753541.fig.002a
(a)  A, B, and C are synchronous, and cycles are aligned
753541.fig.002b
(b) A, B, and C are synchronous, but cycles are not aligned
753541.fig.002c
(c) A, B, and C are asynchronous, and also cycles are not aligned
Figure 2: Synchronous and asynchronous PS nodes’ QS.