An engine is cooled using high pressure water injected into the piston with the water converted to high pressure steam by the heat from combustion with heat transfer taking place in passages in the piston and in and between grooves in the piston and the cylinder sleeve. The positiontime information may be certified as legitimate measured by a portable apparatus with a GPS reception function employed by a user. The active layer includes a quantum well layer formed of Inx1GaN, where 0<x1\u22661, barrier layers formed of Inx2GaN, where 0\u2266x2<1, on opposite surfaces of the quantum well layer, and a diffusion preventing layer formed between the quantum well layer and at least one of the barrier layers. The plate has a plurality of apertures and a plurality of radially oriented closed slots formed therein. The first positioning portion of the light guide is positioned between centers of light emission of adjacent light emitting elements in the main scanning direction of the substrate when the first positioning portion engages the second positioning portion of the holder. In one embodiment, a gradient from substantial chemical reaction to incomplete chemical reaction of the reducible oxides of the blank with the infiltrated metal is formed inside the composite portion.