Dissertations / Theses on the topic 'Diffraction en régime harmonique'
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Dubois, Pierre. "Optimisation de structures rayonnantes métalliques 3D par déformation de surfaces iso-niveaux en régime harmonique." Paris, ENMP, 2005. http://www.theses.fr/2005ENMP1373.
Badia, Ismaïl. "Couplage par décomposition de domaine optimisée de formulations intégrales et éléments finis d’ordre élevé pour l’électromagnétisme." Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0058.
In terms of computational methods, solving three-dimensional time-harmonic electromagnetic scattering problems is known to be a challenging task, most particularly in the high frequency regime and for dielectric and inhomogeneous scatterers. Indeed, it requires to discretize a system of partial differential equations set in an unbounded domain. In addition, considering a small wavelength λ in this case, naturally requires very fine meshes, and therefore leads to very large number of degrees of freedom. A standard approach consists in combining integral equations for the exterior domain and a weak formulation for the interior domain (the scatterer) resulting in a formulation coupling the Boundary Element Method (BEM) and the Finite Element Method (FEM). Although natural, this approach has some major drawbacks. First, this standard coupling method yields a very large system having a matrix with sparse and dense blocks, which is therefore generally hard to solve and not directly adapted to compression methods. Moreover, it is not possible to easily combine two pre-existing solvers, one FEM solver for the interior domain and one BEM solver for the exterior domain, to construct a global solver for the original problem. In this thesis, we present a well-conditioned weak coupling formulation between the boundary element method and the high-order finite element method, allowing the construction of such a solver. The approach is based on the use of a non-overlapping domain decomposition method involving optimal transmission operators. The associated transmission conditions are constructed through a localization process based on complex rational Padé approximants of the nonlocal Magnetic-to-Electric operators. The number of iterations required to solve this weak coupling is only slightly dependent on the geometry configuration, the frequency, the contrast between the subdomains and the mesh refinement
Bériot, Hadrien. "Eléments finis d'ordre élévé pour l'opérateur de Galbrun en régime harmonique." Compiègne, 2008. http://www.theses.fr/2008COMP1791.
Investments in Computational methods for aeroacoustic have grown recently due to their application in the transportation sector. To account for the flow effects in the propagation zones, the Linearized Euler Equations (LEE) are generally preferred. If robust methods are available in the time domain, practically no methods have been proposed in the frequency domain on unstructured grids. In this manuscript, we propose an original finite element method for the operator of Galbrun, known to be physically equivalent to the LEE. To stabilize the numerical scheme and improve the performance, a mixed high-order approach is employed. A complete dispersion analysis of high-order methods in the presence of flow is performed. Validations are proposed in ducted swirling flows based on Pridmore-Brown's model. Acoustic and hydrodynamic phenomenon are examined as well as the use of non reflecting conditions
Patiño, López Luis david. "Caractérisation des propriétés thermoélectriques des composants en régime harmonique : techniques et modélisation." Bordeaux 1, 2004. http://www.theses.fr/2004BOR12792.
Wang, Yaw-Juen. "Modélisation déterministe et probabiliste en régime harmonique d'un convertisseur triphasé à commutation naturelle." Grenoble INPG, 1993. http://www.theses.fr/1993INPG0049.
Touati, Karim. "Photothermoélectricité : Modélisation en régime harmonique et caractérisation de matériaux thermoélectriques solides et liquides." Thesis, Littoral, 2016. http://www.theses.fr/2016DUNK0418/document.
