A fastener includes a body defining a central aperture and an insertion opening in communication with the central aperture. The ring groove also has an upper inner surface and a lower inner surface, both orthogonal to the axial direction of the piston; a radially inward-most, bottom surface connecting the upper and lower inner surfaces; and oil drain holes, each having an opening thereof located on the bottom surface. The network apparatus determines, on the basis of the acquired authentication information, whether to permit activation of the application. Since the computation requirements of data management operations can decrease as the bit lengths of input data decrease, the transformation can reduce the latencies of data management operations in hardware or software. The effusion holes provide fluid flow communication between a cooling air source and the gas path.