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On the influence of bed roughness on saltation in inertial regime
No full textInternational audienceIn extreme tidal environment, occurrences of saltating pebbles have been observed. The ambition to instal hydrokinetic turbines in such environment requires knowledge on the presence of pebbles in saltation in the water column because they can damage the structures. An experimental study is realized in a free-surface flume with no slope and different bed roughnesses as in marine environment. With fast camera the trajectories of hundreds of spherical particles are analysed. Our study deals with saltation in the inertial regime (i.e., large Stokes number) over fixed beds with various roughnesses. In inertial regime, the bed roughness has more influence on the collision process and the trajectory of the particles than for non-inertial motion where viscous forces play a key role. Jump height and length increase with bed roughness, with height increasing quicker than length leading to a more vertical trajectory for higher bed roughness. The vertical restitution coefficient is shown to increase with be
Fair Energy Allocation for Collective Self-Consumption
No full textThis study explores a collective self-consumption community with several houses, a shared distributed energy resource (DER), and a common energy storage system, as a battery. Each house has an energy demand over a discrete planning horizon, met by using the DER, the battery, or purchasing electricity from the main power grid. Excess energy can be stored in the battery or sold back to the main grid. The objective is to determine a supply plan ensuring a fair allocation of renewable energy while minimizing the overall microgrid cost. We investigate and discuss the formulation of these optimization problems using mixed integer linear programming. We show some dominance properties that allow to reformulate the model into a linear program. We study some fairness metrics like the proportional allocation rule and max-min fairness. Finally, we illustrate our proposal in a real case study in France with up to seven houses and a one-day time horizon with 15minute intervals
Multiple-Photon Resonance Enabled Quantum Interference in Emission Spectroscopy of N2+
No full textInternational audienceQuantum interference occurs frequently in the interaction of laser radiation with materials, leading to a series of fascinating effects such as lasing without inversion, electromagnetically induced transparency, Fano resonance, etc. Such quantum interference effects are mostly enabled by single-photon resonance with transitions in the matter, regardless of how many optical frequencies are involved. Here, we report on quantum interference driven by multiple photons in the emission spectroscopy of nitrogen ions that are resonantly pumped by ultrafast infrared laser pulses. In the spectral domain, Fano resonance is observed in the emission spectrum, where a laser-assisted dynamic Stark effect creates the continuum. In the time domain, the fast-evolving emission is measured, revealing the nature of free-induction decay arising from quantum radiation and molecular cooperativity. These findings clarify the mechanism of coherent emission of nitrogen ions pumped with mid-infrared pump laser and are found to be universal. The present work opens a route to explore the important role of quantum interference during the interaction of intense laser pulses with materials near multiple photon resonance
ACES: Generating diverse programming puzzles with autotelic language models and semantic descriptors
No full textInternational audienceFinding and selecting new and interesting problems to solve is at the heart of curiosity, science and innovation. We here study automated problem generation in the context of the open-ended space of python programming puzzles. Existing generative models often aim at modeling a reference distribution without any explicit diversity optimization. Other methods explicitly optimizing for diversity do so either in limited hand-coded representation spaces or in uninterpretable learned embedding spaces that may not align with human perceptions of interesting variations. With ACES (Autotelic Code Exploration via Semantic descriptors), we introduce a new autotelic generation method that leverages semantic descriptors produced by a large language model (LLM) to directly optimize for interesting diversity, as well as few-shot-based generation. Each puzzle is labeled along 10 dimensions, each capturing a programming skill required to solve it. ACES generates and pursues novel and feasible goals to explore that abstract semantic space, slowly discovering a diversity of solvable programming puzzles in any given run. Across a set of experiments, we show that ACES discovers a richer diversity of puzzles than existing diversity-maximizing algorithms as measured across a range of diversity metrics. We further study whether and in which conditions this diversity can translate into the successful training of puzzle solving models
Computing singular and near-singular integrals over curved boundary elements: The strongly singular case
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The Interplay of Cognitive Load and Intrinsic Motivation in Neuroanatomy Learning through Immersive Technologies
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Modélisation des effets de l'injection de fluide sur une instabilité sismique en utilisant les méthodes d'éléments de frontière rapides
No full textEarthquakes due to either natural or anthropogenic sources cause important human and material damage. In both cases, the presence of pore fluids influences the triggering of seismic instabilities.A new and timely question in the community is to show that the earthquake instability could be mitigated by active control of the fluid pressure. In this work, we study the ability of Fast Boundary Element Methods (Fast BEMs) to provide a multi-physic large-scale robust solver required for modeling earthquake processes, human induced seismicity and their mitigation.In a first part, a Fast BEM solver with different temporal integration algorithms is used. We assess the performances of various possible adaptive time-step methods on the basis of 2D seismic cycle benchmarks available for planar faults. We design an analytical aseismic solution to perform convergence studies and provide a rigorous comparison of the capacities of the different solving methods in addition to the seismic cycles benchmarks tested. We show that a hybrid prediction-correction / adaptive time-step