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A mesoscale Eulerian numerical method for short-range repulsion in interfacial dynamics
No full textInternational audienceThe dynamics of bubble and droplet coalescence and repulsion are critical in a variety of natural and industrial multiphase systems. Their direct numerical simulation (DNS) remains challenging due to the multiscale nature of interfacial interactions. This study presents a mesoscale numerical approach that incorporates a repulsive disjoining pressure into an Eulerian framework to model near-contact interactions without explicitly resolving nanoscale forces. The method computes interfacial distances through a transport equation, enabling efficient and scalable implementation across parallel computing architectures. Unlike traditional marker-based or interface-tracking methods, the approach is independant of the number of bubbles or droplets in the domain. The method is validated on representative test cases, including droplet collisions and static foam networks, and is shown to accurately capture both dynamic inertial effects and quasi-static configurations. Notably, it enables DNS of wet foams with reduced liquid fractions compared to conventional level-set methods where repulsive interactions are not accounted for. This approach lays the foundation for simulating more realistic foam structures and analyzing destabilization phenomena such as drainage and coarsening, thus contributing to the predictive modeling of complex gas-liquid systems
Subdiffusive fractional limit of a jump-renewal equation
No full textIn this paper, we consider an age-structured jump model that arises as a description of continuous time random walks with infinite mean waiting time between jumps. We prove that under a suitable rescaling, this equation converges in the long time large scale limit to a time fractional subdiffusion equation
A Cahn--Hilliard--Willmore phase field model for non-oriented interfaces
No full textInternational audienceWe investigate a new phase field model for representing non-oriented interfaces, approximating their area and simulating their area-minimizing flow. Our contribution is related to the approach proposed in arXiv:2105.09627 that involves ad hoc neural networks. We show here that, instead of neural networks, similar results can be obtained using a more standard variational approach that combines a Cahn-Hilliard-type functional involving an appropriate non-smooth potential and a Willmore-type stabilization energy. We show some properties of this phase field model in dimension and, for radially symmetric functions, in arbitrary dimension. We propose a simple numerical scheme to approximate its -gradient flow. We illustrate numerically that the new flow approximates fairly well the mean curvature flow of codimension or interfaces in dimensions and
Symplectic circle actions on manifolds with contact type boundary
No full textInternational audienceMany of the existing results for closed Hamiltonian G-manifolds are based on the analysis of the corresponding Hamiltonian functions using Morse-Bott techniques. In general such methods fail for non-compact manifolds or for manifolds with boundary. In this article, we consider circle actions only on symplectic manifolds that have (convex) contact type boundary. In this situation we show that many of the key ideas of Morse-Bott theory still hold, allowing us to generalize several results from the closed setting. Among these, we show that in our situation any symplectic group action is always Hamiltonian, we show several results about the topology of the symplectic manifold and in particular about the connectedness of its boundary. We also show that after attaching cylindrical ends, a level set of the Hamiltonian of a circle action is either empty or connected. We concentrate mostly on circle actions, but we believe that with our methods many of the classical results can be generalized from closed symplectic manifolds to symplectic manifolds with contact type boundary
A psychoacoustic assessment for enhancing the sound quality of vibrating composite panels
No full textInternational audienceVibrating composite panels are widely used in airplanes, vehicles, and high-speed trains, where noise comfort is required. Optimizing their design requires integrating psychoacoustic assessments alongside vibroacoustic analysis. The research presents a psychoacoustic framework to enhance the sound quality of composite panels while maintaining their structural efficiency. Hence, vibroacoustic models previously validated through vibroacoustic laboratory experiments for various composite panels subjected to mechanical and diffuse acoustic excitations, were used to synthesize the sounds radiated from the panels. The framework required to validate the models perceptually. This ensured the synthesized sounds were perceived by listeners as equivalent to the recorded ones. A psychoacoustic paired-comparison test between recorded and synthesized sounds was conducted to perceptually assess the modeling. Next, the sound quality of composite panel designs was investigated. Hence, synthesized sounds of designs were evaluated through another psychoacoustic test and a preference analysis. The preference analysis identified optimal designs, correlating preferences with psychoacoustic indices, like loudness, and mechanical properties such as stiffness-to-mass ratio and damping. This integrated approach ensures that the resulting designs enhance the sound quality and meet structural performance requirements
Analyse visuelle de la tactique de jeu au tennis de table
No full textSuccess in high-level sport depends on several key factors: physical fitness, technique, mental strength, recovery, nutrition and, in confrontational sports, tactics. Although all of these aspects are important, their relative importance varies depending on the sport. This is particularly true in table tennis, where tactics play a major role in a player's success. In a sport where the score can be 9-9 in the final game, the difference between victory and defeat can be determined by the next two rallies. A tactical error at this crucial moment can lead to the loss of the match. These tactical choices are not made by the players just before the rallies, they are the result of reflection and preparation with the coach before the match. This important task is mainly carried out by the coach, who must analyze past matches and draw on their knowledge of their player and their opponent to define the tactics to be adopted during the match. In this manuscript, we focus on the visual analysis of game tactics in professional table tennis matches. Our goal is to help coaches with their tactical analysis during match preparation. This