**Acknowledgements**

The author would like to thank the National S&T Major Project (Grant No. ZX06901), the Independent Research Projects of Tsinghua University (20111080971) and Research Fund for the Doctoral Program of Higher Education of China(20121010010) for the financial support provided. Also, thanks go to Bing Liu, Youlin Shao, Jing Wang, Junguo Zhu, Bing Yang, Bingzhong Zhang, as my best colleagues. All the results of this chapter are completed together with them. The author himself is responsible for all of the errors of this chapter.
