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J. Mar. Sci. Eng., Volume 11, Issue 3 (March 2023) – 220 articles

Cover Story (view full-size image): The best way to stop the introduction of non-indigenous species (NISs) is by preventing their transport. In the case of ship hulls, this may be accomplished by managing entrainment onto the hull. This study was designed to examine the role of hull husbandry, i.e., cleaning and grooming, in fouling community structure and to determine the effect of husbandry on the recolonization of surfaces after a transplant was performed. Hull husbandry was found to affect coverage and composition, with groomed panels carrying a lower cover of macrofouling in general. The effect of the original location on subsequent fouling composition and recolonization by specific organisms was confirmed for encrusting bryozoans, barnacles, sponges, and tunicates. Hull husbandry also affected subsequent fouling with specific preferences shown for surfaces that had been groomed, cleaned and undisturbed. View this paper
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20 pages, 2233 KiB  
Article
Towards Lower Carbon Emissions: A Distributed Energy Management Strategy-Based Multi-Objective Optimization for the Seaport Integrated Energy System
by Yuxin Zhang, Yang Xiao, Qihe Shan and Tieshan Li
J. Mar. Sci. Eng. 2023, 11(3), 681; https://doi.org/10.3390/jmse11030681 - 22 Mar 2023
Cited by 3 | Viewed by 1505
Abstract
To decrease fuel-based energy consumption, it is important to investigate the optimal energy management problem for the seaport integrated energy system in a fully distributed manner. A multi-objective energy management model is constructed, considering energy consumption, greenhouse gas emission, and carbon trading, which [...] Read more.
To decrease fuel-based energy consumption, it is important to investigate the optimal energy management problem for the seaport integrated energy system in a fully distributed manner. A multi-objective energy management model is constructed, considering energy consumption, greenhouse gas emission, and carbon trading, which satisfy the sustainable development of the international shipping industry advocated by the International Maritime Organization (IMO). The carbon exhaust of a seaport is restrained by integrated carbon capture/storage devices. A fully distributed energy management strategy with dynamic-weighted coefficients is proposed to acquire the optimal solutions for the seaport integrated energy system. Moreover, to decrease the communication resources, an event-triggered mechanism between energy bodies was designed against the bandwidth limitation of the seaport. Finally, a rigorous mathematical analysis based on the multi-agent theory and the case studies proves the effectiveness of the proposed method. Full article
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21 pages, 7670 KiB  
Article
Application of the XBeach-Gravel Model for the Case of East Adriatic Sea-Wave Conditions
by Tonko Bogovac, Dalibor Carević, Damjan Bujak and Hanna Miličević
J. Mar. Sci. Eng. 2023, 11(3), 680; https://doi.org/10.3390/jmse11030680 - 22 Mar 2023
Cited by 1 | Viewed by 1362
Abstract
Croatia’s coast located on the eastern Adriatic is rich with small gravel beaches with limited fetch. This leads to a specific low-energetic wave climate compared to most other beaches, while their gravel composition makes them unique. Most management of these beaches is performed [...] Read more.
Croatia’s coast located on the eastern Adriatic is rich with small gravel beaches with limited fetch. This leads to a specific low-energetic wave climate compared to most other beaches, while their gravel composition makes them unique. Most management of these beaches is performed without understanding the sediment transport occurring on the beaches. XBeach-Gravel is a numerical model capable of simulating bed-level change on gravel beaches, but lacks validation in the case of low significant wave height (under 2.5 m) and low peak periods (under 6 s), conditions that are present on the eastern Adriatic. Based on measurements performed in both laboratory conditions in a water canal in Hannover and actual storm wave conditions on Ploče beach, calibration of the model is performed. Model results are compared between laboratory conditions and field conditions for comparable wave conditions. XBeach-Gravel can simulate low-energetic events resulting in berm formation and berm buildup with a high Brier skill score if calibrated. Simulation of laboratory conditions requires high transport coefficient values and shows more sediment transport than similar wave conditions in the field. Calibration for field conditions is dependent on geodetic survey data capable of isolating wave events with dominant cross-shore transport, but once calibrated, XBeach-Gravel can achieve good to excellent Brier skill score values in simulating sediment change in low-energetic wave conditions on the eastern Adriatic. Full article
(This article belongs to the Section Coastal Engineering)
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17 pages, 3052 KiB  
Article
Techno-Economic Optimal Sizing Design for a Tidal Stream Turbine–Battery System
by Sana Toumi, Yassine Amirat, Elhoussin Elbouchikhi, Zhibin Zhou and Mohamed Benbouzid
J. Mar. Sci. Eng. 2023, 11(3), 679; https://doi.org/10.3390/jmse11030679 - 22 Mar 2023
Viewed by 1426
Abstract
This article deals with the techno-economic optimal sizing of a tidal stream turbine (TST)–battery system. In this study, the TST system consists of a turbine rotor and a permanent magnet synchronous generator (PMSG) associated with a three-phase converter coupled to a DC bus. [...] Read more.
This article deals with the techno-economic optimal sizing of a tidal stream turbine (TST)–battery system. In this study, the TST system consists of a turbine rotor and a permanent magnet synchronous generator (PMSG) associated with a three-phase converter coupled to a DC bus. A battery is used within the system as an energy storage system to absorb excess produced power or cover power deficits. To determine the optimal sizing of the system, an iterative approach was used owing to its ease of implementation, high accuracy, and fast convergence speed, even under environmental constraints such as swell and wave effects. This technique is based on robust energy management, and the recursive algorithm includes the deficiency of power supply probability (DPSP) and the relative excess power generation (REPG) as technical criteria for the system reliability study, and the energy cost (EC) and the total net present cost (TNPC) as economic criteria for the system cost study. As data inputs, the proposed approach used the existing data from the current speed profile, the load, and economic parameters. The desired output is the system component optimal sizing (TST power, and battery capacity). In this paper, the system sizing was studied during a one-year time period to ensure a more reliable and economical system. The results are compared to well-known methods such as genetic algorithms, particle swarm optimization, and software-based (HOMER) approaches. The optimization results confirm the efficiency of the proposed approach in sizing the system, which was simulated using real-world tidal velocity data from a specific deployment site. Full article
(This article belongs to the Special Issue Young Researchers in Ocean Engineering)
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21 pages, 14102 KiB  
Article
Low Temperature Effect on the Mechanical Properties of EH36 with Strain Rates
by Jing Zhang, Xuelei Kang, Xinghua Shi, C. Guedes Soares and Ming Song
J. Mar. Sci. Eng. 2023, 11(3), 678; https://doi.org/10.3390/jmse11030678 - 22 Mar 2023
Cited by 5 | Viewed by 2011
Abstract
With the expansion of the Arctic route, the safety of ship crossing the area in light of the low temperature and ice has become of focus, especially with regards to the ship’s structure. The mechanical properties of the material making up the ship’s [...] Read more.
