Deffuant Guillaume

Irstea − Lisc
9 avenue Blaise Pascal − CS 20085
63178 Aubière − France
+33 4 73 44 06 14
Contact

Head of LISC and of research theme MOTIVE. Social simulation, empathy, machine learning, viability and resilience algorithms.

My research interests are in modelling complex systems (social or ecological dynamics) and assessing their properties such as their viability or resilience. I have a long lasting more personal interest in cognitive sciences and more particularly in the concept of empathy. I did my PhD in cognitive sciences (EHESS - Paris VI University) and I got my Habilitation from Clermont University (topic: modelling complex systems). Administrative status: DR1.

Recent projects:

PATRES (2007-2010).
PRIMA (2008-2011).
DISCO (2010-2013).
RESUS (2015-2016)

From June 2010 to June 2014, I have been co-director of the French network for complex systems (Réseau National des Systèmes Complexes).

The book I edited with Nigel Gilbert from the Patres project: Viability and Resilience of Complex Systems: more info.

Recent publications

Journal Articles (53)

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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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. 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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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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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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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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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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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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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, 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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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. 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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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 (16)

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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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, 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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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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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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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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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, 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, 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, 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.}, }
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In Proceedings (43)

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, 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.}, }
close
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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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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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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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).}, }
close
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.}, }
close
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.}, }
close
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.}, }
close
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.}, }
close
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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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
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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M. Lenormand, F. Jabot, G. Deffuant
Adaptive approximate bayesian computation for complex models
The 11th World Meeting of The International Society for Bayesian Analysis (ISBA2012), 25/06/2012-29/06/2012, Kyoto, JPN , 2012
abs web bib

Approximate Bayesian computation (ABC) is a family of computational techniques in Bayesian statistics. These techniques allow to fit a model to data without relying on the computation of the model likelihood. They instead require to simulate a large number of times the model to be fitted. A number of refinements to the original rejection-based ABC scheme have been proposed, including the sequential improvement of posterior distributions. This technique allows to decrease the number of model simulations required, but it still presents several shortcomings which are particularly problematic for costly to simulate complex models. We here provide a new algorithm to perform adaptive approximate Bayesian computation. We present a modification of the PMC-ABC algorithm proposed by (Beaumont et al., 2009). We compare this new algorithm with the population Monte Carlo ABC algorithm of Beaumont et al. (2009), the replenishment SMC ABC algorithm of Drovandi & Pettitt (2011) and the adaptive SMC ABC algorithm of DelMoral et al. (2011) on a toy example. Finally, we apply our new algorithm to a complex individual-based social model, the PRIMA model. We show that our algorithm outperforms the three other algorithms in the two applications by requiring less simulations to reach the same posterior density quality.
close

@inproceedings{PUB00035591, author = {Lenormand, M. and Jabot, F. and Deffuant, G.}, title = {Adaptive approximate bayesian computation for complex models}, title = {Calcul Bayésien approché adaptatif pour les modèles complexes}, bookTitle = {The 11th World Meeting of The International Society for Bayesian Analysis (ISBA2012), 25/06/2012-29/06/2012, Kyoto, JPN}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00035591}, year = {2012}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {Approximate Bayesian computation (ABC) is a family of computational techniques in Bayesian statistics. These techniques allow to fit a model to data without relying on the computation of the model likelihood. They instead require to simulate a large number of times the model to be fitted. A number of refinements to the original rejection-based ABC scheme have been proposed, including the sequential improvement of posterior distributions. This technique allows to decrease the number of model simulations required, but it still presents several shortcomings which are particularly problematic for costly to simulate complex models. We here provide a new algorithm to perform adaptive approximate Bayesian computation. We present a modification of the PMC-ABC algorithm proposed by (Beaumont et al., 2009). We compare this new algorithm with the population Monte Carlo ABC algorithm of Beaumont et al. (2009), the replenishment SMC ABC algorithm of Drovandi & Pettitt (2011) and the adaptive SMC ABC algorithm of DelMoral et al. (2011) on a toy example. Finally, we apply our new algorithm to a complex individual-based social model, the PRIMA model. We show that our algorithm outperforms the three other algorithms in the two applications by requiring less simulations to reach the same posterior density quality.}, }
close
M. Lenormand, F. Jabot, G. Deffuant
Adaptive approximate Bayesian computation for complex models
8th World Congress in Probability and Statistics, 09/07/2012-14/07/2012, Istanbul, TUR (p. 11), 2012
abs web bib

Approximate Bayesian computation (ABC) is a family of computational techniques in Bayesian statistics. These techniques allow to fit a model to data without relying on the computation of the model likelihood. They instead require to simulate a large number of times the model to be fitted. A number of refinements to the original rejection-based ABC scheme have been proposed, including the sequential improvement of posterior distributions. This technique allows to decrease the number of model simulations required, but it still presents several shortcomings which are particularly problematic for costly to simulate complex models. We here provide a new algorithm to perform adaptive approximate Bayesian computation. We present a modification of the PMC-ABC algorithm proposed by Beaumont et al. (2009). We compare this new algorithm with the population Monte Carlo ABC algorithm of Beaumont et al. (2009), the replenishment SMC ABC algorithm of Drovandi and Pettitt (2011) and the adaptive SMC ABC algorithm of DelMoral et al. (2011) on a toy example. Finally, we apply our new algorithm to a complex individual-based social model, the PRIMA model. We show that our algorithm outperforms the three other algorithms in the two applications by requiring less simulations to reach the same posterior density quality.
close

@inproceedings{PUB00035693, author = {Lenormand, M. and Jabot, F. and Deffuant, G.}, title = {Adaptive approximate Bayesian computation for complex models}, title = {Calcul Bayésien adaptatif pour les modèles complexes}, bookTitle = {8th World Congress in Probability and Statistics, 09/07/2012-14/07/2012, Istanbul, TUR}, pages = {11}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00035693}, year = {2012}, affiliation = {IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UR LISC FRA}, abstract = {Approximate Bayesian computation (ABC) is a family of computational techniques in Bayesian statistics. These techniques allow to fit a model to data without relying on the computation of the model likelihood. They instead require to simulate a large number of times the model to be fitted. A number of refinements to the original rejection-based ABC scheme have been proposed, including the sequential improvement of posterior distributions. This technique allows to decrease the number of model simulations required, but it still presents several shortcomings which are particularly problematic for costly to simulate complex models. We here provide a new algorithm to perform adaptive approximate Bayesian computation. We present a modification of the PMC-ABC algorithm proposed by Beaumont et al. (2009). We compare this new algorithm with the population Monte Carlo ABC algorithm of Beaumont et al. (2009), the replenishment SMC ABC algorithm of Drovandi and Pettitt (2011) and the adaptive SMC ABC algorithm of DelMoral et al. (2011) on a toy example. Finally, we apply our new algorithm to a complex individual-based social model, the PRIMA model. We show that our algorithm outperforms the three other algorithms in the two applications by requiring less simulations to reach the same posterior density quality.}, }
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L. Chapel, G. Deffuant
Inner and outer capture basin approximation with support vector machines
8th International Conference on Informatics in Control, Automation and Robotics, ICINCO 2011, 28/07/2011-31/07/2011, Noordwirjkerhout, NLD (p. 6), 2011
abs web bib

We propose a new approach to solve target hitting problems, that iteratively approximates capture basins at successive times, using a machine learning algorithm (as a particular case, we use Support Vector Machines) trained on points of a grid with boolean labels. We consider two variants of the approximation (from inside and from outside), and we state the conditions on the machine learning procedure that guarantee that the approximations converge to 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 time to hit the target). SVMs provide parcimonious approximations, used to derive fast controllers. We illustrate the method on two simple examples, Zermelo and car on the hill problems.
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@inproceedings{PUB00034525, author = {Chapel, L. and Deffuant, G.}, title = {Inner and outer capture basin approximation with support vector machines}, title = {Approximation par l'intérieur et par l'extérieur de bassin de capture en utilisant des séparateurs à vaste marge}, bookTitle = {8th International Conference on Informatics in Control, Automation and Robotics, ICINCO 2011, 28/07/2011-31/07/2011, Noordwirjkerhout, NLD}, pages = {6}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00034525}, year = {2011}, affiliation = {UNVIERSITE DE BRETAGNE SUD LAB STICC VANNES FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {We propose a new approach to solve target hitting problems, that iteratively approximates capture basins at successive times, using a machine learning algorithm (as a particular case, we use Support Vector Machines) trained on points of a grid with boolean labels. We consider two variants of the approximation (from inside and from outside), and we state the conditions on the machine learning procedure that guarantee that the approximations converge to 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 time to hit the target). SVMs provide parcimonious approximations, used to derive fast controllers. We illustrate the method on two simple examples, Zermelo and car on the hill problems.}, }
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B. Gandar, G. Loosli, G. Deffuant
Dispersion effect on generalisation error in classification: Experimental proof and practical algorithm
ICAART 2011 Conference .3rd Congference on Agents and Artificial Intelligence, 28/01/2011-30/01/2011, Rome, ITA (p. 4), 2011
abs web bib

Recent theoretical work proposes criteria of dispersion to generate learning points. The aim of this paper is to convince the reader, with experimental proofs, that dispersion is a good criterion in practice for generating learning points for classification problems. Problem of generating learning points consists then in generating points with the lowest dispersion. As a consequence, we present low dispersion algorithms existing in the literature, analyze them and propose a new algorithm.
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@inproceedings{PUB00034342, author = {Gandar, B. and Loosli, G. and Deffuant, G.}, title = {Dispersion effect on generalisation error in classification: Experimental proof and practical algorithm}, title = {Effet de la dispersion sur l'erreur en généralisation en classification : preuve expérimentale et algorithme pratique}, bookTitle = {ICAART 2011 Conference .3rd Congference on Agents and Artificial Intelligence, 28/01/2011-30/01/2011, Rome, ITA}, pages = {4}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00034342}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; UNIVERSITE CLERMONT LIMOS UMR 6158 FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {Recent theoretical work proposes criteria of dispersion to generate learning points. The aim of this paper is to convince the reader, with experimental proofs, that dispersion is a good criterion in practice for generating learning points for classification problems. Problem of generating learning points consists then in generating points with the lowest dispersion. As a consequence, we present low dispersion algorithms existing in the literature, analyze them and propose a new algorithm.}, }
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S. Huet, M. Lenormand, G. Deffuant
Modelling a network of rural municipalities
ESSA 2011, 19/09/2011-23/09/2011, Montpellier, FRA , 2011
abs web bib

The poster describes the dynamics of individuals changing activities and status on the labour market in a large individual-based model simulating the rural municipalities. Some results are presented for seven municipalities of the French Cantal department. / Ce poster décrit la dynamique d'activité des individus du modèle PRIMA dédié à la modélisation des municipalités rurales.
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@inproceedings{PUB00033512, author = {Huet,S. and Lenormand,M. and Deffuant,G.}, title = {Modelling a network of rural municipalities }, title = {La modélisation d'un réseau de municipalités rurales}, bookTitle = {ESSA 2011, 19/09/2011-23/09/2011, Montpellier, FRA}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00033512}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {The poster describes the dynamics of individuals changing activities and status on the labour market in a large individual-based model simulating the rural municipalities. Some results are presented for seven municipalities of the French Cantal department. / Ce poster décrit la dynamique d'activité des individus du modèle PRIMA dédié à la modélisation des municipalités rurales.}, }
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M. Lenormand, G. Deffuant, S. Huet
Calibrating a complex social model
European Conference on Complex Systems ECCS'11, 12/09/2011-16/09/2011, Vienne, AUT , 2011
abs web bib

