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The objective of this research was to characterize the performance of a downflow bubblecontact (DBCA) hypolimnetic aerator — Speece Cone-. The effect of two key design factors, inlet water velocity and the ratio of gas flow rate to water flow rate on four standard units of measure was examined: (a) the Oxygen Transfer Coefficient, KLa, corrected to 20°C, KLa₂₀ (hr­-¹), (b) the Standard Oxygen Transfer Rate, SOTR (g0₂.hr­-¹) (c) the Standard Aeration Efficiency, SAE (gO₂kWhr­-¹), and (d) the Standard Oxygen Transfer Efficiency, SOTE (%). Two sources of oxygen, Pressure Swing Adsorption (PSA) oxygen (87% purity) and air, were compared. KLa₂₀, SOTR, and SAE increased with an increase in the ratio of gas flow rate to water flow rate for both air and oxygen, over a range of 0.5% to 5.0%; while SAE deceased. An increase in inlet water velocity resulted in a decrease in KLa, corrected to 20°C, SOTR, and SAE, but an increase in the SOTE. Treatments on air showed similar, but much less dramatic effect of the gas flow rate to water flow rate ratio and water inlet velocity on KLa₂₀, SOTE, SAE, and SOTE, when compared to treatments on PSA oxygen. The best performance was achieved with an inlet water velocity of 6.9-7.6 ms­-¹ and oxygen flow rate to water flow rate ratio of about 2.5%. At this combination, the SOTE was about 66-72%.

The objective of this research was to characterize the performance of a downflow bubblecontact (DBCA) hypolimnetic aerator — Speece Cone-. The effect of two key design factors, inlet water velocity and the ratio of gas flow rate to water flow rate on four standard units of measure was examined: (a) the Oxygen Transfer Coefficient, KLa, corrected to 20°C, KLa₂₀ (hr­-¹), (b) the Standard Oxygen Transfer Rate, SOTR (g0₂.hr­-¹) (c) the Standard Aeration Efficiency, SAE (gO₂kWhr­-¹), and (d) the Standard Oxygen Transfer Efficiency, SOTE (%). Two sources of oxygen, Pressure Swing Adsorption (PSA) oxygen (87% purity) and air, were compared. KLa₂₀, SOTR, and SAE increased with an increase in the ratio of gas flow rate to water flow rate for both air and oxygen, over a range of 0.5% to 5.0%; while SAE deceased. An increase in inlet water velocity resulted in a decrease in KLa, corrected to 20°C, SOTR, and SAE, but an increase in the SOTE. Treatments on air showed similar, but much less dramatic effect of the gas flow rate to water flow rate ratio and water inlet velocity on KLa₂₀, SOTE, SAE, and SOTE, when compared to treatments on PSA oxygen. The best performance was achieved with an inlet water velocity of 6.9-7.6 ms­-¹ and oxygen flow rate to water flow rate ratio of about 2.5%. At this combination, the SOTE was about 66-72%.

