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.
中华文明的连续性不仅载录于史书典籍中，更镌刻在物质文化与基因血脉的深处。多学科手段、方法的运用，使我们有能力借古人不经意间留下的一鳞半爪，窥见文明赓续的脉络。
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集市热热闹闹，总也走不完，像春节庙会。小时候见过扭秧歌、跑旱船、踩高跷，也看放烟花，像看唱戏一样。晚上冻得嘶嘶哈哈，杵在那儿。玩火药的蔡国强，我老感觉见过——冬拍了太多名人，照片多是我挑，挑来挑去，成了老熟人，好像街坊邻居。