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Search Publications

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Displaying 49776 - 49800 of 73697

Lattice Boltzmann Simulations of Single and Multi-Component Flow in Porous Media

July 1, 1999
Author(s)
Nicos Martys, John G. Hagedorn, J E. Devaney
We examine the utility of the lattice Boltzmann method for modeling fluid flow in porous media. First the lattice Boltzmann method is validated for the case of single component flow in several idealized flow geometries. Large scale simulations of fluid

Measurement of the Rheological Properties of Cement Paste: A New Approach

July 1, 1999
Author(s)
Chiara F. Ferraris
This paper presents a new approach for predicting the rheological properties of concrete from rheological measurements on cement paste and from concrete composition. This approach requires measurement of the cement paste rheology under the same conditions

Methods to Remove Distortion Artifacts in Scanned Projections

July 1, 1999
Author(s)
A R. Kalukin, Zachary H. Levine, Charles S. Tarrio, S P. Frigo, I McNulty, S S. Wang, C C. Retsch, M Kuhn, B Winn
Atrifacts induced by distortions which sometimes occur in two-dimensional projection images can appear in the resulting tomographic reconstructions. We describe a procedure for analyzing, correcting and removing experimental atrifacts, and hence reducing

Microscopic Image Analysis of Defect Areas in Optical Disks

July 1, 1999
Author(s)
P L'Hostis, Frederick R. Byers, Fernando L. Podio, Xiao Tang
This paper presents techniques developed in the Information Technology Laboratory of the US National Institute of Standards and Technology (NIST/ITL) for enabling microscopic image analysis of optical data storage media such as optical discs. These non

Modern Wavelength Standards in the Ultraviolet and Vacuum Ultraviolet

July 1, 1999
Author(s)
Joseph Reader, Craig J. Sansonetti
In recent work at the National Institute of Standards and Technology the Atomic Spectroscopy Group has characterized several sources of wavelength standards useful for remote sensing applications. At low resolution, mercury pencil-type lamps are convenient

Multidetector Hemispherical Polarized Optical Scattering Instrument

July 1, 1999
Author(s)
Thomas A. Germer
A multidetector optical scattering instrument is described and characterized. The instrument has twenty-eight detectors surrounding and substantially covering the scattering hemisphere. Each detector contains a polarizer so that each is only sensitive to p

Negative Ion-Neutral Reactions in Townsend Discharges

July 1, 1999
Author(s)
James K. Olthoff, MVVS. Rao
Relative intensities and translational ion-flux energy distributions are presented for negative ions sampled from Townsend discharges in O 2, SF 6, and CF 4 for a high range of density reduced electric fields greater than 2 W 10 -18 V m 2 (> 2 kTd). These

On-Line Monitoring and Fault Detection of Control System Performance

July 1, 1999
Author(s)
J E. Seem, J House, R H. Monroe
Modern energy management and control systems have alarm and trend features that allow building operators to monitor and troubleshoot building systems. The alarm feature can provide nearly immediate feedback when, for instance, a sensor value is ourside

Reference Standards, Uncertainties, and the Future of the NIST Electronic Kilogram

July 1, 1999
Author(s)
Richard L. Steiner, David B. Newell, J. Schwarz, Edwin R. Williams
The National Institute of Standards and Technology (NIST) watt balance experiment recently made a new determination of Planck's constant with a relative standard uncertainty of 87 x 10 -9 (k = 1), concurrently with an upper limit on the drift rate of the

Review of Programming the Finite Element Method, Third Edition

July 1, 1999
Author(s)
William F. Mitchell
Programming the Finite Element Method. 3rd Edition. By I.M. Smith and D.V. Griffiths. John Wiley & Sons Ltd., West Sussex, UK, 1998. $49.95. xii+534pp., paperback. ISBN 0-471-96543-X.This is the third edition of this book. The principal differences between

Rockwell Hardness - A Method-Dependent Standard Reference Material

July 1, 1999
Author(s)
Samuel R. Low III, R J. Gettings, Walter S. Liggett Jr, Jun-Feng Song
Rockwell hardness is not a fundamental physical property of a material. It is a method-dependent measurement of the deformation of the material to an applied force. There are no alternative measurement systems to directly or independently measure Rockwell

Rockwell Hardness - A Method-Dependent Standards Reference Material

July 1, 1999
Author(s)
Samuel Low, R Gettings, Walter S. Liggett Jr, Jun-Feng Song
Rockwell hardness is a method-dependent measurement of the deformation of a material in response to an applied force. It is not a fundamental physical property of a material. There are no alternative measurement systems to directly or independently measure

Spray Flame Measurements for CFD Model Validation

July 1, 1999
Author(s)
J F. Widmann, S R. Charagundla, Cary Presser
Experimental data were collected for the purpose of validating multiphase combustion models and submodels. A spray combustor was fabricated that permits well-defined boundary and input conditions, and measurements were carried out that characterize the

Stray Light Elimination in Making Projection Display Measurements

July 1, 1999
Author(s)
Paul A. Boynton, Edward F. Kelley
Electronic front-projection display specifications are often based on measurements made in ideal darkroom conditions. However, not everyone has access to such a facility. In many environments, ambient light from other sources in the room illuminates the

Studies of Ion Bombardment in High Density Plasmas Containing CF 4

July 1, 1999
Author(s)
James K. Olthoff, Yicheng Wang
We report ion energy distributions, relative ion intensities, and absolute total ion current densities at the grounded electrode of an inductively coupled Gaseous Electronics Conference radio-frequency reference cell for discharges generated in pure C 4
Displaying 49776 - 49800 of 73697
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