1. [1] L.J. Yang, et al.: “An effective method for differentiating inside and outside defects of oil and gas pipelines based on additional eddy current in low-frequency electromagnetic detection technique,” Jpn. J. Appl. Phys. 59 (2020) 096505 (DOI: 10.35848/1347-4065/abaf0c).
2. [2] W.M. Lou, et al.: “Internal Defect Detection in Ferromagnetic Material Equipment Based on Low-Frequency Electromagnetic Technique in 20# Steel Plate,” IEEE Sensors J. 18 (2018) 6540 (DOI: 10.1109/jsen.2018.2850977).
3. [3] X.Y. Lu, et al.: “Study on low frequency AC excitation magnetic flux leakage testing for defects with different depths,” Pressure Vessels and Piping Conference (2018) (DOI: 10.1115/pvp2018-84479).
4. [4] Y. Chang, et al.: “Effects of excitation system on the performance of magnetic-flux- leakage-type non-destructive testing,” Sens. Actuator A-Phys. 268 (2017) 201 (DOI: 10.1016/j.sna.2017.08.009).
5. [5] J.B. Wu, et al.: “Theoretical analyses of MFL signal affected by discontinuity orientation and sensor-scanning direction,” IEEE Trans. Magn. 51 (2015) 6200207 (DOI: 10.1109/TMAG.2014.2350460).