Journal of Marine Science and Engineering

20 pages, 24645 KiB

Open AccessArticle

A Study on the Long-Term Tensile Strength Properties of the Geotextile Tubes

by Myoung-Soo Won, Hyeon Jung Kim, Shamsher Sadiq and Ji-Hwi Gwak

J. Mar. Sci. Eng. 2025, 13(5), 985; https://doi.org/10.3390/jmse13050985 (registering DOI) - 20 May 2025

This study examines the tensile behavior of both plain and seamed geotextiles. Samples were taken from two geotextile tube test beds, one made of composite materials and the other of woven materials, constructed in 2013 and 2016, respectively, in the Saemangeum reclaimed area. [...] Read more.

This study examines the tensile behavior of both plain and seamed geotextiles. Samples were taken from two geotextile tube test beds, one made of composite materials and the other of woven materials, constructed in 2013 and 2016, respectively, in the Saemangeum reclaimed area. These test tubes have been exposed to marine conditions and sunlight for 10 and 8 years, respectively. Based on sunlight exposure, samples of plain and seamed geotextiles were collected from both exposed (top) and non-exposed (bottom) locations. The tensile strength–strain curves, strength degradation, and seam efficiencies of the original samples were compared with those exposed to marine environments and sunlight for 8–10 years. Geotextile tubes have been found to function normally even after being exposed to seawater and sunlight for 8–10 years, with sunlight being identified as the most significant factor affecting long-term tensile strength. The influence of seawater on tensile behavior is minimal, and it was observed that the tensile strength of the seam after 8–10 years is only about 10–19% of the initial plain tensile strength. Nevertheless, the tubes operate without failure, suggesting that the earth pressure acting on stabilized geotextile tubes is relatively low. These findings offer valuable insight into the long-term durability of geotextiles tubes under harsh environmental conditions and serve as a reference for future applications. Full article

(This article belongs to the Section Coastal Engineering)

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11 pages, 2543 KiB

Open AccessArticle

Investigation and Analysis of Anchor Status of Small Coastal Fishing Vessels for Response to Submarine-Cable Risk Factors

by Tae-Ho Lee and Bong-Kyu Jung

J. Mar. Sci. Eng. 2025, 13(5), 984; https://doi.org/10.3390/jmse13050984 (registering DOI) - 19 May 2025

Abstract

This study investigated the status of anchors for small fishing vessels that correspond with the risk factors of submarine cables, which are essential elements for offshore wind farms. As for target vessels, small coastal fishing vessels of less than ten tons were divided [...] Read more.

This study investigated the status of anchors for small fishing vessels that correspond with the risk factors of submarine cables, which are essential elements for offshore wind farms. As for target vessels, small coastal fishing vessels of less than ten tons were divided into four categories by tonnage, and 71 locations were compared from a total of 59 fishing vessels. In the results, the shank showed a difference of approximately 18.2% from 119.3 to 145.8 cm on average, while the stock exhibited a difference of approximately 18.9% from 130.3 to 160.6 cm. The size of the anchor, however, was not proportional to the increase in the tonnage of the fishing vessel, and the anchors were produced in their own forms, based on the experience of the crew in many cases. In the statistical processing results, significant differences occurred in all areas except for the fluke. The stock and shank, which affect the dragging anchor, showed significant differences at a level of p < 0.05 while the bill, bill to bill, and bill to shank exhibited differences at a level of p < 0.01. This indicates that standardized criteria are required for the anchors of small coastal fishing vessels of less than ten tons, and that design standards for materials and reinforcements also need to be prepared as thin rebars or wooden columns are used, in addition to steel pipes, as the materials of the stock in many cases. Full article

(This article belongs to the Topic Application of Concrete Materials in Coastal Port Engineering)

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29 pages, 5264 KiB

Open AccessArticle

Joint Allocation of Shared Yard Space and Internal Trucks in Sea–Rail Intermodal Container Terminals

by Xiaohan Wang, Zhihong Jin and Jia Luo

J. Mar. Sci. Eng. 2025, 13(5), 983; https://doi.org/10.3390/jmse13050983 (registering DOI) - 19 May 2025

Abstract

The sea–rail intermodal container terminal serves as a key transportation hub for green logistics, where efficient resource coordination directly enhances multimodal connectivity and operational synergy. To address limited storage capacity and trans-shipment inefficiencies, this study innovatively proposes a resource-sharing strategy between the seaport [...] Read more.

