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J. Mar. Sci. Eng., Volume 11, Issue 2 (February 2023) – 228 articles

Cover Story (view full-size image): Reef-building symbiont-bearing colonial corals are among the most iconic organisms of the shallow-water realm. In order to overcome the limitations associated with a sessile lifestyle, some symbiont-bearing colonial corals have developed a simple solution: colonizing a “moving” substrate. During their long and successful evolutionary history, corals repeatedly tried to “hitch a ride” on gastropod shells. By doing so, they obtained some of the beneficial traits of a motile lifestyle, including the capability to escape unfavorable conditions, avoid predation, and survive burial. Reefs are born, not made, and as such, their seeds are crucial for their survival. View this paper
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21 pages, 4558 KiB  
Review
Rehabilitation Techniques for Offshore Tubular Joints
by Mohsin Iqbal, Saravanan Karuppanan, Veeradasan Perumal, Mark Ovinis and Adnan Rasul
J. Mar. Sci. Eng. 2023, 11(2), 461; https://doi.org/10.3390/jmse11020461 - 20 Feb 2023
Cited by 5 | Viewed by 1948
Abstract
Exposure to load and offshore environment degrades the load-bearing capacity of tubular joints, necessitating reinforcement of these joints. Reinforcement is sometimes required for lifespan enhancement or qualification based on new requirements. Available reinforcement techniques include welded rings inside/outside the chord, doubler/collar plate at [...] Read more.
Exposure to load and offshore environment degrades the load-bearing capacity of tubular joints, necessitating reinforcement of these joints. Reinforcement is sometimes required for lifespan enhancement or qualification based on new requirements. Available reinforcement techniques include welded rings inside/outside the chord, doubler/collar plate at the brace-chord interface, grout filling, and clamp installation on the joints with/without cement. While these techniques increase the load-bearing capacity of damaged tubular joints, various practical limitations exist. Clamping may require heavy machinery, whereas welding stiffeners involves hot work and may not be permitted sometimes. Fiber-reinforced polymers (FRPs) have immense potential for reinforcing steel structures and are a viable alternative for rehabilitating tubular joints due to their exceptional mechanical and physical characteristics, offering competitive advantages over other methods. FRP reinforcement is becoming more feasible and economical for underwater joints. FRP reinforcement can be either precured, pre-impregnated, or wet layup. Aside from the significance of joint rehabilitation, a document covering the well-known options was lacking. This paper summarizes the advantages and limitations of these reinforcement methods, particularly FRP reinforcement. Possible research directions in FRP reinforcement of tubular joints are also discussed. Full article
(This article belongs to the Special Issue Review Papers in Ocean Engineering)
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19 pages, 5277 KiB  
Article
MPC-Based Collaborative Control of Sail and Rudder for Unmanned Sailboat
by Shuo Liu, Zijing Yu, Tao Wang, Yifan Chen, Yu Zhang and Yong Cai
J. Mar. Sci. Eng. 2023, 11(2), 460; https://doi.org/10.3390/jmse11020460 - 20 Feb 2023
Cited by 2 | Viewed by 1617
Abstract
In the traditional motion control method of an unmanned sailboat, the sail and rudder are divided into two independent controllers. The sail is used to obtain the thrust and the rudder is used to adjust the yaw angle. The traditional control method does [...] Read more.
In the traditional motion control method of an unmanned sailboat, the sail and rudder are divided into two independent controllers. The sail is used to obtain the thrust and the rudder is used to adjust the yaw angle. The traditional control method does not consider the synergy between the two controllers and ignores the influence of the roll angle on sailing. It is easy for these methods to cause an excessive roll angle and large yaw angle error, which will weaken the safe navigation and accurate path tracking of an unmanned sailboat. This paper presents a collaborative control method of sail and rudder based on model predictive control. A four-degree-of-freedom kinematics and dynamics model of the unmanned sailboat considering roll angle was established, with the yaw angle and roll angle as the control objectives at the same time. The collaborative control method outputs sail angle and rudder angle simultaneously. By comparing the motion of this method and the separation control of sail and rudder under the same wind field conditions, it is verified that the collaborative control has better effects of yaw angle control and roll angle limitation and can obtain a more accurate path tracking effect. Full article
(This article belongs to the Special Issue Technology and Equipment for Underwater Robots)
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18 pages, 5617 KiB  
Article
On the Resistance of Cruciform Structures during Ship Collision and Grounding
by Hewei Liu, Kun Liu, Xiufei Wang, Zhenguo Gao and Jiaxia Wang
J. Mar. Sci. Eng. 2023, 11(2), 459; https://doi.org/10.3390/jmse11020459 - 20 Feb 2023
Viewed by 1284
Abstract
This paper presents an experimental, numerical, and analytical study of a novel specimen subjected to local in-plane load, to investigate its crushing deformation and resistance. The specimen was designed and fabricated to simplify the cruciform structure in double-hulled vessels subjected to external loads [...] Read more.
