Análise teórica e experimental de superfícies seletivas de freqüência e suas aplicações em antenas planares

This work presents a theoretical and numerical analysis of structures using frequency selective surfaces applied on patch antennas. The FDTD method is used to determine the time domain reflected fields. Applications of frequency selective surfaces and patch antennas cover a wide area of telecommunications, especially mobile communications, filters and WB antennas. scattering parameters are obteained from Fourier Transformer of transmited and reflected fields in time domain. The PML are used as absorbing boundary condition, allowing the determination of the fields with a small interference of reflections from discretized limit space. Rectangular patches are considered on dielectric layer and fed by microstrip line. Frequency selective surfaces with periodic and quasi-periodic structures are analyzed on both sides of antenna. A literature review of the use of frequency selective surfaces in patch antennas are also performed. Numerical results are also compared with measured results for return loss of analyzed structures. It is also presented suggestions of continuity to this work

Transformação de Helmert generalizada no posicionamento de alta precisão: fundamentação teórica e exemplificações

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A reformulação parafrástica na fundamentação teórica de trabalhos de conclusão de curso de Letras

In this work, we study the types of paraphrases used by the students of the Language and Literature Course when they reformulate a source text in the theoretical section of the monographs produced as texts for the conclusion of the course. Our main goal is to know how the process of textual reformulation takes place in the production of the monographic gender. From the used theoretical orientation (Fuchs,1982; 1994; Charaudeau and Maingueneau, 2006; Fávero et al, 2007; Hilgert, 1997, 2002, 2006; among others) we have worked with the paraphrase notion as an activity of discoursive reformulation, considering as the basic groundings the situation of communication and the subjects, or the wider context. In a more specific way, we have considered that the paraphrase performs alterations in the formal level, in the semantic level and in the functional level. Besides that, we sought to articulate the practice of paraphrasing to the gender of discourse in which it appears and to the contextual implications involved in the producing of the gender in question, and in doing so we were grounded in Baktin´s (2003) and Maingueneau´s (1998; 2001) postulates. For the analysis of the corpus that consists of 19 monographs, we have used the three categories defined by Hilgert (2002, 2006):expansion, condensation and parallelism as a way of identifying, describing and characterizing the types of paraphrases used by the students who produced the monographs when they take up Travaglia´s (1996) text about the language conceptions. The results show that the use of the paraphrastic parallelism (with 69.45 % in relation to only 18.41% of condensation and 12.13 % of expansion) was the most recurrent in the reformulations performed by the students who produced the monographs and this manifestation was characterized mainly by the lexical-semantic repetition of fragments of the source text. We have concluded that the high incidence of paraphrastic parallelism is an indication that the student does not have a command of the ways of production and circulation of the discoursive genders uttered in the academic-scientific realm

Uma análise teórica da evolução da rotação estelar

In the past 50 years, large efforts have been made toward the understanding of the stellar evolution. In the observational context, large sets of precise measurements of projected rotational velocity were produced, in particular by the Natal and Geneva groups. From these data, it is now possible to establish the behavior of stellar rotation from the turnoff to the red giant branch. In addition, these data have shown the role of tidal effects on stellar rotation in close binary systems. Nevertheless, relatively little attention has been paid to theoretical studies on the evolution of rotation along the HR Diagram, a topic itself directly associated to the evolution of the stars. Basically, there are two reasons for such a fact, (i) spherical symmetry is not assumed, what leads to a substantial increase in the numerical complexity of equations and (ii) non rotating models have been very successful in explaining relevant observational data, including the mass-luminosity relation and chemical abundances. In spite of these facts, it is clear that considerable work remains to be done on the role of rotation in the later stages of the evolution, where clear disagreements arise from confrontations between theoretical predictions and observations. In the present work we study the evolutionary behavior of stellar rotation along the HR Diagram, taking into account constraint conditions issued from recent observational survey of rotational velocity carried out with high precision procedures and new evolutionary codes

