Physical Sciences and Mathematics Commons^™

Design, Fabrication, And Characterization Of Advanced High-Power Single-Mode 9xxnm Semiconductor Lasers, Xiaolei Zhao

All Dissertations

This thesis presents the comprehensive design, fabrication, and demonstration of advanced high-power, high-efficiency single-mode semiconductor lasers operating at a wavelength of 9xxnm. We begin with the design of the laser epitaxial structure, serving as the cornerstone for achieving high-power high-efficiency lasers. Our methodology integrates a semi-analytical calculation model, which accounts for Longitudinal Spatial Hole Burning (LSHB) and Two-Photon Absorption (TPA) effects, facilitating a thorough exploration of how design parameters influence output power and conversion efficiency. This approach offers an effective and time-efficient epitaxial structure optimization strategy compared to conventional full 3D simulation models.

Subsequently, we demonstrate high-power, high-efficiency ridge waveguide …

Engineering Multifunctional Silicon Nanostructures From Biorenewable Cellulose Nanocrystals, Nancy Chen

All Dissertations

The imperative search for alternative materials to address the pressing demand for advance energy storage is underscored by the escalating environmental predicaments. Lithium-ion batteries (LIBs) with graphite anodes have become the benchmark in energy storage; however, they are approaching a saturation point in terms of energy density. Silicon emerges as a promising contender to supplant graphite, owing to its profuse availability, cost-effectiveness, and impressive specific capacity of 4200 mAh g^-1. By integrating silicon anodes, LIBs stand to undergo a radical transformation, markedly diminishing in weight and size, thus heralding a novel wave of compact, lightweight energy storage systems. …

To The Torus And Beyond: An X-Ray Study Of Agn Tori Morphology, Andrealuna Pizzetti

All Dissertations

Active Galactic Nuclei (AGN) are among the Universe's most energetic and powerful objects, fueled by an accreting supermassive black hole (SMBH) at the host galaxy's center, surrounded by a toroidal structure of dusty gas. Ultraviolet photons arising from the accretion disk get up-scattered to X-rays via inverse Compton scattering by hot electrons close to the accretion disk. Being produced in the very center of the AGN, X-ray photons are powerful messengers that probe the physics of the accretion system and the matter in the surroundings. The torus, formerly considered homogeneous, appears to be a more complex structure of clouds with …

The Human Side Of Adaptive Autonomy: Design Considerations For Adaptive Autonomous Teammates, Allyson Hauptman

All Dissertations

Ground-breaking advances in artificial intelligence (AI) have led to the possibility of AI agents operating not just as useful tools for teams, but also as full-fledged team members with unique, interdependent roles. This possibility is fueled by the human desire to create more and more autonomous systems that possess computational powers beyond human capability and the promise of increasing the productivity and efficiency of human teams dramatically. Yet, for all the promise and potential of these human-AI teams, the inclusion of AI teammates presents several challenges and concerns for both teaming and human-centered AI.

An important part of teaming is …

Oscillations Of Capillary Surfaces With Volume And Edge Effects, Dingqian Ding

All Dissertations

Capillary surfaces are defined by an interface endowed with surface tension that is partially supported by a solid substrate and are susceptible to oscillations reflecting a balance between fluid inertia and the restorative force of surface tension. The wave dynamics strongly depend upon volume change within the domain and edge effects through the boundary conditions applied at the contact-line formed at the liquid-gas-solid interface, while the spatial wave structure conforms to the geometry of the capillary surface. This dissertation develops mathematical models to address these effects for several canonical capillary surfaces, which are organized into two parts that are focused …

Robust And Trustworthy Deep Learning: Attacks, Defenses And Designs, Bingyin Zhao

All Dissertations

Deep neural networks (DNNs) have achieved unprecedented success in many fields. However, robustness and trustworthiness have become emerging concerns since DNNs are vulnerable to various attacks and susceptible to data distributional shifts. Attacks such as data poisoning and out-of-distribution scenarios such as natural corruption significantly undermine the performance and robustness of DNNs in model training and inference and impose uncertainty and insecurity on the deployment in real-world applications. Thus, it is crucial to investigate threats and challenges against deep neural networks, develop corresponding countermeasures, and dig into design tactics to secure their safety and reliability. The works investigated in this …

Numerical Simulation Of Laser Induced Elastic Waves In Response To Short And Ultrashort Laser Pulses., Alireza Zarei

All Dissertations

In an era of intensified market competition, the demand for cost-effective, high-quality, high-performance, and reliable products continues to rise. Meeting this demand necessitates the mass production of premium products through the integration of cutting-edge technologies and advanced materials while ensuring their integrity and safety. In this context, Nondestructive Testing (NDT) techniques emerge as indispensable tools for guaranteeing the integrity, reliability, and safety of products across diverse industries.

