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Frank D.,Formerly at Center for Ocean EngineeringUniversity of New HampshireDurham | Sou I.M.,National Research Council Postdoctoral Fellow | Calantoni J.,Marine Geosciences Division
Journal of Geophysical Research C: Oceans | Year: 2015

Incipient motion of coarse gravel-sized sediment was investigated under a range of oscillatory flows. This article examines the relative significance of shear stresses and pressure gradients in triggering motion, which was directly measured with electronic Smart Sediment Grains (SSGs). The data suggest that incipient motion was induced by the pressure gradients in flows with large accelerations, by the shear stresses in flows with low accelerations and greater shear, and by the combined effects in intermediate flows. A modified incipient motion criterion was evaluated accounting for the combined effects of the shear stresses and pressure gradients, which may be more widely applicable in the marine environment. © 2014. American Geophysical Union.


Frank D.,University of New Hampshire | Foster D.,University of New Hampshire | Sou I.M.,National Research Council Postdoctoral Fellow | Calantoni J.,U.S. Navy | Chou P.,University of California at Irvine
Journal of Geophysical Research C: Oceans | Year: 2015

Incipient motion of coarse gravel-sized sediment was investigated under a range of oscillatory flows. This article examines the relative significance of shear stresses and pressure gradients in triggering motion, which was directly measured with electronic Smart Sediment Grains (SSGs). The data suggest that incipient motion was induced by the pressure gradients in flows with large accelerations, by the shear stresses in flows with low accelerations and greater shear, and by the combined effects in intermediate flows. A modified incipient motion criterion was evaluated accounting for the combined effects of the shear stresses and pressure gradients, which may be more widely applicable in the marine environment. © 2014. American Geophysical Union. All Rights Reserved.


Kirtley J.D.,National Research Council Postdoctoral Fellow | Qadri S.N.,National Research Council Postdoctoral Fellow | Steinhurst D.A.,Nova Research Inc. | Owrutsky J.C.,U.S. Navy
Journal of Power Sources | Year: 2016

Various in situ probes of solid oxide fuel cells (SOFCs) have advanced recently to provide detailed, real time data regarding materials and chemical processes that relate to device performance and degradation. These techniques offer insights into complex fuel chemistry at the anode in particular, especially in the context of model predictions. However, cell-to-cell variations can hinder mechanistic interpretations of measurements from separate, independent techniques. The present study describes an in situ technique that for the first time simultaneously measures surface temperature changes using near infrared thermal imaging and gas species using Fourier-transform infrared emission spectra at the anodes of operating SOFCs. Electrolyte-supported SOFCs with Ni-based anodes are operated at 700 °C with internal, dry-reformed methane at 75% maximum current and at open circuit voltage (OCV) while electrochemical and optical measurements are collected. At OCV, more cooling is observed coincident with more CO reforming products. Under load, CO decreases while the anode cools less, especially near the current collectors. The extent of cooling is more sensitive to polarization for electrolyte-supported cells because their anodes are thinner relative to anode-supported cells. This study exemplifies how this duplex technique can be a useful probe of electrochemical processes in SOFCs. © 2016


Hutcheson A.L.,U.S. Navy | Phlips B.F.,U.S. Navy | Wulf E.A.,U.S. Navy | Weber B.V.,U.S. Navy | Woolf R.S.,National Research Council Postdoctoral Fellow
Digest of Technical Papers-IEEE International Pulsed Power Conference | Year: 2013

A hybrid coded imaging and detection system developed at the U.S. Naval Research Laboratory (NRL) was used for active interrogation measurements with pulsed bremsstrahlung at the Hermes-III facility at Sandia National Laboratories, Albuquerque. This work follows previous experiments performed in 2011 [1] and explores different targets and system conditions to the previous work. The techniques used and challenges encountered during this work are described. © 2013 IEEE.


Warren H.P.,U.S. Navy | Reep J.W.,National Research Council Postdoctoral Fellow | Crump N.A.,Washington Technology | Simoes P.J.A.,University of Glasgow
Astrophysical Journal | Year: 2016

We exploit the high spatial resolution and high cadence of the Interface Region Imaging Spectrograph (IRIS) to investigate the response of the transition region and chromosphere to energy deposition during a small flare. Simultaneous observations from the Reuven Ramaty High Energy Solar Spectroscopic Imager provide constraints on the energetic electrons precipitating into the flare footpoints, while observations of the X-Ray Telescope, Atmospheric Imaging Assembly, and Extreme Ultraviolet Imaging Spectrometer (EIS) allow us to measure the temperatures and emission measures from the resulting flare loops. We find clear evidence for heating over an extended period on the spatial scale of a single IRIS pixel. During the impulsive phase of this event, the intensities in each pixel for the Si iv 1402.770 Å, C ii 1334.535 Å, Mg ii 2796.354 Å, and O i 1355.598 Å emission lines are characterized by numerous small-scale bursts typically lasting 60 s or less. Redshifts are observed in Si iv, C ii, and Mg ii during the impulsive phase. Mg ii shows redshifts during the bursts and stationary emission at other times. The Si iv and C ii profiles, in contrast, are observed to be redshifted at all times during the impulsive phase. These persistent redshifts are a challenge for one-dimensional hydrodynamic models, which predict only short-duration downflows in response to impulsive heating. We conjecture that energy is being released on many small-scale filaments with a power-law distribution of heating rates. © 2016. The American Astronomical Society. All rights reserved..


Rose P.S.,National Research Council Postdoctoral Fellow | Rose P.S.,Texas A&M University-Corpus Christi
Environmental Sciences: Processes and Impacts | Year: 2014

The May 2012 paper "Radioactive fallout in the United States due to the Fukushima nuclear plant accident" (P. Thakur, S. Ballard and R. Nelson, J. Environ. Monit., 2012, 14, 1317-1324), does not address medical patient excreta as a source of 131I (t1/2 = 8.04 d) to the environment. While 131I is generated during fission reactions and may be released to the environment from nuclear power plants, nuclear weapons tests, nuclear fuel reprocessing and weapons production facilities, it is also produced for medical use. Iodine-131 administered to patients, excreted and discharged to sewer systems is readily measureable in sewage and the environment; the patient-to-sewage pathway is the only source of 131I in many locations. This journal is © the Partner Organisations 2014.

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