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12,143 Matching Results
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Characterization of dislocation wall spacing distributions
While conventionally the length scale of dislocation microstructures has been characterized by only a mean value it is also of interest to know the shape of the wall spacing distribution. In order to investigate the ability to characterize such spacing distributions for near-planar boundaries a model has been developed allowing the construction of a series of dislocation walls that can be sectioned in any plane allowing spacing distributions of the traces to be calculated. Results suggest that distribution shape is not adversely affected by either test section or by realistically low numbers of measurements. Consequently experimental measurements have been made on both low strain ({epsilon} = 0.2 and {epsilon} = 0.3) and high strain ({epsilon} = 2.7) samples. The distributions for all three strains exhibit similar shapes and can be scaled to a single curve for the probability density function.
Date:
December 31, 1997
Creator:
Godfrey, A. & Hughes, D. A.
Object Type:
Article
System:
The UNT Digital Library
Characterization of Plasma Sprayed Beryllium ITER First Wall Mockups
ITER first wall beryllium mockups, which were fabricated by vacuum plasma spraying the beryllium armor, have survived 3000 thermal fatigue cycles at 1 MW/sq m without damage during high heat flux testing at the Plasma Materials Test Facility at Sandia National Laboratory in New Mexico. The thermal and mechanical properties of the plasma sprayed beryllium armor have been characterized. Results are reported on the chemical composition of the beryllium armor in the as-deposited condition, the through thickness and normal to the through thickness thermal conductivity and thermal expansion, the four-point bend flexure strength and edge-notch fracture toughness of the beryllium armor, the bond strength between the beryllium armor and the underlying heat sink material, and ultrasonic C-scans of the Be/heat sink interface.
Date:
December 31, 1997
Creator:
Castro, Richard G.; Vaidya, Rajendra U. & Hollis, Kendall J.
Object Type:
Article
System:
The UNT Digital Library
Characterization of thermally degraded energetic materials
Characterization of the damage state of a thermally degraded energetic material (EM) is a critical first step in understanding and predicting cookoff behavior. Unfortunately, the chemical and mechanical responses of heated EMs are closely coupled, especially if the EM is confined. The authors have examined several EMs in small-scale experiments (typically 200 mg) heated in both constant-volume and constant-load configurations. Fixtures were designed to minimize free volume and to contain gas pressures to several thousand psi. The authors measured mechanical forces or displacements that correlated to thermal expansion, phase transitions, material creep and gas pressurization as functions of temperature and soak time. In addition to these real-time measurements, samples were recovered for postmortem examination, usually with scanning electron microscopy (SEM) and chemical analysis. The authors present results on EMs (HMX and TATB), with binders (e.g., PBX 9501, PBX 9502, LX-14) and propellants (Al/AP/HTPB).
Date:
December 31, 1997
Creator:
Renlund, A. M.; Miller, J. C.; Trott, W. M.; Erickson, K. L.; Hobbs, M. L.; Schmitt, R. G. et al.
Object Type:
Report
System:
The UNT Digital Library
Charge Stripes and Antiferromagnetism in Copper-Oxide Superconductors
Superconducting cuprate compounds are obtained by doping holes into antiferromagnetic insulators. Neutron scattering studies have provided evidence that the doped holes tend to segregate into charge stripes, which act like domain walls between antiferromagnetic regions. The interaction between the spatially segregated holes and the magnetic domains may be responsible for the strong pairing interaction found in the cuprates.
Date:
December 31, 1997
Creator:
Tranquada, J.M.
Object Type:
Article
System:
The UNT Digital Library
Charm decays and high energy photoproduction. Final report, April 1994--May 1997
This project involved continued participation by the Physics Department at the Mayaguez Campus of the University of Puerto Rico (UPR) in high energy physics experiments carried out at Fermilab. The UPR is a member of the E831 collaboration which includes Fermilab and leading US, Italian, Brazilian and Korean universities. E831 is an upgrade to the E687 spectrometer with the goal of a tenfold increase in the statistics for the study of the photoproduction and decay of charmed particles. This spectrometer has been significantly upgraded to maintain and expand its capabilities even at considerably higher beam intensities. E687 completed its last data run in January 1992. Approximately 100,000 charm events were fully reconstructed from this data and results of the analysis have appeared in several publications. The UPR has been participating in E687 since 1985 when the experiment was in its early stages of construction. A grant from the DOE Division of High Energy Physics (starting in April 1994) and another from the DOE EPSCoR Program (starting in October 1994) allowed a considerable increase in the activities of the UPR group. Given the group`s capable performance, the responsibilities assigned to it by the collaboration have increased to the point where they …
Date:
December 31, 1997
Creator:
Lopez, A. M.
