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 THE CONCENTRATION OF HYDROGEN IN INCOMPLETELY AND WHOLLY MELTED TERRESTRIAL BUILDING BLOCKS(2024) Peterson, Liam Donald; Newcombe, Megan E; Geology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Hydrogen (H) is the most abundant element in our solar system and exerts a primary control on the habitability, and geochemical and geodynamic evolution of rocky bodies. Therefore, constraining the source(s), timing of accretion, and abundance of H in the Earth and other bodies is of fundamental importance for understanding how planets evolve. Direct constraints on the source(s) of H and other highly volatile elements (HVEs; e.g., H, C, F, Cl, and S) to the bulk Earth can be provided by analyzing meteorites, which are the remnants of early-formed rocky bodies that were present during the accretion of the terrestrial planets. Such samples either directly sample or provide analogs for terrestrial precursor materials.Rocky solar system materials can be subdivided based upon their nucleosynthetic isotopic compositions (“genetic” tracers; e.g., 50Ti, 54Cr) into two groups, which are thought to correspond to the inner- and outer- solar system. Materials may be further subdivided by their extent of thermal processing (i.e., unmelted, incompletely melted, and wholly melted). Earths H budget is commonly accounted for by addition of unmelted (i.e., chondritic) materials, namely carbonaceous chondrite-like (CC-like) materials, thought to be derived from the outer solar system, which have high H concentrations (up to ~14 wt. % H2O; total H as H2O equivalents) and similar H isotopic compositions to the bulk Earth. Furthermore, chondrites derived from the inner solar system (e.g., ordinary and enstatite chondrites) are H-poor relative to carbonaceous chondrites. Similarly, all melted planetesimals are commonly assumed to be anhydrous. However, recent analyses of enstatite chondrites (ECs), which are formed in the inner solar system and are the closest match to the nucleosynthetic isotopic composition of the bulk Earth, suggest that ECs have a similar H isotopic composition to the bulk Earth and can account for its entire H budget. Furthermore, recent analyses suggest that melted (i.e., achondritic) bodies may retain considerable amounts of H, potentially enough to account for Earth’s H budget in the case of the enstatite achondrites (i.e., aubrites). However, achondritic materials are predominantly highly H-poor relative to chondritic materials, and it is unclear if the aubrites are an anomaly, and at which stage of planetesimal evolution H and other HVEs are lost. In chapter 2, I re-examine prior bulk analyses of H in aubrites, and by extension ECs, using in situ methods and suggest that nearly all H measured in aubrites by bulk methods reflects pervasive terrestrial contamination and alteration, a result which may extend to concurrent bulk H analyses of ECs. In chapters 3 and 4, I examine the H content of incompletely melted (i.e., primitive achondritic) planetesimals to constrain at what stage of planetesimal evolution H is lost. Chapter 3 characterizes the H contents of the ureilites, a group of C-rich primitive achondrites, and chapter 4 characterizes the H contents of the acapulcoite-lodranite clan which represents the “prototypical” primitive achondritic parent body. I find that primitive achondritic parent bodies are highly H-depleted relative to chondrites, requiring that H is efficiently lost prior to or at the onset of planetesimal melting, and that Earth’s H budget is accounted for by accretion of thermally primitive materials (e.g., chondrites). Within my primitive achondrite data sets, I observe apparent disequilibrium with respect to H between olivine, pyroxene, and feldspar. In chapter 5, I explore whether this apparent disequilibrium is the result of extrapolating high pressure experimental data to low pressures. I conduct olivine–melt H partitioning experiments at low pressures (10 – 200 MPa) and find that the olivine-melt H partition coefficient increases at low pressures, contrary to extrapolation from high pressure data. This observation is best explained by a control of H speciation in the melt on the partitioning of H between olivine and melt.Item A VALIDATED MODELING FRAMEWORK FOR PERFORMANCE ANALYSES OF EXPERIMENTAL AND PROVEN DESALINATION TECHNOLOGIES(2022) Romo, Sebastian Antionio; Srebric, Jelena; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)There is a wide array of desalination methods available for treating water at different salinities and production rates, but there are no systemic approaches on how to directly compare performance of different desalination systems. Existing comparison efforts focus solely on isolated performance metrics for a single desalination system, resulting in segregated case studies and/or incomparable systems. Numerical models for desalination systems