Engineering Commons^™

Multi-Objective Radiological Analysis In Real Environments, David Raji

Doctoral Dissertations

Designing systems to solve problems arising in real-world radiological scenarios is a highly challenging task due to the contextual complexities that arise. Among these are emergency response, environmental exploration, and radiological threat detection. An approach to handling problems for these applications with explicitly multi-objective formulations is advanced. This is brought into focus with investigation of a number of case studies in both natural and urban environments. These include node placement in and path planning through radioactivity-contaminated areas, radiation detection sensor network measurement update sensitivity, control schemes for multi-robot radioactive exploration in unknown environments, and adversarial analysis for an urban nuclear …

Exploration Of Event-Based Camera Data With Spiking Neural Networks, Charles Peter Rizzo

Doctoral Dissertations

Neuromorphic computing is a novel, non-von Neumann computing architecture that employs power efficient spiking neural networks on specialized hardware. Taking inspiration from the human brain, spiking neural networks are temporal computation units that propagate information throughout the network via binary spikes. Compared to conventional artificial neural networks, these networks can be more sparse, smaller in size, and more efficient power-wise when realized on neuromorphic hardware. Event-based cameras are novel vision sensors that capture visual information through a temporal stream of events instead of as a conventional RGB frame. These cameras are low-power collections of pixels that asynchronously emit events over …

Development Of Novel Cesium Chloride-Based Ultrafast Inorganic Scintillators For Fast Timing Radiation Detection Applications, Daniel Rutstrom

Doctoral Dissertations

Cs₂ZnCl₄ [dicesium zinc tetrachloride] and Cs₃ZnCl₅ [tricesium zinc pentachloride] are relatively new scintillator materials that appear to be promising for use in fast-timing radiation detection applications owing to their 1 to 2 nanosecond decay times. Moreover, they offer several advantages over the state-of-the-art ultrafast inorganic scintillator BaF₂ [barium fluoride]. To fully realize the potential of these novel materials, growth of crystals having improved optical quality must be demonstrated. The mechanism responsible for the ultrafast decay times, core valence luminescence (CVL), in cesium zinc chloride crystals can also be observed in other compounds containing …

The Role Of Grain Morphology And Individual Grain Fracture On Granular Material Behavior, Anne Katherine Turner

Doctoral Dissertations

Granular materials, such as sand, are multi-scale materials combining an immense number of crushable particles to create an assembly. Numerical approaches to modeling sand’s mechanical behavior often use simplifications, such as treating the volume as a continuum or representing the particles with rigid, idealized spheres using the discrete element method. These approaches overlook crucial nonlinear phenomena, such as individual grain morphology and fracture, which have been shown to influence sand’s strength and plasticity behavior. This research investigated methods to incorporate such phenomena , focusing on simulating single grain crushing tests and 1D confined compression of Ottawa sand using finite element …

Discrete Time State-Space Modeling Framework For Switched-Mode Power Supplies, Jared Baxter

Doctoral Dissertations

Electrical power consumption has become ever prominent in modern society. Switch mode power supplies, now more than ever, have become a foundation for residential, commercial, and industrial electrical needs. These demands require numerous advanced power converters, and modeling plays a vital role in the design of these converters. Commonly, modeling is completed using either dedicated hand analysis, which must be completed individually for each topology, or time-stepping circuit simulations, which are insufficiently rapid for broad analysis considering a wide range of potential designs or operating points. Discrete time state-space modeling of switching converters has shown merits in rapid analysis and …

The Development And Enhancement Of A Forward Mathematical Model Of The Human Knee Joint, Seth Coomer

Doctoral Dissertations

Degenerative joint disease, or osteoarthritis, is a common occurrence in the knee joint. This can often result in joint pain, decrease in range of motion, and ultimately disability. One way to counteract osteoarthritis is the incorporation of a total knee arthroplasty (TKA). TKAs replace the damaged bone and soft tissue surrounding the knee with metal and polyethylene components. Ideally this will improve the joint’s performance and reduce pain. However, there is still a number of TKA patients who remain dissatisfied. In order to investigate this, in depth research must be done on the design and performance of TKAs.

