Página 1 dos resultados de 29 itens digitais encontrados em 0.207 segundos

‣ Wavelet-Galerkin method for one-dimensional elastoplasticity and damage problems: Constitutive modeling and computational aspects

NAVARRO, Helio A.; KAIBARA, Magda K.; RUBERT, Jose B.; MONTAGNOLI, Arlindo N.; CABEZAS-GOMEZ, Luben; SILVA, Renato C. da
Fonte: ELSEVIER SCIENCE INC Publicador: ELSEVIER SCIENCE INC
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
89.51609%
This work presents an analysis of the wavelet-Galerkin method for one-dimensional elastoplastic-damage problems. Time-stepping algorithm for non-linear dynamics is presented. Numerical treatment of the constitutive models is developed by the use of return-mapping algorithm. For spacial discretization we can use wavelet-Galerkin method instead of standard finite element method. This approach allows to locate singularities. The discrete formulation developed can be applied to the simulation of one-dimensional problems for elastic-plastic-damage models. (C) 2007 Elsevier Inc. All rights reserved.

‣ Computational aspects of harmonic wavelet Galerkin methods and an application to a precipitation front propagation model

BARROS, Saulo R. M.; PEIXOTO, Pedro S.
Fonte: PERGAMON-ELSEVIER SCIENCE LTD Publicador: PERGAMON-ELSEVIER SCIENCE LTD
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
79.70488%
This article is dedicated to harmonic wavelet Galerkin methods for the solution of partial differential equations. Several variants of the method are proposed and analyzed, using the Burgers equation as a test model. The computational complexity can be reduced when the localization properties of the wavelets and restricted interactions between different scales are exploited. The resulting variants of the method have computational complexities ranging from O(N(3)) to O(N) (N being the space dimension) per time step. A pseudo-spectral wavelet scheme is also described and compared to the methods based on connection coefficients. The harmonic wavelet Galerkin scheme is applied to a nonlinear model for the propagation of precipitation fronts, with the front locations being exposed in the sizes of the localized wavelet coefficients. (C) 2011 Elsevier Ltd. All rights reserved.; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); CNPq

‣ Avaliação do método Wavelet-Galerkin multi-malha para caracterização das propriedades de petróleo e subprodutos.; Wavelet-Galerkin multigrid method's evaluation for characterization of the properties of petroleum and subproducts.

Carranza Oropeza, María Verónica
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 22/02/2007 Português
Relevância na Pesquisa
69.551%
Atualmente, restrições ambientais impostas à industria de refino de petróleo estão fazendo com que se procure otimizar os seus processos. Uma das maneiras de se alcançar este objetivo é através da melhoria dos métodos analíticos de caracterização e dos métodos de representação, cuja finalidade é permitir maior precisão na simulação. O método mais comum de representação através de pseudocomponentes, apresenta algumas desvantagens, as quais não permitem precisão adequada em determinadas situações. Uma nova metodologia apresentada neste trabalho, que permite superar essas desvantagens foi aplicada em um exemplo de flash de petróleo. Esta metodologia envolve varias etapas: a implementação dos algoritmos necessários à representação das composições da mistura por funções de distribuição contínua e sua aproximação por funções wavelets, e a simplificação do modelo flash com a discretização "Wavelet-Galerkin" e sua resolução através de um enfoque multi-malha adaptativo. Neste contexo, na primeira etapa da tese foram apresentados diferentes aspectos relacionados ao processo complexo de caracterização de petróleos, que consideram sua importância tanto econômica quanto tecnológica. Mostraram-se também...

