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25 March 2021, Volume 38 Issue 2 Previous Issue    Next Issue
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Algorithms in Linear Solver for Large-scale Time-harmonic Maxwell's Equations in SiP Applications: State-of-the-art and Challenges HU Shaoliang, XU Xiaowen, ZHENG Yuteng, ZHAO Zhenguo, WANG Weijie, XU Ran, AN Hengbin, MO Zeyao 2021, 38(2): 131-145.  DOI: 10.19596/j.cnki.1001-246x.8231 Abstract ( )   HTML ( )   PDF (3944KB) ( )   System in package (SiP) is mainstream technology in the design of electronics system. Numerical simulation plays an important role in SiP applications. However, due to the specific complexity of SiP applications, existing algorithms for linear systems arising from time-harmonic Maxwell's equations are faced with great challenges, which become a bottleneck restricting efficiency of large-scale numerical simulations. In this paper, we review algorithms for time-harmonic Maxwell's equations in SiP applications. Based on capability assessment of existing algorithms for realistic SiP models, we propose a preconditioning strategy, and show its feasibility and efficiency. Furthermore, we analyze impact of such applications on performance behavior of current algorithms and the challenges we faced with.

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High-precision Numerical Simulation of Strong Explosion Fireball with Adaptive Mesh LI Kang, LI Shouxian, LIU Na 2021, 38(2): 146-152.  DOI: 10.19596/j.cnki.1001-246x.8230 Abstract ( )   HTML ( )   PDF (6172KB) ( )   A method of adaptive mesh is proposed and simulation of strong explosion radiation hydrodynamics based on Euler method is carried out. To demonstrate feasibility of the approach, comparisons with Zinn's numerical results are made. It shows that profiles of over-pressure and visible output power with adaptive mesh is close to those with uniform mesh with three times grid number. Meanwhile, the time consumed decrease to 1/8.5. It shows that the adaptive mesh method is feasible in high-precision numerical simulation and accuracy and efficiency are increased prominently.

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Vertex Interpolation Methods for Nine-point Scheme on Multi-flow-tube Meshes XU Jinjing, YUAN Guangwei 2021, 38(2): 153-164.  DOI: 10.19596/j.cnki.1001-246x.8212 Abstract ( )   HTML ( )   PDF (2026KB) ( )   The multi-flow tube (MFT) method is mainly designed for two-dimensional (2-D) radiation hydrodynamic problems with multi-material, whose computational mesh is Lagrangian-Eulerian hybrid. Quality of the MFT quadrilateral mesh is usually higher than that of a general quadrilateral mesh. We consider a so-called nine-point diffusion scheme on this kind of meshes, in which the method of calculating vertex unknowns is improved by taking advantage of mesh features. Several methods for eliminating vertex unknowns are proposed by using harmonic averaging points or a gradient reconstruction method. Numerical experiments show that our methods obtain almost second order accuracy on MFT meshes.

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A Plane Flux Expansion Solver for Three-dimensional Pin by Pin SP3 Method LI Zhiyong 2021, 38(2): 165-170.  DOI: 10.19596/j.cnki.1001-246x.8221 Abstract ( )   HTML ( )   PDF (759KB) ( )   Transport SP3 based on pin by pin is an important anticipant in next generation reactor physics numerical methods. The nodal method for pin by pin calculation is not efficient because higher order flux and source expansion is assumed for large nodal size. Since reactor core heterogeneous happens usually in radial direction, a radial 2D plane flux fused with axial traditional nodal method is proposed for 3D pin by pin transport SP3 calculation. A nodal iterations strategy based on nodal face current is adopted in all three directions. With IAEA 2D/3D and typical transport benchmark problem, the method is demonstrated correct and feasible for core transport and diffusion calculations.

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Local Discontinuous Petrov-Galerkin Method in Air Pollution Model ZHANG Xin, ZHAO Guozhong, LI Hong 2021, 38(2): 171-182.  DOI: 10.19596/j.cnki.1001-246x.8192 Abstract ( )   HTML ( )   PDF (4662KB) ( )   A local discontinuous Petrov-Galerkin method for numerical simulation of two kinds of air pollution models is constructed. Firstly, air pollution model equations are transformed into equivalent first-order differential equations with variable substitution. Secondly, discontinuous Petrov-Galerkin method is used to solve the differential equations. The method can choose different test function and trial function space, and maintains advantages of the intermittent Petrov-Galerkin method. Compared with local discontinuous finite element method, calculation formula of the method is simpler. Numerical examples show that the method has third-order accuracy and less error than the finite volume method. The algorithm provides a practical tool for numerical simulation of air pollution models.

