States

Analysis of Two Biomass Gasification/Fuel Cell Scenarios for Small-Scale Power Generation (open access)

Analysis of Two Biomass Gasification/Fuel Cell Scenarios for Small-Scale Power Generation

Two scenarios were examined for small-scale electricity production from biomass using a gasifier/fuel cell system. In one case, a stand-alone BCL/FERC gasifier is used to produce synthesis gas that is reformed and distributed through a pipeline network to individual phosphoric acid fuel cells. In the second design, the gasifier is integrated with a molten carbonate fuel cell stack and a steam bottoming cycle. In both cases, the gasifiers are fed the same amount of material, with the integrated system producing 4 MW of electricity, and the stand-alone design generating 2 MW of electricity.
Date: January 12, 1999
Creator: Amos, W. A.
Object Type: Report
System: The UNT Digital Library
Buildings Research using Infrared Imaging Radiometers with Laboratory Thermal Chambers (open access)

Buildings Research using Infrared Imaging Radiometers with Laboratory Thermal Chambers

Infrared thermal imagers are used at Lawrence Berkeley National Laboratory to study heat transfer through components of building thermal envelopes. Two thermal chambers maintain steady-state heat flow through test specimens under environmental conditions for winter heating design. Infrared thermography is used to map surface temperatures on the specimens' warm side. Features of the quantitative thermography process include use of external reference emitters, complex background corrections, and spatial location markers. Typical uncertainties in the data are {+-} 0.5 C and 3 mm. Temperature controlled and directly measured external reference emitters are used to correct data from each thermal image. Complex background corrections use arrays of values for background thermal radiation in calculating temperatures of self-viewing surfaces. Temperature results are used to validate computer programs that predict heat flow including Finite-Element Analysis (FEA) conduction simulations and conjugate Computational Fluid Dynamics (CFD) simulations. Results are also used to study natural convection surface heat transfer. Example data show the distribution of temperatures down the center line of an insulated window.
Date: January 12, 1999
Creator: Griffith, Brent & Arasteh, Dariush
Object Type: Report
System: The UNT Digital Library
Civilian Marksmanship Program: Corporation Needs to Fully Comply With the Law on Sales of Firearms (open access)

Civilian Marksmanship Program: Corporation Needs to Fully Comply With the Law on Sales of Firearms

A letter report issued by the General Accounting Office with an abstract that begins "Pursuant to a congressional request, GAO reviewed the Corporation for the Promotion of Rifle Practice and Firearms Safety's administration of the Civilian Marksmanship Program (CMP), focusing on: (1) whether CMP's conversion to a private corporation and the Corporation's subsequent firearms sales were conducted in accordance with the 1996 National Defense Authorization Act; (2) the types and value of federal support provided to the Corporation; and (3) the types and number of firearms the Army transferred to the Corporation and was storing for potential transfer."
Date: January 12, 1999
Creator: United States. General Accounting Office.
Object Type: Report
System: The UNT Digital Library
Coupled Simulations of Mechanical Deformation and Microstructural Evolution Using Polycrystal Plasticity and Monte Carlo Potts Models (open access)

Coupled Simulations of Mechanical Deformation and Microstructural Evolution Using Polycrystal Plasticity and Monte Carlo Potts Models

The microstructural evolution of heavily deformed polycrystalline Cu is simulated by coupling a constitutive model for polycrystal plasticity with the Monte Carlo Potts model for grain growth. The effects of deformation on boundary topology and grain growth kinetics are presented. Heavy deformation leads to dramatic strain-induced boundary migration and subsequent grain fragmentation. Grain growth is accelerated in heavily deformed microstructures. The implications of these results for the thermomechanical fatigue failure of eutectic solder joints are discussed.
Date: January 12, 1999
Creator: Battaile, C. C.; Buchheit, T. E.; Holm, E. A.; Neilsen, M. K. & Wellman, G. W.
Object Type: Article
System: The UNT Digital Library
Fluid flow in 0.5-m scale blocks of Topopah Spring tuff (open access)