can bridge this gap as they can take account of specific deployment needs. However, models in the literature are not mutually compatible, and they seldom disclose all the parameters or equations necessary for development and validation. This dissertation conceives a cross-comparison enabling simulation framework for the most relevant desalination processes. To achieve this, modeling approaches and thermophysical property correlations are curated from volumes of literature and used to create metamodels for six relevant desalination methods. The models are integrated into a simulation framework based on parameter hierarchies imposed in the model structures. The simulation suite is validated with data from the literature and actual operational data from desalination facilities in the field. The results show that the cross-comparison across equal parameter hierarchies is possible for all desalination technologies. A comparative analysis between the dominant technologies in the thermal and molecular transport families, Multi-Effect Distillation (MED) and Reverse Osmosis (RO), respectively, shows that energy intensity in MED is an order of magnitude greater for equivalent operational conditions, but actual operational costs are comparable. The models are further refined to reflect conditions from actual systems in the field and an iterative sampling algorithm is developed to find plausible operation scenarios given the scarce data from the field. This method achieves excellent agreement with data from four desalination plants with percent differences ranging between 2.5% and 9.3%. Furthermore, the results identify two plants performing 20% below their theoretically achievable recovery. Apart from evaluating existing deployments, the simulation suite helps identify a niche in the operational map of existing desalination methods characterized by high recovery rates and high feed salinities that is generally unfulfilled by conventional desalination.Item QUANTIFYING THE ADDED VALUE OF AGILE VIEWING RELATIVE TO NON-AGILE VIEWING TO INCREASE THE INFORMATION CONTENT OF SYNTHETIC SATELLITE RETRIEVALS(2022) McLaughlin, Colin; Forman, Barton A; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Satellite sensors typically employ a “non-agile” viewing strategy in which the boresight angle between the sensor and the observed portion of Earth’s surface remains static throughout operation. With a non-agile viewing strategy, it is relatively straightforward to predict where observations will be collected in the future. However, non-agile viewing is limited because the sensor is unable to vary its boresight angle as a function of time. To mitigate this limitation, this project develops an algorithm to model agile viewing strategies to explore how adding agile pointing into a sensor platform can increase desired information content of satellite retrievals. The synthetic retrievals developed in this project are ultimately used in an observing system simulation experiment (OSSE) to determine how agile pointing has the potential to improve the characterization of global freshwater resources.Item TREE TRADE-OFFS IN STREAM RESTORATION: IMPACTS ON RIPARIAN GROUNDWATER QUALITY(2020) Wood, Kelsey Lynn; Kaushal, Sujay; Geology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Restoring urban degraded stream channels in efforts to improve water quality often includes substantial alteration of the riparian zone which can require the removal of mature trees. This study assessed the impact of tree removal on riparian groundwater quality over time and space using a chronosequence of restored sites ages 5-20 years and well transects along groundwater flow paths. The response of multiple elements through various hydrologic conditions was evaluated by monitoring dissolved concentrations of inorganic carbon, organic carbon, total nitrogen, boron, calcium, copper, iron, potassium, magnesium, manganese, sodium, and sulfur over a 2-year period. Results revealed that concentrations of most bioreactive and organically derived elements were significantly elevated and increase along flowpaths at recently restored sites.Item Development of Hybrid Air-Water Rotor Transition Thrust Prediction and Control(2020) Semenov, Ilya Yevgeniyevich; Chopra, Inderjit; Aerospace Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Hybrid vehicles are able to function in some combination of aerial, underwater, and terrestrial environments, which greatly expands the scope of missions a vehicle can perform. Hybrid aerial-water (HAW) vehicles are a promising subcategory that are designed to operate in two vastly different fluid mediums. Multirotor HAW vehicles configurations have advantages in maneuverability, but pose a challenge in the water entry or water exit transitions. The interaction of a powered rotor with the air-water interface and its performance in a mixed air-water medium are poorly understood. Previous