Digital Commons Network^™

Development Of Vs Profiles And Site Periods In The Mexico City Basin, Landon Joel Woodfield

Graduate Theses and Dissertations

This study presents dynamic site characterization measurements at 25 sites within the Mexico City Basin. The primary focus of the testing was along the western edge of the Mexico City Basin. At each site, active source Multi-channel Analysis of Surface Waves (MASW) arrays and passive source Microtremor Array Measurements (MAM) L-arrays and circular arrays were used to acquire dispersion data. Horizontal to Vertical Spectral Ratio (HVSR) data was collected to determine site periods at each location. These experimental dispersion data and site periods were fit using a joint inversion of Rayleigh and Love wave dispersion data and HVSR site period …

College Student Changing Attitudes And Beliefs About The Nature Of And Teaching Of Mathematics And Science, Stephen R. Skinner

Graduate Theses and Dissertations

With an estimated 17.3 million STEM jobs in the US, there exists a need for a STEMready workforce that is science literate with positive attitudes and beliefs toward the learning and teaching of mathematics and science (Graf, Fry, & Funk, 2018). However, the US has seen a steady decline in the number of high school students interested in STEM-related fields with only 16% of interested students with proven proficiency in mathematics and science and are ready to enroll in college STEM programs (ACT, 2017; Osborne & Dillon, 2008; Stake & Mares, 2001). With the decline in student interest, the US …

Shakespeare In The Eighteenth Century: Algorithm For Quotation Identification, Marion Pauline Chiariglione

Graduate Theses and Dissertations

Quoting a borrowed excerpt of text within another literary work was infrequently done prior to the beginning of the eighteenth century. However, quoting other texts, particularly Shakespeare, became quite common after that. Our work develops automatic approaches to identify that trend. Initial work focuses on identifying exact and modified sections of texts taken from works of Shakespeare in novels spanning the eighteenth century. We then introduce a novel approach to identifying modified quotes by adapting the Edit Distance metric, which is character based, to a word based approach. This paper offers an introduction to previous uses of this metric within …

A Study Of Optical Nonlinearities At The Single-Photon Level For Quantum Logic, Balakrishnan Viswanathan

Graduate Theses and Dissertations

In this dissertation, we shall focus on theoretically studying quantum nonlinear optical schemes to construct a conditional phase gate at the single-photon level. With an aim to develop analytical models, we shall carry out a rigorous quantized multimode field analysis of some of these schemes involving only the interacting field operators. More specifically, we shall first study the three-wave mixing process involving two single-photons in a second-order nonlinear medium (x(2)) under two different cases viz. when the photons are traveling with equal velocities and when they are traveling with different velocities, and explore the possibility of using them for building …

A Virtual Space Vectors Based Model Predictive Control For Three-Level Converters, Waleed Saad S. Alhosaini

Graduate Theses and Dissertations

Three-phase three-level (3-L) voltage source converters (VSC), e.g., neutral-point clamped (NPC) converters, T-type converters, etc., have been deemed to be suitable for a wide range of medium- to high-power applications in microgrids (MGs) and bulk power systems. Compared to their two-level (2-L) counterparts, adopting 3-L VSCs in the MG applications not only reduces the voltage stress across the power semiconductor devices, which allows achieving higher voltage levels, but also improves the quality of the converter output waveforms, which further leads to considerably smaller output ac passive filters.

Various control strategies have been proposed and implemented for 3-L VSCs. Among all …

Effects Of Light, Nutrients, And Salts On Microbial Biofilm Productivity And Detrital Processing In Aquatic Mesocosms, Bethanie Brooke Howard-Parker

Graduate Theses and Dissertations

Anthropogenic activities associated with urbanization, agriculture, and resource extraction continue to increase to support increasing needs of the growing population. These activities increase the amounts of pollutants entering freshwater streams and put aquatic ecosystems at structural and functional risk. Aquatic microbes play an important role in detrital processing in streams as a key linkage in moving carbon from detrital stocks into aquatic food webs. My research investigates the effects of light, nutrients, and salts on detrital microbes and decomposition in freshwaters using a mesocosm approach. In chapter one, I modified a current priming effect (PE) hypothesis model to include light …

