A ressonância magnética nuclear no domínio do tempo (RMN-DT), possui inúmeras vantagens em relação à RMN de alta resolução tais como: baixo custo do equipamento, de análise e manutenção e não precisa de operador especializado. Apesar disso a técnica de RMN-DT ainda tem um campo muito grande de desenvolvimento para análise de componente com baixa mobilidade molecular como sólidos amorfos e cristalinos. Isto requer o desenvolvimento de instrumentação e/ou métodos de análise que se consiga medir o sinal de RMN em menos de 10 µs, após a irradiação da amostra. O tempo entre o final da excitação e o começo da aquisição do sinal é conhecido como tempo morto. A opção estudada nesta dissertação para redução do tempo morto foi o uso de pulsos formatados, que já são utilizados em experimentos de RMN em alta resolução e de imagens por RMN, para excitação seletiva. No entanto, pulsos formatados não têm sido utilizados em RMN-DT. A principal vantagem desses pulsos é que eles são projetados para que a potência no final do pulso seja mínima, o que diminui o tempo morto do espectrômetro. No caso do pulso convencional, na forma retangular, a potência no final do pulso é máxima, o que aumenta o tempo morto. Os pulsos formatados utilizados foram pulsos Sinc, Sine e também pulsos com início similar aos pulsos retangulares, com potência máxima, e que depois de certo tempo tem decaimento similar aos pulsos Sinc e Sine. Esses pulsos inéditos foram denominados Reta-Sine e Reta-Sinc. Foram avaliados amostras heterogêneas (solido-líquido) e sólidas como CaSO4.2H2O, farelo de soja, polímeros amido e Policaprolactona. Esses pulsos também foram usados para monitorar reações de polimerização da resina epóxi com poliamida (Araldite®). Com esses métodos foi possível reduzir o tempo morto de espectrômetro de 23MHz 23 µs para 14 µs e de 20 Mhz de 9 para 6 µs. Com isso conclui-se que o pulsos formatados podem reduzir significativamente o tempo morto de espectrômetro de RMN-DT, sem acessórios ou custo financeiro, pois as sequências podem ser instalada e usadas em qualquer espectrômetro moderno. / The nuclear magnetic resonance in the time domain (TD-NMR) It has numerous advantages over the high-resolution NMR such as low cost of equipment, analysis and maintenance and requires no specialized operator. Nevertheless NMR DT technique also has a very large development field for component analysis with a low molecular mobility as amorphous and crystalline solids. This requires the development of instrumentation and / or analysis methods that can measure the NMR signal in less than 10 µs, after irradiation of the sample. The time between the end of excitation and signal acquisition the beginning is known as dead time. The option studied in this work to reduce the dead time was the use of formatted pulses, which are already used in NMR experiments in high resolution and NMR imaging for selective excitation. However, formatted pulses have not been used in NMR DT. The main advantage of these pulses is that they are designed so that the power in the pulse end is minimized, which reduces the dead time of the spectrometer. In the case of conventional pulse in rectangular form, the power in the pulse end is maximum, which increases the dead time. Formatted pulses used were Sync pulses, Sine and also pulses beginning similar to rectangular pulses with maximum power, and after a while has similar decay to Sync and Sine wrists. These unpublished wrists were called Sine and Straight-Line-Sync. They were evaluated heterogeneous samples (solid-liquid) and solid as CaSO4.2H2O, soybean meal, starch polymers and Polycaprolactone. These pulses are also used to monitor polymerization reactions the polyamide epoxy resin (Araldite®). With these sequences it was possible to reduce the dead time of 23 µs 23MHz spectrometer to 14 µs e 20 Mhz from 9 to 6 µs. With this it is concluded that the formatted pulses can significantly reduce the dead time DT-NMR spectrometer, without fittings or financial cost because the sequences can be installed and used in any modern spectrometer.

