points of view, and (2) to demonstrate the relevance of concepts and methods from stochastic viability in reliability problems. On the one hand, reliability aims at evaluating the probability of failure of a system subjected to uncertainty and stochasticity. On the other hand, viability aims at maintaining a controlled dynamical system within a survival set. When the dynamical system is stochastic, this work shows that a viability problem belongs to a specific class of design and maintenance problems in time-variant reliability. Dynamic programming, which is used for solving Markovian stochastic viability problems, then yields the set of design states for which there exists a maintenance strategy which guarantees reliability with a confidence level beta for a given period of time T. Besides, it leads to a straightforward computation of the date of the first outcrossing, informing on when the system is most likely to fail. We illustrate this approach with a simple example of population dynamics, including a case where load increases with time.}, }
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S. Sun, J.D. Mathias, E. Toussaint, M. Grédiac
Characterizing the variance of mechanical properties of sunflower bark for biocomposite applications
Bioresources 9 (1), 2014
abs web bib

Characterizing the variance of material properties of natural fibers is of growing concern due to a wide range of new engineering applications when utilizing these natural fibers. The aim of this study was to evaluate the variance of the Young's modulus of sunflower bark by (i) determining its statistical probability distribution, (ii) investigating its relationship with relative humidity, and (iii) characterizing its relationship with the specimen extraction location. To this end, specimens were extracted at three different locations along the stems. They were also preconditioned in three different relative humidity environments. The ?2-test was used for hypothesis testing with normal, Weibull, and log-normal distributions. Results show that the Young's modulus follows a normal distribution. Two-sample t-test results reveal that the Young's modulus of sunflower stem bark strongly depends on the conditioning's relative humidity and the specimen's extraction location; it significantly decreased as the relative humidity increased and significantly increased from the bottom to the top of the stem. The correlation coefficients between the Young's modulus of different relative humidity values and of specimen extraction locations were determined. The calculation of correlation coefficients shows a linear relation between the Young's modulus and the relative humidity for a given location.
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@article{PUB00043722, author = {Sun, S. and Mathias, J.D. and Toussaint, E. and Grédiac, M.}, title = {Characterizing the variance of mechanical properties of sunflower bark for biocomposite applications}, journal = {Bioresources}, volume = {9}, number = {1}, pages = {922-937}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00043722 / http://www.scopus.com/inward/record.url?eid=2-s2.0-84892514044&partnerID=40&md5=13511bec9f4e13adea4a5bb6ce7504d0}, year = {2014}, affiliation = {UNIVERSITE DE CLERMONT FERRAND I INSTITUT PASCAL FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; UNIVERSITE DE CLERMONT FERRAND I INSTITUT PASCAL FRA ; UNIVERSITE DE CLERMONT FERRAND I INSTITUT PASCAL FRA}, abstract = {Characterizing the variance of material properties of natural fibers is of growing concern due to a wide range of new engineering applications when utilizing these natural fibers. The aim of this study was to evaluate the variance of the Young's modulus of sunflower bark by (i) determining its statistical probability distribution, (ii) investigating its relationship with relative humidity, and (iii) characterizing its relationship with the specimen extraction location. To this end, specimens were extracted at three different locations along the stems. They were also preconditioned in three different relative humidity environments. The ?2-test was used for hypothesis testing with normal, Weibull, and log-normal distributions. Results show that the Young's modulus follows a normal distribution. Two-sample t-test results reveal that the Young's modulus of sunflower stem bark strongly depends on the conditioning's relative humidity and the specimen's extraction location; it significantly decreased as the relative humidity increased and significantly increased from the bottom to the top of the stem. The correlation coefficients between the Young's modulus of different relative humidity values and of specimen extraction locations were determined. The calculation of correlation coefficients shows a linear relation between the Young's modulus and the relative humidity for a given location.}, }
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C. Bernard, S. Martin
Comparing the sustainability of different action policy possibilities: Application to the issue of both household survival and forest preservation in the corridor of Fianarantsoa
Mathematical Biosciences 245 (2), 2013
abs doi web bib

A sustainability issue for the rain forest in the corridor of Fianarantsoa (Madagascar) is to preserve the forest while ensuring the development of the local population. The aim of this paper is to determine whether the current situation is sustainable or not according to different action policy possibilities. We propose a general procedure based on viability analysis: Translation of sustainability issues into constraints on the system state; elaboration of a mathematical model of system evolution rules in the form of controlled dynamical system; computations of the viability kernels according to different action policy possibilities. Among control variables, we focus on monetary transfer. Without monetary transfer, we show that the current situation of the rain forest corridor is not sustainable in our mathematical modeling framework. We then estimate the minimal maximal amount per year necessary to make the current situation sustainable.
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@article{PUB00039047, author = {Bernard, C. and Martin, S.}, title = {Comparing the sustainability of different action policy possibilities: Application to the issue of both household survival and forest preservation in the corridor of Fianarantsoa}, title = {Comparer la durabilité de différentes possibilités de politiques d'actions : application aux enjeux de survie des foyers et de préservation de la forêt dans le corridor forestier de Fianarantsoa}, journal = {Mathematical Biosciences}, volume = {245}, number = {2}, pages = {322-330}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00039047}, doi = {http://dx.doi.org/10.1016/j.mbs.2013.08.002}, year = {2013}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {A sustainability issue for the rain forest in the corridor of Fianarantsoa (Madagascar) is to preserve the forest while ensuring the development of the local population. The aim of this paper is to determine whether the current situation is sustainable or not according to different action policy possibilities. We propose a general procedure based on viability analysis: Translation of sustainability issues into constraints on the system state; elaboration of a mathematical model of system evolution rules in the form of controlled dynamical system; computations of the viability kernels according to different action policy possibilities. Among control variables, we focus on monetary transfer. Without monetary transfer, we show that the current situation of the rain forest corridor is not sustainable in our mathematical modeling framework. We then estimate the minimal maximal amount per year necessary to make the current situation sustainable.}, }
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G. Deffuant, G. Weisbuch, F. Amblard, T. Faure
The results of Meadows and Cliff are wrong because they compute indicator y before model convergence
JASSS-The Journal of Artificial Societies and Social Simulation 16 (1), 2013
abs web bib

Meadows and Cliff (2012) failed to replicate the results of Deffuant et al. (2002) and concluded that our paper was wrong. In this note, we show that the conclusions of Meadows and Cliff are due to a wrong computation of indicator y, which was not fully specified in our 2002 paper. In particular, Meadows and Cliff compute indicator y before model convergence whereas this indicator should be computed after model convergence.
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@article{PUB00039364, author = {Deffuant, G. and Weisbuch, G. and Amblard, F. and Faure, T.}, title = {The results of Meadows and Cliff are wrong because they compute indicator y before model convergence}, journal = {JASSS-The Journal of Artificial Societies and Social Simulation}, volume = {16}, number = {1}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00039364 / http://jasss.soc.surrey.ac.uk/16/1/11.html}, year = {2013}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; ECOLE NORMALE SUPERIEURE PARIS FRA ; IRIT TOULOUSE FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {Meadows and Cliff (2012) failed to replicate the results of Deffuant et al. (2002) and concluded that our paper was wrong. In this note, we show that the conclusions of Meadows and Cliff are due to a wrong computation of indicator y, which was not fully specified in our 2002 paper. In particular, Meadows and Cliff compute indicator y before model convergence whereas this indicator should be computed after model convergence.}, }
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G. Deffuant, T. Carletti, S. Huet
The Leviathan Model: Absolute dominance, generalised distrust, small worlds and other patterns emerging from combining vanity with opinion propagation
JASSS-The Journal of Artificial Societies and Social Simulation 16 (1), 2013
abs web bib

We propose an opinion dynamics model that combines processes of vanity and opinion propagation. The interactions take place between randomly chosen pairs. During an interaction, the agents propagate their opinions about themselves and about other people they know. Moreover, each individual is subject to vanity: if her interlocutor seems to value her highly, then she increases her opinion about this interlocutor. On the contrary she tends to decrease her opinion about those who seem to undervalue her. The combination of these dynamics with the hypothesis that the opinion propagation is more efficient when coming from highly valued individuals, leads to different patterns when varying the parameters. For instance, for some parameters the positive opinion links between individuals generate a small world network. In one of the patterns, absolute dominance of one agent alternates with a state of generalised distrust, where all agents have a very low opinion of all the others (including themselves). We provide some explanations of the mechanisms behind these emergent behaviors and finally propose a discussion about their interest.
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@article{PUB00038235, author = {Deffuant, G. and Carletti, T. and Huet, S.}, title = {The Leviathan Model: Absolute dominance, generalised distrust, small worlds and other patterns emerging from combining vanity with opinion propagation }, title = {Le modèle Léviathan : domination absolue, défiance, "petits mondes" et autres patterns émergeant de la combinaison vanité - propagation d'opinion}, journal = {JASSS-The Journal of Artificial Societies and Social Simulation}, volume = {16}, number = {1}, pages = {32}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00038235 / http://jasss.soc.surrey.ac.uk/16/1/5.html}, year = {2013}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; UNIVERSITY OF NAMUR BEL ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {We propose an opinion dynamics model that combines processes of vanity and opinion propagation. The interactions take place between randomly chosen pairs. During an interaction, the agents propagate their opinions about themselves and about other people they know. Moreover, each individual is subject to vanity: if her interlocutor seems to value her highly, then she increases her opinion about this interlocutor. On the contrary she tends to decrease her opinion about those who seem to undervalue her. The combination of these dynamics with the hypothesis that the opinion propagation is more efficient when coming from highly valued individuals, leads to different patterns when varying the parameters. For instance, for some parameters the positive opinion links between individuals generate a small world network. In one of the patterns, absolute dominance of one agent alternates with a state of generalised distrust, where all agents have a very low opinion of all the others (including themselves). We provide some explanations of the mechanisms behind these emergent behaviors and finally propose a discussion about their interest. }, }
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T. Guélon, R.C. Hunter, J.D. Mathias, G. Deffuant
Homogenization of Pseudomonas aeruginosa PAO1 biofilms from high-resolution visualization by freeze substitution
(p. 1405-1418), Biotechnology and Bioengineering 110 (5), 2013
abs doi web bib

A knowledge of the mechanical properties of bacterial biofilms is required to more fully understand the processes of biofilm formation such as initial adhesion or detachment. The main contribution of this article is to demonstrate the use of homogenization techniques to compute mechanical parameters of Pseudomonas aeruginosa PAO1 biofilms. For this purpose, homogenization techniques are used to analyze freeze substitution electron micrographs of the biofilm cross-sections. The concept of a representative volume element and the study about his representativeness allows us to determine the optimal size in order to analyze these biofilm images. Results demonstrate significant heterogeneities with respect to stiffness and these can be explained by varying cell density distribution throughout the bacterial biofilms. These stiffness variations lead to different mechanical properties along the height of the biofilm. Moreover, a numerical shear stress test shows the impact of these heterogeneities on the detachment process. Several modes of detachment are highlighted according to the local strain energy in the different parts of the biofilm. Knowing where, and how, a biofilm may detach will allow better prediction of accumulation and biomass detachment.
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@article{PUB00037645, author = {Guélon, T. and Hunter, R.C. and Mathias, J.D. and Deffuant, G.}, title = {Homogenization of Pseudomonas aeruginosa PAO1 biofilms from high-resolution visualization by freeze substitution}, title = {Homogénéisation d'un biofilm de Pseudomonas Aeruginosa à partir d'une visualisation de grande résolution obtenue par une méthode de cryo-substitution}, journal = {Biotechnology and Bioengineering}, volume = {110 }, number = {5}, bookTitle = { }, pages = {1405-1418}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00037645}, doi = {http://dx.doi.org/10.1002/bit.24805}, year = {2013}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; HOWARD HUGHES MEDICAL INSTITUTE CALIFORNIA INSTITUTE OF TECHNOLOGY PASADENA USA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {A knowledge of the mechanical properties of bacterial biofilms is required to more fully understand the processes of biofilm formation such as initial adhesion or detachment. The main contribution of this article is to demonstrate the use of homogenization techniques to compute mechanical parameters of Pseudomonas aeruginosa PAO1 biofilms. For this purpose, homogenization techniques are used to analyze freeze substitution electron micrographs of the biofilm cross-sections. The concept of a representative volume element and the study about his representativeness allows us to determine the optimal size in order to analyze these biofilm images. Results demonstrate significant heterogeneities with respect to stiffness and these can be explained by varying cell density distribution throughout the bacterial biofilms. These stiffness variations lead to different mechanical properties along the height of the biofilm. Moreover, a numerical shear stress test shows the impact of these heterogeneities on the detachment process. Several modes of detachment are highlighted according to the local strain energy in the different parts of the biofilm. Knowing where, and how, a biofilm may detach will allow better prediction of accumulation and biomass detachment.}, }
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F. Jabot, T. Faure, N. Dumoulin
EasyABC: Performing efficient approximate Bayesian computation sampling schemes using R
Methods in Ecology and Evolution 4 (7), 2013
abs doi web bib

Approximate Bayesian computation (ABC), a type of likelihood-free inference, is a family of statistical techniques to perform parameter estimation and model selection. It is increasingly used in ecology and evolution, where the models used can be too complex to be handled with standard likelihood techniques. The essence of ABC techniques is to compare simulation outputs to observed data, in order to select the parameter values of the simulations which best fit the data. ABC techniques are thus computationally demanding. This constitutes a key limitation to their implementation. We introduce the R package 'EasyABC' that enables one to launch a series of simulations from the R platform and to retrieve the simulation outputs in an appropriate format for post-processing. The 'EasyABC' package further implements several efficient parameter sampling schemes to speed up the ABC procedure: on top of the standard prior sampling, it implements various algorithms to perform sequential (ABC-sequential) and Markov chain Monte Carlo (ABC-MCMC) sampling schemes. The package functions can furthermore make use of parallel computing. The R package 'EasyABC' complements the package 'abc' which enables various post-processing of simulation outputs. 'EasyABC' makes several state-of-the-art ABC implementations available to the large community of R users in the fields of ecology and evolution. It is a freely available R package under the GPL license, and it can be downloaded at http://cran.r-project.org/web/packages/EasyABC/index.html.
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@article{PUB00038743, author = {Jabot, F. and Faure, T. and Dumoulin, N.}, title = {EasyABC: Performing efficient approximate Bayesian computation sampling schemes using R }, journal = {Methods in Ecology and Evolution}, volume = {4}, number = {7}, pages = {684-687}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00038743}, doi = {http://dx.doi.org/10.1111/2041-210X.12050}, year = {2013}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {Approximate Bayesian computation (ABC), a type of likelihood-free inference, is a family of statistical techniques to perform parameter estimation and model selection. It is increasingly used in ecology and evolution, where the models used can be too complex to be handled with standard likelihood techniques. The essence of ABC techniques is to compare simulation outputs to observed data, in order to select the parameter values of the simulations which best fit the data. ABC techniques are thus computationally demanding. This constitutes a key limitation to their implementation. We introduce the R package 'EasyABC' that enables one to launch a series of simulations from the R platform and to retrieve the simulation outputs in an appropriate format for post-processing. The 'EasyABC' package further implements several efficient parameter sampling schemes to speed up the ABC procedure: on top of the standard prior sampling, it implements various algorithms to perform sequential (ABC-sequential) and Markov chain Monte Carlo (ABC-MCMC) sampling schemes. The package functions can furthermore make use of parallel computing. The R package 'EasyABC' complements the package 'abc' which enables various post-processing of simulation outputs. 'EasyABC' makes several state-of-the-art ABC implementations available to the large community of R users in the fields of ecology and evolution. It is a freely available R package under the GPL license, and it can be downloaded at http://cran.r-project.org/web/packages/EasyABC/index.html. }, }
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M. Lenormand, G. Deffuant
Generating a synthetic population of individuals in households: sample-free vs sample-based methods
JASSS-The Journal of Artificial Societies and Social Simulation 16 (1), 2013
abs web bib

We compare a sample-free method proposed by Gargiulo et al. (2010) and a sample-based method proposed by Ye et al. (2009) for generating a synthetic population, organised in households, from various statistics. We generate a reference population for a French region including 1310 municipalities and measure how both methods approximate it from a set of statistics derived from this reference population. We also perform a sensitivity analysis. The sample-free method better fits the reference distributions of both individuals and households. It is also less data demanding but it requires more pre-processing. The quality of the results for the sample-based method is highly dependent on the quality of the initial sample.
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@article{PUB00039366, author = {Lenormand, M. and Deffuant, G.}, title = {Generating a synthetic population of individuals in households: sample-free vs sample-based methods }, journal = {JASSS-The Journal of Artificial Societies and Social Simulation}, volume = {16}, number = {1}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00039366 / http://jasss.soc.surrey.ac.uk/16/4/12.html}, year = {2013}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {We compare a sample-free method proposed by Gargiulo et al. (2010) and a sample-based method proposed by Ye et al. (2009) for generating a synthetic population, organised in households, from various statistics. We generate a reference population for a French region including 1310 municipalities and measure how both methods approximate it from a set of statistics derived from this reference population. We also perform a sensitivity analysis. The sample-free method better fits the reference distributions of both individuals and households. It is also less data demanding but it requires more pre-processing. The quality of the results for the sample-based method is highly dependent on the quality of the initial sample.}, }
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M. Lenormand, F. Jabot, G. Deffuant
Adaptive approximate Bayesian computation for complex models
Computational Statistics 28 (6), 2013
abs doi web bib

We propose a new approximate Bayesian computation (ABC) algorithm that aims at minimizing the number of model runs for reaching a given quality of the posterior approximation. This algorithm automatically determines its sequence of tolerance levels and makes use of an easily interpretable stopping criterion. Moreover, it avoids the problem of particle duplication found when using a MCMC kernel. When applied to a toy example and to a complex social model, our algorithm is 2–8 times faster than the three main sequential ABC algorithms currently available.
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@article{PUB00038699, author = {Lenormand, M. and Jabot, F. and Deffuant, G.}, title = {Adaptive approximate Bayesian computation for complex models}, title = {Algorithme adaptatif de computation byésienne approchée pour des modèles complexes}, journal = {Computational Statistics}, volume = {28}, number = {6}, pages = {2777-2796}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00038699 / http://link.springer.com/article/10.1007%2Fs00180-013-0428-3}, doi = {http://dx.doi.org/10.1007/s00180-013-0428-3}, year = {2013}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {We propose a new approximate Bayesian computation (ABC) algorithm that aims at minimizing the number of model runs for reaching a given quality of the posterior approximation. This algorithm automatically determines its sequence of tolerance levels and makes use of an easily interpretable stopping criterion. Moreover, it avoids the problem of particle duplication found when using a MCMC kernel. When applied to a toy example and to a complex social model, our algorithm is 2–8 times faster than the three main sequential ABC algorithms currently available.}, }
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H. Mahboubi, S. Bimonte, G. Deffuant, J.P. Chanet, F. Pinet
Semi-automatic design of spatial data cubes from simulation model results
International Journal of Data Warehousing and Mining 9 (1), 2013
abs doi web bib

In this paper we present a semi-automatic method for designing and generating spatial data cubes in order to visualize and analyze the results of simulation models. In our approach users choose their fact of analysis, then the system derives automatically a set of possible measures, dimensions of analysis, and generates the corresponding spatial data cubes. The analysis and visualization of the spatial data cubes are carried out using appropriate SOLAP tools. We also present the SimOLAP system, developed to validate our approach.
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@article{PUB00037171, author = {Mahboubi, H. and Bimonte, S. and Deffuant, G. and Chanet, J.P. and Pinet, F.}, title = {Semi-automatic design of spatial data cubes from simulation model results}, title = {Conception semi automatique de cubes de données spatiales à partir de résultants de modèles de simulation }, journal = {International Journal of Data Warehousing and Mining}, volume = {9}, number = {1}, pages = {70-95}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00037171}, doi = {http://dx.doi.org/10.4018/jdwm.2013010104}, year = {2013}, affiliation = {OSIATIS GRENOBLE FRA ; IRSTEA CLERMONT FERRAND UR TSCF FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR TSCF FRA ; IRSTEA CLERMONT FERRAND UR TSCF FRA}, abstract = {In this paper we present a semi-automatic method for designing and generating spatial data cubes in order to visualize and analyze the results of simulation models. In our approach users choose their fact of analysis, then the system derives automatically a set of possible measures, dimensions of analysis, and generates the corresponding spatial data cubes. The analysis and visualization of the spatial data cubes are carried out using appropriate SOLAP tools. We also present the SimOLAP system, developed to validate our approach.}, }
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J.D. Mathias, M. Lemaire
Reliability analysis of bonded joints with variations in adhesive thickness
Journal of Adhesion Science and Technology 27 (10), 2013
abs doi web bib

Bonded joints are used in several industrial applications as a surrogate of more expensive repairs, but their reliability must be ascertained. Failure in a bonded joint mainly occurs in the adhesive due to stress concentrations that directly depend on the adhesive thickness. In practice, it is difficult to ensure a good accuracy of the final adhesive thickness, leading to uncertainty to its spatial variability. This uncertainty greatly influences the strength of the bonded joint. This work deals with one of the main key issues in bonded joints: the influence of the spatial variations in the adhesive thickness on the reliability of the joint and an excessive shear stress level caused by the adhesive thickness variations may lead to failure. This paper provides reliability analysis by considering the adhesive thickness as a stochastic field. The experimental thickness field is obtained so as to identify the stochastic parameters. These parameters are then introduced in a structural reliability model to evaluate the failure probability. Results show the influence of adhesive thickness uncertainty on bonded joint failure. © 2012 Taylor & Francis.
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@article{PUB00038744, author = {Mathias, J.D. and Lemaire, M.}, title = {Reliability analysis of bonded joints with variations in adhesive thickness}, journal = {Journal of Adhesion Science and Technology}, volume = {27}, number = {10}, pages = {1069-1079}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00038744 / http://www.scopus.com/inward/record.url?eid=2-s2.0-84876750594&partnerID=40&md5=3dd7a71f1b43f1363cd0e94634d43f8d}, doi = {http://dx.doi.org/10.1080/01694243.2012.727176}, year = {2013}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IFMA CLERMONT FERRAND FRA}, abstract = {Bonded joints are used in several industrial applications as a surrogate of more expensive repairs, but their reliability must be ascertained. Failure in a bonded joint mainly occurs in the adhesive due to stress concentrations that directly depend on the adhesive thickness. In practice, it is difficult to ensure a good accuracy of the final adhesive thickness, leading to uncertainty to its spatial variability. This uncertainty greatly influences the strength of the bonded joint. This work deals with one of the main key issues in bonded joints: the influence of the spatial variations in the adhesive thickness on the reliability of the joint and an excessive shear stress level caused by the adhesive thickness variations may lead to failure. This paper provides reliability analysis by considering the adhesive thickness as a stochastic field. The experimental thickness field is obtained so as to identify the stochastic parameters. These parameters are then introduced in a structural reliability model to evaluate the failure probability. Results show the influence of adhesive thickness uncertainty on bonded joint failure. © 2012 Taylor & Francis.}, }
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M.A. Ngo Bieng, T. Pérot, F. De Coligny, F. Goreaud
Spatial pattern of trees influences species productivity in a mature oak-pine mixed forest
European Journal of Forest Research 132 (5-6), 2013
abs doi web bib

Spatial pattern has a key role in the interactions between species in plant communities. These interactions influence ecological processes involved in the species dynamics: growth, regeneration and mortality. In this study, we investigated the effect of spatial pattern on productivity in mature mixed forests of sessile oak and Scots pine. We simulated tree locations with point process models and tree growth with spatially explicit individual growth models. The point process models and growth models were fitted with field data from the same stands. We compared species productivity obtained in two types of mixture: a patchy mixture and an intimate mixture. Our results show that the productivity of both species is higher in an intimate mixture than in a patchy mixture. Productivity difference between the two types of mixture was 11.3% for pine and 14.7% for oak. Both species were favored in the intimate mixture because, for both, intraspecific competition was more severe than interspecific competition. Our results clearly support favoring intimate mixtures in mature oak-pine stands to optimize tree species productivity; oak is the species that benefits the most from this type of management. Our work also shows that models and simulations can provide interesting results for complex forests with mixtures, results that would be difficult to obtain through experimentation.
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@article{PUB00039371, author = {Ngo Bieng, M.A. and Pérot, T. and De Coligny, F. and Goreaud, F.}, title = {Spatial pattern of trees influences species productivity in a mature oak-pine mixed forest}, title = {Effet de la structure spatiale sur la productivité des espèces en forêt mélangée mature chêne-pin}, journal = {European Journal of Forest Research}, volume = {132}, number = {5-6}, pages = {841-850}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00039371 / http://dx.doi.org/10.1007/s10342-013-0716-z}, doi = {http://dx.doi.org/10.1007/s10342-013-0716-z}, year = {2013}, affiliation = {CIRAD UMR SYSTEM MONTPELLIER FRA ; IRSTEA NOGENT SUR VERNISSON UR EFNO FRA ; INRA UMR931 AMAP MONTPELLIER FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, number = {D 5945}, abstract = {Spatial pattern has a key role in the interactions between species in plant communities. These interactions influence ecological processes involved in the species dynamics: growth, regeneration and mortality. In this study, we investigated the effect of spatial pattern on productivity in mature mixed forests of sessile oak and Scots pine. We simulated tree locations with point process models and tree growth with spatially explicit individual growth models. The point process models and growth models were fitted with field data from the same stands. We compared species productivity obtained in two types of mixture: a patchy mixture and an intimate mixture. Our results show that the productivity of both species is higher in an intimate mixture than in a patchy mixture. Productivity difference between the two types of mixture was 11.3% for pine and 14.7% for oak. Both species were favored in the intimate mixture because, for both, intraspecific competition was more severe than interspecific competition. Our results clearly support favoring intimate mixtures in mature oak-pine stands to optimize tree species productivity; oak is the species that benefits the most from this type of management. Our work also shows that models and simulations can provide interesting results for complex forests with mixtures, results that would be difficult to obtain through experimentation.}, }
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A. K. Patel, P. Michaud, H. De Baynast, M. Grédiac, J.D. Mathias
Preparation of chitosan-based adhesives and assessment of their mechanical properties
Journal of Applied Polymer Science 127 (5), 2013
abs doi web bib

The aim of this study is to develop chitosan-based adhesives and to characterize their shear strength. The desirable features of such adhesives are biodegradability, biocompatibility, non-toxicity, and anti-microbial properties. Various eco-friendly polyanionic polysaccharides, acids, and plasticizers, in single or multiple formulations, were associated with chitosan. The resulting crosslinked polymers were glued on some chemically treated aluminum adherends. The shear strength of these formulations was measured with the 'double lap-joint' bonding method, as it features a low-peeling effect. The shear strength of 40.8 MPa obtained for formulations containing chitosan and glycerol plasticizer was the most significant finding in this study. This value is equivalent to that obtained with a synthetic adhesive used in industry.
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@article{PUB00035744, author = {Patel, A. K. and Michaud, P. and De Baynast, H. and Grédiac, M. and Mathias, J.D.}, title = {Preparation of chitosan-based adhesives and assessment of their mechanical properties}, title = {Préparation d'adhésifs à base de chitosane et caractérisation de leurs propriétés mécaniques}, journal = {Journal of Applied Polymer Science}, volume = {127}, number = {5}, pages = {3869-3876}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00035744}, doi = {http://dx.doi.org/10.1002/app.37685}, year = {2013}, affiliation = {UNIVERSITE DE CLERMONT FERRAND I FRA ; UNIVERSITE DE CLERMONT FERRAND I FRA ; UNIVERSITE DE CLERMONT FERRAND I FRA ; UNIVERSITE DE CLERMONT FERRAND I FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {The aim of this study is to develop chitosan-based adhesives and to characterize their shear strength. The desirable features of such adhesives are biodegradability, biocompatibility, non-toxicity, and anti-microbial properties. Various eco-friendly polyanionic polysaccharides, acids, and plasticizers, in single or multiple formulations, were associated with chitosan. The resulting crosslinked polymers were glued on some chemically treated aluminum adherends. The shear strength of these formulations was measured with the 'double lap-joint' bonding method, as it features a low-peeling effect. The shear strength of 40.8 MPa obtained for formulations containing chitosan and glycerol plasticizer was the most significant finding in this study. This value is equivalent to that obtained with a synthetic adhesive used in industry.}, }
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A.K. Patel, J.D. Mathias, P. Michaud
Polysaccharides as adhesives: A critical review
Reviews of Adhesion and Adhesives 1 (3), 2013
abs web bib

Metal, paper and wood bonding industries require huge quantity of synthetic adhesives. The economic, environmental and health aspects for many of these adhesive formulations are a matter of concern for environmental protection agencies and adhesive industries these days. Most of the adhesive formulations are based on depleting petrochemical resources and toxic chemicals. Therefore, the development of cost-effective, environmental and health-friendly green adhesives, based on renewable bioresources, is necessary for consumers today. Research on adhesives development from polysaccharides is growing gradually. Development of potential bioadhesives is inevitable in current situation in order to reduce the use of commercial synthetic adhesives. This review deals with adhesive properties of polysaccharide-based intermediate and fully realized bioadhesives with major emphasis on their bonding strengths to metal, paper and wood adherends and the current perspectives for adhesive market. Its main objective is to provide a unified and complete document for an easy comparison of most of the developments made during the last decades in the area of intermediate and fully biobased adhesives, which has not been presented yet.
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@article{PUB00054416, author = {Patel, A.K. and Mathias, J.D. and Michaud, P.}, title = {Polysaccharides as adhesives: A critical review}, journal = {Reviews of Adhesion and Adhesives}, volume = {1}, number = {3}, pages = {312-345}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00054416}, year = {2013}, affiliation = {UNIVERSITE DE CLERMONT FERRAND I FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; UNIVERSITE DE CLERMONT FERRAND I FRA}, abstract = {Metal, paper and wood bonding industries require huge quantity of synthetic adhesives. The economic, environmental and health aspects for many of these adhesive formulations are a matter of concern for environmental protection agencies and adhesive industries these days. Most of the adhesive formulations are based on depleting petrochemical resources and toxic chemicals. Therefore, the development of cost-effective, environmental and health-friendly green adhesives, based on renewable bioresources, is necessary for consumers today. Research on adhesives development from polysaccharides is growing gradually. Development of potential bioadhesives is inevitable in current situation in order to reduce the use of commercial synthetic adhesives. This review deals with adhesive properties of polysaccharide-based intermediate and fully realized bioadhesives with major emphasis on their bonding strengths to metal, paper and wood adherends and the current perspectives for adhesive market. Its main objective is to provide a unified and complete document for an easy comparison of most of the developments made during the last decades in the area of intermediate and fully biobased adhesives, which has not been presented yet.}, }
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A.K. Patel, P. Michaud, E. Petit, H. De Baynast, M. Grédiac, J.D. Mathias
Development of a chitosan-based adhesive. Application to wood bonding
Journal of Applied Polymer Science 127 (6), 2013
abs doi web bib

The potential of chitosan (CS) as wood adhesive was investigated in this study. The measurement of the bond strength of different CS-based formulations was carried out using double-lap shear tests. The best formulation tested was an adhesive composed of 6% of CS, 1% of glycerol, and 5 mmol/L of trisodium citrate dehydrate. Best bond strength from this formulation was found to be equal to 6.0 MPa in dried conditions and 1.6 MPa in wet conditions (specimens immersed for 3 h at 30C in water). The failure in the double-lap joint tests mainly occurred in wood. Finally, the penetration of the rhodamine-labeled CS at 4% in the pinewood matrix was also studied using microtome and microscopy techniques to show interactions between CS-based adhesive and wood.
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@article{PUB00035743, author = {Patel, A.K. and Michaud, P. and Petit, E. and De Baynast, H. and Grédiac, M. and Mathias, J.D.}, title = {Development of a chitosan-based adhesive. Application to wood bonding}, title = {Développement d'adhésif à base de chitosane : application au collage du bois}, journal = {Journal of Applied Polymer Science}, volume = {127}, number = {6}, pages = {5014-5021}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00035743}, doi = {http://dx.doi.org/10.1002/app.38097}, year = {2013}, affiliation = {UNIVERSITE DE CLERMONT FERRAND I FRA ; UNIVERSITE DE CLERMONT FERRAND I FRA ; UNIVERSITE D'AMIENS FRA ; UNIVERSITE DE CLERMONT FERRAND I FRA ; UNIVERSITE DE CLERMONT FERRAND I FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {The potential of chitosan (CS) as wood adhesive was investigated in this study. The measurement of the bond strength of different CS-based formulations was carried out using double-lap shear tests. The best formulation tested was an adhesive composed of 6% of CS, 1% of glycerol, and 5 mmol/L of trisodium citrate dehydrate. Best bond strength from this formulation was found to be equal to 6.0 MPa in dried conditions and 1.6 MPa in wet conditions (specimens immersed for 3 h at 30C in water). The failure in the double-lap joint tests mainly occurred in wood. Finally, the penetration of the rhodamine-labeled CS at 4% in the pinewood matrix was also studied using microtome and microscopy techniques to show interactions between CS-based adhesive and wood.}, }
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C. Rougé, Y. Ge, X. Cai
Detecting gradual and abrupt changes in hydrodological records
Advances in Water Resources 53, 2013
abs doi web bib

Hydrological time series increasingly exhibit non-stationarity, e.g., variables such as precipitation and streamflow values do not maintain a consistent mean over long periods, due to natural and anthropogenic changes. Detecting whether such shifts are gradual or abrupt is a growing concern for water resources planning and management. This paper shows that conventional trend and change-point tests do not adequately enable these two types of change to be distinguished. We propose a method for combining the rank correlations of the Mann–Kendall and Pettitt statistics to extract an indicator whose value determines whether a shift observed in a given time series is gradual or abrupt. This method allows the success rate to be independent of the length of record, and it is validated with Monte-Carlo experiments. The limitations caused by the short and noisy nature of hydroclimatic time series are discussed. As an application, the proposed method provides useful insights on changes in hydroclimatic variables in the United States during 1910–2009 using time series from 1217 stations in the United States Hydroclimatic Data Network (USHCN).
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@article{PUB00039246, author = {Rougé, C. and Ge, Y. and Cai, X.}, title = {Detecting gradual and abrupt changes in hydrodological records}, title = {Détection des changements abrupts et graduels dans les archives hydrologiques}, journal = {Advances in Water Resources}, volume = {53}, pages = {33-44}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00039246}, doi = {http://dx.doi.org/10.1016/j.advwatres.2012.09.008}, year = {2013}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; UNIVERSITY OF ILLINOIS VEN TE-CHOW HYDROSYSTEMS LABORATORY URBANA USA ; UNIVERSITY OF ILLINOIS VEN TE-CHOW HYDROSYSTEMS LABORATORY URBANA USA}, abstract = {Hydrological time series increasingly exhibit non-stationarity, e.g., variables such as precipitation and streamflow values do not maintain a consistent mean over long periods, due to natural and anthropogenic changes. Detecting whether such shifts are gradual or abrupt is a growing concern for water resources planning and management. This paper shows that conventional trend and change-point tests do not adequately enable these two types of change to be distinguished. We propose a method for combining the rank correlations of the Mann–Kendall and Pettitt statistics to extract an indicator whose value determines whether a shift observed in a given time series is gradual or abrupt. This method allows the success rate to be independent of the length of record, and it is validated with Monte-Carlo experiments. The limitations caused by the short and noisy nature of hydroclimatic time series are discussed. As an application, the proposed method provides useful insights on changes in hydroclimatic variables in the United States during 1910–2009 using time series from 1217 stations in the United States Hydroclimatic Data Network (USHCN).}, }
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C. Rougé, J.D. Mathias, G. Deffuant
Extending the viability theory framework of resilience to uncertain dynamics, and application to lake eutrophication
Ecological Indicators 29, 2013
abs doi web bib

Resilience, the capacity for a system to recover from a perturbation so as to keep its properties and functions, is of growing concern to a wide range of environmental systems. The challenge is often to render this concept operational without betraying it, nor diluting its content. The focus here is on building on the viability theory framework of resilience to extend it to discrete-time stochastic dynamical systems. The viability framework describes properties of the system as a subset of its state space. This property is resilient to a perturbation if it can be recovered and kept by the system after a perturbation: its trajectory can come back and stay in the subset. This is shown to reflect a general definition of resilience. With stochastic dynamics, the stochastic viability kernel describes the robust states, in which the system has a high probability of staying in the subset for a long time. Then, probability of resilience is defined as the maximal probability that the system reaches a robust state within a time horizon. Management strategies that maximize the probability of resilience can be found through dynamic programming. It is then possible to compute a range of statistics on the time for restoring the property. The approach is illustrated on the example of lake eutrophication and shown to foster the use of different indicators that are adapted to distinct situations. Its relevance for the management of ecological systems is also discussed.
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@article{PUB00037792, author = {Rougé, C. and Mathias, J.D. and Deffuant, G.}, title = {Extending the viability theory framework of resilience to uncertain dynamics, and application to lake eutrophication}, title = {Extension du cadre viabiliste de la résilience à des dynamiques incertaines et application à l'eutrophisation d'un lac}, journal = {Ecological Indicators}, volume = {29}, pages = {420-433}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00037792}, doi = {http://dx.doi.org/10.1016/j.ecolind.2012.12.032}, year = {2013}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {Resilience, the capacity for a system to recover from a perturbation so as to keep its properties and functions, is of growing concern to a wide range of environmental systems. The challenge is often to render this concept operational without betraying it, nor diluting its content. The focus here is on building on the viability theory framework of resilience to extend it to discrete-time stochastic dynamical systems. The viability framework describes properties of the system as a subset of its state space. This property is resilient to a perturbation if it can be recovered and kept by the system after a perturbation: its trajectory can come back and stay in the subset. This is shown to reflect a general definition of resilience. With stochastic dynamics, the stochastic viability kernel describes the robust states, in which the system has a high probability of staying in the subset for a long time. Then, probability of resilience is defined as the maximal probability that the system reaches a robust state within a time horizon. Management strategies that maximize the probability of resilience can be found through dynamic programming. It is then possible to compute a range of statistics on the time for restoring the property. The approach is illustrated on the example of lake eutrophication and shown to foster the use of different indicators that are adapted to distinct situations. Its relevance for the management of ecological systems is also discussed.}, }
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S. Sun, J.D. Mathias, E. Toussaint, M. Grédiac
Hygromechanical characterization of sunflower stems
Industrial Crops and Products 46, 2013
abs doi web bib

This study concerns the determination of hygromechanical properties of sunflower stems. Mechanical tests were carried out on specimens of sunflower bark and pith. Particular attention was paid to the influence on the mechanical properties of (i) specimen location along the stem and (ii) moisture content of specimens. For this purpose, specimens were taken from the bottom, middle, and top of the stems. The influence of humidity on the mechanical properties was studied by testing specimens conditioned at three different relative humidities: 0% RH, 33% RH and 75% RH. Moisture diffusion coefficients of bark and pith were deduced assuming Fick's law to predict the variation in moisture content of the specimens during the mechanical test. The Young's modulus of the bark was found to be higher than that of the pith, whereas the moisture diffusion coefficient of the bark was lower than that of the pith. Mechanical and hygroscopic properties of specimens depended on their location along the stem. In order to explain these results, morphological observations have been carried out on the specimen at each location. It was found that porosity of both the bark and the pith are lower at the top of the stem. The presence of sclerenchyma in the bark is also higher at the top of the stem.
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@article{PUB00038746, author = {Sun, S. and Mathias, J.D. and Toussaint, E. and Grédiac, M.}, title = {Hygromechanical characterization of sunflower stems}, journal = {Industrial Crops and Products}, volume = {46}, pages = {50-59}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00038746}, doi = {http://dx.doi.org/10.1016/j.indcrop.2013.01.009}, year = {2013}, affiliation = {UNIVERSITE DE CLERMONT FERRAND FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; UNIVERSITE DE CLERMONT FERRAND FRA ; UNIVERSITE DE CLERMONT FERRAND FRA}, abstract = {This study concerns the determination of hygromechanical properties of sunflower stems. Mechanical tests were carried out on specimens of sunflower bark and pith. Particular attention was paid to the influence on the mechanical properties of (i) specimen location along the stem and (ii) moisture content of specimens. For this purpose, specimens were taken from the bottom, middle, and top of the stems. The influence of humidity on the mechanical properties was studied by testing specimens conditioned at three different relative humidities: 0% RH, 33% RH and 75% RH. Moisture diffusion coefficients of bark and pith were deduced assuming Fick's law to predict the variation in moisture content of the specimens during the mechanical test. The Young's modulus of the bark was found to be higher than that of the pith, whereas the moisture diffusion coefficient of the bark was lower than that of the pith. Mechanical and hygroscopic properties of specimens depended on their location along the stem. In order to explain these results, morphological observations have been carried out on the specimen at each location. It was found that porosity of both the bark and the pith are lower at the top of the stem. The presence of sclerenchyma in the bark is also higher at the top of the stem.}, }
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W. Wei, S. Martin, I. Alvarez
Sustainability analysis: Viability concepts to consider transient and asymptotical dynamics in socio-ecological tourism-based systems
Ecological Modelling 251, 2013
abs doi web bib

With the increasing pressure on natural resources, the sustainability study of socio-ecological systems has become a crucial scientific issue. In this paper we emphasize that transient behaviors have to be taken into account in sustainability analysis. We illustrate their impact with a model of tourism development from the literature, where the sustainability study is based on asymptotic properties. In order to evaluate relevant space and time characteristics of transient dynamics, we propose to use the concepts and tools of the mathematical viability theory. We also extend this analysis to controlled dynamical systems, which are particularly appropriate to model socio-ecological systems when management issues are at stake.
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@article{PUB00037806, author = {Wei, W. and Martin, S. and Alvarez, I.}, title = {Sustainability analysis: Viability concepts to consider transient and asymptotical dynamics in socio-ecological tourism-based systems}, title = {Analyse de durabilité : prendre en compte les comportements transitoires et asymptotiques par la théorie de la viabilité. Application à un modèle de tourisme.}, journal = {Ecological Modelling}, volume = {251}, pages = {103-113}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00037806}, doi = {http://dx.doi.org/10.1016/j.ecolmodel.2012.10.009}, year = {2013}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {With the increasing pressure on natural resources, the sustainability study of socio-ecological systems has become a crucial scientific issue. In this paper we emphasize that transient behaviors have to be taken into account in sustainability analysis. We illustrate their impact with a model of tourism development from the literature, where the sustainability study is based on asymptotic properties. In order to evaluate relevant space and time characteristics of transient dynamics, we propose to use the concepts and tools of the mathematical viability theory. We also extend this analysis to controlled dynamical systems, which are particularly appropriate to model socio-ecological systems when management issues are at stake.}, }
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C. Bernard, S. Martin
Building strategies to ensure langage coexistence in presence of bilingualism
Applied Mathematics and Computation 218 (17), 2012
abs doi web bib

For 20 years many authors have attempted to model language competition. Some models involve two different languages, others include also a bilingual population. The issues are to understand one language extinction or to determine in which parameter range coexistence is possible. A key parameter is the prestige of one language compare to the other. If this parameter remains constant, coexistence is not sustainable. However, prestige may vary with time. In this article, thanks to the viability theory concepts and tools, we study a set of prestige variations which would allow language coexistence in presence of a bilingual population. Among this set, we emphasise slow viable evolutions with the lowest prestige variations that guarantee coexistence.
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@article{PUB00035369, author = {Bernard, C. and Martin, S.}, title = {Building strategies to ensure langage coexistence in presence of bilingualism}, title = {Déterminer des stratégies pour assurer la coexistence de deux langues en présence de bilinguisme}, journal = {Applied Mathematics and Computation}, volume = {218}, number = {17}, pages = {8825-8841}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00035369 / http://www.sciencedirect.com/science/article/pii/S0096300312001683}, doi = {http://dx.doi.org/10.1016/j.amc.2012.02.041}, year = {2012}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {For 20 years many authors have attempted to model language competition. Some models involve two different languages, others include also a bilingual population. The issues are to understand one language extinction or to determine in which parameter range coexistence is possible. A key parameter is the prestige of one language compare to the other. If this parameter remains constant, coexistence is not sustainable. However, prestige may vary with time. In this article, thanks to the viability theory concepts and tools, we study a set of prestige variations which would allow language coexistence in presence of a bilingual population. Among this set, we emphasise slow viable evolutions with the lowest prestige variations that guarantee coexistence.}, }
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B. Bonté, J.D. Mathias, R. Duboz
Moment approximation of infection dynamics in a population of moving hosts
PLoS One 7 (12), 2012
abs doi web bib

The modelling of contact processes between hosts is of key importance in epidemiology. Current studies have mainly focused on networks with stationary structures, although we know these structures to be dynamic with continuous appearance and disappearance of links over time. In the case of moving individuals, the contact network cannot be established. Individual-based models (IBMs) can simulate the individual behaviours involved in the contact process. However, with very large populations, they can be hard to simulate and study due to the computational costs. We use the moment approximation (MA) method to approximate a stochastic IBM with an aggregated deterministic model. We illustrate the method with an application in animal epidemiology: the spread of the highly pathogenic virus H5N1 of avian influenza in a poultry flock. The MA method is explained in a didactic way so that it can be reused and extended. We compare the simulation results of three models: 1. an IBM, 2. a MA, and 3. a mean-field (MF). The results show a close agreement between the MA model and the IBM. They highlight the importance for the models to capture the displacement behaviours and the contact processes in the study of disease spread. We also illustrate an original way of using different models of the same system to learn more about the system itself, and about the representation we build of it.
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@article{PUB00037767, author = {Bonté, B. and Mathias, J.D. and Duboz, R.}, title = {Moment approximation of infection dynamics in a population of moving hosts}, journal = {PLoS One}, volume = {7}, number = {12}, pages = {e51760-}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00037767}, doi = {http://dx.doi.org/10.1371/journal.pone.0051760}, year = {2012}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; CIRAD MONTPELLIER FRA}, abstract = {The modelling of contact processes between hosts is of key importance in epidemiology. Current studies have mainly focused on networks with stationary structures, although we know these structures to be dynamic with continuous appearance and disappearance of links over time. In the case of moving individuals, the contact network cannot be established. Individual-based models (IBMs) can simulate the individual behaviours involved in the contact process. However, with very large populations, they can be hard to simulate and study due to the computational costs. We use the moment approximation (MA) method to approximate a stochastic IBM with an aggregated deterministic model. We illustrate the method with an application in animal epidemiology: the spread of the highly pathogenic virus H5N1 of avian influenza in a poultry flock. The MA method is explained in a didactic way so that it can be reused and extended. We compare the simulation results of three models: 1. an IBM, 2. a MA, and 3. a mean-field (MF). The results show a close agreement between the MA model and the IBM. They highlight the importance for the models to capture the displacement behaviours and the contact processes in the study of disease spread. We also illustrate an original way of using different models of the same system to learn more about the system itself, and about the representation we build of it.}, }
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R. Conte, N. Gilbert, G. Bonelli, C. Cioffi-Revilla, G. Deffuant, J. Kertesz, V. Loreto, S. Moat, J.P. Nadal, A. Sanchez, A. Nowak, A. Flache, M. San Miguel, D. Helbing
Manifesto of computational social science
European Physical Journal-Special Topics 214, 2012
abs doi web bib

The increasing integration of technology into our lives has created unprecedented volumes of data on society’s everyday behaviour. Such data opens up exciting new opportunities to work towards a quantitative understanding of our complex social systems, within the realms of a new discipline known as Computational Social Science. Against a background of financial crises, riots and international epidemics, the urgent need for a greater comprehension of the complexity of our interconnected global society and an ability to apply such insights in policy decisions is clear. This manifesto outlines the objectives of this new scientific direction, considering the challenges involved in it, and the extensive impact on science, technology and society that the success of this endeavour is likely to bring about.
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@article{PUB00036568, author = {Conte, R. and Gilbert, N. and Bonelli, G. and Cioffi-Revilla, C. and Deffuant, G. and Kertesz, J. and Loreto, V. and Moat, S. and Nadal, J.P. and Sanchez, A. and Nowak, A. and Flache, A. and San Miguel, M. and Helbing, D.}, title = {Manifesto of computational social science}, title = {Manifeste pour une science sociale computationnelle}, journal = {European Physical Journal-Special Topics}, volume = {214}, pages = {325-346}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00036568}, doi = {http://dx.doi.org/10.1140/epjst/e2012-01697-8}, year = {2012}, affiliation = {ISTC CNR ITA ; UNIVERSITY OF SURREY CRESS GBR ; ISTC CNR ITA ; GEORGE MASON UNIVERSITY CENTER FOR SOCIAL COMPLEXITY USA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; BUDAPEST UNIVERSITY OF TECHNOLOGY AND ECONOMICS INSTITUTE OF PHYSICS HUN ; SAPIENZA UNIVERSITY OF ROME ITA ; UNIVERSITY COLLEGE LONDON GBR ; CNRS FRA ; GISC CARLOS III UNIVERSITY OF MADRID ESP ; UNIVERSITY OF WARSAW CENTER FOR COMPLEX SYSTEMS POL ; UNIVERSITY OF GRONINGEN ICS NLD ; UNIVERSITY OF THE BALEARIC ISLANDS ESP ; ETH ZURICH CHE}, abstract = {The increasing integration of technology into our lives has created unprecedented volumes of data on society’s everyday behaviour. Such data opens up exciting new opportunities to work towards a quantitative understanding of our complex social systems, within the realms of a new discipline known as Computational Social Science. Against a background of financial crises, riots and international epidemics, the urgent need for a greater comprehension of the complexity of our interconnected global society and an ability to apply such insights in policy decisions is clear. This manifesto outlines the objectives of this new scientific direction, considering the challenges involved in it, and the extensive impact on science, technology and society that the success of this endeavour is likely to bring about.}, }
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G. Deffuant, I. Alvarez, O. Barreteau, B. De Vries, B. Edmonds, N. Gilbert, N. Gotts, F. Jabot, S. Janssen, M. Hilden, O. Kolditz, D. Murray-Rust, C. Rougé, P. Smits
Data and models for exploring sustainability of human well-being in global environmental change
European Physical Journal-Special Topics 214 (1), 2012
abs doi web bib

This position paper proposes a vision for the research activity about sustainability in global environmental change (GEC) taking place in the FuturICT flagship project. This activity will be organised in an “Exploratory”, gathering a core network of European scientists from ICT, social simulation, complex systems, economics, demographics, Earth system science. These research teams will collaborate in building a self-organising network of data sources and models about GEC and in using new facilities fostering stakeholder participation. We develop examples of concrete directions for this research: world wide virtual population with demographic and some economic descriptors, ecosystem services production and distribution, governance systems at various scales.
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@article{PUB00036306, author = {Deffuant, G. and Alvarez, I. and Barreteau, O. and De Vries, B. and Edmonds, B. and Gilbert, N. and Gotts, N. and Jabot, F. and Janssen, S. and Hilden, M. and Kolditz, O. and Murray-Rust, D. and Rougé, C. and Smits, P.}, title = {Data and models for exploring sustainability of human well-being in global environmental change}, title = {Données et modèles pour explorer la durabilité du bien-être humain face aux changements environnementaux planétaires}, journal = {European Physical Journal-Special Topics}, volume = {214}, number = {1}, pages = {519-545}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00036306}, doi = {http://dx.doi.org/10.1140/epjst/e2012-01704-2}, year = {2012}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA MONTPELLIER UR IRMO FRA ; NETHERLANDS ENVIRONMENTAL AGENCY UTRECHT SUSTAINIBILITY INSTITUTE NLD ; CENTER FOR POLICY MODELLING MANCHESTER GBR ; UNIVERSITY OF SURREY CENTRE FOR RESEARCH IN SOCIAL SIMULATION GBR ; JAMES HUTTON INSTITUTE ABERDEEN GBR ; IRSTEA CLERMONT FERRAND UR LISC FRA ; ALTERRA GREEN WORLD RESEARCH WAGENINGEN NLD ; FINNISH ENVIRONMENT INSTITUTE SYKE HELSINKI FIN ; UFZ HELMHOLTZ CENTRE FOR ENVIRONMENTAL RESEARCH LEIPZIG DEU ; UNIVERSITY OF EDINBURGH GBR ; IRSTEA CLERMONT FERRAND UR LISC FRA ; JRC IES JOINT RESEARCH CENTRE INSTITUTE FOR ENVIRONMENT AND SUSTAINABILITY ISPRA ITA}, abstract = {This position paper proposes a vision for the research activity about sustainability in global environmental change (GEC) taking place in the FuturICT flagship project. This activity will be organised in an “Exploratory”, gathering a core network of European scientists from ICT, social simulation, complex systems, economics, demographics, Earth system science. These research teams will collaborate in building a self-organising network of data sources and models about GEC and in using new facilities fostering stakeholder participation. We develop examples of concrete directions for this research: world wide virtual population with demographic and some economic descriptors, ecosystem services production and distribution, governance systems at various scales.}, }
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F. Gargiulo, M. Lenormand, S. Huet, O. Baqueiro Espinosa
Commuting network models: Getting the essentials
JASSS-The Journal of Artificial Societies and Social Simulation 15 (2), 2012
abs web bib

Human mobility and, in particular, commuting patterns have a fundamental role in understanding socio-economic systems. Analysing and modelling the networks formed by commuters, for example, has become a crucial requirement in studying rural areas dynamics and to help decision-making. This paper presents a simple spatial interaction commuting model with only one parameter. The proposed algorithm considers each individual who wants to commute, starting from their residence to all the possible workplaces. The algorithm decides the location of the workplace following the classical rule inspired from the gravity law consisting of a compromise between the job offers and the distance to the job. The further away the job is, the more important the offer should be to be considered for the decision. Inversely, the quantity of offers is not important for the decision when these offers are close by. The presented model provides a simple, yet powerful approach to simulate realistic distributions of commuters for empirical studies with limited data availability. The paper also presents a comparative analysis of the structure of the commuting networks of the four European regions to which we apply our model. The model is calibrated and validated on these regions. The results from the analysis show that the model is very efficient in reproducing most of the statistical properties of the network given by the data sources.
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@article{PUB00035312, author = {Gargiulo, F. and Lenormand, M. and Huet, S. and Baqueiro Espinosa, O.}, title = {Commuting network models: Getting the essentials }, title = {Modèle de réseau de navettage: allons à l'essentiel}, journal = {JASSS-The Journal of Artificial Societies and Social Simulation}, volume = {15}, number = {2}, pages = {6}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00035312 / http://jasss.soc.surrey.ac.uk/15/2/6.html}, year = {2012}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; LEIBNIZ INSTITUTE FOR AGRICULTURAL DEVELOPMENT IN CENTRAL AND EASTERN EUROPE IAMO DEU}, abstract = {Human mobility and, in particular, commuting patterns have a fundamental role in understanding socio-economic systems. Analysing and modelling the networks formed by commuters, for example, has become a crucial requirement in studying rural areas dynamics and to help decision-making. This paper presents a simple spatial interaction commuting model with only one parameter. The proposed algorithm considers each individual who wants to commute, starting from their residence to all the possible workplaces. The algorithm decides the location of the workplace following the classical rule inspired from the gravity law consisting of a compromise between the job offers and the distance to the job. The further away the job is, the more important the offer should be to be considered for the decision. Inversely, the quantity of offers is not important for the decision when these offers are close by. The presented model provides a simple, yet powerful approach to simulate realistic distributions of commuters for empirical studies with limited data availability. The paper also presents a comparative analysis of the structure of the commuting networks of the four European regions to which we apply our model. The model is calibrated and validated on these regions. The results from the analysis show that the model is very efficient in reproducing most of the statistical properties of the network given by the data sources. }, }
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F. Gargiulo, S. Huet
New discussions challenge the organization of societies
Advances in Complex Systems 15 (4), 2012
abs doi web bib

