Teses / dissertações sobre o tema "Décomposition en modes spatiaux"
Crie uma referência precisa em APA, MLA, Chicago, Harvard, e outros estilos
Veja os 35 melhores trabalhos (teses / dissertações) para estudos sobre o assunto "Décomposition en modes spatiaux".
Ao lado de cada fonte na lista de referências, há um botão "Adicionar à bibliografia". Clique e geraremos automaticamente a citação bibliográfica do trabalho escolhido no estilo de citação de que você precisa: APA, MLA, Harvard, Chicago, Vancouver, etc.
Você também pode baixar o texto completo da publicação científica em formato .pdf e ler o resumo do trabalho online se estiver presente nos metadados.
Veja as teses / dissertações das mais diversas áreas científicas e compile uma bibliografia correta.
Rouvière, Clémentine. "Experimental parameter estimation in incoherent images via spatial-mode demultiplexing". Electronic Thesis or Diss., Sorbonne université, 2024. http://www.theses.fr/2024SORUS033.
Texto completo da fonteHistorically, the resolution of optical imaging systems was dictated by diffraction, and the Rayleigh criterion was long considered an unsurpassable limit. In superresolution microscopy, this limit is overcome by manipulating the emission properties of the object. However, in passive imaging, when sources are uncontrolled, reaching sub-Rayleigh resolution remains a challenge. Here, we implement a quantum-metrology-inspired approach for estimating the separation between two incoherent sources, achieving a sensitivity five orders of magnitude beyond the Rayleigh limit. Using a spatial mode demultiplexer, we examine scenes with bright and faint sources, through intensity measurements in the Hermite-Gauss basis. Analysing sensitivity and accuracy over an extensive range of separations, we demonstrate the remarkable effectiveness of demultiplexing for sub-Rayleigh separation estimation. These results effectively render the Rayleigh limit obsolete for passive imaging
Saviot, Alain-Frédéric. "Génération de faisceaux lasers de puissance à distribution d'éclairement homogénéisée par synchronisation intra-cavité des modes spatiaux". Limoges, 1994. http://www.theses.fr/1994LIMO0002.
Texto completo da fonteCHANG, TIEJUN. "Etude experimentale du bruit quantique des diodes laser : role du couplage amplitude-phase et des modes spatiaux transverses". Paris 11, 1999. http://www.theses.fr/1999PA112125.
Texto completo da fonteCognault, Aurore. "Caractérisation de SER Basse Fréquence et Modes Caractéristiques". Phd thesis, Ecole Centrale Paris, 2009. http://tel.archives-ouvertes.fr/tel-00453298.
Texto completo da fonteFruit, Gabriel. "Propagation des ondes MHD dans les couches de courant.Structure des modes et transferts énergétiques.Comparaison avec les données CLUSTER". Phd thesis, Université Paul Sabatier - Toulouse III, 2003. http://tel.archives-ouvertes.fr/tel-00094680.
Texto completo da fontedonnées cette thèse propose un cadre théorique auto-cohérent visant à étudier la réponse linéaire
d'une couche de plasma non homogène à une perturbation initiale, dans l'approximation de la MHD
idéale. En particulier, le calcul est mené jusqu'à la reconstruction finale des signaux
spatio-temporels avec une discussion des amplitudes obtenues et des transferts énergétiques qui en
découlent. Cette dernière étape est essentielle dans la perspective d'une comparaison avec les
données CLUSTER.
L'étude des modes propres de la queue magnétosphérique terrestre montre l'existence de deux
catégories d'oscillations : des modes globaux oscillant à des fréquences discrètes et confinés au
centre de la couche, et des modes continus liés au phénomène d'absorption résonante et dont
l'amplitude décroît au cours du temps. En utilisant diverses géométries de pulses initiaux, nous
étudions le couplage entre l'excitateur et ces modes propres. Il est mis en évidence que le
couplage avec les modes globaux est optimal pour un pulse dont la taille est voisine de l'épaisseur
de la couche. Même dans ce cas, les fluctuations restent cependant modestes. En revanche, avec le
même pulse initial, l'absorption du signal dans le continuum est efficace et conduit à un transfert
d'énergie non négligeable des ondes vers le plasma.
Enfin, un exemple d'oscillations magnétiques mesurées par CLUSTER est analysé et confronté
avec les résultats du modèle théorique. En effet l'étude théorique permet de préciser la nature des
perturbations ainsi que leur origine, dans l'hypothèse où ces fluctuations obéissent à une
description MHD.
