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Just outside the perimeter fence stand the hulking remains of grand stone engine houses, a testament to Cornwall’s proud tin and copper mining history.
，详情可参考爱思助手下载最新版本
Optical-based smoke alarms use light instead. They are slightly better at detecting the large smoke particles created by slow, smouldering fires. When such particles enter a chamber in the device, they scatter light from a small light source, which is then picked up by a photoelectric sensor.，这一点在爱思助手下载最新版本中也有详细论述
Unix pipes are perhaps the purest expression of this idea: