Digital Commons Network^™

Tribological Studies Of Thick Polytetrafluoroethylene Coatings Enhanced By Polydopamine And Nanoparticles, Sujan Kumar Ghosh

Graduate Theses and Dissertations

Polytetrafluoroethylene (PTFE) is a popular low friction solid lubricant with high chemical and thermal stability. Thick PTFE coatings have the potential for many tribological applications, such as replacing Tin-based Babbitt materials in journal bearings. However, the weak bonding strength to the substrate and the high wear rate of PTFE coatings are current limiting factors. The lack of understanding of their tribological properties and wear mechanisms in oil-lubricated conditions and how coating thickness affects the tribological performance further hindered the use of PTFE coatings. In this dissertation, polydopamine (PDA), a bio-inspired adhesive, is used as an underlayer for or as a …

Applications Of Masw And Mhvsr Techniques For Infrastructure Evaluation With A Focus On The Effects Of Different Transformation Techniques And Near-Field Effects On Derived Dispersion Data, Salman Rahimi

Graduate Theses and Dissertations

This dissertation is aimed at understanding two aspects of active surface wave methods to improve the accuracy and reliability of this method. These include (1) the performance of four common wavefield transformation methods for the multichannel analysis of surface wave (MASW) data processing and (2) near-field effects. Toward this end, extensive field measurements were conducted considering different factors affecting these two topics. The MASW and microtremor horizontal to vertical spectral ratio (MHVSR) were then employed to examine their efficiency for infrastructure health monitoring.

Regarding the performance of the four common transformation techniques, it was observed that for sites with a …

Development Of Novel Battery Materials For Lithium-Ion Batteries And Beyond, Jiyu Cai

Graduate Theses and Dissertations

As fossil fuels are depleting and causing environmental issues, it becomes imperative to widely implement renewable energies (e.g., solar and wind power). In this context, electrical energy storage (EES) systems are essential to accommodate the intermittent supply and uneven distribution of renewable energies. To this end, high-energy-density EES devices are highly demanded, such as rechargeable batteries. This dissertation presents my efforts in developing novel battery materials for lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), and solidstate lithium batteries (SSLBs). These efforts include electrochemical evaluations of battery materials, surface modifications of electrodes via atomic layer deposition (ALD), and advanced characterizations of batteries …

Establishment Of Pollinator Habitat Within A Livestock Pasture Ecosystem, Roshani Sharma Acharya

Graduate Theses and Dissertations

Pollinators are important for fertilization, setting fruits, and seed development of more than 78% of the flowering plants that provide food for human beings and other species. Use of pollinators to maximize crop production is a proven agricultural practice; however, it has been less explored in livestock forage production systems. This study investigated pollinator abundance and diversity in pastures using different sampling methods and determined the impact of different pasture management practices on insect pollinators in a livestock pasture ecosystem. In Chapter 2, utility of four different colors of pan trap (blue, green, yellow, and purple) for sampling bees in …

Phase-Field Modeling Of The Polymer Membrane Formation Process For Micro- And Ultra-Filtration, Michael Rosario Cervellere

Graduate Theses and Dissertations

Porous polymer membrane filters are widely used in separation and filtration process. Micro- and ultra-filtration membranes are commonly used in biopharmaceutical applications such as filtering viruses and separating proteins from a carrier solution. The formation of these membrane filters via phase inversion is a complex and interconnected process where varying casting conditions can have a wide variety of effects on the final membrane morphol- ogy. Tailoring membrane filters for specific performance characteristics is a tedious and time consuming process. The time and length scales of membrane formation make it extremely difficult to experimentally observe membrane formation. Modeling the membrane formation …

Data-Driven Methods To Address Truck Parking Shortages For Long-Haul Commercial Truck Drivers, Sharif Mahmud

Graduate Theses and Dissertations

Truck parking is a critical concern for both the trucking industry and the truck drivers. Long-haul commercial truck drivers rely on safe and adequate parking to support interstate commerce, which has become a challenge due to parking shortages. The recent electronic logging device (ELD) mandate, forcing a strict compliance to hours of service (HOS) regulations, are leading to higher demand for parking. A number of federal, regional, and local studies reveal that truck activity will increase and truck parking demand will outpace parking supply in the coming years. Such parking shortages likely disrupt freight flows and pose risks to truck …

