Radiação por fenda em guia de ondas

Dissertação para obtenção do Grau de Mestre em Engenharia Electrotécnica e de Computadores

Propriedades de escala de um guia de ondas periodicamente corrugado

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo e aplicação de guias de ondas integrados ao substrato em frequências de micro-ondas.

Esse trabalho de pesquisa apresenta um estudo detalhado sobre guias de ondas integrados ao substrato (SIW) operando em frequências de micro-ondas com base na teoria de guias de ondas retangulares (RWG). O estudo sobre guias SIW associa equações apresentadas na literatura e utiliza simulações eletromagnéticas para desenvolver um procedimento de projeto bem definido. É considerada a integração entre guias SIW e linhas de transmissão de microfita, projetando-se transições entre essas duas estruturas com o propósito de prover casamento de impedância e de viabilizar a caracterização em frequências de micro-ondas. São apresentadas considerações sobre processos de fabricação de circuitos SIW em substratos constituídos por laminados de alta frequência. Uma vez estabelecidos os procedimentos de fabricação e os critérios de projeto, a tecnologia SIW é aplicada ao projeto de três guias de ondas SIW nas bandas S e X, que foram fabricados empregando laminados de alta-frequência. Foram projetados dois filtros SIW passa-faixa empregando cavidades ressonantes e postes metálicos indutivos. Os dois filtros operam na frequência central de 10,61 GHz, sendo que um deles tem banda de passagem de 7,5%e é de 3ª ordem e o outro filtro tem banda de passagem de 15%, sendo de 5ª ordem. Foram realizadas comparações entre o desempenho simulado e experimental das estruturas SIW projetadas. Os resultados de simulações eletromagnéticas e experimentais demonstraram boa concordância. Os projetos em tecnologia SIW apresentados neste trabalho de pesquisa possuem perdas de retorno melhores que 10 dB na banda de operação e perdas por inserção de 1,0 dB a 1,5 dB. É apresentada a análise da sensibilidade do desempenho dos guias de ondas e filtros SIW projetados a desvios dimensionais típicos do processo de fabricação por microfresagem mecânica. Com os resultados experimentais e de simulação foi possível validar os procedimentos de projeto e de fabricação de circuitos SIW operando em frequências de micro-ondas.

Síntese análise das propriedades magnéticas da ferrita de NiMg e características de absorção de radiação

It was synthesized different Ni1-xMgxFe2O4 (0,2 ≤ x ≤ 0,7) compositions by use of citrate precursor method. Initially, the precursory citrates of iron, nickel and magnesium were mixed and homogenized. The stoichiometric compositions were calcined from 350°C to 1200°C at ambient atmosphere or in argon atmosphere. The calcined powders were characterized by XRD, TGA/DTG, FTIR, magnetic measures and reflectivity using the wave guide method. I was observed pure magnetic phase formation between 350°C and 500°C, with formation of ferrite and hematite after 600°C at ambient atmosphere. The calcined powder at argon atmosphere formed pure ferromagnetic phase at 1100°C and 1200°C. The Rietveld analyses calculated the cations level occupation and the crystallite size. The analyses obtained nanometric crystals (11-66 nm), that at 900°C/3h presents micrometric sizes (0,45 - 0,70 Om). The better magnetization results were 54 Am2/Kg for x= 0,2 composition, calcined at 350°C/3h and 30 min, and 55,6 Am2/Kg for x= 0,2 1200°C, calcined in argon. The hysteresis shows characteristics of soft magnetic material. Two magnetization processes were considered, superparamagnetism at low temperature and the magnetic domains formation at high temperatures. The materials presented absorption less or equal the 50 % in ranges specific frequency. As for the 2,0 and 3,0 thickness (in 11,0 - 11,8 GHz), the reflectivity of the x= 0,3, 0,5 and 0,4 compositions, all calcined at 900°C/3h showed agreement with MS and O. Various factors contribute for the final radiation absortion effect, such as, the particle size, the magnetization and the polymer characteristics in the MARE composition. The samples that presented better magnetization does not obtaining high radiation absorption. It is not clear the interrelaction between the magnetization and the radiation absorption in the strip of frequencies studied (8,2 - 12,4 GHz)

Síntese, caracterização de ferritas espinélio com propriedades magnéticas e absorvedoras de microondas

