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When the guest of honor is a party pro, it better be good: Austin fête celebrates author (open access)

When the guest of honor is a party pro, it better be good: Austin fête celebrates author

Article about Lara Shriftman and Elizabeth Harrison, co-owners of marketing, public relations, and planning firm Harrison & Shriftman and co-authors of the book "Party Confidential."
Date: November 26, 2006
Creator: Scheidnes, Jean
System: The UNT Digital Library
Geometrical dependence of the low-frequency noise in superconducting flux qubits (open access)

Geometrical dependence of the low-frequency noise in superconducting flux qubits

Article reporting on a study of a series of 85 devices of vary design using a general method for directly measuring the low-frequency flux noise (below 10 Hz) in compound Josephson-junction superconducting flux qubits. The results support the hypothesis that local impurities in the vicinity of the qubit wiring are a key source of low-frequency flux noise in superconducting devices.
Date: February 26, 2009
Creator: Lanting, T.; Berkley, A. J.; Bumble, B.; Bunyk, P.; Fung, A.; Johansson, J. et al.
System: The UNT Digital Library
Manifestation of the Color Glass Condensate in Particle Production at RHIC. (open access)

Manifestation of the Color Glass Condensate in Particle Production at RHIC.

In this paper we discuss the experimental signatures of the new form of nuclear matter--the Color Glass Condensate (CGC) in particle production at RHIC. We show that predictions for particle production in p(d)A and AA collisions derived from these properties are in agreement with data collected at RHIC.
Date: July 26, 2004
Creator: Tuchin, K.
System: The UNT Digital Library
Delamination Failure Investigation for Out-Of-Plane Loading in Laminates (open access)

Delamination Failure Investigation for Out-Of-Plane Loading in Laminates

In contrast to failure approaches at the lamina level or the micromechanics level the present work concerns failure characterization at the laminate level. Specifically, attention is given to the ultimate failure characterization for quasi-isotropic laminates. This is in further contrast to the commonly used approaches for initial damage or progressive damage. It is shown that the analytical failure forms decompose into two modes, one for out of plane, delamination type failure and one for in plane, fiber controlled type failure. The work here is mainly given over to the delamination mode of failure. Experimental results are presented for laminates in this mode of failure. These results are then integrated with the analytical forms to give a simple criterion for delamination failure.
Date: March 26, 2003
Creator: Christensen, R M & DeTeresa, S J
System: The UNT Digital Library
Insulated Pressure Vessels for Vehicular Hydrogen Storage: Analysis and Performance Evaluation (open access)

Insulated Pressure Vessels for Vehicular Hydrogen Storage: Analysis and Performance Evaluation

Insulated pressure vessels are cryogenic-capable pressure vessels that can be fueled with liquid hydrogen (LH{sub 2}) or ambient-temperature compressed hydrogen (CH{sub 2}). Insulated pressure vessels offer the advantages of liquid hydrogen tanks (low weight and volume), with reduced disadvantages (fuel flexibility, lower energy requirement for hydrogen liquefaction and reduced evaporative losses). The work described here is directed at verifying that commercially available pressure vessels can be safely used to store liquid hydrogen. The use of commercially available pressure vessels significantly reduces the cost and complexity of the insulated pressure vessel development effort. This paper describes a series of tests that have been done with aluminum-lined, fiber-wrapped vessels to evaluate the damage caused by low temperature operation. All analysis and experiments to date indicate that no significant damage has resulted. Required future tests are described that will prove that no technical barriers exist to the safe use of aluminum-fiber vessels at cryogenic temperatures. Future activities also include a demonstration project in which the insulated pressure vessels will be installed and tested on two vehicles. A draft standard will also be generated for obtaining certification for insulated pressure vessels.
Date: June 26, 2001
Creator: Aceves, S. M.; Martinez-Frias, J.; Garcia-Villazana, O. & Espinosa-Loza, F.
System: The UNT Digital Library
Simultaneous imaging of the near- and far-field intensity distributions of the Ni-like Sn X-ray laser (open access)

