1. Professor, School of Economics and Management, Chang’an Univ., Middle Section of Nanerhuan Rd., Yanta District, Xi’an 710064, P.R. China (corresponding author).
2. Assistant Professor, Dept. of Construction Management, California State Univ., Fresno, 2320 E San Ramon Ave., MS/EE 94, Fresno, CA 93740.
3. Professor, School of Civil Engineering, Chang’an Univ., No. 161, Chang’an Rd., Yanta District, Xi’an 710061, P.R. China.