Dissertations / Theses on the topic 'Surfaces aléatoires'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 48 dissertations / theses for your research on the topic 'Surfaces aléatoires.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
Aubert, Antoine. "Propriétés optiques des surfaces rugueuses aléatoires." ENSMP, 1999. http://www.theses.fr/1999ENMP0900.
Full textBerzin, Corinne. "Surfaces aléatoires : approximation du temps local." Paris 11, 1989. http://www.theses.fr/1989PA112337.
Full textLet { X(t,ω), t ∈ Rd, ω ∈ Ω }, d ≥2, be a real stationary gaussian field, defined on a probability space ( Ω, Around, P ). We look at the asymptotic behavior of a particular stochastic integral, with respect to the geometric measure of the u-level sets, u ∈ R, of the regularized field, obtained by composition of a convolution of X, say Xɛ, with a matrix normalization which contains part of the information contained in the spectral moments matrix of second order of Xɛ. Under the condition that the covariance function is twice continuously differentiable out of a set of zero Lebesgue's measure, this functional converges in L² (Ω ) to the local time of X at the level u. Furthermore, we give a bound for the speed of convergence
Najar, Hatem. "Asymptotique de Lifshitz pour les opérateurs acoustiques aléatoires." Paris 13, 2000. http://www.theses.fr/2000PA132018.
Full textTinsson, Walter. "Plans d'expérience à facteurs quantitatifs et à effets de blocs aléatoires." Pau, 1998. http://www.theses.fr/1998PAUU3021.
Full textBouttier, Jérémie. "Physique statistique des surfaces aléatoires et combinatoire bijective des cartes planaires." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2005. http://tel.archives-ouvertes.fr/tel-00010651.
Full textRobin, Olivier. "Reproduction de champs de pression acoustique aléatoires sur des surfaces planes." Thèse, Université de Sherbrooke, 2013. http://hdl.handle.net/11143/6140.
Full textBelemaalem, Zakaria. "Schémas asynchrones pour des EDPs et génération de surfaces aléatoires à l'aide de groupes localisés." Brest, 2011. http://www.theses.fr/2011BRES2025.
Full textThe study in this thesis proposes an original representation of a random wave field. The main goal is to respect the statistical constraints on a one-point characteristic function (variance, skewness and kurtosis) and also, at a two-point characteristic function (spectrum and slope). The proposed model considers the elevation of the ocean surface as a superposition of random spatial functions with the random amplitudes, grouped into maps depending on the wave vector. This approach leads to the construction of two models, so called “Groupy Wave Model” (GWM) and “Groupy Chopy Wave Model” (GCWM). The first allows the control of the spectrum, skewness (elevations and slopes) and kurtosis (elevations or slopes). The latter takes into account the orbital motions of water particles. The OGWM model is derived from horizontal coordinates of GWM surface. This transformation dresses the spectrum and shows cusps. A method of undressing the spectrum to obtain a surface with a target spectrum, which takes into account the cusps, is also introduced. The obtained results emphasize very different sea state structures, but with identical statistical properties
Borot, Gaetan. "Quelques problèmes de géométrie énumérative, de matrices aléatoires, d'intégrabilité, étudiés via la géométrie des surfaces de Riemann." Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00625776.
Full textBorot, Gaëtan. "Quelques problèmes de géométrie énumérative, de matrices aléatoires, d'intégrabilité, étudiés via la géométrie des surfaces de Riemann." Thesis, Paris 11, 2011. http://www.theses.fr/2011PA112092/document.
Full textComplex analysis is a powerful tool to study classical integrable systems, statistical physics on the random lattice, random matrix theory, topological string theory, … All these topics share certain relations, called "loop equations" or "Virasoro constraints". In the simplest case, the complete solution of those equations was found recently : it can be expressed in the framework of differential geometry over a certain Riemann surface which depends on the problem : the "spectral curve". This thesis is a contribution to the development of these techniques, and to their applications.First, we consider all order large N asymptotics in some N-dimensional integrals coming from random matrix theory, or more generally from "log gases" problems. We shall explain how to use loop equations to establish those asymptotics in beta matrix models within a one cut regime. This can be applied in the study of large fluctuations of the maximum eigenvalue in beta matrix models, and lead us to heuristic predictions about the asymptotics of Tracy-Widom beta law to all order, and for all positive beta. Second, we study the interplay between integrability and loop equations. As a corollary, we are able to prove the previous prediction about the asymptotics to all order of Tracy-Widom law for hermitian matrices.We move on with the solution of some combinatorial problems in all topologies. In topological string theory, a conjecture from Bouchard, Klemm, Mariño and Pasquetti states that certain generating series of Gromov-Witten invariants in toric Calabi-Yau threefolds, are solutions of loop equations. We have proved this conjecture in the simplest case, where those invariants coincide with the "simple Hurwitz numbers". We also explain recent progress towards the general conjecture, in relation with our work. In statistical physics on the random lattice, we have solved the trivalent O(n) model introduced by Kostov, and we explain the method to solve more general statistical models.Throughout the thesis, the computation of some "generalized matrices integrals" appears to be increasingly important for future applications, and this appeals for a general theory of loop equations
Baudier, Céline. "Diffraction d'ondes électromagnétiques par des surfaces rugueuses aléatoires : méthode approchée de Rayleigh et méthode exacte en coordonnées non-orthogonales." Versailles-St Quentin en Yvelines, 2002. http://www.theses.fr/2002VERS0027.
