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.
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item Optimization of Carbon Monoxide Detectors in a Residential Layout and Analysis of Dispersion Characteristics(2012) Engel, Derek; Trouvé, Arnaud; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Current building and life safety standards do not specify the optimal placement of carbon monoxide (CO) detectors in residential structures. Currently, the standards advise to follow manufacturer's instructions, place one centrally on each floor and in each HVAC zone. With the use of computation fluid dynamics (CFD) software FLACS, simulations were run to observe and track CO concentrations, generated from a fire source, throughout a demonstrative box as well as a residential structure under different source and ambient conditions. A MATLAB script was developed to represent CO detector functionality. From this it was possible to evaluate detector placement throughout a structure. The time to detection criterion was analyzed as well as order of alarm in relation to other placements. Final recommendations are presented based upon the dispersion patterns observed.Item Evaluation of Fire Dynamics Simulator for Liquefied Natural Gas Vapor Dispersion Hazards(2011) Kohout, Andrew Joseph; Trouve, Arnaud; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The Federal Energy Regulatory Commission (FERC) and Pipeline and Hazardous Material Administration (PHMSA) require vapor dispersion modeling as part of a siting analysis for liquefied natural gas (LNG) facilities. Guidance issued by PHMSA, in consultation with FERC, establishes a protocol for the scientific assessment, verification, and validation of vapor dispersion models. This thesis provides an evaluation of the Fire Dynamic Simulator (FDS), Version 5.5.1, for LNG vapor dispersion hazards. The scientific assessment demonstrates that FDS is capable of modeling LNG vapor dispersion hazards, but raises potential limitations associated with the specification of the source term, initial conditions, and boundary conditions; the verification calls for third party confirmation of modeling results; and the validation recommends a safety factor of up to 2 for modeling LNG vapor concentrations in unobstructed flow fields and a safety factor of up to 3 for modeling LNG vapor concentrations for obstructed flow fields.Item Productivity Dispersion, Plant Size, and Market Structure(2008-06-16) Bakhtiari, Sasan; Haltiwanger, John C; Economics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Ample evidence from micro data suggests that productivity at establishment level is dominated by idiosyncratic factors. The productivity differences across establishments are very large and persistent even with the narrowest definition of industries. There is an attempt to identify sources of frictions that cause such productivity dispersion and negatively affect the average productivity of industries. This dissertation contemplates a non-monotonic relationship between productivity and input size and studies its importance in shaping the relationship between productivity dispersion and the producer size, a fact that is presented along with supportive empirical results. The role of market structure is then elaborated in creating the observed behavior. The US Census of Manufactures reveals significant productivity dispersion at any employment level. Moreover, this productivity dispersion falls with employment size within most manufacturing industries. This pattern is considerably strong for establishments in industries whose products are primarily locally traded. It will be shown that general approaches such as industry selection and simple statistical aggregation do not explain this pattern convincingly, while sector-specific factors such as market localization can mimic this behavior much more closely. Based on these results, a market structure model is introduced that uses demand size and market localization as constraining forces to generate a bell-shaped relationship between input size and productivity within a market and for locally traded goods. The non-monotonicity of the relationship is a clear departure from most economic models where input size of plants is monotonically increasing with their productivity in the long-run. Because of the bell-shaped relationship, the proposed model predicts significant long-run productivity dispersion at any level of input size. Also this dispersion decreases with input size, in the same way as is observed in the data. The model is calibrated and then simulated using data on Ready-Mix Concrete. First, the relationship between productivity and input size in the data is of a similar bell-shaped form. The effect of market size is also shown to be consistent with model predictions. Second, simulated results produce productivity dispersions that fall with input size with almost the same slope as observed in the data. This, in turn, suggests that the difference between simulated and actual productivity dispersions, summarizing the effect of other frictions, is almost uniform across sizes. Finally the robustness of the results is demonstrated through various tests. Throughout the discussion, a distinction is made between physical and revenue productivities and the theoretical implications of both measures are shown to be qualitatively the same.Item Essays on Asset Purchases and Sales: Theory and Empirical Evidence(2006-08-09) YANG, LIU; Maksimovic, Vojislav; Finance; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation consists of a theory essay and an empirical essay that investigate a firm's decision to buy or sell corporate assets. It seeks to answer the following research questions: (1) why do firms choose to buy or sell assets? (2) what makes assets in an industry more likely to be traded than assets in other industries? and (3) within an industry, why asset sales come in waves and tend to cluster over a certain time period? In my theory essay, "The Real Determinants of Asset Sales", I develop a dynamic equilibrium model that jointly analyzes firms' decisions to buy or sell assets and the activity of asset sales in the industry. In my model, a firm maximizes its value by making two inter-related decisions: how much to invest in new assets and whether to buy or sell existing assets. These decisions are made under both firm- and industry-level productivity shocks. The model is solved through simulations and it is calibrated using the plant-level data from Longitudinal Research database. I show that most of the empirical evidence documented in the literature on asset sales is consistent with value-maximizing behavior. In my empirical essay, "What Drives Asset Sales - The Empirical Evidence", I test the model's predictions using the plant-level data from Longitudinal Research Database on manufacturing firms in the period of 1973 to 2000. The patterns of transactions (firm-level purchase/sale decisions, and the cross-industry and the time-series variation in asset sales activities) are consistent with my theoretical model.