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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
161

Space-Time Discretization of Elasto-Acoustic Wave Equation in Polynomial Trefftz-DG Bases / Discrétisation Espace-Temps d'Équations d'Ondes Élasto-Acoustiques dans des Bases Trefftz-DG Polynomiales

Shishenina, Elvira 07 December 2018 (has links)
Les méthodes d'éléments finis de type Galerkine discontinu (DG FEM) ont démontré précision et efficacité pour résoudre des problèmes d'ondes dans des milieux complexes. Cependant, elles nécessitent un très grand nombre de degrés de liberté, ce qui augmente leur coût de calcul en comparaison du coût des méthodes d'éléments finis continus.Parmi les différentes approches variationnelles pour résoudre les problèmes aux limites, se distingue une famille particulière, basée sur l'utilisation de fonctions tests qui sont des solutions locales exactes des équations à résoudre. L'idée vient de E.Trefftz en 1926 et a depuis été largement développée et généralisée. Les méthodes variationnelles de type Trefftz-DG appliquées aux problèmes d'ondes se réduisent à des intégrales de surface, ce qui devrait contribuer à réduire les coûts de calcul.Les approches de type Trefftz ont été largement développées pour les problèmes harmoniques, mais leur utilisation pour des simulations en domaine transitoire est encore limitée. Quand elles sont appliquées dans le domaine temporel, les méthodes de Trefftz utilisent des maillages qui recouvrent le domaine espace-temps. C'est une des paraticularités de ces méthodes. En effet, les méthodes DG standards conduisent à la construction d'un système semi-discret d'équations différentielles ordinaires en temps qu'on intègre avec un schéma en temps explicite. Mais les méthodes de Trefftz-DG appliquées aux problèmes d'ondes conduisent à résoudre une matrice globale, contenant la discrétisation en espace et en temps, qui est de grande taille et creuse. Cette particularité gêne considérablement le déploiement de cette technologie pour résoudre des problèmes industriels.Dans ce travail, nous développons un environnement Tre#tz-DG pour résoudre des problèmes d'ondes mécaniques, y compris les équations couplées de l'élasto-acoustique. Nous prouvons que les formulations obtenues sont bien posées et nous considérons la difficulté d'inverser la matrice globale en construisant un inverse approché obtenu à partir de la décomposition de la matrice globale en une matrice diagonale par blocs. Cette idée permet de réduire les coûts de calcul mais sa précision est limitée à de petits domaines de calcul. Etant données les limitations de la méthode, nous nous sommes intéressés au potentiel du "Tent Pitcher", en suivant les travaux récents de Gopalakrishnan et al. Il s'agit de construire un maillage espace-temps composé de macro-éléments qui peuvent être traités indépendamment en faisant une hypothèse de causalité. Nous avons obtenu des résultats préliminaires très encourageants qui illustrent bien l'intérêt du Tent Pitcher, en particulier quand il est couplé à une méthode de Trefftz-DG formulée à partir d'intégrales de surface seulement. Dans ce cas, le maillage espace-temps est composé d'éléments qui sont au plus de dimension 3. Il est aussi important de noter que ce cadre se prête à l'utilisation de pas de temps locaux ce qui est un plus pour gagner en précision avec des coûts de calcul réduits. / Discontinuous Finite Element Methods (DG FEM) have proven flexibility and accuracy for solving wave problems in complex media. However, they require a large number of degrees of freedom, which increases the corresponding computational cost compared with that of continuous finite element methods. Among the different variational approaches to solve boundary value problems, there exists a particular family of methods, based on the use of trial functions in the form of exact local solutions of the governing equations. The idea was first proposed by Trefftz in 1926, and since then it has been further developed and generalized. A Trefftz-DG variational formulation applied to wave problems reduces to surface integrals that should contribute to decreasing the computational costs.Trefftz-type approaches have been widely used for time-harmonic problems, while their implementation for time-dependent simulations is still limited. The feature of Trefftz-DG methods applied to time-dependent problems is in the use of space-time meshes. Indeed, standard DG methods lead to the construction of a semi-discrete system of ordinary differential equations in time which are integrated by using an appropriate scheme. But Trefftz-DG methods applied to wave problems lead to a global matrix including time and space discretizations which is huge and sparse. This significantly hampers the deployment of this technology for solving industrial problems.In this work, we develop a Trefftz-DG framework for solving mechanical wave problems including elasto-acoustic equations. We prove that the corresponding formulations are well-posed and we address the issue of solving the global matrix by constructing an approximate inverse obtained from the decomposition of the global matrix into a block-diagonal one. The inversion is then justified under a CFL-type condition. This idea allows for reducing the computational costs but its accuracy is limited to small computational domains. According to the limitations of the method, we have investigated the potential of Tent Pitcher algorithms following the recent works of Gopalakrishnan et al. It consists in constructing a space-time mesh made of patches that can be solved independently under a causality constraint. We have obtained very promising numerical results illustrating the potential of Tent Pitcher in particular when coupled with a Trefftz-DG method involving only surface terms. In this way, the space-time mesh is composed of elements which are 3D objects at most. It is also worth noting that this framework naturally allows for local time-stepping which is a plus to increase the accuracy while decreasing the computational burden.
162

