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477 Matching Results
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Dynamic response of materials on sub-nanosecond time scales, and beryllium properties for inertial confinement fusion
During the past few years, substantial progress has been made in developing experimental techniques capable of investigating the response of materials to dynamic loading on nanosecond time scales and shorter, with multiple diagnostics probing different aspects of the behavior. these relatively short time scales are scientifically interesting because plastic flow and phase changes in common materials with simple crystal structures--such as iron--may be suppressed, allowing unusual states to be induced and the dynamics of plasticity and polymorphism to be explored. Loading by laser ablation can be particularly convenient. The TRIDENT laser has been used to impart shocks and isentropic compression waves from {approx}1 to 200GPa in a range of elements and alloys, with diagnostics including surface velocimetry (line-imaging VISAR), surface displacement (framed area imaging), x-ray diffraction (single crystal and polycrystal), ellipsometry, and Raman spectroscopy. A major motivation has been the study of the properties of beryllium under conditions relevant to the fuel capsule in inertial confinement fusion: magnetically-driven shock and isentropic compression shots at Z were used to investigate the equation of state and shock melting characteristics, complemented by laser ablation experiments to investigate plasticity and heterogeneous response. These results will help to constrain acceptable tolerances on manufacturing, and possible …
Date:
December 9, 2004
Creator:
Swift, D. C.; Tierney, T. E.; Luo, S. N.; Paisley, D. L.; Kyrala, G. A.; Hauer, A. et al.
Object Type:
Article
System:
The UNT Digital Library
Reinforcement of Aluminum Castings with Dissimilar Metals
None
Date:
January 9, 2004
Creator:
Han, Q.; More, K. L.; Myers, M. R.; Warwick, M. J. & Chen, Y. C.
Object Type:
Report
System:
The UNT Digital Library
[Correspondence from Lucile Wise to Eleanor Brown]
Correspondence from Lucile Wise to Eleanor Brown, consisting of a brief letter from Wise to Brown and two enclosures. The first enclosure is a letter from Michael D. Achey with information on how groups and individuals can support the National Advisory Committee (NAC) meeting in May 2005. The second enclosure is a letter from Mary McCleary Posner about the 17th Annual Memorial Day Weekend Salute to Veterans Celebration to be held from May 27-30, 2005.
Date:
2004-12-09/2005-01-12
Creator:
Wise, Lucile
Object Type:
Letter
System:
The Portal to Texas History
Mannford Eagle (Mannford, Okla.), Vol. 23, No. 6, Ed. 1 Wednesday, June 9, 2004
Weekly newspaper from Mannford, Oklahoma that includes local, state, and national news along with advertising.
Date:
June 9, 2004
Creator:
Retherford, Bill R.
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Cherokeean Herald (Rusk, Tex.), Vol. 155, No. 16, Ed. 1 Wednesday, June 9, 2004
Weekly newspaper from Rusk, Texas that includes local, state and national news along with extensive advertising.
Date:
June 9, 2004
Creator:
Whitehead, Marie
Object Type:
Newspaper
System:
The Portal to Texas History
Texas Attorney General Opinion: GA-0213
Document issued by the Office of the Attorney General of Texas in Austin, Texas, providing an interpretation of Texas law. It provides the opinion of the Texas Attorney General, Greg Abbott, regarding a legal question submitted for clarification; Proper procedure, under article III, section 24a of the Texas Constitution, for the Speaker of the House of Representatives to nominate individuals to serve as members of the Texas Ethics Commission (RQ-0194-GA)
Date:
July 9, 2004
Creator:
Texas. Attorney-General's Office.
Object Type:
Text
System:
The Portal to Texas History
Texas Attorney General Opinion: GA-0229
Document issued by the Office of the Attorney General of Texas in Austin, Texas, providing an interpretation of Texas law. It provides the opinion of the Texas Attorney General, Greg Abbott, regarding a legal question submitted for clarification: Whether a county sheriff is authorized to enter into a contract to house federal prisoners or to accept and dispose of federal surplus property (RQ-0181-GA)
Date:
August 9, 2004
Creator:
Texas. Attorney-General's Office.
Object Type:
Text
System:
The Portal to Texas History
Texas Attorney General Opinion: GA-0230
Document issued by the Office of the Attorney General of Texas in Austin, Texas, providing an interpretation of Texas law. It provides the opinion of the Texas Attorney General, Greg Abbott, regarding a legal question submitted for clarification: Determining the applicable deadline for a municipality and a county to complete their certified subdivision regulation agreement as required in section 242.0015, Local Government Code (RQ-0182-GA)
Date:
August 9, 2004
Creator:
Texas. Attorney-General's Office.
