Physical Sciences and Mathematics Commons^™

Aligning Technology, Policy And Culture To Enhance Nuclear Security: A Comparative Analysis Of Nigeria And The U.S., Stephen Olumuyiwa Ariyo Dahunsi, John D. Auxier Ii, Joseph Ruric Stainback Iv, Howard Lewis Hall

International Journal of Nuclear Security

Around the world, current energy and climate change concerns have led to more nations adopting nuclear technology as an option for electricity generation. However, one of the challenges to the peaceful application of this technology is the possibility that it will be misused, or that terrorists with global reach may acquire nuclear materials. Nigeria is one country that has embraced the technology to solve its energy challenges, but the country is now faced with an upsurge in terrorism and uprisings staged by various ethnic groups. In addition, corruption is continually becoming a hindrance to national development. These challenges are critical …

Toward A Non-Nuclear World: The Npt Regime – Nuclear Disarmament And The Challenge Of A Wmdfz In The Middle East, Sameh Aboul-Enein

International Journal of Nuclear Security

This paper aims to provide a comprehensive overview of various approaches for nuclear disarmament and nonproliferation with the intention of determining how best to promote a Weapons of Mass Destruction Free Zone in the Middle East (MEWMDFZ). Using a qualitative approach, I investigate historical cases of agreements regarding nonproliferation zones and examine the causes for deadlock through both a perusal of historic successes and failures and a review of relevant literature. Particular focus is given to the failure of the NPT Review Conference of 2015. Furthermore, I discuss the importance of role-play simulations and their indications of the need for …

Local Moments And Itinerant Electrons: Gaining New Insights Through Investigating Electronic And Dynamical Properties, Nicholas Steven Sirica

Doctoral Dissertations

Magnetic materials are often categorized in terms of either a purely local or a purely itinerant picture despite the fact that the vast majority actually fall within a spectrum that ranges between these two extremes. It is from such a starting point that this thesis aims at developing an understanding of how the complex interplay between local moments and itinerant electrons ultimately affects the electronic and dynamical properties. Such ideas are explored in greater detail using two materials as case studies: the chiral helimagnet Cr_1/3NbS₂ [Cr intercalated Niobium Disulfide] and YFe₂Ge₂ [Yttrium Iron Germanide] …

First-Principles Study Of Point Defect Behavior At Interfaces And In-Plane Strain Fields, Jianqi Xi

Doctoral Dissertations

Interfaces in solid materials are the so-called boundaries, separating crystals with the same structure and chemistry but different orientations, e.g. grain boundaries (GBs), different stacking sequences, e.g. stacking faults (SFs), or crystals with different structures and/or chemistries as well as orientations, e.g. the interface between substrate and thin film. In this study, first-principles calculations are used to investigate the defect behavior at different interfaces and in-plane strain fields, such as stacking fault (SF) in silicon carbide (SiC), in-plane strain field near interfaces in potassium tantalate (KTaO₃), and grain boundary in ceria (CeO₂).

Results show that the …

Metal Oxyhalides And Halides For Use As Electrode Materials In Li-Ion Batteries, Jonathan Mark Powell

Doctoral Dissertations

Synthesis of select metal halides and oxyhalides are explored in the form of direct fluorination using a fluidized bed reactor system, direct chlorination using hydrogen chloride gas, and a degradation dehydration reaction as novel methods towards the synthesis of these select metal halides and oxyhalides. The flexibility of the direct fluorination technique is demonstrated by the ability to vary the degree of fluorination based on the reaction conditions of temperature, time, and fluorine concentration. Conversion electrodes in the form of metal halides and metal oxyhalides are investigated as both anode and cathode materials for lithium ion batteries. The resulting electrochemical …

Surface Modification Of Icy Satellites: Space Weathering Of The Large Moons Of Uranus And Alluvial Fan Formation On Saturn’S Moon Titan, Richard John Cartwright

