The Master's Thesis research focuses on analyzing the possibilities of using Direct Current distribution systems to distribute power to end users. Considering the shift in load types in the past few decades and also a growing demand of distributed generation, DC distribution can potentially offer higher efficiencies and cost savings to utilities. The incorporation of DC distribution offers the opportunity to eliminate multiple conversion stages for devices which are powered using DC electricity. The integration of power sources such as photovoltaics and fuel cells, which produce DC power, offer further incentives to consider the use of DC systems. Using DC systems can help eliminate the conversion losses associated with rectifiers and inverters which would be part of the infrastructure if AC distribution was used. In the literature, the study of DC distribution has been limited to customized systems. The objective of this research is to analyze DC distribution when applied to systems based on standard IEEE test feeder systems. The IEEE 13 node test feeder and the IEEE 37 node test feeder will be used as the basis for the analysis. Issues such as associated costs, protection and integration of appliances will also be addressed.

This dissertation investigates a new design for a magnetostrictive actuator that employs individually controlled coils distributed axially along the magnetostrictive rod. As a quantitative goal, the objective is to show that the multi-coil actuator can operate effectively at frequencies as high as 10,000 Hz with 900 N force and 50 microns of displacement. Conventional, single coil actuators with the same parameters for force and displacement develop significant attenuation in their response at frequencies above the first longitudinal vibration resonance at about 2750 Hz. The goal of the research is to investigate whether multiple coils can effectively increase the frequency range a least four times the range of conventional magnetostrictive actuators. This document derives a new mathematical model of the actuator that represents the spatial distributions of magnetic field and vibration, devises a control design that takes advantage of the multiple inputs to control the displacement of the actuator while consuming minimum electrical power, and describes a prototype multi-coil actuator and experimental system developed to test the idea. The simulations of the multi-coil actuator and control design demonstrate successful transient operation of the actuator over the targeted frequency range with feasible levels of input power and current. Experimental tests of the design, although limited by a computer sampling rate less than 10,000 Hz, are able to validate the predictions of the developed model of the actuator and reproduce the simulated control performance within the constraints of the experimental system.

Made available in DSpace on 2014-06-11T19:22:34Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-12-18Bitstream added on 2014-06-13T20:29:06Z : No. of bitstreams: 1 brito_ltc_me_bauru.pdf: 1279436 bytes, checksum: d3b9eb1dc19df29b8c4458d3d793b0f3 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A transmissão em corrente contínua vem sendo muita valorizada devido a seus baixos custos em relação à transmissão em corrente alternada, principalmente para grande distâncias com o uso de menos cabos para o suprimento de energia em relação ao HVDC (High Voltage Alternating Current). Os dispositivos FACTS (Flexible Alternating Current Transmission System) foram projetados para fornecer um melhor controle de qualidade de energia transmitida, podendo ser conectados na estação geradora ou na carga. Esses dispositivos melhoraram a estabilidade e o suprimento de tensão e potência, sendo muito útil para aumentar a capacidade de transmissão de energia. O presente trabalho a tensão, corrente, potência ativa e reativa consumida pelos conversores na entrada e saída dos filtros, usando um banco de capacitores, e posteriormente, substituindo o banco de capacitores por um SVC (Static Var Compensator) em um circuito HVDC-Clássico. O circuito analisado consiste de uma geração em 60 Hz, 500k V que transmite potência para uma estação de 345K V e 50Hz. Assim, também analisa a eliminação de harmônicos de corrente, comum no conversor de 12 pulsos, e o suporte de reativos para os casos de tensão e corrente reduzidos e uma falta aplicada no lado AC do inversor / The DC transmission has been very prized due the its lower costs relative to the AC transmission, mainly for long distances and with the useful of less cables to supply energy in relation at the HVAC (High Voltage Alternating Current). The FACTS devices (Flexibe Alternating Current Transmission System) were designed to supply a better control and quality of transmitted energy, and can be connected at generator station or at generator station or at load. These devices improve the stability and the capacity to supply voltage and power, being very useful to increase the transmission capacity of energy. The present work analyses the voltage, current, active e reactive power consumed by the converters, before and after the filters, using a capacitor banks, and after that, replacing the capacitor bank by a SVC (Static Var Compensator) in a Classical HVDC circuit. The analzed circuit consists of a 60Hz, 500KV generation which transmits power for a 50Hz, 34K V station. Then, also analyses the current harmonic distortion elimination, common in the 12 pulses converter, and the reactive staff for reduced voltage and current and a 3-phase fault on the inverter AC side

