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J. Mar. Sci. Eng., Volume 12, Issue 10 (October 2024) – 203 articles

Cover Story (view full-size image): The warming of the Mediterranean is already well known, but information is still lacking on its seasonal/annual-to-multidecadal scale and its distribution across water masses, including deep water. New temporal and spatial evidence of this thermal variability has been presented in the Tyrrhenian Sea, with 20-year continuous monitoring by eXpendable BathyThermographs along a fixed route. The warm signal, coming from the Levantine basin and entering from the south, influences the entire Tyrrhenian basin, rapidly spreading towards the north, based on its topography, circulation, strong stratification and climate variability. This observed warming is consistent with trends for the whole Mediterranean Sea. However, around 2014, a shift towards a new warmer state was detected, with average values significantly higher than the previous period, especially from 100 to 450 m depth. View this paper
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14 pages, 3908 KiB  
Article
Numerical Study on Evaluation of Environmental DNA Approach for Estimating Fish Abundance and Distribution in Semi-Enclosed Bay
by Seongsik Park, Seokjin Yoon and Kyunghoi Kim
J. Mar. Sci. Eng. 2024, 12(10), 1891; https://doi.org/10.3390/jmse12101891 - 21 Oct 2024
Viewed by 607
Abstract
Despite efforts to use environmental DNA (eDNA), accurately quantifying fish populations remains a challenge. A recent eDNA approach provided reliable estimates of coastal fish population abundance, but it was not as effective for assessing spatial distribution due to a lack of eDNA samples [...] Read more.
Despite efforts to use environmental DNA (eDNA), accurately quantifying fish populations remains a challenge. A recent eDNA approach provided reliable estimates of coastal fish population abundance, but it was not as effective for assessing spatial distribution due to a lack of eDNA samples relative to the study area. Therefore, we conducted a numerical case study to evaluate the ability of the eDNA approach to estimate fish (Jack mackerel) abundance and distribution based on the number of eDNA samples in a semi-enclosed bay (Jinhae Bay). Our study revealed that the eDNA approach can provide reliable estimates of fish abundance, even with knowledge of the eDNA concentration in just 1% of the study area. However, for estimating spatial distribution and fish school, significant estimates were obtained only when the eDNA concentration was identified in more than 70% of the study area. Our results confirm that the eDNA approach can reflect fish abundance but has limitations in estimating fish distribution. Full article
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16 pages, 7706 KiB  
Article
Vortex-Induced Vibration Performance Analysis of Long-Span Sea-Crossing Bridges Using Unsupervised Clustering
by Tao Chen, Yi-Lun Wu, Xiao-Mei Yang and Shu-Han Yang
J. Mar. Sci. Eng. 2024, 12(10), 1890; https://doi.org/10.3390/jmse12101890 - 21 Oct 2024
Viewed by 478
Abstract
Vortex-induced vibration is a type of wind-induced vibration occurring frequently in large-span sea-crossing bridges under relatively low wind speeds, posing a threat to the structural fatigue performance and driving comfort. Identifying the instantaneous occurrence moments of vortex-induced vibration is a prerequisite for establishing [...] Read more.
Vortex-induced vibration is a type of wind-induced vibration occurring frequently in large-span sea-crossing bridges under relatively low wind speeds, posing a threat to the structural fatigue performance and driving comfort. Identifying the instantaneous occurrence moments of vortex-induced vibration is a prerequisite for establishing a data-driven prediction model for vortex-induced vibration, and it is of great significance for the monitoring and early warning of vortex-induced vibration performance in bridges. To automatically detect the occurrence moments of vortex-induced vibration and establish a correlation model between vortex-induced vibration amplitude and environmental factors, this study proposes a fuzzy C-means clustering-based classification method. In order to detect the occurrence moments of vortex-induced vibration more finely, only short-term or even instantaneous structural vibration indicators were selected and transformed for distribution as clustering features. The entire detection process could be carried out unsupervised, reducing the manual cost of obtaining vortex-induced vibration information from massive monitoring data. Finally, actual vortex-induced vibration test data from a certain overseas bridge was utilized to verify the feasibility of this method. Based on the classification results, the correlation between vortex-induced vibration amplitude and environmental variables was determined, providing valuable guidance for predicting vortex-induced vibration amplitudes. Full article
(This article belongs to the Section Coastal Engineering)
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17 pages, 9091 KiB  
Article
An Updated Analysis of Long-Term Sea Level Change in China Seas and Their Adjacent Ocean with T/P: Jason-1/2/3 from 1993 to 2022
by Lingling Wu, Jiajia Yuan, Zhendong Wu, Liyu Hu, Jiaojiao Zhang and Jianpin Sun
J. Mar. Sci. Eng. 2024, 12(10), 1889; https://doi.org/10.3390/jmse12101889 - 21 Oct 2024
Viewed by 486
Abstract
This study analyzes sea level changes (SLCs) in China seas and their adjacent ocean (CSO) using data from the TOPEX/Poseidon and Jason-1/2/3 satellite altimetry missions from 1993 to 2022. A 30-year time series of sea level anomalies (SLAs) is established, with trends, spatial [...] Read more.
This study analyzes sea level changes (SLCs) in China seas and their adjacent ocean (CSO) using data from the TOPEX/Poseidon and Jason-1/2/3 satellite altimetry missions from 1993 to 2022. A 30-year time series of sea level anomalies (SLAs) is established, with trends, spatial distribution, and periodicities analyzed through least squares linear fitting, Kriging interpolation, and wavelet analysis. The average yearly sea level rise in the CSO is 3.87 mm, with specific rates of 4.15 mm/yr in the Bohai Sea, 3.96 mm/yr in the Yellow Sea, 3.54 mm/yr in the East China Sea, and 4.09 mm/yr in the South China Sea. This study examines the spatiotemporal variations in SLAs and identifies an annual primary cycle, along with a new periodicity of 11 years. Utilizing 30 years of satellite observation data, particularly the newer Jason-3 satellite data, this reanalysis reveals new findings related to cycles. Overall, the research updates previous studies and provides valuable insights for further investigations into China’s marine environment. Full article
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16 pages, 3878 KiB  
Article
Analysis of Impact of Control Strategies on Integrated Electric Propulsion System Performance During Icebreaking Process
by Liang Li, Ping Yi, Shen Wu, Shuai Huang and Tie Li
J. Mar. Sci. Eng. 2024, 12(10), 1888; https://doi.org/10.3390/jmse12101888 - 21 Oct 2024
Viewed by 436
Abstract
Developing an efficient power system is an important way for icebreakers to respond to high maneuverability and strong fluctuation loads under icebreaking conditions. The performance of power systems under short-period, regularly fluctuating load-sea conditions has been intensively studied. However, the performance of the [...] Read more.
