17,788 research outputs found
Conversores Push-Pull PWM CC-CC trifásicos alimentados em corrente
Full text linkTese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Elétrica, Florianópolis, 2010In this thesis, a three-phase current-fed Push-Pull DC-DC converter and its version with active clamping and soft-switching are proposed. First, the topology with passive clamping is studied. When compared to single-phase topologies, this three-phase dc-dc converter increases the power density, uses the magnetic core of the transformer more efficiently, reduces the stresses on the switches and requires smaller filters since the input and output frequencies are three times higher than the switching frequency. To sum up, this topology uses three active switches connected to the same reference, which simplifies the gate drive circuitry. After this, the three-phase current-fed Push-Pull ZVS-PWM DC-DC converter with active clamping is proposed as an improvement to the first topology. In this converter, the active clamping technique is employed by connecting the primary side of the transformer to a three-phase full bridge of switches and a clamping capacitor. This circuit allows the energy from the leakage inductances to be reused, increasing the efficiency of the converter. If appropriate parameters are chosen, soft-switching of the switches (ZVS) can also be achieved. The soft-switching improves the efficiency even further, allows higher switching frequencies to be used and reduces the electromagnetic interference (EMI) significantly. Applications such as fuel cell systems, transportation and uninterruptable power supplies are some examples that can benefit from the advantages presented by this converter. The theoretical analysis, a design example and experimental results from a prototype implementing this topology are presented. The prototype was designed to process 4 kW at full load with an input voltage of 120 V, an output voltage of 400 V and a switching frequency of 40 kHz.Nesta tese, um conversor Push-Pull CC-CC trifásico alimentado em corrente e sua versão com grampeamento ativo e comutação suave são propostos. Primeiramente, a topologia com grampeamento passivo é estudada. Quando comparado com topologias monofásicas, este conversor CC-CC trifásico aumenta a densidade de potência, utiliza o núcleo magnético do transformador mais eficientemente, reduz os esforços nos interruptores e requer filtros menores já que estes são submetidos a uma freqüência igual a três vezes a freqüência de comutação. Além disso, esta topologia usa três interruptores ativos conectados à mesma referência, o que simplifica os circuitos de comando de gatilho. Depois disso, o conversor Push-Pull ZVS-PWM CC-CC trifásico alimentado em corrente com grampeamento ativo é proposto como um aprimoramento à primeira topologia. Neste conversor, a técnica de grampeamento ativo é empregada conectando o lado primário do transformador a uma ponte completa trifásica de interruptores e um capacitor de grampeamento. Este circuito permite que a energia armazenada nas indutâncias de dispersão seja reutilizada, aumentando o rendimento do conversor. Utilizando-se parâmetros adequados, a comutação suave dos interruptores (ZVS) pode também ser obtida. A comutação suave melhora o rendimento do conversor, permite o uso de freqüências de comutação maiores e reduz a interferência eletromagnética (EMI). Aplicações como sistemas de células a combustível, meios de transporte e fontes ininterruptas de energia são exemplos que podem se beneficiar das vantagens apresentadas por este conversor. São apresentados a análise teórica, um exemplo de projeto e resultados experimentais para um protótipo implementando essa topologia. O protótipo foi projetado para processar 4 kW em potência nominal com uma tensão de entrada de 120 V, uma tensão de saída de 400 V e uma freqüência de comutação de 40 kHz
An analysis of the mode of action of carbachol on the chick biventer cervicis nerve--muscle preparation.
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Morphogenesis of the membranous labyrinth in penaeid shrimp cells infected with Penaeus monodon baculovirus (MBV).
No full textIdentification and genetic characterization of yeasts isolated from freshwater prawns, Macrobrachium rosenbergii de Man, in Taiwan.
