Search results for "Différent"
showing 10 items of 28 documents
Spectral properties of random non-self-adjoint operators
2015
In this thesis we are interested in the spectral properties of random non-self-adjoint operators. Weare going to consider primarily the case of small random perturbations of the following two types of operators: 1. a class of non-self-adjoint h-differential operators Ph, introduced by M. Hager [32], in the semiclassical limit (h→0); 2. large Jordan block matrices as the dimension of the matrix gets large (N→∞). In case 1 we are going to consider the operator Ph subject to small Gaussian random perturbations. We let the perturbation coupling constant δ be e (-1/Ch) ≤ δ ⩽ h(k), for constants C, k > 0 suitably large. Let ∑ be the closure of the range of the principal symbol. Previous results o…
Volumes transverses aux feuilletages d'efinissables dans des structures o-minimales
2003
Let Fλ be a family of codimension p foliations defined on a family Mλ of manifolds and let Xλ be a family of compact subsets of Mλ. Suppose that Fλ, Mλ and Xλ are definable in an o-minimal structure and that all leaves of Fλ are closed. Given a definable family Ωλ of differential p-forms satisfaying iZ Ωλ = 0 forany vector field Z tangent to Fλ, we prove that there exists a constant A > 0 such that the integral of on any transversal of Fλ intersecting each leaf in at most one point is bounded by A. We apply this result to prove that p-volumes of transverse sections of Fλ are uniformly bounded.
From optimization to algorithmic differentiation: a graph detour
2021
This manuscript highlights the work of the author since he was nominated as "Chargé de Recherche" (research scientist) at Centre national de la recherche scientifique (CNRS) in 2015. In particular, the author shows a thematic and chronological evolution of his research interests:- The first part, following his post-doctoral work, is concerned with the development of new algorithms for non-smooth optimization.- The second part is the heart of his research in 2020. It is focused on the analysis of machine learning methods for graph (signal) processing.- Finally, the third and last part, oriented towards the future, is concerned with (automatic or not) differentiation of algorithms for learnin…
On the optimal control of the circular restricted three body problem
2011
The context of this work is space mechanics. More precisely, we aim at computing low thrust transfers in the Earth-Moon system modeled by the circular restricted three-body problem. The goal is to calculate the optimal steering of the spacecraft engine with respect to two optimization criteria: Final time and fuel consumption. The contributions of this thesis are of two kinds. Geometric, first, as we study the controllability of the system together with the geometry of the transfers (structure of the command) by means of geometric control tools. Numerical, then, different homotopic methods being developed. A two-three body continuation is used to compute minimum time trajectories, and then …
Differential inclusions involving normal cones of nonregular sets in Hilbert spaces
2017
This thesis is dedicated to the study of differential inclusions involving normal cones of nonregular sets in Hilbert spaces. In particular, we are interested in the sweeping process and its variants. The sweeping process is a constrained differential inclusion involving normal cones which appears naturally in several applications such as elastoplasticity, electrical circuits, hysteresis, crowd motion, etc.This work is divided conceptually in three parts: Study of positively alpha-far sets, existence results for differential inclusions involving normal cones and characterizations of Lyapunov pairs for the sweeping process. In the first part (Chapter 2), we investigate the class of positivel…
Les différentes dimensions de notre corps vécu
2016
International audience
Déterminisme du pouvoir protecteur de Fusarium oxysporum : recherche de gènes impliqués dans l'interaction protectrice avec la tomate
2007
Fusarium oxysporum is a common soil borne fungus, well represented in every type of soils, throughout the world. This species includes pathogenic strains inducing severe diseases in many crops and strains able to protect a plant against the infection by a pathogenic strain. The protective strains are not only non pathogenic strains isolated from suppressive soils but also pathogenic strains applied to a non host plant. The protective capacity of these strains is mainly based on mechanisms of competition and induced resistance of the plant The main objective of this work was to identify fungal genes involved in the protective capacity of these strains and associated to the elicitation of pla…
Différent ? Les Dogs entre énergie punk et héritage sixties
2018
International audience
Etude par analyse thermique différentielle des tranformations de phases sur l'iodate de lithium
1986
International audience; Lithium iodate (LiIO3) exists at room temperature either as hexagonal (alpha) or tetragonal (beta) crystals. Beta-LiIO3 is stable up to the melting point, whereas alpha-LiIO3 is known to undergo phase transitions. We have studied by differential thermal analysis (DTA) the sequence of phase transitions occurring on powders prepared by different processes. An alpha-LiIO3 powder obtained by grinding a single crystal exhibits the well-known transformations alpha-gamma-beta. A powder obtained by fast evaporation of an aqueous solution transforms directly the alpha to the beta and does not exhibit any intermediate gamma phase. Further, DTA investigations point out that the…
Geometric optimal control : homotopic methods and applications
2012
This work is about geometric optimal control applied to celestial and quantum mechanics. We first dealt with the minimum fuel consumption problem of transfering a satellite around the Earth. This brought to the creation of the code HamPath which permits first of all to solve optimal control problem for which the command law is smooth. It is based on the Pontryagin Maximum Principle (PMP) and on the notion of conjugate point. This program combines shooting method, differential homotopic methods and tools to compute second order optimality conditions. Then we are interested in quantum control. We study first a system which consists in two different particles of spin 1/2 having two different r…