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See detailModel-free reinforcement learning as mixture learning
Vlassis, Nikos UL; Toussaint, M.

in Proceedings of the 26th International Conference on Machine Learning (2009)

We cast model-free reinforcement learning as the problem of maximizing the likelihood of a probabilistic mixture model via sampling, addressing both the infinite and finite horizon cases. We describe a ... [more ▼]

We cast model-free reinforcement learning as the problem of maximizing the likelihood of a probabilistic mixture model via sampling, addressing both the infinite and finite horizon cases. We describe a Stochastic Approximation EM algorithm for likelihood maximization that, in the tabular case, is equivalent to a non-bootstrapping optimistic policy iteration algorithm like Sarsa(1) that can be applied both in MDPs and POMDPs. On the theoretical side, by relating the proposed stochastic EM algorithm to the family of optimistic policy iteration algorithms, we provide new tools that permit the design and analysis of algorithms in that family. On the practical side, preliminary experiments on a POMDP problem demonstrated encouraging results. [less ▲]

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See detailModel-Free Robust Adaptive Control for Flexible Rubber Objects Manipulation
Jasim, Ibrahim UL; Plapper, Peter UL; Voos, Holger UL

in 20th IEEE International Conference on Emerging Technologies and Factory Automation (ETFA 2015), Luxembourg 8-11 September 2015 (2015, September 08)

This article addresses the control problem of robots with unknown dynamics and manipulating flexible rubber objects of unknown elasticity. The manipulated rubber object is considered to be interacting ... [more ▼]

This article addresses the control problem of robots with unknown dynamics and manipulating flexible rubber objects of unknown elasticity. The manipulated rubber object is considered to be interacting with arbitrarily-switched constraints. Such a kind of robot system is shown to have switched impedance parameters during a task execution that results in an unknown hybrid nonlinear system with arbitrarily switched signal. A Model-Free Robust Adaptive Control (MFRAC) strategy is proposed for such a robot system that is proved to guarantee global stable performance with all closed loop signals are assured to be bounded. The suggested MFRAC strategy relies on the synergy of the Adaptive Fuzzy System (AFS), the Sliding Mode Control (SMC), and the notion of Common Lyapunov Functions (CLF). The AFS relaxes the need for knowing the precise robot dynamics, the SMC adds robustness against the drift of the dynamics parameters, and the CLF accommodates the arbitrary switching of the impedance parameters. The bounds of the impedance parameters are adapted online and incorporated in the MFRAC design such that a convergent performance is achieved. Experiment is conducted on a KUKA Lightweight Robot (LWR) doing flexible rubber peg-in-hole assembly process that falls in the category of systems considered in this article. From the experimental results, excellent tracking performance is reported when using the proposed MFRAC strategy for the considered robotic system despite the dynamics anonymity and the unknown impedance parameters arbitrary switching. [less ▲]

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See detailUn modèle cellulaire et dynamique de dispersion et ségrégation spatiale périurbaine
Caruso, Geoffrey UL

in XXXIX ème Colloque de l’Association de Science Régionale de Langue Française (2003)

Cette contribution propose d’explorer les processus de dispersion des ménages et de ségrégation par le revenu au sein d’un espace périurbain. La méthode consiste à simuler un modèle économique ... [more ▼]

Cette contribution propose d’explorer les processus de dispersion des ménages et de ségrégation par le revenu au sein d’un espace périurbain. La méthode consiste à simuler un modèle économique urbain avec deux types d’externalités de voisinage sur un espace cellulaire. Il permet la mise en place de processus dynamiques locaux endogènes et offre un éclairage sur la relation qui unit la morphologie des espaces périurbains et les caractéristiques des agents économiques qui s’y localisent. Des structures spatiales diverses sont générées sur deux configurations données des lots fonciers. Les équilibres présentent des structures concentriques constituées de multiples anneaux mais aussi, au cours des étapes de la croissance de la ville, des processus de dégradation cumulée ou des structures plus indépendantes de la distance. [less ▲]