Fluid flow in 0.5-m scale blocks of Topopah Spring tuff

A laboratory experiment was conducted on a 0.5-m scale block of Topopah Spring tuff, to measure fluid flow and mechanical deformation properties under conditions that approximate the near-field environment of a potential nuclear waste repository, and to provide an intermediate-scale test case for numerical model validation. The test specimen is a 0.25 x 0.25 x 0.50 m rectangular prism bisected by an artificial (saw-cut) fracture orthogonal to the tuff fabric. Water was supplied by a point source at the center of the fracture under various pressures of up to 0.04 MPa. Both fluid flow and mechanical properties were found to be anisotropic and strongly correlated with the ash flow fabric. Fluid mass-balance measurements revealed that only minor imbibition of water occurred through the fracture surfaces and that flow rates were independent of normal stress to 14.0 MPa and temperature to 140 C. Flow through the fracture occurred largely through uncorrelated porosity that intersected the fracture plane.
Date: January 12, 1999
Creator: Blair, S C; Carlson, S R & Constantino, M S
Object Type: Article
System: The UNT Digital Library
Introduction to Special Issue on PV Systems Performance and Reliability (open access)

Introduction to Special Issue on PV Systems Performance and Reliability

The papers in this special issue have been selected from the systems and balance-of- systems sessions at the 1998 Photovoltaic Performance and Reliability Workshop. The workshop was held November 3-5, 1998 and hosted by the Florida Solar Energy Center, Cocoa Beach, Florida under sponsorship of the US National Center for Photovoltaics (National Renewable Energy Laboratory and Sandia National Laboratories). The topics and issues addressed by these papers were identified in an invited review paper on PV systems by the guest editors. Their work was published earlier this year in Volume 7, Number 1 of Progress in Photovoltaics ('Photovoltaic Systems: An End-of-Millennium Review'). Experts in the PV community were asked to make presentations on these topics at the workshop. The papers that follow are the results of that effort. The papers are organized by topic: (1) codes and standards; (2) reliability; (3) design issues; and (4) commercialization.
Date: January 12, 1999
Creator: DeBlasio, R.; Post, H.N. & Thomas, M.G.
Object Type: Article
System: The UNT Digital Library
Manufacturing, Technology, and Competitiveness (open access)

Manufacturing, Technology, and Competitiveness

This report discusses increases in the productivity of American firms to maintain competitiveness in the international marketplace.
Date: January 12, 1999
Creator: Schacht, Wendy H.
Object Type: Report
System: The UNT Digital Library
A MODELING STUDY OF PERCHE WATER PHENOMENA IN THE UNSATURATED ZONE AT YUCCA MOUNTAIN (open access)

A MODELING STUDY OF PERCHE WATER PHENOMENA IN THE UNSATURATED ZONE AT YUCCA MOUNTAIN

None
Date: January 12, 1999
Creator: Y.S. WU, A.C. RITEEY AND G.S. BODVARSSON
Object Type: Report
System: The UNT Digital Library
Performing three-dimensional neutral particle transport calculations on tera scale computers (open access)

Performing three-dimensional neutral particle transport calculations on tera scale computers

A scalable, parallel code system to perform neutral particle transport calculations in three dimensions is presented. To utilize the hyper-cluster architecture of emerging tera scale computers, the parallel code successfully combines the MPI message passing and paradigms. The code's capabilities are demonstrated by a shielding calculation containing over 14 billion unknowns. This calculation was accomplished on the IBM SP ''ASCI-Blue-Pacific computer located at Lawrence Livermore National Laboratory (LLNL).
Date: January 12, 1999
Creator: Woodward, C. S.; Brown, P. N.; Chang, B.; Dorr, M. R. & Hanebutte, U. R.
Object Type: Article
System: The UNT Digital Library
Report on Biomass Drying Technology (open access)