Uso da Aplicação Normal de Gauss na poligonização de superfícies implícitas. / Use of the Gauss Normal Application in the polygonization of implicit surfaces.

IWANO, Thiciany Matsudo. 06 July 2018 (has links)
Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-07-06T13:51:44Z No. of bitstreams: 1 THICIANY MATSUDO IWANO - DISSERTAÇÃO PPGMAT 2005..pdf: 3751075 bytes, checksum: 2aaae3fdd115cd9f6f4b653f522d94c8 (MD5) / Made available in DSpace on 2018-07-06T13:51:44Z (GMT). No. of bitstreams: 1 THICIANY MATSUDO IWANO - DISSERTAÇÃO PPGMAT 2005..pdf: 3751075 bytes, checksum: 2aaae3fdd115cd9f6f4b653f522d94c8 (MD5) Previous issue date: 2005-10 / Neste trabalho apresentamos um estudo das principais técnicas de geração de malhas poligonais, a partir de superfícies descritas matematicamente por funções implícitas,isto é, superfícies definidas pelo conjunto S = f−1(0) = {X ∈ R3 | f(X) = 0}, onde f : R3 → R e f é, pelo menos, de classe C2. Mostramos um método para obter as curvaturas gaussiana e média dessas superfícies a partir do vetor ∇f para cada ponto de S. Abordamos questões como a preservação de características geométricas e topológicas do objeto gráfico. Dentre os métodos estudados, ressaltamos o algoritmo Marching Triangles, que gera uma malha a partir de um ponto arbitrário p sobre a superfície S e um referencial local, usando a abordagem do avanço de frentes. Em sua implementação, usamos o raio de curvatura, calculado a partir da curvatura normal máxima absoluta da superfície em cada ponto p pertencente a S, para adaptar o comprimento das arestas da malha triangular à geometria local da superfície S / In this work we present a study about the main techniques of surfaces meshes generation, described by implicit functions, that is, surfaces defined by the set S = f−1(0) = {X ∈ R3 | f(X) = 0}, where f : R3 → R and f is, at least, C2. We discuss aspects involving his preservation of graphic object’s geometry and topology. As special method we cite the Marching Triangles that generates a mesh starting from an arbitrary point p on surface S and a local referencial, using advancing fronts approach. In our implementation, we use the radius of curvature, calculated from surface’s absolute maximum normal curvature in each point p in S and the triangular mesh, to adapt the edges length of the mesh to the local geometry.
163

[en] MULTI-RESOLUTION FOR VISUALIZATION OF NATURAL OIL RESERVOIRS / [pt] MULTI-RESOLUÇÃO PARA A VISUALIZAÇÃO DE RESERVATÓRIOS NATURAIS DE PETRÓLEO

