Physical Sciences and Mathematics Commons^™

Development Of Methods For Surface Modification Of Semiconductor Photocatalysts And Biopolymers For Applications In Water Treatment And 3d Printing, Sabrina Sultana

Electronic Theses and Dissertations

Surface modifications of metal oxides and polymer substrates are widely adopted approaches to alter the properties of these materials for use with specific applications. In the first part of my thesis, I describe how we have modified the surface of magnetic particles (Fe3O4) with layers of SiO2 and TiO2 to generate photocatalysts that remove toxic chemicals from drinking water. Semiconductor photocatalysts, such as TiO2 have gained much interest over the last 20 years as promising materials for water treatment. However, a main drawback centers on the difficulty to remove the catalyst from the water which has made it very difficult …

The Category Of Modules Over A Leavitt Path Algebra, Davis Macdonald

Electronic Theses and Dissertations

In this thesis we establish the technique used to construct universal algebras, and apply this technique to construct Leavitt path algebras. We then establish the basic language of category theory. From there we look at the category of modules over Leavitt Path Algebras over a finite graph, and establish a functorial classification of this category.

Measuring & Planning For Community & Climate Resilience, Joseph Reed

Electronic Theses and Dissertations

How communities respond to shocks has been of large interest to academics and governance since Hurricane Katrina in 2005, the Great Recession in 2008, and very recently the COVID-19 pandemic. The likelihood and extent of these shocks are ever increasing with the threat of climate change, leading to increased pressure on communities to understand and prepare for future shocks. Urban communities are often better prepared to strengthen their resilience due to the vast amount of resources they have available. Smaller, more rural communities typically have fewer resources to strengthen their resilience, making it harder to prepare for future shocks. This …

Spectroscopic Measurements Of Meibum Compositional, Structural, And Functional Relationships To Elucidate The Role Of Meibum In Dry Eye., Anthony Chigozie Ewurum

Electronic Theses and Dissertations

The major aim of my dissertation was to investigate the etiology of dry eye disease which affects about 7 million people in the United States, causing symptoms that can lead to visual disturbance. Correlation between dry eye and an abnormal lipid layer of the tear film has been found. Tear film lipids originate mostly from the meibomian glands. Cholesteryl ester (CE) and Wax ester (WE) lipids make up most of the human meibum lipidome and the CE/WE ratio has been shown to decrease in patients with meibomian gland dysfunction. Model studies using synthetic CE and WE, although providing some insight, …

Hybrid Machine And Deep Learning-Based Cyberattack Detection And Classification In Smart Grid Networks, Adedayo Aribisala

Electronic Theses and Dissertations

Power grids have rapidly evolved into Smart grids and are heavily dependent on Supervisory Control and Data Acquisition (SCADA) systems for monitoring and control. However, this evolution increases the susceptibility of the remote (VMs, VPNs) and physical interfaces (sensors, PMUs LAN, WAN, sub-stations power lines, and smart meters) to sophisticated cyberattacks. The continuous supply of power is critical to power generation plants, power grids, industrial grids, and nuclear grids; the halt to global power could have a devastating effect on the economy's critical infrastructures and human life.

Machine Learning and Deep Learning-based cyberattack detection modeling have yielded promising results when …

Assessing The Long-Term Effects Of Natural Disturbance-Based Silvicultural On The Avian Assemblage At The Acadian Forest Ecosystem Research Program, Carl Pohlman

Electronic Theses and Dissertations

Active forest management alters the resources available to forest-obligate species. Large-scale intensive management practices where timber production is the primary objective can lead to notable ecological changes in forest ecosystems. A key concept of ecological forestry is to design forest management activities to emulate natural disturbance regimes as a way to maintain the ecological integrity of forests. The Acadian Forest Ecosystem Research Program (AFERP) was undertaken as an experimental demonstration of management reflective of the region’s disturbance regime, which typically produces small canopy gaps. AFERP includes nine research areas assigned to three silvicultural treatments: unharvested control, small gap (expanding-group selection …

Finding A Representative Distribution For The Tail Index Alpha, Α, For Stock Return Data From The New York Stock Exchange, Jett Burns