‣ Resolução numérica de EDPs utilizando ondaletas harmônicas; Numerical resolution of partial differential equations using harmonic wavelets

Peixoto, Pedro da Silva
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 16/07/2009 Português
Relevância na Pesquisa
39.207837%
Métodos de resolução numérica de equações diferenciais parciais que utilizam ondaletas como base vêm sendo desenvolvidos nas últimas décadas, mas existe uma carência de estudos mais profundos das características computacionais dos mesmos. Neste estudo analisou-se detalhadamente um método espectral de Galerkin com base de ondaletas harmônicas. Revisou-se a teoria matemática referente às ondaletas harmônicas, que mostrou ter grande similaridade com a teoria referente à base trigonométrica de Fourier. Diversos testes numéricos foram realizados. Ao analisarmos a resolução da equação do transporte linear, e também de transporte não linear (equação de Burgers), obtivemos boas aproximações da solução esperada. O custo computacional obtido foi similar ao método com base de Fourier, mas com ondaletas harmônicas foi possível usar a localidade das ondaletas para detectar características de localidade do sinal. Analisamos ainda uma abordagem pseudo-espectral para os casos não lineares, que resultaram em um expressivo aumento de eficiência. Tendo em vista o uso das propriedades de localidade das ondaletas, usamos o método de Galerkin com base de ondaletas harmônicas para resolver um sistema de equações referente a um modelo de propagação de frentes de precipitação. O método mostrou boas aproximações das soluções esperadas...

‣ Wavelet-Galerkin method for one-dimensional elastoplasticity and damage problems: Constitutive modeling and computational aspects

Navarro, Helio A.; Kaibara, Magda K.; Rubert, Jose B.; Montagnoli, Arlindo N.; Cabezas-Gomez, Luben; da Silva, Renato C.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 904-915
Português
Relevância na Pesquisa
89.51609%
This work presents an analysis of the wavelet-Galerkin method for one-dimensional elastoplastic-damage problems. Time-stepping algorithm for non-linear dynamics is presented. Numerical treatment of the constitutive models is developed by the use of return-mapping algorithm. For spacial discretization we can use wavelet-Galerkin method instead of standard finite element method. This approach allows to locate singularities. The discrete formulation developed can be applied to the simulation of one-dimensional problems for elastic-plastic-damage models. (C) 2007 Elsevier B.V. All rights reserved.

‣ A combined wavelet-element free Galerkin method for numerical calculations of electromagnetic fields

Yang, S. Y.; Ni, G. Z.; Cardoso, JR; Ho, S. L.; Machado, J. M.
Fonte: Institute of Electrical and Electronics Engineers (IEEE) Publicador: Institute of Electrical and Electronics Engineers (IEEE)
Tipo: Artigo de Revista Científica Formato: 1413-1416
Português
Relevância na Pesquisa
49.130396%
A combined wavelet-element free Galerkin (EFG) method is proposed for solving electromagnetic EM) field problems. The bridging scales are used to preserve the consistency and linear independence properties of the entire bases. A detailed description of the development of the discrete model and its numerical implementations is given to facilitate the reader to. understand the proposed algorithm. A numerical example to validate the proposed method is also reported.

‣ Wavelet-Galerkin method for computations of electromagnetic fields - Computation of connection coefficients

Yang, S. Y.; Ni, G. Z.; Ho, S. L.; Machado, J. M.; Rahman, M. A.; Wong, H. C.
Fonte: Institute of Electrical and Electronics Engineers (IEEE) Publicador: Institute of Electrical and Electronics Engineers (IEEE)
Tipo: Artigo de Revista Científica Formato: 644-648
Português
Relevância na Pesquisa
99.69555%
One of the keg issues which makes the wavelet-Galerkin method unsuitable for solving general electromagnetic problems is a lack of exact representations of the connection coefficients. This paper presents the mathematical formulae and computer procedures for computing some common connection coefficients, the characteristic of the present formulae and procedures is that the arbitrary point values of the connection co-efficients, rather than the dyadic point values, can be determined. A numerical example is also given to demonstrate the feasibility of using the wavelet-Galerkin method to solve engineering field problems.

‣ Wavelet-galerkin method for computations of electromagnetic fields-computation of connection coefficients

Yang, Shiyou; Ni, Guangzheng; Ho, S. L.; Machado, Jose Marcio; Rahman, M. A.; Wong, H. C.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 644-648
Português
Relevância na Pesquisa
99.73187%
One of the key issues which makes the waveletGalerkin method unsuitable for solving general electromagnetic problems is a lack of exact representations of the connection coefficients. This paper presents the mathematical formulae and computer procedures for computing some common connection coefficients. The characteristic of the present formulae and procedures is that the arbitrary point values of the connection coefficients, rather than the dyadic point values, can be determined. A numerical example is also given to demonstrate the feasibility of using the wavelet-Galerkin method to solve engineering field problems. © 2000 IEEE.

