4,297 research outputs found
The valley filter efficiency of monolayer graphene and bilayer graphene line defect model
In addition to electron charge and spin, novel materials host another degree
of freedom, the valley. For a junction composed of valley filter sandwiched by
two normal terminals, we focus on the valley efficiency under disorder with two
valley filter models based on monolayer and bilayer graphene. Applying the
transfer matrix method, valley resolved transmission coefficients are obtained.
We find that: i) under weak disorder, when the line defect length is over about
, it functions as a perfect channel (quantized conductance) and
valley filter (totally polarized); ii) in the diffusive regime, combination
effects of backscattering and bulk states assisted intervalley transmission
enhance the conductance and suppress the valley polarization; iii) for very
long line defect, though the conductance is small, polarization is indifferent
to length. Under perpendicular magnetics field, the characters of charge and
valley transport are only slightly affected. Finally we discuss the efficiency
of transport valley polarized current in a hybrid system.Comment: 6 figure
Geometric effects of a quarter of corrugated torus
In the spirit of the thin-layer quantization scheme, we give the effective
Shr\"{o}dinger equation for a particle confined to a corrugated torus, in which
the geometric potential is substantially changed by corrugation. We find the
attractive wells reconstructed by the corrugation not being at identical
depths, which is strikingly different from that of a corrugated nanotube,
especially in the inner side of the torus. By numerically calculating the
transmission probability, we find that the resonant tunneling peaks and the
transmission gaps are merged and broadened by the corrugation of the inner side
of torus. These results show that the quarter corrugated torus can be used not
only to connect two tubes with different radiuses in different directions, but
also to filter the particles with particular incident~energies.Comment: 7 pages, 8 figure
LSF-IDM: Automotive Intrusion Detection Model with Lightweight Attribution and Semantic Fusion
Autonomous vehicles (AVs) are more vulnerable to network attacks due to the
high connectivity and diverse communication modes between vehicles and external
networks. Deep learning-based Intrusion detection, an effective method for
detecting network attacks, can provide functional safety as well as a real-time
communication guarantee for vehicles, thereby being widely used for AVs.
Existing works well for cyber-attacks such as simple-mode but become a higher
false alarm with a resource-limited environment required when the attack is
concealed within a contextual feature. In this paper, we present a novel
automotive intrusion detection model with lightweight attribution and semantic
fusion, named LSF-IDM. Our motivation is based on the observation that, when
injected the malicious packets to the in-vehicle networks (IVNs), the packet
log presents a strict order of context feature because of the periodicity and
broadcast nature of the CAN bus. Therefore, this model first captures the
context as the semantic feature of messages by the BERT language framework.
Thereafter, the lightweight model (e.g., BiLSTM) learns the fused feature from
an input packet's classification and its output distribution in BERT based on
knowledge distillation. Experiment results demonstrate the effectiveness of our
methods in defending against several representative attacks from IVNs. We also
perform the difference analysis of the proposed method with lightweight models
and Bert to attain a deeper understanding of how the model balance detection
performance and model complexity.Comment: 18 pages, 8 figure
Low-energy effective Hamiltonian involving spin-orbit coupling in Silicene and Two-Dimensional Germanium and Tin
Starting from the symmetry aspects and tight-binding method in combination
with first-principles calculation, we systematically derive the low-energy
effective Hamiltonian involving spin-orbit coupling (SOC) for silicene, which
is very general because this Hamiltonian applies to not only the silicene
itself but also the low-buckled counterparts of graphene for other group IVA
elements Ge and Sn, as well as graphene when the structure returns to the
planar geometry. The effective Hamitonian is the analogue to the first graphene
quantum spin Hall effect (QSHE) Hamiltonian. Similar to graphene model, the
effective SOC in low-buckled geometry opens a gap at Dirac points and
establishes QSHE. The effective SOC actually contains first order in the atomic
intrinsic SOC strength , while such leading order contribution of SOC
vanishes in planar structure. Therefore, silicene as well as low-buckled
counterparts of graphene for other group IVA elements Ge and Sn has much larger
gap opened by effective SOC at Dirac points than graphene due to low-buckled
geometry and larger atomic intrinsic SOC strength. Further, the more buckled is
the structure, the greater is the gap. Therefore, QSHE can be observed in
low-buckled Si, Ge, and Sn systems in an experimentally accessible temperature
regime. In addition, the Rashba SOC in silicene is intrinsic due to its own
low-buckled geometry, which vanishes at Dirac point , while has nonzero
value with deviation from the point. Therefore, the QSHE in
silicene is robust against to the intrinsic Rashba SOC.Comment: 11 pages, 3 figure
How are typical urban sewage treatment technologies going in China: from the perspective of life cycle environmental and economic coupled assessment
Sewage treatment is an important public service, but it consumes a lot of energy and chemicals in the process of removing wastewater pollutants, which may cause the risk of pollution transfer. To find the corresponding hot issues, this paper took the lead in integrating life cycle assessment (LCA) with life cycle costing (LCC) to evaluate four most typical sewage treatment technologies with more than 85% share in China. It is found that anaerobic/anoxic/oxic (AAO) was the optimal treatment scheme with relatively small potential environmental impact and economic load. The normalized results show that the trends of the four technologies on eleven environmental impact categories were basically the same. Marine aquatic ecotoxicity potential accounted for more than 70% of the overall environmental impact. Contribution analysis indicates that electricity and flocculant consumption were the main processes responsible for the environmental and economic burden. Overall, electricity consumption was the biggest hot spot. Sensitivity analysis verifies that a 10% reduction in electricity could bring high benefits to both the economy and the environment. These findings are expected to provide effective feedback on the operation and improvement of sewage treatment
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