Partner
UNT Libraries Government Documents Department
313
Oklahoma Historical Society
68
UNT Libraries Special Collections
29
Sterling Municipal Library
11
Carl Albert Congressional Research and Studies Center
7
Alvin Community College
6
San Antonio Public Library
6
Sanger Public Library
5
UNT Libraries
5
UT San Antonio Libraries Special Collections
5
58 More
Collection
Office of Scientific & Technical Information Technical Reports
227
Texas Digital Newspaper Program
127
Oklahoma Digital Newspaper Program
77
Government Accountability Office Reports
62
Tocker Foundation Grant
60
Congressional Research Service Reports
19
Chickasha Newspaper Collection
12
The Gayly Oklahoman
12
Altus Times-Democrat
11
The Baytown Sun
11
97 More
Degree Department
Country
Year
Month
Day
Language
Results:
1 - 24 of
571
next
Oxidation of K-West Basin Spent Nuclear Fuel in Moist Helium Atmosphere
None
Date:
June 15, 1999
Creator:
Abrefah, J. & Sell, R. L.
Object Type:
Report
System:
The UNT Digital Library
ALPS - advanced limiter-divertor plasma-facing systems.
The Advanced Limiter-divertor Plasma-facing Systems (ALPS) program was initiated in order to evaluate the potential for improved performance and lifetime for plasma-facing systems. The main goal of the program is to demonstrate the advantages of advanced limiter/divertor systems over conventional systems in terms of power density capability, component lifetime, and power conversion efficiency, while providing for safe operation and minimizing impurity concerns for the plasma. Most of the work to date has been applied to free surface liquids. A multi-disciplinary team from several institutions has been organized to address the key issues associated with these systems. The main performance goals for advanced limiters and diverters are a peak heat flux of >50 MW/m{sup 2},elimination of a lifetime limit for erosion, and the ability to extract useful heat at high power conversion efficiency ({approximately}40%). The evaluation of various options is being conducted through a combination of laboratory experiments, modeling of key processes, and conceptual design studies. The current emphasis for the work is on the effects of free surface liquids on plasma edge performance.
Date:
September 15, 1999
Creator:
Allain, J. P.; Bastasz, R.; Brooks, J. N.; Evans, T.; Hassanein, A.; Luckhardt, S. et al.
Object Type:
Article
System:
The UNT Digital Library
The Oklahoma Daily (Norman, Okla.), Vol. 83, No. 85, Ed. 1 Friday, January 15, 1999
Student newspaper of the University of Oklahoma in Norman, Oklahoma that includes national, local, and campus news along with advertising.
Date:
January 15, 1999
Creator:
Allam, Heather
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
The Oklahoma Daily (Norman, Okla.), Vol. 83, No. 105, Ed. 1 Monday, February 15, 1999
Student newspaper of the University of Oklahoma in Norman, Oklahoma that includes national, local, and campus news along with advertising.
Date:
February 15, 1999
Creator:
Allam, Heather
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
The Oklahoma Daily (Norman, Okla.), Vol. 83, No. 141, Ed. 1 Thursday, April 15, 1999
Student newspaper of the University of Oklahoma in Norman, Oklahoma that includes national, local, and campus news along with advertising.
Date:
April 15, 1999
Creator:
Allam, Heather
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Sorption and diffusion studies of Pu(IV) and Pu(V)-EDTA onto and through Hanford soil
Plutonium production at U.S. Department of Energy Hanford site has created massive amounts of radioactive and mixed wastes. Over 1.3 trillion liters of liquid waste have been discharged into the ground, the largest part of which has been absorbed by the upper soil layers with a small fraction migrating into the groundwater. Approximately 350 million liters of other low and high-level mixed wastes were stored in underground tanks between 1944 and 1980. These tanks contain organic materials that were introduced during the production and processing of plutonium, such as ethylenediametetraacetic acid (EDTA), tributyl phosphate, hexone, paraffin hydrocarbon and other minor organic and inorganic components. The quantity of EDTA is estimated to be 83 metric tons in the underground tanks. Several single-shell tanks are known or suspected to have leaked. It was reported that since 1995, approximately four million liters of mixed waste might have entered the soil beneath the single-shell tanks. This volume of waste is estimated to contain as much as one million curies of radioactivity.
