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During an earthquake, unanchored equipment within a nuclear power plant facility can slide and interact with safety-critical systems and components. Previous studies on sliding have largely focused on the response due to unidirectional excitation, as computing the response of unanchored components in three dimensions can be complex and computationally expensive. As such, several prediction equations and a standardized approximate method as outlined in ASCE 4-16 have been developed to estimate the peak sliding displacement. This study investigates the effect of bidirectional horizontal interaction and the influence of vertical excitation on the sliding response of an unanchored object when the x, y, and z, components of earthquake excitation are applied simultaneously. The study also evaluates the approximate method detailed in ASCE 4-16. A suite of 40 floor acceleration histories obtained from response history analysis of a representative nuclear power plant facility are used as input for the sliding model. A wide range of friction coefficients is selected for analysis and the nonlinear sliding response of components is determined through the use of a Bouc-Wen type hysteretic model. Computed responses under uni-, bi- and tri-directional excitation reveal that the effect of bidirectional interaction and vertical excitation is greatest for sites with high shaking intensity. It is also concluded that the ASCE 4-16 approximate method is significantly overconservative in all cases. Additionally, the study expands the concept of multi-component excitation to intensity measures. Twelve intensity measures are selected and evaluated. It is found that most efficient intensity measures vary in efficiency depending on the coefficient of friction, and that the top intensity measures are not significantly affected by incorporating multiple components of excitation. / Thesis / Master of Applied Science (MASc) / Earthquakes can pose a huge risk to nuclear facilities. Unanchored objects within the facility may collide and interact with safety-critical equipment. Previous research on sliding behaviour lacks information on the response of an object subjected to earthquake excitation in both the horizontal plane and vertical direction simultaneously. Several prediction equations and an approximate method have been developed to estimate the sliding response as it becomes computationally expensive to solve. This research investigates the influence of simulatenous multi-component excitation on the sliding behaviour and evaluates the current standardized approximate method of estimating sliding displacement. Recommendations are given based on the friction coefficient between the object and the base. The research also explores which characteristics of earthquake ground motion (e.g. acceleration, velocity, energy) are most indicative of sliding behaviour.

Gold-black has emerged as a popular absorptive coating for thermal radiation detectors in aerospace applications. The performance and accuracy of thermal radiation detectors largely depends on the surface optical properties of the absorptive coating. If the absorptivity of the layer is directional or wavelength dependent, then so will be the detector gain itself. This motivates our interest in the manufacture, physical characterization, and study of the wavelength and polarization sensitivity of the directional spectral absorptivity of gold-black. A first-principle model based on lossy antenna theory is presented to predict the polarization dependent directional spectral absorptivity of gold-black in the visible and near infrared. Results for normal spectral absorptivity are in good agreement with measurements reported in the literature. However, suitable experimental data were not available to validate the theory for directional spectral absorptivity. Therefore, an experimental campaign to fabricate and measure the directional spectral behavior of gold-black had to be undertaken to validate the first-principle model. New in-plane bidirectional reflectance distribution function (BRDF) measurements for two thicknesses (~4 μm and ~8 μm) of gold-black laid down on a gold mirror substrate are reported in the visible (532 nm) and near-infrared (800 and 850 nm) for p- and s-polarizations. The investigation is then extended to a three-layer sample, which is shown to exhibit off-specular reflectivity. Described are processes for laying down gold-black coatings and for measuring their in-plane BRDF as a function of thickness, wavelength, and polarization state. A novel method for retrieving the directional absorptivity from in-plane BRDF measurements is presented. The influence of polarization on directional absorptivity is shown to follow our earlier theory except at large incident zenith angles, where an unanticipated mirage effect is observed. / Doctor of Philosophy / Instruments called thermal radiation detectors play an important role in monitoring the global climate from space. Gold-black is often used as an absorptive coating to enhance the performance of these instruments. Users need to know how gold-black coatings influence instrument performance. In general, coating properties depend on the wavelength and direction of incident radiation, as well as on an optical phenomenon called polarization. This dissertation investigates the relationship between the creation of gold-black coatings and their performance. A physical model is postulated for predicting the optical behavior of gold-black in the visible and near infrared. The model produces results that are in good agreement with measurements reported in the literature. However, suitable directional measurements were not available to validate the theory. Therefore, an experimental campaign was mounted to fabricate gold-black coatings and measure their optical behavior in order to validate the mathematical model. We observed the optical behavior of several of our gold-black samples of various thickness and over a range of wavelengths. We also studied a three-layer sample which was found to exhibit an unexpected behavior called off-specular reflectivity. Described are processes for creating gold-black coatings and for measuring and explaining their optical performance. During the course of this investigation an unanticipated mirage effect was observed for the first time.