Mitigating Calcium Oxychloride Damage In Cementitious Paste And Concrete Utilizing Supplementary Cementitious Materials, Casey Jones

Graduate Theses and Dissertations

It is understood among engineers in the United States (U.S.) that improvement is needed throughout the transportation infrastructure. In the 2021 Infrastructure Report Card produced by the American Society of Civil Engineers, the roadways of this nation merit a D. This leaves room for improvement in order to provide durable pavements throughout this nation. Areas with significant winter weather may have exacerbated effects in decreased roadway longevity due to freezing/thawing cycles and the use of chemical deicers to mitigate gelid roadway conditions. Much research focuses on surface scaling and reinforcement corrosion using these materials; however, joint deterioration, due to chemical …

Influence Of Extracellular Matrix Stiffness And Topography On Neuronal Cell Behavior And Neurite Outgrowth, Mohan Yasodharababu

Graduate Theses and Dissertations

The focus of regeneration therapy for traumatic brain injuries and Alzheimer's disease is on the promotion and growth of neuronal cells. In vitro research attempts to improve this by modifying the stiffness and topography of the extracellular matrix (ECM). However, the limitations of in vitro experiments make it difficult to control the individual factors influencing neuronal cell growth. A computational model can be used to decouple individual factors and study them individually to gain a better understanding of the mechanics between the neuronal cell and ECM, which will aid in the design of in vitro experimental studies.

This study develops …

The Plexiglass Ceiling: Exploring Systemic Racism And Sexism In Public Leadership Positions, Kaylin Oliver

Graduate Theses and Dissertations

The numbers of black women who hold leadership positions within public institutions are not correspondingly reflective of their overall numbers within public institutions. The focus of this study is to examine how race and gender discrimination prohibits black women from obtaining leadership positions in public institutions.. I propose a new theory Workplace Intersectional Infringement Theory (WIIT) to increase the efficacy of the study on black women in Public Institutions. Using snowball sampling, I conduct interviews with 11 black women who hold leadership positions across a variety of public institutions within the United States. I found a majority of the participants …

Directed Genome Evolution To Identify Genes For Macrophage Survival By Staphylococcus Agnetis, Sonali Lakshika Anne Lenaduwe Lokuge

Graduate Theses and Dissertations

Bacterial Chondronecrosis with Osteomyelitis (BCO) is a debilitating infection that negatively impacts animal welfare and costs the broiler industry billions of dollars annually. We have previously isolated Staphylococcus agnetis 908 from BCO samples obtained from broilers at the University of Arkansas research farm. This isolate can induce BCO lameness at greater than 50% in broilers exposed to the pathogen in drinking water. We found that S. agnetis 908 is capable of surviving and escaping macrophages compared to a closely related cattle isolate,1379. Through Directed Genome Evolution (DGE) we identified that this difference is at least partially associated with an alanine …

Centropoly: The Structure Of Educational Failures In The U.S., Martha Bradley-Dorsey

Graduate Theses and Dissertations

How did a country birthed in individual liberty and voluntary associations create just the opposite in its inflexible, layered, government-controlled public education system? Here, using public choice theory, I explain how near-sighted and unrelated reforms, often based in private motives, gave us what I call the public education centropoly – a hybrid government organization consisting of a set of monopolies layered beneath two additional government levels that especially fails disadvantaged students.

After defending the use of public choice theory (Chapter 1) and summarizing the U.S. public education system formation (Chapter 2), in Chapter 3 I examine the Elementary and Secondary …

Machine Learning & Big Data Analyses For Wildfire & Air Pollution Incorporating Gis & Google Earth Engine, Abdullah Al Saim

Graduate Theses and Dissertations

The climatic condition, the vegetation type, and the landscape of the United States have made it susceptible to wildfires. This research is divided into two parts based on the analysis of two different aspects of wildfires of two distinct regions. The first part of the study investigates the wildfire susceptibility in Arkansas. Arkansas is a natural state, and it is heavily dependent on its forest and agricultural resources. During the last 30 years, more than 1,000 wildfires occurred in Arkansas and caused more than 10,000 acres of burned areas. Therefore, identifying wildfire-susceptible areas is crucial for ensuring sustainable forest and …

