Digital Commons Network^™

A Novel Approach To Orbital Debris Mitigation, Timothy S. Turk

Doctoral Dissertations

Since mankind launched the first satellite into orbit in 1957, we have been inadvertently, yet deliberately, creating an environment in space that may ultimately lead to the end of our space exploration. Space debris, more specifically, orbital debris is a growing problem that must be dealt with sooner, rather than later. Several ideas have been developed to address the complex problem of orbital debris mitigation.

This research will investigate the possibility of removing orbital debris from the Low Earth Orbit (LEO) regime by using a metaheuristic algorithm to maximize collection of debris resulting from the February 2009 on-orbit collision of …

Psychological Determinants Of Physical Activity And The Prediction Of Physical Activity Levels In African American Men, Alvin L. Morton Iii

Doctoral Dissertations

African American (AA) men experience disproportionally higher rates of non-communicable, chronic diseases (e.g., cardiovascular, type 2 diabetes, and renal failure) than White men. Physical activity (PA) is known to reduce the progression of CVD, type 2 diabetes, and renal failure. National statistics illustrate that AA men are less likely to get sufficient levels of PA to obtain health benefits. Although many factors (e.g., biomedical, socio-cultural) influence participation in PA, the psychological factors at the individual level are essential to beginning and maintaining activity. Therefore, understanding the psychological determinants of PA in AA men and their associations with meeting national guidelines …

Core-Collapse Supernova Simulations With Spectral Two-Moment Neutrino Transport, Ran Chu

Doctoral Dissertations

The primary focus of this dissertation is to develop a next-generation, state-of-the-art neutrino kinetics capability that will be used in the context of the next-generation, state-of-the-art core-collapse supernova (CCSN) simulation frameworks \thornado\ and \FLASH.\index{CCSN} \thornado\ is a \textbf{t}oolkit for \textbf{h}igh-\textbf{or}der \textbf{n}eutrino-r\textbf{ad}iation hydr\textbf{o}dynamics, which is a collection of modules that can be incorporated into a simulation code/framework, such as \FLASH, together with a nuclear equation of state (EOS)\index{EOS} library, such as the \WeakLib\ EOS tables. The first part of this work extends the \WeakLib\ code to compute neutrino interaction rates from~\cite{Bruenn_1985} and produce corresponding opacity tables.\index{Bruenn 1985} The processes of emission, …

Content Externalism And Self-Knowledge, Donnie Gene Barnett Jr.

Doctoral Dissertations

There appears to be a tension between two widely held philosophical theses: content externalism and what is often called “privileged access”. The first is the metaphysical thesis that the contents of many propositional attitude-types are at least partially determined by properties external to the thinking subject. The second is the epistemological thesis that we have a priori access to the contents of our own propositional attitudes. Those who hold that at least one of these theses must be false are called incompatibilists. My goal is to show that the incompatibilists are wrong, that content externalism and privileged access can both …

Coping Styles As Potential Mediators In The Relationships Between Morally Injurious Events, Moral Injury, And Meaning-Making, Marjorie A. Perkins

Doctoral Dissertations

Exposure to morally injurious events has consistently been correlated with negative mental health outcomes for military servicemembers and veterans (Bryan et al., 2014; Currier et al., 2015a; Currier et al., 2015b; Currier et al., 2017; Dennis et al., 2017; Jordan et al., 2017; Maguen et al., 2009, 2010; Maguen, Vogt et al., 2011; Nash et al., 2013). However, some servicemembers and veterans may experience a deeper sense of understanding of the event and/or growth after a potentially morally injurious experience through a process called meaning-making (Park, 2013). The present study seeks to examine the relationship between individual coping styles and …

Determination Of Near-Sol Carbon Impurity Content Due To Divertor Target Leakage Using Carbon-13 Tracers Via Methane Injection On The Diii-D Tokamak, Jonah David Duran

