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Small-angle neutron scattering by the magnetic microstructure of nanocrystalline ferromagnets near saturation
No full textThe paper presents a theoretical analysis of elastic magnetic small-angle neutron scattering (SANS) due to the nonuniform magnetic microstructure in nanocrystalline ferromagnets. The reaction of the magnetization to the magnetocrystalline and magnetoelastic anisotropy fields is derived using the theory of micromagnetics. In the limit where the scattering volume is a single magnetic domain, and the magnetization is nearly aligned with the direction of the magnetic field, closed form solutions are given for the differential scattering cross-section as a function of the scattering vector and of the magnetic field. These expressions involve an anisotropy field scattering function, that depends only on the Fourier components of the anisotropy field microstructure, not on the applied field, and a micromagnetic response function for SANS, that can be computed From tabulated values of the materials parameters saturation magnetization and exchange stiffness constant or spin wave stiffness constant. Based on these results, it is suggested that the anisotropy field scattering function S-H can be extracted from experimental SANS data. A sum rule for S-H suggests measurement of the volumetric mean square anisotropy field. When magnetocrystalline anisotropy is dominant, then a mean grain size or the grain size distribution may be determined by analysis of S-H
Equivalent electrical circuit representations of AC quantized Hall resistance standards
No full textWe use equivalent electrical circuits to analyze the effects of large parasitic impedances existing in all sample probes on four-terminal-pair measurements of the ac quantized Hall resistance R-H. The circuit components include the externally measurable parasitic capacitances, inductances, lead resistances, and leakage resistances of ac quantized Hall resistance standards, as well as components that represent the electrical characteristics of the quantum Hall effect device (QHE). Two kinds of electrical circuit connections to the QHE are described and considered: single-series "offset" and quadruple-series. (We eliminated other connections in earlier analyses because they did not provide the desired accuracy with all sample probe leads attached at the device.) Exact, but complicated, algebraic equations are derived for the currents and measured quantized Hail voltages for these two circuits. Only the quadruple-series connection circuit meets our desired goal of measuring R-H for both ac and de currents with a one-standard-deviation uncertainty of 10(-8) R-H or less during the same cool-down with all leads attached at the device. The single-series "offset" connection circuit meets our other desired goal of also measuring the longitudinal resistance R-x for both ac and de currents during that same cool-down. We will use these predictions to apply small measurable corrections, and uncertainties of the corrections, to ac measurements of R-H in Order to realize an intrinsic ac quantized Halt resistance standard of 10(-8) R-H uncertainty or less
Tests of a two-photon technique for measuring polarization mode dispersion with subfemtosecond precision
No full textAn investigation is made of a recently introduced quantum interferometric method capable of measuring polarization mode dispersion (PMD) on sub-femtosecond scales, without the usual interferometric stability problems associated with such small time scales. The technique makes use of the extreme temporal correlation of orthogonally polarized pairs of photons produced via type-II phase-matched spontaneous parametric down-conversion. When sent into a simple polarization interferometer these photon pairs produce a sharp interference feature seen in the coincidence rate. The PMD of a given sample is determined from the shift of that interference feature as the sample is inserted into the system. The stability and resolution of this technique is shown to be below 0.2 fs. We explore how this precision is improved by reducing the length of the down-conversion crystal and increasing the spectral band pass of the system
Comparative calibration of heat flux sensors in two blackbody facilities
No full textThis paper presents the results of heat flux sensor calibrations in two blackbody facilities: the 25 mm variable temperature blackbody (VTBB) primary facility and a recently developed 51 mm aperture spherical blackbody (SPBB) facility. Three Schmidt-Boelter gages and a Garden gage were calibrated with reference to an electrical substitution radiometer in the VTBB. One of the Schmidt-Boelter gages thus calibrated was used as a reference standard to calibrate other gages in the SPBB. Comparison of the Schmidt-Boelter gages calibrations in the SPBB and the VTBB agreed within the measurement uncertainties. For the Garden gage, the measured responsivity in the SPBB showed a gradual decrease with increasing distance from the aperture. When the gage was located close to the aperture, a distance less than the aperture radius, the responsivity in the SPBB agreed with VTBB measurements. At a distance of about three times the aperture radius, the responsivity showed a decrease of about 4%. This is probably due to higher convection loss from the Garden gage surface compared to the Schmidt-Boelter sensor