Chefs' Perceptions Of Zero Waste Cooking In Restaurants, Josephine Reardon

Graduate Theses and Dissertations

The purpose of this study is to examine chefs’ perceptions and practices relative to current and potentially future efforts to decrease food waste. Through qualitative inquiry, this research aims to identify food waste reduction practices in Northwest Arkansas restaurants; chef’s perceptions of these practices and zero waste cooking; the impact these practices have on successfully implementing sustainability; and the biggest challenges in reducing food waste in restaurants. The results of this study will assist chefs and restaurant owners by providing guidance on practices easily utilized in restaurants currently.

An interview protocol, with five sections, was conducted with ten chefs at …

Soil Microbial Diversity And Litter Decomposition Increase With Time Since Land Use Disturbance In Tropical Montane Forests Of Malaysian Borneo, Renee Sniegocki

Graduate Theses and Dissertations

Logging and forest conversion are occurring at alarming rates in the tropical forests of Southeast Asia. These disturbances alter soil chemistry, microbial diversity, and disrupt carbon cycling through shifts in litter decomposition. Direct links between microbial diversity and soil properties such as pH are well established; however, the indirect impacts of logging and forest conversion on microbial diversity and litter decomposition are poorly understood. We used surface (5 cm) soil to assess soil physicochemical properties, next-generation DNA sequencing to assess soil microbial diversity, and standardized litterbags to assess litter decomposition stabilization at five sites along a land use disturbance gradient …

Achieving Causal Fairness In Machine Learning, Yongkai Wu

Graduate Theses and Dissertations

Fairness is a social norm and a legal requirement in today's society. Many laws and regulations (e.g., the Equal Credit Opportunity Act of 1974) have been established to prohibit discrimination and enforce fairness on several grounds, such as gender, age, sexual orientation, race, and religion, referred to as sensitive attributes. Nowadays machine learning algorithms are extensively applied to make important decisions in many real-world applications, e.g., employment, admission, and loans. Traditional machine learning algorithms aim to maximize predictive performance, e.g., accuracy. Consequently, certain groups may get unfairly treated when those algorithms are applied for decision-making. Therefore, it is an imperative …

Understanding Ice Mixtures Under Pluto Simulated Conditions And Their Implications For Geophysical Processes, Caitlin Joannah Ahrens

Graduate Theses and Dissertations

New Horizons at Pluto has given the planetary science community the first images of Pluto’s surface, including geologic wonders and compositional variability. Methane, nitrogen, and carbon monoxide make up the bulk of the volatile plutonian surface along with water ice. In this work, these three main volatiles are specifically investigated in the laboratory setting to understand the spectral properties and behavior of binary and ternary mixtures. The spectra are taken in the near-infrared wavelengths (1 – 2.5 µm) using Fourier transform infrared (FTIR) spectroscopy techniques utilizing the Pluto Simulation Chamber housed at the University of Arkansas, which can reach conditions …

Area Efficient Device Optimization For Esd Protection In High Speed Interface Ics, Dan Thomas Jarard

Graduate Theses and Dissertations

Electrostatic discharge (ESD) protection is considered as a vital step in integrated circuit (IC) manufacturing process. IC chips are unable to overcome the effects of transient events without adequate discharge protection. Recent trend in the industry has seen the incorporation of system level ESD protection within the IC chip. Incorporating system level on-chip ESD protection often increases cost, degrades circuit performance and consumes layout area which could otherwise be used for improving the circuit performance. These design challenges could be easily overcome if the parasitic components in a circuit were used for ESD protection. Despite the various design challenges, on-chip …

Struvite Behavior And Effects As A Fertilizer-Phosphorus Source Among Arkansas Soils, Ryder Shaw Anderson

Graduate Theses and Dissertations

Phosphorus (P) is a fundamental element that is involved in many essential biological processes in all forms of life and is a major component in commercial fertilizers. Traditional P fertilizers are derived from rock phosphate (RP), which is limited in supply and expected to be depleted over the next 250 years. Phosphorus recovery technology has been an area of recent interest due to the potential food security risk of traditional RP-derived fertilizer-P sources. Magnesium ammonium phosphate (MgNH4PO4 · 6H2O), which is the mineral struvite, is a wastewater-recovered mineral that has gained attention as a potential sustainable fertilizer-P source. The primary …

