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On The Quotient of a Centralized and a Non-centralized Complex Gaussian Random Variable
No full textA detailed investigation of the quotient of two independent complex random variables is presented. The numerator has a zero mean, and the denominator has a non-zero mean. A normalization step is taken prior to the theoretical developments in order to simplify the formulation. Next, an indirect approach is taken to derive the statistics of the modulus and phase angle of the quotient. That in turn enables a straightforward extension of the statistical results to real and imaginary parts. After the normalization procedure, the probability density function of the quotient is found as a function of only the mean of the random variable that corresponds to the denominator term. Asymptotic analysis shows that the quotient closely resembles a normally-distributed complex random variable as the mean becomes large. In addition, the first and second moments, as well as the approximate of the second moment of the clipped random variable, are derived, which are closely related to practical applications in complex-signal processing such as microwave metrology of scattering-parameters. Tolerance intervals associated with the ratio of complex random variables are presented
Improvised Long Test Lengths via Stitching Scale Bar Method:Interim Testing of Laser Trackers
No full textPerformance verifications of laser tracker systems (LTSs) often rely on calibrated length artifacts that are 2.3 m in length or more, as specified in International Standards Organization (ISO) and American Society of Mechanical Engineers (ASME) standards. The 2.3 m length is chosen as the minimum length that will sufficiently expose inaccuracy in LTSs. Embodiment of these artifacts often comes in the form of scale bars, fixed monuments, or a laser rail. In National Institute of Standards and Technology (NIST) Internal Report (IR) 8016, which was published in 2014 and discusses interim testing of LTSs, it was shown that a scale bar with three nests spaced 1.15 m apart was sufficient for exposing errors in LTSs. In that case, the LTS was placed symmetrically with respect to the scale bar so that both a 2.3 m symmetrical length and a 1.15 m asymmetrical length were presented to the LTS. This paper will evaluate whether a scale bar that is only 1.15 m in length can sufficiently expose errors within the LTS when it is stitched together to create a 2.3 m long test length
PPDiffuse: A Quantitative Prediction Tool for Diffusion of Charged Polymers in a Nanopore
No full textConstruction of a Dual Protease Column, Subzero (-30 degrees C) Chromatography System and Multi-channel Precision Temperature Controller for Hydrogen-Deuterium Exchange Mass Spectrometry
No full textThis tutorial provides mechanical drawings, electrical schematics, parts lists, stereolithography (STL) files for producing three-dimensional (3D)-printed parts, initial graphics exchange specification (IGS) files for automated machining, and instructions necessary for construction of a dual protease column, subzero, liquid chromatography system for hydrogen-deuterium exchange mass spectrometry (HDX-MS). Electro-mechanical schematics for construction of two multi-zone temperature controllers that regulate to +/- 0.05 degrees C are also included in this tutorial
Advanced Temperature-Control Chamber for Resistance Standards
No full textCalibration services for resistance metrology have continued to advance their capabilities and establish new and improved methods for maintaining standard resistors. Despite the high quality of these methods, there still exist inherent limitations to the number of simultaneous, measurable resistors and the temperature stability of their air environment. In that context, we report progress on the design, development, and initial testing of a precise temperature-control chamber for standard resistors that can provide a constant-temperature environment with a stability of +/- 6 m degrees C. Achieving this stability involved customizing the chamber design based on airflow simulations. Moreover, microprocessor programming allowed the air flow to be optimized within an unsealed chamber configuration to reduce chamber temperature recovery times. Further tests were conducted to improve the stability of the control system and the efficiency of the chamber
Influence of Machine Anvil Wear on Charpy Test Results
No full textWe investigated the influence of the state of wear of Charpy machine anvils on test results by performing impact tests on NIST specimens of three energy levels with a machine equipped with new anvils (compliant with both ASTM E23 [1] and ISO 148-2 [2]) and worn anvils (anvil corner radii and distance outside ASTM tolerances, but within ISO tolerances). The results obtained, statistically analyzed, unequivocally show that worn anvils tend to increase absorbed energy at all energy levels. On the other hand, data variability does not appear to be significantly affected by anvil wear. This study represents NIST contribution to an international effort spearheaded by the Japan Iron and Steel Federation Standardization Center (Tokyo, Japan)
In Situ Thermography of the Metal Bridge Structures Fabricated for the 2018 Additive Manufacturing Benchmark Test Series (AM-Bench 2018)