Electronic Theses and Dissertations

Statistical inference is a tool for creating models that can accurately display real-world events. Special importance is given to the financial methods that model risk and large price movements. A parameter that describes tail heaviness, and risk overall, is α. This research finds a representative distribution that models α. The absolute value of standardized stock returns from the Center for Research on Security Prices are used in this research. The inference is performed using R. Approximations for α are found using the ptsuite package. The GAMLSS package employs maximum likelihood estimation to estimate distribution parameters using the CRSP data. The …

Risk Gameplay Analysis Using Stochastic Beam Search, Jacob Gillenwater

Electronic Theses and Dissertations

Hasbro’s RISK, first published in 1959, is a complex multiplayer strategy game that has received little attention from the scientific community. Training artificial intelligence (AI) agents using stochastic beam search gives insight into effective strategy when playing RISK. A comprehensive analysis of the systems of play challenges preconceptions about good strategy in some areas of the game while reinforcing those preconceptions in others. This study applies stochastic beam search to discover optimal strategies in RISK. Results of the search show both support for and challenges to traditionally held positions about RISK gameplay. While stochastic beam search competently investigates gameplay on …

Community Structure Analysis Of Mammals Found At The Gray Fossil Site, Tn, Sarah Clark

Electronic Theses and Dissertations

The early Pliocene Gray Fossil Site (GFS) is a biodiverse site with a unique faunal assemblage that represents one of few sites of its age in eastern North America. A community structure analysis of the mammals at GFS was done to characterize species and better understand the paleoenvironment. Data and was gathered from twenty modern communities and five late Neogene sites to compare with GFS. Species from these 26 sites were categorized by body size, locomotor mode, cheek tooth crown height, and diet to characterize niches occupied. Descriptive statistics contrasted proportions of species within categories across communities. Discriminant function analyses …

Water Quality Assessment Of Karst Spring Water As A Private Water Supply Source In Northeast Tennessee, Lukman Fashina

Electronic Theses and Dissertations

Karst springs are an essential source of private water supply for about 10% of households in Tennessee. However, these springs, which can be easily polluted, are unregulated. This study, therefore, assesses water quality spatial patterns and water quality rating of roadside springs in northeast Tennessee.

Karst spring water samples collected from 50 springs were assessed using EPA Standard methods for pathogens, nutrients, radon, and physicochemical parameters. Springs generally met federal and state standards for physicochemical parameters, 90% of samples contained E. coli, and all samples contained fecal coliform. High E. coli was spatially clustered causing a fecal contamination hot …

A Machine Learning Approach For Reconnaissance Detection To Enhance Network Security, Rachel Bakaletz

Electronic Theses and Dissertations

Before cyber-crime can happen, attackers must research the targeted organization to collect vital information about the target and pave the way for the subsequent attack phases. This cyber-attack phase is called reconnaissance or enumeration. This malicious phase allows attackers to discover information about a target to be leveraged and used in an exploit. Information such as the version of the operating system and installed applications, open ports can be detected using various tools during the reconnaissance phase. By knowing such information cyber attackers can exploit vulnerabilities that are often unique to a specific version.

In this work, we develop an …

John Horton Conway: The Man And His Knot Theory, Dillon Ketron

Electronic Theses and Dissertations

John Horton Conway was a British mathematician in the twentieth century. He made notable achievements in fields such as algebra, number theory, and knot theory. He was a renowned professor at Cambridge University and later Princeton. His contributions to algebra include his discovery of the Conway group, a group in twenty-four dimensions, and the Conway Constellation. He contributed to number theory with his development of the surreal numbers. His Game of Life earned him long-lasting fame. He contributed to knot theory with his developments of the Conway polynomial, Conway sphere, and Conway notation.

