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J. Mar. Sci. Eng., Volume 11, Issue 4 (April 2023) – 206 articles

Cover Story (view full-size image): In order to meet the limitations of stringent regulations applied by international regulators, it is important to evaluate the overall performance of ships in different operating conditions. Therefore, assessing ship performance is essential by taking into account the hull and propeller roughness over several years in service. Combining several numerical models based on optimization procedures has become an essential and effective tool to easily estimate, in general, the overall performance of a ship and, in particular, the amount of fuel consumption and exhaust emissions over a ship’s life. From this study, considering as many details as possible will increase the accuracy of the computed results, thus achieving a good estimation of ship performance over the years and maintenance plans. View this paper
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24 pages, 8914 KiB  
Article
Water Structure in the Utrish Nature Reserve (Black Sea) during 2020–2021 According to Thermistor Chain Data
by Ksenia Silvestrova, Stanislav Myslenkov, Oksana Puzina, Artem Mizyuk and Olga Bykhalova
J. Mar. Sci. Eng. 2023, 11(4), 887; https://doi.org/10.3390/jmse11040887 - 21 Apr 2023
Cited by 2 | Viewed by 1516
Abstract
This paper reports the water temperature structure and associated coastal processes in the NE part of the Black Sea. In situ temperature was measured in the water area of the Utrish Nature Reserve. The thermistor chain was moored in 2020 and included 6–10 [...] Read more.
This paper reports the water temperature structure and associated coastal processes in the NE part of the Black Sea. In situ temperature was measured in the water area of the Utrish Nature Reserve. The thermistor chain was moored in 2020 and included 6–10 temperature sensors with an accuracy of ±0.025 °C and time step of one minute. The seasonal variations in the water temperature, upwelling events, internal waves and diurnal cycle were analyzed. The maximum value of SST (28.6 °C) was registered in the subsurface layer in August 2021; the minimum (7.7 °C) was registered in March 2022. Estimates of the diurnal temperature cycle were obtained according to spectral analysis. Summer months show the diurnal cycle more than 60% of the time, and the cold period shows it less than 10% of the time. Internal waves appeared in thermocline with periods from 5 min to 20 h. The strongest Ekman upwelling was registered in September 2021. The water temperature dropped from 26 °C to 16 °C in 10 h. Additionally, quality assessments of two hydrodynamic models were made. The models showed a good correlation (0.9) with water temperature measurements, but RMSE could reach 1–1.8 °C for subsurface layers. Temperature variability and its characteristics are an important basis for future coastal ecosystem studies in the Utrish. Full article
(This article belongs to the Special Issue Upwelling Systems in a Changing Ocean)
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25 pages, 12945 KiB  
Article
Hydrodynamic Shape Design and Self-Propulsion Analysis of a Hybrid-Driven AUG
by Chen-Wei Chen, Zhao-Ye Zhou, Xu-Peng Chen and Xiao-Jing Zhou
J. Mar. Sci. Eng. 2023, 11(4), 886; https://doi.org/10.3390/jmse11040886 - 21 Apr 2023
Viewed by 1368
Abstract
Due to the lack of a powerful propulsion device in conventional autonomous underwater gliders (AUGs), their mobility and flexibility are insufficient, thus not being capable of also ensuring the stability of the motion route. Thus, it is necessary to further develop hybrid-driven AUGs. [...] Read more.
Due to the lack of a powerful propulsion device in conventional autonomous underwater gliders (AUGs), their mobility and flexibility are insufficient, thus not being capable of also ensuring the stability of the motion route. Thus, it is necessary to further develop hybrid-driven AUGs. This paper applied CFD simulation and experimental analysis methods to study and design a hybrid-driven AUG with a propeller optimized from a type of AUG with swept-forward and swept-back wings. Through parameter adjustment, the hydrodynamic configuration was optimized, and the optimal hull design and hydrofoil type selection were proposed. The lift–drag ratio could be improved by up to 22.5% at an angle of attack of 8 degrees. The optimized AUG was combined with a single propeller for self-propulsion simulation. Aiming at the problem caused by the propeller torque on the AUG, the strategy of a contra-rotating propeller (CRP) was conducted to self-eliminate the propeller torque. The simulation results show that in the self-propulsion state, the torque of the contra-rotating propeller could be reduced by more than 92% compared with that of a single propeller, greatly reducing the impact on the hybrid-driven AUG and raising the navigation stability. Full article
(This article belongs to the Special Issue Advances in Ship and Marine Hydrodynamics)
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45 pages, 46634 KiB  
Review
A Survey on Physical Layer Techniques and Challenges in Underwater Communication Systems
by Naveed Ur Rehman Junejo, Mariyam Sattar, Saifullah Adnan, Haixin Sun, Abuzar B. M. Adam, Ahmad Hassan and Hamada Esmaiel
J. Mar. Sci. Eng. 2023, 11(4), 885; https://doi.org/10.3390/jmse11040885 - 21 Apr 2023
Cited by 5 | Viewed by 3199
Abstract
In the past decades, researchers/scientists have paid attention to the physical layer of underwater communications (UWCs) due to a variety of scientific, military, and civil tasks completed beneath water. This includes numerous activities critical for communication, such as survey and monitoring of oceans, [...] Read more.
In the past decades, researchers/scientists have paid attention to the physical layer of underwater communications (UWCs) due to a variety of scientific, military, and civil tasks completed beneath water. This includes numerous activities critical for communication, such as survey and monitoring of oceans, rescue, and response to disasters under the sea. Till the end of the last decade, many review articles addressing the history and survey of UWC have been published which were mostly focused on underwater sensor networks (UWSN), routing protocols, and underwater optical communication (UWOC). This paper provides an overview of underwater acoustic (UWA) physical layer techniques including cyclic prefix orthogonal frequency division multiplexing (CP-OFDM), zero padding orthogonal frequency division multiplexing (ZP-OFDM), time-domain synchronization orthogonal frequency division multiplexing (TDS-OFDM), multiple input multiple output orthogonal frequency division multiplexing (MIMO-OFDM), generalized frequency division multiplexing (GFDM), unfiltered orthogonal frequency division multiplexing (UF-OFDM), continuous phase modulation orthogonal frequency division multiplexing (CPM-OFDM), filter bank multicarrier (FBMC) modulation, MIMO, spatial modulation technologies (SMTs), and orthogonal frequency division multiplexing index modulation (OFDM-IM). Additionally, this paper provides a comprehensive review of UWA channel modeling problems and challenges, such as transmission loss, propagation delay, signal-to-noise ratio (SNR) and distance, multipath effect, ambient noise effect, delay spread, Doppler effect modeling, Doppler shift estimation. Further, modern technologies of the physical layer of UWC have been discussed. This study also discusses the different modulation technology in terms of spectral efficiency, computational complexity, date rate, bit error rate (BER), and energy efficiency along with their merits and demerits. Full article
(This article belongs to the Special Issue Underwater Perception and Sensing with Robotic Sensors and Networks)
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20 pages, 2510 KiB  
Article
An Approach for Shipping Emissions Estimation in Ports: The Case of Ro–Ro Vessels in Port of Vigo
by Ana B. Albo-López, Camilo Carrillo and Eloy Díaz-Dorado
J. Mar. Sci. Eng. 2023, 11(4), 884; https://doi.org/10.3390/jmse11040884 - 21 Apr 2023
Viewed by 1883
Abstract
Despite most atmospheric emissions being produced by vessels when navigating at sea, they are also important when in port because of their proximity to urban areas and their harmful effects on climate change and health. First, we carried out a bibliographical review of [...] Read more.
