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Monte Carlo Simulations of Phosphate Polyhedron Connectivity in Glasses
Monte Carlo simulations of phosphate tetrahedron connectivity distributions in alkali and alkaline earth phosphate glasses are reported. By utilizing a discrete bond model, the distribution of next-nearest neighbor connectivities between phosphate polyhedron for random, alternating and clustering bonding scenarios was evaluated as a function of the relative bond energy difference. The simulated distributions are compared to experimentally observed connectivities reported for solid-state two-dimensional exchange and double-quantum NMR experiments of phosphate glasses. These Monte Carlo simulations demonstrate that the polyhedron connectivity is best described by a random distribution in lithium phosphate and calcium phosphate glasses.
Date:
December 21, 1999
Creator:
ALAM,TODD M.
Object Type:
Article
System:
The UNT Digital Library
Electrochemical corrosion testing of metal waste forms
Electrochemical corrosion tests have been conducted on simulated stainless steel-zirconium (SS-Zr) metal waste form (MWF) samples. The uniform aqueous corrosion behavior of the samples in various test solutions was measured by the polarization resistance technique. The data show that the MWF corrosion rates are very low in groundwaters representative of the proposed Yucca Mountain repository. Galvanic corrosion measurements were also conducted on MWF samples that were coupled to an alloy that has been proposed for the inner lining of the high-level nuclear waste container. The experiments show that the steady-state galvanic corrosion currents are small. Galvanic corrosion will, hence, not be an important mechanism of radionuclide release from the MWF alloys.
Date:
December 14, 1999
Creator:
Abraham, D. P.; Peterson, J. J.; Katyal, H. K.; Keiser, D. D. & Hilton, B. A.
Object Type:
Article
System:
The UNT Digital Library
Theory of high-{Tc} superconducting cuprates based on experimental evidence
A model of superconductivity in layered high-temperature superconducting cuprates is proposed, based on the extended saddle point singularities in the electron spectrum, weak screening of the Coulomb interaction and phonon-mediated interaction between electrons plus a small short-range repulsion of Hund's, or spin-fluctuation, origin. This permits to explain the large values of {Tc}, features of the isotope effect on oxygen and copper, the existence of two types of the order parameter, the peak in the inelastic neutron scattering, the positive curvature of the upper critical field, as function of temperature etc.
Date:
December 10, 1999
Creator:
Abrikosov, A. A.
Object Type:
Article
System:
The UNT Digital Library
An advanced control system for fine coal flotation
None
Date:
December 20, 1999
Creator:
Adel, G. T. & Luttrell, G. H.
Object Type:
Report
System:
The UNT Digital Library
Final Report, December, 1999. Sloan - US Department of Energy joint postdoctoral fellowship in computational molecular biology [Canonical nonlinear methods for modeling and analyzing gene circuits and spatial variations during pattern formation in embryonic development]
The modeling and analysis of the complex interactions between genes and metabolites during development require computational approaches. However, existing methods cannot efficiently account for the large number of interacting players, the nonlinear nature of the interactions, or the disparate scales involved. The latter represents a challenge in modeling developmental systems since reaction rates and diffusion times can vary by several orders of magnitude (depending on the molecular system). Modeling processes of this type results in the pathology of stiffness. Numerically, stiffness occurs when, in order to prevent large amplification of errors, typical (non-stiff) algorithms require a step size much smaller than the scale at which the solution in changing. In this work, a new method to solve large stiff systems of equations in the non-linear power law form was developed. The power-law formatism is a proven powerful tool for biological systems modeling, and has many advantages over other formalisms used for this purpose. The advantages include the fact that it is canonical, and that it is an accurate local approximation to any type of interaction. Representative results are presented.
Date:
December 1, 1999
Creator:
Agresar, Grenmarie & Savageau, Michael A.
