Tsunamis are one of the most catastrophic natural events impacting coastal regions often generated by undersea earthquakes. Nevertheless, in enclosed basins, i.e., fjords, reservoirs and lakes, subaerial or submarine landslides can initiate devastating tsunamis with similar consequences. Although a subaerial or submarine landslide that impinges into a large water body can generate a tsunami, subaerial landslides are much more efficient tsunami generators than its counterpart. In this study we aim to integrate laboratory scale experiments of tsunami generation by subaerial landslide with numerical models. The work focuses on the numerical validation of two three-dimensional Navier-Stokes (3D-NS) models, FLOW-3D and our developed model TSUNAMI3D. The models are validated based on previous large scale laboratory experiments performed by a tsunami research team lead by Dr. Hermann Fritz, Georgia Institute of Technology. Three large scale landslide scenarios were selected from the set of laboratory experiments, namely, fjord like, headland and far field coastline. These scenarios showed that complex wave fields can be generated by subaerial landslides. The correct definition and evolution of the wave field are key to accurate modeling the ensuing tsunami and its effect in coastal regions. In this study, comparisons are performed between numerical results and laboratory experiments. Methodology and key parameters for soil rheology are defined for model validations. Results of the models are expected to be under the allowable errors indicated by the National Tsunami Hazard Mitigation Program (NTHMP), National Oceanic and Atmospheric Administration (NOAA) guidelines for validation of tsunami numerical models. The ultimate goal of this research is to obtain better tsunami calculation tools for real-world application of 3-D models for landslide tsunamis, which are necessary for the construction of inundation maps in the Gulf of Mexico and the Caribbean regions.

This thesis concerns the development and validation of methods for the industrially important area of adsorption isotherm parameter estimation in preparative, nonlinear high performance liquid chromatography (HPLC). Preparative chromatography is a powerful separation method to get pure compounds from more or less complex liquid mixtures, e.g., mixtures of mirror-image molecules. Computer simulations can be used to optimize preparative chromatography, but then competitive adsorption isotherm parameters are usually required. Here two methods to estimate adsorption isotherm parameters are treated: (i) the perturbation peak (PP) method and (ii) the inverse method (IM). A new theory for the PP method was derived and led to a new injection technique which was validated experimentally. This injection technique solved the severe problem with vanishing peaks and enabled us to use the PP method to estimate binary competitive adsorption isotherms valid over a broad concentration range. Also, the injection technique made it possible to estimate competitive adsorption isotherms for a quaternary mixture for the first time. Finally, an interesting perturbation peak phenomenon, known as the “Helfferich Paradox”, was experimentally verified for the first time. The IM is a relatively new method to determine adsorption isotherm parameters. It has the advantage of requiring very small samples, but also requires an advanced computer algorithm. An improved implementation of this computer algorithm was developed and tested experimentally. Also, a variant of the IM called “the inverse method on plateaus” was tested experimentally and the estimated adsorption isotherm parameters were shown to be valid over a broader concentration range than those estimated with the standard IM.