The use of the self-induced Seebeck effect in thermophysical characterization of solid and liquid thermoelectric (TE) materials is described in this manuscript. In previous works, the photothermoelectric technique (PTE) has been developed in our laboratory for the thermal characterization of solid TE materials having low electrical conductivities. In this work, we first generalized the use of the PTE technique to all solid thermoelectric materials (with high or low electrical conductivities). This is achieved by taking into account the Gaussian shape of the thermal source exciting the material as well as by the understanding of the coupling effects between thermal and electrical transport mechanisms when a TE material is submitted to a modulated thermal excitation. In this thesis, several solid thermoelectric materials were studied : Titanium trisulfide (TiS₃),Bi₂Ca₂Co₁,₇Oₓ oxydes and Bismuth Selenido-telluride (Bi₂Te₂,₄Se₀,₆). Then, the self-induced Seebeck voltage was used for the detection of phase transitions exhibited by certain thermoelectric materials. The case of the copper selenide (Cu₂Se) was studied. A new procedure allowing to follow the temperature dependance of the thermal diffusivity of solid TE materials is also presented. In this work, the PTE technique was extended to liquid thermoelectric (LTE) materials. Indeed, a theoretical model describing the signal delivered by a LTE material subject to a periodic thermal excitation has been developed. Then, a study of the evolution of the thermal properties of an electrolyte as function of a solute concentration was performed. Finally, the thermal-wave resonator cavity (TWRC) approach was used to characterize thermally LTE materials. As far as we know, this is the first method proposing a TWRC approach applied directly to the sensor itself. The use of LTE such as heat sensors was also addressed here
Manescu, Léonardo-Géo. "L'étude du régime non-sinusoïdal dans les systèmes électriques." Phd thesis, Grenoble INPG, 1998. http://tel.archives-ouvertes.fr/tel-00821087.
Duruflé, Marc. "Intégration numérique et éléments finis d'ordre élevé appliqués aux équations de Maxwell en régime harmonique." Phd thesis, Paris 9, 2006. http://tel.archives-ouvertes.fr/tel-00068590.
équations de Maxwell en régime fréquentiel, afin de calculer
précisément la signature radar de cibles diverses. Pour avoir
une grande précision nécessaire pour des expérience de grande taille,
nous utilisons des méthodes d'ordre élevé.
Dans le cas scalaire, les éléments finis spectraux hexaédriques
avec condensation de masse, permettent d'obtenir un produit matrice vecteur
rapide et peux coûteux en stockage. Dans le cas vectoriel, les hexaèdres
de la première famille ne réalisent pas la condensation de masse, mais on peut
écrire un algorithme rapide de produit matrice-vecteur. Des résultats
numériques 3-D montrent la performance de l'algorithme proposé.
Nous traitons également le cas où la géométrie présente
une symétrie de révolution. On est alors ramenés à une succession
de problèmes 2-D indépendants.
Nous proposons une méthode éléments finis d'ordre élevé
couplée à des équations intégrales d'ordre élevé.
Bodrero, Alain. "Contrôle d'un champ acoustique à l'intérieur d'une cavité par des moyens passifs en régime harmonique." Rouen, 1999. http://www.theses.fr/1999ROUES029.
Demaldent, Edouard. "Etude de schémas de discrétisation d'ordre élevé pour les équations de Maxwell en régime harmonique." Paris 9, 2009. https://bu.dauphine.psl.eu/fileviewer/index.php?doc=2009PA090028.
This thesis deals with numerical simulation issues, and concerns the study of time- harmonic electromagnetic scattering problems. We are mainly interested in integral re-presentation methods and in simulations that need the use of a direct solver. Their range of application is rapidly limited with classical approximation schemes, since they require a large number of unknowns to achieve accurate results. To overcome this problem, we intend to adapt the spectral finite element method to electromagnetic integral equa-tions, then to the hybrid boundary element - finite element method (BE-FEM). The main advantage of our approach is that the Hdivconforming property (Hdiv-Hcurl within the BE-FEM) is enforced, meanwhile it can be interpreted as a point-based scheme. This al-lows a significant increase of the approximation order, that yields to a dramatical decrease of both the number of unknowns and computational costs, while ensuring the accuracy of the result. Another originality of our study lies in the development of high-order ani-sotropic hexahedral elements, to deal with conducting scatterers coated with a thin layer of material. Key words :computational electromagnetics, Maxwell equations, integral equations, hybrid boundary element - finite element method, method of moments, spectral finite element method, high-order approximation
Manescu, Léonardo-Géo. "L'étude du régime non-sinusoïdal dans les systèmes électriques." Grenoble INPG, 1998. http://www.theses.fr/1998INPG0063.
