TOADER MOROZAN ON HIS 70TH BIRTHDAY
Toader Morozan, an outstanding Romanian expert in probability and stochastics, was born on October 31, 1936 in Negrile¸sti, Galat¸i county, Ro- mania. He studied at Faculty of Mathematics and Physics of the Bucharest University with major in Mathematics, graduating in 1959. In 1965 he got his Ph.D. with a thesis on the stability of the systems with stochastic parameters – the field where he contributed further along more than four decades, obtain- ing an unchallenged expertise and worldwide fame. His thesis supervisor was Professor Miron Nicolescu (1903–1975), member of the Romanian Academy, while the direct advisor was Professor Aristide Halanay (1924–1997) whose sci- entific seminar on qualitative theory of differential equations Morozan joined in 1959 and is now leading (together with C. Vˆarsan).
After four years(1959–1963) spent as an instructor (teaching assistant) at the Department of Mathematical Analysis of the Faculty he graduated, Mo- rozan joined the Institute of Mathematics of the Romanian Academy where he remained up to now: as a researcher, senior researcher and head of divi- sion. He served between 1975 and 1990 (when the Institute of Mathematics practically ceased its existence for non-academic reasons) in the Mathemat- ics Section of INCREST (National Institute of Scientific Creation) as senior researcher of 3rd then of 2nd degree. In 1990 he returned at the Institute of Mathematics and became senior researcher of 1st degree (highest research degree – equivalent to full professor in the university system).
His scientific research activity started with a noteworthy contribution to the field of absolute stability of nonlinear control systems described by ordinary differential equations; his result was soon recognized as important, it being cited by Halanay in his famous book on qualitative theory of differential equations (1963) and then by S. Lefschetz in his book Stability of Control Systems(1965) where this result was offered a separate sub-section.
The following years were dedicated exclusively to stability and control (optimal included) of systems described by stochastic differential equations.
Among the most important results of Morozan we mention: sufficient stability conditions for stochastic control systems (further extended by A. Ichikawa), a rigorous basis of the Liapunov method in continuous time/ discrete sys- tems with stochastic parameters (cited by Helga Bunke in Germany and by Halanay with Wexler in their monographs), a new approach to stochastic
MATH. REPORTS9(59),1 (2007), 1–2
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approximation using Liapunov functions and associating some ordinary dif- ferential equations with the subject analyzed (cited by R.Z. Khasminskii and M.T. Wasan in their worldwide known monographs), necessary and sufficient conditions for the stability of various stochastic dynamical systems, fundamen- tals of dynamic programming for the control of discrete stochastic systems, periodic and almost periodic solutions for affine stochastic systems (cited and extended by Da Prato and Ichikawa), introduction of the stochastic observabil- ity in the operatorial sense for stochastic systems with time varying coefficients – applied to stochastic linear quadratic control, stochastic H∞ control (with V. Dr˘agan and A. Stoica), maximal solutions of non-linear differential equa- tions, in particular the Riccati equation occurring in H2 and H∞ stochastic control, stochastic bounded real lemma and many other. The last years wit- nessed a fruitful cooperation not only in his country (with V. Dr˘agan and A. Stoica) but also abroad – with G. Freiling and T. Damm.
Morozan has published some 120 scientific papers in the most prestigious journals of the field, and also two famous monographs Stability of Systems with Stochastic Parameters (with Editura Academiei in 1969, a book that was awarded the “Gheorghe Laz˘ar“ of the Romanian Academy in 1972), and Mathematical Methods in the Robust Control of Linear Stochastic Systems (with Springer-Verlag, in 2006, with V. Dr˘agan and A. Stoica).
As a recognition of his competence, achievements and results, Morozan has been included in the Editorial Boards of Mathematical Reports and in the Editorial Advisory Board ofInternational Journal of Innovational Com- puting and Information Control (IJCIC). Between 1983 and 2000 he served as a member of the Editorial Board of Stochastic Analysis and Applications.
Several of his results have been cited, applied and extended by such famous specialists as R.E. Kalman, H. Kushner, R.Z. Khasminskii, D. Hinrichsen, A.J.
Pritchard, Helga Bunke, G. Da Prato, O. Costa, A. Ichikawa, G.S. Ladde, and many others.
Now, at 70 but still active and creative, Toader Morozan is greeted by his colleagues and friends, by the entire mathematics community of Romania.
Vladimir R˘asvan