Developing an efficient power system is an important way for icebreakers to respond to high maneuverability and strong fluctuation loads under icebreaking conditions. The performance of power systems under short-period, regularly fluctuating load-sea conditions has been intensively studied. However, the performance of the power system in the face of a long-period, stochastic multi-frequency fluctuation icebreaking process has not been fully explored, especially the parameter uncertainty and battery cycle life. In this study, an integrated electric propulsion system with an optimal control strategy is suggested for improving the power system’s dynamic performance and battery cycle life. First, an energy flow model with a diesel–electric unit as the main body and coupled energy storage system/hybrid energy storage system has been constructed. A comparative analysis of rule-based and optimization-based energy management strategies has been performed, and an optimized strategy with dynamic programming as global regulation at the upper level and model predictive control at the lower level is suggested to integrate the slow and fast dynamic powers and achieve adaptability to strong fluctuation loads. In this control strategy, the uncertainties of energy storage system/hybrid energy storage system parameters have been introduced to eliminate their impact on the system performance. Then, the icebreaking process with multi-frequency fluctuation has been simulated, and the hybrid energy storage system with battery and supercapacitor is recommended to reach multi-objective with the lowest power fluctuation of diesel–electric unit, highest efficiency, and the minimum battery degradation. Finally, the fuel oil consumption and emissions of the hybrid energy storage system have been discussed, and the optimized strategy can save fuel oil by up to 5.33% and reduce the CO2 emission by 22% during the icebreaking process, exhibiting great potential in the environmental friendliness and significant advantages in terms of low fuel oil consumption. Full article
(This article belongs to the Section Ocean Engineering)
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5 pages, 185 KiB  
Editorial
Recent Advances in Geological Oceanography II
by George Kontakiotis, Assimina Antonarakou and Dmitry A. Ruban
J. Mar. Sci. Eng. 2024, 12(10), 1887; https://doi.org/10.3390/jmse12101887 - 21 Oct 2024
Viewed by 478
Abstract
Marine geology is a well-known [...] Full article
(This article belongs to the Special Issue Recent Advances in Geological Oceanography II)
32 pages, 7913 KiB  
Article
Underwater Small Target Classification Using Sparse Multi-View Discriminant Analysis and the Invariant Scattering Transform
by Andrew Christensen, Ananya Sen Gupta and Ivars Kirsteins
J. Mar. Sci. Eng. 2024, 12(10), 1886; https://doi.org/10.3390/jmse12101886 - 21 Oct 2024
Viewed by 502
Abstract
Sonar automatic target recognition (ATR) systems suffer from complex acoustic scattering, background clutter, and waveguide effects that are ever-present in the ocean. Traditional signal processing techniques often struggle to distinguish targets when noise and complicated target geometries are introduced. Recent advancements in machine [...] Read more.
Sonar automatic target recognition (ATR) systems suffer from complex acoustic scattering, background clutter, and waveguide effects that are ever-present in the ocean. Traditional signal processing techniques often struggle to distinguish targets when noise and complicated target geometries are introduced. Recent advancements in machine learning and wavelet theory offer promising directions for extracting informative features from sonar return data. This work introduces a feature extraction and dimensionality reduction technique using the invariant scattering transform and Sparse Multi-view Discriminant Analysis for identifying highly informative features in the PONDEX09/PONDEX10 datasets. The extracted features are used to train a support vector machine classifier that achieves an average classification accuracy of 97.3% using six unique targets. Full article
(This article belongs to the Section Ocean Engineering)
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17 pages, 6863 KiB  
Article
YOLO-GE: An Attention Fusion Enhanced Underwater Object Detection Algorithm
by Qiming Li and Hongwei Shi
J. Mar. Sci. Eng. 2024, 12(10), 1885; https://doi.org/10.3390/jmse12101885 - 21 Oct 2024
Viewed by 721
Abstract
Underwater object detection is a challenging task with profound implications for fields such as aquaculture, marine ecological protection, and maritime rescue operations. The presence of numerous small aquatic organisms in the underwater environment often leads to issues of missed detections and false positives. [...] Read more.
Underwater object detection is a challenging task with profound implications for fields such as aquaculture, marine ecological protection, and maritime rescue operations. The presence of numerous small aquatic organisms in the underwater environment often leads to issues of missed detections and false positives. Additionally, factors such as the water quality result in weak target features, which adversely affect the extraction of target feature information. Furthermore, the lack of illumination underwater causes image blur and low contrast, thereby increasing the difficulty of the detection task. To address these issues, we propose a novel underwater object detection algorithm called YOLO-GE (GCNet-EMA). First, we introduce an image enhancement module to mitigate the impact of underwater image quality issues on the detection task. Second, a high-resolution feature layer is added into the network to improve the problems of missed detections and false positives for small targets. Third, we propose GEBlock, an attention-based fusion module that captures long-range contextual information and suppresses noise from lower-level feature layers. Finally, we combine an adaptive spatial fusion module with the detection head to filter out conflicting feature information from different feature layers. Experiments on the UTDAC2020, DUO and RUOD datasets show that the proposed method achieves an optimal detection accuracy. Full article
(This article belongs to the Section Ocean Engineering)
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14 pages, 11579 KiB  
Article
Role of Organic Matter Present in the Water Column on Turbidity Flows
by Shaheen Akhtar Wahab, Waqas Ali, Claire Chassagne and Rudy Helmons
J. Mar. Sci. Eng. 2024, 12(10), 1884; https://doi.org/10.3390/jmse12101884 - 21 Oct 2024
Viewed by 489
Abstract
Turbidity flows are known to be affected by the density difference between sediment plumes and the surrounding water. However, besides density, other factors could lead to changes in flow propagation. Such a factor is the presence of suspended organic matter. Recently, it was [...] Read more.
Turbidity flows are known to be affected by the density difference between sediment plumes and the surrounding water. However, besides density, other factors could lead to changes in flow propagation. Such a factor is the presence of suspended organic matter. Recently, it was found that flocculation does occur within plumes upon release of a sediment/organic matter mixture in a lock exchange flume. In the present study, mineral sediment (illite clay) was released into the outflow compartment containing water and synthetic organic matter (polyacrylamide flocculant). Even though the density of water was barely affected by the presence of flocculant, flow head velocity was observed to be larger in the presence of flocculant than without. Samples taken at different positions in the flume indicated that flocs were created during the small current propagation time (about 30–60 s) and that their sizes were larger with higher flocculant dosage. The size of flocs depended on their positions in the flow: flocs sampled in the body part of the flow were larger than the ones sampled at the bottom. All these properties are discussed as a function of sediment–flocculant interactions. Full article
(This article belongs to the Special Issue Advanced Studies in Marine Geomechanics and Geotechnics)
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23 pages, 7594 KiB  
Article
Spatiotemporal Point–Trace Matching Based on Multi-Dimensional Feature Fuzzy Similarity Model
by Yi Liu, Ruijie Wu, Wei Guo, Liang Huang, Kairui Li, Man Zhu and Pieter van Gelder
J. Mar. Sci. Eng. 2024, 12(10), 1883; https://doi.org/10.3390/jmse12101883 - 20 Oct 2024
Viewed by 500
Abstract
Identifying ships is essential for maritime situational awareness. Automatic identification system (AIS) data and remote sensing (RS) images provide information on ship movement and properties from different perspectives. This study develops an efficient spatiotemporal association approach that combines AIS data and RS images [...] Read more.
