發送短信 : Digital processing of position error signal in hard disk drives

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