Object Type:
Report
System:
The UNT Digital Library
Chemical kinetics models for semiconductor processing
Chemical reactions in the gas-phase and on surfaces are important in the deposition and etching of materials for microelectronic applications. A general software framework for describing homogeneous and heterogeneous reaction kinetics utilizing the Chemkin suite of codes is presented. Experimental, theoretical and modeling approaches to developing chemical reaction mechanisms are discussed. A number of TCAD application modules for simulating the chemically reacting flow in deposition and etching reactors have been developed and are also described.
Date:
December 31, 1997
Creator:
Coltrin, Michael E.; Creighton, J. Randall; Meeks, Ellen; Grcar, Joseph F.; Houf, William G. & Kee, Robert J.
Object Type:
Article
System:
The UNT Digital Library
Chemical Processes in Astrophysical Radiation Fields
The effects of stimulated photon emission on chemical processes in a radiation field are considered and their influence on the chemistry of the early universe and other astrophysical environments is investigated. Spontaneous and stimulated radiative attachment rate coefficients for H(-), Li(-) and C(-) are presented.
Date:
December 31, 1997
Creator:
Stancil, P. C. & Dalgarno, A.
Object Type:
Article
System:
The UNT Digital Library
Chemical speciation of strontium, americium, and curium in high level waste: Predictive modeling of phase partitioning during tank processing. Annual progress report, October 1996--September 1997
'The program at Florida State University was funded to collaborate with Dr. A. Felmy (PNNL) on speciation in high level wastes and with Dr. D. Rai (PNNL) on redox of Pu under high level waste conditions. The funding provided support for 3 research associates (postdoctoral researchers) under Professor G. R. Choppin as P.I. Dr. Kath Morris from U. Manchester (Great Britain), Dr. Dean Peterman and Dr. Amy Irwin (both from U. Cincinnati) joined the laboratory in the latter part of 1996. After an initial training period to become familiar with basic actinide chemistry and radiochemical techniques, they began their research. Dr. Peterman was assigned the task of measuring Th-EDTA complexation prior to measuring Pu(IV)-EDTA complexation. These studies are associated with the speciation program with Dr. Felmy. Drs. Morris and Irwin initiated research on redox of plutonium with agents present in the Hanford Tanks as a result of radiolysis or from use in separations. The preliminary results obtained thus far are described in this report. It is expected that the rate of progress will continue to increase significantly as the researchers gain more experience with plutonium chemistry.'
Date:
December 31, 1997
Creator:
Felmy, A.R. & Choppin, G.
