Dynamically balanced and plausible trajectory planning for human-like characters

International audience

The Descent of Pluto: Interactive dynamics, specialisation and reciprocity of roles in a Wikipedia debate

International audience

Introduction to geodesics in sub-Riemannian geometry

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Vocabulary and language model adaptation using information retrieval

International audience

Using Kullback-Leibler Distance for Text Categorization

International audience

Asymptotic preserving and time diminishing schemes for rarefied gas dynamic

In this work, we introduce a new class of numerical schemes for rarefied gas dynamic problems described by collisional kinetic equations. The idea consists in reformulating the problem using a micro-macro decomposition and successively in solving the microscopic part by using asymptotic preserving Monte Carlo methods. We consider two types of decompositions, the first leading to the Euler system of gas dynamics while the second to the Navier-Stokes equations for the macroscopic part. In addition, the particle method which solves the microscopic part is designed in such a way that the global scheme becomes computationally less expensive as the solution approaches the equilibrium state as opposite to standard methods for kinetic equations which computational cost increases with the number of interactions. At the same time, the statistical error due to the particle part of the solution decreases as the system approach the equilibrium state. This causes the method to degenerate to the sole solution of the macroscopic hydrodynamic equations (Euler or Navier-Stokes) in the limit of infinite number of collisions. In a last part, we will show the behaviors of this new approach in comparisons to standard Monte Carlo techniques for solving the kinetic equation by testing it on different problems which typically arise in rarefied gas dynamic simulations.

Multiscale Schemes for the BGK--Vlasov--Poisson System in the Quasi-Neutral and Fluid Limits. Stability Analysis and First Order Schemes

This paper deals with the development and the analysis of asymptotically stable and consistent schemes in the joint quasi-neutral and fluid limits for the collisional Vlasov-Poisson system. In these limits, the classical explicit schemes suffer from time step restrictions due to the small plasma period and Knudsen number. To solve this problem, we propose a new scheme stable for choices of time steps independent from the small scales dynamics and with comparable computational cost with respect to standard explicit schemes. In addition, this scheme reduces automatically to consistent discretizations of the underlying asymptotic systems. In this first work on this subject, we propose a first order in time scheme and we perform a relative linear stability analysis to deal with such problems. The framework we propose permits to extend this approach to high order schemes in the next future. We finally show the capability of the method in dealing with small scales through numerical experiments.

Innovations organisationnelles et radicales, Le cas de deux grandes firmes de l’informatique émergente

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Text segmentation using a cache memory

International audience

An Information Theoretic Approach to Automatic Query Expansion

International audience

A comparative study of navigation meshes

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A Fuzzy Decision Strategy for Topic Identification and Dynamic Selection of Language Models

International audience

EACS: Effective Avoidance Combination Strategy

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Reconnaissance thématique à partir de textes dictés et Adaptation dynamique de modèles de langages thématiques

National audience

Combinaison de modèles de langage pour l'identification de thèmes

National audience