Journal of Marine Science and Engineering

23 pages, 7835 KiB

Open AccessArticle

Development of a Key Method for the Optimization of Port Vessel Detection Based on an Improved Multi-Structural Morphology Approach

by Bernard Marie Tabi Fouda, Wenjun Zhang, Jacques Atangana and Helene Carole Edima-Durand

J. Mar. Sci. Eng. 2024, 12(11), 1969; https://doi.org/10.3390/jmse12111969 (registering DOI) - 1 Nov 2024

Abstract

All over the world, many ports have implemented surveillance camera systems to monitor the vessels and activities around them. These types of systems are not very effective in accurately detecting activities around the port due to background noise and congestion interference at the [...] Read more.

All over the world, many ports have implemented surveillance camera systems to monitor the vessels and activities around them. These types of systems are not very effective in accurately detecting activities around the port due to background noise and congestion interference at the sea surface. This is why it is difficult to accurately detect vessels, especially smaller vessels, when it turns dark. It is known that some vessels do not comply with maritime rules, particularly in port and safety zones; these must be detected to avoid incidents. For these reasons, in this study, we propose and develop an improved multi-structural morphology (IMSM) approach to eliminate all of this noise and interference so that vessels can be accurately detected in real time. With this new approach, the target vessel is separated from the sea surface background through the weighted morphological filtering of several datasets of structural components. Then, neighborhood-based adaptive fast median filtering is used to filter out impulse noise. Finally, a characteristic morphological model of the target vessel is established using the connected domain; this allows the sea surface congestion to be eliminated and the movement of vessels to be detected in real time. Multiple tests are carried out on a small and discrete area of moving vessels. The results from several collected datasets show that the proposed approach can effectively eliminate background noise and congestion interference in video monitoring. The detection accuracy rate and the processing time are improved by approximately 3.91% and 1.14 s, respectively. Full article

(This article belongs to the Section Ocean Engineering)

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22 pages, 15149 KiB

Open AccessArticle

A Peridynamics-Smoothed Particle Hydrodynamics Coupling Method for Fluid-Structure Interaction

by Chengjie Cao, Chenxu Gu, Chao Wang, Chunhui Wang, Pei Xu and Hui Wang

J. Mar. Sci. Eng. 2024, 12(11), 1968; https://doi.org/10.3390/jmse12111968 (registering DOI) - 1 Nov 2024

Abstract

Ice–water interaction is a critical issue of engineering studies in polar regions. This paper proposes a methodology to simulate fluid–ice interactions by employing a structure modeled using ordinary state-based peridynamics (OSB-PD) within a smoothed particle hydrodynamics (SPH) framework, effectively representing a deformable moving [...] Read more.

Ice–water interaction is a critical issue of engineering studies in polar regions. This paper proposes a methodology to simulate fluid–ice interactions by employing a structure modeled using ordinary state-based peridynamics (OSB-PD) within a smoothed particle hydrodynamics (SPH) framework, effectively representing a deformable moving boundary. The forces at the fluid–structure interface are delineated by solving the fluid motion equations for normal forces exerted by the fluid on the structure, grounded in the momentum conservation law. Upon validating the PD and SPH methods, a dam break flowing through an elastic gate was simulated. When compared with experimental results, the model exhibited discrepancies of 3.8%, 0.5%, and 4.6% in the maximum horizontal displacement, maximum vertical displacement, and the waterline deviation (W = 0.05 m), respectively. Moreover, the method demonstrated a high degree of accuracy in simulating the fracture of in-situ cantilever ice beams, with deflection closely matching experimental data and a 7.4% error in maximum loading force. The proposed PD-SPH coupling approach demonstrates its effectiveness in capturing the complex fluid–structure interactions and provides a valuable tool for studying the deformation and fracture of structures under the influence of fluid forces. Full article

(This article belongs to the Section Ocean Engineering)

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34 pages, 4110 KiB

Open AccessArticle

Wave and Tidal Energy: A Patent Landscape Study

by Mohamadreza Pazhouhan, Amin Karimi Mazraeshahi, Mohammad Jahanbakht, Kourosh Rezanejad and Mohammad Hossein Rohban

J. Mar. Sci. Eng. 2024, 12(11), 1967; https://doi.org/10.3390/jmse12111967 (registering DOI) - 1 Nov 2024

Abstract

Wave and tidal energy, recognized as vital renewable resources, harness the ocean’s kinetic and potential power. This study aims to provide an in-depth patent analysis of the technological landscape within these sectors. We applied a dual approach: first, a descriptive analysis was conducted [...] Read more.

