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Structural and electronic properties of carbon nanotube tapers

Description: Article on structural and electronic properties of carbon nanotube tapers, a set of nanostructures comprised of straight tubular sections with decreasing diameters, joined to each other via conical funnels and terminated with a hemispherical cap.
Date: October 29, 2001
Creator: Meunier, Vincent; Buongiorno Nardelli, Marco; Roland, Christopher & Bernholc, Jerry
Partner: UNT College of Arts and Sciences
open access

NOVEL INTEGRATING SOLID STATE DETECTOR WITH SEGMENTATION FOR SCANNING TRANSMISSION SOFT X-RAY MICROSCOPY.

Description: An integrating solid state detector with segmentation has been developed that addresses the needs in scanning transmission x-ray microscopy below 1 keV photon energy. The detector is not cooled and can be operated without an entrance window which leads to a total photon detection efficiency close to 100%. The chosen segmentation with 8 independent segments is matched to the geometry of the STXM to maximize image mode flexibility. In the bright field configuration for 1 ms integration time and 5… more
Date: July 29, 2001
Creator: FESER,M. JACOBSEN,C. REHAK,P. DE GERONIMO,G. HOLL,P. STUDER,L.
Partner: UNT Libraries Government Documents Department
open access

Laser Driven High Pressure, High Strain-Rate Materials Experiments

Description: Laser-based experiments are being developed to study the response of solids under high pressure loading. Diagnostic techniques that have been applied include dynamic x-ray diffraction, VISAR wave profile measurements, and post-shock recovery and analysis. These techniques are presented with some results from shocked Si, Al, and Cu experiments.
Date: June 29, 2001
Creator: Kalantar, D. H.; Allen, A. M.; Gregori, F.; Kad, B.; Kumar, M.; Lorenz, K. T. et al.
Partner: UNT Libraries Government Documents Department
open access

Pore-water isotopic compositions and unsaturated-zone flow, Yucca Mountain, Nevada

Description: Isotopic compositions of core-water samples from boreholes USW SD-6 and USW WT-24 indicate that recent water has been introduced at depth. Tritium, carbon, oxygen, and deuterium isotopic compositions all support younger water at depth in the two boreholes. Peaks in tritium concentrations in pore-water samples, indicating younger water than the other samples, observed near the basal vitrophyre of the Topopah Spring Tuff and at the bottom of the CHF and the top of the PP in both boreholes SD-6 an… more
Date: April 29, 2001
Creator: Yang, In C.
Partner: UNT Libraries Government Documents Department
open access

Reaching Ultra High Peak Characteristics in Relativistic Thomson Backscattering

Description: The concept of x-ray laser synchrotron sources (LSS) based on Thomson scattering between laser photons and relativistic electrons leads to future femtosecond light-source facilities fit to multidisciplinary research in ultra-fast structural dynamics. Enticed by these prospects, the Brookhaven Accelerator Test Facility (ATF) embarked into development of the LSS based on a combination of a photocathode RF linac and a picosecond CO{sub 2} laser. We observed the record 1.7 x 10{sup 8} x-ray photons… more
Date: November 29, 2001
Creator: Pogorelsky, I. V.; Ben-Zvi, Ilan; Hirose, T.; Kashiwagi, S.; Yakimenko, V.; Kusche, K. et al.
Partner: UNT Libraries Government Documents Department
open access

Strontium isotope evolution of pore water and calcite in the Topopah Spring Tuff, Yucca Mountain, Nevada

Description: Pore water in the Topopah Spring Tuff has a narrow range of {delta}{sup 87}Sr values that can be calculated from the {delta}{sup 87}Sr values of the rock considering advection through and reaction with the overlying nonwelded tuffs of the PTn. This model can be extended to estimate the variation of {delta}{sup 87}Sr in the pore water through time; this approximates the variation of {delta}{sup 87}Sr measured in calcite fracture coatings. In samples of calcite where no silica can be dated by oth… more
Date: April 29, 2001
Creator: Marshall, Brian D. & Futa, Kiyoto
Partner: UNT Libraries Government Documents Department
open access

Automated real-time testing (ARTT) for embedded control systems (ECS).

Description: Developing real-time automated test systems for embedded control systems has been a real problem. Some engineers and scientists have used customized software and hardware as a solution, which can be very expensive and time consuming to develop. We have discovered how to integrate a suite of commercially available off-the-shelf software tools and hardware to develop a scalable test platform that is capable of performing complete black-box testing for a dual-channel real-time Embedded-PLC-based c… more
Date: October 29, 2001
Creator: Hawkins, J.; Nguyen, H. & Howard, R.
Partner: UNT Libraries Government Documents Department
open access

Evidence for an unsaturated-zone origin of secondary minerals in Yucca Mountain, Nevada

