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Volume 12
Issue 8
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J. Mar. Sci. Eng., Volume 12, Issue 8 (August 2024) – 222 articles

Cover Story (view full-size image): Cathodic protection (CP) is critical to the long-term deployment of steel monopiles used to support offshore wind turbines. The application of CP to internal surfaces has created byproducts which alter seawater chemistry and may accelerate corrosion. One option for this is to incorporate perforations into the design to enable seawater flow. This could also create habitats for marine organisms and contribute to the sustainability goals of the industry. This research investigated aluminum sacrificial anode and impressed current CP applied to the inside of sealed and perforated steel pipes on the basis of current demand, internal water chemistry, and marine life. The CP systems inside the perforated pipes effectively controlled corrosion and behaved similarly to external systems. Marine organisms grew inside the perforated pipes, demonstrating the ability to create habitats for marine life. View this paper
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20 pages, 6721 KiB  
Article
Conceptual Design and Dynamic Analysis of a Wind–Wave Energy Converter with a Mass-Adjustable Buoy
by Yifeng Shi, Jiahuan Lin, Zexin Zhuge, Rongye Zheng and Jun Zhang
J. Mar. Sci. Eng. 2024, 12(8), 1460; https://doi.org/10.3390/jmse12081460 - 22 Aug 2024
Viewed by 645
Abstract
To reduce the levelized cost of energy (LCOE) for offshore wind turbines, a novel wind–wave energy converter (WWEC) with a mass-adjustable buoy is designed. To analyze the impact of buoy mass variations on the system, a coupled comprehensive numerical model is established to [...] Read more.
To reduce the levelized cost of energy (LCOE) for offshore wind turbines, a novel wind–wave energy converter (WWEC) with a mass-adjustable buoy is designed. To analyze the impact of buoy mass variations on the system, a coupled comprehensive numerical model is established to simulate the aerodynamics of the turbine and the hydrodynamics of the platform and buoy. It is found that the occurrence of the buoy out of water significantly reduces the output power. Adjusting the buoy’s mass with suitable strategy can prevent the impact of slamming loads and improve the power output. The mass adjustment strategy is determined based on the output power of the wave energy converter under regular wave conditions. It is found that the mass adjustment strategy can significantly enhance the output power of combined system. The buoy does not move out of the water under the extreme conditions, which avoids the impact of slamming loads on system stability. Moreover, mass-adjustable buoys can reduce the risk of mooring line failure compare to a wind turbine without a buoy. Full article
(This article belongs to the Topic Marine Renewable Energy, 2nd Edition)
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26 pages, 13313 KiB  
Article
Diagenetic Evolution of Syngenetic Volcanogenic Sediment and Their Influence on Sandstone Reservoir: A Case Study in the Southern Huizhou Sag, Pearl River Mouth Basin, Northern South China Sea
by Jiahao Chen, Hongtao Zhu, Guangrong Peng, Lin Ding, Zhiwei Zeng, Wei Wang, Wenfang Tao and Fengjuan Zhou
J. Mar. Sci. Eng. 2024, 12(8), 1459; https://doi.org/10.3390/jmse12081459 - 22 Aug 2024
Viewed by 763
Abstract
The Paleogene sandstone reservoir of Huizhou Sag is an important target for deep exploration in the Pearl River Mouth Basin, South China Sea. Because of the intense volcanic activity, it had a significant impact on the development of reservoirs, making it hard to [...] Read more.
The Paleogene sandstone reservoir of Huizhou Sag is an important target for deep exploration in the Pearl River Mouth Basin, South China Sea. Because of the intense volcanic activity, it had a significant impact on the development of reservoirs, making it hard to predict. The diagenetic process of volcanogenic sediment and their influence of the reservoir have been studied by petrographic analysis, X-ray diffraction and scanning electron microscopy (SEM). Four types of volcanogenic sediment were identified: volcanic dust (<0.05 mm), volcanic rock fragments, crystal fragments (quartz and feldspar) and vitric fragments. The strong tectonic and volcanic activity of the Wenchang Formation resulted in a high content of volcanic materials, which led to significant reservoir compaction. The main sedimentary facies types are fan delta facies and lacustrine facies; the thick lacustrine mudstone can be used as high-quality source rock. After the source rock of the Wenchang Formation matured and discharged acids, feldspar and rock fragments dissolved to form dissolution pores, which effectively increases the porosity of the reservoir, but the argillaceous matrix and clay minerals produced by the volcanic dust alteration would reduce the permeability of the reservoir. With the weaker tectonic activity of the Enping Formation, the sedimentary facies changed into braided river delta, resulting in the greater componential maturity of the reservoir. Due to the relatively small impact of acidic fluids on the reservoir, the pore types of the reservoir are mainly primary pores with good physical properties. Full article
(This article belongs to the Special Issue Recent Developments and Advances in Geological Oceanography and Ocean Observation in the Pacific Ocean and Its Marginal Basins)
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35 pages, 23042 KiB  
Article
On Statistical Features of Ice Loads on Fixed and Floating Offshore Structures
by Chana Sinsabvarodom, Bernt J. Leira, Knut V. Høyland, Arvid Næss, Ilija Samardžija, Wei Chai, Siramas Komonjinda, Chatchawan Chaichana and Sheng Xu
J. Mar. Sci. Eng. 2024, 12(8), 1458; https://doi.org/10.3390/jmse12081458 - 22 Aug 2024
Cited by 1 | Viewed by 777
Abstract
Apart from the mechanisms of ice structure interactions under various scenarios of sea ice conditions and structural configurations, the selection of probabilistic models is crucial in order to cope with the loading uncertainty. Sea ice is the primary contributor to design loads in [...] Read more.
Apart from the mechanisms of ice structure interactions under various scenarios of sea ice conditions and structural configurations, the selection of probabilistic models is crucial in order to cope with the loading uncertainty. Sea ice is the primary contributor to design loads in cold regions. In many cases, ice loads present the highest magnitude. In recent years, the probabilistic study of ice thickness, ice strength coefficient, flexural strength, ice drift speed, etc., has significantly increased, corresponding to the increasing activity of offshore operations in cold regions as well as the development of instrument technology for sea ice observation. This paper reviews existing probabilistic modes of sea ice, which are used to estimate the uncertainty of ice loading with various types of offshore structures, including vertical structures, sloping structures, and stations with floating vessels. The ISO 19906 standard is employed for the probabilistic assessment of vertical and sloping structures. The interactions between ice and structures on sloping structures are considered in both the upward and downward directions. The ice resistance method is applied for station-keeping floating vessels in ice. The key parameters of sea ice properties to estimate the design loads are studied. The effect of correlation between the key parameters of ice loads is investigated. This review shows that most existing probabilistic models are proposed for the estimation of ice loading on the various types of offshore structures. Full article
(This article belongs to the Special Issue Design of Marine Structures against Ice Actions)
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19 pages, 6325 KiB  
Article
Side-Scan Sonar Image Generator Based on Diffusion Models for Autonomous Underwater Vehicles
by Feihu Zhang, Xujia Hou, Zewen Wang, Chensheng Cheng and Tingfeng Tan
J. Mar. Sci. Eng. 2024, 12(8), 1457; https://doi.org/10.3390/jmse12081457 - 22 Aug 2024
Viewed by 1051
Abstract
In the field of underwater perception and detection, side-scan sonar (SSS) plays an indispensable role. However, the imaging mechanism of SSS results in slow information acquisition and high complexity, significantly hindering the advancement of downstream data-driven applications. To address this challenge, we designed [...] Read more.
