Water was the main source of mechanical power, and by the end of the seventeenth century, England alone is thought to have had some 20,000 working mills.

水是机械动力的主要来源，而到了17世纪末，人们认为仅英格兰就有2万个左右的工作磨坊。

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Knowledge is both ownership (by the knowledge worker) and power, a decisive source of competitive advantage.

知识为(知识工作者)所有，也是一种权力，是竞争优势的决定性资源。

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Using non-performing rubber trees as a source of power also helps rejuvenate rubber production by making room for new planting.

VOA: standard.2009.09.13

Do not interrupt the process by intterrupting power source.

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And skeptics are also saying that wind energy is an intermittent fuel that must always be backed up by a power source that can begin generating when the wind dies down, making it expensive to operate.

FORBES: Wind Energy Generating A Lot of Mud

It works by using a power source to pump 10 kV of juice to an electrode, which then polarizes a dielectric plate, causing it to attract your body hair.

ENGADGET: Chilly Chair uses static electricity to raise your arm hair, force an 'emotional reaction' (hands-on video)