Dissertationen zum Thema „Méthodes par décomposition“
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Levy, Marie-Luce. „Méthodes par décomposition temporelle et problèmes d'ordonnancement“. Toulouse, INPT, 1996. http://www.theses.fr/1996INPT012H.
Der volle Inhalt der QuelleHenri, Thibault. „Réduction de modèles par des méthodes de décomposition orthogonale propre“. Rennes, INSA, 2004. http://www.theses.fr/2004ISAR0005.
Der volle Inhalt der QuelleModelling complex systems leads one to solve problems of very high size numerically, for example in case of finite elements discretization. An alternative consists in using a priori known data to reduce the size of the system to solve. Given the solution u of an evolution problem, proper orthogonal decomposition (POD) methods allow one to define a basis of functions from a priori known snapshots u(ti) on which the problem is projected : one speaks of POD-Galerkin methods. This method has been especially implemented in case of fluids mechanics problems. We present a synthesis of POD methods. We show convergence results and estimates in the parabolic case and in the case of general equations in fluids mechanics. The stability of the method is proven. Numerical computations show that the size of systems to solve is very small compared to classical finite elements methods. We present an interesting application to compute the solution of optimal control problems
Arencibia, Noa Yunniel. „Méthodes rigoureuses par décomposition de domaines pour la diffusion électromagnétique par une surface rugueuse 2D“. Thesis, Nantes, 2019. http://www.theses.fr/2019NANT4037.
Der volle Inhalt der QuelleThe modeling of electromagnetic scattering by a (random) rough surface is a very active research subject. lt encounters many environmental applications such as natural soils or sea surface, or for the characterization of surface defects at the optical scale. The rigorous modeling of electromagnetic waves scattering by large abjects compared to the wavelength is a difficult task and can involve the resolution of a linear system of several millions of unknowns. Thus, the calculation of the electromagnetic field scattered by a twodimensional sea surface, has so far never been rigorously solved in the microwave frequency bands, and the cross polarization has not been reliably evaluated. This thesis aims to salve in part this problem by considering a randomly rough and perfectly conducting 2D surface with moderate dimensions. For this, we use the EFIE (Electric Field lntegral Equation) discretized by the method of moments using RWG (Rao-Wilton-Glisson) basis functions. In order to effectively salve the resulting linear system, we have chosen two domain decomposition methods, the SDIM (Subdomain Decomposition lterative Method) and the CBFM (Characteristic Basic Function Method). These methods, hybridized to the ACA (Adaptive Cross Approximation) to accelerate the coupling steps, make it possible to salve linear systems by blacks, with reduced CPU and memory complexities
Cherkaoui, Abdelhai. „Modélisation des séries temporelles par des méthodes de décomposition et applications“. Aix-Marseille 3, 1987. http://www.theses.fr/1987AIX24011.
Der volle Inhalt der QuelleOur work has centered on the study of decomposition methods time series. This was done in four stages. First, we analyse classical methods of linear regression and of smoothing by moving averages. Secondly, we examine the decomposition method of an arima model. In the third stage, we present a method based on the recurrent algorithm of kalman. In the fourth stage, we illustrate our theoretical results and attempt to compare the box-jenkins method and the method of smoothing by moving average
Gest, Brigitte. „Résolution des grands systèmes linéaires par décomposition des domaines et méthodes rapides : comparaison avec d'autres méthodes“. Paris 11, 1985. http://www.theses.fr/1985PA112395.
Der volle Inhalt der QuelleThis work is dedicated to the evaluation of the efficiency of the resolution of some large sparse linear systems using Fast Direct Methods. Although they are based on the use of the same FFT algorithm, they can be divided in three categories: the Fourier analysis, the Cyclic Reduction by blocks and their combination, the F. A. C. R (l). The comparison with classic methods was conducted in configurations requiring the regularity of the domain. Very promising results being obtained, techniques allowing to work in more general domains have then been implemented: the capacitance matrix technique and the combination of the iterative methods with fast methods. The fineness of part of the grid applied to the domain was also investigated. The semi-direct method was selected as reference algorithm for the last comparative numerical tests because it is specially adapted to the structure of the domain under test
Hohweiller, Tom. „Méthodes de décomposition non-linéaire pour l'imagerie X spectrale“. Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI097.
Der volle Inhalt der QuelleSpectral tomodensitometry is a new emerging x-ray imaging modality. If the dual-energy principle was already known for quite some time, new developments on photon-counting detectors now allowing acquiring more energy bins than before. This modality allows reducing some artifacts presents in x-ray imaging, such as beam hardening, but mostly to decompose the data into the chemical composition of the imaged tissue. It also enables the use of new markers (i.e. gold) with an energic discontinuity. The use of these markers also allows to locate and quantify them in the patient, granting great potential for medical imaging. Decomposition in the projection domain followed by a tomographic reconstruction is a classical processing for those spectral data. However, decomposition methods in the projection domain are unstable for a high number of energy bins. Classical calibration technic is numerically unstable for more than two energy bins. This thesis aims to developed new material decomposition methods in the projections domains. After expressing the spectral forward model, the decomposition problem is expressed and dealt as a non-linear inverse problem. It will be solved by minimizing a cost function composed by a term characterizing the fidelity of the decomposition regarding the data and an \textit{a priori} of the decomposed material maps. We will firstly present an adaptation of the cost function that takes into account the Poissonian noise on the data. This formulation allows having better decomposed maps for a high level of noise than classical formulation. Then, two constrained algorithms will be presented. The first one, a projected Gauss-Newton algorithm, that enforces positivity on the decomposed maps, allows having better decomposed maps than an unconstrained algorithm. To improve the first algorithm, another one was developed that also used an egality constrain. The equality allows having images with fewer artifacts than before. These methods are tested on a numerical phantom of a mouse and thorax. To speed up the decomposition process, an automatic choice of parameters is presented, which allow faster decomposition while keeping good maps. Finally, the methods are tested on experimental data that are coming from a spectral scanner prototype
Fontaine, Mathieu. „Apport de la décomposition arborescente pour les méthodes de type VNS“. Phd thesis, Université de Caen, 2013. http://tel.archives-ouvertes.fr/tel-01025435.