Favelier, Thomas. "Couplage de la vélocimétrie par images de particules en deux temps avec la décomposition en modes propres pour la caractérisation d'un écoulement". Phd thesis, Université Claude Bernard - Lyon I, 2006. http://tel.archives-ouvertes.fr/tel-00080473.
Texto completo da fonteUne étude expérimentale de l'écoulement bidimensionnel en moyenne en aval d'un cylindre semi-circulaire, par vélocimétrie par image de particules en deux temps (PIV2T) caractérise l'écoulement
Une analyse POD du champ de vitesse permet d'extraire les modes spatiaux et de définir un paramètre de phase décrivant l'instationnarité à grande échelle qui régit la partie déterministe. La modélisation de l'évolution temporelle des coefficients associés aux modes s'effectue par des fonctions soit harmoniques pour la partie déterministe, soit stochastiques pour la partie aléatoire.
La modélisation est en accord avec les mesures expérimentales des premiers moments statistiques en un point et des fonctions de corrélation spatio-temporelle du champ de vitesse.
Bricard, Damien. "Construction des inégalités des chances en santé à travers les modes de vie". Phd thesis, Université Paris Dauphine - Paris IX, 2013. http://tel.archives-ouvertes.fr/tel-00984626.
Texto completo da fonteBourguignon-Mirebeau, Jennifer. "Préconditionnement de méthodes de décomposition de domaine pour les problèmes de diffraction d'ondes électromagnétiques impliquant une cavité profonde". Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00651957.
Texto completo da fonteLoret, François. "Décomposition sur les mouvements périodiques ou sur les modes résonants pour la simulation de la réponse transitoire d'un problème de tenue à la mer". Phd thesis, Châtenay-Malabry, Ecole centrale de Paris, 2004. http://pastel.archives-ouvertes.fr/pastel-00002503.
Texto completo da fonteZong, Weikai. "Amplitude and frequency modulations of oscillation modes in hot B subdwarf and white dwarf stars from Kepler photometry". Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30306/document.
Texto completo da fonteNonlinear mode interactions, inducing amplitude and frequency modulations, are difficult to observe from ground-based telescopes as these typical timescales of the modulations are of the order of weeks, months, or even years. The launch of space telescopes such as Kepler (operated by NASA) has tremendously changed the situation by providing new data for this research field. In this thesis, we analyze the Kepler photometric data observed for 24 compact pulsators, including 18 hot B subdwarf (sdB) stars and six white dwarf stars. We find that it is a common phenomenon that oscillation modes in these pulsating stars show amplitude and/or frequency variations. We focus in particular on two stars, KIC 08626021, a DB white dwarf, and KIC 10139564, a short period sdB star. KIC 08626021 and KIC 10139564 have been monitored by Kepler in short-cadence mode for nearly two years and more than three years without interruption, respectively. By analyzing in depth these high-quality photometric data, we find that the modes within triplets induced by rotation clearly reveal different types of behaviors : their frequency and amplitude may exhibit either periodic or irregular modulations, or remain constant. These various behaviors can be linked to those predicted within the amplitude equation formalism in the case of the nonlinear resonant mode coupling mechanism, particularly for the modulation timescales. Furthermore, we find that the triplet resonance modes can also interact with outside modes through other types of resonances such as the three-mode resonance v 0 ~ v 1 + v 2 , which is not considered within the current nonlinear theoretical frameworks. These findings constitute the first clear evidence of nonlinear resonant mode couplings occurring in compact pulsators. This should resonate as a warning to projects aiming at measuring the evolutionary change rate of pulsation periods in compact stars in general. Nonlinear modulations of the frequencies can potentially jeopardize any attempt to measure reliably such rates, unless they can be corrected beforehand. The observed modulations characterized in this thesis provide new insights to "nonlinear asteroseismology" and call for new methods to process the signals of variable modes from the observed light curves. We foresee that increasing attention will focus on these nonlinear phenomena in various types of pulsating stars observed from space in the near future, thus reviving interest in the nonlinear oscillation theory in general
Boucher, Pauline. "Spatial mode multiplexing : from fundamental concepts to applications". Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS483.