One such …

Development Of Supg And Stabilized Finite Element Method Solvers For The Two Fluid Plasma Model, Kenneth A. Croft

Doctoral Dissertations

This dissertation describes efforts to employ stabilized finite element method approaches to simulate ideal two fluid plasma dynamics. First, the streamline-upwind/Petrov-Galerkin (SUPG) finite element method, which is well developed and known to be applicable to models containing terms like those in the ideal two fluid plasma model, is employed. Then, in an attempt to address some shortcomings found in that approach, another stabilized finite element method is developed along similar lines, starting from a steady state advection-reaction equation rather than a steady state advection-diffusion equation as was done in the development of the SUPG method. The performance of the SUPG …

Stability Of Quantum Computers, Samudra Dasgupta

Doctoral Dissertations

Quantum computing's potential is immense, promising super-polynomial reductions in execution time, energy use, and memory requirements compared to classical computers. This technology has the power to revolutionize scientific applications such as simulating many-body quantum systems for molecular structure understanding, factorization of large integers, enhance machine learning, and in the process, disrupt industries like telecommunications, material science, pharmaceuticals and artificial intelligence. However, quantum computing's potential is curtailed by noise, further complicated by non-stationary noise parameter distributions across time and qubits. This dissertation focuses on the persistent issue of noise in quantum computing, particularly non-stationarity of noise parameters in transmon processors. It …

Understanding The Impact Of Divertor And Main Chamber Ion Fluxes On Divertor Closure In The Diii-D Tokamak, Kirtan M. Davda

Doctoral Dissertations

The diverted tokamak redirects extreme heat and particles to targets, a plasma-facing component designed for such loads. Here, the local fluxes produce strong particle recycling and sputtering. Recycled neutrals can “leak” into the region between the core and wall, the scrape-off-layer (SOL), impacting plasma performance. Increasing divertor closure can reduce leakage by containing neutrals within the divertor. However, there exists a need to quantify divertor baffle restrictions and understand closure directly from empirical data as opposed to indirectly through modeling.

Our study introduces the Geometric Restriction Parameter (GRP) based on simplifying neutral transport to ballistic pathways. Specifically, it considers the …

Tunable Catalysts And Electrodes With High Material Utilization And Durability For Hydrogen Production, Lei Ding

Doctoral Dissertations

Hydrogen, the future energy carrier, has gained extensive attention due to its advantages of high energy density, low weight, and zero-carbon emission. So far, hydrogen has been widely used in various fields including transportation, oil upgrading, metal refining, etc. Most hydrogen is currently produced from fossil fuels, which can cause serious environmental problems. Water electrolysis was proposed to produce clean hydrogen with carbon-free emission and only byproduct of oxygen. Among various water electrolyzer devices, the proton exchange membrane electrolyzer cell (PEMEC) shows great potential to produce green hydrogen by integrating renewable sources (solar, wind, etc.) due to its advantages of …

Controlling Complex Dynamic Transportation Systems: Development And Adaptation Of A Novel Distributed Cooperative Multi-Agent Learning Technique, Russell Thomas Graves

Doctoral Dissertations

Intelligent transportation systems continue to increase complexity, scale, and scope as more devices contain embedded compute. Cooperation among vehicles, intersections, and other members of the greater traffic ecosystem at a system-of-systems level is critical to improving the efficiency of the multi-billion-dollar asset that is the U.S. roadway infrastructure. This work introduces a negotiations strategy among multi-agent reinforcement learning agents and applies this to both traffic signal control and supervisory control of vehicle platooning. The traffic signal control implementation builds off of many prior research thrusts, and was shown to improve vehicle throughput by an average of 671veh/hr over actuated traffic …

Multimodal Data Fusion And Machine Learning For Advancing Biomedical Applications, Md Inzamam Ul Haque

Doctoral Dissertations

This dissertation delves into the intricate landscape of biomedical imaging, examining the transformative potential of data fusion techniques to refine our understanding and diagnosis of health conditions. Daily influxes of diverse biomedical data prompt an exploration into the challenges arising from relying solely on individual imaging modalities. The central premise revolves around the imperative to combine information from varied sources to achieve a holistic comprehension of complex health issues.

