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Cross-border impacts of nuclear phase-out policies on the European power system: Economic and environmental insights for strategic energy planning
No full textInternational audienceThe European power system plays a strategic role in reducing dependence on fossil fuels while contributing to reaching Europe's CO2 emissions targets. The energy crisis triggered by Russia's war against Ukraine has revived interest in the role of nuclear energy in the European power system. We examine how postponing nuclear phaseout affects optimal dispatch and environmental performance of the interconnected European power system. We use ESMOD, a unit commitment model of the European electric system at the 2030 horizon, built with Antares Simulator, to assess the impact of nuclear phase-out policies in Germany and Belgium. The model accounts for 36 European countries and focuses on cross-border effects and country-level impacts. The model shows that not decommissioning 4 GW of nuclear capacity in these two countries would have reduced European CO2 emissions by 16 million tons in 2030. Strikingly, about 45% of such reductions would have occurred in other European countries and keeping nuclear power plants in operation would have increased the total European surplus by 3 billion euros heterogeneously affecting across countries. To interpret these heterogeneous effects, we analysed the load size, power mix, trader status and interconnections to explain cross-border sensitivities. Finally, we assessed the countries' sensitivity to weather variation across 34 climate years by classifying them using the Kmeans clustering method. The results underscore the central role of European energy policy coordination in shaping future energy strategies that prioritize climate goals and efficient system integration while challenging the economic efficiency and environmental effectiveness of solely national plans
Code de Conduite du GDR-IFM
No full textThis code of conduct was written by the PÉDI committee. On 21 November 2025, the GDR executive committee unanimously approved (with one abstention) a motion that this code has to be accepted by any person participating in any event organised or funded by the GDR.Ce code de bonne conduite a été rédigé par le comité PÉDI. Le comité exécutif du GDR du 21 novembre 2025 a voté à l’unanimité moins un vote blanc le principe selon lequel ce code devait être approuvé par toute personne participant à un événement organisé ou financé par le GDR
A Kernel Correlation-Based Enhanced Resolution Fault-Location Method for Lossy Transmission Lines
No full textInternational audienceThis paper presents a nonlinear fault-location method that leverages a kernel correlation coefficient to map transient fault waveforms into a high-dimensional Hilbert space using a Gaussian radial basis function (RBF) kernel. This approach enhances spatial resolution by nonlinearly amplifying subtle differences between signals that appear similar in the original space. Unlike linear methods, the resolution is not limited by signal wavelength components but is controlled by a tunable kernel scale parameter, enabling a flexible trade-off between accuracy and robustness, even under strong attenuation. Field validation using real fault data from a 10 kV distribution system shows that the proposed method achieves a location error of only 13 m (0.85%), whereas the error of the conventional natural frequency-based method ranges from 67 m to 198 m (6.6%-9.6%). Moreover, a spatial resolution of 60 m based on low frequency components (below 120 kHz) was found, a fivefold improvement over linear correlation metric. The proposed kernel-based framework provides an effective and scalable solution for high-resolution fault location in distribution networks and long HVDC power lines with complex topologies and strong attenuation characteristics
Outils automatisés pour le raisonnement inductif en logique de séparation
No full textThe automated program verification aims to produce formal proofs of correctness for programs with respect to their specifications, requiring minimal user interaction. This technique is based on expressive program logics to capture the properties of programs, and on algorithms or heuristics to decide satisfiability and entailment problems for these logics. Separation logic is one of such logics, specifically designed for reasoning about programs that dynamically allocate memory and mutate this memory through pointers. It includes built-in predicates to specify pointer aliasing, an empty memory cell, an allocated memory cell with its content, as well as a binary separating conjunction operator ⋆ that combines disjoint memory regions. To specify unbounded memory regions, separation logic includes user-defined predicates, usually expressed through inductive rules. The satisfiability and entailment problems are undecidable in general, but they are decidable for specific fragments. For instance, the PCE fragment is a restriction of the symbolic heap fragment, for which the satisfiability is decidable, where the inductively defined predicates satisfy some syntactic and semantic constraints.This thesis proposes two extensions of the PCE fragment. The first extension defines a fragment, including the PCE one and formulas that, although non-PCE, specify data structures that could be represented by PCE formulas. We