The McTronX research group, at the Potchefstroom campus of the North–West University, has been researching Active Magnetic Bearings (AMBs). A fully suspended, flywheel energy storage system (FESS) has been developed. Due to excessive unbalance on the rotor, the motor drive could not be tested up to its rated speed. In the interim, until the rotor can be balanced and other rotor dynamic effects have been investigated, the group decided that the existing drive control should be improved and tested on a high–speed permanent magnet synchronous motor (PMSM), using normal roller element bearings. In order to test the motor control a second (identical) PMSM, mechanically coupled to the former, operates in generator mode which serves as the torque load. Two different control algorithms, namely V/f and vector control, are designed and implemented on a rapid control prototyping system, i.e. dSPACE®. The V/f control is an open–loop, position sensorless technique, whilst the vector controller makes use of a position sensor. From the design and implementation it became clear that the vector control is more robust, in the sense that it is less sensitive on parameter variations and disturbances. It can start up reliably even under full load conditions. The V/f control is an attractive alternative to the vector control, especially in AMB systems, where it may be difficult to mount the position sensor, has to operate in a hazardous environment not suited to the sensor or could degrade the reliability of the AMB system. The cost of the position sensor is not really a concern compared to the cost of an AMB system. The V/f control is more suited to fan and pump applications, which has a low dynamic requirement. The V/f control has high startup currents and is not recommended for applications requiring a high starting torque or fast acceleration during operation. The inverter, which drives the PMSM, also had to be developed. With regard to the motor control, the effects of inverter non–idealities had to be accounted, especially for the V/f control. The implemented control algorithms were tested up to 20 krpm. Discrepancies between the expected and actual results are discussed. Overall, the controllers performed as desired. Generally, the project goals have been reached satisfactorily. / Thesis (M.Ing. (Computer and Electronic Engineering))--North-West University, Potchefstroom Campus, 2011.

The McTronX research group, at the Potchefstroom campus of the North–West University, has been researching Active Magnetic Bearings (AMBs). A fully suspended, flywheel energy storage system (FESS) has been developed. Due to excessive unbalance on the rotor, the motor drive could not be tested up to its rated speed. In the interim, until the rotor can be balanced and other rotor dynamic effects have been investigated, the group decided that the existing drive control should be improved and tested on a high–speed permanent magnet synchronous motor (PMSM), using normal roller element bearings. In order to test the motor control a second (identical) PMSM, mechanically coupled to the former, operates in generator mode which serves as the torque load. Two different control algorithms, namely V/f and vector control, are designed and implemented on a rapid control prototyping system, i.e. dSPACE®. The V/f control is an open–loop, position sensorless technique, whilst the vector controller makes use of a position sensor. From the design and implementation it became clear that the vector control is more robust, in the sense that it is less sensitive on parameter variations and disturbances. It can start up reliably even under full load conditions. The V/f control is an attractive alternative to the vector control, especially in AMB systems, where it may be difficult to mount the position sensor, has to operate in a hazardous environment not suited to the sensor or could degrade the reliability of the AMB system. The cost of the position sensor is not really a concern compared to the cost of an AMB system. The V/f control is more suited to fan and pump applications, which has a low dynamic requirement. The V/f control has high startup currents and is not recommended for applications requiring a high starting torque or fast acceleration during operation. The inverter, which drives the PMSM, also had to be developed. With regard to the motor control, the effects of inverter non–idealities had to be accounted, especially for the V/f control. The implemented control algorithms were tested up to 20 krpm. Discrepancies between the expected and actual results are discussed. Overall, the controllers performed as desired. Generally, the project goals have been reached satisfactorily. / Thesis (M.Ing. (Computer and Electronic Engineering))--North-West University, Potchefstroom Campus, 2011.

