Previous Issue
Volume 12, August
 
 

J. Mar. Sci. Eng., Volume 12, Issue 9 (September 2024) – 39 articles

  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Reader to open them.
Order results
Result details
Section
Select all
Export citation of selected articles as:
16 pages, 3531 KiB  
Article
A Normal Mode Model Based on the Spectral Element Method for Simulating Horizontally Layered Acoustic Waveguides
by Yinuo Zhang, Houwang Tu, Yongxian Wang, Guojun Xu and Dongbao Gao
J. Mar. Sci. Eng. 2024, 12(9), 1499; https://doi.org/10.3390/jmse12091499 - 30 Aug 2024
Viewed by 183
Abstract
Acoustic waves are essential tools for guiding underwater activities. For many years, numerical modeling of ocean acoustic propagation has been a major research focus in underwater acoustics. Normal mode theory, one of the earliest and most extensively studied methods in this field, is [...] Read more.
Acoustic waves are essential tools for guiding underwater activities. For many years, numerical modeling of ocean acoustic propagation has been a major research focus in underwater acoustics. Normal mode theory, one of the earliest and most extensively studied methods in this field, is renowned for its well-established theoretical framework. The core of normal mode theory involves the numerical solution of modal equations. In classical normal mode models, these equations are typically discretized using low-order finite difference methods, which, while broadly applicable, suffer from a limited convergence rate. The spectral element method, widely used in the seismic field, is recognized for its spectral precision and flexibility. In this article, we propose a normal mode model discretized using the spectral element method. The weak form of the modal equation directly satisfies boundary and interface conditions without requiring additional operations. The entire computational domain can be divided into segments of varying number and length, configured according to environmental conditions. The perfectly matched layer technique is employed to simulate acoustic half-space boundary conditions, effectively addressing the high computational costs and numerical instability associated with traditional artificial absorbing layers. Based on these algorithms, we have developed a numerical program (SEM). This research verifies the accuracy of the spectral element model through three different types of numerical experiments. Full article
(This article belongs to the Section Ocean Engineering)
Show Figures

Figure 1

19 pages, 6455 KiB  
Article
An Improved High-Realism Turbulence Simulation of Ocean Scenes in a Maritime Simulator
by Tianhui Zhu, Hongxiang Ren, Haijiang Li and Xiao Yang
J. Mar. Sci. Eng. 2024, 12(9), 1498; https://doi.org/10.3390/jmse12091498 - 30 Aug 2024
Viewed by 185
Abstract
The realism of ocean visual systems is a key challenge in developing maritime simulators within ocean engineering. Achieving high realism in turbulence simulation is crucial for enhancing the effectiveness of these simulators. Traditional spectrum-based methods lack realism and fail to generate turbulent interaction [...] Read more.
The realism of ocean visual systems is a key challenge in developing maritime simulators within ocean engineering. Achieving high realism in turbulence simulation is crucial for enhancing the effectiveness of these simulators. Traditional spectrum-based methods lack realism and fail to generate turbulent interaction effects. To address this, an improved Hybrid Smoothed Particle Hydrodynamics method is proposed for simulating ocean scenes, incorporating advanced micropolar fluid model techniques to enhance detail realism. The proposed algorithm introduces a density constraint solver that directly adjusts particle distribution and couples it with a divergence-free velocity solver, aiming to construct a physical-based fluid simulation framework that enhances detail realism in ocean scene simulations. The results demonstrate that the proposed method effectively accelerates the convergence of constraint conditions, reduces simulation time, and improves overall incompressibility. Additionally, the introduced turbulence model addresses high-frequency detail loss caused by numerical dissipation in the Smoothed Particle Hydrodynamics method, enabling more complex navigation scenarios. This study provides theoretical and technical references for achieving realistic ocean scene simulations in maritime simulators. Full article
(This article belongs to the Special Issue Advances in Marine Engineering Hydrodynamics)
Show Figures

Figure 1

14 pages, 27776 KiB  
Article
Coupling Relationship between Basin Evolution and Hydrocarbon Reservoirs in the Northern Central Myanmar Basin: Insights from Basin and Petroleum System Modeling
by Zengyuan Zhou, Wenxu Peng, Hefeng Sun, Kailong Feng and Weilin Zhu
J. Mar. Sci. Eng. 2024, 12(9), 1497; https://doi.org/10.3390/jmse12091497 - 29 Aug 2024
Viewed by 217
Abstract
The Myanmar region experienced the subduction of the Indian Ocean plate to the West Burma block and suffered from the land–land collision between the Indian continent and the West Burma block that occurred from the Late Cretaceous to the Cenozoic. Its tectonic evolution [...] Read more.
The Myanmar region experienced the subduction of the Indian Ocean plate to the West Burma block and suffered from the land–land collision between the Indian continent and the West Burma block that occurred from the Late Cretaceous to the Cenozoic. Its tectonic evolution has been complex; thus, oil and gas exploration is difficult, and the overall degree of research has been low. Recent exploration has been hindered by a lack of knowledge on the evolution of the petroleum system. To address this, we conducted hydrocarbon generation and accumulation modeling using both the 2D MOVE and Petro-Mod software 2017 for a complex tectonic section in the Northern Central Myanmar Basin. The results show that the maturity threshold depth of the Cretaceous source rocks in the study area is shallow, and the underground depth of 1200 m to 1400 m has reached the hydrocarbon generation threshold, indicating the start of hydrocarbon generation. Since 48 Ma, the Ro of the source rocks has reached 0.7%, became mature quite early. The Late Cretaceous Paleocene and Eocene formation, located in the southeastern part of the study area, migrated and accumulated hydrocarbons towards the western arc zone in the Eocene and Miocene, respectively. It is worth noting that although the oil and gas potential of each layer in the island arc uplift zone is relatively low, which is conducive to the migration and accumulation of oil and gas generated by the source rocks of the depression towards the island arc zone, shallow areas with developed extensional faults should be avoided. This study is the first to conduct a preliminary assessment and prediction of oil and gas resources, which will provide exploration guidance and reference for the study area and its surrounding areas in the future. Full article
(This article belongs to the Special Issue Exploration and Development of Marine Energy)
Show Figures

