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Defect diffusion during annealing of low-energy ion-implanted silicon

Description: We present a new approach for investigating the kinetics of defect migration during annealing of low-energy, ion-implanted silicon, employing a combination of computer simulations and atomic-resolution tunneling microscopy. Using atomically-clean Si(111)-7x7 as a sink for bulk point defects created by 5 keV Xe and Ar irradiation, we observe distinct, temperature-dependent surface arrival rates for vacancies and interstitials. A combination of simulation tools provides a detailed description of … more
Date: March 8, 2000
Creator: Bedrossian, P J; Caturla, M-J & Diaz de la Rubia, T
Partner: UNT Libraries Government Documents Department
open access

Optimal Segmentation Strategy for Compact Representation of Hyperspectral Image Cubes

Description: By producing compact representations of hyperspectral image cubes (hypercubes), image storage requirements and the amount of time it takes to extract essential elements of information can both be dramatically reduced. However, these compact representations must preserve the important spectral features within hypercube pixels and the spatial structure associated with background and objects or phenomena of interest. This paper describes a novel approach for automatically and efficiently generatin… more
Date: February 8, 2000
Creator: Paglieroni, D & Roberts, R
Partner: UNT Libraries Government Documents Department
open access

Design of Racetrack Coils for High Field Dipole Magnets

Description: The magnet group at LBNL is currently in the process of developing high-field accelerator magnets for use in future colliders. One of the primary challenges is to provide a design which is cost-effective and simple to manufacture, at the same time resulting in good training performance and field quality adequate for accelerator operation. Recent studies have focused on a racetrack geometry that has the virtues of simplicity and conductor compatibility. The results have been applied to the desig… more
Date: September 8, 2000
Creator: Sabbi, G.; Caspi, S.; Gourlay, S. A.; Hafalia, R.; Jackson, A.; Lietzke, A. et al.
Partner: UNT Libraries Government Documents Department
open access

Temperature Profile of IR Blocking Windows Used in Cryogenic X-Ray Spectrometers

Description: Cryogenic high-resolution X-ray spectrometers are typically operated with thin IR blocking windows to reduce radiative heating of the detector while allowing good x-ray transmission. We have estimated the temperature profile of these IR blocking windows under typical operating conditions. We show that the temperature in the center of the window is raised due to radiation from the higher temperature stages. This can increase the infrared photon flux onto the detector, thereby increasing the IR n… more
Date: August 8, 2000
Creator: Friedrich, S.; Funk, T.; Drury, O. & Labov, S.E.
Partner: UNT Libraries Government Documents Department
open access

The Advantages of Fixed Facilities in Characterizing TRU Wastes

Description: In May 1998 the Hanford Site started developing a program for characterization of transuranic (TRU) waste for shipment to the Waste Isolation Pilot Plant (WIPP) in New Mexico. After less than two years, Hanford will have a program certified by the Carlsbad Area Office (CAO). By picking a simple waste stream, taking advantage of lessons learned at the other sites, as well as communicating effectively with the CAO, Hanford was able to achieve certification in record time. This effort was further … more
Date: February 8, 2000
Creator: FRENCH, M.S.
Partner: UNT Libraries Government Documents Department
open access

Steady State Creep of Zirconium at High and Intermediate Temperatures

Description: Creep of zirconium and zirconium alloys has been labeled ''anomalous.'' Researchers often report that zirconium and its alloys never reach true steady state creep and have stress exponents that continuously change with stress and temperature. Many varied interpretations have been offered explaining the creep behavior of zirconium. Some have suggested that creep is diffusion controlled, while others maintain that creep is dislocation glide controlled. Cumulative zirconium creep data will be pres… more
Date: April 8, 2000
Creator: Rosen, R.S. & Hayes, T.A.
Partner: UNT Libraries Government Documents Department
open access

Modeling Creep Rupture of Zirconium Alloys

Description: Safe interim dry storage of spent nuclear fuel (SNF) must be maintained for a minimum of twenty years according to the Code of Federal Regulations. The most important variable that must be regulated by dry storage licensees in order to meet current safety standards is the temperature of the SNF. The two currently accepted models to define the maximum allowable storage temperature for SNF are based on a diffusion controlled cavity growth (DCCG) failure mechanism for the cladding. Although these … more
Date: April 8, 2000
Creator: Rosen, R.S. & Hayes, T.A.
Partner: UNT Libraries Government Documents Department
open access

