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Displaying 14776 - 14800 of 73922

Accurate TWSTFT time transfer with indirect links

January 31, 2017
Author(s)
Victor S. Zhang, Zhiheng Jiang, Thomas E. Parker, Jian Yao, Yi-Jiun Huang, Shinn-Yan Lin
The conventional wisdom suggests a direct Two-Way Satellite Time and Frequency Transfer (TWSTFT or TW) time link should result in a smaller uncertainty than that of an indirect TW link over the same baseline [12]. This is why all Coordinated Universal Time

Impact of UV irradiation on multiwall carbon nanotubes in nanocomposites: formation of entangled surface layer and mechanisms of release resistance

January 31, 2017
Author(s)
Tinh Nguyen, Elijah J. Petersen, Bastien T. Pellegrin, Justin M. Gorham, Thomas F. Lam, Minhua Zhao, Li Piin Sung
Carbon nanotubes (CNTs) are increasingly used in consumer and structural polymeric products to enhance a variety of properties. Under weathering, the polymer matrix will degrade and the nanofillers will potentially be released from the products, which

Local Distribution and Calibration of Timing Signals at NIST

January 31, 2017
Author(s)
Joshua J. Savory, Liz C. Forero, Kristopher Maurer, Stefania Romisch
The National Institute of Standards and Technology (NIST) timescale produces a real-time realization of UTC(NIST) in the form of a pulse-per-second (PPS) time signal and a 5 MHz frequency reference. The timing signals are distributed to the international

Long-term instability in UTC time links

January 31, 2017
Author(s)
Victor S. Zhang, Demetrios Matsakis, Zhiheng Jiang
Calibration and link stability are the key issues for the UTC time transfer. This study is made in the framework of a joint task group of the CCTF Working Group on TWSTFT and Working Group on GNSS Time Transfer to investigate the long-term instability of

The development of a new Kalman-filter time scale at NIST

January 31, 2017
Author(s)
Jian Yao, Thomas E. Parker, Judah Levine
We report on a preliminary design of a new Kalman-filter Hydrogen-maser time scale at NIST. The time scale is composed of a few Hydrogen masers and a Cs clock. The Cs clock is used as a reference clock, just for easy operations with the existing data. All

The effects of the January 2016 UTC offset anomaly on GPS clocks monitored at NIST

January 31, 2017
Author(s)
Jian Yao, Michael A. Lombardi, Andrew N. Novick, Bijunath Patla, Jeffrey A. Sherman, Victor S. Zhang
Errors in the Coordinated Universal Time (UTC) offset parameters broadcast by Global Positioning System (GPS) satellites caused many thousands of GPS clocks to be in error by approximately -13 µs on January 25-26, 2016. The erroneous UTC offset information

Trapped-ion optical atomic clocks at the quantum limits

January 31, 2017
Author(s)
David R. Leibrandt, Samuel M. Brewer, Jwo-Sy Chen, Aaron M. Hankin, David B. Hume, David J. Wineland, Chin-Wen Chou
Frequency and its inverse, time, are the most accurately measured quantities. Historically, improvements in the accuracy of clocks have enabled advances in navigation, communication, and science. Since 1967, the definition of the SI second has been based

Tuning flexibility to control selectivity in soft porous crystals

January 31, 2017
Author(s)
Nathan Mahynski, Vincent K. Shen
We use flat-histogram Monte Carlo simulations to study how changing the flexibility of soft porous crystals (SPCs) affects their selective adsorption of a binary, size-asymmetric supercritical fluid. Specifically, we consider mesoporous SPCs which have

2015 Location-Based Services R&D Summit Report

January 30, 2017
Author(s)
Harris Feldman, Adam H. Danielson
The Public Safety Communications Research Program (PSCR) convened over 80 stakeholders at the National Institute of Standards and Technology (NIST) Boulder, CO campus to build on the findings presented in the 2015 Location-Based Services (LBS) Summit- held

2016 PSCR Analytics Summit Report

January 30, 2017
Author(s)
Jeremy E. Benson, Harris Feldman
PSCR hosted over 80 stakeholders from industry, academia, public safety, and government to the NIST Boulder campus in August 2016. The August summit was a follow-up to the Public Safety Analytics R&D Roadmap, published earlier in 2016. This document

