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Search Publications by: Michael R Moldover (Assoc)

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Displaying 51 - 75 of 321

Advances in Thermometry

January 1, 2016
Author(s)
Michael R. Moldover, Weston L. Tew, Howard W. Yoon
The last 25 years have seen tremendous progress in thermometry in the moderate temperature range (1 K to 1235 K). Various primary thermometers — based on different physics —have uncovered errors in the International Temperature Scale of 1990 and set the

CORRELATIONS AMONG ACOUSTIC MEASUREMENTS OF THE BOLTZMANN CONSTANT

September 9, 2015
Author(s)
Michael R. Moldover, Roberto M. Gavioso, David B. Newell
We review correlated uncertainties among the accurate determinations of the Boltzmann constant kB that used the techniques of primary acoustic gas thermometry (AGT). We consider uncertainty contributions from four sources: (1) resonator-dependent

Test of a virtual cylindrical acoustic resonator for determining the Boltzmann constant

August 19, 2015
Author(s)
XiaoJuan Feng, Hong Lin, Keith A. Gillis, Michael R. Moldover, Jintao Zhang
We report progress in determining the Boltzmann constant k B using a virtual acoustic resonator derived by combining the measured frequencies of the longitudinal acoustic modes of two argon-filled, cylindrical, cavity resonators in such a way as to

The Redefinition of the SI: Impact on Calibration Services at NIST

June 1, 2015
Author(s)
Neil M. Zimmerman, Jon R. Pratt, Michael R. Moldover, David B. Newell, Gregory F. Strouse
As most readers are probably at least vaguely aware, it is likely that the SI system of units will be redefied in 2018. This redefinition would fundamentally change the logical structure of the SI, with one result being a substantial change in how mass is

Measuring collected gas with microwave and acoustic resonances

April 23, 2015
Author(s)
Keith A. Gillis, James W. Schmidt, Michael R. Moldover, James B. Mehl
With calibrations of large flow meters in mind, we established the feasibility of determining the mass M of argon gas contained within a 0.3 m 3 commercially manufactured pressure vessel ("tank") with a relative standard uncertainty of u r(M) = 0.0016 at 0

Thermal Effects on Critical Flow Venturis

April 14, 2015
Author(s)
John D. Wright, Aaron N. Johnson, Michael R. Moldover, Woong Kang, Liang Zhang
Critical flow venturis (CFVs) are widely used as working and transfer standards for gas flow measurement because of their long-term calibration stability (5 (e.g., a 2 mm throat diameter flowing air at 1 MPa), CFVs exhibit sensitivity to the environmental

"Weighing" a Gas With Microwave and Acoustic Resonances

March 24, 2015
Author(s)
Keith A. Gillis, James B. Mehl, James W. Schmidt, Michael R. Moldover
With calibrations of large flow meters in mind, we established the feasibility of determining the mass Mof argon gas contained within a 0.3 m 3 commercially manufactured pressure vessel ("tank") with a relative uncertainty of u r(M) = 0.0015 at 0.6 MPa by

Microwave Determination of the Volume of a Pressure Vessel

December 9, 2014
Author(s)
Michael R. Moldover, James W. Schmidt, Keith A. Gillis, James B. Mehl, John D. Wright
Using microwave techniques that are scalable to very large volumes, we measured the interior volume of a 0.3 m 3, commercially-manufactured, pressure vessel with an uncertainty of 0.05 %, as confirmed by independent, more-accurate, gas-expansion

Improvements to NISTs Air Speed Calibration Service

December 8, 2014
Author(s)
Iosif I. Shinder, Michael R. Moldover, Christopher J. Crowley, Bernard J. Filla
We discuss five significant improvements to the Air Speed Calibration Service conducted by the National Institute of Standards and Technology (NIST): 1. Reduced-uncertainty calibration of the secondary standard [Laser Doppler Anemometer, (LDA)] using a

Acoustic Techniques for Measuring Transport Properties of Gases

May 22, 2014
Author(s)
Keith A. Gillis, Michael R. Moldover
We describe the principles, techniques, and performance of acoustic resonators used to measure the shear viscosity, the thermal conductivity, and the bulk viscosity in gases. We developed the Greenspan acoustic viscometer at NIST, where colleagues used it