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Mechanism of strain release in carbon nanotubes

Description: Article on the mechanism of strain release in carbon nanotubes.
Date: February 15, 1998
Creator: Buongiorno Nardelli, Marco; Yakobson, Boris I. & Bernholc, Jerry
Partner: UNT College of Arts and Sciences

Low-energy vibrations at the InSb(110) surface

Description: Article on low-energy vibrations at the InSb(110) surface along the ΓΥ direction.
Date: December 15, 1995
Creator: Buongiorno Nardelli, Marco; Cvetko, D.; De Renzi, V.; Floreano, L.; Morgante, A.; Peloi, M. et al.
Partner: UNT College of Arts and Sciences

Enhancing Access to E-books

Description: Article on a study of enhancing access to e-books.
Date: September 30, 2014
Creator: Harker, Karen & Sassen, Catherine
Partner: UNT Libraries

Microstructure and Performance of Kovar/Alumina Joints Made with Silver-Copper Base Active Metal Braze Alloys

Description: Poor hermeticity performance was observed for Al{sub 2}O{sub 3}-Al{sub 2}O{sub 3} ceramic-ceramic joints having a Kovar{trademark} alloy interlayer. The active Ag-Cu-Ti filler metal was used to braze the substrates together. The Ti active element was scavenged from the filler metal by the formation of a (Fe, Ni, Co){sub x}Ti phase (x= 2-3) that prevented development of a continuous Ti{sub x}O{sub y} layer at the filler metal/Al{sub 2}O{sub 3} interface. Altering the process parameters did not circumvent the scavenging of Ti. Molybdenum barrier layers 1000, 2500, or 5000 {angstrom} thick on the Kovar{trademark} surfaces successfully allowed Ti{sub x}O{sub y} formation at the filler metal/Al{sub 2}O{sub 3} interface and hermetic joints. The problems with the Ag-Cu-Ti filler metal for Kovar{trademark}/Al{sub 2}O{sub 3} braze joints led to the evaluation of a Ag-Cu-Zr filler metal. The Zr (active element) in Ag-Cu-Zr filler metal was not susceptible to the scavenging problem.
Date: December 15, 1999
Creator: STEPHENS, JOHN J.; VIANCO,PAUL T.; HLAVA,PAUL F. & WALKER,CHARLES A.
Partner: UNT Libraries Government Documents Department

New solid state lasers from the ultraviolet to the mid-infrared

Description: The authors discuss three new laser materials that offer improved access to the ultraviolet, near infrared and mid-infrared spectral regions. In order for each of these materials to have been identified, a particular hurdle needed to be overcome with respect to the fundamental laser physics impacting the material. In the case of the 280-320nm Ce:LiSAF laser, the main issue is the need to reduce the loss associated with excited state absorption, while for 1047nm Yb:S-FAP it is the ground state absorption at the laser wavelength that must be minimized. Cr:ZnSe has been down-selected from a number of potential candidates which could lase in the 2200-3000nm region, in order to mitigate the detrimental impact of nonradiative decay. In all three cases the authors discuss how appropriate consideration of fundamental concerns has led to the identification and understanding of the new laser system.
Date: August 15, 1995
Creator: Payne, S.A.; Krupke, W.F. & Beach, R.J.
Partner: UNT Libraries Government Documents Department

The Hanford spent nuclear metal fuel multi-canister overpack and vacuum drying {ampersand} hot conditioning process

