Ce travail porte sur la mise en oeuvre en 3d de la méthode des éléments naturels contrainte CNEM en vue de son utilisation pour la simulation du cisaillage à grande vitesse. La CNEM est une approche à mi-chemin des approches sans maillage et des éléments finis. La construction de son interpolation utilise le diagramme de Voronoï contraint (dual du maillage de Delaunay contraint) associé à un nuage de noeud réparti sur le domaine étudié muni d'une description de sa frontière. La mise en oeuvre de la CNEM comporte trois aspects principaux : i) la construction du diagramme de Voronoï contraint, ii) le calcul des fonctions de forme éléments naturels Sibson, iii) la discrétisation d'une formulation variationnelle générique par utilisation de l'intégration nodale stabilisée conforme, SCNI, introduite par Chen et Al en 2001. Une partie importante de ce travail concerne les deux derniers points. Pour le calcul des fonctions de formes Sibson 3d cinq algorithmes sont présentés, dont deux développés au cours de la thèse, et sont comparés en terme de performance. Par ailleurs, une discrétisation est proposée pour être applicable au cas des domaines fortement non convexes. La mise en oeuvre proposée est validée sur des exemples en élasticité linéaire 3d en petites perturbations (vis à vis de solutions analytiques et de résultats éléments finis) puis en grandes transformations (test de la barre de Taylor). L'application de la CNEM au cisaillage grande vitesse est finalement abordée. Les développements effectués ont été intégrés à la plateforme logicielle Nessy. Cette plateforme a pour objectif la capitalisation du savoir faire du LMSP en simulation numérique.

<p>This thesis presents a complete and fully automatic method for estimating the volume of an airbag, through all stages of its inflation, with multiple synchronized high-speed cameras.</p><p>Using recorded contours of the inflating airbag, its visual hull is reconstructed with a novel method: The intersections of all back-projected contours are first identified with an accelerated epipolar algorithm. These intersections, together with additional points sampled from concave surface regions of the visual hull, are then Delaunay triangulated to a connected set of tetrahedra. Finally, the visual hull is extracted by carving away the tetrahedra that are classified as inconsistent with the contours, according to a voting procedure.</p><p>The volume of an airbag's visual hull is always larger than the airbag's real volume. By projecting a known synthetic model of the airbag into the cameras, this volume offset is computed, and an accurate estimate of the real airbag volume is extracted. </p><p>Even though volume estimates can be computed for all camera setups, the cameras should be specially posed to achieve optimal results. Such poses are uniquely found for different airbag models with a separate, fully automatic, simulated annealing algorithm.</p><p>Satisfying results are presented for both synthetic and real-world data.</p>

Cette thèse traite de l'analyse de nuages de points 3D désorganisé et s'appuie sur deux outils : un algorithme de partitionnement efficace inspiré des C-moyennes floues d'une part, et des outils de filtrage morphologique de représentation à base de triangulation de Delaunay d'autre part. Le cadre applicatif essentiel est la navigation autonome en robotique mobile en environnement inconnu, c'est-à-dire dans modèle. Mais la méthodologie générique développée a été appliquée à d'autres types d'environnements, notamment plus structurés.