Full textSoubret, Antoine. "Diffusion des ondes électromagnétiques par des milieux et des surfaces aléatoires : étude des effets cohérents dans le champ diffusé." Aix-Marseille 2, 2001. http://www.theses.fr/2001AIX22063.
Full textAït, Braham Karim. "Diffusion des ondes électromagnétiques par des surfaces rugueuses aléatoires naturelles : méthode exacte en coordonnées curvilignes et principe du faible couplage." Phd thesis, Université de Versailles-Saint Quentin en Yvelines, 2007. http://tel.archives-ouvertes.fr/tel-00201723.
Full textCe mémoire traite de l'étude de la diffraction d'une onde électromagnétique par une surface rugueuse aléatoire, séparant deux milieux homogènes. Une méthode exacte (méthode C), donnant les intensités cohérentes et incohérentes d'une surface rugueuse 1D ou 2D aléatoire, éclairée par une onde plane, a été développée. Cette méthode est basée sur la résolution des équations de Maxwell dans un système de coordonnées non orthogonales, lié à la surface.
Les surfaces considérées sont des réalisations d'un processus spatial aléatoire gaussien et isotrope. La génération des profils diffractant est assurée par filtrage linéaire. Les paramètres statistiques des profils sont estimés à partir de fichiers numériques de sols agricoles nus.
Nous avons investi la méthode numériquement et comparé nos résultats à la littérature ainsi qu'à des données expérimentales. Nous avons aussi utilisé cette méthode pour étudier l'impact de la rugosité et de l'humidité du sol sur le diagramme de rayonnement.
Ponson, Laurent. "Propagation de fissures dans les matériaux désordonnés : comment déchiffrer les surfaces de rupture." Palaiseau, Ecole polytechnique, 2007. http://www.theses.fr/2007EPXX0069.
Full textDemichel, Yann. "Analyse fractale d'une famille de fonctions aléatoires : les fonctions de bosses." Phd thesis, Clermont-Ferrand 2, 2006. https://theses.hal.science/tel-00250060/document.
Full textDemichel, Yann. "Analyse fractale d'une famille de fonctions aléatoires : les fonctions de bosses." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2006. http://tel.archives-ouvertes.fr/tel-00250060.
Full textla dimension de Hausdorff du graphe de F . La seconde partie de notre thèse est consacrée à l'application des fonctions de bosses à la modélisation de profils rugueux. On met en évidence de nouvelles propriétés théoriques, notamment à l'aide des fonctions de structure. Celles-ci donnent
naissance à des diagrammes logarithmiques, les courbes de structure, qui permettent d'analyser un signal en tenant compte des contraintes expérimentales. Elles sont utilisées pour l'identification d'une fonction de bosses et l'estimation de ses paramètres. Nous proposons pour cela de nombreuses méthodes en construisant des estimateurs adaptés. Il est alors possible de modéliser un signal donné par une fonction de bosses. Les courbes de structure servent encore à l'élaboration de critères de conformité. Des exemples de données théoriques et expérimentales illustrent notre propos.
Orantin, Nicolas. "Du développement topologique des modèles de matrices à la théorie des cordes topologiques : combinatoire de surfaces par la géométrie algébrique." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2007. http://tel.archives-ouvertes.fr/tel-00173162.
Full textje montre que pour un choix particulier des paramètres, ces objets peuvent être rendus invariants modulaires et sont solutions des équations d'anomalie holomorphe de la théorie de Kodaira-Spencer donnant un nouvel élément vers la preuve de la conjecture de Dijkgraaf-Vafa.
Brissonneau, Vincent. "Contrôle de la lumière par éléments de surface désordonnés." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4313.
Full textScattering of electromagnetic waves from rough surfaces is involved in a wide area of research in optronics (cloaking, laser and infrared signature analysis, active imaging, light localisation, high resolution optical imaging, laser-matter interaction and optical signature modelling, photovoltaics, infrared sensors, biotechnologies). Studies performed during the thesis ``Ligth control by random surface elements'' consist in the experimental fabrication of rough surfaces which statistical properties are controled. An experimental setup has been implemented, using the properties of a spatially shaped laser speckle pattern. The photofabricated surfaces show statistical properties that do not exist in nature such as non Gaussian autocorrelation function. Beyond these photofabricated surfaces, we also studied very rough surfaces of semi-conductor known as Black Silicon
Pan, Cihui. "Diffraction électromagnétique par des réseaux et des surfaces rugueuses aléatoires : mise en œuvre deméthodes hautement efficaces pour la résolution de systèmes aux valeurs propres et de problèmesaux conditions initiales." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLV020/document.
Full textWe study the electromagnetic diffraction by gratings and random rough surfaces. The C-method is an exact method developed for this aim. It is based on Maxwell’s equations under covariant form written in a nonorthogonal coordinate system. The C-method leads to an eigenvalue problem, the solution of which gives the diffracted field.We focus on the numerical aspect of the C-method, trying to develop an efficient application of this exact method. For gratings, we have developed a new version of C-method which leads to a differential system with initial conditions. This new version of C-method can be used to study multilayer gratings with homogeneous medium.We implemented high performance algorithms to the original versions of C-method. Especially, we have developed a specifically designed parallel QR algorithm for the C- method and spectral projection method to solve the eigenvalue problem more efficiently. Experiments have shown that the computation time can be reduced significantly
Pecile, Bérénice. "Modèle dynamique d'interaction véhicule-voie ferroviaire en présence de défauts géométriques sur les surfaces en contact." Thesis, Valenciennes, 2017. http://www.theses.fr/2017VALE0004/document.
