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651
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An Application of Trapped-Air Analysis to Large Complex High-Pressure Magnesium Casting
The usual method for simulating die-castings consists of a solidification analysis of the casting process - a computer calculation of heat transfer between the casting and the die components. The use of cyclic simulations, coupled with the geometric accuracy of the finite element method, has advanced this procedure to the point where it is routinely used for reliable prediction of shrinkage defects in die-castings. Filling analysis is also routinely used to get a glimpse of cavity filling and ensures that overflows are at their most effective location. When coupled with heat transfer, a filling analysis is also very effective in demonstrating the effects of heat loss in the fluid and how it consequentially can negatively affect filling.
Date:
July 8, 2004
Creator:
Prindiville, J.; Lee, S. & Gokhale, A.
Object Type:
Report
System:
The UNT Digital Library
Creep of Nearly Lamellar TiAl Alloy Containing W
Effects of W on the creep resistance of two nearly fully lamellar TiAl alloys with 1.0 and 2.0 at.%W have been investigated. In the low stress regime (LS) a nearly quadratic (1.5<n<2) creep behavior was observed. It is found that the addition of W can improve the creep resistance; however, the addition of excess W can result in the formation of {beta} phase, which produces an adverse effect on the creep strength.
Date:
April 8, 2004
Creator:
Hodge, A M; Hsiung, L M & Nieh, T
Object Type:
Article
System:
The UNT Digital Library
Axions from wall decay
The authors discuss the decay of axion walls bounded by strings and present numerical simulations of the decay process. In these simulations, the decay happens immediately, in a time scale of order the light travel time, and the average energy of the radiated axions is <w{sub a}> {approx_equal} 7m{sub a} for v{sub a}/m{sub a} {approx_equal} 500. <w{sub a}> is found to increase approximately linearly with ln(v{sub a}/m{sub a}). Extrapolation of this behavior yields <w{sub a}> {approx_equal} 60 m{sub a} in axion models of interest.
Date:
January 8, 2001
Creator:
Chang, S.; Hagmann, C. & Sikivie, P.
Object Type:
Article
System:
The UNT Digital Library
Environmental Solutions, A Summary of Contributions for CY04: PNNL Contributions to the U.S. Department of Energy
The U.S. Department of Energy's mission is to protect the Columbia River and the public living in communities surrounding the Hanford Site while cleaning up and shrinking the Site. Pacific Northwest National Laboratory is contributing to the cleanup mission and protection of the Columbia River and public. This booklet summarizes work PNNL performed directly for DOE. Work done for Hanford contractors and the Waste Treatment Plant is summarized in the other booklets in this series.
Date:
March 8, 2005
Creator:
Freshley, Mark D.
Object Type:
Report
System:
The UNT Digital Library
Erratum: Simple theory of the line emission profile for the charge-exchange recombination spectroscopy method [Phys. Plasmas, 7, 1315 (2000)]
None
Date:
December 8, 2003
Creator:
Ryutov, D
Object Type:
Article
System:
The UNT Digital Library
Effects of Grain Boundary Constraint on the Constitutive Response of Tantalum Bicrystals
The role of grain boundary constraint in strain localization, slip system activation, slip transmission, and the concomitant constitutive response was examined performing a series of uniaxial compression tests on tantalum bicrystals. Tantalum single crystals were diffusion bonded to form a (011) twist boundary and compressed along the [011] direction. The resulting three-dimensional deformation was analyzed via volume reconstruction. With this, both, the effective states of stress and strain over the cross-sectional area could be measured as a function of distance from the twist boundary, revealing a highly constrained grain boundary. Post-test metallurgical characterization was performed using Electron Back-Scattered-Diffraction (EBSD). The results, a spatial distribution of slip patterning and mapping of crystal rotation around the twist-boundary was analyzed and compared to the known behavior of the individual single crystals. A rather large area near the grain boundary revealed no crystal rotation. Instead, patterns of alternating crystal rotation similar to single crystal experiments were found to be some distance away ({approx} 400 m) from the immediate grain boundary region, indicating the large length scale of the rotation free region.