Object Type:
Report
System:
The UNT Digital Library
Coal diesel combined-cycle project. Annual report, January 1996--January 1997
The Clean Coal Diesel project will demonstrate a new Clean Coal Technology that has technical, economic and environmental advantages over conventional power generating methods. This innovative technology enables utilization of coal-based fuel in large-bore, medium-speed, diesel engines. Modular power generating applications in the 10 to 100 megawatt size range are the target applications. The University of Alaska campus in Fairbanks, Alaska, is the project`s host site. At this location, the University will construct and operate the Clean Coal Diesel System, which will serve as a 6.2 MW diesel powerplant addition. The University will also assemble and operate a 5-ton per hour coal-water fuel processing plant. The plant will utilize local coal, brought by truck from Usibelli`s mine in Healey, AK. The estimated performance characteristics of the mature commercial embodiment of the Clean Coal Diesel, if achieved, will make this technology quite competitive: 48% efficiency; $1,300/kW installed cost; and emission levels controlled to 50--70% below New Source Performance Standards. Specific objectives are to demonstrate that the Coal Diesel Technology: is durable and can operate 6,000 hours in a realistic commercial setting; will meet efficiency targets; can effectively control criteria pollutants to levels that are well below anticipated standards, as well as …
Date:
December 31, 1997
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Coal investment and long-term supply and demand outlook for coal in the Asia-Pacific Region
The theme of this symposium to look ahead almost a quarter century to 2020 gives one the freedom to speculate more than usual in projections for coal. It is important to attempt to take a long term look into the future of coal and energy, so that one can begin to prepare for major changes on the horizon. However, it would be a mistake to believe that the crystal ball for making long term projections is accurate for 2020. Hopefully it can suggest plausible changes that have long term strategic importance to Asia`s coal sector. This paper presents the medium scenario of long term projects of coal production, consumption, imports and exports in Asia. The second part of the paper examines the two major changes in Asia that could be most important to the long term role of coal. These include: (1) the impact of strict environmental legislation on energy and technology choices in Asia, and (2) the increased role of the private sector in all aspects of coal in Asia.
Date:
December 31, 1997
Creator:
Johnson, C.J.
Object Type:
Report
System:
The UNT Digital Library
Collisional {delta}f method
A general method for including various collisional effects, such as the drag and diffusion of test particles due to background plasmas, the effect of particle source and sink, and the like-particle Coulomb collisions, is presented. The marker density g is generally unknown along the particle trajectory, and its evaluation depends on the way particles are initially loaded and new particles are injected into the simulation. The method is demonstrated for the problem of the nonlinear evolution of the Toroidicity Induced Alfven eigenmode, driven by energetic {alpha} particles. The saturation amplitude is found to scale with the collision rate in a way as predicted by theory.
Date:
December 31, 1997
Creator:
Chen, Y. & White, R. B.
Object Type:
Report
System:
The UNT Digital Library
Commercial-Scale Demonstration of the Liquid Phase Methanol (LOMEOH(TM)) Process
The Liquid Phase Methanol (LPMEOH) Demonstration Project at Kingsport, Tennessee, is a $213.7 million effort being conducted under a cooperative agreement between the U.S. Department of Energy (DOE) and Air Products Liquid Phase Conversion Company, L.P. (the Partnership). Air Products and Chemicals, Inc. (Air Products) and Eastman Chemical Company (Eastman) formed the Partnership to execute the Demonstration Project. A demonstration unit producing 80,000 gallons per day (260 tons-per-day (TPD)) of methanol from coal-derived synthesis gas (syngas) was designed, constructed, and began a four-year operational period in April of 1997 at a site located at the Eastman complex in Kingsport. The Partnership will own and operate the facility for the four-year demonstration period. This project is sponsored under the DOE's Clean Coal Technology Program, and its primary objective is to "demonstrate the production of methanol using the LPMEOH?M Process in conjunction with an integrated coal gasification facility." The project will also demonstrate the suitability of the methanol produced for use as a chemical feedstock or as a low-sulfur dioxide, low-nitrogen oxides alternative fiel in stationary and transportation applications. The project may also demonstrate the production of dimethyl ether (DME) as a mixed coproduct with methanol, if laboratory- and pilot-scale research and …
Date:
December 31, 1997
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Comparative testing of slurry monitors
The U.S. Department of Energy (DOE) has millions of gallons of radioactive liquid and sludge wastes stored in underground tanks. These wastes must be retrieved, transferred to treatment facilities, and processed for disposal. Before removal from the storage tanks, the sludge and liquid wastes will typically be combined to create a mixture of suspended solids, generally referred to as a slurry; the slurry is then pumped from the tank to the treatment facilities by pipelines. Since the wastes are radioactive, it is critically important that the slurries are transported safely and successfully. The consequences of pipeline plugging are unacceptable from the perspectives of schedule, cost, and safety. The baseline method of ensuring that the transport properties of the slurries are correct is to sample the slurry in the tank and analyze the sample in the laboratory. This method has some problems. First, there is a delay between the time that the sample is taken and the time that the analytical results are reported. For some types of analysis, this delay could be from 24 to 48 hours. Second, although the tank is being mixed to keep tile solids in suspension during this period, there is no way to determine whether …
Date:
December 31, 1997
Creator:
Hylton, T. D.; Bayne, C. K.; Anderson, M. S. & Van Essen, D. C.
