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Quantum Monte Carlo simulations of disordered magnetic and superconducting materials

Description: Over the last decade, Quantum Monte Carlo (QMC) calculations for tight binding Hamiltonians like the Hubbard and Anderson lattice models have made the transition from addressing abstract issues concerning the effects of electron-electron correlations on magnetic and metal-insulator transitions, to concrete contact with experiment. This paper presents results of applications of �determinant� QMC to systems with disorder such as the conductivity of thin metallic films, the behavior of the magneti… more
Date: January 28, 1998
Creator: Scalettar, R. T.
Partner: UNT Libraries Government Documents Department
open access

Aqueous oxidation of trichloroethene (TCE): a kinetic and thermodynamic analysis

Description: An empirical kinetic rate law was determined for the aqueous oxidation of trichloroethene (TCE). By measuring both the rate of disappearance of TCE and the rate of appearance of carbon dioxide and chloride ion, mass balances were monitored to confirm that `mineralization` was the ultimate reaction. Dilute buffer solutions were used to fix pH and stoichiometrically sufficient amounts of dissolved oxygen were used to make the reactions zero-order in oxygen. Using standard chemical kinetic methods… more
Date: February 28, 1998
Creator: Knauss, K. G., LLNL
Partner: UNT Libraries Government Documents Department
open access

Effect of Fluid Flow on Inclusion Coarsening in Low-Alloy Steel Welds

Description: Oxide inclusions form in welds because of deoxidation reactions in the weld pool. These inclusions control the weld microstructure development. Thermodynamic and kinetic calculation of oxidation reaction can describe inclusion characteristics such as number density, size, and composition. Experimental work has shown that fluid-flow velocity gradients in the weld pool can accelerate inclusion growth by collision and coalescence. Moreover, fluid flow in welds can transport inclusions to different… more
Date: February 28, 1998
Creator: Babu, S.S.; David, S.A.; DebRoy, T. & Hong, T.
Partner: UNT Libraries Government Documents Department
open access

First Annual Meeting of the Institute of Multifluid Science and Technology (IMUST)

Description: This report consists of summaries of the 6 Action Items from the first annual meeting. The 6 Action Items are: (1) to aggressively pursue ''Education'' in multiphase flow; (2) to pursue the work on dispersed flows presented in the last meeting to conclusions; (3) to focus the next meeting on flow regimes; (4) to pursue cooperative efforts toward identifying and settling key flow regime issues; (5) to pursue cooperative efforts towards the understanding and development of design tools, for multi… more
Date: February 28, 1998
Partner: UNT Libraries Government Documents Department
open access

Less minimal supersymmetric standard model

Description: Most of the phenomenological studies of supersymmetry have been carried out using the so-called minimal supergravity scenario, where one assumes a universal scalar mass, gaugino mass, and trilinear coupling at M{sub GUT}. Even though this is a useful simplifying assumption for phenomenological analyses, it is rather too restrictive to accommodate a large variety of phenomenological possibilities. It predicts, among other things, that the lightest supersymmetric particle (LSP) is an almost pure … more
Date: March 28, 1998
Creator: de Gouvea, Andre; Friedland, Alexander & Murayama, Hitoshi
Partner: UNT Libraries Government Documents Department
open access

Assuring safety in the National Ignition Facility

Description: The National Ignition Facility (NIF) is a US Department of Energy inertial confinement laser fusion facility currently under construction at the Lawrence Livermore National Laboratory (LLNL). The NIF mission is to achieve inertial confinement fusion (ICF) ignition, access physical conditions in matter of interest to nuclear weapons effects testing, contribute to the development of inertial fusion for electrical power production, and to support basic science and technology.
Date: April 28, 1998
Creator: Becker, D R; Brereton, S J; Brumburgh, G P; Pryatel, J A; Wolfe, C R & Yatabe, J M
Partner: UNT Libraries Government Documents Department
open access

Curvature of a cantilever beam subjected to an equi-biaxial bending moment

Description: Results from a finite element analysis of a cantilever beam subjected to an equi-biaxial bending moment demonstrate that the biaxial modulus E/(I-v) must be used even for narrow beams.
Date: April 28, 1998
Creator: Krulevitch, P. & Johnson, G.C.
Partner: UNT Libraries Government Documents Department
open access

High performance hand-held gas chromatograph

Description: The Microtechnology Center of Lawrence Livermore National Laboratory has developed a high performance hand-held, real time detection gas chromatograph (HHGC) by Micro-Electro-Mechanical-System (MEMS) technology. The total weight of this hand-held gas chromatograph is about five lbs., with a physical size of 8{close_quotes} x 5{close_quotes} x 3{close_quotes} including carrier gas and battery. It consumes about 12 watts of electrical power with a response time on the order of one to two minutes.… more
Date: April 28, 1998
Creator: Yu, C.M.
Partner: UNT Libraries Government Documents Department
open access

