38 resultados para Contractors Rating of
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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A percepção subjetiva de esforço (PSE) é determinada de forma não invasiva e utilizada juntamente com a resposta lactacidêmica como indicadores de intensidade durante teste incremental. em campo, especialmente na natação, há dificuldades nas coletas sanguíneas; por isso, utilizam-se protocolos alternativos para estimar o limiar anaeróbio. Assim, os objetivos do estudo foram: prescrever um teste incremental baseado na PSE (Borg 6-20) visando estimar os limiares metabólicos determinados por métodos lactacidêmicos [ajuste bi-segmentado (V LL), concentração fixa-3,5mM (V3,5mM) e distância máxima (V Dmáx)]; relacionar a PSE atribuída em cada estágio com a freqüência cardíaca (FC) e com parâmetros mecânicos de nado [freqüência (FB) e amplitude de braçada (AB)], analisar a utilização da escala 6-20 na regularidade do incremento das velocidades no teste e correlacionar os limiares metabólicos com a velocidade crítica (VC). Para isso, 12 nadadores (16,4 ± 1,3 anos) realizaram dois esforços máximos (200 e 400m); os dados foram utilizados para determinar a VC, velocidade de 400m (V400m) e a freqüência crítica de braçada (FCb); e um teste incremental com intensidade inicial baseada na PSE, respectivamente, 9, 11, 13, 15 e 17; sendo monitorados em todos os estágios a FC, lactacidêmia e os tempos de quatro ciclos de braçadas e das distâncias de 20m (parte central da piscina) e 50m. Posteriormente, foram calculadas as velocidades dos estágios, FB, AB, V LL, V3,5mM e V Dmáx. Utilizaram-se ANOVA e correlação de Pearson para análise dos resultados. Não foram encontradas diferenças entre VC, V Dmáx e V LL, porém a V3,5mM foi inferior às demais velocidades (P < 0,05). Correlações significativas (P < 0,05) foram observadas entre VC versus V400m, V Dmáx e V3,5mM; V400m versus V3,5mM e V Dmáx; V Dmáx versus V LL; e no teste incremental entre PSE versus velocidade, [Lac], FC, FB e AB (P < 0,05). Concluímos que a PSE é uma ferramenta confiável no controle da velocidade dos estágios durante teste incremental na natação.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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TEMA: o controle do tamanho da abertura velofaríngea é uma variável importante na caracterização do perfil acústico da fala hipernasal. OBJETIVO: investigar os aspectos espectrais das frequências de F1, F2, F3, formante nasal(FN) e anti-formante, em Hertz, para as vogais [a] e [ã] na presença de aberturas feitas no bulbo de réplicas da prótese de palato de uma paciente com insuficiência velofaríngea. MÉTODO: gravações de produções de quatro palavras (pato/mato e panto/manto) inseridas em frase veículo foram obtidas em cinco condições de funcionamento velofaríngeo: prótese sem aberturas (condição controle: CC), prótese com abertura de 10mm² no bulbo (condição experimental - CE10), com abertura de 20mm² (condição experimental - CE20), com abertura de 30mm² (condição experimental - CE30), e sem prótese (condição experimental aberta - CEA). Cinco fonoaudiólogos julgaram a nasalidade de fala ao vivo, durante a leitura de um texto oral. As gravações foram usadas para análise espectral. RESULTADOS: valores de F1 foram significativamente mais altos para [a] que para [ã] em todas as condições. Valores de F2 para [a] em CE20 e CE30 foram significantemente mais baixos que nas outras condições, aproximando-se dos valores para [ã]. Valores de F3 não foram significativamente diferentes nas diferentes condições. Houve relação entre os achados de FN e anti-formantes e a percepção de nasalidade para as condições CE10 e CE20. CONCLUSÃO: foram observadas mudanças significativas nos valores espectrais estudados de acordo com alterações no tamanho da abertura velofaríngea.
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A novel hybrid three-phase rectifier is proposed. It is capable to achieve high input power factor (PF) and low total harmonic input currents distortion (THDI). The proposed hybrid high power rectifier is composed by a standard three-phase six-pulse diode rectifier (Graetz bridge) with a parallel connection of single-phase Sepic rectifiers in each three-phase rectifier leg. Such topology results in a structure capable of programming the input current waveform and providing conditions for obtaining high input power factor and low harmonic current distortion. In order to validate the proposed hybrid rectifier, this work describes its principles, with detailed operation, simulation, experimental results, and discussions on power rating of the required Sepic converters as related to the desired total harmonic current distortion. It is demonstrated that only a fraction of the output power is processed through the Sepic converters, making the proposed solution economically viable for very high power installations, with fast investment payback. Moreover, retrofitting to existing installations is also feasible since the parallel path can be easily controlled by integration with the existing dc-link. A prototype has been implemented in the laboratory and it was fully demonstrated to both operate with excellent performance and be feasibly implemented in higher power applications.
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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A novel hybrid high power rectifier capable to achieve unity power factor is proposed in this paper. Single-phase SEPIC rectifiers are associated in parallel with each leg of three-phase 6-pulse diode rectifier resulting in a programmable input current waveform structure. In this paper it is described the principles of operation of the proposed converter with detailed simulation and experimental results. For a total harmonic distortion of the input line current (THDI) less than 2% the rated power of the SEPIC rectifiers is 33%. Therefore, power rating of the SEPIC parallel converters is a fraction of the output power, on the range of 20% to 33% of the nominal output power, making the proposed solution economically viable for high power installations, with fast pay back of the investment. Moreover, retrofits to existing installations are also possible with this proposed topology, since the parallel path can be easily controlled by integration with the already existing de-link. Experimental results are presented for a 3 kW implemented prototype, in order to verify the developed analysis.
