Master of Science / Department of Electrical and Computer Engineering / Behrooz Mirafzal / Increasing energy demand, rising oil prices, and environmental concerns have forced attention to alternative energy sources that are environmentally friendly and independent of fossil fuels. Renewable energy sources (RES) have become an attractive alternative to the traditional energy sources for electric power generation. However, one of the main challenges of RES adaption arises when connecting RES to the electric grid. Voltage source inverters (VSIs), typically, connect RES to the electric grid. Similar to any engineering system, detailed dynamic models of the VSIs are needed for design and analysis purposes. However, due to the non-linearity of VSIs, development of dynamic models that can accurately describe their behavior is a complex task. In this thesis, a detailed averaged-state-space model of the two-level three-phase space vector pulse width modulation VSI and its companion LCL filter is derived. Because VSIs can operate under stand-alone and grid-tied modes, two models were derived for each case. In the derived models, the VSI modulation index m and phase angle ϕ are initially considered constant. In practice, however, these parameters are considered the main control parameters. To model these parameters as control inputs, small-signal models of the VSI under stand-alone and grid-tied modes were derived. To verify the accuracy of the developed large-signal and small-signal models, Matlab/Simulink simulations were carried out. The simulation results were compared against the models results. Moreover, the models were verified through lab experiments. The developed models can be used as design and analysis tools. In addition, the developed models can be used as fast and efficient simulation tools for system studies, when the modeling of switching transients is not needed. Nowadays, the number of VSIs connected to the electric grid is growing exponentially. The amount of time and computation needed to simulate VSIs using simulation software packages can be significantly decreased by the use of the developed models.