Approximate Bayesian computation is a family of computational techniques in Bayesian statistics. These techniques allow to fit a model to data without relying on the computation of the model likelihood. A number of improvements to the original ABC scheme have been proposed to speed it up. They include the coupling to Markov chain Monte Carlo to explore the parameter space and the sequential improvement of posterior distributions inspired by sequential Monte Carlo methods. These algorithms present severals shortcomings which are particularly problematic for costly to simulate complex models. In this article an adaptive appoximate Bayesian computation for complex models is proposed which offers improvements to circumvent the limitations of the application of the ABC methods to complex models. We demonstrate our algorithm on a toy example and on a complex social model, the PRIMA model.
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@inproceedings{PUB00033827, author = {Lenormand, M. and Deffuant, G. and Huet, S.}, title = {Calibrating a complex social model}, title = {Calibration d'un modèle social complexe}, bookTitle = {European Conference on Complex Systems ECCS'11, 12/09/2011-16/09/2011, Vienne, AUT}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00033827}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {Approximate Bayesian computation is a family of computational techniques in Bayesian statistics. These techniques allow to fit a model to data without relying on the computation of the model likelihood. A number of improvements to the original ABC scheme have been proposed to speed it up. They include the coupling to Markov chain Monte Carlo to explore the parameter space and the sequential improvement of posterior distributions inspired by sequential Monte Carlo methods. These algorithms present severals shortcomings which are particularly problematic for costly to simulate complex models. In this article an adaptive appoximate Bayesian computation for complex models is proposed which offers improvements to circumvent the limitations of the application of the ABC methods to complex models. We demonstrate our algorithm on a toy example and on a complex social model, the PRIMA model.}, }
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M. Lenormand, G. Deffuant, S. Huet
A commuting generation model requiring only aggregated data
7th European Social Simulation Association Conference, 19/09/2011-23/09/2011, Montpellier, FRA (p. 16), 2011
abs web bib

We recently proposed, in (Gargiulo et al., 2011), an innovative stochastic model with only one parameter to calibrate. It reproduces the complete network by an iterative process stochastically choosing, for each commuter living in the municipality of a region, a workplace in the region. The choice is done considering the job offer in each municipality of the region and the distance to all the possible destinations. The model is quite effective if the region is sufficiently autonomous in terms of job offers. However, calibrating or being sure of this autonomy require data or expertise which are not necessarily available. Moreover the region can be not autonomous. In the present, we overcome these limitations, extending the job search geographical base of the commuters to the outside of the region, and changing the deterrence function form. We also found a law to calibrate the improvement model which does not require data.
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@inproceedings{PUB00033826, author = {Lenormand, M. and Deffuant, G. and Huet, S.}, title = {A commuting generation model requiring only aggregated data}, title = {Un modèle de génération de réseau de navettage nécessitant uniquement des données agrégées}, bookTitle = {7th European Social Simulation Association Conference, 19/09/2011-23/09/2011, Montpellier, FRA}, pages = {16}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00033826}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {We recently proposed, in (Gargiulo et al., 2011), an innovative stochastic model with only one parameter to calibrate. It reproduces the complete network by an iterative process stochastically choosing, for each commuter living in the municipality of a region, a workplace in the region. The choice is done considering the job offer in each municipality of the region and the distance to all the possible destinations. The model is quite effective if the region is sufficiently autonomous in terms of job offers. However, calibrating or being sure of this autonomy require data or expertise which are not necessarily available. Moreover the region can be not autonomous. In the present, we overcome these limitations, extending the job search geographical base of the commuters to the outside of the region, and changing the deterrence function form. We also found a law to calibrate the improvement model which does not require data.}, }
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J.D. Mathias, F. Chuffart, N. Mabrouk, G. Deffuant
Applying a moment approximation to a bacterial biofilm individual-based model
4th International Multi-Conference on Computing in the Global Information Technology, ICCGI 2009 , 23/09/2009-29/09/2009, Nice, FRA (p. 138-143), 2011
abs web bib

We consider a 2D individual-based model of biofilm, in which bacteria can generate a polymeric substance (EPS), The coupling between polymer generation and bacteria creates a variety of biofilm structures. Then, we derive the equations of first and second moment evolution for the bacteria and EPS particle population sizes. This approximation of the dynamics is much lighter to compute than the whole IBM, hence more systematic exploration is easier particularly in case of large bacteria populations. We show that the second moment approximation predicts accurately the quantities of bacteria and polymer. Moreover, it gives relevant information about their spatial distribution.
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@inproceedings{PUB00033283, author = {Mathias, J.D. and Chuffart, F. and Mabrouk, N. and Deffuant, G.}, title = {Applying a moment approximation to a bacterial biofilm individual-based model}, bookTitle = {4th International Multi-Conference on Computing in the Global Information Technology, ICCGI 2009 , 23/09/2009-29/09/2009, Nice, FRA}, pages = {138-143}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00033283}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF AIX EN PROVENCE SGAX FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {We consider a 2D individual-based model of biofilm, in which bacteria can generate a polymeric substance (EPS), The coupling between polymer generation and bacteria creates a variety of biofilm structures. Then, we derive the equations of first and second moment evolution for the bacteria and EPS particle population sizes. This approximation of the dynamics is much lighter to compute than the whole IBM, hence more systematic exploration is easier particularly in case of large bacteria populations. We show that the second moment approximation predicts accurately the quantities of bacteria and polymer. Moreover, it gives relevant information about their spatial distribution. }, }
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B. Gandar, G. Loosli, G. Deffuant
How to generate the best low dispersion samples for active learning in classification ?
Active Learning and Experimental Design Workshop AISTATS, 16/05/2010, Sardaigne, FRA (p. 16), 2010
abs web bib

We consider a problem of active learning classification: we suppose we can determine, with an oracle, the label of any point in a given compact set, and we want to generate a sample of a given size which will allow us to get the best approximation of the oracle function. It's well known that the more numerous the data are, the best quality the modelling is. However obtaining data can be expensive or destructive in consequence we want to get the best value from this investment. We have to choose the best learning set. The first contribution of this paper is to state that dispersion is the most relevant criterion for generating samples in active classification leanring whereas discrepance is the relevant criterion for active regression learning. However low dispersion samples are not easy to generate. The second contribution consists then in making a study of different ways to proceed and in proposing a new algorithm.
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@inproceedings{PUB00030736, author = {Gandar, B. and Loosli, G. and Deffuant, G.}, title = {How to generate the best low dispersion samples for active learning in classification ?}, title = {Comment générer les meilleurs échantillons a faible dispersion pour l'apprentissage actif en classification ?}, bookTitle = {Active Learning and Experimental Design Workshop AISTATS, 16/05/2010, Sardaigne, FRA}, pages = {16}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00030736}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; LIMOS UNIVERSITE BLAISE PASCAL CLERMONT FERRAND FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {We consider a problem of active learning classification: we suppose we can determine, with an oracle, the label of any point in a given compact set, and we want to generate a sample of a given size which will allow us to get the best approximation of the oracle function. It's well known that the more numerous the data are, the best quality the modelling is. However obtaining data can be expensive or destructive in consequence we want to get the best value from this investment. We have to choose the best learning set. The first contribution of this paper is to state that dispersion is the most relevant criterion for generating samples in active classification leanring whereas discrepance is the relevant criterion for active regression learning. However low dispersion samples are not easy to generate. The second contribution consists then in making a study of different ways to proceed and in proposing a new algorithm.}, }
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T. Guelon, J.D. Mathias, G. Deffuant
Homogenization of physical properties of bacterial biofilms
CE2M10 (Changement d'échelle en mécanique des matériaux), 22/08/2010-03/09/2010, Briançon, FRA , 2010
web bib

@inproceedings{PUB00031627, author = {Guelon, T. and Mathias, J.D. and Deffuant, G.}, title = {Homogenization of physical properties of bacterial biofilms}, title = {Homogénéisation des propriétés physiques des biofilms bactériens}, bookTitle = {CE2M10 (Changement d'échelle en mécanique des matériaux), 22/08/2010-03/09/2010, Briançon, FRA}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00031627}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {}, }
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T. Guelon, J.D. Mathias, G. Deffuant
Homogenization of the diffusion of bacterial biofilms
IV European Conference on Computational Mechanics, ECCM2010, 16/05/2010-21/05/2010, Paris , 2010
web bib

@inproceedings{PUB00031628, author = {Guelon, T. and Mathias, J.D. and Deffuant, G.}, title = {Homogenization of the diffusion of bacterial biofilms}, title = {Homogénéisation de la diffusion dans les biofilms bactériens}, bookTitle = {IV European Conference on Computational Mechanics, ECCM2010, 16/05/2010-21/05/2010, Paris}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00031628}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {}, }
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T. Guélon, J.D. Mathias, R.C. Hunter, G. Deffuant
Applying homogenization techniques to determine macroscopic mechanical properties of bacterial biofilms
Biofilms4 International Conference , 01/09/2010-03/09/2010, Winchester, UK, GBR (p. 1), 2010
web bib

@inproceedings{PUB00031563, author = {Guélon, T. and Mathias, J.D. and Hunter, R.C. and Deffuant, G.}, title = {Applying homogenization techniques to determine macroscopic mechanical properties of bacterial biofilms}, title = {Utilisation des techniques d'homogénéisation pour déterminer les propriétés mécaniques macroscopiques des biofilms bactériens}, bookTitle = {Biofilms4 International Conference , 01/09/2010-03/09/2010, Winchester, UK, GBR}, pages = {1}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00031563}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CALIFORNIA INSTITUTE OF TECHNOLOGY PASADENA DIVISION OF BIOLOGY USA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {}, }
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T. Guélon, J.D. Mathias, G. Deffuant
Applying a multiscale approach to explain biofilm formation
Advances in Interaction and Multiscale Mechanics" ( AIMM'10), 30/05/2010-03/06/2010, Jeju, KOR , 2010
abs web bib

In this paper, we study the structure of a biofilm using homogenization techniques, which have been developed to characterize heterogeneous materials in physics. The properties of the biofilm depend therefore on the considered scale where they are calculated. Homogenization techniques are then applied on biofilm in order to determine emergent properties. We especially focus on the nutrient access properties and the link with biofilm structure.
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@inproceedings{PUB00031626, author = {Guélon, T. and Mathias, J.D. and Deffuant, G.}, title = {Applying a multiscale approach to explain biofilm formation}, title = {Application d'une approche multi-échelle pour expliquer la formation des biofilms}, bookTitle = {Advances in Interaction and Multiscale Mechanics" ( AIMM'10), 30/05/2010-03/06/2010, Jeju, KOR}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00031626}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {In this paper, we study the structure of a biofilm using homogenization techniques, which have been developed to characterize heterogeneous materials in physics. The properties of the biofilm depend therefore on the considered scale where they are calculated. Homogenization techniques are then applied on biofilm in order to determine emergent properties. We especially focus on the nutrient access properties and the link with biofilm structure.}, }
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N. Mabrouk, J.D. Mathias, G. Deffuant
Computing the resilience of a wastewater treatment bioreactor
5th International Multi-Conference on Computing in the Global Information Technology, ICCGI 2010, 20/09/2010-25/09/2010, Valencia, ESP (p. 185-188), 2010
abs doi web bib

Biological wastewater treatment reactor are designed to reduce the pollutant content of a wastewater to an acceptable level often fixed by wastewater discharge regulations. The reactor design is often based on average wastewater flow and composition patterns. However, industrial wastewater treatment reactors are often subject to unexpected perturbations (variations in wastewater flow, composition or shift in the microbial communities). Hence the capacity of the reactor to recover from these perturbations in reasonable times should also be considered as an important design criteria. In this work we illustrate how this property can be quantified by calculating reactor resilience using return time concept. We show that a reactor design that maximizes the productivity (in term of mass of pollutant removed per unit of time and unit of reactor volume) may not be optimal in term of resilience. Hence, a compromise between productivity and resilience should be targeted when designing biological wastewater treatment reactors.
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@inproceedings{PUB00032277, author = {Mabrouk, N. and Mathias, J.D. and Deffuant, G.}, title = {Computing the resilience of a wastewater treatment bioreactor}, bookTitle = {5th International Multi-Conference on Computing in the Global Information Technology, ICCGI 2010, 20/09/2010-25/09/2010, Valencia, ESP}, pages = {185-188}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00032277}, doi = {http://dx.doi.org/10.1109/ICCGI.2010.60}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, ISBNISSN = {ISBN 978-076954181-5}, abstract = {Biological wastewater treatment reactor are designed to reduce the pollutant content of a wastewater to an acceptable level often fixed by wastewater discharge regulations. The reactor design is often based on average wastewater flow and composition patterns. However, industrial wastewater treatment reactors are often subject to unexpected perturbations (variations in wastewater flow, composition or shift in the microbial communities). Hence the capacity of the reactor to recover from these perturbations in reasonable times should also be considered as an important design criteria. In this work we illustrate how this property can be quantified by calculating reactor resilience using return time concept. We show that a reactor design that maximizes the productivity (in term of mass of pollutant removed per unit of time and unit of reactor volume) may not be optimal in term of resilience. Hence, a compromise between productivity and resilience should be targeted when designing biological wastewater treatment reactors.}, }
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B. Gandar, G. Loosli, G. Deffuant
Sélection de points en apprentissage actif. Discrépance et dispersion : des critères optimaux ?
MajecSTIC 2009 , 16/11/2009-18/11/2009, Avignon, FRA (p. 8), 2009
abs web bib