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Deterministic Implementation Algorithm of a Physical-based Gas-surface Interaction Model GAO Yuan, LIANG Tengfei 2021, 38(2): 183-191.  DOI: 10.19596/j.cnki.1001-246x.8207 Abstract ( )   HTML ( )   PDF (5402KB) ( )   A deterministic algorithm is developed to implement a physical-based gas-surface interaction model. The key of the algorithm is to calculate discretized matrix by a deterministic way, which represents the scattering kernel of single gas-surface collision and governs the gas molecular velocity distribution function.By considering the attractive potential well and successive gas-surface collisions, this algorithm describes physically the variation of gas molecular velocity distribution functions at the interface.Comparing with existing stochastic implementation algorithm based on Monte Carlo sampling, this deterministic implementation algorithm calculates accurately and efficiently the relation between incident and reflected velocity distributions of gas molecules. Therefore, it provides a better boundary condition for the deterministic simulation methods of rarefied gas flows based on discretized velocity space.

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Algorithm for Multi-point Random Vibration Analysis of a Flight Device Under Strong Fluctuating Pressures and Parallel Implementation FAN Xuanhua, WANG Keying, XIAO Shifu, CHEN Pu 2021, 38(2): 192-198.  DOI: 10.19596/j.cnki.1001-246x.8208 Abstract ( )   HTML ( )   PDF (2911KB) ( )   Random vibration analysis for a flight device under multi-point strong correlated fluctuating pressures in the process of reentry into the atmosphere is studied. Starting from a free body modal analysis and considering strong correlation properties among fluctuating pressures, free body dynamic equations were established and random vibration theory under rigid-elastic modal coupling was deduced. The algorithm design is completed and the code is implemented in a self-developed parallel software platform PANDA. Correctness verification and application research were carried out with a typical numerical example. It shows that rigid body motion of the flight device has a significant impact on the response of structure in low frequency band, and it even plays a leading role. The closer to zero frequency, the greater the impact. In middle and high frequency bands, elastic response gradually takes dominant positions. A self-developed random vibration analysis module simulates well the dynamic response induced by fluctuating pressures in the flight device reentry process. It has a super large-scale parallel computing ability.

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Current-induced Skyrmion Motion in Magnetic Fluted Nanostripes ZHANG Guangfu, ZHANG Saiwen, DENG Yangbao, XIONG Cuixiu, TAN Weishi 2021, 38(2): 199-205.  DOI: 10.19596/j.cnki.1001-246x.8234 Abstract ( )   HTML ( )   PDF (3843KB) ( )   Current-induced skyrmion motion is studied with theory and simulation of micromagnetism. Compared with those in the nanostripe, the maximum driving current density (Jmax) and the maximum skyrmion speed (Vmax) increase significantly in a fluted nanostripe structure which provides greater skyrmion-edge repulsion force to suppress transverse displacement of the skyrmion. As the driving current density increases, the skyrmion speed increases to Vmax, and then decreases or remains unchanged. As increasing the edge width or thickness, Jmax and Vmax increase linearly. We show dependence of the skyrmion speed on edge thickness and width in the fluted nanostripe and explain theoretically with micromagnetics. It provides guidance for the design and development of spintronic devices based on nanostripes.

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Nonlocal Absorption in Gold and Silver Nanostructures LIU Jianxiao, LIU Xiaolan, LU Huali, GAO Yingjie, JIANG Yan, TANG Wanchun 2021, 38(2): 206-214.  DOI: 10.19596/j.cnki.1001-246x.8211 Abstract ( )   HTML ( )   PDF (7628KB) ( )   Nonlocal absorption of gold and silver nanostructures is studied with ADE-FDTD method. A Drude-Lorentz model of metal material is discretized and iterative coefficients are deduced in detail. Absorption characteristics of one-, two- and three-dimensional gold and silver nanostructures are studied. It shows that the nonlocal layered films conforms to the equivalent medium theory. In one- and two-dimensional cases, nonlocal absorption peaks are related to the nano scale and have no relation with the material. The nonlocal absorption properties of three-dimensional nanostructures are related to nanoscale, and to material as well. Nonlocal effect of three-dimensional nano structures is the strongest, and the blue shift of the absorption peak is larger. Therefore, three-dimensional gold and silver nano structures are expected to play a role in nano devices.

