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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.
61

Semiparametric regression with random effects

Lee, Sungwook, January 1997 (has links)
Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 114-117). Also available on the Internet.
62

Spline based controller for nonlinear systems

Karimi, Ali, January 1900 (has links)
Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains viii, 77 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 75-77).
63

2D coordinate space Hartree-Fock-Bogoliubov calculations for neutron-rich nuclei in the A [approximately equal to] 100 mass region

Blazkiewicz, Artur Robert. January 2005 (has links)
Thesis (Ph. D. in Physics)--Vanderbilt University, Dec. 2005. / Title from title screen. Includes bibliographical references.
64

Modelagem geológica por simplóides de Bézier / Geological modeling using Bézier simploids

Freitas, Lucas Batista 18 August 2018 (has links)
Orientador: Stolfi Jorge, Martin Tygel / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Computação / Made available in DSpace on 2018-08-18T10:11:18Z (GMT). No. of bitstreams: 1 Freitas_LucasBatista_D.pdf: 3567527 bytes, checksum: d7c6af3cd4ddab0e7eacc837ade4b106 (MD5) Previous issue date: 2010 / Resumo: A exploração e monitoramento de um reservatório de petróleo ou gás natural exige conhecimento bastante detalhado das estruturas geológicas da região de interesse. A representação matemática e computacional desse conhecimento é um modelo geofísico. Nesta tese descrevemos um sistema geral para modelagem geofísica baseado em elementos finitos polinomiais de graus arbitrários. Adotamos uma abordagem comum na indústria, em que a geometria e as propriedades das formações geológicas são representadas por funções definidas por partes, ou splines, que consistem da justaposição de tais elementos. Neste contexto, apresentamos contribuições teóricas e computacionais. A principal contribuição teórica é uma teoria unificada dos elementos simploidais de Bézier, que incluem os tipos de elementos finitos mais comuns na modelagem por malhas - tais como arcos de Bézier, retalhos de Bézier triangulares e retangulares, blocos de Bézier tetraédricos, prismáticos e hexaédricos, e suas generalizações para dimensões arbitrárias, com graus independentes em cada eixo e cada componente. Como parte testa teoria, desenvolvemos fórmulas genéricas explícitas para conversão entre estes vários tipos de blocos, bem como diferenciação, reparametrização afim e elevação de grau. As contribuições computacionais desta tese incluem a implementação dessa teoria na forma de uma biblioteca (BezEl) que permite a representação e manipulação eficiente de malhas de elementos de Bézier simplodais com dimensões e graus arbitrários. Outra contribuição original desta tese é uma metodologia para realizar o traçado eficiente de raios em malhas de elementos simploidais / Abstract: The exploration and monitoring of a hydrocarbon reservoir demand a very detailed knowledge about the geological structures of the target area. The mathematical and computation representation of this knowledge is a geophysical model. In this thesis, we describe a general system for geophysical modeling based on polynomial finite elements of arbitrary degree. We adopted an approach that is popular in industry, whereby both the geometry and the physical properties of the geological formations are represented by piecewise-defined functions, or splines, that are obtained by the assembly of many such elements. In this context, we present both theoretical and computational contributions. The main theoretical contribution is a unified theory of simploidal Bézier elements, which include the element types most common in mesh based modeling - such as Bézier arcs, triangular and rectangular Bézier patches, tetrahedral, prismatic and hexahedral Bézier blocks, and their generalizations to arbitrary dimensions with independent degrees on each axis and each component. As part of this theory, we developed general explicit formulas for the conversion between these various block types, as well as differentiation, affine reparametrization and degree raising. The computational contributions of this thesis include the implementation of this theory as a library (BezEl) that allows efficient representation and manipulation of meshes of simploidal Bézier elements with arbitrary dimension and degree. Another original contribution of this thesis is a methodology for performing efficient ray tracing in meshes of such simploidal elements / Doutorado / Computação Grafica / Doutor em Ciência da Computação
65

Analise não-parametrica de dados funcionais : uma aplicação a quimiometria / Nonparametric functional data analysis applications to chemometrics

