Journal of Marine Science and Engineering

23 pages, 7095 KiB

Open AccessArticle

Development of a Dual-Input Hybrid Wave–Current Ocean Energy System: Design, Fabrication, and Performance Evaluation

by Farooq Saeed, Tanvir M. Sayeed, Mohammed Abdul Hannan, Abdullah A. Baslamah, Aedh M. Alhassan, Turki K. Alarawi, Osama A. Alsaadi, Muhanad Y. Alharees and Sultan A. Alshehri

J. Mar. Sci. Eng. 2025, 13(8), 1435; https://doi.org/10.3390/jmse13081435 (registering DOI) - 27 Jul 2025

Abstract

This study presents the design, fabrication, and performance assessment of a novel, small-scale (30–70 W), hybrid ocean energy system that captures energy from wave-induced heave motion using a point-absorber buoy and from ocean currents via a vertical axis water turbine (VAWT). Key innovations [...] Read more.

This study presents the design, fabrication, and performance assessment of a novel, small-scale (30–70 W), hybrid ocean energy system that captures energy from wave-induced heave motion using a point-absorber buoy and from ocean currents via a vertical axis water turbine (VAWT). Key innovations include a custom designed and built dual-rotor generator that accepts independent mechanical input from both subsystems without requiring complex mechanical coupling and a bi-directional mechanical motion rectifier with an overdrive. Numerical simulations using ANSYS AQWA (2024R2) and QBLADE(2.0.4) guided the design optimization of the buoy and turbine, respectively. Wave resource assessment for the Khobar coastline, Saudi Arabia, was conducted using both historical data and field measurements. The prototype was designed and built using readily available 3D-printed components, ensuring cost-effective construction. This mechanically simple system was tested in both laboratory and outdoor conditions. Results showed reliable operation and stable power generation under simultaneous wave and current input. The performance is comparable to that of existing hybrid ocean wave–current energy converters that employ more complex flywheel or dual degree-of-freedom systems. This work provides a validated pathway for low-cost, compact, and modular hybrid ocean energy systems suited for remote coastal applications or distributed marine sensing platforms. Full article

(This article belongs to the Section Marine Energy)

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21 pages, 12172 KiB

Open AccessArticle

Risk Assessment of Storm Surge Disasters in a Semi-Enclosed Bay Under the Influence of Cold Waves: A Case Study of Laizhou Bay, China

by Hongyuan Shi, Shengnian Zhao, Ruiqi Zhu, Liqin Sun, Haixia Wang, Qing Wang and Chao Zhan

J. Mar. Sci. Eng. 2025, 13(8), 1434; https://doi.org/10.3390/jmse13081434 (registering DOI) - 27 Jul 2025

Abstract

Laizhou Bay, a semi-enclosed bay, is prone to storm surges from cold waves due to its geographic and environmental characteristics. This study uses satellite data, in situ measurements, and the MIKE numerical model to analyze storm surges along Laizhou Bay’s coast under no-dike [...] Read more.

Laizhou Bay, a semi-enclosed bay, is prone to storm surges from cold waves due to its geographic and environmental characteristics. This study uses satellite data, in situ measurements, and the MIKE numerical model to analyze storm surges along Laizhou Bay’s coast under no-dike conditions. It examines the surges caused by cold waves with different intensities and directions. This study provides the storm surge disaster risk levels along Laizhou Bay’s coast. The results show that the maximum sustained wind speed during cold waves is distributed between the NW and NE. The NE wind direction causes the most severe storm surge along Laizhou Bay. Under NE-directed cold waves with level 12 wind, the maximum risk areas for Level III and IV are approximately 1341 km² and 1294 km², respectively. Dongying, Shouguang, and Hanting exhibit large Level I and II risk zones. The maximum seawater intrusion distance along the Kenli coast is about 41 km. The coastal segment from Kenli to Changyi is most severely affected by storm surges. It is recommended to effectively maintain and heighten seawalls along this segment to mitigate storm surge disasters caused by strong NE winds. Full article

(This article belongs to the Section Physical Oceanography)

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14 pages, 3283 KiB

Open AccessReview

Impact of Internal Solitary Waves on Marine Suspended Particulate Matter: A Review

by Zhengrong Zhang, Xuezhi Feng, Xiuyao Fan, Yuchen Lin and Chaoqi Zhu

J. Mar. Sci. Eng. 2025, 13(8), 1433; https://doi.org/10.3390/jmse13081433 (registering DOI) - 27 Jul 2025

Abstract

Suspended particulate matter (SPM) plays a pivotal role in marine source-to-sink sedimentary systems. Internal solitary waves (ISWs), a prevalent hydrodynamic phenomenon, significantly influence vertical mixing, cross-shelf material transport, and sediment resuspension. Acting as energetic nonlinear waves, ISWs can disrupt the settling trajectories of [...] Read more.

