Resource Type

Degree Department

4,668 Matching Results

Results open in a new window/tab.

Introduction to the differential geometry of quantum groups (open access)

Introduction to the differential geometry of quantum groups

An introduction to the noncommutative differential calculus on quantum groups. The invariant group average is also discussed.
Date: October 31, 1991
Creator: Zumino, B.
System: The UNT Digital Library
Nuclear and particle astrophysics (open access)

Nuclear and particle astrophysics

We discuss the physics of matter that is relevant to the structure of compact stars. This includes nuclear, neutron star matter and quark matter and phase transitions between them. Many aspects of neutron star structure and its dependance on a number of physical assumptions about nuclear matter properties and hyperon couplings are investigated. We also discuss the prospects for obtaining constraints on the equation of state from astrophysical sources. Neuron star masses although few are known at present, provide a very direct constraint in as much as the connection to the equation of state involves only the assumption that Einstein's general of theory of relativity is correct at the macroscopic scale. Supernovae simulations involve such a plethora of physical processes including those involved in the evolution of the precollapse configuration, not all of them known or understood, that they provide no constraint at the present time. Indeed the prompt explosion, from which a constraint had been thought to follow, is now believed not to be mechanism by which most, if any stars, explode. In any case the nuclear equation of state is but one of a multitude on uncertain factors, and possibly one of the least important. The rapid rotation …
Date: October 31, 1990
Creator: Glendenning, N.K.
System: The UNT Digital Library
Tests of a mechanism for H sub 2 S release during coal pyrolysis (open access)

Tests of a mechanism for H sub 2 S release during coal pyrolysis

We have used a temperature programmed, gas evolution technique to compare H{sub 2}S from coal and from pyrite in the presence of minerals or polymers. Pyrite decomposition in coal with H{sub 2}S release can be observed directly only if carbonate minerals, particularly iron-containing carbonates, are absent. Two distinct chemical mechanisms are required to model conversion of pyrite in coal to H{sub 2}S and pyrrhotite. Initially a reaction at pyrite grain surfaces (shrinking core model) occurs that is controlled by the rate of iron movement toward crystallite centers and by hydrogen-donor availability. Tar evolution (as indicated by methane-plus-ethane) also requires H-donors. Organic free radicals compete so efficiently for this scarce commodity that the rate of pyrite decomposition slows. At a 10 K/min heating rate, the rate of H{sub 2}S release by the H-donor mechanism reaches a maximum at 700 K and then decreases. Unimolecular decomposition of coal pyrite to FeS and S{sub 2} then occurs sharply at 830 K. Coal pyrolysis products effectively capture S{sub 2}, and the rate of H{sub 2}S release matches that of sulfur release from pure pyrite in a vacuum (0.07 mg- S/cm{sup 2}/min at 773 K). The high temperature H{sub 2}S evolution peak from coal is …
Date: May 31, 1991
Creator: Coburn, T. T.; Foster, K. G.; Gregg, H. R. & Lindsey, J. A.
System: The UNT Digital Library
WA80 BGO calorimetry electronics (open access)

WA80 BGO calorimetry electronics

This paper describes instrumentation designed for BGO scintillator-based calorimetry of particles covering a very wide range of energies (from less than 50 MeV to 50 GeV). The instrumentation was designed to have a measurement accuracy of 0.1% over as much of the energy range as possible so the energy resolution of BGO would be the limiting factor. Two 1.5-cm{sup 2} photodiodes were used per 2.5 cm {times} 2.5 cm {times} 25 cm BGO crystal. Both a charge-sensitive preamplifier and a pulse processor were developed specifically for the needs of the WA80 experiment. The preamplifier was designed for high detector capacitance (100 to 700 pF), low integral and differential non-linearity and low power consumption (200 mW). The pulse processor is a time-invariant shaping amplifier with integral peak-detect-and-hold and automatic gain selection circuits. The amplifier use quasi-triangular shaping with 4 {mu}s peaking time, and the hold circuit is gated with a fast first level trigger. The system has more than 20 bits of effective resolution when used with an external 12-bit ADC. Results from beam tests at CERN are presented. 6 refs., 5 figs., 1 tab.
Date: October 31, 1991
Creator: Wintenberg, A. L.; Britton, C. L., Jr.; Ericson, M. N.; Maples, R. A.; Young, G. R. & Awes, T. C.
System: The UNT Digital Library
Damage parameters for candidate Fusion Materials Irradiation Test facilities (open access)

