Physical Sciences and Mathematics Commons^™

A Generalized Method For Fissile Material Characterization Using Short-Lived Fission Product Gamma Spectroscopy, Justin Richard Knowles

Doctoral Dissertations

Characterizing the fissile content of nuclear materials is of particular interest to the safeguards and nuclear forensics communities. Short-lived fission product gamma spectroscopy offers a significant reduction in analysis time and detection limits when compared to traditional non-destructive assay measurements. Through this work, a fully generalizable method that can be applied to variations in fissile compositions and neutron spectra was developed for the modeling and measurement of short-lived fission product gamma-rays. This method uses a 238-group neutron flux that was characterized for two pneumatic tube positions in the High Flux Isotope Reactor using flux monitor irradiations. This flux spectrum was …

Characterizing Local Order And Physical Properties Of Rare Earth Complex Oxides, Thomas Jacob Shamblin

Doctoral Dissertations

With more than 500 compositions, materials possessing the pyrochlore structure have a myriad of technological applications and physical phenomena. Three of the most noteworthy properties are the structure’s ability to resist amorphization making it a possible host matrix for spent nuclear fuel, its exotic magnetic properties arising from geometric frustration, and fast ionic conductivity for solid-oxide fuel cell applications. This work focuses on these three aspects of the pyrochlore’s many potential uses. Structural characterization revealed that pyrochlore-type oxides have a tendency to disorder from a high symmetry cubic structure to a lower symmetry orthorhombic arrangement in response to a variety …

Conditional Computation In Deep And Recurrent Neural Networks, Andrew Scott Davis

Doctoral Dissertations

Recently, deep learning models such as convolutional and recurrent neural networks have displaced state-of-the-art techniques in a variety of application domains. While the computationally heavy process of training is usually conducted on powerful graphics processing units (GPUs) distributed in large computing clusters, the resulting models can still be somewhat heavy, making deployment in resource- constrained environments potentially problematic. In this work, we build upon the idea of conditional computation, where the model is given the capability to learn how to avoid computing parts of the graph. This allows for models where the number of parameters (and in a sense, the …

Hybrid Micellar Network Hydrogels Of Thermosensitive Hydrophilic Triblock Copolymers And Thermosensitive Hairy Nanoparticles, Bin Hu

Doctoral Dissertations

Hybrid micellar network hydrogels, composed of thermosensitive hydrophilic triblock copolymers and thermosensitive polymer brush-grafted nanoparticles (hairy NPs), exhibit intriguing rheological properties. This dissertation work studies thermosensitive hybrid hydrogels with NPs positioned either inside or outside the core of block copolymer micelles.

Chapter 1 is an introduction. Chapter 2 examines the effect of NP’s location on properties of hybrid hydrogels of a thermosensitive ABA triblock copolymer and hairy NPs. Two batches of thermoresponsive polymer brush-grafted silica NPs and an ABA triblock copolymer with thermosensitive outer blocks were prepared. When the lower critical solution temperature (LCST) of hairy NPs was similar to …

Synthesis And Application Of Polymer Brush-Grafted Nanoparticles As Hydrogel Gelators And Lubricant Additives, Roger Anthony Emory Wright

Doctoral Dissertations

This dissertation describes the synthesis of polymer brush-grafted nanoparticles (hairy NPs) and an analysis of their behavior or utility in multiple areas. The hairy NPs were synthesized from silica NPs functionalized with initiating moieties by surface-initiated atom transfer radical polymerization. A brief introduction to hairy NPs, with a focus on the synthesis and behavior of stimuli-responsive polymer brush-grafted particles, is given in Chapter 1 to provide context for this work.