Surface-Functionalized Chemiresistive Films That Exploit H-Bonding, Cation-Pi, And Metal-Halide Interactions., Prasadanie Karunarathna Adhihetty

Electronic Theses and Dissertations

The development of gas sensors for detection of volatile organic compounds (VOCs) has been of interest in the sensing field for decades. To date, the use of metal nanoparticle-based chemiresistors for trace VOC detection, particularly gold nanoparticle-based sensors, is of great interest due to their high chemical stability, ease of synthesis, unique optical properties, large surface to volume ratio, and high level of conductivity. Much effort has been devoted towards gold monolayer protected clusters (Au MPCs) as chemiresistors to detect harmful VOCs. The present thesis documents the results of our efforts to exploit the advantages of functionalized Au MPCs chemiresistors …

A Mesonet-Based Analysis Of Severe Convective Winds In West Texas., Quint Long

Electronic Theses and Dissertations

Multiple studies have investigated the occurrence of severe convective-related winds and have increased our understanding of the forces driving severe winds and their spatial and temporal patterns. Data for these studies have come from airport stations maintained by the National Weather Service. Their standardization across the United States makes them ideal for research, but they are limited in their distribution. This study aims to create a similar climatology of severe surface level winds using a mesoscale network (“mesonet”). Like their ASOS (Automated Surface Observing System) and AWOS (Automated Weather Observing System) counterparts, these stations are standardized and well maintained. This …

Beyond Accuracy In Machine Learning., Aneseh Alvanpour

Electronic Theses and Dissertations

Machine Learning (ML) algorithms are widely used in our daily lives. The need to increase the accuracy of ML models has led to building increasingly powerful and complex algorithms known as black-box models which do not provide any explanations about the reasons behind their output. On the other hand, there are white-box ML models which are inherently interpretable while having lower accuracy compared to black-box models. To have a productive and practical algorithmic decision system, precise predictions may not be sufficient. The system may need to have transparency and be able to provide explanations, especially in applications with safety-critical contexts …

Modeling And Debiasing Feedback Loops In Collaborative Filtering Recommender Systems., Sami Khenissi

Electronic Theses and Dissertations

Artificial Intelligence (AI)-driven recommender systems have been gaining increasing ubiquity and influence in our daily lives, especially during time spent online on the World Wide Web or smart devices. The influence of recommender systems on who and what we can find and discover, our choices, and our behavior, has thus never been more concrete. AI can now predict and anticipate, with varying degrees of accuracy, the news article we will read, the music we will listen to, the movies we will watch, the transactions we will make, the restaurants we will eat in, the online courses we will be interested …

Sustainable Nanocatalysis In Water For C–C And C–N Cross-Couplings., Tharique Ahammed Ansari Nalakath

Electronic Theses and Dissertations

The development and application of various micelle-enabled nanopalladium-catalyzed organic transformations are discussed in this dissertation. These methodologies primarily harness the “micellar effect” imparted by the custom-designed amphiphile PS-750-M. Modern spectroscopic and imaging techniques were employed to systematically study the metal-micelle interactions and answer the fundamental questions regarding the operational nature of micellar catalysis. Chapter 1 reviews the history and evolution of organic synthesis, providing a critical outlook regarding the alarming inefficiency of contemporary synthetic practices indicating an inevitable transition to more sustainable synthetic techniques. In this context, the development of micellar catalysis is discussed, emphasizing its basic principles, applications, and …

Structural, Charge Transport, Gas Sensing, Magnetic, Pseudocapacitive, And Electrocatalytic Properties Of Perovskite Oxides., Surendra Bahadur Karki

Electronic Theses and Dissertations

Perovskites are functional materials with the general formula ABO₃ (A = alkali, alkaline earth or lanthanoid cations and B = transition metal or main group cations). These materials are marked by a variety of crystal structures and interesting properties such as colossal magnetoresistance, ferroelectricity, multiferroicity, superconductivity, pseudocapacitance, gas sensing, charge transport, and electrocatalytic properties. The formula of perovskite can be written as AA’BB’O₆, when there is ordering between two cations over A and B-sites. Such compounds are called double perovskite oxides. Some amount of oxygen could be lost from crystal structure without decomposition of the phase. Such …

New Accurate, Explainable, And Unbiased Machine Learning Models For Recommendation With Implicit Feedback., Khalil Damak

Electronic Theses and Dissertations

Recommender systems have become ubiquitous Artificial Intelligence (AI) tools that play an important role in filtering online information in our daily lives. Whether we are shopping, browsing movies, or listening to music online, AI recommender systems are working behind the scene to provide us with curated and personalized content, that has been predicted to be relevant to our interest. The increasing prevalence of recommender systems has challenged researchers to develop powerful algorithms that can deliver recommendations with increasing accuracy. In addition to the predictive accuracy of recommender systems, recent research has also started paying attention to their fairness, in particular …

