Tesis sobre el tema "Maillages courbes"
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Orgeret, Fabrice. "Sur l'approximation discrète des courbures des courbes planes et des surfaces de l'espace euclidien de dimension 3". Phd thesis, Université Claude Bernard - Lyon I, 2007. http://tel.archives-ouvertes.fr/tel-00186301.
Texto completoDuval, Benoît. "Optimisation de maillages non structurés dans des géométries déformables". Rouen, 1996. http://www.theses.fr/1996ROUES022.
Texto completoGhantous, Joyce. "Prise en compte de conditions aux bords d'ordre élevé et analyse numérique de problèmes de diffusion sur maillages courbes à l'aide d'éléments finis d'ordre élevé". Electronic Thesis or Diss., Pau, 2024. http://www.theses.fr/2024PAUU3024.
Texto completoThis thesis focuses on the numerical analysis of partial differential equations involving high-order boundary conditions of the Ventcel type using the finite element method. To define the Laplace-Beltrami operator involved in the boundary condition, the domain is assumed to be smooth: thus, the meshed domain does not correspond to the initial physical domain, resulting in a geometric error. We then use curved meshes to reduce this error and define a lift operator that allows comparing the exact solution defined on the initial domain with the approximate solution defined on the discretized domain. We obtain a priori error estimates, expressed in terms of finite element approximation error and geometric error. We study problems with source terms and spectral problems, as well as scalar equations and vector equations of linear elasticity. Numerical experiments in 2D and 3D validate and complement these theoretical results, particularly highlighting the optimality of the obtained errors. These simulations also identify a super-convergence of the errors on quadratic meshes
Froehly, Algiane. "Couplage d'un schéma aux résidus distribués à l'analyse isogéométrique : méthode numérique et outils de génération et adaptation de maillage". Phd thesis, Université Sciences et Technologies - Bordeaux I, 2012. http://tel.archives-ouvertes.fr/tel-00765918.
Texto completoFroehly, Algiane. "Couplage d’un schéma aux résidus distribués à l’analyse isogéométrique : méthode numérique et outils de génération et adaptation de maillage". Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14563/document.
Texto completoDuring high order simulations, the approximation error may be dominated by the errors linked to the sub-parametric discretization used for the geometry representation. Many works propose to use an isogeometric analysis approach to better represent the geometry and hence solve this problem. In this work, we will present the coupling between the limited stabilized Lax-Friedrichs residual distributed scheme and the isogeometric analysis. Especially, we will build a family of basis functions defined on both triangular and quadrangular elements and allowing the exact representation of conics : the rational Bernstein basis functions. We will then focus in how to generate accurate meshes for isogeometric analysis. Our idea is to create a curved mesh from a classical piecewise-linear mesh of the geometry. We obtain a conforming unstructured mesh which ensures the continuity of the basis functions over the entire mesh. Last, we will detail the curved mesh adaptation methods developed : the order elevation and the isotropic mesh refinement. Of course, the adaptation processes preserve the exact geometry of the initial curved mesh
Charton, Jerome. "Etude de caractéristiques saillantes sur des maillages 3D par estimation des normales et des courbures discrètes". Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0333/document.
Texto completoWith the aim to improve and automate the object reproduction chainfrom acquisition to 3D printing .We sought to characterize the salience on 3D objectsmodeled by a 3D mesh structure. For this, we have a state of the art of estimatingdifferential properties methods, namely normal and curvature on discrete surfaces inthe form of 3D mesh. To compare the behavior of different methods, we took a set ofclassic benchmarks in the domain, which are : accuracy, convergence and robustnesswith respect to variations of the neighbourhood. For this, we have established atest protocol emphasizing these qualities. From this first comparision, it was foundthat all the existing methods have shortcomings as these criteria. In order to havean estimation of the differential properties more reliable and accurate we developedtwo new estimators
Laug, Patrick. "Contribution à la génération automatique de maillages de qualité pour la simulation numérique". Habilitation à diriger des recherches, Université Pierre et Marie Curie - Paris VI, 2006. http://tel.archives-ouvertes.fr/tel-00012000.
Texto completoCe mémoire constitue une synthèse de mes contributions concernant la génération automatique de maillages respectant le mieux possible ces critères de qualité. Ces différents travaux de recherche ont été réalisés au sein du projet Gamma de l'INRIA.
Dans ce document, les thèmes suivants sont abordés successivement :
- la discrétisation de courbes du plan ou de l'espace 3D,
- le maillage de domaines plans de contours fixes ou variables,
- le maillage de surfaces gauches paramétrées ou discrètes.
