Abstract: Quality control of a periodic structure is performed using the damping rate of acoustic waves generated in the periodic structure. In this technique, an excitation light beam illuminates the first layer in the periodic structure to excite an acoustic wave. Possible irregularities in the periodic structure can scatter the acoustic wave, thereby increasing the damping rate of the acoustic wave. A sequence of probe light beams illuminates the periodic structure to measure the acoustic wave as a function of time to generated a temporal signal representing the damping rate of the acoustic signal. The acquired damping rate is employed to evaluate the quality of the periodic structure.

Abstract: Quality control of a periodic structure is performed using the damping rate of acoustic waves generated in the periodic structure. In this technique, an excitation light beam illuminates the first layer in the periodic structure to excite an acoustic wave. Possible irregularities in the periodic structure can scatter the acoustic wave, thereby increasing the damping rate of the acoustic wave. A sequence of probe light beams illuminates the periodic structure to measure the acoustic wave as a function of time to generated a temporal signal representing the damping rate of the acoustic signal. The acquired damping rate is employed to evaluate the quality of the periodic structure.

Abstract: A bottle cap hair clip with a first hair dip member, a second hair dip member, a first top half panel, a second top half panel, a torsion spring and a set of first and second decorative top over panels. The first and second dip members are pivotably attached to each other by a common shaft and employ a torsion spring in a standard way. The first and second dip members each terminate at their upper edge in a hinge member. The first and second top half panels each terminate at their distal edges in a hinge portion that engages with the upper hinge members of the first and second clips. The top half panels are hingedly attached to each other at their central abutting edges. The first and second decorative top over panels are attached to the top surface of the first and second top half panels.