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 BEYOND RISK: VOLUNTARY DISCLOSURE UNDER AMBIGUITY(2022) Rava, Ariel; Zur, Emanuel; Business and Management: Accounting & Information Assurance; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In my dissertation, I examine the impact of ambiguity (Knightian uncertainty), alongside that of risk, on firms’ voluntary disclosure decisions. I confirm the well-known result that an increase in risk—uncertainty over outcomes—is associated with an increase in management guidance (earnings and capital expenditure forecasts). Conversely, I find that an increase in ambiguity—uncertainty over the probabilities of outcomes—is associated with less guidance. Furthermore, I show that ambiguity decreases following voluntary disclosures, consistent with managers being aware of and reacting to heightened ambiguity. Finally, I provide novel empirical evidence showing that guidance under ambiguity has adverse capital market consequences. Even though the ways through which risk impacts managers’ disclosure decisions have been extensively studied in the accounting literature, no extant research has examined whether and how ambiguity impacts these decisions. My findings are consistent with the notion that managers’ take into account the ambiguity in the environment, showing that ambiguity has an important and distinct impact on their voluntary disclosure decisions.Item Essays on Regulatory Uncertainty & Energy Development in the American West(2021) Hunt, Jeffrey; Linn, Joshua; Agricultural and Resource Economics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation undertakes an analysis of regulation in the American West, investigating the effects of expropriation uncertainty and technological change in the leasing process.The first chapter explores the possible expropriation of drilling rights due to the addition of the sage-grouse under the Endangered Species Act. Leveraging prior decisions of the US Fish and Wildlife Service, I estimate there was a 52.6% chance the sage-grouse would be listed. Using the real-options framework of Kellogg (2014) and constructing an extension of his simulation to accommodate expropriation risk parameterized by real-world drilling data, I find that developers are expected to delay spudding wells to wait out the uncertainty. This result is corroborated with a Cox proportional hazards model. Additionally, using a difference-in-differences model I find robust evidence that developers reduce their bids for leases commensurate with the expected reduction in profits from possible regulation, and using a conditional logit discrete choice model I find evidence that firms abandon core sage-grouse habitat. Lastly, I find no evidence that developers increase the extraction rate of drilled wells. The second chapter investigates expropriation risk in the context of ozone pollution controls from the Environmental Protection Agency. Here, I find a hurry-up-and-drill response. I place this result within the literature of the green paradox, and find that the EPA regulation did not produce a green paradox but if costs were lower, or if the regulation were modified, a green paradox would have existed and briefly result in higher emissions under a stricter regulatory regime. The policy takeaway is that regulators should avoid a long announcement period, as it gives developers time to drain wells before regulation occurs. The third chapter is a cost/benefit test of auctioning drilling leases online rather than in-person. I leverage the fact that only specific leasing jurisdictions transitioned to an online system called EnergyNet in late 2016 to estimate the causal effect of moving to online leasing. I estimate that a given parcel sold online versus in-person will generate 40% higher bids against only a 2% extra cost.Item Online Network Design under Uncertainty(2017) Dehghani, Sina; Hajiaghayi, MohammadTaghi; Computer Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Today, computer and information networks play a significant role in the success of businesses, both large and small. Networks provide access to various services and resources to end users and devices. There has been extensive research on de- signing networks according to numerous criteria such as cost-efficiency, availability, adaptivity, survivability, among others. In this dissertation, we revisit some of the most fundamental network design problems in the presence of uncertainty. In most realistic models, we are forced to make decisions in the presence of an incomplete input, which is the source of uncertainty for an optimization algorithm. There are different types of uncertainty. For example, in stochastic settings, we may have some random variables derived from some known/unknown distributions. In online settings, the complete input is not known in a-priori and pieces of the input become available sequentially; leaving the algorithm to make decisions only with partial data. In this dissertation, we consider network design and network optimization problems with uncertainty. In particular, we study online bounded-degree Steiner network design, online survivable network design, and stochastic k-server. We analyze their complexity and design competitive algorithms for them.Item POKES, PRODS, AND PUSHES: INFORMATION AVAILABILITY AND DECISION MAKING IN AMBIGUOUS ENVIRONMENTS(2013) Greenwood, Brad N.; Agarwal, Ritu; Gopal, Anand; Business and Management: Decision & Information Technologies; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In this dissertation I investigate how changes in the availability of information influences decision making in inherently ambiguous environments. As the Internet has not only fostered connectivity, but also catalyzed information generation on an unprecedented scale, my objective is to revisit the concept of information availability and salience in the digital age. I conduct my empirical analysis in the contexts of entrepreneurship and healthcare, which are significant both theoretically as well as in terms of economic and public welfare. In essay one, I examine how rising perceptions of fashion, viz., increased media coverage and herding, influence the willingness of venture capitalists to fund non-co-located entrepreneurs. This essay contributes to extant theory on entrepreneur-VC co-location by identifying the effect that social trends, as opposed to factors which are native only to the focal entrepreneur, can have on the willingness to venture capitalists to fund non-co-located entrepreneurs. In essay two, I explore the interplay