Full textThe appearance of dynamic phenomena during the running of train on track leads to issues such as noise and vibration pollution, which can be further amplified by the presence of defects on the treads. In order to analyze them, it is necessary to predict with reliability the dynamic behavior of the vehicle-track interaction components, in particular the contact forces produced by non perfect treads.The aim of this PhD thesis is to provide a semi-analytical vehicle-track interaction model able to take into account multiple defects on the surfaces in contact. In order to conduct simulations in the time-domain and ensure applicability in the sizing phase, a special attention is given on the compromise between the accuracy of the results and the simulation times.The proposed model is therefore composed of half a bogie running on a ballasted track. This latter is modeled by a pinned-pinned beam with periodic supports located at the sleepers while the vertical behavior of the bogie is given by masses, springs and dampers. These two models are coupled in contact by a discretized Distributed Point Reacting Spring (DPRS) procedure.A validation of the model, based on previous work, is firstly proposed for perfect treads. Then, multiple combinations of defects, either localised as wheelflat or spread as corrugation, are introduced in the simulation. The spatial variability, specific to shelling, is modeled by random fields
Pétrélis, Nicolas. "Localisation d'un polymère en interaction avec une interface." Phd thesis, Université de Rouen, 2006. http://tel.archives-ouvertes.fr/tel-00068229.
Full textsolvants (huile-eau). Ces modèles
donnent tous lieu à une transition entre une phase localisée et une phase délocalisée. Nous prouvons tout d'abord
plusieurs résultats de convergence de modèles discrets vers leurs modèles continus associés. Ces convergences
ont lieu dans le cas d'un couplage faible (haute température) et concernent l'énergie libre d'une part, et la pente
de la courbe critique à l'origine d'autre part. Pour cela, nous développons une méthode de
coarse graining
introduite par Bolthausen et den Hollander que nous généralisons au cas d'un copolymère soumis à un potentiel
d'accrochage aléatoire le long de l'interface huile-eau.
Nous prouvons ensuite un résultat trajectoriel, dans le cas d'un
copolymère soumis, en l'une de ses extrémités, à une force qui le tire loin de l'interface.
Nous montrons, en particulier
qu'à l'intérieur de la phase localisée, le polymère ne touche l'interface qu'un nombre fini de fois.
Enfin, nous étudions le cas d'un homopolymère hydrophobe au voisinage d'une interface (huile-eau) et
soumis également
a un potentiel aléatoire lorsqu'il touche cette interface. Par une méthode consistant à adapter la loi de
chacune des
excusions en dehors de l'interface à son environnement aléatoire local, nous prenons en compte le fait que le polymère
peut viser les sites
où il vient toucher l'interface. Ceci permet d'améliorer de façon quantitative la borne inférieure de la courbe
critique du modèle quenched donnée jusqu'alors par la courbe critique du modèle à potentiel constant.
Akiki, Rock. "Cristaux phononiques aléatoires." Electronic Thesis or Diss., Université de Lille (2022-....), 2022. http://www.theses.fr/2022ULILN027.
Full textIn the early 1990s, a new discipline of physics appeared through the study of phononic crystals. This work focuses on phononic crystals, artificial crystals whose physical properties can be modulated by the nature and/or the geometry of their components. These materials have allowed the manipulation and control of elastic waves with inclusion structures in the order of magnitude of the exciting wavelength. With the 2000's, acoustic metamaterials open new perspectives, based on the physical concept of effective medium at long wavelengths. The origin of acoustic metamaterials is based on the physical concept of eigen resonance of inclusions and thus offer new applications such as negative refraction, cloaking or hyperfocusing. This work is a first approach on the effect of disorder in acoustic metamaterials. For this purpose, we study an acoustic metamaterial structure formed by cylinders on a semi-infinite substrate. The effects of material and geometry of both the cylinders and the surface on the surface acoustic waves is studied. We then study the coupling between pillars and the possibility of propagation along a chain. We highlight the effect of elastic coupling between pillars from the compression mode and the possibility of propagation and control of acoustic waves in sub-wavelength regime. The study is then extended to a two-dimensional surface with a periodic, hyperuniform, and random distribution of the position of the pillars
Kuchumov, Nikolai. "Formes limites pour le modèle de dimères dans des domaines non simplement connexes." Electronic Thesis or Diss., Sorbonne université, 2024. http://www.theses.fr/2024SORUS281.
Full textThis thesis consists of three parts, the goal of the first part is to study random domino tilings of a multiply-connected domain with a height function defined on the universal covering space of the domain. We establish a large deviation principle for the height function in two asymptotic regimes. The first regime covers all domino tilings of the domain. A law of large numbers for height change in this regime will also be derived. The second regime covers domino tilings with a given asymptotic height change.The second part of thesis is an extension of the first part. We prove the existence of a limit shape for the dimer model on planar periodic bipartite graphs with an arbitrary fundamental domain and arbitrary periodic weights.The third part is devoted to computation of the arctic curve of the multiply-connected Aztec diamond in two regimes. The first regime, called an unconstrained case, corresponds to the uniform measure on a set of domino tilings. The second regime, constrained case, puts a condition on the height change of domino tilings
Ghariani, Sondès. "Réponse dynamique de milieux composites aléatoires et déterministes." Paris 6, 1993. http://www.theses.fr/1993PA066374.