With the expansion of the Arctic route, the safety of ship crossing the area in light of the low temperature and ice has become of focus, especially with regards to the ship’s structure. The mechanical properties of the material making up the ship’s structure may not be suitable for the Arctic environment. A series of quasi-static and dynamic tests were performed to investigate the behaviour of EH36 steel, which is used to build Arctic ships, at temperatures ranging from 20 °C to −60 °C. The yield and ultimate tensile stress increased more than 10% as the temperature decreased from 20 °C to −60 °C, whereas the toughness decreased as the temperature decreased. A formula was derived to illustrate the relationship between the temperature reduction and the yield strength by fitting the experimental data. Four common constitutive rigid-perfectly plastic, elastic-perfectly plastic, bilinear elastic-plastic, and multi-linear elastic plastic models were fitted to simulate the hull structure under static loading and low temperature. Additionally, the strain rate effect of EH36 steel at low temperatures was illustrated by quasi-static and high-speed impact tests. A constitutive model including the low temperature and strain rate was introduced based on a modified Cowper-Symonds model, in which the coefficients of the constitutive model are fitted by the test results. It is improved by an iterative numerical method used to obtain more accurate coefficients using a series of numerical analyses. Detailed finite element simulations of the experiment conditions revealed that the constitutive model accurately predicts the dynamic response at low temperatures. Full article
(This article belongs to the Special Issue Advanced Analysis of Marine Structures)
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21 pages, 5074 KiB  
Article
Underwater Target Detection Based on Improved YOLOv7
by Kaiyue Liu, Qi Sun, Daming Sun, Lin Peng, Mengduo Yang and Nizhuan Wang
J. Mar. Sci. Eng. 2023, 11(3), 677; https://doi.org/10.3390/jmse11030677 - 22 Mar 2023
Cited by 21 | Viewed by 5945
Abstract
Underwater target detection is a crucial aspect of ocean exploration. However, conventional underwater target detection methods face several challenges such as inaccurate feature extraction, slow detection speed, and lack of robustness in complex underwater environments. To address these limitations, this study proposes an [...] Read more.
Underwater target detection is a crucial aspect of ocean exploration. However, conventional underwater target detection methods face several challenges such as inaccurate feature extraction, slow detection speed, and lack of robustness in complex underwater environments. To address these limitations, this study proposes an improved YOLOv7 network (YOLOv7-AC) for underwater target detection. The proposed network utilizes an ACmixBlock module to replace the 3 × 3 convolution block in the E-ELAN structure, and incorporates jump connections and 1 × 1 convolution architecture between ACmixBlock modules to improve feature extraction and network reasoning speed. Additionally, a ResNet-ACmix module is designed to avoid feature information loss and reduce computation, while a Global Attention Mechanism (GAM) is inserted in the backbone and head parts of the model to improve feature extraction. Furthermore, the K-means++ algorithm is used instead of K-means to obtain anchor boxes and enhance model accuracy. Experimental results show that the improved YOLOv7 network outperforms the original YOLOv7 model and other popular underwater target detection methods. The proposed network achieved a mean average precision (mAP) value of 89.6% and 97.4% on the URPC dataset and Brackish dataset, respectively, and demonstrated a higher frame per second (FPS) compared to the original YOLOv7 model. In conclusion, the improved YOLOv7 network proposed in this study represents a promising solution for underwater target detection and holds great potential for practical applications in various underwater tasks. Full article
(This article belongs to the Section Ocean Engineering)
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21 pages, 3848 KiB  
Article
Nonparametric Identification Model of Coupled Heave–Pitch Motion for Ships by Using the Measured Responses at Sea
by Xianrui Hou and Xingyu Zhou
J. Mar. Sci. Eng. 2023, 11(3), 676; https://doi.org/10.3390/jmse11030676 - 22 Mar 2023
Viewed by 974
Abstract
In order to simulate or control the coupled heave–pitch motion of ships in waves as realistically as possible, an appropriate mathematical model must be established in advance. In this paper, a nonparametric identification method, based on a combination of a random decrement technique [...] Read more.
In order to simulate or control the coupled heave–pitch motion of ships in waves as realistically as possible, an appropriate mathematical model must be established in advance. In this paper, a nonparametric identification method, based on a combination of a random decrement technique (RDT) and support vector regression (SVR), was proposed to model the coupled heave–pitch motion of ships by only using the measured random responses at sea. First, a mathematical model was established to describe the coupled heave–pitch motion of ships in irregular waves. Second, the random decrement equation and the random decrement signatures were obtained by using RDT. Third, the damped frequency of the coupled heave–pitch motions were obtained by analyzing the random decrement signatures. Fourth, SVR was applied to identify the unknown hydrodynamic functions in the established mathematical model. The applicability and validity of the proposed nonparametric identification method were verified by case studies which were designed based on the simulated data and the model test data, respectively. Results of the study showed that the nonparametric identification method can be applied to identify the coupled heave–pitch motion of ships by only using the measured random responses in irregular waves. Full article
(This article belongs to the Section Ocean Engineering)
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19 pages, 7263 KiB  
Article
The Impact of Slow Steaming on Fuel Consumption and CO2 Emissions of a Container Ship
by Vladimir Pelić, Ozren Bukovac, Radoslav Radonja and Nastia Degiuli
J. Mar. Sci. Eng. 2023, 11(3), 675; https://doi.org/10.3390/jmse11030675 - 22 Mar 2023
Cited by 4 | Viewed by 4966
Abstract
Modern marine propulsion systems must be reliable, energy efficient, environmentally friendly, and economical. Efforts to reduce fuel costs and carbon dioxide (CO2) emissions per nautical mile have a significant impact on the choice of propulsion system. Considering that there is no [...] Read more.
Modern marine propulsion systems must be reliable, energy efficient, environmentally friendly, and economical. Efforts to reduce fuel costs and carbon dioxide (CO2) emissions per nautical mile have a significant impact on the choice of propulsion system. Considering that there is no alternative for maritime transport, various technical and technological solutions are being considered that aim to improve efficiency and reduce the negative impact on the environment. One of the ways to achieve this goal is slow steaming, which reduces fuel consumption and CO2 emissions. The designed speed of the vessel has a significant impact on the efficiency of slow steaming. Slow steaming is particularly suitable for large container ships with a design speed of more than 20 knots. In this paper, the effects of slow steaming are analyzed using the example of a container ship with diesel-engine propulsion. Propulsion systems with low-speed and medium-speed marine diesel engines with mechanical power transmission are investigated. Data on the required engine power and propeller speed were used for the study, obtained from calculations during testing of the ship’s hull model. The effects of speed reduction on specific fuel consumption and emission reduction were analyzed using numerical models of two-stroke and four-stroke diesel engines. The models were calibrated and validated using data provided by the engine manufacturers. The paper analyses four different cases where one or two low-speed diesel engines, or three or four medium-speed diesel engines, are used for propulsion. The analysis concludes that slow steaming can effectively reduce fuel consumption and CO2 emissions, but the choice of the optimal propulsion system is highly dependent on maritime market conditions in maritime transportation. The choice of propulsion system affects the potential of slow steaming. Full article
(This article belongs to the Section Marine Environmental Science)
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14 pages, 10637 KiB  
Article
Research on Underwater Image Restoration Technology Based on Multi-Domain Translation
by Teng Xue, Tianchi Zhang and Jing Zhang
J. Mar. Sci. Eng. 2023, 11(3), 674; https://doi.org/10.3390/jmse11030674 - 22 Mar 2023
Cited by 1 | Viewed by 1273
Abstract
Underwater images are crucial in various underwater applications, including marine engineering, underwater robotics, and subsea coral farming. However, obtaining paired data for these images is challenging due to factors such as light absorption and scattering, suspended particles in the water, and camera angles. [...] Read more.
