531480.fig.002a
(a)
531480.fig.002b
(b)
531480.fig.002c
(c)
531480.fig.002d
(d)
Figure 2: The time response of the first four modes for different excitation frequency Ω: black line, first mode; red line, second mode; blue line, third mode; green line, fourth mode. (a) , (b) and (c) , and (d) (rad/s).