One limitation that applies to hubs and switches alike is that an Ethernet network must be loop-free.

集线器和交换机有同一个局限，即以太网网络必须是无路由循环的。

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A: Try Loop PDF - it's a free service that lets you combine multiple documents, images and even web pages into a single PDF file.

A：你可以试试Loop PDF，他们提供免费服务，可以将多个文档、图片、甚至网页合并进一个PDF文件。

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This paper proposes the concept of Minimum Closed Loop of free curve set, and presents two properties of Minimum Closed Loop.

文章提出了自由曲线集最小闭环的概念，给出了最小闭环的两个性质。

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Ireland have a move where fly-half Jonathan Sexton runs around Brian O'Driscoll to take the return pass on the loop and free the runners out wide.

BBC: Six Nations: Jeremy Guscott on Ireland v England

But losing the wheels can also save a tremendous amount of money, especially in places like Chicago, home of the convenient South Loop neighborhood, with a free ride program on buses and subways for residents age 65 and up.

FORBES: Personal Finance

The firm maintains that it had been pitching its patented noise cancellation to Apple in periodic meetings between 2007 and 2010, only to watch as 1 Infinite Loop used Audience's technology for the iPhone 4 instead -- and supposedly handed some of Noise Free's work to a competitor.

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