This thesis deals with the study, by simulation, of power Systems in non-sinusoidal situations including harmonie pollution effects. First the principal parameters of non-sinusoidal wave shapes and working conditions and some éléments of power theory were reviewed. Novel complementary intégrais and derivatives harmonie distortion factors were proposed as well. Secondly, the modelling of the main types of harmonie sources was studied, either by adapting existing models where possible or by designing new models, such for power converters or TCRs. The linear parts of the System where then treated by the appropriated models or making new proposais (as for power transformers). After evaluating the simulation principles of the power Systems operating in non-sinusoidal conditions, itérative harmonie analysis was selected for localised studies, where its convergence properties were improved. For mil scale system studies, a software program was developed based on the dichotomous method, where the hybrid modelling, in both time and frequency domains, of non-linear éléments is assumed. The results of simulations conducted on the IEEE 14-bus modified test network were used in order to analyse the interactions between the harmonie sources, mainly by using the individual and total harmonie active powers. Finally, the principal types of harmonie pollution effects hâve been studied and detailed for several System constituents
Duclairoir, Eve-Marie. "Rayonnement acoustique dans un écoulement cisaille : une méthode d'éléments finis pour la simulation du régime harmonique." Phd thesis, Ecole Polytechnique X, 2007. http://pastel.archives-ouvertes.fr/pastel-00002409.
Unger, Kévin. "Tomographie de diffraction sans mesure de phase en régime de diffusion multiple." Thesis, Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0513.
Optical diffraction tomography is an imaging technique in which a target issuccessively illuminated by a laser beam under different angles of incidence withan interferometric set up which enables to record both the phase and the intensity of the field in the image space of a microscope. The permittivity of the target is then numerically estimated from the complex field dataset thanks to an inversion procedure. In this type script, we first study the effect of multiple scattering inside the target on the obtained reconstructions by studying different approximations (Born) to speed up the computation. The recording of the phase in the optical domain is tricky, for it requires ainterferometric set up. I have built a reconstruction technique based only on the intensities. I show that the obtained reconstructions are close to those obtained with the complete dataset field + phase. Finally, we propose to adjoin phaseless diffraction tomography to fluorescence structured illumination microscopy. In this framework, we illustrate the impact of the modelization of the illumination excitating the fluorophores on the resolving power of the imaging technique. Moreover, we demonstrate an imaging method which estimates simultaneously the fluorophores and the surrounding media from the join recording of diffraction and fluorescence intensities
Buvat, Fabrice. "Modélisation de la réponse d'un capteur à courants de Foucault comportant un noyau ferromagnétique en régime harmonique." Paris 11, 2004. http://www.theses.fr/2004PA112207.
In aeronautics, non destructive evaluation by eddy-currents is commonly used to detect corrosion area or cracks in structures. Eddy-current testing by using ferrite-cored probes is effective to detect these kinds of defects. So, having a model able to predict these probes responses is a major endeavor. Our work consisted in developping a model determining the ferrite-cored probes response to a defect. To model fields inside both the core and the defect, an integral formulation has been used resulting from the application of the green's theorem onto the equations of propagation. Simulation results have been compared to synthetic data obtained by a finite-element method and they have been validated by comparison with measured impedance data. However as this model may be computationally costly, the use of the so-called non-linear approximation has been tested to tackle the case of long defects. The model has been integrated inside the civa platform developped by the cea
Fol, Hugo. "Méthodes de type Galerkin discontinu pour la résolution numérique des équations de Maxwell 3D en régime harmonique." Nice, 2006. http://www.theses.fr/2006NICE4069.
The general objective of this study is the development and the evaluation of discontinuous Galerkin (DG) methods on unstructured tetrahedral meshes for the numerical resolution of the first order system of 3D Maxwell equations in the frequency domain. In the first part of this thesis, we formulate and analyze centred DG methods based on a P0 local approximation (i. E. Finite volumes or DG-P0 method) and a P1 local approximation (i. E. Linear discontinuous Galerkin or DG-P1 method). The second part is devoted to the design of domain decomposition methods for the solution of the algebraic systems associated to DG methods for the discretization of the time-harmonic Maxwell equations. We first consider the system of Maxwell equations in the continuous case and study the convergence of overlapping and non-overlapping Schwarz algorithms based on a first order (natural) interface condition that corresponds to a Dirichlet condition for characteristic variables associated to incoming waves. We then conduct a convergence analysis in the discrete case corresponding to the finite volume formulation (DG-P0 method) on a quadrilateral mesh. Finally, we study optimized interface conditions in order to accelerate the convergence of the non-overlapping Schwarz algorithm. Preliminary tests in 2D illustrate the performance gains resulting from the use of optimised interface conditions. The third part of the thesis is concerned with a numerical evaluation of the DG-P0 et DG-P1 formulations on tetrahedral meshes. We make use of a series of test cases of increasing complexity dealing with diffraction problems in homogeneous and heterogeneous media. We conduct a detailed analysis of the parallel performances of an overlapping Schwarz algorithm based on natural interface condition. We present results of numerical simulations involving several million unknowns
Bonazzoli, 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.
