【摘要】 给出判断一个覆盖平面有限点集的圆环达到最窄的一组充分条件，同时指出，对于一般的平面有限点集而言，其中的一个条件是不可放弃的．这个结果对于解决所谓圆度问题不仅有理论价值，而且有实际意义．更多还原

【Abstract】 Suppose that S is a set of points in E 2, and C∈ker(S ) is the center of an annulus which covers S and has a locally minimal width. We give a sufficient condition for C to be the center of an annulus which covers S and has the globally minimal width.更多还原