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[en] GEOMETRIC MODELIG FOR FINITE ELEMENTS WITH MULTI-REGIONS AND PARAMETRIC SURFACES / [pt] MODELAGEM GEOMÉTRICA PARA ELEMENTOS FINITOS USANDO MULTI-REGIÕES E SUPERFÍCIES PARAMÉTRICASWILLIAM WAGNER MATOS LIRA 11 July 2002 (has links)
[pt] Este trabalho apresenta um ambiente computacional para
modelagem geométrica aplicada à análise por elementos
finitos usando multi-regiões e superfícies paramétricas
representadas por NURBS. O principal objetivo é gerar
modelos 3D para serem usados em simulações numéricas
baseadas no Método de Elementos Finitos (MEF). Nessa
proposta, a metodologia adotada consiste na combinação de
alguns aspectos da modelagem geométrica tais como a
detecção automática de regiões e a interseção de
superfícies com geração de malhas de elementos finitos.
No contexto da programação orientada a objetos, uma nova
organização de classes para o modelador geométrico usado
neste trabalho, denominado MG, é apresentada. Essa
organização de classes permite a implementação do ambiente
proposto, mantendo a interface com o usuário tão simples e
eficiente quanto à versão original. A organização de
classes também provê suporte para a geração de modelos
usados em análise por elementos finitos. Enquanto as malhas
de elementos finitos requeridas para simulações numéricas
são geradas por algoritmos específicos implementados no
modelador MG, os atributos são gerenciados por um sistema,
denominado ESAM (Extensible System Attributes Management),
que também é incorporado ao MG. Esse sistema permite que os
atributos do modelador MG sejam configurados para o uso em
diversos tipos de problemas de engenharia. A estrutura de
dados usada neste ambiente é representada por um enfoque
híbrido baseado na combinação de uma representação CGC
(Complete Geometric Complex) do modelo e na estrutura de
dados estendida do modelador MG. Além disso, a
determinação da interseção de superfícies é realizada
usando um algoritmo implementado no MG, enquanto que a
representação CGC é responsável pelo reconhecimento de
multi-regiões. O algoritmo de interseção de superfícies é
modificado para tratar casos especiais não considerados na
sua versão original. / [en] This work presents a computational environment for
geometric modeling applied to
finite-element analysis using multi-regions and parametric
surfaces represented as
NURBS. The main goal is to generate 3D models to be used in
numerical simulations
based on the Finite-Element Method (FEM). For this purpose,
the adopted methodology
consists of combining some aspects of geometric modeling,
such as automatic region
detection and surface intersection, with finite-element
mesh generation.
In the context of Object-Oriented Programming, a new class
organization for the
geometric modeler used in this work, called MG (Mesh
Generation), is presented. This
class organization allows the implementation of the
proposed environment, keeping the
user interface as simple and efficient as in the original
version of the MG modeler.
The proposed class organization also provides support for
the generation of models used
in finite-element analysis. While the finite-element meshes
required for the numerical
simulations are generated by specific algorithms
implemented in MG, the attributes are
managed by a system called ESAM (Extensible System
Attributes Management), which
also is incorporated into MG. This system allows the
customization of simulation
attributes in the MG modeler for use in different types of
Engineering problems.
The data structure used in this environment is represented
by a hybrid approach based
on the combination of a CGC (Complete Geometric Complex)
representation and the
MG`s data structure, which has been extended for this
purpose. Moreover, the
computation of surface intersections is accomplished by
using an algorithm
implemented in the MG, while the CGC representation is
responsible for multi-region
recognition. The surface-intersection algorithm has been
modified in order to handle
special cases that have not been treated in the original
version.
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[en] SHELL MODELING WITH PARAMETRIC INTERSECTION / [pt] MODELAGEM DE CASCAS COM INTERSEÇÕES PARAMÉTRICASLUIZ CRISTOVAO GOMES COELHO 26 July 2002 (has links)
[pt] Apresenta-se uma metodologia para modelagem de cascas para elementos finitos definidas em
superfícies paramétricas. A metodologia consiste na criação de curvas e geração de malhas sobre
os retalhos paramétricos constru´ıdos com base nestas curvas, que também são usadas para a conexão
de malhas adjacentes. O modelo final é uma representação de todas as malhas combinadas
em uma única estrutura de dados.
