Fault Current Limiter Using YBCO Coated Conductor-The Limiting Factor and Its Recovery Time

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

GPS Satellites Orbits: Resonance

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Novel high-power-factor ZCS-PWM preregulators

This paper introduces novel zero-current-switching (ZCS) pulsewidth-modulated (PWM) preregulators based on a new soft-commutation cell, suitable for insulated gate bipolar transistor applications. The active switches in these proposed rectifiers turn on in zero current and turn off in zero current-zero voltage. In addition, the diodes turn on in zero voltage and their reverse-recovery effects over the active switches are negligible. Moreover, based on the proposed cell, an entire family of de-to-de ZCS-PWM converters can be generated, providing conditions to obtain naturally isolated converters, for example, derived buck-boost, Sepic. and Zeta converters. The novel ac-to-dc ZCS-PWM boost and Zeta preregulators are presented in order to verify the operation of this soft-commutation cell, In order to minimize the harmonic contents of the input current, increasing the ac power factor, the average-current-mode control is used, obtaining preregulators with ac power factor near unity and high efficiency at wide load range. The principle of operation, theoretical analysis, design example, and experimental results from test units for the novel preregulators are presented. The new boost preregulator was designed to nominal values of 1.6 kW output power, 220 V(rms) input voltage, 400 V(dc) output voltage, and operating at 20 kHz. The measured efficiency and power factor of the new ZCS-PWM boost preregulator were 96.7% and 0,99, respectively, with an input current total harmonic distortion (THD) equal to 3.42% for an input voltage with THD equal to 1.61%, at rated load, the new ZCS-PWM Zeta preregulator was designed to voltage step-down operation, and the experimental results were obtained from a laboratory prototype rated at 500 W, 220 V(rm), input voltage, 110 V(dc) output voltage, and operating at 50 kHz. The measured efficiency of the new ZCS-PWM Zeta preregulator is approximately 96.9% and the input power factor is 0.98, with an input current THD equal to 19.07% while the input voltage THD is equal to 1.96%, at rated load.

A new model for tubular fluorescent lamps operated at high frequencies for dimmable applications

This paper presents a new static model for tubular fluorescent lamps (T12 bulb) operated at high frequencies. The main goal of this paper is to investigate the effects of ambient temperature and nominal switching frequency of operation in the static characteristics of tubular fluorescent lamps. The methodology for obtaining the model is based on several two-dimensional mathematical regressions, used to provide the behavior of the fluorescent lamp according to different independent variables, namely: power processed through the lamp and ambient temperature. In addition, the proposed model can be easily converted to a lamp equivalent resistance model, which can be useful for ballast designers. Finally, the curves obtained using the new model are compared to the correspondent experimental data, in order to verify the accuracy of the proposed methodology.

A 2kW interleaved ZCS-FM boost rectifier digitally controlled by FPGA device

This paper presents a 2kW single-phase high power factor boost rectifier with four cells in interleave connection, operating in critical conduction mode, and employing a soft-switching technique, controlled by Field Programmable Gate Array (FPGA). The soft-switching technique Is based on zero-current-switching (ZCS) cells, providing ZC (zero-current) turn-on and ZCZV (zero-current-zero-voltage) turn-off for the active switches, and ZV (zero-voltage) turn-on and ZC (zero-current) turn-off for the boost diodes. The disadvantages related 'to reverse recovery effects of boost diodes operated in continuous conduction mode (additional losses, and electromagnetic interference (EMI) problems) are minimized, due to the operation in critical conduction mode. In addition, due to the Interleaving technique, the rectifer's features include the reduction in the input current ripple, the reduction in the output voltage ripple, the use of low stress devices, low volume for the EMI input filter, high input power factor (PF), and low total harmonic distortion (THD) In the input current, in compliance with the TEC61000-3-2 standards. The digital controller has been developed using a hardware description language (VHDL) and implemented using a XC2S200E-SpartanII-E/Xilinx FPGA device, performing a true critical conduction operation mode for four interleaved cells, and a closed-loop to provide the output voltage regulation, like as a pre-regulator rectifier. Experimental results are presented for a 2kW implemented prototype with four interleaved cells, 400V nominal output voltage and 220V(rms) nominal input voltage, in order to verify the feasibility and performance of the proposed digital control through the use of a FPGA device.

Alternative proposal for Modal Representation of a Non-transposed Three-Phase Transmission Line with a Vertical Symmetry Plane

The objective of this paper is to show an alternative representation in time domain of a non-transposed three-phase transmission line decomposed in its exact modes by using two transformation matrices. The first matrix is Clarke's matrix that is real, frequency independent, easily represented in computational transient programs (EMTP) and separates the line into quasi-modes a, b and zero. After that, Quasi-modes a and zero are decomposed into their exact modes by using a modal transformation matrix whose elements can be synthesized in time domain through standard curve-fitting techniques. The main advantage of this alternative representation is to reduce the processing time because a frequency dependent modal transformation matrix of a three-phase line has nine elements to be represented in time domain while a modal transformation matrix of a two-phase line has only four elements. This paper shows modal decomposition process and eigenvectors of a non-transposed three-phase line with a vertical symmetry plane whose nominal voltage is 440 kV and line length is 500 km.

