Journal of Marine Science and Engineering

26 pages, 1329 KiB

Open AccessReview

Advancing Maritime Safety: A Literature Review on Machine Learning and Multi-Criteria Analysis in PSC Inspections

by Zlatko Boko, Ivica Skoko, Zaloa Sanchez Varela and Vice Milin

J. Mar. Sci. Eng. 2025, 13(5), 974; https://doi.org/10.3390/jmse13050974 (registering DOI) - 17 May 2025

This literature review provides a structured quantitative analysis of existing research on the application of machine learning models (MLMs) and multi-criteria decision-making methods (MCDM) in the context of port state control (PSC). The aim of the study is to capture current research trends, [...] Read more.

This literature review provides a structured quantitative analysis of existing research on the application of machine learning models (MLMs) and multi-criteria decision-making methods (MCDM) in the context of port state control (PSC). The aim of the study is to capture current research trends, identify thematic priorities, and demonstrate how these analytical tools have been used to support decision-making and risk assessment in the maritime domain. Rather than evaluating the effectiveness of individual models, the study focuses on the distribution and frequency of their use and provides insights into the development of methodological approaches in this area. Although several studies suggest that the integration of MLMs and MCDM techniques can improve the objectivity and efficiency of PSC inspections, this report does not provide a comparative assessment of their performance. Instead, it lays the groundwork for future qualitative studies that will assess the practical benefits and challenges of such integration. The findings suggest a fragmented but growing research interest in data-driven approaches to PSC and highlight the potential of advanced analytics to support maritime safety and regulatory compliance. Full article

(This article belongs to the Section Ocean Engineering)

35 pages, 667 KiB

Open AccessArticle

Feasibility and Cost-Benefit Analysis of Methanol as a Sustainable Alternative Fuel for Ships

by Pei-Chi Wu and Cherng-Yuan Lin

J. Mar. Sci. Eng. 2025, 13(5), 973; https://doi.org/10.3390/jmse13050973 (registering DOI) - 17 May 2025

Abstract

The amendment to MARPOL Annex VI, which limits the sulfur content in marine fuels to a maximum of 0.5 wt.%, came into effect in January 2020. This includes reducing sulfur oxide (SO_X) emissions and establishing nitrogen oxide (NO_X) emission [...] Read more.

The amendment to MARPOL Annex VI, which limits the sulfur content in marine fuels to a maximum of 0.5 wt.%, came into effect in January 2020. This includes reducing sulfur oxide (SO_X) emissions and establishing nitrogen oxide (NO_X) emission standards (Tiers I, II, and III) based on the ship’s engine type and construction date. Furthermore, the regulations require oil tankers to control volatile organic compound (VOC) emissions and prohibit the installation of new equipment containing ozone-depleting substances. After a four-year exploration phase, global shipping companies still lack consistent evaluation criteria for the selection and use of alternative fuels, resulting in divergence across the industry. According to the latest data, methanol can reduce NO_X, SO_X, and particulate matter (PM) emissions by approximately 80%, 99%, and 95%, respectively, compared to traditional heavy fuel oil. Furthermore, green methanol has the potential for near-zero greenhouse gas emissions and can meet the stringent standards of Emission Control Areas. Therefore, this study adopts a cost-benefit analysis method to evaluate the feasibility and implementation benefits of two promising strategies: methanol dual fuel and very low-sulfur fuel oil (VLSFO). A 6600-TEU container ship was selected as a representative case, and the evaluation was conducted by replacing an older ship with a newly built one. The reductions in total pollutants and CO₂-equivalent emissions of the container ship, as well as the cost-effectiveness of each specific strategy, were calculated. This study found that, in the first five years of operation, the total incremental cost of Vessel A, which uses 100% VLSFO, will be significantly lower than that of Vessel B, which uses a blend of 30% e-methanol + 70% VLSFO as fuel. Furthermore, compared to a scenario without any improvement strategies, the total incremental cost for Vessels A and B will increase by 69.90% and 178.15%, respectively, over five years. Vessel B effectively reduced the total greenhouse gas emission equivalent (CO₂e) of CO₂, CH_4, and N₂O by 24.72% over five years, while Vessel A reduced the CO₂e amount by 12.18%. Furthermore, the cost-benefit ratio (CBR) based on total pollutant emission reduction is higher for Vessel A than for Vessel B within five years of operation. However, in terms of the cost-effectiveness of CO₂e emission reduction, the CBR of Vessel A becomes lower than Vessel B after 4.7 years of operation. Therefore, Vessel A’s strategy should be considered a short-term option for reducing CO₂e within 4.7 years, whereas the strategy of Vessel B is more suitable as a long-term solution for more than 4.7 years. Full article

(This article belongs to the Section Marine Environmental Science)

21 pages, 11060 KiB

Open AccessArticle

Study on the Suppression of Tip Leakage Vortex in Axial Flow Pumps Based on Circumferential Grooving in the Rotor Chamber

by Haoran Wu, Desheng Zhang, Xi Shen, Chen Ni and Gang Yang

J. Mar. Sci. Eng. 2025, 13(5), 972; https://doi.org/10.3390/jmse13050972 (registering DOI) - 17 May 2025

Abstract

The stability of axial flow pumps is significantly affected by the tip leakage vortex (TLV), which is generated through the entrainment of the main flow. This study explores the effects of circumferential grooving in the rotor chamber on the tip leakage vortex of [...] Read more.

The stability of axial flow pumps is significantly affected by the tip leakage vortex (TLV), which is generated through the entrainment of the main flow. This study explores the effects of circumferential grooving in the rotor chamber on the tip leakage vortex of an axial flow pump by using the SST k-ω turbulence model. Numerical results were validated with prototype pump experiments. At the design condition, circumferential grooves positioned near the blade leading edge enhance both the pump’s efficiency and head. Grooves implemented at the mid-chord to trailing-edge regions are relatively close to those of the prototype pump. The implementation of grooves at both leading and trailing regions resulted in significantly degraded performance compared to the other two cases. However, at reduced flow rates, grooving in the rotor chamber leads to a decline in performance. Grooves positioned near the blade’s leading edge interfere with the ingress of the TLV into the suction side, suppressing vortex formation. Vortex structures and low-pressure regions are closer to the blade, reducing flow instability. In contrast, grooving in the middle and rear rotor chamber induces instability in the tip region. These findings offer theoretical guidance for suppressing the TLV and enhancing the stability of axial flow pumps. Full article

(This article belongs to the Section Ocean Engineering)

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25 pages, 17946 KiB

Open AccessArticle

Study on Suppression of Vortex-Induced Vibrations of a Rotating Cylinder with Dual Splitter Plates

by Jiaqi Li, Qiongfang Qi, Zonghao Sun, Yongkang Yang, Yaowen Han, Wei Chen, Jiangyan Shao, Binrong Wen and Xiaobin Li

J. Mar. Sci. Eng. 2025, 13(5), 971; https://doi.org/10.3390/jmse13050971 (registering DOI) - 16 May 2025

Abstract

To investigate the suppression method for vortex-induced vibrations (VIV) of two-degree-of-freedom (2-DOF) rotating cylinders with dual splitter plates, numerical simulations are conducted at a Reynolds number of 200, a mass ratio of 2.6, and rotation ratio of 2. The effects of the gap [...] Read more.

