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Displaying 26901 - 26925 of 74141

Shape comparison between 0.4 ym to 2.0 ym and 20 ym to 60 ym cement particles

June 15, 2010
Author(s)
L Holzer, R Flatt, S.T. Erodgan, Jeffrey W. Bullard, Edward Garboczi
Portland cement powder has a wide particle size distribution, from approximately 0.1 υm to 60 υm. This wide powder size distribution arises via the grinding of much larger clinker particles in fact, several percent of the world s energy expenditures are

Statistical Modeling of Harvestable Kinetic Energy for Wearable Medical Sensors

June 15, 2010
Author(s)
Nathalie Yarkony, Kamran Sayrafian, Antonio Possolo
Energy Harvesting (EH) refers to the process of capturing and storing energy from external sources or ambient environment. Kinetic energy harvested from the human body motion seems to be one of the most convenient and attractive solution for wearable

Test Collection Diagnosis and Treatment

June 15, 2010
Author(s)
Ian M. Soboroff
Test collections are a mainstay of information retrieval research. Since the 1990s, large reusable test collections have been developed in the context of community evaluations such as TREC, NTCIR, CLEF, and INEX. Recently, advances in pooling practice as

Tunable laser spectroscopy referenced with dual frequency combs

June 15, 2010
Author(s)
Fabrizio R. Giorgetta, Ian R. Coddington, Esther Baumann, William C. Swann, Nathan R. Newbury
Frequency combs provide broadband spectroscopic measurements with high frequency accuracy and precision. However, because the comb power is distributed over a broad spectrum, the sensitivity can be low unless some form of multiplexed detection or cavity

FRACTURE OF TOOTH ENAMEL FROM INCIPIENT MICROSTRUCTURAL DEFECTS

June 14, 2010
Author(s)
H Chai, James J. Lee, Brian R. Lawn
We present definitive evidence for crack growth from internal defects called 'tufts' in human enamel. Side walls of slices sawn from extracted human teeth are observed during loading to 'failure'. 'Longitudinal' and 'transverse' slices (parallel and normal

Interlaboratory Comparison of Traceable Atomic Force Microscope Pitch Measurements

June 14, 2010
Author(s)
Ronald G. Dixson, Donald Chernoff, Shihua Wang, Theodore V. Vorburger, Ndubuisi G. Orji, Siew-Leng Tan, Joseph Fu
The National Institute of Standards and Technology (NIST), Advanced Surface Microscopy (ASM), and the National Metrology Centre (NMC) of the Agency for Science, Technology, and Research (A*STAR) in Singapore have undertaken a three-way interlaboratory

Introduction to Surface Finish Metrology

June 14, 2010
Author(s)
Theodore V. Vorburger
We discuss the range of methods available to measure surface finish and emphasize the methods of stylus profiling and various types of optical profiling. Documentary standards for measurement of surface texture and comparisons between methods are also

Observation of Transparency of Erbium-doped Silicon nitride in photonic crystal nanobeam cavities

June 14, 2010
Author(s)
Yiyang Gong, Maria Makarova, Selcuk Yerci, Rui Li, Martin Stevens, Burm Baek, Sae Woo Nam, Luca Dal Negro, Jelena Vuckovic
One dimensional nanobeam photonic crystal cavities are fabricated in an Er-doped amorphous silicon nitride layer. Photoluminescence from the cavities around 1.54 mm is studied at cryogenic and room temperatures at different optical pump powers. The

Real Time Data Acquisition Platform for Pulsed Measurements

June 14, 2010
Author(s)
Sergey V. Polyakov, Alan L. Migdall, Sae Woo Nam
We present an inexpensive and simple data acquisition platform based on Field Programmable Gate Arrays (FPGAs) designed to acquire and characterize fast digital or analog electrical signal real time for processing on a generic personal computer. While the

A New Electronic Verification Method for Vector Network Analyzers

June 13, 2010
Author(s)
Ronald A. Ginley, Dylan F. Williams, Denis X. LeGolvan
The National Institute of Standards and Technology (NIST) has recently introduced a new method for the verification of Vector Network Analyzers (VNAs). The technique is based on the new electronic calibration units that are available from several

Calibrations of Current-to-Voltage Transimpedance Amplifiers Using Electrical Standards

June 13, 2010
Author(s)
Howard W. Yoon, George P. Eppeldauer, Dean G. Jarrett, Thomas C. Larason, Wan-Seop Kim
For photocurrent measurements with low uncertainties, a wide-dynamic range current-to-voltage converter traceable to resistance standards has been developed at the NIST. The design and calibration of the converter standard are described. For validation