Date:
September 15, 1999
Creator:
Allen, P G; Hakem, N L & Sylwester, E R
Object Type:
Article
System:
The UNT Digital Library
Origin of the Time-Dependence of Wet Oxidation of AlGaAs
The time-dependence of the wet oxidation of high-Al-content AlGaAs can be either linear, indicating reaction-rate limitation, or parabolic, indicating diffusion-limited rates. The transition from linear to parabolic time dependence can be explained by the increased rate of the formation of intermediate As{sub 2}O{sub 3} vs. its reduction to elemental As. A steadily increasing thickness of the As{sub 2}O{sub 3}-containing region at the oxidation front will shift the process from the linear to the parabolic regime. This shift from reaction-rate-limited (linear) to diffusion-limited (parabolic) time dependence is favored by increasing temperature or increasing Al mole fraction.
Date:
February 15, 1999
Creator:
Allerman, A. A.; Ashby, C. I. H.; Bridges, M. M.; Hammons, B. E. & Hou, H. Q.
Object Type:
Article
System:
The UNT Digital Library
GaAs Self-Aligned JFETS with Carbon-Doped P+ Region
Self-aligned JFETs with a carbon-doped p{sup +} region have been reported for the first time. For these JFETs, both the channel and p{sup +} region were grown by metal organic chemical vapor deposition (MOCVD) and are termed epitaxial JFETs in this study. The epitaxial JFETs were compared to ion implanted JFETs of similar channel doping and threshold voltage. Both JFETs were fabricated using the same self-aligned process for doping the source and drain regions of the JFET and for eliminating excess gate capacitance of conventional JFETs. The gate turn-on voltage for the epitaxial JFETs was 1.06 V, about 0.1 V higher than for the implanted JFETs. The reverse breakdown voltage was similar for both JFETs but the reverse gate leakage current of the epitaxial JFETs was 1-3 orders of magnitude less than the implanted JFETs. The epitaxial JFETs also showed higher transconductance and lower knee voltage than the implanted JFETs.
Date:
February 15, 1999
Creator:
Allerman, A. A.; Baca, A. G.; Chang, P. C. & Drummond, T. J.
Object Type:
Article
System:
The UNT Digital Library
Antiprotons and the Crystal Ball
During the 1998 running of the Crystal Ball experiment, a couple of brief test runs were done with the C6 beamline tuned to produce antiprotons. Specifically, one shift on July 29th produced runs 329-334 with the beam momentum set for 650 MeV/c, run 355 was done on July 31st with a 550 MeV/c beam momentum, and run 926-929 were obtained in a single shift on November 3rd, also with a beam momentum of 550 MeV/c. The beam tune for the November data was greatly superior to that of the July data, however. Therefore, only the November data have been analyzed in detail, and the results of this analysis are presented in this note. Due to the paucity of statistics that were obtained, it was decided not to attempt to publish the results. However, the results are valuable as a tool for planning a possible future program of dedicated measurements of antiproton-proton annihilation into all-neutral final states using the Crystal Ball. The data in fact show that the Crystal Ball with its large angular acceptance and multi-photon capability would be an excellent detector for such an experiment. Only one other such experiment (the Crystal Barrel experiment at CERN/LEAR) has ever been …
Date:
November 15, 1999
Creator:
Allgower, C. & Peaslee, D.
