Journal of Marine Science and Engineering

21 pages, 3060 KB

Open AccessArticle

Shedding Light on the Italian Mesophotic Spongofauna

by Margherita Toma, Marzia Bo, Marco Bertolino, Martina Canessa, Michela Angiolillo, Alessandro Cau, Franco Andaloro, Simonepietro Canese, Silvestro Greco and Giorgio Bavestrello

J. Mar. Sci. Eng. 2024, 12(11), 2110; https://doi.org/10.3390/jmse12112110 - 20 Nov 2024

Cited by 1 | Viewed by 1208

Abstract

An analysis of 483 remotely operated vehicle (ROV) dives carried out along the Italian coast on hard substrata at mesophotic depths (40–200 m) allowed an overview of the rich sponge diversity (53 taxa) of the deep continental platform to be obtained for the [...] Read more.

An analysis of 483 remotely operated vehicle (ROV) dives carried out along the Italian coast on hard substrata at mesophotic depths (40–200 m) allowed an overview of the rich sponge diversity (53 taxa) of the deep continental platform to be obtained for the first time. About 40% of the potential actual species diversity was recognisable using ROV, suggesting that this group is among the richest yet underestimated using this technology in contrast to other megabenthic taxa. Additionally, the study allowed us to gather data on the current basin-scale distribution and bathymetric limits of five common and easily identifiable demosponges with up to 55% occurrence in the explored sites: Aplysina cavernicola, the group Axinella damicornis/verrucosa, Chondrosia reniformis, Foraminospongia spp., and Hexadella racovitzai. Four of these latitudinal distributions were characterised by high occurrence in the Ligurian Sea and a progressive decrease towards the south Tyrrhenian Sea, with an occasional second minor peak of occurrence in the Sicily Channel. In contrast, Foraminospongia spp. showed a maximum occurrence on the offshore reliefs and a second one in the North–central Tyrrhenian Sea, while it was almost absent in the Ligurian Sea. Trophic and biogeographic reasons were discussed as possible causes of the double-peak distributions. The vertical distributions support a more consistent occurrence of all considered taxa in deeper waters than previously known. This suggests that they may more typically belong to the mesophotic realm than the shallow waters, owing to a more extensive sampling effort in the deeper depth range. The five target taxa are typical or associated species of seven reference habitats in the recently revised UNEP/SPA-RAC classification. However, they may create such dense aggregations that they should be listed as new facies in the abovementioned classification. Full article

(This article belongs to the Special Issue 5th International Workshop on Taxonomy of Atlanto-Mediterranean Deep-Sea & Cave Sponges)

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24 pages, 2016 KB

Open AccessArticle

Acoustic Transmission Loss of a Cylindrical Silencer Filled with Multilayer Poroelastic Materials Based on Mode-Matching Method

by Haesang Yang and Woojae Seong

J. Mar. Sci. Eng. 2024, 12(11), 2109; https://doi.org/10.3390/jmse12112109 - 20 Nov 2024

Cited by 1 | Viewed by 1034

Abstract

The efficacy of silencers in reducing piping noise is contingent upon the specific installation and operating environment. Among the various forms of silencers, the acoustic characteristics of dissipative silencers with sound-absorbing materials attached internally exist in an area that is difficult to explain [...] Read more.

The efficacy of silencers in reducing piping noise is contingent upon the specific installation and operating environment. Among the various forms of silencers, the acoustic characteristics of dissipative silencers with sound-absorbing materials attached internally exist in an area that is difficult to explain by existing theories. This is dependent upon the specific type and placement of the attached sound-absorbing materials. This paper presents a methodology for calculating the acoustic transmission loss (TL) of a cylindrical silencer filled with a multilayer poroelastic material, employing the mode-matching method. To describe the numerical process of treating waves propagating within a poroelastic material and determine the modes in accordance with the boundary conditions necessary for analyzing the acoustic performance of the silencer, the Biot model and the Johnson–Champoux–Allard–Lafarge model were employed. The obtained modes were utilized to calculate the acoustic TL of silencers filled with single, double, and triple layers of poroelastic materials. In particular, the results obtained for the single layer were validated by comparing them with the results of a finite element analysis, and the results obtained for multiple layers with the same material were validated by comparing them with the equivalent single-layer results. Moreover, the results of the numerical calculations of the acoustic TLs of the silencer for three distinct types of poroelastic materials, including those with varying degrees of frame rigidity or softness, were compared, and the acoustic characteristics were analyzed in relation to the intrinsic properties of the materials and their arrangement. It is anticipated that the methodology presented in this paper will facilitate the design of silencers using poroelastic materials in accordance with the specific requirements of users or designers by allowing for a comprehensive consideration of the thickness of layers and the arrangement of materials. Full article

(This article belongs to the Topic Advances in Underwater Acoustics and Aeroacoustics)

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30 pages, 6829 KB

Open AccessArticle

Model Sensitivity Analysis for Coastal Morphodynamics: Investigating Sediment Parameters and Bed Composition in Delft3D

by Robert L. Jenkins III, Christopher G. Smith, Davina L. Passeri and Alisha M. Ellis

J. Mar. Sci. Eng. 2024, 12(11), 2108; https://doi.org/10.3390/jmse12112108 - 20 Nov 2024

Viewed by 3169

Abstract

Numerical simulation of sediment transport and subsequent morphological evolution rely on accurate parameterizations of sediment characteristics. However, these data are often not available or are spatially and/or temporally limited. This study approaches the problem of limited sediment grain-size data with a series of [...] Read more.

Numerical simulation of sediment transport and subsequent morphological evolution rely on accurate parameterizations of sediment characteristics. However, these data are often not available or are spatially and/or temporally limited. This study approaches the problem of limited sediment grain-size data with a series of simulations assessing model sensitivity to sediment parameters and initial bed composition configurations in Delft3D, leading to improved modeling practices. A previously validated Delft3D sediment transport and morphology model for Dauphin Island, Alabama, USA, is used as the benchmark case. A method for the generation of representative sediment grain sizes and their spatially varying distributions is presented via end-member analysis of in situ surficial sediment samples. Derived sediment classes and their spatial distributions are applied to two sensitivity case simulations with increasing bed composition complexity. First, multiple sediment classes are applied in a single fully mixed layer, regardless of sediment type. Second, multiple sediment classes are applied in a thin, fully mixed transport layer with underlayers containing only the non-cohesive sediment classes below. Simulations were carried out in a probabilistic, Delft3D MorMerge configuration to capture long-term morphology change for 10 years. We found there is sensitivity to the inclusion of additional sediment classes and sediment distribution made evident in bed level and morphology change. Inclusion of highly mobile fine sediments altered model results in each sensitivity case. The model was also found to be sensitive to initial bed composition in terms of bed level and morphology change, with notable differences between sensitivity cases on decadal timescales, indicating an armoring effect in the second sensitivity case, which used the transport and underlayer bed configuration. The results of this study offer guidance for numerical modelers concerned with sediment behavior in coastal and estuarine environments. Full article

(This article belongs to the Section Coastal Engineering)

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18 pages, 4406 KB

Open AccessArticle

A Baroclinic Fluid Model and Its Application in Investigating the Salinity Transport Process Within the Sediment–Water Interface in an Idealized Estuary

by Jun Zhao, Liangsheng Zhu, Bo Hong and Jianhua Li

J. Mar. Sci. Eng. 2024, 12(11), 2107; https://doi.org/10.3390/jmse12112107 - 20 Nov 2024

Viewed by 1017

Abstract

Understanding the salinity transport process around the sediment–water interface is important for water resources management in the upper reach of an estuary. In this study, we developed a baroclinic fluid dynamic model for investigating the flow and salt transport characteristics within the sediment–water [...] Read more.