Object Type:
Report
System:
The UNT Digital Library
Characterizing the Fabric of the Urban Environment: A Case Study of Sacramento, California
To estimate the impact of light-colored surfaces (roofs and pavements) and urban vegetation (trees, grass, shrubs) on meteorology and air quality of a city, it is essential to accurately estimate the fraction of various urban surfaces. In this report, we estimate the fabric of Sacramento by analyzing high-resolution (0.30-m) aerial color photographs of about 65 square km of the urban area. The analysis show that in downtown Sacramento, vegetation as seen from above the canopy covers 30% of the area, whereas roofs cover 23% and paved surface 41%. Under-the-canopy fabric consists of 52% paved surfaces, 26% roofs, and 12% grass. In the industrial areas, vegetation covers 8-14% of the area, roofs cover 19-23%, and paved surfaces cover 29-44%. The surface-type percentages in the office areas are 21% trees, 16% roofs, and 49% paved surfaces. In commercial areas,vegetation covers 5-20%, roofs 19-20%, paved surfaces 44-68%. Residential areas exhibit a wide range of percentages of surface-types . On average, vegetation covers about 36% of the area, roofs cover about 20%, and paved surfaces about 28%. Trees mostly shade streets, parking lots, grass, and sidewalks. Under the canopy the percentage of paved surfaces is significantly higher. In most non-residential areas, paved surfaces cover …
Date:
December 1, 1999
Creator:
Akbari, Hashen; Rose, L. Shea & Taha, Haider
Object Type:
Report
System:
The UNT Digital Library
Radiation embrittlement studies using anomalous small-angle x-ray scattering
Anomalous small angle x-ray scattering (ASAXS) was performed on an Fe-O.9 wt.% Cu-1.0 wt.% Mn alloy subjected to annealing or electron irradiation. ASAXS takes advantage of natural variations in the atomic scattering factor which exist at energies very near an element's x-ray absorption edge. By performing systematic SAXS experiments at energies near these absorption edges of the constituent alloy elements it is possible to vary the contrast of scattering centers containing the elements and in doing so quantify scatterer composition. The results of such an analysis for the samples in this work indicate the presence of Cu-rich, Cu{sub 85}Mn{sub 15} precipitates in the alloy. By applying the maximum entropy technique to the scattering data, it was possible to extract size distributions of scattering centers fog the different treatments. The results demonstrate the ability to detect and characterize small (11 {angstrom} radius) scatterers at quite low irradiation damage levels (5x10{sup {minus} 4} displacements per atom).
Date:
December 6, 1999
Creator:
Alexander, D. E.; Kestel, B. J.; Seifert, S.; Jemian, P. R.; Odette, G. R.; Klingensmith, D. et al.
Object Type:
Article
System:
The UNT Digital Library
Correlating radiation exposure with embrittlement: Comparative studies of electron- and neutron-irradiated pressure vessel alloys
Comparative experiments using high energy (10 MeV) electrons and test reactor neutrons have been undertaken to understand the role that primary damage state has on hardening (embrittlement) induced by irradiation at 300 C. Electrons produce displacement damage primarily by low energy atomic recoils, while fast neutrons produce displacements from considerably higher energy recoils. Comparison of changes resulting from neutron irradiation, in which nascent point defect clusters can form in dense cascades, with electron irradiation, where cascade formation is minimized, can provide insight into the role that the in-cascade point defect clusters have on the mechanisms of embrittlement. Tensile property changes induced by 10 MeV electrons or test reactor neutron irradiations of unalloyed iron and an Fe-O.9 wt.% Cu-1.0 wt.% Mn alloy were examined in the damage range of 9.0 x 10{sup {minus}5} dpa to 1.5 x 10{sup {minus}2} dpa. The results show the ternary alloy experienced substantially greater embrittlement in both the electron and neutron irradiate samples relative to unalloyed iron. Despite their disparate nature of defect production similar embrittlement trends with increasing radiation damage were observed for electrons and neutrons in both the ternary and unalloyed iron.
Date:
December 22, 1999
Creator:
Alexander, D. E.; Rehn, L. E.; Odette, G. R.; Lucas, G. E.; Klingensmith, D. & Gragg, D.
