A seal assembly is provided for a joint between a first pipe segment and a second pipe segment. The composition of the dispersed fine powders may be oxides, carbides, nitrides, borides, chalcogenides, metals, and alloys. The core can have a star pattern with a series of radially extending segments from a solid hub or a cylindrical shape of a honeycomb or other porous structure that has the requisite strength to resist collapse from compressive loading of the set sealing element while still allowing sufficient flow area for fluid displacement. In addition, a cross-talk phenomenon is prevented with the upper electrode structure and image quality is enhanced. Therefore, at the time of switch of the control mode, the confinement of wheel cylinder pressure is avoided. The return unit is used to return the driving rod.