No / Horizontal-axis tidal turbines (HATTs) have the acknowledged potential to extract a large amount of green renewable energy from ocean tides. Among these, bidirectional HATTs (BHATTs) with centrosymmetric hydrofoils have advantages in terms of reliability and maintenance cost. To improve the performance of BHATTs, this paper investigates the influence of different passive flow control devices (PFCDs), such as wing fences, winglets, and squealers, on the performance of the BHATT. To the end, a three-dimensional (3D) numerical model with a k-ω SST model and a sliding mesh method was applied to simulate a 18 m diameter BHATT. The numerical framework was validated using two experiments. The mesh convergence was tested. The results show that the wing fences can effectively suppress the spanwise flow above the suction surface of blades, although they cannot improve the BHATT performance. To inhibit the wingtip vortices and enhance the torque of the rotor, a series of centrosymmetric winglets are designed and optimized. The optimal BHATT can produce up to 2.3% more energy at design tip speed ratio (TSR).

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Recently, due to the increasing adoption of distributed energy resource (DER) technologies including battery energy storage (BES) and electric vehicle (EV) systems, bidirectional power converters are becoming more popular. These converters are broadly utilized as interface devices and provide a bidirectional power flow in applications where the primary power supply can both supply and receive energy. A dc capacitor, called the dc-link, is an important component of such bidirectional converters. For a wide range of applications, the converter is required to control the dc-link voltage. Commonly, a proportional-integrating (PI) controller is used by the dc capacitor voltage controller to generate a set-point for the inner current controller. This approach tightly regulates the dc-link voltage to a given value. The research presented in this dissertation shows that such an approach compromises the stability margins of the converter for reverse power flow and weak grid conditions. It is shown that by allowing a small variation of dc capacitor voltage in proportion to the amount of power flowing through the converter, the stability and robustness margins are improved. This approach also simplifies the design process and can be applied to both dc/dc and dc/ac (single-phase and three-phase) converters. Moreover, it grants an inherent power sharing capability when multiple converters share the same dc-link terminals; removing the need to a communication link between parallel converters. The proposed controller is equipped with a current limiting mechanism to protect the converter during low-voltage/over-current transients. Detailed analyses, simulations, comparisons, and experimental results are included to illustrate the effectiveness of the proposed control approach. To mathematically establish the properties of the proposed method in a single-phase dc/ac application, this dissertation also derives a new and systematic modeling approach for a grid-connected bidirectional single-phase inverter controlled in stationary frame. Implementing the control system in the stationary frame has advantages over rotating frame. However, the combination of dc and ac state variables and nonlinearities make its stability analysis challenging. In the proposed model, an imaginary subsystem is properly generated and augmented to allow a full transformation to a synchronous rotating frame. The proposed modeling strategy is modular and has a closed form which facilitates further extensions. It is successfully used to demonstrate enhanced stability margins of the proposed controller.

