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A Comprehensive Study Of Uncertainties In The Modeling Of Binary Neutron Star Outflows, Amelia Michele Henkel

Doctoral Dissertations

Binary neutron star (BNS) mergers have recently become a tool to study extreme gravity, nucleosynthesis, and the chemical composition of the Universe in a new way. In order to accurately identify electromagnetic signals of neutron star mergers, both in the future and retroactively, better constraints on their merger signatures are required. Specifically, BNS outflow properties (such as the mass and composition) are particularly insightful, as they provide a link between the intrinsic properties (such as the stellar masses and radii) and observables. In this thesis, I put forth multiple ways of classifying uncertainties associated with BNS mass outflow models. First, …

An Integrated Study Of Instrument Performance And Scientific Yield: Evaluation Of The Grape Design, Karla Georgina Onate Melecio

Doctoral Dissertations

This dissertation presents the end-to-end development, characterization, and in-flight validation of the 3-dimensional Gamma-Ray Polarimeter Experiment (GRAPE), a wide-field-of-view (FoV) Compton polarimeter designed for high-energy astrophysics. The primary scientific motivation is to address unresolved questions in the physics of Gamma-Ray Burst (GRB) jets, for which gamma-ray polarimetry is a critical diagnostic. GRAPE is designed to measure the degree and angle of $\gamma$-ray polarization within a targeted energy band of \SIrange{50}{500}{keV} to cover the peak energy output (E$_{pk}$) of observed GRB spectra. This work establishes the instrument's scientific readiness through two principal contributions. First, the instrument's fundamental low-energy response was characterized …

Efficient Algorithms For Mitigating Uncertainty And Risk In Reinforcement Learning, Xihong Su

Doctoral Dissertations

Reinforcement learning~(RL) studies the methodologies of improving the performance of sequential decision-making for autonomous agents and has achieved remarkable success in domains such as games, robotics, autonomous systems, finance, and healthcare. The Markov Decision Process~(MDP) is a mathematical framework for modeling agent-environment interactions in sequential decision-making problems. There are two primary sources of uncertainty in RL: epistemic uncertainty and aleatoric uncertainty. In RL, risk refers to the potential for an agent's policy to lead to undesirable outcomes, especially when the environment is uncertain. In many domains, researchers seek policies that maximize the objectives while mitigating the uncertainty and risk in …

Teachers' Evaluation And Reporting Orientations And Their Impact On Elementary Students' Motivation: A Secondary Analysis Of Ecls-K: 2011 Data, Melissa L. Lefebvre

Doctoral Dissertations

Few studies examine the specific component of teacher evaluation and reporting and its relationship with student motivation. Student motivation to learn and achieve is a fundamental element of academic success in school. Motivation has been linked to educational outcomes like curiosity, persistence, learning, conceptual understanding, and long-term achievement (Vallerand et al., 1992). Diminished motivation can lead to consequences such as higher dropout rates and increased anxiety. Research indicates that classroom climate and student-teacher relationships have the most significant impact on student motivation (Jansen et al., 2022). This dissertation explores the association of teachers’ evaluation and reporting practices with student motivation. …

Focal Engine: Filling A Gap Between Game Engines And Big-Data Scientific Visualization Packages, Kindrat Beregovyi

Doctoral Dissertations

This dissertation presents Focal Engine, a novel 3D visualization engine designed to bridge the gap between game engines and scientific visualization tools. Game engines offer accessible interfaces and high-performance rendering but struggle with large-scale scientific datasets, while tools like ParaView and VTK handle complex data structures effectively but lack intuitive editing capabilities and modern rendering features. Focal Engine combines the accessibility and rendering performance of game engines with the data handling capabilities and analytical tools of scientific visualization platforms. The engine's capabilities are validated through multiple applications and projects, for example: HabiCAT 3D performs 3D complexity measurements on ocean floor …

Development And Characterization Of Bulk Dsdna-Based Materials Using Biologically Derived Plasmid Dna, Wynter Amythyst Paiva

Doctoral Dissertations

Double-stranded DNA (dsDNA) exhibits many unique sequence-independent properties that remain underutilized in materials science. The exceptional length, solubility, biocompatibility, imageability, molecular recognition capabilities, and topological control of DNA makes it an ideal candidate for the creation of bespoke biomaterials and investigation of fundamental relationships in polymer physics. Unfortunately, translation of DNA-based materials from the microscale to macroscale has been hindered by source constraints and limitations in chemical modification of biologically derived DNA. This work seeks to expand the utility of dsDNA from the benchtop to real world applications. Establishing dsDNA as a commodity polymer will aid in the development of …

