Digital Commons Network^™

Apparatus And Instrumentation Design For Investigation Of Surface Impact Effects On Superconductivity, Austin Back

All Theses

The effects of ion irradiation on the physical properties of materials make EBITs an invaluable tool for many scientific and engineering fields. Many experiments rely on the use of these lab setups to test for device reliability, explore surface physics phenomena, and replicate the environment for many physical systems that are not readily accessible. We seek to extend the capabilities of these experiments using the CUEBIT and a new sample holder installed in section 3.

This thesis begins by presenting an overview of the CUEBIT and the basic operations of the equipment. This is followed by a brief explanation of …

Impacts Of Preferential Flow On Tc-99and Np-237 Vadose Transport In Soils At The Savannah River Site, Josh Parris

All Theses

Since the 1950s, the United States has produced approximately 90,000 metric tons of spent nuclear fuel (SNF) (Office of Nuclear Energy, 2022); however, no long-term storage solutions are available. Technecium-99 and neptunium-237, two fission products found in SNF, readily form highly mobile species in oxidizing conditions (Hu, 2008; Bondietti, 1979) and have respective half-lives of 2.13 x 10⁵ and 2.14 x10⁶ years (Hu, 2010). Considering these characteristics, ⁹⁹Tc and ²³⁷Np are two risk-driving isotopes found in SNF storage. The process of macropore-facilitated preferential flow, transport through cracks within a soil matrix, has been recognized to increase …

The Characterization Of Atmospheric Turbulence And Its Effect On Laser Beam Propagation, Michael Cox

All Theses

Having a controlled environment to measure atmospheric turbulence is essential to understanding its effects on different laser beam characteristics. The Clemson Variable Turbulence Generator (VTG) has the capability to propagate a laser beam up to 100 m and be able to dial many turbulence settings up to a heat flux of 357 W/m². A high-speed camera, power detector, and high-resolution temperature probes characterize the VTG with theoretical turbulence spectrums. The exponent associated with the Rayleigh-Bénard (RB) temperature structure constant equation is studied. Two different laser beam profiles are used throughout this work: Gaussian and Asymmetric Perfect Vortex (APV). …

Individual Differences In Vulnerability To Phishing, Fake News, And Vishing, Jeff Black

All Theses

Digital deception, such as phishing emails, scam phone calls, and fake news, poses a threat to anyone using digital devices. Research on digital deception often points to individual differences like age, cognitive impulsivity, and digital literacy, but has only investigated different types of digital deception independent of each other. Therefore, it is unclear whether users vulnerable to one type of deception are also vulnerable to others, and why. The present research examined relationships between vulnerability to different types of deception, and how this vulnerability is associated with common individual differences like age, cognitive impulsivity, digital literacy, and gullibility, and exploratory …

The Myth Of Perfection: Charting The Rhetoric Of Veteran Disability For A Course To Stability, Nicholas Rader

All Dissertations

This dissertation rhetorically analyzes discrimination in Western institutional discourses and documentation procedures, such as architectural texts and procedures, through a historiographic lens. An analytical methodology will be offered to show how discrimination of intersectional bodies is historically informed and reaffirmed by the manipulation of Western myths and mythos. Specifically, by mapping navigational mathematics and cartographic methods over rhetorical, architectural, and historiographic theory, it will be shown how the manipulation of Western myths establishes and reifies patriarchal discrimination that eventually fissions into eugenicist logics in nineteenth and twentieth century France, England, and the United States. In modernity, the practice of manipulating …

Assessing What We Value: Interactions Between Student Perceptions Of Assessments In The Calculus Classroom And Their Future-Oriented Motivation, Catherine Kenyon

All Dissertations

This work investigates interactions between first-year engineering (FYE) student perceptions of Calculus exams, their perceptions of the future, and their levels of math test anxiety. All phases of this study were conducted at a very high research (R1) institution with a common FYE program and coordinated Calculus courses. An initial pilot study explored how FYE students perceive the purpose of taking Calculus exams and how math test anxiety may play a role in these students’ perceptions of exams and their future in engineering. A second pilot study expanded on these results concerning student perceptions of Calculus exams and math test …

Modeling Antihypertensive Therapeutic Inertia And Intensification To Support Clinical Action Toward Hypertension Control, Benjamin Martin

