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Volume 12
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J. Mar. Sci. Eng., Volume 12, Issue 7 (July 2024) – 203 articles

Cover Story (view full-size image): It is widely acknowledged that pharmaceuticals present a significant threat to aquatic marine ecosystems, primarily due to their biological impact. Pharmaceuticals are employed globally for the treatment of human and animal disorders, as well as for the promotion of livestock growth. In addition to the common inefficiency of removal in wastewater treatment plants, a number of other sources contribute to the contamination of marine environments and subsequent adverse effects. These emerging contaminants interact with specific biochemical and physiological pathways in target organisms, causing alterations in marine species throughout their entire life cycle. Marine fish serve as bioindicators of pharmaceutical contamination in seawater, exhibiting the capacity to bioaccumulate these compounds and manifest their effects. View this paper
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29 pages, 9684 KiB  
Article
Decoupled Analysis of a Multi-Layer Flexible Pipeline Buried in Clay Subjected to Large Lateral Soil Displacement
by Eduardo Ribeiro Malta, Xiaoyu Dong and Hodjat Shiri
J. Mar. Sci. Eng. 2024, 12(7), 1238; https://doi.org/10.3390/jmse12071238 - 22 Jul 2024
Viewed by 768
Abstract
Multilayered flexible subsea pipelines may experience significant lateral movements due to manmade and environmental geohazards. These pipelines incorporate several structural and protective layers to resist different loads, and may require additional protection such as trenching, rock placement, or burial. In practice, simplifications are [...] Read more.
Multilayered flexible subsea pipelines may experience significant lateral movements due to manmade and environmental geohazards. These pipelines incorporate several structural and protective layers to resist different loads, and may require additional protection such as trenching, rock placement, or burial. In practice, simplifications are considered due to the complexities and uncertainties involved in the multi-layer pipe structure and the surrounding soil, compromising the pipe structure or the soil behavior. These simplifications are applied either on the pipe by assuming a rigid section or on the soil by representing it as elastic springs, which may result in inaccuracies. This study proposes a decoupled methodology combining the Coupled Eulerian–Lagrangian (CEL) model for soil displacement with a small-strain finite element analysis of the flexible pipe. This approach aims to accurately capture cross-sectional deformations and local stresses due to soil movement while maintaining reasonable computational effort. A parametric analysis was conducted to assess the impact of several variables on failure risk. The deformed cross-section was then used for a collapse analysis to determine critical loads at maximum operational depth. The study showed that modeling parameters such as soil strength and internal diameter might significantly influence pipe failure and the risk of collapse. Full article
(This article belongs to the Special Issue Advanced Research in Flexible Riser and Pipelines)
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17 pages, 5127 KiB  
Article
A Web-Based Interactive Application to Simulate and Correct Distortion in Multibeam Sonars
by Guillermo Boyra and Udane Martinez
J. Mar. Sci. Eng. 2024, 12(7), 1237; https://doi.org/10.3390/jmse12071237 - 22 Jul 2024
Viewed by 799
Abstract
Multibeam sonars are advanced scientific tools for estimating fish school volume and density, using multiple beams to provide comprehensive size measurements of detected targets. However, challenges remain in accurately estimating target dimensions due to beam geometric expansion and overlap, particularly in athwart-beam measurements, [...] Read more.
Multibeam sonars are advanced scientific tools for estimating fish school volume and density, using multiple beams to provide comprehensive size measurements of detected targets. However, challenges remain in accurately estimating target dimensions due to beam geometric expansion and overlap, particularly in athwart-beam measurements, which tend to be overestimated with increasing distance from the transducer. We present an interactive web application that simulates distortion caused by beam overlap and expansion in multibeam sonars using simple geometric equations. Users can define sonar characteristics, such as the number of beams, swath opening, or degree of overlap, as well as specify an elliptical target’s dimensions, orientation, and distance from the transducer. The application estimates and visualises the true and distorted shapes of the target, calculating the level of distortion. It can run simulations in both forward and inverse directions, either simulating the distortion of a true school or correcting the shape of a distorted school. This tool aims to enhance the interpretation of multibeam sonar signals and improve the accuracy of target dimension estimates, facilitating more effective use of these sonars in scientific research. Full article
(This article belongs to the Section Ocean Engineering)
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21 pages, 11469 KiB  
Article
Development of Hardware-in-the-Loop Simulation Test Bed to Verify and Validate Power Management System for LNG Carriers
by Kwangkook Lee
J. Mar. Sci. Eng. 2024, 12(7), 1236; https://doi.org/10.3390/jmse12071236 - 22 Jul 2024
Viewed by 1064
Abstract
Liquefied natural gas carrier (LNGC) orders are increasing owing to marine environment regulations. The complexity of the integrated system applied to shipbuilding and software errors have increased with the high degree of automation. Direct on-site inspection methods are associated with high costs and [...] Read more.
Liquefied natural gas carrier (LNGC) orders are increasing owing to marine environment regulations. The complexity of the integrated system applied to shipbuilding and software errors have increased with the high degree of automation. Direct on-site inspection methods are associated with high costs and safety risks, whereas software-based simulations rely heavily on the accuracy of the models of power system components. Hardware-in-the-loop simulation (HILS) can be utilized for designing and testing intricate real-time embedded systems. Specifically, HILS offers a reliable means of evaluating power management system (PMS) performance for LNGCs, which are high-value vessels commonly used in offshore plants. This study proposes a PMS–HIL test bed comprising a power supply unit, consumer, simulation control console, and main switchboard. The proposed HILS test bed utilizes the real equipment data of the shipbuilding industry to replicate the conditions associated with actual LNGCs. The proposed system is verified and validated through a software acceptance test procedure. Additionally, load-sharing, load-dependent start, blackout prevention, and preferential tests are performed for the PMS function evaluation. Test results indicate that the proposed system has great potential for conventional PMS commissioning. Therefore, it exhibits the potential to replace traditional factory acceptance tests. Additional development of the system will be conducted for ship automation, utilizing PMS control and an energy management system. Full article
(This article belongs to the Topic Advances in Intelligent Construction, Operation and Maintenance)
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14 pages, 3124 KiB  
Article
Effects of Angle of Attack on Flow-Induced Vibration of a D-Section Prism
by Shiguang Fan, Zhuang Li, Jining Song, Xietian Du and Juan Wang
J. Mar. Sci. Eng. 2024, 12(7), 1235; https://doi.org/10.3390/jmse12071235 - 22 Jul 2024
Viewed by 621
Abstract
The VIVACE device, which utilizes flow-induced vibration for harvesting ocean current energy, has been a research hotspot in the field of renewable energy. In this study, the flow-induced vibration characteristics and energy conversion efficiency of a D-section prism were investigated using the k-ω [...] Read more.