Date:
April 8, 2003
Creator:
Ziegler, A; Campbell, G H; Kumar, M & Stolken, J S
Object Type:
Article
System:
The UNT Digital Library
DESIGN OF 1.2 GEV SCL AS NEW INJECTOR FOR THE BNL AGS.
Gradient Synchrotron (AGS) accelerator complex at the Brookhaven National Laboratory (BNL) to provide an average beam power of 1 MW at the energy of 28 GeV. The facility is to be used primarily as a proton driver for the production of intense neutrino beams [1,2]. A study of a proton Super-Conducting Linac (SCL) as the new injector to the AGS has just been completed [3] and found feasible. We are now initiating a second design phase with more emphasis on engineering considerations, namely: cryogenics, cryostat design, RF cavity design, RF power couplers and power sources, conventional engineering, and insertions for transverse focusing and other beam utilities. Some of these issues are addressed in this paper.
Date:
September 8, 2003
Creator:
RUGGIERO,A. G. ALESSI,J. HARRISON,M. IAROCCI,M. NEHRING,T. RAPARIA,D. ROSER,T. TUOZZOLO,J. WENG,W.
Object Type:
Article
System:
The UNT Digital Library
PEEKING THROUGH THE COLORED GLASS: A PERSPECTIVE ON NEW DIRECTIONS.
I discuss the Color Glass Condensate as a media. I argue that Pomerons, Odderons and Reggeons are the small fluctuation excitations of this media. I argue that understanding the effects of Pomeron loops leads to the idea that this media has a duality symmetry. I discuss the implications of the Color Glass Condensate for the initial conditions at RHIC.
Date:
February 8, 2005
Creator:
McLerran, L.
Object Type:
Article
System:
The UNT Digital Library
AMRSim: an object-oriented performance simulator for parallel adaptive mesh refinement
Adaptive mesh refinement is complicated by both the algorithms and the dynamic nature of the computations. In parallel the complexity of getting good performance is dependent upon the architecture and the application. Most attempts to address the complexity of AMR have lead to the development of library solutions, most have developed object-oriented libraries or frameworks. All attempts to date have made numerous and sometimes conflicting assumptions which make the evaluation of performance of AMR across different applications and architectures difficult or impracticable. The evaluation of different approaches can alternatively be accomplished through simulation of the different AMR processes. In this paper we outline our research work to simulate the processing of adaptive mesh refinement grids using a distributed array class library (P++). This paper presents a combined analytic and empirical approach, since details of the algorithms can be readily predicted (separated into specific phases), while the performance associated with the dynamic behavior must be studied empirically. The result, AMRSim, provides a simple way to develop bounds on the expected performance of AMR calculations subject to constraints given by the algorithms, frameworks, and architecture.
Date:
January 8, 2001
Creator:
Miller, B; Philip, B; Quinlan, D & Wissink, A
Object Type:
Article
System:
The UNT Digital Library
PLASTIC DEFORMATION AND FRACTURE OF STEELS UNDER DYNAMIC BIAXIAL LOADING
Dynamic equi-biaxial bulging of thin AerMet 100 alloy plates was studied. The plates were deformed using a gas-gun driven flyer plate test set-up at impact velocities between 1.0 and 2.0 km/sec. The results indicate that in addition to biaxial stretching (and thinning) of the plate, internal cavitation (spallation fracture) results from the complex wave interactions within the plate. No outward evidence of damage was observed at the lower velocities, in the range of 1.0-1.2 km/sec. Fine scale cracking of the plates was observed at impact velocity above approximately 1.4 km/sec. Complete specimen fracture, in the form of multiple petals and pie-shaped fragments, was observed at impact velocity above 1.6 km/sec. Hydrodynamic computer code simulations were performed, prior to and in conjunction with the experiments, to aid in experiment design and interpretation of the experimental data.
