Digital Commons Network^™

Stress Relaxation Cracking In 347h Austenitic Steel Weldments Under Various Heat Treatments: Experiments And Modeling, Yi Yang

Doctoral Dissertations

347H austenitic stainless steel exhibits exceptional creep and corrosion resistance, rendering it an exemplary candidate for pipeline materials, particularly in mid- to high-temperature working conditions. However, due to constraints in component dimensions, welding has been chosen as the preferred method for joining pipeline systems extensively employed in nuclear power plants, fossil fuel plants, and petrochemical companies. The welding process entails the accumulation of residual stress during the cooling stage, along with the introduction of microstructure evolution. Moreover, the residual stress field and microstructure continuously evolve under service conditions, thereby intensifying the susceptibility of crack initiation and propagation. The initial residual …

Core-Collapse Supernova Simulations With Spectral Two-Moment Neutrino Transport, Ran Chu

Doctoral Dissertations

The primary focus of this dissertation is to develop a next-generation, state-of-the-art neutrino kinetics capability that will be used in the context of the next-generation, state-of-the-art core-collapse supernova (CCSN) simulation frameworks \thornado\ and \FLASH.\index{CCSN} \thornado\ is a \textbf{t}oolkit for \textbf{h}igh-\textbf{or}der \textbf{n}eutrino-r\textbf{ad}iation hydr\textbf{o}dynamics, which is a collection of modules that can be incorporated into a simulation code/framework, such as \FLASH, together with a nuclear equation of state (EOS)\index{EOS} library, such as the \WeakLib\ EOS tables. The first part of this work extends the \WeakLib\ code to compute neutrino interaction rates from~\cite{Bruenn_1985} and produce corresponding opacity tables.\index{Bruenn 1985} The processes of emission, …

Accurate Simulation Of Reads And Improved Strategies For Abundance Estimation Supporting Reduced Representation Sequencing For Metagenomics, Ryan Kuster

Doctoral Dissertations

Next generation sequencing has impacted all areas of biology by providing affordable investigations into some of the most complex processes underpinning life. With its ubiquitous application, there is still benefit in considering the nuances of the technology and its downstream analysis. Sequencing libraries produced by fragmenting DNA with restriction enzyme digests limit the scope of sequencing to a reduced set of genomic loci, allowing for deeper sequencing of those regions at a reduced cost per sample. These sequencing libraries have been used to determine genetic markers within populations of closely related individuals due to their sensitivity and preservation within populations. …

Tokamak 3d Heat Load Investigations Using An Integrated Simulation Framework, Thomas Looby

Doctoral Dissertations

Reactor class nuclear fusion tokamaks will be inherently complex. Thousands of interconnected systems that span orders of magnitude in physical scale must operate cohesively for the machine to function. Because these reactor class tokamaks are all in an early design stage, it is difficult to quantify exactly how each subsystem will act within the context of the greater systems. Therefore, to predict the engineering parameters necessary to design the machine, simulation frameworks that can model individual systems as well as the interfaced systems are necessary. This dissertation outlines a novel framework developed to couple otherwise disparate computational domains together into …

Nuclear Thermal Rocket Engine Control Autonomy Via Embedded Decision, David Sikorski

Doctoral Dissertations

This doctoral dissertation presents an investigation of embedded decision capabilities as a means for developing nuclear reactor autonomous control. Nuclear thermal propulsion (NTP) is identified as a high priority technology for development, and is the focus of this research. First, a background investigation is presented on the state of the art in nuclear thermal rocket (NTR) engine control and modeling practices, resulting in the development of a low order NTR engine dynamic model based on the literature. The engine model was used to perform the following investigation, and is intended to serve as a research platform for the future development …

Medical Sound Simu-Vest, Daniel P. Woods, Luke M. Stanley, Megan Hines, Chris Cochran

Chancellor’s Honors Program Projects

No abstract provided.

Defining Interactions Between Deformable Dna Origami And Lipid Bilayers Through Molecular Dynamics Simulation, Zachary A. Loyd

Chancellor’s Honors Program Projects

No abstract provided.

Medical Sound Simuvest, Luke Stanley, Daniel Woods, Megan Hines, Chris Cochran

Chancellor’s Honors Program Projects

No abstract provided.