In the field of underwater perception and detection, side-scan sonar (SSS) plays an indispensable role. However, the imaging mechanism of SSS results in slow information acquisition and high complexity, significantly hindering the advancement of downstream data-driven applications. To address this challenge, we designed an SSS image generator based on diffusion models. We developed a data collection system based on Autonomous Underwater Vehicles (AUVs) to achieve stable and rich data collection. For the process of converting acoustic signals into image signals, we established an image compensation method based on nonlinear gain enhancement to ensure the reliability of remote signals. On this basis, we developed the first controllable category SSS image generation algorithm, which can generate specified data for five categories, demonstrating outstanding performance in terms of the Fréchet Inception Distance (FID) and the Inception Score (IS). We further evaluated our image generator in the task of SSS object detection, and our cross-validation experiments showed that the generated images contributed to an average accuracy improvement of approximately 10% in object detection. The experimental results validate the effectiveness of the proposed SSS image generator in generating highly similar sonar images and enhancing detection accuracy, effectively addressing the issue of data scarcity. Full article
(This article belongs to the Special Issue Autonomous Marine Vehicle Operations—2nd Edition)
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29 pages, 70114 KiB  
Article
Opening and Closure of the Sulu Sea: Revealed by Its Peripheral Subduction and Collision Processes
by Yunliu Yang, Xinong Xie, Yunlong He and Hao Chen
J. Mar. Sci. Eng. 2024, 12(8), 1456; https://doi.org/10.3390/jmse12081456 - 22 Aug 2024
Viewed by 1138
Abstract
The Sulu Sea is a small marginal sea in the western Pacific, but it is a very complex and tectonically active region, situated amidst the convergence of the Eurasian, Pacific, and India-Australian plates. Deciphering its geodynamic evolution is crucial, but our understanding of [...] Read more.
The Sulu Sea is a small marginal sea in the western Pacific, but it is a very complex and tectonically active region, situated amidst the convergence of the Eurasian, Pacific, and India-Australian plates. Deciphering its geodynamic evolution is crucial, but our understanding of its opening, closure, and tectonic history remains inadequate. The main aim of this study was to systematically study the opening and subsequent closure of the Sulu Sea though discerning tectonic unconformities, structural features, and subduction-collision tectonic zones around margins of the sea. The interpreted sections and gravity anomaly data indicate that the NE Sulu Sea has undergone Neogene extension and contraction due to subduction and collision along the northern margins of the Sulu Sea, whereas the SE Sulu Sea gradually extended from northwest to southeast during the Middle Miocene and has subsequently subducted since the Middle Miocene along the southeastern margins of the Sulu Sea. Several subduction and collision boundaries with different characteristics were developed including continent-continent collision, arc-continent collision, and ocean-arc subduction. The different margins of the Sulu Sea showed distinct asynchronous subduction and collision processes. The northern margins of the Sulu Sea can be divided into three subduction-collision tectonic zones from west to east: the Sabah-Nansha block collision has occurred in NE Borneo since the Early Miocene, followed by the SW Palawan-Cagayan arc collision in SW Palawan Island since the Middle Miocene, and the NW Palawan-Mindoro arc collision since the Late Miocene with further oblique subduction of the Philippine Sea Plate. The southeastern margins can also be divided into two subduction tectonic zones from south to east: the SE Sulu Sea has subducted southward beneath the Celebes Sea since the Middle Miocene, followed by the southeastward subduction beneath the Philippine Sea Plate since the Pliocene. Since the Miocene, the interactions among the Australia-India, the Philippine Sea, and the Eurasian plates have formed the circum-Sulu Sea subduction-collisional margins characterized by microplate collisions, deep-sea trough development, and thick sediments filling in the orogenic foreland. This study is significant for gaining insights into the opening and closure of marginal seas and the dynamics of multiple microplates in Southeast Asia. Full article
(This article belongs to the Special Issue Recent Developments and Advances in Geological Oceanography and Ocean Observation in the Pacific Ocean and Its Marginal Basins)
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18 pages, 10341 KiB  
Article
Synergistic Integration of Multiple Wave Energy Converters with Adaptive Resonance and Offshore Floating Wind Turbines through Bayesian Optimization
by Aghamarshana Meduri and HeonYong Kang
J. Mar. Sci. Eng. 2024, 12(8), 1455; https://doi.org/10.3390/jmse12081455 - 22 Aug 2024
Viewed by 825
Abstract
We developed a synergistic ocean renewable system where an array of Wave Energy Converters (WEC) with adaptive resonance was collocated with a Floating Offshore Wind Turbine (FOWT) such that the WECs, capturing wave energy through the resonance adapting to varying irregular waves, consequently [...] Read more.
We developed a synergistic ocean renewable system where an array of Wave Energy Converters (WEC) with adaptive resonance was collocated with a Floating Offshore Wind Turbine (FOWT) such that the WECs, capturing wave energy through the resonance adapting to varying irregular waves, consequently reduced FOWFT loads and turbine motions. Combining Surface-Riding WECs (SR-WEC) individually designed to feasibly relocate their natural frequency at the peak of the wave excitation spectrum for each sea state, and to obtain the highest capture width ratio at one of the frequent sea states for annual average power in a tens of kilowatts scale with a 15 MW FOWT based on a semi-submersible, Bayesian Optimization is implemented to determine the arrangement of WECs that minimize the annual representation of FOWT’s wave excitation spectra. The time-domain simulation of the system in the optimized arrangement is performed, including two sets of interactions: one set is the wind turbine dynamics, mooring lines, and floating body dynamics for FOWT, and the other set is the nonlinear power-take-off dynamics, linear mooring, and individual WECs’ floating body dynamics. Those two sets of interactions are further coupled through the hydrodynamics of diffraction and radiation. For sea states comprising Annual Energy Production, we investigate the capture width ratio of WECs, wave excitation on FOWT, and nacelle acceleration of the turbine compared to their single unit operations. We find that the optimally arranged SR-WECs reduce the wave excitation spectral area of FOWT by up to 60% and lower the turbine’s peak nacelle acceleration by nearly 44% in highly occurring sea states, while multiple WECs often produce more than the single operation, achieving adaptive resonance with a larger wave excitation spectra for those sea states. The synergistic system improves the total Annual Energy Production (AEP) by 1440 MWh, and we address which costs of Levelized Cost Of Energy (LCOE) can be reduced by the collocation. Full article
(This article belongs to the Special Issue The Control, Modeling, and the Development of Wave Energy Convertors)
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21 pages, 1531 KiB  
Article
Joint Ship Scheduling and Speed Optimization for Naval Escort Operations to Ensure Maritime Security
by Xizi Qiao, Ying Yang, Yong Jin and Shuaian Wang
J. Mar. Sci. Eng. 2024, 12(8), 1454; https://doi.org/10.3390/jmse12081454 - 22 Aug 2024
Viewed by 892
Abstract
Maritime transport is crucial for global trade, as over 80% of goods are transported by sea. Recent conflicts have exposed the vulnerability of shipping routes to disruptions. Therefore, devising an optimal plan for naval escort operations is critical to ensure that ships are [...] Read more.