Description: The unsaturated zone (UZ) in Miocene-age welded tuffs at Yucca Mountain, Nevada, is under consideration as a potential site for the construction of a high-level radioactive waste repository. Secondary calcite and silica minerals deposited on fractures and in cavities in the UZ tuffs are texturally, isotopically, and geochemically consistent with UZ deposition from meteoric water infiltrating at the surface and percolating through the UZ along fractures. Nonetheless, two-phase fluid inclusions w… more
Date: April 29, 2001
Creator: Whelan, Joseph F.; Roedder, Edwin & Paces, James B.
Partner: UNT Libraries Government Documents Department
open access

Age constraints on fluid inclusions in calcite at Yucca Mountain

Description: The {sup 207}Pb/{sup 235}U ages for 14 subsamples of opal or chalcedony layers younger than calcite formed at elevated temperature range between 1.88 {+-} 0.05 and 9.7 {+-} 1.5 Ma with most values older than 6-8 Ma. These data indicate that fluids with elevated temperatures have not been present in the unsaturated zone at Yucca Mountain since about 1.9 Ma and most likely since 6-8 Ma. Discordant U-Pb isotope data for chalcedony subsamples representing the massive silica stage in the formation o… more
Date: April 29, 2001
Creator: Neymark, Leonid A.; Amelin, Yuri V.; Paces, James B.; Peterman, Zell E. & Whelan, Joseph F.
Partner: UNT Libraries Government Documents Department
open access

Novel Integrating Solid State Detector With Segmentation For Scanning Transmission Soft X-Ray Microscopy.

Description: An integrating solid state detector with segmentation has been developed that addresses the needs in scanning transmission x-ray microscopy below 1 keV photon energy. The detector is not cooled and can be operated without an entrance window which leads to a total photon detection efficiency close to 100%. The chosen segmentation with 8 independent segments is matched to the geometry of the STXM to maximize image mode flexibility. In the bright field configuration for 1 ms integration time and 5… more
Date: July 29, 2001
Creator: Feser, M.; Jacobsen, C.; Rehak, P.; De Geronimo, G.; Holl, P. & Studer, L.
Partner: UNT Libraries Government Documents Department
open access

Practical High-Order Adaptive Optics Systems For Extrasolar Planet Searches

Description: Direct detection of photons emitted or reflected by an extrasolar planet is an extremely difficult but extremely exciting application of adaptive optics. Typical contrast levels for an extrasolar planet would be 10{sup 9}-Jupiter is a billion times fainter than the sun. Current adaptive optics systems can only achieve contrast levels of 10{sup 6}, but so-called ''extreme'' adaptive optics systems with 10{sup 4}-10{sup 5} degrees of freedom could potentially detect extrasolar planets. We explore… more
Date: August 29, 2001
Creator: Macintosh, B. A.; Olivier, S.; Bauman, B.; Brase, J.; Carr, E.; Carrano, C. J. et al.
Partner: UNT Libraries Government Documents Department
open access

The National Ignition Facility: Status and Plans for Laser Fusion and High-Energy-Density Experimental Studies

Description: The National Ignition Facility (NIF) currently under construction at the University of California Lawrence Livermore National Laboratory (LLNL) is a 192-beam, 1.8-megajoule, 500-terawatt, 351-nm laser for inertial confinement fusion (ICF) and high-energy-density experimental studies. NIF is being built by the Department of Energy and the National Nuclear Security Agency (NNSA) to provide an experimental test bed for the U.S. Stockpile Stewardship Program to ensure the country's nuclear deterren… more
Date: October 29, 2001
Creator: Wuest, C
Partner: UNT Libraries Government Documents Department
open access

Combining a Multithreaded Scene Graph System with a Tiled Display Environment

Description: This case study highlights the technical challenges of creating an application that uses a multithreaded scene graph toolkit for rendering and uses a software environment for management of tiled display systems. Scene graph toolkits simplify and streamline graphics applications by providing data management and rendering services. Software for tiled display environments typically performs device and event management by opening windows on displays, by gathering and processing input device events,… more
Date: March 29, 2001
Creator: Frank, R & Bethel, W
Partner: UNT Libraries Government Documents Department
open access

Cookoff Response of PBXN-109: Material Characterization and ALE3D Thermal Predictions

Description: Materials properties measurements are made for the RDX-based explosive, PBXN-109, and initial ALE3D model predictions are given for the cookoff temperature in a U.S. Navy test. This work is part of an effort in the U.S. Navy and Department of Energy (DOE) laboratories to understand the thermal explosion behavior of this material. Benchmark cookoff experiments are being performed by the U.S. Navy to validate DOE materials models and computer codes. The ALE3D computer code can model the coupled t… more
Date: May 29, 2001
Creator: McClelland, M A; Tran, T D; Cunningham, B J; Weese, R K & Maienschein, J L
Partner: UNT Libraries Government Documents Department
open access

Investigation of Shock-Induced Chemical Reactions in Mo-Si Powder Mixtures Using Instrumented Experiments with PVDF Stress Gauges