Der volle Inhalt der QuelleSamaké, Abdoulaye. „Méthodes non-conformes de décomposition de domaine à grande échelle“. Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENM066/document.
Der volle Inhalt der QuelleThis thesis investigates domain decomposition methods, commonly classified as either overlapping Schwarz methods or iterative substructuring methods relying on nonoverlapping subdomains. We mainly focus on the mortar finite element method, a nonconforming approach of substructuring method involving weak continuity constraints on the approximation space. We introduce a finiteelement framework for the design and the analysis of the substructuring preconditioners for an efficient solution of the linear system arising from such a discretization method. Particular consideration is given to the construction of the coarse grid preconditioner, specifically the main variantproposed in this work, using a Discontinuous Galerkin interior penalty method as coarse problem. Other domain decomposition methods, such as Schwarz methods and the so-called three-field method are surveyed with the purpose of establishing a generic teaching and research programming environment for a wide range of these methods. We develop an advanced computational framework dedicated to the parallel implementation of numerical methods and preconditioners introduced in this thesis. The efficiency and the scalability of the preconditioners, and the performance of parallel algorithms are illustrated by numerical experiments performed on large scale parallel architectures
Aussal, Matthieu. „Méthodes numériques pour la spatialisation sonore, de la simulation à la synthèse binaurale“. Palaiseau, Ecole polytechnique, 2014. https://tel.archives-ouvertes.fr/tel-01095801/document.
Der volle Inhalt der QuelleResearch conducted during this PhD were initiated by an industrial need identified by Digital Media Solutions, namely the creation of a tool for spatial sound rendering on headphones for blind people. Despite the many existing devices, technical 3D sound on headphones face since their appearance the major obstacle that prevents the achievement of high quality products. Indeed, to make the illusion of a perceptible sound space, it is necessary to individualize listening to each listener. Measurements in the laboratory provide with convincing results, but the process is not yet applicable to the public. Mathematical modeling of this experiment allows to consider replacing the measure by a numerical simulation. This thesis proposes both an efficient calculation engine adapted to the problem, and a 3D audio rendering engine in order to validate the approach
Sun, Xiao Chao. „Résolution de la programmation linéaire en nombres entiers : méthodes des coupes, méthodes de séparation et évaluation et méthodes de décomposition de programmes par matrices d'intervalles et par matrices graphiques“. Clermont-Ferrand 2, 1993. http://www.theses.fr/1993CLF21451.
Der volle Inhalt der QuelleLeni, Pierre-Emmanuel. „Nouvelles méthodes de traitement de signaux multidimensionnels par décomposition suivant le théorème de Superposition de Kolmogorov“. Phd thesis, Université de Bourgogne, 2010. http://tel.archives-ouvertes.fr/tel-00581756.
Der volle Inhalt der QuelleCautres, René. „Discrétisation par volumes finis et méthodes de décomposition de domaine pour des problèmes de convection diffusion“. Aix-Marseille 1, 2004. http://www.theses.fr/2004AIX10008.
Der volle Inhalt der QuelleBerthe, Paul-Marie. „Méthodes de décomposition de domaine de type relaxation d'ondes optimisées pour l'équation de convection-diffusion instationnaire discrétisée par volumes finis“. Thesis, Paris 13, 2013. http://www.theses.fr/2013PA132055.
Der volle Inhalt der QuelleIn the context of nuclear waste repositories, we consider the numerical discretization of the non stationary convection diffusion equation. Discontinuous physical parameters and heterogeneous space and time scales lead us to use different space and time discretizations in different parts of the domain. In this work, we choose the discrete duality finite volume (DDFV) scheme and the discontinuous Galerkin scheme in time, coupled by an optimized Scwharz waveform relaxation (OSWR) domain decomposition method, because this allows the use of non-conforming space-time meshes. The main difficulty lies in finding an upwind discretization of the convective flux which remains local to a sub-domain and such that the multidomain scheme is equivalent to the monodomain one. These difficulties are first dealt with in the one-dimensional context, where different discretizations are studied. The chosen scheme introduces a hybrid unknown on the cell interfaces. The idea of upwinding with respect to this hybrid unknown is extended to the DDFV scheme in the two-dimensional setting. The well-posedness of the scheme and of an equivalent multidomain scheme is shown. The latter is solved by an OSWR algorithm, the convergence of which is proved. The optimized parameters in the Robin transmission conditions are obtained by studying the continuous or discrete convergence rates. Several test-cases, one of which inspired by nuclear waste repositories, illustrate these results
Oudin, Fabienne. „Schémas volumes finis pour problèmes elliptiques : analyse a priori et a posteriori par éléments finis mixtes, méthode de décomposition de domaines“. Lyon 1, 1995. http://www.theses.fr/1995LYO10303.
Der volle Inhalt der QuelleMonroy, Charles. „Simulation numérique de l'interaction houle-structure en fluide visqueux par décomposition fonctionnelle“. Phd thesis, Ecole centrale de nantes - ECN, 2010. http://tel.archives-ouvertes.fr/tel-00600669.
Der volle Inhalt der QuellePotop, Alexandra-Iulia. „Imagerie par rayons X résolue en énergie : Méthodes de décomposition en base de matériaux adaptées à des détecteurs spectrométriques“. Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0096/document.