Saraiva, Marley Apolinario 12 November 2009 (has links)
Orientador: Ronaldo Dias / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matematica, Estatistica e Computação Cientifica / Made available in DSpace on 2018-08-14T19:32:09Z (GMT). No. of bitstreams: 1 Saraiva_MarleyApolinario_M.pdf: 2908252 bytes, checksum: 4161f517f546fb5d5dcd7a8988f11e11 (MD5) Previous issue date: 2009 / Resumo: Devido à grande evolução dos computadores tornou-se comum coletar dados de alta dimensão. A quimiometria, que é a aplicação de métodos estatísticos e matemáticos à dados de origem química, pode ser citada como exemplo, pois nestes casos os dados são espectros que geralmente são observados em vários comprimentos de onda. O problema de como combinar estes espectros de forma ótima com o objetivo de aproximar medidas de concentrações é um problema de calibração multivariada. Em geral, esta calibração é feita com técnicas de estatística multivariada, que por sua vez, apresentam sérias dificuldades em lidar com a alta dimensão dos dados. Nesta dissertação propomos um modelo que considere as características funcionais intrínsecas deste tipo de problema, uma vez que as técnicas de estatística multivariada não consideram tais características. Algumas das técnicas de estatística multivariada mais utilizadas são de regressão linear múltipla multivariada (MLR) e regressão por mínimos quadrados parciais (PLS). Estas técnicas resumem a informação da matriz de dados, seja por escolha de quem está modelando, seja por análise de componentes principais e isto pode ocasionar perda de informa ações importantes para as análises. Devido a estas dificuldades propomos um modelo que considera o dado como ele é, uma função, e não como um dado multivariado e propomos também um modelo funcional para a estrutura de covariância. Ambos os modelos propostos utilizam a análise de dados funcionais (ADF) e por isso não apresentam as dificuldades comuns dos métodos de estatística multivariada, uma vez que a alta dimensão dos dados não é tão restritiva quanto nas técnicas multivariadas. / Abstract: With the computer evolution, the high dimension data collection has become common. The chemometrics, which is the application of statistical and mathematical methods to the chemical data, it can be an example. In these cases the data are spectra that are usually observed in several wavelengths. The problem of how to combine these spectra optimally with the goal of bringing the measurement of concentrations is a multivariate calibration problem. In general, this calibration is done with multivariate statistical techniques but there are severe difficulties in dealing with high-dimensional data. In this dissertation we propose a model that considers the intrinsic functional characteristics of this kind of problem, since the multivariate statistics techniques do not consider such features. Some of useful multivariate statistical techniques are multivariate linear regression (MLR) and partial leas squares (PLS). These techniques summarize the information of the data matrix, either by choosing who is modeling or by principal component analysis and this can cause lost of important information for analysis. Because of these difficulties we propose a model that considers the data as it is, a function, not as a multivariate data and we also propose a working model for the covariance structure. Both proposed models using functional data analysis (ADF) and therefore do not have the common difficulties of the methods of multivariate statistics, since the high-dimensional data is not as restrictive as in multivariate analysis. / Mestrado / Mestre em Estatística
66

Aproximação de funções irregularmente amostradas com bases hierárquicas adaptativas de elementos tensoriais compactos / Sampled irregularly functions approximation with tensorial elements compacts adaptive hierarchical bases