This paper presents an experimental, numerical, and analytical study of a novel specimen subjected to local in-plane load, to investigate its crushing deformation and resistance. The specimen was designed and fabricated to simplify the cruciform structure in double-hulled vessels subjected to external loads during collision and grounding incidents. The study results will provide reliable insights into grounding scenarios as well as side collision scenarios of double-hulled vessels. A quasi-static indentation test and related numerical research showed good agreement regarding deformation mode and force–displacement response. On the basis of the experimental and numerical results, an analytical method is proposed to derive the deformation energy, the instantaneous resistance, and the mean resistance of the deformed structure. The analytical method was verified with recorded test data and a nonlinear finite element analysis. It enables a rapid assessment of the response of the structure under accidental loads, which is a guideline for the design of crashworthy hull structures and the assessment of their crashworthiness. Full article
(This article belongs to the Special Issue Advanced Analysis of Marine Structures)
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15 pages, 2518 KiB  
Article
Southern South China Sea Dynamics: Sea Level Change from Coupled Model Intercomparison Project Phase 6 (CMIP6) in the 21st Century
by Noah Irfan Azran, Hafeez Jeofry, Jing Xiang Chung, Liew Juneng, Syamir Alihan Showkat Ali, Alex Griffiths, Muhammad Zahir Ramli, Effi Helmy Ariffin, Mohd Fuad Miskon, Juliana Mohamed, Kamaruzzaman Yunus and Mohd Fadzil Akhir
J. Mar. Sci. Eng. 2023, 11(2), 458; https://doi.org/10.3390/jmse11020458 - 20 Feb 2023
Viewed by 1922
Abstract
Sea level rise will significantly impact coastal areas around the world. As a coastal country, Malaysia’s rising sea levels are a significant concern because they would affect 70% of its population. The study of sea level rise is important in order to implement [...] Read more.
Sea level rise will significantly impact coastal areas around the world. As a coastal country, Malaysia’s rising sea levels are a significant concern because they would affect 70% of its population. The study of sea level rise is important in order to implement effective mitigation and adaptation strategies. This study investigates the performance of CMIP6 Global Climate Models (GCMs) in simulating sea level rise in the Malaysian seas using various statistical methods. The models’ performances were evaluated by comparing historic CMIP6 GCM runs from 1993 to 2010 with sea level measurements from the satellite altimetry AVISO+ using the Taylor diagram. The SCS (SCSPM and SCSEM) had a higher sea level range and trend in both selected areas than the SM and SS. With 1.5 °C warmings, the multi-model ensemble means predicted that the SCS would rise by 16 mm near the Peninsular, with sea levels increasing by 0.908 m at a rate of 1.5 mm/year, and by 14.5 mm near East Malaysia, with sea levels increasing by 0.895 m at a rate of 1.1 mm/year. In contrast, 2.0 °C warmings project that SCSPM and SCSEM would cause sea levels to rise by 20.2 mm and 21.5 mm, respectively, at a rate of 0.6 mm/year and 0.7 mm/year. This information will provide an insight into Malaysian sea levels between now and the end of the twenty-first century, which will be beneficial for government agencies, academics, and relevant stakeholders. Full article
(This article belongs to the Special Issue Sea Level Rise: Drivers, Variability and Impacts)
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34 pages, 23772 KiB  
Article
Normal Operating Performance Study of 15 MW Floating Wind Turbine System Using Semisubmersible Taida Floating Platform in Hsinchu Offshore Area
by Hoi-Yi Tong, Tsung-Yueh Lin and Shiu-Wu Chau
J. Mar. Sci. Eng. 2023, 11(2), 457; https://doi.org/10.3390/jmse11020457 - 20 Feb 2023
Cited by 1 | Viewed by 2623
Abstract
This study predicted the motion response and power performance of a floating wind turbine system equipped with a semisubmersible Taida platform, an IEA 15 MW wind turbine, and a 3 × 2 mooring design in the Hsinchu offshore area in the Taiwan Strait. [...] Read more.
This study predicted the motion response and power performance of a floating wind turbine system equipped with a semisubmersible Taida platform, an IEA 15 MW wind turbine, and a 3 × 2 mooring design in the Hsinchu offshore area in the Taiwan Strait. The hydrodynamic properties were calculated using ANSYS-AQWA and STAR-CCM+. The motion equations were solved by OrcaFlex to obtain the motion response and generator power, as well as the dynamics of the mooring system and aerodynamics of the wind turbine. The waves were assumed to share the same direction as the wind. This study compared the mean values and standard deviations of the motion response, generator power, and mooring line tension between the potential- and viscous-flow approaches by considering the combination of seven wind directions and four current directions under two wave conditions in the Hsinchu offshore area. The numerical prediction shows that the viscous effect has a larger impact on the hydrodynamic properties in the heave, roll, and pitch motions. The angle between the leading mooring line of the system and dominant wind direction in the Taiwan Strait, which comes from the northeast, should be from 120° to 180° in order to deliver a relatively favorable performance of the system. Full article
(This article belongs to the Special Issue Frontiers in Offshore Wind Energy)
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14 pages, 1495 KiB  
Article
Effect of Light Wavelength on Biomass, Growth, Photosynthesis and Pigment Content of Emiliania huxleyi (Isochrysidales, Cocco-Lithophyceae)
by Jing Zhang, Falong Liu, Qiaohan Wang, Qingli Gong and Xu Gao
J. Mar. Sci. Eng. 2023, 11(2), 456; https://doi.org/10.3390/jmse11020456 - 20 Feb 2023
Cited by 1 | Viewed by 7833
Abstract
Light wavelength is a critical abiotic factor in modulating the development and pigment accumulation of microalgae. In the present study, we investigated the influences of white, red, blue, yellow, and green light on biomass (cell density), growth (cell diameter and dry weight), net [...] Read more.