Object Type:
Text
System:
The Portal to Texas History
Texas Attorney General Opinion: GA-0279
Document issued by the Office of the Attorney General of Texas in Austin, Texas, providing an interpretation of Texas law. It provides the opinion of the Texas Attorney General, Greg Abbott, regarding a legal question submitted for clarification: Whether the placement of one-party foreclosable contractual liens on land by a developer that supersede the homestead rights created in article XVI, section 50 of the Texas Constitution violates the Texas Homestead Act (RQ-0236-GA)
Date:
December 9, 2004
Creator:
Texas. Attorney-General's Office.
Object Type:
Text
System:
The Portal to Texas History
[Man placing fried chicken into cardboard box]
Photograph of a man at a restaurant packing fried chicken into a yellow cardboard box. Three other employees are shown standing behind the man.
Date:
December 9, 2004
Creator:
Castillo, José L.
Object Type:
Photograph
System:
The UNT Digital Library
Texas Attorney General Opinion: GA-0146
Document issued by the Office of the Attorney General of Texas in Austin, Texas, providing an interpretation of Texas law. It provides the opinion of the Texas Attorney General, Greg Abbott, regarding a legal question submitted for clarification: Whether an officer, as bailiff and head of courthouse security, is entitled to judicial immunity from a suit for injuries occurring while removing an individual from the courthouse (RQ-0094-GA)
Date:
February 9, 2004
Creator:
Texas. Attorney-General's Office.
Object Type:
Text
System:
The Portal to Texas History
Structural and Electronic Properties of Isolated Nanodiamonds: A Theoretical Perspective
Nanometer sized diamond has been found in meteorites, proto-planetary nebulae and interstellar dusts, as well as in residues of detonation and in diamond films. Remarkably, the size distribution of diamond nanoparticles appears to be peaked around 2-5 nm, and to be largely independent of preparation conditions. Using ab-initio calculations, we have shown that in this size range nanodiamond has a fullerene-like surface and, unlike silicon and germanium, exhibit very weak quantum confinement effects. We called these carbon nanoparticles bucky-diamonds: their atomic structure, predicted by simulations, is consistent with many experimental findings. In addition, we carried out calculations of the stability of nanodiamond which provided a unifying explanation of its size distribution in extra-terrestrial samples, and in ultra-crystalline diamond films. Here we present a summary of our theoretical results and we briefly outline work in progress on doping of nanodiamond with nitrogen.
Date:
September 9, 2004
Creator:
Raty, J & Galli, G
Object Type:
Article
System:
The UNT Digital Library
Nuclear Testing and Comprehensive Test Ban: Chronology Starting September 1992
None
Date:
November 9, 2004
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Atomistic Shock Hugoniot simulation of single-crystal copper
None
Date:
September 9, 2004
Creator:
Bringa, E M; Cazamias, J U; Erhart, P; Stolken, J; Tanushev, N; Wirth, B D et al.
Object Type:
Article
System:
The UNT Digital Library
Large Eddy Simulation of Turbulent Flow and Dispersion in Urban Areas and Forest Canopies
Under the sponsorship of the U.S. DOE and DHS, we have developed a CFD model for simulating flow and dispersion of chemical and biological agents released in the urban environment. Our model, FEM3MP (Chan and Stevens, 2000), is based on solving the three-dimensional, time-dependent, incompressible Navier-Stokes equations on massively parallel computer platforms. The model uses the finite element method for accurate representation of complex building shapes and variable terrain, together with a semi-implicit projection method and modern iterative solvers for efficient time integration (Gresho and Chan, 1998). Physical processes treated include turbulence modeling via the RANS (Reynolds Averaged Navier-Stokes) and LES (Large Eddy Simulation) approaches, atmospheric stability, aerosols, UV radiation decay, surface energy budget, and vegetative canopies, etc. Predictions from our model are continuously being verified and validated against data from wind tunnel (Chan and Stevens, 2000; Chan, et al., 2001) and field experiments (Chan, et al., 2002, 2003; Lee, et al., 2002; Humphreys, et al., 2003; and Calhoun, et al., 2004). Discussed below are several examples to illustrate the use of FEM3MP in simulating flow and dispersion in urban areas and forest canopies, with model results compared against available field measurements.
Date:
April 9, 2004
Creator:
Chan, Stevens T.
