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A cellular automata-lattice Boltzmann coupled model was established to simulate the grain formation process of aluminum alloy under convection conditions. The influence of flow on crystal grain growth was simulated. Results show that the existence of convection prevents the crystal from growing symmetrically compared with the pure diffusion condition. Moreover, the growth of dendrite at the upstream side is promoted, whereas that at the downstream side is inhibited because of solute segregation. The greater the flow velocity is, the stronger the asymmetry of the grain is. The greater the undercooling is, the greater the dendritic growth driving force is, the faster the dendritic growth is, the dendrite arms coarsen, and the secondary dendrite arms become increasingly developed, thereby increasing the solute concentration at the solid-liquid interface at the tip of the dendrite and aggravating the solute segregation.

In order to make the quantum key agreement process immune to participant attacks, it is necessary to introduce the authentication in the communication process. A quantum key agreement protocol with identity authentication that exploits the measurement correlation of six-particle entangled states is proposed. In contrast to some recently proposed quantum key agreement protocols with authentication, this protocol requires neither a semi-trusted third party nor additional private keys in the authentication process. The entire process of authentication and key agreement can be achieved using only n six-particle entangled states, which saves communication costs and reduces the complexity of the authentication process. Finally, security analysis shows that this scheme is resistant to some important attacks.

Combined with hierarchy simultaneous entanglement swapping, the scheme of the multi-hop quantum teleportation (QT) is proposed by using multi-pair Bell states. The scheme consists of two levels based on simultaneous entanglement swapping, namely Level-1 and Level-2. The former realizes simultaneous entanglement swapping of the inner segment, while the latter completes simultaneous entanglement swapping of the inter segment. Besides, the effect of four different types of noise (phase-damping, amplitude-damping, phase-flip, and bit-flip noise) on our scheme is analyzed by calculating the fidelity and concurrence. The results indicate that the fidelity and concurrence are related to the amplitude parameter, decoherence rate and number of nodes. Furthermore, compared with the scheme of the multi-hop QT adopting simultaneous entanglement swapping, our scheme can greatly reduce classical communication cost, and shows that the optimal classical communication cost can be obtained by selecting different segmentation methods.

In a continuous hot-dip galvanizing vertical furnace for strip steel, zinc vapor oxidizes in the snout of the furnace to form zinc ash. The zinc ash adheres and agglomerates on the inner walls of the snout. If the zinc ash falls off and adheres to the surface of the strip, zinc ash defects will be formed, thereby affecting the surface quality of the galvanized layer. Given that the snout connects the annealing furnace and the zinc pot, the zinc ash will be transported into the annealing furnace and form nodulation on the roller, affecting the normal operation of the equipment. To study the deposition pattern of zinc ash inside the snout, a model of particle movement and deposition is established in this work to predict the movement and deposition characteristics of zinc ash particles, and it is verified by literature. On this basis, the zinc ash deposition patterns of three improvement cases of snout structure are compared. Results show that all three improvement schemes can effectively reduce the deposition rate of the zinc ash particles in the annealing furnace. In the case of slotted-baffle-added-only, although adding slotted baffles reduces the deposition of zinc ash in the furnace, it also increases the deposition rate in the snout and entry sections. In the case of exhaust-duct-added-only, the addition of the exhaust duct not only reduces the overall deposition rate in the furnace, but also effectively reduces the deposition rate in the snout and the entry section. By contrast, the scheme with slotted baffles and exhaust ducts is the most effective in inhibiting the diffusion of zinc ash.

In this paper, a kind of magnetorheological elastomer sandwich plate is proposed. The novel nonlinear differential term is applied to describe the force-displacement curve of the magnetorheological elastomer. The constitutive model of the system is established using the Hamilton Modeling Principle. By Galerkin dispersion, the response equation of the system is obtained, and its stochastic dynamic behavior is discussed. The numerical results are simulated by MATLAB mathematics software and show that the magnetorheological elastomer sandwich plate has rich dynamic characteristics, including stochastic Hopf bifurcation, which can be avoided if the parameters vary and only small amplitude vibrations appear.

We consider the Haldane model, a two-band model in monolayer graphene with non-trivial Chern numbers. Two types of topological defects, monopoles and merons, are derived from the model: (a) the monopole defects occur at the Dirac points, where the system experiences a topological transition and the Chern number C takes an indeterminate value. The sign-change of the mass term after this transition indicates different topological states labeled by different C numbers; (b) the meron defects occur as per a varying mass term. Summing up the topological charges of the merons leads to the C evaluation for the energy bands of an insulating bulk, and the result we obtain is in full agreement to the past literature. Furthermore, in this paper we propose a high-C model through studying the limitation behavior of the Hamiltonian vector in the neighborhood of the topological defects. It is discovered that two conducting states may arise form the edges, where the lower band of the insulating bulk carries a higher Chern number, C = ± 2 .

