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Phase Diagram of Iron, Revised-Core Temperatures
Shock-wave experiments on iron preheated to 1,573 K conducted from 14 to 73 GPa, yield new data for sound velocities of the {gamma}- and liquid-phases. Melting was observed in the highest pressure ({approximately} 71 {+-} 2 GPa) experiments at calculated shock temperatures of 2,775 {+-} 160 K. This single crossing of the {gamma}-liquid boundary measured here agrees closely with the {gamma}-iron melting line determined by Boehler [1993], Saxena et al. [1993], and Jephcoat and Besedin [1997]. This {gamma}-iron melting curve is {approximately} 300 C lower than that of Shen et al. [1998b] at 80 GPa.
Date:
January 27, 1999
Creator:
Ahrens, T.J.; Chen, G.Q. & Holland, K.G.
Object Type:
Article
System:
The UNT Digital Library
Adaptive optics high resolution spectroscopy: present status and future direction
High resolution spectroscopy experiments with visible adaptive optics (AO) telescopes at Starfire Optical Range and Mt. Wilson have demonstrated that spectral resolution can be routinely improved by a factor of - 10 over the seeing-limited case with no extra light losses at visible wavelengths. With large CCDs now available, a very wide wavelength range can be covered in a single exposure. In the near future, most large ground-based telescopes will be equipped with powerful A0 systems. Most of these systems are aimed primarily at diffraction-limited operation in the near IR. An exciting new opportunity will thus open up for high resolution IR spectroscopy. Immersion echelle gratings with much coarser grooves being developed by us at LLNL will play a critical role in achieving high spectral resolution with a compact and low cost IR cryogenically cooled spectrograph and simultaneous large wavelength coverage on relatively small IR detectors. We have constructed a new A0 optimized spectrograph at Steward Observatory to provide R = 200,000 in the optical, which is being commissioned at the Starfire Optical Range 3.5m telescope. We have completed the optical design of the LLNL IR Immersion Spectrograph (LISPEC) to take advantage of improved silicon etching technology. Key words: adaptive …
Date:
July 27, 1999
Creator:
Alcock, C.; Angel, R.; Ciarlo, D.; Fugate, R. O.; Ge, J.; Kuzmenko, P. et al.
Object Type:
Article
System:
The UNT Digital Library
The Oklahoma Daily (Norman, Okla.), Vol. 83, No. 92, Ed. 1 Wednesday, January 27, 1999
Student newspaper of the University of Oklahoma in Norman, Oklahoma that includes national, local, and campus news along with advertising.
Date:
January 27, 1999
Creator:
Allam, Heather
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
The Oklahoma Daily (Norman, Okla.), Vol. 83, No. 151, Ed. 1 Tuesday, April 27, 1999
Student newspaper of the University of Oklahoma in Norman, Oklahoma that includes national, local, and campus news along with advertising.
Date:
April 27, 1999
Creator:
Allam, Heather
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Highly-Efficient Laser with Self-Aligned Waveguide and Current Confinement by Selective Oxidation
We report highly efficient, low-threshold-current edge-emitting lasers where both the optical waveguide and lateral current confinement are achieved by lateral selective oxidation of AlGaAs. External differential quantum efficiency in excess of 95% and 40% wall-plug efficiency are demonstrated in 600 {micro}m-long devices without facet coatings. Shorter, 300-{micro}m-long, uncoated devices have <6 mA threshold currents. This high-performance is a combined result of placement of the oxide layers so as to achieve the minimum optical mode volume and bi-parabolic grading of the Al{sub x}Ga{sub 1{minus}x}As heteroepitaxy for minimum height/potential barriers, less than 15 meV, created by the wide-energy-gap layers required for selective wet oxidation. Since the initial development of wet AlGaAs oxidation methods, a number of oxidized edge-emitting laser concepts have been tried. The most successful of these have used lateral selective oxidation of AlGaAs layers between 100 and 300 nm thickness. These layers have been used as current restricting apertures or for both current restriction and lateral waveguiding. Use of an oxide layer above and below the laser active region offers the ability to create a self-aligned waveguide with current apertures on both sides of the pn-junction in a process requiring only one epitaxial growth step. Previous use apertures for these …
Date:
July 27, 1999
Creator:
Allerman, A.; Blum, O.; Gao, Y. & Vawter, G. A.