Wave and tidal energy, recognized as vital renewable resources, harness the ocean’s kinetic and potential power. This study aims to provide an in-depth patent analysis of the technological landscape within these sectors. We applied a dual approach: first, a descriptive analysis was conducted to explore patent publication trends, technology lifecycle stages, patent activity by country, top assignees, and IPC classifications. Our analysis provided a detailed overview of the sector’s growth and the key players involved. Second, we utilized topic modeling, specifically BERTopic enhanced with large language models, to identify and fine-tune key technological themes within the patent data. In this study, we identified seven distinct clusters each for wave and tidal energy using this approach. This method led to a novel categorization of the patents, revealing latent themes within the patent data. Although our categorization differs from traditional methods, it provides deeper insights into the thematic focus of the patents, highlighting emerging trends and areas of innovation within wave and tidal energy technologies to better exploit and optimize ocean energy conversion infrastructure. Full article

(This article belongs to the Special Issue Exploitation and Optimization of Ocean Energy Conversion Infrastructure)

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14 pages, 3820 KiB

Open AccessArticle

Microbial Mat Dominated by Amphora spp. and Their Adaptative Strategies in an Arsenic-Rich Brackish Pond

by Eleonora Agostino, Angela Macrì, Vincenzo Zammuto, Michela D’Alessandro, Marco Sebastiano Nicolò, Salvatore Giacobbe and Concetta Gugliandolo

J. Mar. Sci. Eng. 2024, 12(11), 1966; https://doi.org/10.3390/jmse12111966 (registering DOI) - 1 Nov 2024

Abstract

Marine diatoms are essential members of both phytoplankton and phytobenthic communities, able to colonize submerged artificial and natural surfaces, contributing to benthic microbial biomass. Diatoms have developed different adaptative mechanisms to cope with various environmental stresses, including high concentrations of heavy metals. The [...] Read more.

Marine diatoms are essential members of both phytoplankton and phytobenthic communities, able to colonize submerged artificial and natural surfaces, contributing to benthic microbial biomass. Diatoms have developed different adaptative mechanisms to cope with various environmental stresses, including high concentrations of heavy metals. The aim of this study was to investigate the arsenic resistance of diatoms, isolated from microbial mats collected from an arsenic-rich brackish pond (Lake Mergolo della Tonnara, Italy), by evaluating (i) their ability to form biofilms in the presence of arsenite (As^III) or arsenate (As^V), and (ii) the variations in the photosynthetic pigments’ contents (i.e., chlorophyll a and c) in their biofilms. The mats were dominated by members of the genus Amphora, and isolates were affiliated with species of A. capitellata, A. coffeaeformis, and A. montana. The strains grew better in the presence of As^V than As^III, which is generally less toxic. After seven days of incubation, each strain exhibited a different ability to form biofilms on glass surfaces in the presence of arsenic (25 ppm), with A. montana strain 27 being the most effective (86%) in the presence of As^III, and A. coffeaeformis strain 26 (74%) with As^V. Photosynthetic pigment levels (chlorophyll a and c) differed in each biofilm, being poorly reduced by As^III in strain 27, and by As^V in strain 26, indicating a species-specific response to arsenic stress. Our results indicated that Amphora species thriving in this environment can form biofilms as an As-resistance mechanism, maintain their levels of photosynthetic pigments, and support the functioning of the pond ecosystem, with A. montana being favored in the presence of As^III, whereas A. coffeaeformis 26 in the presence of As^V. As producers of biofilms, these strains could be useful to develop new strategies to remediate arsenic pollution. Full article

(This article belongs to the Special Issue Marine Microorganisms and Their Biomolecules: Biodiversity, Physiological Adaptation and Biotechnological Applications)

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21 pages, 6757 KiB

Open AccessArticle

Study of Hydrofoil Boundary Layer Prediction with Two Correlation-Based Transition Models

by Changliang Ye, Yang Wang, Dongsen An, Jun Chen, Hongyeyu Yan, Yuan Zheng, Kan Kan and Bart P. M. van Esch

J. Mar. Sci. Eng. 2024, 12(11), 1965; https://doi.org/10.3390/jmse12111965 (registering DOI) - 1 Nov 2024

Abstract

In the realm of marine science and engineering, hydrofoils play a pivotal role in the efficiency and performance of marine turbines and water-jet pumps. In this investigation, the boundary layer characteristics of an NACA0009 hydrofoil with a blunt trailing edge are focused on. [...] Read more.