Doctoral Dissertations

The surfaces of icy satellites are continually modified by space weathering and geologic processes. This dissertation explores the processes changing the surface compositions of the large moons of Uranus and mechanisms for development of possible alluvial fans on the Saturnian moon, Titan. On the Uranian satellites, I hypothesize that the origin and distribution of carbon dioxide ice results from charged particle bombardment, and that spectrally red material originated on retrograde irregular satellites. On Titan, I hypothesize that landforms identified as alluvial fans at low and mid latitudes were formed by sheetfloods, whereas possible alluvial fans at high latitudes were formed …

Total Absorption Spectroscopy Of Neutron Rich Nuclei Across The N=50 Neutron Shell Closure, Kathleen Conner Goetz

Doctoral Dissertations

Decay spectroscopy of neutron rich nuclei near doubly magic 78^Ni [78-Nickel] is relevant to nuclear structure and astrophysics as well as reactor and neutrino physics. β-decay [beta-decay] calorimetry studies are essential to reconstruct the decay strength function and is used to overcome the problems arising from the high density of states leading to nuclear Pandemonium. The Modular Total Absorption Spectrometer, currently located in HRIBF at the Oak Ridge National Laboratory, collected data on 25 fission products of ²³⁸U [238-Uranium] during a run in March 2015. Analysis of the ^84,85,86Br [84, 85 and 86-Bromine] data from the …

Electronic And Magnetic Materials Under External Stimuli, Kenneth Robert O'Neal

Doctoral Dissertations

The interaction between spin, charge, and lattice degrees of freedom leads to exotic and useful properties in multifunctional materials. This delicate balance of energy scales allows external stimuli such as temperature, magnetic field, or pressure to drive to novel phases. As a local probe technique, spectroscopy can provide insight into the microscopic mechanism of the phase transitions. In this dissertation I present spectroscopic studies of functional materials under extreme conditions.

Nanomaterials have attracted attention because nanoscale confinement affects various material properties and often reduces energy scales or suppress phase transitions. Combining Raman and infrared spectroscopies reveals that the breakdown mechanism …

Measurement Of Heavy Flavor Yield And Azimuthal Anisotropy At Forward Angles In Cu + Au Collisions At A Center-Of-Mass Collision Energy Per Nucleon Of 200 Gev, Brandon Kyle Schmoll

Doctoral Dissertations

Heavy flavor quarks are produced early in heavy ion collisions and will experience the full evolution of the Quark Gluon Plasma (QGP). Measurements at forward rapidity may be influenced as much, or more, by the cold nuclear matter effects as by the hot nuclear matter effects associated with a QGP. As the medium evolves, the initial spatial anisotropy of participants is converted to an azimuthal anisotropy in the momentum space of outgoing particles. Therefore, the momentum spectra modification and anisotropy parameters provide useful information about the heavy quark interaction with the bulk medium.

Asymmetric heavy ion collisions, such as Cu+Au, …

New Optical And Electrochemical Probes For Trace Chemicals With Health And Environmental Impacts, Thomas Stewart Carpenter

Doctoral Dissertations

The work in this dissertation focuses on the development of probes for the analysis of trace chemicals in samples with health and environmental impacts. A paper, Cu(copper)-based colorimetric probe was developed for the detection of toxic hydrogen sulfide (H₂S) gas. A modified Kipp’s apparatus was used to generate desired concentrations of H₂S in a total volume of 1.35 L (liters). The probe shows a qualitative response down to 60 ppb (parts per billion), indicating its ability to be used in industrial settings as a replacement for the commonly used lead acetate strips. When used in conjunction …

Synthesis, Characterization, And Reactive Modification Of 2-Vinyl-4,4-Dimethyl Azlactone Polymers, Bethany Michelle Aden

Doctoral Dissertations

Polymeric materials possessing specific functionality have been designed for use in applications such as membranes, biocompatible coatings, lubricants, and tissue engineering. Because the chemical nature of the repeat units set the properties offered by the polymer, the ability to reactively modify polymer chains to integrate specific functionality expands the range of potential applications. Thus, reactive modification of polymer thin films provides a useful route to confer new properties to the underlying material, with the range, strength and type of interaction across the interface dictated by the display of functional groups decorating the surface. To address the links between design, in …

Assessing The Economic Tradeoffs Between Prevention And Suppression Of Forest Fires, Elizabeth Trulia Heines