Despite most atmospheric emissions being produced by vessels when navigating at sea, they are also important when in port because of their proximity to urban areas and their harmful effects on climate change and health. First, we carried out a bibliographical review of the nine most relevant methods to estimate the emission of ships in ports. These methods have been used to estimate the emissions of the sixteen most representatives Ro–Ro (roll-on–roll-off) ships calling at the Port of Vigo. From the results obtained, a new simplified method for estimation is proposed, which is based on linear regression curves and takes into account the number of ships and the average number of hours they remain in port annually. This simplification could be a useful tool when making preliminary assessments of the emissions from ships in port, which can also be extrapolated to other ports or types of ships. Full article
(This article belongs to the Special Issue Water Pollution under Climate Change in Coastal Areas)
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14 pages, 12312 KiB  
Article
Numerical and Experimental Investigations on Non-Linear Wave Action on Offshore Wind Turbine Monopile Foundation
by Sijia Deng, Ming Qin, Dezhi Ning, Lin Lin, Songxiong Wu and Chongwei Zhang
J. Mar. Sci. Eng. 2023, 11(4), 883; https://doi.org/10.3390/jmse11040883 - 21 Apr 2023
Cited by 1 | Viewed by 1595
Abstract
Monopiles are commonly utilized in offshore wind farms but are prone to non-linear wave loads and run-ups, significantly affecting their engineering design. Therefore, it is crucial to pursue a complete understanding of the non-linear wave action on monopile foundations. Both numerical and experimental [...] Read more.
Monopiles are commonly utilized in offshore wind farms but are prone to non-linear wave loads and run-ups, significantly affecting their engineering design. Therefore, it is crucial to pursue a complete understanding of the non-linear wave action on monopile foundations. Both numerical and experimental investigations on the non-linear wave loads and run-ups on an offshore wind turbine monopile foundation are performed in this paper. The experiment is carried out at a scale of 1/30 in a wave flume at the State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, in which the wave loads and run-ups along the monopile are measured. Based on the second-order potential flow model and time-domain higher-order boundary element method (HOBEM), the related numerical tests are conducted to study the non-linear effects further. It is found that the present non-linear potential theory is sufficient for the simulation of wave force and run-ups on the monopile in the range of wave slope kA < 0.15 before wave breaking. “W” type distribution of wave run-up along the monopile is found, in which the peak value occurs at the frontward side (i.e., θ =180°) and is the maximum due to full reflection; the two symmetrical minimum amplitudes lie in the zones of (45° ≤ θ ≤ 90°) and (270° ≤ θ ≤ 315°), whose positions shift downward with the increase of wave non-linearity. Energy transfer among the fundamental wave component and higher-order components is also found, which is most apparent on the backward side. Besides, the transverse resonance occurs in the wave flume due to the wavelength being near the flume width, which induces the wave run-up at the backward position larger than that at the frontward position. Full article
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15 pages, 3774 KiB  
Article
Three-Dimensional-Printed Coral-like Structures as a Habitat for Reef Fish
by Asa Oren, Ofer Berman, Reem Neri, Ezri Tarazi, Haim Parnas, Offri Lotan, Majeed Zoabi, Noam Josef and Nadav Shashar
J. Mar. Sci. Eng. 2023, 11(4), 882; https://doi.org/10.3390/jmse11040882 - 21 Apr 2023
Cited by 3 | Viewed by 2210
Abstract
Coral reefs are three-dimensional biogenic structures that provide habitat for plenty of marine organisms; yet, coral reefs are deteriorating worldwide. Hence, it is essential to identify suitable substitutes for such coral services. This study examines reef fishes’ behavior and reactions to three-dimensional-printed (3DP) [...] Read more.
Coral reefs are three-dimensional biogenic structures that provide habitat for plenty of marine organisms; yet, coral reefs are deteriorating worldwide. Hence, it is essential to identify suitable substitutes for such coral services. This study examines reef fishes’ behavior and reactions to three-dimensional-printed (3DP) corals based on scanned Stylophora pistillata, as well as modified 3DP models. In particular, fishes’ unresponsiveness to the color, shape, morphology, and material of 3DP models both in vitro and in situ experiments was investigated. Coral reef fishes responded to the 3DP corals and demonstrated their usage in a range of services. Moreover, a greater number of fish species interacted more with 3DP models than they did with live corals. Furthermore, specific reef fish species, such as Sea Goldies (Pseudanthias squamipinnis), showed a preference for specific 3DP coral color, and other species demonstrated preferences for specific 3DP model shapes. The current study results show that three-dimensional-printed coral models can substitute for live corals for certain types of reef fish services. Full article
(This article belongs to the Topic Marine Ecology, Environmental Stress and Management)
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23 pages, 12987 KiB  
Article
Influence of Topographic and Geological Features on the Seismic Response of the Reef Site in the South China Sea
by Xin Bao, Jingbo Liu and Fei Wang
J. Mar. Sci. Eng. 2023, 11(4), 881; https://doi.org/10.3390/jmse11040881 - 21 Apr 2023
Cited by 1 | Viewed by 1184
Abstract
Insufficient comprehension of the seismic impact of the reef terrain, geology, and material properties of the reefs in the South China Sea still presents considerable impediments in studying the seismic response of reef engineering sites and assessing their seismic safety. To surmount this [...] Read more.
Insufficient comprehension of the seismic impact of the reef terrain, geology, and material properties of the reefs in the South China Sea still presents considerable impediments in studying the seismic response of reef engineering sites and assessing their seismic safety. To surmount this challenge, a seismic response analysis model of the reef-seawater system is established. This model takes into account the fluid-solid interaction effect, the wave radiation effect of the infinite seawater layer and the semi-infinite seabed, as well as the seismic wave input process of the reef-seawater system. Through targeted parameter analyses, the impact of various factors, including the shear wave velocity, thickness, and slope of distinct reef layers, the width of the reef flat, and the dynamic coupling effect of seawater on the seismic response of reef sites, is thoroughly examined. It has been determined that the seismic response of the reef site is markedly amplified as the shear wave velocity decreases and the thickness of the uppermost reef layer increases. While the effects of the slope gradient of the topmost reef layer and the width of the reef flat on the seismic response of the reef site are chiefly observed in the edge area and the central area, respectively. The layer of seawater plays a crucial role in radiation damping, serving as a medium for the dissipation of seismic energy and thereby weakening the overall seismic response of the reef site. Full article
(This article belongs to the Section Ocean Engineering)
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22 pages, 6946 KiB  
Article
TRFM-LS: Transformer-Based Deep Learning Method for Vessel Trajectory Prediction
by Dapeng Jiang, Guoyou Shi, Na Li, Lin Ma, Weifeng Li and Jiahui Shi
J. Mar. Sci. Eng. 2023, 11(4), 880; https://doi.org/10.3390/jmse11040880 - 21 Apr 2023
Cited by 9 | Viewed by 2297
Abstract
In the context of the rapid development of deep learning theory, predicting future motion states based on time series sequence data of ship trajectories can significantly improve the safety of the traffic environment. Considering the spatiotemporal correlation of AIS data, a trajectory time [...] Read more.
