Lin, S.-C.S.S.-C.S.LinHuang, T.J.T.J.HuangSun, J.-H.J.-H.SunWu, T.-T.T.-T.WuTSUNG-TSONG WU2020-04-282020-04-282009https://scholars.lib.ntu.edu.tw/handle/123456789/487038Gradient-index phononic crystalsjournal article10.1103/PhysRevB.79.0943022-s2.0-64149085752https://www.scopus.com/inward/record.uri?eid=2-s2.0-64149085752&doi=10.1103%2fPhysRevB.79.094302&partnerID=40&md5=b92471ccc6a31e8ed5591f9fe6a10a04