Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-04-25T18:26:00Z No. of bitstreams: 1 ricardovioldossantos.pdf: 2585437 bytes, checksum: 897e63c2118d5c0e74581bbdb80ccb38 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-04-26T12:23:14Z (GMT) No. of bitstreams: 1 ricardovioldossantos.pdf: 2585437 bytes, checksum: 897e63c2118d5c0e74581bbdb80ccb38 (MD5) / Made available in DSpace on 2017-04-26T12:23:14Z (GMT). No. of bitstreams: 1 ricardovioldossantos.pdf: 2585437 bytes, checksum: 897e63c2118d5c0e74581bbdb80ccb38 (MD5) Previous issue date: 2015-08-27 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Buscando corrigir aspectos relacionados à qualidade de energia, bancos de capacitores em derivação são utilizados em alimentadores primários dos sistemas de distribuição. A busca pela melhor forma de alocação constitui um problema complexo de natureza matemática combinatória, ao incluir critérios técnicos conflitantes e restrições do sistema. Este problema não tem solução trivial, tornando-se importante a formulação de metodologias para auxiliar nessa tarefa. Neste trabalho, é proposta uma metodologia para alocação de bancos de capacitores em derivação em nós do sistema elétrico, com possibilidade de alocação desequilibrada, considerando sua natureza discreta, com objetivo de minimizar desequilíbrios de tensão e custos de alocação, baseada em aplicação de algoritmo genético. Foram consideradas também restrições tais como limites de correntes nos alimentadores, limites de tensão para a conformidade com as faixas adequadas de tensão padronizadas pelos órgãos competentes e a disponibilidade de bancos. / Seeking for correcting issues related to power quality, shunt capacitor banks are used in primary feeders of distribution systems. The search for the best allocation is a complex problem of combinatorial mathematical nature, including conflicting technical criteria and constraints of the system. This problem has nontrivial solution, making important the development of methodologies to assist in this task. In this work, it is proposed a methodology for allocation of shunt capacitor banks in electric system nodes, with the possibility of unbalanced allocation, considering its discrete nature, with the purpose of minimizing voltage imbalances and allocating costs, based on genetic algorithm application. Restrictions such as limits of current feeders, voltage limits for compliance with the appropriate standard voltage ranges and the availability of capacitor banks were considered.

In a synchronous machine, radial, tangential, and axial forces are generated. In this thesis, three different technologies to control them are proposed. The first one, involves the utilization of the radial forces that arise between the rotor and the stator. This is achieved by segmenting the rotor field winding into groups of poles and controlling their corresponding magnetization individually. This technology is particularly useful to achieve magnetic balance and to create controllable radial forces. The second technology, involves the control of the rotor field in order to influence the tangential forces that produce torque. This is achieved by inverting the rotor field winding polarity with respect to the stator field. With this technique, breaking and accelerating torques can be created. It is particularly useful to start a synchronous machine. Finally, the application of axial forces with a magnetic thrust bearing is discussed. The main benefits of this technology are higher efficiency and increased reliability. The work presented in this thesis was carried out within the Division of Electricity in the Department of Engineering Sciences at Uppsala University. It is based on original research supported by analytical calculations, computational simulations and extensive experimental work.

En 2008, à l’issue du « Grenelle de l’Environnement » la France prend l’engagement de réduire de 50% les usages en pesticides des agriculteurs à niveaux de production inchangés. Comment y parvenir ? Un tel objectif est-il réalisable ? Cette thèse apporte des éléments de réponses grâce à l’étude de la demande en pesticides des agriculteurs et à son interaction avec l’offre de produits des firmes. L’exploitation de données individuelles permet d’analyser les déterminants des usages des agriculteurs liés aux caractéristiques des produits phytosanitaires. Le premier chapitre estime un système de demande en supposant que les produits sont homogènes au sein des grandes catégories de traitements. Il montre que la demande est peu sensible aux prix des produits à un niveau global. Il met en évidence que seule une taxe ad valorem très élevée permettrait d’atteindre l’objectif du "Grenelle de l’Environnement" , ce qui amputerait significativement les revenus des agriculteurs. Afin d’envisager une solution alternative, la suite de la thèse étudie une action simultanée sur l’offre et sur la demande. Il est préalablement nécessaire de construire un indice des prix qui intègre les spécificités techniques et réglementaires de ces produits. Cela fait l’ objet du second chapitre. Le prix ajusté est utilisé dans le troisième chapitre qui s’intéresse à l’équilibre du marché . La prise en compte de la structure de la concurrence rend possible l’identification des différentes sources de marges des firmes. L’analyse des changements de marges avant et après la modification de la procédure d’homologation des produits souligne une augmentation des marges des firmes après renforcement des exigences environnementales des caractéristiques des produits. / Following the “Grenelle de l’Environnement” the French government takes the commitment to reduce by 50% pesticide use while maintaining current production levels. How can we reach this objective? Is this target sustainable ? This thesis analyzes the demand of farmers and its interaction with firms supply. A desagregated dataset is constructed to analyze the determinants of farmers’ practices related to the characteristics of products and firms that market them. The first chapter estimates a demand system assuming homogeneous products within categories of pesticides. It confirms that the demand is not sensitive to the prices at an aggregated level. It shows that only a very high ad valorem tax would achieve the objective of the ”Grenelle de l’Environnement”. However, this measure would significantly reduce farmers' income. Alternatively, the thesis retains simultaneous action on both the supply and the demand. First, a price index is constructed in the second chapter. It introduces the technical and regulatory specificities of these products by exploiting the panel structure of the price series. Second, the adjusted price computed indexis used in the third chapter which retains structural econometrics framework to analyze the market equilibrium. Taking into account the structure of competition we compute the margins of firms which are generated by different competition conduct. These results are used to evaluate the effect of the modification of the homologation process on margins. We find that important source of margin was generated by this regulation which sustain innovation.

