A circular zone counting method of identifying a Duffing oscillator state transition and determining the critical value in weak signal detection*
Li Meng-Ping, Xu Xue-Mei†, Yang Bing-Chu, Ding Jia-Feng
       
Phase diagrams of Holmes Duffing oscillator. (a) f = 0.82, chaos motion. (b) f = 0.83, the great periodic motion.