An Analysis of an SIRS Epidemic Model with General Direct Immunization in Networks北大核心CSCD

We consider an SIRS epidemic model with a general direct immunization rate on networks. By constructing suitable Lyapunov functions, we find that the dynamical behvaior of the model is completely determined by the epidemic threshold λc. When λ≤λc, the disease-free equilibrium is globally asymptotically stable; when λ>λc, the endemic equilibrium is globally asymptotically stable. In addition, we propose a uniform direct immunization and a targeted direct immunization. The results show that under the same average immunization rate s there exists a critical immunization-lost rate δc so that the epidemic threshold of the targeted direct immunization is smaller (larger) than that of the uniform direct immunization if δ<δc(δ>δc). © 2017, The Journal of Agency of Complex Systems and Complexity Science. All right reserved.     

基于磁性微泡对比剂的超声和磁共振影像融合算法

文中提出了一种新的基于磁性微泡对比剂的超声影像和磁共振影像之间的融合算法．首先利用磁性微泡对比剂对体模进行超声和磁共振显影,并对显影进行边缘分割．运用非采样contourlet变换（nonsubsampled contourlet transform．NSCT）对源图像进行分解,然后对低频子带系数采用自适应动态加权非负矩阵分解（dynamic weighted non-negative matrix factorization．DWNMF）结合分割图像进行融合．然后对各带通方向子带系数采用空间频率激励的脉冲耦合神经网络进行融合,最后利用NSCT逆变换得到融合图像．研究结果表明,利用磁性微泡对比剂并结合上述算法对超声影像和磁共振影像进行融合,可以获得预期的融合效果．     

激光功率对6061-T6铝合金激光填丝焊接头组织及性能的影响

采用激光填丝焊将厚度为2 mm和3 mm的6061-T6铝合金板材进行搭接叠焊,研究激光功率对接头成形质量的影响,分析了接头的显微组织和力学性能。结果表明,增大激光功率可以有效增加热输入量,焊道逐渐宽化,焊缝熔深增加。进一步分析发现,焊缝中心区和热影响区的析出相均为Mg₂Si。硬度试验结果表明,焊缝中心区由于细小等轴晶和析出相的双重作用,硬度远高于母材区与热影响区的。拉伸试验结果表明,接头的抗拉强度随激光功率的增大而升高,激光功率由2.0 kW升高至2.8 kW,抗拉强度升高约39%。     

Parallel Optimization of the Crystal-KMC on Tianhe-2

The Kinetic Monte Carlo(KMC) is one of the commonly used methods for simulating radiation damage of materials. Our team develops a parallel KMC software named Crystal-KMC, which supports the Embedded Atom Method(EAM) potential energy and utilizes the Message Passing Interface(MPI) technology to simulate the vacancy transition of the Copper(Cu) element under neutron radiation. To make better use of the computing power of modern supercomputers, we develop the parallel efficiency optimization model for the Crystal-KMC on Tianhe-2, to achieve a larger simulation of the damage process of materials under irradiation environment. Firstly, we analyze the performance bottleneck of the Crystal-KMC software and use the MIC offload statement to implement the operation of key modules of the software on the MIC coprocessor. We use Open MP to develop parallel optimization for the Crystal-KMC, combined with existing MPI inter-process communication optimization, finally achieving hybrid parallel optimization. The experimental results show that in the single-node CPU and MIC collaborative parallel mode, the speedup of the calculation hotspot reaches 30.1, and the speedup of the overall software reaches 7.43.     

水下航行器多目标制导能力评估方法

水下航行器多目标制导能力评估是目前水下多目标精确制导研究中亟待解决的问题。根据水下航行器多目标制导系统的主要任务和技术特点,运用灰色关联分析理论对水下多目标精确制导能力进行了综合评估研究,提出了水下航行器多目标制导能力评估方法。通过水下攻防对抗仿真试验,验证了该方法的可行性和合理性,为水下航行器多目标制导系统的技术优化和方案决策提供科学的理论依据。     

基于新算法的P码序列捕获处理器设计与实现

通常P码的捕获是利用C/A码来完成的。但是,考虑到实际的战场可用性,利用C/A码引导的P码捕获方式不再具有较好的可靠性。同时考虑到P码信号的特点,对P码信号进行直接、快速的相关捕获是首先要解决的问题。因此,在研究相应理论的基础上,对提出的新的P码直接捕获算法进行硬件设计,实现了P码序列捕获处理器。在实验室环境下对序列捕获处理器进行测试,结果验证序列捕获处理器可以有效捕获GPSP码信号。     

装甲战车训练模拟器综合显示终端仿真系统设计与实现

采用模拟器进行数字化武器装备的操作训练是当今信息化装备发展的需要,综合显示终端仿真系统是装甲战车训练模拟器中重要的组成部分.基于实装通过在PC机上VAPS平台和VC 开发环境相结合来构建仿真系统,可以降低设计成本,缩短设计周期.介绍了仿真系统的结构、设计思想和实现方法,给出了系统组成框图和开发流程,重点研究了仿真界面显示和外部驱动程序等关键问题,实现了某型装甲战车训练模拟器综合显示终端仿真系统,满足了装甲车辆综合显示终端信息化训练的需要,具有较高的军事和经济价值.     

Comparison between several satellite constellation schemes for MEO-TDRSS of China

The satellite constellation classes, which are suitable for the medium earth orbit tracking and data relay satellite system （MEO-TDRSS） of China, are investigated. On the basis of the functionality and the traffic distribution characteristic of MEO-TDRSS, the coverage performance and inter-satellite link properties of four different constellation schemes are compared by simulations. Simulation results indicate that the rosette and common-track constellations, whose satellites are distributed on the celestial sphere more uniformly, are appropriate for the implementation of MEO-TDRSS of China.     

Multiple targets vector miss distance measurement accuracy based on 2-D assignment algorithms

An extension of 2-D assignment approach is proposed for measurement-to-target association for improving multiple targets vector miss distance measurement accuracy. When the multiple targets move so closely, the measurements can not be fully resolved due to finite resolution. The proposed method adopts an auction algorithm to compute the feasible measurement-to-target assignment with unresolved measurements for solving this 2-D assignment problem. Computer simulation results demonstrate the effectiveness and feasibility of this method.