Chemicals and excess materials disposition during facility deactivation as a means of pollution prevention

Description: This paper presents several innovative and common sense approaches to pollution prevention that have been employed during facility deactivation at the Hanford Site in South Central Washington. It also presents several pollution prevention principles applicable to other projects. Innovative pollution prevention ideas employed at the Hanford site during facility deactivation included: (1) Recycling more than 185,000 gallons of radioactively contaminated nitric acid by sending it to an operating n… more
Date: May 28, 1998
Creator: Godfrey, S. D.
Partner: UNT Libraries Government Documents Department
open access

Joint inversion of geophysical data for site characterization and restoration monitoring

Description: The purpose of this project is to develop a computer code for joint inversion of seismic and electrical data, to improve underground imaging for site characterization and remediation monitoring. The computer code developed in this project will invert geophysical data to obtain direct estimates of porosity and saturation underground, rather than inverting for seismic velocity and electrical resistivity or other geophysical properties. This is intended to be a significant improvement in the state… more
Date: May 28, 1998
Creator: Berge, P. A.
Partner: UNT Libraries Government Documents Department
open access

Waste minimization in analytical chemistry through innovative sample preparation techniques.

Description: Because toxic solvents and other hazardous materials are commonly used in analytical methods, characterization procedures result in significant and costly amount of waste. We are developing alternative analytical methods in the radiological and organic areas to reduce the volume or form of the hazardous waste produced during sample analysis. For the radiological area, we have examined high-pressure, closed-vessel microwave digestion as a way to minimize waste from sample preparation operations.… more
Date: May 28, 1998
Creator: Smith, L. L.
Partner: UNT Libraries Government Documents Department
open access

A Lattice for the 50 Gev Muon Collider Ring.

Description: A resent progress report on the lattice design of the 50-50 GeV muon collider is presented. The ring circumference needs to be as small as possible due to the short lifetime of the 50 GeV muons. The background at the detector is affected by the continuous decay of muons into electrons which requires a dipole between the high focusing quadrupoles and the detector. To obtain a luminosity on the order of 1 x 10{sup 33} cm{sup {minus}2} S{sup {minus}1} it is required to have beam intensities on the… more
Date: June 28, 1998
Creator: Trbojevic, D.
Partner: UNT Libraries Government Documents Department
open access

Meta-data based mediator generation

Description: Mediators are a critical component of any data warehouse; they transform data from source formats to the warehouse representation while resolving semantic and syntactic conflicts. The close relationship between mediators and databases requires a mediator to be updated whenever an associated schema is modified. Failure to quickly perform these updates significantly reduces the reliability of the warehouse because queries do not have access to the most current data. This may result in incorrect o… more
Date: June 28, 1998
Creator: Critchlaw, T
Partner: UNT Libraries Government Documents Department
open access

Achieving and maintaining cleanliness in NIF amplifiers

Description: Cleanliness measurements made on AMPLAB prototype National Ignition Facility (NIF) laser amplifiers during assembly, cassette transfer, and amplifier operation are summarized. These measurements include particle counts from surface cleanliness assessments using filter swipe techniques and from airborne particle monitoring. Results are compared with similar measurements made on the Beamlet and Nova lasers and in flashlamp test fixtures. Observations of Class 100,000 aerosols after flashlamp firi… more
Date: July 28, 1998
Creator: Burnham, A. K.; Horvath, J. A.; Letts, S. A.; Menapace, J. A. & Stowers, I. F.
Partner: UNT Libraries Government Documents Department
open access

Experimental capabilities of the transient reactor test (TREAT) facility.

Description: The TREAT facility was designed and built in the 1950s to provide a transient reactor for conducting safety experiments on reactor fuels. Throughout its almost 40-year history, it has proven to be a safe, reliable, and versatile facility, compiling a distinguished record of successful experiments. Several major improvements to the facility have been made, including an expansion of the building and of equipment handling capability, and enlargement of the access hole above the core, rearrangement… more
Date: July 28, 1998
Creator: Crawford, D. C.
Partner: UNT Libraries Government Documents Department
open access

Plasma electrode pockels cell for the National Ignition Facility

Description: The National Ignition Facility (NIF), now under construction at Lawrence Livermore National Laboratory, will be the largest laser fusion facility ever built. The NIF laser architecture is based on a multi-pass power amplifier to reduce cost and maximize performance. A key component in this laser design is an optical switch that closes to trap the optical pulse in the cavity for four gain passes and then opens to divert the optical pulse out of the amplifier cavity. The switch is comprised of a … more
Date: July 28, 1998
Creator: Alger, T.; Biltoft, P.; Boley, C. D.; Fochs, S.; Funkhouser, B. & Rhodes, M. A.
Partner: UNT Libraries Government Documents Department
open access

A review of experiments and results from the transient reactor test (TREAT) facility.

