Archive ouverte HAL-LAAS
Not a member yet
12189 research outputs found
Sort by
Front-surface cooling of infrared thermophotovoltaic cells
No full textInternational audienceThis paper proposes a front-surface cooling method for thermophotovoltaic (TPV) cells utilizing microfluidic channels for efficient heat dissipation. Unlike conventional back-surface cooling, front-surface cooling minimizes thermal resistance by directly cooling the top surface of the cell. The microfluidic channel layer also functions as an antireflection layer through the gradual change in the refractive index. The proposed cooling method was evaluated using a thermo-fluid analysis, considering factors such as the emitter temperature, cell reflectance, thermal resistance, and fluid optical properties. We examined liquids with ideal absorption characteristics and actual liquids whose absorption coefficients were measured. The results showed that front-surface cooling significantly outperformed back-surface cooling in terms of the net power density. This method is particularly advantageous for high emitter temperatures or in cases where the thermal resistance between the cell and backsurface liquid is high. Moreover, this study highlights the potential application of the cooling method in bifacial TPV cells, which can generate electricity from thermal radiation incident on both sides. Bifacial cells offer higher power generation per unit area but face cooling challenges. The proposed cooling technique addresses these challenges, paving the way for innovative TPV system configurations and improved performance
Algorithme de Branch and Price pour la planification des tâches d'une flotte de robots mobiles autonomes pour la logistique interne de systèmes de production
No full textInternational audienceAlgorithme de Branch and Price pour la planification des tâches d'une flotte de robots mobiles autonomes pour la logistique interne de systèmes de productio
BORWin: Exact algorithm based on a Bi-Objective Relaxation for Window-constrained problems
No full textInternational audienceA mixed integer maximization problem involving several additional constraints defined with both a lower and an upper bound is considered. It is assumed that one of such constraints is more restrictive than the others. As it can be seen as a resource window constraint, it defines the so-called window-constrained problem. From a bi-objective perspective, a 2-phase algorithm, called BORWin, is devised. It stands for Bi-Objective Relaxation for Window-constrained problems. The first phase is generic for any window-constrained problem and provides a family of upper bounds based on a bi-objective relaxation of the additional constraints. It is shown that the latter bounds strongly relate to the Lagrangian dual bounds. The second phase is derived for a variant involving a graph structure, namely the window-constrained longest-path problem on an acyclic graph. The aim is to take advantage of the upper bounds to devise an efficient label extension algorithm. It is shown that complementary upper bounds could be derived to further improve performance in some special cases. A typical example is when the additional constraints have special knapsack structures. This is the case for the Hydro-Unit Commitment problem with a single plant (1-HUC). From numerical experiments for the 1-HUC, BOR-Win appears to be very efficient compared to state-of-the-art approaches
Actes de la 9ème édition du colloque Pédagogie et Formation du Groupe INSA: Adaptation des parcours de formation aux nouveaux enjeux des métiers de l'ingénieur : quelles transformations et quels impacts ?
No full textNational audienceL’évolution du métier d’ingénieur implique une nécessaire réévaluation des parcours de formation, deleurs contenus, des méthodes et outils d’enseignement-apprentissage. À partir de retours d’expérienceet d’expérimentations dans nos établissements, nous pourrons analyser l’impact de ces transformationssur les acquis des étudiants, le développement de leurs compétences et réfléchir aux moyens de favoriserleur engagement dans ces différents dispositifs.La 9e édition du colloque Pédagogie et Formation du Groupe INSA entend questionner ces problématiqueset permettre d’échanger sur les actions en place, le déploiement de projets à l’échelle du groupe (notamment INSA 2025) et les partenariats développés ces deux dernières années
Passivity Preservation in Interconnections of Linear Cone Complementarity Systems with State Jumps
No full textInternational audienceThis article is largely concerned with generic interconnections of a class of passive nonsmooth nonlinear dynamical systems, namely linear cone complementarity systems (LCCS). We stipulate that each subsystem admits a positive definite storage function that characterizes the passivity of an underlying nonsmooth mapping. We provide algebraic criteria in terms of these individual storage functions to find the storage function which guarantees passivity of the overall interconnected system. State jumps in the interconnections are studied in detail. Examples from dynamic feedback control, switching DAEs and nonsmooth circuits are included as an illustration of the theoretical developments
How Human Motion Prediction Quality Shapes Social Robot Navigation Performance in Constrained Spaces
No full textAccepted for ACM/IEEE International Conference on Human-Robot Interaction (HRI) 2026 Conference as a full paper.International audienceMotivated by the vision of integrating mobile robots closer to humans in warehouses, hospitals, manufacturing plants, and the home, we focus on robot navigation in dynamic and spatially constrained environments. Ensuring human safety, comfort, and efficiency in such settings requires that robots are endowed with a model of how humans move around them. Human motion prediction around robots is especially challenging due to the stochasticity of human behavior, differences in user preferences, and data scarcity. In this work, we perform a methodical investigation of the effects of human motion prediction quality on robot navigation performance, as well as human productivity and impressions. We design a scenario involving robot navigation among two human subjects in a constrained workspace and instantiate it in a user study () involving two different robot platforms, conducted across two sites from different world regions. Key findings include evidence that: 1) the widely adopted average displacement error is not a reliable predictor of robot navigation performance and human impressions; 2) the common assumption of human cooperation breaks down in constrained environments, with users often not reciprocating robot cooperation, and causing performance degradations; 3) more efficient robot navigation often comes at the expense of human efficiency and comfort
