Thesis (Ph. D.)--University of Hong Kong, 1976. / Fold. maps in pocket.

Thesis (M. Sc.)--University of Hong Kong, 1991.

The knowledge of density current behaviours as a result of two or more fluids of different densities interacting is of particular importance in many practical applications. Within the field of hydraulic engineering, examples include buoyant effluent discharges from desalination plants, advancements of saline water under freshwater in estuaries, and flows occurring when a gate is removed at the outflow/inflow of a river. The main goal of this study is to improve the understanding of the mixing patterns of density currents as well as their related numerical simulation. In this study, first, an advanced numerical solver for 2D variable-density shallow water equations is developed and validated where both well balanced and positivity preserving properties are achieved over an unstructured grid. The improved numerical scheme is flexible, and accounts for flooding over irregular bed topographies by using a triangular grid. Second, a numerical study of two-layer stratified flows over an isolated submerged dune is conducted. This part focuses on modeling density currents created when a narrow channel connects two water bodies with different densities and a stratified two-layer flow is subsequently generated. A 3D Large Eddy Simulation (LES) model is developed in OpenFoam and validated with the experimental data to investigate the flow patterns and entrainment. In addition to the LES model, a RANS numerical model is also used, and the results are compared in order to prove the superiority of the LES method in modeling complex mixing behaviours. LES predictions showed good agreement with the experimental measurements, as the LES model was able to capture the KH instabilities. In the third part of this study, the interaction between inclined negatively buoyant jets and waves, such as in the case of brine discharges from desalination plants into the ocean, is experimentally investigated. In addition to discharges in a wave environment, experiments are also performed in a stagnant environment and a wave-current environment in order to compare the results. A combination of the Particle Image Velocimetry (PIV) technique and the full-field Laser Induced Fluorescence (LIF) technique is employed to reveal the mixing patterns. The results showed that the wave motion affects the inclined negatively buoyant jet geometry, resulting in the jet’s rotation and an increase in its width. This study led to derivation of empirical formulae calculating terminal rise height and minimum dilution at specific points. In the fourth part, the numerical simulations of 45° inclined dense jets in wavy ambient have been conducted using a finite volume model (OpenFOAM). The selected turbulence models include RNG k-ε, realizable k-ε; Nonlinear k-ε; and LRR. The results of this study are compared to the results from experimental investigations in the third part and comparative figures and tables are presented and discussed. It has been observed that the LRR turbulence model as well as the realizable k-ε model predict the flow more accurately among the various turbulence models studied herein.

While the expansion of urbanisation has been occurring on an unexpected scale since the 1960s, urban density has become more and more globalized. Essentially, the dense urban morphology has been benefitted from all aspects of sustainable urban development, despite the consequential problems cannot be ignored. As sustainability is one of the most salient themes across all disciplines currently, it is necessary for the well-developed theory of morphology to contribute to sustainable development in practice. Sustainability assessment of the morphology in high-density cities is making a contribution to achieving a sustainable urban form in specific circumstances. Also, this instrument can be applied to strengthen sustainable development in terms of morphology in all cities. As conventional sustainability assessment mostly depends on the numerical sustainable indicator systems, the diagrammatic assessment approaches provide a straightforward and visual way to qualify sustainability of morphology, and express the form a sustainable urban morphology takes. Finally, it provides a direct grasp for planners, architects and local governments to design a sustainable city form, rather than only by the materials or technology employed. The final goal of this research is to better implement sustainability indicator system to assess sustainable morphology in the high-density context. This study therefore commences with respective demonstrations of the theories of morphology, diagrammatic methods and sustainability indicator systems through a literature review, in order to build up the theoretical underpinnings for the development of diagrammatic methods. At the same time, it explores the virtues of morphological and diagrammatic methods, which are applied as complements to the shortcomings of sustainability indicator systems that have emerged and are utilized to evaluate sustainable morphology. Afterwards, this research attempts to investigate what is sustainable morphology for the purpose of defining sustainable morphology through examining the definite features it should possess, and identifying the overlapped scope between morphology and sustainable development. Based on the exact scope, it categorizes relative indicators in the four respective aspects of sustainability respectively drawn from a proven indicator system – SPeAR® developed by Arup. These indicators are simplified to a radar diagram which is succinct, visual and informative to represent the evaluation results. Moreover, this research compares a series of diagrams concerning sustainable buildings and cities to summarize the referencing diagrams of sustainable morphology characteristics which assist to explain the profile of sustainable morphology on scales. Finally, Hong Kong is taken as the test bed for the application of these diagrammatic approaches due to its outstanding performance of high density. The findings of this research can be viewed as a theoretical complement to urban morphology and sustainability assessment research. The diagrammatic assessment approaches can be applied as guidance for sustainability designs in planning and decision-making processes across all areas. In addition, the proposed assessment methodology is not only suitable for evaluating the high-density morphology, but also can be replicated with relevant alterations responding to different circumstances. / published_or_final_version / Architecture / Master / Master of Philosophy

The structure of the set of density matrices, its linear transformations, generalized linear measurements, and entanglement are studied. The set of density matrices is shown to be a convex and stratified set with simplex and group symmetries. Generalized measurements for density matrices are shown to be reducible to one unitary transformation and one von Neumann measurement carried out with an ancillary system of fixed size. Linear maps of density matrices are considered and the volume of the set of maps is derived. Positive but not completely positive maps are studied in consideration of obtaining a test for entanglement in density matrices. Using the Jamiolkowski representation and Schmidt decomposition of the map eigen matrices, several properties of these maps are shown. An algebraic approach to constructing these positive but not completely positive maps is partially formulated. The positivity of the linear map describing the evolution of an open system and its dependence on the initialized to a zero-discord state, the evolution is shown to be given by a completely positive map. In quantum process tomography, the results obtained from a open system that is initially prepared using von Neumann measurements is shown to be described by a bi-linear map, not a linear map. A method for quantum process tomography is derived for qubit bi-linear maps. The difference between preparing states for an experiment by measurement and by stochastic process is analyzed, and it is shown that the two different methods will give fundamentally different outcomes. / text

published_or_final_version / Architecture / Doctoral / Doctor of Philosophy

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (M.S.) in Teaching--University of Maine, 2006. / Includes vita. Includes bibliographical references (leaves 81-83).

No description available.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy