Search results for "Fluids"

Noise removal using a nonlinear two-dimensional diffusion network

1998

Un reseau electrique non lineaire bidimensionnel, constitue de N×N cellules identiques, et modelisant l’equation de Nagumo discrete est presente. A l’aide d’une nouvelle description de la fonction non lineaire, on peut predire analytiquement l’evolution temporelle de la partie coherente du signal, ainsi que celle des perturbations de petites amplitudes qui lui sont superposees. Enfin, des applications a l’amelioration du rapport signal sur bruit, ou au traitement d’images sont suggerees.

Global dynamical behaviors in a physical shallow water system

2016

International audience; The theory of bifurcations of dynamical systems is used to investigate the behavior of travelling wave solutions in an entire family of shallow water wave equations. This family is obtained by a perturbative asymptotic expansion for unidirectional shallow water waves. According to the parameters of the system, this family can lead to different sets of known equations such as Camassa-Holm, Korteweg-de Vries, Degasperis and Procesi and several other dispersive equations of the third order. Looking for possible travelling wave solutions, we show that different phase orbits in some regions of parametric planes are similar to those obtained with the model of the pressure …

The tennis racket effect in a three-dimensional rigid body

2017

We propose a complete theoretical description of the tennis racket effect, which occurs in the free rotation of a three-dimensional rigid body. This effect is characterized by a flip ($\pi$- rotation) of the head of the racket when a full ($2\pi$) rotation around the unstable inertia axis is considered. We describe the asymptotics of the phenomenon and conclude about the robustness of this effect with respect to the values of the moments of inertia and the initial conditions of the dynamics. This shows the generality of this geometric property which can be found in a variety of rigid bodies. A simple analytical formula is derived to estimate the twisting effect in the general case. Differen…

A flux based conservation approach for acoustic problems

2008

International audience

Galerkin and control-volume FEMs evaluation for acoustic problems

2004

International audience

Analyse de la dispersion de la solution MVCEF pour l'équation de Helmholtz

2006

Implementation of single-qubit quantum gates by adiabatic passage and static laser phases

2006

International audience; We propose and analyse experimentally feasible implementations of single-qubit quantum gates based on stimulated Raman adiabatic passage (STIRAP) between magnetic sublevels in atoms coupled by elliptically polarized pulsed laser fields, in part based on a proposal by Kis and Renzoni [Z. Kis, F. Renzoni, Phys. Rev. A 65 (2002) 032318]. These techniques require only the control of the relative phase of the driving fields but do not involve any dynamical or geometric phases, which makes it independent of the other interaction details: detuning, pulse shapes, pulse areas and pulse durations. The suggested techniques are immune to spontaneous emission since the qubit mani…

Controle de l'orientation et de l'alignement moléculaire par un train d'impulsions soudaines

2005

Les recents progres technologiques dans le domaine des Lasers permettent d'envisager le controle de nombreux processus quantiques jouant un role dans une variete de problemes s'etendant de la reactivite chimique a l'information quantique. Dans ce contexte, nous nous sommes interesses au controle de l'orientation ou de l'alignement moleculaire en utilisant un train d'impulsions soudaines. Nous avons defini des etats cibles qui maximisent a la fois l'orientation ou l'alignement et sa duree dans le temps et montre comment atteindre ces etats a l'aide de strategie systematique ou optimisee.

Localization of the tannin-binding site on the salivary PRP IB5

2014

Localization of the tannin-binding site on the salivary PRP IB5. 10. European Symposium on Saliva

Intermittency in the homopolar dynamo

2005

URL: http://www-spht.cea.fr/articles/s05/152 Rigas Jurmala, Rigas Jurmala, Latvia, June 27 - July 1st, 2005; We study a modified Bullard dynamo and show that this system is equivalent to a nonlinear oscillator subject to a multiplicative noise. The stability analysis of this oscillator is performed. Two bifurcations are identified, first towards an ``intermittent'' state where the absorbing (non-dynamo) state is no more stable but the most probable value of the amplitude of the oscillator is still zero and secondly towards a ``turbulent'' (dynamo) state where it is possible to define unambiguously a (non-zero) most probable value around which the amplitude of the oscillator fluctuates. The …