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Potential Function and Molecular Dynamics Simulation for FexO-SiO2-CaO-MgO-“NiO” Nickel Slag WANG Guohua, CUI Yaru, YANG Ze, LI Xiaoming, TANG Hongliang, YANG Shufeng 2021, 38(2): 215-223.  DOI: 10.19596/j.cnki.1001-246x.8198 Abstract ( )   HTML ( )   PDF (2261KB) ( )   Potential function of FexO-SiO2-CaO-MgO-"NiO" nickel slag in a two-atom model is constructed with nonempirical parameters. Microstructure and physicochemical properties of nickel slag are explored with molecular dynamics simulation. It shows that the potential energy of FexO-SiO2-CaO-MgO-"NiO" nickel slag can be characterized well with BMH(Born-Mayer-Huggins) potential function. It is beneficial to diffusion as CaO content of nickel slag is 15 wt.%, at which the coordination number of Si4+-Si4+ and the polymerization degree of slag are the lowest. The binding capacity of Fe with O2- become stronger as Fe element is converted from Fe2+ to Fe3+, which makes the slag difficult to diffuse. It makes the viscosity of nickel slag increases rapidly and the smelting conditions become deteriorate. Therefore, the ratio of Fe2+/Fe3+ should be controlled strictly during nickel flash smelting. The simulated viscosity is consistent with measured value. It shows that the potential function reflects physical and chemical properties of nickel slag well.

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Effect of Vibrational Excitations of NO on Stereodynamics for Reaction C(3P)+NO(X2Π)→CO(X1Σ+)+N(2D) MA Jianjun, ZOU Yong 2021, 38(2): 224-230.  DOI: 10.19596/j.cnki.1001-246x.8241 Abstract ( )   HTML ( )   PDF (4759KB) ( )   Stereodynamic properties of reaction C(3P)+NO(X2Π)→ CO(X1Σ+) +N(2D) in different initial reagent vibrational states(v=0-3) are studied with quasiclassical trajectory method on potential energy surfaces(2A″ and 2A') at a collision energy of 0.23 eV. Angular distributions (P(θr),P(φr)) and PDDCSs (P00(ωt),P20(ωt)) in initial state are shown. It manifests that the vibrational excitation of NO has obvious influence on stereodynamic property of reaction occurring on 2A' PES, while it has weak effect on that occurring on 2A″ PES. It can be ascribed to character of potential energy surface.The reactions on two PESs are mainly governed by the ‘in-plane’ mechanism.

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A Conservative-chaos-based Key Distribution Protocol and Image Encryption Algorithm KANG Zhijun, CANG Shijian, LI Yue 2021, 38(2): 231-243.  DOI: 10.19596/j.cnki.1001-246x.8209 Abstract ( )   HTML ( )   PDF (29301KB) ( )   Since a chaotic attractor can be reconstructed with time-delay embedding method in dissipative chaotic systems, there are potential problems in chaos-based information encryption. Concerning this issue, we report a conservative-chaos-based key distribution protocol and image encryption algorithm. The encryption algorithm converts image data into initial value of a conservative chaotic system with Hash algorithm and forms an encryption mechanism of one-time pads. Then, a binary keystream is generated by combining conservative chaos with key distribution protocol, which is completed by both sender and receiver. The obtained binary keystream shuffles and diffuses the image data to obtain an encrypted image. It shows that the proposed algorithm is safe and reliable. It hides effectively a plain image, and resists common decryption algorithms. Besides, conservative chaos has no attractor thus the encryption algorithm is hard to crack.

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A Chaotic System with Adjustable Number of Coexisting Attractors YAN Minxiu, XU Hui 2021, 38(2): 244-252.  DOI: 10.19596/j.cnki.1001-246x.8218 Abstract ( )   HTML ( )   PDF (1196KB) ( )   A chaotic system with adjustable number of coexisting attractors was proposed with Silnikov theorem. Firstly, a chaotic system with simple structure is constructed based on a classical chaotic system. Dynamic properties of the system are investigated and chaotic characteristics of the system in the sense of horseshoe are verified. Then, multi-zero piecewise function is introduced into the system to expand balance point of the system with adding invariant set of the system. A chaotic system with adjustable number of coexisting attractors is established. Due to complexity of coexisting attractors, the system has potential application in secure communication.