The widespread application of pressurized SF6 gas and its mixtures as insulating medium in many electric power applications is the result of recent advances in technologies. The likelihood of failure for a Gas Insulated Substation or Transmission Line (GIS/GITL) is primarily due to the presence of defects inside the equipment. Defects can be introduced into the GIS/GITL system for various reasons. Partial discharge (PD) is a natural phenomenon occurring in the GIS/GITL systems, which invariably contains defects. During commissioning or routine tests PD measurements serve to identify the type and status of a defect. Of particular interest for this research work will be the critical review of PD measurement for different types of free conducting particles in the gas using the UHF method due to its superiority among others. The work highlights the integrity of the method as a tool for both commissioning and routine tests and its alignment with the high voltage SF6 test standards is reviewed. 80/20 N2/SF6 mixture is used to reduce the surface roughness effect in pure SF6, as well as for the reduction of economical and environmental risks.

O presente trabalho tem por finalidade a obtenção de curvas que regem o comportamento estático da sustentação e arrasto de uma asa em função da variação de seu câmber através do uso do flape de bordo de ataque, com base em resultados experimentais obtidos em túnel de vento. O estudo inclui uma revisão sobre o uso de flapes de bordo de ataque e uma descrição dos ensaios em túnel de vento. O modelo tridimensional da asa utilizada para os experimentos contém um flape de bordo de ataque em metade de sua envergadura e foi construído segundo o perfil GA(W)-1. O experimento inclui a determinação da sustentação e do arrasto para cada valor do ângulo de ataque da asa e do ângulo do flape de bordo de ataque. O objetivo é obter uma correlação ótima entre estes dois ângulos de forma que, para cada ângulo de ataque da asa seja determinado um ângulo ótimo do flape de bordo de ataque que confira a máxima sustentação. / The present work has for purpose the attainment of curves that conduct the static behavior of the lift and drag of a wing in function of the variation of its camber through the use of the leading edge flap, on the basis of gotten experimental results obtained in the wind tunnel. The study includes a revision of the use of leading edge flaps and a description of the wind tunnel tests. The three-dimensional model of the wing used in the experiments contains a leading edge flap along half of the span and was constructed with a GA(W)-1 section profile. The experiment includes the determination of lift and drag for each value of angle of attack of the wing and each angle of the leading edge flap. The objective is to obtain a good correlation between the two angles in such a way that, for each angle of attack of the wing there is determined an excellent angle of the leading edge flap that confers principle lift.

Recent research developments have indicated that asphalt mixture durability and pavement life can be increased by modifying the Superpave asphalt mixture design method to achieve an in-place density of 95%, 2% higher than the conventional density requirements of approximately 93% (7% air voids content). Doing so requires increasing the design air voids content to 5% from the conventional requirement of 4 percent. After successful laboratory testing of this modified mixture design method, known as Superpave 5, two controlled field trials and one full scale demonstration project, the Indiana Department of Transportation (INDOT) let 12 trial projects across the six INDOT districts based on the design method. The Purdue University research team was tasked with observing the implementation of the Superpave 5 mixture design method, documenting the construction and completing an in-depth analysis of the quality control and quality assurance (QC/QA) data obtained from the projects. QC/QA data for each construction project were examined using various statistical metrics to determine construction performance with respect to INDOT Superpave 5 specifications. The data indicate that, on average, the contractors achieved 5% laboratory air voids, which coincides with the Superpave 5 recommendation of 5% laboratory air voids. However, on average, the as-constructed in-place density of 93.8% is roughly 1% less than the INDOT Superpave 5 specification. The findings of this study will benefit the future implementation of this modified mixture design method.<br>

Este trabalho tem como objetivo estudar a influência da geometria de suspensão do veículo nas atitudes da massa suspensa. Apresenta um confronto entre obras e autores e está segmentada em três partes; onde na primeira parte são definidos os conceitos básicos como dive, squat, lift, anti-dive, anti-squat, anti-lift e equivalente trailing-arm; na segunda parte são apresentadas as limitações e os novos conceitos definidos por R. S. Sharp e na terceira parte é apresentado o modelo dinâmico bidimensional introduzido por Fu-Cheng Wang. Apresenta um modelo virtual em sistema de multi-corpos desenvolvido no programa ADAMS, com todos os subsistemas que compõe um veículo completo. Inova ao trazer como objeto de estudo um veículo de competição (fórmula SAE) que possui como particularidade o sistema de suspensão push-rod. Surpreende com os resultados obtidos, pois, contrariam os conceitos básicos encontrados na maioria dos livros / This work has objective study the influence of suspension geometry on the sprung mass attitudes. It presents a confrontation among works and authors and this segmented in three parts; where in the first part the basic concepts are defined, dive, squat, lift, anti-dive, anti-squat, anti-lift and equivalent trailing-arm; in the second part the limitations are presented and the new concepts are defined for R. S. Sharp and in the third part are presented the bidimensional dynamic model introduced by Fu-Cheng Wang. It presents a virtual model in system of multi-bodies developed in the program ADAMS, with all the subsystems that composes a complete vehicle. It innovates when bringing such object to study one vehicle of competition (formula SAE) that it has a particularity suspension system push-rod. It surprises with results because it’s opposite of the basic concepts which is present in the majority of books

