Supported by Knowledge Innovation Program of the Chinese Academy of Sciences (No. KZCX2-YW-Q07-05;KZCX2-YW-Q07-04);Yantai Municipal Science and Technology Development Program(No. 2007323);the Science and Technology Bureau of Yantai City(No. 2009164);the Natural Science Foundation of Hainan Province (No. 309010);the Science and Research Programme of Education Department of Hainan Province(No. Hj2009-21)