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Il est indispensable pour comprendre la diagenèse, i.e., la formation des roches sédimentaires, le durcissement des matériaux de construction hydrauliques comme le ciment ou le plâtre, ou la biominéralisation, d'identifier les mécanismes élémentaires de la cristallisation minérale. Le taux de réaction macroscopique des minéraux est généralement déduit de mesures de chimie des solutions. A côté de ces mesures macroscopiques, l'étude de la réactivité des minéraux inclut maintenant l'analyse des mécanismes atomiques a l'origine des réactions chimiques. Cela a été rendu possible depuis deux décennies par l'apparition d'outils capables d'observer des surfaces avec une résolution nanométrique, tels que la microscopie à force atomique et l'interférométrie à balayage vertical. Le gypse et la calcite font partie des minéraux dits mous. Ce sont des minéraux extrêmement répandus, que l'on peut trouver autant dans la nature sous forme de roches sédimentaires que dans le monde industriel. Le gypse (CaSO4,2H2O) est une évaporite dont les applications incluent la fabrication des plaques de plâtre, l'ajout au ciment Portland comme retardateur, l'élaboration du plâtre de Paris et l'amendement des sols. La sélénite ou l'albâtre sont des variétés de gypse utilisés comme matériaux pour l'ornement, mais leur faible dureté limite leur durabilité. La calcite, forme la plus stable de CaCO3, est un des principaux biominéraux, et un des constituants majeurs des roches des réservoirs carbonates, stockant naturellement de l'eau, du pétrole ou du gaz naturel. Quand les organismes biologiques font croitre leur coquille, ils contrôlent la morphologie, la taille, l'orientation et même la phase des cristaux de carbonates de calcium qui la constituent. Cela conduit à des biomatériaux présentant des propriétés physiques et chimiques qui diffèrent significativement de ceux de la calcite inorganique. Une connaissance plus approfondie des mécanismes sous-jacents à la réactivité de surface de la calcite et de l'effet des impuretés sur celle-ci permettra de nous rapprocher de la possibilité de synthétiser des minéraux biomimétiques, aux propriétés comparables à celles de la calcite biogénique. Dans ce contexte, ma thèse s'est développée dans trois directions. Dans la première, j'ai étudié l'influence d'une contrainte mécanique sur les mécanismes de dissolution. Mon objectif dans cette partie a été de tacher de déduire le taux de dissolution macroscopique à partir de la cinétique des mécanismes atomiques. La seconde partie de la thèse, la plus conséquente, a consisté à étudier l'influence d'une contrainte mécanique sur la croissance de la calcite, et à sonder le rôle d'un additif organique lors de cette croissance sous contrainte. Dans la troisième partie, je me suis penchée sur la dissolution de cristaux de calcite à l'aide de mesures topographiques quantitatives sur des aires relativement étendues de la surface des cristaux, dans une large gamme de pH. J'ai en particulier étudié l'influence d'un additif organique sur la dissolution et la cinétique de réaction à grande échelle. Les taux de dissolution macroscopique et microscopique, c'est-à-dire déduits de la dynamique d'évènements moléculaires (croissance de piqure d'attaque, migration de marche atomique), ne sont presque jamais en accord, même qualitativement, et l'élaboration d'une théorie générale liant la cinétique du phénomène aux deux échelles est encore en cours. Je présente ici des taux de dissolution microscopique du gypse, mesures par microscopie par force atomique (AFM), en accord quantitatif avec les taux de dissolution macroscopiques. Cet accord inédit a été obtenu en prenant soin de neutraliser le biais induit par le fait que la pointe AFM applique une force sur la surface qu'elle sonde, et en identifiant avec soin les mécanismes moléculaires majeurs à l'œuvre lors de la dissolution...[etc] / Identifying reaction mechanisms of minerals is fundamental to understand diagenesis, i.e, sedimentary rock formation, construction material, like cement or gypsum, hardening, and biomineralization. The macroscopic reaction rates of minerals are generally deduced from solution chemistry measurements. Beside the measurement of macroscopic reaction rates, the study of the reactivity of minerals includes now the investigation of the atomic mechanisms involved in the reactions. This has been made possible for two decades by the use of tools resolving nanometric objects, such as vertical scanning interferometry (VSI) and atomic force microscopy (AFM). Gypsum and calcite are among soft minerals. They are extremely widespread mineral that can be found naturally in sedimentary rocks. They are also used in many industrial fields. Gypsum (CaSO4,2H2O) is an evaporate mineral. Gypsum uses include: manufacture of wallboards, plaster of Paris, soil conditioning, and hardening retarder in Portland cement. Varieties of gypsum known as "satin spar" and "alabaster" are used for a variety of ornamental purposes; however, their low hardness limits their durability. Calcite, the most stable crystalline form of CaCO3, is moreover important as a bio-mineral and a major constituent of host rock in carbonate reservoirs, which host drinking water and natural oil and gas. When biological organisms grow their shells, they control the crystal morphology, size, orientation and even the crystal phase of precipitated calcium carbonate. This results in materials with physical and chemical properties that differ significantly from those of inorganically precipitated calcite. Gaining more insight into the surface reactivity of calcite and the effect of surface impurities will bring us one step closer to being able to synthesize biomimetic material, which mimic the properties of biogenic calcite. In this thesis, I had three main focus points. In the first part I studied the effect of stress on the dissolution mechanisms. I investigated to deduce the dissolution rate from the atomic kinetics. The second and the most extensive was the study of the influence of stress on the calcite growth and probing the role of an organic additive on the dynamics of calcite growth while applying stress. In the third part I emphasised on quantitative topographic measurements of dissolving calcite crystal over a relatively large and fixed view at vast range of pH. I considered the influence of an organic additive on the dissolution and surface reaction kinetics at this larger scale. Both macroscopic and microscopic dissolution rates can also be deduced from the dynamics of molecular events (etch pit growth, atomic step migration), but they hardly ever agree, even qualitatively, and the elaboration of a general theory linking the kinetics at the two scales is still in progress. I presented here microscopic dissolution rates of gypsum, measured by atomic force microscopy (AFM), in quantitative agreement with macroscopic rates. This agreement has been obtained in taking care to neutralize the bias induced by the force applied by the AFM tip on the surface, and to identify clearly the driving molecular mechanism. The force applied by the AFM tip on the surface has been seen to increase the solubility of the mineral, thereby introducing a bias, so I have always worked with a constant and low applied force. This result shows that the determination, among the topographic changes during the dissolution of a mineral, of the dominant one, and the measurement of its dynamics, may permit deducing from AFM experiments a reliable macroscopic dissolution rate. The transformation of loose grains into a cohesive solid requires the crystallites to grow eventually constrained by the surrounding grains. Whereas never measured, this confinement and the associated stress is expected to influence noticeably the growth, and the final properties of the material… [etc]