A Machine Learning Approach To Understanding Emerging Markets, Namita Balani

Graduate Theses and Dissertations

Logistic providers have learned to efficiently serve their existing customer bases with optimized routes and transportation resource allocation. The problem arises when there is potential for logistics growth in an emerging market with no previous data. The purpose of this work is to use industry data for previously known and well-documented markets to apply data analytic techniques such as machine learning to investigate the uncertainty in a new market. The thesis looks into machine learning techniques to predict miles per stop given historical data. It mainly focuses on Random Forest Regression Analysis, but concludes that additional techniques, such as Polynomial …

Essays On Managerial Attributes And Corporate Finance, Juntai Lu

Graduate Theses and Dissertations

In my dissertation, I explore how managerial attributes affect corporate policies.

In my first essay, I examine the effects of public firm CEOs’ prior private equity (PE) target experiences on corporate policies. Based on difference-in-differences and propensity score matching analyses, public firm CEOs previously serving as CEOs in PE targets reduce investment by about 15 percent while enhancing patent values by over 7 percent after taking office compared to CEOs without such experiences. The effects are stronger if these CEOs (1) worked in targets invested by more reputable PE firms, (2) worked in targets invested by PE firms known for …

Evaluating Bioenergetics And Mitochondrial Dynamics In Patient Fibroblasts With Pathogenic Mitochondrial Dna Mutations Causing Leigh Syndrome, Ajibola Bakare

Graduate Theses and Dissertations

Leigh syndrome (LS) is a rare fatal mitochondrial disorder of infants caused by pathogenic mutations in the nuclear (nDNA) or mitochondrial DNA (mtDNA) leading to mitochondrial dysfunction. The extent to which pathogenic mtDNA variants regulate disease severity in LS is not well understood. The heterogeneous nature of this disorder, based in part by complex mitochondrial genetics, and the nuclear and mitochondrial cross-talk has made it particularly challenging to investigate and develop therapies for treating LS . While the prognosis is poor, several studies are underway to understand the pathophysiology of LS. This dissertation provides a comprehensive structural and functional analysis …

Audit Firms’ Response To Audit Failures: Evidence From Partner Resource Reallocation, Elizabeth Cowle

Graduate Theses and Dissertations

I investigate whether audit firms reallocate partner resources following restatement announcements and, consequently, whether a supply-side response is beneficial in mitigating the previously documented implications of realized audit failures. I find a positive association between prior period restatement announcements and the year-over-year percentage change in the number of engagement partners allocated to a local audit office. Further analysis suggests that a supply-side response is beneficial in mitigating the persistence of low-quality audits and lost market share. However, I also find some evidence suggesting that the reallocation of partner resources can be detrimental to audit quality at offices from which partners …

Developing A Lab-Scale Fluidized Bed Dryer System To Enhance Rough Rice Drying Process, Kaushik Luthra

Graduate Theses and Dissertations

For more than half of the world's population, rice (Oryza sativa L.) is a staple meal. However, rice growers encounter difficulties supplying this demand, particularly in developing nations, where rice is susceptible to spoilage if the moisture content is not lowered to a safe level soon after harvest. As a result, traditional drying methods, such as sun drying and natural air drying, are commonly used by rice growers, particularly in underdeveloped nations. However, these procedures are time-consuming and can lead to rice spoilage. On the other hand, fluidized bed drying is a well-established technology that might give rice growers a …

Vulnerability To And Protection Against Covid-19 Fear, Threat, And Worry, Marsha Kim Huh

Graduate Theses and Dissertations

Drawing from a sample of 10,368 adults living in the U.S., the current study examines the role of social and psychological resources in lowering COVID-related fear, threat, and worry, controlling for a number of social vulnerabilities (e.g. gender, race/ethnicity, and presence of children). The impact of social location, particularly in regards to race, and how one accesses and/or utilizes social and psychological resources is also examined through disaggregated regression models. Results demonstrate that some social and psychological resources impact COVID-specific distress (fear/threat/worry), but depending on the resource, relationships vary in direction and significance. The strength of social ties and mastery …