Orientador: André Christóvão Pio Martins / Banca: Newton Geraldo Bretas / Banca: Pedro da Costa Junior / Resumo: A transmissão em corrente contínua vem sendo muita valorizada devido a seus baixos custos em relação à transmissão em corrente alternada, principalmente para grande distâncias com o uso de menos cabos para o suprimento de energia em relação ao HVDC (High Voltage Alternating Current). Os dispositivos FACTS (Flexible Alternating Current Transmission System) foram projetados para fornecer um melhor controle de qualidade de energia transmitida, podendo ser conectados na estação geradora ou na carga. Esses dispositivos melhoraram a estabilidade e o suprimento de tensão e potência, sendo muito útil para aumentar a capacidade de transmissão de energia. O presente trabalho a tensão, corrente, potência ativa e reativa consumida pelos conversores na entrada e saída dos filtros, usando um banco de capacitores, e posteriormente, substituindo o banco de capacitores por um SVC (Static Var Compensator) em um circuito HVDC-Clássico. O circuito analisado consiste de uma geração em 60 Hz, 500k V que transmite potência para uma estação de 345K V e 50Hz. Assim, também analisa a eliminação de harmônicos de corrente, comum no conversor de 12 pulsos, e o suporte de reativos para os casos de tensão e corrente reduzidos e uma falta aplicada no lado AC do inversor / Abstract: The DC transmission has been very prized due the its lower costs relative to the AC transmission, mainly for long distances and with the useful of less cables to supply energy in relation at the HVAC (High Voltage Alternating Current). The FACTS devices (Flexibe Alternating Current Transmission System) were designed to supply a better control and quality of transmitted energy, and can be connected at generator station or at generator station or at load. These devices improve the stability and the capacity to supply voltage and power, being very useful to increase the transmission capacity of energy. The present work analyses the voltage, current, active e reactive power consumed by the converters, before and after the filters, using a capacitor banks, and after that, replacing the capacitor bank by a SVC (Static Var Compensator) in a Classical HVDC circuit. The analzed circuit consists of a 60Hz, 500KV generation which transmits power for a 50Hz, 34K V station. Then, also analyses the current harmonic distortion elimination, common in the 12 pulses converter, and the reactive staff for reduced voltage and current and a 3-phase fault on the inverter AC side / Mestre

The present thesis investigates the grain refinement in solidifying Al-7wt%Si hypoeutectic alloy driven by electric currents. The grain size reduction in alloys generated by electric currents during the solidification has been intensively investigated. However, since various effects of electric currents have the potential to generate the finer equiaxed grains, it is still argued which effect plays the key role in the grain refinement process. In addition, the knowledge about the grain refinement mechanism under the application of electric currents remains fragmentary and inconsistent. Hence, the research objectives of the present thesis focus on the role of electric current effects and the grain refinement mechanism under the application of electric currents. Chapter 1 presents an introduction with respect to the subject of grain refinement in alloys driven by electric current during the solidification process in particular, including the research objectives; the research motivation; a brief review about the research history; a short introduction on the electric currents effects and a review relevant to the research status of grain refinement mechanism. Chapter 2 gives a description of research methods. This chapter shows the employed experiment materials, experimental setup, experimental procedure, the analysis methods of solidified samples, and numerical method, respectively. Chapter 3 focuses on the role of electric current effects in the grain refinement process. A series of solidification experiments are performed under various values of effective electric currents for both, electric current pulse and direct current. The corresponding temperature measurements and flow measurements are carried out with the increase of effective