Nous souhaitons générer des bases d'apprentissage adaptées aux problèmes de classification. Nous montrons tout d'abord que les résultats théoriques privilégiant les suites à discrépance faible pour les problèmes de régression sont inadaptés aux problèmes de classification. Nous donnons ensuite des arguments théoriques et des résultats de simulations montrant que c'est la dispersion des points d'apprentissage qui est le critère pertinent à minimiser pour optimiser les performances de l'apprentissage en classification.
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@inproceedings{PUB00027310, author = {Gandar, B. and Loosli, G. and Deffuant, G.}, title = {Sélection de points en apprentissage actif. Discrépance et dispersion : des critères optimaux ?}, title = {Selection of points in active learning. Discrepancy and dispersion: optimal criterion ? }, bookTitle = {MajecSTIC 2009 , 16/11/2009-18/11/2009, Avignon, FRA}, pages = {8}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00027310}, year = {2009}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; UNIVERSITE BLAISE PASCAL LIMOS CLERMONT FERRAND FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {Nous souhaitons générer des bases d'apprentissage adaptées aux problèmes de classification. Nous montrons tout d'abord que les résultats théoriques privilégiant les suites à discrépance faible pour les problèmes de régression sont inadaptés aux problèmes de classification. Nous donnons ensuite des arguments théoriques et des résultats de simulations montrant que c'est la dispersion des points d'apprentissage qui est le critère pertinent à minimiser pour optimiser les performances de l'apprentissage en classification.}, }
close
B. Gandar, G. Loosli, G. Deffuant
Discrépance et dispersion : des indicateurs optimaux pour approcher des surfaces de réponse par des SVMs ?
Journée du GdR MASCOT-NUM (Groupement de recherche Méthodes d'Analyse Stochastique des Codes et Traitements Numériques), 18/03/2009-18/03/2009, Saint Denis, FRA (p. 1), 2009
abs web bib

--
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@inproceedings{PUB00027309, author = {Gandar, B. and Loosli, G. and Deffuant, G.}, title = {Discrépance et dispersion : des indicateurs optimaux pour approcher des surfaces de réponse par des SVMs ?}, title = {Discrepancy and dispersion : optimal indicator to approach answer reponse with SVMs?}, bookTitle = {Journée du GdR MASCOT-NUM (Groupement de recherche Méthodes d'Analyse Stochastique des Codes et Traitements Numériques), 18/03/2009-18/03/2009, Saint Denis, FRA}, pages = {1}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00027309 / http://www.gdr-mascotnum.fr/}, year = {2009}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; UNIVERSITE BLAISE PASCAL CLERMONT FERRAND II LIMOS FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {--}, }
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B. Gandar, G. Loosli, G. Deffuant
Discrépance et dispersion : des critères optimaux en apprentissage ?
CAP'09 (Conférence en Apprentissage), 25/05/2009-29/05/2009, Hammamet, TUN (p. 4), 2009
abs web bib

Nous souhaitons générer des bases d'apprentissage adaptées à la classification. Nous montrons d'abord que les résultats théoriques privilégiant les suites à discrépance faible pour les problèmes de régression sont inadaptés à la classification. Puis nous donnons des arguments théoriques et des résultats de simulation montrant que c'est la dispersion des points d'apprentissage qui est le critère pertinent à minimiser pour optimiser les performances en classification.
close

@inproceedings{PUB00026366, author = {Gandar, B. and Loosli, G. and Deffuant, G.}, title = {Discrépance et dispersion : des critères optimaux en apprentissage ?}, title = {Discrepance and dispersion : optimum criterion in machine learning ? }, bookTitle = {CAP'09 (Conférence en Apprentissage), 25/05/2009-29/05/2009, Hammamet, TUN}, pages = {4}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00026366}, year = {2009}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CNRS LIMOS UMR 6158 AUBIERE ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {Nous souhaitons générer des bases d'apprentissage adaptées à la classification. Nous montrons d'abord que les résultats théoriques privilégiant les suites à discrépance faible pour les problèmes de régression sont inadaptés à la classification. Puis nous donnons des arguments théoriques et des résultats de simulation montrant que c'est la dispersion des points d'apprentissage qui est le critère pertinent à minimiser pour optimiser les performances en classification.}, }
close
B. Gandar, G. Loosli, G. Deffuant
How to optimize sample in active learning: Dispersion, an optimum criterion for classification ?
ENBIS (European Network for Business and Industrial Statistics) , 01/07/2009-03/07/2009, Saint-Etienne, FRA , 2009
abs web bib

We want generate learning data appropriated to classification problems. First, we show that theorical results about low discrepancy sequences in regression problems are not adequate for classification problems. Then, we show with theorical and experimental arguments that minimising the dispersion of the sample is a relevant strategy to optimize performance of classification learning.
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@inproceedings{PUB00026365, author = {Gandar, B. and Loosli, G. and Deffuant, G.}, title = {How to optimize sample in active learning: Dispersion, an optimum criterion for classification ?}, title = {Comment optimiser les exemples en apprentissage actif : la dispersion, un critère optimal en classification ? }, bookTitle = {ENBIS (European Network for Business and Industrial Statistics) , 01/07/2009-03/07/2009, Saint-Etienne, FRA}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00026365}, year = {2009}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; UNIVERSITE CLERMONT FERRAND FRA LIMOS ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {We want generate learning data appropriated to classification problems. First, we show that theorical results about low discrepancy sequences in regression problems are not adequate for classification problems. Then, we show with theorical and experimental arguments that minimising the dispersion of the sample is a relevant strategy to optimize performance of classification learning.}, }
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S. Huet, G. Deffuant
Openness leads to Opinion Stability and Narrowness to Volatility
ECCS'09, European Conference on Complex Systems, 21/09/2009-25/09/2009, Warwick, GBR (p. 14), 2009
abs 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 trajectories of the model can be related to some stylised facts.
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@inproceedings{PUB00026801, author = {Huet, S. and Deffuant, G.}, title = {Openness leads to Opinion Stability and Narrowness to Volatility}, title = {L'ouverture d'esprit mène à la stabilité des opinions tandis que l'étroitesse les rend volatiles}, bookTitle = {ECCS'09, European Conference on Complex Systems, 21/09/2009-25/09/2009, Warwick, GBR}, pages = {14}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00026801}, year = {2009}, 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 trajectories of the model can be related to some stylised facts.}, }
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S. Huet, G. Deffuant
De l'importance des individus moins engagés pour l'émergence d'une majorité
MASHS : Modèles et Apprentissage en Sciences Humaines et Sociales, 08/06/2009-09/06/2009, Toulouse, FRA (p. 12), 2009
abs web bib

Nous avons proposé un nouveau modèle de dynamique d'opinions basé sur les expériences et les résultats de Wood et al (1996). Un individu a plusieurs attitudes, chacune dotée d'une importance. L'importance de chaque attitude et la distance à un interlocuteur sur chacune des attitudes permet à l'individu de déterminer s'il juge la position de son interlocuteur positivement, négativement ou s'il y est indifférent. Lorsqu'il juge sa position positive, l'individu se rapproche de son interlocuteur sur toutes les dimensions attitudinales. Lorsqu'il la juge négativement, il s'éloigne sur les dimensions où il était proche. Une indifférence n'entraîne aucun changement d'attitude. Le modèle souligne d'une part l'importance de l'existence d'individus ne considérant pas une dimension plus importante que l'autre. Ces individus permettent l'émergence d'une majorité. Il montre également qu'en absence de tels individus, la population s'organise en petits groupes de taille homogène. Elle parvient à cet état en se rapprochant tout d'abord autour des questions peu importantes. Ce rapprochement rend saillant les divergences sur les questions importantes et incite les individus à s'organiser en petits groupes se repoussant et s'attirant en même temps.
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@inproceedings{PUB00026805, author = {Huet, S. and Deffuant, G.}, title = {De l'importance des individus moins engagés pour l'émergence d'une majorité}, title = {Less involved people are very important for a majority emergence}, bookTitle = {MASHS : Modèles et Apprentissage en Sciences Humaines et Sociales, 08/06/2009-09/06/2009, Toulouse, FRA}, pages = {12}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00026805}, year = {2009}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {Nous avons proposé un nouveau modèle de dynamique d'opinions basé sur les expériences et les résultats de Wood et al (1996). Un individu a plusieurs attitudes, chacune dotée d'une importance. L'importance de chaque attitude et la distance à un interlocuteur sur chacune des attitudes permet à l'individu de déterminer s'il juge la position de son interlocuteur positivement, négativement ou s'il y est indifférent. Lorsqu'il juge sa position positive, l'individu se rapproche de son interlocuteur sur toutes les dimensions attitudinales. Lorsqu'il la juge négativement, il s'éloigne sur les dimensions où il était proche. Une indifférence n'entraîne aucun changement d'attitude. Le modèle souligne d'une part l'importance de l'existence d'individus ne considérant pas une dimension plus importante que l'autre. Ces individus permettent l'émergence d'une majorité. Il montre également qu'en absence de tels individus, la population s'organise en petits groupes de taille homogène. Elle parvient à cet état en se rapprochant tout d'abord autour des questions peu importantes. Ce rapprochement rend saillant les divergences sur les questions importantes et incite les individus à s'organiser en petits groupes se repoussant et s'attirant en même temps.}, }
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S. Ternès, F. Gargiulo, S. Huet, G. Deffuant
Double modelling of the dynamic of activities in rural municipalities
7th Brazilian Congress of Agro-informatics (7. Congresso Brasileiro de Agroinformática ), 21/09/2009-25/09/2009, Viçosa, BRA (p. 5), 2009
abs web bib

Land use choices and activity prevalence in a selected territory are determined by individual preferences constrained by the characteristic of the analysed zone: population density, soil properties, urbanization level and other similar factors can drive individuals to make different kind of decisions about their occupations. Different approaches can be used to describe land use change, occupation prevalence and their reciprocal inter-relation. In this paper we describe two different kinds of approaches: an agent based model, centred on individual choices and an aggregated model describing the evolution of activity prevalence in terms of coupled differential equation. We use and we compare the two models to analyse the effect of territorial constraints, like the lack of employment in determined sectors, on the possible activity prevalence scenarios.
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@inproceedings{PUB00026804, author = {Ternès, S. and Gargiulo, F. and Huet, S. and Deffuant, G.}, title = {Double modelling of the dynamic of activities in rural municipalities}, bookTitle = {7th Brazilian Congress of Agro-informatics (7. Congresso Brasileiro de Agroinformática ), 21/09/2009-25/09/2009, Viçosa, BRA}, pages = {5}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00026804}, year = {2009}, 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 = {Land use choices and activity prevalence in a selected territory are determined by individual preferences constrained by the characteristic of the analysed zone: population density, soil properties, urbanization level and other similar factors can drive individuals to make different kind of decisions about their occupations. Different approaches can be used to describe land use change, occupation prevalence and their reciprocal inter-relation. In this paper we describe two different kinds of approaches: an agent based model, centred on individual choices and an aggregated model describing the evolution of activity prevalence in terms of coupled differential equation. We use and we compare the two models to analyse the effect of territorial constraints, like the lack of employment in determined sectors, on the possible activity prevalence scenarios.}, }
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N. Turpin, R. Laplana, D. Kopeva, L. Stapleton, K. Happe, G. Deffuant, F. Brouwer, M. Burghard
PRIMA, Prototypical Policy Impacts on Multi-functional Activities in rural municipalities
AgSAP Conference 2009, 10/03/2009-12/03/2009, Egmond aan Zee, NLD / Van Ittersum, M.K., Wolf J. and Van Laar H.H. (Eds), 2009, Proceedings of the conference on Integrated Assessment of Agriculture and sustainable Development: Setting the Agenda for Science and Policy (AgSAP 2009), Egmond aan Zee, the Netherlands, 10-12 mars 2009 (p. 64-65), Wageningen University and Research Center, Wageningen, NLD, 2009
abs web bib

