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open access

Optimizing parallel reduction operations

Description: A parallel program consists of sets of concurrent and sequential tasks. Often, a reduction (such as array sum) sequentially combines values produced by a parallel computation. Because reductions occur so frequently in otherwise parallel programs, they are good candidates for optimization. Since reductions may introduce dependencies, most languages separate computation and reduction. The Sisal functional language is unique in that reduction is a natural consequence of loop expressions; the paral… more
Date: June 1, 1995
Creator: Denton, S.M.
open access

High-resolution spectroscopy using synchrotron radiation for surface structure determination and the study of correlated electron systems

Description: The surface structure of three molecular adsorbate systems on transition metal surfaces, ({radical}3 x {radical}3)R30{degrees} and (1.5 x 1.5)R18{degrees} CO adsorbed on Cu(111), and c(2x2) N2/Ni(100), have been determined using Angle-Resolved Photoemission Extended Fine Structure (ARPEFS). The adsorption site and bond lengths are reported for the adsorbate-metal bond and the first two substrate layers. The ARPEFS diffraction pattern of the shake-up peak for c(2x2) N2/Ni(100) is also discussed.… more
Date: May 1, 1996
Creator: Moler, E.J. Jr.
open access

Polarization dependence of two-photon transition intensities in rare-earth doped crystals

Description: A polarization dependence technique has been developed as a tool to investigate phonon scattering (PS), electronic Raman scattering (ERS), and two-photon absorption (TPA) transition intensities in vanadate and phosphate crystals. A general theory for the polarization dependence (PD) of two-photon transition intensities has been given. Expressions for the polarization dependent behavior of two-photon transition intensities have been tabulated for the 32 crystallographic point groups. When the wa… more
Date: May 1, 1996
Creator: Le Nguyen, An-Dien
open access

Expanded studies of linear collider final focus systems at the Final Focus Test Beam

Description: In order to meet their luminosity goals, linear colliders operating in the center-of-mass energy range from 3,50 to 1,500 GeV will need to deliver beams which are as small as a few Manometers tall, with x:y aspect ratios as large as 100. The Final Focus Test Beam (FFTB) is a prototype for the final focus demanded by these colliders: its purpose is to provide demagnification equivalent to those in the future linear collider, which corresponds to a focused spot size in the FFTB of 1.7 microns (ho… more
Date: December 1, 1995
Creator: Tenenbaum, Peter Gregory
open access

Interactive graphical tools for three-dimensional mesh redistribution

Description: Three-dimensional meshes modeling nonlinear problems such as sheet metal forming, metal forging, heat transfer during welding, the propagation of microwaves through gases, and automobile crashes require highly refined meshes in local areas to accurately represent areas of high curvature, stress, and strain. These locally refined areas develop late in the simulation and/or move during the course of the simulation, thus making it difficult to predict their exact location. This thesis is a systema… more
Date: March 1, 1996
Creator: Dobbs, Lauri Ann
open access

Conformal field theory on affine Lie groups

Description: Working directly on affine Lie groups, we construct several new formulations of the WZW model, the gauged WZW model, and the generic affine-Virasoro action. In one formulation each of these conformal field theories (CFTs) is expressed as a one-dimensional mechanical system whose variables are coordinates on the affine Lie group. When written in terms of the affine group element, this formulation exhibits a two-dimensional WZW term. In another formulation each CFT is written as a two-dimensional… more
Date: April 1, 1996
Creator: Clubok, K.S.
open access

Synthesis, characterization and physical properties of Al-Cu-Fe quasicrystalline plasma sprayed coatings

Description: Our lab has been working with plasma spraying of both high pressure gas atomized (HPGA) and cast and crushed quasicrystal powders. A major component of this research includes comparative studies of PAS coatings formed with starting powders prepared by both techniques. In addition, a thorough investigation of the effects of starting powder particle size on coating microstructure is included. During the course of the overall research, an interest developed in forming Al-Cu-Fe materials with finer… more
Date: November 9, 1995
Creator: Daniel, S.
open access

Studies of thin films and surfaces with optical harmonic generation and electron spectroscopy

Description: Optical second harmonic generation (SHG) and sum frequency generation (SFG) were used to study C{sup 60} thin solid films (low energy ED forbidden electronic excitations), and electron spectroscopy was used to study organic overlayers (xylenes) on Pt(111). Theory of SHG from a thin film is described in terms of surface and bulk contributions as well as local and nonlocal contributions to the optical nonlinearities. (1)In situ SHG data on C{sub 60} films during UHV film growth can be described i… more
Date: January 1, 1996
Creator: Wilk, D.E.
open access