Chapters 2 and 3 present the synthesis of thermosensitive diblock copolymer brush-grafted nanoparticles designed as hairy NP analogues in place of thermosensitive block copolymers micelles for the construction of hybrid, …

Spectroscopic Imaging Of Aluminum Containing Plasma, David Michael Surmick

Doctoral Dissertations

This dissertation aims to characterize laser-induced plasma from a physics point of view as warm, dense matter. Use of nominal nanosecond pulsed laser radiation initiates a plasma with electron temperatures of the order of 10 electron volts and electron densities of the order of air species densities at standard ambient temperature and pressure. For laser ablation and/or optical breakdown at or near a solid surface, the electron density can amount to be 1000 times greater. Spectroscopic investigations of the plasma emissions provide a method by which the electron density, temperature, and shockwave expansion may be determined. Of particular interest are …

Actinium-225 Production Via Proton Irradiation Of Thorium-232, Justin Reed Griswold

Doctoral Dissertations

High energy proton spallation reactions on natural thorium metal targets have been utilized to produce multi mCi [milliCurie] quantities of Actinium-225. Theoretical cross sections for actinium and thorium isotopes as well as for a select number of the fission products produced in these reactions were generated by the Monte Carlo radiation transport code PHITS to simulate the experimental data obtained from sixteen irradiations of thorium metal targets with 25-210 µA [microampere] proton beams ranging in energies from 77 to 192 MeV. Irradiations were conducted at Brookhaven National Laboratory (BNL) and Los Alamos National Laboratory (LANL), while target dissolution and processing …

Lignin-Based Li-Ion Anode Materials Synthesized From Low-Cost Renewable Resources, Nicholas William Mcnutt

Doctoral Dissertations

In today’s world, the demand for novel methods of energy storage is increasing rapidly, particularly with the rise of portable electronic devices, electric vehicles, and the personal consumption and storage of solar energy. While other technologies have arguably improved at a rate that is exponential in accordance with Moore’s law, battery technology has lagged behind largely due to the difficulty in devising new electric storage systems that are simultaneously high performing, inexpensive, and safe.

In order to tackle these challenges, novel Li-ion battery anodes have been developed at Oak Ridge National Laboratory that are made from lignin, a low-cost, renewable …

Quantitative Metrics For Comparison Of Hyper-Dimensional Lsa Spaces For Semantic Differences, John Christopher Martin

Doctoral Dissertations

Latent Semantic Analysis (LSA) is a mathematically based machine learning technology that has demonstrated success in numerous applications in text analytics and natural language processing. The construction of a large hyper-dimensional space, a LSA space, is central to the functioning of this technique, serving to define the relationships between the information items being processed. This hyper-dimensional space serves as a semantic mapping system that represents learned meaning derived from the input content. The meaning represented in an LSA space, and therefore the mappings that are generated and the quality of the results obtained from using the space, is completely dependent …

Interaction Between Charge-Transfer States Studied By Magnetic Field Effects, Mingxing Li

Doctoral Dissertations

Organic semiconducting materials, consisting mostly of carbon and hydrogen atoms, provide remarkable promise for electronic applications due to their easy processing, chemical tenability, low costs and environmental-friendly characteristics. For realizing electronic applications such as light emitting diodes and photovoltaic cells, charge-transfer states act as an important intermediate state for recombination and dissociation. Interestingly, magnetic field effects on semiconducting materials have been realized based on the suppression of spin mixing in the charge-transfer states. Although lots of studies have been carried out on investigating the properties of charge-transfer states, little has been done to consider the interaction between them. This thesis …

Metabolomics Approaches To Decipher The Antibacterial Mechanisms Of Yerba Mate (Ilex Paraguariensis) Against Staphylococcus Aureus And Salmonella Enterica Serovar Typhimurium, Caroline Sue Rempe

Doctoral Dissertations

The increasing prevalence of drug-resistant pathogens is an urgent problem that requires novel methods of bacterial control. Plant extracts inhibit bacterial pathogens and could contain antibacterial compounds with novel mechanisms of action. Yerba mate, a common South American beverage made from Ilex paraguariensis, has antibiotic activity against a broad range of bacterial pathogens. In this work, an attempt was first made to characterize the antibacterial source of an aqueous yerba mate extract by generating a series of extract fractions, collecting GC-MS and antibacterial activity profiles, and then ranking the hundreds of compounds by their presence in fractions with high antibacterial …