In the realm of marine science and engineering, hydrofoils play a pivotal role in the efficiency and performance of marine turbines and water-jet pumps. In this investigation, the boundary layer characteristics of an NACA0009 hydrofoil with a blunt trailing edge are focused on. The effectiveness of both the two-equation gamma theta (γ-Re_θt) transition model and the one-equation intermittency (γ) transition model in forecasting boundary layer behavior is evaluated. When considering natural transition, these two models outperform the shear stress transport two-equation (SST k-ω) turbulence model, notably enhancing the accuracy of predicting boundary layer flow distribution for chord-length Reynolds numbers (Re_L) below 1.6 × 10⁶. However, as Re_L increases, both transition models deviate from experimental values, particularly when Re_L is greater than 2 × 10⁶. The results indicate that the laminar separation bubble (LSB) is sensitive to changes in angles of attack (AOA) and Re_L, with its formation observed at AOA greater than 2°. The dimensions of the LSB, including the initiation and reattachment points, are found to contract as Re_L increases while maintaining a constant AOA. Conversely, an increase in AOA at similar Re_L values leads to a reduced size of the LSB. The findings are essential for the design and performance optimization of water-jet pumps, particularly in predicting and flow separation and transition phenomena. Full article

(This article belongs to the Special Issue Recent Advances in Hydraulic Machinery and Its Application in Marine Engineering)

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21 pages, 2772 KiB

Open AccessArticle

A Low-Cost Communication-Based Autonomous Underwater Vehicle Positioning System

by Raphaël Garin, Pierre-Jean Bouvet, Beatrice Tomasi, Philippe Forjonel and Charles Vanwynsberghe

J. Mar. Sci. Eng. 2024, 12(11), 1964; https://doi.org/10.3390/jmse12111964 (registering DOI) - 1 Nov 2024

Abstract

Underwater unmanned vehicles are complementary with human presence and manned vehicles for deeper and more complex environments. An autonomous underwater vechicle (AUV) has automation and long-range capacity compared to a cable-guided remotely operated vehicle (ROV). Navigation of AUVs is challenging due to the [...] Read more.

Underwater unmanned vehicles are complementary with human presence and manned vehicles for deeper and more complex environments. An autonomous underwater vechicle (AUV) has automation and long-range capacity compared to a cable-guided remotely operated vehicle (ROV). Navigation of AUVs is challenging due to the high absorption of radio-frequency signals underwater and the absence of a global navigation satellite system (GNSS). As a result, most navigation algorithms rely on inertial and acoustic signals; precise localization is then costly in addition to being independent from acoustic data communication. The purpose of this paper is to propose and analyze the performance of a novel low-cost simultaneous communication and localization algorithm. The considered scenario consists of an AUV that acoustically sends sensor or status data to a single fixed beacon. By estimating the Doppler shift and the range from this data exchange, the algorithm can provide a location estimate of the AUV. Using a robust state estimator, we analyze the algorithm over a survey path used for AUV mission planning both in numerical simulations and at-sea experiments. Full article

(This article belongs to the Special Issue Autonomous Marine Vehicle Operations—2nd Edition)

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20 pages, 10173 KiB

Open AccessArticle

Variability in Water Temperature Vertical Distribution and Advective Influences: Observations from Early Summer 2021 in the Central Yellow Sea

by Baekjin Kim, Seongheon Kim, Soonyeol Kwon, Donhyug Kang and Eung Kim

J. Mar. Sci. Eng. 2024, 12(11), 1963; https://doi.org/10.3390/jmse12111963 (registering DOI) - 1 Nov 2024

Abstract

To analyze variations in the vertical distribution of water temperatures and the impact of advection in the central Yellow Sea, multi-layer water temperature and current observations were conducted from 31 May to 8 June 2021. Water temperatures exhibited a typical three-layer summer structure, [...] Read more.

To analyze variations in the vertical distribution of water temperatures and the impact of advection in the central Yellow Sea, multi-layer water temperature and current observations were conducted from 31 May to 8 June 2021. Water temperatures exhibited a typical three-layer summer structure, with a uniform deep-layer temperature averaging 8.23 ± 0.05 °C. The current field was dominated by northeast–southwest tidal currents, but residual current characteristics indicated that non-tidal components significantly influenced circulation. Water temperature changes lagged tidal changes by about 3 h, with strong correlations (R > 0.7), especially in deep layers. Residual currents showed significant correlations with water temperature variations, which were attributed to advective displacement or baroclinic currents. Empirical orthogonal function (EOF) and complex EOF analyses revealed that thermocline variations (T1, explaining approximately 75% of total variance) were driven by strong northward (C1, approximately 34%) and cyclonic (C2, approximately 32%) advection. In deep layers, slight temperature changes were caused by southward Yellow Sea Cold Water Mass (C1) and northward Yellow Sea Warm Current Water (C2) propagation. This study confirms that vertical water temperature variations result from a complex interaction between various advection patterns, with southward tide-induced residual currents (C3, approximately 12%) playing a key dynamic role. Full article

