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The GALEX Ultraviolet Variability Catalog
Welsh, Barry Y.,Wheatley, Jonathan M.,Heafield, Kenneth,Seibert, Mark,Browne, Stanley E.,Salim, Samir,Rich, R. Michael,Barlow, Tom A.,Bianchi, Luciana,Byun, Yong-Ik,Donas, Jose,Forster, Karl,Friedman, American Institute of Physics 2005 The Astronomical journal Vol.130 No.2
<P>We present version 1.0 of the NASA Galaxy Evolution Explorer (GALEX) ultraviolet variability (GUVV) catalog, which contains information on 84 time-variable and transient sources gained with simultaneous near-ultraviolet (NUV) and far-ultraviolet (FUV) photometric observations. These time-variable sources were serendipitously revealed in the various 1<img entity='fdg' SRC='http://ej.iop.org/icons/Entities/fdg.gif' ALT='fdg' ALIGN='BASELINE' />2 diameter star fields currently being surveyed by the GALEX satellite in two ultraviolet bands (NUV 1750–2750 Å, FUV 1350–1750 Å) with limiting AB magnitudes of 23–25. The largest amplitude variable objects currently detected by GALEX are M dwarf flare stars, which can brighten by 5–10 mag in both the NUV and FUV bands during short-duration (<500 s) outbursts. Other types of large-amplitude ultraviolet variable objects include ab-type RR Lyrae stars, which can vary periodically by 2–5 mag in the GALEX FUV band. This first GUVV catalog lists galactic positions and possible source identifications in order to provide the astronomical community with a list of time-variable objects that can now be repeatedly observed at other wavelengths. We expect the total number of time-variable source detections to increase as the GALEX mission progresses, such that later version numbers of the GUVV catalog will contain substantially more variable sources.</P>
Sokhandani, Navid,Setoodeh, AliReza,Zebarjad, Seyed Mojtaba,Nikbin, Kamran,Wheatley, Greg Techno-Press 2022 Advances in nano research Vol.13 No.1
In the present article, silica nanoparticles (SNPs) were exploited to improve the tribological and mechanical properties of vinyl ester/glass fiber composites. To the best of our knowledge, there hasn't been any prior study on the wear properties of glass fiber reinforced vinyl ester SiO<sub>2</sub> nanocomposites. The wear resistance is a critical concern in many industries which needs to be managed effectively to reduce high costs. To examine the influence of SNPs on the mechanical properties, seven different weight percentages of vinyl ester/nano-silica composites were initially fabricated. Afterward, based on the tensile testing results of the silica nanocomposites, four wt% of SNPs were selected to fabricate a ternary composite composed of vinyl ester/glass fiber/nano-silica using vacuum-assisted resin transfer molding. At the next stage, the tensile, three-point flexural, Charpy impact, and pin-on-disk wear tests were performed on the ternary composites. The fractured surfaces were analyzed by scanning electron microscopy (SEM) images after conducting previous tests. The most important and interesting result of this study was the development of a nanocomposite that exhibited a 52.2% decrease in the mean coefficient of friction (COF) by augmenting the SNPs, which is beneficial for the fabrication/repair of composite/steel energy pipelines as well as hydraulic and pneumatic pipe systems conveying abrasive materials. Moreover, the weight loss due to wearing the ternary composite containing one wt% of SNPs was significantly reduced by 70%. Such enhanced property of the fabricated nanocomposite may also be an important design factor for marine structures, bridges, and transportation of wind turbine blades.
Hooman Esfandyari,AliReza Setoodeh,Hamed Farahmand,Hamed Badjian,Greg Wheatley Techno-Press 2023 Advances in nano research Vol.15 No.1
In this present article, the mechanical behavior of single-walled black phosphorene nanotubes (SW-αPNTs) is simulated using molecular dynamics (MD). The proposed model is subjected to the axial loading and the effects of morphological parameters, such as the mono-vacancy defect and strain rate on the tensile behavior of the zigzag and armchair SW-αPNTs are studied as a pioneering work. In order to assess the accuracy of the MD simulations, the stress-strain response of the current MD model is successfully verified with the efficient quantum mechanical approach of the density functional theory (DFT). Along with reproducing the DFT results, the accurate MD simulations successfully anticipate a significant variation in the stress-strain curve of the zigzag SW-αPNTs, namely the knick point. Predicting such mechanical behavior of SW-αPNTs may be an important design factor for lithium-ion batteries, supercapacitors, and energy storage devices. The simulations show that the ultimate stress is increased by increasing the diameter of the pristine SW-αPNTs. The trend is identical for the ultimate strain and stress-strain slope as the diameter of the pristine zigzag SW-αPNTs enlarges. The obtained results denote that by increasing the strain rate, the ultimate stress/ultimate strain are respectively increased/declined. The stress-strain slope keeps increasing as the strain rate grows. It is worth noting that the existence of mono-atomic vacancy defects in the (12,0) zigzag and (0,10) armchair SW-αPNT structures leads to a drop in the tensile strength by amounts of 11.1% and 12.5%, respectively. Also, the ultimate strain is considerably altered by mono-atomic vacancy defects.