Digital Commons Network^™

Markov Chain Monte Carlo Techniques– Innovations In Lifetime Data Analysis And Missing Value Imputations, Tobias Omondi Oketch

Theses and Dissertations

This dissertation develops scalable Bayesian solutions for two critical challenges in modern data analysis: modeling failure times and imputing missing biological data. First, we introduce an adaptive semi-parametric MCMC framework for Weibull lifetime modeling, addressing the lack of conjugate priors and multidimensional sufficient statistics. Using hierarchical modeling and the No-U-Turn Sampler (NUTS) in STAN, we evaluate 24 prior combinations across 72 simulated datasets. The method yields robust parameter estimates under increasing and decreasing hazard rates and proves effective in predicting prostate cancer patient survival. Second, we assess imputation strategies for high-throughput proteomics data, where missingness distorts signal integrity. We compare …

A Mathematical Theory Of Epitaxial Growth, Brock C. Price

Theses and Dissertations

In this dissertation we investigate several PDE models of Epitaxial growth. These models are fourth-order PDE’s featuring exponential nonlinearities as well the p-Laplacian and 1-Laplacian. The presence of the exponential nonlinearity is what provides the main mathematical difficulty. Theexponent in particular does not have enough estimates to guarantee any compactness. Because of this, one has to allow the inclusion of a singular portion to the exponent in the sense of the Lebesgue decomposition theorem. In thefirst chapter weinvestigate a related epitaxial growth, with transition rates of the Metropo lis variety and a linear exponent. The metropolis rates induce an extra …

Unraveling Quantum Properties Of Novel Two-Dimensional Systems Using A First-Principles Approach, Binod Regmi

Theses and Dissertations

We used first-principles density functional theory (DFT) to investigate the structural, electronic, and magnetic properties of an oxygen crystal in a copper slab, a ferrimagnetic electride with highly tunable magnetic anisotropy energy (MAE), and the Fermi surface analysis of different kagome metal phases. The Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional was used in the Vienna ab initio simulation package (VASP) for all these calculations. Because of dimensionality reduction, the electronic properties of copper change significantly at the two-dimensional (2D) scale due to whichwe observe more reconstruction in the geometry of the Fermi surface. Dimensionality reduction also influences charge transport. Moreover, we present …

Advancing Rangeland Vegetation Mapping Through Integrated Uav And Satellite Imagery: A Comparative Machine Learning Framework For Fractional Cover Classification, Nishat Shermin

Theses and Dissertations

This study presents a multi-scale remote sensing framework to classify fractional vegetation cover (FVC) across rangelands by integrating UAV multispectral imagery, LiDAR structural data, and multisource satellite inputs. Four machine learning models, ranging from UAV-only to fused UAV-LiDAR-Sentinel models, were developed and evaluated using Random Forest (RF) and Extreme Gradient Boosting (XGBoost) algorithms. The research was conducted at Martin Ranch, Texas, using Uncrewed Ariel Vehicle (UAV)-collected multispectral imagery, LiDAR-derived canopy height, and Sentinel-1/2 indices. Model 2 (UAV + LiDAR) emerged as the optimal model for balancing accuracy, processing time, and compatibility with ecological simulation tools. This model captures both spectral …

Thermo-Mechanical Advancements For Very High Strength And Ultra High Performance Concretes, Lana Grayson Brown Sisung

Theses and Dissertations

Interest in the use of high-strength concrete (HSC) has increased in recent years with demand for improved concrete performance. HSCs are widely associated with high heat of hydration and elusive behavior when exposed to high temperatures commonly occurring in mass structures. The optimization of HSC mixture proportioning is difficult due to a wide variety of constituents that influence thermal and mechanical properties. Additionally, determining in-place properties of mass concrete placements is elusive, and there are currently minimal to no test methods available that are both predictive and a direct measurement of mechanical properties. The objective of this dissertation is to …

Mastering Skills Together: Effects Of Video Modeling On Parent-Implemented Academic Intervention, Chelsea S. Thorpe

Theses and Dissertations

Reading proficiency is a fundamental skill for academic success and long-term developmental outcomes. Yet, despite ongoing efforts to strengthen literacy education, a significant number of students continue to face reading difficulties that hinder comprehension, critical thinking, and overall academic achievement. National data demonstrate the urgency of this issue. The 2024 National Assessment of Educational Progress (NAEP) reported that 40% of fourth-grade students and 33% of eighth-grade students scored below the Basic level in reading, marking the highest rate on record for eighth graders. Early reading challenges can often lead to other academic and psychosocial challenges such as low achievement, low …

