两个物体的相互作用力总是大小相等,方向相反,同时出现或消失且作用于同一直线上。
It is a terrible thing for a man to find out suddenly that all his life he has been speaking nothing but the truth.
成功辨识的关键是找到一个足够灵活的模型结构,以捕捉系统的基本特征,同时又足够简单,可以从现有数据中估计出来。