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Ponomarev, Dmitry. "Quelques problèmes inverses avec des données partielles". Thesis, Nice, 2016. http://www.theses.fr/2016NICE4027/document.
Pełny tekst źródłaThe thesis consists of three parts. In Part I, we consider partially overdeterminedboundary-value problemS for Laplace PDE in a planar simply connected domain withLipschitz boundary. Assuming Dirichlet and Neumann data available on its part to be realvaluedfunctions of certain regularity, we develop a non-iterative method for solving thisill-posed Cauchy problem choosing as a regularizing parameter L2 bound of the solutionon complementary part of the boundary. The present complex-analytic approach alsonaturally allows imposing additional pointwise constraints on the solution which, onpractical side, can help incorporating outlying boundary measurements without changingthe boundary into a less regular one. Part II is concerned with spectral structure of atruncated Poisson operator arising in various physical applications. We deduce importantproperties of solutions, discuss connections with other problems and pursue differentreductions of the formulation for large and small values of asymptotic parameter yieldingsolutions by means of solving simpler integral equations and ODEs. In Part III, we dealwith a particular inverse problem arising in real physical experiments performed withSQUID microscope. The goal is to recover certain magnetization features of a sample frompartial measurements of one component of magnetic field above it. We develop newmethods based on Kelvin and Fourier transformations resulting in estimates of netmoment components
Ha, Duong Tuong. "Equations intégrales pour la résolution numérique de problèmes de diffraction d'ondes acoustiques dans R**(3)". Paris 6, 1987. http://www.theses.fr/1987PA066420.
Pełny tekst źródłaCaudron, Boris. "Couplages FEM-BEM faibles et optimisés pour des problèmes de diffraction harmoniques en acoustique et en électromagnétisme". Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0062/document.
Pełny tekst źródłaIn this doctoral dissertation, we propose new methods for solving acoustic and electromagnetic three-dimensional harmonic scattering problems for which the scatterer is penetrable and inhomogeneous. The resolution of such problems is key in the computation of sonar and radar cross sections (SCS and RCS). However, this task is known to be difficult because it requires discretizing partial differential equations set in an exterior domain. Being unbounded, this domain cannot be meshed thus hindering a volume finite element resolution. There are two standard approaches to overcome this difficulty. The first one consists in truncating the exterior domain and renders possible a volume finite element resolution. Given that they approximate the scattering problems at the continuous level, truncation methods may however not be accurate enough for SCS and RCS computations. Inhomogeneous penetrable harmonic scattering problems can also be solved by coupling a volume variational formulation associated with the scatterer and surface integral equations related to the exterior domain. This approach is known as FEM-BEM coupling (Finite Element Method-Boundary Element Method). It is of great interest because it is exact at the continuous level. Classical FEM-BEM couplings are qualified as strong because they couple the volume variational formulation and the surface integral equations within one unique formulation. They are however not suited for solving high-frequency problems. To remedy this drawback, other FEM-BEM couplings, said to be weak, have been proposed. These couplings are actually domain decomposition algorithms iterating between the scatterer and the exterior domain. In this thesis, we introduce new acoustic and electromagnetic weak FEM-BEM couplings based on recently developed Padé approximations of Dirichlet-to-Neumann and Magnetic-to-Electric operators. The number of iterations required to solve these couplings is only slightly dependent on the frequency and the mesh refinement. The weak FEM-BEM couplings that we propose are therefore suited to accurate SCS and RCS computations at high frequencies
Amenoagbadji, Pierre. "Wave propagation in quasi-periodic media". Electronic Thesis or Diss., Institut polytechnique de Paris, 2023. http://www.theses.fr/2023IPPAE020.
Pełny tekst źródłaThe goal of this thesis is to develop efficient numerical methods for the solution of the time-harmonic wave equation in quasiperiodic media, in the spirit of methods previously developed for periodic media. The goal is to use as in quasiperiodic homogenization the idea that an elliptic PDE with quasiperiodic coefficients can be interpreted as the cut of a higher-dimensional PDE which is elliptically degenerate, but with periodic coefficients. The periodicity property allows to use adapted tools, but the non-elliptic aspect makes the mathematical and numerical analysis of the PDE delicate. One application concerns transmission problems between periodic half-spaces (typically photonic crystals) when (1) the interface does not cut the periodic half-spaces in a direction of periodicity, or (2) when the periodic media have noncommensurate periods along the interface
Faucher, Florian. "Contributions à l'imagerie sismique par inversion des formes d’onde pour les équations d'onde harmoniques : Estimation de stabilité, analyse de convergence, expériences numériques avec algorithmes d'optimisation à grande échelle". Thesis, Pau, 2017. http://www.theses.fr/2017PAUU3024/document.