Maritime transport is crucial for global trade, as over 80% of goods are transported by sea. Recent conflicts have exposed the vulnerability of shipping routes to disruptions. Therefore, devising an optimal plan for naval escort operations is critical to ensure that ships are safely escorted. This study addresses the naval escort operation problem by constructing a mixed-integer programming model that integrates escort scheduling of the warship with the speed optimization of liner ships, aiming to minimize overall cargo delay and fuel consumption costs while ensuring the protection of all ships. The results indicate that as the number of container ships increases, ships wait longer before departure with the warship, leading to a higher average delay cost per ship. For instances with a single ship type, ships have similar sailing speeds on different legs. The proposed model balances cargo delivery timeliness with carbon emission reduction, enhancing economic viability and environmental sustainability in crisis-prone maritime scenarios. Future research should explore real-time data integration and adaptive strategies to improve naval escort operations’ robustness and responsiveness. Full article
(This article belongs to the Special Issue Smart Seaport and Maritime Transport Management)
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14 pages, 5243 KiB  
Article
Localization of an Underwater Multitonal Source by Using a Vertically Distributed System in Deep Water
by Hui Li, Yingchao Zhang, Liang Yu and Zhezhen Xu
J. Mar. Sci. Eng. 2024, 12(8), 1453; https://doi.org/10.3390/jmse12081453 - 22 Aug 2024
Viewed by 524
Abstract
This paper presents a localization method for an underwater multitonal source by using a vertically distributed system in deep water. The system is composed of two kinds of nodes. One is a node at large depth, and the other is a node covering [...] Read more.
This paper presents a localization method for an underwater multitonal source by using a vertically distributed system in deep water. The system is composed of two kinds of nodes. One is a node at large depth, and the other is a node covering most of the water column. The former and latter are utilized to estimate the source range and depth, respectively. Specifically, the proposed method estimates the source range by matching the spatial arrival angle measured by the first kind of node with the replicas calculated by the acoustic model. Based on the estimation value of the source range, the second kind of node is utilized to estimate the source depth by using an incoherent time reversal method. The effectiveness of the proposed method is demonstrated through numerical simulations. The effects of the measurement error and the sound speed profile mismatch on the performance of the proposed method are also analyzed. Full article
(This article belongs to the Section Ocean Engineering)
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15 pages, 1847 KiB  
Article
Continuous Field Determination and Ecological Risk Assessment of Pb in the Yellow Sea of China
by Zhiwei Zhang, Dawei Pan, Yan Liang, Md. Abdur Rahman and Xiaofeng Wang
J. Mar. Sci. Eng. 2024, 12(8), 1452; https://doi.org/10.3390/jmse12081452 - 22 Aug 2024
Viewed by 816
Abstract
Field determination and ecological risk assessment of dissolved lead (Pb) were performed at two Yellow Sea sites in China using a continuous automated electrochemical system (CAEDS). This CAEDS instrument includes an automatic triple filter sampler and an electrochemical detection water quality analyzer, which [...] Read more.
Field determination and ecological risk assessment of dissolved lead (Pb) were performed at two Yellow Sea sites in China using a continuous automated electrochemical system (CAEDS). This CAEDS instrument includes an automatic triple filter sampler and an electrochemical detection water quality analyzer, which might be operated automatically four times daily. The dissolved Pb concentrations varied from 0.29 to 1.57 μg/L in the South Yellow Sea over 16 days and from 0.32 to 2.28 μg/L in the North Yellow Sea over 13 days. During the typhoon and algal bloom periods, the Pb concentration was as high as ten times greater than usual. According to the calculation of contamination factors (Cf) and subsequent analysis, seawater quality was classified as Grade II. Through species sensitivity distribution (SSD) method experiments and ecological risk analysis, an average risk quotient (RQ) below 1 for both areas was obtained, indicating a low-to-moderate ecological risk. This system will be helpful for Pb monitoring and assessment in seawater and contribute to the biogeochemical cycling study of Pb. Full article
(This article belongs to the Special Issue Distribution and Content of Trace Elements in Seawater and Sediments)
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23 pages, 5219 KiB  
Article
Multivariate Data Analysis of Maximum Stress Concentration Factors in FRP-Retrofitted Two-Planar KT-Joints under Axial Loads for Offshore Renewables
by Esmaeil Zavvar, Fernanda Sousa, Francisco Taveira-Pinto and Paulo Rosa Santos
J. Mar. Sci. Eng. 2024, 12(8), 1451; https://doi.org/10.3390/jmse12081451 - 22 Aug 2024
Cited by 3 | Viewed by 912
Abstract
With growing concerns about the danger of global climate change and worldwide demand for energy, the interest in the investigation and construction of renewable energy technologies has increased. Fixed platforms are a type of support structure for wind turbines composed of different types [...] Read more.
With growing concerns about the danger of global climate change and worldwide demand for energy, the interest in the investigation and construction of renewable energy technologies has increased. Fixed platforms are a type of support structure for wind turbines composed of different types of tubular joints. These structures are under different kinds of cyclic loadings in ocean environmental conditions, which must be designed and reinforced against fatigue. In the present paper, the relationships between the parameters in DKT-joints reinforced with FRP under axial loads are investigated using several models, under 16 axial loading cases, with different nondimensional parameters and different FRP materials, and orientations were generated in ANSYS (total 5184) and analyzed. The four loading conditions that cause the maximum stress concentration factors were selected. After analyzing the 1296 reinforced models, relevant data were extracted, and possible samples were created. The extracted data were used in a multivariate data analysis of maximum stress concentration factors. The Pearson correlation coefficient is utilized to study the relationship between parameters and subsequently to make predictions. To reduce the number of variables and to group the data points into clusters based on certain similarities, hierarchical and non-hierarchical classifications are used, respectively. Full article
(This article belongs to the Special Issue Development and Utilization of Offshore Renewable Energy)
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22 pages, 3275 KiB  
Review
Ship Maneuvering in Shallow and Narrow Waters: Predictive Methods and Model Development Review
by Mislav Maljković, Ivica Pavić, Toni Meštrović and Marko Perkovič
J. Mar. Sci. Eng. 2024, 12(8), 1450; https://doi.org/10.3390/jmse12081450 - 21 Aug 2024
Viewed by 1805
Abstract
The maneuverability of ships is influenced by several factors, including ship design, size, propulsion system, hull shape, and external conditions such as wind, waves, and currents. The size, shape, and arrangement of the hull, rudder, and propeller are decisive for maneuverability. Hydrodynamic forces [...] Read more.