propose a procedure attempting to compute an equivalent PCE representation of non-PCE formulas. We implemented this procedure and tested it on a benchmark of SL formulas. The second extension supports the specification of overlaid data structures, i.e., data structures that share an unbounded set of locations and are therefore difficult to capture using the separating conjunction. The extension, called OSL, introduces an additional operator, the overlaid separating conjunction ⍟, which allows for composing heaps that share locations as long as they allocate them with distinct fields. We demonstrate that the OSL fragment has a decidable satisfiability problem.La vérification automatisée de programmes vise à produire des preuves formelles de correction de programmes par rapport à leurs spécifications, tout en nécessitant une interaction minimale de la part de l'utilisateur. Cette technique repose sur des logiques de programmes expressives permettant de saisir les propriétés de programmes, et sur des algorithmes ou des heuristiques afin de décider les problèmes de satisfaisabilité et d'implication pour ces logiques. La logique de séparation est l'une de ces logiques, spécialement conçue pour raisonner sur des programmes qui allouent dynamiquement de la mémoire et modifient cette mémoire à l'aide de pointeurs. Elle comprend des prédicats intégrés afin de spécifier l'aliasing de pointeurs, une cellule de mémoire vide, une cellule de mémoire allouée avec son contenu, ainsi qu'un opérateur binaire de conjonction de séparation ⋆ qui combine des régions de mémoire disjointes. Pour spécifier des régions de mémoire illimitées, la logique de séparation comprend des prédicats définis par l'utilisateur, généralement exprimés par des règles inductives. Les problèmes de satisfaisabilité et d'implication sont en général indécidables, mais sont décidables pour des fragments spécifiques. Par exemple, le fragment PCE est une restriction du fragment de ta symbolique, pour lequel la satisfaisabilité est décidable, où les prédicats définis de manière inductive satisfont certaines contraintes syntaxiques et sémantiques.Cette thèse propose deux extensions du fragment PCE. La première extension définit un fragment comprenant le fragment PCE et des formules qui, bien que non PCE, spécifient des structures de données pouvant être représentées par des formules PCE. Nous proposons une procédure visant à calculer une représentation PCE équivalente de formules non-PCE. Nous avons implémenté cette procédure et l'avons testée sur un benchmark de formules SL. La deuxième extension prend en charge la spécification de structures de données superposées, c'est-à-dire des structures de données qui partagent un ensemble illimité d'adresses et qui sont donc difficiles à capturer à l'aide de la conjonction de séparation. L'extension, appelée OSL, introduit un opérateur supplémentaire, la conjonction de séparation superposée ⍟, qui permet de composer des tas qui partagent des adresses tant qu'ils les allouent avec des champs distincts. Nous démontrons que le fragment OSL a un problème de satisfaisabilité décidable
Towards a Movement-sensitive Approach for Collaborative Digital Transformation in Ecologies of Artifacts
No full textToday's digital transformation projects are scarcely beginning from a blank page as they should deal with an installed based of artifacts and practices. The concept of Ecology of Artifacts (EoA) provides an interesting framework highlighting how collaborative activities span over multiple tools that belongs to the participants and their organizations. EoAs are dynamic and undergo evolution over time. These evolutions can be accounted for as movements where the introduction, the replacement or decommissioning of a tool can impact practices and other artifacts, like ripple effects. This exploratory paper presents an under development workshop-based method that aims at supporting collaborative reflection about EoA evolutions. The workshop is structured into two phases: the description of the practice's EoA and the collaborative analysis of its transformations with the participants. We report about a formative expert evaluation of our method with a group of academics engaged in hybrid meetings interested with changing their tools. The participants feedback indicates that the approach is useful for describing the EoA of a collaborative practice and for analyzing movements within them. Their feedback also suggest improvements for future development of our movement-sensitive approach
Altruisme et Objectif d’Équité dans les Jeux de Markov à Motivations Mixtes
No full textInternational audienceCooperation is fundamental for society’s viability, as it enables the emergence of structure within heterogeneous groups that seek collective well-being. However, individuals are inclined to defect in order to benefit from the group’s cooperation without contributing the associated costs, thus leading to unfair situations. In game theory, social dilemmas entail this dichotomy between individual interest and collective outcome. The most dominant approach to multi-agent cooperation is the utilitarian welfare which can produce efficient highly inequitable outcomes. This paper proposes a novel framework to foster fairer cooperation by replacing the standard utilitarian objective with Proportional Fairness. We introduce a fair altruistic utility for each agent, defined on the individual log-payoff space and derive the analytical conditions required to ensure cooperation in classic social dilemmas. We then extend this framework to sequential settings by defining a Fair Markov Game and deriving novel fair Actor-Critic algorithms to learn fair policies. Finally, we evaluate our method in various social dilemma environments
