Radio Frequencies
Mostrando 13-24 de 37 artigos, teses e dissertações.
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13. Modeling of Dual-More resonators with the aid of the FDTD method for project of microwave filters / Modelamento de ressoadores dual-mode com o auxílio do método FDTD para projeto de filtros de microondas
The increasing demand for telecommunications services and the congestion of the radio frequencies spectrum have motivated the development of new devices with performance improved and small dimensions. This work will focus on dual-mode ring resonators and its applicability on the issue of assembly of filters. Initially, the model of the ring resonator and its
Publicado em: 2007
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14. Model of active regions at radio frequencies / Modelo de regiões ativas em rádio freqüências
Este trabalho tem como objetivo modelar em 3 dimensões a atmosfera solar acima de regiões ativas a fim de reproduzir a emissao destas em rádio freqüências. O modelo calcula as equações de transferência radiativa para os mecanismos de emissão bremsstrahlung e giro-ressonância térmicos. Por não existirem medidas das intensidades dos campos magnéti
Publicado em: 2007
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15. Radiodifusão Local na Faixa de 26 MHz Usando DRM: Resultados de Testes em Brasília
The digitalization of the sound broadcasting systems is currently underway throughout the world. One of the systems available for such a process is Digital Radio Mondiale (DRM), which is currently designed to operate in frequencies below 30 MHz. Through the use of the DRM system, a much higher audio quality can be achieved than that of AM radio with the use
Publicado em: 2007
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16. Determination fo the configuration of excited Alfvén waves in tokamak TCABR / Determinação da configuração de ondas de alfvén excitadas no tokamak TCABR
In order to enhance the efficiency of the TCABRs Alfvén waves heating system, called AWES - Alfvén Waves Excitement System a diagnostics for determining the radio-frequency power applied to the plasma and a processing circuit for the magnetic coil system was built, characterized, installed and put into operation. The RF diagnostics system was designed to d
Publicado em: 2007
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17. Avaliação dos modelos de predição de propagação para telefonia móvel celular na cidade do Natal
The development of wireless telecommunication in the last years has been great. It has been taking academics to conceive new ideas and techniques. Their aims are to increase the capacity and the quality of the systems services. Cells that are smaller every time, frequencies that are every time higher and environments that get more and more complex, all those
Publicado em: 2006
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18. Modelo 2,5D de predição de propagação para ambientes interiores utilizando o método do traçado de raios
A 2.5D ray-tracing propagation model is proposed to predict radio loss in indoor environment. Specifically, we opted for the Shooting and Bouncing Rays (SBR) method, together with the Geometrieal Theory of Diffrartion (GTD). Besides the line-of-sight propagation (LOS), we consider that the radio waves may experience reflection, refraction, and diffraction (N
Publicado em: 2005
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19. Análise temática da produção científica em Comunicação no Brasil baseada em um sistema classificatório facetado
The objective is the construction of a faceted classification system for the quantitative themes of scientific production in the field of Communication. For this purpose, general theoretical questions are initially discussed: science and the attempts at classification of scientific knowledge; aspects of the theory of classification, and, within it, of the th
Publicado em: 2005
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20. Exploration of solar chromosphere using high resolution spectroscopic observations
Brazilian Solar Spectroscope (BSS), operating in the frequency range of (1000 ¡ 2500) MHz with high time and frequency resolutions, has observed various fine structures showing intensity variations as functions of time and frequency. Here we are reporting radio bursts observed by BSS, from August to October/2001, exhibiting fine structures with total durati
Brazilian Journal of Physics. Publicado em: 2004-12
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21. Decimetric fine structures as a possible signature of chromospheric evaporation
In this work, we concentrate in the analysis of radio slowly drifting fine structures associated with solar flares recorded in the frequency range of (1000 - 2500) MHz by the Brazilian Solar Spectroscope (BSS), in regular operation at National Institute of Space Research (INPE) - Brazil. The main morphological aspects of each fine structure are narrow-band o
Brazilian Journal of Physics. Publicado em: 2004-12
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22. Solar atmospheric model with spicules applied to radio frequency observations. / Modelo de atmosfera solar com inclusão de espículas aplicado às observações em rádio freqüências
Em atividade desde junho de 1992, o Rádio Heliógrafo de Nobeyama (NoRH) obtém mapas diários do Sol em 17 GHz. Estes mapas refletem a estrutura da cromosfera e da base da coroa solar, devido à emissão nesta freqüência ser formada nesta região da atmosfera. Esta dissertação de Mestrado tem dois objetivos distintos, sendo o primeiro deles analisar e
Publicado em: 2003
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23. MODELLING TO RAIN ATTENUATION EFECTS IN POINT-TO-POINT AND POINT-TO-MULTIPOINT TERRESTRIAL LINKS / MODELAMENTO DE EFEITOS DE ATENUAÇÃO POR CHUVAS EM ENLACES TERRESTRES PONTO-A-PONTO E PONTO-MULTIPONTO
The growing demand for broadband services such as high- speed data, video, audio and multimedia, has lead to the use of point-multipoint radio systems operating in frequencies above of 10 GHz, that are not yet allocated for other services and allow the use of the large bandwidths required by these services. At these frequencies, the main contribution for the
Publicado em: 2003
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24. Microwave study of trap and precipitation of electrons in solar burst / Estudo em microondas do aprisionamento e precipitação de elétrons em explosões solares
We have studied the process of particle number density evolution during solar flares from the microwave emission point of view. In order to do this, we have used the database of Nobeyama Radio Observatory (NRO), with approximately 100 events that occurred between 1998 and 2000 that were observed in seven frequencies (1, 2, 3.8, 9.4, 17, 35, and 80 GHz), in t
Publicado em: 2003