NIST Digital Archives
Not a member yet
149436 research outputs found
Sort by
Improved first-principles calculation of the third virial coefficient of helium
No full textWe employ state-of-the-art pair and three-body potentials with path-integral Monte Carlo (PIMC) methods to calculate the third density virial coefficient C(T ) for helium. The uncertainties are much smaller than those of the best experimental results, and approximately one-fourth the uncertainty of our previous work. We have extended our results in temperature down to 2.6 K, incorporating the effect of spin statistics that become important below approximately 7 K. Results are given for both the 3He and 4He isotopes. We have also performed PIMC calculations of the third acoustic virial coefficient ?a ; our calculated values compare well with the limited experimental data available. A correlating equation for C(T) of 4He is presented; differentiation of this equation provides a reliable and simpler way of calculating ?a
Oral history interview of Richard N. Wright, January 10, 2011 / [persons present]: David Lide, Jim Gross, Richard Wright, Dave Didion, Hans Oser
No full textThomas J. Ohlemiller
No full textThomas J. Ohlemiller
Inducted: 2011
Citation: For leadership in understanding the ignition, smoldering and burning of real-world combustible products and contributions to practical test methods that reduce the deaths and losses from unwanted fires in homes.
Tenure: 1979-2008
Birth: 1941, Peoria, Illinois
Education:
University of Illinois, BS (Chemical Engineering), 1963
Princeton University, PhD (Aerospace and Mechanical Sciences), 1969
Princeton University, Sloan Postdoctoral Fellow (Aerospace and Mechanical Sciences), 1970
Positions held:
Chemical Engineer, Fire Research Division, Center for Fire Research and the Building and Fire Research Laboratory, 1979 2008
Honors:
US Department of Commerce Silver Medal (2003) and Gold Medal (2005)
Co-recipient of ASTM International Simon H. Ingberg Award (2002)
Memberships:
Combustion Institute
International Association for Fire Safety Science
Editorial Board, Fire Safety Journal, 1995-2008
Publications:
More than 110 publications including:
Ohlemiller, T.J., “Modeling of Smoldering Combustion Propagation,” Progress in Energy and Combustion Science, Vol. 11, p. 277 (1985)
Ohlemiller, T.J., “Smoldering Combustion,” Chapter 2-9 of the SFPE Handbook of Fire Protection Engineering, Fourth Edition, Published by the National Fire Protection Association, Quincy, MA, pp. 2-229 (2008)
Ohlemiller, T.J., Gann, R.G., et al, “Quantifying the Ignition Propensity of Cigarettes,” Fire and Materials, Vol. 19, No. 4, p. 155 (1995)
Ohlemiller, T.J. and Gann, R.G., “Estimating Reduced Fire Risk Resulting From An Improved Mattress Flammability Standard,” NIST Technical Note 1446 (August 2002)
Ohlemiller, T.J. and Peacock, R.D., “On the Significance of Transient Heat Release Rate Excursions Above a Set Limit,” Fire Safety Journal, Vol. 43, No. 8, p. 531 (2008)
Ohlemiller, T.J. and Shields, J.R., “Aspects of the Fire Behavior of Thermoplastic Materials”, NIST Technical Note 1493 (January 2008
Measures, Uncertainties, and Significance Test in Operational ROC Analysis
No full textIn receiver operating characteristic (ROC) analysis, the sampling variability can result in uncertainties of performance measures. Thus, while evaluating and comparing the performances of algorithms, the measurement uncertainties must be taken into account. The key issue is how to calculate the uncertainties of performance measures in ROC analysis. Our ultimate goal is to perform the significance test in evaluation and comparison using the standard errors computed. From the operational perspective, based on fingerprint-image matching algorithms on large datasets, the measures and their uncertainties are investigated in the three scenarios: 1) the true accept rate (TAR) of genuine scores at a specified false accept rate (FAR) of impostor scores, 2) the TAR and FAR at a given threshold, and 3) the equal error rate. The uncertainties of measures are calculated using the nonparametric two-sample bootstrap based on our extensive studies of bootstrap variability on large datasets. The significance test is carried out to determine whether the difference between the performance of one algorithm and a hypothesized value, or the difference between the performances of two algorithms where the correlation is taken into account is statistically significant. Examples are provided
Geometric effects when measuring small holes with micro contact probes
No full textA coordinate measuring machine with a suitably small probe can be used to measure micro-features such as the diameter and form of small holes (often about 100 µm in diameter). When measuring small holes, the clearance between the probe tip and the part is sometimes nearly as small as other characteristic lengths (such as probe deflection or form errors) associated with the measurement. Under these circumstances, the basic geometry of the measurement is much different than it is for the measurement of a macroscopic object. Various geometric errors are greatly magnified, and consequently sources of error that are totally irrelevant when measuring macroscopic artifacts can become important. In this article we discuss errors associated with misalignment or non-orthogonality of the probe axes, probe-tip radius compensation, and mechanical filtering
Richard Nelson Thomas
No full textRichard Nelson Thomas
Inducted: 2011
Citation: For his role in conceiving and creating JILA, then a new form of cooperative effort between a State and the Federal Government, and for contributions to our understanding stellar atmospheres.