Submitted by Maria Suzana Diniz (msuzanad@hotmail.com) on 2015-11-06T15:48:55Z No. of bitstreams: 1 arquivototal.pdf: 3791340 bytes, checksum: 58dd4dde93f8552a891a0760151a7c10 (MD5) / Made available in DSpace on 2015-11-06T15:48:55Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 3791340 bytes, checksum: 58dd4dde93f8552a891a0760151a7c10 (MD5) Previous issue date: 2015-02-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The interest for the study of multiphase (more than three phases) machines and variable speed drives has substantially increased in the last two decades. The advantages presented by the multiphase systems compared to their three-phase counterparts have being the the main effort to increase researches all over the world. Reduction in torque oscillation, lower current ratings, high drive reliability, better fault tolerance and harmonic content reduction in the DC bus are some of these advantages. The additional degrees of freedom due to extra phases make multiphase systems very flexible when it comes to control systems and modulation strategies. Although three-phase systems are predominant in industrial applications, the use of multiphase machines and drives has increased in very specific areas such as locomotive traction, electric ship propulsion, aerospace industry (more electric aircraft), electric and hybrid vehicles and industrial high power systems. Due to high coupling degree between electric variables in multiphase systems, modeling of multiphase machines has been and still is a challenge task in research centers. In this present work, analitic modeling of symmetric and asymmetric nine-phase machines using natural variables and space vector decomposition are presented. The principles used in the study are the same used for three-phase systems. However, multiphase systems are analised in multiple d-q planes. PWM modulation strategies based on space vectors theory (SVPWM) for a voltage source inverter (VSI) are presented. The multiphase drive system presented works in the linear operation region with sinusoidal voltage generation. Results for both machines and drive modeled are verified by simulation programs developed in C programming language an Matlab. / O interesse pelo estudo de máquinas de indução multifases (mais de três fases) e dos seus sistemas de acionamento cresceu substancialmente nas últimas duas décadas. As muitas vantagens apresentadas pelos sistemas multifases, em relação aos sistemas trifásicos convencionais, têm sido fatores motivadores para o aumento de pesquisas em todo o mundo. Redução das oscilações de torque, redução da corrente por fase, maior confiabilidade do acionamento, grande tolerância à faltas e redução no conteúdo harmônico da corrente no barramento CC são algumas destas vantagens. O maior grau de liberdade proporcionado pelas fases extras torna os sistemas multifases bastante flexíveis quanto às estratégias de modulação e de controle. Apesar da atual predominância da utilização das máquinas e acionamentos trifásicos na indústria, as máquinas multifases estão sendo cada vez mais utilizadas em áreas de aplicações específicas tais como tração de locomotivas, propulsão de navios elétricos de grande porte, indústria aeroespacial, tração de veículos híbridos e elétricos e sistemas industriais de alta potência. Devido ao alto grau de acoplamento entre as variáveis elétricas de um sistema multifases, a modelagem e análise desses sistemas tem representado uma tarefa desafiadora nos centros de pesquisa. No presente trabalho são apresentadas as modelagens analíticas de uma máquina de indução de nove fases simétrica e de uma máquina de nove fases assimétrica pelo método de variáveis naturais e pelo método de decomposição vetorial. Os princípios utilizados na modelagem são os mesmos utilizados nos sistemas trifásicos. No entanto, sistemas multifases são analisados em múltiplos planos d-q. Estratégias de modulação PWM baseadas na teoria de vetores espaciais (SVPWM) para um inversor de nove fases tipo VSI (Inversor Fonte de Tensão) são apresentadas para acionamento das máquinas. O sistema de acionamento apresentado trabalha na região linear de operação e gera tensão de saída senoidal. Dados de simulação obtidos a partir de programas desenvolvidos em linguagem C e Matlab são apresentados para ambas as máquinas de nove fases modeladas.

Modern embedded systems development poses new challenges to a designer due to the global reachability of the contemporary market. One product shipped to different countries or customers should satisfy varying conditions, standards and constraints. Variability of a developed system should be taken into account by a designer. In a case of the embedded heterogeneous systems, this problem becomes challenging. Along with the variability heterogeneity of a system introduces new tasks, which should be addressed during design process. In this work, we propose a technology independent design flow. The proposed solution is supported by state-of-the-art tools and takes into account variability, partitioning, interfacing and dependency resolving processes. This thesis is conducted as a case study. We explored a design process of an industrial project, identified existing challenges and drawbacks in the existing solutions. We propose a new approach to a design flow of heterogeneous embedded systems. Also, a tool, supporting the presented solution, is implemented, which would allow a developer to include this approach into everyday design flow in order to increase a development speed and enable a task automation.

White light interferometry is a well-developed and very old technique for optical measurements. The thesis describes the design of a vertical scan interferometer system to study the surface topography of surfaces down to nanometers. The desired properties of the system are its simplicity, portability and compact size, making it suitable for use in general labs and for educational purposes. By acquiring a sequence of images of the deformed fringe pattern, the surface topography can be observed, giving greater understanding of the surface roughness. The principle behind the system is coherence peak sensing where the resulting fringe pattern of the object gets changed in accordance with its surface topography. To accomplish this, individual components of the interferometer were studied and a prototype was built in the lab. A series of experiments were performed which validate the working of the system. The results of the validation which are produced in the report give the accuracy of the system. The output from the prototype interferometer is processed by MATLAB to decode the surface topography of the object under measurement. The design of the prototype is also discussed. Possible application of this device for sensing the surface topography of a cylindrical object is also put forward. Even-though the white light interferometer is more common, making them simple and cost effective will be more advantageous for the whole research community.