Band Alignment Measurement by Internal Photoemission Spectroscopy

January 30, 2017
Author(s)
Nhan V. Nguyen
parameters affecting the performance of advanced electronic and optoelectronic devices. Among the common band offset measurement techniques, internal photoemission has been proven to be a novel method which is almost a direct measurement without

Final report on the key comparison, CCM.PK15 in the pressure rangefrom 1.0 x 10-4 Pa to 1.0 Pa

January 30, 2017
Author(s)
Christian Wuethrich, Hitoshi Akimichi, Mercede Bergoglio, James A. Fedchak, Karl Jousten, Sueng Soo Hong, Jorge T. Guzman
The comparison CCM.M.P-K14 is a key comparison in pressure involving six laboratories in three regional metrological organizations (RMO). The measurand of the comparison is the accommodation coefficient of two spinning rotating gauge characterized in

Industrial Wireless Systems: Radio Propagation Measurements

January 30, 2017
Author(s)
Richard Candell, Catherine A. Remley, Jeanne T. Quimby, David R. Novotny, Alexandra Curtin, Peter B. Papazian, Galen H. Koepke, Joseph Diener, Mohamed T. Hany
Radio frequency (RF) propagation measurements were conducted at three facilities representing a cross-section of different classes of industrial environments. Selected sites included a multi-acre transmission assembly factory typical of the automotive

THE USE AND CHALLENGES OF PRECISE TIME IN ELECTRIC POWER SYNCHROPHASOR SYSTEMS

January 30, 2017
Author(s)
Marc A. Weiss, Alison Silverstein, Francis Tuffner, Ya-Shian Li-Baboud
Today, the principal way that power system owners and operators use precision timing is for fault recording, protection system operation and in synchrophasor applications. Synchrophasor applications have among the most stringent precision time and time

Insights into Cruciform Sample Design

January 29, 2017
Author(s)
Adam Creuziger, Mark Iadicola, Timothy J. Foecke, Evan Rust, Dilip Banerjee
Four different cruciform sample designs, based on the work of Abu-Farha et al, were studied in this paper. The original design of Abu-Farha was validated at room temperature for a thicker sample, and two modified sample geometries that would permit thinner

An Overview of Mobile Application Vetting Services for Public Safety

January 27, 2017
Author(s)
Gema E. Howell, Michael A. Ogata
The Middle Class Tax Relief Act of 2012 mandated the creation of the Nation's first nationwide, high-speed communications network dedicated for public safety. The law instantiated a new federal entity, the Federal Responder Network Authority (FirstNet), to

Fabrication of Scanning Electrochemical Microscopy-Atomic Force Microscopy (SECM-AFM) Probes to Image Surface Topography and Reactivity at the Nanoscale

January 27, 2017
Author(s)
Jeyavel Velmurugan, Amit K. Agrawal, Sang M. An, Eric A. Choudhary, Veronika A. Szalai
Electrocatalysts, used in energy applications, rely on the solid-liquid interface to carry out productive chemistry. This interface is generally less amenable to standard surface-science characterization methods, making the investigation of the surface

Increasing evidence indicates low bioaccumulation of carbon nanotubes

January 27, 2017
Author(s)
Rhema Bjorkland, David Tobias, Elijah Petersen
As the production of carbon nanotubes (CNTs) expands, so does the potential for release into the environment. The possibility of bioaccumulation and toxicological effects has prompted research on their fate and potential ecological effects. For many

Uncertainty Assessment of Equations of State Applied to Organic Rankine Cycles

January 27, 2017
Author(s)
Ian H. Bell, Kenneth G. Kroenlein, John P. O'Connell, Jens Abildskov, Jerome Frutiger, Gurkan Sin
This study presents a generic method to analyze and select equations of state (EoS) based on detailed uncertainty analysis of the respective EoS property parameters. A Cubic EoS (i.e. Soave-Redlich-Kwong SRK) is compared to PC-SAFT EoS. The uncertainty
Displaying 14776 - 14800 of 73922
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