For his doctoral thesis, Professor Walløe analysed the transmission of information in neural nets using simulation techniques and information theory. The simulation model was based on a thorough knowledge of the system being modelled. His later work has also reflected this combination of an understanding of biological systems and expertise in modelling. The work for his doctoral thesis resulted in interesting examples of the deduction of system attributes from characteristics of the system's output signal, made possible partly by one of the first research applications of the programming language SIMULA.
Shortly after Professor Walløe completed his doctoral thesis, the first position in cybernetics was established at the University of Oslo. Professor Walløe was appointed, and was able to set the agenda for developments in the field through his own scientific work and the many students he supervised. He also put his administrative skills to good use in building up the new department.
In the first few years after he completed his doctoral thesis, Professor Walløe worked mainly on modelling in the field of neurophysiology, particularly studies of muscle control systems. After this, he began to focus more on blood flow. Two branches of informatics were involved here - signal treatment and simulation. The interest in signal treatment arose because Professor Walløe and his students were at the time actively involved in the development of ultrasound Doppler velocimeters for measuring blood flow, together with the pioneering company VingMed. Simulation was used partly to gain a better understanding of the measurements obtained and also more generally, to understand flow patterns and their importance in normal and pathological physiology.
The research described above was carried out in close cooperation with graduate students and research fellows. Professor Walløe's approach to supervising students has always been an interactive one based to a large extent on discussions. He has also stressed the importance of basing models on a close knowledge of the system that is to be modelled.
Professor Walløe's expertise in modelling has also had a decisive influence on other disciplines than his primary fields of study. For example, when he was involved in the management of major national research programmes on the impacts of acid rain and the regulation of whaling, he ensured that modelling played a key role.
Professor Walløe was head of the Department of Informatics for eight years. The Department was responsible for a young discipline that was developing rapidly and attracting large numbers of students, thus putting great pressure on the Department and its academic staff. Professor Walløe used his impressive administrative capacity to ensure that the Department had sufficient resources for a reasonable rate of growth, including funding for new premises, and to establish simple and non-bureaucratic internal administrative procedures.
Professor Knut Liestøl,