[1] Yale Univ, Sch Engn & Appl Sci, New Haven, CT 06250 USA
[2] Xian Univ Technol, Sch Mat Sci & Engn, Xian 710048, Peoples R China
[3] Shandong Univ, SDU ANU Joint Sci Coll, Weihai 264209, Peoples R China
[4] Xi An Jiao Tong Univ, Sch Elect Sci & Engn, Elect Mat Res Lab, Key Lab, Xian 710049, Peoples R China
[5] Nanyang Technol Univ, Sch Elect & Elect Engn, Singapore 639798, Singapore
[6] North Carolina State Univ, Wilson Coll Text, Raleigh, NC 27695 USA