Figure 1

17 pages, 6415 KiB  
Article
Impact of Pore Structure on Seepage Capacity in Tight Reservoir Intervals in Shahejie Formation, Bohai Bay Basin
by Shaogong Zhu, Yudong Cao, Qiangtai Huang, Haotong Yu, Weiyan Chen, Yujie Zhong and Wenchao Chen
J. Mar. Sci. Eng. 2024, 12(9), 1496; https://doi.org/10.3390/jmse12091496 - 29 Aug 2024
Viewed by 240
Abstract
The exploration and development of conventional oil and gas resources are becoming more difficult, and the proportion of low-permeability reservoirs in newly discovered reservoir resources has expanded to 45%. As the main focus of the oil industry, the global average recovery rate of [...] Read more.
The exploration and development of conventional oil and gas resources are becoming more difficult, and the proportion of low-permeability reservoirs in newly discovered reservoir resources has expanded to 45%. As the main focus of the oil industry, the global average recovery rate of low-permeability reservoir resources is only 20%, and most crude oil is still unavailable, so our understanding of such reservoirs needs to be deepened. The microscopic pore structure of low-permeability reservoir rocks exhibits significant complexity and variability; reservoir evaluation is more difficult. For elucidating the internal distribution of storage space and the mechanisms influencing seepage, we focus on the low-permeability sandstone reservoir of the Shahejie Formation, located on the northern slope of the Chenjiazhuang uplift, Bohai Bay. Employing a suite of advanced analytical techniques, including helium expansion, pressure pulse, high-pressure mercury intrusion (HPMI), and micro-computed tomography (micro-CT) scanning, we examined the main pore–throat size affecting reservoir storage and seepage in the reservoir at both the micrometer and nanometer scales. The results reveal that pores with diameters exceeding 40 μm are sparsely developed within the low-permeability reservoir rocks of the study area. However, pores ranging from 0 to 20 μm predominate, exhibiting an uneven distribution and a clustered structure in the three-dimensional pore structure model. The pore volume showed a unimodal and bimodal distribution, thus significantly contributing to the storage space. The main sizes of the reservoir in this study area are 40–80 μm and 200–400 μm. Micron-sized pores, while present, are not the primary determinants of the reservoir’s seepage capacity. Instead, coarser submicron and nano-pores exert a more substantial influence on the permeability of the rock. Additionally, the presence of micro-fractures is found to enhance the reservoir’s seepage capacity markedly. The critical pore–throat size range impacting the permeability of the reservoir in the study area is identified to be between 0.025 and 0.4 μm. Full article
Show Figures

Figure 1

17 pages, 2450 KiB  
Article
Modeling the Underwater Sound of Floating Offshore Windfarms in the Central Mediterranean Sea
by Marzia Baldachini, Robin D. J. Burns, Giuseppa Buscaino, Elena Papale, Roberto Racca, Michael A. Wood and Federica Pace
J. Mar. Sci. Eng. 2024, 12(9), 1495; https://doi.org/10.3390/jmse12091495 - 29 Aug 2024
Viewed by 253
Abstract
In the shift toward sustainable energy production, offshore wind power has experienced notable expansion. Several projects to install floating offshore wind farms in European waters, ranging from a few to hundreds of turbines, are currently in the planning stage. The underwater operational sound [...] Read more.
In the shift toward sustainable energy production, offshore wind power has experienced notable expansion. Several projects to install floating offshore wind farms in European waters, ranging from a few to hundreds of turbines, are currently in the planning stage. The underwater operational sound generated by these floating turbines has the potential to affect marine ecosystems, although the extent of this impact remains underexplored. This study models the sound radiated by three planned floating wind farms in the Strait of Sicily (Italy), an area of significant interest for such developments. These wind farms vary in size (from 250 MW to 2800 MW) and environmental characteristics, including bathymetry and seabed substrates. Propagation losses were modeled in one-third-octave bands using JASCO Applied Sciences’ Marine Operations Noise Model, which is based on the parabolic equation method, combined with the BELLHOP beam-tracing model. Two sound speed profiles, corresponding to winter and summer, were applied to simulate seasonal variations in sound propagation. Additionally, sound from an offshore supply ship was incorporated with one of these wind farms to simulate maintenance operations. Results indicate that sound from operating wind farms could reach a broadband sound pressure level (Lp) of 100 dB re 1 µPa as far as 67 km from the wind farm. Nevertheless, this sound level is generally lower than the ambient sound in areas with intense shipping traffic. The findings are discussed in relation to local background sound levels and current guidelines and regulations. The implications for environmental management include the need for comprehensive monitoring and mitigation strategies to protect marine ecosystems from potential acoustic disturbances. Full article
(This article belongs to the Section Ocean Engineering)
Show Figures

Figure 1

17 pages, 4938 KiB  
Article
Revisiting the Upwelling Evolution along the Western Iberian Peninsula over the 21st Century Using Dynamically Downscaled CMIP6 Data
by Brieuc Thomas, Xurxo Costoya, Maite deCastro and Moncho Gómez-Gesteira
J. Mar. Sci. Eng. 2024, 12(9), 1494; https://doi.org/10.3390/jmse12091494 - 29 Aug 2024
Viewed by 196
Abstract
Coastal upwelling is of particular importance in the western Iberian Peninsula, considering its socioeconomic impact on the region. Therefore, it is of crucial interest to evaluate how climate change, by modifying wind patterns, might influence its intensity and seasonality. Given the limited spatial [...] Read more.
Coastal upwelling is of particular importance in the western Iberian Peninsula, considering its socioeconomic impact on the region. Therefore, it is of crucial interest to evaluate how climate change, by modifying wind patterns, might influence its intensity and seasonality. Given the limited spatial extension of the area, it is essential to use high-resolution data. Thus, the weather research and forecasting model was used to dynamically downscale data from a multi-model ensemble from the 6th phase of the Coupled Model Intercomparison Project, representing the latest climate projections. Two shared socioeconomic pathways, 2–4.5 and 5–8.5 scenarios, were considered. The results show that climate change will not modify the upwelling seasonality in the area, where the months from April to September represent the period of highest intensity. Conversely, this seasonality might be exacerbated throughout the 21st century, as upwelling is expected to strengthen during these months and decrease during others. Additionally, coastal upwelling shows the highest increase at the northerner locations of the western Iberian Peninsula, resulting in a homogenization of its intensity along this coast. These changes may result from the anticipated intensification and northward shift of the Azores High. Full article
(This article belongs to the Special Issue Latest Advances in Coastal Oceanography)
Show Figures

Figure 1

22 pages, 6893 KiB  
Article
Dynamic Characteristic Analysis of Underwater Suspended Docking Station for Resident UUVs
by Jingqian Guo, Lingshuai Meng, Mengmeng Feng, Jun Liu, Zheng Peng, Wei Feng and Jun-Hong Cui
J. Mar. Sci. Eng. 2024, 12(9), 1493; https://doi.org/10.3390/jmse12091493 - 29 Aug 2024
Viewed by 264
Abstract
The widespread use of Unmanned Underwater Vehicles (UUVs) in seafloor observatory networks highlights the need for docking stations to facilitate rapid recharging and effective data transfer. Floating docks are promising due to their flexibility, ease of deployment, and recoverability. To enhance understanding and [...] Read more.
The widespread use of Unmanned Underwater Vehicles (UUVs) in seafloor observatory networks highlights the need for docking stations to facilitate rapid recharging and effective data transfer. Floating docks are promising due to their flexibility, ease of deployment, and recoverability. To enhance understanding and optimize UUV docking with floating docks, we employ dynamic fluid body interaction (DFBI) to construct a seabed moored suspended dock (SMSD) model that features a guiding funnel, a suspended body, and a catenary of a mooring chain. This model simulates SMSD equilibrium stabilization in various ocean currents. Then, a UUV docking model with contact coupling is developed from the SMSD model to simulate the dynamic contact response during docking. The accuracy of the docking model was validated using previous experimental data. Through investigation of the UUV docking response results, sensitivity studies relating to volume, moment of inertia, mass, and catenary stiffness were conducted, thereby guiding SMSD optimization. Finally, sea tests demonstrated that the SMSD maintained stability before docking. During docking, the SMSD’s rotation facilitated smooth UUV entry. After the UUV docked, the SMSD was restored to its original azimuth, confirming its adaptability, stability, and reliability. Full article
Show Figures

