194 research outputs found
Dynamics of entanglement for a two-parameter class of states in a qubit-qutrit system
We investigate the dynamics of entanglement for a two-parameter class of
states in a hybrid qubit-qutrit system under the influence of various
dissipative channels. Our results show that entanglement sudden death (ESD) is
a general phenomenon and it usually takes place in a qubit-qutrit system
interacting with various noisy channels, not only the case with dephasing and
depolarizing channels observed by others. ESD can only be avoided for some
initially entangled states under some particular noisy channels. Moreover, the
environment affects the entanglement and the coherence of the system in very
different ways.Comment: 9 pages, 6 figures, 1 table. A negligible error for type on Eq(7) is
correcte
Optimal Resource Allocation for Multi-UAV Assisted Visible Light Communication
In this paper, the optimization of deploying unmanned aerial vehicles (UAVs)
over a reconfigurable intelligent surfaces (RISs)-assisted visible light
communication (VLC) system is studied. In the considered model, UAVs are
required to simultaneously provide wireless services as well as illumination
for ground users. To meet the traffic and illumination demands of the ground
users while minimizing the energy consumption of the UAVs, one must optimize
UAV deployment, phase shift of RISs, user association and RIS association. This
problem is formulated as an optimization problem whose goal is to minimize the
transmit power of UAVs via adjusting UAV deployment, phase shift of RISs, user
association and RIS association. To solve this problem, the original
optimization problem is divided into four subproblems and an alternating
algorithm is proposed. Specifically, phases alignment method and semidefinite
program (SDP) algorithm are proposed to optimize the phase shift of RISs. Then,
the UAV deployment optimization is solved by the successive convex
approximation (SCA) algorithm. Since the problems of user association and RIS
association are integer programming, the fraction relaxation method is adopted
before using dual method to find the optimal solution. For simplicity, a greedy
algorithm is proposed as an alternative to optimize RIS association. The
proposed two schemes demonstrate the superior performance of 34:85% and 32:11%
energy consumption reduction over the case without RIS, respectively, through
extensive numerical study
Noise discrimination method based on charge distribution of CMOS detectors for soft X-ray
Complementary metal-oxide semiconductor (CMOS) sensors have been widely used
as soft X-ray detectors in several fields owing to their recent developments
and unique advantages. The parameters of CMOS detectors have been extensively
studied and evaluated. However, the key parameter signal-to-noise ratio in
certain fields has not been sufficiently studied. In this study, we analysed
the charge distribution of the CMOS detector GSENSE2020BSI and proposed a
two-dimensional segmentation method to discriminate signals according to the
charge distribution. The effect of the two-dimensional segmentation method on
the GSENSE2020BSI dectector was qualitatively evaluated. The optimal feature
parameters used in the two-dimensional segmentation method was studied for
G2020BSI. However, the two-dimensional segmentation method is insensitive to
feature parameters.Comment: 19 pages, 13 figures, submitted to NIM-
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