The paper is concerned with two aspects:A necessary and sufficient condition for convex hull of a set in E2 being closed;

本论文以凸体为研究对象，主要涉及两个方面的内容：平面凸集的凸包为闭集的充分必要条件；

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Birds Eye cut 490 of its 1, 250 UK staff when it closed its Hull factory.

BBC: NEWS | Business | Private equity boss defends role

In doing so, Everton closed to within a point of Hull in sixth spot in the table, while Boro move up to eighth.

BBC: Everton 1-1 Middlesbrough

But Network Rail needs to keep the line open to allow Hull services to operate after a collapsed spoil heap closed an alternative route.

BBC: Selby swing bridge closure postponed