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Precise Numerical Differentiation of Thermodynamic Functions with Multicomplex Variables
No full textOral History Interview of Robin "Tuck" Stebbins, July 6, 2021 (Video Pt. 2)
No full textRobin “Tuck” Stebbins discusses his involvement in the Poor Man mine located west of Boulder, CO. Dr. Stebbins was a graduate student at the Joint Institute of Laboratory Astrophysics from 1970 to 1973. He then worked at the National Solar Observatory and in the Physics Department at the University of Colorado/Boulder. In 2001 he became a Senior Research Scientist for NASA at the Goddard Space Flight Center. He describes his involvement in the research done with the laser interferometer located in the Poor Man mine. He explains the significance of that research and the many developments that subsequently evolved from that project
Ultraviolet Radiation Technologies and Healthcare Associated Infections: Standards and Metrology Needs
No full textThe National Institute of Standards and Technology (NIST) hosted an international workshop on ultraviolet-C (UV-C) disinfection technologies on January 14�15, 2020, in Gaithersburg, Maryland, in collaboration with the International Ultraviolet Association (IUVA). This successful public event, as evidenced by the participation of more than 150 attendees, with 65 % from the ultraviolet technology industry, was part of an ongoing collaborative effort between NIST and the IUVA and its affiliates to examine the measurement and standards needs for pathogen abatement with UV-C in the healthcare whole-room environment. Prior to and since this event, stakeholders from industry, academia, government, and public health services have been collaboratively engaged with NIST to accelerate the development and use of accurate measurements and models for UV-C disinfection technologies and facilitate technology transfer. The workshop served as an open forum to continue this discussion with a technical focus centered on the effective design, use, and implementation of UV-C technologies for the prevention and treatment of healthcare-associated infections (HAIs) in complex hospital settings. These settings include patient rooms, operating rooms, common staging areas, ventilation systems, personal protective equipment, and tools for the reprocessing and disinfecting of instruments or devices used in medical procedures, such as catheters and ventilators. The critical need for UV-C technologies for disinfection has been amplified by the outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes coronavirus disease 2019 (COVID-19), stimulating an even greater emphasis on identifying testing and performance metrology needs. This paper discusses these topics based on the international workshop and community activities since the workshop, including a public World-Wide-Web�based seminar with more than 500 registered attendees on September 30, 2020; an international conference on UV-C technologies for air and surface disinfection, December 8�9, 2020; and a webinar on returning to normalcy with the use of UV-C technologies, April 27 and 29, 2021. This article also serves as an introduction to a special section of the Journal of Research of the National Institute of Standards and Technology, where full papers address recent technical, noncommercial, UV-C technology and pathogen-abatement investigations. The set of papers provides keen insights from the vantage points of medicine and industry. Recent technical developments, successes, and needs in optics and photonics, radiation physics, biological efficacy, and the needs of future markets in UV-C technologies are described to provide a concise compilation of the community�s efforts and the state of the field. Standards needs are identified and discussed throughout this special section. This article provides a summary of the essential role of standards for innovation and implementation of UV-C technology for improved patient care and public health
Development of the Advanced Encryption Standard
No full textStrong cryptographic algorithms are essential for the protection of stored and transmitted data throughout the world. This publication discusses the development of Federal Information Processing Standards Publication (FIPS) 197, which specifies a cryptographic algorithm known as the Advanced Encryption Standard (AES). The AES was the result of a cooperative multiyear effort involving the U.S. government, industry, and the academic community. Several difficult problems that had to be resolved during the standard�s development are discussed, and the eventual solutions are presented. The author writes from his viewpoint as former leader of the Security Technology Group and later as acting director of the Computer Security Division at the National Institute of Standards and Technology, where he was responsible for the AES development
Measurement Uncertainty of Surface Temperature Distributions for Laser Powder Bed Fusion Processes
No full textThis paper describes advances in measuring the characteristic spatial distribution of surface temperature and emissivity during laser -metal interaction under conditions relevant for laser powder bed fusion (LPBF) additive manufacturing processes. Detailed descriptions of the measurement process, results, and approaches to determining uncertainties are provided. Measurement uncertainties have complex dependencies on multiple process parameters, so the methodology is demonstrated on one set of process parameters and one material. Well-established literature values for high-purity nickel solidification temperature and emissivity at the solidification temperature were used to evaluate the predicted uncertainty of the measurements. The standard temperature measurement uncertainty is found to be approximately 0.9 % of the absolute temperature (16 degrees C), and the standard relative emissivity measurement uncertainty is found to be approximately 8 % at the solidification point of high-purity nickel, both of which are satisfactory. This paper also outlines several potential sources of test uncertainties, which may require additional experimental evaluation. The largest of these are the metal vapor and ejecta that are produced as process by-products, which can potentially affect the imaging quality, reflectometry results, and thermal signature of the process, while also affecting the process of laser power delivery. Furthermore, the current paper focuses strictly on the uncertainties of the emissivity and temperature measurement approach and therefore does not detail a variety of uncertainties associated with experimental controls that must be evaluated for future generation of reference data
Oral History of Judah Levine - June 29, 202
No full textJudah Levine discusses his involvement in the Poor Man mine located west of Boulder, CO. Dr. Levine joined the NBS-University of Colorado Joint Institute of Laboratory Astrophysics (JILA) as a postdoc in 1967, and then was hired at the National Bureau of Standards (NBS) in 1969. He is currently a Fellow at NIST and is the leader of the Network Synchronization Project in the Time and Frequency Division. He describes the laser interferometer that was built in a shaft of the Poor Man mine and explains its history and its use as an early earth-level strain meter. He further discusses his involvement with the geophysical community resulting from his early work in the mine. The interview was conducted by William Kirchhoff and John Lowe
Evaluations of a Detector-Limited Digital Impedance Bridge
No full textWe tested a simple digital impedance bridge using two nominally equal resistors to form a 1:1 ratio. We focused on resolution and stability of the detectors. Fluctuations of the source voltages were largely removed through postprocessing of the digitized data, and the measurement results were limited by the detector noise. This detector-limited operating condition was first demonstrated using three modified Keysight 3458A multimeters for measurements of the voltage ratios, achieving 0.01 mu V/V type A uncertainty in less than 15 min at 1 kHz. In an effort to extend the applicable frequency range and develop a system with off-the-shelf components, we tested a system using three lock-in detectors for measuring small deviations from the perfect AC ratio of unity magnitude, achieving stabilities and resolutions of 0.1 mu V/V in a few hours for each point from 1 kHz to 5 kHz
Ratio-Based Pulse Shape Discrimination: Analytic Results for Gaussian and Poisson Noise Models
No full text
Oral History Interview of Robin "Tuck" Stebbins, July 6, 2021 (Transcript)
No full textRobin “Tuck” Stebbins discusses his involvement in the Poor Man mine located west of Boulder, CO. Dr. Stebbins was a graduate student at the Joint Institute of Laboratory Astrophysics from 1970 to 1973. He then worked at the National Solar Observatory and in the Physics Department at the University of Colorado/Boulder. In 2001 he became a Senior Research Scientist for NASA at the Goddard Space Flight Center. He describes his involvement in the research done with the laser interferometer located in the Poor Man mine. He explains the significance of that research and the many developments that subsequently evolved from that project