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 The Geographies and Entanglements of Education and Mobility: A Focus on Black Nations and Black Immigrants, Past to Present(2022) Brantuo, Nana Afua Yeboaa; Brown, Dr. Tara; Turner, Dr. Jennifer; Education Policy, and Leadership; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Using Black geographies – a deliberate, decolonial examination of racialization, spatialization, and Black life, situated at the nexus of Black intellectual traditions and modes of inquiry – this study centers and interweaves the narratives of Black im/migrants, along with their artistic, cultural, and intellectual knowledge and artifacts, to interrogate and revise historic and contemporary understandings of Black im/migrant students’ mobility, migration, and agency. The study answers the following questions: 1) How have Black im/migrants, and Black im/migrant students specifically, understood their multiple, intersecting identities, and how do these understandings shape how they navigate societies? 2) How do they understand and engage with/disengage from advocacy, activism, and politics, 3) What do they envision for themselves as students, as migrants, and as citizens (a status that continues to hold loosely for Black people across borders)?, and 4) What bonds and/or communities sustain them transnationally and how do they envision the roles of those bonds and communities in their futures? Also drawing on and in conversation with scholarly literature, archival materials and documents, reports and white papers, government surveillance records, journal entries, letters, laws, policies and treaties, news periodicals, interviews, organizational records, photographs, and speeches, the study elucidates the politics and interrelationships of education, migration, and empire for Black im/migrants across time and space. Implications for theory and research are presented with an emphasis on students’ Diasporic worldmaking praxes and networks as central to reviving and revising the historical and contemporary record of educational and migration research and scholarship.Item Cosmopolitanism, Mobility, and Royal Officials in the Making of the Spanish Empire (1580-1700)(2017) Polo y La Borda, Adolfo; Cañeque, Alejandro; History; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation explores the worldwide mobility of seventeenth-century Spanish imperial officials who traveled around the Americas, Asia, Africa, and Europe. My study focuses on the lower echelon of imperial officials in order to demonstrate how their experiences of service to the king in a variety of locales affected the the governance of the Spanish Empire and how such a polity was imagined by these officials as a global, yet connected and coherent unity. I argue that the officials’ circulation was central for the cohesion and stability of the empire. It allowed the actual and imagined overcoming of the far-flung geography of Spain’s empire and the incorporation, and sometimes exclusion, of diverse subjects across the globe. The intense and extensive mobility of the officials permitted the consolidation of certain imperial political practices, values, and patterns of rule and administration, which played a decisive role in the emergence of a common imperial identity built from the ground up. This imperial identity worked to give cohesion to a polity as heterogeneous as the Spanish Empire. Imperial official’s interactions with very different peoples and cultures spawned a cosmopolitan imperial culture that unified the many cultural, geographic, demographic, and social peculiarities of diverse societies under the umbrella of the imperial mission of enforcement, defense, and expansion of the crown’s rule and spread of Catholicism. This work departs from the traditional national and area models of study by emphasizing the utility of an analytical framework that takes the whole imperial system—and not just one of its component regions—as the unit of analysis, in order to show that the histories of Europe, America, Africa, and Asia were far more entangled than previously thought. Despite the empire’s enormous diversity, extension, discontinuous territoriality, and the near-autonomous status of many imperial outposts, a great number of Spanish imperial subjects saw the empire as an integrated and coherent political unit. I analyze some of the conditions and settings that made possible the global mobility of the officials, and some effects of such circulation in the ruling and political imagination of the empire.Item Essays on the Relationship Between Income and Life Satisfaction in the United States(2015) Swenson, Kendall; Graham, Carol; Public Policy; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation presents three essays concerning the relationship between income and life satisfaction in the United States. The first essay examines whether the receipt of income assistance from public and private sources predicts life satisfaction. It identifies a negative association between the receipt of income assistance from government and private sources and life satisfaction, and finds that the association remains significant even after controlling for family income and other factors. The negative association between the receipt of income assistance and life satisfaction continues to exist across most of the income distribution, although the correlation is more uncertain for respondents in the very lowest income quartile. Another noteworthy finding from this essay is that income assistance from non-governmental sources is just as predictive of lower life satisfaction scores as is assistance from government means-tested welfare programs The second essay examines whether