Nucleate Boiling Under Different Gravity Values: Numerical Simulations & Data-Driven Techniques., Sandipan Banerjee

Electronic Theses and Dissertations

Nucleate boiling is important in nuclear applications and cooling applications under earth gravity conditions. Under reduced gravity or microgravity environment, it is significant too, especially in space exploration applications. Although multiple studies have been performed on nucleate boiling, the effect of gravity on nucleate boiling is not well understood. This dissertation primarily deals with numerical simulations of nucleate boiling using an adaptive Moment-of-Fluid (MoF) method for a single vapor bubble (water vapor or Perfluoro-n-hexane) in saturated liquid for different gravity levels. Results concerning the growth rate of the bubble, specifically the departure diameter and departure time have been provided. The …

New Debiasing Strategies In Collaborative Filtering Recommender Systems: Modeling User Conformity, Multiple Biases, And Causality., Mariem Boujelbene

Electronic Theses and Dissertations

Recommender Systems are widely used to personalize the user experience in a diverse set of online applications ranging from e-commerce and education to social media and online entertainment. These State of the Art AI systems can suffer from several biases that may occur at different stages of the recommendation life-cycle. For instance, using biased data to train recommendation models may lead to several issues, such as the discrepancy between online and offline evaluation, decreasing the recommendation performance, and hurting the user experience. Bias can occur during the data collection stage where the data inherits the user-item interaction biases, such as …

Dental Morphology In A Juvenile Mammal From The Late Cretaceous Of South America: Tooth Eruption And Development., Kayla E Newton

Electronic Theses and Dissertations

Meridiolestids are a diverse and distinct clade of Cretaceous–Miocene South American dryolestoid mammals ranging in size from small shrew-sized insectivores to large dog- sized omnivores. Cronopio dentiacutus from the Cenomanian La Buitrera locality, Rio Negro Province, Argentina (Candeleros Fm.) is the oldest and best known of them, represented by skull material and associated jaws. A juvenile skull as attributed to Cronopio dentiacutus, based on tooth size and morphology, was collected from the type locality. The specimen includes the skull and both articulated lower jaws. The fossil is poorly ossified and partially flattened; CT scanning reveals most of the dentition …

Statistical Methods For Assessing Drug Interactions And Identifying Effect Modifiers Using Observational Data., Qian Xu

Electronic Theses and Dissertations

This dissertation consists of three projects related to causal inference based on observational data. In the first project, we propose a double robust to identify the effect modifiers and estimate optimal treatment. Observational studies differ from experimental studies in that assignment of subjects to treatments is not randomized but rather occurs due to natural mechanisms, which are usually hidden from the researchers. Many statistical methods to identify the treatment effect and select the optimal personalized treatment for experimental studies may not be suitable for observational studies any more. In this project, we propose a exible outcome model to select the …

2d Materials Based Heterostructure For Quantum Tunneling: A Lithography Free Technique., Ali Alzahrani

Electronic Theses and Dissertations

Two-dimensional electron gas (2DEG) systems have played a vital role in the development of superior electronic devices including tunnel junctions consisting of two such 2DEG systems. With the advent of the new 2D electronic material systems, it has opened a new route for 2D–2D tunneling in such extended systems. In this study, we have utilized a plasma enhanced chemical vapor deposition (PECVD) technique to directly deposit graphene (nanowalls) and h-BN on Si/SiO₂ substrates to construct two-dimensional material based, vertically stacked electron tunneling devices free of expensive and cumbersome microfabrication steps. In the first study, we fabricated direct quantum tunneling …

Development And Novel Applications Of Halogenating Agents., Sagar Ravso Mudshinge

Electronic Theses and Dissertations

Organic halides are extensively utilized as synthetic intermediates in areas such as pharmaceuticals, agrochemicals, and material polymers. While many halogenating agents have been developed, they continue to have low efficiency or selectivity, are difficult to handle, and often have limited substrate scope. To address this issue, our laboratory has developed novel halogenating agents with improved stability and efficiency. In these studies, we demonstrated a novel application of halogenating reagent, HCl·DMPU, in the nitrile synthesis. We developed a novel method for C−SCF₃/SeCF₃ cross-coupling reactions using gold redox catalysis. We developed a novel trifluoromethylating agent in a cost-effective and …