Can the discussions about new issues challenge the organization of a society? That is the question we tried to answer with a very simple model considering a society where individuals are organized into groups. An individual discuss its opinion on this new issue following the rule of the bounded confidence model implying that an individual influences and is influenced when it is sufficiently open-minded. One of the main ingredients of the model is the groups that both influence the behaviour of the individual and characterize the social network topology. Individuals choose the group membership according to their opinion. Starting from an initial homogeneous group size distribution, four different prototypical regimes can be reproduced by the model, depending on the individual open-mindedness: from a high heterogeneity condition, with one or two largely major groups, to an invariant situation of homogeneity. The heterogeneity is explained by the dynamics of individuals. In this paper we extend the studies of a previous work on the argument, deepening the analysis on the internal structure of the groups and on the dynamical process itself. To do this we analyze indicators related to the stability of the obtained virtual society. We found that the dynamics of groups is not stable when open-mindedness is small, even if the dynamics of opinions reaches equilibrium. On the other side, for larger values of the open-mindedness, both the opinion and the group dynamics stabilize. Thus our study shows that the introduction of a new topic of discussion in a society can strongly challenge group structures, both concerning their stability and their size. / Dans quelle mesure les discussions autour d'un nouveau problème de société la remettent-elle en cause ? C'est la question à laquelle nous tentons de répondre en partant d'un modèle simple de simulation considérant une société où les individus sont organisés en groupes. Un individu discute son opinion sur le nouveau sujet en utilisant la règle du modèle "bounded confidence" impliquant qu'il influence et est infuencé lorsqu'il a un esprit suffisamment ouvert. L'un des ingrédients principaux du modèle est le groupe qui influence tant le comportement de l'individu qu'il caractérise l'organisation sociale en réseau. Les individus se rattachent à un groupe en fonction de leur opinion. Partant d'une distribution uniforme de la taille des groupes, quatre régimes prototypiques peuvent être reproduit par le model selon le niveau d'ouverture d'esprit des individus : d'une taille de groupes très hétérogène avec un ou deux groupes très grands à un maintien de l'uniformité de la taille des groupes. L'hétérogénéïté est dû aux dynamiques individuelles. Ce papier poursuit les travaux déjà réalisés, analysant plus avant les structures des groupes et les dynamiques permettant d'atteindre ces structures. Les indicateurs de stabilité montrent que la dynamique des groupes est instables lorsque les esprits sont peu ouverts et ce même si les opinions se stabilisent. Pour des esprits esprits, tant les groupes que les opinions se stabilisent. Nous concluons que l'introduction d'un nouveau sujet de société dans les discussions peut remettre en cause la taille et la stabilité des groupes formant cette société.
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@article{PUB00035310, author = {Gargiulo, F. and Huet, S.}, title = {New discussions challenge the organization of societies}, title = {Les nouveaux sujets de discussions remettent en cause la société}, journal = {Advances in Complex Systems}, volume = {15}, number = {4}, pages = {17}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00035310}, doi = {http://dx.doi.org/10.1142/S0219525912500336}, year = {2012}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {Can the discussions about new issues challenge the organization of a society? That is the question we tried to answer with a very simple model considering a society where individuals are organized into groups. An individual discuss its opinion on this new issue following the rule of the bounded confidence model implying that an individual influences and is influenced when it is sufficiently open-minded. One of the main ingredients of the model is the groups that both influence the behaviour of the individual and characterize the social network topology. Individuals choose the group membership according to their opinion. Starting from an initial homogeneous group size distribution, four different prototypical regimes can be reproduced by the model, depending on the individual open-mindedness: from a high heterogeneity condition, with one or two largely major groups, to an invariant situation of homogeneity. The heterogeneity is explained by the dynamics of individuals. In this paper we extend the studies of a previous work on the argument, deepening the analysis on the internal structure of the groups and on the dynamical process itself. To do this we analyze indicators related to the stability of the obtained virtual society. We found that the dynamics of groups is not stable when open-mindedness is small, even if the dynamics of opinions reaches equilibrium. On the other side, for larger values of the open-mindedness, both the opinion and the group dynamics stabilize. Thus our study shows that the introduction of a new topic of discussion in a society can strongly challenge group structures, both concerning their stability and their size. / Dans quelle mesure les discussions autour d'un nouveau problème de société la remettent-elle en cause ? C'est la question à laquelle nous tentons de répondre en partant d'un modèle simple de simulation considérant une société où les individus sont organisés en groupes. Un individu discute son opinion sur le nouveau sujet en utilisant la règle du modèle "bounded confidence" impliquant qu'il influence et est infuencé lorsqu'il a un esprit suffisamment ouvert. L'un des ingrédients principaux du modèle est le groupe qui influence tant le comportement de l'individu qu'il caractérise l'organisation sociale en réseau. Les individus se rattachent à un groupe en fonction de leur opinion. Partant d'une distribution uniforme de la taille des groupes, quatre régimes prototypiques peuvent être reproduit par le model selon le niveau d'ouverture d'esprit des individus : d'une taille de groupes très hétérogène avec un ou deux groupes très grands à un maintien de l'uniformité de la taille des groupes. L'hétérogénéïté est dû aux dynamiques individuelles. Ce papier poursuit les travaux déjà réalisés, analysant plus avant les structures des groupes et les dynamiques permettant d'atteindre ces structures. Les indicateurs de stabilité montrent que la dynamique des groupes est instables lorsque les esprits sont peu ouverts et ce même si les opinions se stabilisent. Pour des esprits esprits, tant les groupes que les opinions se stabilisent. Nous concluons que l'introduction d'un nouveau sujet de société dans les discussions peut remettre en cause la taille et la stabilité des groupes formant cette société.}, }
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T. Guélon, J.D. Mathias, G. Deffuant
Influence of the spatial structure on the effective nutrient diffusion in bacterial biofilm
Journal of Biological Physics 38 (4), 2012
abs doi web bib

The main contribution of this paper is to use homogenization techniques to compute diffusion coefficients from experimental images of microbial biofilms. Our approach requires the analysis of several experimental spatial structures of biofilms in order to derive from them a Representative Volume Element (RVE). Then, we apply a suitable numerical procedure to the RVE to derive the diffusion coefficients. We show that diffusion coefficients significantly vary with the biofilm structure. These results suggest that microbial biofilm structures can favour nutrient access in some cases.
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@article{PUB00037644, author = {Guélon, T. and Mathias, J.D. and Deffuant, G.}, title = {Influence of the spatial structure on the effective nutrient diffusion in bacterial biofilm}, title = {Influence de la structure spatiale sur la diffusion effective à l'intérieur d'un biofilm bactérien}, journal = {Journal of Biological Physics}, volume = {38}, number = {4}, pages = {573-588}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00037644}, doi = {http://dx.doi.org/10.1007/s10867-012-9272-x}, year = {2012}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {The main contribution of this paper is to use homogenization techniques to compute diffusion coefficients from experimental images of microbial biofilms. Our approach requires the analysis of several experimental spatial structures of biofilms in order to derive from them a Representative Volume Element (RVE). Then, we apply a suitable numerical procedure to the RVE to derive the diffusion coefficients. We show that diffusion coefficients significantly vary with the biofilm structure. These results suggest that microbial biofilm structures can favour nutrient access in some cases.}, }
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F. Jabot, J. Bascompte
Bitrophic interactions shape biodiversity in space
Proceedings of the National Academy of Sciences of the United States of America 109 (12), 2012
abs web bib

Ecologists and conservation biologists often study particular trophic groups in isolation, which precludes an explicit assessment of the impact of multitrophic interactions on community structure and dynamics. Network ecology helps to fill this gap by focusing on species interactions, but it often ignores spatial processes. Here, we are taking a step forward in the integration of metacommunity and network approaches by studying a model of bitrophic interactions in a spatial context. We quantify the effect of bitrophic interactions on the diversity of plants and their animal interactors, and we show their complex dependence on the structure of the interaction network, the strength of interactions, and the dispersal rate. We then develop a method to parameterize our model with real-world networks and apply it to 54 datasets describing three types of interactions: pollination, fungal association, and insect herbivory. In all three network types, bitrophic interactions generally lead to an increase of plant and animal spatial heterogeneity by decreasing local species richness while increasing β-diversity.
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@article{PUB00037373, author = {Jabot, F. and Bascompte, J.}, title = {Bitrophic interactions shape biodiversity in space}, title = {Les interactions bi-trophiques façonnent la répartition spatiale de la biodiversité}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {109}, number = {12}, pages = {4521-4526}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00037373}, year = {2012}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; INTEGRATIVE ECOLOGY GROUP SEVILLA SPA}, abstract = {Ecologists and conservation biologists often study particular trophic groups in isolation, which precludes an explicit assessment of the impact of multitrophic interactions on community structure and dynamics. Network ecology helps to fill this gap by focusing on species interactions, but it often ignores spatial processes. Here, we are taking a step forward in the integration of metacommunity and network approaches by studying a model of bitrophic interactions in a spatial context. We quantify the effect of bitrophic interactions on the diversity of plants and their animal interactors, and we show their complex dependence on the structure of the interaction network, the strength of interactions, and the dispersal rate. We then develop a method to parameterize our model with real-world networks and apply it to 54 datasets describing three types of interactions: pollination, fungal association, and insect herbivory. In all three network types, bitrophic interactions generally lead to an increase of plant and animal spatial heterogeneity by decreasing local species richness while increasing β-diversity.}, }
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F. Jabot, J. Pottier
A general modelling framework for resource-ratio and CSR theories of plant community dynamics
Journal of Ecology 100, 2012
abs doi web bib

1. Grime’s CSR and Tilman’s resource-ratio theories are two major contributions to our understanding of plant community dynamics. They have both been corroborated empirically, whilst providing several contradictory predictions. Notably, contrary to Tilman, Grime predicts that competition for soil resources is unimportant on poor soils. 2. We show that Grime’s CSR theory can be modelled with the same type of differential equations for resource and plant biomass dynamics used by Tilman in his resource-ratio theory. 3. Using this unified modelling framework, we demonstrate that both models predict intense competition for soil resources on poor soils, as long as biomass loss per unit mass is modelled as a size-independent process. When considering biomass loss per unit mass as a size-dependent process mimicking farming activities, both models predict a unimodal relationship between soil fertility and the intensity of soil resource competition, and a decreasing relationship between disturbance rate and resource competition. 4. Synthesis. Our modelling analysis reveals that the resource-ratio and CSR theories make different predictions regarding competition on poor soils, not because of their differing schemes of plant strategies, but because of the different disturbance types that they are considering. Tilman’s predictions apply to little disturbed natural habitats, whilst Grime’s predictions apply to disturbed ones.
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@article{PUB00037370, author = {Jabot, F. and Pottier, J.}, title = {A general modelling framework for resource-ratio and CSR theories of plant community dynamics}, title = {Un cadre général de modélisation pour les théories "resource-ratio" et "CSR" de dynamique de communauté de plantes}, journal = {Journal of Ecology}, volume = {100}, pages = {1296-1302}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00037370}, doi = {http://dx.doi.org/10.1111/j.1365-2745.2012.02024.x}, year = {2012}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; INRA CLERMONT FERRAND FRA}, abstract = {1. Grime’s CSR and Tilman’s resource-ratio theories are two major contributions to our understanding of plant community dynamics. They have both been corroborated empirically, whilst providing several contradictory predictions. Notably, contrary to Tilman, Grime predicts that competition for soil resources is unimportant on poor soils. 2. We show that Grime’s CSR theory can be modelled with the same type of differential equations for resource and plant biomass dynamics used by Tilman in his resource-ratio theory. 3. Using this unified modelling framework, we demonstrate that both models predict intense competition for soil resources on poor soils, as long as biomass loss per unit mass is modelled as a size-independent process. When considering biomass loss per unit mass as a size-dependent process mimicking farming activities, both models predict a unimodal relationship between soil fertility and the intensity of soil resource competition, and a decreasing relationship between disturbance rate and resource competition. 4. Synthesis. Our modelling analysis reveals that the resource-ratio and CSR theories make different predictions regarding competition on poor soils, not because of their differing schemes of plant strategies, but because of the different disturbance types that they are considering. Tilman’s predictions apply to little disturbed natural habitats, whilst Grime’s predictions apply to disturbed ones.}, }
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M. Lenormand, S. Huet, G. Deffuant
Deriving the number of jobs in proximity services from the number of inhabitants in french rural municipalities
PLoS One 7 (7), 2012
abs doi web bib

We use a minimum requirement approach to derive the number of jobs in proximity services per inhabitant in French rural municipalities. We first classify the municipalities according to their time distance in minutes by car to the municipality where the inhabitants go the most frequently to get services (called MFM). For each set corresponding to a range of time distance to MFM, we perform a quantile regression estimating the minimum number of service jobs per inhabitant that we interpret as an estimation of the number of proximity jobs per inhabitant. We observe that the minimum number of service jobs per inhabitant is smaller in small municipalities. Moreover, for municipalities of similar sizes, when the distance to the MFM increases, the number of jobs of proximity services per inhabitant increases.
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@article{PUB00035599, author = {Lenormand, M. and Huet, S. and Deffuant, G.}, title = {Deriving the number of jobs in proximity services from the number of inhabitants in french rural municipalities}, title = {Déterminer le nombre d'emplois dans les services de proximité en fonction du nombre d'habitants dans les municipalités rurales françaises}, journal = {PLoS One}, volume = {7}, number = {7}, pages = {8}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00035599 / http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0040001}, doi = {http://dx.doi.org/10.1371/journal.pone.0040001}, year = {2012}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {We use a minimum requirement approach to derive the number of jobs in proximity services per inhabitant in French rural municipalities. We first classify the municipalities according to their time distance in minutes by car to the municipality where the inhabitants go the most frequently to get services (called MFM). For each set corresponding to a range of time distance to MFM, we perform a quantile regression estimating the minimum number of service jobs per inhabitant that we interpret as an estimation of the number of proximity jobs per inhabitant. We observe that the minimum number of service jobs per inhabitant is smaller in small municipalities. Moreover, for municipalities of similar sizes, when the distance to the MFM increases, the number of jobs of proximity services per inhabitant increases.}, }
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M. Lenormand, S. Huet, F. Gargiulo, G. Deffuant
A universal model of commuting networks
PLoS One 7 (10), 2012
abs doi web bib

We show that a recently proposed model generates accurate commuting networks on 80 case studies from different regions of the world (Europe and United-States) at different scales (e.g. municipalities, counties, regions). The model takes as input the number of commuters coming in and out of each geographic unit and generates the matrix of commuting flows between the units. The single parameter of the model follows a universal law that depends only on the scale of the geographic units. We show that our model significantly outperforms two other approaches proposing a universal commuting model (Balcan et al. (2009); Simini et al. (2012)), particularly when the geographic units are small (e.g. municipalities).
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@article{PUB00036161, author = {Lenormand, M. and Huet, S. and Gargiulo, F. and Deffuant, G.}, title = {A universal model of commuting networks}, title = {Un modèle universel de réseaux de navettage}, journal = {PLoS One}, volume = {7}, number = {10}, pages = {11}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00036161 / http://www.plosone.org}, doi = {http://dx.doi.org/10.1371/journal.pone.0045985}, year = {2012}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; CNRS PARIS FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {We show that a recently proposed model generates accurate commuting networks on 80 case studies from different regions of the world (Europe and United-States) at different scales (e.g. municipalities, counties, regions). The model takes as input the number of commuters coming in and out of each geographic unit and generates the matrix of commuting flows between the units. The single parameter of the model follows a universal law that depends only on the scale of the geographic units. We show that our model significantly outperforms two other approaches proposing a universal commuting model (Balcan et al. (2009); Simini et al. (2012)), particularly when the geographic units are small (e.g. municipalities).}, }
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N. Mouquet, V. Devictor, C.N. Meynard, F. Munoz, L.F. Bersier, J. Chave, P. Couteron, A. Dalecky, C. Fontaine, D. Gravel, O.J. Hardy, F. Jabot, S. Lavergne, M. Leibold, D. Mouillot, T. Munkemuller, S. Pavoine, A. Prinzing, A.S.L. Rodrigues, R.P. Roh, E. Thebault, W. Thuiller
Ecophylogenetics: advances and perspectives
Biological Reviews 87, 2012
abs doi web bib

Ecophylogenetics can be viewed as an emerging fusion of ecology, biogeography andmacroevolution. This new and fastgrowing field is promoting the incorporation of evolution and historical contingencies into the ecological research agenda through the widespread use of phylogenetic data. Including phylogeny into ecological thinking represents an opportunity for biologists from different fields to collaborate and has provided promising avenues of research in both theoretical and empirical ecology, towards a better understanding of the assembly of communities, the functioning of ecosystems and their responses to environmental changes. The time is ripe to assess critically the extent to which the integration of phylogeny into these different fields of ecology has delivered on its promise. Here we review how phylogenetic information has been used to identify better the key components of species interactions with their biotic and abiotic environments, to determine the relationships between diversity and ecosystem functioning and ultimately to establish good management practices to protect overall biodiversity in the face of global change. We evaluate the relevance of information provided by phylogenies to ecologists, highlighting current potential weaknesses and needs for future developments. We suggest that despite the strong progress that has been made, a consistent unified framework is still missing to link local ecological dynamics to macroevolution. This is a necessary step in order to interpret observed phylogenetic patterns in a wider ecological context. Beyond the fundamental question of how evolutionary history contributes to shape communities, ecophylogenetics will help ecology to become a better integrative and predictive science.
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@article{PUB00037378, author = {Mouquet, N. and Devictor, V. and Meynard, C.N. and Munoz, F. and Bersier, L.F. and Chave, J. and Couteron, P. and Dalecky, A. and Fontaine, C. and Gravel, D. and Hardy, O.J. and Jabot, F. and Lavergne, S. and Leibold, M. and Mouillot, D. and Munkemuller, T. and Pavoine, S. and Prinzing, A. and Rodrigues, A.S.L. and Roh, R.P. and Thebault, E. and Thuiller, W.}, title = {Ecophylogenetics: advances and perspectives}, title = {Ecophylogénétique : avancées et perspectives}, journal = {Biological Reviews}, volume = {87}, pages = {769-785}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00037378}, doi = {http://dx.doi.org/10.1111/j.1469-185X.2012.00224.x}, year = {2012}, affiliation = {UNIVERSITE DE MONTPELLIER FRA ; UNIVERSITE DE MONTPELLIER FRA ; INRA MONTPELLIER FRA ; IRD MONTPELLIER FRA ; UNIVERSITY OF FRIBOURG CHE ; UNIVERSITE DE TOULOUSE FRA ; IRD MONTPELLIER FRA ; IRD MONTPELLIER FRA ; MUSEUM NATIONAL D'HISTOIRE NATURELLE PARIS FRA ; UNIVERSITE DU QUEBEC RIMOUSKI CAN ; EVOLUTION BIOLOGIQUE ET ECOLOGIE BRUSSELS BEL ; IRSTEA CLERMONT FERRAND UR LISC FRA ; UNIVERSITE DE GRENOBLE FRA ; UNIVERSITY OF AUSTIN TEXAS USA ; UNIVERSITE DE MONTPELLIER FRA ; UNIVERSITY OF AUSTIN TEXAS USA ; MUSEUM NATIONAL D'HISTOIRE NATURELLE PARIS FRA ; UNIVERSITE DE RENNES FRA ; CNRS CENTRE D'ECOLOGIE FONCTIONNELLE ET EVOLUTIVE MONTPELLIER FRA ; UNIVERSITY OF FRIBOURG CHE ; CNRS PARIS FRA ; UNIVERSITE DE GRENOBLE FRA}, abstract = {Ecophylogenetics can be viewed as an emerging fusion of ecology, biogeography andmacroevolution. This new and fastgrowing field is promoting the incorporation of evolution and historical contingencies into the ecological research agenda through the widespread use of phylogenetic data. Including phylogeny into ecological thinking represents an opportunity for biologists from different fields to collaborate and has provided promising avenues of research in both theoretical and empirical ecology, towards a better understanding of the assembly of communities, the functioning of ecosystems and their responses to environmental changes. The time is ripe to assess critically the extent to which the integration of phylogeny into these different fields of ecology has delivered on its promise. Here we review how phylogenetic information has been used to identify better the key components of species interactions with their biotic and abiotic environments, to determine the relationships between diversity and ecosystem functioning and ultimately to establish good management practices to protect overall biodiversity in the face of global change. We evaluate the relevance of information provided by phylogenies to ecologists, highlighting current potential weaknesses and needs for future developments. We suggest that despite the strong progress that has been made, a consistent unified framework is still missing to link local ecological dynamics to macroevolution. This is a necessary step in order to interpret observed phylogenetic patterns in a wider ecological context. Beyond the fundamental question of how evolutionary history contributes to shape communities, ecophylogenetics will help ecology to become a better integrative and predictive science.}, }
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J. Rolland, M.W. Cadotte, J. Davies, V. Devictor, S. Lavergne, N. Mouquet, S. Pavoine, A. Rodrigues, W. Thuiller, L. Turcati, M. Winter, L. Zupan, F. Jabot, H. Morlon
Using phylogenies in conservation: new perspectives
Biology Letters 8 (5), 2012
abs doi web bib

The 2011 meeting of the European Ecological Federation took place in A ´ vila, Spain, from 26th September to 29th September. The French Ecological Society (SFE) and the Foundation for Research on Biodiversity (FRB) sponsored a session entitled ‘Evolutionary history, ecosystem function and conservation biology: new perspectives’. We report on the main insights obtained from this symposium.
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@article{PUB00037379, author = {Rolland, J. and Cadotte, M.W. and Davies, J. and Devictor, V. and Lavergne, S. and Mouquet, N. and Pavoine, S. and Rodrigues, A. and Thuiller, W. and Turcati, L. and Winter, M. and Zupan, L. and Jabot, F. and Morlon, H.}, title = {Using phylogenies in conservation: new perspectives}, title = {Utiliser les phylogénies en écologie : nouvelles perspectives}, journal = {Biology Letters}, volume = {8}, number = {5}, pages = {692-694}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00037379}, doi = {http://dx.doi.org/10.1098/rsbl.2011.1024}, year = {2012}, affiliation = {ECOLE POLYTECHNIQUE PALAISEAU FRA ; UNIVERSITY OF TORONTO CAN ; MCGILL UNIVERSITY DEPARTEMENT OF BIOLOGY MONTREAL CAN ; UNIVERSITE DE GRENOBLE FRA ; UNIVERSITE DE GRENOBLE FRA ; UNIVERSITE DE MONTPELLIER FRA ; MUSEUM NATIONAL D'HISTOIRE NATURELLE PARIS FRA ; CENTRE D'ECOLOGIE FONCTIONNELLE ET EVOLUTIVE CNRS MONTPELLIER FRA ; UNIVERSITE DE GRENOBLE FRA ; MUSEUM NATIONAL D'HISTOIRE NATURELLE PARIS FRA ; HELMHOLTZ CENTRE FOR ENVIRONMENTAL RESEARCH HALLE DEU ; UNIVERSITE DE GRENOBLE FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; ECOLE POLYTECHNIQUE PALAISEAU FRA}, abstract = {The 2011 meeting of the European Ecological Federation took place in A ´ vila, Spain, from 26th September to 29th September. The French Ecological Society (SFE) and the Foundation for Research on Biodiversity (FRB) sponsored a session entitled ‘Evolutionary history, ecosystem function and conservation biology: new perspectives’. We report on the main insights obtained from this symposium.}, }
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N. Sicard, N. Perrot, R. Reuillon, S. Mesmoudi, I. Alvarez, S. Martin
A viability approach to control food processes: Application to a Camembert cheese ripening process
Food Control 23 (2), 2012
abs doi web bib

This paper addresses the issue of studying the viability theory, developed for model exploration purposes and in our example applied to the optimization of a food operation. The aim is to identify the whole set of viable trajectories for a given process. It focuses on the preservation of some specific properties of the system (constraints in the state space). On the basis of this set, a set of actions is identified and robustness is discussed. The proposed framework was adapted to a Camembert ripening model to identify the subset of the space state where almost one evolution starting in the subset remains indefinitely inside of the domain of some viability constraints, that makes it possible to reach a predefined quality target. The results were applied at the pilot scale and are discussed in this paper. The cheese ripening process was shortened by four days without significant changes in the microorganisms kinetics and a good sensory quality of the cheese. / Cet article s'intéresse à l'utilisation de la théorie de la viabilité (Aubin, 1991) pour l'exploration de modèles complexes, en prenant l'exemple de l'affinage du camembert. La démarche consiste à identifier l'ensemble des trajectoires viables du processus : il s'agit de maintenir certaines propriétés du système (des contraintes dans l'espace d'état, avec ici une cible de qualité à atteindre en fin d'affinage). A partir de cet ensemble, des questions d'optimisation et de robustesse peuvent être discutées. Les résultats ont été testés dans un hâloir-pilote et sont présentés dans cet article. Le processus d'affinage a été raccourci de quatre jours (sur 12) sans changement significatif dans la cinétique des microorganismes et en conservant une bonne qualité sensorielle du fromage.
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@article{PUB00033451, author = {Sicard, N. and Perrot, N. and Reuillon, R. and Mesmoudi, S. and Alvarez, I. and Martin, S.}, title = {A viability approach to control food processes: Application to a Camembert cheese ripening process}, title = {Une approche basée sur la viabilité pour le contrôle de procédés agro-alimentaires : application à l'affichage du camembert}, journal = {Food Control}, volume = {23}, number = {2}, pages = {312-319}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00033451}, doi = {http://dx.doi.org/10.1016/j.foodcont.2011.07.007}, year = {2012}, affiliation = {INRA UMR 782 GMPA AGROPARISTECH THIVERVAL GRIGNON FRA ; INRA UMR 782 GMPA AGROPARISTECH THIVERVAL GRIGNON FRA ; ISC PARIS FRA ; UNIVERSITE DE PARIS VI UMR 7606 LIP6 LABORATOIRE D'INFORMATIQUE DE PARIS ; IRSTEA CLERMONT FERRAND UR LISC FRA ; ISC PARIS FRA}, abstract = {This paper addresses the issue of studying the viability theory, developed for model exploration purposes and in our example applied to the optimization of a food operation. The aim is to identify the whole set of viable trajectories for a given process. It focuses on the preservation of some specific properties of the system (constraints in the state space). On the basis of this set, a set of actions is identified and robustness is discussed. The proposed framework was adapted to a Camembert ripening model to identify the subset of the space state where almost one evolution starting in the subset remains indefinitely inside of the domain of some viability constraints, that makes it possible to reach a predefined quality target. The results were applied at the pilot scale and are discussed in this paper. The cheese ripening process was shortened by four days without significant changes in the microorganisms kinetics and a good sensory quality of the cheese. / Cet article s'intéresse à l'utilisation de la théorie de la viabilité (Aubin, 1991) pour l'exploration de modèles complexes, en prenant l'exemple de l'affinage du camembert. La démarche consiste à identifier l'ensemble des trajectoires viables du processus : il s'agit de maintenir certaines propriétés du système (des contraintes dans l'espace d'état, avec ici une cible de qualité à atteindre en fin d'affinage). A partir de cet ensemble, des questions d'optimisation et de robustesse peuvent être discutées. Les résultats ont été testés dans un hâloir-pilote et sont présentés dans cet article. Le processus d'affinage a été raccourci de quatre jours (sur 12) sans changement significatif dans la cinétique des microorganismes et en conservant une bonne qualité sensorielle du fromage.}, }
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C. Badulescu, M. Grédiac, H. Haddadi, J.D. Mathias, X. Balandraud, H.S. Tran
Applying the grid method and infrared thermography to investigate plastic deformation in aluminium multicrystal
Mechanics of Materials 43 (1), 2011
abs doi web bib

Two different full-field measurement techniques were used in this study to investigate the mechanical response of an aluminium multicrystal specimen subjected to a tensile test. The experimental setups corresponding to each of the two techniques are first described. Strain fields were obtained with the grid method, to which a recent image treatment procedure was applied. This procedure leads to a high spatial resolution in strain and provides an accurate description of the plasticity that occurs in grains. Heat sources were derived from temperature maps captured with an infrared camera. Some typical strain maps are shown and significant heterogeneities clearly appear. These strain maps are also compared with their numerical counterparts, obtained using a finite element package suitable for crystal plasticity. The calculation of the heat source distributions from the raw temperature maps is then addressed. The strain, displacement and heat source maps were then processed together to estimate the fraction of anelastic power converted into dissipated power. This quantity was determined over the whole gauge section of the specimen and also for three individual grains.
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@article{PUB00032263, author = {Badulescu, C. and Grédiac, M. and Haddadi, H. and Mathias, J.D. and Balandraud, X. and Tran, H.S.}, title = {Applying the grid method and infrared thermography to investigate plastic deformation in aluminium multicrystal}, journal = {Mechanics of Materials}, volume = {43}, number = {1}, pages = {36-53}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00032263}, doi = {http://dx.doi.org/10.1016/j.mechmat.2010.11.001}, year = {2011}, affiliation = {UNIVERSITE DE CLERMONT FERRAND II IFMA LABORATOIRE DE MECANIQUE ET INGENIERIES CLERMONT FERRAND FRA ; UNIVERSITE DE CLERMONT FERRAND II IFMA LABORATOIRE DE MECANIQUE ET INGENIERIES CLERMONT FERRAND FRA ; CNRS INSTITUT GALILEE UNIVERSITE DE PARIS XIII UPR 9001 LABORATOIRE DES PROPRIETES MECANIQUES ET THERMODYNAMIQUE DES MATERIAUX VILLETANEUSE FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; UNIVERSITE DE CLERMONT FERRAND II IFMA LABORATOIRE DE MECANIQUE ET INGENIERIES CLERMONT FERRAND FRA ; CNRS INSTITUT GALILEE UNIVERSITE DE PARIS XIII UPR 9001 LABORATOIRE DES PROPRIETES MECANIQUES ET THERMODYNAMIQUE DES MATERIAUX VILLETANEUSE FRA}, abstract = {Two different full-field measurement techniques were used in this study to investigate the mechanical response of an aluminium multicrystal specimen subjected to a tensile test. The experimental setups corresponding to each of the two techniques are first described. Strain fields were obtained with the grid method, to which a recent image treatment procedure was applied. This procedure leads to a high spatial resolution in strain and provides an accurate description of the plasticity that occurs in grains. Heat sources were derived from temperature maps captured with an infrared camera. Some typical strain maps are shown and significant heterogeneities clearly appear. These strain maps are also compared with their numerical counterparts, obtained using a finite element package suitable for crystal plasticity. The calculation of the heat source distributions from the raw temperature maps is then addressed. The strain, displacement and heat source maps were then processed together to estimate the fraction of anelastic power converted into dissipated power. This quantity was determined over the whole gauge section of the specimen and also for three individual grains.}, }
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C. Coutand, J.D. Mathias, G. Jeronimidis, J.F. Destrebecq
TWIG: A model to simulate the gravitropic response of a tree axis in the frame of elasticity and viscoelasticity, at intra-annual time scale
Journal of Theoretical Biology 273 (1), 2011
abs doi web bib

Trees are able to maintain or modify the orientation of their axes (trunks or branches) by tropic movements. For axes in which elongation is achieved but cambial growth active, the tropic movements are due to the production of a particular wood, called reaction wood which is prestressed within the growing tree. Several models have been developed to simulate the gravitropic response of axes in trees due to the formation of reaction wood, all within the frame of linear elasticity and considering the wood maturation as instantaneous. The effect viscoelasticity of wood has, to our knowledge, never been considered. The TWIG model presented in this paper aims at simulating the gravitropic movement of a tree axis at the intra-annual scale. In this work we studied both the effect of a non-instantaneous maturation process and of viscoelasticity. For this purpose, we considered the elastic case with maturation considered as an instantaneous process as the reference. The introduction of viscoelasticity in TWIG has been done by coupling TWIG to a model developed for bridges. Indeed from a purely mechanical point of view, bridges and trees are very similar: they are structures which are built in stages, they are made of several materials (composite structures), their materials are prestressed (wood is prestressed during the maturation process as a result of polymerisation of lignin and cellulose to form the secondary cell wall and concrete is prestressed during drying). Simulations gave evidence that the reorientation process of axes can be significantly influenced by the kinetics of maturation. Moreover the model has now to be tested with more experimental data of wood viscoelasticity but it appears that in the range of a relaxation time from 0 to 50 days, viscoelasticity has an important effect on the evolution of tree shape as well as on the values of prestresses.
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@article{PUB00032275, author = {Coutand, C. and Mathias, J.D. and Jeronimidis, G. and Destrebecq, J.F.}, title = {TWIG: A model to simulate the gravitropic response of a tree axis in the frame of elasticity and viscoelasticity, at intra-annual time scale}, journal = {Journal of Theoretical Biology}, volume = {273}, number = {1}, pages = {115-129}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00032275}, doi = {http://dx.doi.org/10.1016/j.jtbi.2010.12.027}, year = {2011}, affiliation = {INRA UMR 547 PIAF CLERMONT FERRAND FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; UNIVERSITY OF READING SCHOOL OF CONSTRUCTION MANAGEMENT AND ENGINEERING READING GBR ; UNIVERSITE DE CLERMONT FERRAND II EA 3867 LABORATOIRE DE MECANIQUE ET INGENIERIES CLERMONT FERRAND FRA}, abstract = {Trees are able to maintain or modify the orientation of their axes (trunks or branches) by tropic movements. For axes in which elongation is achieved but cambial growth active, the tropic movements are due to the production of a particular wood, called reaction wood which is prestressed within the growing tree. Several models have been developed to simulate the gravitropic response of axes in trees due to the formation of reaction wood, all within the frame of linear elasticity and considering the wood maturation as instantaneous. The effect viscoelasticity of wood has, to our knowledge, never been considered. The TWIG model presented in this paper aims at simulating the gravitropic movement of a tree axis at the intra-annual scale. In this work we studied both the effect of a non-instantaneous maturation process and of viscoelasticity. For this purpose, we considered the elastic case with maturation considered as an instantaneous process as the reference. The introduction of viscoelasticity in TWIG has been done by coupling TWIG to a model developed for bridges. Indeed from a purely mechanical point of view, bridges and trees are very similar: they are structures which are built in stages, they are made of several materials (composite structures), their materials are prestressed (wood is prestressed during the maturation process as a result of polymerisation of lignin and cellulose to form the secondary cell wall and concrete is prestressed during drying). Simulations gave evidence that the reorientation process of axes can be significantly influenced by the kinetics of maturation. Moreover the model has now to be tested with more experimental data of wood viscoelasticity but it appears that in the range of a relaxation time from 0 to 50 days, viscoelasticity has an important effect on the evolution of tree shape as well as on the values of prestresses.}, }
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A. Deheeger, J.D. Mathias, M. Grédiac
Studying the thermoviscoelastic response of the Redux 312 adhesive. Part 2: Modeling
International Journal of Adhesion and Adhesives 31 (2), 2011
abs doi web bib

The aim of this work is to propose a numerical model of a bonded joint that takes into account the thermoviscoelastic response of the adhesive to compute the stress distribution in the adhesive as well as in the adherends. The adhesive is assumed to obey a generalized Maxwell model. The effect of temperature is taken into account by considering that the branches of the model change with temperature. The numerical solution is obtained iteratively. The particular case of the Redux 312 adhesive is then considered as an example. The procedure is applied in various cases exhibiting an increasing complexity. Some significant differences are observed with the usual solution obtained within the framework of elasticity if the effects of both temperature and time are taken into account.
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@article{PUB00032266, author = {Deheeger, A. and Mathias, J.D. and Grédiac, M.}, title = {Studying the thermoviscoelastic response of the Redux 312 adhesive. Part 2: Modeling}, journal = {International Journal of Adhesion and Adhesives}, volume = {31}, number = {2}, pages = {57-67}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00032266}, doi = {http://dx.doi.org/10.1016/j.ijadhadh.2010.11.009}, year = {2011}, affiliation = {UNIVERSITE DE CLERMONT FERRAND II EA 3867 LABORATOIRE DE MECANIQUE ET INGENIERIES CLERMONT FERRAND FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; UNIVERSITE DE CLERMONT FERRAND II EA 3867 LABORATOIRE DE MECANIQUE ET INGENIERIES CLERMONT FERRAND FRA}, abstract = {The aim of this work is to propose a numerical model of a bonded joint that takes into account the thermoviscoelastic response of the adhesive to compute the stress distribution in the adhesive as well as in the adherends. The adhesive is assumed to obey a generalized Maxwell model. The effect of temperature is taken into account by considering that the branches of the model change with temperature. The numerical solution is obtained iteratively. The particular case of the Redux 312 adhesive is then considered as an example. The procedure is applied in various cases exhibiting an increasing complexity. Some significant differences are observed with the usual solution obtained within the framework of elasticity if the effects of both temperature and time are taken into account.}, }
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A. Deheeger, J.D. Mathias, M. Grédiac, V. Verney
Studying the thermoviscoelastic response of the Redux 312 adhesive. Part 1: Experimental characterization
International Journal of Adhesion and Adhesives 31 (2), 2011
abs doi web bib

The aim of this study is to investigate the thermoviscoelastic behaviour of the Redux 312 structural adhesive. Two types of tests are performed on bulk specimens: dynamic tests over a wide range of temperature and stressrelaxation tests for five temperatures ranging between -50 and 70 °C. Dynamic tests clearly show that the shear modulus of the adhesive decreases with temperature. The parameters governing the Maxwell model used to model the viscoelastic properties of the adhesive are identified with the curves obtained with the stressrelaxation tests for the five different temperatures. The procedure used to identify these parameters takes into account the evolution of these parameters with temperature. Results obtained are presented and discussed throughout the paper.
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@article{PUB00032265, author = {Deheeger, A. and Mathias, J.D. and Grédiac, M. and Verney, V.}, title = {Studying the thermoviscoelastic response of the Redux 312 adhesive. Part 1: Experimental characterization}, journal = {International Journal of Adhesion and Adhesives}, volume = {31}, number = {2}, pages = {68-74}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00032265}, doi = {http://dx.doi.org/10.1016/j.ijadhadh.2010.11.008}, year = {2011}, affiliation = {UNIVERSITE DE CLERMONT FERRAND II EA 3867 LABORATOIRE DE MECANIQUE ET INGENIERIES CLERMONT FERRAND FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; UNIVERSITE DE CLERMONT FERRAND II EA 3867 LABORATOIRE DE MECANIQUE ET INGENIERIES CLERMONT FERRAND FRA ; UNIVERSITE DE CLERMONT FERRAND II LPMM CLERMONT FERRAND FRA}, abstract = {The aim of this study is to investigate the thermoviscoelastic behaviour of the Redux 312 structural adhesive. Two types of tests are performed on bulk specimens: dynamic tests over a wide range of temperature and stressrelaxation tests for five temperatures ranging between -50 and 70 °C. Dynamic tests clearly show that the shear modulus of the adhesive decreases with temperature. The parameters governing the Maxwell model used to model the viscoelastic properties of the adhesive are identified with the curves obtained with the stressrelaxation tests for the five different temperatures. The procedure used to identify these parameters takes into account the evolution of these parameters with temperature. Results obtained are presented and discussed throughout the paper.}, }
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F. Jabot, J. Chave
Analyzing tropical forest tree species abundance distributions using a nonneutral model and through approximate Bayesian inference
American Naturalist 178 (2), 2011
abs doi web bib

The neutral theory of biodiversity challenges the classical niche-based view of ecological communities, where species attributes and environmental conditions jointly determine community composition. Functional equivalence among species, as assumed by neutral ecological theory, has been recurrently falsified, yet many patterns of tropical tree communities appear consistent with neutral predictions. This may mean that neutral theory is a good first-approximation theory or that species abundance data sets contain too little information to reject neutrality. Here we present a simple test of neutrality based on species abundance distributions in ecological communities. Based on this test, we show that deviations from neutrality are more frequent than previously thought in tropical forest trees, especially at small spatial scales. We then develop a nonneutral model that generalizes Hubbell's dispersal-limited neutral model in a simple way by including one additional parameter of frequency dependence. We also develop a statistical method to infer the parameters of this model from empirical data by approximate Bayesian computation. In more than half of the permanent tree plots, we show that our new model fits the data better than does the neutral model. Finally, we discuss whether observed deviations from neutrality may be interpreted as the signature of environmental filtering on tropical tree species abundance distributions.
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@article{PUB00033035, author = {Jabot, F. and Chave, J.}, title = {Analyzing tropical forest tree species abundance distributions using a nonneutral model and through approximate Bayesian inference}, title = {Analyse de distribution d'abondance d'arbres en forêt tropicale à partir d'un modèle non neutre et par inférence Bayésienne approchée}, journal = {American Naturalist}, volume = {178}, number = {2}, pages = {E37-E47}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00033035 / http://www.jstor.org/stable/10.1086/660829}, doi = {http://dx.doi.org/10.1086/660829}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CNRS UNIVERSITE PAUL SABATIER TOULOUSE LABORATOIRE EVOLUTION ET DIVERSITE BIOLOGIQUE TOULOUSE FRA}, abstract = {The neutral theory of biodiversity challenges the classical niche-based view of ecological communities, where species attributes and environmental conditions jointly determine community composition. Functional equivalence among species, as assumed by neutral ecological theory, has been recurrently falsified, yet many patterns of tropical tree communities appear consistent with neutral predictions. This may mean that neutral theory is a good first-approximation theory or that species abundance data sets contain too little information to reject neutrality. Here we present a simple test of neutrality based on species abundance distributions in ecological communities. Based on this test, we show that deviations from neutrality are more frequent than previously thought in tropical forest trees, especially at small spatial scales. We then develop a nonneutral model that generalizes Hubbell's dispersal-limited neutral model in a simple way by including one additional parameter of frequency dependence. We also develop a statistical method to infer the parameters of this model from empirical data by approximate Bayesian computation. In more than half of the permanent tree plots, we show that our new model fits the data better than does the neutral model. Finally, we discuss whether observed deviations from neutrality may be interpreted as the signature of environmental filtering on tropical tree species abundance distributions.}, }
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H. Mahboubi, S. Bimonte, G. Deffuant
Analyzing demographic and economic simulation model results: a semi-automatic spatial OLAP approach
Lecture Notes in Computer Science 6782, 2011
abs doi web bib

In this paper, we present a semi-automatic SOLAP approach specially dedicated to the analysis of spatial model simulation results. We illustrate it on demographic and economic data of rural municipalities resulting from a model developed in the context of the european project PRIMA.
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@article{PUB00033066, author = {Mahboubi, H. and Bimonte, S. and Deffuant, G.}, title = {Analyzing demographic and economic simulation model results: a semi-automatic spatial OLAP approach}, title = {Analyse des résultats de modèles de simulation démographiques et économiques : une approche OLAP Spatial semi-automatique }, journal = {Lecture Notes in Computer Science}, volume = {6782}, pages = {17-31}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00033066}, doi = {http://dx.doi.org/10.1007/978-3-642-21928-3_2}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR TSCF FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {In this paper, we present a semi-automatic SOLAP approach specially dedicated to the analysis of spatial model simulation results. We illustrate it on demographic and economic data of rural municipalities resulting from a model developed in the context of the european project PRIMA.}, }
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J.D. Mathias, N. Tessier Doyen, P. Michaud
Development of a chitosan-based biofoam: Application to the processing of a porous ceramic material
International Journal of Molecular Sciences 12 (2), 2011
abs doi web bib

Developing biofoams constitutes a challenging issue for several applications. The present study focuses on the development of a chitosan-based biofoam. Solutions of chitosan in acetic acid were dried under vacuum to generate foams with high-order structures. Chitosan concentration influenced significantly the morphology of developed porosity and the organization of pores in the material. Physico-chemical characterizations were performed to investigate the effects of chitosan concentration on density and thermal conductivity of foams. Even if chitosan-based biofoams exhibit interesting insulating properties (typically around 0.06 W·m-1·K-1), it has been shown that their durabilities are limited when submitted to a wet media. So, a way of application consists to elaborate a ceramic material with open porosity from a slurry prepared with an organic solvent infiltrating the porous network of the foam.
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@article{PUB00032271, author = {Mathias, J.D. and Tessier Doyen, N. and Michaud, P.}, title = {Development of a chitosan-based biofoam: Application to the processing of a porous ceramic material}, journal = {International Journal of Molecular Sciences}, volume = {12}, number = {2}, pages = {1175 -1186}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00032271}, doi = {http://dx.doi.org/10.3390/ijms12021175}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; UNIVERSITE DE LIMOGES LABORATOIRE GEMH LIMOGES FRA ; UNIVERSITE DE CLERMONT FERRAND II POLYTECH CLERMONT LABORATOIRE DE GENIE CHIMIQUE ET BIOCHIMIQUE FRA}, abstract = {Developing biofoams constitutes a challenging issue for several applications. The present study focuses on the development of a chitosan-based biofoam. Solutions of chitosan in acetic acid were dried under vacuum to generate foams with high-order structures. Chitosan concentration influenced significantly the morphology of developed porosity and the organization of pores in the material. Physico-chemical characterizations were performed to investigate the effects of chitosan concentration on density and thermal conductivity of foams. Even if chitosan-based biofoams exhibit interesting insulating properties (typically around 0.06 W·m-1·K-1), it has been shown that their durabilities are limited when submitted to a wet media. So, a way of application consists to elaborate a ceramic material with open porosity from a slurry prepared with an organic solvent infiltrating the porous network of the foam.}, }
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T.A. Mrkvicka, F. Goreaud, J. Chadoeuf
Spatial prediction of the mark of a location-dependent marked point process: How the use of a parametric model may improve prediction
Kybernetika 47 (5), 2011
abs web bib

We discuss the prediction of a spatial variable of a multivariate mark composed of both dependent and explanatory variables. The marks are location-dependent and they are attached to a point process. We assume that the marks are assigned independently, conditionally on an unknown underlying parametric field. We compare (i) the classical non-parametric Nadaraya-Watson kernel estimator based on the dependent variable (ii) estimators obtained under an assumption of local parametric model where explanatory variables of the local model are estimated through kernel estimation and (iii) a kernel estimator of the result of the parametric model, supposed here to be a Uniformly Minimum Variance Unbiased Estimator derived under the local parametric model when complete and sufficient statistics are available. The comparison is done asymptotically and by simulations in special cases. The procedure for better estimator selection is then illustrated on a real-life data set.
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@article{PUB00035000, author = {Mrkvicka, T.A. and Goreaud, F. and Chadoeuf, J.}, title = {Spatial prediction of the mark of a location-dependent marked point process: How the use of a parametric model may improve prediction}, journal = {Kybernetika}, volume = {47}, number = {5}, pages = {696 -714}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00035000}, year = {2011}, affiliation = {UNIVERSITY OF SOUTH BOHEMIA CESKE CZE ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; INRA AVIGNON FRA}, abstract = {We discuss the prediction of a spatial variable of a multivariate mark composed of both dependent and explanatory variables. The marks are location-dependent and they are attached to a point process. We assume that the marks are assigned independently, conditionally on an unknown underlying parametric field. We compare (i) the classical non-parametric Nadaraya-Watson kernel estimator based on the dependent variable (ii) estimators obtained under an assumption of local parametric model where explanatory variables of the local model are estimated through kernel estimation and (iii) a kernel estimator of the result of the parametric model, supposed here to be a Uniformly Minimum Variance Unbiased Estimator derived under the local parametric model when complete and sufficient statistics are available. The comparison is done asymptotically and by simulations in special cases. The procedure for better estimator selection is then illustrated on a real-life data set.}, }
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M.A. Ngo Bieng, C. Ginisty, F. Goreaud
Point process models for mixed sessile forest stands
Annals of Forest Science 68 (2), 2011
abs doi web bib

- Background: Growth modelling of complex stands calls for the use of spatially explicit single-tree models. Such models require spatially explicit tree locations as the initial state to run simulations. Given the cost of such data, virtual forest stands, where tree locations are simulated, are generally used as the initial state. - Purpose: The purpose of this study was to present models for simulating the spatial structure of complex stands. It focused on mixed oakScots pine stands of the Orleans forest (France) and on the spatial structure of canopy trees. - Methods: The spatial structure of the oakpine stands was modelled with appropriate point process models. The models consisted of a combination of Poisson, NeymanScott and Soft core. Simulation of the point process models was based on precise characterisation of the studied stands. Twenty-five 1-ha oakpine plots were characterised by the Ripley function. The models were then fitted to the identified spatial structure to reproduce univariate and bivariate spatial patterns in each spatial type. - Conclusion: This paper provides an approach for general modelling of a spatial structure of a particular mixture and may be enriched by other point process models for other types of mixed stand.
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@article{PUB00032477, author = {Ngo Bieng, M.A. and Ginisty, C. and Goreaud, F.}, title = {Point process models for mixed sessile forest stands}, journal = {Annals of Forest Science}, volume = {68}, number = {2}, pages = {267-274}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00032477}, doi = {http://dx.doi.org/10.1007/s13595-011-0033-y}, year = {2011}, affiliation = {CEMAGREF NOGENT SUR VERNISSON UR EFNO FRA ; CEMAGREF NOGENT SUR VERNISSON UR EFNO FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {- Background: Growth modelling of complex stands calls for the use of spatially explicit single-tree models. Such models require spatially explicit tree locations as the initial state to run simulations. Given the cost of such data, virtual forest stands, where tree locations are simulated, are generally used as the initial state. - Purpose: The purpose of this study was to present models for simulating the spatial structure of complex stands. It focused on mixed oakScots pine stands of the Orleans forest (France) and on the spatial structure of canopy trees. - Methods: The spatial structure of the oakpine stands was modelled with appropriate point process models. The models consisted of a combination of Poisson, NeymanScott and Soft core. Simulation of the point process models was based on precise characterisation of the studied stands. Twenty-five 1-ha oakpine plots were characterised by the Ripley function. The models were then fitted to the identified spatial structure to reproduce univariate and bivariate spatial patterns in each spatial type. - Conclusion: This paper provides an approach for general modelling of a spatial structure of a particular mixture and may be enriched by other point process models for other types of mixed stand.}, }
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L. Chapel, X. Castello, C. Bernard, G. Deffuant, V. Eguiluz, S. Martin, M. San Miguel
Viability and resilience of languages in competition
PLoS One 5 (1 (e8681)), 2010
abs doi web bib

We study the viability and resilience of languages, using a simple dynamical model of two languages in competition. Assuming that public action can modify the prestige of a language in order to avoid language extinction, we analyze two cases: (i) the prestige can only take two values, (ii) it can take any value but its change at each time step is bounded. In both cases, we determine the viability kernel, that is, the set of states for which there exists an action policy maintaining the coexistence of the two languages, and we define such policies. We also study the resilience of the languages and identify configurations from where the system can return to the viability kernel (definite resilience), or where one of the languages is lead to disappear (zero resilience). Within our current framework, the maintenance of a bilingual society is shown to be possible by introducing the prestige of a language as a control variable.
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@article{PUB00027990, author = {Chapel, L. and Castello, X. and Bernard, C. and Deffuant, G. and Eguiluz, V. and Martin, S. and San Miguel, M.}, title = {Viability and resilience of languages in competition}, title = {Viabilité et résilience de langues en compétitions}, journal = {PLoS One}, volume = {5}, number = {1 (e8681)}, pages = {11}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00027990 / http://www.plosone.org/article/info:doi/10.1371/journal.pone.0008681}, doi = {http://dx.doi.org/10.1371/journal.pone.0008681}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; IFISC ESP ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; IFISC ESP ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; IFISC ESP}, abstract = {We study the viability and resilience of languages, using a simple dynamical model of two languages in competition. Assuming that public action can modify the prestige of a language in order to avoid language extinction, we analyze two cases: (i) the prestige can only take two values, (ii) it can take any value but its change at each time step is bounded. In both cases, we determine the viability kernel, that is, the set of states for which there exists an action policy maintaining the coexistence of the two languages, and we define such policies. We also study the resilience of the languages and identify configurations from where the system can return to the viability kernel (definite resilience), or where one of the languages is lead to disappear (zero resilience). Within our current framework, the maintenance of a bilingual society is shown to be possible by introducing the prestige of a language as a control variable.}, }
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F. Chuffart, N. Dumoulin, T. Faure, G. Deffuant
SimExplorer: programming experimental design on models and managing quality of modelling process
International Journal of Agricultural and Environmental Information Systems IJAEIS 1 (1), 2010
abs doi web bib

This article describes Simexplorer, a computer framework for managing simulation experiments and, to some extent, the scientific quality of the modelling process. An information system, included in the framework, insures the traceability of the experiments and their reproducibility and thus contributes to the modelling process quality management. Moreover, this information system provides facilities for sharing and exchanging components of experiment scenarios. The authors illustrate the use of the framework on a simple example of modelling process.
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@article{PUB00028275, author = {Chuffart, F. and Dumoulin, N. and Faure, T. and Deffuant, G.}, title = {SimExplorer: programming experimental design on models and managing quality of modelling process}, title = {SimExplorer : programmer des plans d'expérience sur les modèles et gérer la traçabilité des expériences}, journal = {International Journal of Agricultural and Environmental Information Systems IJAEIS}, volume = {1}, number = {1}, pages = {55-68}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00028275}, doi = {http://dx.doi.org/10.4018/jaeis.2010101304}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {This article describes Simexplorer, a computer framework for managing simulation experiments and, to some extent, the scientific quality of the modelling process. An information system, included in the framework, insures the traceability of the experiments and their reproducibility and thus contributes to the modelling process quality management. Moreover, this information system provides facilities for sharing and exchanging components of experiment scenarios. The authors illustrate the use of the framework on a simple example of modelling process. }, }
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G. Deffuant, S. Huet
Collective increase of first impression bias
Complexity 15 (5), 2010
abs web bib

We propose a simple model of first impression bias (FIB), where agents tend to ignore features which contradict their initial view. We consider a population of agents which are all in contact with a media, communicating randomly chosen features of an object. In some cases, we observe on simulations that FIB is significantly more frequent when the agents interact with each other than when they are only in contact with the media. We design an analytical aggregated model of the global agent-based model behaviour which helps to explain the higher number of FIB due to the interactions.
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@article{PUB00026808, author = {Deffuant, G. and Huet, S.}, title = {Collective increase of first impression bias}, title = {Effets amplificateurs de l'interaction sur le biais de primauté}, journal = {Complexity}, volume = {15}, number = {5}, pages = {25-33}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00026808 / http://www3.interscience.wiley.com}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {We propose a simple model of first impression bias (FIB), where agents tend to ignore features which contradict their initial view. We consider a population of agents which are all in contact with a media, communicating randomly chosen features of an object. In some cases, we observe on simulations that FIB is significantly more frequent when the agents interact with each other than when they are only in contact with the media. We design an analytical aggregated model of the global agent-based model behaviour which helps to explain the higher number of FIB due to the interactions.}, }
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F. Gargiulo, S. Ternès, S. Huet, G. Deffuant
An iterative approach for generating statistically realistic populations of households
PLoS One 5 (1), 2010
abs doi web bib

Many different simulation frameworks, in different topics, need to treat realistic datasets to initialize and calibrate the system. A precise reproduction of initial states is extremely important to obtain reliable forecast from the model. This paper proposes an algorithm to create an artificial population where individuals are described by their age, and are gathered in households respecting a variety of statistical constraints (distribution of household types, sizes, age of household head, difference of age between partners and among parents and children). Such a population is often the initial state of microsimulation or (agent) individual-based models. To get a realistic distribution of households is often very important, because this distribution has an impact on the demographic evolution. Usual techniques from microsimulation approach cross different sources of aggregated data for generating individuals. In our case the number of combinations of different households (types, sizes, age of participants) makes it computationally difficult to use directly such methods. Hence we developed a specific algorithm to make the problem more easily tractable. We generate the populations of two pilot municipalities in Auvergne region (France) to illustrate the approach. The generated populations show a good agreement with the available statistical datasets (not used for the generation) and are obtained in a reasonable computational time. / Dans beaucoup de domaines, la simulation nécessite le traitement de données réalistes pour initialiser et calibrer le système. Une reproduction précise de l'état initial contribue largement à l'obtention de prédictions fiables. Ce papier propose un algorithme de création d'une population artificielle composée d'individus décrits par leur âge. Ces individus sont membres de ménages qui respectent une variété de contraintes statistiques (distribution des types de ménages, différences d'âge dans les couples ou entre parents et enfants). Une telle population sert souvent d'état initial pour un modèle de microsimulation ou un modèle agent (ou individus-centré). La qualité de la distribution des ménages est importantes car cette distribution a un impact sur l'évolution démographique. Les techniques usuelles de microsimulation croisent différentes sources de données à des niveaux agrégés pour générer les individus. Dans notre cas, le nombre de combinaisons de différents ménages (types, taille, âge des membres) interdit une telle approche du fait de sa difficulté computationnelle. Nous proposons donc un algorithme permettant la génération relativement rapide et simple d'une telle population. Nous générons la population de deux municipalités Auvergnates pour illustrer l'approche. Les populations générées sont évaluées de bonne qualité par confrontation à des propriétés statistiques - non utilisées pour la génération - des communes qu'elles représentent. Elles sont obtenues en un temps raisonnable.
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@article{PUB00027953, author = {Gargiulo, F. and Ternès, S. and Huet, S. and Deffuant, G.}, title = {An iterative approach for generating statistically realistic populations of households}, title = {Une approche itérative pour la génération de populations de ménages réalistes du point de vue statistique}, journal = {PLoS One}, volume = {5}, number = {1}, pages = {9}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00027953 / http://www.plosone.org/article/info:doi/10.1371/journal.pone.0008828}, doi = {http://dx.doi.org/10.1371/journal.pone.0008828 }, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {Many different simulation frameworks, in different topics, need to treat realistic datasets to initialize and calibrate the system. A precise reproduction of initial states is extremely important to obtain reliable forecast from the model. This paper proposes an algorithm to create an artificial population where individuals are described by their age, and are gathered in households respecting a variety of statistical constraints (distribution of household types, sizes, age of household head, difference of age between partners and among parents and children). Such a population is often the initial state of microsimulation or (agent) individual-based models. To get a realistic distribution of households is often very important, because this distribution has an impact on the demographic evolution. Usual techniques from microsimulation approach cross different sources of aggregated data for generating individuals. In our case the number of combinations of different households (types, sizes, age of participants) makes it computationally difficult to use directly such methods. Hence we developed a specific algorithm to make the problem more easily tractable. We generate the populations of two pilot municipalities in Auvergne region (France) to illustrate the approach. The generated populations show a good agreement with the available statistical datasets (not used for the generation) and are obtained in a reasonable computational time. / Dans beaucoup de domaines, la simulation nécessite le traitement de données réalistes pour initialiser et calibrer le système. Une reproduction précise de l'état initial contribue largement à l'obtention de prédictions fiables. Ce papier propose un algorithme de création d'une population artificielle composée d'individus décrits par leur âge. Ces individus sont membres de ménages qui respectent une variété de contraintes statistiques (distribution des types de ménages, différences d'âge dans les couples ou entre parents et enfants). Une telle population sert souvent d'état initial pour un modèle de microsimulation ou un modèle agent (ou individus-centré). La qualité de la distribution des ménages est importantes car cette distribution a un impact sur l'évolution démographique. Les techniques usuelles de microsimulation croisent différentes sources de données à des niveaux agrégés pour générer les individus. Dans notre cas, le nombre de combinaisons de différents ménages (types, taille, âge des membres) interdit une telle approche du fait de sa difficulté computationnelle. Nous proposons donc un algorithme permettant la génération relativement rapide et simple d'une telle population. Nous générons la population de deux municipalités Auvergnates pour illustrer l'approche. Les populations générées sont évaluées de bonne qualité par confrontation à des propriétés statistiques - non utilisées pour la génération - des communes qu'elles représentent. Elles sont obtenues en un temps raisonnable.}, }
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F. Gargiulo, S. Huet
Opinion dynamics in a group-based society
EPL 91 (58004), 2010
abs doi web bib