Estimating Reliability Of Electric Vehicle Charging Ecosystem Using Principle Of Maximum Entropy, Himanshu Tripathi

Theses and Dissertations

This thesis addresses the challenge of estimating electric vehicle (EV) charging system reliability against unpredictable threats like cyberattacks and extreme weather, where traditional methods fail. We utilize the Principle of Maximum Entropy (PME), a statistical tool that provides unbiased risk estimates using limited information. Applied to the EV charging ecosystem, our case study shows how PME models stress factors to predict failures and optimize maintenance. This approach extends beyond EVs to other complex systems with scarce data, such as smart grids or healthcare devices. By linking uncertainty directly to reliability, PME offers a universal method to improve decision-making under unpredictable …

Bridging Physics And Machine Learning: Physics-Informed Neural Networks (Pinn) For Wire-Arc Additive Manufacturing (Waam) Thermal Prediction, Haiye (Justin) Xie

Theses and Dissertations

Over the past decade, additive manufacturing (AM) has gained substantial use in industry and research. It is a promising alternative to traditional subtractive and casting manufacturing. AM not only saves time and materials but can also construct intricate structures within components for specific purposes. Wire-Arc Directed Energy Deposition (WA-DED) is one of the additive manufacturing technologies that offers a high extrusion rate of metal wire materials to fabricate near-net-shape metal components. Accurate temperature control is crucial for controlling the microstructure of metal components fabricated through the AM process. Machine learning has the ability to analyze real-time sensor data, such as …

Reactive Molecular Dynamics And Method Development For Applications In Renewable Energy And Sorption Equilibria, Woodrow Wilson

Theses and Dissertations

It is crucial to harness energy from sustainable sources to combat the dwindling nonrenewable feedstocks used to produce everyday commodities and fuels. Liquid-phase heterogeneous catalysis has demonstrated remarkable product selectivity and yields for reactions relevant to biomass valorization under mild operating conditions. However, active site characterization is challenging due to the complex solvated environment and interface. Ground-state first-principles (FP) molecular simulations have provided insights into reactive systems in catalysis. These calculations, however, scale poorly with the number of electrons. Observing atomic motion with molecular dynamics (MD) or sampling static properties with Monte Carlo (MC) simulations at statistically relevant lengths- and …

The Effect Of Wall Temperature And Transpiration On Görtler Vortices In High-Speed Boundary Layers, Asmaa Ahaggach

Theses and Dissertations

Görtler vortices are counterrotating flow structures generated as a result of the imbalance between the wall radial pressure gradients and the centrifugal forces in a boundary layer developing on a curved surface. Their presence leads to secondary instabilities and increases the wall shear stress as they accelerate the transition from laminar to turbulent flow. These secondary instabilities can be mitigated using control techniques aimed at decreasing the energy and the wall shear stress. In this thesis, the combined effect of wall temperature and transpiration on Görtler vortices developing in supersonic and hypersonic boundary layers is investigated. Görtler vortices are excited …

Extracting Magnetic Exchange Interactions From Magnetic Pair Distribution Function Data Via Monte Carlo Simulations, Emma Zappala

Theses and Dissertations

The magnetic pair distribution function (mPDF) is a powerful tool used to analyze diffuse magnetic scattering data in real-space. Presently, mPDF is usually used to model real-space spin configurations of materials, offering important insights into the local magnetic structure, but not to directly probe the magnetic interactions giving rise to the magnetic structure in the first place. Using Monte Carlo simulations, a robust algorithm to simulate the magnetic structure of materials, we can connect the underlying magnetic exchange parameters to the spin configurations from experimental mPDF data. We prove this concept using a simple two-dimensional Ising model and then demonstrate …

Transcendental Formulas For The Coefficients Of Ramanujan's Mock Theta Functions, Gradin Anderson

Theses and Dissertations

Ramanujan's 1920 last letter to Hardy contains seventeen examples of mock theta functions, including the famous third order function f(q), which resemble modular forms of weight 1/2. This list has since been expanded by individuals such as Gordon and McIntosh and the McKay--Thompson series arising in moonshine theory. In 1964, Andrews---improving on a result of Dragonette---gave an asymptotic formula for the coefficients of f(q) and conjectured an exact formula: a conditionally convergent series that closely resembles the Hardy--Ramanujan--Rademacher formula for the partition function. A key breakthrough came in 2001, when Zwegers wrote f(q) as the holomorphic component of a vector-valued …