electric current intensity. Meanwhile, numerical simulations are conducted to present the details of the flow structure and the distribution of electric current density and electromagnetic force. Finally, the role of electric current effects is discussed to find the key effect in the grain refinement driven by electric currents. Chapter 4 investigates the grain refinement mechanism driven by electric currents. This chapter mainly focuses on the origin of finer equiaxed grain for grain refinement under the application of electric current on account of the importance of the origin for understanding the grain refinement mechanism. A series of solidification experiments are carried out in Al-7wt%Si alloy and in high purity aluminum. The main origin of equiaxed grain for grain refinement is concluded based on the experiment results. Chapter 5 presents three further investigations based on the achieved knowledge in chapter 3 and 4 about the role of electric current effects and the grain refinement mechanism. According to the insight into the key electric current effect for the grain refinement shown in chapter 3, this chapter presents a potential approach to promote the grain refinement. In addition, the solute distribution under the influence of electric current is examined based on the knowledge about the electric current effects. Moreover, the grain refinement mechanism under application of travelling magnetic field is investigated by performing a series of solidification experiments to compare with the experiments about the grain refinement mechanism driven by electric currents shown in chapter 4. Chapter 6 summarizes the main conclusions from the presented work.

We have extended the HOLA molecular dynamics (MD) code to run slider-on-block friction experiments for Al and Cu. Both objects are allowed to evolve freely and show marked deformation despite the hardness difference. We recover realistic coefficients of friction and verify the importance of cold-welding and plastic deformations in dry sliding friction. Our first data also show a mechanism for decoupling between load and friction at high velocities. Such a mechanism can explain an increase in the coefficient of friction of metals with velocity. The study of the effects of currents on our system required the development of a suitable electrodynamic (ED) solver, as the disparity of MD and ED time scales threatened the efficiency of our code. Our first simulations combining ED and MD are presented. / text

The transport critical current density (J(_c)) of a 37 filament Bi-2223/Ag tape has been measured as a function of field and temperature from 4.2 K up to 90 K. Data have been obtained over a large current range from 10 mA up to 100 A and in fields up to 23 T with the tape in 3 orientations with respect to field. These comprehensive data have been used to test the predictions of the flux creep and weak link models used to explain J(_c) in Bi-2223 tapes. The J(_c)(B,T) dependence of optimised Bi-2223 tapes has been calculated using a curved film model. The model assumes perfect grain connectivity and that the local superconducting properties are equivalent to those in the best reported thin films. A comparison between the calculations and measured J(_c)(B,T) dependencies suggest that in high fields at 20 K, J(_c) in presently available industrially processed tapes is only a factor of 8 below the performance of ideal fully optimised tapes. Transport measurements have been made on Bi-2223 single filaments extracted from an alloy sheathed multifilamentary tape in liquid nitrogen at 77 K in fields up to 300 mT with the field aligned parallel and perpendicular to the a-b planes. Further Jc(B,T) data have been taken in a variable temperature insert at temperatures between 60 to 90 K in fields up to 15 T. In a study of the electric field-current density {E-J) characteristics of the c-axis orientated data at 77 K, negative curvature is observed in traces below 280 mT. However, the 280 mT trace exhibits both positive and negative curvature in different current regimes in contrast to the predictions of standard theory. A laboratory scale Bi-2223 superconducting magnet producing a maximum field of 1.29 T at 4.2 K has been designed and fabricated. The magnet comprises 6 resin impregnated double wound pancakes with a 40 mm bore fabricated via the react and wind route. Critical current density measurements have been made as a function of magnetic field, angle and strain at 4.2 K and 77 K on short samples of the constituent tape. The E-J characteristics of all component coils have been measured and a comparison with short sample data shows that minimal additional damage occurred beyond that produced by the bending strain on the tape and the long length variation in J(_c). Sufficient detail is provided for the non-specialist to assess the potential use of brittle superconducting tapes for magnet technology and construct a laboratory scale magnet.