Understanding the salinity transport process around the sediment–water interface is important for water resources management in the upper reach of an estuary. In this study, we developed a baroclinic fluid dynamic model for investigating the flow and salt transport characteristics within the sediment–water interface under tidal forcing. The validation showed robust model performance on the salinity transport within the sediment–water interface. The results revealed that the turbulent kinetic energy, dissipation rate, and kinetic energy production rate exhibited periodic variations within the seabed boundary layer. The thickness of the viscous sublayer and the mean flow showed an inverse relationship. Water and salinity exchange within the sediment–water interface occurred predominantly via turbulent diffusion, with extreme turbulent kinetic energy production rates appearing during the tidal reversal, flood, and ebb stages. The sediment acted as a source of salinity release during ebb tides and a sink for salinity absorption during flood tides. As the sediment depth increased, fluctuations in salinity were weakened. These results clearly illustrated that the sediment layer is important in modulating the salinity transport in the upper reach of an estuary. However, such an important process was usually excluded by previous studies. The model developed in this study can be used as a sediment–water interface module that, coupled with other hydrodynamic models, can evaluate the contributions of the sediment layer to the salinity exchange in coastal water. Full article

(This article belongs to the Special Issue Hydrodynamics and Water Quality in Coastal Systems: Numerical Modelling and Observations)

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24 pages, 4821 KB

Open AccessArticle

Nonstationary Control Parameter Prediction for Underwater Gliders Utilizing an Innovative Transformer-Based Model

by Yv Jing, Chao Ma, Jianpeng An, Zezhong Li, Xinlin Sun and Wei Guo

J. Mar. Sci. Eng. 2024, 12(11), 2106; https://doi.org/10.3390/jmse12112106 - 20 Nov 2024

Viewed by 1122

Abstract

As a new type of unmanned autonomous marine observation platform, underwater gliders (UGs) offer advantages such as low energy consumption and long operational ranges. However, during the gliding process, the complex marine environment often leads to abrupt changes in short-term control parameters, complicating [...] Read more.

As a new type of unmanned autonomous marine observation platform, underwater gliders (UGs) offer advantages such as low energy consumption and long operational ranges. However, during the gliding process, the complex marine environment often leads to abrupt changes in short-term control parameters, complicating the data and rendering them more challenging to predict. This typically poses difficulties in adjusting control parameters based on human experience, thereby significantly reducing UG control efficiency. To address this issue, this paper proposes a novel method termed DFFormer, aimed at enhancing the predictive accuracy of the rudder angles during UG motion. The proposed method integrates discrete wavelet transform (DWT) for rudder angle signal decomposition and employs a fast Fourier transform-based attention mechanism (FFT-Attention) to effectively capture and analyze its frequency- and time-domain characteristics. Notably, the method leverages a Transformer architecture to process the decomposed signals through multiple parallel pathways, substantially improving the capability to forecast the complex and variable control parameters of UGs. The effectiveness and practicality of the proposed method are demonstrated through actual sea trials. The experimental results indicate that the proposed method surpasses traditional approaches in terms of accuracy and computational efficiency, exhibiting superior performance in predicting UG control parameters and, to some extent, enhancing their heading-keeping ability. Full article

(This article belongs to the Section Ocean Engineering)

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16 pages, 11514 KB

Open AccessArticle

Design and Experimental Study of a Robotic Tuna with Shell-like Tensegrity Joints

by Yanwen Liu, Guangyuan Jin, Jiekai Cao, Liang Zhou and Hongzhou Jiang

J. Mar. Sci. Eng. 2024, 12(11), 2105; https://doi.org/10.3390/jmse12112105 - 20 Nov 2024

Viewed by 1280

Abstract

We developed an untethered robotic tuna featuring tensegrity joints for the purposes of simplifying the design procedure, reserving enough internal space, reducing the frictional loss of structures and generating a relatively smooth fish body wave. To achieve these objectives, a novel shell-like tensegrity [...] Read more.

We developed an untethered robotic tuna featuring tensegrity joints for the purposes of simplifying the design procedure, reserving enough internal space, reducing the frictional loss of structures and generating a relatively smooth fish body wave. To achieve these objectives, a novel shell-like tensegrity joint was introduced, paired with a single-motor multiple-joint driving mechanism. The morphology matching design method of the tensegrity joint was proposed to fit the streamlined fish body, where the deflection angles of each joint were predetermined to generate the specific body waveform. Stiffness analysis shows that the tensegrity joint could function equivalently to a traditional rotational joint, given certain geometric conditions. Based on the fabricated robotic tuna prototype, extensive free-swimming experiments were performed to optimize its swimming performance by varying key parameters, including the caudal fin‘s shape, flexibility and rotational stiffness and joint deflection angles. The results reveal that the robotic tuna achieved the highest swimming speed of 1.31 body lengths per second (BL/s) at a driving frequency of 2.4 Hz, and the maximum stride length increased to 0.81 BL/cycle at 1 Hz, demonstrating the effectiveness of the proposed design scheme. This study provides valuable insight for developing high-performance bio-inspired autonomous underwater vehicles. Full article

(This article belongs to the Section Ocean Engineering)

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18 pages, 11716 KB

Open AccessArticle

Performance Analysis of Underwater Radiofrequency Communication in Seawater: An Experimental Study

by Raji Alahmad, Hussam Alraie, Ryosuke Hasaba, Kazuhiro Eguchi, Tohlu Matsushima, Yuki Fukumoto and Kazuo Ishii

J. Mar. Sci. Eng. 2024, 12(11), 2104; https://doi.org/10.3390/jmse12112104 - 20 Nov 2024

Cited by 4 | Viewed by 2433

Abstract

Communication with the underwater vehicles during their tasks is one of the most important issues. The need for real-time data transfer raises the necessity of developing communication systems. Conventional underwater communication systems, such as acoustic systems, cannot satisfy applications that need a high [...] Read more.

Communication with the underwater vehicles during their tasks is one of the most important issues. The need for real-time data transfer raises the necessity of developing communication systems. Conventional underwater communication systems, such as acoustic systems, cannot satisfy applications that need a high transmission data rate. In this study, we investigate the radio frequency communication system in seawater, which is crucial for real-time data transfer with underwater vehicles. The experiments were in a water tank full of seawater and a real environment in the ocean. Three types of antennae were used: loop antenna, wire antenna, and helical antenna. An Autonomous Underwater Vehicle (AUV) is used as a transmitter to measure the transmission rate as a function of distance. The helical antenna showed better performance regarding the coverage area. Furthermore, the AUV could move freely within the helical and capture live video streaming successfully. This investigation underscores the potential of radio frequency communication systems for enhancing underwater vehicle operations, offering promising avenues for future research and practical implementation. Full article

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

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24 pages, 9119 KB

Open AccessArticle

Nearshore Migration of Munitions and Canonical Objects Under Large-Scale Laboratory Forcing

by Temitope E. Idowu, Emily Chapman, Manoj K. Gangadharan, Jacob Stolle and Jack A. Puleo

J. Mar. Sci. Eng. 2024, 12(11), 2103; https://doi.org/10.3390/jmse12112103 - 20 Nov 2024

Cited by 1 | Viewed by 1027

Abstract

A quantitative understanding of the migration of munitions and canonical objects in the nearshore is needed for the effective management of contaminated sites. Migrations of munitions with a density range of 2000 kg/m³ to 5720 kg/m³ were quantified in a large-scale [...] Read more.