Pełny tekst źródłaIn this project, we investigate the recovery of subsurface Earth parameters. Weconsider the seismic imaging as a large scale iterative minimization problem, anddeploy the Full Waveform Inversion (FWI) method, for which several aspects mustbe treated. The reconstruction is based on the wave equations because thecharacteristics of the measurements indicate the nature of the medium in whichthe waves propagate. First, the natural heterogeneity and anisotropy of the Earthrequire numerical methods that are adapted and efficient to solve the wavepropagation problem. In this study, we have decided to work with the harmonicformulation, i.e., in the frequency domain. Therefore, we detail the mathematicalequations involved and the numerical discretization used to solve the waveequations in large scale situations.The inverse problem is then established in order to frame the seismic imaging. Itis a nonlinear and ill-posed inverse problem by nature, due to the limitedavailable data, and the complexity of the subsurface characterization. However,we obtain a conditional Lipschitz-type stability in the case of piecewise constantmodel representation. We derive the lower and upper bound for the underlyingstability constant, which allows us to quantify the stability with frequency andscale. It is of great use for the underlying optimization algorithm involved to solvethe seismic problem. We review the foundations of iterative optimizationtechniques and provide the different methods that we have used in this project.The Newton method, due to the numerical cost of inverting the Hessian, may notalways be accessible. We propose some comparisons to identify the benefits ofusing the Hessian, in order to study what would be an appropriate procedureregarding the accuracy and time. We study the convergence of the iterativeminimization method, depending on different aspects such as the geometry ofthe subsurface, the frequency, and the parametrization. In particular, we quantifythe frequency progression, from the point of view of optimization, by showinghow the size of the basin of attraction evolves with frequency. Following the convergence and stability analysis of the problem, the iterativeminimization algorithm is conducted via a multi-level scheme where frequencyand scale progress simultaneously. We perform a collection of experiments,including acoustic and elastic media, in two and three dimensions. Theperspectives of attenuation and anisotropic reconstructions are also introduced.Finally, we study the case of Cauchy data, motivated by the dual sensors devicesthat are developed in the geophysical industry. We derive a novel cost function,which arises from the stability analysis of the problem. It allows elegantperspectives where no prior information on the acquisition set is required
Gaudron, Renaud. "Réponse acoustique de flammes prémélangées soumises à des ondes sonores harmoniques". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLC073/document.
Pełny tekst źródłaThermoacoustic instabilities, also known as combustion instabilities, are a major concern in the aerospace and energy production industries. They are due to an energy transfer that occurs between a heat source, usually a flame stabilized inside a combustor, and the surrounding acoustic field and may lead to undesirable phenomena such as flame extinction, increased heat fluxes, very large sound emissions at certain frequencies, vibration, structural damage and even catastrophic failure in some cases. Given the potential consequences of such phenomena, a large research effort has been devoted to predicting the onset of combustion instabilities in modern boilers, rocket engines and gas turbines during the past few decades. Unfortunately, the theoretical framework associated with the study of thermoacoustic instabilities is complex and multi-physics and the geometry of practical combustors is an intricate arrangement of 3D cavities. As a consequence, predicting the thermoacoustic stability of a combustor at an early design stage is a challenging task to date... (See inside the manuscript for the remainder of the abstract)
Goulet, Pierre. "Contribution à l'étude des molécules à symétrie C4v, à l'aide de la spectroscopie hertzienne". Dijon, 1990. http://www.theses.fr/1990DIJOS022.
Pełny tekst źródłaPeynaud, Emilie. "Rayonnement sonore dans un écoulement subsonique complexe en régime harmonique : analyse et simulation numérique du couplage entre les phénomènes acoustiques et hydrodynamiques". Thesis, Toulouse, INSA, 2013. http://www.theses.fr/2013ISAT0019/document.