Poster décrivant le projet Prima
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@inproceedings{PUB00026414, author = {Turpin, N. and Laplana, R. and Kopeva, D. and Stapleton, L. and Happe, K. and Deffuant, G. and Brouwer, F. and Burghard, M.}, title = {PRIMA, Prototypical Policy Impacts on Multi-functional Activities in rural municipalities}, bookTitle = {AgSAP Conference 2009, 10/03/2009-12/03/2009, Egmond aan Zee, NLD / Van Ittersum, M.K., Wolf J. and Van Laar H.H. (Eds), 2009, Proceedings of the conference on Integrated Assessment of Agriculture and sustainable Development: Setting the Agenda for Science and Policy (AgSAP 2009), Egmond aan Zee, the Netherlands, 10-12 mars 2009}, address = {Wageningen, NLD}, publisher = {Wageningen University and Research Center}, pages = {64-65}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00026414}, year = {2009}, affiliation = {CEMAGREF CLERMONT FERRAND UR MECF UMR METAFORT FRA ; CEMAGREF BORDEAUX UR ADBX FRA ; - ; UNIVERSITY OF SUSSEX GBR ; - ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; LEI WAGENINGEN NLD ; -}, ISBNISSN = {ISBN 978-90-8585-401-2}, abstract = {Poster décrivant le projet Prima}, }
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L. Chapel, G. Deffuant
Utiliser des machines à vecteurs de support pour approcher les contours d'une fonction valeur dans des problèmes d'atteinte de cible
12ème Journée Scientifique de l'Ecole Doctorale Sciences Pour l'Ingénieur Apprentisage Statistique Apprentissage Symbolique, 04/06/2008-04/06/2008, Clermont Ferrand, FRA (p. 10), 2008
abs web bib

Nous proposons d'utiliser un algorithme d'apprentissage particulier, les SVMs, pour résoudre des problèmes d'atteinte de cible en temps minimal. La cible correspond à un état souhaité, en sachant que le système se détériore dans une certaine région de l'espace (lorsqu'il transgresse un ensemble de contraintes de viabilité). Le bassin de capture au temps t correspond à l'ensemble des états qui peuvent atteindre la cible en un temps inférieur ou égal à t, sans quitter l'ensemble des contrainte de viabilité. Les frontières d'un bassin de capture au temps t correspondent alors aux contours d'une fonction valeur au temps t. Les bassins de capture peuvent alors être utilisés pour définir une fonction de contrôle qui permet au système d'atteindre la cible en un temps minimal. Nous proposons une nouvelle approche, basée sur les SVMs, qui permet d'approcher les bassins de capture successifs et définissons une procédure de contrôle qui permet de contrôler le système afin qu'il atteigne la cible. Nous illustrons cette méthode sur un exemple simple : le problème de la voiture sur la colline.
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@inproceedings{PUB00024732, author = {Chapel, L. and Deffuant, G.}, title = {Utiliser des machines à vecteurs de support pour approcher les contours d'une fonction valeur dans des problèmes d'atteinte de cible}, title = {Using Support Vector Machines to approach value function contours in case of reaching target problems}, bookTitle = {12ème Journée Scientifique de l'Ecole Doctorale Sciences Pour l'Ingénieur Apprentisage Statistique Apprentissage Symbolique, 04/06/2008-04/06/2008, Clermont Ferrand, FRA}, pages = {10}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00024732}, year = {2008}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {Nous proposons d'utiliser un algorithme d'apprentissage particulier, les SVMs, pour résoudre des problèmes d'atteinte de cible en temps minimal. La cible correspond à un état souhaité, en sachant que le système se détériore dans une certaine région de l'espace (lorsqu'il transgresse un ensemble de contraintes de viabilité). Le bassin de capture au temps t correspond à l'ensemble des états qui peuvent atteindre la cible en un temps inférieur ou égal à t, sans quitter l'ensemble des contrainte de viabilité. Les frontières d'un bassin de capture au temps t correspondent alors aux contours d'une fonction valeur au temps t. Les bassins de capture peuvent alors être utilisés pour définir une fonction de contrôle qui permet au système d'atteindre la cible en un temps minimal. Nous proposons une nouvelle approche, basée sur les SVMs, qui permet d'approcher les bassins de capture successifs et définissons une procédure de contrôle qui permet de contrôler le système afin qu'il atteigne la cible. Nous illustrons cette méthode sur un exemple simple : le problème de la voiture sur la colline.}, }
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F. Chuffart, T. Faure, N. Dumoulin, R. Reuillon, G. Deffuant
Design and analysis of computer experiments with SimExplorer
ESM'2008 European Simulation and Modelling Conference, 27/10/2008-29/10/2008, Le Havre, FRA (p. 575-577), EUROSIS, 2008
abs web bib

SimExplorer is a framework that includes an API and an IDE dedicated to design and analysis of computer experiments. SimExplorer combines blind computing on demand service access, traceability and reporting features and sensitivity analysis tools. This tutorial provides the concepts and exemplifies a typical use of SimExplorer, performing a global sensitivity analysis of a given individual-based predator prey model.
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@inproceedings{PUB00024933, author = {Chuffart, F. and Faure, T. and Dumoulin, N. and Reuillon, R. and Deffuant, G.}, title = {Design and analysis of computer experiments with SimExplorer}, title = {Conception et analyse de plans d'expériences avec SimExplorer}, bookTitle = {ESM'2008 European Simulation and Modelling Conference, 27/10/2008-29/10/2008, Le Havre, FRA}, publisher = {EUROSIS}, pages = {575-577}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00024933}, year = {2008}, 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}, abstract = {SimExplorer is a framework that includes an API and an IDE dedicated to design and analysis of computer experiments. SimExplorer combines blind computing on demand service access, traceability and reporting features and sensitivity analysis tools. This tutorial provides the concepts and exemplifies a typical use of SimExplorer, performing a global sensitivity analysis of a given individual-based predator prey model. }, }
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B. Gandar, G. Deffuant, G. Loosli
Les suites à discrépance faible : un moyen de réduire le nombre de vecteurs supports des SVMs
12ème Journée Scientifique de l'Ecole Doctorale Sciences Pour l'Ingénieur Apprentisage Statistique Apprentissage Symbolique, 04/06/2008-04/06/2008, Clermont Ferrand, FRA (p. 9), 2008
abs web bib

L'apprentissage statistique consiste à déterminer une fonction mathématique à partir d'exemples supposés indépendants et identiquement distribués. Dans le cadre de l'apprentissage actif, nous pouvons choisir ces exemples. Des travaux théoriques dans le cas de la régression, ont prouvé que l'utilisation d'une base d'apprentissage issue de suites à discrépance faible permettait d'améliorer la vitesse de convergence des algorithmes d'apprentissage. Des expériences numériques, réalisées en classification avec des réseaux de neurones, ont montré que l'utilisation de ces suites augmente la qualité d'apprentissage. Ce papier reprend les résultats théoriques connus en régression et explique pourquoi ceux-ci ne se transposent pas en classification. Il présente également des tests numériques sur l'algorithme de classification des SVMs (Support Vector Machine ou Séparateur à Vaste Marge) avec des bases d'apprentissage issues de suites à discrépance faible. Les résultats obtenus ne montrent pas une amélioration de la performance, mais les SVMs obtenus sont plus compacts : ce qui peut engendrer un gain de vitesse de prédiction dans des applications de ces derniers.
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@inproceedings{PUB00024705, author = {Gandar, B. and Deffuant, G. and Loosli, G.}, title = {Les suites à discrépance faible : un moyen de réduire le nombre de vecteurs supports des SVMs}, title = {The low discrepancy sequences: a way of reducing the number of supports vectors of SVMs}, bookTitle = {12ème Journée Scientifique de l'Ecole Doctorale Sciences Pour l'Ingénieur Apprentisage Statistique Apprentissage Symbolique, 04/06/2008-04/06/2008, Clermont Ferrand, FRA}, pages = {9}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00024705}, year = {2008}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {L'apprentissage statistique consiste à déterminer une fonction mathématique à partir d'exemples supposés indépendants et identiquement distribués. Dans le cadre de l'apprentissage actif, nous pouvons choisir ces exemples. Des travaux théoriques dans le cas de la régression, ont prouvé que l'utilisation d'une base d'apprentissage issue de suites à discrépance faible permettait d'améliorer la vitesse de convergence des algorithmes d'apprentissage. Des expériences numériques, réalisées en classification avec des réseaux de neurones, ont montré que l'utilisation de ces suites augmente la qualité d'apprentissage. Ce papier reprend les résultats théoriques connus en régression et explique pourquoi ceux-ci ne se transposent pas en classification. Il présente également des tests numériques sur l'algorithme de classification des SVMs (Support Vector Machine ou Séparateur à Vaste Marge) avec des bases d'apprentissage issues de suites à discrépance faible. Les résultats obtenus ne montrent pas une amélioration de la performance, mais les SVMs obtenus sont plus compacts : ce qui peut engendrer un gain de vitesse de prédiction dans des applications de ces derniers.}, }
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S. Huet, G. Deffuant
Bounded confidence with rejection: clusters or scattered opinions ?
5th Conference of the European Social Simulation Association ESSA 2008, 01/09/2008-05/09/2008, Brescia, ITA / Proceedings of the Fifth Conference of the European Social Simulation Association (ESSA'08) (p. 12), University of Brescia, Brescia, ITA, 2008
abs web bib

Huet and Deffuant (2007) propose a new opinion dynamics model based on the bounded confidence principles, with a rejection mechanism. We study new simulations of the agent-based model for a population of 10000 individuals. We generally observe fewer clusters than the classical bounded confidence model, and below a threshold of the uncertainty, no cluster appear: all opinions remain scattered. We build an aggregated model of this agent-based model (ABM), in the limit case of an infinite population, in order to better understand this dynamical behaviour. When adding a small perturbation in the initial distribution, the aggregated model and ABM yield similar numbers of clusters for the same parameters. Below a critical value of uncertainty, the aggregated model forms no cluster and the distribution remains uniform. The critical value is higher for the aggregated model than for the ABM, indicating a finite size effect that we discuss.
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@inproceedings{PUB00024581, author = {Huet, S. and Deffuant, G.}, title = {Bounded confidence with rejection: clusters or scattered opinions ?}, title = {Confiance bornée avec rejet: organisation en groupe d'opinion ou changement permanent d'opinion}, bookTitle = {5th Conference of the European Social Simulation Association ESSA 2008, 01/09/2008-05/09/2008, Brescia, ITA / Proceedings of the Fifth Conference of the European Social Simulation Association (ESSA'08)}, address = {Brescia, ITA}, publisher = {University of Brescia}, pages = {12}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00024581}, year = {2008}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {Huet and Deffuant (2007) propose a new opinion dynamics model based on the bounded confidence principles, with a rejection mechanism. We study new simulations of the agent-based model for a population of 10000 individuals. We generally observe fewer clusters than the classical bounded confidence model, and below a threshold of the uncertainty, no cluster appear: all opinions remain scattered. We build an aggregated model of this agent-based model (ABM), in the limit case of an infinite population, in order to better understand this dynamical behaviour. When adding a small perturbation in the initial distribution, the aggregated model and ABM yield similar numbers of clusters for the same parameters. Below a critical value of uncertainty, the aggregated model forms no cluster and the distribution remains uniform. The critical value is higher for the aggregated model than for the ABM, indicating a finite size effect that we discuss.}, }
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S. Huet, G. Deffuant
Bounded confidence with rejection: the infinite population limit with perfect uniform initial density
Modèles et Apprentissages en Sciences Humaines et Sociales (MASH), 05/06/2008-06/06/2008, Créteil, FRA (p. 10), 2008
abs web bib