Doctoral Dissertations

Experiments with outer strike point injection of isotopically enriched methane (¹³CD­₄) in DIII-D L-mode discharges have demonstrated the ability to infer near scrape-off-layer (SOL) impurity density profiles based on: far-SOL collector probe (CP) measurements; a stable isotopic mixing model; and SOL impurity transport modelling. This work enables one of the first in-depth investigations on the source and transport of SOL impurities which could hinder performance of future fusion devices. Modelling by DIVIMP and 3DLIM of ¹³C SOL evolution is consistent with diagnostic observations and indicates that the buildup of injected impurities on plasma-facing surfaces must …

Constrained Collective Movement In Human-Robot Teams, Joshua Fagan

Doctoral Dissertations

This research focuses on improving human-robot co-navigation for teams of robots and humans navigating together as a unit while accomplishing a desired task. Frequently, the team’s co-navigation is strongly influenced by a predefined Standard Operating Procedure (SOP), which acts as a high-level guide for where agents should go and what they should do. In this work, I introduce the concept of Constrained Collective Movement (CCM) of a team to describe how members of the team perform inter-team and intra-team navigation to execute a joint task while balancing environmental and application-specific constraints. This work advances robots’ abilities to participate along side …

Research Data Management Policy & Organizational Compliance: An Exploratory Study In The Academic Context, Monica Inez Ihli

Doctoral Dissertations

Research data management (RDM) describes a broad array of processes and activities aimed at ensuring that data are documented, organized, findable, and preserved for future access. In January 2023, the National Institutes of Health will begin enforcing the strictest data management requirements of a U.S. federal agency to date, including potential consequences for organizations whose researchers fail to demonstrate compliance with commitments to data management and sharing. This dissertation makes two major assessment-based contributions in support of organizational preparedness for policy compliance. First, it reports the results of a pilot study at a high research institution for a survey instrument, …

The Dangerous/Endangered Modern Woman In Four Interwar Spanish Novels (1917-1936), Holly Villines

Doctoral Dissertations

The Modern Woman was a figure perpetually discussed in the early twentieth century, as she embodied the increasingly public role and greater mobility of women in industrialized cities. A century later, historians and literary critics still explore the significance of this female archetype, who was at the center of debates regarding feminism and changing gender dynamics, because the Modern Woman’s defiance of social conventions opened the way for the independent lifestyle and freedoms of women today. Yet, still left unexplored is the image of the Modern Woman as both dangerous and in danger and what this contradictory depiction reveals about …

Elucidating The Importance Of Structure, Surfaces, And Interfaces In Polymer Nanoparticles And Nanocomposites, Jacob E. Fischer

Doctoral Dissertations

This dissertation details research conducted to elucidate the importance of structure, surfaces, and interfaces in both polymeric nanoparticles and polymer nanocomposites. The fundamental understanding that is garnered in these studies provides a foundation to rationally develop nanocomposites tailored for unique functionalities, performance and applications.

Soft polymeric nanoparticles, have shown to imbue non-traditional diffusive properties, the strength of which decreases with crosslinking density of the nanoparticle. The crosslinking dependent morphology of these nanoparticles is first characterized in a dilute solution of good solvent (Chapter 2). The scattering results revealed that the structure ranges from a swollen polymer in good solvent (0% …

Controlling Polymer Molecular Structure And Morphology: From Illumination Of Conjugated Polymers To Polymer Chain Depolymerization, Josh Moncada

Doctoral Dissertations

Polymers remain a prominent component of our lives, and finding methods to control their structure or morphology are needed to tune material properties. This dissertation reports methods to alter the conformation, morphology, or structure of polymeric materials. Chapter two describes the impact of exposure to white light during annealing of conjugated polymer blends on their morphology and optoelectronic performance. The observed changes in the morphology correlate strongly to the variation in photoluminescence (PL) with illumination, including that the PL varies less with illumination at higher Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] loadings, offering foundational understanding to guide the structure and optoelectronic performance of conjugated polymer …

An Exploration Of Photography As A Wellness Tool For Counselors-In-Training, Charaya Chontay Upton

Doctoral Dissertations

Counselors-in-training (CIT) often experience a myriad of challenges during their academic studies. From balancing time, finances, acclimating to a new environment, fears of being judged or receiving negative feedback (Patterson & Levitt, 2012; Prosek et al., 2013; Warren & Nash, 2019), CIT physical (Neviyarni et al., 2018), mental (Prosek et al., 2013), and overall wellness (Lenz et al., 2012) tend to be impacted negatively. For these reasons, Counselor Educators (CE) have used wellness models and assessments to assist in the educational journey; however, wellness practices continue to decline for both CIT and practicing counselors (Abel et al., 2012; Lenz et …