Suspended particulate matter (SPM) plays a pivotal role in marine source-to-sink sedimentary systems. Internal solitary waves (ISWs), a prevalent hydrodynamic phenomenon, significantly influence vertical mixing, cross-shelf material transport, and sediment resuspension. Acting as energetic nonlinear waves, ISWs can disrupt the settling trajectories of suspended particles, enhance lateral transport above the pycnocline, and generate nepheloid layers nearshore. Meanwhile, intense turbulent mixing induced by ISWs accumulates large quantities of SPM at both the leading surface and trailing bottom of the waves, thereby altering the structure and dynamics of the intermediate nepheloid layers. This review synthesizes recent advances in the in situ observational techniques for SPM under the influence of ISWs and highlights the key mechanisms governing their interactions. Particular attention is given to representative field cases in the SCS, where topographic complexity and strong stratification amplify ISWs–sediment coupling. Finally, current limitations in observational and modeling approaches are discussed, with suggestions for future interdisciplinary research directions that better integrate hydrodynamic and sediment transport processes. Full article

(This article belongs to the Special Issue Marine Geohazards: Characterization to Prediction)

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18 pages, 884 KiB

Open AccessArticle

Dynamic Leader Election and Model-Free Reinforcement Learning for Coordinated Voltage and Reactive Power Containment Control in Offshore Island AC Microgrids

by Xiaolu Ye, Zhanshan Wang, Qiufu Wang and Shuran Wang

J. Mar. Sci. Eng. 2025, 13(8), 1432; https://doi.org/10.3390/jmse13081432 (registering DOI) - 27 Jul 2025

Abstract

Island microgrids are essential for the exploitation and utilization of offshore renewable energy resources. However, voltage regulation and accurate reactive power sharing remain significant technical challenges that need to be addressed. To tackle these issues, this paper proposes an algorithm that integrates a [...] Read more.

Island microgrids are essential for the exploitation and utilization of offshore renewable energy resources. However, voltage regulation and accurate reactive power sharing remain significant technical challenges that need to be addressed. To tackle these issues, this paper proposes an algorithm that integrates a dynamic leader election (DLE) mechanism and model-free reinforcement learning (RL). The algorithm aims to address the issue of fixed leaders restricting reactive power flow between buses during heavy load variations in island microgrids, while also overcoming the challenge of obtaining model parameters such as resistance and inductance in practical microgrids. First, we establish a voltage containment control and reactive power error model for island alternating current (AC) microgrids and construct a corresponding value function based on this error model. Second, a dynamic leader election algorithm is designed to address the issue of fixed leaders restricting reactive power flow between buses due to preset voltage limits under unknown or heavy load conditions. The algorithm adaptively selects leaders based on bus load, allowing the voltage limits to adjust accordingly and regulating reactive power flow. Then, to address the difficulty of accurately acquiring parameters such as resistance and inductance in microgrid lines, a model-free reinforcement learning method is introduced. This method relies on real-time measurements of voltage and reactive power data, without requiring specific model parameters. Ultimately, simulation experiments on offshore island microgrids are conducted to validate the effectiveness of the proposed algorithm. Full article

(This article belongs to the Section Ocean Engineering)

25 pages, 14813 KiB

Open AccessArticle

Research on the Influence of Hydrofoil Propulsive Parameters on Propulsion Efficiency

by Meng Cui, Zhihao Liu, Fei Lu, Jiaye Gong and Zheng Fu

J. Mar. Sci. Eng. 2025, 13(8), 1431; https://doi.org/10.3390/jmse13081431 (registering DOI) - 27 Jul 2025

Abstract

Oscillating hydrofoils can be used to simplify the study of the swinging caudal fin propulsive mode of fish, where the motion parameters have a direct impact on the hydrodynamic performance and propulsive efficiency. In this study, numerical calculations were carried out on two-dimensional [...] Read more.