Small-Scale Variability In Warm Season, Precipitation Around An Urban Area: A Case Study Of Louisville-Jefferson County, Ky., Isaiah I. Kingsberry

Electronic Theses and Dissertations

Numerous studies have detected anomalous precipitation patterns occurring up to 50 km downwind of major cities, providing major evidence that cities inadvertently modify precipitation and atmospheric circulations. Louisville is one such major city with a growing body of evidence of inadvertent precipitation modification. Despite these efforts, the physical mechanisms driving small-scale and unintentional changes in urban precipitation are little understood, being rooted largely in theory rather than in physical observations. This study seeks to build upon previous research by analyzing ground-based precipitation observations recorded by a high-density gauge network located within approximately 40 km of Louisville’s urban center. The results …

The Impact Of Sea-Level Rise In Numerically Modeled Landfalling Hurricanes: Katrina And The Gulf Coast., Serenity Nadirah Mercuri

Electronic Theses and Dissertations

With climate change, landfalling hurricanes become an increasing threat to coastal regions. However, the interactions between the coastal landscape and landfalling hurricanes are often overlooked when addressing sea-level rise outside of inundation and independent of sea surface temperature. This study analyzed the potential impacts regarding structure and intensity as a result of sea-level rise in the Gulf of Mexico using the WRF-ARW numerical model coupled with a 1D ocean model. Analysis showed that 10 m windspeed from landfall forward was higher in modified coastlines, and minimum sea-level pressure post-landfall was consistently lower for modified runs where storms maintain a higher …

Nanomaterials For Sustainability: Using Spectroscopy And Quantum Chemistry For Microkinetic Modeling Of Thermo- And Photo- Catalysts, Amir Rahmani Chokanlu

Electronic Theses and Dissertations

Heterogeneous catalysis, including thermal- and photocatalysis, is a key technology toward developing industrial processes for a sustainable future. Therefore, the study of surface reactions and catalyst properties includes most studies in this area. There has been extensive work put into developing experimental and computational tools to understand surface and interface phenomena, describe mechanistic chemical transformations, and simulate the behavior of surface reactions to develop better catalysts and more efficient processes.

This thesis describes experimental and theoretical investigations to explain the reaction mechanism of ethanol conversion to value-added products over an MgO/SiO2 catalyst, a kinetic model describing the surface changes during …

Characterizing Carbon In Agricultural Landscapes, Lauren Ann Weller

Electronic Theses and Dissertations

Soil organic matter (SOM) is an important pillar of soil fertility and ecosystem health. However, uncertainty exists both in the evaluation of agricultural conservation measures for specific local contexts and the sensitivity of the analytical tools used. Therefore, the objective of this thesis was to characterize organic matter from agricultural soils, focusing specifically on addressing field- and analytically based uncertainties associated with the ultraviolet-Visible (UV-Vis) and fluorescence spectroscopy of water-extractable organic matter (WEOM), and using the clay-dominated soils of Essex County as a case study. Here I explored optical spectroscopy properties across a gradient of agricultural practices and restoration to …

Functionalized 𝜹-Hexalactones (Fdhls): Bio-Derivable Monomers To Synthesize Renewable Polyester Thermoplastics, Atik Faysal

Electronic Theses and Dissertations

Most thermoplastics are made from limited fossil-fuel sources and these plastics have very deleterious impacts on the environment. Finding a renewable source to synthesize new thermoplastic polymers with tunable properties like biodegradability, heat resistance, and moisture resistance are ongoing research interests. Lignocellulosic biomass is a promising renewable feedstock for biobased monomers and polymers production. In this work, functionalized 𝛿-hexalactone (FDHL) monomers are hypothesized to be synthesizable from lignocellulosic sourced hydroxymethyl furfural (HMF) and lignin-derived pendant groups, generating a variety of aliphatic polyesters and potentially overcome current polymer challenges. Achieving a higher glass transition temperature (T_g) is one of …