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703 Matching Results
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Derivation Of Probabilistic Damage Definitions From High Fidelity Deterministic Computations
This paper summarizes a methodology used by the Underground Analysis and Planning System (UGAPS) at Lawrence Livermore National Laboratory (LLNL) for the derivation of probabilistic damage curves for US Strategic Command (USSTRATCOM). UGAPS uses high fidelity finite element and discrete element codes on the massively parallel supercomputers to predict damage to underground structures from military interdiction scenarios. These deterministic calculations can be riddled with uncertainty, especially when intelligence, the basis for this modeling, is uncertain. The technique presented here attempts to account for this uncertainty by bounding the problem with reasonable cases and using those bounding cases as a statistical sample. Probability of damage curves are computed and represented that account for uncertainty within the sample and enable the war planner to make informed decisions. This work is flexible enough to incorporate any desired damage mechanism and can utilize the variety of finite element and discrete element codes within the national laboratory and government contractor community.
Date:
October 26, 2004
Creator:
Leininger, L D
Object Type:
Report
System:
The UNT Digital Library
Trade Promotion Authority and Fast-Track Negotiating Authority for Trade Agreements: Chronology of Major Votes
None
Date:
August 26, 2004
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Geothermal Prospecting using Hyperspectral Imaging and Field Observations, Dixie Meadows, NV
In an ongoing project to relate surface hydrothermal alteration to structurally controlled geothermal aquifers, we mapped a 16 km swath of the eastern front of the Stillwater Range using Hyperspectral fault and mineral mapping techniques. The Dixie Valley Fault system produces a large fractured aquifer heating Pleistocene aged groundwater to a temperature of 285 C at 5-6 km. Periodically over the last several thousand years, seismic events have pushed these heated fluids to the surface, leaving a rich history of hydrothermal alteration in the Stillwater Mountains. At Dixie Hot Springs, the potentiometric surface of the aquifer intersects the surface, and 75 C waters flow into the valley. We find a high concentration of alunite, kaolinite, and dickite on the exposed fault surface directly adjacent to a series of active fumaroles on the range front fault. This assemblage of minerals implies interaction with water in excess of 200 C. Field spectra support the location of the high temperature mineralization. Fault mapping using a Digital Elevation Model in combination with mineral lineation and field studies shows that complex fault interactions in this region are improving permeability in the region leading to unconfined fluid flow to the surface. Seismic studies conducted 10 km …
Date:
April 26, 2004
Creator:
Kennedy-Bowdoin, T; Silver, E; Martini, B & Pickles, W
Object Type:
Article
System:
The UNT Digital Library
The President Pro Tempore of the Senate: History and Authority of the Office
This report traces the constitutional origins and development of the office of President pro tempore of the Senate, reviews its current role and authority, and provides information on Senators who have held this office -- and the more recently-created subsidiary offices -- over the past two centuries.
Date:
July 26, 2004
Creator:
Sachs, Richard C.
Object Type:
Report
System:
The UNT Digital Library
Nonlinear Rayleigh-Taylor growth in convergine geometry
The early nonlinear phase of Rayleigh-Taylor growth is typically described in terms of the classic Layzer model in which bubbles of light fluid rise into the heavy fluid at a constant rate determined by the bubble radius and the gravitational acceleration. However, this model is strictly valid only for planar interfaces and hence ignores any effects which might be introduced by the spherically converging interfaces of interest in inertial confinement fusion. Here a generalization of the Layzer nonlinear bubble rise rate is given for a self-similar spherically converging flow of the type studied by Kidder. A simple formula for the bubble amplitude is found showing that, while the bubble initially rises with a constant velocity similar to the Layzer result, during the late phase of the implosion, an acceleration of the bubble rise rate occurs. The bubble rise rate is verified by comparison with numerical hydrodynamics simulations.