Were synthesized spinel-type ferrites with general formula Ni0,8Mg0.2-xMxFe2O4, where M represents the doping Mn, Co or Mn + Co simultaneously, x ranges for the values 0.02, 0.05 and 0.1. The value of x was divided by 2 in cases where M equals Mn and Co conjugates. We used the citrate precursor method and heat treatment to obtain the phases at 1100°C. The materials were characterized by XRD, TGA/ DTGA, SEM, MAV and reflectivity measurements by the method of waveguide. Powders to 350°C/3.5 h were crystalline and nanosized. According to the results this temperature all powders have a percentage of ferrite phase over 90%. The composition had the addition of Mn and Co simultaneously showed a higher percentage of secondary phase NiO, 5.8%. The TGA/DTGA curves indicate that this sample reached phase (s) crystalline (s) at lowest temperatures. The X-ray diffractograms of the samples calcined at 350°C and 1100°C were treated with the Rietveld refinament technique. The powders calcined at 1100 °C/3h in air show to be 100% except spinel phase composition with 0.02 doping. The micrographs show clusters of particles with sizes smaller than 1 μm in calcination temperature of 1100°C which agreed with the result of Rietveld refinement. In the compositions doped with Mn were higher values of magnetization (45.90 and 53.20 Am2/kg), which did not cause high microwave absorption. The theoretical calculation of magnetization (MT) was consistent with the results, considering that there was agreement between the increase of magnetization experimental and theoretical. It was observed that there was the interrelation of the final effect of absorption with the thickness of MARE, the composition of ferrimagnetic materials and in particular the specific values of frequency. The analysis shows that the reflectivity increases in the concentration of cobalt increased the frequency range and also for absorption 10.17 GHz and 84%, respectively. The best result of chemical homogeneity and the value of 2.96 x 10-2 tesla coercive field were crucial for high performance ferrite absorber with 0.1 cobalt. The Cobalt has high magnetocrystalline anisotropy, it is associated with an increased coercive field, Hc. Therefore, this property improves the results of reflectivity of spinel ferrites

Desenvolvimento de um ressoador retangular de fenda com múltiplas camadas de substrato e com utilização de material PBG para sistema de comunicação sem fio

In the globalized world modern telecommunications have assumed key role within the company, causing a large increase in demand for the wireless technology of communication, which has been happening in recent years have greatly increased the number of applications using this technology. Due to this demand, new materials are developed to enable new control mechanisms and propagation of electromagnetic waves. The research to develop new technologies for wireless communication presents a multidisciplinary study that covers from the new geometries for passive antennas, active up to the development of materials for devices that improve the performance at the frequency range of operation. Recently, planar antennas have attracted interest due to their characteristics and advantages when compared with other types of antennas. In the area of mobile communications the need for antennas of this type has become increasingly used, due to intensive development, which needs to operate in multifrequency antennas and broadband. The microstrip antennas have narrow bandwidth due to the dielectric losses generated by irradiation. Another limitation is the degradation of the radiation pattern due to the generation of surface waves in the substrate. Some techniques have been developed to minimize this limitation of bandwidth, such as the study of type materials PBG - Photonic Band Gap, to form the dielectric material. This work has as main objective the development project of a slot resonator with multiple layers and use the type PBG substrate, which carried out the optimization from the numerical analysis and then designed the device initially proposed for the band electromagnetic spectrum between 3-9 GHz, which basically includes the band S to X. Was used as the dielectric material RT/Duroid 5870 and RT/Duroid 6010.LM where both are laminated ceramic-filled PTFE dielectric constants 2.33 and 10.2, respectively. Through an experimental investigation was conducted an analysis of the simulated versus measured by observing the behavior of the radiation characteristics from the height variation of the dielectric multilayer substrates. We also used the LTT method resonators structures rectangular slot with multiple layers of material photonic PBG in order to obtain the resonance frequency and the entire theory involving the electromagnetic parameters of the structure under consideration. xviii The analysis developed in this work was performed using the method LTT - Transverse Transmission Line, in the field of Fourier transform that uses a component propagating in the y direction (transverse to the real direction of propagation z), thus treating the general equations of the fields electric and magnetic and function. The PBG theory is applied to obtain the relative permittivity of the polarizations for the sep photonic composite substrates material. The results are obtained with the commercial software Ansoft HFSS, used for accurate analysis of the electromagnetic behavior of the planar device under study through the Finite Element Method (FEM). Numerical computational results are presented in graphical form in two and three dimensions, playing in the parameters of return loss, frequency of radiation and radiation diagram, radiation efficiency and surface current for the device under study, and have as substrates, photonic materials and had been simulated in an appropriate computational tool. With respect to the planar device design study are presented in the simulated and measured results that show good agreement with measurements made. These results are mainly in the identification of resonance modes and determining the characteristics of the designed device, such as resonant frequency, return loss and radiation pattern

Descargas parciais em barras estatóricas de hidrogeradores: modelagem por guia de onda e análise de um acoplador

Neste trabalho, tem-se como objetivo modelar as barras estatóricas de hidrogeradores por guias de onda multicamadas e estudar a aplicabilidade de um acoplador (sensor) para monitoramento das ocorrências de descargas parciais no interior dessas barras (mais precisamente, na sua camada isolante). Para isso, inicia-se por uma abordagem conceitual do fenômeno de descargas parciais, na qual é mostrada a importância do monitoramento das mesmas para identificar os sintomas de fragilidade dielétrica dos materiais isolantes dessas barras. Posteriormente, realiza-se uma apresentação sobre os métodos de monitoramento das descargas parciais, analisam-se os sinais de pulsos elétricos produzidos por elas e seus parâmetros típicos. Em seguida, estudam-se os modos de propagação de ondas eletromagnéticas produzidas pelas descargas parciais nas barras estatóricas de hidrogeradores, modelando-as por meio de guias de onda multicamadas. Para finalizar, apresenta-se um modelo de acoplador eletromagnético ou sensor, formado por uma linha de microfita, enfocando a sua aplicabilidade no sistema de monitoramento dessas ondas eletromagnéticas.

