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Physics

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Displaying 1351 - 1375 of 2516

The 2015 TWSTFT calibration for UTC and related time links

April 4, 2016
Author(s)
Zhiheng Jiang, Dirk Piester, Christian Schlunegger, Erik Dierks, Javier Galindo, Demetrios Matsakis, Victor S. Zhang
Two-Way Satellite Time and Frequency Transfer (TWSTFT or TW) is one of the primary time transfer techniques for UTC generation. Although it has expensive financial requirements it provides highly accurate calibration, and provides both robustness and

Measuring Time and Comparing Clocks

April 1, 2016
Author(s)
Judah Levine
I will discuss methods of comparing and synchronizing clocks and the procedure of characterizing their performance in terms of the two-sample Allan variance. I will describe methods that are used when the device under test and the reference device are in

Towards Establishing Compact Imaging Spectrometer Standards

March 31, 2016
Author(s)
David W. Allen, Elmer T. Slonecker, Ronald G. Resmini
Remote sensing science is currently undergoing a tremendous expansion in the area of hyperspectral imaging (HSI) technology. Spurred largely by the explosive growth of Unmanned Aerial Vehicles (UAV), sometimes called Unmanned Aircraft Systems (UAS), or

Probing beyond the laser coherence time in optical clock comparisons

March 30, 2016
Author(s)
David B. Hume, David R. Leibrandt
We develop protocols that circumvent the laser noise limit in optical clock comparisons by synchronous probing of two clocks using phase-locked local oscillators. This allows for probe times longer than the laser coherence time, avoids the Dick effect, and

EUV-induced oxidation of carbon on TiO2

March 25, 2016
Author(s)
Nadir S. Faradzhev, Shannon B. Hill
Previously we reported on the etch rates of C on TiO2 by oxidizers including NO, O3 and H2O2 when irradiated by extreme ultraviolet (EUV) radiation at 13.5 nm [Faradzhev et al., J.Phys. Chem. C, 117 (2013) 23072-23081]. We demonstrated that the intensity

Dispersion engineered resonator on-a-chip

March 14, 2016
Author(s)
Scott A. Diddams, Ki Youl Yang, Xu Yi, Hansuek Lee, Dong Yoon Oh, Kerry J. Vahala, Katja M. Beha, Daniel C. Cole, Pascal P. Del'Haye, Scott B. Papp
Control of dispersion in fiber optical waveguides has long been important in optical fiber communications systems, and more recently for continuum generation through self phase modulation. The wavelength at which the group velocity dispersion crosses zero

Oscillator PM-noise reduction from correlated AM-noise

March 11, 2016
Author(s)
Archita Hati, Craig W. Nelson, David A. Howe
We demonstrate a novel technique for reducing the phase modulation (PM) noise of an oscillator in steady state as well as under vibration. It utilizes correlation between PM noise and amplitude modulation (AM) noise that can originate from the oscillator's

Usage analysis of a national internet time service

March 8, 2016
Author(s)
Jeffrey A. Sherman, Judah Levine
The Internet Time Service (ITS) at the National Institute of Standards and Technology (NIST) currently receives over 12 billion time requests per day. ITS servers derive their system time from the NIST atomic-referenced timescale and distribute it freely

Cross-spectrum Measurement of Thermal-noise Limited Oscillators

March 1, 2016
Author(s)
Archita Hati, Craig W. Nelson, David A. Howe
Cross-spectrum analysis is a commonly-used technique for the detection of phase and amplitude noise of a signal in the presence of interfering noise. It extracts the desired correlated noise from two time series which also contain uncorrelated interfering

Validation and Verification of Collisional-Radiative Models

February 25, 2016
Author(s)
Yuri Ralchenko
Quality control is as relevant to scientific computing as to any other software. For complex collisional-radiative (CR) models that are used to calculate plasma population kinetic parameters and spectra, each computer code is expected to be thoroughly

The lifetime of 4p54d levels in highly ionized atoms

February 16, 2016
Author(s)
G. Gaigalas, P. Rynkun, Charlotte F. Fischer
Energy levels, lifetimes, and wave function compositions have been computed for all atomic states of the 4p6 and 4p54d configurations using a single-reference (SR) configuration state along with single- and double-substitutions (SD) to generate expansions

An Overview of Spectral Imaging of Human Skin toward Face Recognition

February 13, 2016
Author(s)
David W. Allen
Spectral imaging is a form of remote sensing that provides a means of collecting information from surroundings without physical contact. Differences in spectral reflectance over the electromagnetic spectrum allow for the detection, classification, or

Rapid, broadband spectroscopic temperature measurement of CO 2 using VIPA spectroscopy

January 28, 2016
Author(s)
Andrew M. Klose, Gabriel Ycas, Flavio Caldas da Cruz, Daniel I. Maser, Scott Diddams
Rapid spectroscopic temperature measurements of a sealed carbon dioxide sample cell were realized with an optical frequency comb combined with a two-dimensional dispersive spectrometer. A supercontinuum laser source based on an erbium mode-locked laser was

Demonstration of near-IR line-referenced electro-optical laser comb for precision radial velocity measurement in astronomy

January 27, 2016
Author(s)
Scott A. Diddams, K Vahala, J Li, Gabriel G. Ycas, P Plavchan, S Leifer, J Sandhu, G Vasisht, P Chen, P Gao, J Gagne, M Bottom, E.C. Martin, M.P. Fitzgerald, G Doppmann, C Beichman, X Yi
We describe a successful effort to produce a laser comb around 1.55 micron in the astronomical H band (1.5-1.8 micron) using a method based on a line-referenced, electro-optical-modulation frequency comb (LR-EOFC). The LR-EOFC is a spectrum of equally

High-contrast and fast electrochromic switching enabled by plasmonics

January 27, 2016
Author(s)
Ting Xu, Erich C. Walter, Amit Agrawal, Christopher C. Bohn, Jeyavel Velmurugan, Wenqi Zhu, Henri Lezec, Albert A. Talin
With vibrant colours and simple, room-temperature processing methods, electrochromic polymers have attracted attention as active materials for flexible, low-power-consuming devices. However, slow switching speeds in devices realized to date, as well as the

Mechanically mediated microwave frequency conversion

January 26, 2016
Author(s)
Florent Q. Lecocq, Jeremy B. Clark, Raymond W. Simmonds, Jose A. Aumentado, John D. Teufel
We report the observation of efficient and low-noise frequency conversion between two microwave modes, mediated by the motion of a mechanical resonator subjected to radiation pressure. We achieve the coherent conversion of more than 10^{12} photons/s with
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