UMD Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/3
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 given thesis/dissertation in DRUM.
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Item A Micro-Level Examination of the Impact of Rail Transit Investments on the Patterns of Firm Dynamics(2018) Saeed, Basheer A.; Iseki, Hiroyuki; Urban and Regional Planning and Design; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Transit-oriented development has been increasingly implemented at stations of both existing and new fixed transit systems across the U.S. to stimulate local economy and create livable communities. A common belief among planners in favor of transit-oriented development is that the provision of passenger rail systems promotes urban development around rail stations. There is a lack of empirical evidence, however, that supports this presumption. To address the gap in relevant literature, this dissertation examines the impact of passenger rail stations on the four different patterns of firm dynamics in the State of Maryland—firm birth and inward relocation as positive impacts, and firm closure and outward relocation as negative impacts. This dissertation uses both standard and propensity-score-weighted negative binomial regression methods to analyze the dependent variables of firm dynamics constructed from the National Establishment Time Series (NETS) panel data of the State of Maryland from 1990 to 2010. By examining both positive and negative impacts of firm dynamics, this dissertation estimates the likelihood of firm retainment and net relocation for areas in proximity of the passenger rail stations, while controlling for a number of potentially confounding factors. Positive and statistically significant relationships are found between proximity to the passenger rail stations and the rates of firm births and inward relocating firms in Maryland, regardless of differences in the level of maturity of stations. From 1990 to 2010, the areas of passenger rail stations in Maryland experienced a wide range of rates of growth in firm density, depending on the year of station opening. The results of the four different patterns of firm dynamics suggest that areas near passenger rail stations gain belated economic benefits, well after the introduction of rail stations, shown by higher likelihood of firm retainment and net relocation around the mature rail stations opened before 1990. In comparison, areas near the less mature stations that opened after 1990 had predominantly lower likelihood of firm retainment and net firm relocation. Planners and policymakers should be proactive in directing development near rail stations by adopting a variety of measures and policies that support or at least consistent with transit-oriented development.Item Nonlinear Interactions in Planar Jet Flow with High Frequency Excitation(2016) Kreutzfeldt, Timothy; Chopra, Inderjit; Glaz, Bryan; Aerospace Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)An experimental active flow control study was conducted involving excitation of a tabletop planar turbulent jet with a high frequency piezoelectric actuator. The excitation frequencies considered corresponded to the dissipative subrange of turbulent kinetic energy and were orders of magnitude greater than classical shear layer instability modes. Single-wire and dual-wire hot wire probes were used to determine how excitation induces alterations to bulk flow quantities as well as nonlinear interactions. Differences in flow receptivity to high frequency excitation were investigated by varying the development length of the turbulent jet at a Reynolds number of 8,700 and Strouhal number of 21.3. Excitation of developed turbulent flow yielded larger increases in the energy dissipation rate and higher magnitude velocity power spectrum peaks at the forcing frequency than undeveloped turbulent flow. Further tests with excitation of reduced mean velocity flow at a Reynolds number of 6,600 and a Strouhal number of 27.8 demonstrated that high frequency forcing resulted in transfer of energy from large to small scales in the turbulent kinetic energy spectrum. This phenomenon appeared to support past literature that indicated that the mechanics of high frequency forcing are fundamentally different from conventional instability-based forcing. Theoretical arguments are presented to support these experimental observations where it is shown that coupling between the applied forcing and background turbulent fluctuations is enhanced. An eddy viscosity model first proposed under the assumption of instability-based forcing was shown to be an effective approximation for the experimental measurements presented here in which the flow was forced directly at turbulence scales. Dimensional analysis of the coupling between the induced oscillations and the turbulent fluctuations supported experimental findings that receptivity to excitation was increased for forced flow with higher turbulent kinetic energy, higher excitation amplitude, and lower energy dissipation rate. This study is the first to present such results which validate a model that offers theoretical insight into flow control mechanics when directly forcing small scale turbulent fluctuations.Item Ending and "Copping Out": Completeness and Closure in the Plays of Sam Shepard(2006-05-16) Couch, Joseph Dennis; Richardson, Brian; English Language and Literature; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation analyzes the interpretive dilemmas arising from treatments of completeness and closure in Sam Shepard's plays, an undertaking that raises two key questions about its own academic exigence. Shepard's plays expand the discourse on closure by providing dramatic texts to which the terms "the open work," "the sense of ending," "anti-closure," and the reading of texts in socio-political contexts can apply. More significantly, Shepard's theory of closure as a "cop-out" to resolution complicates the previous discourse on closure with texts that complementarily deny formal and thematic closure in ways that previous critics do not explore. The "unloosened ends," specifically, that each ending does not resolve not only draw attention to the unresolved status of an American socio-political theme but actually implicate the audience in the larger and false cultural assumption that the theme was closed before the start of the play and now need the audience's help offstage and therefore outside the boundaries of the text to resolve the issue. In terms of categories within the context of closure in drama, Shepard's endings combine Schmidt's categories of "unmediated" and "ironic" as a reflection of their thematic implication of the collective American audience's "cop-out" regarding the assumed closed discourse on a socio-political issue. Additionally, the endings "frustrate" the audience's expectations for closure thematically and formally even when they provide a moment of "cessation" in Schlueter's terms. The reason lies in the fact that the "consensus" required from the audience, as Schmidt claims, relies on the audience to close the work by closing the discourse on the issue that the endings suggest that the audience should recognize as open and unresolved. The issues of fate, home, family, and memory cannot truly reach a moment of cessation, Shepard's interrogations of closure reveal, until the audience makes the discourse cease by not "copping-out" to the false sense of closure that America's conventional society, both on and offstage, provides.