will save time in analyses that can be very lengthy, simplify the exploration of tactics, and also objectify the analyses using precise figures.Throughout this manuscript, we will address all the essential steps in tactical analysis in table tennis. In the first part, we will look at the process of collecting structured data, which is crucial for any relevant analysis. We will justify the choice of developing a semi-automatic data collection interface that strikes a balance between accuracy and speed. We also propose a data benchmark open to the community to study the automation of data collection. We will also study the influence of the positions of the cameras recording the matches on the accuracy of the position data extracted from the videos.In the second part, we will focus on analyzing the structured data extracted in order to provide concrete elements for analysis. This will be done through three studies, the first on game metrics related to dominance throughout the game. The second will characterize serves, focusing on rebound zones and their attributes. And the last will study returns and how they are influenced by the serves that precede them.In the third part, we will discuss communication and data visualization. This will be done through three different approaches. The first will focus on creating dashboards that allow users to explore game sequences. The second will focus on developing new visualizations that allow players' positions and rebounds to be viewed in a new reference frame centered on the player's position. And finally, the last will focus on integrating visualization into video, studying the player's accessibility zones based on a physical model according to their position and the direction and speed of their movement.La réussite dans le sport de haut niveau repose sur plusieurs facteurs clef, le physique, la technique, le mental, la récupération, l'alimentation et pour les sports de confrontation, la tactique. Bien que l'ensemble de ces axes soient importants, l'importance de ces facteurs est différente en fonction du sport. Cela est particulièrement vrai pour le tennis de table, où la tactique joue un rôle important dans la réussite d'un joueur. Dans un sport où on peut se retrouver à 9-9 au dernier set, la différence entre la victoire et la défaite peut être déterminée sur les deux points qui suivent. Une erreur tactique à ce moment crucial peut conduire à la perte du match. Ces choix tactiques, ne sont pas pris par les joueurs juste avant les points, il s'agit d'une réflexion et d'une préparation faites avec le coach avant le match. Cette tâche importante est principalement réalisée par le coach qui doit analyser les matchs passés et se baser sur la connaissance de son joueur et de son adversaire pour définir les tactiques à adopter durant le match. Dans cette thèse, nous nous intéressons à l'analyse visuelle de la tactique de jeu des matchs de tennis de table professionnels. Notre objectif est de pouvoir aider les coachs dans l'analyse tactique faite lors de la préparation des matchs. Cela permettra à la fois de gagner du temps dans les analyses qui peuvent être très longues, de simplifier l'exploration des tactiques et aussi d'objectiver les analyses à l'aide de chiffres précis.Tout au long de cette thèse, nous aborderons toutes les étapes essentielles à l'analyse tactique dans le tennis de table. Dans la première partie, nous verrons le processus de collecte de données structurées qui est indispensable pour toute analyse pertinente. Nous justifierons le choix du développement d'une interface de collecte de données semi-automatique permettant un compromis entre précision et rapidité. Nous proposons aussi un benchmark de données ouvert à la communauté dans le but d'étudier l'automatisation de la collecte de données. Nous étudierons aussi l'influence des positions des caméras qui enregistrent les matchs sur la précision des données de positions extraites des vidéos.Dans la deuxième partie, nous nous intéresserons à l'analyse des données structurées extraites dans le but de donner des éléments concrets d'analyse. Cela se fera à travers 3 études, la première sur des indicateurs de performances liés à la domination tout au long du match. La deuxième sur la caractérisation des services en se concentrant sur les zones de rebonds et leurs attributs. Et la dernière sur l'étude des retours et comment ils sont influencés par les services qui les précèdent.Dans la troisième partie, nous aborderons la communication et les visualisations des données. Cela se fera à travers 3 différentes approches, la première sur la réalisation de tableaux de bord permettant l'exploration des séquences de jeu. La deuxième sur le développement de nouvelles visualisations permettant de visualiser les données de positions des joueurs et des rebonds dans un nouveau référentiel centré sur la position du joueur. Et enfin la dernière sur l'intégration de visualisation dans la vidéo, en étudiant les zones d'accessibilité du joueur basé sur un modèle physique en fonction de sa position et de l'orientation et de la vitesse de son déplacement
Bridging the gap between lab and field sleep studies: a proof-of-concept for studying wild rats in semi-captive environments
No full textInternational audienceSleep is a vital and universal behavior distinct from mere inactivity, yet its ecological role remains poorly understood due to methodological limitations in recording sleep in the wild. Using a small, low-power biologger, collecting brain activity, body movements, and physiology, we recorded key sleep parameters in wild black rats (Rattus rattus) under semi-captive conditions. We developed a rapid (<1 h) surgical procedure using a custom subdermal flexible electrode, providing signal quality comparable to standard cortical electrodes. Our validated semi-captive setup allowed animals to remain in their natural environment with ad libitum food and social contact while minimizing interactions. This protocol enables the study of sleep’s ecological role and the influence of environmental factors on sleep expression, offering insights into its evolution. Additionally, it can help clarify sleep’s central role in the context of global environmental change. By monitoring general behavior and sleep patterns in four wild rats for up to 10 days post-surgery, as well as feeding behavior for over a month, we observed no signs of pain or stress, with sleep patterns stabilizing within 2 days. This approach provides a unique tool to assess sleep variability and flexibility, demonstrating its feasibility for studying sleep in small (<200 g) wild animals
ReluMotion - Conception d'une chaîne de conversion électrique sans terres rares pour véhicules légers intermédiaires
No full textInternational audienc
