Esta dissertação tem por propósito analisar os impactos da geração distribuída sobre as correntes de curto-circuito e sobre a proteção das redes de média tensão das concessionárias de distribuição de energia elétrica usando uma abordagem paramétrica. A principal motivação deste trabalho são os recentes incentivos regulatórios que estão fomentando a geração distribuída no Brasil. Contudo, as redes de distribuição convencionais foram projetadas para serem passivas e a introdução da geração poderá causar problemas de ordem técnica que ainda precisam ser resolvidos. Tais problemas foram pesquisados e aqueles relacionados com os impactos sobre as correntes de curto-circuito foram enfatizados. As normas técnicas das concessionárias também foram investigadas porque seus requisitos, como a ligação dos transformadores de acoplamento, influem nas correntes de curto-circuito. Para se calcular as correntes de curto-circuito, desenvolveu-se uma planilha eletrônica cujos resultados foram validados com programas comerciais de análise de redes elétricas. Esta ferramenta foi utilizada para demonstrar, através de exemplos, o impacto causado pela geração distribuída sobre as correntes de curto-circuito e, posteriormente, para realizar as análises paramétricas nas quais a influência de cada variável foi avaliada. A aplicação do método paramétrico permitiu o estudo de possíveis limites para a potência de um gerador distribuído em função dos impactos admissíveis, de seu ponto de conexão, de seus parâmetros elétricos e dos parâmetros elétricos da rede. / The purpose of this thesis is to analyse the impacts of distributed generation on short-circuit currents and protection of the distribution utilities medium voltage networks using a parametric approach. The new regulations that are promoting the distributed generation in Brazil are the main motivation for this work. However, the conventional distribution networks were designed to be passive; therefore the integration of generation may cause some technical problems yet to be solved. Such problems were researched and those related to the impacts on short-circuit currents were emphasized. The utilities technical standards were also explored as their requirements affect the short-circuit currents (e.g. the transformers connections). A spreadsheet was developed in order to calculated the short-circuit currents and it was validated comparing its results to those of a commercial network analysis software. This tool was used to expose the impacts of distributed generation on short-circuit currents through examples and also to carry out parametric analysis in which the influence of every variable was evaluated. The application of a parametric method made it possible to define the maximum installed capacity of a distributed generator as a function of the allowed limits to the impacts on the short-circuit currents, its point of coupling, its electrical parameters and the electrical parameters of the network.