Doctoral Dissertations

The number of large-scale, high-severity forest fires occurring in the United States is increasing, as is the cost to suppress these fires. These trends have prompted investigations into alternative fuels methods to help prevent these large wildfires. One of the key challenges in studying the costs and benefits of forest fire prevention management is the incorporation of risk and uncertainty surrounding management decisions. We use a technique developed by William Reed to incorporate the stochasticity of the time of a forest fire into our optimal control problems. The goal of these problems is to determine the optimal fire prevention management …

On Laser-Induced Plasma Containing Hydrogen, Ghaneshwar Gautam

Doctoral Dissertations

Laser-induced micro-plasma dynamics are investigated in laboratory air, ultra-high-pure hydrogen gas, and hydrogen-nitrogen gas mixtures. The dissertation focuses on atomic spectroscopy of hydrogen in the visible region.

Line-of-sight measurements are analyzed to obtain spatial distributions of electron densities and excitation temperatures. The studies include evaluation of self-absorption phenomena. The plasma dynamics occur initially well above re-entry speeds and diminish to hypersonic and then supersonic expansions. Expansion velocities are measured that are above three hundred times the speed of sound in standard atmosphere. Optical breakdown is induced by using pulsed laser radiation. Emission spectra are collected by employing a spectrometer equipped …

Data Analysis Methods Using Persistence Diagrams, Andrew Marchese

Doctoral Dissertations

In recent years, persistent homology techniques have been used to study data and dynamical systems. Using these techniques, information about the shape and geometry of the data and systems leads to important information regarding the periodicity, bistability, and chaos of the underlying systems. In this thesis, we study all aspects of the application of persistent homology to data analysis. In particular, we introduce a new distance on the space of persistence diagrams, and show that it is useful in detecting changes in geometry and topology, which is essential for the supervised learning problem. Moreover, we introduce a clustering framework directly …

Construction And Classification Results For Commuting Squares Of Finite Dimensional *-Algebras, Chase Thomas Worley

Doctoral Dissertations

In this dissertation, we present new constructions of commuting squares, and we investigate finiteness and isolation results for these objects. We also give applications to the classification of complex Hadamard matrices and to Hopf algebras.

In the first part, we recall the notion of commuting squares which were introduced by Popa and arise naturally as invariants in Jones' theory of subfactors. We review some of the main known examples of commuting squares such as those constructed from finite groups and from complex Hadamard matrices. We also recall Nicoara's notion of defect which gives an upper bound for the number of …

Classification Results Of Hadamard Matrices, Gregory Allen Schmidt

Masters Theses

In 1893 Hadamard proved that for any n x n matrix A over the complex numbers, with all of its entries of absolute value less than or equal to 1, it necessarily follows that

|det(A)| ≤ n^n/2 [n raised to the power n divided by two],

with equality if and only if the rows of A are mutually orthogonal and the absolute value of each entry is equal to 1 (See [2], [3]). Such matrices are now appropriately identified as Hadamard matrices, which provides an active area of research in both theoretical and applied fields …

Approximation Of Invariant Subspaces, Faruk Yilmaz

Doctoral Dissertations

For a real number α [alpha] the Dirichlet-type spaces 𝔇_α [script D sub alpha] are the family of Hilbert spaces consisting of all analytic functions f(z) = ∑_n=0^∞[sum over n equals zero to infinity] ˆf(n) [f hat of n] zⁿ [z to the n] defined on the open unit disc 𝔻 [unit disc] such that

∑_n=0^∞ (n+1)^α | ˆf(n) |²

[sum over n equals 0 to infinity] [(n+1) to α] [ | f hat of n | to 2]

is finite.

