Physical Sciences and Mathematics Commons^™

Understanding The Interfacial Reactions Initiating On Lithium Metal Surfaces In Next-Generation Battery Technologies, Joshua A. Lochala

Graduate Theses and Dissertations

Li-ion batteries have started to reach the theoretical maximum energy. Next-generation batteries represent the future of portable energy sources for vehicle electrification and grid energy storage. Li metal battery is one of the most promising next-generation battery technologies that could potentially double the cell-level energy of conventional Li-ion batteries. However, Li metal has multiple drawbacks that require addressing before realization. These drawbacks include dendrite formation leading to internal short and increasing internal resistance due to the breakdown of electrolyte, leading to rapid cell death. These problems stem from the interfacial reactions occurring during the plating and stripping of Li metal. …

Phenotypic Switching Of Bacterial Cells In Extreme Environments, Sudip Nepal

Graduate Theses and Dissertations

A large number of terrestrial microbial lives thrive in extremes of environmental conditions, including extremes of pressure, temperature, salinity, pH, and a combination of them. For example, all the marine biomass thrive at high hydrostatic pressure depending on depth. The temperature in the ocean can be very high near the hydrothermal vents and salinity and pH depends on the composition of salt in the surrounding areas. On the surface, hot springs, lakes and geysers provide high temperature conditions, while many places are permafrost regions with subzero temperatures. There is an emerging body of work on the viability, genomics, and metagenomics …

Investigation Of The Structural, Electronic, And Thermoelectric Properties Of Mono- Chalcogenides, Aida Sheibani

Graduate Theses and Dissertations

The structural, electronic, and thermoelectric properties of GeTe are studied using density functional theory and Boltzmann transport equations. This material has a rhombohedral crystal structure in ambient temperature with a ferroelectric behavior due to lack of inversion symmetry. This study suggests that the presence of asymmetry in GeTe can lead to an improvement in the thermoelectric properties of this material. In addition, studies on introducing Group III, IV, and V dopants to GeSe show that while these impurities can improve the power factor and decrease the lattice thermal conductivity, they cannot enhance the figure of merit.

Measuring Sexual Excitation And Sexual Inhibition In A Dutch-Speaking Sample, Malachi Willis

Graduate Theses and Dissertations

Background: Individual differences in sexual excitation and sexual inhibition are important predictors of sexual functioning. Psychometric instruments for these aspects of sexual response were originally developed separately for men (Sexual Inhibition /Sexual Excitation Scales [SIS/SES]) and women (Sexual Excitation/Sexual Inhibition Inventory for Women [SESII-W]). These measures were then adapted to function similarly in samples comprising both men and women (Sexual Inhibition/Sexual Excitation Scales-Short Form [SIS/SES-SF] and Sexual Excitation/Sexual Inhibition Inventory for Women and Men [SESII-W/M], respectively). No published study to our knowledge has administered the SIS/SES and SESII-W/M questionnaires to a sample of both women and men. In the present …

Earthworm Dynamics In Tallgrass Prairies In The Ozark Highlands Region Of Northwest Arkansas, Carlee Hensley

Graduate Theses and Dissertations

Tallgrass prairie was a historic and is presently a unique and endangered natural ecosystem throughout the Ozark Highlands region in the mid-southern United States. Tallgrass prairies have been disturbed for agricultural production and/or urban expansion; thus, as a result, efforts have been undertaken to reclaim areas previously used for agricultural production to mitigate the loss of tallgrass prairies. Limited research exists on earthworm dynamics in mounded tallgrass prairies or prairie restorations, particularly in the Ozark Highlands region of northwest Arkansas. The objectives of this study were to i) evaluate the effects of soil moisture regime (SMR; aquic and udic), landscape …

Environmental Influences On Tree-Driven Karst Bedrock Physical Weathering, Cole Robert Jimerson

Graduate Theses and Dissertations

The role of tree roots as stressors that contribute to physical weathering processes and thus soil generation remains an open question in critical zone science. While evidence suggests roots may be able to damage rock by accessing pre-existing fractures, where they can expand due to water uptake or generate forces on rock in response to wind gusts, these processes have not been investigated in temperate karst regions until now. I monitored forces at the root-rock interface for an American elm and Hackberry tree between September 2019 and May 2020. I used piezoelectric force sensors to determine if differences in species, …