Lítio e rotação nas estrelas análogas solares: análise teórica das observações

The projected rotational velocity together with lithium abundance and the onset of the dilution by the deepening in mass of the convective envelope provide a key tool to investigate the so far poorly understood processes at work in stellar interiors of solar-analog stars. To investigate the link between abundances, convection and rotational velocities in solar-analog G dwarf stars, we study a bona fide sample of 118 selected solar-analog G dwarf stars presenting measured lithium abundances, rotational velocities, and fundamental parameters together with computed evolutionary tracks (Toulouse-Geneva code) for a range of stellar masses around 1 M and metallicity consistent with the solar-analog range. The aim of this work is to build up an evolution of lithium and rotation as a function of stellar age, mass, effective temperature, and convection. We analyze the evolutionary status of the sample of 118 solar-analog G dwarf in the HR diagram based on Hipparcos data and using a grid of stellar models in the effective temperature and mass range of the solar-analog stars. We discuss the deepening (in mass) of the convective envelope and the influence on the Li abundances and projected rotational velocities. We determined the stellar mass and the mass of the convective envelope for a bona fide sample of 118 selected solar-analog G dwarf and checked the evolutionary link between the rotational velocity, lithium abundance, and the deepening of the convective envelope. Fast rotators (vsini 6 km s��1) are also stars with high Li content. Slow rotators present a wide range of values of log n(Li). Our results shed new light on the lithium and rotational behavior in G dwarf stars. We confirmed the presence of a large Li abundance spread among the solar-analog stars and concluded that the solar twins probably share a similar mixing history with the Sun

Análise teórica da interação de CO, CO2 e NH3 com ZnO

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Ambigüidade gerada pela homonímia: revisitação teórica, linhas limítrofes com a polissemia e proposta de critérios distintivos

O presente trabalho almeja expor o fenômeno da homonímia no português do Brasil, enquanto ambigüidade presente em uma língua natural, por meio de uma revisitação teórica em diversos autores e em confronto com a polissemia. Ademais, pretende-se, além de redefinir conceitualmente a homonímia, propor critérios semânticos distintivos para esse fenômeno lingüístico, tais como a análise sêmica, o campo léxico, o uso de expressões cristalizadas e a ocorrência de traços especificadores.

Programação linear por partes: revisão teórica e aplicações

Procura-se resgatar a importância de uma subárea da Programação Matemática conhecida como Programação Linear Por Partes - PLP. de fato a PLP tem inúmeras aplicações tanto na área teórica como em situações reais. Este trabalho apresenta os resultados de uma pesquisa bibliográfica, efetuada nas principais revistas técnicas e livros disponíveis relacionados com Pesquisa Operacional, que visou situar o estado da'arte da Programação Linear por Partes, bem como a abrangência de sua aplicabilidade. Particularmente, no contexto da PLP, este texto deslaca a Programação em Redes Lineares por Partes devido a sua relevância em muitas situações práticas.

A construção teórica do real: Uma questão para a produção do conhecimento em educação

The central theme of this article is the research in education. The aim is to bring up the contribution developed by Mirian Limoeiro Cardoso in Brazil for the production of knowledge in education, besides the propositions of foreign authors, often used as references to base of the research. The starting point, here described, is the statement that the empirical real is not the object of knowledge, but what is presented as an object to be known, is always the real that, in different forms, is an object involved by theory. Thinking about the research in this view the necessecity of revision of the meaning of the object to be known, the object that is also an educative action in its different and several manifestations and the discussion of its importance for the teachers? and researchers? formation.

Política fiscal e dívida pública: Uma abordagem teórica a partir de keynes e abba lerner

The fiscal policies of national governments are an important instrument of economic policy, as they contribute directly or indirectly to growth and economic development. Since Keynes, the utilization of active fiscal policy is unavoidable during periods of crisis, especially a policy of public investment spending aimed at reducing macroeconomic uncertainty. In the same way, Abba Lerner and functional finances indicate the use of fiscal policy in favor of macroeconomic stability, and not according to a single objective of seeking equilibrium in the public accounts. However, at the present time, the debate on fiscal policy is not sufficient to guarantee public sector financial equilibrium. The article picks up on the contributions of Keynes and Abba Lerner regarding the importance of the public budget in economic activity, and discusses the present scenario for fiscal policy.

Conflitos conjugais e seus efeitos sobre o comportamento de crianças: Uma revisão teórica

Marital conflicts have been largely investigated in research, especially because of its impact on child development. Based on a literature review, this article aims to present some reflections about marital conflicts and its possible associations with children's behavior, particularly through parental practices. Emphasis is made on a systemic view of causality between marital conflict and child behavior, which offers a better comprehension of the family functioning. This perspective also allows us to enlarge the analysis scope beyond linear correlations between both variables.

La influencia de las variables financieras sobre las exportaciones bajo un régimen de racionamiento de crédito: una aproximación teórica y su aplicación al caso chileno

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La política de las políticas públicas: propuesta teórica y metodológica para el estudio de las políticas públicas en países de frágil institucionalidad

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El campesinado en América Latina: una aproximación teórica

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