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See detailUn modèle cellulaire et dynamique de dispersion et ségrégation spatiale périurbaine
Caruso, Geoffrey UL

in Buisson, Marie-Andrée; Mignot, Dominique (Eds.) Concentration économique et ségréegation spatiale (2005)

Cette contribution propose d’explorer les processus de dispersion des ménages et de ségrégation par le revenu au sein d’un espace périurbain. La méthode consiste à simuler un modèle économique urbain avec ... [more ▼]

Cette contribution propose d’explorer les processus de dispersion des ménages et de ségrégation par le revenu au sein d’un espace périurbain. La méthode consiste à simuler un modèle économique urbain avec deux types d’externalités de voisinage sur un espace cellulaire. Il permet la mise en place de processus dynamiques locaux endogènes et offre un éclairage sur la relation qui unit la morphologie des espaces périurbains et les caractéristiques des agents économiques qui s’y localisent. Des structures spatiales diverses sont générées sur deux configurations données des lots fonciers. Les équilibres présentent des structures concentriques constituées de multiples anneaux mais aussi, au cours des étapes de la croissance de la ville, des processus de dégradation cumulée ou des structures plus indépendantes de la distance. [less ▲]

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See detailUn modèle en pistes causales pour appréhender la complexité du phénomène d’accrochage scolaire lors de la transition primaire-secondaire
Poncelet, Débora UL; Lafontaine, Dominique

in Mesure et Evaluation en Education [=MEE] (2011), 34(1), 55-95

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See detail« Le modèle Internet en question (années 1970-2010) »
Musiani, Francesca; Schafer, Valerie UL

in Flux : Cahiers Scientifiques Internationaux Réseaux et Territoires = International Scientific Quarterly on Networks and Territories (2011), 3

Cet article se propose de montrer comment le « modèle Internet » – entendu comme un écosystème en évolution constante, sous l’effet du développement du Web, de ses usages commerciaux et grand public, des ... [more ▼]

Cet article se propose de montrer comment le « modèle Internet » – entendu comme un écosystème en évolution constante, sous l’effet du développement du Web, de ses usages commerciaux et grand public, des (re)compositions de la chaî- ne de valeur Internet – pose, depuis le développement d’Arpanet à la fin des années 1960, des questions de modélisa- tion et de gestion des flux. [less ▲]

Detailed reference viewed: 32 (0 UL)
See detailUn modèle multi-agents de structuration sociale de la ville
Lemoy, Rémi UL; Raux, Charles; Jensen, Pablo

in Antoni, Jean-Philippe (Ed.) Modéliser la ville. Forme urbaine et politiques de transport (2010)

Detailed reference viewed: 24 (0 UL)
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See detailModèles de comportements collectifs et coopératifs
Provitolo, Damienne; Frankhauser, Pierre; Morer, Myriam et al

in Dominique, Frankhauser Pierre Et Ansel (Ed.) La Décision d'Habiter Ici ou Ailleurs (2012)

Le choix résidentiel est considéré comme un acte individuel ou celui d'un " mini-groupe " (famille) qui est conditionné par des références collectives. De ce fait, il s'appuie sur des informations ... [more ▼]

Le choix résidentiel est considéré comme un acte individuel ou celui d'un " mini-groupe " (famille) qui est conditionné par des références collectives. De ce fait, il s'appuie sur des informations (renommée de quartiers, d'une école, accessibilité à des services, commerces ...) mais il contribue également à l'émergence de tendances (préférence de certains modes de vie et de quartiers ...) qui peuvent \^etre à l'origine de flux migratoires. Ces derniers participent à l'émergence de nouvelles configurations spatiales à l'échelle d'une ville, donc de phénomènes macroscopiques. De telles tendances sont donc le résultat d'interactions entre individus et groupe sociaux, entre individus et société, ce qui nous amène à considérer les phénomènes émergents dans ce chapitre d'ouvrage. Afin d'aborder les comportements émergents dans le domaine de la mobilité quotidienne et résidentielle, quatre théories, qui constituent l'ossature de ce chapitre, sont présentées : deux d'entre elles s'inscrivent dans des champs disciplinaires, à savoir la physique et la psychologie sociale, tandis que les deux autres sont du domaine des systèmes complexes. Il s'agit respectivement des théories de la synergétique (issue de la physique des lasers) et de la dissonance cognitive (issue de la psychologie sociale) et des théories de l'auto-organisation critique (Bak (1996)) et des jeux (von Neumann (1944)). Le choix de ces quatre cadres théoriques n'est pas anodin. Ces derniers permettent, du point de vue du théoricien et du modélisateur, de centrer l'analyse des phénomènes émergents autour des interactions et des jeux d'échelles, autour de l'étude des phénomènes critiques et des points de rupture (synergétique, auto-organisation critique) ou des équilibres (usage de la théorie des jeux coopératifs et non coopératifs en économie), et autour des dynamiques lentes et rapides des systèmes. Les auteurs ont pris le parti d'associer à chacune de ces présentations théoriques des modèles, certains con cus spécifiquement dans le cadre de du projet ECDESUP, d'autres construits par nos prédécesseurs. [less ▲]

