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The dihadron fragmentation function and its evolution

Description: Dihadron fragmentation functions and their evolution arestudied in the process of e+e- annihilation. Under the collinearfactorization approximation and facilitated by the cut-vertex technique,the two hadron inclusive cross section at leading order (LO) is shown tofactorize into a short distance parton cross section and a long distancedihadron fragmentation function. We provide the definition of such adihadron fragmentation function in terms of parton matrix elements andderive its DGLAP evolutio… more
Date: February 24, 2004
Creator: Majumder, Abhijit & Wang, Xin-Nian
Partner: UNT Libraries Government Documents Department
open access

Asymmetric injection of cathodic arc plasma into a macroparticlefilter

Description: The cathodic arc plasmas produced by cathode spots usuallyinclude macroparticles, which is undesirable for many applications. Acommon way of removing macroparticles is to use curved solenoid filterswhich guide the plasma from the source to the substrate. In this work, anarc source with relatively small cathode is used, limiting the possiblelocations of plasma production. The relative position of cathodic arcsource and macroparticle filtered was systematically varied and thefiltered plasma curre… more
Date: February 11, 2004
Creator: Anders, Andre & MacGill, Robert A.
Partner: UNT Libraries Government Documents Department
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Large plasma pressure perturbations and radial convective transport in a tokamak

Description: Strongly localized plasma structures with large pressure inhomogeneities (such as plasma blobs in the scrape-off-layer (SOL)/shadow regions, pellet clouds, ELMs) observed in the tokamaks, stellarators and linear plasma devices. Experimental studies of these phenomena reveal striking similarities including more convective rather than diffusive radial plasma transport. We suggest that rather simple models can describe many essentials of blobs, ELMs, and pellet clouds dynamics. The main ingredient… more
Date: February 4, 2004
Creator: Krasheninnikov, S.; Ryutov, D. & Yu, G.
Partner: UNT Libraries Government Documents Department
open access

Reduction of laser beam spray at 0.527 (micron)m in an ignition scale length plasma with temporal beam smoothing

Description: We have measured the effect of laser smoothing by spectral dispersion (SSD) on beam spray, transmission and deflection of a 2{omega} (527 nm) high intensity (10{sup 15} W/cm{sup 2}) interaction beam through an underdense large scale length plasma. We observe a 40% reduction of the beam spray when SSD is used, consistent with modeling by a fluid laser-plasma interaction code (pF3d). We measured a decrease in beam transmission with increasing laser intensity, consistent with the onset of parametr… more
Date: February 4, 2004
Creator: Niemann, C.; Divol, L.; Froula, D. H.; Glenzer, S. H.; Gregori, G.; Kirkwood, R. K. et al.
Partner: UNT Libraries Government Documents Department
open access

Interconnection Testing of Distributed Resources: Preprint

Description: With the publication of IEEE 1547-2003(TM) Standard for Interconnecting Distributed Resources With Electric Power Systems, the electric power industry has a need to develop tests and procedures to verify that interconnection equipment meets 1547 technical requirements. A new standard, IEEE P1547.1(TM), is being written to give detailed tests and procedures for confirming that equipment meets the interconnection requirements. The National Renewable Energy Laboratory has been validating test proc… more
Date: February 1, 2004
Creator: Kroposki, B.; Basso, T. & DeBlasio, R.
Partner: UNT Libraries Government Documents Department
open access

Speckle Imaging of Titan at 2 microns: Surface Albedo, Haze Optical Depth, and Tropospheric Clouds 1996-1998

Description: We present results from 14 nights of observations of Titan in 1996-1998 using near-infrared (centered at 2.1 microns) speckle imaging at the 10-meter W.M. Keck Telescope. The observations have a spatial resolution of 0.06 arcseconds. We detect bright clouds on three days in October 1998, with a brightness about 0.5% of the brightness of Titan. Using a 16-stream radiative transfer model (DISORT) to model the central equatorial longitude of each image, we construct a suite of surface albedo model… more
Date: February 11, 2004
Creator: Gibbard, S. G.; Gavel, D.; Ghez, A. M.; de Pater, I.; Max, C. E.; Young, E. F. et al.
Partner: UNT Libraries Government Documents Department
open access