Date:
April 26, 2004
Creator:
Clark, D S & Tabak, M
Object Type:
Article
System:
The UNT Digital Library
A Geostatistical Analysis of Historical Field Data on Tritium, Technetium-99, Iodine-129, and Uranium
The purpose of the study described in this report was to generate maps and statistics that quantify contamination in groundwater, based on historical groundwater concentration data for multiple points in time. The results generated from this study include several quantitative summaries of contaminant distributions (e.g., the location of the center of mass of contaminant plumes and the total mass of contaminants in the plume) and are collectively referred to as history matching data. A primary goal of this study was to use geostatistical and Monte Carlo methods that allow one to provide an estimate of uncertainty in the history matching data generated.
Date:
April 26, 2004
Creator:
Murray, Christopher J.; Chien, Yi-Ju & Thorne, Paul D.
Object Type:
Report
System:
The UNT Digital Library
EVALUATED NUCLEAR STRUCTURE DATA FILE AND RELATED PRODUCTS.
The Evaluated Nuclear Structure Data File (ENSDF) is a leading resource for the experimental nuclear data. It is maintained and distributed by the National Nuclear Data Center, Brookhaven National Laboratory. The file is mainly contributed to by an international network of evaluators under the auspice of the International Atomic Energy Agency. The ENSDF is updated, generally by mass number, i.e., evaluating together all isobars for a given mass number. If, however, experimental activity in an isobaric chain is limited to a particular nuclide then only that nuclide is updated. The evaluations are published in the journal Nuclear Data Sheets, Academic Press, a division of Elsevier.
Date:
September 26, 2004
Creator:
TULI,J. K.
Object Type:
Article
System:
The UNT Digital Library
Hydrogen Sensor Based on Yttria-Stabilized Zirconia Electrolyte and Tin-Doped Indium Oxide Sensing Electrode
A solid state electrochemical sensor has been developed for hydrogen leak detection in ambient air. The sensor uses an yttria-stabilized electrolyte with a tin-doped indium oxide sensing electrode and a Pt reference electrode. Excellent sensitivity, and response time of one second or less, are reported for hydrogen gas over the concentration range of 0.03 to 5.5% in air. Cross-sensitivity to relative humidity and to CO{sub 2} are shown to be low. The response to methane, a potentially significant source of interference for such a sensor, is significantly less than that for hydrogen. The sensor shows good reproducibility and was unaffected by thermal cycling over the course of this investigation. The effects of sensing electrode thickness and thermal aging are also reported, and the sensing mechanism is discussed. The sensor is intended for use in vehicles powered by hydrogen fuel cells and hydrogen internal combustion engines. Those vehicles will use and/or store significant quantities of hydrogen, and will require safety sensor for monitoring potential hydrogen leakage in order to ensure passenger safety.
Date:
March 26, 2004
Creator:
Martin, L P & Glass, R S
Object Type:
Article
System:
The UNT Digital Library
Laboratory Studies of the Fe K-shell Emission
An overview is given of measurements of the Fe K-shell spectrum from low-density laboratory sources. The measurements include wavelengths, electron-impact collision cross sections, innershell ionization phenomena, dielectronic recombination resonance strengths, charge exchange recombination, electron beam polarization effects, resonance excitation, and radiative cascade contributions. K-shell spectra have now also been obtained with microcalorimeters, including microcalorimeter arrays that are twins of the ASTRO-E and ASTRO-E2 missions, which illustrate typical resolving powers and spectral capabilities.
