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4,323 Matching Results
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A Critique to the Mythology of Lamkang Tribe Manipur
A published critique to the mythology of the Lamkang tribe.
Date:
2000
Creator:
Dilbung, Avince Anthony
System:
The UNT Digital Library
Open cycle thermoacoustics
A new type of thermodynamic device combining a thermodynamic cycle with the externally applied steady flow of an open thermodynamic process is discussed and experimentally demonstrated. The gas flowing through this device can be heated or cooled in a series of semi-open cyclic steps. The combination of open and cyclic flows makes possible the elimination of some or all of the heat exchangers (with their associated irreversibility). Heat is directly exchanged with the process fluid as it flows through the device when operating as a refrigerator, producing a staging effect that tends to increase First Law thermodynamic efficiency. An open-flow thermoacoustic refrigerator was built to demonstrate this concept. Several approaches are presented that describe the physical characteristics of this device. Tests have been conducted on this refrigerator with good agreement with a proposed theory.
Date:
January 1, 2000
Creator:
Reid, Robert Stowers
System:
The UNT Digital Library
Electron-capture delayed fission properties of neutron-deficient einsteinium nuclei
Electron-capture delayed fission (ECDF) properties of neutron-deficient einsteinium isotopes were investigated using a combination of chemical separations and on-line radiation detection methods. {sup 242}Es was produced via the {sup 233}U({sup 14}N,5n){sup 242}Es reaction at a beam energy of 87 MeV (on target) in the lab system, and was found to decay with a half-life of 11 {+-} 3 seconds. The ECDF of {sup 242}Es showed a highly asymmetric mass distribution with an average pre-neutron emission total kinetic energy (TKE) of 183 {+-} 18 MeV. The probability of delayed fission (P{sub DF}) was measured to be 0.006 {+-} 0.002. In conjunction with this experiment, the excitation functions of the {sup 233}U({sup 14}N,xn){sup 247{minus}x}Es and {sup 233}U({sup 15}N,xn){sup 248{minus}x}Es reactions were measured for {sup 243}Es, {sup 244}Es and {sup 245}Es at projectile energies between 80 MeV and 100 MeV.
Date:
January 5, 2000
Creator:
Shaughnessy, Dawn A.
System:
The UNT Digital Library
Electron-impact ionization of atomic hydrogen
Since the invention of quantum mechanics, even the simplest example of collisional breakup in a system of charged particles, e{sup {minus}} + H {r_arrow} H{sup +} + e{sup {minus}} + e{sup {minus}}, has stood as one of the last unsolved fundamental problems in atomic physics. A complete solution requires calculating the energies and directions for a final state in which three charged particles are moving apart. Advances in the formal description of three-body breakup have yet to lead to a viable computational method. Traditional approaches, based on two-body formalisms, have been unable to produce differential cross sections for the three-body final state. Now, by using a mathematical transformation of the Schrodinger equation that makes the final state tractable, a complete solution has finally been achieved, Under this transformation, the scattering wave function can be calculated without imposing explicit scattering boundary conditions. This approach has produced the first triple differential cross sections that agree on an absolute scale with experiment as well as the first ab initio calculations of the single differential cross section.
Date:
February 14, 2000
Creator:
Baertschy, Mark D.
System:
The UNT Digital Library
Inertial Conference Fusion Semiannual Report October 1999 - March 2000, Volume 1, Number 1
This first issue of the ''ICF Semiannual Report'' contains articles whose diverse subjects attest to the broad technical and scientific challenges that are at the forefront of the ICF program at LLNL. The first article describes the progress being made at solving the surface roughness problem on capsule mandrels. All NIF capsule options, except machined beryllium, require a mandrel upon which the ablator is deposited. This mandrel sets the baseline sphericity of the final capsule. Problems involving defects in the mandrel have been overcome using various techniques so that 2-mm-size mandrels can now be made that meet the NIF design specification. The second article validates and provides a detailed numerical investigation of the shadowgraph technique currently used to diagnose the surface roughness of a fuel ice layer inside of a transparent capsule. It is crucial for the success of the indirect-drive ignition targets that the techniques used to characterize ice-surface roughness be well understood. This study identifies methods for analyzing the bright band that give an accurate measure of the ice-surface roughness. The third article describes a series of realistic laser and target modifications that can lead to 3-4 times more energy coupling and 10 times greater yield from a …
Date:
March 1, 2000
Creator:
Hammel, B. A.
