基金This work was supported in part by Natural Science Foundation of China under Grant No. 11501412. The second author＇s research is supported by Natural Science Foundation of China under Grant No. 11531014.
基金supported by National Natural Science Foundation of China(No.51308058)the “Hundred Talents Program”of Shaanxi Province, the Project of Shaanxi Province Collaboration and Innovation Program (No.2015XT-29)+1 种基金the Fundamental Research Funds for the Central Universities(No.CHD2011TD015)Application Basic Research Project of the Ministry of Transport (No.2014 319 812 240)