Nonlinear Dimensionality Reduction For The Thermodynamics Of Small Clusters Of Particles, Aditya Dendukuri

Graduate Theses and Dissertations

This work employs tools and methods from computer science to study clusters comprising a small number N of interacting particles, which are of interest in science, engineering, and nanotechnology. Specifically, the thermodynamics of such clusters is studied using techniques from spectral graph theory (SGT) and machine learning (ML). SGT is used to define the structure of the clusters and ML is used on ensembles of cluster configurations to detect state variables that can be used to model the thermodynamic properties of the system. While the most fundamental description of a cluster is in 3N dimensions, i.e., the Cartesian coordinates of …

Ensemble And Single Particle Studies Of Cation Exchange In Cuins2/Zns Qds And Their Application In Super-Resolution Imaging, Anh Tue Nguyen

Graduate Theses and Dissertations

Colloidal quantum dots (QDs) have great potential in many applications such as bioimaging, light emitting diodes, solar cells and lasers. However, a great number of studies have been focused on Cd based (II-VI) and Pb (IV-VI) based materials which are not suitable for mass production. Therefore, alternative types of QD containing less toxic materials have been introduced, including CuInS2 QDs. This I-III-VI semiconductor nanocrystals also attract lots of attention due to their large Stock shift, long fluorescence lifetime and high defect tolerance, making them attractive emitters for applications in bioimaging, photovoltaics and light emitting diodes.

In the first project, we …

Effects Of Terrestrial Weathering On Rare Earth Element Concentrations And Sulfur Isotopic Signatures Of Carbonaceous And Ordinary Chondrites, Ruby Virginia Patterson

Graduate Theses and Dissertations

Understanding the effects of weathering of chondrites is essential to gaining accurate and useful information about the formation of our solar system, as well as a more detailed account of the mobilization of chondritic compounds when they encounter terrestrial conditions. Elemental concentrations and stable isotope analyses of chondrites, considered to be the most primordial material in the solar system, are two tools which help unlock the weathering patterns of these specimens when they enter the earth system. However, it is not currently known exactly how time spent in the field alters rare earth element (REE) concentration or δ34S signatures within …

Fayetteville And Imo Shales: Punctuated Upper Mississippian Shallowing Upward Sequence, Southern Ozark Region, Northern Arkansas, Joshua Stevens

Graduate Theses and Dissertations

The late Mississippian lithostratigraphic succession in the southern Ozark region, northern Arkansas, include, in ascending order, the Meramecan Moorefield Shale, Batesville Sandstone (with Hindsville Member); Chesterian Fayetteville Shale and Pitkin Limestone (with Imo Member). This interval is now interpreted as a single transgressive-regressive, unconformity-bounded, eustatic, third order cycle (Stevens and Manger, 2018). The Moorefield lowstand wedge is bound by a basal unconformity and succeeded by the transgressive Batesville Sandstone with its Hindsville Member. This succession reflects accretionary deposition along strike of the rising strand line, likely as a barrier island system, as its equivalents are shale (basinward) and limestone (laterally …

Projected Surface Water For Fruit And Vegetable Irrigation Under A Changing Climate In The Us, Marty Matlock, Greg Thoma, Kieu Ngoc Le, Eric Cummings, Zach Morgan, Andrew Shaw

Water Systems

Increasing greenhouse gas concentrations in the atmosphere, resulting in climate impacts, are raising concerns over the hydrologic cycle and its effects upon agricultural productivity. If rainfall patterns change, meeting an increased demand for fruits and vegetables will pose a challenge for domestic production regions in the United States (U.S.). Information on potential water supply scarcity in the current production regions provides decision makers with critical information for risk mitigation for future production. We used a hydrologic balance-based model of historic and future water availability to evaluate risk of available irrigation water to support major fruit and vegetable production the US. …

On The Explanation And Implementation Of Three Open-Source Fully Homomorphic Encryption Libraries, Alycia Carey