The 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
Saracco, Ginette. "Propagation acoustique en régime harmonique et transitoire à travers un milieu inhomogène : méthodes asymptotiques et transformation en ondelettes." Aix-Marseille 2, 1989. https://tel.archives-ouvertes.fr/tel-00178676.
Bruyant, Nicolas. "Etude et commande généralisées de filtres actifs parallèles : compensation globale ou sélective des harmonique : régime équilibré ou désiquilibré." Nantes, 1999. http://www.theses.fr/1999NANT2097.
Hildenbrand, Anne. "Etude de l’endommagement laser dans les cristaux non linéaires en régime nanoseconde." Aix-Marseille 3, 2008. http://www.theses.fr/2008AIX30055.
Lasers become more and more powerful and compact. This raises laser induced damage issues in optical components, especially in nonlinear crystals. This thesis deals with nanosecond laser damage investigations in nonlinear crystals used for frequency conversion (KTP, KDP LBO) and electro-optic applications (RTP, KDP). First, due to nonlinear and anisotropic effects of the crystals, the development of a metrology dedicated to laser damage studies of crystals was necessary. This metrology was then applied to the study of KTP and RTP isomorphous crystals, and LBO crystals. The influence of many parameters on the laser damage resistance, such as wavelength, polarization and crystal orientation, was studied allowing a better understanding of the laser damage phenomena in these crystals. Moreover, laser induced damage characterization was realized on these crystals with a high number of shots and in the real operating conditions, showing that the laser damage threshold of the component depends on its use. For example, the coexistence of multiple wavelengths inside the crystal takes a great part in the damage phenomena
Lutz, Yves. "Caractérisation du niobate de potassium comme doubleur de fréquence d'un laser saphir dopé titane fonctionnant en régime impulsionnel." Mulhouse, 1996. http://www.theses.fr/1996MULH0443.
Després, Bruno. "Méthodes de décomposition de domaine pour la propagation d'ondes en régime harmonique. Le théorème de Borg pour l'équation de Hill vectorielle." Paris 9, 1991. https://portail.bu.dauphine.fr/fileviewer/index.php?doc=1991PA090032.
Peynaud, 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.
This 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
Dubois, Anthony. "Etude de l'interaction d'une onde électromagnétique avec une structure matérielle en régime temporel : problèmes directs et inverses." Aix-Marseille 3, 2005. http://www.theses.fr/2005AIX30024.
This work deals with inverse scattering problem in electromagnetism. It consists in determining characteristics of targets using the scattered field only. The multi-frequencial character of transient data (by considering a Laplace transform) enables to combine the convergence of iterative inversion scheme guaranteed at low frequency and the resolution at upper frequency. Three different approaches were explored in two configurations: “free homogeneous space” and “buried objects” (half-space). Harmonic inversion (several sources, one frequency) was combined with the Decomposition of the Time Reversal Operator method when targets were buried in a cluttered environment. Inversion of transient data (one source, several frequencies weighted by the spectrum of the incident field) was tackled. At least, a multi-frequencial and multi-sourcial approach was developed and validated by using experimentally measured fields
Gdoura, Souhir. "Identification électromagnétique de petites inclusions enfouies." Phd thesis, Université Paris Sud - Paris XI, 2008. http://tel.archives-ouvertes.fr/tel-00651167.
Hildenbrand, Anne. "Etude de l'endommagement laser dans les cristaux non linéaires en régime nanoseconde." Phd thesis, Université Paul Cézanne - Aix-Marseille III, 2008. http://tel.archives-ouvertes.fr/tel-00411083.
Dalle, Christophe. "Contribution à l'étude des dispositifs à jonction P-N en gamme millimétrique : application aux diodes avalanche en régime de génération directe et harmonique." Lille 1, 1986. http://www.theses.fr/1986LIL10099.
Baba, Yehia el. "Contribution au développement de techniques d'analyse de signaux triphasés en régime harmonique : application à la caractérisation du fonctionnement d'une association convertisseur machine synchrone." Le Havre, 1996. http://www.theses.fr/1996LEHA0006.