Full textPHAN, THANH BINH. "Polydiméthylsiloxane : réseaux aléatoires (RMN) et propriétés électriques." Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10013.
Full textYang, Liming. "Recalage robuste à base de motifs de points pseudo aléatoires pour la réalité augmentée." Thesis, Ecole centrale de Nantes, 2016. http://www.theses.fr/2016ECDN0025.
Full textRegistration is a very important task in Augmented Reality (AR). It provides the spatial alignment between the real environment and virtual objects. Unlike tracking (which relies on previous frame information), wide baseline localization finds the correct solution from a wide search space, so as to overcome the initialization or tracking failure problems. Nowadays, various wide baseline localization methods have been applied successfully. But for objects with no or little texture, there is still no promising method. One possible solution is to rely on the geometric information, which sometimes does not vary as much as texture or color. This dissertation focuses on new wide baseline localization methods entirely based on geometric information, and more specifically on points. I propose two novel point pattern matching algorithms, RRDM and LGC. Especially, LGC registers 2D or 3D point patterns under any known transformation type and supports multipattern recognitions. It has a linear behavior with respect to the number of points, which allows for real-time tracking. It is applied to multi targets tracking and augmentation, as well as to 3D model registration. A practical method for projector-camera system calibration based on LGC is also proposed. It can be useful for large scale Spatial Augmented Reality (SAR). Besides, I also developed a method to estimate the rotation axis of surface of revolution quickly and precisely on 3D data. It is integrated in a novel framework to reconstruct the surface of revolution on dense SLAM in real-time
Diallo, Amadou thierno. "Etude de l’effet plasmonique des nanoparticules métalliques aléatoires sur les performances des diodes électroluminescences organiques." Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCD079.
Full textThis thesis focuses on the utilization of localized surface plasmon resonances (LSPR) of metallic nanoparticles (NPs) to improve the performance of Organic Light Emitting Diodes (OLEDs). In particular, we focused on randomly dispersed NPs by thermal evaporation during the OLED fabrication process. In the first part of the experimental work, we focused on the fabrication and study of random NPs of silver. The effects of their position with respect to the emissive layer (EML) were studied. The results show improvements in electrical and optical performance of OLEDs incorporating these NPs for EML-NPs distances greater than 15 nm. Subsequently, we were interested in the study of the plasmonic field range action by developing an original method based on the use of a DCM red-emitting layer embedded in Alq3 green EML. By varying the position of this thin layer of DCM, it was possible to probe at the nanoscale the extent of the effects of Au NPs in particular on the variation of the luminous efficiency of the OLED. Finally, we studied the influence of Al plasmonic nanoparticles (NPs) on the performance of a blue OLED subjected to the emission of exciplexes. The results show that in the case of OLED with Al-NPs, the emission of exciplexes is reduced thanks to the LSPR effect and the luminous efficiency of the plasmonic device indicates a 53% improvement over that of the OLED without NPs
Golkin, Stanislav. "Simulation de la propagation d'ondes SH dans des structures périodiques et de la diffusion multiple d'ondes de volume en milieux aléatoires." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR1A002/document.
Full textThe study is concerned with acoustic waves in elastic media with a different nature of in homogeneity consisting in either periodically continuous or piece wise variation of material properties, or in random sets of defects embedded into a homogeneous matrix, with a given statistical distribution. The scope of problems is topical in non-destructive testing and other applications of ultrasound.Theoretical methods describing involved acoustic phenomena (complex dispersion features, coherent wave in random media, ensemble average techniques) often rely on certain a priori assumptions which render numerical verification especially important.The thesis presents results of analytical modelling of the propagation of surface acoustic waves along periodic half-space, for which the dispersion spectrum is rather complex (discontinuous spectrum of propagation for the surface waves). A 2nd order FDTD numerical code has been developed in order to perform numerical experiments in the space and time domains, and to corroborate the analytical predictions in the frequency domain. A good agreement of simulated results with analytical modelling demonstrates applicability and consistency of the numerical tool. Finally, the code has been used for extracting numerically the coherent wave regime (mean wave over ensemble averaging of the positions of scatterers) for the acoustic propagation in different types of populations of randomly distributed scatterers. The results indicate ranges of validity of some multiple scattering analytical techniques
Le, Khanh Toan. "Identification des caractéristiques aléatoires de remblais à partir du suivi de santé des structures : application aux structures portuaires." Nantes, 2012. http://www.theses.fr/2012NANT2021.
