step-by-step method

2 is closely approximate to that obtained from " successive approximation method".

２非常接近用“逐步逼近法”［１］得到的σ０。

Under certain conditions,these systems are proved by mean value method and successive approximation method to have almost periodic solutions.

研究具有两个时间变量的概周期微分方程系的概周期解的存在性问题,在某些条件下,利用平均值法和逐步逼近法证明了这类方程系具有概周期解。