Coding For Nonstandard Channels: A Capacity-Oriented Approach, J Daniel Harman

Theses and Dissertations

This work addresses the issue of coding for non-standard channel models with an emphasis on capacity-oriented channel analysis and system design. The first channel studied is the Wyner wiretap channel. Channel sounding results were obtained to calculate the capacity for the multi-antenna case of the Wyner wiretap channel to ascertain the potential for secure communication via secrecy coding. The second channel studied is an asymmetric binary crossover erasure channel (ABCEC) with a short-blocklength constraint. The capacity for this channel was derived, and linear codes were chosen and tested. Another study was conducted on the ABCEC within a degraded wiretap channel …

Enhanced Nanomechanical, Tribological And Electrical Properties Of Ni-Cr Coatings Via Max Phase Reinforcement And Metallic Interlayers, Mohammad Ashikul Alam

Theses and Dissertations

Nickel-Chromium (Ni-Cr) coatings are widely used in industrial applications due to their resistance to oxidation, thermal stability, and adjustable electrical and mechanical properties. However, achieving improved multifunctional performance across various use cases ranging from extreme tribological environments to microscale device integration remains a significant challenge. This thesis explores two complementary strategies for enhancing the performance of Ni-Cr coatings in both thick and thin film configurations, aiming to address limitations in wear resistance, durability, adhesion, and electrical conductivity. For thick coatings, Ni-Cr was reinforced with Ti3SiC2 MAX phase particles and processed using selective laser sintering (SLS) with optimized parameters. The addition …

Classification And Analysis Of Families Of Graphs With Focus On Nordhaus-Gaddum Bounds, Sibi Pranav Muthuprakash

Theses and Dissertations

Nordhaus-Gaddum type problems focus on bounding characteristics of graph and its complement. There are certain families of graphs which yield optimal upper bounds on various Nordhaus-Gaddum characteristics of graph. In this paper, we will talk about bounding combinatorial algebraic connectivity, normalized algebraic connectivity, the Cheeger constant, and the isoperimetric number of a graph and its complement. We will identify some optimal or near optimal families of graphs and conduct an analysis on these families that will help to bound these characteristics. We will also prove and conjecture some bounds that can help in formulating stronger bounds on these characteristics of …

Flowdb: A Complete Method For Extracting Queries From Functional Programs, Koby J. Lewis

Theses and Dissertations

Programmers working on database-backed applications frequently face trade-offs between designing maintainable software and efficient software due to the overhead of querying a database. We demonstrate FlowDB, an analysis for database-backed programs that can aid in program transformations that allow a program to be written in a maintainable style while still being performant. FlowDB employs demand-driven control flow analysis (DCFA) to produce a set of query sites that may be evaluated during the execution of a program. This set of query sites may then be used by a developer or compiler to cache needed results.

Reverse-Chinoiserie: Qing Imperial Porcelain And The Reappropriation Of European Rococo, Yifan (Mia) Ye

Theses and Dissertations

This thesis introduces “reverse-chinoiserie” to describe the Qing court’s reappropriation of European Rococo aesthetics in imperial porcelain. Through case studies of 18th-century ceramic diplomacy and design, it reveals how cultural imitation was reengineered into visual sovereignty. It examines how China responded to, absorbed, and redirected European fantasies of empire.

Cartography, Botany, And Violence In The Codex Rodriguez-MondragóN, Maria Davison

Theses and Dissertations

This thesis examines how Sandy Rodriguez deploys the visual language of the Florentine Codex and other sixteenth-century Mesoamerican sources to examine the persisting effects of colonialism on people and land in Mexico-U.S. borderlands in Codex Rodriguez-Mondragón (2017-present), her ongoing series of maps, botanical illustrations, and landscape paintings.

The Effect Of An Invasive Species (Lantana Camara) And A Fast-Growing Herb (Acanthus Pubescens) On The Plant And Animal Communities In Kibale National Park, Uganda, Kathleen Bufka

Theses and Dissertations

Fast-growing plant species, like Lantana camara and Acanthus pubescens, could threaten biodiversity in Kibale National Park, Uganda. I surveyed plants and wildlife in areas where these plants were frequently encountered compared to those areas where they are infrequent. I found mixed results based on plant traits and the animals considered. My findings support management efforts on these two species to prevent forest degradation.

