Journal of Marine Science and Engineering doi: 10.3390/jmse14171654

Authors: Junhui Chen Fei Tang Heshan Lin

Fujian has one of China’s most tide-dominated and heavily engineered coasts, yet no segment-scale vulnerability assessment exists. We assessed 2449 km of mainland shoreline in 1 km segments using the classic six-variable coastal vulnerability index, from public data. Change rates came from thirty annual Landsat-based shorelines, giving a complete index for 2293 segments. The very high vulnerability class (defined by provincial quartiles) is predominantly concentrated in Putian (51.9 percent) and Quanzhou (42.8 percent). Those differences follow shoreline type. Eighty percent of the remaining 115 km of sandy shore is very high, against 53 percent of rocky shore in the low class. An exact decomposition gives each segment a dominant contributor from tide in Ningde to waves in Zhangzhou. Thirty percent of the 1.70 million people within 1 km of the coast live behind the very high quarter. Eleven sensitivity runs move individual segments, but none breaks the link to shoreline type, and Putian and Quanzhou lead even without the rate variable. The two published conventions for scoring tidal range rank different prefectures first, and each matches a different hazard. The storm-framed convention leads with Zhangzhou, where 99.7 percent of the province’s 2020 storm-surge damage fell.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171653

Authors: Laixiang Xu Jun Cheng Zhidong Liu Zhihui Zhou Xiao Ning Xinyuan Liu Tian Zhang

To accurately assess the time-dependent reliability of bridge piers in marine environments, this paper proposes a time-dependent reliability evaluation method for bridge piers based on a Dynamic Bayesian Network (DBN). By establishing a resistance degradation model under the combined effects of reinforcement corrosion and concrete deterioration and embedding it into the DBN framework, dynamic prediction and updating of pier time-dependent reliability are achieved. A case study of a twin-column pier was conducted for verification, showing that the computational results of the proposed DBN model align well with the first-order reliability method (FORM), validating its accuracy and feasibility in time-dependent reliability prediction. Further, using the most severe service condition, that is, the tidal-spray zone as an example, the DBN prediction results were updated with inspection data to achieve dynamic assessment of the actual pier lifespan. Additionally, a comparative analysis of environmental zones revealed that the tidal-spray zone exhibits the fastest reliability degradation, followed by the atmospheric zone, while the submerged zone shows the slowest.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171652

Authors: Francis Noblesse Jiayi He

This study considers the Fourier component in the basic Rankine–Fourier decomposition of the flows created by pulsating sources and dipoles (with time-harmonic strength) uniformly distributed over a general flat triangle that steadily advances in calm deep water. The Fourier potentials related to these basic flows are decomposed into a wave component defined by a single (one-fold) Fourier integral of an elementary exponential/trigonometric wave function, and a local-flow component defined by a single Fourier integral of the logarithmic function and the complex exponential integral function. These single Fourier integral representations of the waves and the local flows created by sources or dipoles distributed over a general flat triangle do not involve approximations, i.e., are exact, and are simple and well suited for reliable and practical numerical evaluation.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171651

Authors: Yuefeng Liao Jiarui Dong Xiao Han Duo Yang Xiaoxue Wan

Multi-module DC–DC converters are well suited to shipboard DC power systems with stringent requirements for high power density, operational safety, and continuous power supply. By distributing the system voltage, current, and power among multiple submodules (SMs), the modular architecture reduces device stresses and facilitates capacity expansion, maintenance, and redundant operation. Among the available modular configurations, the input-series output-parallel (ISOP) structure is particularly suitable for interfacing high-voltage DC buses with low-voltage, high-current loads. However, conventional voltage- or current-sharing strategies generally neglect efficiency differences among SMs. Under equal power sharing, low-efficiency SMs generate greater losses and experience higher thermal stress, resulting in thermal imbalance and accelerated aging. To address this issue, an efficiency-consensus-based power-distribution strategy is proposed for ISOP LLC-DAB hybrid converters. A distributed efficiency observer based on multi-agent consensus theory dynamically regulates the power references according to the relative efficiencies of the SMs, allowing high-efficiency modules to process more power while reducing the loading of low-efficiency modules. Experimental results obtained from a three-module prototype include comparative efficiency measurements and temperature-distribution tests. The results demonstrate that the proposed strategy improves the efficiency consistency among the three SMs, redistributes power according to their relative efficiency states, and reduces the temperature difference among the modules, thereby mitigating localized loss concentration and thermal imbalance. The proposed method provides a feasible solution for improving the electrothermal operating conditions of modular DC–DC converters. The achieved reduction in thermal imbalance may contribute to enhanced long-term reliability by alleviating uneven electrothermal stress.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171650

Authors: Weimin Chen Dongmei Song Bin Wang

Spaceborne Global Navigation Satellite System Reflectometry (GNSS-R) archives usually provide only one delay–Doppler map (DDM) for each recorded observation condition, limiting the representation of residual DDM variability. This study proposes a Position-Guided Conditional Normalizing Flow (PGCFlow) for observation-grounded probabilistic expansion of ocean bistatic radar cross section (BRCS) DDMs. PGCFlow uses four invertible affine coupling blocks to map a 17 × 11 DDM to an equal-dimensional Gaussian latent space. Wind–Auxiliary Condition Modulation incorporates a seven-dimensional condition vector into affine-parameter prediction, while Position-Guided Cross-Partition Aggregation (PGCA) uses deterministic grid descriptors to retain explicit cell locations and facilitate spatial-dependence modeling. Experiments used 5,819,042 quality-controlled CYGNSS observations from 2024. PGCFlow was compared with a conditional variational autoencoder and a generic conditional invertible neural network on 8000 held-out recorded conditions drawn from the same empirical observation domain, with 16 generated DDMs per condition. Although the cVAE achieved the highest balanced-aggregate structural similarity (SSIM) of 0.9396, PGCFlow obtained the lowest Fair Energy Score (FES) and Variogram Score (VS) of 0.2242 and 0.0641 and the closest relative local-neighborhood dispersion to unity at 1.0501. It also achieved the lowest frozen-estimator response RMSE and response MAE of 1.1900 and 0.9129 m/s, respectively. Ablation results indicated individual contributions from both proposed modules. Overall, PGCFlow achieved a favorable trade-off among the evaluated fidelity, dependence, dispersion, and response-consistency measures.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171649

Authors: Ramazan Tufan Azrak Bülent Düz Yordan Garbatov Bahadır Uğurlu

A residual multilayer perceptron (ResNetMLP) surrogate framework is presented to predict the broadband radiated sound power spectra of submerged circular cylindrical shells. The surrogate maps the shell mean radius, wall thickness, and longitudinal excitation position to the unit-force sound power spectra generated by a high-fidelity frequency-domain solver. The trained model is deployed within a diagonal power superposition scheme using equivalent nodal forces derived from an unsteady computational fluid dynamics surface pressure field. Comparing surrogate predictions with direct diagonal vibroacoustic calculations confirms the high predictive accuracy within the diagonal approximation. Crucially, a key limitation of sound power-based surrogates is highlighted: because acoustic power is a quadratic scalar quantity, it cannot capture phase-coherent load interaction, providing a clear rationale for future pressure-based surrogate formulations.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171648

Authors: Miaomiao Meng Wei Deng Kaijun Xu Zhongliang Wu Jin Liang Jianping Li

The integrated fusion and inversion of seismic data and marine controlled-source electromagnetic (MCSEM) data can identify the gas hydrate distributions. However, due to differences in observation systems and scales between seismic and MCSEM data, current fusion methods have failed to effectively address the critical issue of physical property variation within gas hydrate reservoirs. This research seeks to consolidate the two datasets into a cohesive observational framework. By transforming the MCSEM data into low-frequency constraints applicable to seismic impedance inversion, it is possible to realize an effective integrative interpretation that combines both seismic and MCSEM data. Using a 3 km-long seismic dataset and MCSEM data from the Shenhu Sea area in the South China Sea as a case study, we apply the Poisson blending algorithm to integrate seismic and MCSEM data, enabling precise identification and characterization of gas hydrate reservoirs and underlying gas-bearing fluids. The gas hydrate saturation results, derived from seismic inversion constrained by MCSEM data, demonstrate strong consistency with well logging and geological interpretation. This concordance validates the efficacy of the integrated fusion and inversion methodology and highlights its advantages in accurately predicting the spatial distribution of gas hydrate enrichment. The developmental positions of deep gas-bearing fluid pathways, coupled with the fault locations within the free gas zone and gas hydrate-bearing layer, play significant roles in the heterogeneous enrichment of gas hydrates. This research provides important technical and theoretical support for the precise and efficient prediction of gas hydrate reservoirs.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171647

Authors: Junjie Li Bolong Liu Xiaojun Xu Yaxin Xie

This study investigates the hydrodynamic behavior of an amphibious rescue and operation platform equipped with detachable floating boxes and a front bucket system, and it further develops a control-oriented turning optimization framework for a two-bucket steering configuration. Calm-water resistance, free-surface evolution, running attitude, and roll decay were analyzed using a Reynolds-averaged Navier–Stokes/volume-of-fluid solver with overset grids and dynamic fluid–body interaction. Straight-ahead non-rotating cases were computed using a symmetry-based half-domain model, whereas roll- and turning-related cases were simulated in the full domain. The numerical method was validated against towing-tank data for a benchmark amphibious vehicle, and the predicted resistance showed an overall deviation of 2.11%. The results show that the detachable floating boxes slightly increase resistance at 2 km/h, but reduce resistance by approximately 11.4% at 8 km/h owing to favorable wave interference. They also reduce trim and heave over the investigated speed range and markedly improve transverse stability, with the roll motion decaying to nearly zero within about 20 s. By contrast, the installation of the bucket substantially increases hydrodynamic resistance; at the design cruising speed of 8 km/h, the resistance increase reaches about 74.4%, while a bucket-induced bow-down moment modifies the running attitude and suppresses heave. At cruising speed, the bucket swing-arm angle has a non-monotonic influence: the resistance reaches a local peak near 6°, the minimum resistance is obtained at 20°, and the smallest trim is achieved at 4°. Based on these findings, a symmetry-preserving hydrodynamic surrogate and a constrained optimization strategy were established for bucket-controlled turning-radius allocation. The results indicate that differential bucket motion is the primary steering mechanism, whereas the bucket-arm angle provides secondary steering amplification at the cost of additional drag. The present study provides an integrated hydrodynamic basis for the design, operation, and steering-oriented control allocation of amphibious rescue platforms.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171646

Authors: Chenyu Wang Jiaqi Xu Xiangwei Liu

Inland-vessel speed reductions targeted at priority segments can reallocate a normalized burden proxy across a fixed corridor. We develop a route-integrity speed-planning model that accepts a plan only when it attains the priority target, preserves route-wide improvement, and caps the largest non-priority-segment increase. The kinematics distinguish speed over ground, along-route current, and speed through water; without voyage-matched current or speed-through-water observations, the cases use zero-current analytical references. We evaluate two AIS-derived cases: the 27-point Case A as a sparse stress test and Case B as the primary spatial case after WGS84 and ESA WorldCover alignment checks. Under the equal-time constraint, an unprotected 2% target induces local deterioration. With a 0.5% non-priority cap, Case B supports a certified maximum target of 0.999%; a 2% late-arrival allowance raises the certified maximum target to 11.912%. Direct search over 0.1-kn commands finds a feasible plan for Case B; however, none of 1000 sampled ±0.2-kn execution-error profiles remains feasible. The framework identifies model-internal proxy transfer rather than measured energy, emissions, or exposure effects.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171644

Authors: Siqing Guo Yubing Wang Mingyuan Yue Lei Dai Hao Hu Shaosong Zhu Yuni Li

Battery-powered propulsion offers a pathway for reducing inland shipping emissions. However, low battery energy density limits sailing range and may require energy replenishment during a voyage, thereby complicating energy and voyage planning for inland electric vessels. Time-of-use (TOU) pricing creates cost-saving opportunities but further complicates planning because energy replenishment and sailing speed are closely coupled. This study develops a joint optimization framework for an inland electric vessel under TOU pricing that determines replenishment ports, technologies, amounts, and leg-specific sailing speeds to minimize total replenishment costs. The problem is formulated as a mixed-integer nonlinear programming model and reformulated as a mixed-integer linear programming approximation through equivalent linearization and speed discretization. A Yangtze River case study with five operating conditions evaluates the proposed framework. The results show that, under the proposed framework, TOU pricing reduces total replenishment costs by 42.4–43.4% compared to fixed pricing. Relative to a sailing-speed optimization benchmark, joint optimization under TOU pricing reduces replenishment costs by 9.8–12.5% and energy consumption by 4.2–5.6%. The cost-saving potential also varies with the voyage time limit, voyage start time, relative charging and battery swapping rates, and the availability of opportunity charging.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171645

Authors: Iva Mrša Diana Mance Davor Mance Zoran Mrša

This study develops a SCHISM-based hydrodynamic model and an offline Lagrangian virtual-particle workflow for the Zadar Channel, a geometrically complex island–mainland passage in the eastern Adriatic. Independent hourly observations from the MP Zadar tide gauge operated by the Hydrographic Institute of the Republic of Croatia (HHI) were used to evaluate the modelled free-surface response. After exclusion of the first 24 h ramping period, 192 matched hourly pairs gave a Pearson correlation of 0.913, a mean bias of 0.012 m, a mean absolute error of 0.051 m, and a root-mean-square error of 0.070 m; cross-correlation was maximized at zero lag. The model reproduced the timing of the observed oscillations but underestimated their amplitude, with simulated and observed standard deviations of 0.117 and 0.157 m, respectively. The adopted unstructured mesh contains 16,962 triangular elements and 9081 nodes. In four 24 h particle-sensitivity tests, maximum reach ranges from 8.4 to 14.2 km; a 15-fold change in horizontal diffusivity affects reach less than sampling a lower model layer, which reduces reach by 32.8%. In the June 2025 event calculation, cumulative numerical shoreline contact increases from zero to all 1000 particles. The approximately 4 km Copernicus regional product masks the narrow interior passages and is therefore used only to assess spatial representativeness, not to validate channel currents. The tide-gauge comparison supports the modelled sea-level response and its timing at one station, but does not constitute direct validation of local current velocities. The reported trajectories are current-driven passive-particle diagnostics; wave–current coupling, Stokes drift, and material-specific fate processes are not represented.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171643

Authors: Nan Li Jinhao Wu Chaokui Hu Guangjun Song Zhaohui Wang Yutong Liu Lun Song Kun Wang

Winter ice-cover periods pose substantial risks to Apostichopus japonicus aquaculture in northern China. We combined field monitoring of three representative aquaculture ponds between 2014 and 2017 with controlled single-factor laboratory exposures to low temperature, hypoxia, and hyposalinity in adult and juvenile sea cucumbers. Field observations revealed pronounced temporal, vertical, spatial, and interannual variability in water temperature, salinity, and dissolved oxygen (DO) during freezing and ice-melting periods. All three stressors caused clear deterioration in physiological condition, with juveniles generally exhibiting greater short-term sensitivity than adults under low-temperature and hypoxic exposure, whereas severe hyposalinity caused pronounced deterioration in both life stages. Lactate, malondialdehyde (MDA), and glutathione (GSH) showed distinct treatment- and time-dependent responses, consistent with stress-associated changes in anaerobic metabolism, lipid peroxidation, and glutathione-associated antioxidant status. Integration of field observations with laboratory responses indicated that water temperatures approaching 0 °C and salinities approaching approximately 20‰ represent environmentally relevant conditions associated with elevated overwintering risk. DO concentrations approaching approximately 3 mg/L may warrant intensified monitoring and management intervention, whereas 2 mg/L represents a more severe experimental hypoxia condition. The more extreme treatments of −2 °C and 15‰ should similarly be regarded as severe experimental scenarios rather than commonly occurring field conditions. These environmental values should therefore be interpreted as preliminary management-oriented risk references rather than definitive physiological thresholds. Overall, the study provides an empirical field-to-laboratory basis for biologically informed winter environmental monitoring and risk-based overwintering management of A. japonicus aquaculture.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171642

Authors: Zhengyuan Zhu Yuda Sheng Minshuo Chen Lei Huang Wei Qin Jianlong Yang Ruisi Guo

Direct-drive wave power generation systems based on permanent magnet linear generators (PMLGs) produce fluctuating electromagnetic power under irregular wave excitation, which may affect DC-bus voltage stability and load-side power quality. To smooth the fluctuating output power, this paper develops an empirical mode decomposition (EMD)-based power allocation strategy for a battery–supercapacitor hybrid energy storage system (HESS). In the proposed strategy, EMD is used to decompose the fluctuating electromagnetic power into low-frequency and high-frequency components according to their time-scale characteristics. The low-frequency component is assigned to the battery for energy buffering, while the high-frequency component is assigned to the supercapacitor for transient power compensation. Finite-control-set model predictive current control (FCS-MPCC) is adopted on the generator side to improve the current response of the PMLG, and an MPC-based HESS controller is designed to track the assigned power commands and regulate the DC-bus voltage. Simulation results show a battery power-tracking error of 3.93 W and a DC-bus voltage standard deviation of 0.108 V; compared with LPF, EMD reduced the load-step voltage deviation by 11.94%. Experiments confirm that the PMLG back-EMF follows the translator velocity, the storage currents track their references, and the DC-bus voltage remains within ±2 V of its reference.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171641

