This volume is dedicated to Professor Xiaqi Ding,an academician of the Chinese Academy of Sciences,on the occasion of his eightieth birthday. Professor Xiaqi Ding was born on May 25,1928,in Tao Jiang county,Hunan province.He was graduated in 1951 from the Department of Mathematics,Wuhan University.Because of his outstanding academic performance,he was selected right after college for his study and research at