As ferramentas básicas para geração de tais malhas são uma interface para modelagem de
curvas espaciais e os algoritmos geom´etricos para construcão de mapeamentos nos domínios
elementares. O problema central em modelagens compostas é o tratamento dado às malhas
em superfícies que se interceptam. Um algoritmo capaz de modelar com precisão as curvas
de interseção e de ajustar as duas malhas para as novas restrições geradas é apresentado neste trabalho.
O algoritmo é parte de um programa completo para modelagem interativa de cascas, que
tem sido usado no projeto de grandes sistemas flutuantes para explotação de petróleo em águas
profundas. O uso de uma variante da estrutura de dados DCEL, que usa árvores de ordenação
espacial para armazenar as entidades topol´ogicas ao invés de listas ou vetores, permite que malhas bastante refinadas sejam reconstru´ıdas em tempo compatível com o trabalho interativo. Estas
árvores aceleram os cálculos de interseção necessários à determinação dos pontos de interpolação
das curvas de trimming, permitindo tamb´em a reconstrução das malhas usando-se apenas consultas
locais. / [en] We present a methodology for modeling finite-element
meshes defined on parametric surface
patches. The idea is to build curves and generate meshes
over the parametric patches built with
these curves, which also connect adjacent meshes. The
final model is a representation of all
meshes combined into a single data structure.
The basic tools to generate such meshes are the user
interface to model space curves and
the geometric algorithms to construct the elementary
domain mappings. The main problem in
composite modeling is how to handle mesh surfaces that
intersect each other. We present an
algorithm that models the intersection curves precisely
and adjusts both meshes to the newly
formed borders. The algorithm is part of an interactive
shell modeling program, which has been
used in the design of large offshore oil structures. We
avoid unacceptable interaction delays by
using a variant of the DCEL data structure that stores
topological entities in spatial indexing trees
instead of linked lists. These trees speed up the
intersection computations required to determine
points of the trimming curves, and also allows mesh
reconstruction using only local queries.
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[en] A QUADRATIC OPTIMIZATION APPROACH FOR THE RESERVOIR GEOMECHANICAL MESH GENERATION / [pt] UMA METODOLOGIA BASEADA EM OTIMIZAÇÃO QUADRÁTICA PARA GERAÇÃO DE MALHAS GEOMECÂNICAS DE RESERVATÓRIOSJEFERSON ROMULO PEREIRA COELHO 31 July 2018 (has links)
[pt] A geração de malhas geomecânicas de reservatórios ainda é uma tarefa tediosa que consome muito tempo. Para acelerar este processo, soluções que reconstroem analiticamente a geometria do reservatório têm sido propostas, mas essas soluções não são as mais adequadas para modelagem de objetos naturais. Este trabalho propõe uma modelagem discreta para a geometria do reservatório, onde os vértices da malha são posicionados por meio da solução de um problema de otimização quadrático e convexo. O problema de otimização é modelado de forma a garantir que as malhas geomecânicas de saída sejam suaves e que ao mesmo tempo respeitem as restrições do reservatório e dos horizontes presentes. Além disso, a metodologia proposta permite uma implementação eficiente, paralelizável e de baixo consumo de memória. Casos de teste com milhões de variáveis são apresentados para validar essa abordagem. Finalmente, a metodologia proposta neste trabalho para malhas de geomecânica pode ser naturalmente estendida para a modelagem estrutural de sub-superfícies na interpretação sísmica e de restauração geológica. / [en] Geomechanical mesh generation of complex reservoirs remains a tedious task prone to errors. Recently proposed solutions based on analytical reconstruction of the sub-surfaces are not capable to represent all the geometric details of natural objects. This work proposes a discrete model where the mesh vertices are positioned based on a convex quadratic optimization process. The optimization problem seeks to guarantee smooth meshes that conform with prescribed constraints. The resulting mesh therefore respects, as far as
possible, the finite volume mesh of the reservoir pay zone and the existing horizons. Finally, the proposed methodology for Geomechanical meshes can be easily extend to model sub-surfaces present in the structural interpretation and geological restauration.