Computer Science and Computer Engineering Undergraduate Honors Theses

While fully homomorphic encryption (FHE) is a fairly new realm of cryptography, it has shown to be a promising mode of information protection as it allows arbitrary computations on encrypted data. The development of a practical FHE scheme would enable the development of secure cloud computation over sensitive data, which is a much-needed technology in today's trend of outsourced computation and storage. The first FHE scheme was proposed by Craig Gentry in 2009, and although it was not a practical implementation, his scheme laid the groundwork for many schemes that exist today. One main focus in FHE research is the …

Engagement Of Information Systems Professionals In Open Source Software Development, Md Saifur Rahman Bhuiyan

Graduate Theses and Dissertations

Open source (OS) development of software is becoming increasingly desirable for individuals and organizations alike. Organizations that heavily resisted this new way of developing software are now actively participating in this process. Participation of information systems (IS) professionals in the open source environment has been a focal point in this stream of research in information systems. The dissertation goes beyond participation and examines engagement of IS professionals in the open source environment. The concept of engagement facilitates a more comprehensive understanding of the relationship between a person and a his or her work. The three essays in the dissertation examine …

In Situ Plant Uptake Of Excess Nutrients And Consequential Alteration Of Rhizosphere Dynamics, Srusti Maddala

Crop, Soil and Environmental Sciences Undergraduate Honors Theses

The use of phytoremediation in ecological remediation projects has numerous benefits including soil stabilization and nutrient uptake. Recently, microdialysis, a diffusion-based sampling technique commonly used in biomedical research, has been recognized as a candidate for monitoring chemical changes in the rhizosphere. The real-time, in situ data it provides about nutrient diffusion may improve the management and success of restoration projects. Therefore, the objective of this study was to employ the technique of microdialysis in the novel application of quantifying the diffusive flux of inorganic nitrogen compounds in the rhizosphere of native plants of Arkansas. The microdialysis technique was first optimized …

Irrigation Design In Montana: Accommodating Varying Water Accessibility Across The Continental Divide., John Garrett Lampson

Biological and Agricultural Engineering Undergraduate Honors Theses

The design work performed in this project was conducted over two summers (2018, 2019) of internship experience with the Natural Resources Conservation Service (NRCS) across the state of Montana. The first summer’s design work was based out of Glendive, MT, in Dawson County, approximately 50 kilometers from the North Dakota border. The second summer was in Missoula, MT, in Missoula County, near the Idaho border. The two areas differ significantly in topography, weather, and water availability with the main separating geographic influence being the Rocky Mountains.

This paper focuses on the design process and requirements for two farms located outside …

Design Of A Shallow-Aero Ebb And Flow Hydroponics System And Associated Educational Module For Tri Cycle Farms, Julie Halveland

Biological and Agricultural Engineering Undergraduate Honors Theses

Tri Cycle Farms, whose main mission is to reduce food insecurity in their community, is a non- profit urban farm in Fayetteville, Arkansas. The “Tri” in their name refers to the three parts of their foundation: giving a third of their yield to volunteers, giving a third to local food pantries, and selling a third to sustain the farm and demonstrate the economy of local food production. They want to expand on the third part and have a vision of building a hydroponic greenhouse with the intention that it will create more crops to sell and give, as well as …

Utilization Of Recycled Filament For 3d Printing For Consumer Goods, Alexa Peterson

Apparel Merchandising and Product Development Undergraduate Honors Theses

The 3D printing market has been used in a wide variety of manufacturing industries including textile and apparel. Many consumers can now own a personal 3D printer at home for recreational printing. There are even websites dedicated to 3D printing patterns made by consumers. However, the materials used in the 3D printing process pose a problem for the environment due to their plastic-based nature. 3D printing is a layered process with each layer being printed depending on the layer below it for strength and stability. During the 3D printing process, great amounts of waste are produced as a result of …

Effect Of Charged Lipids On The Ionization Behavior Of Glutamic Acid Containing Transmembrane Helices, Brooke Nunn