Report on Biomass Drying Technology

Using dry fuel provides significant benefits to combustion boilers, mainly increased boiler efficiency, lower air emissions, and improved boiler operation. The three main choices for drying biomass are rotary dryers, flash dryers, and superheated steam dryers. Which dryer is chosen for a particular application depends very much on the material characteristics of the biomass, the opportunities for integrating the process and dryer, and the environmental controls needed or already available.
Date: January 12, 1999
Creator: Amos, W. A.
Object Type: Report
System: The UNT Digital Library
Rural Development: Rural Business--Cooperative Service's Lending and the Financial Condition of Its Loan Portfolio (open access)

Rural Development: Rural Business--Cooperative Service's Lending and the Financial Condition of Its Loan Portfolio

A letter report issued by the General Accounting Office with an abstract that begins "Pursuant to a congressional request, GAO provided information on the: (1) number and dollar value of business assistance loans approved by the Department of Agriculture's Rural Business-Cooperative Service (RBS); (2) federal government's costs associated with the agency's loans; and (3) financial condition of the agency's loan portfolio, including the losses incurred."
Date: January 12, 1999
Creator: United States. General Accounting Office.
Object Type: Report
System: The UNT Digital Library
Shadow penumbras by depth-dependent filtering (open access)

Shadow penumbras by depth-dependent filtering

A large number of the small optics procurements for the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) will be in the form of completely assembled, tested, and cleaned subsystems. These subsystems will be integrated into the NIF at LLNL. To accomplish this task, the procurement packages will include, optical and mechanical drawings, acceptance test and cleanliness requirements. In January 1999, the first such integrated opto-mechanical assembly was received and evaluated at LLNL. With the successful completion of this important trial procurement, we were able to establish the viability of purchasing clean, ready to install, opto-mechanical assemblies from vendors within the optics industry. 32 vendors were chosen from our supplier database for quote, then five were chosen to purchase from. These five vendors represented a cross section of the optics industry. From a ''value'' catalog supplier (that did the whole job internally) to a partnership between three specialty companies, these vendors demonstrated they have the ingenuity and capability to deliver cost competitive, NIF-ready, opto- mechanical assemblies. This paper describes the vendor selection for this procurement, technical requirements including packaging, fabrication, coating, and cleanliness specifications, then testing and verification. It also gives real test results gathered from inspections performed …
Date: January 12, 1999
Creator: Keating, B. & Max, N.
Object Type: Article
System: The UNT Digital Library
Supplemental Security Income: Increased Receipt and Reporting of Child Support Could Reduce Payments (open access)

Supplemental Security Income: Increased Receipt and Reporting of Child Support Could Reduce Payments

A letter report issued by the General Accounting Office with an abstract that begins "GAO provided information on: (1) opportunities for increasing the number of Supplemental Security Income (SSI) single-parent families receiving child support and for improving the reporting of such support to the Social Security Administration (SSA); (2) the potential for reducing SSI payments by increasing the extent to which SSI children in single-parent families are served by the Child Support Enforcement (CSE) program and have support collected for them and the extent to which support collected by CSE programs is reported by custodial parents to SSA."
Date: January 12, 1999
Creator: United States. General Accounting Office.
Object Type: Report
System: The UNT Digital Library
Thermomechanical effects on permeability for a 3-D model of YM rock (open access)

Thermomechanical effects on permeability for a 3-D model of YM rock

The authors estimate how thermomechanical processes affect the spatial variability of fracture permeability for a 3-D model representing Topopah Spring tuff at the nuclear-waste repository horizon in Yucca Mountain, Nevada. Using a finite-difference code, they compute thermal stress changes. They evaluate possible permeability enhancement resulting from shear slip along various mapped fracture sets after 50 years of heating, for rock in the near-field environment of the proposed repository. The results indicate permeability enhancement of a factor of 2 for regions about 10 to 30 m above drifts, for north-south striking vertical fractures. Shear slip and permeability increases of a factor of 4 can occur in regions just above drifts, for east-west striking vertical fractures. Information on how permeability may change over the lifetime of a geologic repository is important to the prediction and evaluation of repository performance.
Date: January 12, 1999
Creator: Berge, P A; Blair, S C & Wang, H F
Object Type: Article
System: The UNT Digital Library
Thin-film silica sol-gels doped with ion responsive fluorescent lipid bilayers (open access)