Oscillating hydrofoils can be used to simplify the study of the swinging caudal fin propulsive mode of fish, where the motion parameters have a direct impact on the hydrodynamic performance and propulsive efficiency. In this study, numerical calculations were carried out on two-dimensional hydrofoils for sinusoidal and non-sinusoidal heave oscillation, and the numerical results of sinusoidal hydrofoils were compared with the experimental values, which were in good agreement. An analysis of how different motion parameters of the sinusoidal hydrofoil affect the hydrodynamic performance was conducted, and the recommended operating condition range was given in combination with the flow field analysis. A unique non-sinusoidal curve was defined, which can enable the motion to enter the crest and trough earlier or later. The parameters for controlling the degree of non-sinusoidal were also defined. A detailed discussion was carried out on how the non-sinusoidal parameters affect the hydrodynamic performance and the change in the flow field. The corresponding recommended working conditions and application scope were given. Further studies can reveal the propulsive mechanism of the swinging caudal fin and provide a reference for the engineering and design of the next generation of bionic fish. Full article

(This article belongs to the Section Ocean Engineering)

18 pages, 8969 KiB

Open AccessArticle

Hierarchical Joint Elastic Full Waveform Inversion Based on Wavefield Separation for Marine Seismic Data

by Guowang Han, Yuanyuan Li and Jianping Huang

J. Mar. Sci. Eng. 2025, 13(8), 1430; https://doi.org/10.3390/jmse13081430 (registering DOI) - 27 Jul 2025

Abstract

In marine seismic surveys, towed streamers record only pressure data with limited offsets and insufficient low-frequency content, whereas Ocean Bottom Nodes (OBNs) acquire multi-component data with wider offset and sufficient low-frequency content, albeit with sparser spatial sampling. Elastic full waveform inversion (EFWI) is [...] Read more.

In marine seismic surveys, towed streamers record only pressure data with limited offsets and insufficient low-frequency content, whereas Ocean Bottom Nodes (OBNs) acquire multi-component data with wider offset and sufficient low-frequency content, albeit with sparser spatial sampling. Elastic full waveform inversion (EFWI) is used to estimate subsurface elastic properties by matching observed and synthetic data. However, using only towed streamer data makes it impossible to reliably estimate shear-wave velocities due to the absence of direct S-wave recordings and limited illumination. Inversion using OBN data is prone to acquisition footprint artifacts. To overcome these challenges, we propose a hierarchical joint inversion method based on P- and S-wave separation (PS-JFWI). We first derive novel acoustic-elastic coupled equations based on wavefield separation. Then, we design a two-stage inversion framework. In Stage I, we use OBN data to jointly update the P- and S-wave velocity models. In Stage II, we apply a gradient decoupling algorithm: we construct the P-wave velocity gradient by combining the gradient using PP-waves from both towed streamer and OBN data and construct the S-wave velocity gradient using the gradient using PS-waves. Numerical experiments demonstrate that the proposed method enhances the inversion accuracy of both velocity models compared with single-source and conventional joint inversion methods. Full article

(This article belongs to the Special Issue Modeling and Waveform Inversion of Marine Seismic Data)

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18 pages, 7474 KiB

Open AccessArticle

Fuzzy Reinforcement Learning Disturbance Cancellation Optimized Course Tracking Control for USV Autopilot Under Actuator Constraint

by Xiaoyang Gao, Xin Hu and Ang Yang

J. Mar. Sci. Eng. 2025, 13(8), 1429; https://doi.org/10.3390/jmse13081429 (registering DOI) - 27 Jul 2025

Abstract

Unmanned surface vehicles (USVs) course control research constitutes a vital branch of ship motion control studies and serves as a key technology for the development of marine critical equipment. Aiming at the problems of model uncertainties, external marine disturbances, performance optimization, and actuator [...] Read more.

Unmanned surface vehicles (USVs) course control research constitutes a vital branch of ship motion control studies and serves as a key technology for the development of marine critical equipment. Aiming at the problems of model uncertainties, external marine disturbances, performance optimization, and actuator constraints encountered by the autopilot system, this paper proposes a composite disturbance cancellation optimized control method based on fuzzy reinforcement learning. Firstly, a coupling design of the finite-time disturbance observer and fuzzy logic system is conducted to estimate and reject the composite disturbance composed of internal model uncertainty and ocean disturbances. Secondly, a modified backstepping control technique is employed to design the autopilot controller and construct the error system. Based on the designed performance index function, the fuzzy reinforcement learning is utilized to propose an optimized compensation term for the error system. Meanwhile, to address the actuator saturation issue, an auxiliary system is introduced to modify the error surface, reducing the impact of saturation on the system. Finally, the stability of the autopilot system is proved using the Lyapunov stability theory. Simulation studies conducted on the ocean-going training ship “Yulong” demonstrate the effectiveness of the proposed algorithm. Under the strong and weak ocean conditions designed, this algorithm can ensure that the tracking error converges within 7 s. Full article

(This article belongs to the Special Issue Control and Optimization of Ship Propulsion System)

