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Scalability of preconditioners as a strategy for parallel computation of compressible fluid flow

Description: Parallel implementations of a Newton-Krylov-Schwarz algorithm are used to solve a model problem representing low Mach number compressible fluid flow over a backward-facing step. The Mach number is specifically selected to result in a numerically {open_quote}stiff{close_quotes} matrix problem, based on an implicit finite volume discretization of the compressible 2D Navier-Stokes/energy equations using primitive variables. Newton`s method is used to linearize the discrete system, and a preconditioned Krylov projection technique is used to solve the resulting linear system. Domain decomposition enables the development of a global preconditioner via the parallel construction of contributions derived from subdomains. Formation of the global preconditioner is based upon additive and multiplicative Schwarz algorithms, with and without subdomain overlap. The degree of parallelism of this technique is further enhanced with the use of a matrix-free approximation for the Jacobian used in the Krylov technique (in this case, GMRES(k)). Of paramount interest to this study is the implementation and optimization of these techniques on parallel shared-memory hardware, namely the Cray C90 and SGI Challenge architectures. These architectures were chosen as representative and commonly available to researchers interested in the solution of problems of this type. The Newton-Krylov-Schwarz solution technique is increasingly being investigated for computational fluid dynamics (CFD) applications due to the advantages of full coupling of all variables and equations, rapid non-linear convergence, and moderate memory requirements. A parallel version of this method that scales effectively on the above architectures would be extremely attractive to practitioners, resulting in efficient, cost-effective, parallel solutions exhibiting the benefits of the solution technique.
Date: May 1, 1996
Creator: Hansen, G.A.
Partner: UNT Libraries Government Documents Department

Parallel sphere rendering

Description: Sphere rendering is an important method for visualizing molecular dynamics data. This paper presents a parallel algorithm that is almost 90 times faster than current graphics workstations. To render extremely large data sets and large images, the algorithm uses the MIMD features of the supercomputers to divide up the data, render independent partial images, and then finally composite the multiple partial images using an optimal method. The algorithm and performance results are presented for the CM-5 and the M.
Date: October 1, 1996
Creator: Krogh, M.; Painter, J. & Hansen, C.
Partner: UNT Libraries Government Documents Department

Depleted uranium risk assessment for Jefferson Proving Ground using data from environmental monitoring and site characterization. Final report

Description: This report documents the third risk assessment completed for the depleted uranium (DU) munitions testing range at Jefferson Proving Ground (JPG), Indiana, for the U.S. Army Test and Evaluation command. Jefferson Proving Ground was closed in 1995 under the Base Realignment and Closure Act and the testing mission was moved to Yuma Proving Ground. As part of the closure of JPG, assessments of potential adverse health effects to humans and the ecosystem were conducted. This report integrates recent information obtained from site characterization surveys at JPG with environmental monitoring data collected from 1983 through 1994 during DU testing. Three exposure scenarios were evaluated for potential adverse effects to human health: an occasional use scenario and two farming scenarios. Human exposure was minimal from occasional use, but significant risk were predicted from the farming scenarios when contaminated groundwater was used by site occupants. The human health risk assessments do not consider the significant risk posed by accidents with unexploded ordnance. Exposures of white-tailed deer to DU were also estimated in this study, and exposure rates result in no significant increase in either toxicological or radiological risks. The results of this study indicate that remediation of the DU impact area would not substantially reduce already low risks to humans and the ecosystem, and that managed access to JPG is a reasonable model for future land use options.
Date: October 1996
Creator: Ebinger, M. H. & Hansen, W. R.
Partner: UNT Libraries Government Documents Department

Technical evaluation of Solar Cells, Inc., CdTe modules and array at NREL

Description: The Engineering and Technology Validation Team at the National Renewable Energy Laboratory (NREL) conducts in-situ technical evaluations of polycrystalline thin-film photovoltaic (PV) modules and arrays. This paper focuses on the technical evaluation of Solar Cells, Inc., (SCI) cadmium telluride (CdTe) module and array performance by attempting to correlate individual module and array performance. This is done by examining the performance and stability of the modules and array over a period of more than one year. Temperature coefficients for module and array parameters (P{sub max}V{sub oc}, V{sub max}, I{sub sc}, I{sub max}) are also calculated.
Date: May 1, 1996
Creator: Kroposki, B.; Strand, T. & Hansen, R.
Partner: UNT Libraries Government Documents Department