Chemistry & Biochemistry Undergraduate Honors Theses

Transmembrane proteins make up critical components of living cells. Protein function can be greatly impacted by the charged state of its respective components, the side chains of amino acid residues. Thus far, in the lipid membrane, little is known about the properties of residues such as glutamic acid. To explore these properties, I have included glutamic acid in a suitable model peptide-lipid system for fundamental biophysical experiments. Within the system, I have placed a glutamic acid residue instead of leucine in the L14 position of the helical hydrophobic peptide GWALP23 (acetyl-GGALWLALALALAL¹⁴ALALWLAGA-amide). Substitutions of glutamine and aspartic acid serve …

Hydrodynamic Instability Simulations Using Front-Tracking With Higher-Order Splitting Methods, Dillon Trinh

Mathematical Sciences Undergraduate Honors Theses

The Rayleigh-Taylor Instability (RTI) is an instability that occurs at the interface of a lighter density fluid pushing onto a higher density fluid in constant or time-dependent accelerations. The Richtmyer-Meshkov Instability (RMI) occurs when two fluids of different densities are separated by a perturbed interface that is accelerated impulsively, usually by a shock wave. When the shock wave is applied, the less dense fluid will penetrate the denser fluid, forming a characteristic bubble feature in the displacement of the fluid. The displacement will initially obey a linear growth model, but as time progresses, a nonlinear model is required. Numerical studies …

Construction Of A Hyperspectral Imager Using 3d-Printed And Off-The-Shelf Components, Joshua Moorhouse

Mechanical Engineering Undergraduate Honors Theses

The Arkansas Center for Space and Planetary Sciences is working in collaboration with the Mechanical Engineering department to create a relatively cheap and modifiable hyperspectral imager. It is constructed using 3D-printed and off-the-shelf components from Edmund Optics and Amazon. The iteration created in this paper delivers spectrograms in the visible spectrum. The long-term goals of the camera are to create hyperspectral images from these spectrograms and to advance the imager into the infrared and near-infrared spectra. This imager is being developed to be used in the Arkansas Center for Space and Planetary Sciences environmental test chambers to further the scientific …

Enhancement Of Phase Change Material Sorbitol By Nanoparticle Inclusion For Improving Thermal Energy Storage Capabilities, Joshua Kasitz

Mechanical Engineering Undergraduate Honors Theses

Thermal management of electronic devices has become an increasingly vital field of study with the rapid miniaturization of many key electrical components. With the significant improvement of semiconductor manufacturing and intensified focus on interconnects, electronic devices have decreased in size at an incredible rate. Decreasing spatial requirements is essential to improving device capabilities as the electronic system is able to incorporate more components. Currently, electronic systems are drastically limited by the capabilities of their cooling mechanisms. Smaller devices lead to large increases in the energy density of the system and require more powerful cooling systems to maintain proper component operating …

A Capacitive Sensing Gym Mat For Exercise Classification & Tracking, Adam Goertz

Computer Science and Computer Engineering Undergraduate Honors Theses

Effective monitoring of adherence to at-home exercise programs as prescribed by physiotherapy protocols is essential to promoting effective rehabilitation and therapeutic interventions. Currently physical therapists and other health professionals have no reliable means of tracking patients' progress in or adherence to a prescribed regimen. This project aims to develop a low-cost, privacy-conserving means of monitoring at-home exercise activity using a gym mat equipped with an array of capacitive sensors. The ability of the mat to classify different types of exercises was evaluated using several machine learning models trained on an existing dataset of physiotherapy exercises.

An Exploration Of Methods For Classifying Air-Written Letters From The Spanish Alphabet, Manuel Serna-Aguilera

Computer Science and Computer Engineering Undergraduate Honors Theses

The ability to recognize human activity, especially air-writing, is an interesting challenge as one could identify any letter from many languages. I intend to investigate this problem of air-writing, but with the added twist of including the following letters from the Spanish alphabet: Á, É, Í, Ó, Ú, Ü, and Ñ. With this new alphabet, I set out to see what kinds of classifiers work best and on what kinds of data, since letters can be represented in multiple ways.

