1. National Key Laboratory of Science and Technology on Helicopter Transmission, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, PR China
2. Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
3. Key Laboratory for Precision and Non-traditional Machining Technology of the Ministry of Education, Dalian University of Technology, Dalian 116023, PR China