Leonardo da Vinci is usually credited with conducting the first systematic study of friction in the late 15th century, a subfield now known as tribology that deals with the dynamics of interacting surfaces in relative motion. Da Vinci's notebooks depict how he pulled rows of blocks using weights and pulleys, an approach that is still used in frictional studies today, as well as examining the friction produced in screw threads, wheels, and axles. The authors of this latest paper used an experimental setup similar to da Vinci's.
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深圳坚持将整座城市作为新技术的试验场。在福田，人形机器人探索参与地铁安检；在南山，机器人跟随民警街头巡逻；在宝安，机器人提供“不打烊”的夜间政务服务。
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In public order situations, the security committee - rather than the police - has legal authority over decisions concerning escalation of force.
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