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Search Publications

NIST Authors in Bold

Displaying 18076 - 18100 of 73697

A New Modem for Two Way Satellite Time and Frequency Transfer

April 13, 2015
Author(s)
Shengkang Zhang, Xueyun Wang, Haifeng Wang, Hongbo Wang, Yuan Yuan, Keming Feng
Two Way Satellite Time Frequency Transfer (TWSTFT) is a highly precise time & frequency remote comparison technique, which is widely used in time metrology, satellite navigation, etc. Nowadays, most of the time metrology laboratories in Europe, America and

An Analysis of the Use of a Collaboration Tool in the Intelligence Community

April 13, 2015
Author(s)
Jean C. Scholtz, Emile L. Morse, Michelle P. Steves
In this paper we present a broad look at the use of Groove as a collaboration tool in the analytic community. This work was carried out through the Research Development and Experimental Collaboration program (RDEC). The goal of this program is to bring

Bias Corrections in Primary Frequency Standards

April 13, 2015
Author(s)
Thomas E. Parker, Thomas P. Heavner, Steven R. Jefferts
Primary frequency standards serve the function of calibrating the rate of International Atomic Time, TAI, and therefore play a critical role in the accuracy of the world's time. The Working Group on Primary and Secondary Frequency Standards, WGPSFS, is an

Bias Corrections in Primary Frequency Standards

April 13, 2015
Author(s)
Steven R. Jefferts, F Levi
Corrections to Primary Frequency Standards (PFS) or Secondary Frequency Standards (SFS) for offsets caused by various physical phenomena, e.g. Zeeman shifts or Blackbody radiation shifts, are typically corrected using formulae that contain “known”

Configurable Robotic Millimeter-Wave Antenna Facility

April 13, 2015
Author(s)
Jeffrey R. Guerrieri, Joshua A. Gordon, David R. Novotny, Michael H. Francis, Ronald C. Wittmann, Miranda L. Butler
This paper introduces the Configurable Robotic Millimeter-Wave Antenna (CROMMA) facility by the Antenna Metrology Lab at the National Institute of Standards and Technology (NIST). NIST set out to develop an antenna measurement facility that would be

Constraint Handling In Combinatorial Test Generation Using Forbidden Tuples

April 13, 2015
Author(s)
Raghu N. Kacker, David R. Kuhn, Yu Lei
Constraint handling is a challenging problem in combinatorial test generation. In general, there are two ways to handle constraints, i.e., constraint solving and forbidden tuples. In our early work we proposed a constraint handling approach based on

Improving IPOGs Vertical Growth Based on a Graph Coloring Scheme

April 13, 2015
Author(s)
Raghu N. Kacker, David R. Kuhn, Yu Lei
In this paper, we show that the vertical growth phase of IPOG is optimal for t-way test generation when t = 2, but it is no longer optimal when t is greater than 2. We present an improvement that reduces the number of tests generated during vertical growth

Long-Term Uncertainty in Time Transfer Using GPS and TWTFT Techniques

April 13, 2015
Author(s)
Victor S. Zhang, Thomas E. Parker, Jian Yao
The techniques of GPS time and frequency transfer (code based and carrier phase) and two-way satellite time and frequency transfer (TWSTFT) are widely used in remote clock comparison and in the computation of International Atomic Time (TAI). Many timing

Nearly-linear light cones in long-range interacting quantum systems

April 13, 2015
Author(s)
Michael S. Foss-Feig, Zhexuan Gong, Charles W. Clark, Alexey V. Gorshkov
In non-relativistic quantum theories with short-range Hamiltonians, a velocity $v$ can be chosen such that the influence of any local perturbation is approximately confined to within a distance $r$ until a time $t \sim r/v$, thereby defining a linear light

NIST's Fully Dynamic Gravimetric Liquid Flowmeter Standard.

