25 kHz amorphous core transformer for induction heating applications

The analysis of the feasibility and economics of amorphous core power transformers for induction heating applications in the field 10-50 kHz is developped. The results obtained on a 25 kHz-150 kVA concentric winding trial unit are presented. © 1990.

Improvements for ZCS-PWM commutation cell in high-power-factor preregulator application

A Summary of different topological arrangements concerning a ZCS-PWM cell is presented, based on the analysis of its application in boost rectifying preregulators, controlled by the technique of instantaneous average values of input current, with the purpose of obtaining high-input-power-factor rectifier and high efficiency in single-phase applications in telecommunication systems. The main characteristics of each switching cell are described, providing conditions to establish a qualitative comparison among the structures. In addition, experimental results are presented for a prototype of the latest version of the ZCS-PWM boost rectifier, implemented for processing normal values of 1200 W output power and 400 V output average voltage, at 220 V Input RMS voltage and 50 kHz switching frequency.

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.

Dynamic analysis of a new piezoelectric flextensional actuator using the J1-J4 optical interferometric method

Piezoelectric actuators are widely used in positioning systems which demand high resolution such as scanning microscopy, fast mirror scanners, vibration cancellation, cell manipulation, etc. In this work a piezoelectric flextensional actuator (PFA), designed with the topology optimization method, is experimentally characterized by the measurement of its nanometric displacements using a Michelson interferometer. Because this detection process is non-linear, adequate techniques must be applied to obtain a linear relationship between an output electrical signal and the induced optical phase shift. Ideally, the bias phase shift in the interferometer should remain constant, but in practice it suffers from fading. The J1-J4 spectral analysis method provides a linear and direct measurement of dynamic phase shift in a no-feedback and no-phase bias optical homodyne interferometer. PFA application such as micromanipulation in biotechnology demands fast and precise movements. So, in order to operate with arbitrary control signals the PFA must have frequency bandwidth of several kHz. However as the natural frequencies of the PFA are low, unwanted dynamics of the structure are often a problem, especially for scanning motion, but also if trajectories have to be followed with high velocities, because of the tracking error phenomenon. So the PFA must be designed in such a manner that the first mechanical resonance occurs far beyond this band. Thus it is important to know all the PFA resonance frequencies. In this work the linearity and frequency response of the PFA are evaluated up to 50 kHz using optical interferometry and the J1-J4 method.

Desenvolvimento e implementação de um sistema para detecção de falhas em estruturas usando microcontrolador

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Influência de parâmetros físicos e do processamento digital utilizado nos sinais oriundos do ensaio charpy instrumentado

Pós-graduação em Engenharia Civil - FEIS

Tool Condition Monitoring of Single-Point Dresser Using Acoustic Emission and Neural Networks Models

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

Analysis of linearity and frequency response of a novel piezoelectric flextensional actuator using a homodyne interferometer and the J(1)-J(4) method

Piezoelectric transducers are widely used in high-resolution positioning systems. This paper reports the experimental analysis of a novel piezoelectric flextensional actuator (PFA), which is designed by using the topology-optimization method through a low-cost homodyne Michelson interferometer. By applying the J(1) - J(4) method for signal demodulation, which provides a linear and direct measurement of dynamic optical phase shift independent of fading, the nanometric displacements of the PFA were determined. Linearity and frequency response of the PFA were evaluated up to 50 kHz. PFA calibration factor and amplification rate were determined for the PFA operating in the quasi-static regime. To confirm the observed frequencies of resonance, an impedance analyzer is also utilized to measure the magnitude and phase of the PFA admittance.

Capacidade cardiorrespiratória e distribuição de gordura corporal de mulheres com 50 anos ou mais

Verificar a relação entre capacidade cardiorrespiratória e gordura corporal em mulheres. Foram analisadas 229 mulheres com idade entre 50 e 84 anos. Foi realizada avaliação antropométrica e calculada a razão cintura/quadril, bem como o índice de conicidade. A capacidade cardiorrespiratória foi avaliada pelo teste de caminhada de seis minutos. Com o pedômetro foi possível avaliar: velocidade, comprimento da passada e total de passos. Os resultados foram distribuídos em quartil, e a comparação feita pela análise de variância com post-hoc. A relação entre teste de caminhada de seis minutos e a antropometria foi feita pela correlação de Pearson. Os resultados revelaram que mulheres com capacidade cardiorrespiratória no quartil4 apresentaram idade estatisticamente menor (p<0,05) que as do quartil1. As medidas antropométricas apresentaram valores menores (p<0,05), quando comparados os resultados dos quartis3 e 4 com os quartis1 e 2. Conclui-se que mulheres com maior tecido adiposo e acúmulo de gordura central apresentam menor capacidade cardiorrespiratória.

