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No description available.

No description available.

No description available.

Prediction of the sound field in large urban environments has been limited thus far by the heavy computational requirements of conventional numerical methods such as boundary element (BE), finite-difference time-domain (FDTD), or ray-tracing methods. Recently, a considerable amount of work has been devoted to developing energy-based methods for this application, and results have shown the potential to compete with conventional methods. However, these developments have been limited to two-dimensional (2-D) studies (along street axes), and no real description of the phenomena at issue has been exposed (e.g., diffraction effects on the predictions). The main objectives of the present work were (i) to evaluate the feasibility of an energy-based method, the diffusion model (DM), for sound-field predictions in large, 3-D complex urban environments, (ii) to propose a numerical hybrid method that could improve the accuracy and computational time of these predictions, and (iii) to verify the proposed hybrid method against conventional numerical methods. The proposed numerical hybrid method consists of a full-wave model coupled with an energy-based model. The full-wave model is used for predicting sound propagation (i) near the source, where constructive and destructive interactions between waves are substantial, and (ii) outside the cluttered environment, where free-field-like conditions apply. The energy-based model is used in regions where diffusion conditions are met. The hybrid approach, as implemented in this work, is a combination of FDTD and DM models. Results from this work show the role played by diffraction near buildings edges close to the source and near the exterior boundaries of the computational domain, and its impact on the predictions. A wrong modeling of the diffraction effects in the environment leads to significant under or overpredictions of the sound levels in some regions, as compared to conventional numerical methods (in these regions, some differences are as high as 10 dB). The implementation of the hybrid method, verified against a full FDTD model, shows a significant improvement of the predictions. The mean error thus obtained inside the cluttered region of the environment is 1.5 dB. / Master of Science

Enzyme-catalyzed biofuel cells would be a great alternative to current battery technology, as they are clean, safe, and capable of using diverse and abundant renewable biomass with high energy densities, at mild reaction conditions. However, currently, three largest technical challenges for emerging enzymatic fuel cell technologies are incomplete oxidation of most fuels, limited power output, and short lifetime of the cell. Synthetic pathway biotransformation is a technology of assembling a number of enzymes coenzymes for producing low-value biocommodities. In this work, it was applied to generate bioelectricity for the first time. Non-natural enzymatic pathways were developed to utilize maltodextrin and glucose in enzymatic fuel cells. Three immobilization approaches were compared for preparing enzyme electrodes. Thermostable enzymes from thermophiles were cloned and expressed for improving the lifetime and stability of the cell. To further increase the power output, non-immobilized enzyme system was demonstrated to have higher power densities compared to those using immobilized enzyme system, due to better mass transfer and retained native enzyme activities. With the progress on pathway development and power density/stability improvement in enzymatic fuel cells, a high energy density sugar-powered enzymatic fuel cell was demonstrated. The enzymatic pathway consisting of 13 thermostable enzymes enabled the complete oxidation of glucose units in maltodextrin to generate 24 electrons, suggesting a high energy density of such enzymatic fuel cell (300 Wh/kg), which was several folds higher than that of a lithium-ion battery. Maximum power density was 0.74 mW/cm2 at 50 deg C and 20 mM fuel concentration, which was sufficient to power a digital clock or a LED light. These results suggest that enzymatic fuel cells via synthetic pathway biotransformation could achieve high energy density, high power density and increased lifetime. Future efforts should be focused on further increasing power density and enzyme stability in order to make enzymatic fuel cells commercially applicable. / Ph. D.

Recent concepts for controlled magneto-inertial fusion (MIF), such as magnetized liner inertial fusion (MagLIF), have suffered from magnetohydrodynamic (MHD) instabilities that lead to degradations in fusion yield. High levels of azimuthally-correlated MHD instability structures have been observed on cylindrical liner experiments without a pre-imposed axial magnetic field (Bz=0) elsewhere in the literature and are believed to be seeded from surface machining roughness. This dissertation uses highly resolved (0.5 μm and less resolution) 1D and 2D resistive magnetohydrodynamics (MHD) arbitrary-Lagrangian-Eulerian (ALE) simulations of electrical wire explosions (EWEs) and liner implosions to show that micrometer-scale surface roughness seeds the electrothermal instability (ETI), which induces early melting in pockets across the conductor and leads to millimeter-scale instability growth. The relationship between the ETI and the MRTI in liner implosions is also described in this dissertation, which shows that the traditional growth rates associated with these modes are coupled together and are not linearly independent. This dissertation also describes the preliminary implementation of a Koopman neural network architecture for learning the nonlinear dynamics of a high energy density (HED) exploding or imploding electrical conductor. / Doctor of Philosophy / Researchers have been working on controlling nuclear fusion and harnessing it as a power source since the discovery that nuclear fusion powers stars. In many of these controlled nuclear fusion concepts the aim is to heat the fuel until it forms a high-temperature plasma state of matter and then compress it to the point that the atoms are close enough and at high enough speeds that they collide fuse together. In the magnetized liner inertial fusion (MagLIF) concept these temperatures, densities, and pressures are achieved by surrounding the fusion fuel with a cylindrical piece of metal called a liner and using magnetic fields to implode the liner inward. Experiments have shown, however, that these liner implosions do not occur smoothly and that the system becomes unstable and can mix liner material into the fuel, which disrupts the fusion process. This dissertation investigates the stability of liner implosions and electrical wire explosions. In particular, this dissertation shows that surface roughness imparted on the surface of a solid fusion target by a machining process can grow into a millimeter-scale perturbation. It also describes the relationship between two common types of instabilities found in current-driven nuclear fusion: the magneto-Rayleigh-Taylor instability and the electrothermal instability. Finally, it looks at using neural networks to better understand the dynamics of electrical wire explosions.