A quantitative understanding of the migration of munitions and canonical objects in the nearshore is needed for the effective management of contaminated sites. Migrations of munitions with a density range of 2000 kg/m³ to 5720 kg/m³ were quantified in a large-scale wave flume. The forcing consisted of six cases of varying wave heights, periods, still water depths, and durations. The cross-shore profile, typical of natural sandy beaches, was sub-divided into swash, surf, and offshore zones. Overall, 2228 migration measurements were recorded with 16% and 84% of the migration observations classified as “motion” (net distance > 0.5 m) and “no motion” (net distance ≤ 0.5 m), respectively. The probability of munitions migration increased with proximity to the shoreline. There was a nearly equal probability of onshore or offshore migration in the swash zone. Migration in the surf zone tended to be offshore-directed (65%), while migration was onshore-dominant (65%) in the offshore zone. Migration in the offshore zone was preferentially onshore due to skewed waves over flat bathymetry. Less dense munitions in the offshore zone may have migrated offshore likely still related to the skewed nature of the wave profile causing transport in both directions through the majority of the wave phase. The largest migration distances occurred in the surf zone likely due to downslope gravity. Migration in the surf and swash zones is a balance between skewed/asymmetric forcing and downslope gravity, with downslope gravity tending to be pronounced provided the forcing is sufficient to initiate motion. An exception was sometimes observed in the swash zone where onshore forcing was sufficient to transport munitions to the seaward side of the berm where they became trapped in a bathymetric depression between the dune and berm. Relating overall migration (Lagrangian) to fixed hydrodynamic measurements (Eulerian) was ineffective. Parameters such as the Shields number, wave skewness, and wave asymmetry estimated from the closest measurement location were insufficient to predict migration. Large scatter in the migration data resulting from competing hydrodynamic, morphodynamic, and munitions response processes makes robust deterministic predictions with flow statistics and dimensionless numbers difficult. Full article

(This article belongs to the Section Coastal Engineering)

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13 pages, 7332 KB

Open AccessArticle

Study on the Influence of Wind Load on the Safety of Magnetic Adsorption Wall-Climbing Inspection Robot for Gantry Crane

by Jun Liu, Chaoyu Xie, Yongsheng Yang and Xiaoxi Wan

J. Mar. Sci. Eng. 2024, 12(11), 2102; https://doi.org/10.3390/jmse12112102 - 20 Nov 2024

Viewed by 1096

Abstract

The maintenance of the surface of steel structures is crucial for ensuring the quality of shipbuilding cranes. Various types of wall-climbing robots have been proposed for inspecting diverse structures, including ships and offshore installations. Given that these robots often operate in outdoor environments, [...] Read more.

The maintenance of the surface of steel structures is crucial for ensuring the quality of shipbuilding cranes. Various types of wall-climbing robots have been proposed for inspecting diverse structures, including ships and offshore installations. Given that these robots often operate in outdoor environments, their performance is significantly influenced by wind conditions. Consequently, understanding the impact of wind loads on these robots is essential for developing structurally sound designs. In this study, SolidWorks software was utilized to model both the wall-climbing robot and crane, while numerical simulations were conducted to investigate the aerodynamic performance of the magnetic wall-climbing inspection robot under wind load. Subsequently, a MATLAB program was developed to simulate both the time history and spectrum of wind speed affecting the wall-climbing inspection robot. The resulting wind speed time-history curve was analyzed using a time-history analysis method to simulate wind pressure effects. Finally, modal analysis was performed to determine the natural frequency and vibration modes of the frame in order to ensure dynamic stability for the robot. The analysis revealed that wind pressure predominantly concentrates on the front section of the vehicle body, with significant eddy currents observed on its windward side, leeward side, and top surface. Following optimization efforts on the robot’s structure resulted in a reduction in vortex formation; consequently, compared to pre-optimization conditions during pulsating wind simulations, there was a 99.19% decrease in induced vibration displacement within the optimized inspection robot body. Modal analysis indicated substantial differences between the first six non-rigid natural frequencies of this vehicle body and those associated with its servo motor frequencies—indicating no risk of resonance occurring. This study employs finite element analysis techniques to assess stability under varying wind loads while verifying structural safety for this wall-climbing inspection robot. Full article

(This article belongs to the Section Ocean Engineering)

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18 pages, 4138 KB

Open AccessArticle

A Submersible Power Station: Part A Helium Power Conversion Unit

by Jon Serna, Eduardo Anselmi Palma, Stefania Romero, Dimitrios Fouflias and Pericles Pilidis

J. Mar. Sci. Eng. 2024, 12(11), 2101; https://doi.org/10.3390/jmse12112101 - 19 Nov 2024

Cited by 1 | Viewed by 1167

Abstract

Nuclear power continues to hold great promise in the green revolution, however public opinion regarding its deployment is mixed. A submersible nuclear power station concept is presented here that is expected to allay many concerns that are holding back the growth of nuclear [...] Read more.

Nuclear power continues to hold great promise in the green revolution, however public opinion regarding its deployment is mixed. A submersible nuclear power station concept is presented here that is expected to allay many concerns that are holding back the growth of nuclear power. This submersible can move under its own power during emergencies and routine maintenance. Being stationed at sea it is earthquake proof. In the case of a tsunami it could decouple from the coast and sail to a location several miles to deeper waters in less than 30 min. Furthermore, it could be built, commissioned, maintained, refueled and scrapped in a country like the UK. This makes it proliferation-proof, a key concern with the wider deployment of nuclear power. In the present evaluation the philosophy and the electric power generation capability of the submersible power station are investigated. This includes a pre-feasibility visualization of the design. An evaluation is carried out into fitting it in a submersible of a size similar to the largest existing nuclear submarines. These designs may enable it to deliver 0.6 to 1 GW of electrical power. Full article

(This article belongs to the Special Issue Advanced Technologies of Ship Power Plants and Infrastructure of Seaports)

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18 pages, 6714 KB

Open AccessArticle

Impact of Wind-Assisted Propulsion on Fuel Savings and Propeller Efficiency: A Case Study

by Ante Čalić, Zdeslav Jurić and Marko Katalinić

J. Mar. Sci. Eng. 2024, 12(11), 2100; https://doi.org/10.3390/jmse12112100 - 19 Nov 2024

Cited by 5 | Viewed by 4943

Abstract

In order to meet current and future efforts to reduce fuel consumption and gas emissions, an increasing number of ships are being retrofitted with one of the wind-assisted propulsion solutions. In this paper, the effects of retrofitted wind-assisted propulsion on the efficiency of [...] Read more.

In order to meet current and future efforts to reduce fuel consumption and gas emissions, an increasing number of ships are being retrofitted with one of the wind-assisted propulsion solutions. In this paper, the effects of retrofitted wind-assisted propulsion on the efficiency of the propeller are investigated. The installed ship propeller is usually designed to operate under specific conditions; once the thrust force from the sails is added, the operating point of the propeller changes. Taking into consideration the reduced efficiency of the propeller, which is no longer operating in its optimal regime, the actual wind-assisted propulsion contribution can be calculated. The wind-assisted contribution is calculated with a velocity prediction program as a reduction in conventional propulsion power output by maintaining the vessel’s designed speed. From the calculated variations in sail thrust force, dependent on the wind speed, the propeller efficiency is analyzed for different operating states. The propulsion efficiency of the propeller was analyzed with a performance characteristics calculation tool that has been developed and presented in this paper. From the meteorological data obtained from Copernicus Marine Services and available ship documentation, a case study was conducted for a selected route. Full article

(This article belongs to the Special Issue Green Shipping Corridors and GHG Emissions)

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17 pages, 10112 KB

Open AccessArticle

Typhoon Storm Surge Simulation Study Based on Reconstructed ERA5 Wind Fields—A Case Study of Typhoon “Muifa”, the 12th Typhoon of 2022

by Xu Zhang, Changsheng Zuo, Zhizu Wang, Chengchen Tao, Yaoyao Han and Juncheng Zuo

J. Mar. Sci. Eng. 2024, 12(11), 2099; https://doi.org/10.3390/jmse12112099 - 19 Nov 2024

Cited by 1 | Viewed by 2717

Abstract

A storm surge, classified as an extreme natural disaster, refers to unusual sea level fluctuations induced by severe atmospheric disturbances such as typhoons. Existing reanalysis data, such as ERA5, significantly underestimates the location and maximum wind speed of typhoons. Therefore, this study initially [...] Read more.