ABSTRACT Research in GIScience has identified agent-based simulation methodologies as effective in the study of complex adaptive spatial systems (CASS). CASS are characterized by the emergent nature of their spatial expressions and by the changing relationships between their constituent variables and how those variables act on the system's spatial expression over time. Here, emergence refers to a CASS property where small-scale, individual action results in macroscopic or system-level patterns over time. This research develops and executes a spatially-explicit agent based model of Muscovy Duck home range behavior. Muscovy duck home range behavior is regarded as a complex adaptive spatial system for this research, where this process can be explained and studied with simulation techniques. The general animal movement model framework presented in this research explicitly considers spatial characteristics of the landscape in its formulation, as well as provides for spatial cognition in the behavior of its agents. Specification of the model followed a three-phase framework, including: behavioral data collection in the field, construction of a model substrate depicting land cover features found in the study area, and the informing of model agents with products derived from field observations. This framework was applied in the construction of a spatially-explicit agent-based model (SE-ABM) of Muscovy Duck home range behavior. The model was run 30 times to simulate point location distributions of an individual duck's daily activity. These simulated datasets were collected, and home ranges were constructed using Characteristic Hull Polygon (CHP) and Minimum Convex Polygon (MCP) techniques. Descriptive statistics of the CHP and MCP polygons were calculated to characterize the home ranges produced and establish internal model validity. As a theoretical framework for the construction of animal movement SE-ABM's, and as a demonstration of the potential of geosimulation methodologies in support of animal home range estimator validation, the model represents an original contribution to the literature. Implications of model utility as a validation tool for home range extents as derived from GPS or radio telemetry positioning data are discussed.

We study various binomial and monomial ideals arising in the theory of divisors, orientations, and matroids on graphs. We use ideas from potential theory on graphs and from the theory of Delaunay decompositions for lattices to describe their minimal polyhedral cellular free resolutions. We show that the resolutions of all these ideals are closely related and that their Z-graded Betti tables coincide. As corollaries, we give conceptual proofs of conjectures and questions posed by Postnikov and Shapiro, by Manjunath and Sturmfels, and by Perkinson, Perlman, and Wilmes. Various other results related to the theory of chip-firing games on graphs also follow from our general techniques and results.

La modélisation 3d automatique d'un environnement à partir d'images est un sujet toujours d'actualité en vision par ordinateur. Ce problème se résout en général en trois temps : déplacer une caméra dans la scène pour prendre la séquence d'images, reconstruire la géométrie, et utiliser une méthode de stéréo dense pour obtenir une surface de la scène. La seconde étape met en correspondances des points d'intérêts dans les images puis estime simultanément les poses de la caméra et un nuage épars de points 3d de la scène correspondant aux points d'intérêts. La troisième étape utilise l'information sur l'ensemble des pixels pour reconstruire une surface de la scène, par exemple en estimant un nuage de points dense.Ici nous proposons de traiter le problème en calculant directement une surface à partir du nuage épars de points et de son information de visibilité fournis par l'estimation de la géométrie. Les avantages sont des faibles complexités en temps et en espace, ce qui est utile par exemple pour obtenir des modèles compacts de grands environnements comme une ville. Pour cela, nous présentons une méthode de reconstruction de surface du type sculpture dans une triangulation de Delaunay 3d des points reconstruits. L'information de visibilité est utilisée pour classer les tétraèdres en espace vide ou matière. Puis une surface est extraite de sorte à séparer au mieux ces tétraèdres à l'aide d'une méthode gloutonne et d'une minorité de points de Steiner. On impose sur la surface la contrainte de 2-variété pour permettre des traitements ultérieurs classiques tels que lissage, raffinement par optimisation de photo-consistance ... Cette méthode a ensuite été étendue au cas incrémental : à chaque nouvelle image clef sélectionnée dans une vidéo, de nouveaux points 3d et une nouvelle pose sont estimés, puis la surface est mise à jour. La complexité en temps est étudiée dans les deux cas (incrémental ou non). Dans les expériences, nous utilisons une caméra catadioptrique bas coût et obtenons des modèles 3d texturés pour des environnements complets incluant bâtiments, sol, végétation ... Un inconvénient de nos méthodes est que la reconstruction des éléments fins de la scène n'est pas correcte, par exemple les branches des arbres et les pylônes électriques.