Object Type:
Article
System:
The UNT Digital Library
Two-Element Phased Array of Anti-Guided Vertical-Cavity Lasers
We demonstrate for the first time anti-guided coupling of two adjacent vertical-cavity surface-emitting lasers (VCSEL's), obtaining a 1-by-2 phase-locked array at 869 nm. The lateral index modification required for anti-guiding is achieved by a patterned 3-rim etch performed between two epitaxial growths. In contrast with prior evanescently coupled VCSEL's, adjacent anti-guided VCSEL's can emit in-phase and produce a single on-axis lobe in the far field. Greater than 2 mW of in-phase output power is demonstrated with two VCSEL's separated by 8 {micro}m. Moreover, phase locking of two VCSEL's separated by 20 {micro}m is observed, indicating the possibility of a new class of optical circuits based upon VCSEL's that interact horizontally and emit vertically.
Date:
September 27, 1999
Creator:
Allerman, Andrew A.; Choquette, Kent D.; Geib, Kent M.; Hadley, G. Ronald & Serkland, Darwin K.
Object Type:
Article
System:
The UNT Digital Library
Domain decomposition methods for a parallel Monte Carlo transport code
Achieving parallelism in simulations that use Monte Carlo transport methods presents interesting challenges. For problems that require domain decomposition, load balance can be harder to achieve. The Monte Carlo transport package may have to operate with other packages that have different optimal domain decompositions for a given problem. To examine some of these issues, we have developed a code that simulates the interaction of a laser with biological tissue; it uses a Monte Carlo method to simulate the laser and a finite element model to simulate the conduction of the temperature field in the tissue. We will present speedup and load balance results obtained for a suite of problems decomposed using a few domain decomposition algorithms we have developed.
Date:
January 27, 1999
Creator:
Alme, H J; Rodrigue, G H & Zimmerman, G B
Object Type:
Article
System:
The UNT Digital Library
A Numerical Analysis of 3D EM Imaging from a Single Borehole
In this study we analyze the feasibility of three dimensional (3D) electromagnetic (EM) imaging from a single borehole. The proposed logging tool consists of three mutually orthogonal magnetic dipole sources and multiple three component magnetic field receivers. A sensitivity analysis indicates that the most important sensor configuration for providing 3D geological information about the borehole consists of a transmitter with moment aligned parallel to the axis of the borehole, and receivers aligned perpendicular to the axis. The standard coaxial logging configuration provides the greatest depth of sensitivity compared to other configurations, but offers no information regarding 3D structure. Two other tool configurations in which both the source and receiver are aligned perpendicular to the borehole axis provide some directional information and therefore better image resolution, but not true 3D information. A 3D inversion algorithm has been employed to demonstrate the plausibility of 3D inversion using data collected with the proposed logging tool. This study demonstrates that an increase in image resolution results when three orthogonal sources are incorporated into the logging tool rather than a single axially aligned source.
Date:
July 27, 1999
Creator:
Alumbaugh, David L. & Wilt, Michael J.
Object Type:
Article
System:
The UNT Digital Library
Diffractive results from the Tevatron
Hard diffraction in events with dijets and rapidity gaps has been studied by D0 and CDF for three processes: hard color singlet exchange, hard single diffraction, and hard double pomeron exchange, using Tevatron {anti p}p data at {radical}s = 630 GeV and 1.8 TeV. Measurements of rates, {eta}, E{sub T} and {radical}s dependencies are presented and comparisons made with predictions of several models.
Date:
May 27, 1999
Creator:
Alves, Gilvan A.
