1. School of Electrical and Photoelectronic Engineering, Changzhou Institute of Technology, No. 299 South Tongjiang Road, Changzhou, Jiangsu 213002, P. R. China
2. Department of Electrical and Computer Engineering, The University of Auckland, Auckland, New Zealand
3. Department of Chemical and Materials Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore City 639798, Singapore