[1] Huazhong Univ Sci & Technol, Sch Elect & Elect Engn, State Key Lab Adv Electromagnet Engn & Technol, Wuhan 430074, Hubei, Peoples R China
[2] Univ Rhode Isl, Dept Elect Comp & Biomed Engn, Kingston, RI 02881 USA
[3] Univ Liverpool, Dept Elect Engn & Elect, Liverpool L69 3GJ, Merseyside, England