For α < 0, the spaces 𝔇_α are known as weighted Bergman spaces. When …

A Predictive Model For Brook Trout Restoration In The Cherokee National Forest, Caylor Garrett Romines

Masters Theses

Over the course of the last century, Brook Trout (Salvelinus fontinalis) have been reduced in abundance and extirpated from many high elevation streams throughout the southern Appalachian Mountains. These fish have been threatened by anthropogenic factors that restrict their distribution across the longitudinal gradient of the streams they occupy. A large portion of Tennessee's Brook Trout streams are located within the Cherokee National Forest (CNF). Many agencies in the southern Appalachian Mountains are working to restore Brook Trout populations throughout this species’ historic native range. The purpose of this research is to develop a model of important habitat …

A Gpu Implementation Of Distance-Driven Computed Tomography, Ryan D. Wagner

Masters Theses

Computed tomography (CT) is used to produce cross-sectional images of an object via noninvasive X-ray scanning of the object. These images have a wide range of uses including threat detection in checked baggage at airports. The projection data collected by the CT scanner must be reconstructed before the image may be viewed. In comparison to filtered backprojection methods of reconstruction, iterative reconstruction algorithms have been shown to increase overall image quality by incorporating a more complete model of the underlying physics. Unfortunately, iterative algorithms are generally too slow to meet the high throughput demands of this application. It is therefore …

Efficient Methods For Multidimensional Global Polynomial Approximation With Applications To Random Pdes, Peter A. Jantsch

Doctoral Dissertations

In this work, we consider several ways to overcome the challenges associated with polynomial approximation and integration of smooth functions depending on a large number of inputs. We are motivated by the problem of forward uncertainty quantification (UQ), whereby inputs to mathematical models are considered as random variables. With limited resources, finding more efficient and accurate ways to approximate the multidimensional solution to the UQ problem is of crucial importance, due to the “curse of dimensionality” and the cost of solving the underlying deterministic problem.

The first way we overcome the complexity issue is by exploiting the structure of the …

Generalizations And Variations Of The Zero-Divisor Graph, Grace Elizabeth Mcclurkin

Doctoral Dissertations

We explore generalizations and variations of the zero-divisor graph on commutative rings with identity. A zero-divisor graph is a graph whose vertex set is the nonzero zero-divisors of a ring, wherein two distinct vertices are adjacent if their product is zero. Variations of the zero-divisor graph are created by changing the vertex set, the edge condition, or both. The annihilator graph and the extended zero-divisor graph are both variations that change the edge condition, whereas the compressed graph and ideal-based graph change the vertex set. By combining these concepts, we define and investigate graphs where both the vertex set and …

Numerical Methods For Non-Divergence Form Second Order Linear Elliptic Partial Differential Equations And Discontinuous Ritz Methods For Problems From The Calculus Of Variations, Stefan Raymond Schnake

Doctoral Dissertations

This dissertation consists of three integral parts. Part one studies discontinuous Galerkin approximations of a class of non-divergence form second order linear elliptic PDEs whose coefficients are only continuous. An interior penalty discontinuous Galerkin (IP-DG) method is developed for this class of PDEs. A complete analysis of the proposed IP-DG method is carried out, which includes proving the stability and error estimate in a discrete W^2;p-norm [W^2,p-norm]. Part one also studies the convergence of the vanishing moment method for this class of PDEs. The vanishing moment method refers to a PDE technique for approximating these PDEs by a …

Bats Roosting In Buildings In Great Smoky Mountains National Park: Ecology, Human Dimensions, And Management Implications, Kirstin Emily Fagan

Masters Theses

During summer, bats are regularly observed in buildings of Great Smoky Mountains National Park (GRSM or the Park), the most visited National Park in the USA. As a result, natural and cultural resources managers seek to ensure public safety and protect historic structures while minimizing impacts on bats, especially in light of declines in bat populations as a result of white-nose syndrome. To inform management decisions, I examined the ecological and human dimensions of bats roosting in buildings in GRSM.