To investigate the suppression method for vortex-induced vibrations (VIV) of two-degree-of-freedom (2-DOF) rotating cylinders with dual splitter plates, numerical simulations are conducted at a Reynolds number of 200, a mass ratio of 2.6, and rotation ratio of 2. The effects of the gap distance and the width of splitter plates on the vibration response, hydrodynamic coefficients, and flow wakes of rotating cylinders are examined. The numerical results show the existence of distinct suppression mechanisms between low gap distances (G/D = 0.25–0.5) and high gap distances (G/D = 0.75–2.0). Furthermore, the width (W/D) is considered as a critical factor in suppression effectiveness. The distributions of wake patterns under different gap distance and width are analyzed, and six wake patterns are observed. Finally, lift and drag coefficients are examined, revealing their distinct sensitivities to G/D and W/D. The optimal gap distance and width parameters of dual splitter plates for rotating cylinders suppression are determined. Marine drilling is persistently subjected to VIV, which critically compromise structural stability. The findings of this study deliver engineering value for marine riser VIV suppression. Full article

(This article belongs to the Section Ocean Engineering)

30 pages, 4334 KiB

Open AccessArticle

Qualitative Risk Assessment Methodology for Maritime Autonomous Surface Ships: Cognitive Model-Based Functional Analysis and Hazard Identification

by Seong Na, Dongjun Lee, Jaeha Baek, Seonjin Kim and Choungho Choung

J. Mar. Sci. Eng. 2025, 13(5), 970; https://doi.org/10.3390/jmse13050970 - 16 May 2025

Abstract

Maritime Autonomous Surface Ships (MASSs) incorporate advanced digital technologies, thus rendering their systems more complex and diverse than those of conventional ships. Furthermore, the operation of MASSs, which introduces new risks not encountered in conventional ship operations, differs significantly from that of conventional [...] Read more.

Maritime Autonomous Surface Ships (MASSs) incorporate advanced digital technologies, thus rendering their systems more complex and diverse than those of conventional ships. Furthermore, the operation of MASSs, which introduces new risks not encountered in conventional ship operations, differs significantly from that of conventional manned vessels. These challenges highlight the necessity for a more systematic and structured approach to risk analysis and control. This study presents a qualitative risk assessment methodology to identify and manage hazardous scenarios associated with MASS operations systematically. The key feature of the proposed methodology is the integration of cognitive model-based functional analysis with the widely adopted hazard identification (HAZID) method, which enables a structured and comprehensive analysis process. Functional analysis is used to examine the functions required for MASS operations and to analyze interconnected systems to fulfill these functions. Subsequently, HAZID is performed to identify hazardous scenarios that may cause functional degradation or failure. To illustrate the proposed methodology, a case study is presented based on a qualitative risk assessment conducted in preparation for the field trial of an Autonomous Navigation System. Practical applications, including the presented case study, demonstrated the effectiveness of this methodology as a systematic tool for identifying and evaluating potentially hazards in MASS operations. Full article

(This article belongs to the Special Issue Advancements in Maritime Safety and Risk Assessment)

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33 pages, 3090 KiB

Open AccessReview

Unmanned Surface Vessels in Marine Surveillance and Management: Advances in Communication, Navigation, Control, and Data-Driven Research

by Zhichao Lv, Xiangyu Wang, Gang Wang, Xuefei Xing, Chenlong Lv and Fei Yu

J. Mar. Sci. Eng. 2025, 13(5), 969; https://doi.org/10.3390/jmse13050969 - 16 May 2025

Abstract

Unmanned Surface Vehicles (USVs) have emerged as vital tools in marine monitoring and management due to their high efficiency, low cost, and flexible deployment capabilities. This paper presents a systematic review focusing on four core areas of USV applications: communication networking, navigation, control, [...] Read more.

Unmanned Surface Vehicles (USVs) have emerged as vital tools in marine monitoring and management due to their high efficiency, low cost, and flexible deployment capabilities. This paper presents a systematic review focusing on four core areas of USV applications: communication networking, navigation, control, and data-driven operations. First, the characteristics and challenges of acoustic, electromagnetic, and optical communication methods for USV networking are analyzed, with an emphasis on the future trend toward multimodal communication integration. Second, a comprehensive review of global navigation, local navigation, cooperative navigation, and autonomous navigation technologies is provided, highlighting their applications and limitations in complex environments. Third, the evolution of USV control systems is examined, covering group control, distributed control, and adaptive control, with particular attention given to fault tolerance, delay compensation, and energy optimization. Finally, the application of USVs in data-driven marine tasks is summarized, including multi-sensor fusion, real-time perception, and autonomous decision-making mechanisms. This study aims to reveal the interaction and coordination mechanisms among communication, navigation, control, and data-driven operations from a system integration perspective, providing insights and guidance for the intelligent operations and comprehensive applications of USVs in marine environments. Full article

(This article belongs to the Special Issue Unmanned Marine Vehicles: Perception, Planning, Control and Swarm—2nd Edition)

25 pages, 5502 KiB

Open AccessArticle

Numerical Study of the Energy-Saving Effect of the Gate Rudder System

by Hujia Cui, Donglei Zhang, Yuan Kong and Xianzhou Wang

J. Mar. Sci. Eng. 2025, 13(5), 968; https://doi.org/10.3390/jmse13050968 - 16 May 2025

Abstract

Energy-saving device (ESD) plays an important role in mitigating the emission of greenhouse gases in ship industry. It is necessary to study a promising ESD, a gate rudder, for its great potential in promoting energy efficiency. In the present study, ship resistance and [...] Read more.

Energy-saving device (ESD) plays an important role in mitigating the emission of greenhouse gases in ship industry. It is necessary to study a promising ESD, a gate rudder, for its great potential in promoting energy efficiency. In the present study, ship resistance and self-propulsion simulations were conducted to investigate the energy-saving effects of gate rudder using a viscous in-house CFD solver. First, verification and validation studies were performed to estimate the accuracy and reliability of the numerical method and the results are in good agreement with experimental data. Afterward, resistance and self-propulsion simulations of a crude carrier equipped with the conventional rudder and the gate rudder were carried out respectively. Ship resistance and self-propulsion characteristics with different sailing velocities and propeller revolution rates were compared to study the energy-saving ability of the gate rudder as well as its effects on ship hydrodynamic performance. The results indicate that the gate rudder can greatly optimize the energy efficiency of the ship. Meantime, the ship equipped with the gate rudder shows better resistance and propulsion performance in a self-propelled state. Full article

(This article belongs to the Special Issue Maritime Efficiency and Energy Transition)

17 pages, 892 KiB

Open AccessArticle

An Integrated Design of Course-Keeping Control and Extended State Observers for Nonlinear USVs with Disturbances

by Nianzhe Wu, Jianning Li and Ju Xiong

J. Mar. Sci. Eng. 2025, 13(5), 967; https://doi.org/10.3390/jmse13050967 - 16 May 2025

Abstract

The integrated design problem of non-fragile controllers and extended state observers (ESOs) for nonlinear unmanned surface vehicles (USVs) under mismatched disturbances is addressed in this paper. First, an integrated model combining the USV system and the rudder system is developed, which includes a [...] Read more.

