6Saka M,Salam Akanda M A.Ultrasonic measurement of the crack depth and the crack opening stress intensity factor under a no load condition[J].Journal of Nondestructive Evaluation,2004,23 (2):49-63.
7飞思科技产品研究中心.神经网络理论与实现[M].北京:电子工业出版社,2005:44-107.
8MULDOON R, CHALKER A, FOFDE M C, et al. Identifying voids in plastic ducts in post-tensioning prestressed concretemembers by resonant frequency of impact - echo, SIBIE and tomography [ J ]. Construction and Building Materials, 2007 (21)527 -537.