The NIST length scale interferometer
No full textThe National Institute of Standards and Technology (NIST) interferometer for measuring graduated length scales has been in use since 1965. It was developed in response to the redefinition of the meter in 1960 from the prototype platinum-iridium bar to the wavelength of light. The history of the interferometer is recalled, and its design and operation described. A continuous program of modernization by making physical modifications, measurement procedure changes and computational revisions is described, and the effects of these changes are evaluated. Results of a long-term measurement assurance program, the primary control on the measurement process, are presented, and improvements in measurement uncertainty are documented
Status report on the first round of the development of the advanced encryption standard
No full textIn 1997, the National Institute of Standards and Technology (NIST) initiated a process to select a symmetric-key encryption algorithm to be used to protect sensitive (unclassified) Federal information in furtherance of NIST's statutory responsibilities. In 1998, NIST announced the acceptance of 15 candidate algorithms and requested the assistance of the cryptographic research community in analyzing the candidates. This analysis included an initial examination of the security and efficiency characteristics for each algorithm. NIST has reviewed the results of this research and selected five algorithms (MARS, RC6(TM), Rijndael, Serpent and Twofish) as finalists. The research results and rationale for the selection of the finalists are documented in this report. The five finalists will be the subject of further study before the selection of one or more of these algorithms for inclusion in the Advanced Encryption Standard
James Skillington Jr.
No full textJAMES E. SKILLINGTON, JR
Inducted: 1999
Citation:
For his sound management of the NBS science and technology budget, particularly as chief of the Budget Division.
Tenure: 1960 -1977
Birth: 1918
Education:
Dickinson College, BA, 1940
University of Buffalo, MA (American History and Government), 1951
American University, PhD (Public Administration), 1951
Positions held:
Budget Officer
Assistant to Associate Director for Administration
Honors:
U.S. Department of Commerce: Silver Medal, 1969; Gold Medal, 197
Portrait of Harry S. Hertz
No full textHarry S. Hertz was inducted into the NIST Gallery of Distinguished Scientists, Engineers, and Administrators in 2014. The citation for his induction read, “For visionary leadership, stewardship, and advocacy in promoting the Baldrige performance excellence framework and concepts nationally and internationally and for exemplary leadership and advancement of the analytical chemical sciences.”
His tenure at NIST: 1973-2013.
Education:
B.S., Chemistry, Polytechnic Institute of Brooklyn, 1967
Ph.D., Organic Chemistry, Massachusetts Institute of Technology, 1971
Alexander von Humboldt Fellowship, University of Munich, 1971-1973. Executive Development, National Academy of Public Administration and Federal Executive Institute.
Positions held:
Research Chemist, Trace Organic Analysis Group, Analytical Chemistry Division, National Measurement Laboratory (NML), 1973-1978.
Chief, Organic Analytical Research Division, Center for Analytical Chemistry, NML, 1978-1983. Director, Center for Analytical Chemistry, NML, 1983-1991
Director, Chemical Science and Technology Laboratory, 1991-1992
Deputy Director, Baldrige National Quality Program (BNQP), 1992-1995
Director, Baldrige Performance Excellence Program (formerly BNQP), 1995-2013
Director Emeritus, Baldrige Performance Excellence Program (BPEP), 2013- present
Honors:
NIST Bronze Medal (1981); Department of Commerce Silver Medal (1986), Gold Medal (1998)Arthur S. Flemming Award (1986)
Senior Executive Service Meritorious Executive Rank Award (1987)
Fellow, American Association for the Advancement of Science (1992)
Quality Digest, recognized as one of 15 people driving quality today (October 2005)
Honorary Fellow, American College of Healthcare Executives (2011)
Harry S. Hertz Leadership Award, Foundation for the Malcolm Baldrige National Quality Award, namesake and first recipient (2013)
Memberships:
American Association for the Advancement of Science
American Chemical Society
American Friends of the Alexander von Humboldt Foundation
Sigma X
Karen H. Brown (1999)
No full textDr. Karen H. Brown was appointed Deputy Director of the National Institute of Standards and Technology (NIST) in 1999 and served as Acting Director from 2000-2001. Prior to NIST she had a 22-year career at IBM in Hopewell Junction, NY, focused on microelectronics engineering. Image Source: Karen H. Brown Biographical File, NIST Archives