Full textThe in-service behavior of some prototype structures (like Civil Engineering Structures) is often different from that initially assume during the design. Even if assumptions during design are conservative they hold the understanding of the real behavior off. The modeling of in-service behavior is of first importance when reassessing complex structures like harbor structures and performing risk analysis. To this aim, the Structural Health Monitoring (SHM) is of first importance because it allows us to assess the real level of loading and to provide more realistic models for mechanical behavior or value of their parameters. This thesis proposes to use information from instrumentation in a probabilistic context. This is to identify parameters of a behavior model under form of random variables represented by a vector X which integrate in part the natural hazard and another for a model error. The research is performed in two stages: (1) simulation of the structure behavior by using a set of a priori parameters as input value of the finite element code (PLAXIS) on a simple model M (X) which is calibrated by a quadratic polynomial response surface model RS (X) for points well chosen. This approach allow to converge to the same asymptotic properties for realizations of X not sampled in the base of calibration. This reduces the sample size, which represents a better advantage than using Bayesian or Neuronal networks; (2) an inverse analysis is realized on a large number of situations measured to identify X and to give Y that Y= RS (X). We propose to apply this method to the instrumentation of pile supported wharfs to determine site characteristics, previously unavailable in probabilistic models
Durant, Stéphane. "Propagation de la lumière en milieu aléatoire : rôle de l'absorption, de la diffusion dépendante et du couplage surface-volume." Phd thesis, Ecole Centrale Paris, 2003. http://tel.archives-ouvertes.fr/tel-00004154.
Full textLa majeure partie de cette thèse est consacrée à cet aspect : la détermination des paramètres de l'ETR pour un milieu contenant des particules de taille comparable à la longueur d'onde, aléatoirement disposées dans un milieu absorbant. Alors que les modèles pour l'obtention de ces paramètres décrits dans la littérature en présence d'absorption sont tous phénoménologiques, nous présentons une méthode basée sur une théorie de champ rigoureuse et qui permet de définir sans ambiguïté ces paramètres. Nous analysons par ailleurs le rôle des corrélations en milieu absorbant (diffusion dépendante).
Nous nous intéressons aux milieux fortement chargés pour lesquels les corrélations sur les positions des diffuseurs jouent un rôle fondamental et rendent le calcul très complexe. Nous présentons les premiers pas d'une méthode numérique capable de prendre en compte toutes les corrélations entre les paires de particules, ce qui permet de calculer le coefficient d'extinction au delà de l'approximation de la diffusion indépendante.
Enfin, nous cherchons à évaluer les propriétés radiatives d'un système couramment rencontré : celui d'une couche diffusante a la fois en surface et en volume. Nous étudions en particulier le rôle de la diffusion multiple entre l'interface rugueuse et le volume chargé.
Baylard, Christophe. "Modélisation de la réflexion et de la transmission par une surface rugueuse aléatoire 2D : étude des effets non spéculaires." Châtenay-Malabry, Ecole centrale de Paris, 1996. http://www.theses.fr/1996ECAP0519.
Full textCampagne, Gaëlle. "Simulation numérique directe de l'intéraction turbulence / surface libre pour l'analyse du transfert intercomposantes." Toulouse, INPT, 2006. http://ethesis.inp-toulouse.fr/archive/00000435/.
Full textA Direct Numerical Simulation of the interaction between no-shear turbulence and a free-slip surface is performed using a pseudo-spectral method. The originality of the configuration yields in the fact that the turbulence is created by a distant random forcing term localised in the vicinity of a plane parallel to the surface. The flow is therefore statistically steady and the surface layer is continuously fed by turbulent diffusion. The evolutions of the statistical quantities and of Reynolds shear stresses are studied and are used to define the structure of the interaction layer. A new method of analyzing and quantifying the elementary structures, that contribute to the intercomponent energy transfers, is proposed and evaluated. It allows some improvements in the understanding of the mechanisms linked to the influence on the pressure-deformation correlation, in the presence of an impermeable surface
Harel, Marie-Alice. "Modélisation du ruissellement sur une surface à infiltrabilité aléatoire par la théorie des files d'attente : protection, organisation et connexité de la lame d'eau." Paris 6, 2013. http://www.theses.fr/2013PA066094.
Full textThe objective of this work is to model, by means of theoretical developments and numerical simulations, the production, the spatial organisation and the connectivity of runoff generated on flat 1D and 2D surfaces with random infiltrability and uniform rainfall. The queueing theory framework is used to solve the runoff-runon equation for the permanent and transient states. Thanks to this theory, the link between the statistics of infiltrability and runoff is established. Several infiltrability distributions are simulated and compared with respect to rainfall intensity. The influence of boundary conditions, domain length, correlation and nugget in the infiltrability field are studied. Numerical simulations validate the theoretical results found for the exponential and bimodal distributions
Fiche, Anthony. "Distributions alpha-stable pour la caractérisation de phénomènes aléatoires observés par des capteurs placés dans un environnement maritime." Phd thesis, Université de Bretagne occidentale - Brest, 2012. http://tel.archives-ouvertes.fr/tel-00835073.
Full textPonson, Laurent. "Propagation de fissures dans les matériaux désordonnés : comment déchiffrer les surfaces de rupture." Phd thesis, Ecole Polytechnique X, 2006. http://pastel.archives-ouvertes.fr/pastel-00002920.
Full textKassel, Adrien. "Laplaciens des graphes sur les surfaces et applications à la physique statistique." Thesis, Paris 11, 2013. http://www.theses.fr/2013PA112101.
Full textWe study the determinant of the Laplacian on vector bundles on graphs and use it, combined with discrete complex analysis, to study models of statistical physics. We compute exact lattice constants, construct scaling limits for excursions of the loop-erased random walk on surfaces, and study some Gaussian fields and determinantal processes
Roussel, Clément J. "Stochastic differential equations for the electromagnetic field scattered by the sea surface : applications to remote sensing." Thesis, Brest, École nationale supérieure de techniques avancées Bretagne, 2019. http://www.theses.fr/2019ENTA0007.
