325 resultados para TOPOLOGIA


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Pós-graduação em Ciência Florestal - FCA

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Pós-graduação em Engenharia Elétrica - FEIS

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Os ambientes da L´ogica e da Topologia tˆem a compacidade como uma propriedade importante. Nos dois diferentes contextos as no¸c˜oes de compacidade s˜ao diversas. Na l´ogica, dizemos que um conjunto de f´ormulas ∆ ´e compacto quando a existˆencia de modelo para todo subconjunto finito de ∆ implica que tamb´em ∆ tem modelo. A l´ogica ´e compacta, se o conjunto de suas f´ormulas v´alidas ´e compacto. Na topologia, um conjunto A ´e compacto, caso qualquer cobertura de A por abertos admita uma subcobertura finita. Neste trabalho, mostramos uma maneira de relacionar tais no¸c˜oes de compacidade.

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This paper shows the modeling and control of a single-phase full-bridge inverter with high-frequency transformer that may be used as part of a two-stage converter with transformerless DC-DC side or as a single-stage converter (simple DC-AC converter) for grid-connected PV applications. The inverter is modeled in order to obtain a small-signal transfer function used to design the P+Resonant current controller. A highfrequency step-up transformer results in reduced voltage switches and better efficiency compared with converters in which the transformer is used on the DC-DC side. Simulations and experimental results with a 200 W prototype are shown. 1

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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This work describes the development of an electro-mechanical micro-discharges device operating at ambient condition of pressure and temperature, capable to produce plasma jets for surface finishing. The discharges are produced through a needle shape electrode hollow cathode type by which flows the helium gas. The voltage applied on the electrode is provided for an AC/AC switching voltage converter of full-bridge topology. The converter is energized by a power line of 110/220 VAC, 60 Hz and gives a 1000 V peak-to-peak from 5 kHz to 40 kHz square waveform output. The output frequency is defined by a control signal provided by an external signal generator. The equipment setup includes output acquisition of voltage and current and a photo-detector for photo-electrical measurements, which allows an optical characterization of the plasma jet

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This work describes the development of an electro-mechanical micro-discharges device operating at ambient condition of pressure and temperature, capable to produce plasma jets for surface finishing. The discharges are produced through a needle shape electrode hollow cathode type by which flows the helium gas. The voltage applied on the electrode is provided for an AC/AC switching voltage converter of full-bridge topology. The converter is energized by a power line of 110/220 VAC, 60 Hz and gives a 1000 V peak-to-peak from 5 kHz to 40 kHz square waveform output. The output frequency is defined by a control signal provided by an external signal generator. The equipment setup includes output acquisition of voltage and current and a photo-detector for photo-electrical measurements, which allows an optical characterization of the plasma jet

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We discuss relationships in Lindelof spaces among the properties "indestructible". "productive", "D", and related properties. (C) 2011 Elsevier B.V. All rights reserved.