(This article belongs to the Section Physical Oceanography)

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33 pages, 11304 KiB

Open AccessArticle

Intercomparison of Surface Currents Obtained Using SCHISM and the HF Radar Data in Galveston Bay and Sabine Lake, Texas

by Cletus O. Ogbodo, Rosa M. Fitzgerald, Christopher Fuller, Jungwoo Lee, Roberto Perea and Javier Polanco-Gonzalez

J. Mar. Sci. Eng. 2024, 12(11), 1962; https://doi.org/10.3390/jmse12111962 (registering DOI) - 1 Nov 2024

Abstract

This study provides a comprehensive analysis and intercomparison of surface currents, for Galveston Bay and Sabine Lake, Texas, obtained from High-Frequency (HF) radars and SCHISM model. We established a methodology based on qualitative and quantitative analyses to compare measured and modeled surface currents. [...] Read more.

This study provides a comprehensive analysis and intercomparison of surface currents, for Galveston Bay and Sabine Lake, Texas, obtained from High-Frequency (HF) radars and SCHISM model. We established a methodology based on qualitative and quantitative analyses to compare measured and modeled surface currents. One-month HF radar data, in April 2023, were extracted from the two newly installed HF radar networks comprising two and three HF radar stations at Sabine Lake and Galveston Bay, respectively. The extracted surface current data were compared to corresponding SCHISM-simulated currents to assess the model’s performance in predicting currents. The comparison encompassed qualitative and quantitative assessments by evaluating current vectors and the magnitude of eastward and northward velocity components from both methods. The results showed the ocean current predictive capabilities of SCHISM exemplified by their strong correlations (up to 0.94), high index of agreement (up to 0.95), and low error metrics, during the study period. The disparities in the eastward and northward current measurements across the dates underscore the complex interplay between prevailing winds, bay-ocean interactions, and regional weather patterns. This study sheds light on the intricate dynamics of the surface currents in estuaries and nearshore lakes with the underlying efficacy of both the HF radar and SCHISM surface current determinations. The findings can contribute to advancing the understanding of coastal dynamics and determining the strategies for environmental monitoring and management. Full article

(This article belongs to the Section Physical Oceanography)

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14 pages, 5222 KiB

Open AccessArticle

Optimization of Production Scheduling for the Additive Manufacturing of Ship Models Using a Hybrid Method

by Kyeongho Kim, Soonjo Kwon and Minjoo Choi

J. Mar. Sci. Eng. 2024, 12(11), 1961; https://doi.org/10.3390/jmse12111961 (registering DOI) - 1 Nov 2024

Abstract

This paper introduces a hybrid optimization method that leverages either linear programming (LP) or a genetic algorithm (GA) based on the problem size to enhance the parallel additive manufacturing (AM) process for ship models. The LP ensures optimality but can experience exponential increases [...] Read more.

This paper introduces a hybrid optimization method that leverages either linear programming (LP) or a genetic algorithm (GA) based on the problem size to enhance the parallel additive manufacturing (AM) process for ship models. The LP ensures optimality but can experience exponential increases in the computation time as the problem size grows. To address this limitation, the GA is employed for larger problems, providing optimal solutions within reasonable quality and time constraints. The method optimizes the module allocation to AM machines and determines the build processing sequence for each machine, while also considering the availability of workers preparing for consecutive module production. Applied to a case study, the proposed method achieves a 14% reduction in the completion time compared to a heuristic method from a previous study. Furthermore, the method is validated by benchmarking against the heuristic method across various problem sizes, consistently demonstrating superior performance. Full article

(This article belongs to the Special Issue Novel Maritime Techniques and Technologies, and Their Safety)

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22 pages, 13706 KiB

Open AccessArticle

Multiparameter Collaborative Optimization and Analysis of the Non-Penetrating Tunnel Thruster

by Jinyu Guo, Yi Yang, Chao Wang, Zhiqiang Hu, Quan Zheng and Chuanzhi Fan

J. Mar. Sci. Eng. 2024, 12(11), 1960; https://doi.org/10.3390/jmse12111960 (registering DOI) - 1 Nov 2024

Abstract

A brand new non-penetrating tunnel thruster (short for NPT thruster) is proposed in this paper. The tunnel structural parameters of the thruster are optimized, and the performance and optimization effect are verified by experiments. First, the design and function of the NPT thruster [...] Read more.

