1. Information on http: /baike. baidu. com/view/1083305. htm.
2. Jiang Xingyu, Wang Shijie, Zhao Kai, Wang Wanshan: submitted to Journal of Mechanical Engineering (2010) (in Chinese).
3. Guo Jinyu, Zhang Zhong-bin, Sun Qing-yun: submitted to China Safety Science Journal(2008) (in Chinese).
4. Wang Xiulun,Yu Xiaoyang,Huang Yongsheng: submitted toJournal of Dalian Railway Institute(2005) (in Chinese).