Teses / dissertações sobre o tema "Diffusion non linéaire des ondes"
Crie uma referência precisa em APA, MLA, Chicago, Harvard, e outros estilos
Veja os 50 melhores trabalhos (teses / dissertações) para estudos sobre o assunto "Diffusion non linéaire des ondes".
Ao lado de cada fonte na lista de referências, há um botão "Adicionar à bibliografia". Clique e geraremos automaticamente a citação bibliográfica do trabalho escolhido no estilo de citação de que você precisa: APA, MLA, Harvard, Chicago, Vancouver, etc.
Você também pode baixar o texto completo da publicação científica em formato .pdf e ler o resumo do trabalho online se estiver presente nos metadados.
Veja as teses / dissertações das mais diversas áreas científicas e compile uma bibliografia correta.
Lombard, Olivier. "Diffusion multiple et non linéaire des ondes acoustiques dans les milieux bulleux". Thesis, Sorbonne Paris Cité, 2016. http://www.theses.fr/2016USPCC144/document.
Texto completo da fonteMultiple scattering and non linear effects are antagonists so it is not commun to observea coupling of those two effects. In acoustics, non linear effects are important when they are cumulative,therefore dispersion relation is modified by multiple scattering and non linear effects cannotbe cumulative. Bubbles are known to have a non linear behavior and also to be good scatterers witha scattering cross section higher than the geometric cross section at resonance frequency. Therefore,bubbly media seem to be good to observe multiple scattering in non linear regime. A bubbly-mediumhas three different regimes. At low frequency, non linear effects are important and cumulative butthere is no multiple scattering effects. At bubbles resonance frequency, non linear behavior and alsomultiple scattering effects are important but the non linear effects cannot be cumulative. At high frequency,multiple scattering effects are important but without no non linear effects. The experimentsin this thesis show, on the one hand, a high frequency wave propagating in a bubbly-medium andon the other hand, the resonance frequency wave propagation. At high frequency, a coda is observedin experiment and modeled by a diffusion equation. At resonance frequency, the model, confirmed bythe experiments, leads us to some applications : acoustic frequency doubler, acoustic diode and phaseconjugation mirror
Laurent, Jérôme. "Étude d'un matériau granulaire sec par ondes ultrasonores : effet non linéaire, atténuation et diffusion". Phd thesis, Université Paris-Est, 2011. http://tel.archives-ouvertes.fr/tel-00657286.
Texto completo da fonteSpire, Alexandra. "Diffusion des ondes linéaires dans des milieux nonlinéaires". Montpellier 2, 2001. http://www.theses.fr/2001MON20038.
Texto completo da fonteDorkenoo, Kokou Dodzi. "Diffusion Rayleigh d'aile stimulée large bande dans le disulfure de carbone - développement d'instabilités - couplage deux ondes". Paris 11, 1995. http://www.theses.fr/1995PA112520.
Texto completo da fonteJoudrier, Valérie. "Etude de la diffusion optique non linéaire et de sa contribution à la limitation". Palaiseau, Ecole polytechnique, 1998. http://www.theses.fr/1998EPXX0025.
Texto completo da fonteTournat, Vincent. "Effet non linéaire d'auto-démodulation d'amplitude dans les milieux granulaires : théories et expériences". Le Mans, 2003. http://www.theses.fr/2003LEMA1003.
Texto completo da fonteIn this thesis, opération of the parametrie antenne in unconsolidated granuler mate- rials is studied. The parametrie antenne, widely used in underwater acoustics, involves a nonlinear acoustie effect that can be interpreted as an amplitude self-demodulation Several models of parametrie antenna are developed to take into account absorption, scattering, or dispersion phenomena, as well as évanescent feature of the waves. Experiments in disordered packings of glass beads, in qualitative agreement with theoretical prédictions are performed. Shear waves for emission are used for the first time, and produce a low frequency demodulated longitudinal signal. This nonlinear dilatancy phenonienon is tested in different expérimental configurations and is shown to be very sensitive to the nonlinear anisotropy of the force chains network
Binczak, Stéphane. "Etude d'un système expérimental de diffusion non linéaire : application au traitement du signal". Dijon, 1999. http://www.theses.fr/1999DIJOS003.
Texto completo da fonteMonsaingeon, Léonard. "Modèles de diffusion non linéaire issus de la théorie de la fusion par confinement inertiel". Toulouse 3, 2011. http://thesesups.ups-tlse.fr/1499/.
Texto completo da fonteThis PhD thesis is devoted to the study of two reaction-diffusion models arising in Inertial Confinement Fusion. In chapter 1 we derive a new thermodiffusive model, describing a stabilization at short wave-lengths by transversal mass ablation. A self-consistent analysis [SMC06] of the full thermo-hydrodynamical model yielded a heuristic dispersion relation. It was suggested in [Masse,Clavin 2004] that the stabilization can be investigated looking at a much simpler model, namely the linear relaxation of wrinkled fronts. A first rigorous analysis was performed for an approximated model in [Clavin,Masse,Roquejoffre 2011], where a very similar dispersion relation was obtained. We prove here that, in the context of a longitudinal flow approximation, the dispersion relation obtained in our model is exactly the self-consistent one. In chapter 2, we establish an existence result for traveling wave solutions in some non-linear flame model with a shear flow and growth condition at infinity in the propagation direction. We show that this solutions exists for propagation speeds larger than some critical speed explicitly computed in terms of the flow. This solution, which has a free boundary, is very similar to the planar traveling wave existing for the Porous Media Equation. The main novelty is here the presence of a prescribed longitudinal shear flow. In the last chapter we use numerical simulations to investigate the free boundary, in which corners seem to appear. We give a semi-heuristic argument, which may allow one to study the free boundary regularity and its geometrical description
Rougemont, Frédéric de. "Interactions non linéaires intracavité : diffusion raman stimulée et mélange à quatre ondes quasidégénérées en fréquence". Paris 11, 1987. http://www.theses.fr/1987PA112102.