Der volle Inhalt der QuelleScintillator based integrating detectors are used in conventional X-ray imaging systems. The new generation of energy-resolved semiconductor radiation detectors, based on CdTe/CdZnTe, allows counting the number of photons incident on the detector and measure their energy. The LDET laboratory developed pixelated spectrometric detectors for X-ray imaging, associated with a fast readout circuit, which allows working with high fluxes and while maintaining a good energy resolution. With this thesis, we bring our contribution to data processing acquired in radiographic and tomographic modes for material components quantification. Osteodensitometry was chosen as a medical application. Radiographic data was acquired by simulation with a detector which presents imperfections as charge sharing and pile-up. The methods chosen for data processing are based on a material decomposition approach. Basis material decomposition models the linear attenuation coefficient of a material as a linear combination of the attenuations of two basis materials based on the energy related information acquired in each energy bin. Two approaches based on a calibration step were adapted for our application. The first is the polynomial approach used for standard dual energy acquisitions, which was applied for two and three energies acquired with the energy-resolved detector. We searched the optimal configuration of bins. We evaluated the limits of the polynomial approach with a study on the number of channels. To go further and take benefit of the elevated number of bins acquired with the detectors developed in our laboratory, a statistical approach implemented in our laboratory was adapted for the material decomposition method for quantifying mineral content in bone. The two approaches were compared using figures of merit as bias and noise over the lengths of the materials traversed by X-rays. An experimental radiographic validation of the two approaches was done in our laboratory with a spectrometric detector. Results in material quantification reflect an agreement with the simulations
Riton, Julien. „Problème de contact avec frottement : analyse et convergence par méthodes de sous-domaines“. Caen, 2011. http://www.theses.fr/2011CAEN2004.
Der volle Inhalt der QuelleWe propose three non-overlapping domain decomposition methods to approximate contact problem with Tresca friction between two elastic bodies. Two of them are Neumann-Neumann algorithms, the third is a Lions (Robin) one. We prove their convergence in continuous case and their robustness in discrete case. Some numerical experiments illustrate the robustness of these parallel algorithms
Dailly, Paul. „Décomposition "à la Kronecker" dans les anneaux de Krull par immersion dans des anneaux principaux“. Paris 6, 2002. http://www.theses.fr/2002PA066087.
Der volle Inhalt der QuelleFortin, Thomas. „Une méthode d'éléments finis à décomposition L2 d'ordre élevé motivée par la simulation des écoulements diphasiques bas Mach“. Paris 6, 2006. http://www.theses.fr/2006PA066526.
Der volle Inhalt der QuelleRey, Valentine. „Pilotage de stratégies de calcul par décomposition de domaine par des objectifs de précision sur des quantités d’intérêt“. Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLN018/document.
Der volle Inhalt der QuelleThis research work aims at contributing to the development of verification tools in linear mechanical problems within the framework of non-overlapping domain decomposition methods.* We propose to improve the quality of the statically admissible stress field required for the computation of the error estimator thanks to a new methodology of stress reconstruction in sequential context and thanks to optimizations of the computations of nodal reactions in substructured context.* We prove guaranteed upper and lower bounds of the error that separates the algebraic error (due to the iterative solver) from the discretization error (due to the finite element method) for both global error measure mentand goal-oriented error estimation. It enables the definition of a new stopping criterion for the iterative solver which avoids over-resolution.* We benefit the information provided by the error estimator and the Krylov subspaces built during the resolution to set an auto-adaptive strategy. This strategy consists in sequel of resolutions and takes advantage of adaptive remeshing and recycling of search directions .We apply the steering of the iterative solver by objective of precision on two-dimensional mechanical examples
Leroux, Jean-Daniel. „Contribution aux méthodes de reconstruction d'images appliquées à la tomographie d'émission par positrons par l'exploitation des symétries du système“. Thèse, Université de Sherbrooke, 2014. http://hdl.handle.net/11143/5398.
Der volle Inhalt der QuelleSaleh, Marwan. „Étude mathématique et numérique des méthodes de réduction dimensionnelle de type POD et PGD“. Thesis, La Rochelle, 2015. http://www.theses.fr/2015LAROS004/document.
Der volle Inhalt der QuelleThis thesis is formed of four chapters. The first one presents the mathematical notions and tools used in this thesis and gives a description of the main results obtained within. The second chapter presents our generalization of a result obtained by Rousselet-Chenais in 1990 which describes the sensitivity of eigensubspaces for self-adjoint compact operators. Rousselet-Chenais were limited to sensitivity for specific subspaces of dimension 1, we have extended their result to higher dimensions. We applied our results to the Proper Orthogonal Decomposition (POD) in the case of parametric, temporal and spatial variations (Gappy- POD). The third chapter discusses the optical flow estimate with quadratic or linear energies at infinity. Mathematical results of convergence are shown for the method Progressive Generalized Decomposition (PGD) in the case of quadratic energies. Our proof is based on the decomposition of Brézis-lieb via the convergence almost everywhere of the PGD sequence gradients. A detailed numerical study is made on different types of images : on the passive scalar transport equations, whose displacement fields are solutions of the Navier-Stokes equations. These equations present a challenge for optical flow estimates because of the presence of low gradient regions in the image. We applied our method to the MRI image sequences to estimate the movement of the abdominal organs. PGD presented a superiority in both computing time level (even in 2D) and accuracy representation of the estimated motion. The local diffusion of standard methods (Horn Schunck, for example) limits the convergence rate, in contrast to the PGD which is a more global approach by construction. The last chapter deals with the application of PGD method in the case of variational elliptic equations whose energy present all challenges to classical variational methods : lack of convexity, lack of coercivity and lack of boundedness. We prove convergence results for the weak topology, the PGD sequences converge (when they are well defined) to two extremal solutions on the Nehari manifold. Several mathematical questions about PGD remain open in this chapter. These questions are part of our research perspectives
Perez, Saul. „Application à des problèmes d'environnement radar de méthodes itératives de résolution d'un problème électromagnétique par partition“. Toulouse, INSA, 2007. http://eprint.insa-toulouse.fr/archive/00000168/.