37 pages, 1679 KiB

Open AccessArticle

Distributed Robust Predefined-Time Sliding Mode Control for AUV-USV Heterogeneous Multi-Agent Systems Based on Memory Event-Triggered Mechanism Under Input Saturation

by Haitao Liu, Luchuan Li, Xuehong Tian and Qingqun Mai

J. Mar. Sci. Eng. 2025, 13(8), 1428; https://doi.org/10.3390/jmse13081428 (registering DOI) - 27 Jul 2025

Abstract

This paper studies the distributed robust predefined-time sliding mode control (DRPSC) problem for high-order heterogeneous multi-agent systems under input saturation while considering external disturbances and model uncertainties. Firstly, a distributed predefined-time state observer (PTSO) is designed for each agent to achieve individual estimation [...] Read more.

This paper studies the distributed robust predefined-time sliding mode control (DRPSC) problem for high-order heterogeneous multi-agent systems under input saturation while considering external disturbances and model uncertainties. Firstly, a distributed predefined-time state observer (PTSO) is designed for each agent to achieve individual estimation of the state information of the virtual leader within a predefined time, and the observer does not need to count on the global information of the system. Secondly, a predefined-time auxiliary dynamic system (PTADS) is developed to solve the actuator’s input saturation problem. Thirdly, a distributed predefined-time sliding mode controller (PTSMC) is proposed, which ensures that the error converges to a small region near zero within a predefined time and combines H_∞ control to deal with the lumped uncertainty disturbances in the system to improve the robustness of the system. In addition, a memory event-triggered mechanism (METM) is designed to reduce the communication frequency of the underactuated AUV-USV multi-agent system and reduce the consumption of communication resources. Finally, Lyapunov theory is employed to prove that the closed-loop system is predefined-time stable, and the simulation results demonstrate that the proposed method is effective. Full article

(This article belongs to the Special Issue Control and Optimization of Ship Propulsion System)

17 pages, 3368 KiB

Open AccessArticle

A Heave Motion Prediction Approach Based on Sparse Bayesian Learning Incorporated with Empirical Mode Decomposition for an Underwater Towed System

by Zhu-Fei Lu, Heng-Chang Yan and Jin-Bang Xu

J. Mar. Sci. Eng. 2025, 13(8), 1427; https://doi.org/10.3390/jmse13081427 (registering DOI) - 27 Jul 2025

Abstract

Underwater towed systems (UTSs) are widely used in underwater exploration and oceanographic data acquisition. However, the heave motion information of the towing ship is usually affected by the measurement transmitting delay, sensor noise and surface waves, which will result in uncontrolled depth variation [...] Read more.

Underwater towed systems (UTSs) are widely used in underwater exploration and oceanographic data acquisition. However, the heave motion information of the towing ship is usually affected by the measurement transmitting delay, sensor noise and surface waves, which will result in uncontrolled depth variation of the towed vehicle, so as to adversely affect the monitoring performance and mechanical robustness of the UTS. To resolve this problem, a heave motion prediction approach based on sparse Bayesian learning (SBL) incorporated with empirical mode decomposition (EMD) for the UTS is proposed in this paper. With the proposed approach, a heave motion model of the towing ship with random waves is firstly developed based on strip theory. Meanwhile, the EMD is employed to eliminate the high-frequency noise of the measurement data to restore low-frequency towing ship motion. And then, the SBL is utilized to train the weight parameters in the built model to predict the heave motion, which not only reconstruct the heave motion from non-stationary sensor signals with noise but also prevent overfitting. Furthermore, the depth compensation of the towed vehicle is then performed using the predicted heave motion. Finally, experimental results demonstrate that the proposed EMD-SBL method significantly improves both the prediction accuracy and model adaptability under various sea conditions, and it also guarantees that the maximum prediction depth error of the heave motion does not exceed 1 cm. Full article

(This article belongs to the Section Ocean Engineering)

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19 pages, 44058 KiB

Open AccessArticle

Geomorphological Features and Formation Process of Abyssal Hills and Oceanic Core Complexes Linked to the Magma Supply in the Parece Vela Basin, Philippine Sea: Insights from Multibeam Bathymetry Analysis

by Xiaoxiao Ding, Junjiang Zhu, Yuhan Jiao, Xinran Li, Zhengyuan Liu, Xiang Ao, Yihuan Huang and Sanzhong Li

J. Mar. Sci. Eng. 2025, 13(8), 1426; https://doi.org/10.3390/jmse13081426 (registering DOI) - 26 Jul 2025

Abstract

Based on the new high-resolution multibeam bathymetry data collected by the “Dongfanghong 3” vessel in 2023 in the Parece Vela Basin (PVB) and previous magnetic anomaly data, we systematically analyze the seafloor topographical changes of abyssal hills and oceanic core complexes (OCCs) in [...] Read more.