A brand new non-penetrating tunnel thruster (short for NPT thruster) is proposed in this paper. The tunnel structural parameters of the thruster are optimized, and the performance and optimization effect are verified by experiments. First, the design and function of the NPT thruster are introduced. Second, the computational fluid dynamics method is used to calculate the hydrodynamic performance of the NPT thruster and to analyze the static mooring thrust performance. Third, the tunnel structural parameters of the NPT thruster are optimized with the method of the response surface methodology. The pressure distributions and the flow fields on the tunnel surface of the NPT thrusters before and after optimization are compared with simulations. Finally, the mooring static thrust of the NPT thrusters is tested with experiments. The results show that the average increase in the mooring static thrust for the optimized thruster is 12.4%, and the maximum increase can reach 21.79% when the rotational speed is from 3000 rpm to 6500 rpm. Full article

(This article belongs to the Section Ocean Engineering)

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17 pages, 3923 KiB

Open AccessArticle

Estimation of Tug Pulling Power (Bollard Pull) and Number of Tugs Required During Ship Mooring Operations

by Vytautas Paulauskas, Donatas Paulauskas and Martynas Simutis

J. Mar. Sci. Eng. 2024, 12(11), 1959; https://doi.org/10.3390/jmse12111959 (registering DOI) - 1 Nov 2024

Abstract

Harbour tugs are usually used to moor ships if large ships do not have their own additional propulsion devices (thrusters). Alternatively, during ship loading operations, ships sometimes have to be transferred from one quay to another, and in some cases, port users (shipping [...] Read more.

Harbour tugs are usually used to moor ships if large ships do not have their own additional propulsion devices (thrusters). Alternatively, during ship loading operations, ships sometimes have to be transferred from one quay to another, and in some cases, port users (shipping companies or other companies) have to pay for port tug services. In such cases, it is very important to guarantee the safety of shipping during mooring operations and to use tugboats optimally and at the same time reduce the cost of tugboat services for ship operators and other companies. For the optimal use of tugboats, it is very important to accurately estimate the required traction force (bollard pull) of tugboats and their quantity, taking into account the parameters of moored ships, the locations of berths, hydro-meteorological and hydrological conditions, and clearance (the gap between the ship’s hull and the bottom of the water area), in order to guarantee the safety of navigation and not to order an excess of tugboats in terms of their quantity and powers. This article presents a methodology developed for estimating the required bollard pull and the number of tugs, taking into account the parameters of the ship, hydro-meteorological and hydrological conditions, clearance, and the locations of berths. The developed methodology for estimating the number of tugboats and their traction force (bollard pull) was tested in real conditions (with real ships and tugboats) and using a calibrated simulator, and we found that it can be successfully applied in any port or other complex shipping area by adapting it to specific conditions. The developed methodology for calculating the traction power (bollard pull) of tugboats allows us to determine the required traction force of tugboats in advance with sufficient accuracy, achieved by assessing the specific parameters and environmental conditions of the vessel served by tugboats. In the most difficult areas of the port, in terms of the use of tugboats, this methodology allows us to make reasonable decisions regarding the number of tugboats and the traction force (bollard pull) required and at the same time reduces the risk of emergency situations. Full article

(This article belongs to the Special Issue Advances in Navigability and Mooring (2nd Edition))

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17 pages, 563 KiB

Open AccessArticle

Research on Underwater Sensor Network Adaptive Clustering Algorithm for Marine Environment Monitoring

by Libin Xue, Chunjie Cao and Rongxin Zhu

J. Mar. Sci. Eng. 2024, 12(11), 1958; https://doi.org/10.3390/jmse12111958 (registering DOI) - 1 Nov 2024

Abstract

In recent years, underwater environmental monitoring has primarily relied on monitoring systems based on underwater sensor networks (UWSNs). The underwater sensor node using a self-powered monitoring system has not been widely used because of the complicated design and high cost of its energy-harvesting [...] Read more.

In recent years, underwater environmental monitoring has primarily relied on monitoring systems based on underwater sensor networks (UWSNs). The underwater sensor node using a self-powered monitoring system has not been widely used because of the complicated design and high cost of its energy-harvesting device. Thus, the mobile monitoring nodes within UWSNs are typically powered by batteries with limited energy, and replacement on the seabed is challenging. As a result, optimizing the energy consumption of the mobile monitoring network is of significant importance. The clustering algorithm for UWSNs is acknowledged as a vital approach to balancing and reducing network energy consumption. Nevertheless, most existing clustering algorithms employ fixed schemes to balance the energy consumption among nodes, which are unable to dynamically adapt to changes in network topology and do not account for the complexities of the underwater channel environment, thus not aligning with the actual scenarios of marine environment monitoring. Consequently, this paper introduces an adaptive clustering algorithm for marine environment monitoring (MEMAC). The algorithm incorporates the multipath channel information of the underwater environment and the traffic weight between nodes into the probability model to calculate the probability of the node being elected as the cluster head (CH). The final calculated expected revenues are the user’s revenues after participating in the game under the influence of the multipath effect, and the revenues of all users jointly determine the performance of the clustering algorithm proposed in this paper. When the energy consumption of the CH node is too much and needs to be rotated, MEMAC, through a CH rotation mechanism and a comprehensive analysis of the overall remaining energy of the network, further optimizes the CH selection strategy while ensuring network stability. Simulation results indicate that the network lifetime of the proposed MEMAC method is extended by 58.9% and 19.17% compared to the two latest clustering algorithms, the Game Theory-Based Clustering Scheme (GTC) and the Centralized Control-Based Clustering Scheme (CCCS), respectively. This demonstrates that the algorithm can achieve efficient energy utilization and notably enhance network performance. Full article

