摘要
Ⅰ. INTRODUCTIONIn the real world, many practical systems may be unstable in the sense of Lyapunov but are stable in the sense of practical stability introduced by LaSalle and Lefschetz. For ex-ample, an aircraft or a missile may move along an orbit which is unstable in the sense of Lyapunov, but it is practically stable. For deterministic systems, the results of a
基金
Project supported by the National Natural Science Foundation of China and by the Foundation of State Educational Committee of China