Light wavelength is a critical abiotic factor in modulating the development and pigment accumulation of microalgae. In the present study, we investigated the influences of white, red, blue, yellow, and green light on biomass (cell density), growth (cell diameter and dry weight), net photosynthetic rate, and pigment contents (chlorophyll a, fucoxanthin, and lutein) of the coccolithophore Emiliania huxleyi. The effects of light wavelength change on its cell density and fucoxanthin content were also evaluated. The results showed that blue light significantly stimulated the cell proliferation and photosynthetic activity of E. huxleyi. The cell diameter, dry weight, net photosynthetic rate, and the content of fucoxanthin under red light were significantly greater than under white light. E. huxleyi could not effectively utilize green light and yellow light for growth, photosynthesis, and pigment synthesis. Compared with white, blue, and red light, significantly greater cell density and fucoxanthin content were found under blue light, followed by red light. These findings indicated that light wavelength could significantly affect the growth, photosynthesis, and pigments of E. huxleyi. The combination of blue and red light is likely to be an effective measure to enhance its biomass and fucoxanthin production. Full article
(This article belongs to the Special Issue Biological Aspects and Biotechnological Potential of Microalgae)
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23 pages, 16482 KiB  
Article
Age and Depositional Environment of Whale-Bearing Sedimentary Succession from the Lower Pliocene of Tuscany (Italy): Insights from Palaeomagnetism, Calcareous Microfossils and Facies Analyses
by Mattia Marini, Luca Maria Foresi, Viviana Barbagallo, Michelangelo Bisconti, Agata Di Stefano, Giovanni Muttoni and Ivan Martini
J. Mar. Sci. Eng. 2023, 11(2), 455; https://doi.org/10.3390/jmse11020455 - 19 Feb 2023
Cited by 1 | Viewed by 1549
Abstract
A c. 31 m thick section straddling the fossil find of an Early Pliocene baleen whale (“Brunella”, hereafter), made in 2007 in the sedimentary fill of the Middle Ombrone Basin of Tuscany, is investigated for depositional age and environment combining palaeomagnetic, micropalaeontological (Foraminifera [...] Read more.
A c. 31 m thick section straddling the fossil find of an Early Pliocene baleen whale (“Brunella”, hereafter), made in 2007 in the sedimentary fill of the Middle Ombrone Basin of Tuscany, is investigated for depositional age and environment combining palaeomagnetic, micropalaeontological (Foraminifera and calcareous nannofossils) and sedimentary facies analyses. Resting unconformably onto Late Miocene continental deposits, the Early Pliocene marine deposits include, from bottom to top, a coarse-grained wave-winnowing lag, the few metres-thick fossiliferous sandstone bedset from which Brunella was unearthed, and several metres of clays. The stratigraphic organisation of these deposits indicate deposition in a deepening upward inner shelf environment. Successful isolation of characteristic remanent magnetisation and calcareous nannofossil content indicate the investigated marine section was deposited during the interval of polarity Chron C3n.2n corresponding to the basal part of the Mediterranean nannofossil zone MNN13 (between Helicosphaera sellii Base common and the Amaurolithus primus Top) and allow estimating the depositional age of Brunella to c. 4.6 Ma. Sedimentary facies, benthic Foraminifera association and anisotropy of magnetic susceptibility characterising the deposits that embedded Brunella suggest deposition above the fair-weather base level. Full article
(This article belongs to the Special Issue Advances in Marine Micropaleontology)
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17 pages, 4963 KiB  
Article
Enhancement of the Robustness on Advancing Layer Method with Trimmed Hexahedral Volume Mesh for the Generation of the Boundary Layer Grids
by Kwang-Leol Jeong, Sunho Park and Se-Min Jeong
J. Mar. Sci. Eng. 2023, 11(2), 454; https://doi.org/10.3390/jmse11020454 - 18 Feb 2023
Viewed by 1402
Abstract
When performing simulations using computational fluid dynamics, the grid systems in the viscous boundary layer regions are important because the velocity and pressure change very rapidly in these regions. Especially for the turbulent flows, thin grids should be arranged densely in the direction [...] Read more.