Full textRadar remote sensing in a maritime context is often hindered by radar waves reflected by the sea, termed sea clutter due to its noise-like character. A thorough understanding of it is required for detection and imaging applications. Statistical models have long been used for the sea clutter (K distribution, Weibull distribution etc) but they are static in nature. We propose to use a dynamic model developed by T. R. Field, which represents the sea clutter as a stochastic process solving stochastic differential equations. We introduce Field's model for the sea surface radar cross section (RCS) and speckle. The complex reflectivity of the sea surface then depends on three parameters: A, B and α. We compute the transition probabilities of the RCS and speckle by analytical resolution of Fokker-Planck equations, and propose to use them as a tool for synchronizing observations taken at differents positions and times, as in Synthetic Aperture Radar. We derive maximum likelihood (ML) estimators for A and B, and show numerically that the exact transition probabilities from the Fokker-Planck equations can be approximated in a satisfactory manner by Gaussians using Euler-Maruyama's scheme. α, for its part, is estimated by ergodicity (moment). We adapt Field's model to account for the presence of a simple target and show that it is possible to estimate the target constant by ML using Gaussian approximations for the transition probabilities. In the last part, we address the nonobservability of the RCS by estimating it from the complex reflectivity (observable). We obtain a sequence of estimators applicable to real data. Finally, bayesian estimation of the clutter parameters, and target detection, are introduced and discussed as potential future directions for research
Campagne, Gaelle. "Simulation numérique directe de l'interaction turbulence/surface libre pour l'analyse du transfert intercomposantes." Phd thesis, Institut National Polytechnique de Toulouse - INPT, 2006. http://tel.archives-ouvertes.fr/tel-00326401.
Full textDejean, Sébastien. "Comparaison de procédures d'estimation dans le cadre des modèles non linéaires à paramètres aléatoires : application à la modélisation de l'évolution temporelle de l'indice de surface foliaire de cultures observées par télédétection spatiale." Toulouse 3, 2002. http://www.theses.fr/2002TOU30062.
Full textIn the spatial remote sensing for agriculture framework, we deal with the estimation of a crop leaf area index evolution model from high temporal resolution images ; the scope of the work is the improvement of yield prediction over a large area. Regular measurements can be considered as longitudinal data of a population of pixels. We propose a random parameter modelling to express between-pixels variability and to deal with the whole pixels simultaneously. We present parametric and non parametric expressions of the between-pixels variability. We focus on the parametric model for which we review estimation methods based either on a per-pixel approach or on the maximization of an approximated global likelihood. .
Bonaventure, Julien. "Influence of random surface roughness on friction in elastohydrodynamic, mixed and boundary lubrication." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEC038/document.
Full textMost mechanical systems include lubricated contacts submitted to important strengths. The present work deals with the influence of surface roughness on friction in the elastohydrodynamic (EHD), mixed and boundary lubrication regimes, with operating conditions that are typically those found in an internal combustion engine. Most of the surfaces used in the experiments are machined steel, with or with a Diamond-Like Carbon (DLC) coating. Given the friction in boundary and mixed lubrication being higher than in EHD lubrication, it is crucial to predict the transitions between these regimes. These strongly depend on surface roughness. There are very few experimental works that deal with this issue, and the theoretical attempts to include the influence of random surface roughness are based on roughness parameters that are difficult to measure because of their dependence towards the sampling conditions and their non-stationarity. Based on numerous topographical surveys (using interferometry and AFM), a method is implemented to ensure the representativeness of roughness statistical parameters in order to characterize a range of surface roughnesses within the interval [0.001 ; 1] μm. Then, these surfaces are rubbed against each other using Stribeck procedures in order to correlate their morphology to their friction behaviour. The high-pressure rheology of poly-α olefins is measured in smooth contacts with respect to the pressure and the temperature. This not only allows to quantify the friction force for any contact operating in EHD lubrication, but also to set a criterion to spot the onset of mixed lubrication. At high entrainment speed, the viscous shear stress vanishes, which is often attributed to shear heating. It is shown that thermal effects can not explain such a drop of friction for our own experiments. However, the widening of the pressure profile — which becomes significant when the film thickness becomes comparable to a tenth the contact length — is more likely to explain this behaviour. Our results show that the product of the inlet viscosity with the entrainment speed, spotted at the mixed-EHD transition, follows a super linear power law with the RMS roughness, whatever the materials involved, which allows to predict whether a contact operate in mixed lubrication or not. The transition from mixed to boundary lubrication reveals material and roughness-dependent with a clearly different behaviour between DLC/DLC contacts and contacts involving at least one steel body. Regarding the DLC/DLC contacts, the boundary friction is due to the plastic shearing of the lubricant, which explains why surface roughness has no influence on boundary friction for these contacts. With Steel/DLC and steel/steel contacts, the boundary friction presents two monotonous trends versus the composite RMS roughness. Eventually, a mixed bearing model based on the Greenwood-Willimason assumptions was implemented and allowed to reproduce quite closely the experimentally obtained Stribeck curves. This implementation indicates in particular the sampling conditions that are optimal to capture relevant asperity parameters
Deregnaucourt, Thomas. "Prédiction spatio-temporelle de surfaces issues de l'imagerie en utilisant des processus stochastiques." Thesis, Université Clermont Auvergne (2017-2020), 2019. http://www.theses.fr/2019CLFAC088.