Next Generation Energy Storage: An Examination Of Lignin-Based Carbon Composite Anodes For Sodium Ion Batteries Through Modeling And Simulation, Dayton G. Kizzire

Doctoral Dissertations

The current energy market relies heavily on fossil fuel sources; however, we are amidst a momentous shift towards wind, solar, and water based renewable energies. Large-scale energy storage allows renewable energy to be stored and supply the grid with consistent energy despite changing weather conditions. Improvements to large-scale energy storage in terms of cost, safety, and sustainability are crucial to wide-scale adoption. A promising candidate for large-scale energy storage are sodium-ion batteries using hard carbon anodes. Sodium is globally available, cheaper, and more sustainable than lithium, but requires a different anode structure. A sustainable hard carbon anode with excellent Li-ion …

Computer Simulations Of Biological Systems: From Protein Dynamics To Drug Discovery, Rupesh Agarwal

Doctoral Dissertations

Computational biophysics methods such as molecular dynamics (MD) simulations are often used in combination with experimental techniques like neutron scattering, NMR, and FTIR to explore protein conformational landscapes. With the improvements in experimental techniques, there is also a need to continually optimize the MD forcefield parameters to make precise predictions that match experimental results. To complement many of these experiments, an accurate model of deuteration is frequently required, but has been elusive. In our work, we developed a novel method to capture isotope effects in classical MD simulations by re-parameterization of the bonded terms of the CHARMM forcefield using quantum …

The Role Of Water Solubility And Diffusion Coefficient In Air Of Chlorine Dioxide Gas During Surface Decontamination And Compatibility Of Selected Plastics And Elastomers, Mario Ernesto Bermudez Gonzalez

Masters Theses

Food safety is a concern for all individuals involved in the food supply chain. Besides controlling the food product itself to improve safety, washing and sanitizing surfaces and equipment are critical. Chlorine dioxide (ClO2) is a green-yellow gas, known as a strong antimicrobial agent against multiple pathogenic microorganisms and effective on biofilms. Plastics such as polypropylene (PP), polyester (PET), cast nylon, ultra-high-molecular-weight polyethylene (UHMWPE), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF) and white Acetal; and elastomers like nitrile rubber (Buna-N), ethylene propylene diene monomer (EPDM), and fluoroelastomer (FKM) are widely used in food processing surfaces and equipment. However, few studies have been …

Efficient Elevator Algorithm, Sean M. Toll, Owen Barbour, Carl Edwards, Daniel Nichols, Austin Day

Chancellor’s Honors Program Projects

No abstract provided.

Fusion Machine Scale Wall Material Erosion And Redeposition Modeled With Gitr As A Part Of An Integrated Simulation To Evaluate Tungsten Plasma Facing Component Lifetimes And Feedback On Fusion Plasmas, Timothy Younkin

Doctoral Dissertations

Creating a neutron source via fusion in a confined core plasma and extracting the necessary energy creates an adverse environment at the plasma-material interface. In order for the fusion reaction to be sustainable, the response of the coupled plasma-surface interaction must radiate in the edge plasma while an atomic fraction of 10⁻⁵ of W in the core will make fusion unachievable. Because of this limitation, the underlying physics in the plasma-material interaction must be understood in order to make fusion feasible and economical. This dissertation extends simulation capabilities of the plasma-surface interaction to higher fidelity with the inclusion of multi-scale …

Modeling And Simulation Of The Dynamic Effects Of Pressure Variations On Hydraulic Bladder And Piston Style Accumulators, Colin Loudermilk

Masters Theses

Hydraulic accumulators, being critical for system control, must meet performance parameters depending on system requirements. Multiple types of accumulators exist which provide varying levels of performance. These levels are not well-defined in most technical literature. A mathematical model was developed and computer simulation was used to fill some of the gap. Multiple accumulator systems were mathematically modeled in the Simulink environment and their performance characteristics were determined. Gas-charged bladder and double-acting piston accumulators were simulated with varying degrees of damping due to friction, the main factor that separates the two types. It is shown that a bladder accumulator will in …

Extraction Of Thorium Dioxide And Other Ree Oxides From Monazite Ore, Bradley M. Bennett, Julia Johnson, Kelsey Hay, Chelsea Connolly-Horton

Chancellor’s Honors Program Projects

No abstract provided.

