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: Aaron Johnson (Fed)

Search Title, Abstract, Conference, Citation, Keyword or Author
Displaying 1 - 25 of 107

SLowFlowS: A novel flow standard for semiconductor process gases

March 1, 2025
Author(s)
Jodie Gail Pope, Keith A. Gillis, Aaron Johnson, Joey Boyd, John Wright
Numerous process gases are used in the production of semiconductor chips. Accurate metering of these gases into process chambers is critical for maximizing device throughput and yield. A national flow standard for semiconductor process gases does not exist

Calibrating laser Doppler anemometers utilizing an optical chopper

January 31, 2025
Author(s)
Christopher Crowley, Iosif Isaakovich Shinder, Michael R. Moldover, Joey Boyd, James Filla, Aaron Johnson
Laser Doppler anemometers (LDAs) use scattered light to determine velocity components of a flowing fluid. The operating principal of LDAs is simple conceptually; however, it is impractical to trace the LDA-determined velocities to the SI by characterizing

Non-nulling Protocols for Fast, Accurate, 3-D Velocity Measurements in Stacks

July 28, 2023
Author(s)
Iosif Isaakovich Shinder, Aaron Johnson, James Filla, Vladimir B. Khromchenko, Michael R. Moldover, Joey Boyd, John D. Wright, John R. Stoup
We present protocols for making fast, accurate, 3-D velocity measurements in the stacks of coal-fired power plants. The measurements are traceable to internationally-recognized standards; therefore, they provide a rigorous basis for measuring and/or

Gas Flow Standards and Their Uncertainty

December 12, 2022
Author(s)
John D. Wright, Aaron Johnson, Michael R. Moldover, Shin-ichi Nakao
We review diverse types of gas flow standards that are used to calibrate other gas flow meters. For each type of standard, we describe the principles of its operation and at least one hardware example. We identify the practical limits of the example's

Thermal Boundary Layers in Critical Flow Venturis

July 30, 2021
Author(s)
John D. Wright, Aaron Johnson, Michael R. Moldover, Woong Kang, Liang Zhang, Bodo Mickan
We improve the usefulness of small (diameter 10 mm) critical flow venturis (CFVs) as transfer standards for gas flow by measuring and explaining how their discharge coefficients depend on the temperature T of their environment. At Reynolds numbers Re 2.5

Facility for calibrating anemometers as a function of air velocity vector and turbulence

July 19, 2021
Author(s)
Iosif Isaakovich Shinder, Michael R. Moldover, James Filla, Aaron Johnson, Vladimir B. Khromchenko
NIST calibrates anemometers as a function of airspeed vector and turbulence intensity (Tu). The vector capability (sometimes called '3D') is particularly important for calibrating multi-hole differential-pressure probes that are often used to quantify

LIQUID FLOW METER CALIBRATIONS WITH NIST's 15 kg/s WATER FLOW STANDARD

June 15, 2021
Author(s)
Jodie Gail Pope, Aaron Johnson, James Filla, Vern E. Bean, Michael R. Moldover, Joey Boyd, Christopher J. Crowley, Iosif Isaakovich Shinder, Keith A. Gillis, John D. Wright
We describe the 15 kg/s water flow calibration standard operated by the Fluid Metrology Group of the National Institute of Standards and Technology (NIST) to calibrate liquid flow meters for customers. The 15 kg/s standard is a dynamic, gravimetric, liquid

Blow-Down Calibration of a Large Ultrasonic Flow Meter

April 21, 2021
Author(s)
Aaron Johnson, Eric Harman, Joey Boyd
Oil and gas production industries use large (diameter > 0.8 m) ultrasonic flow meters (USMs) to measure exhaust gas from flare stacks, emissions from smokestacks, flow of natural gas, etc. Since most flow laboratories do not have compressors with

Faster, More Accurate, Stack-Flow Measurements

February 25, 2020
Author(s)
Aaron N. Johnson, Iosif I. Shinder, Bernard J. Filla, Joey T. Boyd, Rodney A. Bryant, Michael R. Moldover, Thomaa D. Martz, Matthew Gentry
Exhaust flows from coal-fired electricity-generating-plants are determined by measuring the flue gas velocity at prescribed points in the stack cross section. These velocity measurements are made using EPA-approved differential pressure probes such as the

Non Nulling Measurements of Flue Gas Flows in a Coal-Fired Power Plant Stack

June 28, 2019
Author(s)
Aaron N. Johnson, Iosif I. Shinder, Bernard J. Filla, Joey T. Boyd, Rodney A. Bryant, Michael R. Moldover
Exhaust flows from coal-fired stacks are determined by measuring the flue gas velocity at prescribed points in the stack cross section. During the last 30+ years these velocity measurements have been made predominantly using S-type pitot probes. These

Improving Measurement for Smokestack Emissions - Workshop Summary

September 21, 2018
Author(s)
Rodney A. Bryant, Aaron N. Johnson, John D. Wright, Tamae M. Wong, James R. Whetstone, Michael R. Moldover, Iosif I. Shinder, Scott Swiggard, Chris Gunning, David Elam, Tom Martz, Eric Harman, David Nuckols, Liang Zhang, Woong Kang, Salvator Vigil
The complex flow conditions inherent in power plant smokestacks make accurate flow measurements challenging, which in turn limits the accuracy of hazardous emissions measurements. While stack composition measurements are assessed daily via comparison to a

Characterization of Five-Hole Probes used for Flow Measurement in Stack Emission Testing

May 16, 2018
Author(s)
Iosif Isaakovich Shinder, Aaron Johnson, Michael R. Moldover, James Filla, Vladimir Khromchenko
We report progress towards the goal of reducing the errors in industrial smokestack flow measurements to 1 % by replacing S-probes with calibrated 3-D probes (i.e., probes that measure 3 components of velocity). NIST calibrated a commercially-manufactured

Progress Towards Accurate Monitoring of Flue Gas Emissions

May 16, 2018
Author(s)
Aaron Johnson, Iosif Isaakovich Shinder, Michael R. Moldover, Joey Boyd, James Filla
The amounts of CO2 and other pollutants emitted by a coal-fired power plant are measured using a continuous emissions monitoring system (CEMS) permanently installed in the exhaust smokestack. The pollutant flux is the product of the pollutant's

Errors in Rate of Rise Gas Flow Measurements from Flow Work

March 20, 2018
Author(s)
John D. Wright, Aaron Johnson, Gina Kline, Michael R. Moldover
The rate of rise (RoR) method measures the time rate of change of the mass of gas in a collection volume as it is filled via a flow meter under test. The mass of gas is calculated from time-stamped pressure and temperature data gathered from the known