Full textThe prediction of a surface is now an important problem due to its use in multiple domains, such as computer vision, the simulation of avatars for cinematography or video games, etc. Since a surface can be static or dynamic, i.e. evolving with time, this problem can be separated in two classes: a spatial prediction problem and a spatio-temporal one. In order to propose a new approach for each of these problems, this thesis works have been separated in two parts.First of all, we have searched to predict a static surface, which is supposed cylindrical, knowing it partially from curves. The proposed approach consisted in deforming a cylinder on the known curves in order to reconstruct the surface of interest. First, a correspondence between known curves and the cylinder is generated with the help of shape analysis tools. Once this step done, an interpolation of the deformation field, which is supposed Gaussian, have been estimated using maximum likelihood and Bayesian inference. This methodology has then been applied to real data from two domains of imaging: medical imaging and infography. The obtained results show that the proposed approach exceeds the existing methods in the literature, with better results using Bayesian inference.In a second hand, we have been interested in the spatio-temporal prediction of dynamic surfaces. The objective was to predict a dynamic surface based on its initial surface. Since the prediction needs to learn on known observations, we first have developed a spatio-temporal surface analysis tool. This analysis is based on shape analysis tools, and allows a better learning. Once this preliminary step done, we have estimated the temporal deformation of the dynamic surface of interest. More precisely, an adaptation, with is usable on the space of surfaces, of usual statistical estimators has been used. Using this estimated deformation on the initial surface, an estimation of the dynamic surface has been created. This process has then been applied for predicting 4D expressions of faces, which allow us to generate visually convincing expressions
Maloku, Kaltrina. "Génération de séries temporelles infra-journalières de précipitations surfaciques moyennes partout en Suisse en combinant un générateur stochastique de précipitations journalières et une cascade aléatoire multiplicative." Electronic Thesis or Diss., Université Grenoble Alpes, 2024. http://www.theses.fr/2024GRALU023.
Full textContinuous hydro-meteorological simulation is a powerful approach for generating the long-time series of river discharge required for flood risk analysis. This approach requires long precipitation time series as inputs, which can be generated by a stochastic weather generator (WGEN). For small catchments (10 - 1,000 km²), where a lumped hydrological model is relevant and the hydrological response can be rapid, sub-daily mean areal precipitation (MAP) scenarios are required.To answer these objectives, this PhD thesis investigates the potential of a hybrid sub-daily WGEN consisting of two stochastic models for that purpose. The first model, GWEX, is dedicated to generating daily time series. It models precipitation occurrences with a Markov chain and precipitation amounts with a heavy-tailed distribution adapted to extreme events. The second model disaggregates the daily scenarios to hourly resolution.In this PhD, we propose a new disaggregation model based on the microcanonical multiplicative random cascade (MRC) approach, where the properties of the cascade generator depend continuously on the temporal scale, the precipitation intensity, and a so-called precipitation asymmetry index, introduced to account for the temporal pattern of the local precipitation sequence. We compare this MRC model with previous versions based on a similar approach. The performance of the models is assessed by disaggregating daily observations from 81 rain gauge stations across Switzerland. The overall performance of this MRC model is very satisfactory at different temporal resolutions. Accounting for precipitation asymmetry significantly improves the reproduction of autocorrelation, which previous models based on this approach have struggled with.We evaluate the performance of the hybrid WGEN to generate mean areal precipitation (MAP) time series for different spatial scales ranging from 10 to 1,000 km². The parameters of GWEX and MRC are estimated on the observed MAP time series extracted from CombiPrecip, an hourly gridded precipitation product of MeteoSwiss based on radar and rain gauge measurements with a spatial resolution of 1 km². The performance of the model is tested for an ensemble of locations and spatial scales in Switzerland by generating long precipitation scenarios and comparing their statistics with the observed ones. The results show a satisfactory performance of the model for different spatial and temporal scales.Finally, we compare different approaches for obtaining the parameters of the sub-daily WGEN over Switzerland. Initially, different mapping models based on kriging and thin plate splines are considered for interpolation of the at-site parameter estimates obtained from the rain gauge data. The mapping models give very accurate results. Then, the possibility of estimating parameters from CombiPrecip data is investigated. Multiple and long scenarios are generated for an ensemble of locations and different precipitation characteristics are estimated on the scenarios to compare both approaches. Both approaches are generally equivalent, although some differences can be observed with marked seasonal and regional variations.The hybrid model shows satisfactory performance in different evaluation contexts. It is parsimonious and parameters can be robustly estimated, leading to a strong spatial and seasonal coherence. The model is easy to implement with fast estimation and simulation procedures, facilitating end-user applications
Duménil, Charles. "Expected Size of the 3-Dimensional Delaunay Triangulation of Random Points on a Surface." Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0050.