The determination of economic control charts and the determination of specification limits with minimum cost are two different research topics. In this study, we first combine the design of economic control charts and the determination of specification limits to maximize the expected profit per unit time for the smaller the better quality variable following the gamma distribution. Because of the asymmetric distribution, we design the EWMA control chart with asymmetric control limits. We simultaneously determine the economic EWMA control chart and upper specification limit with maximum expected profit per unit time. Then, extend the approach to determine the economic variable sampling interval EWMA control chart and upper specification limit with maximum expected profit per unit time. In all our numerical examples of the two profit models, the optimum expected profit per unit time under inspection is higher than that of no inspection. The detection ability of the EWMA chart with an appropriate weight is always better than the X-bar probability chart. The detection ability of the VSI EWMA chart is also superior to that of the fixed sampling interval EWMA chart. Sensitivity analyses are provided to determine the significant parameters for the optimal design parameters and the optimal expected profit per unit time.

Ce travail s'attache tout autant à améliorer les techniques d'acquisition qu'à préciser les modèles physiologiques qui permettent la caractérisation de la perfusion cérébrale en IRM. La fonction d'entrée artérielle (AIF), sur laquelle repose de nombreux modèles, a été mesurée par une technique d'imagerie optique au niveau de la carotide chez le rat. La reproductibilité et la répétabilité de l'AIF sont examinées et une fonction modèle est proposée. Nous comparons ensuite deux techniques de mesure de l'index de taille des vaisseaux (VSI) chez le rat porteur d'un gliome. La technique de référence, utilisant un agent de contraste (AC) de type USPIO, est confrontée à l'approche dynamique qui estime ce paramètre au passage d'un bolus de Gd. Cette dernière technique présente l'avantage d'être utilisée en clinique. Les résultats obtenus à 4,7T par ces deux approches sont semblables et l'utilisation du VSI dans les protocoles cliniques est fortement encouragée à haut champ. Les mécanismes en jeu (relaxivités R1 et R2*) sont alors étudiés via une approche en multi-échos de gradient. Une séquence spirale multi-échos est développée et une méthode qui permet la refocalisation entre chaque écho est présentée. Cette séquence est utilisée pour caractériser l'impact des effets R1 au passage de deux injections successives de Gd. Enfin, nous avons développé un outil de simulant le signal RMN sur une géométrie 2D tenant compte de la perméabilité de la BHE et de la diffusion de l'AC dans l'espace interstitiel. A TE court, l'effet de la diffusion sur le signal est négligeable. A contrario, les effets de la diffusion et la perméabilité semblent pouvoir être séparés à temps d'écho long. Enfin nous montrons que, lors de l'extravasation de l'AC, l'homogénéisation du champ magnétique local lié à la baisse de différence de susceptibilité magnétique à l'interface vasculaire est rapidement contre balancée par les perturbations induites par les interfaces cellulaires du compartiment extravasculaire.

At present, one of the big challenges is to develop a precise surface measurement method for mechanical parts. Especially, to study cylindrical surface, the cause of many difficulties because of its geometry shape. This thesis presents a quite good solution for analyzing topography of cylindrical surface with White Light Interferometry optical system which is one of the important and suitable tools in optics. In the construction period, the aim was to build a system which can be easily mounted on the sample. This is done by a very simple and compact design that also enables us to use it in research laboratories. In the project, a cylindrical surface analysis is achieved by taking subsequent images with different nano-scale distance from the sample and stitched the acquired images. To achieve this implementation, subsequent images with the highest intensity are first determined and then located in a single image. In the stitching process, cross correlation method that is extremely useful to find out relative point of the images is used to merge the acquired images. Additionally, stitching process is helped us to extend the area where research can be done. In the project, MATLAB & LABVIEW are used for analyzing the images and controlling the motors, respectively.

Distributed energy resources like solar power (PV Panels) are usually connected to the AC grid through a single phase voltage source inverter (VSI). The major drawback associated with single phase grid tie inverters is the double frequency component of the grid that appears on the DC bus link. Large electrolytic capacitors are generally employed in the inverters to eliminate the ripple component. However, their bulkiness and relatively short lifetime are motivational factors to replace them with small film capacitors. This paper presents a synchronous boost/buck based active power decoupling circuit in parallel with the dc-bus link capacitor and discusses the different types of control strategies implemented. Simulation results are presented for each control technique and it is shown that the ripple on the DC bus link is largely reduced due to inclusion of this circuit along with an expected extension of the lifetime due to the reduction in the amount of dc-bus capacitance used. / text