The Baroclinic Route To Acoustic Streaming: Mechanisms Of Mean-Flow Generation And Heat Transport In Acoustically-Forced Stratified Fluids, Remil Mushthaq

Doctoral Dissertations

Standing acoustic waves in density-stratified fluids confined within horizontal channels generate fluctuating vorticity baroclinically, driving mean streaming flows that are much stronger and qualitatively distinct from classical Rayleigh streaming. Theoretical and numerical studies have shown that these baroclinic acoustic streaming flows can reach speeds comparable to the maximum speed of the oscillatory sound-wave field, enabling fully two-way wave/mean-flow coupling: the streaming flow modifies the background density field, which then alters the structure of the acoustic waves. Extending this framework, Massih (2022) quantified the heat-transfer enhancement arising from baroclinic streaming as a function of the channel aspect ratio (δ). The present …

Investigation Of Cross-Flow Turbines With Varying Structural And Surface Properties, Nicole Marone

Doctoral Dissertations

The oceans are a largely untapped resource with regard to their tidal, wave, and ocean current energy potential and could significantly contribute to clean energy objectives. Cross-flow turbines (CFTs) can be used to extract energy from tidal currents and provide electrical energy to the power grid. However, one of their main barriers to market entry is their levelized cost of energy (LCOE), which at present is still quite high. Three parameters that have not previously been studied together, and that could make CFTs more cost-competitive, include the use of less rigid and less expensive materials, a reduction in the number …

Adrift: The Influence Of Shelf Circulation And Larval Dispersal On Coastal Biogeography At Basin And Global Scales, Will Lush

Doctoral Dissertations

The dispersal of larvae plays an important role in determining the distribution of benthic meroplanktonic organisms in the coastal ocean. The work presented in this defense uses biophysical modeling approaches to examine the interaction of larval dispersal with coastal circulation and the impact of these interactions on contemporary coastal biogeography at global scales.I begin by presenting a novel method for validating numerical dispersal estimates against drifter observations from the Global Drifter Program. We find that median dispersal estimates match observations to within 5 percent, while model estimates underpredict the spread of drifters around this median by between 30 and 50 …

Secret Key Generation Based On The Physical Layer Characteristics For Iot Networks, Abdullah Dakhlallah Alshamdayn

Doctoral Dissertations

The rapid expansion of low-resource devices, coupled with advances in telecommunications, has significantly increased the number of connected devices and enabled the development of affordable, energy-efficient, portable, and high-performance sensors for diverse applications. However, this convenience comes with security and privacy concerns related to the reliability of hardware, software, and communication infrastructure. The extensive interconnectivity of limited-resource devices and the transmission of large data volumes pose significant security challenges in wireless networks. The future wireless technologies, such as 5G, will enable the transfer of critical data, including personal, financial, military, and industrial information, necessitating secure communication in wireless networks. Generally, …

Advanced Plant Growth Using Halloysite Nanotubes (Hnts) And Waste Extraction For Medical Applications, Zeinab Jabbari Velisdeh

Doctoral Dissertations

This dissertation presents an integrated research framework that bridges nanotechnology, green chemistry, and sustainable agriculture, aiming to address two critical global challenges: enhancing plant growth under resource-limited conditions and valorizing agricultural waste for bioactive compound extraction. The study is divided into three major projects that together highlight the innovative application of magnesium oxide-coated halloysite nanotubes (MgO-HNTs) and the development of environmentally conscious extraction methods for high-value phytochemicals. The first component of this work investigates the design, fabrication, and functional evaluation of MgO-HNTs as advanced nanocarriers for promoting seed germination and early root development in tomato plants. MgO-HNTs were synthesized via …

Towards Robust Autonomous Systems: Handling Multi-Modal Uncertainties In Gps-Denied Environments, Vivya Kalidindi

Doctoral Dissertations

This dissertation focuses on designing a robust and uncertainty-aware framework for autonomous systems operating in GPS-denied environments, such as indoor infrastructures, underground tunnels, and lunar surfaces. The proposed framework addresses the challenges posed by multi-modal uncertainties, including sensor noise, distributional shifts under adverse conditions, and conflicting decision-making preferences. These challenges compromise the reliability and adaptability of autonomous platforms. To overcome these challenges, the proposed framework adopts a layered architecture that integrates advanced methodologies across the sensing, perception, and decision-making layers. At the sensing layer, an Edge-Kalman Filter combined with a density ratio-based update mechanism is employed to reduce aleatoric uncertainty …