My tracking system will consist of a regular camera and a subject who will draw with a brightly colored marker …

Dependency Mapping Software For Jira, Project Management Tool, Bentley Lager

Computer Science and Computer Engineering Undergraduate Honors Theses

Efficiently managing a software development project is extremely important in industry and is often overlooked by the software developers on a project. Pieces of development work are identified by developers and are then handed off to project managers, who are left to organize this information. Project managers must organize this to set expectations for the client, and ensure the project stays on track and on budget. The main block in this process are dependency chains between tasks. Dependency chains can cause a project to take much longer than anticipated or result in the under utilization of developers on a project. …

Identifying Privacy Policy In Service Terms Using Natural Language Processing, Ange-Thierry Ishimwe

Computer Science and Computer Engineering Undergraduate Honors Theses

Ever since technology (tech) companies realized that people's usage data from their activities on mobile applications to the internet could be sold to advertisers for a profit, it began the Big Data era where tech companies collect as much data as possible from users. One of the benefits of this new era is the creation of new types of jobs such as data scientists, Big Data engineers, etc. However, this new era has also raised one of the hottest topics, which is data privacy. A myriad number of complaints have been raised on data privacy, such as how much access …

Speech Processing In Computer Vision Applications, Nicholas Waterworth

Computer Science and Computer Engineering Undergraduate Honors Theses

Deep learning has been recently proven to be a viable asset in determining features in the field of Speech Analysis. Deep learning methods like Convolutional Neural Networks facilitate the expansion of specific feature information in waveforms, allowing networks to create more feature dense representations of data. Our work attempts to address the problem of re-creating a face given a speaker's voice and speaker identification using deep learning methods. In this work, we first review the fundamental background in speech processing and its related applications. Then we introduce novel deep learning-based methods to speech feature analysis. Finally, we will present our …

Investigating Machine Learning Techniques For Gesture Recognition With Low-Cost Capacitive Sensing Arrays, Michael Fahr Jr.

Computer Science and Computer Engineering Undergraduate Honors Theses

Machine learning has proven to be an effective tool for forming models to make predictions based on sample data. Supervised learning, a subset of machine learning, can be used to map input data to output labels based on pre-existing paired data. Datasets for machine learning can be created from many different sources and vary in complexity, with popular datasets including the MNIST handwritten dataset and CIFAR10 image dataset. The focus of this thesis is to test and validate multiple machine learning models for accurately classifying gestures performed on a low-cost capacitive sensing array. Multiple neural networks are trained using gesture …

Wayne E. Sabbe Arkansas Soil Fertility Studies 2019, Nathan A. Slaton

Arkansas Agricultural Experiment Station Research Series

Rapid technological changes in crop management and production require that the research efforts be presented in an expeditious manner. The contributions of soil fertility and fertilizers are major production factors in all Arkansas crops. The studies described within will allow producers to compare their practices with the university’s research efforts. Additionally, soil-test data and fertilizer sales are presented to allow comparisons among years, crops, and other areas within Arkansas.

Applying Imitation And Reinforcement Learning To Sparse Reward Environments, Haven Brown

Computer Science and Computer Engineering Undergraduate Honors Theses

The focus of this project was to shorten the time it takes to train reinforcement learning agents to perform better than humans in a sparse reward environment. Finding a general purpose solution to this problem is essential to creating agents in the future capable of managing large systems or performing a series of tasks before receiving feedback. The goal of this project was to create a transition function between an imitation learning algorithm (also referred to as a behavioral cloning algorithm) and a reinforcement learning algorithm. The goal of this approach was to allow an agent to first learn to …

Design Of Submicron Structured Guided-Mode-Resonance Near-Infrared Polarizer, Marzia Zaman

Graduate Theses and Dissertations

The objective of this research is to design a larger submicron linear polarizer in the near-infrared wavelength range with a wide bandwidth which can be fabricated using the conventional thin-film microfabrication technology to reduce cost. For this purpose, a gold (Au) wire-grid transmission-type transverse-magnetic (TM) polarizer and a silicon (Si) wire-grid reflection-type TM polarizer, were designed using the guided-mode-resonance filter. The Au wire-grid TM polarizer of 700nm grating width and 1200nm grating period has 95% transmittance at 2400nm, more than 1000nm resonance peak bandwidth, and an extinction ratio (ER) of around 300 with a moderated level of sidebands. The 700nm …