Pełny tekst źródłaThis thesis deals with the numerical simulation of time harmonic acoustic propagation in an arbitrary mean flow in an unbounded domain. Our approach is based on an equation equivalent to the linearized Euler equations called the Galbrun equation. It is derived from a mixed Eulerian-Lagrangian formulation and results in a single equation whose only unknown is the perturbation of the Lagrangian displacement. A direct solution using finite elements is unstable but this difficulty can be overcome by using an augmented equation which is constructed by adding a new unknown, the vorticity, defined as the curl of the displacement. This leads to a set of equations coupling a wave like equation with a time harmonic transport equation which allows the use of perfectly matched layers (PML) at artificial boundaries to bound the computational domain. The first part of the thesis is a study of the time harmonic transport equation and its approximation by means of a discontinuous Galerkin scheme, the difficulties coming from the oscillating behaviour of its solutions. Once these difficulties have been overcome, it is possible to deal with the resolution of the acoustic propagation problem. The approximation method is based on a mixed continuous-Galerkin and discontinuous-Galerkin finite element scheme. The well-posedness of both the continuous and discrete problems is established and the convergence of the approximation under some mean flow conditions is proved. Finally a numerical implementation is achieved and numerical results are given which confirm the validity of the method and also show that it is relevant in complex cases, even for unstable flows
Stutzmann, Eléonore. "Tomographie du manteau a partir des modes harmoniques des ondes de surface". Paris 7, 1993. http://www.theses.fr/1993PA077102.
Pełny tekst źródłaGuyétand, Olivier. "Photoionisation simple et double à deux couleurs d'atomes de gaz rares". Paris 11, 2008. http://www.theses.fr/2008PA112327.
Pełny tekst źródłaThe present work deals with simple and double ionization of rare gases by harmonic radiation produced by, and combined with, an intense femtosecond infrared laser. Technical aspects related to the use of harmonic generation and to the detection of ions and electrons in coincidence are exposed. Theoretical backgroung for two colour, few photon, single and double ionization is detailed. Spectra and angular distributions of the photoelectrons measured in helium are described and compared with TDSE theoretical calculations, for various conditions of the harmonic photons. The shape of the angular distributions can be explained within the frame of two distinct analytic approaches : the perturbation theory and the soft-photon approximation. The double ionization measurements have been performed on xenon, a complex atom characterized by many possible routes leading to double ionization. The analysis of energy and angular correlations of the two photoelectrons proves the feasibility of such experiments, which combine harmonic and infrared radiations. It shows that two step processes are dominant in the case of xenon. This work appeals for extending few photon, double ionization experiments to lighter rare gases
Thaury, Cédric. "Génération d’harmoniques d’ordres élevés sur miroir plasma". Paris 11, 2008. http://www.theses.fr/2008PA112322.
Pełny tekst źródłaWhen an intense laser beam is focused on a solid target, its surface is rapidly ionized and forms a dense plasma that reflects the incident field. For laser intensities above few 1015Wcm-2, high order harmonics of the laser frequency, associated in the time domain to a train of attosecond pulses (1as = 10-18s), can be generated upon this reflection. Because such a plasma mirror can be used with arbitrarily high laser intensities, this process should eventually lead to the production of very intense pulses in the X-ray domain. In this thesis, we demonstrate that for laser intensities about 1019Wcm-2, two mechanisms can contribute to the generation of high order harmonics: the coherent wake emission and the relativistic emission. These two mechanisms are studied both theoretically and experimentally. In particular, we show that, thanks to very different properties, the harmonics generated by these two processes can be unambiguously distinguished experimentally. We then investigate the phase properties of the harmonic, in the spectral and in the spatial domain. Finally, we illustrate how to exploit the coherence of the generation mechanisms to get information on the dynamics of the plasma electrons
Makki, Ali. "Modélisation des moteurs asynchrones monophases à condensateur avec saturation et harmoniques d'espace". Lyon 1, 1996. http://www.theses.fr/1996LYO10297.
Pełny tekst źródłaHaessler, Stefan. "Generation of attosecond pulses in atoms and molecules". Paris 11, 2009. http://www.theses.fr/2009PA112224.
Pełny tekst źródłaIn several experiments, we demonstrate the potential of the process of high-order harmonic generation for observing ultrafast intra-molecular electron and nuclear dynamics. The largest part of this thesis treats experiments where molecules constitute the generating medium and the recolliding electron wavepacket takes the role of a ‘self-probe’. Measurements of phase and amplitude of the harmonic emission from CO2 and N2 molecules aligned in the laboratory frame allow us to extract the recombination dipole matrix element. The latter contains the signature of quantum interference between the free and bound parts of the total electronic wavefunction. The utilization of this interference for the shaping of the attosecond (1as=10−18s) XUV emission is demonstrated. Furthermore, we study theoretically molecular orbital tomography from the recombination dipole matrix elements and demonstrate its experimental feasibility. This opens the perspective of imaging ultrafast distortions of a frontier orbital during a chemical reaction. In a second part of this thesis, we use the coherent XUV light emitted by argon atoms to photoionize N2 molecules and measure how an auto-ionizing resonance modifies the spectral phase of the ejected photoelectron wavepacket. The last chapter of this thesis describes studies of the generation of XUV attosecond pulses in a different medium: ablation plasmas. The first temporal characterization of such a source demonstrates its femtosecond and attosecond structure
Rembert, Pascal. "Études des résonances acoustiques par des méthodes quasi-harmoniques et impulsionnelles : phase spectrale". Le Havre, 1991. http://www.theses.fr/1991LEHA0006.
