| 摘要 |
<p>On each of its faces the plate has cavities which open outwardly successive cavities to alternate faces. The plate has a circular contour which is followed by the cavities which are distributed in a series of concentric rings. The cavities extend over a part of the circumference only, pairs of cavities in a ring being separated by a rib. The ribs separating the cavities of successive rings are on the same radius. The cavities of the innermost ring are in a frustrum of a pyramid with a triangular base. A conical skirt surrounds the periphery of the plate and has cavities over at least part of its height.</p> |