Video editing and object recognition are two significant fields in computer vi- sion: the first has remarkably assisted digital production and post-production tasks of a digital video footage; the second is considered fundamental to image classification or image based search in large databases (e.g. the web). In this thesis, we address two problems, namely we present a novel formulation that tackles video editing tasks and we develop a mechanism that allows to generate more robust descriptors for objects in an image. Concerning the first problem, this thesis proposes two variational models to perform temporally coherent video editing. These models are applied to change an object’s (rigid or non-rigid) texture throughout a given video sequence. One model is based on propagating color information from a given frame (or be- tween two given frames) along the motion trajectories of the video; while the other is based on propagating gradient domain information. The models we present in this thesis require minimal user intervention and they automatically accommodate for illumination changes in the scene. Concerning the second problem, this thesis addresses the problem of affine invariance in object recognition. We introduce a way to generate geometric affine invariant quantities that are used in the construction of feature descrip- tors. We show that when these quantities are used they do indeed achieve a more robust recognition than the state of the art descriptors. i / La edición de vídeo y el reconocimiento de objetos son dos áreas fundamentales en el campo de la visión por computador: la primera es de gran utilidad en los procesos de producción y post-producción digital de vídeo; la segunda es esencial para la clasificación o búsqueda de imágenes en grandes bases de datos (por ejemplo, en la web). En esta tesis se acometen ambos problemas, en concreto, se presenta una nueva formulación que aborda las tareas de edición de vídeo y se desarrolla un mecanismo que permite generar descriptores más robustos para los objetos de la imagen. Con respecto al primer problema, en esta tesis se proponen dos modelos variacionales para llevar a cabo la edición de vídeo de forma coherente en el tiempo. Estos modelos se aplican para cambiar la textura de un objeto (rígido o no) a lo largo de una secuencia de vídeo dada. Uno de los modelos está basado en la propagación de la información de color desde un determinado cuadro de la secuencia de vídeo (o entre dos cuadros dados) a lo largo de las trayectorias de movimiento del vídeo. El otro modelo está basado en la propagación de la información en el dominio del gradiente. Ambos modelos requieren una intervención mínima por parte del usuario y se ajustan de manera automática a los cambios de iluminación de la escena. Con respecto al segundo problema, esta tesis aborda el problema de la invariancia afín en el reconocimiento de objetos. Se introduce un nuevo método para generar cantidades geométricas afines que se utilizan en la generación de descriptores de características. También se demuestra que el uso de dichas cantidades proporciona mayor robustez al reconocimiento que los descriptores existentes actualmente en el estado del arte.

Pas de résumé / No abstract

L'objectif de cette thèse est de développer des techniques de modélisation et de simulation multi-échelle avancées et efficaces pour étudier les phénomènes d'instabilité dans trois structures d'ingénierie courantes: membrane, film/substrat et structures sandwich, en combinant la technique des coefficients de Fourier lentement variables (TSVFC) et la méthode numérique asymptotique (ANM). À cette fin, basée sur les équations de la plaque de Von Karman, la TSVFC été utilisée pour développer un modèle de Fourier à bidimensionnel (2D) qui a également été implémenté dans ABAQUS via sa sous-routine UEL. Ensuite, un 2D modèle de Fourier est construit pour le film/substrat. En outre, en utilisant leurs caractéristiques de déformation, un 1D modèle de Fourier est développé en utilisant à la fois le TSVFC et le CUF. Par la suite, sur la base d'une cinématique Zig-Zag d'ordre supérieur, un 2D modèle de Fourier est déduit pour une plaque sandwich. Les équations directrices pour les modèles ci-dessus sont discrétisées par la méthode des éléments finis, et les systèmes non linéaires résultants sont résolus par le solveur non linéaire efficace et robuste ANM. Ces modèles sont ensuite adoptés pour étudier les instabilités dans ces structures. Les résultats montrent que les modèles établis peuvent simuler avec précision et efficacité divers phénomènes d'instabilité. En outre, on constate que l'instabilité membranaire est sensible aux conditions aux limites et qu'il existe un paramètre sans dimension presque constant près du point de bifurcation pour différents cas de charge et paramètres géométriques, ce qui peut être utile pour prédire rapidement l'apparition des rides / The main aim of this thesis is to develop advanced and efficient multi-scale modeling and simulation techniques to study instability phenomena in three common engineering structures, i.e., membrane, film/substrate and sandwich structures, by combining the Technique of Slowly Variable Fourier Coefficients (TSVFC) and the Asymptotic Numerical Method (ANM). Towards this end, based on the Von Karman plate equations, the TSVFC has been firstly used to develop a two-dimensional (2D) Fourier double-scale model for membrane, which has also been implemented into ABAQUS via its subroutine UEL. Then a 2D Fourier model is constructed for film/substrate. Further, making use of deformation features of the film/substrate, a 1D Fourier model is developed by using both the TSVFC and the Carrera’s Unified Formulation (CUF). Subsequently, based on high-order kinematics belonging to Zig-Zag theory, a 2D Fourier model is deduced for sandwich plate. The governing equations for the above models are discretized by the Finite Element Method, and the resulting nonlinear systems are solved by the efficient and robust nonlinear solver ANM. These models are then adopted to study instabilities in these structures. Results show that the established models could accurately and efficiently simulate various instability phenomena. Besides, it’s found that the membrane instability is very sensitive to boundary conditions, and there exists a dimensionless parameter that is almost constant near bifurcation point for various loading cases and geometric parameters, which may be helpful for fast predicting the occurrence of wrinkles