Souza, Gilcélia Regiane, 1978 10 November 2013 (has links)
Orientador: Jorge Stolfi / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Matemática, Estatística e Computação Científica / Made available in DSpace on 2018-08-23T21:50:35Z (GMT). No. of bitstreams: 1 Souza_GilceliaRegiane_D.pdf: 73618372 bytes, checksum: 838a3831340c678bc9b7622ebc3ed1ca (MD5) Previous issue date: 2013 / Resumo: Nesta tese, desenvolvemos algoritmos eficientes para a aproximação de funções que tem importantes detalhes de pequena escala confinados em pequenas região do domínio. Assumimos que a função objetivo é amostrada em um número finito de pontos dados, com densidade uniforme ou densidade não uniforme. Neste trabalho optamos por utilizar uma base multinível (ou multiresolução), em que os centros dos elementos em cada nível são um subconjunto de uma grade regular de centros, independentemente dos pontos de amostragem. As bases em questão têm estrutura multiescala semelhante à usada na análise wavelet em d dimensões. No entanto, os seus elementos são funções explícitas definidas pelo produto de d funções univariadas de suporte limitado (tais como pseudo-gaussianas modelada por polinômios truncados ou spline). Descrevemos um algoritmo incremental de aproximação, que procede do nível mais grosseiro para o mais detalhado, sendo que em cada nível são usados apenas os elementos da base localizados nas regiões onde a aproximação é ainda insuficientemente precisa. Em cada nível, usamos um processo iterativo com o método de mínimos quadrados que é projetado para ignorar dados discrepantes e detalhes que só podem ser aproximados em escalas menores / Abstract: I this thesis we develop efficient algorithms for the approximation of functions that have important small-scale details confined to small portions of their domain. We assume that the target function is sampled at a finite number of data points, with either uniform or non-uniform density. In this thesis we chose to use a multilevel (or multiresolution) basis in which the elements centers at each level are a subset of a regular grid of centers, regardless of the sampling points. The bases in question have multiscale structure similar to that used in wavelet analysis in d dimensions. However, its elements are explicit functions defined by the product of d univariate functions of limited support (such as pseudo-Gaussians modeled by truncated polynomials or splines). We describe an incremental algorithm, which proceeds from the coarser level to the most detailed one, and in each level uses only the elements of the basis that are located in the regions where the approximation is still insufficiently precise. At each level, we use an iterative least squares methods that is designed to ignore outlier data and details that can only be approximated at smaller scales / Doutorado / Matematica Aplicada / Doutora em Matemática Aplicada
67

Desenvolvimento de um modelo de fluidodinâmica computacional para o estudo da dispersão de efluentes miscíveis em rios com contornos irregulares / Development of a fluid dynamic model to study the dispersion of miscible effluents in river sections of irregular geometry

Souza, Bruno Abdalla de 19 August 2018 (has links)
Orientadores: Jose Roberto Nunhez, Everton Moraes Matos / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-19T09:09:57Z (GMT). No. of bitstreams: 1 Souza_BrunoAbdallade_M.pdf: 2758240 bytes, checksum: dff63551b21966090787c9b791a8e131 (MD5) Previous issue date: 2009 / Resumo: Este trabalho apresenta um modelo fluido-dinamico para a simulação da dispersão continua de efluentes miscíveis em rios de geometria irregular. Devido a geometria irregular do rio, as equações de conservação de massa e de momentum são descritas em um sistema de coordenadas generalizadas. Utilizando pontos conhecidos de cada margem de rio, foi usado o Método Spline Cúbico para encontrar as funções mais suaves possíveis que passem por esses pontos. Estas funções tornaram possível a obtenção das linhas de corrente e, então, usando o principio da ortogonalidade, as linhas potenciais foram estimadas. Desta forma, a malha e formada pela intersecção entre as linhas potenciais e as linhas de corrente. Apesar da irregularidade da geometria, as variáveis não costumam apresentar altos gradientes e, por isso, não e necessário utilizar um complexo modelo de turbulência. Portanto, um modelo de turbulência de ordem zero foi escolhido para considerar a turbulência. As equações de conservação de massa e de momentum foram discretizadas através do Método dos Volumes Finitos. Os resultados mostram que o modelo e satisfatório na obtenção dos perfis de velocidade e concentração do efluente de seções de rio de geometria irregular. Alem disso, foi previsto com sucesso a influencia no perfil de concentração do efluente da variação da vazão do rio, do coeficiente de difusão do efluente na água, da concentração do efluente descartada na margem do rio, da área afetada pela emissão do efluente e da região da emissão do efluente / Abstract: This work presents a fluid dynamic model for the simulation of the dispersion of miscible effluents in river sections of irregular geometry. Due to the irregular geometry, the equations of mass and momentum conservation are described in a generalized coordinate system. Using known coordinates (points) of each riverbank, it was used a modified Cubic Spline Method to find the smoother functions to fit these known points. These functions make possible to obtain the streamlines and then using the principle of orthogonality, the potential lines were estimated. So the mesh is formed by points obtained with the intersection of the potential lines and the streamlines. Despite the irregularity of the geometry, the variables do not usually present high gradients and, for this reason, it is not necessary to use a complex turbulence model for this study. Therefore, a zero-order turbulence model was chosen to account for turbulence. The equations for mass and momentum conservation were discretized using the Finite Volume Method. The results show that the model is satisfactory to obtain the effluent velocity and concentration for river sections with irregular geometry. Moreover, it was successfully predicted the influence in the effluent concentration profile of the variations of the river flow, the diffusion coefficient of the effluent in water, the effluent concentration discarded at the riverbank, the area affected by effluent emission and the region of effluent emission / Mestrado / Desenvolvimento de Processos Químicos / Mestre em Engenharia Química
68

