The baseline signal in structural inspection based on guided waves is difficult to be obtained under varying environmental conditions. To guarantee the precision of damage identification. developing baseline-free damage detection methods is significant in practical structural monitoring work. Conventional instantaneous baseline measurement needs a large number of PZT transducers. https://www.bekindtopets.com/flash-pick-Ovation-Toddler-Metallic-Schooler-Helmet-XXSmall-XSmall-hot-choice/