Made available in DSpace on 2014-06-11T19:33:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-12-18Bitstream added on 2014-06-13T20:45:15Z : No. of bitstreams: 1 pimentel_ecg_dr_jabo.pdf: 351573 bytes, checksum: 4ed13e3cadb5bcefe457a98cb28d9baf (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O objetivo da pesquisa descrita nesta tese foi estudar possíveis aplicações do método das rotações modificadas de Givens na solução de sistemas de equações lineares tipicamente observados em problemas de melhoramento animal. Duas aplicações foram consideradas: a predição de valores genéticos com base em informação fenotípica e genealógica, por meio da metodologia dos modelos mistos; e a predição de valores genéticos com base em informação molecular, obtida pela genotipagem de painéis densos de SNPs. Na primeira aplicação, delineou-se o emprego de um modelo animal reduzido, combinado a uma ordenação do sistema que permitiu uma abordagem multi-frontal de decomposição. As matrizes frontais foram definidas como sendo as partes da triangular superior pertinentes a cada rebanho. Com isso, o problema pôde ser desmembrado em n subproblemas em que n é o número de rebanhos. Um conjunto de programas foi desenvolvido de modo a decompor as matrizes de dados de cada rebanho independentemente, e depois combinar as informações de todos eles na solução do sistema triangular geral, por retro-substituição. Concluiu-se que o método pode ser empregado em um sistema para atualização de predições de valor genético sob modelo animal reduzido, em que se aninham os efeitos de vacas dentro de rebanhos. Na segunda aplicação, comparou-se o emprego das rotações de Givens com o método do Gradiente Conjugado, na solução de sistemas lineares envolvidos na estimação de efeitos de SNPs em valores genéticos. O método das rotações demandou menos tempo de processamento e mais memória. Concluiu-se que, dado o crescente avanço em capacidade computacional, o método das rotações pode ser um método numérico viável e apresenta a vantagem de permitir o cálculo dos erros-padrão das estimativas. / The aim of this study was to investigate possible applications of the modified Givens rotations on the solution of linear systems that typically arise in animal breeding problems. Two applications were considered: prediction of breeding values based on phenotypes and relationships, using mixed model methods; and prediction of breeding values based on molecular information, using genotypes from high density SNP chips. In the first application, the use of a reduced animal model, combined with a specific ordering of the system, made it possible to apply a multi-frontal decomposition approach. The frontal matrices were defined as the parts of the upper triangular corresponding to each herd. In this way, the problem could be partitioned into n subproblems, where n is the number of herds. A set of programs was developed in order to factorize the data matrix of each herd independently, and then combine the information from all of them while solving the overall triangular system, by back-substitution. The conclusion was that Givens rotations can be used as a numerical method for updating predicted breeding values under a reduced animal model, if dam effects are nested within herds. In the second application, the modified Givens rotations were compared to the Conjugate Gradient method for solving linear systems that arise in the estimation of SNP effects on breeding values. Givens rotations required less processing time but a greater amount of high speed memory. The conclusion was that, given the increasing rate of advance in computer power, Givens rotations can be regarded as a feasible numerical method which presents the advantage that it allows for the calculation of standard errors of estimates.

No description available.