Texto completo da fonteMitri, Farid-Georges. "The dynamic radiation force of ultrasound : applications for material characterization and medical imaging". Lyon 1, 2004. http://www.theses.fr/2004LYO10133.
Texto completo da fonteGainville, Olaf. "Modélisation de la propagation atmosphérique des ondes infrasonores par une méthode de tracé de rayons non linéaire". Ecully, Ecole centrale de Lyon, 2008. http://www.theses.fr/2008ECDL0007.
Texto completo da fonteIn the framework of the comprehensive test bang treaty, we wish to link measured signals with infrasonic source characteristics (kind, power, motion\dots), in order to analyze and to understand International Monitoring System infrasonic network barometric measurements. Because of the complexity and the time variability of the atmosphere, modeling is necessary for atmospheric propagation. The goal of the work conducted during this thesis is to model the long range proagation of infrasonic wavesemitted by various source kinds. A better understanding of atmospheric propagation and the identification of phenomena which influence wave propagation are first steps in this direction. We need to quantify convection, diffraction, scattering, non linearity, atmospheric asorption effects onboth acoustic pressure levels and pressure signatures. In this thesis report, we develop an infrasonic wave propagation model based on a ray tracing method. A mathematical asymptotic analysis of motion equations for a relaxing thermoviscous fluid is performed under the hypothesis of a high frequency approximation and of a locally plane wave. The waveform evolution follows a generalized Burgers equation which takes into account non linearity for weak shocks, and atmospheric absorption. Caustic phase shift is also included. The physical model is solved using adapted numerical methods. These methods include an efficient eigenray research method for 3D problems. The generalized Burgers' equation is integrated using an adaptative mesh and step Fourier Galerkin spectral method. Finally we study two infrasound propagation problems. The Misty Picture experiment consists in a 4684 ton of ANFO exposure realized in 1987 in New Mexico (United States). This particularly well instrumente experiment is a long range infrasound propagation reference study at very low frequencies (0. 1\,Hz). This study shows that acoustic energy in the shadow zone is associated to scattering by atmospheric inhomogeneities. Daily Concorde infrasonic records performed since 1998 until 2003 at Flers station (France) offer numerous studies. In spite of the acoustical pressure level spreading complexity, infrasonic recorded arrivals are identified. The year 2002 is systematically studying to evaluate seasonal atmospheric variations effects on atmospheric infrasonic wave propagation. Ray tracing simulations, in agreement with measures, show the importance of non linear effects and of scattering ont he pressure signature. These studies are also used to characterize and quantify ray tracing method limits. In spite of a strong sensitivity of results to the atmospheric conditions, we show that the ray tracing method is adapted to model the propagation of infrasonic waves of central frequency higher than 1 Hertz
Baussard, Alexandre. "Résolution de problèmes inverses non linéaires : applications en imagerie à ondes électromagnétiques". Cachan, Ecole normale supérieure, 2002. http://www.theses.fr/2002DENSA010.
Texto completo da fonteHarazi, Maxime. "Diffusion multiple et retournement temporel des ondes ultrasonores dans les milieux granulaires secs et immergés". Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC024/document.
Texto completo da fonte: Time reversal (TR) is a technique which gives the possibility to make a wave relive its life in reverse chronology, and to focus back to its source. In this thesis, TR of ultrasound in granular media has been investigated experimentally and numerically. By propagating from grain to grain, ultrasounds provide a unique probe of the heterogeneous 3D contact network. We show that for multiply scattered waves, the focusing is essentially robust but sensitive to displacements of grains on a scale much smaller than the wavelength. In this respect, the ultrasound propagation through the discrete and metastable contact network between the grains appears to represent an intermediary situation between the instability in the propagation of a particle in a Lorentz gas and the propagation of ultrasounds in an homogeneous medium filled with scatterers. When the source amplitude is increased, a non-linear regime is reached where the wave itself triggers rearrangements in the medium, thus degrading the quality of the TR focusing. In this regime, the wave acts not only as a probe, but also as a « pump ». Finally, we show that the TR of a small-amplitude multiply-scattered wave can be used to focus a high-amplitude wave in the medium and trigger in a controlled way irreversible rearrangements of the contact network. These results are supported by a vectorial numerical model based on a 2D percolated masses-springs network
Yang, Yougu. "Propagation des ondes acoustiques dans les milieux granulaires confinés". Phd thesis, Université Paris-Est, 2013. http://tel.archives-ouvertes.fr/tel-01037954.
Texto completo da fonteDe, Oliveira Lage ferreira Cynthia. "Dynamique non linéaire des filaments d'actine et d'ADN". Toulouse, INSA, 2009. http://eprint.insa-toulouse.fr/archive/00000322/.
Texto completo da fonteThis thesis is dedicated to the mathematical study of some properties of biopolymers dynamics. We propose a mathematical justification of a nonlinear capacitance relation for an actin filament using the Poisson-Boltzmann equation. We also introduce a first methodology to derive a qualitatively simple model coupling the dynamics of a charged biopolymer and its surrounding counterions via electrostatic effects. We consider the case of a single actin filament represented by a zig-zag chain model. This model is calibrated using experimental data on the stiffness constant of actin. We derive a discrete diffusion equation for the density of ionic surrounding charges in a one-dimensional grid along actin from de continuum drift-diffusion model describing counterion dynamics. Numerical simulations of the coupled model show that mechanical waves propagating along the polymer can generate charge density waves with intensities in the pA range, in agreement with experimental measurements of ionic currents along actin. Finally, we study the existence of discrete breathers in a modified version of the Peyrard-Bishop model for DNA breathing in which the reclosing of base pairs is hindered by an energy barrier. Using a new kind of continuation from infinity, we prove for weak couplings the existence of large amplitude and low frequencies breathers lying outside resonance zones. These results are completed by numerical simulations of the model
Viard, Nicolas. "Contribution expérimentale à l'étude de la diffusion multiple des ultrasons en régimes de propagation linéaire et non linéaire". Phd thesis, Université Paris-Diderot - Paris VII, 2014. http://pastel.archives-ouvertes.fr/pastel-00955942.