Runge-Kutta method allows not only for an accurate solving but also to incorporate both inertial effects and hydro-mechanical couplings in dynamic fault rupture simulations.In a second part, once the numerical tools are developed for standard fault configurations, our objective is to take into account fluid injection effects on the seismic slip. We choose the poroelastodynamic framework to incorporate injection effects on the earthquake instability. A complete poroelastodynamic model would require non-negligible computational costs or approximations. We justify rigorously which predominant fluid effects are at stake during an earthquake or a seismic cycle. To this aim, we perform a dimensional analysis of the equations, and illustrate the results using a simplified 1D poroelastodynamic problem. We formally show that at the timescale of the earthquake instability, inertial effects are predominant whereas a combination of diffusion and elastic deformation due to pore pressure change should be privileged at the timescale of the seismic cycle, instead of the diffusion model mainly used in the literature.Les tremblements de terre d'origine naturelle ou anthropique provoquent d'importants dégâts humains et matériels. Dans les deux cas, la présence de fluides interstitiels influe sur le déclenchement des instabilités sismiques. Une nouvelle question d'actualité dans la communauté est de montrer que l'instabilité sismique peut être atténuée par un contrôle actif de la pression des fluides. Dans ce travail, nous étudions la capacité des méthodes d'éléments de frontière rapides (Fast BEMs) à fournir un solveur robuste multi-physique à grande échelle nécessaire à la modélisation des processus sismiques, de la sismicité induite et de leur atténuation.Dans une première partie, un solveur BEM rapide avec différents algorithmes d'intégration temporelle est utilisé. Nous évaluons les performances de diverses méthodes à pas de temps adaptatif sur la base de problèmes de cycles sismiques 2D usuels pour les failles planes.Nous proposons une solution asismique analytique pour effectuer des études de convergence et fournir une comparaison rigoureuse des capacités des différentes méthodes en plus des problèmes de cycles sismiques de référence testés.Nous montrons qu'une méthode hybride prédiction-correction / Runge-Kutta à pas de temps adaptatif permet non seulement une résolution précise mais aussi d'incorporer à la fois les effets inertiels et les couplages hydro-mécaniques dans les simulations de rupture dynamique de faille.Dans une deuxième partie, une fois les outils numériques développés pour des configurations standards, notre objectif est de prendre en compte les effets de l'injection de fluide sur le glissement sismique. Nous choisissons le cadre poroélastodynamique pour incorporer les effets de l'injection sur l'instabilité sismique. Un modèle poroélastodynamique complet nécessiterait des coûts de calcul ou des approximations non négligeables. Nous justifions rigoureusement quels effets fluides prédominants sont en jeu lors d'un tremblement de Terre ou d'un cycle sismique. Pour cela, nous effectuons une analyse dimensionnelle des équations, et illustrons les résultats en utilisant un problème de poroelastodynamique 1D simplifié. Plus précisément, nous montrons qu'à l'échelle de temps de l'instabilité sismique, les effets inertiels sont prédominants alors qu'une combinaison de la diffusion du fluide et de la déformation élastique de la matrice solide due à la variation de la pression interstitielle devrait être privilégiée à l'échelle de temps du cycle sismique, au lieu du modèle de diffusion principalement utilisé dans la littérature
Palladium-catalyzed C-H alkoxycarbonylation of benzadehydes using a transient directing group strategy
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Reducing the wrapping effect of set computation via Delaunay triangulation for guaranteed state estimation of nonlinear discrete-time systems
No full textInternational audienceAbstract Set computation methods have been widely used to compute reachable sets, design invariant sets and estimate system state for dynamic systems. The wrapping effect of such set computation methods plays an essential role in the accuracy of their solutions. This paper studies the wrapping effect of existing interval, zonotopic and polytopic set computation methods and proposes novel approaches to reduce the wrapping effect for these set computation methods based on the task of computing the dynamic evolution of a nonlinear uncertain discrete-time system with a set as the initial state. The proposed novel approaches include the partition of a polytopic set via Delaunay triangulation and also the representation of a polytopic set by the union of small zonotopes for the following set propagation. The proposed novel approaches with the reduced wrapping effect has been further applied to state estimation of a nonlinear uncertain discrete-time system with improved accuracy. Similar to bisection for interval and zonotopic sets, Delaunay triangulation has been introduced as a set partition tool for polytopic sets, which has opened new research directions in terms of novel set partition, set representation and set propagation for reducing the wrapping effect of set computation
Fully higher-order coupling of finite element and level set methods for two-phase flow with a new explicit projection method
No full textInternational audienceThis work presents the development of a higher-order finite element method for modeling unsteady, incompressible and inviscid two-phase flows using the level set method. A new explicit projection method is introduced to solve the incompressible Euler equation, where the pressure and the velocity fields are solved separately. To implement high order temporal schemes, the Hodge decomposition in this projection method is not applied to the velocity but to its time derivative. A discontinuous Galerkin discretization is used to solve both the level set and the nonlinear advection terms present in the Euler equations, while a Galerkin discretization is used to solve the pressure Poisson equation. The present method is a fully high order numerical approach, both in space and temporal dimensions. Numerical results provided by several 2D benchmark test cases in naval hydrodynamics (i.e hydrostatic equilibrium, sloshing and dam break) validate the computational code, illustrating the power of the proposed method. Compared to the CFD codes based on low order VOF/finite-volume methods, the present approach demonstrates greater accuracy on coarse meshes, leading to reduced CPU time