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Numerical experiments on unstructured PIC stability

Day, David M.

Particle-In-Cell (PIC) is a method for plasmas simulation. Particles are pushed with Verlet time integration. Fields are modeled using finite differences on a tensor product mesh (cells). The Unstructured PIC methods studied here use instead finite element discretizations on unstructured (simplicial) meshes. PIC is constrained by stability limits (upper bounds) on mesh and time step sizes. Numerical evidence (2D) and analysis will be presented showing that similar bounds constrain unstructured PIC.

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TYPE SAND Report YEAR 2011
DOIOSTI

Characterization and assessment of novel bulk storage technologies : a study for the DOE Energy Storage Systems program

Huff, Georgianne

This paper reports the results of a high-level study to assess the technological readiness and technical and economic feasibility of 17 novel bulk energy storage technologies. The novel technologies assessed were variations of either pumped storage hydropower (PSH) or compressed air energy storage (CAES). The report also identifies major technological gaps and barriers to the commercialization of each technology. Recommendations as to where future R&D efforts for the various technologies are also provided based on each technology's technological readiness and the expected time to commercialization (short, medium, or long term). The U.S. Department of Energy (DOE) commissioned this assessment of novel concepts in large-scale energy storage to aid in future program planning of its Energy Storage Program. The intent of the study is to determine if any new but still unproven bulk energy storage concepts merit government support to investigate their technical and economic feasibility or to speed their commercialization. The study focuses on compressed air energy storage (CAES) and pumped storage hydropower (PSH). It identifies relevant applications for bulk storage, defines the associated technical requirements, characterizes and assesses the feasibility of the proposed new concepts to address these requirements, identifies gaps and barriers, and recommends the type of government support and research and development (R&D) needed to accelerate the commercialization of these technologies.

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TYPE SAND Report YEAR 2011
DOIOSTI

Effect of polymer architecture and ionic aggregation on the scattering peak in model ionomers

Physical Review Letters

Hall, Lisa M.; Stevens, Mark J.; Frischknecht, Amalie L.

We perform molecular dynamics simulations of coarse-grained ionomer melts with two different architectures. Regularly spaced charged beads are placed either in the polymer backbone (ionenes) or pendant to it. The ionic aggregate structure is quantified as a function of the dielectric constant. The low wave vector ionomer scattering peak is present in all cases, but is significantly more intense for pendant ions, which form compact, discrete aggregates with liquidlike interaggregate order. This is in qualitative contrast to the ionenes, which form extended aggregates. © 2011 American Physical Society.

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TYPE Journal Article YEAR 2011
ScopusOSTI

Factors impacting performance of multithreaded sparse riangular solvet

Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)

Heroux, Michael A.; Boman, Erik G.

As computational science applications grow more parallel with multi-core supercomputers having hundreds of thousands of computational cores, it will become increasingly difficult for solvers to scale. Our approach is to use hybrid MPI/threaded numerical algorithms to solve these systems in order to reduce the number of MPI tasks and increase the parallel efficiency of the algorithm. However, we need efficient threaded numerical kernels to run on the multi-core nodes in order to achieve good parallel efficiency. In this paper, we focus on improving the performance of a multithreaded triangular solver, an important kernel for preconditioning. We analyze three factors that affect the parallel performance of this threaded kernel and obtain good scalability on the multi-core nodes for a range of matrix sizes. © 2011 Springer-Verlag Berlin Heidelberg.

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TYPE Conference YEAR 2011
OSTIScopus

The stability of Lomer-Cottrell jogs in nanopillars

Scripta Materialia

Weinberger, C.R.

Single arm spiral sources, or truncated Frank-Read sources, have been used frequently to interpret the size dependent plasticity in micropillars. The basis for these sources is strong pinning points which have been proposed to exist based on immobile Lomer-Cottrell jogs. Here, we show, using molecular dynamics of face-centered cubic nanopillars, that Lomer-Cottrell jogs are not as immobile as initially thought and that they do not provide strong pinning points for single arm sources. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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TYPE Journal Article YEAR 2011
OSTIScopus

High-performance computing for materials design to advance energy science

MRS Bulletin

Lusk, Mark T.; Mattsson, Ann E.

The development of new materials typically requires an iterative sequence of synthesis and characterization, but high-performance computing (HPC) adds another dimension to the process: materials can be synthesized and/or characterized virtually as well, and it is often an overlapping quilt of data from these four aspects of design that is used to develop a new material. This is made possible, in large measure, by the algorithms and hardware collectively referred to as HPC. Prominent within this developing approach to materials design is the increasingly important role that quantum mechanical analysis techniques have come to play. These techniques are reviewed with an emphasis on their application to materials design. This issue of MRS Bulletin highlights specific examples of how such HPC tools are used to advance energy science research in the areas of nuclear fission, electrochemical batteries, photovoltaic energy conversion, hydrocarbon catalysis, hydrogen storage, clathrate hydrates, and nuclear fusion. © 2011 Materials Research Society.