In the context of the rapid development of deep learning theory, predicting future motion states based on time series sequence data of ship trajectories can significantly improve the safety of the traffic environment. Considering the spatiotemporal correlation of AIS data, a trajectory time window panning and smoothing filtering method is proposed for the abnormal values existing in the trajectory data. The application of this method can effectively deal with the jump values and outliers in the trajectory data, make the trajectory smooth and continuous, and ensure the temporal order and integrity of the trajectory data. In this paper, for the features of spatiotemporal data of trajectories, the LSTM structure is integrated on the basis of the deep learning Transformer algorithm framework, abbreviated as TRFM-LS. The LSTM module can learn the temporal features of spatiotemporal data in the process of computing the target sequence, while the self-attention mechanism in Transformer can solve the drawback of applying LSTM to capture the sequence information weakly at a distance. The advantage of complementarity of the fusion model in the training process of trajectory sequences with respect to the long-range dependence of temporal and spatial features is realized. Finally, in the comparative analysis section of the error metrics, by comparing with current state-of-the-art methods, the algorithm in this paper is shown to have higher accuracy in predicting time series trajectory data. The research in this paper provides an early warning information reference for autonomous navigation and autonomous collision avoidance of ships in practice. Full article
(This article belongs to the Section Ocean Engineering)
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25 pages, 13191 KiB  
Article
Adaptive Graph-Learning Convolutional Network for Multi-Node Offshore Wind Speed Forecasting
by Jingjing Liu, Xinli Yang, Denghui Zhang, Ping Xu, Zhuolin Li and Fengjun Hu
J. Mar. Sci. Eng. 2023, 11(4), 879; https://doi.org/10.3390/jmse11040879 - 21 Apr 2023
Cited by 5 | Viewed by 1518
Abstract
Multi-node wind speed forecasting is greatly important for offshore wind power. It is a challenging task due to unknown complex spatial dependencies. Recently, graph neural networks (GNN) have been applied to wind forecasting because of their capability in modeling dependencies. However, existing methods [...] Read more.
Multi-node wind speed forecasting is greatly important for offshore wind power. It is a challenging task due to unknown complex spatial dependencies. Recently, graph neural networks (GNN) have been applied to wind forecasting because of their capability in modeling dependencies. However, existing methods usually require a pre-defined graph structure, which is not optimal for the downstream task and limits the application scope of GNN. In this paper, we propose adaptive graph-learning convolutional networks (AGLCN) that can automatically infer hidden associations among multi-nodes through a graph-learning module. It simultaneously integrates the temporal and graph convolutional modules to capture temporal and spatial features in the data. Experiments are conducted on real-world multi-node wind speed data from the China Sea. The results show that our model achieves state-of-the-art results in all multi-scale wind speed predictions. Moreover, the learned graph can reveal spatial correlations from a data-driven perspective. Full article
(This article belongs to the Special Issue Innovative Development of Offshore Wind Technology)
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22 pages, 5631 KiB  
Article
Effects of Lateral Flows on the Supercavitation and Hydrodynamic Characteristics of Underwater Series and Parallel High-Speed Projectiles
by Lite Zhang, Chengwei Zhang, Huixia Jia and Ruoling Dong
J. Mar. Sci. Eng. 2023, 11(4), 878; https://doi.org/10.3390/jmse11040878 - 21 Apr 2023
Viewed by 1138
Abstract
In this paper, the supercavitation of the parallel and tandem projectiles moving underwater with high-speed under the condition with/without lateral flows is numerically simulated by the volume of fraction (VOF) model. The motion of the projectiles was handled by the overlapping grid and [...] Read more.
In this paper, the supercavitation of the parallel and tandem projectiles moving underwater with high-speed under the condition with/without lateral flows is numerically simulated by the volume of fraction (VOF) model. The motion of the projectiles was handled by the overlapping grid and six degrees of freedom (DOF) techniques. The supercavitation evolution and the hydrodynamic characteristics of the projectiles were analyzed for the parallel and tandem projectiles under different conditions. The results show that the cavity shape is symmetrical under the condition without lateral flows, but is no longer symmetrical under the conditions with lateral flows. The asymmetry of the cavity contour increases with the velocity of the lateral flow. For the parallel projectiles, the change trends of the axial velocity of projectile 1 and projectile 2 are nearly the same. The offset velocity of projectile 1 and projectile 2 increases with the increase in the velocity of the lateral flow. The deflection angle of projectile 1 decreases with the increase in the lateral flow velocity but that of projectile 2 increases with the increase in the lateral flow velocity. At t = 3.0 ms, the deflection angle of projectile 2 is up to 20° under the condition of the lateral flow velocity of 11.25%, while the deflection angle of projectile 1 and 2 under other conditions is in the range of 5°. For the tandem projectiles, the axial velocity of projectile 1 gradually decreases. The change trend of the axial velocity of projectile 2 at first is the same as that of projectile 1, and then the change is dependent on the velocity of the lateral flow. Under the condition of the lateral flow velocity with 11.25%Vp, projectile 2 cannot enter the cavity of the front projectile. The change trend of the axial velocity of projectile 2 is similar as but somewhat slower than that of projectile 1. For the parallel projectiles, the ballistic stability of the projectile on the oncoming side is better than that of the projectile on the backflow side. Whether parallel or tandem projectiles, the ballistic stability of projectile 2 becomes worse with the increase in the lateral flow velocity. Full article
(This article belongs to the Section Physical Oceanography)
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17 pages, 4362 KiB  
Article
Influence of Firefighting Intervention on Fire Spread Characteristics in Ship Engine Room
by Chenfeng Li, Jiayin Mao, Zixiong Kang, Shengzhu Zhao and Huilong Ren
J. Mar. Sci. Eng. 2023, 11(4), 877; https://doi.org/10.3390/jmse11040877 - 21 Apr 2023
Cited by 2 | Viewed by 1906
Abstract
The purpose of this paper is to investigate and evaluate the ship engine room fire spreading characteristics based on the effect of firefighting interventions. The large eddy simulation (LES) and theoretical models are employed to simulate a fire scene in the engine room. [...] Read more.