The chapters included here contain articles and excerpts from published works. The study unfolds through an examination of four distinct applications of data fusion techniques. It commences with refining clinical task …

Experimental Quantum Key Distribution In Turbulent Channels, Kazi Mh Reaz

Doctoral Dissertations

Quantum Key Distribution (QKD) ensures security by relying on the laws of quantum physics rather than the mathematical intricacy of encryption algorithms. The transmission medium is a critical restricting factor for any quantum communication protocol. Fiber-based optical networks suffer great losses, making quantum communication impossible beyond metropolitan scales. Here free-space quantum communication can be a great alternative for long-distance communication. Even though modern Communications are mostly wireless the atmosphere poses a challenge for QKD. So QKD must be resistant to both atmospheric loss and variations in transmittance. In this thesis we conduct an experiment to strengthen the BB84 protocol's resistance …

Urban Ecohydrology And The Watershed Microbial Continuum, Victoria C. Rexhausen

Doctoral Dissertations

A rapidly urbanizing world is adding unprecedented stress to water resources. Urbanization results in high rates of stream impairment, including but not limited to ecological stress, pollution, and flooding. A fully integrated and holistic perspective is necessary for effective remediation strategies for these wicked problems. This monitoring study from a heterogeneous urban watershed investigated the geospatial and seasonal interactions between urban hydrology and biological processes using stable isotope compositions, anions, and microbial.

This research found that nitrate concentrations in an urban watershed were ecologically driven. NO₃^- concentrations ranged from 0.4 to 12.7 mg/L throughout the watershed. Nitrate concentrations …

Computational Study Of Confined Cytoskeletal Assemblies: Simple Rules, Complex Behavior, Oghosa Honor Akenuwa

Doctoral Dissertations

The actin cytoskeleton is crucial for cellular processes and proper organization in cells. Physical regulators like actin crosslinking proteins, molecular motors, and physical confinement significantly impact the organization of the actin cytoskeleton. Despite advances, much remains unknown about how these physical regulators affect actin organization. In this thesis, we employ coarse-grained computer simulations to investigate the effect of physical regulators on the dynamics and organization of semiflexible actin filaments. First, we explore the role of crosslinker properties and confinement shape on actin organization by varying the system shape, the number and type of crosslinking proteins, and the length of filaments. …

Discrete-Event Simulation Process Model For The Pyrochemical Processing Of Plutonium At Los Alamos National Laboratory, Devin C. Kimball

Doctoral Dissertations

The pyrochemical metal production operations that occur in the Plutonium Facility at Los Alamos National Laboratory perform plutonium purification with the aim to provide plutonium metal for a variety of defense- and non-defense missions within the National Nuclear Security Administration. The demands and constraints associated with the pyrochemical processing of plutonium are complex, making decision analyses challenging for program managers who require plutonium production for their mission applications. A full description is provided of the development of a discrete-event simulation process model, constructed in the ExtendSim™ [trademark] software, to measure and report the process capacity, material throughput, equipment requirements, and …

Integrated Approaches In Wastewater Surveillance Of Sars-Cov-2: Monitoring, Persistence, Sampling Optimization, And Impacts On Microbial Community Structure, Ye Li

Doctoral Dissertations

Wastewater-based epidemiology (WBE) serves as a crucial tool for monitoring SARS-CoV-2 prevalence on university campuses, yet concerns persist regarding its effectiveness as an early warning system for COVID-19 outbreaks. This study aimed to address these concerns through a comprehensive field trial conducted at the University of Tennessee, Knoxville. We investigated correlations between SARS-CoV-2 concentrations, both with and without normalization using Pepper Mild Mottle Virus (PMMoV), and various parameters. Significant positive correlations were observed between SARS-CoV-2 concentrations and active cases in the weeks prior to, during, and following the monitoring period, unaffected by PMMoV normalization. Concurrently, the persistence of SARS-CoV-2 RNA …

Uniting Cognitive Models And Ai: Early Alzheimer’S Screening Through Language Analysis, Ziming Liu

Doctoral Dissertations

Alzheimer's Disease (AD) and related dementias (PwADRD) often lead to memory issues, language difficulties, and cognitive impairments. These symptoms can cause social isolation, anxiety, depression, accelerating cognitive decline, and negatively impacting quality of life. Traditional diagnostic and rehabilitation methods, relying on Artificial Intelligence (AI) or clinical observations, sometimes lack transparency and explainability for the growing population affected by AD. My research aims to address these challenges by developing AI systems that analyze affective states and cognitive deficits in PwADRD interactions. This involves creating more precise diagnostic tools and rehabilitation methods, as well as trustworthy AI agents to improve PwADRD's quality …