The sea–rail intermodal container terminal serves as a key transportation hub for green logistics, where efficient resource coordination directly enhances multimodal connectivity and operational synergy. To address limited storage capacity and trans-shipment inefficiencies, this study innovatively proposes a resource-sharing strategy between the seaport and the railway container terminal, focusing on the joint allocation of yard space and internal trucks. For indirect trans-shipment operations between ships, the port, the railway container terminal, and trains, a mixed-integer programming model is formulated with the objective of minimizing the container trans-shipment cost and the weighted turnaround time of ships and trains. This model simultaneously determines yard allocation, container transfers, and truck allocation. A two-layer hybrid heuristic algorithm incorporating adaptive Particle Swarm Optimization and Greedy Rules is designed. Numerical experiments verify the model and algorithm performance, revealing that the proposed method achieves an optimality gap of only 1.82% compared to CPLEX in small-scale instances while outperforming benchmark algorithms in solution quality. And the shared yard strategy enhances ship and train turnaround efficiency by an average of 33.45% over traditional storage form. Sensitivity analysis considering multiple realistic factors further confirms the robustness and generalizability. This study provides a theoretical foundation for sustainable port–railway collaboration development. Full article

(This article belongs to the Section Ocean Engineering)

16 pages, 3830 KiB

Open AccessArticle

Analysis of Damage to Shipping Container Sides During Port Handling Operations

by Sergej Jakovlev, Tomas Eglynas, Valdas Jankunas, Mindaugas Jusis and Miroslav Voznak

J. Mar. Sci. Eng. 2025, 13(5), 982; https://doi.org/10.3390/jmse13050982 (registering DOI) - 19 May 2025

Abstract

The damage to shipping containers during port handling operations continues to pose a significant challenge that adversely affects operational efficiency, equipment integrity, and supply chain accountability. This study utilises real-world measurement data gathered through accelerometers to examine the occurrence and dynamics of physical [...] Read more.

The damage to shipping containers during port handling operations continues to pose a significant challenge that adversely affects operational efficiency, equipment integrity, and supply chain accountability. This study utilises real-world measurement data gathered through accelerometers to examine the occurrence and dynamics of physical impacts, particularly side and rear collisions, during the handling of containers at Klaipėda City Port. The research prioritises two critical scenarios: side impacts during stacking operations with reach stackers and rear impacts during trailer loading procedures. Impact events are meticulously recorded and analysed to ascertain the magnitudes of acceleration across multiple axes. This reveals that side impacts produce significantly greater forces, particularly in the lateral direction, than rear impacts. This study employs sensor-based monitoring, advanced data visualisation techniques, and structured scenario analysis to delineate the variability and intensity of mechanical interactions during these operations. The findings emphasise the structural stress that containers experience and underscore the importance of embedded monitoring technologies for real-time event detection and damage prevention. The results contribute to the expanding body of knowledge that supports the digital transformation of container terminals and furnish actionable insights for enhancing handling protocols, informing insurance assessments, and improving safety measures within both automated and conventional port environments. Full article

(This article belongs to the Special Issue Maritime Transport and Port Management)

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19 pages, 4031 KiB

Open AccessArticle

The Prediction of the Valve Opening Required for Slugging Control in Offshore Pipeline Risers Based on Empirical Closures and Valve Characteristics

by Jiqiang Fu, Quanhong Wu, Jie Sun, Hanxuan Wang and Suifeng Zou

J. Mar. Sci. Eng. 2025, 13(5), 981; https://doi.org/10.3390/jmse13050981 (registering DOI) - 19 May 2025

Abstract

Topside choking is a common way to eliminate severe slugging flow in pipeline riser systems in offshore oil and gas fields. However, a lack of fundamentals in two-phase flow gives rise to difficulty in the model selection of valves and the effective control [...] Read more.