Der volle Inhalt der QuelleWith a multiplication of complex and large objects (>>λ) the RCS computation of these objects is important for the aviation community to determine the impact on radio navigation systems like radar. These objects are far greater than the wavelength but asymptotic methods cannot be applied to solve this type of complex problem. The integral method is a popular choice for solving electromagnetic scattering by an arbitrary object. However it is well known that the traditional integral method suffers from the storage requirement (increasing in the order of O(N²)) and computational complexity (increasing in the order of O(N3)) for large scale problem. These limitations impose on the one hand the use of a cluster to share out the storage and the computational complexity cost and on the other hand the use of an iterative method (increasing in the order of O(N²)) combined with an accelerating method to reduce the computational complexity cost. We propose a method for RCS computation of long internally complex, dielectric objects such as wind turbine blades. The method proposed is an improved iterative algorithm whose convergence is proven. Moreover the algorithm can be easily adapted to parallel computation. This method is based into classical integral method and interface decomposition. The integral method consist in the description of electromagnetic field in terms of electric and magnetic currents defined on the surface of the electromagnetic scatterer. The interface decomposition consist in the decomposition of the surface of the scatterer in different zones. In order to accelerate the convergence rate we propose the use of three accelerating methods. The first accelerating method allows the elimination of the internal degrees of freedom. The second accelerating method (matrix compression QR) accelerates all the matrix vector products used in the preconditioning procedure as well as in the GMRES iterative resolution. The third one consists in using a “geometric-neighboring” preconditioner adapted to the physical aspect of the problem
Giraud, Denis. „Diagnostic des systèmes industriels complexes par agrégation de méthodes : application à une station d'épuration“. Nancy 1, 1998. http://www.theses.fr/1998NAN10002.
Der volle Inhalt der QuelleBalin, Nolwenn. „Etude de méthodes de couplage pour la résolution des équations de Maxwell : application au calcul de la signature radar d’aéronefs par hybridation de méthodes exactes et asymptotiques“. Toulouse, INSA, 2005. http://www.theses.fr/2005ISAT0012.
Der volle Inhalt der QuelleThis thesis is concerned with the numerical simulation of the scattering of an electromagnetic wave by air-breathing aircraft, represented by a deep and narrow cavity within a large perfectly conducting structure. Due to the size and the complexity of this object, the classical methods (full-wave and asymptotic) cannot be successfully applied. The aim of this study is to develop a new hybrid method to solve this kind of problem. The methods have first been developed and validated in the 2D case and then extended to the 3D case. At first, for the treatment of the cavity, a new substructuring domain decomposition method based on a boundary element formulation and a frontal forward substitution was developed. After this step, the remaining equations are set on the aperture of the cavity and the rest of the boundary of the structure. Next, to reduce the size of the resulting external problem, we use a Schwarz method associated with an overlapping boundary decomposition well-suited for the boundary integral equations. Finally, for the part of the boundary that does not cover the aperture of the cavity, we introduce an asymptotic method, based on the radiation of equivalent currents by a Generalized Ray Expansion process. The use of the previous algorithm ensures a strong coupling between the subdomains. We have mathematically established the stability and solvability of the cavity factorization method. We have also numerically demonstrated the efficiency of these three elementary steps and of the whole hybridization process
Aujol, Jean-François. „Contribution à l'analyse de textures en traitement d'images par méthodes variationnelles et équations aux dérivées partielles“. Phd thesis, Université de Nice Sophia-Antipolis, 2004. http://tel.archives-ouvertes.fr/tel-00006303.
Der volle Inhalt der QuelleL'objectif des deux premières parties de cette thèse
est de proposer un modèle pour décomposer une image f en trois composantes : f=u+v+w.
La première composante, u, contient l'information géométrique. On peut la considérer comme une esquisse de l'image originale f.
La seconde composante, v, contient l'information texture.
La troisième composante, w, contient le bruit présent dans l'image originale.
Notre approche repose sur l'utilisation d'espaces mathématiques
adaptés à chaque composante: l'espace BV des fonctions à variations bornées pour u, un espace G proche du dual de BV pour les textures, et un espace de Besov d'exposant négatif E pour le bruit.
Nous effectuons l'étude mathématique complète des différents modèles que nous proposons.
Nous illustrons notre approche par de nombreux exemples, et donnons deux applications concrètes : une première en restauration d'images RSO, et une seconde en compression d'images.
Dans la troisième et dernière partie de cette thèse, nous nous intéressons
spécifiquement à la composante texturée.
Nous proposons un algorithme de classification supervisée pour les images texturées. L'approche utilisée est basée sur l'utilisation de la méthode des contours actifs et d'un terme d'attache aux donnés spécifiques au textures. Ce dernier est construit à partir d'une transformée en paquets d'ondelettes. Nous obtenons ainsi une fonctionnelle, dont le minimum correspond à la classification cherchée. Nous résolvons numériquement ce problème à l'aide d'un système couplé d'EDP que nous plongeons dans un schéma dynamique. Nous illustrons notre démarche par de nombreux exemples numériques. Nous effectuons également l'étude théorique de la fonctionnelle de classification.
Lescic, Sergiu. „Etude théorique du mécanisme de décomposition d'adduits de spin issus du piégeage de radicaux alkylperoxyle par des N-oxy-pyrrolines“. Electronic Thesis or Diss., Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4752.