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TYPE Journal Article YEAR 2011
ScopusOSTI

An experimental assembly for precise measurement of thermal accommodation coefficients

Review of Scientific Instruments

Trott, Wayne M.; Castaeda, Jaime N.; Torczynski, John R.; Gallis, Michael A.; Rader, Daniel J.

An experimental apparatus has been developed to determine thermal accommodation coefficients for a variety of gas-surface combinations. Results are obtained primarily through measurement of the pressure dependence of the conductive heat flux between parallel plates separated by a gas-filled gap. Measured heat-flux data are used in a formula based on Direct Simulation Monte Carlo (DSMC) simulations to determine the coefficients. The assembly also features a complementary capability for measuring the variation in gas density between the plates using electron-beam fluorescence. Surface materials examined include 304 stainless steel, gold, aluminum, platinum, silicon, silicon nitride, and polysilicon. Effects of gas composition, surface roughness, and surface contamination have been investigated with this system; the behavior of gas mixtures has also been explored. Without special cleaning procedures, thermal accommodation coefficients for most materials and surface finishes were determined to be near 0.95, 0.85, and 0.45 for argon, nitrogen, and helium, respectively. Surface cleaning by in situ argon-plasma treatment reduced coefficient values by up to 0.10 for helium and by ∼0.05 for nitrogen and argon. Results for both single-species and gas-mixture experiments compare favorably to DSMC simulations. © 2011 American Institute of Physics.

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TYPE Journal Article YEAR 2011
OSTIScopus

The thermodynamic ladder in geomicrobiology

American Journal of Science

Bethke, Craig M.; Sanford, Robert A.; Kirk, Matthew F.; Jin, Qusheng; Flynn, Theodore M.

A tenet of geomicrobiology is that anaerobic life in the subsurface arranges itself into zones, according to a thermodynamic ladder. Iron reducers, given access to ferric minerals, use their energetic advantage to preclude sulfate reduction. Sulfate reducers exclude methanogens in the same way, by this tenet, wherever the environment provides sulfate. Examining usable energy-the energy in excess of a cell's internal stores-in subsurface environments, we find that in groundwater of near neutral pH the three functional groups see roughly equivalent amounts. Iron reducers hold a clear energetic advantage under acidic conditions, but may be unable to grow in alkaline environments. The calculations fail to identify a fixed thermodynamic hierarchy among the groups. In long-term bioreactor experiments, usable energy did not govern microbial activity. Iron reducers and sulfate reducers, instead of competing for energy, entered into a tightly balanced mutualistic relationship. Results of the study show thermodynamics does not invariably favor iron reducers relative to sulfate reducers, which in turn do not necessarily have an energetic advantage over methanogens. The distribution of microbial life in the subsurface is controlled by ecologic and physiologic factors, and cannot be understood in terms of thermodynamics alone.

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TYPE Journal Article YEAR 2011
ScopusOSTIDOI

Assessing the Near-Term Risk of Climate Uncertainty:Interdependencies among the U.S. States

Backus, George A.; Trucano, Timothy G.; Robinson, David G.; Adams, Brian M.; Richards, Elizabeth H.; Siirola, John D.; Boslough, Mark; Taylor, Mark A.; Conrad, Stephen H.; Kelic, Andjelka; Roach, Jesse D.; Warren, Drake E.; Ballantine, Marissa D.; Stubblefield, William A.; Snyder, Lillian A.; Finley, Ray E.; Horschel, Daniel S.; Ehlen, Mark; Klise, Geoffrey T.; Malczynski, Leonard A.; Stamber, Kevin L.; Tidwell, Vincent C.; Vargas, Vanessa N.; Zagonel, Aldo A.

Abstract not provided.

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TYPE Conference YEAR 2011
OSTI

Raman and infrared thermometry for microsystems

Phinney, Leslie; Lu, Wei-Yang; Serrano, Justin R.

This paper compares measurements made by Raman and infrared thermometry on a SOI (silicon on insulator) bent-beam thermal microactuator. Both techniques are noncontact and used to experimentally measure temperatures along the legs and on the shuttle of the thermal microactuators. Raman thermometry offers micron spatial resolution and measurement uncertainties of {+-}10 K; however, typical data collection times are a minute per location leading to measurement times on the order of hours for a complete temperature profile. Infrared thermometry obtains a full-field measurement so the data collection time is much shorter; however, the spatial resolution is lower and calibrating the system for quantitative measurements is challenging. By obtaining thermal profiles on the same SOI thermal microactuator, the relative strengths and weaknesses of the two techniques are assessed.