Many models have been proposed to analyze the evolution of opinion structure due to the interaction of individuals in their social environment. Such models analyze the spreading of ideas both in completely interacting backgrounds and on social networks, where each person has a finite set of interlocutors. In this paper we analyze the reciprocal feedback between the opinions of the individuals and the structure of the interpersonal relationships at the level of community structures. For this purpose we define a group based random network and we study how this structure co-evolves with opinion dynamics processes. We observe that the adaptive network structure affects the opinion dynamics process helping the consensus formation. The results also show interesting behaviors in regards to the size distribution of the groups and their correlation with opinion structure.
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@article{PUB00029366, author = {Gargiulo, F. and Huet, S.}, title = {Opinion dynamics in a group-based society}, title = {Dynamique d'opinion d'une société organisée en groupes}, journal = {EPL}, volume = {91}, number = {58004}, pages = {1-6}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00029366}, doi = {http://dx.doi.org/10.1209/0295-5075/91/58004}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {Many models have been proposed to analyze the evolution of opinion structure due to the interaction of individuals in their social environment. Such models analyze the spreading of ideas both in completely interacting backgrounds and on social networks, where each person has a finite set of interlocutors. In this paper we analyze the reciprocal feedback between the opinions of the individuals and the structure of the interpersonal relationships at the level of community structures. For this purpose we define a group based random network and we study how this structure co-evolves with opinion dynamics processes. We observe that the adaptive network structure affects the opinion dynamics process helping the consensus formation. The results also show interesting behaviors in regards to the size distribution of the groups and their correlation with opinion structure.}, }
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S. Huet, G. Deffuant
Openness leads to opinion stability and narrowness to volatility
Advances in Complex Systems 13 (3), 2010
abs doi web bib

We propose a new opinion dynamic model based on the experiments and results of Wood et al (1996). We consider pairs of individuals discussing on two attitudinal dimensions, and we suppose that one dimension is important, the other secondary. The dynamics are mainly ruled by the level of agreement on the main dimension. If two individuals are close on the main dimension, then they attract each other on the main and on the secondary dimensions, whatever their disagreement on the secondary dimension. If they are far from each other on the main dimension, then too much proximity on the secondary dimension is uncomfortable, and generates rejection on this dimension. The proximity is defined by comparing the opinion distance with a threshold called attraction threshold on the main dimension and rejection threshold on the secondary dimension. With such dynamics, a population with opinions initially uniformly drawn evolves to a set of clusters, inside which secondary opinions fluctuate more or less depending on threshold values. We observe that a low attraction threshold favours fluctuations on the secondary dimension, especially when the rejection threshold is high. The opinion evolutions of the model can be related to some stylised facts.
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@article{PUB00029104, author = {Huet, S. and Deffuant, G.}, title = {Openness leads to opinion stability and narrowness to volatility}, title = {L'ouverture d'esprit entraîne la stabilité des opinions tandis que le contraire entraîne leur volatilité}, journal = {Advances in Complex Systems}, volume = {13}, number = {3}, pages = {405-423}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00029104}, doi = {http://dx.doi.org/10.1142/10.1142/S0219525910002633}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {We propose a new opinion dynamic model based on the experiments and results of Wood et al (1996). We consider pairs of individuals discussing on two attitudinal dimensions, and we suppose that one dimension is important, the other secondary. The dynamics are mainly ruled by the level of agreement on the main dimension. If two individuals are close on the main dimension, then they attract each other on the main and on the secondary dimensions, whatever their disagreement on the secondary dimension. If they are far from each other on the main dimension, then too much proximity on the secondary dimension is uncomfortable, and generates rejection on this dimension. The proximity is defined by comparing the opinion distance with a threshold called attraction threshold on the main dimension and rejection threshold on the secondary dimension. With such dynamics, a population with opinions initially uniformly drawn evolves to a set of clusters, inside which secondary opinions fluctuate more or less depending on threshold values. We observe that a low attraction threshold favours fluctuations on the secondary dimension, especially when the rejection threshold is high. The opinion evolutions of the model can be related to some stylised facts.}, }
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H.S. Kim, M. Cho, J. Lee, A. Deheeger, M. Grédiac, J.D. Mathias
Three dimensional stress analysis of a composite patch using stress functions
International Journal of Mechanical Sciences 52 (12), 2010
abs doi web bib

A stress function-based analysis is proposed to provide a simple and efficient approximation method of three-dimensional (3D) state of stress that exists near the free edge of bonded composite patches. In order to apply plane strain assumption in a composite patch, a linear superposition of sliced section from a bonded patch is used. In addition, to describe the load transfer mechanism from the substrate to the composite patch, a simple shear lag model is introduced. The 3D stress behavior at the free edge of the composite patch is modeled by Lekhnitskii stress functions, and the governing equations of the given composite patch are obtained by applying the principle of complementary virtual work. After a suitable expansion of the functions, the governing equations are transformed into two coupled ordinary differential equations, and they are solved by a general eigenvalue solution procedure. As the number of base functions increases, the interlaminar stresses converge. The interlaminar stresses reach maximum at the free edge and decrease sharply at the inner part of the patch. The interlaminar stresses are concentrated at the interface between the layers because of the mismatch of material properties and the geometric singularity. Since the proposed method accurately predicts the 3D stresses in a composite patch bonded on the metal substrate, it can be used as a simple and efficient analytical tool for designing such structural components.
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@article{PUB00030654, author = {Kim, H.S. and Cho, M. and Lee, J. and Deheeger, A. and Grédiac, M. and Mathias, J.D.}, title = {Three dimensional stress analysis of a composite patch using stress functions }, journal = {International Journal of Mechanical Sciences}, volume = {52}, number = {12}, pages = {1646-1659}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00030654 / http://www.sciencedirect.com}, doi = {http://dx.doi.org/10.1016/j.ijmecsci.2010.08.006 }, year = {2010}, affiliation = {DEPARTMENT OF MECHNICAL ROBOTICS AND ENERGY ENGINEERING DONGGUK UNIVERSITY SEOUL KOR ; SCHOOL OF MECHANICAL AND AEROSPACE ENGINEERING SEOUL NATIONAL UNIVERSITY KOR ; SCHOOL OF MECHANICAL AND AEROSPACE ENGINEERING SEOUL NATIONAL UNIVERSITY KOR ; IFMA UNIVERSITE DE CLERMONT FERRAND II FRA ; IFMA UNIVERSITE DE CLERMONT FERRAND II FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {A stress function-based analysis is proposed to provide a simple and efficient approximation method of three-dimensional (3D) state of stress that exists near the free edge of bonded composite patches. In order to apply plane strain assumption in a composite patch, a linear superposition of sliced section from a bonded patch is used. In addition, to describe the load transfer mechanism from the substrate to the composite patch, a simple shear lag model is introduced. The 3D stress behavior at the free edge of the composite patch is modeled by Lekhnitskii stress functions, and the governing equations of the given composite patch are obtained by applying the principle of complementary virtual work. After a suitable expansion of the functions, the governing equations are transformed into two coupled ordinary differential equations, and they are solved by a general eigenvalue solution procedure. As the number of base functions increases, the interlaminar stresses converge. The interlaminar stresses reach maximum at the free edge and decrease sharply at the inner part of the patch. The interlaminar stresses are concentrated at the interface between the layers because of the mismatch of material properties and the geometric singularity. Since the proposed method accurately predicts the 3D stresses in a composite patch bonded on the metal substrate, it can be used as a simple and efficient analytical tool for designing such structural components.}, }
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N. Mabrouk, G. Deffuant, T. Tolker Nielsen, C. Lobry
Bacteria can form interconnected microcolonies when a self-excreted product reduces their surface motility: evidence from individual-based model simulations
Theory in Biosciences 129 (1), 2010
abs web bib

Recent experimental observations of Pseudomonas aeruginosa, a model bacterium in biofilm research, reveal that, under specific growth conditions, bacterial cells form patterns of interconnected microcolonies. In the present work, we use an individual-based model to assess the involvement of bacteria motility and self-produced extracellular substance in the formation of these patterns. In our simulations, the pattern of interconnected microcolonies appears only when bacteria motility is reduced by excreted extracellular macromolecules. Immotile bacteria form isolated microcolonies and constantly motile bacteria form flat biofilms. Based on experimental data and computer simulations, we suggest a mechanism that could be responsible for these interconnected microcolonies. / Des observations récentes de Pseudomonas aeruginosa, une bactérie-modèle dans la recherche sur les biofilms, ont montré que sous certaines conditions cette bactérie forme des colonies interconnectées. Dans ce travail nous utilisons un modèle individus-centré pour explorer le rôle de la mobilité des bactéries et la production d'exopolymère dans la formation de ces structures. Nos simulations montrent que les microcolonies interconnectées se forment lorsque la mobilité des bactéries est réduite par l'excrétion de ma cromolécules. Les bactéries immobiles forment des microcolonies isolées et les bactéries mobiles forment des biofilms plats. En se basant sur les observations expérimentales et les simulations numériques nous suggérant que la réduction de la mobilité des bactéries par la production d'exopolymère pourrait être responsable de ces structures.
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@article{PUB00027304, author = {Mabrouk, N. and Deffuant, G. and Tolker Nielsen, T. and Lobry, C.}, title = {Bacteria can form interconnected microcolonies when a self-excreted product reduces their surface motility: evidence from individual-based model simulations}, title = {Modélisation individus-centrée de la formation de colonies connectées dans un système de bactéries mobiles excrétant un exopolymère qui réduit leur mobilité}, journal = {Theory in Biosciences}, volume = {129}, number = {1}, pages = {1-13}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00027304}, year = {2010}, affiliation = {INRIA MONTPELLIER MERE PROJECT FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; UNIVERSITY OF COPENHAGEN DEPARTMENT OF INTERNATIONAL HEALTH DNK ; INRIA MONTPELLIER MERE PROJECT FRA}, ISBNISSN = {ISSN: 1431-7613 }, abstract = {Recent experimental observations of Pseudomonas aeruginosa, a model bacterium in biofilm research, reveal that, under specific growth conditions, bacterial cells form patterns of interconnected microcolonies. In the present work, we use an individual-based model to assess the involvement of bacteria motility and self-produced extracellular substance in the formation of these patterns. In our simulations, the pattern of interconnected microcolonies appears only when bacteria motility is reduced by excreted extracellular macromolecules. Immotile bacteria form isolated microcolonies and constantly motile bacteria form flat biofilms. Based on experimental data and computer simulations, we suggest a mechanism that could be responsible for these interconnected microcolonies. / Des observations récentes de Pseudomonas aeruginosa, une bactérie-modèle dans la recherche sur les biofilms, ont montré que sous certaines conditions cette bactérie forme des colonies interconnectées. Dans ce travail nous utilisons un modèle individus-centré pour explorer le rôle de la mobilité des bactéries et la production d'exopolymère dans la formation de ces structures. Nos simulations montrent que les microcolonies interconnectées se forment lorsque la mobilité des bactéries est réduite par l'excrétion de ma cromolécules. Les bactéries immobiles forment des microcolonies isolées et les bactéries mobiles forment des biofilms plats. En se basant sur les observations expérimentales et les simulations numériques nous suggérant que la réduction de la mobilité des bactéries par la production d'exopolymère pourrait être responsable de ces structures.}, }
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H. Mahboubi, T. Faure, S. Bimonte, G. Deffuant, J.P. Chanet, F. Pinet
A multidimensional model for data warehouses of simulation results
International Journal of Agricultural and Environmental Information Systems IJAEIS 1 (2), 2010
abs doi web bib

This paper deals with the multidimensional modeling of a data warehouse for simulation results. It aims at answering new needs for data management which appear when exploring complex simulation models. Indeed, testing different parameter values and different versions of such models produces a huge volume of data, especially when simulations cover long time periods. These data must often be studied extensively at different levels of aggregation. We propose a generic multidimensional schema to analyze the results of a simulation model. This schema can guide modelers in designing specific data warehouses. We also propose an adaptation of an OLAP client tool in order to provide an adequate visualization of data. As an example, we implement a data warehouse for the analysis of results produced from a savanna simulation model, using a Relational OLAP architecture.
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@article{PUB00029041, author = {Mahboubi, H. and Faure, T. and Bimonte, S. and Deffuant, G. and Chanet, J.P. and Pinet, F.}, title = {A multidimensional model for data warehouses of simulation results }, title = {Un modèle multidimensionnel pour les entrepôts de résultats de simulation}, journal = {International Journal of Agricultural and Environmental Information Systems IJAEIS}, volume = {1}, number = {2}, pages = {1-19}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00029041}, doi = {http://dx.doi.org/10.4018/jaeis.2010070101}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR TSCF FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR TSCF FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR TSCF FRA ; CEMAGREF CLERMONT FERRAND UR TSCF FRA}, abstract = {This paper deals with the multidimensional modeling of a data warehouse for simulation results. It aims at answering new needs for data management which appear when exploring complex simulation models. Indeed, testing different parameter values and different versions of such models produces a huge volume of data, especially when simulations cover long time periods. These data must often be studied extensively at different levels of aggregation. We propose a generic multidimensional schema to analyze the results of a simulation model. This schema can guide modelers in designing specific data warehouses. We also propose an adaptation of an OLAP client tool in order to provide an adequate visualization of data. As an example, we implement a data warehouse for the analysis of results produced from a savanna simulation model, using a Relational OLAP architecture.}, }
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T. Perot, F. Goreaud, C. Ginisty, J.F. Dhôte
A model bridging distance-dependent and distance-independent tree models to simulate the growth of mixed forests
Annals of Forest Science 67 (5), 2010
abs doi web bib

It is widely believed that distance independent tree models fail to take into account the complexity of mixed stands due to the fact that spatial structure often has a greater impact on growth and dynamics in mixed stands than in pure stands. On the other hand, distance-dependent tree models are difficult to use because they require a map of the stand, which is not only very costly but also impracticable in a routine management context. This paper reports the development of a model bridging distance-dependent and distance independent tree models, and that is designed to simulate the growth of a mixed forest. The model used distributions of the number of neighbours to reconstruct tree neighbourhoods and compute the competition indices needed as inputs to the growth model. Data were collected from a mixed forest of sessile oak and Scots pine in central France. The study showed that local competition indices explained a significant proportion of growth variability and that intraspecific competition was greater than interspecific competition. The model based on neighbourhood distributions gave consistent predictions compared to a distance-dependent model. This type of model could be used instead of distance-dependent models in management contexts. / On considère généralement que les modèles arbre indépendant des distances ne permettent pas de rendre compte de la complexité des peuplements mélangés. En effet, la structure spatiale a souvent un rôle plus important sur la croissance et la dynamique dans ces peuplements que dans les peuplements purs. Les modèles arbre dépendant des distances sont quant à eux difficile à utiliser, car ils nécessitent une cartographie du peuplement qui est une information très coûteuse à obtenir et qui n'est pas disponible dans un cadre de gestion courante. Cet article présente un modèle intermédiaire entre un modèle arbre indépendant des distances et un modèle arbre dépendant des distances. Ce modèle a été développé pour simuler la croissance de peuplements mélangés. Il utilise des distributions de nombre de voisins pour reconstruire le voisinage des arbres. Ces voisinages reconstruits permettent ensuite de calculer les indices de compétition nécessaires dans l'équation de croissance. Les données ont été récoltées dans des peuplements mélangés de chêne sessile et de pin sylvestre dans le centre de la France. Ce travail montre que des indices de compétition locaux expliquent une part significative de la croissance individuelle et que la compétition intraspécifique est supérieure à la compétition interspécifique. Le modèle basé sur les distributions de voisinage donne des prédictions cohérentes par rapport au modèle arbre dépendant des distances. Ce type de modèle pourrait être utilisé à la place des modèles arbre dépendant des distances dans des contextes de gestion.
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@article{PUB00028722, author = {Perot, T. and Goreaud, F. and Ginisty, C. and Dhôte, J.F.}, title = {A model bridging distance-dependent and distance-independent tree models to simulate the growth of mixed forests}, title = {Un modèle intermédiaire entre un modèle arbre dépendant et indépendant des distances pour simuler la croissance des peuplements mélangés}, journal = {Annals of Forest Science}, volume = {67}, number = {5}, pages = {502p1-502p11}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00028722 / http://www.afs-journal.org/index.php?option=article&access=doi&doi=10.1051/forest/2010004}, doi = {http://dx.doi.org/10.1051/forest/2010004}, year = {2010}, affiliation = {CEMAGREF NOGENT SUR VERNISSON UR EFNO FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF NOGENT SUR VERNISSON UR EFNO FRA ; LERFOB UMR INRA ENGREF 1092 CHAMPENOUX}, abstract = {It is widely believed that distance independent tree models fail to take into account the complexity of mixed stands due to the fact that spatial structure often has a greater impact on growth and dynamics in mixed stands than in pure stands. On the other hand, distance-dependent tree models are difficult to use because they require a map of the stand, which is not only very costly but also impracticable in a routine management context. This paper reports the development of a model bridging distance-dependent and distance independent tree models, and that is designed to simulate the growth of a mixed forest. The model used distributions of the number of neighbours to reconstruct tree neighbourhoods and compute the competition indices needed as inputs to the growth model. Data were collected from a mixed forest of sessile oak and Scots pine in central France. The study showed that local competition indices explained a significant proportion of growth variability and that intraspecific competition was greater than interspecific competition. The model based on neighbourhood distributions gave consistent predictions compared to a distance-dependent model. This type of model could be used instead of distance-dependent models in management contexts. / On considère généralement que les modèles arbre indépendant des distances ne permettent pas de rendre compte de la complexité des peuplements mélangés. En effet, la structure spatiale a souvent un rôle plus important sur la croissance et la dynamique dans ces peuplements que dans les peuplements purs. Les modèles arbre dépendant des distances sont quant à eux difficile à utiliser, car ils nécessitent une cartographie du peuplement qui est une information très coûteuse à obtenir et qui n'est pas disponible dans un cadre de gestion courante. Cet article présente un modèle intermédiaire entre un modèle arbre indépendant des distances et un modèle arbre dépendant des distances. Ce modèle a été développé pour simuler la croissance de peuplements mélangés. Il utilise des distributions de nombre de voisins pour reconstruire le voisinage des arbres. Ces voisinages reconstruits permettent ensuite de calculer les indices de compétition nécessaires dans l'équation de croissance. Les données ont été récoltées dans des peuplements mélangés de chêne sessile et de pin sylvestre dans le centre de la France. Ce travail montre que des indices de compétition locaux expliquent une part significative de la croissance individuelle et que la compétition intraspécifique est supérieure à la compétition interspécifique. Le modèle basé sur les distributions de voisinage donne des prédictions cohérentes par rapport au modèle arbre dépendant des distances. Ce type de modèle pourrait être utilisé à la place des modèles arbre dépendant des distances dans des contextes de gestion.}, }
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A. Sordoni, J.P. Briot, I. Alvarez, E. Vasconcelos, M.A. Irving, G. Melo
Design of a participatory decision making agent architecture based on argumentation and influence function application to a serious game about biodiversity conservation
RAIRO-Operations Research 44 (4), 2010
abs doi web bib

This paper addresses an ongoing experience in the design of an artificial agent taking decisions and combining them with the decisions taken by human agents. The context is a serious game research project, aimed at computer-based support for participatory management of protected areas (and more specifically national parks) in order to promote biodiversity conservation and social inclusion. Its objective is to help various stakeholders (e.g., environmentalist, tourism operator) to collectively understand conflict dynamics and explore negotiation strategies for the management of parks. In this paper, after introducing the design of our serious game, named SimParc, we will describe the architecture of the decision making agent playing the role of the park manager. In the game, the park manager makes final decisions based on its own analysis and also on the votes of the stakeholders. It includes two modules: 1) individual decision based on a model of argumentation, which also provides a basis to justify and explain the decision; 2) participatory decision to take into account the preferences/votes from the stakeholders. / Cet article présente notre expérience de conception d'un agent artificiel prenant des décisions et capable de prendre également en compte les décisions d'agents humains. Le contexte est un projet de recherche de type jeu sérieux, pour la gestion participative d'espaces protégés (et plus particulièrement de parcs nationaux), de manière à promouvoir conservation de la biodiversité et inclusion sociale. Son objectif est d'aider les différents acteurs sociaux (« stakeholders », ex : environnementaliste, opérateur de tourisme) à comprendre la dynamique collective des conflits et d'explorer des stratégies de négociation pour la gestion de parcs. Dans cet article, après avoir introduit la conception du jeu sérieux, nommé SimParc (pour « simulation de gestion participative de parcs »), nous décrivons l'architecture de l'agent décideur jouant le rôle d'un gestionnaire de parc. Dans le jeu, le gestionnaire du parc prend la décision finale en fonction de sa propre analyse de la situation ainsi que des propositions des acteurs sociaux. Il inclut deux modules : (1) décision individuelle basé sur un modèle d'argumentation, ce qui offre également un point de départ pour justifier et expliquer la décision ; (2) décision participative pour prendre en compte les préférences/votes des acteurs sociaux.
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@article{PUB00030854, author = {Sordoni, A. and Briot, J.P. and Alvarez, I. and Vasconcelos, E. and Irving, M.A. and Melo, G.}, title = {Design of a participatory decision making agent architecture based on argumentation and influence function application to a serious game about biodiversity conservation}, title = {Conception d'une architecture d'agent de décision participative, basée sur l'argumentation et les fonctions d'influence : application à un jeu sérieux sur la conservation de la biodiversité}, journal = {RAIRO-Operations Research}, volume = {44}, number = {4}, pages = {269-283}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00030854}, doi = {http://dx.doi.org/10.1051/ro/2010024}, year = {2010}, affiliation = {UNIVERSITE DE PARIS VI LIP6 FRA ; UNIVERSITE DE PARIS VI LIP6 FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; PONTIFICIA UNVERSIDADE CATOLICA RIO DE JANEIRO BRA ; UNIVERSIDADE FEDERAL DE RIO DE JANEIRO BRA ; UNIVERSIDADE FEDERAL DE RIO DE JANEIRO BRA}, abstract = {This paper addresses an ongoing experience in the design of an artificial agent taking decisions and combining them with the decisions taken by human agents. The context is a serious game research project, aimed at computer-based support for participatory management of protected areas (and more specifically national parks) in order to promote biodiversity conservation and social inclusion. Its objective is to help various stakeholders (e.g., environmentalist, tourism operator) to collectively understand conflict dynamics and explore negotiation strategies for the management of parks. In this paper, after introducing the design of our serious game, named SimParc, we will describe the architecture of the decision making agent playing the role of the park manager. In the game, the park manager makes final decisions based on its own analysis and also on the votes of the stakeholders. It includes two modules: 1) individual decision based on a model of argumentation, which also provides a basis to justify and explain the decision; 2) participatory decision to take into account the preferences/votes from the stakeholders. / Cet article présente notre expérience de conception d'un agent artificiel prenant des décisions et capable de prendre également en compte les décisions d'agents humains. Le contexte est un projet de recherche de type jeu sérieux, pour la gestion participative d'espaces protégés (et plus particulièrement de parcs nationaux), de manière à promouvoir conservation de la biodiversité et inclusion sociale. Son objectif est d'aider les différents acteurs sociaux (« stakeholders », ex : environnementaliste, opérateur de tourisme) à comprendre la dynamique collective des conflits et d'explorer des stratégies de négociation pour la gestion de parcs. Dans cet article, après avoir introduit la conception du jeu sérieux, nommé SimParc (pour « simulation de gestion participative de parcs »), nous décrivons l'architecture de l'agent décideur jouant le rôle d'un gestionnaire de parc. Dans le jeu, le gestionnaire du parc prend la décision finale en fonction de sa propre analyse de la situation ainsi que des propositions des acteurs sociaux. Il inclut deux modules : (1) décision individuelle basé sur un modèle d'argumentation, ce qui offre également un point de départ pour justifier et expliquer la décision ; (2) décision participative pour prendre en compte les préférences/votes des acteurs sociaux. }, }
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C. Badulescu, M. Grédiac, J.D. Mathias, D. Roux
A procedure for accurate one-dimensional strain measurement using the grid method
Experimental Mechanics 49, 2009
abs doi web bib

This paper deals with the accurate calculation of strain using the grid method. The strain field is first directly deduced from the fringe pattern without calculating the displacement field. This procedure is validated with two numerical examples. Two types of experiment are then carried out: a translation and a tensile test. It is observed that some additional fictitious strains appear in both cases. They are due to two main reasons which interact with each other: the grid defects and the displacement of the grid lines during testing. A suitable procedure is proposed to cancel out these fictitious strains. This procedure is successfully applied in two cases of fringe patterns.
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@article{PUB00027757, author = {Badulescu, C. and Grédiac, M. and Mathias, J.D. and Roux, D.}, title = {A procedure for accurate one-dimensional strain measurement using the grid method }, title = {Methode de grille 1D}, journal = {Experimental Mechanics}, volume = {49}, pages = {841-854}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00027757}, doi = {http://dx.doi.org/10.1007/s11340-008-9203-8}, year = {2009}, affiliation = {IFMA UNIVERSITE DE CLERMONT FERRAND FRA ; IFMA UNIVERSITE DE CLERMONT FERRAND FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; UNIVERSITE DE CLERMONT FERRAND LABORATOIRE DE MATHEMATIQUES FRA}, abstract = {This paper deals with the accurate calculation of strain using the grid method. The strain field is first directly deduced from the fringe pattern without calculating the displacement field. This procedure is validated with two numerical examples. Two types of experiment are then carried out: a translation and a tensile test. It is observed that some additional fictitious strains appear in both cases. They are due to two main reasons which interact with each other: the grid defects and the displacement of the grid lines during testing. A suitable procedure is proposed to cancel out these fictitious strains. This procedure is successfully applied in two cases of fringe patterns. }, }
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C. Badulescu, M. Grédiac, J.D. Mathias
Investigation of the grid method for accurate in-plane strain measurement
Measurement Science & Technology 20 (9), 2009
abs doi web bib

This paper deals with the accurate measurement of the in-plane strain components on a deformed specimen using the grid method. A crossed grid transferred on the specimen surface is used for this purpose. Images of this grid are captured with a CCD camera before and after deformation. The complete strain state is deduced by processing these images with a suitable procedure described in the paper. The originality of this procedure is twofold. The first one is to determine the phase derivatives directly from the images. The second one is to compensate local variations of the grid pitch as well as local rotations of the grid, because these two phenomena may corrupt the final strain maps if they are not taken into account. The metrological performance of this procedure is assessed and discussed in terms of accuracy, measurement noise and spatial resolution. Two types of tests are used for this purpose: a translation and a rotation. These tests simulate the effect of rigid-body motion in a strain field that is rigorously equal to zero. One example finally illustrates the procedure: a tensile test performed on an open-hole specimen.
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@article{PUB00027756, author = {Badulescu, C. and Grédiac, M. and Mathias, J.D.}, title = {Investigation of the grid method for accurate in-plane strain measurement }, title = {Méthode de grille pour les problèmes plans}, journal = {Measurement Science & Technology}, volume = {20}, number = {9}, pages = {17}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00027756}, doi = {http://dx.doi.org/10.1088/0957-0233/20/9/095102}, year = {2009}, affiliation = {IFMA UNIVERSITE DE CLERMONT FERRAND FRA ; IFMA UNIVERSITE DE CLERMONT FERRAND FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {This paper deals with the accurate measurement of the in-plane strain components on a deformed specimen using the grid method. A crossed grid transferred on the specimen surface is used for this purpose. Images of this grid are captured with a CCD camera before and after deformation. The complete strain state is deduced by processing these images with a suitable procedure described in the paper. The originality of this procedure is twofold. The first one is to determine the phase derivatives directly from the images. The second one is to compensate local variations of the grid pitch as well as local rotations of the grid, because these two phenomena may corrupt the final strain maps if they are not taken into account. The metrological performance of this procedure is assessed and discussed in terms of accuracy, measurement noise and spatial resolution. Two types of tests are used for this purpose: a translation and a rotation. These tests simulate the effect of rigid-body motion in a strain field that is rigorously equal to zero. One example finally illustrates the procedure: a tensile test performed on an open-hole specimen.}, }
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A. Deheeger, J.D. Mathias, M. Grédiac
A closed-form solution for the thermal stress distribution in rectangular metal/composite bonded joints
International Journal of Adhesion and Adhesives 29, 2009
abs web bib

The aim of this paper is to provide a closed-form solution for the thermal stress distribution in a rectangular metal/composite bonded joint. This distribution depends on two directions, so it is suitable for studying bidimensional structures such as metallic plates reinforced with a rectangular composite patch. The solution is obtained using Fourier series. The relevance of the approach proposed in this paper is highlighted through various examples that clearly show that some coupling effects between the two directions of the problem take place. The influence of the nature of the composite plate used is analysed and discussed.
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@article{PUB00027754, author = {Deheeger, A. and Mathias, J.D. and Grédiac, M.}, title = {A closed-form solution for the thermal stress distribution in rectangular metal/composite bonded joints }, title = {Solution analytique pour la distribution pour des patchs rectangulaires}, journal = {International Journal of Adhesion and Adhesives}, volume = {29}, pages = {515-524}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00027754}, year = {2009}, affiliation = {IFMA UNIVERSITE DE CLERMONT FERRAND FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; IFMA UNIVERSITE DE CLERMONT FERRAND FRA}, abstract = {The aim of this paper is to provide a closed-form solution for the thermal stress distribution in a rectangular metal/composite bonded joint. This distribution depends on two directions, so it is suitable for studying bidimensional structures such as metallic plates reinforced with a rectangular composite patch. The solution is obtained using Fourier series. The relevance of the approach proposed in this paper is highlighted through various examples that clearly show that some coupling effects between the two directions of the problem take place. The influence of the nature of the composite plate used is analysed and discussed. }, }
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A. Deheeger, C. Badulescu, J.D. Mathias, M. Grédiac
Experimental study of thermal stresses in a bonded joint
Journal of Physics: Conference Series 181 (1), 2009
abs doi web bib

This paper deals with the assessment of the thermal stress distribution in a composite/aluminium bonded joint. An aluminum specimen symmetrically reinforced with two composite patches is heated while both thermal and displacement fields are measured with an infrared camera and a CCD camera, respectively. The grid method is used to obtain the displacement fields in the composite patch. This displacement field is in good agreement with theoretical expectations. This enables us to deduce the longitudinal strain in the composite patch by fitting the displacement field with a suitable model and differentiating it. The shear stress peak which takes place in the adhesive near the free edge of the patch is finally estimated.
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@article{PUB00032269, author = {Deheeger, A. and Badulescu, C. and Mathias, J.D. and Grédiac, M.}, title = {Experimental study of thermal stresses in a bonded joint }, journal = {Journal of Physics: Conference Series}, volume = {181}, number = {1}, pages = {6}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00032269}, doi = {http://dx.doi.org/10.1088/1742-6596/181/1/012041}, year = {2009}, affiliation = {UNIVERSITE BLAISE PASCAL CLERMONT FERRAND LABORATOIRE DE MECANIQUE ET INGENIERIES AUBIERE FRA ; UNIVERSITE BLAISE PASCAL CLERMONT FERRAND LABORATOIRE DE MECANIQUE ET INGENIERIES AUBIERE FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; UNIVERSITE BLAISE PASCAL CLERMONT FERRAND LABORATOIRE DE MECANIQUE ET INGENIERIES AUBIERE FRA}, abstract = {This paper deals with the assessment of the thermal stress distribution in a composite/aluminium bonded joint. An aluminum specimen symmetrically reinforced with two composite patches is heated while both thermal and displacement fields are measured with an infrared camera and a CCD camera, respectively. The grid method is used to obtain the displacement fields in the composite patch. This displacement field is in good agreement with theoretical expectations. This enables us to deduce the longitudinal strain in the composite patch by fitting the displacement field with a suitable model and differentiating it. The shear stress peak which takes place in the adhesive near the free edge of the patch is finally estimated.}, }
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C. Le Pichon, G. Gorges, J. Baudry, F. Goreaud, P. Boët
Spatial metrics and methods for riverscapes: quantifying variability in riverine fish habitat patterns
Environmetrics 20 (5), 2009
abs doi web bib

Defining the optimal configuration of all habitats required during a life cycle, called vital habitat, is a necessary step for effective management of riverine fishes and restoration of river habitats. Landscape ecology provides many metrics and methods to study the composition and configuration of habitats, but they need to be adapted for fishes in river environments or riverscapes. For example, hydrographic distance seems more appropriate than Euclidean distance for measuring distances between vital habitats in riverscapes.We adapted some metrics to assess habitats patterns of a threatened cyprinid species (Barbus barbus) for natural and artificial riverscapes of the Seine river, France. Composition metrics provided essential quantification of the relative abundance of the vital habitats, whereas configuration metrics were relevant to quantify their spatial arrangement and spatial relationships. Nearest-neighbor hydrographic distance was useful to evaluate the influence of flow variability in the natural riverscape, but was not relevant to discriminate the artificial riverscape from the natural one. Conversely, a proximity index revealed high fragmentation in the artificial riverscape. Spatial habitat relationships between feeding and resting habitats, evaluated with a moving window analysis, provided a map of daily activity patches and emphasized the gaps in the biological continuity of the riverscape. The spatial metrics and methods we adapted to the particularities of the Seine river allowed us to detect natural and artificial variability in fish habitat patterns. They should help in evaluating impacts of habitat alteration and isolation and prioritize preservation and restoration policies in human-impacted rivers.
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@article{PUB00024927, author = {Le Pichon, C. and Gorges, G. and Baudry, J. and Goreaud, F. and Boët, P.}, title = {Spatial metrics and methods for riverscapes: quantifying variability in riverine fish habitat patterns}, journal = {Environmetrics}, volume = {20}, number = {5}, pages = {512-526 }, url = {http://irsteadoc.irstea.fr/cemoa/PUB00024927}, doi = {http://dx.doi.org/10.1002/env.948}, year = {2009}, affiliation = {CEMAGREF ANTONY UR HBAN FRA ; CEMAGREF ANTONY UR HBAN FRA ; INRA SAD ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF BORDEAUX UR EPBX FRA}, abstract = {Defining the optimal configuration of all habitats required during a life cycle, called vital habitat, is a necessary step for effective management of riverine fishes and restoration of river habitats. Landscape ecology provides many metrics and methods to study the composition and configuration of habitats, but they need to be adapted for fishes in river environments or riverscapes. For example, hydrographic distance seems more appropriate than Euclidean distance for measuring distances between vital habitats in riverscapes.We adapted some metrics to assess habitats patterns of a threatened cyprinid species (Barbus barbus) for natural and artificial riverscapes of the Seine river, France. Composition metrics provided essential quantification of the relative abundance of the vital habitats, whereas configuration metrics were relevant to quantify their spatial arrangement and spatial relationships. Nearest-neighbor hydrographic distance was useful to evaluate the influence of flow variability in the natural riverscape, but was not relevant to discriminate the artificial riverscape from the natural one. Conversely, a proximity index revealed high fragmentation in the artificial riverscape. Spatial habitat relationships between feeding and resting habitats, evaluated with a moving window analysis, provided a map of daily activity patches and emphasized the gaps in the biological continuity of the riverscape. The spatial metrics and methods we adapted to the particularities of the Seine river allowed us to detect natural and artificial variability in fish habitat patterns. They should help in evaluating impacts of habitat alteration and isolation and prioritize preservation and restoration policies in human-impacted rivers.}, }
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J.D. Mathias, P.M. Geffroy, J.F. Silvain
Architectural optimization for microelectronic packaging
Applied Thermal Engineering 29, 2009
abs doi web bib

The aim of this paper is to provide a methodical approach for architectural optimization of power microelectronic devices. Because critical parameters of electronic devices are linked with reliability, architectural optimization, selection of the geometrical parameters of device and optimization of these parameters by iteration method associated by numerical analysis of reliability have to be achieved. In this way, this paper discusses about a methodical and numerical approach for the optimization of reliability in electronic devices, in particular the influence of geometrical parameters on the device reliability.
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@article{PUB00027753, author = {Mathias, J.D. and Geffroy, P.M. and Silvain, J.F.}, title = {Architectural optimization for microelectronic packaging }, title = {Optimisation topologique}, journal = {Applied Thermal Engineering}, volume = {29}, pages = {2391-2395}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00027753}, doi = {http://dx.doi.org/10.1016/j.applthermaleng.2008.12.037}, year = {2009}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; SPCTS SCIENCE DES PROCEDES CERAMIQUES ET DE TRAITEMENTS DE SURFACE LIMOGES FRA ; CNRS UNIVERSITE DE BORDEAUX ICMCB FRA}, abstract = {The aim of this paper is to provide a methodical approach for architectural optimization of power microelectronic devices. Because critical parameters of electronic devices are linked with reliability, architectural optimization, selection of the geometrical parameters of device and optimization of these parameters by iteration method associated by numerical analysis of reliability have to be achieved. In this way, this paper discusses about a methodical and numerical approach for the optimization of reliability in electronic devices, in particular the influence of geometrical parameters on the device reliability.}, }
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J.D. Mathias, P. Stoodley
Applying the digital image correlation method to estimate the mechanical properties of bacterial biofilms subjected to a wall shear stress
Biofouling 25 (8), 2009
abs web bib

A digital image correlation (DIC) method was applied to characterize the mechanical behavior of Pseudomonas aeruginosa biofilms in response to wall shear stress using digital video micrographs taken from biofilm flow cells. The appearance of the biofilm in the transmitted light photomicrographs presented a natural texture which was highly conducive to random encoding for DIC. The displacement fields were calculated for two biofilm specimens. The DIC method concurred with previous analysis showing that biofilms exhibit viscoelastic behavior, but had the advantage over simple length measurements of longitudinal strain that it could precisely measure local strains in length (x) and width (y) within biofilm clusters with a 2 μm resolution as a function of time and wall shear stress. It was concluded that DIC was more accurate at measuring elastic moduli than simple length measurements, but that time-lapse 3D images would enable even more accurate estimates to be performed.
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@article{PUB00027755, author = {Mathias, J.D. and Stoodley, P.}, title = {Applying the digital image correlation method to estimate the mechanical properties of bacterial biofilms subjected to a wall shear stress }, title = {Correlation pour les biofilms}, journal = {Biofouling}, volume = {25}, number = {8}, pages = {695-703}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00027755}, year = {2009}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CENTER FOR GENOMIC SCIENCES ALLEGHENY-SINGER RESEARCH INSTITUTE PITTSBURGH USA}, abstract = {A digital image correlation (DIC) method was applied to characterize the mechanical behavior of Pseudomonas aeruginosa biofilms in response to wall shear stress using digital video micrographs taken from biofilm flow cells. The appearance of the biofilm in the transmitted light photomicrographs presented a natural texture which was highly conducive to random encoding for DIC. The displacement fields were calculated for two biofilm specimens. The DIC method concurred with previous analysis showing that biofilms exhibit viscoelastic behavior, but had the advantage over simple length measurements of longitudinal strain that it could precisely measure local strains in length (x) and width (y) within biofilm clusters with a 2 μm resolution as a function of time and wall shear stress. It was concluded that DIC was more accurate at measuring elastic moduli than simple length measurements, but that time-lapse 3D images would enable even more accurate estimates to be performed.}, }
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I. Alvarez, S. Huet
Automatic diagnosis of engine of agricultural tractors: the BED experiment
Biosystems Engineering 100 (3), 2008
abs web bib

The test bed for evaluation and diagnosis (BED) is a simple device designed to perform a quick and automatic diagnosis of the engine of agricultural tractors. It compares the present performance of a tractor to the OECD test. Firstly, a test of the tractor is performed which measures the power take-off speed, the engine torque, the fuel consumption and several environmental variables. The performance curves of the tractor are then plotted against their official reference curves. A rule-based system (Scorpio) compares the present performance to the reference, analyses the differences and suggests which parts may be responsible for the lack of performance. A statistical validation of the expert system was carried out using a database of tests collected over 10 years. The output of the system was compared to the expert decision, which was available for more than a thousand records. This validation of the BED was confirmed by an in situ validation protocol conducted by a tractor repairer. The basic principles of the BED and the results of the validation studies are described / Le BED, (banc d'essai et de diagnostic) est un outil d'aide au diagnostic des moteurs de tracteurs. Il compare les performances actuelles d'un tracteur aux performances du test de référence OCDE. En premier lieu il permet d'effectuer un test du tracteur, en mesurant le couple à la prise de force, la consommation de carburant et des variables d'environnement en fonction de la vitesse à la prise de force. Les courbes de performance sont affichées en regard des courbes de référence. Un système à base de règle (Scorpio) compare les performances actuelles à la référence, analyse les différences et suggère les réglages à effectuer. Une validation statistique du système expert a été conduite sur une base de tests couvrant plus de 10 ans d'expérimentation, en comparant les propositions du système de diagnostic aux conclusion d'un expert pour plus de mille cas. Cette validation a été confirmée sur le terrain par un réparateur. Les principes de base du BED ainsi que les résultats des études de validation sont décrites dans cet article.
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@article{PUB00025620, author = {Alvarez, I. and Huet, S.}, title = {Automatic diagnosis of engine of agricultural tractors: the BED experiment}, title = {Diagnostic automatique des moteurs de tracteurs agricoles : l'expérience du BED}, journal = {Biosystems Engineering}, volume = {100}, number = {3}, pages = {362-369}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00025620 / http://dx.doi.org/10.1016/j.biosystemseng.2008.04.003}, year = {2008}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC}, abstract = {The test bed for evaluation and diagnosis (BED) is a simple device designed to perform a quick and automatic diagnosis of the engine of agricultural tractors. It compares the present performance of a tractor to the OECD test. Firstly, a test of the tractor is performed which measures the power take-off speed, the engine torque, the fuel consumption and several environmental variables. The performance curves of the tractor are then plotted against their official reference curves. A rule-based system (Scorpio) compares the present performance to the reference, analyses the differences and suggests which parts may be responsible for the lack of performance. A statistical validation of the expert system was carried out using a database of tests collected over 10 years. The output of the system was compared to the expert decision, which was available for more than a thousand records. This validation of the BED was confirmed by an in situ validation protocol conducted by a tractor repairer. The basic principles of the BED and the results of the validation studies are described / Le BED, (banc d'essai et de diagnostic) est un outil d'aide au diagnostic des moteurs de tracteurs. Il compare les performances actuelles d'un tracteur aux performances du test de référence OCDE. En premier lieu il permet d'effectuer un test du tracteur, en mesurant le couple à la prise de force, la consommation de carburant et des variables d'environnement en fonction de la vitesse à la prise de force. Les courbes de performance sont affichées en regard des courbes de référence. Un système à base de règle (Scorpio) compare les performances actuelles à la référence, analyse les différences et suggère les réglages à effectuer. Une validation statistique du système expert a été conduite sur une base de tests couvrant plus de 10 ans d'expérimentation, en comparant les propositions du système de diagnostic aux conclusion d'un expert pour plus de mille cas. Cette validation a été confirmée sur le terrain par un réparateur. Les principes de base du BED ainsi que les résultats des études de validation sont décrites dans cet article.}, }
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L. Chapel, G. Deffuant, S. Martin, C. Mullon
Defining yield policies in a viability approach
Ecological Modelling 212 (1-2), 2008
abs doi web bib

Mullon et al. [Mullon, C., Curry, P., Shannon, L., 2004. Viability model of trophic interactions in marine ecosystems. Nat. Resour. Model. 17 (1), 2758] proposed a dynamical model of biomass evolution in the Southern Benguela ecosystem, including five different groups (detritus, phytoplankton, zooplankton, pelagic fish and demersal fish). They studied this model in a viability perspective, trying to assess, for a given constant yield, whether each species biomass remains inside a given interval, taking into account the uncertainty on the interaction coefficients. Instead of studying the healthy states of this marine ecosystem with a constant yield, we focus here on the yield policies which keep the system viable. Using the mathematical concept of viability kernel, we examine how yield management might guarantee viable fisheries. One of the main practical difficulties up to now with the viability theory was the lack of methods to solve the problem in large dimensions. In this paper, we use a new method based on SVMs, which gives this theory a larger practical potential. Solving the viability problem provides all yield policies (if any) which guarantee a perennial system. We illustrate our main findings with numerical simulations.
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@article{PUB00024646, author = {Chapel, L. and Deffuant, G. and Martin, S. and Mullon, C.}, title = {Defining yield policies in a viability approach}, title = {Définir des politiques de pêche grâce à la théorie de la viabilité}, journal = {Ecological Modelling}, volume = {212}, number = {1-2}, pages = {10-15}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00024646}, doi = {http://dx.doi.org/10.1016/j.ecolmodel.2007.10.007 }, year = {2008}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC ; IRD UR GEODES BONDY}, abstract = {Mullon et al. [Mullon, C., Curry, P., Shannon, L., 2004. Viability model of trophic interactions in marine ecosystems. Nat. Resour. Model. 17 (1), 2758] proposed a dynamical model of biomass evolution in the Southern Benguela ecosystem, including five different groups (detritus, phytoplankton, zooplankton, pelagic fish and demersal fish). They studied this model in a viability perspective, trying to assess, for a given constant yield, whether each species biomass remains inside a given interval, taking into account the uncertainty on the interaction coefficients. Instead of studying the healthy states of this marine ecosystem with a constant yield, we focus here on the yield policies which keep the system viable. Using the mathematical concept of viability kernel, we examine how yield management might guarantee viable fisheries. One of the main practical difficulties up to now with the viability theory was the lack of methods to solve the problem in large dimensions. In this paper, we use a new method based on SVMs, which gives this theory a larger practical potential. Solving the viability problem provides all yield policies (if any) which guarantee a perennial system. We illustrate our main findings with numerical simulations.}, }
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M. Edwards, F. Goreaud, N. Ferrand
Simulating heterogeneity in a consumption model linked to a water resource model: When is the linear approximation relevant?
Simulation Modelling Practice and Theory 16 (1), 2008
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Water resource represents an important stake for human development. Studies show that under the currently growing demand this resource can become scarce, therefore, leading to the necessity of reducing unnecessary demand. Household needs often represent an important proportion of the overall demand, while individual costs are not high enough to lead the consumer to restrict his demand to the essential. Therefore, besides pricing policies, evaluating the impact of various incentives and information policies in reducing household demand represents a current stake in modelling for water management support. One of the major difficulties for this is to account for local information ignoring spatial inter-dependence of the resource and heterogeneity in the population. In this paper, we tackle the possibility of simulating a composite population of water consumers and/or more than one water resource by a linear approximation derived from simple configurations (a single consumer population linked to a single resource). We model a reversible diffusion of careful consumption behaviours in a population influenced by public information on the resource. Our results show that the adequacy of linear approximation depends on the choice of information provided to the consumers, and more particularly on the definition of a state of crisis. We discuss implications of this result from various points of view.
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@article{PUB00024898, author = {Edwards, M. and Goreaud, F. and Ferrand, N.}, title = {Simulating heterogeneity in a consumption model linked to a water resource model: When is the linear approximation relevant?}, journal = {Simulation Modelling Practice and Theory}, volume = {16}, number = {1}, pages = {65-75}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00024898}, doi = {http://dx.doi.org/10.1016/j.simpat.2007.10.003 }, year = {2008}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF MONTPELLIER IRMO UMR G-EAU}, abstract = {Water resource represents an important stake for human development. Studies show that under the currently growing demand this resource can become scarce, therefore, leading to the necessity of reducing unnecessary demand. Household needs often represent an important proportion of the overall demand, while individual costs are not high enough to lead the consumer to restrict his demand to the essential. Therefore, besides pricing policies, evaluating the impact of various incentives and information policies in reducing household demand represents a current stake in modelling for water management support. One of the major difficulties for this is to account for local information ignoring spatial inter-dependence of the resource and heterogeneity in the population. In this paper, we tackle the possibility of simulating a composite population of water consumers and/or more than one water resource by a linear approximation derived from simple configurations (a single consumer population linked to a single resource). We model a reversible diffusion of careful consumption behaviours in a population influenced by public information on the resource. Our results show that the adequacy of linear approximation depends on the choice of information provided to the consumers, and more particularly on the definition of a state of crisis. We discuss implications of this result from various points of view.}, }
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P.M. Geffroy, J.D. Mathias, J.F. Silvain
Heat sink material selection in electronic devices by computational approach
Advanced Engineering Materials 10 (4), 2008
abs doi web bib

A study was conducted to investigate the heat sink material selection in electronic devices by computational approach. The thermal stress and strain analyses in the study was carried out making use of FEMLAB multi-physics software, which was used to predict the stress history of complex structure materials and solder joint life of electronic assemblies. Power semiconductor modules are characterized by the multi-layer structure of different materials, including insulators, conductors, and semiconductors. Mechanical behaviors of multi-layer thin films was predicted with a thermo-mechanical model for the study, with the temperature distribution used to drive the thermo-mechanical analysis being available directly from the FEMLAB heat transfer module. It was also concluded that the study had demonstrated a strategy where computational mechanics is coupled with heat sink material selection for predicting the reliability electronic devices.
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@article{PUB00025852, author = {Geffroy, P.M. and Mathias, J.D. and Silvain, J.F.}, title = {Heat sink material selection in electronic devices by computational approach }, title = {Choix du dissipateur de chaleur par simulation}, journal = {Advanced Engineering Materials}, volume = {10}, number = {4}, pages = {400-405}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00025852}, doi = {http://dx.doi.org/10.1002/adem.200700285}, year = {2008}, affiliation = {ENSCI LIMOGES ; CEMAGREF CLERMONT FERRAND LISC ; INSTITUT DE LA CHIMIE ET DE LA MATIERE CONDENSEE BORDEAUX}, abstract = {A study was conducted to investigate the heat sink material selection in electronic devices by computational approach. The thermal stress and strain analyses in the study was carried out making use of FEMLAB multi-physics software, which was used to predict the stress history of complex structure materials and solder joint life of electronic assemblies. Power semiconductor modules are characterized by the multi-layer structure of different materials, including insulators, conductors, and semiconductors. Mechanical behaviors of multi-layer thin films was predicted with a thermo-mechanical model for the study, with the temperature distribution used to drive the thermo-mechanical analysis being available directly from the FEMLAB heat transfer module. It was also concluded that the study had demonstrated a strategy where computational mechanics is coupled with heat sink material selection for predicting the reliability electronic devices.}, }
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S. Huet, G. Deffuant
Differential equation models derived from an individual-based model can help to understand emergent effects
JASSS-The Journal of Artificial Societies and Social Simulation 11 (2), 2008
abs web bib

We study a model of primacy effect on individual's attitude. Typically, when receiving a strong negative feature first, the individual keeps a negative attitude whatever the number of moderate positive features it receives afterwards. We consider a population of individuals, which receive the features from a media, and communicate with each other. We observe that interactions favour the primacy effect, compared with a population of isolated individuals. We derive a differential equation system ruling the evolution of probabilities that individuals retain different sets of features. The study of this aggregated model of the IBM shows that interaction can increase or decrease the number of individuals exhibiting a primacy effect. We verify on the IBM that the interactions can decrease the primacy effect in the conditions suggested by the study of the aggregated model. We finally discuss the interest of such a double-modelling approach (using a model of the individual based model) for this application.
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@article{PUB00024126, author = {Huet, S. and Deffuant, G.}, title = {Differential equation models derived from an individual-based model can help to understand emergent effects}, title = {Les modèles d'équations différentielles, dérivés d'un modèle individu centré, peuvent aider à la compréhension des effets émergents}, journal = {JASSS-The Journal of Artificial Societies and Social Simulation}, volume = {11}, number = {2}, pages = {16}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00024126 / http://jasss.soc.surrey.ac.uk/11/2/10.html}, year = {2008}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC}, abstract = {We study a model of primacy effect on individual's attitude. Typically, when receiving a strong negative feature first, the individual keeps a negative attitude whatever the number of moderate positive features it receives afterwards. We consider a population of individuals, which receive the features from a media, and communicate with each other. We observe that interactions favour the primacy effect, compared with a population of isolated individuals. We derive a differential equation system ruling the evolution of probabilities that individuals retain different sets of features. The study of this aggregated model of the IBM shows that interaction can increase or decrease the number of individuals exhibiting a primacy effect. We verify on the IBM that the interactions can decrease the primacy effect in the conditions suggested by the study of the aggregated model. We finally discuss the interest of such a double-modelling approach (using a model of the individual based model) for this application.}, }
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S. Huet, G. Deffuant, W. Jager
Rejection mechanism in 2D bounded confidence provides more conformity
Advances in Complex Systems 11 (4), 2008
abs doi web bib

This paper explores the dynamics of attitude change in 2 dimensions (2D) as a result of social interaction. We add a rejection mechanism into the 2D bounded confidence (BC) model proposed by Deffuant et al (2001). Individuals are characterised by twodimensional continuous attitudes, each associated with an uncertainty u, supposed constant in this first study. Individuals interact by random pairs. If their attitudes are closer than u on both dimensions, or further than u on both dimensions, or closer than u on one dimension and not further than u + delta u on the other dimension, then the rules of the BC model apply. But if their attitudes are closer than u on one dimension and further than u + delta u on the other dimension, then the individuals are in a dissonant state. They tend to solve it by shifting away their close attitudes. The model shows metastable clusters, which maintain themselves through opposite influences of competitor clusters. Our analysis and first experiments support the hypothesis that, for a large range of uncertainty values, the number of clusters grows linearly with the inverse of the uncertainty, whereas this growth is quadratic in the BC model.
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@article{PUB00024189, author = {Huet, S. and Deffuant, G. and Jager, W.}, title = {Rejection mechanism in 2D bounded confidence provides more conformity}, title = {Un mécanisme de rejet dans un modèle de confiance limitée 2D engendre davantage de conformité}, journal = {Advances in Complex Systems}, volume = {11}, number = {4}, pages = {529-549}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00024189}, doi = {http://dx.doi.org/10.1142/S0219525908001799}, year = {2008}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC ; FACULTY OF ECONOMICS AND BUSINESS UNIVERSITY OF GRONINGEN NLD}, abstract = {This paper explores the dynamics of attitude change in 2 dimensions (2D) as a result of social interaction. We add a rejection mechanism into the 2D bounded confidence (BC) model proposed by Deffuant et al (2001). Individuals are characterised by twodimensional continuous attitudes, each associated with an uncertainty u, supposed constant in this first study. Individuals interact by random pairs. If their attitudes are closer than u on both dimensions, or further than u on both dimensions, or closer than u on one dimension and not further than u + delta u on the other dimension, then the rules of the BC model apply. But if their attitudes are closer than u on one dimension and further than u + delta u on the other dimension, then the individuals are in a dissonant state. They tend to solve it by shifting away their close attitudes. The model shows metastable clusters, which maintain themselves through opposite influences of competitor clusters. Our analysis and first experiments support the hypothesis that, for a large range of uncertainty values, the number of clusters grows linearly with the inverse of the uncertainty, whereas this growth is quadratic in the BC model.}, }
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J.D. Mathias, M. Grédiac
Applying the grid method to validate a numerical model predicting the transverse shear stress distributions in patched structures
Composites Part A: Applied Science and Manufacturing 39 (8), 2008
abs web bib