Huet and Deffuant (2007) propose a new opinion dynamics model based on the bounded confidence principles, with a rejection mechanism. The simulations of the agent-based model show that this new model leads generally to fewer clusters than the classical bounded confidence model. We build an aggregated model of this agent-based model (ABM), considering the limit case of an infinite population, in order to better understand the clustering process in the ABM. The dynamics of the aggregated model, starting from a perfectly uniform distribution of opinions, and the dynamics of the ABM are significantly different. However, the aggregated model provides relevant information about how the rejection mechanism and bounding the attitude space influence the clustering process. It firstly outlines that, with a perfectly symmetric density, the clustering process is almost impossible and that the only final stable state is one centred cluster. Secondly we notice that one centred cluster can be lead with the only rejection mechanism or with an unbounded attitude space.
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@inproceedings{PUB00024188, author = {Huet, S. and Deffuant, G.}, title = {Bounded confidence with rejection: the infinite population limit with perfect uniform initial density}, title = {Confiance limitée et rejet: l'effet d'une taille de population infinie pour une densité initiale parfaitement uniforme}, bookTitle = {Modèles et Apprentissages en Sciences Humaines et Sociales (MASH), 05/06/2008-06/06/2008, Créteil, FRA}, pages = {10}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00024188}, year = {2008}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {Huet and Deffuant (2007) propose a new opinion dynamics model based on the bounded confidence principles, with a rejection mechanism. The simulations of the agent-based model show that this new model leads generally to fewer clusters than the classical bounded confidence model. We build an aggregated model of this agent-based model (ABM), considering the limit case of an infinite population, in order to better understand the clustering process in the ABM. The dynamics of the aggregated model, starting from a perfectly uniform distribution of opinions, and the dynamics of the ABM are significantly different. However, the aggregated model provides relevant information about how the rejection mechanism and bounding the attitude space influence the clustering process. It firstly outlines that, with a perfectly symmetric density, the clustering process is almost impossible and that the only final stable state is one centred cluster. Secondly we notice that one centred cluster can be lead with the only rejection mechanism or with an unbounded attitude space.}, }
close

Miscellaneous (1)

M. Lenormand, S. Huet, G. Deffuant
Predicting the presence and the number of jobs in different services in Auvergne municipalities
2010
abs web bib

Nous décrivons dans ce rapport une méthode permettant de prédire la présence de différents services (école, boulangerie...) dans une commune en fonction des caractéristiques de celle-ci. Nous présentons aussi une méthode permettant de prédire le nombre d'emplois dans différentes sortes de services. Les deux méthodes sont testées sur les communes d'Auvergne.
close

@misc{PUB00035311, note = {Autres}, author = {Lenormand, M. and Huet, S. and Deffuant, G.}, title = {Predicting the presence and the number of jobs in different services in Auvergne municipalities}, title = {Prédire la présence et le nombre d'emplois dans les services pour les communes d'Auvergne}, pages = {9}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00035311}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA}, abstract = {Nous décrivons dans ce rapport une méthode permettant de prédire la présence de différents services (école, boulangerie...) dans une commune en fonction des caractéristiques de celle-ci. Nous présentons aussi une méthode permettant de prédire le nombre d'emplois dans différentes sortes de services. Les deux méthodes sont testées sur les communes d'Auvergne.}, }
close

Dissertations (1)

G. Deffuant
Modéliser des systèmes complexes : quelques pistes pour relever le défi
Habilitation à Diriger des Recherches, Ecole doctorale SPI de l'Université Blaise Pascal de Clermont-Ferrand, soutenue le 3 mars 2004, 2004
abs web bib

Des hyperplans séparateurs dans des espaces déployés : les Support Vector Machines Les réseaux géométriques dynamiques Modèles géométriques dynamiques pour la diffusion d'opinions : comparer le modèle individu-centré à son approximation agrégée Projet européen IMAGES : un modèle individu-centré de propagation de l'innovation
close

@phdthesis{PUB00014157, author = {Deffuant, G.}, title = {Modéliser des systèmes complexes : quelques pistes pour relever le défi}, publisher = {Habilitation à Diriger des Recherches, Ecole doctorale SPI de l'Université Blaise Pascal de Clermont-Ferrand, soutenue le 3 mars 2004}, pages = {133}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00014157 / http://wwwlisc.clermont.cemagref.fr/Labo/MembresEtPagesIntermediaires/pagesperso/membres_actuels/deffuant/HDRDeffuantV3.pdf}, year = {2004}, affiliation = {CEMAGREF CLERMONT FERRAND LISC}, number = {LI04 2 ; }, abstract = {Des hyperplans séparateurs dans des espaces déployés : les Support Vector Machines Les réseaux géométriques dynamiques Modèles géométriques dynamiques pour la diffusion d'opinions : comparer le modèle individu-centré à son approximation agrégée Projet européen IMAGES : un modèle individu-centré de propagation de l'innovation }, }
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Technical Reports (10)

S. Huet, N. Dumoulin, G. Deffuant, F. Gargiulo, M. Lenormand, O. Baqueiro Espinosa, S. Ternes
Micro-simulation model of municipality network in the Auvergne case study
2012
abs web bib

How do European rural areas evolve? Some tend to decrease dramatically, as in the Netherlands or in the United Kingdom, where the urban areas tend to spread all over the country. Their population can also be drastically depleting through a large rural exodus, as observed in for instance France, Bulgaria or Croatia in the first part of the last Century. They can also keep steady population densities occupied in leisure services offered to urban people and agriculture with various proportions of inhabitants commuting to the cities for their work. Better understanding these evolutions is what the PRIMA simulation model presented in this report is interested in. / Ce document décrit un modèle de micro-simulation de communes développé dans le cadre du projet européen PRIMA (EU ENV 2007-1). Ce modèle permet d'étudier l'évolution des populations rurales sous l'effet des interactions spatiales et des dynamiques économiques locales.
close

@techreport{PUB00036510, author = {Huet, S. and Dumoulin, N. and Deffuant, G. and Gargiulo, F. and Lenormand, M. and Baqueiro Espinosa, O. and Ternes, S.}, title = {Micro-simulation model of municipality network in the Auvergne case study }, title = {Modèle de micro-simulation d'un réseau de communes : étude de cas en Auvergne}, pages = {66}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00036510}, year = {2012}, 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 ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IAMO INSTITUTE OF AGRICULTURAL DEVELOPMENT IN CENTRAL AND EASTERN EUROPE LEIBNITZ DEU ; IAMO INSTITUTE OF AGRICULTURAL DEVELOPMENT IN CENTRAL AND EASTERN EUROPE LEIBNITZ DEU}, abstract = {How do European rural areas evolve? Some tend to decrease dramatically, as in the Netherlands or in the United Kingdom, where the urban areas tend to spread all over the country. Their population can also be drastically depleting through a large rural exodus, as observed in for instance France, Bulgaria or Croatia in the first part of the last Century. They can also keep steady population densities occupied in leisure services offered to urban people and agriculture with various proportions of inhabitants commuting to the cities for their work. Better understanding these evolutions is what the PRIMA simulation model presented in this report is interested in. / Ce document décrit un modèle de micro-simulation de communes développé dans le cadre du projet européen PRIMA (EU ENV 2007-1). Ce modèle permet d'étudier l'évolution des populations rurales sous l'effet des interactions spatiales et des dynamiques économiques locales.}, }
close
N. Turpin, B. Hautdidier, R. Laplana, D. Kopeva, M. Raley, O. Baqueiro, G. Deffuant, G. Woltjer, B. Meyer, M. Njavro, L. Jelinek, G. Abrami, O. Aznar, O. Barreteau, I. Bezlepkina, A. Bouwman, R. Franic, G. Garrod, M. Gomez, Wander Jager, S. Huet, E. Kozáková, M. Lenormand, J.B. Marsat, M. Delin, E. Perret, K. Rodseth, E. Romstad, B. ¦akic Bobic, F. Schaft, H. Talbot, Q. Zhang
Final Report D0.4, PRIMA collaborative project, EU 7th Framework Programme, contract no. 212345
2012
abs web bib

Facing structural change, European rural areas still fulfil multiple social, economic and ecological functions. Because of scale interplays and sustainability trade-offs, their future dynamics are still difficult to ascertain. In addition to the inherent difficulties of this undertaking, challenges in actual assessments also depend on external shocks to the economy at large or to particular regions, along with spillover effects among neighbouring regions. PRIMA proposes to improve knowledge in scaling down this assessment. It focuses on agriculture, forestry, tourism, and ecosystem services, with special attention to the structural effects of the European policies at municipality levels. The six case studies of PRIMA, conducted in Germany, United Kingdom, France, Croatia, Czech Republic, and Bulgaria, are important for two main reasons: they provide test cases for the PRIMA approaches, and they have influenced the development of the PRIMA approaches. These case studies have been chosen for their variety of rural dynamics and governance organisation. Because of the bottom-up governance of the European cohesion policy, a large variety has been observed in the priorities and measures, targeted to several pillars of sustainable development. This variety has been narrowed in a pre-modelling stage, where 2 groups of stakeholders were interviewed: those who can assist in scenario and model development (coming from the institutions which implement policy), and the actors who may be affected by the policy and hence whose related behavioural changes should be captured by the model framework. A conceptual model has then been developed. This model focuses on the population dynamics in rural municipalities and on the decision making behaviours observed. The conceptual micro-simulation model was successfully adapted to three of the study regions (France, United Kingdom and Germany). Additionally, the developed agent-based model was adapted for the United Kingdom region; this allowed studying the effects of social aspects that are not captured in the micro-simulation model. For validation purposes, a series of workshops were conducted on the case study areas. The orientation of these workshops depended on the availability of the models for the given case study area. The workshops promoted stakeholder learning about modelling. On the whole, participants recognised models as simplifications of reality. They found explanations about the model components comprehensible, and reacted fairly favourably to the idea of having such a decision-support tool available. However, the lack of good data at a low geographical scale in most case study areas was seen as a severe limitation. Beyond pathways for model revision, some methodological advances in the field of participatory modelling have been identified. Among these is making explicit the role of a model broker, the endorsement of which should improve the various interpretations of participants. Scenario development, though far in advance of their technical skills, has also proved an efficient tool to involve stakeholders in challenging a model. Further conceptual work was identified and undertaken concerning the design of methods to reconstruct commuting network for regions where data was unavailable, to calibrate models with several number of variables and of new approaches to dynamically derive services jobs availability. PRIMA also developed a conceptual work that includes the MAGNET (formerly LEITAP) model for downscaling from world level to the country level, and a downscaling tool from country level towards the NUTS2 level. An interface has been developed for easy downscaling of scenarios. Special attention has been paid to procedures to process data from Eurostat towards a database useful as input for the downscaling model. Last, we progressed towards recommendations enhancing the scope of IA methods, with a review of literature and extensive work between all workpackages.
close