Texto completo da fonteFahmi, Abdelilah. "Contrôle des effets non linéaires dans des liquides en mélange d'ondesApplication à la mesure de la susceptibilité non linéaire et à la conjugaison de phase". Angers, 1995. http://www.theses.fr/1995ANGE0022.
Texto completo da fonteTOURNAT, Vincent. "Effet non linéaire d'auto-démodulation d'amplitude dans les milieux granulaires: théories et expériences". Phd thesis, Université du Maine, 2003. http://tel.archives-ouvertes.fr/tel-00004227.
Texto completo da fonteDans ce travail de thèse, le fonctionnement de l'antenne paramétrique en émission dans les milieux granulaires non consolidés est étudié. L'antenne paramétrique, utilisée largement en acoustique sous-marine, met en jeu un effet d'acoustique non linéaire qui peut s'interpréter comme un phénomène d'auto-démodulation d'amplitude ou encore comme un phénomène de génération de fréquence différence. Ainsi, à partir de l'émission d'ondes intenses, composées de plusieurs hautes fréquences proches (de l'ordre de 100 kHz), des ondes de plus basses fréquences (1-10 kHz) sont générées par effet non linéaire dans le milieu de propagation. Les principaux intérêts de cette méthode sont i) la possible haute directivité du rayonnement de basse fréquence, utile pour sonder sélectivement les matériaux à tester, ii) la conversion de l'énergie émise vers des ondes de basses fréquences qui se propagent plus facilement dans les milieux fortement absorbants et / ou diffusants.
En premier lieu, plusieurs modèles d'antenne paramétrique sont développés afin de prendre en compte les phénomènes d'absorption, de diffusion, de dispersion de vitesse, ou encore le caractère évanescent des modes de propagation acoustique. Des expériences de propagation solidienne dans des assemblages désordonnés de billes de verre sont réalisées et interprétées. Ces expériences sont en accord qualitatif avec les prédictions théoriques.
En second lieu, des ondes de cisaillement sont utilisées en émission pour l'antenne paramétrique, et permettent de générer, par auto-démodulation, des ondes longitudinales de basses fréquences. Ce phénomène de dilatance non linéaire est mis en évidence dans plusieurs configurations expérimentales. L'amplitude du signal démodulé en fonction de l'amplitude des ondes de cisaillement initialement émises est tout d'abord quadratique puis exhibe une transition vers une dépendance en puissance 3/2. Il est démontré que le phénomène de clappement, ouverture puis fermeture des contacts inter-billes sous l'action de l'onde acoustique, est responsable de cette transition. La localisation de cette transition permet de caractériser qualitativement la distribution des déformations statiques des contacts dans le milieu, notamment dans la région des contacts faibles.
Enfin, le changement de la direction de polarisation des ondes de cisaillement permet de mettre en évidence une anisotropie du paramètre de non-linéarité quadratique du milieu, conséquence d'une anisotropie des chaînes de force, créées lorsqu'une contrainte statique uni-axiale est appliquée sur le milieu granulaire.
Pausader, Benoît. "Problèmes bien posés et diffusion pour des équations non linéaires dispersives d'ordre quatre". Cergy-Pontoise, 2008. http://www.theses.fr/2008CERG0361.
Texto completo da fonteGnofam, Wagbe. "Contribution à l'intégration monolithique des fonctions non linéaires nécessaires à la réalisation de systèmes à grande diffusion au voisinage de 60 ghz". Lille 1, 1994. http://www.theses.fr/1994LIL10188.
Texto completo da fonteToumi, Souad. "Caractérisation des matériaux complexes et de leurs endommagements par la technique de la coda ultrasonore alliée à l'acoustique non linéaire". Electronic Thesis or Diss., Le Mans, 2017. http://www.theses.fr/2017LEMA1024.
Texto completo da fonteNonlinear Resonance (NR) and Coda Wave Interferometry (CWI) have proved to be efficient to detect and follow the evolution of micro-cracks within a strongly scattering media (concrete, rocks, etc.). Nevertheless, the localization of the cracks using the same techniques is not straight forward. In order to avoid the conditioning and its subsequent relaxation effect related to NR, CWI is simultaneously applied when concrete samples are vibrating in the linear regime. Based on a comparative study of the coda signals contents (non ballistic part) in the absence and under the weak linear vibration, the localization of the mechanically induced scatterers was possible depending on the scatterers' main direction with respect to the vibration plane. The latter point raises the issue of the generated types of vibration at the scatterers. Therefore, investigations were performed using the Acoustic Emission (AE) technique, which has served to verify that the acoustic activity during the linear vibrations does change depending on the considered experimental configuration. The latter, has also a direct effect on the frequency content of the recorded AE hits showing the potential link existing between the quantitative analysis of AE hits and the generated vibration mechanisms of the existing micro-cracks
Cazier, Nicolas. "Effets d’optique non-linéaire d’ordre trois dans les cavités à cristaux photoniques en silicium : auto-oscillations GHz dues aux porteurs libres et diffusion Raman stimulée". Thesis, Paris 11, 2013. http://www.theses.fr/2013PA112337/document.