ANTONIO CARLOS PEREIRA DE AZAMBUJA 06 June 2005 (has links)
[pt] Atualmente, as malhas de simulação do fluxo em reservatórios naturais de petróleo (RNPs) são modelos compostos por centenas de milhares de células hexaédricas, cada uma podendo ser decomposta em 12 triângulos, de modo que a visualização interativa dessas malhas, através das estações gráficas atuais, ainda não é factível. À medida que os computadores e as placas gráficas aumentam sua capacidade de processamento, as malhas de simulação também crescem. A solução para esse tipo de problema passa, normalmente, por técnicas de aceleração, dentre as quais está a multi-resolução (MR). Ocorre, entretanto, que os modelos de multi-resolução atualmente conhecidos não são aplicáveis às malhas de simulação de RNPs, devido aos requisitos específicos da área, tais como a preservação do modelo de células hexaédricas e a descontinuidade entre células. Na realidade, as técnicas de multi-resolução tendem a enfocar a Visualização Realista, enquanto o problema de RNPs é de Visualização Científica, para a qual ainda não existem soluções genéricas. Esta dissertação propõe um modelo de MR específico para o problema de visualização das malhas de simulação em RNPs, no qual a partição descontínua do espaço, a semântica baseada em células hexaédricas e as características de visualização do problema são pontos considerados. O modelo proposto permite uma construção eficiente da estrutura de MR, a partir da qual, em tempo real, são extraídas malhas adaptativas dependentes: (a) do erro geométrico da aproximação, (b) da câmera e (c) do número desejado de polígonos na malha. Além disso, o modelo permite a utilização conjunta de outra técnica de aceleração, o descarte, possibilitando o descarte hierárquico de regiões da malha que estão fora do volume de visão. O modelo proposto foi implementado em um sistema que permitiu uma extensa bateria de testes, cujos resultados permitiram traçar algumas conclusões e recomendações. / [en] Current flow-simulation meshes of natural oil reservoirs (NOR) are composed of hundreds of thousands of hexahedral cells. The visualization of the geometry of these cells superimposed with color attributes to represent properties and flow results requires the rendering of an unstructured mesh of millions of triangles. Current graphics hardware does not allow for an interactive visualization of such meshes. As computers and graphics boards increase their processing capacity, simulation meshes also grow and the solution to the rendering problem usually includes acceleration techniques, one of which is multi-resolution (MR). However, currently known MR models are not applicable to NOR simulation meshes due to this field`s specific requirements, such as the preservation of the hexahedral- cell model and discontinuities among cells. In fact, MR techniques tend to focus on Realistic Visualization, while the NOR problem is one of Scientific Visualization, for which generic solutions still do not exist. The present work proposes a specific MR model for the visualization problem concerning NOR simulation meshes, in which discontinuous space partition, hexahedral-cell-based semantics and the problem`s visualization characteristics are taken into account. The proposed model allows an efficient construction of a MR structure, from which, in real time, adaptive meshes can be extracted that depend on: (a) the geometric error approximation, (b) the view, and (c) the polygon budget. This model can also be used combined with another acceleration technique, frustum culling, which allows for the hierarchical elimination of regions in the mesh that are out of the view volume. The proposed model was implemented in a system on which extensive testing was performed, providing results that allowed us to draw some conclusions and recommendations.
164

