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A comparison of thermoelectric phenomena in diverse alloy systems

Description: The study of thermoelectric phenomena in solids provides a wealth of opportunity for exploration of the complex interrelationships between structure, processing, and properties of materials. As thermoelectricity implies some type of coupled thermal and electrical behavior, it is expected that a basic understanding of transport behavior in materials is the goal of such a study. However, transport properties such as electrical resistivity and thermal diffusivity cannot be fully understood and int… more
Date: January 1, 1999
Creator: Cook, Bruce
Partner: UNT Libraries Government Documents Department
open access

Crenulative Turbulence in a Converging Nonhomogeneous Material

Description: Crenulative turbulence is a nonlinear extension of the Bell-Plesset instability, usually observed in a converging system in which there is a nonhomogeneous response of stress to strain and/or strain rate. In general, crenelation occurs in any circumstance in which the mean flow streamlines converge the material more strongly than the compressibility can accommodate. Elements of the material slip past each other, resulting in local fluctuations in velocity from that of the mean flow, producing a… more
Date: January 1, 1999
Creator: Romero, Casildo A.
Partner: UNT Libraries Government Documents Department
open access

Microstructural characterization of a Zr-Ti-Ni-Mn-V-Cr based AB{sub 2}-type battery alloy

Description: Transmission Electron Microscopy (TEM), combined with X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) was employed to investigate a proprietary and multicomponent AB{sub 2} type Nickel-Metal Hydride (Ni-MH) battery alloy. This material was prepared by High Pressure Gas Atomization (HPGA) and examined in both the as-atomized and heat treated condition. TEM examination showed a heavily faulted dendritic growth structure in as-atomized powder. Selected Area Diffraction (SAD) showed … more
Date: January 1, 1999
Creator: Shi, Zhan
Partner: UNT Libraries Government Documents Department
open access

Search for the B{sub c} meson in hadronic Z{sup 0} decays using the OPAL detector at LEP

Description: A search for decays of the B{sub c} meson was performed using data collected from 1990--1995 with the OPAL detector on or near the Z{sup 0} peak at LEP. The decay channels B{sub c}{sup +} {r_arrow} J/{psi}{pi}{sup +}, B{sub c}{sup +} {r_arrow} J/{psi}a{sub 1}{sup +} and B{sub c}{sup +} {r_arrow} J/{psi}{ell}{sup +}{nu} were investigated, where {ell} denotes an electron or a muon. Two candidates are observed in the mode B{sub c}{sup +} {r_arrow} J/{psi}{pi}{sup +}, with an estimated background o… more
Date: January 1, 1999
Creator: Herndon, M.F.
Partner: UNT Libraries Government Documents Department
open access

Femtosecond Photoelectron Spectroscopy: A New Tool for the Study of Anion Dynamics

Description: A new experimental technique for the time-resolved study of anion reactions is presented. Using femtosecond laser pulses, which provide extremely fast ({approx} 100 fs) time resolution, in conjunction with photoelectron spectroscopy, which reveals differences between anion and neutral potential energy surfaces, a complex anion reaction can be followed from its inception through the formation of asymptotic products. Experimental data can be modeled quantitatively using established theoretical ap… more
Date: February 1, 1999
Creator: Greenblatt, B. J.
Partner: UNT Libraries Government Documents Department
open access

Historical Exposures to Chemicals at the Rocky Flats Nuclear Weapons Plant: A Pilot Retrospective Exposure Assessment

Description: In a mortality study of white males who had worked at the Rocky Flats Nuclear Weapons Plant between 1952 and 1979, an increased number of deaths from benign and unspecified intracranial neoplasms was found. A case-control study nested within this cohort investigated the hypothesis that an association existed between brain tumor death and exposure to either internally deposited plutonium or external ionizing radiation. There was no statistically significant association found between estimated ra… more
Date: February 1, 1999
Creator: Robertson, Janeen Denise
Partner: UNT Libraries Government Documents Department
open access

Magnetic fields and density functional theory

Description: A major focus of this dissertation is the development of functionals for the magnetic susceptibility and the chemical shielding within the context of magnetic field density functional theory (BDFT). These functionals depend on the electron density in the absence of the field, which is unlike any other treatment of these responses. There have been several advances made within this theory. The first of which is the development of local density functionals for chemical shieldings and magnetic susc… more
Date: February 1, 1999
Creator: Salsbury Jr., Freddie
Partner: UNT Libraries Government Documents Department
open access

Principles and techniques for designing precision machines

Description: This thesis is written to advance the reader's knowledge of precision-engineering principles and their application to designing machines that achieve both sufficient precision and minimum cost. It provides the concepts and tools necessary for the engineer to create new precision machine designs. Four case studies demonstrate the principles and showcase approaches and solutions to specific problems that generally have wider applications. These come from projects at the Lawrence Livermore Nationa… more
Date: February 1, 1999
Creator: Hale, L C
Partner: UNT Libraries Government Documents Department
open access

