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Maximum Likelihood and Restricted Likelihood Solutions in Multiple-Method Studies
No full textA formulation of the problem of combining data from several sources is discussed in terms of random effects models. The unknown measurement precision is assumed not to be the same for all methods. We investigate maximum likelihood solutions in this model. By representing the likelihood equations as simultaneous polynomial equations, the exact form of the Groebner basis for their stationary points is derived when there are two methods. A parametrization of these solutions which allows their comparison is suggested. A numerical method for solving likelihood equations is outlined, and an alternative to the maximum likelihood method, the restricted maximum likelihood, is studied. In the situation when methods variances are considered to be known an upper bound on the between-method variance is obtained. The relationship between likelihood equations and moment-type equations is also discussed
Edwin Ross Williams
No full textEdwin Ross Williams
Inducted: 2011
Citation: For world-leading research on the measurement of fundamental constants providing the foundation for NIST’s core electrical metrology program, setting the stage for a future redefinition of the SI.
Tenure: 1971-2008
Birth: 1942, Denver, Colorado
Education:
Nebraska Wesleyan University, BA (Physics), 1964
University of Colorado, MA (Physics), 1966
Wesleyan University, PhD (Physics), 1970
Positions held:
Research Physicist, Electricity Division, Institute for Basic Standards, 1971-1992
Leader, Fundamental Electrical Measurements Group, Electronics and Electrical Engineering Laboratory, 1992-1994
Leader, Quantum Voltage and Current Project, EEEL, 1994-1998
Leader, Fundamental Electrical Measurements Group, Electricity Division, EEEL, 1998-1999
Senior Research Physicist, EEEL, 1999-2005
NIST Fellow, 2005-2008
Honors:
US Department of Commerce Silver Medal (1978) and Gold Medals (1989 and 2006)
Fellow, American Physical Society (1994)
NIST Stratton Award (1999)
Fellow, NIST (2005)
Memberships:
Fellow, American Physical Society; IEEE Instrumentation & Measurement Society; Sigma Xi.
NIST Delegate, Consultative Committee on Electricity and Magnetism (1995, 1997, and 1999) Consultative Committee on Units (2005)
Technical Committee for the Conference on Precision Electromagnetic Measurements (1988, 1996, co-chair 1998, 2000)
Invited Guest Researcher, Electrotechnical Laboratory, Tsukuba, Japan (1987), Service de Physique du Solide, C.E.N. Saclay, France (1991), and Laboratoire National de Metrologie et d’Essais, Trappes, France (2006)
Member, NBS - VNIIM (USSR) Collaboration Panel in Moscow (1979)
Publications:
More than 70 publications including:
Mills, I.M., Mohr, P.J., Quinn, T.J., Taylor, B.N., and Williams, E.R., �Adapting the International System of Units to the 21st Century,� Phil. Trans. Royal Society A: Mathematical, Physical and Engineering Sciences (2011)
Williams, E.R., �Toward the SI System Based on Fundamental Constants: Weighing the Electron,� IEEE Trans. Instrum. Meas., Vol. 56-2, 646-650 (2007)
Mills, I.M., Mohr, P.J., Quinn, T.J., Taylor, B.N., and Williams, E.R., �Redefinition of the Kilogram, Ampere, Kelvin and Mole: A Proposed Approach to Implementing CIPM Recommendation1 (CI-2005),� Metrologia, 43, 3, 227-246 (2006)
Williams, E.R., Steiner, R.L., and Newell, D.B., �An Accurate Measurement of the Planck Constant,� Physical Review Letters, 81, No. 12, 2404-2407 (1998)
Williams, E.R., Jones, Jr., G.R., Ye, S., Liu, R., Sasaki, H., Olsen, P.T., Phillips, W.D., and Layer, H.P., �A Low Field Determination of the Proton Gyromagnetic Ratio in Water,� IEEE Trans. Instrum. Meas., 38, No. 2, 233-237 (1989)
Williams, E.R. and Olsen, P.T., �New Measurement of the Proton Gyromagnetic Ratio and a Derived Value of the Fine-Structure Constant Accurate to a Part in 107,� Physical Review Letters, 42, No. 24, 1575-1579 (1979
Portrait of Albert C. Parr
No full textInducted in 2011 into the NIST Gallery of Distinguished Scientists, Engineers, and Administrators for “technical leadership in the establishment of a national measurement system for radiometry and photometry based upon absolute detectors.”
