(a) Voltage signal measured by a pressure transducer is plotted as a function of time. indicates the free flight time in which the pressure exerted by the granular pile vanishes. indicates the adhesion time when the granular pile contacts and moves together with the sieve plate. (b) A series of successive snapshots, photographed by a high-speed camcorder with the sample rate 600 frames per second, illustrate the motions of the particles bulk. t = 105 ms, the granular pile contacts with the sieve plate; t = 118 ms, the granular pile launches into air, detaching from the plate. No particles from the pile can pass through the upper surface of the sieve plate, which is indicated by a red, solid line; t = 135 ms; the granular pile rises highest in air; t = 152 ms, the granular pile falls down and just contacts the plate, the flow resumes; t = 167 ms, the granular pile stays on the plate, moving together with plate; t = 172 ms. The granular pile continues in contact and the flow becomes more apparent. The vibration condition is f = 15 Hz, .