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Displaying 28676 - 28700 of 73830

First Order Sideband Pulling in Atomic Frequency Standards

April 1, 2009
Author(s)
Jon H. Shirley, Thomas P. Heavner, Steven R. Jefferts
Many high performance atomic frequency standards, including cesium fountains and most optical standards, operate with pulsed measurements, that is, an atomic sample is prepared for measurement, the measurement is made, and the process is repeated at fixed

Generation of 20 GHz, sub-40 fs pulses at 960 nm via repetition rate multiplication

April 1, 2009
Author(s)
Matthew S. Kirchner, Danielle Braje, Tara M. Fortier, A.M. Weiner, Leo Hollberg, Scott A. Diddams
Optical filtering of a stabilized 1 GHz optical frequency comb produces a 20 GHz comb with ~40 nm bandwidth (FWHM) at 960 nm. Using a low finesse Fabry-Perot cavity in a double pass configuration provides a broad cavity coupling bandwidth (delta lambda

Impact of polymer modulus on water accumulation at polymer / metal oxide interfaces

April 1, 2009
Author(s)
Alper Karul, Kar T. Tan, Christopher C. White, Donald L. Hunston, Steve marshall, Bulent Akgun, Sushil K. Satija, Christopher Soles, Bryan D. Vogt
Ambient moisture is known to accumulate at the interface between polymers and metal oxides, leading to detrimental consequences on physical properties such as modulus and adhesion. Direct measurement of the interfacial profile has utilized neutron

Improvements in the NIST Johnson Noise Thermometry System

April 1, 2009
Author(s)
Samuel P. Benz, Jifeng Qu, Horst Rogalla, D. R. White, Paul D. Dresselhaus, Weston L. Tew, Sae Woo Nam
We have developed a Johnson noise thermometry (JNT) system that is calibrated by precision waveforms synthesized with a quantized voltage noise source (QVNS). Significant improvements to the QVNS and the cross-correlation measurement electronics have

Modelling of Thermodynamics and Diffusion in Multicomponent Systems

April 1, 2009
Author(s)
Ursula R. Kattner, Carelyn E. Campbell
The availability of reliable materials data is key to the successful design of materials and manufacturing processes. Commercial alloys rarely consist of only two or three elements, but rather may contain a large number of elements for which the needed

Precision Differential Sampling Measurements of Low-Frequency Synthesized Sine Waves with an AC Programmable Josephson Voltage Standard

April 1, 2009
Author(s)
Alain Rufenacht, Charles J. Burroughs, Samuel P. Benz, Paul D. Dresselhaus, Bryan C. Waltrip, Thomas L. Nelson
We have developed a precision technique to measure sine wave sources with the use of a quantum-accurate ac programmable Josephson voltage standard. This paper describes a differential method that uses an integrating sampling voltmeter to precisely

Progress toward a 1 V Pulse-Driven AC Josephson Voltage Standard

April 1, 2009
Author(s)
Samuel P. Benz, Paul D. Dresselhaus, Alain Rufenacht, Norman F. Bergren, Joseph R. Kinard Jr., Regis Landim
We present a new record rms output voltage of 275 mV, which is a 25 % improvement over the maximum achieved with previous ac Josephson voltage standard (ACJVS) circuits. We demonstrate operating margins for these circuits and use them to measure the

The SIM Time Network and its Contributions to Metrology in the Americas

April 1, 2009
Author(s)
Michael A. Lombardi
The SIM Time Network (SIMTN) has been one of the great success stories of the Sistema Interamericano de Metrologia (SIM), a regional metrology organization (RMO) that includes the 34 member nations of the Organization of American States (OAS). The SIMTN

Thermopower of Co-doped FeSe0.82

April 1, 2009
Author(s)
Evan L. Thomas, Winnie K. Wong-Ng, Daniel P. Phelan
The effect of cobalt doping (0.05 ≤ x ≤ 0.50) on the thermopower of the newly discovered superconductor FeSe0.82 is investigated through electrical and thermal transport measurements. Our results point to the destruction of superconductivity at very low Co

Variable Termination Unit for Noise-Parameter Measurements

April 1, 2009
Author(s)
Dazhen Gu, Dave K. Walker, James P. Randa
NIST has upgraded its measurement capability of noise parameters on low-noise amplifiers with a variable termination unit (VTU) in the 1 to 12.4 GHz frequency range. Such a unit allows improved time efficiency and accuracy in the noise-temperature

A Location-Based Mechanism for Mobile Device Security

March 31, 2009
Author(s)
Wayne Jansen, Vlad Korolev
While mobile handheld devices, such as cell phones and PDAs, provide productivity benefits, they also pose new risks. A vital safeguard against unauthorized access to a device s contents is authentication. This paper describes a location-based

Cryocoolers: State of the art and recent developments

March 31, 2009
Author(s)
Ray Radebaugh
Cryocooler performance and reliability are continually improving. Consequently, they are more and more frequently implemented by physicists in their laboratory experiments or for commercial and space applications. The five types of cryocoolers most

Nanofluidic Structures with Complex Three Dimensional Surfaces

March 31, 2009
Author(s)
Samuel M. Stavis, Elizabeth Strychalski, Michael Gaitan
A fabrication process was developed to construct nanofluidic devices with complex three dimensional (3D) topographies. A single layer of grayscale photolithography enabled arbitrary and simultaneous control of numerous nanoscale etch depths in a fused

Sensitivity of SEM width measurements to model assumptions

March 31, 2009
Author(s)
John S. Villarrubia, Zejun Ding
The most accurate width measurements in a scanning electron microscope (SEM) require raw images to be corrected for instrumental artifacts. Corrections are based upon a physical model that describes the sample-instrument interaction. Models differ in their

Standard Radio CommunicationTest Method for Mobile Ground Robots

March 31, 2009
Author(s)
Kate Remley, Galen H. Koepke
This paper describes a proposed standard method for conducting a performance evaluation of wireless communications links used for the control and telemetry systems on mobile ground robots. Range performance metrics are determined under open line-of-sight

A Bose-Einstein Condensate in a Uniform Light-Induced Vector Potential

March 30, 2009
Author(s)
Yu-Ju Lin, Robert L. Compton, Abigail R. Perry, William D. Phillips, James V. Porto, Ian B. Spielman
We use a two-photon dressing field to create an effective vector gauge potential for Bose-condensed ^87Rb atoms in the F=1 hyperfine ground state. The dressed states in this Raman field are spin and momentum superpositions, and we adiabatically load the

A History of Fire Testing: Past, Present, and Future.

March 30, 2009
Author(s)
James R. Lawson
This paper discusses the breakthroughs in science and engineering that have brought fire testing technology to its current state of maturity and provides insight into the possibilities for future fire test development by highlighting some areas where

A History of Fire Testing: Past, Present, and Future.

March 30, 2009
Author(s)
James R. Lawson
This paper discusses the breakthroughs in science and engineering that have brought fire testing technology to its current state of maturity and provides insight into the possibilities for future fire test development by highlighting some areas where
Displaying 28676 - 28700 of 73830
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