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-09-26T13:42:32Z No. of bitstreams: 1 MÚCIO MARCOS SILVA NÓBREGA - TESE (PPGEP) 2007.pdf: 5674260 bytes, checksum: b79349f8d5a305a7090f3fa7ae22559e (MD5) / Made available in DSpace on 2018-09-26T13:42:32Z (GMT). No. of bitstreams: 1 MÚCIO MARCOS SILVA NÓBREGA - TESE (PPGEP) 2007.pdf: 5674260 bytes, checksum: b79349f8d5a305a7090f3fa7ae22559e (MD5) Previous issue date: 2007-11-21 / CNPq / O presente trabalho tem como objetivo o desenvolvimento de compósitos poliméricos reforçados com fibras de Caroá Neoglaziovia variegata para avaliação de seu desempenho mecânico, bem como suas características de sorção de água. Foi utilizado como matriz polimérica uma resina de poliéster insaturado e fibras de Caroá originárias do cariri paraibano. Os compósitos foram confeccionados com diferentes teores de fibras, cortadas em tamanhos de aproximadamente 3 cm, e moldados por compressão em molde metálico para avaliação das propriedades mecânicas. A composição de amostras de melhor desempenho mecânico foi escolhida para os ensaios de sorção de água, com amostras de 20x20mm² com 3cm e 6cm de espessura na temperatura de 25°C, 50°C e 70°C. Uma modelagem matemática tridimensional transiente foi usada para predizer a transferência de massa durante a sorção de água destes compósitos. Os resultados indicam que as propriedades mecânicas em tração dos compósitos estudados aumentam com o teor de fibras acima de 24% em massa até um volume crítico, em torno de 30%.Resistência ao impacto aumentou para todas as composições em virtude da eficiência de transferência de tensão para as fibras. Os resultados obtidos para o módulo de elasticidade dos compósitos evidenciam que estes são superiores ao da matriz, para todos os teores abaixo de 45% de fibras, o que é associado às características das fibras. A cinética de sorção de água nos compósitos mostrou ser influenciada pela relação área/volume. Pôde-se observar que em tempos curtos, aproximadamente 100 horas, os corpos com menor relação apresentam uma maior velocidade de sorção. Em tempos longos os compósitos com maior relação área/volume apresentam maiores teores de água sorvida. O teor de umidade de equilíbrio dos compósitos com 30% de fibras de caroá apresentaram valores de 14,48% à 25ºC e 16,52% à 70ºC, para as espessuras de 3 e 6 mm, respectivamente. A modelagem matemática utilizada para a obtenção da solução numérica de sorção de água nos compósitos reforçados por fibras de caroá foi adequada e satisfatória e a técnica de volumes finitos mostrou-se eficiente para discretizar a equação de difusão no sistema de coordenadas cartesianas para um sólido paralelepípedo, possibilitando a análise de fenômenos difusivos transientes nestes sólidos. / This research has the objective of developing polymeric composites enhanced with Caroá fibers Neoglaziovia variegata, in order to evaluate its mechanical performance and water sorption. It was used as polymeric matrix an unsaturated polyester resin and Caroá fibers originated from Paraiba state. The composites were made with different fiber contents, cut approximately with 3cm length and molded by compression in a metallic mould in order to evaluate its mechanical properties. The better mechanical composition of the sample was chosen to water sorption test in sample with dimension 20x20mm² and 3cm and 6cm thickness in the temperature of 25°C, 50°C and 70°C. A tri-dimensional transient mathematical modeling was used to predict mass transfer during the water sorption by these composites. Results indicates enhancement of mechanical properties of composites with 24% of mass made of the fibers until a critical volume of 30%. For the impact resistance this increases occurred for all compositions because of the transference of tension for the fibers. The results for elasticity modulus of composite shows that are higher than to the matrix for all fiber contents lower than 45%, which is related with the fiber properties. The water sorption kinetic was related with the area/volume relationship. We can observe that in short period of time, 100 hours, that composites with lower area/volume relationship absorbs water faster. On the order hand, the ones with higher area/volume relationship show more sorption in longer periods of time. The equilibrium moisture content for 30% fiber composite show results of 14.48% in 25°C and 16.52% in 70°C, for 3mm and 6mm thickness respectively. Mathematical models used to obtain numerical solution of water sortion in composites enhanced with Caroá fibers were satisfactory and the finite volume techniques was adequated to discretize the diffusion equation in Cartesian coordinate system for a parallelepiped solids, permitting the analyze of transient diffusive phenomena in this solids.

O principal objetivo deste trabalho é estudar as singularidades e hipersingularidades existentes nas formulações: singular - clássica - e hipersingular no Método dos Elementos de Contorno (MEC). Também é proposto um esquema residual h-adaptativo para a solução numérica do problema físico governado pela equação de Laplace. Usa-se malha poligonal, juntamente, com funções de interpolação - distribuição - de forma, dos tipos: constantes e lineares. Para controlar o erro a posteriori, é considerado o valor do resíduo, fora dos pontos de colocação. Também é testada uma técnica de quadratura numérica chamada adaptativa, específica para subelementos, no sentido de verificar se a precisão no cálculo das integrais com singularidades é melhorada. O uso de funções hierárquicas é discutido na forma de um algoritmo para atualização da matriz principal do sistema linear. / The main purpose of this work is to study the existing singularities and hypersingularities in the Boundary Element Method (BEM) with singular - classical - and hypersingular formulations. Also, an h-adaptive residual scheme for the numerical solution of the physical problem, driven by Laplace equation, is proposed. Boundary polygonal mesh, with constant and linear interpolation - distribution - shape functions together are used. To control the a posteriori error, is considered the residue value outside the collocation points. Also, a sub-element specific adaptive numerical quadrature technique, in an effort to verify if the precision when dealing with integrals possessing singularities is increased, is tested. The use of hierarchical functions is discussed, as an algorithm to update the linear system main matrix.