All Dissertations

Background

Hypertension is the leading modifiable risk factor for cardiovascular disease and consequent mortality worldwide. In the U.S., more than half of hypertension cases remain uncontrolled, despite availability of effective pharmaceutical treatment options. Evidence suggests that therapeutic inertia, defined as clinician failure to initiate or increase therapy when treatment goals are unmet, is the most influential barrier to improving hypertension control. Substantial rates of therapeutic inertia have been reported in ambulatory primary care settings where hypertension is typically treated and managed. Understanding and overcoming the forces driving therapeutic inertia in hypertension management is a critical strategy to reach population health …

Hydrothermal Synthesis Of Frustrated Lanthanide Pyrochlores And Transition Metal Double Perovskites And Germanates, Matthew S. Powell

All Dissertations

Magnetically frustrated materials hold promise of unique behavior allowing for the novel study of quantum phenomena. Such materials are poised to become an integral foundation for technological advancement in the post-Silicon Age. Crystalline materials are given special focus where the rigid lattice allows more detailed study of these quantized effects and frustration behavior. As opposed to polycrystalline powders, large single crystals can be preferentially aligned enabling the study of anisotropic behavior. Two cubic structure types have garnered significant interest due to their 3-D tetrahedral arrangement of symmetry-related metal centers with the potential for magnetic frustration: pyrochlores and perovskites.

The supercritical …

Accelerating The Derivation Of Optimal Powertrain Control Strategies Using Reinforcement Learning And Virtual Prototypes, Daniel Egan

All Dissertations

The push for improvements in fuel economy while reducing tailpipe emissions has resulted in significant increases in automotive powertrain complexity, subsequently increasing the resources, both time and money, needed to develop them. Powertrain performance is heavily influenced by the quality of their controller/calibration with modern powertrains reaching levels of complexity where using traditional design of experiment-based methodologies to develop them can take years. Recently, reinforcement learning (RL), a machine learning technique, has emerged as a method to rapidly create optimal controllers for systems of unlimited complexity directly which creates an opportunity to use RL to reduce the overall time and …

Multiparametric Continuous And Mixed-Integer Nonlinear Optimization With Parameters In General Locations, Andrew Pangia

All Dissertations

Convex programming has been a research topic for a long time, both theoretically and algorithmically. Frequently, these programs lack complete data or contain rapidly shifting data. In response, we consider solving parametric programs, which allow for fast evaluation of the optimal solutions once the data is known. It has been established that, when the objective and constraint functions are convex in both variables and parameters, the optimal solutions can be estimated via linear interpolation. Many applications of parametric optimization violate the necessary convexity assumption. However, the linear interpolation is still useful; as such, we extend this interpolation to more general …

Deep Reinforcement Learning And Game Theoretic Monte Carlo Decision Process For Safe And Efficient Lane Change Maneuver And Speed Management, Shahab Karimi

All Dissertations

Predicting the states of the surrounding traffic is one of the major problems in automated driving. Maneuvers such as lane change, merge, and exit management could pose challenges in the absence of intervehicular communication and can benefit from driver behavior prediction. Predicting the motion of surrounding vehicles and trajectory planning need to be computationally efficient for real-time implementation. This dissertation presents a decision process model for real-time automated lane change and speed management in highway and urban traffic. In lane change and merge maneuvers, it is important to know how neighboring vehicles will act in the imminent future. Human driver …

Elucidating The Mechanical And Transport Properties Of Lignin-Based Hydrogel Composites, Nicholas Gregorich

All Dissertations

The use of lignin in the fabrication of soft composites has become an emerging area of research in polymer science and polymer chemistry. These lignin-based materials present numerous benefits, notably, a reduction in the use of petroleum-based precursor, improved structural benefits to otherwise soft host polymers, as well as the inherent antimicrobial and antioxidant properties of lignin, making it suitable for biomaterials. Herein, we present two chemical reaction pathways of incorporating lignin that was fractionated and cleaned using the Aqueous Lignin Purification with Hot Agents (ALPHA) process into poly(vinyl alcohol) (PVA) hydrogel composites for aqueous-based separations. By leveraging the ALPHA …

