Search results for "instabilité"
showing 10 items of 10 documents
Chemical and dimensional evolution of cationic ions exchange resins in cement pastes
2013
Ion exchange resins (IERs) are widely used by the nuclear industry to decontaminate radioactive effluents. After use they are usually encapsulated in cementitious materials. However, the solidified waste forms can exhibit a strong expansion, possibly leading to cracking. Its origin is not well understood as well as the conditions when it occurs.In this work, the interactions between cationic resins in the Na+ or Ca2+ form and tricalcium silicate (C3S), Portland cement (CEM I) or Blastfurnace slag cement (CEM III/C) are investigated at an early age in order to gain a better understanding of the expansion process.The results show that during the hydration of a paste of C3S or CEM I containing…
ultra-short pulse propagation at 160-Gb/s in dispersion managed optical fiber lines
2004
This thesis presents a study on ultra-short pulse propagation at 160-Gb/s in dispersion managed optical fiber lines. In a first part, we describe the experimental design of a SHG-FROG setup able to characterize high repetition rate pulse trains. Secondly, we demonstrate the efficiency of multiple four wave mixing phenomenon for the generation of a 160-GHz pulse train through the compression of a sinusoidal beat-signal. Then, in order to compare the experimental and theoretical results, we present the development of an optical fiber characterization benchtop based on modulational instability. In the last part of this thesis, we built and compare several recirculating loop setups. On the one …
Incidence du passage obligatoire aux normes comptables IAS / IFRS sur le risque d'instabilité bancaire
2011
In this thesis, we study the economic consequences, in terms of instability, of the mandatory IAS/IFRS adoption in the banking industry. The thesis is organized as follows. In a first part (Chapter I), we develop a theoretical framework whose purpose is to understand the mechanisms through which the mandatory IAS/IFRS adoption by banks may influence the probability of occurrence of a banking crisis. At this stage, we show that several arguments, derived from the contractual and informational perspectives of accounting, can be mobilized in order to justify the hypothesis that the mandatory IAS/IFRS adoption has a positive or a negative influence on banking stability. The second part of the t…
From equilibrium to chaos and back : methodological evaluation of research of the majority rule
2000
According to the canonical model situated at the heart of the " economic " - or, as the political scientists prefer to call it, rational-choice - theory of (democratic) politics, whenever the matter to be decided raises, or consists of, at least two distinct issues, it is generally impossible to reach a determinate decision by using the majority rule. This problem, referred to as that of disequilibrium, equilibrium instability, or even"chaos", was first underplayed and then deemed ominous to the point of seriously undermining the development prospects of the whole theory. However, more recently, the concern it was the source o f until the 1980s has given way to a state of renewed confidence…
INSTABILITY OF HAMILTONIAN SYSTEMS IN THE SENSE OF CHIRIKOV AND BIFURCATION IN A NON LINEAR EVOLUTION PROBLEM EMANATING FROM PHYSICS
2004
We prove the existence of a minimal geometrico-dynamical condition to create hyperbolicity in section in the vicinity of a transversal homoclinic partially hyperbolic torus in a near integrable Hamiltonian system with three degrees of freedom. We deduce in this context a generalization of the Easton's theorem of symbolic dynamics. Then we give the optimal estimation of the Arnold diffusion time along a transition chain in the initially hyperbolic Hamiltonian systems with three degrees of freedom with a surrounding chain of hyperbolic periodic orbits .In a second part, we describe geometrically a mechanism of diffusion studied by Chirikov in a near integrable Hamiltonian system with three de…
Complex rogue wave in the fiber optics
2016
This manuscript presents the generation of complex rogue waves related to nonlinear instabilities occurring through the propagation of light in standard optical fibers. Linear and nonlinear physical phenomena involved are first listed, in particular some of them by analogy with the field of hydrodynamics. The different forms of rogue waves induced by the modulation instability process are then presented. They are also known as "breathers", and they are obtained by solving the nonlinear Schrödinger equation. From these exact solutions, various experimental systems were designed by means of numerical simulations based on two rogue-wave excitation methods. The first one is an exact generation …
Représentation et présence de l'auteure dans The Golden Notebook de Doris Lessing
2012
The Golden Notebook offre, certes, une représentation de l'écrivaine, mais pas seulement. Le texte est en effet traversé par la présence de celle-ci tant dans l'écriture que la composition. La structure disjointe du roman, les ruptures dans l'écriture, le brouillage des limites entre les différentes sections ainsi qu'entre personnage et narratrice autobiographique reflètent l'écartèlement de la femme qui se veut aussi écrivaine et la fragilité de sa position. Ecartèlement et fragilité qui la mènent au bord de la folie. Mais la superposition des textes secondaires - brouillons, coupures de journaux, et journal intime - met au centre du roman le travail d'une écriture qui se veut consciemment…
Polarisation attraction and incoherent modulation instability in optical fibers
2006
This thesis, entitled « Polarisation attraction and incoherent modulation instability in optical fibers », presents a theoretical and experimental study of two new processes from the nonlinear optic in optical fibers domain. We introduce in the first chapter some theoretical notions useful for the comprehension of this work. Then, we demonstrate in the second chapter that it is possible to generate some modulation instability in optical fibers using a partially coherent optical beam. We highlight and observe the main properties of the phenomenon. We study the polarisation attraction in isotropic fibers process in the third chapter. Our work proves the existence of the phenomenon, and permit…
Understanding the health care pattern of homeless children through their residential journey
2021
En Île-de-France, l’hôtel social est souvent mobilisé par les associations pour héberger des familles, principalement migrantes et accompagnées d’enfants de moins de 6 ans. À cet âge, l’enfant nécessite un suivi de soins régulier auprès des professionnels pédiatriques. Nous supposons que ce suivi est dépendant de la mobilité résidentielle inhérente au système d’hébergement hôtelier. Cet article a pour objectif de reconstituer le parcours résidentiel des familles et le parcours de soins de leurs enfants et de saisir comment ces derniers s’influencent. La démonstration repose sur 18 entretiens biographiques spatialisés réalisés entre 2013 et 2016 auprès des familles sans logement hébergées en…
Hétérogénéité spatiale : principes et méthodes
2004
Spatial Heterogeneity : Principles and Methods This article has a dual purpose . First , it describes the main econometric specifications which can be used to represent spatial heterogeneity , reflected in an instability of parameters in space and / or a heteroscedasticity of error terms . Only the specifications valid in cross-section are examined . Second , it explains the links between spatial heterogeneity and autocorrelation , the other major feature of localised data , defined by the absence of independence between geographical observations . In particular , we look at the extent to which traditional tests of heteroscedasticity or instability need to be amended to take account of spat…