Congruences For Quotients Of Klein Forms, Jeffery Opoku

Theses and Dissertations

This dissertation investigates the arithmetic properties of some modular forms and eta quotients, focusing on the divisibility properties and congruence relations satisfied by these. The first part examines quotients of the Rogers-Ramanujan and Rogers-Selberg functions, defined by \[ f(\tau) = q^{r} (q^5; q^5)^{a_0} (q, q^4; q^5)^{a_1} (q^2, q^3; q^5)^{a_2}= \sum_{n=r}^{\infty} P_{a_0,a_1,a_2}(n-r) q^n, \] and \[ g(\tau) = q^{s} (q^7; q^7)^{a_0} (q, q^6; q^7)^{a_1} (q^2, q^5; q^7)^{a_2} (q^3, q^4; q^7)^{a_3}= \sum_{n=s}^{\infty} P_{a_0,a_1,a_2,a_3}(n-s) q^n, \] respectively. We establish conditions on the exponents \(a_0, a_1, a_2, a_3\) and residue classes \(r\) and $s$ modulo $p$ such that \(P_{a_0, a_1, a_2}(pn - r) \equiv …

Barriers To Hispanic Post-Secondary Education In Science Fields, Luis Slayton

Theses and Dissertations

The study aimed to examine whether external barriers could be identified and are present throughout a Hispanic individual's educational life. The beliefs of the Hispanic community regarding education and the nature of acquiring an education could be relevant to the factors that impede the completion of high school. A survey approach was chosen as the methodology for the study due to the confidential nature of a questionnaire. Human nature tends to be more honest when not asked personal questions face-to-face. Additionally, there is potential to generalize attributes from a small sample to a larger population, allowing inferences about the identified …

Low-Dimensional Learning For Remaining Useful Life Prediction Of Batteries Operating Under Various Environments, Rodrigo Benavides

Theses and Dissertations

In reliability, we typically define the standard operating conditions under which a component operates. However, the differences in battery operating conditions cause variability in the degradation patterns of identically manufactured batteries, rendering remaining useful life prediction a major challenge. To aid this task, several sensors are utilized to monitor battery state-of-health. However, traditional prognostics algorithms do not scale well to the volume of data generated. Furthermore, several authors do not explicitly consider operating environments in their prediction models. Therefore, we present a high-dimensional data analytics framework that integrates operating environment information for battery prognostics. This framework combines Multilinear Principal Component …

Arginine Vasotocin And Corticosterone In Nesting And Non-Nesting Loggerhead Sea Turtles In X’Cacel-X’Cacelito Sanctuary, Krista Blair Reed

Theses and Dissertations

Sea turtles exhibit distinct behaviors before and after egg laying, however, not all individuals successfully oviposit. Some females display disruptions in their typical nesting behavior, returning to the water without laying eggs, which is referred to as a non-nesting emergence (NNE). NNEs can be due to external disturbances on the beach, but why they occur is often unclear. Arginine vasotocin (AVT) is a neuropeptide involved in various physiological processes, including stimulating smooth muscle contraction of the oviduct to facilitate egg deposition in nesting sea turtles. On the other hand, corticosterone is the primary stress hormone in sea turtles and is …

Comparative Analysis Of Sequential And Non-Sequential Modeling Techniques For Ddos Attack Detection With Explainable Ai, Vincent Agbenyeavu

Theses and Dissertations

Cybersecurity is known today as one of the greatest challenges of the modern era. Among the various types of cyber-attacks that threaten our security, the Distributed Denial of Service (DDoS) attack is among some of the most common, effective, and well-recognized attack strategies. Since this form of attack is meant to disrupt the availability factor covertly, it can be detrimental to the targeted machines and difficult to discover. Because of that, there have been several approaches, as well as solutions that have been devised to detect it as accurately and efficiently as possible. In this study, four sequential data modeling …

Machine Learning Applications For Evaporation Predictions From Small Reservoirs: Potential Water Savings For Lower Rio Grande Valley, Texas, Syed Muhammad Fahad Abdullah