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See detailModèles de mesure et évaluation des compétences complexes
Burton, Réginald UL; Dierendonck, Christophe UL

in Actes du 16e congrès de l’Association Mondiale des Sciences de l’Education (AMSE). (2010)

Detailed reference viewed: 36 (9 UL)
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See detailModèles pour le contenu des tâches d’assemblage de faces géométriques et difficulté des items
Dickes, Paul; Houssemand, Claude UL; Reuter, Monique

in Psychologie Française (1996), 41

Deux modèles théoriques pour décrire l'univers des configurations à quatre faces et deux couleurs dans une tâche d'assemblage de type Kohs sont proposés. Le premier se base sur les relations qui existent ... [more ▼]

Deux modèles théoriques pour décrire l'univers des configurations à quatre faces et deux couleurs dans une tâche d'assemblage de type Kohs sont proposés. Le premier se base sur les relations qui existent entre les faces et le second sur les caractéristiques distinctives entre les items. L'isomorphisme entre les deux modèles est souligné. Le modèle relationnel explique 49% et le modèle en saillance 42% de la variance de la difficulté des 1296 items de l'univers, déterminée par une recherche empirique avec des enfants et des étudiants. L'utilité des deux modèles est discutée. [less ▲]

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See detailModeling a BSG-E automotive system with the Timing augmented description language
Peraldi-Frati, M.-A.; Goknil, A.; Adedjouma, Morayo UL et al

in Proceedings of 5th International Symposium of Leveraging Applications of Formal Methods, Verification and Validation. Applications and Case Studies (2012)

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See detailModeling Adsorption and Reactions of Organic Molecules at Metal Surfaces
Liu, Wei; Tkatchenko, Alexandre UL; Scheffler, Matthias

in ACCOUNTS OF CHEMICAL RESEARCH (2014), 47(11, SI), 3369-3377

CONSPECTUS: The understanding of adsorption and reactions of (large) organic molecules at metal surfaces plays an increasingly important role in modern surface science and technology. Such hybrid ... [more ▼]