Texto completo da fonteThis thesis is dedicated to spatial mode multiplexing, from its fundamental concepts to its applications. The work is associated with the multi-plane light converter (MPLC) technology developed by CAILabs. This study is divided into two main parts. First, we investigate the use of independent spatial mode shaping to measure or modify spatial parameters of the electromagnetic field. We make the theoretical demonstration that the best sensitivity for the measurement of small displacements of a beam – or of the distance between two incoherent beams – is reached when an intensity measurement is made on the Hermite-Gaussian mode basis. By building the adequate MPLC system, we make the experimental validation of this result. We also make the demonstration that a MPLC system can be designed and used to transfer the control of one spatial parameter of a beam onto another. We built an experimental setup which allows to control the position of the focal point of a beam using transverse displacement and tilt. The second project we conducted was a theoretical and numerical study of the statistical transport properties of the MPLC using tools from random matrix theory. We aim at identifying the underlying physical processes which make up for the efficiency of this transformation technique
Abdulhay, Enas. "Une nouvelle méthode non-invasive d'estimation cycle à cycle du volume d'éjection cardiaque dans le signal de plethysmographie respiratoire par inductance : algorithme de "double décomposition empirique"". Université Joseph Fourier (Grenoble ; 1971-2015), 2009. http://www.theses.fr/2009GRE10220.
Texto completo da fonteThe main objective that guides the signal processing approaches ofthis thesis is the development of a tool that oould be part of an integrative physiology approach where, at each scale, the model of signais may be different We seek here the restriction of asstnnptions a priori to a set: of rules goveming the physiological interactions between physiological functions in the absence of fannal and mathematical assumptions. We applied this approach to the problem of cardiac waves detection and estimation of cycle-to-cycle stroke volume in the RIP signal (Respiratory Inductive Plethysmography). The empirical decomposition approach seems to be particularly adapted to our logic. We propose here the first version of an algorithm based on RIP double decomposition. The method and its COITeSpül1ding tools have been tested on two types of data, simulated signais and real signais recorded at healthy volunteers. Our aim is also therefore to develop a cardio-respiratory model that can serve as a tool for ventilatory, cardiac and RIP signals simulation along with the simulation of the effect of each system on the other. The results show that the proposed method is suitable for RIP signal analysis and for stroke volume estimation
Diakite, Cheick. "Identification d’un modèle de mesure au sol du diagramme de rayonnement des antennes installées sur aéronefs". Thesis, Université Côte d'Azur (ComUE), 2018. http://www.theses.fr/2018AZUR4007.
Texto completo da fonteAircraft antennas radiation pattern must be measured before radiofrequency systems deployment. When an antenna is on the aircraft, radiating structure is not only antenna element but it’s the set antenna and aircraft. Radiation pattern have to be determined at great distance from the radiating structure. This distance is located in area called far field area depending on the frequency of operation and the maximal size of the aircraft. For example, to measure an antenna on an aircraft of 12 m of long at 88 MHz; the far field area is at 85m.To get this distance, flight measurement is performed. During flight test, radiation pattern is determined by a ground station which is at 80 km of the aircraft. This method is very expensive and takes much time and causes serious delays on aircraft delivery. For these reasons Airbus Helicopters explores new innovative solution, like as radiation pattern measurement on the ground. The last one disturbs the radiation pattern. The proposed method allows to perform measurement in compact volume and cancel out the ground influence. Proposed solution is based on cylindrical near field measurement, and cylindrical modes decomposition. Near field data are scanned on cylinder surface, then an algorithm developed on MATLAB environment do near field to far field transformation. Cylindrical modes decomposition and modal filtering rid of ground reflections. Proposed solution has been validated numerically through comparison with electromagnetic simulator software results. Antenna measurement range in the laboratory has served to validate experimentally the proposed solution on a prototype in scale size
Missoffe, Alexia. "Réduction d'ordre de modèle d'un phénomène d'amortissement non-linéaire dans le cadre des microsystèmes". Phd thesis, Ecole Centrale Paris, 2010. http://tel.archives-ouvertes.fr/tel-00552076.
Texto completo da fonteCagniart, Nicolas. "Quelques approches non linéaires en réduction de complexité". Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS194/document.
Texto completo da fonteModel reduction methods provide a general framework for substantially reducing computational costs of numerical simulations. In this thesis, we propose to extend the scope of these methods. The common point of the topics discussed here is the attempt to go beyond the standard linear "reduced basis" framework, which only deals with cases where the solution manifold have a small Kolmogorov width. We shall see how truncate, translate, rotate, stretch, compress etc. and then recombine the solutions, can sometimes help to overcome the problem when this Kolmogorov width is not small. We will also discuss the need for tailor-made stabilisation methods for the reduced frame
Nowakowski, Thibault. "Localisation et calibration acoustiques par des réseaux distribués en milieux réverbérants". Sorbonne Paris Cité, 2015. http://www.theses.fr/2015USPCC209.