Texto completo da fonteIn this thesis, we studied third order nonlinear optical effects in photonic crystal cavities. The first of those effects is is the phenomenon of high frequency (GHz) self-pulsing in these cavities, which originates from a modulation of the transmission of the cavity due to the interaction between the free-carrier dispersion and the two-photon absorption. We have observed these self-induced oscillations for the first time in silicon photonic crystal nanocavities, with a frequency of about 3 GHz and a high spectral purity. We have developed a model to analyze the mechanisms that govern the onset of these oscillations, as well as the amplitudes of the fundamental and harmonic frequencies of these oscillations. This self-pulsing phenomenon would allow us to realize realize ultra-compact microwave sources made of silicon. The second phenomenon studied is that of Raman scattering, which is the only way to obtain lasers fully in silicon demonstrated so far. The Raman scattering was measured first in narrow photonic crystals waveguides (W0.63) of length 100 microns, where we could obtain a number of Stokes photons up to 9, showing that the stimulated Raman scattering predominated in these waveguides, although we have not been able to obtain a true Raman laser effect in them. We then measured the Raman scattering in doubly resonant nanocavities specifically designed from these waveguides to optimize the Raman effect, with quality factors up to 235000 for the Stokes resonance. Although we could only measure spontaneous Raman scattering in these cavities, with a Purcell factor of 2.9, the theoretical study that we conducted on the Raman lasers, which agrees perfectly with the experimental results, shows that it would be possible to obtain a Raman laser in these cavities with a threshold below the milliwatt, provided we reduce the losses due to the free-carrier absorption. This could be accomplished by decreasing the free-carrier lifetime, for example by removing the free carriers from the silicon using a MSM junction
Abi, rizk Lara. "Ondes progressives et propriétés de propagation pour un problème d’épidémiologie évolutive non-local". Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0244.
Texto completo da fonteIn this thesis we study the existence of a travelling wave solutions for an integro-differential system of equations from evolutionary epidemiology. We use ideas from dynamical system ideas theory coupled with estimates of the asymptotic behaviour of profiles. We prove that the wave solutions have a rather simple structure. This analysis allows us to reduce the infinite dimensional travelling wave profile system of equations to a four dimensional ODE system. The latter is used to prove the existence of travelling wave solutions for any wave speed larger than a minimal wave speed c?, provided that the epidemic threshold R0, which is expressed as a function of the principal eigenvalue of a certain integral operator, is strictly greater than 1. This same threshold condition is also used to prove that any travelling wave connects two determined stationary states. In the second part, we study the propagation properties of the solutions for the same spatially distributed system of equations, when the initial density of infected plants is a compactly supported function with the space variable x. When R0 > 1, we prove that spreading occurs with a definite spreading speed that coincides with the minimal speed c? of the travelling wave solutions discussed in the first part. Moreover, the solution of the Cauchy problem asymptotically converges to some specific function for which the moving frame variable x and the phenotype one y are separated
Ngapasare, Arnold. "Waves in disordered and nonlinear mechanical structures". Thesis, Le Mans, 2020. http://www.theses.fr/2020LEMA1036.
Texto completo da fonteThis work is devoted to the theoretical and numerical study of elastic wave propagation in disordered mechanical structures. The main goal is to investigate how the localization induced by disorder is affected by nonlinearity and by the presence of rotational motion. Firstly, we study a finite granular chain and show that not only Anderson localization is broken but also energy equipartition is achieved due to the discontinuous nonlinearity which is particular to granular chains. Furthermore, we extend our studies to a micropolar lattice that supports rotational waves. We show that in the linear limit the energy spreading is facilitated both by low frequency extended waves and a set of high frequency quasiextended modes. Also, we identify a case where energy is completely localized by tuning the stiffness. Finally, for a nonlinear architected LEGO chain featuring both transverse and rotational motion we study how nonlinearity breaks Anderson localization in this polarized system. The dynamics is found to have a unique character resembling a combination of the Fermi-Pasta-Ulam Tsingou and Klein-Gordon models regarding the asymptotic dynamical behavior and chaoticity
Cazier, Nicolas. "Effets d'optique non-linéaire d'ordre trois dans les cavités à cristaux photoniques en silicium : auto-oscillations GHz dues aux porteurs libres et diffusion Raman stimulée". Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00924642.
Texto completo da fonteGuillotel, Erwan. "Caractérisation optique et structurale de guides d'ondes non-linéaires GaAs/AlOx". Phd thesis, Université Paris-Diderot - Paris VII, 2010. http://tel.archives-ouvertes.fr/tel-00527196.
Texto completo da fonteBrunet, Thomas. "Etude des milieux granulaires secs et mouillés à l'aide des ondes ultrasonores". Phd thesis, Université de Marne la Vallée, 2006. http://tel.archives-ouvertes.fr/tel-00129738.
Texto completo da fontedenses sous contrainte. Elles permettent de sonder de manière non invasive la structure, les
propriétés viscoélastiques et les comportements non linéaires des réseaux de forces de contact dans
un tel milieu. Dans une première partie, nous rappelons quelques résultats concernant la propagation
linéaire d'ondes ultrasonores dans les matériaux granulaires (modes effectifs cohérents, diffusion
multiple des ondes élastiques). Nous montrons alors comment extraire les modules élastiques à l'aide
des ondes cohérentes et la dissipation interne à l'aide des ondes multiplement diffusées. En particulier,
l'étude de l'influence de la présence d'un fluide interstitiel en très faible quantité (< 0,1%)
et l'influence de l'état de surface des billes, sur les propriétés viscoélastiques de milieux granulaires
secs et mouillés, nous permet d'identifier deux mécanismes de dissipation : frictionnelle et visqueuse.
Enfin, nous nous intéressons au régime de propagation non linéaire des ondes élastiques dans les
milieux granulaires. Après avoir caractérisé expérimentalement l'élasticité non linéaire hertzienne
réversible du matériau granulaire par la génération d'harmoniques supérieures, nous discutons un
résultat original sur les processus d'interaction irréversibles onde-matière granulaire liés aux non
linéarités hystérétiques de type Mindlin entraînant une nette diminution du module élastique du
matériau granulaire et des micro-réarrangement à l'échelle des aspérités de grains.
Tretinnikov, Pavel. "New developments on the interpretative model of ITER diagnostics using microwaves". Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0027.