A Textural Image Analysis Study Of Mars-Analog Sediment: Comparisons Of 2d And 3d Textural Analysis Methods, Image Resolution, And The Effects Of Shadows, Mary Agnes Eibl

Masters Theses

Sediments from Mars-analog, basaltic, aeolian (Moses Lake dunes, WA) and fluvial (Death Valley region, CA) environments were analyzed for textural properties (grain size, roundness, sphericity) to understand how well image-based analyses compare with actual sediment characteristics. Three interrelated studies determined: (1) how well high-resolution, two-dimensional (2D) image analysis compares with three-dimensional (3D) sediment textures, (2) the extent to which decreasing image resolution affects textural analyses by comparison with high-resolution images, and (3) the extent to which shadows at different incident solar angles has on textural measurements. In both aeolian and fluvial environments, 2D grain-size distributions and statistics closely match 3D …

Surface Plasmon Modes In Toroidal Nanostructures And Applications, Marouane Salhi

Doctoral Dissertations

A special interest in Plasmon mode resonance in toroidal nano-particles where a full and comprehensive analytical investigation is presented for different toroidal nano-structure within the quasi-static approximation. Then the optical response of gold nanorings and the associated near-field mapping when exposed to a broadband electromagnetic wave were obtained by the implementation of numerical methods to solve for the transient response. The numerical and analytical investigation lead to the design of an optical nano-trapping system and the identification of strong coupling interaction between toroidal plasmons and J-aggregate dye molecules a promising component in the design of novel optoelectronic material.

Extension Theorems On Matrix Weighted Sobolev Spaces, Christopher Ryan Loga

Doctoral Dissertations

Let D a subset of Rⁿ [R n] be a domain with Lipschitz boundary and 1 ≤ p < ∞ [1 less than or equal to p less than infinity]. Suppose for each x in Rⁿ that W(x) is an m x m [m by m] positive definite matrix which satisfies the matrix A_p [A p] condition. For k = 0, 1, 2, 3;... define the matrix weighted, vector valued, Sobolev space [L p k of D,W] with

[the weighted L p k norm of vector valued f over D to the p power equals the sum over all alpha with order less than k of the integral over D of the the pth power …

Anthrax Models Involving Immunology, Epidemiology And Controls, Buddhi Raj Pantha

Doctoral Dissertations

This dissertation is divided in two parts. Chapters 2 and 3 consider the use of optimal control theory in an anthrax epidemiological model. Models consisting system of ordinary differential equations (ODEs) and partial differential differential equations (PDEs) are considered to describe the dynamics of infection spread. Two controls, vaccination and disposal of infected carcasses, are considered and their optimal management strategies are investigated. Chapter 4 consists modeling early host pathogen interaction in an inhalational anthrax infection which consists a system of ODEs that describes early dynamics of bacteria-phagocytic cell interaction associated to an inhalational anthrax infection.

First we consider a …

Development Of Instrumentation For The Analysis Of Photoconductivity In Functional Materials, Brandon L. Chapman 9741174

Chancellor’s Honors Program Projects

No abstract provided.

Mathematical Approaches To Sustainability Assessment And Protocol Development For The Bioenergy Sustainability Target Assessment Resource (Bio-Star), Nathan Louis Pollesch

Doctoral Dissertations

Bioenergy is renewable energy made of materials derived from biological, non-fossil sources. In addition to the benefits of utilizing an energy source that is renewable, bioenergy is being researched for its potential positive impact on climate change mitigation, job creation, and regional energy security. It has also been studied to investigate possible challenges related to indirect and direct land-use change and food security. Bioenergy sustainability assessment provides a method to identify, quantify, and interpret indicators, or metrics, of bioenergy sustainability in order to study trade-offs between environmental, social, and economic aspects of bioenergy production and use. Assessment is crucial to …

Variable Selection Via Penalized Regression And The Genetic Algorithm Using Information Complexity, With Applications For High-Dimensional -Omics Data, Tyler J. Massaro

Doctoral Dissertations

This dissertation is a collection of examples, algorithms, and techniques for researchers interested in selecting influential variables from statistical regression models. Chapters 1, 2, and 3 provide background information that will be used throughout the remaining chapters, on topics including but not limited to information complexity, model selection, covariance estimation, stepwise variable selection, penalized regression, and especially the genetic algorithm (GA) approach to variable subsetting.

