1．Department of Information Engineering , North China Institute of Water Conserv ancy and Hydroelectric Power ,Zhengz hou 450008,China；2．Department of Mathematics ,Yellow River Conserv ancy Technical In- stit ute ,Kaifeng 475001,China
About author:YANG Qiao（1955－） male native of Xiayi Henan an associate professor of North China Instituter of Water Conservancy and Hydroelectric Power M．S．D． engages in differential equations and complex approximation theory .