Hyperbolic Endomorphisms Of Free Groups, Jean Pierre Mutanguha

Graduate Theses and Dissertations

We prove that ascending HNN extensions of free groups are word-hyperbolic if and only if they have no Baumslag-Solitar subgroups. This extends Brinkmann's theorem that free-by-cyclic groups are word-hyperbolic if and only if they have no Z2 subgroups. To get started on our main theorem, we first prove a structure theorem for injective but nonsurjective endomorphisms of free groups. With the decomposition of the free group given by this structure theorem, we (more or less) construct representatives for nonsurjective endomorphisms that are expanding immersions relative to a homotopy equivalence. This structure theorem initializes the development of (relative) train track theory …

Data Breach Consequences And Responses: A Multi-Method Investigation Of Stakeholders, Hamid Reza Nikkhah

Graduate Theses and Dissertations

The role of information in today’s economy is essential as organizations that can effectively store and leverage information about their stakeholders can gain an advantage in their markets. The extensive digitization of business information can make organizations vulnerable to data breaches. A data breach is the unauthorized access to sensitive, protected, or confidential data resulting in the compromise of information security. Data breaches affect not only the breached organization but also various related stakeholders. After a data breach, stakeholders of the breached organizations show negative behaviors, which causes the breached organizations to face financial and non-financial costs. As such, the …

Study Of A Symmetrical Llc Dual-Active Bridge Resonant Converter Topology For Battery Storage Systems, John K. George

Graduate Theses and Dissertations

A symmetrical LLC resonant converter topology with a fixed-frequency quasi-triple phase-shift modulation method is proposed for battery-powered electric traction systems with extensions to other battery storage systems. Operation of the converter with these methods yields two unique transfer characteristics and is dependent on the switching frequency. The converter exhibits several desirable features: 1) load-independent buck-boost voltage conversion when operated at the low-impedance resonant frequency, allowing for dc-link voltage regulation, zero-voltage switching across a wide load range, and intrinsic load transient resilience; 2) power flow control when operated outside the low-impedance resonance for integrated battery charging; 3) and simple operational mode …

Cybersecurity Methods For Grid-Connected Power Electronics, Stephen Joe Moquin

Graduate Theses and Dissertations

The present work shows a secure-by-design process, defense-in-depth method, and security techniques for a secure distributed energy resource. The distributed energy resource is a cybersecure, solar inverter and battery energy storage system prototype, collectively called the Cybersecure Power Router. Consideration is given to the use of the Smart Green Power Node for a foundation of the present work. Metrics for controller security are investigated to evaluate firmware security techniques. The prototype's ability to mitigate, respond to, and recover from firmware integrity degradation is examined. The prototype shows many working security techniques within the context of a grid-connected, distributed energy resource. …

Stay-At-Home Motor Rehabilitation: Optimizing Spatiotemporal Learning On Low-Cost Capacitive Sensor Arrays, Reid Sutherland

Graduate Theses and Dissertations

Repeated, consistent, and precise gesture performance is a key part of recovery for stroke and other motor-impaired patients. Close professional supervision to these exercises is also essential to ensure proper neuromotor repair, which consumes a large amount of medical resources. Gesture recognition systems are emerging as stay-at-home solutions to this problem, but the best solutions are expensive, and the inexpensive solutions are not universal enough to tackle patient-to-patient variability. While many methods have been studied and implemented, the gesture recognition system designer does not have a strategy to effectively predict the right method to fit the needs of a patient. …

Comparative Geochemical Analysis Of Ordovician And Mississippian Cherts In Relation To The Northern Arkansas And The Tri-State Mississippi Valley-Type Ore Districts, Jonathan T. Chick