When performing simulations using computational fluid dynamics, the grid systems in the viscous boundary layer regions are important because the velocity and pressure change very rapidly in these regions. Especially for the turbulent flows, thin grids should be arranged densely in the direction perpendicular to the wall. In this study, the advancing layer method, which has been applied mostly to tetrahedral meshes, is applied to trimmed hexahedral meshes. To generate boundary layer meshes with non-intersecting grid lines near the wall boundaries having concave corners and narrow gaps, the directional vectors of grid lines and faces are smoothed, and the displacement vector fields calculated using the Laplace equation were utilized. Firstly, the details on the newly developed methods are introduced showing simple two-dimensional cases as examples. After applying the methods for a complex three-dimensional geometry to check its applicability and investigating the generated grid systems, the numerical simulations of propeller open water test for INSEAN E779A marine propeller were carried out by simpleFoam, one of the standard solvers of OpenFOAM. The computational results showed good agreement with the experimental results. Therefore, in conclusion, the developed advancing layer method is an appropriate method for generating boundary layer grids of a trimmed hexahedral mesh. Full article
(This article belongs to the Special Issue CFD Analysis in Ocean Engineering)
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22 pages, 3437 KiB  
Article
Phytoplankton of the High-Latitude Arctic: Intensive Growth Large Diatoms Porosira glacialis in the Nansen Basin
by Larisa Pautova, Vladimir Silkin, Marina Kravchishina, Alexey Klyuvitkin, Elena Kudryavtseva, Dmitry Glukhovets, Anna Chultsova and Nadezhda Politova
J. Mar. Sci. Eng. 2023, 11(2), 453; https://doi.org/10.3390/jmse11020453 - 18 Feb 2023
Cited by 4 | Viewed by 1504
Abstract
In August 2020, during a dramatical summer retreat of sea ice in the Nansen Basin, a study of phytoplankton was conducted on the transect from two northern stations in the marginal ice zone (MIZ) (north of 83° N m and east of 38° [...] Read more.
In August 2020, during a dramatical summer retreat of sea ice in the Nansen Basin, a study of phytoplankton was conducted on the transect from two northern stations in the marginal ice zone (MIZ) (north of 83° N m and east of 38° E) through the open water to the southern station located in the Franz Victoria Trench. The presence of melted polar surface waters (mPSW), polar surface waters (PSW), and Atlantic waters (AW) were characteristic of the MIZ. There are only two water masses in open water, namely PSW and AW, at the southernmost station; the contribution of AW was minimal. In the MIZ, first-year and multiyear ice species and Atlantic species were noted; Atlantic species and first-year ice species were in open water, and only ice flora was at the southernmost station. The maximum phytoplankton biomass (30 g · m−3) was recorded at the northernmost station of the MIZ, and 99% of the phytoplankton consisted of a large diatom Porosira glacialis. Intensive growth of this species occurred on the subsurface halocline separating mPSW from PSW. A thermocline was formed in open water south of the MIZ towards the Franz Victoria Trench. A strong stratification decreases vertical nutrient fluxes, so phytoplankton biomass decreases significantly. Phytoplankton formed the maximum biomass in the thermocline. When moving south, biomass decreased and its minimum values were observed at the southernmost station where the influence of AW is minimal or completely absent. A transition from the silicon-limited state of phytoplankton (MIZ area) to nitrogen-limited (open water) was noted. Full article
(This article belongs to the Special Issue Phytoplankton Dynamics and Biogeochemistry of Marine Ecosystems)
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16 pages, 4472 KiB  
Article
A Novel Intelligent Detection Algorithm of Aids to Navigation Based on Improved YOLOv4
by Rong Zhen, Yingdong Ye, Xinqiang Chen and Liangkun Xu
J. Mar. Sci. Eng. 2023, 11(2), 452; https://doi.org/10.3390/jmse11020452 - 18 Feb 2023
Cited by 4 | Viewed by 1261
Abstract
Aiming at the problem of high-precision detection of AtoN (Aids to Navigation, AtoN) in the complex inland river environment, in the absence of sufficient AtoN image types to train classifiers, this paper proposes an automatic AtoN detection algorithm Aids-to-Navigation-YOLOv4 (AN-YOLOv4) based on improved [...] Read more.
