Método híbrido para projeto de superfícies seletivas em frequência

This thesis presents a hybrid technique of frequency selective surfaces project (FSS) on a isotropic dielectric layer, considering various geometries for the elements of the unit cell. Specifically, the hybrid technique uses the equivalent circuit method in conjunction with genetic algorithm, aiming at the synthesis of structures with response single-band and dual-band. The equivalent circuit method allows you to model the structure by using an equivalent circuit and also obtaining circuits for different geometries. From the obtaining of the parameters of these circuits, you can get the transmission and reflection characteristics of patterned structures. For the optimization of patterned structures, according to the desired frequency response, Matlab™ optimization tool named optimtool proved to be easy to use, allowing you to explore important results on the optimization analysis. In this thesis, numeric and experimental results are presented for the different characteristics of the analyzed geometries. For this, it was determined a technique to obtain the parameter N, which is based on genetic algorithms and differential geometry, to obtain the algebraic rational models that determine values of N more accurate, facilitating new projects of FSS with these geometries. The optimal results of N are grouped according to the occupancy factor of the cell and the thickness of the dielectric, for modeling of the structures by means of rational algebraic equations. Furthermore, for the proposed hybrid model was developed a fitness function for the purpose of calculating the error occurred in the definitions of FSS bandwidths with transmission features single band and dual band. This thesis deals with the construction of prototypes of FSS with frequency settings and band widths obtained with the use of this function. The FSS were initially reviewed through simulations performed with the commercial software Ansoft Designer ™, followed by simulation with the equivalent circuit method for obtaining a value of N in order to converge the resonance frequency and the bandwidth of the FSS analyzed, then the results obtained were compared. The methodology applied is validated with the construction and measurement of prototypes with different geometries of the cells of the arrays of FSS.

A comparison of fixed-step-size and Bayesian staircases for sensory threshold estimation

Fixed-step-size (FSS) and Bayesian staircases are widely used methods to estimate sensory thresholds in 2AFC tasks, although a direct comparison of both types of procedure under identical conditions has not previously been reported. A simulation study and an empirical test were conducted to compare the performance of optimized Bayesian staircases with that of four optimized variants of FSS staircase differing as to up-down rule. The ultimate goal was to determine whether FSS or Bayesian staircases are the best choice in experimental psychophysics. The comparison considered the properties of the estimates (i.e. bias and standard errors) in relation to their cost (i.e. the number of trials to completion). The simulation study showed that mean estimates of Bayesian and FSS staircases are dependable when sufficient trials are given and that, in both cases, the standard deviation (SD) of the estimates decreases with number of trials, although the SD of Bayesian estimates is always lower than that of FSS estimates (and thus, Bayesian staircases are more efficient). The empirical test did not support these conclusions, as (1) neither procedure rendered estimates converging on some value, (2) standard deviations did not follow the expected pattern of decrease with number of trials, and (3) both procedures appeared to be equally efficient. Potential factors explaining the discrepancies between simulation and empirical results are commented upon and, all things considered, a sensible recommendation is for psychophysicists to run no fewer than 18 and no more than 30 reversals of an FSS staircase implementing the 1-up/3-down rule.

A ansiedade infantil : vulnerabilidades da criança e influência dos pais

Tese de Doutoramento em Psicologia na área de especialidade Psicologia Clínica

A participação das forças armadas na segurança pública de Cabo Verde: que colaboração?

Tendo em conta o nível de desenvolvimento que Cabo Verde tem vindo a conhecer, o crescimento rápido da sua população, o aparecimento de novos factos criminais e ainda o facto de possuir um enorme Zona Económica Exclusiva, associado ao facto de ser um país de fracos recursos económicos, é motivo para que se optimizem os recursos, encontrando respostas legalmente adequadas, eficazes e eficientes ao fenómeno do crime e da insegurança, projectados pelas novas ameaças. Com a revisão Constitucional de 1999, as Forças Armadas (FA) ganharam competência no âmbito de segurança interna, para colaborem com as Forças e Serviços de Segurança (FSS) e sob a responsabilidade destas. Este estudo debruça sobre “A Participação das Forças Armadas na Segurança Pública em Cabo Verde”, no intuito de analisar e perceber que tipo de colaboração prevê a Constituição, perceber à que nível pode ocorrer a actuação das FA na segurança e ordem pública e quais os limites dessa actuação. Para fazer o estudo recorreu-se à análise documental e fez-se uso do método de qualitativo, tendo como instrumento de recolha de informação a entrevista (semiestruturada), seguido de uma análise de conteúdo permitindo confrontar os resultados com as ideias existentes no enquadramento teórico. Conclui-se que as FA têm competências para actuar na segurança interna somente em colaboração com as FSS. Mas mostra-se que perante o quadro socioeconómico de Cabo Verde não se pode dispensar esta colaboração.

Fadiga em pacientes da Coorte Brasília de artrite reumatoide (AR) : estudo da prevalência e comparação entre diferentes instrumentos de avaliação

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Medicina, Programa de Pós-Graduação em Ciências Médicas, 2016.