Kwok, Vincent. "Méthodes de contrôlabilité exacte et de décomposition de domaine pour la résolution numérique des équations de l'électromagnétisme en régime harmonique dans un milieu hétérogène." Paris 6, 1995. http://www.theses.fr/1995PA066359.
Durand, William. "Sur quelques problèmes de valeur au bord dans une bande infinie et application à la diffraction par un dièdre." Orléans, 1999. http://www.theses.fr/1999ORLE2035.
Averseng, Frédéric. "Synthèse et étude des propriétés optiques non linéaires de complexes de bases de Schiff diamagnétiques et paramagnétiques." Toulouse 3, 2000. http://www.theses.fr/2000TOU30175.
Aubreton, Thierry. "Application des méthodes asymptotiques transitoires et harmoniques aux antennes et à la compatibilité électromagnétique." Limoges, 1996. http://www.theses.fr/1996LIMO0016.
Khenchaf, Ali. "Contribution des méthodes haute résoltion à l'analyse des paramètres d'obstacles éclairés par une onde électromagnétique." Nantes, 1992. http://www.theses.fr/1992NANT2058.
Roux, Jean-François. "Contribution à l'étude du coupleur a réseau non linéaire : génération de second harmonique dans des guides d'ondes organiques." Grenoble INPG, 1995. http://www.theses.fr/1995INPG0023.
Laroche, Thierry. "Génération de second harmonique pour la nano-optique et la microscopie optique en champ proche." Phd thesis, Université de Franche-Comté, 2004. http://tel.archives-ouvertes.fr/tel-00008888.
Njilie, Adamou Franck Éric. "Modélisation et évaluation de l'amortissement de structures sandwichs." Paris 6, 2002. http://www.theses.fr/2002PA066276.
Legendre, Guillaume. "Rayonnement acoustique dans un fluide en écoulement : analyse mathématique et numérique de l'équation de Galbrun." Phd thesis, Paris 6, 2003. http://tel.archives-ouvertes.fr/tel-00004930.
Abdesselam, Mohamed. "Contribution à l'étude analytique du problème du dimensionnement thermique des bâtiments : application à la conception thermique des bâtiments en pays chauds." Paris, ENMP, 1997. http://www.theses.fr/1997ENMP0002.
The study of instationnary linear thermic systems through integral matrices highlights two types of elementary exchanges so called transmittances. The exploitation of the properties of these functions of exchange can be considered in two different ways of study : - The global approach, rather competive in terms of analysing the behaviour of the thermal, but no very efficient in localizing and orientating the intervenings for the thermic conceiving of the wrapping. – The modular approach, more adapted for dealing and making clear, in their entirely, the aspects inherent in the problem of sizing. The latter reduces the study of a complex system to the study of its components, which is best mastered. The applications of this work are shown in the elaboration of a method for sizing buildings in natural air conditioning in the Ivory Coast, and in the contribution it makes to a guide for air conditioning in the DOM
Liu, Jingfei. "L'interaction des ultrasons avec des structures périodiques et les structures composites." Thesis, Université de Lorraine, 2013. http://www.theses.fr/2013LORR0329/document.
The research presented in this thesis contains two parts : the interaction of ultrasound with periodic structures and the interaction of ultrasound with composite materials. The investigation in the interaction of ultrasound with periodic structures is made in two aspects : study of the physical phenomenon of ultrasound diffraction and nondestructive characterization of the coorugated structures using ultrasonic techniques. Chapter II and III represent the investigation of two physical phenomena of ultrasound diffraction, i.e. acoustic Wood anomaly and the so-called sub-harmonic diffraction, respectively. In chapter IV the principle of Bragg diffraction is applied to the nondestructive characterization of the periodicity of periodic structures using air-coupled ultrasonic technique; while a more general geometrical characterization of periodic surface using high frequency ultrasonic C-scan imaging technique is presented in chapter V. In this thesis the research work of the interaction of ultrasound with composite structures focuses on the characterization of impact defects of composite plates. This work contains two parts : the spectral analysis of impact defects and the comparison of different techniques in impact defects characterization. The first part of the work tries to deal with the situation where the received signals for defect characterization are corrupted by the avoidable high-level noise caused by the data acquisition system. While in the second part different testing configurations, different transducers and different data processing methods are compared in order to optimize the defect characterization
Guyomar, Daniel. "Théorie et méthodes de la diffraction impulsionnelle dans les milieux sans perte et dans les milieux atténuants." Paris 7, 1986. http://www.theses.fr/1986PA077085.
