發送短信 : Realization of an acoustic third-order topological insulator

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