Authors: Xinge Geng Weiguo Wu Yongshui Lin

This study investigates the influence mechanism of biomimetic microstructures on propeller pressure fluctuations and radiated noise using numerical simulations. Based on the SST k-ω turbulence model and Lighthill’s acoustic analogy, the flow field and acoustic performance of propellers with and without microstructures are comparatively analyzed under different advance coefficients. Results show that microstructures arranged at the trailing edge optimize surface pressure distribution and promote a more uniform flow field. More importantly, they facilitate orderly vortex generation and shedding, reducing blade surface vortex intensity and suppressing flow-induced pressure fluctuations at the source. Acoustic analysis confirms that microstructures effectively reduce discrete noise at characteristic frequencies, with far-field maximum sound pressure level reductions of 5.94 dB at J = 0.5 and 3.11 dB at J = 1, while the noise directivity pattern is transformed from a “figure-of-eight” to a “heart-shaped” distribution. This study reveals the hydrodynamic mechanism of passive flow control for noise reduction via biomimetic microstructures, providing novel insights and theoretical foundations for low-noise propeller design and acoustic stealth technology development.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171639

Authors: Wanni Li Jiachen Yan Zhengyi Sang Hengwei Zhang Le Cao

Near-seabed contact operations with underwater hexapod robots can require one leg to execute a contact task, which reduces the stability of the remaining asymmetric five-legged support. To address this problem, this study proposes a five-legged asymmetric coordinated stability control method that integrates gait rhythm planning with attitude feedback. The method decouples the left middle leg from support, propulsion, and CPG phase evolution to form a ‘5+1’ asymmetric support base. This configuration creates an asymmetric support base intended for future task execution while the reserved leg is maintained in a prescribed safe/task posture in the present simulations. Meanwhile, a five-legged Hopf-CPG rhythm maintains continuous gait under asymmetric support. Low-bandwidth attitude feedback modulation is introduced between the CPG-generated foot trajectory and the inverse-kinematics input to balance attitude correction with foot-contact continuity. Full-degree-of-freedom Webots simulations, rather than physical near-seabed experiments, show that, at a longitudinal flow speed of 0.8 m/s, the method reduces combined attitude RMS by 41.52% relative to the no-feedback strategy. Relative to high-gain PD control, it reduces the RMS rate of change of the control output by 71.32%. These results demonstrate improved command smoothness and metric-level compatibility with the five-legged CPG rhythm under a prescribed task-reserved leg posture, with a moderate trade-off in transient attitude suppression. The method therefore provides a simulation-verified control strategy for balancing attitude regulation and gait rhythm continuity under asymmetric five-legged support.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171637

Authors: Qi Su Ruolong Ma Shuo Zhang Xiulong Yang Hui Ma Xuecai Ma Ziming Zeng Fei Xie Zuoyou Li Jianhua He

The marine shale of the Ordovician Wulalike Formation in the northwestern Ordos Basin is an important target for shale gas exploration in northern China. The shale is thermally mature to locally highly mature, and generally has relatively low total organic carbon (TOC) and gas contents. Consequently, the paleoenvironmental controls on organic matter enrichment and the criteria for identifying favorable exploration intervals remain poorly constrained. This study integrates newly generated data from Wells LY1 and NBY1 with compiled data from seven representative wells (LY1, NBY1, QT9, ZP1, YT1, HT1, and L105). Organic geochemical, biomarker, major- and trace-element, rare earth element, and mineralogical data are used to reconstruct paleowater depth, bottom-water redox conditions, water-mass restriction, paleoclimate, paleosalinity, and paleoproductivity. The results reveal an upward transition from comparatively deeper water, weaker ventilation, and more reducing conditions in the Wu-3 Member to shallower, better-circulated, and more oxygenated conditions in the Wu-1 Member. The Wu-3 Member records the strongest bottom-water reduction and water-mass restriction, the greatest nutrient availability and paleoproductivity, and the most favorable preservation conditions. The Wu-2 Member records intermediate conditions, whereas the Wu-1 Member accumulated in relatively shallow, oxic–dysoxic water. Organic matter was derived predominantly from marine algae, phytoplankton, and acritarchs, with limited terrigenous input, and the silica was mainly biogenic. Organic matter enrichment was jointly controlled by primary productivity, reducing preservation conditions, rapid burial, and dilution by carbonate and terrigenous material. The lower Wu-3 and middle Wu-2 members are identified as the most favorable shale gas exploration intervals. These findings clarify the coupling between paleoceanographic evolution and organic matter accumulation and provide a geological basis for predicting shale gas sweet spots in the Wulalike Formation of the northwestern Ordos Basin.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171640

Authors: Zhiyuan Zeng Jie Wen Chunxu Li Yue Zheng Xiongfei Geng

Reliable near-coastal localization is difficult because LiDAR and scanning radar fail in complementary regimes: LiDAR provides precise local geometry but loses support over open water, whereas radar preserves long-range observations but suffers from clutter, multipath, and low spatial resolution. We present RACIF-SLAM, a reliability-aware framework that unifies continuous localization and hierarchical occupancy mapping. RACIF-SLAM transforms sensor-native motion increments into a common vessel frame, infers temporally filtered reliability from registration evidence, and applies an innovation gate to suppress the less credible modality under cross-sensor conflict before fusion on SE(2). When LiDAR tracking collapses, a radar bridge sustains motion estimation and re-anchors the recovered LiDAR segment without trajectory discontinuity. For mapping, LiDAR retains local occupied/free-space authority, while spatially broadened radar evidence extends support beyond the effective LiDAR range. In the four evaluated near-coastal segments, every reported pose was supported by at least one accepted sensor increment; the dead-reckoning fallback was not invoked. Against synchronized dual-antenna GNSS, RACIF-SLAM achieves a mean ATE of 0.700 m and a 10-frame translational RPE of 0.183 m, reductions of 66.3% and 65.1%, respectively, over the next-best evaluated method. These segment-specific results indicate that evidence-dependent authority transfer can improve localization continuity while retaining fine local map structure.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171638

Authors: Yuping Liu Haining Lyu Xinran Liu Maozhen Xia Zhiyong Xu

To address sustained deviation from coverage lanes when an unmanned surface vehicle (USV) executes a complete boustrophedon coverage path under current disturbances, this study proposes an adaptive current-aware line-of-sight (ACA-LOS) guidance method based on online current estimation. The local current is estimated online from the kinematic velocity relationship between the USV and the surrounding water, and its path-normal component is extracted. The estimated path-normal current is used both to construct a current-compensating heading correction and, together with the cross-track error, to adjust the LOS lookahead distance and generate the desired ACA-LOS heading. Complete-path simulations are conducted under constant, time-varying, and spatially varying currents with different current speeds and directions. Relative to conventional LOS, ACA-LOS reduces the mean cross-track root mean square error (RMSE) by 40.80%, increases the tolerance-band compliance rate (Rb) by 27.48 percentage points, and reduces the cumulative cross-track deviation area (Ad) by 68.68%. ACA-LOS suppresses sustained lane deviation caused by current disturbances and improves lane keeping throughout complete boustrophedon path execution. The method supports the extension of USV operation from single-trajectory tracking to long-duration, continuous coverage execution and provides a reference for unmanned and intelligent waterborne operational equipment.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171636

Authors: Rui Cong Dajun Liu Yan Yin Yaochuan Wang Haiyang Zhong

In this paper, based on a theory given by Gori, we have introduced a flat-topped lattice named a multi-cosine-multi-Gaussian correlated beam (McMGCB); the coherence function of the McMGCB consists of a multi-cosine component and a multi-Gaussian component, and the array composed of flat-topped beamlets can be realized by this McMGCB. Based on the extended Huygens-Fresnel integral, the propagation equation of such McMGCB is derived. The McMGCB with smaller δ will split into a beam array faster. And the number of beamlets is determined by Nx and Ny. The flatness of the beamlets is controlled by F. Moreover, the beamlets of such a McMGCB in stronger oceanic turbulence can overlap and merge into one spot. The characterizations of this flat-topped lattice with its adjustable parameters provide a method to generate a rectangular flat-topped beam array, which may have applications that demand a flat-topped array.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171635

Authors: Elena Piscitelli Loredana Manfra Fabio Matano Diego Vicinanza Alice Rotini

Posidonia oceanica (Delile) is a Mediterranean seagrass species whose fallen leaves accumulate along shorelines, forming compact structures known as banquettes. Despite their ecological and protective functions, these deposits remain insufficiently documented across the Mediterranean and are frequently removed before the summer season due to tourism and aesthetic considerations. This study develops and tests a Geographic Information System (GIS)-based methodology for mapping and inventorying P. oceanica beach-casts across five representative pilot areas along the Italian coastline (Western Sardinia; Liguria; Northwestern Sicily; Elba and Giglio Islands, Tuscany; Gargano coast, Apulia). The approach integrates historical Google Earth imagery with spatial datasets to characterize beach-cast occurrence and persistence and to describe their distribution in relation to selected geomorphological, environmental, and anthropogenic variables. Based on historical Google Earth imagery covering approximately three decades (~1998–present), beach-casts were identified at least once on 94% of the 393 surveyed beaches, indicating that the phenomenon is widespread across the investigated areas, with permanent banquettes representing a substantial component (63%). The spatial distribution of beach-casts was also examined in relation to shoreline dynamics, beach surface type, coastal vulnerability, and beach use, providing a descriptive characterization of their environmental and anthropogenic context, while the relative influence of the considered factors requires further investigation. The resulting standardized and reproducible framework provides a basis for future monitoring and susceptibility assessments across broader coastal sectors and can support evidence-based management of P. oceanica beach-casts.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171634

Authors: Wenxuan Ma Xianku Zhang Teer Guo

To improve the prediction reliability of model predictive control under model mismatch and environmental disturbances, this paper proposes a prediction-error-compensated MPC method with a forgetting factor for ship trajectory tracking and collision avoidance. The proposed method is developed within a Frenet-frame virtual ship group framework. A compensation term is introduced to correct the predicted heading-output sequence in the MPC prediction horizon, and a forgetting factor is used to regulate the influence of historical prediction errors on the current compensation term. Candidate trajectories are generated in the Frenet frame and evaluated using a hierarchical cost function to select a feasible obstacle avoidance path. Simulation experiments were conducted using the MMG model of the “Yukun” ship in three types of maritime encounter scenarios (head-on encounter, crossing encounter, and overtaking encounter) and a comprehensive obstacle scenario. The simulation results show that the proposed method can generate feasible local collision avoidance trajectories in complex obstacle environments and typical encounter scenarios, and maintain good trajectory tracking performance. It provides an effective scheme for trajectory tracking and collision avoidance of underactuated ships with great theoretical and practical value.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171633

Authors: Wujun Tong Yingying Wang Zeqing Lin Dingwen Huang Haibo Li Xinzhong Li

As a critical regulating component in subsea Christmas tree systems, the cage-type choke valve governs the overall production efficiency and operational reliability of offshore oil and gas exploitation owing to its unique internal flow field characteristics. In accordance with the in situ operating conditions of the target oilfield, this paper performs a numerical simulation and systematic analysis on the flow field behaviors of a cage-type choke valve. Based on the fundamental theories of computational fluid dynamics (CFD), a three-dimensional coupled flow and heat transfer numerical model for the target choke valve is constructed via the FLUENT solver. Flow parameters under diverse pressure difference conditions are measured, validating the accuracy and feasibility of the established numerical model. Corresponding model hypothesis criteria and boundary condition configuration schemes are explicitly defined. Spatial distribution characteristics of the internal temperature, velocity, and pressure fields of the choke valve under different operating conditions are obtained through numerical simulation. Ten monitoring nodes uniformly arranged along the fluid domain from the inlet to the outlet are selected for quantitative analysis. The research results clarify that lower seawater temperature intensifies heat dissipation, leading to the observed temperature decrement, and confirm that the cage orifice structure dominates the flow acceleration, with the pressure drop magnitude linearly correlating with the inlet–outlet differential pressure. The research methodology and numerical findings of this study can provide a reliable basis for structural optimization and operating condition matching of cage-type choke valves applied in subsea oil and gas production systems.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171631

Authors: Yu Zhao Chao Wang Cong Sun Yi-Ming Hu Hao-Yu Liu Min Liu

This study employs a Contracted and Loaded Tip (CLT) propeller to replace the conventional pump-jet rotor, and a comparative analysis is conducted using the Detached Eddy Simulation (DES) method. The reliability of the numerical method is first validated through open-water tests. The CLT pump-jet propulsors are systematically investigated in two series: the varying endplate width (CW) and varying endplate length (CL). The results indicate that varying the endplate width has a significant impact on the hydrodynamic performance. A smaller width leads to a more pronounced decrease in the thrust coefficient, torque coefficient, and efficiency. In contrast, varying the endplate length primarily affects the efficiency at high advance coefficients. Regarding the vortical characteristics, the gap region is dominated by the tip leakage vortex (TLV) and tip separation vortex (TSV), whose intensity and evolution are influenced by the endplate structure. A reduced endplate width expands the low-velocity region within the gap, while an increased length contributes to a more stable vortex development. In terms of the noise performance, the varying-width designs effectively suppress pressure fluctuations and achieve noise reduction. Specifically, the CW3 model exhibits maximum reductions in the overall sound source level of 5.7 dB and 4.0 dB at distances of 1 m and 20 m, respectively. Conversely, the varying-length designs intensify the pressure fluctuations and show no significant noise reduction effect.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171632

Authors: Junwei Zhou Letong Li Lei Mei Yiyan Zhang Liping Shi Weichao Shi

Numerous studies indicate that a flapping-foil thruster installed at a ship’s bow can convert wave energy into propulsive power and reduce added wave resistance while improving dynamic stability. Based on the preliminary exploration of the drag reduction mechanism of an elastic bow-flapping-foil system in waves, this paper further compares the effects and universality of this system on the resistance and motion response of different ship types under similar operating conditions, using three classic ship types (DTMB 5415, KCS, and Wigley) as research objects. Using the ISIS-CFD solver in NUMECA software, the study simulates the ship coupled with a semi-active elastic flapping foil in head waves, analyzing the influences of spring stiffness, foil size, installation position, and encounter phase on system performance. Numerical results show effective wave energy harvesting, boosting propulsion and stability. Under optimized parameters, ship pitch and heave amplitudes decrease by up to 20.14%, resistance reduction reaches 9.60%, and DTMB 5415 achieves a comprehensive drag-reduction and thrust-increase ratio of 31.39%. Further analysis reveals that thrust performance does not rise proportionally with spring stiffness, whereas drag and heaving reduction improve with increasing stiffness. The system performs best at a wavelength-to-ship-length ratio of 1.2 and a foil encounter phase of −90°. This work supports parameter optimization for such systems based on practical application scenarios and requirements.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171630

Authors: Limin Cui Yangyang Zhou Zhiting Yan Haitian Zhu Wentao An Lei Huang Weiliang Zhang Yinghui Fang

Wind shear coefficients (WSCs) are fundamental parameters for wind resource assessment, wind turbine design, and offshore wind farm operation. This work focuses on positive wind shear coefficients (WSCs); hereafter, WSC refers exclusively to positive-value wind shear coefficients derived from positive shear profiles. However, the characteristics of positive WSCs in the offshore waters of Zhuanghe have not yet been systematically investigated. In this study, two years of in situ observational data (2015–2017) were analyzed to characterize the temporal variability of positive WSCs under different atmospheric stability conditions. The results indicate that the atmospheric boundary layer in the study area exhibits pronounced seasonal and diurnal variations in stability, with stable and unstable conditions showing a distinct annual cycle. Increasing wind speed promotes neutral conditions as mechanically generated turbulence becomes dominant over buoyancy effects. The WSC ranges from 0.01 to 0.32 and exhibits pronounced seasonal and monthly variability. Under neutral and unstable atmospheric conditions, the diurnal variation in WSC is relatively consistent among different measurement heights, whereas stable conditions produce appreciable vertical differences in WSC throughout most of the year. These findings improve our understanding of offshore wind shear characteristics across various atmospheric stability regimes. Furthermore, they offer valuable guidance for offshore wind resource assessment, wind profile modeling, and the overall design and operation of wind farms in the Zhuanghe region.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171629

Authors: Tianyi Gao Mengdi Ma Sudong Xu Weikai Tan Hao Chen

Accurate short-term significant-wave-height forecasting is important for the safe and efficient operation of coastal and offshore activities. However, forecasting across sparse buoy networks remains challenging because wave conditions exhibit complex temporal variability and spatial dependence. This study proposes an Enhanced Crossformer, a dual-tower spatiotemporal framework that combines a Crossformer branch for modelling long-range inter-station dependencies with a Cheb–LSTM branch for capturing localised graph-based interactions. The framework was evaluated using 3-hourly significant-wave-height observations from 52 National Data Buoy Centre stations along the U.S. West Coast over the period 2020–2024. Missing observations were first estimated using a graph neural network imputation model, which achieved test-set R2 values ranging from 0.85 to 0.95 on artificially masked observations. Forecasting performance was then assessed for lead times of 3–24 h and compared with LSTM, Transformer, Cheb–LSTM, and Crossformer baselines. The Enhanced Crossformer achieved the lowest MAE, MSE, and MAPE values and the highest R2 and correlation values at all forecast steps. Relative to the strongest baseline, it reduced MSE by up to approximately 8.7% at short lead times and maintained positive improvements through the 24 h horizon. Forecast skill was strongest under low-to-moderate sea states but decreased for high-energy wave conditions and several sheltered stations in the Southern California Bight. These results demonstrate the potential of combining global attention with graph-based local recurrence for short-term multi-buoy wave forecasting.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171628

Authors: Yan Li Keping Jiang Zhibin Han

Flexible hoses connecting seabed mining vehicles to relay stations must remain suspended, limit vehicle loads, satisfy bending constraints, and maintain stable slurry transport. This study combines a lumped mass hose model, time domain vehicle motion analysis, and sequential structural-to-flow coupling with CFD–DEM to determine the safe operating domain of a 220 m single-arch hose. Thirteen buoyancy layouts were screened using seabed clearance, effective tension, curvature, and vehicle loads. Among the tested layouts, a buoyancy section extending from the vehicle end to 0.6L provided the best compromise. During outward travel, turning-induced peaks governed structural safety; after path optimization, the peak longitudinal and lateral hose loads were 17.78 and 22.38 kN, respectively, and the minimum bending radius remained above 2 m. At a reference slurry velocity of 5 m/s and solid volume fraction of 10%, a 40 m vehicle–relay spacing produced strong particle slip and concentration rebound near the lower bend, whereas 197 m promoted particle accumulation and a thicker moving bed. Integrating structural and conveying constraints yielded a recommended horizontal spacing of 80–160 m. Scaled pool tests and a published vertical pipe benchmark supported the numerical approach. The resulting domain provides a practical basis for path boundary design under the assumptions adopted here.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171627