‣ O metodo de Galerkin descontinuo com difusividade implicita e h-adaptabilidade baseada em tecnicas Wavelet

Jorge Lizardo Diaz Calle
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 15/01/2002 Português
Relevância na Pesquisa
49.96622%
O presente trabalho apresenta técnicas inovadoras para a aproximação numérica de leis de conservação sobre malhas não estruturadas. Implementa se um algoritmo h-adaptativo que utiliza um esquema numérico baseado em espaços de aproximação de funções polinomiais descontínuas. A escolha adaptável do refinamento h é feita mediante uma análise da regularidade da solução utilizando-se técnicas de análise wavelet. Esta análise permite determinar sub-domínios ou regiões de suavidade nos quais os elementos finitos são levados a níveis menos refinados, ou regiões de singularidade nas quais os elementos são refinados. Para evitar possíveis oscilações numéricas, um termo difusivo é aplicado no interior dos elementos finitos de uma região de singularidade ou próximo a ela. A análise wavelet também é utilizada para estabelecer a magnitude do termo difusivo. O esquema proposto aproveita idéias do método Runge-Kutta Galerkin descontínuo [16] e o método streamline difusion [33]. Como resultado, o esquema, na sua forma mais simples, é o método de volumes finitos h-adaptativo, e no caso de usar ordem de interpolação p ? 1, é o método Galerkin descontínuo h-adaptativo com esquema Euler no tempo e dispensando o uso de limitadores. é apresentado um estudo para estabelecer uma relação adequada entre o valor do número CFL (condição de estabilidade - Courant Priedrichs Lewi) e o coeficiente máximo do termo difusivo interno de tal forma a garantir a estabilidade do esquema e obter precisão numérica ótima. Quando o termo difusivo ?? ?...

‣ Wavelet Galerkin method for solving singular integral equations

Maleknejad,K; Nosrati,M; Najafi,E
Fonte: Sociedade Brasileira de Matemática Aplicada e Computacional Publicador: Sociedade Brasileira de Matemática Aplicada e Computacional
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2012 Português
Relevância na Pesquisa
47.889453%
An effective technique upon linear B-spline wavelets has been developed for solving weakly singular Fredholm integral equations. Properties of these wavelets and some operational matrices are first presented. These properties are then used to reduce the computation of integral equations to some algebraic equations. The method is computationally attractive, and applications are demonstrated through illustrative examples. Mathematical subject classification: 45A05, 32A55, 34A25, 65T60.

‣ Wavelet-Petrov-Galerkin Method for the Numerical Solution of the KdV Equation

Villegas G., Jairo; Casta??o B., Jorge; Duarte V., Julio; Fierro Y., Esper
Fonte: Hikari; Grupo de Investigaci??n An??lisis Funcional y Aplicaciones; Escuela de Ciencias y Humanidades Publicador: Hikari; Grupo de Investigaci??n An??lisis Funcional y Aplicaciones; Escuela de Ciencias y Humanidades
Tipo: info:eu-repo/semantics/article; article; Art??culo; publishedVersion
Português
Relevância na Pesquisa
69.495015%
The development of numerical techniques for obtaining approximate solutions of partial differential equations has very much increased in the last decades. Among these techniques are the finite element methods and finite difference. Recently, wavelet methods are applied to the numerical solution of partial differential equations, pioneer works in this direction are those of Beylkin, Dahmen, Jaffard and Glowinski, among others. In this paper, we employ the Wavelet-Petrov-Galerkin method to obtain the numerical solution of the equation Korterweg-de Vries (KdV).

‣ An efficient space-time adaptive wavelet Galerkin method for time-periodic parabolic partial differential equations

Kestler, Sebastian; Steih, Kristina; Urban, Karsten
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 22/01/2014 Português
Relevância na Pesquisa
59.19213%
We introduce a multitree-based adaptive wavelet Galerkin algorithm {for} space-time discretized linear parabolic partial differential equations, focusing on time-periodic problems. It is shown that the method converges with the best possible rate in linear complexity and can be applied for a wide range of wavelet bases. We discuss the implementational challenges arising from the Petrov-Galerkin nature of the variational formulation and present numerical results for the heat and a convection-diffusion-reaction equation.