The maneuverability of ships is influenced by several factors, including ship design, size, propulsion system, hull shape, and external conditions such as wind, waves, and currents. The size, shape, and arrangement of the hull, rudder, and propeller are decisive for maneuverability. Hydrodynamic forces such as bank effect and squat significantly impact the maneuverability of large ships in narrow channels. With the increasing trend of building ever-larger ships, the demand to evaluate the maneuvering performance of the ship at the design stage has become more critical than ever. Both experimental and computational methods are used to obtain accurate maneuvering characteristics of vessels. In this study, the methods for predicting ship maneuvering characteristics are analyzed using a systematic review based on the preferred reporting items for systematic reviews and meta-analyses (PRISMA). This article contributes to a deeper understanding of the hydrodynamic capabilities of ships and identifies possible future challenges in the field of ship hydrodynamics. The findings inform educators and the shipping industry about the importance of predicting the maneuvering performance of ships, with an emphasis on the education and training of seafarers needed to make timely decisions in critical situations. Full article
(This article belongs to the Special Issue Advances in Navigability and Mooring)
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24 pages, 12556 KiB  
Article
Evolutionary Game Strategy Research on PSC Inspection Based on Knowledge Graphs
by Chengyong Liu, Qi Wang, Banghao Xiang, Yi Xu and Langxiong Gan
J. Mar. Sci. Eng. 2024, 12(8), 1449; https://doi.org/10.3390/jmse12081449 - 21 Aug 2024
Viewed by 732
Abstract
Port state control (PSC) inspections, considered a crucial means of maritime safety supervision, are viewed by the industry as a critical line of defense ensuring the stability of the international supply chain. Due to the high level of globalization and strong regional characteristics [...] Read more.
Port state control (PSC) inspections, considered a crucial means of maritime safety supervision, are viewed by the industry as a critical line of defense ensuring the stability of the international supply chain. Due to the high level of globalization and strong regional characteristics of PSC inspections, improving the accuracy of these inspections and efficiently utilizing inspection resources have become urgent issues. The construction of a PSC inspection ontology model from top to bottom, coupled with the integration of multisource data from bottom to top, is proposed in this paper. The RoBERTa-wwm-ext model is adopted as the entity recognition model, while the XGBoost4 model serves as the knowledge fusion model to establish the PSC inspection knowledge graph. Building upon an evolutionary game model of the PSC inspection knowledge graph, this study introduces an evolutionary game method to analyze the internal evolutionary dynamics of ship populations from a microscopic perspective. Through numerical simulations and standardization diffusion evolution simulations for ship support, the evolutionary impact of each parameter on the subgraph is examined. Subsequently, based on the results of the evolutionary game analysis, recommendations for PSC inspection auxiliary decision-making and related strategic suggestions are presented. The experimental results show that the RoBERTa-wwm-ext model and the XGBoost4 model used in the PSC inspection knowledge graph achieve superior performance in both entity recognition and knowledge fusion tasks, with the model accuracies surpassing those of other compared models. In the knowledge graph-based PSC inspection evolutionary game, the reward and punishment conditions (n, f) can reduce the burden of the standardization cost for safeguarding the ship. A ship is more sensitive to changes in the detention rate β than to changes in the inspection rate α. To a certain extent, the detention cost CDC plays a role similar to that of the detention rate β. In small-scale networks, relevant parameters in the ship’s standardization game have a more pronounced effect, with detention cost CDC having a greater impact than standardization cost CS on ship strategy choice and scale-free network evolution. Based on the experimental results, PSC inspection strategies are suggested. These strategies provide port state authorities with auxiliary decision-making tools for PSC inspections, promote the informatization of maritime regulation, and offer new insights for the study of maritime traffic safety management and PSC inspections. Full article
(This article belongs to the Section Ocean Engineering)
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12 pages, 4824 KiB  
Article
An Experimental Study of Pulp-Lift Characteristics Using a High-Viscous Fluid Simulating Deep Muddy Seawater
by Sakai Onishi, Yurie Itagaki, Naoki Nakatani, Kyara Ohara, Hiroyuki Katayama and Tetsuo Yamazaki
J. Mar. Sci. Eng. 2024, 12(8), 1448; https://doi.org/10.3390/jmse12081448 - 21 Aug 2024
Viewed by 479
Abstract
Rare-earth mud and manganese nodules coexist on the seafloor around Minamitorishima Island. To investigate the feasibility of a pulp-lift system that can ensure economic efficiency by pumping manganese using rare-earth mud as the working fluid, we conducted pulp-lift experiments at a head of [...] Read more.
Rare-earth mud and manganese nodules coexist on the seafloor around Minamitorishima Island. To investigate the feasibility of a pulp-lift system that can ensure economic efficiency by pumping manganese using rare-earth mud as the working fluid, we conducted pulp-lift experiments at a head of 5.0 m using a squeeze pump for mortar pumping. In the study, we used carboxymethylcellulose (CMC) as the working fluid, which is a pseudo-plastic fluid like deep muddy seawater. We investigated the effects of the viscosity of the working fluid and the pump pulsation characteristics on lifting. The results revealed that the drag force acting on the pumped ore increased as the fluid became more viscous and the pulsation period became higher, while the reverse flow rate increased due to the negative pulsation pressure. This suggests that there is an optimum value for the viscosity of the working fluid. Full article
(This article belongs to the Special Issue Deep-Sea Mining Technologies: Recent Developments and Challenges)
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15 pages, 8155 KiB  
Article
Numerical Determination of Anisotropic Permeability for Unconsolidated Hydrate Reservoir: A DEM–CFD Coupling Method
by Ruirui Li, Zhenhua Han, Luqing Zhang, Jian Zhou, Song Wang and Fuyou Huang
J. Mar. Sci. Eng. 2024, 12(8), 1447; https://doi.org/10.3390/jmse12081447 - 21 Aug 2024
Cited by 1 | Viewed by 637
Abstract
Natural gas hydrate (NGH) is considered as a type of clean energy to replace coal and oil. During exploitation, permeability is one of the key parameters controlling production efficiency, reservoir stability, and greenhouse gas sequestration. Limited by experimental and numerical simulation tools, in [...] Read more.
Natural gas hydrate (NGH) is considered as a type of clean energy to replace coal and oil. During exploitation, permeability is one of the key parameters controlling production efficiency, reservoir stability, and greenhouse gas sequestration. Limited by experimental and numerical simulation tools, in current research, the directionality of permeability is usually ignored. In this work, a DEM–CFD coupling simulation method is developed to compute the anisotropic permeability. The sedimentary process of reservoir sediments is reconstructed, enabling the acquisition of numerical models that possess pore structures consistent with the actual fabric characteristics. The fluid transport process in various directions can be simulated with a finite element method. Taking the natural gas hydrate reservoir in the Shenhu area of the South China Sea as an example, the proposed method is validated and applied to explore the effect of compaction stress on permeability anisotropy. With the increase in compaction stress, the permeability anisotropy exhibited a rapid initial increase, followed by a sustained stabilization. The primary cause is the rearrangement of sediment particles. The non-spherical particles are driven to align in a predominantly horizontal orientation, thereby enhancing anisotropy. The proposed method provides a tool for the efficient exploitation of hydrate resources. Full article
(This article belongs to the Section Marine Energy)
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18 pages, 64907 KiB  
Article
Autonomous Underwater Vehicle Path Planning Based on Improved Salp Swarm Algorithm
by Xuan Guo, Dongming Zhao, Tingting Fan, Fei Long, Caihua Fang and Yang Long
J. Mar. Sci. Eng. 2024, 12(8), 1446; https://doi.org/10.3390/jmse12081446 - 21 Aug 2024
Viewed by 841
Abstract
Aiming at the problem of path planning for autonomous underwater vehicle (AUV) to cope with the influence of obstacles and eddies in complex marine environments, a path planning method based on an improved salp swarm algorithm (ISSA) is proposed. Firstly, the motion model [...] Read more.
