1. Associate Professor, Dept. of Engineering Mathematics, Riga Technical Univ., Riga, Latvia LV 1658; Presently, Visiting scholar, Dept. of Civil Engineering, Hong Kong Univ. of Science & Technology, Kowloon, Hong Kong.
2. Associate Professor, Dept. of Civil Engineering, The Hong Kong Univ. of Science & Technology, Kowloon, Hong Kong (corresponding author).