Der volle Inhalt der QuelleIn the field of electron paramagnetic resonance (EPR) spectroscopy, the detection of some radical species with a very short half-life time is possible using the spin-trapping method. This technique allows us to characterize transient radicals by trapping them with a diamagnetic molecule (nitrone for example) to give rise to a persistent paramagnetic species (spin-adduct), whose EPR spectrum is characteristic of the trapped radical. Half-life times are strongly correlated to the nature of the nitrone and the trapped radical (alkyl, alkoxyl, alkylperoxyl, ...). However, the link between the structure of the adduct and its half-life time is still not clear. Therefore, we carried out a theoretical study of the reactions involved in the decay of spin-adducts resulting from the trapping of alkylperoxyl radicals by pyrroline-N-oxide nitrones. More precisely, we were interested in the mechanism of the two-step unimolecular degradation. Given the difficulty to discribe the spin states in the considered compounds, we chose to rationalize this study by means of ab initio multireference approach (CASSCF). The ab initio CASSCF calculations of a series of nitroxides allowed to validate this mechanism in organic solvents and to better understand the relationship between the structure of the spin-adduct and its half-life time
Hauville, Frédéric. „Optimisation des méthodes de calculs d'écoulements tourbillonnaires instationnaires“. Phd thesis, Université du Havre, 1996. http://tel.archives-ouvertes.fr/tel-00125000.
Der volle Inhalt der QuelleLe cadre général de cette thèse est l'amélioration de l'efficacité de ces méthodes sous trois aspects :
- décomposition linéaire / non linéaire
- approximation par domaine
- la programmation parallèle (PVM).
Des applications concernant des problèmes d'énergie éoliens, soit sur des générateurs à hélice (éolienne), soit sur les voiles de bateau pour l'interaction fluide/structure sont développés.
Nion, Dimitri. „Méthodes PARAFAC généralisées pour l'extraction aveugle de sources : Application aux systèmes DS-CDMA“. Cergy-Pontoise, 2007. http://www.theses.fr/2007CERG0322.
Der volle Inhalt der QuelleThe goal of this PhD Thesis is to develop generalized PARAFAC decompositions for blind source extraction in a multi-user DS-CDMA system. The spatial, temporal and code diversities allow to store the samples of the received signal in a third order tensor. In order to blindly estimate the symbols of each user, we decompose this tensor in a sum of users' contributions. Until now, this multilinear approach has been used in wireless communications for instantaneous channels, in which case the problem is solved by the PARAFAC decomposition. However, in multipath channels with Inter-Symbol-Interference, this decomposition has to be generalized. The main contribution of this Thesis is to build tensor decompositions more general than PARAFAC to take this propagation scenario into account
Negrello, Camille. „Méthodes fortement parallèles pour la simulation numérique en mécanique non linéaire des structures“. Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLN049/document.
Der volle Inhalt der QuelleThis thesis is aimed to contribute to the adoption of virtual testing, an industrial practice still embryonic which consists in optimizing and certifying by numerical simulations the dimensioning of critical industrial structures. The virtual testing will allow colossal savings in the design of mechanical parts and a greater respect for the environment, thanks to optimized designs. In order to achieve this goal, new calculation methods must be implemented, satisfying more requirements concerning safety, respect for hardware architectures, fastness, and compatibility with the time constraints of engineering.We are interested in the parallel resolution of large nonlinear problems by domain decomposition methods. Our goal is to approximate the exact solution by minimizing communication between subdomains. In order to do this, we want to maximize the computations performed independently by subdomain, using nonlinear relocation approaches. We also try to control the convergence criteria of the nested solvers in order to avoid over-resolution and divergences, to improve the construction of conditions Of mixed interface, and non-linearizing the preconditioning step of the solver. The ultimate objective being to deal with problems of industrial complexity, the robustness of the methods we develop will be a constant concern.Conventionally, non-linear problems are solved by constructing a sequence of linear systems that can be solved in parallel using iterative methods, such as Krylov solvers. We wish to question this usual procedure by trying to construct a sequence of small independent nonlinear systems to be solved in parallel. Such a technique involves the use of interleaved iterative solvers, whose convergence criteria must be dynamically tuned in order to avoid both over-resolution and loss of convergence. The robustness of the method can be ensured in particular by the use of well-constructed mixed interface conditions and well-chosen preconditioners
Kechkar, Mohamed Adel. „Méthodes de reconstruction et de quantification pour la microscopie de super-résolution par localisation de molécules individuelles“. Thesis, Bordeaux 2, 2013. http://www.theses.fr/2013BOR22130/document.
Der volle Inhalt der QuelleThe field of fluorescence microscopy has witnessed a real revolution these last few years, allowing nanometric spatial resolutions, well below the diffraction limit predicted by Abe more than a century ago. Single molecule-based super-resolution techniques such as PALM (Photo-Activation Light Microscopy) or (d)STORM (direct Stochastic Optical Reconstruction Microscopy) allow the image reconstruction of biological samples in 2 and 3 dimensions, with close to molecular resolution. However, while they require a quite straightforward instrumentation, they need heavy computation, limiting their use in routine. In practice, few tens of thousands of raw images with more than one million molecules must be acquired and analyzed to reconstruct a single super-resolution image. Most of the available tools require post-acquisition processing, making the acquisition protocol much heavier. In addition, the quantification of the organization, dynamics but also the stoichiometry of biomolecular complexes at nanometer scales can be a key determinant to elucidate the origin of certain diseases. Novel localization microscopy techniques offer such capabilities, but dedicated analysis methods still have to be developed. In order to democratize this new generation of localization microscopy techniques and make them usable in routine by non-experts, it is essential to develop simple and easy to use localization and quantitative analysis methods. During this PhD thesis, we first developed a new technique for real-time localization and reconstruction based on wavelet decomposition and the use of GPU cards for super-resolution microscopy in 2 and 3 dimensions. Second, we have proposed a quantitative method based on the visualization and the photophysics of organic fluorophores for measuring the stoichiometry of AMPA receptors in synapses at the molecular scale
Moreau, Antoine. „Calcul des propriétés homogénéisées de transfert dans les matériaux poreux par des méthodes de réduction de modèle : Application aux matériaux cimentaires“. Thesis, La Rochelle, 2022. http://www.theses.fr/2022LAROS024.
