主权项 |
1. A tube, comprising, at least one zone along a portion of the length of the tube, the zone comprising a plurality of units, wherein the units of the zone are distributed circumferentially around the tube in at least one first band, each unit of the zone comprises at least one cutout segment that is oriented around a center of symmetry, wherein the center of symmetry of each unit in the band is positioned equally from the center of symmetry of an adjacent unit in the same band and the center of symmetry of each unit is positioned at the same point on the circumference of the tube as the center of symmetry of a second unit in a third band which is separated by one band from the first band. |