La ventilation naturelle est une stratégie passive qui permet l'échange naturel d'air entre le bâtiment et l'environnement extérieur. Elle assure une bonne qualité de l'air intérieur, améliore le confort thermique et elle réduit les besoins énergétiques, les émissions de gaz à effet de serre et les symptômes liés au syndrome du bâtiment malsain. Bien que les avantages et les bénéfices de la ventilation naturelle soient multiples, son usage est rare dans l'architecture contemporaine. Bien sûr, il existe des limites à sa mise en œuvre dans certains bâtiments, comme la mauvaise qualité de l'air extérieur, mais ces problèmes ne justifient pas une utilisation si peu répandue. La cause de sa faible diffusion est principalement liée à la difficulté de la conception plutôt que aux facteurs physiques liés à l'environnement. La thèse vise à fournir différents outils pour comprendre la dynamique des fluides dans les bâtiments et développer des techniques et des méthodes pour aider la conception des bâtiments ventilés naturellement. L'approche adoptée dans la thèse est modélisée selon les besoins du concepteur qui peut choisir d'utiliser différents types de supports tels que: utiliser des outils graphiques ou des modélisations numériques, s'inspirer de l'architecture contemporaine et répéter les solutions technologiques existantes, utiliser des outils de modélisation physique, s'inspirer du passé ou du monde naturel. Ici plusieurs aspects de la ventilation naturelle sont traités en apportant à chacun une contribution innovante afin de créer des outils d'aide pour différents phases de la conception : Les objectifs de la thèse sont de créer des outils innovants qui simplifient la conception à des niveaux différents. Nous avons créé donc, des outils et des modèles graphiques simplifiés pour choisir la forme du bâtiment et son orientation, des lignes directrices pour le dimensionnement des dispositifs de ventilation (cheminées de toit), des méthodes expérimentales simplifiées associées à des codes de lecture des écoulements d'air. Nous avons également élargit le panorama culturel et historiques et nous avons créé des indications morphologiques dérivant de l'analyse de l'architecture biomimétique. Grâce à une analyse CFD paramétrique, des outils graphiques sont générés pour évaluer, de manière comparative, les performances de ventilation d'une famille morphologique de bâtiments et choisir la forme du bâtiment, son orientation et la position des ouvertures. Nous créons des lignes directrices pour la conception et le pré-dimensionnement des dispositifs de ventilation. Les règles sont déterminées par une analyse comparative de neuf projets de bâtiments contemporains ventilés naturellement dans lesquels le dispositif de ventilation est présent. Une soufflerie est conçue et réalisée pour simplifier les visualisations des écoulements d'air autour des modèles de bâtiments et nous proposons une méthode pour réaliser des expérimentations de support à la conception. Le système de refroidissement géothermique d'une ancienne villa à Costozza (Vicence, Italie) est étudié. Cette section élargit la connaissance du patrimoine architectural italien et souligne l'importance de redécouvrir des solutions technologiques bioclimatiques existantes, toujours en fonction. On analyse une structure animale: le nid d'un insecte. Il s'agit d'un archétype bioclimatique qu'il peut être utilisé dans l'architecture en tant que technologie biomimétique / Natural ventilation is a passive ventilation strategy of confined spaces that consists of natural air exchange between the building and the outdoor environment. Natural ventilation ensures a good indoor air quality, it improves the thermal comfort and it reduces the greenhouses gases emission, the energy demand and the symptoms associated with the Sick Building Syndrome. Although the advantages and benefits of natural ventilation are multiple, its application is rare to contemporary architecture. By the way, there are some limits to its implementation, such as the bad quality of outdoor air, but that does not justify a so limited design of naturally ventilated buildings. The cause of its rare diffusion is primarily the difficulty of design rather than the factors related to the environment. The thesis intends to provide multiple tools for understanding the fluid dynamics in buildings and to develop techniques and methods to support the design of naturally ventilated buildings. The approach adopted in the thesis is modeled according to the needs of the designer. In fact, a designer can choose to use different types of support tools such as: use of graphic tools or numerical models, inspiration to contemporary architecture to provide the existing technology solutions, use of physical modeling tools, inspiration to the past or to the nature. Often, the design is a global process and does not need a single tool but the designer uses more than one. Here, several aspects of natural ventilation are dealt with, trying to make an innovative contribution to each of these themes, in particular : Through a parametric CFD analysis, graphical tools are generated to evaluate, adopting a comparative approach, the ventilative performance of a morphological family of buildings and to choose the shape of the building, its orientation and the position of the openings. Guidelines are set for the design and pre-dimensioning of ventilation devices. The rules are determined by a comparative analysis of nine contemporary ventilation projects in which the ventilation device is present. An optimized wind tunnel is created to simplify airflow visualizations around building models. We provide also a method to make simplified experimentations, an aiding-design tool, and a code that allows to understand the views with the smoke. We study the geothermal cooling system of an ancient villa in Costozza (Vicenza, Italy). This section extends the knowledge of the Italian architectural heritage and highlights the importance of rediscovering existing bioclimatic technology solutions, still in operation. An animal structure is analysed: the bug of an insect. This is a bioclimatic archetype and therefore it can be applied to architecture as a biomimetic technology

Esta dissertação tem por propósito analisar os impactos da geração distribuída sobre as correntes de curto-circuito e sobre a proteção das redes de média tensão das concessionárias de distribuição de energia elétrica usando uma abordagem paramétrica. A principal motivação deste trabalho são os recentes incentivos regulatórios que estão fomentando a geração distribuída no Brasil. Contudo, as redes de distribuição convencionais foram projetadas para serem passivas e a introdução da geração poderá causar problemas de ordem técnica que ainda precisam ser resolvidos. Tais problemas foram pesquisados e aqueles relacionados com os impactos sobre as correntes de curto-circuito foram enfatizados. As normas técnicas das concessionárias também foram investigadas porque seus requisitos, como a ligação dos transformadores de acoplamento, influem nas correntes de curto-circuito. Para se calcular as correntes de curto-circuito, desenvolveu-se uma planilha eletrônica cujos resultados foram validados com programas comerciais de análise de redes elétricas. Esta ferramenta foi utilizada para demonstrar, através de exemplos, o impacto causado pela geração distribuída sobre as correntes de curto-circuito e, posteriormente, para realizar as análises paramétricas nas quais a influência de cada variável foi avaliada. A aplicação do método paramétrico permitiu o estudo de possíveis limites para a potência de um gerador distribuído em função dos impactos admissíveis, de seu ponto de conexão, de seus parâmetros elétricos e dos parâmetros elétricos da rede. / The purpose of this thesis is to analyse the impacts of distributed generation on short-circuit currents and protection of the distribution utilities medium voltage networks using a parametric approach. The new regulations that are promoting the distributed generation in Brazil are the main motivation for this work. However, the conventional distribution networks were designed to be passive; therefore the integration of generation may cause some technical problems yet to be solved. Such problems were researched and those related to the impacts on short-circuit currents were emphasized. The utilities technical standards were also explored as their requirements affect the short-circuit currents (e.g. the transformers connections). A spreadsheet was developed in order to calculated the short-circuit currents and it was validated comparing its results to those of a commercial network analysis software. This tool was used to expose the impacts of distributed generation on short-circuit currents through examples and also to carry out parametric analysis in which the influence of every variable was evaluated. The application of a parametric method made it possible to define the maximum installed capacity of a distributed generator as a function of the allowed limits to the impacts on the short-circuit currents, its point of coupling, its electrical parameters and the electrical parameters of the network.