Privacy-Preserving Cloud-Assisted Data Analytics, Wei Bao

Graduate Theses and Dissertations

Nowadays industries are collecting a massive and exponentially growing amount of data that can be utilized to extract useful insights for improving various aspects of our life. Data analytics (e.g., via the use of machine learning) has been extensively applied to make important decisions in various real world applications. However, it is challenging for resource-limited clients to analyze their data in an efficient way when its scale is large. Additionally, the data resources are increasingly distributed among different owners. Nonetheless, users' data may contain private information that needs to be protected.

Cloud computing has become more and more popular in …

A Multicase Study Exploring The Motivation Of Support Staff In The Office Of The Registrar, April M. Martin

Graduate Theses and Dissertations

Although a large body of research exists within higher education that focuses on factors related to faculty motivation and student motivation, there is limited research concentrated on the motivation of college and university administrative staff. This study examined how job duties, work processes, elements of the work environment, and leadership styles are related to employee motivation, specifically the motivation of front-line support staff who work in the Office of the Registrar. Additionally, I aimed to identify any disconnect between what support staff need and want from supervisors in the Office of the Registrar pertaining to motivation and supervisors’ behavior to …

Investigation Of Membrane Based Processes For Biomedical Applications, Efecan Pakkaner

Graduate Theses and Dissertations

As substantial developments were achieved in nanotechnology and polymer engineering, especially in the last few decades, the use of membranes and membrane-based procedures was found to be expanding into more and more research and development areas; including biological engineering, life sciences and biomedical engineering. Not only have they been the main focus of meaningful research, but they have also been the main pieces of the solutions to very thorny problems encountered within a wide range of applications from microfluidics to water treatment, thanks to their versatility, cost-effectiveness and biocompatibility, when compared to conventional separation techniques. To celebrate and embrace these …

Scheduling Allocation And Inventory Replenishment Problems Under Uncertainty: Applications In Managing Electric Vehicle And Drone Battery Swap Stations, Amin Asadi

Graduate Theses and Dissertations

In this dissertation, motivated by electric vehicle (EV) and drone application growth, we propose novel optimization problems and solution techniques for managing the operations at EV and drone battery swap stations. In Chapter 2, we introduce a novel class of stochastic scheduling allocation and inventory replenishment problems (SAIRP), which determines the recharging, discharging, and replacement decisions at a swap station over time to maximize the expected total profit. We use Markov Decision Process (MDP) to model SAIRPs facing uncertain demands, varying costs, and battery degradation. Considering battery degradation is crucial as it relaxes the assumption that charging/discharging batteries do not …

Are Rice Markets In Bangladesh Efficiently Pricing Rice Based On Quality? An Empirical Assessment, Indrani Saha

Graduate Theses and Dissertations

Rice is an important staple for more than half of the world’s population and is the main staple in Bangladesh, accounting for 65 percent to 70 percent of the daily calorie intake. The importance of rice consumption and the high level of food insecurity in Bangladesh highlights the importance of having markets that efficiently price rice according to consumer preferences. This study aims to assess how effectively rice prices in Bangladesh are reflective of rice quality. More specifically, we estimate how the rice market is currently pricing selected rice quality attributes, such as broken percentage, chalk percentage, kernel size and …

A Time-Course Characterization Of Muscle Function And Mitochondrial Markers During Colorectal Cancer-Induced Cachexia In Tumor-Bearing Male Mice, Ana Cabrera Ayuso

Graduate Theses and Dissertations

Cachexia is a multisystemic and multifactorial syndrome prevalent in cancer patients. It is clinically defined by involuntary loss of >5% weight in a six-month window, despite nutritional interventions. A negative energy balance characterizes cancer cachexia (CC), it is associated with weakness and fatigue in skeletal muscle. Impaired muscle function is associated with lower quality of life in cancer patients. Defects in mitochondrial function are strongly associated with muscle wasting. This study explored muscular contractile function and mitochondrial quality control (MQC) markers in soleus, gastrocnemius, and tibialis anterior (TA) muscles of C26-induced male tumor-bearing mice during a 25-day time course. It …

