أرسل هذا في رسالة قصيرة: Investigation on crack failure of helical gear system of the gearbox in wind turbine: mesh stiffness calculation and vibration characteristics recognition

   _____    _____    __   __   __   __    ____    
  / ___//  |  ___||  \ \\/ //  \ \\/ //  |  _ \\  
  \___ \\  | ||__     \   //    \ ` //   | |_| || 
  /    //  | ||__     / . \\     | ||    | .  //  
 /____//   |_____||  /_//\_\\    |_||    |_|\_\\  
`-----`    `-----`   `-`  --`    `-`'    `-` --`