Object Type:
Article
System:
The UNT Digital Library
Isopiestic Determination of the Osmotic and Activity Coefficients of NaCl + SrCl2 + H2O at 298.15 K, and Representation with an Extended Ion-Interaction Model
Isopiestic vapor-pressure measurements were made at 298.15 K for aqueous NaCl + SrCl{sub 2} solutions, using NaCl(aq) as the reference standard. The measurements for these ternary solutions were made at NaCl ionic strength fractions of y{sub 1} = 0.17066, 0.47366, and 0.82682 for the water activity range 0.9835 {ge} a{sub w} {ge} 0.8710. Our results, and those from two previous isopiestic studies, were combined and used with previously determined parameters for NaCl(aq) and those for SrCl{sub 2}(aq) determined here to evaluate the mixing parameters{sup S}{Theta}{sub Na,Sr} = (0.0562 {+-} 0.0007) kg {center_dot} mol{sup -1} and {Psi}{sub Na,Sr,Cl} = -(0.00705 {+-} 0.00017) kg{sup 2} {center_dot} mol{sup -2} for an extended form of Pitzer's ion-interaction model. These model parameters are valid for ionic strengths of I {le} 7.0 mol {center_dot} kg{sup -1}, where higher-order electrostatic effects have been included in the mixture model. If the fitting range is extended to the saturated solution molalities, then {sup S}{Theta}{sub Na,Sr} = (0.07885 {+-} 0.00195) kg {center_dot} mol{sup -1} and {Psi}{sub Na,Sr,Cl} = -(0.01230 {+-} 0.00033) kg{sup 2} {center_dot} mol{sup -2}. The extended ion-interaction model parameters obtained from available isopiestic data for SrCl{sub 2}(aq) at 298.15 K yield recommended values of the water activities and …
Date:
November 9, 2004
Creator:
Clegg, S. L.; Rard, J. A. & Miller, D. G.
Object Type:
Article
System:
The UNT Digital Library
Major Tax Issues in the 108th Congress
Tax policy is frequently considered by policymakers as a tool for boosting economic performance in various ways, and the likely economic effects of tax policy are often hotly debated. A brief overview of the current economic context is thus a good starting point for looking at tax issues facing the current Congress. This report provides an overview of major tax issues. The report begins by describing three aspects of the economic context in which the tax policy debate during 2004 is likely to occur: the general state of the U.S. economy; the position of the federal budget; and the level of taxes in the United States.
Date:
September 9, 2004
Creator:
Brumbaugh, David L.
Object Type:
Report
System:
The UNT Digital Library
Alternative Transportation Fuels and Vehicles: Energy, Environment, and Development Issues
This report reviews several issues relating to alternative fuels and vehicles, mainly to combat dependence on petroleum imports and reduce greenhouse gas emissions. The report discusses the advantages and drawbacks of various alternative fuels and vehicles, as well as related legislation.
Date:
January 9, 2004
Creator:
Yacobucci, Brent D.
Object Type:
Report
System:
The UNT Digital Library
Investigating the Affinities and Persistence of VX Nerve Agent in Environmental Matrices
Laboratory experiments were conducted to determine environmental variables that affect the affinities and persistence of the nerve agent O-ethyl S-(2-diisopropylaminoethyl) methylphosphonothiolate (VX) at dilute concentrations in environmental matrices. Quantitative analyses of VX and its degradation products were performed using LC-MS. Batch hydrolysis experiments demonstrated an increasing hydrolysis rate as pH increased, as shown in previous studies, but also indicated that dissolved aqueous constituents can cause significant differences in the absolute hydrolysis rate. Adsorption isotherms from batch aqueous experiments revealed that VX has a high affinity for hydrophobic organics, a moderate affinity for montmorillonite clay, and a very low affinity for an iron-oxyhydroxide soil mineral, goethite. The adsorption on goethite was increased with the presence of dissolved organic matter in solution. VX degraded rapidly when dried onto goethite, when an inner-sphere complex was forced. No enhanced degradation occurred with goethite in small amounts water. These results suggest that aqueous conditions have important controls on VX adsorption and degradation in the environment and a more mechanistic understanding of these controls is needed in order to enable accurate predictions of its long-term fate and persistence.