Pełny tekst źródłaWalti, Olivier. "Contribution à la caractérisation des matériaux magnétiques soumis à des ondes complexes". Lille 1, 1995. http://www.theses.fr/1995LIL10078.
Pełny tekst źródłaDardenne, Sébastien. "Amélioration de la linéarité des amplificateurs de puissance par injection de composantes basses fréquences et d'intermodulation, pour des applications de radiocommunications mobiles". Poitiers, 2005. http://www.theses.fr/2005POIT2289.
Pełny tekst źródłaThe aim of this thesis is the analysis and the design of a linearization technique applied to Power Amplifiers for mobile radiocommunications. First, classical linearization and efficiency enhancement techniques and architectures are presented. Then, a study of frequency injection at input and/or at output of the amplifier shows how it can improve the behaviour of the amplifier in term of linearity. This second part highlighted the fact that we can use both low frequency and intermodulation injection in order to linearize an amplifier. The third part of the thesis details the chosen architecture. Intermodulation components are generated by the non linear behaviour of a first stage of a two stages amplifier topology. Correct amplitude and phase are adjusted with gate bias level of the first stage. The low frequency component is detected at the output of the second stage. At low power output levels, low frequency injection does improve the linearity of the amplifier. Between medium output power levels and up to compression, low frequency injection is completed with a dynamic bias level of the first stage. Combination of the two techniques allows an improvement of 10 up to 15 dB of the linearity of the power amplifier for all output power levels
Abou-Akar, Atef. "Modélisation des moteurs asynchrones triphasés à cage". Lyon 1, 1991. http://www.theses.fr/1991LYO10124.
Pełny tekst źródłaFontaine, Jean. "Une Equation semi-linéaire des ondes sur les espaces hyperboliques". Nice, 1996. http://www.theses.fr/1996NICE4939.
Pełny tekst źródłaBonazzoli, Marcella. "Méthodes d'ordre élevé et méthodes de décomposition de domaine efficaces pour les équations de Maxwell en régime harmonique". Thesis, Université Côte d'Azur (ComUE), 2017. http://www.theses.fr/2017AZUR4067/document.
Pełny tekst źródłaThe time-harmonic Maxwell’s equations present several difficulties when the frequency is large, such as the sign-indefiniteness of the variational formulation, the pollution effect and the problematic construction of iterative solvers. We propose a precise and efficient solution strategy that couples high order finite element (FE) discretizations with domain decomposition (DD) preconditioners. High order FE methods make it possible for a given precision to reduce significantly the number of unknowns of the linear system to be solved. DD methods are then used as preconditioners for the iterative solver: the problem defined on the global domain is decomposed into smaller problems on subdomains, which can be solved concurrently and using robust direct solvers. The design, implementation and analysis of both these methods are particularly challenging for Maxwell’s equations. FEs suited for the approximation of the electric field are the curl-conforming or edge finite elements. Here, we revisit the classical degrees of freedom (dofs) defined by Nédélec to obtain a new more friendly expression in terms of the chosen high order basis functions. Moreover, we propose a general technique to restore duality between dofs and basis functions. We explicitly describe an implementation strategy, which we embedded in the open source language FreeFem++. Then we focus on the preconditioning of the linear system, starting with a numerical validation of a one-level overlapping Schwarz preconditioner, with impedance transmission conditions between subdomains. Finally, we investigate how two-level preconditioners recently analyzed for the Helmholtz equation work in the Maxwell case, both from the theoretical and numerical points of view. We apply these methods to the large scale problem arising from the modeling of a microwave imaging system, for the detection and monitoring of brain strokes. In this application accuracy and computing speed are indeed of paramount importance
Soudais, Paul. "Contribution à la résolution des équations de Maxwell harmoniques par une méthode numérique hybride". Châtenay-Malabry, Ecole centrale de Paris, 1995. http://www.theses.fr/1995ECAP0448.
