Theses and Dissertations from UMD
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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
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Item Prediction of Upward Flame Spread over Polymers(2016) Leventon, Isaac Tibor; Stoliarov, Stanislav I; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In this work, the existing understanding of flame spread dynamics is enhanced through an extensive study of the heat transfer from flames spreading vertically upwards across 5 cm wide, 20 cm tall samples of extruded Poly (Methyl Methacrylate) (PMMA). These experiments have provided highly spatially resolved measurements of flame to surface heat flux and material burning rate at the critical length scale of interest, with a level of accuracy and detail unmatched by previous empirical or computational studies. Using these measurements, a wall flame model was developed that describes a flame’s heat feedback profile (both in the continuous flame region and the thermal plume above) solely as a function of material burning rate. Additional experiments were conducted to measure flame heat flux and sample mass loss rate as flames spread vertically upwards over the surface of seven other commonly used polymers, two of which are glass reinforced composite materials. Using these measurements, our wall flame model has been generalized such that it can predict heat feedback from flames supported by a wide range of materials. For the seven materials tested here – which present a varied range of burning behaviors including dripping, polymer melt flow, sample burnout, and heavy soot formation – model-predicted flame heat flux has been shown to match experimental measurements (taken across the full length of the flame) with an average accuracy of 3.9 kW m-2 (approximately 10 – 15 % of peak measured flame heat flux). This flame model has since been coupled with a powerful solid phase pyrolysis solver, ThermaKin2D, which computes the transient rate of gaseous fuel production of constituents of a pyrolyzing solid in response to an external heat flux, based on fundamental physical and chemical properties. Together, this unified model captures the two fundamental controlling mechanisms of upward flame spread – gas phase flame heat transfer and solid phase material degradation. This has enabled simulations of flame spread dynamics with a reasonable computational cost and accuracy beyond that of current models. This unified model of material degradation provides the framework to quantitatively study material burning behavior in response to a wide range of common fire scenarios.Item A Generalized Model for Wall Flame Heat Flux During Upward Flame Spread on Polymers(2015) Korver, Kevin; Stoliarov, Stanislav; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)A current model accurately predicts flame to surface heat flux during upward flame spread on PMMA based on a single input parameter, the mass loss rate. In this study, the model was generalized to predict the heat flux for a broad range of polymers by adding the heat of combustion as a second input parameter. Experimental measurements were conducted to determine mass loss rate during upward flame spread and heat of combustion for seven different polymers. Four types of heat of combustion values were compared to determine which generated the most accurate model predictions. The complete heat of combustion yielded the most accurate predictions (± 4 kW/m2 on average) in the generalized model when compared to experimental heat flux measurements collected in this study. Flame heat flux predictions from FDS direct numerical simulations were also compared to the generalized model predictions in an exploratory manner and found to be similar.Item EVOLUTION OF FLAME TO SURFACE HEAT FLUX DURING UPWARD FLAME SPREAD ON POLYMETHYL METHACRYLATE (PMMA)(2011) Leventon, Isaac Tibor; Stoliarov, Stanislav I; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The heat feedback profile across 5cm wide, 15cm tall samples of PMMA is measured as a flame spreads vertically across its surface. Incident heat flux to a water cooled gauge is determined with peak values averaging to 36kW/m^2 across the height of the sample. This heat flux has been separated into its convective and radiative components and, at this scale, radiative heat transfer is shown to account for between 5 and 15% of total flame to surface heat flux. Based on these measurements, net heat flux into the pyrolyzing material can be determined. Correlations, expressed solely as a function of sample burning rate, predicting net heat feedback to the material's surface are developed.Item Multidimensional Microfluidic Bioseparation Systems With Spatial Multiplexing(2008-12-19) Yang, Shuang; DeVoe, Donald L; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Despite the refinement of liquid chromatography and peptide mass fingerprinting techniques for protein analysis, two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) separations of intact proteins remain a core technology for proteomic studies due to their high peak capacities and resolving power. In 2-D PAGE, denatured intact proteins are separated on the basis of their charge state by isoelectric focusing (IEF), followed by a size-based separation using sodium dodecyl sulfate (SDS)-PAGE. While 2-D PAGE is most commonly practiced with backend analysis of proteins by mass spectrometry, 2-D PAGE expression maps alone can provide valuable insight for differential studies, including the analysis of post-translational modifications, by yielding information about the approximate isoelectric point (pI) and molecular weight (MW) of differentially expressed species within complex samples. However, conventional slab-gel 2-D PAGE remains a labor intensive and low throughput process, which significantly constrains its utility. In this dissertation, a novel microfluidic 2-D PAGE platform is developed which employs a combination of multifunctional photopolymerized polyacrylamide (PAAm) gels and a discontinuous sodium dodecyl sulfate (SDS)-PAGE buffer system. The PAAm gel is used as a highly-resolving separation medium for gel electrophoresis, while discrete PAAm gel plugs integrated into specific regions of the chip enable acid, base, and ampholyte solutions to be fully isolated prior to chip operation. The gel plugs allow different separation buffers to be stored within the chip, enabling the use of a discontinuous buffer system chosen to provide sample stacking during the second-dimension separation. The gel plugs are also employed as on-chip SDS containers, allowing defined volumes of SDS to be repeatably injected and complexed with the IEF-focused proteins, without the need for external intervention. The IEF channel itself possesses an angled geometry to minimize sample tailing, and the chip design employs backbiasing channels which eliminate sample leakage and enable uniform sample transfer between the separation dimensions. Validation of the full 2-D system is presented using fluorescently-labeled E. coli cell lysate as a model system.