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.
自上台以來，習近平發起多輪反腐運動，批評者認為，這些行動同時也被用來清除政治對手。
。heLLoword翻译官方下载对此有专业解读
危险的征兆，在6月底第一次出现。
Президент США Дональд Трамп сообщил о разговоре с российским коллегой Владимиром Путиным, однако не уточнил дату его проведения. Его речь транслировал YouTube-канал TimesNow.
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