Do ponto de vista da hidrodinâmica clássica, o problema de impacto hidrodinâmico configura-se como um problema de contorno com fronteiras móveis cuja posição deve ser determinada simultaneamente à solução da equação de campo. Essa característica traz dificuldades para obtenção de soluções analíticas e numéricas. Nesse sentido, o presente trabalho propõe o desenvolvimento de um método numérico específico para analisar o problema de impacto hidrodinâmico de corpos sólidos rígidos contra a superfície livre da água. A solução da equação dinâmica não linear do problema de impacto depende da determinação do tensor de massa adicional a cada instante de tempo, o qual depende da posição e atitude do corpo no instante considerado. Um método variacional específico é empregado, através do qual os coeficientes de massa adicional são determinados com erro de segunda ordem, na posição considerada. Tal método é exemplo de técnicas numéricas dessingularizadas, através das quais o potencial de velocidade é aproximado em um espaço finito-dimensional formado por funções-teste derivadas de soluções potenciais elementares, tais como pólos, dipolos, anéis de dipolos, de vórtices, etc. O problema potencial de impacto hidrodinâmico, que se caracteriza pela dominância das forças de inércia, é formulado admitindo-se a superfície líquida como equipotencial, o que permite a analogia com o limite assintótico de frequência infinita do problema de radiação de ondas causada pelo movimento de corpos flutuantes. O método desenvolvido é então aplicado ao caso de impacto vertical de corpos axissimétricos, formulando o problema sob o chamado modelo de von Kármán generalizado (GvKM). Nesse modelo as condições de contorno na geometria exata do corpo são satisfeitas, porém os efeitos do empilhamento de água junto às raízes do jato, que se forma ao longo da intersecção com a superfície livre, não são considerados no caso geral. Resultados numéricos do coeficiente de massa adicional para uma família de esferoides são apresentados e tabulados para o pronto uso em análise e projeto. Além disso, considerações acerca da inclusão do efeito de empilhamento de água junto às raízes do jato, ou seja, da elevação da superfície livre são também feitas para o caso de esferas, fazendo uso de abordagens analíticas encontradas na literatura especializada. / In terms of classical hydrodynamics, the hydrodynamic impact problem is characterized as a boundary problem with moving boundary which position must be determined simultaneously with the solution of the field equation. This feature brings difficulties to get analytical and numerical solutions. In this sense, the purpose of this work is to present a variational method technique specifically designed for the hydrodynamic impact problem of axisymmetric rigid bodies on the free surface. The solution of the nonlinear dynamic equation of the impacting motion depends on the determination of the added mass tensor and its derivative with respect to time at each integration time step. This is done through a variational method technique that leads to a second-order error approximation for the added mass if a first-order error approximation is sought for the velocity potential. This method is an example of desingularized numerical techniques, through which the velocity potential is approximated in a sub-space of finite dimension, formed by trial functions derived from elementary potential solutions, such as poles, dipoles, and vortex rings, which are placed inside the body. The potential problem of hydrodynamic impact, characterized by the dominance of inertial forces, is here formulated by assuming the liquid surface as equipotential, what allows the analogy with the infinity frequency limit in the usual free surface oscillating floating body problem. The method is applied to the vertical hydrodynamic impact of axisymmetric bodies within the so-called Generalized von Kármán Model (GvKM). In such approach, the exact body boundary condition is full-filled and the wet correction is not taken into account. Numerical results for the added mass coefficient for a family of spheroids are presented. Moreover, considerations are made on the effects of the free surface elevation for the specific case of an impacting sphere, through analytical approaches.