發送短信 : Stress waves in functionally gradient materials and its use for material characterization

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