Adapting high-resolution speckle imaging to moving targets and platforms

Description: High-resolution surveillance imaging with apertures greater than a few inches over horizontal or slant paths at optical or infrared wavelengths will typically be limited by atmospheric aberrations. With static targets and static platforms, we have previously demonstrated near-diffraction limited imaging of various targets including personnel and vehicles over horizontal and slant paths ranging from less than a kilometer to many tens of kilometers using adaptations to bispectral speckle imaging … more
Date: February 5, 2004
Creator: Carrano, C J & Brase, J M
Partner: UNT Libraries Government Documents Department
open access

In-Situ TEM Observations of Interface Sliding and Migration in a Refined Lamellar TiAl Alloy

Description: The stability of lamellar interfaces in lamellar TiAl by straining at ambient temperatures has been investigated using in-situ straining techniques performed in a transmission electron microscope in order to obtain direct evidence to support the previously proposed creep mechanisms in refined lamellar TiAl based upon the interface sliding in association with the cooperative motion of interfacial dislocations. The results have revealed that both sliding and migration of lamellar interfaces can t… more
Date: February 18, 2004
Creator: Schwartz, A J; Nieh, T G & Hsiung, L M
Partner: UNT Libraries Government Documents Department
open access

Slow Nonradiative Decay for Rare Earths in KPb2Br5 and RbPb2Br5

Description: We report on spectroscopic investigations of Nd{sup 3+}- and Tb{sup 3+}- doped low phonon energy, moisture-resistant host crystals, KPb{sub 2}Br{sub 5} and RbPb{sub 2}Br{sub 5}, and their potential to serve as new solid state laser materials at new wavelengths, especially in the long wavelength infrared region. This includes emission spectra, emission lifetime measurements, Raman scattering spectra as well as calculations of the multiphonon decay rate, radiative lifetimes and quantum efficienci… more
Date: February 27, 2004
Creator: Rademaker, K.; Petermann, K.; Huber, G.; Krupke, W.; Page, R.; Payne, S. et al.
Partner: UNT Libraries Government Documents Department
open access

Including dislocation flux in a continuum crystal plasticity model to produce size scale effects

Description: A novel model has been developed to capture size scale and gradient effects within the context of continuum crystal plasticity by explicitly incorporating details of dislocation transport, coupling dislocation transport to slip, evolving spatial distributions of dislocations consistent with the flux, and capturing the interactions among various dislocation populations. Dislocation flux and density are treated as nodal degrees of freedom in the finite element model, and they are determined as pa… more
Date: February 13, 2004
Creator: Becker, R.; Arsenlis, A.; Bulatov, V. V. & Parks, D. M.
Partner: UNT Libraries Government Documents Department
open access

THE PROPERTIES AND MICROSTRUCTURE OF NB-47TI SUPERCONDUCTOR WITH MAGNETIC PINNING CENTERS.

Description: We have investigated Nb-47Ti multifilament wire with artificial pinning centers (APC). The superconducting properties and proximity effect in wires with ferromagnetic and non-magnetic pins will be discussed. Magnetization and transport measurements will be presented and the pinning characteristics will be discussed as a function of magnetic field, temperature and volume percent pins. In addition, field emission scanning electron microscopy of the pin nanostructure will be presented.
Date: February 4, 2004
Creator: MOTOWIDLO,L. R. RUDZIAK,M. D. WONG,T. COOLEY,L. D. LEE,P. J.
Partner: UNT Libraries Government Documents Department
open access

Implicit Occluders

Description: In this paper we propose a novel visibility-culling technique for optimizing the computation and rendering of opaque isosurfaces. Given a continuous scalar field f (x) over a domain D and an isovalue w, our technique exploits the continuity of f to determine conservative visibility bounds implicitly, i.e., without the need for actually computing the isosurface f{sup -1}(w). We generate Implicit Occluders based on the change in sign of f *(x) = f (x)-w, from positive to negative (or vice versa) … more
Date: February 3, 2004
Creator: Pesco, S; Lindstrom, P; Pascucci, V & Silva, C T
Partner: UNT Libraries Government Documents Department
open access