A storm surge, classified as an extreme natural disaster, refers to unusual sea level fluctuations induced by severe atmospheric disturbances such as typhoons. Existing reanalysis data, such as ERA5, significantly underestimates the location and maximum wind speed of typhoons. Therefore, this study initially assesses the accuracy of tropical cyclone positions and peak wind speeds in the ERA5 reanalysis dataset. These results are compared against tropical cyclone parameters from the IBTrACS (International Best Track Archive for Climate Stewardship). The position deviation of tropical cyclones in ERA5 is mainly within the range of 10 to 60 km. While the correlation of maximum wind speed is significant, there is still considerable underestimation. A wind field reconstruction model, incorporating tropical cyclone characteristics and a distance correction factor, was employed. This model considers the effects of the surrounding environment during the movement of the tropical cyclone by introducing a decay coefficient. The reconstructed wind field significantly improved the representation of the typhoon eyewall and high-wind-speed regions, showing a closer match with wind speeds observed by the HY-2B scatterometer. Through simulations using the FVCOM (Finite Volume Community Ocean Model) storm surge model, the reconstructed wind field demonstrated higher accuracy in reproducing water level changes at Tanxu, Gaoqiao, and Zhangjiabang stations. During the typhoon’s landfall in Shanghai, the area with the greatest water level increase was primarily located in the coastal waters of Pudong New Area, Shanghai, where the highest total water level reached 5.2 m and the storm surge reached 4 m. The methods and results of this study provide robust technical support and a valuable reference for further storm surge forecasting, marine disaster risk assessment, and coastal disaster prevention and mitigation efforts. Full article

(This article belongs to the Section Physical Oceanography)

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20 pages, 4567 KB

Open AccessArticle

Holocene and Reworked Pleistocene Sediments in Mud Depocenters of the Inner Continental Shelf of Sao Paulo Bight (Southeast Brazil)

by Antonio Scardua Neto and Javier Alcántara-Carrió

J. Mar. Sci. Eng. 2024, 12(11), 2098; https://doi.org/10.3390/jmse12112098 - 19 Nov 2024

Cited by 1 | Viewed by 1048

Abstract

Mud depocenters are found across most siliciclastic continental shelves, occurring in various bathymetric ranges and typically dating to the Holocene. This study analyzes the sedimentary characteristics and formation processes of mud depocenters in the central sector of the inner continental shelf of the [...] Read more.

Mud depocenters are found across most siliciclastic continental shelves, occurring in various bathymetric ranges and typically dating to the Holocene. This study analyzes the sedimentary characteristics and formation processes of mud depocenters in the central sector of the inner continental shelf of the São Paulo Bight. A total of 1700 km of high-resolution seismic profiles, four gravity cores, and 1346 surface sediment samples were analyzed. The sedimentary analysis involved determining grain size parameters, organic matter content, carbonates content, and radiocarbon dating. Seafloor sedimentary mapping shows the predominance of very fine siliciclastic sand, together with three mud depocenters located shallower than the 30-m isobath. The northern depocenter comprises one sedimentary unit (SU-NZ-01), while the central depocenter consists of two sedimentary units (SU-CZ-01 and SU-CZ-02) and the southern depocenter is made up of two other sedimentary units (SU-SZ-01 and SU-SZ-02). Units SU-SZ-02, SU-CZ-02, and SU-NZ-01 were deposited on Precambrian rock surfaces during the Holocene transgression and include reworked sediments from nearby Upper Pleistocene coastal plains, characterized by a transparent seismic pattern. Above these, units SU-SZ-01 and SU-CZ-01 developed following the Holocene Transgression Maximum, associated with local mud input from the Peruíbe River mouth and the Santos Estuary, respectively. The paleorelief of Precambrian rocks favored the formation of these depocenters by creating wave shadow zones and trapping mud within the paleovalleys. Full article

(This article belongs to the Section Geological Oceanography)

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18 pages, 6723 KB

Open AccessArticle

Design and Development of 10,000-Meter Class Autonomous Underwater Vehicle

by Jiali Xu, Zhaopeng Du, Xianqing Huang, Chong Ren, Shuai Fa and Shaoqiong Yang

J. Mar. Sci. Eng. 2024, 12(11), 2097; https://doi.org/10.3390/jmse12112097 - 19 Nov 2024

Cited by 1 | Viewed by 4029

Abstract

As a significant subset of unmanned underwater vehicles (UUVs), autonomous underwater vehicles (AUVs) possess the capability to autonomously execute tasks. Characterized by its flexibility, cost-effectiveness, extensive operational range, and robust environmental adaptability, AUV has emerged as the primary technological apparatus for deep-sea exploration [...] Read more.

As a significant subset of unmanned underwater vehicles (UUVs), autonomous underwater vehicles (AUVs) possess the capability to autonomously execute tasks. Characterized by its flexibility, cost-effectiveness, extensive operational range, and robust environmental adaptability, AUV has emerged as the primary technological apparatus for deep-sea exploration and research. In this paper, we present the design of a 10,000 m class AUV equipped with capabilities such as fixed-depth navigation, regional autonomous cruising, full-depth video recording, and temperature and salinity profiling. Initially, we outline the comprehensive design of the AUV, detailing its structural configuration, system components, functional module arrangement, and operational principles. Subsequently, we compute the hydrodynamic parameters using a spatial kinematics model. Finally, the AUV designed in this paper is tested for its functions and performance, such as fixed-depth sailing, maximum speed, and maximum diving depth, and its reliability and practicability are verified. Full article

(This article belongs to the Special Issue Marine Autonomous Vehicles: Design, Test and Operation—Second Edition)

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20 pages, 15268 KB

Open AccessArticle

Automatic Reading and Reporting Weather Information from Surface Fax Charts for Ships Sailing in Actual Northern Pacific and Atlantic Oceans

by Jun Jian, Yingxiang Zhang, Ke Xu and Peter J. Webster

J. Mar. Sci. Eng. 2024, 12(11), 2096; https://doi.org/10.3390/jmse12112096 - 19 Nov 2024

Cited by 1 | Viewed by 1933

Abstract

This study is aimed to improve the intelligence level, efficiency, and accuracy of ship safety and security systems by contributing to the development of marine weather forecasting. The accurate and prompt recognition of weather fax charts is very important for navigation safety. This [...] Read more.