(This article belongs to the Special Issue Intelligent Approaches to Marine Engineering Research)

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18 pages, 1602 KiB

Open AccessArticle

First Long-Term Measurements on Kazakhstan Shelf of the Caspian Sea Reveal Alternating Currents and Energetic Temperature Variability

by Peter O. Zavialov, Andrey G. Kostianoy, Philipp V. Sapozhnikov, Valentina M. Khan, Nurgazy K. Kurbaniyazov and Abilgazi K. Kurbaniyazov

J. Mar. Sci. Eng. 2024, 12(11), 1957; https://doi.org/10.3390/jmse12111957 (registering DOI) - 1 Nov 2024

Abstract

Moored near-bottom current velocity and water temperature measurements were performed during a period of 194 days (from October 2022 through April 2023) with a 15-min sampling rate at two locations on the shelf of the Kazakhstan sector of the Caspian Sea in its [...] Read more.

Moored near-bottom current velocity and water temperature measurements were performed during a period of 194 days (from October 2022 through April 2023) with a 15-min sampling rate at two locations on the shelf of the Kazakhstan sector of the Caspian Sea in its Middle Caspian basin. The area has not been covered by in situ measurements over several decades. The two stations were separated by a distance of 22 km along the coast. The velocity and temperature data collected at 14 m depth were analyzed together with the wind data from the local meteorological station, NCEP/NCAR reanalysis of wind curl data over the Caspian Sea, as well as multi-mission satellite imagery. The analysis revealed that the currents were predominantly along-shore and highly variable in direction, with nearly zero average over the observation period. The along-shore and cross-shore components of velocity exhibited rather high correlation with the along-shore wind stress with the maximum (r = 0.68 and r = 0.53, respectively) at a time lag of about 9.5 h. The velocity series were not significantly correlated with the wind curl averaged over the entire Caspian Sea at any temporal lag, while there were weak but significant correlations between the along-shore current velocity and the curl of the wind fields over the Middle Caspian and Northern Caspian basins with time lags from one to nine days. The along-shore current velocities at the two stations were highly correlated (r = 0.78) with each other at no temporal lag. The temperature at both stations demonstrated nearly identical seasonal march, but a higher frequency variability superimposed on the latter was also evident with amplitudes as high as 2.79 °C. Somewhat surprisingly, the series of these anomalies at the two stations were not correlated either with each other or with surface wind forcing. However, there is evidence pointing to their connection with the cross-shore component of near bottom velocity, i.e., the cross-shore, up or down the bottom slope excursions of water from deeper or shallower depths, retaining a different temperature. During intense winter cooling of the surface layer, this effect is manifested as «warm upwelling» creating strong positive temperature anomalies or the opposite «cold downwelling» and negative anomalies. Full article

(This article belongs to the Section Physical Oceanography)

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23 pages, 12871 KiB

Open AccessArticle

A Tank Experiment of the Autonomous Detection of Seabed-Contacting Segments for Submarine Pipelaying Operations

by Bo Wang, Jie Wang, Chen Zheng, Ye Li, Jian Cao and Yueming Li

J. Mar. Sci. Eng. 2024, 12(11), 1956; https://doi.org/10.3390/jmse12111956 (registering DOI) - 1 Nov 2024

Abstract

Due to the weak structural features of pipelines and underwater light attenuation, the complex and harsh environment of the seabed greatly increases the possibility of an underwater autonomous remotely operated vehicle losing a detected seabed-contacting segment during pipe-laying operations. To address this problem, [...] Read more.