CONSPECTUS: The understanding of adsorption and reactions of (large) organic molecules at metal surfaces plays an increasingly important role in modern surface science and technology. Such hybrid inorganic/organic systems (HIOS) are relevant for many applications in catalysis, light emitting diodes, single-molecule junctions, molecular sensors and switches, and photovoltaics. Obviously, the predictive modeling and understanding of the structure and stability of such hybrid systems is an essential prerequisite for tuning their electronic properties and functions. At present, density-functional theory (DFT) is the most promising approach to study the structure, stability, and electronic properties of complex systems, because it can be applied to both molecules and solids comprising thousands of atoms. However state-of-the-art approximations to DFT do not provide a consistent and reliable description for HIOS, which is largely due to two issues: (i) the self-interaction of the electrons with themselves arising from the Hartree term of the total energy that is not fully compensated in approximate exchange-correlation functionals, and (ii) the lack of long-range part of the ubiquitous van der Waals (vdW) interactions. The self-interaction errors sometimes lead to incorrect description of charge transfer and electronic level alignment in HIOS, although for molecules adsorbed on metals these effects will often cancel out in total energy differences. Regarding vdW interactions, several promising vdW-inclusive DFT-based methods have been recently demonstrated to yield remarkable accuracy for intermolecular interactions in the gas phase. However, the majority of these approaches neglect the nonlocal collective electron response in the vdW energy tail, an effect that is particularly strong in condensed phases and at interfaces between different materials. Here we show that the recently developed DFT+vdW(surf) method that accurately accounts for the collective electronic response effects enables reliable modeling of structure and stability for a broad class of organic molecules adsorbed on metal surfaces. This method was demonstrated to achieve quantitative accuracy for aromatic hydrocarbons (benzene, naphthalene, anthracene, and diindenoperylene), C-60, and sulfur/oxygen-containing molecules (thiophene, NTCDA, and PTCDA) on dose-packed and stepped metal surfaces, leading to an overall accuracy of 0.1 angstrom in adsorption heights and 0.1 eV in binding energies with respect to state-of-the-art experiments. An unexpected finding is that vdW interactions contribute more to the binding of strongly bound molecules on transition-metal surfaces than for molecules physisorbed on coinage metals. The accurate inclusion of vdW interactions also significantly improves tilting angles and adsorption heights for all the studied molecules, and can qualitatively change the potential-energy surface for adsorbed molecules with flexible functional groups. Activation barriers for molecular switches and reaction precursors are modified as well. [less ▲]

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See detailModeling and Analysis of CPU Usage in Safety-Critical Embedded Systems to Support Stress Testing
Nejati, Shiva UL; Di Alesio, Stefano; Sabetzadeh, Mehrdad UL et al

in 15th ACM/IEEE International Conference on Model Driven Engineering Languages & Systems (2012)

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See detailModeling and Analysis of UVB Influence on IL-1 induced NF-kappaB Signaling
Witt, Johannes; Husser, Sebastian; Kulms, Dagmar et al

in Proceedings of the FOSBE, September 9-12, Stuttgart, Germany (2007)

Enhancement of UVB-induced apoptosis has recently been reported upon co-stimulation of cells with IL-1. The phenomenon has been shown to be NF-kappaB dependent and coincides with a sustained absence of ... [more ▼]

Enhancement of UVB-induced apoptosis has recently been reported upon co-stimulation of cells with IL-1. The phenomenon has been shown to be NF-kappaB dependent and coincides with a sustained absence of the inhibitor of NF-kappaB, IkappaBalpha. The exact mechanisms are the subject of present research. In order to investigate the behavior of IkappaBalpha, a mathematical model for the IL-1 receptor is developed based on ordinary differential equations. It is coupled with an existing NF-kappaB signaling module and parameterized using experimental and literature data. The model provides a more realistic input for the NF-kappaB module and is suitable for fitting the experimental data of IkappaBalpha following IL-1 stimulation. It is used to test and reject the hypothesis that the sustained absence of IkappaBalpha upon IL-1+UVB stimulation is due to an altered internalization behavior of the IL-1 receptor. [less ▲]

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See detailModeling and Control of Aerial Manipulation Vehicle with Visual sensor
Kannan, Somasundar UL; Olivares Mendez, Miguel Angel UL; Voos, Holger UL

in Second Workshop on Research, Development and Education on Unmanned Aerial Systems (RED-UAS 2013) (2013, November)

Modeling and control of a Quadrotor with robotic arm which uses vision sensor is discussed. A quadrotor model coupled with a two link manipulator is first developed and then the integrated control ... [more ▼]

Modeling and control of a Quadrotor with robotic arm which uses vision sensor is discussed. A quadrotor model coupled with a two link manipulator is first developed and then the integrated control mechanism is investigated. An Image Based Visual Servo system is introduced and then used with the aerial manipulator to successfully perform specific tasks of positioning and stabilization during manipulation. [less ▲]

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See detailModeling and Evaluating Cooperation in Multi-Context Systems using Conviviality
Efthymiou, Vasileios UL; Caire, Patrice UL; Bikakis, Antonis

in Proceedings of BNAIC 2012 The 24th Benelux Conference on Artificial Intelligence (2012)