Full textThis thesis aims at evaluating the size of the Delaunay triangulation of points drawn on a surface with a random distribution. The Delaunay triangulation, is a geometrical object that appeared recurrently in the scientific history. In dimension 2, the Delaunay triangulation of X is the set of triangles for which the circumscribing circle does not contain other points of X. This definition is generalizable in higher dimensions. Today, the Delaunay triangulation is one the most studied structures in computational geometry. For the 2 dimensional case, we know that the size of the Delaunay triangulation remains linear with the number of points. In 3 dimension, it is not anymore the case. The size of the 3D-Delaunay triangulation can range from linear to quadratic. This size depends on how the points are distributed in R^3. On a surface, the size of the Delaunay triangulation will depend both on the surface and on how they are distributed on this surface. To model points, we choose to use a Poisson point process since it verifies properties of homogeneity and independence that are convenient for the computations. In order to prove the expected O(n log n) bound for the uniform sample distributed on a cylinder, Devillers et al. remarked that the intersection of the cylinder with a sphere passing though two points p and q on the cylinder always contains a specific triangle drawn on the cylinder. That leads them to study a 2-dimensional graph in which two points are neighbors if there exists such a triangle that does not contain other data points. Such a graph has expected size O(n log n), and this is how they obtain the O(n log n) bound. In Part II, we define a kind of empty region graphs, we formalize a method to compute lower and upper bounds on their expected size, and give tight results for such graphs. As Attali et al. pointed out, the intersection of a sphere with a generic surface has almost an elliptic shape, aligned with the curvature directions of the surface. This leads us to study a particular empty region graph for which the regions are axis-aligned ellipses. We prove, in Part II, that if theinvolved ellipses have an aspect ratio ranging from b to 1, with 0 < b < 1, then the expected number of neighbors of any point in the graph is O(ln b). In order to illustrate the method, we compute, in Part III, tight asymptotic bounds on the expected size of the 3D-Delaunay triangulation in two specific cases. In Part III, Chapter 12, we consider a cylinder of revolution and reprove the O(N ln N) bound but for a Poisson point process. Considering the similarity between uniform and Poisson sample, the goal of this chapteris mainly to present concretely the method in a 3-dimensional simple case. Then, in Chapter 13, we compute the size of the 3D-Delaunay triangulation of a Poisson process distributed on a flattened sphere. We show that the expected size of the triangulation is O(N). Finally in Part IV, we treat the case of generic surfaces. Even if an oblate spheroid is a specific surface, we will be able to reuse some computations in this part up to some adaptations. Indeed the oblate spheroid is the surface of a convex body, that is not generally the case. It has a lot of symmetries,that is not generally the case either. In this part, we focus more on how to deal with these adaptations than on the computations that were already quite tedious in the spheroid case
Braud, Isabelle. "Etude méthodologique de l'analyse en composantes principales de processus bidimensionnels : effets des approximations numériques et de l'échantillonnage et utilisation pour la simulation de champs aléatoires : application au traitement des températures de surface de la mer sur l'Atlantique intertropical." Phd thesis, Grenoble INPG, 1990. http://www.theses.fr/1990INPG0042.
Full textGasnier, Nicolas. "Use of multi-temporal and multi-sensor data for continental water body extraction in the context of the SWOT mission." Electronic Thesis or Diss., Institut polytechnique de Paris, 2022. http://www.theses.fr/2022IPPAT002.
Full textSpaceborne remote sensing provides hydrologists and decision-makers with data that are essential for understanding the water cycle and managing the associated resources and risks. The SWOT satellite, which is a collaboration between the French (CNES) and American (NASA, JPL) space agencies, is scheduled for launch in 2022 and will measure the height of lakes, rivers, and oceans with high spatial resolution. It will complement existing sensors, such as the SAR and optical constellations Sentinel-1 and 2, and in situ measurements. SWOT represents a technological breakthrough as it is the first satellite to carry a near-nadir swath altimeter. The estimation of water levels is done by interferometry on the SAR images acquired by SWOT. Detecting water in these images is therefore an essential step in processing SWOT data, but it can be very difficult, especially with low signal-to-noise ratios, or in the presence of unusual radiometries. In this thesis, we seek to develop new methods to make water detection more robust. To this end, we focus on the use of exogenous data to guide detection, the combination of multi-temporal and multi-sensor data and denoising approaches. The first proposed method exploits information from the river database used by SWOT (derived from GRWL) to detect narrow rivers in the image in a way that is robust to both noise in the image, potential errors in the database, and temporal changes. This method relies on a new linear structure detector, a least-cost path algorithm, and a new Conditional Random Field segmentation method that combines data attachment and regularization terms adapted to the problem. We also proposed a method derived from GrabCut that uses an a priori polygon containing a lake to detect it on a SAR image or a time series of SAR images. Within this framework, we also studied the use of a multi-temporal and multi-sensor combination between Sentinel-1 SAR and Sentinel-2 optical images. Finally, as part of a preliminary study on denoising methods applied to water detection, we studied the statistical properties of the geometric temporal mean and proposed an adaptation of the variational method MuLoG to denoise it
Baroth, Julien. "Analyse par éléments finis stochastiques de la propagation d'incertitudes dans un modèle mécanique non linéaire." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2005. http://tel.archives-ouvertes.fr/tel-00397666.
Full textAhmad, Ola. "Stochastic representation and analysis of rough surface topography by random fields and integral geometry - Application to the UHMWPE cup involved in total hip arthroplasty." Phd thesis, Ecole Nationale Supérieure des Mines de Saint-Etienne, 2013. http://tel.archives-ouvertes.fr/tel-00905519.
Full textkestener, pierre. "Analyse multifractale 2D et 3D à l'aide de la transformation en ondelettes : application en mammographie et en turbulence développée." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2003. http://tel.archives-ouvertes.fr/tel-00004013.
Full textPisane, Jonathan. "Automatic target recognition using passive bistatic radar signals." Phd thesis, Supélec, 2013. http://tel.archives-ouvertes.fr/tel-00963601.
Full text