The blood flow through the Bidirectional Glenn shunt (BGS) and modified Blalock-Taussig shunt (mBTS) to the pulmonary arteries (PAs) was analyzed using Computational Fluid Dynamics. This study consisted of the steady and pulsatile cases. In case one, the results of blood flow through the BGS for the Newtonian and non-Newtonian viscosity models were compared. Case two focused on having an additional pulsatile blood flow through the mBTS using the non-Newtonian Carreau viscosity model. The geometries were created based on the angiograms. In case one, boundary conditions to be specified at the inlets were obtained from the flow rate measurements via Doppler flow studies in children and young adults. The averaged velocities were obtained from these flow rates and specified as parabolic velocity profiles at the inlets. The average PA pressures were obtained from the catheterization data and specified at the branches of the PA outlets. In case two, boundary conditions at the same inlets were constant during the cardiac cycle. The pulsatile PA and aortic pressure tracings obtained from the catheterization data were specified at the outlets and mBTS inlet, respectively. A comparison is made between the first and second case results.

Este trabalho visa o estudo das regiões de operação de conversores CC/CC isolados bidirecionais do tipo DAB (Dual Active Bridge). É feito um estudo do comportamento do circuito com a variação dos valores das reatâncias de acoplamento, avaliando-se aspectos como eficiência, fator de potência, reativos, entre outros. A seguir é proposta uma estrutura de controle que permite a operação com tensões nos barramentos DC diferentes das nominais, minimizando as correntes absorvidas. Além disso, propõe-se uma estratégia de controle para regular a potência transferida. O trabalho inclui modelagem teórica, implementação em simulação computacional e medidas em protótipo experimental. / This work investigates operation regions of Dual Active Bridge DC-DC isolated bidirectional converters, studying circuit behavior with the variation of the coupling reactance, evaluating parameters like efficiency, power factor, reactive flow etc. A control structure is proposed which allows operating with DC voltages different from nominal voltages, reducing the AC currents. Furthermore, a control strategy to regulate the power transferred is proposed. Methodology includes theoretical modeling, computer simulation and experimental prototype measurements.

O projeto consiste em uma pesquisa sobre a comunicação digital, especialmente sobre os blogs , como ferramenta de relacionamento direta entre a organização e seus públicos. Neste contexto, as relações públicas (dentro do contexto da comunicação organizacional) são fundamentais para identificar que públicos têm condições de se relacionar por meio da Web e qual é o melhor conteúdo, layout, ferramenta e funcionalidades que o meio digital deve apresentar para atingir com efetividade o target visado. Além disso, acredita-se que a comunicação simétrica de mão dupla ganha força com a comunicação digital, o que contribui para o fortalecimento dos relacionamentos criados pela comunicação organizacional e pelas relações públicas digitais. / This project consists of research about digital communication, especially weblogs, as a relationship tool between the companies and their publics. In this context, the public relations are fundamental to identify which publics have conditions to interact via web and what are the best content, layout, tool and functionality that digital vehicles should present to target the audiences effectively. Besides that, the simetric and bidirectional communication gets stronger with digital communications, which contributes to a better relationship created by digital public relations.

Este trabalho visa o estudo das regiões de operação de conversores CC/CC isolados bidirecionais do tipo DAB (Dual Active Bridge). É feito um estudo do comportamento do circuito com a variação dos valores das reatâncias de acoplamento, avaliando-se aspectos como eficiência, fator de potência, reativos, entre outros. A seguir é proposta uma estrutura de controle que permite a operação com tensões nos barramentos DC diferentes das nominais, minimizando as correntes absorvidas. Além disso, propõe-se uma estratégia de controle para regular a potência transferida. O trabalho inclui modelagem teórica, implementação em simulação computacional e medidas em protótipo experimental. / This work investigates operation regions of Dual Active Bridge DC-DC isolated bidirectional converters, studying circuit behavior with the variation of the coupling reactance, evaluating parameters like efficiency, power factor, reactive flow etc. A control structure is proposed which allows operating with DC voltages different from nominal voltages, reducing the AC currents. Furthermore, a control strategy to regulate the power transferred is proposed. Methodology includes theoretical modeling, computer simulation and experimental prototype measurements.