A ressonância magnética nuclear no domínio do tempo (RMN-DT), possui inúmeras vantagens em relação à RMN de alta resolução tais como: baixo custo do equipamento, de análise e manutenção e não precisa de operador especializado. Apesar disso a técnica de RMN-DT ainda tem um campo muito grande de desenvolvimento para análise de componente com baixa mobilidade molecular como sólidos amorfos e cristalinos. Isto requer o desenvolvimento de instrumentação e/ou métodos de análise que se consiga medir o sinal de RMN em menos de 10 µs, após a irradiação da amostra. O tempo entre o final da excitação e o começo da aquisição do sinal é conhecido como tempo morto. A opção estudada nesta dissertação para redução do tempo morto foi o uso de pulsos formatados, que já são utilizados em experimentos de RMN em alta resolução e de imagens por RMN, para excitação seletiva. No entanto, pulsos formatados não têm sido utilizados em RMN-DT. A principal vantagem desses pulsos é que eles são projetados para que a potência no final do pulso seja mínima, o que diminui o tempo morto do espectrômetro. No caso do pulso convencional, na forma retangular, a potência no final do pulso é máxima, o que aumenta o tempo morto. Os pulsos formatados utilizados foram pulsos Sinc, Sine e também pulsos com início similar aos pulsos retangulares, com potência máxima, e que depois de certo tempo tem decaimento similar aos pulsos Sinc e Sine. Esses pulsos inéditos foram denominados Reta-Sine e Reta-Sinc. Foram avaliados amostras heterogêneas (solido-líquido) e sólidas como CaSO4.2H2O, farelo de soja, polímeros amido e Policaprolactona. Esses pulsos também foram usados para monitorar reações de polimerização da resina epóxi com poliamida (Araldite®). Com esses métodos foi possível reduzir o tempo morto de espectrômetro de 23MHz 23 µs para 14 µs e de 20 Mhz de 9 para 6 µs. Com isso conclui-se que o pulsos formatados podem reduzir significativamente o tempo morto de espectrômetro de RMN-DT, sem acessórios ou custo financeiro, pois as sequências podem ser instalada e usadas em qualquer espectrômetro moderno. / The nuclear magnetic resonance in the time domain (TD-NMR) It has numerous advantages over the high-resolution NMR such as low cost of equipment, analysis and maintenance and requires no specialized operator. Nevertheless NMR DT technique also has a very large development field for component analysis with a low molecular mobility as amorphous and crystalline solids. This requires the development of instrumentation and / or analysis methods that can measure the NMR signal in less than 10 µs, after irradiation of the sample. The time between the end of excitation and signal acquisition the beginning is known as dead time. The option studied in this work to reduce the dead time was the use of formatted pulses, which are already used in NMR experiments in high resolution and NMR imaging for selective excitation. However, formatted pulses have not been used in NMR DT. The main advantage of these pulses is that they are designed so that the power in the pulse end is minimized, which reduces the dead time of the spectrometer. In the case of conventional pulse in rectangular form, the power in the pulse end is maximum, which increases the dead time. Formatted pulses used were Sync pulses, Sine and also pulses beginning similar to rectangular pulses with maximum power, and after a while has similar decay to Sync and Sine wrists. These unpublished wrists were called Sine and Straight-Line-Sync. They were evaluated heterogeneous samples (solid-liquid) and solid as CaSO4.2H2O, soybean meal, starch polymers and Polycaprolactone. These pulses are also used to monitor polymerization reactions the polyamide epoxy resin (Araldite®). With these sequences it was possible to reduce the dead time of 23 µs 23MHz spectrometer to 14 µs e 20 Mhz from 9 to 6 µs. With this it is concluded that the formatted pulses can significantly reduce the dead time DT-NMR spectrometer, without fittings or financial cost because the sequences can be installed and used in any modern spectrometer.

Este trabalho descreve o desenvolvimento de um sistema de controle com compensação de tempo morto aplicado a um ventilador para simular os efeitos do vento em modelos de embarcações. O sistema é instalado no tanque de provas do Departamento de Engenharia Naval da Escola Politécnica da USP. Um sistema de controle baseado em computador é elaborado para a realização dos testes e validação, procedendo-se inicialmente a identificação do sistema a ser controlado. Na malha de controle, o sinal de referência é a velocidade do vento desejada em uma distância pré-definida do ventilador e pode ser tanto um valor constante (representando um vento constante) ou um valor variante no tempo (representando uma rajada de vento). O sistema atuador consiste de um inversor de frequência que aciona o ventilador e a velocidade do vento é medida por um anemômetro, cujo sinal é usado como realimentação para o controlador. A sintonia da malha é realizada pelo método do modelo interno (IMC) e o efeito do tempo morto é observado nos testes, aplicando-se o compensador baseado no Preditor de Smith para minimizá-lo. Pelos resultados dos ensaios, conclui-se que o Preditor de Smith melhora o desempenho do sistema de geração de vento. / This paper describes the development of a control system with dead time compensation applied to a fan to simulate wind effects in models of vessels. The system is installed on the academic towing tank of the Naval Architecture and Oceanic Engineering Department of the University of São Paulo. A control system based on computer is designed for testing and validation, proceeding initially to identify the system to be controlled. In the control loop, the set-point is the desired speed of the wind on a pre-defined distance from the fan and it can be either a constant value (representing a constant wind) or a time-varying value (representing a wind gust). The actuator system consists of a frequency-inverter that drives the fan and the wind speed is measured by an anemometer, whose signal is used as feedback to the controller. The tuning of the controller is made by the internal model control (IMC) and the effect of dead time is observed in the tests, applying the compensator based on Smith Predictor to minimize it. Through the results from the tests, it was concluded that the Smith Predictor improves the performance of the wind generation system.

