1997: Visiting Faculty, Dept. of Computer Science, Purdue University, West Lafayette, Indiana, 1997 (August). 1996: Visiting Faculty, Dept. of Applied Mathematics, Cambridge University, UK, (August-September). Visit was financially supported by the Royal Society(UK)  and the Lebanese  National Council for Scientific Research. 1995: Visiting Faculty, Dept. of Computer Science, Arizona State University,  USA, (September). 1994: Visiting Faculty, Dept. of Computer Science, Arizona State University,  USA, (September). 1993: Visiting Faculty, Dept. of Computer Science, Arizona State University,  USA, (summer). 1992 - Present: Assistant Professor, Dept. of Math., Faculty of Arts and Sciences,  American University of Beirut, Lebanon. 1992: Visiting Research Engineer, Dept. of Ocean Engineering, Massachusetts  Institute of Technology, USA, (summer). 1992: Invited visitor, Hewlett-Packard Factories, Germany, (February). 1987 - 1992:  Assistant Professor in computer science, Dept. of Math. and Computer Science, United Arab Emirates University, United Arab Emirates 1989 : Visiting Lecturer and Researcher, Fachbereich Mathematik und Informatik,   University of Bremen,  Germany, (summer). 1985 - 1987:   Assistant Professor in computer science, Dept. of Math.,  Lebanese  University, Lebanon.  I was the chairman of the Committee of Computer Science.