Aiming at the problem of path planning for autonomous underwater vehicle (AUV) to cope with the influence of obstacles and eddies in complex marine environments, a path planning method based on an improved salp swarm algorithm (ISSA) is proposed. Firstly, the motion model of the AUV and eddy current model are constructed, including the relationship between position, velocity, attitude, and control inputs. Secondly, the improved SSA is proposed, which introduces the Levy flight strategy to enhance the algorithm’s optimization seeking ability and adds a nonlinear convergence factor to enhance the convergence ability of the algorithm. The stability and robustness of the improved algorithm are verified by test functions. Finally, the ISSA is applied to AUV path planning, which optimizes the AUV travel distance, improves the search efficiency and accuracy, and avoids the local optimum of the algorithm. The ISSA enhances the adaptive ability and robustness of the algorithm by introducing a dynamic adjustment strategy and feedback mechanism. Experimental verification is carried out using a simulated marine environment. The results show that the ISSA is better than the traditional algorithm in terms of path length as well as algorithm stability, and can effectively improve the navigation performance of AUV. Full article
(This article belongs to the Section Ocean Engineering)
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16 pages, 3482 KiB  
Article
Identification of Key Habitats of Bowhead and Blue Whales in the OSPAR Area of the North-East Atlantic—A Modelling Approach towards Effective Conservation
by Moritz Mercker, Miriam Müller, Thorsten Werner and Janos Hennicke
J. Mar. Sci. Eng. 2024, 12(8), 1445; https://doi.org/10.3390/jmse12081445 - 21 Aug 2024
Viewed by 738
Abstract
Effective protection of highly mobile and data-poor species constitutes a great challenge amid growing ocean exploitation and use. Blue whales and bowhead whales in the North-East Atlantic face several threats, such as climate change, ship strikes, pollution, and entanglement in fishing gear. Consequently, [...] Read more.
Effective protection of highly mobile and data-poor species constitutes a great challenge amid growing ocean exploitation and use. Blue whales and bowhead whales in the North-East Atlantic face several threats, such as climate change, ship strikes, pollution, and entanglement in fishing gear. Consequently, the OSPAR (“Oslo-Paris Convention for the Protection of the Marine Environment of the North-East Atlantic”) Commission recognised their need for protection and included them on the OSPAR List of Threatened and/or Declining Species. Two actions to protect these endangered species that OSPAR Contracting Parties have agreed on are (i) identifying areas that play an essential role in the species’ life cycle—subsequently called key habitats, and (ii) ensuring that those key habitats are covered by OSPAR marine protected areas (MPAs). In addition, OSPAR has committed to expanding its network of MPAs and other effective area-based conservation measures by 2030 to cover at least 30% of the OSPAR maritime area (termed the 30 × 30 target) from today’s approx. 11%. In this paper, we present the results of modelling key habitats for the bowhead and blue whales in the North-East Atlantic, including Arctic waters. Due to the sparse data situation for these species, we apply presence-only modelling methods. As this method can, in principle, produce somewhat biased results, we recommend that systematic, regular surveys on these species in Arctic waters be significantly intensified for future analyses to overcome the data paucity and allow using presence–absence/count data modelling approaches. Key habitats of blue whales were identified between Iceland and Svalbard, extending to the Azores. For bowhead whales, key habitats were identified in the Fram Strait. However, our findings show that only 11.8% of blue whale key habitats and 4.1% of bowhead whale key habitats are currently covered by OSPAR MPAs. To protect 30% of key habitats for these species in the most efficient way, our analyses suggest that suitable areas to designate new OSPAR MPAs are located around the Azores for blue whales and in the Fram Strait for bowhead whales. With these additional MPAs, OSPAR would substantially improve the protection of the two endangered species and, at the same time, progress towards its 30 × 30 target. Full article
(This article belongs to the Special Issue Population Dynamics, Movements, and Foraging Ecology of Polar Cetaceans)
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35 pages, 2392 KiB  
Article
SAPEVO-PC: Integrating Multi-Criteria Decision-Making and Machine Learning to Evaluate Navy Ships
by Igor Pinheiro de Araújo Costa, Arthur Pinheiro de Araújo Costa, Miguel Ângelo Lellis Moreira, Marcos Alexandre Castro Junior, Daniel Augusto de Moura Pereira, Carlos Francisco Simões Gomes and Marcos dos Santos
J. Mar. Sci. Eng. 2024, 12(8), 1444; https://doi.org/10.3390/jmse12081444 - 21 Aug 2024
Viewed by 818
Abstract
The selection of a navy ship is essential to guarantee a country’s sovereignty, deterrence capabilities, and national security, especially in the face of possible conflicts and diplomatic instability. This paper proposes the integration of concepts related to multi-criteria decision making (MCDM) methodology and [...] Read more.
The selection of a navy ship is essential to guarantee a country’s sovereignty, deterrence capabilities, and national security, especially in the face of possible conflicts and diplomatic instability. This paper proposes the integration of concepts related to multi-criteria decision making (MCDM) methodology and machine learning, creating the Simple Aggregation of Preferences Expressed by Ordinal Vectors—Principal Components (SAPEVO-PC) method. The proposed method proposes an evolution of the SAPEVO family, allowing the inclusion of qualitative preferences, and adds concepts from Principal Component Analysis (PCA), aiming to simplify the decision-making process, maintaining precision and reliability. We carried out a case study analyzing 32 warships and ten quantitative criteria, demonstrating the practical application and effectiveness of the method. The generated rankings reflected both subjective perceptions and the quantitative performance data of each ship. This innovative integration of qualitative data with a quantitative machine learning algorithm ensures comprehensive and robust analyses, facilitating informed and strategic decisions. The results showed a high degree of consistency and reliability, with the top and bottom rankings remaining stable across different decision-makers’ perspectives. This study highlights the potential of SAPEVO-PC to improve decision-making efficiency in complex, multi-criteria environments, contributing to the field of marine science. Full article
(This article belongs to the Section Marine Environmental Science)
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20 pages, 6408 KiB  
Review
Climate Change and Tidal Hydrodynamics of Guadalquivir Estuary and Doñana Marshes: A Comprehensive Review
by Inês Couto, Ana Picado, Marisela Des, Alejandro López-Ruiz, Manuel Díez-Minguito, Ricardo Díaz-Delgado, Rita Bastos and João Miguel Dias
J. Mar. Sci. Eng. 2024, 12(8), 1443; https://doi.org/10.3390/jmse12081443 - 21 Aug 2024
Viewed by 968
Abstract
The Doñana Protected Area, Western Europe’s largest protected wetland and UNESCO World Heritage Site, is of great importance for the Spanish biodiversity. Despite its ecological value, there is a noticeable scarcity of scientific and technical information about its hydrology and expected climate change [...] Read more.
