利用有限元理论，求一二维梁的固有频率和振型。短边固定，给定长度、横截面积，弹性模量及材料密度已知。并对比理论计算结果进行分析。各参数自己设定。-Using finite element theory, seeking a two-dimensional beam natural frequencies and modes. The short side is fixed, given the length, cross-sectional area, modulus of elasticity

对各种PID 控制算法的详细说明描述，并比较各种PID的用法-Detailed descr iption of the PID control algorithm described in age and compare the usage of the PID

汽车碰撞整车模型，主要用的壳单元模型，比较详细，可以用在汽车安全的仿真计算。-The automobile collision vehicle model, compare the shell element model, mainly used in detail, can be used in the simulation of automobile safety calculation.