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Search Publications by: Michael R Moldover (Assoc)

Displaying 176 - 200 of 321

The Viscosity of Seven Gases Measured with a Greenspan Viscometer

November 1, 2003

Author(s)

John J. Hurly, Keith A. Gillis, J B. Mehl, Michael R. Moldover

We determined the viscosity of seven gases (Ar, CH4, C3H8, N2, SF6, CF4, C2F6) by interpreting frequency-response data from a Greenspan acoustic viscometer with a detailed model developed by Gillis, Mehl, and Moldover. The model contains a parameter er

Volumetric Gas Flow Standard with Uncertainty of 0.02% to 0.05%

November 1, 2003

Author(s)

John D. Wright, Michael R. Moldover, Aaron N. Johnson, A Mizuno

A new pressure, volume, temperature, and time (PVTt) primary gas flow standard for calibrating flowmeters has an expanded uncertainty (k = 2) of between 0.02% and 0.05%. The standard diverts a steady flow into a collection tank of known volume during a

Comment On 'General Principles for the Definition of the Base Units in the SI'

October 1, 2003

Author(s)

Michael R. Moldover, Dean C. Ripple

Recently, Kose et al. proposed general principles that should guide any future discussions regarding the redefinition of the SI base units and they illustrated their principles with an example of a revised SI. Part of their example (redefinition of the

Progress in Primary Acoustic Thermometry at NIST: 273 K to 505 K

September 1, 2003

Author(s)

Gregory F. Strouse, Dana R. Defibaugh, Michael R. Moldover, Dean C. Ripple

The NIST Acoustic Thermometer determines the thermodynamic temperature by measuring the speed of sound of argon in a spherical cavity. We obtained the thermodynamic temperature of three fixed points on the Interna-tionalTemperature Scale of 1990: the

Techniques for Primary Acoustic Thermometry to 800 K

September 1, 2003

Author(s)

Dean C. Ripple, Dana R. Defibaugh, Michael R. Moldover, Gregory F. Strouse

The NIST Primary Acoustic Thermometer will measure the difference between the International TemperatureScale of 1990 and the Kelvin Thermodynamic Scale throughout the range 273 K to 800 K with uncertainties of only afew millikelvins. The acoustic

Temperature Characterization in the Collection Tank of the NIST 26 m(3) PVTt Gas Flow Standard

September 1, 2003

Author(s)

Aaron N. Johnson, John D. Wright, Michael R. Moldover, Pedro I. Espina

Gas temperature gradients created during the filling stage of a PVTt (Pressure-Volume-Temperature-time) calibration cycle, and those imposed by inhomogeneous room conditions, lead to uncertainties in the average gas temperature in the collection tank

Theory of the Greenspan Viscometer

July 1, 2003

Author(s)

Keith A. Gillis, J B. Mehl, Michael R. Moldover

We present a detailed acoustic model of the Greenspan acoustic viscometer, a practical instrument for accurately measuring the viscosity eta of gases. As conceived by Greenspan, the viscometer is a Helmholtz resonator composed of two chambers coupled by a

Relative Permittivity and Refractive Index

March 28, 2003

Author(s)

Michael R. Moldover, K N. Marsh, J M. Barthel, R Buchner

Measurements of the relative electric permittivity (dielectric constant or relative permittivity) e(p,T) and refractive index of fluids n(p,T) as a function of the pressure and the temperature can be used to determine a wide range of thermodynamic

Dielectric Permittivity of Eight Gases Measured with Cross Capacitors

March 1, 2003

Author(s)

James W. Schmidt, Michael R. Moldover

A 4-ring, toroidal cross capacitor was used to measure accurately the relative dielectric permittivity ε(p,T) of He, Ar, N 2, O 2, CH 4, C 2H 6, C 3H 8, and CO 2. (ε is often called the dielectric constant. ) The data are in the range from 0 C to 50 C and

Design and Uncertainty Analysis for a PVTt Gas Flow Standard

February 1, 2003

Author(s)

John D. Wright, Aaron N. Johnson, Michael R. Moldover

A new pressure, volume, temperature, and time (PVTt) primary gas flow standard has been constructed at the National Institute of Standards and Technology with an expanded uncertainty of between 0.02 % and 0.05 % (k = 2). The standard covers a flow range of

Acoustic Measurements in Gases, Chapter 10

September 15, 2001

Author(s)

Michael R. Moldover, Keith A. Gillis, John J. Hurly, J B. Mehl, J Wilhelm

Cylindrical acoustic resonators developed at the National Institute of Standards and Technology (NIST) are routinely used to measure the speed of sound in gases with uncertainties of 0.01% or less. The pressure dependence of the data is fitted with model

Accurate Measurements of Thermodynamic and Transport Properties of Industrial Gases with Acoustic Resonators.

September 2, 2001

Author(s)

Keith A. Gillis, John J. Hurly, Michael R. Moldover

Acoustic resonators have been developed at NIST as tools to measure the thermodynamic and transport properties of gases. High Q cylindrical acoustic resonators are routinely used to measure the speed of sound in gases with uncertainties of 0.01% or less

Reference Values of the Dielectric Constant of Natural Gas Components Determined with a Cross Capacitor

May 1, 2001

Author(s)

Michael R. Moldover, T J. Buckley

We used a novel toroidal cross capacitor to measure accurately the dielectric polarizability e(p) (i.e., the dielectric constant) of helium, argon, nitrogen, methane, and carbon dioxide at T = 50 degrees C. The data extend up to 7 MPa (5 MPa for CO 2) and

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