The integrated design problem of non-fragile controllers and extended state observers (ESOs) for nonlinear unmanned surface vehicles (USVs) under mismatched disturbances is addressed in this paper. First, an integrated model combining the USV system and the rudder system is developed, which includes a second-order underdamped system and a Norrbin nonlinear model incorporating uncertainties. Due to the coupling issues in the design of controllers and observers caused by parameter perturbations or other unmodeled dynamics, an integrated design method, which enables the simultaneous computation of controller gains, observer gains, and disturbance compensation gains, is proposed, effectively addressing these issues. Ultimately, the performance of the designed strategy is verified through a simulation, with the data used in the simulation derived from the real Qingshan USV. Full article

(This article belongs to the Section Ocean Engineering)

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24 pages, 22764 KiB

Open AccessArticle

The TSformer: A Non-Autoregressive Spatio-Temporal Transformers for 30-Day Ocean Eddy-Resolving Forecasting

by Guosong Wang, Min Hou, Mingyue Qin, Xinrong Wu, Zhigang Gao, Guofang Chao and Xiaoshuang Zhang

J. Mar. Sci. Eng. 2025, 13(5), 966; https://doi.org/10.3390/jmse13050966 - 16 May 2025

Abstract

Ocean forecasting is critical for various applications and is essential for understanding air–sea interactions, which contribute to mitigating the impacts of extreme events. While data-driven forecasting models have demonstrated considerable potential and speed, they often primarily focus on spatial variations while neglecting temporal [...] Read more.

Ocean forecasting is critical for various applications and is essential for understanding air–sea interactions, which contribute to mitigating the impacts of extreme events. While data-driven forecasting models have demonstrated considerable potential and speed, they often primarily focus on spatial variations while neglecting temporal dynamics. This paper presents the TSformer, a novel non-autoregressive spatio-temporal transformer designed for medium-range ocean eddy-resolving forecasting, enabling forecasts of up to 30 days in advance. We introduce an innovative hierarchical U-Net encoder–decoder architecture based on 3D Swin Transformer blocks, which extends the scope of local attention computation from spatial to spatio-temporal contexts to reduce accumulation errors. The TSformer is trained on 28 years of homogeneous, high-dimensional 3D ocean reanalysis datasets, supplemented by three 2D remote sensing datasets for surface forcing. Based on the near-real-time operational forecast results from 2023, comparative performance assessments against in situ profiles and satellite observation data indicate that the TSformer exhibits forecast performance comparable to leading numerical ocean forecasting models while being orders of magnitude faster. Unlike autoregressive models, the TSformer maintains 3D consistency in physical motion, ensuring long-term coherence and stability. Furthermore, the TSformer model, which incorporates surface auxiliary observational data, effectively simulates the vertical cooling and mixing effects induced by Super Typhoon Saola. Full article

(This article belongs to the Section Ocean Engineering)

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23 pages, 1455 KiB

Open AccessArticle

Oxidative Stress Responses and Recovery of Marine Medaka (Oryzias melastigma) in Early-Life Stages After Acute Exposure to Crude Oil

by Xishan Li, Yuekun Dai, Xin Li, Haiqiang Guo, Jiarui Dai, Haonan Wang, Deqi Xiong and Guoxiang Liao

J. Mar. Sci. Eng. 2025, 13(5), 965; https://doi.org/10.3390/jmse13050965 - 15 May 2025

Abstract

Oil spills pose a significant threat to marine ecosystems, with potentially adverse impacts on fish in early-life stages. Despite numerous studies reporting the developmental toxicity of oil exposure, knowledge about the recovery capacity of fish after oil exposure remains limited. Therefore, this study [...] Read more.

Oil spills pose a significant threat to marine ecosystems, with potentially adverse impacts on fish in early-life stages. Despite numerous studies reporting the developmental toxicity of oil exposure, knowledge about the recovery capacity of fish after oil exposure remains limited. Therefore, this study investigated the effects of water-accommodated fractions (WAFs) of Oman crude oil on the development and oxidative stress of marine medaka (Oryzias melastigma) embryos during a 7-day acute exposure period followed by a 14-day recovery period in clean seawater. Results revealed that WAF exposure caused concentration-dependent developmental toxicity gradually becoming apparent during the recovery period, including reduced survival and hatching rates, and increased morphological abnormalities. During the exposure period, low WAF concentrations triggered antioxidant responses (elevated SOD and CAT activities, and GSH content), while higher concentrations caused a concentration-dependent increase in lipid peroxidation (elevated MDA content). Differently, during the recovery period, all groups showed impaired antioxidant capacity (decreased SOD, CAT, GSH) and immune function (reduced AKP activity). Principal component analysis revealed strong correlations between survival, oxidative stress markers, and developmental toxicity. These findings could provide valuable insights into the recovery capacity of fish exposed to crude oil and give references for assessing the recovery potential of marine ecosystems after oil spills. Full article

(This article belongs to the Section Marine Biology)

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17 pages, 10034 KiB

Open AccessArticle

Elastic Wave Phase Inversion in the Local-Scale Frequency–Wavenumber Domain with Marine Towed Simultaneous Sources

by Shaobo Qu, Yong Hu, Xingguo Huang, Jingwei Fang and Zhihai Jiang

J. Mar. Sci. Eng. 2025, 13(5), 964; https://doi.org/10.3390/jmse13050964 - 15 May 2025

Abstract

Elastic full waveform inversion (EFWI) is a crucial technique for retrieving high-resolution multi-parameter information. However, the lack of low-frequency components in seismic data may induce severe cycle-skipping phenomena in elastic full waveform inversion (EFWI). Recognizing the approximately linear relationship between the phase components [...] Read more.

Elastic full waveform inversion (EFWI) is a crucial technique for retrieving high-resolution multi-parameter information. However, the lack of low-frequency components in seismic data may induce severe cycle-skipping phenomena in elastic full waveform inversion (EFWI). Recognizing the approximately linear relationship between the phase components of seismic data and the properties of subsurface media, we propose an Elastic Wave Phase Inversion in local-scale frequency–wavenumber domain (LFKEPI) method. This method aims to provide robust initial velocity models for EFWI, effectively mitigating cycle-skipping challenges. In our approach, we first employ a two-dimensional sliding window function to obtain local-scale seismic data. Following this, we utilize two-dimensional Fourier transforms to generate the local-scale frequency–wavenumber domain seismic data, constructing a corresponding elastic wave phase misfit. Unlike the Elastic Wave Phase Inversion in the frequency domain (FEPI), the local-scale frequency–wavenumber domain approach accounts for the continuity of seismic events in the spatial domain, enhancing the robustness of the inversion process. We subsequently derive the gradient operators for the LFKEPI methodology. Testing on the Marmousi model using a land seismic acquisition system and a simultaneous-source marine towed seismic acquisition system demonstrates that LFKEPI enables the acquisition of reliable initial velocity models for EFWI, effectively mitigating the cycle-skipping problem. Full article

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

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19 pages, 14125 KiB

Open AccessArticle

Spatio-Temporal Dynamics of Particulate Organic Carbon and Its Response to Climate Change: Evidence of the East China Sea from 2003 to 2022

by Zhenghan Liu, Yingfeng Chen, Xiaofeng Lin and Wei Yang

J. Mar. Sci. Eng. 2025, 13(5), 963; https://doi.org/10.3390/jmse13050963 - 15 May 2025

Abstract

Particulate organic carbon (POC) plays a crucial role in oceanic climate change. However, existing research is limited by several factors, including the scarcity of long-term data, extensive datasets, and a comprehensive understanding of POC dynamics. This study utilizes monthly average POC remote sensing [...] Read more.

Particulate organic carbon (POC) plays a crucial role in oceanic climate change. However, existing research is limited by several factors, including the scarcity of long-term data, extensive datasets, and a comprehensive understanding of POC dynamics. This study utilizes monthly average POC remote sensing data from the MODIS/AQUA satellite to analyze the spatiotemporal variations of POC in the East China Sea from 2003 to 2022. Employing correlation analysis, spatial autocorrelation models, and the Geodetector model, we explore responses to key influencing factors such as climatic elements. The results indicate that POC concentrations are higher in the western nearshore areas and lower in the eastern offshore regions of the East China Sea (ECS). Additionally, concentrations are observed to be lower in southern regions compared to northern ones. From 2003 to 2022, POC concentrations exhibited a fluctuating downward trend with an average annual concentration of 121.05 ± 4.57 mg/m³. Seasonally, monthly average POC concentrations ranged from 105.48 mg/m³ to 158.36 mg/m³; notably higher concentrations were recorded during spring while summer showed comparatively lower levels. Specifically, POC concentrations peaked in April before rapidly declining from May to June—reaching a minimum—and then gradually increasing again from June through December. Correlation analysis revealed significant influences on POC levels by particulate inorganic carbon (PIC), sea surface temperature (SST), chlorophyll (Chl), and photosynthetically active radiation (PAR). The Geodetector model further elucidated that these factors vary in their impact: Chl was identified as having the strongest influence (q = 0.84), followed by PIC (q = 0.75) and SST (q = 0.64) as primary influencing factors; PAR was recognized as a secondary factor with q = 0.30. This study provides new insights into marine carbon cycling dynamics within the context of climate change. Full article

(This article belongs to the Section Marine Ecology)

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24 pages, 19789 KiB

Open AccessArticle

Incremental Learning with Dynamic Adaptive Elastic Weight Consolidation for Adaptive, Scalable, and Generalizable User-Defined Behavior Recognition and Analysis of Cetacean and Pinniped Species

by Shih-Pang Tseng, Shen-Hang Chu, Jhing-Fa Wang, Dawei Tao and I-Fan Jen

J. Mar. Sci. Eng. 2025, 13(5), 962; https://doi.org/10.3390/jmse13050962 - 15 May 2025

Abstract

Traditional animal behavior recognition models require extensive labeled datasets and frequent retraining, limiting their adaptability across species and environments. Additionally, existing systems rely on predefined behavior categories, making it difficult for researchers to customize recognition models to specific behavioral patterns relevant to their [...] Read more.

Traditional animal behavior recognition models require extensive labeled datasets and frequent retraining, limiting their adaptability across species and environments. Additionally, existing systems rely on predefined behavior categories, making it difficult for researchers to customize recognition models to specific behavioral patterns relevant to their studies. Different research fields, such as animal welfare monitoring, conservation, and behavioral ecology, often require distinct behavior classifications, yet current systems lack the flexibility to accommodate these varying needs. This study aims to develop an expandable and user-driven animal behavior recognition system utilizing DeepLabCut for pose estimation and a BiLSTM-based classification model. By integrating Dynamic Adaptive Elastic Weight Consolidation (DA-EWC), the system enables incremental learning, allowing new behaviors to be added with minimal annotation while preserving previously learned behaviors. The proposed system is trained on dolphin behavior datasets using DeepLabCut for keypoint extraction and a BiLSTM model for sequence classification. Additionally, a user-friendly interface is implemented to facilitate behavior annotation and efficient model updates. The proposed system achieves 96.5% accuracy in behavior classification, surpassing conventional models such as Faster R-CNN. Compared to standard EWC, DA-EWC maintains an average of 8.3% higher accuracy when incorporating new behaviors. Furthermore, the system reduces annotation efforts by 9.3%, enabling users to expand behavior categories efficiently. This expandable behavior recognition system significantly enhances adaptability and efficiency in animal behavior monitoring. By supporting user-driven incremental learning, it provides a scalable solution for behavior analysis across different research domains, addressing the need for customizable and evolving behavior classification. Full article

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16 pages, 2171 KiB

Open AccessArticle

First Application of a New Rapid Method of Age Determination in European Anchovy (Engraulis encrasicolus) by Fourier Transform Near-Infrared Spectroscopy

by Gualtiero Basilone, Miryam Fortuna, Gabriella Lo Cicero, Simona Genovese, Giovanni Giacalone, Ignazio Fontana, Angelo Bonanno, Salvatore Aronica and Rosalia Ferreri

J. Mar. Sci. Eng. 2025, 13(5), 961; https://doi.org/10.3390/jmse13050961 - 15 May 2025

Abstract

Age determination through reading annual rings in whole otoliths is a complicated, time-consuming task that can lead to errors in population age structure, negatively affecting marine fish management plans. Recently, Fourier transform near-infrared spectroscopy (FT-NIRS) has been successfully used to evaluate annual age, [...] Read more.

Age determination through reading annual rings in whole otoliths is a complicated, time-consuming task that can lead to errors in population age structure, negatively affecting marine fish management plans. Recently, Fourier transform near-infrared spectroscopy (FT-NIRS) has been successfully used to evaluate annual age, at least in several long-life fish species. European anchovy (Engraulis encrasicolus) is an important pelagic species for its ecological role and socioeconomic value. In the Mediterranean Sea, anchovy stocks are regularly monitored for assessment purposes, and fish age is calculated by traditional otolith reading. In the present study, anchovies, caught over a decade (2012 to 2023) during on-board surveys in four different areas (i.e., North Tyrrhenian, South Tyrrhenian, North of Sicily, and Strait of Sicily), provided an otolith collection used to acquire absorption spectra by FT-NIRS. These spectra were processed to optimize calibration models, and the best linear models obtained revealed a good predictability for anchovy annual age (coefficient of determination of 0.90, mean squared error 0.3 years, bias < 0.001 years). The calibration model developed for all regions combined proved more robust than the models for each area, demonstrating its efficacy for the entire study area. FT-NIRS analyses proved suitable for predicting age, when applied to E. encrasicolus individuals within the age range of 0 to 3, also when compared to traditional aging methods. Moreover, this methodology improved the standardization of age estimates. Finally, this preliminary study encourages the further application of FT-NIRS also to short-life pelagic species involved in stock assessment plans. Full article

(This article belongs to the Section Marine Biology)

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26 pages, 3498 KiB

Open AccessArticle

An Adaptive Neural Network Fuzzy Sliding Mode Controller for Tracking Control of Deep-Sea Mining Vehicles

by Shidong Wang, Zida Shan, Jialuan Xiao, Junjun Cao, He Zhang and Nan Sun

J. Mar. Sci. Eng. 2025, 13(5), 960; https://doi.org/10.3390/jmse13050960 - 15 May 2025

Abstract

Traditional track-driven deep-sea nodule mining solutions significantly disrupt seabed ecosystems, making them unsuitable for commercial application. In contrast, ROV-like alternatives, such as the hovering mining vehicle, or HMV, offer substantial improvement in this regard and are deemed to be a viable way forward. [...] Read more.