This paper describes the application of a full-field measurement technique to validate a numerical model developed to calculate the stress distribution in metallic structures reinforced with composite patches. The numerical model is based on a finite differences scheme. Tensile tests are performed on circular patches to validate the model. Displacement fields are measured on the patches with the grid method. Strain are derived from these measurements using a suitable technique and stresses are deduced using the constitutive equations of the composite. In most cases, a good agreement is observed between stresses deduced from the measurements and their numerical counterparts.
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@article{PUB00025855, author = {Mathias, J.D. and Grédiac, M.}, title = {Applying the grid method to validate a numerical model predicting the transverse shear stress distributions in patched structures }, title = {Utilisation de la méthode de grille pour valider un modèle de prédiction de contraintes dans des structures renforcées}, journal = {Composites Part A: Applied Science and Manufacturing}, volume = {39}, number = {8}, pages = {1194-1209}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00025855}, year = {2008}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; IFMA LAMI CLERMONT FERRAND}, abstract = {This paper describes the application of a full-field measurement technique to validate a numerical model developed to calculate the stress distribution in metallic structures reinforced with composite patches. The numerical model is based on a finite differences scheme. Tensile tests are performed on circular patches to validate the model. Displacement fields are measured on the patches with the grid method. Strain are derived from these measurements using a suitable technique and stresses are deduced using the constitutive equations of the composite. In most cases, a good agreement is observed between stresses deduced from the measurements and their numerical counterparts.}, }
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J.D. Mathias, N. Tessier-Doyen
Homogenization of glass/alumina two-phase materials using a cohesive zone model
Computational Materials Science 43 (4), 2008
abs web bib

This paper is devoted to glass/alumina materials which can exhibit important damages at the interface in the case of a difference of the coefficients of thermal expansion between the matrix and the inclusions. One of the key-issue for this type of materials use is to determine and quantify this damage. This paper presents numerical and experimental approaches for this purpose. A numerical model is used and coupled to a homogenization procedure to evaluate damages provoked by the difference of the coefficients of thermal expansion. Cohesive elements have been introduced in the FE model so as to simulate the interface damage. Some thermal tests have been done on two-phase specimens. Experimental and numerical results are compared and analyzed.
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@article{PUB00025856, author = {Mathias, J.D. and Tessier-Doyen, N.}, title = {Homogenization of glass/alumina two-phase materials using a cohesive zone model }, title = {Homogénéisation d'un verre/alumine utilisant un modèle CZM}, journal = {Computational Materials Science}, volume = {43}, number = {4}, pages = {1081-1085}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00025856}, year = {2008}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; ENSCI GROUPE D'ETUDE DES MATERIAUX HETEROGENES GEMH LIMOGES}, abstract = {This paper is devoted to glass/alumina materials which can exhibit important damages at the interface in the case of a difference of the coefficients of thermal expansion between the matrix and the inclusions. One of the key-issue for this type of materials use is to determine and quantify this damage. This paper presents numerical and experimental approaches for this purpose. A numerical model is used and coupled to a homogenization procedure to evaluate damages provoked by the difference of the coefficients of thermal expansion. Cohesive elements have been introduced in the FE model so as to simulate the interface damage. Some thermal tests have been done on two-phase specimens. Experimental and numerical results are compared and analyzed.}, }
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J.D. Mathias, M. Grédiac, X. Balandraud
Design of optimized patches to reinforce damaged wings
AIAA Journal 46 (1), 2008
abs doi web bib

This paper describes the optimization process of composite patches designed to reinforce damaged wings. The main objective is to reduce the stress level in a damaged area located near the anchorage of the wing to the fuselage. Genetic algorithms are used for optimizing the ply orientations of the stacking sequence as well as the location and shape of the patch. The stress field in the structure is computed with the ANSYS finite element package. Several examples illustrate the fact that the stress flow within the wing is deviated, thus leading to a decrease of the stress level in the damaged area to be relieved.
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@article{PUB00025854, author = {Mathias, J.D. and Grédiac, M. and Balandraud, X.}, title = {Design of optimized patches to reinforce damaged wings}, title = {Optimisation de patchs pour ailes endommagées}, journal = {AIAA Journal}, volume = {46}, number = {1}, pages = {46-53}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00025854}, doi = {http://dx.doi.org/10.2514/1.24300}, year = {2008}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; IFMA LAMI CLERMONT FERRAND ; IFMA LAMI CLERMONT FERRAND}, abstract = {This paper describes the optimization process of composite patches designed to reinforce damaged wings. The main objective is to reduce the stress level in a damaged area located near the anchorage of the wing to the fuselage. Genetic algorithms are used for optimizing the ply orientations of the stacking sequence as well as the location and shape of the patch. The stress field in the structure is computed with the ANSYS finite element package. Several examples illustrate the fact that the stress flow within the wing is deviated, thus leading to a decrease of the stress level in the damaged area to be relieved.}, }
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T. Perot, F. Goreaud, C. Ginisty
Quels modèles de croissance pour les peuplements mélangés ? Exemple du mélange chêne sessile-pin sylvestre
Revue Forestière Française 60 (2), 2008
abs web bib

Mixed forests currently account for 50% of the French forest cover. Nonetheless, there are very few management aid tools in France relating to these stands. Growth model describe the development of stands over time and are able to simulate forestry practices in this respect, they are very useful tools for planning operations and harvesting, or as aids in producing silvicultural guidelines. The purpose of this article is to present a specific issue raised by these models: the choice of the level of detail for a growth model. This choice can indeed have significant implications for the use of the model. So as to choose the level of detail, we propose building and comparing a series of simplified models. This method is applied to the growth of sessile oak / Scots pine stands in the context of a partnership between the French Forestry Board (ONF) and Cemagref. We sampled 101 oaks and 116 pines distributed in four experimental plots in the Orleans state forest for the purpose of studying radial increment. With this data, we built a first model a distance-dependent tree model. With this model, we were able to specify the interaction between and within species. One finding was that pines surrounded by pines are at a disadvantage compared to those surrounded by oak. The model was integrated in a module of the Capsis forest simulation system. Starting from an actual stand, we conducted simulations that enabled us to quantify the production of the mixture and furthermore to provide information or input as to the future development of that combination. We also showed the relevance of the distant-dependent tree model for testing marking strategies on the scale of the individual tree. This work is a first step in building a family of models for sessile oak / Scots pine stands at various levels of detail. In the longer term, by comparing the various models in the family, we hope to identify the appropriate scale for one or several management issues. We will then be able to supplement this model by bringing regeneration into the equation so as to develop a comprehensive management aid tool for these mixtures. / Les peuplements mélangés couvrent actuellement 50% de la surface forestière française. Pour autant il existe en France très peu d'outils d'aide à la gestion de ces peuplements. Les modèles de croissance décrivent l'évolution d'un peuplement au cours du temps et sont capables de simuler des interventions sylvicoles : ils sont, à ce titre, des outils très intéressants pour la planification des travaux et des récoltes ou pour l'aide à la production de guides sylvicoles.L'objectif de cet article est de présenter une question spécifique posée par ces modèles : le choix du niveau de détail d'un modèle de croissance. En effet, ce choix peut avoir des implications importantes par rapport à l'utilisation du modèle. Pour choisir ce niveau de détail nous proposons de construire et de comparer une série de modèles simplifiés. Cette méthode est appliquée à la croissance des peuplements mélangés chêne sessile pin sylvestre dans le cadre d'un partenariat entre l'ONF et le Cemagref. Pour étudier la croissance radiale, nous avons effectué des sondages dans 101 chênes et 116 pins répartis dans 4 dispositifs de la forêt domaniale d'Orléans. Nous avons utilisé ces données pour construire un premier modèle : un modèle arbre dépendant des distances. Ce modèle nous a permis de préciser les interactions intra et interspécifiques. Il ressort notamment que les pins entourés de pins sont plus défavorisés que les pins entourés de chênes. Le modèle a été intégré dans un module de la plateforme de simulation forestière Capsis. A partir d'un peuplement réel, nous avons réalisé des simulations qui nous ont permis de quantifier la production du mélange mais aussi d'apporter des éléments de réponses ou de réflexion sur le devenir du mélange. Nous avons également illustré l'intérêt du modèle arbre dépendant des distances pour tester des stratégies de martelage à l'échelle de l'arbre. Ce travail est un premier pas vers la construction d'une famille de modèles des peuplements chêne sessile-pin sylvestre à différents niveaux de détail. A terme, la comparaison des différents modèles de cette famille nous permettra d'identifier l'échelle adéquate pour une ou plusieurs problématiques de gestion. Nous pourrons ensuite compléter ce modèle pour prendre en compte notamment la régénération et développer un outil complet d'aide à la gestion de ces peuplements mélangés.
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@article{PUB00024951, author = {Perot, T. and Goreaud, F. and Ginisty, C.}, title = {Quels modèles de croissance pour les peuplements mélangés ? Exemple du mélange chêne sessile-pin sylvestre}, title = {Mixed stand growth models - The sessile oak / Scots pine combination}, journal = {Revue Forestière Française}, volume = {60}, number = {2}, pages = {215-232}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00024951 / http://hdl.handle.net/2042/18145}, year = {2008}, affiliation = {CEMAGREF NOGENT SUR VERNISSON EFNO ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF NOGENT SUR VERNISSON EFNO}, abstract = {Mixed forests currently account for 50% of the French forest cover. Nonetheless, there are very few management aid tools in France relating to these stands. Growth model describe the development of stands over time and are able to simulate forestry practices in this respect, they are very useful tools for planning operations and harvesting, or as aids in producing silvicultural guidelines. The purpose of this article is to present a specific issue raised by these models: the choice of the level of detail for a growth model. This choice can indeed have significant implications for the use of the model. So as to choose the level of detail, we propose building and comparing a series of simplified models. This method is applied to the growth of sessile oak / Scots pine stands in the context of a partnership between the French Forestry Board (ONF) and Cemagref. We sampled 101 oaks and 116 pines distributed in four experimental plots in the Orleans state forest for the purpose of studying radial increment. With this data, we built a first model a distance-dependent tree model. With this model, we were able to specify the interaction between and within species. One finding was that pines surrounded by pines are at a disadvantage compared to those surrounded by oak. The model was integrated in a module of the Capsis forest simulation system. Starting from an actual stand, we conducted simulations that enabled us to quantify the production of the mixture and furthermore to provide information or input as to the future development of that combination. We also showed the relevance of the distant-dependent tree model for testing marking strategies on the scale of the individual tree. This work is a first step in building a family of models for sessile oak / Scots pine stands at various levels of detail. In the longer term, by comparing the various models in the family, we hope to identify the appropriate scale for one or several management issues. We will then be able to supplement this model by bringing regeneration into the equation so as to develop a comprehensive management aid tool for these mixtures. / Les peuplements mélangés couvrent actuellement 50% de la surface forestière française. Pour autant il existe en France très peu d'outils d'aide à la gestion de ces peuplements. Les modèles de croissance décrivent l'évolution d'un peuplement au cours du temps et sont capables de simuler des interventions sylvicoles : ils sont, à ce titre, des outils très intéressants pour la planification des travaux et des récoltes ou pour l'aide à la production de guides sylvicoles.L'objectif de cet article est de présenter une question spécifique posée par ces modèles : le choix du niveau de détail d'un modèle de croissance. En effet, ce choix peut avoir des implications importantes par rapport à l'utilisation du modèle. Pour choisir ce niveau de détail nous proposons de construire et de comparer une série de modèles simplifiés. Cette méthode est appliquée à la croissance des peuplements mélangés chêne sessile pin sylvestre dans le cadre d'un partenariat entre l'ONF et le Cemagref. Pour étudier la croissance radiale, nous avons effectué des sondages dans 101 chênes et 116 pins répartis dans 4 dispositifs de la forêt domaniale d'Orléans. Nous avons utilisé ces données pour construire un premier modèle : un modèle arbre dépendant des distances. Ce modèle nous a permis de préciser les interactions intra et interspécifiques. Il ressort notamment que les pins entourés de pins sont plus défavorisés que les pins entourés de chênes. Le modèle a été intégré dans un module de la plateforme de simulation forestière Capsis. A partir d'un peuplement réel, nous avons réalisé des simulations qui nous ont permis de quantifier la production du mélange mais aussi d'apporter des éléments de réponses ou de réflexion sur le devenir du mélange. Nous avons également illustré l'intérêt du modèle arbre dépendant des distances pour tester des stratégies de martelage à l'échelle de l'arbre. Ce travail est un premier pas vers la construction d'une famille de modèles des peuplements chêne sessile-pin sylvestre à différents niveaux de détail. A terme, la comparaison des différents modèles de cette famille nous permettra d'identifier l'échelle adéquate pour une ou plusieurs problématiques de gestion. Nous pourrons ensuite compléter ce modèle pour prendre en compte notamment la régénération et développer un outil complet d'aide à la gestion de ces peuplements mélangés.}, }
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E. Sauquet, M.H. Ramos, L. Chapel, P. Bernardara
Stream flow scaling properties: investigating characteristic scales from different statistical approaches
Hydrological Processes 22 (CHHLY.24610), 2008
abs doi web bib

This paper studies the links between scaling properties of river flow time series by comparing the results of three techniques applied to an extended data set of 34 French discharge gauging stations. The three approaches used are based on different mathematical tools and hypotheses: 1) the shape analysis of flood hydrographs, 2) the multifractal framework through spectral and moment analyses, and 3) the flood frequency analysis through the fitting of flood duration frequency curves (QdF). The general aim is to test the hypothesis of scaling invariance of river flow and the shape invariance of the hydrographs, in order to investigate the link between scaling properties and flow dynamics. In particular, the coherence between different approaches widely used in the literature to describe these characteristics is evaluated through the estimation of parameters defining the range of time scales on which the scaling properties are valid. The results show that most of these timescale parameters are linked to the flow dynamics and suggest that the approaches applied are interrelated.
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@article{PUB00024610, author = {Sauquet, E. and Ramos, M.H. and Chapel, L. and Bernardara, P.}, title = {Stream flow scaling properties: investigating characteristic scales from different statistical approaches}, title = {Propriétés d'invariance d'échelle dans les séries de débit. Une comparaison entre méthodes statistiques}, journal = {Hydrological Processes}, volume = {22}, pages = {3462-3475}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00024610}, doi = {http://dx.doi.org/10.1002/hyp.6952}, year = {2008}, affiliation = {CEMAGREF LYON HHLY ; CEMAGREF LYON HHLY ; CEMAGREF LYON HHLY ; EDF CHATOU}, number = {CHHLY.24610}, abstract = {This paper studies the links between scaling properties of river flow time series by comparing the results of three techniques applied to an extended data set of 34 French discharge gauging stations. The three approaches used are based on different mathematical tools and hypotheses: 1) the shape analysis of flood hydrographs, 2) the multifractal framework through spectral and moment analyses, and 3) the flood frequency analysis through the fitting of flood duration frequency curves (QdF). The general aim is to test the hypothesis of scaling invariance of river flow and the shape invariance of the hydrographs, in order to investigate the link between scaling properties and flow dynamics. In particular, the coherence between different approaches widely used in the literature to describe these characteristics is evaluated through the estimation of parameters defining the range of time scales on which the scaling properties are valid. The results show that most of these timescale parameters are linked to the flow dynamics and suggest that the approaches applied are interrelated. }, }
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G. Deffuant, S. Huet
Propagation effects of filtering incongruent information
Journal of Business Research 60 (8), 2007
abs web bib

This report proposes for a simple individual-based model of information filtering, while focusing in particular on some of its implications for the attitude toward an object. The model assumes that a filter selects only important features, with a higher threshold of importance when the attitude toward the feature is incongruent with the global attitude toward the object. Individuals transmit only features that are congruent with their global attitude. This article considers two variants of the model. To both applies that different orders of feature reception can lead to different attitudes. For instance, a positive attitude toward an object can at a certain point become negative, even though the object is globally neutral (the sum of the feature attitudes is zero). The interactions among individuals can significantly increase the probability of such non-rational attitudes.
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@article{PUB00021835, author = {Deffuant, G. and Huet, S.}, title = {Propagation effects of filtering incongruent information}, title = {Effet de la propagation du filtrage d'informations incongruentes}, journal = {Journal of Business Research}, volume = {60}, number = {8}, pages = {816-825}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00021835}, year = {2007}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC}, abstract = {This report proposes for a simple individual-based model of information filtering, while focusing in particular on some of its implications for the attitude toward an object. The model assumes that a filter selects only important features, with a higher threshold of importance when the attitude toward the feature is incongruent with the global attitude toward the object. Individuals transmit only features that are congruent with their global attitude. This article considers two variants of the model. To both applies that different orders of feature reception can lead to different attitudes. For instance, a positive attitude toward an object can at a certain point become negative, even though the object is globally neutral (the sum of the feature attitudes is zero). The interactions among individuals can significantly increase the probability of such non-rational attitudes.}, }
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G. Deffuant, L. Chapel, S. Martin
Approximating viability kernels with support vector machines
IEEE Transactions on Automatic Control 52 (5), 2007
abs web bib

We propose an algorithm which performs a progressive approximation of a viability kernel, iteratively using a classification method. We establish the mathematical conditions that the classification method should fulfill to guarantee the convergence to the actual viability kernel. We study more particularly the use of support vector machines (SVMs) as classification techniques. We show that they make possible to use gradient optimisation techniques to find a viable control at each time step, and over several time steps. This allows us to avoid the exponential growth of the computing time with the dimension of the control space. It also provides simple and efficient control procedures. We illustrate the method with some examples inspired from ecology.
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@article{PUB00036305, author = {Deffuant, G. and Chapel, L. and Martin, S.}, title = {Approximating viability kernels with support vector machines}, title = {Approcher des noyaux de viabilité avec des machines à vecteurs supports}, journal = {IEEE Transactions on Automatic Control}, volume = {52}, number = {5}, pages = {933-937}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00036305}, year = {2007}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {We propose an algorithm which performs a progressive approximation of a viability kernel, iteratively using a classification method. We establish the mathematical conditions that the classification method should fulfill to guarantee the convergence to the actual viability kernel. We study more particularly the use of support vector machines (SVMs) as classification techniques. We show that they make possible to use gradient optimisation techniques to find a viable control at each time step, and over several time steps. This allows us to avoid the exponential growth of the computing time with the dimension of the control space. It also provides simple and efficient control procedures. We illustrate the method with some examples inspired from ecology. }, }
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N. Dumoulin
SimAquaLife : un cadriciel pour la modélisation de la dynamique spatiale d'organismes aquatiques
Technique et Science Informatiques 26 (6), 2007
abs web bib

Individual-based modelling of ecosystems necessitates a multi-disciplinary approach, making tough the development and the maintenance of these models. Several individual-based modelling platforms exist and make possible to simplify the design and maintenance tasks, however we consider that we could improve by isolating aspects related to modeling from the other aspects mainly related to the simulation techniques and to the display of results. Without taking into account aspect-oriented programming, we propose a software framework which makes an intensive use of metadatas to simplify the use and development of models, and also to produce automatically graphical user interfaces for data settings and results display. This approach is based on the metamodelling concept of model engineering. The software framework has been mainly developed for the spatialized and individual-centered simulation of aquatic organisms movements, mainly river fresh water fishes and eels at different development stages. / a modélisation individu-centrée d'écosystèmes fait intervenir plusieurs disciplines, ce qui a pour effet de compliquer le développement et la maintenance de ces modèles. Plusieurs plate-formes de modélisation individu-centrée existent et permettent de faciliter ces tâches. Nous considérons qu'elles pourraient être encore plus efficaces en isolant les aspects liés à la modélisation des autres aspects principalement liés à la simulation et à la visualisation des résultats. Sans faire appel à la programmation par aspects, nous proposons un cadriciel qui utilise intensivement les métadonnées pour faciliter l'écriture et l'utilisation modèles, et pour produire automatiquement les interfaces utilisateurs de saisie des données et d'affichage des résultats. Cette approche repose sur le concept de métamodélisation de l'ingénierie des modèles. Le cadriciel proposé a été développé principalement .pour la simulation spatialisée et individu-centrée des déplacements d'organismes aquatiques tels que les poissons et les anguilles d'eau douce à différents stades de leur développement.
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@article{PUB00022542, author = {Dumoulin, N.}, title = {SimAquaLife : un cadriciel pour la modélisation de la dynamique spatiale d'organismes aquatiques}, title = {SimAquaLife: a framework for aquatic organisms spatial dynamics modelling}, journal = {Technique et Science Informatiques}, volume = {26}, number = {6}, pages = {701-721}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00022542}, year = {2007}, affiliation = {CEMAGREF CLERMONT FERRAND LISC}, abstract = {Individual-based modelling of ecosystems necessitates a multi-disciplinary approach, making tough the development and the maintenance of these models. Several individual-based modelling platforms exist and make possible to simplify the design and maintenance tasks, however we consider that we could improve by isolating aspects related to modeling from the other aspects mainly related to the simulation techniques and to the display of results. Without taking into account aspect-oriented programming, we propose a software framework which makes an intensive use of metadatas to simplify the use and development of models, and also to produce automatically graphical user interfaces for data settings and results display. This approach is based on the metamodelling concept of model engineering. The software framework has been mainly developed for the spatialized and individual-centered simulation of aquatic organisms movements, mainly river fresh water fishes and eels at different development stages. / a modélisation individu-centrée d'écosystèmes fait intervenir plusieurs disciplines, ce qui a pour effet de compliquer le développement et la maintenance de ces modèles. Plusieurs plate-formes de modélisation individu-centrée existent et permettent de faciliter ces tâches. Nous considérons qu'elles pourraient être encore plus efficaces en isolant les aspects liés à la modélisation des autres aspects principalement liés à la simulation et à la visualisation des résultats. Sans faire appel à la programmation par aspects, nous proposons un cadriciel qui utilise intensivement les métadonnées pour faciliter l'écriture et l'utilisation modèles, et pour produire automatiquement les interfaces utilisateurs de saisie des données et d'affichage des résultats. Cette approche repose sur le concept de métamodélisation de l'ingénierie des modèles. Le cadriciel proposé a été développé principalement .pour la simulation spatialisée et individu-centrée des déplacements d'organismes aquatiques tels que les poissons et les anguilles d'eau douce à différents stades de leur développement.}, }
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F. Goreaud, R. Allain, B. Courbaud, M.A. Ngo Bieng, T. Pérot, J.N. Piroche
Simuler des peuplements de structures variées pour faciliter l'utilisation des modèles "arbre" spatialisés
Revue Forestière Française LIX (2), 2007
abs web bib

In order to study mixed or uneven forest stands, foresters have modelled the dynamics of each individual tree as a function of its characteristics and local neighbourhood. These spatially-explicit individual-based models can be difficult to use, because the characteristics and location of each tree in the initial state have to be specified before running a simulation. Modellers have therefore developed specific tools to simulate such spatially-explicit initial state. The aim of this paper is to detail this concept of spatially-explicit initial state simulation, and to illustrate how such tools can facilitate the use of individual-tree growth models. We first present two applications, one on a regular stand, and another one on a mixed uneven stand. Then we propose a formalisation of these tools, and discuss their advantages and drawbacks. / Pour étudier les peuplements forestiers mélangés ou irréguliers, les dendrométriciens construisent des modèles de l'évolution individuelle de chaque arbre, en fonction de ses caractéristiques et de son environnement local. Ces modèles "arbre" dépendants des distances peuvent être difficiles à utiliser, car il faut spécifier au simulateur les caractéristiques et la position de chaque arbre dans l'état initial. Les modélisateurs ont donc développé des outils pour simuler de tels états initiaux spatialisés. L'objectif de cet article est de présenter ce concept de simulation d'état initial spatialisé, et de montrer comment ces outils peuvent faciliter l'utilisation des modèles "arbre" dépendant des distances. Pour cela, nous proposons tout d'abord deux exemples d'application, sur un peuplement régulier, puis sur un peuplement irrégulier mélangé. Ensuite, nous proposons une formalisation des méthodes utilisées, avant de discuter de leurs avantages et inconvénients.
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@article{PUB00022159, author = {Goreaud, F. and Allain, R. and Courbaud, B. and Ngo Bieng, M.A. and Pérot, T. and Piroche, J.N.}, title = {Simuler des peuplements de structures variées pour faciliter l'utilisation des modèles "arbre" spatialisés}, title = {Simulating forest stands of variable structure to facilitate the use of tree level distance dependant models}, journal = {Revue Forestière Française}, volume = {LIX}, number = {2}, pages = {137-161}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00022159}, year = {2007}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; ONF DIRECTION TECHNIQUE ; CEMAGREF GRENOBLE EMGR ; CEMAGREF NOGENT SUR VERNISSON EFNO ; CEMAGREF NOGENT SUR VERNISSON EFNO ; CEMAGREF NOGENT SUR VERNISSON EFNO}, abstract = {In order to study mixed or uneven forest stands, foresters have modelled the dynamics of each individual tree as a function of its characteristics and local neighbourhood. These spatially-explicit individual-based models can be difficult to use, because the characteristics and location of each tree in the initial state have to be specified before running a simulation. Modellers have therefore developed specific tools to simulate such spatially-explicit initial state. The aim of this paper is to detail this concept of spatially-explicit initial state simulation, and to illustrate how such tools can facilitate the use of individual-tree growth models. We first present two applications, one on a regular stand, and another one on a mixed uneven stand. Then we propose a formalisation of these tools, and discuss their advantages and drawbacks. / Pour étudier les peuplements forestiers mélangés ou irréguliers, les dendrométriciens construisent des modèles de l'évolution individuelle de chaque arbre, en fonction de ses caractéristiques et de son environnement local. Ces modèles "arbre" dépendants des distances peuvent être difficiles à utiliser, car il faut spécifier au simulateur les caractéristiques et la position de chaque arbre dans l'état initial. Les modélisateurs ont donc développé des outils pour simuler de tels états initiaux spatialisés. L'objectif de cet article est de présenter ce concept de simulation d'état initial spatialisé, et de montrer comment ces outils peuvent faciliter l'utilisation des modèles "arbre" dépendant des distances. Pour cela, nous proposons tout d'abord deux exemples d'application, sur un peuplement régulier, puis sur un peuplement irrégulier mélangé. Ensuite, nous proposons une formalisation des méthodes utilisées, avant de discuter de leurs avantages et inconvénients. }, }
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S. Huet, M. Edwards, G. Deffuant
Taking into account the variations of neighbourhood sizes in the mean-field approximation of the threshold model on a random network
JASSS-The Journal of Artificial Societies and Social Simulation 10 (1), 2007
abs web bib

We compare the individual-based "threshold model" of innovation diffusion in the version which has been studied by Young (1998), with an aggregate model we derived from it. This model allows us to formalise and test hypotheses on the influence of individual characteristics upon global evolution. The classical threshold model supposes that an individual adopts a behaviour according to a trade-off between a social pressure and a personal interest. Our study considers only the case where all have the same threshold. We present an aggregated model, which takes into account variations of the neighbourhood sizes, whereas previous work assumed this size fixed (Edwards et al. 2003a). The comparison between the aggregated models (the first one assuming a neighbourhood size and the second one, a variable one) points out an improvement of the approximation in most of the value of parameter space. This proves that the average degree of connectivity (first aggregated model) is not sufficient for characterising the evolution, and that the node degree variability has an impact on the diffusion dynamics. Remaining differences between both models give us some clues about the specific ability of individual-based model to maintain a minority behaviour which becomes a majority by an addition of stochastic effects.
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@article{PUB00021336, author = {Huet, S. and Edwards, M. and Deffuant, G.}, title = {Taking into account the variations of neighbourhood sizes in the mean-field approximation of the threshold model on a random network }, title = {Prendre en compte les variations de taille de voisinage social au sein d'une approximation par champ moyen d'un modèle à seuil sur un réseau aléatoire}, journal = {JASSS-The Journal of Artificial Societies and Social Simulation}, volume = {10}, number = {1}, pages = {15}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00021336 / http://jasss.soc.surrey.ac.uk/10/1/10.html}, year = {2007}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC}, abstract = {We compare the individual-based "threshold model" of innovation diffusion in the version which has been studied by Young (1998), with an aggregate model we derived from it. This model allows us to formalise and test hypotheses on the influence of individual characteristics upon global evolution. The classical threshold model supposes that an individual adopts a behaviour according to a trade-off between a social pressure and a personal interest. Our study considers only the case where all have the same threshold. We present an aggregated model, which takes into account variations of the neighbourhood sizes, whereas previous work assumed this size fixed (Edwards et al. 2003a). The comparison between the aggregated models (the first one assuming a neighbourhood size and the second one, a variable one) points out an improvement of the approximation in most of the value of parameter space. This proves that the average degree of connectivity (first aggregated model) is not sufficient for characterising the evolution, and that the node degree variability has an impact on the diffusion dynamics. Remaining differences between both models give us some clues about the specific ability of individual-based model to maintain a minority behaviour which becomes a majority by an addition of stochastic effects.}, }
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C. Le Pichon, G. Gorges, J. Baudry, H. Boussard, F. Goreaud, T. Faure, P. Boët
Méthodes et outils d'analyse spatiale des habitats des poissons en contexte fluvial anthropisé
Ingénieries - E A T, 2007
abs web bib

Effective management and restoration of habitat for fish should consider how the different vital habitats need to be arranged spatially and their connectivity, especially in human-impacted rivers. As few operational methods are available to study these issues, we propose a riverscape approach based on landscape ecology and stream ecology concepts. It uses a GIS-based habitat mapping and methods and software tools, adapted to the running water characteristics, to make the spatial analysis of fish habitats patterns. These methods allow the detection of the effects of physical alteration and flow regulation on the spatial structure of fish habitats. An illustration is made with the common barbel (Barbus barbus), a threatened species in human-impacted European rivers. / Pour qu'elles soient efficaces, les mesures de gestion et de restauration des habitats piscicoles devraient considérer la structure spatiale et la connectivité des habitats vitaux nécessaires au cycle de vie des espèces menacées, tout particulièrement dans les cours d'eau fortement aménagés. Or, peu de méthodes opérationnelles de quantification de la structure spatiale et de la connectivité de ces habitats sont disponibles pour établir un diagnostic préalable aux actions de restauration. L'approche décrite dans cet article repose sur le couplage des concepts et des outils de l'écologie des cours d'eau et de l'écologie du paysage. Elle propose un mode de représentation cartographique des habitats des poissons utilisant le système d'informations géographiques et des méthodes et outils logiciels pour en faire leur analyse spatiale qui sont adaptés aux particularités des milieux d'eau courante. Ces méthodes permettent, en particulier, de détecter l'effet des aménagements physiques et de la régulation des débits sur la structure spatiale des habitats vitaux des poissons. L'illustration porte sur le barbeau fluviatile (Barbus barbus), une espèce menacée des grands cours d'eau européens aménagés.
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@article{PUB00023149, author = {Le Pichon, C. and Gorges, G. and Baudry, J. and Boussard, H. and Goreaud, F. and Faure, T. and Boët, P.}, title = {Méthodes et outils d'analyse spatiale des habitats des poissons en contexte fluvial anthropisé}, title = {Methods and tools for the spatial analysis of fish habitats in human impacted rivers}, journal = {Ingénieries - E A T}, number = {50}, pages = {21-33}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00023149}, year = {2007}, affiliation = {CEMAGREF ANTONY HBAN ; CEMAGREF ANTONY HBAN ; INRA SAD RENNES ; INRA SAD RENNES ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF BORDEAUX EPBX}, abstract = {Effective management and restoration of habitat for fish should consider how the different vital habitats need to be arranged spatially and their connectivity, especially in human-impacted rivers. As few operational methods are available to study these issues, we propose a riverscape approach based on landscape ecology and stream ecology concepts. It uses a GIS-based habitat mapping and methods and software tools, adapted to the running water characteristics, to make the spatial analysis of fish habitats patterns. These methods allow the detection of the effects of physical alteration and flow regulation on the spatial structure of fish habitats. An illustration is made with the common barbel (Barbus barbus), a threatened species in human-impacted European rivers. / Pour qu'elles soient efficaces, les mesures de gestion et de restauration des habitats piscicoles devraient considérer la structure spatiale et la connectivité des habitats vitaux nécessaires au cycle de vie des espèces menacées, tout particulièrement dans les cours d'eau fortement aménagés. Or, peu de méthodes opérationnelles de quantification de la structure spatiale et de la connectivité de ces habitats sont disponibles pour établir un diagnostic préalable aux actions de restauration. L'approche décrite dans cet article repose sur le couplage des concepts et des outils de l'écologie des cours d'eau et de l'écologie du paysage. Elle propose un mode de représentation cartographique des habitats des poissons utilisant le système d'informations géographiques et des méthodes et outils logiciels pour en faire leur analyse spatiale qui sont adaptés aux particularités des milieux d'eau courante. Ces méthodes permettent, en particulier, de détecter l'effet des aménagements physiques et de la régulation des débits sur la structure spatiale des habitats vitaux des poissons. L'illustration porte sur le barbeau fluviatile (Barbus barbus), une espèce menacée des grands cours d'eau européens aménagés.}, }
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O. Bokanowski, S. Martin, R. Munos, H. Zidani
An anti-diffusive scheme for viability problems
Applied Numerical Mathematics 56 (9), 2006
abs doi web bib

The value function associated with viability problem is discontinuous. We investigate the Ultra-Bee scheme, particularly interesting for its anti-diffusive property in the transport of discontinuous functions. Our numerical results are very encouraging.
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@article{PUB00020443, author = {Bokanowski, O. and Martin, S. and Munos, R. and Zidani, H.}, title = {An anti-diffusive scheme for viability problems}, title = {Un schéma anti-diffusif pour des problèmes de viabilité}, journal = {Applied Numerical Mathematics}, volume = {56}, number = {9}, pages = {1147-1162}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00020443}, doi = {http://dx.doi.org/doi:10.1016/j.apnum.2006.03.004}, year = {2006}, affiliation = {UNIVERSITE PIERRE ET MARIE CURIE LABORATOIRE JACQUES-LOUIS LIONSPARIS, ; CEMAGREF CLERMONT FERRAND LISC ; ECOLE POLYTECHNIQUE CENTRE DE MATHEMATIQUES PALAISEAU ; ENSTA PARIS}, abstract = {The value function associated with viability problem is discontinuous. We investigate the Ultra-Bee scheme, particularly interesting for its anti-diffusive property in the transport of discontinuous functions. Our numerical results are very encouraging.}, }
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G. Deffuant, S. Moss, W. Jager
Dialogues concerning a (possibly) new science
JASSS-The Journal of Artificial Societies and Social Simulation 9 (1), 2006
abs web bib

The paper relates virtual dialogues about social simulation, with the implicit reference to Galieo's 'dialogues concerning two new sciences'.
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@article{PUB00020397, author = {Deffuant, G. and Moss, S. and Jager, W.}, title = {Dialogues concerning a (possibly) new science}, title = {Dialogues à propos d'une (possible) nouvelle science}, journal = {JASSS-The Journal of Artificial Societies and Social Simulation}, volume = {9}, number = {1}, pages = {7}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00020397 / http://jasss.soc.surrey.ac.uk/9/1/1.html}, year = {2006}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; MANCHESTER METROPOLITAN UNIVERSITY GBR ; UNIVERSITY OF GRONINGEN NLD}, abstract = {The paper relates virtual dialogues about social simulation, with the implicit reference to Galieo's 'dialogues concerning two new sciences'.}, }
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G. Deffuant
Comparing extremism propagation patterns in continuous opinion models
JASSS-The Journal of Artificial Societies and Social Simulation 9 (3), 2006
abs web bib

We compare patterns of extremism propagation yielded by 4 continuous opinion models, when the main parameters vary, on different types of networks (total connection, random network, lattice). In two models the individuals take into account the uncertainty of their interlocutor, and they show similar patterns, with a higher probability of double extreme convergence than in the other couple of models (in which the interlocutor's uncertainty is not taken into account). The addition of noise does not change significantly the results, except that it favours the single extreme convergence in some models. The lattice topology of interactions provides results which are significantly different from the ones obtained with a random network of similar connection density. We identify 3 typical behaviours with a single initial extremist, which help to explain the different results. In particular, we observe that the single extreme convergence is favoured by small shortest paths between all pairs of nodes in the network.
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@article{PUB00020398, author = {Deffuant, G.}, title = {Comparing extremism propagation patterns in continuous opinion models}, title = {Formes de propagation de l'extrémisme dans des modèles d'opinions continues}, journal = {JASSS-The Journal of Artificial Societies and Social Simulation}, volume = {9}, number = {3}, pages = {24}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00020398 / http://jasss.soc.surrey.ac.uk/9/3/8.html}, year = {2006}, affiliation = {CEMAGREF CLERMONT FERRAND LISC}, abstract = {We compare patterns of extremism propagation yielded by 4 continuous opinion models, when the main parameters vary, on different types of networks (total connection, random network, lattice). In two models the individuals take into account the uncertainty of their interlocutor, and they show similar patterns, with a higher probability of double extreme convergence than in the other couple of models (in which the interlocutor's uncertainty is not taken into account). The addition of noise does not change significantly the results, except that it favours the single extreme convergence in some models. The lattice topology of interactions provides results which are significantly different from the ones obtained with a random network of similar connection density. We identify 3 typical behaviours with a single initial extremist, which help to explain the different results. In particular, we observe that the single extreme convergence is favoured by small shortest paths between all pairs of nodes in the network. }, }
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F. Goreaud, I. Alvarez, B. Courbaud, F. De Coligny
Long-Term influence of the spatial structure of an initial state on the dynamics of a forest growth model: a simulation study using the Capsis platform
Simulation 82 (7), 2006
abs web bib

Spatially explicit Individual Based Models are more and more often used in forest modelling, especially because they take into account the influence of the spatial structure on the dynamics. However, they are potentially very sensitive to the initial spatial structure used for a simulation, which can be problematic if the initial state is not known, or is simulated in an unrealistic way. The aim of our paper is to study this sensitivity to initial spatial structure in the case of the Mountain model, an individual based model of irregular spruce stands implemented in the Capsis platform. In order to characterise the influence of the initial spatial structure on the dynamics of the model, we simulated different initial spatial structures and compared the results of long term simulations. We showed that the initial spatial structure can highly influence the dynamics of the model, not only during the first cycle of the evolution, but also at very long term in the evolution of the next generations. We also illustrated how some disturbances, such as a periodic gap opening through storms, can modify both the long term dynamics of the stand and the duration of the influence of the initial spatial structure. / Les modèles individus centrés et spatialement explicites sont de plus en plus souvent utilisés en modélisation forestière, en particulier parce qu'ils prennent en compte l'influence de la structure spatiale sur la dynamique. Cependant, ils peuvent être très sensibles à la structure spatiale initiale utilisée dans les simulations, ce qui peut poser problème si on ne connait pas l'état initial, ou si il n'est pas simulé de façon réaliste. L'objectif de cet article est d'étudier cette sensibilité à la structure spatiale initiale dans le cas du modèle "Mountain", un modèle individus centré de pessières irrégulières de montagne implémenté dans la plate-forme CAPSIS. Pour caractériser l'influence de la structure spatiale initiale sur la dynamique du modèle, nous avons simulé des états initiaux de différentes structures spatiales, et comparé les résultats de simulations à long terme. Nous avons montré que la structure spatiale initiale peut influencer fortement la dynamique du modèle, non seulement pendant le premier cycle de l'évolution, mais également à très long terme dans les générations suivantes. Nous avons également montré comment des perturbations, comme l'ouverture de clairières par des tempêtes, peut modifier à la fois la dynamique à long terme du modèle, et la durée de l'influence de la structure spatiale initiale.
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@article{PUB00020509, author = {Goreaud, F. and Alvarez, I. and Courbaud, B. and De Coligny, F.}, title = {Long-Term influence of the spatial structure of an initial state on the dynamics of a forest growth model: a simulation study using the Capsis platform}, title = {Influence à long terme de la structure spatiale d'un état initial sur la dynamique d'un modèle de croissance forestière : une étude simulatoire sur la plate-forme CAPSIS}, journal = {Simulation}, volume = {82}, number = {7}, pages = {475-495}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00020509}, year = {2006}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF GRENOBLE EPGR ; INRA MONTPELLIER}, number = {K LI06 1 ; 06/0072}, abstract = {Spatially explicit Individual Based Models are more and more often used in forest modelling, especially because they take into account the influence of the spatial structure on the dynamics. However, they are potentially very sensitive to the initial spatial structure used for a simulation, which can be problematic if the initial state is not known, or is simulated in an unrealistic way. The aim of our paper is to study this sensitivity to initial spatial structure in the case of the Mountain model, an individual based model of irregular spruce stands implemented in the Capsis platform. In order to characterise the influence of the initial spatial structure on the dynamics of the model, we simulated different initial spatial structures and compared the results of long term simulations. We showed that the initial spatial structure can highly influence the dynamics of the model, not only during the first cycle of the evolution, but also at very long term in the evolution of the next generations. We also illustrated how some disturbances, such as a periodic gap opening through storms, can modify both the long term dynamics of the stand and the duration of the influence of the initial spatial structure. / Les modèles individus centrés et spatialement explicites sont de plus en plus souvent utilisés en modélisation forestière, en particulier parce qu'ils prennent en compte l'influence de la structure spatiale sur la dynamique. Cependant, ils peuvent être très sensibles à la structure spatiale initiale utilisée dans les simulations, ce qui peut poser problème si on ne connait pas l'état initial, ou si il n'est pas simulé de façon réaliste. L'objectif de cet article est d'étudier cette sensibilité à la structure spatiale initiale dans le cas du modèle "Mountain", un modèle individus centré de pessières irrégulières de montagne implémenté dans la plate-forme CAPSIS. Pour caractériser l'influence de la structure spatiale initiale sur la dynamique du modèle, nous avons simulé des états initiaux de différentes structures spatiales, et comparé les résultats de simulations à long terme. Nous avons montré que la structure spatiale initiale peut influencer fortement la dynamique du modèle, non seulement pendant le premier cycle de l'évolution, mais également à très long terme dans les générations suivantes. Nous avons également montré comment des perturbations, comme l'ouverture de clairières par des tempêtes, peut modifier à la fois la dynamique à long terme du modèle, et la durée de l'influence de la structure spatiale initiale.}, }
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C. Le Pichon, G. Gorges, P. Boët, J. Baudry, F. Goreaud, T. Faure
A spatially explicit resource-based approach for managing stream fishes in riverscapes
Environmental Management 37 (3), 2006
abs doi web bib

The article describes a riverscape approach based on landscape ecology concepts, which aims at studying the multiscale relationships between the spatial pattern of stream fish habitat patches and processes depending on fish movements. A review of the literature shows that few operational methods are available to study this relationship due to multiple methodological and practical challenges inherent to underwater environments. We illustrated the approach with literature data on a cyprinid species (Barbus barbus) and an actual riverscape of the Seine River, France. We represented the underwater environment of fishes for different discharges using two-dimensional geographic information system-based maps of the resource habitat patches, defined according to activities (feeding, resting, and spawning). To quantify spatial patterns at nested levels (resource habitat patch, daily activities area, subpopulation area), we calculated their composition, configuration, complementation, and connectivity with multiple spatial analysis methods: patch metrics, moving-window analysis, and least cost modeling. The proximity index allowed us to evaluate habitat patches of relatively great value, depending on their spatial context, which contributes to the setting of preservation policies. The methods presented to delimit potential daily activities areas and subpopulation areas showed the potential gaps in the biological connectivity of the reach. These methods provided some space for action in restoration schemes.
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@article{PUB00019456, author = {Le Pichon, C. and Gorges, G. and Boët, P. and Baudry, J. and Goreaud, F. and Faure, T.}, title = {A spatially explicit resource-based approach for managing stream fishes in riverscapes }, journal = {Environmental Management}, volume = {37}, number = {3}, pages = {322-335}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00019456}, doi = {http://dx.doi.org/10.1007/s00267-005-0027-3 }, year = {2006}, affiliation = {CEMAGREF ANTONY HBAN ; CEMAGREF ANTONY HBAN ; CEMAGREF ANTONY HBAN ; INRA SAD RENNES ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC}, abstract = {The article describes a riverscape approach based on landscape ecology concepts, which aims at studying the multiscale relationships between the spatial pattern of stream fish habitat patches and processes depending on fish movements. A review of the literature shows that few operational methods are available to study this relationship due to multiple methodological and practical challenges inherent to underwater environments. We illustrated the approach with literature data on a cyprinid species (Barbus barbus) and an actual riverscape of the Seine River, France. We represented the underwater environment of fishes for different discharges using two-dimensional geographic information system-based maps of the resource habitat patches, defined according to activities (feeding, resting, and spawning). To quantify spatial patterns at nested levels (resource habitat patch, daily activities area, subpopulation area), we calculated their composition, configuration, complementation, and connectivity with multiple spatial analysis methods: patch metrics, moving-window analysis, and least cost modeling. The proximity index allowed us to evaluate habitat patches of relatively great value, depending on their spatial context, which contributes to the setting of preservation policies. The methods presented to delimit potential daily activities areas and subpopulation areas showed the potential gaps in the biological connectivity of the reach. These methods provided some space for action in restoration schemes. }, }
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M.A. Ngo Bieng, C. Ginisty, F. Goreaud, T. Perot
A first typology of Oak and Scots pine mixed stands in the Orleans forest (France), based on the canopy spatial structure
New Zealand Journal of Forestry Science 36 (2-3), 2006
abs web bib

In recent years there has been a growing interest in uneven-aged or mixed forest stands. This interest is the result of both new demands of society and changing forestry practices. Unfortunately, due to their high complexity, the dynamics of these stands are more difficult to understand than those of pure and even-aged stands. Thus, new research questions have arisen in terms of stand description, stand dynamics and growth modelling. The first step toward better management of such mixed or uneven-aged stands is to describe them precisely, and especially to take into account their variability by defining different types of stands. This step corresponds to a classical typological approach. As spatial structure plays a key role in the dynamics of such stands, spatial structure analysis can be used to infer certain types of information on the biological processes involved in the growth and the dynamics of heterogeneous stands, and thus to build a typology. The aim of this paper is to present a first typology of oak and Scots pine mixed stands, based on a spatial structure analysis of canopy trees. In order to answer this question, we analysed the spatial structure in a mixed stand of oak and Scots pine from the French Centre region. We used the classical Ripley function L(r), and intertype function L12(r) to characterise the specific spatial structure of each population, and the structure of the interaction between populations. We then used the results of this analysis to build a typology for these stands, with four main types. Finally we discuss how the four types may have resulted from ecological processes and historical management, and how such a typology could be used to simulate realistic virtual stands when real data are unavailable.
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@article{PUB00020653, author = {Ngo Bieng, M.A. and Ginisty, C. and Goreaud, F. and Perot, T.}, title = {A first typology of Oak and Scots pine mixed stands in the Orleans forest (France), based on the canopy spatial structure}, title = {Une première typologie de peuplements mélangés Pin sylvestre et Chêne de la forêt d'Orléans (France), basée sur la structure spatiale des arbres de la canopée}, journal = {New Zealand Journal of Forestry Science}, volume = {36}, number = {2-3}, pages = {325-346}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00020653 / http://www.scionresearch.com/nzjfs+articles+to+download.aspx}, year = {2006}, affiliation = {CEMAGREF NOGENT SUR VERNISSON EFNO ; CEMAGREF NOGENT SUR VERNISSON EFNO ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF NOGENT SUR VERNISSON EFNO}, number = {D 5275}, abstract = {In recent years there has been a growing interest in uneven-aged or mixed forest stands. This interest is the result of both new demands of society and changing forestry practices. Unfortunately, due to their high complexity, the dynamics of these stands are more difficult to understand than those of pure and even-aged stands. Thus, new research questions have arisen in terms of stand description, stand dynamics and growth modelling. The first step toward better management of such mixed or uneven-aged stands is to describe them precisely, and especially to take into account their variability by defining different types of stands. This step corresponds to a classical typological approach. As spatial structure plays a key role in the dynamics of such stands, spatial structure analysis can be used to infer certain types of information on the biological processes involved in the growth and the dynamics of heterogeneous stands, and thus to build a typology. The aim of this paper is to present a first typology of oak and Scots pine mixed stands, based on a spatial structure analysis of canopy trees. In order to answer this question, we analysed the spatial structure in a mixed stand of oak and Scots pine from the French Centre region. We used the classical Ripley function L(r), and intertype function L12(r) to characterise the specific spatial structure of each population, and the structure of the interaction between populations. We then used the results of this analysis to build a typology for these stands, with four main types. Finally we discuss how the four types may have resulted from ecological processes and historical management, and how such a typology could be used to simulate realistic virtual stands when real data are unavailable.}, }
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N. Svetoslav, S. Clodong
Hyperchaos chaos hyperchaos transition in modified Rössler systems
Chaos, solitons & fractals 25 (1), 2006
abs doi web bib

We consider in this paper a family of modified hyperchaotic Rössler systems and investigate both problems of understanding hyperchaoschaoshyperchaos transition and computing the prediction time. These systems were obtained and numerically investigated by Nikolov and Clodong [Nikolov S, Clodong S. Occurrence of regular, chaotic and hyperchaotic behavior in a family of modified Rossler hyperchaotic systems. Chaos, Solitons & Fractals 2004;22:40731]. Our studies confirm that transition hyperchaoschaoshyperchaos (i) depends on the change of the sign of the corresponding characteristic equation roots or (ii) can be obtained as a result of the absorption/repulsion of the repeller originally located out of the attractor by the growing attractor. It is also shown that the prediction time is a more reliable predictor of the evolution than the information dimension. We conclude that the prediction time in hyperchaotic regimes is at least one order of magnitude smaller than those in chaotic zones.
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@article{PUB00022822, author = {Svetoslav, N. and Clodong, S.}, title = {Hyperchaos chaos hyperchaos transition in modified Rössler systems}, journal = {Chaos, solitons & fractals }, volume = {25}, number = {1}, pages = {252-263}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00022822}, doi = {http://dx.doi.org/10.1016/j.chaos.2005.05.031}, year = {2006}, affiliation = {INSTITUTE OF MECHANIS SOFIA BGR ; CEMAGREF CLERMONT FERRAND LISC}, abstract = {We consider in this paper a family of modified hyperchaotic Rössler systems and investigate both problems of understanding hyperchaoschaoshyperchaos transition and computing the prediction time. These systems were obtained and numerically investigated by Nikolov and Clodong [Nikolov S, Clodong S. Occurrence of regular, chaotic and hyperchaotic behavior in a family of modified Rossler hyperchaotic systems. Chaos, Solitons & Fractals 2004;22:40731]. Our studies confirm that transition hyperchaoschaoshyperchaos (i) depends on the change of the sign of the corresponding characteristic equation roots or (ii) can be obtained as a result of the absorption/repulsion of the repeller originally located out of the attractor by the growing attractor. It is also shown that the prediction time is a more reliable predictor of the evolution than the information dimension. We conclude that the prediction time in hyperchaotic regimes is at least one order of magnitude smaller than those in chaotic zones.}, }
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G. Deffuant, S. Huet, F. Amblard
An individual-based model of innovation diffusion mixing social influence and rational anticipation
American Journal of Sociology 110 (4), 2005
abs web bib

We propose an individual-based model of innovation diffusion and explore its main dynamical properties. In the model, individuals give an a priori social value to the innovation, which evolves during their interactions with the Relative agreement influence model. This model offers the possibility of including a minority of extremists, with extreme and very certain opinions. Individuals who give a good social value to the innovation, tend to look for information which allows them to evaluate a more precise individual benefit of the adoption. They can get such information from their associates or from the media. If their social value is bad, neither they consider the information or transmit it. Individuals adopt the innovation if the overall evaluation including the social value and the individual benefit is good enough with a sufficient certainty. The main result of the model exploration is that innovations with high social values and bad individual benefit have more chances to succeed, than innovations with bad social value and high individual benefit. Moreover, in some cases, a minority of extremists can have a very important impact on the propagation, by polarizing the social value. / Nous proposons un modèle individu-centré de diffusion de l'innovation et explorons ses principales propriétés dynamiques. Dans notre modèle, les individus donnent une valeur sociale a priori à l'innovation. Cette valeur évolue durant les interactions entre les individus selon le modèle d'influence "Relative agreement". Ce modèle permet de prendre en compte les minorités dotées d'opinions extrêmes et certaines. Les individus pensant l'innovation bonne socialement recherchent l'information qui leur permettra d'évaluer précisément l'impact à titre personnel de l'adoption. Une telle information peut être disponible auprès d'un de leur collègue ou des medias. Lorsqu'ils pensent l'innovation mauvaise socialement, ils ne considèrent pas l'information et ne la transmettent pas. Les individus adoptent l'innovation si l'évaluation globale (incluant valeur sociale et impact à titre personnel) est suffisamment positive avec une certitude suffisante. Le résultat principal de l'exploration du modèle est que les innovations dotées d'une valeur sociale forte et d'un impact personnel mauvais ont davantage de chances d'être adoptées que les innovations dotées d'une mauvaise valeur sociale et d'un impact personnel bon. Par ailleurs, dans certains cas, une minorité d'extrémistes peut avoir un impact important sur la diffusion en diffusant à tous leurs opinions extrêmes sur la valeur sociale positive de l'innovation.
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@article{PUB00018516, author = {Deffuant, G. and Huet, S. and Amblard, F.}, title = {An individual-based model of innovation diffusion mixing social influence and rational anticipation}, title = {Un modèle individu-centré de diffusion de l'innovation mixant influence sociale et anticipation rationnelle}, journal = {American Journal of Sociology}, volume = {110}, number = {4}, pages = {1041-1069}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00018516}, year = {2005}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC}, abstract = {We propose an individual-based model of innovation diffusion and explore its main dynamical properties. In the model, individuals give an a priori social value to the innovation, which evolves during their interactions with the Relative agreement influence model. This model offers the possibility of including a minority of extremists, with extreme and very certain opinions. Individuals who give a good social value to the innovation, tend to look for information which allows them to evaluate a more precise individual benefit of the adoption. They can get such information from their associates or from the media. If their social value is bad, neither they consider the information or transmit it. Individuals adopt the innovation if the overall evaluation including the social value and the individual benefit is good enough with a sufficient certainty. The main result of the model exploration is that innovations with high social values and bad individual benefit have more chances to succeed, than innovations with bad social value and high individual benefit. Moreover, in some cases, a minority of extremists can have a very important impact on the propagation, by polarizing the social value. / Nous proposons un modèle individu-centré de diffusion de l'innovation et explorons ses principales propriétés dynamiques. Dans notre modèle, les individus donnent une valeur sociale a priori à l'innovation. Cette valeur évolue durant les interactions entre les individus selon le modèle d'influence "Relative agreement". Ce modèle permet de prendre en compte les minorités dotées d'opinions extrêmes et certaines. Les individus pensant l'innovation bonne socialement recherchent l'information qui leur permettra d'évaluer précisément l'impact à titre personnel de l'adoption. Une telle information peut être disponible auprès d'un de leur collègue ou des medias. Lorsqu'ils pensent l'innovation mauvaise socialement, ils ne considèrent pas l'information et ne la transmettent pas. Les individus adoptent l'innovation si l'évaluation globale (incluant valeur sociale et impact à titre personnel) est suffisamment positive avec une certitude suffisante. Le résultat principal de l'exploration du modèle est que les innovations dotées d'une valeur sociale forte et d'un impact personnel mauvais ont davantage de chances d'être adoptées que les innovations dotées d'une mauvaise valeur sociale et d'un impact personnel bon. Par ailleurs, dans certains cas, une minorité d'extrémistes peut avoir un impact important sur la diffusion en diffusant à tous leurs opinions extrêmes sur la valeur sociale positive de l'innovation. }, }
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M. Edwards, N. Ferrand, F. Goreaud, S. Huet
The relevance of aggregating a water consumption model cannot be disconnected from the choice of information available on the resource
Simulation Modelling Practice and Theory 13 (4), 2005
abs doi web bib