Comparison of Near-Field Methods at NIST

June 13, 2010
Author(s)
Katherine MacReynolds
A comparison of the planar, spherical and cylindrical near-field techniques was completed at the National Institute of Standards and Technology (NIST) for a Ku-band cassegrain reflector antenna. This paper discusses the measurement results for the near-to

Design of the NIST 10 V programmable Josephson voltage standard system

June 13, 2010
Author(s)
Charles J. Burroughs, Paul Dresselhaus, Alain Rufenacht, Mike Elsbury, Samuel Benz
NIST has developed and implemented a new Programmable Josephson Voltage Standard (PJVS) that operates at 10 V. This next-generation system is optimized for both dc metrology and stepwise-approximated ac voltage measurements for frequencies up to a few

Development and investigation of intrinsically shunted junction series arrays for ac Josephson voltage standards

June 13, 2010
Author(s)
Johannes Kohlmann, Franz Mueller, Oliver F. kieler, D. Schleussner, B Egeling, Ralf Behr, David I. Olaya, Paul Dresselhaus, Samuel Benz
Different types of intrinsically shunted Josephson junctions have been developed and inves¬tigated for ac voltage standard applications at PTB. The first type for generation of voltages up to 10 V is driven by a 70 GHz sinusoidal microwave signal and

Development of a Four-channel System for Johnson Noise Thermometry

June 13, 2010
Author(s)
Alessio Pollarolo, Jifeng Qu, Horst Rogalla, Paul Dresselhaus, Samuel Benz
Long integration time is necessary to reach low uncertainty when measuring temperature through Johnson Noise Thermometry (JNT). The main goal of the NIST JNT experiment is to achieve a 6 10-6 relative uncertainty in the measurement of the water triple

Error in calorimetric effective efficiency measurements due to DC losses

June 13, 2010
Author(s)
Thomas P. Crowley
A phenomenon in which DC loss in a transfer standard results in incorrect calorimetric effective efficiency measurements is described. The DC loss occurs within the 4-wire leads of the transfer standard or its connector. It therefore affects calorimetric

Establishing an ac Josephson voltage standard at NRC

June 13, 2010
Author(s)
Piotr S. Filipski, M. Boecker, Samuel Benz, Charles J. Burroughs
NRC recently established an AC Josephson Voltage Standard (ACJVS) system based on a NIST pulse-driven Josephson-junction array. This paper describes the efforts undertaken at NRC and the experience that was gained. An experimental method of measuring

Evaporator Optimization for Non-Uniform Air Distribution

June 13, 2010
Author(s)
Piotr A. Domanski, David A. Yashar, Sunil Lee
This study demonstrates the performance improvements that can be achieved by accounting for the in-situ air flow distribution during the design phase of a heat exchanger. The heat exchanger used in this study was a two-slab, A-shaped finned-tube evaporator

INTERCOMPARISON OF W-BAND STANDARD GAIN HORN ANTENNAS

June 13, 2010
Author(s)
Katherine MacReynolds, J. Kang, N. Kang, D. Gentle, Michael H. Francis
An intercomparison of power gain for W-band (75 GHz to 110 GHz) standard horn antennas has been performed among KRISS, NPL and NIST. This paper describes the comparison and its measurement results.

Microwave Optimization of 10 V PJVS Circuits

June 13, 2010
Author(s)
Paul D. Dresselhaus, Mike Elsbury, Charles J. Burroughs, Samuel P. Benz
Proper operation of programmable Josephson voltage standard arrays depends on the uniform distribution of microwaves to a large number of Josephson junctions. Too much or too little microwave power will change the current range of a junction s constant

Power Spectral Density: Is it right?

June 13, 2010
Author(s)
Ulf Griesmann, John Lehan, Jiyoung Chu
We concentrate on the instrumental issues surrounding power spectral density (PSD) determination, using as an example, the most common optical shop QA tool, the Fizeau interferometer. We briefly discuss the properties of an ideal calibration method for PSD

Quantifying How Lighting and Focus Affect Face Recognition Performance

June 13, 2010
Author(s)
J. R. Beveridge, David Bolme, Bruce A. Draper, Geof H. Givens, Yui M. Lui, P. Jonathon Phillips
Recent studies show that face recognition in uncontrolled images remains a challenging problem, although the reasons why are less clear. Changes in illumination are one possible explanation, although algorithms developed since the advent of the PIE and
Displaying 26901 - 26925 of 74141
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