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 DATA-DRIVEN ASSESSMENT FOR UNDERSTANDING THE IMPACTS OF LOCALIZED HAZARDS(2022) Ghaedi, Hamed; Reilly, Allison C.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Both the number of disasters in the U.S. and federal outlays following disasters are rising. Thus, evaluating the impact of varying natural hazards on the built environment and communities rapidly and at various spatial scales is of the utmost importance. Many hazards can cause significant and repetitive economic and social damages. This dissertation is a collection of studies that broadly evaluates resilience outcomes in urban areas using data-driven approaches. I do this over three chapters, each of which explores a unique aspect of hazards and their impact on society. The first two chapters are devoted to federal disaster programs aimed at supporting recovery and building resilience. I especially seek to understand how characteristics of hazards intersect with aspects of the physical and social environment to drive federal intervention. The final chapter explores the heterogenous impacts of natural hazards in urban communities and how disparities correlate with various socioeconomic and demographic characteristics. The first two studies examine two major federal disaster programs in the U.S. – FEMA Public Assistance (PA) and FEMA National Flood Insurance Program (NFIP) – at varying spatial and temporal scales. Both leverage parametric and non-parametric statistical learning algorithms to understand how measures of hazard intensity and local factors drive federal intervention. These studies could be used by federal/state-level resource managers for planning the level of aid that may be required after a disaster. This study can also potentially be useful for decision-makers to identify the potential causes of increased disaster spending over time. In the final chapter, I evaluate the links between public transit disruptions, socioeconomic characteristics, and precipitation. By analyzing the spatial distribution and clustering of infrastructure disruptions, I identify the area(s) susceptible to a disproportionate amount of disruptions. Additionally, spatial statistical models are developed to investigate the relationship between infrastructure disruptions and the characteristics of the communities by including variables related to socioeconomic, demographics, social vulnerability, traffic volume, transit system, road connectivity, and the built environment characteristics. For the decision-makers with the goal of improving the performance and resilience of the transit system, this study can provide insight to locate critical areas impacted by such disruptions.Item SPECTROSCOPY OF TWO LEVEL DEFECTS & QUASIPARTICLES IN SUPERCONDUCTING RESONATORS(2021) Kohler, Timothy; Osborn, Kevin D; Anlage, Steven; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Superconducting films are inherently limited by losses due to two-level system (TLS) defects within the amorphous oxide layers surrounding them and from quasiparticles in the film. In this thesis I will discuss novel theoretical and experimental methods toward understanding superconducting resonator loss from deleterious surface TLS defects as well as a loss transition from non-equilibrium quasiparticles in granular TiN. I will show using finite element solver software that a resonator with submicron linewidth and linespacing can be used to better characterize and simulate surface TLS as part of a circuit QED system. I have observed individual surface TLS and found coupling values in the range of g/2π =50 kHz -280 kHz with a maximum dipole moment pz-max = 4.5 Debye (.93 eÅ). I have found in in simulation of experiment that over 80% of the strongly coupled TLS reside within 50 nm of the corner between the Metal-Substrate (MS) and Substrate-Air (SA) interface. Additionally I have studied a loss transition from non-equilibrium quasiparticles in TiN films. These films exhibit an anomalous loss dependence on substrate treatment and film thickness. The films of interest are ones grown thin on oxidized substrates, which exhibit an order of magnitude decrease in internal quality factor (Qi) relative to either thicker ˝films or films grown without the oxidized substrate. These films additionally exhibit a grain size on average of 7.5 nm, a higher inhomogeneous gap, a transition to lower stress and a preference for the [111] crystal growth. The temperature dependence of the conductivity is fit and a factor of two difference in quasiparticle lifetime is found between the two films where the thinner film has a shorter lifetime. A two gap quasiparticle trapping model is fit to the temperature dependent loss data. The data is consistent with a model where non-equilibrium quasi-particles are trapped in low gapped grains on the inside of the films. From these works and others presented in my thesis the understanding of TLSs on surfaces and non-equilibrium quasiparticles in TiN has improved. This will help illuminate some of the most important absorption mechanisms plaguing superconducting qubits and resonators.Item The Influence of Landscape Position on Coastal Marsh Loss(2004-04-29) Rogers, Andrew Stephen; Kearney, Michael S.; Marine-Estuarine-Environmental SciencesCoastal marshes are considered as important features of the landscape that are at risk of loss. Accurately assessing their prospects for survival is difficult in view of the wide possible causes of loss, the large areas involved and that most research is done on relatively small parcels. This project examined the probability of conversion of marsh surface parcels to open water as a function of distance from roadways across marshes, tidal creeks, and upland areas, and the distance upstream, and the size of a marsh parcel. These are understood to be stand-ins for hydrology, elevation and other factors that are more difficult to measure. The study area was divided into a MidAtlantic coastal region and a large bays region comprising the Chesapeake and Delaware Bays. A semi-automated system was developed for measuring the extent and severity of coastal marsh loss using Thematic Mapper (TM) data. The data derived from the TM analysis were used to develop algorithms to examine the impacts of the five factors listed above. The factors were examined individually using ordinary least squares (OLS) regression, and collectively using logistic regression. The OLS regression revealed that distance from uplands and distance from the nearest tidal creek were highly correlated with marsh loss in both areas. For the Atlantic Coast, however, the loss was negatively related to distance from tidal creeks, the opposite of what was expected. Distance upstream was negatively correlated with marsh loss as predicted. The relationship between distance from roads and marsh loss indicated that marshes are healthier near roads than farther away. The relationship between parcel size and marsh loss was non-linear, with small and large marshes having a lower probability of degradation than mid-sized marshes. The logistic regression model is useful for identifying areas with higher probabilities of conversion to open water. Sea level rise (SLR), tidal range, easting and northing were examined for use with the logistic models. SLR and tidal range added no information to the bay areas, but sea level rise was weakly negatively correlated with marsh loss on the Atlantic Coast and tidal range was weakly positively related.