Dechirping of multicomponent chirp signal based on time-space decomposition and H∞ filter

In time-space domain, the multicomponent chirp signal is deoomposed into several monocornponent chirp signals. Based on H∞ filter, dechirping for the monocornponent chirp signal is achieved. When date length of the multicomponent chirp signal is short and SNR is low, this approach is applicable. It is insensitive to the exact knowledge of the statistics of the unknown disturbance and noise. Simulation results are presented to show the validity of the approach.

超细晶粒钢焊接热影响区微观组织的模拟研究

本实验对焊接热循环下热影响区晶粒结构的演变过程进行了模拟．特别时sS400超细晶粒钢焊接热影响区晶粒长大进行了实验研究。开发出基于微软系统的焊缝热影响区晶粒生长综合型三维MC仿真模拟系统。结果表明，MC仿真模拟系统是探讨焊接热影响区晶粒生长的有效方法。该方法不仅能模拟焊缝热影响区晶粒生长的非等温动力学过程，而且还能逼真地显现奥氏体颗粒。此外，还可轻易地将熟钉扎效应纳入到仿真模拟过程中。从MC仿真模拟获得的不同热输入下焊接热影响粗晶区颗粒尺寸与实际焊接头的实验测定结果基本相符．而且，模拟显示超细晶粒钢的晶粒增长程度大于传统钢种。随着热输入的增加，焊接热影响粗晶区晶粒生长迅速加快。由于Ss400超细晶粒钢晶粒增长的活化能较低，奥氏体颗粒可以在一个相时较低的温度下生长，所以焊接热影响粗晶区的范围变宽。