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At least 235 records · Page 13
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DOE OSTI2025

Chiral rank-$k$ truncations for the multigrid preconditioner of Wilson fermions in lattice QCD

We present a modification to the setup algorithm for the multigrid preconditioner of Wilson fermions in lattice QCD. A larger number of test vectors than that used in conventional multigrid is generated by the smoother. This set of test vectors is then truncated by a singular value decomposition on the chiral components of the test vectors, which are subsequently used to form the prolongation and restriction matrices of the multigrid hierarchy. This modification is demonstrated to improve the convergence of linear equations on an anisotropic lattice with 𝑚𝜋 ≈ 280 MeV from the Hadron Spectrum Collaboration and an isotropic lattice with 𝑚𝜋 ≈ 220 MeV from the MILC Collaboration. The lattice volume dependence of the method is also examined.

Whyte, Travis [Jülich Supercomputing Center, Jülic↗
NASA NTRS1972

Rank-k Maximal Statistics for Divergence and Probability of Misclassification

A technique is developed for selecting from n-channel multispectral data some k combinations of the n-channels upon which to base a given classification technique so that some measure of the loss of the ability to distinguish between classes, using the compressed k-dimensional data, is minimized. Information loss in compressing the n-channel data to k channels is taken to be the difference in the average interclass divergences (or probability of misclassification) in n-space and in k-space.

Decell, H. P., Jr.↗
NASA NTRS1977

Effect of test conditions on relative toxicity rankings of fifteen materials

Fifteen materials were evaluated for relative toxicity of pyrolysis effluents, using different test conditions in the USF methodology. Wool fabrics were consistently among the most toxic materials, and polystyrene and polychloroprene flexible foam were consistently among the least toxic materials.

Hilado, C. J.↗
NASA NTRS1978

Thermal power systems small power systems applications project. Decision analysis for evaluating and ranking small solar thermal power system technologies. Volume 1: A brief introduction to multiattribute decision analysis

The principal concepts of the Keeney and Raiffa approach to multiattribute decision analysis are described. Topics discussed include the concepts of decision alternatives, outcomes, objectives, attributes and their states, attribute utility functions, and the necessary independence properties for the attribute states to be aggregated into a numerical representation of the preferences of the decision maker for the outcomes and decision alternatives.

Feinberg, A.↗
NASA NTRS1981

Control system development for an organic Ranking cycle engine

An organic Rankine cycle engine is used as part of a solar thermal power conversion assembly (PCA). The PCA, including a direct-heated cavity receiver and a shaft-mounted alternator, is mounted at the focal point of a parabolic dish concentrator. The engine controls are required to maintain approximately constant values of turbine inlet temperature and shaft speed, despite variation in the concentrated solar power input to the receiver. The controls design approach, system models, and initial stability and performance analysis results are presented herein.

Bergthold, F. M., Jr.↗
NASA NTRS1981

The application of simulation modeling to the cost and performance ranking of solar thermal power plants

A computer simulation code was employed to evaluate several generic types of solar power systems (up to 10 MWe). Details of the simulation methodology, and the solar plant concepts are given along with cost and performance results. The Solar Energy Simulation computer code (SESII) was used, which optimizes the size of the collector field and energy storage subsystem for given engine-generator and energy-transport characteristics. Nine plant types were examined which employed combinations of different technology options, such as: distributed or central receivers with one- or two-axis tracking or no tracking; point- or line-focusing concentrator; central or distributed power conversion; Rankin, Brayton, or Stirling thermodynamic cycles; and thermal or electrical storage. Optimal cost curves were plotted as a function of levelized busbar energy cost and annualized plant capacity. Point-focusing distributed receiver systems were found to be most efficient (17-26 percent).