No Brasil 72% dos óbitos são decorrentes de complicações destas doenças. Associado ao alto custo do Sistema Público de Saúde e elevado risco às doenças secundárias, o excesso de peso, pode ocasionar a lipodistrofia localizada, esta, caracterizada pelas poucas alternativas de tratamento, sendo o tratamento cirúrgico o mais realizado. Poucos estudos demonstram a utilização de terapia auxiliar para a redução da lipodistrofia localizada e ainda há maior restrição em pesquisas específicas visando o tratamento da lipodistrofia abdominal. O presente estudo procurou verificar os efeitos de uma terapia não invasiva, em uma região específica predisponente ao acúmulo de gordura, o abdome. Foi realizado um estudo longitudinal, de abordagem quantitativa, do tipo descritiva, composto por 33 mulheres, com acúmulo de adiposidade abdominal, na faixa etária dos 20 a 35 anos. Inicialmente todas assinaram o Termo de Consentimento Livre e Esclarecido (TCLE); sequencialmente, houve uma divisão da amostra em dois grupos: A, que realizou dez sessões seguidas do protocolo fisioterapêutico e B, que realizou cinco sessões, seguida de uma pausa e realizou outras cinco sessões do protocolo. Todas as voluntárias responderam o questionário e realizaram a primeira avaliação corporal que foi repetida após a quinta e décima sessão do protocolo fisioterapêutico além da realização do exame de Densitometria por Absorciometria de Raios X de Dupla Energia (DXA) que foi realizado ao início e término das sessões, que consistiu na aplicação abdominal de um protocolo desenvolvido baseado em associação de duas técnicas fisioterapêuticas: o ultrassom de 3MHz e a corrente alternada de média frequência. Foram analisados inicialmente os dados coletados da amostra geral seguido da análise de comparação entre os grupos A e B, para a verificação da normalidade da distribuição utilizou-se o teste de Shapiro-Wilk e para a comparação dos dados utilizou-se a ANOVA de Friedman. Os resultados encontrados para as variáveis analisadas da amostra geral: massa, perimetria de cintura, perimetria de cicatriz umbilical, perimetria da menor circunferência abdominal, perimetria da maior circunferência abdominal e percentual de gordura de tronco avaliado por meio da DXA, apresentou o valor de p<0,001 verificando uma diferença significativa comparada à avaliação inicial à final. Em relação ao percentual de gordura corporal total avaliado pela DXA, o valor de “p” foi p=0,779, demonstrando uma redução com variação de 0,1% a 2,7% entre as voluntárias. Quando comparados os grupos A e B, observou-se homogeneidade entre os grupos e não foi apresentada diferença estatística entre eles, portanto não houve alteração do resultado final. Sendo assim, este protocolo foi desenvolvido especificamente para o tratamento da lipodistrofia abdominal feminina e durante o estudo se mostrou eficaz no tratamento para redução deste tipo de adiposidade em mulheres jovens. / In Brazil the complications of these illnesses are responsible for 72% of the deaths. Overweight combined with not only the high costs of health service provided by the government, but also with the high risk of secondary diseases, can cause localized lipodystrophy which has few alternatives for treatment, being surgical treatment the most common. Few studies show the usage of adjunctive therapy in order to reduce localized lipodystrophy and still they have greater restriction in specific research aiming at the treatment of localized abdominal lipodystrophy. The objective of this study was to verify the results of a non-invasive therapy in a specific area more predisposed to fat accumulation – the abdomen. A longitudinal study was performed, using a quantitative-descriptive research composed of 33 women with abdominal fat accumulation, with an age range of 20 to 35 years old. All of them signed an informed consent term (TCLE) and the sample was divided in two groups: A, which held ten physiotherapy sessions according to the physiotherapy protocol and B, which held five physiotherapy sessions, followed by a pause, and then held other five sessions according to the protocol. All the volunteers answered a questionnaire and went through their first body evaluation, which was repeated after the fifth and tenth session according to the physiotherapy protocol. They also underwent a Dual-Energy X-ray absorptiometry (DXA) test, repeated in the beginning and in the end of the sessions, which consisted of an application of a protocol, in the abdomen, developed based on the association of two physiotherapy techniques: 3-MHz ultrasound and medium-frequency alternating current. Initially, the general sample data was analyzed, followed by the comparative analysis between groups A and B. A Shapiro- Wilk test was performed to check the normality of the distribution and ANOVA Friedman was used to compare the data. The results for the