Thermal treatment of superconductor thin film of the BSCCO system using domestic microwave oven

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

Influence of glass forming histories on the structural and thermal properties of tellurite glasses

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effects of glass-forming histories on the crystallization kinetic of the 20Li(2)O-80TeO(2) glass

In the present work, tellurite 20Li(2)O-80TeO(2) glasses were prepared with identical nominal composition under different glass-forming histories to produce a stressed and stress-free samples. X-ray Diffraction (XRD) and Differential Scanning Calorimetry (DSC) techniques were used to study the effects of the glass-forming histories on the thermal and structural properties of these glasses. The gamma-TeO2 (metastable), alpha-TeO2 and alpha-Li2Te2O5 phases were identified during the controlled devitrification in these glasses. The mestastable character of the gamma-TeO2 phase was clearly observed in the glass under stress but this effect is not so clear in the stress-free glass. The gamma-TeO2 and alpha-TeO2 phases crystallizes during the initial stages of crystallization in both studied glasses while the alpha-Li2Te2O5 phase crystallize in the final stages of the crystallization. The activation energies and Avrami exponent were calculated for both studied glasses with different particle size leading to E-3 > E-2 > E-1 for stressed glass and E-3 > E-2 approximate to E-1 for stress-free glass, where E-1, E-2 and E-3 were associated to the gamma-TeO2, alpha-TeO2 and alpha-Li2Te2O5 phases, respectively. The observed distinct (n) over bar (1) < <(n)over bar>(2) < <(n)over bar>(3) in both glasses is an indicative that nucleation and growth takes place by more than one mechanism in the early stages of the crystallization. (C) 2011 Elsevier B.V. All rights reserved.

PHYSICAL PROPERTIES of TELLURITE GLASSES PREPARED UNDER DIFFERENT THERMAL HISTORIES

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Qualidade de vida de pacientes com deformidade dentofacial

In the last decade, an increasing number of studies focusing on the impact of oral deformities on quality of life have been published. However, the evaluation of patients at different phases of the treatment has not been performed. Therefore, the purpose of this study was to determine the impact that dentofacial deformities have on patients` quality of life, as well as the influence exerted by social, economic, demographic and orthodontic factors, type and severity of malocclusion. A bicentric study - of the cross-sectional type of repeated panels - involving two cities - Natal and Rio de Janeiro - was carried out. A total of 227 patients participated in the study: 71 patients in the initial phase of the treatment (before any orthosurgical procedure), 115 patients in the pre-surgical (with braces) phase and 41 patients in the postoperative phase. The quality of life was measured using the Orthognatic Quality of Life Questionnnaire - OQLQ, translated and validated into Portuguese. The normative and aesthetic need for treatment was assessed with the Index of Orthodontic Treatment Need (IOTN) and the Dental Aesthetic Index (DAI); the social, economic and demographic factors, the type of service and malocclusion were also assessed. The data were analyzed through χ2/ Fisher`s exact test to seek the association between the nominal categorical variables in the three phases of treatment, Mann Whitney and Kruskal-Wallis test for gauging the existence of significant differences between two and three groups regarding each domain of OQLQ, respectively. For all tests, it was adopted a significance level of 5%. There was a statistically significant difference (p <0.001) in the general scores of OQLQ and in the domains of social aspects, facial aesthetics and oral function, when the "postoperative group" was compared to the "initial" and "orthodontic preparation" groups. Women, single, aged between 31 and 59 and living in Natal had the greatest impact on quality of life among patients in the "orthodontic preparation" group. Only the variable "income" (2 to 3 minimum wages), for the "initial" group, and gender (female) for the "postoperative" group, showed significant association with quality of life. The normative variable IOTN (DHC and AC) showed significant association with the OQLQ for the "initial" group, and the IOTN-AC-auto in the group of orthodontic preparation, being less important to women. We conclude that the ortho-surgical therapy has positive effects on quality of life after orthognathic surgery

The spiny dogfish ('cacao-bagre'): description of an envenoming in a fisherman, with taxonomic and toxinologic comments on the Squalus gender

The authors report an injury caused by a spiny dogfish (Squalus sp) in a professional fisherman that was got hurt in the left hand for a spine in the dorsal fin of the fish and felt excruciating local pain for 6 h and manifested local edema and erythema. The sharks of the Squalus gender, in a similar way to the gender Heterodontus, present two spines in position previous to the dorsal fins, with channels presenting a whitish mass, composed of great and vacuolated cells that produce venom. The Squalus gender has a complex taxonomy, with five nominal species mentioned in Brazil: S. acanthias, S., blainvillei, S. cubensis, S. megalops and S. mitsukurii. The species associated to the injury belongs to the group 'megalops/cubensis'. A detailed study on the taxonomy and toxinology of the Squalus gender in Brazil would be of vital importance in the resolution of those problems and it would serve as subsidy for any other works involving their representatives, besides with aspects of envenoming that this gender can cause and that has rare citations in the literature. (c) 2005 Elsevier Ltd. All rights reserved.