Identifying ships is essential for maritime situational awareness. Automatic identification system (AIS) data and remote sensing (RS) images provide information on ship movement and properties from different perspectives. This study develops an efficient spatiotemporal association approach that combines AIS data and RS images for point–track association. Ship detection and feature extraction from the RS images are performed using deep learning. The detected image characteristics and neighboring AIS data are compared using a multi-dimensional feature similarity model that considers similarities in space, time, course, and attributes. An efficient spatial–temporal association analysis of ships in RS images and AIS data is achieved using the interval type-2 fuzzy system (IT2FS) method. Finally, optical images with different resolutions and AIS records near the waters of Yokosuka Port and Kure are collected to test the proposed model. The results show that compared with the multi-factor fuzzy comprehensive decision-making method, the proposed method can achieve the best performance (F1 scores of 0.7302 and 0.9189, respectively, on GF1 and GF2 images) while maintaining a specific efficiency. This work can realize ship positioning and monitoring based on multi-source data and enhance maritime situational awareness. Full article
(This article belongs to the Section Ocean Engineering)
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22 pages, 647 KiB  
Article
Adaptive Event-Triggered Consensus Control of Nonlinear Multi-Agent Systems via Output Feedback Methodology: An Application to Energy Efficient Consensus of AUVs
by Muhammad Arsal, Muhammad Rehan, Muhammad Khalid and Keum-Shik Hong
J. Mar. Sci. Eng. 2024, 12(10), 1882; https://doi.org/10.3390/jmse12101882 - 20 Oct 2024
Viewed by 629
Abstract
For dealing with the energy consumption in multi-agent systems (MASs), an event-triggered (ET) methodology is promising, which relies on the activation of communication devices only when communication of data is needed. This paper explores the leaderless consensus for nonlinear MASs using an adaptive [...] Read more.
For dealing with the energy consumption in multi-agent systems (MASs), an event-triggered (ET) methodology is promising, which relies on the activation of communication devices only when communication of data is needed. This paper explores the leaderless consensus for nonlinear MASs using an adaptive ET approach via an output feedback methodology. This adaptive ET scheme is preferred as it can adapt to the environment through setting a communication threshold. The proposed approach renders the observed states of agents by use of nonlinear observers in an output feedback control dilemma, making it more practical. Simple Luenberger observers are developed to avoid the problem of always measuring agents’ states. The strategy of adaptive ET-based control is employed to minimize resource use and information transmission. Design conditions for the observer-based adaptive ET consensus control of nonlinear MASs have been derived via a Lyapunov function, containing state estimation error, consensus error, adaptation term, and nonlinearity bounds. In contrast to the existing methods, the present approach applies a more practical output feedback schema, uses adaptive ET proficiency, and deals with nonlinear agents. An example of a formation of autonomous underwater vehicles achieving the basic consensus realization between displacement and velocity is included to illustrate the viability of the resultant approach. Full article
(This article belongs to the Section Ocean Engineering)
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18 pages, 7440 KiB  
Article
A Novel Method for the Estimation of Sea Surface Wind Speed from SAR Imagery
by Zahra Jafari, Pradeep Bobby, Ebrahim Karami and Rocky Taylor
J. Mar. Sci. Eng. 2024, 12(10), 1881; https://doi.org/10.3390/jmse12101881 - 20 Oct 2024
Viewed by 629
Abstract
Wind is one of the important environmental factors influencing marine target detection as it is the source of sea clutter and also affects target motion and drift. The accurate estimation of wind speed is crucial for developing an efficient machine learning (ML) model [...] Read more.
Wind is one of the important environmental factors influencing marine target detection as it is the source of sea clutter and also affects target motion and drift. The accurate estimation of wind speed is crucial for developing an efficient machine learning (ML) model for target detection. For example, high wind speeds make it more likely to mistakenly detect clutter as a marine target. This paper presents a novel approach for the estimation of sea surface wind speed (SSWS) and direction utilizing satellite imagery through innovative ML algorithms. Unlike existing methods, our proposed technique does not require wind direction information and normalized radar cross-section (NRCS) values and therefore can be used for a wide range of satellite images when the initial calibrated data are not available. In the proposed method, we extract features from co-polarized (HH) and cross-polarized (HV) satellite images and then fuse advanced regression techniques with SSWS estimation. The comparison between the proposed model and three well-known C-band models (CMODs)—CMOD-IFR2, CMOD5N, and CMOD7—further indicates the superior performance of the proposed model. The proposed model achieved the lowest Root Mean Squared Error (RMSE) and Mean Absolute Error (MAE), with values of 0.97 m/s and 0.62 m/s for calibrated images, and 1.37 and 0.97 for uncalibrated images, respectively, on the RCM dataset. Full article
(This article belongs to the Special Issue Remote Sensing Applications in Marine Environmental Monitoring)
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30 pages, 10656 KiB  
Review
A Comprehensive Review of an Underwater Towing Cable Array: A Discussion on the Dynamic Characteristics of the Towing Cable Array During the Outspread Process
by Dapeng Zhang, Yangyang Luo, Yi Zhang, Yunsheng Ma, Keqiang Zhu and Shengqing Zeng
J. Mar. Sci. Eng. 2024, 12(10), 1880; https://doi.org/10.3390/jmse12101880 - 20 Oct 2024
Viewed by 464
Abstract
Towing cable arrays have made significant contributions across various fields, and their outspread process is crucial for realizing their functionalities. However, research on the dynamic characterization of the outspread process of towed cable arrays lacks systematic organization. This paper reviews, organizes, and analyzes [...] Read more.
Towing cable arrays have made significant contributions across various fields, and their outspread process is crucial for realizing their functionalities. However, research on the dynamic characterization of the outspread process of towed cable arrays lacks systematic organization. This paper reviews, organizes, and analyzes the outspread process of towing cable arrays, drawing on relevant models, case studies, and structural features. It ingeniously applies concepts from parachute outspread to the analysis of towing-cable-array deployment. The study systematically examines the deployment of towing cable arrays under varying cable lengths, wave conditions, and the interactions between line arrays. The goal is to integrate existing research on the outspread of towing cable arrays, addressing the gaps in the description of this process and providing a comprehensive analysis of the outspread characteristics under different conditions. Additionally, this paper identifies current limitations in this area and provides insights for future developments. Furthermore, it explores the potential application of AI to address these challenges. The aim of this paper is to contribute meaningfully to this field. Full article
(This article belongs to the Special Issue Advances in the Performance of Ships and Offshore Structures)
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32 pages, 10733 KiB  
Article
Energy Use and Carbon Footprint Assessment in Retrofitting a Novel Energy Saving Device to a Ship
by Eren Uyan, Mehmet Atlar and Osman Gürsoy
J. Mar. Sci. Eng. 2024, 12(10), 1879; https://doi.org/10.3390/jmse12101879 - 19 Oct 2024
Viewed by 614
Abstract
The Gate rudder system (GRS) was recently introduced as an innovative energy-saving device (ESD) for ships, and it is the most attractive ESD currently used in the market, with double figures of fuel savings in full-scale (>10–35%) compared with a ship with a [...] Read more.
