A New Method of Shock Dynamic Analysis of Multi-degree-of-freedom Systems

A new method is presented to analyze multi-degree-of-freedom （MDOF） dynamic systems subjected to an external shock excitation. A two-degree-of-freedom theoretical system with linear characteristics is exemplified to illustrate the procedure of this method. The equations of motion of the dynamic system are established via matrix method. The dynamic responses of the dynamic system under an external shock excitation of a half-sine type are obtained by MATLAB and ANSYS. It is proved that the new method is helpful to analyze MDOF dynamic systems.     

新型高功率高重复频率脉冲电源研制

介绍了一台适用于某强流电子束加速器的高功率、高重复频率脉冲电源,其基本电路采用三相半波整流构成直流电源,利用LRC直流谐振充电原理实现脉冲电源的重复频率运行。     

包晶Nd-Fe-B合金定向凝固与形核有关的组织选择

对Nd_(14)Fe_(79)B_7合金进行了定向凝固试验与形核有关的凝固组织形成研究.发现凝固速率为200和500μm/s试样中局部区域有粗大等轴Fe枝晶形成;并且在凝固速率500 μm/s的试样中存在α-Fe枝晶与Nd_2Fe_(14)B枝晶交替生长的带状组织.分析表明,当凝固速率为200μm/s时,定向生长的Fe枝晶界面前沿液相中的温度分布相对于γ-Fe平衡液相线是过冷的;当凝固速率为500μm/s时,Fe枝晶生长界面前沿相对于γ-Fe和Nd_2Fe_(14)B平衡液相线均会产生过冷.理论分析可以解释定向凝固试样中等轴晶和枝晶带状组织的形成.