[1] LAI Y,WU Y,SHENG P,et al.Hybrid elastic solids[J].Nature Materials,2011,10:620-624.

[8] LEE S H,PARK C M,SEO Y M,et al. Composite acoustic medium with simultaneously negative density and modulus[J].Physical Review Letters,2010,104(5):054301.

[13] AO X Y,CHAN C T.Complex band structures and effective medium descriptions of periodic acoustic composite systems[J]. Physical Review B:Condensed Matter,2009,80(23):308-310.