Based on the new high-resolution multibeam bathymetry data collected by the “Dongfanghong 3” vessel in 2023 in the Parece Vela Basin (PVB) and previous magnetic anomaly data, we systematically analyze the seafloor topographical changes of abyssal hills and oceanic core complexes (OCCs) in the “Chaotic Terrain” region, and the revised seafloor spreading model is constructed in the PVB. Using detailed analysis of the seafloor topography, we identify typical geomorphological features associated with seafloor spreading, such as regularly aligned abyssal hills and OCCs in the PVB. The direction variations of seafloor spreading in the PVB are closely related to mid-ocean ridge rotation and propagation. The formation of OCCs in the “Chaotic Terrain” can be explained by links to the continuous and persistent activity of detachment faults and dynamic adjustments controlled by variations of deep magma supply in the different segments in the PVB. We use 2D discrete Fourier image analysis of the seafloor topography to calculate the aspect ratio (AR) values of abyssal hills in the western part of the PVB. The AR value variations reveal a distinct imbalance in magma supply across various regions during the basin spreading process. Compared to the “Chaotic Terrain” area, the region with abyssal hills indicates a higher magma supply and greater linearity on seafloor topography. AR values fluctuated between 2.1 and 1.7 of abyssal hills in the western segment, while in the “Chaotic Terrain”, they dropped to 1.3 due to the lower magma supply. After the formation of the OCC-1, AR values increased to 1.9 in the eastern segment, and this shows the increase in magma supply. Based on changes in seafloor topography and variations in magma supply across different segments of the PVB, we propose that the seafloor spreading process in the magnetic anomaly linear strip 9-6A of the PVB mainly underwent four formation stages: ridge rotation, rift propagation, magma-poor supply, and the maturation period of OCCs. Full article

(This article belongs to the Section Geological Oceanography)

26 pages, 11770 KiB

Open AccessArticle

Flow Dynamics and Local Scour Around Seabed-Mounted Artificial Reefs: A Case Study from Torbay, UK

by Amir Bordbar, Jakub Knir, Vasilios Kelefouras, Samuel John Stephen Hickling, Harrison Short and Yeaw Chu Lee

J. Mar. Sci. Eng. 2025, 13(8), 1425; https://doi.org/10.3390/jmse13081425 (registering DOI) - 26 Jul 2025

Abstract

This study investigates the flow dynamics and local scour around a Reef Cube^® artificial reef deployed in Torbay, UK, using computational fluid dynamics. The flow is modelled using Reynolds-Averaged Navier–Stokes (RANS) equations with a k-ω SST turbulence model. A novel hydro-morphodynamic model [...] Read more.

This study investigates the flow dynamics and local scour around a Reef Cube^® artificial reef deployed in Torbay, UK, using computational fluid dynamics. The flow is modelled using Reynolds-Averaged Navier–Stokes (RANS) equations with a k-ω SST turbulence model. A novel hydro-morphodynamic model employing the generalized internal boundary method in HELYX (OpenFOAM-based) is used to simulate scour development. Model performance was validated against experimental data for flow fields, bed shear stress, and local scour. Flow simulations across various scenarios demonstrated that parameters such as the orientation angle and arrangement of Reef Cubes significantly influence flow patterns, bed shear stress, and habitat suitability. The hydro-morphodynamic model was used to simulate scouring around a reef cube in the Torbay marine environment. Results indicate that typical tidal flow velocity flow in the region is barely sufficient to initiate sediment motion, whereas extreme flow events, represented by doubling the mean flow velocity, significantly accelerate scour development, producing holes up to ten times deeper. These findings underscore the importance of considering extreme flow conditions in scour analyses due to their potential impact on the stability and failure risk of AR projects. Full article

(This article belongs to the Section Ocean Engineering)

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25 pages, 3182 KiB

Open AccessArticle

From Efficiency to Safety: A Simulation-Based Framework for Evaluating Empty-Container Terminal Layouts

by Cristóbal Vera-Carrasco, Cristian D. Palma and Sebastián Muñoz-Herrera

J. Mar. Sci. Eng. 2025, 13(8), 1424; https://doi.org/10.3390/jmse13081424 (registering DOI) - 26 Jul 2025

Abstract

Empty container depot (ECD) design significantly impacts maritime terminal efficiency, yet traditional evaluation approaches assess limited operational factors, constraining comprehensive performance optimization. This study develops an integrated discrete event simulation (DES) framework that simultaneously evaluates lifting equipment utilization, truck turnaround times, and potential [...] Read more.