The purpose of this paper is to investigate and evaluate the ship engine room fire spreading characteristics based on the effect of firefighting interventions. The large eddy simulation (LES) and theoretical models are employed to simulate a fire scene in the engine room. The fire spreading characteristics and the mechanism of the use of a fine water mist are obtained by varying the ventilation conditions and parameters of the water sprinkler. The results show that the reason why a pool fire can be more easily extinguished as the spray speed increases is because the water mist with a higher spray speed has a larger spray area. Meanwhile, the temperature in the engine room would drop more rapidly with the increasing spray area due to the higher evaporation rate. Furthermore, the arrangement of the ventilation conditions had an obvious effect on the fire spreading characteristics, as the depletion of the combustion medium affects the combustion situation. Full article
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21 pages, 1593 KiB  
Article
Adaptive Beamforming with Hydrophone Arrays Based on Oblique Projection in the Presence of the Steering Vector Mismatch
by Yan Dai and Chao Sun
J. Mar. Sci. Eng. 2023, 11(4), 876; https://doi.org/10.3390/jmse11040876 - 20 Apr 2023
Viewed by 1302
Abstract
In sonar systems, the performance of adaptive beamformers severely degrades when mismatches occur between the actual and presumed steering vectors of the desired signal, mainly due to hydrophone position errors, amplitude-phase errors, and the scattered effect of arrays. Similarly, an inadequate number of [...] Read more.
In sonar systems, the performance of adaptive beamformers severely degrades when mismatches occur between the actual and presumed steering vectors of the desired signal, mainly due to hydrophone position errors, amplitude-phase errors, and the scattered effect of arrays. Similarly, an inadequate number of “training” samples can lead to performance degradations similar to those caused by mismatches. In this paper, an adaptive beamforming algorithm based on oblique projection (OP-ABF) mismatch compensation is proposed to remove the degradation caused by the arbitrary-type steering vector mismatch of the desired signal. The proposed algorithm is motivated by the fact that the weight vector of adaptive beamforming can be represented as a linear combination of the optimal one and the oblique projection (OP) vector, which is generated by the steering vector mismatch and does not exist without this. Our algorithm was developed by constructing the oblique projection mismatch compensation vector (OPMCV) to provide the minimum variance distortionless response (MVDR) beamformer. Then, the algorithm could be implemented by the solution of the OP matrix with the formulation of the covariance matrix loading (CML). The simulation results of a uniform linear array (ULA) and a half-cylindrical conformal array (HCCA) show that the OP-ABF can optimize the original weight vector as much as possible without sacrificing the output signal-to-interference-plus-noise ratio (SINR) under different conditions. Experimental results for the HCCA also confirm the effectiveness of this algorithm. Full article
(This article belongs to the Special Issue Underwater Acoustics and Digital Signal Processing)
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23 pages, 6193 KiB  
Article
Multi-Target Tracking in Multi-Static Networks with Autonomous Underwater Vehicles Using a Robust Multi-Sensor Labeled Multi-Bernoulli Filter
by Yuexing Zhang, Yiping Li, Shuo Li, Junbao Zeng, Yiqun Wang and Shuxue Yan
J. Mar. Sci. Eng. 2023, 11(4), 875; https://doi.org/10.3390/jmse11040875 - 20 Apr 2023
Cited by 1 | Viewed by 1378
Abstract
This paper proposes a centralized MTT method based on a state-of-the-art multi-sensor labeled multi-Bernoulli (LMB) filter in underwater multi-static networks with autonomous underwater vehicles (AUVs). The LMB filter can accurately extract the number of targets and trajectories from measurements affected by noise, missed [...] Read more.
This paper proposes a centralized MTT method based on a state-of-the-art multi-sensor labeled multi-Bernoulli (LMB) filter in underwater multi-static networks with autonomous underwater vehicles (AUVs). The LMB filter can accurately extract the number of targets and trajectories from measurements affected by noise, missed detections, false alarms and port–starboard ambiguity. However, its complexity increases as the number of sensors increases. In addition, due to the time-varying underwater environment, AUV detection probabilities are time-varying, and their mismatches often lead to poor MTT performance. Consequently, we detail a robust multi-sensor LMB filter that estimates detection probabilities and multi-target states simultaneously in real time. Moreover, we derive an effective approximate form of the multi-sensor LMB filter using Kullback–Leibler divergence and develop an efficient belief propagation (BP) implementation of the multi-sensor LMB filter. Our method scales linearly with the number of AUVs, providing good scalability and low computational complexity. The proposed method demonstrates superior performance in underwater multi-AUV network MTT simulations. Full article
(This article belongs to the Section Ocean Engineering)
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20 pages, 10690 KiB  
Article
Numerical Simulation of Hydrodynamic Performance of Podded Propulsion under Maneuvering Condition
by Weimin Chen, Jiachen Ma, Jian Hu and Li Zhang
J. Mar. Sci. Eng. 2023, 11(4), 874; https://doi.org/10.3390/jmse11040874 - 20 Apr 2023
Cited by 1 | Viewed by 1286
Abstract
Podded propulsion offers excellent maneuverability without the need for mechanically complex transmission systems. However, the hydrodynamic performance of podded propulsion under maneuvering conditions has not yet been adequately investigated. This study proposes a Reynolds-averaged Navier–Stokes (RANS)-based method to investigate the hydrodynamic performance of [...] Read more.
Podded propulsion offers excellent maneuverability without the need for mechanically complex transmission systems. However, the hydrodynamic performance of podded propulsion under maneuvering conditions has not yet been adequately investigated. This study proposes a Reynolds-averaged Navier–Stokes (RANS)-based method to investigate the hydrodynamic performance of pod thrusters under maneuvering conditions. The accuracy of the numerical method is verified based on a comprehensive convergence analysis and experimental comparison. A comparative analysis of the difference in thrust, moment and their coefficients between maneuvering and steady-state conditions is performed. Additionally, the impact of the advance number on the propeller hydrodynamic performance under maneuvering conditions is examined. The results demonstrate that the thrust coefficient and the torque coefficient of the propeller at positive and negative oblique flow angles exhibit asymmetry owing to the influence of the incoming flow velocity. Furthermore, the thrust and torque under maneuvering conditions increase significantly compared with those under the steady-state condition. Full article
(This article belongs to the Special Issue CFD Analysis in Ocean Engineering)
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22 pages, 5645 KiB  
Article
Multi-AUV Formation Predictive Control Based on CNN-LSTM under Communication Constraints
by Juan Li, Zhenyang Tian, Gengshi Zhang and Wenbo Li
J. Mar. Sci. Eng. 2023, 11(4), 873; https://doi.org/10.3390/jmse11040873 - 20 Apr 2023
Cited by 4 | Viewed by 1167
Abstract
For the problem of hydroacoustic communication constraints in multi-AUV leader follower formation, this paper designs a formation control method combining CNN-LSTM prediction and backstepping sliding mode control. First, a feedback linearization method is used to transform the AUV nonlinear model into a second-order [...] Read more.