Underwater images are crucial in various underwater applications, including marine engineering, underwater robotics, and subsea coral farming. However, obtaining paired data for these images is challenging due to factors such as light absorption and scattering, suspended particles in the water, and camera angles. Underwater image recovery algorithms typically use real unpaired dataset or synthetic paired dataset. However, they often encounter image quality issues and noise labeling problems that can affect algorithm performance. To address these challenges and further improve the quality of underwater image restoration, this work proposes a multi-domain translation method based on domain partitioning. Firstly, this paper proposes an improved confidence estimation algorithm, which uses the number of times a sample is correctly predicted in a continuous period as a confidence estimate. The confidence value estimates are sorted and compared with the real probability to continuously optimize the confidence estimation and improve the classification performance of the algorithm. Secondly, a U-net structure is used to construct the underwater image restoration network, which can learn the relationship between the two domains. The discriminator uses full convolution to improve the performance of the discriminator by outputting the true and false images along with the category to which the true image belongs. Finally, the improved confidence estimation algorithm is combined with the discriminator in the image restoration network to invert the labels for images with low confidence values in the clean domain as images in the degraded domain. The next step of image restoration is then performed based on the new dataset that is divided. In this way, the multi-domain conversion of underwater images is achieved, which helps in the recovery of underwater images. Experimental results show that the proposed method effectively improves the quality and quantity of the images. Full article
(This article belongs to the Special Issue Advances in Underwater Robots for Intervention)
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21 pages, 6928 KiB  
Article
Stratification Breakdown by Fall Cold Front Winds over the Louisiana Shelf in the Northern Gulf of Mexico: A Numerical Experiment
by Mohammad Nabi Allahdadi, Chunyan Li and Nazanin Chaichitehrani
J. Mar. Sci. Eng. 2023, 11(3), 673; https://doi.org/10.3390/jmse11030673 - 22 Mar 2023
Viewed by 947
Abstract
Cold fronts are meteorological phenomena that impact the northern Gulf of Mexico, mostly between the fall and spring seasons. On average, they pass the region every 3–7 days, with a duration ranging between 24 and 74 h. In the present study, a high-resolution [...] Read more.
Cold fronts are meteorological phenomena that impact the northern Gulf of Mexico, mostly between the fall and spring seasons. On average, they pass the region every 3–7 days, with a duration ranging between 24 and 74 h. In the present study, a high-resolution FVCOM model with an unstructured mesh was used to simulate the effect of the fall cold front winds on water column mixing over the Louisiana shelf, which is often stratified in the summer, leading to hypoxia. Numerical experiments were conducted for October 2009, a period with five consecutive cold front events. Winds from an offshore station forced the model, while climatological temperature/salinity profiles prepared by NOAA for September were used for model initialization. The model performance was evaluated by comparing it with the surface current measurements at two offshore stations, and the results showed a good agreement between the model results and observations. Shelf mixing and stratification were investigated through examining the simulated sea surface temperature as well as the longitudinal and cross-shelf vertical sections. Simulation results showed a significant effect on shelf mixing, with the mixed layer depth increasing from the initial values of 5 m to 25 m at the end of simulation at different parts of the shelf, with maximum mixed layer depths corresponding to the peak of cold fronts. The buoyancy frequency, Richardson number, and the average potential energy demand (APED) for mixing the water column were used to quantify the stratification at two selected locations over the shelf. Results showed that all these parameters almost continuously decreased due to mixing induced by cold front wind events during this time. At the station off the Terrebonne Bay with a water depth of 20 m, the water column became fully mixed after three of the cold front events, with Richardson numbers smaller than 0.25 and approaching zero. This continued mixing trend was also proven by obtaining a decreasing trend of APED from 100 to 5 kg/m.s2 with several close to zero energy demand values. Full article
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14 pages, 1338 KiB  
Article
Potential Detritivorous Diet of the Invasive Apple Snail (Pomacea canaliculata Lamarck, 1822) in Mangroves: The Relationship between Feeding Indicators and Chemical Characteristics of Decaying Leaf Litter
by Jinling Liu, Zhihua Chen, Yunhui Li, Danying Chen, Yulin He, Benliang Zhao, Yuexin Liao and Jing Guo
J. Mar. Sci. Eng. 2023, 11(3), 672; https://doi.org/10.3390/jmse11030672 - 22 Mar 2023
Viewed by 1338
Abstract
Invasive species have had substantial impacts on global mangrove forests. Apple snails (Pomacea canaliculata) have invaded mangrove forests in China. To clarify the potential detritivorous diet of P. canaliculata, the growth and feeding indicators of invasive juvenile snails collected from [...] Read more.
Invasive species have had substantial impacts on global mangrove forests. Apple snails (Pomacea canaliculata) have invaded mangrove forests in China. To clarify the potential detritivorous diet of P. canaliculata, the growth and feeding indicators of invasive juvenile snails collected from mangroves in Guangzhou, China, were studied using decaying leaf litter from five mangrove species, including Acanthus ilicifolius, Acrostichum aureum, Kandelia candel, Aegiceras corniculatum, and Sonneratia apetala. The growth indicators of the survival ratio and specific growth rate were calculated by measuring the live weight of the snails and the number of dead snails after 30 days. The feeding indicator of the weight-specific daily feeding rate (WDR) was calculated by measuring the snail weight and the amount of leaf litter ingested after 120 h. A multiple-choice experiment was performed on the snails by providing the decaying leaf species together, while a no-choice experiment was performed using a single species of decaying leaf litter. The survival and specific growth ratio of P. canaliculata feeding on decaying leaf litter of A. ilicifolius were higher than those for A. aureum. The WDR values of P. canaliculata feeding on the decaying leaf litter of A. ilicifolius and S. apetala were both significantly higher than those for A. corniculatum, A. aureum, and K. candel. The lowest WDR value of P. canaliculata feeding on decaying leaf litter was observed for A. aureum in the no-choice experiment. P. canaliculata mainly fed on decaying leaf litter of A. ilicifolius and S. apetala. The phosphorous contents and ash of the decaying leaf litter positively affected the WDR values of P. canaliculata obtained in the multiple-choice and no-choice experiments. The contents of lignin, tannin, and flavonoid negatively affected the WDR values of P. canaliculata. The potential diet of invasive P. canaliculata in mangroves was closely tied to the chemical characteristics of the decaying leaf litter. P. canaliculata can invade A. ilicifolius and/or S. apetala mangroves by utilizing the debris on the mangrove ground. Understanding the potential detritivorous diet of P. canaliculata in invaded mangroves can help us to assess this species’ dispersal risk and provide support for mangrove management. Full article
(This article belongs to the Section Marine Biology)
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32 pages, 27098 KiB  
Article
Deriving Coastal Shallow Bathymetry from Sentinel 2-, Aircraft- and UAV-Derived Orthophotos: A Case Study in Ligurian Marinas
by Lorenza Apicella, Monica De Martino, Ilaria Ferrando, Alfonso Quarati and Bianca Federici
J. Mar. Sci. Eng. 2023, 11(3), 671; https://doi.org/10.3390/jmse11030671 - 22 Mar 2023
Cited by 4 | Viewed by 1542
Abstract
Bathymetric surveys of shallow waters are increasingly necessary for navigational safety and environmental studies. In situ surveys with floating acoustic sensors allow the collection of high-accuracy bathymetric data. However, such surveys are often unfeasible in very shallow waters in addition to being expensive [...] Read more.
