Wang Yongan, bom in 1979, he is a Ph.D candidate in Mechanical Engineering Department of Dalian University of Technology. He also received his B.S. and M.S. degrees from ShanDong University of Science and Technology in 2002 and 2005 respectively. His research interests include the simulation of flow characteristic for complicate hydraulic channel system and the optimal design for hydraulic manifold block. To whom correspondenee should be addressed. E-mail: wangyong-an@126.com