Topside choking is a common way to eliminate severe slugging flow in pipeline riser systems in offshore oil and gas fields. However, a lack of fundamentals in two-phase flow gives rise to difficulty in the model selection of valves and the effective control of the valves. In this study, the prediction of the valve opening required for slugging control based on measurable parameters is investigated experimentally and theoretically. It is found that the resistance coefficient factor of the valve is almost the same for pipeline risers and simple vertical pipes when severe slugging is eliminated. Therefore, fluid parameters can be approximated by the conditions of a simple vertical pipe. The target of control is to achieve dual-frequency fluctuation, and it is quantitatively converted to the pressure drop of the valve. Based on these two empirical enclosures, the valve opening can be worked out by using the gas fraction model and the theoretical model of valve flow resistance. The non-slip model is found to be better than the drift-flux model in the final prediction of the optimal valve opening. An explicit model for the calculation of the optimal resistance factor and the corresponding valve opening is established, making it more convenient to select the valve in the design stage of offshore oil and gas exploitation. The average absolute error of the proposed model is +0.01%, which is smaller than the simulation performed by OLGA 7.0 software (+4.91% before tuning and +0.08% after tuning). A field case with a flexible S-shape riser proves the good applicability of the model (with a deviation smaller than ±2%). The applications of the prediction model in the model selection of the valve and uncertain factors in the operation are also discussed. Full article

(This article belongs to the Special Issue Advanced Research in Flexible Riser and Pipelines)

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30 pages, 20750 KiB

Open AccessArticle

A Proposal for Alternative Navigation Routes Following the Development of Offshore Wind Farms in the Waters of the Republic of Korea

by Sung-Wook Ohn and Ho Namgung

J. Mar. Sci. Eng. 2025, 13(5), 980; https://doi.org/10.3390/jmse13050980 (registering DOI) - 19 May 2025

Abstract

In the future, electricity generation through eco-friendly renewable energy will accelerate. Surrounded by sea on three sides, the Republic of Korea is gaining attention for offshore wind power as a future industry, leveraging advantages of its maritime environment. However, maritime navigation remains active [...] Read more.

In the future, electricity generation through eco-friendly renewable energy will accelerate. Surrounded by sea on three sides, the Republic of Korea is gaining attention for offshore wind power as a future industry, leveraging advantages of its maritime environment. However, maritime navigation remains active in waters, with maritime transportation being crucial, as it accounts for over 95% of the country’s cargo volume. Therefore, ensuring the safety of vessel operations is vital when constructing offshore wind farms. This study proposed alternative routes to ensure the safety of vessels and secure existing routes in the waters of the southwestern sea, where intensive development of OWFs is expected. The routes were determined based on the Permanent International Association of Navigation Congresses (PIANC) Guidelines and Maritime Traffic Safety Act’s implementation guidelines. Clearance between a maritime route and OWF was set to the rule of 6 L + 0.3 NM + 500 m for safety. The route width was calculated while considering vessel maneuverability, environmental factors, seabed conditions, the depth-to-draft ratio, and two-way traffic. The alternative routes were categorized into four types—maritime highways, maritime provincial routes, approach routes for departure/arrival, and recommended routes based on vessel positions, engine status, and route function. By considering traffic flow and applying international and domestic standards, these routes will ensure safe, efficient, and orderly vessel operations. Full article

(This article belongs to the Special Issue Maritime Traffic Engineering)

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26 pages, 2141 KiB

Open AccessReview

Intelligent Maritime Shipping: A Bibliometric Analysis of Internet Technologies and Automated Port Infrastructure Applications

by Yangqiong Zou, Guangnian Xiao, Qingjun Li and Salvatore Antonio Biancardo

J. Mar. Sci. Eng. 2025, 13(5), 979; https://doi.org/10.3390/jmse13050979 (registering DOI) - 19 May 2025

Abstract

Amid the dual imperatives of global trade expansion and low-carbon transition, intelligent maritime shipping has emerged as a central driver for the innovation of international logistics systems, now entering a critical window period for the deep integration of Internet technologies and automated port [...] Read more.