Damage parameters for candidate Fusion Materials Irradiation Test facilities

A comparison was made of damage parameters for carbon, iron, and molybdenum irradiated in spectra for d-Li, spallation, and beam-plasma (d-t) neutron sources and a reference DEMO first wall spectrum. The transmutation results emphasize the need to define the neutron spectra at low energies; only the DEMO spectrum was so defined. The spallation spectra were also poorly defined at high neuron energies; they were too soft to produce the desired gas production rates. The treatments of neutron-induced displacement reactions were limited to below 20 MeV and transmutation reactions to below 50 MeV by the limited availability of calculational tools. Recommendations are given for further work to be performed under an international working group. 12 refs., 6 figs., 3 tabs.
Date: July 31, 1990
Creator: Doran, D. G.; Mann, F. M. & Greenwood, L. R.
System: The UNT Digital Library
NMR measurement of pore structure (open access)

NMR measurement of pore structure

An attempt was made to pursue [sup 129]Xe NMR as a pore measurement technique. Samples studied were synthetic imogolite (tubular aluminosilicate with gibbsite structure), sodium Y-zeolite, and an aerogel and a xerogel. Gases used were normal Xe, [sup 13]CO[sub 2], and [sup 15]N[sub 2]. Although a completely general NMR technique for measuring pore size distributions may not be possible, information about molecular motion and interactions can be obtained, because NMR is sensitive to short range interactions (1 nm or less) and to molecular dynamics in the range 10[sup [minus]2] to 10[sup [minus]6]s.
Date: May 31, 1993
Creator: Earl, W.L. (Los Alamos National Lab., NM (United States)); Kim, Yong-Wah (Los Alamos National Lab., NM (United States) New Mexico Univ., Albuquerque, NM (United States). Center for Microengineered Ceramics) & Smith, D.M. (New Mexico Univ., Albuquerque, NM (United States). Center for Microengineered Ceramics)
System: The UNT Digital Library
Advanced turbine cooling, heat transfer, and aerodynamic studies (open access)

Advanced turbine cooling, heat transfer, and aerodynamic studies

The contractual work is in three parts: Part I - Effect of rotation on enhanced cooling passage heat transfer, Part II - Effect of Thermal Barrier Coating (TBC) spallation on surface heat transfer, and Part III - Effect of surface roughness and trailing edge ejection on turbine efficiency under unsteady flow conditions. Each section of this paper has been divided into three parts to individually accommodate each part. Part III is further divided into Parts IIIa and IIIb.
Date: December 31, 1995
Creator: Han, Je-Chin & Schobeiri, Meinhard T.
System: The UNT Digital Library
Disilene Addition to C{sub 70} (open access)

Disilene Addition to C{sub 70}

Semiempirical and ab initio Hartree Fock computational results indicate that the highly reactive dienophile tetramethyldisilene, Me{sub 2}Si=SiMe{sub 2}, is an excellent candidate for a novel functionalization of the equator of C{sub 70} via a [2+4] cycloaddition to the 21, 22, 23, 42 carbons. Thermal or photochemical generation of tetramethyldisilene in the presence of C{sub 70} results in similar complex mixtures in which the major product appears to be that of [2+2] cycloaddition to the 7,8 carbons of C{sub 70}. A minor product clearly results from [2+2] cycloaddition to the 1,9 carbons. Both of these products are hydrolytically unstable and are converted nonspecifically to mixtures of 1,9- and 7,8-C{sub 70}H{sub 2} which are also present in HPLC traces of the reaction mixtures.
Date: December 31, 1994
Creator: Jacobs, S. J.; Cahill, P. A. & Rohlfing, C. M.
System: The UNT Digital Library
Pilot gasification and hot gas cleanup operations (open access)