System:
The UNT Digital Library
Lasershot peening--a means to strengthen metals
Lasershot peening is an emerging modern process that impresses a compressive stress into the surfaces of metals, improving their operational lifetime. Almost everyone is familiar with taking a strip of metal or a wire and bending it multiple times until it breaks. In this situation, when the metal is bent, the surface of outer radius is stretched into a tensile state. Under tension, any flaw or micro-crack will grow in size with each bending of the metal until the crack grows through the entire strip, breaking it into two pieces. Flexure of metal components occurs in most applications. The teeth of a transmission gear flex as they deliver torque in a vehicle. Springs and valves flex every time they transfer loads. If fatigue failure from flexing occurs in the tooth of a transmission gear of light or heavy vehicles, in a fan blade of a diesel engine, in shock-absorbers or safety-related supporting structures, significant loss of assets and potentially loss of human life occurs. Lasershot peening, better than any other technique, has the potential to extend the fatigue lifetime of metal components. In the process, the laser generates a high intensity shock wave at the surface of the metal, straining …
Date:
March 1, 2000
Creator:
Chen, H. L.
System:
The UNT Digital Library
Inertial fusion technology spin-offs-history provides a glimpse of the future
The development and demonstration of inertial fusion is incredibly challenging because it requires simultaneously controlling and precisely measuring parameters at extreme values in energy, space, and time. The challenges range from building megajoule (10{sup 6} J) drivers that perform with percent-level precision to fabricating targets with submicron specifications to measuring target performance at micron scale (10{sup -6} m) with picosecond (10{sup -12} s) time resolution. Over the past 30 years in attempting to meet this challenge, the inertial fusion community around the world has invented new technologies in lasers, particle beams, pulse power drivers, diagnostics, target fabrication, and other areas. These technologies have found applications in diverse fields of industry and science. Moreover, simply assembling the teams with the background, experience, and personal drive to meet the challenging requirements of inertial fusion has led to spin-offs in unexpected directions, for example, in laser isotope separation, extreme ultraviolet (EUV) lithography for microelectronics, compact and inexpensive radars, advanced laser materials processing, and medical technology. It is noteworthy that more than 40 R&D 100 awards, the ''Oscars of applied research'' have been received by members of the inertial fusion community over this period. Not surprisingly, the inertial fusion community has created many new …
Date:
March 7, 2000
Creator:
Powell, H
System:
The UNT Digital Library
The Virgin of Verona and the Queen of the Nile
Thesis written by a student in the UNT Honors College discussing William Shakespeare's characters, Juliet and Cleopatra. The author examines both characters as strong women doing their best to take control of the paternalistic worlds they live in.
Date:
Spring 2000
Creator:
Cobos, Cara
System:
The UNT Digital Library
Ultrafast excited state dynamics of tris-(2,2'-bipyridine) Ruthenium (II)
None
Date:
March 29, 2000
Creator:
Yeh, A.T.W.
System:
The UNT Digital Library
Cooling of highly charged ions in a Penning trap
Highly charged ions are extracted from an electron beam ion trap and guided to Retrap, a cryogenic Penning trap, where they are merged with laser cooled Be{sup +} ions. The Be{sup +} ions act as a coolant for the hot highly charged ions and their temperature is dropped by about 8 orders of magnitude in a few seconds. Such cold highly charged ions form a strongly coupled nonneutral plasma exhibiting, under such conditions, the aggregation of clusters and crystals. Given the right mixture, these plasmas can be studied as analogues of high density plasmas like white dwarf interiors, and potentially can lead to the development of cold highly charged ion beams for applications in nanotechnology. Due to the virtually non existent Doppler broadening, spectroscopy on highly charged ions can be performed to an unprecedented precision. The density and the temperature of the Be{sup +} plasma were measured and highly charged ions were sympathetically cooled to similar temperatures. Molecular dynamics simulations confirmed the shape, temperature and density of the highly charged ions. Ordered structures were observed in the simulations.
Date:
March 31, 2000
Creator:
Gruber, L
System:
The UNT Digital Library
Creep of SiC Hot-Pressed with Al, B, and C
None
Date:
March 31, 2000
Creator:
Sixta, M.
