[9] [9] CHALLA V R,PRASAD M G,SHI Yong,et al.A vibration energy harvesting device with bidirectional resonance frequency tunability［J］.Smart Materials and Structures,2008,17(1):15035-15010.

[14] [14] XIONG Y,SONG F,LENGX.A piezoelectric cantilever-beam energy harvester(PCEH) with a rectangular hole in the metal substrate［J］.Microsystem Technologies,2020,26(2/3):1-10.