Reconciling Self-Censorship: A Qualitative Study Of The Experiences Of University Staff And Administrators, Leigh C. Morales

Doctoral Dissertations

In addition to a global pandemic, the past three years have been marked by racial, social, and political unrest. These circumstances add meaningful context to examine and better understand factors that undermine free expression and contribute to self-censorship among university staff and administrators. To date, few studies have holistically explored the unique experiences of university staff and administrators with self-censorship and how this phenomenon affects their experience on college and university campuses. Understanding why staff and administrators choose to self-censor may allow for a deeper discussion about speech climate and the degree to which colleges and universities implement and uphold …

Three Essays In Experimental And Behavioral Economics, Vasudha Chopra

Doctoral Dissertations

This dissertation presents three essays that use experimental economics methods. The first essay examines how behavior in inter-group contests is altered when players have incomplete information on their opponent. The game is a Tullock contest with heterogeneous groups (differences in cost-of-effort, prize value, and group-size), and players only know the probability their opponent is a particular type. For cost and value treatments, incomplete information increases effort in uneven contests but has no effect in even contests. Group-level effort is higher in group-size treatments, but incomplete information does not systematically alter effort. Overall, group-level effort is much higher than what standard …

Natural, Experimental, And Educational Explorations Of The Interiors Of Terrestrial Planetary Bodies, Nadine L. Grambling

Doctoral Dissertations

Planetary interiors are enigmatic, inaccessible, and vital to the processes that have formed the rocks we see on the surface of bodies in the inner Solar System today. Based on geophysical explorations of the Moon and Earth, along with information gleaned from rocks at the surface today, there is understanding of the basic structure and processes at depth. Using a combination of natural samples and experimental studies, we attempt to learn more about the physical conditions beneath the surface, and their effect on material properties and tectonics processes in the mantle.

On Earth, mid-ocean ridge processes have long been debated, …

Hardware For Memristive Neuromorphic Systems With Reliable Programming And Online Learning, Ryan Weiss

Doctoral Dissertations

Alternative computing technologies are highly sought after due to limitations on transistor fabrication improvements. Fabricated memristive technology allows for a non-volatile analog memory for neuromorphic computing. In an integrated CMOS process, the synapse circuits designed for a spiking neuromorphic system can use memristors to regulate accumulation in the neuron circuits. Testing the fabricated memristive devices composed of hafnium oxide and developing a model to represent the key device characteristics lead to specific design choices in implementing the analog memory core of the synapse circuit. The circuits I designed for neuromorphic computing in this process take advantage of the unique capabilities …

Election Day Registration And Same Day Registration In State Legislative Districts, Rachel Fuentes

Doctoral Dissertations

Decades of research into the effects of voter registration requirements on turnout has found that voter registration disproportionately suppresses turnout among marginalized racial and socioeconomic groups that traditionally are represented by the Democratic Party. Research also shows that enacting Same Day or Election Day Registration (EDR/SDR) increases voter turnout for Democratic candidates in national elections. The conclusion drawn has been that EDR/SDR increases the representation of marginalized groups. The study in this paper challenges these findings in three ways. First, although EDR/SDR results in a larger total democratic vote, the claims of increased representation may be overstated. This study of …

Intra-Skeletal Variation In Stable Isotopes Through Non-Destructive Approaches: Applications Of The Patterns Of Skeletal Remodeling To Biological Anthropology, Armando Anzellini

Doctoral Dissertations

Stable isotope analysis is a well-established method in biological anthropology used to deliver data on residence, diet, and life history. Samples for these analyses are often collected from the diaphyses of long bones with an assumption of an expected rate of turnover between five and ten years, depending on the skeletal element. However, the biological foundations of this assumption are still uncertain, especially concerning the intra-skeletal and intra-element variation of isotopic signatures that may relate to patterns of remodeling. Exploring these gaps in intra-element isotopic variation requires fine-grained work using multiple bones from multiple individuals, but such work is limited …

Highlighting Teacher Voices: Discussions On Race And Racism In The Elementary Classroom, Carrie Lynn Buckner

Doctoral Dissertations

Throughout my career in education, I have observed that teachers are challenged by engaging in discussions involving race and racism. This study seeks to understand teachers’ feelings further when discussing race and racism in the elementary classroom by answering the research question: How do elementary teachers experience race and racism in their schools and classrooms?