Investigation Of Electrochemical Corrosion Fatigue Mitigation Strategies For Mild Carbon Steel, Joel Andrew Hudson

Doctoral Dissertations

Corrosion fatigue remains a critical durability challenge for steels used in boiler tubes and other safety-critical components, where the interaction of cyclic stresses and corrosive environments accelerates material degradation. This dissertation comprises three experimental studies aimed at advancing mitigation strategies and test methodologies: (1) enhancing corrosion resistance through electrodeposited Fe-Ni anodic coatings, (2) inducing synthetic crack closure to suppress fatigue crack growth, and (3) developing an accessible, low-cost, automated testing system to investigate environmentally assisted cracking (EAC) under controlled laboratory conditions. The first study examined the corrosion behavior of Fe and Fe-Ni electrodeposits synthesized from sulfate-based baths and applied to …

Synthetic And Analytical Methods For Metal Targeting Peptides For The Sensing And Removal Of Metals Across Various Matrices, Emily Andrews

Doctoral Dissertations

Metal chelators developed from peptides boast favorable attributes such as low toxicity, ease of synthesis, and high tunabilty to the target metal ion. It is for these reasons that peptides are used for metal sensing and sequestration in the body and environment. Herein, two unique sets of metal targeting peptides are discussed: (1) bifunctional Szeto-Schiller and Kelley peptide probes to signal the presence of and remove labile iron (Fe2+ and Fe3+) in the mitochondria, to mitigate the progression of Ferroptosis and (2) Pb2+ targeting peptides designed to exist in aqueous environments for the removal of toxic lead ions from waterways. …

Multiscale Modeling And Analysis Of Biomedically Relevant Uhmwpe-Based Composite Materials, Stanislav Buklovskyi

Doctoral Dissertations

The development of ultra-high-molecular-weight-polyethylene (UHMWPE) based composite materials continues to present significant opportunities in biomedical engineering, particularly in joint arthroplasty and implant technologies. As applications expand, the need for accurate modeling of microstructure–property relationships to guide informed material design and manufacturing decisions is increasing. This dissertation presents a multiscale numerical modeling framework informed by X-ray micro-computed tomography (μCT) data to corelate the effective mechanical, thermal, and electrical properties of biomedically relevant composite systems with their microstructure.

Two material systems are considered: UHMWPE reinforced with conductive carbon black (CB) nanoparticles, and porous UHMWPE with two processes of pores generation. For CB/UHMWPE …

From Structure To Specificity: Biophysical Characterization Of Functional Interfaces In Protein Systems, Logan M. Brown

Doctoral Dissertations

Proteins are nature’s dynamic molecular machines, operating across a spectrum from highly ordered scaffolds to intrinsically disordered systems, and executing functions that depend on both precise structures and conformational flexibility. Yet, the mechanistic rules linking sequence, structure, and activity particularly in disordered proteins and specialized functional adaptations remain incompletely understood. This dissertation addresses that gap by integrating structural biology, biophysics, and protein engineering to dissect molecular recognition, stability, and function across three diverse yet thematically connected protein systems. Building on this understanding of protein structure and function, the following four projects apply these concepts to address diverse biological questions, ranging …

Interpolated Factored Green's Function (Ifgf) Method Of Acceleration For Electromagnetic Scattering Off Of A Perfectly Electrically Conducting Surface, Mathew D'Amico

Doctoral Dissertations

Boundary integral equation (BIE) methods are advantageous in scattering problems due to their reduction of the problem's dimensionality as well as their automatic satisfaction of far-field radiation conditions. Specifically, for electromagnetic scattering off of perfectly electrically conducting (PEC) geometries, we are concerned with the magnetic field integral equation (MFIE). Typically, BIE implementation is iterative, with each direct integration requiring $\mathcal{O}(N^2)$ operations for a grid size $N$. For large $N$, this incurs very large computation times. To date, all existing methods that reduce the asymptotic operational complexity of evaluating the MFIE integral to $\mathcal{O}(N\log N)$ rely on use of the Fast …

Investigations Into Prior Knowledge And Self-Efficacy As Predictors Of Exam Performance In General Chemistry, And Student Interactions With Chemistry Textbooks, Gordon Hunter

