Theses and Dissertations from UMD
Permanent URI for this communityhttp://hdl.handle.net/1903/2
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 Cutting Edge Injury Prevention(2024) Boland, Margaret Kenneday; May, Lindsey; Architecture; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The growing childcare crisis in the United States leaves many families without access to quality, affordable care. This crisis is not just a matter of statistics but a deeply emotional experience for those who find themselves torn between professional responsibilities to sustain their households and proper care for their children. This thesis explores the design of physically and emotionally safe spaces for children and their caregivers that catalyze a positive transformation in the country’s childcare infrastructure. Focused on the relationship between architecture and childhood development, this work explores innovative design solutions that consider functionality, the scale of a child, and the well-being of both children and their caregivers. Through a synthesis of research, case studies, and innovative design solutions, this work aspires to create architectural spaces that consider the unique needs of children. In doing so, it promotes a new narrative where the American dream encompasses not just economic success but also the well-being of children, the most significant investment in the nation’s future.Item Applying Green Complete Streets on Georgia Avenue NW: Redesigning an Urban Right-of-Way for Sustainable Mobility and Urban Water Quality(2023) Mejias, Aliya; Ellis, Christopher D.; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The public right-of-way (ROW) makes up nearly one-third of all the public space in cities. With the majority global population expected to reside in cities by 2050, climate change posing a significant threat to urban residents and infrastructure, impervious urban surface impacts on water quality, and knowing traffic fatalities in the US reached a 16-year high, cities must reconsider how this public good can serve people and the environment over to car-centric mobility. Using a segment of Georgia Avenue NW in Washington, DC, this thesis removes automobiles from the ROW to demonstrate how Green Complete Streets, which prioritizes sustainable transportation and urban water quality, can support urban livability on a corridor scale.Item EFFECTS OF EXTERNAL PRESSURE ON SOLID STATE DIFFUSION OF LITHIUM IN LITHIUM-ION BATTERIES(2016) Williard, Nicholas Dane; Pecht, Michael; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Electrochemical-mechanical effects in lithium-ion batteries refer to the phenomena that give way to the piezo-electrochemical properties observed during intercalation of lithium into lithium-ion battery electrodes. By applying perturbations to the external pressure of a lithium-ion battery, the dynamics of lithium intercalation, in particular the diffusion rate of lithium-ions onto and out of battery electrodes, can be studied with respect to the open-circuit potential and the applied hydrostatic pressure. In this study, commercial thin film batteries were subjected to tests in a low-pressure chamber and in a dynamic materials analyzer simulating hydrostatic pressures between 0 and 115 KPa. Under each hydrostatic pressure condition, galvanostatic intermittent titration technique (GITT) was performed to measure and correlate lithium diffusivity to battery strain, open-circuit potential, and applied hydrostatic force. From the data a model was developed for lithium diffusivity as a function of open circuit potential and hydrostatic pressure. The implications of this work extend from the use of lithiated graphite for energy harvesting and actuation to policy and regulations for how batteries should be safely transported. To provide some insight into how this work can be applied to policy actions, current international regulations regarding the air transport of lithium-ion batteries are critically reviewed. The pre-shipping tests are outlined and evaluated to assess their ability to fully mitigate risks during battery transport. In particular, the guidelines for shipping second-use batteries are considered. Because the electrochemical state of previously used batteries is inherently different from that of new batteries, additional considerations must be made to evaluate these types of cells. Additional tests are suggested that evaluate the risks of second-use batteries, which may or may not contain incipient faults. Finally, this work is extended to supercapacitors through the development of a model to predict the oxidation of functional groups on the surface of graphite electrodes with respect to operational temperature and voltage. This model is used to predict the operational life of supercapacitors and validates the model on accelerated testing data. The final results are compared to previous models proposed in literature.Item Semi-Active Magnetorheological Seat Suspensions for Enhanced Crashworthiness and Vibration Isolation of Rotorcraft Seats(2007-09-27) Hiemenz, Gregory J; Wereley, Norman M; Aerospace Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This research focuses on the use of magnetorheological (MR) dampers for enhanced occupant protection during harsh vertical landings as well as isolation of the occupant from cockpit vibrations. The capabilities of the current state-of-the-art in helicopter crew seat energy absorption systems are highly limited because they cannot be optimally adapted to each individual crash scenario (i.e. variations in both occupant weight and crash load level). They also present an unnecessarily high risk of injury by not minimizing the load transmitted to the occupant during a crash. Additionally, current rotorcraft seats provide no means of isolating the occupant from harmful cockpit vibrations. The objective of this research was to investigate and demonstrate the feasibility and benefits of an MR-based suspension for rotorcraft seats. As such, this research began with an in-depth investigation into design feasibility. Three MR seat suspension design cases are investigated: 1) for only vibration isolation, 2) for adaptive occupant protection, and 3) for combined adaptive occupant protection and vibration isolation. It is shown that MR-based suspensions are feasible for each of these cases and the performance benefits and tradeoffs are discussed for each case. Next, to further illustrate the occupant protection benefits gained with an MR-based suspension, three control strategies were developed and performance metrics were compared. It was shown that MR dampers can be controlled such that they will automatically adapt to the crash load level as well as occupant weight. By using feedback of sensor signals, MR dampers were adjusted to utilize the full stroke capability of the seat suspension regardless crash level and occupant weight. The peak load transmitted to the occupant and the risk of spinal injury, therefore, was always minimized. Because this control significantly reduced or eliminated injury risk during less severe landings, it is a significant advance over the current state-of-the-art rotorcraft seat suspensions which can provide no better than 20% risk of occupant injury. Finally, an MR-based seat suspension designed solely for the purposes of vibration isolation was designed, analyzed, and experimentally demonstrated. MR dampers were integrated into the current crashworthy SH-60 crew seat with minimal weight impact such that the original crashworthy capabilities were maintained. Then, utilizing semi-active control, experimental vibration testing demonstrated that the system reduced vertical cockpit vibrations transmitted to the occupant by 76%. This is a significant advance over current state-of-the-art rotorcraft seats which provide no attenuation of cockpit vibrations.