The Gate rudder system (GRS) was recently introduced as an innovative energy-saving device (ESD) for ships, and it is the most attractive ESD currently used in the market, with double figures of fuel savings in full-scale (>10–35%) compared with a ship with a conventional rudder system (CRS). Although there are few new ship applications of GRS, the recently completed EC-H2020 GATERS project successfully demonstrated its unique energy-saving and manoeuvrability benefits as a “retrofit” solution for an existing general cargo vessel for the first time. The project results suggested that the GRS holds significant potential for retrofitting existing ships to enhance fuel efficiency (~35%) and improve manoeuvrability. Nevertheless, the application was a comprehensive undertaking requiring various work tasks such as component manufacturing, removing existing systems, and modification and upgrading works, with substantial energy consumption and environmental impacts. Therefore, it was insightful to study energy use and environmental impacts in a GRS retrofit process. This study developed and implemented a comprehensive energy consumption and carbon footprint assessment framework for the GRS retrofit in the GATERS project. A detailed assessment of energy consumption and related carbon emissions was performed during the major stages of manufacturing, system removals, and modifications and assembly in the GRS retrofit. Also, the potential savings in energy use and emissions were addressed. The results demonstrated that the manufacturing stage was the most energy-intensive phase, being responsible for 91.4% of total electricity and 46.7% of fuel-based thermal energy use. The system removals accounted for 53.3% of the fuel-based thermal energy, whereas the modification and assembly work accounted for about 7.7% of the total electricity use. Additionally, various measures such as clean electrification, energy efficiency, mould/tool reuse, and component reuse to reduce the energy consumption and related carbon emissions in future GRS retrofit applications were addressed and discussed together with their reduction potentials. Full article
(This article belongs to the Special Issue Advances in Ships and Marine Structures)
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32 pages, 21139 KiB  
Article
Numerical Simulation on Two-Dimensional Dual-Zone Axisymmetric Consolidation for Marine Soft Soil Improved by PVTD Considering Interfacial Thermal Resistance
by Kejie Tang, Minjie Wen, Yi Tian, Xiaoqiang Gu, Wenbing Wu, Yiming Zhang, Guoxiong Mei, Pan Ding, Yuan Tu, Anyuan Sun and Kaifu Liu
J. Mar. Sci. Eng. 2024, 12(10), 1878; https://doi.org/10.3390/jmse12101878 - 19 Oct 2024
Viewed by 442
Abstract
Prefabricated vertical drains combined with heating is a new approach to improving the mechanical properties of soft clay foundations. Rising temperatures cause the formation of concentric and radially aligned soil regions with distinct heterogeneous characteristics. This results in incomplete contact between adjacent soil [...] Read more.
Prefabricated vertical drains combined with heating is a new approach to improving the mechanical properties of soft clay foundations. Rising temperatures cause the formation of concentric and radially aligned soil regions with distinct heterogeneous characteristics. This results in incomplete contact between adjacent soil layers, with the water in the interstices impeding heat transfer and manifesting as a thermal resistance effect. Based on the theory of thermo-hydro-mechanical coupling, a two-dimensional dual-zone axisymmetric marine soft soil model improved by a prefabricated vertical thermo-drain has been established. A generalized incomplete thermal contact model has been proposed to describe the thermal resistance effect at the interface of concentric soil regions. The effectiveness of the numerical solution presented in this paper is verified by comparison with semi-analytical solutions and model experiments. The thermal consolidation characteristics of concentric regions of soil at various depths under different thermal contact models were discussed by comprehensively analyzing the effects of different parameters under various thermal contact models. The outcomes indicate that the generalized incomplete thermal contact model provides a more accurate description of the radial thermal consolidation characteristics of concentric regions of soil. The influence of the thermal conductivity coefficient on the consolidation characteristics of the concentric regions soil is related to the thermal resistance effect. Full article
(This article belongs to the Section Coastal Engineering)
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15 pages, 5474 KiB  
Article
Modulation Classification of Underwater Communication Signals Based on Channel Estimation
by Xiaodan Yang, Zulin Wang, Tongsheng Shen and Dexin Zhao
J. Mar. Sci. Eng. 2024, 12(10), 1877; https://doi.org/10.3390/jmse12101877 - 19 Oct 2024
Viewed by 496
Abstract
Classifying modulated signals for non-cooperative underwater acoustic communication is challenging due to signal distortion caused by fading and multipath effects in the underwater acoustic channel. Our proposed method utilizes channel estimation parameters to measure and correct signal distortion, thereby enhancing the recognition performance [...] Read more.
Classifying modulated signals for non-cooperative underwater acoustic communication is challenging due to signal distortion caused by fading and multipath effects in the underwater acoustic channel. Our proposed method utilizes channel estimation parameters to measure and correct signal distortion, thereby enhancing the recognition performance of the received signal. Modulation classification experiments were conducted on a public dataset with various modulation schemes, as well as on the same dataset with simulated underwater acoustic channels. The results indicate that our method effectively mitigates the impact of the underwater acoustic channel on modulation signal classification, improves recognition accuracy, and is broadly applicable to a wide range of machine learning classifiers. Finally, we validated these findings using real underwater communication data. Full article
(This article belongs to the Section Physical Oceanography)
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24 pages, 4718 KiB  
Article
Combined Freak Wave, Wind, and Current Effects on the Dynamic Responses of Offshore Triceratops
by Nagavinothini Ravichandran
J. Mar. Sci. Eng. 2024, 12(10), 1876; https://doi.org/10.3390/jmse12101876 - 18 Oct 2024
Viewed by 543
Abstract
Offshore structures are exposed to various environmental loads, including extreme and abnormal waves, over their operational lifespan. The existence of wind and current can exacerbate the dynamic response of these structures, posing threats to safety and integrity. This study focuses on the dynamic [...] Read more.
Offshore structures are exposed to various environmental loads, including extreme and abnormal waves, over their operational lifespan. The existence of wind and current can exacerbate the dynamic response of these structures, posing threats to safety and integrity. This study focuses on the dynamic responses of offshore triceratops under different environmental conditions characterized by the superimposition of freak waves, uniform wind, and current. The free surface profile of the freak wave was generated using the dual superposition model. The numerical model of the offshore platform designed for ultra-deep-water applications was developed using the ANSYS AQWA 2023 R2 modeler. Numerical investigations, including the free decay tests and time-domain analysis under random sea states, including freak waves, were initially carried out. Then, the combined effects of freak waves, wind, and current were studied in detail under different loading scenarios. The results revealed the increase in structural response under the freak wave action at the focus time. Wind action resulted in a mean shift in responses, while the inclusion of current led to a pronounced increase in the total response of the platform, encompassing deck and buoyant legs, alongside the tether tension variation. Notably, considerable variations in the response were observed after freak wave exposure under the combined influence of wind, freak wave, and current. The results underscore the profound effects induced by wind and current in the presence of freak waves, providing valuable insights for analyzing similar offshore structures under ultimate design conditions. Full article
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25 pages, 15710 KiB  
Article
TG-PGAT: An AIS Data-Driven Dynamic Spatiotemporal Prediction Model for Ship Traffic Flow in the Port
by Jianwen Ma, Yue Zhou, Yumiao Chang, Zhaoxin Zhu, Guoxin Liu and Zhaojun Chen
J. Mar. Sci. Eng. 2024, 12(10), 1875; https://doi.org/10.3390/jmse12101875 - 18 Oct 2024
Viewed by 587
Abstract
Accurate prediction of ship traffic flow is essential for developing intelligent maritime transportation systems. To address the complexity of ship traffic flow data in the port and the challenges of capturing its dynamic spatiotemporal dependencies, a dynamic spatiotemporal model called Temporal convolutional network-bidirectional [...] Read more.