No full textThis document provides details on the files available for download in the data set ""In situ thermography of the metal bridge structures fabricated for the 2018 Additive Manufacturing Benchmark Test Series (AM-Bench 2018)."" The experiments were performed to support the 2018 AM-Bench' Class 01 experiments consisting of metal three-dimensional (3D) builds. The modeling community was invited to predict the following: (1) part deflection, (2) residual elastic strains, (3) microstructure, (4) phase fractions, and (5) phase evolution. Details for these proposed challenges and the postprocess measurement results can be found at their respective links on the AM-Bench website.(1) This document describes the experiments conducted on a commercial laser powder bed fusion (LPBF) machine and the in situ thermography and explains the resulting measurement data. The purpose of disseminating these data is twofold: (1) to provide layer-wise thermal history data for part-scale model validation and (2) to provide insight into the thermal history responsible for the postprocess distortion, residual strain, and microstructure. Measurements are reported in radiance temperature. The calculation of true temperature for direct comparison with model results requires knowledge of the effective surface emissivity. At this time, the effective emissivity is unknown, but assumptions can be applied based on the literature. The following sections detail the experiment and measurement setup, describe the data files, and provide equations to enable the calculation of true temperature from the measured radiant temperature
Fast Methods for Finding Multiple Effective Influencers in Real Networks
No full textWe present scalable first hitting time methods for finding a collection of nodes that enables the fastest time for the spread of consensus in a network. That is, given a graph G = (V, E) and a natural number k, these methods find k vertices in G that minimize the sum of hitting times (expected number of steps of random walks) from all remaining vertices. Although computationally challenging for general graphs, we exploited the characteristics of real networks and utilized Monte Carlo methods to construct fast approximation algorithms that yield near-optimal solutions
History of Atmospheric Cosmic Ray Research at the National Bureau of Standards
No full textIn the late 1930s, a team of physicists from the National Bureau of Standards (now the National Institute of Standards and Technology) published eight papers on the investigation of cosmic rays in the atmosphere. Payloads launched with weather balloons, also known as radiosondes, were equipped with sensors to measure temperature, relative humidity, pressure, and radiation dose. A battery-operated telemetry system was used to continuously transmit at 60 MHz to a base station. They measured the radiation dose profiles of cosmic radiation in the atmosphere up to 21 km. Calibration of the Geiger-Muller counters with a standard radium source allowed them to calculate a radiation dose rate at an altitude corresponding to 10 kPa that was 180 times the dose rate near sea level in Washington, DC. Ascents in Washington, DC (latitude 39 degrees) and Lima, Peru (near equator) allowed them to demonstrate the effects of Earth's magnetic field on incident galactic cosmic rays; the dose rate in Peru was only half that in Washington, DC
NORMAN B. BELECKI
No full textTENURE AT NBS/NIST: 1970-1999
INDUCTED into NIST Gallery of Distinguished Scientists, Engineers, and Administrators: 2020
Birth: 1939, Rochester, New York
EDUCATION:
Clarkson University, BS (Physics), 1962
George Washington University, MSE (Metrology), 1967
CITATION: For his exemplary contributions to improved dissemination of the Nation's electrical units, and the development and promotion of an internationally accepted system to assure the traceability of measurement results nationwide to the SI
POSITIONS HELD AT NBS/NIST:
Physicist, Volt Facility, Electricity Division, Institute for Basic Standards, 1970-1971
Leader, Electrical Reference Standards Group, Electricity Division, Electronics and Electrical Engineering Laboratory (EEEL) and predecessors, 1971-1996
Senior Scientist, EEEL, 1996-1999
HONORS:
U.S. Department of Commerce Silver Metal (1982)
Andrew Woodington Award (1985)
Allen V. Astin Measurement Science Award (1986)
William A. Wildhack Award (1999)
Fellow, IEEE (1999)
MEMBERSHIPS:
Conference on Precision Electromagnetic Measurements
IEEE Instrumentation and Measurement Society
NCSL International
NCSLI Measure, the Journal of Measurement Science, Technical Support Team
American Physical Society
American Society for Quality, Measurement Quality Division
Precision Measurements Association
PUBLICATIONS:
More than 30 publications including:
Belecki, N.B., Dunfee, B.L., and Petersons, O., The National Measurement System for Electricity, NIST NBSIR 75-935 (1978)
Belecki, N.B., Dziuba, R.F., Field, B.F., and Taylor, B.N., Guidelines for Implementing the New Representations of the Volt and Ohm Effective January 1, 1990, NIST Technical Note 1263 (1989)
Belecki, N.B., Guest Editor, IEEE Transactions on Instrumentation and Measurement, Special Issue of Selected Papers, CPEM 1990, Vol. 40, Issue: 2 (1991)
Dziuba, R., Belecki, N.B, and Mayo-Wells, J.F., “Stability of Double-Walled Manganin Resistors”, A Century of Excellence in Measurements, Standards, and Technology (Lide, D.R., ed), NIST SP 958, (2001)
Belecki, N.B., “Rules, Tools and Good Judgment”, MEASURE FOR MEASURE Column, Quality Progress, (January 2005)
Belecki, N.B., Shah, D., Poulton, D., Lapinskis, M., Suraci, J.M., Simmons, P., Simmons, J.H., and Harris, G.L., “Joe D. Simmons Memorial Scholarship”, NCSLI Conference Proceedings (2008