Made available in DSpace on 2014-10-09T12:32:59Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:11Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Nesta dissertação apresentamos os conceitos e ferramentas necessárias para análise do comportamento da função resposta dielétrica de meios dielétricos, levando em conta efeitos da temperatura. Nos primeiros capítulos apresentamos uma breve revisão da literatura especializada, expondo alguns modelos que foram propostos para a descrição da função resposta dielétrica. A seguir apresentamos alguns modelos teóricos encontrados na literatura que incorporam efeitos da temperatura à resposta dielétrica. Considerando o modelo proposto por Dissado-Hill, mostramos que os efeitos da temperatura podem ser incorporados aos parâmetros (m) e (n) que caracterizam o modelo. / In this work we present the concepts and tools required to analyze the behavior of the dielectric response function of dielectric media, taking into account the effects of temperature. In the early chapters, we present a brief review of the literature, exposing some models that have been proposed to describe the dielectric response function, then we include the presentation of some models found in the literature that incorporate the effects of temperature to dielectric response for some materials. In order to include the effects of temperature in the dielectric response of interest materials for electronic (such as ceramics), we assuming the Dissado-Hill model, and show that the effects of temperature may be included in the parameters (m) and (n) that characterizing the model.

Nesta dissertação apresentamos os conceitos e ferramentas necessárias para análise do comportamento da função resposta dielétrica de meios dielétricos, levando em conta efeitos da temperatura. Nos primeiros capítulos apresentamos uma breve revisão da literatura especializada, expondo alguns modelos que foram propostos para a descrição da função resposta dielétrica. A seguir apresentamos alguns modelos teóricos encontrados na literatura que incorporam efeitos da temperatura à resposta dielétrica. Considerando o modelo proposto por Dissado-Hill, mostramos que os efeitos da temperatura podem ser incorporados aos parâmetros (m) e (n) que caracterizam o modelo. / In this work we present the concepts and tools required to analyze the behavior of the dielectric response function of dielectric media, taking into account the effects of temperature. In the early chapters, we present a brief review of the literature, exposing some models that have been proposed to describe the dielectric response function, then we include the presentation of some models found in the literature that incorporate the effects of temperature to dielectric response for some materials. In order to include the effects of temperature in the dielectric response of interest materials for electronic (such as ceramics), we assuming the Dissado-Hill model, and show that the effects of temperature may be included in the parameters (m) and (n) that characterizing the model.

Made available in DSpace on 2014-10-09T12:32:59Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:11Z (GMT). No. of bitstreams: 0 / Estudos recentes demonstram que o sistema cerâmico zircônia-escândia-céria (ScCeSZ) apresenta-se promissor para aplicações como eletrólito sólido em células a combustível de óxido sólido de temperaturas intermediárias de operação (600 a 800 °C). Neste trabalho, foi realizada a sinterização convencional, de duas etapas e assistida por campo elétrico do ZrO2 contendo 10% em mol de Sc2O3 e 1% em mol de CeO2 comercializado pela Fuel Cell Materials visando melhorar a densificação com reduzido tamanho médio de grãos. A condutividade elétrica de amostras densas de ScCeSZ sinterizadas pelos diferentes métodos foi investigada por espectroscopia de impedância. Diferentes condições de sinterização foram analisadas. A taxa de retração dos compactos é máxima a 1180 °C, determinada pela análise de dilatometria. Foi confirmado por difração de raios X que a adição de céria à zircônia-escândia promove a estabilização da fase cúbica à temperatura ambiente. No entanto, dependendo das condições de sinterização pode haver a formação de fases secundárias, as quais foram detectadas por difração de raios X e espectroscopia Raman. A sinterização assistida por campo elétrico promoveu a formação das fases cúbica e tetragonal. Considerando os métodos convencional e de duas etapas, para a obtenção do material cúbico monofásico é necessária uma seleção cuidadosa das condições de sinterização. Os valores de condutividade elétrica estão de acordo com as condutividades do ScCeSZ reportadas na literatura. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

This thesis develops a method for obtaining the complex resonant frequency of a post dielectric resonator in the presence of a lossy conductor. A full field analysis is performed on an infinite dielectric rod from which the complex propagation constant and modal solutions are found. Using a single dominant mode (HEM_ll), the boundary conditions at the end of the resonator are enforced, to obtain a complex reflection coefficient. Using the propagation constant from the infinite dielectric rod and the reflection coefficient derived from considering the dielectric-air interface at the resonator ends, a two dimensional search is performed to find the complex frequency for which the gain/phase criterion of the resonator is satisfied. In the final step, boundary conditions are enforced for a lossy conductor at a distance Az from the dielectric which yields the objective -- the complex resonate frequency of a post dielectric in close proximity of a lossy conductor / Master of Science

In this thesis, an analysis of the scattering of a rough perfect electric conductor (PEC) surface under illumination by a Gaussian beam using the Kirchhoff approximation is presented. The analysis assumes a source distribution which yields a Gaussian beam solution as a radiated field. This field is used to excite a current density on the surface using the Kirchhoff approximation. A vector potential approach utilizes this current to calculate the fields scattered by the surface. The analysis is carried out for the backscatter case and near-normal incidence in order to reduce the final numerical evaluation to a two-dimensional integration. The normalized radar cross-section (NRCS) is calculated and compared with the result for plane wave illumination. The analysis explores the effects of varying the source aperture size, rough surface correlation length and rms height on the NRCS. An asymptotic evaluation of the mean squared field is presented, as well as the mathematical form of the fourth moment of the scattered field. As a further study, the NRCS of a rough surface under a Gaussian tapered plane wave illumination is presented. The interplay of the beam spot and correlation length for such illuminated surfaces is discussed. / Master of Science

published_or_final_version / abstract / Electrical and Electronic Engineering / Master / Master of Philosophy

Thesis. 1975. Ph.D.--Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science. / Vita. / Includes bibliographical references. / Ph.D.

References: p.71. / Contract DA36-039-AMC-03200(E). Grant DA-SIG-36-039-61-G14.

Thesis (Ph.D.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (February 27, 2007) Vita. Includes bibliographical references.