Department of Mechanical and Industrial Engineering, Southern Illinois University Ed-wardsville, IL 62026-1805, USA
Fax: +1 618 650 2555 Email: aluo@siue.edu
Department of Mathematics, IHN, Blekinge Institute of Technology, S-371 79 Karlskrona, Swe-den
Fax: +46 455 385 407 Email: nib@bth.se