SectionBuilder is an innovative finite element based tool, developed for analysis and design of composite beam cross-sections. The tool can handle the cross-sections with parametric shapes and arbitrary configurations. It can also handle arbitrary lay-ups for predefined beam cross-section geometries in a consistent manner. The material properties for each layer of the cross-section can be defined on the basis of the design requirements. This tool is capable of dealing with multi-cell composite cross-sections with arbitrary lay-ups. It has also the benefit of handling the variation of thickness of skin and D-spars for beams such as rotor blades. A typical cross-section is considered as a collection of interconnected walls. Walls with arbitrary lay-ups based on predefined geometries and material properties are generated first. The complex composite beam cross-sections are developed by connecting the walls using various types of connectors. These connectors are compatible with the walls, i.e., the thickness of the layers of the walls must match with those of the connectors at the place of connection. Cross-sections are often reinforced by core material for constructing realistic rotor blade cross-sections. The tool has the ability to integrate core materials into the cross-sections. A mapped mesh is considered for meshing parametric shapes, walls and various connectors, whereas a free mesh is considered for meshing the core materials. A new algorithm based on the Delaunay refinement algorithm is developed for creating the best possible free mesh for core materials. After meshing the cross-section, the tool determines the sectional properties using finite element analysis. This tool computes sectional properties including stiffness matrix, compliance matrix, mass matrix, and principal axes. A visualization environment is integrated with the tool for visualizing the stress and strain distributions over the cross-section.

This thesis presents a complete and fully automatic method for estimating the volume of an airbag, through all stages of its inflation, with multiple synchronized high-speed cameras. Using recorded contours of the inflating airbag, its visual hull is reconstructed with a novel method: The intersections of all back-projected contours are first identified with an accelerated epipolar algorithm. These intersections, together with additional points sampled from concave surface regions of the visual hull, are then Delaunay triangulated to a connected set of tetrahedra. Finally, the visual hull is extracted by carving away the tetrahedra that are classified as inconsistent with the contours, according to a voting procedure. The volume of an airbag's visual hull is always larger than the airbag's real volume. By projecting a known synthetic model of the airbag into the cameras, this volume offset is computed, and an accurate estimate of the real airbag volume is extracted. Even though volume estimates can be computed for all camera setups, the cameras should be specially posed to achieve optimal results. Such poses are uniquely found for different airbag models with a separate, fully automatic, simulated annealing algorithm. Satisfying results are presented for both synthetic and real-world data.

Orientador: Hugo Enrique Hernandez Figueroa / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-09T06:26:18Z (GMT). No. of bitstreams: 1 Hsu_AtilioClaudio_M.pdf: 6986419 bytes, checksum: 5d1120daa8d4126ad4a6fd84fd5ac188 (MD5) Previous issue date: 2007 / Resumo: Nesta dissertação apresenta-se o desenvolvimento e a implementação de algoritmos para geração de malhas adaptativas de elementos triangulares, visando o estudo de problemas de propagação eletromagnética em domínios bidimensionais. Foram implementadas duas técnicas de refinamento, uma baseada no método da troca de arestas denominado Delaunay e a outra baseada na técnica de suavização de Laplace. O gerador implementado leva em conta interfaces de curvatura arbitrária e, também, pode ser facilmente integrado aos programas desenvolvidos no Departamento de Microonda e Óptica (DMO) / Abstract: This work presents the development of algorithms for adaptive mesh generation of triangular elements applicable to electromagnetic propagation problems in bidimensional domains. Several techniques were used, such as edgeflip, known as Delaunay method, and the Laplacian¿s smoothing method. The program considers arbitrary curvature interfaces and can be easily integrated to the programs created in the Department of Microwaves and Optics (DMO) / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

Image segmentation plays an important role in medical image analysis. Many segmentation algorithms exist. Most of them produce data which are more or less not suitable for further surface extraction and anatomical modeling of human tissues. In this thesis, a novel segmentation technique based on the 3D Delaunay triangulation is proposed. A modified variational tetrahedral meshing approach is used to adapt a tetrahedral mesh to the underlying CT volumetric data, so that image edges are well approximated in the mesh. In order to classify tetrahedra into regions/tissues whose characteristics are similar, three different clustering schemes are presented. Finally, several methods for improving quality of the mesh and its adaptation to the image structure are also discussed.