Energy harvesting is identified as a promising alternative solution for powering implantable biosensors. It can completely replace the batteries, which are introducing many limitations, and it enables the development of self-powered implantable biosensors. An interface circuit is necessary to correct for differences in the voltage and power levels provided by an energy harvesting device from one side, and required by biosensor circuits from another. This thesis investigates the available energy harvesting sources within the human body, selects the most suitable one and proposes the power management unit (PMU), which serves as an interface between a harvester and biosensor circuits. The PMU targets the efficient power transfer from the selected source to the implantable biosensor circuits. Based on the investigation of potential energy harvesting sources, a thermoelectric energy harvester is selected. It can provide relatively high power density of 100 μW/cm2 at very low temperature difference available in the human body. Additionally, a thermoelectric energy harvester is miniature, biocompatible, and it has an unlimited lifetime. A power management system architecture for thermoelectric energy harvesters is proposed. The input converter, which is the critical block of the PMU, is implemented as a boost converter with an external inductor. A detailed analysis of all potential losses within the boost converter is conducted to estimate their influence on the conversion efficiency. The analysis showed that the inevitable conduction and switching losses can be reduced by the proper sizing of the converter’s switches and that the synchronization losses can be almost completely eliminated by an efficient control circuit. Additionally, usually neglected dead time losses are proved to have a significant impact in implantable applications, in which they can reduce the efficiency with more than 2%. An ultra low power control circuit for the boost converter is proposed. The control is utilizing zero-current switching (ZCS) and zero-voltage switching (ZVS) techniques to eliminate the synchronization losses and enhance the efficiency of the boost converter. The control circuit consumes an average power of only 620 nW. The boost converter driven by the proposed control achieves the peak efficiency higher than 80% and can operate with harvested power below 5 μW. For high voltage conversion ratios, the proposed boost converter/control combination demonstrates significant efficiency improvement compared to state-of-the-art solutions. / <p>QC 20150413</p>

La mission Franco-chinoise SVOM (Space based multi-band Variable astronomical Object Monitor), est dédiée à l'étude des sursauts ƴ, intenses et brèves bouffées de photons en X et ƴ, associées à la formation catastrophique de trous noirs. SVOM embarquera en 2021 quatre instruments observant du visible jusqu'aux rayonnements ƴ. ECLAIRs, télescope principal, est une caméra à masque codé capable de détecter et localiser, environ 200 sursauts pendant les trois années de vie de la mission. Son plan de détection compte 6400 détecteurs CdTe à contact Schottky, qui sont regroupés en matrice de 32 formant un module. Le plan est divisé en huit secteurs électroniquement indépendants, composés chacun de 25 modules. Chaque électronique est dédiée à la lecture et au codage du temps, de la position, de la multiplicité et des énergies des événements détectés sur un secteur. La validation des fonctionnalités de l'électronique de lecture a permis de s'assurer du bon codage des événements, d'estimer les limites de l'électronique et de construire un modèle analytique de correction efficace des événements perdus. Une application à une courbe de lumière d'un sursaut brillant a permis de valider théoriquement ce modèle et des mesures réalisées sur le prototype ont permis de le valider expérimentalement. D'autre part, un modèle complet de la réponse spectrale a été construit afin de caractériser chaque détecteur pavant le secteur du prototype et d'estimer la réponse du plan de détection des photons mono-énergétiques. Les processus physiques des interactions rayonnement-matière ont été simulés ainsi qu'un modèle de perte de charges puis une convolution gaussienne permet de considérer le bruit électronique. Ce modèle, comptant six paramètres libres, est ajusté à des spectres réalisés sur le prototype. L'étude des paramètres extraits caractérise les performances de chaque détecteur dans toutes les configurations de tension et de t peaking et