This study is aimed to improve the intelligence level, efficiency, and accuracy of ship safety and security systems by contributing to the development of marine weather forecasting. The accurate and prompt recognition of weather fax charts is very important for navigation safety. This study employed many artificial intelligent (AI) methods including a vectorization approach and target recognition algorithm to automatically detect the severe weather information from Japanese and US weather charts. This enabled the expansion of an existing auto-response marine forecasting system’s applications toward north Pacific and Atlantic Oceans, thus enhancing decision-making capabilities and response measures for sailing ships at actual sea. The OpenCV image processing method and YOLOv5s/YOLO8vn algorithm were utilized to make template matches and locate warning symbols and weather reports from surface weather charts. After these improvements, the average accuracy of the model significantly increased from 0.920 to 0.928, and the detection rate of a single image reached a maximum of 1.2 ms. Additionally, OCR technology was applied to retract texts from weather reports and highlighted the marine areas where dense fog and great wind conditions are likely to occur. Finally, the field tests confirmed that this auto and intelligent system could assist the navigator within 2–3 min and thus greatly enhance the navigation safety in specific areas in the sailing routes with minor text-based communication costs. Full article

(This article belongs to the Special Issue Ship Performance in Actual Seas)

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21 pages, 12271 KB

Open AccessArticle

Detection of Marine Oil Spill from PlanetScope Images Using CNN and Transformer Models

by Jonggu Kang, Chansu Yang, Jonghyuk Yi and Yangwon Lee

J. Mar. Sci. Eng. 2024, 12(11), 2095; https://doi.org/10.3390/jmse12112095 - 19 Nov 2024

Cited by 7 | Viewed by 2658

Abstract

The contamination of marine ecosystems by oil spills poses a significant threat to the marine environment, necessitating the prompt and effective implementation of measures to mitigate the associated damage. Satellites offer a spatial and temporal advantage over aircraft and unmanned aerial vehicles (UAVs) [...] Read more.

The contamination of marine ecosystems by oil spills poses a significant threat to the marine environment, necessitating the prompt and effective implementation of measures to mitigate the associated damage. Satellites offer a spatial and temporal advantage over aircraft and unmanned aerial vehicles (UAVs) in oil spill detection due to their wide-area monitoring capabilities. While oil spill detection has traditionally relied on synthetic aperture radar (SAR) images, the combined use of optical satellite sensors alongside SAR can significantly enhance monitoring capabilities, providing improved spatial and temporal coverage. The advent of deep learning methodologies, particularly convolutional neural networks (CNNs) and Transformer models, has generated considerable interest in their potential for oil spill detection. In this study, we conducted a comprehensive and objective comparison to evaluate the suitability of CNN and Transformer models for marine oil spill detection. High-resolution optical satellite images were used to optimize DeepLabV3+, a widely utilized CNN model; Swin-UPerNet, a representative Transformer model; and Mask2Former, which employs a Transformer-based architecture for both encoding and decoding. The results of cross-validation demonstrate a mean Intersection over Union (mIoU) of 0.740, 0.840 and 0.804 for all the models, respectively, indicating their potential for detecting oil spills in the ocean. Additionally, we performed a histogram analysis on the predicted oil spill pixels, which allowed us to classify the types of oil. These findings highlight the considerable promise of the Swin Transformer models for oil spill detection in the context of future marine disaster monitoring. Full article

(This article belongs to the Special Issue Remote Sensing Applications in Marine Environmental Monitoring)

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20 pages, 6553 KB

Open AccessArticle

Model-Driven Cooperative Path Planning for Dynamic Target Searching of Unmanned Unterwater Vehicle Formation

by Dezhou Qin, Huachao Dong, Siqing Sun, Zhiwen Wen, Jinglu Li and Tianbo Li

J. Mar. Sci. Eng. 2024, 12(11), 2094; https://doi.org/10.3390/jmse12112094 - 19 Nov 2024

Cited by 2 | Viewed by 1326

Abstract

With the increasing complexity of ocean missions, using multiple unmanned underwater vehicles to collaborate in executing tasks has become an effective way to improve the overall efficiency of ocean operations. Current research on path planning for multiple unmanned underwater vehicles mainly focuses on [...] Read more.

With the increasing complexity of ocean missions, using multiple unmanned underwater vehicles to collaborate in executing tasks has become an effective way to improve the overall efficiency of ocean operations. Current research on path planning for multiple unmanned underwater vehicles mainly focuses on the basis of particle models or fully known environmental information, while research directions mainly focus on single indicators such as completion time and energy consumption. This paper first constructs a UUV model and a task scenario with detection success rate as the objective function. Then, a parameterization method based on a spiral search path was proposed for designing variables. A hierarchical control strategy is designed to ensure handle formation constraints. A general optimization framework for task scenarios has been constructed and combined with algorithms to solve optimization problems. Finally, this study compared and analyzed the performance of different optimization algorithms under the optimization framework, evaluated the optimization results of different search strategies, and explored the impact of dynamic objectives on the detection success rate. The results showed that the optimized path had a search success rate that increased by more than 50% compared to the direct path and the cover search path, which verified the effectiveness of the proposed method and strategy. Full article

(This article belongs to the Section Ocean Engineering)

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31 pages, 6033 KB

Open AccessReview

Advancements in DNA Metabarcoding Protocols for Monitoring Zooplankton in Marine and Brackish Environments

by Jorge Moutinho, Filipe O. Costa and Sofia Duarte

J. Mar. Sci. Eng. 2024, 12(11), 2093; https://doi.org/10.3390/jmse12112093 - 19 Nov 2024

Cited by 2 | Viewed by 3687

Abstract

Over the past century, numerous studies have proposed various organisms for the biomonitoring of aquatic systems, but only recently has zooplankton emerged as a promising indicator of water quality. The traditional identification methods, however, can be inefficient in the context of monitoring efforts, [...] Read more.

Over the past century, numerous studies have proposed various organisms for the biomonitoring of aquatic systems, but only recently has zooplankton emerged as a promising indicator of water quality. The traditional identification methods, however, can be inefficient in the context of monitoring efforts, as they are often time consuming and costly. DNA metabarcoding offers a powerful alternative, providing a more efficient and reliable approach to monitor zooplankton communities. In this review, we assess the current state-of-the-art methodologies used to evaluate marine and brackish zooplankton communities through the DNA metabarcoding workflow. While several emerging approaches have been reported, no standardization has been achieved so far. The DNA extraction step has gained the most consensus, with the widespread use of commercial kits (DNeasy Blood & Tissue kit employed in ca. 25% of the studies), though there is still a significant variation in kit selection. Additionally, 18S and COI were the main molecular markers employed (ca. 61% and 54%, respectively) though the target region varied in the former. Moreover, many methodologies, particularly those used for processing zooplankton samples, lack practical validation. Some studies also fail to provide sufficient detail in their methodology descriptions hindering reproducibility. Overall, DNA metabarcoding shows great potential for the efficient monitoring of zooplankton communities, but further effort is needed to establish standardized practices and optimize the current approaches across the entire methodological pipeline. Full article

(This article belongs to the Special Issue New Biomonitoring Methodologies for Key Coastal and Estuary Species and Habitats)

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21 pages, 9708 KB

Open AccessArticle

ULOTrack: Underwater Long-Term Object Tracker for Marine Organism Capture

by Ju He, Yang Yu, Hongyu Wei and Hu Xu

J. Mar. Sci. Eng. 2024, 12(11), 2092; https://doi.org/10.3390/jmse12112092 - 19 Nov 2024

Cited by 2 | Viewed by 1412

Abstract

Underwater object tracking holds considerable significance in the field of ocean engineering. Additionally, it serves as a crucial component in the operations of autonomous underwater vehicles (AUVs), particularly during tasks associated with capturing marine organisms. However, the attenuation and scattering of light result [...] Read more.

