An automatic centrifugal clutch is interposed in a power transmission system between an engine and a driving wheel. A new relational formula is derived for punch-through voltage in gray scale display, where the visibility of flicker, screen burn-in, and the like is high, and in-plane differential in counter electrode potential, which are an index of the overcharging effect. According to aspects of embodiments, accuracy in the calculation of a thermal stress value can be improved by designing the weight function such that changes in physical properties of a material that change according to temperature changes are considered. From there they are delivered to a reactor for the sequential creation of desired compounds. The coating of cladding material can be varied at selective regions to provide contrast in cosmetic appearance.