Tenure: 1957-1973
Birth: 1921, Omaha, Nebraska
Death: 1994
Education:
Harvard University, BS (Physics), 1942
Harvard University, PhD (Astrophysics), 1948
Positions held:
Research Physicist, Consultant to the Director (Boulder) 1957-1961
Research Physicist and Senior Research Fellow, JILA (Boulder) 1962 – 1973
Honors:
US Department of Commerce Gold Medal (1963)
Fellow, JILA (1962)
Sigma Xi 1947
Phi Beta Kappa 1942
Memberships:
International Astronomical Union
Commission 12, Radiation and Structure of the Solar Atmosphere
Commission 36, Theories of Stellar Atmospheres, President 1970-73
Societe Royale des Sciences de Liege, Foreign Correspondent
Royal Astronomical Society
Annales d’Astrophysique (1959-67)
Physics of Fluids (1960-63), Board of Editors
Annual Reviews, Inc., Board of Directors
Journal of Quantitative Spectroscopy, Board of Editors (1964-70)
Medal Committee, Centre International d’Astrophysique de l’Observatoire de Nice
Yale Series in Science, International Advisory Board
University of Colorado-University of Sydney Astrophysics Association, Co-Chairman
NASA-CNRS Monograph Series on Nonthermal Phenomena in Stellar Atmospheres, (The Orange Series), Organizer/Editor
Publications:
More than 250 publications on Astrophysics, non Equilibrium Thermodynamics, Astroballistics, including three books:
Thomas, Richard, N. and Athay, R.G., Physics of the Solar Chromosphere, Interscience, New York (1961) and Russian Trans. State Publishing House for the Foreign Literature, Moscow (1965)
Thomas, Richard, N., Some Aspects of Non-Equilibrium Thermodynamics in the Presence of a Radiation Field, University of Colorado Press, Boulder, Colorado (1965)
Thomas, Richard, N., Stellar Atmospheric Structural Patterns, Series on Nonthermal Phenomena in Stellar Atmospheres - NASA/CNRS, Paris-Washington, D.C., National Aeronautics and Space Administration, Washington, DC (1983
The SIM time network
No full textThe Sistema Interamericano de Metrologia (SIM) is a regional metrology organization (RMO) whose members are the national metrology institutes (NMIs) located in the 34 nations of the Organization of American States (OAS). The SIM/OAS region extends throughout North, Central, and South America and the Caribbean Islands. About half of the SIM NMIs maintain national standards of time and frequency and must participate in international comparisons in order to establish metrological traceability to the International System (SI) of units. The SIM time network (SIMTN) was developed as a practical, cost effective, and technically sound way to automate these comparisons.The SIMTN continuously compares the time standards of SIM NMIs and produces measurement results in near real-time by utilizing the Internet and the Global Positioning System (GPS). Fifteen SIM NMIs have joined the network as of December 2010. This paper provides a brief overview of SIM and a technical description of the SIMTN. It presents international comparison results and examines the measurement uncertainties. It also discusses the metrological benefits that the network provides to its participants
Re-optimized energy levels and Ritz wavelengths of 198Hg I
No full textThe procedure of level optimization for the 198Hg I spectrum emitted by electrodeless discharge lamps is revisited. Wavelength-measurement uncertainties and systematic shifts caused by interactions with the buffer gas and by calibration procedures are carefully analyzed and accounted for. Based on this extended analysis of the original measurements, the energy levels are re-optimized, which results in an improved set of level values consistent with the revised measured wavelengths. The newly obtained reliable Ritz wavelengths can be used as secondary wavelength standards in the wide range from 1200 Å to 65 000 Å
The role of lattice matching techniques in the characterization of polymorphic forms
No full textAn inspection of the recent literature reveals that polymorphism is a frequently encountered phenomenon. The recognition of polymorphic forms plays a vital role in the materials sciences because such structures are characterized by different crystal packing and accordingly have different physical properties. In the pharmaceutical industry, recognition of polymorphic forms can be critical for, in certain cases, a polymorphic form of a drug may be an ineffective therapeutic agent due to its unfavorable physical properties. A check of the recent literature has revealed that in some cases new polymorphic forms are not recognized. In other instances, a supposedly new polymeric form is actually the result of an incorrect structure determination. Fortunately, lattice-matching techniques, which have proved invaluable in the identification and characterization of crystal structures, represent a powerful tool for analyzing polymorphic forms. These lattice-matching methods are based on either of two strategies: (a) the reduced cell strategy -- the matching of reduced cells of the respective lattices or (b) the matrix strategy -- the determination of a matrix or matrices relating the two lattices coupled with an analysis of the matrix elements. Herein, these techniques are applied to three typical cases -- (a) the identification of a new polymorphic form, (b) the demonstration that a substance may not be a new polymorphic form due to missed symmetry, and (c) the evaluation of pseudo polymorphism because of a missed lattice. To identify new polymorphic forms and to prevent errors, it is recommended that these lattice matching techniques become an integral part of the editorial review process of crystallography journals
Portrait of Arden Bement
No full textServed as director of the National Institute of Standards and Technology from 2001 through 2004