Object Type:
Article
System:
The UNT Digital Library
A Method for Treating Discretization Error in Nondeterministic Analysis
A response surface methodology-based technique is presented for treating discretization error in non-deterministic analysis. The response surface, or metamodel, is estimated from computer experiments which vary both uncertain physical parameters and the fidelity of the computational mesh. The resultant metamodel is then used to propagate the variabilities in the continuous input parameters, while the mesh size is taken to zero, its asymptotic limit. With respect to mesh size, the metamodel is equivalent to Richardson extrapolation, in which solutions on coarser and finer meshes are used to estimate discretization error. The method is demonstrated on a one dimensional prismatic bar, in which uncertainty in the third vibration frequency is estimated by propagating variations in material modulus, density, and bar length. The results demonstrate the efficiency of the method for combining non-deterministic analysis with error estimation to obtain estimates of total simulation uncertainty. The results also show the relative sensitivity of failure estimates to solution bias errors in a reliability analysis, particularly when the physical variability of the system is low.
Date:
January 27, 1999
Creator:
Alvin, Kenneth F.
Object Type:
Article
System:
The UNT Digital Library
Costs of Storing and Transporting Hydrogen
An analysis was performed to estimate the costs associated with storing and transporting hydrogen. These costs can be added to a hydrogen production cost to determine the total delivered cost of hydrogen. Storage methods analyzed included compressed gas, liquid hydrogen, metal hydride, and underground storage. Major capital and operating costs were considered over a range of production rates and storage times.
Date:
January 27, 1999
Creator:
Amos, W. A.
Object Type:
Report
System:
The UNT Digital Library
Electrostriction in Field-Structured Composites: Basis for a Fast Artificial Muscle?
The electrostriction of composites consisting of dielectric particles embedded in a gel or elastomer is discussed. It is shown that when these particles are organized by a uniaxial field before gelation, the resulting field-structured composites are expected to exhibit enhanced electrostriction in a uniform field applied along the same axis as the structuring field. The associated stresses might be large enough to form the basis of a polymer-based fast artificial muscle.
Date:
January 27, 1999
Creator:
Anderson, R. A. & Martin, J. E.
Object Type:
Article
System:
The UNT Digital Library
Titanium K-Shell X-Ray Production from High Velocity Wire Arrays Implosions on the 20-MA Z Accelerator
The advent of the 20-MA Z accelerator [R.B. Spielman, C. Deeney, G.A. Chandler, et al., Phys. Plasmas 5, 2105, (1997)] has enabled implosions of large diameter, high-wire-number arrays of titanium to begin testing Z-pinch K-shell scaling theories. The 2-cm long titanium arrays, which were mounted on a 40-mm diameter, produced between 75{+-}15 to 125{+-}20 kJ of K-shell x-rays. Mass scans indicate that, as predicted, higher velocity implosions in the series produced higher x-ray yields. Spectroscopic analyses indicate that these high velocity implosions achieved peak electron temperatures from 2.7{+-}0.1 to 3.2{+-}0.2 keV and obtained a K-shell emission mass participation of up to 12%.
Date:
January 27, 1999
Creator:
Apruzese, J.P.; Beg, F.N.; Clark, R.C.; Coverdale, C.A.; Davis, J.; Deeney, C. et al.
Object Type:
Article
System:
The UNT Digital Library
Dynamics of Wet Oxidation of High-AL-Content III-V Materials
Oxidation of layers of high-Al-content III-V materials by water vapor has become the enabling process for high-efficiency vertical cavity surface emitting lasers (VCSELS) and has potential applications for reducing substrate current leakage in GaAs-on-insulator (GOI) MESFETS. Because of the established importance of wet oxidation in optoelectronic devices and its potential applications in electronic devices, it has become increasingly important to understand the mechanism of wet oxidation and how it might be expected to affect both the fabrication and subsequent operation of devices that have been made using this technique. The mechanism of wet oxidation and the consequence of this mechanism for heterostructure design and ultimate device operation are discussed here.