Object Type:
Article
System:
The UNT Digital Library
Comparing Candidate Hospital Report Cards
We present graphical and analytical methods that focus on multivariate outlier detection applied to the hospital report cards data. No two methods agree which hospitals are unusually good or bad, so we also present ways to compare the agreement between two methods. We identify factors that have a significant impact on the scoring.
Date:
December 31, 1997
Creator:
Burr, Tom L.; Rivenburgh, Reid D.; Scovel, James C. & White, James M.
Object Type:
Article
System:
The UNT Digital Library
Comparison of elastic-viscous-plastic and viscous-plastic dynamics models using a high resolution Arctic sea ice model
A nonlinear viscous-plastic (VP) rheology proposed by Hibler (1979) has been demonstrated to be the most suitable of the rheologies commonly used for modeling sea ice dynamics. However, the presence of a huge range of effective viscosities hinders numerical implementations of this model, particularly on high resolution grids or when the ice model is coupled to an ocean or atmosphere model. Hunke and Dukowicz (1997) have modified the VP model by including elastic waves as a numerical regularization in the case of zero strain rate. This modification (EVP) allows an efficient, fully explicit discretization that adapts well to parallel architectures. The authors present a comparison of EVP and VP dynamics model results from two 5-year simulations of Arctic sea ice, obtained with a high resolution sea ice model. The purpose of the comparison is to determine how differently the two dynamics models behave, and to decide whether the elastic-viscous-plastic model is preferable for high resolution climate simulations, considering its high efficiency in parallel computation. Results from the first year of this experiment (1990) are discussed in detail in Hunke and Zhang (1997).
Date:
December 31, 1997
Creator:
Hunke, E. C. & Zhang, Y.
Object Type:
Report
System:
The UNT Digital Library
Comparison of Materials for Use in the Precision Grinding of Optical Components
Precision grinding of optical components is becoming an accepted practice for rapidly and deterministically fabrication optical surfaces to final or near-final surface finish and figure. In this paper, a comparison of grinding techniques and materials is performed. Flat and spherical surfaces were ground in three different substrate materials: BK7 glass, chemical vapor deposited (CVD) silicon carbide ceramic, and sapphire. Spherical surfaces were used to determine the contouring capacity of the process, and flat surfaces were used for surface finish measurements. The recently developed Precitech Optimum 2800 diamond turning and grinding platform was used to grind surfaces in 40mm diameter substrates sapphire and silicon carbide substrates and 200 mm BK7 glass substrates using diamond grinding wheels. The results of this study compare the surface finish and figure for the three materials.
Date:
December 31, 1997
Creator:
Evans, Boyd M. III; Miller, Arthur C. Jr. & Egert, Charles M.
Object Type:
Article
System:
The UNT Digital Library
A comparison of performance-enhancing strategies for parallel numerical object-oriented frameworks
Performance short of that of C or FORTRAN 77 is a significant obstacle to general acceptance of object-oriented C++ frameworks in high-performance parallel scientific computing, nonetheless, their value in simplifying complex computations is inarguable. Singular data points of good performance for object-oriented libraries/frameworks have been interesting, but a systematic analysis of the performance issues has not been done. This paper explores just a few of these issues and reports on the use of three mechanisms for enhancing the performance of object-oriented frameworks within numerical computation. The first is the commonly-use of binary overloaded operators (though implemented with substantial internal optimizations), the second is the use of expression templates, and the third is the use of an optimizing preprocessor. The first two have been completely implemented and are available within the A++/P++ array class library, the third, ROSE++, represents work in progress. This paper provides some perspective on the types of optimizations that the authors consider important within their numerical applications using OVERTURE involving complex geometry and AMR on parallel architectures.
Date:
December 31, 1997
Creator:
Bassetti, F.; Davis, K. & Quinlan, D.