Date:
July 8, 2004
Creator:
Syn, C; Moreno, J; Goto, D M; Belak, J & Grady, D
Object Type:
Article
System:
The UNT Digital Library
Evaluation of the Impact of CO2, Aqueous Fluid, and Reservoir Rock Interactions on the Geologic Sequestration of CO2 with Special Emphasis on Economic Implications
Lowering the costs of front-end processes in the geologic sequestration of CO{sub 2} can dramatically lower the overall costs. One approach is to sequester less-pure CO{sub 2} waste streams that are less expensive or require less energy to separate from flue gas, a coal gasification process, etc. The objective of this research is to evaluate the impacts of an impure CO{sub 2} waste stream on geologic sequestration using both reaction progress and reactive transport simulators. The simulators serve as numerical laboratories within which a series of computational experiments can be designed, carried out, and analyzed to quantify sensitivity of the overall injection/sequestration process to specific compositional, hydrologic, structural, thermodynamic, and kinetic parameters associated with the injection fluid and subsurface environment.
Date:
March 8, 2001
Creator:
Knauss, K. G.; Johnson, J. W.; Steefel, C. I. & Nitao, J. J.
Object Type:
Article
System:
The UNT Digital Library
Formation of GEMS from shock-accelerated crystalline dust in Superbubbles
Interplanetary dust particles (IDPs) contain enigmatic sub-micron components called GEMS (Glass with Embedded Metal and Sulfides). The compositions and structures of GEMS indicate that they have been processed by exposure to ionizing radiation but details of the actual irradiation environment(s) have remained elusive. Here we propose a mechanism and astrophysical site for GEMS formation that explains for the first time the following key properties of GEMS; they are stoichiometrically enriched in oxygen and systematically depleted in S, Mg, Ca and Fe (relative to solar abundances), most have normal (solar) oxygen isotopic compositions, they exhibit a strikingly narrow size distribution (0.1-0.5 {micro}m diameter), and some of them contain ''relict'' crystals within their silicate glass matrices. We show that the compositions, size distribution, and survival of relict crystals are inconsistent with amorphization by particles accelerated by diffusive shock acceleration. Instead, we propose that GEMS are formed from crystalline grains that condense in stellar outflows from massive stars in OB associations, are accelerated in encounters with frequent supernova shocks inside the associated superbubble, and are implanted with atoms from the hot gas in the SB interior. We thus reverse the usual roles of target and projectile. Rather than being bombarded at rest by …
Date:
December 8, 2004
Creator:
Westphal, A & Bradley, J P
Object Type:
Article
System:
The UNT Digital Library
Study of the Direct Oxidation of Methane in Solid Oxide Fuel Cells
Solid oxide fuel cells (SOFCs) are electrochemical devices that have received great interest recently because of their promise for clean and efficient power generation. Since SOFCs generate electricity directly through electrochemical processes that do not involve combustion, fuel cells are not limited by the Carnot cycle and thus, very high efficiency can be achieved. For instance, current state-of-the-art fuel cells can reach 50% efficiency while that of conventional power generation devices are generally below 30%. The high efficiency is a key mean that will enable the use of fossil fuels at reduced carbon emissions. The ideal fuel for fuel cells is hydrogen. However, hydrogen is not available directly in nature but must be made using another fossil fuel and/or energy sources. For the immediate future, except for a few niche markets, fuel cells will have to use hydrocarbons as fuel. The ideal hydrocarbon fuel would be natural gas since a natural gas infrastructure readily exists. Natural gas has indeed been used to run various fuel cells. However, natural gas cannot be used directly as a fuel for fuel cells because of its low reactivity. Natural gas must be converted to more reactive components, typically to carbon monoxide and hydrogen via …
Date:
February 8, 2002
Creator:
Pham, A. Q.
Object Type:
Report
System:
The UNT Digital Library
Study of Higher Order Modes in High Current Multicell SRF Cavities.
