Physical Sciences and Mathematics Commons^™

Questing For The Grail: Core Collapse Supernova Simulations With Boltzmann Neutrino Transport, Otis Earl Messer

Doctoral Dissertations

The importance of exact neutrino transport in spherically symmetric core collapse supernova simulations is explored in this dissertation. The primary tool for these studies is the neutrino radiation hydrodynamics code AGILE-BOLTZTRAN (Mezzacappa & Bruenn 1993a,b,c; Mezzacappa & Messer 1998; Liebendörfer 2000). AGILE-BOLTZTRAN couples the solution of the Boltzmann equation for all three flavors of neutrinos and antineutrinos to a one-dimensional, implicit, adaptive grid hydrodynamics code. Emission, absorption, and scattering of neutrinos from nucleons and nuclei, neutrino-electron scattering, and pair production and annihilation are included as neutrino-matter couplings. Details of the code are described, including the equations solved and their finite …

Electronic Excitations In Metals And Semiconductors: Ab Initio Studies Of Realistic Many-Particle Systems, Wei Ku

Doctoral Dissertations

Electronic excitations in metals and semiconductors, measured through inelastic x-ray scattering, electronic energy-loss spectroscopy, and angle-resolved photoemission, provide valuable information about the intrinsic many-body interactions between electrons in the crystal environment. These dynamical interactions are usually analyzed with intuitive simple models. With the problems studied, which correspond to linear response and quasi-particle excitation, it will be shown that ab initio approaches not only can provide more realistic understanding of microscopic processes and mechanisms, but also result in new theoretical interpretations that resolve a number of remarkable "anomalies." Specifically, these problems include the dispersion of the plasmon lifetime in potassium, the …

Searches For Neutral Higgs Bosons In Quark-Antiquark Tau-Antitau Final States Using The Opal Detector At Lep, James Andrew Hocker '91

Doctoral Dissertations

Searches for neutral Higgs bosons have been performed with the OPAL detector at LEP. Approximately 170 /pb of e+e- collision data at a center-of-mass energy of 189 GeV have been used to search for the SM process e+e- to HZ as well as for the processes e+e- to hZ and e+e- to hA which occur in extended Higgs theories. The searches are sensitive to final states containing quarks and tau leptons, for which an artificial neural network for the identification of tau leptons was designed. The results have been combined with OPAL searches for other final states to obtain a …

The Development Of A Lutetium Recovery Plant, Peter Michael Smith

Doctoral Dissertations

This research project focused on the scale-up of an industrial facility for the continuous counter-current solvent extraction (CCCSX) separation of lutetium. CCCSX involves a multistage apparatus for the mixing in each stage of two immiscible liquid phases to transfer an analyte from one phase to the other. The two phases continuously flow in opposite directions in a CCCSX system. In this research, aqueous lutetium solutions, obtained from the acid leaching of lutetium oxyorthosilicate, were mixed with kerosene solutions of phosphorus based metal extractants (e.g. mono-2-ethylhexyl-(2- ethylhexyl) phosphonic acid, MEHEHP). This system extracted the lutetium from the aqueous phase, transferring the …

Laser Spark Ignition Modeling, Ivan George Dors

Doctoral Dissertations

Laser spark phenomena are studied in air and ammonia-oxygen mixtures by the use of a two-dimensional, axially-symmetric, time-accurate computational fluid dynamic model. The initial laser spark temperature distribution is generated to simulate a post-breakdown profile that is consistent with theoretical, experimental, and computational investigations for a nominal 10-ns optical breakdown laser pulse. Thermodynamic properties of various species are extended to 35,000 K to cover the range of the initial temperature distribution. The developed computational model includes a kinetics mechanism that implements plasma equilibrium kinetics in ionized regions.

The computational model time-accurately predicts species concentrations, free electron number density decay, blast …

Fluid Flow In Micro-Channels: A Stochastic Approach, Hilda Marino Black

Doctoral Dissertations

In this study free molecular flow in a micro-channel was modeled using a stochastic approach, namely the Kolmogorov forward equation in three dimensions. Model equations were discretized using Central Difference and Backward Difference methods and solved using the Jacobi method. Parameters were used that reflect the characteristic geometry of experimental work performed at the Louisiana Tech University Institute for Micromanufacturing.

