By the end of the Song Dynasty, the Chinese invented multiple-stage rockets.
到宋朝末期，中国人发明了多极火箭。
2
The optimization problem was formulated as a multiple-stage optimal control problem and solved by a forward and backward iteration loop.
整个最优化问题被描述成一个多阶段系统优化控制问题，通过一个向前和向后的迭代循环解决。
3
The decolorization ratio of syrup in sulfitation process is higher through experiments with multiple-stage flotation of syrup than that with single-stage flotation.