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
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item EFFECTS OF MEDICAID STATE PLAN DENTAL BENEFITS ON DENTAL VISITS AMONG NON-ELDERLY ADULTS(2018) Marthey, Daniel Joseph; Franzini, Luisa; Health Services Administration; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Using the Behavioral Risk Factor Surveillance Survey and optional Health Care Access module, I analyzed dental visits between insurance types and between three levels of Medicaid dental coverage for non-elderly adults in each state defined as no benefits or emergency-only, offering 1-4 services and offering 5 or more service types. I find Medicaid adults are less likely to experience a dental visit compared with adults covered by private insurance. I also find a statistically significant relationship between the level of benefits offered to beneficiaries and the odds of experiencing a dental visit in the previous year. Understanding factors associated with the use of dental services is necessary to adequately address health needs of the Medicaid population and unnecessary emergency room use for non-emergency dental services.Item COVERAGE AND ROUTING IN DYNAMIC NETWORKS(2016) Rabieekenari, Ladan; Baras, John S.; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Dynamic networks have become ubiquitous in the current technological framework. Such networks have widespread applications in commercial, public safety and military domains. Systems utilizing these networks are deployed in scenarios influencing critical aspects of human lives, e.g. connecting first responders to command center in disasters, wildlife monitoring, vehicular communication, and health care systems. %Dynamicity of a communication network can be either due to network dynamics or input dynamics. Network dynamics means the topology of the network changes over time. In these networks, nodes and edges may come and go. Input dynamics refers to changes in load of the network. In this dissertation, we explore two significant aspects of dynamic networks. In the first part of the dissertation, we study coverage problem in dynamic networks such as public safety networks. Networking infrastructure can partially (or sometimes fully) breakdown during a catastrophe. At the same time, unusual peaks in traffic load could lead to much higher blocking probability or service interruptions for critical communication. Lack of adequate communication among emergency responders or public safety personnel could put many lives at risks. One possible solution to deal with such scenarios is through the use of mobile/portable infrastructures, commonly referred to as Cells on Wheels (COW) or Cells on Light Trucks (COLT). These mobile cells can effectively complement the existing undamaged infrastructure or enable a temporary emergency network by themselves. Given the limited capacity of each cell, variable and spatially non-uniform traffic across the disaster area can make a big impact on the network performance. Not only judicious deployment of the cells can help to meet the coverage and capacity demands across the area, but also intelligent relocation strategies can optimally match the network resources to potentially changing traffic demands. Assuming that each cell can autonomously change its location, in this dissertation, we investigate such opportunities and constraints. We propose strategies for autonomous relocation of the mobile resource to adapt network coverage and increase the supported user traffic. We demonstrate the performance improvement for several scenarios via simulations using our algorithms. In practical scenarios, typically there are some areas in the field where mobile base stations cannot move into. Structural obstacles, areas with outstanding water or other hazardous materials, or surfaces with debris are examples of prohibited areas that mobile cells are expected to avoid. Such prohibited areas introduce additional constraints on designing intelligent relocation strategies. We propose a decentralized relocation algorithm that enables mobile cells to adapt their positions in response to potentially changing traffic patterns in a field with such prohibited areas. In the second part of dissertation, we study routing problem in dynamic networks. Routing is critical when there is no direct link connecting source to its destination. Performance of this algorithm is critical in many different applications. Two important metrics in routing are delay and throughput. We propose a throughput-optimal routing and scheduling algorithm that improves delay performance by accounting for the network topology. First, we propose algorithm for the fixed topology scenario. We improve delay performance by solving an optimization problem which aims to send packets mostly to greedy neighbors, subject to throughput-optimality constraints. Next, we consider the network with dynamic topology, where routers or links may be added or removed during time. We propose variations of the proposed algorithm for networks with dynamic topology. We identify key design parameters and illustrate the performance of our schemes through simulations.Item SELF ORGANIZING WIRELESS SENSOR NETWORKS(2007-10-26) Kordari, Kamiar; Blankenship, Gilmer L; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation is concerned with the