Doctoral Dissertations

The first chapter addresses the validity and reliability of the Motivated Strategies for Learning Questionnaire (MSLQ) as a tool for chemistry education research. The study shows that the original MSLQ did not meet modern standards of reliability and presents a modified version that better captures self-efficacy in chemistry-specific contexts. The revised instrument shows improved model fit, reinforcing the importance of refining assessment tools for chemistry education research.The effects of prior knowledge and self-efficacy on student performance in a first-semester general chemistry course are investigated in the second chapter. Self-efficacy, defined as a learner's belief in their capability to successfully accomplish …

Planning Responses To Drinking Water System Emergencies, Jingyan Huang

Doctoral Dissertations

Despite extensive efforts to ensure clean and safe drinking water, drinking water contamination emergencies remain a persistent challenge in the United States. These events can result in widespread public health impacts, economic losses, and long-term environmental damage, particularly when triggered by hazardous chemical releases. Effective management of such crises requires a dual focus on both technical preparedness and human decision-making. This dissertation addresses these challenges through a two-part investigation that bridges pre-incident planning and post-incident response. It is guided by two core research objectives: (1) to evaluate commonly applied emergency countermeasures from both resilience and sustainability perspectives; and (2) to …

Psychological Factors Of Acting Talent And Success: You've Got "It", Lorelei Tierney Himlin

Doctoral Dissertations

The goal of an actor is to become invisible, bringing a character to life so convincingly that the audience forgets the actor exists outside the role. Different schools of acting often describe differing methods of portraying characters to this same general effect. To followers of the Meisner school, for example, “acting is behaving truthfully under imaginary circumstances” (Meisner et al., 1987). The “truthful” part involves creating a comprehensive mental model of a character’s imagined personality in order to fully embody that personality and extrapolate it to a situation. Then the actor uses a variety of acting techniques to think and …

Multi-Level Characterization And Testing Of Fatigue, Fracture And Creep Of The Ultra-High Strength Low-Alloy Steel Fabricated Via Laser Powder Bed Fusion, Nemanja Kljestan

Doctoral Dissertations

This dissertation presents a comprehensive experimental investigation of the mechanical behavior of an high-strength low-alloy (HSLA) steel fabricated via laser powder bed fusion (LPBF). The work focuses on fatigue strength, laser shock peening (LSP) effects, creep behavior, fatigue crack growth and fracture toughness. Fatigue strength was assessed using rotating bending tests, showing superior performance of LPBF specimens compared to as-cast materials due to the dual-variant martensitic microstructures. Laser shock peening enhanced fatigue life by inducing compressive residual stresses, delaying crack initiation and slowing crack propagation. Creep behavior was evaluated for different layer thicknesses, with thinner layers improving secondary creep resistance …

Analyzing Regions For The Study Of Localized Fluctuations In The Ground Magnetic Field For The Development Of A Global Risk-Assessment Forecast, Michael Kavanagh Coughlan

Doctoral Dissertations

The dynamic relationship between the solar wind and the Earth's magnetic field can produce rapid changes in the geomagnetic field measured on the ground ($dB_H/dt$). The fluctuations can be highly localized, with differences of up to 100s of nT/min in a small geographic area. The field of space weather is entering a more data-driven era, with enormous amounts of publicly available datasets from satellites and ground measurements. In this work modern machine learning techniques were employed to make forecasting risk-assessment predictions of large and localized $dB_H/dt$, and model explainability methods were employed to understand the non-linear connections being made. These …

Counting Kelp: Development And Assessment Of Modelling Approaches To Improve Understanding Of Kelp Bed Abundance And Resilience In The Gulf Of Maine, Constance N. Tyler

Doctoral Dissertations

Kelp habitats in the Gulf of Maine are threatened by rising ocean temperatures and marine invasions. The replacement of kelps with red turf macroalgae fundamentally alters these habitats and disrupts the ecosystem services they provide. Thorough assessment and monitoring of kelp habitats is needed for proper conservation of these habitats, but most long-term monitoring is performed using traditional survey methods that are restricted in the amount of space they can cover. Habitat modelling approaches are required to expand our knowledge of Gulf of Maine kelp habitats, and to better understand the interactions between kelp and red turf habitats across the …

Verifying Interchange Reconnection Models For Magnetic Switchbacks Using The Parker Solar Probe And Mms, Emily Owen Mcdougall

