1. School of Mechanical Engineering, Northwestern Polytechnical University, Xi’an 710072, P. R. China
2. Shaanxi Engineering Research Center for Digital Manufacturing Technology, Northwestern Polytechnical University, Xi’an 710072, P. R. China
3. School of Physical Science and Technology, Northwestern Polytechnical University, Xi’an 710129, P. R. China
4. Inner Mongolia Institute of Dynamical Machinery, Hohhot, Inner Mongolia 010010, China