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Chemistry

Chemical engineering & processing

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Displaying 526 - 550 of 781

Reference Viscosities of H 2 , CH 4 , Ar and Xe at Low Densities

August 1, 2007
Author(s)
E May, Robert F. Berg, Michael R. Moldover
We determined the zero-density viscosity eta of hydrogen, methane and argon in the temperature range 200 K to 400 K, with standard uncertainties of 0.084 % for hydrogen and argon and 0.096 % for methane. These uncertainties are dominated by the uncertainty

The Polarizability of Helium and Gas Metrology

June 22, 2007
Author(s)
James W. Schmidt, R Gavioso, E May, Michael R. Moldover
Using a quasi-spherical, microwave cavity resonator, we measured the refractive index of helium to deduce its molar polarizability A ε in the limit of zero density. We obtained (A ε,meas - A ε,theory)/A ε = (-1.8plus or minus} 8.4)× 10 -6, where the

Direct Electrostatic Calibration of Hybrid Sensors for Small Force Measurement

June 4, 2007
Author(s)
Koo-Hyun Chung, Gordon A. Shaw, Jon R. Pratt
The measurement of forces from piconewtons to millinewtons is an area of interest from both an applied and pure research standpoint, however creating a link between small forces and the International System of Units (SI) has been difficult. In this work, a

Traceable Micro-Force Sensor for Instrumented Indentation Calibration

April 10, 2007
Author(s)
Douglas T. Smith, Gordon A. Shaw, R M. Seugling, D Xiang, Jon R. Pratt
Instrumented indentation testing (IIT), commonly referred to as nanoindentation when small forces are used, is a popular technique for determining the mechanical properties of small volumes of material. Sample preparation is relatively easy, usually

A Piezoresistive Cantilever Force Sensor for Direct AFM Force Calibration

April 8, 2007
Author(s)
Jon R. Pratt, John A. Kramar, Gordon A. Shaw, Douglas T. Smith, John M. Moreland
We describe the design, fabrication, and calibration testing of a new piezoresistive cantilever force sensor suitable for the force calibration of atomic force microscopes in a range between tens of nanonewtons to hundreds of micronewtons. The sensor is

EQUATION OF STATE AND THERMOPHYSICAL PROPERTIES OF HELIUM-3

April 3, 2007
Author(s)
Yonghua Huang, G.B. Chen, V. Arp, Ray Radebaugh
Experimental data of the thermophysical properties of 3He were mined into a searchable database. Equilibrium equations along the vapor-liquid and liquid-solid lines were proposed. A general equation of state for normal fluid 3He based on the Debye specific

NIST Calibration Services for Water Flowmeters Water Flow Calibration Facility

August 1, 2006
Author(s)
Iosif I. Shinder, Iryna V. Marfenko
This document describes the Water Flow Calibration Facility (WFCF) at the National Institute of Standards and Technology (NIST). This facility has three parallel pipelines with diameters of 100, 200 and 400 mm and three weighing systems with capacities of

Proposed Rapid Cooldown Technique for Pulse Tube Cryocoolers

June 14, 2006
Author(s)
Ray Radebaugh, Agnes O?Gallagher, Michael A. Lewis, Peter E. Bradley
Some cryocooler applications, such as those for military operations dealing with high temperature superconducting (HTS) magnets, motors, or generators, require faster cooldown times than what can normally be provided with a cryocooler designed to

Solution and Surface Composition Gradients via Microfluidic Confinement: Fabrication of a Statistical-Copolymer-Brush Composition Gradient

June 6, 2006
Author(s)
Chang Xu, Susan E. Barnes, Tao Wu, Daniel A. Fischer, Dean M. DeLongchamp, J Batteas, Kathryn L. Beers
A simple method to generate solution gradients through microfluidic confinement is described. The solution gradient inside a microchannel was formed by varying the relative infusion rates of two solutions that differed in compositions. The establishment
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