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NIST Authors in Bold

Displaying 29076 - 29100 of 74855

Steering a Time Scale

December 1, 2008
Author(s)
Judah Levine
A time scale is a procedure for combining the data from an ensemble of clocks or frequency standards. The input data to the ensemble algorithm are generally the time (or frequency) differences between each of the members and the reference device for the

The SIM Time and Frequency Network

December 1, 2008
Author(s)
Michael A. Lombardi, Andrew N. Novick, Jose M. Lopez, Francisco Jimenez, Jean-Simon Boulanger, Raymond Pelletier, Ricardo de Carvalho, Raul Solis, Carlos Donado, Harold Sanchez, Carlos A. Quevedo, Gregory Pascoe, Daniel Perez
The Sistema Interamericano de Metrologia (SIM) consists of national metrology institutes (NMIs) located in the 34 member nations of the Organization of American States (OAS), which extends throughout North, Central, and South America, and the Caribbean

The Sixteenth Text REtrieval Conference (TREC 2007)

December 1, 2008
Author(s)
Ellen M. Voorhees
This report constitutes the proceedings of the 2007 Text REtrieval Conference, TREC 2007, held in Gaithersburg, Maryland November 6-9, 2007. TREC 2007 is the latest in a series of workshops designed to foster research in text retrieval and related

Time and Frequency Transfer Activities at NIST

December 1, 2008
Author(s)
Victor S. Zhang, Michael A. Lombardi
The National Institute of Standards and Technology (NIST) maintains one of the world s most accurate and stable time scales, and also developed and maintains the primary frequency standard for the United States. Various techniques are used to compare the

Vibration-induced PM Noise of A Rigid Optical Fiber Spool

December 1, 2008
Author(s)
Jennifer A. Taylor, Craig W. Nelson, Archita Hati, Neil Ashby, David A. Howe
Oscillators operating in field applications are subject to much more strenuous environmental effects than those in the laboratory. These environmental effects, like vibration and temperature fluctuation, have a great impact on the performance of the

A Novel Topology Control Scheme for Future Wireless Mesh Networks

November 30, 2008
Author(s)
Yi Qian, Kejie Lu, Tao Zhang, Shengli Fu
In this paper, we address the topology control issue for future wireless mesh networks (WMNs) based on the principle of service-oriented design. In particular, we propose a novel topology control scheme that attempts to maximize the overall throughput in

A Secure VANET MAC Protocol for DSRC Applications

November 30, 2008
Author(s)
Yi Qian, Nader Moayeri, Kejie Lu
Vehicular ad hoc networking is an important component of Intelligent Transportation Systems. The main benefit of vehicular ad hoc network (VANET) communication is seen in active safety systems that increase passenger safety by exchanging warning messages

Diversity Performance of a Practical Non-Coherent Detect-and-Forward Receiver

November 30, 2008
Author(s)
Michael R. Souryal, Huiqing You
We propose a non-coherent receiver for the fixed detect-and-forward relay channel and derive a closed-form tight upper bound on its bit error probability in Rayleigh fading channels. Using this upper bound, we show that the receiver achieves nearly full

Non-Coherent Amplify-and-Forward Generalized Likelihood Ratio Test Receiver

November 30, 2008
Author(s)
Michael R. Souryal
This paper proposes a simple non-coherent amplify-and-forward receiver for the relay channel and evaluates its diversity performance for Rayleigh fading channels. We use the generalized likelihood ratio test to obtain the decision rule in closed form

Security Challenges in Seamless Mobility - How to ``Handover'' the Keys?

November 30, 2008
Author(s)
Katrin Hoeper, Lidong Chen, Antonio Izquierdo Manzanares, Nada T. Golmie
In this paper, we discuss key management challenges for seamless handovers across heterogeneous wireless networks. We focus on fast access authentication protocols that allow expedited network entry by utilizing existing keying material from previous

Computational Parameters in Simulation of Microscope Images

November 28, 2008
Author(s)
Egon Marx, James E. Potzick
The simulation of microscope images computed from scattered fields determined using integral equations depend on a number of parameters that are not related to the scatterer or to the microscope but are choices made for the computation method. The effect

Integral Equations for 3-D Scattering: Finite Strip on a Substrate

November 28, 2008
Author(s)
Egon Marx
Singular integral equations that determine the exact fields scattered by a dielectric or conducting finite strip on a substrate are presented. The computation of the image of such a scatterer from these fields by Fourier optics methods is also shown.