Guérin, Christophe. "Détermination des pertes par courants de Foucault dans les cuves de transformateurs : modélisation de régions minces et prise en compte de la saturation des matériaux magnétiques en régime harmonique." Phd thesis, Grenoble INPG, 1994. http://tel.archives-ouvertes.fr/tel-00526516.
Chanaud, Mathieu. "Conception d’un solveur haute performance de systèmes linéaires creux couplant des méthodes multigrilles et directes pour la résolution des équations de Maxwell 3D en régime harmonique discrétisées par éléments finis." Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14324/document.
Multigrid algorithm. The system is solved thanks to a direct method on the coarse mesh anditerative splitting method on refined meshes; inter-grid operators are defined to interpolate theapproximate solutions on the different refinement levels. Applied to 3D electromagnetic simulations(Nédélec first order finite element approximation of time harmonic Maxwell equations) thissolver is used either as a stationary method or as a preconditioner for a Krylov subspace method(GMRES)
Goddet, Jean-Philippe. "Etude et développement de sources laser XUV par injection d’harmoniques d’ordre élevé." Palaiseau, Ecole polytechnique, 2009. http://pastel.paristech.org/5837/01/These_Jean-Philippe_GODDET.pdf.
The work in this thesis aimed to study a geometry of XUV lasers inspired by high power laser. This architecture, consisting of an injector (a source of high-order harmonics) coupled to an amplifier (plasma created by laser), corresponds to that of a laser chain in the spectral range of the XUV. The laser at 32. 8 nm studied here, is produced by the injection of high-order harmonic in a krypton plasma created by Optical Field Ionization (OFI). This scheme, initially tested by T. Ditmire in 1995, was validated in 2003 with a plasma amplifier created by the interaction of intense laser and a gaseous medium at the Laboratoire d’Optique Appliquée. This thesis is a continuation of that work in trying to address different aspects, not only a better understanding the physical processes involved, but also the spatio-temporal characterization of this type of source. We have demonstrated experimentally for the first time a source in the XUV, witch can be both highly compact, energetic (1 μJ per pulse), close to the diffraction limit and Fourier transform limited. Indeed, through the spatial filtering of harmonics by the amplifying medium, the injected XUV laser at 32. 8 nm shows a Gaussian spatial profile with a divergence of 0. 7 mrad (at 1/e2). The wavefront was measured with a Hartmann sensor and presents a value of l/17 in standard deviation, demonstrating that the XUV source is diffraction limited. The temporal characterization of laser shows that the coherence time is of the order of the duration of spontaneous emission of the amplifier. The temporal coherence presents a Gaussian profile with a relative spectral width Dl/l equal to 10-5 (FWHM) corresponding to a pulse duration of about 5 ps
Caudron, 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.
In 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
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.
Blau, Gerd. "Doubleurs de fréquences en optique intégrée utilisant des polymères et des nano-réseaux de diffraction." Grenoble INPG, 1996. http://www.theses.fr/1996INPG0110.
Gasperini, David. "A multi-harmonic finite element method for the micro-Doppler effect, with an application to radar sensing." Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0026.
A finite element method in the frequency domain is proposed for solving wave scattering problems with moving or, more generally, deforming boundaries. First, the original problem is rewritten as an equivalent weak formulation set in a fixeddomain. Next, this formulation is approximated as a simpler weak form based on asymptotic expansions when the amplitude of the movements or the deformations is small. Fourier series expansions of some geometrical quantities under the assumption that the movement is periodic, and of the solution are next introduced to obtain a coupled multi-harmonic frequency domain formulation. Standard finite element methods can then be applied to solve the resulting problem and a block diagonal preconditioner is proposed to acceleratethe Krylov subspace solution of the linear system for high frequency problems.The efficiency of the resulting method is demonstrated on a radar sensing application for the automotive industry.A finite element method in the frequency domain is proposed for solving wave scattering problems with moving or, more generally, deforming boundaries. First, the original problem is rewritten as an equivalent weak formulation set in a fixeddomain. Next, this formulation is approximated as a simpler weak form based on asymptotic expansions when the amplitude of the movements or the deformations is small. Fourier series expansions of some geometrical quantities under the assumption that the movement is periodic, and of the solution are next introduced to obtain a coupled multi-harmonic frequency domain formulation. Standard finite element methods can then be applied to solve the resulting problem and a block diagonal preconditioner is proposed to acceleratethe Krylov subspace solution of the linear system for high frequency problems.The efficiency of the resulting method is demonstrated on a radar sensing application for the automotive industry
Caudron, Boris. "Couplages FEM-BEM faibles et optimisés pour des problèmes de diffraction harmoniques en acoustique et en électromagnétisme." Electronic Thesis or Diss., Université de Lorraine, 2018. http://www.theses.fr/2018LORR0062.