Pilot gasification and hot gas cleanup operations

The Morgantown Energy Technology Center (METC) has an integrated gasification hot gas cleanup facility to develop gasification, hot particulate and desulfurization process performance data for IGCC systems. The objective of our program is to develop fluidized-bed process performance data for hot gas desulfurization and to further test promising sorbents from lab-scale screening studies at highpressure (300 psia), and temperatures (1,200{degrees}F) using coal-derived fuel gases from a fluid-bed gasifier. The 10-inch inside diameter (ID), nominal 80 lb/hr, air blown gasifier is capable of providing about 300 lb/hr of low BTU gas at 1,000{degrees}F and 425 psig to downstream cleanup devices. The system includes several particle removal stages, which provide the capability to tailor the particle loading to the cleanup section. The gas pressure is reduced to approximately 300 psia and filtered by a candle filter vessel containing up to four filter cartridges. For batch-mode desulfurization test operations, the filtered coal gas is fed to a 6-inch ID, fluid-bed reactor that is preloaded with desulfurization sorbent. Over 400 hours of gasifier operation was logged in 1993 including 384 hours of integration with the cleanup rig. System baseline studies without desulfurization sorbent and repeatability checks with zinc ferrite sorbent were conducted before testing …
Date: December 31, 1995
Creator: Rockey, John M.; Galloway, Edwin; Thomson, Teresa A.; Rutten, Jay & Lui, Alain
System: The UNT Digital Library
Heavy duty gas turbine combustion tests with simulated low BTU coal gas (open access)

Heavy duty gas turbine combustion tests with simulated low BTU coal gas

There is an increasing industry interest in integrated gas turbine combined cycle plants in which coal gasifiers provide the fuel for the gas turbines. Some gasifier plant designs, including the air-blown processes, some integrated oxygen blown processes and some oxygen-blown processes followed by heavy moisturization, produce fuel gases which have lower heating values ranging from 130 to below 100 BTU/scf for which there is little gas turbine combustion experience. This program has the objectives to: Parametrically determine the effects of moisture, nitrogen and carbon dioxide as diluents so that the combustion characteristics of many varieties of gasification product gases can be reasonably predicted without physically testing each specific gas composition; determine emissions characteristics including NO{sub x}, CO, levels etc. associated with each of the diluents; operate with two syngas compositions; DOE chosen air-blown and integrated oxygen-blown, to confirm that the combustion characteristics are in line with predictions; determine if ``logical`` refinements to the fuel nozzle will yield improved performance for LBTU fuels; determine the conversion rate of ammonia to NO{sub x}; determine the effects of methane inclusion in the fuel.
Date: December 31, 1992
Creator: Ekstrom, T. E.; Battista, R. A. & Maxwell, G. P.
System: The UNT Digital Library
An improvement in the modified finite element procedure for underwater shock analysis (open access)

An improvement in the modified finite element procedure for underwater shock analysis

The modified finite element procedure for underwater shock analysis decomposes the total pressure field into the incident, reflected and radiated pressure. The incident pressure is calculated by using a closed form solution. The reflected and radiated pressure are calculated in two separate finite element analyses. Artificial damping is added in the finite element analyses. Since these two pressures are generated from the fluid-structure interface and mostly propagate away from the interface, the artificial damping has no significant effect on the result. The modified finite element procedure was developed using a displacement formulated finite element to model the fluid region. In the paper, a pressure formulated finite element is used to model the fluid region which has a potential of saving 90 percent of the computer time. In doing so, the reflected and radiated pressure are calculated in one analysis which greatly simplifies the analysis procedure and saves more computer time. Two verification examples are given.
Date: December 31, 1992
Creator: Chan, S. K.
System: The UNT Digital Library
FLASH predictions of the MB-2 steam line break tests (open access)