Traditional track-driven deep-sea nodule mining solutions significantly disrupt seabed ecosystems, making them unsuitable for commercial application. In contrast, ROV-like alternatives, such as the hovering mining vehicle, or HMV, offer substantial improvement in this regard and are deemed to be a viable way forward. This paper proposes an adaptive neural network fuzzy sliding mode controller architecture for the underwater trajectory tracking of HMV. The algorithm, named the Adaptive Radial Basis Function Neural Network Fuzzy Sliding Mode Controller (ARFSMC), replaces modeled vehicle dynamics with a radial basis function neural network (RBFNN). To enhance disturbance rejection, an adaptive mechanism is applied to the RBFNN output weighting matrix. Additionally, a fuzzy inference system (FIS) is implemented as the switching term, replacing the traditional signum function, to reduce high-frequency oscillations in the control signal. The stability of the algorithm under unknown external disturbance was confirmed via Lyapunov stability analysis. To validate the ARFSMC’s performance, three numerical simulation cases were conducted, each designed to reflect an expected operation scenario of the HMV, through which the tracking performance of the ARFSMC under time-varying system inertia is validated and benchmarked against conventional sliding mode control (CSMC) and double-loop sliding mode control (DSMC). The simulation results confirm that comparing the above two controllers, the root mean square error (RMSE) of the ARFSMC is reduced by 15.0% and 11.4%, respectively. And when comparing the CSMC, the chattering is reduced by 97.8%. Both indicate their high robustness and superior performance in tracking control. The controller development and numerical validation in this work are aimed at the trajectory tracking challenge of the HMV in deep-sea mining operation. The dynamical modeling of the vehicle is based on parameters of the HaiMa ROV. External disturbance from currents were considered as sinusoidal functions modified with random noise. Full article

(This article belongs to the Section Ocean Engineering)

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24 pages, 7039 KiB

Open AccessArticle

Performance Study of Spark-Ignited Methanol–Hydrogen Engine by Using a Fractal Turbulent Combustion Model Coupled with Chemical Reaction Kinetics

by Yingting Zhang, Yu Ding, Xiaohui Ren and La Xiang

J. Mar. Sci. Eng. 2025, 13(5), 959; https://doi.org/10.3390/jmse13050959 - 15 May 2025

Abstract

Methanol, a renewable and sustainable fuel, provides an effective strategy for reducing greenhouse gas emissions when synthesized through carbon dioxide hydrogenation integrated with carbon capture technology. The incorporation of hydrogen into methanol-fueled engines enhances combustion efficiency, mitigating challenges such as pronounced cycle-to-cycle variations [...] Read more.

Methanol, a renewable and sustainable fuel, provides an effective strategy for reducing greenhouse gas emissions when synthesized through carbon dioxide hydrogenation integrated with carbon capture technology. The incorporation of hydrogen into methanol-fueled engines enhances combustion efficiency, mitigating challenges such as pronounced cycle-to-cycle variations and cold-start difficulties. A simulation framework was developed using Python 3.13 and the Cantera 3.1.0 library to model the combustion system of a four-stroke spark-ignited (SI) methanol–hydrogen engine. This framework integrates a fractal turbulent combustion model with chemical reaction kinetics, complemented by early flame development and near-wall combustion models to address limitations during the initial and terminal combustion phases. The model was validated by using experimental data measured from a spark-ignited methanol engine. The effects of varying Hydrogen Energy Rates (HER) on engine power performance, combustion characteristics, and emissions (like formaldehyde and carbon monoxide) were subsequently analyzed under different operating loads, whilst the knock limit boundaries were established for different operational conditions. Findings demonstrate that increasing HER improves the engine power output and thermal efficiency, shortens the combustion duration, and reduces the formaldehyde and carbon monoxide emissions. Nevertheless, under high-load conditions, higher HER increases the knocking tendency, which constrains the maximum permissible HER decreasing from approximately 40% at 15% load to 20% at 100% load. The model has been developed into a Python library and will be open-sourced on Github. Full article

(This article belongs to the Special Issue Developments in Zero-Carbon Fuels for Smart, Safe, and Reliable Waterborne Applications)

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20 pages, 6633 KiB

Open AccessArticle

A Water Body Boundary Search Method Combining Chemotaxis Mechanism and High-Resolution Grid Based on Unmanned Surface Vehicles

by Jiao Deng, Yang Long, Jiming Zhang, Hang Gao and Song Liu

J. Mar. Sci. Eng. 2025, 13(5), 958; https://doi.org/10.3390/jmse13050958 - 15 May 2025

Abstract

To address the issues of poor environmental adaptability and high costs associated with traditional methods of measuring water body boundaries, this paper proposes an innovative path planning approach for water body boundary measurement based on Unmanned Surface Vehicles (USVs)—the Chemotactic Search Traversal (CST) [...] Read more.

To address the issues of poor environmental adaptability and high costs associated with traditional methods of measuring water body boundaries, this paper proposes an innovative path planning approach for water body boundary measurement based on Unmanned Surface Vehicles (USVs)—the Chemotactic Search Traversal (CST) algorithm. This method incorporates the chemotaxis operation mechanism of the Bacterial Foraging Optimization algorithm, integrating it with high-resolution grid maps to enable efficient traversal and accurate measurement of water body boundaries within large-scale grid environments. Simulation experiments demonstrate that the CST algorithm outperforms the Brute Force Algorithm (BFA), Roberts operator, Canny operator, Log operator, Prewitt operator, and Sobel operator in terms of optimal pathfinding, stability, and path smoothness. The feasibility and reliability of this algorithm in real water environments are validated through experiments conducted with actual USVs. These findings suggest that the CST algorithm not only enhances the accuracy and efficiency of water body boundary measurement but also offers a cost-effective and practical solution for measuring water body areas. Full article

(This article belongs to the Section Ocean Engineering)

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19 pages, 6096 KiB

Open AccessArticle

Experimental Investigation on Water-Exit Dynamics of Slender Cylinders: Effects of Velocity, Geometry, and Material Properties

by Hualin Zheng, Hongfu Qiang, Yujie Zhu, Dudou Wang, Yuxiang Liu and Xiafei Guan

J. Mar. Sci. Eng. 2025, 13(5), 957; https://doi.org/10.3390/jmse13050957 - 15 May 2025

Abstract

This work studies the water-exit problems of slender cylinders under various conditions through experimental investigation. An experimental platform was equipped with high-speed photography. A total of 13 experimental cases with varying head shapes (conical, spherical, and truncated cone designs), length-to-diameter ratios (5:1–7:1), ejection [...] Read more.

This work studies the water-exit problems of slender cylinders under various conditions through experimental investigation. An experimental platform was equipped with high-speed photography. A total of 13 experimental cases with varying head shapes (conical, spherical, and truncated cone designs), length-to-diameter ratios (5:1–7:1), ejection velocities (7.24–17.93 m/s), and elastic moduli (227.36–279.14 MPa) were conducted to capture water-exit characteristics. The investigation identified ejection velocity as the predominant parameter governing cavity morphology and stability, with higher velocities correlating to increased cavity dimensions and reduced drag coefficients by 54%. Conical head shape resulted in superior drag reduction characteristics, forming a typical cigar-shaped cavity with clear and regular boundaries. Additionally, an increased length-to-diameter ratio substantially improved drag reduction performance by 33%. Material elastic moduli proved crucial for water-exit stability, as cylinders with lower moduli experienced severe bending deformation and even trajectory changes, while higher moduli cylinders maintained their form with minimal deformation. This study illuminates the physical mechanisms of slender body water-exit under multi-factor coupling conditions, providing experimental evidence and theoretical guidance for cross-media vehicle design and underwater equipment optimization. Full article

(This article belongs to the Special Issue Advanced Studies in Marine Mechanical and Naval Engineering)

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21 pages, 2435 KiB

Open AccessArticle

DC-WUnet: An Underwater Ranging Signal Enhancement Network Optimized with Depthwise Separable Convolution and Conformer

by Xiaosen Liu, Juan Li, Jingyao Zhang, Yajie Bai and Zhaowei Cui

J. Mar. Sci. Eng. 2025, 13(5), 956; https://doi.org/10.3390/jmse13050956 - 14 May 2025

Viewed by 110

Abstract

Marine ship-radiated noise and multipath Doppler effect reduce the positioning accuracy of linear frequency modulation (LFM) signals in ocean waveguide environments. However, the assumption of Gaussian noise underlying most time–frequency domain algorithms limits their effectiveness in mitigating non-Gaussian interference. To address this issue, [...] Read more.