Texto completo da fonteIn rooms, acoustic source localization with distributed microphones arrays is a difficult task because of the reverberation and various obstacles modifying the sound propagation. The main acoustic imaging methods that are successful in free field, like the beamforming algorithm, fait to give a good estimation of the sources positions in these close environments. New approaches have to be developed. When no information is avaitabte about the propagation environment, we choose to use a method to approximate the solutions to the Helmholtz equation thanks to linear combinations of harmonic polynomials, like Fourier-Bessel functions or plane waves. Thanks to this approach, the direct field generated by the sources can be isolated. The sources can then be localized with sparse reconstruction methods. We first validate numerically and then with several experiments. To reduce the number of required microphones, we introduce a concept of virtual measurements to partially take into account the room geometry. Afterwards, we propound a "semi-blind" dereverberation method based on Green's functions estimation from cross-correlations of the acoustic field. Setting up a microphone array in reverberant medium brings several calibration issues. We propose two complementary methods based on time-domain correlations of the reverberated field and the interpolation of the eigenmodes of the medium, to estimate the microphones positions. Finally, we develop an original approach based on our previous results to estimate a membrane shape from a set of acoustic measurements
Bouyssier, Julien. "Transports couplés en géométries complexes". Toulouse 3, 2012. http://thesesups.ups-tlse.fr/1929/.
Texto completo da fonteThis work interest is about stationary transfer and non-stationary transport by convection-diffusion onto complex geometries. For transport issues, complex refers to convection into flattened cavity of arbitrary transverse shape, slowly varying along the longitudinal direction. In the context of transfer, complex refers to non-axisymmetric domains of arbitrary transverse shape along which one or several parallel tubes convect heat or mass. For the transfer problem, this work extends the principle, validates the use, and illustrates the efficiency of Graetz modes decompositions for exchanges prediction in realistic exchangers configurations. This decomposition permits to formulate the initial 3D problem as a generalysed 2D eigenvalue problem, the numerical evaluation of which is drastically reduced. We generalyze Graetz modes solutions for arbitrary applied lateral boundary conditions. In the particular case of balanced exchangers, we bring to the fore a new neutral mode whose longitudinal variations are linear as opposed to classical Graetz modes displaying exponential decay. The numerical computation of those modes for semi-infinite configurations with lateral periodic boundary conditions shows that a few number of those provides a very good approximation for exchanges. In the case of finite exchangers coupled with inlet/oulet tubes, we show how to evaluate the amplitudes of Graetz modes in the various domains (inlet, exchanger, outlet) from functional minimization associated with input/output boundary conditions. The evaluation of these amplitudes permit a systematic parametric study of temperature fields, heat fluxes between fluid and solid, and hot/cold performance of a couple-tube exchanger. Our results indicate that the typical exchange length is governed by the first Graetz mode at large P\'eclet number. We also show that a symmetric exchanger has a symmetric spectrum and a upward/backward symmetric evolution. In the case transport we elaborate theoretically the conservative form of 3D Taylor dispersion equations into variable cavities which generalyzes the framework already known in 2D. We numerically implement these averaged dispersion equations with finite element, and validate in 2D the obtained results. We show that 3D longitudinal variations of a cavity has a strong impact on the longitudinal dispersion
Drouart, F. "Non-linéarité Kerr dans les Fibres Optiques Microstructurées". Phd thesis, Université Paul Cézanne - Aix-Marseille III, 2008. http://tel.archives-ouvertes.fr/tel-00438491.
Texto completo da fonteRenaud, Antoine. "Étude de la stabilisation des flammes et des comportements transitoires dans un brûleur étagé à combustible liquide à l'aide de diagnostics rapides". Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLC003/document.
Texto completo da fonteA promising way to reduce jet engines pollutant emissions is the use of lean premixed prevaporized combustion but it tends to trigger thermo-acoustic instabilities. To improve the stability of these flames, a procedure called staging consists in splitting the fuel injection to control its spatial distribution. This however leads to an increased complexity and unexpected phenomena can occur.In the present work, a model gas turbine combustor fed with liquid dodecane is used. It is equipped with two fuel injection stages to control the fuel distribution in the burner. Different flame stabilizations can be observed and a bistable case where two flame shapes can exist for the same operating conditions is highlighted.High-speed optical diagnostics (fuel droplets Mie scatering and chemiluminescence measurements) are coupled with advanced post-processing methods like Dynamic Mode Decomposition. The results enable to propose mechanisms leading to flame stabilization and flame shape transitions. They show a strong interplay between the gaseous flow, the fuel droplets and the flame itself
Laurant, Yann. "Variabilité aérodynamique d'un moteur à combustion interne pendant la phase d'admission : Vers l'origine des fluctuations cycliques". Ecully, Ecole centrale de Lyon, 2008. http://bibli.ec-lyon.fr/exl-doc/TH_T2122_ylaurant.pdf.