Due to the weak structural features of pipelines and underwater light attenuation, the complex and harsh environment of the seabed greatly increases the possibility of an underwater autonomous remotely operated vehicle losing a detected seabed-contacting segment during pipe-laying operations. To address this problem, we propose a cascade attention module and a prefusion module with a convolutional neural network. The cascade attention module samples the feature maps in a non-convolutional form to realize the interaction between structure and channels, and the attention map is generated by cascading attention. The prefusion module pre-fuses the three layers of feature maps from different stages in the backbone, and the delicate features of the shallow feature maps are fused with the deeper feature maps to generate richer feature maps with space location and semantic classification information. We conduct experiments to verify our modules, both on the underwater pipeline dataset and in a tank test. The results show that our modules can improve the performance of different neural network models for seabed-contacting segment detection. The target detection and instance segmentation performance of the best model is improved through a 6.3% increase in AP and a 3.8% increase in mean intersection over union compared with the baseline model. Full article

(This article belongs to the Section Ocean Engineering)

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16 pages, 4851 KiB

Open AccessArticle

Underwater Refractive Stereo Vision Measurement and Simulation Imaging Model Based on Optical Path

by Guanqing Li, Shengxiang Huang, Zhi Yin, Jun Li and Kefei Zhang

J. Mar. Sci. Eng. 2024, 12(11), 1955; https://doi.org/10.3390/jmse12111955 (registering DOI) - 1 Nov 2024

Abstract

When light passes through air–glass and glass–water interfaces, refraction occurs, which affects the accuracy of stereo vision three-dimensional measurements of underwater targets. To eliminate the impact of refraction, we developed a refractive stereo vision measurement model based on light propagation paths, utilizing the [...] Read more.

When light passes through air–glass and glass–water interfaces, refraction occurs, which affects the accuracy of stereo vision three-dimensional measurements of underwater targets. To eliminate the impact of refraction, we developed a refractive stereo vision measurement model based on light propagation paths, utilizing the normalized coordinate of the underwater target. This model is rigorous in theory, and easy to understand and apply. Additionally, we established an underwater simulation imaging model based on the principle that light travels the shortest time between two points. Simulation experiments conducted using this imaging model verified the performance of the underwater stereo vision measurement model. The results demonstrate that the accuracy achieved by the new measurement model is comparable to that of the stereo vision measurement model in the air and significantly higher than that of the existing refractive measurement model. This is because the light rays from the camera’s optical center to the refraction point at the air–glass interface do not always intersect. The experiments also indicate that the deviation in the refractive index of water lead to corresponding systematic errors in the measurement results. Therefore, in real underwater measurements, it is crucial to carefully calibrate the refractive index of water and maintain the validity of the calibration results. Full article

(This article belongs to the Section Ocean Engineering)

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20 pages, 5672 KiB

Open AccessArticle

A Novel Approach to Enhancing the Accuracy of Prediction in Ship Fuel Consumption

by Tianrui Zhou, Jinggai Wang, Qinyou Hu and Zhihui Hu

J. Mar. Sci. Eng. 2024, 12(11), 1954; https://doi.org/10.3390/jmse12111954 - 31 Oct 2024

Abstract

Ship fuel consumption plays a crucial role not only in understanding ships’ energy efficiency but also in gaining insights into their emissions. However, enhancing the accuracy of these predictions poses significant challenges due to data limitations and the methods employed. Due to these [...] Read more.

Ship fuel consumption plays a crucial role not only in understanding ships’ energy efficiency but also in gaining insights into their emissions. However, enhancing the accuracy of these predictions poses significant challenges due to data limitations and the methods employed. Due to these factors, such as data variability and equipment characteristics, ship fuel consumption exhibits certain fluctuations under specific conditions. Previous fuel consumption prediction methods primarily generate a single specific value, making it difficult to capture the volatility of and variability in fuel consumption. To overcome this limitation, this paper proposes a novel method that integrates Gaussian process prediction with quantile regression theory to perform interval predictions of ship fuel consumption, providing a range of possible outcomes. Through comparative analyses with traditional methods, the possibility of using the method is verified and its results are validated. The results indicate the following: (1) at a 95% confidence level, the proposed method achieves a prediction interval coverage probability of 0.98 and a prediction interval normalized average width of 0.123, which are significantly better than those of the existing backpropagation neural network (BPNN) and gradient boosting decision tree (GBDT) quantile regression models; (2) the prediction accuracy of the proposed method is 92% for point forecasts; and (3) the proposed method is applicable to main datasets, including both noon report and sensor datasets. These findings provide valuable insights into interval predictions of ship fuel consumption and highlight their potential applications in related fields, emphasizing the importance of accurate interval predictions in intelligent energy efficiency optimization. Full article

(This article belongs to the Special Issue Smart and Low Carbon Emission-Oriented Maritime Traffic Management and Controlling)

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17 pages, 6692 KiB

Open AccessArticle

Adaptive Pitch-Tracking Control with Dynamic and Static Gains for Remotely Operated Towed Vehicles

by Cong Tian, Hang Xu, Songkai Ren, Longchuan Guo, Xiaoqing Tian and Jiyong Wang

J. Mar. Sci. Eng. 2024, 12(11), 1953; https://doi.org/10.3390/jmse12111953 - 31 Oct 2024

Abstract

The pitch angle regulation in Remotely Operated Towed Vehicles (ROTVs) is essential to ensure the robustness of emitted signals within the maritime surveillance domain. Characterized by inherent nonlinear dynamics and stochastic uncertainties, the pitch angle model poses significant challenges to conventional tracking controls [...] Read more.