This qualitative, critical narrative inquiry dissertation focused on three participant interviews with public-school elementary teachers in Tennessee. The data generated from these interviews informed narratives and were then analyzed through the lens of Critical Race Theory. This was followed by In Vivo and structural coding …

Peer-Mediated Interventions To Improve The Transition Behavior Of Children And Young Adolescents With Disabilities: A Systematic Review Of 50 Years Of Literature, Jorge A. Sandoval

Doctoral Dissertations

The purpose of this dissertation was to investigate the research available on the use of peer-mediated instruction and interventions (PMIIs) to improve the transition behavior of children and young adolescents with autism spectrum disorders (ASD) and intellectual and developmental disorders (IDD). PMIIs are evidence-based practices that involve the use of peers without disabilities to engage children with autism spectrum disorders (ASD) in positive and meaningful social interactions. The use of PMIIs is founded is on the premise that practitioners can use an individual with ASD/IDD’s possible response to a peer or peer’s social initiation as a teaching tool (McConnell, 2002). …

A Hydropower Facility As An Energy Water Signal Processor, Asha Shibu

Doctoral Dissertations

In recent times, various efforts have been made to address the challenge of adequately representing hydropower systems in modeling frameworks, accounting for the lack of data to represent the multiple constraints in hydropower operation. This research is a pilot data-driven methodology for characterizing, classifying, and comparing the water-to-energy and energy-to-water signal transformations that hydropower facilities as signal processors accomplish. In this study, a Box Jenkins transfer function/noise model is used to identify the relationship between reservoir inflows and outflows. For examining the feasibility of this methodology, 5-minute fleet data for five storage and five run-of-river facilities was provided by the …

Evaluation Of Distributed Programming Models And Extensions To Task-Based Runtime Systems, Yu Pei

Doctoral Dissertations

High Performance Computing (HPC) has always been a key foundation for scientific simulation and discovery. And more recently, deep learning models' training have further accelerated the demand of computational power and lower precision arithmetic. In this era following the end of Dennard's Scaling and when Moore's Law seemingly still holds true to a lesser extent, it is not a coincidence that HPC systems are equipped with multi-cores CPUs and a variety of hardware accelerators that are all massively parallel. Coupling this with interconnect networks' speed improvements lagging behind those of computational power increases, the current state of HPC systems is …

A Study On Early Age Properties Of Concrete For Precast And 3d Printing, Debalina Ghosh

Doctoral Dissertations

Concrete is the second-most consumed material, leading the global Portland cement production of 4.1 billion tons in 2020 and 5-8% of global Carbon dioxide (CO₂) emission annually. As with any other material and practice, the construction industry is also ever-changing to meet market demand, evolving technology, and resource limitation. In the case of concrete construction, one of the main concerns is the lack of automation. In the last few decades, some new construction methods have risen to address this concern. Some of these economic and successful practices are precast construction, self-compacting concrete (SCC), and 3D printing of concrete(3DPC). …

Principal In Name Only: A Mixed Methods Study Of How Catholic School Governance Models Affect Leadership, Davis H. Bodie

Doctoral Dissertations

Catholic school principal effectiveness has been studied for years, along with the retention and attrition rates of Catholic school principals. Throughout the long history of Catholic education in the United States and around the world, there has not been a meaningful study of how the different governance models available to Catholic schools affect these school leaders. Through this explanatory sequential mixed methods research study, connections between different governance models and interactions with religious authority figures and offices and principal job satisfaction, retention, and attrition were evaluated. Results will allow current and future principals to be more informed concerning the best …

Examining Perceptual And Categorical Influences On Visual Working Memory, Kara Nicole Lowery