Texto completo da fonteKnowledge of airflow in the combustion chamber is of great interest to improve the performance of internal combustion engines, thereby reducing emissions. Present work analyzes cycle to cycle fluctuations of aerodynamics flow during the intake part of a 4-stroke engine in order point out main phenomena leading to cycle to cycle fluctuations at the low break-even point. Two stages allow a gradual approach to the complexity of the flow (turbulence, confinement, moving geometry). In a first step, the admissions system is characterized on a steady flow test bench. High speed particle image velocimetry measurements (TR-PIV) highlight different types of instationnarities: the flapping of the valve jet and the generation of vortex structures in shear layers. The spatial and temporal characteristics of these instationnarities are quantified by advanced signal processing (POD). They are in good agreement with those derived from a Large Eddy Simulation (LES) carried out in the same configuration. In a second step, the flow is studied using an optical motored engine. Results show that acoustic fluctuations and aerodynamic variability upstream the valve have very little influence on the structure and variability of the flow into the combustion chamber. Fluctuations in the aerodynamic field at the low break-even point are primarily related to the flapping valve jet during the intake stroke
Lessinnes, Thomas. "Magnetohydrodynamic turbulence modelling: application to the dynamo effect". Doctoral thesis, Universite Libre de Bruxelles, 2010. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210042.
Texto completo da fonteIl est surprenant qu'alors que les mouvements fluides à l'intérieur de ces objets célestes sont turbulents, les champs magnétiques généré soient de grande échelle spatiale et stables sur de longues périodes de temps. De plus, ils peuvent présenter une dynamique temporelle régulière comme c'est le cas pour le champ magnétique solaire dont la polarité s'inverse tous les onze ans.
Décrire et prédire les mouvements d'un fluide turbulent reste l'un des problèmes les plus difficiles de la mécanique classique.
%La description aussi bien analytique que numérique d'un fluide hautement turbulent est d'une effroyable complexité, si pas tout simplement impraticable. Dans cette situation,
Il est donc utile de construire des modèles aussi proches que possible du système de départ mais de moindre complexité de sorte que des études théoriques et numériques deviennent envisageables.
Deux approches ont été considérées ici. D'une part, nous avons développé des modèles présentant un très petit nombre de degrés de liberté (de l'ordre de la dizaine). Une étude analytique est alors possible. Ces modèles ont une dépendance en les paramètres physiques - nombres de Reynolds cinétique et magnétique et injection d'hélicité - qualitativement similaire aux dynamos célestes et expérimentales.
D'autre part, les modèles en couches permettent de caractériser les transferts d'énergie entre les structures de différentes tailles présentes au sein du champ de vitesse. Nous avons développé un nouveau formalisme qui permet d'étudier aussi les échanges avec le champ magnétique.
De plus, nous proposons une étude de la MHD dans le cadre de la décomposition hélicoïdale des champs solénoïdaux - une idée similaire à la décomposition de la lumière en composantes polarisées et que nous sommes les premiers à appliquer à la MHD. Nous avons montré comment exploiter cette approche pour déduire systématiquement des modèles simplifiés de la MHD. En particulier, nos méthodes multiplient le nombre de situations descriptibles par les modèles en couche comme par exemple le problème anisotrope de la turbulence en rotation. Elles permettent aussi de construire des modèles à basse dimension en calquant les résultats de simulations numériques directes. Ces modèles peuvent alors être étudiés à moindre coûts.
_______________
Magnetohydrodynamics (MHD) is both the science and the formalism that describe the motion of an electro-conducting fluid. Such motion may yield the dynamo effect consisting in the spontaneous generation of a large scale stationary magnetic field. This phenomenon is most likely the reason behind the existence of planetary, stellar and galactic magnetic fields.
\
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
Tissot, Gilles. "Réduction de modèle et contrôle d'écoulements". Thesis, Poitiers, 2014. http://www.theses.fr/2014POIT2284/document.
Texto completo da fonteControl of turbulent flows is still today a challenge in aerodynamics. Indeed, the presence of a high number of active degrees of freedom and of a complex dynamics leads to the need of strong modelling efforts for an efficient control design. During this PhD, various directions have been followed in order to develop reduced-order models of flows in realistic situations and to use it for control. First, dynamic mode decomposition (DMD), and some of its variants, have been exploited as reduced basis for extracting at best the dynamical behaviour of the flow. Thereafter, we were interested in 4D-variational data assimilation which combines inhomogeneous informations coming from a dynamical model, observations and an a priori knowledge of the system. POD and DMD reduced-order models of a turbulent cylinder wake flow have been successfully derived using data assimilation of PIV measurements. Finally, we considered flow control in a fluid-structure interaction context. After showing that the immersed body motion can be represented as an additional constraint in the reduced-order model, we stabilized a cylinder wake flow by vertical oscillations
Lalizel, Gildas. "Caractérisation expérimentale de l'aérodynamique d'un jet annulaire à très grand rapport de diamètres". Phd thesis, Université de Rouen, 2004. http://tel.archives-ouvertes.fr/tel-00012179.