Design And Validation Of Manufacturing Performance Measurement System Using A Case Study, Vijayakrishnan Poondi Srinivasan

Masters Theses

Many manufacturing organizations have used different measures and measurement systems to determine their performance. Yet, one can improve only what one can measure. Performance measurement is indispensable and is a requirement to identify the issue, troubleshoot, and improve the production system. There are various types of performance measurement systems (PMS) presented in the literature and some of them are commonly used, for example, the balanced scorecard. However, there is little experience of performance measurement in research organizations and only 0.5% of publications are related to performance measurement systems. More specifically, the type of research organization referred in this study is …

An Inquiry Into Supply Chain Strategy Implications Of The Sharing Economy For Last Mile Logistics, Vincent Emanuel Castillo

Doctoral Dissertations

As the prevalence of e-commerce and subsequent importance of effective and efficient omnichannel logistics strategies continues to rise, retail firms are exploring the viability of sourcing logistics capabilities from the sharing economy. Questions arise such as, “how can crowdbased logistics solutions such as crowdsourced logistics (CSL), crowdshipping, and pickup point networks (PPN) be leveraged to increase performance?” In this dissertation, empirical and analytical research is conducted that increases understanding of how firms can leverage the sharing economy to increase logistics and supply chain performance. Essay 1 explores crowdsourced logistics (CSL) by employing a stochastic discrete event simulation set in New …

Simulating Microbial Electrolysis For Renewable Hydrogen Production Integrated With Separation In Biorefinery, Christian James Wilson

Masters Theses

Biomass conversion to hydrocarbon fuels requires significant amounts of hydrogen. Fossil resources typically supply hydrogen via steam reforming. A new technology called microbial electrolysis cells (MECs) has emerged which can generate hydrogen from organic sources and biomass. The thermochemical route to fuels via pyrolysis generates bio-oil aqueous phase (BOAP) which can be used to make hydrogen. A process engineering and economic analysis of this technology was conducted for application in biorefineries of the future. Steam methane reforming, bio-oil separation and microbial electrolysis unit operations were simulated in Aspen Plus to derive the mass and energy balance for conversion of biomass. …

Dynamic Simulation And Analysis Of Gait Modification For Treating Knee Osteoarthritis, Taylor Elyse Schlotman

Doctoral Dissertations

Roughly 47.5 million people in the US have a disability, with 8.6 million reporting arthritis as their main cause of disability, making arthritis the leading cause of physical disability. With decreased mortality rates and a large, aging baby boomer generation, there will be more adults living with chronic musculoskeletal conditions causing disabilities that limit walking. Since walking ability is directly related to an individual’s independence at home and in the community, losing this ability is a major setback for patients with arthritis. Knee osteoarthritis (OA) is the most prevalent form of arthritis affecting approximately 27 million adults and accounts for …

The Loewner Equation And Weierstrass' Function, Gavin Ainsley Glenn

Chancellor’s Honors Program Projects

No abstract provided.

Characterization Of Reactor Background Radiation At Hfir For The Prospect Experiment, Blaine Alexander Heffron

Masters Theses

This work describes an investigation of the background radiation present at the High Flux Isotope Reactor (HFIR) on behalf of the PROSPECT collaboration. The PROSPECT experiment is designed to make a precision measurement of the antineutrino spectrum at HFIR and search for sterile neutrinos. Temporal and spacial variation of neutron and gamma backgrounds at the experiment site for the PROSPECT detector are measured in order to determine if the reactor correlated radiation will contribute a significant background to the inverse beta decay signal. Knowledge of spacial background variation will also be used to inform the design of a local shield …

Incentive Payments For Planting Upland Bird Habitat Field Borders In Tennessee, Nathaniel Scott Bruce

Masters Theses

Crop yields along field perimeters that are adjacent to trees and other tall-herbaceous are known to have the lowest yields in a field. An alternative use of these areas that might be more profitable and sustainable is to remove the land from crop production and enroll these areas into the upland bird habitat (UBH) buffer program. However, the adoption of UBH buffers have been limited by producers, despite being eligible for receiving an incentive payment for adopting UBH buffers. Therefore, the objective of this thesis was to determine the breakeven incentive payment for corn [Zea mays L.] and soybean …

Multiscale Modeling Of Electrolytes For Energy Storage And Conversion, Fatemeh Sepehr

Doctoral Dissertations

Fuel cells, redox flow batteries, and secondary ion batteries are under active investigation to fulfill the requirements of efficient and sustainable energy storage and conversion technologies. The discovery of high-performance stable electrolytes that are relatively cheap and versatile is crucial to the commercialization of these electrochemical devices and necessitates a comprehensive understanding of the materials (i.e., from the atomistic to continuum levels). This dissertation is on multiscale modeling and simulations of several electrolytes under consideration in vanadium redox flow batteries (VRFBs), alkaline fuel cells (AFCs), or secondary magnesium batteries.