Development Of A Novel Predictive Model And Prosthetic System To Assess Dynamic Leg Length Based Gait Biomechanics In Lower Limb Prosthesis Users, Therese Parr

All Dissertations

Individuals with transfemoral amputation often rely on a prosthesis as a replacement for their missing extremity’s structure and function. Lower-limb prosthetic devices are developed with the goal of restoring biomechanical abilities and mitigating secondary health risks for users. However, biomechanical deficits for unilateral transfemoral prosthesis users are very common and are induced by both leg length discrepancy (LLD) and current prosthetic design shortcomings. Lack of push off power as well as difficulty shortening the leg for toe clearance can result in gait compensations that lead to asymmetric limb loading, increased muscle activity, and an increased incidence of falling due to …

Women's Advancement To U.S. Higher Education Executive Leadership: An Intersectional, Secondary Data Analysis, Ann Marie Alexander

All Dissertations

This study focused on the issue that women are underrepresented in higher education executive and senior leadership roles at four-year colleges and universities in the United States (Dominici et al., 2009; Ginsberg et al., 2019; Gomez, 2020; Hannum et al., 2015; O’Conner, 2019; Smith, D., 2017; Teague 2015). A theoretical framework of intersectionality was used. Significant literature review findings were that the majority of studies on women in U.S. higher education leadership were qualitative and located at one university or in a single region of the country. Another finding was that more studies examining the races and ethnicity of these …

Our Voices Matter: Engaging Middle Grades Hispanic Students In A Summer Literacy Program, Macy Christine James

All Dissertations

This study explored the literacy engagement of Hispanic rising seventh grade adolescents during a summer literacy program. Using a participatory social justice mixed methods design (Creswell & Plano-Clark, 2018), students’ voices were used to design and refine an instructional model proposed to increase their level of engagement in literacy tasks. Through a literacy motivation survey and focus group interviews, students’ perception of motivating and demotivating literacy experiences affecting their levels of engagement were gathered and analyzed. Following this exploration, a design-based approach was employed to create an initial model that would be refined by identifying the enhancing and inhibiting factors …

Vanet Applications Under Loss Scenarios & Evolving Wireless Technology, Adil Alsuhaim

All Dissertations

In this work we study the impact of wireless network impairment on the performance of VANET applications such as Cooperative Adaptive Cruise Control (CACC), and other VANET applications that periodically broadcast messages. We also study the future of VANET application in light of the evolution of radio access technologies (RAT) that are used to exchange messages. Previous work in the literature proposed fallback strategies that utilizes on-board sensors to recover in case of wireless network impairment, those methods assume a fixed time headway value, and do not achieve string stability. In this work, we study the string stability of a …

My Superintendent Journey From Educator To Activist: An Autoethnography Across Three Decades, Betty Bagley

All Dissertations

Superintendents rise to the highest level of professional educational leadership within local communities. National statistics show increasing turnover in that district-level position. Superintendents come and go, which means their accomplishments fade in time. Superintendents rarely tell their stories of successes, failures, pressures, expectations, challenges, or any experiences within their highly visible role. This gap shows a lack of access to superintendents’ perspectives, and that gap may affect current and aspiring superintendents’ potential.

Given a two-century historical gap in the literature about educational leadership with few accounts from superintendents’ perspectives, my study described my journey through three superintendencies from 1993 to …

A Study On Asymmetric Perfect Vortex: Fractional Orbital Angular Momentum And Nonlinear Interaction, Kunjian Dai

All Dissertations

In this work, the manipulation including generation and detection of the asymmetric perfect vortex (APV) carrying fractional orbital angular momentum (OAM) was demonstrated and discussed. All the manipulation of the modes is in real-time which provides a perfect tool for sensing the dynamic properties of complex media. The OAM-involved nonlinear conversion, specifically the second-harmonic generation (SHG) using the APV and asymmetric Bessel-Gaussian (BG) beams was studied in detail.