Marine ship-radiated noise and multipath Doppler effect reduce the positioning accuracy of linear frequency modulation (LFM) signals in ocean waveguide environments. However, the assumption of Gaussian noise underlying most time–frequency domain algorithms limits their effectiveness in mitigating non-Gaussian interference. To address this issue, we propose a Deep-separable Conformer Wave-Unet (DC-WUnet)-based underwater acoustic signal enhancement network designed to reconstruct signals from interference and noise. The encoder incorporates the Conformer module and skip connections to enhance the network’s multiscale feature extraction capability. Meanwhile, the network introduces depthwise separable convolution to reduce the number of parameters and improve computational efficiency. The decoder applies a slope-based linear interpolation method for upsampling to avoid introducing high-frequency noise during decoding. Additionally, the loss function employs joint time–frequency domain constraints to prevent signal loss and compression, particularly under low Signal-to-Noise Ratio (SNR) conditions. Experimental evaluations under an SNR of −10 dB indicate that the proposed method achieves at least a 32% improvement in delay estimation accuracy and a 2.3 dB enhancement in output SNR relative to state-of-the-art baseline algorithms. Consistent performance advantages are also observed under varying SNR conditions, thereby validating the effectiveness of the proposed approach in shipborne noisy environments. Full article

(This article belongs to the Section Ocean Engineering)

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22 pages, 29320 KiB

Open AccessArticle

Synergistic Effects of Ocean Background and Tropical Cyclone Characteristics on Tropical Cyclone-Induced Sea Surface Cooling in the Western North Pacific

by Rao Rao, Chengcheng Yu, Peng Bai and Bo Li

J. Mar. Sci. Eng. 2025, 13(5), 955; https://doi.org/10.3390/jmse13050955 - 14 May 2025

Viewed by 74

Abstract

Tropical cyclones (TCs) induce intense mixing in the upper ocean, which significantly impacts sea surface temperature (SST) and marine environment. Previous studies have shown that TCs can cause a decrease in sea surface temperature (DSST), while further research is required to elucidate the [...] Read more.

Tropical cyclones (TCs) induce intense mixing in the upper ocean, which significantly impacts sea surface temperature (SST) and marine environment. Previous studies have shown that TCs can cause a decrease in sea surface temperature (DSST), while further research is required to elucidate the factors influencing SST changes. This study employs satellite observations and reanalysis data from the western North Pacific during 2002–2020 to investigate the relationship between DSST and the ocean background state (BG). In addition, by incorporating TC characteristics, we construct indices to explore the synergistic effects of TCs and BG on DSST, enabling a more comprehensive understanding of the mechanisms governing DSST variability. The results indicate that DSST exhibits significant monthly variations, with the maximum DSST in September for coastal regions and in August for offshore regions. Regardless of TC characteristics, when the mixed layer depth (MLD) exceeds 60 m or thermocline depth (TD) exceeds 115 m, it is difficult for the DSST to exceed 1 °C. In both coastal and offshore regions, MLD and TD exhibit moderate negative correlations with DSST, with values around −0.3. When TC characteristics are incorporated, these correlations rise to approximately 0.6, highlighting the importance of jointly considering BG and TC effects in characterizing DSST. The findings of this study provide theoretical support for improving the capability to predict DSST changes before the TC approaches the coast. Full article

(This article belongs to the Special Issue Air-Sea Interaction and Marine Dynamics)

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28 pages, 3564 KiB

Open AccessArticle

CIDNet: A Maritime Ship Detection Model Based on ISAR Remote Sensing

by Fei Liu, Boyang Liu, Hang Zhou, Song Han, Kunlin Zou, Wenjie Lv and Chang Liu

J. Mar. Sci. Eng. 2025, 13(5), 954; https://doi.org/10.3390/jmse13050954 - 14 May 2025

Viewed by 68

Abstract

Inverse synthetic aperture radar (ISAR) ship target detection is of great significance and has broad application prospects in scenarios such as protecting marine resources and maintaining maritime order. Existing ship target detection techniques, especially target detection methods and detection models in complex settings, [...] Read more.

Inverse synthetic aperture radar (ISAR) ship target detection is of great significance and has broad application prospects in scenarios such as protecting marine resources and maintaining maritime order. Existing ship target detection techniques, especially target detection methods and detection models in complex settings, have problems such as long inference time and unstable robustness, meaning that they can easily miss the best time for detecting ship targets and cause intelligence loss. To solve these problems, this study proposes a new ISAR target detection model for ships based on deep learning—Complex ISAR Detection Net (CIDNet). The model is based on the Boundary Box Efficient Transformer (BETR) architecture, which combines super-resolution preprocessing, a deep feature extraction network, a feature fusion technique, and a coordinate maintenance mechanism to improve the detection accuracy and real-time performance of ship targets in complex settings. The CIDNet improves the resolution of the input image via the super-resolution preprocessing technique, which enhances the rendering of details of ship targets in the image. The feature extraction part of the model combines the efficient feature extraction capability of YOLOv10 with the global attention mechanism of BETR. It efficiently combines information from different scales and levels through a feature fusion strategy. In addition, the model integrates a coordinated attention mechanism to enhance the focus on the target region and optimize the detection accuracy. The experimental results show that CIDNet exhibits stable performance on the test dataset. Compared with existing models such as YOLOv10 and Faster R-CNN, CIDNet improves precision, recall, and the F1 score, especially when dealing with smaller targets and complex background conditions. In addition, CIDNet achieves a detection frame rate of 63, demonstrating its fine real-time processing capabilities. Full article

(This article belongs to the Special Issue Remote Sensing for Maritime Monitoring and Ship Surveillance)

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16 pages, 7784 KiB

Open AccessArticle

Analysis of Sandbar–Trough Bed Level Changes Under Regular Wave Conditions—A Case Study of Ten-Mile Silver Beach, Hailing Island, China

by Xiaodong Bian, Zhiqiang Li, Yan Sun, Daoheng Zhu, Tao Chen and Chunhua Zeng

J. Mar. Sci. Eng. 2025, 13(5), 953; https://doi.org/10.3390/jmse13050953 - 14 May 2025

Viewed by 136

Abstract

Understanding the evolution of the sandbar–trough system under regular wave conditions is essential for revealing the dynamic responses of coastal morphology in non-extreme environments and provides a scientific basis for long-term beach stability assessments and coastal erosion management. This study conducted a three-day [...] Read more.