No description available.

This thesis focuses on problematics of segmentation of unbalanced datasets by the useof artificial inteligence. Numerous existing methods for dealing with unbalanced datasetsare examined, and some of them are then applied to real problem that consist of seg-mentation of dataset with class ratio of more than 6000:1.

The Master's thesis deals with the mechanical design of electric machine rotor. Within the first two chapters of the practical part of the thesis two simplified computational models of the rotor (level 1 models) are compiled. Specifically, the model of flexible rotor mounted on rigid supports and model of rigid rotor mounted on flexible supports. The essence of these computational models lies in solvability using simple equations. Using these models can save time when constructing a pre-design of the rotor geometry. The following chapter is devoted to comparing different approaches to computational modeling of rotor using FEM. A predetermined preliminary design of a high-speed massive rotor is investigated. Computational models of different levels at stress-strain analysis and modal analysis are presented. It also includes a suggestion on how to proceed effectively in a given analysis.

No description available.

No description available.

High-speed ADC is essential in radio network systems for communications. However, accuracy is an important feature for them, their precision can be affected by minor discrepancies, e.g., offset voltage of comparators, which is a primary contributor to these discrepancies. This master thesis focuses on evaluating offset calibration techniques used for high-speed comparators. To start, a literature review is performed to learn about high-speed comparators and various offset calibration techniques, which helps to understand existing problems and new ideas in offset calibration. As the next step, evaluation and implementation of the reviewed literatures are done, which involves the implementation of schematics at the transistor level, where the calibration procedure's controller is implemented in Verilog-A. Finally, an extensive set of simulations, i.e., done by the electronic design automation tool, is conducted on the designed offset calibration techniques and how they affect the general operation of high-speed ADCs.  Among the reviewed calibration techniques, two discrete adjustment methods (trans-conductance and capacitive DAC) and three voltage-controlled methods (unbalanced clocks, second differential pair, and body bias) are implemented and evaluated. The discrete methods use digital circuits, which have large variations in step sizes due to mismatches, leading to higher offsets after calibration. Monte Carlo simulations are done to show this drawback clearly better. However, using thermometer code instead of the binary-weighted would help by making the step sizes more consistent, which yields better-offset calibration results. On the other hand, the voltage-controlled methods rely on external voltages, which require more design work because of the Digital-to-Analog Converter (DAC) units. During a calibration test with various input offsets, the 'Body Bias' technique exhibited the highest precision by achieving the smallest remaining offset.

The aim of this study is to explore ways to maximise the economic returns of road infrastructure investment. In order to achieve this objective, the study was divided into five parts involving the following: analysing the nature of road infrastructure, determining the relationship between road infrastructure investment and economic development, considering aspects of economic modelling, developing a formula of road investment, and refocusing road investment practices. In the first part the characteristics of road infrastructure are examined and the demand and supply approaches to road investment outlined. The focus is on the balanced approach versus the unbalanced approach to infrastructure investment. The second part analyses the causal relationship between road investment and economic development. Four components are highlighted, namely the investment component, the network-performance component, the transport economic component and the economic development component. The third part analyses the applicability of modelling techniques. In the fifth part, the formula of road investment and economic development is focused on four markets. Finally, it is argued that road infrastructure investment must be refocused. The following was found: Road infrastructure investment must be demand led. This is because of the characteristics of roads, namely their indivisibility, long gestation period, lumpiness and high cost. Road infrastructure investment can only realise economic development if the four causality components are complied with simultaneously. Input-output modelling is preferred in South Africa. The modelling strategy developed in this study is recommended for transport economic studies. The probability of economic returns of road infrastructure investment is a function of the real estate market, the land development market, the urban economic market and the infrastructure market. An agenda for reform in the road investment industry was also proposed. The study clearly identifies the relationship between road infrastructure investment and economic development, and the proposed formula is an appropriate tool for a first-order priority system. / Transport Economics, Logistics and Tourism / D. Com. (Transport Economics)