The solution to the model equations provided the probability density function of the distance traveled by a particle in the micro-channel. From this distribution we obtained the distribution of the residence time of a particle in the micro-channel. Knowledge of …

A Hybrid Finite Element-Finite Difference Method For Thermal Analysis In A Double-Layered Thin Film, Teng Zhu

Doctoral Dissertations

Thin film technology is of vital importance in microtechnology applications. For instance, thin films of metals, of dielectrics such as SiO2, or Si semiconductors are important components of microelectronic devices. The reduction of the device size to the microscale has the advantage of enhancing the switching speed of the device. The reduction, on the other hand, increases the rate of heat generation that leads to a high thermal load on the microdevice. Heat transfer at the microscale with an ultrafast pulsed-laser is also a very important process for thin films. Hence, studying the thermal behavior of thin films or of …

Cramer-Rao Bound And Optimal Amplitude Estimator Of Superimposed Sinusoidal Signals With Unknown Frequencies, Shaohui Jia

Doctoral Dissertations

This dissertation addresses optimally estimating the amplitudes of superimposed sinusoidal signals with unknown frequencies. The Cramer-Rao Bound of estimating the amplitudes in white Gaussian noise is given, and the maximum likelihood estimator of the amplitudes in this case is shown to be asymptotically efficient at high signal to noise ratio but finite sample size. Applying the theoretical results to signal resolutions, it is shown that the optimal resolution of multiple signals using a finite sample is given by the maximum likelihood estimator of the amplitudes of signals.

Bottom-Up Design Of Artificial Neural Network For Single-Lead Electrocardiogram Beat And Rhythm Classification, Srikanth Thiagarajan

Doctoral Dissertations

Performance improvement in computerized Electrocardiogram (ECG) classification is vital to improve reliability in this life-saving technology. The non-linearly overlapping nature of the ECG classification task prevents the statistical and the syntactic procedures from reaching the maximum performance. A new approach, a neural network-based classification scheme, has been implemented in clinical ECG problems with much success. The focus, however, has been on narrow clinical problem domains and the implementations lacked engineering precision. An optimal utilization of frequency information was missing. This dissertation attempts to improve the accuracy of neural network-based single-lead (lead-II) ECG beat and rhythm classification. A bottom-up approach defined …

The Microchannel Flow Of A Micropolar Fluid, Guohua Liu

Doctoral Dissertations

Micro-channel flows have been computed to investigate the influence of Navier-Stokes formulation for the slip-flow boundary condition, and a micro-polar fluid model, respectively.

The results of the slip boundary condition show that the current methodology is valid for slip-flow regime (i.e., for values of Knudsen number less than approximately 0.1). Drag reduction phenomena apparent in some micro-channels can be explained by slip-flow theory. These results are in agreement with some computations and experiments.

An ad hoc micro-polar fluid model is developed to investigate the influence of micro effects, such as micro-gyration, in micro-scale flows. The foundation of the ad hoc …

The Dynamics Of Cyberspace: Examining And Modelling Online Social Structure, Brian S. Butler '89

Doctoral Dissertations

It has been proposed that online social structures represent new forms of organizing which are fundamentally different from traditional social structures. However, while there is a growing body of empirical research that considers behavioral aspects of online activity, research on online social structure structural remains largely anecdotal. This work consists of three papers that combine previous studies of traditional social structures, empirical analysis of longitudinal data from a sample of Internet listservs, and computational modeling to examine the dynamics of social structure development in networked environments.

The first paper (Title: When is a Group not a Group: An Empirical Examination …

A Systematic Integration Of Register Allocation And Instruction Scheduling, Yukong Zhang

Doctoral Dissertations

In order to achieve high performance, processor architecture has become more and more complicated. As a result, compiler-time optimizations have become more and more important for the effective use of a complex processor. One of the promising compiler-time optimizations is the integration of register allocation and instruction scheduling based on register-reuse chains. In the previous approach, however, the generation of register-reuse chains was not completely systematic and consequently created many unnecessary dependencies that restrict instruction scheduling.

This research proposes a new register allocation technique based on a systematic generation of register-reuse chains. The first phase of the proposed technique is …

Graphical Display And Data Structure For Virtual Prototyping, David William Manry

Doctoral Dissertations

One of the goals of engineering firms is to bring better products to market faster. Although concurrent engineering can aid in this endeavor, it requires that all areas of an organization work simultaneously. Thus, current product data must be accessible to everyone.