Authors: Xiang Ji Lei Han Yan Zhang

Feature Mode Decomposition (FMD) adaptively decomposes signals into band-limited modes through an adaptive finite impulse response (FIR) filter bank optimized via correlated kurtosis (CK) maximization, yet its denoising performance is highly sensitive to four hyperparameters—the number of decomposition modes nm, the filter length L, the CK shift order M, and the characteristic-period scaling Tscale—whose manual tuning is impractical for multi-channel floating offshore wind turbine monitoring deployments. We propose GLO-FMD, an adaptive denoising framework coupling the Gray Langurs Optimizer (GLO) with FMD. GLO autonomously optimizes the FMD parameters, thereby aligning the CK objective with structural modal periods rather than impulsive fault periods. Although the search space spans (nm,L,M,Tscale), the CK shift order M is fixed at 2 and Tscale is estimated automatically from the dominant autocorrelation peak; consequently, only (nm,L) are actively optimized. The optimized FMD decomposes multi-axis tower-base signals into band-limited modes through iterative CK-maximizing FIR filter optimization; each mode identifies a dominant periodic component, and the original signal is zero-phase band-pass filtered around the identified frequencies to preserve physical phase during reconstruction. Validation employs (i) semi-synthetic signals reproducing the measured tower-base structure (a smooth 0.15 Hz structural mode plus an impulse-excited 3.77 Hz resonance) with exactly known ground truth—a best-case benchmark by construction that isolates denoising capability from reference uncertainty—and (ii) real strapdown inertial sensor data acquired at 8 Hz from the tower-base interface of a floating offshore wind turbine at an operational site in Chinese coastal waters, over a six-day measurement campaign (18–23 April 2023). Six kinematic channels spanning triaxial acceleration (north, up, east) and triaxial velocity (north, up, east) are analyzed, with 200-s (1600-sample) continuous windows extracted for algorithmic evaluation. On the semi-synthetic data, GLO-FMD achieves a 9.6–10.2 dB SNR improvement over default wavelet thresholding against the known ground truth, and the GLO optimization is essential for reliability—the default FMD configuration is unstable across noise realizations, whereas the optimized parameters recover the clean components consistently. GLO-FMD also achieves pseudo-reference-relative SNR gains of 5.3–7.8 dB over default wavelet thresholding across all six real-data channels. Bootstrap resampling over 12 independent segments confirms statistical significance (p<0.001, Cohen’s d>8), and a no-reference smoothness index provides complementary evaluation independent of the pseudo-reference assumption. Multi-day consistency analysis yields coefficients of variation below 5%, demonstrating short-term consistency across the environmental conditions represented in the six-day dataset. The online denoising stage requires approximately 1.5 s per channel, supporting potential deployment on edge-computing hardware at the turbine controller level.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171626

Authors: Xiaohui Chang Huimin Zhao Wentian Cui

The synchronous grouting layer in subsea shield tunnels is continuously exposed to seawater during long-term service. Sustained migration and diffusion of seawater ions can induce deterioration of the pore structure and degradation of mechanical properties, thereby diminishing the support and load-transfer functions provided to the segmental lining and ultimately compromising the long-term structural safety of the tunnel. In this study, synchronous grouting mortar obtained from an actual subsea shield tunnel project was subjected to freshwater and natural seawater immersion. Compressive strength tests and X-ray computed tomography were combined to investigate the evolution of mechanical properties and three-dimensional pore structure under prolonged exposure to natural seawater. Repeated scans were performed on the same group of samples at different immersion ages to determine total porosity, connected porosity, and pore connectivity. Quantitative relationships were then established between immersion time and both connected porosity and compressive strength. The results indicate that natural seawater exerts a pronounced influence on compressive strength at different stages, shifting from an initial enhancement to progressive deterioration during prolonged immersion. At 420 d, the compressive strength was approximately 23% lower than the peak value measured at 28 d. During prolonged immersion, total porosity increased gradually, whereas connected porosity and pore connectivity exhibited substantial increases. The difference shows that the internal structural evolution was governed primarily by the propagation and interconnection of existing pores and microcracks rather than by a substantial increase in total pore volume. With increasing immersion time, the pore structure progressively evolved from a dispersed and weakly connected state into a more continuous network of pores and cracks, accompanied by the enlargement and interconnection of local defects. The evolution of connected porosity with immersion time was well described by a square root function based on the characteristic time scale of Fickian diffusion, while the variation in compressive strength followed an exponential relationship. Increased connectivity of pores and cracks provided more continuous pathways for the inward transport of seawater ions and progressively disrupted the internal load-bearing framework, thereby contributing to the degradation of macroscopic mechanical properties. The findings provide experimental support for the durability design of synchronous grouting materials and the long-term maintenance of subsea shield tunnels.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171625

Authors: Xiong Xiong Xiaoyan Chen Bing Yang Lina Yin Bohuai Yao

High-density underwater fish multi-object tracking remains difficult because occlusion, small targets, background similarity, and noisy observations destabilize identity evidence. We study a reliability-first temporal identity memory in which a successful association does not automatically authorize an identity-memory update. AquaMambaTrack (AMT) decouples geometric/motion-state updates from admission to an online per-track FIFO: only observations that satisfy stage, geometry, appearance, and crowd-reliability checks enter the history aggregated by Mamba. With fixed official MFT25 detections and official TrackEval, AMT-L48 obtains 53.473 HOTA, 41.112 AssA, 59.543 IDF1, 85.265 MOTA, and 507 IDSW. In the write-policy ladder, unfiltered FIFO writing gives 47.973 HOTA and 33.189 AssA, whereas the complete policy gives 53.473 and 41.112; the GT-evaluable history-contamination rate decreases from 27.89% to 14.35%. Online track-conditioned history exceeds detection-linked history without fallback by 5.933 HOTA and the documented T = 1 fallback path by 4.210 HOTA. Across seeds 0, 1, and 2, L = 48 gives 52.662 ± 0.769 HOTA, and Mamba has the highest mean association metrics among the evaluated encoders in the same pipeline. The gain is not universal: at the common detection-score threshold of 0.15, SU-T has fewer raw ID switches (381) on MFT25; in the internal cross-scene case study, AMT leads HOTA, DetA, and MOTA but not AssA or IDF1, and has the most raw ID switches (82). Under precomputed detections, the cold-cache tracking pipeline runs at 30.33 ± 2.72 FPS.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171624

Authors: Xiang Ji Lei Han Yan Zhang

Floating offshore wind turbines (FOWTs) experience coupled aero–hydro–servo-elastic excitations that produce structurally distinct kinematic responses at different measurement heights. While field monitoring campaigns increasingly deploy multi-level inertial sensors, the quantitative spectral partitioning of response energy across measurement levels and its relationship to operational and environmental conditions remain poorly characterised for operational FOWTs. This study presents a systematic multi-level spectral decomposition of operational FOWT structural response using synchronised tower-base and nacelle strapdown inertial measurements acquired at 8 Hz over a six-day campaign (18–23 April 2023) at a semi-submersible FOWT in Chinese coastal waters. Six kinematic channels—three translational acceleration components and three translational velocity components—from each sensor are decomposed into four physically defined frequency bands: drift (0.005–0.05 Hz), wave (0.05–0.30 Hz), structural (0.30–0.50 Hz), and rotor (0.50–0.80 Hz). Three derived scalar metrics—band energy ratio (BER), Wave-to-Structural Dominance Ratio (WSDR), and Structural Amplification Factor (SAF)—are defined, with their complete computation specifications and parameter sensitivity analysis provided to ensure reproducibility. Across 36 ten-minute windows spanning diverse conditions (mean wind 4.2–12.1 m/s, Hs 0.8–3.1 m), results reveal a pronounced and consistent spectral separation: the tower base is strongly wave-dominated (BERwave = 75.9%, coefficient of variation CV = 15.0% across days), whereas the nacelle exhibits substantially elevated structural-band energy (BERstruct = 10.3%, 4.72-fold amplification relative to tower base, 95% CI [3.63, 5.81]) and rotor-band energy (11.8%, 3.77-fold amplification). The WSDR at the tower base (mean 200.9, 95% CI [101.4, 300.4]) exceeds that at the nacelle (mean 48.4, 95% CI [13.1, 83.7]) by a factor of 4.1×. One-way analysis of variance (ANOVA) reveals that nacelle structural-band BER is significantly modulated by SCADA operational regime (F=5.20, p=0.024, η2=0.16) and by significant wave height (p=0.031), while tower-base wave-band BER is primarily driven by Hs (p=0.018). Comparison with baseline features—root-mean-square acceleration, spectral peak frequency, and traditional broad-band energy ratio—demonstrates that the band-resolved BER provides finer discrimination between excitation mechanisms than aggregate metrics. Importantly, no structural damage events occurred during the monitoring period; therefore, the reported stability of these features is interpreted as a baseline characterisation under normal operational conditions, which could support future anomaly detection efforts but does not constitute validation of damage detection capability. A comprehensive limitations assessment is provided, covering single-turbine validation, frequency-band sensitivity, regime sample imbalance, and generalisability constraints.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171623

Authors: Xinyu Hu Lumin Sun Bing Xie Haojun Guan Jiahong Zeng Zikun Song Changyi Lu

Estuarine intertidal sediments are important sinks for riverine mercury (Hg), yet the effects of organic matter sources and BC fractions on Hg partitioning are still poorly understood. We analyzed sediments from reed-covered and unvegetated flats in the Yangtze Estuary for total Hg (THg), operationally defined Hg fractions, total organic carbon (TOC), total nitrogen (TN), n-alkanes, and BC fractions (char and soot). THg ranged from 60.3 to 228.5 ng g−1, averaging 114.6 ± 38.9 ng g−1. THg was significantly higher in reed-covered sediments and in surface layers, and was positively correlated with TOC and TN (p < 0.01, n = 20), indicating that vegetation-driven organic matter accumulation promoted Hg enrichment. Hg partitioning differed between habitats: reed-covered sediments showed co-dominance of oxidizable Hg and residual Hg, whereas unvegetated flats were dominated by residual Hg (62.0 ± 10.8%), suggesting stronger Hg stabilization in the absence of fresh plant inputs. n-Alkane patterns indicated that vegetation type controlled sediment organic matter composition more strongly than site or depth. While no significant correlations were observed between BC fractions and Hg fractions in individual habitats, soot exhibited significant positive correlations with labile Hg (acid-soluble and reducible Hg) in a depth-averaged analysis of merged surface and subsurface layers (p < 0.05, n = 10), a preliminary signal constrained by the small number of sites, which suggests that soot may facilitate the sedimentary retention of reactive Hg. These results highlight source-specific controls on Hg partitioning beyond bulk TOC.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171619

Authors: Xiong Deng Linfeng Li Xia Yang Dingfeng Yu Yiyun Peng Yan Luo Yanyang Wu

To address the limitations of poor adaptability and insufficient versatility of current surface capture technologies for autonomous underwater vehicles (AUVs) under high sea state conditions, this study proposes an ROV-based capture system equipped with guidance and clamping mechanisms for efficient and stable recovery of AUVs and similar floating targets in rough seas. This work is intended to provide technical support for solving AUV capture challenges in high sea states. Through a systematic investigation of capture methods and associated operational systems, the overall design of the dynamic surface AUV capture device is established. A three-dimensional model is developed to verify the feasibility of the overall operational sequence. Computational fluid dynamics (CFD) simulations are performed to analyze the hydrodynamic performance of the ROV carrier, with particular focus on the drag force and pressure distribution under flow velocities corresponding to Sea State 4 and below. The simulation results indicate that when the ROV inflow velocity reaches 3 m/s, the maximum drag force is approximately 5862 N and the maximum pressure on the frontal area is about 4570 Pa. Based on these data, the overall structural stability is verified, and the results confirm that the structure maintains adequate stability under the target operating conditions. Kinematic simulations are further conducted to investigate the collision force between the target AUV and the guidance/capture device under various initial attitudes and velocities in Sea State 4, thereby determining the overall capture tolerance envelope. Through design manual buffer parameter tuning and comparative improvement analysis, the collision force between the guidance device and the target is reduced by approximately 60%.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171622

Authors: Ying Wei Fenghui Han Huairui Li Wenhua Li Zhe Wang

Leveraging existing subsea natural gas pipelines for hydrogen blending offers a practical route for offshore low-carbon energy transport. However, traditional T-pipes require long distances to achieve uniform mixing conditions, raising the risks of stratification and hydrogen embrittlement. In this study, the conventional pipe fittings—elbows are innovatively adopted as passive mixing elements for hydrogen-blended natural gas pipes, expecting to use curvature-induced secondary flow and vortex reorganization to accelerate homogenization without extra flow mixers. Numerical simulations were performed to investigate the effects of the distance L1 between the hydrogen branch and the elbow inlet and the elbow curvature radius Rc. Hydrogen distributions, coefficient of variation, homogeneous mixing path, and flow vorticities were analyzed to make comparisons between the elbow configurations and the conventional T-pipe. The results show that a smaller L1 shortens the homogeneous mixing path Sh, while a smaller elbow curvature radius Rc generates stronger secondary flows but also intensifies the asymmetric hydrogen enrichment induced by centrifugal force. The mixing effect of the elbow configuration is more significant when HBR ≥ 20%, which gradually weakens as the HBR decreases. In this paper, the shortest mixing path Sh = 11.73 m is obtained in the optimal structure with L1 = 0 and Rc/D = 4, achieving a reduction of 67.3% relative to the conventional T-pipe. It proves that elbow structures can significantly enhance the mixing efficiency of hydrogen-blended natural gas pipes, providing new solutions for hydrogen blending in offshore pipelines.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171621

Authors: Tianwei Zhang Liangjie Mao Jiaxin Wang

In deepwater open-loop drilling of ultra-shallow high-build-rate horizontal wells, the drill string spans the exposed seawater section, the mudline transition, and the constrained downhole section. Existing studies have not yet established a unified coupled dynamic model covering the full string, and the response patterns and parameter-control mechanisms remain insufficiently understood. This study examines a surface-hole operation in a block of the South China Sea. A six-degree-of-freedom spatial Euler–Bernoulli beam finite element model was established from the measured wellbore trajectory. Structural and fluid inertia, geometric stiffness due to axially varying force, Morison-type current loading, a wake-oscillator model for vortex-induced vibration (VIV), wellbore contact and friction, and bit loads were coupled within one framework. The generalized-alpha method was used for time discretization, and the nonlinear dynamic equilibrium equations were solved by within-step iteration for multiple operating conditions. Under the baseline condition, the peak in-line displacement was 6.3–6.4 m and occurred in the middle of the seawater section; the peak cross-flow displacement was approximately 0.43 m, the maximum bending moment was approximately 36 kN m, and the maximum equivalent stress was approximately 230 MPa. The high internal-force values were concentrated in the mudline transition and the upper BHA, demonstrating spatial separation between deformation and internal force. Surface current velocity controlled the in-line response amplitude: increasing the velocity from 0.4 to 0.8 m/s increased the peak in-line displacement by approximately 230%. WOB had a limited effect on global deformation and acted mainly on the local near-bit section. These results provide numerical reference for mechanistic analysis and parameter control of drill-string dynamics in comparable deepwater open-loop drilling operations.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171620

Authors: Yichen Liu Lili Zhou Yuqing Ren Yingbang Huang

Ship collisions emerge from interactions among human, vessel, environmental, and management factors. Aggregate accident networks can, however, combine relations across events and evidence levels, obscuring whether recurrent topology represents event-level pathways. We coded 364 official Chinese collision investigation reports using Systems-Theoretic Process Analysis and constructed a directed binary network of 46 factors and 269 relations. Induced triads were evaluated against degree-preserving and functional block-preserving null models and then traced to accidents, responsible vessels, and responsibility chains. Four triads, 021C, 021U, 021D, and 030T, were overrepresented in the primary network. Frequency weighting preserved H1, H9, and H19 as the three highest-ranked nodes by total strength, whereas only 030T remained concentrated on high-support edges after block-stratified weight permutation. Evidence-tier filtering was more restrictive: the cumulative E1–E4 network retained 112 relations, and none of the four motifs remained significant under the functional block-preserving null model. Event-level support was strongest for 021C and 021U, whereas 030T mainly reflected aggregate transitive closure. The primary motifs therefore characterize structures generated by the complete report coding framework, not experimentally identified causal mechanisms. Combining constrained topology, recurrence weights, evidence grading, and event-level back-tracing provides an auditable basis for safety questions without conflating structural enrichment with causal strength.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171618

Authors: Mingxin Li Haolin Yang Chao Ma Yulei Zhu Xide Cheng Haoqin Huang

Reliable collision-risk warning during low-speed ship docking requires accurate and efficient hydrodynamic prediction. This study develops a physics-SVR (support vector regression) framework combining a three-degree-of-freedom maneuvering model with three SVR models that learn residuals in longitudinal force, lateral force, and yaw moment from computational fluid dynamics (CFD) data. The corrected loads support 120 s trajectory prediction and hull-envelope reconstruction. Minimum lateral and longitudinal clearances and their times to safety-threshold crossing distinguish normal, warning-alert, and emergency-alarm states. The database comprises 20 model-development conditions and three condition-level holdout tests representing unseen loading/draft, heading, and lateral-offset conditions. Across the holdout tests, overall relative errors decrease from 22.00–30.20% for the baseline model to 14.91–19.93%. In two hazardous cases, warning alerts precede contact by 154.9 and 172.09 s, while the non-hazardous control case triggers no alarm. The complete prediction-and-warning update requires 0.32 s on average, demonstrating potential for shore-based docking assistance under calm-water conditions.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171617

Authors: Arif Savaş Samet Uslu Oğuzhan Der Bulut Ozan Ceylan Fatih Kirma Ramazan Şener

The maritime sector’s greenhouse gas reduction targets are increasing interest in sustainable fuels compatible with existing diesel engine infrastructure. In this study, pure biodiesel of animal origin (AN100), pure biodiesel of plant origin (VG100), and conventional diesel fuel were experimentally compared in a single-cylinder, direct-injection diesel engine under controlled load conditions relevant to small-scale marine diesel applications. Brake specific fuel consumption (BSFC), brake thermal efficiency (BTE), and CO, HC, CO2, and NOx emissions were measured at six different engine loads. The data obtained were transferred to a representative 90-min operating cycle to determine total fuel consumption and emissions. Compared to diesel, AN100 and VG100 reduced CO emissions by 44.3% and 55.5%, and HC emissions by 18.2% and 26.0%, respectively. In contrast, CO2 emissions increased by 36.2% and 31.3%, while NOx emissions increased by 59.6% and 67.3%. Total fuel consumption also increased by 15.4% and 9.0% for AN100 and VG100, respectively, while BTE decreased by 8.1% and 0.3%. The operation cycle results confirmed that feedstock selection affects cumulative fuel demand and emissions. VG100 provided higher energy conversion performance, while AN100 offered a more balanced emission profile due to lower NOx and CO2 increases. The results indicate that the appropriate biodiesel selection should be made by considering fuel economy, emission priorities, and NOx reduction requirements together.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171615

Authors: Chenguang Liu Jialun Liu Xiumin Chu Xiao Lang

With the rapid advancement of artificial intelligence (AI), maritime autonomous surface ships (MASSs)—also referred to as autonomous vessels—have emerged as an important avenue of research in the maritime industry [...]