Der volle Inhalt der QuelleIn this thesis, we manage to combine two existing tools in mechanics: periodic homogenization, and reduced-order modelling, to modelize corrosion of reinforced concrete structures. Indeed, chloride and carbonate diffusion take place their pores and eventually oxydate their steel skeleton. The simulation of this degradation is difficult to afford because of both the material heterogenenity, and its microstructure variability. Periodic homogenization provides a multiscale model which takes care of the first of these issues. Nevertheless, it assumes the existence of a representative elementary volume (REV) of the material at the microscopical scale. I order to afford the microstructure variability, we must solve the equations which arise from periodic homogenization in a reduced time. This motivates the use of model order reduction, and especially the POD. In this work we design geometrical transformations that transport the original homogenization equations on the fluid domain of a unique REV. Indeed, the POD method can’t be directly performed on a variable geometrical space like the material pore network. Secondly, we adapt model order reduction to the Poisson-Boltzmann equation, which is strongly nonlinear, and which rules ionic electro diffusion at the Debye length scale. Finally, we combine these new methods to other existing tools in model order reduction (ITSGM interpolatin, MPS method), in order to couple the micro- and macroscopic components of periodic homogenization
Molina-Sepulveda, Roberto. „Hybridization of FETI Methods“. Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066455/document.
Der volle Inhalt der QuelleIn this work new domain decomposition methods and new implementations for existing methods are developed. A new method based on previous domain decomposition methods is formulated. The classic FETI plus FETI-2LM methods are used to build the new Hybrid-FETI. The basic idea is to develop a new algorithm that can use both methods at the same time by choosing in each interface the most suited condition depending on the characteristics of the problem. By doing this we search to have a faster and more robust code that can work with configurations that the base methods will not handle it optimally by himself. The performance is tested on a contact problem. The following part involves the development of a new implementation for the S-FETI method, the idea is to reduce the memory usage of this method, to make it able to work in larger problem. Different variation for this method are also proposed, all searching the reduction of directions stored each iteration of the iterative method. Finally, an extension of the FETI-2LM method to his block version as in S-FETI, is developed. Numerical results for the different algorithms are presented
Lescic, Sergiu. „Etude théorique du mécanisme de décomposition d'adduits de spin issus du piégeage de radicaux alkylperoxyle par des N-oxy-pyrrolines“. Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4752.
Der volle Inhalt der QuelleIn the field of electron paramagnetic resonance (EPR) spectroscopy, the detection of some radical species with a very short half-life time is possible using the spin-trapping method. This technique allows us to characterize transient radicals by trapping them with a diamagnetic molecule (nitrone for example) to give rise to a persistent paramagnetic species (spin-adduct), whose EPR spectrum is characteristic of the trapped radical. Half-life times are strongly correlated to the nature of the nitrone and the trapped radical (alkyl, alkoxyl, alkylperoxyl, ...). However, the link between the structure of the adduct and its half-life time is still not clear. Therefore, we carried out a theoretical study of the reactions involved in the decay of spin-adducts resulting from the trapping of alkylperoxyl radicals by pyrroline-N-oxide nitrones. More precisely, we were interested in the mechanism of the two-step unimolecular degradation. Given the difficulty to discribe the spin states in the considered compounds, we chose to rationalize this study by means of ab initio multireference approach (CASSCF). The ab initio CASSCF calculations of a series of nitroxides allowed to validate this mechanism in organic solvents and to better understand the relationship between the structure of the spin-adduct and its half-life time
Schneider, Antoine. „Contribution à l'identification et la commande de systèmes stochastiques discrets par des méthodes hiérarchisées : Application au modèle d'un convertisseur d'acier“. Nancy 1, 1987. http://www.theses.fr/1987NAN10248.
Der volle Inhalt der QuelleAl, Daas Hussam. „Résolution de systèmes linéaires issus de la modélisation des réservoirs“. Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS329.
Der volle Inhalt der QuelleThis thesis presents a work on iterative methods for solving linear systems that aim at reducing the communication in parallel computing. The main type of linear systems in which we are interested arises from a real-life reservoir simulation. Both schemes, implicit and explicit, of modelling the system are taken into account. Three approaches are studied separately. We consider non-symmetric (resp. symmetric) linear systems. This corresponds to the explicit (resp. implicit) formulation of the model problem. We start by presenting an approach that adds multiple search directions per iteration rather than one as in the classic iterative methods. Then, we discuss different strategies of recycling search subspaces. These strategies reduce the global iteration count of a considerable factor during a sequence of linear systems. We review different existing strategies and present a new one. We discuss the parallel implementation of these methods using a low-level language. Numerical experiments for both sequential and parallel implementations are presented. We also consider the algebraic domain decomposition approach. In an algebraic framework, we study the two-level additive Schwarz preconditioner. We provide the algebraic explicit form of a class of local coarse spaces that bounds the spectral condition number of the preconditioned matrix by a number pre-defined
Guibert, David. „Analyse de méthodes de résolution parallèles d’EDO/EDA raides“. Thesis, Lyon 1, 2009. http://www.theses.fr/2009LYO10138/document.
Der volle Inhalt der QuelleThis PhD Thesis deals with the development of parallel numerical methods for solving Ordinary and Algebraic Differential Equations. ODE and DAE are commonly arising when modeling complex dynamical phenomena. We first show that the parallelization across the method is limited by the number of stages of the RK method or DIMSIM. We introduce the Schur complement into the linearised linear system of time integrators. An automatic framework is given to build a mask defining the relationships between the variables. Then the Schur complement is coupled with Jacobian Free Newton-Krylov methods. As time decomposition, global time steps resolutions can be solved by parallel nonlinear solvers (such as fixed point, Newton and Steffensen acceleration). Two steps time decomposition (Parareal, Pita,...) are developed with a new definition of their grids to solved stiff problems. Global error estimates, especially the Richardson extrapolation, are used to compute a good approximation for the second grid. Finally we propose a parallel deferred correction
Lenain, Roland. „Amélioration des méthodes de calcul de cœurs de réacteurs nucléaires dans APOLLO3 : décomposition de domaine en théorie du transport pour des géométries 2D et 3D avec une accélération non linéaire par la diffusion“. Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112180/document.