Doctoral Dissertations

Ever since their initial observation by the Ulysses probe, many models of magnetic switchbacks were put forth, but relatively little empirical evidence exists to verify these models, especially in terms of the ions that make up the accompanying plasma. I take energetic particle data from the Parker Solar Probe within switchbacks to provide experimental evidence to bolster the interchange reconnection driven models with particular interest in the interchange reconnection driven linear model. Statistical Analysis of switchbacks in the vicinity of CMEs, solar flares, and high-speed streams show properties consistent with the linear interchange reconnection model, and an analysis of switchbacks …

Bio-Acoustical Statistical Signal Processing For Detection, Classification, And Population Estimation In Wildlife Monitoring, Yue Liang

Doctoral Dissertations

Sound is a primary way for many animal species to communicate, forage, navigate, and assess their environment. As a result, passive acoustic monitoring (PAM), the recording and analysis of animal vocalizations, has become a valuable, non-invasive alternative to visual surveys. However, the massive volume of acoustic data generated annually, often reaching hundreds of terabytes, presents a significant challenge for efficient analysis. Since manual inspection of every frame in such data is infeasible, it is essential to develop automated detection and classification tools.

This thesis investigates and develops several statistical signal processing and machine learning techniques to address this challenge. The …

Resolving The Role Of Wave-Induced Pressure Gradients On The Movement Of Sediments In Nearshore Environments, Melissa Marry

Doctoral Dissertations

Characterizing the hydrodynamic forces responsible for the initiation of sediment motion is fundamental for improved understanding of large-scale sediment transport processes in nearshore environments. Traditional sediment transport models assume incipient sediment motion is only driven by the force applied by bed stress (Bagnold, 1966; Shields, 1936) while more recent work has shown that incipient motion is influenced by the forcing of the horizontal pressure gradient due to surface gravity waves (Foster et al., 2006; Frank et al., 2015; Sleath, 1999). Wave-induced vertical pressure gradients can also destabilize the sediment bed through the process of momentary liquefaction (Florence et al., 2022b; …

Essays On International Trade, Aochen Xiao

Doctoral Dissertations

This dissertation has two chapters.In Chapter 1, I develop a model of international trade with innovation and trade surplus to examine the effects of China’s large trade surplus on productivity. I abstract from future benefits from holding a present trade surplus and focus on the present gains in productivity. I find that the average productivity increase caused by trade surplus ranges from 1.2 percentage points to 5.46 percentage points when the innovation cost changes. These results explain China’s long-term export promotion policies and align with its new policy goal of developing “new productivity forces”. I also identify a negative effect …

Technologies To Support Remote Work For Collaborative Groups, Alberta Ansah

Doctoral Dissertations

The nature of work continues to evolve, particularly in the aftermath of the COVID-19 pandemic. While a substantial number of employees have returned to traditional, in-person work environments, many continue to engage in remote or hybrid work arrangements. Online meetings are a significant aspect of remote work, and while there has been a significant increase in this area, there are still aspects of these meetings that are not fully understood. Existing research in this area has primarily focused on the development of tools to facilitate meeting execution and content management. In contrast, relatively few studies have explored the social dynamics …

Eastern Oyster, Crassostrea Virginica, Genomics In A Well-Mixed Estuarine System: Examining Population Structure, Viability, And Response To Stressors, Alyssa Strickland

Doctoral Dissertations

Eastern oysters, Crassostrea virginica, are foundational estuarine species that contribute to a variety of ecosystem services including water filtration, nutrient cycling, habitat creation, and shoreline protection. However, populations have declined due to disease, overharvesting, habitat loss, and climate change, especially in northern systems such as New Hampshire’s Great Bay Estuary (GBE), located in the Gulf of Maine, one of the world’s fastest warming waters. This dissertation uses genomic and transcriptomic approaches to understand the drivers of population structure, decline, and resilience in GBE oyster populations, aiming to aid restoration and aquaculture. Chapter 1 used low-coverage whole-genome sequencing to understand population …

Addressing Economic Valuation Issues Of Outdoor Recreation: Case Studies Of Lake Michigan Invasive Carp And Plum Island Visits, Iris Tryfoni

Doctoral Dissertations

Environmental valuation is the process of assigning monetary value on environmental goods and services, which do not easily have market prices. It is, however, possible to over- or underestimate the economic valuation of outdoor recreation issues, specifically (1) recreational fishing and (2) beach recreation. Despite their different focuses, both case studies share a common objective of refining methodologies to better understand and address complex environmental issues from an economic perspective. Traditional recreation valuation techniques often lack explicit connection to ecology, which can be impacted by various factors. Addressing this gap, in the first part of my dissertation, I propose a …