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In this paper is proposed and analyzed a digital hysteresis modulation using a FPGA (Field Programmable Gate Array) device and VHDL (Hardware Description Language), applied at a hybrid three-phase rectifier with almost unitary input power factor, composed by parallel SEPIC controlled single-phase rectifiers connected to each leg of a standard 6-pulses uncontrolled diode rectifier. The digital control allows a programmable THD (Total Harmonic Distortion) at the input currents, and it makes possible that the power rating of the switching-mode converters, connected in parallel, can be a small fraction of the total average output power, in order to obtain a compact converter, reduced input current THD and almost unitary input power factor. The proposed digital control, using a FPGA device and VHDL, offers an important flexibility for the associated control technique, in order to obtain a programmable PFC (Power Factor Correction) hybrid three-phase rectifier, in agreement with the international standards (IEC, and IEEE), which impose limits for the THD of the AC (Alternate Current) line input currents. Finally, the proposed control strategy is verified through experimental results from an implemented prototype. ©2008 IEEE.
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In this paper is proposed and analyzed a digital hysteresis modulation using a FPGA (Field Programmable Gate Array) device and VHDL (Hardware Description Language), applied at a hybrid three-phase rectifier with almost unitary input power factor, composed by parallel SEPIC controlled single-phase rectifiers connected to each leg of a standard 6-pulses uncontrolled diode rectifier. The digital control allows a programmable THD (Total Harmonic Distortion) at the input currents, and it makes possible that the power rating of the switching-mode converters, connected in parallel, can be a small fraction of the total average output power, in order to obtain a compact converter, reduced input current THD and almost unitary input power factor. Finally, the proposed digital control, using a FPGA device and VHDL, offers an important flexibility for the associated control technique, in order to obtain a programmable PFC (Power Factor Correction) hybrid three-phase rectifier, in agreement with the international standards (IEC, and IEEE), which impose limits for the THD of the AC (Alternate Current) line input currents. The proposed strategy is verified by experiments. © 2008 IEEE.
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This paper proposal presents the development and the experimental analysis of a new single-phase hybrid rectifier structure with high power factor (PF) and low harmonic distortion of current (THDI), suitable for application in traction systems of electrical vehicles pulled by electrical motors (trolleybus), which are powered by urban distribution network. This front-end rectifier structure is capable of providing significant improvements in trolleybuses systems and in the urban distribution network costs, and efficiency. The proposed structure is composed by an ordinary single-phase diode rectifier with parallel connection of a switched converter. It is outlined that the switched converter is capable of composing the input line current waveform assuring high power factor (HPF) and low THDI, as well as ordinary front-end converter. However, the power rating of the switched converter is about 34% of the total output power, assuring robustness and reliability. Therefore, the proposed structure was named single-phase HPF hybrid rectifier. A prototype rated at 15kW was developed and analyzed in laboratory. It was found that the input line current harmonic spectrum is in accordance with the harmonic limits imposed by IEC61000-3-4. The principle of operation, the mathematical analysis, the PWM control strategy, and experimental results of a 15kW prototype are also presented in this paper. © 2009 IEEE.
Influência da seleção dos estágios incrementais sobre a intensidade de lactato mínimo: Estudo piloto
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The purposes of this study were to assess the influence of stage selection from the incremental phase and the use of peak lactate after hyperlactatemia induction on the determination of the lactate minimum intensity (iLACmin). Twelve moderately active university students (23±5 years, 78.3±14.1 kg, 175.3±5.1 cm) performed a maximal incremental test to determine the respiratory compensation point (RCP) (initial intensity at 70 W and increments of 17.5 W every 2 minutes) and a lactate minimum test (induction with the Wingate test, the incremental test started at 30 W below RCP with increments of 10 W every 3 minutes) on a cycle ergometer. The iLACmin was determined using second order polynomial adjustment applying five exercise stage selection: 1) using all stages (iLACmin P); 2) using all stages below and two stages above iLACminP(iLACminA); 3) using two stages below and all stages above iLACminP(iLACminB); 4) using the largest and same possible number of stages below and above the iLACminP(iLACminI); 5) using all stages and peak lactate after hyperlactatemia induction (iLACminD). No differences were found between the iLACminP(138.2±30.2 W), iLACminA(139.1±29.1 W), iLACminB(135.3±14.2 W), iLACminI(138.6±20.5 W) and iLACmiD(136.7±28.5 W) protocols, and a high level of agreement between these intensities and iLACminPwas observed. Oxygen uptake, heart rate, rating of perceived exertion and lactate corresponding to these intensities was not different and was strongly correlated. However, the iLACminBpresented the lowest success rate (66.7%). In conclusion, stage selection did not influence the determination of iLACmin but modified the success rate. © Creative Commom.
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Pós-graduação em Saúde Coletiva - FMB
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Pós-graduação em Agronomia - FEIS
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Pós-graduação em Engenharia Elétrica - FEIS