Tenure at NIST: 1980-2007.
Birth: 1942, Tooele, Utah.
Education:
B.S. Mathematics, Oregon State University, 1964
B.S. Physics, Oregon State University, 1964
M.S., Physics, University of Chicago, 1965.
Ph.D. Physics, University of Chicago, 1971.
Positions at NIST:
NIST Guest Researcher, Physics Laboratory, 2007-
Chief, Radiometric Physics Division/Optical Technology Division, Physics Laboratory, 1991-2007.
Leader, Spectral Radiometry Group, Radiometric Physics Division, Center for Radiation Research, National Measurement Laboratory, 1986-1991.
Physicist, Radiation Physics Division, Center for Radiation Research, NML, 1980-1986
Verna Brown Hines
No full textVerna Brown Hines
Inducted: 2011
Citation:
For educating Congress on NIST research and programs that broadened Congressional members’ understanding of and support for NIST research and increased NIST’s budget by $190M.
Tenure: 1975-2006
Birth: 1948, Bethesda, Maryland
Education:
Hood College, MA (Public Affairs), 1985
University of Maryland, BA (Government and Politics), 1970
Positions held:
Senior Legislative Analyst, 1975-1998
Director, NIST Office of Congressional and Legislative Affairs, 1998-2006
Honors:
US Department of Commerce Silver Medal (1976) and Gold Medal (2005)
Impact:
For exceptional leadership in working closely with the Senate Commerce Committee chairman Senator Hollings, to make the first major legislative changes to the NBS/NIST Organic Act since its inception in 1901 resulting in seminal changes to the enabling NIST legislation including provisions that would improve America’s competitiveness in a growing global market. This bill modernized the NIST laboratories, changed the name of the agency from NBS to NIST and established new programs and activities at NIST. Ms. Hines is recognized for her work in educating Congress about NIST’s core competencies including:
NIST’s need for funding to construct needed world class laboratory space resulting in the Advanced Chemical Science Laboratory (ACSL) Building in 1996 and the Advanced Measurement Laboratory (AML) in 2004
NIST’s fire research where she worked diligently with Congress to ensure the rewrite of Fire Prevention Act
NIST and BFRL’s capabilities and unique research facilities to perform historic research why the World Trade Center buildings collapsed on 11 September 2011
Ms. Hines maintained effective communications with Congress as modifications to the Fastener Quality Act were made to the law. Ms. Hines wrote/edited a great amount of testimony that helped ensure Congress, the funders for much of the NIST work, understand why NIST research and programs are critical to the nation. Ms. Hines closely worked with external stakeholders as part of her daily activities -- Congress, associations, and universities -- keeping them up to date on NIST programs and research of interest to each of them and significantly increased Congressional visits to NIST
(Audio) Oral history interview of Richard N. Wright, January 10, 2011 / [persons present]: David Lide, Jim Gross, Richard Wright, Dave Didion, Hans Oser
No full textComparison of two dimension-reduction methods for network simulation models
No full textExperimenters characterize the behavior of simulation models for data communications networks by measuring multiple responses under selected parameter combinations. The resulting multivariate data may include redundant responses reflecting aspects of a smaller number of underlying behaviors. Reducing the dimension of multivariate responses can reveal the most significant model behaviors, allowing subsequent analyses to focus on one response per behavior. This paper investigates two methods for reducing dimension in multivariate data generated from simulation models. One method combines correlation analysis and clustering. The second method uses principal components analysis. We apply both methods to reduce a 22-dimensional dataset generated by a network simulator. We identify issues that an analyst must decide, and we compare the reductions suggested by the methods. We have used these methods to identify significant behaviors in simulated networks, and we suspect they may be applied to reduce the dimension of empirical data measured from real networks
Long-term stability of the NIST Conical Reference Transducer
No full textThe National Institute of Standards and Technology (NIST) Conical Reference Transducer (CRT) is designed for purposes requiring frequency response characteristics much more uniform than those attainable with ultrasonic transducers conventionally used for acoustic emission (AE) nondestructive testing. The high performance of the CRT results from the use of design elements radically different from those of conventional transducers. The CRT was offered for sale for 15 years (1985 to 2000). Each CRT was furnished with data which expressed, as a function of frequency, the transducer sensitivity in volts per micrometer of normal displacement on the test block. Of the 22 transducers constructed, eight were reserved for long term research and were stored undisturbed in a laboratory with well controlled temperature and humidity. In 2009, the sensitivities of these eight units were redetermined. The 2009 data have been compared with data from similar tests conducted in 1985. The results of this comparison verify the claim “Results of tests of the long term stability of CRT characteristics indicate that, if proper care is taken, tens of years of service can reasonably be expected.” made in the CRT specifications document furnished to prospective customers