Simultaneous imaging of the near- and far-field intensity distributions of the Ni-like Sn X-ray laser

We report on 2D near-field imaging experiments of the 11.9-nm Sn X-ray laser that were performed with a set of novel Mo/Y multilayer mirrors having reflectivities of up to {approx}45% at normal and at 45 incidence. Second-moment analysis of the X-ray laser emission was used to determine values of the X-ray beam propagation factor M{sup 2} for a range of irradiation parameters. The results reveal a reduction of M{sup 2} with increasing prepulse amplitude. The spatial size of the output is a factor of {approx}2 smaller than previously measured for the 14.7-nm Pd X-ray laser, while the distance of the X-ray emission with respect to the target surface remains roughly the same.
Date: July 26, 2004
Creator: Staub, F; Braud, M; Balmer, J E; Nilsen, J & Bajt, S
System: The UNT Digital Library
Concentration of selected trace elements and PCBs in sediments from the Adriatic Sea (open access)

Concentration of selected trace elements and PCBs in sediments from the Adriatic Sea

A broad baseline study of the levels and distributions of trace metals and PCB compounds in sediments has been undertaken. PCB concentrations in surface sediments reflect the source of these contaminates in the region. The highest PCB concentrations as Aroclor 1260 (approximately 10 ng g{sup -1}) were found in sediments near the outflow of the Po river. The lowest concentrations (1.5 ng g{sup -1} dry) were associated with the sediments from the Jabuka Pit in the Middle Adriatic. These values are quite similar to total PCBs (<1.0-17) measured in surface sediments sampled off the coast of Croatia in 1977-78. Thus, based on the limited amount of new data available, it appears that there has been little, if any, decrease in PCB loading in Adriatic sediments over the past 15 years. Downcore profiles of PCBs in sediment cores are also discussed from a pollution history standpoint. Likewise, total mercury in surface sediments was also highest at stations off the Po (403-499 ng g{sup -1} dry) and lowest (67-224 ng g{sup -1}) in the Jabuka Pit. In one core located just south of the Po outflow, total Hg concentrations at all depths were relatively high decreasing gradually from approximately 400 ng g{sup …
Date: July 26, 2000
Creator: Fowler, S. W.; Hamilton, T. F.; Coquery, M.; Villeneuve, J.-P. & Horvat, M.
System: The UNT Digital Library
Proposed Specification of EUVL Mask Substrate Roughness (open access)

Proposed Specification of EUVL Mask Substrate Roughness

A revised specification of mask substrate roughness was proposed at the 1st International EUVL Symposium in Dallas in 2002 [1]. This document describes the reasoning behind the proposed revision in more detail. The specification of mask substrate roughness should be based on its effect on lithographic performance. The effects of mask roughness can be considered according to the spatial frequency. At high frequencies (f > M x NA/{lambda}) corresponding to spatial periods too small to be resolved, light is scattered outside the angular acceptance of the camera effectively reducing the reflectivity of the mask. At lower frequencies, f > M x NA/{lambda}, light is scattered within the acceptance angle of the camera and can degrade the aerial image quality. The loss in reflectivity due to high-spatial frequency roughness (HSFR) is given by R/R{sub 0} = exp(-(4{pi}{sigma}/{lambda}){sup 2}), (1) where R{sub 0} is the peak reflectivity of the coating on a smooth substrate, {sigma} is the HSFR after multilayer coating. The relationship between top surface roughness and substrate roughness depends on the multilayer deposition process and significant smoothing of substrate roughness has been demonstrated [2]. Ultimately the specification of HSFR may be best decided based on the multilayer deposition process. For …
Date: September 26, 2003
Creator: Gullikson, E.; Walton, C. C. & Taylor, J. S.
System: The UNT Digital Library
Effects of processing conditions on the physical and electrochemical properties of carbon aerogel composites (open access)

Effects of processing conditions on the physical and electrochemical properties of carbon aerogel composites