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Processing Geometric Models of Assemblies to Structure and Enrich them with Functional Information / Analyse de modèles géométriques d'assemblages pour les structures et les enrichir avec des informations fonctionnellesShahwan, Ahmad 29 August 2014 (has links)
La maquette numérique d'un produit occupe une position centrale dans le processus de développement de produit. Elle est utilisée comme représentation de référence des produits, en définissant la forme géométrique de chaque composant, ainsi que les représentations simplifiées des liaisons entre composants. Toutefois, les observations montrent que ce modèle géométrique n'est qu'une représentation simplifiée du produit réel. De plus, et grâce à son rôle clé, la maquette numérique est de plus en plus utilisée pour structurer les informations non-géométriques qui sont ensuite utilisées dans diverses étapes du processus de développement de produits. Une demande importante est d'accéder aux informations fonctionnelles à différents niveaux de la représentation géométrique d'un assemblage. Ces informations fonctionnelles s'avèrent essentielles pour préparer des analyses éléments finis. Dans ce travail, nous proposons une méthode automatisée afin d'enrichir le modèle géométrique extrait d'une maquette numérique avec les informations fonctionnelles nécessaires pour la préparation d'un modèle de simulation par éléments finis. Les pratiques industrielles et les représentations géométriques simplifiées sont prises en compte lors de l'interprétation d'un modèle purement géométrique qui constitue le point de départ de la méthode proposée. / The digital mock-up (DMU) of a product has taken a central position in the product development process (PDP). It provides the geometric reference of the product assembly, as it defines the shape of each individual component, as well as the way components are put together. However, observations show that this geometric model is no more than a conventional representation of what the real product is. Additionally, and because of its pivotal role, the DMU is more and more required to provide information beyond mere geometry to be used in different stages of the PDP. An increasingly urging demand is functional information at different levels of the geometric representation of the assembly. This information is shown to be essential in phases such as geometric pre-processing for finite element analysis (FEA) purposes. In this work, an automated method is put forward that enriches a geometric model, which is the product DMU, with function information needed for FEA preparations. To this end, the initial geometry is restructured at different levels according to functional annotation needs. Prevailing industrial practices and representation conventions are taken into account in order to functionally interpret the pure geometric model that provides a start point to the proposed method.
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Do modelo geom?trico ao modelo f?sico: o tridimensional na educa??o do arquiteto e urbanistaCosta, Fernando Jos? de Medeiros 02 March 2013 (has links)
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Previous issue date: 2013-03-02 / In the teaching practice of architecture and urbanism in Brazil, educational legislation
views modeling laboratories and workshops as an indispensable component of the
infrastructure required for the good functioning of any architectural course of study.
Although the development of information technology at the international level has
created new possibilities for digital production of architectural models, research in
this field being underway since the early 1990s, it is only from 2007 onwards that
such technologies started to be incorporated into the teaching activity of architecture
and urbanism in Brazil, through the pioneering experience at LAPAC/FEC/UNICAMP.