Figure 1

24 pages, 8399 KiB  
Article
Research on Fatigue Crack Propagation Prediction for Marine Structures Based on Automated Machine Learning
by Ping Li, Yuefu Yang and Chaohe Chen
J. Mar. Sci. Eng. 2024, 12(9), 1492; https://doi.org/10.3390/jmse12091492 - 29 Aug 2024
Viewed by 257
Abstract
In the field of offshore engineering, the prediction of the crack propagation behavior of metals is crucial for assessing the residual strength of structures. In this study, fatigue experiments were conducted for large-scale T-pipe joints of Q235 steel using the automatic machine learning [...] Read more.
In the field of offshore engineering, the prediction of the crack propagation behavior of metals is crucial for assessing the residual strength of structures. In this study, fatigue experiments were conducted for large-scale T-pipe joints of Q235 steel using the automatic machine learning (AutoML) technique to predict crack propagation. T-pipe specimens without initial cracks were designed for the study, and fatigue experiments were conducted at a load ratio of 0.067. Data such as strain and crack size were monitored by strain gauges and Alternating Current Potential Drop (ACPD) to construct a dataset for AutoML. Using the AutoML technique, the crack propagation rate and size were predicted, and the root mean square error (RMSE) was calculated. The prediction accuracy of the AutoML ensemble learning approach and the machine learning foundation model were evaluated. It was found that when the strain decreases by more than 3% compared to the initial value, crack initiation may occur in the vicinity of the monitoring point, at which point targeted measurements are required. In addition, the AutoML model utilizes ensemble learning techniques to show higher accuracy than a single machine learning model in the identification of crack initiation points and the prediction of crack propagation behavior. In the crack size prediction in this paper, the ensemble learning approach achieves an accuracy improvement of 5.65% over the traditional machine learning model. This result significantly enhances the reliability of crack prediction and provides a new technical approach for the next step of fatigue crack monitoring of large-scale T-tube joint structures in corrosive environments. Full article
Show Figures

Figure 1

17 pages, 9694 KiB  
Article
Dynamic Characteristics and Flow Field Evolution of Flat Plate Water Entry Slamming Based on Smoothed Particle Hydrodynamics
by Zhongming Li, Yingfei Zan, Ruinan Guo, Yaogang Sun and Nan Sun
J. Mar. Sci. Eng. 2024, 12(9), 1491; https://doi.org/10.3390/jmse12091491 - 29 Aug 2024
Viewed by 237
Abstract
Water entry slamming is a complicated issue in marine engineering, characterized by significant impact loads and complex flow. This paper establishes a 3D numerical model of flat plate water entry slamming based on smoothed particle hydrodynamics (SPH), and the dynamics and flow field [...] Read more.
Water entry slamming is a complicated issue in marine engineering, characterized by significant impact loads and complex flow. This paper establishes a 3D numerical model of flat plate water entry slamming based on smoothed particle hydrodynamics (SPH), and the dynamics and flow field evolution are analyzed during water entry. The results indicate that SPH effectively captures the key dynamic characteristics of flat plate water entry. The experimental data validate the model, and the SPH particles reproduce the phenomena of jet formation, cavity development, and fluid splashing. The observed pressure is maximum at the center of the flat plate, and the maximum pressure and vertical force of the flat plate exhibit a quadratic relationship with the water entry velocity. The flow field evolution from initial jet formation at the time of slamming to droplet splashing shows obvious stages. As the water entry depth of the flat plate increases, the growth rates of the cavity width and splash height gradually slow under fluid viscosity and drag. The water entry velocity has the greatest influence on droplet splashing, whereas its influence on the jet separation point and the position of the free liquid surface is less significant. Full article
(This article belongs to the Section Ocean Engineering)
Show Figures

Figure 1

17 pages, 3137 KiB  
Article
CIS: A Coral Instance Segmentation Network Model with Novel Upsampling, Downsampling, and Fusion Attention Mechanism
by Tianrun Li, Zhengyou Liang and Shuqi Zhao
J. Mar. Sci. Eng. 2024, 12(9), 1490; https://doi.org/10.3390/jmse12091490 - 28 Aug 2024
Viewed by 350
Abstract
Coral segmentation poses unique challenges due to its irregular morphology and camouflage-like characteristics. These factors often result in low precision, large model parameters, and poor real-time performance. To address these issues, this paper proposes a novel coral instance segmentation (CIS) network model. Initially, [...] Read more.
Coral segmentation poses unique challenges due to its irregular morphology and camouflage-like characteristics. These factors often result in low precision, large model parameters, and poor real-time performance. To address these issues, this paper proposes a novel coral instance segmentation (CIS) network model. Initially, we designed a novel downsampling module, ADown_HWD, which operates at multiple resolution levels to extract image features, thereby preserving crucial information about coral edges and textures. Subsequently, we integrated the bi-level routing attention (BRA) mechanism into the C2f module to form the C2f_BRA module within the neck network. This module effectively removes redundant information, enhancing the ability to distinguish coral features and reducing computational redundancy. Finally, dynamic upsampling, Dysample, was introduced into the CIS to better retain the rich semantic and key feature information of corals. Validation on our self-built dataset demonstrated that the CIS network model significantly outperforms the baseline YOLOv8n model, with improvements of 6.3% and 10.5% in PB and PM and 2.3% and 2.4% in mAP50B and mAP50M, respectively. Furthermore, the reduction in model parameters by 10.1% correlates with a notable 10.7% increase in frames per second (FPS) to 178.6, thus effectively meeting real-time operational requirements. Full article
(This article belongs to the Section Marine Biology)
Show Figures

Figure 1

16 pages, 562 KiB  
Article
Adaptive Transmission Interval-Based Self-Triggered Model Predictive Control for Autonomous Underwater Vehicles with Additional Disturbances
by Pengyuan Zhang, Liying Hao and Runzhi Wang
J. Mar. Sci. Eng. 2024, 12(9), 1489; https://doi.org/10.3390/jmse12091489 - 28 Aug 2024
Viewed by 223
Abstract
Most existing model predictive control (MPC) methods overlook the network resource limitations of autonomous underwater vehicles (AUVs), limiting their applicability in real systems. This article addresses this gap by introducing an adaptive transmission, interval-based, and self-triggered model predictive control for AUVs operating under [...] Read more.
Most existing model predictive control (MPC) methods overlook the network resource limitations of autonomous underwater vehicles (AUVs), limiting their applicability in real systems. This article addresses this gap by introducing an adaptive transmission, interval-based, and self-triggered model predictive control for AUVs operating under ocean disturbances. This approach enhances system stability while reducing resource consumption by optimizing MPC update frequencies and communication resource usage. Firstly, the method evaluates the discrepancy between system states at sampling instants and their optimal predictions. This significantly reduces the conservatism in the state-tracking errors caused by ocean disturbances compared to traditional approaches. Secondly, a self-triggering mechanism was employed, limiting information exchange to specified triggering instants to conserve communication resources more effectively. Lastly, by designing a robust terminal region and optimizing parameters, the recursive feasibility of the optimization problem is ensured, thereby maintaining the stability of the closed-loop system. The simulation results illustrate the efficacy of the controller. Full article
(This article belongs to the Special Issue Unmanned Marine Vehicles: Navigation, Control and Sensing)
Show Figures