Graduate Theses and Dissertations

It has been hypothesized that Ordovician, Mississippian, and younger carbonate and clastic formations found within the Ouachita Basin of west-central Arkansas and northward onto the Ozark Dome have experienced interaction with hydrothermal fluids due to tectonic forces produced by the Ouachita Orogeny. Lead (Pb) isotope analyses and resulting values produced through previous and concurrent geochemical studies of several formations indicate that the Mississippi Valley-type (MVT) ores were produced from a mixing and cooling of these sedimentary basinal brines by meteoric or connate waters. Reduction of sulfate to sulfide is one of the possible mechanisms by which MVT ore precipitation may …

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 …

An Evaluation Of Unmanned Aircraft Systems' Ability To Assess Stripe Rust In Large Wheat Breeding Nursies, Jamison T. Murry

Graduate Theses and Dissertations

Stripe Rust (Puccinia striiformis f. sp. tritici) is a foliar disease that significantly impacts global wheat production, and resistant cultivars provide the most efficient method of control. High-throughput phenotyping using unmanned aircraft systems (UAS) offers a potentially more efficient method for field-based phenotyping compared to visual assessment. Here we tested the ability of remote sensing to predict stripe rust severity in a diverse population of 594 soft red winter wheat lines, planted in single-rows, and evaluated them by visually rating stripe rust intensity and remotely using the dark green color index (DGCI), normalized difference vegetation index (NDVI) and blue NDVI. …

Improvement Of Geometric Quality Inspection And Process Efficiency In Additive Manufacturing, Yu Jin

Graduate Theses and Dissertations

Additive manufacturing (AM) has been known for its ability of producing complex geometries in flexible production environments. In recent decades, it has attracted increasing attention and interest of different industrial sectors. However, there are still some technical challenges hindering the wide application of AM. One major barrier is the limited dimensional accuracy of AM produced parts, especially for industrial sectors such as aerospace and biomedical engineering, where high geometric accuracy is required. Nevertheless, traditional quality inspection techniques might not perform well due to the complexity and flexibility of AM fabricated parts. Another issue, which is brought up from the growing …

From Start To Finish: Predicting Enrollment And Attainment In Arkansas Postsecondary Education, Katherine Kopotic

Graduate Theses and Dissertations

Postsecondary education has become a popular option for students, as evidenced by increases in enrollment over the last two decades. However, while enrollment has increased, completion has not. It is therefore important to investigate the factors that could lead to students’ enrollment, persistence, and completion of college. This dissertation examines two broad topics over three chapters. Chapters 1 and 2 focus examine the impact of a policy change that resulted in backloading the award disbursement of a state-wide merit-based scholarship program in Arkansas on college enrollment and success. Chapter 3 examines factors that influence the predictive nature of high school …

Teacher Turnover And Teacher Retirement, Dillon Fuchsman

Graduate Theses and Dissertations

Teachers have an important impact on students in the short- and long-term, but only teachers’ experience consistently predicts high teacher quality. This dissertation, divided into three chapters, investigates two topics that are related to teachers’ experience levels: turnover and retirement.

The first chapter studies the relationship between voluntary beginning teacher turnover and teachers’ levels of conscientiousness. It uses the data from the Beginning Teacher Longitudinal Study and the effort that teachers put on a survey taken during their first year in the profession as a proxy for teachers’ levels of conscientiousness. The results of this chapter indicate that teachers putting …

Hydroponic And Soilless Culture Systems And Transplant Practices Influence Production Of Basil (Omicum Basilicum L.), Samuel Warren Edward Doty

Graduate Theses and Dissertations

Two controlled-environment greenhouse experiments evaluated (1) plant growth and morphology of basil (Omicum basilicum L.) grown in three different hydroponic and soilless substrate systems and (2) seedling tray cell-count and transplant date into hydroponic culture effects on basil growth and yield at harvest. For the first experiment, four basil cultivars (‘Genovese’, ‘Mrs. Burns Lemon’, ‘Sweet Thai’, and ‘Cinnamon’) were grown in deep flow technique (DFT) hydroponics, nutrient film technique (NFT) hydroponics, and a novel shallow aggregate ebb-and-flood (SAEF) soilless substrate system and were harvested after 21 d. Plant yield and morphological characteristics measured at harvest included shoot fresh mass, shoot …