The VIVACE device, which utilizes flow-induced vibration for harvesting ocean current energy, has been a research hotspot in the field of renewable energy. In this study, the flow-induced vibration characteristics and energy conversion efficiency of a D-section prism were investigated using the k-ω SST turbulence model and Newmark-β method. The vibration amplitude, frequency, equilibrium position offset, and energy conversion efficiency of the two-degree-of-freedom cylinder were systematically analyzed at seven angles of attack between 0 and 180 degrees. The Reynolds number ranged from 368 to 14,742, corresponding to equivalent speeds of 2 to 20. The results indicate that the angle of attack has a significant influence on the flow-induced vibration response of the D-section prism. As the angle of attack changes, the vibration amplitude of the cylinder continuously increases, and the cylinder sequentially enters the vortex-induced vibration, vortex-induced vibration-galloping, and fully galloping branches. The change in the angle of attack disrupts the symmetry of the cylinder’s vibration in the streamwise direction, leading to a shift in the equilibrium position of the cylinder’s vibration. When the angle of attack is 0°, the energy conversion efficiency of the column reaches a maximum of 11.75%. Additionally, at high Reynolds numbers, the vibration of the cylinder is not self-limiting, making it more advantageous for energy conversion devices compared to cylinders with circular cross-sections. Full article
(This article belongs to the Special Issue The State of the Art of Marine Risers and Pipelines)
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26 pages, 22542 KiB  
Article
Numerical Study on the Anti-Sloshing Effect of Horizontal Baffles in a Cargo Hold Loaded with Liquefied Cargo
by Jianwei Zhang, Anqi Wang, Peng Chen, Jian Liu and Deqing Yang
J. Mar. Sci. Eng. 2024, 12(7), 1234; https://doi.org/10.3390/jmse12071234 - 22 Jul 2024
Viewed by 736
Abstract
Sloshing of liquefied bulk granular cargoes weakens the stability of cargo carriers when at sea. Using the horizontal rectangle baffle is a promising way to restrain its sloshing motion. But the location height and optimal baffle area rate to achieve a better anti-sloshing [...] Read more.
Sloshing of liquefied bulk granular cargoes weakens the stability of cargo carriers when at sea. Using the horizontal rectangle baffle is a promising way to restrain its sloshing motion. But the location height and optimal baffle area rate to achieve a better anti-sloshing effect should be studied first. The discrete element method was adopted to establish the simulation model, and the direct shear test was used for verification. Through the static tilt tests, the definite relationship between the effects of moisture content on cargo motion and particle friction coefficients was acquired. Then, liquefied cargo motion in a cargo hold without baffles and with one and two pairs of horizontal baffles was simulated. Based on variations in the cargo gravity center offset and the sloshing-induced force on the cargo hold, the anti-sloshing effect of different settings of the baffles was compared. Results show that the baffles have the ability to restrain cargo sloshing, and this is important for sea transportation safety. The anti-sloshing effect is better when the baffle plane is right on the cargo top surface compared to the other location heights. Further, there is an optimal length–width combination, e.g., a single baffle plane with a length of 0.26 L and a width of 0.46 B, at which a better anti-sloshing effect could be achieved with the smallest baffle area rate. This study could be useful for the practical application of horizontal baffles for bulk granular cargo carriers. Full article
(This article belongs to the Special Issue Innovative Technologies in Safety and Reliability of Marine Engineering)
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16 pages, 4745 KiB  
Article
Influence of Grid Resolution and Assimilation Window Size on Simulating Storm Surge Levels
by Xin Bi, Wenqi Shi, Junli Xu and Xianqing Lv
J. Mar. Sci. Eng. 2024, 12(7), 1233; https://doi.org/10.3390/jmse12071233 - 22 Jul 2024
Viewed by 676
Abstract
Grid resolution and assimilation window size play significant roles in storm surge models. In the Bohai Sea, Yellow Sea, and East China Sea, the influence of grid resolution and assimilation window size on simulating storm surge levels was investigated during Typhoon 7203. In [...] Read more.
Grid resolution and assimilation window size play significant roles in storm surge models. In the Bohai Sea, Yellow Sea, and East China Sea, the influence of grid resolution and assimilation window size on simulating storm surge levels was investigated during Typhoon 7203. In order to employ a more realistic wind stress drag coefficient that varies with time and space, we corrected the storm surge model using the spatial distribution of the wind stress drag coefficient, which was inverted using the data assimilation method based on the linear expression Cd = (a + b × U10) × 10−3. Initially, two grid resolutions of 5′ × 5′ and 10′ × 10′ were applied to the numerical storm surge model and adjoint assimilation model. It was found that the influence of different grid resolutions on the numerical model is almost negligible. But in the adjoint assimilation model, the root mean square (RMS) errors between the simulated and observed storm surge levels under 5′ × 5′ and 10′ × 10′ grid resolutions were 11.6 cm and 15.6 cm, and the average PCC and WSS values for 10 tidal stations changed from 89% and 92% in E3 to 93% and 96% in E4, respectively. The results indicate that the finer grid resolution can yield a closer consistency between the simulation and observations. Subsequently, the effects of assimilation window sizes of 6 h, 3 h, 2 h, and 1 h on simulated storm surge levels were evaluated in an adjoint assimilation model with a 5′ × 5′ grid resolution. The results show that the average RMS errors were 11.6 cm, 10.6 cm, 9.6 cm, and 9.3 cm under four assimilation window sizes. In particular, the RMS errors for the assimilation window sizes of 1 h and 6 h at RuShan station were 3.9 cm and 10.2 cm, a reduction of 61.76%. The PCC and WSS values from RuShan station in E4 and E7 separately showed significant increases, from 85% to 98% and from 92% to 99%. These results demonstrate that when the assimilation window size is smaller, the simulated storm surge level is closer to the observation. Further, the results show that the simulated storm surge levels are closer to the observation when using the wind stress drag coefficient with a finer grid resolution and smaller temporal resolution. Full article
(This article belongs to the Special Issue Ocean Modeling and Data Assimilation)
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17 pages, 9060 KiB  
Article
The Influence of Pre-Chamber Parameters on the Performance of a Two-Stroke Marine Dual-Fuel Low-Speed Engine
by Hao Guo, Zhongcheng Wang, Song Zhou, Ming Zhang and Majed Shreka
J. Mar. Sci. Eng. 2024, 12(7), 1232; https://doi.org/10.3390/jmse12071232 - 22 Jul 2024
Viewed by 759
Abstract
With increasing environmental pollution from ship exhaust emissions and increasingly stringent International Maritime Organization carbon regulations, there is a growing demand for cleaner and lower-carbon fuels and near-zero-emission marine engines worldwide. Liquefied natural gas is a low-carbon fuel, and when liquefied natural gas [...] Read more.
With increasing environmental pollution from ship exhaust emissions and increasingly stringent International Maritime Organization carbon regulations, there is a growing demand for cleaner and lower-carbon fuels and near-zero-emission marine engines worldwide. Liquefied natural gas is a low-carbon fuel, and when liquefied natural gas (LNG) is used on ships, dual-fuel methods are often used. The pre-chamber plays a key role in the working process of dual-fuel engines. In this paper, an effective three-dimensional simulation model based on the actual operating conditions and structural characteristics of a marine low-pressure dual-fuel engine is established. In addition, the effects of changing the Precombustion chamber (PCC) volume ratio and the PCC orifice diameter ratio on the mixture composition, engine combustion performance, and pollutant generation were thoroughly investigated. It was found that a small PPC volume ratio resulted in a higher flame jet velocity, a shorter stagnation period, and an acceleration of the combustion process in the main combustion chamber. When the PCC volume was large, the Nitrogen oxygen (NOx) ratio emission was elevated. Moreover, the angle of the PCC orifice affected the flame propagation direction of the pilot fuel. Optimizing the angle of the PCC orifice can improve combustion efficiency and reduce the generation of NOx. Furthermore, reasonable arrangement of the PCC structure can improve the stability of ignition performance and accelerate the flame jet velocity. Full article
(This article belongs to the Topic Safety, Reliability and Effectiveness of Internal Combustion Engines)
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29 pages, 11126 KiB  
Article
Design of Inner Ribs with Unequal Stiffness for Deep-Sea Highly Pressure-Resistant Cylindrical Shells and Utilizing NSGA-2 for Lightweight Optimization
by Yizhe Huang, Xiao Wang, Zhiqiang Liu, Ying You and Haoxiang Ma
J. Mar. Sci. Eng. 2024, 12(7), 1231; https://doi.org/10.3390/jmse12071231 - 21 Jul 2024
Viewed by 977
Abstract
For conducting scientific research at depths in the ocean, deep-sea probes are essential pieces of equipment. The cylindrical shell is the most sensible and rational packaging structure for these detectors. New technical challenges for enhancing the pressure resistance and lightweight design of the [...] Read more.