Date:
March 9, 2004
Creator:
Love, A H; Vance, A L; Reynolds, J G & Davisson, M L
Object Type:
Article
System:
The UNT Digital Library
The National Ignition Facility: Laser Performance and First Experiments
The National Ignition Facility (NIF) at the 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 with room for nearly 100 experimental diagnostics. NIF will be the world's largest and most energetic laser experimental system, providing a scientific center to study inertial confinement fusion (ICF) and matter at extreme energy densities and pressures. NIF's energetic laser beams will compress fusion targets to conditions required for thermonuclear burn, liberating more energy than required to initiate the fusion reactions. Other NIF experiments will study physical processes at temperatures approaching 108 K and 1011 bar, conditions that exist naturally only in the interior of stars, planets and in nuclear weapons. NIF has successfully activated, commissioned, and utilized the first four beams of the laser system to conduct over 300 shots between November 2002 and August 2004. NIF laser scientists have established that the laser meets nearly all performance requirements on a per beam basis for energy, uniformity, timing, and pulse shape. Using these four beams, ICF and high-energy-density physics researchers have conducted a number of experimental campaigns resulting in high quality data that could not be reached on any …
Date:
September 9, 2004
Creator:
Wuest, C R & Moses, E I
Object Type:
Article
System:
The UNT Digital Library
Spatial and Temporal Characterization of Femtosecond Pulses at High-Numerical Aperture Using Collinear, Background-Free, Third-Harmonic Autocorrelation
We show that a simple plane wave analysis can be used even under tight focusing conditions to predict the dependence of third-harmonic generation on the polarization state of the incident beam. Exploiting this fact, we then show that circularly polarized beams may be used to spatially characterize the beam focus and temporally characterize ultrashort pulses in high numerical aperture systems by experimentally demonstrating, for the first time, novel collinear, background-free, third-harmonic intensity autocorrelations in time and space in a high numerical aperture microscope. We also discuss the possibility of using third harmonic generation with circularly polarized beams for background-free collinear frequency resolved optical gating.
Date:
August 9, 2004
Creator:
Fittinghoff, D N; der Au, J A & Squier, J A
Object Type:
Article
System:
The UNT Digital Library
Normalized Texture Motifs and Their Application to Statistical Object Modeling
A fundamental challenge in applying texture features to statistical object modeling is recognizing differently oriented spatial patterns. Rows of moored boats in remote sensed images of harbors should be consistently labeled regardless of the orientation of the harbors, or of the boats within the harbors. This is not straightforward to do, however, when using anisotropic texture features to characterize the spatial patterns. We here propose an elegant solution, termed normalized texture motifs, that uses a parametric statistical model to characterize the patterns regardless of their orientation. The models are learned in an unsupervised fashion from arbitrarily orientated training samples. The proposed approach is general enough to be used with a large category of orientation-selective texture features.
Date:
March 9, 2004
Creator:
Newsam, S D
Object Type:
Article
System:
The UNT Digital Library
The WARP Code: Modeling High Intensity Ion Beams
The Warp code, developed for heavy-ion driven inertial fusion energy studies, is used to model high intensity ion (and electron) beams. Significant capability has been incorporated in Warp, allowing nearly all sections of an accelerator to be modeled, beginning with the source. Warp has as its core an explicit, three-dimensional, particle-in-cell model. Alongside this is a rich set of tools for describing the applied fields of the accelerator lattice, and embedded conducting surfaces (which are captured at sub-grid resolution). Also incorporated are models with reduced dimensionality: an axisymmetric model and a transverse ''slice'' model. The code takes advantage of modern programming techniques, including object orientation, parallelism, and scripting (via Python). It is at the forefront in the use of the computational technique of adaptive mesh refinement, which has been particularly successful in the area of diode and injector modeling, both steady-state and time-dependent. In the presentation, some of the major aspects of Warp will be overviewed, especially those that could be useful in modeling ECR sources. Warp has been benchmarked against both theory and experiment. Recent results will be presented showing good agreement of Warp with experimental results from the STS500 injector test stand. Additional information can be found on …
Date:
December 9, 2004
Creator:
Grote, D. P.; Friedman, A.; Vay, J. L. & Haber, I.
Object Type:
Article
System:
The UNT Digital Library
Experimental and theoretical evaluation of density sensitive N VII, Ar XIV and Fe XXII line ratios
The line ratios of the 2p-3d transitions in the B-like spectra Ar XIV and Fe XXII have been measured using the electron beam ion traps at Livermore. Radiative-collisional model calculations show these line ratios to be sensitive to the electron density in the ranges ne = 10{sup 10} to 10{sup 12} cm{sup -3} and ne = 10{sup 13} to 10{sup 15} cm{sup -3}, respectively. In our experiment, the electron beam density of about 10{sup 11} cm{sup -3} was varied by about a factor of 5. Our data show a density effect for the line doublet in Ar XIV, and good agreement with theory is found. The relative intensity of the Fe XXII doublet shows good agreement with our predicted low density limit. The N VI K-shell spectrum was used to infer the actual electron density in the overlap region of ion cloud and electron beam, and systematic measurements and calculations of this spectrum are presented as well. The Ar XIV and Fe XXII spectra promise to be reliable density diagnostics for stellar coronae, complementing the K-shell diagnostics of helium-like ions.
Date:
January 9, 2004
Creator:
Chen, H; Beiersdorfer, P; Heeter, L A; Liedahl, D A; Naranjo-Rivera, K L; Trabert, E et al.
Object Type:
Article
System:
The UNT Digital Library