In 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
Lasbrugnas, Carine. "Matériaux doubleurs de fréquence : verres et vitrocéramiques à base d'oxyde de tellure - élaboration et caratérisation." Limoges, 2004. http://aurore.unilim.fr/theses/nxfile/default/24b68565-a51b-44b2-b6c7-0d98432e04c6/blobholder:0/2004LIMO0048.pdf.
. The increasing interest in materials with non–linear optical properties has been greatly influenced by the important industrial need of " all-optical " devices. Tellurium dioxide-based glasses are very good potential candidates for such applications because of their high linear and non-linear refrative indices. The origin of these properties is attributed to the stereochemical activity of the TeIV atoms. These are very often reinforced when elements d0 such as W6+ are added. Second harmonic generation in bulk thermally poled glasses offers new opportunities in material research and device development for optics. Then, the study was about glasses and glass-ceramics with 84,15% TeO2 – 14,85% WO3 – 2% SbO1,5 molar composition. This composition allows to obtain by heating the crystallisation of the non-centrosymmetric metastable γ-TeO2 phase which presents second harmonic generation. After optimisation of poling conditions, second harmonic signals have been successfully generated for thermally poled glasses and glass-ceramics. Structural and optical characterisations have been undergone before and after poling with the aim of explaining the origin of the second order non-linearity
Tran, Ngoc Minh. "Applications of nonlinear magneto-photonics at the nanoscale." Thesis, Le Mans, 2018. http://www.theses.fr/2018LEMA1029/document.
Owing to surface and interface sensitivity, the magnetic Second Harmonic Generation (mSHG) represents a useful tool to probe magnetic interfaces and nanostructures. This work investigates the coupling and interaction of the mSHG with electromagnetic waves propagating along the surface. Two types of surface waves have been studied: (i) surface plasmon polaritons (SPP) at surfaces of metallic thin films and multilayers, and (ii) the diffraction anomaly at the surface of periodically arranged metallic nanostructures. To study influence of linear and nonlinear excitation of surface waves on the mSHG, the reflected second harmonic (SH) intensity and the magnetic SH contrast in the transverse magneto-optical geometry were measured as a function of the angle of incidence. The use of different femtosecond light sources in the near-infrared optical range, where the SPP dispersion and damping exhibit significant variations, made it possible to disentangle linear and nonlinear contributions to the excitation of surface waves. In this thesis, it is proven that phase-matching of the mSHG and surface electromagnetic waves can lead to the enhancement of both the SH yield and the nonlinear magneto-optical signal. These results are important for controlling of the nonlinear magneto-optical response and could impact the development of magnetic storage devices, label-free biosensors and nonlinear magneto-optical switches
Luc, Jérôme. "Propriétés optiques non linéaires et structuration photo-induite de nouveaux complexes organométalliques à base de ruthénium." Phd thesis, Université d'Angers, 2008. http://tel.archives-ouvertes.fr/tel-00351578.
Nous déterminons, à l'aide de diverses techniques expérimentales (DFWM, SHG, THG, Zscan), l'influence de la fonctionnalisation de ces structures moléculaires sur l'amélioration de leurs propriétés ONL du deuxième et troisième ordre en jouant notamment sur la nature du fragment accepteur et du transmetteur π-conjugué. Nous présentons les résultats de calculs théoriques de chimie quantique afin de proposer une étude ONL de ces complexes à l'échelle moléculaire. Enfin, nous complétons ce travail sur des complexes ruthéniumacétylure contenant un fragment azobenzène dans leur système organique p-conjugué, par la diffusion des rayons X aux grands angles (WAXS) et par l'étude, en régime picoseconde, de la dynamique de formation de réseaux de surface photo-induits (SRGs) en utilisant une technique d'holographie en transmission et la microscopie à force atomique (AFM).