Multi-Context Systems is a rule-based representation model for distributed, heterogeneous knowledge agents, which cooperate by sharing parts of their local knowledge through a set of bridge rules also ... [more ▼]

Multi-Context Systems is a rule-based representation model for distributed, heterogeneous knowledge agents, which cooperate by sharing parts of their local knowledge through a set of bridge rules also known as mappings. The concept of conviviality was recently proposed for modeling and measuring cooperation among agents in multiagent systems. In this paper, we describe how conviviality can be used to model and evaluate cooperation in Multi-Context Systems. As a potential application, we also propose a conviviality based method for inconsistency resolution based on the idea that the optimal solution is the one that minimally decreases the conviviality of the system. [less ▲]

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See detailModeling and experimental validation of the signal transduction via the Escherichia coli sucrose phospho transferase system.
Sauter, Thomas UL; Gilles, E. D.

in Journal of Biotechnology (2004), 110(2), 181-99

Bacterial signal processing was investigated concerning the sucrose phosphotransferase system (sucrose PTS) in the bacterium Escherichia coli as an example. The about 20 different phosphotransferase ... [more ▼]

Bacterial signal processing was investigated concerning the sucrose phosphotransferase system (sucrose PTS) in the bacterium Escherichia coli as an example. The about 20 different phosphotransferase systems (PTSs) of the cell fulfill besides the transport of various carbohydrates, also the function of one signal processing system. Extra- and intracellular signals are converted within the PTS protein chain to important regulatory signals affecting, e.g. carbon metabolism and chemotaxis. A detailed dynamical model of the sucrose PTS was developed describing transport and signal processing function. It was formulated using a detailed description of complex formation and phosphate transfer between the chain proteins. Model parameters were taken from literature or were identified with own experiments. Simulation studies together with experimental hints showed that the dynamic behavior of phosphate transfer in the PTS runs within 1 s. Therefore a description of steady state characteristics is sufficient for describing the signaling properties of the sucrose PTS. A steady state characteristic field describes the degree of phosphorylation of the PTS protein EIIACrr as a function of the input variables extracellular sucrose concentration and intracellular phosphoenolpyruvate (PEP):pyruvate ratio. The model has been validated with different experiments performed in a CSTR using a sucrose positive E. coli W3110 derivative. A method for determining intracellular metabolite concentrations has been developed. A sample preparation technique using a boiling ethanol buffer solution was successfully applied. The PTS output signal degree of phosphorylation of EIIACrr was also measured. Steady state conditions with varying dilution rate and dissolved oxygen concentration and dynamical variations applying different stimuli to the culture were considered. Pulse, and stop feeding experiments with limiting sucrose concentrations were performed. Simulation and experimental results matched well. The same holds for the expanded sucrose PTS and glycolysis model. [less ▲]

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See detailModeling and Reconfiguration of critical Business Processes for the purpose of a Business Continuity Management respecting Security Risk and Compliance requirements at Credit Suisse using Algebraic Graph Transformation
Brandt, Christoph; Hermann, Frank UL; Engel, Thomas UL

in Enterprise Distributed Object Computing Conference Workshops, 2009. EDOCW 2009. 13th, Proc. International Workshop on Dynamic and Declarative Business Processes (DDBP 2009) (2009)

Critical business processes can fail. Therefore, continuity processes are needed as backup solutions. At the same time business processes are required to comply with security, risk and compliance ... [more ▼]

Critical business processes can fail. Therefore, continuity processes are needed as backup solutions. At the same time business processes are required to comply with security, risk and compliance requirements. In the context discussed here, they should be modeled in a decentralized local and declarative way, including methodological support by tools. By discussing a simplified loan granting process in the context of a Business Continuity Management System at Credit Suisse, we show how algebraic graph transformation can contribute a methodologically sound solution being compatible with all these requirements in a coherent way. As a consequence significant benefits of automation and quality can be realized. The presented contribution is theoretically sound and implementable by the people in the field. [less ▲]

Detailed reference viewed: 112 (3 UL)