Low Temperature Cold Atom Ion Source (LoTIS)
No full textAn experimental prototype of a cold-atom ion source for focused ion beam applications. \n\n Building upon the Nobel Prize-winning laser cooling techniques of NIST's Bill Phillips and Dave Wineland, NIST physicist Jabez McClelland applied laser cooling techniques to the field of nanotechnology, where researchers work with structures 100 billionths of a meter or less in size. Using lasers to lower the temperature of atoms causes the atoms to move in a less random way, which enables the positioning of the atoms to be more precisely controlled. In the mid-2000s, McClelland and his colleagues in the NIST Center for Nanoscale Science and Technology determined that ionizing, or electrically charging, the cold atoms would further improve the ability to place an atom at a desired location on the surface of a nanoscale object. They also calculated that an ionized cloud of laser-cooled atoms should make a high-brightness focused ion beam. \n\n Focused Ion Beams (FIB) are an established technology. FIBs are used to carve minute patterns into materials, and to initiate chemical reactions that construct nanoscale features. They are also a standard tool in the semiconductor industry for circuit edit, the in-situ rewiring of chips to test circuit modifications. However, the increasing demands for smaller nanoscale devices required more accurate FIB technology than was available on the market. In 2012, McClelland and NIST post-doctoral researchers Adam Steele and Brenton Knuffman built this proof-of-concept Low-Temperature Ion Source (LoTIS). The ion source develops extremely high brightness by taking advantage of laser cooling to reduce the transverse velocity spread of an atomic beam to microkelvin temperatures. It consists of four stages: a two-dimensional magneto-optical trap that captures cesium atoms from a vapor and forms them into a slow atomic beam; a magneto-optical compressor that compresses the size of the atomic beam without heating it; a polarization gradient cooling region that reduces the transverse temperature even further, and an ionization region, where a pair of crossed, focused laser beams ionize the atoms to form an ion beam. In 2013, this device demonstrated that their laser-cooled ion beam had a 10-fold improvement in sensitivity over existing FIB technology. Later prototypes increased the sensitivity to 24-fold. At the end of their post-doctoral appointments in 2013, Steele and Knuffman formed a private company to license the NIST patented LoTIS for further development and commercialization. The introduction of this source promises better performance in focused ion beam applications where large currents are needed in very small spot sizes, such as nanoscale milling for semiconductor circuit editing or secondary ion mass spectroscopy. Steel frame with glass lens.[H]73.66 cm __[W]30.48 cm __[D]30.48 c
Electromagnetic Metrology on Concrete and Corrosion
No full textTo augment current methods for the evaluation of reinforcing bar (rebar) corrosion within concrete, we are exploring unique features in the dielectric and magnetic spectra of pure iron oxides and corrosion samples. Any signature needs to be both prominent and consistent in order to identify corrosion within concrete bridge deck or other structures. In order to measure the permittivity and propagation loss through concrete as a function of temperature and humidity, we cut and carefully fitted samples from residential concrete into three different waveguides. We also poured and cured a mortar sample within a waveguide that was later measured after curing 30 days. These measurements were performed from 45 MHz to 12 GHz. Our concrete measurements showed that the coarse granite aggregate that occupied about half the sample volume reduced the electromagnetic propagation loss in comparison to mortar. We also packed ground corrosion samples and commercially available iron-oxide powders into a transmission-line waveguide and found that magnetite and corrosion sample spectra are similar, with a feature between 0.5 GHz and 2 GHz that may prove useful for quantifying corrosion. We also performed reflection (S11) measurements at various corrosion surfaces and in loose powders from 45 MHz to 50 GHz. These results are a first step towards quantifying rebar corrosion in concrete
RECIST Applied to Realistic Tumor Models
No full textLevine RECIST (Response Evaluation Criteria in Solid Tumors) is a linear measure intended to predict tumor size in medical computed tomography (CT). In this work, using purely geometrical considerations, we estimate how well RECIST can predict the volume of randomly-oriented tumor models, each composed of the union of ellipsoids. The principal conclusion is that RECIST is likely to work less well for realistic tumors than for ellipsoids