Pełny tekst źródłaLévêque, Jean-Jacques. "Etude du manteau supérieur de la terre par inversion anisotrope des ondes de surface et de leurs harmoniques". Université Louis Pasteur (Strasbourg) (1971-2008), 1987. http://www.theses.fr/1987STR13028.
Pełny tekst źródłaRamananjaona, Christophe Jean Gabriel. "Méthodes d'ensembles de niveaux pour la résolution de problèmes inverses des ondes". Versailles-St Quentin en Yvelines, 2002. http://www.theses.fr/2002VERS0026.
Pełny tekst źródłaCette étude traite de la reconstruction non linéaire d'un objet homogène bidimensionnel (infiniment long dans la direction axiale) de connexité simple ou multiple, enfoui dans un espace libre ou un demi-espace, à partir de mesures de champ d'ondes harmoniques diffractées par celui-ci. Il s'agit d'un problème inverse dont la solution est recherchée itérativement à l'aide d'une représentation de l'objet sous forme d'un ensemble de niveaux, dont la déformation est contrôlée par une vitesse satisfaisant des conditions de minimisation d'une fonctionnelle objectif caractérisant l'erreur entre le champ diffracte et le champ reconstruit; les champs étant calculés sans approximation grâce à une méthode de moments reposant sur des intégrales de domaine. La nouveauté de ce travail tient notamment à l'extension de la méthode à la configuration stratifiée, ainsi qu'à l'utilisation d'une formulation lagrangienne de la fonctionnelle objectif, afin de calculer convenablement la dérivée, grâce au bon usage des propriétés des fonctions de Green, qui rassemblent de manière synthétique toute la configuration géométrique de l'expérience. L'analyse a été développée pour les ondes electromagnétiques en polarisation Transverses Magnétique (TM) et Electrique (TE), l'accent étant porté sur le mode TE-dont l'analyse est nouvelle-, qui numériquement requiert une attention particulière. Un algorithme alliant une méthode d'optimisation utilisant les ensembles de niveaux et la méthode de Levenberg-Marquardt a permis d'autre part de reconstruire des objets de contraste inconnu. Enfin, il a été développé un algorithme de point fixe qui, mettant en jeu une discrétisation directe des conditions d'optimalité, et moyennant la connaissance du volume de l'objet a reconstruire, permet d'obtenir un résultat satisfaisant en une ou deux itérations. Des données expérimentales acquises en laboratoire sur des objets conducteurs ou diélectriques en régime microonde ont été traitées avec de bons résultats
Tomas, Corinne. "Etude de la corrélation entre émission photoélectrique et génération d'harmoniques à partir de métaux". Lyon 1, 1998. http://www.theses.fr/1998LYO10178.
Pełny tekst źródłaKhamlichi, Drissi Khalil El. "Synthèse analytique des convertisseurs statiques par la méthode de conservation de la puissance instantanée : application à la détermination des harmoniques des courants d'entrée". Lille 1, 1990. http://www.theses.fr/1990LIL10005.
Pełny tekst źródłaReby, Fabrice. "Réduction des harmoniques haute fréquence générés par les convertisseurs statiques : méthode de la dérivée continue appliquée au contrôle du gradient de courant pendant les commutations". Lille 1, 1999. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/1999/50376-1999-271.pdf.
Pełny tekst źródłaKharchi, Rachid. "Etude de la minimisation des harmoniques créés par l'utilisation d'un pont redresseur triphasé : application à un pont de Graëtz à G.T.O". Mulhouse, 1992. http://www.theses.fr/1992MULH0239.
Pełny tekst źródłaIgnatova, Vanya. "Méthodes d'analyse de la qualité de l'énergie électrique : application aux creux de tension et à la pollution harmonique". Grenoble 1, 2006. http://www.theses.fr/2006GRE10157.
Pełny tekst źródłaThe power quality concerns all the actors in the energy domains, that they are network administrators, suppliers, producers, or consumers of electricity. The research work presented in this PhD thesis is situated in the field of the power quality monitoring. Its objective is to introduce new techniques for analysis of power quality problems. There different methods designed for the analysis of the power quality disturbances. This method reaches very good performances in the voltage dips analysis, as it allows segmenting, classifying and characterising these power quality disturbances. The periodic systems method allows the theorical study of the generation and the propagation of harmonic disturbances in the network. Finally, the statistical matrix method has the objective to represent statistically electrical signals without loss of important information
Ajendouz, Abdelilah. "Etude théorique et expérimentale de la génération d’harmoniques micro-ondes dans un magnétoplasma : application à la détection de la turbulence". Aix-Marseille 1, 2008. http://www.theses.fr/2008AIX11085.