Managing Materials Information in the Supply Chain

November 28, 2008
Author(s)
John V. Messina, Eric D. Simmon
One important aspect of sustainable manufacturing is the acquisition and management of product material information. This information may be used to improve the design and manufacturing process, facilitate recycling, and to help comply with regulations

Neutron Transmission of Single-Crystal Magnesium Fluoride

November 27, 2008
Author(s)
John Barker, David F. Mildner, Jose Rodriguez Rivera, P. Thiyagarajan
The neutron attenuation through single-crystal magnesium fluoride has been measured as a function of wavelength at both room temperature and 77 K. These data confirm a total cross section that is lower than MgO for wavelengths greater than 0.2 nm. MgF 2

Addressing Y-Chromosome Short Tandem Repeat(Y-STR) Allele Nomenclature

November 25, 2008
Author(s)
John M. Butler, Margaret C. Kline, Amy E. Decker
Currently 120 different Y-chromosome short tandem repeat (Y-STR) markers are used by various genetic genealogy testing laboratories. In some cases, different laboratories may designate the same Y-STR allele with two different nomenclatures making data

Measuring intensity correlations with a two-element superconducting nanowire single-photon detector

November 24, 2008
Author(s)
Eric Dauler, Martin Stevens, Burm Baek, Richard J. Molnar, Scott A. Hamilton, Richard Mirin, Sae Woo Nam, Karl Berggren
Second-order intensity correlation measurements were made using a two-element superconducting nanowire single photon detector (SNSPD) without the need for an optical beam splitter. This approach can be used to obtain a 50-ps full width at half maximum

Pressure-induced volume-collapsed tetragonal phase of CaFe 2 As 2 as seen via neutron scattering

November 24, 2008
Author(s)
A. Kreyssig, Mark Green, Y. Lee, G. D. Samolyuk, Pawel Zajdel, Jeffrey Lynn, S. L. Bud'ko, M. S. Torikachvili, N. Ni, S. Nandi, Juscelino Leao, Sarah Poulton, D. N. Argyriou, B. N. Harmon, R. J. McQueeny, P. C. Canfield, A. I. Goldman
Recent investigations of the superconducting iron-arsenide families have highlighted the role of pressure, be it chemical or mechanical, in fostering superconductivity. Here we report that CaFe2As2 undergoes a pressure-induced transition to a nonmagnetic

Designing artificial cells to harness the biological ion gradient

November 23, 2008
Author(s)
Jian Xu, David A. LaVan
Cell membranes contain numerous natural nanoscale conductors, i.e. ion channels and ion pumps1-4, that work in concert to form transmembrane or transcellular ion gradients that can be triggered to release an action potential (AP)1, 5. Can artificial cells

Yb Optical Lattice Clock

November 23, 2008
Author(s)
Nathan D. Lemke, Andrew Ludlow, Zeb Barber, N Poli, C.W. Hoyt, Long-Sheng Ma, Jason Stalnaker, Christopher W. Oates, Leo Hollberg, James C. Bergquist, A. Brusch, Tara Fortier, Scott Diddams, Thomas P. Heavner, Steven R. Jefferts, Tom Parker
We describe the development and latest results of an optical lattice clock based on neutral Yb atoms, including investigations based on both even and odd isotopes. We report a fractional frequency uncertainty below 10 -15 for 171Yb.

Josephson phase qubit circuit for the evaluation of advanced tunnel barrier materials

November 21, 2008
Author(s)
Jeffrey S. Kline, Haohua Wang, Seongshik Oh, John M. Martinis, David P. Pappas
We have found that crystalline Josephson junctions have critical current density control problems which decrease circuit yield. We present a qubit circuit designed to accommodate a factor-of-five variation in critical current density for the evaluation of
Displaying 29076 - 29100 of 74855