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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Impacts of tidal currents on the assessment of the wave energy resource of the west coast of Canada

Beya, Ignacio 27 August 2020 (has links)
Numerous studies have identified the west coast of Canada as an attractive place for the development of wave energy projects. To evaluate the viability of these projects, an accurate description of the wave resource is crucial. Most of the previous efforts to characterize the wave climate in B.C. at shallower waters, where wave energy converters (WECs) are most likely to be deployed, lack the necessary nearshore spatial resolution, and were driven by overly simplistic wave boundary conditions. In addition, none of the previous studies have included the effect of tidal currents, which have been proven to be significant in wave resource characterizations in other locations. This work increased the fidelity of the wave resource characterization and developed an understanding of the impact of tidal currents on the wave conditions in this region by generating two most accurate, long-term (14 years, 2004 to 2017), high resolution (in space and time) datasets of the wave resource for the west coast of Canada. The two datasets were generated using nearly identical SWAN wave models, which their only difference was that one of them (V5), did not incorporate the effect of currents, while the other (V6) included tidal currents as forcing. Thus, the pure influence of the tidal currents on the wave characteristics was able to be identified when comparing the two wave model results. This study developed simple, robust, and objective metrics to support the calibration process and to evaluate the performance of the models. Utilizing these metrics, the V5 and V6 models presented substantial improvements in reproducing the wave conditions of about 18% and 20%, respectively and in relation to the previous most complete and accurate wave model of the region (V4). Their better performance was largely achieved by a significant increment in their ability to reproduce the significant wave height (H_m0) and energy period (T_e). The inclusion of tidal currents in the wave model increased the accuracy of the wave resource characterization, mainly by improving the model’s ability in simulating T_e by 5.1%. The most sensitive wave parameter to the tidal currents was the peakedness of the wave spectrum (Q_p), which was consistently and significantly reduced by values even larger than 2.5. In some regions, directions characterized by the mean wave direction (D_m) and the directional spreading (D_spr) were also noticeably very sensitive to the currents, which even deflected D_m to its opposite direction and drove changes in D_spr that reached values of up to 40°. However, these significant transformations were less frequent and reduced in magnitude at exposed (to swell-waves) sites, where strong currents have affected waves in a reduced part of their trajectory. Typically, tidal currents had the effect of reducing the wave power density (P), but in a relatively small amount, however, during rare events, tidal currents were able to induce changes in this parameter ranging -140 kW/m to 75 kW/m. At these extreme events, it was observed that the peak of the wave spectra became flatter, with some of its wave height variance redistributed to near increasing and decreasing frequencies and directions, regardless to the magnitude and direction of the local tidal currents. Impacts of the tidal currents on P were largely attributed to the induced changes in H_m0 and T_e. Although D_spr and Q_p were greatly transformed by the action the tidal currents, they account very little in explaining the variations in P. These four wave parameters together, and how they are transformed under the presence of currents, can explain a large part of the changes in P, however, other transformations of the wave spectrum due to the currents, not investigated in this study, must account for a considerable part of the changes in P. / Graduate
2

Projeto de antenas e caracterização do substrato de nanofios (MnM) para aplicações em ondas milimétricas. / Antenna design and characterization of the nanowire substrate (MnM) for millimeter-waves applications.