The Christoffel function: Applications, connections and extensions
No full textInternational audienceWe provide an introduction to the Christoffel function (CF), a well-known (and old) tool from the theory of approximation and orthogonal polynomials. We then describe how it provides a simple and easy-to-use tool to address some problems in data analysis and mining, and in approximation and interpolation of discontinuous functions. Finally we also reveal some surpris- ing links of the CF with seemingly different disciplines, including polynomial optimization, positivity certificates, and equilibrium measures of compact set
Simulation numérique directe de la combustion d'une particule d'aluminium isolée sous divers environnements
No full textThe authors acknowledge the French Defense Agency for funding L.P.’s scholarship and CALMIP supercomputing centre in Toulouse (France) for providing us computational resources.International audienceThis study presents a comprehensive numerical investigation of single aluminum particle combustion under varying convective oxidizing flow conditions, using Direct Numerical Simulations. A three-dimensional, boundary-layer-resolved model is developed to capture the complex interplay of gas-phase chemistry, surface reactions, and multiphase transport phenomena. The model incorporates aluminum evaporation, aluminum suboxide reactions at the particle's surface, and alumina formation both on the surface and in the gas phase. It also introduces an original scheme to account for the dissolution of alumina into the molten particle, based on parameters derived from molecular dynamics simulations. The model was validated against experimental burn time data. The unsteady combustion of a 125 μm-aluminum particle in various flowing O2/N2 conditions is then investigated in terms of standoff flame distance, gas-phase temperature and chemistry, particle temperature and surface chemistry. The results demonstrate that gas-phase reactions remain the dominant source of heat release, although surface reactions, particularly under highly oxygenated environments, play a significant role in modulating local combustion kinetics. The formation of liquid alumina at the particle's surface, its partial dissolution into the molten aluminum, and the limited surface coverage even at high O2 concentrations highlight the importance of coupling surface chemistry with thermal transport. While this mathematical model successfully reproduces the main macroscopic characteristics such as flame temperature, burn time-radius relationship, gas-phase composition, and fluxes, some discrepancies appear near the particle surface, i.e. at the microscale. These deviations can be attributed to radiative heat transfer effects which are not considered or to an incomplete understanding of surface reactions
Positive to negative photoconductance switching in plasmonic gold nanoparticle networks
No full textInternational audienceThe elaboration of versatile materials in which electrical conduction is tuned by light irradiation is of paramount relevance to such diverse applications as photodetectors, photodiodes, solar cells or light sensors. Although positive photoconductance is increasingly common, systems with negative photoconductance are scarcely reported. In this work, a switching from positive to negative photoconductance is observed upon simple annealing of well-organized networks of gold nanoparticles stabilized by dodecanethiols. The photoconductance properties are investigated experimentally using impedance spectroscopy. The measured Nyquist plots and resonance curves of the impedance are analyzed in terms of equivalent electrical circuits consisting in parallel resistance, capacitance and photoconductance. The positive and negative photo-current conversion efficiencies of the nanoparticles network are estimated k PPC = 389 ± 40 nS.W -1 .cm 2 and k NPC = -241 ± 40 nS.W -1 .cm 2 , respectively. With the aid of density functional theory calculations, the origin of the photoconductance is discussed, at the nanoscale level, in terms of changes of molecular conformation. Such molecular effects assist charge carrier tunneling between first neighbor nanoparticles, and favor the formation of traps introduced by the annealing of the sample. The present work contributes to the understanding of plasmo-electronic properties of hybrid molecule-nanoparticle self-assembled nano-structures
Causal Deterministic SLAM: Representation and Compensation of Independent Systems of Errors
No full textThis paper addresses the emblematic Simultaneous Localization And Mapping (SLAM) problem through the lens of causality. The proposed approach explicitly represents the causal deterministic relationships on the robot's relative motion and actuator/sensor signals, together with the effect of exogenous random errors, into a structural causal model and associated causal graph. The SLAM solution is obtained by "compensating" these errors. This adjustment process can take place only when a loop closure occurs, and proceeds in two stages: first, the errors are partitioned into conditionally independent subsets through d-separation analysis; then, each obtained subset is compensated separately by means of a dedicated algorithm which ensures the respect of Gaussian assumptions and the satisfaction of constraints. The estimation of the robot trajectory and landmark poses comes as a by-product of error compensation. Throughout the paper, the conceptual differences with the standard probabilistic view of SLAM are highlighted. The strengths and limits of the alternative causal approach are discussed, and illustrated on experiments built with synthetic and real data