Defining Marriageability: Black Men Graduate Student’S Definition Of A Marriageable Man, Gabriel Evans

Graduate Theses and Dissertations

The project aims to explore Black graduate men's conception of the term Marriageable Man. Traditionally, men's marriageability has been defined by their ability to attain consistent income and or in their ability to provide for a wife or a family (Johnson and Loscocco 2015; King and Allen 2009a). However, there is a need for more holistic marriageability measurements due to the evolution of marriage practices and desires (Coontz 2006, 2007). Marriageability is contextualized through classed definitions and presents different requirements for one's SES standing (Bridges and Boyd 2016). This project seeks to add to the literature by exploring Black men …

Rethinking Immigration Justice: Mexican Community Activism While Serving Migrants In Transit., Angélica Villagrana

Graduate Theses and Dissertations

This research study focuses on the externalization of migration control and its effects on staffmembers of community organizations that serve Central American migrants in transit. While literature on migration enforcement places emphasis on border control and internal removals, research on new forms of migration enforcement has paid little attention to the extension of border control beyond physical borders. This study employed an ethnographic approach to address the overarching question of how community organizers have responded to the adoption of US practices on extraterritorial migration control by the Mexican government while serving migrants in transit. Data collected provide empirical evidence contextual …

Unintended Consequences Of Public Policy And Government Regulation On Supply Chain Structure, Conduct, And Performance, Jonathan Phares

Graduate Theses and Dissertations

Supply chains, and the firms within them, change their behaviors in response to industry conditions so they can provide efficiency, effectiveness, strategic enablement, and customer utility. Social and economic policies enacted to promote social welfare by correcting market failures can alter these conditions. While these policies may serve their intended purposes, they may also create unintended consequences that may make managing logistics, operations, and supply chains more challenging. This dissertation contributes to the nascent body of knowledge concerning the intended and unintended consequences of policy on supply chain management by examining three unique contextual settings using different methodologies and levels …

Leveraging The Supply Chain: An Assessment Of Supply Chain Partners' Influence On Organizational Performance, Jordan M. Barker

Graduate Theses and Dissertations

The supply chain is recognized as an integral part of the value creation process and a critical driver of performance. Indeed, a supply chain relationship grants buyers and suppliers the opportunity to share in the value generated by their partners, access partner capabilities and resources to enact their own strategic initiatives, and jointly generate value above what each firm could produce in isolation. The purpose of this dissertation is to investigate how firms can leverage the supply chain to attain superior organizational performance. Specifically, three essays, each focused on a distinct organizational process, explore how supply chain partners influence a …

Experimental And Analysis Of Electromagnetic Characterization Of Biological And Non-Biological Materials In Microwave, Millimeter-Wave, And Terahertz Frequency Bands, Nagma Vohra

Graduate Theses and Dissertations

The goal of this research is to characterize the electromagnetic properties of biological and non-biological materials at terahertz (THz), millimeter-wave, and microwave frequency bands. The biological specimens are measured using the THz imaging and spectroscopy system, whereas the non-biological materials are measured using the microwave and millimeter-wave free-space system. These facilities are located in the Engineering Research Center at the University of Arkansas. The THz imaging system (TPS 3000) uses a Ti-Sapphire laser directed on the photoconductive antennas to generate a THz time domain pulse. Upon using the Fourier Transform, the spectrum of the pulsed THz signal includes frequencies from …

Quantitative Set-Based Design For Complex System Development, Nicholas J. Shallcross

Graduate Theses and Dissertations

This dissertation comprises a body of research facilitating decision-making and complex system development with quantitative set-based design (SBD). SBD is concurrent product development methodology, which develops and analyzes many design alternatives for longer time periods enabling design maturation and uncertainty reduction. SBD improves design space exploration, facilitating the identification of resilient and affordable systems. The literature contains numerous qualitative descriptions and quantitative methodologies describing limited aspects of the SBD process. However, there exist no methodologies enabling the quantitative management of SBD programs throughout the entire product development cycle. This research addresses this knowledge gap by developing the process framework and …