Bathymetric surveys of shallow waters are increasingly necessary for navigational safety and environmental studies. In situ surveys with floating acoustic sensors allow the collection of high-accuracy bathymetric data. However, such surveys are often unfeasible in very shallow waters in addition to being expensive and requiring specific sectorial skills for the acquisition and processing of raw data. The increasing availability of optical images from Uncrewed Aerial Vehicles, aircrafts and satellites allows for bathymetric reconstruction from images thanks to the application of state-of-the-art algorithms. In this paper, we illustrate a bathymetric reconstruction procedure involving the classification of the seabed, the calibration of the algorithm for each class and the subsequent validation. We applied this procedure to high-resolution, UAV-derived orthophotos, aircraft orthophotos and Sentinel-2 Level-2A images of two marinas along the western Ligurian coastline in the Mediterranean Sea and validated the results with bathymetric data derived from echo-sounder surveys. Our findings showed that the aircraft-derived bathymetry is generally more accurate than the UAV-derived and Sentinel-2 bathymetry in all analyzed scenarios due to the smooth color of the aircraft orthophotos and their ability to reproduce the seafloor with a considerable level of detail. Full article
(This article belongs to the Special Issue Remote Sensing Techniques in Marine Environment)
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20 pages, 20842 KiB  
Article
Preliminary Investigation on Marine Radar Oil Spill Monitoring Method Using YOLO Model
by Bo Li, Jin Xu, Xinxiang Pan, Rong Chen, Long Ma, Jianchuan Yin, Zhiqiang Liao, Lilin Chu, Zhiqiang Zhao, Jingjing Lian and Haixia Wang
J. Mar. Sci. Eng. 2023, 11(3), 670; https://doi.org/10.3390/jmse11030670 - 22 Mar 2023
Cited by 3 | Viewed by 1468
Abstract
Due to the recent rapid growth of ocean oil development and transportation, the offshore oil spill risk accident probability has increased unevenly. The marine oil spill poses a great threat to the development of coastal cities. Therefore, effective and reliable technologies must be [...] Read more.
Due to the recent rapid growth of ocean oil development and transportation, the offshore oil spill risk accident probability has increased unevenly. The marine oil spill poses a great threat to the development of coastal cities. Therefore, effective and reliable technologies must be used to monitor oil spills to minimize disaster losses. Based on YOLO deep learning network, an automatic oil spill detection method was proposed. The experimental data preprocessing operations include noise reduction, gray adjustment, and local contrast enhancement. Then, real and synthetically generated marine radar oil spill images were used to make slice samples for training the model in the YOLOv5 network. The detection model can identify the effective oil spill monitoring region. Finally, an adaptive threshold was applied to extract the oil slicks in the effective oil spill monitoring regions. The YOLOv5 detection model generated had the advantage of high efficiency compared with existing methods. The offshore oil spill detection method proposed can support real-time and effective data for routine patrol inspection and accident emergency response. Full article
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19 pages, 10759 KiB  
Article
Statistical Analysis of Hybrid Atmospheric Ducts over the Northern South China Sea and Their Influence on Over-the-Horizon Electromagnetic Wave Propagation
by Yang Shi, Shuwen Wang, Fan Yang and Kunde Yang
J. Mar. Sci. Eng. 2023, 11(3), 669; https://doi.org/10.3390/jmse11030669 - 22 Mar 2023
Cited by 5 | Viewed by 1613
Abstract
Atmospheric ducts are special super-refractive atmospheric structures that can cause over-the-horizon propagation of electromagnetic waves. Different types of atmospheric ducts have different influences on electromagnetic wave propagation. Owing to the complex marine atmospheric environment, different types of atmospheric ducts often occur together. When [...] Read more.
Atmospheric ducts are special super-refractive atmospheric structures that can cause over-the-horizon propagation of electromagnetic waves. Different types of atmospheric ducts have different influences on electromagnetic wave propagation. Owing to the complex marine atmospheric environment, different types of atmospheric ducts often occur together. When evaluating the performance of an electromagnetic system near the sea surface, the combined influence of various atmospheric ducts should be considered comprehensively. In this paper, the statistical distribution of atmospheric ducts over the northern South China Sea is analyzed using sounding data and reanalysis data. This paper uses the parabolic equation model to analyze the propagation characteristics of microwaves near the sea surface in the presence of both surface and evaporation ducts. It is found that compared with cases where only one type of atmospheric duct is considered, a hybrid atmospheric duct structure can capture more microwave energy at a lower receiving height. At an antenna height of 5 m, the path loss begins to fluctuate beyond a propagation distance of 50 km, with the maximum fluctuation reaching about 15 dB. Microwave propagation characteristics at different microwave frequencies and antenna heights are also simulated and analyzed. Full article
(This article belongs to the Section Marine Environmental Science)
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15 pages, 1647 KiB  
Article
Optimization Study of Marine Energy Harvesting from Vortex-Induced Vibration Using a Response-Surface Method
by Peng Xu, Shanshan Jia, Dongao Li, Ould el Moctar and Changqing Jiang
J. Mar. Sci. Eng. 2023, 11(3), 668; https://doi.org/10.3390/jmse11030668 - 22 Mar 2023
Cited by 2 | Viewed by 1462
Abstract
Vortex-induced vibration (VIV) of bluff bodies is one type of flow-induced vibration phenomenon, and the possibility of using it to harvest hydrokinetic energy from marine currents has recently been revealed. To develop an optimal harvester, various parameters such as mass ratio, structural stiffness, [...] Read more.
Vortex-induced vibration (VIV) of bluff bodies is one type of flow-induced vibration phenomenon, and the possibility of using it to harvest hydrokinetic energy from marine currents has recently been revealed. To develop an optimal harvester, various parameters such as mass ratio, structural stiffness, and inflow velocity need to be explored, resulting in a large number of test cases. This study primarily aims to examine the validity of a parameter optimization approach to maximize the energy capture efficiency using VIV. The Box–Behnken design response-surface method (RSM-BBD) applied in the present study, for an optimization purpose, allows for us to efficiently explore these parameters, consequently reducing the number of experiments. The proper combinations of these operating variables were then identified in this regard. Within this algorithm, the spring stiffness, the reduced velocity, and the vibrator diameter are set as level factors. Correspondingly, the energy conversion efficiency was taken as the observed value of the target. The predicted results were validated by comparing the optimized parameters to values collected from the literature, as well as to our simulations using a computational-fluid dynamics (CFD) model. Generally, the optimal operating conditions predicted using the response-surface method agreed well with those simulated using our CFD model. The number of experiments was successfully reduced somewhat, and the operating conditions that lead to the highest efficiency of energy harvesting using VIV were determined. Full article
(This article belongs to the Special Issue Advanced Marine Energy Harvesting Technologies)
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19 pages, 9256 KiB  
Article
Study on the Effect of Air Injection Location on the Drag Reduction in SWATH with Air Lubrication
by Dapeng Zhang, Yunbo Li and Jiaye Gong
J. Mar. Sci. Eng. 2023, 11(3), 667; https://doi.org/10.3390/jmse11030667 - 22 Mar 2023
Cited by 2 | Viewed by 1631
Abstract
In this paper, the air lubrication method is applied to high-speed SWATH (small waterplane area twin hull) to reduce the resistance. The influence of air injection locations on drag reduction is investigated. The computed results are compared with experimental results, and the grid [...] Read more.