The objective of this research was to characterize the performance of a downflow bubblecontact (DBCA) hypolimnetic aerator — Speece Cone-. The effect of two key design factors, inlet water velocity and the ratio of gas flow rate to water flow rate on four standard units of measure was examined: (a) the Oxygen Transfer Coefficient, KLa, corrected to 20°C, KLa₂₀ (hr­-¹), (b) the Standard Oxygen Transfer Rate, SOTR (g0₂.hr­-¹) (c) the Standard Aeration Efficiency, SAE (gO₂kWhr­-¹), and (d) the Standard Oxygen Transfer Efficiency, SOTE (%). Two sources of oxygen, Pressure Swing Adsorption (PSA) oxygen (87% purity) and air, were compared. KLa₂₀, SOTR, and SAE increased with an increase in the ratio of gas flow rate to water flow rate for both air and oxygen, over a range of 0.5% to 5.0%; while SAE deceased. An increase in inlet water velocity resulted in a decrease in KLa, corrected to 20°C, SOTR, and SAE, but an increase in the SOTE. Treatments on air showed similar, but much less dramatic effect of the gas flow rate to water flow rate ratio and water inlet velocity on KLa₂₀, SOTE, SAE, and SOTE, when compared to treatments on PSA oxygen. The best performance was achieved with an inlet water velocity of 6.9-7.6 ms­-¹ and oxygen flow rate to water flow rate ratio of about 2.5%. At this combination, the SOTE was about 66-72%. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Este trabalho de pesquisa foi realizado na busca de melhor entendimento do comportamento estrutural de pavimentos de concreto no que tange a transferência de carga em juntas, de quais os fatores que influenciam essa transferência de esforços nas juntas e a determinação, em caráter preliminar, de como as condições climáticas vigentes na área tropical dos estudos afeta o fenômeno. Para a realização dos experimentos foi empregada a pista experimental USP/FAPESP, construída em 1999, e até então não empregada para a determinação dos efeitos de transferência de cargas em juntas com e sem barra de transferência de carga. Paralelamente, para retroanalisar os parâmetros de transferência de carga, foram necessárias a avaliação e a análise estrutural de respostas a carregamentos dinâmicos das placas de concreto da pista experimental, possibilitando a determinação de diversos parâmetros em jogo, em especial, do módulo de elasticidade de concretos e do módulo de reação do subleito. Os estudos permitiram determinar que a ausência de barras de transferência de cargas em juntas transversais torna menos eficiente tal transferência além de apresentar nesse caso forte dependência da temperatura do concreto. Em juntas com barras de transferência de carga, para qualquer época do ano, a transferência de cargas é sempre igual ou superior a 90%, aproximadamente, independentemente da geometria das placas. Não existindo tais dispositivos o valor da transferência de cargas variou de 60 a 75%. Não foram observadas dependências importantes quanto a diferentes níveis de carregamento durante os testes, bem como para espessuras de placas de concreto, em placas com barras de transferência. Observou-se, também, embora em escala inferior ao que se narra na literatura passada, que o módulo de reação do subleito para carga de borda é maior que aquele para carga de centro. As faixas de valores de módulos de elasticidade para concretos de placas e para concretos compactados com rolo em sub-bases coincidiram com as faixas de valores encontrados em laboratório com medidas efetuadas na época da construção dos pavimentos. O processo de retroanálise com o programa ISLAB2000 mostrou-se um recurso valioso para a parametrização dos pavimentos de concreto estudados. / This research was proposed aiming an in deep study of the mechanism of load transfer across concrete pavement joints including the analysis of which factors influence such load transfers with special regards to the climate factors as concrete temperature. The concrete pavements under study were built in 1999 as a research supported by FAPESP, whose experimental sections has not been used before for such a goal. Backcalculation techniques were employed to analyze deflection data collected with FWD tests over the slabs and it was possible to define values for the test sections materials parameters like concrete modulus of elasticity and the modulus of subgrade reaction. Tests detected loss of load transfer efficiency on the dependence of concrete temperature for non dowelled joints. For dowelled joints, whatever the season of the year or period of the day, joint load transfer efficiency was at least 90% approximately. However, without dowels, efficiency ranged from 60 to 75%. No expressive dependence on the load level was observed during tests, as well as on the slab thicknesses, for cases of dowelled joints. It was observed the increase in the value of the modulus of subgrade reaction when loads were applied in joint position, although not so expressive as sometimes described in the literature. Ranges for concrete and rolled compacted concrete modulus of elasticity resulted similar to former values got from the construction period in laboratory. Therefore, backcalculation procedures using ISLAB2000 software is understood as a valuable tool for concrete slab characterization.

Simulation, optimization, and implementation of a capacitor-loaded wireless power transfer structure at 6.78 MHz for a target transfer distance of one meter are presented. First, an investigation into the operating principles behind a capacitor-loaded coupled loop structure is carried out via simulation. By adjusting the structural design parameters, it is found that an optimal configuration for this structure is coplanar. A prototype constructed using thin 18 AWG wire for the loops and a variable capacitor for tuning is used to verify simulation. To reduce losses in the wire, thick 9 AWG wire is implemented and measured. Thick wire is necessary for high efficiency yet undesirable for planarization. Since current flows only on the surface of the wire, ‘unwrapping’ that portion yields copper strips that reduce loss by increasing only the width. Thus, by replacing thick wires with copper strips, a planarized structure can be obtained that can reduce ohmic losses without sacrificing its form factor. Next, additional advantages of a capacitor-loaded system, which include reduced electric near-field and the possibility of resonant frequency tuning, are investigated. It is shown by simulation that the capacitor-loaded structure is not strongly affected by nearby dielectric materials since the stored electric energy is significantly lower than the stored magnetic energy in air at resonance. Finally, further optimizations of the structure are considered along with the analytical expressions for maximum efficiency. / text