permet d'optimiser les performances de l'instrument. / The french-chinese mission SVOM (Space-based multi-band variable Astronomical Object Monitor), is dedicated to the study of ƴ-rays bursts, brief and intense X and ƴ photons flashes, associated with the catastrophic formation of black holes. SVOM will embark in 2021 four instruments observing from the visible to ƴ rays. ECLAIRs, the main telescope, is a coded mask camera able to detect and locate, about 200 bursts during the three years nominal life time of SVOM. Its detection plan counts 6400 Schottky CdTe detectors, grouped into a matrix of 32 pixels forming a module. The plan is divided into eight electronically independent sectors, each consisting of 25 modules. Each electronic is dedicated to read and encode, the time, the position, the multiplicity and the energies of the detected events on a sector. The validation of each functionality of the readout electronics allows to ensure the correct encoding of the events, to estimate the limits of the electronics and to build an analytical model of lost events efficient correction. An application to a lightcurve of a bright GRB permits to validate theoretically this model and measurements carried out on the prototype validates it experimentally. On the other hand, a complete model of the spectral response has been established to characterize each detector on the sector of the prototype and to estimate the response of the plan of detection of the mono-energetic photons. The physical processes of the radiation-matter interactions are simulated as well as a model of lost charges then a Gaussian convolution takes into account the electronic noise. This model, counting six free parameters, is fitted to spectra measured on the prototype. The study of the extracted parameters characterizes the performance of each detector in every voltage and t peaking configurations optimizing the performance of the instrument.

Thesis (Ph.D.); Submitted to North Carolina State Univ., Raleigh, NC (US); 6 Apr 2005. / Published through the Information Bridge: DOE Scientific and Technical Information. "UCRL-TH-211400" Dashdorj, D. 04/06/2005. Report is also available in paper and microfiche from NTIS.

Submitted by Geandra Rodrigues (geandrar@gmail.com) on 2018-05-15T18:53:08Z No. of bitstreams: 1 gabrielazevedofogli.pdf: 14398243 bytes, checksum: 29f4f96b36d404d928ede5833fc882f8 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-05-22T14:44:16Z (GMT) No. of bitstreams: 1 gabrielazevedofogli.pdf: 14398243 bytes, checksum: 29f4f96b36d404d928ede5833fc882f8 (MD5) / Made available in DSpace on 2018-05-22T14:44:16Z (GMT). No. of bitstreams: 1 gabrielazevedofogli.pdf: 14398243 bytes, checksum: 29f4f96b36d404d928ede5833fc882f8 (MD5) Previous issue date: 2018-03-26 / Este trabalho apresenta um estudo sobre a integração de uma fonte despachável, baseada em um grupo motor gerador diesel, em uma microrrede em corrente alternada através de um conversor de dois estágios, formado por dois conversores fonte de tensão em conexão back-to-back. A microrrede pode operar conectada à rede secundária de distribuição, injetando a potência ativa proveniente da fonte despachável, ou de modo isolado. Para este segundo caso, duas estratégias de funcionamento são propostas. A primeira interliga diretamente o grupo motor gerador ao barramento de cargas, enquanto o conversor de dois estágios funciona como filtro ativo de potência. A outra opção consiste em utilizar o conversor de dois estágios no modo formador de rede, alimentando o barramento de cargas. Como cada uma das unidades que compõem o conversor de dois estágios tem uma finalidade, os controladores utilizados de cada um dos lados possuem particularidades. O conversor conectado aos terminais do grupo motor gerador é responsável por drenar correntes senoidais e regular a tensão do barramento de corrente contínua. Para este conversor é utilizado um controlador proporcional—integral, projetado no sistema de coordenadas síncrono. Uma estratégia de compensação dos parâmetros do tempo morto dos interruptores semicondutores foi implementada para reduzir a geração de harmônicos não característicos. Do outro lado, no conversor de saída, responsável pela integração com a rede secundária, foi utilizado um controlador proporcional—integral, projetado no sistema de coordenadas síncrono, com múltiplos integradores, adicionados para compensar correntes harmônicas. De acordo com o modo de funcionamento do sistema é utilizado um método para obtenção das correntes