The carbon aerogel/carbon paper composites have physical properties similar to those of monolithic carbon aerogels but do not require supercritical extraction during fabrication. The resorcinol-formaldehyde based carbon aerogel phase is intertwined between the fibers of a commercial carbon paper. The resulting composites have variable densities (0.4-0.6 g/cc), high surface areas (300-600 m{sup 2}/g), and controllable pore sizes and pore distribution. The effects of the resorcinol-formaldehyde concentrations (50-70% w/v) and the pyrolysis temperature (600-1050 C) were studied in an attempt to tailor the aerogel microstructure and properties. The composite physical properties and structure were analyzed by transmission electron microscopy and multipoint-BET analyses and related to electrochemical capacitive data in 5M KOH. These thin carbon aerogel/carbon paper composite electrodes are used in experiments with electrochemical double-layer capacitors and capacitive deionization.
Date: October 26, 2000
Creator: Tran, T D; Lenz, D; Kinoshita, K & Droege, M
System: The UNT Digital Library
Influence of Environmental Variables on the Susceptibility of Alloy 22 to Environmentally Assisted Cracking (open access)

Influence of Environmental Variables on the Susceptibility of Alloy 22 to Environmentally Assisted Cracking

In its current design, the high-level nuclear waste containers include an external layer of Alloy 22 (NO6022). This material was selected to provide long-term corrosion resistance since if water enters in contact with the containers, they may undergo corrosion. The model for the degradation of the containers includes three modes of corrosion, namely general corrosion, localized corrosion and environmentally assisted cracking (EAC). The objective of the current research was to quantify the susceptibility of Alloy 22 to EAC in several environmental conditions with varying solution composition, temperature and electrochemical potential. The susceptibility to EAC was evaluated using constant deformation (deflection) U-bend specimens in both the wrought and welded conditions. Results show that after more than five years exposure in the vapor and liquid phases of alkaline (PH {approx} 10) and acidic (pH {approx} 3) multi-ionic environments at 60 C and 90 C, Alloy 22 was free from EAC.
Date: September 26, 2002
Creator: Fix, D. V.; Estill, J. C.; King, K. J.; Day, S. D. & Rebak, R. B.
System: The UNT Digital Library
NEW WEB-BASED ACCESS TO NUCLEAR STRUCTURE DATASETS. (open access)

NEW WEB-BASED ACCESS TO NUCLEAR STRUCTURE DATASETS.

As part of an effort to migrate the National Nuclear Data Center (NNDC) databases to a relational platform, a new web interface has been developed for the dissemination of the nuclear structure datasets stored in the Evaluated Nuclear Structure Data File and Experimental Unevaluated Nuclear Data List.
Date: September 26, 2004
Creator: WINCHELL,D. F.
System: The UNT Digital Library
RECENT TEST RESULTS OF THE FAST-PULSED 4 T COS DIPOLE GSI 001. (open access)

RECENT TEST RESULTS OF THE FAST-PULSED 4 T COS DIPOLE GSI 001.

For the FAIR-project at GSI a model dipole was built at BNL with the nominal field of 4 T and a nominal ramp rate of 1 T/S. The magnet design was similar to the RHIC dipole, with some changes for loss reduction and better cooling. The magnet was already successfully tested in a vertical cryostat, with good training behavior. Cryogenic losses were measured and first results of field harmonics were published. However, for a better understanding of the cooling process, quench currents at several ramp rates were investigated. Detailed measurements of the field harmonics at 2 T/S between 0 and 4 T were performed.
Date: May 26, 2005
Creator: Moritz, G.; Kaugerts, J.; Escallier, J.; Ganetis, G.; Jain, A.; Marone, A. et al.
System: The UNT Digital Library
Recent Results from EBIT-II Using a Spare Astro-E Microcalorimeter (open access)

Recent Results from EBIT-II Using a Spare Astro-E Microcalorimeter

A spare NASA/GSFC Astro-E microcalorimeter has been installed, tested, and run successfully on EBIT-II at the Lawrence Livermore National Laboratory. A brief overview of results including measurements by the microcalorimeter of absolute excitation cross sections, time dependent spectra, and spectra as a function of Maxwellian temperature are discussed.
Date: June 26, 2001
Creator: Brown, G V; Behar, E; Beiersdorfer, P; Boyce, K R; Chen, H; Gendreau, K C et al.
System: The UNT Digital Library
Adaptive Sampling for Noisy Problems (open access)