Journal of Marine Science and Engineering doi: 10.3390/jmse14171616

Authors: Dan Yu Lijing Dong

Unmanned Underwater Vehicle (UUV) swarms operating in complex marine environments must accurately assess threats from surrounding targets to ensure mission success and navigational safety. However, existing threat assessment methods face three fundamental bottlenecks when applied to underwater swarms: the inability to track temporally evolving target intentions, reliance on subjective indicator weighting for multi-target ranking, and vulnerability to spatially heterogeneous sonar noise. This paper proposes a hierarchical threat assessment framework that addresses these bottlenecks through three integrated modules. First, a Dynamic Bayesian Network with a specially designed heading factor tracks target intention over time, propagating threat probabilities across sequential observations and enabling early warning before the closest point of approach. Second, a Vieta’s theorem-based algebraic ranking algorithm constructs comprehensive threat vectors via elementary symmetric polynomials of six indicator utilities, avoiding explicit expert-defined weighting coefficients in the multi-attribute ranking stage while capturing both independent and synergistic indicator interactions. Third, a distance-weighted swarm aggregation strategy suppresses individual sonar noise by assigning higher fusion weights to geographically closer nodes, exploiting the spatial diversity inherent in swarm configurations. Simulation experiments under representative target-motion scenarios validate the framework across four complementary experimental studies. Results demonstrate that the DBN reduces output variance by over 56% compared to static Bayesian networks and responds to abrupt intention changes within 15 s. The algebraic ranking algorithm achieves identical prioritization to TOPSIS without requiring any manual or data-dependent weights. The distance-weighted aggregation reduces root mean square error by 63.2% and improves signal-to-noise ratio by 8.7 dB over equal-weight averaging. The proposed framework provides a principled and interpretable solution for simulation-based autonomous threat perception in representative underwater swarm scenarios.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171614

Authors: Zidong Zhao Haoran Ren Yuxiang Wu Zhaolin Zhu Guoxin Chen Xiaoyu Zhang

Marine seismic imaging is affected by limited acquisition aperture, nonuniform illumination, and complex features such as seafloor structures and low-velocity gas clouds. These factors can produce blurred reflectors, amplitude imbalance, and migration artifacts in conventional reverse-time migration (RTM). Point-spread-function (PSF)-based image-domain least-squares migration (ID-LSM) compensates for spatially varying imaging responses through deconvolution, but its ill-conditioned inverse problem can amplify weakly constrained spectral components. We propose HQS-LR, an HQS-inspired, physics-guided unrolled framework for PSF-based ID-LSM. Each of its T stages performs a closed-form Fourier-domain PSF-based data-consistency update, applies a U-Net-based module for learned structural regularization and reflectivity refinement, and fuses the two estimates using a relaxation weight. HQS-LR is trained end-to-end using supervised triplets of reflectivity patches, migrated-image patches, and PSF patches generated from the Marmousi model. Sequential calibration on the Sigsbee2A synthetic model selects a six-stage configuration for the subsequent experiments. In the Sigsbee2A calibration-set comparison, this configuration achieves a Pearson correlation coefficient (CC) of 0.681 and a normalized PSF forward-matching residual of 0.035, providing a favorable balance between reflectivity similarity and consistency with the PSF imaging model while reducing ringing and preserving reflector continuity and fault geometry. Applied to the Mobil AVO Viking Graben Line 12 dataset, HQS-LR improves reflector focusing and continuity, suppresses localized oscillatory artifacts, and exhibits broader effective wavenumber support than the evaluated alternatives. These results indicate the potential of combining PSF-based physical constraints with learned structural priors for marine seismic reflectivity inversion.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171613

Authors: Amélie Guitard Benjamin de Jourdan Noelle Babin Carter Eagles Atsushi Hagiwara Jae-Seong Lee Jeonghoon Han Jordan Jun Chul Park

As environmental pressures intensify, sustaining ecologically and economically important marine species such as the American lobster has become an increasing challenge. Climate-driven stressors are expected to disproportionately affect early life stages of the American lobster (Homarus americanus), as sea surface temperatures are warming more rapidly than benthic habitats. In addition, environmental pollutants, including micro- and nanoplastics, trace metals, persistent organic pollutants, and per- and polyfluoroalkyl substances, can interact with climate change to exacerbate physiological stress. Previous studies have demonstrated that changes in temperature, salinity, and pH significantly influence development, moulting, cardiac function, survival, and disease susceptibility in H. americanus. In this context, aquaculture-based approaches are being explored as complementary tools to support stock resilience and reduce reliance on wild populations. Recirculating aquaculture systems (RAS) offer a controlled framework to investigate the combined effects of environmental stressors on H. americanus physiology while assessing the feasibility of closed-system rearing. Overall, this review synthesizes current knowledge on the physiological responses of H. americanus to multiple environmental stressors, with particular emphasis on identifying optimal rearing conditions in RAS. By integrating these findings, the review aims to inform strategies for improving the sustainability and long-term viability of American lobster production under changing environmental conditions.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171612

Authors: Alexandra Pliss Knut Vilhelm Høyland Bernt Johan Leira Nicolas Serré Sigurd Henrik Teigen Dmitry V. Divine

An empirical ridge statistic that correlates weekly level ice thickness with keel depth and weekly number of ridges was investigated using upward looking sonars (ULS) data from 2006 to 2020 in the Fram Strait. The applied methodology was similar to the previous studies for the Beaufort Sea. The data were divided into weekly segments. For each of them, level ice thickness (hi), the number of ridges (N) and the average (hk) and deepest (hk_deep) keel depth were calculated based on the Rayleigh criterion with a threshold of 2.5 m and a minimum keel draft of 5 m. The broader idea was to compare regions with different ice regimes, in order to see how the ridge statistics change and how well the model can handle these differences. In this paper, we compare the Beaufort Sea and the Fram Strait. Both have a positive correlation between level ice thickness and keel depth. Linear regressions hk=5.91+ 0.60hi and hk_deep=8.67+ 5.91hi with Pearson correlation coefficients r=0.48 and r=0.45, respectively, are established in this study, which are both lower than the Beaufort Sea results.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171611

Authors: Runbang Liu Zhiyu Zhu Huilin Ge Jing Wang Yongdong Shu Qingshan Ji

Infrared and visible images provide complementary cues for maritime ship detection, but practical dual-sensor systems often produce image pairs that are not strictly registered. Directly fusing such unregistered pairs may introduce ghosting artifacts, blurred target boundaries, and feature conflicts, especially over weak-texture sea surfaces where reliable correspondence cues are sparse. To address this problem, we propose UA-FusionDet, an unregistered-aware infrared-visible fusion framework with cross-modal feature alignment for maritime ship detection. The proposed framework extracts visible and infrared features with a dual-branch encoder, aligns the visible feature to the infrared reference through cross-modal deformable feature alignment, and suppresses unstable background offsets using sea-surface saliency guidance. Wavelet-guided complementary fusion then decomposes the aligned features into low- and high-frequency sub-bands, enabling frequency-aware fusion of infrared thermal saliency and visible structural details before feeding the fused representation to both a lightweight reconstruction decoder and a ship detection head. The reconstruction decoder provides auxiliary image-level regularization, while the detection branch supervises the task-oriented fused representation with ship bounding-box annotations. UA-FusionDet does not require registration ground truth or fused-image ground truth during training, making it suitable for realistic maritime monitoring scenarios with imperfectly aligned visible and infrared sensors. Experiments on 3132 unregistered visible–LWIR maritime image pairs show that UA-FusionDet achieves a precision of 0.904, a recall of 0.866, an mAP50 of 0.912, and an mAP50–95 of 0.566, exceeding the strongest competing method by 2.5 and 2.4 percentage points on the two mAP metrics, respectively, while maintaining an inference speed of 52.6 FPS. These results demonstrate that the proposed alignment and fusion framework improves detection accuracy under cross-modal misregistration while retaining practical inference efficiency.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171610

Authors: Shuitao Peng Jing Luo Lei Du Hao Wang

In order to maintain stable formations of the underactuated unmanned surface vehicles (USVs) under ocean disturbances and reduce control chattering, a fuzzy adaptive super-twisting sliding mode control method combined with dynamic cooperative error correction is introduced in this paper. At the kinematic level, a dynamic cooperative error correction scheme is presented to include the relative positions of the neighboring vehicles. This results in a transition from independent tracking to interactive cooperation, thus improving the rigidity of the formation during maneuvers. Secondly, a composite inner-loop structure is designed by employing a nonlinear disturbance observer to counteract the effects of external loads. A fuzzy logic system is included to modify the super-twisting sliding mode gains in real-time. This approach effectively combines rapid error reduction with signal smoothness, addressing the trade-off between response speed and chatter suppression. Moreover, tracking differentiators and low-pass filters are utilized to obtain continuous control signals. The Lyapunov analysis indicates that the closed-loop system achieves semi-global uniform ultimate boundedness. Simulation results show that the proposed method can maintain high formation precision and obtain smooth control outputs with reduced chattering.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171609

Authors: Jiayin Li Zhi Zhang Wenxue Zheng Jie Hu Lijian Yang

In long-distance subsea pipelines, pipeline inspection gauge (PIG) speed fluctuations under complex operating conditions can cause a mismatch between the sampling frequency and the operating state. This mismatch may compromise the integrity of defect detection signals. To address this problem, this study proposes an adaptive sampling method for in-line inspection of pipeline data based on multi-sensor fusion and a spatial sampling interval model predictive controller (SSI-MPC). The impact of PIG velocity fluctuations on defect detection signal integrity was analyzed, and a multi-sensor velocity fusion estimation model based on Kalman filtering was established to fuse inertial measurement unit (IMU) acceleration data with cumulative displacement information from the odometer. The sampling frequency adjustment was formulated as a spatial sampling interval tracking problem, and an SSI-MPC controller was developed. The effectiveness of the proposed method was verified through comparative simulations with fixed-time sampling and odometer-based equidistant sampling. The results indicate that SSI-MPC adaptive sampling more effectively restores the key quantitative features of defect detection signals under velocity-jump and high-speed conditions. The RSE and RAE of the defect detection signals are controlled within 3.44% and 2.10%, respectively. Compared with fixed-time sampling, the proposed method reduces the detection signal data volume by 39.37%.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171608

Authors: Hui Liu Yuhang Liu Shuqiang Xue Han Cheng Wang Zhang

Continuity and reliability are critical for underwater gravity aided inertial navigation, while variations in gravity field suitability, sensor noise, and environmental disturbances can degrade gravity matching and navigation performance. To address this issue, a data-driven matching error compensation framework is proposed for gravity aided inertial navigation. Within this framework, a Hampel filter identifies unreliable gravity matching outputs based on local temporal consistency, and a CNN–BiLSTM–Attention model predicts compensated position increments for the flagged updates. The model maps INS position increments and measured gravity anomaly sequences to reliable gravity matching increments through local feature extraction, temporal modeling, and attention-based weighting, with offline training and online deployment. Reliable training samples were selected offline using reference trajectories, with synchronized GNSS positions serving only as the reference for sample screening in the marine experiments. Experiments were conducted across five simulated gravity field regions with five gravity matching algorithms and along three measured trajectories acquired using two types of marine gravimeters. In the marine experiments, the proposed method achieved mean APE-O values of 1.60, 1.06, and 1.06 n miles on L6, L7, and L8, respectively. The improvement was most evident on L6 with relatively extended error intervals, while the conventional RBIM method achieved comparable performance on the more regular and localized L8 error interval. Across the evaluated datasets, the proposed framework provided effective compensation for degraded gravity matching updates and improved the continuity of position corrections.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171607

Authors: Jiangsong Yin Sa Li Wenli Ji Siguo Liu

Reliable prediction of monopile self-weight penetration depth is essential for drivability assessment and installation planning but remains challenging because of nonlinear pile–soil interaction and limited field data. This study compiles records from 143 large-diameter monopiles at five Chinese offshore wind farms and develops a framework combining physics-guided feature engineering, conventional machine learning, and a physics-regularized neural network (PRNN). Variable-length profiles were encoded using up to 10 actual stratigraphic layers, and raw geotechnical features were compared with API-derived unit shaft and tip resistances. Eight conventional models and the PRNN were evaluated on a representative 80:20 pile-level split; robustness was further assessed using 50 repeated splits, leave-one-site-out (LOSO) validation, and paired bootstrap analysis, with the API method as a mechanics-based baseline. On the representative split, XGBoost achieved the highest R2 (0.790), lowest RMSE (2.762 m), and lowest MAPE (12.49%), while Random Forest yielded the lowest MAE (2.268 m). A controlled matched-network ablation showed that equilibrium-based regularization moderately improved mean predictive accuracy and physical consistency. The framework is therefore promising for within-domain prediction, while cross-site application requires further validation.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171606

Authors: Alexander Wacker Melanie E. Köhne Laura M. Wienhausen Ilka Carina Stephan

With climate change, marine heatwaves become more frequent and may favour the emergence of cyanobacterial blooms. Because cyanobacteria lack long-chain polyunsaturated fatty acids, they provide poor dietary quality for consumers, potentially altering the fatty acid composition of primary consumers and propagating nutritional stress through food webs. We examined how a simulated heatwave (12 °C to 18 °C) and an associated cyanobacterial bloom-like dominance may affect trophic transfer from phytoplankton to the herbivorous rotifer Brachionus plicatilis and further to its predator, the mysid Neomysis integer. Rotifers were fed either high-quality algae or a low-quality cyanobacteria-dominated diet mixture. Rotifers were then rinsed to remove external residual phytoplankton and subsequently offered as prey to mysids. We analyzed the fatty acid profiles of both rotifers and mysids and monitored mysid survival. High temperature and the presence of cyanobacteria at the base of the food web reduced mysid survival. Both factors also influenced the fatty acid composition of rotifers and mysids. For mysids at the third trophic level, warming modulated how strongly diet quality affected their fatty acid profile. These results suggest that concurrent heatwaves and cyanobacterial blooms may intensify cyanobacteria’s negative impacts on food webs by altering the transfer of key fatty acids across trophic levels.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171605

Authors: Mathieu Adgé Laetitia Hédouin Etienne Drahi Serge Planes

Floating photovoltaic (FPV) systems deployed in saltwater environments represent a promising renewable energy solution for remote regions, like coral reef islands, but their environmental effects remain poorly documented. Here, we conducted a year-long empirical assessment of FPV impacts on underwater light regimes and water temperature in a coral reef lagoon using four platforms with contrasting shading and UV-filtering configurations. FPV installations substantially reduced direct light reaching the seafloor. Platforms engineered to provide similar shading exhibited comparable direct light attenuation at a given position, although spatial heterogeneity beneath most of the structures resulted in additional attenuation. In contrast, reflected light was more homogeneous across platforms and appeared primarily influenced by local substrate topography, with differences between shading levels smaller than those observed for direct light. UV attenuation followed a clear gradient among platforms, whereas spectral modifications within the photosynthetically active radiation range were minor and limited to wavelengths above 600 nm. No effect of FPV installations on water temperature was detected. Overall, FPV systems induce multiple interacting modifications of the underwater light environment. While this complexity constrains the isolation of individual ecological drivers under in situ conditions, our results provide a robust physical framework for assessing the potential ecological impacts of FPV installations in coral reef ecosystems.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171604

Authors: Zhaoyang Zhang Yuan Wei Jinyong Liu Yufei Sun Huasen Sang Qiuwan Shen Shian Li