de referência. Quatro modos de funcionamento podem ser aplicados neste sistema: (i) alimentador de rede, (ii) formador de rede, (iii) auxiliador de rede e (iv) condicionador de rede. Para o modo Formador de Rede faz-se necessário a inclusão de uma malha de controle externa projetado para regular a tensão CA no barramento de cargas. Resultados experimentais são apresentados para validar os modelos matemáticos e as estratégias de controle usadas neste trabalho. Todo o algoritmo de controle é implementado em um controlador digital de sinais TMS320F28335 fabricado pela Texas Instruments. / This document presents a study on dispatchable source based on Diesel Gen-set connected to AC microgrid. The Diesel generator is connected to network grid through two-stage converter composed of two Voltage-sourced converters in back-to-back (B2B-VSC) connection. The AC microgrid can operate in a grid-connected mode, injecting active power from the dispatchable source, or in an isolated mode. In the second case, two operating conditions are proposed, in which the first option interconnects Diesel gen-set direct to load bus and B2B-VSC works as Active Power Filter. Another option is to operate the B2B-VSC as grid—former. Due the fact that each converter of B2B-VSC has a specific goal, different control strategies are used for each one. The VSC connected to Diesel generator terminals is responsible to drain sinusoidal currents and to regulate the DC voltage. In the this converter, PI—SRF Controller is applied in a inner current control loop together with a dead-time compensation strategy. In the other side of B2B-VSC, responsible of multi-task control, is applied a control strategy modelled in a synchronous coordinate system with multiple integrators to mitigate the harmonic currents. According to the operation mode is used a different current reference is given. Four operation modes can be used in this microgrid: (i) grid-feeding, (ii) grid-forming, (iii) grid-supporting and (iv) grid-conditioning. In grid—forming mode an outer loop is added to regulate the AC load bus voltage. Experimental results are presented to validate the mathematical modelling and controller strategies. Finally, suggestions to continue this research are proposed. The control algorithm is implemented in a digital signal processor TMS320F28335 made by Texas Instruments.

Modellbasierte virtuelle Sensoren (VS) ermöglichen die Messung von qualitätsbestimmenden Prozessparametern (bzw. Hilfsregelgrößen) dort, wo eine direkte Messung zu teuer oder gar nicht möglich ist. Für die adaptiven VS, die ihr internes Prozessmodell nach Data-Driven-Methode bilden (z. B. durch die Benutzung künstlicher neuronaler Netze (KNN)), besteht das Problem der Abschätzung der Prädiktionsstabilität. Aktuelle Lösungsansätze lösen dieses Problem nur für wenige KNN-Typen und erfordern enormen Entwurfs- und Rechenaufwand. In dieser Arbeit wird eine alternative Methode vorgestellt, welche für eine breite Klasse von KNN gilt und keinen hohen Entwurfs- und Rechenaufwand erfordert. Die neue Methode wurde anhand realer Anwendungsbeispiele getestet und hat sehr gute Ergebnisse geliefert. Für die nicht adaptiven virtuellen Sensoren wurde eine aufwandsreduzierte Adaption nach Smith-Schema vorgeschlagen. Dieses Verfahren ermöglicht die Regelung totzeitbehafteter und zeitvarianter Prozesse mit VS in einem geschlossenen Regelkreis. Im Vergleich zu anderen Regelungsstrategien konnte damit vergleichbare Regelungsqualität bei einem deutlich geringeren Entwurfsaufwand erzielt werden. / Model-based virtual sensors allow the measurement of parameters critical for process quality where a direct measurement is too expensive or not at all possible. For the adaptive virtual sensors built after data-driven method (e.g., by use of an ANN model) there is a problem of the prediction stability. Current solutions attempt to solve this problem only for a few ANN types and require a very high development effort. In this dissertation a new method for the solution of this problem is suggested, which is valid for a wide class of the ANNs and requires no high development effort. The new method was tested on real application examples and has delivered very good results. For the non-adaptive virtual sensors a simple adaptation mechanism was suggested. This technique allows the control of dead-time and time-variant processes in closed loop. Besides, in comparison to other control strategies the comparable results were achieved with smaller development effort.