On Three Dimensional High Lift Flow Computations

Gopalakrishna, N January 2014 (has links) (PDF)
Computing 3D high lift flows has been a challenge to the CFD community because of three important reasons: complex physics, complex geometries and large computational requirements. In the recent years, considerable progress has been made in understanding the suitability of various CFD solvers in computing 3D high lift flows, through the systematic studies carried out under High Lift Prediction workshops. The primary focus of these workshops is to assess the ability of the CFD solvers to predict CLmax and αmax associated with the high lift flows, apart from the predictability of lift and drag of such flows in the linear region. Now there is a reasonable consensus in the community about the ability of the CFD solvers to predict these quantities and fresh efforts to further understand the ability of the CFD solvers to predict more complex physics associated with these flows have already begun. The goal of this thesis is to assess the capability of the computational methods in predicting such complex flow phenomena associated with the 3D High-Lift systems. For evaluation NASA three element Trapezoidal wing configuration which poses a challenging task in numerical modeling was selected. Unstructured data based 3D RANS solver HiFUN (HiFUN stands for High Resolution Flow Solver for UNstructured Meshes) is used in investigating the high lift flow. The computations were run fully turbulent, using the one equation Spalart-Allmaras turbulence model. A summary of the results obtained using the flow solver HiFUN for the 3D High lift NASA Trapezoidal wing are presented. Hybrid unstructured grids have been used for the computations. Grid converged solution obtained for the clean wing and the wing with support brackets, are compared with experimental data. The ability of the solver to predict critical design parameters associated with the high lift flow, such as αmax and CLmax is demonstrated. The utility of the CFD tools, in predicting change in aerodynamic parameters in response to perturbational changes in the configuration is brought out. The solutions obtained for the high lift configuration from two variants of the Spalart-Allmaras turbulence model are compared. To check the unsteadiness in the flow, particularly near stall, unsteady simulations were performed on static grid. Lastly, hysteresis on lower leg of lift curve is discussed, the results obtained for quasi-steady and dynamic unsteady simulations are presented. Inferences from the study on useful design practices pertaining to the 3D high lift flow simulations are summarized.
165

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 / Mesh surface analysis by construction and comparison of mean models and by decomposition into graphs based on discrete curvatures : application to the study of the human cornea

Polette, Arnaud 03 December 2015 (has links)
Cette 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. 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 la connaissance de l'anatomie cornéenne, la modélisation de la cornée normale permet de détecter tout écart significatif par rapport à la normale permettant un diagnostic précoce de pathologies. 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 pour une application de biométrie. L’idée est de quantifier la différence entre chaque surface et une surface donnée, et de déterminer un seuil permettant la reconnaissance. Deux méthodes sont proposées et 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 en différentes catégorie de carreaux. Ensuite un graphe d'adjacence est construit avec un nœud pour chaque carreau. 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. / 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. 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.
166