variables analyzed in general sample were: mass, waist measurement, umbilical scar measurement, narrowest abdominal circumference measurement, widest abdominal circumference measurement and midsection fat percentage p<0,001, evaluated by DXA, showing a considerable difference if compared from the initial evaluation to the final. The percentage of total body fat evaluated by DXA was p=0,779 demonstrating reduction with a variation of 0,1% to 2,7% among all the volunteers. Comparing groups A and B, homogeneity could be observed and there was no statistic difference between them. Therefore, this protocol was developed specifically for the treatment of abdominal lipodystrophy in women and during the present study it demonstrated to be efficient for the treatment of reduction for this type of adiposity in young women.

CAPES / Uma má qualidade de energia elétrica gera grandes prejuízos para a sociedade. Desta forma são utilizados equipamentos denominados analisadores de qualidade de energia elétrica para quantizar os valores destes distúrbios e assim determinar as causas destas anormalidades. O grande problema destes equipamentos é o custo elevado e geralmente são importados inviabilizando uma medição multiponto do sistema elétrico do cliente. Neste cenário, este trabalho objetiva fornecer subsídios e alternativas para o desenvolvimento de equipamentos analisadores de qualidade de energia, que consiste de um conjunto com sensores de corrente e tensão e um módulo central de processamento. No desenvolvimento de quaisquer sensores ou instrumentação surgem algumas dificuldades de condicionamento de sinal por causa das características elétricas do componente usado e principalmente por causa do ruído. Alguns meios de contornar estes problemas são a utilização de uma instalação adequada dos equipamentos de medição, blindagens eletromagnéticas e projeto de PCB’s. No caso de sensores magnéticos, a histerese, saturação magnética e as interferências por campos magnéticos externos introduzem erro de medida no sistema e para a resolução destes problemas foram adotadas configurações de sensores Hall em malha fechada e diferencial. Outro componente que pode ser usado é o sensor Flux-gate que possui potencialidade para medições de corrente de pequena ordem além de oferecer a vantagem de maior integrabilidade ao sistema medidor. Na sequência foi projetado e construído um registrador de tensão e corrente para análise de qualidade de energia elétrica, denominado PQ-Logger, que pode usar estes sensores mencionados anteriormente. O uso de um DSP e um chip para acessar um pendrive genérico permite o armazenamento destes dados. O PQ-Logger-Tran é outro equipamento que foi idealizado para armazenar trechos de transiente de média frequência. Os resultados indicam positivamente o uso conjunto destes sensores de corrente e o equipamento desenvolvido para o propósito de medição destes parâmetros de forma rápida e econômica na infraestrutura elétrica do cliente. / A poor quality power causes large losses to society. Thus it is used an equipment named power quality analyzers for magnitude measurement of these disturbances and determine the causes of these abnormality. The principal problem with these devices is the high cost and they usually are imported that invalidates multipoint measurement of client’s electrical system. In this scenario, this work aims to provide support and alternatives for the development of power quality analyzers, which consists of a set with voltage and current sensors and a central processing module. In the development of any sensors or instrumentation there are difficulties on signal conditioning generated from the used component’s electrical characteristics and principally noise. Some solutions for these problems is the use of proper measuring equipment installation, electromagnetic shielding and design of PCBs. For magnetic sensors, the hysteresis, magnetic saturation and interference by external magnetic fields introduce measurement error in the system and to solve these problems it was adopted Hall sensors in closed-loop and differential configurations. Another component that can be used is the Flux-gate sensor that has potential use in small range current measurements and offers the advantage of higher integrability in the meter system. Following is designed and built a voltage and current logger for Power quality analysis, called PQ-Logger that may utilize the sensors mentioned above. The use of a DSP and a chip for accessing a generic flash drive allows storage of these data. The PQ-Logger-Tran is other equipment that was designed to store snippets of mid-frequency transient. The results positively indicate the combined use of these current sensors and equipment developed for the measuring purpose of these parameters in a quickly and economically form in the customer‘s electrical infrastructure.