System:
The UNT Digital Library
The ideal strength and mechanical hardness of solids
Relationships between intrinsic mechanical hardness and atomic-scale properties are reviewed, Hardness scales closely and linearly with shear modulus for a given class of material (covalent, ionic or metallic). A two-parameter fit and a Peierls-stress model produce a more universal scaling relationship, but no model can explain differences in hardness between the transition metal carbides and nitrides. Calculations of ''ideal strength'' (defined by the limit of elastic stability of a perfect crystal) are proposed. The ideal shear strengths of fcc aluminum and copper are calculated using ab initio techniques and allowing for structural relaxation of all five strain components other than the imposed strain. The strengths of Al and Cu are similar (8-9% of the shear modulus), but the geometry of the relaxations in Al and Cu is very different. The relaxations are consistent with experimentally measured third-order elastic constants. The general thermodynamic conditions of elastic stability that set the upper limits of mechanical strength are derived. The conditions of stability are shown for cubic (hydrostatic), tetragonal (tensile) and monoclinic (shear) distortions of a cubic crystal. The implications of this stability analysis to first-principles calculations of ideal strength are discussed, and a method to detect instabilities orthogonal to the direction of …
Date:
April 1, 2000
Creator:
Krenn, Christopher
System:
The UNT Digital Library
Image reconstruction for a Positron Emission Tomograph optimized for breast cancer imaging
The author performs image reconstruction for a novel Positron Emission Tomography camera that is optimized for breast cancer imaging. This work addresses for the first time, the problem of fully-3D, tomographic reconstruction using a septa-less, stationary, (i.e. no rotation or linear motion), and rectangular camera whose Field of View (FOV) encompasses the entire volume enclosed by detector modules capable of measuring Depth of Interaction (DOI) information. The camera is rectangular in shape in order to accommodate breasts of varying sizes while allowing for soft compression of the breast during the scan. This non-standard geometry of the camera exacerbates two problems: (a) radial elongation due to crystal penetration and (b) reconstructing images from irregularly sampled data. Packing considerations also give rise to regions in projection space that are not sampled which lead to missing information. The author presents new Fourier Methods based image reconstruction algorithms that incorporate DOI information and accommodate the irregular sampling of the camera in a consistent manner by defining lines of responses (LORs) between the measured interaction points instead of rebinning the events into predefined crystal face LORs which is the only other method to handle DOI information proposed thus far. The new procedures maximize the use …
Date:
April 1, 2000
Creator:
Virador, Patrick R.G.
System:
The UNT Digital Library
An implicit Smooth Particle Hydrodynamic code
An implicit version of the Smooth Particle Hydrodynamic (SPH) code SPHINX has been written and is working. In conjunction with the SPHINX code the new implicit code models fluids and solids under a wide range of conditions. SPH codes are Lagrangian, meshless and use particles to model the fluids and solids. The implicit code makes use of the Krylov iterative techniques for solving large linear-systems and a Newton-Raphson method for non-linear corrections. It uses numerical derivatives to construct the Jacobian matrix. It uses sparse techniques to save on memory storage and to reduce the amount of computation. It is believed that this is the first implicit SPH code to use Newton-Krylov techniques, and is also the first implicit SPH code to model solids. A description of SPH and the techniques used in the implicit code are presented. Then, the results of a number of tests cases are discussed, which include a shock tube problem, a Rayleigh-Taylor problem, a breaking dam problem, and a single jet of gas problem. The results are shown to be in very good agreement with analytic solutions, experimental results, and the explicit SPHINX code. In the case of the single jet of gas case it has …
Date:
April 1, 2000
Creator:
Knapp, Charles E.
System:
The UNT Digital Library
Measurement of a Weak Polarization Sensitivity to the Beam Orbit of the CEBAF Accelerator
An accelerator-based experiment was performed using the CEBAF accelerator of the Thomas Jefferson National Accelerator Facility to investigate a predicted sensitivity of the beam polarization to the vertical betatron orbit in the recirculation arcs. This is the first measurement of any such effect at CEBAF, and provides information about the polarized beam delivery performance of the accelerator. A brief description of the accelerator is given, followed by the experimental methods used and the relevant issues involved in measuring a small ({approximately} 10{sup {minus}2}) change in the beam polarization. Results of measurements of the polarization sensitivity parameters and the machine energy by polarization transport techniques are presented. The parameters were obtained by measurement of the strength of the effect as a function of orbit amplitude and spin orientation, to confirm the predicted coupling between the spin orientation and the quadrupole fields in the beam transport system. This experiment included characterizing the injector spin manipulation system and 5 MeV Mott polarimeter, modeling of the polarization transport of the accelerator, installation of magnets to create a modulated orbit perturbation in a single recirculation arc, and detailed studies of the Hall C Moeller polarimeter.
