Background
He was born in Galaţi, Romania on July 7, 1928.
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(15 Liapunov's "second method" eliminates this drawback an...)
15 Liapunov's "second method" eliminates this drawback and leads to accurate conclusions regarding the stability of well-defined families of systems. This method made it natural to introduce the new notion of "absolute stability" whose origin can be traced to a work of . A. I. Lur'e and V. N. Post nikov 1. The results of the many investigations effected to date in the field of absolute stability have been presented in a number of monographs, from which we mention (in chrono logical order) . A. I. Lur'e 1, . A. M. Letov 1, . A. Halanay Fig. 1. 2 1, M . . A . . Aizerman and F. R. Gantmacher 1 and S. Lef schetz 1. Without going into a detailed exposition of these results (see the final chapter of this book), we shall discuss here only the manner in which one defines the families of systems that are studied. These systems are characterized by the fact that in Relation (4) - which describes the non-linear block B2 (Fig. 1. 1) - the function cp is continuous, vanishes for v = 0 and satisfies the inequality cp( v)v > 0 for every v =/= o. (6) In other words, the graph of function cp is entirely contained in the quadrants I and III; it may have, for instance, a shape similar to that shown in Fig. 1. 2. The object of the study of absolute stability consists in finding a criterion which secures simultaneously the stability of all the systems characterized by Condition (6) .
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He was born in Galaţi, Romania on July 7, 1928.
He is well known for having developed a method to analyze stability of nonlinear dynamical systems, now known as Popov criterion. He received the engineering degree in electronics from the Bucharest Polytechnic Institute in 1950. He worked for a few years as Assistant Professor at the Bucharest Polytechnic Institute in the Faculty of Electronics.
His main research interests during this period were in frequency modulation and parametric oscillations.
In the mid 1950s, he joined the Institute for Energy of Romanian Academy of Science in Bucharest. In the 1960s, Popov headed the Control group at the Institute of Energy of the Romanian Academy.
In 1968 Popov left Romania. He was a visiting professor at the Electrical Engineering departments of University of California, Berkeley, and Stanford University, and then Professor in the department of electrical engineering at the University of Maryland College Park.
In 1975 he joined the mathematics department of University of Florida Gainesville.
He retired in 1993 and currently resides in Gainesville, Florida, United States of America.
(15 Liapunov's "second method" eliminates this drawback an...)