Theses and Dissertations

Local-scale reservoirs are important to regional water balance, but these are often overlooked. This study presents a robust machine learning (ML) approach leveraging reanalysis datasets to estimate daily evaporation for local-scale reservoirs in semi-arid South Texas. Selected models were trained with daily lake evaporation model (DLEM) estimates and used climatic and reservoir-specific properties as feature input variables. The multi-reservoirs training approach ensured applicable model generalization. Results show promising predictive performance with R² values ranging from 0.55–0.67 (testing) and 0.64–0.78 (validation), NSE values ranged from 0.54 0.67 (testing) and 0.64–0.78 (validation), and RMSE values ranged between 1.52–1.80 mm/day (testing) and 1.22–1.58 …

Low-Cost Monitoring And Fingerprinting Of High-Powered Electric Systems, Kwabena Buamono Aboagye-Otchere

Theses and Dissertations

Electric motors are vital to industry, transport, and energy, yet their maintenance challenges persist. While traditional reactive maintenance leads to costly downtime and safety risks, predictive maintenance, especially through IoT and machine learning offers early fault detection and operational efficiency. However, this shift introduces security concerns due to unintended magnetic emissions from motors. These emissions, though useful for non-intrusive monitoring, can be exploited to eavesdrop on sensitive industrial processes. This dissertation explores the dual nature of magnetic emissions: their value in motor diagnostics and their potential as a security vulnerability. It demonstrates how emissions can identify motors, monitor health, and …

Computational Calculations On Zno (0001) And Zno (1010) Surfaces With And Without Pd Adatoms, Amit Aich

Theses and Dissertations

In this research work, first-principles density functional theory (DFT) was used to study O-terminated, Zn-terminated ZnO (0001) surfaces and non-polar ZnO (1010) surfaces. Both clean surfaces and those with Pd or PdO adatoms were examined. Adsorption was considered at O, Zn and hollow sites. After structural relaxation, we analyzed the electronic, optical and adsorption properties. The O-terminated ZnO (0001) surface has a larger band gap of 0.76 eV and p-type conduction. The Zn-terminated surface has a smaller band gap of 0.15 eV and shows n-type behavior. Pd adsorption modifies ZnO’s electronic structure in a site-dependent manner. On O-terminated surfaces, it …

Advancing Real-World Implementation Of The Well Optimized Linear Finder (Wolf) High-Speed Atmospheric Turbulence Compensation Method, Timothy Evan Coon

Theses and Dissertations

This dissertation advances the real-world implementation of the Well Optimized Linear Finder (WOLF) method for high-speed Atmospheric Turbulence Compensation (ATC). Atmospheric turbulence introduces phase aberrations into optical wavefronts and degrades image quality in terrestrial imaging systems. Traditional phase diversity methods are computationally intensive and poorly suited to real-time operation. The WOLF method addresses these limitations through a novel, point-wise formulation of the optical transfer function (OTF) as a structured autocorrelation of the generalized pupil function (GPF). This formulation enables the estimation of phase aberrations at individual spatial coordinates with distributed computational complexity.

The research begins by developing a MATLAB-based simulation …

Investigating Global Lightning Observed From Ground And Space, And Its Relationship To Solar Activity, Megan Diane Mark

Theses and Dissertations

The extremes of lightning, specifically lightning with long-lasting continuing currents and lightning with extremely high peak currents, are investigated from both ground- and space-based observations. Additionally, the potential solar influence on lightning is investigated on large spatial scales.

Continuing currents may occur following the impulsive flow of current during a cloud-to-ground (CG) return stroke and are usually low amplitude (from a few amperes to a few kiloamperes) and long duration (several to hundreds of milliseconds). Remotely estimating their duration from the electromagnetic fields measured by existing ground-based lightning locating systems (LLSs) is not possible, but some space-based lightning detection systems …

Investigation Of Wireless Communication Sub-Optimizing Factors And Ai-Based Optimization For Ber Reduction, Lalan Jee Mishra

Theses and Dissertations

The increasing demand for high-throughput, low-latency, and reliable wireless communication has led to significant advancements of cellular wireless technologies since the early ‘80s. However, in dynamic and interference-prone environments—particularly those involving Unmanned Aerial Vehicles (UAVs)—signal degradation due to pathloss, multipath propagation, co-channel interference, and weather-induced attenuation continues to undermine performance. These factors contribute to elevated bit error rates (BER), inefficient spectrum usage, and unreliable communication links, thereby limiting the practical utility of wireless systems in aerial applications. Traditional mitigation techniques, while effective under certain conditions, often fail to adapt to rapidly changing wireless environments. This shortcoming underscores the need for …