舰载箔条对抗相参体制末制导雷达技术研究

针对相参体制末制导雷达具有较高的抗箔条技术这一特点,对舰载质心箔条的极化特性、干扰特性和布放技术进行了分析,提出了改革箔条丝加工技术、改进质心箔条使用方法的干扰相参体制末制导雷达技术对策。     

IP网络流量测量的研究与实现

网络流量测量是研究网络行为的基础．也是分析网络状况、掌握网络流量特性的有效方法。为了更好地管理网络资源．保障服务质量，对网络流量测量体系框架及测量系统的实现进行了研究．并基于TMA（Traffic Monitor and Analyzer）监测数据对IP网络的流量特性进行了分析．为网络规划及技术研究提供了参考。     

材料科学中的高分辨电子显微学—发展历史、现状与展望

本文综述了材料科学中的高分辨电子显微学发展历史、现状与展望。重点讨论了在高分辨电子显微学中能直接观察物质中原子排列的直接成像法 ,能区分原子种类的选择成像法、能量过滤选择成像法和 Z-衬度像 ,能研究物质结构变化动态过程的分辨时间高分辨电子显微学 ,能定量地分析物质结构的定量高分辨电子显微学和遥控电子显微术的发展以及其在材料科学中的应用和展望     

Impact of extrinsic and intrinsic parameter fluctuations on CMOScircuit performance

The yield of CMOS logic circuits satisfying a specific high performance requirement is demonstrated to be significantly influenced by the magnitude of critical-path delay deviations due to both extrinsic and intrinsic parameter fluctuations. To evaluate the impact of these parameter fluctuations, a static CMOS critical-path delay distribution is calculated from rigorously derived device and circuit models that enable projections for future technology generations. Two possible options are explored to attain a desired yield: (1) reduce performance by operating at a lower clock frequency; and (2) increase the supply voltage and, consequently, power dissipation, to satisfy the nominal critical-path delay. For the 50-nm technology generation, the delay and power dissipation increases are 12%-29% and 22%-6%, respectively, for extrinsic parameter standard deviations ranging from (a) 5% for effective channel length and 0% for gate oxide thickness and channel doping concentration to (b) 10% for effective channel length and 5% for gate oxide thickness and channel doping concentration. Combining both extrinsic and intrinsic fluctuations, the delay and power dissipation increase to 18%-32% and 31%-53%, respectively, thus demonstrating the significance of including the random dopant placement effect in future CMOS logic designs     

基于稀疏重构的全极化SAR联合多维重建

各极化通道独立处理和三维分步成像会忽视数据之间的关联性,造成散射中心的失配以及极化散射矩阵获取的不准确。鉴于此,该文提出一种基于稀疏重构的全极化联合多维重建方法。该方法通过设置联合稀疏约束对所有极化通道及所有维度进行联合,将全极化多维重建建模为多通道联合稀疏重构问题。通过数据插值对模型简化后,结合三维快速傅里叶变换、共轭梯度法和牛顿迭代法给出一种高效的模型求解方法,可以同时得到极化散射矩阵和目标三维信息。该文方法保证了不同极化通道、不同维度的稀疏支撑集一致,且充分利用了数据之间的关联性带来的额外信息。基于仿真数据和电磁计算数据的实验结果表明,该方法的性能不受目标类型影响,具有一定的抗噪性,能有效地获取目标的多维重建结果,得到的三维成像结果分辨率高且极化散射矩阵估计精度高。      

On Analysis of the Contention Access Period of IEEE 802.15.4 MAC and its Improvement

The release of IEEE 802.15.4 medium access control (MAC) and physical layer specifications represents a significant milestone in promoting deployment of wireless sensor networks. This paper first analyzes the performance of the contention access period (CAP) specified in the IEEE 802.15.4 standard by integrating the discrete-time Markov chain models of the node states and the channel states. Then a modified CAP is analyzed, which could significantly improve the performance of the system. Based on the theoretical analysis of the CAP and the effect of the modification, we have that in the saturated network of IEEE 802.15.4, the collision probability is large, and the throughput is small. The main reasons are the employment of slotted carrier sense multiple access-collision avoidance and the mechanism that if a frame transmission cannot be completed before the end of the CAP, it has to wait until the start of the next CAP. Thus an enhanced collision-avoidance MAC protocol, which achieves a better performance and is compatible with the IEEE 802.15.4 standard, is proposed to improve the performance of the system. Extensive simulations validate our conclusions.     

Atomic‐Scale CoOx Species in Metal–Organic Frameworks for Oxygen Evolution Reaction

The activity of electrocatalysts strongly depends on the number of active sites, which can be increased by downsizing electrocatalysts. Single‐atom catalysts have attracted special attention due to atomic‐scale active sites. However, it is a huge challenge to obtain atomic‐scale CoO_x catalysts. The Co‐based metal–organic frameworks (MOFs) own atomically dispersed Co ions, which motivates to design a possible pathway to partially on‐site transform these Co ions to active atomic‐scale CoO_x species, while reserving the highly porous features of MOFs. In this work, for the first time, the targeted on‐site formation of atomic‐scale CoO_x species is realized in ZIF‐67 by O₂ plasma. The abundant pores in ZIF‐67 provide channels for O₂ plasma to activate the Co ions in MOFs to on‐site produce atomic‐scale CoO_x species, which act as the active sites to catalyze the oxygen evolution reaction with an even better activity than RuO₂.     

宽带卫星Mesh网多址接入信道预测分配方案研究

该文针对具有网状(Mesh)拓扑结构的宽带卫星通信网,研究了分布式控制多址接入信道分配策略。提出了一种基于自相似业务流量混沌预测的混合动态分配方案。利用OPNET软件建立了仿真系统,研究比较了信道分配周期、信道负载以及业务流自相似程度对几种方案性能的影响。仿真结果表明,对于采用地球同步轨道(GEO)卫星、低轨(LEO)和中轨(MEO)卫星星座的宽带卫星Mesh网,所提出方案在高信道负载条件下都具有明显的优势。     

BOARD-LEVEL BUILT-IN SELF-REPAIR METHOD OF RAM

This paper describes the method of built-in self-repairing of RAM on board,designs hardware circuit,and logic for the RAM's faults self-repairing system based on FPGA.The key technology is that it util...