The Doñana Protected Area, Western Europe’s largest protected wetland and UNESCO World Heritage Site, is of great importance for the Spanish biodiversity. Despite its ecological value, there is a noticeable scarcity of scientific and technical information about its hydrology and expected climate change effects, as highlighted by several authors. This article reviews the existing research on the Guadalquivir River and Doñana National Park, examining the interplay between hydrodynamics, climate change scenarios, and the potential impact of the removal of the current dike which was built to limit tidal flooding. In this context, the hydrodynamic changes predicted by a hydrodynamic model were examined under both present (including the current mean sea level and the presence of the dike) and predicted future conditions (encompassing a mean sea level rise of 0.84 m and the removal of the dike). These hydrodynamic changes were assessed in terms of the maximum predicted water levels, mean velocity, amplitude, and phase of M2 and M4 tidal constituents, tidal asymmetry, and tidal prims. The results reveal that the removal of the dike and a sea level rise will have a significant impact on the protected area, resulting in the complete flooding of the Doñana national marshes during spring tides. Such changes could have negative impacts, as increased environmental alterations would require more demanding adaptation measures. Full article
(This article belongs to the Special Issue The 10th Anniversary of JMSE - Review Collection)
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19 pages, 1621 KiB  
Article
Trajectory Tracking Control for an Underactuated AUV via Nonsingular Fast Terminal Sliding Mode Approach
by Yuan Wang and Zhenbin Du
J. Mar. Sci. Eng. 2024, 12(8), 1442; https://doi.org/10.3390/jmse12081442 - 21 Aug 2024
Viewed by 723
Abstract
This paper studies the trajectory tracking issue for an underactuated autonomous underwater vehicle (AUV) in the horizontal plane. The desired velocity–tracking error relationship (DVTER) is constructed according to the kinematics and kinetic equation, which means that the expected velocities are built so that [...] Read more.
This paper studies the trajectory tracking issue for an underactuated autonomous underwater vehicle (AUV) in the horizontal plane. The desired velocity–tracking error relationship (DVTER) is constructed according to the kinematics and kinetic equation, which means that the expected velocities are built so that the position tracking errors converge to 0. Moreover, the limitation of obtaining the expected velocity by directly differentiating the desired position values is avoided. Then, the nonsingular fast terminal sliding mode (TSM) controller is developed to ensure that the velocities converge to the designed expected values in finite time, and tracking speed is improved by comparing with the traditional nonsingular terminal sliding mode method. It turns out that the expected trajectory can be tracked by an underactuated AUV. Finally, the efficiency of the constructed control mechanism is confirmed by simulation results. Full article
(This article belongs to the Section Ocean Engineering)
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22 pages, 7491 KiB  
Article
Computational Study of Overtopping Phenomenon over Cylindrical Structures Including Mitigation Structures
by Gustavo A. Esteban, Xabier Ezkurra, Iñigo Bidaguren, Iñigo Albaina and Urko Izquierdo
J. Mar. Sci. Eng. 2024, 12(8), 1441; https://doi.org/10.3390/jmse12081441 - 20 Aug 2024
Viewed by 670
Abstract
Wave overtopping occurring in offshore wind renewable energy structures such as tension leg platforms (TLPs) or semi-submersible platforms is a phenomenon that is worth studying and preventing in order to extend the remaining useful life of the corresponding facilities. The behaviour of this [...] Read more.
Wave overtopping occurring in offshore wind renewable energy structures such as tension leg platforms (TLPs) or semi-submersible platforms is a phenomenon that is worth studying and preventing in order to extend the remaining useful life of the corresponding facilities. The behaviour of this phenomenon has been extensively reported for linear coastal defences like seawalls. However, no referenced study has treated the case of cylindrical structures typical of these applications to a similar extent. The aim of the present study is to define an empirical expression that portrays the relative overtopping rate over a vertical cylinder including a variety of bull-nose type mitigation structures to reduce the overtopping rate in the same fashion as for the linear structures characteristic of shoreline defences. Hydrodynamic interaction was studied by means of an experimentally validated numerical model applied to a non-impulsive regular wave regime and the results were compared with the case of a plain cylinder to evaluate the expected improvement in the overtopping performance. Four different types of parapets were added to the crest of the base cylinder, with different parapet height and horizontal extension, to see the influence of the geometry on the mitigation efficiency. Computational results confirmed the effectivity of the proposed solution in the overtopping reduction, though the singularity of each parapet geometry did not lead to an outstanding difference between the analysed options. Consequently, the resulting overtopping decrease in all the proposed geometries could be modelled by a unique specific Weibull-type function of the relative freeboard, which governed the phenomenon, showing a net reduction in comparison with the cylinder without the geometric modifications. In addition, the relationship between the reduced relative overtopping rate and the mean flow thickness over the vertical cylinder crest was studied as an alternative methodology to assess the potential damage caused by overtopping in real structures without complex volumetric measurements. The collection of computational results was fitted to a useful function, allowing for the definition of the overtopping discharge once the mean flow thickness was known. Full article
(This article belongs to the Section Ocean Engineering)
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25 pages, 11296 KiB  
Article
Ensuring Operational Performance and Environmental Sustainability of Marine Diesel Engines through the Use of Biodiesel Fuel
by Sergii Sagin, Oleksiy Kuropyatnyk, Oleksii Matieiko, Roman Razinkin, Tymur Stoliaryk and Oleksandr Volkov
J. Mar. Sci. Eng. 2024, 12(8), 1440; https://doi.org/10.3390/jmse12081440 - 20 Aug 2024
Viewed by 717
Abstract
This article considers the issues of ensuring operational performance and environmental sustainability of marine diesel engines by using biodiesel fuel. This research was conducted on 5S60ME-C8 MAN-B&W Diesel Group and 6DL-16 Daihatsu Diesel marine diesel engines, which are operated using RMG380 petroleum fuel [...] Read more.
This article considers the issues of ensuring operational performance and environmental sustainability of marine diesel engines by using biodiesel fuel. This research was conducted on 5S60ME-C8 MAN-B&W Diesel Group and 6DL-16 Daihatsu Diesel marine diesel engines, which are operated using RMG380 petroleum fuel and B10 and B30 biodiesel fuels. The efficiency of biofuel usage was assessed based on environmental (reduced nitrogen oxide concentration in exhaust gases) and economic (increased specific effective fuel consumption) criteria. It was found that the use of B10 and B30 biofuels provides a reduction in nitrogen oxide concentration in exhaust gases by 14.71–25.13% but at the same time increases specific effective fuel consumption by 1.55–6.01%. Optimum fuel injection advance angles were determined that ensure the best thermal energy, economic and environmental performance of diesel engines. The optimum angle of biofuel supply advance is determined experimentally and should correspond to the limits recommended by the diesel engine operating instructions. It has been proven experimentally that the use of biofuel increases the environmental sustainability of marine diesel engines by 13.75–29.42%. It increases the diesel engines environmental safety in case of emergency situations as well as accidental and short-term emissions of exhaust gases with an increased content of nitrogen oxides into the atmosphere phenomena that are possible in starting modes of diesel engine operation as well as in modes of sudden load changes. It is the increase in the environmental friendliness of marine diesel engines in the case of using biofuel that is the most positive criterion and contributes to the intensity of biofuel use in power plants of sea vessels. Full article
(This article belongs to the Special Issue Maritime Alternative Fuel and Sustainability)
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24 pages, 28638 KiB  
Article
Spatial Patterns and Evolution Features of Marine Cold Spells in the Arabian Sea during the Past Three Decades
by Qianqian Wang, Zhihua Zhang and M. James C. Crabbe
J. Mar. Sci. Eng. 2024, 12(8), 1439; https://doi.org/10.3390/jmse12081439 - 20 Aug 2024
Viewed by 1045
Abstract
Marine Cold Spell (MCS) events are cold sea states with potentially devastating impacts on marine environments and ecosystems. In this study, we analyzed different MCS types with various severe categories in the Arabian Sea during 1994–2023. We found that all four types of [...] Read more.