Pełny tekst źródłaThe microwave techniques, e. G. Reflectometry, have been extensively used as diagnostic of the fusion plasmas. In our study, we develop a new technique based on the transmitted signal - in contrast to reflectometry - in an inhomogeneous magnetized toroidal plasma. This diagnostic is based of the generation of the second harmonic of an extraordinary probing wave. Inside the upper hybrid resonance layer, the wave exhibits a resonant interaction with the plasma particles and this leads to the excitation of the second harmonic of the injected wave. It is shown theoretically and experimentally that the excitation level is high at the UHR and decreases rapidly away the UHR layer. The results demonstrate that the second harmonic can propagate through the plasma without cut-off. The new electromagnetic wave is capable to propagate outside the plasma. The second harmonic generation is used in this work as a wave diagnostics when the UHR layer is turbulent. It is shown that the frequency spectrum around the frequency probing exhibits two satellite frequencies excited by the interaction between the electromagnetic wave and the low frequency electrostatic wave. The detection of this satellite constitutes a remote diagnostic of the electrostatic fluctuation. The detection of the turbulence is sensitively dependent on the frequency of the injected wave and we show that the level is increased when the upper hybrid frequency is resonant inside the turbulent layer
Mansour, Gihane. "Méthode de décomposition de Domaine pour les équations de Laplace et de Helmholtz : Equation de Laplace non linéaire". Paris 13, 2009. http://www.theses.fr/2009PA132013.
Pełny tekst źródłaThis work is divided into two parts : First, a domain decomposition method for the resolution of the Poisson equation and the Helmholtz equation in a bounded domain,with Dirich let boundary condition. Second, The study of the Laplace equation, with non linear boundary condition g. Using the Min-Max method. First, we elaborate some essential tools to introduce our equations, then we present two indirect methods for solving the Poisson equation : there laxed barycentric Dirichlet-Neumann algorithm and the symmetric Dirichlet-Neumann algorithm. The first algorithm was introduced and studied by A. Quarteroni, A. Valli. We present in this work a new proof of its convergence. The second scheme presented is new : we give asymmetric version of the Dirichlet-Neumann condition. We prove that this algorithm is convergent. The theoretical results show that both of the discretization methods are convergent and estimation son the error of convergence are given. We test the two methods numerically, using Comsol with Matlab solver. We notice that the symmetric method converges faster than the barycentric one
Ah-Jaco, Aimé. "Modélisation des moteurs asynchrones triphasés en régime transitoire avec saturation et harmoniques d'espace : application au diagnostic". Lyon 1, 1997. http://www.theses.fr/1997LYO10187.
Pełny tekst źródłaAubreton, Thierry. "Application des méthodes asymptotiques transitoires et harmoniques aux antennes et à la compatibilité électromagnétique". Limoges, 1996. http://www.theses.fr/1996LIMO0016.
Pełny tekst źródłaMazzieri, Ilario. "Non-conforming high order methods for the elastodynamics equation". Nice, 2012. http://www.theses.fr/2012NICE4014.
Pełny tekst źródłaIn this thesis, we present a new discretization approach to combine the Discontinuous Galerkin Spectral Element (DGSE) and the Mortar Spectral Element (MSE) methods with suitable time advancing schemes for the simulation of the elastic wave propagation in heterogeneous media. To overcome the limitations of the existing approaches we apply the non-conforming paradigm only at the subdomain level. We show that the resulting formulations are stable, enjoy optimal approximation properties, and suffer from low dispersion and dissipation errors. Applications of the DGSE and MSE methods to simulate realistic seismic wave propagation problems in three dimensions are also considered
Lévêque, Jean-Jacques. "Etude du manteau supérieur de la terre par inversion anisotrope des ondes de surface et de leurs harmoniques". Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37607381q.
Pełny tekst źródłaParolin, Émile. "Méthodes de décomposition de domaine sans recouvrement avec opérateurs de transmission non-locaux pour des problèmes de propagation d'ondes harmoniques". Thesis, Institut polytechnique de Paris, 2020. http://www.theses.fr/2020IPPAE011.