Underwater object tracking holds considerable significance in the field of ocean engineering. Additionally, it serves as a crucial component in the operations of autonomous underwater vehicles (AUVs), particularly during tasks associated with capturing marine organisms. However, the attenuation and scattering of light result in shortcomings such as poor contrast in underwater images. Additionally, the motion deformation of marine organisms poses a significant challenge. Therefore, existing tracking algorithms face difficulty in direct application to underwater object tracking. To overcome this challenge, we propose a novel tracking architecture for the marine organism capturing of AUVs called ULOTrack. ULOTrack is based on a performance discrimination and re-detection framework and constitutes three modules: (1) an object tracker, which can extract multi-feature information of the underwater target; (2) a multi-layer tracking performance discriminator, which serves the purpose of evaluating the stability of the current tracking state, thereby reducing potential model drift; and (3) lightweight detection, which can predict the candidate boxes to relocate the lost tracked underwater object. We conduct comprehensive experiments to validate the efficacy of the designed modules. Finally, the results of the experimentation demonstrate that ULOTrack significantly outperforms existing approaches. In the future, we aim to carefully scrutinize and select more suitable features to enhance tracking accuracy and speed. Full article

(This article belongs to the Section Ocean Engineering)

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18 pages, 7824 KB

Open AccessArticle

Vessel Traffic Flow Prediction in Port Waterways Based on POA-CNN-BiGRU Model

by Yumiao Chang, Jianwen Ma, Long Sun, Zeqiu Ma and Yue Zhou

J. Mar. Sci. Eng. 2024, 12(11), 2091; https://doi.org/10.3390/jmse12112091 - 19 Nov 2024

Cited by 4 | Viewed by 1934

Abstract

Vessel traffic flow forecasting in port waterways is critical to improving safety and efficiency of port navigation. Aiming at the stage characteristics of vessel traffic in port waterways in time sequence, which leads to complexity of data in the prediction process and difficulty [...] Read more.

Vessel traffic flow forecasting in port waterways is critical to improving safety and efficiency of port navigation. Aiming at the stage characteristics of vessel traffic in port waterways in time sequence, which leads to complexity of data in the prediction process and difficulty in adjusting the model parameters, a convolutional neural network (CNN) based on the optimization of the pelican algorithm (POA) and the combination of bi-directional gated recurrent units (BiGRUs) is proposed as a prediction model, and the POA algorithm is used to search for optimized hyper-parameters, and then the iterative optimization of the optimal parameter combinations is input into the best combination of iteratively found parameters, which is input into the CNN-BiGRU model structure for training and prediction. The results indicate that the POA algorithm has better global search capability and faster convergence than other optimization algorithms in the experiment. Meanwhile, the BiGRU model is introduced and compared with the CNN-BiGRU model prediction; the POA-CNN-BiGRU combined model has higher prediction accuracy and stability; the prediction effect is significantly improved; and it can provide more accurate prediction information and cycle characteristics, which can serve as a reference for the planning of ships’ routes in and out of ports and optimizing the management of ships’ organizations. Full article

(This article belongs to the Special Issue Management and Control of Ship Traffic Behaviours)

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26 pages, 17296 KB

Open AccessArticle

Design by Optimization on the Nozzle and the Stator Blades of a Rim-Driven Pumpjet

by Marco Lugaresi, Diego Villa and Stefano Gaggero

J. Mar. Sci. Eng. 2024, 12(11), 2090; https://doi.org/10.3390/jmse12112090 - 19 Nov 2024

Cited by 1 | Viewed by 1315

Abstract

The design of the stator and nozzle of a rim-driven pumpjet thruster (RDPJ) is addressed through a simulation-based design optimization approach built on a parametric description of the main geometrical characteristics of the system, a RANS solver with actuator disk model, and a [...] Read more.

The design of the stator and nozzle of a rim-driven pumpjet thruster (RDPJ) is addressed through a simulation-based design optimization approach built on a parametric description of the main geometrical characteristics of the system, a RANS solver with actuator disk model, and a genetic algorithm. As the propeller blades’ geometry is fixed, the rotor/stator (RDPJ-R/S) configuration is considered for the optimal design from a multi-objective optimization process aimed at minimizing the resistance keeping the cavitation inception index at the lowest possible value. Steady-state (moving reference frame plus mixing plane interface) and unsteady simulations (sliding meshes) with fully resolved rotor geometry were finally carried out on six selected optimal geometries to validate the optimization process and the performance improvements provided by the RDPJ configuration when compared with the original rim-driven thruster (RDT). Full article

(This article belongs to the Special Issue New Advances on Energy and Propulsion Systems for Ship—Edition II)

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23 pages, 716 KB

Open AccessArticle

Influence of Foundation–Soil–Foundation Interaction on the Dynamic Response of Offshore Wind Turbine Jackets Founded on Buckets

by Carlos Romero-Sánchez, Jacob D. R. Bordón and Luis A. Padrón

J. Mar. Sci. Eng. 2024, 12(11), 2089; https://doi.org/10.3390/jmse12112089 - 19 Nov 2024

Cited by 2 | Viewed by 1991

Abstract

This study investigates the impact of soil–structure interaction (SSI) and foundation–soil–foundation interaction (FSFI) on the dynamic behaviour of jacket substructures founded on buckets for offshore wind turbines. A parametric analysis was conducted, focusing on critical load cases for conservative foundation design. Different load [...] Read more.

This study investigates the impact of soil–structure interaction (SSI) and foundation–soil–foundation interaction (FSFI) on the dynamic behaviour of jacket substructures founded on buckets for offshore wind turbines. A parametric analysis was conducted, focusing on critical load cases for conservative foundation design. Different load configurations were examined: collinear wind and wave (fluid–structure interaction) loads, along with misaligned configurations at 45° and 90°, to assess the impact of different loading directions. The dynamic response was evaluated through key structural parameters, including axial forces, shear forces, bending moments, and stresses on the jacket. Simulations employed the National Renewable Energy Laboratory (NREL) 5MW offshore wind turbine mounted on the OC4 project jacket founded on suction buckets. An additional optimised jacket design was also studied for comparison. An OpenFAST model incorporating SSI and FSFI considering a homogeneous soil profile was employed for the dynamic analysis. The results highlight the significant role of the FSFI on the dynamic behaviour of multi-supported jacket substructure, affecting the natural frequency, acceleration responses, and internal forces. Full article

(This article belongs to the Section Ocean Engineering)

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19 pages, 15114 KB

Open AccessArticle

Study on the Vibration-Damping Mechanism of a New Phononic Crystal Suspension Equipped on Underwater Gliders

by Qindong Sun, Yuhan Yang, Pan Wu, Ming Yang, Tongshuai Sun, Wendong Niu and Shaoqiong Yang

J. Mar. Sci. Eng. 2024, 12(11), 2088; https://doi.org/10.3390/jmse12112088 - 19 Nov 2024

Cited by 2 | Viewed by 1487

Abstract

The vibration caused by the movement of internal actuating components within an acoustic underwater glider can interfere with onboard sensors. However, as a new vibration-damping material, phononic crystals can effectively reduce this impact. Using simulation and an underwater test, this work studied the [...] Read more.

The vibration caused by the movement of internal actuating components within an acoustic underwater glider can interfere with onboard sensors. However, as a new vibration-damping material, phononic crystals can effectively reduce this impact. Using simulation and an underwater test, this work studied the vibration-damping mechanism of the phononic crystal suspension (PCS) designed by Tianjin University, China. The bandgaps and the modes of PCS were calculated first, which offered basic data for the following simulation. Then, the relationship between the modes and attenuation zones (AZs) were broadly considered to reveal the variation law of the AZs with the change in modes, both in the air and under water. Finally, an underwater test was carried out to verify the good vibration-damping effect of the PCS. The results show that the cutoff frequency of the AZs could be predicted by finding the relevant modes. The PCS showed a good vibration-damping effect from 170 Hz to 5000 Hz in the underwater test, with a maximum decrease of 6 dB at 2000 Hz. Finally, the damping of the PCS could suppress the overlap of modes that resulted from Bragg scattering. This work will also provide theoretical guidance for further study on the optimization of phononic crystal mechanisms for vibration damping. Full article

(This article belongs to the Special Issue Marine Autonomous Vehicles: Design, Test and Operation)

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18 pages, 3329 KB

Open AccessArticle

Distributionally Robust Optimal Scheduling of Hybrid Ship Microgrids Considering Uncertain Wind and Wave Conditions

by Fang Lu, Yubin Tian, Hongda Liu and Chuyuan Ling

J. Mar. Sci. Eng. 2024, 12(11), 2087; https://doi.org/10.3390/jmse12112087 - 19 Nov 2024

Cited by 2 | Viewed by 1417

Abstract

A hybrid ship uses integrated generators, an energy storage system (ESS), and photovoltaics (PV) to match its propulsion and service loads, and together with optimal power and voyage scheduling, this can lead to a substantial improvement in ship operation cost, ensuring compliance with [...] Read more.