Object Type:
Report
System:
The UNT Digital Library
Multiscale modeling of radiation effects in fcc and bcc metals
The prospect of using computer simulations to calculate radiation-induced defect production and its influence on microstructure evolution and mechanical property changes during prolonged irradiation of nuclear materials has been a beckoning, yet elusive goal for many years. However, the enormous progress achieved in computational physics for calculating reliable, yet tractable interatomic potentials, coupled with vast improvements in computational power have brought this hope to near reality. In order to develop modeling and simulation tools for predicting the irradiation response of nuclear structural materials, models must be implemented and tested across all relevant length and time scales. We discuss the development and implementation of a modeling methodology that consists of the linkage and hierarchical use of ab initio electronic structure calculations, molecular dynamics (MD) simulations, and kinetic Monte Carlo (KMC) simulations. This methodology can describe length and time scales from nanometers to hundreds of microns and from picoseconds to years, respectively. The ideas are demonstrated in two applications. First, we describe simulations that describe the irradiation and subsequent isochronal annealing of Pb, a low melting point fcc metal, and compare the results to experiments. Second, we show how these methods can be used to investigate damage production and freely migrating defect …
Date:
July 15, 1999
Creator:
Alonso, E; Caturla, M; Diaz de la Rubia, T; Felter, T; Fluss, M; Perlado, J et al.
Object Type:
Article
System:
The UNT Digital Library
Phonon density of states in Fe/Cr (001) superlattices and Tb-Fe thin-film alloys.
Inelastic nuclear scattering of X-rays from the 14.413 keV nuclear resonance of {sup 57}Fe was employed to measure directly the Fe-projected phonon density of states (DOS) in MBE-grown Fe/Cr(00l) superlattices on MgO(001). The Moessbauer-inactive {sup 56}Fe isotope was used in the Fe layers. A 1{angstrom} thick Moessbauer-active {sup 57}Fe-probe layer (95% enriched) was placed at different locations within the Fe layers. This procedure permits one to distinguish phonon density of states at the Fe-Cr-interface from that at the center of the Fe-film. Distinct differences have been observed in the DOS of our samples. The phonon DOS of an amorphous Tb{sub 33}Fe{sub 67} alloy film was found to be a broad and structureless hump, contrary to that of an epitaxial TbFe{sub 2} film, which exhibits characteristic features.
Date:
February 15, 1999
Creator:
Alp, E. E.; Keune, W.; Roehlsberger, R.; Ruckert, T.; Schror, H. & Sturhahn, W.
Object Type:
Article
System:
The UNT Digital Library
A Hybrid Hydrologic-Geophysical Inverse Technique for the Assessment and Monitoring of Leachates in the Vadose Zone
The objective of this study is to develop and field test a new, integrated Hybrid Hydrologic-Geophysical Inverse Technique (HHGIT) for characterization of the vadose zone at contaminated sites. This new approach to site characterization and monitoring can provide detailed maps of hydrogeological heterogeneity and the extent of contamination by combining information from 3D electric resistivity tomography (ERT) and/or 2D cross borehole ground penetrating radar (XBGPR) surveys, statistical information about heterogeneity and hydrologic processes, and sparse hydrologic data. Because the electrical conductivity and dielectric constant of the vadose zone (from the ERT and XBGPR measurements, respectively) can be correlated to the fluid saturation and/or contaminant concentration, the hydrologic and geophysical measurements are related.
Date:
June 15, 1999
Creator:
Alumbaugh, David L.; Yeh, Jim; Labrecque, Doug; Glass, Robert J.; Brainard, James & Rautman, Chris
Object Type:
Report
System:
The UNT Digital Library
New experiments elucidating the current limiting mechanisms of Ag-sheathed (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} tapes.
Multiple current limiting mechanisms exist from the nanometer to millimeter scale in Ag-sheathed (Bi,Pb)-2223 tapes. Recent studies of the zero-field critical current density (J{sub c} (0T, 77K)), the irreversibility field (H*) and the crack microstructure elucidate these properties. We show that H*(77K) can vary significantly over the range {approximately}120-260 mT, independently of J{sub c} (0T, 77K). Cracks, actual or incipient, exist on the sub to several hundred micron scale. Surface magneto optical imaging of whole tapes, correlated to subsequent ultrasonic fracture analysis of. the bare 2223 filaments extracted by dissolving away the Ag shows that even composites having J{sub c} (0T, 77K) values of 60 kA/cm{sup 2} exhibit strong signs of unhealed rolling damage. These combined studies show that today's very best 2223 tapes are still far from full optimization.
Date:
January 15, 1999
Creator:
Anderson, J. W.; Babcock, S. E.; Cai, X. Y.; Dorris, S. E.; Feldmann, M.; Jiang, J. et al.