In the current situation of carbon reduction in the shipping industry, hydrogen as a future energy source is the key to hydrogen-powered ships. Onboard methanol steam reforming (MSR) hydrogen production technology is of great significance in solving the hydrogen safety issues of hydrogen-powered ships. The key to this technology is to obtain MSR catalysts with lower CO selectivity and higher hydrogen production performance for use as hydrogen sources in high-temperature proton-exchange membrane fuel cells (HT-PEMFCs). A new Cu0.75Mg0.25Ga0.7Fe1.3O4 spinel catalyst was synthesized and subsequently dispersed at a nominal loading of 15 wt% onto three distinct oxide supports: CeO2, ZrO2, and Cr2O3. The synthesized samples were characterized, and their catalytic behavior in MSR was evaluated in a fixed-bed reactor. The results establish that the loading procedure leaves the bulk spinel structure intact. Among the series, the CeO2-supported specimen exhibits a higher degree of active-phase dispersion, a loosely packed and highly porous architecture, and more extensive interfacial contact between the spinel crystallites and the support. Relative to its ZrO2- and Cr2O3-supported counterparts, Cu0.75Mg0.25Ga0.7Fe1.3O4@CeO2 delivers markedly superior overall catalytic performance. Under conditions of 320 °C, a water-to-methanol molar ratio of 3:1, and a liquid hourly space velocity (LHSV) of 15 h−1, complete methanol conversion (100%) is achieved, together with a hydrogen production rate of 8.71 mmol·min−1·gcat−1 and CO selectivity approaching zero. The outstanding catalytic behavior may be attributed to the interface synergy between the spinel active center and CeO2 support, particularly the synergistic effect of oxygen vacancies and Ce4+/Ce3+ redox shuttle, which facilitates substrate replacement while inhibiting CO production. This catalyst architecture provides a promising material platform for on-line methanol reforming integrated with fuel cell power systems on hydrogen-powered ships.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171603

Authors: Ramesh Babu Govindaraj Isak Andersen Inge Lotsberg Per Lindström Lussi

Wire arc additive manufacturing (WAAM) is increasingly being considered for large marine components because it offers design flexibility, reduced material waste, and potential benefits for manufacturing cost. However, the fatigue and fracture performance of WAAM materials in seawater remains insufficiently established for safety-critical applications such as marine propellers. This study evaluates the corrosion fatigue and fracture behavior of WAAM-manufactured 316L/316LSi austenitic stainless steel intended for propeller applications. A propeller-representative WAAM component was manufactured using gas metal arc welding, and fatigue specimens were extracted in both the weld and build directions. Axial fatigue testing was performed mainly in artificial seawater at stress ranges of 200, 250, 280, 300, and 330 MPa, with a test frequency of 5 Hz and a run-out criterion of 1 × 106 cycles. Chemical composition, ferrite prediction, hardness, Charpy impact behavior, S–N response, and SEM/EDS fractography were assessed to evaluate the impact on structural integrity. The deposited material showed a chemical composition consistent with 316L/316LSi stainless steel and an estimated ferrite content of approximately 8%, indicating a generally sound austenitic weld–metal microstructure. Several specimens reached run-out at stress ranges up to 250–300 MPa, whereas valid gauge-section fatigue failures occurred in higher stress ranges. Premature failures outside the gauge section were attributed to fixture-related effects and were not considered representative of intrinsic material behavior. SEM/EDS examination of a valid fatigue fracture identified an aluminum- and oxygen-rich crack-initiation feature consistent with an aluminum oxide inclusion. This observation indicates that the fatigue response of WAAM 316L/316LSi should be interpreted not only based on stress-life data but also using principles of fracture mechanics and damage tolerance, where surface or near-surface discontinuities may act as initial flaws and promote ΔK-driven crack growth in seawater. The results demonstrate promising fatigue performance within the experimentally validated range, but they also show that bulk mechanical properties alone are insufficient for qualifying WAAM propeller components. For the investigated WAAM process route, specimen surface conditions, stress ratio (R = 0.053), artificial seawater environment, and experimentally validated cycle range of up to 1 × 106 cycles, a preliminary engineering stress-range limit of Δσ = 200 MPa is recommended for pilot applications. This value should not be interpreted as a general design limit and should not be extrapolated to other WAAM processes, geometries, surface conditions, environments, stress ratios, or service-life regimes without additional qualification testing. Further high-cycle fatigue testing, mean-stress correction, fatigue crack-growth testing in seawater, fracture-toughness assessment, realistic defect-size characterization, non-destructive testing correlation, and component-scale validation are required before broader class acceptance of WAAM-manufactured propeller components.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171602

Authors: Changhwan Jang Geunyeong Lee Seungjin Lee

Spectral wave models such as SWAN provide reliable harbor wave fields but require repeated, computationally expensive runs during preliminary design. This study develops a domain-knowledge-guided, U-Net-based surrogate model that rapidly approximates two-dimensional wave fields from SWAN simulations. The model takes water depth, incident significant wave height, incident wave direction, and a signed distance field (SDF) encoding structure geometry as inputs, and it combines a dynamic-resolution preprocessing scheme that preserves the terrain aspect ratio with a shadow-weighted loss function that emphasizes the sheltered zone behind breakwaters. Trained on 240 SWAN scenarios that combine 8 idealized geometries with 5 incident directions and 6 wave heights (about 15.7 million grid points), the model reproduced the SWAN significant wave height with a coefficient of determination of R2 = 0.8807 and a mean absolute error of 0.07 m over the whole domain under an untrained but within-range (interpolated) wave height condition, with comparable accuracy in the region of interest behind breakwaters (ROI R2 = 0.85). In a real sea application to Sokcho Harbor benchmarked against SWAN rather than field data, the model reproduced the offshore to harbor wave height pattern; along entrance and propagation-axis transects, it followed the SWAN profiles with high correlation (R ≈ 0.94–0.95), while overestimating the innermost calm zone waves by a non-negligible margin. The model is thus suited to rapid wave-field screening in preliminary harbor design.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171601

Authors: Zixiang Lin Bing Fu Yuxuan Gao

Aiming at the vulnerability of nodes within collaborative task execution links and the slow response of link reconfiguration under limited communication conditions and sudden equipment failure scenarios at sea, and noting that existing approaches mainly rely on static optimization or offline planning without an integrated online reconfiguration framework, this paper proposes an A-star enhanced Multi-Objective Collaborative Reconfiguration (A-MOCR). By constructing a node state probability model and a multi-layer complex network framework, the proposed method sets maximization of task completion probability and network resilience as dual optimization objectives, and leverages the NSGA-III algorithm to generate primary links and corresponding backup link pools. Link reconfiguration is activated through real-time monitoring of node anomaly indicators; available surviving routes from the backup pool are prioritized for matching. If matching cannot be achieved, local A-star search or global path replanning will be initiated. Comparative simulation experiments against two baseline approaches demonstrate that the proposed A-MOCR achieves comparable mission success rates and link survival duration while significantly reducing the average reconfiguration time by over 50%. With equivalent task success probability, A-MOCR completes link reconfiguration within shorter time and maintains steady performance advantages under varying communication coverage parameters. Unlike conventional methods that require global re-planning after each failure, A-MOCR decouples offline optimization from online matching, enabling millisecond-level switching. The method realizes millisecond-level link switching and provides effective technical support for the adaptive reconfiguration of collaborative task execution links for marine multi-platform systems.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171600

Authors: Guosheng Guo Renwei Ji Kareem M. Tonbol Sheng Xu Jiacheng Shi Ho-Seong Yang Minwei Yin Surasak Phoemsapthawee Ratthakrit Reabroy

As marine development extends into deep and far-offshore waters, fixed breakwaters become increasingly costly and difficult to construct and may have greater environmental impacts. Floating breakwaters (FBs) offer flexible deployment across a wide range of water depths and have therefore received growing attention. Yet the dominant wave attenuation mechanisms and key hydrodynamic responses differ among FB configurations, making it difficult to compare their performance and select suitable analysis methods. This review examines advances in FB configurations, analysis methods, and hydrodynamic characteristics. It summarizes structural types and shows that FB design has evolved from reliance on principal dimensions and wave reflection toward the combined use of multiple attenuation mechanisms. The applicability and limitations of empirical methods, potential flow methods, computational fluid dynamics, and experimental methods are compared. Structural optimization, mooring system design, wave attenuation mechanisms, and fluid–structure interaction are also reviewed, with attention paid to motions, loads, and local flows. Key unresolved challenges include broadband attenuation of long-period waves, safety under extreme sea states, performance trade-offs in multifunctional systems, and scale effects and prototype validation. By linking FB configuration characteristics with dominant wave attenuation mechanisms, key hydrodynamic responses, and the applicability of different analysis methods, this review provides an integrated comparative framework for evaluating FB performance, selecting appropriate analysis methods, and supporting engineering assessment in deep and far-offshore waters.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171599

Authors: Amir Bordbar Konstantinos Georgoulas Amin Nazemian Myo Zin Aung Mina Tadros Vasili Savitski Andrew Gardner Saishuai Dai Evangelos Boulougouris

This study investigates the turbulent skin friction behaviour of original coated, slime/algae-covered, and laser-cleaned marine surfaces through a combined experimental and numerical approach under fully developed channel flow conditions. Numerical validation was performed against established smooth-wall experimental datasets over the investigated Reynolds number range using Reynolds-Averaged Navier–Stokes (RANS) and Large-Eddy Simulation (LES) approaches. LES provided the closest agreement with the reference data, while the two-dimensional wall function RANS k-ω SST model was selected for subsequent rough-wall simulations based on its balance between predictive accuracy and computational cost. The selected RANS approach was independently validated against rough-wall experimental data, showing good agreement in predicted skin friction behaviour. Measured surface elevation data were used to estimate equivalent sand grain roughness for the original coated, slime/algae-covered, and post-cleaning surfaces. The post-cleaning surfaces exhibited lower measured roughness and predicted skin friction coefficients than the slime/algae-covered surfaces, while the three investigated laser configurations produced broadly similar roughness characteristics and hydrodynamic responses. However, the original coating was characterised before immersion, whereas the fouled and post-cleaning surfaces had undergone water exposure. Because the coating is hydrolysing/self-polishing, the observed post-cleaning roughness reduction may be partly or entirely associated with immersion-induced coating changes and cannot be attributed uniquely to laser treatment. The results therefore demonstrate an association between the post-cleaning surface condition and reduced roughness and predicted skin friction, but do not establish a causal relationship between laser treatment and these reductions.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171598

Authors: Dejun Wang Jun Huang Xianhong Feng Huaqing Liu Yuqi Dong Zhimeng Gong Zhihui Jiao Yunfei Teng Zhichao Shen Yan Qu

Numerical simulations are conducted to investigate the near-bed flow behaviors of submarine canyons with periodic ridge-valley topography on continental slopes. In the numerical simulation, two topographic parameters are defined: α represents the basal slope angle of the continental slope, and β denotes the side slope angle of the submarine canyon. The topographic modulation of these two parameters on near-bed flow velocity and pipeline on-bottom stability is explored. The results show that the ribbed slope exerts two distinct modulation mechanisms on near-bed flow fields, which are governed by the relative angle between incoming flow and ridge-valley structures. When the flow is perpendicular to the canyon axis (θ = 0°), local topographic contraction and expansion accelerate flow over ridge crests and reduce near-bed velocity in valleys as β increases. In contrast, when the flow is parallel to the canyon (θ = 90°), lateral confinement by bilateral ridges forms a topographic channel, leading to persistent flow acceleration throughout the entire valley area. Moreover, such directional velocity differences substantially alter the on-bottom stability of pipelines deployed within the canyon. Two pipe-soil interaction models are employed in the stability analysis: the Verley-Lund model for a flat clayey seabed and the Slope-Silt model for a sloping silty seabed. The sensitivity of their predictions to soil undrained shear strength is further evaluated.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171597

Authors: Qichao Liu Wenjing Yu Guo Cheng

Low-frequency pressure pulsations generated by shipboard pumps can propagate through liquid-filled pipeline systems and exhibit distinct line-spectrum characteristics, potentially affecting ship acoustic stealth. Because the secondary path varies with operating conditions, fixed offline models are susceptible to modeling mismatch, making online secondary-path modeling essential for reliable active control performance. However, conventional auxiliary-noise-injection-based methods suffer from coupling between the modeling and control processes, while continuous auxiliary-noise injection may deteriorate steady-state noise reduction performance. To address these issues, this paper proposes a variable-step-size online secondary-path modeling method based on multi-power regulation. By jointly regulating the modeling process, control process, and auxiliary excitation power, the proposed method adaptively adjusts the modeling-filter step size, control-filter step size, and auxiliary excitation level, thereby reducing coupling-induced modeling bias and limiting the persistent influence of auxiliary excitation on the residual error signal. Simulation results demonstrate that, compared with typical online secondary-path modeling methods, the proposed method achieves lower steady-state modeling errors and improved noise reduction performance. Furthermore, experiments conducted on a liquid-filled pipeline test rig show that the proposed method achieves low-frequency pressure-pulsation line-spectrum attenuation levels ranging from 8.32 to 14.09 dB under different operating conditions, demonstrating its effectiveness for active pulsation control in liquid-filled pipeline systems.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171596

Authors: Peng Zhang Xiaokang Liu Ziguang Jia Zhengjie He Ran An Qingmin Hou

Operational modal analysis (OMA) is important for continuous structural health monitoring (SHM) of in-service offshore jacket platforms. In practice, long monitoring records increase the computational cost of SSI, while environmental and measurement interference can affect the recorded response. This study applies a hybrid procedure combining Kalman filtering (KF), the Random Decrement Technique (RDT), and Stochastic Subspace Identification (SSI). KF is used as a fixed-parameter preprocessing step, RDT extracts shorter free-decay signatures, and SSI is used to identify the natural frequency. The procedure is examined using a finite element (FE) model, a laboratory-scale model, and full-scale measurements from the same operating offshore platform represented by the FE model. For a representative 50 Hz record, RDT reduced the data entering SSI from 38,553 to 1200 samples (96.89%) and reduced the number of Hankel-matrix elements by 97.05%. Under identical SSI settings, the complete KF-RDT-SSI procedure required about one-fifth of the Standard SSI runtime in the benchmark environment. In the four-channel laboratory test, the dominant spectral peak remained at 6.1279 Hz before and after KF processing. KF-RDT-SSI identified 6.1204–6.1353 Hz, with a mean absolute relative deviation of 0.095% from the FFT result. The field measurements identified the fundamental natural frequency at approximately 1.56–1.57 Hz under transient and continuous operating conditions. The full-scale measurements provide the main evidence for the field applicability of the procedure. A systematic assessment under controlled noise types and signal-to-noise ratios is left for future work.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171595

Authors: Yutong Qian Weiqian Xu Runze Mao Peihua Han Ning Yuan Guoyuan Li Houxiang Zhang

Remaining useful life (RUL) prediction for offshore wind turbines is important for predictive maintenance. However, its practical use is limited by the lack of reliable RUL labels, the small number of fault events, and the complex degradation links among turbine components. Most existing data-driven methods require labeled failure data and cannot fully capture how the degradation of different components is related. To address these limitations, a Dual-Pathway Degradation-Aware Network for label-free RUL prediction is proposed. The proposed method first constructs component-level health indicators (HIs) from SCADA data in a self-supervised manner and generates pseudo-RUL labels through a linear countdown strategy. It then jointly models the global degradation evolution and cross-component interactions using a global temporal branch and a fully connected graph branch, where residual aggregation is adopted to fuse node representations for RUL estimation. Experiments are conducted on the German North Sea Farm B dataset under a leave-one-out cross-validation (LOOCV) protocol. From the obtained results, the proposed method achieves an MAE of 111.3 h and an RMSE of 122.6 h, reducing the average MAE by approximately 19% compared with the strongest baseline. The proposed method achieves the best performance on three of the five turbines with fault events. Furthermore, the proposed method demonstrates superior capability in capturing component interaction patterns and provides an effective label-free solution for offshore wind turbine RUL prediction under limited fault data.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171594

Authors: Yu Lin Mingming Wen Shuiyuan He Laiyong Song

Background: Underwater optical imagery used in marine inspection is degraded by wavelength-dependent attenuation and scattering, which couple color cast with structural haze. Existing restorers either treat both degradations in one stage or cascade separate networks and exchange information only through reconstructed images. Methods: This paper proposes RGI-Net, combining (i) a shared-weight two-pass pipeline that disentangles Lab chromatic correction from RGB structure refinement without duplicating the backbone and (ii) a 1×1 Gated Injection Bridge that transfers Pass-1 bottleneck features into Pass 2 under a learned element-wise gate, together with a recursive contrastive objective that includes a cross-pass consistency term. All methods are compared on identical test partitions under one evaluation pipeline (UIEB train/test, LSUI, EUVP, U45, C60). Results: Against WaterNet, PUIE-Net, CCL-Net, and Phaseformer, RGI-Net attains the best UIEB UIQM (2.21) and UCIQE (0.372), with PSNR/SSIM statistically indistinguishable from Phaseformer (Wilcoxon p>0.5). On the reported GPU, wall-clock latency is 41.00 ms, versus 61.64 ms for Phaseformer at 256×256, while RGI-Net has the largest parameter count and FLOPs in the comparison. Conclusions: Shared two-pass decoupling with gated bottleneck injection improves UIEB no-reference indices. Lower latency than Phaseformer on one workstation GPU is not a claim of overall computational efficiency, given the larger parameter and FLOP counts. UIQM and UCIQE are operational scores, not perceptual or inspection-task evidence; on EUVP, the best UIQM/UCIQE coincide with the lowest PSNR/SSIM among compared methods, which remains a substantial limitation.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171593

Authors: Quankai Xu Junwei Cao Ling Liu Xiaoshun Yan Jingxi Liu

Predicting wave slamming pressures on bulbous bows is essential for ship structural safety. This study employs an overset-grid RANS-VOF framework to investigate viscous scale effects on bulbous bow slamming loads. Multi-scale simulations were conducted across four geometric scale ratios of 1:50, 1:20, 1:15, and 1:10 (α = 50, 20, 15, 10) under critical pitch-heave resonant head waves (λ/LWL = 1.2). While global motion responses follow Froude similitude, local dynamic slamming pressures show notable scale disparities. Smaller physical models develop a relatively thicker viscous boundary layer that acts as a hydrodynamic cushion, reducing peak pressures while broadening pulse durations. Consequently, direct Froude scaling from small-scale models tends to underestimate full-scale impact loads. To account for these viscous scale effects, an engineering extrapolation approach based on multi-scale regression is proposed, which demonstrates a reasonable linear correlation across the investigated range (R2 = 0.88–0.99) in the primary impact region. This study provides physical insights into the scaling behavior of bulbous bow slamming and offers a practical reference for full-scale load estimation.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171592