Adaptive Sampling for Noisy Problems

The usual approach to deal with noise present in many real-world optimization problems is to take an arbitrary number of samples of the objective function and use the sample average as an estimate of the true objective value. The number of samples is typically chosen arbitrarily and remains constant for the entire optimization process. This paper studies an adaptive sampling technique that varies the number of samples based on the uncertainty of deciding between two individuals. Experiments demonstrate the effect of adaptive sampling on the final solution quality reached by a genetic algorithm and the computational cost required to find the solution. The results suggest that the adaptive technique can effectively eliminate the need to set the sample size a priori, but in many cases it requires high computational costs.
Date: March 26, 2004
Creator: Cantu-Paz, E
System: The UNT Digital Library
NUCLEAR SCIENCE REFERENCES AS A TOOL FOR DATA EVALUATION. (open access)

NUCLEAR SCIENCE REFERENCES AS A TOOL FOR DATA EVALUATION.

For several decades, the Nuclear Science References database has been maintained as a tool for data evaluators and for the wider pure and applied research community. This contribution will describe the database and recent developments in web-based access.
Date: September 26, 2004
Creator: WINCHELL,D. F.
System: The UNT Digital Library
Thermal Explosion Violence of HMX-Based and RDX-Based Explosives - Effects of Composition, Confinement, and Solid Phase Using the Scaled Thermal Explosion Experiment (open access)

Thermal Explosion Violence of HMX-Based and RDX-Based Explosives - Effects of Composition, Confinement, and Solid Phase Using the Scaled Thermal Explosion Experiment

The Scaled Thermal Explosion Experiment (STEX) has been developed to quantify the violence of thermal explosion under well defined and carefully controlled initial and boundary conditions. Here we present results with HMX-based explosives (LX-04 and PBX-9501) and with Composition B. Samples are 2 inches (50 mm) in diameter and 8 inches (200 mm) in length, under confinement of 7,500-30,000 psi (50-200 MPa), with heating rates of 1-3 C/hr. We quantify reaction violence by measuring the wall velocity in the ensuing thermal explosion, and relate the measured velocity to that expected from a detonation. Results with HMX-based explosives (LX-04 and PBX-9501) have shown the importance of confinement and HMX solid phase, with reaction violence ranging from mild pressure bursts to near detonations. By contrast, Composition B has shown very violent reactions over a wide range of conditions.
Date: August 26, 2002
Creator: Maienschein, J L & Wardell, J F
System: The UNT Digital Library
Effect of multiple and delayed jet impact and penetration on concrete target borehole diameter (open access)

Effect of multiple and delayed jet impact and penetration on concrete target borehole diameter

The effect of multiple and delayed jet impact and penetration on the borehole diameter in concrete targets is discussed in this paper. A first-order principle of shaped-charge jet penetration is that target hole volume is proportional to the energy deposited in the target by the jet. This principle is the basis for the relation that target borehole diameter at any depth along the penetration path is proportional to the jet energy deposited in the target at that location. Our current research shows that the 'jet energy per unit hole volume constant' for concrete can be substantially altered by the use of multiple and delayed jet impacts. It has been shown that enhanced entrance crater formation results from the simultaneous impact and penetration of three shaped-charge jets. We now demonstrate that enhanced borehole diameter is also observed by the simultaneous impact and penetration of multiple shaped-charge jets followed by the delayed impact and penetration of a single shaped-charge jet.
Date: January 26, 2001
Creator: Murphy, M J; Baum, D W; Kuklo, R M & Simonson, S C
System: The UNT Digital Library
Electron-Cloud Simulation and Theory for High-Current Heavy-Ion Beams (open access)