@techreport{PUB00035265, author = {Turpin, N. and Hautdidier, B. and Laplana, R. and Kopeva, D. and Raley, M. and Baqueiro, O. and Deffuant, G. and Woltjer, G. and Meyer, B. and Njavro, M. and Jelinek, L. and Abrami, G. and Aznar, O. and Barreteau, O. and Bezlepkina, I. and Bouwman, A. and Franic, R. and Garrod, G. and Gomez, M. and Wander Jager, and Huet, S. and Kozáková, E. and Lenormand, M. and Marsat, J.B. and Delin, M. and Perret, E. and Rodseth, K. and Romstad, E. and ¦akic Bobic, B. and Schaft, F. and Talbot, H. and Zhang, Q.}, title = {Final Report D0.4, PRIMA collaborative project, EU 7th Framework Programme, contract no. 212345}, title = {Rapport final du projet européen PRIMA}, pages = {54}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00035265 / https://prima.cemagref.fr/}, year = {2012}, affiliation = {IRSTEA CLERMONT FERRAND UMR METAFORT FRA ; IRSTEA BORDEAUX UR ADBX FRA ; IRSTEA BORDEAUX UR ADBX FRA ; UNWE SOFIA BGR ; UNEW NEWCASTLE UPON TYNE GBR ; INSTITUTE OF AGRICULTURAL DEVELOPMENT IN CENTRAL AND EASTERN DEU ; IRSTEA CLERMONT FERRAND UR LISC FRA ; WAGENINGEN UNIVERSITY NLD ; UNIVERSITY OF TECHNOLOGY DORTMUND DEU ; UNIVERSITE DE ZAGREB KRO ; UNIVERSITE DE ZAGREB KRO ; IRSTEA MONTPELLIER UR IRMO FRA ; IRSTEA CLERMONT FERRAND UMR METAFORT FRA ; IRSTEA MONTPELLIER IRMO ; LEI WAGENINGEN NLD ; - ; FACULTY OF AGRICULTURE AND TOURISM OF ZAGREB CRO ; CENTRE FOR RURAL ECONOMY SCHOOL OF AGRICULTURE, FOOD AND RURAL DEVELOPMENT NEWCASTLE UNIVERSITY GBR ; IRSTEA CLERMONT FERRAND UMR METAFORT FRA ; - ; IRSTEA CLERMONT FERRAND UR LISC FRA ; - ; IRSTEA CLERMONT FERRAND UR LISC FRA ; IRSTEA CLERMONT FERRAND UMR METAFORT FRA ; INSTITUTE OF ARGICULTURAL ECONOMICS AND INFORMATION CZR ; IRSTEA CLERMONT FERRAND UMR METAFORT FRA ; - ; UNIVERSITY OF NORWAY AAS NOR ; - ; - ; - ; -}, abstract = {Facing structural change, European rural areas still fulfil multiple social, economic and ecological functions. Because of scale interplays and sustainability trade-offs, their future dynamics are still difficult to ascertain. In addition to the inherent difficulties of this undertaking, challenges in actual assessments also depend on external shocks to the economy at large or to particular regions, along with spillover effects among neighbouring regions. PRIMA proposes to improve knowledge in scaling down this assessment. It focuses on agriculture, forestry, tourism, and ecosystem services, with special attention to the structural effects of the European policies at municipality levels. The six case studies of PRIMA, conducted in Germany, United Kingdom, France, Croatia, Czech Republic, and Bulgaria, are important for two main reasons: they provide test cases for the PRIMA approaches, and they have influenced the development of the PRIMA approaches. These case studies have been chosen for their variety of rural dynamics and governance organisation. Because of the bottom-up governance of the European cohesion policy, a large variety has been observed in the priorities and measures, targeted to several pillars of sustainable development. This variety has been narrowed in a pre-modelling stage, where 2 groups of stakeholders were interviewed: those who can assist in scenario and model development (coming from the institutions which implement policy), and the actors who may be affected by the policy and hence whose related behavioural changes should be captured by the model framework. A conceptual model has then been developed. This model focuses on the population dynamics in rural municipalities and on the decision making behaviours observed. The conceptual micro-simulation model was successfully adapted to three of the study regions (France, United Kingdom and Germany). Additionally, the developed agent-based model was adapted for the United Kingdom region; this allowed studying the effects of social aspects that are not captured in the micro-simulation model. For validation purposes, a series of workshops were conducted on the case study areas. The orientation of these workshops depended on the availability of the models for the given case study area. The workshops promoted stakeholder learning about modelling. On the whole, participants recognised models as simplifications of reality. They found explanations about the model components comprehensible, and reacted fairly favourably to the idea of having such a decision-support tool available. However, the lack of good data at a low geographical scale in most case study areas was seen as a severe limitation. Beyond pathways for model revision, some methodological advances in the field of participatory modelling have been identified. Among these is making explicit the role of a model broker, the endorsement of which should improve the various interpretations of participants. Scenario development, though far in advance of their technical skills, has also proved an efficient tool to involve stakeholders in challenging a model. Further conceptual work was identified and undertaken concerning the design of methods to reconstruct commuting network for regions where data was unavailable, to calibrate models with several number of variables and of new approaches to dynamically derive services jobs availability. PRIMA also developed a conceptual work that includes the MAGNET (formerly LEITAP) model for downscaling from world level to the country level, and a downscaling tool from country level towards the NUTS2 level. An interface has been developed for easy downscaling of scenarios. Special attention has been paid to procedures to process data from Eurostat towards a database useful as input for the downscaling model. Last, we progressed towards recommendations enhancing the scope of IA methods, with a review of literature and extensive work between all workpackages.}, }
close
G. Deffuant, N. Mabrouk, J.D. Mathias, C. Deygout, F. Campillo, A. Lesne
Livrable 2.1 du projet DISCO : Modèles individus-centrés et simulations Monte-Carlo
2011
abs web bib

Les équipes du projet collaborent à plusieurs modèles individus-centrés dans une démarche commune au projet DISCO: ces modèles individus-centrés sont confrontés à la fois à des modèles de type équations aux dérivées partielles ou équations différentielles ordinaires (démarche de "double modélisation") et à des observations venant de démarches expérimentales spécifiques. Cette démarche permet d'identifier clairement les effets spécifiques de l'introduction d'un modèle à partir d'individus. Les modèles individus-centrés donnent lieu aussi dans certains cas à l'émergence de structures spatiales (dans les deux exemples de modèles 2 D) qui étaient difficilement prédictibles initialement. Nous cherchons ensuite à comprendre les mécanismes donnant lieu à ces structures, notamment en définissant des modèles plus simples. Ce rapport présente ces modèles de manière très condensée, le lecteur intéressé pourra trouver les détails dans les documents cités dans les références.
close

@techreport{PUB00034524, author = {Deffuant, G. and Mabrouk, N. and Mathias, J.D. and Deygout, C. and Campillo, F. and Lesne, A.}, title = {Livrable 2.1 du projet DISCO : Modèles individus-centrés et simulations Monte-Carlo}, pages = {6}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00034524 / http://sites.google.com/site/anrdisco/prepr}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; INRIA SOPHIA ANTIPOLIS FRA ; INRIA SOPHIA ANTIPOLIS FRA ; UNIVERSITE PIERRE ET MARIE CURIE LPTMC PARIS FRA}, abstract = {Les équipes du projet collaborent à plusieurs modèles individus-centrés dans une démarche commune au projet DISCO: ces modèles individus-centrés sont confrontés à la fois à des modèles de type équations aux dérivées partielles ou équations différentielles ordinaires (démarche de "double modélisation") et à des observations venant de démarches expérimentales spécifiques. Cette démarche permet d'identifier clairement les effets spécifiques de l'introduction d'un modèle à partir d'individus. Les modèles individus-centrés donnent lieu aussi dans certains cas à l'émergence de structures spatiales (dans les deux exemples de modèles 2 D) qui étaient difficilement prédictibles initialement. Nous cherchons ensuite à comprendre les mécanismes donnant lieu à ces structures, notamment en définissant des modèles plus simples. Ce rapport présente ces modèles de manière très condensée, le lecteur intéressé pourra trouver les détails dans les documents cités dans les références.}, }
close
N. Turpin, D. Kopeva, M. Raley, O. Baqueiro, G. Deffuant, G. Woltjer, B. Meyer, M. Njavro, L. Jelinek, B. Haudidier, R. Laplana
2nd Periodic Report D0.3b. PRIMA collaborative project, EU 7th Framework Programme, contract n° 212345
2011
abs web bib

Facing structural change, European rural areas still fulfil multiple social, economic and ecological functions. Because of scale interplays and sustainability trade-offs, their future dynamics are still difficult to ascertain. In addition to the inherent difficulties of this undertaking, challenges in actual assessments also depend on external shocks to the economy at large or to particular regions, along with spillover effects among neighbouring regions. PRIMA proposes to improve knowledge in scaling down this assessment. It focuses on agriculture, forestry, tourism, and ecosystem services, with special attention to the structural effects of the European policies at municipality levels. The six case studies of PRIMA, conducted in Germany, United Kingdom, France, Croatia, Czech Republic, and Bulgaria, are important for two main reasons: They provide test cases for the PRIMA approaches, and they have influenced the development of the PRIMA approaches. These case studies have been chosen for their variety of rural dynamics and governance organisation. The strategic and planning documents in these study areas highlights that many measures are targeted to several pillars of sustainable development, even though multifunctionality concept is often not directly addressed. Because of the bottom-up governance of the European cohesion policy, a large variety of priorities and measures has been observed in the priorities and measures, targeted to several pillars of sustainable development. This variety has been narrowed in a pre-modelling stage, where 2 groups of stakeholders were interviewed: Those who can assist in scenario and model development (coming from the institutions which implement policy), and the actors who may be affected by the policy and hence those related behavioural changes should be captured by the model framework. A conceptual model has then been developed from extensive literature review and information collected during the surveys. This model focuses on the population dynamics in rural municipalities and on the decision making behaviours observed. The conceptual micro-simulation model was successfully adapted to three of the study regions (France, United Kingdom and Germany). Additionally, the developed agent-based model was adapted for the United Kingdom region; this allowed studying the effects of social aspects that are not captured in the micro-simulation model. A strong effort was made to adapt the models to the remaining regions (Czech Republic, Bulgaria and Croatia) but the lack of sufficient data would have made the adaptations unstable in the sense that small changes in policy could lead to unexpectedly large changes on key behavioural aspects. For validation purposes, a series of workshops were conducted on the case study areas. The orientation of these workshops depended on the availability of the models for the given case study area. The workshops promoted stakeholder learning about modelling. On the whole, participants recognised models as simplifications of reality. They found explanations about the model components comprehensible, and reacted fairly favourably to the idea of having such a decision-support tool available. However, the lack of good data Contract no. 212345 | Deliverable no. | 07/01/2012 Periodic Report 10/85 at a low geographical scale in most case study areas was seen as a severe limitation. Beyond pathways for model revision, stakeholder on-model involvement in PRIMA’s workshops identified some methodological advances in the field of participatory modelling have been identified. Among these is making explicit the role of a model broker, the endorsement of which should improve the various interpretations of participants. Scenario development, though far in advance of their technical skills, has also proved an efficient tool to involve stakeholders in challenging a model. Adaptation of these models to local conditions revealed their limitations and scope. Further conceptual work was identified and undertaken concerning the design of methods to reconstruct commuting network for regions where data was unavailable, to, to calibrate models with several number of variables and of new approaches to dynamically derive services jobs availability. PRIMA also developed a conceptual work and an integrated simulation tool that includes the MAGNET (formerly LEITAP) model for downscaling from world level to the country level, and a downscaling tool from country level towards the NUTS2 level. An interface has been developed for easy downscaling of scenarios. Special attention has been paid to procedures to process data from EUROSTAT towards a database useful as input for the downscaling model. Last, we progressed towards recommendations enhancing the scope of IA methods, with a review of literature and extensive work between all workpackages.
close