consumption is a better predictor of life satisfaction than is income. The essay finds that income and consumption are both predictors of life satisfaction, but that several other factors are even more predictive of well-being. In the full regression models health, marriage, and unemployment are much more predictive of life satisfaction than either income or consumption. The third essay examines the link between childhood family incomes and future life satisfaction. To analyze this topic, longitudinal data from the PSID is used to obtain mean family incomes when people were ages 13 to 17 between 1968 and 1994 and examines the life satisfaction of these individuals as adults in 2011. The primary finding from this essay is that the family incomes of youths are not strongly predictive of their future life satisfaction scores.Item Connectivity and Data Transmission over Wireless Mobile Systems(2011) Frangiadakis, Nikolaos; Roussopoulos, Nick; Computer Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)We live in a world where wireless connectivity is pervasive and becomes ubiquitous. Numerous devices with varying capabilities and multiple interfaces are surrounding us. Most home users use Wi-Fi routers, whereas a large portion of human inhabited land is covered by cellular networks. As the number of these devices, and the services they provide, increase, our needs in bandwidth and interoperability are also augmented. Although deploying additional infrastructure and future protocols may alleviate these problems, efficient use of the available resources is important. We are interested in the problem of identifying the properties of a system able to operate using multiple interfaces, take advantage of user locations, identify the users that should be involved in the routing, and setup a mechanism for information dissemination. The challenges we need to overcome arise from network complexity and heterogeneousness, as well as the fact that they have no single owner or manager. In this thesis I focus on two cases, namely that of utilizing "in-situ" WiFi Access Points to enhance the connections of mobile users, and that of establishing "Virtual Access Points" in locations where there is no fixed roadside equipment available. Both environments have attracted interest for numerous related works. In the first case the main effort is to take advantage of the available bandwidth, while in the second to provide delay tolerant connectivity, possibly in the face of disasters. Our main contribution is to utilize a database to store user locations in the system, and to provide ways to use that information to improve system effectiveness. This feature allows our system to remain effective in specific scenarios and tests, where other approaches fail.Item Modeling and Characterization of 4H-SIC MOSFETs: High Field, High Temperature, and Transient Effects(2008-11-21) Potbhare, Siddharth; Goldsman, Neil; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)We present detailed physics based numerical models for characterizing 4H-Silicon Carbide lateral MOSFETs and vertical power DMOSFETs for high temperature, high field, DC, AC and transient switching operating conditions. A complete 2-D Drift-Diffusion based device simulator has been developed specifically for SiC MOSFETs, to evaluate device performance in a variety of operating scenarios, and to extract relevant physical parameters. We have developed and implemented room and high temperature mobility models for bulk phonon and impurity scattering, surface phonon scattering, Coulomb scattering from interface traps, and surface roughness scattering. High temperature models for interface trap density of states and occupation probability of interface traps are also implemented. By rigorous comparison of simulated I-V characteristics to experimental data at high temperatures, physical parameters like interface trap density of states, surface step height, saturation velocity, etc. have been extracted. Insight into relative importance of scattering mechanisms influencing transport in SiC MOSFETs has been provided. We show that the strongest contribution to low current in SiC MOSFETs is from the loss of mobile inversion charge due to large amount of trapping at the interface, and due to very low surface mobility arising due to a rough SiC-SiO2 interface. We show that surface roughness scattering dominates at high gate biases and is the most important scattering mechanism in 4H-SiC MOSFETs. Switching characteristics of SiC lateral MOSFETs have been modeled and simulated using our custom device simulator. A comprehensive generation-recombination model for interaction between inversion layer electrons and interface traps has been developed. Using this model, we have modeled the time-dependent occupation of interface traps spread inside the SiC bandgap. We have measured the transient characteristics of these devices, and compare our simulation to experiment and have extracted capture cross-sections of interface traps. Using the coupled experiment and modeling approach, we are able to distinguish between fast interface traps and slow oxide traps, and explain how they contribute to threshold voltage instability. High power 4H-SiC DMOSFET operation in the ON and the OFF states has also been analyzed. We show that in current generation SiC DMOSFETs, the ON resistance is dominated by the channel resistance instead of the drift-layer resistance. This makes the design of SiC DMOSFETs far from ideal. OFF state blocking capability and breakdown due to impact ionization of the DMOSFETs are also modeled and simulated. We show that the 4H-SiC DMOSFETs have excellent leakage characteristics and can support extremely high OFF state drain voltages.