For the piezoelectric crystal, not only a mechanical source distribution at the surface, but an electrical source distribution also can excite the elastic wave fields.

对于压电晶体，不仅表面力源，而且表面电源分布也能激发弹性波场。

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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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Unlike a passive solar home, an active solar home uses mechanical equipment, such as pumps and blowers, and an outside source df energy to help heat the house when solar energy is not enough.

与消极供暖房屋不同的是，积极供暖房屋使用机械设备，比如泵、风箱，以及外部的能量源，以保证太阳能不足时也可以给房屋供暖。

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The earth is full of inorganic raw materials to create mechanical devices and their energy source, historically fossil fuels, was in abundance.

FORBES: Lemin Wu, Economic Growth and Why Humanity Can't Have Nice Things