The generation and detection of the APV are based on the HOBBIT concept which includes acoustic optical deflector (AOD) and log-polar coordinate transformation optics. The RF signal driving the AOD allows the …

Computational Modeling Of Patterned Membranes And Spacers For Improved Hydrodynamics And Fouling Reduction In Reverse Osmosis Water Treatment Processes, Zuo Zhou

All Dissertations

My research goal is to discover ways to improve the hydrodynamics of reverse osmosis (RO) membrane systems through creative membrane surface patterning and spacer designs. Since concentration polarization (CP) usually promotes membrane fouling, improving hydrodynamics would result in reduced fouling and better membrane performance. With computational fluid dynamics (CFD), we can explore dozens or even hundreds of models with different geometries and boundary conditions. Through plotting their velocity profile, streamlines, shear stress, pressure profile, concentration profile, and so on, we can determine which design would lead to the best performance.

At first, patterned membranes were evaluated and compared with flat …

Accessible Virtual Reality For Older Adults, Aaron Gluck

All Dissertations

Virtual reality (VR) has grown significantly since the commercial release of the Oculus Rift in March 2016. This growth accelerated during the COVID-19 pandemic, revolutionizing how individuals and businesses work, socialize, exercise, and stay entertained. However, commercial VR systems are not designed to be accessible to people with disabilities. While researchers have explored aspects of VR accessibility for people with disabilities, there is minimal research on accessible VR for older adults. Older adults (65+) self-report the highest rate of disabilities which may result in VR accessibility barriers, making this the ideal group to study the accessibility of VR.

This dissertation …

Two Essays In Human Capital, Illia Polovnikov

All Dissertations

This dissertation is comprised of two essays on human capital. I analyze how early-life human capital boost shapes micro-level outcomes among disadvantaged children in the US. In the second chapter, I study the productivity convergence among OECD countries and evaluate to what extent the labor force’s sectoral allocation (due to different human capital profiles across countries) contributes to it. In the first chapter, which is joint work with Jorge Garc´ia and William Dougan, we analyze a large-scale trial of an early-childhood education program targeting premature, low-birthweight children, thereby oversampling twins. We find that failing to account for this oversampling obscures …

Explainable Physics-Informed Deep Learning For Rainfall-Runoff Modeling And Uncertainty Assessment Across The Continental United States, Sadegh Sadeghi Tabas

All Dissertations

Hydrologic models provide a comprehensive tool to calibrate streamflow response to environmental variables. Various hydrologic modeling approaches, ranging from physically based to conceptual to entirely data-driven models, have been widely used for hydrologic simulation. During the recent years, however, Deep Learning (DL), a new generation of Machine Learning (ML), has transformed hydrologic simulation research to a new direction. DL methods have recently proposed for rainfall-runoff modeling that complement both distributed and conceptual hydrologic models, particularly in a catchment where data to support a process-based model is scared and limited.

This dissertation investigated the applicability of two advanced probabilistic physics-informed DL …

Studies Of The Ionosphere-Thermosphere Responses To Multi-Scale Energy Deposition Processes, Haonan Wu

All Dissertations

The Ionosphere-Thermosphere (I-T) system is greatly affected by the magnetospheric energy deposition from above and subjected to forcing from the lower atmosphere simultaneously. A central problem in studying the coupled I-T system is to analyze the multi-scale processes naturally embedded in both ways. Magnetospheric energy input such as auroral precipitation and electric field demonstrates multi-scale structures during magnetic storms, resulting in multi-scale I-T responses when deposited into the I-T system. To better quantify the multi-scale aurora and electric field, we developed a new data assimilation model based on a multi-resolution Gaussian process model to synthesize empirical models and observational data …

Explaining Spatio-Temporal Evolution Of Extreme Hydro-Climatic Events Using A Complex Network Framework, Somnath Mondal

All Dissertations

Severe hydroclimatic extreme events, such as droughts, heatwaves, and heavy rainfall, are occurring with increasing frequency and causing significant impacts on both people and the environment. These events also compound in space and time, leading to even more significant consequences. Therefore, it is essential to comprehend these phenomena' concurrent and time-delayed progression across different temporal and spatial scales to address adaptation and mitigation effectively. To accurately understand and map the co-evolution of extreme events, it's necessary to have a thorough grasp of their spatiotemporal patterns, how they propagate and interact with one another, and the underlying mechanisms driving their occurrence. …

Annotations Of Awareness: A Framework For Externalizing Thinking To Promote Metacognitive Discourse In High School English And Social Studies Classrooms, Todd Howard

