| 1974 - 1976 |
Research Assistant, Lehrstuhl A für Mathematik, RWTH Aachen |
| 1976 - 1981 |
Wissenschaftlicher Assistent, Institute of Applied Mathematics |
| 1979 - 1980 |
Research Fellowship, IBM T.J. Watson Research Center, Yorktown Heights, NY, USA |
| 1981-1987 |
Professor (C3) Mathematics, University of Bielefeld |
| 1987 - 1992 |
Professor (C4) Mathematics, Free University of Berlin |
| 1992 - 2017 |
Professor (C4) Mathematics, RWTH Aachen |
| May 1998 |
Offer of the position of the Director of the Institute of Applied Mathematics, Purdue University, USA |
| Feb. 2003 |
Offer of a full Professorship, DFG Research Center, TU Berlin |
| Aug. 2005 |
Adjunct professorship, University of Columbia, South Carolina, USA |