Der volle Inhalt der QuelleThis thesis is devoted to the implementation of a domain decomposition method applied to the neutron transport equation. The objective of this work is to access high-fidelity deterministic solutions to properly handle heterogeneities located in nuclear reactor cores, for problems’ size ranging from colorsets of assemblies to large reactor cores configurations in 2D and 3D. The innovative algorithm developed during the thesis intends to optimize the use of parallelism and memory. The approach also aims to minimize the influence of the parallel implementation on the performances. These goals match the needs of APOLLO3 project, developed at CEA and supported by EDF and AREVA, which must be a portable code (no optimization on a specific architecture) in order to achieve best estimate modeling with resources ranging from personal computer to compute cluster available for engineers analyses. The proposed algorithm is a Parallel Multigroup-Block Jacobi one. Each subdomain is considered as a multi-group fixed-source problem with volume-sources (fission) and surface-sources (interface flux between the subdomains). The multi-group problem is solved in each subdomain and a single communication of the interface flux is required at each power iteration. The spectral radius of the resolution algorithm is made similar to the one of a classical resolution algorithm with a nonlinear diffusion acceleration method: the well-known Coarse Mesh Finite Difference. In this way an ideal scalability is achievable when the calculation is parallelized. The memory organization, taking advantage of shared memory parallelism, optimizes the resources by avoiding redundant copies of the data shared between the subdomains. Distributed memory architectures are made available by a hybrid parallel method that combines both paradigms of shared memory parallelism and distributed memory parallelism. For large problems, these architectures provide a greater number of processors and the amount of memory required for high-fidelity modeling. Thus, we have completed several modeling exercises to demonstrate the potential of the method: 2D full core calculation of a large pressurized water reactor and 3D colorsets of assemblies taking into account the constraints of space and energy discretization expected for high-fidelity modeling
Stauffert, Maxime. „Simulation numérique d'écoulements compressibles complexes par des méthodes de type Lagrange-projection : applications aux équations de Saint-Venant“. Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLV045/document.
Der volle Inhalt der QuelleIn this thesis we study a family of numerical schemes solving the shallow water equations system. These schemes use a Lagrange-projection like splitting operator technique in order to separate the gravity waves and the transport waves. An implicit-explicit treatment of the acoustic system (linked to the gravity waves) allows the schemes to stay stable with large time step. The correction of the pressure fluxes enables the obtain of a precise approximation solution whatever the regime flow is with respect to the Froude number. A particular attention has been paid over the source term treatment which permits to take the topography into account. We especially obtain the so-called well-balanced property giving the exact conservation of some steady states, namely the "lake at rest" state. 1D and 2D versions of this methods have been studied and implemented in the finite volumes framework. Finally, a high order discontinuous Galerkin extension has been proposed in 1D with classical limiters along with a combined MOOD loop a posteriori limiting strategy
Labiod, Lazhar. „Contribution au formalisme relationnel des classifications simultanées de deux ensembles“. Paris 6, 2008. http://www.theses.fr/2008PA066461.
Der volle Inhalt der QuelleZepeda, Salvatierra Joaquin. „Nouvelles méthodes de représentations parcimonieuses ; application à la compression et l'indexation d'images“. Phd thesis, Université Rennes 1, 2010. http://tel.archives-ouvertes.fr/tel-00567851.
Der volle Inhalt der QuelleNiang, Oumar. „Décomposition Modale Empirique : Contribution à la Modélisation Mathématique et Application en Traitement du Signal et de l'Image“. Phd thesis, Université Paris XII Val de Marne, 2007. http://tel.archives-ouvertes.fr/tel-00878354.
Der volle Inhalt der QuelleSzydlarski, Mikolaj. „Algebraic Domain Decomposition Methods for Darcy flow in heterogeneous media“. Phd thesis, Université Pierre et Marie Curie - Paris VI, 2010. http://tel.archives-ouvertes.fr/tel-00550728.
Der volle Inhalt der QuelleAli, Hassan Sarah. „Estimations d'erreur a posteriori et critères d'arrêt pour des solveurs par décomposition de domaine et avec des pas de temps locaux“. Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066098/document.
Der volle Inhalt der QuelleThis work contributes to the developpement of a posteriori error estimates and stopping criteria for domain decomposition methods with optimized Robin transmission conditions on the interface between subdomains. We study several problems. First, we tackle the steady diffusion equation using the mixed finite element subdomain discretization. Then the heat equation using the mixed finite element method in space and the discontinuous Galerkin scheme of lowest order in time is investigated. For the heat equation, a global-in-time domain decomposition method is used for both conforming and nonconforming time grids allowing for different time steps in different subdomains. This work is then extended to a two-phase flow model using a finite volume scheme in space. For each model, the multidomain formulation can be rewritten as an interface problem which is solved iteratively. Here at each iteration, local subdomain problems are solved, and information is then transferred to the neighboring subdomains. For unsteady problems, the subdomain problems are time-dependent and information is transferred via a space-time interface. The aim of this work is to bound the error between the exact solution and the approximate solution at each iteration of the domain decomposition algorithm. Different error components, such as the domain decomposition error, are identified in order to define efficient stopping criteria for the domain decomposition algorithm. More precisely, for the steady diffusion problem, the error of the domain decomposition method and that of the discretization in space are estimated separately. In addition, the time error for the unsteady problems is identified. Our a posteriori estimates are based on the reconstruction techniques for pressures and fluxes respectively in the spaces H1 and H(div). For the fluxes, local Neumann problems in bands arround the interfaces extracted from the subdomains are solved. Consequently, an effective criterion to stop the domain decomposition iterations is developed. Numerical experiments, both academic and more realistic with industrial data, are shown to illustrate the efficiency of these techniques. In particular, different time steps in different subdomains for the industrial example are used
Clautiaux, François. „New collaborative approaches for bin-packing problems“. Habilitation à diriger des recherches, Université de Technologie de Compiègne, 2010. http://tel.archives-ouvertes.fr/tel-00749419.
