Table 2 The instantaneous frequencies in IMF1 to IMF6 at the first and last time points of the three phases

IMF1

25.4(23.9, 27.2)

13.1(11.2,14.0)***

13.3(11.4, 15.4)

13.4(12.2, 15.1)

14.3(12.0, 16.2)

27.2(24.9, 27.9)***

IMF2

16.2(14.1, 17.1)

10.3(9.0, 11.5)***

10.2(9.4, 11.2)

9.9(9.0, 11.4)

10.8(9.9, 12.2)

19.0(17.1, 20.1)***

IMF3

11.3(9.5, 12.8)

7.9(7.2, 9.0)***

8.2(7.0, 9.3)

8.4(7.6, 9.1)

8.7(7.4, 9.2)

13.6(12.3, 15.1)***

IMF4

7.9(6.2, 9.6)

6.0(4.8, 7.3)*

6.7(4.4, 7.7)

6.9(5.7, 8.1)

6.9(5.2, 8.0)

10.4(9.3, 11.5)***

IMF5

6.5(2.6, 8.1)

5.2(3.8, 6.1)

4.9(3.0, 6.3)

5.3(3.2, 6.2)

5.7(3.0, 7.5)

7.8(5.9, 8.7)**

IMF6

5.6(2.8, 7.6)

3.6(1.8, 5.5)*

2.6(1.3, 4.7)

4.4(2.5, 5.7)

4.3(2.8, 5.2)

7.1(5.2, 8.0)***