Various NDT techniques, including ultrasonic testing, computed tomography, thermography, and acoustic emissions, have long served as cornerstones for inspecting materials and structures. Among these, ultrasonic testing stands out as the most prevalent method, …

Experimental Analyses Of Emission Lines In The Uv/Vis/Nir Range For Astrophysically-Important Elements: From The Iron Group To R-Process Elements, Brynna Neff

All Dissertations

Analysis of astrophysical phenomena requires an understanding of the electronic

structure and transition probabilities of the elements present in that environment,

yet there are still many charge states of heavy elements whose electronic

structures and spectroscopic properties are not yet well understood. To address this,

we investigated the spectroscopic properties of three different elements through an

analysis of spectra collected from three different experimental apparatuses.

In order to better understand the spectroscopic properties of Ni I and II, we

analyzed spectra collected from the Compact Toroidal Hybrid (CTH) apparatus at

Auburn University. In this experiment, a nickel sample was inserted …

Carbon "Quantum" Dots: Structures, Properties, And Issues, Weixiong Liang

All Dissertations

Carbon dots (CDots) are small carbon nanoparticles (CNPs) with effective surface passivation. The effective passivation has been achieved by the surface functionalization of pre-existing CNPs with organic molecules, mostly molecules containing primary or secondary amine moieties. In the studies highlighted in this dissertation, CNPs were functionalized by selected organic molecules, including especially the use of radical addition reactions, to generate CDots with strong absorption and bright fluorescence emissions. A good demonstration of the approach was the N-ethylcarbazole (NEC) radical addition to CNPs under microwave irradiation. Spectroscopy and microscopy methods were employed to characterize the resulting NEC-CDots, and the results …

Domain Decomposition Methods For Fluid-Structure Interaction Problems Involving Elastic, Porous, Or Poroelastic Structures, Hemanta Kunwar

All Dissertations

We introduce two global-in-time domain decomposition methods, namely the Steklov-Poincare method and Schwarz waveform relaxation (SWR) method using Robin transmission conditions (or the Robin method), for solving fluid-structure interaction systems involving elastic, porous, or poroelastic structure. These methods allow us to formulate the coupled system as a space-time interface problem and apply iterative algorithms directly to the evolutionary problem. Each time-dependent fluid and the structure subdomain problem is solved independently, which enables the use of different time discretization schemes and time step sizes in the subsystems. This leads to an efficient way of simulating time-dependent multiphysics phenomena. For the fluid-porous …

Code For Care: Hypertension Prediction In Women Aged 18-39 Years, Kruti Sheth

Electronic Theses, Projects, and Dissertations

The longstanding prevalence of hypertension, often undiagnosed, poses significant risks of severe chronic and cardiovascular complications if left untreated. This study investigated the causes and underlying risks of hypertension in females aged between 18-39 years. The research questions were: (Q1.) What factors affect the occurrence of hypertension in females aged 18-39 years? (Q2.) What machine learning algorithms are suited for effectively predicting hypertension? (Q3.) How can SHAP values be leveraged to analyze the factors from model outputs? The findings are: (Q1.) Performing Feature selection using binary classification Logistic regression algorithm reveals an array of 30 most influential factors at an …

On Cheeger Constants Of Knots, Robert Lattimer

Electronic Theses, Projects, and Dissertations

In this thesis, we will look at finding bounds for the Cheeger constant of links. We will do this by analyzing an infinite family of links call two-bridge fully augmented links. In order to find a bound on the Cheeger constant, we will look for the Cheeger constant of the link’s crushtacean. We will use that Cheeger constant to give us insight on a good cut for the link itself, and use that cut to obtain a bound. This method gives us a constructive way to find an upper bound on the Cheeger constant of a two-bridge fully augmented link. …