No full textThe construction of Karen Karnak: The multi-author-function
No full textThis thesis is situated within the comparatively recent developments of Web 2.0 and the emergence of interactive WikiMedia, and explores the mode of authorship within a Read/Write culture compared to that of a Read/Only tradition. The hypothesis of this study is that the role of the audience has become merged with the author, and as such, represents new functions and attributes, distinct from a more conventional concept of authorship, in which the roles of audience and author are more separate. Read/Write and participatory culture, as defined by this study, is focused on collaboration, and includes the influences of D.I.Y. culture, Open-Source practices and the production of text by multiple authors. Multi-authorship presents a re-thinking of several concepts which support the notion of the individual author, since the focus of multi-authorship is not on attribution and ownership of a finished text, but on the continued malleability of a text. Modes of multi-authorship, demonstrated in the use of the pseudonyms Alan Smithee and Karen Eliot, represent declarative authors whose names signify multiple origins, whilst concurrently indicating a distinct body of work. The function of these names form an important context to this study, since primary research involves the construction of an experimental mode of multi-authorship utilising WikiMedia technology and the interaction of thirty nine participants, who are invited to create a body of work under the collective pseudonym Karen Karnak. The data generated by this experiment is analysed using aspects of Michel Foucault's author-function to identify and determine power structures inherent in the WikiMedia context. The interplay of power structures, including concepts such as identity, ownership and the body of work, affect the resulting mode of authorship and contribute to the construction of Karen Karnak, suggesting further areas of research into the emerging multi-author
The effects of Bu Yang Huan Wu Tang on post-stroke epilepsy: a nationwide matched study
No full textShu-Wen Weng,1,* Ta-Liang Chen,2–4 Chun-Chieh Yeh,5,6 Hsin-Long Lane,7 Chien-Chang Liao,2–4,8,* Chun-Chuan Shih7,9 1Department of Chinese Medicine, Taichung Hospital, Ministry of Health and Welfare, Taichung, Taiwan; 2Department of Anesthesiology, Taipei Medical University Hospital, Taipei, Taiwan; 3Anesthesiology and Health Policy Research Center, Taipei Medical University Hospital, Taipei, Taiwan; 4Department of Anesthesiology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan; 5Department of Surgery, China Medical University Hospital, Taichung, Taiwan; 6Department of Surgery, University of Illinois, Chicago, IL, USA; 7School of Chinese Medicine for Post-Baccalaureate, I-Shou University, Kaohsiung, Taiwan; 8School of Chinese Medicine, China Medical University, Taichung, Taiwan; 9Program for the Clinical Drug Discovery from Botanical Herbs, Taipei Medical University, Taipei, Taiwan *These authors contributed equally to this work Objective: To compare the long-term risk of epilepsy in stroke patients who use Bu Yang Huan Wu Tang (BYHWT) and those who do not. Methods: In the Taiwanese national insurance claims data, we identified newly diagnosed stroke patients receiving inpatient care in the years 2000–2004. Using propensity score-matched pairs to balance the baseline characteristics, we selected eligible stroke patients who did (n=8,971) and did not (n=8,971) receive BYHWT. These two groups were followed up until the end of 2009 to track the occurrence of epilepsy. We used Cox proportional hazard models to calculate the adjusted HRs and 95% CIs for post-stroke epilepsy during the follow-up period according to BYHWT use. Results: Compared with the control group, stroke patients with BYHWT had a reduced risk of epilepsy during the 5–9 years of the follow-up period (HR 0.69, 95% CI 0.61–0.77). The association between BYHWT and reduced post-stroke epilepsy was significant in various subgroups of stroke patients. There was a dose-dependent decrease in the frequency of epilepsy with increasing quantities of BYHWT use from 1 package (HR 0.77, 95% CI 0.66–0.90) to ≥6 packages (HR 0.52, 95% CI 0.42–0.65). Conclusion: Stroke patients who received BYHWT therapy had a reduced long-term risk of epilepsy, and the beneficial effect could be observed in various subgroups. However, future clinical trials will be necessary to corroborate the present findings and identify the biochemical mechanism involved. Keywords: stroke, epilepsy, Bu Yang Huan Wu Tang, long-term ris
Detection of Penaeus monodon Baculovirus (MBV) mRNA in hepatopancreatic cells of the Penaeus monodon Fabricius by in situ hybridization.
No full textDetection of Penaeus-monodon-type baculovirus (MBV) infection in Penaeus-monodon Fabricius by in-situ hybridization.
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