In FIG. 14, a weaving manner of the mesh which adheres tothe surface of the plate 13 is plain weave, but this weave is not limited and any of various weaves inclusive of twill weave can be used.No particular restriction is put on a technique for sticking the mesh 14 on the plate 13, and any means such as welding or bonding can be utilized, as long as the mesh 14 stuck on the tubular structure havi