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Chemistry

Chemical engineering & processing

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Displaying 451 - 475 of 781

Optimizing Acoustic Measurements of the Boltzmann Constant

November 22, 2009
Author(s)
Michael R. Moldover
We review the progress in acoustic metrology of gases that has occurred since the 1988 measurement of the universal gas constant R using a spherical acoustic resonator. The advances in understanding resonators and in calculating the thermophysical

Perturbations from Ducts on the Modes of Acoustic Thermometers

September 1, 2009
Author(s)
Keith A. Gillis, Michael R. Moldover, Hong Lin
We examine the perturbations of the modes of an acoustic thermometer caused by circular ducts used either for gas flow or as acoustic waveguides coupled to remote transducers. We calculate the acoustic admittance of circular ducts using a model based on

Reference measurements of Hydrogen's Dielectric Permittivity

August 10, 2009
Author(s)
James W. Schmidt, Michael R. Moldover, Eric F. May
We used a quasi-spherical cavity resonator to measure the relative dielectric permittivity ε r of H 2 at frequencies from 2.4 GHz to 7.3 GHz, at pressures up to 6.5 MPa, and at the temperatures 273 K and 293 K. The resonator was calibrated using auxiliary

High Definition Flow

August 1, 2009
Author(s)
John D. Wright, Michael R. Moldover
From pharmaceutical production to the natural gas market, exact flow measurements are critical. Here's how NIST helps keep us all on the same page.

Optimization Calculations for a 30 HZ, 4 K Regenerator with Helium-3 Working Fluid

June 28, 2009
Author(s)
Ray Radebaugh, Yonghua Huang, Agnes A. O'Gallagher, John M. Gary
The NIST numerical software, REGEN3.3, which incorporates both He-4 and He-3 properties, was used to calculate the losses and second law efficiencies of 4 K regenerators operating at 30 Hz. Operating parameters, such as average pressure, pressure ratio

Effect of Dissolved Nitrogen Gas on the Density of Di-2-Ethylhexyl Sebacate: Working Fluid of the NIST Oil Ultrasonic Interferometer Manometer Pressure Standard

June 1, 2009
Author(s)
Jay H. Hendricks, Jacob R. Ricker, Justin H. Chow, Douglas A. Olson
The National Institute of Standards and Technology (NIST) Low Pressure Manometry Laboratory maintains national pressure standards ranging from 1 mPa to 360 kPa through the operation of four ultrasonic interferometer manometer (UIM) pressure standards. NIST

On the determination of C0 (or A0), D0K, H0K, and some dark states for symmetric-top molecules from infrared spectra without the need for localized perturbations

May 4, 2009
Author(s)
Alfons Weber, Jintao Zhang, Tony Masiello, Thomas A. Blake, J Nibler
For symmetric top molecules, the normal k = 0, l = 0 and k = 1, l = 1 selection rules for parallel and perpendicular bands, respectively, do not allow the determination of the K-dependent rotational constants, C0 (or A0), D0K, and H0K. However, we
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