Individual-based models, which permit a fine description of the dynamics of a population are costly in computation time and need many simulations for outlining global laws. Conversely aggregate models take less time for simulation and provide analytical understanding of the global evolution. Therefore they can sometimes profitably replace individual-based models. However, in many cases these models are linked to a model of environment which evolves over time. In this paper we show that the relevance of using an aggregate vs. an individual based model of water consumption highly depends on the information available on the resource. We use two versions of a consumption model (individual-based and aggregate), simulating a reversible diffusion process which depends on the information available on the resource. We compare the results of the two models for various kinds links between the resource and consumption models and corresponding to the information about the resource provided to the consumers. We propose and test different properties of this information which might lead to difference of the results. / Les modèles individus centrés, qui permettent de décrire finement la dynamique d'une population, sont coûteux en temps et nécessitent de nombreuses simulations pour comprendre leur comportement. Inversement, les modèles agrégés sont plus rapides à simuler, et donnent des interprétations analytiques des comportement globaux. C'est pourquoi ils peuvent parfois remplacer des modèles individus centrés. Cependant, dans de nombreux cas ces modèles doivent être couplés à des modèles de l'environnement, qui évolue au cours du temps. Dans cet article, nous montrons que, dans le cas des modèles de consommation d'eau, la pertinence d'utiliser un modèles agrégé plutôt qu'un modèle individus centré dépend fortement de l'information disponible sur la ressource. Nous utilisons deux versions d'un modèle de consommation d'eau (individus centré et agrégé), et simulons un processus réversible de diffusion des comportements qui dépend de l'information disponible sur la ressource. Nous comparons les résultats des deux modèles pour différents types de couplage entre la ressource et les modèles de consommation, qui correspondent à l'information sur la ressource donnée aux consommateurs. Nous testons comment différentes propriétés de ces informations peuvent entraîner des différences sur les résultats des simulations.
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@article{PUB00016842, author = {Edwards, M. and Ferrand, N. and Goreaud, F. and Huet, S.}, title = {The relevance of aggregating a water consumption model cannot be disconnected from the choice of information available on the resource}, title = {La pertinence de l'agrégation d'un modèle de consommation d'eau ne peut être évaluée indépendamment du choix de l'information disponible sur la ressource}, journal = {Simulation Modelling Practice and Theory}, volume = {13}, number = {4}, pages = {287-307}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00016842}, doi = {http://dx.doi.org/10.1016/j.simpat.2004.11.008}, year = {2005}, affiliation = {LIP6 PARIS ; CEMAGREF MONTPELLIER IRMO UMR G-EAU ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC}, number = {05/IRMO-PUB16842}, abstract = {Individual-based models, which permit a fine description of the dynamics of a population are costly in computation time and need many simulations for outlining global laws. Conversely aggregate models take less time for simulation and provide analytical understanding of the global evolution. Therefore they can sometimes profitably replace individual-based models. However, in many cases these models are linked to a model of environment which evolves over time. In this paper we show that the relevance of using an aggregate vs. an individual based model of water consumption highly depends on the information available on the resource. We use two versions of a consumption model (individual-based and aggregate), simulating a reversible diffusion process which depends on the information available on the resource. We compare the results of the two models for various kinds links between the resource and consumption models and corresponding to the information about the resource provided to the consumers. We propose and test different properties of this information which might lead to difference of the results. / Les modèles individus centrés, qui permettent de décrire finement la dynamique d'une population, sont coûteux en temps et nécessitent de nombreuses simulations pour comprendre leur comportement. Inversement, les modèles agrégés sont plus rapides à simuler, et donnent des interprétations analytiques des comportement globaux. C'est pourquoi ils peuvent parfois remplacer des modèles individus centrés. Cependant, dans de nombreux cas ces modèles doivent être couplés à des modèles de l'environnement, qui évolue au cours du temps. Dans cet article, nous montrons que, dans le cas des modèles de consommation d'eau, la pertinence d'utiliser un modèles agrégé plutôt qu'un modèle individus centré dépend fortement de l'information disponible sur la ressource. Nous utilisons deux versions d'un modèle de consommation d'eau (individus centré et agrégé), et simulons un processus réversible de diffusion des comportements qui dépend de l'information disponible sur la ressource. Nous comparons les résultats des deux modèles pour différents types de couplage entre la ressource et les modèles de consommation, qui correspondent à l'information sur la ressource donnée aux consommateurs. Nous testons comment différentes propriétés de ces informations peuvent entraîner des différences sur les résultats des simulations.}, }
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F. Goreaud, F. De Coligny, B. Courbaud, J.F. Dhôte, P. Dreyfus, T. Perot
La modélisation : un outil pour la gestion et l'aménagement en forêt
VertigO 6 (2), 2005
abs web bib

In order to predict the evolution of forest stands, and thus to facilitate forest management, researchers have developed different types of models of stand dynamics. In this paper, we illustrate the interest of such models as management tools. We consider three applications : (i) in a pure, even-aged oak stand, the use of a model in order to take into account the effect of productivity changes on growth ; (ii) in mixed, uneven-aged stands of spruce and fir, the comparison through simulation of a classical thinning to a thinning with openings ; (iii) in large-scale areas, the modelling of the dynamics of species composition of mixed stands. We finally discuss the limitations of models and future perspectives for research in this field. / Pour prédire l'évolution des peuplements forestiers, et ainsi faciliter l'aménagement, les chercheurs ont mis au point différents types de modèles de dynamique forestière. Dans cet article, nous illustrons l'intérêt de ces modèles comme outils pour la gestion. Nous présentons 3 applications : (i) dans un peuplement régulier de chênes, l'utilisation d'un modèle pour prendre en compte l'effet d'un changement de productivité sur la croissance ; (ii) dans un peuplement mélangé irrégulier épicéas - sapins, la comparaison par simulation d'un scénario sylvicole classique et d'un scénario d'éclaircies par trouées ; (iii) à l'échelle d'un massif forestier, la modélisation de l'évolution de la composition de peuplements mélangés. Nous discutons ensuite des limites des modèles ainsi que des perspectives de recherche.
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@article{PUB00018777, author = {Goreaud, F. and De Coligny, F. and Courbaud, B. and Dhôte, J.F. and Dreyfus, P. and Perot, T.}, title = {La modélisation : un outil pour la gestion et l'aménagement en forêt}, title = {Models : tools for forest management}, journal = {VertigO}, volume = {6}, number = {2}, pages = {12}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00018777 / http://www.vertigo.uqam.ca/vol6no2/art6vol6no2/vertigovol6no2_goreaud_et_coll.pdf}, year = {2005}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; INRA MONTPELLIER UMR UMAP ; INRA MONTPELLIER UMR AMAP ; INRA AVIGNON ; CEMAGREF GRENOBLE EPGR ; CEMAGREF NOGENT SUR VERNISSON EFNO}, abstract = {In order to predict the evolution of forest stands, and thus to facilitate forest management, researchers have developed different types of models of stand dynamics. In this paper, we illustrate the interest of such models as management tools. We consider three applications : (i) in a pure, even-aged oak stand, the use of a model in order to take into account the effect of productivity changes on growth ; (ii) in mixed, uneven-aged stands of spruce and fir, the comparison through simulation of a classical thinning to a thinning with openings ; (iii) in large-scale areas, the modelling of the dynamics of species composition of mixed stands. We finally discuss the limitations of models and future perspectives for research in this field. / Pour prédire l'évolution des peuplements forestiers, et ainsi faciliter l'aménagement, les chercheurs ont mis au point différents types de modèles de dynamique forestière. Dans cet article, nous illustrons l'intérêt de ces modèles comme outils pour la gestion. Nous présentons 3 applications : (i) dans un peuplement régulier de chênes, l'utilisation d'un modèle pour prendre en compte l'effet d'un changement de productivité sur la croissance ; (ii) dans un peuplement mélangé irrégulier épicéas - sapins, la comparaison par simulation d'un scénario sylvicole classique et d'un scénario d'éclaircies par trouées ; (iii) à l'échelle d'un massif forestier, la modélisation de l'évolution de la composition de peuplements mélangés. Nous discutons ensuite des limites des modèles ainsi que des perspectives de recherche. }, }
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L. Rousseau, G. Deffuant
Gestion des territoires : aider à la formulation collective des problèmes
Natures Sciences Sociétés 13 (1), 2005
abs web bib

Making decisions about land and water management and about urban planning in Europe involves an increasingly diverse range of actors representing heterogeneous stakes, skills and legitimacy. This situation emphasizes the importance of organizing a stage specifically devoted to problem formulation in the negotiation process. The facilitators and institutions managing the discussions are therefore keenly interested in methods and tools that help integrate the viewpoints of each actor into a common problem'. Our research aims to provide such tools and methods. We propose a conceptual framework in which the problem formulation process involves nested and alternating cycles of individual viewpoint elaboration and group discussions, confronting individual viewpoints. Our framework emphasises the crucial role of viewpoint comparison to link individual and group processes. In order to facilitate such comparisons, we suppose that viewpoints include a model of the territory and an evaluation (or preference) model. A viewpoint takes as input a hypothetical set of actions and yields as output the set of probable consequences of these actions, and the actor's evaluation (preference) of these consequences. We argue that the use of such viewpoints and comparison helps to progressively clarify the viewpoints through the discussion, to define a collective problem and to organize interactions. Following this framework, we defined and tested an operational method and a software tool called SICOPTER. The operational method organizes the whole process into phases based on simple paper representations of viewpoints and problems. SICOPTER enables the actors express their preferences about the results of expert territory models, and compare them with other stakeholders' ones, via computer representations. We present and discuss a set of tests that confirm the interest of viewpoint comparisons to facilitate group problem formulations. / La législation définissant les procédures de gestion des territoires impose de prendre en compte des enjeux d'acteurs représentatifs des différentes composantes du territoire. Nous présentons un cadre de formalisation de cette prise en compte qui fournit aux décideurs et animateurs une description systématique des problèmes définis lors de la procédure et une synthèse de la définition du territoire. Ces deux produits permettent à l'animateur de proposer de nouvelles actions possibles à la discussion et l'évaluation des acteurs. Chaque acteur construit son point de vue décrivant les conséquences de ces actions et l'évaluation que l'acteur en fait, puis le rend public. La comparaison de ces points de vue dans un cadre privé, d'une part, puis la discussion autour du résultat des comparaisons des points de vue publics, d'autre part, forment un cycle de formulation des problèmes parcourus autant que nécessaire. Le cadre est évalué par le test de deux outils dérivés.
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@article{PUB00018533, author = {Rousseau, L. and Deffuant, G.}, title = {Gestion des territoires : aider à la formulation collective des problèmes}, title = {Integrated group problem formulation}, journal = {Natures Sciences Sociétés}, volume = {13}, number = {1}, pages = {21-32}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00018533}, year = {2005}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC}, abstract = {Making decisions about land and water management and about urban planning in Europe involves an increasingly diverse range of actors representing heterogeneous stakes, skills and legitimacy. This situation emphasizes the importance of organizing a stage specifically devoted to problem formulation in the negotiation process. The facilitators and institutions managing the discussions are therefore keenly interested in methods and tools that help integrate the viewpoints of each actor into a common problem'. Our research aims to provide such tools and methods. We propose a conceptual framework in which the problem formulation process involves nested and alternating cycles of individual viewpoint elaboration and group discussions, confronting individual viewpoints. Our framework emphasises the crucial role of viewpoint comparison to link individual and group processes. In order to facilitate such comparisons, we suppose that viewpoints include a model of the territory and an evaluation (or preference) model. A viewpoint takes as input a hypothetical set of actions and yields as output the set of probable consequences of these actions, and the actor's evaluation (preference) of these consequences. We argue that the use of such viewpoints and comparison helps to progressively clarify the viewpoints through the discussion, to define a collective problem and to organize interactions. Following this framework, we defined and tested an operational method and a software tool called SICOPTER. The operational method organizes the whole process into phases based on simple paper representations of viewpoints and problems. SICOPTER enables the actors express their preferences about the results of expert territory models, and compare them with other stakeholders' ones, via computer representations. We present and discuss a set of tests that confirm the interest of viewpoint comparisons to facilitate group problem formulations. / La législation définissant les procédures de gestion des territoires impose de prendre en compte des enjeux d'acteurs représentatifs des différentes composantes du territoire. Nous présentons un cadre de formalisation de cette prise en compte qui fournit aux décideurs et animateurs une description systématique des problèmes définis lors de la procédure et une synthèse de la définition du territoire. Ces deux produits permettent à l'animateur de proposer de nouvelles actions possibles à la discussion et l'évaluation des acteurs. Chaque acteur construit son point de vue décrivant les conséquences de ces actions et l'évaluation que l'acteur en fait, puis le rend public. La comparaison de ces points de vue dans un cadre privé, d'une part, puis la discussion autour du résultat des comparaisons des points de vue publics, d'autre part, forment un cycle de formulation des problèmes parcourus autant que nécessaire. Le cadre est évalué par le test de deux outils dérivés.}, }
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G. Weisbuch, G. Deffuant, F. Amblard
Persuasion dynamics
Physica A-Statistical Mechanics and its Applications 353, 2005
abs web bib

We here discuss a model of continuous opinion dynamics in which agents adjust continuous opinions as a result of random binary encounters whenever their difference in opinion is below a given threshold. We concentrate on the version of the model in the presence of few extremists which might drive the dynamics to generalised extremism. A network version of the dynamics is presented here, and its results are compared to those previously obtained for the full-mixng case. The same dynamical regimes are observed, but in rather different parameter regions. We here show that the combination of meso-scale features resulting from the first interaction steps. determines the asymptotic state of the dynamics.
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@article{PUB00018534, author = {Weisbuch, G. and Deffuant, G. and Amblard, F.}, title = {Persuasion dynamics}, title = {Dynamiques de persuasion}, journal = {Physica A-Statistical Mechanics and its Applications}, volume = {353}, pages = {27}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00018534}, year = {2005}, affiliation = {ECOLE NORMALE SUPERIEURE ; CEMAGREF CLERMONT FERRAND LISC ; UNIVERSITE DE TOULOUSE}, abstract = {We here discuss a model of continuous opinion dynamics in which agents adjust continuous opinions as a result of random binary encounters whenever their difference in opinion is below a given threshold. We concentrate on the version of the model in the presence of few extremists which might drive the dynamics to generalised extremism. A network version of the dynamics is presented here, and its results are compared to those previously obtained for the full-mixng case. The same dynamical regimes are observed, but in rather different parameter regions. We here show that the combination of meso-scale features resulting from the first interaction steps. determines the asymptotic state of the dynamics.}, }
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I. Alvarez
Explication géométrique du résultat dans les arbres de décision
Revue d'intelligence artificielle 18 (3), 2004
abs web bib

This article is devoted to the problem of the explanation of the result given by a decision tree (DT) when it is used as a decision aid system, to classify input data and to provide the output class as a result. At now the end-user can rely mainly on some estimation of the error-rate or on the trace of the classification, that is the path run through the DT. We propose here two new methods to qualify the result given by the DT for each particular case. These methods are based on a geometric study of the inverse image of the different classes (the decision surface). First we identify the tests in the tree that are the most relevant to explain the final class, by the way of sensitivity analysis: the vector of initial data is projected onto the decision surface. Second, we study the distribution of errors in relation to the decision surface: the distance to this surface is computed for a sample. The distance of a new case is then presented to the end-user in this context. / Cet article s'intéresse au problème de l'explication des résultats fournis par un arbre de décision utilisé en tant que système d'aide à la décision. On cherche à apporter une information supplémentaire à la classe prédite pour chaque vecteur particulier de données d'entrée. Actuellement on dispose surtout de la trace du classement (le chemin parcouru dans l'arbre), et d'une estimation du taux d'erreur ou d'un risque associé à un mauvais classement. Nous proposons ici deux nouvelles méthodes de qualification du résultat, basées sur une étude géométrique de la frontière de l'image inverse des différentes classes (la surface de décision). La première méthode consiste à identifier les séparateurs les plus déterminants pour expliquer le résultat, en effectuant une analyse de sensibilité, par projection des données initiales sur la surface de décision. La deuxième méthode consiste à caractériser la distribution des erreurs relativement à la surface de décision, en calculant la distance à cette surface pour un ensemble de données, et à replacer chaque nouveau cas dans ce contexte.
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@article{PUB00015174, author = {Alvarez, I.}, title = {Explication géométrique du résultat dans les arbres de décision}, journal = {Revue d'intelligence artificielle}, volume = {18}, number = {3}, pages = {411-441}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00015174}, year = {2004}, affiliation = {CEMAGREF CLERMONT FERRAND LISC}, number = {K LI04 4}, abstract = {This article is devoted to the problem of the explanation of the result given by a decision tree (DT) when it is used as a decision aid system, to classify input data and to provide the output class as a result. At now the end-user can rely mainly on some estimation of the error-rate or on the trace of the classification, that is the path run through the DT. We propose here two new methods to qualify the result given by the DT for each particular case. These methods are based on a geometric study of the inverse image of the different classes (the decision surface). First we identify the tests in the tree that are the most relevant to explain the final class, by the way of sensitivity analysis: the vector of initial data is projected onto the decision surface. Second, we study the distribution of errors in relation to the decision surface: the distance to this surface is computed for a sample. The distance of a new case is then presented to the end-user in this context. / Cet article s'intéresse au problème de l'explication des résultats fournis par un arbre de décision utilisé en tant que système d'aide à la décision. On cherche à apporter une information supplémentaire à la classe prédite pour chaque vecteur particulier de données d'entrée. Actuellement on dispose surtout de la trace du classement (le chemin parcouru dans l'arbre), et d'une estimation du taux d'erreur ou d'un risque associé à un mauvais classement. Nous proposons ici deux nouvelles méthodes de qualification du résultat, basées sur une étude géométrique de la frontière de l'image inverse des différentes classes (la surface de décision). La première méthode consiste à identifier les séparateurs les plus déterminants pour expliquer le résultat, en effectuant une analyse de sensibilité, par projection des données initiales sur la surface de décision. La deuxième méthode consiste à caractériser la distribution des erreurs relativement à la surface de décision, en calculant la distance à cette surface pour un ensemble de données, et à replacer chaque nouveau cas dans ce contexte.}, }
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F. Amblard, G. Deffuant
The role of network topology on extremism propagation with the relative agreement opinion
Physica A-Statistical Mechanics and its Applications 343, 2004
abs doi web bib

In Deffuant et al. (J. Artif. Soc. Soc. Simulation 5 (2002) 4), we proposed a simple model of opinion dynamics, which we used to simulate the influence of extremists in a population. Simulations were run without any specific interaction structure and varying the simulation parameters, we observed different attractors such as predominance of centrism, or of extremism. We even observed in certain conditions, that the whole population drifts to one extreme of the opinion, even if initially there are an equal number of extremists at each extreme of the opinion axis. In the present paper, we study the influence of the social networks on the presence of such a dynamical behavior. In particular, we use small-world networks with variable connectivity and randomness of the connections. We find that the drift to a single extreme appears only beyond a critical level of connectivity, which decreases when the randomness increases.
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@article{PUB00015776, author = {Amblard, F. and Deffuant, G.}, title = {The role of network topology on extremism propagation with the relative agreement opinion}, journal = {Physica A-Statistical Mechanics and its Applications}, volume = {343}, pages = {725-738}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00015776}, doi = {http://dx.doi.org/10.1016/j.physa.2004.06.102}, year = {2004}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC}, abstract = {In Deffuant et al. (J. Artif. Soc. Soc. Simulation 5 (2002) 4), we proposed a simple model of opinion dynamics, which we used to simulate the influence of extremists in a population. Simulations were run without any specific interaction structure and varying the simulation parameters, we observed different attractors such as predominance of centrism, or of extremism. We even observed in certain conditions, that the whole population drifts to one extreme of the opinion, even if initially there are an equal number of extremists at each extreme of the opinion axis. In the present paper, we study the influence of the social networks on the presence of such a dynamical behavior. In particular, we use small-world networks with variable connectivity and randomness of the connections. We find that the drift to a single extreme appears only beyond a critical level of connectivity, which decreases when the randomness increases.}, }
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S. Martin
The cost of restoration as a way of defining resilience: a viability approach applied to a model of lake eutrophication
Ecology and Society 9 (2), 2004
abs web bib

Multiple stable states or alternative equilibria in ecological systems have been recognized since the 1960s in the ecological literature. Very often, the shift between alternative states occurs suddenly and the resource flows from these systems are modified. Resilience is the capacity of a system to undergo disturbance and maintain its functions and controls. It has multiple levels of meaning, from the metaphorical to the specific. However, most studies that explore resilience-related ideas have used resilience as a metaphor or theoretical construct. In a few cases, it has been defined operationally in the context of a model of a particular system. In this paper, resilience is defined consistently with the theoretical uses of the term, in the context of ecosystem models within an application to a simple model of lake eutrophication. The theoretical definitions of resilience and the characteristics of the operational definition that are necessary for ensuring consistency are reviewed. A mathematical formulation of resilience is built in the framework of the viability theory. This formulation emphasizes the link between resilience and the cost of the recovery after a disturbance. This cost is first chosen in relation to the time of crisis in the application to a model of lake eutrophication. The resilience values are then obtained by numerical integration. For another choice of the cost function, the viability algorithm is needed to compute the resilience values. These applications demonstrate the usefulness of our operational definition.
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@article{PUB00015017, author = {Martin, S.}, title = {The cost of restoration as a way of defining resilience: a viability approach applied to a model of lake eutrophication}, journal = {Ecology and Society}, volume = {9}, number = {2}, pages = {19}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00015017 / http://www.ecologyandsociety.org/vol9/iss2/art8}, year = {2004}, affiliation = {CEMAGREF CLERMONT FERRAND LISC}, number = {K LI04 4}, abstract = {Multiple stable states or alternative equilibria in ecological systems have been recognized since the 1960s in the ecological literature. Very often, the shift between alternative states occurs suddenly and the resource flows from these systems are modified. Resilience is the capacity of a system to undergo disturbance and maintain its functions and controls. It has multiple levels of meaning, from the metaphorical to the specific. However, most studies that explore resilience-related ideas have used resilience as a metaphor or theoretical construct. In a few cases, it has been defined operationally in the context of a model of a particular system. In this paper, resilience is defined consistently with the theoretical uses of the term, in the context of ecosystem models within an application to a simple model of lake eutrophication. The theoretical definitions of resilience and the characteristics of the operational definition that are necessary for ensuring consistency are reviewed. A mathematical formulation of resilience is built in the framework of the viability theory. This formulation emphasizes the link between resilience and the cost of the recovery after a disturbance. This cost is first chosen in relation to the time of crisis in the application to a model of lake eutrophication. The resilience values are then obtained by numerical integration. For another choice of the cost function, the viability algorithm is needed to compute the resilience values. These applications demonstrate the usefulness of our operational definition.}, }
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G. Deffuant, G. Weisbuch, F. Amblard, T. Faure
Simple is beautiful... and necessary
JASSS-The Journal of Artificial Societies and Social Simulation 6 (1), 2003
abs web bib

A contribution to the JASSS forum, in reaction to the paper in Frankfurter Allgemeine Zeitung about our model of extremism. / Une contribution au forum de JASSS, en réaction à l'article du Frankfurter Allgemeine Zeitung à propos de notre modèle de l'extrémisme.
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@article{PUB00011230, author = {Deffuant, G. and Weisbuch, G. and Amblard, F. and Faure, T.}, title = {Simple is beautiful... and necessary}, journal = {JASSS-The Journal of Artificial Societies and Social Simulation}, volume = {6}, number = {1}, pages = {4}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00011230 / http://jasss.soc.surrey.ac.uk/6/1/6.html}, year = {2003}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; ECOLE NORMALE SUPERIEURE LABORATOIRE DE PHYSIQUE STATISTIQUE PARIS ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC}, number = {03/0007}, abstract = {A contribution to the JASSS forum, in reaction to the paper in Frankfurter Allgemeine Zeitung about our model of extremism. / Une contribution au forum de JASSS, en réaction à l'article du Frankfurter Allgemeine Zeitung à propos de notre modèle de l'extrémisme.}, }
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M. Edwards, S. Huet, F. Goreaud, G. Deffuant
Comparing an individual-based model of behaviour diffusion with its mean field aggregate approximation.
JASSS-The Journal of Artificial Societies and Social Simulation 6 (4), 2003
abs web bib

In this paper we compare a version of the individual-based 'threshold model' of innovation diffusion with an aggregate deterministic model that we constructed from it. The classical threshold model supposes that an individual adopts a behaviour according to a trade-off between a social pressure (the number of neighbours adopting the behaviour) and a personal interest or resistance to change (the threshold). The aggregate model makes approximations in order to estimate the evolution of groups of individuals with the same number of neighbours of similar behaviour. We compare both models at different points of the parameter space. We find that the aggregate model gives a good approximation of the individual in some cases; however in other cases the behaviour of the aggregate approximation differs. Using theoretical interpretation of this difference based on a study of the attractors of the aggregate model, we hypothesise that the two models have the same behaviour when the aggregate model has only one attractor and that differences can occur when it has two. / Nous comparons un modèle individu-centré à seuil de diffusion de l'innovation (Valente 1995) dans la version étudiée par P. Young, et un modèle agrégé déterministe que nous avons construit en cohérence. Le modèle classique de diffusion de l'innovation à seuil suppose qu'un individu adopte un comportement suivant un compromis entre la pression sociale (le nombre de ses voisins ayant adopté ce comportement) et un intérêt personnel de résistance au changement (le seuil). Le modèle agrégé fait appel à des approximations pour estimer l'évolution de groupes d'individus ayant le même nombre de voisins suivant un certain comportement. Nous comparons ces deux modèles en différents points de l'espace des paramètres. Nous trouvons que le modèle agrégé approxime bien le modèle individu-centré dans certains cas ; toutefois, il s'avère également parfois que le comportement du modèle agrégé diffère. En nous appuyant sur une interprétation théorique de cette différence, fondée sur une étude des attracteurs du modèle agrégé, nous proposons l'hypothèse que les deux modèles suivent le même comportement lorsque le modèle agrégé n'a qu'un seul attracteur, et que des différences peuvent apparaître quand il en a deux.
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@article{PUB00018793, author = {Edwards, M. and Huet, S. and Goreaud, F. and Deffuant, G.}, title = {Comparing an individual-based model of behaviour diffusion with its mean field aggregate approximation.}, title = {Comparaison d'un modèle individu-centré de diffusion de l'innovation avec son approximation par champ moyen}, journal = {JASSS-The Journal of Artificial Societies and Social Simulation}, volume = {6}, number = {4}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00018793 / http://jasss.soc.surrey.ac.uk/6/4/9.html}, year = {2003}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC}, abstract = {In this paper we compare a version of the individual-based 'threshold model' of innovation diffusion with an aggregate deterministic model that we constructed from it. The classical threshold model supposes that an individual adopts a behaviour according to a trade-off between a social pressure (the number of neighbours adopting the behaviour) and a personal interest or resistance to change (the threshold). The aggregate model makes approximations in order to estimate the evolution of groups of individuals with the same number of neighbours of similar behaviour. We compare both models at different points of the parameter space. We find that the aggregate model gives a good approximation of the individual in some cases; however in other cases the behaviour of the aggregate approximation differs. Using theoretical interpretation of this difference based on a study of the attractors of the aggregate model, we hypothesise that the two models have the same behaviour when the aggregate model has only one attractor and that differences can occur when it has two. / Nous comparons un modèle individu-centré à seuil de diffusion de l'innovation (Valente 1995) dans la version étudiée par P. Young, et un modèle agrégé déterministe que nous avons construit en cohérence. Le modèle classique de diffusion de l'innovation à seuil suppose qu'un individu adopte un comportement suivant un compromis entre la pression sociale (le nombre de ses voisins ayant adopté ce comportement) et un intérêt personnel de résistance au changement (le seuil). Le modèle agrégé fait appel à des approximations pour estimer l'évolution de groupes d'individus ayant le même nombre de voisins suivant un certain comportement. Nous comparons ces deux modèles en différents points de l'espace des paramètres. Nous trouvons que le modèle agrégé approxime bien le modèle individu-centré dans certains cas ; toutefois, il s'avère également parfois que le comportement du modèle agrégé diffère. En nous appuyant sur une interprétation théorique de cette différence, fondée sur une étude des attracteurs du modèle agrégé, nous proposons l'hypothèse que les deux modèles suivent le même comportement lorsque le modèle agrégé n'a qu'un seul attracteur, et que des différences peuvent apparaître quand il en a deux.}, }
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F. Goreaud, R. Pelissier
Avoiding misinterpretation of biotic interactions with the intertype K12-function: population independence vs. random labelling hypotheses
Journal of Vegetation Science 14 (K LI03 13), 2003
abs web bib

The interactions between plants of different species, age or size play an important role in the dynamics of an ecosystem and can induce specific structures. These interactions can be studied by analysing the spatial structure of the corresponding bivariate patterns. The intertype L12-function has recently been successfully used in many papers for that purpose. However, when interpreting the results obtained with ecological data, at least two different null hypotheses - independence or random labelling - can be appropriate, depending on the context of the study and the nature of the data. As these two hypotheses correspond to different confidence intervals, an inappropriate choice of the null hypothesis can lead to misinterpretations of biotic interactions when studying ecological data. Moreover, this problem has rarely been mentioned in the literature. In this paper we clarify the differences between these two null hypotheses, and illustrate the risk of misinterpretation when using an inappropriate null hypothesis. We review the main characteristics of these two hypotheses, and analyse the spatial structure of both real data from forest stands and simulated virtual stands of different structures. We demonstrate that the risk of misinterpretation is quite high, and that extreme misinterpretations, i.e. cases leading to opposite conclusions in terms of spatial interaction, can occur in a significant number of cases. We therefore propose some guidelines to help ecologists avoid such misinterpretations. / Les interactions entre des plantes d'espèce, de taille et d'âge différents joue un rôle important dans la dynamique d'un écosystème, et peut être à l'origine de structures particulières. Ces interactions peuvent être étudiées en analysant la structure spatiale du semis de point bivarié correspondant. Depuis quelque temps, plusieurs auteurs ont utilisé avec succès la fonction intertype L12 dans cet objectif. Cependant, selon le contexte de l'étude et la nature des données, l'interprétation des résultats obtenus sur des données écologiques peut faire appel à au moins deux hypothèses nulles : l'hypothèse d'indépendance et l'hypothèse d'étiquetage aléatoire. Comme ces deux hypothèses correspondent à des intervalles de confiance différents, une erreur dans le choix de l'hypothèse nulle peut mener à des erreurs d'interprétation des interactions dans les exemples écologiques étudiés. De plus, ce problème est rarement abordé dans la littérature. Dans cet article, nous clarifions les différences entre ces deux hypothèses nulles, et illustrons le risque d'erreur d'interprétation lorsque une mauvaise hypothèse nulle est utilisée. Nous présentons les caractéristiques principales de ces deux hypothèses, et analysons la structure spatiale de données réelles de peuplements forestiers et de peuplements virtuels simulés de structures variées. Nous montrons que le risque d'erreur d'interprétation est très élevé, et que des cas d'erreurs extrêmes, c'est à dire des cas où l'analyse amène à conclure sur une structure spatiale contraire à la structure réelle, peuvent survenir fréquemment. Nous proposons donc quelques conseils pour aider les écologues à éviter de telles erreurs.
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@article{PUB00014161, author = {Goreaud, F. and Pelissier, R.}, title = {Avoiding misinterpretation of biotic interactions with the intertype K12-function: population independence vs. random labelling hypotheses}, title = {Avoiding misinterpretation of biotic interactions with the intertype K12-function: population independence vs. random labelling hypotheses}, journal = {Journal of Vegetation Science}, volume = {14}, pages = {681-692}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00014161}, year = {2003}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; IRD UMR AMAP MONTPELLIER}, number = {K LI03 13}, abstract = {The interactions between plants of different species, age or size play an important role in the dynamics of an ecosystem and can induce specific structures. These interactions can be studied by analysing the spatial structure of the corresponding bivariate patterns. The intertype L12-function has recently been successfully used in many papers for that purpose. However, when interpreting the results obtained with ecological data, at least two different null hypotheses - independence or random labelling - can be appropriate, depending on the context of the study and the nature of the data. As these two hypotheses correspond to different confidence intervals, an inappropriate choice of the null hypothesis can lead to misinterpretations of biotic interactions when studying ecological data. Moreover, this problem has rarely been mentioned in the literature. In this paper we clarify the differences between these two null hypotheses, and illustrate the risk of misinterpretation when using an inappropriate null hypothesis. We review the main characteristics of these two hypotheses, and analyse the spatial structure of both real data from forest stands and simulated virtual stands of different structures. We demonstrate that the risk of misinterpretation is quite high, and that extreme misinterpretations, i.e. cases leading to opposite conclusions in terms of spatial interaction, can occur in a significant number of cases. We therefore propose some guidelines to help ecologists avoid such misinterpretations. / Les interactions entre des plantes d'espèce, de taille et d'âge différents joue un rôle important dans la dynamique d'un écosystème, et peut être à l'origine de structures particulières. Ces interactions peuvent être étudiées en analysant la structure spatiale du semis de point bivarié correspondant. Depuis quelque temps, plusieurs auteurs ont utilisé avec succès la fonction intertype L12 dans cet objectif. Cependant, selon le contexte de l'étude et la nature des données, l'interprétation des résultats obtenus sur des données écologiques peut faire appel à au moins deux hypothèses nulles : l'hypothèse d'indépendance et l'hypothèse d'étiquetage aléatoire. Comme ces deux hypothèses correspondent à des intervalles de confiance différents, une erreur dans le choix de l'hypothèse nulle peut mener à des erreurs d'interprétation des interactions dans les exemples écologiques étudiés. De plus, ce problème est rarement abordé dans la littérature. Dans cet article, nous clarifions les différences entre ces deux hypothèses nulles, et illustrons le risque d'erreur d'interprétation lorsque une mauvaise hypothèse nulle est utilisée. Nous présentons les caractéristiques principales de ces deux hypothèses, et analysons la structure spatiale de données réelles de peuplements forestiers et de peuplements virtuels simulés de structures variées. Nous montrons que le risque d'erreur d'interprétation est très élevé, et que des cas d'erreurs extrêmes, c'est à dire des cas où l'analyse amène à conclure sur une structure spatiale contraire à la structure réelle, peuvent survenir fréquemment. Nous proposons donc quelques conseils pour aider les écologues à éviter de telles erreurs.}, }
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G. Deffuant, F. Amblard, G. Weisbuch, T. Faure
How can extremism prevail? A study based on the relative agreement model
JASSS-The Journal of Artificial Societies and Social Simulation 5 (4), 2002
abs web bib

We model opinion dynamics in populations of agents with continuous opinion and uncertainty. The opinions and uncertainties are modified by random pair interactions. We propose a new model of interactions, called relative agreement model, which is a variant of the previously discussed bounded confidence. In this model, uncertainty as well as opinion can be modified by interactions. We introduce extremist agents by attributing a much lower uncertainty (and thus higher persuasion) to a small proportion of agents at the extremes of the opinion distribution. We study the evolution of the opinion distribution submitted to the relative agreement model. Depending upon the choice of parameters, the extremists can have a very local influence or attract the whole population. We propose a qualitative analysis of the convergence process based on a local field notion. The genericity of the observed results is tested on several variants of the bounded confidence model. / Nous modélisons la dynamique des opinions d'une population d'agents ayant une opinion continue et une incertitude associée, en proposant un nouveau modèle d'interaction, le modèle d'accord relatif, qui est une variante des modèles de confiance limitée précédemment discutés. Dans ce modèle, l'incertitude ainsi que l'opinion peuvent être modifiées suite aux interactions aléatoires entre des paires d'agents. Nous introduisons des agents extrémistes dans la population en attribuant une incertitude très inférieure (et ainsi une force de persuasion plus élevée) à une proportion d'agents située aux extrémités de la distribution d'opinion. Nous étudions par la suite l'évolution de la distribution d'opinions. Suivant la valeur des paramètres, les extrémistes peuvent avoir une influence très locale ou au contraire attirer la population tout entière. Nous proposons une analyse qualitative du processus de convergence basée sur la notion de champ local.
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@article{PUB00011226, author = {Deffuant, G. and Amblard, F. and Weisbuch, G. and Faure, T.}, title = {How can extremism prevail? A study based on the relative agreement model}, title = {Comment l'extrémisme règne ? Une étude basée sur le modèle d'accord relatif}, journal = {JASSS-The Journal of Artificial Societies and Social Simulation}, volume = {5}, number = {4}, pages = {27}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00011226 / http://jasss.soc.surrey.ac.uk/5/4/1.html}, year = {2002}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; ECOLE NORMALE SUPERIEURE LABORATOIRE DE PHYSIQUE STATISTIQUE PARIS ; - ; -}, number = {K LI02 3}, abstract = {We model opinion dynamics in populations of agents with continuous opinion and uncertainty. The opinions and uncertainties are modified by random pair interactions. We propose a new model of interactions, called relative agreement model, which is a variant of the previously discussed bounded confidence. In this model, uncertainty as well as opinion can be modified by interactions. We introduce extremist agents by attributing a much lower uncertainty (and thus higher persuasion) to a small proportion of agents at the extremes of the opinion distribution. We study the evolution of the opinion distribution submitted to the relative agreement model. Depending upon the choice of parameters, the extremists can have a very local influence or attract the whole population. We propose a qualitative analysis of the convergence process based on a local field notion. The genericity of the observed results is tested on several variants of the bounded confidence model. / Nous modélisons la dynamique des opinions d'une population d'agents ayant une opinion continue et une incertitude associée, en proposant un nouveau modèle d'interaction, le modèle d'accord relatif, qui est une variante des modèles de confiance limitée précédemment discutés. Dans ce modèle, l'incertitude ainsi que l'opinion peuvent être modifiées suite aux interactions aléatoires entre des paires d'agents. Nous introduisons des agents extrémistes dans la population en attribuant une incertitude très inférieure (et ainsi une force de persuasion plus élevée) à une proportion d'agents située aux extrémités de la distribution d'opinion. Nous étudions par la suite l'évolution de la distribution d'opinions. Suivant la valeur des paramètres, les extrémistes peuvent avoir une influence très locale ou au contraire attirer la population tout entière. Nous proposons une analyse qualitative du processus de convergence basée sur la notion de champ local.}, }
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F. Goreaud, M. Loreau, C. Millier
Spatial structure and the survival of an inferior competitor: a theoretical model of neighbourhood competition in plants
Ecological Modelling, 2002
abs doi web bib

Recent changes in forestry practices raise new scientific issues concerning the dynamics of mixed forests, and especially the coexistence of different species. The spatial structure of such forest stands is known to play a key role in their dynamics, but classical forest models are not adapted to study this phenomenon. Foresters have therefore begun to build distance-dependent individual-based forest models. As far as theoretical models are concerned, the relation between competition and the coexistence of various plant species in a mixed community has been studied extensively in theoretical ecology, but few of the corresponding models explicitly take the spatial structure of the community into account. The aim of this paper is to present a simple individual-based mechanistic model of neighbourhood competition that allows to study the relation between the spatial structure of mixed stands and the survival of an inferior competitor. We have build this model as an extension of former theoretical models of competition for a soil resource, by adding explicit spatial interactions. We have studied it both analytically and through simulations, using generalised Gibbs processes to simulate stands of various spatial structures. At the individual scale, we have obtained an explicit relation between the survival of a tree, the specific composition of its neighbourhood, and soil fertility. At the stand scale, we have linked the number of surviving trees to the spatial structure, and shown how interspecific repulsion and aggregated patterns improve the survival of inferior competitors. We have also illustrated how the competition process modifies the spatial structure of the stand. Such a neighbourhood competition model is thus a useful tool to study the relation between the spatial structure of a community and its dynamics. / L'objectif de cet article est de présenter un modèle simple, mécaniste, individus-centré, de la compétition entre plantes voisines, qui permet d'étudier la relation entre la structure spatiale d'un peuplement mélangé et la survie d'une espèce moins compétitive. Nous avons construit ce modèle à partir de modèles théoriques de compétition pour les ressources du sol, en ajoutant la prise en compte explicite des interactions spatiales. Nous avons étudié ce modèle à la fois analytiquement et par simulation, en utilisant des processus de Gibbs généralisés pour simuler des peuplements de structure spatiale variée. A l'échelle de l'individu, nous avons obtenu une relation explicite entre la survie d'un arbre, la composition spécifique de son voisinage, et la fertilité du sol. A l'échelle du peuplement, nous avons pu relier le nombre de survivants à la structure spatiale, et montrer comment les structures de répulsion interspécifique et la présence d'agrégats améliorait la survie d'une espèce moins compétitive. Nous avons également illustré comment le processus de compétition modifie la structure spatiale du peuplement. Un tel modèle de compétition entre plantes voisines est donc un outil utile pour étudier la relation entre la structure spatiale d'une communauté et sa dynamique.
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@article{PUB00011348, author = {Goreaud, F. and Loreau, M. and Millier, C.}, title = {Spatial structure and the survival of an inferior competitor: a theoretical model of neighbourhood competition in plants}, title = {Structure spatiale et survie en mélange d'une espèce moins compétitive : un modèle théorique de la compétition entre plantes voisines}, journal = {Ecological Modelling}, number = {158}, pages = {1-19}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00011348}, doi = {http://dx.doi.org/10.1016/S0304-3800(02)00058-3}, year = {2002}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; ECOLE NORMALE SUPERIEURE LABORATOIRE D'ECOLOGIE PARIS ; ENGREF PARIS}, abstract = {Recent changes in forestry practices raise new scientific issues concerning the dynamics of mixed forests, and especially the coexistence of different species. The spatial structure of such forest stands is known to play a key role in their dynamics, but classical forest models are not adapted to study this phenomenon. Foresters have therefore begun to build distance-dependent individual-based forest models. As far as theoretical models are concerned, the relation between competition and the coexistence of various plant species in a mixed community has been studied extensively in theoretical ecology, but few of the corresponding models explicitly take the spatial structure of the community into account. The aim of this paper is to present a simple individual-based mechanistic model of neighbourhood competition that allows to study the relation between the spatial structure of mixed stands and the survival of an inferior competitor. We have build this model as an extension of former theoretical models of competition for a soil resource, by adding explicit spatial interactions. We have studied it both analytically and through simulations, using generalised Gibbs processes to simulate stands of various spatial structures. At the individual scale, we have obtained an explicit relation between the survival of a tree, the specific composition of its neighbourhood, and soil fertility. At the stand scale, we have linked the number of surviving trees to the spatial structure, and shown how interspecific repulsion and aggregated patterns improve the survival of inferior competitors. We have also illustrated how the competition process modifies the spatial structure of the stand. Such a neighbourhood competition model is thus a useful tool to study the relation between the spatial structure of a community and its dynamics. / L'objectif de cet article est de présenter un modèle simple, mécaniste, individus-centré, de la compétition entre plantes voisines, qui permet d'étudier la relation entre la structure spatiale d'un peuplement mélangé et la survie d'une espèce moins compétitive. Nous avons construit ce modèle à partir de modèles théoriques de compétition pour les ressources du sol, en ajoutant la prise en compte explicite des interactions spatiales. Nous avons étudié ce modèle à la fois analytiquement et par simulation, en utilisant des processus de Gibbs généralisés pour simuler des peuplements de structure spatiale variée. A l'échelle de l'individu, nous avons obtenu une relation explicite entre la survie d'un arbre, la composition spécifique de son voisinage, et la fertilité du sol. A l'échelle du peuplement, nous avons pu relier le nombre de survivants à la structure spatiale, et montrer comment les structures de répulsion interspécifique et la présence d'agrégats améliorait la survie d'une espèce moins compétitive. Nous avons également illustré comment le processus de compétition modifie la structure spatiale du peuplement. Un tel modèle de compétition entre plantes voisines est donc un outil utile pour étudier la relation entre la structure spatiale d'une communauté et sa dynamique.}, }
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F. Goreaud, B. Courbaud
La simulation de peuplements forestiers virtuels : un outil pour l'aide à la gestion
Natures Sciences Sociétés 10, supp. 1, 2002
abs doi web bib

In this document, we propose a synthetic presentation of the principles of simulation of virtual forest stands, and of the possible uses for research and management. / Dans ce document, nous proposons une présentation synthétique de la démarche de simulation de peuplements forestiers virtuels, et des utilisations possibles pour la recherche et la gestion.
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@article{PUB00011349, author = {Goreaud, F. and Courbaud, B.}, title = {La simulation de peuplements forestiers virtuels : un outil pour l'aide à la gestion}, title = {Simulation of virtual forest stands: a tool for forest management}, journal = {Natures Sciences Sociétés}, volume = {10, supp. 1}, pages = {23-24}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00011349}, doi = {http://dx.doi.org/10.1016/S1240-1307(02)80131-5}, year = {2002}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF GRENOBLE EPGR}, abstract = {In this document, we propose a synthetic presentation of the principles of simulation of virtual forest stands, and of the possible uses for research and management. / Dans ce document, nous proposons une présentation synthétique de la démarche de simulation de peuplements forestiers virtuels, et des utilisations possibles pour la recherche et la gestion.}, }
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G. Weisbuch, G. Deffuant, F. Amblard, J.P. Nadal
Interacting Agents and Continuous Opinions Dynamics
Lecture Notes in Economics and Mathematical Systems 521 (02/0815 ; K LI02 4), 2002
abs web bib

We present a model of opinion dynamics in which agents adjust continuous opinions as a result of random binary encounters whenever their difference in opinion is below a given threshold. High thresholds yield convergence of opinions towards an average opinion, whereas low thresholds result in several opinion clusters. This model is further generalised to threshold heterogeneity, adaptive thresholds and binary strings of opinions. / Nous présentons un modèle de dynamique d'opinions dans lequel les agents ajustent des opinions continues en fonction de rencontres par paires aléatoires quand la différence entre leurs opinions est en dessous d'un seuil donné. Des seuils élevés conduisent à une convergence des opinions vers une opinion moyenne, alors que des seuils faibles résultent en plusieurs groupes d'opinions. Ce modèle est ensuite généralisé à des seuils hétérogènes, des seuils adaptatifs et des chaînes d'opinions binaires.
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@article{PUB00011231, author = {Weisbuch, G. and Deffuant, G. and Amblard, F. and Nadal, J.P.}, title = {Interacting Agents and Continuous Opinions Dynamics}, title = {Agents en interactions et dynamique d'opinions continues}, journal = {Lecture Notes in Economics and Mathematical Systems}, volume = {521}, pages = {225-242}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00011231}, year = {2002}, affiliation = {ECOLE NORMALE SUPERIEURE LABORATOIRE DE PHYSIQUE STATISTIQUE PARIS ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC}, number = {02/0815 ; K LI02 4}, abstract = {We present a model of opinion dynamics in which agents adjust continuous opinions as a result of random binary encounters whenever their difference in opinion is below a given threshold. High thresholds yield convergence of opinions towards an average opinion, whereas low thresholds result in several opinion clusters. This model is further generalised to threshold heterogeneity, adaptive thresholds and binary strings of opinions. / Nous présentons un modèle de dynamique d'opinions dans lequel les agents ajustent des opinions continues en fonction de rencontres par paires aléatoires quand la différence entre leurs opinions est en dessous d'un seuil donné. Des seuils élevés conduisent à une convergence des opinions vers une opinion moyenne, alors que des seuils faibles résultent en plusieurs groupes d'opinions. Ce modèle est ensuite généralisé à des seuils hétérogènes, des seuils adaptatifs et des chaînes d'opinions binaires.}, }
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G. Weisbuch, G. Deffuant, F. Amblard, J.P. Nadal
Meet, discuss and segregate !
Complexity 7 (3), 2002
abs doi web bib

We present a model of opinion dynamics in which agents adjust continuous opinions as a result of random binary encounters whenever their difference in opinion is below a given threshold. High thresholds yield convergence of opinions toward an average opinion, whereas low thresholds result in several opinion clusters. The model is further generalized to network interactions, theshold heterogeneity, adaptive thresholds, and binary strings of opinions. / Nous présentons un modèle de dynamique d'opinions dans lequel les agents ajustent des opinions continues suite à des rencontres binaires aléatoires quand la différence d'opinion est en dessous d'un seuil fixé. Des seuils importants conduisent à une convergence des opinions vers une opinion moyenne, alors que des seuils plus faibles résultent en plusieurs clusters d'opinions. Le modèle est ensuite généralisé à des interactions sur réseau, des seuils hétérogènes, des seuils adaptatifs et des chaines binaires d'opinions.
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@article{PUB00010879, author = {Weisbuch, G. and Deffuant, G. and Amblard, F. and Nadal, J.P.}, title = {Meet, discuss and segregate !}, journal = {Complexity}, volume = {7}, number = {3}, pages = {55-63}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00010879}, doi = {http://dx.doi.org/10.1002/cplx.1003}, year = {2002}, affiliation = {ECOLE NORMALE SUPERIEURE LABORATOIRE DE PHYSIQUE STATISTIQUE PARIS ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC}, abstract = {We present a model of opinion dynamics in which agents adjust continuous opinions as a result of random binary encounters whenever their difference in opinion is below a given threshold. High thresholds yield convergence of opinions toward an average opinion, whereas low thresholds result in several opinion clusters. The model is further generalized to network interactions, theshold heterogeneity, adaptive thresholds, and binary strings of opinions. / Nous présentons un modèle de dynamique d'opinions dans lequel les agents ajustent des opinions continues suite à des rencontres binaires aléatoires quand la différence d'opinion est en dessous d'un seuil fixé. Des seuils importants conduisent à une convergence des opinions vers une opinion moyenne, alors que des seuils plus faibles résultent en plusieurs clusters d'opinions. Le modèle est ensuite généralisé à des interactions sur réseau, des seuils hétérogènes, des seuils adaptatifs et des chaines binaires d'opinions.}, }
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S. Auvergne, B. Fallet, L. Rousseau
Proposition d'une méthode d'aide à la concertation
Ingénieries - E A T, 2001
abs web bib

The authors outline the elements of a full support process for the development of collective projects. They place themselves in a context wherein those involved have multiple and interdependent objectives, their fields of intervention and of competence are interlinked, the overall necessity is to establish resources controlled by others and the criteria of a good decision are unclear and external to the deciding powers (sustainable development). The method of the scenarios and prospective analysis are used to express, construct and compare each party's point of view. To do so, modelling (graphs, maps, etc.) is used to highlight the relationships perceived by each party between the objects, between the implications of these objects, and between those concerned by what is at stake (the objects). / Les auteurs esquissent les éléments d'une démarche complète d'appui à l'élaboration de projets collectifs. Ils se placent dans un contexte où les objectifs des acteurs impliqués sont multiples et interdépendants, leurs domaines d'intervention et de compétence intriqués, la nécessité générale de mettre en oeuvre des ressources contrôlées par d'autres acteurs, les critères de bonne décision flous et externes aux décideurs (développement soutenable). La méthode des scénarios et l'analyse prospective sont mis au service de l'expression, de la construction et de la comparaison des points de vue des acteurs. Pour cela la modélisation est mobilisée pour mettre en lumière au moyen d'artefacts (graphes, cartes, etc.) les liaisons perçues par chaque acteur entre les objets, entre les enjeux associés à ces objets, entre les acteurs concernés par ces enjeux (ces objets).
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@article{PUB00009175, author = {Auvergne, S. and Fallet, B. and Rousseau, L.}, title = {Proposition d'une méthode d'aide à la concertation}, title = {Proposal of a method to assist consulting}, journal = {Ingénieries - E A T}, number = {spécial Multifonctionnalité de l'agriculture et CTE}, pages = {119-130}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00009175}, year = {2001}, affiliation = {CEMAGREF GRENOBLE DTGR ; CEMAGREF CLERMONT FERRAND LISC}, number = {01/0147}, abstract = {The authors outline the elements of a full support process for the development of collective projects. They place themselves in a context wherein those involved have multiple and interdependent objectives, their fields of intervention and of competence are interlinked, the overall necessity is to establish resources controlled by others and the criteria of a good decision are unclear and external to the deciding powers (sustainable development). The method of the scenarios and prospective analysis are used to express, construct and compare each party's point of view. To do so, modelling (graphs, maps, etc.) is used to highlight the relationships perceived by each party between the objects, between the implications of these objects, and between those concerned by what is at stake (the objects). / Les auteurs esquissent les éléments d'une démarche complète d'appui à l'élaboration de projets collectifs. Ils se placent dans un contexte où les objectifs des acteurs impliqués sont multiples et interdépendants, leurs domaines d'intervention et de compétence intriqués, la nécessité générale de mettre en oeuvre des ressources contrôlées par d'autres acteurs, les critères de bonne décision flous et externes aux décideurs (développement soutenable). La méthode des scénarios et l'analyse prospective sont mis au service de l'expression, de la construction et de la comparaison des points de vue des acteurs. Pour cela la modélisation est mobilisée pour mettre en lumière au moyen d'artefacts (graphes, cartes, etc.) les liaisons perçues par chaque acteur entre les objets, entre les enjeux associés à ces objets, entre les acteurs concernés par ces enjeux (ces objets).}, }
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O. Barreteau, F. Cernesson, N. Ferrand
Pluralité des références spatiales et sociales pour les acteurs d'un contrat de rivière
Montagnes Méditerranéennes, 2001
abs web bib

River contracts lead smoothly stakeholders in a watershed to share points of view and enhance the emergence of collective and coherent projects. With a methodology based on collective decision support experiments, we have interviewed a set of stakeholders of Orb Valley River Contract. Ibis shows a variability of relevant spaces within our stakeholders sample, according to their physical location within or outside the basin, as well as according to their domain of action. These différences are not only based on zoning but also on the relevance of the basin as the common space. As from the social point of view, embedded actors are perceived more through the local consequences of their actions than through actual interactions. Ibis enhances issues of coherence and conflicts. Orb valley institution seems the main co-ordination place. / Les contrats de rivière amènent d'une manière assez souple les acteurs concernés par la gestion de l'eau sur un bassin versant à partager des points de vue et favorisent l'émergence de projets communs et cohérents. A partir d'expériences en aide à la décision collective, nous avons mené un travail d'enquêtes auprès d'acteurs du Contrat de Rivière de l'Orb. II en ressort une variabilité des espaces de référence parmi les acteurs interviewés, selon leur localisation physique à l'intérieur ou à l'extérieur du bassin versant, et selon le rayonnement de leur activité (local ou global). Cette variabilité relève non seulement du découpage du même espace d'ensemble, le bassin versant, mais aussi de sa pertinence. Les acteurs, quant à eux, sont plus perçus à travers les conséquences locales de leurs actions que par de réelles interactions, d'où des problèmes de cohérence et de conflits perçus entre ces actions. Le syndicat mixte de la vallée de l'Orb semble le principal lieu de coordination.
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@article{PUB00010892, author = {Barreteau, O. and Cernesson, F. and Ferrand, N.}, title = {Pluralité des références spatiales et sociales pour les acteurs d'un contrat de rivière}, title = {Plurality of space and social references for actors of a river contract}, journal = {Montagnes Méditerranéennes}, number = {14}, pages = {47-56}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00010892}, year = {2001}, affiliation = {CEMAGREF MONTPELLIER IRMO ; CEMAGREF MONTPELLIER LCMO ; CEMAGREF CLERMONT FERRAND LISC}, number = {01/0920 ; G04 MON 0995}, abstract = {River contracts lead smoothly stakeholders in a watershed to share points of view and enhance the emergence of collective and coherent projects. With a methodology based on collective decision support experiments, we have interviewed a set of stakeholders of Orb Valley River Contract. Ibis shows a variability of relevant spaces within our stakeholders sample, according to their physical location within or outside the basin, as well as according to their domain of action. These différences are not only based on zoning but also on the relevance of the basin as the common space. As from the social point of view, embedded actors are perceived more through the local consequences of their actions than through actual interactions. Ibis enhances issues of coherence and conflicts. Orb valley institution seems the main co-ordination place. / Les contrats de rivière amènent d'une manière assez souple les acteurs concernés par la gestion de l'eau sur un bassin versant à partager des points de vue et favorisent l'émergence de projets communs et cohérents. A partir d'expériences en aide à la décision collective, nous avons mené un travail d'enquêtes auprès d'acteurs du Contrat de Rivière de l'Orb. II en ressort une variabilité des espaces de référence parmi les acteurs interviewés, selon leur localisation physique à l'intérieur ou à l'extérieur du bassin versant, et selon le rayonnement de leur activité (local ou global). Cette variabilité relève non seulement du découpage du même espace d'ensemble, le bassin versant, mais aussi de sa pertinence. Les acteurs, quant à eux, sont plus perçus à travers les conséquences locales de leurs actions que par de réelles interactions, d'où des problèmes de cohérence et de conflits perçus entre ces actions. Le syndicat mixte de la vallée de l'Orb semble le principal lieu de coordination.}, }
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G. Deffuant, D. Neau, F. Amblard, G. Weisbuch
Mixing beliefs among interacting agents
Advances in Complex Systems, 2001
abs web bib