Pełny tekst źródłaThe pioneering work of B. Després then M. Gander, F. Magoulès and F. Nataf have shown that it is mandatory, at least in the context of wave equations, to use impedance type transmission conditions in the coupling of subdomains in order to obtain convergence of non-overlapping domain decomposition methods (DDM). In the standard approach considered in the literature, the impedance operator involved in the transmission conditions is local and leads to algebraic convergence of the DDM in the best cases. In later works, F. Collino, S. Ghanemi and P. Joly then F. Collino, P. Joly and M. Lecouvez have observed that using non local impedance operators such as integral operators with suitable singular kernels could lead to a geometric convergence of the DDM.This thesis extends these works (that mainly concerned the scalar Helmholtz equation) with the extension of the analysis to electromagnetic wave propagation. Besides, the numerical analysis of the method is performed for the first time, proving the stability of the convergence rate with respect to the discretization parameter, hence the robustness of the approach. Several integral operators are then proposed as transmission operators for Maxwell equations in the spirit of those constructed for the acoustic setting. An alternative to integral operators, based on the resolution of elliptic auxiliary problems, is also advocated and analyzed. Extensive numerical results are conducted, illustrating the high potential of the new approach. Based on a recent work by X. Claeys, the last part of this work consists in exploiting the multi-trace formalism to extend the convergence analysis to the case of partitions with junction points, which is a difficult problem that attracted a lot of attention recently. The new approach relies on a new operator that communicates information between sub-domains, which replaces the classical point-to-point exchange operator. A proof of geometrical convergence of the associated iterative algorithm, again uniform with respect to the discretization parameter, is available and we show that one recovers the standard algorithm in the absence of junction points
Teissier, Maurice. "Auto-amorçage d'une génératrice asynchrone triphasée autonome en charge équilibrée ou non". Lyon 1, 1997. http://www.theses.fr/1997LYO10293.
Pełny tekst źródłaJammal, Ahmad. "Etude d'un variateur de vitesse asynchrone à fréquence constante et court-circuiteur périodique statique". Lyon 1, 1988. http://www.theses.fr/1988LYO10040.
Pełny tekst źródłaDubois, Dominique. "Propriétés de résolution d'un système à nombre d'équations et d'inconnues différent : exemple d'application en traction électrique". Lille 1, 1998. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/1998/50376-1998-237.pdf.
Pełny tekst źródłaBekka, Nassim. "Modélisation et optimisation d'actionneurs rotatifs fort couple pour systèmes embarqués". Nantes, 2015. https://archive.bu.univ-nantes.fr/pollux/show/show?id=b0badb6d-3747-42eb-bcf7-0e81b1bc02de.
Pełny tekst źródłaPermanent magnet machines with fractional slot concentrated windings are very suited in low speed high torque applications, thanks to their high torque density and low manufacturing costs. However, they are characterized by low fundamental winding factor and high content of magnetomotive force (MMF) space harmonics that can lead to undesirable effects, such as eddy current losses in the magnets, acoustic noise and vibration. To overcome these drawbacks, two novel methodologies for optimal design of fractional slot with concentrated windings have been proposed, passive and active methods. The passive method acts on the winding parameters (coil span, number of turns, slot distribution, etc. ) to optimize the winding layout. The active method uses two identical windings shifted in space and fed by currents shifted in time in a manner that the MMF waveforms produced by the two windings will be in phase for the torque harmonic and in opposite phase for the undesirable harmonic ranks. These two methods have been applied to optimize the winding layout of the permanent magnet machine with a 12×nbase slots/10×nbase poles (nbase is an integer number). Two new winding layouts were then obtained. Permanent magnet machines with the optimized windings are then designed for a 10 kW-50rpm application. The electromagnetic performances of the optimized windings are investigated and compared with conventional winding topology. It is found that the proposed approaches allow the emergence of new windings with higher performances
Xu, Jianhong. "Filtrage actif parallèle des harmoniques des réseaux de distribution d'électricité". Vandoeuvre-les-Nancy, INPL, 1994. http://docnum.univ-lorraine.fr/public/INPL_T_1994_XU_J.pdf.
Pełny tekst źródłaSwan, Jean-Paul. "Suppression des harmoniques 5 et 7 des courants d'entrée des redresseurs triphasés par injection de courants". Lille 1, 1988. http://www.theses.fr/1988LIL10027.
Pełny tekst źródłaRobert, Gilles. "Invariants topologiques et géométriques reliés aux longueurs des géodésiques et aux sections harmoniques de fibrés". Université Joseph Fourier (Grenoble), 1994. http://www.theses.fr/1994GRE10185.
Pełny tekst źródłaAdane, Yacine. "Caractérisation inverse de sources pour l'évaluation de l'exposition humaine aux ondes électromagnétiques émises par les antennes de station de base". Paris 6, 2004. http://www.theses.fr/2004PA066348.