Development Of A General Purpose Flow Solver For Euler Equations

Shende, Nikhil Vijay 07 1900 (has links) (PDF)
No description available.
167

[pt] OTIMIZAÇÃO TOPOLÓGICA USANDO MALHAS POLIÉDRICAS / [en] TOPOLOGY OPTIMIZATION USING POLYHEDRAL MESHES

22 February 2019 (has links)
[pt] A otimização topológica tem se desenvolvido bastante e possui potencial para revolucionar diversas áreas da engenharia. Este método pode ser implementado a partir de diferentes abordagens, tendo como base o Método dos Elementos Finitos. Ao se utilizar uma abordagem baseada no elemento, potencialmente, cada elemento finito pode se tornar um vazio ou um sólido, e a cada elemento do domínio é atribuído uma variável de projeto, constante, denominada densidade. Do ponto de vista Euleriano, a topologia obtida é um subconjunto dos elementos iniciais. No entanto, tal abordagem está sujeita a instabilidades numéricas, tais como conexões de um nó e rápidas oscilações de materiais do tipo sólido-vazio (conhecidas como instabilidade de tabuleiro). Projetos indesejáveis podem ser obtidos quando elementos de baixa ordem são utilizados e métodos de regularização e/ou restrição não são aplicados. Malhas poliédricas não estruturadas naturalmente resolvem esses problemas e oferecem maior flexibilidade na discretização de domínios não Cartesianos. Neste trabalho investigamos a otimização topológica em malhas poliédricas por meio de um acoplamento entre malhas. Primeiramente, as malhas poliédricas são geradas com base no conceito de diagramas centroidais de Voronoi e posteriormente otimizadas para uso em análises de elementos finitos. Demonstramos que o número de condicionamento do sistema de equações associado pode ser melhorado ao se minimizar uma função de energia relacionada com a geometria dos elementos. Dada a qualidade da malha e o tamanho do problema, diferentes tipos de resolvedores de sistemas de equações lineares apresentam diferentes desempenhos e, portanto, ambos os resolvedores diretos e iterativos são abordados. Em seguida, os poliedros são decompostos em tetraedros por um algoritmo específico de acoplamento entre as malhas. A discretização em poliedros é responsável pelas variáveis de projeto enquanto a malha tetraédrica, obtida pela subdiscretização da poliédrica, é utilizada nas análises via método dos elementos finitos. A estrutura modular, que separa as rotinas e as variáveis usadas nas análises de deslocamentos das usadas no processo de otimização, tem se mostrado promissora tanto na melhoria da eficiência computacional como na qualidade das soluções que foram obtidas neste trabalho. Os campos de deslocamentos e as variáveis de projeto são relacionados por meio de um mapeamento. A arquitetura computacional proposta oferece uma abordagem genérica para a solução de problemas tridimensionais de otimização topológica usando poliedros, com potencial para ser explorada em outras aplicações que vão além do escopo deste trabalho. Finalmente, são apresentados diversos exemplos que demonstram os recursos e o potencial da abordagem proposta. / [en] Topology optimization has had an impact in various fields and has the potential to revolutionize several areas of engineering. This method can be implemented based on the finite element method, and there are several approaches of choice. When using an element-based approach, every finite element is a potential void or actual material, whereas every element in the domain is assigned to a constant design variable, namely, density. In an Eulerian setting, the obtained topology consists of a subset of initial elements. This approach, however, is subject to numerical instabilities such as one-node connections and rapid oscillations of solid and void material (the so-called checkerboard pattern). Undesirable designs might be obtained when standard low-order elements are used and no further regularization and/or restrictions methods are employed. Unstructured polyhedral meshes naturally address these issues and offer fl exibility in discretizing non-Cartesians domains. In this work we investigate topology optimization on polyhedra meshes through a mesh staggering approach. First, polyhedra meshes are generated based on the concept of centroidal Voronoi diagrams and further optimized for finite element computations. We show that the condition number of the associated system of equations can be improved by minimizing an energy function related to the element s geometry. Given the mesh quality and problem size, different types of solvers provide different performances and thus both direct and iterative solvers are addressed. Second, polyhedrons are decomposed into tetrahedrons by a tailored embedding algorithm. The polyhedra discretization carries the design variable and a tetrahedra subdiscretization is nested within the polyhedra for finite element analysis. The modular framework decouples analysis and optimization routines and variables, which is promising for software enhancement and for achieving high fidelity solutions. Fields such as displacement and design variables are linked through a mapping. The proposed mapping-based framework provides a general approach to solve three-dimensional topology optimization problems using polyhedrons, which has the potential to be explored in applications beyond the scope of the present work. Finally, the capabilities of the framework are evaluated through several examples, which demonstrate the features and potential of the proposed approach.
168

Verteilt agierendes System zur Bereitstellung von geometrie- und bild-basierten Approximationen für das Multiresolution Rendering

