supported by SciTech Found of the CAEP Key Laboratory of Precision Manufacturing Technology(2012CJMZZ00009,2014ZA001);Visiting Scholar Found of the State Key Laboratory of Fundamental Science of Micro/Nano-Device and System Technology(Chongqing University)(2013MS04);IEE CAEP SciTech Innovation Found(S20141203);SWUST Postgraduate Innovation Found(13YCJJ36,14YCX107,14YCX109,14YCX111)