For the problem of hydroacoustic communication constraints in multi-AUV leader follower formation, this paper designs a formation control method combining CNN-LSTM prediction and backstepping sliding mode control. First, a feedback linearization method is used to transform the AUV nonlinear model into a second-order integral model; then, the influence of hydroacoustic communication constraints on the multi-AUV formation control problem is analyzed, and a sliding window-based formation prediction control strategy is designed; for the characteristics of AUV motion trajectory with certain temporal order, the CNN-LSTM prediction model is selected to predict the trajectory state of the leader follower and compensate the effect of communication delay on formation control, and combine the backstepping method and sliding mode control to design the formation controller. Finally, the simulation experimental results show that the proposed CNN-LSTM prediction and backstepping sliding mode control can improve the effect of hydroacoustic communication constraints on formation control. Full article
(This article belongs to the Special Issue Motion Control and Path Planning of Marine Vehicles)
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14 pages, 1479 KiB  
Article
Semi-Analytical Solution of Transverse Vibration of Cylinders with Non-Circular Cross-Section Partially Submerged in Water
by Huixuan Han, Yishuo Guo and Ruili Huo
J. Mar. Sci. Eng. 2023, 11(4), 872; https://doi.org/10.3390/jmse11040872 - 20 Apr 2023
Viewed by 760
Abstract
The free transverse vibration of a surface-piercing, vertical cylinder partially submerged in water was studied. The cylinder had an arbitrary non-circular, but symmetric, cross-section in the vibration direction. The water was assumed to be an incompressible and inviscid fluid. The effect of the [...] Read more.
The free transverse vibration of a surface-piercing, vertical cylinder partially submerged in water was studied. The cylinder had an arbitrary non-circular, but symmetric, cross-section in the vibration direction. The water was assumed to be an incompressible and inviscid fluid. The effect of the surface waves of water was neglected in the analysis. The exact solution of velocity potential of water was derived by the method of separation of variables. The unknown coefficients in the solution of the velocity potential were expressed in the form of integral equations, including the dynamic deformation of the beam. Then, the governing differential equation of bending vibration of the cylinder under the hydrodynamic pressure was obtained. The Galerkin method was used to obtain the eigenvalue equation by expanding the wet modes of the cylinder into a series of dry modes. The elliptical cylinders partially submerged in water were taken as the numerical example. The accuracy of the proposed method was evaluated by the convergence studies. As a consequent result, the non-dimensional added virtual mass incremental (NAVMI) factor solutions were compared to the present Galerkin solutions, which can be used as a benchmark test for more sophisticated numerical simulations of computational fluid dynamics. Full article
(This article belongs to the Special Issue Risk Assessment and Safety of Ships and Offshore Structures)
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32 pages, 49797 KiB  
Article
Computing Vegetation Indices from the Satellite Images Using GRASS GIS Scripts for Monitoring Mangrove Forests in the Coastal Landscapes of Niger Delta, Nigeria
by Polina Lemenkova and Olivier Debeir
J. Mar. Sci. Eng. 2023, 11(4), 871; https://doi.org/10.3390/jmse11040871 - 20 Apr 2023
Cited by 12 | Viewed by 2429
Abstract
This paper addresses the issue of the satellite image processing using GRASS GIS in the mangrove forests of the Niger River Delta, southern Nigeria. The estuary of the Niger River Delta in the Gulf of Guinea is an essential hotspot of biodiversity on [...] Read more.
This paper addresses the issue of the satellite image processing using GRASS GIS in the mangrove forests of the Niger River Delta, southern Nigeria. The estuary of the Niger River Delta in the Gulf of Guinea is an essential hotspot of biodiversity on the western coast of Africa. At the same time, climate issues and anthropogenic factors affect vulnerable coastal ecosystems and result in the rapid decline of mangrove habitats. This motivates monitoring of the vegetation patterns using advanced cartographic methods and data analysis. As a response to this need, this study aimed to calculate and map several vegetation indices (VI) using scripts as advanced programming methods integrated in geospatial studies. The data include four Landsat 8-9 OLI/TIRS images covering the western segment of the Niger River Delta in the Bight of Benin for 2013, 2015, 2021, and 2022. The techniques included the ’i.vi’, ’i.landsat.toar’ and other modules of the GRASS GIS. Based on the GRASS GIS ’i.vi’ module, ten VI were computed and mapped for the western segment of the Niger River Delta estuary: Atmospherically Resistant Vegetation Index (ARVI), Green Atmospherically Resistant Vegetation Index (GARI), Green Vegetation Index (GVI), Difference Vegetation Index (DVI), Perpendicular Vegetation Index (PVI), Global Environmental Monitoring Index (GEMI), Normalized Difference Water Index (NDWI), Second Modified Soil Adjusted Vegetation Index (MSAVI2), Infrared Percentage Vegetation Index (IPVI), and Enhanced Vegetation Index (EVI). The results showed variations in the vegetation patterns in mangrove habitats situated in the Niger River Delta over the last decade as well as the increase in urban areas (Onitsha, Sapele, Warri and Benin City) and settlements in the Delta State due to urbanization. The advanced techniques of the GRASS GIS of satellite image processing and analysis enabled us to identify and visualize changes in vegetation patterns. The technical excellence of the GRASS GIS in image processing and analysis was demonstrated in the scripts used in this study. Full article
(This article belongs to the Special Issue Estuaries, Coasts, and Seas in a Changing Climate)
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18 pages, 4227 KiB  
Review
Underwater Acoustic Technology-Based Monitoring of Oil Spill: A Review
by Huaxin Pan, Kangxu Tang, Jia Zhuo, Yuming Lu, Jialong Chen and Zhichao Lv
J. Mar. Sci. Eng. 2023, 11(4), 870; https://doi.org/10.3390/jmse11040870 - 20 Apr 2023
Cited by 1 | Viewed by 2768
Abstract
Acoustic monitoring is an efficient technique for oil spill detection, and the development of acoustic technology is conducive to achieving real-time monitoring of underwater oil spills, providing data references and guidance for emergency response work. Starting from the research background of oil spills, [...] Read more.
Acoustic monitoring is an efficient technique for oil spill detection, and the development of acoustic technology is conducive to achieving real-time monitoring of underwater oil spills, providing data references and guidance for emergency response work. Starting from the research background of oil spills, this review summarizes and evaluates the existing research on acoustic technology for monitoring underwater oil spills. Underwater oil spills are more complex than surface oil spills, and further research is needed to investigate the feasibility of acoustic technology in underwater oil spill monitoring, verify the accuracy of monitoring data, and assess its value. In the future, the impact mechanism and dynamic research of acoustic technology in oil spill monitoring should be explored, and the advantages and differences between acoustic technology and other detection techniques should be compared. The significance of auxiliary mechanisms combined with acoustic technology in oil spill monitoring should be studied. Moreover, acoustic research methods and experimental techniques should be enriched and improved to fully tap into the future value of acoustic technology. Full article
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13 pages, 2627 KiB  
Article
Relative Contribution of Atmospheric Forcing, Oceanic Preconditioning and Sea Ice to Deep Convection in the Labrador Sea
by Yang Wu, Xiangjun Zhao, Zhengdong Qi, Kai Zhou and Dalei Qiao
J. Mar. Sci. Eng. 2023, 11(4), 869; https://doi.org/10.3390/jmse11040869 - 20 Apr 2023
Viewed by 1400
Abstract
The relative contribution of atmospheric forcing, oceanic preconditioning, and sea ice to Labrador Sea Deep Convection (LSDC) is investigated by conducting three ensemble experiments using a global coupled sea ice–ocean model for the first time. Simulated results show that the atmospheric activities dominate [...] Read more.