Object Type:
Article
System:
The UNT Digital Library
Compartmentalization analysis using discrete fracture network models
This paper illustrates how Discrete Fracture Network (DFN) technology can serve as a basis for the calculation of reservoir engineering parameters for the development of fractured reservoirs. It describes the development of quantitative techniques for defining the geometry and volume of structurally controlled compartments. These techniques are based on a combination of stochastic geometry, computational geometry, and graph theory. The parameters addressed are compartment size, matrix block size and tributary drainage volume. The concept of DFN models is explained and methodologies to compute these parameters are demonstrated.
Date:
December 31, 1997
Creator:
La Pointe, P.R.; Eiben, T.; Dershowitz, W. & Wadleigh, E.
Object Type:
Article
System:
The UNT Digital Library
Compliance with the Nevada Test Site`s waste acceptance criteria for vitrified cesium-loaded crystalline silicotitanate (CST)
Oak Ridge National Laboratory (ORNL) and Savannah River Technology Center (SRTC) are involved in a joint project for immobilization of radionuclides from the Melton Valley Storage Tanks (MVST) at Oak Ridge (OR). The supernate from Tank W-29 of the MVST will be treated by passage through a crystalline silicotitanate (CST) ion exchange medium. The CST was designed to sorb cesium, the primary radio nuclide (Cs-137) in the supernate of MVST`s. A smaller amount of strontium (Sr-90) will also be sorbed. This demonstration will be performed by ORNL. One column volume of cesium-loaded CST ({approximately}10 gallons or 38 liters) will then be shipped to SRTC where it will be mixed with glass formers and fed as an aqueous slurry to a joule-heated melter within the SRTC Shielded Cells. A borosilicate glass formulation which will incorporate the CST has been developed as part oft SRTC`s role in this project. The molten glass ({approximately}1150{degrees}C) will be poured into 500 ml stainless steel beakers which in turn will be placed in 30 gallon drums for disposal. An import&f part of this project is to demonstrate that the glass waste form produced will meet the Waste Acceptance Criteria (WAC) for disposal at the Nevada Test …
Date:
December 31, 1997
Creator:
Harbour, J.R. & Andrews, M.K.
Object Type:
Article
System:
The UNT Digital Library
Computational Modeling and Experimental Studies on NO(x) Reduction Under Pulveerized Coal Combustion Conditions. Quarterly technical progress report, July 1 - September 30, 1997
Several experiments were conducted during this quarter to study the NO{sub x} reduction effectiveness of lignite coal, activated carbon and catalytic sites such as calcium sulfide and calcium carbide. While some of the coals/chemicals could be fed easily, some needed the mixing with silica gel to result in a uniform flow through the feeder. Several trial runs were performed to ensure proper feeding of the material before conducting the actual experiment to record NO{sub x} reduction. The experimental approach has been the same as presented in the past two quarterly reports with the coal reburning experiments. Partial reduction is achieved through methane addition for SR2=0.95 conditions and then coal or the catalyst is introduced to see if there is further reduction. Presented below are the results of the experiments conducted during this quarter.
Date:
December 31, 1997
Creator:
Kumpaty, S. K.; Subramanian, K.; Darboe, A. & Kumpati, S. K.
Object Type:
Report
System:
The UNT Digital Library
Concentrations of a water soluble, gas-phase mercury species in ambient air: Results from measurements and modeling
There are few reliable data on the speciation of Hg in ambient air, although this information is critical to understanding the fate of Hg once released from point sources. The water soluble species of Hg that are thought to exist in flue gases would be subject to far greater local removal rates than is elemental Hg vapor, but methods are lacing to quantify this species. The authors developed a method using refluxing mist chambers to measure the airborne concentrations of reactive gaseous mercury (RGM) in short-term samples under ambient conditions. The method exhibits an effective detection limit of 0.02 ng/m{sup 3} and a precision for ambient concentration levels of {+-}20--30%. Using a model that simulates atmospheric transport and fate of anthropogenic mercury emissions over the contiguous United States, the authors generated 24-hr RGM concentrations to compare to the measurement data. The average RGM concentrations measured with their mist chambers at sites in Tennessee (TN) and Indiana (IN) were 0.065 ng/m{sup 3} and 0.100 ng/m{sup 3}, respectively. These averages represent about 3% of total gaseous mercury (TGM), and RGM generally exceeds regional particulate Hg. The 24-hr model-simulated RGM concentration averages in the modeling grid cells representing TN and IN are 0.051 …
Date:
December 31, 1997
Creator:
Lindberg, S. E.; Stratton, W. J.; Pai, P. & Allan, M. A.