Although two-dimensional conjugated metal–organic frameworks (2D c-MOFs) provide an ideal platform for precise tailoring of capacitive electrode materials, high-capacitance 2D c-MOFs for non-aqueous supercapacitors remain to be further explored. Herein, we report a novel phthalocyanine-based nickel-bis(dithiolene) (NiS4)-linked 2D c-MOF (denoted as Ni2[CuPcS8]) with outstanding pseudocapacitive properties in 1 M TEABF4/acetonitrile. Each NiS4 linkage is disclosed to reversibly accommodate two electrons, conferring the Ni2[CuPcS8] electrode a two-step Faradic reaction with a record-high specific capacitance among the reported 2D c-MOFs in non-aqueous electrolytes (312 F g–1) and remarkable cycling stability (93.5% after 10,000 cycles). Multiple analyses unveil that the unique electron-storage capability of Ni2[CuPcS8] originates from its localized lowest unoccupied molecular orbital (LUMO) over the nickel-bis(dithiolene) linkage, which allows the efficient delocalization of the injected electrons throughout the conjugated linkage units without inducing apparent bonding stress. The Ni2[CuPcS8] anode is used to demonstrate an asymmetric supercapacitor device that delivers a high operating voltage of 2.3 V, a maximum energy density of 57.4 Wh kg–1, and ultralong stability over 5000 cycles.

Several measurements may be used as error signals to determine how to appropriately control a sound field. These include pressure, particle velocity, energy density and intensity. In this thesis, numerical models are used to show which signals perform best in is free-field active noise control (ANC) using error sensors located in the near field of the sound sources. The second is equalization in a free field and a semi-free field. Minimized energy density total power output (MEDToPO) plots are developed; these indicate the maximum achievable attenuation for a chosen error sensor as a function of location. A global listening area equalization coefficient (GLAEC) is found to evaluate the performance of the equalization methods. It is calculated by finding the average of the spectral standard deviation of several frequency response measurements in a specified listening area. For free-field ANC employing error sensors located in the near field, pressure-based measurements perform the best. For free-field equalization over an extended listening region, total energy density performs best. Equalization of an extended listening region is more successful over a limited low-frequency bandwidth.

O objetivo deste trabalho foi estudar o perfil oxidativo de concentrados para bovinos adicionados de óleo de soja, refinado e degomado, em um período de armazenamento de 15 dias, sob as temperaturas de 25ºC e 40ºC. Foram formados cinco grupos de alimentos: controle (C) sem adição de óleo, tratamentos (T) 1, 2, 3 e 4 com adição de 2, 4, 6 e 8%, respectivamente, de óleo de soja refinado ou degomado. Para tal, foram avaliados os índices de peróxidos e de acidez. Com relação à influência da temperatura de estocagem, ao longo do período experimental à 25ºC, não houve alteração com relação aos valores de índice de peróxido quando se adicionou óleo de soja refinado aos concentrados, contudo, à 40ºC, houve aumento observando-se um valor máximo em torno de 0,9 mEq/kg de concentrado. O índice de acidez do óleo refinado extraído dos concentrados armazenados à 25ºC não foi alterado ao longo do período de armazenamento, e à 40ºC resultou em aumento de 19, 25, 44 e 44% para os respectivos T1, T2, T3 e T4 em relação ao controle. Quanto à influência do tipo de óleo processado na oxidação lipídica dos concentrados armazenados à 40ºC, a adição de óleo de soja refinado não alterou os índices de peróxidos dos concentrados ao longo dos 15 dias de experimento, e para o degomado observou-se um aumento no 3º dia de armazenamento em 57%, 44%, 123% e 93% para os respectivos T1, T2, T3 e T4, em relação ao controle. Também, o efeito da adição de óleo de soja degomado resultou em aumento do índice de acidez de 21%, 36%, 43% e 57% a partir do 5º dia de experimento, em relação ao 1º dia. Conclui-se que durante os 15 dias de armazenamento, houve diferença no perfil oxidativo dos concentrados adicionados de óleo de soja quando se comparou as temperaturas de 25ºC e 40ºC, mas se manteve inalterado quando se avaliou os tipos de óleo refinado e degomado em diferentes porcentagens. Assim, a adição de óleo de soja refinado ou degomado não altera o perfil oxidativo do concentrado para bovino sob as condições deste estudo. / The objective of this work was to study the oxidative profile of concentrates for cattle added soybean oil, refined and degummed in a storage period of 15 days, at temperatures of 25ºC and 40ºC. Were formed five food groups: control (C) without addition of oil, treatments (T) 1, 2, 3 and 4 with the addition of 2, 4, 6 and 8%, respectively, of refined or degummed soybean oil. For this purpose ware available index of peroxide and of acidic. Regarding the influence of storage temperature, the addition of refined soybean oil did not alter the values of the peroxide during the trial period at 25ºC, however, at 40ºC of storage of food alter this parameter and was shown a maximum value about 0.9 mEq/kg of concentrate. The acidity of refined oil extracted from concentrates stored at 25ºC was not changed during the storage period, and 40ºC resulted in an increase of 19, 25, 44 and 44% for the respective T1, T2, T3 and T4 compared the control. Regarding the influence of oil processed in lipid oxidation of concentrates stored at 40ºC, the addition of refined soybean oil did not alter the levels of peroxide concentrates over the 15 days of experiment, and the degummed observed an increase in 3rd day of storage in 57%, 44%, 123% and 93% for the respective T1, T2, T3 and T4, compared to control. Also, the effect of addition of crude soybean oil resulted in increased acid value of 21%, 36%, 43% and 57% from the 5th day of experiment, as compared to day 1. Thus, the addition of refined soybean oil or degummed not change profile for bovine oxidative concentrated under the conditions of this study.