Release of gas fission products in nuclear fuels is a practically important phenomenon based on the bubble diffusivity in crystal lattice. The bubble diffusion coefficient can be expressed through the volume and surface self-diffusion coefficients Dvol and Dsurf.

When properly designed, hypolimnetic aeration and oxygenation systems can replenish dissolved oxygen in water bodies while preserving stratification. A comprehensive literature review of design methods for the three primary devices was completed. Using fundamental principles, a discrete-bubble model was first developed to predict plume dynamics and gas transfer for a circular bubble-plume diffuser. This approach has subsequently been validated in a large vertical tank and applied successfully at full-scale to an airlift aerator as well as to both circular and linear bubble-plume diffusers. The unified suite of models, all based on simple discrete-bubble dynamics, represents the current state-of-the-art for designing systems to add oxygen to stratified lakes and reservoirs. An existing linear bubble plume model was improved, and data collected from a full-scale diffuser installed in Spring Hollow Reservoir, Virginia (U.S.A.) were used to validate the model. The depth of maximum plume rise was simulated well for two of the three diffuser tests. Temperature predictions deviated from measured profiles near the maximum plume rise height, but predicted dissolved oxygen profiles compared very well to observations. Oxygen transfer within the hypolimnion was independent of all parameters except initial bubble radius. The results of this work suggest that plume dynamics and oxygen transfer can successfully be predicted for linear bubble plumes using the discrete-bubble approach. To model the complex interaction between a bubble plume used for hypolimnetic oxygenation and the ambient water body, a model for a linear bubble plume was coupled to two reservoir models, CE-QUAL-W2 (W2) and Si3D. In simulations with a rectangular basin, predicted oxygen addition was directly proportional to the update frequency of the plume model. W2 calculated less oxygen input to the basin than Si3D and significantly less mixing within the hypolimnion. The coupled models were then applied to a simplified test of a full-scale linear diffuser. Both the W2 and Si3D coupled models predicted bulk hypolimnetic DO concentrations well. Warming within the hypolimnion was overestimated by both models, but more so by W2. The lower vertical resolution of the reservoir grid in W2 caused the plume rise height to be over-predicted, enhancing erosion of the thermocline. / Ph. D.

Flotation is a complex, multiphase process used to separate minerals. Four problems central to the fundamentals of the flotation process were studied. A multiphase grid turbulence experiment was conducted to verify particle collision models. The slip velocities of solid particles and bubbles were measured using Digital Particle Image Velocimetry (DPIV). The experimental results were compared with the predictions from empirical and theoretical collision models. Time-resolved DPIV was used to measure the turbulent velocity field in a Rushton turbine around the impeller region. The turbulence quantities were found by removing the periodic component from the blade passing, which is a dominant part of the measured velocities near the impeller. We provide evidence that larger, biased dissipation and turbulent kinetic energy values are estimated in the vicinity of the impeller due to the periodic component of the blade passage. The flow was found to be anisotropic close to the impeller. Vortex detection revealed that the tip vortices travel in a nearly radial direction from the impeller for small Reynolds numbers and with a wider distribution for higher Reynolds numbers. The rise of a buoyant bubble and its interaction with a free liquid surface was experimentally investigated using Time-Resolved Digital Particle Image Velocimetry as a function of bubble size, and surfactant concentration of the fluid medium. It is shown that the presence of a surfactant significantly affected the characteristics of the velocity field during the rise and interaction with the free surface. This difference is attributed to the adsorption coverage of the surfactant at the bubble-fluid interface. Wake profiles were compared. The presence of large vortices were observed and found to play a significant role. Finally, Numerical and experimental results of stable and unstable foams are presented by comparing liquid fractions and bubble sizes. There was good agreement between the experiments and numerical modeling in free drainage and forced drainage experiments. In addition, foam coarsening was measured and characterized experimentally. Each of the problems investigated have added to the understanding in the underlying physics of the flotation process and can lead to more accurate modeling. The ultimate goal of this work is to contribute to the design of more effective and efficient flotation machines. / Ph. D.