Amid the dual imperatives of global trade expansion and low-carbon transition, intelligent maritime shipping has emerged as a central driver for the innovation of international logistics systems, now entering a critical window period for the deep integration of Internet technologies and automated port infrastructure. While existing research predominantly focuses on isolated applications of intelligent technologies, systematic evaluations of the synergistic effects of technological integration on maritime ecosystems, policy compatibility, and contributions to global carbon emission governance remain under-explored. Leveraging bibliometric analysis, this study systematically examines 488 publications from the Web of Science (WoS) Core Collection (2000–2024), yielding three pivotal findings: firstly, China dominates the research landscape, with a 38.5% contribution share, where Artificial Intelligence (AI), the Internet of Things (IoT), and port automation constitute the technological pillars. However, critical gaps persist in cross-system protocol standardization and climate-adaptive modeling, accounting for only 2.7% and 4.2% of the literature, respectively. Secondly, international collaboration networks exhibit pronounced “Islamization”, characterized by an inter-team collaboration rate of 17.3%, while the misalignment between rapid technological iteration and existing maritime regulations exacerbates industry risks. Thirdly, a dual-track pathway integrating Cyber–Physical System (CPS)-based digital twin ports and open-source vertical domain-specific large language models is proposed. Empirical evidence demonstrates its efficacy in reducing cargo-handling energy consumption by 15% and decision-making latency by 40%. This research proposes a novel tripartite framework, encompassing technological, institutional, and data sovereignty dimensions, to resolve critical challenges in integrating multi-source maritime data and managing cross-border governance. The model provides academically validated and industry-compatible strategies for advancing sustainable maritime intelligence. Subsequent investigations should expand data sources to include regional repositories and integrate interdisciplinary approaches, ensuring the adaptability of both technical systems and international policy coordination mechanisms across diverse maritime ecosystems. Full article

(This article belongs to the Section Ocean Engineering)

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15 pages, 1888 KiB

Open AccessArticle

Navigating Coastal Vulnerability: Introducing the Coastal Fuzzy Vulnerability Index (CFVI)

by Zekâi Şen

J. Mar. Sci. Eng. 2025, 13(5), 978; https://doi.org/10.3390/jmse13050978 (registering DOI) - 19 May 2025

Abstract

Vulnerability impacts have increased in an unprecedented way with the effects of global warming, climate change, erosion, sea level rise, tsunami, flood, and drought—natural events that jointly cause geomorphological changes, especially in coastal zones. There are no analytical mathematical formulations under a set [...] Read more.