FLASH predictions of the MB-2 steam line break tests

If a main steam line from a pressurized water reactor (PWR) steam generator were to rupture, the effect would be a depressurization of the secondary side and a consequential overcooling transient on the primary side. Analyses must accurately predict the effects of the rapid cooldown of the reactor vessel coolant on positive nuclear-kinetic reactivity feedback to the core plus thermal shock to the reactor vessel and other primary system components. Many early studies of the steam line break (SLB) transient made extremely conservative assumptions to maximize the primary to secondary heat transfer which in turn maximized the reactor vessel cooldown rate. Among the more significant of these assumptions was that flow from the break was pure steam and that the tube bundle remained covered until the secondary mass inventory was significantly reduced. The Model F commercial PWR steam generator testing performed in the Model Boiler No. 2 (MB-2) facility located at the Westinghouse Engineering Test Facility in Tampa, Florida provided data to better qualify the actual variation in these key parameters. A conclusion of this analysis is that the MB-2 steam line break data base is accurate and of sufficient detail to provide a valuable basis for making comparisons relative …
Date: December 31, 1992
Creator: Lincoln, F. W.; Coffield, R. D. & Johnson, E. G.
System: The UNT Digital Library
Polarized protons in large center of mass collisions (open access)

Polarized protons in large center of mass collisions

We present a scheme for polarized proton operation in the RHIC collider complex. For low energies the partial siberian snake project in the AGS is reviewed. As the energy is increased the difficulties of preserving the polarization also increases. A plan for preserving the polarization at high energies in RHIC using two Siberian Snakes is discussed. Spin rotators will be used around the collision points so that the helicity can be varied.
Date: December 31, 1992
Creator: Tepikian, S.
System: The UNT Digital Library
Some Measurements for Determining Strangeness Matrix Elements in the Nucleon (open access)

Some Measurements for Determining Strangeness Matrix Elements in the Nucleon

Some experiments to measure strangeness matrix elements of the proton are proposed. Two of these suggestions are described in some detail, namely electro-production of phi mesons and the difference between neutrino and antineutrino scattering for isospin zero targets such as deuterium.
Date: December 31, 1991
Creator: Henley, Ernest M.; Pollock, S. J.; Ying, S.; Frederico, T.; Krein, & Williams, A. G.
System: The UNT Digital Library
Logistics for the implementation of lead-free solders on electronic assemblies (open access)

Logistics for the implementation of lead-free solders on electronic assemblies

The prospects of legislative and regulatory action aimed at taxing, restricting or banning lead-bearing materials from manufactured products has prompted the electronics community to examine the implementation of lead-free solders to replace currently used lead-containing alloys in the manufacture of electronic devices and assemblies. The logistics for changing the well established ``tin-lead solder technology`` require not only the selection of new compositions but also the qualification of different surface finishes and manufacturing processes. The meniscometer/wetting balance technique was used to evaluate the wettability of several candidate lead-free solders as well as to establish windows on processing parameters so as to facilitate prototype manufacturing. Electroplated and electroless 100Sn coatings, as well as organic preservatives, were also examined as potential alternative finishes for device leads and terminations as well as circuit board conductor surfaces to replace traditional tin-lead layers. Sandia National Laboratories and AT&T have implemented a program to qualify the manufacturing feasibility of surface mount prototype circuit boards using several commercial lead-free solders by infrared reflow technology.
Date: December 31, 1993
Creator: Vianco, P. T. & Artaki, I.
System: The UNT Digital Library
Efficient data transmission from silicon wafer strip detectors (open access)

Efficient data transmission from silicon wafer strip detectors

An architecture for on-wafer processing is proposed for central silicon-strip tracker systems as they are currently designed for high energy physics experiments at the SSC, and for heavy ion experiments at RHIC. The data compression achievable with on-wafer processing would make it possible to transmit all data generated to the outside of the detector system. A set of data which completely describes the state of the wafer for low occupancy events and which contains important statistical information for more complex events can be transmitted immediately. This information could be used in early trigger decisions. Additional data packages which complete the description of the state of the wafer vary in size and are sent through a second channel. By buffering this channel the required bandwidth can be kept far below the peak data rates which occur in rate but interesting events. 18 refs.
Date: December 31, 1991
Creator: Cooke, B. J.; Lackner, K. S.; Palounek, A. P. T.; Sharp, D. H.; Winter, L. & Ziock, H. J.
System: The UNT Digital Library
Turbine-engine applications of thermographic-phosphor temperature measurements (open access)

