Temporal broadening of pulsed waves propagating through turbulent media

Pulse signals, propagating through a turbulent medium such as the ionosphere, can be distorted by dispersion and scattering from both the background medium and irregularities embedded in. Thus, the mean square pulse width is changed, and temporal broadening is introduced. We carry out a study on the temporal broadening with theoretical analyses and numerical simulations by using an analytical solution of two-frequency mutual coherence function obtained recently by iteration. As a case of study, pulse broadening is investigated in detail in trans-ionospheric propagation. Results show that most contributions are mainly from the dispersion of the background ionosphere and scattering effects of electron density irregularities in most cases.     

美军应对电磁环境效应与频谱支持的做法

电子系统的电磁环境适应性与频谱依赖系统的频谱需求的满足程度都将影响系统效能的有效发挥,这些问题对现代和未来战场的影响越来越突出。从政策文件要求、实现程序与方法方面介绍了美国国防部解决电磁环境效应控制和频谱支持问题的方法,可对我军在相关领域的发展提供良好的借鉴。     

用数字技术改进外语教学课件的探讨

本文设想利用图像、灯光、音乐的数字化，营造一种全方位外语学习环境，寓教于乐，全面提高学生的听、说、读、写、译能力，培养出具有较高外语水平的复合型人才。     

湍流介质中传播的脉冲时间展宽特性

脉冲信号通过诸如电离层等湍流介质传播时, 受来自介质背景和分布其中的不规则体的色散和散射的影响, 将导致波形形变. 均方脉冲宽度将发生改变, 导致时域内的展宽效应. 利用最近由迭代方法而得到的双频互相干函数的解析解, 从理论分析和数值模拟两方面研究了脉冲的时间展宽特性. 作为例子, 详细研究了穿透电离层传播的情况. 结果表明在大多数情况下展宽的贡献主要来自于背景电离层的色散和电子浓度不规则体的散射效应.