Date:
January 27, 1999
Creator:
Ashby, C.I.H.
Object Type:
Article
System:
The UNT Digital Library
Practical superconductor development for electrical power applications annual report for FY 1998.
Development of useful high-T{sub c} superconductors requires synthesis of superconducting compounds; fabrication of wires, tapes, and films from these compounds; production of composite structures that incorporate stabilizers or insulators; and design and testing of efficient components. This report describes FY 1998 technical progress of research and development efforts aimed at producing superconducting components in the Bi-(Pb)-Sr-Ca-Cu and Y-Ba-Cu oxide systems. Topics discussed are synthesis and heat treatment of high-T{sub c} superconductors, formation of monolithic and composite conductors, characterization of structures and superconducting and mechanical properties, and fabrication and testing of prototype components. Collaborations with industry and academia are documented.
Date:
January 27, 1999
Creator:
Askew, T. R.; Balachandran, U.; Cha, Y. S.; Dorris, S. E.; Dusek, J. T.; Emerson, J. E. et al.
Object Type:
Report
System:
The UNT Digital Library
Polymer Aging Techniques Applied to Degradation of a Polyurethane Propellant Binder
The oxidative thermal aging of a crosslinked hydroxy-terminated polybutadiene (HTPB)/isophorone diisocyanate (IPDI) polyurethane rubber, commonly used as the polymeric binder matrix in solid rocket propellants, was studied at temperatures of RT to 125 C. We investigate changes in tensile elongation, mechanical hardening, polymer network properties, density, O{sub 2} permeation and molecular chain dynamics using a range of techniques including solvent swelling, detailed modulus profiling and NMR relaxation measurements. Using extensive data superposition and highly sensitive oxygen consumption measurements, we critically evaluate the Arrhenius methodology, which normally assumes a linear extrapolation of high temperature aging data. Significant curvature in the Arrhenius diagram of these oxidation rates was observed similar to previous results found for other rubber materials. Preliminary gel/network properties suggest that crosslinking is the dominant process at higher temperatures. We also assess the importance of other constituents such as ammonium perchlorate or aluminum powder in the propellant formulation.
Date:
July 27, 1999
Creator:
Assink, R. A.; Celina, M.; Graham, A. C. & Minier, L. M.
Object Type:
Article
System:
The UNT Digital Library
Atmospheric Radiation Measurement Program Facilities Newsletter, September 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:
September 27, 1999
Creator:
Atmospheric Radiation Measurement Program (U.S.)
Object Type:
Journal/Magazine/Newsletter
System:
The UNT Digital Library
Multitasking TORT Under UNICOS: Parallel Performance Models and Measurements
The existing parallel algorithms in the TORT discrete ordinates were updated to function in a UNI-COS environment. A performance model for the parallel overhead was derived for the existing algorithms. The largest contributors to the parallel overhead were identified and a new algorithm was developed. A parallel overhead model was also derived for the new algorithm. The results of the comparison of parallel performance models were compared to applications of the code to two TORT standard test problems and a large production problem. The parallel performance models agree well with the measured parallel overhead.
Date:
September 27, 1999
Creator:
Azmy, Y. Y. & Barnett, D. A.
Object Type:
Article
System:
The UNT Digital Library
Improving the Accuracy of High-Order Nodal Transport Methods
This paper outlines some recent advances towards improving the accuracy of neutron calculations using the Arbitrarily High Order Transport-Nodal (AHOT-N) Method. These transport advances consist of several contributions: (a) A formula for the spatial weights that allows for the polynomial order to be raised arbitrarily high without suffering from pollution from round-off, error; (b) A reconstruction technique for the angular flux, based upon a recursive formula, that reduces the pointwise error by one order; (c) An a posterior error indicator that estimates the true error and its distribution throughout the domain, so that it can be used for adaptively reftig the approximation. Present results are mainly for ID, extension to 2D-3D is in progress.
