U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Search Publications by: Michael R Moldover (Assoc)

Search Title, Abstract, Conference, Citation, Keyword or Author
Displaying 26 - 50 of 161

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 NIST’s 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

Viscosity-ratio measurements with capillary viscometers

May 20, 2014
Author(s)
Robert F. Berg, Eric F. May, Michael R. Moldover
Viscosity-ratio measurements made with capillary viscometers exploit the accurate values of the viscosity of helium resulting from ab initio calculations. Accurate values of the argon-to-helium viscosity ratio are now used for primary acoustic thermometry

Acoustic Gas Thermometry

January 16, 2014
Author(s)
Michael R. Moldover, Roberto M. Gavioso, James B. Mehl, Laurent Pitre, Michael de Podesta, Jintao Zhang
Primary acoustic gas thermometry (AGT) exploits the simple relationship between the speed of sound in a dilute gas u and the thermodynamic temperature T of the gas. For monatomic gases such as argon and helium, u2 = (5/3) kT/m, in the limit of zero

ACOUSTIC GAS THERMOMETRY

January 16, 2014
Author(s)
Michael R. Moldover, Roberto M. Gavioso, James B. Mehl, Laurent Pitre, Michael de Podesta, Jintao Zhang
We review the principles, techniques and results from primary acoustic gas thermometry (AGT). Since the establishment of ITS-90, the International Temperature Scale of 1990, spherical and quasi-spherical cavity resonators have been used to realize primary

Viscosity-ratio measurements with capillary viscometers

November 27, 2013
Author(s)
Robert F. Berg, Eric F. May, Michael R. Moldover
Viscosity-ratio measurements made with capillary viscometers exploit the accurate values of the viscosity of helium calculated ab initio. Accurate values of the argon-to-helium viscosity ratio are now used for primary acoustic gas thermometry and for the

IMPROVEMENTS TO NIST'S AIR SPEED CALIBRATION SERVICE

September 24, 2013
Author(s)
Iosif I. Shinder, Christopher J. Crowley, Bernard J. Filla, Michael R. Moldover
We discuss five significant improvements to the Air Speed Calibration Service conducted by the National Institute of Standards and Technology (NIST): 1. Reduced-uncertainty calibrations of the secondary standard [Laser Doppler Anemometer, (LDA)] using a

The Effect of Turbulence on a Multi-Hole Pitot Calibration

June 10, 2013
Author(s)
Christopher J. Crowley, Iosif I. Shinder, Michael R. Moldover
Abstract- Accurate calibrations of multi-hole Pitot tubes require thousands of measurements spanning ranges of the fluid’s velocity, and the pitch and yaw angles. When calibrating a commercially-manufactured multi-hole Pitot tube in NIST’s low-turbulence

Microwave measurements for gas thermometry up to the copper point

May 13, 2013
Author(s)
XiaoJuan Feng, Keith A. Gillis, Michael R. Moldover, James B. Mehl
We measured 5 microwave resonance frequencies f N of an argon-filled cylindrical cavity at temperatures up to 1349 K. The repeatability of both the measured frequencies u(f N) and the scaled half-widths u(g N)/ f N was better than 10 -6f N. The measurement

Recommended viscosities of 11 dilute gases at 25?degC

December 13, 2012
Author(s)
Robert F. Berg, Michael R. Moldover
Commercially manufactured meters that measure the flow of a process gas are often calibrated with a known flow of a surrogate gas. This requires an accurate model of the flow meter and accurate values of the relevant thermophysical properties for both

Room Temperature Acoustic Transducers for High-Temperature Thermometry

July 9, 2012
Author(s)
Dean C. Ripple, William E. Murdock, Gregory F. Strouse, Keith A. Gillis, Michael R. Moldover
We have successfully conducted highly-accurate, primary acoustic thermometry at 600 K using a sound source and a sound detector at room temperature. We describe the source, the detector, and the ducts that connected them to our cavity resonator. This

TESTING LONG-WAVELENGTH ACOUSTIC FLOWMETER CONCEPTS FOR FLUE GAS FLOWS

June 22, 2012
Author(s)
Lee J. Gorny, Keith A. Gillis, Michael R. Moldover
As a part of NIST’s program to standardize measurements of greenhouse gas emissions, we are developing a long-wavelength acoustic flowmeter (LWAF) for accurate, economical measurements of exhaust flows from coal-burning power plants. Measurements of the