Rosenberg, L. S.↗
NASA NTRS1989

Near-infrared photometry and stellar populations of first-ranked galaxies in a complete sample of nearby Abell clusters

Eighty-four brightest cluster members (BCMs) in the complete sample of high Galactic latitude nearby Abell clusters of Hoessel, Gunn, and Thuan (HGT) are investigated. The stellar populations in BCMs using near-infrared and optical-near-infrared colors are studied. Brighter BCMs have redder (J-K) and (V-K) colors, suggesting a metallicity increase in brighter galaxies. The larger dispersion of their colors implies that BCMs possess more heterogeneous stellar populations than their lower luminosity counterparts, the normal elliptical galaxies. Special attention is paid to BCMs associated with cooling flows. BCMs with larger accretion rates have bluer (V-K) colors due to ultraviolet excesses and are brighter in the visual wavelength region, but not in the infrared. It is suggested that part of the X-ray emitting cooling gas is converted into high- and intermediate-mass stars emitting in the blue and visible, but not in the infrared. The properties of BCMs as standard candles in the near-infrared are examined and compared with those in the optical.

Thuan, Trinx X.↗
NASA NTRS1990

The possibility of a reversal of material flammability ranking from normal gravity to microgravity

The purpose of the discussion is to show, by a theoretical model, that one of the material flammability indices, the flammability limit, can be reversed in proper circumstances. A stagnation-point diffusion flame adjacent to a spherical solid-fuel surface is considered. It is shown that a reversal of the limiting oxygen indices from normal gravity and microgravity is possible. Although the example is based on a particular theoretical model with a particular flame configuration and specifically for an oxygen limit, the flammability-limit reversal phenomenon is believed to be more general.

T'Ien, James S.↗
NASA NTRS1989

The oxygen sensitivity/compatibility ranking of several materials by different test methods

Eleven materials were evaluated for oxygen compatibility using the following test methods: heat of combustion (ASTM D 2015), liquid oxygen impact (ASTM D 2512), pneumatic impact (ASTM G 74), gaseous mechanical impact (ASTM G 86), autogenous ignition temperature by pressurized differential scanning calorimeter, and the determination of the 50 percent reaction level in liquid oxygen using silicon carbide as a reaction enhancer. The eleven materials evaluated were: Teflon TFE, Vespel SP-21, Krytox 240AC, Viton PLV5010B, Fluorel E2160, Kel F 81, Fluorogold, Fluorogreen E-600, Rulon A, Garlock 8573, nylon 6/6.

Lockhart, Billy J.↗
NASA NTRS1991

Monte Carlo simulation of errors in the anisotropy of magnetic susceptibility - A second-rank symmetric tensor

Monte Carlo perturbations of synthetic tensors to evaluate the Hext/Jelinek elliptical confidence regions for anisotropy of magnetic susceptibility (AMS) eigenvectors are used. When the perturbations are 33 percent of the minimum anisotropy, both the shapes and probability densities of the resulting eigenvector distributions agree with the elliptical distributions predicted by the Hext/Jelinek equations. When the perturbation size is increased to 100 percent of the minimum eigenvalue difference, the major axis of the 95 percent confidence ellipse underestimates the observed eigenvector dispersion by about 10 deg. The observed distributions of the principal susceptibilities (eigenvalues) are close to being normal, with standard errors that agree well with the calculated Hext/Jelinek errors. The Hext/Jelinek ellipses are also able to describe the AMS dispersions due to instrumental noise and provide reasonable limits for the AMS dispersions observed in two Hawaiian basaltic dikes. It is concluded that the Hext/Jelinek method provides a satisfactory description of the errors in AMS data and should be a standard part of any AMS data analysis.

Lienert, Barry R.↗
NASA NTRS1995

Annual report to the Chairman and Ranking Minority Members, House and Senate Committees on Appropriations. Status of open recommendations: Improving operations of federal departments and agencies

Each year, GAO's work contributes to many legislative and executive branch actions that result in significant financial savings and other improvements in government operations. Some, but not all, are identified through GAO's system for periodically following up to determine the status of actions taken on the recommendations made in its audit and evaluation reports. In fiscal year 1994, GAO made 1,450 recommendations, but, more importantly, about 4,400 GAO recommendations made over the past 5 years have been implemented. This report includes summary information on the status of all GAO recommendations that have not been fully implemented and highlights some of the key ones. This information should help congressional and agency leaders prepare for upcoming appropriations and oversight activities and stimulate further actions to achieve the desired improvements in government operations. In addition to including printed issue area summaries highlighting the ipact of GAO's work and the key open recommendations, this volume includes a set of computer diskettes with details on all open recommendations.

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