A Rank-Based Reward between a Principal and a Field of Agents: Application to Energy Savings

In this paper, we consider the problem of a Principal aiming at designing a reward function for a population of heterogeneous agents. We construct an incentive based on the ranking of the agents, so that a competition among the latter is initiated. We place ourselves in the limit setting of mean-field type interactions and prove the existence and uniqueness of the equilibrium distribution for a given reward, for which we can find an explicit representation. Focusing first on the homogeneous setting, we characterize the optimal reward function using a convex reformulation of the problem and provide an interpretation of its behaviour. We then show that this characterization still holds for a sub-class of heterogeneous populations. For the general case, we propose a convergent numerical method which fully exploits the characterization of the mean-field equilibrium. We develop a case study related to the French market of Energy Saving Certificates based on the use of realistic data, which shows that the ranking system allows to achieve the sobriety target imposed by the regulation

Investigation on enhanced impact toughness and deformation mechanisms of an additively manufactured 17-4 PH stainless steel

International audienceThis study investigated the effect of solution treatment temperature on the microstructure and mechanical (hardness, tensile and impact toughness) properties of 17-4 PH stainless steel produced by laser powder bed fusion (PBF-LB). We applied three solution treatments (900 °C, 1040 °C, and 1125 °C) to the as-built material, followed by a standardized ageing treatment (620 °C/4 h). Microstructural characterization revealed that the lowest temperature (900 °C) failed to fully homogenize the initial structure, leading to elemental segregation (Cr, Ni, Cu). In contrast, the highest temperature (1125 °C) produced a fully homogenized and recrystallized microstructure but also caused significant coarsening of SiO2 oxide particles, which became concentrated along grain boundaries. From a mechanical perspective, the 900 °C treatment produced the lowest yield and ultimate tensile strengths; however, it provided high ductility, strong strain-hardening capacity, and excellent impact toughness, comparable to that of conventionally processed 17-4 PH. This behaviour is attributed to the formation of a duplex-matrix microstructure composed of δ-ferrite and martensite, combined with controlled SiO2 particle size and distribution. In contrast, the 1125 °C treatment, despite yielding a more homogeneous microstructure, significantly reduced toughness due to the formation of coarse oxide particles and distribution along grain boundaries. This work demonstrates that the use of a low (non-standard) solution treatment temperature offers additional opportunities for tailoring the mechanical properties of PBF-LB components

Intégration de la précarité numérique dans la RSE : quelles responsabilités pour lesentreprises face à l’illectronisme ?

International audienceThis article examines how major French companies integrate digital vulnerabilityinto their corporate social responsibility (CSR) strategies. Based on a qualitative study conducted with five organizations (SFR, Bouygues, La Poste, EDF, SNCF), it analyzes the perceptions, mechanisms, and limitations of their engagement in this domain. The findings reveal often fragmented approaches, largely outsourced to nonprofit partners. Building on the frameworks of Selwyn (2004), Van Dijk (2005), and Gond et al. (2009), the article highlights the tensions between image management, authenticity, and transformative impact. From a managerial perspective, it advocates for a more integrated governance of digital inclusion and the strategic evaluation of einclusion within CSR policies.Cet article interroge la manière dont les grandes entreprises françaises intègrent laprécarité numérique dans leur stratégie RSE. À partir d’une enquête qualitative menée auprès de cinq groupes (SFR, Bouygues, La Poste, EDF, SNCF), il analyse les perceptions, dispositifs et limites de ces engagements. Les résultats mettent en évidence des démarches souvent fragmentées et en grande partie confiées à des partenaires associatifs. S’inspirant de Selwyn (2004), Van Dijk (2005) et Gond et al. (2009), l’article met en lumière les tensions entre image, sincérité et transformation. Sur le plan managérial, il plaide pour une gouvernance plus intégrée de l’inclusion numérique et pour l’évaluation stratégique de l’e-inclusion au sein des politiques RSE

Accounting for grain crushing and pore collapse for strain localization in rocks

We present a model for crushable granular rocks by embedding breakage mechanics in the Cosserat continuum. This model features a dependence on an enriched set of state variables (the elastic strains and curvatures, the density, the solid fraction, and the breakage state variable), demonstrates a dependence of the yield surface on the Lode angle, breakage and solid fraction, and evolution laws that tightly couple the competing processes. We then outline the notion of linear stability analysis and how we use this technique to obtain both the thickness and orientation of any shear bands that may form in the system. The model is then calibrated from data available in the literature on Fontainebleau sandstone and other similar granular rocks. We compare the model predictions with experimental measures of both the stress-strain response, and the width and angle of shear bands, and find good agreement with the results that have been previously reported