Au cours de ces opérations de discrétisation et de maillage, la taille et la forme des éléments sont contrôlées par un champ de métriques traduisant des contraintes géométriques et/ou physiques. Les méthodes présentées ont toutes été validées sur de nombreux exemples académiques ou industriels, notamment en mécanique des solides et en mécanique des fluides.
Diatta, Daouda. "Calcul effectif de la topologie de courbes et surfaces algébriques réelles". Phd thesis, Université de Limoges, 2009. http://tel.archives-ouvertes.fr/tel-00438817.
Texto completoZhao, Chang Sheng. "Reconstruction de surfaces tridimensionnelles en vision par ordinateur". Grenoble INPG, 1993. http://tel.archives-ouvertes.fr/tel-00343706.
Texto completoPolette, Arnaud. "Analyse de maillages surfaciques par construction et comparaison de modèles moyens et par décomposition par graphes s'appuyant sur les courbures discrètes : application à l'étude de la cornée humaine". Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4084/document.
Texto completoThis thesis comprises three parts. The first two parts concern the development of methods for the construction of mean geometric models and for model comparison. Several issues are addressed, such as the construction of an average cornea and the comparison of corneas. Currently, there are few studies with these objectives because the matching of corneal surfaces is a non-trivial problem. In addition to help to develop a better understanding of the corneal anatomy, 3D models of normal corneas can be used to detect any significant deviation from the norm, thereby allowing for an early diagnosis of diseases or abnormalities using the shape of the cornea. The second part of this thesis aims to develop a method for recognizing a surface from a group of surfaces using their 3D acquisitions in a biometric application pertinent to the cornea. The concept behind this method is to quantify the difference between each surface and a given surface and to determine the threshold for recognition. Two complementary methods are proposed. A cascading methodology using both methods to combine the advantages of each method is also proposed. The third and final part of this thesis focuses on a new method for decomposing 3D triangulated meshes into graphs. We use discrete curvature maps as the shape descriptor to split the mesh in eight different categories. Next, an adjacency graph is built with a node for each patch. These graphs are used to extract geometric characteristics described by patterns that allow for the detection of specific regions in a 3D model or recurrent characteristics
Nguyen, Tan Khoi. "Surfaces polyédriques et surfaces paramétriques : une reconstruction par approximation via les surfaces de subdivision". Thesis, Aix-Marseille 2, 2010. http://www.theses.fr/2010AIX22055/document.
Texto completoComputer Aided Geometric Design (CAGD) which allows us to design the physical objects from mathematical models is used in many sectors of industry. It is currently a general wish to take advantage of the two these approaches rather than the antagonists : The goal that the continuous geometric model creates the continuous objects represented by the modelof the surfaces B-splines or NURBS) and the discreet geometric model made by eitherthe meshes or the subdivision surfaces. This duality of the approach has many potential industrial applications and therefore submits interesting significant science. The polyhedral surfaces and the subdivision surfaces in particular which offer the intrinsically discretization,are a very simple manipulation, but they do not replace the surfaces B-splines or NURBS.The works presented in this thesis aim to the reciprocal passage from a parametric surfaceto a polyhedral surface. We are more specialy interested to subdivisions surfaces considering as a liaison between the polyhedral surface and the parametric surface, because after a few steps of subdivision, the polyhedron characteristic converges to a parametric surface corresponding.We have proposed the schemas of the inverse subdivision allowing recreating the polyhedral surface coarse of subdivision precedent. We thus presented two methods for there construction of a parametric curve/surface : one for using the schema of uniform inverse subdivision and the other for non-uniform inverse subdivision. To improve the results of reconstruction by the inverse subdivision methods, we associate these methods with the process of adjustment the approximation which allows reducing the error of reconstruction.The results obtained have been compared with a well-known least squares method. Our methods are very promising in terms of approximation and compression
Morand, Marion. "Surface de symétrie d’une structure 3D : application à l’étude des déformations scoliotiques du dos". Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS107.