Description: Shock-induced chemical reactions in {approx}58% dense Mo+2Si powder mixtures were investigated using time-resolved instrumented experiments, employing PVDF-piezoelectric stress gauges placed at the front and rear surfaces of the powders to measure the input and propagated stresses, and wave speed through the powder mixture. Experiments performed on the powders at input stresses less than 4 GPa, showed characteristics of powder densification and dispersed propagated wave stress profiles with ris… more
Date: May 29, 2001
Creator: Vandersall, K S & Thadhani, N N
Partner: UNT Libraries Government Documents Department
open access

An Opportunity to Immobilize 1.6 MT or More of Weapons-Grade Plutonium at the Mayak and Krasnoyarsk-26 Sites

Description: The Mayak Production Association (PA Mayak), an industrial site in Russia, will be assigned multiple new plutonium disposition missions in order to implement the ''Agreement Between The Government Of The United States Of America And The Government Of Russian Federation Concerning The Management And Disposition Of Plutonium Designated As No Longer Required For Defense Purposes And Related Cooperation'' signed September 1, 2000, by Gore and Kasyanov, In addition, the mission of industrial-scale m… more
Date: June 29, 2001
Creator: Jardine, L J; Borisov, G B; Rovny, S I; Kudinov, K G & Shvedov, A A
Partner: UNT Libraries Government Documents Department
open access

An Algorithm for Projecting Points onto a Patched CAD Model

Description: We are interested in building structured overlapping grids for geometries defined by computer-aided-design (CAD) packages. Geometric information defining the boundary surfaces of a computation domain is often provided in the form of a collection of possibly hundreds of trimmed patches. The first step in building an overlapping volume grid on such a geometry is to build overlapping surface grids. A surface grid is typically built using hyperbolic grid generation; starting from a curve on the sur… more
Date: May 29, 2001
Creator: Henshaw, W D
Partner: UNT Libraries Government Documents Department
open access

Superbend Era Begins Swiftly at the ALS

Description: The successful installation and commissioning of high-field superconducting bend magnets (superbends) in three curved sectors of ALS storage ring was the first time the magnet lattice of an operating synchrotron light source has been retrofitted in this fundamental way. As a result, the ALS now offers an expanded spectral range well into the hard x-ray region without compromising either the number of undulators or their high brightness in the soft x-ray region for which the ALS design was origi… more
Date: November 29, 2001
Creator: Robinson, Art & Tamura, Lori
Partner: UNT Libraries Government Documents Department
open access

Hydrologic characteristics of faults at Yucca Mountain, Nevada

Description: Yucca Mountain is under study as a potential site for underground storage of high-level radioactive waste, with the principle goal being the safe isolation of the waste from the accessible environment. This paper addresses the hydrogeologic characteristics of the fault zones at Yucca Mountain, focusing primarily on the central part of the mountain where the potential repository block is located.
Date: April 29, 2001
Creator: Dickerson, Robert P.
Partner: UNT Libraries Government Documents Department
open access

Fracture imaging with converted elastic waves

Description: This paper examines the seismic signatures of discrete, finite-length fractures, and outlines an approach for elastic, prestack reverse-time imaging of discrete fractures. The results of this study highlight the importance of incorporating fracture-generated P-S converted waves into the imaging method, and presents an alternate imaging condition that can be used in elastic reverse-time imaging when a direct wave is recorded (e.g., for crosswell and VSP acquisition geometries).
Date: May 29, 2001
Creator: Nihei, K.T.; Nakagawa, S. & Myer, L.R.
Partner: UNT Libraries Government Documents Department
open access

A Tritiated-Water Detector with U-232/Th-228 Source

Description: The detection capabilities of the new U-232/Th-228 source are comparable to those of the Na-24 source. The main benefit in using the new source is the ease of operation. Elimination of the neutron activation step required for Na-24 sources saves about 24 hours in planning, scheduling, and executing. With the new U-232/Th-228 source, the monitor can be put in operation in less than 15 minutes. The long half-life of the U-232/Th-228 source also eliminates the need to record calibration and measur… more
Date: May 29, 2001
Creator: Baumann, N.P.
Partner: UNT Libraries Government Documents Department
open access

A Simple, Inexpensive in Situ Method for Assessing Acute Toxicity of Effluents to Fish

Description: Test chambers for conducting in situ fish bioassays were constructed from 8L polyethylene bottles. Yearling fathead minnows (Pimephales promelas) and young-of-the-year bluegill (Lepomis macrochirus) demonstrated greater than 50 percent survival in the chambers after 65 days of exposure in a reservoir, river, and creek. Fathead minnow survival was substantially greater than that of bluegills. The chambers provide a simple, inexpensive, sensitive technique to screen effluents for toxicity.
Date: May 29, 2001
Creator: Wilde, E.W.
Partner: UNT Libraries Government Documents Department
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