(a)
(b)
(c)
(d)
Figure 4: Bistability behaviors with different fractional orders. (a) α = 0.75, two sets of the initial values (0.1, 0.1, 0.2) and (0.1, 0.1, −0.2); (b) α = 0.96 and two sets of the initial values (4, 0.1, 4) and (−2, 0.1, 1); (c) α = 0.97 and two sets of the initial values (4, 0.1, 4) and (−2, 0.1, 1); (d) α = 0.99 and two sets of the initial values (−4, 0.1, 4) and (0, 0.1, −1).