أرسل هذا في رسالة قصيرة: Study on several novel topological phases in sonic wave systems

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