Accurate prediction of ship traffic flow is essential for developing intelligent maritime transportation systems. To address the complexity of ship traffic flow data in the port and the challenges of capturing its dynamic spatiotemporal dependencies, a dynamic spatiotemporal model called Temporal convolutional network-bidirectional Gated recurrent unit-Pearson correlation coefficient-Graph Attention Network (TG-PGAT) is proposed for predicting traffic flow in port waters. This model extracts spatial features of traffic flow by combining the adjacency matrix and spatial dynamic coefficient correlation matrix within the Graph Attention Network (GAT) and captures temporal features through the concatenation of the Temporal Convolutional Network (TCN) and Bidirectional Gated Recurrent Unit (BiGRU). The proposed TG-PGAT model demonstrates higher prediction accuracy and stability than other classic traffic flow prediction methods. The experimental results from multiple angles, such as ablation experiments and robustness tests, further validate the critical role and strong noise resistance of different modules in the TG-PGAT model. The experimental results of visualization demonstrate that this model not only exhibits significant predictive advantages in densely trafficked areas of the port but also outperforms other models in surrounding areas with sparse traffic flow data. Full article
(This article belongs to the Special Issue Management and Control of Ship Traffic Behaviours)
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16 pages, 13038 KiB  
Article
Underwater Gyros Denoising Net (UGDN): A Learning-Based Gyros Denoising Method for Underwater Navigation
by Chun Cao, Can Wang, Shaoping Zhao, Tingfeng Tan, Liang Zhao and Feihu Zhang
J. Mar. Sci. Eng. 2024, 12(10), 1874; https://doi.org/10.3390/jmse12101874 - 18 Oct 2024
Viewed by 509
Abstract
Autonomous Underwater Vehicles (AUVs) are widely used for hydrological monitoring, underwater exploration, and geological surveys. However, AUVs face limitations in underwater navigation due to the high costs associated with Strapdown Inertial Navigation System (SINS) and Doppler Velocity Log (DVL), hindering the development of [...] Read more.
Autonomous Underwater Vehicles (AUVs) are widely used for hydrological monitoring, underwater exploration, and geological surveys. However, AUVs face limitations in underwater navigation due to the high costs associated with Strapdown Inertial Navigation System (SINS) and Doppler Velocity Log (DVL), hindering the development of low-cost vehicles. Micro Electro Mechanical System Inertial Measurement Units (MEMS IMUs) are widely used in industry due to their low cost and can output acceleration and angular velocity, making them suitable as an Attitude Heading Reference System (AHRS) for low-cost vehicles. However, poorly calibrated MEMS IMUs provide an inaccurate angular velocity, leading to rapid drift in orientation. In underwater environments where AUVs cannot use GPS for position correction, this drift can have severe consequences. To address this issue, this paper proposes Underwater Gyros Denoising Net (UGDN), a method based on dilated convolutions and LSTM that learns and extracts the spatiotemporal features of IMU sequences to dynamically compensate for the gyroscope’s angular velocity measurements, reducing attitude and heading errors. In the experimental section of this paper, we deployed this method on a dataset collected from field trials and achieved significant results. The experimental results show that the accuracy of MEMS IMU data denoised by UGDN approaches that of fiber-optic SINS, and when integrated with DVL, it can serve as a low-cost underwater navigation solution. Full article
(This article belongs to the Special Issue Autonomous Marine Vehicle Operations—2nd Edition)
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20 pages, 4544 KiB  
Article
Risk Assessment of Polar Drillship Operations Based on Bayesian Networks
by Qi Wang, Zixin Wang, Hongen Li, Xiaoming Huang, Qianjin Yue, Xiufeng Yue and Yanlin Wang
J. Mar. Sci. Eng. 2024, 12(10), 1873; https://doi.org/10.3390/jmse12101873 - 18 Oct 2024
Viewed by 402
Abstract
In the extreme polar marine environment, safety risks pose a significant threat to drilling vessels. By conducting a safety risk assessment, potential hazards can be predicted and identified, thereby significantly reducing the frequency of accidents and promoting the sustained stability of economic activities. [...] Read more.
In the extreme polar marine environment, safety risks pose a significant threat to drilling vessels. By conducting a safety risk assessment, potential hazards can be predicted and identified, thereby significantly reducing the frequency of accidents and promoting the sustained stability of economic activities. This paper investigates a Bayesian-network-based risk assessment model for polar drilling operations. Grey relational analysis was employed to identify the main risk factors. The model is trained using 525 valid incident sample data and is combined with expert knowledge. The accuracy rate is above 88%. Additionally, corresponding decision-making recommendations are provided through sensitivity analysis. The three most sensitive elements to fire nodes are human error, other causes, and equipment damage, with sensitivity coefficients of 0.046, 0.042, and 0.022, respectively. In terms of deck/handrail collision nodes, the highly sensitive elements are related to lifting (totally more than 0.1). For the events that have already transpired, the probabilities of most related nodes are 0.73 and 0.74, both of which are above 0.5, thereby validating the accuracy of forward and backward reasoning. Risk assessments based on Bayesian networks can offer pertinent decision-making recommendations and preventive measures. Full article
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17 pages, 5741 KiB  
Article
Investigation into Using CFD for Estimation of Ship Specific Parameters for the SPICE Model for Prediction of Sea Spray Icing: Part 1—The Proposal
by Sujay Deshpande and Per-Arne Sundsbø
J. Mar. Sci. Eng. 2024, 12(10), 1872; https://doi.org/10.3390/jmse12101872 - 18 Oct 2024
Viewed by 427
Abstract
A machine learning model for prediction of icing on vessels and offshore structures, Spice, was recently developed by Deshpande 2023. Some variables required for the prediction of icing rates in most prediction models, including Spice, such as the spray flux, cannot be easily [...] Read more.
