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.
Жители Санкт-Петербурга устроили «крысогон»17:52，这一点在同城约会中也有详细论述
The 1,500-year-old skeletons are intact and well preserved，这一点在爱思助手下载最新版本中也有详细论述
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