A Spline Framework for Optimal Representation of Semiperiodic Signals

Guilak, Farzin G. 24 July 2015 (has links)
Semiperiodic signals possess an underlying periodicity, but their constituent spectral components include stochastic elements which make it impossible to analytically determine locations of the signal's critical points. Mathematically, a signal's critical points are those at which it is not differentiable or where its derivative is zero. In some domains they represent characteristic points, which are locations indicating important changes in the underlying process reflected by the signal. For many applications in healthcare, knowledge of precise locations of these points provides key insight for analytic, diagnostic, and therapeutic purposes. For example, given an appropriate signal they might indicate the start or end of a breath, numerous electrophysiological states of the heart during the cardiac cycle, or the point in a stride at which the heel impacts the ground. The inherent variability of these signals, the presence of noise, and often, very low signal amplitudes, makes accurate estimation of these points challenging. There has been much effort in automatically estimating characteristic point locations. Approaches include algorithms operating in the time domain, on various transformations of the data, and using different models of the signal. These methods apply a wide variety of techniques ranging from simple thresholds and search windows to sophisticated signal processing and pattern recognition algorithms. Existing approaches do not explicitly use prior knowledge of characteristic point locations in their estimation. This dissertation first develops a framework for an efficient parametric representation of semiperiodic signals using splines. It then implements an instance of that framework to optimally estimate locations of characteristic points, incorporating prior knowledge from manual annotations on training data. Splines represent signals in a piecewise manner by applying an interpolant to constraint points on the signal known as knots. The framework allows choice of interpolant, objective function, knot initialization algorithm, and optimization algorithm. After initialization it iteratively modifies knot locations until the objective function is met. For optimal estimation of characteristic points the framework relies on a Bayesian objective function, the a posteriori probability of knot locations given the observed signal. This objective function fuses prior knowledge, the observed signal, and its spline estimate. With a linear interpolant, knot locations after optimization serve as estimates of the signal's characteristic points. This implementation was used to determine locations of 11 characteristic points on a prospective test set comprising 200 electrocardiograph (ECG) signals from 20 subjects. It achieved a mean error of -0.4 milliseconds, less than one quarter of a sample interval. A low bias is not sufficient, however, and the literature recognizes error variance to be the more important factor in assessing accuracy. Error variances are typically compared to the variance of manual annotations provided by reviewers. The algorithm was within two standard deviations for six of the characteristic points, and within one sample interval of this criterion for another four points. The spline framework described here provides a complementary option to existing methods for parametric modeling of semiperiodic signals, and can be tailored to represent semiperiodic signals with high fidelity or to optimally estimate locations of their characteristic points.
69

Initial-value Technique For Singularly Perturbed Two Point Boundary Value Problems Via Cubic Spline

Negron, Luis G. 01 January 2010 (has links)
A recent method for solving singular perturbation problems is examined. It is designed for the applied mathematician or engineer who needs a convenient, useful tool that requires little preparation and can be readily implemented using little more than an industry-standard software package for spreadsheets. In this paper, we shall examine singularly perturbed two point boundary value problems with the boundary layer at one end point. An initial-value technique is used for its solution by replacing the problem with an asymptotically equivalent first order problem, which is, in turn, solved as an initial value problem by using cubic splines. Numerical examples are provided to show that the method presented provides a fine approximation of the exact solution. The first chapter provides some background material to the cubic spline and boundary value problems. The works of several authors and a comparison of different solution methods are also discussed. Finally, some background into the specific singularly perturbed boundary value problems is introduced. The second chapter contains calculations and derivations necessary for the cubic spline and the initial value technique which are used in the solutions to the boundary value problems. The third chapter contains some worked numerical examples and the numerical data obtained along with most of the tables and figures that describe the solutions. The thesis concludes with some reflections on the results obtained and some discussion of the error bounds on the calculated approximations to the exact solutions for the numeric examples discussed
70

Bivariate box splines and surface subdivision

Kelil, Abey Sherif 03 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2013. / Please refer to full text to view abstract.

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