A machine learning model for prediction of icing on vessels and offshore structures, Spice, was recently developed by Deshpande 2023. Some variables required for the prediction of icing rates in most prediction models, including Spice, such as the spray flux, cannot be easily measured. Existing models estimate these using empirical formulations that have been heavily criticized. Most existing models are also incapable of providing the distribution of icing on the structure. The current study demonstrates a method to estimate the local wind speeds, along with spray duration, spray period, and spray flux at different locations on the surface of a moving vessel. These, along with other easily measurable values of air temperature, water temperature, and salinity, are used to predict the icing rates. The result is a model, dubbed Spice2—an upgrade of the existing Spice model—that is able to provide the icing rates and the distribution of icing on the surface of vessels and other offshore structures. The model was demonstrated with a case study of a totally enclosed lifeboat where icing rates were predicted at different locations on its surface. Successful implementation of a two-phase simulation with a coupled wind–wave domain and a moving vessel was demonstrated. Research into simplification of the currently computationally expensive method is suggested. Validation of the proposed Spice2 model against a full-scale measurement is covered in part 2 of the study. Full article
(This article belongs to the Special Issue Novel Maritime Techniques and Technologies, and Their Safety)
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19 pages, 14529 KiB  
Article
Morphology and Effect of Load on Bridge Piers Impacted by Continuous Sea Ice
by Li Gong, Yue Cui, Yunfei Du, Long Qin and Xinyuan Zhao
J. Mar. Sci. Eng. 2024, 12(10), 1871; https://doi.org/10.3390/jmse12101871 - 18 Oct 2024
Viewed by 448
Abstract
In order to study the collision of sea ice on bridge piers of a sea-crossing bridge, this study establishes a finite element model of the impact of sea ice on bridge piers in aqueous media based on explicit dynamics analysis software and programming [...] Read more.
In order to study the collision of sea ice on bridge piers of a sea-crossing bridge, this study establishes a finite element model of the impact of sea ice on bridge piers in aqueous media based on explicit dynamics analysis software and programming software using the arbitrary Lagrangian Eulerian (ALE) method. The results show that, when the sea-ice spacing is larger than the sea-ice edge length, the increase in sea-ice spacing leads to a decrease in the collision force and a significant increase in the probability of climbing and overturning. The increase in sea-ice mass significantly increases the impact force on the bridge abutment, and the peak value increases linearly with the increase in mass, and the sea-ice climbing and overturning phenomena are obvious. Different shapes of sea ice are obtained by cutting the sea-ice field with the two-dimensional Voronoi method, and the maximum impact force increases significantly with the increase in the average area. Irregularly shaped sea ice leads to a larger impact force and triggers the accumulation climbing phenomenon, which is verified by experiments, and the experimental values are in good agreement with the simulated values. In conclusion, this study reveals the significant effects of the spacing, mass, and shape of sea ice on the impact force of bridge piers, which provides an important reference for the design of bridge structures. Full article
(This article belongs to the Special Issue Numerical Analysis and Modeling of Floating Structures)
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23 pages, 6148 KiB  
Article
An Analysis of the Flexural Stiffness and Horizontal Bearing Capacity of CFRP Composite Pipe Piles in Marine Environments
by Wei Zhang, Wei Shao and Yinghui Nie
J. Mar. Sci. Eng. 2024, 12(10), 1870; https://doi.org/10.3390/jmse12101870 - 18 Oct 2024
Viewed by 476
Abstract
Carbon-fiber-reinforced polymer (CFRP) is a composite material consisting of a resin matrix reinforced with carbon fibers. This study focuses on CFRP composite pipe piles as the subject of investigation, exploring the impact of substituting steel bars with CFRP bars on the bending performance [...] Read more.
Carbon-fiber-reinforced polymer (CFRP) is a composite material consisting of a resin matrix reinforced with carbon fibers. This study focuses on CFRP composite pipe piles as the subject of investigation, exploring the impact of substituting steel bars with CFRP bars on the bending performance of pipe piles through rigorous three-point bending tests. The attenuation of flexural stiffness in CFRP pipe piles under a chloride salt environment was anticipated. The lateral bearing capacity of CFRP pipe piles was calculated by introducing a stiffness degradation coefficient for the piles and utilizing the finite difference method. The findings of the analysis suggest that as the CFRP reinforcement replacement rate increases, the initial bending stiffness of the composite pipe pile experiences a corresponding decrease. After serving for 28.15 years, the steel reinforcement within the pipe pile commences rusting, resulting in a nonlinear decline in the bending stiffness of the composite pipe pile. As the service time of pipe piles increases, a higher replacement rate of CFRP reinforcement results in a slower attenuation of pile stiffness. Consequently, both the horizontal displacement at the top of the pile and the bending moment along the body of the composite pipe pile gradually increase over time. During the same service period, the higher the rate of CFRP reinforcement, the less noticeable the attenuation in the horizontal bearing capacity of the pile shaft. Full article
(This article belongs to the Section Ocean Engineering)
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18 pages, 6599 KiB  
Article
Study on the Prediction of Motion Response of Offshore Platforms Based on ResCNN-LSTM
by Feng Diao, Tianyu Liu, Franck Aurel Likeufack Mdemaya and Gang Xu
J. Mar. Sci. Eng. 2024, 12(10), 1869; https://doi.org/10.3390/jmse12101869 - 18 Oct 2024
Viewed by 472
Abstract
In the random sea environment, offshore platforms are influenced by factors such as wind, waves, and currents, as well as their interactions, leading to complex motion phenomena that affect the safety of offshore platform operations. Consequently, accurately predicting the motion response of offshore [...] Read more.
In the random sea environment, offshore platforms are influenced by factors such as wind, waves, and currents, as well as their interactions, leading to complex motion phenomena that affect the safety of offshore platform operations. Consequently, accurately predicting the motion response of offshore platforms has long been a key focus in the fields of naval architecture and ocean engineering. This paper utilizes STAR-CCM+ to simulate time-history data of offshore platform motion responses under both regular and irregular waves. Furthermore, a predictive model combining residual convolutional neural networks and long short-term memory neural networks using neural network technology is also studied. This model utilizes an autoregressive approach to predict the motion responses of offshore platforms, with its predictive accuracy validated through comprehensive evaluations. Under regular wave conditions, the coefficient of determination (R2) for the platform’s heave and pitch responses consistently exceeds 0.99. Meanwhile, under irregular wave conditions, the R2 values remain generally above 0.4. Additionally, the model exhibits commendable performance in terms of Mean Squared Error (MSE) and Mean Absolute Percentage Error (MAPE) metrics. The aim of this study is to present a novel approach to predicting offshore platform motion responses, while providing a more scientific basis for decision-making in offshore platform operations. Full article
(This article belongs to the Section Ocean Engineering)
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28 pages, 9539 KiB  
Article
Improved Fracture Permeability Evaluation Model for Granite Reservoirs in Marine Environments: A Case Study from the South China Sea
by Jianhong Guo, Baoxiang Gu, Hengyang Lv, Zuomin Zhu and Zhansong Zhang
J. Mar. Sci. Eng. 2024, 12(10), 1868; https://doi.org/10.3390/jmse12101868 - 18 Oct 2024
Viewed by 508
Abstract
Permeability is a crucial parameter in the exploration and development of oil and gas reservoirs, particularly in unconventional ones, where fractures significantly influence storage capacity and fluid flow. This study investigates the fracture permeability of granite reservoirs in the South China Sea, introducing [...] Read more.