O presente trabalho tem por finalidade a obtenção de curvas que regem o comportamento estático da sustentação e arrasto de uma asa em função da variação de seu câmber através do uso do flape de bordo de ataque, com base em resultados experimentais obtidos em túnel de vento. O estudo inclui uma revisão sobre o uso de flapes de bordo de ataque e uma descrição dos ensaios em túnel de vento. O modelo tridimensional da asa utilizada para os experimentos contém um flape de bordo de ataque em metade de sua envergadura e foi construído segundo o perfil GA(W)-1. O experimento inclui a determinação da sustentação e do arrasto para cada valor do ângulo de ataque da asa e do ângulo do flape de bordo de ataque. O objetivo é obter uma correlação ótima entre estes dois ângulos de forma que, para cada ângulo de ataque da asa seja determinado um ângulo ótimo do flape de bordo de ataque que confira a máxima sustentação. / The present work has for purpose the attainment of curves that conduct the static behavior of the lift and drag of a wing in function of the variation of its camber through the use of the leading edge flap, on the basis of gotten experimental results obtained in the wind tunnel. The study includes a revision of the use of leading edge flaps and a description of the wind tunnel tests. The three-dimensional model of the wing used in the experiments contains a leading edge flap along half of the span and was constructed with a GA(W)-1 section profile. The experiment includes the determination of lift and drag for each value of angle of attack of the wing and each angle of the leading edge flap. The objective is to obtain a good correlation between the two angles in such a way that, for each angle of attack of the wing there is determined an excellent angle of the leading edge flap that confers principle lift.

The main sources of airframe noise in commercial aircrafts are the landing gear and the highlift devices. Among the high-lift devices, the slat deserves special attention since it represents a distributed source along the wing span. During approach and landing the noise generated by the slat can be comparable to the engine generated noise. For the design of quieter high-lift systems, it is important to understand the physics responsible for the slat noise generation. The objective of the work described in this thesis is to correlate the dynamics of large scale turbulent structures at different airfoil configurations with the characteristics of the noise generated by these structures. Four different configurations were investigated, ranging two airfoil angles of attack and three slat positions relative to the main element. The unsteady flow data was provided by a Lattice-Boltzmann based computational code. The Proper Orthogonal Decomposition technique was used for the objective identification of large scale structures in the slat region. Two different metrics were considered for the eduction of the coherent structures: one based on the Turbulent Kinetic Energy of the structures; and one based on their correlation to the noise emitted by the slat. The results of the transient simulations showed good agreement with wind tunnel measurements, providing confidence on the relevance of the analysis. The noise spectra of three of the cases simulated were dominated by a series of narrowband peaks at low frequency, while the spectrum of the remaining case was broadband in nature. Analysis of the averaged flow showed a large variation of the size and shape of the recirculating zone inside the slat cove and on the reattachment position of the mixing layer, between the simulated cases. The results indicated that, as the reattachment point approximates the region of the gap between the slat and the main element, the noise emission power increases. The large scale structures most correlated to the noise were typically two-dimensional and their shape suggests they resulted from the growth of disturbances in the mixing layer due to the inflectional instability. The dynamics of the noise correlated structures at the frequencies of the peaks was consistent with the existence of an acoustic feedback mechanism acting inside the slat cove. Based on the observation of the educed structures a model to predict the frequencies of peaks was proposed, showing good agreement with the frequencies computed from the unsteady flow data. / As principais fontes de ruído não propulsivo em aeronaves comerciais são os trens-de-pouso e os dispositivos híper-sustentadores. Entre os dispositivos híper-sustentadores, o eslate se destaca por constituir uma fonte distribuída ao longo da envergadura da asa. Durante a fase de aproximação e aterrissagem, o eslate pode gerar ruído com níveis comparáveis ao gerado pelos motores. Para viabilizar projetos de aerofólios com eslates menos ruidosos, é importante compreender os fenômenos fluidodinâmicos responsáveis pela geração desse ruído. O trabalho descrito neste texto tem por objetivo verificar se existe correlação entre o comportamento de grandes estruturas turbulentas em diferentes configurações do aerofólio com as características do ruído aeroacústico gerado por elas. O escoamento em quatro configurações diferentes foi estudado, abrangendo dois ângulos de ataque e três posições do eslate em relação ao elemento principal. Os dados do escoamento para análise foram gerados através de simulações numéricas não estacionárias utilizando um código comercial baseado no Método Lattice-Boltzmann. O método da Decomposição Ortogonal Apropriada foi utilizado para a identificação das estruturas de grande escala baseada em critérios objetivos. Duas métricas distintas foram utilizadas, uma baseada na energia cinética turbulenta e outra baseada na correlação com as ondas acústicas geradas a partir do eslate. Os resultados das simulações transientes apresentaram boa concordância com resultados experimentais. O espectro de ruído de três casos simulados são dominados por picos de baixa frequência, enquanto o espectro do quarto caso é tipicamente de banda larga. A análise do escoamento indica uma tendência de aumento do ruído à medida que o recolamento se aproxima do bordo de fuga do eslate. As estruturas mais correlacionadas com o ruído são tipicamente bi-dimensionais e seu formato indica que são resultado do crescimento de perturbações na camada de mistura devido à instabilidade inflexional. A dinâmica das estruturas correlecionadas com o ruído na frequência dos picos é consistentes com a existência de uma retro-alimentação das perturbações da camada de mistura por ondas acústica na cova do eslate. Um modelo para previsão das frequências dos picos foi proposto a partir da observação das estruturas identificadas pela Decomposição Ortogonal Apropriada, mostrando boa concordância com as frequências observadas nos espectros calculados com base nos dados transientes das simulações.