Texto completo da fonteLes instabilités se développant dans les couches de mélange externe et interne de la zone de recirculation ont été résolues spatialement et temporellement. L'utilisation conjointe de mesures P.I.V. décorrélées en temps de la zone de recirculation, de la P.O.D. et d'une mesure temporelle locale par A.D.L. a permis d'établir un scénario de l'évolution temporelle du sillage.
La zone de jet pleinement développé a également été étudiée à partir de mesures d'A.D.L. et de fil chaud. Les évolutions des grandeurs intégrales (quantité de mouvement, débit, vitesses, demi largeur du jet, nombre de Reynolds turbulent), des différentes échelles (échelles de Kolmogorov, de Taylor et intégrale) et du taux de dissipation moyen ont été mesurées sur l'axe du jet. Une comparaison des variations de ces différentes grandeurs a permis d'inclure le jet rond comme un cas asymptotique des jets annulaires.
Lülf, Fritz Adrian. "An integrated method for the transient solution of reduced order models of geometrically nonlinear structural dynamic systems". Phd thesis, Conservatoire national des arts et metiers - CNAM, 2013. http://tel.archives-ouvertes.fr/tel-00957455.
Texto completo da fonteLegrand, Nicolas. "Numerical and modeling methods for multi-level large eddy simulations of turbulent flows in complex geometries". Thesis, Normandie, 2017. http://www.theses.fr/2017NORMIR16/document.
Texto completo da fonteLarge-Eddy Simulation (LES) has become a major tool for the analysis of highly turbulent flows in complex geometries. However, due to the steadily increase of computational resources, the amount of data generated by well-resolved numerical simulations is such that it has become very challenging to manage them with traditional data processing tools. In Computational Fluid Dynamics (CFD), this emerging problematic leads to the same "Big Data" challenges as in the computer science field. Some techniques have already been developed such as data partitioning and ordering or parallel processing but still remain insufficient for modern numerical simulations. Hence, the objective of this work is to propose new processing formalisms to circumvent the data volume issue for the future 2020 exa-scale computing objectives. To this aim, a massively parallel co-processing method, suited for complex geometries, was developed in order to extract large-scale features in turbulent flows. The principle of the method is to introduce a series of coarser nested grids to reduce the amount of data while keeping the large scales of interest. Data is transferred from one grid level to another using high-order filters and accurate interpolation techniques. This method enabled to apply modal decomposition techniques to a billion-cell LES of a 3D turbulent turbine blade, thus demonstrating its effectiveness. The capability of performing calculations on several embedded grid levels was then used to devise the multi-resolution LES (MR-LES). The aim of the method is to evaluate the modeling and numerical errors during an LES by conducting the same simulation on two different mesh resolutions, simultaneously. This error estimation is highly valuable as it allows to generate optimal grids through the building of an objective grid quality measure. MR-LES intents to limit the computational cost of the simulation while minimizing the sub-grid scale modeling errors. This novel framework was applied successfully to the simulation of a turbulent flow around a 3D cylinder
Kerkeni, Leila. "Analyse acoustique de la voix pour la détection des émotions du locuteur". Thesis, Le Mans, 2020. http://www.theses.fr/2020LEMA1003.
Texto completo da fonteThe aim of this thesis is to propose a speech emotion recognition (SER) system for application in classroom. This system has been built up using novel features based on the amplitude and frequency (AM-FM) modulation model of speech signal. This model is based on the joint use of empirical mode decomposition (EMD) and the Teager-Kaiser energy operator (TKEO). In this system, the discrete (or categorical) emotion theory was chosen to represent the six basic emotions (sadness, anger, joy, disgust, fear and surprise) and neutral emotion.Automatic recognition has been optimized by finding the best combination of features, selecting the most relevant ones and comparing different classification approaches. Two reference speech emotional databases, in German and Spanish, were used to train and evaluate this system. A new database in French, more appropriate for the educational context was built, tested andvalidated
Tayachi, Manel. "Couplage de modèles de dimensions hétérogènes et application en hydrodynamique". Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENM031/document.