properties of self-organizing network systems, where a large number of distributed sensor nodes with limited sensing, processing and communication capability organize themselves into a cooperative network without any centralized control or management. Due to the distributed nature of the management and lack of global information for in-node decision making, sensor management in such networks is a complicated task. The dynamics of such networks are characterized by constraints and uncertainty, and the presence of disturbances that significantly affect aggregate system behavior. In this dissertation we examine several important topics in the management of self-organizing wireless sensor networks. The first topic is a statistical analysis to determine the minimum requirements for the deployment phase of a random sensor network to achieve a desired degree of coverage and connectivity. The second topic focuses on the development of a viable online sensor management methodology in the absence of global information. We consider consensus based sensor data fusion as a motivating problem to demonstrate the capability of the sensor management algorithms. The approach that has been widely investigated in the literature for this problem is the fusion of information from all the sensors. It does not involve active control of the sensors as part of the algorithm. Our approach is to control the operations of the nodes involved in the consensus process by associating costs with each node to emphasize those with highest payoff. This approach provides a practical, low complexity algorithm that allows the nodes to optimize their operations despite the lack of global information. In the third topic we have studied sensor networks that include "leaders," "followers," and "disrupters." The diffusion of information in a network where there are conflicting strategies is investigated through simulations. These results can be used to develop algorithms to manage the roles in the network in order to optimize the diffusion of information as well as protect the network against disruption.Item Improving the Coverage of Earth Targets by Maneuvering Satellite Constellations(2007-08-10) Santos, Michel; Shapiro, Benjamin; Aerospace Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Satellite constellations around Earth can be used for observing and/or communicating with targets on the surface. This work addresses maneuvering existing satellite constellations in order to improve coverage of multiple targets over a timespan of 30 to 120 days. A direct relationship is established between a satellite's orbital geometry and the coverage provided by that satellite. This is accomplished by (1) identifying the view of the satellite orbit from an inertial sphere centered on the Earth, and (2) utilizing information from all the orbital views across the target's inertial latitude in order to arrive at lower and upper bounds on coverage. Altering a satellite orbit also alters the coverage that it provides. Gauss' variational equations are used to find maneuvering strategies that effect maximal changes in orbital geometry. These distinct maneuvering strategies are then compiled into a list that will be used in the subsequent optimization. The problem of reconfiguring existing satellite constellations in order to improve coverage is phrased as a multiobjective optimization problem. In it, each satellite in the satellite constellation can be assigned any one of the maneuvering strategies as well as an allotment of propellant that will be consumed during the maneuvering. These become the parameters in the optimization problem. An algorithm that is well suited for solving this optimization problem is a multiobjective evolutionary/genetic algorithm. Such an algorithm is capable of handling, without further transformations, the three difficulties with the stated problem: (1) continuous and discrete optimization parameters (e.g. propellant allotment, a distinct maneuvering strategy, etc.), (2) nonlinear optimization objectives (e.g. total coverage time, number of coverage windows, etc.), and (3) multiple optimization objectives (e.g. total coverage time over Target 1, total coverage over Target 2, etc.). This algorithm is implemented by adopting features from other similar algorithms. Finally, a set of examples is investigated in order to study the effectiveness of this approach.Item Televising the Space Age: A Descriptive Chronology of CBS News Special Coverage of Space Exploration From 1957 to 2003(2005-05-04) Hogan, Alfred Robert; Gomery, Douglas; Journalism; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)From the liftoff of the Space Age with the Earth-orbital beeps of Sputnik 1 on 4 October 1957, through the videotaped tragedy of space shuttle Columbia's reentry disintegration on 1 February 2003 and its aftermath, critically acclaimed CBS News televised well more than 500 hours of special events, documentary, and public affairs broadcasts dealing with human and robotic space exploration. Much of that was memorably anchored by Walter Cronkite and produced by Robert J. Wussler. This research synthesizes widely scattered data, much of it internal and/or unpublished, to partially document the fluctuating patterns, quantities, participants, sponsors, and other key details of that historic, innovative, riveting coverage.