It is therefore a recent experiment whose challenges can be highlighted through the
following examples: (i) The implementation of digital prototyping laboratories in
undergraduate courses of architecture and urbanism is still rare in Brazil; (ii) As a
new developing field with few references and application to undergraduate programs,
it is hard to define methodological procedures suitable for the pedagogical curricula
already implemented or which have already been consolidated over the years; (iii)
The new digital ways for producing tridimensional models are marked with
specificities which make it difficult to fit them within the existing structures of model
laboratories and workshops. Considering the above, the present thesis discusses the
tridimensional model as a tool which may contribute to the development of students
skills in perceiving, understanding and representing tridimensional space. Analysis is
made of the relation between different forms of models and the teaching of
architectural project, with emphasis on the design process. Starting from the
conceptualization of the word model as it is used in architecture and urbanism, an
attempt is made to identify types of tridimensional models used in the process of
project conception, both through the traditional, manual way of model construction as
well as through the digital ones. There is also an explanation on how new
technologies for digital production of models through prototyping are being
introduced in undergraduate academic programs of architecture and urbanism in
Brazil, as well as a review of recent academic publications in this area. Based on the
paradigm of reflective practice in teaching as designed by Sch?n (2000), the
experiment applied in the research was undertaken in the integrated workshop
courses of architectural project in the undergraduate program of architecture and
urbanism at Universidade Federal do Rio Grande do Norte. Along the experiment,
physical modeling, geometric modeling and digital prototyping are used in distinct
moments of the design process with the purpose of observing the suitability of each
model to the project s phases. The procedures used in the experiments are very
close to the Action Research methodology in which the main purpose is the
production of theoretical knowledge by improving the practice. The process was
repeated during three consecutive semesters and reflection on the results which
were achieved in each cycle helped enhancing the next one. As a result, a
methodological procedure is proposed which consists of the definition of the
Tridimensional Model as the integrating element for the contents studied in a specific
academic period or semester. The teaching of Architectural Project as it is developed
along the fifth academic period of the Architecture and Urbanism undergraduate
program of UFRN is taken as a reference / Na pr?tica do ensino de Arquitetura e Urbanismo no Brasil, verifica-se a exist?ncia
de laborat?rios e oficinas de maquetes, reconhecidas pela legisla??o educacional
como parte da infraestrutura necess?ria para o funcionamento de um curso. Embora
a evolu??o da tecnologia da informa??o no ?mbito internacional disponibilize novas
possibilidades para a produ??o digital de maquetes e modelos de Arquitetura com
pesquisas produzidas desde o in?cio da d?cada de 1990, no Brasil essas tecnologias
s? come?aram a ser apropriadas pelo ensino de Arquitetura e Urbanismo a partir de
2007 com a experi?ncia pioneira do LAPAC/FEC/UNICAMP. Trata-se, portanto de
uma experi?ncia recente e que evidencia a desafios. Por exemplo: (i) s?o raros os
casos de implanta??o de laborat?rios de prototipagem digital em cursos de
Arquitetura e Urbanismo no Pa?s; (ii) por ser um campo em desenvolvimento com
poucas refer?ncias de aplica??es na gradua??o, h? dificuldades na defini??o de
procedimentos metodol?gicos que sejam adequados aos projetos pedag?gicos j?
implantados e consolidados; (iii) as novas formas digitais de produ??o de modelos
tridimensionais cont?m especificidades que dificultam a compatibiliza??o com as
estruturas de laborat?rios e oficinas de maquetes j? existentes. Considerando o
exposto, na presente tese se discute o modelo tridimensional como instrumento
auxiliar no desenvolvimento da capacidade do estudante de perceber, compreender
e representar o espa?o tridimensional. Analisa-se a rela??o entre diferentes formas
de modelos e o ensino de projeto de Arquitetura e Urbanismo com interesse no
processo projetual. Partindo da conceitua??o do modelo em Arquitetura e
Urbanismo, busca-se identificar os tipos de modelos tridimensionais utilizados no
processo de elabora??o do projeto, tanto nas formas tradicionais de constru??o
manual de maquetes e modelos quanto nos meios digitais. Procura-se conhecer
como as novas tecnologias para a produ??o digital de modelos por meio da
prototipagem digital est?o sendo introduzidas nos cursos de gradua??o de
Arquitetura e Urbanismo no Brasil, assim como a produ??o acad?mica recente na
?rea. Considerando o paradigma do ensino pr?tico reflexivo concebido por Sch?n
(2000), o experimento realizado na pesquisa tem como ambiente de estudo o ateli?
