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 ESSAYS ON TARGETED PROGRAMS IN EDUCATION(2019) Witzen, Brian Heath; Turner, Lesley J; Economics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation examines three examples of education policy that affect students' decision-making at three different stages of the academic career. In the first chapter, I examine how grant aid can affect the re-enrollment and graduation rates of bachelor's degree-seeking students. I use administrative data from the State of Maryland to study the state's largest need-based grant aid program using a regression discontinuity design. I find positive effects of grant receipt on re-enrollment beginning in the second year and a 10\% increase in the rate of persistence to the fourth year, with similar-sized, but more imprecise effects on graduation within 5 years of entry. In the second chapter, I study State Loan Repayment Programs which pay down a physician's medical school debt in exchange for a period of service in a health care provider shortage area. I gather data from individual states on the amounts that their programs offer over time and use changes in designations of health care provider shortage areas to implement a generalized differences-in-differences strategy. I find no overall effect of the programs on the physician-to-population ratio of an area eligible for the program, though I do find evidence of a positive effect on the physician-to-population ratio when I focus on the age group where physicians are most likely to be recent medical school graduates. In the third chapter, I examine the effect of high school Career and Technical Education coursework completion on postsecondary enrollment, degree completion, and early career earnings. I utilize two estimation strategies. The first is a propensity score matching approach and the second is an instrumental variables approach based on the distance between a student's high school and a CTE Center that offers the coursework. The two strategies generally find that CTE is associated with a substitution from four-year programs to two-year programs, and positive effects on early career earnings.Item ADVANCEMENT OF MOIRÉ INTERFEROMETRY FOR RATE-DEPENDENT MATERIAL BEHAVIOR AND MICROMECHANICAL DEFORMATIONS(2018) Wu, Bulong; Han, Bongtae; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Moiré interferometry is an optical technique to map full field in-plane deformations with extremely high resolution and signal to noise ratio. The technique is advanced and implemented to study the rate-dependent thermo-mechanical behavior of Sn-based Pb-free solder alloys and micromechanical deformations. In Part I, the mechanical/optical configuration of moiré interferometry for real-time observation of thermal deformations is enhanced to provide measurement capabilities required for the analyses. Two most notable advancements are (1) development of a conduction-based thermal chamber for a wide range of ramp rates with accurate temperature control, and (2) implementation of microscope objectives in the imaging system to observe a microscopic field of view. The advanced system is implemented to analyze the anisotropic behavior of Sn-based Pb-free solder alloys. A novel copper-steel specimen frame is developed to apply a controlled loading to single-grain solder joints. After measuring the grain orientation by electron backscatter diffraction (EBSD), detailed in-situ deformation evolutions and accumulated deformations of solder alloys are documented during a thermal cycle of -40 °C to 125 °C. The results quantify grain orientation-dependent deformations that can lead more accurate anisotropic constitutive properties of Sn-based Pb-free solder alloys. In Part II, an advanced immersion microscopic moiré interferometry system based on an achromatic configuration is developed and implemented for higher displacement sensitivity and spatial resolution. In order to achieve the desired displacement resolution, a high frequency grating (2500 lines/mm) is fabricated on a silicon substrate using lithography first. The square profile is subsequently modified by reactive-ion etching so that it can be used to produce a specimen grating by replication. Secondly, the algorithm of the optical/digital fringe multiplication method is improved to further enhance the measurement resolution of the immersion microscopic moiré interferometry. The system and the noise-free grating are used to analyze thermal deformations of micro-solder bumps. With the basic contour interval of 200 nm, the displacement resolution of 25 nm is achieved with the multiplication factor of 8.