Natural attenuation assessment of multiple VOCs in a deep vadose zone

Description: The fate of six volatile organic compounds (VOC) in a 150-meter deep vadose zone was examined in support of a RCRA Corrective Measures Study of the Chemical Waste Landfill at Sandia National Laboratories, Albuquerque, New Mexico. The study focused on the modeling of potential future transport of the VOCs to exposure media upon the completion of two separate voluntary corrective measures--soil vapor extraction and landfill excavation--designed to significantly reduce contaminant levels in subsur… more
Date: March 8, 2000
Creator: Peterson, David M.; Singletary, Michael A.; Studer, James E. & Miller, David R.
Partner: UNT Libraries Government Documents Department
open access

Quench sensitivity of hot extruded 6061-T6 and 6069-T6 aluminum alloys

Description: The purpose of this study is to investigate the quench sensitivity of mechanical properties of hot extruded 6061 and 6069 aluminum alloys. The relationship between mechanical properties and quench delzty time at various temperatures between 200-500 C was determined. It was concluded that the 6069-T6 was somewhat more quench sensitive than 6061, which may be consistent with the composition difference.
Date: August 8, 2000
Creator: Bergsma, S C; Kassner, M E; Li, X & Rosen, R S
Partner: UNT Libraries Government Documents Department
open access

Recent developments in understanding five-power-law creep in metals

Description: This work describes recent advances on the effects of subgrain boundaries on elevated-temperature plasticity. Particular attention is devoted to recent developments regarding internal back-stresses. This will include discussions of recent convergent beam electron diffraction (CBED) experiments on metals to evaluate internal stresses in association with dislocation heterogeneities.
Date: April 8, 2000
Creator: Kassner, M E; Perez-Prado, M-T; Rosen, R S & Bergsma, S C
Partner: UNT Libraries Government Documents Department
open access

Polarized light propagation through tissue and tissue phantoms

Description: We show that standard tissue phantoms can be used to mimic the intensity and polarization properties of tissue. Polarized light propagation through biologic tissue is typically studied using tissue phantoms consisting of dilute aqueous suspensions of microspheres. The dilute phantoms can empirically match tissue polarization and intensity properties. One discrepancy between the dilute phantoms and tissue exist: common tissue phantoms, such as dilute Intralipid and dilute 1-{micro}m-diameter pol… more
Date: February 8, 2000
Creator: Sankaran, V; Walsh, J T JR & Maitland, D J
Partner: UNT Libraries Government Documents Department
open access

Temperature Measurement on Shocked Surfaces

Description: We have used a two-stage gas gun to address issues relating to the accurate determination of the temperature of a shocked metal surface at a metal/LiF interface. We have investigated the light flash generated by the dynamics at the interface, the light sources at the LiF boundary that can contaminate the emission from the metal surface, and the light emitted from defects in the LiF crystal as it is being shocked. A seven-channel spectrometer with fiber-optic transmission of light from the targe… more
Date: August 8, 2000
Creator: Poulseu, P.; Baum, D.; Fiske, P. & Holtkamp, D.
Partner: UNT Libraries Government Documents Department
open access

Atomic-scale identification of Ge/Si intermixing on Si(100) at submonolayer Ge coverages

Description: The positions of Ge atoms intermixed in the Si(100) surface at very low concentration are identified using empty-state imaging in scanning tunneling microscopy. A measurable degree of place exchange occurs at temperatures as low as 330 K. Contrary to earlier conclusions, good differentiation between Si atoms and Ge atoms can be achieved by proper imaging conditions.
Date: February 8, 2000
Creator: QIN,X.R.; SWARTZENTRUBER,BRIAN S. & LAGALLY,M.G.
Partner: UNT Libraries Government Documents Department
open access

Numerical simulation of two-phase flow with front-capturing

Description: Because of the complexity of two-phase flow phenomena, two-phase flow codes rely heavily on empirical correlations. This approach has a number of serious shortcomings. Advances in parallel computing and continuing improvements in computer speed and memory have stimulated the development of numerical simulation tools that rely less on empirical correlations and more on fundamental physics. The objective of this work is to take advantage of developments in massively parallel computing, single-pha… more
Date: February 8, 2000
Creator: Tzanos, C. P. & Weber, D. P.
Partner: UNT Libraries Government Documents Department
open access