Date:
September 27, 1999
Creator:
Azmy, Y. Y.; Buscaglia, G. C. & Zamonsky, O. M.
Object Type:
Article
System:
The UNT Digital Library
Effect of Material Heterogeneity on the Performance of DSA for Even-Parity S<sub>n</sub> Methods
A spectral analysis is conducted for the Source Iteration (SI), and Diffusion Synthetic Acceleration (DSA) operators previously formulated for solving the Even-Parity Method (EPM) equations. In order to accommodate material heterogeneity, the analysis is performed for the Periodic Horizontal Interface (PHI) configuration. The dependence of the spectral radius on the optical thickness of the two PHI layers illustrates the deterioration in the rate of convergence with increasing material discontinuity, especially when one of the layers approaches a void. The rate at which this deterioration occurs is determined for a specific material discontinuity in order to demonstrate the conditional robustness of the EPM-DSA iterations. The results of the analysis are put in perspective via numerical tests with the DANTE code (MCGhee, et al., 1997) which exhibits a deterioration in the spectral radius consitent with the theory.
Date:
September 27, 1999
Creator:
Azmy, Y.Y.; Morel, J. & Wareing, T.
Object Type:
Article
System:
The UNT Digital Library
Effect of Material Homogeneity on the Performance of DSA for Even-Parity S<sub>n</sub> Methods
A spectral analysis is conducted for the Source Iteration (SI), and Diffusion Synthetic Acceleration (DSA) operators previously formulated for solving the Even-Parity Method (EPM) equations. In order to accommodate material heterogenity, the analysis is performed for the Periodic Horizontal Interface (PHI) configuration. The dependence of the spectral radius on the optical thickness of the two PHI layers illustrates the deterioration in the rate of convergence with increasing material discontinuity, especially when one of the layers approaches a void. The rate at which this deterioration occurs is determined for a specific material discontinuity in order to demonstrate the conditional robustness of the EPM-DSA iterations. The results of the analysis are put in perspective via numerical tests with the DANTE code (McGhee, et. al., 1997) which exhibits a deterioration in the spectral radius consistent with the theory.
Date:
September 27, 1999
Creator:
Azmy, Y.Y.; Morel, J. & Wareing, T.
Object Type:
Article
System:
The UNT Digital Library
DETECTOR BACKGROUNDS FOR A HIGH ENERGY MUON COLLIDER.
None
Date:
September 27, 1999
Creator:
BENARY,O.
Object Type:
Article
System:
The UNT Digital Library
The Graft Tool: An All-Hexahedral Transition Algorithm for Creating a Multi-Directional Swept Volume Mesh
Sweeping algorithms have become very mature and can create a semi-structured mesh on a large set of solids. However, these algorithms require that all linking surfaces be mappable or submappable. This restriction excludes solids with imprints or protrusions on the linking surfaces. The grafting algorithm allows these solids to be swept. It then locally modifies the position and connectivity of the nodes on the linking surfaces to align with the graft surfaces. Once a high-quality surface mesh is formed on the graft surface, it is swept along the branch creating a 2 3/4-D mesh.
Date:
September 27, 1999
Creator:
BENZLEY,STEVEN E.; JANKOVICH,STEVEN R.; MITCHELL,SCOTT A. & SHEPHERD,JASON F.
Object Type:
Article
System:
The UNT Digital Library
A Method for Controlling Skew on Linked Surfaces
A new method for lessening skew in mapped meshes is presented. This new method involves progressive subdivision of a surface into loops consisting of four sides. Using these loops, constraints can then be set on the curves of the surface, which will propagate interval assignments across the surface, allowing a mesh with a better skew metric to be generated.
Date:
September 27, 1999
Creator:
BENZLEY,STEVEN E.; KERR,ROBERT A.; MITCHELL,SCOTT A. & WHITE,DAVID R.
Object Type:
Article
System:
The UNT Digital Library