The relative contribution of atmospheric forcing, oceanic preconditioning, and sea ice to Labrador Sea Deep Convection (LSDC) is investigated by conducting three ensemble experiments using a global coupled sea ice–ocean model for the first time. Simulated results show that the atmospheric activities dominate the interannual and decadal variability, accounting for 70% of LSDC. Oceanic preconditioning is more significant in the shallow LSDC years that the water column is stable, accounting for 21%, especially in the central Labrador Sea and Irminger Sea. Moreover, the sea ice contribution is negligible over the whole Labrador Sea, while its contribution is significant in the sea ice-covered slope regions, accounting for 20%. The increasingly importance of sea ice on LSDC and the water mass transformation will be found in the North Atlantic Ocean, if the Arctic sea ice declines continuously. Additionally, there is a 10 Sv increase (85%) in atmospheric forcing to the subpolar gyre in the North Atlantic Ocean, while oceanic preconditioning contributes a 7 Sv decrease (12%). These findings highlight the importance of summer oceanic preconditioning to LSDC and the subpolar gyre, and therefore it should be appropriately accounted for in future studies. Full article
(This article belongs to the Special Issue Numerical Modelling of Atmospheres and Oceans II)
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13 pages, 4806 KiB  
Article
Mechanism of Phase-Locked Ice Crushing against Offshore Structures
by Bin Wang, Shan Gao, Yan Qu, Haoyang Yin and Zhenju Chuang
J. Mar. Sci. Eng. 2023, 11(4), 868; https://doi.org/10.3390/jmse11040868 - 20 Apr 2023
Viewed by 1139
Abstract
This paper addresses a detailed analysis of the ice–structure interaction process of the phase-locked ice crushing (PLC) against offshore structures. Directly measured ice load, structure response data, and in situ observation from the field measurements on the Molikpaq lighthouse and jacket platform were [...] Read more.
This paper addresses a detailed analysis of the ice–structure interaction process of the phase-locked ice crushing (PLC) against offshore structures. Directly measured ice load, structure response data, and in situ observation from the field measurements on the Molikpaq lighthouse and jacket platform were used in the study. This paper summarizes a new ductile damage-collapse (DDC) failure mechanism for the PLC process. The DDC mechanism shows that the ice failure is a discrete ductile crushing process rather than a ductile–brittle transition process. The analysis identifies that the ice has a failure length in PLC and this failure length plays an important role in understanding the interaction. It reveals that PLC can occur on most vertical-sided offshore structures when the velocity of the ice sheet falls within the range of the failure length divided by the natural period of the structure. This paper proposes that this relationship between ice failure length and the natural period of the structure can be used as one of the PLC occurrence conditions. The DDC failure mechanism provides a basis for another technical route to solve the PLC problem. Full article
(This article belongs to the Special Issue Ice-Structure Interaction in Marine Engineering)
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21 pages, 1926 KiB  
Review
Application of Deep Learning-Based Object Detection Techniques in Fish Aquaculture: A Review
by Hanchi Liu, Xin Ma, Yining Yu, Liang Wang and Lin Hao
J. Mar. Sci. Eng. 2023, 11(4), 867; https://doi.org/10.3390/jmse11040867 - 20 Apr 2023
Cited by 6 | Viewed by 3855
Abstract
Automated monitoring and analysis of fish’s growth status and behaviors can help scientific aquaculture management and reduce severe losses due to diseases or overfeeding. With developments in machine vision and deep learning (DL) techniques, DL-based object detection techniques have been extensively applied in [...] Read more.
Automated monitoring and analysis of fish’s growth status and behaviors can help scientific aquaculture management and reduce severe losses due to diseases or overfeeding. With developments in machine vision and deep learning (DL) techniques, DL-based object detection techniques have been extensively applied in aquaculture with the advantage of simultaneously classifying and localizing fish of interest in images. This study reviews the relevant research status of DL-based object detection techniques in fish counting, body length measurement, and individual behavior analysis in aquaculture. The research status is summarized from two aspects: image and video analysis. Moreover, the relevant technical details of DL-based object detection techniques applied to aquaculture are also summarized, including the dataset, image preprocessing methods, typical DL-based object detection algorithms, and evaluation metrics. Finally, the challenges and potential trends of DL-based object detection techniques in aquaculture are concluded and discussed. The review shows that generic DL-based object detection architectures have played important roles in aquaculture. Full article
(This article belongs to the Special Issue Fisheries and Aquaculture: Current Situation and Future Perspectives)
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24 pages, 5611 KiB  
Article
An EMD–PSO–LSSVM Hybrid Model for Significant Wave Height Prediction
by Gang Tang, Jingyu Zhang, Jinman Lei, Haohao Du, Hongxia Luo, Yide Wang and Yuehua Ding
J. Mar. Sci. Eng. 2023, 11(4), 866; https://doi.org/10.3390/jmse11040866 - 20 Apr 2023
Cited by 2 | Viewed by 1508
Abstract
The accurate prediction of significant wave height (SWH) offers major safety improvements for coastal and ocean engineering applications. However, the significant wave height phenomenon is nonlinear and nonstationary, which makes any prediction work a non-straightforward task. The aim of the research presented in [...] Read more.
The accurate prediction of significant wave height (SWH) offers major safety improvements for coastal and ocean engineering applications. However, the significant wave height phenomenon is nonlinear and nonstationary, which makes any prediction work a non-straightforward task. The aim of the research presented in this paper is to improve the predicted significant wave height via a hybrid algorithm. Firstly, an empirical mode decomposition (EMD) is used to preprocess nonlinear data, which are decomposed into several elementary signals. Then, a least squares support vector machine (LSSVM) with nonlinear learning ability is adopted to predict the SWH, and a particle swarm optimization (PSO) automatically performs the parameter selection of the LSSVM modeling. The results show that the EMD–PSO–LSSVM model can compensate for the lag in the prediction timing of the prediction models. Furthermore, the prediction performance of the hybrid model has been greatly improved in the deep-sea area; the prediction accuracy of the coefficient of determination (R2) increases from 0.991, 0.982, and 0.959 to 0.993, 0.987, and 0.965, respectively. The prediction performance results show that the proposed EMD–PSO–LSSVM performs better than the EMD–LSSVM and LSSVM models. Therefore, the EMD–PSO–LSSVM model provides a valuable solution for the prediction of SWH. Full article
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13 pages, 2684 KiB  
Article
Immobilization on Polyethylenimine and Chitosan Sorbents Modulates the Production of Valuable Fatty Acids by the Chlorophyte Lobosphaera sp. IPPAS C-2047
by Svetlana Vasilieva, Karina Shibzukhova, Alexei Solovchenko, Olga Chivkunova, Christina Antipova, Alexey Morozov and Elena Lobakova
J. Mar. Sci. Eng. 2023, 11(4), 865; https://doi.org/10.3390/jmse11040865 - 19 Apr 2023
Cited by 1 | Viewed by 1175
Abstract
Green microalgae, including those from the genus Lobosphaera, are exploited in various fields of biotechnology to obtain valuable fatty acids (e.g., arachidonic acid (C20:4, ARA)) for the production of infant formulae, food and feed additives. In nature, microalgae frequently exist in naturally [...] Read more.
