A hook clamp has surfaces allowing the clamp to be placed on a support and clamped thereto. Typically, in such power supplies, each of the phases has one or more power cells providing a pulse width modulated output. The rim 10r is formed as a boundary between a concave spherical surface of a diameter \u03a61 and a concave spherical surface of a diameter \u03a62 disposed as concentric circles with the through hole 10h. The antenna pair of coils are preferably made of copper. Unfortunately, the gas dries slurry remaining on the surface, causing slurry particles to stick to the polished surface, which ultimately cause defects in integrated circuits. According to some embodiments, each task is associated with a deadline.