Object Type:
Article
System:
The UNT Digital Library
Exploiting the power of DSM and SMP clusters for parallel CFD
The new generation of powerful DSM and SMP cluster computers enables simulations of fluid dynamics at sufficient resolution to compute the complex nonlinear interactions of small-scale turbulent motions with a large-scale driving flow. With a new programming model of hierarchical shared memory multitasking, it is possible to exploit these new systems without disrupting the flow of small and medium-sized jobs that makes their existence possible.
Date:
March 15, 1999
Creator:
Anderson, S. E.; Cohen, R. H.; Curtis, B. C.; Dannevik, W. P.; Dimits, A. M.; Dinge, D. et al.
Object Type:
Article
System:
The UNT Digital Library
Ultrasonic Velocities in Unconsolidated Sand/Clay Mixtures at Low Pressures
Effective seismic interrogation of the near subsurface requires that measured parameters, such as compressional and shear velocities and attenuation, be related to important soil properties. Porosity, composition (clay content), fluid content and type are of particular interest. The ultrasonic (100-500 kHz) pulse transmission technique was used to collect data for highly attenuating materials appropriate to the vadose zone. Up to several meters of overburden were simulated by applying low uniaxial stress of 0 to about 0.1 MPa to the sample. The approach was to make baseline measurements for pure quartz sand, because the elastic properties are relatively well known except at the lowest pressures. Clay was added to modify the sample microstructure and ultrasonic measurements were made to characterize the effect of the admixed second phase. Samples were fabricated from Ottawa sand mixed with a swelling clay (Wyoming bentonite). The amount of clay added was 1 to 40% by mass. Compressional (P) velocities are low (228-483 m/s), comparable to the sound velocity in air. Shear (S) velocities are about half of the compressional velocity (120-298 m/s), but show different sensitivity to microstructure. Adding clay increases the shear amplitude dramatically with respect to P, and also changes the sensitivity of the …
Date:
October 15, 1999
Creator:
Aracne-Ruddle, C. M.; Bonner, B. P.; Trombino, C. N.; Hardy, E. D.; Berge, P. A.; Boro, C. O. et al.
Object Type:
Article
System:
The UNT Digital Library
Early Inflation and Cosmology in Theories with Sub-Millimeter Dimensions
We discuss early cosmology in theories where the fundamental Planck mass is close to the TeV scale. In such theories the standard model fields are localized to a (3 + 1)-dimensional wall with n new transverse sub-millimeter sized spatial dimensions. The topics touched upon include: early inflation that occurs while the size of the new dimensions are still small, the spectrum and magnitude of density perturbations, the post-inflation era of contraction of our world while the internal dimensions evolve to their final ''large'' radius, and the production of gravitons in the bulk during these two eras. The radion moduli problem is also discussed.
Date:
March 15, 1999
Creator:
Arkani-Hamed, Nima
Object Type:
Report
System:
The UNT Digital Library
Rapid asymmetric inflation and early cosmology in theories with sub-millimeter dimensions
It was recently pointed out that the fundamental Planck mass could be close to the TeV scale with the observed weakness of gravity at long distances being due the existence of new sub-millimeter spatial dimensions. In this picture the standard model fields are localized to a (3+1)-dimensional wall or ''3-brane''. We show that in such theories there exist attractive models of inflation that occur while the size of the new dimensions are still small. We show that it is easy to produce the required number of efoldings, and further that the density perturbations {delta}{rho}/{rho} as measured by COBE can be easily reproduced, both in overall magnitude and in their approximately scale-invariant spectrum. In the minimal approach, the inflaton field is just the moduli describing the size of the internal dimensions, the role of the inflationary potential being played by the stabilizing potential of the internal space. We show that under quite general conditions, the inflationary era is followed by an epoch of contraction of our world on the brane, while the internal dimensions slowly expand to their stabilization radius. We find a set of exact solutions which describe this behavior, generalizing the well-known Kasner solutions. During this phase, the production …
Date:
March 15, 1999
Creator:
Arkani-Hamed, Nima
Object Type:
Report
System:
The UNT Digital Library
The FEL development at the Advanced Photon Source.