The electron cooling project for RHIC luminosity upgrade and future projects such as eRHIC (electron-ion collider) demand cavities operating at high average current and high bunch charge in CW energy recovery mode. This paper describes the investigation of Higher Order Modes (HOMs) in such a cavity. This work is part of an ongoing effort to develop a 5-cell superconducting cavity for such high current and high bunch charge energy-recovery superconducting linac. The frequency of the cavity is 703.75 MHz with an iris of 17cm and two ferrite absorbers for HOM damping. The main focus of this paper is to identify and investigate possible trapped HOM modes that might result in multibunch instabilities. Detailed MAFIA calculations were performed using the e-module for different end cell geometries. Results from these calculations will be presented. Beam breakup results using TDBBU due to dipole HOM's will also be presented. A beam breakup threshold of above 1.8 A was calculated.
Date:
September 8, 2003
Creator:
Calaga, R.; Ben-Zvi, Ilan; Zhao, Y.; Wang, D. & Wu, G.
Object Type:
Article
System:
The UNT Digital Library
SCIENTIFIC PRESENTATIONS: 11TH MEETING OF THE MANAGEMENT STEERING COMMITTEE OF THE RIKEN BNL COLLABORATION (RBRC SCIENTIFIC ARTICLE, VOLUME 11)
None
Date:
June 8, 2005
Creator:
SAMIOS, N. P. (ORGANIZER)
Object Type:
Report
System:
The UNT Digital Library
Gene recovery microdissection (GRM) a process for producing chromosome region-specific libraries of expressed genes
Gene Recovery Microdissection (GRM) is a unique and cost-effective process for producing chromosome region-specific libraries of expressed genes. It accelerates the pace, reduces the cost, and extends the capabilities of functional genomic research, the means by which scientists will put to life-saving, life-enhancing use their knowledge of any plant or animal genome.
Date:
February 8, 2001
Creator:
Christian, A T; Coleman, M A & Tucker, J D
Object Type:
Report
System:
The UNT Digital Library
Low Dose Radiation Hypersensitivity is Caused by p53-dependent Apoptosis
Exposure to environmental radiation and the application of new clinical modalities, such as radioimmunotherapy, have heightened the need to understand cellular responses to low dose and low-dose rate ionizing radiation. Many tumor cell lines have been observed to exhibit a hypersensitivity to radiation doses below 50 cGy, which manifests as a significant deviation from the clonogenic survival response predicted by a linear-quadratic fit to higher doses. However, the underlying processes for this phenomenon remain unclear. Using a gel microdrop/flow cytometry assay to monitor single cell proliferation at early times post irradiation, we examined the response of human A549 lung carcinoma, T98G glioma and MCF7 breast carcinoma cell lines exposed to gamma radiation doses from 0 to 200 cGy delivered at 0.18 and 22 cGy/min. The A549 and T98G cells, but not MCF7 cells, showed the marked hypersensitivity at doses <50 cGy. To further characterize the low-dose hypersensitivity, we examined the influence of low-dose radiation on cell cycle status and apoptosis by assays for active caspase-3 and phosphatidylserine translocation (annexin-V binding). We observed that caspase-3 activation and annexin-V binding mirrored the proliferation curves for the cell lines. Furthermore, the low-dose hypersensitivity and annexin-V binding to irradiated A549 and T98G cells were …
Date:
April 8, 2004
Creator:
Enns, L; Bogen, K; Wizniak, J; Murtha, A & Weinfeld, M
Object Type:
Article
System:
The UNT Digital Library
Breadboard Testing of a Phase Conjugate Engine with an Interferometric Wave-Front Sensor and a MEMS - Based Spatial Light Modulator
Laboratory breadboard results of a high-speed adaptive optics system are presented. The wave-front sensor for the adaptive optics system is based on a quadrature interferometer, which directly measures the turbulence induced phase aberrations. The laboratory experiments were conducted using Kolmogorov phase screens to simulate atmospheric phase distortions with the characterization of these plates presented below. The spatial light modulator used in the phase conjugate engine was a MEMS-based piston-only correction device with 1024 actuators. The overall system achieved correction speeds in excess of 800 hz and Strehl ratios greater than 0.5 with the Kolmogorov phase screens.