For conducting scientific research at depths in the ocean, deep-sea probes are essential pieces of equipment. The cylindrical shell is the most sensible and rational packaging structure for these detectors. New technical challenges for enhancing the pressure resistance and lightweight design of the pressure-resistant cylindrical shell arise from the need to ensure that the detector packaging structure can withstand the immense water pressure at tens of thousands of meters in the underwater environment, while simultaneously reducing the detector packaging structure’s self-weight. This article examines the detection system’s deep-sea pressure-resistant cylindrical shell. To address the issue of the pressure-resistant shell’s insufficient ability to counteract the overall instability caused by the inability to form unstable half-waves in the radial direction when the ring rib pressure-resistant shell experiences it, a design method for the ribs inside the unequal-stiffness pressure-resistant cylindrical shell is suggested. The shell’s instability pressure increases by 9.65 MPa following the stiffness adjustment. Simultaneously, in order to attain even more lightweight optimization, the optimal inner rib section was obtained by applying the orthogonal topology optimization method, which also reduced the weight by 106.8 g and effectively improved the compression stability of the high-pressure cylindrical shell structure. Based on this, key optimization variables were found by performing sensitivity analysis on the cylindrical shell structure’s parameters. Then, with lightweighting as the primary objective, the high-pressure-resistant cylindrical shell’s optimal structural parameters were found using a multi-objective optimization process using the second-generation fast non-dominated genetic algorithm (NSGA-2). This resulted in a weight reduction of 1.2492 kg, or 17.26% of the original pressure-resistant shell. This has led to the development of a lightweight, highly pressure-resistant method for packaging marine exploration equipment structures. Full article
(This article belongs to the Section Ocean Engineering)
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14 pages, 3002 KiB  
Article
Uncertainty Analysis and Maneuver Simulation of Standard Ship Model
by Hui Li, Nan Zhao, Jian Zhou, Xiangyu Chen and Chenxu Wang
J. Mar. Sci. Eng. 2024, 12(7), 1230; https://doi.org/10.3390/jmse12071230 - 21 Jul 2024
Viewed by 895
Abstract
Maneuver simulation of a standard ship model gives indication of numerical accuracy. In the numerical calculation of ship maneuvering, uncertainty analysis is a necessary step to ensure the accuracy of the calculation. In this study, uncertainty pair analysis is carried out in the [...] Read more.
Maneuver simulation of a standard ship model gives indication of numerical accuracy. In the numerical calculation of ship maneuvering, uncertainty analysis is a necessary step to ensure the accuracy of the calculation. In this study, uncertainty pair analysis is carried out in the simulation of the turning circle motion of the standard ship model ONRT in waves. According to the uncertainty analysis procedure recommended by the International Towing Tank Conference (ITTC), the change of ship resistance caused by the number of grids is studied to determine the influence of grid density on the numerical prediction. The simulation of turning motion in waves is carried out based on the uncertainty analysis. It is found that the minimum number of overset grids for this simulation is 1.4 million. The numerical results are fairly accurate compared to experimental results, and this technique provides a method with low calculated cost for this simulation. Full article
(This article belongs to the Special Issue Application of Advanced Technologies in Maritime Safety)
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31 pages, 7679 KiB  
Article
Numerical Study of the Ultra-High-Speed Aerodynamically Alleviated Marine Vehicle Motion Stability in Winds and Waves
by Yani Song, Xiaoxu Du and Yuli Hu
J. Mar. Sci. Eng. 2024, 12(7), 1229; https://doi.org/10.3390/jmse12071229 - 21 Jul 2024
Viewed by 763
Abstract
The ultra-high-speed aerodynamically alleviated marine vehicle (AAMV) is a high-performance vessel that combines a hydrodynamic configuration and an aerodynamic wing to reduce wave-making resistance during the high-speed planing phase. The forces of the AAMV exhibit strong nonlinear and water–air coupling characteristics, resulting in [...] Read more.
The ultra-high-speed aerodynamically alleviated marine vehicle (AAMV) is a high-performance vessel that combines a hydrodynamic configuration and an aerodynamic wing to reduce wave-making resistance during the high-speed planing phase. The forces of the AAMV exhibit strong nonlinear and water–air coupling characteristics, resulting in particularly complex motion characteristics. This paper presents a longitudinal and lateral stability model of the AAMV, which considers the effects of aerodynamic alleviation. Additionally, a numerical model of wind and wave turbulence forces is established, which considers viscous correction based on the potential theory. Finally, the effect of wind and wave turbulence forces on the motion stability of the AAMV under regular and irregular waves is analyzed by numerical solution. The simulation results demonstrate the influence of these disturbance forces on the stability of the AAMV under different sea states. The motion parameters of the AAMV exhibit a pronounced response to changes in sea state level. The aerodynamically alleviated effect is enhanced as speed increases, and the influence of winds and waves on the AAMV is greatly weakened, reducing the possibility of instability. During the cruising phase under class V sea state, the pitch, roll, and heave response are 0.210°, 0.0229°, and 0.0734 m, respectively. This effect can effectively improve the motion stability of the AAMV in winds and waves. Full article
(This article belongs to the Section Ocean Engineering)
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16 pages, 1946 KiB  
Article
Polyhydroxybutyrate Production from the Macroalga Rugulopteryx okamurae: Effect of Hydrothermal Acid Pretreatment
by Agustín Romero-Vargas, Luis Alberto Fdez-Güelfo, Ana Blandino and Ana Belén Díaz
J. Mar. Sci. Eng. 2024, 12(7), 1228; https://doi.org/10.3390/jmse12071228 - 21 Jul 2024
Viewed by 1102
Abstract
This study focuses on mitigating the socio-economic and environmental damage of the invasive macroalga Rugulopteryx okamurae and counteracting the pollution from petroleum-based plastics by using the alga as a feedstock for polyhydroxybutyrate (PHB) production. The enzymatic hydrolysis of R. okamurae, non-pretreated and hydrothermally [...] Read more.