Authors: Dionysia Mintza John A. Theodorou

Harmful algal blooms (HABs) pose a growing ecotoxicological threat to bivalve molluscs and their consumers. Current regulatory frameworks governing shellfish safety, however, rely on acute human toxicity limits that poorly capture the biological complexity of bivalve–HAB interactions. This narrative review synthesises the published literature on the effects of HAB toxins on bivalves. It assesses their physiology, immune function, and stress resilience, comparing these findings against the limits set by the EU, the United States (US) and Australia/New Zealand. Sublethal responses from immunosuppression and impaired reproduction to oxidative stress and altered valve activity frequently occur at concentrations below current action levels. Environmental variables such as marine heatwaves, salinity fluctuations and hypoxia shift toxin bioaccumulation and depuration in ways that existing safety limits fail to capture. The main toxin groups, their mechanisms of action and species-specific accumulation and elimination kinetics are examined alongside current monitoring and management strategies. The review concludes that bridging the gap between shellfish-safety regulation and bivalve ecotoxicology requires integrating physiological stress indicators into regulatory frameworks. Such integration must draw on advanced monitoring technologies and adaptive management capable of responding to a rapidly changing ocean.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171591

Authors: Candela Maceiras Tajes Manuel Vázquez Neira Francisco J. Pérez-Castelo José A. Orosa

The transition towards low-carbon shipping has accelerated the adoption of alternative marine fuels such as ammonia, hydrogen, methanol and liquefied natural gas (LNG). Although these fuels reduce greenhouse gas emissions, they introduce new operational hazards related to toxicity, flammability, cryogenic storage and explosion risk. Existing comparative assessments are predominantly deterministic, representing accident probability and consequence severity by single values while neglecting operational uncertainty. This study proposes a probabilistic consequence-weighted risk assessment framework for alternative marine fuels operating within high-density Traffic Separation Schemes (TSSs). The methodology integrates historical traffic data, a location-specific contextual vulnerability multiplier and fuel-specific accident characteristics, propagating uncertainty through Monte Carlo simulation using Beta distributions for conditional loss-of-containment probability and triangular distributions for consequence severity. One million simulations per fuel-location combination were adopted after numerical convergence checks. The framework was applied to three Spanish TSSs (Tarifa, Cabo de Gata and Finisterre) and four candidate fuels (ammonia, hydrogen, methanol and LNG). Unlike deterministic approaches, the methodology provides complete risk distributions, P5–P95 uncertainty intervals and probabilistic fuel rankings. Results show that geographical location materially modifies operational risk and must be considered jointly with fuel-specific hazard; within the adopted scenario matrix, Tarifa remains the most critical location. Ammonia consistently exhibits the highest consequence-weighted risk. The framework is intended as a transparent comparative screening and decision-support tool rather than as a substitute for an absolute quantitative risk assessment based on physical consequence endpoints and observed accident frequencies.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171590

Authors: Byungmo Kim Kiyoung Sung Junghee Lee Cheonhong Min

Syntactic foams combine low density and thermal-insulation capability, but their dynamic flexural properties at subzero temperatures remain insufficiently characterized. This study applied an Euler–Bernoulli beam-based inverse framework to natural frequencies and damping ratios of four epoxy syntactic-foam specimens representing four formulations at 0, −20, and −40 °C. Apparent storage, loss, and complex flexural moduli and equivalent modal loss factors were identified for the first two bending modes, with intermodal consistency and analytical sensitivity evaluated. The storage flexural modulus increased with decreasing temperature for every specimen and mode, with first-mode increases of approximately 5.8–11.0% from 0 to −40 °C. At equal nominal weight fractions, the S38HS-based specimens exhibited higher storage flexural moduli than the corresponding S28HS-based specimens. First- and second-mode estimates agreed within 5% for most conditions, while S4 showed a 10.93% discrepancy at −40 °C. Equivalent modal loss factors were non-monotonic and more variable in the second mode; the maximum values, η2 = 0.1040 and E2′′ = 0.298 GPa, occurred for S3 at −40 °C. Effective free length showed the greatest normalized influence on the inverse estimate. The identified properties provide temperature- and mode-specific, coupon-level effective inputs for preliminary vibration analyses of moderately low-temperature marine insulation components under comparable conditions.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171589

Authors: Rui Liu Dewei Wang Shuaikang Zhao Jierui Tang Xue Li Wenli Qiao

Storm surge current-time estimations are strongly influenced by recent water-level conditions, while the temporal dependence among samples from the same typhoon event can complicate the assessment of model generalization to unseen events. This study evaluated storm surge estimation at the Lianyungang tide gauge using 2168 samples from 28 typhoon events during 2002–2024. A 41-feature extreme gradient boosting (XGBoost) model integrating historical surge and physics-motivated information was evaluated using fully nested event-grouped cross-validation, with complete outer-test typhoon events excluded from hyperparameter optimization, early stopping, and model fitting. The 41-feature XGBoost model achieved a mean absolute error (MAE) of 0.083 m, a root mean square error (RMSE) of 0.128 m, and a coefficient of determination (R2) of 0.794. On the common valid sample subset, its RMSE was 9.15% lower than that of Persistence, and it achieved a lower event-level RMSE in 18 of the 28 independently held-out typhoon events. Controlled information-source experiments showed that historical surge information accounted for most of the aggregate predictive skill, whereas adding core storm-state variables and the complete set of physics-motivated descriptors produced only limited changes in overall performance. The relative improvement over Persistence was larger for samples in which the shortest available historical surge lag was 3–6 h than for those with a 1 h lag, but this advantage did not extend consistently to the highest-surge conditions, where systematic underestimation remained evident. These results demonstrate the importance of event-independent validation for assessing machine-learning storm surge estimation and show that the model skill depends strongly on both information availability and the surge magnitude. The framework should be interpreted as a retrospective, single-station current-time estimation approach rather than an operational forecasting or extreme-surge warning system.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171588

Authors: Zijie Li Shufen Guo Dejin Zhang Weichen Shi Jialong Sun Baozhang Chen

Island ecosystems are highly sensitive to climate change and intensive human activities. However, most existing assessments rely on subjective weighting and linear assumptions, which may not capture nonlinear temporal evolution and can be distorted by spatial-scale effects, including extreme density outliers on micro-islands. Focusing on five representative islands in Jiangsu Province, China (2014–2024), this study applies a data-driven evaluation framework. First, we constructed an Island Ecological Quality Index (IEQI) using principal component analysis (PCA) to integrate multidimensional ecological-state variables. Second, to reduce sensitivity to selected scale-related extremes in spatially restricted units, we employed a geographical detector model to identify explanatory factors and characterize interactive associations. The IEQI showed a nonlinear temporal trajectory, with fluctuations followed by recovery and stabilization after 2021. Under the robust adaptive Jenks classification, the factor detector showed high relative explanatory power for Artificial Shoreline Ratio (q = 0.8457), Population Density (q = 0.8339), Terrain Index (q = 0.8135), Tourist Density (q = 0.6282), and Built-up Ratio (q = 0.3189). Interaction analysis identified bi-factor enhancement between Terrain Index and Population Density (q = 0.8364) and nonlinear enhancement between Policy Count and Built-up Ratio (q = 0.6424). These q statistics describe spatial explanatory associations rather than causal effects. These findings challenge linear and generalized coastal management paradigms. We propose a “one island, one policy” framework that explicitly distinguishes micro-islands by their topographic buffering capacity and anthropogenic pressure profiles, enabling spatially targeted conservation and restoration strategies.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171587

Authors: Zhengqi Wang Shuaiyu Yao Chenyi Zhao Wendi Ouyang

The Arctic Northeast Passage is of growing economic and strategic importance, while its harsh and highly variable navigation environment poses substantial challenges for vessel operation. Existing assessment approaches often rely on predefined structural assumptions or sacrifice interpretability for numerical performance. This study proposes a data-driven evolutionary belief rule base model that integrates an adaptive reference value field mechanism with differential evolution-based structural optimization for rule pruning and growth. The inputs are observed vessel-operational and environmental variables from the Oden and Tian En datasets, and the output targets are three-grade expert-consensus navigation safety risk distributions aggregated from 100 independent votes per sample. Under the repeated random-split evaluations, ARVF-DEBRB achieved the lowest mean MAE on Oden and errors comparable to the leading learned baselines; on Tian En, its mean errors were comparable to those of the strongest learned baselines while lower than those of several conventional and deep baselines. Complementary chronological rolling-window evaluations over three disjoint future test windows provided future-only evidence as follows: ARVF-DEBRB ranked second in RMSE and third in MAE on Oden, and first in RMSE and second in MAE on Tian En. The rolling factorial ablation obtained the lowest mean errors for the complete configuration on both datasets. These results indicate competitive predictive performance under the reported evaluation protocols, while preserving transparent IF-THEN reasoning semantics and a compact rule structure. The data-adaptive ARVF construction and DE-based rule-structure refinement provide a methodological basis for recalibrating the framework to new operational settings.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171586

Authors: Siheng Zhao Zixiang Zhu Shifei Ma Jing Zhang Tingting Li Zhihua Chen

Fault risks in marine diesel engines (MDEs) propagate across coupled subsystems and evolve with component degradation, but existing methods rarely integrate accident narratives, causal structure, and time-varying reliability. This study develops a novel framework that integrates large language models (LLMs), rough–fuzzy DEMATEL, interpretive structural modeling (ISM), and Bayesian networks (BNs) with service-time-dependent priors for time-varying failure analysis. First, the risk-influencing factors (RIFs) are extracted from accident and maintenance records using LLMs, text embeddings, semantic clustering, and expert consolidation. Rough–fuzzy DEMATEL and ISM are used to identify causal relationships and the hierarchical structure. The RIFs, bottom-level components, and target failure are then mapped into a multilayer BN parameterized using Noisy-OR relationships and Weibull-derived time-varying priors. In a case study of MDE hard starting, 338 cause descriptions from 35 records yielded 12 RIFs, with semantic coverage above 93% across four evaluation models. When hard starting was observed, the posterior probability of mechanical failure of the fuel injection system reached 60.92%, compared with 36.91% for governor and mechanical actuation system failure. Over 0–10,000 h of cumulative service, the model-inferred probability of hard starting during a single starting attempt increased from 38.09% to 75.23% under the specified model parameterization. The framework supports causal interpretation, troubleshooting prioritization, and service-time-dependent maintenance prioritization.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171585

Authors: Qingming Tan Duankai Li Jiawei Jiang Kunxiang Ge

To address the problem of the fault mode discrimination accuracy of marine rotating machinery under the conditions of noise interference and limited training samples, a fault diagnosis method based on a particle swarm optimization-driven kernelized cascade forest is proposed. This method introduces RBF kernel mapping in the hierarchical structure of the cascade forest and uses PSO to conduct global optimization of the key parameters of the kernel function. Based on the marine fan test platform driven by a three-phase asynchronous motor, the frequency domain features are extracted as the model input, and the predicted probability distribution is utilized during the hierarchical training process. The experimental results show that in a noise-free environment and a noisy environment with Gaussian white noise, the test accuracy of the diagnostic accuracy rate is 98.05% and 97.10%, respectively, with a performance decrease of only 0.95%; it still maintains stable recognition accuracy under the condition of small samples, demonstrating superior small-sample learning ability compared to the benchmark method. Compared with the forest-based baseline method, the proposed method can reduce the performance degradation caused by noise and effectively improve the diagnostic performance of the model under noise and small-sample conditions, and this method may become a potential solution for fault intelligent diagnosis in marine rotating machinery.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171584

Authors: Yaocheng Zou Cui Guo

Vertical environmental gradients are important in structuring marine microbial communities, yet microbial responses to localized reversals within vertical environmental profiles remain less well resolved. We investigated bacterial and microeukaryotic plankton communities at ten depths between 5 and 250 m at station G4 in the northern South China Sea (SCS), with intensified sampling between 122 and 163 m around a localized subsurface dissolved oxygen (DO) reversal. Continuous CTD observations confirmed a reversal in the local DO–depth gradient within this interval. Bacterial and picoeukaryotic abundances peaked at the deep chlorophyll a maximum, while both bacterial and microeukaryotic communities exhibited clear depth-related changes in diversity and composition. Multivariate analyses showed that community variation was associated with a broader vertical environmental gradient involving temperature, salinity, density, nutrients, and chlorophyll a, whereas DO did not show a clear independent association after accounting for depth. Bacterial and microeukaryotic communities nevertheless exhibited broadly concordant vertical turnover. Taxonomically, surface waters were characterized by greater contributions from Cyanobacteriia and Dinophyceae, whereas deeper assemblages contained increased proportions of Gammaproteobacteria, Syndiniales, Polycystinea, and other subsurface-associated groups. Together, these observations suggest that the localized DO reversal occurred within a broader vertical environmental transition accompanied by coordinated changes in bacterial and microeukaryotic community structure.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171583

Authors: Soonhyun Lee Hyungju Kim Kwang-Jun Paik Seong-Jin Eom Sooyeon Kwon

Small coastal crafts are often equipped with stock propellers selected from limited commercial options, without detailed matching among the hull, main engine, reduction gear, and propeller. This study presents a practical and integrated procedure for evaluating propulsion performance and designing a propeller tailored to a G/T 4.99 coastal craft under the fully loaded departure condition. The CFD resistance simulations were validated against model test measurements of resistance, sinkage, and trim and were applied over a wide range of vessel speeds. Self-propulsion simulations were subsequently conducted to evaluate the propulsive characteristics of the target vessel. Based on the evaluated self-propulsion characteristics, actual engine specifications and propeller installation data from Korean coastal vessels were used to select the main engine and reduction gear and to define practical ranges for the propeller diameter and pitch ratio. An initial propeller was determined using the Bp−δ method, after which the mean pitch ratio was iteratively corrected through full-scale performance prediction. The final propeller was selected by matching the predicted rotational speed under the trial condition to the target value determined by the engine and reduction gear while confirming the attainable vessel speed under the service condition with a 15% sea margin. The final propeller was evaluated through CFD self-propulsion simulations and compared with the stock propeller. At 16 and 18 knots, the designed propeller increased the overall propulsive efficiency by 8.4% and 10.1%, respectively, while reducing the required delivered power by 7.8% and 9.2%. These results demonstrate that the proposed procedure can improve the matching among the hull, machinery, and propeller and provide a practical basis for designing efficient propellers for small coastal crafts.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171582

Authors: Kyeong-Tae Lee Myung Sook Kim Jong-Seop Shin Yeong-Ji Park Hyun-Sung Yang

Crustose coralline algae (CCA) are key reef-building organisms, yet their bleaching dynamics and associated environmental factors in natural ecosystems remain poorly understood. This is particularly relevant to Jeju Island, Korea, where declines in canopy-forming macroalgae and the expansion of CCA-dominated barren grounds are reshaping benthic communities, highlighting the need to monitor how CCA respond to environmental stress. In this study, bleaching dynamics were monitored monthly using Autonomous Reef Monitoring Structures (ARMS) deployed at Bomok, southern Jeju Island, Korea, during a 13-month period (August 2022–August 2023). Total CCA cover, bleached CCA cover, and bleached CCA ratio were quantified and compared with seawater temperature and daytime light intensity. Despite persistently high total CCA cover, the bleached CCA ratio varied markedly over time, with multiple peaks and subsequent declines, reaching a maximum of 65.8%. The bleached CCA ratio was positively correlated with daytime light intensity (ρ = 0.709, p = 0.015), whereas no significant association was detected with seawater temperature. Nine bleached specimens were assigned to the genus Porolithon based on psbA phylogenetic analysis, representing the first molecular identification of bleached CCA from Korea. These findings provide a temporal baseline for understanding CCA bleaching within the rapidly changing benthic communities of Jeju Island and indicate that light intensity may be an important environmental correlate of bleaching.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171581

Authors: Yingjie Guan Xiaoyang Deng Yougang Bian Xuan Zeng Xiaojun Zhuo Xu Liu

Hydrodynamic models underpin Autonomous Underwater Vehicle (AUV) design, motion control, and performance evaluation. Existing methods face two critical bottlenecks: (1) conventional explicit CFD requires predefined trajectories, which fails to capture true motion responses under combined rudder-propeller action and creates a disconnect between simulation and real operations; (2) the widely adopted Standard Submarine Motion Equations (SSME) suffer from high parameter redundancy, while high-precision non-parametric models incur prohibitive computational costs, hindering embedded deployment. To address these gaps, this paper proposes an implicit CFD-driven framework for fully appended AUVs equipped with through-body thrusters. It requires no preset trajectories, directly coupling periodic propeller thrust and rudder angle excitations to achieve 5-degree-of-freedom (5DOF) spatial motion simulations aligned with real navigation states. Parametric and non-parametric models are identified via Least Squares (LS) and Neural Networks (NN), respectively. Sobol global sensitivity analysis reduces SSME dimensionality, yielding a Basic Submarine Motion Equation (BSME) with only 25 key parameters—cutting the parameter count by 55% with negligible accuracy loss. Validation shows the non-parametric NN model reduces prediction error by over 10% compared to its parametric counterpart, while the streamlined BSME enables real-time forecasting in low-power computing scenarios. This approach balances accuracy and efficiency for rapid hydrodynamic prediction during early AUV design and embedded controller deployment.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171580