Figure 1

21 pages, 3358 KiB  
Article
Sediment Types with Alternation of Sandy and Rocky Shores Influence the Distribution of Clams in an Area Characterized by High-Energy Hydrodynamic Conditions
by Jean-Claude Dauvin, Olivier Basuyaux and Jean-Philippe Pezy
J. Mar. Sci. Eng. 2024, 12(9), 1488; https://doi.org/10.3390/jmse12091488 - 28 Aug 2024
Viewed by 333
Abstract
To identify short-term changes (14–69 days) in the adult abundance of two closely related shallow-burrowing bivalves (Ruditapes spp.), a series of observations and displacement assessments were made during the 2014–2018 period. This study was initiated to estimate the natural displacement of clams [...] Read more.
To identify short-term changes (14–69 days) in the adult abundance of two closely related shallow-burrowing bivalves (Ruditapes spp.), a series of observations and displacement assessments were made during the 2014–2018 period. This study was initiated to estimate the natural displacement of clams in a high-energy hydrodynamic tidal regime along the western coast of Cotentin in Normandy, France (western basin of the English Channel, northeastern Atlantic). The raking of several different surfaces and sediment types at successive periods separated by about one month shows clam displacement in most of the selected quadrats. The mean abundance displacement derived from all the observations carried out in 2014, 2016 and 2018 is estimated at 1.8 ind·m−2 mo−1, a value that should be compared with the mean density of between 2.0 and 12.5 ind·m−2 along the western coast of Cotentin. These displacements are confirmed with experiments using clams marked with an inox metal washer and detected with a Minelab Sovereign GT multi-frequency metal detector. During the course of the experiments, about 20% of the clams show a displacement. Most of the displacements are moderate, being less than 2 m, but some clams could be displaced by more than 20 m. Full article
(This article belongs to the Section Marine Ecology)
Show Figures

Figure 1

17 pages, 5368 KiB  
Article
The Suppression of Flow-Induced Vibrations for a Single and Two Tandem-Arrangement Cylinders Using Three Splitter Plates
by Zhongming Hu, Jiasong Wang, Yuankun Sun and Ke Lin
J. Mar. Sci. Eng. 2024, 12(9), 1487; https://doi.org/10.3390/jmse12091487 - 28 Aug 2024
Viewed by 348
Abstract
Some very useful methods for suppressing the flow-induced vibration (FIV) of a single cylinder are known to potentially have a limited efficiency for tandem-arrangement cylinders. In this paper, three splitter plates uniformly attached around a cylinder with an angle of 120° are proposed [...] Read more.
Some very useful methods for suppressing the flow-induced vibration (FIV) of a single cylinder are known to potentially have a limited efficiency for tandem-arrangement cylinders. In this paper, three splitter plates uniformly attached around a cylinder with an angle of 120° are proposed to suppress the FIVs of both a single cylinder and two tandem-arrangement cylinders in a wind tunnel at Re = 4000–45,200. The splitter plates’ length to diameter ratios, L/Ds (where L is the length of the splitter plate and D is the cylinder diameter), are set from 0.1 to 0.8. The results show that the proposed method not only effectively suppresses the vortex-induced vibration (VIV) for a single cylinder, but also successfully mitigates the wake-induced galloping (WIG) for two tandem-arrangement cylinders. The vibrations of the single cylinders are effectively suppressed, consistently achieving suppression efficiencies over 95% for L/Ds = 0.2–0.8, with a notable peak efficiency of 98.4% at L/D = 0.2. For the two tandem-arrangement cylinders at S/D = 4.0 (where S is the center-to-center spacing between the two cylinders), the suppression efficiencies of the upstream cylinder exceed 96% for L/D = 0.2–0.8, with an optimal efficiency of 97.4% at L/D = 0.6. The downstream cylinder exhibits vibration only at L/Ds = 0.1, 0.2, and 0.4, resulting in suppression efficiencies of 80.3%, 67.1%, and 91.0%. The vibrations remain fully suppressed throughout the entire reduced velocity range for L/Ds = 0.6–0.8, reaching an optimal efficiency of 98.7% at L/D = 0.6. Three regimes of fs/fn characteristics can be classified for the single cylinder, and the wake structures show that shear layers develop along the front plate before attaching on the cylinder and are then offset to either side of the cylinder by the two rear splitter plates, contributing to the absence of periodic vortex shedding. Full article
(This article belongs to the Special Issue The State of the Art of Marine Risers and Pipelines)
Show Figures

Figure 1

17 pages, 4199 KiB  
Article
Impact of Krill Meal on Enhancing Skin Mucosal Health and Reducing Sea Lice in Atlantic Salmon
by Kiranpreet Kaur, Mearge A. Okubamichael, Susanne Håvardstun Eide and Karin Pittman
J. Mar. Sci. Eng. 2024, 12(9), 1486; https://doi.org/10.3390/jmse12091486 - 27 Aug 2024
Viewed by 432
Abstract
The salmon industry’s challenges with skin health and sea lice emphasize the necessity for fish-sensitive measures like functional nutrition to boost skin health and fish welfare. The present study investigated the efficacy of krill meal (KM) for skin mucosal health and sea lice [...] Read more.
The salmon industry’s challenges with skin health and sea lice emphasize the necessity for fish-sensitive measures like functional nutrition to boost skin health and fish welfare. The present study investigated the efficacy of krill meal (KM) for skin mucosal health and sea lice in Atlantic salmon (170 g). Following an 8-week feeding period, in duplicate tanks, on test diets (8% KM, 12% KM, and the control group), fish underwent a 2-week sea lice challenge, reaching 350 g. The 8% KM diet group had thicker skin epithelium (72.3 µ) compared to the 12% KM (51.3 µ) and the control groups (43.8 µ) after 8 weeks. Additionally, skin mucosal health parameters—cell size (208 µ2), cell density (25.2%), and defense activity (1.19)—were significantly enhanced with 8% KM compared to the 12% KM (cell size: 162.3 µ2, cell density: 17%, defense activity: 1.04) and the control group (cell size: 173.5 µ2, cell density: 16.4%, defense activity: 0.93). Furthermore, fish fed with 8% KM significantly showed the lowest sea lice, along with reduced cell size while maintaining a high abundance of skin mucous cells, suggesting efficient turnover of the skin mucosal layer to remove sea lice effectively. This study highlights the potential of KM as part of a functional nutrition strategy to enhance skin mucosal health and mitigate sea lice challenges. Full article
(This article belongs to the Special Issue Nutrition and Physiology of Marine Fish)
Show Figures