Thin-film silica sol-gels doped with ion responsive fluorescent lipid bilayers

A metal ion sensitive, fluorescent lipid-b i layer material (5oA PSIDA/DSPC) was successfully immobilized in a silica matrix using a tetramethoxysilane (TMOS) sol-gel procedure. The sol-gel immobilization method was quantitative in the entrapment of seif-assembled Iipid-bilayers and yielded thin films for facile configuration to optical fiber piatforms. The silica matrix was compatible with the solvent sensitive lipid bilayers and provided physical stabilization as well as biological protection. Immobilization in the silica sol-gel produced an added benefit of improving the bilayer's metal ion sensitivity by up to two orders of magnitude. This enhanced performance was attributed to a preconcentrator effect from the anionic surface of the silica matrix. Thin gels (193 micron thickness) were coupled to a bifurcated fiber optic bundle to produce a metal ion sensor probe. Response times of 10 - 15 minutes to 0.1 M CUCIZ were realized with complete regeneration of the sensor using an ethylenediarninetetraacetic acid (EDTA) solution.
Date: January 12, 1999
Creator: Sasaki, Darryl Y.; Shea, Lauren E. & Sinclair, Michael B.
Object Type: Article
System: The UNT Digital Library
Thomson scattering from laser plasmas (open access)

Thomson scattering from laser plasmas

Thomson scattering has recently been introduced as a fundamental diagnostic of plasma conditions and basic physical processes in dense, inertial confinement fusion plasmas. Experiments at the Nova laser facility [E. M. Campbell et al., Laser Part. Beams 9, 209 (1991)] have demonstrated accurate temporally and spatially resolved characterization of densities, electron temperatures, and average ionization levels by simultaneously observing Thomson scattered light from ion acoustic and electron plasma (Langmuir) fluctuations. In addition, observations of fast and slow ion acous- tic waves in two-ion species plasmas have also allowed an independent measurement of the ion temperature. These results have motivated the application of Thomson scattering in closed-geometry inertial confinement fusion hohlraums to benchmark integrated radiation-hydrodynamic modeling of fusion plasmas. For this purpose a high energy 4{omega} probe laser was implemented recently allowing ultraviolet Thomson scattering at various locations in high-density gas-filled hohlraum plasmas. In partic- ular, the observation of steep electron temperature gradients indicates that electron thermal transport is inhibited in these gas-filled hohlraums. Hydrodynamic calcula- tions which include an exact treatment of large-scale magnetic fields are in agreement with these findings. Moreover, the Thomson scattering data clearly indicate axial stagnation in these hohlraums by showing a fast rise of the …
Date: January 12, 1999
Creator: Moody, J. D.; Alley, W. E.; De Groot, J. S.; Estabrook, K. G.; Glenzer, S. H.; Hammer, J. H. et al.
Object Type: Article
System: The UNT Digital Library
What Changed in Article 690-Solar Photovoltaic Systems- of the 1999 National Electrical Code? (open access)

What Changed in Article 690-Solar Photovoltaic Systems- of the 1999 National Electrical Code?

Article 690, Solar Photovoltaic Power Systems, has been in the National Electrical Code (NEC) since 1984. An NFPA-appointed Task Group for Article 690 proposed changes to Article 690 for both the 1996 and 1999 codes. The Task Group, supported by more than 50 professionals from throughout the photovoltaic (PV) industry, met seven times during the 1999 code cycle to integrate the needs of the industry with the needs of electrical inspectors and end users to ensure the safety of PV systems. The Task Group proposed 57 changes to Article 690, and all the changes were accepted in the review process. The performance and cost of PV installations were always a consideration as these changes were formed but safety was the number-one priority. All of the proposals were well substantiated and coordinated throughout the PV industry and with representatives of Underwriters Laboratories, Inc (UL). The most significant changes that were made in Article 690 for the 1999 NEC along with some of the rationale are discussed in the remainder of this article.
Date: January 12, 1999
Creator: Bower, W. & Wiles, J.
Object Type: Article
System: The UNT Digital Library
1999 Gordon Research Conference on Mammalian DNA Repair. Final Progress Report (open access)