All Dissertations

Teachers find it challenging to integrate metacognition into the classroom to promote critical thinking, but such rigorous instruction is one way to improve access to quality education for all students, no matter their access to outside-of-school resources. To help teachers find more comfort and confidence in designing for increased critical thinking and metacognitive discourse and to help close the theory-practice gap in metacognition research, I conducted a mixed-methods case study focusing on assessment-design interventions. Using the Metacognitive Framework for Assessment Design and Annotations of Awareness, both designed in response to my literature review, my 90-day action research included three Plan-Do-Study-Act …

Supramolecular Pi-Donor/Acceptor Arrays Based On Redox-Active Metal-Organic Coordination Assemblies, Paola Benavides

All Dissertations

Coordination-driven self-assembly is an attractive strategy for constructing thermodynamically stable supramolecular coordination complexes, ranging from discrete metallacycles and cages to infinite coordination polymers and metal-organic frameworks for a variety of applications.

Chapter 1 discusses strategies for preparing supramolecular charge-transfer π-donor/acceptor assemblies and their potential applications.

Chapter 2 demonstrates that tricomponent self-assembly method, which was believed to yield 3D-cages, based on tetrapyridyl porphyrin (M’TPP, M’ = Zn or H₂), dicarboxylate ligands (XDC), and caped cis-Pt(II) corners, actually yields 2D-bowties featuring an M’TPP core and two parallel XDC linkers held together by four heteroligated PtII(N,O) corners. The 2D-bowties showed …

Designing Noncentrosymmetric Multifunctional Materials, Ebube Oyeka

All Dissertations

Noncentrosymmetric (NCS) materials with crystal lattices lacking spatial inversion symmetry display a wide range of exciting functionalities. This dissertation covers two classes of functional NCS materials: magnetic skyrmion-host compounds and multifunctional materials. Magnetic skyrmion and multifunctional materials combining optical and magnetic responses are providing avenues for developing and optimizing the performance of electronic devices that can have uses in memory storage, laser technology, medicine, sensors, etc. The formation of skyrmions is driven by asymmetric Dzyaloshinskii–Moriya (DM) interaction facilitated by broken spatial inversion symmetry and large spin-orbit coupling (SOC), while multiple functionalities arise when spin carriers and optical chromophores are optimally …

Advancements In Fluid Simulation Through Enhanced Conservation Schemes, Sean Ingimarson

All Dissertations

To better understand and solve problems involving the natural phenomenon of fluid and air flows, one must understand the Navier-Stokes equations. Branching several different fields including engineering, chemistry, physics, etc., these are among the most important equations in mathematics. However, these equations do not have analytic solutions save for trivial solutions. Hence researchers have striven to make advancements in varieties of numerical models and simulations. With many variations of numerical models of the Navier-Stokes equations, many lose important physical meaningfulness. In particular, many finite element schemes do not conserve energy, momentum, or angular momentum. In this thesis, we will study …

The Search For Heavily Obscured Active Galactic Nuclei In The Local Universe, Ross Silver

All Dissertations

Active galactic nuclei (AGN) are supermassive black holes (SMBHs) in the center of galaxies that accrete surrounding gas and emit across the entire electromagnetic spectrum. They are the most energetic persistent emitters in the Universe, capable of outshining their host galaxies despite their emission originating from a region smaller than our Solar System. AGN were some of the first sources discovered that helped teach us that there were galaxies outside of our own, and they proved the existence of black holes. Moreover, AGN can give us valuable insights into other branches of astrophysics. For example, they can be used to …

Machine Learning-Based Data And Model Driven Bayesian Uncertanity Quantification Of Inverse Problems For Suspended Non-Structural System, Zhiyuan Qin

All Dissertations

Inverse problems involve extracting the internal structure of a physical system from noisy measurement data. In many fields, the Bayesian inference is used to address the ill-conditioned nature of the inverse problem by incorporating prior information through an initial distribution. In the nonparametric Bayesian framework, surrogate models such as Gaussian Processes or Deep Neural Networks are used as flexible and effective probabilistic modeling tools to overcome the high-dimensional curse and reduce computational costs. In practical systems and computer models, uncertainties can be addressed through parameter calibration, sensitivity analysis, and uncertainty quantification, leading to improved reliability and robustness of decision and …