Figure 1

25 pages, 6705 KiB  
Article
Investigating the Structural and Power Performance of a 15 MW Class Wind Energy Generation System under Experimental Wind and Marine Loading
by Sajid Ali, Hongbae Park and Daeyong Lee
J. Mar. Sci. Eng. 2024, 12(9), 1485; https://doi.org/10.3390/jmse12091485 - 27 Aug 2024
Viewed by 566
Abstract
The global transition to renewables in response to climate change has largely been supported by the expansion of wind power capacity and improvements in turbine technology. This is being made possible mainly due to improvements in the design of highly efficient turbines exceeding [...] Read more.
The global transition to renewables in response to climate change has largely been supported by the expansion of wind power capacity and improvements in turbine technology. This is being made possible mainly due to improvements in the design of highly efficient turbines exceeding a 10 MW rated power. Apart from power efficiency, wind turbines must withstand the mechanical stress caused by wind–hydro conditions. Such comprehensive structural analysis has rarely been performed previously, especially for large-scale wind turbines under real environmental conditions. The present work analyzes the energy production and structural performance of an NREL-IEA 15 MW wind turbine using measured wind and hydro data. First of all, an optimum operating range is determined in terms of the wind speed and blade pitch angle to maximize the power coefficient. Then, at this optimum range, a detailed breakdown of the forces and moments acting on different components of the wind turbine is presented. It was found that wind speeds of 9 to 12 m/s are best suited for this wind turbine, as the power coefficient is at its maximum and the mechanical loads on all components are at a minimum. The loads are at a minimum due to the optimized blade pitch angle. The bending force on a monopile foundation (fixed on the seabed) is found to be at a maximum and corresponds to nearly 2000 kN. The maximum blade force is nearly 700 kN, whereas on the tower it is almost 250 kN. The maximum force on the tower occurs at a point which is found to be undersea, whereas above-sea, the maximum force on the tower is nearly 20% less than the undersea maximum force. Finally, seasonal and annual energy production is also estimated using locally measured wind conditions. Full article
(This article belongs to the Section Coastal Engineering)
Show Figures

Figure 1

23 pages, 7993 KiB  
Review
Formation Control of a Multi-Unmanned Surface Vessel System: A Bibliometric Analysis
by Jie Xue, Yuanming Song and Hao Hu
J. Mar. Sci. Eng. 2024, 12(9), 1484; https://doi.org/10.3390/jmse12091484 - 27 Aug 2024
Viewed by 515
Abstract
This study provides an overview of the literature on multi-unmanned surface vessel (multi-USV) systems, addressing the increasing attention on formation control of USVs due to their enhanced task execution ability, efficiency, and robustness in complex marine environments. Despite numerous studies on USVs covering [...] Read more.
This study provides an overview of the literature on multi-unmanned surface vessel (multi-USV) systems, addressing the increasing attention on formation control of USVs due to their enhanced task execution ability, efficiency, and robustness in complex marine environments. Despite numerous studies on USVs covering fields, such as autonomous decision making, motion control, perception, and communication technologies, there is a significant lack of systematic literature review and bibliometric analysis specifically focused on a multi-USV system. This study aims to summarize advancements in multi-USV research, highlighting key aspects, including publication trends, influential scholars and papers, research hotspots, challenges, and future opportunities. By reviewing the current state of multi-USV research, this study contributes to the field as a beneficial reference for researchers, practitioners, and policymakers. It will not only highlight the progress made so far but also shed light on the gap that needs to be addressed to advance the field. Full article
(This article belongs to the Special Issue Unmanned Marine Vehicles: Perception, Planning, Control and Swarm)
Show Figures

Figure 1

19 pages, 2652 KiB  
Article
Conceptual Models for Exploring Sea-Surface Temperature Variability Vis-à Long-Range Weather Forecasting
by Sergei Soldatenko
J. Mar. Sci. Eng. 2024, 12(9), 1483; https://doi.org/10.3390/jmse12091483 - 27 Aug 2024
Viewed by 607
Abstract
This paper analyzes the ability of three conceptual stochastic models (one-box, two-box, and diffusion models) to reproduce essential features of sea surface temperature variability on intra-annual time scales. The variability of sea surface temperature, which is particularly influenced by feedback mechanisms in ocean [...] Read more.
This paper analyzes the ability of three conceptual stochastic models (one-box, two-box, and diffusion models) to reproduce essential features of sea surface temperature variability on intra-annual time scales. The variability of sea surface temperature, which is particularly influenced by feedback mechanisms in ocean surface–atmosphere coupling processes, is characterized by power spectral density, commonly used to analyze the response of dynamical systems to random forcing. The models are aimed at studying local effects of ocean–atmosphere interactions. Comparing observed and theoretical power spectra shows that in dynamically inactive ocean regions (e.g., north-eastern part of the Pacific Ocean), sea surface temperature variability can be described by linear stochastic models such as one-box and two-box models. In regions of the world ocean (e.g., north-western Pacific Ocean, subtropics of the North Atlantic, the Southern Ocean), in which the observed sea surface temperature spectra on the intra-annual time scales do not obey the ν2 law (where ν is a regular frequency), the formation mechanisms of sea surface anomalies are mainly determined by ocean circulation rather than by local ocean–atmosphere interactions. The diffusion model can be used for simulating sea surface temperature anomalies in such areas of the global ocean. The models examined are not able to reproduce the variability of sea surface temperature over the entire frequency range for two primary reasons; first, because the object of study, the ocean surface mixed layer, changes during the year, and second, due to the difference in the physics of processes involved at different time scales. Full article
(This article belongs to the Special Issue Latest Advances in Physical Oceanography—2nd Edition)
Show Figures

Figure 1

21 pages, 11641 KiB  
Article
Study on Strain Field Reconstruction Method of Long-Span Hull Box Girder Based on iFEM
by Guocai Chen, Xueliang Wang, Nan Zhao, Zhentao Jiang, Fei Li, Haozheng Chen, Pengyu Wei and Tao Zhang
J. Mar. Sci. Eng. 2024, 12(9), 1482; https://doi.org/10.3390/jmse12091482 - 26 Aug 2024
Viewed by 379
Abstract
The box girder’s condition significantly impacts the safety and overall performance of the entire ship because it is the primary stress component of the hull construction. This work used experimental research on the long-span hull box girder based on IFEM (Inverse Finite Element [...] Read more.
The box girder’s condition significantly impacts the safety and overall performance of the entire ship because it is the primary stress component of the hull construction. This work used experimental research on the long-span hull box girder based on IFEM (Inverse Finite Element Method) technology to ensure the structural safety of the hull box girder. Due to the limitations of conventional experiments in this technical field, such as their reliance on finite element data and lack of input from physical tests, numerous research methods combining the strain sensing data from physical tests with the strain data from virtual sensors were conducted. The strain fields of the top plate, side plate, and bottom plate were each reconstructed in turn, and the verifier measuring points in the physical model test were used to assess the accuracy of the reconstruction results. The findings demonstrate that the top plate, side plate, and bottom plate reconstructions had relative errors of 0.24–7.86%, 0.75–8.13%, and 3.31–2.52%, respectively. This enables the reconstruction of the strain field of the long-span hull box girder using physical test data and promotes the use of iFEM technology in the field of structural health monitoring of large marine structures. Full article
Show Figures