Der volle Inhalt der QuelleGarcia, Arias Jenny. „Disparités de mortalité par causes en Amérique latine : l'hypothèse du «biais urbain»“. Thesis, Paris 1, 2020. http://www.theses.fr/2020PA01H014.
Der volle Inhalt der QuelleIn 1977, Michael Lipton introduced the Urban Bias Thesis as a framework for understanding how most macro- and microeconomic policy initiatives have historically benefited the over-development of urban areas and the underdevelopment of rural areas. In Latin America, urbanization and mortality decline have historically been positively related: the health transition in the region has been initiated in the main cities and has tended to proceed more rapidly in countries with higher levels of urbanization. This research looks for evidence on: the persistence of an urban advantage in mortality; and traces of an "urban bias" in the causes of death patterns in the region. Using a sample of Latin American countries over the period 2000-2010, I apply decomposition methods on life expectancy at birth to analyze the disparities in mortality patterns and causes of death when urban and rural areas are considered separately. Urban is defined as a continuum category instead of a dichotomous concept. Hence, three types of spatial groups are recognizable in each country. The countries under analysis are Brazil, Chile, Colombia, Ecuador, Mexico, Peru and Venezuela. The results indicate that the urban advantage is persistent and that rural-urban mortality differentials have consistently favored cities. This advantage in mortality comes as an outcome of lower rates for causes of death that are amenable to primary interventions, meaning they are made amenable by the existence of basic public infrastructures as well as by the provision of basic goods and services
Xing, Feng. „Méthode de décomposition de domaines pour l’équation de Schrödinger“. Thesis, Lille 1, 2014. http://www.theses.fr/2014LIL10127/document.
Der volle Inhalt der QuelleThis thesis focuses on the development and implementation of domain decomposition methods (DD) for the linear or non-linear Schrödinger equations in one or two dimensions. In the first part, we focus on the Schwarz waveform relaxation method (SWR) for the one dimensional Schrödinger equation. In the case the potential is linear and time-independent, we propose a new algorithm that is scalable and allows a significant reduction of computation time compared with the classical algorithm. For a general potential, we use a linear operator previously defined as a preconditioner. This ensures high scalability. We also generalize the work of Halpern and Szeftel on transmission condition. We use the absorbing boundary conditions recently constructed by Antoine, Besse and Klein as the transmission condition. We also adapt the codes developed originally on Cpus to the Gpu. The second part concerns with the methods DD for the Schrödinger equation in two dimensions. We generalize the new algorithm and the preconditioned algorithm proposed in the first part to the case of two dimensions. Furthermore, in Chapter 6, we generalize the work of Loisel on the optimized Schwarz method with cross points for the Laplace equation, which leads to the SWR method with cross points. In the last part, we apply the domain decomposition methods we studied to the simulation of Bose-Einstein condensate that could not only reduce the total computation time, but also realise the larger simulations
Machui, Jürgen. „Simulation magnétostatique de têtes magnétiques en 3D par décomposition du domaine“. Paris 11, 1988. http://www.theses.fr/1988PA112055.
Der volle Inhalt der QuelleThis work concerns the simulation of planar magnetic recording heads in the context of its industrial development. Finite elements and reduced potential are used for the 3D calculation of the magnetostatic problem. The particular difficulty of magnetic recording heads lies in the enormous difference in scale between the gap and the whole head. We resolve this difficulty using an iteratif algorithm for domain decomposition for symmetrical heads that converges very rapidly. The non-linear saturation problem can be resolved using the Newton-Raphson method. Our decomposition algorithm is equally efficient for this kind of problem
Ouali, Abdelkader. „Méthodes hybrides parallèles pour la résolution de problèmes d'optimisation combinatoire : application au clustering sous contraintes“. Thesis, Normandie, 2017. http://www.theses.fr/2017NORMC215/document.
Der volle Inhalt der QuelleCombinatorial optimization problems have become the target of many scientific researches for their importance in solving academic problems and real problems encountered in the field of engineering and industry. Solving these problems by exact methods is often intractable because of the exorbitant time processing that these methods would require to reach the optimal solution(s). In this thesis, we were interested in the algorithmic context of solving combinatorial problems, and the modeling context of these problems. At the algorithmic level, we have explored the hybrid methods which excel in their ability to cooperate exact methods and approximate methods in order to produce rapidly solutions of best quality. At the modeling level, we worked on the specification and the exact resolution of complex problems in pattern set mining, in particular, by studying scaling issues in large databases. On the one hand, we proposed a first parallelization of the DGVNS algorithm, called CPDGVNS, which explores in parallel the different clusters of the tree decomposition by sharing the best overall solution on a master-worker model. Two other strategies, called RADGVNS and RSDGVNS, have been proposed which improve the frequency of exchanging intermediate solutions between the different processes. Experiments carried out on difficult combinatorial problems show the effectiveness of our parallel methods. On the other hand, we proposed a hybrid approach combining techniques of both Integer Linear Programming (ILP) and pattern mining. Our approach is comprehensive and takes advantage of the general ILP framework (by providing a high level of flexibility and expressiveness) and specialized heuristics for data mining (to improve computing time). In addition to the general framework for the pattern set mining, two problems were studied: conceptual clustering and the tiling problem. The experiments carried out showed the contribution of our proposition in relation to constraint-based approaches and specialized heuristics
Zeraidi, Bubakr. „Méthode de décomposition en sous-domaines, approximation par volumes finis et implémentation sur machines parallèles“. Aix-Marseille 1, 1998. http://www.theses.fr/1998AIX11064.
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