This study focuses on mitigating the socio-economic and environmental damage of the invasive macroalga Rugulopteryx okamurae and counteracting the pollution from petroleum-based plastics by using the alga as a feedstock for polyhydroxybutyrate (PHB) production. The enzymatic hydrolysis of R. okamurae, non-pretreated and hydrothermally acid-pretreated (0.2 N HCl, 15 min), was carried out, reaching reducing sugar (RS) concentrations of 10.7 g/L and 21.7 g/L, respectively. The hydrolysates obtained were used as a culture medium for PHB production with Cupriavidus necator, a Gram-negative soil bacterium, without supplementation with any external carbon and nitrogen sources. The highest yield (0.774 g PHB/g RS) and biopolymer accumulation percentage (89.8% cell dry weight, CDW) were achieved with hydrolysates from pretreated macroalga, reaching values comparable to the highest reported in the literature. Hence, it can be concluded that hydrolysates obtained from algal biomass hydrothermally pretreated with acid have a concentration of sugars and a C/N ratio that favour PHB production. Full article
(This article belongs to the Special Issue Marine Microorganisms and Their Biomolecules: Biodiversity, Physiological Adaptation and Biotechnological Applications)
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14 pages, 1889 KiB  
Article
Fishing Eco-Efficiency of Ports in Northwest Spain
by Luis T. Antelo and Amaya Franco-Uría
J. Mar. Sci. Eng. 2024, 12(7), 1227; https://doi.org/10.3390/jmse12071227 - 21 Jul 2024
Viewed by 1028
Abstract
Fishing is an essential economic activity and source of livelihood for millions of people worldwide. However, overfishing and unsustainable practices have led to a decline in fish populations and the degradation of marine ecosystems. Moreover, fishing activities can contribute to climate change through [...] Read more.
Fishing is an essential economic activity and source of livelihood for millions of people worldwide. However, overfishing and unsustainable practices have led to a decline in fish populations and the degradation of marine ecosystems. Moreover, fishing activities can contribute to climate change through the emission of greenhouse gases (e.g., carbon dioxide and methane) from fishing vessels and seafood transportation. To mitigate the environmental impacts of fishing activities, sustainable fishing practices must be implemented to minimize the negative impacts of fishing on the environment while maintaining the productivity and diversity of fish populations and ecosystems. These practices include using selective fishing gear, avoiding fishing in vulnerable habitats, implementing fishery management plans, and reducing the carbon footprint of the fishing industry. To this end, and as a first step in defining efficient and effective measures towards the sustainability of capture fishing activity, an analysis of the environmental sustainability of the Galician fishing sector, one of the main European regions in this field, is presented in this work. An ecosystem-based indicator (ecological footprint, calculated by adding the so-called fishing ground footprint and the carbon footprint) was employed to quantify the main impacts of capture fishing during extractive activity. The catch composition and fuel consumption of the fleet based on the vessels’ power, and economic benefits, were the parameters used in this analysis. The results showed that ports with larger vessels and fleets seem to be more eco-efficient than those concentrating smaller vessels in targeting lower trophic level species. Full article
(This article belongs to the Section Marine Environmental Science)
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18 pages, 6110 KiB  
Article
An Algorithm for Ship Detection in Complex Observation Scenarios Based on Mooring Buoys
by Wenbo Li, Chunlin Ning, Yue Fang, Guozheng Yuan, Peng Zhou and Chao Li
J. Mar. Sci. Eng. 2024, 12(7), 1226; https://doi.org/10.3390/jmse12071226 - 20 Jul 2024
Viewed by 1023
Abstract
Marine anchor buoys, as fixed-point profile observation platforms, are highly susceptible to the threat of ship collisions. Installing cameras on buoys can effectively monitor and collect evidence from ships. However, when using a camera to capture images, it is often affected by the [...] Read more.
Marine anchor buoys, as fixed-point profile observation platforms, are highly susceptible to the threat of ship collisions. Installing cameras on buoys can effectively monitor and collect evidence from ships. However, when using a camera to capture images, it is often affected by the continuous shaking of buoys and rainy and foggy weather, resulting in problems such as blurred images and rain and fog occlusion. To address these problems, this paper proposes an improved YOLOv8 algorithm. Firstly, the polarized self-attention (PSA) mechanism is introduced to preserve the high-resolution features of the original deep convolutional neural network and solve the problem of image spatial resolution degradation caused by shaking. Secondly, by introducing the multi-head self-attention (MHSA) mechanism in the neck network, the interference of rain and fog background is weakened, and the feature fusion ability of the network is improved. Finally, in the head network, this model combines additional small object detection heads to improve the accuracy of small object detection. Additionally, to enhance the algorithm’s adaptability to camera detection scenarios, this paper simulates scenarios, including shaking blur, rain, and foggy conditions. In the end, numerous comparative experiments on a self-made dataset show that the algorithm proposed in this study achieved 94.2% mAP50 and 73.2% mAP50:95 in various complex environments, which is superior to other advanced object detection algorithms. Full article
(This article belongs to the Special Issue Modeling and Monitoring of Coastal Ocean, Nearshore and Estuarine Environments)
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17 pages, 2694 KiB  
Article
A Ternary Diagram Approach to Investigate the Competition within the Bohai Sea Rim Multi-Port Group
by Qin Lin, Manel Grifoll, Peijun Zhuang and Hongxiang Feng
J. Mar. Sci. Eng. 2024, 12(7), 1225; https://doi.org/10.3390/jmse12071225 - 20 Jul 2024
Viewed by 911
Abstract
The Bohai Rim region constitutes the third prominent “growth pole” in China’s economic landscape, wherein the Bohai Rim multi-port system, encompassing Tianjin Port, Dalian Port, and Qingdao Port, engages in intense competition to establish itself as the foremost shipping hub in northern China. [...] Read more.
The Bohai Rim region constitutes the third prominent “growth pole” in China’s economic landscape, wherein the Bohai Rim multi-port system, encompassing Tianjin Port, Dalian Port, and Qingdao Port, engages in intense competition to establish itself as the foremost shipping hub in northern China. This study compares the ternary diagram method and employs the comprehensive concentration index (CCI), Lerner index (LI), and spatial shift-share analysis (SSSA) methods to delve into the intricacies of concentration, inequality, and evolving competitive dynamics within the Bohai Rim multi-port system over the four decades spanning from 1981 to 2023. The aim is to analyze the evolutionary trajectory and underlying dynamic mechanisms of this multipartite port system. The analysis delineates the development trajectory of the system into three stages: the dominant stage of Tianjin Port from 1981 to 1990, the efficiency competition stage from 1991 to 1996, and the ascendancy of Qingdao Port from 1997 to 2023. The results indicate that: (i) the Bohai Rim multi-port system exhibits a relatively low level of concentration, ensuring balanced growth within a non-monopolistic competitive environment; (ii) the internal competitiveness of the Bohai Rim multi-port system has gradually shifted from Tianjin Port to Qingdao Port, with Dalian Port experiencing steady development in its container transport capabilities. (iii) Dalian Port has witnessed a decline in container throughput since 2015, indicating a weakening competitive posture. These revelations suggest that Qingdao Port is a viable candidate for development into the northern China shipping center, leveraging its increasing competitiveness and strategic location. The method applied in this study may also prove beneficial for similar multi-port systems elsewhere. Full article
(This article belongs to the Special Issue 10th International Conference on Maritime Transport (MT’24))
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27 pages, 4121 KiB  
Article
An Improved NSGA-II Algorithm for MASS Autonomous Collision Avoidance under COLREGs
by Zuopeng Liang, Fusheng Li and Shibo Zhou
J. Mar. Sci. Eng. 2024, 12(7), 1224; https://doi.org/10.3390/jmse12071224 - 20 Jul 2024
Cited by 1 | Viewed by 1043
Abstract
Autonomous collision avoidance decision making for maritime autonomous surface ships (MASS), as one of the key technologies for MASS autonomous navigation, is a research hotspot focused on by relevant scholars in the field of navigation. In order to guarantee the rationality, efficacy, and [...] Read more.
