Affiliation: | a Lanzhou Railway Institute, Lanzhou, Gansu 730070, People's Republic of China b National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan c Core Research for Evolutional Science and Technology (CREST), JST, 2-1-6 Sengen, Tsukuba, 305-0047, Japan |