Empty container depot (ECD) design significantly impacts maritime terminal efficiency, yet traditional evaluation approaches assess limited operational factors, constraining comprehensive performance optimization. This study develops an integrated discrete event simulation (DES) framework that simultaneously evaluates lifting equipment utilization, truck turnaround times, and potential collisions to support terminal decision-making. This study combines operational efficiency metrics with safety analytics for non-automated ECDs using Top Lifters and Reach Stackers. Additionally, a regression analysis examines efficiency metrics’ effect on safety risk. A case study at a Chilean multipurpose terminal reveals performance trade-offs between indicators under different operational scenarios, identifying substantial efficiency disparities between dry and refrigerated container operations. An analysis of four distinct collision zones with varying historical risk profiles showed the gate area had the highest potential collisions and a strong regression correlation with efficiency metrics. Similar models showed a poor fit in other conflict zones, evidencing the necessity for dedicated safety indicators complementing traditional measures. This integrated approach quantifies interdependencies between safety and efficiency metrics, helping terminal managers optimize layouts, expose traditional metric limitations, and reduce safety risks in space-constrained maritime terminals. Full article

(This article belongs to the Special Issue New Trends in Engineering and Operational Research on Container Supply Chain Management for Resilience, Digitalization, Intelligence and Sustainability)

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15 pages, 5378 KiB

Open AccessArticle

A Strong Misalignment Tolerance Wireless Power Transfer System for AUVs with Hybrid Magnetic Coupler

by Haibing Wen, Xiaolong Zhou, Yu Wang, Zhengchao Yan, Kehan Zhang, Jie Wen, Lei Yang, Yaopeng Zhao, Yang Liu and Xiangqian Tong

J. Mar. Sci. Eng. 2025, 13(8), 1423; https://doi.org/10.3390/jmse13081423 (registering DOI) - 25 Jul 2025

Abstract

Wireless power transfer systems require not only strong coupling capabilities but also stable output under various misalignment conditions. This paper proposes a hybrid magnetic coupler for autonomous underwater vehicles (AUVs), featuring two identical arc-shaped rectangular transmitting coils and a combination of an arc-shaped [...] Read more.

Wireless power transfer systems require not only strong coupling capabilities but also stable output under various misalignment conditions. This paper proposes a hybrid magnetic coupler for autonomous underwater vehicles (AUVs), featuring two identical arc-shaped rectangular transmitting coils and a combination of an arc-shaped rectangular receiving coil and two anti-series connected solenoid coils. The arc-shaped rectangular receiving coil captures the magnetic flux generated by the transmitting coil, which is directed toward the center, while the solenoid coils capture the axial magnetic flux generated by the transmitting coil. The parameters of the proposed magnetic coupler have been optimized to enhance the coupling coefficient and improve the system’s tolerance to misalignments. To verify the feasibility of the proposed magnetic coupler, a 300 W prototype with LCC-S compensation topology is built. Within a 360° rotational misalignment range, the system’s output power maintains around 300 W, with a stable power transmission efficiency of over 92.14%. When axial misalignment of 40 mm occurs, the minimum output power is 282.8 W, and the minimum power transmission efficiency is 91.6%. Full article

(This article belongs to the Section Ocean Engineering)

20 pages, 18201 KiB

Open AccessArticle

A Virtual-Beacon-Based Calibration Method for Precise Acoustic Positioning of Deep-Sea Sensing Networks

by Yuqi Zhu, Binjian Shen, Biyuan Yao and Wei Wu

J. Mar. Sci. Eng. 2025, 13(8), 1422; https://doi.org/10.3390/jmse13081422 - 25 Jul 2025

Abstract

The rapid expansion of deep-sea sensing networks underscores the critical need for accurate underwater positioning of observation base stations. However, achieving precise acoustic localization, particularly at depths exceeding 4 km, remains a significant challenge due to systematic ranging errors, clock drift, and inaccuracies [...] Read more.

