[Liao, Calvin C. Y.] Cent China Normal Univ, Natl Engn Res Ctr E Learning, Wuhan, Hubei, Peoples R China.^[Chang, Wan-Chen] Natl Cent Univ, Grad Inst Learning & Instruct, Taoyuan, Taiwan.^[Chan, Tak-Wai] Natl Cent Univ, Grad Inst Network Learning Technol, Taoyuan, Taiwan.