We present a model of opinion dynamics in which agents adjust continuous opinions as a result of random binary encounters whenever their difference in opinion is below a given threshold. High thresholds yield convergence of opinions towards an average opinion, whereas low thresholds result in several opinion clusters: members of the ame cluster share the same opinion but are no longer influenced by members of other clusters. / Nous présentons un modèle de dynamique des opinions dans lequel les agents ajustent des opinions continues en fonction de rencontres binaires aléatoires, lorsque la différence entre leurs opinions est en-dessous d'un certain seuil. Les seuils hauts conduisent à une convergence des opinions vers une opinion moyenne, alors que les seuils plus bas conduisent à plusieurs agglomérats d'opinion : les membres d'un même agglomérat partageant la même opinion mais n'étant plus influencés par les membres d'autres agglomérats.
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@article{PUB00009956, author = {Deffuant, G. and Neau, D. and Amblard, F. and Weisbuch, G.}, title = {Mixing beliefs among interacting agents}, title = {Evolution des croyances entre agents en interactions}, journal = {Advances in Complex Systems}, number = {3}, pages = {11}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00009956}, year = {2001}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; ECOLE NORMALE SUPERIEURE LABORATOIRE DE PHYSIQUE STATISTIQUE PARIS ; - ; -}, number = {01/0652 ; K LI01 5}, abstract = {We present a model of opinion dynamics in which agents adjust continuous opinions as a result of random binary encounters whenever their difference in opinion is below a given threshold. High thresholds yield convergence of opinions towards an average opinion, whereas low thresholds result in several opinion clusters: members of the ame cluster share the same opinion but are no longer influenced by members of other clusters. / Nous présentons un modèle de dynamique des opinions dans lequel les agents ajustent des opinions continues en fonction de rencontres binaires aléatoires, lorsque la différence entre leurs opinions est en-dessous d'un certain seuil. Les seuils hauts conduisent à une convergence des opinions vers une opinion moyenne, alors que les seuils plus bas conduisent à plusieurs agglomérats d'opinion : les membres d'un même agglomérat partageant la même opinion mais n'étant plus influencés par les membres d'autres agglomérats.}, }
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T. Faure, H. Isaka, B. Guillemet
Mapping neural network computation of high-resolution radiant fluxes of inhomogeneous clouds
Journal of geophysical research-atmospheries, 2001
abs web bib

In this study, we evaluated the ability of Mapping Neural Network (MNNs) to calculate the high-resolution radiant fluxes of one-dimensional and two-dimensional inhomogeneous clouds. The test were done for different types of clouds, radiand fluxes, and wavelenghts under different conditions of illumination. The MNNs were trained with training data sets composed of the Monte Carlo (MC) radiant fluxes of bounded cascade clouds and used to compute first the high-resolution MC radiant fluxes (reflectance, transmittance, and absorptance) of bounded cascade inhomogeneous clouds. The test showed their rather good performance, which was compared with that of the Nonlocal Independent Pixel Approximation when possible. Their generalization ability was, second, tested with inhomogeneous clouds of other types : white noise clouds and bounded cascade inhomogeneous clouds with fractional cloud cover. In these cases, the MNNs, trained with different fields, have still good performance. However, the results were found to be much better for the reflectance than for the transmittance and absorptance. In the case of the fractionnal cloud cover, debased responses appear as well in transition zones. We show that the generalization ability could be improved significantly by completing the training sets with new additional patterns when they are applied to types of inhomogeneous clouds different, than the clouds of the training set. These results reveal that the MNNs represent a flexible method of function approximation to compute the high-resolution radiant flux of bounded cascade and other inhomogeneous clouds.
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@article{PUB00009973, author = {Faure, T. and Isaka, H. and Guillemet, B.}, title = {Mapping neural network computation of high-resolution radiant fluxes of inhomogeneous clouds}, journal = {Journal of geophysical research-atmospheries}, pages = {47}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00009973}, year = {2001}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; CNRS AUBIERE ; UNIVERSITE BLAISE PASCAL CLERMONT FERRAND II}, number = {01/0665 ; K LI01 2}, abstract = {In this study, we evaluated the ability of Mapping Neural Network (MNNs) to calculate the high-resolution radiant fluxes of one-dimensional and two-dimensional inhomogeneous clouds. The test were done for different types of clouds, radiand fluxes, and wavelenghts under different conditions of illumination. The MNNs were trained with training data sets composed of the Monte Carlo (MC) radiant fluxes of bounded cascade clouds and used to compute first the high-resolution MC radiant fluxes (reflectance, transmittance, and absorptance) of bounded cascade inhomogeneous clouds. The test showed their rather good performance, which was compared with that of the Nonlocal Independent Pixel Approximation when possible. Their generalization ability was, second, tested with inhomogeneous clouds of other types : white noise clouds and bounded cascade inhomogeneous clouds with fractional cloud cover. In these cases, the MNNs, trained with different fields, have still good performance. However, the results were found to be much better for the reflectance than for the transmittance and absorptance. In the case of the fractionnal cloud cover, debased responses appear as well in transition zones. We show that the generalization ability could be improved significantly by completing the training sets with new additional patterns when they are applied to types of inhomogeneous clouds different, than the clouds of the training set. These results reveal that the MNNs represent a flexible method of function approximation to compute the high-resolution radiant flux of bounded cascade and other inhomogeneous clouds.}, }
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T. Faure, H. Isaka, B. Guillemet
Neural network retrieval of cloud parameters of inhomogeneous and fractional clouds feasibility study
Remote Sensing of Environment 77 (2), 2001
abs doi web bib

One of the major issues of cloud parameter retrieval is how to optimize the improved observational capability of new radiometers to retrieve additional information about cloud characteristics. To investigate this problem, we developed a neural network approach for simultaneous retrieval of cloud parameters of inhomogeneous clouds with fractional cloud cover. We defined a simple inverse inhomogeneous cloud model with four parameters: mean optical depth, effective radius, relative cloud inhomogeneity and fractional cloud cover. The retrieval algorithm, based on the use of a mapping neural network (MNN) with two hidden layers, was implemented and tested with synthetic multispectral reflectance data prepared for 2D clouds generated with a modified bounded cascade cloud model. We found that these cloud parameters could be retrieved from the moderate-resolution multispectral reflectance data with reasonable accuracy: for example with our data base, optical depth has a root mean square error of 1.7 for an ensemble of 1000 samples with optical depth up to 30, However. this accuracy depends on measurements errors and noises. A comparison with plan-parallel hypothesis shows the expected improvement of such an inhomogeneous cloud model. We show that the relevance of these cloud parameters is a function of the horizontal scale of averaging due to the net horizontal photon transport to and from adjacent cloud pixels. We tested the inclusion of ancillary data (reflectance of the neighbouring pixels) into the retrieval algorithm, and showed that the use of these ancillary data could partially correct the modeling error and significantly improve the performance of cloud parameter retrieval.
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@article{PUB00009975, author = {Faure, T. and Isaka, H. and Guillemet, B.}, title = {Neural network retrieval of cloud parameters of inhomogeneous and fractional clouds feasibility study}, journal = {Remote Sensing of Environment}, volume = {77}, number = {2}, pages = {123-138}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00009975}, doi = {http://dx.doi.org/10.1016/S0034-4257(01)00199-7}, year = {2001}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; CNRS AUBIERE ; UNIVERSITE BLAISE PASCAL CLERMONT FERRAND II}, abstract = {One of the major issues of cloud parameter retrieval is how to optimize the improved observational capability of new radiometers to retrieve additional information about cloud characteristics. To investigate this problem, we developed a neural network approach for simultaneous retrieval of cloud parameters of inhomogeneous clouds with fractional cloud cover. We defined a simple inverse inhomogeneous cloud model with four parameters: mean optical depth, effective radius, relative cloud inhomogeneity and fractional cloud cover. The retrieval algorithm, based on the use of a mapping neural network (MNN) with two hidden layers, was implemented and tested with synthetic multispectral reflectance data prepared for 2D clouds generated with a modified bounded cascade cloud model. We found that these cloud parameters could be retrieved from the moderate-resolution multispectral reflectance data with reasonable accuracy: for example with our data base, optical depth has a root mean square error of 1.7 for an ensemble of 1000 samples with optical depth up to 30, However. this accuracy depends on measurements errors and noises. A comparison with plan-parallel hypothesis shows the expected improvement of such an inhomogeneous cloud model. We show that the relevance of these cloud parameters is a function of the horizontal scale of averaging due to the net horizontal photon transport to and from adjacent cloud pixels. We tested the inclusion of ancillary data (reflectance of the neighbouring pixels) into the retrieval algorithm, and showed that the use of these ancillary data could partially correct the modeling error and significantly improve the performance of cloud parameter retrieval.}, }
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T. Faure, H. Isaka, B. Guillemet
Neural network analysis of the radiative interaction between neighboring pixels in inhomogeneous clouds
Journal of geophysical research-atmospheries, 2001
abs web bib

In this study, we analyzed the effect of the radiative interaction between neighboring pixels on the high-resolution radiant flux of bounded cascade inhomogeneous clouds by using a one-layer mapping : neural network as generalized regression analysis. The analysis was done for reflectance : transmittance, and absorptance at different wavelengths under different conditions of illumination. The sign and magnitude of output coefficients indicate how neighboring pixels contribute to the radiant flux of a target pixel. We found that the variation of output, coefficients with the distance from the target pixels changes significantly in its shape and horizontal extent not only with the type of radiant flux we consider but also with the wavelength and solar zenith angle. The mapping neural network clearly reveals the asymmetric feature of radiative interaction between neighboring pixels under oblique illumination, which illustrates the shadowing : and enhancing effects of local cloud inhomogeneity. The present analysis shows that , the mapping neural network is a flexible method of analysis when used as a generalized regression analysis.
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@article{PUB00009974, author = {Faure, T. and Isaka, H. and Guillemet, B.}, title = {Neural network analysis of the radiative interaction between neighboring pixels in inhomogeneous clouds}, journal = {Journal of geophysical research-atmospheries}, pages = {59}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00009974}, year = {2001}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; CNRS ; UNIVERSITE BLAISE PASCAL CLERMONT FERRAND II}, number = {01/0666 ; K LI01 3}, abstract = {In this study, we analyzed the effect of the radiative interaction between neighboring pixels on the high-resolution radiant flux of bounded cascade inhomogeneous clouds by using a one-layer mapping : neural network as generalized regression analysis. The analysis was done for reflectance : transmittance, and absorptance at different wavelengths under different conditions of illumination. The sign and magnitude of output coefficients indicate how neighboring pixels contribute to the radiant flux of a target pixel. We found that the variation of output, coefficients with the distance from the target pixels changes significantly in its shape and horizontal extent not only with the type of radiant flux we consider but also with the wavelength and solar zenith angle. The mapping neural network clearly reveals the asymmetric feature of radiative interaction between neighboring pixels under oblique illumination, which illustrates the shadowing : and enhancing effects of local cloud inhomogeneity. The present analysis shows that , the mapping neural network is a flexible method of analysis when used as a generalized regression analysis.}, }
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R. Pelissier, F. Goreaud
A practical approach to the study of spatial structure in simple cases of heterogeneous vegetation
Journal of Vegetation Science 12 (01/0075 ; K MSP 7), 2001
abs web bib

Spatial heterogeneity is a characteristic of most natural ecosystems which is difficult to handle analytically, particularly in the absence of knowledge about the exogenous factors responsible for this heterogeneity. While classical methods for analysis of spatial point patterns usually require the hypothesis of homogeneity, we present a practical approach for partitioning heterogeneous vegetation plots into homogeneous subplots in simple cases of heterogeneity without drastically reducing the data. It is based on the detection of endogenous variations of the pattern using local density and second-order local neighbour density functions that allow delineation of irregularly shaped subplots that could be considered as internally homogeneous. Spatial statistics, such as Ripley's K-function adapted to analyse plots of irregular shape, can then be computed for each homogeneous subplots. Two applications to forest ecological field data demonstrate that the method, addressed to ecologists, can avoid misinterpretations of the spatial structure of heterogeneous vegetation stands. / L'hétérogénéité spatiale est une caractéristique de la plupart des écosystèmes qu'il est difficile de prendre en compte analytiquement, en particulier lorsque les facteurs exogènes responsables de cette hétérogénéité sont inconnus. Alors que la plupart des méthodes d'analyse de la structure spatiale nécessitent l'hypothèse d'homogénéité, nous présentons un approche pratique pour définir des zones homogènes à l'intérieur d'une placette hétérogène, sans diminuer excessivement les données disponibles, dans des cas simples d'hétérogénéité de la végétation. Le principe de cette approche est de détecter des variations de densité locale ou des fonctions de voisinage à l'intérieur de la placette, afin de délimiter des zones de formes irrégulières qui peuvent être considérées comme homogènes. Des outils d'analyse de la structure spatiale, comme la fonction K(r) de Ripley, une fois adaptés à ces zones de formes irrégulières, peuvent être utilisés dans chaque zone homogène. Nous montrons sur deux exemples d'application, sur des données forestières, comment cette approche permet d'éviter des erreurs d'interprétation de la structure spatiale dans le cas de végétation hétérogène.
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@article{PUB00009061, author = {Pelissier, R. and Goreaud, F.}, title = {A practical approach to the study of spatial structure in simple cases of heterogeneous vegetation}, title = {Une approche pratique pour étudier la structure spatiale dans des cas simples de végétation hétérogène}, journal = {Journal of Vegetation Science}, volume = {12}, pages = {99-108}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00009061}, year = {2001}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; IRD ORLEANS}, number = {01/0075 ; K MSP 7}, abstract = {Spatial heterogeneity is a characteristic of most natural ecosystems which is difficult to handle analytically, particularly in the absence of knowledge about the exogenous factors responsible for this heterogeneity. While classical methods for analysis of spatial point patterns usually require the hypothesis of homogeneity, we present a practical approach for partitioning heterogeneous vegetation plots into homogeneous subplots in simple cases of heterogeneity without drastically reducing the data. It is based on the detection of endogenous variations of the pattern using local density and second-order local neighbour density functions that allow delineation of irregularly shaped subplots that could be considered as internally homogeneous. Spatial statistics, such as Ripley's K-function adapted to analyse plots of irregular shape, can then be computed for each homogeneous subplots. Two applications to forest ecological field data demonstrate that the method, addressed to ecologists, can avoid misinterpretations of the spatial structure of heterogeneous vegetation stands. / L'hétérogénéité spatiale est une caractéristique de la plupart des écosystèmes qu'il est difficile de prendre en compte analytiquement, en particulier lorsque les facteurs exogènes responsables de cette hétérogénéité sont inconnus. Alors que la plupart des méthodes d'analyse de la structure spatiale nécessitent l'hypothèse d'homogénéité, nous présentons un approche pratique pour définir des zones homogènes à l'intérieur d'une placette hétérogène, sans diminuer excessivement les données disponibles, dans des cas simples d'hétérogénéité de la végétation. Le principe de cette approche est de détecter des variations de densité locale ou des fonctions de voisinage à l'intérieur de la placette, afin de délimiter des zones de formes irrégulières qui peuvent être considérées comme homogènes. Des outils d'analyse de la structure spatiale, comme la fonction K(r) de Ripley, une fois adaptés à ces zones de formes irrégulières, peuvent être utilisés dans chaque zone homogène. Nous montrons sur deux exemples d'application, sur des données forestières, comment cette approche permet d'éviter des erreurs d'interprétation de la structure spatiale dans le cas de végétation hétérogène.}, }
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B. Courbaud, F. Goreaud, P. Dreyfus, F. Bonnet
Sylviculture et modèle de croissance dépendant des distances : mise en oeuvre du logiciel CAPSIS 3.0 sur des pessières irrégulières de montagne
Revue Forestière Française 5 (00/0909 ; K IAS 13 ; MEM 1514 ; DD 1302), 2000
abs web bib

Dynamic models for forest stands have until now essentially been used in France for the purposes of resource forecasting and drawing up forestry strategies for regular, single-species stands. With the upland spruce module in the Capsis 3.0 package, more thorough investigation of irregular stand silviculture can be conducted based on their spatial organisation. Three examples of this approach are given - simulation of thinning performed on an irregular uneven-aged plot, investigation of the effect of the spatial distribution of thinning on growth and regeneration in a two-storied stand and establishment of a strategy for making forest stands irregular. The tools described are intended for researchers and moreover for forest managers. They are particularly suitable for training purpose, dialogue between practitioners and for elaborating detailed silvicultural strategies. / Les modèles de dynamique de peuplements forestiers ont été jusqu'à présent utilisés en France essentiellement dans un cadre de prévision de ressource et d'élaboration de stratégies sylvicoles dans des peuplements réguliers mono spécifiques. L'utilisation du module Epicéa de montagne du logiciel Capsis 3.0 permet aujourd'hui de réfléchir de manière plus fine à la gestion des peuplements irréguliers en tenant compte de leur organisation spatiale. L'utilisation du modèle présenté requiert la description d'un peuplement (ou d'une placette représentative) par la liste des arbres qui le composent avec la position, la hauteur, le diamètre et l'âge de chacun d'entre eux. Ces peuplements peuvent correspondre à des placettes réelles de terrain ou à des placettes partiellement ou entièrement virtuelles composées grâce à l'utilisation d'un générateur de positions. Les accroissements annuels des arbres dépendent de leur environnement local au travers du calcul de leur éclairement individuel. L'élaboration d'un scénario sylvicole est quant à lui rendu facile par les fonctionnalités du logiciel Capsis, proposant une interface conviviale de type Windows. Un premier exemple d'utilisation présente la simulation de la dynamique d'une placette réelle de terrain. Les deux suivants montrent l'utilisation de placettes virtuelles, dans un cas pour comparer deux stratégies d'éclaircie dans un peuplement à deux étages et dans l'autre pour tester la possibilité d'irrégulariser un peuplement. Les outils présentés sont destinés aux chercheurs mais aussi et avant tout aux gestionnaires forestiers. Ils nous semblent aujourd'hui particulièrement appropriés à l'enseignement, au dialogue entre praticiens et à l'élaboration de stratégies fines de sylviculture.
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@article{PUB00009669, author = {Courbaud, B. and Goreaud, F. and Dreyfus, P. and Bonnet, F.}, title = {Sylviculture et modèle de croissance dépendant des distances : mise en oeuvre du logiciel CAPSIS 3.0 sur des pessières irrégulières de montagne}, title = {Silviculture and distance-dependant growth models - implemenation of the capsis 3.0 program on irregular upland spruce stands}, journal = {Revue Forestière Française}, volume = {5}, pages = {425-440}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00009669}, year = {2000}, affiliation = {CEMAGREF GRENOBLE EPGR ; CEMAGREF CLERMONT FERRAND LISC ; INRA AVIGNON ; -}, number = {00/0909 ; K IAS 13 ; MEM 1514 ; DD 1302}, abstract = {Dynamic models for forest stands have until now essentially been used in France for the purposes of resource forecasting and drawing up forestry strategies for regular, single-species stands. With the upland spruce module in the Capsis 3.0 package, more thorough investigation of irregular stand silviculture can be conducted based on their spatial organisation. Three examples of this approach are given - simulation of thinning performed on an irregular uneven-aged plot, investigation of the effect of the spatial distribution of thinning on growth and regeneration in a two-storied stand and establishment of a strategy for making forest stands irregular. The tools described are intended for researchers and moreover for forest managers. They are particularly suitable for training purpose, dialogue between practitioners and for elaborating detailed silvicultural strategies. / Les modèles de dynamique de peuplements forestiers ont été jusqu'à présent utilisés en France essentiellement dans un cadre de prévision de ressource et d'élaboration de stratégies sylvicoles dans des peuplements réguliers mono spécifiques. L'utilisation du module Epicéa de montagne du logiciel Capsis 3.0 permet aujourd'hui de réfléchir de manière plus fine à la gestion des peuplements irréguliers en tenant compte de leur organisation spatiale. L'utilisation du modèle présenté requiert la description d'un peuplement (ou d'une placette représentative) par la liste des arbres qui le composent avec la position, la hauteur, le diamètre et l'âge de chacun d'entre eux. Ces peuplements peuvent correspondre à des placettes réelles de terrain ou à des placettes partiellement ou entièrement virtuelles composées grâce à l'utilisation d'un générateur de positions. Les accroissements annuels des arbres dépendent de leur environnement local au travers du calcul de leur éclairement individuel. L'élaboration d'un scénario sylvicole est quant à lui rendu facile par les fonctionnalités du logiciel Capsis, proposant une interface conviviale de type Windows. Un premier exemple d'utilisation présente la simulation de la dynamique d'une placette réelle de terrain. Les deux suivants montrent l'utilisation de placettes virtuelles, dans un cas pour comparer deux stratégies d'éclaircie dans un peuplement à deux étages et dans l'autre pour tester la possibilité d'irrégulariser un peuplement. Les outils présentés sont destinés aux chercheurs mais aussi et avant tout aux gestionnaires forestiers. Ils nous semblent aujourd'hui particulièrement appropriés à l'enseignement, au dialogue entre praticiens et à l'élaboration de stratégies fines de sylviculture.}, }
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P. Grenier, I. Alvarez, J.M. Roger, V. Steinmetz, P. Barre, J.M. Sablayrolles
Artificial intelligence in wine-making
Journal International des Sciences de la Vigne et du Vin 34 (2), 2000
abs web bib

In this paper, some terms of Artificial Intelligence are defined. Some present and potential applications of knowledge based systems are presented in the field of wine-making. Areas of concern were: multi sensor fusion, prediction by model cooperation, and diagnosis. Artificial intelligence techniques can indeed be applied for aiding the wine-maker in his choices. They facilitate the combination between experience and recent progress in technology. When associated with statistical processing, they allow knowledge sources to be used more effectively. Beyond wine-making, the prospects of artificial intelligence are promising for research and food industry, especially for improving the robustness of measurement systems (multi-sensors, sensors interpreted or validated by models), and for process diagnosis (risk prediction, action proposal). / Certains termes d'Intelligence Artificielle (IA) sont définis dans cette publication. Quelques applications en cours ou potentielles de systèmes fondés sur la connaissance sont présentés dans le domaine de la vinification. Les domaines d'étude sont : la fusion multi-capteurs, la prédiction par coopération de modèles, et le diagnostic. Les techniques IA peuvent aider le vinificateur dans ses choix par une symbiose entre expérience et progrès technologiques. En association avec des traitements statistiques, ces techniques permettent une utilisation plus efficace des sources de connaissances. Au-delà de la vinification, les perspectives de l'intelligence artificielle sont prometteuses en industrie alimentaire, en particulier pour améliorer la robustesse d'un système de mesure (fusion de capteurs, validation d'un capteur par un modèle) ou pour élaborer un diagnostic sur l'évolution d'un procédé (prédiction de risques, proposition d'intervention).
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@article{PUB00008877, author = {Grenier, P. and Alvarez, I. and Roger, J.M. and Steinmetz, V. and Barre, P. and Sablayrolles, J.M.}, title = {Artificial intelligence in wine-making}, title = {L'intelligence artificielle en oenologie}, journal = {Journal International des Sciences de la Vigne et du Vin}, volume = {34}, number = {2}, pages = {61-66}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00008877}, year = {2000}, affiliation = {CEMAGREF MONTPELLIER GIMO ; INRA IPV MONTPELLIER ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC}, number = {00/0664 ; BGI 0826}, abstract = {In this paper, some terms of Artificial Intelligence are defined. Some present and potential applications of knowledge based systems are presented in the field of wine-making. Areas of concern were: multi sensor fusion, prediction by model cooperation, and diagnosis. Artificial intelligence techniques can indeed be applied for aiding the wine-maker in his choices. They facilitate the combination between experience and recent progress in technology. When associated with statistical processing, they allow knowledge sources to be used more effectively. Beyond wine-making, the prospects of artificial intelligence are promising for research and food industry, especially for improving the robustness of measurement systems (multi-sensors, sensors interpreted or validated by models), and for process diagnosis (risk prediction, action proposal). / Certains termes d'Intelligence Artificielle (IA) sont définis dans cette publication. Quelques applications en cours ou potentielles de systèmes fondés sur la connaissance sont présentés dans le domaine de la vinification. Les domaines d'étude sont : la fusion multi-capteurs, la prédiction par coopération de modèles, et le diagnostic. Les techniques IA peuvent aider le vinificateur dans ses choix par une symbiose entre expérience et progrès technologiques. En association avec des traitements statistiques, ces techniques permettent une utilisation plus efficace des sources de connaissances. Au-delà de la vinification, les perspectives de l'intelligence artificielle sont prometteuses en industrie alimentaire, en particulier pour améliorer la robustesse d'un système de mesure (fusion de capteurs, validation d'un capteur par un modèle) ou pour élaborer un diagnostic sur l'évolution d'un procédé (prédiction de risques, proposition d'intervention).}, }
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F. Goreaud, R. Pelissier
On explicit formulas of edge effect correction for Ripley' s K-function
Journal of Vegetation Science 10 (99/0262), 1999
abs web bib

The analysis of spatial pattern in plant ecology usually implies the solution of some edge effect problems. We present in this paper some explicit formulas of edge effect correction that should enable plant ecologists to analyse a wider range of real field data. We consider the local correcting factor of edge effect for Ripley's K-function, that can also be used for other statistics of spatial analysis based on the counting of neighbours within a given distance. For both circular and rectangular study areas, we provide a review of explicit formulas and an extension of these formulas for long and narrow plots. In the case of irregular-shaped study plots, we propose a generalization of the method that computes edge effect correction by excluding triangular surfaces from a simple (rectangular or circular) initial shape. A short example in forest ecology, where the soil characteristics determine a study plot of complex shape, illustrate how this edge effect correction can be effective to avoid misinterpretations." / L'analyse de la structure spatiale des formations végétales rencontre souvent des problèmes d'effet de bord. Dans cet article, nous proposons des formules explicites qui devraient permettre aux écologues de corriger les biais dûs à ces problèmes, et d'améliorer l'analyse des données spatiales. Nous nous intéressons plus particulièrement à la correction locale des effets de bord pour la fonction K(r) de Ripley, qui peut également être appliquée à d'autres outils statistiques basés sur le dénombrement de voisins à des distances fixées. Nous présentons une synthèse des formules classiques pour les placettes circulaires et rectangulaires, et une extension au cas des placettes très allongées. Nous proposons également une généralisation de cette correction locale pour le cas de placettes de forme irrégulière, définie par exclusion de triangles à partir d'un domaine initial circulaire ou rectangulaire. L'intéret de la méthode est illustré sur un exemple d'écologie forestière, dans lequel les caractéristiques du sol déterminent la forme complexe du domaine d'étude.
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@article{PUB00007276, author = {Goreaud, F. and Pelissier, R.}, title = {On explicit formulas of edge effect correction for Ripley' s K-function}, title = {Formules explicites de correction des effets de bord pour la fonction de Ripley K(r)}, journal = {Journal of Vegetation Science}, volume = {10}, pages = {433-438}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00007276}, year = {1999}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; IRD ORLEANS}, number = {99/0262}, abstract = {The analysis of spatial pattern in plant ecology usually implies the solution of some edge effect problems. We present in this paper some explicit formulas of edge effect correction that should enable plant ecologists to analyse a wider range of real field data. We consider the local correcting factor of edge effect for Ripley's K-function, that can also be used for other statistics of spatial analysis based on the counting of neighbours within a given distance. For both circular and rectangular study areas, we provide a review of explicit formulas and an extension of these formulas for long and narrow plots. In the case of irregular-shaped study plots, we propose a generalization of the method that computes edge effect correction by excluding triangular surfaces from a simple (rectangular or circular) initial shape. A short example in forest ecology, where the soil characteristics determine a study plot of complex shape, illustrate how this edge effect correction can be effective to avoid misinterpretations." / L'analyse de la structure spatiale des formations végétales rencontre souvent des problèmes d'effet de bord. Dans cet article, nous proposons des formules explicites qui devraient permettre aux écologues de corriger les biais dûs à ces problèmes, et d'améliorer l'analyse des données spatiales. Nous nous intéressons plus particulièrement à la correction locale des effets de bord pour la fonction K(r) de Ripley, qui peut également être appliquée à d'autres outils statistiques basés sur le dénombrement de voisins à des distances fixées. Nous présentons une synthèse des formules classiques pour les placettes circulaires et rectangulaires, et une extension au cas des placettes très allongées. Nous proposons également une généralisation de cette correction locale pour le cas de placettes de forme irrégulière, définie par exclusion de triangles à partir d'un domaine initial circulaire ou rectangulaire. L'intéret de la méthode est illustré sur un exemple d'écologie forestière, dans lequel les caractéristiques du sol déterminent la forme complexe du domaine d'étude.}, }
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G. Deffuant
Les modèles cognitifs à l'épreuve des formes du religieux : proposition de directions de recherche centrées sur l'empathie
Intellectica, 1998
abs web bib

This article proposes several directions of research on the interpretation and understanding of certain religious or social forms (archaic or traditionally hierarchical societies, monotheistic revealed religion, modern individualism). We put forward the hypothesis that elementary social interactions are based on cognitive functions in which empathy plays the role of a central operator. On thishypothesis, the elementary interactions constitute dynamic systems, and the various social forms in question appear as attractors in these dynamic systems. This approach gives rise to a new way of rendering these social forms intelligible. / Cet article propose plusieurs directions de recherhce sur l'interprétation et la compréhension de certaines formes religieuses ou sociales (sociétés archaîques, traditionnelles, hiérarchiques, les religions monothéistes révélées, l'individualisme moderne), à l'aide d'hypothèses sur le fonctionnement cognitif responsable des interactions sociales élémentaires. L'empathie est vue comme opérateur central et nous tentons de montrer qu'il permet une intelligibilité nouvelle de ces formes sociales, qui apparaissent comme différents types d'attracteurs de systèmes dynamiques régis par ces interactions élémentaires.
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@article{PUB00051708, author = {Deffuant, G.}, title = {Les modèles cognitifs à l'épreuve des formes du religieux : proposition de directions de recherche centrées sur l'empathie}, title = {Cognitive models and religious forms:a testing-ground for the concept of empathy}, journal = {Intellectica}, number = {n° 26-27}, pages = { 89-109}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00051708}, year = {1998}, affiliation = {CEMAGREF CLERMONT FERRAND LISC}, number = {K IAS 12}, abstract = {This article proposes several directions of research on the interpretation and understanding of certain religious or social forms (archaic or traditionally hierarchical societies, monotheistic revealed religion, modern individualism). We put forward the hypothesis that elementary social interactions are based on cognitive functions in which empathy plays the role of a central operator. On thishypothesis, the elementary interactions constitute dynamic systems, and the various social forms in question appear as attractors in these dynamic systems. This approach gives rise to a new way of rendering these social forms intelligible. / Cet article propose plusieurs directions de recherhce sur l'interprétation et la compréhension de certaines formes religieuses ou sociales (sociétés archaîques, traditionnelles, hiérarchiques, les religions monothéistes révélées, l'individualisme moderne), à l'aide d'hypothèses sur le fonctionnement cognitif responsable des interactions sociales élémentaires. L'empathie est vue comme opérateur central et nous tentons de montrer qu'il permet une intelligibilité nouvelle de ces formes sociales, qui apparaissent comme différents types d'attracteurs de systèmes dynamiques régis par ces interactions élémentaires.}, }
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G. Deffuant
L'autonomie est-elle création ou rupture d'une clôture? Tentative d'articulation entre les visions de l'autonomie de F. Varela et de C. Castoriadis
Revue internationale de systémique, 1997
abs web bib

This text proposes an attempt for articuling F. Varela and C. Castoriadis' concepts of autonomy. Varela considers the biological cell as a typical example of autonomous system, and asssociates autonomy with the creation of an operational closure. Caastoriadis focuses on the man in society, taking as typical example the autonomy of the Greek polis, associated with the breaking of the closure of social imaginary signification imposed from outside. For articuling these approach, we first distinguish between the physical closure of operations, and closure of signification (cognitive closure). The closure of signification supposes autonomy because it is the assessment of an autonomous world, for the system. We propose then to interpret important stages in the cognitive evolution as creation of a new closure of operations (Varela's view) and breaking a closure of signification toward a larger new one (Castoriadis' view). Breaking the closure og signification in the Greek polis correponds to the creation of a new closure of social operations (competition among equals). These different types of closure allow us to propose a new understanding of the modren period. Our thesis is that Varela and Castoriadis talk about the same object but from two different points of view. / Ce texte propose une tentative d'articulation entre deux visoins de l'autonomie : celle de F. Varela et celle de C. Castoriadis. Varela part de la cellule biologique comme exemple typique et associe l'autonomie à la création d'une clôture opérationnelle. Castoriadis se focalise sur l'homme en société en prenant comme exemple typique l'autonomie de la polis Grecque, associée à une rupture de la clôture des significations imaginaires sociales imposées de l'extérieur. L'articulation proposée repose tout d'abord sur une distinction entre clôture physique des opérations et clôture des significations (clôture du pour-soi). La clôture du pour-soi suppose l'autonomie, car elle est l'affirmation d'un monde autonome, pour soi. Nous proposons une interprétation des étape de l'évolution cognitive par l'instauration d'une nouvelle clôture des opérations (vision de Varela) mais aussi comme rupture d'une clôture du pour-soi, qui est remplacée par une clôture plus large (vision de Castoriadis). La rupture de la clôture des significations imaginaires sociales dans la polis Grecque est une rupture de la clôture pour-soi des société hétéronomes, et correspond donc à la crétion d'une clôture des opérations (les interactions sociales) d'un type nouveau (celui de la compétition entre égaux). Ces différents types de clôtures identifiés nous permettent de proposer une compréhension renouvelée de l'époque moderne. Notre thèse est donc que Castoriadis et Varela parlent bien de la même chose mais sous deux angles différents.
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@article{PUB00051709, author = {Deffuant, G.}, title = {L'autonomie est-elle création ou rupture d'une clôture? Tentative d'articulation entre les visions de l'autonomie de F. Varela et de C. Castoriadis}, journal = {Revue internationale de systémique}, number = {vol. 11, n° 5}, pages = {516-534}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00051709}, year = {1997}, affiliation = {CEMAGREF CLERMONT FERRAND LISC}, number = {K IAS 14}, ISBNISSN = {ISSN 0980-1472}, abstract = {This text proposes an attempt for articuling F. Varela and C. Castoriadis' concepts of autonomy. Varela considers the biological cell as a typical example of autonomous system, and asssociates autonomy with the creation of an operational closure. Caastoriadis focuses on the man in society, taking as typical example the autonomy of the Greek polis, associated with the breaking of the closure of social imaginary signification imposed from outside. For articuling these approach, we first distinguish between the physical closure of operations, and closure of signification (cognitive closure). The closure of signification supposes autonomy because it is the assessment of an autonomous world, for the system. We propose then to interpret important stages in the cognitive evolution as creation of a new closure of operations (Varela's view) and breaking a closure of signification toward a larger new one (Castoriadis' view). Breaking the closure og signification in the Greek polis correponds to the creation of a new closure of social operations (competition among equals). These different types of closure allow us to propose a new understanding of the modren period. Our thesis is that Varela and Castoriadis talk about the same object but from two different points of view. / Ce texte propose une tentative d'articulation entre deux visoins de l'autonomie : celle de F. Varela et celle de C. Castoriadis. Varela part de la cellule biologique comme exemple typique et associe l'autonomie à la création d'une clôture opérationnelle. Castoriadis se focalise sur l'homme en société en prenant comme exemple typique l'autonomie de la polis Grecque, associée à une rupture de la clôture des significations imaginaires sociales imposées de l'extérieur. L'articulation proposée repose tout d'abord sur une distinction entre clôture physique des opérations et clôture des significations (clôture du pour-soi). La clôture du pour-soi suppose l'autonomie, car elle est l'affirmation d'un monde autonome, pour soi. Nous proposons une interprétation des étape de l'évolution cognitive par l'instauration d'une nouvelle clôture des opérations (vision de Varela) mais aussi comme rupture d'une clôture du pour-soi, qui est remplacée par une clôture plus large (vision de Castoriadis). La rupture de la clôture des significations imaginaires sociales dans la polis Grecque est une rupture de la clôture pour-soi des société hétéronomes, et correspond donc à la crétion d'une clôture des opérations (les interactions sociales) d'un type nouveau (celui de la compétition entre égaux). Ces différents types de clôtures identifiés nous permettent de proposer une compréhension renouvelée de l'époque moderne. Notre thèse est donc que Castoriadis et Varela parlent bien de la même chose mais sous deux angles différents.}, }
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Book Chapters (24)

S. Huet, G. Deffuant
The Leviathan model without gossips and vanity: The richness of influence based on perceived hierarchy
Advances in Social Simulation 2015, Advances in Intelligent Systems and Computing 528 (p. 149-162), Springer, 2017
abs web bib

This paper studies a model of agents having an opinion about each other agent and about themselves. During dyadic meetings, the agents change their opinion about themselves and about their interlocutor in the direction of a noisy perception of the opinions of their interlocutor. Moreover highly valued agents are more influential. This model produces several patterns depending on the parameter values. In particular, in some cases several highly influential agents (called leaders) emerge and sometimes the leaders have a low opinion of each other.
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@book{PUB00054554, author = {Huet, S. and Deffuant, G.}, author = {Jager, W. and Verbrugge, R. and Flache, A. and De Roo, G. and Hoogduin, L. and Hemelrijk, C.}, title = {The Leviathan model without gossips and vanity: The richness of influence based on perceived hierarchy}, title = {Le modèle Leviathan sans commérage ou vanité : la richesse d'une influence basée sur la hiérarchie perçue}, bookTitle = {Advances in Social Simulation 2015, Advances in Intelligent Systems and Computing 528}, publisher = {Springer}, pages = {149-162}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00054554}, year = {2017}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {This paper studies a model of agents having an opinion about each other agent and about themselves. During dyadic meetings, the agents change their opinion about themselves and about their interlocutor in the direction of a noisy perception of the opinions of their interlocutor. Moreover highly valued agents are more influential. This model produces several patterns depending on the parameter values. In particular, in some cases several highly influential agents (called leaders) emerge and sometimes the leaders have a low opinion of each other.}, }
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S. Huet
The social functions of gossip and the Leviathan model
Understanding Interactions in Complex Systems ; Toward a Science of Interaction (p. 139-175), Cambridge Scholar Publishing, 2017
abs web bib

In this paper, we are interested in understanding the relation between gossip and two social phenomena: consensus and the positivity bias. These two properties of a population together seem somewhat counterintuitive: a population needs some consensus to act as a group, at the same time the positivity bias is said to be quite universal and it means people diverge. This paradox can perhaps be solved by the understanding of its links to gossip and its social functions (Foster, 2004). Deffuant, Carletti, and Huet (2013) have shown that the Leviathan model is able to exhibit these two social phenomena. They emerge from the individual’s need to form a valuation of themselves (i.e. self-valuation), as well as defining the value of others, through direct interaction and gossip. The particular role of gossip in their emergence and maintenance has not been exhaustively investigated in this model. That is the purpose of this paper, which starts from four hypotheses: gossip leads to consensus which increases with its intensity; gossip decreases the strength of the positivity bias and can suppress it; positivity bias and disagreement are linked to each other; the positivity bias and bias to negativity occurring in the Leviathan model appear conjointly whatever the level of gossip (they have been conjointly diagnosed in the first investigations of Deffuant et al. 2013). Overall, our hypotheses are confirmed. We especially find that consensus is almost never reached without gossip. We also show how an asymmetrical level of openness to the influence of others, depending on how high they are held in esteem, is important for the positivity bias, as well as for the bias to negativity. The number of peers discussed during a meeting is also shown to be essential for consensus.
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@book{PUB00055529, author = {Huet, S.}, author = {Debarsy, N. and Cordier, S. and Ertur, C. and Nemo, F. and Nourrit-Lucas, D. and Poisson, G. and Vrain, C.}, title = {The social functions of gossip and the Leviathan model}, title = {Les fonctions sociales du commérage et le modèle Leviathan}, bookTitle = {Understanding Interactions in Complex Systems ; Toward a Science of Interaction}, publisher = {Cambridge Scholar Publishing}, pages = {139-175}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00055529}, year = {2017}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {In this paper, we are interested in understanding the relation between gossip and two social phenomena: consensus and the positivity bias. These two properties of a population together seem somewhat counterintuitive: a population needs some consensus to act as a group, at the same time the positivity bias is said to be quite universal and it means people diverge. This paradox can perhaps be solved by the understanding of its links to gossip and its social functions (Foster, 2004). Deffuant, Carletti, and Huet (2013) have shown that the Leviathan model is able to exhibit these two social phenomena. They emerge from the individual’s need to form a valuation of themselves (i.e. self-valuation), as well as defining the value of others, through direct interaction and gossip. The particular role of gossip in their emergence and maintenance has not been exhaustively investigated in this model. That is the purpose of this paper, which starts from four hypotheses: gossip leads to consensus which increases with its intensity; gossip decreases the strength of the positivity bias and can suppress it; positivity bias and disagreement are linked to each other; the positivity bias and bias to negativity occurring in the Leviathan model appear conjointly whatever the level of gossip (they have been conjointly diagnosed in the first investigations of Deffuant et al. 2013). Overall, our hypotheses are confirmed. We especially find that consensus is almost never reached without gossip. We also show how an asymmetrical level of openness to the influence of others, depending on how high they are held in esteem, is important for the positivity bias, as well as for the bias to negativity. The number of peers discussed during a meeting is also shown to be essential for consensus.}, }
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S. Huet, N. Dumoulin, G. Deffuant
A calibration to properly design a model integrating residential mobility and migration in rural area
Advances in Social Simulation 2015, Advances in Intelligent Systems and Computing 528 (p. 163-179), Springer, 2017
abs web bib

We propose a hybrid microsimulation and agent-based model of mobility integrating migration and residential mobility. We tested it on the evolution of the population of the Cantal, a French “département” with 150,000 inhabitants. We calibrated it using various data sources from 1990 to 2006, and tested its predictions on other data of the same period and on the period 2007-2012. The spatial heterogeneity of the evolution is well reproduced and the model makes surprisingly correct predictions despite numerous simplifying assumptions. From this calibration we learnt more about how to model residential mobility and migration considering an agent-based model approach.
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@book{PUB00054555, author = {Huet, S. and Dumoulin, N. and Deffuant, G.}, author = {Jager, W. and Verbrugge, R. and Flache, A. and De Roo, G. and Hoogduin, L. and Hemelrijkn C.}, title = {A calibration to properly design a model integrating residential mobility and migration in rural area}, title = {Une calibration pour une modélisation pertinente de la mobilité résidentielle et de la migration en zone rurale}, bookTitle = {Advances in Social Simulation 2015, Advances in Intelligent Systems and Computing 528}, publisher = {Springer}, pages = {163-179}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00054555}, year = {2017}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {We propose a hybrid microsimulation and agent-based model of mobility integrating migration and residential mobility. We tested it on the evolution of the population of the Cantal, a French “département” with 150,000 inhabitants. We calibrated it using various data sources from 1990 to 2006, and tested its predictions on other data of the same period and on the period 2007-2012. The spatial heterogeneity of the evolution is well reproduced and the model makes surprisingly correct predictions despite numerous simplifying assumptions. From this calibration we learnt more about how to model residential mobility and migration considering an agent-based model approach.}, }
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Briot J.P., M. Irving, J. Vasconcelos, G. de Melo, I. Alvarez, A. Sordoni, C. de Lucena
Participatory Management of Protected Areas for Biodiversity Conservation and Social Inclusion: Experience of the SimParc Multi-Agent Based Serious Game
Multi-agent based simulations applied to biological and environmental systems, (p. 295-332), IGI Global, 2016
abs web bib

The objective of this paper is to reflect on our experience in a serious game research project, named SimParc, about multi-agent support for participatory management of protected areas for biodiversity conservation and social inclusion. Our project has a clear filiation with the MAS-RPG (Multi-Agent-Simulation – Role-Playing Games) methodology developed by the ComMod action-research community about participatory management of renewable resources, where multi-agent simulation (MAS) computes the dynamics of the resources and role-playing game (RPG) represents the actions and dialogue between stakeholders about the resources. Meanwhile, we have explored some specific directions, such as: dialogue support for negotiation; argumentation-based decision making and its explanation; technical assistance to the players based on viability modeling. In fact, in our project multi-agent based simulation focuses on the negotiation process itself, performed by human players and some artificial participants/agents, rather than on the simulation of the resources dynamics. Meanwhile, as we will see, we have also reintroduced the modeling of the socioecosystem dynamics, but as a local technical assistance/analysis tool for the players and not as a global system modeling. In this proposed chapter, we aim at discussing the rationales for these specificities and for the whole project, as well as summarizing the architecture of our prototype system, current results and experience produced and, last but not the least, lessons learned and prospects for future works.
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@book{PUB00055491, author = {Briot, J.P., and Irving, M. and Vasconcelos, J. and de Melo, G. and Alvarez, I. and Sordoni, A. and de Lucena, C.}, author = {Adamatti, D.F.}, title = {Participatory Management of Protected Areas for Biodiversity Conservation and Social Inclusion: Experience of the SimParc Multi-Agent Based Serious Game}, title = {SimParc, un jeu sérieux pour la gestion participative des espaces protégés pour la conservation de la biodiversité et l'inclusion sociale}, bookTitle = {Multi-agent based simulations applied to biological and environmental systems,}, publisher = {IGI Global}, pages = {295-332}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00055491 / https://hal.archives-ouvertes.fr/hal-01359644}, year = {2016}, affiliation = {UPMC LIP6 ; PUC ; EICOS -UFRJ ; UNIFOR ; IRSTEA CLERMONT FERRAND UR LISC FRA ; - ; -}, abstract = {The objective of this paper is to reflect on our experience in a serious game research project, named SimParc, about multi-agent support for participatory management of protected areas for biodiversity conservation and social inclusion. Our project has a clear filiation with the MAS-RPG (Multi-Agent-Simulation – Role-Playing Games) methodology developed by the ComMod action-research community about participatory management of renewable resources, where multi-agent simulation (MAS) computes the dynamics of the resources and role-playing game (RPG) represents the actions and dialogue between stakeholders about the resources. Meanwhile, we have explored some specific directions, such as: dialogue support for negotiation; argumentation-based decision making and its explanation; technical assistance to the players based on viability modeling. In fact, in our project multi-agent based simulation focuses on the negotiation process itself, performed by human players and some artificial participants/agents, rather than on the simulation of the resources dynamics. Meanwhile, as we will see, we have also reintroduced the modeling of the socioecosystem dynamics, but as a local technical assistance/analysis tool for the players and not as a global system modeling. In this proposed chapter, we aim at discussing the rationales for these specificities and for the whole project, as well as summarizing the architecture of our prototype system, current results and experience produced and, last but not the least, lessons learned and prospects for future works. }, }
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J.D. Mathias, M. Grédiac, P. Michaud
Bio-based adhesives
Biopolymers and biotech admixtures for eco-efficient construction materials (p. 369-385), Elsevier Inc., 2016
abs doi web bib

Bio-based adhesives are of growing interest in recent decades not only due to their environmental interest but also due to their mechanical and chemical properties that are becoming increasingly efficient. The purpose of this chapter is to give a general overview of bio-based adhesives of the key issues for future development. We present the background of bio-based adhesives in terms of mechanical testing and the existing families of adhesives. We also present how future development may entangle market trends through the development of mixed adhesives.
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@book{PUB00048370, author = {Mathias, J.D. and Grédiac, M. and Michaud, P.}, author = {Pacheco Torgal, F. and Ivanov, V. and Karak, N. and Jonkers, H.}, title = {Bio-based adhesives}, bookTitle = {Biopolymers and biotech admixtures for eco-efficient construction materials}, publisher = {Elsevier Inc.}, pages = {369-385}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00048370}, doi = {http://dx.doi.org/10.1016/B978-0-08-100214-8.00016-6}, year = {2016}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; UNIVERSITE DE CLERMONT FERRAND I INSTITUT PASCAL FRA ; CNRS CLERMONT FERRAND FRA}, ISBNISSN = {ISBN 978-008100214-8}, abstract = {Bio-based adhesives are of growing interest in recent decades not only due to their environmental interest but also due to their mechanical and chemical properties that are becoming increasingly efficient. The purpose of this chapter is to give a general overview of bio-based adhesives of the key issues for future development. We present the background of bio-based adhesives in terms of mechanical testing and the existing families of adhesives. We also present how future development may entangle market trends through the development of mixed adhesives.}, }
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F. Massol, F. Jabot, S. Manel, F. Munoz
Etude des réseaux en écologie
Analyse des réseaux sociaux appliquée à l’éthologie et l’écologie ; (p. 49-98), Editions Matériologiques, 2015
abs web bib

L'objectif du chapitre est de montrer de quelle manière des systèmes écologiques peuvent être formalisés sous la forme de réseaux et étudiés par des approches de modélisation mathématique et statistique liées à la théorie des graphes. Dans un premier temps, nous définirons les différents objets écologiques formalisés sous forme de réseau (section 1). Ensuite nous présenterons les grandes questions auxquelles l'étude de ces réseaux permet de répondre (section 2). Nous présenterons alors plus spécifiquement l'analyse dynamique des réseaux écologiques (sections 3 et 4). Par la suite, pour l’ensemble des définitions techniques (termes écrits en capitales à leur première occurrence) liées aux notions de réseaux et de graphes, le lecteur pourra se référer au glossaire en fin de chapitre.
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@book{PUB00044372, author = {Massol, F. and Jabot, F. and Manel, S. and Munoz, F.}, author = {Sueur, C.}, title = {Etude des réseaux en écologie}, bookTitle = {Analyse des réseaux sociaux appliquée à l’éthologie et l’écologie ; }, series = {Modélisations,simulations, systèmes}, publisher = {Editions Matériologiques}, pages = {49-98}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00044372}, year = {2015}, affiliation = {UNIVERSITE DE LILLE FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; ECOLE PRATIQUE DES HAUTES ETUDES PARIS FRA ; UNIVERSITE DE MONTPELLIER 2 FRA}, ISBNISSN = {ISBN 978-2-919694-98-3}, abstract = {L'objectif du chapitre est de montrer de quelle manière des systèmes écologiques peuvent être formalisés sous la forme de réseaux et étudiés par des approches de modélisation mathématique et statistique liées à la théorie des graphes. Dans un premier temps, nous définirons les différents objets écologiques formalisés sous forme de réseau (section 1). Ensuite nous présenterons les grandes questions auxquelles l'étude de ces réseaux permet de répondre (section 2). Nous présenterons alors plus spécifiquement l'analyse dynamique des réseaux écologiques (sections 3 et 4). Par la suite, pour l’ensemble des définitions techniques (termes écrits en capitales à leur première occurrence) liées aux notions de réseaux et de graphes, le lecteur pourra se référer au glossaire en fin de chapitre.}, }
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S. Huet, M. Lenormand, G. Deffuant, F. Gargiulo
Parameterisation of individual working dynamics
Empirical Agent-Based Modelling – Challenges and Solutions. Volume 1, The Characterisation and Parameterisation of Empirical Agent-Based Models (p. 133-169), Springer, New York, USA, 2014
abs doi web bib

During the PRIMA European project, we conceived a conceptual model dedicated to the study of the evolution of the European Rural Areas in terms of demography and occupation of their populations. This is a hybrid agent-microsimulation model considering inhabitants as the basic elements composing in households. On the other hand, municipalities are the basic spatial element and the providers for employment and housings. This chapter presents the main objects and their relationships are identified as a first generic way to parameterize the dynamics of such a conceptual model for an implementation of a European region. This chapter explains how dynamics can be parameterised from data for an implementation for a French region. It focusses on the dynamics of work statuses and professions which can be derived from the European Labour Force Survey (LFS). The individual is considered from her entering on the labour market until the moment she decides to retire. Meanwhile, she can be fired, searching for a job when she is unemployed or already employed but also deciding becoming inactive for a while. Jobs are defined by a profession and an activity sector. The job offer is located at the municipality level and can correspond to the searched profession of an individual having a municipality of residence. The French implementation is described starting from the employment survey in France, which is the French declination of the LFS.
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@book{PUB00039099, author = {Huet, S. and Lenormand, M. and Deffuant, G. and Gargiulo, F.}, author = {Smajgl, A. and Barreteau, O.}, title = {Parameterisation of individual working dynamics}, title = {Paramétrisation de la dynamique individuelle relative au travail}, bookTitle = {Empirical Agent-Based Modelling – Challenges and Solutions. Volume 1, The Characterisation and Parameterisation of Empirical Agent-Based Models}, address = {New York, USA}, publisher = {Springer}, pages = {133-169}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00039099}, doi = {http://dx.doi.org/10.1007/978-1-4614-6134-0_8}, year = {2014}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR TSCF FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, ISBNISSN = {ISBN 978-1-4614-6133-3}, abstract = {During the PRIMA European project, we conceived a conceptual model dedicated to the study of the evolution of the European Rural Areas in terms of demography and occupation of their populations. This is a hybrid agent-microsimulation model considering inhabitants as the basic elements composing in households. On the other hand, municipalities are the basic spatial element and the providers for employment and housings. This chapter presents the main objects and their relationships are identified as a first generic way to parameterize the dynamics of such a conceptual model for an implementation of a European region. This chapter explains how dynamics can be parameterised from data for an implementation for a French region. It focusses on the dynamics of work statuses and professions which can be derived from the European Labour Force Survey (LFS). The individual is considered from her entering on the labour market until the moment she decides to retire. Meanwhile, she can be fired, searching for a job when she is unemployed or already employed but also deciding becoming inactive for a while. Jobs are defined by a profession and an activity sector. The job offer is located at the municipality level and can correspond to the searched profession of an individual having a municipality of residence. The French implementation is described starting from the employment survey in France, which is the French declination of the LFS.}, }
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I. Alvarez, S. Martin, O. Dordan, X. Litrico, P. Saint-Pierre
Indicateurs de sécurité et de restauration dynamiques
Agir en situation d'incertitude en agriculture : regards pluridisciplinaires au Nord et au Sud (p. 14), Peter Lang, Bruxelles, BEL, 2013
abs web bib

Les systèmes agricoles au sens large et leur environnement peuvent être décrits comme des systèmes dynamiques : par exemple, des activités agricoles utilisent chaque année des engrais phosphatés. Ces engrais ne se fixent pas dans le sol, mais descendent par infiltration ou écoulement de surface vers les écosystèmes aquatiques – rivières, lacs, baies. Les concentrations excessives de substances nutritives dans ces bassins aquatiques provoquent la prolifération de nappes d’algues. Ces systèmes agricoles sont soumis à des contraintes de rentabilité bien sûr, mais pas uniquement. En effet, les populations riveraines d'un lac souhaitent qu'il conserve un état d'eau claire (oligotrophe), et éviter la prolifération des algues impose des contraintes supplémentaires sur les activités agricoles, en l'occurrence, limiter les apports d'engrais dans le bassin versant. Enfin, ces systèmes agricoles sont soumis à des incertitudes. Viennent immédiatement à l'esprit les aléas climatiques, mais pour rester dans l'exemple du lac, un événement pluvieux intense peut provoquer un ruissellement important qui a pour conséquence immédiate d'augmenter brusquement la concentration de phosphore dissous. Face à des systèmes qui évoluent soumis à des contraintes et des incertitudes, quelles informations fournir au gestionnaire ?
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@book{PUB00040096, author = {Alvarez, I. and Martin, S. and Dordan, O. and Litrico, X. and Saint-Pierre, P.}, author = {Ancey, V. and Avelange, I. and Dedieu, B.}, title = {Indicateurs de sécurité et de restauration dynamiques}, title = {Security and restoration indicators}, bookTitle = {Agir en situation d'incertitude en agriculture : regards pluridisciplinaires au Nord et au Sud}, series = {EcoPolis - volume 17 }, address = {Bruxelles, BEL}, publisher = {Peter Lang}, pages = {14}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00040096}, year = {2013}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; UNIVERSITE DE BORDEAUX FRA ; LYONNAISE DES EAUX BORDEAUX FRA ; UNIVERSITE PARIS DAUPHINE PARIS FRA}, abstract = {Les systèmes agricoles au sens large et leur environnement peuvent être décrits comme des systèmes dynamiques : par exemple, des activités agricoles utilisent chaque année des engrais phosphatés. Ces engrais ne se fixent pas dans le sol, mais descendent par infiltration ou écoulement de surface vers les écosystèmes aquatiques – rivières, lacs, baies. Les concentrations excessives de substances nutritives dans ces bassins aquatiques provoquent la prolifération de nappes d’algues. Ces systèmes agricoles sont soumis à des contraintes de rentabilité bien sûr, mais pas uniquement. En effet, les populations riveraines d'un lac souhaitent qu'il conserve un état d'eau claire (oligotrophe), et éviter la prolifération des algues impose des contraintes supplémentaires sur les activités agricoles, en l'occurrence, limiter les apports d'engrais dans le bassin versant. Enfin, ces systèmes agricoles sont soumis à des incertitudes. Viennent immédiatement à l'esprit les aléas climatiques, mais pour rester dans l'exemple du lac, un événement pluvieux intense peut provoquer un ruissellement important qui a pour conséquence immédiate d'augmenter brusquement la concentration de phosphore dissous. Face à des systèmes qui évoluent soumis à des contraintes et des incertitudes, quelles informations fournir au gestionnaire ?}, }
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L. Chapel, G. Deffuant
SVM approximation of value function contours in target hitting problems
Informatics in control, automation and robotics. 8th International Conference, ICINCO 2011 Noordwijkerhout, the Netherlands, July 28-31, 2011, Revised Selected Papers (p. 37-48), Springer, 2013
abs doi web bib