O propósito principal deste trabalho é investigar experimentalmente os efeitos aerodinâmicos de um gerador de vórtice tipo serrilhado colocado no bordo de fuga do elemento principal para aumentar a turbulência na camada limite da superfície superior do flape. Esse gerador de vórtice serrilhado consiste em triângulos no bordo de fuga do elemento principal da asa utilizado para promover uma mistura entre o escoamento de alta pressão da superfície inferior, com o escoamento na superfície superior. Essa mistura pode reduzir a separação no bordo de fuga da asa e também injetar vorticidade na camada limite do flape, atrasando a ocorrência da separação. Conseqüentemente, um aumento da sustentação pode ser produzido para um menor arrasto de pressão. Foram feitas extensivas análises experimentais no túnel de vento com diversas configurações para o ângulo de ataque no modelo e foram usadas duas configurações geométricas para o gerador de vórtice serrilhado. Medidas de forças e tomadas de pressão foram feitas para uma asa bidimensional com um único flape. Foi utilizada também anemometria a fio quente para um mapeamento da camada limite confluente. Uma visualização do escoamento usando a técnica de sublimação foi realizada na asa-flape. Os resultados mostram que os vórtices criados e injetados na camada limite do flape atrasam a separação consideravelmente e que esses efeitos são dependentes da geometria do gerador serrilhado. / The main purpose of this work was the experimental investigation of the effect of a saw-tooth trailing edge of a wing main element on the aerodynamics characteristics of a single flap. The saw-tooth trailing edge consists of triangles on the trailing edge of the main element of the wing in order to promote mixing between the higher-pressure flow from the lower surface with the flow on the upper surface. This mixing may reduce wing trailing edge separation and also inject vorticity into flap boundary layer, thus delaying separation. Therefore, more lift may be produced for less pressure drag. Extensive wind tunnel experiments were made for a series of saw-tooth trailing edge geometries. Forces and chordwise pressure measurements were performed for a two-dimensional wing with a single flap, as well as hot wire anemometry mapping of the confluent boundary layer. Flow visualization in the wing-flap gap was performed using a sublimation technique. Results show that the vorticity injected into the flap boundary layer by the saw-tooth trailing edge can delay flap separation substantially and that the effect is dependent on saw-tooth geometry.

by Fong Kin-wai, Stephen. / Bibliography : leaf 105 / Thesis (M.B.A.)--Chinese University of Hong Kong, 1984

Bismuth Hall effect sensors with active sizes in the range 0.1µm - 2µm have been fabricated by electron beam lithography and lift-off techniques for applications in scanning Hall probe microscopy (SHPM). The key figures of merit of the sensors have been systematically characterised as a function of device size. The miniumum detectable field of 100nm probes at room temperature is found to be Bmin=0.9mT/Hz0.5, with scope for more than a factor of ten reduction by using higher Hall probe currents. This is significantly lower than in similar samples fabricated by focussed ion beam (FIB) milling of continuous Bi films, suggesting that the elimination of FIB damage and Ga+ ion incorporation through the use of lift-off techniques leads to superior figures of merit. A number of ways in which the T=300K performance of our sensors could be improved still futher are discussed. High resolution scanning Hall probe microscopy (SHPM) with semiconductor 2DEG Hall probe devices has been used to search for novel phases of vortex matter in single crystals of the high temperature superconductor Bi2Sr2CaCu2O8+. In the crossing lattices regime of these highly anisotropic superconductors under tilted magnetic fields two orthogonal types of flux structure are formed known as Josephson and pancake vortices (JVs and PVs). SHPM has been used to study interacting JV-PV matter with very high in-plane fields. The spacing of JV chains has been systematically quantified as a function of both in-plane and out-of-plane fields. Surprisingly, it is found that the JV chain spacing is not solely a function of the in-plane field, as previously assumed, and the effective anisotropy, γ_eff, is shown to depend strongly on the out-of-plane field strength. Moreover, for a fixed in-plane field the JV stack spacing shows pronounced sawtooth-like oscillations as a function of the out-of-plane field. These measurements are giving us unique new insights into the properties of crossing vortex lattices in highly anisotropic cuprate superconductors at high Josephson vortex stack densities.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering; and, (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / Includes bibliographical references. / by Graham Taber Skinner. / M.S.