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Displaying 28651 - 28675 of 73812

Electron Microscope Study of Strain in InGaN Quantum Wells in GaN Nanowires

April 1, 2009
Author(s)
Roy H. Geiss, David T. Read
GaN nanowires with InGaN quantum wells (QW) were grown on heated Si(111) substrates by molecular beam epitaxy (MBE) using elemental Ga and In and a radio-frequency-plasma N2 source. The growth procedures and the morphology of these nanowires have been

Evaluation of Oral Fluid Testing Devices

April 1, 2009
Author(s)
Lorna T. Sniegoski, Jocelyn L. Prendergast, Michael J. Welch, Alim A. Fatah, M Gackstetter, R. Q. Thompson
Several point-of-collection (POC) devices for detection of drugs of abuse in oral fluid were studied. The ability of the devices to meet the manufacturers' claims and their practical application to detection of drugs of abuse at low concentrations in oral

Fire-Front Propagation Using the Level Set Method

April 1, 2009
Author(s)
Ronald G. Rehm, Randall J. McDermott
Propagation of an outdoor fire front in wildland or in a combination of wildland and structural fuels (the so-called wildland-urban interface or WUI fire), can be modeled as an initial-value problem using either a Lagrangian or an Eulerian description. The

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
Displaying 28651 - 28675 of 73812
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