1. School of Chemistry and Chemical Engineering, Beifang Univ. of Nationalities, No. 204 Wenchang, North-St., Xixia District, 750021 Yinchuan, Ningxia, CN
2. School of Electromechanical Engineering, Beifang Univ. of Nationalities, No. 204 Wenchang, North-St., Xixia District, 750021 Yinchuan, Ningxia, CN (Corresponding author), e-mails: zdlsir@163.com; zdlsir@nun.edu.cn
3. State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi'an Jiaotong Univ., 28 West Xianning Rd., 710049 Xi'an, CN