The pitch angle regulation in Remotely Operated Towed Vehicles (ROTVs) is essential to ensure the robustness of emitted signals within the maritime surveillance domain. Characterized by inherent nonlinear dynamics and stochastic uncertainties, the pitch angle model poses significant challenges to conventional tracking controls relying on linearization. This study introduces an adaptive pitch-control algorithm designed for ROTVs, which adeptly manages nonlinear dynamics as well as unmeasurable states through a synergistic integration of dynamic and static gains. A key feature of our approach is the incorporation of a high-order observer that adeptly estimates the system’s unmeasurable states, thereby enhancing control precision. Our proposed algorithm greatly exceeds traditional PID and fuzzy PID methods in both settling time and steady-state error, particularly in high-order nonlinear and unmeasurable state scenarios. Compared to sliding mode control, the proposed control strategy improved the settling time by 74% and the steady-state error was enhanced from

10^{- 6}

to

10^{- 8}

, as confirmed by numerical simulations. The efficacy of the algorithm in achieving the desired tracking trajectories highlights its potential for deep-water operations and fine-tuned attitude adjustments for ROTVs. Full article

(This article belongs to the Special Issue Advanced Research in Sustainable and Intelligent Navigation Control Systems for Marine Vehicles)

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15 pages, 2167 KiB

Open AccessArticle

Underwater Acoustic Target Recognition Based on Sub-Regional Feature Enhancement and Multi-Activated Channel Aggregation

by Zhongxiang Zheng and Peng Liu

J. Mar. Sci. Eng. 2024, 12(11), 1952; https://doi.org/10.3390/jmse12111952 - 31 Oct 2024

Abstract

Feature selection and fusion in ship radiated noise-based underwater target recognition have remained challenging tasks. This paper proposes a novel feature extraction method based on multi-dimensional feature selection and fusion. Redundant features are filtered through feature visualization techniques. The Sub-regional Feature Enhancement modules [...] Read more.

Feature selection and fusion in ship radiated noise-based underwater target recognition have remained challenging tasks. This paper proposes a novel feature extraction method based on multi-dimensional feature selection and fusion. Redundant features are filtered through feature visualization techniques. The Sub-regional Feature Enhancement modules (SFE) and Multi-activated Channel Aggregation modules (MCA) within the neural network are utilized to achieve underwater target recognition. Experimental results indicate that our network, named Sub-Regional Channel Aggregation Net (SRCA-Net), utilizing 3-s sound segments for ship radiated noise recognition, surpasses existing models, achieving an accuracy of 78.52% on the public DeepShip dataset. Full article

(This article belongs to the Section Ocean Engineering)

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17 pages, 12804 KiB

Open AccessArticle

An Early-Stage Structural Design of a Semi-Submersible Platform for Floating Offshore Wind Turbines in Chilean Waters

by Yordan Gallardo, Gonzalo Tampier, Víctor Palma, Cristian Cifuentes, José Miguel Ahumada, Claudio Troncoso and Michael Y. Mendoza

J. Mar. Sci. Eng. 2024, 12(11), 1951; https://doi.org/10.3390/jmse12111951 - 31 Oct 2024

Abstract

To advance offshore wind energy technologies in South America, this study addresses the early-stage design challenges of a floating support structure for a 5 MW wind turbine. The aim is to develop a robust and efficient floating structure capable of withstanding the diverse [...] Read more.

To advance offshore wind energy technologies in South America, this study addresses the early-stage design challenges of a floating support structure for a 5 MW wind turbine. The aim is to develop a robust and efficient floating structure capable of withstanding the diverse forces imposed by the Valdivian environment. Utilizing SolidWorks, a 3D model based on a comprehensive review of semi-submersible structures with three columns is proposed. The structural model is subjected to a rigorous evaluation using the finite element method, with which linear static and buckling analyses are performed in compliance with the Det Norske Veritas (DNV) classification society. The proposed tri-floater platform design shows a 30% weight reduction when compared with other proposed models. The finite element analysis includes an extreme condition of 13 m waves that suggests the adequate performance of the proposed platform in Chilean waters, and offers a conceptual preliminary step for floating support structure designs in Chile. Full article

(This article belongs to the Section Coastal Engineering)

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Journal of Marine Science and Engineering

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