The thesis presents the design and analysis of a Twin Tensioner for a Belt-driven Integrated Starter-generator (B-ISG) system. The B-ISG is an emerging hybrid transmission closely resembling conventional serpentine belt drives. Models of the B-ISG system's geometric properties and dynamic and static states are derived and simulated. The objective is to reduce the magnitudes of static tension in the belt for the ISG-driving phase. A literature review of hybrid systems, serpentine belt drive modeling and automotive tensioners is included. A parametric study evaluates tensioner parameters with respect to their impact on static tensions. Design variables are selected from these for an optimization study. The optimization uses a genetic algorithm (GA) and a hybrid GA. Results of the optimization indicate the optimal system contains spans with static tensions that are significantly lower in magnitude than that of the original design. Implications of the research on future work are discussed in closing.

The thesis presents the design and analysis of a Twin Tensioner for a Belt-driven Integrated Starter-generator (B-ISG) system. The B-ISG is an emerging hybrid transmission closely resembling conventional serpentine belt drives. Models of the B-ISG system's geometric properties and dynamic and static states are derived and simulated. The objective is to reduce the magnitudes of static tension in the belt for the ISG-driving phase. A literature review of hybrid systems, serpentine belt drive modeling and automotive tensioners is included. A parametric study evaluates tensioner parameters with respect to their impact on static tensions. Design variables are selected from these for an optimization study. The optimization uses a genetic algorithm (GA) and a hybrid GA. Results of the optimization indicate the optimal system contains spans with static tensions that are significantly lower in magnitude than that of the original design. Implications of the research on future work are discussed in closing.