between the broadcast and social media, as well as the ability of these media to incentivize firm formation on the part of nascent entrepreneurs. Applying the lens of agenda setting theory I demonstrate that the social media will moderate the impact of the broadcast media when entrepreneurs and financiers seek to found and fund new ventures. This study augments existing literature by considering not only the intensity of non-novel information, but also how participation will impact decision making. The third essay investigates a persistent puzzle in the medical literature: how different physicians react to medical guideline release (i.e. the release of new and novel information) which call into question the efficacy of long standing treatment options. Situating this essay within two theoretical tensions in the literature, the trade-off between agility and routines and the debate between costless and costly information assimilation, I find that while physicians are discerning in their reaction to new information their reactions are not quick, creating significant public welfare deficits. Moreover, I find that physician characteristics, such as tenure, board certification, and freelancer status, significantly moderate physician response to new guidelines. Taken together these essays contribute to the literature on Information Systems and Strategic Management by augmenting understanding of the construct of information availability, and how it affects decision makers in ambiguous environments.Item Assessing the uncertainty of emergy analyses with Monte Carlo simulations(2012) Hudson, Amy; Tilley, David R; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Crop production systems were used to show the presence and propagation of uncertainty in emergy analyses and the effect of source variance on the variance of the yield unit emergy value (UEV). Data on energy/masses and UEVs for each source and yield were collected from the emergy literature and considered as inputs for the Monte Carlo simulation. The inputs were assumed to follow normal, lognormal, or uniform probability distributions. Using these inputs and a tabular method, two models ran Monte Carlo simulations to generate yield UEVs. Supplemental excel files elucidate the Monte Carlo simulations' calculations. The nitrogen fertilizer UEV and net topsoil loss energy were the inputs with the largest impact on the variance of the yield's UEV. These two sources also make the largest emergy contributions to the yield and should be the focus of a manager intent on reducing total system uncertainty. The selection of a statistical distribution had an impact on the yield UEV and thus these analyses may need to remain system- or even source- specific.Item PRECAUTIONARY SAVINGS IN SMALL OPEN ECONOMIES(2010) Roitman, Agustin S.; Vegh, Carlos A; Economics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Emerging markets are more volatile and face different types of shocks, in size and nature, compared to their developed counterparts. Accurate identification of the stochastic properties of shocks is difficult. We show evidence suggesting that uncertainty about the underlying stochastic process is present in commodity prices. In addition, we build a dynamic stochastic general equilibrium model with informational frictions, which explicitly considers uncertainty about the nature of shocks. When formulating expectations, the economy assigns some probability to the shocks being temporary even if they are actually permanent. Parameter instability in the stochastic process implies that optimal saving levels (debt holdings) should be higher (lower) compared to a process with fixed parameters. Imperfect information about the nature of shocks matters when commodity GDP shares are high. Thus, economic policies based on misperception of the underlying regime can lead to substantial over/under saving with important associated costs. Later, I introduce the first example of a particular class of preferences characterized by a negative third derivative and a constant and invariant coefficient of relative prudence in the sense of Kimball (1990). This particular feature enables us to isolate the effect of risk aversion on precautionary savings. Furthermore, I use this particular class of preferences to assess the effects of volatility, risk aversion, interest rates and intertemporal distortions on precautionary savings in finite and infinite horizon models of a small open economy. The effects of risk aversion, intertemporal distortions and interest rates on average assets holdings are qualitatively identical as the ones observed for CES preferences. Using an infinite horizon model I can evaluate the effects of persistence and volatility of shocks on precautionary savings and verify that these are qualitatively identical to the ones observed with CES preferences.Item OMI Tropospheric Sulfur Dioxide Retreival: Validation and Analysis(2007-08-28) McClure, Brittany; Dickerson, Russell R; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)SO2 impacts the radiative balance of the Earth and is the precursor to the major acid and much of the particulate matter in the atmosphere. Improved spectrometer resolution of the Ozone Monitoring Instrument (OMI) enables SO2 retrieval in the planetary boundary layer. OMI has a small spatial resolution of 13 km x 24 km and daily near-global coverage. I have evaluated the accuracy of the OMI by comparing aircraft measurements in Northeast China to the OMI retrieval of three different algorithms: the Band Residual Difference (BRD), the Spectral Fit (SF), and a combination of the two (SF & BRD). The SF algorithm shows the best agreement with a less than 15% difference for high SO2 loading (greater than 1 DU). The SF & BRD has a ~ -0.25 DU bias, the BRD and SF a ~ -0.1 DU bias. The noise of the OMI is reduced to ~0.2 DU by averaging over 100 days and is not improved by increasing the averaging time. The OMI is also able to track SO2 as it moves away from its source region in the PBL and once it is lofted above this layer.Item The Influence of Heterogeneous Risk Preferences on Water Market Activity: an Application to the Paloma System of the Limarí Water Basin, Chile(2007-02-07) Cristi, Oscar Enrique; Olson, Lars; Agricultural and Resource Economics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation contributes to our knowledge about water markets by analyzing the factors that explain market transactions of water rights when there is also a spot market for water volumes. I hypothesize that risk heterogeneity among farmers can