Doctoral Dissertations

Visual working memory (VWM) refers to the limited capacity storage of visual information used for behaviors like problem-solving, planning, or reasoning. VWM is a crucial component of cognition, and individual differences in capacity during childhood have been linked to outcomes in academic achievement, fluid intelligence, and socioemotional development. VWM increases in capacity and precision throughout development. Very few studies have investigated what factors influence changes in VWM abilities in preschool-aged children. The first goal of this study was to examine VWM precision development in this age-range. This was accomplished by administering a delayed estimation task. In this task, children touched …

Specificity Of Infant Statistical Word Segmentation, Sara Parvanezadeh Esfahani

Doctoral Dissertations

By their first birthday, infants develop sensitivity to language-general (e.g., transitional probability (TP) between syllables) and language-specific (e.g., lexical stress pattern) cues to identify word boundaries. Across 5 experiments, I investigated two questions: 1) how do English learning 8-month-old infants segment high TP (TP=1; HTP) words in non-native languages that have a different rhythm and prosody? 2) how do English learning 8-month-old infants represent nascent word representations across indexical (i.e., talker’s voice), segmental (i.e., onset consonant) and suprasegmental (i.e., stress pattern) information? To that end, in each experiment, using HTPP, I familiarized infants with a familiarization corpus with two embedded …

Analysis Of Physicochemical Properties And Terrestrial Dynamics Of Mechanically Formed Micro-Nano Scaled Particles From Agricultural Plastic Mulches, Anton Friedrich Astner

Doctoral Dissertations

Release of microplastics (MPs) and nanoplastics (NPs) into agricultural fields is of great concern due to their reported ecotoxicity to organisms that provide beneficial service to the soil such as earthworms, and the potential ability of MPs and NPs to enter the food chain. Most fundamental studies of the fate and transport of plastic particulates in terrestrial environments employ idealized MP materials as models, such as monodisperse polystyrene spheres. In contrast, plastics that reside in agricultural soils consist of polydisperse fragments resulting from degraded films employed in agriculture. There exists a need for more representative materials in fundamental studies of …

Local Ipos And Retail Investor Trading, Guanhuan Wang

Doctoral Dissertations

This paper examines how salient events affect retail investors’ trading behavior. Using data on households’ trading records from a large discount broker between 1991 and 1996, I find that Initial Public Offerings (IPOs) significantly increase the trading activities of local retail investors of stocks in the same industry over the subsequent year. The effect is stronger for less sophisticated investors and investors who live closer to the IPO firm’s headquarters, consistent with salience as the channel. I also find that retail investors are net buyers of stocks right after the local IPOs and become net sellers after a year and …

Light Matter Interactions: A Study Of Soft Materials Using Linear And Nonlinear Spectroscopy, Muhammad Redwan Hassan

Doctoral Dissertations

The adoption of complex fluids for various industrial applications is becoming normal. Complex fluids offer tunability, wide range solubility, and chemical and thermal stability which are the factors that conventional polar and non-polar solvents often lack. However, fundamental studies of these fluid systems are still lacking which is limiting the appropriate use of these complex fluids in many applications. The goal of this dissertation was to study and characterize complex fluids for application in electrolytes for redox flow batteries. Chapter 3 and chapter 4 feature the study of microemulsions and deep eutectic solvents (DES) by fluorescence techniques. Fluorescence studies of …

Geochemical And Climatic Controls On The Sulfur Cycle In Volcanic Settings: Implications For The Origin Of Sulfur-Rich Deposits Investigated By The Spirit And Opportunity Rovers On Mars, Rhianna D. Moore

Doctoral Dissertations

On Earth, volcanic activity with elevated sulfur (S) degassing in the presence of water leads to the formation of hydrothermal deposits enriched in S-bearing minerals. Similar processes may have been an important source of S on Mars. The landing sites of Gusev crater and Meridiani Planum investigated by the Spirit and Opportunity rovers, respectively, showed elevated SO₄^2- [sulfate] concentrations, suggesting high- and low-temperature aqueous processes. However, the SO₄^2- contribution from subsequent aqueous weathering of hydrothermal S deposits has been poorly constrained, thus its importance to regional S cycling in the landing sites is unclear. In this …