Elaboração de um material didático aplicado ao ensino de física para utilização do experimento virtual da dupla fenda

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Alguns aspectos da transposição de uma sequencia didática sobre o comportamento de partículas e ondas

This work presents a partial analysis of the implementation of a didactic sequence aimed at undergraduate students of quantum chemistry. The sequence develops on some fundamental concepts to understand the behavior of the objects particles and waves in the doubleslit experiment. The analysis is based on the didactic transposition theory, proposed by Yves Chevallard, which allows reflection upon the scientific knowledge reorganized to be used in teaching contexts. Our interest in this study lays on the dynamics of transposition of knowledge-to-be-taught into knowledge-taught, particularly the importance of making concepts more comprehensible. Results showed that the communication of knowledge by the students is presented with interruptions, gaps and colloquial language. The analysis allowed the identification of needs and possibilities of learning, as well as a turn in the teacher practice, through a dynamic process of action and reflection.

Determinação espectrofotométrica de hexametilenotetramina (HMT) em medicamentos, utilizando ácido cromotrópico e forno de micro-ondas

This paper proposes a methodology for spectrophotometric determination of hexamethylenetetramine (HMT) by using chromotropic acid in a phosphoric acid media employing a domestic microwave oven as a source of heating. The reddish-purple soluble product is quantitatively formed after 30 s of irradiation and obeys the Beer´s law in the range between 0.1-1.2 mg L-1 HMT (r = 0.99925). The method was applied successfully in commercial pharmaceutical preparations containing dyes in their composition. The results showed that the method proposed is feasible for simplicity, speed, low cost, precision and accuracy when compared with United States Pharmacopeia official method.

Definição de shelf life para produtos químicos: a importância de um guia de estabilidade específico para o segmento

The chemical industries worldwide are passing through a very particular moment of re-adaptation due to the implementation of an European regulation called, Registration, Evaluation, Authorization and Restriction of Chemicals (REACH). In Brazil, the Brazilian Chemical Industry needs urgently a specific guide of chemical products stability. The main purpose of this work is to present a proposal of a guide of stability for chemical products based on the reference guides of the International Conference on Harmonization (ICH). Thus, this work proposes an innovation in terms of methodology which will be useful for shelf life definition purpose for chemical industry products.

Guia para a determinação da estabilidade de produtos químicos

Companies worldwide are reviewing their working process to avoid waste, become aligned with environmental management standards and to fulfill specifications defined for national and international regulations. In this context, it is important that Brazilian Chemical companies have a specific stability guide for their products. The main purpose of this work is to present a stability guide for chemical products based on the existing guides of the Pharmaceutical and Cosmetics segments. Furthermore, this work proposes to offer an additional period of shelf life for chemical products, provided they meet certain prerequisites.

Sintonizando emoções : o futebol e o radio : uma viagem nas ondas da midia radiofonica

Universidade Estadual de Campinas . Faculdade de Educação Física

Propagacão das ondas de rossby nos invernos de máxima freqüência de ocorrência de geadas na pampa úmida

Neste trabalho estudou-se a influência dos padrões de onda extratropicais, que favorecem o desenvolvimento de eventos extremos frios no sudeste Sul-Americano, e em particular na região conhecida como Pampa Úmida. O aquecimento anômalo observado na região do oceano Pacífico tropical ocidental a nordeste da Austrália, durante os invernos de máxima freqüência de ocorrência de Geadas Generalizadas (GG) no centro-leste da Argentina, (região conhecida como Pampa Úmida - PU), atua como disparador de ondas de Rossby, as quais se propagam até o continente, favorecendo assim a ocorrência daqueles eventos. O padrão de propagação obtido nas simulações numéricas com um modelo baroclínico global, mostra o predomínio de um número de onda 3. Adicionalmente, foram analisadas as correlações do vento meridional em altos e baixos níveis observados para os eventos de GG, selecionados dentro dos invernos de máxima freqüência de ocorrência desses eventos. O vento meridional global em 250hPa apresenta regiões com correlação estatisticamente significativa com o vento meridional médio na PU. A configuração obtida no caso do vento meridional global em 250hPa, correlacionado com o vento meridional na PU, pode estar associada ao padrão de propagação das ondas simuladas numericamente a partir da forçante tropical. Igualmente importantes e significativos são os valores de correlação do vento sul nos baixos níveis, em particular para toda região da PU. O padrão de ondas simulado está bem representado pelas significativas correlações entre o vento meridional hemisférico em altos níveis e a temperatura no dia de evento de GG.