基金Foundation item： Supported by the National Natural Science Foundation of China（10771064） Supported by the Natural Science Foundation of Zhejiang Province（YT080197, Y6090036, Y6100219） Supported by the Foundation of Creative Group in Colleges and Universities of Zhejiang Province（T200924） Acknowledgement The author would like to express his thanks to his supervisor, Prof HU Zhang-jian, for his guidence.