HAW vehicle strategies avoid a powered rotor with additional propulsion and buoyancy systems, constraining the design space. A custom test stand was constructed to better understand rotor performance during the air-water transition. By recording powered rotor performance during controlled water entries and exits in a large tank, several novel observations were made. Previously unrecorded phenomenon such as the gradual height and RPM dependent transition and the underwater ceiling effect are determined. These observations inform the development of the Transition Index TI, a novel metric that indicates the transition state of the rotor, without the need for specialized sensors or computationally intensive modeling. TI is applied to experimental data to make further observations, and is also used in a novel thrust prediction formulation. The first known low-order prediction of thrust through the transition is validated against experimental data, and allows for the development of a TI based controller. A preliminary controller implementation shows promising results in maintaining constant thrust through the air-water transition. Finally, a HAW vehicle to apply this controller is built. Careful consideration to the waterproofing and motor choice is shown and preliminary flight tests are demonstrated. Future expansion on the application of the novel TI and thrust prediction has great potential to advance the capabilities of hybrid aerial-water vehicles.Item MEADWORKS – HYDROLOGY, ECOLOGY, MEAD AND ARCHITECTURE(2019) Huck, Kyle Patrick; Noonan, Peter; Architecture; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This thesis seeks to redefine the relationship between communities and water infrastructure through a scalable and adaptable hybrid architectural solution. By focusing on the ambiguous intersection of nature and the built environment, this thesis will make an attempt at place-making in a setting typically disregarded by cities and communities. Challenging the boundaries of public infrastructure, architecture, and landscape architecture, this thesis will provide a dynamic solution to the water pollution epidemic of the Chesapeake Bay that involves subliminal community awareness and engagement. Through the program of a meadery, beekeeping, agriculture, and brewing will integrate with water treatment infrastructure to mutually benefit all processes.Item Water and Architecture: An Amphibious Solution to Urban Flooding(2018) Asson, Bryan Jonathan; Gabrielle, Julie; Architecture; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This thesis intends to address the phenomenon of urban erosion through an understanding and application of Metabolist principles. One of the core elements of the Metabolist movement is a versatile was a megastructure that would create a framework onto which program modules could be attached. Currently, cities like Cape Town in South Africa seek refuge as the water crisis looms overhead. However, In the United States continues to debate whether global warming is an issue. With storms and sea level changes becoming more prevalent it is clear that many cities and suburbs are at risk of being caught under water. At its core, this thesis exploration seeks to create proactive solutions to this global challenge by connecting people to the ecological systems that surround them. To achieve this, this thesis will look to determine place making modules and the interplay between a living space, a home, a community and an ecology.Item EVALUATION AND IMPROVEMENT OF MECHANICAL AND CHEMICAL RESILIENCE OF INTERMEDIATE-TEMPERATURE SOLID OXIDE FUEL CELL ANODES(2017) Hays, Thomas; Wachsman, Eric D; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Solid oxide fuel cells are in the process of reaching maturity as an energy generation technology, but a number of technical challenges exist, namely mechanical and chemical resilience, that hinder the realization of their full potential and widespread deployment. As more research and development work has been performed on intermediate temperature SOFCs based on gadolinium doped ceria, there persists a number of gaps in the understanding of the behavior of these devices. The mechanical properties of component material and SOFC structures in non-ambient conditions, the nature and degree of damage caused by sulfurized hydrocarbon fuels, and the potential for leveraging produced thermal energy are not satisfactorily characterized for GDC-based SOFCs. Mechanical testing of porous GDC and anode supported SOFC coupons from room temperature to 650°C was performed in air and reducing conditions using a test system designed and built for this application. Spherical porosity was determined to result in the higher strength compared to other pore geometries and a positive linear dependence between temperature and strength was determined for SOFC coupons. Additionally, placing the electrolyte layer in compressive