Theory and suppression of multibunch beam breakup in linear colliders

Description: The authors recently developed an analytic theory of cumulative multibunch beam breakup that includes a linear variation of transverse focusing across the bunch train. The focusing variation saturates the exponential growth of the beam breakup and establishes an algebraic decay of the transverse bunch displacement versus bunch number. In this paper they illustrate how the focusing variation works to suppress multibunch beam breakup, as well as how the mechanism scales with accelerator and beam … more
Date: August 8, 2000
Creator: Ng, Courtlandt L. Bohn and King-Yuen
Partner: UNT Libraries Government Documents Department
open access

Residual stress determination from a laser-based curvature measurement

Description: Thermally sprayed coating characteristics and mechanical properties are in part a result of the residual stress developed during the fabrication process. The total stress state in a coating/substrate is comprised of the quench stress and the coefficient of thermal expansion (CTE) mismatch stress. The quench stress is developed when molten particles impact the substrate and rapidly cool and solidify. The CTE mismatch stress results from a large difference in the thermal expansion coefficients of… more
Date: May 8, 2000
Creator: Swank, W. D.; Gavalya, R. A.; Wright, J. K. & Wright, R. N.
Partner: UNT Libraries Government Documents Department
open access

U.S. SUPPORT PROGRAM CONTRIBUTIONS TO REMOTE MONITORING

Description: Since 1993, the IAEA has made great progress in the implementation of remote monitoring. Equipment has been developed and tested, and installed systems are being used for safeguards purposes. The cost of equipment, the complexity of communication technology, and maintenance of the equipment are challenges that still face the IAEA. Resolution of these challenges will require significant effort. The USSP is committed to assisting the IAEA to overcome these challenges.
Date: May 8, 2000
Creator: Pepper, Susan E.
Partner: UNT Libraries Government Documents Department
open access

Electrical breakdown in thin oxides during bias-temperature ramps

Description: Electrical breakdown in thin oxides is assessed by a new bias-temperature ramp technique. No significant effect of radiation exposure on breakdown is observed for high quality thermal and nitrided oxides, up to 20 Mrad(SiO{sub 2}).
Date: February 8, 2000
Creator: FLEETWOOD,D.M.; RIEWE,LEONARD CHARLES; WINOKUR,PETER S. & SEXTON,FREDERICK W.
Partner: UNT Libraries Government Documents Department
open access

Developing collaborative environments - A Holistic software development methodology

Description: Sandia National Laboratories has been developing technologies to support person-to-person collaboration and the efforts of teams in the business and research communities. The technologies developed include knowledge-based design advisors, knowledge management systems, and streamlined manufacturing supply chains. These collaborative environments in which people can work together sharing information and knowledge have required a new approach to software development. The approach includes an empha… more
Date: March 8, 2000
Creator: Petersen, Marjorie B. & Mitchiner, John L.
Partner: UNT Libraries Government Documents Department
open access

Origin of the pseudogap in high temperature superconductors

Description: Underdoped high temperature superconductors (HTS) exhibit a normal state for energies E > E{sub g} and/or temperatures T > T{sub 0}, and a pseudogap in their electronic spectrum for E < E{sub g} and/or T{sub 0} > T > {Tc}. Strikingly similar behavior occurs in the transition metal dichalcogenides (TMD) 2H-MX{sub 2}, where M = Ta, Nb, and X = S, Se, both in the normal (T > T{sub 0}) and in the incommensurate charge-density wave (T{sub ICDW} > T > T{sub c}) states. Such st… more
Date: February 8, 2000
Creator: Klemm, R. A.
Partner: UNT Libraries Government Documents Department
open access

Q-Switched Operation of a Coupled-Resonator Vertical-Cavity Laser Diode

Description: The authors report Q-switched operation from an electrically-injected monolithic coupled-resonator structure which consists of an active cavity with InGaAs quantum wells optically coupled to a passive cavity. The passive cavity contains a bulk GaAs region which is reverse-biased to provide variable absorption at the lasing wavelength of 990 nm. Cavity coupling is utilized to effect large changes in output intensity with only very small changes in passive cavity absorption. The device is shown t… more
Date: February 8, 2000
Creator: Fischer, Arthur J.; Chow, Weng W.; Choquette, Kent D.; Allerman, Andrew A. & Geib, Kent M.
Partner: UNT Libraries Government Documents Department
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