Description: The TREAT Facility was designed and built in the late 1950s at Argonne National Laboratory to provide a transient reactor for safety experiments on samples of reactor fuels. It first operated in 1959. Throughout its history, experiments conducted in TREAT have been important in establishing the behavior of a wide variety of reactor fuel elements under conditions predicted to occur in reactor accidents ranging from mild off normal transients to hypothetical core disruptive accidents. For much of… more
Date: July 28, 1998
Creator: Deitrich, L. W.
Partner: UNT Libraries Government Documents Department
open access

Thin film contamination effects on laser-induced damage of fused silica surfaces at 355 nm

Description: Fused silica windows were artificially contaminated to estimate the resistance of target chamber debris shields against laser damage during NIF operation. Uniform contamination thin films (1 to 5 nm thick) were prepared by sputtering various materials (Au, Al, Cu, and B<sub>4</sub>C). The loss of transmission of the samples was first measured. They were then tested at 355 nm in air with an 8-ns Nd:YAG laser. The damage morphologies were characterized by Nomarski optical microscopy and SEM. Both… more
Date: July 28, 1998
Creator: Burnham, A. K.; Cordillot, C.; Fornier, A.; Genin, F. Y.; Rubenchick, A. M.; Schirmann, D. et al.
Partner: UNT Libraries Government Documents Department
open access

Enhanced adhesion buffer layer for deep x-ray lithography using hard x-rays.

Description: The first step in the fabrication of microstructure using deep x-ray lithography (DXRL) is the irradiation of a x-ray sensitive resist like polymethylmethacrylate (PMMA) by hard x-rays. At the Advanced Photon Source, a dedicated beamline allows the proper exposure of very thick (several mm) resists. To fabricate electroformed metal microstructure with heights of several mm, a PMMA sheet is glued onto a metallic plating base. An important requirement is that the PMMA layer must adhere well to th… more
Date: August 28, 1998
Creator: De Carlo, F.
Partner: UNT Libraries Government Documents Department
open access

First Results for a Superconducting Imaging-Surface Sensor Array for Magnetocardiography

Description: The authors have completed fabrication and preliminary testing of a 12-channel SQUID array using the superconducting image-surface gradiometer concept. Sensor response to point dipole magnetic sources, and uniform fields used to simulate ambient magnetic fields followed predicted values to high precision. Edge effects were not observed for sources, within 5cm of the center of the imaging surface independent of whether the source is close or far from the surface. The superconducting imaging-surf… more
Date: August 28, 1998
Creator: Kraus, R. H., Jr.; Flynn, E. R.; Espy, M. A.; Matlachov, A.; Overton, W.; Wood, C. C. et al.
Partner: UNT Libraries Government Documents Department
open access

Phonon densities of states and related thermodynamic properties of high temperature ceramics.

Description: Structural components and semiconductor devices based on silicon nitride, aluminum nitride and gallium nitride are expected to function more reliably at elevated temperatures and at higher levels of performance because of the strong atomic bonding in these materials. The degree of covalency, lattice specific heat, and thermal conductivity are important design factors for the realization of advanced applications. We have determined the phonon densities of states of these ceramics by the method o… more
Date: August 28, 1998
Creator: Loong, C.-K.
Partner: UNT Libraries Government Documents Department
open access

Physics with the STAR detector at RHIC.

Description: The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory will collide beams of nuclei (as light as protons and as heavy as gold) at energies of up to 200 GeV per nucleon. At these energies, the probability of detecting a phase transition to a state of matter where quarks and gluons are not confined to nucleons is large. (The nuclear densities are approaching nucleon densities) Additionally, the collision is occurring in a kinematic regime where perturbative QCD is expected t… more
Date: August 28, 1998
Creator: LeCompte, T. J.
Partner: UNT Libraries Government Documents Department
open access

Stability of the graphite and diamond phases of finite carbon cluster

Description: The stability of particulate carbon formed in the detonation of high explosives has been investigated with first principles and semiempirical molecular orbital calculations carried out on carbon clusters. The dangling surface bonds were capped wit/r hydrogen atoms and the surface contributions to the cohesive energy were removed by extrapolation as a function of the cluster size. Comparison of the calculated heat of formation of graphite and diamond particles as a function of size predicts that… more
Date: August 28, 1998
Creator: Ree, F & Winter, N W
Partner: UNT Libraries Government Documents Department
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