Texto completo da fonteThe turbulence in thermonuclear fusion plasma can lead to increase of the plasma transport coefficient that enhances the particles and energy losses therefore deteriorates the plasma confinement. That is why measurements of the plasma turbulence is important for description of the plasma transport processes. Microwave plasma diagnostics is an efficient kind of the active plasma diagnostics to characterize the turbulence. Their principles are based on the collection of information integrated over the probed plasma volume, and printed on the reflected or scattered waves reaching the detector, for which interpretative models are required to extract the turbulence properties. The radial correlation reflectometry (RCR) and the Doppler reflectometry are widely used technics that provide information on plasma turbulence characteristics. The Collective Thomson Scattering (CTS) is a valuable microwave diagnostic that can give the information about such plasma parameters as the bulk ion temperature, bulk ion composition, the fast particles (alpha particles or ions of a heating beam) velocity distribution. The knowledge of the alpha particle velocity distribution is especially interesting and important to evaluate the ITER performance where the energy amplification of plasma heating power Q is expected to achieve the value about 10. The actual data analysis of the microwave diagnostics, or interpretations of a measured signal is fulfilled assuming a smooth Gaussian probing beam. It was demonstrated that the microwave beams can be significantly distorted due to the edge plasma turbulence, that may lead to misleading interpretations of the diagnostic signal, based on the microwaves, so the diagnostics interpretative models should be analyzed taken into account to the probing beam distortion. The improvement of the microwave diagnostics interpretative models is the main object of the study presented in this thesis.The aim of this PhD work is to include these missing effects in an interpretative model for CTS using X-mode probing beam
Toumi, Souad. "Caractérisation des matériaux complexes et de leurs endommagements par la technique de la coda ultrasonore alliée à l'acoustique non linéaire". Thesis, Le Mans, 2017. http://www.theses.fr/2017LEMA1024/document.
Texto completo da fonteNonlinear Resonance (NR) and Coda Wave Interferometry (CWI) have proved to be efficient to detect and follow the evolution of micro-cracks within a strongly scattering media (concrete, rocks, etc.). Nevertheless, the localization of the cracks using the same techniques is not straight forward. In order to avoid the conditioning and its subsequent relaxation effect related to NR, CWI is simultaneously applied when concrete samples are vibrating in the linear regime. Based on a comparative study of the coda signals contents (non ballistic part) in the absence and under the weak linear vibration, the localization of the mechanically induced scatterers was possible depending on the scatterers' main direction with respect to the vibration plane. The latter point raises the issue of the generated types of vibration at the scatterers. Therefore, investigations were performed using the Acoustic Emission (AE) technique, which has served to verify that the acoustic activity during the linear vibrations does change depending on the considered experimental configuration. The latter, has also a direct effect on the frequency content of the recorded AE hits showing the potential link existing between the quantitative analysis of AE hits and the generated vibration mechanisms of the existing micro-cracks
Van, Der Biest François. "Diffusion multiple et renversement du temps ultrasonore dans des milieux périodiques et désordonnés". Phd thesis, Université Paris-Diderot - Paris VII, 2005. http://tel.archives-ouvertes.fr/tel-00011354.
Texto completo da fonteNous avons tout d'abord conçu et caractérisé des échantillons périodiques, autrement appelés "cristaux phononiques". Ces matériaux se comportent comme des filtres fréquentiels et présentent un grand intérêt technologique et théorique.
Nous avons étudié le temps de groupe à la traversée de monocristaux, qui révèle un effet analogue à l'effet tunnel en mécanique quantique. Dans une structure de type Fabry-Pérot constituée de deux cristaux phononiques, nous avons mis en évidence des résonances en transmission. L'étude du temps de groupe montre un phénomène de piégeage de l'onde dans la cavité, analogue de l'effet tunnel résonant. Les résultats obtenus sont confirmés par la modélisation numérique.
Par la suite, des expériences de Retournement Temporel dans les cristaux phononiques ont révélé une absence d'hyperfocalisation, caractéristique des milieux désordonnés.
Nous avons ensuite cherché à mettre en évidence la diffusion multiple en régime non-linéaire dans les nuages de bulles. A cet effet, nous avons conçu un dispositif expérimental qui nous a permis de générer des populations de bulles relativement stables et contrôlées. Plusieurs méthodes de caractérisation de la fonction de distribution du rayon des bulles ont été mises en oeuvre, et l'une d'elles nous a permis d'estimer la fraction volumique de bulles.
Les densités de bulles mises en jeu n'ont pas permis de mettre en évidence un régime de diffusion multiple fort, tandis que l'origine des non-linéarités observées reste incertaine.
Dessup, Tommy. "Instabilités et dynamiques de particules en interaction dans un système quasi-unidimensionnel". Thesis, Sorbonne Paris Cité, 2016. http://www.theses.fr/2016USPCC121/document.
Texto completo da fonteIn this thesis, we provide a detailed theoretical and numerical study of instabilities and dynamics in quasi-one-dimensional systems of repulsively interacting particles in a thermal bath.When the transverse confinement decreases, theses systems display a structural transition from a line to an homogeneous or inhomogeneous staggered row configuration. We have exhibited and explained the supercritical or subcritical character of the bifurcation according to the particles interaction and to the system geometry. The quantitative description of stable equilibrium configurations called "bubbles" has been done, their shapes consist in coexistence of line and zigzag phases.The "bubble" dynamics has been modelized by considering an effective particle that diffuses in a periodic potential induced by the discrete character of the system. When several "bubbles" coexist, they interact and evolve towards a single stable "bubble" through coalescence and collapse mechanisms. We have shown that the configuration topology has to be taken into account and exhibited frustration effects leading to either an attractive or repulsive interaction between "bubbles". Then we have shown the divergence of the mean squared transverse displacements of the particles near the transition thresholds and analytically explained these critical behaviors by the existence of a soft mode in the configuration vibrational spectrum. With this eigenmodes description, we have also interpreted a diffusion enhancement of a particle file moving on an asymmetrical periodic potential with respect to the free file diffusion
Bioud, Fatma Zohra. "Microscopie de mélange à quatre ondes résolue en polarisation pour sonder l’ordre moléculaire dans les milieux biologiques". Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4380.
