1. Ningbo Institute of Material Technology and Engineering (NIMTE), Chinese Academy of Sciences, Ningbo, Zhejinag Province 315201, China
2. Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario M5S 3G8, Canada
3. Department of Materials Science and Engineering, The University of Seoul, 90 Jeonnong-dong, Dongdaemoon-ku, Seoul 130-743, Republic of Korea
4. Department of Mechanical Engineering, Cheju National University, 690-756 Jeju-do, Republic of Korea