Virtual prototyping allows this simultaneous exchange of information. Virtual prototyping not only replaces the physical model in product development with a virtual model, but also it goes further by allowing data associated with each part of the model to be accessed. This data is not limited to just geometric properties but could contain other quantifiable properties, such as …

Stability Of Paleosinks And Karstic Carbonates In The Southern Fire Clay Mining District Of Missouri, Robert Weiser Dillon

Doctoral Dissertations

"The Southern Fire Clay District of Missouri was intensely mined during the late-1800’s to mid-1900’s for its valuable resource of high refractory clays deposited within Pennsylvanian sinkholes “paleosinks”. Mining operations have produced modifications in the Ozark aquifer, which in effect has possibly increased the instability of this paleokarst terrain and the potential of further environmental impacts to the land. Evidence supporting this hypothesis are: (1) A southerly shift in the regional groundwater divide relative to the topographic divide. This possibly is caused by the distribution of leaking clay pits, which suggests that the bedrock permeability or hydraulic conductivity has been …

Fuzzy Logic Applied To System Control To Enhance Commercial Appliance Performance, Glenn Moffett

Doctoral Dissertations

The purpose of this research is to determine the usefulness of fuzzy logic and fuzzy control when applied to a commercial appliance. Fuzzy logic is a structured, model-free estimator that approximates a function through linguistic input/output associations. Fuzzy rule-based systems apply these methods to solve many types of "real-world" problems, especially where a system is difficult to model, is controlled by a human operator or expert, or where ambiguity or vagueness is common.

This dissertation presents fuzzy sets, fuzzy systems, and fuzzy control, with an example conveying the use of fuzzy control of a consumer product and an overview of …

Cessation Of Grand Cycle Deposition In The Framework Of Passive Margin Evolution: Controlling Mechanisms And Effects On Carbonate Deposition And Diagenesis, Cambrian Maynardville Formation, Southern Appalachians, Bosiljka Glumac

Doctoral Dissertations

The Middle and Upper Cambrian deposits of the southern Appalachians reveal the existence of a broad carbonate platform that was facing the Iapetus Ocean to the east and was separated from the exposed craton to the west by the Conasauga intrashelf basin. This study focuses on the Maynardville Formation, which was deposited during the early Late Cambrian along the western carbonate platform margin. As the uppermost carbonate unit of the alternating shale and carbonate units or Grand Cycles of the Conasauga Group (Middle to Upper Cambrian), the Maynardville marks a change in style of passive-margin deposition reflected in the cessation …

Extensions Of Commutative Rings With Linearly Ordered Intermediate Rings, Michael Scott Gilbert

Doctoral Dissertations

This work concerns λ-extensions of (commutative) rings, which are defined as ring extensions R ⊆ T whose set of intermediate rings is linearly ordered by inclusion. λ-extensions from a subclass of the ∆-extensions of Gilmer-Huckaba and generalize the adjacent extensions of Ferrand-Oliver, Modica, and Dechene.

In Chapter I, we characterize λ-domains (i.e., integral domains R with quotient field K such that R ⊆ K is a λ-extension), showing that they form a subclass of quasilocal i-domains. These results parallel results of Gilmer-Huckaba for ∆-domains. We relate λ-domains to divided domains and pseudovaluation domains.

Chapter II concerns λ-extensions R ⊆ T …

Applications Of Optimal Control, Katherine Renee Fister

Doctoral Dissertations

In this dissertation, we investigate optimal control of partial and ordinary differential equations. We prove the existence of an optimal control for which the objective functional is maximized. The goal is to characterize the optimal control in terms of the solution of the optimality system. The optimality system consists of the state equations coupled with the adjoint equations. To obtain the optimality system we differentiate the objective functional with respect to the control. This process is applied to harvesting in a predator-prey parabolic system, to analyzing surface runoff in a parabolic problem, and to controlling the effect of the HIV …

Study Of The Equilibria Of Parabolic Differential Equations With Interfaces Intersecting The Boundary, Michal Kowalczyk

Doctoral Dissertations

Existence of steady state solutions for the Allen-Cahn and Cahn-Hilliard equations in two dimensional domains is discussed. We are in particular interested in establishing existence of single layered equilibria with the property that their transition layer intersects the boundary. In the case of the Allen-Cahn equation we consider bone-like domains and seek solutions intersecting the flat part of the boundary. We establish conditions for the domain which ensure existence of such equilibria. Their stability is also analyzed. For the Cahn-Hilliard equations we show that there exist equilibria near every point of a local maximum of the curvature of the boundary.