stress resulted in higher strengths. Standard SOFCs were operated while exposed to hydrogen and methane containing ppm level hydrogen sulfide concentration. An infiltration technique was used to deposit a fine layer of GDC on the inner surfaces of some cell anodes, and the results of sulfur expose was compared between infiltrated and unmodified cells. GDC infiltration allowed cells to operate stably for hundreds of hours on sulfurized fuel while unmodified cells were fatally damaged in less than two days. A primary and a resulting secondary degradation mechanism were identified and associated with sulfur and carbon respectively through surface analysis. A novel technique for measuring thermal power output of small-scale SOFCs operating on a variety of fuels was developed and used to evaluate electrical and thermal outputs while operating on simulated anaerobic digester biogas. These findings were used to propose a multi-utility generation system centered on a nominal 10 kW SOFC unit fed by anaerobic digesters and capable of producing clean water and electricity for 50 individuals through direct contact membrane distillation driven by captured waste heat from the SOFC.Item ALLIES OR ADVERSARIES? THE AUTHORITARIAN STATE AND CIVIL SOCIETY IN ENVIRONMENTAL GOVERNANCE: A CASE STUDY OF THE MEKONG DELTA(2017) Wallace, Jennifer; Haufler, Virginia; Government and Politics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Natural resources are collective goods that the state has the authority and responsibility to protect from overuse and overexploitation. In order to achieve this protection, the state must rely on the actions of local actors, experts, and business leaders who are most closely connected to the natural resource base. The dependence of the state on local actors to implement resource-protection policies makes the conduct of environmental management within authoritarian regimes a particularly interesting area in which to observe the state’s strategic choices concerning its relations with civil society. The potential threat to state control posed by an emergent civil society means that the state must weigh its interests in maintaining its authoritarianism against the benefits provided by civil society, such as the ability to analyze and implement the state’s policies effectively. This dissertation focuses on how the government of Vietnam manages these apparent tensions between allowing participation on a critical issue area and maintaining its control as an authoritarian state. I argue that the state does not respond uniformly or consistently to all types of civil society actors, even within a single issue area such as natural resources protection. Prevailing explanations of why the authoritarian state has shown permissiveness toward civil society actors fail to account for variation in the state’s response to different actors and across levels of governance. In this paper I present an alternative framework that provides a more nuanced understanding of the state’s interests with respect to various types of civil society actors. I argue that the state’s engagement with various civil society organizations depends primarily on three characteristics: 1) the organization’s mobilizing capacity; 2) issue independence; and 3) the external strategic value of the organization. These three characteristics shape whether the authoritarian state of Vietnam views the organization as a threat to be subverted and repressed in order to maintain its own authority, or a cooperative partner in the management of the state’s natural resources. In addition, this dissertation discusses the implications for successful water management in the region.Item SUSTAINABLE ISLAND WATER CULTURE COLLECT, PROTECT, RESPECT(2016) Manongdo, Justin Agustin; Simon, Madlen; Architecture; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)As fresh water globally declines, our local communities are affected. This phenomenon is particularly acute in the islands of Hawai’i. The Hawaiians have a concept called Ahupua’a, which refers to the traditional land division system in Hawai’i. The goal of the research is to see how we can re-imagine island water culture to reintroduce authentic principles of the Ahupua’a to make modern developments sustainable. By addressing and understanding the experience, value of water, and history of its context, architecture can better be used as a tool for collecting, protecting and respecting water to create a deeper appreciation of this resource. This thesis project explores the human connection between water and landscape by utilizing architecture as a means for understanding the importance of this delicate resource. The research will be applied to the design of the Ala Wai Canal waterfront and boathouse in Waikiki. This project will serve as a test case for modern development with a focus on principles of the Ahupua’a and lessons to take for global uses.