1. College of Mechanical and Electrical Engineering, Qingdao University, Qingdao 266071, P. R. China
2. State Key Laboratory of Bio-Fibers and Eco-Textiles, Qingdao University, Qingdao 266071, P. R. China
3. State Key Laboratory of High-Efficiency Utilization of Coal and Green Chemical Engineering, Ningxia University, Yinchuan 750021, P. R. China