1999 Gordon Research Conference on Mammalian DNA Repair. Final Progress Report

This Conference will examine DNA repair as the key component in genomic surveillance that is so crucial to the overall integrity and function of mammalian cells. Recent discoveries have catapulted the field of DNA repair into a pivotal position for fundamental investigations into oncology, aging, environmental health, and developmental biology. We hope to highlight the most promising and exciting avenues of research in robust discussions at this conference. This Mammalian DNA Repair Gordon Conference differs from the past conferences in this series, in which the programs were broader in scope, with respect to topics and biological systems covered. A conference sponsored by the Genetics Society in April 1998 emphasized recombinational mechanisms for double-strand break repair and the role of mismatch repair deficiency in colorectal cancer. These topics will therefore receive somewhat less emphasis in the upcoming Conference. In view of the recent mechanistic advances in mammalian DNA repair, an upcoming comprehensive DNA repair meeting next autumn at Hilton Head; and the limited enrollment for Gordon Conferences we have decided to focus session-by-session on particular areas of controversy and/or new developments specifically in mammalian systems. Thus, the principal presentations will draw upon results from other cellular systems only to the extent …
Date: February 12, 1999
Creator: unknown
Object Type: Article
System: The UNT Digital Library
Aluminum powder metallurgy processing (open access)

Aluminum powder metallurgy processing

The objective of this dissertation is to explore the hypothesis that there is a strong linkage between gas atomization processing conditions, as-atomized aluminum powder characteristics, and the consolidation methodology required to make components from aluminum powder. The hypothesis was tested with pure aluminum powders produced by commercial air atomization, commercial inert gas atomization, and gas atomization reaction synthesis (GARS). A comparison of the GARS aluminum powders with the commercial aluminum powders showed the former to exhibit superior powder characteristics. The powders were compared in terms of size and shape, bulk chemistry, surface oxide chemistry and structure, and oxide film thickness. Minimum explosive concentration measurements assessed the dependence of explosibility hazard on surface area, oxide film thickness, and gas atomization processing conditions. The GARS aluminum powders were exposed to different relative humidity levels, demonstrating the effect of atmospheric conditions on post-atomization processing conditions. The GARS aluminum powders were exposed to different relative humidity levels, demonstrating the effect of atmospheric conditions on post-atomization oxidation of aluminum powder. An Al-Ti-Y GARS alloy exposed in ambient air at different temperatures revealed the effect of reactive alloy elements on post-atomization powder oxidation. The pure aluminum powders were consolidated by two different routes, a conventional consolidation …
Date: February 12, 1999
Creator: Flumerfelt, J.F.
Object Type: Report
System: The UNT Digital Library
The analysis of aqueous mixtures using liquid chromatography-electrospray mass spectrometry (open access)

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

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 chromatography, as well as capillary electrophoresis (CE). For an aqueous sample, these LC-ES-MS and CE-ES-MS techniques require no sample preparation or analyte derivatization, which makes it possible to observe a wide variety of analytes as they exist in solution. The majority of this work focuses on the use of LC-ES-MS for the determination of unknown products and intermediates formed during electrochemical incineration (ECI), an experimental waste remediation process. This report contains a general introduction to the project and the general conclusions. Four chapters have been removed for separate processing. Titles are: Chapter 2: Determination of small carboxylic acids by ion exclusion chromatography with electrospray mass spectrometry; Chapter 3: Electrochemical incineration of benzoquinone in aqueous media using a quaternary metal oxide electrode in the absence of a soluble supporting electrolyte; Chapter 4: The …
Date: February 12, 1999
Creator: Johnson, S.
Object Type: Thesis or Dissertation
System: The UNT Digital Library
The blending strategy for the plutonium immobilization program (open access)