Marine Cold Spell (MCS) events are cold sea states with potentially devastating impacts on marine environments and ecosystems. In this study, we analyzed different MCS types with various severe categories in the Arabian Sea during 1994–2023. We found that all four types of MCS events shared a similar spatial pattern in terms of frequency, mean duration, mean intensity, and total days, but the frequency of 1-MCS events had a sharply decreasing trend compared with any other type of MCS events, indicating that ocean warming mainly led to the significant disappearance of short-period MCS events. Moreover, the MCS events in offshore Somalia had the highest occurring frequency, longest duration, largest intensity, and maximal total days, and were significantly different from those in other regions of the Arabian Sea. This is originated from that the cold–warm changes of the Somali current make larger fluctuations in the sea surface temperatures of the waters off Somalia, enhancing the occurring probability of MCS events, especially during the summers. Full article
(This article belongs to the Section Physical Oceanography)
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16 pages, 2202 KiB  
Article
Containment-Based Distributed Secondary Control for AC Shipboard Microgrids under General Noise
by Liangbin Wang, Fei Teng and Qi Xu
J. Mar. Sci. Eng. 2024, 12(8), 1438; https://doi.org/10.3390/jmse12081438 - 20 Aug 2024
Viewed by 769
Abstract
This paper investigates the secondary control problem of shipboard microgrids (SMGs) with a high percentage of new energy sources under general noise. Firstly, a polymorphic SMG model is constructed, which enables the software-defined functionality of the control strategy and allows heterogeneous distributed generators [...] Read more.
This paper investigates the secondary control problem of shipboard microgrids (SMGs) with a high percentage of new energy sources under general noise. Firstly, a polymorphic SMG model is constructed, which enables the software-defined functionality of the control strategy and allows heterogeneous distributed generators (DGs) in AC SMGs to exchange packets of different types. Secondly, due to the presence of highly dynamic and high-power loads in the SMGs, a containment-based distributed secondary control strategy is proposed to improve the flexibility of the DG voltage regulation. Then, considering the complexity and diversity of disturbances during ship navigation, general noise is introduced instead of white noise to describe various disturbances. Furthermore, based on the random differential equations (RDEs), the NOS stability of the proposed strategy is proved using Lyapunov theory, which proves the effectiveness of the containment-based distributed secondary control strategy under general noise. And, the containment error is obtained to prove that the voltage and frequency of the system converge to the convex hull spanned by the virtual leaders, ensuring the high quality of the power supply. Finally, the validity of the proposed containment-based strategy is verified by an AC SMG model with four DGs in three cases. Full article
(This article belongs to the Special Issue Advanced Technologies for New (Clean) Energy Ships)
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21 pages, 7267 KiB  
Article
Numerical Study on Hydroelastic Responses of Submersible High-Density Polyethylene Circular Seaweed Platforms Held by Single-Point Mooring System and Buoys
by Huu-Phu Nguyen, Chenxuan Huang, Brian von Herzen and Chien-Ming Wang
J. Mar. Sci. Eng. 2024, 12(8), 1437; https://doi.org/10.3390/jmse12081437 - 20 Aug 2024
Viewed by 619
Abstract
This paper investigates the hydroelastic behavior of submersible circular seaweed platforms under wave action. The circular platform comprises circular collars constructed from high-density polyethylene (HDPE) pipes and seaweed grow-out lines arranged in the radial direction. The HDPE pipes may be filled with air, [...] Read more.
This paper investigates the hydroelastic behavior of submersible circular seaweed platforms under wave action. The circular platform comprises circular collars constructed from high-density polyethylene (HDPE) pipes and seaweed grow-out lines arranged in the radial direction. The HDPE pipes may be filled with air, seawater, or pressurized seawater. The platform is kept in place by using a single-point mooring system and buoys. The platform may be lowered to over a hundred meters below the water surface to allow the seaweed to be soaked in cold nutrient-rich waters during the night and be raised to the surface for photosynthesis during the day. Also, the platform will be submerged during storms to avoid strong surface waves. The submergence is achieved by using a service vessel and surface buoys that secure the submerged platform with ropes. The hydroelastic analysis of the platform is performed using AquaSim software (v. 2.18), which has been developed specifically for hydroelastic analysis of aquaculture infrastructure. It is found that the hydroelastic response of the seaweed platform can be reduced by filling HDPE pipes with seawater and through the installation of seaweed grow-out lines. It is also found that the compressive stresses in HDPE pipes can be reduced by pressurizing the filled seawater, thereby keeping them below the allowable compressive stresses for severe sea states where pipes with unpressurized seawater show excessive compressive stresses. Full article
(This article belongs to the Special Issue Hydroelastic Behaviour of Floating Offshore Structures)
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16 pages, 3569 KiB  
Article
Stability Assessment of a Catamaran Using Sea Trials
by Nigel Matthews, Keith F. Joiner and Warren F. Smith
J. Mar. Sci. Eng. 2024, 12(8), 1436; https://doi.org/10.3390/jmse12081436 - 20 Aug 2024
Viewed by 808
Abstract
Despite the continued rise in popularity of powered catamarans for recreational and commercial applications, there is limited published research on the factors that improve or reduce a powered catamaran’s hydrodynamic stability. There is no definitive research on a catamaran’s hydrodynamic stability during a [...] Read more.
Despite the continued rise in popularity of powered catamarans for recreational and commercial applications, there is limited published research on the factors that improve or reduce a powered catamaran’s hydrodynamic stability. There is no definitive research on a catamaran’s hydrodynamic stability during a turn, and current regulations to control the risks are proving ineffective for modern speeds and power. Research on the hydrodynamic stability of catamarans was conducted using a custom-built vessel and its multi-sensor data logger. Test results confirmed serious concerns for safety regulation and acceptance testing of powered catamarans for hydrodynamic stability. The experiments have produced new insights as to why powered catamarans are at risk of capsizing and created a baseline for future testing. The work reported in this article provides an original characterisation of the multi-factor relationships that impact the instability of a powered planing catamaran. The results provide a starting point for the creation of a predictive model and approach to improve catamaran design and safety. Full article
(This article belongs to the Special Issue Novel Maritime Techniques and Technologies, and Their Safety)
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20 pages, 8549 KiB  
Article
Experimental Characterization of Stiffness of a Polyester Mooring Rope for a CFPSO
by Limei Feng, Qian Wang, Shan Wang and Sheng Xu
J. Mar. Sci. Eng. 2024, 12(8), 1435; https://doi.org/10.3390/jmse12081435 - 20 Aug 2024
Viewed by 894
Abstract
Synthetic ropes are increasingly favored for use in offshore systems. Accurate predictions of the coupled hydrodynamic performance and structural response of offshore structures depends on a thorough understanding of the nonlinear characteristics of fiber materials. The objective of this study is to experimentally [...] Read more.