In chapter 4, we fully develop the framework for performing GA subset selection in logistic regression models. We present advantages of this approach against stepwise and elastic net regularized regression in selecting variables from a …

The Use Of Sodium Persulfate In Hydraulic Fracturing Fluids: A Degradation Study Based On Furfural, Katherine Elizabeth Manz

Masters Theses

Hydraulic fracturing has allowed natural gas to become a viable energy source via extraction of unconventional shale reserves, but this process requires an enormous amount of water. To ensure a productive fracture, a proprietary blend of chemical additives is added to the water. In this research, a hydraulic fracturing chemical additive – an enzyme breaking agent – is analyzed for organic components using gas chromatography mass spectrometry. The chemical changes that occur over the course of a fracture are also investigated using one model chemical found in the additive, furfural, in order to help assess the environmental risk that hydraulic …

Testing The Temporal Stability Of The Climate Response Of Tree Species At Norris Dam State Park, Tennessee, U.S.A., Allison Elizabeth Ingram

Masters Theses

Temporal stability of the climate-tree growth relationship means that over time, tree species were responding to a specific climate variable and continue to respond to that variable into the present. The stability of this response is important to test prior to attempting to reconstruct past climate. In this study, I sampled oaks (white oak = Quercus alba L. and chestnut oak = Quercus montana Willd.) and pines (Virginia pine = Pinus virginiana Mill. and shortleaf pine = Pinus echinata Mill.) growing in Norris Dam State Park in eastern Tennessee and tested the temporal stability of these species and their potential …

Role Of Sorting On The Composition Of Siliciclastic Sediment: Implications For Interpreting Provenance After Limited Transport In An Arid Climate, Forrest Christopher Driscoll

Masters Theses

This study tested whether transport distances (< 500 m) have the capacity to shape the geochemistry of sediments across multiple grain-size populations due to sorting derived from a single source. In the Stepladder Mountains, Mojave Desert, CA, a < 1 km² [square kilometers] watershed allows for a controlled study to understand how modern sediments acquire their composition from a single granodioritic source in an arid climate where there is no chemical weathering. Sediments are naturally sorted into distinct grain-size populations, with modes ranging from very fine sand to gravel within a single, alluvial channel. Sediment samples representative of each population were petrographically and geochemically analyzed in order to test the effectiveness of commonly used discrimination diagrams. Sediments became proportionally enriched in plagioclase and biotite and depleted in K-feldspar and quartz with decreasing grain …

Advanced Sequential Monte Carlo Methods And Their Applications To Sparse Sensor Network For Detection And Estimation, Kai Kang

Doctoral Dissertations

The general state space models present a flexible framework for modeling dynamic systems and therefore have vast applications in many disciplines such as engineering, economics, biology, etc. However, optimal estimation problems of non-linear non-Gaussian state space models are analytically intractable in general. Sequential Monte Carlo (SMC) methods become a very popular class of simulation-based methods for the solution of optimal estimation problems. The advantages of SMC methods in comparison with classical filtering methods such as Kalman Filter and Extended Kalman Filter are that they are able to handle non-linear non-Gaussian scenarios without relying on any local linearization techniques. In this …

Numerical Solutions Of Stochastic Differential Equations, Liguo Wang

Doctoral Dissertations

In this dissertation, we consider the problem of simulation of stochastic differential equations driven by Brownian motions or the general Levy processes. There are two types of convergence for a numerical solution of a stochastic differential equation, the strong convergence and the weak convergence. We first introduce the strong convergence of the tamed Euler-Maruyama scheme under non-globally Lipschitz conditions, which allow the polynomial growth for the drift and diffusion coefficients. Then we prove a new weak convergence theorem given that the drift and diffusion coefficients of the stochastic differential equation are only twice continuously differentiable with bounded derivatives up to …