Object Type:
Article
System:
The UNT Digital Library
Oral History Interview with Shuford M. Alexander, Jr., December 2, 1999
Access:
Use of this item is restricted to the UNT Community
Interview with engineer and Army Air Forces veteran Shuford M. Alexander, Jr. The interview includes Alexander's personal experiences about being a fighter pilot in Italy during World War II, basic training, flight training, various assignments and transfers, Operation STRANGLE, being shot down by flak over Piacenza, and being rescued by Italian partisans. Additionally, Alexander talks about his link-up with a British A-4 Mission and his attempt to reach Allied lines, his betrayal by a German agent and his subsequent capture, escaping and continuing his search for Allied lines, his observations and opinions about the partisans, a second encounter with a British A-4 Mission, the Martani family in the village of Tosca, his group's trek through mountain snow to reach Allied lines, meeting with British paratroopers and with African-American soldiers from the 92nd Infantry Division, and his reunion with his squadron in Pisa. The interview includes an appendix with a narrative by Alexander.
Date:
December 2, 1999
Creator:
Alexander, William J. & Alexander, Shuford M., Jr.
Object Type:
Book
System:
The UNT Digital Library
GUIDELINES FOR MIXING AND PLACING THERMALLY CONDUCTIVE CEMENTITIOUS GROUT (MIX 111).
None
Date:
December 14, 1999
Creator:
Allan, M. L.
Object Type:
Report
System:
The UNT Digital Library
In situ study of dislocation behavior in columnar Al thin film on Si substrate during thermal cycling
In situ transmission electron microscopy (150 kV) has been employed to study the evolution of dislocation microstructure during relatively rapid thermal cycling of a 200 nm Al thin film on Si substrate. After a few thermal cycles between 150 and 500 C, nearly stable Al columnar grain structure is established with average grain less than a {micro}m. On rapid cooling (3--30+ C/s) from 500 C, dislocations first appear at a nominal temperature of 360--380 C, quickly multiplying and forming planar glide plane arrays on further cooling. From a large number of such experiments the authors have attempted to deduce the dislocation evolution during thermal cycling in these polycrystalline Al films and to account qualitatively for the results on a simple dislocation model.
Date:
December 13, 1999
Creator:
Allen, C. W.; Schroeder, H. & Hiller, J. M.
Object Type:
Article
System:
The UNT Digital Library
Inelastic scattering of synchrotron radiation from electrons and nuclei for lattice dynamics studies.
The inelastic scattering of x-rays, one of the first applications of x-rays to the field of condensed matter physics, has been rejuvenated in the last decade. The availability of synchrotrons radiation from wiggler and undulator sources combined with advances in monochromatization of the incident beam and analysis of the scattered beam with meV resolution led to the measurement of phonon dispersion relations. In addition, the use of Moessbauer nuclei as scatterer and analyzers has led to the discovery of the inelastic nuclear resonant scattering technique. This new method allows extraction of partial phonon density of states from amorphous materials, thin films, multilayers and interfaces, and liquids.
Date:
December 3, 1999
Creator:
Alp, E. E.; Sturhahn, W.; Sinn, H.; Toellner, T.; Hu, M.; Sutter, J. et al.
Object Type:
Article
System:
The UNT Digital Library
Development and evaluation of high resolution quadrupole mass analyzer and an inductively coupled plasma-Mach disk
By definition a plasma is an electrically conducting gaseous mixture containing a significant concentration of cations and electrons. The Inductively Coupled Plasma (ICP) is an electrodeless discharge in a gas at atmospheric pressure. This discharge is an excellent one for vaporizing, atomizing, and ionizing elements. The early development of the ICP began in 1942 by Babat and then by Reed in the early 1960s. This was then followed by the pioneering work of Fassel and coworkers in the late 1960s. Commercial ICP spectrometers were introduced in the mid 1970s. A major breakthrough in the area of ICP took place in the early 1980s when the ICP was shown to be an excellent ion source for mass spectrometry.