In this paper, the air lubrication method is applied to high-speed SWATH (small waterplane area twin hull) to reduce the resistance. The influence of air injection locations on drag reduction is investigated. The computed results are compared with experimental results, and the grid independence test is performed. Then, the numerical method is used to simulate the resistance of SWATH in calm water with airflow. The hull is divided into different areas, and the influence of the air injection location on the drag reduction in different areas of the hull is studied through different air injection locations and airflow rates. It could be seen that the air injection location on the underwater body is more conducive to the drag reduction in SWATH than the air injection location on the strut. Besides, the air injection location near the bow of the underwater body could cause a better drag reduction effect of SWATH. There are obvious differences in the drag reduction effect of different areas of the underwater body. Full article
(This article belongs to the Section Ocean Engineering)
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17 pages, 562 KiB  
Article
Cross-Layer Protocol Based on Directional Reception in Underwater Acoustic Wireless Sensor Networks
by Yao Sun, Wei Ge, Yingsong Li and Jingwei Yin
J. Mar. Sci. Eng. 2023, 11(3), 666; https://doi.org/10.3390/jmse11030666 - 21 Mar 2023
Cited by 3 | Viewed by 1450
Abstract
The long propagation delay of acoustic links leads to the complex randomness of packet collision, which reduces the network packet delivery rate (PDR) and aggravates network congestion. A single vector hydrophone with directional reception characteristics can concentrate the reception gain on a certain [...] Read more.
The long propagation delay of acoustic links leads to the complex randomness of packet collision, which reduces the network packet delivery rate (PDR) and aggravates network congestion. A single vector hydrophone with directional reception characteristics can concentrate the reception gain on a certain direction, which can increase spatial reuse, reduce packet collision, and help to improve the performance of the underwater acoustic wireless sensor networks (UASNs). Herein, this paper proposes a cross-layer protocol with low interference and low congestion (CLIC) based on directional reception. An integrated routing-medium access control (MAC) design is also devised in the CLIC scheme to use the directional beams to create the least-interfering, highest-capacity data transmission links, weighing key factors affecting network performance to obtain routes with low collisions and low congestion. Simulation results show that the CLIC has a higher packet delivery rate (PDR) and higher energy efficiency compared to the QELAR, CITP, and VBF protocols. Full article
(This article belongs to the Special Issue Underwater Wireless Communications: Recent Advances and Challenges)
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13 pages, 29325 KiB  
Article
Experimental Study on Corrosion Development Model and Fatigue Performance of Strand Steel for Coastal Structures
by Wei Peng and Weijie Fan
J. Mar. Sci. Eng. 2023, 11(3), 665; https://doi.org/10.3390/jmse11030665 - 21 Mar 2023
Cited by 1 | Viewed by 1131
Abstract
In order to study the corrosion time-varying law and fatigue properties of high-strength steel strands used for marine environment structures, the accelerated corrosion test of steel strands was carried out by using a climate simulation chamber, and samples with different corrosion times were [...] Read more.
In order to study the corrosion time-varying law and fatigue properties of high-strength steel strands used for marine environment structures, the accelerated corrosion test of steel strands was carried out by using a climate simulation chamber, and samples with different corrosion times were taken out for mass weighing, morphology observation, and fatigue testing. Steel strand specimens with different corrosion times (from 1 month to 14 years) for use in the real marine environment were developed in an indoor climate simulation test chamber. The average mass corrosion ratio curve of the steel strands in the marine environment and the changes in the corrosion pit size over time were obtained by performing data analysis based on weight and appearance. The time-varying rule of the fatigue life of coastal-structure steel strands was determined by conducting a fatigue test and fracture scanning electron microscopy (SEM) analysis of steel strands with different corrosion degrees. The results of the experimental study show that the mass corrosion rate and pit size of steel strands change with the service time as a piecewise function, fatigue performance changes with the service time is as an exponential function, and fatigue performance changes with the mass corrosion ratio are similar to a linear function. Furthermore, the corrosion pit has a significant impact on the fatigue life of the steel strand. Full article
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15 pages, 1182 KiB  
Article
Service Operation Vessels Fleet Size and Mix Location Routing for the Maintenance of an Offshore Floating Wind Farm
by Lis M. R. Silva, He Li and C. Guedes Soares
J. Mar. Sci. Eng. 2023, 11(3), 664; https://doi.org/10.3390/jmse11030664 - 21 Mar 2023
Cited by 2 | Viewed by 1980
Abstract
Mixed-integer linear programming is adopted to translate the routing of service operation vessels that support the logistic aspects of the maintenance of offshore floating wind farms into mathematical language. The models attempt to help the decision-makers by providing quantified tools to screen out [...] Read more.
Mixed-integer linear programming is adopted to translate the routing of service operation vessels that support the logistic aspects of the maintenance of offshore floating wind farms into mathematical language. The models attempt to help the decision-makers by providing quantified tools to screen out the optimal planning for preventive maintenance. The models search for the optimal offshore base location, vessel’s routing per day, vessel’s capacity, and vessel fleet composition that minimize the total fixed and variable infrastructure cost. The integration of the vehicle fleet size and mix problem, facility location–allocation problem, and vehicle-routing problem with time window advances the state of the art. A realistic case study is shown, and the results and discussions demonstrated that the practical insights of the solutions, as well as the identification of the route patterns through a navigation route table, may improve the decision planning of preventive maintenance. Full article
(This article belongs to the Special Issue Offshore Wind Energy)
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19 pages, 3958 KiB  
Article
Arthrospira platensis Variants: A Comparative Study Based on C-phycocyanin Gene and Protein, Habitat, and Growth Conditions
by Nawal Abd El-Baky, Neama Mahmoud Fattouh Rezk and Amro A. Amara
J. Mar. Sci. Eng. 2023, 11(3), 663; https://doi.org/10.3390/jmse11030663 - 21 Mar 2023
Cited by 2 | Viewed by 1907
Abstract
This study aimed to map the differences between Arthrospira sp. and Arthrospira platensis strains and variants from the order Oscillatoriales at the gene and protein levels of C-phycocyanin alpha chain via multiple alignment, phylogenetic trees of species, and analysis of the nucleotide and [...] Read more.
