4,924 research outputs found
The Photometric Investigation of V921 Her using the Lunar-based Ultraviolet Telescope of Chang'e-3 mission
The light curve of V921 Her in ultraviolet band observed by the Lunar-based
Ultraviolet Telescope (LUT) is analyzed by the Wilson-Devinney code. Our
solutions conclude that V921 Her is an early type marginal contact binary
system with an additional close-in component. The binary system is under poor
thermal contact with a temperature difference of nearly between the two
components. The close-in component contributes about of the total
luminosity in the triple system. Combining the radial velocity study together
with our photometric solutions, the mass of the primary star and secondary one
are calculated to be , . The evolutionary scenario of V921 Her is discussed.
All times of light minimum of V921 Her available in the bibliography are taken
into account and the curve is analyzed for the first time. The most
probable fitting results are discussed in the paper, which also confirm the
existence of a third component ( year) around the binary system. The
period of V921 Her is also undergoing a continuously rapid increase at a rate
of , which may due to mass
transfer from the less massive component to the more massive one
Boosting Fronthaul Capacity: Global Optimization of Power Sharing for Centralized Radio Access Network
The limited fronthaul capacity imposes a challenge on the uplink of
centralized radio access network (C-RAN). We propose to boost the fronthaul
capacity of massive multiple-input multiple-output (MIMO) aided C-RAN by
globally optimizing the power sharing between channel estimation and data
transmission both for the user devices (UDs) and the remote radio units (RRUs).
Intuitively, allocating more power to the channel estimation will result in
more accurate channel estimates, which increases the achievable throughput.
However, increasing the power allocated to the pilot training will reduce the
power assigned to data transmission, which reduces the achievable throughput.
In order to optimize the powers allocated to the pilot training and to the data
transmission of both the UDs and the RRUs, we assign an individual power
sharing factor to each of them and derive an asymptotic closed-form expression
of the signal-to-interference-plus-noise for the massive MIMO aided C-RAN
consisting of both the UD-to-RRU links and the RRU-to-baseband unit (BBU)
links. We then exploit the C-RAN architecture's central computing and control
capability for jointly optimizing the UDs' power sharing factors and the RRUs'
power sharing factors aiming for maximizing the fronthaul capacity. Our
simulation results show that the fronthaul capacity is significantly boosted by
the proposed global optimization of the power allocation between channel
estimation and data transmission both for the UDs and for their host RRUs. As a
specific example of 32 receive antennas (RAs) deployed by RRU and 128 RAs
deployed by BBU, the sum-rate of 10 UDs achieved with the optimal power sharing
factors improves 33\% compared with the one attained without optimizing power
sharing factors
Threshold Resummation Effects in Neutral Higgs Boson Production by Bottom Quark Fusion at the CERN Large Hadron Collider
We investigate the QCD effects in the production of neutral Higgs bosons via
bottom quark fusion in both the standard model and the minimal supersymmetric
standard model at the CERN Large Hadron Collider. We include the
next-to-leading order (NLO) QCD corrections (including supersymmetric QCD) and
the threshold resummation effects. We use the soft-collinear effective theory
to resum the large logarithms near threshold from soft gluon emission. Our
results show that the resummation effects can enhance the total cross sections
by about 5% compared with the NLO results.Comment: 29pages, 14 figures, version to appear in Physical Review
Next-to-leading order QCD corrections to the single top quark production via model-independent t-q-g flavor-changing neutral-current couplings at hadron colliders
We present the calculations of the complete next-to-leading order (NLO) QCD
effects on the single top productions induced by model-independent
flavor-changing neutral-current couplings at hadron colliders. Our results show
that, for the coupling the NLO QCD corrections can enhance the total
cross sections by about 60% and 30%, and for the coupling by about 50%
and 20% at the Tevatron and LHC, respectively, which means that the NLO
corrections can increase the experimental sensitivity to the FCNC couplings by
about 10%30%. Moreover, the NLO corrections reduce the dependence of the
total cross sections on the renormalization or factorization scale
significantly, which lead to increased confidence on the theoretical
predictions. Besides, we also evaluate the NLO corrections to several important
kinematic distributions, and find that for most of them the NLO corrections are
almost the same and do not change the shape of the distributions.Comment: minor changes, version published in PR
- …