Authors: Su-Hyung Kim Min-Gyu Lee

The maneuverability standards established by the International Maritime Organization (IMO) primarily address merchant ships, while large fishing vessels generally fall outside their scope. This study investigated the relationships between selected design characteristics and maneuvering performance using full-scale trial data from four large fishing vessels. Their principal design characteristics and maneuvering indices were compared with the distributions of a 226-ship merchant-ship database and with four reference merchant ships for which complete design and trial data were available. The fishing-vessel cases were positioned toward the lower ranges of the available merchant-ship distributions for L/B and Cb/(L/B), whereas their B/d values substantially overlapped the principal merchant-ship range. Their P/Δ values were higher than those of the four reference merchant ships. Within the four fishing-vessel cases, B/d and P/Δ showed the most apparent tendencies with the Turning indices, L/B and Cb with the Zig-zag Overshoot angles, and Cb and P/Δ with Track reach/L. These observations indicate that the design variables associated with the most apparent tendencies differed among turning, course-checking, and stopping responses. Although the limited dataset does not permit statistical generalization or the establishment of causal relationships, the results suggest that the maneuvering characteristics of large fishing vessels are better characterized by considering combined hull-form and propulsion characteristics together with the balance among multiple maneuvering responses, rather than by interpreting individual design variables in isolation. These full-scale observations provide a basis for further systematic investigation and maneuverability assessment of large fishing vessels.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171579

Authors: Zhongchao Zhou Mohd Yuhyi Mohd Tadza Zhisheng Zhou

Offshore wind power has expanded rapidly in recent decades and is expected to continue growing through the deployment of larger turbines in deeper waters. The safe and stable operation of offshore wind turbines (OWTs) depends critically on foundation performance, which is severely threatened by seabed scour. To better understand these threats, this paper reviews recent studies on the effects of seabed scour on the structural performance and safety of fixed-bottom offshore wind turbine foundations (OWTFs), focusing on four aspects: (1) the changes induced by scour in both the seabed morphology and the soil mechanical state, which form the basis for the subsequent analyses; (2) the effects of scour on the bearing capacity and natural frequency of the foundation, covering both its static and dynamic performance; (3) the behavior of scoured foundations under long-term cyclic loading during normal operation and under transient seismic action during extreme events; and (4) the role of scour protection in enhancing structural safety. Several future research directions are also highlighted. This review offers helpful insights for assessing scour-induced risk and for designing scour protection from a structural safety perspective, thereby supporting the safe operation of OWTs.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171578

Authors: Chu Xie Ting Yang Ruotong Qu Qing Xiao Changjun Gao Kunshan Bao

The Guangdong Haifeng Coastal Wetlands (Ramsar Site No. 1727) in Shanwei City are a critical habitat for migratory birds, but the long-term evolution and driving mechanisms of ecological vulnerability under rapid urbanization remain insufficiently understood. In particular, few studies have quantitatively characterized the temporal shifts in the relative roles of anthropogenic pressures and conservation policies over decadal scales. This study developed a landscape pattern-based ecological vulnerability assessment model integrating spatial autocorrelation, Geodetector, the PLUS model, and spatial overlay analysis to diagnose the dynamics and driving mechanisms of the wetlands from 1980 to 2018. The results showed that farmland and woodland dominated Shanwei City, while water bodies consistently dominated the Haifeng Wetlands. Ecological vulnerability exhibited significant spatial heterogeneity, with levels higher in the northwest and lower in the southeast. Forest and water expansion overlapped with vulnerability reduction, whereas built-up and farmland expansion matched increases in vulnerability. Land-use intensity, elevation, and mean annual temperature were identified as the primary drivers. The drivers of built-up land expansion shifted from population-related pressures during 1980–2000 to stronger policy regulation effects after 2000, indicating a transition in human–land interactions. Conservation policies, including nature reserve establishment and Ramsar designation, provided important institutional support for ecological management. These findings highlight the importance of integrating long-term land-use dynamics with natural, socioeconomic and policy contexts to improve the understanding and management of coastal wetlands vulnerability under rapid urbanization.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171577

Authors: Jiayi Sun Wenquan Zhang Ailian Hu Chengbing Song Juan Yang

With increasing global demand for deep-sea resources, polymetallic nodule mining has become a potential approach for accessing critical minerals. To identify potential areas of ecological concern associated with future deep-sea mining activities, this study predicted the suitable habitat distribution of Balaenoptera species in the Pacific polymetallic nodule areas using the Maximum Entropy Model (MaxEnt). The results showed that environmental variables, such as temperature, salinity, and chlorophyll-a concentration, were the major contributors to Balaenoptera habitat suitability, with their combined contribution exceeding 70% across four species. Temperature showed the highest contribution to habitat suitability predictions for B. acutorostrata, B. edeni, and B. physalus, with contribution values of 38.2%, 46.4%, and 45.4%, respectively. In contrast, salinity contributed the highest (38.4%) to the habitat suitability of B. musculus. Moreover, future climate scenarios posed different changes in the predicted suitable habitats for different Balaenoptera species. Under the current climate scenario, a large proportion of suitable habitat (PSH) were affected in the eastern Pacific mining areas, including 8.52% for B. acutorostrata, 54.94% for B. edeni, 53.73% for B. musculus, and 20.74% for B. physalus. Under future climate scenarios, the PSH of B. acutorostrata and B. musculus showed an increasing trend, which was especially pronounced under the SSP1-2.6 climate scenario (3.96% and 17.27% respectively); while B. edeni showed opposite trends, with a decrease (−6.14%) under SSP1-2.6 and an increase (4.91%) under SSP5-8.5 scenario. The PSH of B. physalus showed a slight decrease (−0.43% and −0.32%) under both scenarios. These findings may support future environmental management and impact assessment for deep-sea polymetallic nodule exploitation.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171576

Authors: Haoda Huang Qingsong Liu Chun Li Wanfu Zhang Musa Bashir Gregorio Iglesias

Floating vertical-axis wind turbines (VAWTs) couple intrinsically unsteady rotor aerodynamics with the motions of their supporting platforms, producing complex temporal variations in power output, aerodynamic loads, and wake transport. A structured search of the Web of Science Core Collection and Scopus, supplemented by citation tracking, identified peer-reviewed studies published from database inception to 30 June 2026. The reviewed computational fluid dynamics (CFD) studies were classified as decoupled or fully coupled according to whether bidirectional feedback between the flow field and platform response was resolved. The evidence shows that motion-induced velocities alter blade-relative inflow and effective angle of attack, thereby modifying dynamic stall, loads, and wake evolution. Scaled testing is limited by the incompatibility between Froude and Reynolds similitude. Under identical pitch conditions, the mean power coefficient increased by 16.42% at full scale but decreased by 56.71% at 1:100 scale. Platform motion generally increases power and load fluctuations but may accelerate wake recovery; effects on mean performance remain configuration- and scale-dependent, so no universally optimal rotor-platform design has emerged. Overall, this review provides an integrated understanding of the effects of platform motion on the unsteady aerodynamics, load responses, and wake evolution of floating VAWTs, and clarifies the applicability of decoupled and fully coupled CFD methods to mechanism identification and system-level assessment.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171575

Authors: Hongda Zhang Rui Zhang Shuyu Yan Le Qi Yong Wang Jinbo Chen Yan Bao Hongbo Zhu

Tension-leg platform (TLP) horizontal-axis wind turbines (TLP-HAWTs) have become increasingly important in deep-water offshore wind energy development. However, their performance is strongly affected by coupled platform motions induced by wind and wave loads, making fully coupled simulations a critical prerequisite for accurate performance assessment. Conventional fully coupled approaches often struggle to balance computational efficiency and numerical fidelity. In this study, a simplified sequential coupled modeling framework is proposed based on the commercial solvers OrcaFlex and STAR-CCM+. In this framework, OrcaFlex is employed to simulate the hydrodynamic response of the floating platform, and the resulting platform motions are subsequently imposed as prescribed inputs in high-fidelity CFD-based aerodynamic simulations. Based on the proposed framework, a series of case studies of a 15 MW TLP-HAWT are conducted to investigate the effects of wind-induced and wave-induced platform motions on aerodynamic performance. The results indicate that wind-induced platform motions have a negligible impact on local inflow conditions and vortex intensity, and their influence on mean blade loads and wake topology can be safely ignored under rated conditions. In contrast, wave-induced motions significantly enhance unsteady aerodynamic loads, intensify vortex shedding, alter torque distribution along the blades, and increase wake turbulence intensity as well as velocity deficit. These findings suggest that wave-induced platform dynamics dominate the unsteady aerodynamic response and wake evolution of TLP-HAWTs under rated conditions, while wind-induced motions play a secondary role. The results provide valuable insights for reduced-order modeling, control strategy development, and the design optimization of efficient floating offshore wind turbines.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171574

Authors: Minsi Liang Zhijie Ding Hanbo Zheng Panpan Shen Aiwu Yang Hao Zhang

Tetrapod piled jacket foundations, widely adopted for large-capacity offshore wind turbines, are frequently affected by scour, which substantially alters their lateral mechanical responses. Nevertheless, existing studies on this subject remain limited and mostly adopt simplified uniform scour assumptions that deviate significantly from actual field conditions. This study conducted lateral-loading model tests on scoured tetrapod piled jacket foundations, with the local scour geometry idealized based on the non-uniform scour-hole morphology reported in field monitoring and flume test studies. The evolution law of the lateral bearing capacity of the foundations with scour development is revealed, and the differences in lateral bearing performance under uniform and non-uniform scour are systematically compared. A three-dimensional finite element model is established and validated against test data to verify its accuracy and reliability. Additionally, comprehensive parametric analyses are performed to supplement the experimental results, exploring the influences of flow angles, corresponding scour-hole morphologies and lateral load directions on the lateral bearing performance of tetrapod piled jacket foundations. The pile bearing mechanism and internal force distribution characteristics are further clarified. The research findings can provide a theoretical basis for the safe service of offshore wind turbines supported by tetrapod piled jacket foundations.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171573

Authors: Sungwoo Song Heemoon Kim Jongsu Kim Seongwan Kim Hyeonmin Jeon

Bearing damage caused by electric discharge machining (EDM) is a concern in electric ship propulsion drives, particularly during low-speed operations such as maneuvering and slow steaming. In a modular multilevel converter (MMC) operated with nearest-level modulation (NLM), rounding of the three-phase submodule insertion numbers produces a residual imbalance that appears as common-mode voltage (CMV) and charges the bearing film capacitance. The peak bearing voltage rises from 6.4 V at 60 Hz to 20.0 V at 10 Hz, while the thinning lubricant film lowers the dielectric breakdown threshold. Always-on CMV reduction approaches apply a corrected switching candidate in every control period, including intervals where the bearing voltage stays well below the threshold. This paper proposes a selective NLM correction driven by predicted bearing voltage risk: a reduced-order RC model predicts the bearing voltage the conventional NLM candidate would produce, and a hysteretic controller applies a zero-CMV candidate only when that prediction approaches the insulation threshold. Using a worst-case discharge criterion and thresholds of 5.9–29 V derived from elastohydrodynamic film thickness estimates, simulations at 10 Hz show that the method eliminates EDM events over the full evaluated threshold range. It achieves the same zero-EDM outcome as always-on correction while reducing the correction mode activation ratio from 100% to at most 30.8%, and remains inactive where conventional NLM is already safe.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171572

Authors: Heng Zhou Lejingyi Zhou Haibo Wu Minghao Xu Lindan Zhang Jia Guo Wei Fu Hengchi Zheng Tian Ni

As the core equipment for in situ deep-sea scientific research, the design quality and operational performance of the sampling platform determine the efficiency of deep-sea operations, including long-term continuous observation, high-quality sampling and preservation, and in situ experimental studies. To address technical bottlenecks commonly observed in conventional platforms, including track sinkage, excessive motion drag, and low propulsion efficiency, this study proposes the design and development of a novel sampling platform with tracked-propeller dual-mode propulsion, deployable from either a surface vessel or a large manned submersible, capable of high-throughput, multi-sequence fidelity water sampling, in situ sediment incubation, and seabed mudstone sampling in deep sea. Through hydrodynamic performance analysis and design optimization, both lightweight design and drag reduction were achieved. Furthermore, load verification of the main frame under multiple operating conditions was conducted; results demonstrate that the structure meets strength and stiffness requirements and ensures reliability in typical service environments. This study provides a theoretical basis and technical reference for the development of similar deep-sea sampling platforms and holds substantial engineering application value.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171571

Authors: Ping Dong Yun Li Fei-Yun Wu

Endpoint detection is a key preprocessing step for passive acoustic monitoring of marine biological sounds, but underwater noise can obscure onset and offset boundaries, especially at low signal-to-noise ratios (SNRs). This study proposes a wavelet-domain adaptive composite thresholding (WD-ACT) method for robust endpoint detection. The method applies Daubechies 4 (Db4) wavelet enhancement with soft-thresholding, then fuses short-time energy, non-zero-lag autocorrelation, and spectral variation into a frame-level composite detection score. An adaptive dual-threshold strategy estimated from background-frame statistics is used to determine the onset and offset of effective acoustic segments. Experiments were conducted on three manually annotated marine mammal vocalization segments, including seal, dolphin, and walrus calls, mixed with white noise, pink noise, ship noise, and wind–wave noise at SNRs from −5 to 15 dB. For each combination of acoustic segment, noise type, and SNR level, 100 noise-mixing trials were performed. Compared with short-time energy and zero-crossing rate (STE-ZCR), time-domain autocorrelation detection (TDA), wavelet-domain detection (WD), and spectral-flux detection (SFD), WD-ACT achieved the lowest median missed detection rate (5.56%), the lowest median boundary mean absolute error (222.49 ms), and the highest median frame-level accuracy (87.17%). An additional generalization evaluation using nine independent vocalization segments from five further marine mammal categories provided additional evidence of cross-signal applicability without species-specific parameter tuning. These results indicate that WD-ACT provides a robust and interpretable preprocessing method for marine bioacoustic endpoint detection.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171570

Authors: Zhicheng Liu Ying Xie Fanhao Meng Chen An Menglan Duan

Despite the growing use of FLNG in offshore gas development, LNG hose safety during tandem offloading remains a critical challenge. Existing studies often analyze mooring dynamics and hose mechanics separately, lacking a unified framework that integrates multiple failure modes. This fragmented approach leads to unclear safety boundaries and inadequate risk control. Therefore, this study proposes a multi-parameter safe operating zone threshold method based on coupled dynamic analysis. First, a three-dimensional time-domain dynamic analysis model is developed using OrcaFlex, which integrates the floating bodies, hoses, and mooring system into a unified coupling framework based on hydrodynamic theory, simulating the dynamic response of the offloading system under combined wind, wave, and current actions. Second, tension, bending moment, and curvature are selected as safety evaluation parameters. These three parameters correspond to the core criteria of typical failure modes, namely axial overload failure, ultimate bending failure, and local joint failure, respectively. By comparing them with their allowable values, the safety status of the hose under various operating conditions is determined. Finally, a coupled safety threshold analysis method incorporating both “sea state return period” and “operational vessel distance” is proposed. The results indicate that, at a fixed vessel distance, the dynamic response of the hose increases significantly with worsening sea states. Tension satisfies the safety factor requirements under most sea conditions. However, the bending moment first exceeds the limit starting from the 5-year return period, making it the primary failure control indicator. Curvature exceeds the limit notably under the 50-year return period and beyond, becoming the main risk source under extreme sea states. The safe operational vessel distances under different sea states are also calculated, systematically revealing the response patterns and failure sequences of tension, curvature, and bending moment of the LNG hose under combined wind, wave, and current actions. Furthermore, by integrating safety margin calculations, an operational classification standard comprising a safe zone, a warning zone, and a danger zone is proposed, along with the upper limits of safe vessel distance and operational windows for each sea state. The threshold determination method established in this paper can provide effective engineering support for FLNG offloading operation planning, hose selection, and operational risk management.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171569

Authors: Hunyong Shin Jinsu Ahn Dongyoung Kim Jin Ho Ahn Jinyong Kim Jonggeun Kim Sungshin Kim

Unmanned Surface Vehicles (USVs) increasingly require on-board policies capable of engagement-level tactical decisions under discrete mission-system constraints. Most existing systems, however, remain rule-based and predictable, and many maritime reinforcement learning studies still focus on low-level continuous control. This paper proposes TAP-DDQN, a GRU-enhanced dueling deep Q-network trained with a multiplicative Tactical Approach Potential (TAP) and a dynamic target curriculum for discrete tactical decision-making in adversarial maritime engagements. The proposed TAP couples a desired engagement-range ring with an aspect-aware tactical term so that angular shaping becomes active mainly inside the tactical band, providing dense guidance without encouraging irrelevant long-range aspect optimization. The method is implemented through the non-invasive TRNLE wrapper, which enables learning and deployment without modifying the legacy combat-management software stack. In a 1-vs-1 surface-engagement scenario, the proposed agent achieves a DGAR of 54.87±4.19% and consistently outperforms feedforward and non-TAP baselines on reward-aligned diagnostics and maneuver consistency; relative to the strongest learning baseline (DQN+MLP without TAP), the improvement is 8.13 percentage points. Qualitative analyses further show that the learned policy approaches the desired engagement ring, stabilizes a favorable stern-quarter geometry, and exhibits more coherent maneuver behavior than rule-based or additive-reward baselines. These results support multiplicative TAP shaping as an effective and deployment-compatible approach for USV tactical autonomy and intelligent adversary generation in naval training environments.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171568

Authors: Haoshi Song Shuaidong Jia Xianpeng Liu Zikang Song Qiqian Sun

Coastal geomorphology is a key component of nearshore representation on nautical charts. However, its cartographic generalization remains constrained by incomplete knowledge-system modeling, limited task-oriented guidance, and insufficient quantitative descriptions of generalization quality. To address these limitations, this study proposes a knowledge-graph-based approach for cartographic generalization of coastal geomorphology in nautical charts. A three-layer graph framework, consisting of a concept layer, an entity layer, and a rule layer, was constructed around shorelines, coastline categories, and generalization rules. Textual knowledge extraction and spatial-feature extraction were then conducted using cartographic specifications, historical chart samples, and expert-experience documents to support the unified organization and population of multi-source knowledge. A reasoning mechanism integrating spatial constraints and semantic associations was further developed to generate quantitative reference indicators and evaluate shoreline generalization quality. The results show that the proposed knowledge graph can organize domain knowledge in a structured and traceable form, identify rule-compliance differences among different shoreline generalization results, and provide descriptive reference benchmarks for quality evaluation. The method offers a knowledge-driven basis for improving the objectivity and explainability of coastal geomorphology generalization in nautical-chart production.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171567

Authors: Huanhuan Li Lu Zou Sheng Xu Zifei Xu

Digitalisation is reshaping the relationship between the ocean and information [...]