Aiming at the problem of high-precision detection of AtoN (Aids to Navigation, AtoN) in the complex inland river environment, in the absence of sufficient AtoN image types to train classifiers, this paper proposes an automatic AtoN detection algorithm Aids-to-Navigation-YOLOv4 (AN-YOLOv4) based on improved YOLOv4 (You Only Look Once, Yolo). Firstly, aiming at the problem of an insufficient number of existing AtoN datasets, the Deep Convolutional Generative Adversarial Networks (DCGAN) is used to expand and enhance the AtoN image dataset. Then, aiming at the problem of small target recognition accuracy, the image pyramid is used to multi-scale zoom the dataset. Finally, the K-means clustering algorithm is used to correct the candidate box of AN-YOLOv4. The test on the test dataset shows that the improvement effect of AN-YOLOv4 is obvious. The accuracy rate of small targets is 92%, and the average accuracy (mAP) of eight different types of AtoN is 92%, which is 14% and 13% higher than the original YOLOv4, respectively. This research has important theoretical significance and reference value for the intelligent perception of the navigation environment under the intelligent shipping system. Full article
(This article belongs to the Special Issue AI for Navigation and Path Planning of Marine Vehicles)
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16 pages, 4048 KiB  
Article
A High Abundance of Holothuria (Halodeima) atra (Holothuroidea Aspidochirotida) in a Halimeda Dominated Habitat
by Vanyarat Kongsap, Ekkalak Rattanachot, Anchana Prathep, Witthaya Buaphol and Jaruwan Mayakun
J. Mar. Sci. Eng. 2023, 11(2), 451; https://doi.org/10.3390/jmse11020451 - 18 Feb 2023
Cited by 1 | Viewed by 1606
Abstract
High-value sea cucumber species are overexploited, and the focus of fishing has shifted to low-value species, e.g., Holothuria (Halodeima) atra. In this study, the population of H. atra was investigated in three different habitats: a seagrass habitat, a seaweed habitat, and bare sand, [...] Read more.
High-value sea cucumber species are overexploited, and the focus of fishing has shifted to low-value species, e.g., Holothuria (Halodeima) atra. In this study, the population of H. atra was investigated in three different habitats: a seagrass habitat, a seaweed habitat, and bare sand, at an intertidal zone of Lidee Island, Mu Ko Phetra National Park, Satun Province, Thailand. The habitat type was the predictor which had a significant impact on the density and frequency distribution of the body length of H. atra individuals. H. atra was only found in the seaweed and seagrass habitats. The highest density of this species, 91.1 ± 9.6 inds 100 m−2, was found in the seaweed habitat. The frequency distribution of the body length of H. atra individuals in the seagrass habitat showed no significant change throughout the study period, but the mode of the length frequency distribution in the seaweed habitat gradually rose from 9 to 22 cm from January−September 2019. Asexual reproduction was the major source of recruitment. The occurrence of recently fissioned individuals was slightly higher in the seaweed habitat than in the seagrass habitat (6.0 ± 1.1% and 2.2 ± 0.6%, respectively). This study showed that H. atra was most abundant in the seaweed habitat, which is likely because of the greater availability in this habitat of food sources, microhabitats, and protection against sun irradiance, desiccation, and stress during low tides. Full article
(This article belongs to the Topic Marine Ecology, Environmental Stress and Management)
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15 pages, 4630 KiB  
Article
State Compensation for Maritime Autonomous Surface Ships’ Remote Control
by Shijun Chen, Xin Xiong, Yuanqiao Wen, Jiaxin Jian and Yamin Huang
J. Mar. Sci. Eng. 2023, 11(2), 450; https://doi.org/10.3390/jmse11020450 - 17 Feb 2023
Cited by 3 | Viewed by 1302
Abstract
With the development of emerging techniques, maritime autonomous surface ships (MASS) have attracted much attention, and the remote control ships’ future seems promising. However, due to communication issues, ship–shore transmission faces the challenge of time delay. The use of the transmitted information without [...] Read more.
With the development of emerging techniques, maritime autonomous surface ships (MASS) have attracted much attention, and the remote control ships’ future seems promising. However, due to communication issues, ship–shore transmission faces the challenge of time delay. The use of the transmitted information without compensation could reduce the effectiveness of controlling or could cause the remote control to be unstable. To eliminate the negative effects of uncertain delays during navigation, an Augmented State Cubature Kalman Filter (AS-CKF) is proposed. First, the uncertainty of the transmission delays is modeled using a probability density function (PDF). Second, the ship’s states are updated and estimated using the delayed observed data, and then the real state of the ship is simultaneously corrected in the augmented state vector. In this way, the delay compensation problem becomes a one-step prediction problem. To test the proposed AS-CKF for MASS, we simulate scenarios with the remote control ship under different communication time delays. The results show improvements compared to the traditional CKF, EKF, or AS-EKF, which indicates the potential of the proposed methods in remote control MASS. Full article
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12 pages, 2409 KiB  
Article
Efficiency Evaluation of a Small Container Terminal with Perpendicular Yard Layout Using Shuttle Carriers
by Maja Stojaković and Elen Twrdy
J. Mar. Sci. Eng. 2023, 11(2), 449; https://doi.org/10.3390/jmse11020449 - 17 Feb 2023
Viewed by 1381
Abstract
Productivity is an extremely important factor in the competitiveness of a container terminal. Productivity itself is largely influenced by the handling mechanisation, the main task of which is to serve the quay cranes on one side and the yard cranes on the other. [...] Read more.