Engineering Of Functional Hybrid Nanocomposites For Renewable Energy Applications Via Laser Ablation, Mahshid Mokhtarnejad

Doctoral Dissertations

Carbon-based hybrid nanocomposites (HNCs) have increasingly gained prominence in the materials science community due to their widespread applications in advanced energy storage and conversion devices. Yet, current, and conventional methods to synthesize tailored HNC structures involve complex and multi-step processes that often require harsh chemical reagents. To address the majority of these shortcomings, this thesis proposes Laser Ablation Synthesis in Solution (LASiS) as a rapid, inexpensive, and facile technique for synthesis of Metal-Organic Framework (MOF)–derived and Metal Oxide/reduced Graphene Oxide (rGO) HNCs in an environmentally friendly fashion. These engineered composite nanomaterials show superior properties as (1) non-precious medal based electrocatalysts …

Characterization Of A Proof-Of-Concept Imager To Safeguard Spent Nuclear Fuel Using Passive Fast Neutron Emission Tomography, Mairead Montague

Doctoral Dissertations

A primary part of nuclear nonproliferation and nuclear security principles involves verification of spent fuel to ensure no material diversion has occurred. As a result, various verification technologies have been developed to detect when irradiated fuel pins have gone outside of regulatory control. One proposed method of spent nuclear fuel verification includes using a fast neutron emission tomography system for spent nuclear fuel. This system would allow for imaging of individual fuel pins and quantifications of neutron source strength. A proof-of concept fast neutron emission tomography system for verification of spent nuclear fuel was constructed at ORNL. An analytic neutron …

Advancing Power Equipment And Line Protection With Practical Solutions, Russell W. Patterson

Doctoral Dissertations

This dissertation is the culmination of an academic and professional career dedicated to power system protection. It begins with an emphasis on the need for excellence in analysis of power system fault events with the goal of improving system protection and reliability. The bulk of this work describes the detailed analysis of various misoperations of protective relays and the solutions that those analysis led to. The last chapters round out the manuscript with two innovations that the author advanced, and which are now becoming part of the state of the art in generator protection being incorporated into Institute of Electrical …

Thermal Runaway Of Li-Ion Batteries: Triggering, Emission, And Mitigation, Liwen Zhang

Doctoral Dissertations

In the contemporary landscape, lithium-ion batteries (LIBs) are key components powering a wide array of electronic devices and electric vehicles (EVs). As society increasingly relies on these batteries for their efficiency and functionality, understanding and mitigating potential risks, such as thermal runaway (TR) events, become imperative. The objective of this dissertation is to comprehensively understand TR characteristics of LIBs through a combination of experiments and numerical simulation, thereby enhancing battery safety, refining design standards, and providing insights and guidelines for the prevention and management of TR events.

Firstly, this dissertation explores the safety regime of LIBs TR through a computational …

Motor Control Quantification And Necessary Improvements For Individuals With Post-Stroke Gait: Implications For Future Customizable Rehabilitation Approaches, Azarang Asadi

Doctoral Dissertations

Although often taken for granted, walking is an extremely complex motor skill that requires sensory inputs, neural communication, advanced control strategies, and coordination of the muscles and joints. Electrical signals traveling from the brain to the muscles are transformed to mechanical forces to achieve desired motion. A stroke damages the central nervous system and neural pathways, limiting the ability of survivors to walk. Walking speed is significantly decreased and asymmetrical walking patterns emerge. A crucial component of stroke rehabilitation is gait training, a therapeutic intervention to help individuals to improve their walking ability, as walking is essential for functional independence …

Development Of An Integrated Workflow For Nucleosome Modeling And Simulations, Ran Sun

Doctoral Dissertations

Nucleosomes are the building blocks of eukaryotic genomes and thus fundamental to to all genetic processes. Any protein or drug that binds DNA must either cooperate or compete with nucleosomes. Given that a nucleosome contains 147 base pairs of DNA, there are approximately 4^147 or 10^88 possible sequences for a single nucleosome. Exhaustive studies are not possible. However, genome wide association studies can identify individual nucleosomes of interest to a specific mechanism, and today's supercomputers enable comparative simulation studies of 10s to 100s of nucleosomes. The goal of this thesis is to develop and present and end-to-end workflow that serves …