A hybrid ship uses integrated generators, an energy storage system (ESS), and photovoltaics (PV) to match its propulsion and service loads, and together with optimal power and voyage scheduling, this can lead to a substantial improvement in ship operation cost, ensuring compliance with the environmental constraints and enhancing ship sustainability. During the operation, significant uncertainties such as waves, wind, and PV result in considerable speed loss, which may lead to voyage delays and operation cost increases. To address this issue, a distributionally robust optimization (DRO) model is proposed to schedule power generation and voyage. The problem is decoupled into a bi-level optimization model, the slave level can be solved directly by commercial solvers, the master level is further formulated as a two-stage DRO model, and linear decision rules and column and constraint generation algorithms are adopted to solve the model. The algorithm aims at minimizing the operation cost, limiting greenhouse gas (GHG) emissions, and satisfying the technical and operational constraints considering the uncertainty. Extensive simulations demonstrate that the expected total cost under the worst-case distribution is minimized, and compared with the conventional robust optimization methods, some distribution information can be incorporated into the ambiguity sets to generate fewer conservative results. This method can fully ensure the on-time arrival of hybrid ships in various uncertain scenarios while achieving expected operation cost minimization and limiting greenhouse gas (GHG) emissions. Full article

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

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14 pages, 1754 KB

Open AccessArticle

Ecosystem Structure and Function in the Sea Area of Zhongjieshan Islands Based on Ecopath Model

by Yao Qu, Zhongming Wang, Yongdong Zhou, Jun Liang, Kaida Xu, Yazhou Zhang, Zhenhua Li, Qian Dai, Qiuhong Zhang and Yongsheng Jiang

J. Mar. Sci. Eng. 2024, 12(11), 2086; https://doi.org/10.3390/jmse12112086 - 18 Nov 2024

Cited by 1 | Viewed by 1481

Abstract

Based on the field survey and reference data of the sea area of the Zhongjieshan Islands from 2021 to 2022, the Ecopath model was used to analyze the energy flow structure of the marine ecosystem of the sea area of the Zhongjieshan Islands; [...] Read more.

Based on the field survey and reference data of the sea area of the Zhongjieshan Islands from 2021 to 2022, the Ecopath model was used to analyze the energy flow structure of the marine ecosystem of the sea area of the Zhongjieshan Islands; the energy structure of the marine ecosystem was divided into 21 functional groups, and its nutrient structure, energy flow, and total system characteristics were analyzed. The results show that the credibility of the model is 0.414, which is at a medium level. The trophic level of each functional group of the ecosystem in the sea area of Zhongjieshan Islands was 1–3.48, the energy flow structure of the system was mainly concentrated in the first five grades, and the trophic level was relatively simple, with the average energy transfer efficiency of the system being 8.11%, the energy flow range being 2.81–13.04%, the energy transfer efficiency of the primary producers of the system being 7.25%, and the energy conversion efficiency of the system debris being 9.12%. The total system throughput was 2125.96 t·km⁻²; The analysis of the overall characteristics of the ecosystem showed that the system connectance index and the system omnivory index were 0.45 and 0.24, respectively, while the Finn’s cycling index was 8.24, the Finn’s mean path length of the system was 2.72, and the total primary production/total respiration was 1.71. In this study, the marine ecosystem model of the sea area of the Zhongjieshan Islands was studied to understand the trophic structure and ecosystem status of the sea area, which is conducive to the sustainable utilization and scientific management of fishery resources in the sea area. Full article

(This article belongs to the Topic Conservation and Management of Marine Ecosystems)

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22 pages, 8642 KB

Open AccessArticle

A Quasi Time-Domain Method for Fatigue Analysis of Reactor Pressure Vessels in Floating Nuclear Power Plants in Marine Environments

by Fuxuan Ma, Huanming Li, Meng Zhang and Xiangiang Qu

J. Mar. Sci. Eng. 2024, 12(11), 2085; https://doi.org/10.3390/jmse12112085 - 18 Nov 2024

Cited by 4 | Viewed by 1328

Abstract

The reactor pressure vessel (RPV) in onshore nuclear power plants is typically analysed for fatigue life by considering the temperature, internal pressure, and seismic effects using a simplified time-domain fatigue analysis. In contrast, the frequency-domain fatigue analysis method is commonly employed to assess [...] Read more.

The reactor pressure vessel (RPV) in onshore nuclear power plants is typically analysed for fatigue life by considering the temperature, internal pressure, and seismic effects using a simplified time-domain fatigue analysis. In contrast, the frequency-domain fatigue analysis method is commonly employed to assess the fatigue life of ship structures. The RPV of a floating nuclear power plant (FNPP) is subjected to a combination of temperature, internal pressure, and wave loads in the marine environment. Consequently, it is essential to effectively integrate the frequency-domain fatigue analysis method used for hull structures with the time-domain fatigue analysis method for RPVs in FNPPs or, alternatively, to develop a suitable method that effectively accounts for the temperature, internal pressure, and wave loads. In this study, a quasi-time-domain method is proposed for the fatigue analysis of RPVs in FNPPs. In this method, secondary components of marine environmental loads are filtered out using principal component analysis. Subsequently, the stress spectrum induced by waves is transformed into a stress time history. Fatigue stress under the combined influence of temperature, internal pressure, and wave loads is then obtained through a stress component superposition method. Finally, the accuracy of the quasi-time-domain method was validated through three numerical examples. The results indicate that the calculated values obtained by the quasi-time-domain method are slightly higher than those obtained by the traditional time-domain method, with a maximum deviation of no more than 24%. Additionally, the computation time of the quasi-time-domain method is reduced by 98.67% compared to the traditional time-domain method. Full article

(This article belongs to the Special Issue Health Monitoring and Reliability Assessment of Marine and Offshore Structure)

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28 pages, 6240 KB

Open AccessArticle

The Contribution of Siliceous Plankton to Vertical Export Flux in the Eastern Mediterranean: A Comparative Study of the North Aegean, Cretan, and Ionian Seas

by Ioanna Nikolopoulou, Elisavet Skampa, Ioanna Varkitzi, Margarita D. Dimiza, Constantine Parinos, Georgia Kambouri, Ioanna Stavrakaki, Alexandra Gogou and Maria V. Triantaphyllou

J. Mar. Sci. Eng. 2024, 12(11), 2084; https://doi.org/10.3390/jmse12112084 - 18 Nov 2024

Cited by 4 | Viewed by 1350

Abstract

This study investigates the intricate dynamics of siliceous plankton species within the open marine regions of the Greek Seas, focusing on their seasonal and spatial variability. For this purpose, vertical export fluxes of diatoms (DtF), silicoflagellates (SF), and radiolaria (RF) were analyzed in [...] Read more.