Date:
December 26, 2004
Creator:
Beiersdorfer, P
Object Type:
Article
System:
The UNT Digital Library
XRD and NMR investigation of Ti-compound formation in solution-doping of sodium aluminum hydrides: Solubility of Ti in NaAlH4 crystals grown in THF
Sodium aluminum hydrides have gained attention due to their high hydrogen weight percent (5.5% ideal) compared to interstitial hydrides, and as a model for hydrides with even higher hydrogen weight fraction. The purpose of this paper is to investigate the Ti-compounds that are formed under solution-doping techniques, such as wet doping in solvents such as tetrahydrofuran (THF). Compound formation in Ti-doped sodium aluminum hydrides is investigated using x-ray diffraction (XRD) and magic angle spinning (MAS) nuclear magnetic resonance (NMR). We present lattice parameter measurements of crushed single crystals, which were exposed to Ti during growth. Rietveld refinements indicate no lattice parameter change and thus no solubility for Ti in NaAlH{sub 4} by this method of exposure. In addition, x-ray diffraction data indicate that no Ti substitutes in NaH, the final decomposition product for the alanate. Reaction products of completely reacted (33.3 at. %-doped) samples that were solvent-mixed or mechanically milled are investigated. Formation of TiAl{sub 3} is observed in mechanically milled materials, but not solution mixed samples, where bonding to THF likely stabilizes Ti-based nano-clusters. The Ti in these clusters is activated by mechanical milling.
Date:
August 26, 2004
Creator:
Majzoub, E. H.; Herberg, J. L.; Stumpf, R.; Spangler, S. & Maxwell, R. S.
Object Type:
Article
System:
The UNT Digital Library
Experimental Determination of Thermodynamic Properties of Ion-Exchange in Heulandite: Binary Ion-Exchange Experiments at 55 and 85 oC Involving Ca2+, Sr2+, Na+, and K+
Heulandite is a common rock-forming zeolite that exhibits wide solid solution of extra framework cations, presumably due to ready ion exchange with aqueous solutions. In order to provide a quantitative basis for interpreting and predicting the distribution of aqueous species between heulandite and aqueous solutions, ion exchange equilibrium between heulandite and aqueous solutions with respect to the binary cation pairs Ca{sup 2+} - K{sup +}, Ca{sup 2+} - Na{sup +}, K{sup +} - Na{sup +}, K{sup +} - Sr{sup 2+}, Na{sup +} - Sr{sup 2+}, and Ca{sup 2+} - Sr{sup 2+} was investigated. Homoionic Ca-, K-, and Na-heulandites prepared from natural heulandite were equilibrated with 0.1 N Cl{sup -} solutions containing various proportions of the cations in a given binary pair at 55 and 85 C to define isotherms describing partitioning of the cations over a wide range of heulandite and solution composition with respect to the cations in each pair. In general, the experiments equilibrated rapidly, within 11-15 weeks at 55 C and 3-4 weeks at 85 C. The exception was the Ca{sup 2+} - Sr{sup 2+} binary exchange, which did not equilibrate even after 3 months at 55 C and 4 weeks at 85 C. Slow exchange of …
Date:
April 26, 2004
Creator:
Fridriksson, T.; Neuhoff, P. S.; Viani, B. E. & Bird, D. K.
Object Type:
Article
System:
The UNT Digital Library
Quadratic Finite Element Method for 1D Deterministic Neutron Transport
None
Date:
July 26, 2004
Creator:
Tolar, Jr., D R & Ferguson, J M
Object Type:
Article
System:
The UNT Digital Library
REVERSIBLE N-BIT TO N-BIT INTEGER HAAR-LIKE TRANSFORMS
We introduce TLHaar, an n-bit to n-bit reversible transform similar to the S-transform. TLHaar uses lookup tables that approximate the S-transform, but reorder the coefficients so they fit into n bits. TLHaar is suited for lossless compression in fixed-width channels, such as digital video channels and graphics hardware frame buffers. Tests indicate that when the incoming image data has lines or hard edges TLHaar coefficients compress better than S-transform coefficients. For other types of image data TLHaar coefficients compress up to 2.5% worse than those of the S-transform, depending on the data and the compression method used.
