Like other employees, professors retire when they turn 65. But there are exceptions. This week: Expert in acoustical imaging, Prof. Dries Gisolf (68).
Dries Gisolf graduated in 1971 with a degree in physical engineering. He completed his PhD in Utrecht in 1975. His career with Shell brought him to back to TU Delft as a professor in 2000, via Rijswijk, Oman, Drenthe, Australia, Malaysia, The Hague and Nigeria. He retired in 2010. He is also active as a musician, playing trombone in two big bands.
The room in the Applied Sciences Building appears remarkably bright and orderly. A colourful painting hangs on the wall above an empty table. No, Prof. Gisolf does not spend much time here. He spends most of his time at YesDelft, where his start-up company Delft Inversion is located. Today, he spent the entire day there as well, apart from a visit to the garage and two hours in the dentist’s chair. He cannot make an estimate of the number of hours. Five days, evenings and weekends – how many is that? “What is work, and what a hobby? For me, there’s no difference. I simply do what fascinates me”.
Despite the fact that Gisolf is in his golden years, (he began his studies at the Delft Institute of Technology in 1963), the Professor Emeritus seems more like a young entrepreneur. Until the age of 55, Gisolf worked for Shell and travelled all over the world. He enjoyed working on practical matters, all the while remaining a scientist, sitting at a table with a physics book on Sunday afternoons. He gradually developed the notion that the seismology used in industry had reached its limits. The interpretation of reflections of sound waves from the subsoil depends upon the physical soil model that is used. “They were simple models including a few geological layers and interfaces. these hadn’t changed in 30 years”.
When he was 55 and working in Nigeria, he applied for the position of Professor of Acoustical Imaging at TU Delft. This job offered him the opportunity to elaborate his ideas for improved modelling and, conversely, improved imaging. “The model has now been expanded with multiple reflections. This has made it more widely applicable, and we are now able to use the entire signal, where we previously used 10% and treated the remaining 90% as noise. That was the breakthrough”.
After his retirement in 2010, Gisolf worked with two former PhD students (Dr Peter Haffinger and Dr Panos Doulgeris) to build the company Delft Inversion, which offers the improved form of seismological analysis as a service to oil and gas companies. Before that time, Gisolf had been the leader of the acoustical imaging group. That involved signing paperwork, serving as head of personnel, thinking strategically and being an active presence in the faculty. “I am happy to have been able to set that aside”, remarks Gisolf. “I immediately dived back into technology with both arms”.
Gisolf’s ambitions are very practical. He does not care much about publications. His motivation is to come up with things and then carry them out. Although of course the aim is for the start-up to thrive, Gisolf is not yet sure how large the company should become. “Everyone says that a company must grow. I’m not much of a believer in that. When you grow, the tasks change. Instead of developing new ideas and talking with clients, you’re back to managing – and I was so happy to be finished with that”.
The finish line is not yet in sight, “as long as things are going well and as long as I remain healthy”. He does not have a real life motto. One thing he does impress upon his students that they should develop a real skill that will always get them work.