Electron-Cloud Simulation and Theory for High-Current Heavy-Ion Beams

Stray electrons can arise in positive-ion accelerators for heavy ion fusion or other applications as a result of ionization of ambient gas or gas released from walls due to halo-ion impact, or as a result of secondary- electron emission. We summarize the distinguishing features of electron cloud issues in heavy-ion-fusion accelerators and a plan for developing a self-consistent simulation capability for heavy-ion beams and electron clouds. We also present results from several ingredients in this capability: (1) We calculate the electron cloud produced by electron desorption from computed beam-ion loss, which illustrates the importance of retaining ion reflection at the walls. (2) We simulate of the effect of specified electron cloud distributions on ion beam dynamics. We consider here electron distributions with axially varying density, centroid location, or radial shape, and examine both random and sinusoidally varying perturbations. We find that amplitude variations are most effective in spoiling ion beam quality, though for sinusoidal variations which match the natural ion beam centroid oscillation or breathing mode frequencies, the centroid and shape perturbations can also have significant impact. We identify an instability associated with a resonance between the beam-envelope ''breathing'' mode and the electron perturbation. We estimate its growth rate, which …
Date: July 26, 2004
Creator: Cohen, R; Friedman, A; Lund, S; Molvik, A; Lee, E; Azevedo, T et al.
System: The UNT Digital Library
Automatic Blocking Of QR and LU Factorizations for Locality (open access)

Automatic Blocking Of QR and LU Factorizations for Locality

QR and LU factorizations for dense matrices are important linear algebra computations that are widely used in scientific applications. To efficiently perform these computations on modern computers, the factorization algorithms need to be blocked when operating on large matrices to effectively exploit the deep cache hierarchy prevalent in today's computer memory systems. Because both QR (based on Householder transformations) and LU factorization algorithms contain complex loop structures, few compilers can fully automate the blocking of these algorithms. Though linear algebra libraries such as LAPACK provides manually blocked implementations of these algorithms, by automatically generating blocked versions of the computations, more benefit can be gained such as automatic adaptation of different blocking strategies. This paper demonstrates how to apply an aggressive loop transformation technique, dependence hoisting, to produce efficient blockings for both QR and LU with partial pivoting. We present different blocking strategies that can be generated by our optimizer and compare the performance of auto-blocked versions with manually tuned versions in LAPACK, both using reference BLAS, ATLAS BLAS and native BLAS specially tuned for the underlying machine architectures.
Date: March 26, 2004
Creator: Yi, Q; Kennedy, K; You, H; Seymour, K & Dongarra, J
System: The UNT Digital Library
Staggered grid lagrangian method with local structured adaptive mesh refinement for modeling shock hydrodynamics (open access)

Staggered grid lagrangian method with local structured adaptive mesh refinement for modeling shock hydrodynamics

A new method for the solution of the unsteady Euler equations has been developed. The method combines staggered grid Lagrangian techniques with structured local adaptive mesh refinement (AMR). This method is a precursor to a more general adaptive arbitrary Lagrangian Eulerian (ALE-AMR) algorithm under development, which will facilitate the solution of problems currently at and beyond the boundary of soluble problems by traditional ALE methods by focusing computational resources where they are required. Many of the core issues involved in the development of the ALE-AMR method hinge upon the integration of AMR with a Lagrange step, which is the focus of the work described here. The novel components of the method are mainly driven by the need to reconcile traditional AMR techniques, which are typically employed on stationary meshes with cell-centered quantities, with the staggered grids and grid motion employed by Lagrangian methods. These new algorithmic components are first developed in one dimension and are then generalized to two dimensions. Solutions of several model problems involving shock hydrodynamics are presented and discussed.
Date: September 26, 2000
Creator: Anderson, R W; Pember, R B & Elliot, N S
System: The UNT Digital Library
A Reduced Model of Kinetic Effects Related to the Saturation of Stimulated Brillouin Scattering (open access)

A Reduced Model of Kinetic Effects Related to the Saturation of Stimulated Brillouin Scattering

