Theses and Dissertations from UMD
Permanent URI for this communityhttp://hdl.handle.net/1903/2
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item IDENTIFYING SMOKE DETECTION BIASES WITHIN DIFFERING ROOM CONFIGURATIONS FOR ZONE AND COMPUTATIONAL FLUID DYNAMIC MODELS(2022) Lee, Adam; Milke, James A; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This research project aims to identify room configuration conditions in which FDS, a CFD model, and CFAST, a zone model, may differ in detector activation time. A total of four configurations, with varying aspect ratios, were explored. Additionally, a range of four ceiling heights were also modeled. Furthermore, a total of three statistically significant models were developed to relate the differences between detection times within CFAST and FDS. It was found that FDS and CFAST discrepancies were a result of the compartment volume to doorway area ratios. Larger volumes compared to the doorway area resulted in better agreement between FDS and CFAST. Additionally, for larger ceilings in FDS, larger variability in activation times were present. Furthermore, for higher ceilings, FDSs’ ability to account for thermal buoyancy within the smoke plume resulted in quicker activation within FDS.Item CHARACTERIZING THE DURATION, PERIODICITY AND CHEMICAL IMPACT OF FLUID TRANSPORT IN THE SUBDUCTING SLAB: INSIGHTS FROM ISOTOPE GEOCHEMISTRY OF HIGH-PRESSURE METAMORPHOSED OCEANIC CRUST(2021) Hoover, William Floyd; Penniston-Dorland, Sarah C; Geology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Subduction zones are key loci of geochemical cycling and natural hazards on Earth including large earthquakes and explosive volcanic eruptions. Fluids produced during subduction are thought to play a role in all these processes, however, many aspects of fluid transport in subduction zones remain enigmatic. In this dissertation, three types of fluid-related features are examined: 1) an eclogite-facies vein and 2) an eclogite- facies shear zone block and metasomatic rind, both from the Monviso Ophiolite (Western Alps), and 3) two amphibolite-facies mélange blocks and rinds from the Catalina Schist (CA). The mechanisms, episodicity and duration of fluid transport associated with these fluid pathways are investigated with bulk and in situ Li isotope geochemistry, in situ Sr isotope and trace element geochemistry, and quantitative transport modeling. In the eclogite-facies vein, evidence for five distinct locally-derived fluid compositions suggests a complex process of fluid-rock interaction. The unusual geometry of alteration features in the host rock suggests that initial host rock heterogeneity led to the development of reactive porosity channels. A method for in situ measurement of Li isotopes in garnet by secondary ion mass spectrometry is developed to explore the relative chronology of fluid rock interaction preserved in mineral zoning. The equivalence of natural garnet and garnet-like glass reference materials is demonstrated and a correction procedure for instrumental mass fractionation due to MnO and FeO is proposed. The resulting method is highly adaptable and attains 2-4‰ precision at the 20-μm-scale. Application of this method to garnet from the eclogite-facies shear zone block and rind reveals negative ?7Li excursions to values as low as -9‰ that record fluid-driven Li diffusion and rapid garnet growth. Multiple negative excursions within a single garnet require at least four episodes of fluid infiltration in the shear zone. Lastly, the first fluid transport durations for the subduction interface are obtained by inverting Li isotopes profiles from the amphibolite-facies mélange blocks and rinds using an advection-diffusion model. Uniform durations of ~60 years for metasedimentary rock-derived fluid flow near peak metamorphic conditions suggest fluid infiltration was pervasive and episodic, with earlier episodes erased by the expansion of rinds into blocks.Item How Far Does the Grid Go?(2019) Pantelis, Irene Noemi; Richardson, William C; Art; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)My artwork probes the connection between daily life and what I perceive as the larger grid out there—a mesh that entangles all peoples, beings and things, cuts across all time, and is always in flux. Drawing from my everyday life and experiences as a Latin American immigrant, I incorporate materials from my suburban home environment in my multidisciplinary approach. I create organic forms and grids that abstract, excavate, ground and find universal truths in the quotidian. They also serve as platforms for engaging obliquely with history, science, archeology, philosophy, and magic realism. My artwork invites viewers to reach interpretations based on their own associations, experiences, and feelings. It thus brings attention to the power of our imagination to infuse the material world, particularly nature, with fluid possibilities of meaning and subjectivity.Item MULTI-SCALE MODELING AND COMPUTATIONS(2009) Zhang, Linbao; Liu, Jian-Guo; Mathematics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In the rarefied gas dynamics, the classic kinetic models are more accurate and complicated, while the fluid models are much simpler but fail in some cases. In this thesis, we propose a new local up-scaling model to couple Euler equations with the kinetic model when the previous up-scaling model in [19] does not apply, e.g. when the Boltzmann equation is solved by the particle method, like DSMC. By means of the first order Chapman-Enskog expansion we propose a new NSLU model to couple the Navier-Stokes equations with the kinetic models. We also propose the zero-moment projection based on the macro-micro decomposition ([34]) to correct the non-fluid part in the up-scaling models. Numerical tests of these local up-scaling models have been done in various multi-scale problems, including the Jin-Xin relaxation model for the traveling shock, 1D1D BGK model for the dynamics of a small perturbation of an equilibrium, 1D3D BGK model for the stationary shock and the simulation of a planar Couette flow by direct simulation of Monte Carlo (DSMC) for the Boltzmann equation. The implicit-explicit scheme for the relaxation models is applied, which is shown to preserve the positiveness of the distribution function, the conservation laws and entropy inequality. Numerical results show that the zero-projection is necessary to ensure the stability and accuracy for the up-scaling models, especially when non-kinetic schemes are applied in the moment equations. NSLU model must be applied to replace the up-scaling model in [19] if the macroscopic approximation is the viscous fluid. The similar scaling exists in the relaxation-time model for the semiconductor device when electric field is low. The DrDiLU model based on drift-diffusion model for the diode is proposed which is similar to NSLU model for the rarefied gas. Numerical experiments show it is stable and accurate compared with the results from the relaxation-time model.Item A Self-Contained Cold Plate Utilizing Force-Fed Evaporation for Cooling of High-Flux Electronics(2007-12-11) Baummer, Thomas Buchanan; Ohadi, Michael M; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In recent years, the rapid increase in the functionality, speed, and power density of electronics has introduced new challenges, which have led to demand for high heat flux electronics cooling at levels that cannot be met by conventional technologies. The next generation of high power electronics will require advanced cooling beyond the methodologies currently available. This thesis describes work done on a novel form of two-phase heat transfer, named "Force-Fed Evaporation," which addresses this need. This process utilizes evaporation of a liquid in a microchannel surface to produce high heat transfer coefficient cooling at very high heat flux while maintaining a low hydraulic pressure drop. Component level tests were conducted to demonstrate the capability of this process. This led to the development of a self-contained, two-phase cold plate suitable for cooling a high power circuit board. The results show that this technology bears promise for the future of electronics cooling.