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Optimisation stochastique de systèmes complexes composés d'énergies renouvelables.
No full textIn this thesis, we investigate the impact of integrating energy considerations into production planning problems.On one side, we focus on modeling complex systems under uncertainty.On the other side, we explore approaches to translate the concept of fairness in mathematical models.The first part focuses on jointly optimizing production planning and energy supply management in an industrial setting with renewable energy and storage systems.Formulated as a multistage stochastic problem with continuous and binary variables, it presents challenges due to its size, uncertainties, and integer constraints.We explore various solution strategies comparing their performance across different setups.The second part introduces a new methodology to solve Multistage Stochastic mixed-binary Linear Programs (MSbLP), with stagewise independent noises.First, we develop an abstract framework, relying on the scenario tree structure, that aims to coordinate SDDP-- that solves the continuous relaxation efficiently-- and Branch-and-Bound procedures-- that deal with binary variables.This leads to an exact algorithm to solve MSbLPs, relying on partial relaxations of the problem.The algorithm consists of iteratively growing a small subtree on which the integrality constraints are maintained.The rest of the problem, continuously relaxed, is represented through value functions obtained via SDDP.This allows to balance between solution accuracy and computational feasibility.We discuss heuristics inspired by B&B techniques to grow this subtree and evaluate their effectiveness in various industrial-inspired problem settings.The third part shifts focus to fairness in aggregating prosumers in electricity markets.We investigate fair resource allocation strategies that ensure each participant benefits from aggregation.Using acceptability constraints and fairness operators,we design multi-period stochastic models that incorporate fairness by construction.Unlike traditional financial compensation mechanisms, our approach emphasizes fair decision-making in dynamic, uncertain environments, tested on both deterministic and stochastic models.Dans cette thèse, nous nous intéressons à l'intégration d'aspects énergétiques dans les problèmes de planification de la production. D'une part, nous traitons la modélisation de systèmes complexes sous incertitude et développons des méthodes de résolution adaptées. D'autre part, nous explorons des approches pour traduire le concept d'équité mathématiquement. Dans la première partie, nous proposons un modèle qui vise à optimiser conjointement la planification de la production d'une usine et la gestion de son approvisionnement en énergie, en présence de sources d'énergie renouvelables et de batteries. Le problème est formulé comme un PSMLB.Sa résolution est numériquement difficile en raison de sa taille, de la présence incertitudes et des contraintes d'intégrité. Nous explorons diverses stratégies de résolution (MPC, SDP) puis développons une heuristique qui utilise l'algorithme SDDP. En deuxième partie, nous élaborons une nouvelle méthodologie pour résoudre des PSMLBs. Cette méthodologie s'inscrit dans un cadre abstrait, qui repose sur la structure des arbres de scénarios, et dont le but est de coordonner SDDP et le B&B. Cela conduit à un algorithme efficace et exact pour résoudre les PSMLBs. Plus précisément, l'algorithme résout itérativement des relaxations partielles du problème qui reposent sur la structure de sous-arbres, où l'intégrité est maintenue, les portions élaguées étant approximées à l'aide de SDDP. Cela permet de trouver un compromis entre qualité de la solution et temps de calcul. Enfin, nous proposons des heuristiques inspirées des techniques B&B pour faire grandir le sous-arbre. Enfin, la troisième partie se concentre sur l'équité dans un contexte d'agrégation des prosumers (ou grands consommateurs) sur les marchés de l'électricité. Nous examinons différentes manières de trouver une allocation des bénéfices équitables et qui garantissent que chaque participant bénéficie de l'agrégation. Nous concevons des modèles stochastiques multi-périodes intégrant l'équité par construction grâce à des contraintes d'acceptabilité et des opérateurs d'équité. Notre approche met l'accent sur une prise de décision équitable dans des environnements dynamiques et incertains
Marine snow morphology drives sinking and attenuation in the ocean interior
No full textInternational audienceSimultaneous measurements of marine snow (particles larger than 600 µm) morphologies, estimates of their in situ sinking speeds, and midwater attenuation in export plumes were performed for the first time using a biogeochemical (BGC)-Argo float equipped with optical and imaging sensors. The float was deployed and recovered after drifting for 1 year in the sluggish-flow regime of the Angola Basin. Six consecutive chlorophyll a and particulate matter accumulation events were recorded at the surface, each followed by an export plume of sinking aggregates. Objects larger than 600 µm were classified using machine learning recognition and clustered into four morphological categories of marine aggregates. Plankton images were validated by an expert in a few broad categories. Results show that different types of aggregates were produced and exported from the different blooms. The different morphological categories of marine snow had different sinking speeds and attenuation for a similar size, indicating the effect of morphology on sinking speed. However, a typical size-to-sinking relationship for two of the categories and over the larger observed size range (100 µm to a few millimeters) was also observed, indicating the importance of size for sinking. Surprisingly, in situ-calculated sinking speeds were constantly in the lower range of known values usually assessed ex situ, suggesting a methodological effect, which is discussed. Moving away from purely size-based velocity relationships and incorporating these additional morphological aggregate properties will help to improve the mechanistic understanding of particle sinking and provide more accurate flux estimates. When used from autonomous platforms at high frequency, they will also provide increased spatio-temporal resolution for the observation of intermittent export events naturally occurring or induced by human activities
The vicious circle of xenophobia: immigration and right wing populism
No full textInternational audienceWe investigate the bidirectional relationship between immigration and right-wing populism, which we characterize as a self-reinforcing dynamic process where anti-immigrant rhetoric and populist policies lead to a deterioration in the average education and skill level of immigrants. The deterioration in the ratio of high-skill to low-skill immigrants in turn fuels populist support and anti-immigration attitudes, creating what we call “the vicious circle of xenophobia.” We review some historical and contemporary studies that are suggestive of such a vicious circle. In particular, recent cross-country evidence shows that low-skill immigration tends to exacerbate populism, whereas high-skill immigration tends to mitigate it. Conversely, populist policies and xenophobic attitudes have a strong repulsive effect on highly skilled immigrants and result in adverse immigrant selection. We use the empirical results from those studies to inform a theoretical model of joint determination of immigrants’ skill ratio and right-wing populism levels. The model displays multiple equilibria, with the inferior equilibrium—corresponding to our vicious circle—characterized by high levels of right-wing populism and a high proportion of low-skill workers among immigrants. In this framework, structural trends such as Internet penetration, economic erosion of the middle class, demographic pressure from poor countries as well as adverse cyclical shocks make the good, efficient equilibrium less likely and the inferior equilibrium of explosive populism and adverse immigrants’ selection more likely
Shaping the Future of Mobility Culture: An Expert-Driven Policy Roadmap
No full textInternational audienceDaily mobility patterns vary across regions but share key similarities, shaped by spatial, social, economic, and cultural factors. Mobility can be seen as a “culture” in itself, and in Europe, this culture is currently undergoing significant evolution. The Horizon 2020 project REBALANCE, involving six participants from six European countries until 2022, sought to explore the values and culture of future mobility. The project’s goal was to encourage a paradigm shift in mobility policy, urging greater attention to social values in decision-making and alignment with the Sustainable Development Goals (SDGs).REBALANCE initiated discussions about the foundations of current mobility policies. By reflecting on existing frameworks, it brought together a broad network of experts and stakeholders to explore new mobility cultures and policies. The objective was to converge on a sustainable, shared vision and create a roadmap for a new mobility paradigm. What set REBALANCE apart was its focus on engaging high-level interdisciplinary thinkers who have traditionally not been involved in transport research. Philosophers, sociologists, psychologists, geographers, and legal experts played a crucial role in challenging the assumptions underlying conventional mobility paradigms. In addition to this interdisciplinary engagement, the project involved a group of visionaries and 14 transport experts. A key outcome was the creation of a Manifesto for a New Mobility Culture.The project aimed to significantly influence European public policies on mobility and transport. It examined the evolution of mobility culture, identifying emerging trends through expert insights. These trends were translated into future scenarios, distinguishing between desirable and probable trajectories. Through surveys across European countries and extensive input from experts and thinkers, REBALANCE articulated a vision for the future of mobility. This vision was formalized in a manifesto addressed to European policymakers, calling for integration into future public policies. Supported by a roadmap containing concrete actions, timelines, and policy guidance, the manifesto offered a plan to break free from outdated paradigms. Additionally, it underscored the importance of communication in shaping mobility culture, examined the public interest in mobility issues, and proposed new methods for evaluating mobility projects to better address the necessary changes.This presentation will focus on the roadmap and guide for future European mobility policies. It will detail the methodology employed to translate the REBALANCE vision into the manifesto and, ultimately, into the roadmap and policy guide. An innovative workshop, inspired by the Delphi method, was conducted to bring together experts, including scientists, associations, and industry representatives, to achieve a high level of consensus at every stage of the process
Effect of sediment composition and accumulation on pharmaceutical product spatial distributions at the suburban pond scale (Beulie pond, SNO Observil, France)
No full textInternational audiencePharmaceutical products (PPs) are found in several compartments of the environment, and are mostly emitted by wastewater treatment plants effluents. Their occurrence in the particulate phase, in opposition with the dissolved one, also promotes their occurrence in retention areas, where particles transported by streams settle. The study focuses on understanding how different constituents of pond sediment are distributed within a suburban pond, revealing patterns or hotspots of PPs accumulation. Results confirmed the heterogeneous spatial distributions of the granulometric fractions, total organic carbon, quantitative palynofacies, crystalline phase distributions and PPs contents. The delta preferentially concentrates total organic carbon (14.5 ± 2.2 %), and particularly terrigenous organic matter and neutral PPs, while the main decantation area accumulates mostly fine particles (58.2 ± 7.7 %), kaolinite, algal organic matter and cationic PPs. The potential role played by OM and kaolinite in PPs adsorption is supported by their respective spatial trends at the pond scale. Further attention should be paid to surface sediments components and PPs sensitivity to seasonal variations, especially in terms of flow, pH and oxygenation of the water-column. This spatial approach allowed to identify preferential accumulation and concentration areas within the pond, where the following extensive characterization of interface sediments highlighted the factor likely to influence PPs trapping within the pond