We developed a reduced description of kinetic effects that is included in a fluid model of stimulated Brillouin backscattering (SBS) in low Z plasmas (e.g. He, Be). Following hybrid-PIC simulations, the modified ion distribution function is parametrized by the width {delta} of the plateau created by trapping around the phase velocity of the SBS-driven acoustic wave. An evolution equation is derived for {delta}, which affects SBS through a frequency shift and a reduced Landau damping. This model recovers the linear Landau damping value for small waves and the time-asymptotic nonlinear frequency shift calculated by Morales and O'Neil. Finally we compare our reduced model with Bzohar simulations of a Be plasma representative of experiments that have shown evidence of ion trapping.
Date: August 26, 2003
Creator: Divol, L.; Williams, E. A.; Cohen, B. I.; Langdon, A. B. & Lasinski, B. F.
System: The UNT Digital Library
Development of LLNL Methodology for Nonnuclear Safety Bases (open access)

Development of LLNL Methodology for Nonnuclear Safety Bases

The objective of this paper is to introduce the process and philosophies used to develop LLNL methodology for performing nonnuclear safety bases. Our former approach needed revision in order to implement the new Work Smart Standard (WSS), 'Safety Basis Requirements for Nonnuclear Facilities at Lawrence Livermore National Laboratory Site Specific Standard' (UCRL-ID-150214), approved in 2003 and revised January, 2004. This work relates directly to the following workshop theme: 'Improvements in Chemical, Biological, and Non-nuclear Safety analysis.' A requirements document, Environmental Safety and Health Manual, Document 3.1 provides safety bases methodology 'how-to' for LLNL personnel. This methodology document had to undergo a major revision, and essentially was completely re-written, since the nonnuclear requirements underwent a major change due to the new standard. The new methodology was based on a graded approach respective to risk level for each hazard type and facility classification. The development process included input from a cross-section of representatives of LLNL organizations at every step in the process. The initial methodology was tested in a pilot project that resulted in completed safety basis analyses and documentation for a major facility at LLNL. Feedback from the pilot was used to refine the methodology. The new methodology promotes a graded …
Date: April 26, 2004
Creator: van Warmerdam, C M & Pinkston, D M
System: The UNT Digital Library
Creating Ensembles of Decision Trees Through Sampling (open access)

Creating Ensembles of Decision Trees Through Sampling

Recent work in classification indicates that significant improvements in accuracy can be obtained by growing an ensemble of classifiers and having them vote for the most popular class. This paper focuses on ensembles of decision trees that are created with a randomized procedure based on sampling. Randomization can be introduced by using random samples of the training data (as in bagging or boosting) and running a conventional tree-building algorithm, or by randomizing the induction algorithm itself. The objective of this paper is to describe the first experiences with a novel randomized tree induction method that uses a sub-sample of instances at a node to determine the split. The empirical results show that ensembles generated using this approach yield results that are competitive in accuracy and superior in computational cost to boosting and bagging.
Date: July 26, 2001
Creator: Kamath, C. & Cantu-Paz, E.
System: The UNT Digital Library
Absorptance Measurements of Optical Coatings - A Round Robin (open access)

Absorptance Measurements of Optical Coatings - A Round Robin

An international round robin study was conducted on the absorption measurement of laser-quality coatings. Sets of optically coated samples were made by a ''reactive DC magnetron'' sputtering and an ion beam sputtering deposition process. The sample set included a high reflector at 514 nm and a high reflector for the near infrared (1030 to 1318 nm), single layers of silicon dioxide, tantalum pentoxide, and hafnium dioxide. For calibration purposes, a sample metalized with hafnium and an uncoated, superpolished fused silica substrate were also included. The set was sent to laboratory groups for absorptance measurement of these coatings. Whenever possible, each group was to measure a common, central area and another area specifically assigned to the respective group. Specific test protocols were also suggested in regards to the laser exposure time, power density, and surface preparation.
Date: October 26, 2000
Creator: Chow, R; Taylor, J R; Wu, Z L; Boccara, C A; Broulik, U; Commandre, M et al.
System: The UNT Digital Library