Today, our highly esteemed colleague Karlheinz Lehner is leaving us for his well-deserved retirement after 34 years.

After his scientific career had already begun in the mid-1980s at the University of Dortmund (now the Technical University of Dortmund), employment at the university followed directly after his studies in computer science and math. He worked as a research assistant in the field of "Information and Communication Technology" with a focus on "Civil Engineering" under Prof. habil. Dr.-Ing. Hartmann. In the following years he and Karlheinz moved together to Bochum. After passing his Dr. - Ing dissertation, he became particularly involved in teaching, research and science administration.

Students knew him especially from the subjects of the optional area: Modern Programming Concepts in Engineering, Parallel Computing and Knowledge-Based Methods. But not only because of that. He had a heart for students; with his calm and relaxed manner he was always ready to help them with questions and problems. This was also reflected in the large amount of final theses Karlheinz supervised over the years. This not only concerned the students of the RUB but also those of the Vietnamese-German University (VGU). At VGU, he repeatedly gave lectures in Modern Programming Concepts and Design Optimization for a few weeks as part of the Computational Engineering course from 2009-2017.

He is also highly appreciated by the Collaborative Research Center (SFB) 837 and his work over many years. In particular, his technical and organizational achievements in the area of major publications and project proposals are worth mentioning. "Without you, this would not have been possible."

Karlheinz was often in the background, but all the more one knew that one could rely on him. If his help or expertise was needed, he was always available with advice and action - and not only for the LaTeX witchcraft.

Karlheinz we all look back on many years together, to which you made a great contribution, with all large and small tasks.

Many thanks for your work and support in all areas!!!

...and so on and so forth...