Green microalgae, including those from the genus Lobosphaera, are exploited in various fields of biotechnology to obtain valuable fatty acids (e.g., arachidonic acid (C20:4, ARA)) for the production of infant formulae, food and feed additives. In nature, microalgae frequently exist in naturally immobilized state (as biofilms) with a limited cell division rate and increased stress resilience. In the fields of biotechnology, immobilization of microalgae on artificial cell carriers simplifies biomass harvesting and increases culture robustness and productivity. The choice of a suitable cell carrier is central to biotechnology involving immobilized cultures. Cell carriers based on the natural amine-containing polymer chitosan and synthetic polyethylenimine (PEI) are promising candidates for immobilization of phototrophic microorganisms. This is the first report on the effects of immobilization on PEI and chitosan on the accumulation and composition of polyunsaturated fatty acids, including ARA, in Lobosphaera sp. IPPAS C-2047. Immobilization on PEI increased the ARA percentage in the total fatty acids and ARA accumulation by 72% and 81% compared to the suspended cells cultured in complete or nitrogen-deprived medium 14 days, respectively. Immobilization of Lobosphaera sp. on the chitosan-based carrier reduced the ARA percentage but increased oleic and α-linoleic acid percentages. The mechanisms of the effects of immobilization on the fatty acid profiles of the microalgae are discussed. Full article
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26 pages, 11689 KiB  
Article
Numerical Study on the Waterjet–Hull Interaction of a Free-Running Catamaran
by Yanlin Zou, Dakui Feng, Weihua Deng, Jun Yang and Hang Zhang
J. Mar. Sci. Eng. 2023, 11(4), 864; https://doi.org/10.3390/jmse11040864 - 19 Apr 2023
Viewed by 1231
Abstract
Waterjet–hull interaction is the hot point and research focus in the research of waterjet-propelled crafts. This paper presents numerical studies on the interaction between a waterjet system and a catamaran. Numerical simulations of both bare hull and self-propulsion hull were carried out based [...] Read more.
Waterjet–hull interaction is the hot point and research focus in the research of waterjet-propelled crafts. This paper presents numerical studies on the interaction between a waterjet system and a catamaran. Numerical simulations of both bare hull and self-propulsion hull were carried out based on the URANS method. The SST k-ω model is selected for the closure of the URANS equations. The level set method together with the dynamic overset grid approach is used for the simulations. The body force model with the PI speed controller is used to simulate the rotational motion of the rotor in the simulations for the self-propulsion hull. Moreover, uncertainty analyses of the numerical method are conducted to verify the accuracy of the numerical solver. The numerical results of the bare hull and self-propulsion hull are compared in detail, such as the wave pattern, pressure distribution, hull attitude, and so on. The waterjet reduces the pressure on the hull surface near the stern and makes the height of the wave near the stern lower. This leads to a more violent change in hull attitude and the thrust deduction is positive, ranging from 0.1 to 0.2. The energy conversion is analyzed based on the ITTC recommended procedures, which shows the overall efficiency of the waterjet behind the hull is about 0.75~0.8 times the free stream efficiency. Full article
(This article belongs to the Special Issue Novel Numerical Methods for Complicated and Violent Flows)
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15 pages, 4785 KiB  
Article
Analysis and Compensation of Installation Perpendicularity Error in Unmanned Surface Vehicle Electro-Optical Devices by Using Sea–Sky Line Images
by Jia Zheng, Jincai Chen, Xinjian Wu, Han Liang, Zhi Zheng, Chuanbo Zhu, Yifan Liu, Chao Sun, Chuanqin Wang and Dahua He
J. Mar. Sci. Eng. 2023, 11(4), 863; https://doi.org/10.3390/jmse11040863 - 19 Apr 2023
Cited by 2 | Viewed by 1176
Abstract
As an important sensor of an unmanned surface vehicle (USV), an electro-optical device is usually used to detect ships and obstacles in USV autonomous navigation and collision avoidance. However, the installation perpendicularity error of the electro-optical device greatly impacts the line-of-sight (LOS) stability [...] Read more.
As an important sensor of an unmanned surface vehicle (USV), an electro-optical device is usually used to detect ships and obstacles in USV autonomous navigation and collision avoidance. However, the installation perpendicularity error of the electro-optical device greatly impacts the line-of-sight (LOS) stability control. This error is difficult to eliminate through mechanical calibration because the platform inertial navigation axis cannot be led out. This study aims to establish the model for the perpendicularity error of electro-optical devices during circumferential scanning and analyze its impact on the stability of LOS. In addition, we present a measurement technique for perpendicularity errors utilizing sea–sky line images. Through this method, we find an error function of LOS elevation angle, which is a convex function that can quickly search out high-precision perpendicularity errors step by step. Finally, we measured and compensated the perpendicularity error according to experimental data collected by the electro-optical device. The findings of this research demonstrate that the suggested approach can efficiently mitigate low-frequency disruptions and minor amplitude high-frequency vibrations of LOS in the elevation direction. As a result, it considerably enhances the precision of stability and image observation effect of electro-optical devices. Full article
(This article belongs to the Section Physical Oceanography)
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14 pages, 10943 KiB  
Article
Effects of Water Velocity on Growth, Physiology and Intestinal Structure of Coral Trout (Plectropomus leopardus)
by Zhenjia Qian, Jincheng Xu, Andong Liu, Jianjun Shan, Chenglin Zhang and Huang Liu
J. Mar. Sci. Eng. 2023, 11(4), 862; https://doi.org/10.3390/jmse11040862 - 19 Apr 2023
Viewed by 1323
Abstract
This study aimed to investigate the effects of different water velocities on the growth performance, blood physiology, and digestive capacity of coral trout (Plectropomus leopardus) in a Recirculating aquaculture system (RAS). One hundred and twenty healthy, uniformly sized coral trout (body [...] Read more.
