[Zhu, Zhiyuan] Chinese Inst Elect, Consulting & Stand Res Ctr, Beijing, Peoples R China.^[Ren, Dongchun] Beijing 7Invensun Technol Co Ltd, Res Ctr, Beijing, Peoples R China.^[Zhou, Guangyou;Zhou, Yin] Cent China Normal Univ, Sch Comp, Wuhan, Hubei, Peoples R China.