Este trabalho de pesquisa foi realizado na busca de melhor entendimento do comportamento estrutural de pavimentos de concreto no que tange a transferência de carga em juntas, de quais os fatores que influenciam essa transferência de esforços nas juntas e a determinação, em caráter preliminar, de como as condições climáticas vigentes na área tropical dos estudos afeta o fenômeno. Para a realização dos experimentos foi empregada a pista experimental USP/FAPESP, construída em 1999, e até então não empregada para a determinação dos efeitos de transferência de cargas em juntas com e sem barra de transferência de carga. Paralelamente, para retroanalisar os parâmetros de transferência de carga, foram necessárias a avaliação e a análise estrutural de respostas a carregamentos dinâmicos das placas de concreto da pista experimental, possibilitando a determinação de diversos parâmetros em jogo, em especial, do módulo de elasticidade de concretos e do módulo de reação do subleito. Os estudos permitiram determinar que a ausência de barras de transferência de cargas em juntas transversais torna menos eficiente tal transferência além de apresentar nesse caso forte dependência da temperatura do concreto. Em juntas com barras de transferência de carga, para qualquer época do ano, a transferência de cargas é sempre igual ou superior a 90%, aproximadamente, independentemente da geometria das placas. Não existindo tais dispositivos o valor da transferência de cargas variou de 60 a 75%. Não foram observadas dependências importantes quanto a diferentes níveis de carregamento durante os testes, bem como para espessuras de placas de concreto, em placas com barras de transferência. Observou-se, também, embora em escala inferior ao que se narra na literatura passada, que o módulo de reação do subleito para carga de borda é maior que aquele para carga de centro. As faixas de valores de módulos de elasticidade para concretos de placas e para concretos compactados com rolo em sub-bases coincidiram com as faixas de valores encontrados em laboratório com medidas efetuadas na época da construção dos pavimentos. O processo de retroanálise com o programa ISLAB2000 mostrou-se um recurso valioso para a parametrização dos pavimentos de concreto estudados. / This research was proposed aiming an in deep study of the mechanism of load transfer across concrete pavement joints including the analysis of which factors influence such load transfers with special regards to the climate factors as concrete temperature. The concrete pavements under study were built in 1999 as a research supported by FAPESP, whose experimental sections has not been used before for such a goal. Backcalculation techniques were employed to analyze deflection data collected with FWD tests over the slabs and it was possible to define values for the test sections materials parameters like concrete modulus of elasticity and the modulus of subgrade reaction. Tests detected loss of load transfer efficiency on the dependence of concrete temperature for non dowelled joints. For dowelled joints, whatever the season of the year or period of the day, joint load transfer efficiency was at least 90% approximately. However, without dowels, efficiency ranged from 60 to 75%. No expressive dependence on the load level was observed during tests, as well as on the slab thicknesses, for cases of dowelled joints. It was observed the increase in the value of the modulus of subgrade reaction when loads were applied in joint position, although not so expressive as sometimes described in the literature. Ranges for concrete and rolled compacted concrete modulus of elasticity resulted similar to former values got from the construction period in laboratory. Therefore, backcalculation procedures using ISLAB2000 software is understood as a valuable tool for concrete slab characterization.

