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Search Publications by: Michael R Moldover (Assoc)

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Displaying 101 - 125 of 321

Airspeed Calibration Services: Laser Doppler Anemometer Calibration and Its Uncertainty

June 20, 2012
Author(s)
Iosif I. Shinder, Michael R. Moldover, J. M. Hall, Mike Duncan, Joe Keck
The National Institute of Standards and Technology (NIST) and the Oak Ridge National Laboratory (ORNL) are improving their airspeed calibration services. Both laboratories use spinning disks to generate linear velocities that are traceable to NIST’s length

Calibration of Laminar Flow Meters for Process Gases

June 1, 2012
Author(s)
John D. Wright, Thiago Cobu, Robert F. Berg, Michael R. Moldover
We calibrated three models of commercially-manufactured, laminar flow meters (LFMs) at four pressures (100 kPa, 200 kPa, 300 kPa, and 400 kPa) with five gases (N2, Ar, He, CO2, and SF6) over a 10:1 flow range using NIST’s primary flow standards as

Extended Lee model for the turbine meter & calibrations with surrogate fluids

May 1, 2012
Author(s)
Jodie G. Pope, John D. Wright, Aaron N. Johnson, Michael R. Moldover
We developed a physical model termed the “extended Lee model” for calibrating turbine meters to account for 1) fluid drag on the rotor, 2) bearing static drag and 3) bearing viscous drag. We tested the extended Lee model using a dual rotor, 2.5 cm diameter

Calibrations of Multi-Hole Pitot Tubes Depend on Tubulence

March 19, 2012
Author(s)
Iosif I. Shinder, Christopher J. Crowley, Michael R. Moldover
NIST is developing techniques to calibrate 2- and 3-dimensional anemometer systems (such as multi-hole pitot tubes) with a resolution of 0.3 %. The pitch and yaw response of multi-hole pitot tubes is complicated; therefore, calibrations require hundreds of

Semiclassical fifth virial coefficients for improved ab initio helium--4 standards

February 15, 2012
Author(s)
Katherine Shaul, Andrew Schultz, David A. Kofke, Michael R. Moldover
For helium-4, we present ab initio, semi-classical calculations of virial coefficients Bn for for n = 2, 3, 4, and 5 from 50 K to 1000 K. Using our values of B4 and B5 and the more accurate literature values of B2 and B3, we argue that the ab initio virial

Improved First-Principles Calculation of the Third Virial Coefficient of Helium

August 31, 2011
Author(s)
Giovanni Garberoglio, Michael R. Moldover, Allan H. Harvey
We employ state-of-the-art pair and three-body potentials for helium to calculate its third density virial coefficient C(T) with uncertainties much smaller than those of the best experimental results, and approximately one-fourth the uncertainty of our

Present Estimates of the Differences Between Thermodynamic Temperatures and the ITS-90

January 29, 2011
Author(s)
Joachim Fischer, M. DePodesta, K. D. Hill, Michael R. Moldover, Laurent Pitre, R. Rusby, Peter Steur, Osamu Tamura, R. White, L. Wolber
In 2005, the Consultative Committee for Thermometry (CCT) recommended the creation of a Mise en pratique for the definition of the kelvin and envisioned that future versions of the Mise en pratique would recommend values of the differences between

Accurate Measurements of Process Gas Flow with Laminar Flow Meters

October 15, 2010
Author(s)
Thiago Cobu, Robert F. Berg, John D. Wright, Michael R. Moldover
We calibrated three models of commercially-manufactured, laminar flow meters (LFMs) with nitrogen at four pressures (100 kPa, 200 kPa, 300 kPa, and 400 kPa) over a 10:1 flow range using NIST’s primary flow standards and a physical model. Without additional

Cylindrical Acoustic Resonator for the Re-determination of the Boltzmann Constant

June 1, 2010
Author(s)
J.T. Zhang, H. Lin, X.J. Feng, Keith A. Gillis, Michael R. Moldover
We describe progress towards re-determining the Boltzmann constant k B using two fixed-path, gas-filled, cylindrical, acoustic cavity resonators. The longitudinal acoustic resonance modes of a cylindrical cavity have lower quality factors Q than the radial

Feasibility of an Accurate Dynamic Standard for Water Flow

June 1, 2010
Author(s)
Iosif I. Shinder, Michael R. Moldover
We used NIST's primary water flow standard to study the feasibility of accurately determining mass flow rates m dot of water "dynamically," that is from the time derivative of the weight W of the collection tank: m dot,dynamic = (dW/dt)/g. When data for a