Turbine-engine applications of thermographic-phosphor temperature measurements

The thermographic-phosphor (TP) method can measure temperature, heat flux, strain, and other physical quantities remotely in hostile and/or inaccessible environments such as the first-stage turbine components in turbine engines. It is especially useful in situations in which no other known method works well. This paper is a brief review of engine tests that demonstrated the utility of the TP method. For the most part, the results presented here are discussed only qualitatively. The papers in the bibliography describe these and other experiments and results in detail. The first viewgraph summarizes the many desirable features of the TP method. The second viewgraph describes TPs, and the third summarizes how the TP method works. To measure single-point temperatures in turbine-engine applications, we use the decay-time method, which depends on the fact that the luminescence following an impulse of ultraviolet excitation decays, with a characteristic decay time that. Is a monotonically decreasing function of temperature over some range of temperatures. The viewgraph is a set of calibration curves showing the behavior of some useful emission lines for ten important TPs. Consider Lu PO{sub 4}:Eu as an example. Below the {open_quotes}quenching{close_quotes} temperature near 900 Y, the decay time is nearly constant. Above it, the …
Date: December 31, 1995
Creator: Noel, B. W.; Turley, W. D. & Allison, S. W.
System: The UNT Digital Library
Applications of neural networks to monitoring and decision making in the operation of nuclear power plants. Summary (open access)

Applications of neural networks to monitoring and decision making in the operation of nuclear power plants. Summary

Application of neural networks to monitoring and decision making in the operation of nuclear power plants is being investigated under a US Department of Energy sponsored program at the University of Tennessee. Projects include the feasibility of using neural networks for the following tasks: (1) diagnosing specific abnormal conditions or problems in nuclear power plants, (2) detection of the change of mode of operation of the plant, (3) validating signals coming from detectors, (4) review of ``noise`` data from TVA`s Sequoyah Nuclear Power Plant, and (5) examination of the NRC`s database of ``Letter Event Reports`` for correlation of sequences of events in the reported incidents. Each of these projects and its status are described briefly in this paper. This broad based program has as its objective the definition of the state-of-the-art in using neural networks to enhance the performance of commercial nuclear power plants.
Date: December 31, 1990
Creator: Uhrig, R. E.
System: The UNT Digital Library
Korringa-Kohn-Rostoker electronic structure method for space-filling cell potentials (open access)

Korringa-Kohn-Rostoker electronic structure method for space-filling cell potentials

The multiple scattering theory (MST) method of Korringa, and of Kohn and Rostoker for determining the electronic structure of solids, originally developed in connection with potentials bounded by non-overlapping spheres (muffin-tin (MT) potentials), is generalized to the case of space-filling potential cells of arbitrary shape through the use of a variational formalism. This generalized version of MST retains the separability of structure and potential characteristic of the application of MST to MT potentials. However, in contrast to the MT case, different forms of MST exhibit different convergence rates for the energy and the wave function. Numerical results are presented which illustrate the differing convergence rates of the variational and nonvariational forms of MST for space-filling potentials.
Date: December 31, 1991
Creator: Gonis, A.; Butler, W. H. & Zhang, X.-G.
System: The UNT Digital Library
Nuclear disarmament verification (open access)

Nuclear disarmament verification

Arms control treaties, unilateral actions, and cooperative activities -- reflecting the defusing of East-West tensions -- are causing nuclear weapons to be disarmed and dismantled worldwide. In order to provide for future reductions and to build confidence in the permanency of this disarmament, verification procedures and technologies would play an important role. This paper outlines arms-control objectives, treaty organization, and actions that could be undertaken. For the purposes of this Workshop on Verification, nuclear disarmament has been divided into five topical subareas: Converting nuclear-weapons production complexes, Eliminating and monitoring nuclear-weapons delivery systems, Disabling and destroying nuclear warheads, Demilitarizing or non-military utilization of special nuclear materials, and Inhibiting nuclear arms in non-nuclear-weapons states. This paper concludes with an overview of potential methods for verification.
Date: December 31, 1993
Creator: DeVolpi, A.
System: The UNT Digital Library
DOE`s perspective: Reaching success by standing on a three legged stool (open access)

