Ultrasonic guided wave-based defect detection in extra-long, small-diameter, thin-walled solar heat-absorbing tubes with heterogeneous salt filmsXinyi Ni, Xiaomeng Xu, Qiang Wang, Luowei Cao, Lei Zhang, Le Li and Guodong JiaMATEC Web Conf., 413 (2025) 07006DOI: https://doi.org/10.1051/matecconf/202541307006