Autonomous collision avoidance decision making for maritime autonomous surface ships (MASS), as one of the key technologies for MASS autonomous navigation, is a research hotspot focused on by relevant scholars in the field of navigation. In order to guarantee the rationality, efficacy, and credibility of the MASS autonomous collision avoidance scheme, it is essential to design the MASS autonomous collision avoidance algorithm under the stipulations of the Convention on the International Regulations for Preventing Collisions at Sea (COLREGs). In order to enhance the autonomous collision avoidance decision-making capability of MASS in accordance with the relevant provisions of COLREGs, an improved NSGA-II autonomous collision avoidance decision-making algorithm based on the good point set method (GPS-NSGA-II) is proposed, which incorporates the collision hazard and the path cost of collision avoidance actions. The experimental results in the four simulation scenarios of head-on situation, overtaking situation, crossing situation, and multi-ship encounter situation demonstrate that the MASS autonomous collision avoidance decision making based on the GPS-NSGA-II algorithm under the constraints of COLREGs is capable of providing an effective collision avoidance scheme that meets the requirements of COLREGs in common encounter situations and multi-ship avoidance scenarios promptly, with a promising future application. Full article
(This article belongs to the Special Issue Autonomous Marine Vehicle Operations—2nd Edition)
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19 pages, 18332 KiB  
Article
Regional Difference in Distribution Pattern and Morphological Characteristics of Embayed Sandy Beaches in Zhejiang Province, Eastern China
by Junli Guo, Lianqiang Shi, Min Zhang, Zhaohui Gong, Wei Chen and Xiaoming Xia
J. Mar. Sci. Eng. 2024, 12(7), 1223; https://doi.org/10.3390/jmse12071223 - 20 Jul 2024
Viewed by 813
Abstract
The distribution pattern and the morphology of sandy beaches have been extensively studied, while those in turbid coastal environments near large river estuaries are still unclear. This study analyzes the distribution pattern, morphological characteristics, and influencing factors of Zhejiang sandy beaches using statistical [...] Read more.
The distribution pattern and the morphology of sandy beaches have been extensively studied, while those in turbid coastal environments near large river estuaries are still unclear. This study analyzes the distribution pattern, morphological characteristics, and influencing factors of Zhejiang sandy beaches using statistical analysis, based on field data and historical records. Results show that the mean grain size distribution of Zhejiang sandy beaches ranges from fine sand to very coarse sand, and the beach slope and sediment grain size correspond well with the wave heights in the three regions of Zhejiang. The extent of beach headlands in central Zhejiang appeared the largest, suggesting an increased susceptibility to wave erosion due to the less sheltered headlands. Most sandy beaches in Zhejiang formed on the islands and the areas far from the estuaries, showing quantity difference in beach distribution. The comparison of the regional difference in Zhejiang sandy beaches shows that embayment is the main factor affecting the beach distribution pattern and morphological characteristics. The different embayment characteristics provide the space for beach formation and the interaction with the coastal process, the sediment supply, the nearshore hydrodynamic environment, and human intervention also have influence on the morphological characteristics of Zhejiang beaches. Full article
(This article belongs to the Special Issue Advance in Sedimentology and Coastal and Marine Geology—2nd Edition)
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19 pages, 12105 KiB  
Article
Underwater Mapping and Optimization Based on Multibeam Echo Sounders
by Feihu Zhang, Tingfeng Tan, Xujia Hou, Liang Zhao, Chun Cao and Zewen Wang
J. Mar. Sci. Eng. 2024, 12(7), 1222; https://doi.org/10.3390/jmse12071222 - 20 Jul 2024
Viewed by 1087
Abstract
Multibeam echo sounders (MBESs) enable extensive underwater environment exploration. However, due to weak correlation between adjacent multibeam sonar data and difficulties in inter-frame feature matching, the resulting underwater mapping accuracy frequently falls short of the desired level. To address this issue, this study [...] Read more.
Multibeam echo sounders (MBESs) enable extensive underwater environment exploration. However, due to weak correlation between adjacent multibeam sonar data and difficulties in inter-frame feature matching, the resulting underwater mapping accuracy frequently falls short of the desired level. To address this issue, this study presents the development of a multibeam data processing system, which includes functionalities for sonar parameter configuration, data storage, and point cloud conversion. Subsequently, an Iterative Extended Kalman Filter (iEKF) algorithm is employed for odometry estimation, facilitating the initial construction of the point cloud map. To further enhance mapping accuracy, we utilize the Generalized Iterative Closest Point (GICP) algorithm for point cloud registration, effectively merging point cloud data collected at different times from the same location. Finally, real-world lake experiments demonstrate that our method achieves an Absolute Trajectory Error (ATE) of 15.10 m and an average local point cloud registration error of 0.97 m. Furthermore, we conduct measurements on various types of artificial targets. The experimental results indicate that the average location error of the targets calculated by our method is 4.62 m, which meets the accuracy requirements for underwater target exploration. Full article
(This article belongs to the Special Issue Applications of Underwater Acoustics in Ocean Engineering)
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20 pages, 2669 KiB  
Article
Maneuver Planning for Multiple Pursuit Intelligent Surface Vehicles in a Sequence of Zero-Sum Pursuit–Evasion Games
by Le Hong, Weicheng Cui, Hao Chen, Changhui Song and Weikun Li
J. Mar. Sci. Eng. 2024, 12(7), 1221; https://doi.org/10.3390/jmse12071221 - 20 Jul 2024
Viewed by 683
Abstract
Unmanned surface pursuit is a complex and challenging engineering problem, especially when conducted by multiple intelligent surface vehicles (ISVs). To enhance the pursuit performance and facilitate strategic interaction during the target pursuit, this paper proposes a novel game theory-based maneuver planning method for [...] Read more.
Unmanned surface pursuit is a complex and challenging engineering problem, especially when conducted by multiple intelligent surface vehicles (ISVs). To enhance the pursuit performance and facilitate strategic interaction during the target pursuit, this paper proposes a novel game theory-based maneuver planning method for pursuit ISVs. Firstly, a specific two-player zero-sum pursuit–evasion game (ZSPEG)-based target-pursuit model is formed. To ensure the vehicles reach a quick consensus, a target-guided relay-pursuit mechanism and the corresponding pursuit payoffs are designed. Meanwhile, under the fictitious play framework, the behavioral pattern and the strategies of the target could be fictitiously learned. Furthermore, mixed-strategy Nash equilibrium (MNE) is employed to determine the motions for the vehicles, the value of which is the best response in the proposed ZSPEG model. Finally, simulations verify the effectiveness of the above methods in multi-ISV surface pursuit. Full article
(This article belongs to the Section Ocean Engineering)
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25 pages, 4075 KiB  
Article
A Robust Sparse Sensor Placement Strategy Based on Indicators of Noise for Ocean Monitoring
by Qiannan Zhang, Huafeng Wu, Li’nian Liang, Xiaojun Mei, Jiangfeng Xian and Yuanyuan Zhang
J. Mar. Sci. Eng. 2024, 12(7), 1220; https://doi.org/10.3390/jmse12071220 - 19 Jul 2024
Cited by 1 | Viewed by 729
Abstract
A well-performing data-driven sparse sensor deployment strategy is critical for marine monitoring systems, as it enables the optimal reconstruction of marine physical quantities with fewer sensors. However, ocean data typically contain substantial amounts of noise, including outliers (incomplete data) and inherent measurement noise, [...] Read more.