DOE`s perspective: Reaching success by standing on a three legged stool

Gridlock, inertia, conflict, outrage, bureaucracy, obstruction, media sensationalizing, courts, and politicians. These are the things that characterize any attempt to implement a public policy today. It is worse today than it has ever been because the middle has dropped out of public opinion. We have today no consensus of public values. At Fernald, we have come to recognize that in order to achieve any success we must first build a public consensus about what success will look like. We do this through a three-part approach we call the three legged stool. It includes public information, management involvement, and person-to-person communication. Each of these elements is essential.
Date: January 31, 1995
Creator: Hamric, J. P. & Morgan, K. L.
System: The UNT Digital Library
Thermal treatment of high explosives at Mason & Hanger/Pantex Plant (open access)

Thermal treatment of high explosives at Mason & Hanger/Pantex Plant

The Pantex plant presently processes about 45,000 kg (100,000 lb) of high explosives annually by outdoor burning. About half of the explosives are weapon components weighing over 5 kg (10 lb) which come directly out of nuclear weapons being removed from the stockpile. The other half is generated from various support processes, special tests, etc. Burning serves the three-fold purpose of demilitarizing, removing all classified characteristics, and eliminating the severe hazard posed by the explosives themselves. Transporting such large quantities of classified high explosives for such processing at another site would be prohibitive. Computerized atmospheric modelling of the burning process was conducted during the past year. The results were somewhat surprising in that oxides of nitrogen and carbon monoxide, two ``criteria pollutants,`` were not of great concern even though it is known that high explosives contain significant amounts of nitrogen and they generate measureable amounts of carbon monoxide when they are burned. Rather, it was determined that hydrogen fluoride gas is of much greater concern, and stringent controls on the burning operation have been implemented to address this concern. Although the amount of fluorine-containing explosive must be restricted, other kinds of air emissions are not a great concern. This favorable …
Date: December 31, 1993
Creator: Patterson, W. E. & Phelan, P. F.
System: The UNT Digital Library
A comparison of the evolution of cold and hot deformation microstructures and textures in fcc metals (open access)

A comparison of the evolution of cold and hot deformation microstructures and textures in fcc metals

Microstructures and textures which develop during cold deformation are compared to those which develop during hot deformation. This comparison is made using the evolutionary framework of grain subdivision and the formation of low energy dislocation structures. During deformation grains are subdivided into differently deforming regions separated by geometrically necessary dislocation boundaries. These boundaries include dense dislocation walls, microbands, lamellar boundaries and subgrains. Grain subdivision occurs as a result of the requirement for strain accommodation balanced by energy considerations. This grain subdivision weakens the texture and increases the texture scatter. The tendency for grain subdivision decreases with increasing temperature of deformation with implications for the microstructural evolution and the texture formation.
Date: December 31, 1993
Creator: Hughes, D. A. & Hansen, N.
System: The UNT Digital Library
Solar neutrino experiments: An update (open access)

Solar neutrino experiments: An update

The situation in solar neutrino physics has changed drastically in the past few years, so that now there are four neutrino experiments in operation, using different methods to look at different regions of the solar neutrino energy spectrum. These experiments are the radiochemical {sup 37}Cl Homestake detector, the realtime Kamiokande detector, and the different forms of radiochemical {sup 71}Ga detectors used in the GALLEX and SAGE projects. It is noteworthy that all of these experiments report a deficit of observed neutrinos relative to the predictions of standard solar models (although in the case of the gallium detectors, the statistical errors are still relatively large). This paper reviews the basic principles of operation of these neutrino detectors, reports their latest results and discusses some theoretical interpretations. The progress of three realtime neutrino detectors that are currently under construction, SuperKamiok, SNO and Borexino, is also discussed.
Date: December 31, 1993
Creator: Hahn, R. L.
System: The UNT Digital Library