Date:
December 8, 2003
Creator:
Tucker, J.; Olsen, J.; Minden, M. L.; Gavel, D.; Baker, K. L.; Stappaerts, E. A. et al.
Object Type:
Article
System:
The UNT Digital Library
THE NAIVE PARTON MODEL AND BRAHMS MEASUREMENTS.
The Naive Parton Model is revisited in conjunction with some data collected with BRAHMS spectrometers at RHIC.
Date:
February 8, 2003
Creator:
DEBBE,R. FOR THE BRAHMS COLLABORATION
Object Type:
Article
System:
The UNT Digital Library
Quench sensitivity of hot extruded 6061-T6 and 6069-T6 aluminum alloys
The purpose of this study is to investigate the quench sensitivity of mechanical properties of hot extruded 6061 and 6069 aluminum alloys. The relationship between mechanical properties and quench delzty time at various temperatures between 200-500 C was determined. It was concluded that the 6069-T6 was somewhat more quench sensitive than 6061, which may be consistent with the composition difference.
Date:
August 8, 2000
Creator:
Bergsma, S C; Kassner, M E; Li, X & Rosen, R S
Object Type:
Article
System:
The UNT Digital Library
A NIF 3-D High Mach Number Feature Experiment
None
Date:
July 8, 2004
Creator:
Weber, S; Blue, B; Glendinning, S G; Robey, H; Stry, P & Woods, D T
Object Type:
Article
System:
The UNT Digital Library
40 Years of Discovery
History is most interesting when seen through the eyes of those who lived it. In this 40th anniversary retrospective of bioscience research at Lawrence Livermore National Laboratory, we've asked 19 scientists to share their personal recollections about a major accomplishment in the program's history. We have not tried to create a comprehensive or seamless story. Rather, we've attempted to capture the perspectives of key individuals, each of whom worked on a research program that met significant milestones. We have focused particularly on programs and accomplishments that have shaped the current Biology and Biotechnology Research Program (BBRP). In addition, we have included a timeline of biosciences at LLNL, a history of the directorate that appeared in the Laboratory's magazine, ''Science & Technology Review'', in 2002, and a list of bioscience-related articles that have appeared over the years in ''Science & Technology Review and its predecessor, Energy & Technology Review''. The landscape of biological science today is stunningly different from 40 years ago. When LLNL bioscience began in 1963, we knew about the structure of DNA and that it was the carrier of genetic information. However, it would be another year before scientists would understand how DNA codes for the production of …
Date:
July 8, 2003
Creator:
Heller, Arnie; Henke, Amy; Weinstein, Bert & Thomas, Cindy
Object Type:
Report
System:
The UNT Digital Library
Status of Radioactive Elements in the Atomic Weights Table.
During discussions within the Inorganic Chemistry Division Committee, that dealt with the Periodic Table of the Chemical Elements and the official IUPAC position on its presentation, the following question was raised. When the various chemical elements are presented, each with their appropriate atomic weight value, how should the radioactive elements be presented? The Atomic Weights Commission has treated this question in a number of different ways during the past century, almost in a random manner. This report reviews the position that the Commission has taken as a function of time, as a prelude to a discussion in Ottawa about how the Commission should resolve this question for the future.
Date:
August 8, 2003
Creator:
Holden, N. E.
Object Type:
Article
System:
The UNT Digital Library
Carbon Tetrachloride and Chloroform Partition Coefficients Derived from Aqueous Desorption of Contaminated Hanford Sediments
Researchers at PNNL determined CCl4 and CHCl3 groundwater/sediment partition coefficients (Kd values) for contaminated aquifer sediments collected from borehole C3246 (299-W15-46) located in the 200 West Area adjacent to the Z-9 trench. Having realistic values for this parameter is critical to predict future movement of CCl4 in groundwater from the 200 West Area.
Date:
July 8, 2005
Creator:
Riley, Robert G.; Sklarew, Debbie S.; Brown, Christopher F.; Gent, Philip M.; Szecsody, Jim E.; Mitroshkov, Alexandre V. et al.
Object Type:
Report
System:
The UNT Digital Library