Vulnerability impacts have increased in an unprecedented way with the effects of global warming, climate change, erosion, sea level rise, tsunami, flood, and drought—natural events that jointly cause geomorphological changes, especially in coastal zones. There are no analytical mathematical formulations under a set of assumptions due to the complexity of the interactive associations of these natural events, and the only way that seems open in the literature is through empirical formulations that depend on expert experiences. Among such empirical formulations are the Coastal Vulnerability Index (CVI), the Environmental Vulnerability Index (EVI), the Socioeconomic Vulnerability Index (SVI), and the Integrated Coastal Vulnerability Index (ICVI), which is composed of the previous indices. Although there is basic experience and experimental information for the establishment of these indices, unfortunately, logical aspects are missing. This paper proposes a Coastal Fuzzy Vulnerability Index (CFVI) based on fuzzy logic, aiming to improve the limitations of the traditional Coastal Vulnerability Index (CVI). Traditional CVI relies on binary logic and calculates vulnerability through discrete classification (such as “low”, “medium”, and “high”) and arithmetic or geometric means. It has problems such as mutation risk division, ignoring data continuity, and unreasonable parameter weights. To this end, the author introduced fuzzy logic, quantified the nonlinear effects of various parameters (such as landforms, coastal slope, sea level changes, etc.) through fuzzy sets and membership degrees, and calculated CFVI using a weighted average method. The study showed that CFVI allows continuous transition risk assessment by fuzzifying the parameter data range, avoiding the “mutation” defect of traditional methods. Taking data from the Gulf of Mexico in the United States as an example, the calculation result range of CFVI (0.38–3.04) is significantly smaller than that of traditional CVI (0.42–51), which is closer to the rationality of actual vulnerability changes. The paper also criticized the defects of traditional CVI, being that it relies on subjective experience and lacks a logical basis, and pointed out that CFVI can be expanded to integrate more variables or combined with other indices (such as the Environmental Vulnerability Index (EVI)) to provide a more scientific basis for coastal management decisions. This study optimized the coastal vulnerability assessment method through fuzzy logic, improved the ability to handle nonlinear relationships between parameters, and provided a new tool for complex and dynamic coastal risk management. Further research possibilities are also mentioned throughout the text and in the Conclusion section. Full article

(This article belongs to the Section Coastal Engineering)

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Graphical abstract

43 pages, 4492 KiB

Open AccessArticle

Integrated Approach to Ship Electrification Using Fuel Cells and an Ammonia Decomposition System

by Onur Yuksel, Eduardo Blanco-Davis, David Hitchmough, G Viknash Shagar, Andrew Spiteri, Maria Carmela Di Piazza, Marcello Pucci, Nikolaos Tsoulakos, Milad Armin and Jin Wang

J. Mar. Sci. Eng. 2025, 13(5), 977; https://doi.org/10.3390/jmse13050977 (registering DOI) - 18 May 2025

Abstract

This study investigates the environmental and economic performance of integrating a proton exchange membrane fuel cell, battery systems, and an organic Rankine cycle-based waste heat recovery system for ship electrification. The analysis examines an onboard ammonia decomposition system for hydrogen production and ammonia [...] Read more.

This study investigates the environmental and economic performance of integrating a proton exchange membrane fuel cell, battery systems, and an organic Rankine cycle-based waste heat recovery system for ship electrification. The analysis examines an onboard ammonia decomposition system for hydrogen production and ammonia production pathways. Additionally, the study benchmarks the effectiveness of onboard ammonia decomposition against green hydrogen bunkering scenarios (H₂-BS). The analysis is based on data collected over two years from a bulk carrier provided by Laskaridis Shipping Co., Ltd. The environmental analysis includes well-to-wake emissions calculations. At the same time, economic performance is assessed through levelised cost of energy (LCOE) computations for 2025 and 2040, factoring in different fuel and carbon price scenarios. Consequently, the analysis utilises the Complex Proportional Assessment method to compare configurations featuring various ammonia production pathways across economic cases. The results indicate that green and pink ammonia feedstocks achieve maximum equivalent carbon dioxide reductions in the electrification plant of up to 47.28% and 48.47%, respectively, compared to H₂-BS and 95.56% and 95.66% compared to the base scenario. Ammonia decomposition systems prove more economically viable than H₂-BS due to lower storage and fuel costs, leading to competitive LCOE values that improve under higher carbon pricing scenarios. Full article

(This article belongs to the Special Issue Marine Fuel Cell Technology: Latest Advances and Prospects)

14 pages, 5483 KiB

Open AccessArticle

A Saturation Adaptive Nonlinear Integral Sliding Mode Controller for Ship Permanent Magnet Propulsion Motors

by Xi Wang, Zhaoting Liu, Peng Zhou, Baozhu Jia, Ronghui Li and Yuanyuan Xu

J. Mar. Sci. Eng. 2025, 13(5), 976; https://doi.org/10.3390/jmse13050976 (registering DOI) - 18 May 2025

Abstract

The conventional-speed Sliding Mode Controller (SMC) for ship PM propulsion motors, which employs exponential reaching laws and linear sliding surface functions, demonstrates susceptibility to oscillatory phenomena. To solve this problem, this paper proposes a saturation adaptive nonlinear integral sliding mode controller (SANI-SMC) which [...] Read more.