On LP Solutions Of Second Order Linear Differential Equations, James C. Smith

Doctoral Dissertations

In this dissertation we study the L_p solutions of second order linear differential equations. The question as to when the equation -(q_o(x)y'(x))' + q₁(x)y(x) = f(x), α ≤ x < ∞, admits L_p solutions y(x) for arbitrary f(x) in L_p is investigated. We show the condition Re(q₁(x)) ≥ 1 or the conditions Re(q₁(x)) ≥ 0 and Im(q₁(x)) ≥ 1 are sufficient for a L_p solution y(x) to exist.

Functions that bound a solution of the homogeneous equation …

Reflected Light Microscopy, Electron Microscopy, Electron Spectroscopy, And X-Ray Diffraction Mineralogical Characterization Of Electric Arc Furnace (Eaf) Dusts, Ann M. Hagni

Doctoral Dissertations

"The secondary steel industry in the United States generates 600,000 tons of electric arc furnace (EAF) dust each year. Over 5,000,000 tons of EAF dust are generated annually world wide. The dust, which is removed from off-gasses from the high temperature furnaces, is considered by the Environmental Protection Agency to be hazardous waste due to its leachable lead, cadmium, and chromium. In addition to hazardous components, EAF dust contains valuable zinc, averaging 19%. This study was initiated to determine the mineralogy and characterization of the dust to aid in the processing of the dust for metals recovery and rendering the …

Synthesis And Characterization Of Binuclear And Unsymmetrical Phthalocyanines, Jiang Yang

Doctoral Dissertations

"The metal free planar binuclear phthalocyanines sharing a benzene or naphthalene ring have been synthesized and characterized. The position of Q band of binuclear phthalocyanine sharing a naphthalene ring is red shifted compared to binuclear phthalocyanine sharing a benzene ring. The compounds are shown to form the liquid crystal mesophases at room temperature.

The unique unsymmetrical phthalocyanines with steric hindrance tetraphenyl or “opposite” octaphenyl substitution have been synthesized with the aid of computer modeling. The compounds are characterized by UV-visible near IR absorption and NMR spectroscopy. Mesophase is observed by optical microscopy and differential scanning calorimetry.

The aggregation behavior has …

Production And Extraction Of Polarized Electrons From An Optically Pumped Helium Discharge, Raymond James Vandiver

Doctoral Dissertations

"Polarized electron sources are needed to study the spin dependent processes in atomic and molecular systems. This area of physics has enjoyed much success in the past decade due to the development of polarized electron sources of high electron polarization and current. We have investigated the production and extraction of polarized electrons from an optically pumped helium discharge.

We have directly extracted electrons with polarizations between 6% and 7% at currents greater than 200 µA from a helium DC discharge where the helium 2³S₁ metastable atoms are optically pumped to nearly 100% polarization. These high metastable polarizations …

Depositional History, Sequence Stratigraphy And Diagenesis Of The Maryville Limestone (Middle Cambrian) Southern Appalachians, Krishnan Srinivasan

Doctoral Dissertations

The Conasauga Group constitutes part of a thick pericratonic Cambro-Ordovician passive-margin sequence along the eastern North American continent. The Cambrian carbonate platform was flanked by a high-relief shelf margin towards the east, facing the open ocean, while to the west the carbonate platform sloped into an intrashelf basin. It is this western shelf margin that is the topic of the present study. Detailed lithofacies analysis of the Middle Cambrian Maryville Limestone along a shelf-to-basin depositional transect reveals that the shelf evolved from a gently basinward sloping ramp to a rimmed platform fringed with steeper slopes. Cyanobacterial buildups (Renalcis-Girvanella) …

Lithostratigraphy, Structure, And Metamorphism Of A Crystalline Thrust Terrane, Western Inner Piedmont, North Carolina, Timothy L. Davis

Doctoral Dissertations

The geology of the western Inner Piedmont of North Carolina, from knowledge gained in an area called the Columbus Promontory, is characterized by a stack of crystalline thrust sheets. In this study the stratigraphic, structural, and metamorphic development of this crystalline thrust terrane was examined.

