A shutter device includes a stationary plate having a plurality of driving electrodes movable element opposes the stationary plate and including a sheet subjected to an electret-forming process. The work table is positioned on the machine support. The two Q-enhancement circuits are combined to generate sufficient negative impedance to compensate for the loss in the on-chip low Q inductors. A heat spreader is thermally connected to the thermal vias. A mating unit is removably secured to the mounting unit, the mating unit comprising an adjustable shackle and a locking mechanism, the adjustable shackle operative to secure an object, such as a surfboard, snowboard, wakeboard, or skis, to the mating unit and mounting bracket. Another technique for test case generation is disclosed, which uses combinatorial selection algorithms to guarantee coverage of the system under test from the aspect of interaction between stimuli at different stages or transitions in the test case.