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RISS 인기검색어
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- 저자 : Scott Jordan (검색결과 4 건)
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BROAD H<i>β</i>EMISSION-LINE VARIABILITY IN A SAMPLE OF 102 LOCAL ACTIVE GALAXIES
Runco, Jordan N.,Cosens, Maren,Bennert, Vardha N.,Scott, Bryan,Komossa, S.,Malkan, Matthew A.,Lazarova, Mariana S.,Auger, Matthew W.,Treu, Tommaso,Park, Daeseong American Astronomical Society 2016 The Astrophysical journal Vol.821 No.1
<P>A sample of 102 local (0.02 <= z <= 0.1) Seyfert galaxies with black hole masses M-BH > 10(7)M(circle dot) was selected from the Sloan Digital Sky Survey (SDSS) and observed using the Keck 10 m telescope to study the scaling relations between M-BH and host galaxy properties. We study profile changes of the broad H beta emission line within the three to nine year time frame between the two sets of spectra. The variability of the broad H beta emission line is of particular interest, not only because it is used to estimate M-BH, but also because its strength and width are used to classify Seyfert galaxies into different types. At least some form of broad-line variability (in either width or flux) is observed in the majority (similar to 66%) of the objects, resulting in a Seyfert-type change for similar to 38% of the objects, likely driven by variable accretion and/or obscuration. The broad H beta line virtually disappears in 3/102 (similar to 3%) extreme cases. We discuss potential causes for these changing look active galactic nuclei. While similar dramatic transitions have previously been reported in the literature, either on a case-by-case basis or in larger samples focusing on quasars at higher redshifts, our study provides statistical information on the frequency of H beta line variability in a sample of low-redshift Seyfert galaxies.</P>
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Neutrality between a Vertically Integrated Cable Provider and an Over-the-Top Video Provider
Wei Dai,백지원,Scott Jordan 한국통신학회 2016 Journal of communications and networks Vol.18 No.6
We are concerned with whether a vertically integratedbroadband and content provider can unreasonably advantage itselfover competing content providers, either by selling quality-ofservice(QoS) to content providers at unreasonably high prices, orby refusing to provide access to QoS to competing content. We addressthis question by modeling the competition between one suchvertically integrated provider and one over-the-top (OTT) contentprovider. The broadband provider decides whether to deploy QoS,and if so it also determines the QoS price if sold to either the OTTcontent provider or directly to users. We analytically determinewhen the broadband provider will sell QoS and when the OTT contentprovider or users will purchase QoS. We characterize the optimalQoS and video service prices. The Internet service provider(ISP)’s market share increases with the difference in the value ofthe two video services and decreases with the difference in the correspondingcosts. Numerical results illustrate the effect of QoSprice on content price, the variation of prices and profit with QoSprice, and the variation of prices and market shares with the benefitof QoS. The ISP may sell QoS to users at a lower price thanwhenQoS is sold to theOTT provider.
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Neutrality between a Vertically Integrated Cable Provider and an Over-the-Top Video Provider
Dai, Wei,Baek, Ji Won,Jordan, Scott The Korea Institute of Information and Commucation 2016 Journal of communications and networks Vol.18 No.6
We are concerned with whether a vertically integrated broadband and content provider can unreasonably advantage itself over competing content providers, either by selling quality-of-service (QoS) to content providers at unreasonably high prices, or by refusing to provide access to QoS to competing content. We address this question by modeling the competition between one such vertically integrated provider and one over-the-top (OTT) content provider. The broadband provider decides whether to deploy QoS, and if so it also determines the QoS price if sold to either the OTT content provider or directly to users. We analytically determine when the broadband provider will sell QoS and when the OTT content provider or users will purchase QoS. We characterize the optimal QoS and video service prices. The Internet service provider (ISP)'s market share increases with the difference in the value of the two video services and decreases with the difference in the corresponding costs. Numerical results illustrate the effect of QoS price on content price, the variation of prices and profit with QoS price, and the variation of prices and market shares with the benefit of QoS. The ISP may sell QoS to users at a lower price than when QoS is sold to the OTT provider.
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Improved fission neutron energy discrimination with <sup>4</sup>He detectors through pulse filtering
Zhu, Ting,Liang, Yinong,Rolison, Lucas,Barker, Cathleen,Lewis, Jason,Gokhale, Sasmit,Chandra, Rico,Kiff, Scott,Chung, Heejun,Ray, Heather,Baciak, James E.,Enqvist, Andreas,Jordan, Kelly A. Elsevier 2017 Nuclear Instruments & Methods in Physics Research. Vol.848 No.-
<P><B>Abstract</B></P> <P>This paper presents experimental and computational techniques implemented for <SUP>4</SUP>He gas scintillation detectors for induced fission neutron detection. Fission neutrons are produced when natural uranium samples are actively interrogated by 2.45MeV deuterium-deuterium fusion reaction neutrons. Fission neutrons of energies greater than 2.45MeV can be distinguished by their different scintillation pulse height spectra since <SUP>4</SUP>He detectors retain incident fast neutron energy information. To enable the preferential detection of fast neutrons up to 10MeV and suppress low-energy event counts, the detector photomultiplier gain is lowered and trigger threshold is increased. Pile-up and other unreliable events due to the interrogating neutron flux and background radiation are filtered out prior to the evaluation of pulse height spectra. With these problem-specific calibrations and data processing, the <SUP>4</SUP>He detector's accuracy at discriminating fission neutrons up to 10MeV is improved and verified with <SUP>252</SUP>Cf spontaneous fission neutrons. Given the <SUP>4</SUP>He detector's ability to differentiate fast neutron sources, this proof-of-concept active-interrogation measurement demonstrates the potential of special nuclear materials detection using a <SUP>4</SUP>He fast neutron detection system.</P>
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