The rapid expansion of deep-sea sensing networks underscores the critical need for accurate underwater positioning of observation base stations. However, achieving precise acoustic localization, particularly at depths exceeding 4 km, remains a significant challenge due to systematic ranging errors, clock drift, and inaccuracies in sound speed modeling. This study proposes and validates a three-tier calibration framework consisting of a Dynamic Single-Difference (DSD) solver, a geometrically optimized reference buoy selection algorithm, and a Virtual Beacon (VB) depth inversion method based on sound speed profiles. Through simulations under varying noise conditions, the DSD method effectively mitigates common ranging and clock errors. The geometric reference optimization algorithm enhances the selection of optimal buoy layouts and reference points. At a depth of 4 km, the VB method improves vertical positioning accuracy by 15% compared to the DSD method alone, and nearly doubles vertical accuracy compared to traditional non-differential approaches. This research demonstrates that deep-sea underwater target calibration can be achieved without high-precision time synchronization and in the presence of fixed ranging errors. The proposed framework has the potential to lower technological barriers for large-scale deep-sea network deployments and provides a robust foundation for autonomous deep-sea exploration. Full article

30 pages, 21742 KiB

Open AccessArticle

Drift Characteristics and Predictive Modeling of Life Rafts in Island and Reef Waters

by Zhengzhou Li, Xiangyu Tang, Chenzhuo Hu, Haiwen Tu and Lin Mu

J. Mar. Sci. Eng. 2025, 13(8), 1421; https://doi.org/10.3390/jmse13081421 - 25 Jul 2025

Abstract

Accurate prediction of drifting trajectories is essential for improving the operational efficiency of maritime search and rescue (SAR), particularly within the complex geomorphological settings of island and reef regions, such as those in the South China Sea. This study investigates the drift characteristics [...] Read more.

Accurate prediction of drifting trajectories is essential for improving the operational efficiency of maritime search and rescue (SAR), particularly within the complex geomorphological settings of island and reef regions, such as those in the South China Sea. This study investigates the drift characteristics of life rafts under varying loading conditions across both open-sea and island–reef regions. Comprehensive field experiments were conducted over 15 days in the waters around the Wanshan Archipelago, using advanced instruments to collect wind, current, and drift trajectory data. Based on these observations, two models—the AP98 leeway model and a BP neural network model—were developed and validated. The results show that the AP98 model performs better in open-sea conditions, whereas the BP neural network provides more accurate predictions in island and reef areas with complex environmental factors. A Monte Carlo simulation was also integrated to enhance the robustness of drift area predictions. These findings offer valuable insights into life raft drift behavior in complex marine environments and provide technical support for improving SAR operations in island–reef regions. Full article

(This article belongs to the Section Ocean Engineering)

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16 pages, 2654 KiB

Open AccessReview

Volcanic Islands as Reservoirs of Geoheritage: Current and Potential Initiatives of Geoconservation

by Esther Martín-González, Juana Vegas, Inés Galindo, Carmen Romero and Nieves Sánchez

J. Mar. Sci. Eng. 2025, 13(8), 1420; https://doi.org/10.3390/jmse13081420 - 25 Jul 2025

Abstract

Volcanic islands host exceptional geological features that illustrate complex endogenic processes and interactions with climatic and marine forces, while also being particularly vulnerable to the impacts of climate change. Despite their scientific, educational, touristic, and aesthetic values, such islands remain underrepresented within the [...] Read more.

Volcanic islands host exceptional geological features that illustrate complex endogenic processes and interactions with climatic and marine forces, while also being particularly vulnerable to the impacts of climate change. Despite their scientific, educational, touristic, and aesthetic values, such islands remain underrepresented within the UNESCO Global Geoparks (UGGp). This study reviews current volcanic island geoparks and evaluates territories with potential for future designation, based on documented geoheritage, geosite inventories, and geoconservation frameworks. Geoparks are categorized according to their dominant narratives—ranging from recent Quaternary volcanism to broader tectonic, sedimentary, and metamorphic histories. Through an analysis of their distribution, management strategies, and integration into territorial planning, this work highlights the challenges that insular territories face, including vulnerability to global environmental change, limited legal protection, and structural inequalities in access to international resources recognition. It concludes that volcanic island geoparks represent strategic platforms for implementing sustainable development models, especially in ecologically and socially fragile contexts. Enhancing their global representation will require targeted efforts in ecologically and socially fragile contexts. Enhancing their global representation will require targeted efforts in capacity building, funding access, and regional cooperation—particularly across the Global South. Full article

(This article belongs to the Special Issue Feature Review Papers in Geological Oceanography)

27 pages, 4457 KiB

Open AccessArticle

Trajectory Tracking Design of Autonomous Surface Vessels with Multiple Perturbations: A Robust Adaptive Fuzzy Approach

by Yung-Hsiang Chen, Sheng-Yan Pan and Yung-Yue Chen

J. Mar. Sci. Eng. 2025, 13(8), 1419; https://doi.org/10.3390/jmse13081419 - 25 Jul 2025

Abstract

To achieve robust trajectory tracking performance for autonomous surface vessels (ASVs), a robust adaptive fuzzy control (RAFC) scheme is proposed. The trajectory tracking problem of ASVs is addressed through a unified control framework that integrates a nonlinear controller with an adaptive fuzzy estimator. [...] Read more.