Permeability is a crucial parameter in the exploration and development of oil and gas reservoirs, particularly in unconventional ones, where fractures significantly influence storage capacity and fluid flow. This study investigates the fracture permeability of granite reservoirs in the South China Sea, introducing an enhanced evaluation model for planar fracture permeability based on Darcy’s law and Poiseuille’s law. The model incorporates factors such as fracture heterogeneity, tortuosity, angle, and aperture to improve permeability assessments. Building on a single-fracture model, this research integrates mass transfer equations and trigonometric functions to assess intersecting fractures’ permeability. Numerical simulations explore how tortuosity, angle, and aperture affect individual fracture permeability and the influence of relative positioning in intersecting fractures. The model makes key assumptions, including minimal consideration of horizontal stress and the assumption of unidirectional laminar flow in cross-fractures. Granite outcrop samples were systematically collected, followed by full-diameter core drilling. A range of planar models with varying fracture apertures were designed, and permeability measurements were conducted using the AU-TOSCAN-II multifunctional core scanner with a steady-state gas injection method. The results showed consistency between the improved model and experimental findings regarding the effects of fracture aperture and angle on permeability, confirming the model’s accuracy in reflecting the fractures’ influence on reservoir flow capacity. For intersecting fractures, a comparative analysis of core X-ray computed tomography (X-CT) scanning results and experimental outcomes highlighted discrepancies between actual permeability measurements and theoretical simulations based on tortuosity and aperture variations. Limitations exist, particularly for cross-fractures, where quantifying complexity is challenging, leading to potential discrepancies between simulation and experimental results. Further comparisons between core experiments and logging responses are necessary for model refinement. In response to the challenges associated with evaluating absolute permeability in fractured reservoirs, this study presents a novel theoretical assessment model that considers both single and intersecting fractures. The model’s validity is demonstrated through actual core experiments, confirming the effectiveness of the single-fracture model while highlighting the need for further refinement of the dual-fracture model. The findings provide scientific support for the exploration and development of granite reservoirs in the South China Sea and establish a foundation for permeability predictions in other complex fractured reservoir systems, thereby advancing the field of fracture permeability assessment. Full article
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13 pages, 752 KiB  
Article
Contribution of Lab Radon Flux Measurements for Evaluating Submarine Groundwater Discharge in Coastal Areas
by Daniel M. Bonotto, José R. C. Nery, Tatiani P. P. Sabaris, Luis H. Mancini, Marina Lunardi, Cristiano Cigagna, Lucas P. Fontanetti and Gabrielle R. Ceccato
J. Mar. Sci. Eng. 2024, 12(10), 1867; https://doi.org/10.3390/jmse12101867 - 18 Oct 2024
Viewed by 476
Abstract
Laboratory-scale experiments were conducted on Carboniferous Limestone gravels from the Mendip Hills area, England; sandstones from the Pirambóia and Botucatu formations, Paraná sedimentary basin, Brazil; samples of schist and quartzite from Caldas Novas Hydrothermal Complex, Brazil; and the minerals tantalite, cassiterite, and columbite [...] Read more.
Laboratory-scale experiments were conducted on Carboniferous Limestone gravels from the Mendip Hills area, England; sandstones from the Pirambóia and Botucatu formations, Paraná sedimentary basin, Brazil; samples of schist and quartzite from Caldas Novas Hydrothermal Complex, Brazil; and the minerals tantalite, cassiterite, and columbite from mining areas at Rio Grande do Norte State, Brazil, with the purpose of evaluating the release of 222Rn to the water phase. The specific surface area of the samples corresponded to 1.69–81.36 cm2g−1, which provided values of 0.001–1.68 dpm/g and 3.18 × 10−6 to 0.59 for the radon released and radon emanation coefficient, respectively. These results allowed us to calculate the radon flux with respect to the radon leakage, which corresponded to values of 0.00016–0.00158 Bq/m2/d for the denser materials and 0.018–0.43 Bq/m2/d for limestones and sandstones. They also permitted us to find an inverse, significant relationship between the radon generated by the minerals/rocks and the radon flux into the water phase, which was tested for sediments in coastal and inland Brazilian areas, demonstrating utility for evaluating the diffusive radon flux from the sediments, which is an important parameter to monitor submarine groundwater discharge (SGD) by means of radon as a natural tracer. Full article
(This article belongs to the Special Issue Distribution and Content of Trace Elements in Seawater and Sediments)
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10 pages, 2049 KiB  
Article
An Investigation into Using CFD for the Estimation of Ship Specific Parameters for the SPICE Model for the Prediction of Sea Spray Icing: Part 2—The Verification of SPICE2 with a Full-Scale Test
by Per-Arne Sundsbø and Sujay Deshpande
J. Mar. Sci. Eng. 2024, 12(10), 1866; https://doi.org/10.3390/jmse12101866 - 18 Oct 2024
Viewed by 432
Abstract
A hybrid CFD–ML model for the prediction of sea spray icing, SPICE2, was developed in Part 1 of this study in Deshpande et al., 2024. The SPICE2 model is an extension of the ML model, SPICE, where some of the variables required for [...] Read more.
A hybrid CFD–ML model for the prediction of sea spray icing, SPICE2, was developed in Part 1 of this study in Deshpande et al., 2024. The SPICE2 model is an extension of the ML model, SPICE, where some of the variables required for icing rate predictions: local wind speed, spray duration, spray period, and spray flux, are computed from CFD simulations. These, along with the air and water temperatures, and the salinity from the metocean data are used for the prediction of icing rates at different locations on a moving vessel. The existing full-scale icing measurements proved to be not detailed enough for the purpose of the verification of sea spray icing prediction models and the verification of the SPICE2 required distribution of sea spray icing data on the vessel surface in addition to the vessel design for simulation. A full-scale sea spray icing test was conducted in 2018 by Sundsbø et al. on a fully enclosed lifeboat equipped for the Goliat field in the Barents Sea. The 3D design of the same lifeboat, together with the corresponding metocean conditions and ship characteristics was used for the simulation of the vessel-specific parameters required for the verification of the icing rate and distribution prediction from the SPICE2 model against the measured distribution of sea spray icing rates on the lifeboat surface. The availability of the 3D model of this lifeboat, in addition to the fact that the icing measurements from this test were detailed enough to attempt a model verification served the purpose of validating the SPICE2 model. The icing rates measured on this lifeboat are used for the full-scale validation of the SPICE2 model that is proposed in Part 1 of this study. It was seen that the icing rates predicted by SPICE2 concurred with 9 of 13 selected locations on the lifeboat. The ones which did not showed very little deviation from the measurements. The icing rate and distribution prediction with SPICE2 were satisfactorily validated against full-scale icing measurements. This is a first attempt in modelling sea spray generation using CFD and further research into CFD for the estimation of spray flux is suggested. Full article
(This article belongs to the Special Issue Novel Maritime Techniques and Technologies, and Their Safety)
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20 pages, 6186 KiB  
Article
Optimizing Ship Draft Observation with Wave Energy Attenuation and PaddlePaddle-OCR in an Anti-Fluctuation Device
by Yaoming Wei, Huan Du, Qinyou Hu and Hu Wang
J. Mar. Sci. Eng. 2024, 12(10), 1865; https://doi.org/10.3390/jmse12101865 - 18 Oct 2024
Viewed by 550
Abstract
With the development and application of artificial intelligence (AI) in the shipping industry, using AI to replace traditional draft survey methods in bulk carriers can significantly reduce manpower, lower the risks associated with visual observations, improve measurement accuracy, and minimize the impact of [...] Read more.