Understanding the evolution of the sandbar–trough system under regular wave conditions is essential for revealing the dynamic responses of coastal morphology in non-extreme environments and provides a scientific basis for long-term beach stability assessments and coastal erosion management. This study conducted a three-day field observation on Ten-Mile Silver Beach, Hailing Island, China, to investigate the coupling relationships between hydrodynamic factors and bed elevation changes during the morphological evolution of the sandbar–trough system. The results indicate that gravity wave (>0.04 Hz) energy is a key driver of bed elevation changes. During the erosion phase, gravity wave energy increases, and the peak wave energy frequency shifts toward lower frequencies, accompanied by a contraction of low-frequency energy and an expansion of high-frequency energy. In contrast, the accretion phase exhibits the opposite pattern. As the sandbar–trough system developed, the explanatory power of hydrodynamic factors on bed elevation decreased by 41% in the trough region and increased by 3.7% in the sandbar region, indicating a spatially differentiated pattern characterized by weakened forcing in the trough and enhanced response over the sandbar. During the geomorphic adjustment process, the trough area exhibited increased sensitivity, with gravity wave energy, near-infragravity wave (0.01–0.04 Hz) energy, far-infragravity wave (0.004–0.01 Hz) energy, mean wave height, and significant wave steepness reversing their influence directions on bed elevation. In contrast, the sandbar area maintained a more stable hydrodynamic control mechanism, with only the influence pattern of significant wave steepness undergoing a shift. This study enhances the understanding of geomorphology–hydrodynamics coupling within nearshore sandbar–trough systems and provides theoretical insights and technical support for monitoring and evaluating coastal erosion and accretion processes under normal wave conditions. Full article

(This article belongs to the Special Issue Morphological Changes in the Coastal Ocean)

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27 pages, 11465 KiB

Open AccessArticle

Scenario-Based Economic Analysis of Underwater Biofouling Using Artificial Intelligence

by Min-Ho Park, Jae-Jung Hur, Gwi-Ho Yun and Won-Ju Lee

J. Mar. Sci. Eng. 2025, 13(5), 952; https://doi.org/10.3390/jmse13050952 - 14 May 2025

Viewed by 132

Abstract

This study presents a novel framework to evaluate the impact of a certain cycle of underwater hull and propeller cleaning. The artificial neural network model was created to predict fuel consumption, and the coefficients for the six voyages were calculated. Three scenarios, in [...] Read more.

This study presents a novel framework to evaluate the impact of a certain cycle of underwater hull and propeller cleaning. The artificial neural network model was created to predict fuel consumption, and the coefficients for the six voyages were calculated. Three scenarios, in which the coefficients changed in different ways, were established, and the monthly fuel consumption values were calculated accordingly. The annual fuel cost saving when the cycle of underwater hull and propeller cleaning was four months was USD 10,402–26,685, and it was USD 9653–24,102 for a cycle of six months. We confirmed that using the novel framework we presented, the optimal hull cleaning timing could be determined for oceangoing vessels worldwide, considering economic impact based on data and machine learning models. Full article

(This article belongs to the Section Ocean Engineering)

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3 pages, 149 KiB

Open AccessEditorial

Advanced Research in Shipping Informatics and Communications

by Nikitas Nikitakos and Iosif Progoulakis

J. Mar. Sci. Eng. 2025, 13(5), 951; https://doi.org/10.3390/jmse13050951 - 14 May 2025

Viewed by 78

Abstract

The shipping industry, a vital part of global trade and the maritime transport system (MTS) and a critical infrastructure for all nations, is undergoing a technological evolution through the integration of advanced information and communication technologies [...] Full article

(This article belongs to the Special Issue Advanced Research in Shipping Informatics and Communications)

12 pages, 4494 KiB

Open AccessArticle

Visualization of Coastal Carbonate Lithosomes: Color-Intensity Patterns and Georadar Imaging of a Semi-Lithified Strandplain, Eleuthera Island, The Bahamas

by Ilya V. Buynevich, Michael Savarese and H. Allen Curran

J. Mar. Sci. Eng. 2025, 13(5), 950; https://doi.org/10.3390/jmse13050950 - 14 May 2025

Viewed by 141

Abstract

Quaternary carbonate strandplains serve as archives of land–sea interaction, including the impacts of storms and tsunamis. Incipient lithification, especially of compound beach/dune ridges within the action zone of salt spray, presents challenges to geological research, which is often limited to exposures. This study [...] Read more.

Quaternary carbonate strandplains serve as archives of land–sea interaction, including the impacts of storms and tsunamis. Incipient lithification, especially of compound beach/dune ridges within the action zone of salt spray, presents challenges to geological research, which is often limited to exposures. This study combines aerial image analysis with geophysical datasets to assess the morphostratigraphy and internal structure of the Freedom Beach Strandplain along southern Eleuthera Island, The Bahamas. Color-intensity analysis of field photographs and satellite images revealed general patterns that can be used to distinguish between areas with different grayscale parameters (sand-covered surfaces, lithified ridges, vegetation, etc.). Cross-shore (dip-section) high-resolution (800 MHz) georadar images across ten ridges (A-J) documented the internal architecture of swash-aligned ridge–swale sets. Signatures attributed to storms include truncations in shore-normal radargrams, scour features in alongshore (strike-section) images, and an extensive accumulation of large mollusk shells along one of the oldest ridges (ridge J). Preliminary radiocarbon dating yielded ages of up to 600 years, suggesting intense storms with 50–60-year periodicity as a possible mechanism for ridge formation. Full article

(This article belongs to the Special Issue Learning from Geomorphological Adaptation of Coasts at Different Time Scales (2nd Edition))

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15 pages, 3232 KiB

Open AccessArticle

Effect of Methanol Injection Timing on Performance of Marine Diesel Engines and Emission Reduction

by Hao Guo, Veysi Başhan, Cairui Yu, Firat Bolat, Hakan Demirel and Xin Tian

J. Mar. Sci. Eng. 2025, 13(5), 949; https://doi.org/10.3390/jmse13050949 - 13 May 2025

Viewed by 167

Abstract

Methanol is a promising low-carbon fuel that can effectively reduce environmental pollution from ships compared to traditional fuels. The timing of methanol injection is a major factor affecting the performance of internal combustion engines, and either too late or too early injection can [...] Read more.

Methanol is a promising low-carbon fuel that can effectively reduce environmental pollution from ships compared to traditional fuels. The timing of methanol injection is a major factor affecting the performance of internal combustion engines, and either too late or too early injection can severely impact the combustion efficiency of an engine. This paper focused on a 4135Aca marine diesel engine produced by the Shanghai Diesel Engine Factory in China. Using CONVERGE/3.0 software for numerical simulation, the study analyzed the impact of methanol injection timing on the combustion and emission characteristics of marine diesel engines. It was found that the determination of methanol injection timing should comprehensively consider the effects of the combustion start point, mixture quality, flame front propagation speed, and evaporation heat absorption. Appropriate methanol injection timing can improve the combustion duration, cylinder pressure, and heat release rate, enhancing the power performance of marine diesel engines. This study shows that methanol injection at −30 °CA can effectively control the in-cylinder combustion process, improve combustion efficiency, and significantly reduce the emissions of pollutants such as soot (by 60.5%), HC (by 3.6%), CO (by 95.3%), etc. However, it can lead to an increase in NOx (by 3.7%) generation under high-temperature conditions. This research can provide a certain reference for the engineering application of methanol direct injection engines for ships. Full article

(This article belongs to the Special Issue Advancing Marine Sustainability: Alternative Fuels and Decarbonizing Technologies for a Low-Carbon Future)

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23 pages, 9390 KiB

Open AccessArticle

Reservoir Characterization Based on Bayesian Amplitude Versus Offset Inversion of Marine Seismic Data

by Jianhua Wang, Xinpeng Pan, Wenbo Sun, Chao Li, Ying Zheng and Xiaolong Zhao

J. Mar. Sci. Eng. 2025, 13(5), 948; https://doi.org/10.3390/jmse13050948 - 13 May 2025

Viewed by 101

Abstract

Young’s modulus and Poisson’s ratio are critical parameters for reservoir characterization using marine seismic data. Conventional amplitude versus offset (AVO) inversion methods often assume a constant S-to-P wave velocity ratio to simplify the inversion, leading to significant errors, particularly in heterogeneous reservoirs. To [...] Read more.