integrado de projeto do Curso de Arquitetura e Urbanismo da Universidade Federal
do Rio Grande do Norte. No experimento a Modelagem f?sica, a Modelagem
Geom?trica e a Prototipagem Digital s?o inseridas em momentos do processo do
projeto com o objetivo de se observar a adequa??o do modelo ?s fases do projeto. A
metodologia empregada nos experimentos muito se aproxima da Pesquisa A??o na
qual o alvo principal ? a cria??o de conhecimento te?rico com o aprimoramento da
pr?tica. O processo se repetiu por tr?s semestres consecutivos e a reflex?o sobre os
resultados alcan?ados em cada ciclo forneceram subs?dios para aprimoramento no
seguinte. Como resultado prop?e-se um procedimento metodol?gico no qual o
Modelo Tridimensional constitui elemento integrador de conte?dos desenvolvidos em
um per?odo curricular, tendo como refer?ncia o ensino de Projeto Arquitet?nico e
Urban?stico no quinto per?odo do Curso de Arquitetura e Urbanismo da UFRN
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[en] STATISTICAL OPTIMIZATION OF SPATIAL HIERARCHICAL STRUCTURES SEARCHS / [pt] OTIMIZAÇÃO ESTATÍSTICA DE BUSCAS PARA ESTRUTURAS HIERÁRQUICAS ESPACIAISRENER PEREIRA DE CASTRO 29 May 2008 (has links)
[pt] Este trabalho surgiu da seguinte observação: os clássicos
algoritmos de busca em 2d-tree começam da raiz para acessar
dados armazenados nas folhas. Entretanto, como as folhas
são os nós mais distantes da raiz, por que começar as
buscas pela raiz? Com representações clássicas de 2d-trees,
não existe outra forma de acessar uma folha. Existem 2d-
trees, porém, que permitem acessar em tempo constante
qualquer nó, dado sua posição e seu nível. Para o algoritmo
de busca, a posição é conhecida, mas o nível
não. Para estimar o nível de um nó qualquer, um método de
otimização estatística do custo médio das buscas é
proposto. Como os piores custos de busca são obtidos quando
se começa da raiz, este método melhora ambos: o consumo de
memória pelo uso de 2d-trees que permitem acessar em
tempo constante qualquer nó, e o tempo de execução através
da otimização proposta. / [en] This work emerged from the following observation: usual
search procedures for 2d-trees start from the root to
retrieve the data stored at the leaves. But since the
leaves are the farthest nodes to the root, why
start from the root? With usual 2d-trees representations,
there is no other way to access a leaf. However, there
exist 2d-trees which allow accessing any node in constant
time, given its position in space and its depth in the
2d-tree. Search procedures take the position as an input,
but the depth remains unknown. To estimate the depth of an
arbitrary node a statistical optimization of the average
cost for the search procedures is introduced. Since the
highest costs of these algorithms are obtained when
starting from the root, this method improves on both, the
memory footprint by the use of 2d-trees which allow
accessing any node in constant time, and execution
time through the proposed optimization.