Productivity is an extremely important factor in the competitiveness of a container terminal. Productivity itself is largely influenced by the handling mechanisation, the main task of which is to serve the quay cranes on one side and the yard cranes on the other. One of the most effective types of mechanisation in this segment is shuttle carriers, which are used primarily in the larger terminals. The objective of this study was to determine if they can also be used effectively in smaller container terminals with different yard layouts. Therefore, this study shows the impact of the selected layout and handling mechanisation on terminal productivity. The focus is on the berth productivity, as it has the greatest impact on the handling of the vessel in the port. To this end, a discrete-event simulation modelling approach was used in a container terminal of small capacity. The performed simulations included all operations between berth and yard, focusing on the correct allocation of shuttle carriers to ensure optimal results on the sea side of the terminal. The result showed that the use of shuttle carriers brings a substantial performance effect to the container terminal and also has a different effect considering different terminal layouts in terminals with an annual throughput not exceeding 1 million TEU. Full article
(This article belongs to the Section Ocean Engineering)
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14 pages, 3911 KiB  
Article
Study on Wave Loads during Steady-State Gap Resonance with Free Heave Motion of Floating Structure
by Junliang Gao, Shukai Gong, Zhiwei He, Huabin Shi, Jun Zang, Tao Zou and Xu Bai
J. Mar. Sci. Eng. 2023, 11(2), 448; https://doi.org/10.3390/jmse11020448 - 17 Feb 2023
Cited by 9 | Viewed by 1354
Abstract
Fluid resonance may occur in a narrow gap between two side-by-side vessels under wave actions, which can cause significant wave height amplification inside the gap and further induce large wave loads and motion responses of the vessel. Based on an open-sourced computational fluid [...] Read more.
Fluid resonance may occur in a narrow gap between two side-by-side vessels under wave actions, which can cause significant wave height amplification inside the gap and further induce large wave loads and motion responses of the vessel. Based on an open-sourced computational fluid dynamics (CFD) package, OpenFOAM, the steady-state gap resonance phenomenon formed in between two side-by-side boxes and triggered by the incident regular waves is simulated, where the upriver box keeps fixed and the downriver one heaves freely under wave actions. This article comprehensively investigates the influence of the vertical degree of freedom of the downriver box on the wave loads exerting on both boxes and further reveals how the relative position of the heaving box with respect to the incident wave direction affects the characteristics of wave loads during the steady-state gap resonance. The results show that both the normalized largest wave loads and the dimensionless wavenumber where the normalized largest wave loads occur are significantly affected by both the incident wave heights and the relative position of the heaving box to the incident wave direction. Full article
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14 pages, 1861 KiB  
Article
UMGAN: Underwater Image Enhancement Network for Unpaired Image-to-Image Translation
by Boyang Sun, Yupeng Mei, Ni Yan and Yingyi Chen
J. Mar. Sci. Eng. 2023, 11(2), 447; https://doi.org/10.3390/jmse11020447 - 17 Feb 2023
Cited by 13 | Viewed by 2597
Abstract
Due to light absorption and scattering underwater images suffer from low contrast, color distortion, blurred details, and uneven illumination, which affect underwater vision tasks and research. Therefore, underwater image enhancement is of great significance in vision applications. In contrast to existing methods for [...] Read more.
Due to light absorption and scattering underwater images suffer from low contrast, color distortion, blurred details, and uneven illumination, which affect underwater vision tasks and research. Therefore, underwater image enhancement is of great significance in vision applications. In contrast to existing methods for specific underwater environments or reliance on paired datasets, this study proposes an underwater multiscene generative adversarial network (UMGAN) to enhance underwater images. The network implements unpaired image-to-image translation between the underwater turbid domain and the underwater clear domain. It has a great enhancement impact on several underwater image types. Feedback mechanisms and a noise reduction network are designed to optimize the generator and address the issue of noise and artifacts in GAN-produced images. Furthermore, a global–local discriminator is employed to improve the overall image while adaptively modifying the local region image effect. It resolves the issue of over- and underenhancement in local regions. The reliance on paired training data is eliminated through a cycle consistency network structure. UMGAN performs satisfactorily on various types of data when compared quantitatively and qualitatively to other state-of-the-art algorithms. It has strong robustness and can be applied to various enhancement tasks in different scenes. Full article
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23 pages, 8893 KiB  
Article
Numerical Simulation of Hydrodynamics and Sediment Transport in the Surf and Swash Zone Using OpenFOAM®
by Ioannis Kazakis and Theophanis V. Karambas
J. Mar. Sci. Eng. 2023, 11(2), 446; https://doi.org/10.3390/jmse11020446 - 17 Feb 2023
Viewed by 2091
Abstract
This study focuses on the numerical investigation of the 3D hydrodynamic processes of coastal zones such as wave breaking, wave-induced currents, and sediment transport, using the multiphase, interFoam solver of OpenFOAM® (a state-of-the-art, open-source CFD numerical tool). The numerical scheme is suitably [...] Read more.