Description: Nuclear production reactors operated at the U.S. Department of Energy`s Hanford Site from 1944 until 1988 to produce plutonium. Most of the irradiated fuel from these reactors was processed onsite to separate and recover the plutonium. When the processing facilities were closed in 1992, about 1,900 metric tons of unprocessed irradiated fuel remained in storage. Additional fuel was irradiated for research purposes or was shipped to the Hanford Site from offsite reactor facilities for storage or recovery of nuclear materials. The fuel inventory now in storage at the Hanford Site is predominantly N Reactor irradiated fuel, a metallic uranium alloy that is coextruded into zircaloy-2 cladding. The Spent Nuclear Fuel Project has rommitted to an accelerated schedule for removing spent nuclear fuel from the Hanford Site K Basins to a new interim storage facility in the 200 Area. Under the current proposed accelerated schedule, retrieval of spent nuclear fuel stored in the K East and West Basins must begin by December 1997 and be completed by December 1999. A key part of this action is retrieving fuel canisters from the water-filled K Basin storage pools and transferring them into multi@ister overpacks (MCOS) that will be used to handle and process the fuel, then store it after conditioning. The Westinghouse Hanford Company has developed an integrated process to deal with the K Basin spent fuel inventory. The process consists of cleaning the fuel, packaging it into MCOS, vacuum drying it at the K Basins, then transporting it to the Canister Storage Building (CSB) for staging, hot conditioning, and interim storage. This presentation dekribes the MCO function, design, and life-cycle, including an overview of the vacuum drying and hot conditioning processes.
Date: May 15, 1996
Creator: Irwin, J.J.
Partner: UNT Libraries Government Documents Department

Penetrating radiation impact on NIF final optic components

Description: Goal of the National Ignition Facility (NIF) is to achieve thermonuclear ignition in a laboratory environment in inertial confinement fusion (ICF). This will enable NIF to service the DOE stockpile stewardship management program, inertial fusion energy goals, and advance scientific frontiers. All of these applications will make use of the extreme conditions that the facility will create in the target chamber. In the case of a prospected 20 MJ yield scenario, NIF will produce 10{sup 19} neutrons with DT fusion 14 MeV energy per neutron. There will also be high-energy x rays as well as solid, liquid, and gaseous target debris produced either directly or indirectly by the inertial confinement fusion process. A critical design issue is the protection of the final optical components as well as sophisticated target diagnostics in such a harsh environment.
Date: October 15, 1996
Creator: Marshall, C.D.; Speth, J.A.; DeLoach, L.D. & Payne, S.A.
Partner: UNT Libraries Government Documents Department

Massively parallel simulation of flow and transport in variably saturated porous and fractured media

Description: This paper describes a massively parallel simulation method and its application for modeling multiphase flow and multicomponent transport in porous and fractured reservoirs. The parallel-computing method has been implemented into the TOUGH2 code and its numerical performance is tested on a Cray T3E-900 and IBM SP. The efficiency and robustness of the parallel-computing algorithm are demonstrated by completing two simulations with more than one million gridblocks, using site-specific data obtained from a site-characterization study. The first application involves the development of a three-dimensional numerical model for flow in the unsaturated zone of Yucca Mountain, Nevada. The second application is the study of tracer/radionuclide transport through fracture-matrix rocks for the same site. The parallel-computing technique enhances modeling capabilities by achieving several-orders-of-magnitude speedup for large-scale and high resolution modeling studies. The resulting modeling results provide many new insights into flow and transport processes that could not be obtained from simulations using the single-CPU simulator.
Date: January 15, 2002
Creator: Wu, Yu-Shu; Zhang, Keni & Pruess, Karsten
Partner: UNT Libraries Government Documents Department

Search for top and bottom squarks

Description: Searches for the lightest scalar top quark {bar t}{sub 1} and scalar bottom quark {bar b}{sub 1} performed at LEP2 with a center-of-mass energy of up to {radical}s = 209 GeV and at Tevatron using data collected at {radical}s = 1.8 TeV during Run I and at {radical}s = 1.96 TeV during Run II, are discussed. Different possible decay modes were considered and no evidence for any such signal was observed. Exclusion limits were extracted.
Date: October 15, 2003
Creator: Rott, C.
Partner: UNT Libraries Government Documents Department

MICROBIAL TRANSFORMATIONS OF URANIUM COMPLEXED WITH ORGANIC AND INORGANIC LIGANDS.

Description: Biotransformation of various chemical forms of uranium present in wastes, contaminated soils and materials by microorganisms under different process conditions such as aerobic and anaerobic (denitrifying, iron-reducing, fermentative, and sulfate-reducing) conditions will affect the solubility, bioavailability, and mobility of uranium in the natural environment. Fundamental understanding of the mechanisms of microbial transformations of uranium under a variety of environmental conditions will be useful in developing appropriate remediation and waste management strategies as well as predicting the microbial impacts on the long-term stewardship of contaminated sites.
Date: September 15, 2002
Creator: FRANCIS,A.J.
Partner: UNT Libraries Government Documents Department

Nonintercepting imaging diagnostics for the APS injector during storage ring top-up operations.

