1. School of Mechanical and Electrical EngineeringXi'an University of Architecture and Technology No. 13 Yanta Road Xi'an Shaanxi Province 710055 P. R. China
2. Laboratory for Automotive Transportation Safety Enhancement Technology of the Ministry of Communication (RPC)Chang'an University Middle-section of Nan'er Huan Road Xi'an Shaanxi Province 710064 P. R. China