This study focuses on the numerical investigation of the 3D hydrodynamic processes of coastal zones such as wave breaking, wave-induced currents, and sediment transport, using the multiphase, interFoam solver of OpenFOAM® (a state-of-the-art, open-source CFD numerical tool). The numerical scheme is suitably framed by initial conditions of wave propagation and absorption using waves2Foam wave library. The turbulence closure problem is handled using a buoyancy modified kω SST model. In order to predict the sediment transport rate due to waves and currents (bed load, sheet flow, and suspended load over ripples), a transport-rate formula involving unsteady aspects of the sand transport phenomenon is implemented. For the suspended load in the surf zone, the Bailard formula is adopted after considering that the dissipation mechanism is the wave breaking. Results concerning wave height, longshore current, turbulence kinetic energy, and sediment transport are compared against experimental data and semi-empirical expressions. Full article
(This article belongs to the Special Issue Hydrodynamic Circulation Modelling in the Marine Environment)
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18 pages, 13098 KiB  
Article
A Control Method for Water Cannon of Unmanned Fireboats Considering Wind and Ship Motion Disturbances
by Diju Gao, Weixi Xie, Chunteng Bao, Bin Liu and Jiaxing Zhuang
J. Mar. Sci. Eng. 2023, 11(2), 445; https://doi.org/10.3390/jmse11020445 - 17 Feb 2023
Cited by 1 | Viewed by 1284
Abstract
In order to realize accurate and fast firefighting at sea, a control method for water cannons of unmanned fireboats considering wind and ship motion disturbances is presented. This method combines information fusion, computer vision, and prediction technology based on neural network. Firstly, a [...] Read more.
In order to realize accurate and fast firefighting at sea, a control method for water cannons of unmanned fireboats considering wind and ship motion disturbances is presented. This method combines information fusion, computer vision, and prediction technology based on neural network. Firstly, a prediction model of the jet trajectory of the fire water cannon considering the disturbances of constant horizontal wind is established, and the effective range of the water cannon’s angles under the target working environment is obtained. Secondly, fusing the visual recognition information and predicted ship motion attitudes information, a double adaptive fuzzy controller is designed to compensate for the disturbances caused by the change in ship motion attitudes. Meanwhile, the online particle swarm optimization (PSO) is applied to fuzzy control to improve operational accuracy while enhancing the ability to adapt to environmental changes. The proposed control method was experimentally verified. As a result, the adaptive fuzzy controller based on the PSO can self-adjust the parameters to adapt to the changes in the working environment within 0.6 s, and the efficiency is improved by about 20%∼50% compared with the traditional fuzzy control. The double adaptive fuzzy control can reach a stable and effective working state within 10 simulation steps, and the RMSE of the drop point error is only 3 ×103 m for 40 simulation steps after stabilization, which can effectively resist disturbances and improve efficiency and control accuracy. The control method can provide a practical reference for engineering applications of water cannon control of unmanned fireboats. Full article
(This article belongs to the Section Ocean Engineering)
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13 pages, 1420 KiB  
Article
The Effect of Environmental Dredging of Muck on an Assemblage of Benthic Amphipods
by Nayan Mallick, Kevin B. Johnson and Charles A. Jacoby
J. Mar. Sci. Eng. 2023, 11(2), 444; https://doi.org/10.3390/jmse11020444 - 17 Feb 2023
Cited by 3 | Viewed by 1547
Abstract
To yield environmental benefits, fine sediments with ~10% organic matter, termed muck, were dredged from a tributary to the Indian River Lagoon. Key changes were documented by sampling amphipods, sediments, and the water column near the bottom before dredging, and approximately one month [...] Read more.
To yield environmental benefits, fine sediments with ~10% organic matter, termed muck, were dredged from a tributary to the Indian River Lagoon. Key changes were documented by sampling amphipods, sediments, and the water column near the bottom before dredging, and approximately one month and one year after dredging. Overall, muck yielded the fewest taxa, muck or sediments in creeks that were dredged yielded a moderate number of taxa, and undisturbed sediments in the lagoon yielded the highest number of taxa. Amphipods did not appear in areas with muck until one month and one year after dredging. In contrast, amphipods in sediments that were not muck decreased after dredging. Increases in the occurrence of amphipods paralleled increases in concentrations of dissolved oxygen and decreases in the water, silt/clay, and organic content of sediments. Overall, results indicated that conditions for amphipods were improved by removing muck, and that dredging sandier sediment led to decreased taxonomic richness and numbers of amphipods, which resembled the effects of navigational dredging. Thus, this study suggested that managers should consider the type of sediment to be dredged when permitting projects. Full article
(This article belongs to the Special Issue Benthic Ecology in Coastal and Brackish Systems)
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20 pages, 12551 KiB  
Article
Differences in Thermo-Rheological Structure between Qiongdongnan Basin and Pearl River Mouth Basin: Implications for the Extension Model in the Northwestern Margin of the South China Sea
by Chaoyang Li, Pengyao Zhi, Renwei Ding, Lihong Zhao, Wei Gong, Zhonghua Li and Jiayu Ge
J. Mar. Sci. Eng. 2023, 11(2), 443; https://doi.org/10.3390/jmse11020443 - 17 Feb 2023
Cited by 1 | Viewed by 1000
Abstract
This study combines surface heat flow, multi-channel seismic reflection profiles, and ocean-bottom seismometer (OBS) profiles to determine the thermo-rheological structure of the Qiongdongnan Basin (QDNB) and Pearl River Mouth Basin (PRMB), with the aim of researching the west–east variation of the passive continental [...] Read more.