April 13, 2015
Author(s)
Jodie G. Pope, Aaron N. Johnson, Bernard J. Filla, Joey T. Boyd, Vern E. Bean, Christopher J. Crowley
We describe a new dynamic, gravimetric, liquid flow standard (LFS) that determines flow by measuring the rate of change of the liquid mass accumulating in a collection tank. The LFS is a fully- automated,15 kg/s system that uses a proportional–integral

Traceability for Microwave Power Measurements: Past, Present, and Future

April 13, 2015
Author(s)
Ronald A. Ginley
The need for traceable microwave power measurements for use in communications, defense, spectral line investigation, molecular particle signature identification, material property characterization and others is well established. Traceability for power

Comparison of Two Continuous GPS Carrier-Phase Time Transfer Techniques

April 12, 2015
Author(s)
Jian Yao, Skakun Ivan, Zhiheng Jiang, Judah Levine
Global Positioning System (GPS) carrier-phase (CP) time transfer, as a widely accepted high-precision time transfer method, frequently shows a data-batch boundary discontinuity of up to 1 ns, because of the inconsistency of the phase ambiguities between

Practical Limitations of NTP Time Transfer

April 12, 2015
Author(s)
Andrew N. Novick, Michael A. Lombardi
The Network Time Protocol (NTP) is commonly utilized to synchronize computer clocks in packet-switched, wide area networks (WANs) such as the public Internet. The delay asymmetry in WANs, often due to inconsistent routing and/or bandwidth saturation, is

Time Signals Converging within Cyber-Physical Systems

April 12, 2015
Author(s)
Marc A. Weiss, Sundeep Chandhoke, Hugh Melvin
Time is central to predicting, measuring and controlling properties of the physical world, and is one of the most important constraints distinguishing Cyber-Physical Systems (CPS) from distributed computing in general. However mixing the cyber and the

Assembling a complex quantum ensemble

April 10, 2015
Author(s)
Ian B. Spielman
Statistical mechanics provides a systematic approach for predicting the behavior of systems when only partial information is present. The key assumption underlying all of statistical mechanics is that every allowed configuration of the system, called a

High-efficiency superconducting nanowire single-photon detectors fabricated from MoSi thin-films

April 10, 2015
Author(s)
Varun B. Verma, Boris Korzh, Felix Bussieres, Robert D. Horansky, Shellee D. Dyer, Adriana E. Lita, Igor Vayshenker, Francesco Marsili, Matthew D. Shaw, Hugo Zbinden, Richard P. Mirin, Sae Woo Nam
We demonstrate high-efficiency superconducting nanowire single-photon detectors (SNSPDs) fabricated from MoSi thin-films. We measure a maximum system detection efficiency (SDE) of 87 ± 0.5 % at 1542 nm at a temperature of 0.7 K, with a jitter of 76 ps

Light shifts in a pulsed cold-atom coherent-population-trapping clock

April 10, 2015
Author(s)
Eric M. Blanshan, Elizabeth A. Donley, John E. Kitching
Field-grade atomic clocks capable of primary standard performance in compact physics packages would be of significant value in a variety of applications. A cold-atom coherent population trapping clock featuring laser-cooled 87Rb atoms and pulsed Ramsey

Research Needs to Advance Concrete Pumping Technology

April 10, 2015
Author(s)
Chiara F. Ferraris, Nicos Martys, Myoungsung Choi, Van Bui, Trey Hamilton, Didier Lootens
With the increasing use of pumping to place concrete, the development and refinement of the industry practice to ensure successful concrete pumping is becoming an important need for the concrete construction industry. To date, research on concrete pumping

Calibration of Millimeter-wave Channel Sounders for Super-resolution Multipath Component Extraction

April 9, 2015
Author(s)
Peter B. Papazian, Jae-Kark Choi, Jelena Senic, Peter J. Jeavons, Camillo Gentile, Nada T. Golmie, Roy Sun, David R. Novotny, Kate Remley
Millimeter-wave communication systems will rely on highly directional antennas to compensate for the greater pathloss expected in their frequency bands of operation. Electronic beamforming, hence, will form a cornerstone for the technology. For the

Direct correlation of charge transfer absorption with molecular donor:acceptor interfacial area via photothermal deflection spectroscopy

April 9, 2015
Author(s)
Lee J. Richter, Dean M. DeLongchamp, Natalie Stingelin, Alberto Salleo, Martin Heeney, Aram Amassian, John deMello, James Bannock, Fiona H. Scholes, Scott Watkins, Zhuping Fei, Koen Vandewal
ABSTRACT: Here, we show that the Charge Transfer (CT) absorption signal in bulk (BHJ) solar cell blends, measured by photothermal deflection spectroscopy (PDS), is directly proportional to the density of molecular donor/acceptor interfaces. Since the

Evaluating automatic face recognition systems with human benchmarks

April 9, 2015
Author(s)
P. Jonathon Phillips, Alice O'Toole
Human face recognition skills are often considered the gold standard against which machines must compete. Over the last two decades, however, international tests of computer-based face recognition algorithms have shown steady improvements in accuracy with
Displaying 18076 - 18100 of 73697
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