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TYPE Conference YEAR 2011
OSTI

Aligned mesoporous architectures and devices

Brinker, C.J.

This is the final report for the Presidential Early Career Award for Science and Engineering - PECASE (LDRD projects 93369 and 118841) awarded to Professor Yunfeng Lu (Tulane University and University of California-Los Angeles). During the last decade, mesoporous materials with tunable periodic pores have been synthesized using surfactant liquid crystalline as templates, opening a new avenue for a wide spectrum of applications. However, the applications are somewhat limited by the unfavorabe pore orientation of these materials. Although substantial effort has been devoted to align the pore channels, fabrication of mesoporous materials with perpendicular pore channels remains challenging. This project focused on fabrication of mesoporous materials with perpendicularly aligned pore channels. We demonstrated structures for use in water purification, separation, sensors, templated synthesis, microelectronics, optics, controlled release, and highly selective catalysts.

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TYPE SAND Report YEAR 2011
DOIOSTI

The effect of chrome adhesion layer on quartz resonator aging

Wessendorf, Kurt O.; Ohlhausen, J.A.

This SAND report documents a late start LDRD designed to determine the possible aging effects of a quartz resonator gold adhesion layer. Sandia uses quartz resonators for applications. These applications require a very stable frequency source with excellent aging (low drift) characteristics. These parts are manufactured by one of our qualified vendors outside Sandia Laboratories, Statek Corp. Over the years we, Sandia and the vendor, have seen aging variations that have not been completely explained by the typical mechanisms known in the industry. One theory was that the resonator metallization may be contributing to the resonator aging. This LDRD would allow us to test and analyze a group of resonators with known differentiating metallization and via accelerated aging determine if a chrome adhesion layer used to accept the final gold plating may contribute to poor aging. We worked with our main vendor to design and manufacture a set of quartz resonators with a wide range of metallization thickness ratios between the chrome and gold that will allow us determine the cause of this aging and which plating thickness ratios provide the best aging performance while not degrading other key characteristics.

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TYPE SAND Report YEAR 2011
DOIOSTI

Report on accelerated corrosion studies

Glass, Sarah J.; Mowry, Curtis D.

Sandia National Laboratories (SNL) conducted accelerated atmospheric corrosion testing for the U.S. Consumer Product Safety Commission (CPSC) to help further the understanding of the development of corrosion products on conductor materials in household electrical components exposed to environmental conditions representative of homes constructed with problem drywall. The conditions of the accelerated testing were chosen to produce corrosion product growth that would be consistent with long-term exposure to environments containing humidity and parts per billion (ppb) levels of hydrogen sulfide (H{sub 2}S) that are thought to have been the source of corrosion in electrical components from affected homes. This report documents the test set-up, monitoring of electrical performance of powered electrical components during the exposure, and the materials characterization conducted on wires, screws, and contact plates from selected electrical components. No degradation in electrical performance (measured via voltage drop) was measured during the course of the 8-week exposure, which was approximately equivalent to 40 years of exposure in a light industrial environment. Analyses show that corrosion products consisting of various phases of copper sulfide, copper sulfate, and copper oxide are found on exposed surfaces of the conductor materials including wires, screws, and contact plates. The morphology and the thickness of the corrosion products showed a range of character. In some of the copper wires that were observed, corrosion product had flaked or spalled off the surface, exposing fresh metal to the reaction with the contaminant gasses; however, there was no significant change in the wire cross-sectional area.

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TYPE SAND Report YEAR 2011
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A preliminary benefit-cost study of a Sandia wind farm

Griffin, Taylor

In response to federal mandates and incentives for renewable energy, Sandia National Laboratories conducted a feasibility study of installing an on-site wind farm on Sandia National Laboratories and Kirtland Air Force Base property. This report describes this preliminary analysis of the costs and benefits of installing and operating a 15-turbine, 30-MW-capacity wind farm that delivers an estimated 16 percent of 2010 onsite demand. The report first describes market and non-market economic costs and benefits associated with operating a wind farm, and then uses a standard life-cycle costing and benefit-cost framework to estimate the costs and benefits of a wind farm. Based on these 'best-estimates' of costs and benefits and on factor, uncertainty and sensitivity analysis, the analysis results suggest that the benefits of a Sandia wind farm are greater than its costs. The analysis techniques used herein are applicable to the economic assessment of most if not all forms of renewable energy.

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TYPE SAND Report YEAR 2011
DOIOSTI
Results 69401–69600 of 99,299
Results 69401–69600 of 99,299