Texto completo da fonteThe capacity to quantify molecular orientational order in tissues is of a great interest since pathologies (skin lesion, neurodegenerative diseases, etc) can induce strong modifications in proteins’ organization. While numerous studies have been undertaken using polarization resolved second order nonlinear optical microscopy which is only specific to non-centrosymmetric organizations, higher order effects have been less explored. Four-wave mixing (FWM) microscopy and its resonant counterpart coherent anti-Stokes Raman scattering (CARS) can be of a great utility as label free diagnosis tools benefiting from less constraining symmetry rules. In this work, we implement incident polarizations tuning in FWM and CARS microscopy to probe molecular order, using a generic method to read-out symmetry information.Fourier analysis of the polarization-resolved FWM/CARS signal processed with an analytical model provides a fast and direct determination of the symmetry orders of the distribution function of the probed molecules. This method does not require a priori knowledge of the organization structure and provides quantitatively its second and fourth order symmetries. We applied this technique on different systems, from crystalline to less organized (multilamellar vesicles and proteins aggregates). We show that this new approach brings additional and more refined information on supra-molecular structures in complex media
Zhao, Dan. "Force calibration and wavefield synthesis for acoustical tweezers". Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS411.
Texto completo da fonteSingle beam acoustical tweezers have been developed and applied to numerous applications in biological and biochemical domains. Their application in precise manipulations requires accurate control of the acoustical trap. This work sets out to calibrate the force exerted by acoustical tweezers and synthesize the desired wavefield. The single beam acoustical tweezers are achieved by a focused vortex beam. An object in interaction with the acoustic waves is trapped thanks to the radiation pressure. This three-dimensional force can be obtained by knowing the incident beam shape coefficients as well as the scattering coefficients. Therefore, the computation of the forces can be achieved by measuring the wavefield. The first part of the thesis concentrates on assessing different methods to compute the beam shape coefficients from the pressure field to estimate the radiation force exerted on an elastic sphere. Then, in the second part, the synthesis of the field using the inverse filtering method is carried out. A proper synthesis of the field requires a suitable distribution of control points where the wave propagation information is recorded. To synthesize the appropriate vortex beam, three kinds of distributions were compared. For the single beam acoustical tweezers, the most challenging part is the axial restoring force. In order to overcome this difficulty, the spherical vortex beam with high pressure gradient in the axial direction is introduced. This spherical vortex beam is intended to trap large spheres with diameters close to the wavelength. The feasibility of this vortex is analyzed numerically and experimentally
Barbier, Margaux. "Génération de paires de photons corrélés par mélange à quatre ondes spontané dans des fibres microstructurées à coeur liquide". Thesis, Palaiseau, Institut d'optique théorique et appliquée, 2014. http://www.theses.fr/2014IOTA0011/document.
Texto completo da fonteQuantum telecommunication technologies rely on correlated photon pair sources, which are often based on the third-order nonlinear process of spontaneous four-wave mixing in silica-core photonic crystal fibres. A fibred architecture is advantageous because it minimizes the coupling losses between the optical source and the other components of quantum communication networks. Moreover, using a photonic crystal fibre rather than a conventional silica fibre offers the possibility of improving the photon generation (thanks to a small effective core area) and extending the wavelength coverage (thanks to dispersion management through the microstructuration design). However, the performances of silica-core photonic crystal fibre sources are limited in terms of quantum purity, because of the ubiquitous spontaneous Raman scattering process, which is a source of uncorrelated broadband noise photons in silica. We propose an original solution to this Raman problem by replacing the silica core by a liquid core, thanks to a hollow-core photonic crystal fibre filled with a nonlinear liquid. We actually performed the first experimental demonstration of the generation of correlated photon pairs in a liquid-core fibre, and demonstrated that, thanks to the specific Raman properties of liquids (which usually exhibit thin-line Raman spectra), it is possible to reduce the Raman noise level by several orders of magnitude. This work opens the way for the development of high quantum quality correlated photon pair fibred sources
Al, Haj Mohammad. "Modèles discrets de dislocations : ondes progressives et dynamique de particules". Thesis, Paris Est, 2014. http://www.theses.fr/2014PEST1001/document.
Texto completo da fonteThis work focuses on the study of the dislocation dynamics in the crystal lattice and it is splitted into two parts : the first part is concerned with the horizontal motion of a chain of interacting atoms containing a dislocation. While, the second part deals with the accumulation of dislocations forming what is known as walls of dislocations. In the first part, we consider a fully nonlinear generalization of the discrete reaction diffusion equations “fully overdamped Frenkel-Kontorova models” that describe the dynamics of crystal defects (dislocations) in a lattice. We study both : the bistable and the monostable non-linearities. Under sufficient conditions, we show the existence and uniqueness of traveling wave solution for the bistable non-linearity case. For the monostable case, we study the existence of branch of traveling waves solutions for general Lipschitz non-linearity. We also prove that the minimal velocity is non-negative and bounded below. In this part, we as well study the generalization of Frenkel-Kontorova model for which we can add a driving force parameter. We also illustrate, in this case, the variation of the velocity of propagation of traveling waves in terms of the parameter force. In the second part, we study the accumulation of dislocations in walls of dislocations. We prove actually the convergence of several interacting dislocations to walls of dislocations. We also present results of some numerical experiments that confirm the theoretical results that we obtain
Lafontaine, David. "Effets dispersifs et asymptotique en temps long d'équations d'ondes dans des domaines extérieurs". Thesis, Université Côte d'Azur (ComUE), 2018. http://www.theses.fr/2018AZUR4067/document.