Improvement of electrical properties of Sr-modified (Pb,Ca)TiO3 thin films grown by soft chemistry route

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

The self-polarization effect in Pb(Zr0.50Ti0.50)O-3 thin films with no preferential orientation

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

Structural depth profile and nanoscale piezoelectric properties of randomly oriented Pb(Zr0.50Ti0.50)O-3 thin films

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

Determinação das doses letal 50 e 100 do propofol em nanoemulsão ou em emulsão lipídica pela via intraperitoneal em camundongos

The formulation of a drug can interfere with its absorption into the circulatory system and may result in changes in the dose required to achieve that particular effect. The aim of this study was to determine the lethal dose 50 (LD 50) and 100 (LD100) of a nanoemulsion of propofol and the lipid emulsion in mice intraperitoneally. One hundred sixty animals weighing 36.47 +/- 4.6g, which were distributed randomly into two groups: NANO and EMU who received propofol 1% in the nanoemulsion and lipid emulsion, respectively, intraperitoneally. Began with a dose of 250mg/kg (n=10) and from this isdecreased or increased the dose until achieving 0 and 100% of deaths in each group thus formed were seven subgroups in NANO (each subgroup n = 10) at doses 200, 250, 325, 350, 400, 425 and 475 mg/kg and in EMU eight subgroups (n= 10 each subset) 250, 325, 350, 400, 425, 475, 525 and 575 mg/kg. In the CONTROL group (n= 10) animals received saline in the largest volume used in the other groups to rule out death by the volume injected. Analysis of LD 50 and LD 100 were obtained by linear regression. The LD 50 was 320, 95 mg / kg and 4243, 51mg / kg and the LD 100 was445.99 mg / kg and 595.31 mg / kg to groups NANO and EMU, respectively. It follows that nanoemulsion is propofol in 25% more potent compared to the lipid emulsionintraperitoneally.

Comparative study of the topical effectiveness of the andiroba oil (Carapa guianensis) and DEET 50% as repellent for Aedes sp

O DEET (N, N-dietil-3-metilbenzamida) é hoje o repelente mais efetivo disponível, porém, seu uso pode apresentar importantes efeitos colaterais tópicos e sistêmicos. Alguns compostos botânicos, como a Andiroba (Carapa guianensis), têm demonstrado propriedades repelentes a um baixo custo e baixa toxicidade. Quatro voluntários hígidos submeteram seus antebraços recobertos com óleo de Andiroba a 100%, DEET 50% (controle positivo), óleo de soja refinado, óleo de Andiroba 15% e na ausência de produtos (controles negativos), diretamente a picadas de fêmeas saudáveis de Aedes sp. Foram aferidos os tempos da primeira e terceira picadas. Os resultados mostraram que a mediana da primeira picada nos antebraços sem produto foi 17.5s e a terceira picada, 40.0s. No óleo de soja, as picadas ocorreram em 60.0s e 101.5s. No óleo de Andiroba 100%, em 56.0s e 142.5s. Com Andiroba 15%, em 63.0s e 97.5s. Usando DEET 50% não houve picadas após 3600s na maioria dos experimentos (p < 0.001 Wilcoxon). O óleo de Andiroba 100% comparado ao óleo de soja, antebraço sem produto e óleo de Andiroba 15%, mostrou discreta superioridade (p < 0.001 Wilcoxon). Concluímos que o óleo puro de Andiroba apresenta efeito repelente discreto contra picada de Aedes sp., sendo significativamente inferior ao DEET 50%.

Comparison between 100-g glucose tolerance test and two other screening tests for gestational diabetes: combined fasting glucose with risk factors and 50-g glucose tolerance test

CONTEXTO E OBJETIVO: A falta de consenso sobre os protocolos de rastreamento e diagnóstico do diabetes gestacional, associada às dificuldades na realização do teste oral simplificado do diabete gestacional (o teste de tolerância a 100 g de glicose, considerado padrão-ouro) justificam a comparação com alternativas. O objetivo deste trabalho é comparar o teste padrão-ouro a dois testes de rastreamento: associação de glicemia de jejum e fatores de risco (GJ + FR) e o teste oral simplificado de tolerância a 50 g de glicose (TTG 50 g), com o teste de tolerância a 100 g de glicose (TTG 100 g). TIPO DE ESTUDO E LOCAL: Estudo de coorte longitudinal, prospectivo, realizado no Serviço de Ginecologia e Obstetrícia do Hospital Universitário da Universidade Federal de Mato Grosso do Sul. MÉTODOS: 341 gestantes foram submetidas aos três testes. Calcularam-se os índices de sensibilidade (S), especificidade (E), valores preditivos (VPP e VPN), razões de probabilidade (RPP e RPN) e resultados falsos (FP e FN), positivos e negativos da associação GJ + FR e do TTG 50 g em relação ao TTG 100 g. Compararam-se as médias das glicemias de uma hora pós-sobrecarga (1hPS) com 50 e 100 g. Na análise estatística, empregou-se o teste t de Student, com limite de significância de 5%. RESULTADOS: A associação GJ + FR encaminhou mais gestantes (53,9%) para a confirmação diagnóstica que o TTG 50 g (14,4%). Os dois testes foram equivalentes nos índices de S (86,4 e 76,9%), VPN (98,7 e 98,9%), RPN (0,3 e 0,27) e FN (15,4 e 23,1%). As médias das glicemias 1hPS foram semelhantes, 106,8 mg/dl para o TTG 50 g e 107,5 mg/dl para o TTG 100 g. CONCLUSÕES: Os resultados da eficiência diagnóstica associados à simplicidade, praticabilidade e custo referendaram a associação GJ + FR como o mais adequado para o rastreamento. A equivalência das glicemias de 1hPS permitiram a proposição de um novo protocolo de rastreamento e diagnóstico do diabete gestacional, com menores custo e desconforto.