1. Department of Civil Engineering, National Chi Nan University, 1 University Road, Puli, Nantou, Taiwan 565, R. O. C. e-mail:
2. Faculty of Science, Department of Mathematics, Benha University, Benha, 13518Egypt
3. Department of Civil Engineering, National Chi Nan University, 1 University Road, Puli, Nantou, Taiwan 565, R. O. C.