Physical Sciences and Mathematics Commons^™

Conservation Of Grassland Bird Populations On Military Installations In The Eastern United States With Special Emphasis On Fort Campbell Army Base, Kentucky, James J. Giocomo

Doctoral Dissertations

Grassland bird populations have decline significantly over the past 30 years because of the dramatic decrease of native grasslands through clearing of non-forested land for agriculture, and discontinued use of fire. It is imperative to understand the distribution and productivity of these birds and the potential for grassland management to enhance these declining populations, especially in land areas where the landuses may be compatible with grassland bird conservation.

This study was conducted to provide needed basic life history and nest site habitat use information as well as information about populations and potential region-wide habitat availability to enhance current and future …

Atomistic Investigation Of Anomalous Diffusion On Surfaces: A Deterministic Approach, James Wesley Mancillas

Doctoral Dissertations

The observation of anomalous diffusion rates on surfaces by recent experiments has renewed interest in diffusion mechanics. In order to provide a better understanding of the atomistic motions resulting in anomalous diffusion, we have investigated the diffusion dynamics of sodium on a copper surface using conservative molecular dynamics. The properties of diffusing adatoms transitioning between normal diffusive motion and anomalous motion have then been examined. Utilizing short time approximation Lyapunov exponents, stable cantori within chaotic manifolds are identified. At the periphery of these stable cantori from which anomalous diffusion originates, we have examined the transition properties of diffusive motions with …

Overcoming Statistical Error And Bias In Quantum Monte Carlo: Application To Metal-Doped Helium Clusters, Gary Lee Warren Jr.

Doctoral Dissertations

Quantum Monte Carlo (QMC) methods are a class of powerful computer simulation techniques for solving the many-body Schrӧdinger equation. These techniques deliver essentially exact results and boast favorable computational scaling with system size. Calculations provide a full quantum mechanical treatment and may be carried to arbitrary precision. These characteristics make QMC a promising choice for the investigation of doped helium clusters, where quantum effects are substantial.

Stochastic in nature, QMC methods are susceptible to statistical bias and error, which must be carefully controlled. Moreover, the relationship between the finite sampling error and the statistical uncertainty in observables has never been …

Experimental Studies Of Intra- And Intermolecular Chemical Structure, Cara Lynn Nygren

Doctoral Dissertations

The purpose of this study was two fold. The determination of hydrogen atom positions by X-ray diffraction methods is widely underused. With advances in instrument and computing technology, the use of X-ray diffraction experiments to accurately image the electron density associated with a hydrogen bond has become feasible. Secondly, general crystallographic computing programs analyze diffraction data by employing a spherical atom model. However, no such atom can be defined solely by a sphere when bound in a molecule. The use of spherical harmonics to model diffraction data enables a more complete description of the electron density in a molecular system. …

The Challenge Of Realizing Sustainable Natural Resource Management On Private Lands: Problems And Promise, Jamey L. Pavey

Doctoral Dissertations

Today’s natural resource problems are more complex than ever and many have yet to be effectively addressed in the United States by regulations or management policies. The challenges presented by these problems require new approaches to the governance of natural resources in the United States. These approaches must recognize that the governance of natural resources is not only a technical task, but a social process. The management of natural resources on private lands presents a unique set of problems and a unique set of opportunities to provide environmental benefits. However, without adequate incentives, landowners are unlikely to manage their land …

Syntheses, Structures, And Reactivities Of Early-Transition-Metal Silyl, Amide, And Imide Complexes, Xianghua Yu

Doctoral Dissertations

This dissertation describes syntheses, characterization, and reactivities of Groups 4 and 5 metal amide silyl complexes free of anionic π-ligands such as cyclopentadienyl (Cp).

A summary of the research in this dissertation is provided in Chapter 1. Chapter 2 reports unusual equilibria involving zirconium amides, silyl anions, and zirconium silyl complexes through amide-silyl ligand exchange reactions. Silyl anion SiBu^{tPh_{2− (}}2) was found to substitute an amide ligand in Zr(NMe2)4 (3) to give (Me2N)3Zr(SiButPh2)2− (1a) and Zr(NMe2)5− (1b) in THF. Silyl anion 2 also selectively attacks the –N(SiMe3)2 ligand in (Me2N)3Zr[N(SiMe3)2] …

Development Of Novel Synthetic Methods Utilizing Group Iii And Iv Reagents, Gang Dong

Doctoral Dissertations

This dissertation summarizes the development of novel synthetic methods involving Group III & IV reagents. These newly discovered reactions include the rhodium-catalyzed direct cross-coupling of allylic alcohols with aryl- and vinylboronic acids; palladium-catalyzed coupling reaction of Baylis-Hillman acetate adducts with both potassium organotrifluoroborate reagents and organosiloxanes; efficient syntheses of functionalized allylmetals such as allylboranes, allylsilanes, and allylgermanes; application of allylboranes to the synthesis of homoallylic alcohols; syntheses of 4-(1-alkynyl)-2(5H)-furanones and coumarins; utilization of potassium alkynyltrifluoroborates in the synthesis of conjugated enediynes; and application of potassium alkynyltrifluoroborates as reagents in the Petasis reaction.

