Why It's Unique: With a 76-foot diameter, Yerba BuenaIsland Tunnel is the world's widest single-bore tunnel, an impressivefeat considering it opened in November of 1936.
The Bore is the diameterof the cylinder. The stroke is the distance the piston travels from BDC (Bottom dead center) to TDC (top dead center). The Bore is always mentioned first.
内径指的是气缸的直径；行程是活塞从下止点运行到上止点的距离。表述时，内径总是写在前面。
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Mean borediameter: arithmetical mean of the largest and smallest single bore diameters in one plane.