A well-performing data-driven sparse sensor deployment strategy is critical for marine monitoring systems, as it enables the optimal reconstruction of marine physical quantities with fewer sensors. However, ocean data typically contain substantial amounts of noise, including outliers (incomplete data) and inherent measurement noise, which heightens the complexity of sensor deployment. Therefore, this study optimizes the sparse sensor placement model by establishing noise indicators, including small noise weight and large noise weight, which are measured by entropy to minimize the prediction bias. Building on this, a robust sparse sensor placement algorithm is proposed, which utilizes the block coordinate update (BCU) iteration method to solve the function. During the iterative updating process, the proposed algorithm simultaneously updates the selection matrix, reconstruction matrix, and noise matrix. This allows for effective identification and mitigation of noise in the data through evaluation. Consequently, the deployed sensors achieve superior reconstruction performance compared to other deployment methods that do not incorporate noise evaluation. Experiments are also conducted on datasets of sea surface temperature (SST) and global ocean salinity, which demonstrate that our strategy significantly outperforms several other considered methods in terms of reconstruction accuracy while enabling autonomous sensor deployment under noisy conditions. Full article
(This article belongs to the Special Issue Advances in Underwater Acoustic Communication and Ocean Sensor Networks)
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19 pages, 8549 KiB  
Article
Short-Term Photovoltaic Power Prediction Based on a Digital Twin Model
by Chuan Xiang, Bohan Li, Pengfei Shi, Tiankai Yang and Bing Han
J. Mar. Sci. Eng. 2024, 12(7), 1219; https://doi.org/10.3390/jmse12071219 - 19 Jul 2024
Viewed by 727
Abstract
Due to the influence of meteorological conditions, shipboard photovoltaic (PV) systems have problems such as large fluctuation and inaccurate prediction of the output power. In this paper, a short-term PV power prediction method based on a novel digital twin (DT) model and BiLSTM [...] Read more.
Due to the influence of meteorological conditions, shipboard photovoltaic (PV) systems have problems such as large fluctuation and inaccurate prediction of the output power. In this paper, a short-term PV power prediction method based on a novel digital twin (DT) model and BiLSTM is proposed. Firstly, a PV mechanism model and a data-driven model were established, in which the data-driven model was updated iteratively in real time using the sliding time window update method; then, these two models were converged to construct a PV DT model according to the DS evidence theory. Secondly, a BiLSTM model was built to make short-term predictions of the PV power using the augmented dataset of the DT model as an input. Finally, the method was tested and verified by experiments and further compared with main PV prediction methods. The research results indicate the following: firstly, the absolute error of the DT model was smaller than that of the mechanism model and the data-driven model, being as low as 5.62 W after the data update of the data-driven model; thus, the DT model realized data augmentation and high fidelity. Secondly, compared to several main PV prediction models, the PV DT model combined with BiLSTM had the lowest RMSE, MAE, and MAPE; the best followability; and the smallest absolute error under different weather conditions, which was especially obvious under cloudy weather conditions. In summary, the method can accurately predict the shipboard PV power, which has great theoretical significance and application value for improving the economy and reliability of solar ship operation. Full article
(This article belongs to the Special Issue Sustainable Utilization of Marine Renewable Energy)
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16 pages, 2212 KiB  
Article
Simulation Model of Hydraulic System States for Ship Cranes
by Mate Jurjević
J. Mar. Sci. Eng. 2024, 12(7), 1218; https://doi.org/10.3390/jmse12071218 - 19 Jul 2024
Viewed by 631
Abstract
The aim of this research is to devise a continuous simulation model for predicting ship crane failures to increase their reliability and reduce unplanned downtime during cargo loading and unloading operations. To predict the condition of the hydraulic system, a database from the [...] Read more.
The aim of this research is to devise a continuous simulation model for predicting ship crane failures to increase their reliability and reduce unplanned downtime during cargo loading and unloading operations. To predict the condition of the hydraulic system, a database from the GALIOT software package was used for carrying out maintenance on cranes at m/v “O” over a period of 120,000 working hours. In the research, fault tree analysis (FTA) was used to identify causal relationships between system failures and basic events, while the Markov mathematical model was used to model the system state and predict transitions between different failure states. A system dynamics simulation model was developed to simulate the behavior of a system using POWERSIM PowerSim Constructor 2.5.d (4002), and regression analysis was performed to analyze the simulation results and understand the relationships between dependent and independent variables. The results show that a model for predicting failures in the hydraulic motors and pumps of ship cranes was developed, and the Markov model makes it possible to estimate the frequency of transitions between states under the condition that the sum of reliability equals one. The simulation model shows high reliability of the cranes and a constant frequency of failures throughout the 120,000 operating hours, while the regression analysis confirms the validity of the simulation model and shows a strong correlation between the analyzed variables. These models are used to improve the planning of ship crane maintenance, reduce unplanned downtime, and predict and promptly detect failures, which overall minimizes maintenance costs and failures. Full article
(This article belongs to the Section Ocean Engineering)
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12 pages, 2690 KiB  
Article
Underwater Image Enhancement Based on Light Field-Guided Rendering Network
by Chia-Hung Yeh, Yu-Wei Lai, Yu-Yang Lin, Mei-Juan Chen and Chua-Chin Wang
J. Mar. Sci. Eng. 2024, 12(7), 1217; https://doi.org/10.3390/jmse12071217 - 19 Jul 2024
Cited by 2 | Viewed by 944
Abstract
Underwater images often encounter challenges such as attenuation, color distortion, and noise caused by artificial lighting sources. These imperfections not only degrade image quality but also impose constraints on related application tasks. Improving underwater image quality is crucial for underwater activities. However, obtaining [...] Read more.
Underwater images often encounter challenges such as attenuation, color distortion, and noise caused by artificial lighting sources. These imperfections not only degrade image quality but also impose constraints on related application tasks. Improving underwater image quality is crucial for underwater activities. However, obtaining clear underwater images has been a challenge, because scattering and blur hinder the rendering of true underwater colors, affecting the accuracy of underwater exploration. Therefore, this paper proposes a new deep network model for single underwater image enhancement. More specifically, our framework includes a light field module (LFM) and sketch module, aiming at the generation of a light field map of the target image for improving the color representation and preserving the details of the original image by providing contour information. The restored underwater image is gradually enhanced, guided by the light field map. The experimental results show the better image restoration effectiveness, both quantitatively and qualitatively, of the proposed method with a lower (or comparable) computing cost, compared with the state-of-the-art approaches. Full article
(This article belongs to the Special Issue Earth System Modeling, Data Assimilation, Artificial Intelligence, Deep Learning and Ocean Information Engineering II)
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18 pages, 5728 KiB  
Article
NUAM-Net: A Novel Underwater Image Enhancement Attention Mechanism Network
by Zhang Wen, Yikang Zhao, Feng Gao, Hao Su, Yuan Rao and Junyu Dong
J. Mar. Sci. Eng. 2024, 12(7), 1216; https://doi.org/10.3390/jmse12071216 - 19 Jul 2024
Viewed by 813
Abstract
Vision-based underwater exploration is crucial for marine research. However, the degradation of underwater images due to light attenuation and scattering poses a significant challenge. This results in the poor visual quality of underwater images and impedes the development of vision-based underwater exploration systems. [...] Read more.