Bubble plume oxygenation systems are commonly used to mitigate anoxia and its deleterious effects on water quality in thermally stratified lakes and reservoirs. Following installation, increases in sediment oxygen flux (JO2) are typically observed during oxygenation and are positively correlated with the bubble plume gas flow rate. Studies show that JO2 is controlled by the thickness of the diffusive boundary layer (DBL) at the sediment-water interface (SWI), which is in turn controlled by turbulence. As a result, JO2 can be quite spatially and temporally variable. Accurately predicting oxygenation-induced JO2 is vitally important for ensuring successful oxygenation system design and operation. Yet despite the current understanding of physical and chemical controls on JO2, methods for predicting oxygenation-induced JO2 are still based on empirical correlations and factors of safety. As hypolimnetic oxygenation becomes more widely used as a lake management tool for improving and maintaining water quality, there is a need to move from the current empirically based approach to a mechanistic approach and improve the ability to predict induced JO2. This work details field campaigns to investigate and identify appropriate models of oxygen supply to the SWI and oxygen demand exerted from the sediment, with the intent to use these models to predict oxygenation-induced JO2. Oxygen microprofiles across the SWI and near-sediment velocity measurements were collected in situ during three field campaigns on two oxygenated lakes, providing simultaneous measurements of JO2 and turbulence. Field observations show that oxygenation can increase JO2 by increasing bulk hypolimnetic oxygen concentrations, which increases the concentration gradient across the SWI. Oxygenation can also enhance turbulence, which decreases the DBL thickness and increases JO2. Existing models of interfacial flux were compared to field measurements to determine which model best predicted the observed JO2. Models based on the Batchelor scale, friction velocity, and film-renewal theory all agree reasonably well with field observations in both lakes. Additionally, the oxygen microprofiles were used to fit a transient model of oxygen kinetics in lake sediment and determine the appropriate kinetic model. Oxygen microprofiles in both lakes can be described using zero-order kinetics, rather than first-order kinetics. The interfacial flux and sediment kinetic models are incorporated into a coupled bubble plume and 3-D hydrodynamic lake model, allowing for spatial and temporal variation in simulated JO2. This comprehensive model was calibrated and validated to field data from two separate field campaigns on Carvin's Cove Reservoir, Virginia. Simulated temperature profiles agreed quite well with field observations, while simulated oxygen profiles differed from observed profiles, particularly in the bottom 1 m of the water column. The model overestimates oxygen concentrations near the sediment, which results in higher simulated JO2 than was observed during the field campaigns. These discrepancies are attributed to oxygen-consuming chemical processes, such as oxidation of soluble metals, which are not accounted for in the hydrodynamic model. Despite this, the model is still able to capture the impact of bubble plume operation on JO2, as simulated JO2 is higher when the diffusers are operating. With some additional improvements to the water quality modeling aspects of the model, as well as further calibration and validation, the model should be able to reproduce observed JO2 provided oxygen concentrations near the SWI are accurately reproduced as well. The current work is an attempt to push toward a comprehensive lake oxygenation model. A comprehensive model such as this should improve the ability to predict oxygenation-induced JO2 and lead to improvements in the design and operation of hypolimnetic oxygenation systems. / Ph. D.

A submerged-media biological aerated filter (BAF) has been studied to 1) evaluate oxygen transfer kinetics under conditions without biological growth and 2) determine the influence of biological growth on the rate of oxygen transfer. Collectively, the study evaluates the rates of supply and consumption of oxygen in BAFs. The mass-transfer characteristics of a submerged-media BAF were initially determined over a wide range of gas and liquid flow rates without the presence of bacteria. The mass-transfer coefficients (KLa(T)) were measured using a nitrogen gas stripping method and were found to increase as both gas and liquid superficial velocities increase, with values ranging from approximately 40 to 380 h??. The effect of parameters including the gas and liquid velocities, dirty water to clean water ratio, and temperature dependence was successfully correlated within +/- 20% of the experimental KLa value. The effects of the media size and gas holdup fractions were also investigated. Stagnant gas holdup did not significantly influence the rate of oxygen transfer. Dynamic gas holdup and the difference between total and stagnant gas holdup were found to increase with an increase in gas velocity. Neither liquid velocity nor liquid temperature was determined to have a significant impact on gas holdup. A tertiary nitrification BAF pilot unit was then operated for 5 months downstream of a secondary treatment unit at a domestic wastewater treatment facility. The study investigated the oxygen transfer capabilities of the nitrifying unit with high oxygen demand requirements through a series of aeration process tests and explored the presence of oxygen transfer enhancements by further analyzing the actual transfer mechanism limitations. It was determined that (assuming OTE equals 20 percent) aerating the BAF pilot unit based on the stoichiometric aeration demand resulted in overaeration of the unit, especially at lower pollutant loading rates. Endogenous respiration contributed to only 2 to 7 percent of the total oxygen demand with regions of biomass activity changing with varying loading conditions. An enhanced oxygen transfer factor was determined in the biologically active pilot. Although it cannot be definitively concluded that the observed oxygen transfer factor is either due to biological activity or not simply an artifact of measurement/analysis techniques, the enhancement factor can be mathematically accounted for by either an increase in the KLa factor or the associated driving force using a proposed enhanced bubble theory. / Master of Science