Fretting wear is one of the most important failure forms of alloy 690 heat exchanger tubes in nuclear power plants. The key to understanding the fretting wear of alloys lies in the friction process, especially at the atomic scale. In this study, molecular dynamics simulations were performed on alloy 690 to investigate the nanoscale friction behavior and its influencing factors, laying a foundation for further understanding the fretting wear mechanism of alloy 690. The friction processes of a single-asperity (probe) on a smooth polycrystalline surface (matrix) were investigated by molecular dynamics simulations at the atomic scale, and the variation law of friction force during the friction process was calculated. The factors that affected the friction force were discussed, including the pressing depth, temperature, and sliding speed of the probe, and the friction force was positively correlated with the pressing depth and sliding speed of the probe, while the temperature had little effect on the friction force. Observations of the generation and evolution of dislocations during the friction process and related factors such as grinding grooves and wear debris were also reported.

The development of hypersonic vehicles puts forward new requirements for simulation capabilities of ground wind tunnel facilities. MHD acceleration has brought great interests as a means of enhancing gas speed and become an important breakthrough. Two-dimensional numerical simulation of electron MHD(EMHD) acceleration process in continuous Faraday channel is carried out using MHD five-equation model of based on low magnetic Reynolds number. The thermal, electromagnetic, flow characteristics and its interactions in the channel are analyzed. The results show that the distribution of potential in the channel is no longer symmetrical due to the existence of Lorentz force, resulting in Hall effect. The current density whose maximum value exceeds 4×104 A/m2, is concentrated at the edge of the electrode, which would become more and more obvious as the magnetic induction intensity increases. Influenced jointly by the Lorentz force and the Hall effect, the direction of current shifts to the right, which in turn causes the Lorentz force shift upward. The effects of electrical conductivity σ, magnetic induction intensity B and applied voltage U on the flow field are analyzed. As σ increases, a large amount of Joule heat which reaches 3.24×108 J at σ=0.1 S/m is generated in the channel, making the Mach number of airflow decrease gradually. As B increases, the electromagnetic effect is significantly enhanced, while the Joule heat is reduced, about 32% at B=6 T. Therefore, the airflow is effectively accelerated. The load factor of EMHD channel is affected by applied voltage and magnetic field jointly. The effect of the applied voltage on airflow is more significant than that of magnetic induction intensity at small B. But at large B, the influence of the magnetic induction intensity on airflow will dominate.

To implement remote control operations in quantum networks, two schemes for the multi-hop quantum operation teleportation are proposed by using different partially entangled states. One is to adopt high-level partially Bell states as quantum channels, the other is to use high-level partially GHZ-Bell states. By comparing the two schemes, it is found that although both schemes have the same communication delay, the latter has less classical information cost and higher success probability of the communication.

We study the massless scalar quasinormal frequencies of an asymptotically flat static and spherically symmetric black hole with a nonzero magnetic charge in four-dimensional extended scalar-tensor-Gauss–Bonnet theory. The results show that the real part of the quasinormal frequency becomes larger and the imaginary part becomes smaller with increasing the magnetic charge or the angular harmonic index. The existence of magnetic charges will reduce the damping of scalar perturbation, but increase the frequency. We also study the absorption cross-section of the scalar field in this black hole. We find that its curve will become lower as the magnetic charge increases, i.e. the magnetic charge will weaken the absorption capacity of the black hole. Meanwhile, the high-frequency limit of the total absorption cross-section is just the area of black hole shadow.

This paper studies how the Nb content affected mechanical properties and microstructures of automotive steel processed by quenching and tempering (Q-T) and quenching-partitioning-tempering (Q-P-T) with the help of tensile testers, X-ray diffractometers, scanning electron microscopes, transmission electron microscopes and other equipment. It was demonstrated that when the Nb content remained the same, Agt (total elongation at maximum force), A (elongation after fracture) and R m·A (the product of strength with ductility) of the steel processed by Q-P-T were higher than those of the steel processed by Q-T; and when the steel was treated by the same thermal process, as the Nb content increased, its R p0.2 (yield strength) and R m (tensile strength) would grow, while A gt, A and R m·A would rise first and then decline. No matter if treated by Q-T or Q-P-T, the microstructures of the steel containing 0% and 0.03% of Nb separately were always lath martensite and film-like retained austenite located between laths. When processed by Q-P-T, the steel containing 0.03% Nb saw the largest strength-ductility product. This was because Nb could help refine the sizes of the original austenite grain and the lath martensite and precipitate nano-sized NbC; and the Q-P-T process was more effective in thickening the film-like retained austenite in steel and promoting the dispersed precipitation of the NbC.