A study of the {sup 16}O (e, e'p) reaction at deep missing energies

Description: The {sup 16}O(e,e'p)#8; reaction was studied in the #6;first physics experiment performed at Jefferson lab Hall A. In the quasielastic region cross sections were measured for both quasi#11;parallel and perpendicular kinematics at q = 1000 MeV and #2;{omega} = 445#14;#14;#15; MeV. From the data acquired in quasi#11;parallel kinematics#4; longitudinal and transverse response functions#4; R{sub L} and R{sub T} were separated for E{sub miss} < 60 MeV. The perpendicular kinematics data were used to … more
Date: February 1, 1999
Creator: Liyanage, Nilanga
Partner: UNT Libraries Government Documents Department
open access

The analysis of aqueous mixtures using liquid chromatography-electrospray mass spectrometry

Description: The focus of this dissertation is the use of chromatographic methods coupled with electrospray mass spectrometry (ES-MS) for the determination of both organic and inorganic compounds in aqueous solutions. The combination of liquid chromatography (LC) methods and ES-MS offers one of the foremost methods for determining compounds in complex aqueous solutions. In this work, LC-ES-MS methods are devised using ion exclusion chromatography, reversed phase chromatography, and ion exchange chromatograp… more
Date: February 12, 1999
Creator: Johnson, S.
Partner: UNT Libraries Government Documents Department
open access

Calibration of laser ablation inductively coupled plasma mass spectrometry using dried solution aerosols for the quantitative analysis of solid samples

Description: Inductively coupled plasma mass spectrometry (ICP-MS) has become the method of choice for elemental and isotopic analysis. Several factors contribute to its success. Modern instruments are capable of routine analysis at part per trillion levels with relative detection limits in part per quadrillion levels. Sensitivities in these instruments can be as high as 200 million counts per second per part per million with linear dynamic ranges up to eight orders of magnitude. With standards for only a f… more
Date: February 12, 1999
Creator: Leach, J.
Partner: UNT Libraries Government Documents Department
open access

Capillary electrophoresis separation of neutral organic compounds, pharmaceutical drugs, proteins and peptides, enantiomers, and anions

Description: Addition of a novel anionic surfactant, namely lauryl polyoxyethylene sulfate, to an aqueous-acetonitrile electrolyte makes it possible to separate nonionic organic compounds by capillary electrophoresis. Separation is based on differences in the association between analytes and the surfactant. Highly hydrophobic compounds such as polyaromatic hydrocarbons are well separated by this new surfactant. Migration times of analytes can be readily changed over an unusually large range by varying the a… more
Date: February 12, 1999
Creator: Ding, W.L.
Partner: UNT Libraries Government Documents Department
open access

Capillary electrophoretic study of individual exocytotic events in single mast cells

Description: The peak profile of individual degranulation events from the on-column release of serotonin from single rat peritoneal mast cells (RPMCs) was monitored using capillary electrophoresis with laser-induced native fluorescence detection (CE-LINF). Serotonin, an important biogenic amine, is contained in granules (0.25 fL) within RPMCs and is extruded by a process termed exocytosis. The secretagogue, Polymyxin B sulfate, was used as the CE running buffer after injection of a single RPMC into the sepa… more
Date: February 12, 1999
Creator: Ho, A.M.W.
Partner: UNT Libraries Government Documents Department
open access

Chiral separation of pharmaceutical compounds using electrochemically modulated liquid chromatography (EMLC)

Description: This research explores the application of a new technique, termed electrochemically modulated liquid chromatography (EMLC), to the chiral separations of pharmaceutical compounds. The introduction section provides a literature review of the technique and its applications, as well as brief overview of the research described in each of the next two chapters. Chapter 2 investigates the EMLC-based enantiomeric separation of a group of chiral benzodiazepines with {beta}-cyclodextrin as a chiral mobil… more
Date: February 12, 1999
Creator: Wang, S.
Partner: UNT Libraries Government Documents Department
open access

Collision-induced dissociation reactions and pulsed field ionization photoelectron

Description: This report summarized the four parts of the research study and describes the general conclusions. Individual chapters have been removed for separate processing. The chapter titles are: A study of the dissociation of CH{sub 3}SH{sup +} by collisional activation: Observation of non-statistical behavior; High resolution vacuum ultraviolet pulsed field ionization photoelectron band for OCS{sup +}(X{sup 2}{Pi}): An experimental and theoretical study; Rotationally resolved pulsed field ionization ph… more
Date: February 12, 1999
Creator: Stimson, S.
Partner: UNT Libraries Government Documents Department
open access

Gas atomization processing of tin and silicon modified LaNi{sub 5} for nickel-metal hydride battery applications

Description: Numerous researchers have studied the relevant material properties of so-called AB{sub 5} alloys for battery applications. These studies involved LaNi{sub 5} substituted alloys which were prepared using conventional cast and crush alloying techniques. While valuable to the understanding of metal hydride effects, the previous work nearly ignored the potential for alternative direct powder production methods, like high pressure gas atomization (HPGA). Thus, there is a need to understand the relat… more
Date: February 12, 1999
Creator: Ting, J.
Partner: UNT Libraries Government Documents Department
open access