Date:
April 1, 2000
Creator:
Grames, Joseph
System:
The UNT Digital Library
Microcalorimetry and the transition-edge sensor
Many scientific and industrial applications call for quantum-efficient high-energy-resolution microcalorimeters for the measurement of x rays. The applications driving the development of these detectors involve the measurement of faint sources of x rays in which few photons reach the detector. Interesting astrophysical applications for these microcalorimeters include the measurement of composition and temperatures of stellar atmospheres and diffuse interstellar plasmas. Other applications of microcalorimeter technology include x-ray fluorescence (XRF) measurements of industrial or scientific samples. We are attempting to develop microcalorimeters with energy resolutions of several eV because many sources (such as celestial plasmas) contain combinations of elements producing emission lines spaced only a few eV apart. Our microcalorimeters consist of a metal-film absorber (250 {micro}m x 250{micro}m x 3 {micro}m of copper) coupled to a superconducting transition-edge-sensor (TES) thermometer. This microcalorimeter demonstrated an energy resolution of 42 eV (FWHM) at 6 keV, excellent linearity, and showed no evidence of position dependent response. The response of our microcalorimeters depends both on the temperature of the microcalorimeter and on the electrical current conducted through the TES thermometer. We present a microcalorimeter model that extends previous microcalorimeter theory to include additional current dependent effects. The model makes predictions about the effects of …
Date:
April 1, 2000
Creator:
Lindeman, M A
System:
The UNT Digital Library
Concurrences in the U. S. Supreme Court
Thesis written by a student in the UNT Honors College discussing different types of opinions within the United States Supreme Court, with an emphasis on the history and practice of concurrences.
Date:
April 3, 2000
Creator:
Watson, Takiesha
System:
The UNT Digital Library
P-type doping of GaN
After implantation of As, As + Be, and As + Ga into GaN and annealing for short durations at temperatures as high as 1500 C, the GaN films remained highly resistive. It was apparent from c-RBS studies that although implantation damage did not create an amorphous layer in the GaN film, annealing at 1500 C did not provide enough energy to completely recover the radiation damage. Disorder recovered significantly after annealing at temperatures up to 1500 C, but not completely. From SIMS analysis, oxygen contamination in the AIN capping layer causes oxygen diffusion into the GaN film above 1400 C. The sapphire substrate (A1203) also decomposed and oxygen penetrated into the backside of the GaN layer above 1400 C. To prevent donor-like oxygen impurities from the capping layer and the substrate from contaminating the GaN film and compensating acceptors, post-implantation annealing should be done at temperatures below 1500 C. Oxygen in the cap could be reduced by growing the AIN cap on the GaN layer after the GaN growth run or by depositing the AIN layer in a ultra high vacuum (UHV) system post-growth to minimize residual oxygen and water contamination. With longer annealing times at 1400 C or at …
Date:
April 10, 2000
Creator:
Wong, R.K.
System:
The UNT Digital Library
Baryon stopping and hadronic spectra in Pb-Pb collisions at 158 GeV/nucleon
Baryon stopping and particle production in Pb+Pb collisions at 158 GeV/nucleon are studied as a function of the collision centrality using new proton, antiproton, charged kaon and charged pion production data measured with the NA49 experiment at the CERN Super Proton Synchrotron (SPS). Stopping, which is measured by the shift in rapidity of net protons or baryons from the initial beam rapidity, increases in more central collisions. This is expected from a geometrical picture of the collisions. The stopping data are quantitatively compared to models incorporating various mechanisms for stopping. In general, microscopic transport calculations which incorporate current theoretical models of baryon stopping or use phenomenological extrapolations from simpler systems overestimate the dependence of stopping on centrality. Approximately, the yield of produced pions scales with the number of nucleons participating in the collision. A small increase in yield beyond this scaling, accompanied by a small suppression in the yield of the fastest pions, reflects the variation in stopping with centrality. Consistent with the observations from central collisions of light and heavy nuclei at the SPS, the transverse momentum distributions of all particles are observed to become harder with increasing centrality. This effect is most pronounced for the heaviest particles. This …
Date:
April 12, 2000
Creator:
Cooper, Glenn E.