Pdroid, Joe Larry Allen

Masters Theses

When an end user attempts to download an app on the Google Play Store they receive two related items that can be used to assess the potential threats of an application, the list of permissions used by the application and the textual description of the application. However, this raises several concerns. First, applications tend to use more permissions than they need and end users are not tech-savvy enough to fully understand the security risks. Therefore, it is challenging to assess the threats of an application fully by only seeing the permissions. On the other hand, most textual descriptions do not …

A Computational Geometric And Graph Theoretic Approach To Reducing Dimensionality On Raster Data Problems, Matthew James Robert Bachstein

Masters Theses

Large scale mathematical models often involve a trade off between computational length and detail. In general, the more detailed the data, the more time it takes for the model to process. Models that use geographic scale data are particularly susceptible to this inflation; fine resolution data (on the order of m2 [meters squared]) brings great benefits, but demolishes the computation time. This thesis presents a method for reducing the dimensionality of large scale data in a systematic manner to maximize the benefits of fine resolution data while minimizing the computational time increase, then applying the method to a simulated invasive …

Petrology Of The Paired Dominion Range 2010 Howardites: Indications Of Magmatic Complexity On Asteroid Vesta, Timothy Michael Hahn Jr.

Masters Theses

A comprehensive petrologic and geochemical characterization of six paired howardites collected from the Dominion Range, Antarctica was conducted. These howardites are megaregolith samples from the asteroid 4 Vesta. Collectively, they contain an assortment of igneous rock fragments that indicate magmatic processes were capable of producing a variety of rock types; 22 chemically and texturally discrete basaltic eucrite, cumulate eucrite, and diogenite lithologies are recognized. The implications for remote-sensing observations of Vesta are discussed. The petrogenesis of two previously unrecognized lithologies are described in further detail: an evolved dacite that we propose is a residual melt from extensive crystallization, and a …

Regional Dynamic Price Relationships Of Distillers Dried Grains In U.S. Feed Markets, Matthew Fulton Johnson

Masters Theses

Distillers dried grains with solubles (DDGS) is now a mainstream substitute in U.S. animal feed rations. DDGS is rich in fat and protein content and serves as a competitive feed source in livestock markets. The objective of this study is to identify dynamic price relationships among DDGS, corn, soybean meal, and livestock outputs in context of specific livestock sectors and their geographic location. Four locations associated with a predominant livestock sector are selected for analysis by measuring density and relative proportion of a livestock sector’s grain consumption at the county level. A vector error correction model is applied to post-mandate …

Microbial Extracellular Enzymes In Marine Sediments: Methods Development And Potential Activities In The Baltic Sea Deep Biosphere, Jenna Marie Schmidt

Masters Theses

The deep biosphere is defined as the subsurface ecosystem in which little energy is available to microorganisms and microorganisms can live for thousands of years. Heterotrophic microbes survive in the deep biosphere even though organic matter is limited and highly recalcitrant in nature. Measuring microbial extracellular enzyme activity provides a potential means to evaluate the rate at which microorganisms are performing carbon remineralization in the energy limited sediment beneath the seafloor. Extracellular enzymes breakdown organic compounds so that the nutrients can move inside the cell and be used for energy. This study explored the role extracellular enzymes play in the …

Control System Requirements For A Nuclear Thermal Propulsion System, Adam Hasse, Michael Smith, Bradley Pershke, Andrew Adams, Stephen GilliAm

Chancellor’s Honors Program Projects

No abstract provided.

Toward A Precision Measurement Of The Theta_13 Mixing Angle With The Double Chooz Detectors, Ben Thomas Rybolt

Doctoral Dissertations

Neutrinos are the most numerous and least understood particle in the universe. In the last few decades numerous experiments have been devoted to discovering their properties. The Double Chooz experiment was designed to make a precise measurement of θ₁₃ [theta 13], the neutrino mixing parameter which describes flavor oscillations governing short baselines. To accomplish this measurement, two identical neutrino detectors have been deployed at a near and far baseline outside two commercial nuclear reactors. The neutrino flux and spectrum at the near and far detector sites will determine the disappearance of anti-neutrinos created inside the reactors.

I have contributed …