Currently the trend of electronic product development is to ward ¡§light and thin, multi-functional, high density and durability¡¨. When the microelectronic chips tend to be high power, high density and high speed, the rapid increase of heat in a reduced unit area of package size, will lead to failure of electronic products. The contents of thesis is to find out the dominant factors in heat transfer by changing the geometries and material properties of QFN and BGA packages. It also aims to achieve the beat the thermal performance by reducing the probability of failure. In industries it needs a lot of cost and time in experiment work due to the changes of size and materials. Herein, the softwares of ANSYS and ICEPAK are adopted to model the QFN and BGA packages with the statistical experimental design of Taguchi method L18 (21¡Ñ37) orthogonal array setting parameters and obtain the degree of effect for each factor. Eventually, we use the analysis of variance ANOVA to obtain the contribution of each factor and to identify the significant degree for various parameters by variance error integration. From the results the die attach thermal conductivity affects the contribution of thermal performance up to 81.46% for QFN package in comparison with other controlling factors of high significance and high impact effects. Die attach thermal conductivity between 0.5 W/m•k and 1.5 W/m•k the Tj declines much larger than that between 1.5 W/m•k and 8 W/m•k. Die /PKG area ratio affects the contribution of the thermal performance to 64.24% and increasing Die /PKG area ratio can reduce the Tj for BGA package. The significant effect is also higher than other factors. However, the contribution of substrate layers is 18.83% at 99% confidence level.

Non-radiative wireless power transfer using the coupled mode resonance phenomenon has been widely reported in the literature. However, the distance over which such phenomenon exists is very short when measured in terms of wavelength. In this dissertation, how efficient wireless power transfer can be realized in the radiating near-field region beyond the coupled mode resonance region is investigated. First, electrically small folded cylindrical helix (FCH) dipole antennas are designed to achieve efficient near-field power transfer. Measurements show that a 40% power transfer efficiency (PTE) can be realized at the distance of 0.25λ between two antennas in the co-linear configuration. These values come very close to the theoretical upper bound derived based on the spherical mode theory. The results also highlight the importance of antenna radiation efficiency and impedance matching in achieving efficient wireless power transfer. Second, antenna diversity is explored to further extend the range or efficiency of the power transfer. For transmitter diversity, it is found that a stable PTE region can be created when multiple transmitters are employed at sufficiently close spacing. For receiver diversity, it is found that the overall PTE can be improved as the number of the receivers is increased. Third, small directive antennas are investigated as a means of enhancing near-field wireless power transfer. Small directive antennas based on the FCH design are also implemented to enhance the PTE. It is shown that the far-field realized gain is a good surrogate for designing small directive antennas for near-field power transfer. Fourth, to examine the effects of surrounding environments on near-field coupling, an upper bound for near-field wireless power transfer is derived when a transmitter and a received are separated by a spherical material shell. The derived PTE bounds are verified using full-wave electromagnetic simulation and show good agreement for both TM mode and TE mode radiators. Using the derived theory, lossy dielectric material effects on wireless power transfer are studied. Power transfer measurements through walls are also reported and compared with the theory. Lastly, electrically small circularly polarized antennas are investigated as a means of alleviating orientation dependence in near-field wireless power transfer. An electrically small turnstile dipole antenna is designed by utilizing top loading and multiple folding. The circularly polarization characteristic of the design is first tested in the far field, before the antennas are placed in the radiating near-field region for wireless power transfer. It is shown that such circularly polarized antennas can lessen orientation dependence in near-field coupling. / text

This thesis investigates near-field wireless power transfer using multiple transmitters or multiple receivers. First, transmitter diversity is investigated in terms of the power transfer efficiency (PTE). It is found that an improvement in the PTE can be achieved by increasing the number of transmitters. Furthermore, a region of constant PTE can be created with the proper arrangement of transmitters. Next, receiver diversity is investigated in detail. An improvement in the PTE can be also achieved by increasing the number of receivers. However, it is shown that when two or more receivers are closely located, the PTE is reduced due to mutual coupling between receivers. This is termed a ‘sink’ phenomenon, and it is investigated through measurement and simulation. Finally, to account for more general situations of multiple transmitters and multiple receivers, Monte-Carlo simulation is applied. The cumulative distribution function (CDF) is used to interpret the results of the Monte-Carlo simulation. The transmitter and receiver diversity gain can be found based on the CDF. Moreover, the sink phenomenon can be observed by analyzing the CDF curve. Several strategies for positioning receivers are introduced to reduce the sink phenomenon. The results of the Monte-Carlo simulation also show that a saturation in the transmitter or receiver gain is reached when the number of transmitters or receivers is increased. Therefore, increasing the number of transmitters or receivers beyond a certain number does not help increase the PTE. / text