Description: The recently implemented top-up operating mode of the Advanced Photon Source (APS) storage ring has motivated an emphasis on nonintercepting imaging diagnostics in the injectors. We present the upgrades to the optical synchrotron radiation (OSR) monitors on the accumulator ring and injector synchrotron as well as the plans for a new OSR monitor on a chicane dipole in the linac and for an optical diffraction radiation (ODR) monitor for the 7-GeV transport line to the storage ring. Two key issues are signal strength for a single macropulse in the chicane and discriminating key transverse information from the visible light ODR, respectively.
Date: May 15, 2002
Creator: Lumpkin, A. H. L.; Berg, W. J. B. & Yang, B. X. Y.
Partner: UNT Libraries Government Documents Department

Higgs searches and prospects at CDF

Description: The Standard model of electroweak interactions (SM) has been extremely successful in describing interactions of elementary particles over the last decades. The Higgs scalar boson is one of the key elements of the SM: Higgs interactions with the other particles generate the particle masses and allow to keep the theory renormalizable at electroweak scale. All the particles predicted by the SM but the Higgs boson have already been observed experimentally and therefore search for the Higgs is one of the most important scientific goals for high energy physics. The current lower limit on the SM Higgs mass M{sub H} > 114.4 GeV at 95% CL has been established by LEP experiments. In this paper we review CDF Run I results on Higgs searches including the Higgs bosons predicted by the minimal supersymmetric extention of the Standard Model (MSSM) and discuss the Run II prospects.
Date: January 15, 2003
Creator: Murat, Pavel A
Partner: UNT Libraries Government Documents Department

Noise propagation in iterative reconstruction algorithms with line searches

Description: In this paper we analyze the propagation of noise in iterative image reconstruction algorithms. We derive theoretical expressions for the general form of preconditioned gradient algorithms with line searches. The results are applicable to a wide range of iterative reconstruction problems, such as emission tomography, transmission tomography, and image restoration. A unique contribution of this paper comparing to our previous work [1] is that the line search is explicitly modeled and we do not use the approximation that the gradient of the objective function is zero. As a result, the error in the estimate of noise at early iterations is significantly reduced.
Date: November 15, 2003
Creator: Qi, Jinyi
Partner: UNT Libraries Government Documents Department

Near-Surface Engineered Environmental Barrier Integrity

Description: The INEEL Environmental Systems Research and Analysis (ESRA) program has launched a new R and D project on Near-Surface Engineered Environmental Barrier Integrity to increase knowledge and capabilities for using engineering and ecological components to improve the integrity of near-surface barriers used to confine contaminants from the public and the environment. The knowledge gained and the capabilities built will help verify the adequacy of past remedial decisions and enable improved solutions for future cleanup decisions. The research is planned to (a) improve the knowledge of degradation mechanisms (weathering, biological, geological, chemical, radiological, and catastrophic) in times shorter than service life, (b) improve modeling of barrier degradation dynamics, (c) develop sensor systems to identify degradation prior to failure, and (d) provide a better basis for developing and testing of new barrier systems to increase reliability and reduce the risk of failure. Our project combine s selected exploratory studies (benchtop and field scale), coupled effects accelerated aging testing and the meso-scale, testing of new monitoring concepts, and modeling of dynamic systems. The performance of evapo-transpiration, capillary, and grout-based barriers will be examined.
Date: May 15, 2002
Creator: Piet, S. J. & Breckenridge, R. P.
Partner: UNT Libraries Government Documents Department

Development of Neutron Probes for Characterization of Hazardous Materials in the Sub-surface Medium