With the development and application of artificial intelligence (AI) in the shipping industry, using AI to replace traditional draft survey methods in bulk carriers can significantly reduce manpower, lower the risks associated with visual observations, improve measurement accuracy, and minimize the impact of human subjective factors. Ultimately, the integration of software and hardware technologies will replace human visual observations with automated draft measurement calculations. A similar anti-fluctuation device described in this article has been used in ship draft observation based on AI-assisted proving, which can ease the fluctuation of the wave inside the pipe. Observers can directly read the water surface inside the pipe and compare it to the ship’s draft mark to obtain the final draft, effectively improving draft observation accuracy. However, some surveyors refuse to accept the readings obtained from this device, citing a lack of theoretical basis or the absence of accreditation from relevant technical authorities, leading to the rejection of results. To address these issues, this paper integrates wave energy attenuation theory with PaddlePaddle-OCR recognition to further validate the anti-fluctuation device for accurate ship draft observation. The experimental results are as follows: first, the pipe effectively suppresses the amplitude of external water surface fluctuations by 75%, explaining the fundamental theory that wave heights within the anti-fluctuation device are consistent with external swell heights. When taking a draft measurement, the system dynamically adjusts the position of the main tube in response to the ship’s movements, maintaining the stability of the measurement section and significantly reducing the difficulty of observations. Due to the reduction in fluctuation amplitude, there is a noticeable improvement in observation accuracy. Full article
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17 pages, 1379 KiB  
Article
Range-Domain Subspace Detector in the Presence of Direct Blast for Forward Scattering Detection in Shallow-Water Environments
by Jiahui Luo, Chao Sun and Mingyang Li
J. Mar. Sci. Eng. 2024, 12(10), 1864; https://doi.org/10.3390/jmse12101864 - 17 Oct 2024
Viewed by 405
Abstract
This paper aims to detect a target that crosses the baseline connecting the source and the receiver in shallow-water environments, which is a special scenario for a bistatic sonar system. In such a detection scenario, an intense sound wave, known as the direct [...] Read more.
This paper aims to detect a target that crosses the baseline connecting the source and the receiver in shallow-water environments, which is a special scenario for a bistatic sonar system. In such a detection scenario, an intense sound wave, known as the direct blast, propagates directly from the source to the receiver without target scattering. This direct blast usually arrives at the receiver simultaneously with the forward scattering signal and exhibits a larger intensity than the signal, posing a significant challenge for target detection. In this paper, a range-domain subspace is constructed by the horizontal distance between the source/target and each element of a horizontal linear array (HLA) when the ranges of environmental parameters are known a priori. Meanwhile, a range-domain subspace detector based on direct blast suppression (RSD-DS) is proposed for forward scattering detection. The source and the target are located at different positions, so the direct blast and the scattered signal are in different range-domain subspaces. By projecting the received data onto the orthogonal complement subspace of the direct blast subspace, the direct blast can be suppressed and the signal that lies outside the direct blast subspace is used for target detection. The simulation results indicate that the proposed RSD-DS exhibits a performance close to the generalized likelihood ratio detector (GLRD) while requiring less prior knowledge of environments (only known are the ranges of the sediment sound speed and the bottom sound speed), and its robustness to environmental uncertainties is better than that of the latter. Moreover, the proposed RSD-DS exhibits better immunity against the direct blast than the GLRD, since it can still work effectively at a signal-to-direct blast ratio (SDR) of −30 dB, while the GLRD stops working in this case. Full article
(This article belongs to the Special Issue Applications of Underwater Acoustics in Ocean Engineering)
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25 pages, 27177 KiB  
Article
Bollard Pull and Self-Propulsion Performance of a Waterjet Propelled Tracked Amphibian
by Taehyung Kim, Donghyeon Yoon, Jeongil Seo and Jihyeun Wang
J. Mar. Sci. Eng. 2024, 12(10), 1863; https://doi.org/10.3390/jmse12101863 - 17 Oct 2024
Viewed by 552
Abstract
This paper describes the unique full-scale bollard pull and self-propulsion tests of a large amphibious tracked military vehicle with two waterjet propulsors. To provide a reference for the self-propulsion and cavitation performance, a series of sea trials and bollard pull tests were performed [...] Read more.
This paper describes the unique full-scale bollard pull and self-propulsion tests of a large amphibious tracked military vehicle with two waterjet propulsors. To provide a reference for the self-propulsion and cavitation performance, a series of sea trials and bollard pull tests were performed in a military sea bay and in a large test basin, respectively. Good overall agreement between the sea trial and the computation was observed in the speed–power relationship. The cavitation-induced breakdown phenomenon was further explored via numerical simulations. The results indicated that the uncertainties in the numerical results were dominated by the scales of vapor bubbles. The analysis showed that the selection of the vapor bubble scale factors of 1.0 for growth and 0.05 for collapse were in good agreement with the experimental results. Rapid performance breakdown occurred when sufficient suction side-attached cavities were extended into the blade mid-chord and tip-board regions. Full article
(This article belongs to the Special Issue Ship Performance in Actual Seas)
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16 pages, 4906 KiB  
Article
SC-DiatomNet: An Efficient and Accurate Algorithm for Diatom Classification
by Jiongwei Li, Chengshuo Jiang, Lishuang Yao and Shiyuan Zhang
J. Mar. Sci. Eng. 2024, 12(10), 1862; https://doi.org/10.3390/jmse12101862 - 17 Oct 2024
Viewed by 515
Abstract
Detecting the quantity and diversity of diatoms is of great significance in areas such as climate change, water quality assessment, and oil exploration. Here, an efficient and accurate object detection model, named SC-DiatomNet, is proposed for diatom detection in complex environments. This model [...] Read more.
Detecting the quantity and diversity of diatoms is of great significance in areas such as climate change, water quality assessment, and oil exploration. Here, an efficient and accurate object detection model, named SC-DiatomNet, is proposed for diatom detection in complex environments. This model is based on the YOLOv3 architecture and uses the K-means++ algorithm for anchor box clustering on the diatom dataset. A convolutional block attention module is incorporated in the feature extraction network to enhance the model’s ability to recognize important regions. A spatial pyramid pooling module and adaptive anchor boxes are added to the encoder to improve detection accuracy for diatoms of different sizes. Experimental results show that SC-DiatomNet can successfully detect and classify diatoms accurately without reducing detection speed. The recall, precision, and F1 score were 94.96%, 94.21%, and 0.94, respectively. It further improved the mean average precision (mAP) of YOLOv3 by 9.52% on the diatom dataset. Meanwhile, the detection accuracy was improved compared with those of other advanced deep learning algorithms. SC-DiatomNet has potential applications in water quality analysis and monitoring of harmful algal blooms. Full article
(This article belongs to the Section Ocean Engineering)
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