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Stirling engines are promising candidates for applications where air breathing engines cannot be used. Self contained engines capable of operating independently of the environment are required to convert thermal energy into electric power, or to perform other necessary functions. These are ideally suited for power generation onboard spacecrafts with radioisotope heat source. These engines can power interplanetary missions to Mars and beyond. The problem of parametric analysis, sensitivity and numerical optimization of Stirling cycle engine is discussed and applied to a specific example of a 2kWe free piston Stirling engine. Stirling cycle simulation programs are generated with emphasis and adaptations peculiar to free piston design for space use. Design algorithms are generated in MatLab and optimization toolbox is used for the parametric analysis adopted in this thesis. A free piston beta Stirling engine with a linear alternator configuration has been studied for the interdependency and performance effects of various important operational parameters. The analysis has been carried out in order to optimize the primary parameters, weight vis a vis envelope (length and diameter) and stroke of the engine, to make it suitable for space use. The major cycle parameters considered are operating pressure, linear speed, dead space ratio and swept volume ratio, classified as secondary parameters. The whole analysis has been carried out at a cycle temperature ratio of 0.4 for a heat source temperature of 873 K, typical of a radioisotope heat source. The optimization is carried out for the defined design requirements viz. envelope of 50 × 50 cm , stroke of less than 10 cm, and heat source temperature of 873 K. The process of parametric optimization of the primary parameters viz engine envelope and stroke are carried out with respect to the secondary parameters. Iterations are carried out on the design programs in MatLab. The results indicate that the three primary parameters have a different set each, of the secondary parameter values when optimized to the design requirement. The fmincon solver of MatLab in the optimization tool box is selected in order to validate the optimization results. The solver is used to find a minimum of a constrained nonlinear multivariable function defining the primary parameters. The results obtained concur with the optimization results generated by the design algorithm. Further, the interdependency amongst the primary and secondary parameters is studied by generating MatLab plots for all possible combinations among the various parameters. The effect of variations in the pressure and linear speed on the system envelope and stroke are more pronounced at lower range values of the pressure and speed and the variations of the primary parameter values are constant at higher ranges. The effect of dead space ratio and swept volume ratio (>1.0) is not pronounced. The requirements in the environment of space place a number of constraints upon a Stirling engine/alternator design that are not present in terrestrial applications. High specific power is achieved by designing the engine for higher pressure and frequency operation than a terrestrial Stirling engine, and by using light weight materials where appropriate. Cylinder is the heart of the engine and it forms a major proportion of the total system mass. Mass and heat loss estimates and analysis have been carried out on the cylinder for various materials of construction. Based on the analysis feasibility exists for a Cu-Ni combination. The system would have a mass of 7kg with a specific power estimate of 0.28kW/kg and a conduction heat loss to mass ratio of 159W/kg. The system obtained by numerical analysis is modeled in system simulation software SIMULATIONX. The simulation of the system is studied and a sensitivity analysis performed in order to assess the parametric interdependency of the whole free piston Stirling engine system. The system sensitivity to piston and displacer mass is studied using the simulation model. Sensitivity results indicate that there is a range of mass values within which the system is operational, mass values outside the range makes the system non-functional. Also the range is a function of various parameters and detailed analysis is required in this direction in order to further optimize all the functional parameters. Engineering approximation is carried out using the curve fitting toolbox in MatLab to generate design equations in order to provide preliminary design data for the designer, further a scaling study is carried out at various power levels in order to assess the sensitivity of system geometry at various power levels.

The subject of the diploma thesis is the stress analysis of the circular and elliptical shaft from material jet grouting. A new advanced constitutive Shotcrete model will be applied on the material jet grouting. In the thesis, the shaft tensile strength factor and the size of the ground pressures will be primarily examined. The practical part of the diploma thesis is completed by the comparison of the analytical and numerical calculation of the normal force of the circular and elliptical shafts.

The mechanisms that control the lateral response of stiff column-supported shallow foundations, resulting from the application of horizontal load on shallow foundations supported by stiff columns, are uncertain. Stiff columns constructed in soft clayey soil have been used to support retaining walls and in such cases, the lateral thrust applied behind these geotechnical structures is a source of horizontal loading. For seismic events, stiff columns constructed in soft clayey soil have been used to support shallow foundations subjected to horizontal load coming from the upper structure of buildings. Due to its practical applications, it has become important to understand the consequences of subjecting a shallow foundation supported by stiff columns to horizontal load by identifying the factors that control the lateral response of such systems. A series of centrifuge tests were carried out to examine the lateral response of stiff column-supported shallow foundations. The experimental trends suggested that the thickness of the coarse-granular mattress placed above the soil-column composite, called the Load Transfer Platform (LTP), controlled the lateral capacity and the overall lateral response of these systems. A numerical study using the finite element method confirmed the experimental trends. A parametric analysis was conducted with the purpose of investigating the influence of different geometry-based and material-based variables in the lateral response of these systems. The results of the parametric analysis further confirmed the importance of the thickness of the LTP in controlling the lateral response. The parametric results also emphasized the contribution of other variables to this lateral response, and these variables included the undrained shear strength of the soft clayey soil around the stiff columns, the stiff column diameter, and the spacing of the stiff columns after they are constructed in the soft clayey soil. / Doctor of Philosophy / Ground improvement is the process of improving the properties of weak soils. In practice, there are several ways to accomplish the ground improvement of weak soils. One way is to use stiff columns. Stiff columns are solid cylinders that are constructed in the weak soil in order to produce a stiff and strong soil-column composite capable of better supporting the square-shaped foundations of structures. Under horizontal load, there is uncertainty on the factors that control the lateral behavior of the stiff columns when used for the support of the square-shaped foundations of structures. An experimental and numerical approach was used to determine these factors and to understand their influence in the lateral behavior of such systems. The findings showed that the controlling factors of this lateral behavior included the thickness of a sand layer placed above the stiff columns, the diameter of the stiff columns, the spacing of the stiff columns after they are constructed in the weak soil, and the strength of the soil around the stiff columns. These findings will aid in improving the design of stiff columns used for the support of square-shaped foundations of structures subjected to horizontal load.