1. School of Mechanical and Precision Instrument Engineering, Xi’an University of Technology, Xi’an 710048, P. R. China
2. Rubber Research Institute, Chinese Academy of Tropical Agricultural Science, Haikou 570100, P. R. China
3. School of Civil Engineering and Architecture, Xi’an University of Technology, Xi’an 710048, P. R. China
4. Huanghe S & T University, Zhengzhou 450006, P. R. China
5. Department of Mechanical and Electrical Engineering, Sichuan Engineering Technical College, Deyang, Sichuan 618000, P. R. China