1994.4--1995.8           Computer Graphics Lab, Brigham Young University

1997.2--1997.7           CAD/CAM Center, Hong Kong University of 

                                  Science and Technology

1999.7--2000.4           Computer Science Department, Brigham Young 

                                  University

2000.1--2000.1           Computer Science Department, Rice  University

2001.7--2001.9           Department of Computer Science and Information

                                  system, University of  Hong Kong

2002.7---2002.8           Department of Computer Science and Information

                                   System,  University of Hong Kong

2002.11—2002.11       School of Computing, National Singapore University

2003.08---2003.09       Institute of Applied Geometry, John--Kepler Unverisity (Linz)          

2005.01--2005.02         Department of Computer Science, Rice University.