Description: Neutron probes are being developed at the Idaho National Engineering and Environmental Laboratory (INEEL) for the detection, identification and quantification of hazardous materials in the ground. Such materials include plutonium, uranium, americium, chlorine and fluorine. Both a Neutron Gamma (NG) probe and a Prompt Fission Neutron (PFN) probe are being developed. The NG probe is used primarily for nuclide identification and quantification measurements. The PFN is used mostly for the detection and measurement of fissile material, but also for the determination of thermal neutron macroscopic absorption cross sections of the various elements comprising the ground matrix. Calibration of these probes will be carried out at the INEEL using an indoor facility that has been designed for this activity.
Date: May 15, 2002
Creator: Keegan, R.P.; McGrath, C.A. & Lopez, J.C.
Partner: UNT Libraries Government Documents Department

CDF tau triggers, analysis and other developments

Description: This note is a write-up of contribution made by the author to the HCP2002 conference. It has two principal subjects. The first subject concerns the CDF {tau} triggers, {tau}-cone algorithms and {tau} physics analysis. {tau} physics is going to be very important in Run II because {tau}'s can extend SUSY searches at large tan {beta} in particular, {tau}'s will help in the searches for {tilde {chi}}{sub 1}{sup {+-}}{tilde {chi}}{sub 2}{sup 0}, MSSM Higgs and other non Standard Model (SM) processes. Also, {tau} events are important for various Standard Model processes including Precision Electroweak, t{bar t}, and SM Higgs searches. {tau} triggers are installed and operating at CDF. The second subject of this contribution to the HCP2002 conference concerns the algorithms of backwards differentiation abstracted from their usual setting inside of Automatic Differentiation software packages. Backwards differentiation (reverse-mode differentiation) provides a useful means for optimizing many kinds of problems.
Date: January 15, 2003
Creator: Smith, J. R.
Partner: UNT Libraries Government Documents Department

Sort-First, Distributed Memory Parallel Visualization and Rendering

Description: While commodity computing and graphics hardware has increased in capacity and dropped in cost, it is still quite difficult to make effective use of such systems for general-purpose parallel visualization and graphics. We describe the results of a recent project that provides a software infrastructure suitable for general-purpose use by parallel visualization and graphics applications. Our work combines and extends two technologies: Chromium, a stream-oriented framework that implements the OpenGL programming interface; and OpenRM Scene Graph, a pipelined-parallel scene graph interface for graphics data management. Using this combination, we implement a sort-first, distributed memory, parallel volume rendering application. We describe the performance characteristics in terms of bandwidth requirements and highlight key algorithmic considerations needed to implement the sort-first system. We characterize system performance using a distributed memory parallel volume rendering application, a nd present performance gains realized by using scene specific knowledge to accelerate rendering through reduced network bandwidth. The contribution of this work is an exploration of general-purpose, sort-first architecture performance characteristics as applied to distributed memory, commodity hardware, along with a description of the algorithmic support needed to realize parallel, sort-first implementations.
Date: July 15, 2003
Creator: Bethel, E. Wes; Humphreys, Greg; Paul, Brian & Brederson, J. Dean
Partner: UNT Libraries Government Documents Department

Progress in the study of mesh refinement for particle-in-cell plasma simulations and its application to heavy ion fusion

Description: The numerical simulation of the driving beams in a heavy ion fusion power plant is a challenging task, and, despite rapid progress in computer power, one must consider the use of the most advanced numerical techniques. One of the difficulties of these simulations resides in the disparity of scales in time and in space which must be resolved. When these disparities are in distinctive zones of the simulation region, a method which has proven to be effective in other areas (e.g. fluid dynamics simulations) is the Adaptive-Mesh-Refinement (AMR) technique. We follow in this article the progress accomplished in the last few months in the merging of the AMR technique with Particle-In-Cell (PIC) method. This includes a detailed modeling of the Lampel-Tiefenback solution for the one-dimensional diode using novel techniques to suppress undesirable numerical oscillations and an AMR patch to follow the head of the particle distribution. We also report new results concerning the modeling of ion sources using the axisymmetric WARPRZ-AMR prototype showing the utility of an AMR patch resolving the emitter vicinity and the beam edge.
Date: September 15, 2002
Creator: Vay, J.-L.; Friedman, A. & Grote, D.P.
Partner: UNT Libraries Government Documents Department