Large-scale dynamic compaction of natural salt

Description: A large-scale dynamic compaction demonstration of natural salt was successfully completed. About 40 m{sup 3} of salt were compacted in three, 2-m lifts by dropping a 9,000-kg weight from a height of 15 m in a systematic pattern to achieve desired compaction energy. To enhance compaction, 1 wt% water was added to the relatively dry mine-run salt. The average compacted mass fractional density was 0.90 of natural intact salt, and in situ nitrogen permeabilities averaged 9X10{sup -14}m{sup 2}. This established viability of dynamic compacting for placing salt shaft seal components. The demonstration also provided compacted salt parameters needed for shaft seal system design and performance assessments of the Waste Isolation Pilot Plant.
Date: May 1, 1996
Creator: Hansen, F.D. & Ahrens, E.H.
Partner: UNT Libraries Government Documents Department

Technical evaluation of two 6-kW mono-Si photovoltaic systems at the National Renewable Energy Laboratory

Description: This paper presents an analysis of performance data on the two 6-kW{sub ac} grid-connected photovoltaic systems at the National Renewable Energy Laboratory (NREL). The performance parameters analyzed include dc and ac power, aperture efficiency, energy, capacity factor and performance index which are compared to plane-of-array irradiance, ambient temperature, and back-of-module temperature as a function of time, either daily or monthly. Power ratings of the systems were also obtained for data corresponding to different test conditions. This study has shown, in addition to expected seasonal trends, that system monitoring is a valuable tool in assessing performance and detecting faulty equipment. In addition, methods applied for this study may be used to evaluate and compare systems employing different cell technologies.
Date: May 1, 1996
Creator: Dyk, E.E. van; Strand, T. & Hansen, R.
Partner: UNT Libraries Government Documents Department

SERF photovoltaic systems. Technical report on system performance for the period, August 1, 1994--July 31, 1995

Description: This report presents an analysis of performance data on the two identical, 6 kW{sub ac}, grid-connected photovoltaic systems located on the roof of the Solar Energy Research Facility building at the National Renewable Energy Laboratory in Golden, Colorado. The data cover the monitoring period August 1, 1994, to July 31, 1995, and the performance parameters analyzed include direct current and alternating current power, aperture-area efficiency, energy, capacity factor, and performance index. These parameters are compared to plane-of-array irradiance, ambient temperature, and back-of-module temperature as a function of time, either daily or monthly. We also obtained power ratings of the systems for data corresponding to different test conditions. This study has shown, in addition to expected seasonal trends, that system monitoring is a valuable tool in assessing performance and detecting faulty equipment. Furthermore, methods applied for this analysis may be used to evaluate and compare systems using cells of different technologies. The systems were both found to be operating at approximately 7% below their estimated rating, which was based on Photovoltaics for Utility-Scale Applications test conditions. This may be attributed to the design inverter efficiency being estimated at 95% compared to measured values of approximately 88%, as well as the fact that aperture-area efficiency that was overestimated at 12.8% compared to a measured value of 11.0%. The continuous monitoring also revealed faulty peak-power point tracking equipment.
Date: June 1, 1996
Creator: Dyk, E.E. van; Strand, T.R. & Hansen, R.
Partner: UNT Libraries Government Documents Department

Siemens solar CIS photovoltaic module and system performance at the National Renewable Energy Laboratory

Description: This paper evaluates the individual module and array performance of Siemens Solar Industries` copper indium diselenide (CIS) polycrystalline thin-film technology. This is accomplished by studying module and array performance over time. Preliminary temperature coefficients for maximum power, maximum-power voltage, maximum-power current, open-circuit voltage, short-circuit current, and fill factor are determined at both the module and array level. These coefficients are used to correct module/array performance to 25{degrees}C to evaluate stability. We show that CIS exhibits a strong inverse correlation between array power and back-of-module temperature. This is due mainly to the narrow bandgap of the CIS material, which results in a strong inverse correlation between voltage and temperature. We also show that the temperature-corrected module and array performance has been relatively stable over the evaluation interval (=2 years).
Date: May 1, 1996
Creator: Strand, T.R.; Kroposki, B.D. & Hansen, R.
Partner: UNT Libraries Government Documents Department

D-Zero muon readout electronics design

Description: The readout electronics designed for the D{null} Muon Upgrade are described. These electronics serve three detector subsystems and one trigger system. The front-ends and readout hardware are synchronized by means of timing signals broadcast from the D{null} Trigger Framework. The front-end electronics have continuously running digitizers and two levels of buffering resulting in nearly deadtimeless operation. The raw data is corrected and formatted by 16- bit fixed point DSP processors. These processors also perform control of the data buffering. The data transfer from the front-end electronics located on the detector platform is performed by serial links running at 160 Mbit/s. The design and test results of the subsystem readout electronics and system interface are discussed.
Date: November 1, 1996
Creator: Baldin, B.; Hansen, S.; Los, S.; Matveev, M. & Vaniev, V.
Partner: UNT Libraries Government Documents Department

