164504.fig.002a
(a)
164504.fig.002b
(b)
164504.fig.002c
(c)
164504.fig.002d
(d)
Figure 2: , , , and . When , is stable for ( ). Stable 2-periodic points emerge at . When , stable 2-periodic points become stable 4-periodic points with the increase of . When , there is chaos for . When , stable 3-periodic points become stable 6-periodic points and then become stable 3-periodic points again.