The lithostratigraphic framework of the Columbus Promontory is divisible into four distinct and mappable rock units that include the Henderson Gneiss, Sugarloaf gneiss, Poor Mountain Formation, and the Mill Spring Complex. This lithostratigraphic framework helps define three crystalline thrust sheets within the Columbus Promontory herein, called the Tumblebug Creek, Sugarloaf Mountain, and Mill Spring thrust …

Structural Development, Strain History, And Timing Of Deformation In The Eastern Great Smoky Mountains, Jeffrey B. Connelly

Doctoral Dissertations

The present investigation reveals that the Greenbrier and Dunn Creek thrust sheets preserve well-formed ramp-related folds within the Great Smoky Mountains area. The Greenbrier thrust sheet preserves a ramp anticline at klippes of the Greenbrier thrust sheet in the eastern Great Smoky Mountains that can be traced discontinuously to the western Great Smoky Mountains where this anticline has been modified by later displacement along the Rabbit Creek fault. A ramp-related fold is also preserved in the main Greenbrier thrust sheet. The main Greenbrier fault was subsequently folded by an underlying ramp anticline within the Dunn Creek thrust sheet. These earliest …

Genetic Algorithms With 3-Parent Crossover, L. Vincent Edmondson

Doctoral Dissertations

"A new genetic algorithm which uses a 3-parent uniform crossover operator is developed and analyzed. Uniform crossover operators are shown to be based on the premise that all bit-level genetic information should be passed from parents to children. The 3-parent uniform crossover operator is shown to adhere to this premise. The 3-parent uniform crossover operator is shown to be better than the 2-parent uniform crossover operator on the De Jong test functions.

Two new genetic algorithms which use 3-parent traditional crossover operators are developed and analyzed. The first uses a strategy of randomly selecting 3 of the 6 children resulting …

Self-Diffusion Studies In Polymer-Solvent Systems By Pulsed-Gradient Spin-Echo Nuclear Magnetic Resonance, R. Allen Waggoner

Doctoral Dissertations

"Pulsed gradient NMR techniques have been used to study self-diffusion in polymer solutions. The systems studied include toluene, cyclohexane, ethylbenzene, chloroform, t-butyl acetate, and methyl ethyl ketone in polystyrene; methyl methacrylate in poly(methyl methacrylate); poly(ethylene oxide) in water; and water in biological tissue. The polymer diffusion data are evaluated in terms of scaling theory as they relate to the scaling of the polymer diffusion coefficient with molecular weight. The solvent diffusion data are evaluated with kinetic and free-volume theories. In addition a relatively simple dependence of diffusion coefficient on polymer volume fraction is derived from free-volume theory. The solvent diffusion …

Solid State 13C Nmr And Thermal Analysis Of Conformational Motion And Disorder In Small And Large Molecules, Jinlong Cheng

Doctoral Dissertations

In this work it is attempted to explore the conformational motion and disorder through a large number of examples of molecular systems differing in shape, rigidity, and molecular weight: a series of tetra-n-alkylammonium bromides and iodides, a liquid-crystal-forming molecule, N,N'-bis(4-n-octyloxybenzal)-1,4-phenylenediamine (OOBPD), and polymers, poly[oxy-1,4-(3-methylphenylene)ethylene-1,4-phenyleneoxynonamethylene] (MBPE-9) and poly[oxy-1,4-(3-methylphenylene)ethylene-1,4-phenyleneoxypentamethylene] (MPBE-5). The techniques used to study the conformational motion and disorder are mainly solid state ¹³C nuclear magnetic resonance (NMR) spectroscopy and thermal analysis.

The results of this work show that conformational disordered states (condis crystals) exist indeed in these molecules containing flexible chemical bonds (single …

Atomic Collision Processes Of Interest In Controlled Thermonuclear Fusion Research, Victor Dewitt Irby

Doctoral Dissertations

"This thesis examines several atomic collisional processes involved in controlled thermonuclear fusion. Specifically, experimental studies have been made on the state- selective single capture reaction

³He²⁺ + He —> ³He⁺(n) + He⁺(n'), (1)

on the double capture reaction

³He²⁺ + H e—> ³He + He²⁺ , (2)

and on the single ionization of atomic targets X

A^q+ + X —> A^q+ + X⁺ + e^- (3)

by charged projectiles A^q+. Reactions (1) and (2) have an importance in plasma energy balance and in …