Extrinsic germanium photoconductors for far-IR astronomy: Research results and works in progress

Description: The authors report on Ge:Ga and Ge:Sb photoconductor materials and detectors that are under development. The best unstressed Ge:Ga devices exhibit dark currents lower than 200 electrons per second with a concurrent responsivity of 2 A/W and detective quantum efficiency (DQE) of 5%. For higher backgrounds an operating temperature of 3 K can be used. This increases the DQE to 7% and the responsivity to 4.5 A/W. The figures of merit are roughly the same for stressed Ge:Ga operated at 1.5 K and 2 K. Recently the authors began investigating n-type Ge:Sb as an alternative photoconductor material. Two crystals of Ge:Sb were grown and a number of test detectors were fabricated and evaluated. A t2 K the best device produced dark currents of less than 100 e{sup {minus}}/s with concurrent responsivity of 1 A/W and DQE of 4%. At 3 K the dark current increases to 10{sup 5} e{sup {minus}}/s, the DQE rises to 7% and responsivity to 4 A/W. Using p-type Ge:Ga crystals the authors are in the process of constructing 2-D monolithic photoconductor arrays. The monolithic approach should afford low cost array fabrication and sensitivity similar to cavity-mounted devices.
Date: September 1, 1996
Creator: Beeman, J.W.; Hansen, W.L. & Haller, E.E.
Partner: UNT Libraries Government Documents Department

Properties of dynamically compacted WIPP salt

Description: Dynamic compaction of mine-run salt is being investigated for the Waste Isolation Pilot Plant (WIPP), where compacted salt is being considered for repository sealing applications. One large-scale and two intermediate-scale dynamic compaction demonstrations were conducted. Initial fractional densities of the compacted salt range form 0.85 to 0.90, and permeabilities vary. Dynamically-compacted specimens were further consolidated in the laboratory by application of hydrostatic pressure. Permeability as a function of density was determined, and consolidation microprocesses were studied. Experimental results, in conjunction with modeling results, indicate that the compacted salt will function as a viable seal material.
Date: July 1, 1996
Creator: Brodsky, N.S.; Hansen, F.D. & Pfeifle, T.W.
Partner: UNT Libraries Government Documents Department

Salt-saturated concrete strength and permeability

Description: Laboratory-scale experiments applicable to the use of salt-saturated concrete as a seal material for a transuranic waste repository have been completed. Nitrogen gas permeability measurements were made using a flexible-wall permeameter, a confining pressure of 1 MPa, and gas pressure gradients ranging from 0.3 MPa to 0.75 MPa. Results show that salt-saturated concrete has very low intrinsic permeability with values ranging from 9.4 {times} 10{sup {minus}22} m{sup 2} to 9.7 {times} 10{sup {minus}17} m{sup 2}. Strength and deformation characteristics were investigated under conditions of triaxial compression with confining pressures ranging from 0 to 15 MPa using either axial strain-rate or axial stress-rate control and show that the failure strength of concrete increases with confining pressure which can be adequately described through pressure-sensitive failure criteria. Axial, radial, and volumetric strains were also measured during each test and these data were used to determine elastic properties. Experimental results are applicable in the design and analysis of scale-related functions and apply to other concrete structures subjected to compressive loadings such as dams and prestressed structural members.
Date: November 1, 1996
Creator: Pfeifle, T.W.; Hansen, F.D. & Knowles, M.K.
Partner: UNT Libraries Government Documents Department

Shock transmissibility of threaded joints

Description: Sandia National Laboratories (SNL) designs mechanical systems with threaded joints that must survive high shock environments. These mechanical systems include penetrators that must survive soil and rock penetration; drilling pipe strings that must survive rock-cutting, shock environments; and laydown weapons that must survive delivery impact shock. This paper summarizes an analytical study and an experimental evaluation of compressive, one-dimensional, shock transmission through a threaded joint in a split Hopkinson bar configuration. Thread geometries were scaled to simulate large diameter threaded joints with loadings parallel to the axis of the threads. Both strain and acceleration were evaluated with experimental measurements and analysis. Analytical results confirm the experimental conclusions that in this split Hopkinson bar configuration, the change in the one-dimensional shock wave by the threaded joint is localized to a length equal to a few diameters` length beyond the threaded joint.
Date: December 31, 1996
Creator: Hansen, N.R.; Bateman, V.I. & Brown, F.A.
Partner: UNT Libraries Government Documents Department