Lay Latitude: Latter-Day Saint Women's Agency In Northwest Arkansas, Andrew Tompkins

Graduate Theses and Dissertations

The question of women’s agency in gender-traditional religions has been the subject of much scholarly attention over the past four decades, but little research has been done focusing specifically on Latter-day Saint women and their identities and roles within the structure and practice of the Church. In popular media representations, Latter-Day Saint women are often depicted as submissive or surviving, either powerless pawns or resistant warriors. However, many Latter-day Saint women find fulfillment and empowerment within and because of, rather than outside or in spite of, the institutional Church. In this thesis, I explore women’s agency in Northwest Arkansas’ Greendale …

An Isotopic Assessment Of Late Prehistoric Interregional Warfare In The Southcentral Us, John R. Samuelsen

Graduate Theses and Dissertations

Skull burials are found all over the world. The cause of such ancient Native Americans deposits often lead to disagreement among scholars torn between warfare and ancestor veneration. One skull-and-mandible deposit, representing at least 352 people (A.D. 1253-1399), was uncovered at the Crenshaw site, a multiple-mound Caddo ceremonial center in southwest Arkansas. Most previous research suggested they were victims of interregional warfare from the Southern Plains or Mississippi Valley. One previous study hypothesized that this was a Caddo burial practice which expanded during the Middle Caddo period (A.D. 1200-1500) due to the adoption of maize as a staple and a …

Secure And Efficient Models For Retrieving Data From Encrypted Databases In Cloud, Sultan Ahmed A Almakdi

Graduate Theses and Dissertations

Recently, database users have begun to use cloud database services to outsource their databases. The reason for this is the high computation speed and the huge storage capacity that cloud owners provide at low prices. However, despite the attractiveness of the cloud computing environment to database users, privacy issues remain a cause for concern for database owners since data access is out of their control. Encryption is the only way of assuaging users’ fears surrounding data privacy, but executing Structured Query Language (SQL) queries over encrypted data is a challenging task, especially if the data are encrypted by a randomized …

Detection Of Woody Breast Condition In Broiler Carcasses And Product Utilization In Further Processing, Juan Pablo Caldas Cueva

Graduate Theses and Dissertations

Woody Breast (WB) myopathy causes significant economic losses to the global poultry industry and the lack of objective, non-invasive and rapid methods for its detection as well as profitable alternatives for its utilization are contributing factors. This dissertation is divided into two main areas. The first area aimed to determine if there are carcass conformation changes that can be used to identify WB characteristics in commercial broilers using image analysis. In the first experiment, images of broiler carcasses were captured before evisceration to obtain and evaluate carcass measurements from the breast region. Eight image measurements and four ratios were used …

An Fpga-Based Hardware Accelerator For The Digital Image Correlation Engine, Keaten Stokke

Graduate Theses and Dissertations

The work presented in this thesis was aimed at the development of a hardware accelerator for the Digital Image Correlation engine (DICe) and compare two methods of data access, USB and Ethernet. The original DICe software package was created by Sandia National Laboratories and is written in C++. The software runs on any typical workstation PC and performs image correlation on available frame data produced by a camera. When DICe is introduced to a high volume of frames, the correlation time is on the order of days. The time to process and analyze data with DICe becomes a concern when …

Quantifying Greenhouse Gas Emissions And Ammonia Volatilization From Soil Amended With Excreta From Ruminants Fed Alternative Forage-Based Diets, Samuel Park

Graduate Theses and Dissertations

Forage-based ruminant diets supplemented with condensed tannins or polyphenolic-containing legumes may alter nitrogen (N) metabolism in the animal and reduce gas emissions from soil receiving excreta. The objective of the study was to determine if soil receiving urine or manure from sheep fed forage diets supplemented with condensed tannin or polyphenolic-containing legumes would decrease N gas emissions. Two field trials were conducted: in the first trial, sheep were fed alfalfa (Medicago sativa L.) silage diets supplemented with 0, 9, 18, or 27% sericea lespedeza (Lespedeza cuneate [Dumont de Courset] G. Don) (n = 4). In the second trial sheep were …