Figure 1

14 pages, 2159 KiB  
Article
Metagenomic Profiling of Bacterial Communities and Functional Genes in Penaeus monodon
by Juan Chen, Yundong Li, Song Jiang, Qibin Yang, Jianhua Huang, Lishi Yang, Jianzhi Shi, Zhibin Lu, Yan Zhang, Shigui Jiang and Falin Zhou
J. Mar. Sci. Eng. 2024, 12(9), 1481; https://doi.org/10.3390/jmse12091481 - 26 Aug 2024
Viewed by 320
Abstract
Penaeus monodon is one of the world’s most important aquaculture species, with its host-associated microbial community playing a crucial role in its growth, metabolism, immune response, and adaptation. In our study, we utilized Illumina high-throughput sequencing to investigate the composition, structure, and function [...] Read more.
Penaeus monodon is one of the world’s most important aquaculture species, with its host-associated microbial community playing a crucial role in its growth, metabolism, immune response, and adaptation. In our study, we utilized Illumina high-throughput sequencing to investigate the composition, structure, and function of the intestinal microbial communities of P. monodon from two different regions in Guangdong. Our results identified 176 phyla across both populations, with Proteobacteria and Firmicutes being predominant. Furthermore, we identified 3095 genera, with Photobacterium, Vibrio, and Aliiroseovarius being the most dominant. Functional gene analysis based on KEGG data indicated that the carbohydrate metabolism and amino acid metabolism were significant at the secondary metabolic pathway level. The eggNOG functional annotation revealed that the genes involved in replication, recombination, and repair are of paramount importance. The CAZy annotation results indicated that Glycoside Hydrolases (GH) have the highest abundance. The Pfam annotation analysis showed that the two most prevalent domains are P-loop NTPase and NADP Rossmann. Our investigation provides a reference for species-level and functional-level analyses of the intestinal microbiota of P. monodon, contributing valuable insights into its microbial ecology. Full article
(This article belongs to the Section Marine Biology)
Show Figures

Figure 1

12 pages, 2132 KiB  
Article
Metagenomic Analysis of Seasonal Variations in Viral Dynamics and Diversity in Seawater of Jeju Island, Republic of Korea
by Jinik Hwang, Eun Gyoung Oh and Youngguk Jin
J. Mar. Sci. Eng. 2024, 12(9), 1480; https://doi.org/10.3390/jmse12091480 - 26 Aug 2024
Viewed by 338
Abstract
Jeju, the largest island in Korea, is the most economically important in terms of marine aquaculture. We investigated the marine viral composition adjacent to Jeju Island over four seasons in 2022 and sequenced DNA libraries extracted from samples in March, June, September, and [...] Read more.
Jeju, the largest island in Korea, is the most economically important in terms of marine aquaculture. We investigated the marine viral composition adjacent to Jeju Island over four seasons in 2022 and sequenced DNA libraries extracted from samples in March, June, September, and December using Illumina HiSeq 2000. We obtained 212,402, 186,542, 235,441, and 224,513 contigs from the four-season samples, respectively. Among the identified metagenomes, bacteriophages were dominant in all the samples. Bacillus phage G was the dominant species in March and June, whereas Pelagibacter phage HTVC 008M was the dominant species in September and December. Additionally, the number of viruses that infected algal hosts was higher in December than in other seasons. Marine viruses appeared in all seasons and infected marine vertebrates such as fish. Functional analysis using MG-RAST revealed that cell wall- and capsule-related metabolism groups were activated in March and June, whereas virulence-, disease-, and defense-related metabolism groups were activated in September and December. Conclusively, this study revealed seasonal changes in marine viral communities in the sea adjacent to Jeju Island. Our data will be useful in identifying emerging marine viral pathogens and for further community studies on marine organisms. Full article
(This article belongs to the Section Marine Biology)
Show Figures

Figure 1

15 pages, 21052 KiB  
Article
Response of a Coral Reef Sand Foundation Densified through the Dynamic Compaction Method
by Linlin Gu, Weihao Yang, Zhen Wang, Jianping Wang and Guanlin Ye
J. Mar. Sci. Eng. 2024, 12(9), 1479; https://doi.org/10.3390/jmse12091479 - 26 Aug 2024
Viewed by 353
Abstract
Dynamic compaction is a method of ground reinforcement that uses the huge impact energy of a free-falling hammer to compact the soil. This study presents a DC method for strengthening coral reef foundations in the reclamation area of remote sea islands. Pilot tests [...] Read more.
Dynamic compaction is a method of ground reinforcement that uses the huge impact energy of a free-falling hammer to compact the soil. This study presents a DC method for strengthening coral reef foundations in the reclamation area of remote sea islands. Pilot tests were performed to obtain the design parameters before official DC operation. The standard penetration test (SPT), shallow plate-load test (PLT), and deformation investigation were conducted in two improvement regions (A1 and A2) with varying tamping energies. During the deformation test, the depth of the tamping crater for the first two points’ tamping and the third full tamping was observed at two distinct sites. The allowable ground bearing capacity at two disparate field sites was at least 360 kPa. The reinforcement depths were 3.5 and 3.2 m in the A1 and A2 zones, respectively. The DC process was numerically analyzed by the two-dimensional particle flow code, PFC2D. It indicated that the reinforcement effect and effective reinforcement depth were consistent with the field data. The coral sand particles at the bottom of the crater were primarily broken down in the initial stage, and the particle-crushing zone gradually developed toward both sides of the crater. The force chain developed similarly at the three tamping energies (800, 1500, and 2000 kJ), and the impact stress wave propagated along the sand particles primarily in the vertical direction. Full article
(This article belongs to the Special Issue Advances in Marine Geological and Geotechnical Hazards)
Show Figures

Figure 1

17 pages, 8539 KiB  
Article
Kinematic Stability Analysis of Anchor Cable Structures in Submerged Floating Tunnel under Combined Parametric–Vortex Excitation
by Jiaming Xiong, Song Sang, Youwei Du, Chaojie Gan, Ao Zhang and Fugang Liu
J. Mar. Sci. Eng. 2024, 12(9), 1478; https://doi.org/10.3390/jmse12091478 - 25 Aug 2024
Viewed by 468
Abstract
The submerged floating tunnel is a marine transportation infrastructure that links two shorelines. The tunnel tube body’s buoyancy exceeds gravity, with anchoring ensuring equilibrium. Anchoring reliability is crucial. This study presents a three-way coupled kinematic model for the mooring structure, formulated on Hamilton’s [...] Read more.
The submerged floating tunnel is a marine transportation infrastructure that links two shorelines. The tunnel tube body’s buoyancy exceeds gravity, with anchoring ensuring equilibrium. Anchoring reliability is crucial. This study presents a three-way coupled kinematic model for the mooring structure, formulated on Hamilton’s principle and Kirchhoff’s assumption. It explores the impact of the tube body’s buoyancy-to-weight ratio and the sea current’s angle of incidence on mooring motion response. By solving the motion analysis model, Hill’s equation system is derived to assess the parameter instability of the anchor cable structure. The coefficient of excitation instability intervals for the submerged floating tunnel is determined and validated. The findings indicate the following: (1) Increasing the float-weight ratio reduces displacement response amplitudes in all directions, bringing downstream and transverse currents closer to their initial positions; (2) Changes in current direction angles result in decreased downstream excitation strength and increased transverse displacement response with the same excitation direction; (3) The instability interval visualization effectively predicts anchor cable structure instability under parametric excitation. Structures within the instability region are deemed unstable, while those outside are considered stable. Full article
(This article belongs to the Section Coastal Engineering)
Show Figures