Three-color resonance ionization spectroscopy of Zr in Si

Description: It has been proposed that the composition of the solar wind could be measured directly by transporting ultrapure collectors into space, exposing them to the solar wind, and returning them to earth for analysis. In a study to help assess the applicability of present and future postionization secondary neutral mass spectrometers for measuring solar wind implanted samples, measurements of Zr in Si were performed. A three-color resonant ionization scheme proved to be efficient while producing a background count rate limited by secondary ion signal (5 x 10{sup {minus}4} counts/laser pulse). This lowered the detection limit for these measurements to below 500 ppt for 450,000 averages. Unexpectedly, the Zr concentration in the Si was measured to be over 4 ppb, well above the detection limit of the analysis. This high concentration is thought to result from contamination during sample preparation, since a series of tests were performed that rule out memory effects during the analysis.
Date: September 1, 1996
Creator: Hansen, C.S.; Calaway, W.F.; Pellin, M.J.; Wiens, R.C. & Burnett, D.S.
Partner: UNT Libraries Government Documents Department

A two-fold reduction in measurement time for neutron assay: Initial tests of a prototype dual-gated shift register

Description: Neutron coincidence counting (NCC) is used routinely around the world for nondestructive mass assay of uranium and plutonium in many forms, including waste. Compared with other methods, NCC is generally the most flexible, economic, and rapid. Many applications of NCC would benefit from a reduction in counting time required for a fixed random error. We have developed and tested the first prototype of a dual- gated, shift-register-based electronics unit that offers the potential of decreased measurement time for all passive and active NCC applications.
Date: September 1, 1996
Creator: Stewart, J.E.; Bourret, S.C.; Krick, M.S.; Hansen, W.J. & Harker, W.C.
Partner: UNT Libraries Government Documents Department

A study of shock mitigating materials in a split Hopkinson bar configuration

Description: Sandia National Laboratories (SNL) designs mechanical systems with electronics that must survive high shock environments. These mechanical systems include penetrators that must survive soil, rock, and ice penetration, nuclear transportation casks that must survive transportation environments, and laydown weapons that must survive delivery impact of 125-fps. These mechanical systems contain electronics that may operate during and after the high shock environment and that must be protected from the high shock environments. A study has been started to improve the packaging techniques for the advanced electronics utilized in these mechanical systems because current packaging techniques are inadequate for these more sensitive electronics. In many cases, it has been found that the packaging techniques currently used not only do not mitigate the shock environment but actually amplify the shock environment. An ambitious goal for this packaging study is to avoid amplification and possibly attenuate the shock environment before it reaches the electronics contained in the various mechanical system. As part of the investigation of packaging techniques, a two part study of shock mitigating materials is being conducted. This paper reports the first part of the shock mitigating materials study. A study to compare three thicknesses (0.125, 0.250, and 0.500 in.) of seventeen, unconfined materials for their shock mitigating characteristics has been completed with a split Hopkinson bar configuration. The nominal input as measured by strain gages on the incident Hopkinson bar is 50 fps {at} 100 {micro}s for these tests. It is hypothesized that a shock mitigating material has four purposes: to lengthen the shock pulse, to attenuate the shock pulse, to mitigate high frequency content in the shock pulse, and to absorb energy. Both time domain and frequency domain analyses of the split Hopkinson bar data have been performed to compare the materials` achievement of these purposes.
Date: December 31, 1996
Creator: Bateman, V.I.; Bell, R.G. III; Brown, F.A. & Hansen, N.R.
Partner: UNT Libraries Government Documents Department

Evaluation of constitutive models for crushed salt

Description: Three constitutive models are recommended as candidates for describing the deformation of crushed salt. These models are generalized to three-dimensional states of stress to include the effects of mean and deviatoric stress and modified to include effects of temperature, grain size, and moisture content. A database including hydrostatic consolidation and shear consolidation tests conducted on Waste Isolation Pilot Plant (WIPP) and southeastern New Mexico salt is used to determine material parameters for the models. To evaluate the capability of the models, parameter values obtained from fitting the complete database are used to predict the individual tests. Finite element calculations of a WIPP shaft with emplaced crushed salt demonstrate the model predictions.
Date: May 1, 1996
Creator: Callahan, G.D.; Loken, M.C.; Hurtado, L.D. & Hansen, F.D.
Partner: UNT Libraries Government Documents Department