Propriedades magnéticas e magnetorresistência em filmes finos de Ni81Fe19

The ferromagnetic materials play an important role in the development of various electronic devices and, have great importance insofar as they may determine the efficiency, cost and, size of the devices. For this reason, many scientific researches is currently focused on the study of materials at ever smaller scales, in order to understand and better control the properties of nanoscale systems, i.e. with dimensions of the order of nanometers, such as thin film ferromagnetic. In this work, we analyze the structural and magnetic properties and magnetoresistance effect in Permalloy-ferromagnetic thin films produced by magnetron sputtering. In this case, since the magnetoresistance effect dependent interfaces of thin films, this work is devoted to the study of the magnetoresistance in samples of Permalloy in nominal settings of: Ta[4nm]/Py[16nm]/Ta[4nm], Ta[4nm]/Py[16nm]/O2/Ta[4nm], Ta[4nm]/O2/Py[16nm]/Ta[4nm], Ta[4nm]/O2/Py[16n m]/O2/Ta[4nm], as made and subjected to heat treatment at temperatures of 160ºC, 360ºC e 460ºC, in order to verify the influence of the insertion of the oxygen in the layer structure of samples and thermal treatments carried out after production of the samples. Results are interpreted in terms of the structure of the samples, residual stresses stored during deposition, stresses induced by heat treatments and magnetic anisotropies

Consenso em reumatologia pediátrica: parte I - definição dos critérios de doença inativa e remissão em artrite idiopática juvenil/artrite reumatóide juvenil

Não há critérios universalmente aceitos para a remissão clínica em artrite idiopática juvenil/artrite reumatóide juvenil (AIJ/ARJ). OBJETIVO: formar consenso sobre estes critérios. MÉTODOS: foi utilizado um inquérito pelo método Delphi para reunir os critérios vigentes e utilizados por especialistas em reumatologia pediátrica (RP) no mundo todo. A análise dos resultados constituiu a base para uma Consensus Conference utilizando a nominal group technique (NGT) para alcançar o consenso nas questões não resolvidas após a análise dos questionários deste inquérito. Cento e trinta RP de 34 países responderam ao inquérito e 20 RP de nove países elegeram os critérios durante dois dias, em processo de discussão estruturada, para formar consenso pela NGT. RESULTADOS: os critérios de doença inativa deveriam incluir: 1) nenhuma articulação com artrite em atividade; 2) ausência de febre, rash, serosite, esplenomegalia ou linfadenopatia generalizada atribuída à AIJ/ARJ; 3) ausência de uveíte em atividade; 4) VHS ou PCR negativas (se ambos forem testados, ambos devem ser normais); 5) a avaliação global pelo médico deve indicar o melhor escore possível, indicando doença inativa. CONCLUSÕES: de acordo com o voto de consenso, seis meses contínuos de doença inativa são necessários para se considerar um paciente em estado de remissão com medicação; 12 meses contínuos de doença inativa e sem medicação são necessários para considerar um paciente em estado de remissão sem medicação. O critério para remissão sem medicação deve prever com acurácia de 95% a probabilidade inferior a 20% de recaída em cinco anos.

A new species of mullet (Teleostei : Mugilidae) from Venezuela, with a discussion on the taxonomy of Mugil gaimardianus

The original description of Mugil gaimardianus has created various taxonomic problems in the past since the description is ambiguous and the type specimen is apparently lost. The name M. gaimardianus could not be reliably applied to any known species and was suppressed by the International Commission on Zoological Nomenclature (ICZN) (Bulletin of Zoological Nomenclature, 51: 286-287, 1994). Nevertheless, karyological evidence has shown that there is a species of mullet in Venezuelan coastal waters that does not conform to the description of any other mullet from the Western Central Atlantic and has the feature of a red eye that was often used by earlier authors to define nominal M. gaimardianus. The purpose of this study was to make a morphological description of these unusual specimens, provide a morphological diagnosis from other species of Mugil present in the Caribbean and Western Central Atlantic and establish a valid name for the species. (c) 2007 the Authors Journal complication (c) 2007 the Fisheries Society of the British Isles.