No description available.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 60-61). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 60-61). Also available on the Internet.

Orientador: Benjamin Bordin / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matematica, Estatistica e Computação Científica / Made available in DSpace on 2018-07-16T20:01:55Z (GMT). No. of bitstreams: 1 Garcia_JoaoBatista_M.pdf: 1412168 bytes, checksum: 10b9465fea06ccd286bb2837cca77c6c (MD5) Previous issue date: 1982 / Resumo: Não informado. / Abstract: Not informed. / Mestrado / Mestre em Matemática

Since the discovery in the early 1950's, frames have emerged as an important tool in signal processing, image processing, data compression and sampling theory etc. Today, powerful tools from operator theory and Banach space theory are being introduced to the study of frames producing deep results in frame theory. In recent years, many mathematicians generalized the frame theory from Hilbert spaces to Hilbert C*-modules and got significant results which enrich the theory of frames. Also there is growing evidence that Hilbert C*-modules theory and the theory of wavelets and frames are tightly related to each other in many aspects. Both research fields can benefit from achievements of the other field. Our purpose of this dissertation is to work on several basic problems on frames for Hilbert C*-modules. We first give a very useful characterization of modular frames which is easy to be applied. Using this characterization we investigate the modular frames from the operator theory point of view. A condition under which the removal of element from a frame in Hilbert C*-modules leaves a frame or a non-frame set is also given. In contrast to the Hilbert space situation, Riesz bases of Hilbert C*-modules may possess infinitely many alternative duals due to the existence of zero-divisors and not every dual of a Riesz basis is again a Riesz basis. We will present several such examples showing that the duals of Riesz bases in Hilbert $C^*$-modules are much different and more complicated than the Hilbert space cases. A complete characterization of all the dual sequences for a Riesz basis, and a necessary and sufficient condition for a dual sequence of a Riesz basis to be a Riesz basis are also given. In the case that the underlying C*-algebra is a commutative W*-algebra, we prove that the set of the Parseval frame generators for a unitary group can be parameterized by the set of all the unitary operators in the double commutant of the unitary group. Similar result holds for the set of all the general frame generators where the unitary operators are replaced by invertible and adjointable operators. Consequently, the set of all the Parseval frame generators is path-connected. We also prove the existence and uniqueness of the best Parseval multi-frame approximations for multi-frame generators of unitary groups on Hilbert C*-modules when the underlying C*-algebra is commutative. For the dilation results of frames we show that a complete Parseval frame vector for a unitary group on Hilbert C*-module can be dilated to a complete wandering vector. For any dual frame pair in Hilbert C*-modules, we prove that the pair are orthogonal compressions of a Riesz basis and its canonical dual basis for some larger Hilbert C*-module. For the perturbation of frames and Riesz bases in Hilbert C*-modules we prove that the Casazza-Christensen general perturbation theorem for frames in Hilbert spaces remains valid in Hilbert C*-modules. In the Hilbert space setting, under the same perturbation condition, the perturbation of any Riesz basis remains a Riesz basis. However, this no longer holds for Riesz bases in Hilbert C*-modules. We also give a complete characterization on all the Riesz bases for Hilbert C*-modules such that the perturbation (under Casazza-Christensen's perturbation condition) of a Riesz basis still remains a Riesz basis.

We consider the problem of structural optimization which has many important applications in the engineering sciences. The goal is to find an optimal distribution of the material within a certain volume that will minimize the mechanical and/or thermal compliance of the structure. The physical system is governed by the standard models of elasticity and heat transfer expressed in terms of boundary-value problems for elliptic systems of partial differential equations (PDEs). The structural optimization problem is then posed as a suitably constrained PDE optimization problem, which can be solved numerically using a gradient approach. As a main contribution to the thesis, we derive expressions for gradients (sensitivities) of different objective functionals. This is done in both the continuous and discrete setting using the Riesz representation theorem and adjoint analysis. The sensitivities derived in this way are then tested computationally using simple minimization algorithms and some standard two-dimensional test problems. / Thesis / Master of Science (MSc)

Nous étudions le problème d'unicité, de l'interpolation faible et de la convergence de la série d'interpolation de Lagrange dans les espaces de Fock pondérés par des poids radiaux. Nous étudions aussi les suites d'échatillonnage, d'interpolation et les bases de Riesz dans les petit espaces de Fock. / We study the uniqueness sets, the weak interpolation sets, and convergence of the Lagrange interpolation series in radial weighted Fock spaces. We study also sampling, interpolation and Riesz bases in small radial weighted Fock spaces

Neste trabalho estudamos a integral de Kurzweil para funções definidas em um intervalo fechado limitado da reta e a valores em um espaço de Riesz. Apresentamos algumas propriedades básicas dessa integral e teoremas que relacionam a convergência uniforme de uma seqüência de funções Kurzweil integráveis com a convergência da seqüência formada pelas respectivas integrais. / In this work we study the Kurzweil integral for functions defined in a compact interval and with values in a Riesz space. We present some elementary properties for this integral and we prove theorems that relate the uniform convergence of a sequence of Kurzweil integrable functions to the convergence of the sequence of their integrals.

Neste trabalho estudamos a integral de Kurzweil para funções definidas em um intervalo fechado limitado da reta e a valores em um espaço de Riesz. Apresentamos algumas propriedades básicas dessa integral e teoremas que relacionam a convergência uniforme de uma seqüência de funções Kurzweil integráveis com a convergência da seqüência formada pelas respectivas integrais. / In this work we study the Kurzweil integral for functions defined in a compact interval and with values in a Riesz space. We present some elementary properties for this integral and we prove theorems that relate the uniform convergence of a sequence of Kurzweil integrable functions to the convergence of the sequence of their integrals.

In this dissertation we study the Laplace operator acting on functions on a smooth, compact Riemannian manifold. Our approach is based on the study of the spectrum of the aforementioned operator. The main objects of our interest are the counting function of the Laplacian and its Riesz means. We discuss the asymptotics of aforementioned functions when the argument approaches infinity.