Figure 1

11 pages, 6977 KiB  
Article
Modal Decomposition of Internal Tides in the Luzon Strait through Two-Dimensional Fourier Bandpass Filtering
by Botao Xie, Qi Zhang, Feilong Lin, Weifang Jin and Zijian Cui
J. Mar. Sci. Eng. 2024, 12(9), 1477; https://doi.org/10.3390/jmse12091477 - 25 Aug 2024
Viewed by 417
Abstract
Internal tides are pivotal dynamic processes enhancing the mixing of oceanic waters and facilitating energy transfer across various scales within the ocean. In recent years, the proliferation of satellite altimetry observations has enabled global predictions of the elevation and phase of internal tides. [...] Read more.
Internal tides are pivotal dynamic processes enhancing the mixing of oceanic waters and facilitating energy transfer across various scales within the ocean. In recent years, the proliferation of satellite altimetry observations has enabled global predictions of the elevation and phase of internal tides. This study, leveraging the advanced global internal tide prediction model known as the Multivariate Inversion of Ocean Surface Topography-Internal Tide Model (MIOST-IT), employs a two-dimensional Fourier bandpass filtering approach to decompose the internal tides in the Luzon Strait, thereby addressing the east–west directional blind zones inherent in along-track satellite altimetry-based modal decomposition. To further elucidate the propagation trajectories of individual tidal modes in different directions, we introduce the directional Fourier filter method to characterize the spatial distribution features of each modal internal tide in the vicinity of the Luzon Strait. This work significantly enhances the accuracy and reliability of extracting parameters for distinct modal internal tides, furnishing a scientific basis for subsequent studies on internal tide dynamics and model refinement. Full article
(This article belongs to the Special Issue New Advances in Marine Remote Sensing Applications)
Show Figures

Figure 1

22 pages, 38794 KiB  
Article
Inception of Constructional Submarine Conduit by Asymmetry Generated by Turbidity Current
by Daniel Bayer da Silva, Eduardo Puhl, Rafael Manica, Ana Luiza de Oliveira Borges and Adriano Roessler Viana
J. Mar. Sci. Eng. 2024, 12(9), 1476; https://doi.org/10.3390/jmse12091476 - 24 Aug 2024
Viewed by 420
Abstract
Submarine conduits are features responsible for transporting clastic debris from continents to the deep ocean. While the architecture of conduits has been extensively studied, the process of their inception remains unclear. This study highlights the possibility that some conduits are initiated by depositional [...] Read more.
Submarine conduits are features responsible for transporting clastic debris from continents to the deep ocean. While the architecture of conduits has been extensively studied, the process of their inception remains unclear. This study highlights the possibility that some conduits are initiated by depositional processes involving turbidity currents. Here, we present the results of eight experiments where gravity currents were allowed to develop their own pathways. The simulation tank represented natural scales of continental shelves, slopes, and basins. The initial experiments involved sediment-laden flows with low density (1–10% in volume). In first experiment runs (Series I), sediment deposition occurred primarily on the shelf and slope, resulting in an asymmetric transverse profile. This asymmetry facilitated subsequent conservative currents (1034 to 1070 kg/m3 due to salt dissolution) flowing alongside during the second series, resulting in the formation of a constructive submarine conduit. This feature is analogous to gully formations observed in various locations. This study correlates these findings with gully-like features and proposes a model where non-confined density flows can evolve into confined flows through the construction of asymmetric topography. An evolutionary model is proposed to explain the mechanism, which potentially elucidates the formation of many submarine conduits. Full article
(This article belongs to the Section Geological Oceanography)
Show Figures

Figure 1

25 pages, 11818 KiB  
Article
Research on the Power Output of Different Floating Wind Farms Considering the Wake Effect
by Jiaping Cui, Xianyou Wu, Pin Lyu, Tong Zhao, Quankun Li, Ruixian Ma and Yingming Liu
J. Mar. Sci. Eng. 2024, 12(9), 1475; https://doi.org/10.3390/jmse12091475 - 24 Aug 2024
Viewed by 496
Abstract
For floating wind turbines, one of the most interesting and challenging issues is that the movement of the rotor is strongly related to its floating platform, which results in corresponding variations in the wake characteristics of the turbine. Because the aerodynamic efficiency of [...] Read more.
For floating wind turbines, one of the most interesting and challenging issues is that the movement of the rotor is strongly related to its floating platform, which results in corresponding variations in the wake characteristics of the turbine. Because the aerodynamic efficiency of the downstream turbines is affected by the wake characteristics, the power output will consequently vary depending on the different types of floating wind turbines and floating wind farms used. In this study, the rotor movement, wake characteristics, and corresponding wind farm power output are analyzed using a numerical method for three typical floating wind turbines: the semisubmersible type, spar buoy type, and tension leg platform type with a 5 MW configuration. A fixed-bottom monopile wind turbine is adopted as a benchmark. The simulation results show that of the three floating wind turbines, the rotor position and wake center are most dispersed in the case of the spar buoy type, and its wake also has the lowest impact on downstream wind turbines. Additionally, the power output of the corresponding spar buoy type wind farm is also the highest at different wind speeds, followed by the semisubmersible type, tension leg platform type, and then the fixed-bottom type. In particular, at low wind speeds, the wake effects differ significantly among the various types of wind turbines. Full article
(This article belongs to the Special Issue Advances in Offshore Wind—2nd Edition)
Show Figures

Figure 1

16 pages, 3628 KiB  
Article
Combustion Control of Ship’s Oil-Fired Boilers Based on Prediction of Flame Images
by Chang-Min Lee
J. Mar. Sci. Eng. 2024, 12(9), 1474; https://doi.org/10.3390/jmse12091474 - 24 Aug 2024
Viewed by 366
Abstract
This study proposes and validates a novel combustion control system for oil-fired boilers aimed at reducing air pollutant emissions through flame image prediction. The proposed system is easily applicable to existing ships. Traditional proportional combustion control systems supply fuel and air at fixed [...] Read more.
This study proposes and validates a novel combustion control system for oil-fired boilers aimed at reducing air pollutant emissions through flame image prediction. The proposed system is easily applicable to existing ships. Traditional proportional combustion control systems supply fuel and air at fixed ratios according to the set steam load, without considering the emission of air pollutants. To address this, a stable and immediate control system is proposed, which adjusts the air supply to modify the combustion state. The combustion control system utilizes oxygen concentration predictions from flame images via SEF+SVM as control inputs and applies internal model control (IMC)-based proportional-integral (PI) control for real-time combustion control. Due to the complexity of modeling the image-based system, IMC filter constant tuning through experimentation is essential for achieving effective control performance. Experimental results showed that optimal control performance was achieved when the filter constant λ was set to 1.5. In this scenario, the peak overshoot Mp was reduced to 0.19245, and the Integral of Squared Error (ISE) was minimized to 10.1159, ensuring a stable response with minimal oscillation and maintaining a fast response speed. The results demonstrate the potential of the proposed system to improve combustion efficiency and reduce emissions of air pollutants. This study provides a feasible and effective solution for enhancing the environmental performance of marine oil-fired boilers. Given its ease of application to existing ships, it is expected to contribute to sustainable air pollution reduction across the maritime environment. Full article
(This article belongs to the Section Ocean Engineering)
Show Figures