The hydrated structure and associated solvation Gibbs energies were determined for …

Automatic Sleep Stages Classification, Maryam Zokaeinikoo

Masters Theses

In this thesis, we first develop an efficient automated classification algorithm for sleep stages identification. Polysomnography recordings (PSGs) from twenty subjects were used in this study and features were extracted from the time{frequency representation of the electroencephalography (EEG) signal. The classification of the extracted features was done using random forest classifier. The performance of the new approach is tested by evaluating the accuracy of each sleep stages and total accuracy. The results shows improvement in all five sleep stages compared to previous works.

Then, we present a simulation decision algorithm for switching between sleep interventions. This method improves the percentage …

An Application Of The Universal Verification Methodology, Rui Ma

Masters Theses

The Universal Verification Methodology (UVM) package is an open-source SystemVerilog library, which is used to set up a class-based hierarchical testbench. UVM testbenches improve the reusability of Verilog testbenches. Direct Memory Access (DMA) plays an important role in modern computer architecture. When using DMA to transfer data between a host machine and field-programmable gate array (FPGA) accelerator, a modularized DMA core on the FPGA frees the host side Central Processing Unit(CPU) during the transfer, helps to save FPGA resources, and enhances performance. Verifying the functionality of a DMA core is essential before mapping it to the FPGA. In this thesis, …

Performance Analysis And Modeling Of Task-Based Runtimes, Blake Andrew Haugen

Doctoral Dissertations

The shift toward multicore processors has transformed the software and hardware landscape in the last decade. As a result, software developers must adopt parallelism in order to efficiently make use of multicore CPUs. Task-based scheduling has emerged as one method to reduce the complexity of parallel computing. Although task-based scheduling has been around for many years, the inclusion of task dependencies in OpenMP 4.0 suggests the paradigm will be around for the foreseeable future.

While task-based schedulers simplify the process of parallel software development, they can obfuscate the performance characteristics of the execution of an algorithm. Additionally, they can create …

Failure Simulations At Multiple Length Scales In High Temperature Structural Alloys, Chao Pu

Doctoral Dissertations

A number of computational methodologies have been developed to investigate the deformation and damage mechanism of various structural materials at different length scale and under extreme loading conditions, and also to provide insights in the development of high-performance materials.

In microscopic material behavior and failure modes, polycrystalline metals of interest include heterogeneous deformation field due to crystalline anisotropy, inter/intra grain or phase and grain boundary interactions. Crystal plasticity model is utilized to simulate microstructure based polycrystalline materials, and micro-deformation information, such as lattice strain evolution, can be captured based on crystal plasticity finite element modeling (CPFEM) in ABAQUS. The comparison …

Joint Optimization Of Allocation And Release Policy Decisions For Surgical Block Time Under Uncertainty, Mina Loghavi

Doctoral Dissertations

The research presented in this dissertation contributes to the growing literature on applications of operations research methodology to healthcare problems through the development and analysis of mathematical models and simulation techniques to find practical solutions to fundamental problems facing nearly all hospitals.

In practice, surgical block schedule allocation is usually determined regardless of the stochastic nature of case demand and duration. Once allocated, associated block time release policies, if utilized, are often simple rules that may be far from optimal. Although previous research has examined these decisions individually, our model considers them jointly. A multi-objective model that characterizes financial, temporal, …

Newly Licensed Registered Nurses' Experiences With Clinical Simulation, Carrie Ann Bailey

Doctoral Dissertations

The purpose of this study was to understand how new graduate nurses perceive the value of simulation in making the transition into professional practice. This study will use a descriptive qualitative approach with a sample of first year nurses. Kolb’s Experiential Learning Model serves as this study’s conceptual framework. For the current study, the sample consisted of 10 newly graduated, female nurses with less than one year of experience working in the hospital setting were interviewed. Data analysis included interviews and transcription by the researcher. Finally, participants were asked about themes to increase rigor. Four themes emerged from this research: …

Computational Framework For Small Animal Spect Imaging: Simulation And Reconstruction, Sang Hyeb Lee

Doctoral Dissertations

Small animal Single Photon Emission Computed Tomography (SPECT) has been an invaluable asset in biomedical science since this non-invasive imaging technique allows the longitudinal studies of animal models of human diseases. However, the image degradation caused by non-stationary collimator-detector response and single photon emitting nature of SPECT makes it difficult to provide a quantitative measure of 3D radio-pharmaceutical distribution inside the patient. Moreover, this problem exacerbates when an intra-peritoneal X-ray contrast agent is injected into a mouse for low-energy radiotracers.

In this dissertation, we design and develop a complete computational framework for the entire SPECT scan procedure from the radio-pharmaceutical …