Hilbert, Karsten 07 April 2010 (has links)
In dieser Arbeit wird ein applikationsunabhängiges Reduktionssystem entworfen, das selbstständig und effizient für die ihm übergebenen Modellteile in allen Betrachtersituationen aus einem möglichen Spektrum von geometrie- und bild-basierten Approximationsformen jeweils die geeignete Approximation generiert, deren Komplexität möglichst gering ist und bei deren Verwendung ein Szenenbild erzeugt werden kann, dessen Bildfehler die vom Nutzer vorgegebenen Schranken nicht überschreitet. Das System nutzt bild- und geometrie-basierte Approximationsformen für unterschiedliche Bereiche im Sichtvolumen des Betrachters. Nailboards sind die benutzten bild-basierten Approximationen. In dieser Arbeit werden neue Nailboardarten vorgestellt, die für die Approximation von semi-transparenten Objekten und von dynamisch beleuchteten Objekten effizient verwendet werden können. Die vorgestellten Erzeugungs- und Darstellungsmethoden nutzen die Fähigkeiten der aktuellen Hardware intensiv aus, um die Nailboards im Echtzeitkontext nutzbar zu machen. Texturierte, sichtabhängige geometrie-basierte Approximationen werden aus einem texturierten Viewdependent Progressive Mesh (VDPM) gewonnen. In dieser Arbeit wird eine effiziente Methode zur Erzeugung von VDPM vorgestellt, aus der Approximationen mit optimal angepassten Parameterkoordinaten gewonnen werden können, ohne dass ein der VDPM-Erzeugung nachgeschalteter Optimierungsschritt der Parameterkoordinaten aller im VDPM kodierten Approximationen notwendig ist. Die Erzeugung der notwendigen Texturen erfolgt unter Nutzung einer schnellen Parametrisierungsmethode und hardware-gestützter Methoden zur Erzeugung dicht gepackter Texturatlanten. Durch die Kombination von selektiven Zugriffsmethoden auf TFGR mit effizienten Randanpassungsmethoden, wird erstmals ein effizientes und qualitativ hochwertiges Multiresolution Rendering mittels TFGR ermöglicht. Aus dem TFGR werden texturierte sichtunabhängige Approximationen gewonnen. Zur echtzeitfähigen, vollautomatischen Erzeugung aller drei Approximationsformen wird in dieser Arbeit ein Reduktionssystem vorgeschlagen, das diese Approximationsformen verteilt generiert. Für eine effiziente Kommunikation innerhalb dieses Systems werden entsprechende Kompressions-, Caching- und State-Differencing-Mechanismen vorgeschlagen. Lastverteilungsmechanismen sichern eine effiziente Ausnutzung der zur Verfügung stehenden Ressourcen ab. / In this thesis, an application-independent system for the distributed generation of object approximations used for multi-resolution rendering is proposed. The system generates approximations of objects of a scene sent to him in an efficient and fully automatic manner. The system is able to generate different kinds of geometry-based and image-based object approximations. For each given objects of a scene it generates that kind of approximation that is suitable for the current view. That means that its complexity is minimal and that it causes an error in the image generated with this approximation that does not exceed a user-specified threshold. Nailboards are image-based approximations that approximate objects whose size is small compared to the whole scene. In this thesis new kinds of nailboards are presented which can be used efficiently for the approximation of semi-transparent objects and objects in scenes with a dynamic illumination. Capabilities of current graphics hardware are intensively used to generate and render all kinds of Nailboards in real-time. So-called textured view-dependent progressive meshes (VDPM) are used as view dependent geometry-bases approximations for objects whose size is large compared to the whole scene. In this thesis an efficient method for generating VDPM is presented. This method allows the extraction of approximations with optimally adapted texture coordinates without the necessity of an separate optimization step for the texture coordinates in the generation procedure. The textures necessary for the compensation of detail loss are generated using a fast parameterization method from Yoshizawa. The generation of texture atlases is done hardware-accelerated. Further on a hardware-accelerated method for hardware-accelerated multi-resolution rendering using multi chart geometry images (MCGIM) is presented. Out of the MCGIM view-independent geometry-based approximations are extracted. Finally a system for the distributed generation of object approximations is proposed. It generates all three kinds of approximations fully automatic and almost in real time. For an efficient communication within this system suitable compression, caching and state-differencing mechanisms are proposed. Load balancing mechanisms ensure efficient utilization of available resources.
169

Uniform Error Estimation for Convection-Diffusion Problems

Franz, Sebastian 20 January 2014 (has links)
Let us consider the singularly perturbed model problem Lu := -epsilon laplace u-bu_x+cu = f with homogeneous Dirichlet boundary conditions on the unit-square (0,1)^2. Assuming that b > 0 is of order one, the small perturbation parameter 0 < epsilon << 1 causes boundary layers in the solution. In order to solve above problem numerically, it is beneficial to resolve these layers. On properly layer-adapted meshes we can apply finite element methods and observe convergence. We will consider standard Galerkin and stabilised FEM applied to above problem. Therein the polynomial order p will be usually greater then two, i.e. we will consider higher-order methods. Most of the analysis presented here is done in the standard energy norm. Nevertheless, the question arises: Is this the right norm for this kind of problem, especially if characteristic layers occur? We will address this question by looking into a balanced norm. Finally, a-posteriori error analysis is an important tool to construct adapted meshes iteratively by solving discrete problems, estimating the error and adjusting the mesh accordingly. We will present estimates on the Green’s function associated with L, that can be used to derive pointwise error estimators.
170