The conventional-speed Sliding Mode Controller (SMC) for ship PM propulsion motors, which employs exponential reaching laws and linear sliding surface functions, demonstrates susceptibility to oscillatory phenomena. To solve this problem, this paper proposes a saturation adaptive nonlinear integral sliding mode controller (SANI-SMC) which combines a nonlinear integral sliding surface function with an adaptive saturation gain reaching rate. The nonlinear integral sliding surface function improves the system responsiveness, and then enhances the stability and robustness of the system. The adaptive saturation gain reaching rate not only mitigates the chattering effect induced by the sign function in traditional exponential reaching rates, but also weakens the underlying oscillations. This approach effectively solves the overshoot problem inherent in traditional PI controllers, and has better anti-interference ability under sudden load variations. Finally, the proposed controller is experimentally verified based on an electric propulsion semi-physical experimental platform consisting of Rapid Control Prototyping (RCP), and compared with a Proportional–Integral (PI) controller and an SMC. Moreover, the integral absolute error (IAE), integral time-weighted absolute error (ITAE), and integral of the square value (ISV) metrics are calculated for the PI controller, SMC, and SANI-SMC based on experimental data collection. The results demonstrate that the SANI-SMC exhibits superior stability and robustness compared to both the PI controller and SMC. Full article

(This article belongs to the Section Ocean Engineering)

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15 pages, 7154 KiB

Open AccessArticle

Microbial and Functional Gene Dynamics in Long-Term Fermented Mariculture Sediment

by Guochao Zhang, Mengyuan Luo, Cuilian Xu, Xinru Pan, Guoqiang Yi, Wei Xiao, Chenghao Wang, Zhen Zhao and Ruilong Li

J. Mar. Sci. Eng. 2025, 13(5), 975; https://doi.org/10.3390/jmse13050975 (registering DOI) - 18 May 2025

Abstract

The microorganisms of mariculture sediments are key to regulating and maintaining their ecosystem balance and have garnered research interest. Although the microbial composition and functional potential of mariculture sediments have been extensively explored in the past, the effects of long-term aquaculture on microbial [...] Read more.

The microorganisms of mariculture sediments are key to regulating and maintaining their ecosystem balance and have garnered research interest. Although the microbial composition and functional potential of mariculture sediments have been extensively explored in the past, the effects of long-term aquaculture on microbial communities and functional genes have been scarcely studied. Sediment samples from mariculture ponds with durations of 1 year, 6 years, and 10 years were collected in this study. A high-throughput metagenomic analysis was then conducted. The results showed that the sediments fermented for 1 year had the highest α-diversity, creating conditions for the divergence of functional microbial communities. Due to nutrient competition, long-term fermentation led to a decrease in both diversity and functional redundancy. Key functional groups exhibited different temporal succession patterns. In addition, long-term fermentation, especially fermentation over 10 years, resulted in significant differentiation of functional genes, particularly those related to carbon and nitrogen metabolism. This study reveals the distribution pattern of the microbiome during the natural fermentation process and its temporal coupling relationship with the functions of the pond ecosystem. It clarifies the dynamic evolution of functional genes, providing a theoretical basis for the sustainable management of mariculture. Full article

(This article belongs to the Section Marine Aquaculture)

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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

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Abstract

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

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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

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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

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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, 4335 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

Viewed by 23

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

Viewed by 22

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

Viewed by 11

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

Viewed by 22

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

Viewed by 14

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

Viewed by 91

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

Viewed by 133

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

Viewed by 142

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

Viewed by 87

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

Viewed by 69

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

Viewed by 126

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

Viewed by 136

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

Viewed by 132

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

Viewed by 133

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 183

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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