The scooter is powered by standard nickel and metal hydride electric batteries. However, Kamen's research firm is working on an emission-free engine that recycles much of its own heat.

踏板车使用标准的镍氢电池作动力，但卡门的研究部门正在研制一种能再次利用其本身大部分热量的零排放发动机。

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Discover how to add a fast, capable, open source, and free search engine to a PHP site.

通过本文了解如何向php站点中添加一个快速、高效、开源和免费的搜索引擎。

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A search engine for free photos come from many sources and are license-specific.

免费的图片搜索引擎，其资源多来自于免费的照片和一些有特殊许可的照片。

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The first is a standard engine produced by a supplier, with current engine makers free to build their own to the same design.

BBC: Alonso in quit threat over rules

Risk-taking is the essence of free enterprise, the engine of progress.

FORBES: Fact and Comment

Today, we're announcing that we've partnered with Epic Games to release a custom, Oculus-ready version of the Unreal Development Kit (UDK), the free edition of Unreal Engine 3 (UE3).

ENGADGET: Unreal Engine 3 adding Oculus Rift support this April, Epic Citadel demo packed in