أرسل هذا في رسالة قصيرة: A tribological study of double-walled and triple-walled carbon nanotube oscillators

   _____     ___     _    _     _____     ______  
  / ___//   / _ \\  | || | ||  |  ___||  /_   _// 
  \___ \\  | / \ || | || | ||  | ||__      | ||   
  /    //  | \_/ || | \\_/ ||  | ||__     _| ||   
 /____//    \___//   \____//   |_____||  /__//    
`-----`     `---`     `---`    `-----`   `--`