Date:
December 10, 1999
Creator:
Amad, Ma'an Hazem
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Southwest Retort, Volume 52, Number 4, December 1999
This publication of the Dallas-Fort Worth Section of the American Chemical Society includes information about research, prominent scientist, organizational business, and various other stories of interest to the community.
Date:
December 1999
Creator:
American Chemical Society. Dallas/Fort Worth Section.
Object Type:
Journal/Magazine/Newsletter
System:
The UNT Digital Library
Scenario analysis of hybrid class 3-7 heavy vehicles.
The effects of hybridization on heavy-duty vehicles are not well understood. Heavy vehicles represent a broader range of applications than light-duty vehicles, resulting in a wide variety of chassis and engine combinations, as well as diverse driving conditions. Thus, the strategies, incremental costs, and energy/emission benefits associated with hybridizing heavy vehicles could differ significantly from those for passenger cars. Using a modal energy and emissions model, they quantify the potential energy savings of hybridizing commercial Class 3-7 heavy vehicles, analyze hybrid configuration scenarios, and estimate the associated investment cost and payback time. From the analysis, they conclude that (1) hybridization can significantly reduce energy consumption of Class 3-7 heavy vehicles under urban driving conditions; (2) the grid-independent, conventional vehicle (CV)-like hybrid is more cost-effective than the grid-dependent, electric vehicle (EV)-like hybrid, and the parallel configuration is more cost-effective than the series configuration; (3) for CV-like hybridization, the on-board engine can be significantly downsized, with a gasoline or diesel engine used for SUVs perhaps being a good candidate for an on-board engine; (4) over the long term, the incremental cost of a CV-like, parallel-configured Class 3-4 hybrid heavy vehicle is about %5,800 in the year 2005 and $3,000 in 2020, while …
Date:
December 23, 1999
Creator:
An, F.; Stodolsky, F.; Vyas, A.; Cuenca, R. & Eberhardt, J. J.
Object Type:
Article
System:
The UNT Digital Library
D0 HVAC System Heat Pump Controller Programming, Networking, and Operating Information
The purpose of this engineering note is to provide the necessary information to setup, program, and network the Electronic Systems USA Heat Pump Controller with the LON network card and Intellution Fix32 to operate properly within the HVAC system at D-Zero. The heat pump controllers are used for local temperature control of the office environments on the fifth and six floors of D-Zero. Heat pump units 1-6 are located in the ceiling of the sixth floor. Heat pump units 7-12 are found in the fifth floor ceiling. Heat pump unit 13 is in the Southeast corner of the fifth floor. Prior to installation the heat pump controller must be properly prepared to operate correctly in the HVAC system. Each heat pump unit must contain firmware (software) version 1.31 to operate properly on the network. Controllers with version 1.30 will not be able to communicate over the LON network. The manufacturer can only update the firmware version. Before installation a series of heat pump setpoints must be manually set using the Intelligent Stat. Connect the Intelligent Stat via the serial cable or wired connection.
Date:
December 2, 1999
Creator:
Anderson, B.
Object Type:
Report
System:
The UNT Digital Library
Results of R. F. Noise Coupling Tests Done in Building 141
As part of the lightning protection plan at the Pantex plant, coupling measurements were made by LLNL to determine the transfer functions of the work areas (cell or bay). From these measured transfer functions the susceptibility of the cell to a lightning strike can be determined, and the appropriate mitigating measures put into effect. The transfer functions are determined by injecting a current on the outside of the cell and measuring the electric field inside. The ratio of electric field to the injected current over a broad frequency range is the transfer function. During one of our tests a comparison of LLNL and SNLA instrumentation was done. The major difference in the systems was that the SNLA system used batteries for power and a fiber optic link to decouple the antenna from the receiver. LLNL used AC power and a cable for the antenna connection. The comparison showed a discrepancy between LLNL and SNLA results. The source of this error was unwanted signal (noise) coupling into the local AC power source from the injected current. Since this source was used to power the equipment, the noise was fed directly to the electric field measuring antenna, causing errors in the measurement. …
Date:
December 1, 1999
Creator:
Anderson, R. A.