Shoreland Development And Disturbances: A Hedonic Analysis Of Lakefront Properties In Northeastern Wisconsin, Usa, Susan Borchardt

Theses and Dissertations

Shoreland development, encompassing features like boat lifts, manicured lawns, artificial beaches, and erosion control measures, offers considerable benefits to property owners. Nevertheless, this development disrupts natural conditions and is associated with increased sediment and pollutant loading, which negatively impacts aesthetics, recreation, and habitat for fish and other aquatic species. This thesis conducts two analyses, which respectively quantify the benefits of shoreland development to homeowners and evaluate the relationship between shoreland development and lake water quality. In the first analysis, a hedonic property model is employed to value shoreland development along Wisconsin inland lakes. The model considers various shoreland development features, …

Predicting Energy Expenditure From Physical Activity Videos Using Optical Flows And Deep Learning, Gayatri Kasturi

Theses and Dissertations

This thesis presents a novel approach for predicting energy expenditure of physical activity from videos using optical flows and deep learning. Conventional approaches mainly rely on wearable sensors, which, despite being widely used, are constrained by practicality and accuracy concerns. This proposal introduces a new strategy that utilizes a three-dimensional Convolutional Neural Network (3D-CNN) to evaluate video data and accurately estimate energy costs in metabolic equivalents (METs). Our model utilizes optical flow extraction to analyze video, capturing complex motion patterns and their changes over time. The results are good indicating potential for this method to be deployed in various healthcare …

Conceptual Understanding Of Linear Relationships Across Various Mathematics Courses, Melissa Manley

Theses and Dissertations

This cross-sectional study investigated the conceptual understanding of linear relationships for 195 students enrolled in a single school in a large, urban district across five mathematics courses: Grade 7 Math (n = 24), Grade 8 Math (n = 52), Geometry (n = 43), Algebra 1 (n = 31), and Algebra 2 (n = 45). The following questions guided this study: (1) What differences exist in students’ conceptual understanding of linear relationships across mathematics courses? (2) What are common strengths and weaknesses in students’ conceptual understanding of linear relationships?

An assessment was created to assess three constructs of conceptual understanding of …

Comparison Of Multidecadal Variability In Climate Reanalyses And Global Models, Andrew A. Westgate

Theses and Dissertations

Superimposed on the linear upward trend of observed global surface air temperature anomalies since the late nineteenth century is, what appears to be, a multidecadal undulation. However, this undulation is either muted or virtually absent in both the previous and current generations of the state-of-the-art climate models used to not only simulate past climates but also predict future climates. One possibility is that this signal is due to a series of complex responses to the global climate forcing; an alternative is that this signal is contained within the internal variability and teleconnected via atmospheric channels. Either way, the existential threat …

Authigenic Minerals In Volcaniclastics From An Eastern African Paleolake: A Proxy For Paleoenvironment, Kaitlyn Truss

Theses and Dissertations

Olduvai Gorge exposes the stratigraphy of Paleolake Olduvai, an often saline-alkaline rift lake that records volcanism from the Ngorongoro Volcanic Highlands. In 2014, cores retrieved from the study area revealed new stratigraphy, including the lacustrine Naibor Soit Formation (Fm) and the volcaniclastic Ngorongoro Fm. In the Ngorongoro Fm part of the cores, mineralogy and geochemistry are the best paleoenvironmental proxies, since under saline-alkaline conditions, volcanic glass alters into specific authigenic minerals (e.g., zeolite, feldspar). This study employs X-Ray Diffraction, X-Ray Fluorescence, and Scanning Electron Microscopy to analyze authigenic mineralogy and geochemistry. The lower Ngorongoro Fm experienced the most alteration, with …

Markov Chain Model Of Three-Dimensional Daphnia Magna Movement, Helen L. Kafka

Theses and Dissertations

Daphnia magna make turns through an antennae-whipping action. This action occursevery few seconds, hence, during the intervening time, the animal either remains in place or continues movement roughly along its current course. We view their movement in three dimensions. We divide the movement in the three dimensions into the movement on a two-dimensional lattice and the movement between the different planes. For the movement on the lattice, we construct a second-order Markov chain model to make predictions about which region of the lattice the animal moves to based on where it was at the last two time points. The movement …

Analytic Approximations Of Higher Order Moments In Terms Of Lower Order Moments, Sven Detlef Bergmann

Theses and Dissertations

The Cloud Layers Unified By Binormals (CLUBB) model uses the sum of two normal probability density function (pdf) components to represent subgrid variability within a single grid layer of an atmospheric model. This binormal approach, while computationally efficient, restricts the model’s ability to capture the full spectrum of potential shapes encountered inreal-world atmospheric data.