Propuesta de diseño de mallas de perforación y voladura empleando modificación al modelo matemático de Pearse con la finalidad de optimizar la fragmentación de rocas en la mina Tacaza de Consorcio de Ingenieros Ejecutores Mineros S.A. (CIEMSA)

Zamora Paredes, Vidal Enrike 16 November 2020 (has links)
En los últimos años, la minería se ha enfrentado a una disminución paulatina del precio de los metales, generando una reducción de la rentabilidad del negocio producto de menores reservas minerales. Esto ha ocasionado que se adopten esquemas operativos enfocados en la mejora continua de cada uno de los procesos dentro del ciclo de minado, a fin de reducir los costos. Por tal motivo, es necesario visualizar cada una de las actividades involucradas, como la perforación y voladura, las cuales tienen un impacto productivo y económico en el proceso global. En consecuencia, la presente investigación se enfoca en optimizar la fragmentación de rocas, a través de un diseño de malla de perforación y voladura, mediante la integración de los conceptos de ingeniería de la voladura y caracterización del macizo rocoso. Para esto, se aplicará el modelo matemático de Pearse, a fin de calcular los parámetros controlables del diseño y obtener los resultados esperados. Asimismo, el alcance del trabajo abarca el análisis de la productividad del ciclo de minado, así como, la cuantificación del impacto de la propuesta en materia de costos. Se comienza con el análisis de línea base, que consta de la medición de resultados producto de los diseños actuales de malla de P&V, con la finalidad de determinar las variables que están generando fragmentación gruesa de rocas. Posteriormente, se plantea la propuesta de diseño de malla considerando la mayor cantidad de datos e información del tajo Tacaza. Luego se ejecutan los trabajos en campo, que consta del seguimiento y control de actividades, a fin de cumplir con los parámetros diseñados. Finalmente, se miden los resultados de fragmentación en el software Wipfrag, y se analiza la productividad y costos en el ciclo de minado. De los resultados se obtiene una mejora en la fragmentación, ya que se logra reducir el diámetro de rocas de 13.0 a 5.0 pulgadas en promedio. Esto conlleva a un incremento en el rendimiento efectivo de los equipos y una reducción de costos de US$ 9,600 mensuales aproximadamente. Estas nuevas medidas generan valor agregado a la compañía, a través de una operación minera sostenible, que busca hacer rentable el negocio desde una visión holística del proceso. / In recent years, mining has faced a gradual decrease in the metal´s prices, generating a reduction in the profitability of the business as a result of lower mineral reserves. This has led to the adoption of operational schemes focused on the continuous improvement of each of the processes within the mining cycle, in order to reduce costs. For this reason, it is necessary to visualize each of the activities involved, such as drilling and blasting, which have a productive and economic impact on the global process. Consequently, this research focuses on optimizing rock fragmentation, through a drill and blast mesh design, by integrating the engineering concepts of blasting and characterization of the rock mass. For this, the Pearse mathematical model will be applied, in order to calculate the controllable parameters of the design and obtain the expected results. Likewise, the scope of the work includes the analysis of the productivity of the mining cycle, as well as the quantification of the impact of the proposal in terms of costs. It begins with the baseline analysis, which consists of measuring the results of current P&V mesh designs, in order to determine the variables that are generating coarse rock fragmentation. Subsequently, the mesh design proposal is proposed considering the greater amount of data and information from the Tacaza pit. Then the field work is carried out, consisting of the monitoring and control of activities, in order to comply with the designed parameters. Finally, the fragmentation results are measured in the Wipfrag software, and the productivity and costs in the mining cycle are analyzed. From the results, an improvement in fragmentation is obtained, since it is possible to reduce the diameter of rocks from 13.0 to 5.0 inches on average. This leads to an increase in the effective performance of the equipment and a cost reduction of approximately US $ 9,600 per month. These new measures generate added value for the company, through a sustainable mining operation, which seeks to make the business profitable from a holistic view of the process. / Tesis

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