Object Type:
Report
System:
The UNT Digital Library
Studying Wind Energy/Bird Interactions: A Guidance Document
This guidance document is a product of the Avian Subcommittee of the National Wind Coordinating Committee (NWCC). The NWCC was formed to better understand and promote responsible, credible, and comparable avian/wind energy interaction studies. Bird mortality is a concern and wind power is a potential clean and green source of electricity, making study of wind energy/bird interactions essential. This document provides an overview for regulators and stakeholders concerned with wind energy/bird interactions, as well as a more technical discussion of the basic concepts and tools for studying such interactions.
Date:
December 1, 1999
Creator:
Anderson, R.; Morrison, M.; Sinclair, K. & Strickland, D.
Object Type:
Book
System:
The UNT Digital Library
LOUISIANA COASTAL WETLANDS MODELING
None
Date:
December 1, 1999
Creator:
Ansari, Dr. Ali & Santos, Ms. Lilibeth de Los
Object Type:
Report
System:
The UNT Digital Library
Extracellular iron-sulfur precipitates from growth of Desulfovibrio desulfuricans
The authors have examined extracellular iron-bearing precipitates resulting from the growth of Desulfovibrio desulfuricans in a basal medium with lactate as the carbon source and ferrous sulfate. Black precipitates were obtained when D. desulfuricans was grown with an excess of FeSO{sub 4}. When D. desulfuricans was grown under conditions with low amounts of FeSO{sub 4}, brown precipitates were obtained. The precipitates were characterized by iron K-edge XAFS (X-ray absorption fine structure), {sup 57}Fe Moessbauer-effect spectroscopy, and powder X-ray diffraction. Both were noncrystalline and nonmagnetic (at room temperature) solids containing high-spin Fe(III). The spectroscopic data for the black precipitates indicate the formation of an iron-sulfur phase with 6 nearest S neighbors about Fe at an average distance of 2.24(1) {angstrom}, whereas the brown precipitates are an iron-oxygen-sulfur phase with 6 nearest O neighbors about Fe at an average distance of 1.95(1) {angstrom}.
Date:
December 20, 1999
Creator:
Antonio, M. R.; Tischler, M. L. & Witzcak, D.
Object Type:
Article
System:
The UNT Digital Library
State Governance of Elementary and Secondary Education
None
Date:
December 31, 1999
Creator:
Apling, Richard N.
Object Type:
Report
System:
The UNT Digital Library
[News report: Gays vow to keep fighting for rights]
News report about a woman named Sue Reardon coping with the Hawaiian Supreme Court's ruling upholding current state marriage laws.
Date:
December 11, 1999
Creator:
Arakawa, Lynda
Object Type:
Text
System:
The UNT Digital Library
Development of a Coaxiality Indicator
Access:
Use of this item is restricted to the UNT Community
The geometric dimensioning and tolerancing concept of coaxiality is often required by design engineers for balance of rotating parts and precision mating parts. In current practice, it is difficult for manufacturers to measure coaxiality quickly and inexpensively. This study examines feasibility of a manually-operated, mechanical device combined with formulae to indicate coaxiality of a test specimen. The author designs, fabricates, and tests the system for measuring coaxiality of holes machined in a steel test piece. Gage Repeatability and Reproducibility (gage R&R) and univariate analysis of variance is performed in accordance with Measurement System Analysis published by AIAG. Results indicate significant design flaws exist in the current configuration of the device; observed values vary greatly with operator technique. Suggestions for device improvements conclude the research.
Date:
December 1999
Creator:
Arendsee, Wayne C.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Trail of Lights
Photograph of a scene during the Trail of Lights event at the Duncan City Park.
Date:
December 11, 1999
Creator:
Argo, Jim
Object Type:
Photograph
System:
The Gateway to Oklahoma History