Object Type:
Report
System:
The UNT Digital Library
Construction of genome-wide physical BAC contigs using mapped cDNA as probes: Toward an integrated BAC library resource for genome sequencing and analysis. Annual report, July 1995--January 1997
The goal of human genome project is to characterize and sequence entire genomes of human and several model organisms, thus providing complete sets of information on the entire structure of transcribed, regulatory and other functional regions for these organisms. In the past years, a number of useful genetic and physical markers on human and mouse genomes have been made available along with the advent of BAC library resources for these organisms. The advances in technology and resource development made it feasible to efficiently construct genome-wide physical BAC contigs for human and other genomes. Currently, over 30,000 mapped STSs and 27,000 mapped Unigenes are available for human genome mapping. ESTs and cDNAs are excellent resources for building contig maps for two reasons. Firstly, they exist in two alternative forms--as both sequence information for PCR primer pairs, and cDoreen genomic libraries efficiently for large number of DNA probes by combining over 100 cDNA probes in each hybridization. Second, the linkage and order of genes are rather conserved among human, mouse and other model organisms. Therefore, gene markers have advantages over random anonymous STSs in building maps for comparative genomic studies.
Date:
December 31, 1997
Creator:
Mitchell, S.C.; Bocskai, D. & Cao, Y.
Object Type:
Report
System:
The UNT Digital Library
Containment and surveillance -- A principal IAEA safeguards measure
The growth of the safeguards inspectorate of the Agency, spanning more than 40 years, has produced a variety of interesting subjects (legal, technical, political, etc.) for recollection, discussion, and study. Although the Agency was established in 1957, the first practical inspections did not occur until the early 1960s. In the early inspections, thee was little C/S equipment available, and no optical surveillance was used. However, by the third decade of the IAEA, the 1980s, many technology advances were made, and the level of C/S equipment activities increased. By the late 1980s, some 200 Twin Minolta film camera systems were deployed by the Agency for safeguards use. At the present time, the Agency is evaluating and beginning to implement remote monitoring as part of the Strengthened Safeguards System. However, adoption of remote monitoring by international agencies cannot occur rapidly because of the many technical and policy issues associated with this activity. A glimpse into the future indicates that an important element of safeguards instrumentation will be the merging of C/S and NDA equipment into integrated systems. The use of modern interior area monitors in International Safeguards also offers a great potential for advancing C/S measures. The research in microsensors is in …
Date:
December 31, 1997
Creator:
Drayer, D. D.; Dupree, S. A. & Sonnier, C. S.
Object Type:
Article
System:
The UNT Digital Library
Control of beryllium powder at a DOE facility
Beryllium is contained in a number of domestic and national defense items. Although many items might contain beryllium in some manner, few people need worry about the adverse effects caused by exposure to beryllium because it is the inhalable form of beryllium that is most toxic. Chronic beryllium disease (CBD), a granulomas and fibrotic lung disease with long latency, can be developed after inhalation exposures to beryllium. It is a progressive, debilitating lung disease. Its occurrence in those exposed to beryllium has been difficult to predict because some people seem to react to low concentration exposures whereas others do not react to high concentration exposures. Onset of the disease frequently occurs between 15 to 20 years after exposure begins. Some people develop the disease after many years of low concentration exposures but others do not develop CBD even though beryllium is shown to be present in lungs and urine. Conclusions based on these experiences are that their is some immunological dependence of developing CBD in about 3--4% of the exposed population, but the exact mechanism involved has not yet been identified. Acute beryllium disease can occur after a single exposure to a concentration of greater than 0.100 mg/m3 (inhalation exposure); …
Date:
December 31, 1997
Creator:
Langner, G. C.; Creek, K. L. & Castro, R. G.
Object Type:
Article
System:
The UNT Digital Library