Texto completo da fonteWe are concerned with Schrödinger and wave equations, both linear and non linear, in exterior domains. In particular, we are interested in the so-called Strichartz estimates, which are a family of dispersive estimates measuring decay for the linear flow. They turn out to be particularly useful in order to study the corresponding non linear equations. In non-captive geometries, where all the rays of geometrical optics go to infinity, many results show that Strichartz estimates hold with no loss with respect to the flat case. Moreover, the local smoothing estimates for the Schrödinger equation, respectively the local energy decay for the wave equation, which are another family of dispersive estimates, are known to fail in any captive geometry. In contrast, we show Strichartz estimates without loss in an unstable captive geometry: the exterior of many strictly convex obstacles verifying Ikawa's condition. The second part of this thesis is dedicated to the study of the long time asymptotics of the corresponding non linear equations. We expect that they behave linearly in large times, or scatter, when the domain they live in does not induce too much concentration effect. We show such a result for the non linear critical wave equation in the exterior of a class of obstacles generalizing star-shaped bodies. In the exterior of two strictly convex obstacles, we obtain a rigidity result concerning compact flow solutions, which is a first step toward a general result. Finally, we consider the non linear Schrödinger equation in the free space but with a potential. We prove that solutions scatter for a repulsive potential, and for a sum of two repulsive potentials with strictly convex level surfaces. This provides a scattering result in a framework similar to the exterior of two strictly convex obstacles
Diallo, Souleymane. "Utilisation des non-linéarités Kerr et Brillouin dans les résonateurs à mode de galerie cristallins pour la synthèse de micro-ondes". Thesis, Besançon, 2016. http://www.theses.fr/2016BESA2028/document.
Texto completo da fonteWhispering galery mode resonators are dielectric cavities that support modes with ultra-high quality factor and small volume that remain confined in their inner periphery for time duratioons that can be as long as few microseconds. The strong confinement of these modes for such long durations strongly enhances nonlinear effect suchs as Kerr effect or Brillouin effect. These resonators can therefore be used for several applications such as spectroscopy, telecommunications or microwave generation. The objective of this thesis is to use Kerr and Brillouin nonlinearities in these resonators at the laser wavelength of 1550 nm, in order to generate high spectral purity microwave signals with frequencies rangong fros 5 to 30 GHz. The first chapter oh the thesis intriduces the theory, fabrication, coupling and characterisation of whispering gallery mode resonators. The second chapter is about the generation of Kerr optical frequency combs in these resonators and their application to the generation of microwave signals. We present our experimental resuktsdn the numerical modelling of Kerr combs, the analysis of oscillatory instabilities (due to thermal effect) observed during our experiments, and conclue. The third chapter concerns photon-phonon interactions via stimulated Brillouin scattering in these resonators and their application to the generation of microwave signals. We present our experimental results and the temporal model that we developed to track the dynamics of the forward and backscattered fields. The last chapter conclude the thesis. The research presented in this thesis has benne funded by the European Research Council through the project Nextphase
Vedadi, A. "Etude et applications des amplificateurs paramétriques à fibre optique". Phd thesis, Université de Franche-Comté, 2008. http://tel.archives-ouvertes.fr/tel-00544865.
Texto completo da fonteNgo, Duc Duy. "Optique non-linéaire et équation des ondes non-linéaire semi-classique". Nice, 2006. http://www.theses.fr/2006NICE4074.
Texto completo da fonteFoulon, Michel-François. "Métamatériaux térahertz en régime linéaire et non linéaire". Thesis, Lille 1, 2008. http://www.theses.fr/2008LIL10121/document.
Texto completo da fonteArtificial materials so called «metamaterials» are studied theoretically and characterized at few hundred of GigaHetrz frequencies. Frequencial and temporal (electro-optic) methods are used to prove their left handed behaviour. For this study, two approaches have been considered : - the first one is based on the fabrication of micro-resonators and metallic wires arrays aiming at operating at 100 GHz. An experimental evidence of a left handed dispersion branch is then made from vectorial analysis. - the second approach takes profit of phase advance effects that can be obtained from a transmission line periodically loaded with a series capacitance and a parallel inductance. The specificity of this study is a coherent time domain approach that allows us to directly visualize a phase advance and the corresponding left handed behaviour. Those results are confirmed by the calculations of Fourier transforms up to 1 TeraHertz. Non linear properties of those circuits are then studied by introducing a non linearity by the mean of a Heterostructure Barrier Varactor component. The extension of this study to the non linear regime is treated via the dynamic characterization of this component. Finally, two types of non linear regimes are studied for a left handed transmission line loaded with HBV diodes with respectively harmonic generation and parametric amplification
Hmima, Abdelhamid. "Dynamique non-linéaire dans les oscillateurs optoélectroniques micro-ondes". Université de Franche-comté. UFR des sciences et techniques, 2012. http://www.theses.fr/2012BESA2042.
Texto completo da fonteThis work is part of the effort undertaken in order to improve the performance of optoelectronic oscillators (OEOs) with delay line optical _ber. This OEO was recently introduced and rapidly gained a great interest for several research laboratories in the world. This is due to its great spectral purity which is required for micro-wave radars and geolocalisation systems. We studied the standard architecture using optical _ber delay line in order to deal with the speci_cs of the OEO at time-frequency and optics domain interface. Frequency stability levels achieved by the OEO are interesting. Therefore we explored the potential of a new architecture of OEO that takes advantage on nonlinear dynamics. Indeed this architecture can deliver in addition of the microwave signal, optical pulses with very short duration and low time jitter. This is made possible by the spectral properties of the OEO and the by introducing temporal compression and optical regeneration techniques. These pulses operate at telecommunications wavelengths, particularly at 1:55 _m. This type of OEO with optical compression can be dedicated to Optical Time Division Multiplexing (OTDM) systems. We have experimentally determined a spectral purity, respectively, -60 and -140 dBc/Hz at 101 and 2_104 Hz from 10 GHz carrier. The optical pulses generated at 10 GHz repetition rate have 4. 1 ps durations with a time jitter of 2. 7 and 83 fs respectively in the ranges [1 to 10 kHz] and [10 Hz to 100 kHz]. This work opens the way to the use of other nonlinear phenomena to improve the spectral purity of microwave oscillators
Heiderich, Anne. "Diffusion multiple en milieu non linéaire ou anisotrope". Université Joseph Fourier (Grenoble), 1995. http://www.theses.fr/1995GRE10200.
Texto completo da fonteBarthelet, Pierre. "Dynamique non linéaire des ondes interfaciales entre deux fluides cisaillés". Toulouse, INPT, 1995. http://www.theses.fr/1995INPT104H.
Texto completo da fonteHajj, Chehade Hana. "Contribution aux problèmes de diffusion non linéaire en hydrologie". Amiens, 2013. http://www.theses.fr/2013AMIE0103.
