船载卫通天线圆极化方式切换改进方案

对船载卫通天线圆极化状态下A、B极化切换方案进行了分析,阐述了现行切换方案会改变和差通道传输特性,致使跟踪接收机校相值全部作废的缺点。由此提出了在原和差网络的基础上,增加组成B极化和差网络的改进方案,以及将圆极化器单向转动的基础上,增加反方向转动45°的改进方案。这2套改进方案均易于实现,且均克服了现行方案的不足,可在不改变和差通道传输特性的条件下快速完成极化切换。     

物联网感知层的安全机制优化探究

文中针对物联网感知层的核心技术RFID的安全问题加以探究,基于PUF技术和A5流密码,有效地将两种技术结合起来,提出了一种改进的安全机制,可很好地抵御信息传输中跟踪与窃听攻击、重放攻击,以及保证信息传输的机密性和完整性,同时该改进的安全机制可以使得标签廉价。这种折中的安全体制,可以很好地改善RFID系统现有的安全体制,促进物联网安全健康发展。     

船载卫星天线风载特性数值分析

论述了利用计算流体动力学数值计算方法分析抛物面天线风载的原理。采用基于Reynolds时均N-S方程K-Omiga湍流模型对抛物面天线表面风压进行数值模拟,得到了天线表面风压、风速分布情况,并分析了风压、风速在天线正面和背面的分布特性。在此基础上,计算了层流、K_Epsilon、RNK_Epsilon和LES大涡模拟等湍流模型的数值模拟结果,分析不同湍流模型对风阻的影响,同时阐述了不同风速与风载、风载系数的关系。     

Effect of traps' adjacency on the electric field dependence of mobility in organic systems

In some organic materials, varying the finite distance between adjacent carrier traps modifies the Coulomb potential around each trap, resulting in a more complex field-dependence of mobility, differing from（but not incompatible with） the usually considered relationship of ln μ∝E^1/2, a relationship which has been successfully explained by the Poole–Frenkel effect. To investigate the influence of the adjacency of traps, a model system is proposed, which consists of two traps separated by distance α. Our numerical calculation shows that with increasing α, the dependence of mobility on the electric field changes from linear to exponential. Moreover, beyond a certain large α, i.e., as the distance to the nearest trap approaches infinity, the proposed model is essentially the same as the Poole–Frenkel effect. The proposed model accounts for the effect of the energy barrier shape, especially the effect of the location of the potential-energy maximum, a phenomenon which is not accommodated in the Poole–Frenkel model. Because the model assumes the Coulomb interaction between the adjacent traps, it applies to those charged traps which may exist in organic materials for various reasons.     

基于改进鲸鱼优化算法的最大2维熵图像分割

为了避免原鲸鱼优化算法早熟收敛、易陷入局部最优等缺陷,首先在原鲸鱼优化算法初始化过程中采用了猫映射产生混沌序列结合反向解方法取代随机产生初始种群;其次在位置更新机制上采用了疯狂算子和黄金正弦算法的方法;最后将改进鲸鱼优化算法用于寻求图像2维最大熵来确定图像分割最佳阈值的选取.对10个经典基准函数进行了试验仿真验证,得到...     

一种完全集成的单光子雪崩二极管探测器

针对单光子雪崩二极管探测器,提出了一种紧凑的主动淬灭电路和读出电路,能够快速控制雪崩电流淬灭,对光子雪崩脉冲进行线性和对数方式的模拟计数。该电路能够最大限度地减少淬灭时间,缩短死区时间,扩大读数的动态范围,大幅度减小每个像素单元的面积,提高像素密度。采用SMIC 0.18 μm CMOS工艺进行仿真,得到输入雪崩脉冲宽度约为8 ns,线性计数达到10³次,而对数计数可以达到10⁵次,像素单元占空比得到显著提高。