‣ On Wavelet-Galerkin methods for Semilinear Parabolic Equations with Additive Noise

Kovács, M.; Larsson, S.; Urban, K.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
59.04048%
We consider the semilinear stochastic heat equation perturbed by additive noise. After time-discretization by Euler's method the equation is split into a linear stochastic equation and a non-linear random evolution equation. The linear stochastic equation is discretized in space by a non-adaptive wavelet-Galerkin method. This equation is solved first and its solution is substituted into the nonlinear random evolution equation, which is solved by an adaptive wavelet method. We provide mean square estimates for the overall error.; Comment: 18 pages

‣ Multiresolution Galerkin method for solving the functional distribution of anomalous diffusion described by time-space fractional diffusion equation

Zhang, Zhijiang; Deng, Weihua
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 09/09/2015 Português
Relevância na Pesquisa
48.953364%
The functional distributions of particle trajectories have wide applications, including the occupation time in half-space, the first passage time, and the maximal displacement, etc. The models discussed in this paper are for characterizing the distribution of the functionals of the paths of anomalous diffusion described by time-space fractional diffusion equation. This paper focuses on providing effective computation methods for the models. Two kinds of time stepping schemes are proposed for the fractional substantial derivative. The multiresolution Galerkin method with wavelet B-spline is used for space approximation. Compared with the finite element or spectral polynomial bases, the wavelet B-spline bases have the advantage of keeping the Toeplitz structure of the stiffness matrix, and being easy to generate the matrix elements and to perform preconditioning. The unconditional stability and convergence of the provided schemes are theoretically proved and numerically verified. Finally, we also discuss the efficient implementations and some extensions of the schemes, such as the wavelet preconditioning and the non-uniform time discretization.; Comment: 31 pages, 1 figure

‣ Wavelet Galerkin method for fractional elliptic differential equations

Deng, Weihua; Lin, Yuwei; Zhang, Zhijiang
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 27/05/2014 Português
Relevância na Pesquisa
69.52571%
Under the guidance of the general theory developed for classical partial differential equations (PDEs), we investigate the Riesz bases of wavelets in the spaces where fractional PDEs usually work, and their applications in numerically solving fractional elliptic differential equations (FEDEs). The technique issues are solved and the detailed algorithm descriptions are provided. Compared with the ordinary Galerkin methods, the wavelet Galerkin method we propose for FEDEs has the striking benefit of efficiency, since the condition numbers of the corresponding stiffness matrixes are small and uniformly bounded; and the Toeplitz structure of the matrix still can be used to reduce cost. Numerical results and comparison with the ordinary Galerkin methods are presented to demonstrate the advantages of the wavelet Galerkin method we provide.; Comment: 20 pages, 0 figures

‣ Wavelet methods to eliminate resonances in the Galerkin-truncated Burgers and Euler equations

Pereira, Rodrigo M.; Nguyen-van-yen, Romain; Farge, Marie; Schneider, Kai
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
39.470835%
It is well known that solutions to the Fourier-Galerkin truncation of the inviscid Burgers equation (and other hyperbolic conservation laws) do not converge to the physically relevant entropy solution after the formation of the first shock. This loss of convergence was recently studied in detail in [S. S. Ray et al., Phys. Rev. E 84, 016301 (2011)], and traced back to the appearance of a spatially localized resonance phenomenon perturbing the solution. In this work, we propose a way to remove this resonance by filtering a wavelet representation of the Galerkin-truncated equations. A method previously developed with a complex-valued wavelet frame is applied and expanded to embrace the use of real-valued orthogonal wavelet basis, which we show to yield satisfactory results only under the condition of adding a safety zone in wavelet space. We also apply the complex-valued wavelet based method to the 2D Euler equation problem, showing that it is able to filter the resonances in this case as well.