In a problem of target hitting, the capture basin at cost c is the set of states that can reach the target with a cost lower or equal than c, without breaking the viability constraints. The boundary of a c-capture basin is the c-contour of the problem value function. In this paper, we propose a new algorithm that solves target hitting problems, by iteratively approximating capture basins at successive costs. We show that, by a simple change of variables, minimising a cost may be reduced to the problem of time minimisation, and hence a recursive backward procedure can be set. Two variants of the algorithm are derived, one providing an approximation from inside (the approximation is included in the actual capture basin) and one providing a outer approximation, which allows one to assess the approximation error. We use a machine learning algorithm (as a particular case, we consider Support Vector Machines) trained on points of a grid with boolean labels, and we state the conditions on the machine learning procedure that guarantee the convergence of the approximations towards the actual capture basin when the resolution of the grid decreases to 0. Moreover, we define a control procedure which uses the set of capture basin approximations to drive a point into the target. When using the inner approximation, the procedure guarantees to hit the target, and when the resolution of the grid tends to 0, the controller tends to the optimal one (minimizing the cost to hit the target). We illustrate the method on two simple examples, Zermelo and car on the hill problems.
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@book{PUB00036003, author = {Chapel, L. and Deffuant, G.}, author = {Ferrier, J.L. and Bernard, A. and Gusikhin, O. and Madani, K.}, title = {SVM approximation of value function contours in target hitting problems }, title = {Approximation par SVM des contours d'une fonction valeur pour résoudre un problème d'atteinte de cible}, bookTitle = {Informatics in control, automation and robotics. 8th International Conference, ICINCO 2011 Noordwijkerhout, the Netherlands, July 28-31, 2011, Revised Selected Papers }, series = {Lecture Notes in electrical engineering, vol. 174}, publisher = {Springer}, pages = {37-48}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00036003 / http://www.springerlink.com/content/t5124057t68x374w/}, doi = {http://dx.doi.org/10.1007/978-3-642-31353-0_3}, year = {2013}, affiliation = {UNIVERSITE DE BRETAGNE SUD FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, ISBNISSN = {ISBN 978-3642313523}, abstract = {In a problem of target hitting, the capture basin at cost c is the set of states that can reach the target with a cost lower or equal than c, without breaking the viability constraints. The boundary of a c-capture basin is the c-contour of the problem value function. In this paper, we propose a new algorithm that solves target hitting problems, by iteratively approximating capture basins at successive costs. We show that, by a simple change of variables, minimising a cost may be reduced to the problem of time minimisation, and hence a recursive backward procedure can be set. Two variants of the algorithm are derived, one providing an approximation from inside (the approximation is included in the actual capture basin) and one providing a outer approximation, which allows one to assess the approximation error. We use a machine learning algorithm (as a particular case, we consider Support Vector Machines) trained on points of a grid with boolean labels, and we state the conditions on the machine learning procedure that guarantee the convergence of the approximations towards the actual capture basin when the resolution of the grid decreases to 0. Moreover, we define a control procedure which uses the set of capture basin approximations to drive a point into the target. When using the inner approximation, the procedure guarantees to hit the target, and when the resolution of the grid tends to 0, the controller tends to the optimal one (minimizing the cost to hit the target). We illustrate the method on two simple examples, Zermelo and car on the hill problems. }, }
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G. Deffuant, S. Huet, T. Carletti
La complexité d’un modèle simplifié d’interactions sociales : le modèle Leviathan
Modéliser & simuler. Epistémologie et pratiques de la modélisation et de la simulation (p. 749-778), Editions Matériologiques, Paris, 2013
abs web bib

Nous décrivons un modèle de dynamique d’opinions dans lequel les agents se rencontrent deux à deux de manière aléatoire et font évoluer les opinions qu’ils ont les uns des autres par des mécanismes de vanité et de propagation. Les simulations révèlent une grande richesse de comportements du modèle lorsque les paramètres varient. Nous avons identifié cinq types de dynamiques : égalité, élite, crise, hiérarchie, domination. Nous étudions l’apparition de ces types de dynamiques lorsque les paramètres du modèle varient et nous en proposons des explications théoriques partielles. Enfin, nous discutons l’intérêt de cette approche dans une perspective plus large des sciences sociales.
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@book{PUB00038246, author = {Deffuant, G. and Huet, S. and Carletti, T.}, author = {Varenne, F. and Silberstein, M.}, title = {La complexité d’un modèle simplifié d’interactions sociales : le modèle Leviathan}, title = {The complexity of a simplified model of social interactions: the Leviathan model}, bookTitle = {Modéliser & simuler. Epistémologie et pratiques de la modélisation et de la simulation}, series = {Sciences & Philosophie}, address = {Paris}, publisher = {Editions Matériologiques}, pages = {749-778}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00038246 / http://www.materiologiques.com/Modeliser-simuler-Epistemologies}, year = {2013}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; UNIVERSITE DE NAMUR BEL}, ISBNISSN = {ISBN : 978-2-919694-19-8}, abstract = {Nous décrivons un modèle de dynamique d’opinions dans lequel les agents se rencontrent deux à deux de manière aléatoire et font évoluer les opinions qu’ils ont les uns des autres par des mécanismes de vanité et de propagation. Les simulations révèlent une grande richesse de comportements du modèle lorsque les paramètres varient. Nous avons identifié cinq types de dynamiques : égalité, élite, crise, hiérarchie, domination. Nous étudions l’apparition de ces types de dynamiques lorsque les paramètres du modèle varient et nous en proposons des explications théoriques partielles. Enfin, nous discutons l’intérêt de cette approche dans une perspective plus large des sciences sociales. }, }
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H. Richard, H. Monod, J. Wang, J. Couteau, N. Dumoulin, B. Poussin, J.C. Soulié, É. Ramat
La boîte à outils Mexico, un environnement générique pour piloter l'exploration numérique de modèles ( Chapitre 9)
Analyse de sensibilité et exploration de modèles : application aux sciences de la nature et de l'environnement (p. 233-253), Quae, 2013
abs web bib

This chapter is about the development of a generic software environment for managing the explorations of numerical models. / Ce chapitre s’intéresse au développement d’un environnement informatique générique pour piloter l’exploration de modèles.
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@book{PUB00038239, author = {Richard, H. and Monod, H. and Wang, J. and Couteau, J. and Dumoulin, N. and Poussin, B. and Soulié, J.C. and Ramat, É.}, author = {Faivre, R. and Iooss, B. and Mahévas, S. and Makowski, D. and Monod, H.}, title = {La boîte à outils Mexico, un environnement générique pour piloter l'exploration numérique de modèles ( Chapitre 9)}, title = {Mexico Toolbox: A generic software environment for managing the explorations of numerical models}, bookTitle = {Analyse de sensibilité et exploration de modèles : application aux sciences de la nature et de l'environnement}, series = {Savoir faire}, publisher = {Quae}, pages = {233-253}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00038239 / http://www.quae.com/fr/r2142-analyse-de-sensibilite-et-exploration-de-modeles.html}, year = {2013}, affiliation = {INRA AVIGNON FRA ; INRA JOUY EN JOSAS FRA ; INRA JOUY EN JOSAS FRA ; CODE LUTIN SAINT SEBASTIEN SUR LOIRE FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; CODE LUTIN SAINT SEBASTIEN SUR LOIRE FRA ; CIRAD MONTPELLIER FRA ; UNIVERSITE DU LITTORAL CALAIS FRA}, ISBNISSN = {ISBN 978-2-7592-1906-3}, abstract = {This chapter is about the development of a generic software environment for managing the explorations of numerical models. / Ce chapitre s’intéresse au développement d’un environnement informatique générique pour piloter l’exploration de modèles. }, }
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I. Alvarez, S. Martin
Geometric robustness of viability kernels and resilience basins
Viability and resilience of complex systems: concepts, methods and case studies from ecology and society (p. 193-218), Springer, 2011
doi web bib

@book{PUB00033189, author = {Alvarez, I. and Martin, S.}, author = {Deffuant, G. and Gilbert, N.}, title = {Geometric robustness of viability kernels and resilience basins}, bookTitle = {Viability and resilience of complex systems: concepts, methods and case studies from ecology and society}, series = {Understanding complex systems}, publisher = {Springer}, pages = {193-218}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00033189}, doi = {http://dx.doi.org/10.1007/978-3-642-20423-4}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, ISBNISSN = {ISBN-13: 978-3642204227}, abstract = {}, }
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J.M. Calabrese, G. Deffuant, V. Grimm
Bridging the gap between computational models and viability based resilience in Savanna ecosystems
Viability and resilience of complex systems: concepts, methods and case studies from ecology and society (p. 107-130), Springer, 2011
doi web bib

@book{PUB00033183, author = {Calabrese, J.M. and Deffuant, G. and Grimm, V.}, author = {Deffuant, G. and Gilbert, N.}, title = {Bridging the gap between computational models and viability based resilience in Savanna ecosystems}, bookTitle = {Viability and resilience of complex systems: concepts, methods and case studies from ecology and society}, series = {Understanding complex systems}, publisher = {Springer}, pages = {107-130}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00033183}, doi = {http://dx.doi.org/10.1007/978-3-642-20423-4}, year = {2011}, affiliation = {SMITHSONIAN CONSERVATION BIOLOGY INSTITUTE FRONT ROYAL VA USA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; UFZ HELMHOLTZ CENTRE FOR ENVIRONMENTAL RESEARCH LEIPZIG DEU}, ISBNISSN = {ISBN-13: 978-3642204227}, abstract = {}, }
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X. Castello, F. Vazquez, V.M. Eguiluz, L. Loureiro-Porto, M. San Miguel, L. Chapel, G. Deffuant
Viability and resilience in the dynamics of language competition
Viability and resilience of complex systems: ; concepts, methods and case studies from ecology and society (p. 39-73), Springer, 2011
doi web bib

@book{PUB00033181, author = {Castello, X. and Vazquez ,F. and Eguiluz, V.M. and Loureiro-Porto, L. and San Miguel, M. and Chapel, L. and Deffuant, G.}, author = {Deffuant, G. and Gilbert, N.}, title = {Viability and resilience in the dynamics of language competition}, bookTitle = {Viability and resilience of complex systems: ; concepts, methods and case studies from ecology and society}, series = {Understanding complex systems}, publisher = {Springer}, pages = {39-73}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00033181}, doi = {http://dx.doi.org/10.1007/978-3-642-20423-4}, year = {2011}, affiliation = {IFISC UNIVERSITAT ILLES BALEARS PALMA DE MALLORCA ESP ; MPI PKS MAX PLANK INSTITUTE FOR THE PHYSICS OF COMPLEX SYSTEMS DRESDEN DEU ; IFISC UNIVERSITAT ILLES BALEARS PALMA DE MALLOCA ESP ; DEPARTMENT OF SPANISH MODERN LANGUAGES AND LATIN UNIVERSITAT ILLES BALEARS ESP ; IFISC UNIVERSITAT ILLES BALEARS PALMA DE MALLOCA ESP ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, ISBNISSN = {ISBN-13: 978-3642204227}, abstract = {}, }
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L. Chapel, G. Deffuant
Approximating viability kernels and resilience values: algorithms and practical issues illustrated with KAVIAR software
Viability and resilience of complex systems: concepts, methods and case studies from ecology and society (p. 161-192), Springer, 2011
doi web bib

@book{PUB00033188, author = {Chapel, L. and Deffuant, G.}, author = {Deffuant, G. and Gilbert, N.}, title = {Approximating viability kernels and resilience values: algorithms and practical issues illustrated with KAVIAR software}, bookTitle = {Viability and resilience of complex systems: concepts, methods and case studies from ecology and society}, series = {Understanding complex systems}, publisher = {Springer}, pages = {161-192}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00033188}, doi = {http://dx.doi.org/10.1007/978-3-642-20423-4}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, ISBNISSN = {ISBN-13: 978-3642204227}, abstract = {}, }
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G. Deffuant, N. Gilbert
Viability and resilience of complex systems: concepts, methods and case studies from ecology and society
Springer, 2011
abs doi web bib

One common characteristic of a complex system is its ability to withstand major disturbances and the capacity to rebuild itself. Understanding how such systems demonstrate resilience by absorbing or recovering from major external perturbations requires both quantitative foundations and a multidisciplinary view of the topic. This book demonstrates how new methods can be used to identify the actions favouring the recovery from perturbations on a variety of examples including the dynamics of bacterial biofilms, grassland savannahs, language competition and Internet social networking sites. The reader is taken through an introduction to the idea of resilience and viability and shown the mathematical basis of the techniques used to analyse systems. The idea of individual or agent-based modelling of complex systems is introduced and related to analytically tractable approximations of such models. A set of case studies illustrates the use of the techniques in real applications, and the final section describes how one can use new software tools for carrying out the necessary calculations. The book is intended for a general scientific audience of readers from the natural and social sciences, although it requires some mathematics to gain a full understanding of the more theoretical chapters. It is an essential point of reference for those interested in the practical application of the concepts of resilience and viability.
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@book{PUB00033170, author = {Deffuant, G. and Gilbert, N.}, title = {Viability and resilience of complex systems: concepts, methods and case studies from ecology and society}, series = {Understanding complex systems}, publisher = {Springer}, pages = {233}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00033170}, doi = {http://dx.doi.org/10.1007/978-3-642-20423-4}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; UNIVERSITY OF SURREY CENTRE FOR RESEARCH IN SOCIAL SIMULATION GUILFORD GBR}, ISBNISSN = {ISBN-13: 978-3642204227}, abstract = {One common characteristic of a complex system is its ability to withstand major disturbances and the capacity to rebuild itself. Understanding how such systems demonstrate resilience by absorbing or recovering from major external perturbations requires both quantitative foundations and a multidisciplinary view of the topic. This book demonstrates how new methods can be used to identify the actions favouring the recovery from perturbations on a variety of examples including the dynamics of bacterial biofilms, grassland savannahs, language competition and Internet social networking sites. The reader is taken through an introduction to the idea of resilience and viability and shown the mathematical basis of the techniques used to analyse systems. The idea of individual or agent-based modelling of complex systems is introduced and related to analytically tractable approximations of such models. A set of case studies illustrates the use of the techniques in real applications, and the final section describes how one can use new software tools for carrying out the necessary calculations. The book is intended for a general scientific audience of readers from the natural and social sciences, although it requires some mathematics to gain a full understanding of the more theoretical chapters. It is an essential point of reference for those interested in the practical application of the concepts of resilience and viability.}, }
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T. Guelon, J.D. Mathias, P. Stoodley
Advances in biofilm mechanics
Biofilm Highlights (p. 111-139), Springer, 2011
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@book{PUB00033613, author = {Guelon, T. and Mathias, J.D. and Stoodley, P.}, author = {Flemming, H.C. and Wingender, J. and Szewzyk, U.}, title = {Advances in biofilm mechanics}, title = {Les avancées dans la mécanique des biofilms}, bookTitle = {Biofilm Highlights}, series = {Springer Series on Biofilms, Vol. 5}, publisher = {Springer}, pages = {111-139}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00033613 / http://www.springer.com/life+sciences/microbiology/book/978-3-642-19939-4}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; NATIONAL CENTRE FOR ADVANCED TRIBOLOGY UNIVERSITY OF SOUTHAMPTON GBR}, ISBNISSN = {ISBN 978-3-642-19939-4}, abstract = {}, }
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N. Mabrouk, J.D. Mathias, G. Deffuant
Viability and resilience of a bacterial biofilm individual-based model
Viability and resilience of complex systems: concepts, methods and case studies from ecology and society (p. 131-157), Springer, 2011
doi web bib

@book{PUB00033187, author = {Mabrouk, N. and Mathias, J.D. and Deffuant, G.}, author = {Deffuant, G. and Gilbert, N.}, title = {Viability and resilience of a bacterial biofilm individual-based model}, bookTitle = {Viability and resilience of complex systems: concepts, methods and case studies from ecology and society}, series = {Understanding complex systems}, publisher = {Springer}, pages = {131-157}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00033187}, doi = {http://dx.doi.org/10.1007/978-3-642-20423-4}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, ISBNISSN = {ISBN-13: 978-3642204227}, abstract = {}, }
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S. Martin, G. Deffuant, J.M. Calabrese
Defining resilience mathematically: from attractors to viability
Viability and resilience of complex systems: ; concepts, methods and case studies from ecology and society (p. 15-36), Springer, 2011
doi web bib

@book{PUB00033173, author = {Martin, S. and Deffuant, G. and Calabrese, J.M.}, author = {Deffuant, G. and Gilbert, N.}, title = {Defining resilience mathematically: from attractors to viability}, bookTitle = {Viability and resilience of complex systems: ; concepts, methods and case studies from ecology and society}, series = {Understanding complex systems}, publisher = {Springer}, pages = {15-36}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00033173}, doi = {http://dx.doi.org/10.1007/978-3-642-20423-4}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; UFZ HELMHOLTZ CENTRE FOR ENVIRONMENTAL RESEARCH LEIPZIG DEU}, ISBNISSN = {ISBN-13: 978-3642204227}, abstract = {}, }
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J.P. Aubin, S. Martin
Travel time tubes regulating transportation traffic
Nonlinear analysis and optimization: II: Optimization (p. 1-25), American Mathematical Society, 2010
abs web bib

The issue addressed is the computation at each arrival time and at each state at any node of the network, of the travel time needed to join any node of the network to this state at this arrival date by a prototypical vehicle and of the regulation law governing such viable evolutions. We assume that is known the time dependent controlled dynamics of a prototypical vehicle, the network on which it is constrained to evolve at each instant, and the nodes from which it starts or through which it passes at prescribed times. The basic question we address is the determination of the arrival sets at each arrival time made of terminal states at which arrive evolutions governed by the control system, viable in the network, starting from the departure set for some travel time or prescribed travel time. A subsidiary problem is to determine the associated nodes, through the Cournot set-valued map we define at the end of this paper. We use viability techniques summarized in an appendix, which, translated in terms of travel time problems, allow us, for instance, to characterize the arrival tubes, define the "homoclinic" pairs at which any two nodes can be connected, prove a Lax-Hopf Formula characterizing these tubes by an easy formula whenever the control system does not depend either on the time or on the state, propose a concept of solution to a "system of Hamilton-Jacobi-Bellman inclusions" of which the arriving tube is the unique solution, adapt to those systems the dual concept of Barron-Jensen/Frankowska extension of viscosity solutions to usual Hamilton-Jacobi-Bellman solutions, optimize intertemporal criteria and minimize travel times. We derive the main properties of the Moskowitz Travel Time model of the Lighthill, Whitham and Richards' theory.
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@book{PUB00029633, author = {Aubin, J.P. and Martin, S.}, author = {Leizarowitz, A. and Mordukhovich, B.S. and Shafrir, I. and Zaslavski, A.J.}, title = {Travel time tubes regulating transportation traffic}, title = {Tubes de temps de voyage pour réguler le trafic dans les transports}, bookTitle = {Nonlinear analysis and optimization: II: Optimization}, series = {Contemporary Mathematics, vol .514}, publisher = {American Mathematical Society}, pages = {1-25}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00029633 / http://www.ams.org/bookstore?fn=20&arg1=conmseries&ikey=CONM-514}, year = {2010}, affiliation = {SOCIETE VIMADES PARIS FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, ISBNISSN = {ISBN-10 0-8218-4835-6}, abstract = {The issue addressed is the computation at each arrival time and at each state at any node of the network, of the travel time needed to join any node of the network to this state at this arrival date by a prototypical vehicle and of the regulation law governing such viable evolutions. We assume that is known the time dependent controlled dynamics of a prototypical vehicle, the network on which it is constrained to evolve at each instant, and the nodes from which it starts or through which it passes at prescribed times. The basic question we address is the determination of the arrival sets at each arrival time made of terminal states at which arrive evolutions governed by the control system, viable in the network, starting from the departure set for some travel time or prescribed travel time. A subsidiary problem is to determine the associated nodes, through the Cournot set-valued map we define at the end of this paper. We use viability techniques summarized in an appendix, which, translated in terms of travel time problems, allow us, for instance, to characterize the arrival tubes, define the "homoclinic" pairs at which any two nodes can be connected, prove a Lax-Hopf Formula characterizing these tubes by an easy formula whenever the control system does not depend either on the time or on the state, propose a concept of solution to a "system of Hamilton-Jacobi-Bellman inclusions" of which the arriving tube is the unique solution, adapt to those systems the dual concept of Barron-Jensen/Frankowska extension of viscosity solutions to usual Hamilton-Jacobi-Bellman solutions, optimize intertemporal criteria and minimize travel times. We derive the main properties of the Moskowitz Travel Time model of the Lighthill, Whitham and Richards' theory.}, }
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G. Deffuant
The empathon: Towards a computational agent mimicking empathy
Activity-Based Modeling and Simulation (p. 37-51), Presses Universitaires Blaise Pascal, Clermont-Ferrand, 2010
abs web bib

This paper investigates a basic model simulating empathy. The model is abstracted from recent advances in neurobiology, such as the discovery of mirror neurons or of neurons coding for both visual recognition and connected action plans. In a very simplified computational environment, we define agents which associate action plans with visual stimuli, and are also able to feel such action plans when they observe another agent in a similar situation. We propose a first set of experiments involving only a pair of agents, with different action abilities.
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@book{PUB00030679, author = {Deffuant, G.}, author = {Hill, D.R.C. and Muzy, A. and Zeigler B.P. }, title = {The empathon: Towards a computational agent mimicking empathy }, bookTitle = {Activity-Based Modeling and Simulation}, address = {Clermont-Ferrand}, publisher = {Presses Universitaires Blaise Pascal}, pages = {37-51}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00030679 / http://www.msh-clermont.fr/IMG/pdf/03-DEFFUANT_37-51_.pdf}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {This paper investigates a basic model simulating empathy. The model is abstracted from recent advances in neurobiology, such as the discovery of mirror neurons or of neurons coding for both visual recognition and connected action plans. In a very simplified computational environment, we define agents which associate action plans with visual stimuli, and are also able to feel such action plans when they observe another agent in a similar situation. We propose a first set of experiments involving only a pair of agents, with different action abilities.}, }
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G. Deffuant, S. Huet, S. Skerratt
An agent based model of agri-environmental measure diffusion: What for ?
Agent based modelling in natural resource management (p. 55-73), INSISOC, Valladolid, ESP, 2008
abs web bib

This paper focuses on the agent based model of the diffusion of agri-environmental measures developed in the IMAGES European project (1997 2001). We describe the main stages of this model elaboration, showing that it synthesises different modelling points of view. We then illustrate its representative power using a case study in Scotland. Finally, we point out some difficulties in the practical use of such models, particularly as decision supports for policy makers. We advocate a more careful study of the model through systematic experiments, and for the further development of a model of its aggregated dynamics, in order to give more reliable information to policy makers.
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@book{PUB00024125, author = {Deffuant, G. and Huet, S. and Skerratt, S.}, author = {Lopez Paredes, A. and Hernandez Iglesias, C.}, title = {An agent based model of agri-environmental measure diffusion: What for ?}, title = {Un modèle agent de diffusion de mesures agri-environnementales: pourquoi ?}, bookTitle = {Agent based modelling in natural resource management}, address = {Valladolid, ESP}, publisher = {INSISOC}, pages = {55-73}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00024125}, year = {2008}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; SCOTTISH AGRICULTURAL COLLEGE EDINBURGH GBR}, ISBNISSN = {ISBN 978-84-205-4560-8}, abstract = {This paper focuses on the agent based model of the diffusion of agri-environmental measures developed in the IMAGES European project (1997 2001). We describe the main stages of this model elaboration, showing that it synthesises different modelling points of view. We then illustrate its representative power using a case study in Scotland. Finally, we point out some difficulties in the practical use of such models, particularly as decision supports for policy makers. We advocate a more careful study of the model through systematic experiments, and for the further development of a model of its aggregated dynamics, in order to give more reliable information to policy makers. }, }
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G. Deffuant, G. Weisbuch
Probability distribution dynamics explaining agent model convergence to extremism
Social Simulation, technologies, advances and new discoveries (p. 43-60), Information Science Reference, Hershey, USA, 2008
abs web bib

This chapter studies continuous opinion models with extremists, and we use probability distribution models which approximate the behaviour of agents based models in order to explain their attractor patterns. The probability distribution is defined on a discrete grid in the opinion / uncertainty space. We compute the equations of probability flows between each couple of sites of the grid for different variants of the opinion influence model (bounded confidence, relative agreement and two others). The simulations show that the probability distribution models yield attractor patterns very similar to those obtained with the agent based models. Moreover, a study of the probability distribution evolution helps to better understand the process of convergence to single and double extreme attractors observed in agent based models.
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@book{PUB00025788, author = {Deffuant, G. and Weisbuch, G.}, author = {Edmonds, B. and Hernandez, C. and Troitzsch, K.}, title = {Probability distribution dynamics explaining agent model convergence to extremism}, title = {Des modèles d'évolution de distribution de probabilité pour expliquer la convergence vers l'extrémisme de modèles individus-centrés}, bookTitle = {Social Simulation, technologies, advances and new discoveries}, address = {Hershey, USA}, publisher = {Information Science Reference}, pages = {43-60}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00025788}, year = {2008}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; ENS ECOLE NORMALE SUPERIEURE PARIS LABORATOIRE DE PHYSIQUE STATISTQUE FRA}, ISBNISSN = {ISBN 978-1-59904-522-1}, abstract = {This chapter studies continuous opinion models with extremists, and we use probability distribution models which approximate the behaviour of agents based models in order to explain their attractor patterns. The probability distribution is defined on a discrete grid in the opinion / uncertainty space. We compute the equations of probability flows between each couple of sites of the grid for different variants of the opinion influence model (bounded confidence, relative agreement and two others). The simulations show that the probability distribution models yield attractor patterns very similar to those obtained with the agent based models. Moreover, a study of the probability distribution evolution helps to better understand the process of convergence to single and double extreme attractors observed in agent based models.}, }
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G. Deffuant, F. Amblard, S. Huet, S. Bernard, N. Ferrand, J.P. Bousset, G. Amon, J. Henriot, N. Gilbert, E. Chattoe, G. Weisbuch
Simulation de l'évolution des conversions à l'agriculture biologique dans le département de l'Allier entre 1994 et 1999 par un modèle multi-agents department
Complexity and Ecosystem Management: the Theory and Practice of Multi-agent Systems (p. 19), Edward Elgar Publishers, Cheltenham, UK/Northampton, MA, USA, 2002
abs web bib

We present a model allowing to simulate the evolution of the conversions to organic farming in Allier department from 1994 to 1999. The model is made up of investigations carried out in the field as well as various statistical data. It is based on a statistically valid reconstruction of farmers of the department and their situation per district. The social networks of farmers (made up with other farmers and institutional actors) are considered in the model. The conversion decision is modelled like the result of a process including several stages. Social interactions and economic calculations closely mixed in this process. The aim in the long term is to provide prospective trends on the future evolutions of conversions, according to assumptions on the economic and political context. / Nous présentons un modèle permettant de simuler l'évolution des conversions à l'agriculture biologique dans le département de l'Allier entre 1994 et 1999. Le modèle se nourrit d'enquêtes réalisées sur le terrain ainsi que de données statistiques diverses. Il se fonde sur une reconstitution valide statistiquement de la population d'agriculteurs du département et leur localisation par commune. Les réseaux sociaux des agriculteurs (constitués d'autres agriculteurs et d'acteurs institutionnels) sont considérés dans le modèle. La décision de conversion est modélisée comme le résultat d'un processus comprenant plusieurs étapes. Interactions sociales et calculs économiques se mêlent étroitement dans ce processus. L'objectif du modèle à terme est de fournir des tendances prospectives sur les évolutions futures des conversions, en fonction d'hypothèses sur l'évolution du contexte économique et politique.
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@book{PUB00013158, author = {Deffuant, G. and Amblard, F. and Huet, S. and Bernard, S. and Ferrand, N. and Bousset, J.P. and Amon, G. and Henriot, J. and Gilbert, N. and Chattoe, E. and Weisbuch, G.}, author = {Janssen, M.A.}, title = {Simulation de l'évolution des conversions à l'agriculture biologique dans le département de l'Allier entre 1994 et 1999 par un modèle multi-agents department}, title = {Agent-based simulation of organic farming conversion in Allier }, bookTitle = {Complexity and Ecosystem Management: the Theory and Practice of Multi-agent Systems}, address = {Cheltenham, UK/Northampton, MA, USA}, publisher = {Edward Elgar Publishers}, pages = {19}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00013158}, year = {2002}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND DFCF ; CEMAGREF CLERMONT FERRAND DFCF ; CEMAGREF CLERMONT FERRAND DFCF ; UNIVERSITY OF SURREY GUILDBORD GBR ; UNIVERSITY OXFORD GBR ; ENS PARIS FRA}, number = {02/0948 ; K LI02 8}, abstract = {We present a model allowing to simulate the evolution of the conversions to organic farming in Allier department from 1994 to 1999. The model is made up of investigations carried out in the field as well as various statistical data. It is based on a statistically valid reconstruction of farmers of the department and their situation per district. The social networks of farmers (made up with other farmers and institutional actors) are considered in the model. The conversion decision is modelled like the result of a process including several stages. Social interactions and economic calculations closely mixed in this process. The aim in the long term is to provide prospective trends on the future evolutions of conversions, according to assumptions on the economic and political context. / Nous présentons un modèle permettant de simuler l'évolution des conversions à l'agriculture biologique dans le département de l'Allier entre 1994 et 1999. Le modèle se nourrit d'enquêtes réalisées sur le terrain ainsi que de données statistiques diverses. Il se fonde sur une reconstitution valide statistiquement de la population d'agriculteurs du département et leur localisation par commune. Les réseaux sociaux des agriculteurs (constitués d'autres agriculteurs et d'acteurs institutionnels) sont considérés dans le modèle. La décision de conversion est modélisée comme le résultat d'un processus comprenant plusieurs étapes. Interactions sociales et calculs économiques se mêlent étroitement dans ce processus. L'objectif du modèle à terme est de fournir des tendances prospectives sur les évolutions futures des conversions, en fonction d'hypothèses sur l'évolution du contexte économique et politique.}, }
close

In Collections (1)

F. De Coligny, P. Ancelin, G. Cornu, B. Courbaud, P. Dreyfus, F. Goreaud, S. Gourlet Fleury, C. Meredieu, L. Saint André
CAPSIS: Computer-aided projection for strategies in silviculture: advantages of a shared forest modelling platform
Modelling forest systems ; (p. 319-323), CABI publishing ; Amaro, A. ; Reed, D. ; Soares, P., Wallingford, UK, 2003
abs web bib

Forest scientists build models to study, understand and represent stand growth and dynamics. They are particularly interested in the evolution of ecosystems, at the tree and compartment levels and in the consequences of forest management on volume, shape, wood quality, structural evolution of the stand or sensitivity to meteorological and sanitary problems. Specific computer tools are often developed to implement these models, to test and to explore the consequences of the underlying hypotheses on real or virtual stands. Sometimes, a team may invest in the development of a more integrated tool, based on a parameterisable growth model.The Capsis project aims at integrating several types of forest growth and dynamics models - stand models, distance independent or spatially explicit tree models... - and providing forest management tools to establish and compare different silvicultural scenarios. The objective is to build a perennial, open and dynamic software platform (1) to contribute to the development of models and test their sensitivity to some parameters by simulating the manager's actions, (2) to share tools and methods, (3) to compare results of different models, (4) to transfer models to the managers and (5) to serve as teaching material.Capsis is a portable software, designed around a kernel which provides an organizational data structure - session, project, scenario step. The kernel also proposes generic data descriptions - stand, compartment, tree... These descriptions can be completed in modules - one for each model - which implement a proper data structure and a specific evolution function (growth, mortality, regeneration, dissemination...) with a chosen simulation step. A plug-in architecture provides the possibility to build tools for management, construction of graphics, data exportation, tree group construction, stand representation or connections with other software. At the present time, Capsis hosts six modules, several other integration projects are planned and model integration training sessions are periodically proposed.
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@incollection{PUB00013563, author = {De Coligny, F. and Ancelin, P. and Cornu, G. and Courbaud, B. and Dreyfus, P. and Goreaud, F. and Gourlet Fleury, S. and Meredieu, C. and Saint André, L.}, title = {CAPSIS: Computer-aided projection for strategies in silviculture: advantages of a shared forest modelling platform}, bookTitle = {Modelling forest systems ; }, address = {Wallingford, UK}, publisher = {CABI publishing ; Amaro, A. ; Reed, D. ; Soares, P.}, pages = {319-323}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00013563}, year = {2003}, affiliation = {UMR AMAP ; UMR AMAP ; CIRAD ; CEMAGREF GRENOBLE EPGR ; INRA UR FORET ; CEMAGREF CLERMONT FERRAND LISC ; CIRAD ; INRA ; CIRAD}, number = {MEM 1944-1 ; MEM 1944-2 ; 03/0763}, abstract = {Forest scientists build models to study, understand and represent stand growth and dynamics. They are particularly interested in the evolution of ecosystems, at the tree and compartment levels and in the consequences of forest management on volume, shape, wood quality, structural evolution of the stand or sensitivity to meteorological and sanitary problems. Specific computer tools are often developed to implement these models, to test and to explore the consequences of the underlying hypotheses on real or virtual stands. Sometimes, a team may invest in the development of a more integrated tool, based on a parameterisable growth model.The Capsis project aims at integrating several types of forest growth and dynamics models - stand models, distance independent or spatially explicit tree models... - and providing forest management tools to establish and compare different silvicultural scenarios. The objective is to build a perennial, open and dynamic software platform (1) to contribute to the development of models and test their sensitivity to some parameters by simulating the manager's actions, (2) to share tools and methods, (3) to compare results of different models, (4) to transfer models to the managers and (5) to serve as teaching material.Capsis is a portable software, designed around a kernel which provides an organizational data structure - session, project, scenario step. The kernel also proposes generic data descriptions - stand, compartment, tree... These descriptions can be completed in modules - one for each model - which implement a proper data structure and a specific evolution function (growth, mortality, regeneration, dissemination...) with a chosen simulation step. A plug-in architecture provides the possibility to build tools for management, construction of graphics, data exportation, tree group construction, stand representation or connections with other software. At the present time, Capsis hosts six modules, several other integration projects are planned and model integration training sessions are periodically proposed.}, }
close

In Proceedings (89)

S. Martin, S. Huet, P. Gend, Mohamed A. A. Oumajoud, G. Deffuant, A. Nugier, S. Guimond
Bounded confidence in extreme opinion evolution : An online experiment
International Conference on Computational Social Science (IC2S2 2017), 10/07/2017-13/07/2017, Cologne, DEU (p. 3), 2017
abs web bib

Le modèle d'influence "bounded confidence" est ici partiellement confronté aux résultats d'expériences on-line. Le caractère borné de l'influence est confirmé. Cette influence dépend de la distance relative à un individu (relativement à la distance aux autres individus influenceurs). Les résultats montrent par ailleurs que l'influencé est sensible aux nombre d'influenceurs du groupe dans lequel il se situe. Des expériences complémentaires sont nécessaires pour aller plus loin.
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@inproceedings{PUB00056564, author = {Martin, S. and Huet, S. and Gend, P. and Oumajoud, Mohamed A. A. and Deffuant, G. and Nugier, A. and Guimond, S.}, title = {Bounded confidence in extreme opinion evolution : An online experiment}, title = {Confiance bornée et évolution des opinions extrêmes : expérience en ligne}, bookTitle = {International Conference on Computational Social Science (IC2S2 2017), 10/07/2017-13/07/2017, Cologne, DEU}, pages = {3}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00056564}, year = {2017}, affiliation = {UNIVERSITE DE LORRAINE CRAN NANCY FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; UNIVERSITE DE LORRAINE CRAN NANCY FRA ; UNIVERSITE DE LORRAINE CRAN NANCY FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; UCA LAPSCO CLERMONT FERRAND FRA ; UCA LAPSCO CLERMONT FERRAND FRA}, abstract = {Le modèle d'influence "bounded confidence" est ici partiellement confronté aux résultats d'expériences on-line. Le caractère borné de l'influence est confirmé. Cette influence dépend de la distance relative à un individu (relativement à la distance aux autres individus influenceurs). Les résultats montrent par ailleurs que l'influencé est sensible aux nombre d'influenceurs du groupe dans lequel il se situe. Des expériences complémentaires sont nécessaires pour aller plus loin.}, }
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S. Huet
When ego-involved and non ego-involved agents lead to polarization despite a large consensus
Social Simulation Conference 2016, 19/09/2016-23/09/2016, Rome, ITA , 2016
abs web bib

Huet & Deffuant showed polarisation on minor issues can be reproduced by a dynamics inspired from laboratory experiments considering a population of self-involved agents on a main issue. This paper studies the impact of a mixed population of self-involved and not self-involved agents. The dynamics of self-involved agents is based on Huet & Deffuant meaning agents are attracted on every issues if they are close on to the main issue but reject their peer’s opinion if they are only close onto secondary issue. The dynamics of non self-involved agents is a simple 2D bounded confidence model. In this paper, we focus on the level of polarisation of agents when they are majorly gathered into one cluster. We observe the emergence of various types of “extreme minor clusters”. They can lead the population to a polarisation on minor issues, but also on fundamental ones. A very long transitory state of in group polarisation on secondary issues has been also exhibited. Some of these states are specific to mixed populations.
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@inproceedings{PUB00052594, author = {Huet, S.}, title = {When ego-involved and non ego-involved agents lead to polarization despite a large consensus}, title = {Lorsque la co-présence d'individus engagés et non engagés mène à la polarisation de tous malgré un large consensus modéré initial}, bookTitle = {Social Simulation Conference 2016, 19/09/2016-23/09/2016, Rome, ITA}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00052594}, year = {2016}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {Huet & Deffuant showed polarisation on minor issues can be reproduced by a dynamics inspired from laboratory experiments considering a population of self-involved agents on a main issue. This paper studies the impact of a mixed population of self-involved and not self-involved agents. The dynamics of self-involved agents is based on Huet & Deffuant meaning agents are attracted on every issues if they are close on to the main issue but reject their peer’s opinion if they are only close onto secondary issue. The dynamics of non self-involved agents is a simple 2D bounded confidence model. In this paper, we focus on the level of polarisation of agents when they are majorly gathered into one cluster. We observe the emergence of various types of “extreme minor clusters”. They can lead the population to a polarisation on minor issues, but also on fundamental ones. A very long transitory state of in group polarisation on secondary issues has been also exhibited. Some of these states are specific to mixed populations.}, }
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S. Huet, N. Dumoulin, G. Deffuant
A calibration to properly design a model integrating residential mobility and migration in a rural area
11th Conference of the European Social Simulation Association: Social Simulation Conference, 14/09/2015-18/09/2015, Groningen, NLD , 2015
abs web bib

We propose a hybrid microsimulation and agent-based model of mobility integrating migration and residential mobility. We tested it on the evolution of the population of the Cantal, a French “département” with 150,000 inhabitants. We calibrated it using various data sources from 1990 to 2006, and tested its predictions on other data of the same period and on the period 2007-2012. The spatial heterogeneity of the evolution is well reproduced and the model makes surprisingly correct predictions despite numerous simplifying assumptions. From this calibration we learnt more about how to model residential mobility and migration considering an agent-based model approach.
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@inproceedings{PUB00046433, author = {Huet, S. and Dumoulin, N. and Deffuant, G.}, title = {A calibration to properly design a model integrating residential mobility and migration in a rural area}, title = {Une calibration pour la conception pertinente d'un modèle intégrant mobilité résidentielle et migration dans l'espace rural}, bookTitle = {11th Conference of the European Social Simulation Association: Social Simulation Conference, 14/09/2015-18/09/2015, Groningen, NLD}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00046433}, year = {2015}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {We propose a hybrid microsimulation and agent-based model of mobility integrating migration and residential mobility. We tested it on the evolution of the population of the Cantal, a French “département” with 150,000 inhabitants. We calibrated it using various data sources from 1990 to 2006, and tested its predictions on other data of the same period and on the period 2007-2012. The spatial heterogeneity of the evolution is well reproduced and the model makes surprisingly correct predictions despite numerous simplifying assumptions. From this calibration we learnt more about how to model residential mobility and migration considering an agent-based model approach.}, }
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S. Huet, G. Deffuant
The Leviathan model without gossips and vanity: the richness of influence based on perceived hierarchy
Social Simulation Conference 2015, 14/09/2015-18/09/2015, Groningen, NLD (p. 13), 2015
abs web bib

This paper studies a simplified version of the Leviathan model, without gossip and vanity processes. During dyadic meetings, the agents change their opinion about themselves and about their interlocutor. Speakers highly valued by their listeners are more influential. Only due to the asymmetry of the influence function, the model produces several patterns depending on the parameter values, some of which not yet identified in the first Leviathan model study. In particular, in some cases the leaders have a high opinion of other leaders whereas in other cases they have a low one
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@inproceedings{PUB00045203, author = {Huet, S. and Deffuant, G.}, title = {The Leviathan model without gossips and vanity: the richness of influence based on perceived hierarchy}, title = {Le modèle Leviathan sans commérage ni vanité : la richesse d'une dynamique d'influence basé sur la hiérarchie perçue}, bookTitle = {Social Simulation Conference 2015, 14/09/2015-18/09/2015, Groningen, NLD}, pages = {13}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00045203}, year = {2015}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {This paper studies a simplified version of the Leviathan model, without gossip and vanity processes. During dyadic meetings, the agents change their opinion about themselves and about their interlocutor. Speakers highly valued by their listeners are more influential. Only due to the asymmetry of the influence function, the model produces several patterns depending on the parameter values, some of which not yet identified in the first Leviathan model study. In particular, in some cases the leaders have a high opinion of other leaders whereas in other cases they have a low one}, }
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G. Lassalle, T. Rougier, H. Drouineau, N. Dumoulin, T. Faure, G. Deffuant, P. Jatteau, E. Rochard, P. Lambert
Allis shad: A concrete example of how niche shift modelling studies could help in the definition of conservation measures
Aquatic Biodiversity and Ecosystems Conference, 30/08/2015-05/09/2015, Liverpool, GBR (p. 19), 2015
abs web bib

For most species, only the realized climate niche can realistically be estimated through correlative distribution models. For some species, it has become possible to determine the fundamental niche based on physiological information and a mechanistic understanding. Predicting the future species distributions using both correlative and mechanistic distribution models under climate change scenarios remains as such a rare application. The Allis shad (Alosa alosa) benefited from the attention of the scientific community given its dramatically decreasing trend in all Western European fresh waters. Conservation and restoration measures for the species are undertaken in two key systems of its distribution range where the species was formally a highly abundant exploited natural resource. Both types of distribution models were developed for allis shad and used for predictions but conclusions were never confronted. In the present study, a joint analysis of their results were undertaken to refine conservation actions in the light of climate change impacts. We raised two main concerns regarding: (i) the potential local adaptation of northern populations and (2) the importance of managing a target watershed considering potential existing neighbouring sources of migrants.
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@inproceedings{PUB00045764, author = {Lassalle, G. and Rougier, T. and Drouineau, H. and Dumoulin, N. and Faure, T. and Deffuant, G. and Jatteau, P. and Rochard, E. and Lambert, P.}, title = {Allis shad: A concrete example of how niche shift modelling studies could help in the definition of conservation measures}, bookTitle = {Aquatic Biodiversity and Ecosystems Conference, 30/08/2015-05/09/2015, Liverpool, GBR}, pages = {19}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00045764}, year = {2015}, affiliation = {IRSTEA BORDEAUX UR EABX FRA ; IRSTEA BORDEAUX UR EABX FRA ; IRSTEA BORDEAUX UR EABX FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA BORDEAUX UR EABX FRA ; IRSTEA BORDEAUX UR EABX FRA ; IRSTEA BORDEAUX UR EABX FRA}, abstract = {For most species, only the realized climate niche can realistically be estimated through correlative distribution models. For some species, it has become possible to determine the fundamental niche based on physiological information and a mechanistic understanding. Predicting the future species distributions using both correlative and mechanistic distribution models under climate change scenarios remains as such a rare application. The Allis shad (Alosa alosa) benefited from the attention of the scientific community given its dramatically decreasing trend in all Western European fresh waters. Conservation and restoration measures for the species are undertaken in two key systems of its distribution range where the species was formally a highly abundant exploited natural resource. Both types of distribution models were developed for allis shad and used for predictions but conclusions were never confronted. In the present study, a joint analysis of their results were undertaken to refine conservation actions in the light of climate change impacts. We raised two main concerns regarding: (i) the potential local adaptation of northern populations and (2) the importance of managing a target watershed considering potential existing neighbouring sources of migrants.}, }
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S. Westrelin, N. Dumoulin, I. Pauwels
Premiers pas vers la modélisation de la dynamique spatiale d’une population de brochets dans une retenue hydro-électrique
Journées de la Modélisation, 02/06/2015-03/06/2015, Clermont-Ferrand, FRA (p. 17), 2015
abs web bib

Présentation d'une démarche de modélisation initiée sur les déplacements de brochets adultes suivis par télémétrie acoustique dans un réservoir.
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@inproceedings{PUB00047038, author = {Westrelin, S. and Dumoulin, N. and Pauwels, I.}, title = {Premiers pas vers la modélisation de la dynamique spatiale d’une population de brochets dans une retenue hydro-électrique}, title = {First steps towards the modelling of the spatial dynamics of a pike population in a reservoir.}, bookTitle = {Journées de la Modélisation, 02/06/2015-03/06/2015, Clermont-Ferrand, FRA}, pages = {17}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00047038}, year = {2015}, affiliation = {IRSTEA AIX EN PROVENCE UR HYAX FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; INBO BRUXELLES BEL}, abstract = {Présentation d'une démarche de modélisation initiée sur les déplacements de brochets adultes suivis par télémétrie acoustique dans un réservoir.}, }
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S. Bimonte, N. Dumoulin
SimOLAP: A system for the semi-automatic implementation of simulation datawarehouses
10èmes journées francophones sur les Entrepôts de Données et l’Analyse en ligne EDA, 05/06/2014-06/06/2014, Vichy (p. 4), RNTI, 2014
abs web bib

Data Warehouses and OLAP systems allow decision-makers exploring and analyzing huge volumes of data modeled according the multidimensional model, and extracted from heterogeneous data sources. Usually, DW design is a complex, and time and resources consuming task. Then, DWexperts are necessary during design and implementation phases. In this paper, we present a new methodology and a tool allowing modelers (DW unskilled users) to design and implement DWs for analyzing simulation results data by themselves, without any intervention of DW experts.
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@inproceedings{PUB00040995, author = {Bimonte, S. and Dumoulin, N.}, title = {SimOLAP: A system for the semi-automatic implementation of simulation datawarehouses}, title = {SimOLAP : un système pour l'implémentation semi-automatique d'entrepôts de données de simulation}, bookTitle = {10èmes journées francophones sur les Entrepôts de Données et l’Analyse en ligne EDA, 05/06/2014-06/06/2014, Vichy}, publisher = {RNTI}, pages = {4}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00040995}, year = {2014}, affiliation = {IRSTEA CLERMONT FERRAND UR TSCF FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {Data Warehouses and OLAP systems allow decision-makers exploring and analyzing huge volumes of data modeled according the multidimensional model, and extracted from heterogeneous data sources. Usually, DW design is a complex, and time and resources consuming task. Then, DWexperts are necessary during design and implementation phases. In this paper, we present a new methodology and a tool allowing modelers (DW unskilled users) to design and implement DWs for analyzing simulation results data by themselves, without any intervention of DW experts.}, }
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C. Druilhe, S. Huet, A. Trémier, G. Debenest
Temporal and spatial distribution of organic waste physical properties along composting process
9th Conference on Organic Resources and Biological Treatment, ORBIT 2014, 26/06/2014-28/06/2014, Gödöllo, HUN (p. 14), 2014
abs web bib

As an aerobic biological treatment, the composting process is influenced by the physical properties of organic waste. On one hand, material settlement, air permeability and free air space affect the aeration efficiency and the composting performance. On the other hand, the organic matter biodegradation during the process leads to a variation of material physical properties. The aim of this study was to investigate the time variation and the spatial distribution of the physical properties of a sludge and bulking agent mixture during its composting treatment. Composting was carried out in 300L pilot-scale reactors with forced aeration. In order to follow the spatial distribution in each reactor, the material was divided in three layers. Reactors were respectively stopped after 1.5, 3, 7, 14 and 31 composting days, and each material layer was characterized for moisture content, bulk density, free air space (FAS) and air permeability (K). The results showed that the changes in material properties were different according to the considered layer. The deepest layer, impacted by the air inlet in the reactor, had the highest decrease of moisture content and bulk density, a steady K and the highest FAS increase, whereas the surface layer, impacted by a condensate dropout, showed a slight increase of moisture content, steady density and FAS, and a very strong increase of K. Then, a physical structural reorganization of material occurred during the process. In the future, the obtained results could help to improve composting models, taking into account the temporal and spatial distribution of physical properties in the porous media.
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@inproceedings{PUB00052663, author = {Druilhe, C. and Huet, S. and Trémier, A. and Debenest, G.}, title = {Temporal and spatial distribution of organic waste physical properties along composting process}, bookTitle = {9th Conference on Organic Resources and Biological Treatment, ORBIT 2014, 26/06/2014-28/06/2014, Gödöllo, HUN}, pages = {14}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00052663}, year = {2014}, affiliation = {IRSTEA RENNES UR OPAALE FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA RENNES UR OPAALE FRA ; IMFT TOULOUSE FRA}, abstract = {As an aerobic biological treatment, the composting process is influenced by the physical properties of organic waste. On one hand, material settlement, air permeability and free air space affect the aeration efficiency and the composting performance. On the other hand, the organic matter biodegradation during the process leads to a variation of material physical properties. The aim of this study was to investigate the time variation and the spatial distribution of the physical properties of a sludge and bulking agent mixture during its composting treatment. Composting was carried out in 300L pilot-scale reactors with forced aeration. In order to follow the spatial distribution in each reactor, the material was divided in three layers. Reactors were respectively stopped after 1.5, 3, 7, 14 and 31 composting days, and each material layer was characterized for moisture content, bulk density, free air space (FAS) and air permeability (K). The results showed that the changes in material properties were different according to the considered layer. The deepest layer, impacted by the air inlet in the reactor, had the highest decrease of moisture content and bulk density, a steady K and the highest FAS increase, whereas the surface layer, impacted by a condensate dropout, showed a slight increase of moisture content, steady density and FAS, and a very strong increase of K. Then, a physical structural reorganization of material occurred during the process. In the future, the obtained results could help to improve composting models, taking into account the temporal and spatial distribution of physical properties in the porous media.}, }
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M. Grédiac, F. Sur, C. Badulescu, J.D. Mathias
Deconvolving strain maps obtained with the grid method
Annual Conference on Experimental and Applied Mechanics 2013, 03/06/2013-05/06/2013, Lombard, Illinois, USA / Proceedings of the Society for Experimental Mechanics Series (p. 21-26), 2014
abs doi web bib

The use of various deconvolution techniques to enhance strain maps obtained with the grid method is addressed in this study. Since phase derivative maps obtained with this measurement technique can be approximated by their actual counterparts convolved by the envelope of the kernel used to extract phases and phase derivatives, non-blind restoration techniques can be used to perform deconvolution. Six deconvolution techniques are compared here in order to restore a synthetic phase derivative map. Obtained results are analyzed and discussed.
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@inproceedings{PUB00043723, author = {Grédiac, M. and Sur, F. and Badulescu, C. and Mathias, J.D.}, title = {Deconvolving strain maps obtained with the grid method}, volume = {3}, bookTitle = {Annual Conference on Experimental and Applied Mechanics 2013, 03/06/2013-05/06/2013, Lombard, Illinois, USA / Proceedings of the Society for Experimental Mechanics Series}, pages = {21-26}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00043723 / http://www.scopus.com/inward/record.url?eid=2-s2.0-84886740307&partnerID=40&md5=df83c948f9c9db4f192e8c1401cd2730}, doi = {http://dx.doi.org/10.1007/978-3-319-00768-7_4}, year = {2014}, affiliation = {UNIVERSITE DE CLERMONT FERRAND I INSTITUT PASCAL FRA ; UNIVERSITE DE LORRAINE LABORATOIRE LORRAIN DE RECHERCHE EN INFORMATIQUE ET SES APPLICATIONS VANDOEUVRE LES NANCY FRA ; ENSTA BREST FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {The use of various deconvolution techniques to enhance strain maps obtained with the grid method is addressed in this study. Since phase derivative maps obtained with this measurement technique can be approximated by their actual counterparts convolved by the envelope of the kernel used to extract phases and phase derivatives, non-blind restoration techniques can be used to perform deconvolution. Six deconvolution techniques are compared here in order to restore a synthetic phase derivative map. Obtained results are analyzed and discussed. }, }
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S. Huet, G. Deffuant
The Leviathan model
METACOG 2014, the 2nd International Conference on Metacognition, 09/09/2014-10/09/2014, Clermont-Ferrand, FRA , 2014
abs web bib

The Leviathan model simulates a group of agents holding opinions on each other. During dyadic meetings, they propagate their opinions of each other and of some other agents (gossip). Highly valued agents are more influential. Listeners decrease their opinion about the speaker when feeling undervalued and increase it when feeling overvalued. Various dynamic opinion structures emerge in the group: absolute dominance, hierarchy of opinions, crisis, equality and elite.
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@inproceedings{PUB00041831, author = {Huet, S. and Deffuant, G.}, title = {The Leviathan model}, title = {Le modèle Leviathan}, bookTitle = {METACOG 2014, the 2nd International Conference on Metacognition, 09/09/2014-10/09/2014, Clermont-Ferrand, FRA}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00041831}, year = {2014}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {The Leviathan model simulates a group of agents holding opinions on each other. During dyadic meetings, they propagate their opinions of each other and of some other agents (gossip). Highly valued agents are more influential. Listeners decrease their opinion about the speaker when feeling undervalued and increase it when feeling overvalued. Various dynamic opinion structures emerge in the group: absolute dominance, hierarchy of opinions, crisis, equality and elite. }, }
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S. Huet, A. Shtiliyanova
Communication apprehension, self-esteem and the Leviathan model
Social Simulation Conference SSC 2014, 01/09/2014-05/09/2014, Barcelone, ESP (p. 11), 2014
abs web bib

Mc Corskey and al, 1977 have shown there is a link between a high aversion to oral communication and a lower self-esteem. We investigate if the Leviathan model which considers agents gossiping and having an opinion of each other (Deffuant et al 2013) is able to reproduce such a correlation. Our virtual agents form their opinions in face-to-face meetings. During these meetings, they act in self-defence applying vanity, and influence each other. They also gossip about their peers. In direct meeting and gossiping, a highly valued speaker compared to listener’s self-opinion is more influential. The vanity impact depends on the distance between one’s opinion of one self and the opinion conveyed by the speaker. Listeners felt held in low esteem sanction their speakers by decreasing their opinion of them. Those felt held in high esteem reward them by increasing their opinion of them. We modified the probability to talk of agents to consider a heterogeneous one: static depending on the agent itself, or dynamic depending on her self-esteem. The simplest law to obtain a heterogeneous probability to talk is sufficient to reproduce our search correlation. However, we also discover that the model argue it is possible to have a higher self-esteem for someone talking less than the others in some circumstances.
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@inproceedings{PUB00041835, author = {Huet, S. and Shtiliyanova, A.}, title = {Communication apprehension, self-esteem and the Leviathan model }, title = {Appréhension à la communication, estime de soi et modèle Léviathan}, bookTitle = {Social Simulation Conference SSC 2014, 01/09/2014-05/09/2014, Barcelone, ESP}, pages = {11}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00041835}, year = {2014}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; INRA CLERMONT FERRAND UR UREP FRA}, abstract = {Mc Corskey and al, 1977 have shown there is a link between a high aversion to oral communication and a lower self-esteem. We investigate if the Leviathan model which considers agents gossiping and having an opinion of each other (Deffuant et al 2013) is able to reproduce such a correlation. Our virtual agents form their opinions in face-to-face meetings. During these meetings, they act in self-defence applying vanity, and influence each other. They also gossip about their peers. In direct meeting and gossiping, a highly valued speaker compared to listener’s self-opinion is more influential. The vanity impact depends on the distance between one’s opinion of one self and the opinion conveyed by the speaker. Listeners felt held in low esteem sanction their speakers by decreasing their opinion of them. Those felt held in high esteem reward them by increasing their opinion of them. We modified the probability to talk of agents to consider a heterogeneous one: static depending on the agent itself, or dynamic depending on her self-esteem. The simplest law to obtain a heterogeneous probability to talk is sufficient to reproduce our search correlation. However, we also discover that the model argue it is possible to have a higher self-esteem for someone talking less than the others in some circumstances.}, }
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S. Huet, G. Deffuant
In the Leviathan Model, the average opinion is higher when vanity is weaker with lower valued agents
5th World Conference on Social Simulation (WCSS), 04/11/2014-07/11/2014, Sao Paulo, BRA (p. 12), 2014
abs web bib

