1. Department of Mechanical and Electrical Engineering, Hebei Agricultural University, Baoding 071001, China;
2. Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, OH 43210
3. Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, OH 43210 e-mail:
4. Department of Mechanical and Electrical Engineering, Hebei Agricultural University, Baoding 071001, China