‣ A wavelet-Galerkin algorithm of the E/B decomposition of CMB polarization maps

Cao, Liang; Fang, Li-Zhi
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 24/10/2009 Português
Relevância na Pesquisa
49.19213%
We develop an algorithm of separating the $E$ and $B$ modes of the CMB polarization from the noisy and discretized maps of Stokes parameter $Q$ and $U$ in a finite area. A key step of the algorithm is to take a wavelet-Galerkin discretization of the differential relation between the $E$, $B$ and $Q$, $U$ fields. This discretization allows derivative operator to be represented by a matrix, which is exactly diagonal in scale space, and narrowly banded in spatial space. We show that the effect of boundary can be eliminated by dropping a few DWT modes located on or nearby the boundary. This method reveals that the derivative operators will cause large errors in the $E$ and $B$ power spectra on small scales if the $Q$ and $U$ maps contain Gaussian noise. It also reveals that if the $Q$ and $U$ maps are random, these fields lead to the mixing of the $E$ and $B$ modes. Consequently, the $B$ mode will be contaminated if the powers of $E$ modes are much larger than that of $B$ modes. Nevertheless, numerical tests show that the power spectra of both $E$ and $B$ on scales larger than the finest scale by a factor of 4 and higher can reasonably be recovered, even when the power ratio of $E$- to $B$-modes is as large as about 10$^2$, and the signal-to-noise ratio is equal to 10 and higher. This is because the Galerkin discretization is free of false correlations...

‣ Implementation of the Wavelet-Galerkin method for boundary value problems

Scheider, Adam
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
70.400044%
The objective of this work is to develop a systematic method of implementing the Wavelet-Galerkin method for approximating solutions of differential equations. The beginning of this project included understanding what a wavelet is, and then becoming familiar with some of the applications. The Wavelet-Galerkin method, as applied in this paper, does not use a wavelet at all. In actuality, it uses the wavelet's scaling function. The distinction between the two will be given in the following sections of this paper. The sections of this thesis will include defining wavelets and their scaling functions. This will give the reader valued insight to wavelets and Discrete Wavelet Transforms (DWT). Following this will be a section defining the Galerkin method. The purpose of this section will be to give the reader an understanding of how weighted residual methods work, in particular, the Galerkin Method. Next will be a section on how Scaling functions will be implemented in the Galerkin method, forming the Wavelet-Galerkin Method. The focus of this investigation will deal with solutions to a basic homogeneous differential equation. The solution of this basic equation will be analyzed using three separate, distinct methods, and then the results will be compared. These methods include the Wavelet-Galerkin Method...

‣ Wavelet-galerkin method for computations of electromagnetic fields-computation of connection coefficients

Yang, Shiyou; Ni, Guangzheng; Ho, S. L.; Machado, Jose Marcio; Rahman, M. A.; Wong, H. C.
Fonte: Institute of Electrical and Electronics Engineers (IEEE) Publicador: Institute of Electrical and Electronics Engineers (IEEE)
Tipo: Artigo de Revista Científica Formato: 644-648
Português
Relevância na Pesquisa
99.73187%
One of the key issues which makes the waveletGalerkin method unsuitable for solving general electromagnetic problems is a lack of exact representations of the connection coefficients. This paper presents the mathematical formulae and computer procedures for computing some common connection coefficients. The characteristic of the present formulae and procedures is that the arbitrary point values of the connection coefficients, rather than the dyadic point values, can be determined. A numerical example is also given to demonstrate the feasibility of using the wavelet-Galerkin method to solve engineering field problems. © 2000 IEEE.

‣ An adaptive wavelet-galerkin method for parabolic partial differential equations

Vampa,Victoria; Martín,María T
Fonte: Revista de Matemática Teoría y Aplicaciones Publicador: Revista de Matemática Teoría y Aplicaciones
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2015 Português
Relevância na Pesquisa
89.27924%
In this paper an Adaptive Wavelet-Galerkin method for the solution of parabolic partial differential equations modeling physical problems with different spatial and temporal scales is developed. A semi-implicit time difference scheme is applied and B-spline multiresolution structure on the interval is used. As in many cases these solutions are known to present localized sharp gradients, local error estimators are designed and an efficient adaptive strategy to choose the appropriate scale for each time is developed. Finally, experiments were performed to illustrate the applicability and efficiency of the proposed method.