System:
The UNT Digital Library
Community Economic Development in the Banking Industry: Banks and Their Involvement in the Communities They Serve
Thesis written by a student in the UNT Honors College discussing the support and involvement of banks in Community Economic Development.
Date:
April 18, 2000
Creator:
McFerrin, Christopher T.
System:
The UNT Digital Library
Adolescent Goals and Their Reports of What They do to Achieve Those Goals
Twenty-five adolescents' ranking of a set of equally highly valued goals on a Paired-comparisons Survey was compared with what adolescents say they are doing to achieve those goals. Results of the Paired-comparisons Survey showed that adolescents ranked career, interpersonal, and educational goals rather high and reputation and self-presentation goals rather low. Results analyzed with a contingency coefficient and biserial correlation indicated that not all number one ranked goals had the same value for a particular adolescent, and that number one ranked goals were correlated with verbal reports of concrete actions directed at achieving those goals.
Date:
May 2000
Creator:
Lucky, Derek
System:
The UNT Digital Library
Analysis and Development of Post Secondary Curriculum on Sustainability
This thesis examines existing curricula at colleges and universities about sustainability and uses results to develop an introductory post secondary course curriculum. The proposed course is organized around three major elements - - science, philosophy, and economics - - all integral to understanding sustainability. Materials needed to teach the proposed 3-semester hour course including syllabus, teaching modules, transparencies, handouts, and exams were developed. Suggestions on how to teach a one-semester hour course on sustainability and a workshop on sustainability are also presented. The following research and curriculum development was a project established and funded by the Texas Energy Office, Renewable Resources and Sustainability Program.
Date:
May 2000
Creator:
White, Miki Machell
System:
The UNT Digital Library
An Analysis of the Composition Process of Bartók's Eight Improvisations on Hungarian Peasant Songs, Op. 20
Access:
Use of this item is restricted to the UNT Community
This is a study of Bartók's compositional process as it relates to the Improvisations, Op. 20. The study, which focuses on the analysis of the draft manuscript 50PS1, compares the draft and other relevant sources with the final composition. Bartók's framework for the entire Improvisations is based on a compositional strategy of pairing individual improvisations combined with systematic revision of the draft copy by the introduction of tritones as tonal equivalents and movement by fifths from semitones, to achieve structural coherence in the individual improvisations. The tonic-dominant relationship is used to rearrange the individual improvisations in the draft and tritones as tonal equivalents are used to propel the movement between the improvisations to produce a coherent whole.
Date:
May 2000
Creator:
Kochbeck, Olivia M.
System:
The UNT Digital Library
An Analytical Study of the Variations on the Theme of Paganini's Twenty-Fourth Caprice, Op. 1 by Busoni, Friedman, and Muczynski
The purpose of this study is to analyze sets of variations on Paganini's theme by three twentieth-century composers: Ferruccio Busoni, Ignaz Friedman, and Robert Muczynski, in order to examine, identify, and trace different variation techniques and their applications. Chapter 1 presents the purpose and scope of this study. Chapter 2 provides background information on the musical form "theme and variations" and the theme of Paganini's Twenty-fourth Caprice, Op. 1. Chapter 2 also deals with the question of which elements have made this theme so popular. Chapters 3,4, and 5 examine each of the three sets of variations in detail using the following format: theme, structure of each variation, harmony and key, rhythm and meter, tempo and dynamics, motivic development, grouping of variations, and technical problems. Chapter 6 summarizes the findings from this study and attempts to compare those elements among the three variations. Special attention is given to the application of the motivic cells, which are drawn from the original Paganini theme, in the development of succeeding variations. This study shows how these motivic cells contribute to the construction of new motives and melodies in each variation. Additionally, this study attempts to examine each composer's efforts in expanding variation procedure …
Date:
May 2000
Creator:
Ahn, Kwang Sun
System:
The UNT Digital Library