Texto completoIn this thesis we are interested in the study of the symmetry of 3D meshes. Usually, this is defined as an orthogonal symmetry with respect to a plane. However, this characterisation is only fully relevant in case of "straight" bilateral structures. For our case about scoliotic deformations of the back surface, the analysis of asymmetries is very imprecise.Therefore we propose to generalise the notion of 3D mesh symmetry by defining an orthogonal symmetry with respect to any non-planar surface.After having studied the limits of plane symmetry, we suggest a new method to calculate a surface of symmetry for a 3D mesh. This iterative algorithm is based on the decomposition of the studied structure into a set of adaptive bands, defined orthogonally to a symmetry curve, and then on the calculation of local symmetry planes for each of these bands. These bands are later interpolated to obtain the surface of symmetry. A particular focus is put into the robustness of the algorithm, which must be able to adapt to the various possible deformations of the mesh.We then propose a method able to compute a curved and standardised asymmetry map from the surface of symmetry.Lastly, we present an application of our contributions for the study of scoliosis-induced deformities.We then show that the study of the surface of symmetry of the back makes it possible to categorise the different types of scoliosis and build a 3D model of the spine, without resorting to radiative imaging
Christoff, Vesselinova Nicole. "Détection et caractérisation d'attributs géométriques sur les corps rocheux du système solaire". Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0565/document.
Texto completoOne of the challenges of planetary science is the age determination of the surfaces of the different celestial bodies in the solar system, to understand their formation and evolution processes. An approach relies on the analysis of the crater impact density and size. Due to the huge quantity of data to process, automatic approaches have been proposed for automatically detecting impact craters in order to facilitate this dating process. They generally use the color values from images or the elevation values from Digital Elevation Model (DEM). In this PhD thesis, we propose a new approach for detecting craters rims. The main idea is to combine curvature analysis with Neural Network based classification. This approach contains two main steps: first, each vertex of the mesh is labeled with the value of the minimal curvature; second, this curvature map is injected into a neural network to automatically detect the shapes of interest. The results show that detecting forms are more efficient using a two-dimensional map based on the computation of discrete differential estimators, than by the value of the elevation at each vertex. This approach significantly reduces the number of false negatives compared to previous approaches based on topographic information only. The validation of the method is performed on DEMs of Mars, acquired by a laser altimeter aboard NASA’s Mars Global Surveyor spacecraft and combined with a database of manually identified craters
Leonardi, Valentin. "Modélisation dynamique et suivi de tumeur dans le volume rénal". Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4056/document.
Texto completoThis Ph.D. thesis deals with the 3D dynamic modeling of the kidney and tracking a tumor of this organ. It is in line with the KiTT project (Kidney Tumor Tracking) which gathers researchers from different fileds: geometric modeling, radiology and urology. This work arised from the tendency of nowadays surgical gestures to be less and less invasive (HIFU, coelioscopy). Its goal is to result in a totally non-invasive protocol of kidney tumors eradication by transmitting ultrasound waves through the skin without breaking in it. As the kidney presents motions and deformations during the breathing phase, the main issue is to know the kidney and tumor positions at any time in order to adjust the waves accordingly
Polette, Arnaud. "Analyse de maillages surfaciques par construction et comparaison de modèles moyens et par décomposition par graphes s’appuyant sur les courbures discrètes : application à l’étude de la cornée humaine". Thèse, 2015. http://hdl.handle.net/1866/13715.
Texto completoCette thèse se découpe en trois parties. Les deux premières portent sur le développement de méthodes pour la construction de modèles géométriques moyens et pour la comparaison de modèles. Ces approches sont appliquées à la cornée humaine pour l’élaboration d’atlas et pour l’étude biométrique robuste. La troisième partie porte sur une méthode générique d'extraction d'informations dans un maillage en s'appuyant sur des propriétés différentielles discrètes afin de construire une structure par graphe permettant l'extraction de caractéristiques par une description sémantique. Les atlas anatomiques conventionnels (papier ou CD-ROM) sont limités par le fait qu'ils montrent généralement l'anatomie d'un seul individu qui ne représente pas nécessairement bien la population dont il est issu. Afin de remédier aux limitations des atlas conventionnels, nous proposons dans la première partie d’élaborer un atlas numérique 3D contenant les caractéristiques moyennes et les variabilités de la morphologie d'un organe, plus particulièrement de la cornée humaine. Plusieurs problématiques sont abordées, telles que la construction d'une cornée moyenne et la comparaison de cornées. Il existe à ce jour peu d'études ayant ces objectifs car la mise en correspondance de surfaces cornéennes est une problématique non triviale. En plus d'aider à développer une meilleure connaissance de l'anatomie cornéenne, la modélisation 3D de la cornée normale permet de détecter tout écart significatif par rapport à la "normale" permettant un diagnostic précoce de pathologies ou anomalies de la forme de la cornée. La seconde partie a