Figure 1

18 pages, 2625 KiB  
Article
An Adaptive Characteristic Model-Based Event-Triggered Sigmoid Prescribed Performance Control Approach for Tracking the Trajectory of Autonomous Underwater Vehicles
by Chao Wang, Jing Wang, Yichao Qin and Shaowei Rong
J. Mar. Sci. Eng. 2024, 12(9), 1473; https://doi.org/10.3390/jmse12091473 - 23 Aug 2024
Viewed by 338
Abstract
This paper introduces an event-triggered sigmoid prescribed performance control method, enhanced by an adaptive characteristic model, for tracking the trajectory of autonomous underwater vehicles (AUVs). The AUV model is simplified into a function reliant solely on second-order parameter information through the use of [...] Read more.
This paper introduces an event-triggered sigmoid prescribed performance control method, enhanced by an adaptive characteristic model, for tracking the trajectory of autonomous underwater vehicles (AUVs). The AUV model is simplified into a function reliant solely on second-order parameter information through the use of characteristic modeling and a compression algorithm, which is then approximated by a neural network. We propose integrating prescribed performance control into event-triggered sliding mode control to accelerate convergence in AUV trajectory tracking. A novel prescribed performance function is employed in this integration, creating an event-triggered, non-singular terminal sliding mode control strategy. The stability of this controller is rigorously proven. This control strategy is not only robust against model uncertainties but also mitigates the jitter commonly associated with sliding mode control and the singularities from preset performance control due to sudden random disturbances. Comparative simulation experiments demonstrate that the proposed control method achieves superior control accuracy and a quicker response. Full article
(This article belongs to the Section Ocean Engineering)
Show Figures

Figure 1

15 pages, 41457 KiB  
Article
MSFE-UIENet: A Multi-Scale Feature Extraction Network for Marine Underwater Image Enhancement
by Shengya Zhao, Xinkui Mei, Xiufen Ye and Shuxiang Guo
J. Mar. Sci. Eng. 2024, 12(9), 1472; https://doi.org/10.3390/jmse12091472 - 23 Aug 2024
Viewed by 346
Abstract
Underwater optical images have outstanding advantages for short-range underwater target detection tasks. However, owing to the limitations of special underwater imaging environments, underwater images often have several problems, such as noise interference, blur texture, low contrast, and color distortion. Marine underwater image enhancement [...] Read more.
Underwater optical images have outstanding advantages for short-range underwater target detection tasks. However, owing to the limitations of special underwater imaging environments, underwater images often have several problems, such as noise interference, blur texture, low contrast, and color distortion. Marine underwater image enhancement addresses degraded underwater image quality caused by light absorption and scattering. This study introduces MSFE-UIENet, a high-performance network designed to improve image feature extraction, resulting in deep-learning-based underwater image enhancement, addressing the limitations of single convolution and upsampling/downsampling techniques. This network is designed to enhance the image quality in underwater settings by employing an encoder–decoder architecture. In response to the underwhelming enhancement performance caused by the conventional networks’ sole downsampling method, this study introduces a pyramid downsampling module that captures more intricate image features through multi-scale downsampling. Additionally, to augment the feature extraction capabilities of the network, an advanced feature extraction module was proposed to capture detailed information from underwater images. Furthermore, to optimize the network’s gradient flow, forward and backward branches were introduced to accelerate its convergence rate and improve stability. Experimental validation using underwater image datasets indicated that the proposed network effectively enhances underwater image quality, effectively preserving image details and noise suppression across various underwater environments. Full article
(This article belongs to the Special Issue Advancements in New Concepts of Underwater Robotics)
Show Figures

Figure 1

10 pages, 2398 KiB  
Article
Population Characteristics and Habitat Management of the Useful Seaweed Silvetia siliquosa
by Chang Geun Choi, Young Jae Choi, Seong Jae Hong, Jae Ho Lee and Seung Wook Jung
J. Mar. Sci. Eng. 2024, 12(9), 1471; https://doi.org/10.3390/jmse12091471 - 23 Aug 2024
Viewed by 320
Abstract
We aimed to analyze the natural population characteristics and habitat growth conditions of the valuable seaweed Silvetia siliquosa. Its population characteristics and habitat conditions were assessed monthly from May 2022 to April 2023 and April to August 2022, respectively, on selected habitats. [...] Read more.
We aimed to analyze the natural population characteristics and habitat growth conditions of the valuable seaweed Silvetia siliquosa. Its population characteristics and habitat conditions were assessed monthly from May 2022 to April 2023 and April to August 2022, respectively, on selected habitats. The average population density, coverage, and frequency of S. siliquosa were 579 ± 94.18 ind./m2, 27.82 ± 6.92%/m2, and 78.37 ± 5.98/m2, respectively. The average thallus length and width were 47.53 ± 4.35 and 46.33 ± 4.17 mm, respectively, while the branch width, thickness, and frequency were 2.35 ± 0.03 mm, 0.59 ± 0.12 mm, and 2.8 ± 0.2 times, with a receptacle length and width of 24.13 ± 2.07 and 2.81 ± 0.19 mm, respectively. Among the 40 previously known natural habitats of S. siliquosa, growth was confirmed only in Sepo, Sebang, and Bangpo. The causes for the declining S. siliquosa populations could be attributed to habitat changes due to construction, coastal road maintenance projects, habitat disturbances, and increased pollutants. Habitat substrate disturbances and changes were the main causes of the decrease in S. siliquosa growth. Studies on environmental factors and habitat degradation, growth related to environmental factors, mass cultivation, and the marine ecosystem restoration of S. siliquosa are needed. Full article
(This article belongs to the Special Issue Marine Biota Distribution and Biodiversity)
Show Figures

Figure 1

24 pages, 6311 KiB  
Article
Air-Lift Pumping System for Hybrid Mining of Rare-Earth Elements-Rich Mud and Polymetallic Nodules around Minamitorishima Island
by Yoshiyuki Shimizu, Masatoshi Sugihara, Koichiro Fujinaga, Kentaro Nakamura and Yasuhiro Kato
J. Mar. Sci. Eng. 2024, 12(9), 1470; https://doi.org/10.3390/jmse12091470 - 23 Aug 2024
Viewed by 329
Abstract
REE-rich mud under the seabed at a 5500–5700 m water depth around Minamitorishima island and polymetallic nodules buried in the deep seabed are very promising and attractive to explore and develop. REEs are critical to develop due to the recent paradigm shift to [...] Read more.
REE-rich mud under the seabed at a 5500–5700 m water depth around Minamitorishima island and polymetallic nodules buried in the deep seabed are very promising and attractive to explore and develop. REEs are critical to develop due to the recent paradigm shift to renewable energies based on green technologies. Numerical analysis using a one-dimensional drift–flux model for gas–liquid–solid three-phase flow and gas–liquid two-phase flow was conducted to examine the characteristics of an air-lift pumping system for mining these mineral resources. Empirical equations of REE-rich mud and the physical properties of polymetallic nodules around Minamitorishima island were utilized in the analysis. As a result, the characteristics, i.e., the performance of the system, were clarified in three cases: REE-rich mud, polymetallic nodules, and both. The time transient, i.e., the unsteady characteristics of the system, was also shown, such as the start-up and feeding slurry with REE-rich mud and polymetallic nodules. The findings from the unsteady characteristics will be useful in considering the operation of a real project or a commercial system in the future. Full article
(This article belongs to the Special Issue Deep-Sea Mining Technologies: Recent Developments and Challenges)
Show Figures

Figure 1

Previous Issue
Back to TopTop