Synthetic ropes are increasingly favored for use in offshore systems. Accurate predictions of the coupled hydrodynamic performance and structural response of offshore structures depends on a thorough understanding of the nonlinear characteristics of fiber materials. The objective of this study is to experimentally characterize the stiffness of a polyester mooring rope for a cylindrical floating production storage and offloading system. The quasi-static stiffness of the ropes and aged ropes after installation and the dynamic stiffness in various loading conditions were computed based on sub-rope tests following the guidelines from the American Bureau of Shipping. The quasi-static stiffness curves exhibited a linear decrease in values as the logarithm of the loading period (in minutes) increased. The dynamic stiffness was, in general, much higher than the quasi-static stiffness. The dynamic stiffness under various loading conditions revealed the complexities of the mechanical properties of polyester rope. Parameters such as the mean load, load amplitude, loading period, and loading cycles all had a notable impact. More tests are required to have a better understanding of their effects. Full article
(This article belongs to the Special Issue Hydrodynamics and Mooring Analysis of Floating Structures)
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19 pages, 2477 KiB  
Article
Variations in the Abundance, Biodiversity, and Assemblage Structure of Larval Fish in the Restricted Waters of the Wang-an Light Fishery off Penghu, Taiwan
by Lu-Chi Chen, Chia-Wei Hu, Jinn-Shing Weng, Kuo-Wei Lan, Chen-Te Tseng and Hernyi Justin Hsieh
J. Mar. Sci. Eng. 2024, 12(8), 1434; https://doi.org/10.3390/jmse12081434 - 19 Aug 2024
Viewed by 678
Abstract
This study examined the abundance, biodiversity, and assemblage structure of larval fish inside and outside the restricted fishing zone of the Wang-an light fishery, which is located off Penghu, Taiwan. A total of 97 taxa belonging to 48 families of larval fish were [...] Read more.
This study examined the abundance, biodiversity, and assemblage structure of larval fish inside and outside the restricted fishing zone of the Wang-an light fishery, which is located off Penghu, Taiwan. A total of 97 taxa belonging to 48 families of larval fish were identified through plankton tows conducted during the present investigation. Upeneus japonicus from the Mullidae family emerged as the dominant species in the surveyed area. Diurnal variation in larval fish abundance was evident, with higher abundance observed at night-time than during daytime. However, no significant difference was observed between the larval fish abundance inside and outside the restricted zone. Moreover, fish egg abundance and larval fish biodiversity did not exhibit notable differences between sampling locations or times. Cluster analysis revealed the presence of two groups of seasonal species. The major species in the spring group were Abudefduf vaigiensis and Pomacentrus coelestis, which prefer a low-temperature environment. The major species in the summer group was U. japonicus, which prefers a high-temperature environment. The seasonal succession of water masses under the influence of monsoon activity likely contributed to the observed grouping patterns of larval fish assemblages in the study area. These patterns were closely linked to the marine environmental conditions in this area. The study outcomes provide scientific insights and recommendations regarding the importance and benefits of establishing a restricted fishing zone for sustaining fishery resources. Full article
(This article belongs to the Special Issue Advances in Marine Biodiversity and Conservation)
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18 pages, 9476 KiB  
Article
Grabbing Path Extraction of Deep-Sea Manganese Nodules Based on Improved YOLOv5
by Chunlu Cui, Penglei Ma, Qianli Zhang, Guijie Liu and Yingchun Xie
J. Mar. Sci. Eng. 2024, 12(8), 1433; https://doi.org/10.3390/jmse12081433 - 19 Aug 2024
Viewed by 847
Abstract
In an effort to enhance the efficiency and accuracy of deep-sea manganese nodule grasping behavior by a manipulator, a novel approach employing an improved YOLOv5 algorithm is proposed for the extraction of the shortest paths to manganese nodules targeted by the manipulator. The [...] Read more.
In an effort to enhance the efficiency and accuracy of deep-sea manganese nodule grasping behavior by a manipulator, a novel approach employing an improved YOLOv5 algorithm is proposed for the extraction of the shortest paths to manganese nodules targeted by the manipulator. The loss function of YOLOv5s has been improved by integrating a dual loss function that combines IoU and NWD, resulting in better accuracy for loss calculations across different target sizes. Additionally, substituting the initial C3 module in the network backbone with a C2f module is intended to improve the flow of gradient information while reducing computational demands. Once the geometric center of the manganese nodules is identified with the improved YOLOv5 algorithm, the next step involves planning the most efficient route for the manipulator to pick up the nodules using an upgraded elite strategy ant colony algorithm. Enhancements to the ACO algorithm consist of implementing an elite strategy and progressively decreasing the number of ants in each round. This method reduces both the number of iterations and the time required for each iteration, while also preventing the occurrence of local optimal solutions. The experimental findings indicate that the improved YOLOv5s detection algorithm boosts detection accuracy by 2.3%. Furthermore, when there are fewer than 30 target planning points, the improved algorithm requires, on average, 24% fewer iterations than the ACO algorithm to determine the shortest path. Additionally, the speed of calculation for each iteration is quicker while still providing the optimal solution. Full article
(This article belongs to the Topic Applications and Development of Underwater Robotics and Underwater Vision Technology)
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17 pages, 12049 KiB  
Article
The Mesozoic Subduction Zone over the Dongsha Waters of the South China Sea and Its Significance in Gas Hydrate Accumulation
by Pibo Su, Zhongquan Zhao and Kangshou Zhang
J. Mar. Sci. Eng. 2024, 12(8), 1432; https://doi.org/10.3390/jmse12081432 - 19 Aug 2024
Viewed by 794
Abstract
The Mesozoic subduction zone over the Dongsha Waters (DSWs) of the South China Sea (SCS) is a part of the westward subduction of the ancient Pacific plate. Based on the comprehensive interpretation of deep reflection seismic profile data and polar magnetic anomaly data, [...] Read more.
The Mesozoic subduction zone over the Dongsha Waters (DSWs) of the South China Sea (SCS) is a part of the westward subduction of the ancient Pacific plate. Based on the comprehensive interpretation of deep reflection seismic profile data and polar magnetic anomaly data, and the zircon dating results of igneous rocks drilled from well LF35-1-1, the Mesozoic subduction zone in the northeast SCS is accurately identified, and a Mesozoic subduction model is proposed. The accretion wedges, trenches, and igneous rock zones together form the Mesozoic subduction zone. The evolution of the Mesozoic subduction zone can be divided into two stages: continental subduction during the Late Jurassic and continental collision during the late Cretaceous. The Mesozoic subduction zone controlled the structural pattern and evolution of the Chaoshan depression (CSD) during the Mesozoic and Neogene eras. The gas source of the hydrate comes from thermogenic gas, which is accompanied by mud diapir activity and migrates along the fault. The gas accumulates to form gas hydrates at the bottom of the stable domain; BSR can be seen above the mud diapir structure; that is, hydrate deposits are formed under the influence of mud diapir structures, belonging to a typical leakage type genesis model. Full article
(This article belongs to the Special Issue Advances in Marine Gas Hydrate Exploration and Discovery)
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1 pages, 171 KiB  
Correction
Correction: Feistel, R.; Hellmuth, O. Irreversible Thermodynamics of Seawater Evaporation. J. Mar. Sci. Eng. 2024, 12, 166
by Rainer Feistel and Olaf Hellmuth
J. Mar. Sci. Eng. 2024, 12(8), 1431; https://doi.org/10.3390/jmse12081431 - 19 Aug 2024
Viewed by 612
Abstract
A sign error has been found in Equation (32) of the paper [...]
JW=−Dfln1+SMW1−SMS+ln⁡ψfxV,T,p[...] Full article
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