Effects of Ultrasonic-Frequency Pulse Current on Arc Stability, Acoustic Signal Emission and Weld Quality in Underwater Wet Multi-Layer Multi-Pass Welding with Q345 Steel. - Li, Hongliang; Yang, Rui; Hu, Junjie; Zhao, Rui; Wang, Jida; Jin, Zeshi; Yu, Feng (Polish Maritime Research, 2026)