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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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"I just think it's kind of a dangerous precedent for social media companies to request 3D scans of your face or official documents without there being any kind of knowledge of how that information is being protected or stored," he tells the BBC.
最重要的事情，其实非常简单：养成每日练习的习惯。艺术不是一个项目，不是一门生意，甚至不只是职业。艺术是一种生活。
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A new California law says all operating systems, including Linux, need to have some form of age verification at account setup。51吃瓜对此有专业解读