Hierarchy-based fuzzy segmentation and marker learning layer: theory and algorithms
No full textInternational audienceImage segmentation is inherently challenging because it is often difficult to automatically identify the object of interest in an image. To mitigate this, human-provided markers can be incorporated into the segmentation process, greatly improving accuracy. However, human interaction is an expensive resource and methods that reduce effort in interactive segmentation are of great interest. In this work, we introduce a novel marker-based segmentation layer for deep neural networks, enabling end-to-end training of a marker creation network. Our training methodology includes a loss function with two main components: (i) segmentation loss using the new differentiable segmentation layer, and (ii) a set of regularization functions that ensure the generated markers have the desired shape properties. We show that by using the proposed method, the network can automatically generate markers that achieve effective segmentation and have desirable shape characteristics. We validate our results in the training dataset and in five unseen datasets
Mental Geometry
No full textInternational audienceThis article illustrates pedagogy through training in the handling of abstractions. Mental arithmetic is not limited to numerical calculation; one can mentally calculate primitives and simplify analytical expressions. Even if there is software that does this very well, this training retains its pedagogical value. Can we go further and consider geometric mental arithmetic: mentally proceeding with transformations of simple figures allowing the calculation of areas or volumes?It turns out that the intuition that allowed Archimedes to obtain his main geometric results, if we take only the ideas without the old-fashioned style, provides the opportunity for a pleasant and quite rich mental game that I present here in the form of a short narrative dialogue, not a philosophical tale because it does not bring any thesis, simply a story to be classified among the invitations to exercise the mind. It starts with the area of a triangle and ends with Guldin's two theorems.Cet article illustre la pédagogie par l'entrainement à manier des abstractions. Le calcul mental n'est pas limité au calcul numérique, on peut calculer mentalement des primitives, simplifier des expressions analytiques. Même s'il y a des logiciels qui font cela très bien, cet entraînement conserve une valeur pédagogique. Peut-on aller plus loin et envisager du calcul mental géométrique : procéder mentalement à des transformations de figures simples permettant de calculer des aires ou des volumes ? Il se trouve que l'intuition qui permit à Archimède d'obtenir ses principaux résultats géométriques, si l'on n'en prend que les idées sans les lourdeurs d'expression, fournit l'occasion d'un jeu mental plaisant et assez riche que je présente ici sous forme d'un petit dialogue narratif, non pas un conte philosophique car il n'amène aucune thèse, simplement un récit à ranger parmi les invitations à s'exercer l'esprit. Ça commence avec l'aire d'un triangle et se termine par les deux théorèmes de Guldin
Investigating the effect of Cu2+ sorption in montmorillonite using density functional theory and molecular dynamics simulations
No full textInternational audienceMontmorillonite (MMT) is the main mineral component of bentonite, which is currently proposed as a sealing material in deep geological repositories (DGRs) for used nuclear fuel. In the Canadian program, which will utilize copper-cladded used fuel containers, safety analysis considers the effect of copper corrosion, during which Cu ions could potentially be adsorbed by the surrounding MMT. In such a scenario, ion exchange between Na and Cu is expected. In this study, a multiscale approach that combines electronic density functional theory (DFT) and force-field-based molecular dynamics (MD) simulations was employed to study the effect of introducing Cu ions to MMT. An extension to the ClayFF force field is parameterized and validated using DFT to model how Cu interacts with clay systems. MD simulations were performed to calculate the interaction free energies between MMT platelets containing Cu ions (Cu-MMT) and compared them to inter-platelet interaction energies in Na-MMT and Ca-MMT. Our calculations suggest Cu-MMT develops swelling pressures between those of Ca-MMT and Na-MMT. Furthermore, our MD simulations suggest that Cu has MMT interlayer mobility that is significantly slower than that of Ca2＋
Aux origines d'une ambition
No full textInternational audienceThis text is the introduction of the book. It presents its main purpose and its historiographical context in the various disciplines involved.Ce texte est l'introduction de l'ouvrage dont il présente les objectifs et le contexte historiographique dans plusieurs disciplines impliquées
25 Additional Problems -- Extension to the Book "125 Problems in Text Algorithms"
No full textThis very preliminary text is related to ``Algorithms on Texts'', also called ``Algorithmic Stringology''. It is an extension of the book ``125 Problems in Text Algorithms'' providing, in the same compact style, more problems with solutions. We refer also to the companions to ``Text algorithms'' available at http://monge.univ-mlv.fr/~mac/CLR/clr1-20.pdf and at the web page http://125-problems.univ-mlv.fr, where all 150 problems (including the ones presented here) are briefly announced. The selected problems satisfy three criteria: challenging, having short tricky solutions and solvable with only very basic background in stringology. For the basics in stringology we refer to http://monge.univ-mlv.fr/~mac/CLR/clr1-20.pdf