Journal of Marine Science and Engineering doi: 10.3390/jmse14171566

Authors: Jianxing Wang Wenji Wang Junyang Cheng Yang Zhao Chenggang Xian Zhitong Zhang Fenglin Niu Laibin Zhang Zonghao Guo Xin Yao

Marine low-permeability gas-bearing sandstones are commonly characterized by thin sand–mud interbeds, poor reservoir properties, limited seismic bandwidth, and heterogeneous pore structures and fluid distributions, which make stable fluid prediction from conventional prestack seismic attributes difficult. This study proposes an uncertainty-weighted robust frequency-scanning amplitude variation with offset (AVO) inversion method, termed URFS-AVO, for gas-bearing sandstone identification in the Xihu Sag, East China Sea. Under a fluid-matrix decoupled AVO framework, a frequency-dependent P-to-P (PP) reflection-coefficient equation related to the fluid bulk modulus is combined with matching-pursuit Wigner–Ville distribution (MP-WVD) spectral decomposition to obtain local time–frequency spectra from prestack angle gathers. Moving narrow frequency windows are then used to estimate local fluid-dispersion attributes within the effective seismic bandwidth. Rather than extracting the maximum response, URFS-AVO fuses multi-window estimates using local inversion uncertainty and frequency-domain consistency. Tests based on the Chapman pore–microcrack model and the generalized propagator matrix show that the proposed attribute is sensitive to gas-bearing variations. Compared with maximum-window frequency-scanning AVO (FS-AVO), URFS-AVO produces a more focused target-layer response and suppresses unstable background fluctuations, especially under noisy conditions. Application to marine prestack seismic data from the Xihu Sag shows that high URFS-AVO responses are generally consistent with gas-bearing intervals interpreted from well logs. The method provides a stable seismic constraint for fluid prediction in marine low-permeability gas-bearing sandstone reservoirs.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171565

Authors: Chi Yu Sheng Zhang Yi Long Cheng Zhang

As critical components of offshore wind farms, suspend export cables have attracted increasing attention owing to their complex dynamic responses under combined wave–current loading and cable–soil interaction, leading to structural failure and fatigue damage. A numerical framework is developed in the present study to investigate the dynamic responses of a power cable extending from an offshore wind turbine foundation located in the South China Sea. The model of the cable is described by using the absolute nodal coordinate formulation, considering the hydrodynamic load and cable–seabed interaction via the Morison equation and Randolph–Quiggin model, respectively. After model validation, the response characteristics of the cable under different metocean conditions are analyzed. The effects of waves, currents, and related environmental factors on structural strength, fatigue damage, and wear damage are further evaluated. The dynamic response of the cable exhibits pronounced non-uniformity along the arc length. The wave return period mainly affects the response amplitude, whereas the incident angle has a more significant influence on the dynamic response. Damage assessment further shows that instantaneous strength failure is not critical, as the maximum stresses remain below the allowable stress. Instead, fatigue damage and contact wear are concentrated near the transition region and touchdown point, where oblique wave–current action intensifies cyclic bending and wear growth. The results are expected to provide theoretical support and useful reference for the design, installation, operation and maintenance of cables in offshore wind farms.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171564

Authors: Peiming Li Juan Hui Rongrong Zhu Qinchuan Zhang Weiyu Tan Wenwu Wang

This study evaluates adaptive spatial matrix filtering (AMF) combined with MUSIC for underwater acoustic direction-of-arrival estimation under strong out-of-sector interference and extends the method to coherent sources by incorporating forward spatial smoothing (FSS) into the AMF design. Simulations compared AMF-MUSIC with conventional MUSIC and continuous matrix filter (CMF)-MUSIC. For a 20-sensor array with targets at −2° and 1°, an interferer at 50°, an SNR of −5 dB, and an INR of 20 dB, both AMF-MUSIC and CMF-MUSIC resolved the targets under a common −25 dB stopband bound, but AMF-MUSIC produced a smoother out-of-sector background. Tightening the CMF bound to −40 dB reduced background peaks but degraded target resolution. In coherent-source simulations using a 25-sensor array, AMF-FSS-MUSIC resolved the targets for all tested subarray lengths when the angular separation was at least 4.5°, achieving resolution probabilities of at least 95%. A 900–1100 Hz broadband simulation maintained an approximately −15 dB stopband response and a passband-response error below −12 dB. For the SWellEx-96 narrowband data, AMF-MUSIC reduced the DOA-estimation RMSE from 11.16° to 5.18° and increased the mean spatial-spectrum SIR from −0.41 dB to 13.18 dB, while the broadband results qualitatively demonstrated interference suppression. These results indicate a favorable configuration-dependent suppression–fidelity tradeoff, while robustness to other coherent-source conditions and broader measured-data validation require further investigation.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171563

Authors: Zhirui Zhang Long Zheng Ji Wu Yiming Zhong Songxiong Wu Wei Shi Wei Chai Chana Sinsabvarodom Ming Qin

As offshore wind development moves toward deeper waters, floating offshore wind turbines have become essential for carbon-neutral energy systems. This study experimentally investigates the hydrodynamic coefficients of typical column–heave-plate components under forced oscillations, focusing on the influence of pitch-induced inclination. A circular column without a heave plate and a circular column equipped with a hexagonal heave plate were tested under heave and surge motions with varying periods, amplitudes, and static inclination angles. The static inclinations were used to represent the attitude variation of platform components during large-amplitude pitch responses. Added mass and damping coefficients were identified using the least squares method. The results show that for the heave-plate-equipped column, increasing the inclination from 0° to 5° and 10° reduced the nondimensional heave added mass by approximately 4.3% and 5.9%, respectively, and reduced the nondimensional heave damping by approximately 7.1% and 6.8%. The corresponding reductions in surge added mass were approximately 5.3% and 10.5%, whereas the reductions in surge damping reached approximately 8.2% and 16.4%, indicating that the surge damping is most sensitive to static inclination. These variations may be associated with the altered geometric projection and disturbed flow symmetry of the inclined component, which may affect the attached-fluid volume and energy-dissipation process during forced oscillation. Future studies should further verify the corresponding local separation and vortex-formation mechanisms through detailed flow-field measurements, PIV, or CFD.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171562

Authors: Jinli Pan Zuoyou Li Xiulong Yang Hui Ma Xuecai Ma Yunfei Shangguan

Organic matter enrichment in marine–continental transitional shales is influenced by volcanism, continental weathering, and paleoceanographic evolution, but their interactions during the Late Paleozoic Ice Age (LPIA) remain unclear. Mineralogical, elemental, and organic geochemical data from the Upper Carboniferous Yanghugou Formation, western Ordos Basin, were used to reconstruct volcanic input, weathering intensity, productivity, redox conditions, and organic carbon accumulation. High Hg/TOC, Zr/Al2O3, and Zr/Cr ratios indicate strong volcanic input during early deposition, followed by an upward decline. Chemical Index of Alteration values of 76.5–91.5 increase upward, indicating intensified chemical weathering under warmer and more humid conditions. Increasing Corg/P, MoEF, and UEF values record a shift from oxic–suboxic to predominantly anoxic bottom waters. The weak relationship between productivity proxies and TOC suggests that volcanic fertilization was not the main control on organic matter enrichment. Instead, negative δ13Corg values, high Al2O3 contents, organic matter–clay associations, and reducing conditions indicate that enhanced terrestrial organic matter input and improved preservation jointly promoted organic carbon accumulation. Volcanism likely intensified climatic warming and weathering, whereas subsequent organic carbon burial contributed to atmospheric CO2 drawdown and climatic feedbacks during the LPIA.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171561

Authors: Yiling Sun Menghao Fan Haonan Wei Fantong Kong

Underwater acoustic target recognition (UATR) is challenging due to the complex, multi-scale physical characteristics of marine targets and the strict computational limits of edge platforms like unmanned surface vehicles. To navigate the severe interference of underwater environments, existing methods increasingly rely on heavyweight architectures to achieve high recognition accuracy. However, the massive computational overhead of these models is fundamentally at odds with the restricted power and processing capabilities of practical deployment platforms. To resolve this conflict between performance and deployability, we propose LHK-Net, a lightweight Heterogeneous Kernel Network. By integrating a Heterogeneous Kernel Pyramid with Residual Depthwise Separable Convolutions, LHK-Net dynamically captures multi-scale acoustic features, from macroscopic steady-state harmonics to localized transient impulses, while compressing the model size to merely 0.82 M parameters. Additionally, a dual-domain Time–Frequency Attention module and an Adaptive SK-Fusion mechanism are incorporated for robust noise suppression. Experiments on the DeepShip dataset demonstrate that LHK-Net achieves state-of-the-art accuracy, outperforming heavyweight models at real-time speeds. Extensive visual analyses further validate that the network possesses strong physical interpretability, effectively aligning its internal feature representations with the intrinsic acoustic properties of the targets.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171560

Authors: Yunling Ye Bowen Niu Guanxi Guo Jiale Zhang Jiayi Liu Weide Wang Mengzhen Li

Rapidly deployable floating bridges face coupled challenges in compact deployment, structural load-bearing, and controllable module maneuvering, which cannot be fully evaluated through a single-stage structural or hydrodynamic assessment. To close this gap, this study proposes a rigid–flexible hybrid floating bridge composed of rigid deck plates, inflatable buoyancy bladders, scissor linkages, and integrated waterjet propulsors. A multi-stage assessment was conducted through inflation and calm-water maneuvering tests, gas–solid coupled finite-element analysis, and hydrodynamic and mooring simulations. The inflation experiment revealed three stages in the inflation process of the rigid–flexible specimen, including filling, transition, and pressurization stages. A remotely controlled scale model completed longitudinal, lateral, rotational, and compound motions, demonstrating the feasibility of module-level maneuvering under manual remote control. The finite-element results showed that increasing the initial internal pressure improved the load-bearing capacity and reduced local plastic deformation of the upper deck, while further improvement became limited above 70 kPa. Under the specified wave–current conditions, the ten-module assembly exhibited maximum mooring tension, horizontal displacement, and rotation of 34.7 kN, 0.276 m, and 5.525°, respectively. These results demonstrate the potential of the proposed configuration for bearing capacity, rapid deployment, and resistance to the investigated current and wave conditions while providing a multi-stage framework for further engineering design.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171559

Authors: Clémence Podgorny Sarat Chandra Mohapatra C. Guedes Soares

This paper presents a mathematical model to investigate how waves and currents interact with a flexible perforated floating membrane in finite water depth within the framework of linear wave theory. The perforated flexible membrane is modeled based on Darcy’s law and the one-dimensional string equation. The complex dispersion relation in the presence of current velocity is derived from the Green’s function technique using a fundamental source potential solution. The dispersion curve is analyzed by comparing the phase and group velocities for different water depths. Further, a physical model associated with the effect of current on a moored finite floating perforated flexible membrane integrated with a vertical wall is formulated. Then, the theoretical solution of a physical boundary value problem near a vertical rigid wall is obtained using the matching technique and the roots of the dispersion relation derived from the Green’s function technique. Numerical simulations are provided to verify the convergence of the series solution and the accuracy of the obtained analytical findings are evaluated against previously published analytical and experimental datasets. Further, several numerical results on the membrane deflection, hydrodynamic coefficients, and horizontal force on the wall for various structural parameters, mooring stiffness, and current velocities are analyzed. It is observed that the present analysis with this perforated membrane breakwater will be helpful to coastal and marine engineers to understand the influence of current velocity.

Journal of Marine Science and Engineering doi: 10.3390/jmse14171558

Authors: Utkarsh Bhardwaj

Reliability assessments of subsea systems are generally performed at two levels: structural reliability analysis of individual components and functional reliability analysis of the overall system using generic failure-rate databases. This study develops a component-to-system multi-scale framework that integrates these two levels for a subsea separation system operating at 3000 m water depth. At the component level, a Gaussian process regression (GPR) surrogate is developed from 474 finite element simulations of a vertical gravity separator. First-order reliability method (FORM) and Monte Carlo simulation (MCS) are then employed to assess the structural reliability, followed by a time-variant reliability analysis that accounts for corrosion effects. At the system level, the structural reliability model is integrated with functional failure rates through a Bayesian network that considers five equipment items and relevant risk-influencing factors. The surrogate model accurately predicts collapse pressure with an R2 value of 0.996. The intact separator achieves a reliability index of 4.55, satisfying the DNV high-safety-class target, with the structural failure mode contributing only 0.0034% of the separator failure rate. Under a corrosion rate of 0.4 mm/year, the reliability index decreases to 3.12 over a 25-year service period. The structural failure rate crosses the DNV medium-safety-class target of 10−4 per year at year 12, increasing the structural contribution to the overall system failure frequency to 0.33%. Sensitivity analysis indicates that initial ovality and wall thickness are the most influential parameters affecting structural reliability and should therefore be prioritized in design and integrity management strategies. The framework is demonstrated on this physics-consistent dataset; validation against independent nonlinear finite element analyses and experimental collapse data is identified as the necessary next step before the results are used for design.

Journal of Marine Science and Engineering doi: 10.3390/jmse14161557

Authors: Yafei Ge Xiaoming Xia

This paper investigates a formation tracking problem for underactuated surface vessels (USVs) subject to collision avoidance and input saturation constraints. Many existing APF-based formation-control approaches formulate collision avoidance using a single reference point or an inter-center distance, which may provide insufficient geometric information during close-range maneuvers. To improve navigation safety, an elliptical disk-based collision avoidance mechanism is developed by introducing safety points at the bow, stern, port, and starboard sides of each USV, such that multiple characteristic-point distance constraints can be simultaneously enforced. To address unknown nonlinearities caused by model uncertainties and external disturbances, a neural network-based observer is designed to estimate unavailable velocity states and lumped disturbances. Distributed control laws are synthesized by integrating artificial potential functions (APFs), the observer, and a backstepping technique. Additional controllers are introduced to address the input saturation and underactuated issues while preserving the collision avoidance capability. Stability of the closed-loop system is rigorously established via Lyapunov theory. Simulation results demonstrate that the proposed approach achieves safer close-range maneuvering performance compared with conventional single-point methods.

Journal of Marine Science and Engineering doi: 10.3390/jmse14161556

Authors: Yuqi Wu Yuanzheng Yang Hao Liang

This paper proposes an annular suction caisson specifically designed to reinforce in-service monopiles and upgrade existing offshore wind farms to accommodate larger-capacity wind turbines. During penetration of the annular suction caisson into clay, the existing monopile restricts the inward migration of soil into the internal space of the caisson, promoting upward soil displacement and consequently increasing the height of the soil plug formed inside the caisson. In addition, the strain-softening behavior causes varying degrees of strength degradation in the clay along the caisson wall. The softened zones extend approximately one caisson wall thickness on the inner side and 1.2 times the wall thickness on the outer side of the caisson. Both effects should be considered for accurately predicting the penetration resistance of annular suction caissons. Therefore, three-dimensional large-deformation finite element analyses were performed to investigate the penetration behavior of annular suction caissons in strain-softening clay. A comprehensive parametric study was conducted to quantify the soil plug heave and overall penetration resistance. Meanwhile, the soil flow mechanism at the caisson tip, the evolution of clay strength along the caisson wall, and the formation characteristics of the internal soil plug were systematically examined. Based on the numerical results, a theoretical approach was developed to evaluate the penetration resistance of annular suction caissons.

Journal of Marine Science and Engineering doi: 10.3390/jmse14161555

Authors: Yan Wang Xupu Geng Yan Li Xiaohui Li Chenghan Luo Shaoping Shang Feng Zhang

Synthetic Aperture Radar (SAR) enables high-resolution sea-surface wind speed retrieval. However, the enhanced spatial resolution of SAR imagery introduces substantial challenges, from small-scale contamination sources that significantly degrade retrieval accuracy. Particularly in coastal regions, non-wind-related backscatter signals, such as ships and oil slicks, can severely bias wind speed estimates at sub-kilometer scales. In this study, the first-order moment (average, m1) and second-order moment (variance, m2) are computed from the normalized radar cross-section (NRCS) within sub-images of Sentinel-1 SAR data acquired in Interferometric Wide (IW) mode. Analysis reveals that clean-sea-surface signals in both VV and VH polarizations cluster around an approximately linear empirical trend, m2 = 2m1 + b, in the m1-m2 statistical feature space, whereas the examined contamination types deviate from this trend and occupy separable regions. Based on this characteristic, a quality-control framework is proposed for the systematic separation of clean sea surface from image noise (border noise and inter-swath stripe noise) and non-ocean targets (land contamination, bright targets, and dark spots). Validation using independent SAR data from the Taiwan Strait was conducted separately for native 10 m and height-adjusted 3 m buoy observations. For the native 10 m observations, the RMSE and MBE were essentially unchanged at 1.5 m/s and −0.3 m/s, respectively. For the height-adjusted nearshore observations, the RMSE decreased from 3.2 m/s to 2.1 m/s and the MBE changed from −1.5 m/s to −1.1 m/s.