Date:
July 26, 2004
Creator:
Senecal, J G; Duchaineau, M A & Joy, K I
Object Type:
Article
System:
The UNT Digital Library
Simulation of the Future LSST Data Pipelines
In this paper we describe our approach to build a pipeline simulator for the future Large-scale Synoptic Survey Telescope (LSST). The simulated pipeline will be used to research and evaluate software architectures that are efficient and flexible. It will also be used to define the real-time software and hardware requirements needed to support the anticipated LSST data rates. The LSST data pipeline requirements are still being defined, however, previous surveys can provide a good source for data requirements. Our approach is to use the SuperMacho data pipeline as a prototyping tool to identify a framework for building Modular Data-Centric Pipeline (MDCP) architectures. The prototyping is done in a hierarchical fashion to help capture and define the general data attributes (schema) first. We then model other necessary components based on science and performance requirements. We use identified schemas or data attributes as a way to define a data model for LSST.
Date:
July 26, 2004
Creator:
Abdulla, Ghaleb M.
Object Type:
Article
System:
The UNT Digital Library
Automated Image Data Exploitation Final Report
The automated production of maps of human settlement from recent satellite images is essential to detailed studies of urbanization, population movement, and the like. Commercial satellite imagery is becoming available with sufficient spectral and spatial resolution to apply computer vision techniques previously considered only for laboratory (high resolution, low noise) images. In this project, we extracted the boundaries of human settlements from IKONOS 4-band and panchromatic images using spectral segmentation together with a form of generalized second-order statistics and detection of edges and corners.
Date:
January 26, 2004
Creator:
Kamath, C; Poland, D; Sengupta, S K & Futterman, J H
Object Type:
Report
System:
The UNT Digital Library
Safe Drinking Water Act: Implementation and Issues
This report contains information regarding the Safe Drinking Water Act. Amendments to the act, drinking water infrastructure funding, and drinking water security are among topics discussed in this report.
Date:
August 26, 2004
Creator:
Tiemann, Mary
Object Type:
Report
System:
The UNT Digital Library
Miranda Reconsidered: Supreme Court Review of Miranda Rights in United States v. Patane Missouri v. Seibert, and Fellers v. United States
None
Date:
July 26, 2004
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Health Care Spending: Context and Policy
The United States spends a large and growing share of national income on health care. In 2004, health spending is expected to approach $1.8 trillion and account for more than 16% of gross domestic product. This report contains information on the background of the healthcare industry in the United States, key issues for Congress in this policy area, and three policy directions to consider: changing health care, changing federal programs, and changing tax policy.
Date:
August 26, 2004
Creator:
Jenson, Jennifer
Object Type:
Report
System:
The UNT Digital Library
Suits Against State Employers Under the Family and Medical Leave Act: Analysis of Nevada Department of Human Resources v. Hibbs
None
Date:
May 26, 2004
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
LLNL Microsensors Program
The Microsensors Program was born out the need for enhanced sensor technology in support of the Weapons Program. In the interest of expanded diagnostic capabilities to provide true performance characteristics of weapon assemblies in flight and ground tests, a suite of sensor requirements was proposed. These potential new sensor technologies were envisioned to be completely unobtrusive and allow for the development of test vehicles (mock warheads and bomb assemblies) that were designed to mechanical and electrical specifications as close to the stockpile weapon design configuration as possible. The closeness of a test vehicle design to the respective stockpile weapon design is referred to as ''fidelity,'' with the term ''high-fidelity'' to mean all components are designed to emulate, very closely, the true system design. These efforts were in line with many activities associated with Stockpile Stewardship and were intended to enable better modeling and performance assessment without the need for underground testing. Several weapons are currently undergoing Life Extension Programs (LEP) to lengthen each weapon system's respective service life. The ability to assess the projected life of these complex assemblies is crucial to the success of the LEP activities.
Date:
April 26, 2004
Creator:
Lavietes, A
Object Type:
Article
System:
The UNT Digital Library
LARGE-X RESUMMATIONS IN QCD.
None
Date:
July 26, 2004
Creator:
Vogelsang, W.