Machine Learning for Scientific Computing and Numerical Analysis

MasterThis MSc course introduces and develops advanced methods at the intersection of machine learning and scientific computing, with a special emphasis on solving and analyzing forward and inverse problems governed by partial differential equations. Students will learn how to combine classical numerical methods with modern neural-network architectures to approximate functions, operators, and solution maps, while critically assessing stability, generalization, and interpretability

Indoor turbulent airflow modelling with a new integral buoyant wall function

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Disentangling estuarine conditions that shape the temporal dynamics of anadromous European (Alosa spp.) spawning migration across environmentally contrasted estuaries

International audienceAnadromous fish travel through estuaries when migrating between their marine growth habitats and their freshwater spawning grounds. In these dynamic transitional environments, strong currents and extreme dissolved oxygen and turbidity levels can result in stressful conditions for fish, impeding longitudinal connectivity. This study examined how estuarine hydro-environmental variables influence the temporal dynamics of spawning migration in threatened European shads (Alosa alosa and Alosa fallax, undistinguished) across five environmentally contrasted estuaries along the French Atlantic coast. In the first part, focusing on the Loire estuary, catch per unit effort (CPUE) from commercial fisheries were consistent with individual tracking data from a 2011 telemetry study, revealing more intense migration activity during neap tides than during spring tides. Consistently, statistical models (Boosted Regression Trees) built over a longer period (2011-2018) showed higher CPUE under conditions of low turbidity, elevated oxygen saturation, and moderate ebb current velocity. In the second part, the temporal patterns of shad migration and hydro-environmental conditions were compared across estuaries. A fortnightly periodicity (14 to 15 days) was detected in the Loire and Gironde estuaries, in line with the neap-spring tidal cycle. This periodicity was not observed in the Seine, Vilaine and Adour estuaries, where oxygen and turbidity levels were less extreme during spring tides. These findings support the hypothesis that the estuarine turbidity maximum zone can act as a partial barrier to migration during spring tides, thereby structuring the long-term migration dynamics in macrotidal turbid estuaries

Exponential twist of probability measures: drift correction in term of a generalized gradient

In this paper we study the exponential twist, i.e. a path-integral exponential change of measure, of a Markovian reference probability measure $\P$. This type of transformation naturally appears in variational representation formulae originating from the theory of large deviations and can be interpreted in some cases, as the solution of a specific stochastic control problem. Under a very general Markovian assumption on $\P$, we fully characterize the exponential twist probability measure as the solution of a martingale problem and prove that it inherits the Markov property of the reference measure. The ''generator'' of the martingale problem shows a drift depending on a {\it generalized gradient} of some suitable {\it value function} $v$

Détermination expérimentale de l’énergie de fissuration de bétons coquillers par corrélation d’images numériques

International audienceDans le cadre de la réduction de l'empreinte environnementale des bétons, de récentes études ont permis de montrer qu'il était possible de substituer 50% des gravillons naturels par des co-produits coquilliers d'huîtres, tout en conservant des propriétés mécaniques suffisantes pour des bétons porteurs et en améliorant leurs propriétés de durabilité. Cependant, l'impact de ces granulats alternatifs sur la fissuration des bétons n'a pas encore été étudié. Le travail présenté ici s'intéresse à la fissuration et plus particulièrement à l'énergie de fissuration de bétons incluant des co-produits coquilliers. Des essais de flexion trois points sur éprouvettes entaillées ont été réalisés. L'utilisation de la corrélation d'images numériques (CIN) a permis de mesurer les champs de déplacement et d'observer la propagation de la fissure au cours de l'essai. En particulier, une méthode utilisant l'identification des séries de Williams par méthode intégrée a été utilisée. Elle permet de déterminer les facteurs d'intensité du matériau et de déduire l'énergie de fissuration pour chaque éprouvette

From Benchmarks to Production: Transferring Time Series Anomaly Detection Methods for Electricity Production Monitoring

International audienceAccurate forecasting of electricity production is essential for maintaining the operational efficiency and strategic planning of energy utilities. In industrial settings, such forecasts are generated daily to ensure supply-demand balance and optimal management of production assets. However, the increasing complexity of modern power systems and data flows poses significant challenges for ensuring the reliability and consistency of these forecasts. This paper addresses the problem of anomaly detection in short-term production forecasts at EDF, formulated as identifying atypical intra-day patterns that may signal data quality issues or operational irregularities. We introduce TAMIS, a scalable and interpretable system that analyzes daily production time series to automatically detect anomalous days based on deviations from historical patterns learned from past data. Designed for human-in-the-loop workflows, TAMIS surfaces top-ranked anomalies through an automated daily newsletter, enabling efficient expert review and continuous monitoring. An extensive experimental evaluation on real-world industrial data demonstrates that TAMIS achieves the best accuracy-efficiency trade-off compared to baseline methods. To foster further research and reproducibility, we publicly release the anonymized application datasets used in our study