Young’s modulus and Poisson’s ratio are critical parameters for reservoir characterization using marine seismic data. Conventional amplitude versus offset (AVO) inversion methods often assume a constant S-to-P wave velocity ratio to simplify the inversion, leading to significant errors, particularly in heterogeneous reservoirs. To address this, we derive a novel four-term PP-wave reflection coefficient by reparameterizing Poisson’s ratio, effectively reducing the nonlinearity associated with the velocity ratio and enhancing the stability of Poisson’s ratio estimation. Building on this, we propose a Bayesian AVO inversion framework incorporating Cauchy prior and low-frequency model regularizations. The elastic parameters are estimated using a maximum a posteriori (MAP) approach by minimizing the negative log-posterior function. Numerical simulations and seismic gather data from East China demonstrate that the proposed inversion method yields more accurate estimates of Young’s modulus and Poisson’s ratio compared to conventional approaches. This improved AVO approximation offers a more reliable tool for delineating reservoir heterogeneity in complex geological settings using marine seismic data. Full article

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

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22 pages, 7493 KiB

Open AccessArticle

YOLO-DAFS: A Composite-Enhanced Underwater Object Detection Algorithm

by Shengfu Luo, Chao Dong, Guixin Dong, Rongmin Chen, Bing Zheng, Ming Xiang, Peng Zhang and Zhanwei Li

J. Mar. Sci. Eng. 2025, 13(5), 947; https://doi.org/10.3390/jmse13050947 - 13 May 2025

Viewed by 182

Abstract

In computer vision applications, the primary task of object detection is to answer the following question: “What object is present and where is it located?”. However, underwater environments introduce challenges, such as poor lighting, high complexity, and diverse marine organism shapes, leading to [...] Read more.

In computer vision applications, the primary task of object detection is to answer the following question: “What object is present and where is it located?”. However, underwater environments introduce challenges, such as poor lighting, high complexity, and diverse marine organism shapes, leading to missed detections or false positives in deep learning-based algorithms. To improve detection accuracy and robustness, this paper proposes an enhanced YOLOv11-based algorithm for underwater object detection that strengthens the ability to capture both local and global details and global contextual information in complex underwater environments. To better capture local and global features while integrating contextual information, the proposed method introduces several enhancements. The backbone incorporates a DualBottleneck module to enhance feature extraction, replacing the standard bottleneck structure in C3k, thus enhancing the feature extraction and the channel aggregation. The detection head adopts DyHead-GDC, integrating ghost depthwise separable convolution with DyHead for greater efficiency. Furthermore, the ADown module replaces conventional feature extraction and downsampling convolutions, reducing parameters and FLOPs by 14%. The C2PSF module, combining focal modulation and C2, strengthens local feature extraction and global context processing. Additionally, a SCSA module is inserted before the detection head to fully utilize multi-semantic information, improving the detection performance in complex underwater scenes. Experimental results confirm the effectiveness of these improvements. The model achieves 84.2% mAP50 on UTDAC2020, 84.4% on DUO and 86.7% on RUOD, surpassing the baseline by 2.5%, 1.6% and 1.2%, respectively. It remains lightweight, with 6.5 M parameters and a computational cost of 7.1 GFLOPs. Full article

(This article belongs to the Section Ocean Engineering)

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18 pages, 7358 KiB

Open AccessArticle

Multiscale Structural Patterns of Intertidal Salt Marsh Vegetation in Estuarine Wetlands and Its Interactions with Tidal Creeks

by Jianfang Hu, Jiapan Yan, Zhenbang Bian, Zhaoning Gong and Duowen Zhu

J. Mar. Sci. Eng. 2025, 13(5), 946; https://doi.org/10.3390/jmse13050946 - 13 May 2025

Viewed by 147

Abstract

The intertidal zones of estuarine wetlands serve as critical components in maintaining and promoting the sustainable development of regional ecosystems. Salt marsh vegetation, a crucial element of these zones, is experiencing significant deterioration across multiple scales due to various stressors. Despite considerable attention [...] Read more.

The intertidal zones of estuarine wetlands serve as critical components in maintaining and promoting the sustainable development of regional ecosystems. Salt marsh vegetation, a crucial element of these zones, is experiencing significant deterioration across multiple scales due to various stressors. Despite considerable attention given to the spatial patterns and temporal evolution of salt marsh vegetation, few studies have quantitatively assessed its dynamic interactions with tidal creeks. Tidal creeks serve as primary conduits for material, energy, and information exchange between intertidal zones and adjacent ecosystems. There is a complex feedback mechanism between the development of the tidal creeks and vegetation communities. We investigated the distribution patterns and successional characteristics of salt marsh vegetation at both landscape and pixel scales, with particular emphasis on coupling dynamics with tidal creeks. Our results revealed a distinct spatial gradient in vegetation distribution across the study area. While the invasion of S. alterniflora exhibited limited direct competitive effects on S. salsa, it demonstrated significant influence on tidal creek geomorphological evolution. Notably, S. salsa exhibited pronounced sensitivity to hydrological conditions, with its growth being substantially constrained by tidal creek development and associated soil modifications. Full article

(This article belongs to the Special Issue Coastal Wetland Management, Restoration and Conservation)

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20 pages, 2727 KiB

Open AccessSystematic Review

Maritime Pilotage and Sustainable Seaport: A Systematic Review

by Seyed Behbood Issa-Zadeh and Claudia Lizette Garay-Rondero

J. Mar. Sci. Eng. 2025, 13(5), 945; https://doi.org/10.3390/jmse13050945 - 13 May 2025

Viewed by 165

Abstract

The long-term sustainability of seaports depends on various operational factors, including infrastructure efficiency, digital innovation, environmental management, and regulatory compliance, among which maritime pilotage plays a crucial role in ensuring safe navigation and minimizing environmental, economic, and social risks. This research employed the [...] Read more.

The long-term sustainability of seaports depends on various operational factors, including infrastructure efficiency, digital innovation, environmental management, and regulatory compliance, among which maritime pilotage plays a crucial role in ensuring safe navigation and minimizing environmental, economic, and social risks. This research employed the PRISMA-ScR framework to evaluate the environmental, economic, and social impacts of pilotage on the sustainability of seaports. The findings demonstrate efficient navigation and spill avoidance, which reduce emissions, safeguard marine biodiversity, and maintain water quality. Economically, it reduces delays, optimizes operational expenses, and increases port competitiveness by increasing maritime traffic. Moreover, pilotage improves navigational safety, local professional skill development, and community interactions via ecological conservation and operational efficiency. It also indicates how environmental initiatives benefit the economy, increase port competitiveness, and promote job security and community happiness. The results also emphasize the significance of pilotage in sustainable seaport operations by quantifying pollution reductions, cost savings, and safety. The result also suggests that successful pilotage enhances ports’ viability and responsibility in global shipping networks while addressing environmental, economic, and social concerns. Full article

(This article belongs to the Section Ocean Engineering)

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J. Mar. Sci. Eng., Volume 13, Issue 5 (May 2025) – 150 articles

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