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(Audio Part 1 of 3) Oral history interview of John Hoffman, May 8, 2003
No full textDr. John Hoffman discusses his long career at NIST. His career spanned the years 1954 to 1982, during which time he was in various leadership positions, including Director of the Institute for Materials Research and Director of the National Measurement laboratory
(Audio Part 2 of 3) Oral history interview of John Hoffman, May 8, 2003
No full textDr. John Hoffman discusses his long career at NIST. His career spanned the years 1954 to 1982, during which time he was in various leadership positions, including Director of the Institute for Materials Research and Director of the National Measurement laboratory
(Audio Part 2 of 4) Oral history interview of John Hoffman, May 23, 2003
No full textDr. John Hoffman discusses his long career at NIST. His career spanned the years 1954 to 1982, during which time he was in various leadership positions, including Director of the Institute for Materials Research and Director of the National Measurement laboratory
(Audio Part 4 of 4) Oral history interview of John Hoffman, May 23, 2003
No full textDr. John Hoffman discusses his long career at NIST. His career spanned the years 1954 to 1982, during which time he was in various leadership positions, including Director of the Institute for Materials Research and Director of the National Measurement laboratory
(Audio Part 3 of 3) Oral history interview of George Porter, March 3, 2003 / by Norm Belecki, Reeves Tilley, and Lisa Greenhouse
No full textGeorge Porter, former head of the Personnel Division of NBS, discusses his nearly 24 years working at the Bureau. Porter came to NBS in 1950 and was Chief of the Personnel Division from 1951-1974. Porter discusses the attitudes of scientists at the Bureau towards the civil service system in the 1950s and 1960s, management and staff relations, and notable events including the AD-X2 controversy. Also mentioned are the NBS Graduate School Program, the relocation of the Bureau from Washington, D.C. to Gaithersburg, and the role of women in the Bureau
Ernest K. Smith
No full textERNEST K. SMITH
NBS: 1951 - 1965
B: May 31, 1922, Peking, China
D: October 21, 2009
EDUCATION:
Peking American School class of 1940
Swarthmore College, BA (Physics) 1944
Cornell University, MS (EE) 1951; PhD (Radio wave Propagation) 1956
PRINCIPAL FIELDS:
Radio wave propagation, ionospheric physics (particularly sporadic E), radio meteorology and natural radio noise (30 MHz - 100 GHz) and earth-space considerations
POSITIONS HELD AT NBS (BOULDER):
Chief, Ionospheric Research Section, Radio Propagation Physics Division
Chief, Ionosphere Research and Propagation Division
Chief, Upper Atmosphere and Space Physics Division
Chief, Aeronomy division
HONORS:
Diplome d’Honneur, International Radio consultative Committee of the International Telecommunications Union
MEMBERSHIPS:
Institute of Electrical and Electronics Engineers (Fellow)
American Association for the Advancement of Science (Fellow)
IEEE Wave Propagation Standards Committee (Chair)
IEEE Fellow Selection Committee
Sigma Xi
Electromagnetic Academy, Science Advisory Group for the Voice of America
PUBLICATIONS:
Authored or coauthored about 40 papers, books, and chapters in books including:
Worldwide Occurrence of Sporadic E, NBS Circular 582 (1957)
Ionospheric Sporadic E, eds. Smith and Matsushita, Pergamon Press (1962)
“Centimeter and millimeter wave attenuation and brightness temperature due to atmospheric oxygen and water vapor,” Radio Science 17 (1982) 1455-146
A double-primary dead-weight tester for pressures (35-175) kPa in gage mode
No full textPrimary pressure standards in the atmospheric pressure range are often established using mercury manometers. Less frequently, controlled-clearance dead-weight testers in which one component ( normally the piston) has been dimensionally measured have also been used. Recent advances in technology on two fronts i) the fabrication of large-diameter pistons and cylinders with good geometry; and ii) the ability to measure the dimensions of these components, have allowed some dead-weight testers at NIST to approach total relative uncertainties (k = 2) in dimensionally-derived effective areas near 5 x 10(-6). This paper describes a single piston/cylinder assembly (NIST-PG201WC/ WC) that serves as both a primary gage in which both piston and cylinder are measured dimensionally and a controlled-clearance primary gage ( employing the Heydemann-Welch method). Thus it allows some previous assumptions about the modeling of dead-weight testers to be