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Simulador eletromagnético em um ambiente de grades computacionais / Eletromagnetic simulator in a grid computing environmentFreitas, Igor José Ferreira de 09 August 2010 (has links)
Orientadores: Hugo Enrique Hernández-Figueroa, Marli de Freitas Gomes Hernández / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-17T00:31:12Z (GMT). No. of bitstreams: 1
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Previous issue date: 2010 / Resumo: Este trabalho tem por objetivo desenvolver os estágios de Pré e Pós-processamento de um pacote de simulação eletromagnética, batizado de SSAR-BR, e também de um ambiente de grades computacionais que permitirá a resolução de problemas eletromagnéticos de grande porte. O estágio de processamento já foi desenvolvido como parte de uma tese de doutorado pertencente ao grupo de pesquisa deste departamento e se baseia no método das Diferenças Finitas no Domínio do Tempo (FDTD). O estágio de Pré-Processamento envolve um modelador básico de duas e três dimensões para modelagem geométrica de dispositivos de telecomunicações (fontes radiantes, terminais móveis e antenas) e modelos biológicos (partes do corpo humano e cobaias). O estágio de Pós-Processamento, por outro lado, permite visualizar os resultados das simulações eletromagnéticas executadas, através de gráficos em duas e três dimensões. Estes dois estágios já foram desenvolvidos nas linguagens Java e OpenGL. O ambiente computacional paralelo está baseado no conceito de Grade Computacional (do inglês Grid), isto é, numa infra-estrutura de software e hardware que visa à integração de recursos computacionais geograficamente dispersos, interconectados através de uma rede, com o objetivo de compartilhar tais recursos sob determinadas políticas de acesso, formando um ambiente computacional escalável, de baixo custo e de alto desempenho. A camada de software localizada entre a aplicação do usuário e o sistema operacional responsável por controlar o acesso aos recursos da Grade Computacional, é chamada de middleware. O middleware adotado é o UNICORE 6, que se caracteriza por fornecer acesso aos recursos da Grade Computacional de forma transparente e segura, seguindo padrões abertos definidos pela comunidade OGF (Open Grid Forum / Abstract: The aim of this work is to develop the Pre and Post-Processing stages from an electromagnetic simulation suite, called SSAR-BR, and also a grid computational environment, which permits the execution of large electromagnetic problems. The processing stage, based in the Finite Difference Time Domain (FDTD) method, has been already developed as part of a doctorate thesis made by a researcher from this department. The Pre-processing stage involves a fundamental modeling tool capable to model telecommunications devices (radiant sources, mobile terminals and antennas) and biological models (human body parts and guinea-pig). On the other hand, the Post-Processing stage permits visualizing the electromagnetic simulations results in a two and three dimensions way. Both stages were developed in Java and OpenGL languages. The parallel computational environment is based on Grid Computing paradigm which consists in software and hardware infra-structure that integrates dispersed computational resources interconnected across a network. Its purpose is to share such resources under an access control policy and establishing a scalable, low-cost and high performance computational environment. The middleware is the layer between the user and operation systems responsible to manage the Grid resources and, for this work, the UNICORE 6 was adopted. The mainly reasons were its safe and transparent access to the distributed environment and, most important, it follows the open patterns from OGF (Open Grid Forum) community / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica
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Résolution de contraintes géométriques en guidant une méthode homotopique par la géométrie / Solving geometric constraints by a continuation method led by geometryImbach, Rémi 08 October 2013 (has links)
Suivant le domaine où on les sollicite, les solutions d’un système de contraintes géométriques (SCG) peuvent être : – formelles et exactes : elles prennent par exemple la forme d’un plan de construction produisant toutes les solutions, obtenu en appliquant des règles dérivées de lemmes de géométrie. Beaucoup de SCG, surtout en 3D, résistent à cette approche ; – numériques et approchées : elles sont les solutions d’un système d’équations construit à partir des contraintes et trouvées grâce à des méthodes numériques efficaces quand elles ne recherchent qu’une solution. De par la nature des problèmes traités, chercher toutes les solutions conduit à une complexité exponentielle. Les méthodes par continuation, ou homotopie, permettent d’obtenir toutes les solutions d’un système d’équations polynomiales. Leur application à des SCG est coûteuse et difficilement sujette aux raisonnements permis par l’origine géométrique du problème car elles opèrent hors de l’espace des figures géométriques. Notre travail a pour objet la spécialisation d’une méthode par continuation à des SCG. La géométrie simplifie et justifie sa mise en œuvre dans l’espace des figures, ou des raisonnements géométriques sont possibles. On aborde également les cas ou l’ensemble de solutions d’un problème contient des éléments isolés et des continuums. Des solutions proches d’une esquisse fournie par un utilisateur sont d’abord trouvées. La recherche d’autres solutions, malgré sa complexité exponentielle, est rendue envisageable par une approche itérative. Une nouvelle méthode de décomposition est proposée pour maîtriser le coût de la résolution. / Depending on the required application field, the solutions of a geometric constraints system (GCS) are either : – symbolic and exact such as construction plans, providing all the solutions, obtained by applying geometric rules. Many problems, mostly in a 3D context, resist to this approach ; – or numerical and approximated : they are the solutions of a system of equations built from the constraints, provided by generical numerical methods that are efficient when only one solution is sought. However, searching all the solutions leads to an exponential computation cost, due to the nature of problems. Continuation methods, also called homotopic methods, find all the solutions of a polynomial system. Using them to solve systems of equations associated to systems of constraints is nevertheless costly. Moreover, combining them with geometric reasoning is a challenge, because they act in a projective complex space and not in the realizations space. The aim of this work is to specialize a continuation method to GCS. Geometry is exploited to simplify and justify its adaptation in the space of realizations, so allowing geometric reasoning. Cases where the connected components of the solution space of a problem have heterogeneous dimensions are addressed. The method discussed here provides in a first step solutions that are similar to a sketch drawn by the user. Then a procedure is proposed to search new solutions. Its iterative nature seems to make the exponential complexity of this task bearable. A new decomposition method is proposed, that restrains the resolution cost.