Pełny tekst źródłaRabus, David. "Résonateur à ondes élastiques de volume à harmoniques élevés (HBARs) pour mesures gravimétriques : application à la détection de gaz". Phd thesis, Université de Franche-Comté, 2013. http://tel.archives-ouvertes.fr/tel-00923625.
Pełny tekst źródłaRoman, Christophe. "Contrôle frontière de l'équation des ondes avec amortissement distribué". Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAT053/document.
Pełny tekst źródłaThis thesis is concerned by the boundary control of the one dimensional wave equation, which can be used to model a string (like a guitar string). The objective is to act at one boundary to control and stabilize the otherboundary which is considered to be an unstable dynamic boundary condition. This thesis suggests answers to both following questions:Consider that the unstable dynamics boundary condition has some unknown parameters. Is a nonlinear adaptive control law still performing efficiently, if the viscous damping taken equal to zero for its design is no longer neglected?How can we take into account the in-domain damping in order to stabilize the wave equation subject to dynamic boundary conditions?This thesis suggests a method to derive a Lyapunov analysis in order to prove the robustness mismatch ofparticular nonlinear adaptive control law as the answer of the first question. Then using infinite dimensionalbackstepping technique we develop feedback control law that exponentially stabilize the considered wave equation
Hembert, Francky. "Etude et réalisation d'un filtre actif monophasé à structure multiniveaux obtenue par mise en série de ponts à quatre interrupteurs". Lille 1, 1996. http://www.theses.fr/1996LIL10196.
Pełny tekst źródłaAlali, Mohamad Alaa Eddin. "Contribution à l'Etude des Compensateurs Actifs des Réseaux Electriques Basse Tension : (Automatisation des systèmes de puissance électriques)". Université Louis Pasteur (Strasbourg) (1971-2008), 2002. http://www.theses.fr/2002STR13026.
Pełny tekst źródłaIn an electrical network, unbalanced and harmonic currents generated by nonlinear and unbalanced loads can cause harmonics and unbalanced voltage. These voltage perturbations along with voltage sag can strongly degrade customer power quality. Nowadays, the active filtres such as shunt, series and combined shunt-series are studied as a flexible solution to compensate all current and voltage perturbations. Therefore, in order to improve power system quality, we have studied advanced control methods applied on the structures of the above mentioned active filtres. For such requirements, we have developed a new RST control method in order to extend the application spectrum of RST controller. Thus, an universal shunt active filter has been developed using a continuous and discret time experimental
Boussalem, Mohamed David Jacques Choubani Fethi. "Étude et modélisation de structures de transmission non uniformes applications à l'adaptation d'impédance et au filtrage /". Toulouse : INP Toulouse, 2007. http://ethesis.inp-toulouse.fr/archive/00000462.
Pełny tekst źródłaThèse soutenue en co-tutelle. Titre provenant de l'écran-titre. Bibliogr. 59 réf.
Olivier, Augustin. "Contribution à l'étude des propriétés dynamiques des lasers semiconducteurs 1,5 um à multipuits quantiques". Lille 1, 1990. http://www.theses.fr/1990LIL10075.
Pełny tekst źródłaThalin, Pascal. "Réduction des perturbations en courants harmoniques et en champ magnétique créées par les installations de chauffage à induction". Toulouse, INPT, 1998. http://www.theses.fr/1998INPT034H.
Pełny tekst źródłaMaunoury, Matthieu. "Méthode de visualisation adaptée aux simulations d'ordre élevé : application à la compression-reconstruction de champs rayonnés pour des ondes harmoniques". Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30021.
Pełny tekst źródłaWhile high order methods allow to perform very accurate simulations with low costs, there is a lack of tools to analyze and exploit results obtained by these new schemes. The objective of this thesis is to design a framework and efficient algorithms to visualize solutions computed by high order methods. Our approach is based on the construction of an optimized affine approximation of the numerical solution which can be handled by any standard visualization software. A representation mesh is created via an a posteriori estimate which control visualization error between the numerical solution and its representation, and is performed pointwise. A strategy is established to ensure that (dis)continuities are well-rendered. A special work is done to treat high order elements (curved elements) and in particular use specific a posteriori estimates. Several numerical examples demonstrate the potential of the visualization method. In a second part, we examine the computation and reconstruction of radiated fields for wave problems in harmonic regime. We propose a methodology to generate an accurate reconstruction of radiated fields while limiting the information needed (i.e. compressing the data). For this purpose, we rely on basis functions composed of high order polynomials and plane waves, as well as a development of the kernel used for the integral representation. The visualization method allows to faithfully represent (decompression process) the cartographies obtained