Synchronization of complex spatio-temporal dynamics with lasers
No full textInternational audienceAbstract Synchronization is the spontaneous alignment of the dynamics of weakly-coupled oscillators. In addition to temporal dynamics like periodic and chaotic oscillations, also the spatio-temporal dynamics of spatially-extended systems like wildlife populations can synchronize. We exploit here the intrinsic spatio-temporal complex dynamics of broad area lasers to demonstrate such synchronization at lab-scale. Broad-area vertical-cavity surface-emitting lasers (BA-VCSELs) exhibit chaos from the nonlinear coupling between laser modes with different spatial profiles and polarization. When coupling two BA-VCSELs, several synchronization and anti-synchronization regimes are observed, highlighting the complex interplay between oscillating modes with different frequencies and spatial patterns. The correlation coefficient varies between 0.2 and 0.9 depending on the dynamics and on the time scale under analysis. Besides its fundamental interest, our experiment with commercial devices marks the first step towards real-world spatial multiplexing in multiple user physical-layer secure communication based on chaos synchronization
State of Health Evaluation of Lithium-Ion Batteries Using the Statistical Properties of the Voltage
No full textInternational audienceConventional indicators of battery health, such as capacity and energy, are difficult to measure directly and are therefore often estimated. This article proposes assessing lithium-ion battery health using the statistical properties of the voltage across the battery terminals, a measurement already available in battery management systems. The evolution of the voltage probability density function during the cycle is assessed using Kullback–Leibler divergence (KLD) as a health indicator. It is studied for two battery chemistries (Lithium iron Phosphate (LFP) and Nickel Manganese Cobalt (NMC)). The batteries are subjected to cycles with a dynamic current profile derived from globally harmonised test cycles for light vehicles (WLTC). Spearman’s correlation coefficients, above 86% for NMC cells and 74% for LFP cells, also indicate that this new health indicator is strongly correlated with conventional measurements of battery health (capacity or energy). The analysis also shows that the divergence not only closely follows the degradation trend even at high noise levels (SNR = 10 dB) but is also insensitive to noise levels higher than 30 dB
ARMAGNAC: A New Parametric Batch Normalization Layer for SPDNet Architecture
No full textSoumission EUSIPCO 2026This paper introduces ARMAGNAC (bAtch noR-Malisation pArametric Geometric harmoNic ArithmetiC), a new batch normalization layer for deep learning architectures on Symmetric Positive Definite (SPD) matrices. Unlike standard existing approaches that rely on computationally expensive Fréchet means with iterative eigenvalue decompositions, ARMAGNAC leverages a parametric mean that automatically adapts between simple arithmetic and harmonic means. This learnable parametrization enables the layer to adjust to the specific characteristics of the problem at hand while maintaining computational efficiency through explicit formulas of the backpropagation gradients. Experimental results demonstrate that ARMAGNAC correctly learn the parameter to use the most appropriate mean between arithmetic and harmonic on simulated data, and achieves superior performance results on real-data classification tasks
Medispeech: a French Reading and Spontaneous Speech Corpus for Sleepiness Estimation
No full textInternational audienceExcessive Daytime Sleepiness (EDS) is associated with several diseases and therefore negatively affects the daily life of impacted people. Its diagnosis and follow-up are difficult because they require testing at the hospital for one full day. Monitoring patients regularly in ecological conditions may be done through speech analysis. Although several corpora containing speech from sleepy subjects exist, they do not suit ecological requirements regarding either the device used for recording or the speech elicitation tasks. In this paper, we introduce the Medispeech corpus containing reading, daily-life semi-spontaneous, and medically-oriented spontaneous tasks. Fifty-nine French subjects were recorded with both a professional-quality microphone and a smartphone using a dedicated application, resulting in 1,729 recordings for a total duration of 21 hours. Their EDS diagnosis was assessed by both a physiological objective measurement (mean sleep latency measured during a clinical test) and a subjective questionnaire (Karolinska Sleepiness Scale). Phenotyping of subjects is assured by collecting socio-demographic and medical data related to diverse dimensions of sleepiness, comorbidities, and addictions. Finally, we analyse the validity of our data collection protocol by measuring the effective duration of speech (after discarding pauses) and assessing its links with the collected subjects' characteristics