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Représentation des maillages multirésolutions : application aux volumes de subdivision / Representation of multiresolution meshes : an application to subdivision volumesUntereiner, Lionel 08 November 2013 (has links)
Les maillages volumiques sont très répandus en informatique graphique, en visualisation scientifique et en calcul numérique. Des opérations de subdivision, de simplification ou de remaillage sont parfois utilisées afin d’accélérer les traitements sur ces maillages. Afin de maîtriser la complexité de l’objet et des traitements numériques qui lui sont appliqués, une solution consiste alors à le représenter à différentes échelles. Les modèles existants sont conçus pour des approches spécifiques rendant leur utilisation limitée aux applications pour lesquelles ils ont été pensés. Nos travaux de recherche présentent un nouveau modèle pour la représentation de maillages multirésolutions en dimension quelconque basé sur le formalisme des cartes combinatoires. Nous avons d’abord appliqué notre modèle aux volumes de subdivision multirésolutions. Dans ce cadre, nous présentons plusieurs algorithmes de raffinement d’un maillage grossier initial. Ces algorithmes supportent des hiérarchies obtenues par subdivision régulière et adaptative. Nous proposons ensuite deux représentations, opposés en terme de coût spatial et temporel, pour ce modèle. / Volume meshes are widespread in computer graphics, scientific visualization and numerical computation. Subdivision, simplification or remeshing operations are sometimes used to speed up processing of these meshes. A solution to manage the complexity of the object and numerical processing applied to it consist in presenting this object at different scales. Nevertheless, existing models are designed for specific approaches making them limited to applications for which they were designed. Our research work present a new model for the representation of multiresolution meshes in any dimension based on the combinatorial maps model. We first applied our model to the multiresolution subdivision volumes. In this framework, we present several refinement algorithms of an initial coarse mesh. These algorithms support hierarchies obtained by regular and adaptive subdivision. Finally, we propose two representations, opposed in term of time and space complexity, of this model.
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Modélisation dynamique et suivi de tumeur dans le volume rénal / Dynamic modeling and tumor tracking for the kidneyLeonardi, Valentin 13 November 2014 (has links)
Ce travail de thèse porte sur la modélisation dynamique 3D du rein et le suivi d’une tumeur de cet organe. Il s’inscrit dans le projet KiTT (Kidney Tumor Tracking) qui regroupe des chercheurs issus de plusieurs domaines : la modélisation géométrique, la radiologie et l’urologie. Le cadre de cette thèse suit une tendance de mini-invasivité des gestes chirurgicaux observée ces dernières années (HIFU, coelioscopie). Sa finalité est d’aboutir à un nouveau protocole de destruction de tumeurs rénales totalement non-invasif, par la diffusion d’agents physiques (ondes d’ultrasons) à travers la peau et focalisés sur la tumeur. Devant le mouvement et la déformation que le rein présente au cours du cycle respiratoire, la problématique de ces travaux de recherche est de connaître en permanence la position de la tumeur afin d’ajuster à moyen terme la diffusion des ondes en conséquence. / This 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.
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