This study aimed to investigate the effects of different water velocities on the growth performance, blood physiology, and digestive capacity of coral trout (Plectropomus leopardus) in a Recirculating aquaculture system (RAS). One hundred and twenty healthy, uniformly sized coral trout (body mass (92.01 ± 8.04) g; body length (15.40 ± 0.65) cm) were randomly assigned to three flow velocity groups (1 bl/s, 2 bl/s, and 2.5 bl/s) and one control group (0 bl/s). The results show that the weight gain rate (WGR) and specific growth rate (SGR) of coral trout in the 2.5 bl/s water flow velocity group were significantly lower than those in the control group and 1 bl/s water flow velocity group (p < 0.05), while their feed coefficient (FC) values were significantly higher than those of the control group and 1 bl/s water flow velocity group (p < 0.05). The blood glucose (GLU) concentration of coral trout in the 2 bl/s water flow velocity group and the 2.5 bl/s water flow velocity group significantly decreased compared to those in the control group (p < 0.05), while the lactic acid (LD) concentration increased. As the cortisol (COR) concentration and lipase (LPS) enzyme activity of coral trout did not significantly change (p > 0.05), the α- AMS enzyme activity significantly decreased (p < 0.05). Under 2.5 bl/s water flow velocity, the intestinal structure of coral trout changed, and the number of goblet cells decreased. High-water flow velocities affect the physiological homeostasis and intestinal digestion of coral trout, resulting in a decrease in their growth performance, indicating that coral trout is more sensitive to high-water flow velocities. In actual RAS aquaculture, the flow rate should be controlled within 1 bl/s. Full article
(This article belongs to the Special Issue New Techniques in Marine Aquaculture)
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20 pages, 3091 KiB  
Article
Efficient Underwater Acoustical Localization Method Based on TDOA with Sensor Position Errors
by Ying Liu, Yingmin Wang and Cheng Chen
J. Mar. Sci. Eng. 2023, 11(4), 861; https://doi.org/10.3390/jmse11040861 - 19 Apr 2023
Cited by 3 | Viewed by 1145
Abstract
Underwater acoustic localization (UWAL) is extremely challenging due to the multipath nature of extreme underwater environments, the sensor position uncertainty caused by unpredictable ocean currents, and the lack of underwater observation data due to sparse array, which all affect localization performance. Addressing these [...] Read more.
Underwater acoustic localization (UWAL) is extremely challenging due to the multipath nature of extreme underwater environments, the sensor position uncertainty caused by unpredictable ocean currents, and the lack of underwater observation data due to sparse array, which all affect localization performance. Addressing these issues, this paper proposes a simple and effective underwater acoustic localization method using the time difference of arrival (TDOA) measurements based on the multipath channel effect of the underwater environment. By introducing the calibration source, localization performance was improved, and the sensor position error was corrected. The Cramér–Rao lower bound (CRLB) was derived, and the proposed method was able to achieve the CRLB with small deviation. Numerical simulations confirm the improved performance of the proposed method, including (1) a 20 dB and 30 dB reduction in the CRLB for far and near source scenarios, respectively, indicating improved accuracy and reliability when estimating unknown sources; (2) better Mean Squared Error (MSE) performance compared to existing methods and an efficiency of over 90% in low noise and above 80% in moderate noise in several scenarios, with a delayed threshold effect; and (3) achieving CRLB performance with only three sensors in a 3D space, even under moderate noise, while existing methods require at least five sensors for comparable performance. Our results demonstrate the efficacy of the proposed method in enhancing the accuracy and efficiency of source localization. Full article
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9 pages, 1104 KiB  
Brief Report
Complete Mitochondrial DNA Genomes of Deep-Sea Eels Synaphobranchus brevidorsalis and S. affinis and New Record of S. brevidorsalis from the East Mariana Basin
by Jeonghoon Han, Han-Jun Kim, Kyun-Woo Lee and Young-Ung Choi
J. Mar. Sci. Eng. 2023, 11(4), 860; https://doi.org/10.3390/jmse11040860 - 19 Apr 2023
Viewed by 1074
Abstract
In this study, we document the first recorded range extension of the genus Synaphobranchus from the East Mariana Basin in the Western Pacific Ocean. We sequenced the complete mitochondrial (mt) genome of two deep-sea eels (Synaphobranchus brevidorsalis and S. affinis) collected [...] Read more.
In this study, we document the first recorded range extension of the genus Synaphobranchus from the East Mariana Basin in the Western Pacific Ocean. We sequenced the complete mitochondrial (mt) genome of two deep-sea eels (Synaphobranchus brevidorsalis and S. affinis) collected in the East Mariana Basin in the Western Pacific Ocean. The complete mt genomes of S. brevidorsalis and S. affinis were 16,686 bp and 16,677 bp in length, respectively, and consisted of 13 protein-coding genes, 22 tRNA genes, and two rRNA genes. Molecular phylogenetic analysis of the two deep-sea eel species was performed, based on the mt cytochrome c oxidase subunit I (COI) gene using the maximum likelihood method. The molecular phylogenetic tree demonstrated that S. brevidorsalis and S. affinis were congeneric species of S. brevidorsalis and S. affinis reported in previous studies with bootstrap values of 100% and 100%, respectively. This is the first report on the complete mt genomes of S. brevidorsalis and S. affinis collected in the East Mariana Basin in the Western Pacific Ocean. Overall, our study highlights the potential of molecular approaches in identifying species diversity and distribution in the Western Pacific Ocean. Full article
(This article belongs to the Special Issue Deep-Sea Fish and Fisheries)
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3 pages, 185 KiB  
Editorial
Larval Settlement on Marine Surfaces: The Role of Physico-Chemical Interactions
by Francesca Cima
J. Mar. Sci. Eng. 2023, 11(4), 859; https://doi.org/10.3390/jmse11040859 - 19 Apr 2023
Viewed by 697
Abstract
Biofouling is the association of sessile aquatic organisms that rapidly settle on artificial hard substrata, thereby posing a large problem worldwide since its growth often causes severe damage to submerged structures [...] Full article
17 pages, 3742 KiB  
Article
A Distributed Underwater Multi-Target Tracking Algorithm Based on Two-Layer Particle Filter
by Kunhu Kou, Bochen Li, Lu Ding and Lei Song
J. Mar. Sci. Eng. 2023, 11(4), 858; https://doi.org/10.3390/jmse11040858 - 19 Apr 2023
Viewed by 1146
Abstract
Underwater multi-target tracking is one of the key technologies for military missions, including patrol and combat in the crucial area. Since the underwater environment is complex and targets’ trajectories may intersect when they are in a dense area, it is challenging to guarantee [...] Read more.
Underwater multi-target tracking is one of the key technologies for military missions, including patrol and combat in the crucial area. Since the underwater environment is complex and targets’ trajectories may intersect when they are in a dense area, it is challenging to guarantee the precision of observed information. In order to provide high-precision underwater localization and tracking services over an underwater monitoring network, a dynamic network resource allocation mechanism and an underwater multi-target tracking algorithm based on a two-layer particle filter with distributed probability fusion (TLPF-DPF) are proposed. The position estimation model based on geometric constraints and the dynamic allocation mechanism of network resources based on prior position estimation are designed. Using the improved filtering algorithm with known initial states, the reliable tracking of multiple targets with trajectory intersection in a small area under complex noises is achieved. In the non-Gaussian environment, the average positioning error of TLPF-DPF is less by nearly 30% than alternative algorithms. When switching from a Gaussian environment to a non-Gaussian environment, the performance degradation of TLPF-DPF is less than 12%, which exhibits stability compared with other algorithms when targets are close to each other with crossing trajectories. Full article
(This article belongs to the Section Ocean Engineering)
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