We examined the effects of acoustic excitations on the water retention curve, i.e., the relationship between capillary pressure (PCtrue) and water saturation true(SWtrue) in unsaturated porous media, during drainage. The water retention curves were measured under static and dynamic conditions, where water was withdrawn from a sandbox with three different pumping rates, 12.6, 19.7, and 25.2 mL/s. Excitations with frequencies of 75, 100, 125, and 150 Hz were applied. The acoustic excitations had no effect on the static water retention curve but altered the dynamic water retention curve. The acoustic excitations lowered the dynamic  PC, especially under the dynamic condition where the pumping rate was 25.2 mL/s and when SW varied between 0.6 and 0.95. The differences between the capillary pressures measured under static and dynamic conditions decreased when acoustic excitations were applied. We link this finding to the change in contact angle induced by the acoustic excitation. The dynamic coefficients,  τ, for the dynamic water retention curves that we fitted to the experimental data were smaller with than without acoustic excitations. We attribute the decrease of the dynamic coefficient to the combination of the increase in the permeability and the decline in the air‐entry pressure caused by adding acoustic excitations.

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Independent component analysis (ICA) is used to detect the mura regions with varying sizes and brightness levels before thresholding, then individually analyzed the mura regions in order to avoid unnecessary background effect. Defects detection is performed by partitioning test image into overlapping sub-windows and Classifying each sub-window as normal or mura region by comparing the difference of spatial distance between ICs of defective and non-defective. During the experimental process, a median filter and a high-pass filter are also respectively used to filter out the noise and enhance mura gray intensity. In this research, we developed ICA to achieve off-line learning and on-line detection.

The physical problem - We consider a jet of water discharging from a nozzle submerged at a depth D below the free surface of a large body of water at rest, as in the experimental study of Bernal and Madnia (1989). The free surface is taken as the plane Z = 0 and the Z-axis points upward. The X-axis is chosen aligned with the jet and pointing in the same direction. The origin of the X-axis is taken directly above the nozzle, which thus is located at the point (X = 0, Y = 0, Z = -D). The jet is unstable to axially symmetric disturbances, which result in the formation of a periodic train of fairly coherent ring-like vortices. These vortices are created at a frequency co, and are convected downstream with a speed U roughly 70% of the jet exit velocity. The vortices grow in amplitude until nonlinear motions destroy their coherence, within 5 to 8 diameters of the jet exit, as is described in several experimental studies noted in Bernal and Madnia (1989), notably Yule (1978), Zaman and Hussain (1980), Hussain and Zaman (1980), Crow and Champagne (1971), and Hussain and Zaman (1981). An understanding of the free-surface disturbance created by a coherent periodic system of traveling vortices and observed in the experimental study of Bernal and Madnia (1989) is sought.