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Displaying 30776 - 30800 of 74893

CHARACTERIZATION OF LOADING EFFECTS IN PRECISION 1 Ohm RESISTORS

June 1, 2008
Author(s)
George R. Jones Jr., Randolph Elmquist
Precision standard resistors manufactured within the last two decades using improved construction techniques and materials, such as the resistance alloy Evanohm, have been shown to have excellent environmental characteristics. Power dissipation (or loading

Consideration and Influence of Complexed forms of Mercury Species on the reactivity Patterns Determined by Speciated Isotope Dilution Model Approaches: A Case for Natural Biological Reference Materials

June 1, 2008
Author(s)
David Point, J. I. Garcia Alonso, William C. Davis, Steven J. Christopher, Aurore Guichard, O.F. X. Donard, Paul R. Becker, Gregory C. Turk, Stephen A. Wise
The origins and the processes driving the inadvertent transformations of inorganic mercury (iHg) and methylmercury (MeHg) in cryogenically stored and homogenized fresh-frozen versus freeze-dried biological Standard Reference Materials (SRM) were

Design And Fabrication Of MJTCs On Quartz Substrates At NIST

June 1, 2008
Author(s)
Thomas E. Lipe Jr., Joseph R. Kinard Jr., Luciana Scarioni
Wet and dry etching are employed in the fabrication of new planar, thin-film multijunction thermal converters (MJTCs) on quartz membranes and crystalline quartz chips at NIST. The use of crystalline quartz as a material for the membrane and for the chip

HIGH RESISTANCE SCALING FROM 10 k(OHM) AND QHR STANDARDS USING A CRYOGENIC CURRENT COMPARATOR

June 1, 2008
Author(s)
Randolph Elmquist, George R. Jones Jr., Brian J. Pritchard, Marcos E. Bierzychudek, Felipe L. Hernandez
We describe a cryogenic current comparator (CCC) bridge for resistance scaling that provides improved measurement uncertainty over a range of resistance values from 100 k(Ω) to 1 G(Ω). This CCC is designed for high resistance scaling based directly on a

Practical Combinatorial Testing: Beyond Pairwise

June 1, 2008
Author(s)
David R. Kuhn, Yu Lei, Raghu N. Kacker
With new algorithms and tools, developers can apply high-strength combinatorial testing to detect elusive failures that occur only when multiple components interact. In pairwise testing, all possible pairs of parameter values are covered by at least one

REACT: Reducing Early-Age Cracking Today

June 1, 2008
Author(s)
Dale P. Bentz, W Weiss
Concrete is generally viewed as a durable and long-lasting construction material. However, the long-term performance of a concrete structure can be greatly compromised by early-age cracking. One recent informal estimate from the industry places this as a

SIM COMPARISON OF DC RESISTANCE AT 1 Ohm, 1 MOhm, AND 1 GOhm

June 1, 2008
Author(s)
Dean G. Jarrett, Randolph Elmquist, Nien F. Zhang, Alejandra Tonina, Janice Fernandes, Daniel Izquierdo, Dave Inglis, Felipe Hernandez-Marquez
A regional comparison of DC resistance standards at the nominal values of 1 Ohm, 1 MOhm, and 1 GOhm has recently been completed in the System Interamericano de Metrogia (SIM) region. The motivation, design, standards, and results of this regional

Transformer-Like Devices for High-Accuracy Current Measurements.

June 1, 2008
Author(s)
T. M. Souders
A theoretical and practical framework is presented to aid in the design, fabrication and testing of transformer-like devices for use in high-accuracy ac current metering applications. Current transformers, two-stage current transformers, and current

UNCERTAINTY EVALUATION IN A TWO-TERMINAL CRYOGENIC CURRENT COMPARATOR

June 1, 2008
Author(s)
Marcos E. Bierzychudek, Randolph Elmquist
In this paper we present the uncertainty evaluation of a new cryogenic current comparator (CCC) bridge designed to compare two-terminal 1M Ω} and 10M Ω} standard resistors with the quantized Hall resistance (QHR) and then scale from these values to other

Low Signal-to-noise Ratio Underwater Acoustic Communications

May 31, 2008
Author(s)
Wen-Bin Yang, T.C. Yang
Communications with low input signal-to-noise ratio (SNR) is often called covert communications as the probability of detection and interception decreases with decreasing SNR . Direct-sequence spread-spectrum signaling works at low SNR because of the
Displaying 30776 - 30800 of 74893