the National Natural Science Foundation of China under Grant No.90409007(国家自然科学基金);the11th Five Years Key Programs for Sci.&Tech.De-velopment of China under grant No.2006038002003(国家"十一五"科技支撑项目);the Tackle Key Problem Fund of Sichuan Province under Grant No.2006Z01-027(四川省科技攻关项目);Sichuan University Youth Foundation under Grant No.06036(四川大学青年基金)