A shaft seal system for the Waste Isolation Pilot Plant

Description: As part of the demonstration of compliance with federal regulations, a shaft seal system has been designed for the Waste Isolation Pilot Plant. The system completely fills the 650 m shafts with components consisting of the common engineering materials, each of which possesses low permeability, longevity, and can be constructed using available technology. Design investigations couple rock mechanics and fluid flow analysis and tests of these materials within the natural geological setting, and demonstrate the effectiveness of the design.
Date: July 1, 1996
Creator: Hansen, F.D.; Ahrens, E.H.; Dennis, A.W.; Hurtado, L.D.; Knowles, M.K.; Tillerson, J.R. et al.
Partner: UNT Libraries Government Documents Department

High Efficiency Thermionics (HET-IV) and Converter Advancement (CAP) programs. Final reports

Description: This report contains the final report of the High Efficiency Thermionics (HET-IV) Program, Attachment A, performed at Rasor Associates, Inc. (RAI); and the final report of the Converter Advancement Program (CAP), performed at the Bettis Atomic Power Laboratory, Attachment B. The phenomenology of cesium-oxygen thermionic converters was elucidated in these programs, and the factors that had prevented the achievement of stable, enhanced cesium-oxygen converter performance for the previous thirty years were identified. Based on these discoveries, cesium-oxygen vapor sources were developed that achieved stable performance with factor-of-two improvements in power density and thermal efficiency, relative to conventional, cesium-only ignited mode thermionic converters. Key achievements of the HET-IV/CAP programs are as follows: a new technique for measuring minute traces of oxygen in cesium atmospheres; the determination of the proper range of oxygen partial pressures for optimum converter performance--10{sup {minus}7} to 10{sup {minus}9} torr; the discovery, and analysis of the cesium-oxygen liquid migration and compositional segregation phenomena; the successful use of capillary forces to contain the migration phenomenon; the use of differential heating to control compositional segregation, and induce vapor circulation; the development of mechanically and chemically stable, porous reservoir structures; the development of precise, in situ oxygen charging methods; stable improvements in emitter performance, up to effective emitter bare work functions of 5.4 eV; stable improvements in barrier index, to value below 1.8 Volts; the development of detailed microscopic models for cesium-oxygen reservoir dynamics and collector work function behavior; and the discovery of new relationships between electrode geometry and Schock Instability.
Date: April 1996
Creator: Geller, C. B.; Murray, C. S.; Riley, D. R.; Desplat, J. L.; Hansen, L. K.; Hatch, G. L. et al.
Partner: UNT Libraries Government Documents Department

Transportable Vitrification System: Operational experience gained during vitrification of simulated mixed waste

Description: The Transportable Vitrification System (TVS) is a large-scale, fully-integrated, transportable, vitrification system for the treatment of low-level nuclear and mixed wastes in the form of sludges, soils, incinerator ash, and similar waste streams. The TVS was built to demonstrate the vitrification of actual mixed waste at U. S. Department of Energy (DOE) sites. Currently, Westinghouse Savannah River Company (WSRC) is working with Lockheed Martin Energy Systems (LMES) to apply field scale vitrification to actual mixed waste at Oak Ridge Reservation`s (ORR) K-25 Site. Prior to the application of the TVS to actual mixed waste it was tested on simulated K-25 B and C Pond waste at Clemson University. This paper describes the results of that testing and preparations for the demonstration on actual mixed waste.
Date: November 21, 1996
Creator: Whitehouse, J.C.; Burket, P.R.; Crowley, D.A.; Hansen, E.K.; Jantzen, C.M.; Smith, M.E. et al.
Partner: UNT Libraries Government Documents Department

Initial report on the application of laser ablation - inductively coupled plasma mass spectrometry for the analysis of radioactive Hanford Tank Waste materials

Description: Initial LA/MS analyses of Hanford tank waste samples were performed successfully using laboratory and hot cell LA/MS instrumentation systems. The experiments described in this report have demonstrated that the LA/MS data can be used to provide rapid analysis of solid, radioactive Hanford tank waste samples to identify major, minor, and trace constituents (elemental and isotopic) and fission products and radioactive isotopes. The ability to determine isotopic constituents using the LA/MS method yielded significant advantages over ICP/AES analysis by providing valuable information on fission products and radioactive constituents.
Date: December 1, 1996
Creator: Smith, M.R.; Hartman, J.S.; Alexander, M.L.; Mendoza, A.; Hirt, E.H.; Stewart, T.L. et al.
Partner: UNT Libraries Government Documents Department