1. 1 Department of Electrical Engineering , Hebei Vocational University of Technology and Engineering , Xingtai , Hebei , , China .
2. 2 SEGI College Kota Damansara, SEGI University , Petaling Jaya , Selangor , , Malaysia .
3. 3 Engineering Training Center , Yanshan University , Qinhuangdao , Hebei , , China .