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Displaying 49126 - 49150 of 74178

Microstructure and Elastic-Constant Measurements of Two-Phase Materials

November 1, 1999
Author(s)
H M. Ledbetter, Martin Dunn
Considering two-phase materials, we focus on the relationship between microstructure and physical properties, especially elastic constants. Microstructure includes occlusion concentration, orientation, shape, size, and distribution. Isotropic materials

Migdall Responds II: More Correlated Photon Metrology History

November 1, 1999
Author(s)
Alan L. Migdall
I appreciate the comments of Mike Gruntman (Sept., page 80) concerning the history of using correlated pairs of particles(photons) to determine absolute detector quantum efficiencies. Unfortunately there is an overall misunderstanding of the technique

NIST 101. Computational Chemistry Comparison and Benchmark Database

November 1, 1999
Author(s)
Russell D. Johnson III
The CCCBDB is a collection of experimental and theoretical thermochemical properties for 580 neutral gas-phase species. The goal of the database/website is to provide a benchmark set of molecules and reactions for the evaluation of ab initio computational

NIST Programs for Calibrations in the Far Ultraviolet Spectral Region

November 1, 1999
Author(s)
Robert E. Vest, L R. Canfield, Mitchell L. Furst, R M. Graves, A D. Hamilton, L R. Hughey, Thomas B. Lucatorto, R P. Madden
The National Institute of Standards and Technology (NIST) serves the growing ultraviolet user community by providing calibration services throughout the spectral range from 2 nm to 400 nm. In this paper we describe the far ultraviolet transfer standard

NIST Realization of the Gallium Triple Point

November 1, 1999
Author(s)
Gregory F. Strouse
The gallium trip point (302.9166 K) instead of the gallium melting point (302.9146 K) is used at NIST in the realization of the International Temperature Scale of 1990 (ITS-90). Four different sources of gallium with purities of at least 99.999 995% were

Noise Behavior of Pulsed Vertical-Cavity Surface-Emitting Lasers

November 1, 1999
Author(s)
T. W. Garrison, M. Beck, David H. Christensen
We determine the pulse energy fluctuations of vertical-cavity surface-emitting lasers by measuring the number of photoelectrons produced when a laser pulse is incident upon a photodetector.

Nonlinear Ultrasonic Parameter in Precipitate-Hardened Steels

November 1, 1999
Author(s)
Donna C. Hurley, Davor Balzar, P T. Purtscher
We have investigated several specimens of ASTM A710 steel containing copper-rich precipates with variations in the final aging treatment. X-ray diffraction line-broadening and small-angle neutron-scattering experiments revealed the existence of the

Off- Diagonal Elastic Constants in Fiber-Reinforced Composites

November 1, 1999
Author(s)
H M. Ledbetter, C M. Fortunko, Paul R. Heyliger
We present an alternative to the usual rod-resonance and pulse-echo measurement methods for determining off-diagonal C ij. The new approach - acoustic resonance spectroscopy (ARS) - avoids the above problems by treating, for example, C 12 the same as C 11

Photoionization Efficiency Spectrum And Ionization Energy of Obro

November 1, 1999
Author(s)
R P. Thorn, L J. Stief, T J. Buckley, Russell D. Johnson III, P S. Monks, R B. Klemm
The photoionization efficiency (PIE) spectrum of OBrO was measured over the wavelength range [Lambda] = 86 - 126 nm by using a discharge flow-photoionization mass spectrometer (DF-PIMS) apparatus coupled to a VUV synchrotron radiation source. Bromine

Polymer Composites for Repairing of Portland Cement Concrete: Compatibility Project

November 1, 1999
Author(s)
L Czarnecki, A Garbacz, P Lukowski, J R. Clifton
The impetus for this project has been the continuing deterioration of, and the necessity to repair, a large stock of concrete structures. A two-component system, portland cement concrete (substrate) in contact with a polymer composite (repair) is produced

Pressure Effect on CH 3 and C 2 H 3 Cross-Radical Reactions

November 1, 1999
Author(s)
Askar Fahr, Allan H. Laufer, D C. Tardy
The effect of pressure on the cross- radical reactions of vinyl and methyl radicals have been investigated. These radicals were produced by excimer laser photolysis of methyl vinyl ketone (CH 3COC 2H 3) at 193 nm. The reaction products were detected and

Rearrangement of Perfluorocyclobutyne

November 1, 1999
Author(s)
K B. Wiberg, M Marquez, Carlos A. Gonzalez
The energies of cyclobutyne, perfluorocyclobutyne and related compounds have been calculated at levels from MP2/6-31G* through QCISD(T)/6-311+G*, and also at B3LYP and B3PW91/6-311+G*. The relative energies found with the larger basis sets are quite

Reference Verification Fluids for Flash Point Determination

November 1, 1999
Author(s)
R G. Montemayor, J E. Rogerson, Jennifer C. Colbert, Susannah B. Schiller
The flash point of a liquid material is used to classify whether the material is flammable or combustible. 1,4-dimethylbenzene (p-xylene) has been used historically to verify the proper operation of different flash point test equipment. Because of the
Displaying 49126 - 49150 of 74178