Texto completo da fonteThe work presented here focuses on electrodes made of silicon, a promising material to replace graphite as an anode active material for Li-ion Batteries (LIBs). The first part of the manuscript is dedicated to the study of silicon (de)lithiation mechanisms by Auger Electron Spectroscopy (AES). By using this technique of surface characterization, which allows investigating individual particles in their electrode environment, our results show that the first silicon lithiation occurs through a two-phase region mechanism cr-Si / a-Li3,1Si, whereas the following (de)lithiation steps are solid solution type process. Upon (de)alloying with lithium, silicon particles undergo huge volume variations leading to a quick capacity fading. By combining several techniques of characterization, the failure mechanisms of a silicon electrode are studied during aging. In particular, by using electrochemical impedance spectroscopy and mercury porosimetry analyses, an impressive dynamic upon cycling of the electrode porosity is shown. A model, which mainly attributes the capacity fading to the Solid Electrolyte Interphase instability at the silicon particles surface, is proposed. To try to stabilize this passivation layer and thus improve silicon electrodes electrochemical performances, the influence of two parameters is studied: the electrolyte and the “lithiation domain” of silicon; the latter is associated with the evolution of the active material composition upon cycling. Finally, by using these last results, promising performances are obtained for silicon electrode containing LIBs
Boubehziz, Toufik. "Simulation en quasi temps réel d’une capsule sous écoulement grâce à des Modèles d’Ordre Réduit". Thesis, Compiègne, 2022. http://www.theses.fr/2022COMP2678.
Texto completo da fonteThe motion of a liquid-filled microcapsule flowing in a microchannel is a complex problem tosimulate. Two innovative reduced-order data-driven models are proposed to replace the Fluid Structure Interaction (FSI) model using a collected database from high-fidelity simulations. The objective is to replace the existing Full Order Model (FOM) with a fast-simulation model that can simulate the capsule deformation in flow at a low cost in terms of time and calculation. The first model consists in building from a space-time-parameter datacube a reduced model to simulate the deformation of the microcapsule for any admissible configuration of parameters. Time evolution of the capsule deformation is treated by identifying the nonlinear low-order manifold of the reduced variables. Then, manifold learning is applied using the Diffuse Approximation (DA) method to predict capsule deformation for a query configuration of parameters and a chosen time discretization. The second model is based on rewriting the FSI model under the form of a reduced-order dynamic system. In this latter, the spectral displacement and velocity coefficients are related through a dynamic operator to be identified. To determine this operator, we suggest the use of a dynamic mode decomposition approach. Numerical validations prove the reliability and stability of the two new models compared to the high order model. A software application has been developed to explore the capsule deformation evolution for any couple of admissible parameters
Costini, Pierre. "Applicabilité de la réduction de modèles à la conception aérothermique collaborative des systèmes d'air secondaire des turbomachines". Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0109.
Texto completo da fonteA non intrusive method to create surrogate models describing the flow in jet engines’ secondary air system is desired. The resulting model must be integrated in a thermal model describing the whole engine during a complete mission under the wing. This requires the model to use a high number of input and output parameters and to be valid on a broad domain of variation of its parameters. Several approches are explored in this thesis and applied to a simplified turbine cavity :— Surrogate modeling of terms of the ANOVA decomposition of wall fluxes.— Surrogate modeling of wall fluxes combined with an adaptive refinement method exploiting the trajectory followed by the input parameters during the coupling between the metamodel and the structural model.— Dimensionality reduction of the interface data exchanged during the coupling between flow and structure thermal model and surrogate modeling of the resulting reduced coordinate.This last approach leads to good results on the test case considered in this thesis with fixed inlet boundary conditions and then with variations of some of the inlet parameters
Danlos, Amélie. "Dynamique des jets contrôlés : Application à l'étude du mélange dans des écoulements de jets annulaires à très grand rapport de diamètres". Phd thesis, Université de Rouen, 2009. http://tel.archives-ouvertes.fr/tel-00649177.
Texto completo da fonteDeparday, Julien. "Etudes expérimentales de l'Interaction fluide-structure sur les voiles de bateaux au portant". Thesis, Brest, 2016. http://www.theses.fr/2016BRES0044/document.
