交替前进

提出了交替前进张拉法。

The text puts forward Forward Alternately Tension Method .

在此基础上，又提出了交替前进张拉法，在不增加施工难度及工期的基础上，减小了张拉步长，保证大桥各部件在施工过程中安全。

Based on this , the method of stretch leapfrogging is put forward , stretch step size is reduced and the safety of bridge can be ensured during the construction without increasing construction difficulty and duration .

百余年来，我国高等师范教育的发展无不围绕着高师教育体系的定向与非定向、封闭与开放的反复交替而曲折前进。

Among hundreds of years , the development of higher normal education in our country advanced to the alternation of closed or open system way .

两个头部交替迈步沿微管前进，最快每秒100步（800纳米）。

The heads take turns stepping along the microtubule , at a rate of up to100 steps ( 800 nanometers ) per second .