Subsea pipelines are prone to developing cracks during long-term service, and traditional methods often suffer from low localization accuracy and poor stability in complex noisy environments. This study investigates defect localization based on an improved cross-correlation time delay estimation method for acoustic emission (AE) signals, which is significant for identifying and localizing sudden AE events under challenging conditions. AE detection technology, as a dynamic, real-time, and non-destructive evaluation method, captures transient elastic waves generated by internal structural changes due to stress or environmental variations, enabling early warning of potential damage and accurate health monitoring of structures. Experimental results demonstrate that the improved cross-correlation time delay method effectively enhances the localization accuracy for AE sources, achieving an average localization error of 0.0133 m and a relative error of 2.67%, which sufficiently meets practical requirements. The findings indicate that this method possesses high practical value for damage detection and localization analysis in complex structures.

This study investigates the hydrodynamic response of polar transport ships under ice-propeller-rudder multi-body interactions in brash ice channels. The study develops a numerical ice tank and a discrete element model for brash ice using a coupled Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) integrated with overset grid technology. The research analyzes the self-propulsion characteristics of ships navigating in brash ice channels. The reliability of the Discrete Element Method (DEM) is validated through quantitative comparisons between numerical results and experimental data for ice-induced resistance. The analysis examines the influence of propeller rotational speed on the hydrodynamic performance of the propeller-rudder system under different loading conditions, considering both ice-free and ice-covered environments. Results indicate that the propeller rotational speed required to achieve the self-propulsion point at scantling draft condition is higher than that required at design draft condition. Furthermore, the study compares the force characteristics of the propeller-rudder system in both time and frequency domains, contrasting environments with and without brash ice. These findings provide valuable insights for predicting ice loads and ensuring navigational safety of ships in ice-covered waters.

High-precision localization of pipeline damage using acoustic emission technology in the marine environment remains challenging. A hybrid path optimization-based localization method for structural damage source localization is proposed. First, the short-time Fourier transform (STFT) maps acoustic signals into the time-frequency domain, with K-means cluster grouping signals to separate different damage sources. Subsequently, the ROTH dual-weighted cross-correlation algorithm is employed to accurately estimate the time difference of acoustic wave arrivals at sensors under strong noise conditions, extracting temporal characteristics of the acoustic waves. Next, an initial propagation path is generated via the Rapidly-exploring Random Tree (RRT) algorithm, and further optimized through an improved D* dynamic path optimization algorithm to determine the optimal propagation path. Finally, acoustic emission source locations are calculated by using hyperbolic equations and weighted least squares based on geometric localization methods. Experimental results demonstrate that this method can accurately locate the structural damage source in complex environments, significantly outperforming traditional approaches.