Possibilities for increasing the upper limit of floatable particle sizs in the froth flotation process have been examined since the early beginnings of mineral flotation. The economic implications of such an incresae are far ranging; from decreased grinding costs and increased recoveries to simplified flow-sheet design and increased throughput, all leading to increased revenue. Bubble-particle detachment has been studied to better understand the factors influencing the strength of attachment and the energies involved. Direct measurements of bubble particle detachment were performed using a hanging balance apparatus (KSV Sigma 70 tensiometer) and using a submerged hydrophobic plate in water. Three experiments were used; direct force measurement of bubble-particle detachment, detachment force and energy of a bubble from a submerged hydrophobic plate, and detachment force and energy of a cetyltrimethylammonium bromide coated silica sphere from a flat bubble. Octadecyltrichlorosilane was used as a hydrophobic coating in the first two experimental methods. These experiments were recorded with a CCD camera to identify the detachment processes involved. Energies for both methods were calculated and divided into the two main steps of the detachment process: Three-Phase-Contact pinning and three phase contact line sliding. The first step represents the energy barrier which must be overcome before detachment can begin. It is directly related to contact angle hysteresis. Detachment occurs during the second step, where the solid-vapor interface is replaced by solid-liquid and liquid-vapor. This step corresponds to the work of adhesion. The effects of surface tension, contact angle and hysteresis were well demonstrated with the three experimental methods. Good correlation was found between theoretical work of adhesion and measured energies. / Master of Science

No / This study assesses experimentally the role of gas dissolution in gas entrainment which hitherto has been speculated on but not measured. In this paper, we used dip coating as the model experimental flow and performed the experiments with a dip coater encased in a vacuum chamber in which we admitted various gases. An appropriate choice of gases (air, carbon dioxide and helium) coupled with low pressure conditions from atmospheric down to 75 mbar enables us to test whether gas solubility is a key determinant in gas entrainment. The data presented here track the evolution in time of the size of bubbles of gas entrained in the liquid (silicone oil) which we observed to always occur at a critical speed, immediately after the dynamic wetting line breaks from a straight line into a serrated line with tiny vees the downstream apices of which are the locations from which the bubbles stream out. The results suggest that permeability combining solubility and diffusivity as a single parameter dictates the rate of dissolution when at atmospheric pressure. Helium, despite its comparatively sluggish rate of dissolution/growth into silicone oil was observed to have a more enhanced gas entrainment speed than air and carbon dioxide. Thus, the hypothetical contention from previous work (Miyamoto and Scriven, 1982) that gas can be entrained as a thin film which breaks into bubbles before dynamic wetting failure occurs is not realised, at least not in dip coating. The data presented here reinforce recent work by Benkreira and Ikin (2010) that thin film gas viscosity is the critical factor, over-riding dissolution during gas entrainment. This finding is fundamentally important and new and provides the experimental basis needed to develop and underpin new models for gas entrainment in coating flows.

This dissertation applies covariant density functional theory (CDFT), one of the modern theoretical approaches for describing finite nuclei and neutron stars, to investigate the density distribution of nuclei, which is a manifestation of the nodal structure of the single-particle states in physical phenomena, including charge radii and bubbles. A systematic global investigation of differential charge radii has been performed within the CDFT framework for the first time. Available experimental data is compared with theoretical charge radii across the neutron shell closures at N = 28, 50, 82, and 126. Odd-even staggering (OES) in charge radii are believed to be primarily caused by the pairing. Our research proposes a new approach where a considerable contribution to OES in charge radii is provided by the fragmentation of the single-particle content of the ground state in odd-mass nuclei due to particle-vibration coupling. The proton-neutron interaction explained with the nodal structure of the products of the proton and neutron wave functions. However, proton core is responsible for a major contribution to the buildup of differential charge radii. This interaction between protons and neutrons causes a rearrangement of the single-particle density of occupied proton states, which affects the charge radii. According to our microscopic analysis, the shape of the proton potential, the overall proton density, and the energies of the single-particle proton states are all influenced by self-consistency effects, but they have a minimal impact on the differential charge radii. A detailed and microscopic analysis of bubble physics strongly suggests that single-particle processes are primarily responsible for the creation of bubble shapes in superheavy nuclei. The creation of bubble structure is also influenced by nuclear saturation processes and self-consistency effects, and it is dependent on the availability of low-�� single-particle states for occupation since single-particle densities. For the first time, we investigated how nuclear bubbles are formed in the central classically prohibited area at the bottom of the wine bottle potentials, resulting in decreased s state densities at r = 0.

Predicting U.S. recessions using the slope of the Treasury yield curve has been the focus of extensive research over the past two decades. This yield curve has consistently predicted economic downturns in the United States whenever the curve becomes flat or inverted and recent research has concluded that adding the federal funds rate produces a more accurate model. With the recent recession of 2008 and the housing market's suspected role, I use new data and add a housing index variable to previous models in order to test the correlation and improve the predictive power of the overall model. I run multiple probit regressions to estimate probabilities of a recession within a number of future quarters. I find that models that include the housing index variable in addition to the yield curve and federal funds rate variables give a better in-sample fit and performance than models that do not use it. I discuss the implication of these results in light of the recent recession, and in terms of what this could imply for the future.

京都大学 / 新制・課程博士 / 博士(農学) / 甲第25347号 / 農博第2613号 / 新制||農||1108(附属図書館) / 京都大学大学院農学研究科地域環境科学専攻 / (主査)教授 野口 良造, 教授 飯田 訓久, 教授 近藤 直 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM