321 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
Fault-Tolerant Control for Systems with Unmatched Actuator Faults and Disturbances
A fault-tolerant control (FTC) scheme for a class of nonlinear systems with unmatched actuator redundancy and unmatched disturbances is proposed in this note. A methodology to construct unified smooth sliding mode control laws and update laws is proposed such that the equivalent injections of the first-order time derivatives of the unmatched actuator faults and unmatched disturbances can appear in the unmatched channels. The unmatched actuator faults and unmatched disturbances are completely canceled by these equivalent injections. Based on this methodology and using the backstepping design procedure, a set of smooth FTC sliding surfaces, FTC laws and update laws are then designed. With the help of the FTC law selecting mechanism, the output tracking errors of the closed-loop FTC system converge to zero asymptotically, and time-varying faults and disturbances are reconstructed. A simulation example is presented to illustrate the effectiveness of the proposed FTC method
Threshold dynamics of a nonlocal diffusion West Nile virus model with spatial heterogeneity
In this study, we investigated the threshold dynamics of a spatially heterogeneous nonlocal diffusion West Nile virus model. By employing semigroup theory and continuous Fréchet-differentiable, we established the well-posedness of the solution. The expression for the basic reproduction number derived using the next-generation matrix method. The authors demonstrated the threshold dynamics of the system by constructing a Lyapunov function and applying the comparison principle. Finally, numerical simulations were used to validate the theorem results. It can be suggested that to control disease development rapidly, measures should be taken to reduce the spread of mosquitoes and birds
Design of FPGA-Implemented Reed-Solomon Erasure Code (RS-EC) Decoders With Fault Detection and Location on User Memory
Reed–Solomon erasure codes (RS-ECs) are widely used in packet communication and storage systems to recover erasures. When the RS-EC decoder is implemented on a field-programmable gate array (FPGA) in a space platform, it will suffer single-event upsets (SEUs) that can cause failures. In this article, the reliability of an RS-EC decoder implemented on an FPGA when there are errors in the user memory is first studied. Then, a fault detection and location scheme is proposed based on partial reencoding for the faults in the user memory of the RS-EC decoder. Furthermore, check bits are added in the generator matrix to improve the fault location performance. The theoretical analysis shows that the scheme could detect most faults with small missing and false detection probability. Experimental results on a case study show that more than 90% of the faults on user memory could be tolerated by the decoder, and all the other faults can be detected by the fault detection scheme when the number of erasures is smaller than the correction capability of the code. Although false alarms exist (with probability smaller than 4%), they can be used to avoid fault accumulation. Finally, the fault location scheme could accurately locate all the faults. The theoretical estimates are very close to the experiment results, which verifies the correctness of the analysis done.This work was supported in part by the National Natural Science Foundation of China under Grant 61501321, in part by the China Postdoctoral Science Foundation and Luoyang Newvid Technology Company, Ltd., and in part by the ACHILLES Project PID2019-104207RB-I00 funded by the Spanish Ministry of Science and Innovation
The thermal-fluid-mechanical (TFM) coupling method based on discrete element method (DEM) and the application of CO2 fracturing analysis
Acknowledgments The authors express their appreciation to the National Natural Science Foundation of China (Grant No.52004236), the Key Program of National Natural Science Foundation of China (Grant No. 52234003), the Open Project Program of Engineering Research Center of Geothermal Resources Development Technology and Equipment, Ministry of Education (Grant No.22016), the Starting Project of SWPU (Grant No.2019QHZ009), and the Chinese Scholarship Council (CSC) funding (CSC NO.202008515107).Peer reviewedPostprin
Quantum Transports in Two-Dimensions with Long Range Hopping: Shielding, Localization and the Extended Isolated State
We investigate the effects of disorder and shielding on quantum transports in
a two dimensional system with all-to-all long range hopping. In the weak
disorder, cooperative shielding manifests itself as perfect conducting channels
identical to those of the short range model, as if the long range hopping does
not exist. With increasing disorder, the average and fluctuation of conductance
are larger than those in the short range model, since the shielding is
effectively broken and therefore long range hopping starts to take effect. Over
several orders of disorder strength (until times of nearest
hopping), although the wavefunctions are not fully extended, they are also
robustly prevented from being completely localized into a single site. Each
wavefunction has several localization centers around the whole sample, thus
leading to a fractal dimension remarkably smaller than 2 and also remarkably
larger than 0, exhibiting a hybrid feature of localization and delocalization.
The size scaling shows that for sufficiently large size and disorder strength,
the conductance tends to saturate to a fixed value with the scaling function
, which is also a marginal phase between the typical metal
() and insulating phase (). The all-to-all coupling expels
one isolated but extended state far out of the band, whose transport is
extremely robust against disorder due to absence of backscattering. The bond
current picture of this isolated state shows a quantum version of short circuit
through long hopping.Comment: 15 pages, 8 figure
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