pour objectif de développer une méthode pour reconnaître une surface parmi un groupe de surfaces à l’aide de leurs acquisitions 3D respectives, dans le cadre d’une application de biométrie sur la cornée. L’idée est de quantifier la différence entre chaque surface et une surface donnée, et de déterminer un seuil permettant la reconnaissance. Ce seuil est dépendant des variations normales au sein d’un même sujet, et du bruit inhérent à l’acquisition. Les surfaces sont rognées et trouées de façon imprévisible, de plus il n’y a pas de point de mise en correspondance commun aux surfaces. Deux méthodes complémentaires sont proposées. La première consiste à calculer le volume entre les surfaces après avoir effectué un recalage, et à utiliser ce volume comme un critère de similarité. La seconde approche s’appuie sur une décomposition en harmoniques sphériques en utilisant les coefficients comme des descripteurs de forme, qui permettront de comparer deux surfaces. Des résultats sont présentés pour chaque méthode en les comparant à la méthode la plus récemment décrite dans la littérature, les avantages et inconvénients de chacune sont détaillés. Une méthodologie en cascade utilisant ces deux méthodes afin de combiner les avantages de chacune est aussi proposée. La troisième et dernière partie porte sur une nouvelle méthode de décomposition en graphes de maillages 3D triangulés. Nous utilisons des cartes de courbures discrètes comme descripteur de forme afin de découper le maillage traité en huit différentes catégorie de carreaux (ou peak, ridge, saddle ridge, minimal, saddle valley, valley, pit et flat). Ensuite, un graphe d'adjacence est construit avec un nœud pour chaque carreau. Toutes les catégories de carreaux ne pouvant pas être adjacentes dans un contexte continu, des jonctions intermédiaires sont ajoutées afin d'assurer une cohérence continue entre les zones. Ces graphes sont utilisés pour extraire des caractéristiques géométriques décrites par des motifs (ou patterns), ce qui permet de détecter des régions spécifiques dans un modèle 3D, ou des motifs récurrents. Cette méthode de décomposition étant générique, elle peut être appliquée à de nombreux domaines où il est question d’analyser des modèles géométriques, en particulier dans le contexte de la cornée.
This thesis comprises three parts. The first two parts concern the development of methods for the construction of mean geometric models and for model comparison. These approaches are applied to the human cornea for the construction of atlases and a robust biometric study. The third part focuses on a generic method for the extraction of information in a mesh. This approach is based on discrete differential properties for building a graph structure to extract features using a semantic description. Conventional anatomical atlases (paper or CD-ROM) are limited by the fact they generally show the anatomy of a single individual who does not necessarily represent the population from which they originate. To address the limitations of conventional atlases, we propose in the first part of this thesis to construct a 3D digital atlas containing the average characteristics and variability of the morphology of an organ, especially that of the human cornea. Several issues are addressed, such as the construction of an average cornea and the comparison of corneas. Currently, there are few studies with these objectives because the matching of corneal surfaces is a non-trivial problem. In addition to help to develop a better understanding of the corneal anatomy, 3D models of normal corneas can be used to detect any significant deviation from the norm, thereby allowing for an early diagnosis of diseases or abnormalities using the shape of the cornea. The second part of this thesis aims to develop a method for recognizing a surface from a group of surfaces using their 3D acquisitions in a biometric application pertinent to the cornea. The concept behind this method is to quantify the difference between each surface and a given surface and to determine the threshold for recognition. This threshold depends on normal variations within the same subject and noise due to the acquisition system. The surfaces are randomly trimmed and pierced ; moreover, there is no common landmark on the surfaces. Two complementary methods are proposed. The first method consists of the computation of the volume between the surfaces after performing geometrical matching and the use of this volume as a criterion of similarity. The second approach is based on a decomposition of the surfaces into spherical harmonics using the coefficients as shape descriptors to compare the two surfaces. Each result of the proposed methods is compared to the most recent method described in the literature, with the benefits and disadvantages of each one described in detail. A cascading methodology using both methods to combine the advantages of each method is also proposed. The third and final part of this thesis focuses on a new method for decomposing 3D triangulated meshes into graphs. We use discrete curvature maps as the shape descriptor to split the mesh in eight different categories (peak, ridge, saddle ridge, minimal, saddle valley, valley, pit and flat). Next, an adjacency graph is built with a node for each patch. Because all categories of patches cannot be adjacent in a continuous context, intermediate junctions are added to ensure the continuous consistency between patches. These graphs are used to extract geometric characteristics described by patterns that allow for the detection of specific regions in a 3D model or recurrent characteristics. This decomposition method, being generic, can be used in many applications to analyze geometric models, especially in the context of the cornea.
Zhao, Changsheng. "Reconstruction de surfaces tridimensionnelles en vision par ordinateur". Phd thesis, 1993. http://tel.archives-ouvertes.fr/tel-00343706.
Texto completo