Texto completo da fonteA full-scale experimental study on an instrumented sailing yacht is conducted to better assess the aero-elastic behaviour of the sails and rigging in downwind navigations. The downwind sail shape is a non-developable surface with high curvature leading to massive flow separation. In addition, spinnakers are thin and flexible sails leading to a strongly coupled Fluid-Structure Interaction. Due to the non-respect of some rules of similitude, the unsteady behaviour of downwind sails cannot be easily investigated with wind tunnel tests that would need comparison with full-scale experiments. Moreover unsteady numerical simulations modelling the aero-elastic behaviour of the sails and rigging require validations. An inboard instrumentation system has been developed on a 8 meter J/80 sailboat to simultaneously and dynamically measure the flying shape of the spinnaker, the aerodynamic loads transmitted to the rigging, the pressure distribution on the sail as well as the boat and wind data. The shape of the spinnaker while sailing is acquired by a photogrammetric system developed during this PhD. The accuracy of this new system, better than 1.5%, is used to measure the global shape and the main dynamic deformations, such as the flapping of the luff. The aerodynamic load produced by the spinnaker is assessed by the measurements of the load magnitudes and directions on the three corners of the sail (head, tack and clew), and also by the pressure distribution on the spinnaker. The global behaviour of the spinnaker is analysed according to the apparent wind angle. A new representation using Bézier triangular surfaces defines the spinnaker 3D shape. A few control points enable to represent the sail and can easily characterise the type of sail. A typical unsteady behaviour of the spinnaker is also analysed. Letting the luff of the sail flap is known by sailors as the optimal trim but has never been scientifically studied before. It is found that it is a complex three dimensional fluid-structure interaction problem where a high suction near the leading edge occurs, producing a temporary increase of the force coefficient that would not be possible otherwise
André, Thierry. "Contrôle actif de la transition laminaire-turbulent en écoulement hypersonique". Thesis, Orléans, 2016. http://www.theses.fr/2016ORLE2022/document.
Texto completo da fonteDuring a hypersonic flight (Mach 6, 20 km altitude), the boundary layer developing on the forebody of a vehicle is laminar. This state may destabilize the scramjet engine propelling the vehicle. To overcome this problem during the flight, the boundary layer transition has to be forced using a control device whose effect is fixed (passive) or adjustable (active). In this work, we analyze the efficiency of a jet in crossflow in forcing the boundary layer transition on a generic forebody. The flow is computed with a Large Eddy Simulations (LES) approach. A parametric study of the injection pressure allows the efficiency of the jet in tripping the boundary layer to be quantified. The influence of flight conditions (Mach, altitude) on the transition is also studied. Dynamic Mode Decomposition (DMD) is applied to the simulation results to determine the transition leading to dynamic modes and to understand underlying transition mechanisms. Experiments in the Purdue University quiet wind tunnel (BAM6QT) were performed to quantify the efficiency of a passive transition device (diamond roughnesses) and an active transition device (single air jet) in tripping the boundary layer. A thermo-sensitive paint and pressure transducers (Kulite, PCB) were used to determine the state of the boundary layer on the generic forebody. Experimental and numerical results show a sonic injection is sufficient to induce transition. We observe from the experiments that for the same penetration height, a single roughness is less efficient than a single air jet in destabilizing the boundary layer
Sorba, Grégoire. "Etude expérimentale et modélisation numérique des écoulements de compression dans les composites stratifiés visqueux à plis discontinus". Thesis, Ecole centrale de Nantes, 2017. http://www.theses.fr/2017ECDN0038.
Texto completo da fonteThe design freedom of composites can be improved by combining continuous and discontinuous prepregs. The forming of a pre-heated blank made of optimally oriented and distributed discontinuous prepreg plies may lead to unacceptable defects such as in-plane and out-of-plane wrinkles, sliding of plies, rotation of adjacent plies, bending of fibres induced by transverse squeeze flow and finally to inappropriate and inefficient fibre distribution. This arises because the individual discontinuous plies are free to move and deform in the mould during the forming step. First, this work presents some experiments conducted to identify the behaviour of a stack of unidirectional and woven discontinuous viscous prepregs subjected to through-thickness compression. Then a model based on a heterogeneous transverse isotropic fluid approach is gradually developped in agreement with the experimental findings. It is shown that the various observed phenomena are retrieved for the unidirectional and partly for the woven prepreg by the numerical model. The predicted values are in good agreement with measurements, when the problem is solved in 3D with a relatively fine mesh in the thickness. Finally an attempt is made to reduce the computational cost by the use of advanced numerical simulation techniques
Danlos, Amélie. "Dynamique des jets contrôlés : Application à l’étude du mélange dans des écoulements de jets annulaires à très grand rapport de diamètres". Phd thesis, Rouen, 2009. http://www.theses.fr/2009ROUES055.
Texto completo da fonteBerrebi, Johanna. "Contribution à l'intégration d'une liaison avionique sans fil. L'ingénierie système appliquée à une problématique industrielle". Phd thesis, Ecole Polytechnique X, 2013. http://pastel.archives-ouvertes.fr/pastel-00800141.
Texto completo da fonte