This study aimed to map the differences between Arthrospira sp. and Arthrospira platensis strains and variants from the order Oscillatoriales at the gene and protein levels of C-phycocyanin alpha chain via multiple alignment, phylogenetic trees of species, and analysis of the nucleotide and amino acid composition of the studied sequences. The links between gene/protein and environmental features of the habitat or source of isolation were also investigated. Phycocyanin was extracted from three A. platensis strains: an Egyptian isolate cultivated in the laboratory under static conditions in a highly saline medium and two commercial products. The French commercial strain showed the highest extraction yield but the lowest C-phycocyanin purity, and the color intensity of the extracted pigment from the Egyptian isolate was significantly weaker than those of the two commercial strains. All the analyzed species and strains had GC content of more than 54.5% in C-phycocyanin alpha chain gene and showed high abundance of alanine, an amino acid encoded exclusively by GC-biased codons, in their protein. The frequencies of the acidic amino acids aspartic acid and glutamic acid were 5.2% and 5.0% on average, respectively, which were slightly higher than those of the basic residues (4.3% arginine, 0.6% histidine, and 5.0% lysine). Data relating to the isolation source of most of the analyzed species revealed harsh conditions, such as high alkalinity, salinity, CO2 saturation, and/or temperature. These findings may link the gene/protein of C-phycocyanin, which is one of the most important bioactive proteins of A. platensis, to the adaptation of this organism to harsh environmental conditions and associate the color of the pigment to cultivation conditions and/or isolation source. Full article
(This article belongs to the Section Marine Biology)
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13 pages, 12412 KiB  
Article
Real-World Underwater Image Enhancement Based on Attention U-Net
by Pengfei Tang, Liangliang Li, Yuan Xue, Ming Lv, Zhenhong Jia and Hongbing Ma
J. Mar. Sci. Eng. 2023, 11(3), 662; https://doi.org/10.3390/jmse11030662 - 21 Mar 2023
Cited by 3 | Viewed by 2366
Abstract
In recent years, with the increasingly serious problems of resource shortage and environmental pollution, the exploration and development of underwater clean energy were particularly important. At the same time, abundant underwater resources and species have attracted a large number of scientists to carry [...] Read more.
In recent years, with the increasingly serious problems of resource shortage and environmental pollution, the exploration and development of underwater clean energy were particularly important. At the same time, abundant underwater resources and species have attracted a large number of scientists to carry out research on underwater-related tasks. Due to the diversity and complexity of underwater environments, it is difficult to perform related vision tasks, such as underwater target detection and capture. The development of digital image technology has been relatively mature, and it has been applied in many fields and achieved remarkable results, but the research on underwater image processing technology is rarely effective. The underwater environment is much more complicated than that on land, and there is no light source underwater. Underwater imaging systems must rely on artificial light sources for illumination. When light travels through water, it is severely attenuated by water absorption, reflection, and scattering. The collected underwater images inevitably have problems such as limited visible range, blur, low contrast, uneven illumination, incoherent colors, and noise. The purpose of image enhancement is to improve or solve one or more of the above problems in a targeted manner. Therefore, underwater image enhancement technology has become one of the key contents of underwater image processing technology research. In this paper, we proposed a conditional generative adversarial network model based on attention U-Net which contains an attention gate mechanism that could filter invalid feature information and capture contour, local texture, and style information effectively. Furthermore, we formulate an objective function through three different loss functions, which can evaluate image quality from global content, color, and structural information. Finally, we performed end-to-end training on the UIEB real-world underwater image dataset. The comparison experiments show that our method outperforms all comparative methods, the ablation experiments show that the loss function proposed in this paper outperforms a single loss function, and finally, the generalizability of our method is verified by executing on two different datasets, UIEB and EUVP. Full article
(This article belongs to the Section Ocean Engineering)
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17 pages, 34204 KiB  
Article
Numerical Analysis of Flow Characteristics in Impeller-Guide Vane Hydraulic Coupling Zone of an Axial-Flow Pump as Turbine Device
by Fan Yang, Zhongbin Li, Yuting Lv, Jindong Li, Guangxin Zhou and Ahmed Nasr
J. Mar. Sci. Eng. 2023, 11(3), 661; https://doi.org/10.3390/jmse11030661 - 21 Mar 2023
Cited by 1 | Viewed by 1325
Abstract
An axial-flow pump as a turbine (PAT), as compared to the conventional Francis turbine, has the advantages of not being restricted by the terrain and having lower cost to reverse the pump as a turbine for power generation. When an axial-flow pump is [...] Read more.
An axial-flow pump as a turbine (PAT), as compared to the conventional Francis turbine, has the advantages of not being restricted by the terrain and having lower cost to reverse the pump as a turbine for power generation. When an axial-flow pump is reversed as a turbine, the internal flow pattern is more complicated than when in the pump mode, which can cause instability in the whole system and result in degradation of the hydraulic performance and structural vibration. The impeller and guide vane are the core of the axial-flow PAT unit. This research compares the experimental and numerical simulation results in order to verify the energy performance and pressure pulsation signal of the axial-flow PAT. The unsteady flow regime, fluid force, and pressure pulsation characteristics of the impeller-guide vane hydraulic coupling zone are analyzed in detail. The findings demonstrate that both the dominant frequency of the fluid force pulsation signal and the flow field pressure pulsation signal appear at 3 times of the rotation frequency. The blade passing frequency (BPF) of the impeller is the dominant frequency, and other frequency components are also dominated by the harmonic frequency of the BPF. The impeller and guide vane are primarily subject to radial fluid force. Under partial working conditions, the pressure pulsation intensity in the flow field greatly increases, and the pressure pulsation amplitude at the guide vane outlet and impeller outlet appears to be more sensitive to the flow rate change. Full article
(This article belongs to the Section Ocean Engineering)
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22 pages, 9639 KiB  
Article
Automated Atmospheric Correction of Nanosatellites Using Coincident Ocean Color Radiometer Data
by Sean McCarthy, Summer Crawford, Christopher Wood, Mark D. Lewis, Jason K. Jolliff, Paul Martinolich, Sherwin Ladner, Adam Lawson and Marcos Montes
J. Mar. Sci. Eng. 2023, 11(3), 660; https://doi.org/10.3390/jmse11030660 - 21 Mar 2023
Cited by 4 | Viewed by 1684
Abstract
Here we present a machine-learning-based method for utilizing traditional ocean-viewing satellites to perform automated atmospheric correction of nanosatellite data. These sensor convolution techniques are required because nanosatellites do not usually possess the wavelength combinations required to atmospherically correct upwelling radiance data for oceanographic [...] Read more.
Here we present a machine-learning-based method for utilizing traditional ocean-viewing satellites to perform automated atmospheric correction of nanosatellite data. These sensor convolution techniques are required because nanosatellites do not usually possess the wavelength combinations required to atmospherically correct upwelling radiance data for oceanographic applications; however, nanosatellites do provide superior ground-viewing spatial resolution (~3 m). Coincident multispectral data from the Suomi National Polar-Orbiting Partnership Visible Infrared Imaging Radiometer Suite (Suomi NPP VIIRS; referred to herein as “VIIRS”) were used to remove atmospheric contamination at each of the nanosatellite’s visible wavelengths to yield an estimate of spectral water-leaving radiance [Lw(l)], which is the basis for surface ocean optical products. Machine learning (ML) algorithms (KNN, decision tree regressors) were applied to determine relationships between Lw and top-of-atmosphere (Lt)/Rayleigh (Lr) radiances within VIIRS training data, and then applied to test cases for (1) the Marine Optical Buoy (MOBY) in Hawaii and (2) the AErosol RObotic Network Ocean Color (AERONET-OC), Venice, Italy. For the test cases examined, ML-based methods appeared to improve statistical results when compared to alternative dark spectrum fitting (DSF) methods. The results suggest that ML-based sensor convolution techniques offer a viable path forward for the oceanographic application of nanosatellite data streams. Full article
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20 pages, 2793 KiB  
Article
Neural Network, Nonlinear-Fitting, Sliding Mode, Event-Triggered Control under Abnormal Input for Port Artificial Intelligence Transportation Robots
by Yaping Zhu, Qiang Zhang, Yang Liu, Yancai Hu and Sihang Zhang
J. Mar. Sci. Eng. 2023, 11(3), 659; https://doi.org/10.3390/jmse11030659 - 21 Mar 2023
Cited by 1 | Viewed by 1148
Abstract
A new control algorithm was designed to solve the problems of actuator physical failure, remote network attack, and sudden change in trajectory curvature when a port’s artificial intelligence-based transportation robots track transportation in a freight yard. First of all, the nonlinear, redundant, saturated [...] Read more.