@techreport{PUB00035264, author = {Turpin, N. and Kopeva, D. and Raley, M. and Baqueiro, O. and Deffuant, G. and Woltjer, G. and Meyer, B. and Njavro, M. and Jelinek, L. and Haudidier, B. and Laplana, R.}, title = {2nd Periodic Report D0.3b. PRIMA collaborative project, EU 7th Framework Programme, contract n° 212345}, title = {PRIMA, second rapport périodique}, pages = {87}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00035264}, year = {2011}, affiliation = {CEMAGREF CLERMONT FERRAND UR MECF UMR METAFORT FRA ; UNIVERSITY OF SUSSEX GBR ; UNIVERSITY OF NEWCASTLE GBR ; INSTITUTE OF AGRICULTURAL DEVELOPMENT IN CENTRAL AND EASTERN DEU ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; WAGENINGEN UNIVERSITY NLD ; UNIVERSITY OF TECHNOLOGY DORTMUND DEU ; UNIVERSITE DE ZAGREB KRO ; INSTITUTE OF AGRICULTURAL ECONOMICS AND INFORMATION CZR ; CEMAGREF BORDEAUX UR ADBX FRA ; CEMAGREF BORDEAUX UR ADBX FRA}, abstract = {Facing structural change, European rural areas still fulfil multiple social, economic and ecological functions. Because of scale interplays and sustainability trade-offs, their future dynamics are still difficult to ascertain. In addition to the inherent difficulties of this undertaking, challenges in actual assessments also depend on external shocks to the economy at large or to particular regions, along with spillover effects among neighbouring regions. PRIMA proposes to improve knowledge in scaling down this assessment. It focuses on agriculture, forestry, tourism, and ecosystem services, with special attention to the structural effects of the European policies at municipality levels. The six case studies of PRIMA, conducted in Germany, United Kingdom, France, Croatia, Czech Republic, and Bulgaria, are important for two main reasons: They provide test cases for the PRIMA approaches, and they have influenced the development of the PRIMA approaches. These case studies have been chosen for their variety of rural dynamics and governance organisation. The strategic and planning documents in these study areas highlights that many measures are targeted to several pillars of sustainable development, even though multifunctionality concept is often not directly addressed. Because of the bottom-up governance of the European cohesion policy, a large variety of priorities and measures has been observed in the priorities and measures, targeted to several pillars of sustainable development. This variety has been narrowed in a pre-modelling stage, where 2 groups of stakeholders were interviewed: Those who can assist in scenario and model development (coming from the institutions which implement policy), and the actors who may be affected by the policy and hence those related behavioural changes should be captured by the model framework. A conceptual model has then been developed from extensive literature review and information collected during the surveys. This model focuses on the population dynamics in rural municipalities and on the decision making behaviours observed. The conceptual micro-simulation model was successfully adapted to three of the study regions (France, United Kingdom and Germany). Additionally, the developed agent-based model was adapted for the United Kingdom region; this allowed studying the effects of social aspects that are not captured in the micro-simulation model. A strong effort was made to adapt the models to the remaining regions (Czech Republic, Bulgaria and Croatia) but the lack of sufficient data would have made the adaptations unstable in the sense that small changes in policy could lead to unexpectedly large changes on key behavioural aspects. For validation purposes, a series of workshops were conducted on the case study areas. The orientation of these workshops depended on the availability of the models for the given case study area. The workshops promoted stakeholder learning about modelling. On the whole, participants recognised models as simplifications of reality. They found explanations about the model components comprehensible, and reacted fairly favourably to the idea of having such a decision-support tool available. However, the lack of good data Contract no. 212345 | Deliverable no. | 07/01/2012 Periodic Report 10/85 at a low geographical scale in most case study areas was seen as a severe limitation. Beyond pathways for model revision, stakeholder on-model involvement in PRIMA’s workshops identified some methodological advances in the field of participatory modelling have been identified. Among these is making explicit the role of a model broker, the endorsement of which should improve the various interpretations of participants. Scenario development, though far in advance of their technical skills, has also proved an efficient tool to involve stakeholders in challenging a model. Adaptation of these models to local conditions revealed their limitations and scope. Further conceptual work was identified and undertaken concerning the design of methods to reconstruct commuting network for regions where data was unavailable, to, to calibrate models with several number of variables and of new approaches to dynamically derive services jobs availability. PRIMA also developed a conceptual work and an integrated simulation tool that includes the MAGNET (formerly LEITAP) model for downscaling from world level to the country level, and a downscaling tool from country level towards the NUTS2 level. An interface has been developed for easy downscaling of scenarios. Special attention has been paid to procedures to process data from EUROSTAT towards a database useful as input for the downscaling model. Last, we progressed towards recommendations enhancing the scope of IA methods, with a review of literature and extensive work between all workpackages.}, }
close
N. Turpin, D. Kopeva, M. Raley, O. Baqueiro, G. Deffuant, G. Woltjer, B. Meyer, M. Njavro, L. Jelinek, B. Haudidier, R. Laplana
Periodic Report D0.3 PRIMA collaborative project, EU 7th Framework Programme, contract no. 212345
2010
abs web bib

Facing structural change, European rural areas still fulfil multiple social, economic and ecological functions. Because of scale interplays and sustainability trade-offs, their future dynamics are yet particularly difficult to ascertain. PRIMA aims to develop methods for scaling down the assessment of policy impacts on multifunctional land-use and economic activities. The project focuses on agriculture, forestry, tourism, and ecosystem services, with special attention to the structural effects of the policies. An analysis of the strategic and planning documents in the case study areas highlights that many measures are targeted to several pillars of sustainable development, even though multifunctionality (MF) concept is often unaddressed. Because of the bottom-up governance of the European cohesion policy, a large variety of priorities and measures has been observed, so we oriented the first stakeholders interviews towards their major objectives and the specific measures they activate from the cohesion policy to reach their own objectives. Two groups of stakeholders were identified: those who can assist in scenario and model development and in model validation (drawn from the institutions which implement policy), and the actors who may be affected by the policy and whose behaviour will be captured in the AB model. Two rounds of interviews have been performed, the first one to gain contextual information about the wider case study information. From cluster analysis and this information, sets of municipalities were selected, then a second round of interviews was conducted to identify relevant policy issues and appropriate policy measures. These interviews provide the main events which have occurred during the last 20 years, policy outcomes, the EU funding streams, proposals for new measures. A conceptual model has been developed from extensive literature review and information collected during the surveys. This model focuses on the population dynamics in rural municipalities and on the decision making behaviours observed in such areas, including indicators requirements to match with IA methods. A general method for generating households from different available data at municipality level has been designed: at this level, only average data are available and the method enables to generate relevant individual data to be included in the models. The model has been adapted to the case studies: at this stage, downscaling occurs to input data for the models. We developed a working regional economic model that interacts between global changes (GTAP-IMAGE interactions) and multi-agent based tool at local level. It covers activities agriculture, forestry, services and nature. A start has been made with a program for downscaling. We are working on a procedure to generate the basic regional data for the input. We have to start data generation and theoretical and empirical work to improve on the allocation procedures of national developments to regions. Considering backbone scenarios, first modelling at European level started, with the identification of key economic and demographic factors that drive land use patterns at regional and local levels. External drivers and policies have been distinguished. GTAP and IMAGES have been linked to provide a working modelling framework. Last, we progressed towards enhancing the scope of IA methods, with a review of literature and extensive work between all workpackages. / Le rapport présente le déroulement et les avancées du projet PRIMA à mi parcours de réalisation. Sont présentés les développements en termes d'analyse des politiques et des scénarios, d'implication des parties prenantes dans les processus de modélisation, de conceptualisation des modèles et d'apports pour les procédures d'évaluation des impacts.
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@techreport{PUB00030749, author = {Turpin, N. and Kopeva, D. and Raley, M. and Baqueiro, O. and Deffuant, G. and Woltjer, G. and Meyer, B. and Njavro, M. and Jelinek, L. and Haudidier, B. and Laplana, R.}, title = {Periodic Report D0.3 PRIMA collaborative project, EU 7th Framework Programme, contract no. 212345}, pages = {69}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00030749 / https://prima.irstea.fr}, year = {2010}, affiliation = {CEMAGREF CLERMONT FERRAND UR MECF UMR METAFORT FRA ; CEMAGREF CLERMONT FERRAND UR MECF UMR METAFORT FRA ; CEMAGREF CLERMONT FERRAND UR MECF UMR METAFORT FRA ; INSTITUTE OF AGRICULTURAL DEVELOPMENT IN CENTRAL AND EASTERN DEU ; CEMAGREF CLERMONT FERRAND UR LISC FRA ; CEMAGREF CLERMONT FERRAND UR MECF UMR METAFORT FRA ; UNIVERSITY OF TECHNOLOGY DORTMUND DEU ; UNIVERSITE DE ZAGREB KRO ; INSTITUTE OF AGRICULTURAL ECONOMICS AND INFORMATION CZR ; CEMAGREF BORDEAUX UR ADBX FRA ; CEMAGREF BORDEAUX UR ADBX FRA}, abstract = {Facing structural change, European rural areas still fulfil multiple social, economic and ecological functions. Because of scale interplays and sustainability trade-offs, their future dynamics are yet particularly difficult to ascertain. PRIMA aims to develop methods for scaling down the assessment of policy impacts on multifunctional land-use and economic activities. The project focuses on agriculture, forestry, tourism, and ecosystem services, with special attention to the structural effects of the policies. An analysis of the strategic and planning documents in the case study areas highlights that many measures are targeted to several pillars of sustainable development, even though multifunctionality (MF) concept is often unaddressed. Because of the bottom-up governance of the European cohesion policy, a large variety of priorities and measures has been observed, so we oriented the first stakeholders interviews towards their major objectives and the specific measures they activate from the cohesion policy to reach their own objectives. Two groups of stakeholders were identified: those who can assist in scenario and model development and in model validation (drawn from the institutions which implement policy), and the actors who may be affected by the policy and whose behaviour will be captured in the AB model. Two rounds of interviews have been performed, the first one to gain contextual information about the wider case study information. From cluster analysis and this information, sets of municipalities were selected, then a second round of interviews was conducted to identify relevant policy issues and appropriate policy measures. These interviews provide the main events which have occurred during the last 20 years, policy outcomes, the EU funding streams, proposals for new measures. A conceptual model has been developed from extensive literature review and information collected during the surveys. This model focuses on the population dynamics in rural municipalities and on the decision making behaviours observed in such areas, including indicators requirements to match with IA methods. A general method for generating households from different available data at municipality level has been designed: at this level, only average data are available and the method enables to generate relevant individual data to be included in the models. The model has been adapted to the case studies: at this stage, downscaling occurs to input data for the models. We developed a working regional economic model that interacts between global changes (GTAP-IMAGE interactions) and multi-agent based tool at local level. It covers activities agriculture, forestry, services and nature. A start has been made with a program for downscaling. We are working on a procedure to generate the basic regional data for the input. We have to start data generation and theoretical and empirical work to improve on the allocation procedures of national developments to regions. Considering backbone scenarios, first modelling at European level started, with the identification of key economic and demographic factors that drive land use patterns at regional and local levels. External drivers and policies have been distinguished. GTAP and IMAGES have been linked to provide a working modelling framework. Last, we progressed towards enhancing the scope of IA methods, with a review of literature and extensive work between all workpackages. / Le rapport présente le déroulement et les avancées du projet PRIMA à mi parcours de réalisation. Sont présentés les développements en termes d'analyse des politiques et des scénarios, d'implication des parties prenantes dans les processus de modélisation, de conceptualisation des modèles et d'apports pour les procédures d'évaluation des impacts. }, }
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G. Deffuant
An analytical solution to support vector training: the recursive projection algorithm
2003
abs web bib

We propose an algorithm which provides an analytical solution to the problem of norm 2 margin support vector machines (svm) computation. We consider a geometric interpretation of the problem : the svm is defined as the point of a convex polyhedron which is the closest to a particular right line. Our algorithm performs iterative tests of facets of the polyhedron. Each test computes the point of the subspace defining the facet which is the closest to the right line. We show that the svm is such a point satisfying simple conditions. The non satisfaction of these conditions gives indications on the next facet to test. We prove the convergence of the algorithm, and of its use in a variant of the chunking strategy, in general. Our preliminary empirical study of the method suggests that the number of facet tests necessary to find the svm is linear with the number of support vectors. Therefore, the method is particularly interesting when the number of support vectors is low. / Nous proposons un algorithme qui apporte une solution analytique au problème du calcul de support vector machines (svm) dans le cas de l'utilisation de la norme 2 pour traiter les exemples mal classés. Nous considérons une interprétation géométrique du problème. Le svm est défini comme le point d'un polyèdre convexe qui est le plus proche d'une droite particulière de l'espace. Notre algorithme exécute des tests itératifs des facettes du polyèdre. Chaque test calcule le point du sous-espace définissant la facette qui est la plus proche de la droite. Nous montrons que le svm est un tel point satisfaisant des conditions particulières.La non satisfaction de ces conditions donne des indications sur la prochaine facette à tester. Nous prouvons la convergence de l'algorithme et de son utilisation dans une variante de la stratégie chunking, en général.Notre étude empirique préliminaire des méthodes suggère que le nombre de facettes nécessaires pour trouver le svm est linéaire avec le nombre de support vectors.Par conséquent, la méthode est particulièrement intéressante quand le nombre de support vectors est faible.
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@techreport{PUB00011519, author = {Deffuant, G.}, title = {An analytical solution to support vector training: the recursive projection algorithm}, title = {Une solution analytique au problème de l'apprentissage des support vector machines : l'algorithme projection récursive.}, pages = {18}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00011519}, year = {2003}, affiliation = {CEMAGREF CLERMONT FERRAND LISC}, number = {03/0081 ; LI03 1}, abstract = {We propose an algorithm which provides an analytical solution to the problem of norm 2 margin support vector machines (svm) computation. We consider a geometric interpretation of the problem : the svm is defined as the point of a convex polyhedron which is the closest to a particular right line. Our algorithm performs iterative tests of facets of the polyhedron. Each test computes the point of the subspace defining the facet which is the closest to the right line. We show that the svm is such a point satisfying simple conditions. The non satisfaction of these conditions gives indications on the next facet to test. We prove the convergence of the algorithm, and of its use in a variant of the chunking strategy, in general. Our preliminary empirical study of the method suggests that the number of facet tests necessary to find the svm is linear with the number of support vectors. Therefore, the method is particularly interesting when the number of support vectors is low. / Nous proposons un algorithme qui apporte une solution analytique au problème du calcul de support vector machines (svm) dans le cas de l'utilisation de la norme 2 pour traiter les exemples mal classés. Nous considérons une interprétation géométrique du problème. Le svm est défini comme le point d'un polyèdre convexe qui est le plus proche d'une droite particulière de l'espace. Notre algorithme exécute des tests itératifs des facettes du polyèdre. Chaque test calcule le point du sous-espace définissant la facette qui est la plus proche de la droite. Nous montrons que le svm est un tel point satisfaisant des conditions particulières.La non satisfaction de ces conditions donne des indications sur la prochaine facette à tester. Nous prouvons la convergence de l'algorithme et de son utilisation dans une variante de la stratégie chunking, en général.Notre étude empirique préliminaire des méthodes suggère que le nombre de facettes nécessaires pour trouver le svm est linéaire avec le nombre de support vectors.Par conséquent, la méthode est particulièrement intéressante quand le nombre de support vectors est faible.}, }
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L. Rousseau, S. Bernard, G. Deffuant
Confronting evaluations of scenarios via Internet
2003
abs web bib