LiV{sub 2}O{sub 4}: A heavy fermion transition metal oxide

Description: The format of this dissertation is as follows. In the remainder of Chapter 1, brief introductions and reviews are given to the topics of frustration, heavy fermions and spinels including the precedent work of LiV{sub 2}O{sub 4}. In Chapter 2, as a general overview of this work the important publication in Physical Review Letters by the author of this dissertation and collaborators regarding the discovery of the heavy fermion behavior in LiV{sub 2}O{sub 4} is introduced [removed for separate pro… more
Date: February 12, 1999
Creator: Kondo, Shinichiro
Partner: UNT Libraries Government Documents Department
open access

Optically detected magnetic resonance studies on {pi}-conjugate polymers and novel carbon allotropes

Description: This report describes the following: introduction to photoluminescence detected magnetic resonance (PLDMR); introduction to {pi}-conjugated systems; PLDMR measurements on poly(p-phenylene)-type ladder polymers; PLMDR measurements on poly(p-phenylene ethylene); and PLDMR measurements on C{sub 70}, polythiophene, poly(p-phenylene vinylene) and Dan-40. Appendices to this report describe: Operation of ODMR (optically detected magnetic resonance) spectrometer; ODMR system parameters; and Special pur… more
Date: February 12, 1999
Creator: Partee, J.
Partner: UNT Libraries Government Documents Department
open access

Single- and multi-photon ionization studies of organosulfur species

Description: Accurate ionization energies (IE`s) for molecular species are used for prediction of chemical reactivity and are of fundamental importance to chemists. The IE of a gaseous molecule can be determined routinely in a photoionization or a photoelectron experiment. IE determinations made in conventional photoionization and photoelectron studies have uncertainties in the range of 3--100 meV (25--250 cm{sup {minus}1}). In the past decade, the most exciting development in the field of photoionization a… more
Date: February 12, 1999
Creator: Cheung, Y. S.
Partner: UNT Libraries Government Documents Department
open access

Structure sensitive adsorption of hydrogen on ruthenium and ruthenium-silver catalysts supported on silica

Description: Supported metal catalysts typically consist of particles with sizes less than 10 nm, and because of the small crystallite size, low coordination number sites (edges and corners) represent a significant fraction of all surface sites. Furthermore, it has been demonstrated that adsorption rates can be much greater at these low coordination sites than on basal plane sites. What has not been generally appreciated, however, is that preferential adsorption at edge and corner sites may explain the mech… more
Date: February 12, 1999
Creator: Kumar, N.
Partner: UNT Libraries Government Documents Department
open access

Surface structures of Al-Pd-Mn and Al-Cu-Fe icosahedral quasicrystals

Description: In this dissertation, the author reports on the surface structure of i-Al-Pd-Mn twofold, threefold, fivefold and i-Al-Cu-Fe fivefold surfaces. The LEED studies indicate the existence of two distinct stages in the regrowth of all four surfaces after Ar{sup +} sputtering. In the first stage, upon annealing at relatively low temperature: 500K--800K (depending on different surfaces), a cubic phase appears. The cubic LEED patterns transform irreversibly to unreconstructed quasicrystalline patterns u… more
Date: February 12, 1999
Creator: Shen, Z.
Partner: UNT Libraries Government Documents Department
open access

Syntheses and studies of organosilicon compounds

Description: The syntheses of polycarbosilanes and polysilanes as silicon carbide ceramic precursors have been active research areas in the Barton Research Group. In this thesis, the work is focused on the preparation of polycarbosilanes and polysilanes as stoichiometric silicon carbide precursor polymers. The syntheses of the precursor polymers are discussed and the conversions of these precursors to silicon carbide via pyrolysis are reported. The XRD pattern and elemental analyses of the resulting silicon… more
Date: February 12, 1999
Creator: Xie, R.
Partner: UNT Libraries Government Documents Department
open access

A Fuzzy Logic Framework for Integrating Multiple Learned Models

Description: The Artificial Intelligence field of Integrating Multiple Learned Models (IMLM) explores ways to combine results from sets of trained programs. Aroclor Interpretation is an ill-conditioned problem in which trained programs must operate in scenarios outside their training ranges because it is intractable to train them completely. Consequently, they fail in ways related to the scenarios. We developed a general-purpose IMLM solution, the Combiner, and applied it to Aroclor Interpretation. The Comb… more
Date: March 1, 1999
Creator: Hartog, Bobi Kai Den
Partner: UNT Libraries Government Documents Department
open access

Camelot's Mystique

Description: Thesis written by a student in the UNT Honors College discussing John F. Kennedy's rise through American politics, his death, and the conspiracy theories that surround his assassination.
Date: Spring 1999
Creator: Stephens, LynDee
Partner: UNT Honors College
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