Inductively coupled plasma spectrometry: Noise characteristics of aerosols, application of generalized standard additions method, and Mach disk as an emission source

Description: This dissertation is focused on three problem areas in the performance of inductively coupled plasma (ICP) source. The noise characteristics of aerosols produced by ICP nebulizers are investigated. A laser beam is scattered by aerosol and detected by a photomultiplier tube and the noise amplitude spectrum of the scattered radiation is measured by a spectrum analyzer. Discrete frequency noise in the aerosol generated by a Meinhard nebulizer or a direct injection nebulizer is primarily caused by … more
Date: October 6, 1995
Creator: Shen, Luan
open access

Simulations of longitudinal beam dynamics of space-charge dominated beams for heavy ion fusion

Description: The longitudinal instability has potentially disastrous effects on the ion beams used for heavy ion driven inertial confinement fusion. This instability is a {open_quotes}resistive wall{close_quotes} instability with the impedance coining from the induction modules in the accelerator used as a driver. This instability can greatly amplify perturbations launched from the beam head and can prevent focusing of the beam onto the small spot necessary for fusion. This instability has been studied usin… more
Date: December 1, 1994
Creator: Miller, D.A.C.
open access

Application of the Environmental Protection Agency`s data quality objective process to environmental monitoring quality control

Description: The United States Environmental Protection Agency`s (EPA) Data Quality Objectives (DQO) process was applied to two environmental monitoring networks for the purpose of optimizing field quality control sampling to give the highest quality monitoring data with minimal impact on resources. The DQO process, developed primarily to aid in cleanup and restoration activities, is a systematic approach to designing sampling, and analysis programs with improved efficiency, cost savings, and measureable an… more
Date: November 1, 1995
Creator: Garcia, L.M.
open access

Multifragmentation in intermediate energy {sup 129}Xe-induced heavy-ion reactions

Description: The {sup 129}Xe-induced reactions on {sup nat}Cu, {sup 89}Y, {sup 165}Ho, and {sup 197}Au at bombarding energies of E/A = 40 & 60 MeV have been studied theoretically and experimentally in order to establish the underlying mechanism of multifragmentation at intermediate energy heavy-Ion collisions. Nuclear disks formed in central heavy-ion collisions, as simulated by means of Boltzmann-like kinetic equations, break up into several fragments due to a new kind of Rayleigh-like surface instability.… more
Date: May 1, 1996
Creator: Tso, Kin
open access

Quantum effects in unimolecular reaction dynamics

Description: This work is primarily concerned with the development of models for the quantum dynamics of unimolecular isomerization and photodissociation reactions. We apply the rigorous quantum methodology of a Discrete Variable Representation (DVR) with Absorbing Boundary Conditions (ABC) to these models in an attempt to explain some very surprising results from a series of experiments on vibrationally excited ketene. Within the framework of these models, we are able to identify the experimental signature… more
Date: December 1, 1995
Creator: Gezelter, J.D.
open access

RHEED studies of Ag/Si(111) growth at low temperatures

Description: This thesis showed that it is possible to achieve well ordered growth at low temperatures when chaing fluxes during the course of the deposition. It was also demonstrated that nucleation theory fails to predict or explain at least part of the results, in particular when deposition takes place at an initially low rate, with presumably a relatively low nucleation density, followed by a change to a high flux rate. This points to an inherent lack of nucleation theory; alternative explanations are p… more
Date: January 2, 1996
Creator: Koehler, U.
open access

Development of a high-resolution soft x-ray (30--1500 eV) beamline at the Advanced Light Source and its use for the study of angle-resolved photoemission extended fine structure

Description: ALS Bending magnet beamline 9.3.2 is for high resolution spectroscopy, with circularly polarized light. Fixed included-angle SGM uses three gratings for 30--1500 eV photons; circular polarization is produced by an aperture for selecting the beam above or below the horizontal plane. Photocurrent from upper and lower jaws of entrance slit sets a piezoelectric drive feedback loop on the vertically deflecting mirror for stable beam. End station has a movable platform. With photomeission data from S… more
Date: February 1, 1996
Creator: Huff, W. R. A.
open access

Magnetohydrodynamic simulations of noninductive helicity injection in the reversed-field pinch and tokamak