High-resolution crystal spectrometer for the 10-60 (angstrom) EUV region

Description: A vacuum crystal spectrometer with nominal resolving power approaching 1000 is described for measuring emission lines with wavelength in the extreme ultraviolet region up to 60 Angstroms. The instrument utilizes a flat octadecyl hydrogen maleate (OHM) crystal and a thin-window 1-D position-sensitive gas proportional detector. This detector employs a 1 {micro}m-thick 100 x8 mm{sup 2} aluminized polyimide window and operates at one atmosphere pressure. The spectrometer has been implemented on the… more
Date: February 20, 2004
Creator: Beiersdorfer, P; Brown, G V; Goddard, R & Wargelin, B J
Partner: UNT Libraries Government Documents Department
open access

The National Ignition Facility

Description: The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory is a stadium-sized facility containing a 192-beam, 1.8-Megajoule, 500-Terawatt, ultraviolet laser system together with a 10-meter-diameter target chamber and room for 100 diagnostics. NIF is the world's largest and most energetic laser experimental system, providing a scientific center to study inertial confinement fusion and matter at extreme energy densities and pressures. NIF's energetic laser beams will compress … more
Date: February 6, 2004
Creator: Miller, G H; Moses, E I & Wuest, C R
Partner: UNT Libraries Government Documents Department
open access

A multi-wavelength scattered light analysis of the dust grain population in the GG Tau circumbinary ring

Description: We present the first 3.8 {micro}m image of the dusty ring surrounding the young binary system GG Tau, obtained with the W. M. Keck II 10m telescope's adaptive optics system. THis is the longest wavelength at which the ring has been detected in scattered light so far, allowing a multi-wavelength analysis of the scattering proiperties of the dust grains present in this protoplanetary disk in combination with previous, shorter wavelengths, HST images. We find that the scattering phase function of … more
Date: February 4, 2004
Creator: Duchene, G; McCabe, C; Ghez, A & Macintosh, B
Partner: UNT Libraries Government Documents Department
open access

Arsenic Mobilization from Contaminated Sediments: A Full-scale Experiment in Progress

Description: The mobilization of arsenic was examined in a system where the deposition of iron and arsenic have been substantially modified by large-scale manipulations. This engineering practice was designed to decrease arsenic concentrations in water supplied to the City of Los Angeles. Accomplishing this objective, however, has resulted in significant accumulation of arsenic and iron in the sediments of a reservoir on the Los Angeles Aqueduct. Arsenic and iron are released into the porewater at depth in … more
Date: February 3, 2004
Creator: O'Day, P A; Campbell, K; Dixit, S & Hering, J G
Partner: UNT Libraries Government Documents Department
open access

Properties of Fluid Deuterium under Double-Shock Compression to Several Mbar

Description: The compressibility of fluid deuterium up to several Mbar has been probed using laser-driven shock waves reflected from a quartz anvil. Combining high-precision ({approx} 1 %) shock velocity measurements with the double-shock technique, where differences in equation of state (EOS) models are magnified, has allowed us to accurately discriminate between various theoretical predictions. Our data are consistent with EOS models that show approximately fourfold compression on the principal Hugoniot f… more
Date: February 3, 2004
Creator: Vianello, E; Celliers, P M; Hicks, D G; Boehly, T R; Collins, T B; Moon, S J et al.
Partner: UNT Libraries Government Documents Department
open access

Effects of the Electron Energy Distribution Function on Modeled X-ray Spectra

Description: This paper presents the results of a broad investigation into the effects of the electron energy distribution function on the predictions of non-LTE collisional-radiative atomic kinetics models. The effects of non-Maxwellian and suprathermal (''hot'') electron distributions on collisional rates (including three-body recombination) are studied. It is shown that most collisional rates are fairly insensitive to the functional form and characteristic energy of the electron distribution function as … more
Date: February 19, 2004
Creator: Shlyaptseva, A S & Hansen, S B
Partner: UNT Libraries Government Documents Department
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