22,800 research outputs found
Determining the core radio luminosity function of radio AGNs via copula
The radio luminosity functions (RLFs) of active galactic nuclei (AGNs) are
traditionally measured based on total emission, which doesn't reflect the
current activity of the central black hole. The increasing interest in compact
radio cores of AGNs requires determination of the RLF based on core emission
(i.e., core RLF). In this work we have established a large sample (totaling
1207) of radio-loud AGNs, mainly consisting of radio galaxies (RGs) and
steep-spectrum radio quasars (SSRQs). Based on the sample, we explore the
relationship between core luminosity () and total luminosity () via a
powerful statistical tool called "Copula". The conditional probability
distribution is obtained. We derive the core
RLF as a convolution of with the total RLF
which was determined by previous work. We relate the separate RG and SSRQ core
RLFs via a relativistic beaming model and find that SSRQs have an average
Lorentz factor of , and that most are seen within
of the jet axis. Compared with
the total RLF which is mainly contributed by extended emission, the core RLF
shows a very weak luminosity-dependent evolution, with the number density
peaking around for all luminosities. Differences between core
and total RLFs can be explained in a framework involving a combination of
density and luminosity evolutions where the cores have significantly weaker
luminosity evolution than the extended emission.Comment: Accepted for publication in the ApJ
Regenerative and Adaptive schemes Based on Network Coding for Wireless Relay Network
Recent technological advances in wireless communications offer new
opportunities and challenges for relay network.To enhance system performance,
Demodulate-Network Coding (Dm-NC) scheme has been examined at relay node; it
works directly to De-map the received signals and after that forward the
mixture to the destination. Simulation analysis has been proven that the
performance of Dm-NC has superiority over analog-NC. In addition, the
Quantize-Decode-NC scheme (QDF-NC) has been introduced. The presented
simulation results clearly provide that the QDF-NC perform better than
analog-NC. The toggle between analogNC and QDF-NC is simulated in order to
investigate delay and power consumption reduction at relay node.Comment: 11 pages, 8 figures, International Journal of Computer Networks &
Communications (IJCNC), Vol.4, No.3, May 201
Charm elliptic flow at RHIC
Charm elliptic flow in heavy ion collisions at the Relativistic Heavy Ion
Collider (RHIC) is studied in a multiphase transport model. Assuming that the
cross section for charm quark scattering with other light quarks is the same as
that between light quarks, we find that both charm and light quark elliptic
flows are sensitive to the value of the cross section. Compared to that of
light quarks, the elliptic flow of charm quarks is smaller at low transverse
momentum but approaches comparable values at high transverse momentum. Similar
features are seen in the elliptic flow of charmed mesons as well as that of the
electrons from their semileptonic decays when the charmed mesons are produced
from quark coalescence during hadronization of the partonic matter. To describe
the large electron elliptic flow observed in available experimental data
requires a charm quark scattering cross section that is much larger than that
given by the perturbative QCD
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