This thesis proposes to introduce a third normal pdf component strategically positioned between the existing two, significantly enhancing the model’s representational flexibility. This trinormal representation allows for a wider range of grid-layer shapes while permitting analytic solutions for certain higher order moments.

The core of this …

Coarse Homotopy Extension Property And Its Applications, William Braubach

Theses and Dissertations

A pair (X, A) has the homotopy extension property if any homotopy of A the extends overX × {0} can be extended to a homotopy of X. The main goal of this dissertation is to define a coarse analog of the homotopy extension property for coarse homotopies and prove coarse versions of results from algebraic topology involving this property. First, we define a notion of a coarse adjunction metric for constructing coarse adjunction spaces. We use this to redefine coarse CW complexes and to construct a coarse version of the mapping cylinder. We then prove various pairs of spaces have …

Examination Of Chemical Variations In Fossil Resin With Two-Photon Excitation Fluorescence And Paleobotanical Inventory Reports On National Park Service Units, Katherine Mae Maxine Bober

Theses and Dissertations

Fossil resin can be difficult to chemically characterize due to its complex chemistry which can be complicated by a unique chemistry for each fossil resin sample. Using two-photon excitation fluorescence micro-spectroscopy, we measured the wavelengths at peak emission intensity: we compared these fluorescence results to FTIR spectra. There are variations in fluorescence which indicate differences in botanic origin. This method may be used in future research to better understand botanic origin when more traditional analyses fail.There has been a need for a comprehensive paleobotanical inventory report for NPS units. Four teams consisting of graduate students and mentors are completing the …

Utilizing Arma Models For Non-Independent Replications Of Point Processes, Lucas M. Fellmeth

Theses and Dissertations

The use of a functional principal component analysis (FPCA) approach for estimatingintensity functions from prior work allows us to obtain component scores of replicated point processes under the assumption of independent replications. We show these component scores can be modeled using classical autoregressive moving average (ARMA) models, thus allowing us to also apply the FPCA model to non-independent replications. The Divvy bike-sharing system in the city of Chicago is showcased as an application.

Bayesian Change Point Detection In Segmented Multi-Group Autoregressive Moving-Average Data For The Study Of Covid-19 In Wisconsin, Russell Latterman

Theses and Dissertations

Changepoint detection involves the discovery of abrupt fluctuations in population dynamics over time. We take a Bayesian approach to estimating points in time at which the parameters of an autoregressive moving average (ARMA) change, applying a Markov chain Monte Carlo method. We specifically assume that data may originate from one of two groups. We provide estimates of all multi-group parameters of a model of this form for both simulated and real-world data sets. We include a provision to resolve the problem of confounding ARMA parameter estimates and variance of segment data. We apply our model to identify points in time …

Tpm^Ph Derivative Of Tungsten; Hydrogen-Bonding In 7-Coordinate Cation Complex, Olivia Ryon Simcox

Undergraduate Honors Thesis Collection

Tpm^Ph, or tris(3-phenylpyrazolyl)methane reacts with tungsten hexacarbonyl to form the ligand-metal complex tris(3-phenylpyrazolyl)methane tungsten tricarbonyl, or Tpm^PhW(CO)3. The further complexes of Tpm^PhW(CO)3 and Tpm^PhMo(CO)3 are not known. This project aims to explore how the addition of a phenyl substituent to the pyrazole ring on Tpm impacts the synthesis of [Tpm^PhW(CO)3I]+X– and [Tpm^PhW(CO)3H]+X–. The inclusion of this phenyl substituent may impact the possible hydrogen bonding of then hydrogen contained in the carbon-hydrogen bond. This work aims to explore the extent of hydrogen-bonding of the carbon-hydrogen bond of the Tpm^Ph ligand in cationic metal complexes.

