[1] Georgia Inst Technol, Atlanta, GA 30332 USA
[2] Hong Kong Polytech Univ, Hong Kong, Hong Kong, Peoples R China
[3] George Washington Univ, Washington, DC 20052 USA
[4] Ohio State Univ, Columbus, OH 43210 USA
[5] City Univ Hong Kong, Hong Kong, Hong Kong, Peoples R China
[6] CNR Ist Informat & Telemat, Rome, Italy