Vision-based underwater exploration is crucial for marine research. However, the degradation of underwater images due to light attenuation and scattering poses a significant challenge. This results in the poor visual quality of underwater images and impedes the development of vision-based underwater exploration systems. Recent popular learning-based Underwater Image Enhancement (UIE) methods address this challenge by training enhancement networks with annotated image pairs, where the label image is manually selected from the reference images of existing UIE methods since the groundtruth of underwater images do not exist. Nevertheless, these methods encounter uncertainty issues stemming from ambiguous multiple-candidate references. Moreover, they often suffer from local perception and color perception limitations, which hinder the effective mitigation of wide-range underwater degradation. This paper proposes a novel NUAM-Net (Novel Underwater Image Enhancement Attention Mechanism Network) that addresses these limitations. NUAM-Net leverages a probabilistic training framework, measuring enhancement uncertainty to learn the UIE mapping from a set of ambiguous reference images. By extracting features from both the RGB and LAB color spaces, our method fully exploits the fine-grained color degradation clues of underwater images. Additionally, we enhance underwater feature extraction by incorporating a novel Adaptive Underwater Image Enhancement Module (AUEM) that incorporates both local and long-range receptive fields. Experimental results on the well-known UIEBD benchmark demonstrate that our method significantly outperforms popular UIE methods in terms of PSNR while maintaining a favorable Mean Opinion Score. The ablation study also validates the effectiveness of our proposed method. Full article
(This article belongs to the Section Ocean Engineering)
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16 pages, 4252 KiB  
Article
Research on the Construction of a Digital Twin System for the Long-Term Service Monitoring of Port Terminals
by Jinqiang Bi, Peiren Wang, Wenjia Zhang, Kexin Bao and Liu Qin
J. Mar. Sci. Eng. 2024, 12(7), 1215; https://doi.org/10.3390/jmse12071215 - 19 Jul 2024
Cited by 2 | Viewed by 888
Abstract
Structural damage is a prevalent issue in long-term operations of harbor terminals. Addressing the lack of transparency in terminal infrastructure components, the limited integration of sensor monitoring data, and the insufficient support for feedback on service performance, we propose a novel digital twin [...] Read more.
Structural damage is a prevalent issue in long-term operations of harbor terminals. Addressing the lack of transparency in terminal infrastructure components, the limited integration of sensor monitoring data, and the insufficient support for feedback on service performance, we propose a novel digital twin system construction methodology tailored for the long-term monitoring of port terminals. This study elaborates on the organization and processing of foundational geospatial data, sensor monitoring information, and oceanic hydrometeorological data essential for constructing a digital twin of the terminal. By mapping relationships between physical and virtual spaces, we developed comprehensive dynamic and static models of terminal facilities. Employing a “particle model” approach, we visually represented oceanic and meteorological elements. Additionally, we developed a multi-source heterogeneous data fusion model to facilitate the rapid creation of data indexes for harbor elements under high concurrency conditions, effectively addressing performance issues related to scene-rendering visualization and real-time sensor data storage efficiency. Experimental validation demonstrates that this method enables the rapid construction of digital twin systems for port terminals and supports practical application in business scenarios. Data analysis and comparison confirm the feasibility of the proposed method, providing an effective approach for the long-term monitoring of port terminal operations. Full article
(This article belongs to the Special Issue Intelligent Ships and Waterways: Design, Operation and Advanced Technology)
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13 pages, 2070 KiB  
Article
A Parallelized Climatological Drifter-Based Model of Sargassum Biomass Dynamics in the Tropical Atlantic
by Karl Payne, Khalil Greene and Hazel A. Oxenford
J. Mar. Sci. Eng. 2024, 12(7), 1214; https://doi.org/10.3390/jmse12071214 - 19 Jul 2024
Viewed by 1122
Abstract
The movement and biomass fluctuations of sargassum across the Tropical Atlantic have profound implications when influxes reach the Eastern Caribbean. These influxes have cross-cutting impacts across ecological, economic, and social systems. The objective of this work is to quantify sargassum biomass accumulation in [...] Read more.
The movement and biomass fluctuations of sargassum across the Tropical Atlantic have profound implications when influxes reach the Eastern Caribbean. These influxes have cross-cutting impacts across ecological, economic, and social systems. The objective of this work is to quantify sargassum biomass accumulation in the Eastern Caribbean, accounting for the spatial variability in sea surface temperature and morphotype diversity. A parallel implementation of a climatological drifter-based model was used to simulate advection of sargassum across the model domain. After determining the trajectory of virtual sargassum particles, Monte Carlo simulations using 1000 realizations were run to quantify biomass accumulations along these tracks. For simulations with a single morphotype, the biomass accumulation as predicted by the model effectively reproduced the seasonal distributions of sargassum for the simulated period (May 2017 to August 2017). The model closely approximated an observed increase during the period from May to July 2017, followed by a subsequent decline in sargassum abundance. A major factor that led to the discrepancy between the simulated and observed biomass accumulation is the occlusion of the optical satellite signal from cloud cover, which led to underestimates of sargassum abundance. The mean maximum growth rate required to reproduce the observed sargassum biomass was 0.05 day−1, which is consistent with other published experimental and computational studies that have reported similar growth rates for sargassum populations under comparable environmental conditions. An innovative aspect of this study was the investigation of the biomass dynamics of the three dominant morphotypes found in the study area. The results from these simulations show that the accumulation of the fastest growing morphotype, Sargassum fluitans var. fluitans, closely approximates the profiles of the overall prediction with a single morphotype. Full article
(This article belongs to the Section Marine Biology)
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8 pages, 1058 KiB  
Article
Size-Dependent Microplastic Fragmentation Model
by Vicente Pérez-Muñuzuri
J. Mar. Sci. Eng. 2024, 12(7), 1213; https://doi.org/10.3390/jmse12071213 - 19 Jul 2024
Viewed by 917
Abstract
Plastic fragmentation alters the size distribution of plastic waste in aquatic habitats, which is accelerated by mechanical stress and weathering degradation processes. Microplastic pieces constitute the vast bulk of plastic pollution in terms of quantity. Their size distribution has been shown to follow [...] Read more.
Plastic fragmentation alters the size distribution of plastic waste in aquatic habitats, which is accelerated by mechanical stress and weathering degradation processes. Microplastic pieces constitute the vast bulk of plastic pollution in terms of quantity. Their size distribution has been shown to follow a power-law for larger fragments. This work introduces a novel model inspired by raindrop formation, incorporating local oceanographic processes and fragment size, aiming to improve the understanding and prediction of plastic fragmentation in marine environments. Particles can fragment when they reach a certain size, or when shear forces become too strong. Plastic aging’s effect on size distribution is also investigated. Full article
(This article belongs to the Section Physical Oceanography)
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18 pages, 4391 KiB  
Article
Seasonal Variability of Hydrological Parameters and Estimation of Circulation Patterns: Application to a Mediterranean Coastal Lagoon
by Nikolaos Simantiris and Alexander Theocharis
J. Mar. Sci. Eng. 2024, 12(7), 1212; https://doi.org/10.3390/jmse12071212 - 18 Jul 2024
Viewed by 681
Abstract
Coastal lagoons are among the most important, but also threatened, marine systems of our planet. Rainfall, wind, seawater, and freshwater discharges control water circulation in lagoons, determining the water properties that are vital for the lagoon’s biodiversity. The present work is the first [...] Read more.