Development And Characterization Of Injectable, Cell-Encapsulated Chitosan-Genipin Hydrogels, Tyler R. Priddy-Arrington

Doctoral Dissertations

Over 150,000 patients undergo lower extremity amputation every year in the United States, most commonly caused by complications due to diabetes mellitus, peripheral vascular disease, and trauma. Diseased or damaged tissues that are unable to naturally repair themselves must either be fully removed or replaced, otherwise the injuries can lead to further complications such as infection or death. Tissue resection and amputation, as forms of removing damaged tissue, are not favorable to patients as they can cause pain, reduce mobility, and negatively impact quality of life. However, replacing lost or damaged tissues with donor tissues carries the risks of tissue …

Selective Targeting Of Microglia By Quantum Dots And Green Synthesis Of Metal Organic Biohybrids; Applications In Dynamic Cell And Assay Systems, Navya Uppu

Doctoral Dissertations

Neurological disorders are the leading cause of physical and cognitive disability across the globe, currently affecting approximately 15% of the worldwide population. Part of the glioma microenvironment are microglia, resident immune cells of the CNS that were thought to be involved in the pathogenesis of diverse neurodegenerative diseases. Though it remains uncertain what triggers microglial activation in these disorders, targeting and tracking microglial functions using nanotools like Quantum Dots (QDs) could help us elucidate them in such neurological diseases. This research focuses on the comparative study of different QDs formulations and their selective uptake by brain microglia in primary cultures …

Blow-Spun Hybrid Pcl-Peo/Hnts Scaffolds With Enhanced Biological And Mechanical Properties, Meichen Liu

Doctoral Dissertations

With the development of technology and engineering, nanotechnology has been a multidisciplinary scientific field applied in nearly all science areas, including medicine, genetics, food industry, robotics. In this respect, nanomedicine has gained increasing attention and been a useful, effective therapy for cancer diagnosis, gene transfer, and drug delivery. To design an ideal nano drug delivery system with controlled drug releasing and improved encapsulated drug’s pharmacokinetic and pharmacodynamic profiles, hydrogels and polymer composites have witnessed increased research interest during the last decades. Recently, numerous polymers have been studied to fabricate the ideal wound dressing with biocompatibility, biodegradability, porous structural, and suitable …

Advanced Manufacturing Of Nanomaterials For Energy Storage And Biomedical Applications, Hiep Pham

Doctoral Dissertations

"Nanomaterials have emerged as an important component to the advancement of many fields, ranging from advanced energy materials in the energy field to highly sophisticated treatment vehicles in the biomedical field. Understanding the physical behavior of nanomaterials is critical to design materials with excellent properties and performance for the many disciplines in which they are utilized and is necessary to master the various manufacturing processes that influence nanomaterial properties and behavior. This research focused on a fundamental study into the behaviors of newly developed nanomaterials under both conventional and new manufacturing processes for high performance lithium-ion batteries and for advanced …

Melt Pool Feature Extraction, A State-Space Model And Spatial Layer-To-Layer Control For Powder Bed Fusion, Xin Wang

Doctoral Dissertations

"Powder Bed Fusion (PBF) is an Additive Manufacturing (AM) technique which can reduce material waste and is a fast-prototyping technique for complex geometries. However, the lack of consistent quality is a major problem in industrial applications. An InfraRed (IR) camera is a common tool to monitor a surface temperature field and melt pool morphology in PBF. With melt pool features from camera videos, manufacturing researchers use spatial feature maps to visualize defect locations and control researchers use layer-to-layer control to achieve more uniform melt pools and less defects.

Paper I presents a simulation method to characterize the effect of down-sampling …

Material Models For Simulation Of Steel Hot Rolling Process Using Experimentally Determined Properties At Elevated Temperatures And Strain Rates, Siva Sai Krishna Dasari

Doctoral Dissertations

"Hot rolling is one of the most important and complex process that includes large material deformation, different contact conditions, complex geometries and different temperature gradients along with micro structural changes such as viscoplasticity, dynamic recrystallization, and static softening. In the present work, the viscoplasticity, damage evolution, static softening and void closure of alloyed metal during hot rolling process was numerically investigated. Gleeble^TM hot compression and double hit tests were performed to provide experimental stress-strain curves at recrystallization temperatures and at different strain rates. Johnson-Cook viscoplastic model was calibrated using experimental stress-strain curves. Static softening model was developed at varying …