In the Leviathan model, agents form opinions about each other. During dyadic meetings, they directly influence each other, or talk about peers through gossip. Speakers highly valued by their listeners are more influential. Moreover, they are subject to a vanity process; if an agent feels undervalued, then he decreases his opinion about the despising agent and on the contrary he increases his opinion about a compliment-giver agent. This model produces several different patterns depending on the parameter values, but the average opinion is always negative whatever the emerging pattern. As a consequence, the gossips tend to be mostly negative. Since this is not in complete accordance with the social–psychology literature indicating that both mostly negative and positive gossip can be observed, we investigate the changes to operate to obtain also mostly positive gossips. We found that when the vanity process is less triggered by agents held in low esteem, the average opinion significantly increases. We check that with this modification, the model still yields the same patterns.
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@inproceedings{PUB00041833, author = {Huet, S. and Deffuant, G.}, title = {In the Leviathan Model, the average opinion is higher when vanity is weaker with lower valued agents }, title = {Dans le modèle Leviathan, l'opinion moyenne est meilleure quand la vanité s'exerce moins avec les agents moindrement estimés}, bookTitle = {5th World Conference on Social Simulation (WCSS), 04/11/2014-07/11/2014, Sao Paulo, BRA}, pages = {12}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00041833}, year = {2014}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {In the Leviathan model, agents form opinions about each other. During dyadic meetings, they directly influence each other, or talk about peers through gossip. Speakers highly valued by their listeners are more influential. Moreover, they are subject to a vanity process; if an agent feels undervalued, then he decreases his opinion about the despising agent and on the contrary he increases his opinion about a compliment-giver agent. This model produces several different patterns depending on the parameter values, but the average opinion is always negative whatever the emerging pattern. As a consequence, the gossips tend to be mostly negative. Since this is not in complete accordance with the social–psychology literature indicating that both mostly negative and positive gossip can be observed, we investigate the changes to operate to obtain also mostly positive gossips. We found that when the vanity process is less triggered by agents held in low esteem, the average opinion significantly increases. We check that with this modification, the model still yields the same patterns.}, }
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J.D. Mathias, S. Huet, G. Deffuant
Bounded confidence model with fixed uncertainties and extremists: the opinions can keep fluctuating indefinitely
5th World Conference on Social Simulation (WCSS), 04/11/2014-07/11/2014, Sao Paulo, BRA (p. 12), 2014
abs web bib

The bounded confidence model and its variants applied to moderate and extremist agents exhibit three types of attractors: central clusters, double extreme and single extreme clusters. These attractors are observed when the models include a dynamics on the uncertainties tending to decrease the moderate uncertainties when interacting with extremists. We show here that a new stationary state appears when the uncertainties are fixed, for large uncertainties of the moderates. In this stationary state, the opinions of moderate agents keep fluctuating without clustering, altogether forming a stable density which shape changes significantly when the parameters vary.
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@inproceedings{PUB00041834, author = {Mathias, J.D. and Huet, S. and Deffuant, G.}, title = {Bounded confidence model with fixed uncertainties and extremists: the opinions can keep fluctuating indefinitely}, title = {Le modèle de confiance bornée avec des incertitudes fixes et des extrêmistes: les opinions peuvent changer indéfiniment}, bookTitle = {5th World Conference on Social Simulation (WCSS), 04/11/2014-07/11/2014, Sao Paulo, BRA}, pages = {12}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00041834}, year = {2014}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {The bounded confidence model and its variants applied to moderate and extremist agents exhibit three types of attractors: central clusters, double extreme and single extreme clusters. These attractors are observed when the models include a dynamics on the uncertainties tending to decrease the moderate uncertainties when interacting with extremists. We show here that a new stationary state appears when the uncertainties are fixed, for large uncertainties of the moderates. In this stationary state, the opinions of moderate agents keep fluctuating without clustering, altogether forming a stable density which shape changes significantly when the parameters vary. }, }
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I. Alvarez, R. De Aldama, S. Martin, R. Reuillon
Assessing the resilience of socio-ecosystems: coupling viability theory and active learning with kd-Trees. Application to bilingual societies
International Joint Conference on Artificial Intelligence 2013 ( IJCAI), 03/08/2013-09/08/2013, Beijing, CHN (p. 2776-2782), 2013
abs web bib

This paper proposes a new algorithm to compute the resilience of a social system or an ecosystem when it is defined in the framework of the mathematical viability theory. It is applied to the problem of language coexistence: Although bilingual societies do exist, many languages have disappeared and some seem endangered presently. Mathematical models of language competition generally conclude that one language will disappear, except when the relative prestige of the languages can be modified. The viability theory provides concepts and tools that are suitable to study the resilience, but with severe computational limits since it uses extensive search on regular grids. The method we propose considers the computation of the viability output sets as an active learning problem with the objective of restraining the number of calls to the model and information storage. We adapt a kd-tree algorithm to approximate the level sets of the resilience value. We prove that this algorithm converges to the output sets defined by the viability theory (viability kernel and capture basin). The resilience value we compute can then be used to propose a policy of action in risky situations such as migration flows. / Cet article propose un algorithme couplé pour calculer la résilience d'un socio-écosystème dans le cadre de la théorie mathématique de la viabilité, illustré sur le problème des sociétés bilingues. Les modèles mathématiques de telles sociétés montrent que l'extinction d'un langage est en général inéluctable, sauf s'il est possible de modifier le prestige des langues. La méthode de calcul de la résilience que nous proposons repose sur un algorithme adapté des kd-trees. La convergence de l'algorithme de viabilité dans ce cadre est démontrée. Le calcul de la résilience est utilisé pour proposer des politiques d'action en cas de flux migratoires.
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@inproceedings{PUB00039946, author = {Alvarez, I. and De Aldama, R. and Martin, S. and Reuillon, R.}, title = {Assessing the resilience of socio-ecosystems: coupling viability theory and active learning with kd-Trees. Application to bilingual societies}, title = {Evaluer la résilience des socio-écosystèmes : coupler la théorie de la viabilité avec l'apprentissage actif à partir de kd-trees. Application à la coexistence des langues.}, bookTitle = {International Joint Conference on Artificial Intelligence 2013 ( IJCAI), 03/08/2013-09/08/2013, Beijing, CHN}, pages = {2776-2782}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00039946 / http://ijcai.org/papers13/Papers/IJCAI13-409.pdf}, year = {2013}, affiliation = {UNIVERSITE PIERRE ET MARIE CURIE LIP6 PARIS FRA ; INSTITUT DES SYSTEMES COMPLEXES ISC PIF PARIS FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; INSTITUT DES SYSTEMES COMPLEXES ISC PIF PARIS FRA}, abstract = {This paper proposes a new algorithm to compute the resilience of a social system or an ecosystem when it is defined in the framework of the mathematical viability theory. It is applied to the problem of language coexistence: Although bilingual societies do exist, many languages have disappeared and some seem endangered presently. Mathematical models of language competition generally conclude that one language will disappear, except when the relative prestige of the languages can be modified. The viability theory provides concepts and tools that are suitable to study the resilience, but with severe computational limits since it uses extensive search on regular grids. The method we propose considers the computation of the viability output sets as an active learning problem with the objective of restraining the number of calls to the model and information storage. We adapt a kd-tree algorithm to approximate the level sets of the resilience value. We prove that this algorithm converges to the output sets defined by the viability theory (viability kernel and capture basin). The resilience value we compute can then be used to propose a policy of action in risky situations such as migration flows. / Cet article propose un algorithme couplé pour calculer la résilience d'un socio-écosystème dans le cadre de la théorie mathématique de la viabilité, illustré sur le problème des sociétés bilingues. Les modèles mathématiques de telles sociétés montrent que l'extinction d'un langage est en général inéluctable, sauf s'il est possible de modifier le prestige des langues. La méthode de calcul de la résilience que nous proposons repose sur un algorithme adapté des kd-trees. La convergence de l'algorithme de viabilité dans ce cadre est démontrée. Le calcul de la résilience est utilisé pour proposer des politiques d'action en cas de flux migratoires.}, }
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B. Bonté, F. de Morogues, T. Cordonnier, J.D. Mathias
Impacts de l'intensification des fonctions de préservation de la biodiversité et de production de bois sur la flexibilité de la sylviculture en futaie irrégulière
FORGECO 2013 - Forêts et écosystèmes cultivés : vers une intensification écologique ?, 03/12/2013-04/12/2013, Grenoble, FRA (p. 43-47), 2013
abs web bib

Les interventions réalisées dans le cadre de ce séminaire s’intéressent à la gestion intégrée des écosystèmes, à une production épargnant, utilisant ou valorisant les écosystèmes, ou encore à une préservation des écosystèmes consciente des conséquences, sur la production, des mesures préconisées. Elles peuvent s’appuyer sur des études de cas, mais veillent à donner une certaine représentativité ou généricité à leurs conclusions de manière à comparer non seulement les méthodes, mais aussi les enseignements tirés de la gestion des forêts et autres écosystèmes cultivés.
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@inproceedings{PUB00040258, author = {Bonté, B. and de Morogues, F. and Cordonnier, T. and Mathias, J.D.}, title = {Impacts de l'intensification des fonctions de préservation de la biodiversité et de production de bois sur la flexibilité de la sylviculture en futaie irrégulière }, title = {Impact of the intensification of the biodiversity preservation function and of the wood production function, on the flexibility of sylviculture in uneven-aged forests}, bookTitle = {FORGECO 2013 - Forêts et écosystèmes cultivés : vers une intensification écologique ?, 03/12/2013-04/12/2013, Grenoble, FRA}, pages = {43-47}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00040258 / http://www.gip-ecofor.org/?q=node/873}, year = {2013}, affiliation = {IRSTEA CLERMONT UR LISC FRA ; FCBA FRA ; IRSTEA GRENOBLE UR EMGR FRA ; IRSTEA CLERMONT UR LISC FRA}, abstract = {Les interventions réalisées dans le cadre de ce séminaire s’intéressent à la gestion intégrée des écosystèmes, à une production épargnant, utilisant ou valorisant les écosystèmes, ou encore à une préservation des écosystèmes consciente des conséquences, sur la production, des mesures préconisées. Elles peuvent s’appuyer sur des études de cas, mais veillent à donner une certaine représentativité ou généricité à leurs conclusions de manière à comparer non seulement les méthodes, mais aussi les enseignements tirés de la gestion des forêts et autres écosystèmes cultivés.}, }
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B. Bonté, V. Lafond, T. Cordonnier, J.D. Mathias
Using an individual-based model of uneven-aged forests for studying trade-off between timber production and deadwood preservation
ICCGI 2013, The Eighth International Multi-Conference on Computing in the Global Information Technology, 21/07/2013-26/07/2013, Nice, FRA / The Eighth International Multi-Conference on Computing in the Global Information Technology, ICCGI 2013 (p. 175-180), IARIA, 2013
abs web bib

Integrating the multi-functional role of forests in forestry practices constitutes a challenging example of complex system management. Usually, win-win situations between functions are seldom and trade-offs have to be considered. This paper proposes a framework to study dynamical relationships between two important functions in forests: timber production and biodiversity conservation. We built an individual-based model of uneven-aged forests that explicitly takes into account timber harvesting options and dead wood dynamics. Dead wood compartment was selected because it represents a relevant surrogate for biodiversity in forests. We used dynamics metrics based on viability theory framework to evaluate simulations that contrasted different thinning intensities and thinning frequencies. Thanks to this model and the metrics used, we are able to discuss optimal strategies for preserving biodiversity while guaranteeing timber production.
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@inproceedings{PUB00038853, author = {Bonté, B. and Lafond,V. and Cordonnier, T. and Mathias, J.D.}, title = {Using an individual-based model of uneven-aged forests for studying trade-off between timber production and deadwood preservation}, title = {Utiliser un modèle de dynamique forestière en peuplement irrégulier pour étudier le compromis entre production de bois et préservation du bois mort}, bookTitle = {ICCGI 2013, The Eighth International Multi-Conference on Computing in the Global Information Technology, 21/07/2013-26/07/2013, Nice, FRA / The Eighth International Multi-Conference on Computing in the Global Information Technology, ICCGI 2013}, publisher = {IARIA}, pages = {175-180}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00038853 / http://www.thinkmind.org/index.php?view=article&articleid=iccgi_2013_9_20_10204}, year = {2013}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA GRENOBLE UR EMGR FRA ; IRSTEA GRENOBLE UR EMGR FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, ISBNISSN = {ISBN 978-1-61208-283-7}, abstract = {Integrating the multi-functional role of forests in forestry practices constitutes a challenging example of complex system management. Usually, win-win situations between functions are seldom and trade-offs have to be considered. This paper proposes a framework to study dynamical relationships between two important functions in forests: timber production and biodiversity conservation. We built an individual-based model of uneven-aged forests that explicitly takes into account timber harvesting options and dead wood dynamics. Dead wood compartment was selected because it represents a relevant surrogate for biodiversity in forests. We used dynamics metrics based on viability theory framework to evaluate simulations that contrasted different thinning intensities and thinning frequencies. Thanks to this model and the metrics used, we are able to discuss optimal strategies for preserving biodiversity while guaranteeing timber production.}, }
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B. Bonté, T. Cordonnier, J.D. Mathias
Applying the viability theory for studying forest pratices in the global change context
European Conference on Complex Systems (ECCS'13), 15/09/2013-20/09/2013, Barcelona, ESP (p. 1), 2013
abs web bib

Within the context of forest multifunctionality there is a great challenge for forest management policies and legislation to evolve from purely economic management to a management that considers also ecological and recreational values and social estate preservation associated with a forest. Because of this multifunctional aspect of the forest, it is important to integrate the socio-economic behaviour in forest management strategies as a part of the forest system. Focusing on two challenges facing society that forest management must address today, we use the viability theory, in order to establish the room for manoeuvre of a forest owner whose forest would provide both, timber production and biodiversity preservation services. These services have to be maintained despite low growth due to climate change.
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@inproceedings{PUB00039192, author = {Bonté, B. and Cordonnier, T. and Mathias, J.D.}, title = {Applying the viability theory for studying forest pratices in the global change context}, title = {Appliquer la théorie de la viabilité pour étudier les pratiques forestières dans un contexte de changement climatique}, bookTitle = {European Conference on Complex Systems (ECCS'13), 15/09/2013-20/09/2013, Barcelona, ESP}, pages = {1}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00039192}, year = {2013}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA GRENOBLE UR EMGR FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {Within the context of forest multifunctionality there is a great challenge for forest management policies and legislation to evolve from purely economic management to a management that considers also ecological and recreational values and social estate preservation associated with a forest. Because of this multifunctional aspect of the forest, it is important to integrate the socio-economic behaviour in forest management strategies as a part of the forest system. Focusing on two challenges facing society that forest management must address today, we use the viability theory, in order to establish the room for manoeuvre of a forest owner whose forest would provide both, timber production and biodiversity preservation services. These services have to be maintained despite low growth due to climate change.}, }
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S. Huet
The target of the sel-management process makes the level of positivity to others
Interactions dans les systèmes complexes, 17/06/2013-19/06/2013, Orléans, FRA (p. 21), 2013
abs web bib

We study the Leviathan model in which individuals have opinions on each other (Deffuant et al 2013). The model couples the management of face-to-face meetings through direct interaction implying influence depending on esteem of the other and self-management (reward or punishment depending on the returned image by the other); and gossip having an influence depending of the level of esteem of the hearer for the talker. It is shown that the chosen target of the self-management process leads to a positive or a negative world. Mainly punishing or rewarding people held in high esteem can lead to a global positivity or global negativity to others while punishing or rewarding mostly everyone or only people held in low esteem leads to global negatives relationship. Moreover, choosing a self-management targeting more those held in high esteem keeps the same, and even enlarges, the richness of the various leaderships and organisations emerging from the model.
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@inproceedings{PUB00039555, author = {Huet, S.}, title = {The target of the sel-management process makes the level of positivity to others}, title = {La cible du processus de gestion de soi fait le niveau de positivité vis-à-vis d'autrui}, bookTitle = {Interactions dans les systèmes complexes, 17/06/2013-19/06/2013, Orléans, FRA}, pages = {21}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00039555}, year = {2013}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {We study the Leviathan model in which individuals have opinions on each other (Deffuant et al 2013). The model couples the management of face-to-face meetings through direct interaction implying influence depending on esteem of the other and self-management (reward or punishment depending on the returned image by the other); and gossip having an influence depending of the level of esteem of the hearer for the talker. It is shown that the chosen target of the self-management process leads to a positive or a negative world. Mainly punishing or rewarding people held in high esteem can lead to a global positivity or global negativity to others while punishing or rewarding mostly everyone or only people held in low esteem leads to global negatives relationship. Moreover, choosing a self-management targeting more those held in high esteem keeps the same, and even enlarges, the richness of the various leaderships and organisations emerging from the model.}, }
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S. Huet
Formes de leadership, défense de soi et commérage
Septièmes journées francophones Modèles Formels de l'Interaction, MFI'13, 01/07/2013-05/07/2013, Lille, FRA / http://pfia2013.univ-lille1.fr/doku.php%3Fid=fr:mfi.html (p. 15), 2013
abs web bib

Nous étudions une dynamique simplifiée du modèle Leviathan (Deffuant et al 2013) : les agents se rencontrent deux à deux de manière aléatoire et font évoluer les opinions qu’ils ont les uns des autres par des mécanismes de défense de soi et de propagation d’opinion sur des tiers. Nous nous intéressons à trois états de la population engendrés par ce modèle : la crise stigmatisée par une absence de leader ; la dominance où règne un leader quasi absolu mais renversable ; la hiérarchie au sein de laquelle chaque individu a son rang propre. Nous étudions l’effet de l’intensité du commérage inter-individuel mesuré via le nombre de personnes évoquées durant un face-à-face. Nous focalisons sur l’effet de l’ouverture aux autres qui amène un individu à être influencé par des individus qu’il n’estime pas. Nous montrons que partant d’une tendance systématique à l’état de crise, l’ouverture aux autres et le commérage permettent la mise en place d’un leadership charismatique stabilisant les relations inter-individus.
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@inproceedings{PUB00039556, author = {Huet, S.}, title = {Formes de leadership, défense de soi et commérage}, title = {Leadership styles, self-management and gossip}, bookTitle = {Septièmes journées francophones Modèles Formels de l'Interaction, MFI'13, 01/07/2013-05/07/2013, Lille, FRA / http://pfia2013.univ-lille1.fr/doku.php%3Fid=fr:mfi.html}, pages = {15}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00039556}, year = {2013}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {Nous étudions une dynamique simplifiée du modèle Leviathan (Deffuant et al 2013) : les agents se rencontrent deux à deux de manière aléatoire et font évoluer les opinions qu’ils ont les uns des autres par des mécanismes de défense de soi et de propagation d’opinion sur des tiers. Nous nous intéressons à trois états de la population engendrés par ce modèle : la crise stigmatisée par une absence de leader ; la dominance où règne un leader quasi absolu mais renversable ; la hiérarchie au sein de laquelle chaque individu a son rang propre. Nous étudions l’effet de l’intensité du commérage inter-individuel mesuré via le nombre de personnes évoquées durant un face-à-face. Nous focalisons sur l’effet de l’ouverture aux autres qui amène un individu à être influencé par des individus qu’il n’estime pas. Nous montrons que partant d’une tendance systématique à l’état de crise, l’ouverture aux autres et le commérage permettent la mise en place d’un leadership charismatique stabilisant les relations inter-individus.}, }
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F. Jabot, T. Faure, N. Dumoulin
EasyABC: performing efficient approximate Bayesian computation sampling schemes using R
ABC (Approximate Bayesian Computation), 30/05/2013-31/05/2013, Rome, ITA , 2013
abs web bib

1.Approximate Bayesian computation (ABC), also called likelihood-free inference, is a family of statistical techniques to perform parameter inference and model comparison. It is increasingly used in ecology and evolution, where the models used can be too complex to be handled with standard likelihood techniques. The essence of ABC techniques is to compare model simulation outputs to observed data, in order to select the model simulations (and their associated parameter values) which best fit the data. ABC techniques therefore require a large number of model simulations. 2.We introduce the R package 'EasyABC' that enables to launch a series of simulations of a computer code from the R platform and to retrieve the simulation outputs in an appropriate format for post-processing treatments. The 'EasyABC' package further implements several efficient parameter sampling schemes to speed up the ABC procedure: on top of the standard prior sampling, it implements various algorithms to perform sequential (ABC-sequential) and Markov chain Monte Carlo (ABC-MCMC) sampling schemes. The package functions can furthermore make use in parallel of several cores of a multi-core computer. 3.The R package 'EasyABC' complements the package 'abc' which enables various post-processing treatments of simulation outputs. 'EasyABC' will make the up-to-date ABC implementations available to the large community of R users in the fields of ecology and evolution. It is a freely available R package under the GPL license, and it can be downloaded at http://cran.r-project.org/web/packages/EasyABC/index.html .
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@inproceedings{PUB00040536, author = {Jabot, F. and Faure, T. and Dumoulin, N.}, title = {EasyABC: performing efficient approximate Bayesian computation sampling schemes using R}, title = {EasyABC : effectuer des protocoles d'échantillonnages efficaces pour le calcul Bayésien approché avec R}, bookTitle = {ABC (Approximate Bayesian Computation), 30/05/2013-31/05/2013, Rome, ITA}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00040536}, year = {2013}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {1.Approximate Bayesian computation (ABC), also called likelihood-free inference, is a family of statistical techniques to perform parameter inference and model comparison. It is increasingly used in ecology and evolution, where the models used can be too complex to be handled with standard likelihood techniques. The essence of ABC techniques is to compare model simulation outputs to observed data, in order to select the model simulations (and their associated parameter values) which best fit the data. ABC techniques therefore require a large number of model simulations. 2.We introduce the R package 'EasyABC' that enables to launch a series of simulations of a computer code from the R platform and to retrieve the simulation outputs in an appropriate format for post-processing treatments. The 'EasyABC' package further implements several efficient parameter sampling schemes to speed up the ABC procedure: on top of the standard prior sampling, it implements various algorithms to perform sequential (ABC-sequential) and Markov chain Monte Carlo (ABC-MCMC) sampling schemes. The package functions can furthermore make use in parallel of several cores of a multi-core computer. 3.The R package 'EasyABC' complements the package 'abc' which enables various post-processing treatments of simulation outputs. 'EasyABC' will make the up-to-date ABC implementations available to the large community of R users in the fields of ecology and evolution. It is a freely available R package under the GPL license, and it can be downloaded at http://cran.r-project.org/web/packages/EasyABC/index.html . }, }
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M. Lenormand, S. Huet, G. Deffuant, F. Gargiulo
University laws in commuting flows
2013
abs web bib

We propose an individual based model to generate commuting networks from data giving numbers of in and out commuters of every locations of a region. It is inspired from the gravity model. We exhibit from the calibration of 80 various case studies that the only remaining parameter can be suppressed since it follows a law depending on the average surface of the locations. We compare our model to the only one other universal existing approach (Simini et al, 2012) at various scales. We show our model performs better for small locations (in terms of surface and/or number of inhabitants).
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@inproceedings{PUB00039558, author = {Lenormand, M. and Huet, S. and Deffuant, G. and Gargiulo, F.}, title = {University laws in commuting flows}, pages = {1}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00039558}, year = {2013}, affiliation = {IFISC PALMA DE MALLORCA ESP ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; NAXYS UNAMUR NAMUR BEL}, abstract = {We propose an individual based model to generate commuting networks from data giving numbers of in and out commuters of every locations of a region. It is inspired from the gravity model. We exhibit from the calibration of 80 various case studies that the only remaining parameter can be suppressed since it follows a law depending on the average surface of the locations. We compare our model to the only one other universal existing approach (Simini et al, 2012) at various scales. We show our model performs better for small locations (in terms of surface and/or number of inhabitants).}, }
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M. Lenormand, S. Huet, G. Deffuant, F. Gargiulo
Universality laws in commuting flows
2013
abs web bib

We propose an individual based model to generate commuting networks from data giving numbers of in and out commuters of every locations of a region. It is inspired from the gravity model. We exhibit from the calibration of 80 various case studies that the only remaining parameter can be suppressed since it follows a law depending on the average surfaces of the locations. We compare our model to the only one other universal existing approach (Simini et al, 2012) at various scales. We show our model performs better for small locations (in terms of surface and/or number of inhabitants).
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@inproceedings{PUB00039020, author = {Lenormand, M. and Huet, S. and Deffuant, G. and Gargiulo, F.}, title = {Universality laws in commuting flows}, title = {Lois universelles des réseaux de navettage}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00039020}, year = {2013}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {We propose an individual based model to generate commuting networks from data giving numbers of in and out commuters of every locations of a region. It is inspired from the gravity model. We exhibit from the calibration of 80 various case studies that the only remaining parameter can be suppressed since it follows a law depending on the average surfaces of the locations. We compare our model to the only one other universal existing approach (Simini et al, 2012) at various scales. We show our model performs better for small locations (in terms of surface and/or number of inhabitants).}, }
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J.D. Mathias, C. Rougé, G. Deffuant
Lake eutrophication and environmental change: A viability framework for resilience, vulnerability and adaptive capacity
2013
abs web bib

We present a simple stochastic model of lake eutrophication to demonstrate how the mathematical framework of viability theory fosters operational definitions of resilience, vulnerability and adaptive capacity, and then helps understand which response one should bring to environmental changes. The model represents the phosphorus dynamics, given that high concentrations trigger a regime change from oligotrophic to eutrophic, and causes ecological but also economic losses, for instance from tourism. Phosphorus comes from agricultural inputs upstream of the lake, and we will consider a stochastic input. We consider the system made of both the lake and its upstream region, and explore how to maintain the desirable ecological and economic properties of this system. In the viability framework, we translate these desirable properties into state constraints, then examine how, given the dynamics of the model and the available policy options, the properties can be kept. The set of states for which there exists a policy to keep the properties is called the viability kernel. We extend this framework to both major perturbations and long-term environmental changes. In our model, since the phosphorus inputs and outputs from the lake depend on rainfall, we will focus on extreme rainfall events and long-term changes in the rainfall regime. They can be described as changes in the state of the system, and may displace it outside the viability kernel. Its response can then be described using the concepts of resilience, vulnerability and adaptive capacity. Resilience is the capacity to recover by getting back to the viability kernel where the dynamics keep the system safe, and in this work we assume it to be the first objective of management. Computed for a given trajectory, vulnerability is a measure of the consequence of violating a property. We propose a family of functions from which cost functions and other vulnerability indicators can be derived for any trajectory. There can be several vulnerability functions, representing for instance social, economic or ecological vulnerability, and each representing the violation of the associated property, but these functions need to be ultimately aggregated as a single indicator. Due to the stochastic nature of the system, there is a range of possible trajectories. Statistics can be derived from the probability distribution of the vulnerability of the trajectories. Dynamic programming methods can then yield the policies which, among available policies, minimize a given trajectory. Thus, this viability framework gives indication on both the possible consequences of a hazard or an environmental change, and on the policies that can mitigate or avert it. It also enables to assess the benefits of extending the set of available policy options, and we define adaptive capacity as the reduction in a given vulnerability statistic due to the introduction of new policy options.
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@inproceedings{PUB00039249, author = {Mathias, J.D. and Rougé, C. and Deffuant, G.}, title = {Lake eutrophication and environmental change: A viability framework for resilience, vulnerability and adaptive capacity}, title = {Eutrophisation d'un lac et changement environnemental : un cadre viabiliste pour la résilience, la vulnérabilité et la capacité d'adaptation}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00039249}, year = {2013}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {We present a simple stochastic model of lake eutrophication to demonstrate how the mathematical framework of viability theory fosters operational definitions of resilience, vulnerability and adaptive capacity, and then helps understand which response one should bring to environmental changes. The model represents the phosphorus dynamics, given that high concentrations trigger a regime change from oligotrophic to eutrophic, and causes ecological but also economic losses, for instance from tourism. Phosphorus comes from agricultural inputs upstream of the lake, and we will consider a stochastic input. We consider the system made of both the lake and its upstream region, and explore how to maintain the desirable ecological and economic properties of this system. In the viability framework, we translate these desirable properties into state constraints, then examine how, given the dynamics of the model and the available policy options, the properties can be kept. The set of states for which there exists a policy to keep the properties is called the viability kernel. We extend this framework to both major perturbations and long-term environmental changes. In our model, since the phosphorus inputs and outputs from the lake depend on rainfall, we will focus on extreme rainfall events and long-term changes in the rainfall regime. They can be described as changes in the state of the system, and may displace it outside the viability kernel. Its response can then be described using the concepts of resilience, vulnerability and adaptive capacity. Resilience is the capacity to recover by getting back to the viability kernel where the dynamics keep the system safe, and in this work we assume it to be the first objective of management. Computed for a given trajectory, vulnerability is a measure of the consequence of violating a property. We propose a family of functions from which cost functions and other vulnerability indicators can be derived for any trajectory. There can be several vulnerability functions, representing for instance social, economic or ecological vulnerability, and each representing the violation of the associated property, but these functions need to be ultimately aggregated as a single indicator. Due to the stochastic nature of the system, there is a range of possible trajectories. Statistics can be derived from the probability distribution of the vulnerability of the trajectories. Dynamic programming methods can then yield the policies which, among available policies, minimize a given trajectory. Thus, this viability framework gives indication on both the possible consequences of a hazard or an environmental change, and on the policies that can mitigate or avert it. It also enables to assess the benefits of extending the set of available policy options, and we define adaptive capacity as the reduction in a given vulnerability statistic due to the introduction of new policy options.}, }
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C. Rouge, J.D. Mathias, G. Deffuant
Finding a compromise between viability maximization and cost minimization: A stochastic dynamic programming algorithm
2nd International Workshop "Aux frontières de la viabilité et de l'économie", Université Paris Dauphine, 26/11/2013-27/11/2013, Paris, FRA , 2013
abs web bib

In a stochastic controlled dynamical system, stochastic dynamic programming is used for either cost minimization or viability maximization. We propose a change in variables that enables the minimization of a linear combination of expected costs and exit probabilities, thus effectively combining the expected value and worst-case approaches to a problem. The resulting algorithm facilitates the discussion of the possible trade-offs between the two kind of objectives through an example of water supply from a reservoir.
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@inproceedings{PUB00039467, author = {Rouge, C. and Mathias, J.D. and Deffuant, G.}, title = {Finding a compromise between viability maximization and cost minimization: A stochastic dynamic programming algorithm}, title = {Trouver des compromis entre maximisation de la viabilité et minimisation du coût : un algorithme de programmation dynamique}, bookTitle = {2nd International Workshop "Aux frontières de la viabilité et de l'économie", Université Paris Dauphine, 26/11/2013-27/11/2013, Paris, FRA}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00039467}, year = {2013}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {In a stochastic controlled dynamical system, stochastic dynamic programming is used for either cost minimization or viability maximization. We propose a change in variables that enables the minimization of a linear combination of expected costs and exit probabilities, thus effectively combining the expected value and worst-case approaches to a problem. The resulting algorithm facilitates the discussion of the possible trade-offs between the two kind of objectives through an example of water supply from a reservoir.}, }
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C. Rougé, J.D. Mathias, G. Deffuant
Resilience and vulnerability to a natural hazard: A mathematical framework based on viability theory
2013
abs web bib

This deals with the response of a coupled human and natural system (CHANS) to a natural hazard by using the concepts of resilience and vulnerability within the mathematical framework of viability theory. This theory applies to time-evolving systems such as CHANS and assumes that their desirable properties can be defined as a subset of their state space. Policies can also apply to influence the dynamics of such systems: viability theory aims at finding the policies which keep the properties of a controlled dynamical system for so long as no disturbance hits it. The states of the system such that the properties are guaranteed constitute what is called the viability kernel. This viability framework has been extended to describe the response to a perturbation such as a natural hazard. Resilience describes the capacity of the CHANS to recover by getting back in the viability kernel, where its properties are guaranteed until the onset of the next major event. Defined for a given controlled trajectory that the system may take after the event ends, resilience is (a) whether the system comes back to the viability kernel within a given budget such as a time constraint, but also (b) a decreasing function of vulnerability. Computed for a given trajectory as well, vulnerability is a measure of the consequence of violating a property. We propose a family of functions from which cost functions and other vulnerability indicators can be derived for a certain trajectory. There can be several vulnerability functions, representing for instance social, economic or ecological vulnerability, and each representing the violation of an associated property, but these functions need to be ultimately aggregated as a single indicator. Computing the resilience and vulnerability of a trajectory enables the viability framework to describe the response of both deterministic and stochastic systems to hazards. In the deterministic case, there is only one response trajectory for a given action policy, and methods exist to find the actions which yield the most resilient trajectory, namely the least vulnerable trajectory for which recovery is complete. In the stochastic case however, there is a range of possible trajectories. Statistics can be derived from the probability distribution of the resilience and vulnerability of the trajectories. Dynamic programming methods can then yield either the policies that maximize the probability of being resilient by achieving recovery within a given time horizon, or these which minimize a given vulnerability statistic. These objectives are different and can be in contradiction, so that trade-offs may have to be considered between them. The approach is illustrated in both the deterministic and stochastic cases through a simple model of lake eutrophication, for which the desirable ecological properties of the lake conflict with the economic interest of neighboring farmers.
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@inproceedings{PUB00039248, author = {Rougé, C. and Mathias, J.D. and Deffuant, G.}, title = {Resilience and vulnerability to a natural hazard: A mathematical framework based on viability theory}, title = {Résilience et vulnérabilité à un aléa : un cadre mathématique basé sur la théorie de la viabilité}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00039248}, year = {2013}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {This deals with the response of a coupled human and natural system (CHANS) to a natural hazard by using the concepts of resilience and vulnerability within the mathematical framework of viability theory. This theory applies to time-evolving systems such as CHANS and assumes that their desirable properties can be defined as a subset of their state space. Policies can also apply to influence the dynamics of such systems: viability theory aims at finding the policies which keep the properties of a controlled dynamical system for so long as no disturbance hits it. The states of the system such that the properties are guaranteed constitute what is called the viability kernel. This viability framework has been extended to describe the response to a perturbation such as a natural hazard. Resilience describes the capacity of the CHANS to recover by getting back in the viability kernel, where its properties are guaranteed until the onset of the next major event. Defined for a given controlled trajectory that the system may take after the event ends, resilience is (a) whether the system comes back to the viability kernel within a given budget such as a time constraint, but also (b) a decreasing function of vulnerability. Computed for a given trajectory as well, vulnerability is a measure of the consequence of violating a property. We propose a family of functions from which cost functions and other vulnerability indicators can be derived for a certain trajectory. There can be several vulnerability functions, representing for instance social, economic or ecological vulnerability, and each representing the violation of an associated property, but these functions need to be ultimately aggregated as a single indicator. Computing the resilience and vulnerability of a trajectory enables the viability framework to describe the response of both deterministic and stochastic systems to hazards. In the deterministic case, there is only one response trajectory for a given action policy, and methods exist to find the actions which yield the most resilient trajectory, namely the least vulnerable trajectory for which recovery is complete. In the stochastic case however, there is a range of possible trajectories. Statistics can be derived from the probability distribution of the resilience and vulnerability of the trajectories. Dynamic programming methods can then yield either the policies that maximize the probability of being resilient by achieving recovery within a given time horizon, or these which minimize a given vulnerability statistic. These objectives are different and can be in contradiction, so that trade-offs may have to be considered between them. The approach is illustrated in both the deterministic and stochastic cases through a simple model of lake eutrophication, for which the desirable ecological properties of the lake conflict with the economic interest of neighboring farmers.}, }
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C. Rougé, J.D. Mathias, G. Deffuant
Résilience et vulnérabilité dans le cadre de la théorie de la viabilité et des systèmes dynamiques stochastiques contrôlés
2013
abs web bib

Les concepts de résilience et de vulnérabilité sont tous les deux introduits dans le cadre des systèmes dynamiques stochastiques contrôlés. Cela permet de mettre en lumière la complémentarité de ces concepts.
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@inproceedings{PUB00039264, author = {Rougé, C. and Mathias, J.D. and Deffuant, G.}, title = {Résilience et vulnérabilité dans le cadre de la théorie de la viabilité et des systèmes dynamiques stochastiques contrôlés}, title = {Resilience and vulnerability in the framework of viability and stochastic controlled dynamical systems}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00039264}, year = {2013}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {Les concepts de résilience et de vulnérabilité sont tous les deux introduits dans le cadre des systèmes dynamiques stochastiques contrôlés. Cela permet de mettre en lumière la complémentarité de ces concepts.}, }
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C. Rougé, J.D. Mathias, G. Deffuant
Resilience and vulnerability from a stochastic dynamical system perspective
2013
abs web bib

We recall the viability framework for resilience, then present its extension to stochastic systems. The concept of vulnerability is also introduced in the framework of stochastic controlled dynamical systems. We discuss the links between both concepts.
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@inproceedings{PUB00039263, author = {Rougé, C. and Mathias, J.D. and Deffuant, G.}, title = {Resilience and vulnerability from a stochastic dynamical system perspective}, title = {Résililience et vulnérabilité à travers une perspective de systèmes dynamiques stochastiques contrôlés}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00039263}, year = {2013}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {We recall the viability framework for resilience, then present its extension to stochastic systems. The concept of vulnerability is also introduced in the framework of stochastic controlled dynamical systems. We discuss the links between both concepts.}, }
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C. Rougé, J.D. Mathias, G. Deffuant
Resilience, vulnerability and adaptive capacity to environmental change in a dynamical system, and application to a nonlinear lake model
2013
abs web bib

We use the mathematical framework of viability theory to give operational definitions to the concepts of resilience, vulnerability and adaptive capacity in a context of environmental change. These three concepts are widely used to describe the problem of managing a social and / or ecological system submitted to such a change. Resilience and vulnerability are two complementary notions which respectively refer to the possibility of maintaining or recovering a set of properties and functions after a disturbance, and to the cost of losing them, whether temporarily or permanently. Adaptive capacity, which is concerned with the capacity of the system to cope with or recover from a change, is an essential determinant of both resilience and vulnerability. The operational definitions we propose can apply to any stochastic controlled discrete-time dynamical system, and are especially useful for nonlinear systems. The goal is to use these concepts to describe the adaptation of the management strategy of a social-ecological system in the presence of environmental change. Such a strategy must keep or recover the desirable properties of that system. To define it, we thereby introduce a concept of baseline management, using a subset of the state space for which the decision taken is uniform and stationary. This baseline decision is implemented provided such management does not endanger the system’s core properties. Thus, this is the way it is managed unless these properties are threatened, leading to an emergency situation, for which other decisions must be taken. Stochastic viability theory then uses stochastic dynamic programming to find the baseline strategies, which both incorporate the baseline management and maximize the viability of the system: its probability of maintaining its desirable properties over the planning period. The set of states for which this probability tops a given confidence level is called the stochastic viability kernel, and such strategies are called viable baseline strategies if the states for which the baseline decision is taken belong to the stochastic viability kernel. Indeed, the latter represents the set of safe states, and the baseline decision only applies to such states. Viable baseline strategies are valid under given environmental conditions, i.e., under a given set of system parameters. When environmental change occurs, the baseline strategy may not be adequate to allow for the continuing functioning of the system, and may need to be modified. Adaptive management is simply defined as a change of the set of the available baseline strategies. It is not instantaneous, and is characterized by its rate as well by its total magnitude. Thus, it consists in a temporal sequence in which the set of available baseline strategies changes at each time step. In this context, dynamic programming can be used to maximize resilience, defined as the probability to eventually reach the stochastic viability kernel of a new viable baseline strategy. It can also be used to minimize vulnerability, a statistic defined on the distribution of possible costs. Adaptive capacity then measures the impact of adaptive management in terms of resilience and vulnerability. We provide an illustration to a nonlinear model of lake eutrophication, in which phosphorus inputs to the lake originating from economic activities have to be limited to keep it in a desirable, clear water state. Adaptive management of an abrupt shift in the lake dynamics through a reduction in phosphorus inputs illustrates how our framework helps determine the determinants adaptive capacity. Results suggest that strengthening adaptation rates is more important than reducing the lag in implementing adaptation to a change of the lake system, and show nonlinear shifts of the resilience and adaptation depending on the values of the adaptation parameters.
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@inproceedings{PUB00039260, author = {Rougé, C. and Mathias, J.D. and Deffuant, G.}, title = {Resilience, vulnerability and adaptive capacity to environmental change in a dynamical system, and application to a nonlinear lake model}, title = {Résilience, vulnérabilité et capacité d'adaptation d'un système dynamique à des changements environnementaux, et application à un modèle de lac non-linéaire}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00039260}, year = {2013}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {We use the mathematical framework of viability theory to give operational definitions to the concepts of resilience, vulnerability and adaptive capacity in a context of environmental change. These three concepts are widely used to describe the problem of managing a social and / or ecological system submitted to such a change. Resilience and vulnerability are two complementary notions which respectively refer to the possibility of maintaining or recovering a set of properties and functions after a disturbance, and to the cost of losing them, whether temporarily or permanently. Adaptive capacity, which is concerned with the capacity of the system to cope with or recover from a change, is an essential determinant of both resilience and vulnerability. The operational definitions we propose can apply to any stochastic controlled discrete-time dynamical system, and are especially useful for nonlinear systems. The goal is to use these concepts to describe the adaptation of the management strategy of a social-ecological system in the presence of environmental change. Such a strategy must keep or recover the desirable properties of that system. To define it, we thereby introduce a concept of baseline management, using a subset of the state space for which the decision taken is uniform and stationary. This baseline decision is implemented provided such management does not endanger the system’s core properties. Thus, this is the way it is managed unless these properties are threatened, leading to an emergency situation, for which other decisions must be taken. Stochastic viability theory then uses stochastic dynamic programming to find the baseline strategies, which both incorporate the baseline management and maximize the viability of the system: its probability of maintaining its desirable properties over the planning period. The set of states for which this probability tops a given confidence level is called the stochastic viability kernel, and such strategies are called viable baseline strategies if the states for which the baseline decision is taken belong to the stochastic viability kernel. Indeed, the latter represents the set of safe states, and the baseline decision only applies to such states. Viable baseline strategies are valid under given environmental conditions, i.e., under a given set of system parameters. When environmental change occurs, the baseline strategy may not be adequate to allow for the continuing functioning of the system, and may need to be modified. Adaptive management is simply defined as a change of the set of the available baseline strategies. It is not instantaneous, and is characterized by its rate as well by its total magnitude. Thus, it consists in a temporal sequence in which the set of available baseline strategies changes at each time step. In this context, dynamic programming can be used to maximize resilience, defined as the probability to eventually reach the stochastic viability kernel of a new viable baseline strategy. It can also be used to minimize vulnerability, a statistic defined on the distribution of possible costs. Adaptive capacity then measures the impact of adaptive management in terms of resilience and vulnerability. We provide an illustration to a nonlinear model of lake eutrophication, in which phosphorus inputs to the lake originating from economic activities have to be limited to keep it in a desirable, clear water state. Adaptive management of an abrupt shift in the lake dynamics through a reduction in phosphorus inputs illustrates how our framework helps determine the determinants adaptive capacity. Results suggest that strengthening adaptation rates is more important than reducing the lag in implementing adaptation to a change of the lake system, and show nonlinear shifts of the resilience and adaptation depending on the values of the adaptation parameters.}, }
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C. Rougé, G. Deffuant
Performance of water extraction in an endangered aquifer when management is not all powerful: a theoretical framework based on viability theory
2013
abs web bib

We address the performance of an aquifer system where water is extracted at a given baseline pumping rate under the following conditions: 1) the possibility of management to reduce the pumping rate if necessary is limited, 2) catastrophic events such as saltwater intrusion or pollution can interrupt water extraction, and 3) recharge is a stochastic process. We argue that the mathematical framework of stochastic viability theory is relevant for addressing this problem, and for complementing the usual performance indicators of reliability, resiliency and vulnerability (R-R-V) which, alone, are not adapted to describe situations where the baseline pumping rate cannot be restored. Indeed, viability theory allows for the derivation of the stochastic viability kernel, defined as the set of all the values of the aquifer storage for which the baseline pumping rate can be applied while ensuring continued water extraction with a high probability in a large time horizon. For lower values of aquifer storage, pumping has to be reduced to avoid adverse events, so that the baseline pumping rate cannot be met. A fourth indicator, the probability of resilience, then represents the probability for the catastrophic event not to occur before aquifer storage is restored to levels where it is safe to resume baseline extraction rates. Viability theory allows for finding the management actions that minimize the risk of event occurrence. For a given baseline pumping rate and for given limits to management, one can then derive R-R-V indicators to describe the performance of the system. This viability framework provides insights into the connection between the choice of higher baseline extraction rates and a lower system performance. Besides, the values of these indicators increase when management can reduce pumping rates more quickly, thus evidencing the importance of empowering management instances, both for avoiding catastrophes and for having an effective extraction policy. The applicability of the framework to conditions of extreme droughts is also discussed.
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@inproceedings{PUB00039262, author = {Rougé, C. and Deffuant, G.}, title = {Performance of water extraction in an endangered aquifer when management is not all powerful: a theoretical framework based on viability theory}, title = {Performance de l'extraction d'eau dans un aquifère en péril quand le gestionnaire n'est pas tout-puissant : un cadre théorique basé sur la théorie de la viabilité}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00039262}, year = {2013}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {We address the performance of an aquifer system where water is extracted at a given baseline pumping rate under the following conditions: 1) the possibility of management to reduce the pumping rate if necessary is limited, 2) catastrophic events such as saltwater intrusion or pollution can interrupt water extraction, and 3) recharge is a stochastic process. We argue that the mathematical framework of stochastic viability theory is relevant for addressing this problem, and for complementing the usual performance indicators of reliability, resiliency and vulnerability (R-R-V) which, alone, are not adapted to describe situations where the baseline pumping rate cannot be restored. Indeed, viability theory allows for the derivation of the stochastic viability kernel, defined as the set of all the values of the aquifer storage for which the baseline pumping rate can be applied while ensuring continued water extraction with a high probability in a large time horizon. For lower values of aquifer storage, pumping has to be reduced to avoid adverse events, so that the baseline pumping rate cannot be met. A fourth indicator, the probability of resilience, then represents the probability for the catastrophic event not to occur before aquifer storage is restored to levels where it is safe to resume baseline extraction rates. Viability theory allows for finding the management actions that minimize the risk of event occurrence. For a given baseline pumping rate and for given limits to management, one can then derive R-R-V indicators to describe the performance of the system. This viability framework provides insights into the connection between the choice of higher baseline extraction rates and a lower system performance. Besides, the values of these indicators increase when management can reduce pumping rates more quickly, thus evidencing the importance of empowering management instances, both for avoiding catastrophes and for having an effective extraction policy. The applicability of the framework to conditions of extreme droughts is also discussed.}, }
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C. Rougé, J.D. Mathias, G. Deffuant
Viability theory to formalize resilience and vulnerability
2013
abs web bib

This proposes to use stability landscapes, also known as ball-and-cup diagrams, to illustrate what the viability framework brings to the joint definition of resilience and vulnerability in social-ecological systems (SESs). Stability landscapes are generally used to describe the resilience of a system when the states that hold its desirable properties coincide with basins of attraction. The viability framework for resilience was originally developed to overcome two major shortcomings of the use of basins of attraction: 1) it shifts the focus of resilience from the system itself towards its properties of interest, which are represented by state constraints that may not coincide with the potential basins of attraction of the dynamic; and 2) it allows for the incorporation of action policies on the system. We show how the former translates into the setting of thresholds that do not affect the stability landscape, yet casts aside some regions of a basin of attraction as undesirable – e.g. because they are economically unacceptable. We also point out that action policies result in reshaping the stability landscape. Viability theory generalizes the concept of attractor by introducing the viability kernel, defined as the set of states for which there is an action policy that enables the continued respect of the properties. Resilience and vulnerability both are concepts that deal with how SESs fare under the pressure from natural hazards such as environmental changes and extreme events. Such hazards can be depicted by changes in the state of the system, changes in the stability landscape, or both. The viability framework originally focuses on resilience which is defined as the ability to keep or recover the properties of interest by getting back to the viability kernel after an event. The set of states from which the system can keep or recover the property of interest is the resilience basin, a mathematical object which generalizes the notion of basin of attraction since it can be defined in the absence of attractors and in the presence of action policies. Then, we define vulnerability as a measure of the potential harm associated with losing the property, even if the system stays within the resilience basin. Thus, the properties can be vulnerable yet resilient. In that sense, the viability framework can deal with both resilience and vulnerability as complementary concepts, while respecting their respective intuitive meanings. We propose to illustrate the framework using ball-and-cup diagrams extracted from the classic nonlinear dynamics of lake eutrophication. Moreover, the proposed framework and its illustration using stability landscapes are expected to foster discussion on the concepts related to adaptation.
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@inproceedings{PUB00039257, author = {Rougé, C. and Mathias, J.D. and Deffuant, G.}, title = {Viability theory to formalize resilience and vulnerability}, title = {La théorie de la viabilité pour formaliser la résilience et la vulnérabilité}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00039257}, year = {2013}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {This proposes to use stability landscapes, also known as ball-and-cup diagrams, to illustrate what the viability framework brings to the joint definition of resilience and vulnerability in social-ecological systems (SESs). Stability landscapes are generally used to describe the resilience of a system when the states that hold its desirable properties coincide with basins of attraction. The viability framework for resilience was originally developed to overcome two major shortcomings of the use of basins of attraction: 1) it shifts the focus of resilience from the system itself towards its properties of interest, which are represented by state constraints that may not coincide with the potential basins of attraction of the dynamic; and 2) it allows for the incorporation of action policies on the system. We show how the former translates into the setting of thresholds that do not affect the stability landscape, yet casts aside some regions of a basin of attraction as undesirable – e.g. because they are economically unacceptable. We also point out that action policies result in reshaping the stability landscape. Viability theory generalizes the concept of attractor by introducing the viability kernel, defined as the set of states for which there is an action policy that enables the continued respect of the properties. Resilience and vulnerability both are concepts that deal with how SESs fare under the pressure from natural hazards such as environmental changes and extreme events. Such hazards can be depicted by changes in the state of the system, changes in the stability landscape, or both. The viability framework originally focuses on resilience which is defined as the ability to keep or recover the properties of interest by getting back to the viability kernel after an event. The set of states from which the system can keep or recover the property of interest is the resilience basin, a mathematical object which generalizes the notion of basin of attraction since it can be defined in the absence of attractors and in the presence of action policies. Then, we define vulnerability as a measure of the potential harm associated with losing the property, even if the system stays within the resilience basin. Thus, the properties can be vulnerable yet resilient. In that sense, the viability framework can deal with both resilience and vulnerability as complementary concepts, while respecting their respective intuitive meanings. We propose to illustrate the framework using ball-and-cup diagrams extracted from the classic nonlinear dynamics of lake eutrophication. Moreover, the proposed framework and its illustration using stability landscapes are expected to foster discussion on the concepts related to adaptation.}, }
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S. Sun, J.D. Mathias, E. Toussaint, M. Grédiac
Characterization of the mechanical behavior of sunflower stem for bio-composite applications
2012 Annual Conference on Experimental and Applied Mechanics, Society for Experimental Mechanics (SEM) , 11/06/2012-14/06/2012, Cosa Mesa, USA / Mechanics of Biological Systems and Materials, Volume 5. ; Proceedings of the 2012 Annual Conference on Experimental and Applied Mechanics.Series: Conference Proceedings of the Society for Experimental Mechanics Series. Prorok, B.; Barthelat, F.; Korach, C.; Grande-Allen, K.J.; Lipke, E.; Lykofatitits, G.; Zavattieri, P. (Eds.) ; (p. 7-13), Springer, 2013
abs doi web bib

The aim of this study is to investigate the mechanical properties of sunflower stems. Sunflower stems have two parts: the bark and the pith. Since the mechanical properties of the bark and those of the pith are different, separate mechanical tests were performed. The influence of both the moisture content and of the location of the specimens along the stem was studied. An increase of moisture content of bark and pith was found to reduce their Young’s modulus. The Young’s modulus increases with the location of the specimen along the stem.
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@inproceedings{PUB00035747, author = {Sun, S. and Mathias, J.D. and Toussaint, E. and Grédiac, M.}, title = {Characterization of the mechanical behavior of sunflower stem for bio-composite applications}, title = {Caractérisation du comportement mécanique de tiges de tournesol}, bookTitle = {2012 Annual Conference on Experimental and Applied Mechanics, Society for Experimental Mechanics (SEM) , 11/06/2012-14/06/2012, Cosa Mesa, USA / Mechanics of Biological Systems and Materials, Volume 5. ; Proceedings of the 2012 Annual Conference on Experimental and Applied Mechanics.Series: Conference Proceedings of the Society for Experimental Mechanics Series. Prorok, B.; Barthelat, F.; Korach, C.; Grande-Allen, K.J.; Lipke, E.; Lykofatitits, G.; Zavattieri, P. (Eds.) ; }, publisher = {Springer}, pages = {7-13}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00035747 / http://www.springer.com/materials/mechanics/book/978-1-4614-4426-8}, doi = {http://dx.doi.org/10.1007/978-1-4614-4427-5_2}, year = {2013}, affiliation = {UNIVERSITE DE CLERMONT FERRAND I FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; UNIVERSITE DE CLERMONT FERRAND I FRA ; UNIVERSITE DE CLERMONT FERRAND I FRA}, ISBNISSN = {ISBN 978-1-4614-4426-8}, abstract = {The aim of this study is to investigate the mechanical properties of sunflower stems. Sunflower stems have two parts: the bark and the pith. Since the mechanical properties of the bark and those of the pith are different, separate mechanical tests were performed. The influence of both the moisture content and of the location of the specimens along the stem was studied. An increase of moisture content of bark and pith was found to reduce their Young’s modulus. The Young’s modulus increases with the location of the specimen along the stem.}, }
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A. Bridier, T. Bouchez, F. Jabot
Measuring species interactions during biofilm development.
ISME 14 Symposium, 19/08/2012-24/08/2012, Copenhague, DNK (p. 1), 2012
abs web bib

Biofilms are structured communities of microorganisms and are now recognized as the prevailing mode of life of bacteria in natural and man-made environments. Bacterial biofims participate therefore to a large number of beneficial ecological processes but can also have a considerable negative impact on human well-being throughout their involvement in biodeterioration or biofouling processes and even by causing serious infectious diseases. The functional roles of biofilms leading to these positive or negative impacts are intimately related to the spatial architecture and organization of the community. Since biofilms are recognized as complex associations of numerous different species in our environments, a better deciphering of the nature of the interactions between bacterial populations become an important ecological parameter required to better understand, predict and control biofilm functions. Individuals of two different bacterial species can interact in biofilms in different ways. They may compete for ressources and space, just as conspecific individuals do. They may also interact in more complex ways, in which intra-specific interactions differ from inter-specific ones. For instance, different species may share different common goods or have complementary feeding needs. We are here interested in these last types of interactions, which modify the dynamics of each species in the presence of the other. These interactions make the coupled dynamics of the two species different from the juxtaposition of the two monospecific dynamics, so that it should be possible to detect these by the careful analysis of biofilm growth patterns. In this aim, mono-species and bi-species biofilms were grown under flow in three-channel flow-cells. 3D biofilm structure was then scanned every hour during biofilm development using time-lapse confocal laser scanning microscopy combined to genetically modified bacterial strains expressing constitutively green or red fluorescent protein (GFP or mCherry). We built a simple individual-based model of biofilm development, where intra-specific interactions did not differ from inter-specific ones. We developed a statistical method to parameterize the different processes represented in the biofilm model (growth, mobility, attachment and detachment) using our temporal series of biofilm images obtained by confocal microscopy. By setting the model directly with these experimental data, we limit the number of hypothesis that we formulated and therefore, we limit the bias caused by these hypothesis in the model. This parameterization relied on the comparison between the structural patterns observed during biofilm development in vitro and in silico. Namely, biofilm structural patterns were quantified thanks to a number of summary statistics (number of clusters and the first four moments of the cluster size distribution) at the different time points both in the simulations and in the experimental images. And model parameter values with which model simulations best fit empirical observations were retained. We demonstrate in this contribution that our simple model of biofilm growth can be parameterized with temporal series of biofilm images, and that it satisfactorily represents the biofilm growth dynamics observed in our experiments. We finally demonstrate how to use this simple model of biofilm growth as a null model to detect non-trivial interactions between pairs of bacterial species.
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@inproceedings{PUB00038250, author = {Bridier, A. and Bouchez, T. and Jabot, F.}, title = {Measuring species interactions during biofilm development.}, title = {Mesurer les interactions entre espèces pendant le développement de biofilm.}, bookTitle = {ISME 14 Symposium, 19/08/2012-24/08/2012, Copenhague, DNK}, pages = {1}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00038250}, year = {2012}, affiliation = {IRSTEA ANTONY UR HBAN FRA ; IRSTEA ANTONY UR HBAN FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {Biofilms are structured communities of microorganisms and are now recognized as the prevailing mode of life of bacteria in natural and man-made environments. Bacterial biofims participate therefore to a l

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