A new control algorithm was designed to solve the problems of actuator physical failure, remote network attack, and sudden change in trajectory curvature when a port’s artificial intelligence-based transportation robots track transportation in a freight yard. First of all, the nonlinear, redundant, saturated sliding surface was designed based on the redundant information of sliding mode control caused by the finite nature of control performance; the dynamic acceleration characteristic of super-twisted sliding mode reaching law was considered to optimize the control high frequency change caused by trajectory mutation; and an improved super-twist reaching law was designed. Then, a nonlinear factor was designed to construct a nonlinear, fault-tolerant filtering mechanism to compensate for the abnormal part of the unknown input that cannot be executed by adaptive neural network reconstruction. On this basis, the finite-time technology and parameter-event-triggered mechanism were combined to reduce the dependence on communication resources. As a result, the design underwent simulation verification to verify its effectiveness and superiority. In the comparative simulation, under a consistent probability of a network attack, the tracking accuracy of the algorithm proposed in this paper was 22.65%, 12.69% and 11.48% higher those that of the traditional algorithms. Full article
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11 pages, 2155 KiB  
Article
A State-Dependent Hypoplastic Bounding Surface Model for Gassy Sand
by Mingyuan Wang, Jizhu Sun and Yong Wang
J. Mar. Sci. Eng. 2023, 11(3), 658; https://doi.org/10.3390/jmse11030658 - 21 Mar 2023
Viewed by 1164
Abstract
As a kind of partially saturated soil often containing dissolved gas with a high degree of saturation (S > 85%), gassy sand sediment widely exists in the marine environment all over the world. Due to the effect of gas dissolution and exsolution on [...] Read more.
As a kind of partially saturated soil often containing dissolved gas with a high degree of saturation (S > 85%), gassy sand sediment widely exists in the marine environment all over the world. Due to the effect of gas dissolution and exsolution on the pore fluid compressibility, its stress–strain and pore pressure responses are quite different from those of common saturated and unsaturated soils when subjected to undrained loading. Since almost all the gas bubbles are occluded in the pore water of offshore gassy sand, the matric suction may be neglected, and an undrained constitutive model for gassy sand is developed based on the existing hypoplastic bounding surface model for saturated sand. Both Boyle’s and Henry’s laws are employed in the model to characterize the equilibrium behavior of the gas compressibility and solubility, and then the equivalent compressibility coefficient of the pore fluid is obtained. To avoid unrealistic volumetric expansion, the concepts of the critical state and state-dependent dilatancy stress ratio are incorporated to describe its ultimate shear strength and dilatancy characteristics, respectively. Finally, the triaxial undrained test results on gas-charged sand from Hangzhou Bay are analyzed at three initial saturation degrees of 85%, 90%, and 100%, and two effective confining pressures of 50 kPa and 200 kPa. Moreover, carbon dioxide (CO2) was selected in the test, and the samples were loose with a relative density of 30%. It is noted that a good agreement is achieved between the simulation results and the experimental data, including the influence of gas content and confining pressure on the shear dilatancy and the mean effective stress increase at the beginning of the effective stress path, among others. Full article
(This article belongs to the Special Issue Advances in Offshore Geotechnics)
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14 pages, 4177 KiB  
Article
Uncertainty Assessment of Wave Elevation Field Measurement Using a Depth Camera
by Hoyong Kim, Chanil Jeon, Kiwon Kim and Jeonghwa Seo
J. Mar. Sci. Eng. 2023, 11(3), 657; https://doi.org/10.3390/jmse11030657 - 21 Mar 2023
Cited by 1 | Viewed by 1265
Abstract
The present study suggests a methodology for acquiring wave elevation fields using a depth camera sensor, with assessment results for the test uncertainty. The depth camera module of an Azure Kinect is calibrated using marker arrays on the optic table, to obtain a [...] Read more.
The present study suggests a methodology for acquiring wave elevation fields using a depth camera sensor, with assessment results for the test uncertainty. The depth camera module of an Azure Kinect is calibrated using marker arrays on the optic table, to obtain a polynomial mapping function between the pixel-wise and physical position. For installation of the depth camera in a wave channel, the system is aligned using the built-in inertial measurement unit of Azure Kinect to be perpendicular to the calm water surface. The systematic and random standard uncertainties were evaluated from the analysis of calibration and repeated tests, respectively. The wave height measurement results for the depth camera were compared to those for the capacitance-type and ultrasonic wave height gauges. The test uncertainty of the depth camera increased in large wave stiffness conditions, where the time-of-flight sensor has a disadvantage in measurement. Full article
(This article belongs to the Section Physical Oceanography)
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17 pages, 16130 KiB  
Article
Application of Buoyancy Support System to Secure Residual Buoyancy of Damaged Ships
by Gyeong Joong Lee, Jang-Pyo Hong, Kwang Keun Lee and Hee Jin Kang
J. Mar. Sci. Eng. 2023, 11(3), 656; https://doi.org/10.3390/jmse11030656 - 20 Mar 2023
Cited by 2 | Viewed by 1801
Abstract
SOLAS (Safety of Life at Sea), which was first enacted in 1914 as a result of the Titanic disaster, presents mandatory requirements for ship safety, such as the adoption of watertight bulkheads. However, ship accidents continue to occur despite the development and application [...] Read more.
SOLAS (Safety of Life at Sea), which was first enacted in 1914 as a result of the Titanic disaster, presents mandatory requirements for ship safety, such as the adoption of watertight bulkheads. However, ship accidents continue to occur despite the development and application of numerous safety technologies. In the case of a marine accident, the risk of sinking or capsizing due to flooding can be reduced by subdividing the watertight area, but shipbuilding costs, the weight increase for light ships, and the intact stability of the vessel must be considered together. For this reason, in this study, a BSS (buoyancy support system) was designed in accordance with ISO 23121-1 and ISO 23121-2. The characteristics of watertight and non-watertight spaces were reviewed and the BSS was implemented for a small car ferry. By applying additional safety technologies while securing economic feasibility in terms of ship construction and operation, an alternative to reduce the loss of human lives, environmental damage, and property losses in the case of a ship accident was proposed. Full article
(This article belongs to the Special Issue Damage Stability of Ships)
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11 pages, 1899 KiB  
Article
New Finding of Eggs and Leptocephalus for Muraenesox cinereus off Jeju Island, Korea and Its Relation to Environmental Variables
by Hwan-Sung Ji, Hyo-Jae Yu, Seung-Jong Lee, Sukyung Kang and Jin-Koo Kim
J. Mar. Sci. Eng. 2023, 11(3), 655; https://doi.org/10.3390/jmse11030655 - 20 Mar 2023
Viewed by 1127
Abstract
The daggertooth pike conger, Muraenesox cinereus, is an important demersal fish species in East Asia but the catch amount has declined in recent years. Spawning areas of M. cinereus have not yet been determined; identifying these have serious implications for resource management. [...] Read more.
