Research Associate, Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, Pa., U.S.A., June 2 - Dec 15, 1972. Research Associate, Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, Pa., U.S.A., May 15 - Aug 6, 1976. Visiting Research Assistant Professor, Solid Mechanics Division, University of Waterloo, Waterloo, Ontario, Canada, Sept 1 - Nov 30, 1978. Visiting Associate Professor of Applied Mathematics, Department of Applied Mathematics and Computer Science, University of Virginia, Charlottesville, Va., U.S.A., Jan 16 - May 30, 1981. Visiting Research Professor, Department of Civil Engineering, University of Waterloo, Waterloo, Ontario, Canada, July 1 - Aug 15, 1986. Visiting Professor, Department of Solid Mechanics, Lund Institute of Technology, Sweden, Feb 1 - March 31, 1993. Professor of Mechanics, Division of Mechanics, Lund Institute of Technology, Lund University, Sweden, 1995-1997. Visiting Professor, Department of Mechanical Engineering, University of Sussex, England, July 13 - Aug 3, 1997. Charles Schmidt Distinguished Visiting Professor, Center for Applied Stochastics Research, Florida Atlantic University, Boca Raton, Florida, Aug 15 - Sept 15, 1998. Senior Research Associate, Department of Civil Engineering and Geological Sciences, University of Notre Dame, Indiana, July 11 - 25, 1999. Visiting Scholar, Department of Civil Engineering and Geological Sciences, University of Notre Dame, Indiana, July 17 – Aug 1, 2000. Melchor Visiting Professor, Department of Civil Engineering and Geological Sciences, University of Notre Dame, Indiana, Sept 10 – Nov 10, 2001. Ph.D. course ‘Non-Linear Modeling and Analysis of Structures and Solids’, Laboratory of Structural Mechanics, Helsinki University of Technology, Aug 30 – Sept 3, 2004. Visiting Professor, Federico Santa Maria University, Valparaiso, Chile, Nov 12-19, 2005. Ph.D. course ‘Finite element method – Nonlinear systems’, Lund Institute of Technology, October-December, 2005.