Description: Numerical computation is used to investigate resistive magnetohydrodynamic (MHD) fluctuations in the reversed-field pinch (RFP) and in tokamak-like configurations driven solely by direct current (DC) helicity injection. A Lundquist number (S) scan of RFP turbulence without plasma pressure produces the weak scaling of S{sup -0.18} for the root-mean-square magnetic fluctuation level for 2.5x10{sup 3}{le}S{le}4x10{sup 4}. The temporal behavior of fluctuations and the reversal parameter becomes mor… more
Date: December 31, 1995
Creator: Sovinec, C. R.
open access

Rayleigh scattering and nonlinear inversion of elastic waves

Description: Rayleigh scattering of elastic waves by an inclusion is investigated and the limitations determined. In the near field of the inhomogeneity, the scattered waves are up to a factor of 300 stronger than in the far field, excluding the application of the far field Rayleigh approximation for this range. The investigation of the relative error as a function of parameter perturbation shows a range of applicability broader than previously assumed, with errors of 37% and 17% for perturbations of {minus… more
Date: December 1, 1995
Creator: Gritto, R.
open access

Search for {Sigma}{sub c} {yields} {Lambda}{sub c}{pi} using {Lambda}{sub c} {yields} {Sigma}{sub s}{pi}{pi} in 250 GeV {pi}{sup {minus}}-nucleon interactions

Description: Combined cross section times branching fraction limits are given for {Sigma}{sub c}{sup +}{sup +} {r_arrow} {Lambda}{sub c}{sup +}{pi}{sup +} and {Sigma}{sub c}{sup 0} {r_arrow} {Lambda}{sub c}{sup +}{pi}{sup {minus}} where {Lambda}{sub c}{sup +} {r_arrow} {Sigma}{sub s}{sup {plus_minus}}{pi}{sup {plus_minus}}{pi}{sup +}. The {Lambda}{sub c}{sup +} is reconstructed with partial information on the {Sigma}{sub s}; the missing {Sigma}{sub s} momentum is established through momentum conservation im… more
Date: October 10, 1995
Creator: Passmore, D.A.
open access

XRF and leaching characterization of waste glasses derived from wastewater treatment sludges

Description: Purpose of this study was to investigate use of XRF (x-ray fluorescence spectrometry) as a near real-time method to determine melter glass compositions. A range of glasses derived from wastewater treatment sludges associated with DOE sites was prepared. They were analyzed by XRF and wet chemistry digestion with atomic absorption/inductively coupled emission spectrometry. Results indicated good correlation between these two methods. A rapid sample preparation and analysis technique was developed… more
Date: December 1, 1994
Creator: Ragsdale, R.G., Jr
open access

INDEEP Annual report (1995-1996)

Description: The International database on Energy Efficiency Programs (INDEEP) project is designed to make available information on electric and gas utility demand-side management (DSM) programs, as well as DSM programs carried out by government agencies and others. Efforts in the program for this time period are described.
Date: June 1996
Creator: Vine, E.
open access

Fully implicit kinetic modelling of collisional plasmas

Description: This dissertation describes a numerical technique, Matrix-Free Newton Krylov, for solving a simplified Vlasov-Fokker-Planck equation. This method is both deterministic and fully implicit, and may not have been a viable option before current developments in numerical methods. Results are presented that indicate the efficiency of the Matrix-Free Newton Krylov method for these fully-coupled, nonlinear integro-differential equations. The use and requirement for advanced differencing is also shown. … more
Date: May 1, 1996
Creator: Mousseau, V.A.
open access

Solid phase epitaxial regrowth of (100)GaAs

Description: This thesis showed that low temperature (250 C) SPE of stoichiometrically balanced ion implanted GaAs layers can yield good epitaxial recovery for doses near the amorphization threshold. For 250 C anneals, most of the regrowth occurred in the first 10 min. HRTEM revealed much lower stacking fault density in the co-implanted sample than in the As-only and Ga-only samples with comparable doses. After low temp annealing, the nonstoichiometric samples had a large number of residual defects. For hig… more
Date: February 1, 1996
Creator: Almonte, M. I.
open access

A new post-column reactor-laser induced fluorescence detector for capillary electrophoresis

Description: Capillary zone electrophoresis (CZE), a powerful separation method based on the differential migration of charged species under the influence of an electric field, has been widely used for separations covering from small ions to big biomolecules. Chapter 1 describes the method, then discusses detection of the separated analytes by laser induced fluorescence and by chemical derivatization, and the use of O-phthaldialdehyde (OPA) as a post-column reagent. Chapter 2 describes a post-column reactor… more
Date: January 2, 1996
Creator: Liling, Zhang
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