Simulating Ice Particle Properties Under Varying Electric Fields, Joseph Thomas Cooney

Undergraduate Honors Capstone Projects

In this study, the interactions between atmospheric water molecules and an electrically charged dust particle were simulated in python to determine the role of electric charge and electric fields in atmospheric ice formation. Multiple levels of electric charge were tested, corresponding to different strengths of atmospheric electric fields. The TIP4P-2005 model for water was used to simulate these molecules under the influence of a central electric potential to represent the charged dust particle. These included a control group with no electric field (0 C), a group under a fair-weather strength of electric field (1.6*10-14 C), a foul-weather electric field (1.6*10-12 …

Rice Biomass Response To Various Phosphorus Fertilizers In A Phosphorus-Deficient Soil Under Simulated Furrow-Irrigation, Jonathan B. Brye

Crop, Soil and Environmental Sciences Undergraduate Honors Theses

Wastewater-recovered phosphorus (P), in the form of the mineral struvite (MgNH4PO4⋅6H2O), may provide a sustainable alternative to rapidly decreasing rock phosphate reserves. Struvite can be generated via chemical and/or electrochemical precipitation methods, potentially reducing the amount of P runoff to aquatic ecosystems. The objective of this greenhouse tub study was to evaluate the effects of chemically- and electrochemically precipitated struvite (CPST and ECST, respectively) on above- and belowground plant response in a hybrid rice cultivar (Gemini 214, RiceTec) grown using furrow-irrigation compared to other common fertilizer-P sources [i.e., triple super phosphate (TSP) and diammonium phosphate (DAP)] in a P-deficient silt …

Atmospheric Deposition Trends Are Primarily Decreasing In Arkansas And Tennessee, Anna Mccarty

Crop, Soil and Environmental Sciences Undergraduate Honors Theses

Atmospheric deposition has likely changed with the influence of increasing global temperatures and subsequent changes in precipitation across the United States and globally. The objective of this project was to analyze atmospheric deposition across northern Arkansas and Tennessee. The three specific objectives were to: i) evaluate trends in atmospheric deposition of various element/compounds, ii) assess the relationship between atmospheric deposition and rainfall, and iii) evaluate if rainfall-adjusted atmospheric deposition is changing over time. Six sites were analyzed from 1980 to 2022, including AR16, AR27, TN00, TN04, TN11, and TN14, which span over northern Arkansas and across Tennessee. The Mann-Kendall Test …

Super Mario Evolution By The Augmentation Of Topology, Russell A. Autin

University of New Orleans Theses and Dissertations

This paper describes the creation and development of an implementation of the NeuroEvolution of Augmenting Topologies (NEAT) architecture to train an agent to play Super Mario Brothers. Building off of a basic implementation of NEAT, this thesis project shows the process of refining the fitness calculation that ranks the networks in the population and also defines the creation and application of a dataset to train the agent. The use of a dataset to train an agent is a novel idea in the world of reinforcement learning because, generally, reinforcement learning trains an agent to complete a singular task like the …

Using Pre-Trained Models For Vision-Language Understanding Tasks, Rui Cao

Dissertations and Theses Collection (Open Access)

In recent years, remarkable progress has been made in Artificial Intelligence (AI), with an increasing focus on integrating AI systems into people’s daily lives. In the context of our diverse world, research attention has shifted towards applying AI to multimodal understanding tasks. This thesis specifically addresses two key modalities, namely, vision and language, and explores Vision-Language Understanding (VLU).

In the past, addressing VLU tasks involved training distinct models from scratch using task-specific data. However, limited by the amount of training data, models may easily overfit the training data and fail to generalize. A recent breakthrough is the development of Pre-trained …

3-D Reconstruction For Underwater Robots With A Monocular Camera And Lights, Monika Roznere

Dartmouth College Ph.D Dissertations

Before a robot can act, it must perceive its environment. Though, this is not a simple task when considering the challenges in underwater domains -- poor visibility conditions, limited sensor configurations, and lack of readily accessible localization. Underwater robots have, nevertheless, improved dramatically with more extensive sensor and navigation equipment. Robot and sensor use have enabled us to explore all reaches of our oceans. On the other hand, these same robots are not easily accessible or transferable to many practical tasks, including fishery management, infrastructure maintenance, disaster response, site conservation, and ecological surveys. There is a growing need for robots …