The new synthetic methodologies involving Group III & …

Approaches To Uniform-Morphology: Polymer-Based Sers Substrates, Kathleen Sue Giesfeldt

Doctoral Dissertations

Polymer-nano-metallic-particle composites have demonstrated technological potential due to their unique optical and electrical properties. We report on composites prepared via physical vapor deposition of silver and gold onto pliable polydimethlysiloxane (PDMS) polymer. Rapid metal diffusion and nano-metallic-particle formation in a phase-separated surface layer of the PDMS creates unique sub-surface-based composites that vary in properties based on rate of deposition and average metal thickness. In addition, nano-metallicparticle spacing can be altered with fair reproducibility and reversibility by physically manipulating the composite. A practical technological characteristic of these composite materials arises from their potential to be molded into functional devices. Surface enhanced …

Neutron Scattering Studies On Magnetism And Phonon In The Electron-Doped Nd2-Xcexcuo4 And Pr1-Xlacexcuo4, Hye Jung Kang

Doctoral Dissertations

We present comprehensive neutron scattering studies on the electron-doped superconductors Nd_2-xCe_xCuO₄ and Pr_1-xLaCe_xCuO₄ to understand how magnetic properties and phonon are related to superconductivity. For the superconducting Nd_1.85Ce_0.15CuO₄, a c-axis magnetic field enhances the commensurate antiferromagnetic order, while an ab-plane magnetic field induces spin-flop transition from the noncollinear to the collinear magnetic structure. The c-axis field-induced effect is absent in both the parent Nd₂CuO₄ and the as-grown nonsuperconducting Nd_1.85Ce_0.15CuO₄ samples. These results, combined …

Evaluating Online Trust Using Machine Learning Methods, Weihua Song

Doctoral Dissertations

Trust plays an important role in e-commerce, P2P networks, and information filtering. Current challenges in trust evaluations include: (1) fnding trustworthy recommenders, (2) aggregating heterogeneous trust recommendations of different trust standards based on correlated observations and different evaluation processes, and (3) managing efficiently large trust systems where users may be sparsely connected and have multiple local reputations. The purpose of this dissertation is to provide solutions to these three challenges by applying ordered depth-first search, neural network, and hidden Markov model techniques. It designs an opinion filtered recommendation trust model to derive personal trust from heterogeneous recommendations; develops a reputation …

Obstruction Sets For Classes Of Cubic Graphs, Joshua Hughes

Doctoral Dissertations

This dissertation establishes two theorems which characterize the set of minimal obstructions for two classes of graphs. A minimal obstruction for a class of graphs is a graph that is not in the class but every graph that it properly contains, under some containment relation, is in the class. In Chapter 2, we provide a characterization of the class of cubic outer-planar graphs in terms of its minimal obstructions which are also called cubic obstructions in this setting. To do this, we first show that all the obstructions containing loops can be obtained from the complete set of loopless obstructions …

The Bipartite Clique: A Topological Paradigm For Web User Search Customization And Web Site Restructuring, Brenda F. Choyce-Miles

Doctoral Dissertations

The objective of this dissertation research is to aid the Web user to achieve his search objective at a host Web site by organizing a strongly connected neighborhood of Web pages that are thematically and spatially related to the user's search interest. Therefore, methods were developed to (1) find all Web pages at a given Web site that are thematically similar to a user's initial choice of a Web page (selected from the set of Web pages returned in response to a query by any popular search engine), and (2) organize these pages hierarchically in terms of their relevance to …

Developing A B -Tagging Algorithm Using Soft Muons At Level-3 For The Dø Detector At Fermilab, Mayukh Das

Doctoral Dissertations

The current data-taking phase of the DØ detector at Fermilab, called Run II, is designed to aid the search for the Higgs Boson. The neutral Higgs is postulated to have a mass of 117 GeV. One of the channels promising the presence of this hypothetical particle is through the decay of b-quark into a muon. The process of identifying a b-quark in a jet using muon as a reference is b-tagging with a muon tag.

At the current data taking and analysis rate, it will take long to reach the process of identifying valid events. The triggering mechanism of the …

Integrated Modeling And Parallel Computation Of Laser-Induced Axisymmetric Rod Growth, Hong Lan

Doctoral Dissertations

To fully investigate a pyrolytic Laser-induced chemical vapor deposition (LCVD) system for growing an axisymmetric rod, a novel integrated three-dimensional mathematical model was developed not only to describe the heat transport in the deposit and substrate, but also to simulate the gas-phase in the heated reaction zone and its effect on growth rate. The integrated model consists of three components: the substrate, rod, and gas-phase domains. Each component is a separate model and the three components are dynamically integrated into one model for simulating the iterative and complex process of rod deposition.

The gas-phase reaction is modeled by the gas-phase …

A Numerical Method For Obtaining An Optimal Temperature Distribution In A 3d Triple-Layered Cylindrical Skin Structure, Le Zhang

Doctoral Dissertations

In recent years, it has been interesting to research hyperthermia combined with radiation and cytotoxic drugs to enhance the killing of tumors. The crucial problem is that when heating the tumor tissues, one needs to keep the surrounding normal tissue below a temperature that will produce harm. Thus, it is important to obtain the temperature field of the entire treatment region. The objective of this dissertation is to develop a numerical model for obtaining an optimal temperature distribution in a 3D triple-layered cylindrical skin structure. To this end, we pre-specify the temperatures to be obtained at the center and perimeter …

Bootstrap Prediction Intervals For Multivariate Time Series, Florian Sebastian Rueck

Doctoral Dissertations

"The theory and methodology of obtaining bootstrap prediction intervals for univariate time series using the forward representation of the series is extended to vector autoregressive (VAR) models. Kim has shown that simultaneous prediction intervals based on the Bonferroni method and the backward representation of the time series achieve coverage close to nominal when the parameter estimates are corrected for small sample bias. To utilize his method, it is necessary to assume that the innovations are normally distributed to maintain independence of the innovations associated with the backward representation of the time series. This assumption is not necessary if the forward …