explain those transactions. To test the aforementioned hypothesis I model farmers' decisions on investment in water rights each season under the assumptions that they face output risk and that uncertainty is generated by future water availability and price. The first order condition to this problem, which is represented by the Euler Equation, indicates that the current period reservation value of a water right depends on the current value of the amount of water accorded to water rights in the spot market, the stochastic discount factor, and the expected future prices of water rights. Using the relationship between the reservation value of a water right and the stochastic discount factor I show analytically how heterogeneous preferences are a sufficient condition for an active market for water rights. Then, I test for heterogeneous preferences by allowing them to be a function of specific characteristics of farmers. That requires the estimation of a system of equations that includes a parametric specification of the Euler Equation and the first order conditions for optimal input quantities. For that, I use an exponential utility function and a production function of the Just-Pope type. I jointly estimate the parameters that describe a farmer's utility function along with production function parameters. The empirical application uses farmer micro-level data from a two-round survey that I conducted on a sample of Limarí Basin farmers. That Basin is located in the northern part of Chile and is characterized by an active water market that has existed since 1981. Evidence rejects the hypothesis of homogeneity among farmers and suggests that those better educated and more experienced Limarí Basin farmers are less risk-averse. Results also show that water, labor and fertilizers have a positive impact on mean output per hectare but their effect on yield variability implies that those inputs are risk increasing.Item Robust Optimization Model for Bus Priority under Arterial Progression(2005-10-05) Vasudevan, Meenakshy; Chang, Gang-Len; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The purpose of this study is to design a real-time robust arterial signal control system that gives priority to buses while simultaneously maximizing progression bandwidths and optimizing signal timing plans at each intersection along the arterial. The system architecture is divided into three levels. At the progression control level bandwidths are maximized. Existing progression strategies do not use real-time traffic data or use simple mathematical models to estimate traffic evolution. The proposed model eliminates this drawback by using real-time data to develop a neural network model for predicting traffic flows. Rather than using pre-specified values, queue clearance and minimum green times are computed as functions of the predicted queues. To eliminate uncertainty in the prediction due to the long time horizon, robust discrete optimization technique is used to determine the progression bands. At the intersection control level, signal timing plans are optimized subject to bandwidth constraints to allow for uninterrupted arterial flow, and minimum green constraints for driver safety and to discharge average waiting queues. At the bus priority control level, whenever a bus is detected and is a candidate for priority it is granted priority based on a performance index that is a function of bus schedule delay, automobile and bus passenger delays, and vehicle delays, subject to bandwidth and minimum green constraints. Minimum green constraints ensure that other traffic users are not unduly penalized. Bandwidth constraints allow for uninterrupted arterial flow despite a preferential treatment of buses. The performance of the proposed system is evaluated through a case study conducted in a laboratory environment using CORSIM. Results show that the models developed at the three levels are superior to the signal control implemented in the field, and the alternatives that use the off-line MULTIBAND model for progression for all traffic scenarios. Robust optimization was highly effective in reducing control delays, stop times, queues, and bus delays, and increasing throughput and speeds, when traffic volumes were high. The model that integrated bus priority with robust arterial signal control produced the most reductions in bus delays while not causing significant delays to automobiles.Item Managing Uncertainty and Ontologies in Databases(2005-04-18) Hung, Edward; Subrahmanian, V.S.; Computer Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Nowadays a vast amount of data is generated in Extensible Markup Language (XML). However, it is necessary for applications in some domains to store and manipulate uncertain information, e.g. when the sensor inputs are noisy, or we want to store data that is uncertain. Another big change we can see in applications and web data is the increasing use of ontologies to describe the semantics of data, i.e., the semantic relationships between the terms in the databases. As such information is usually absent from traditional databases, there is tremendous opportunity to ask new kinds of queries that could not be handled in the past. This provides new challenges on how to manipulate and maintain such new kinds of database systems. In this dissertation, we will see how we can (i) incorporate and manipulate uncertainty in databases, and (ii) efficiently compute aggregates and maintain views on ontology databases. First, I explain applications that require manipulating uncertain information in XML databases and maintaining web ontology databases written in Resource Description Framework (RDF). I then introduce the probabilistic semistructured PXML data model with two formal semantics. I describe a set of algebraic operations and its efficient implementation. Aggregations of PXML instances are studied with two semantics proposed: possible-worlds semantics and expectation semantics. Efficient algorithms with pruning are given and evaluated to show their feasibility. I introduce PIXML, an interval probability version of PXML, and develop a formal semantics for it. A query language and its operational semantics are given and proved to be sound and complete. Based on XML, RDF is a language used to describe web ontologies. RDQL, an RDF query language, is extended to support view definition and aggregations. Two sets of algorithms are given to maintain non-aggregate and aggregate views. Experimental results show that they are efficient compared with standard relational view maintenance algorithms.