To assess roost selection by building-roosting bats, I surveyed 140 buildings in the Park for bats during May to August, …

Localization Of Large Scale Structures, Ryan James Jensen

Doctoral Dissertations

We begin by giving the definition of coarse structures by John Roe, but quickly move to the equivalent concept of large scale geometry given by Jerzy Dydak. Next we present some basic but often used concepts and results in large scale geometry. We then state and prove the equivalence of various definitions of asymptotic dimension for arbitrary large scale spaces. Some of these are generalizations of asymptotic dimension for metric spaces, and many of the proofs are new. Particularly useful in proving the equivalences of the various definitions is the notion of partitions of unity, originally set forth by Jerzy …

Generalizations Of Coarse Properties In Large Scale Spaces, Kevin Michael Sinclair

Doctoral Dissertations

Many results in large scale geometry are proven for a metric space. However, there exists many large scale spaces that are not metrizable. We generalize several concepts to general large scale spaces and prove relationships between them. First we look into the concept of coarse amenability and other variations of amenability on large scale spaces. This leads into the definition of coarse sparsification and connections with coarse amenability. From there, we look into an equivalence of Sako's definition of property A on uniformly locally finite spaces and prove that finite coarse asymptotic definition implies it. As well, we define large …

Dependence Structures In Lévy-Type Markov Processes, Eddie Brendan Tu

Doctoral Dissertations

In this dissertation, we examine the positive and negative dependence of infinitely divisible distributions and Lévy-type Markov processes. Examples of infinitely divisible distributions include Poissonian distributions like compound Poisson and α-stable distributions. Examples of Lévy-type Markov processes include Lévy processes and Feller processes, which include a class of jump-diffusions, certain stochastic differential equations with Lévy noise, and subordinated Markov processes. Other examples of Lévy-type Markov processes are time-inhomogeneous Feller evolution systems (FES), which include additive processes. We will provide a tour of various forms of positive dependence, which include association, positive supermodular association (PSA), positive supermodular dependence (PSD), and positive …

Various Topics On Graphical Structures Placed On Commutative Rings, Darrin Weber

Doctoral Dissertations

In this dissertation, we look at two types of graphs that can be placed on a commutative ring: the zero-divisor graph and the ideal-based zero-divisor graph. A zero-divisor graph is a graph whose vertices are the nonzero zero-divisors of a ring and two vertices are connected by an edge if and only if their product is 0. We classify, up to isomorphism, all commutative rings without identity that have a zero-divisor graph on 14 or fewer vertices.

An ideal-based zero-divisor graph is a generalization of the zero-divisor graph where for a ring R and ideal I the vertices are { …

Statistical Computational Topology And Geometry For Understanding Data, Joshua Lee Mike

Doctoral Dissertations

Here we describe three projects involving data analysis which focus on engaging statistics with the geometry and/or topology of the data.

The first project involves the development and implementation of kernel density estimation for persistence diagrams. These kernel densities consider neighborhoods for every feature in the center diagram and gives to each feature an independent, orthogonal direction. The creation of kernel densities in this realm yields a (previously unavailable) full characterization of the (random) geometry of a dataspace or data distribution.

In the second project, cohomology is used to guide a search for kidney exchange cycles within a kidney paired …

Spatial Analysis Of Tornado Warning System Understanding And Relationship With Tornado Occurrence, Chesnea A. Skeen

Pursuit - The Journal of Undergraduate Research at The University of Tennessee

Tornadoes present a significant threat to life and property. The National Weather Service watch and warning system warns the public of tornadoes. If these warnings are not heeded by the public, the potential fatalities and destruction of property cannot be minimized. Thus, to prevent further loss of life and property, it is necessary to understand how the public understands the watch and warning system, as well as how they react. This paper aims to understand the correlation between understanding of watches and warnings and the occurrence of tornadoes, as well as how understanding varies spatially. Survey data were collected from …

Streambank Erosion Mapping On The Nottoway River Using Gps-Based Above-Water Video, Emine Fidan

Pursuit - The Journal of Undergraduate Research at The University of Tennessee

This project concerns the development of streambank erosion maps on military installations utilizing GPS-based above-water video mapping and image georeferencing techniques. The river mapped was the Nottoway River at the Fort Pickett military installation on October 10-11, 2015. Kayak-mounted above-water cameras were utilized to capture georeferenced images of streambank erosion. These GIS-based erosion classifications were utilized to develop erosion maps for determining streambank erosion conditions along the river. Areas of high erosion were identified as about two percent of the river (2167 ft. of streambank length). These maps allow for the opportunity to revisit the sites to determine changes in …