Object Type:
Article
System:
The UNT Digital Library
Flash X-Ray Injector Study
The study described in this report1 models the FXR injector from the cathode to the exit of the injector. The calculations are compared to actual experimental measurements, table 1. In these measurements the anode voltage was varied by changing the Marks-Bank charging voltage. The anode-cathode spacing was varied by adjusting the location of the cathode in hopes of finding an island of minimum emittance (none found). The bucking coil current was set for zero field on the cathode. In these measurements, a pepper-pot mask was inserted into FXR at beam bug 135 and viewed downstream via a wiggle probe diagnostic at cell gap J21, figure 1. The observed expansion of the beamlets passing through the mask of known geometric layout and hole size allow a calculation of the phase space beam properties.
Date:
March 26, 2004
Creator:
Paul, A C
Object Type:
Report
System:
The UNT Digital Library
Modeling the Long-Term Isolation Performance of Natural and Engineered Geologic CO2 Storage Sites
Long-term cap rock integrity represents the single most important constraint on the long-term isolation performance of natural and engineered geologic CO{sub 2} storage sites. CO{sub 2} influx that forms natural accumulations and CO{sub 2} injection for EOR/sequestration or saline-aquifer disposal both lead to concomitant geochemical alteration and geomechanical deformation of the cap rock, enhancing or degrading its seal integrity depending on the relative effectiveness of these interdependent processes. This evolution of cap-rock permeability can be assessed through reactive transport modeling, an advanced computational method based on mathematical models of the coupled physical and chemical processes catalyzed by the influx event. Using our reactive transport simulator (NUFT), supporting geochemical databases and software (SUPCRT92), and distinct-element geomechanical model (LDEC), we have shown that influx-triggered mineral dissolution/precipitation reactions within typical shale cap rocks continuously reduce microfrac apertures, while pressure and effective-stress evolution first rapidly increase then slowly constrict them. For a given shale composition, the extent of geochemical enhancement is nearly independent of key reservoir properties (permeability and lateral continuity) that distinguish saline aquifer and EOR/sequestration settings and CO{sub 2} influx parameters (rate, focality, and duration) that distinguish engineered disposal sites and natural accumulations, because these characteristics and parameters have negligible impact on …
Date:
July 26, 2004
Creator:
Johnson, J. W.; Nitao, J. J. & Morris, J. P.
Object Type:
Article
System:
The UNT Digital Library
Reactive Transport Modelling of CO2 Storage in Saline Aquifers to Elucidate Fundamental Processes, Trapping Mechanisms, and Sequestration Partitioning
The ultimate fate of CO{sub 2} injected into saline aquifers for environmental isolation is governed by three interdependent yet conceptually distinct processes: CO{sub 2} migration as a buoyant immiscible fluid phase, direct chemical interaction of this rising plume with ambient saline waters, and its indirect chemical interaction with aquifer and cap-rock minerals through the aqueous wetting phase. Each process is directly linked to a corresponding trapping mechanism: immiscible plume migration to hydrodynamic trapping, plume-water interaction to solubility trapping, and plume-mineral interaction to mineral trapping. In this study, reactive transport modeling of CO{sub 2} storage in a shale-capped sandstone aquifer at Sleipner has elucidated and established key parametric dependencies of these fundamental processes, the associated trapping mechanisms, and sequestration partitioning among them during consecutive 10-year prograde (active-injection) and retrograde (post-injection) regimes. Intra-aquifer permeability structure controls the path of immiscible CO{sub 2} migration, thereby establishing the spatial framework of plume-aquifer interaction and the potential effectiveness of solubility and mineral trapping. Inter-bedded thin shales--which occur at Sleipner--retard vertical and promote lateral plume migration, thereby significantly expanding this framework and enhancing this potential. Actual efficacy of these trapping mechanisms is determined by compositional characteristics of the aquifer and cap rock: the degree of solubility …
Date:
July 26, 2004
Creator:
Johnson, J. W.; Nitao, J. J. & Knauss, K. G.
Object Type:
Article
System:
The UNT Digital Library