Coastal lagoons are among the most important, but also threatened, marine systems of our planet. Rainfall, wind, seawater, and freshwater discharges control water circulation in lagoons, determining the water properties that are vital for the lagoon’s biodiversity. The present work is the first study on the circulation patterns and seasonal variability of hydrological parameters in Antinioti lagoon in western Greece, building a reference level on our knowledge of the hydrodynamic functioning of this marine ecosystem. This study shows that the lagoon’s water properties’ fluctuations and circulation variability are affected by an antagonistic effect between freshwater (river discharge, underground spring, rainfall) and seawater inputs. This effect, influenced by atmospheric forcing (rainfall, atmospheric temperature), controls the heat and salt budgets of the lagoon. Nevertheless, the lagoon keeps an almost balanced annual cycle, returning from June 2020 to June 2021 to similar values for all parameters. Full article
(This article belongs to the Section Physical Oceanography)
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24 pages, 9893 KiB  
Article
Diatoms of the Macroalgae Epiphyton and Bioindication of the Protected Coastal Waters of the Kazantip Cape (Crimea, the Sea of Azov)
by Anna Bondarenko, Armine Shiroyan, Larisa Ryabushko and Sophia Barinova
J. Mar. Sci. Eng. 2024, 12(7), 1211; https://doi.org/10.3390/jmse12071211 - 18 Jul 2024
Viewed by 755
Abstract
This article is about the diversity of diatoms in the benthos of the upper sublittoral near Kazantip Cape, located on the shore of the Sea of Azov in the northeastern part of Crimea. The study was conducted in 2022 and 2023 at a [...] Read more.
This article is about the diversity of diatoms in the benthos of the upper sublittoral near Kazantip Cape, located on the shore of the Sea of Azov in the northeastern part of Crimea. The study was conducted in 2022 and 2023 at a depth of 0.1 to 1 m at temperatures from 3.7 °C to 29 °C and salinity from 13.6 to 15.6 psu on the following 11 species of macroalgae: Phaeophyta of Ericaria crinita, Gongolaria barbata, and Cladosiphon mediterraneus; Chlorophyta—Bryopsis hypnoides, Cladophora liniformis, Ulva intestinalis, and Ulva linza; and Rhodophyta—Callithamnion corymbosum, Ceramium arborescens, Polysiphonia denudata, and Pyropia leucosticta. A total of 97 taxa of Bacillariophyta belonging to 3 classes, 21 orders, 30 families, and 45 genera were found. The highest number of diatom species was found on U. linza (61 species), P. denudata (45), E. crinita (40), the lowest number was recorded on thalli P. leucosticta (9). On macroalgae were found of 80% benthic diatoms, 50% marine species, 36% brackish-marine, 9% freshwater, 5% brackish, and 36% cosmopolites. The maximum abundance of the diatom community was 243.4 × 103 cells/cm2 (P. denudata in September at 23.9 °C and 15.0 psu) with dominance by the diatom of Licmophora abbreviata, and the minimum was 3.8 × 103 cells/cm2 (P. leucosticta in January at 3.7 °C and 15.0 psu). The presence in the epiphyton of diatoms—indicators of moderate organic water pollution (32 species), which developed in masse in late summer—indicate a constant inflow of organic matter into the coastal waters of the Kazantip Cape. The bioindicator and statistical studies indicate the effectiveness of the conservation regime, especially at stations within the IUCN reserve, despite relatively high saprobity rates at stations exposed to recreational pressure and poorly treated domestic wastewater. Full article
(This article belongs to the Special Issue Challenges in Monitoring and Management of Water Quality in Coastal Areas)
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18 pages, 22988 KiB  
Article
MEvo-GAN: A Multi-Scale Evolutionary Generative Adversarial Network for Underwater Image Enhancement
by Feiran Fu, Peng Liu, Zhen Shao, Jing Xu and Ming Fang
J. Mar. Sci. Eng. 2024, 12(7), 1210; https://doi.org/10.3390/jmse12071210 - 18 Jul 2024
Viewed by 761
Abstract
In underwater imaging, achieving high-quality imagery is essential but challenging due to factors such as wavelength-dependent absorption and complex lighting dynamics. This paper introduces MEvo-GAN, a novel methodology designed to address these challenges by combining generative adversarial networks with genetic algorithms. The key [...] Read more.
In underwater imaging, achieving high-quality imagery is essential but challenging due to factors such as wavelength-dependent absorption and complex lighting dynamics. This paper introduces MEvo-GAN, a novel methodology designed to address these challenges by combining generative adversarial networks with genetic algorithms. The key innovation lies in the integration of genetic algorithm principles with multi-scale generator and discriminator structures in Generative Adversarial Networks (GANs). This approach enhances image details and structural integrity while significantly improving training stability. This combination enables more effective exploration and optimization of the solution space, leading to reduced oscillation, mitigated mode collapse, and smoother convergence to high-quality generative outcomes. By analyzing various public datasets in a quantitative and qualitative manner, the results confirm the effectiveness of MEvo-GAN in improving the clarity, color fidelity, and detail accuracy of underwater images. The results of the experiments on the UIEB dataset are remarkable, with MEvo-GAN attaining a Peak Signal-to-Noise Ratio (PSNR) of 21.2758, Structural Similarity Index (SSIM) of 0.8662, and Underwater Color Image Quality Evaluation (UCIQE) of 0.6597. Full article
(This article belongs to the Special Issue Application of Deep Learning in Underwater Image Processing)
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22 pages, 10384 KiB  
Article
Numerical Research on a T-Foil Control Method for Trimarans Based on Phase Lag
by Yifang Sun, Yiqun Wang, Dapeng Zhang, Zongduo Wu and Guoqing Jin
J. Mar. Sci. Eng. 2024, 12(7), 1209; https://doi.org/10.3390/jmse12071209 - 18 Jul 2024
Viewed by 707
Abstract
The lift force of a T-foil, which varies with ship motion, can counteract the wave exciting force during wave encounters. The phase difference between the periodic lift force and the wave exciting force significantly impacts the T-foil’s effectiveness. This study investigates the phase [...] Read more.
The lift force of a T-foil, which varies with ship motion, can counteract the wave exciting force during wave encounters. The phase difference between the periodic lift force and the wave exciting force significantly impacts the T-foil’s effectiveness. This study investigates the phase difference between lift force and motion to optimize the control equation for the T-foil’s angle, thereby reducing negative feedback. The T-foil’s hydrodynamic performance is first calculated using computational fluid dynamics. Time-domain calculations of the phase lag between lift force and motion under open-loop control in still water are then used to determine the dimensionless phase lag of the T-foil’s angle at various frequencies, facilitating further optimization of the control method. Finally, calculations of trimaran heave and pitch in regular waves are conducted. The results demonstrate that, under phase lag control, the T-foil’s lift force phase precedes ship motion by approximately 0.2 s, reducing hysteresis in the anti-vertical motion effect. Comparisons of vertical hull motions between different control methods reveal a 20% reduction in vertical motion with phase lag control compared to pitch control. This study concludes that phase lag is a crucial factor in T-foil control optimization. Full article
(This article belongs to the Special Issue Advances in the Performance of Ships and Offshore Structures)
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