We propose a generic software tool supporting participatory decision processes based on simulation of scenarios. The main objective of the tool is to provide information about the state of the participatory process, by enhancing the current consensus and conflicts. The tool provides a generic interface, which is connected to a database of model results. The user can visualise the results corresponding to the scenarios for different attributes of objects located in the space, and a variety of indicators related to these variables. The user expresses evaluations of scenarios by specifying thresholds of acceptance of objects attribute values. The software provides then indicators of comparisons between the expressed evaluations, highlighting the differences of similarities between the expressed evaluation. A series of tests with a group of potential users is currently in progress.
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@techreport{PUB00011350, author = {Rousseau, L. and Bernard, S. and Deffuant, G.}, title = {Confronting evaluations of scenarios via Internet}, title = {Confronter des évaluations sur Internet}, pages = {16}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00011350}, year = {2003}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC}, number = {03/0018 ; LI03 2}, abstract = {We propose a generic software tool supporting participatory decision processes based on simulation of scenarios. The main objective of the tool is to provide information about the state of the participatory process, by enhancing the current consensus and conflicts. The tool provides a generic interface, which is connected to a database of model results. The user can visualise the results corresponding to the scenarios for different attributes of objects located in the space, and a variety of indicators related to these variables. The user expresses evaluations of scenarios by specifying thresholds of acceptance of objects attribute values. The software provides then indicators of comparisons between the expressed evaluations, highlighting the differences of similarities between the expressed evaluation. A series of tests with a group of potential users is currently in progress.}, }
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P. Eynard, M. Mas, A. Penciolelli, C. Tinet, G. Deffuant
Développement d'un outil pour la modélisation du risque ESST dans les filières viandes et co-produits, pour l'aide à la décision en matière de réglementation et de prévention : rapport de recherche
2001
abs web bib

To reduce the risk of transfer of bovine spongiform encephalopathy infectivity to man and cattle, specified risk material have been excluded from entering the food chain. A stochastic model has been developed to compute a risk level taking into account the technical features of the process as well as the characteristics of the risk management system. The model computes flows of products - especially those of tissues which potentially carry BSE infectivity. Software including a man-machine interface for the designing of models and a tree computation algorithm allows a number of applications such as comparing scenarios or ranking the preventive measures according to their efficiency in risk reduction. These applications are illustrated using to particular models : i) the slaughtering process, ii) the collection, rendering and eventually destruction of wastes. Then the possibility of combining these two models in order to characterise the risk along the all slaughtering and waste processing chain is demonstrated. / Pour réduire le risque de transmission de l'encéphalopathie spongiforme bovine à l'homme et à l'animal, les matières à risques sont retirées de la chaîne alimentaire. Un modèle stochastique a été développé afin d'apprécier ce risque en tenant compte des défaillances possibles du système de retrait ainsi que des caractéristiques techniques du procédé. Ce modèle calcule les flux de matières -et donc en particulier des tissus potentiellement vecteurs de l'agent de l'ESB- au cours des procédés de transformation de la filière viande et des filières des co-produits. Une maquette logicielle, composée d'une interface de création du modèle de filière associée à un algorithme de parcours d'arbre, permet plusieurs applications de la méthode : comparaison de scénarios, hiérarchisation des mesures de maîtrise du risque. Elles sont illustrées dans le rapport grâce à deux modèles : celui du procédé d'abattage et celui de la collecte et de la transformation des déchets. On montre ensuite comment les résultats obtenus sur ces deux modèles partiels peuvent être combinés pour aboutir à une caractérisation globale du risque.
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@techreport{PUB00010058, author = {Eynard, P. and Mas, M. and Penciolelli, A. and Tinet, C. and Deffuant, G.}, title = {Développement d'un outil pour la modélisation du risque ESST dans les filières viandes et co-produits, pour l'aide à la décision en matière de réglementation et de prévention : rapport de recherche}, title = {Modeling the risk related to ESST in the meat and by-products production chains : a tool for decision making: research report}, pages = {27}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00010058}, year = {2001}, affiliation = {CEMAGREF CLERMONT FERRAND UR TSCF FRA ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC}, number = {01/0787 ; TS01 13}, abstract = {To reduce the risk of transfer of bovine spongiform encephalopathy infectivity to man and cattle, specified risk material have been excluded from entering the food chain. A stochastic model has been developed to compute a risk level taking into account the technical features of the process as well as the characteristics of the risk management system. The model computes flows of products - especially those of tissues which potentially carry BSE infectivity. Software including a man-machine interface for the designing of models and a tree computation algorithm allows a number of applications such as comparing scenarios or ranking the preventive measures according to their efficiency in risk reduction. These applications are illustrated using to particular models : i) the slaughtering process, ii) the collection, rendering and eventually destruction of wastes. Then the possibility of combining these two models in order to characterise the risk along the all slaughtering and waste processing chain is demonstrated. / Pour réduire le risque de transmission de l'encéphalopathie spongiforme bovine à l'homme et à l'animal, les matières à risques sont retirées de la chaîne alimentaire. Un modèle stochastique a été développé afin d'apprécier ce risque en tenant compte des défaillances possibles du système de retrait ainsi que des caractéristiques techniques du procédé. Ce modèle calcule les flux de matières -et donc en particulier des tissus potentiellement vecteurs de l'agent de l'ESB- au cours des procédés de transformation de la filière viande et des filières des co-produits. Une maquette logicielle, composée d'une interface de création du modèle de filière associée à un algorithme de parcours d'arbre, permet plusieurs applications de la méthode : comparaison de scénarios, hiérarchisation des mesures de maîtrise du risque. Elles sont illustrées dans le rapport grâce à deux modèles : celui du procédé d'abattage et celui de la collecte et de la transformation des déchets. On montre ensuite comment les résultats obtenus sur ces deux modèles partiels peuvent être combinés pour aboutir à une caractérisation globale du risque.}, }
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S. Huet, G. Deffuant
Calcul de l'impact économique de la conversion à l'agriculture biologique : projet IMAGES, modèle Allier Conversion à l'agriculture biologique
2001
abs web bib

The objective was to simulate the calculation that farmers from Allier department can make when they have to take a decision about using or not an environmental measure. Farms diversity has been taken into account. The calculation was based on three steps: identification of available data and possible variation of Images model parameters - modelling of the calculation - selection of parameters to be used for impact calculation by Images model. / Ce travail a pour objectif de définir un calcul d'impact économique de la conversion à l'agriculture biologique pour les exploitations agricoles du département de l'Allier. Il s'inscrit dans le cadre du modèle élaboré dans le projet IMAGES, qui simule les processus de décision des agriculteurs confrontés au choix d'adopter ou non une mesure agri-environnementale. L'objectif est donc ici de simuler le calcul que peuvent faire les agriculteurs au moment de la décision, c'est-à-dire en tenant compte de nombreuses incertitudes. Le modèle IMAGES a pour objectifs de simuler les décisions de l'ensemble de la population des agriculteurs de l'Allier, en prenant au maximum en compte la diversité des exploitations. Le calcul d'impact économique de la conversion doit donc être applicable avec le maximum de réalisme à l'ensemble de cette diversité. Ce type de calcul n'existe pas dans la littérature. En effet, il n'existe pour le moment aucune référence solide, applicable dans tous les cas de figure et admise par tous, qui permette de mesurer les rendements en agriculture biologique. Ainsi, pour réaliser un tel calcul, trois grandes étapes sont nécessaires : - identification des données disponibles et des plages de variations possibles des paramètres du modèle - modélisation du calcul réalisé par le technicien de la Chambre d'Agriculture de l'Allier - exploration des paramètres du modèle et sélection de jeux de paramètres à utiliser pour le calcul d'impact du modèle Images par élimination des résultats paraissant aberrants. L'innovation principale de ce travail est de proposer des évaluations du potentiel de l'agriculture biologique en Auvergne et dans l'Allier en terme d'exploitations économiquement intéressées à se convertir (nombre d'exploitations, caractéristiques, ...).
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@techreport{PUB00009543, author = {Huet, S. and Deffuant, G.}, title = {Calcul de l'impact économique de la conversion à l'agriculture biologique : projet IMAGES, modèle Allier Conversion à l'agriculture biologique}, title = {Effect calculation of conversion to biologic agriculture on economy: IMAGES project, Allier Department model Conversion to biologic agriculture}, pages = {77}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00009543}, year = {2001}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC}, number = {01/0399 ; IAS 78}, abstract = {The objective was to simulate the calculation that farmers from Allier department can make when they have to take a decision about using or not an environmental measure. Farms diversity has been taken into account. The calculation was based on three steps: identification of available data and possible variation of Images model parameters - modelling of the calculation - selection of parameters to be used for impact calculation by Images model. / Ce travail a pour objectif de définir un calcul d'impact économique de la conversion à l'agriculture biologique pour les exploitations agricoles du département de l'Allier. Il s'inscrit dans le cadre du modèle élaboré dans le projet IMAGES, qui simule les processus de décision des agriculteurs confrontés au choix d'adopter ou non une mesure agri-environnementale. L'objectif est donc ici de simuler le calcul que peuvent faire les agriculteurs au moment de la décision, c'est-à-dire en tenant compte de nombreuses incertitudes. Le modèle IMAGES a pour objectifs de simuler les décisions de l'ensemble de la population des agriculteurs de l'Allier, en prenant au maximum en compte la diversité des exploitations. Le calcul d'impact économique de la conversion doit donc être applicable avec le maximum de réalisme à l'ensemble de cette diversité. Ce type de calcul n'existe pas dans la littérature. En effet, il n'existe pour le moment aucune référence solide, applicable dans tous les cas de figure et admise par tous, qui permette de mesurer les rendements en agriculture biologique. Ainsi, pour réaliser un tel calcul, trois grandes étapes sont nécessaires : - identification des données disponibles et des plages de variations possibles des paramètres du modèle - modélisation du calcul réalisé par le technicien de la Chambre d'Agriculture de l'Allier - exploration des paramètres du modèle et sélection de jeux de paramètres à utiliser pour le calcul d'impact du modèle Images par élimination des résultats paraissant aberrants. L'innovation principale de ce travail est de proposer des évaluations du potentiel de l'agriculture biologique en Auvergne et dans l'Allier en terme d'exploitations économiquement intéressées à se convertir (nombre d'exploitations, caractéristiques, ...).}, }
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G. Deffuant, F. Amblard, S. Huet, S. Bernard, N. Ferrand, J.P. Bousset, G. Amon, J. Henriot
Projet européen IMAGES :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 Rapport d'avancement du cas Allier
2000
abs web bib

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 (constitué 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. Intéractions sociales et calculs économiques se mêlent étroitement dans ce processus. L'objectf 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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@techreport{PUB00009312, 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.}, title = {Projet européen IMAGES :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 Rapport d'avancement du cas Allier}, pages = {21}, url = {http://irsteadoc.irstea.fr/cemoa/PUB00009312}, year = {2000}, affiliation = {CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND LISC ; CEMAGREF CLERMONT FERRAND DFCF ; CEMAGREF CLERMONT FERRAND DFCF ; CEMAGREF CLERMONT FERRAND DFCF}, number = {00/0843}, abstract = {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 (constitué 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. Intéractions sociales et calculs économiques se mêlent étroitement dans ce processus. L'objectf 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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