Système complexe adaptatif

Un système complexe adaptatif ou système complexe auto-adaptatif est l'ensemble des cas particuliers d'un système complexe capable de s'adapter à son environnement par des expériences d'apprentissage. Le terme anglais complex adaptive systems (CAS) a été introduit par l'Institut interdisciplinaire de Santa Fe notamment par John H. Holland et Murray Gell-Mann. Observations En 1962, Vero Copner Wynne-Edwards a observé la sélection de groupe à l’œuvre dans les communautés d’oiseaux sauvages. Il a conclu que les individus capables de trouver des solutions aux problèmes sont récompensés par la domination, une nourriture variée, un logement confortable et des privilèges sexuels ; à l’inverse, les individus étant dans l’ sont isolés par le réseau social, puis appauvris avant d’être éliminés. Par ailleurs, a démontré qu’un réseau social qui applique les règles du constitue la plus puissante machine à apprendre et gagne presque à tous les coups. Howard Bloom estime que la règle

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vignette|Le processus de fonctionnement de l'organisation en tant que système ouvert La théorie générale des systèmes est l'étude interdisciplinaire des systèmes. Un système est un conglomérat cohésif

vignette|Visualisation sous forme de graphe d'un réseau social illustrant un système complexe. Un système complexe est un ensemble constitué d'un grand nombre d'entités en interaction dont l'intégrati

Un système est un ensemble d' interagissant entre eux selon certains principes ou règles. Par exemple une molécule, le système solaire, une ruche, une société humaine, un parti, une armée etc. Un s

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Predictors and predictands of linear response in spatially extended systems

Umberto Maria Tomasini

The goal of response theory, in each of its many statistical mechanical formulations, is to predict the perturbed response of a system from the knowledge of the unperturbed state and of the applied perturbation. A new recent angle on the problem focuses on providing a method to perform predictions of the change in one observable of the system using the change in a second observable as a surrogate for the actual forcing. Such a viewpoint tries to address the very relevant problem of causal links within complex system when only incomplete information is available. We present here a method for quantifying and ranking the predictive ability of observables and use it to investigate the response of a paradigmatic spatially extended system, the Lorenz '96 model. We perturb locally the system and we then study to what extent a given local observable can predict the behaviour of a separate local observable. We show that this approach can reveal insights on the way a signal propagates inside the system. We also show that the procedure becomes more efficient if one considers multiple acting forcings and, correspondingly, multiple observables as predictors of the observable of interest.

SPRINGER HEIDELBERG2021

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Three Essays on Methodologies for Dynamic Modeling of Emerging Socio-technical Systems

Mohammad Amin Dehdarian

Socio-technical energy transitions are long-term and major transformations in incumbent energy infrastructures. They include fundamental changes in technologies as well as institutions and social patterns. Transition studies are primarily focused on frameworks for analyzing the entire transition process by investigating the historical cases of transitions. A multi-phase approach to transition posits this process begins with a pre-development phase characterized by technological and institutional lock-ins, and resistance from incumbent actors. This period is critical for a forward-looking approach to transitions, since early developments shape path-dependent and irreversible processes leading to the emergence of new transition pathways. However, our understanding about the mechanisms and dynamics of this phase is still very limited. This is mainly due to lack of data, weak conceptualization and the necessity of developing new methods proper to deal with these limitations. This dissertation develops methodologies for investigating some complex questions arising in the pre-development phase, by focusing on the case of smart grid development. The first essay uses insights from modeling interventions in complex systems and builds a System Dynamics model to investigate the cost allocation problem of smart metering roll-out. The second essay takes ideas from Technological Innovation System approach and develops a method to analyze the emergence of spatial diversity in smart grid development by combining Social Network Analysis and Agent-Based Modeling. The third essay builds on ideas from network theory and evolutionary modeling to develop a method for identifying the main path of knowledge development and analyzing knowledge trajectories in smart grid initiatives.

EPFL2017

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A prescriptive Dirichlet power allocation policy with deep reinforcement learning

Yuan Tian

Prescribing optimal operation based on the condition of the system, and thereby potentially prolonging its remaining useful lifetime, has tremendous potential in terms of actively managing the availability, maintenance, and costs of complex systems. Reinforcement learning (RL) algorithms are particularly suitable for this type of problem given their learning capabilities. A special case of a prescriptive operation is the power allocation task, which can be considered as a sequential allocation problem whereby the action space is bounded by a simplex constraint. A general continuous action-space solution of such sequential allocation problems has still remained an open research question for RL algorithms. In continuous action space, the standard Gaussian policy applied in reinforcement learning does not support simplex constraints, while the Gaussian-softmax policy introduces a bias during training. In this work, we propose the Dirichlet policy for continuous allocation tasks and analyze the bias and variance of its policy gradients. We demonstrate that the Dirichlet policy is bias-free and provides significantly faster convergence, better performance, and better robustness to hyperparameter changes as compared to the Gaussian-softmax policy. Moreover, we demonstrate the applicability of the proposed algorithm on a prescriptive operation case in which we propose the Dirichlet power allocation policy and evaluate its performance on a case study of a set of multiple lithium-ion (Li-I) battery systems. The experimental results demonstrate the potential to prescribe optimal operation, improving the efficiency and sustainability of multi-power source systems.

2022

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PHYS-460: Nonlinear dynamics, chaos and complex systems

The course provides students with the tools to approach the study of nonlinear systems and chaotic dynamics. Emphasis is given to concrete examples and numerical applications are carried out during the exercise sessions.

PHYS-435: Statistical physics III

This course introduces statistical field theory, and uses concepts related to phase transitions to discuss a variety of complex systems (random walks and polymers, disordered systems, combinatorial optimisation, information theory and error correcting codes).

ME-524: Advanced control systems

This course covers some theoretical and practical aspects of robust and adaptive control. This includes H-2 and H-infinity control in model-based and data-driven framework by convex optimization, direct, indirect and switching adaptive control. The methods are implemented in a hands-on lab.