This study investigates the intricate dynamics of siliceous plankton species within the open marine regions of the Greek Seas, focusing on their seasonal and spatial variability. For this purpose, vertical export fluxes of diatoms (DtF), silicoflagellates (SF), and radiolaria (RF) were analyzed in three sediment trap time series obtained from the North Aegean, Cretan, and Ionian Seas. Special attention was given to diatom assemblages, resulting in the estimation of the DtF community structure and diversity for each studied site. Diatom flux values reached 353.9 × 10³ valves m⁻² day⁻¹, 77.7 × 10³ valves m⁻² day⁻¹, and 42.4 × 10³ valves m⁻² day⁻¹ in the North Aegean, Ionian, and Cretan Seas, respectively. SF maxima were 1309.8 × 10³ skeletons m⁻² day⁻¹ in the North Aegean Sea, 35.2 × 10³ skeletons m⁻² day⁻¹ in the Ionian Sea, and 11.9 × 10³ skeletons m⁻² day⁻¹ in the Cretan Sea (South Aegean Sea). RF values reached 13.9 × 10³ radiolaria m⁻² day⁻¹, 11.9 × 10³ radiolaria m⁻² day⁻¹, and 5.4 × 10³ radiolaria m⁻² day⁻¹ in the North Aegean, Ionian, and Cretan Seas, respectively. The North Aegean Sea exhibited significantly higher mean total fluxes, particularly for diatoms, driven by the north-to-south oligotrophy gradient, which was influenced by riverine inflows and the nutrient-rich Black Sea water. In the Cretan and Ionian Seas, convective mixing and atmospheric deposition, especially during increased rainfall (precipitation) events, were identified as primary drivers for the increased siliceous plankton fluxes recorded in the late winter–spring months. Diatom communities were dominated by Naviculales and Fragilariales; the prevalence of the former in the North Aegean Sea is likely linked to the higher nutrient levels in its upper photic zone, as Naviculales includes species with a high affiliation to nutrient enrichment. Full article

(This article belongs to the Special Issue Plankton Community in Marine Ecological Environment: Latest Advances and Prospects)

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24 pages, 28615 KB

Open AccessArticle

Modal Parameter Identification of Jacket-Type Offshore Wind Turbines Under Operating Conditions

by Chen Zhang, Xu Han, Chunhao Li, Bernt Johan Leira, Svein Sævik, Dongzhe Lu, Wei Shi and Xin Li

J. Mar. Sci. Eng. 2024, 12(11), 2083; https://doi.org/10.3390/jmse12112083 - 18 Nov 2024

Cited by 1 | Viewed by 1866

Abstract

Operational modal analysis (OMA) is essential for long-term health monitoring of offshore wind turbines (OWTs), helping identifying changes in structural dynamic characteristics. OMA has been applied under parked or idle states for OWTs, assuming a linear and time-invariant dynamic system subjected to white [...] Read more.

Operational modal analysis (OMA) is essential for long-term health monitoring of offshore wind turbines (OWTs), helping identifying changes in structural dynamic characteristics. OMA has been applied under parked or idle states for OWTs, assuming a linear and time-invariant dynamic system subjected to white noise excitations. The impact of complex operating environmental conditions on structural modal identification therefore requires systematic investigation. This paper studies the applicability of OMA based on covariance-driven stochastic subspace identification (SSI-COV) under various non-white noise excitations, using a DTU 10 MW jacket OWT model as a basis for a case study. Then, a scaled (1:75) 10 MW jacket OWT model test is used for the verification. For pure wave conditions, it is found that accurate identification for the first and second FA/SS modes can be achieved with significant wave energy. Under pure wind excitations, the unsteady servo control behavior leads to significant identification errors. The combined wind and wave actions further complicate the picture, leading to more scattered identification errors. The SSI-COV based modal identification method is suggested to be reliably applied for wind speeds larger than the rated speed and with sufficient wave energy. In addition, this method is found to perform better with larger misalignment of wind and wave directions. This study provides valuable insights in relation to the engineering applications of in situ modal identification techniques under operating conditions in real OWT projects. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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20 pages, 5608 KB

Open AccessArticle

Cross-Granularity Infrared Image Segmentation Network for Nighttime Marine Observations

by Hu Xu, Yang Yu, Xiaomin Zhang and Ju He

J. Mar. Sci. Eng. 2024, 12(11), 2082; https://doi.org/10.3390/jmse12112082 - 18 Nov 2024

Cited by 1 | Viewed by 1512

Abstract

Infrared image segmentation in marine environments is crucial for enhancing nighttime observations and ensuring maritime safety. While recent advancements in deep learning have significantly improved segmentation accuracy, challenges remain due to nighttime marine scenes including low contrast and noise backgrounds. This paper introduces [...] Read more.

Infrared image segmentation in marine environments is crucial for enhancing nighttime observations and ensuring maritime safety. While recent advancements in deep learning have significantly improved segmentation accuracy, challenges remain due to nighttime marine scenes including low contrast and noise backgrounds. This paper introduces a cross-granularity infrared image segmentation network CGSegNet designed to address these challenges specifically for infrared images. The proposed method designs a hybrid feature framework with cross-granularity to enhance segmentation performance in complex water surface scenarios. To suppress feature semantic disparity against different feature granularity, we propose an adaptive multi-scale fusion module (AMF) that combines local granularity extraction with global context granularity. Additionally, incorporating a handcrafted histogram of oriented gradients (HOG) features, we designed a novel HOG feature fusion module to improve edge detection accuracy under low-contrast conditions. Comprehensive experiments conducted on the public infrared segmentation dataset demonstrate that our method outperforms state-of-the-art techniques, achieving superior segmentation results compared to professional infrared image segmentation methods. The results highlight the potential of our approach in facilitating accurate infrared image segmentation for nighttime marine observation, with implications for maritime safety and environmental monitoring. Full article

(This article belongs to the Section Ocean Engineering)

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16 pages, 5187 KB

Open AccessArticle

Effect of High-Stress Levels on the Shear Behavior of Geosynthetic-Reinforced Marine Coral Sands

by Lixing Liu, Zhixiong Chen, Xuanming Ding and Qiang Ou

J. Mar. Sci. Eng. 2024, 12(11), 2081; https://doi.org/10.3390/jmse12112081 - 18 Nov 2024

Cited by 1 | Viewed by 1025

Abstract

As an important construction material, the mechanical and deformation properties of marine coral sand determine the safety and stability of related island and coastal engineering construction. The porous and easily broken characteristics of coral sand often make it difficult to meet engineering construction [...] Read more.

As an important construction material, the mechanical and deformation properties of marine coral sand determine the safety and stability of related island and coastal engineering construction. The porous and easily broken characteristics of coral sand often make it difficult to meet engineering construction needs. In particular, coral sand undergoes a large amount of particle breakage under high-stress conditions, which in turn negatively affects its mechanical and deformation properties. In this study, the macro- and micro-mechanical behavior of geosynthetic-reinforced coral sand under high confining pressure was investigated and compared with unreinforced cases using the three-dimensional discrete element method (DEM), which was verified by indoor triaxial tests. The results showed that the stress–strain responses of unreinforced and reinforced coral sand under high confining pressure showed completely different trends, i.e., the hardening tendency shown in the reinforced case. Geosynthetic reinforcement can significantly inhibit the stress–strain softening and bulging deformation of coral sand under high confining pressure, thus improving the shear mechanical performance of the reinforced sample. At the microscopic scale, high confining pressure and reinforcement affected the contact force distribution pattern and stress level between particles, determining the macroscopic mechanical and deformation performance. In addition, the breakage of particles under high confining pressure was mainly affected by shear strain and reinforcement. The particle fragment distribution, particle gradation, and relative breakage index exhibited different trends at different confining pressure levels. These breakage characteristics were closely related to the deformation and stress levels of unreinforced and reinforced samples. Full article

(This article belongs to the Section Ocean Engineering)

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J. Mar. Sci. Eng., Volume 12, Issue 11 (November 2024) – 219 articles

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