Texto completo da fonteIn this thesis, we model the interface (sharp interface) that exists naturally between sea water and fresh water in a homogenous confined coastal aquifer. We prove existence and uniqueness of some radial solutions. We consider then a fully nonlinear parabolic problem that generalizes the interface problem and prove a priori gradient estimates. Many applications are given such that the porous medium problem and the doubly nonlinear diffusion problem. For the last problem, we present too the self similar solutions and verify then the gradient estimates. Finally, we study existence of travelling waves for the interface equation with some source term
Baccouche, Yousra. "Caractérisation non linéaire de l'endommagement des matériaux composites par ondes guidées". Phd thesis, Université du Maine, 2013. http://tel.archives-ouvertes.fr/tel-00840424.
Texto completo da fonteKasparian, Jérôme. "ÉTUDE DE SPECTROSCOPIE LINÉAIRE ET NON-LINÉAIRE D'AÉROSOLS ATMOSPHÉRIQUES". Phd thesis, Université Claude Bernard - Lyon I, 1997. http://tel.archives-ouvertes.fr/tel-00011446.
Texto completo da fonteLe premier axe est la mesure quantitative des aérosols urbains au-dessus de Lyon par une nouvelle méthode combinant la télédétection optique par lidar et l'analyse de particules prélevées par impaction sur des filtres classiques. La composition et la distribution de taille des aérosols prélevés sont déterminés par microscopie optique et microanalyse. Ces informations servent à calculer les coefficients d'extinction et de rétrodiffusion grâce à un algorithme dont la particularité est de prendre en compte la nature fractale des plus petites particules.
Ce calcul permet de calibrer l'inversion du signal Lidar. Cette méthode combine ainsi la richesse des informations issues des filtres avec la souplesse du lidar qui donne accès à la dynamique spatiale et temporelle de la concentration globale des aérosols. Simultanément, une étude épidémiologique est effectuée sur l'exposition de volontaires aux aérosols, au travers d'une collaboration avec de Département d'Écologie Urbaine de la Ville de Lyon.
Parallèlement, en vue de mesurer l'efficacité des processus chimiques hétérogènes à la surface des aérosols, nous développons une enceinte de simulation permettant d'étudier une particule isolée. Dans ce but, nous avons mis au point des méthodes d'analyse optique non-destructive des particules, piégées dans un champ électrique. Nous mesurons leur taille à partir de la figure de diffusion de Mie, leur composition par spectroscopie micro-Raman, et leurs paramètres optiques utiles à l'inversion des signaux lidar grâce à une sphère intégratrice.
Enfin, les gouttes sphériques microscopiques se comportent comme des microcavités qui amplifient considérablement les processus optiques non-linéaires. Dans le but de développer de nouvelles techniques de détection, nous avons étudié la diffusion non-linéaire par des gouttes d'eau dont le rayon est de quelques dizaines de microns, et en particulier la génération de troisième harmonique pompée par un laser à impulsions ultrabrèves. La distribution angulaire correspondante est considérablement plus simple que celle de la diffusion de Mie linéaire, et dépend peu de la taille des gouttes. Par ailleurs, nos résultats suggèrent que les longueurs relatives de l'impulsion et de la cavité pourraient avoir une importance capitale dans la génération des processus stimulés. Ceci nous conduit à envisager un lidar non-linéaire qui serait sélectivement sensible aux particules de petites tailles.
Paquerot, Jean-François. "Dynamique non linéaire des ondes de pression sanguine dans les grosses artères". Dijon, 1995. http://www.theses.fr/1995DIJOS041.
Texto completo da fonteVu, Quang Anh. "Evaluation du béton d'enrobage par acoustique non linéaire et ondes de surface". Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4712/document.
Texto completo da fonteThis thesis is related to the field of nondestructive evaluation of concrete by ultrasound. We focus our study on nonlinear acoustic-based measurements that allow the concrete auscultation at mesoscopic scale where waves interact with microcracks and porosity network. The nonlinear parameters are known to be much more sensitive than those from linear measurements. Concrete is a heterogeneous and complex material. Its behavior is highly nonlinear with increasing damaged state.We develop in this thesis a type of nonlinear measurement: Dynamic Acousto-Elastic Testing (DAET). This technique is based on the principle of a dynamic excitation of the material, using ultrasounds to follow the variation of the elastic behavior depending on the excitation amplitude. We focus our study on the problem of concrete cover which holds a key role in the life of a civil engineering structure. We study the interaction of the DAET measurement with the Rayleigh waves which propagate in the concrete cover. We show the high sensitivity evolution of non-linear parameters in function of thermal damage and carbonation.Subsequently, we propose a new methodology of DAET measurement, in which the transient vibration is generated by an impact and ultrasounds are generated continuously. We present different applications of the proposed method including the case of large specimens. This approach opens broad possibilities of transposing measurements for on-site application
Seck, Ousmane. "Sur un modèle de diffusion non linéaire en dynamique des populations". Nancy 1, 1986. http://www.theses.fr/1986NAN10162.
Texto completo da fonteAttouchi, Amal. "Etude qualitative des équations de Hamilton-Jacobi avec diffusion non linéaire". Thesis, Paris 13, 2014. http://www.theses.fr/2014PA132022/document.
Texto completo da fonteThis thesis is devoted to the study of qualitative properties of solutions of an evolution equation of Hamilton-Jacobi type with a p-Laplacian diffusion. It is mainly concerned with the study of the effect of the non-linear diffusion on the gradient blow-up phenomenon. The main issues we are studying are: local existence and uniqueness, regularity, spatial profile of gradient blow-up and localization of the singularities. We provide examples where the gradient blow-up set is reduced to a single point. In Chapter 4, a viscosity solution approachis used to extend the blowing-up solutions beyond the singularities and an ergodic problem is also analyzed in order to study their long time behavior. In the penultimate chapter, we address the question of boundedness of global solutions to the one-dimensional problem. In the last chapter we prove a local in space, gradient estimate and we use it to obtain a Liouville-type theorem