A eletrônica empregada no desenvolvimento de estimuladores elétricos funcionais contempla enorme diversificação de técnicas e tecnologias, cujas soluções para o estágio de saída variam desde circuitos transistorizados (bipolares ou MOSFETs), transformadores de pulso até amplificadores operacionais de alta tensão. Desenvolver um estimulador elétrico neuromuscular bifásico com saída em ponte H isolada eletricamente. O sistema de estimulação elétrica neuromuscular bifásico contém saída em ponte H utilizando somente transistores MOSFET canal N, permitindo a geração de pulsos bifásicos e monofásicos com controle de amplitude independente para cada pulso, por meio de uma plataforma eletrônica flexível, que possibilita sua utilização com diversos tipos de elementos de controle, desde microcontroladores e FPGA até dispositivos de instrumentação virtual do tipo LabView. Foram realizados testes de bancada que permitiram avaliar o desempenho do instrumento todo e de seus módulos separadamente. A faixa de alimentação utilizada nos testes foi de 12 a 24V, sendo relacionada diretamente a técnica de geração da alta tensão empregada que permitiu produzir de 280 V a 300 V, utilizados na ponte H, que por sua vez, apresentou o desempenho esperado fornecendo pulsos bifásicos com valores de pico a pico de até 600 V, que pudendo ter sua amplitude dos pulsos controlada individualmente com uma resolução de 73,26 mV (4096 passos), permitindo, assim, a geração de diferentes padrões estimulatórios criados a partir da interface gráfica. O estimulador projetado propiciou o desenvolvimento de uma nova técnica de saída em ponte H utilizando transistores MOSFET canal N na construção de estimuladores elétricos neuromusculares com saída bifásica e com controle de amplitude independente para cada pulso. Tal funcionalidade poderá contribuir para novos estudos e trabalhos em reabilitação empregando estimulação elétrica neuromuscular, considerando que, por meio da interface gráfica criada, formas de ondas estimulatórias específicas podem ser geradas. / The electronics used in the development of functional electrical stimulators include huge diversification of techniques and technologies, whose solutions for the output stage range from transistor circuits (bipolar or MOSFET), to pulse transformers and high-voltage operational amplifiers. To develop a biphasic neuromuscular electrical stimulator with electrically isolated H-bridge output. The electrical neuromuscular stimulation system contains biphasic H-bridge output using only N-channel MOSFET transistors, allowing the generation of mono and biphasic pulses whose pulse amplitudes are independently controlled by a flexible electronics platform, which enables its use with different types of control elements, from microcontroller and FPGA devices to Labview virtual instrument. Bench tests were performed that allowed to assess the performance of the instrument and all its modules separately. The power range used in the tests was 12 to 24V, the technique is directly related to generate the high voltage used which allowed to produce 280 V to 300 V, used in the H bridge, which in turn performed as expected providing pulses biphasic with peak to peak values of 600 V, which pudendal have its amplitude pulses individually controlled with a resolution of 73.26 mV (step 4096), thus allowing the generation of stimulatory different patterns created from the graphical interface. The project developed led the design of a new technique for H-bridge output using transistors N-channel MOSFET in the construction of biphasic neuromuscular electrical stimulator with independent amplitude control for each pulse. Such functionality can contribute to new studies and rehabilitation using neuromuscular electrical stimulation, whereas through the graphical user interface created stimulatory specific waveforms can be generated.