Leonardo Amorese Gallo Gomes 15 December 2017 (has links)
O substrato de nanofios (MnM) é uma nova tecnologia de interposers visando aplicações em ondas-mm que vêm recebendo atenção devido à facilidade de se fabricar vias de interconexão e estruturas de onda lenta de alto desempenho com resultados no estado-da-arte. Entretanto, embora as estruturas de interconexão, como vias e linhas de transmissão, já estejam bem definidas, ainda não se verificou a viabilidade de se usar essa tecnologia como base para antenas planares, uma parte vital de qualquer aplicação de transmissão de dados sem fio. Esse trabalho visa preencher essa lacuna, apresentando métodos para se realizar a caracterização elétrica do substrato através da extração de sua constante dielétrica relativa e tangente de perdas, e para se projetar antenas de uso frequente em aplicações de ondas-mm através de softwares de simulação eletromagnética. Esse trabalho apresenta também as etapas de fabricação da tecnologia numa visão geral e aplicada às estruturas desenvolvidas, seguida da caracterização das estruturas até 110 GHz. Os resultados mostraram um substrato com constante dielétrica relativa de 7 ± 0,2 e com tangente de perdas de 0,03 ± 0,005. Simulações das antenas projetadas mostraram que o substrato MnM é um candidato viável para antenas do tipo end-fire, cuja irradiação acontece paralela ao plano do substrato, devido ao fato dos parâmetros do substrato não interferirem demasiadamente na eficiência de irradiação desse tipo de antena. Entretanto, as simulações também mostraram que esse substrato é um candidato ruim para antenas tipo back-fire, com irradiação perpendicular ao plano do substrato, devido às baixas figuras de eficiência de irradiação e ganho. / The nanowire substrate (MnM) is a novel interposer technology for mm-waves applications that has been receiving more and more attention thanks to the ease of fabricating high performance interconnection vias and slow-wave structures, whose results are in the state-of-the-art. However, even though the interconnection structures, such as transmission lines and vias, are already well-defined, no one has analyzed the potential of the MnM substrate as a planar antenna substrate, a core component of any wireless communications application. This work aims to fill this gap by presenting substrate characterization methods, that involves determining its dielectric constant and loss tangent, and by presenting planar antenna design methods using electromagnetic simulation softwares. This work presents also a general overview of the manufacturing processes being developed, followed by structure measurement up until 110 GHz. The results showed a substrate with a dielectric constant of 7 ± 0.2 and with a loss tangent of 0.03 ± 0.005. Simulations of the designed antennas indicated that this substrate is a viable choice for end-fire antennas, whose radiation is parallel to the plane of the substrate, because the substrate parameters doesn\'t seem to degrade the radiation efficiency of this kind of antenna. However, simulations also showed that the MnM substrate is a poor candidate for back-fire antennas, whose radiation is perpendicular to the plane of the substrate, given the low figures of radiation efficiency and gain.
3

Projeto de antenas e caracterização do substrato de nanofios (MnM) para aplicações em ondas milimétricas. / Antenna design and characterization of the nanowire substrate (MnM) for millimeter-waves applications.

Gomes, Leonardo Amorese Gallo 15 December 2017 (has links)
O substrato de nanofios (MnM) é uma nova tecnologia de interposers visando aplicações em ondas-mm que vêm recebendo atenção devido à facilidade de se fabricar vias de interconexão e estruturas de onda lenta de alto desempenho com resultados no estado-da-arte. Entretanto, embora as estruturas de interconexão, como vias e linhas de transmissão, já estejam bem definidas, ainda não se verificou a viabilidade de se usar essa tecnologia como base para antenas planares, uma parte vital de qualquer aplicação de transmissão de dados sem fio. Esse trabalho visa preencher essa lacuna, apresentando métodos para se realizar a caracterização elétrica do substrato através da extração de sua constante dielétrica relativa e tangente de perdas, e para se projetar antenas de uso frequente em aplicações de ondas-mm através de softwares de simulação eletromagnética. Esse trabalho apresenta também as etapas de fabricação da tecnologia numa visão geral e aplicada às estruturas desenvolvidas, seguida da caracterização das estruturas até 110 GHz. Os resultados mostraram um substrato com constante dielétrica relativa de 7 ± 0,2 e com tangente de perdas de 0,03 ± 0,005. Simulações das antenas projetadas mostraram que o substrato MnM é um candidato viável para antenas do tipo end-fire, cuja irradiação acontece paralela ao plano do substrato, devido ao fato dos parâmetros do substrato não interferirem demasiadamente na eficiência de irradiação desse tipo de antena. Entretanto, as simulações também mostraram que esse substrato é um candidato ruim para antenas tipo back-fire, com irradiação perpendicular ao plano do substrato, devido às baixas figuras de eficiência de irradiação e ganho. / The nanowire substrate (MnM) is a novel interposer technology for mm-waves applications that has been receiving more and more attention thanks to the ease of fabricating high performance interconnection vias and slow-wave structures, whose results are in the state-of-the-art. However, even though the interconnection structures, such as transmission lines and vias, are already well-defined, no one has analyzed the potential of the MnM substrate as a planar antenna substrate, a core component of any wireless communications application. This work aims to fill this gap by presenting substrate characterization methods, that involves determining its dielectric constant and loss tangent, and by presenting planar antenna design methods using electromagnetic simulation softwares. This work presents also a general overview of the manufacturing processes being developed, followed by structure measurement up until 110 GHz. The results showed a substrate with a dielectric constant of 7 ± 0.2 and with a loss tangent of 0.03 ± 0.005. Simulations of the designed antennas indicated that this substrate is a viable choice for end-fire antennas, whose radiation is parallel to the plane of the substrate, because the substrate parameters doesn\'t seem to degrade the radiation efficiency of this kind of antenna. However, simulations also showed that the MnM substrate is a poor candidate for back-fire antennas, whose radiation is perpendicular to the plane of the substrate, given the low figures of radiation efficiency and gain.

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