78,630 research outputs found
Spin-filtered and Spatially Distinguishable Crossed Andreev Reflection in a Silicene-Superconductor Junction
We theoretically investigate the quantum transports in a junction between a
superconductor and a silicene nanoribbon, under the effect of a magnetic
exchange field. We find that for a narrow nanoribbon of silicene, remarkable
crossed Andreev reflection (with a fraction ) can be induced in the
energy window of the elastic cotunneling, by destroying some symmetries of the
system. Since the energy responses of electrons to the exchange field are
opposite for opposite spins, these transport channels can be well spin
polarized. Moreover, due to the helicity conservation of the topological edge
states, these three transport channels are spatially separated in three
different locations of the device, making them experimentally distinguishable.
This crossed Andreev reflection is a nonlocal quantum interference between
opposite edges through evanescent modes. If two superconducting leads with
different phases are connected to two edges of the silicene nanoribbon, the
crossed Andreev reflection can present Josephson type oscillations, with a
maximal fraction .Comment: 8 pages, 7 figure
Graphs with 3-rainbow index and
Let be a nontrivial connected graph with an edge-coloring
, where adjacent edges
may be colored the same. A tree in is a if no two edges
of receive the same color. For a vertex set , the tree
connecting in is called an -tree. The minimum number of colors that
are needed in an edge-coloring of such that there is a rainbow -tree for
each -set of is called the -rainbow index of , denoted by
. In \cite{Zhang}, they got that the -rainbow index of a tree is
and the -rainbow index of a unicyclic graph is or . So
there is an intriguing problem: Characterize graphs with the -rainbow index
and . In this paper, we focus on , and characterize the graphs
whose 3-rainbow index is and , respectively.Comment: 14 page
On Channel Reciprocity to Activate Uplink Channel Training for Downlink Wireless Transmission in Tactile Internet Applications
We determine, for the first time, the requirement on channel reciprocity to
activate uplink channel training, instead of downlink channel training, to
achieve a higher data rate for the downlink transmission from a multi-antenna
base station to a single-antenna user. We first derive novel closed-form
expressions for the lower bounds on the data rates achieved by the two channel
training strategies by considering the impact of finite blocklength. The
performance comparison result of these two strategies is determined by the
amount of channel reciprocity that is utilized in the uplink channel training.
We then derive an approximated expression for the minimum channel reciprocity
that enables the uplink channel training to outperform the downlink channel
training. Through numerical results, we demonstrate that this minimum channel
reciprocity decreases as the blocklength decreases or the number of transmit
antennas increases, which shows the necessity and benefits of activating the
uplink channel training for short-packet communications with multiple transmit
antennas. This work provides pivotal and unprecedented guidelines on choosing
channel training strategies and channel reciprocity calibrations, offering
valuable insights into latency reduction in the Tactile Internet applications.Comment: 6 pages, 3 figures, Submitted to IEEE ICC 2018 Worksho
Distributed interaction between computer virus and patch: A modeling study
The decentralized patch distribution mechanism holds significant promise as
an alternative to its centralized counterpart. For the purpose of accurately
evaluating the performance of the decentralized patch distribution mechanism
and based on the exact SIPS model that accurately captures the average dynamics
of the interaction between viruses and patches, a new virus-patch interacting
model, which is known as the generic SIPS model, is proposed. This model
subsumes the linear SIPS model. The dynamics of the generic SIPS model is
studied comprehensively. In particular, a set of criteria for the final
extinction or/and long-term survival of viruses or/and patches are presented.
Some conditions for the linear SIPS model to accurately capture the average
dynamics of the virus-patch interaction are empirically found. As a
consequence, the linear SIPS model can be adopted as a standard model for
assessing the performance of the distributed patch distribution mechanism,
provided the proper conditions are satisfied
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