Construction of a single-pass free-electron laser (FEL) based on the self-amplified spontaneous emission (SASE) mode of operation is nearing completion at the Advanced Photon Source (APS) with initial experiments imminent. The APS SASE FEL is a proof-of-principle fourth-generation light source. As of January 1999 the undulator hall, end-station building, necessary transfer lines, electron and optical diagnostics, injectors, and initial undulatory have been constructed and, with the exception of the undulatory, installed. All preliminary code development and simulations have also been completed. The undulator hall is now ready to accept first beam for characterization of the output radiation. It is the project goal to push towards fill FEL saturation, initially in the visible, but ultimately to W and VUV, wavelengths.
Date:
March 15, 1999
Creator:
Arnold, N. D.; Benson, C.; Berg, S.; Berg, W.; Biedron, S. G.; Chae, Y. C. et al.
Object Type:
Article
System:
The UNT Digital Library
Atmospheric Radiation Measurement Program Facilities Newsletter, June 1999.
Monthly newsletter discussing news and activities related to the Atmospheric Radiation Measurement Program, articles about weather and atmospheric phenomena, and other related topics.
Date:
July 15, 1999
Creator:
Atmospheric Radiation Measurement Program (U.S.)
Object Type:
Journal/Magazine/Newsletter
System:
The UNT Digital Library
Anomalies
I discuss the role of anomalies in the modern development of quantum field theory and their implications for physics.
Date:
February 15, 1999
Creator:
Bardeen, William A.
Object Type:
Article
System:
The UNT Digital Library
Weak matrix elements in the large N{sub c} limit
The matrix elements of the four quark operators needed to predict many weak interaction processes can be evaluated using the large N{sub c} limit of quantum chromodynamics. At leading order in the large N{sub c} expansion, the weak matrix elements of four quark operators factorize into independent matrix elements of two quark operators, a common approximation being used today. At the next leading order, the weak matrix elements acquire the leading scale and scheme dependence expected for these matrix elements in full QCD. They discuss methods to evaluate these matrix elements which involve matching perturbative QCD calculations at short distance to non-perturbative hadronic matrix elements at long distance.
Date:
October 15, 1999
Creator:
Bardeen, William A.
Object Type:
Article
System:
The UNT Digital Library
News Bulletin (Castroville, Tex.), Vol. 41, No. 15, Ed. 1 Thursday, April 15, 1999
Weekly newspaper from Castroville, Texas that includes local, state, and national news along with extensive advertising.
Date:
April 15, 1999
Creator:
Barnes, Thomas
Object Type:
Newspaper
System:
The Portal to Texas History
News Bulletin (Castroville, Tex.), Vol. 41, No. 28, Ed. 1 Thursday, July 15, 1999
Weekly newspaper from Castroville, Texas that includes local, state, and national news along with extensive advertising.
Date:
July 15, 1999
Creator:
Barnes, Thomas
Object Type:
Newspaper
System:
The Portal to Texas History
High Frequency Mechanical Pyroshock Simulations for Payload Systems
Sandia National Laboratories (SNL) designs mechanical systems with components that must survive high frequency shock environments including pyrotechnic shock. These environments have not been simulated very well in the past at the payload system level because of weight limitations of traditional pyroshock mechanical simulations using resonant beams and plates. A new concept utilizing tuned resonators attached to the payload system and driven with the impact of an airgun projectile allow these simulations to be performed in the laboratory with high precision and repeatability without the use of explosives. A tuned resonator has been designed and constructed for a particular payload system. Comparison of laboratory responses with measurements made at the component locations during actual pyrotechnic events show excellent agreement for a bandwidth of DC to 4 kHz. The bases of comparison are shock spectra. This simple concept applies the mechanical pyroshock simulation simultaneously to all components with the correct boundary conditions in the payload system and is a considerable improvement over previous experimental techniques and simulations.
Date:
December 15, 1999
Creator:
Bateman, Vesta I.; Brown, Frederick A.; Cap, Jerome S. & Nusser, Michael A.
Object Type:
Article
System:
The UNT Digital Library