To achieve robust trajectory tracking performance for autonomous surface vessels (ASVs), a robust adaptive fuzzy control (RAFC) scheme is proposed. The trajectory tracking problem of ASVs is addressed through a unified control framework that integrates a nonlinear controller with an adaptive fuzzy estimator. In this framework, a nonlinear transformation is employed to first generate the trajectory tracking error dynamics, and then the adaptive fuzzy estimator is utilized to accurately estimate the effects of multiple ocean perturbations. This unified design ensures both robustness and high-precision trajectory tracking for the controlled ASVs. To validate the effectiveness of the proposed method, two challenging simulation scenarios are investigated. The simulation results demonstrate the superior control performance and robustness of the proposed approach. Full article

(This article belongs to the Special Issue Advanced Research in Guidance, Navigation, and Control for Autonomous Surface Vehicle)

19 pages, 3997 KiB

Open AccessArticle

Adaptive Power-Controlled Energy-Efficient Depth-Based Routing Protocol for Underwater Wireless Sensor Networks

by Hongling Chu, Biao Wang, Tao Fang and Biao Liu

J. Mar. Sci. Eng. 2025, 13(8), 1418; https://doi.org/10.3390/jmse13081418 - 25 Jul 2025

Abstract

In this paper, we propose the Adaptive Power-Controlled Energy-Efficient Depth-Based Routing (APC-EEDBR) protocol. This protocol is designed to address the challenges posed by complex environments and limited resources in underwater-sensor networks. Employing a dual-weight adjustment mechanism and adaptive power control enables the protocol [...] Read more.

In this paper, we propose the Adaptive Power-Controlled Energy-Efficient Depth-Based Routing (APC-EEDBR) protocol. This protocol is designed to address the challenges posed by complex environments and limited resources in underwater-sensor networks. Employing a dual-weight adjustment mechanism and adaptive power control enables the protocol to achieve energy-efficient relay selection and enhance the link stability. The protocol adopts a cluster-free, hop-by-hop communication strategy and a cross-layer design to improve path stability and forwarding efficiency while mitigating hotspot issues in data aggregation areas. The simulation results demonstrate that the APC-EEDBR protocol effectively reduces energy consumption and communication overhead by approximately 16%, and significantly prolongs the network lifetime by about 39% compared with EEDBR. Full article

(This article belongs to the Section Ocean Engineering)

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19 pages, 6886 KiB

Open AccessArticle

Nonparametric Prediction of Ship Maneuvering Motions Based on Interpretable NbeatsX Deep Learning Method

by Lijia Chen, Xinwei Zhou, Kezhong Liu, Yang Zhou and Hewei Tian

J. Mar. Sci. Eng. 2025, 13(8), 1417; https://doi.org/10.3390/jmse13081417 - 25 Jul 2025

Abstract

With the development of the shipbuilding industry, nonparametric prediction has become the mainstream method for predicting ship maneuvering motion. However, the lack of transparency and interpretability make the output process of the prediction results challenging to track and understand. An interpretable deep learning [...] Read more.

With the development of the shipbuilding industry, nonparametric prediction has become the mainstream method for predicting ship maneuvering motion. However, the lack of transparency and interpretability make the output process of the prediction results challenging to track and understand. An interpretable deep learning framework based on the NbeatsX model is presented for nonparametric ship maneuvering motion prediction. Its three-tier fully connected architecture incorporates trend, seasonal, and exogenous constraints to decompose motion data, enhancing temporal and contextual learning while rendering the prediction process transparent. On the KVLCC2 zig-zag maneuver dataset, NbeatsX achieves NRMSEs of 0.01872, 0.01234, and 0.01661 for surge speed, sway speed, and yaw rate, with SMAPEs of 9.21%, 6.40%, and 7.66% and R² values all above 0.995, yielding a more than 20% average error reduction compared with LS-SVM, LSTM, and LSTM–Attention and reducing total training time by about 15%. This method unifies high-fidelity forecasting with transparent decision tracing. It is an effective aid for ship maneuvering, offering more credible support for maritime navigation and safety decision-making, and it has substantial practical application potential. Full article

(This article belongs to the Section Ocean Engineering)

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Journal of Marine Science and Engineering

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