U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Search Publications

NIST Authors in Bold

Displaying 37876 - 37900 of 74137

A New Technique for Estimating Frequency from GPS Carrier-Phase Time Transfer Data

August 28, 2004
Author(s)
C Hackman, Judah Levine, Tom Parker, Dirk Piester, Juergen Becker
GPS carrier-phase time transfer (GPSCP1T) offers high frequency stability at short averaging times, approaching a fractional frequency stability of 10-15 at averaging times of one day. However, a discontinuity occurs in the time transfer estimates between

Experimental Studies of Integrated Cognitive Systems

August 26, 2004
Author(s)
P Langley, Elena R. Messina
In this paper, we examine the issues that arise in the experimental study of integrated cognitive systems. We review the reasons why such artifacts are dicult to evaluate, then consider some dependent measures that can be used to characterize their

Autonomous Road Driving Arenas for Performance Evaluation

August 24, 2004
Author(s)
Christopher J. Scrapper Jr, Stephen B. Balakirsky, Brian Weiss
The development of performance metrics is critical in the evaluation and advancement of intelligent systems. Obtaining the pinnacle of intelligence in autonomous vehicles requires evolutionary standards and community support. In order to analyze and

Comparing Algorithms: Rules of Thumb and an Example

August 24, 2004
Author(s)
Stephen B. Balakirsky, Thomas R. Kramer
This paper provides twenty rules of thumb for comparing algorithms having the same function, one of which is to be selected for use in an intelligent system. The rules are illuminated by a specific example, the comparison of three algorithms for dealing

Modeling Quantum Information Systems

August 24, 2004
Author(s)
Paul E. Black, Andrew W. Lane
A simulator for quantum information systems cannot be both general, that is, easily used for every possible system, and efficient. Therefore, some systems will have aspects which can only be simulated by cunning modeling. On the other hand, a simulation

Power dissipation in a vertically integrated chip-scale atomic clock

August 24, 2004
Author(s)
John Kitching, Svenja A. Knappe, Li-Anne Liew, P Schwindt, V Shah, John Moreland, Leo W. Hollberg
The physics package of a vertically-integrated chip-scale atomic clock based on Cs has recently been demonstrated at NIST. This device requires 69 mW of electrical power to maintain the vapor cell 34 K above the temperature of the baseplate. The physics

Improvements in NIST-F1 and a Resulting Accuracy of df/f = 0.61 * 10 -15

August 23, 2004
Author(s)
Thomas P. Heavner, Steven R. Jefferts, Elizabeth A. Donley, Jon H. Shirley, Thomas E. Parker
Over the last several years we have made many improvements to NIST-F1 (a laser-cooled cesium fountain primary frequency standard) resulting in a reduction in the uncertainty by nearly a factor of 2 in the realization of the SI second at NIST. We recently

Microfabricated Atomic Frequency References

August 23, 2004
Author(s)
Svenja A. Knappe, P Schwindt, V Shah, Leo W. Hollberg, John Kitching, Li-Anne Liew, John Moreland
We report on the fabrication of a physics package for a chip-scale atomic clock with a volume of 9.5 mm^3, consuming 75 m W of power. The design is described in detail and is strongly motivated by the goal of wafer-level fabrication and assembly. A

The Cesium Physics Package Design for the PARCS Experiment

August 23, 2004
Author(s)
Eric A. Burt, William Klipstein, Steven R. Jefferts
The Primary Atomic Reference Clock in Space (PARCS) is a collaboration between the National Institute of Standards and Technology (NIST), the Jet Propulsion Laboratory (JPL) and the University of Colorado to build a laser-cooled cesium-beam atomic clock as

Theo1 Confidence Intervals

August 23, 2004
Author(s)
T Tasset, David A. Howe, Donald B. Percival
Theoretical variance #1 (Theo1) has been developed at NIST to improve the estimation of long-term frequency stability. Its square-root (Theo1-dev) has two significant improvements over the Allan deviation XX called ¿Adev" in estimlating long-term frequency

Theo1: Characterization of very long-term frequency stability

August 23, 2004
Author(s)
David A. Howe, T Tasset
Theo1 is the first new species of variance that addresses a particularly difficult measurement problem, namely, obtaining reliable estimation of frequency stability for sample periods that are long compared to the length of a data run. Theo1 has

W-band dual channel PM/AM noise measurement system

August 23, 2004
Author(s)
Archita Hati, Craig Nelson, J Nava, David A. Howe, Fred L. Walls
We discuss the performance of a W-band (92 to 96 GHz) PM and AM noise measurement system. The system uses two nearly identical channels to measure the AM or P M noise added by an amplifier or any passive component. It is principally designed to measure

Transport Coefficients of the Lennard-Jones Model Fluid. I. Viscosity

August 22, 2004
Author(s)
J Meier, Arno D. Laesecke, Stephan Kabelac
In an extensive computer simulation study, the transport coefficients of the Lennard-Jones model were determind with high accuracy from equilibrium molecular-dynamics simulations. In the frame of time correlation function theory, the generalized Einstein

Reversible Proton Transfer Dynamics in Bacteriorhodopsin

August 20, 2004
Author(s)
Y. S. Lee, Morris Krauss
Proton transfer in bacteriorhodopsin from the cytoplasm to the extracellular side is initiated from protonated asp96 in the cytoplasmic region towards the deprotonated Schiff base. This occurs in the transition from the photocycle late M state to the N

Large Area Pt/n-GaN Schottky Photodiodes With Extremely Low Leakage Current

August 19, 2004
Author(s)
A Shahid, Robert E. Vest, D Franz, F Yan, Y Zhao, D B. Mott
Pt/n-type GaN Schottky photodiodes with very large active areas (0.25 cm 2 and 1 cmu2 ) which exhibit extremely low leakage currents at low reverse bias are reported. The Schottky photodiodes were fabricated from n-/n+ epitaxial layers grown by low

Nanotechnology in Integrative Systems: Introduction to Integrative Systems

August 17, 2004
Author(s)
Michael Gaitan
These days it's hard to imagine life without the benefits of integration, computers, and the internet. Even simple tasks such as shopping for food have gone 'high tech' with computerized checkout, laser scanners, digital scales, and electronic transactions
Displaying 37876 - 37900 of 74137