The blending strategy for the plutonium immobilization program

The Department of Energy (DOE) has declared approximately 38.2 tonnes of weapons-grade plutonium to be excess to the needs of national security, 14.3 tonnes of fuel- and reactor-grade plutonium excess to DOE needs, and anticipates an additional 7 tonnes to be declared excess to national security needs. Of this 59.5 tonnes, DOE anticipates that {approximately} 7.5 tonnes will be dispositioned as spent fuel at the Geologic Repository and {approximately} 2 tonnes will be declared below the safeguards termination limit and be discard3ed as TRU waste at WIPP. The remaining 50 tonnes of excess plutonium exists in many forms and locations around the country, and is under the control of several DOE offices. In addition to the plutonium, the feed stock also contains about 17 tonnes of depleted uranium, about 600 kg of highly enriched uranium, and many kilograms of neptunium and thorium and about 8 to 10 tonnes of tramp impurities. The Materials Disposition Program (MD) will be received materials packaged by these other Programs to disposition in a manor that meets the spent fuel standard. To minimize the cost of characterization of the feedstock and to minimize purification processes, a blending strategy will be followed. The levelization of the …
Date: February 12, 1999
Creator: Ebbinghaus, B. B.; Edmunds, T. A.; Gentry, S.; Gray, L. W.; Riley, D. C.; Spingarn, J. et al.
Object Type: Article
System: The UNT Digital Library
Calibration of laser ablation inductively coupled plasma mass spectrometry using dried solution aerosols for the quantitative analysis of solid samples (open access)

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

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 few elements, rapid semiquantitative analysis of over 70 elements in an individual sample can be performed. Less than 20 years after its inception ICP-MS has shown to be applicable to several areas of science. These include geochemistry, the nuclear industry, environmental chemistry, clinical chemistry, the semiconductor industry, and forensic chemistry. In this introduction, the general attributes of ICP-MS will be discussed in terms of instrumentation and sample introduction. The advantages and disadvantages of current systems are presented. A detailed description of one method of sample introduction, laser ablation, is given. The paper also gives conclusions and suggestions for future work. Chapter 2, Quantitative analysis of solids by laser ablation inductively coupled plasma mass spectrometry using dried solution aerosols for calibration, has been removed …
Date: February 12, 1999
Creator: Leach, J.
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Capillary electrophoresis separation of neutral organic compounds, pharmaceutical drugs, proteins and peptides, enantiomers, and anions (open access)

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

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 additive concentration and the proportion of acetonitrile in the electrolyte. Several examples are given, including the separation of four methylbenz[a]anthracene isomers and the separation of normal and deuterated acetophenone. The effect of adding this new surfactant to the acidic electrolyte was also investigated. Incorporation of cetyltrimethylammonium bromide in the electrolyte is shown to dynamically coat the capillary and reverse electroosmotic flow. Chiral recognition mechanism is studied using novel synthetic surfactants as chiral selectors, which are made from amino acids reacting with alkyl chloroformates. A satisfactory separation of both inorganic and organic anions is obtained using electrolyte solutions as high as 5 M sodium chloride using direct photometric detection. The effect of various salts on electrophoretic and electroosmotic mobility is further discussed. Several examples are given under high-salt conditions.
Date: February 12, 1999
Creator: Ding, W.L.
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Capillary electrophoretic study of individual exocytotic events in single mast cells (open access)

Capillary electrophoretic study of individual exocytotic events in single mast cells

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 separation capillary to stimulate the release of the granules. Because the release process occurs on a ms time scale, monitoring individual exocytotic events is possible with the coupling of high-speed CE and LINF detection.
Date: February 12, 1999
Creator: Ho, A.M.W.
Object Type: Thesis or Dissertation
System: The UNT Digital Library