1. Research Assistant Professor, Dept. of Mechanical Engineering–Engineering Mechanics, Michigan Technological Univ., 1400 Townsend Dr., Houghton, MI 49931. E-mail: qingdai@mtu.edu
2. Donald and Rose Ann Tomasini Assistant Professor of Transportation Engineering, Dept. of Civil and Environmental Engineering, Michigan Technological Univ., 1400 Townsend Drive, Houghton, MI 49931. E-mail: zyou@mtu.edu