The daggertooth pike conger, Muraenesox cinereus, is an important demersal fish species in East Asia but the catch amount has declined in recent years. Spawning areas of M. cinereus have not yet been determined; identifying these have serious implications for resource management. Ichthyoplankton surveys are an effective method of distinguishing fish spawning areas and periods. Fish eggs were sampled from the waters adjacent to South Korea in August 2020 and 2022 using a Multiple Opening/Closing Net and Environmental Sensing System or a bongo net. In 2021, M. cinereus eggs were not collected. Three unidentified eggs (2.0–2.2 mm in diameter) were collected from the southeastern sea of Jeju Island at a seawater depth of 20–30 m and temperature of 20–22 °C. Muraenesox cinereus preleptocephali were gathered at 10–20 m depths from Jeju Island’s southernmost and eastern sea areas. The eggs and preleptocephali were identified as M. cinereus by their mitochondrial DNA 16S rRNA sequences. This is a new finding of eggs and leptocephalus of Muraenesox cinereus off Jeju Island, South Korea, which increases our understanding of the recruitment process of M. cinereus to facilitate resource management and species conservation. Full article
(This article belongs to the Section Marine Biology)
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25 pages, 21339 KiB  
Article
Coastal Erosion Identification and Monitoring in the Patras Gulf (Greece) Using Multi-Discipline Approaches
by Nikolaos Depountis, Dionysios Apostolopoulos, Vasileios Boumpoulis, Dimitris Christodoulou, Athanassios Dimas, Elias Fakiris, Georgios Leftheriotis, Alexandros Menegatos, Konstantinos Nikolakopoulos, George Papatheodorou and Nikolaos Sabatakakis
J. Mar. Sci. Eng. 2023, 11(3), 654; https://doi.org/10.3390/jmse11030654 - 20 Mar 2023
Cited by 7 | Viewed by 2345
Abstract
The primary objective of this research is to demonstrate advanced surveying methods and techniques for coastal erosion identification and monitoring in a densely human-populated coastline, the southern coastline of the Gulf of Patras (Greece), which diachronically suffers erosion problems expected to become worse [...] Read more.
The primary objective of this research is to demonstrate advanced surveying methods and techniques for coastal erosion identification and monitoring in a densely human-populated coastline, the southern coastline of the Gulf of Patras (Greece), which diachronically suffers erosion problems expected to become worse in the forthcoming years due to climate change and human intervention. Its importance lies in the fact that it presents a robust methodology on how all modern scientific knowledge and techniques should be used in coastal erosion problems. The presented methods include the use of satellite and aerial photo imaging, shallow seabed bathymetry and morphology, sediment sampling, geotechnical investigations, as well as hydrodynamic modelling. The results are extensively analyzed in terms of their importance in coastal erosion studies and are cross-validated to define those areas most vulnerable to erosion. Towards this scope, the seabed erosion rate produced by hydrodynamic modelling is compared with the coastal vulnerability index (CVI) calculations performed in the examined area to identify which coastal zones are under a regime of intensive erosion. The results between the CVI and the seabed erosion rate appear to coincide in terms of the erosion potential, especially in zones where the vulnerability regime has been calculated as being high or very high, with the P. oceanica meadows playing an important role in reducing erosion. Full article
(This article belongs to the Special Issue Estuaries, Coasts, and Seas in a Changing Climate)
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25 pages, 19644 KiB  
Article
Study of the Optimal Grid Resolution and Effect of Wave–Wave Interaction during Simulation of Extreme Waves Induced by Three Ensuing Typhoons
by Shih-Chun Hsiao, Han-Lun Wu and Wei-Bo Chen
J. Mar. Sci. Eng. 2023, 11(3), 653; https://doi.org/10.3390/jmse11030653 - 20 Mar 2023
Cited by 4 | Viewed by 1384
Abstract
Three typhoons, Meranti, Malakas, and Megi, occurred successively in eastern Taiwanese waters in September 2016, causing extreme waves (significant wave height > 10.0 m), and these events were selected to investigate the effect of model grid resolution and wave–wave interaction on simulating typhoon-driven [...] Read more.
Three typhoons, Meranti, Malakas, and Megi, occurred successively in eastern Taiwanese waters in September 2016, causing extreme waves (significant wave height > 10.0 m), and these events were selected to investigate the effect of model grid resolution and wave–wave interaction on simulating typhoon-driven waves. The WAVEWATCH III (WW3) model, with 0.50 deg, 0.25 deg, 0.20 deg, 0.10 deg, and 0.05 deg grid resolutions, and two reanalysis wind fields were adopted to simulate ocean waves during these three typhoons. The results indicated that the exertion of the Climate Forecast System version 2 (CFSv2) winds over the WW3 model with 0.10 deg grid resolution yielded optimum simulations of typhoon waves in a compromise between accuracy and elapsed time. In the present study, the WW3 model modeled nonlinear wave–wave interactions using discrete interaction approximation (DIA). The numerical experiments revealed that the underestimations of typhoon waves were significant when the WW3 model excluded nonlinear wave–wave interactions, especially when employing a higher grid resolution. This study also found that the WW3 model is superior to the Wind Wave Model III (WWM-III) using the CFSv2 winds because the WWM-III tended to overestimate the extreme waves in all three of these eastern Taiwan typhoon events that occurred in September 2016. Full article
(This article belongs to the Special Issue Coastal Risk Prediction, Prevention and Management)
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19 pages, 3575 KiB  
Article
An Improved Method for Optimizing CNC Laser Cutting Paths for Ship Hull Components with Thicknesses up to 24 mm
by Xuan Liu and Daofang Chang
J. Mar. Sci. Eng. 2023, 11(3), 652; https://doi.org/10.3390/jmse11030652 - 20 Mar 2023
Cited by 1 | Viewed by 1509
Abstract
In this paper, the essence and optimization objectives of the hull parts path optimization problem of CNC laser cutting are described, and the shortcomings of the existing optimization methods are pointed out. Based on the optimization problem of the hull parts CNC laser [...] Read more.
In this paper, the essence and optimization objectives of the hull parts path optimization problem of CNC laser cutting are described, and the shortcomings of the existing optimization methods are pointed out. Based on the optimization problem of the hull parts CNC laser cutting path, a new part-cutting constraint rule based on partial cutting is proposed, which aims to overcome the drawbacks of the traditional algorithms with serial cutting constraint rules. This paper addresses the problem of optimizing the path for CNC laser cutting of hull parts, including an empty path and the order and directions used for the provided cut contours. Based on the discretization of the part contour segments, a novel toolpath model for hull parts called hull parts cutting path optimization problems based on partial cutting rules (HPCPO) is proposed in this paper. To solve the HPCPO problem, a segmented genetic algorithm based on reinforcement learning (RLSGA) is proposed. In RLSGA, the population is viewed as an intelligent agent, and the agent’s state is the population’s diversity coefficient. Three different segmented crossover operators are considered as the agent’s actions, and the agent’s reward is related to the changes in the population’s fitness and diversity coefficients. Two benchmark problems for HPCPO were constructed to evaluate the performance of RLSGA and compared with four other algorithms. The results showed that RLSGA outperformed the other algorithms and effectively solved the HPCPO problem. Full article
(This article belongs to the Special Issue Fatigue and Fracture Mechanics of Marine Structures)
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