The failure of commutation will cause the abrupt change of the operating parameters of the DC system. In this paper, the mechanism and physical process of commutation failure are analyzed. In view of the changing characteristics of inverter side valve current and DC current in the case of commutation failure, two kinds of S transform entropy are introduced into the detection of commutation failure of DC system in combination with S transform entropy’s excellent signal change feature recognition ability. In addition, the detection performance of the two s-transform entropies is fully considered in the case of no commutation failure, critical commutation failure and commutation failure. The simulation results based on PSCAD/EMTDC preliminarily verify the validity and accuracy of the two kinds of S transform entropy in dc system fault detection, which provides a basis for the further application of S transform entropy in dc system fault detection field.

Slitless spectral sky survey is a critical direction of international astronomical research. Compared with ground-based sky survey, space-based sky survey can achieve full-band observation, and its imaging quality and resolution capability are restricted by the efficiency and size of dispersive elements. Transmission blazed gratings are often used as the dispersive elements in the UV band. Holographic interference lithography produces the photoresist mask of a grating, and the ion beam etching vertically transfers the pattern to the substrate to form the SiO2 mask of a grating. To reduce the effect of ion beam divergence on the uniformity of the groove shape, the grating mask is etched tilted by the ion beam passing through a narrow slit to obtain a blazed grating with consistent structural parameters. Moreover, two-dimensional scanning of the sample stage enables the etching of large-size samples. A UV transmission blazed grating with a linear density of 333 lines mm−1, a blazing angle of 11.8°, and a dimension of 99.2mm × 60.0mm × 6.0mm was successfully fabricated with an average diffraction efficiency of 66%, a PV diffraction wavefront of 0.169λ (λ = 632.8 nm) and low stray light.

Magnesium stearate was used to modify the surface of aluminum hydroxide, and a composite system composed of magnesium stearate and red phosphorus was used to study the flame retardancy of HDPE sheath. By testing the oxygen index, impact strength, bending strength, melt flow rate and hardness of the composite, the results show that aluminum hydroxide and red phosphorus can play a synergistic effect of flame retardancy. With the increase of aluminum hydroxide content, when the content of aluminum hydroxide is 60 phr, the flame retardancy of the composite can reach UL94 V2 level, and the bending strength and hardness will also be improved, but the impact strength and melt flow rate decreased.

The low-voltage distribution network field wiring is very complicated and there are many changes in the relationship between households and changes, which brings great difficulties to the topology identification and line loss management of the transformer area. This paper proposed an intelligence low-voltage power system based on edge computing in order to improve the automation level of low-voltage distribution area, and to solve problems such as identification inaccuracy of topological relations in the low-voltage distribution area at present and singleness of condition monitoring parameters in station area, etc. The terminal is implanted with two edge calculation models based on artificial intelligence technology, which can realize topology identification and state parameters monitoring. The multistate parameter monitoring and decision analysis provides functions of event monitoring and early warning of abnormal state for the low voltage distribution system. In the topology identification analysis, the Markov random field was applied to establish the mathematical model of non-oriented graph and the joint probability distribution to describe the correlation between the nodes in the distribution network, thus realizing topology-relation identification of nodes in respective layers of the distribution area. On this basis, taking a low-voltage station as an example, a case analysis was undertaken. It was verified via the effectiveness and accuracy of the intelligence low-voltage station, which lays a foundation for research of the intelligent and fine management of the low voltage station system.

We demonstrate an efficient way of tuning the atomic buckling in stanene to open a topologically nontrivial energy gap. By tuning the growth kinetics, we obtain an unexpected high-buckled 3 × 3 stanene on the Bi(111) substrate. Scanning tunneling microscopy study combined with density functional theory calculation confirms that the 3 × 3 stanene is a distorted 1 × 1 structure with a high-buckled Sn in every three 1 × 1 unit cells. The high-buckled 3 × 3 stanene favors a large band inversion at the Γ point, and the spin–orbit coupling opens a topologically nontrivial energy gap. This study provides an alternate way to tune the topology of monolayer topological materials.

We grew a series of NaFe1−x V x As (0 ≤ x ≤ 0.03) single crystals and performed the measurements of resistance, magnetic susceptibility, and specific heat to study the superconducting phase diagram by doping V into NaFeAs. Both the structural and the spin-density-wave (SDW) transitions are slightly suppressed by V-doping. While superconducting transition temperature is enhanced to the maximum value of ∼ 15 K when the optimal doping level x = 0.007 and then is suppressed rapidly with further V-doping, displaying a small superconducting dome. Our results suggest that V-impurities should act as strong magnetic scattering centers which cause the sharp suppression of superconductivity in NaFe1−x V x As.