checked. For the gage described in this paper the piston/cylinder clearance obtained from the two analyses have relative differences of 4 x 10(-6) to 7 x 10(-6) over the pressure range 35 kPa to 175 kPa. Some implications of these results will be discussed. From the dimensional characterizations and auxiliary measurements we have determined that the effective area for this gauge at 20 degreesC is: A(eff,20) = 1961.0659 mm(2) (1 + 3.75 x 10(-12) P/Pa +3.05 x 10(-12) P-J/Pa), where P is the system pressure and P-J is a control pressure. The estimated relative uncertainty in effective area is 8.2 x 10(-6) + 1.4 x 10(-11) P/Pa (k = 2). The temperature coefficient for the area was measured and found to be (9.06 +/- 0.04) x 10(-6)/ K. Thus using the gage at a reference temperature of 23 degreesC yields an effective area: A(eff,23) = 1961.1192 mm(2) (1 + 3.75 x 10(-12) P/Pa +3.05 x 10(-12) P-J/Pa), with almost no increase in the uncertainty over that at 20 degreesC
Design and uncertainty analysis for a PVTt gas flow standard
No full textA new pressure, volume, temperature, and, time (PVTt) primary gas flow standard at the National Institute of Standards and Technology has an expanded uncertainty (k = 2) of between 0.02 % and 0.05 %. The standard spans the flow range of 1 L/min to 2000 L/min using two collection tanks and two diverter valve systems. The standard measures flow by collecting gas in a tank of known volume during a measured time interval. We describe the significant and novel features of the standard and analyze its uncertainty. The gas collection tanks have a small diameter and are immersed in a uniform, stable, thermostatted water bath. The collected gas achieves thermal equilibrium rapidly and the uncertainty of the average gas temperature is only 7 mK ( 22 x 10(-6) T). A novel operating method leads to essentially zero mass change in and very low uncertainty contributions from the inventory volume. Gravimetric and volume expansion techniques were used to determine the tank and the inventory volumes. Gravimetric determinations of collection tank volume made with nitrogen and argon agree with a standard deviation of 16 x 10(-6) V-T. The largest source of uncertainty in the flow measurement is drift of the pressure sensor over time, which contributes relative standard uncertainty of 60 x 10(-6) to the determinations of the volumes of the collection tanks and to the flow measurements. Throughout the range 3 L/min to 110 L/min, flows were measured independently using the 34 L and the 677 L collection systems, and the two systems agreed within a relative difference of 150 x 10(-6). Double diversions were used to evaluate the 677 L system over a range of 300 L/min to 1600 L/min, and the relative differences between single and double diversions were less than 75 x 10(-6)
Comparison of the NIST and BIPM medium-energy X-ray air-kerma measurements
No full textThe air-kerma standards used for the measurement of medium-energy x rays were compared at the National Institute of Standards and Technology (NIST) and at the Bureau International des Poids et Mesures (BIPM). The comparison involved a series of measurements at the BIPM and the NIST using the air-kerma standards and two NIST reference-class transfer ionization standards. Reference beam qualities in the range from 60 kV to 300 kV were used. The results show the standards to be in agreement within the combined standard uncertainty of the comparison of 0.35 %
The normalized reduced form and cell mathematical tools for lattice analysis - Symmetry and similarity
No full textTo intelligently and effectively use crystallographic databases, mathematical and computer tools are required that can elucidate diverse types of intra- and interlattice relationships. Two such tools are the normalized reduced form and normalized reduced cell. Practical experience has revealed that the first tool - the normalized reduced form - is very helpful in establishing lattice metric symmetry as it enables one to readily deduce significant relationships between the elements of the reduced form. Likewise research with crystallographic databases has demonstrated that the second tool - the normalized reduced cell - plays a vital role in determining metrically similar lattices. Knowledge of similar lattices has practical value in solving structures, in assignment of structure types, in materials design, and in nano-technology. In addition to using the reduced cell, it is recommended that lattice-matching strategies based on the normalized reduced cell be routinely carried out in database searching, in data evaluation, and in experimental work