This study combines surface heat flow, multi-channel seismic reflection profiles, and ocean-bottom seismometer (OBS) profiles to determine the thermo-rheological structure of the Qiongdongnan Basin (QDNB) and Pearl River Mouth Basin (PRMB), with the aim of researching the west–east variation of the passive continental margin rifting. Based on the initial lithospheric rheological model of a jelly sandwich-1 (JS-1) regime, the current architecture of the continental margin is identified to be the result of a non-uniform extension. Due to the decoupled crust–mantle relationship caused by the weak lower crust, the non-uniform extension led to the rupture of the mantle lithosphere before the crust. The central Xisha Trough falls into the JS-2 regime with only one brittle load layer, which is close to the rigid oceanic lithosphere of the Northwest Sub-basin (NSB). The high-velocity layers (HVLs) and detachment faults beneath the Xisha Trough are considered to be the result of the cooling of a thinned lower crust with mantle underplating during the middle stage of continental margin rifting. A seaward-increasing trend of lithospheric rheological strength is exhibited across the PRMB, from the crème brûlée-1 (CB-1) regime at the continental shelf to the JS-2 regime at the NSB. Unlike the HVLs of the Xisha Trough, the lower crustal HVLs beneath the eastern PRMB formed during the late stage of continental margin rifting due to the mantle lateral flow. The absence of HVLs beneath the western PRMB may indicate that the mantle lateral flow demonstrates a limited impact. Full article
(This article belongs to the Section Geological Oceanography)
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27 pages, 2017 KiB  
Article
An Integrated Scheme of the Data-Driven Multi-Block FCMs for Modeling the Steady Turning Motion of Motorboats
by Xiaori Gao, Lidong Wang, Zeyu Wu and Xiaodong Liu
J. Mar. Sci. Eng. 2023, 11(2), 442; https://doi.org/10.3390/jmse11020442 - 17 Feb 2023
Viewed by 1076
Abstract
The steady turning motion of merchant ships is modeled according to industry specifications. However, challenges arise when motorboats are modeled. This study proposes a novel data-driven multi-block fuzzy cognitive map (FCM) model trained based on sea trials with four ship states. The optimal [...] Read more.
The steady turning motion of merchant ships is modeled according to industry specifications. However, challenges arise when motorboats are modeled. This study proposes a novel data-driven multi-block fuzzy cognitive map (FCM) model trained based on sea trials with four ship states. The optimal positions sampled by two different types of sensors were modeled using inverse variance weighting, which takes both Cartesian coordinate transformation and the constraints of the locations of the apparatuses into consideration. Combining these samplings with a scheme of multi-block FCMs, we conducted a study on data from motorboat trials. Our results closely approximate the data from motorboat trials at sea and are validated by a generated dataset of the classical model. Furthermore, we reveal the characteristics of our scheme, including the number of data blocks, the boundary of each block, and the parameters of the FCM for each block. As opposed to the classical method, the proposed scheme is insensitive to speed. This study presents a promising step toward mining modeling information from ship trials. Full article
(This article belongs to the Section Ocean Engineering)
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15 pages, 5915 KiB  
Article
Trace Element Evidence of Subduction-Modified Mantle Material in South Mid-Atlantic Ridge 18–21°S Upper Mantle
by Tianxiao Ji and Zhigang Zeng
J. Mar. Sci. Eng. 2023, 11(2), 441; https://doi.org/10.3390/jmse11020441 - 17 Feb 2023
Cited by 1 | Viewed by 1922
Abstract
Mid-ocean ridge basalts (MORBs), produced at mid-ocean ridge where the continents and subduction zones are distant, are the product of partial melting of the upper mantle and their chemical composition can provide information about the mantle itself. The geochemical characteristics of MORBs enable [...] Read more.
Mid-ocean ridge basalts (MORBs), produced at mid-ocean ridge where the continents and subduction zones are distant, are the product of partial melting of the upper mantle and their chemical composition can provide information about the mantle itself. The geochemical characteristics of MORBs enable us to be more informed about the geological processes of the upper mantle below the mid-ocean ridge, and assist us in understanding mantle heterogeneity and geodynamic processes. In this paper, new data of major elements, trace elements, and Nd-Hf isotopes of south mid-Atlantic ridge (SMAR) 18–21°S MORBs are presented. TAS diagram shows that the samples belong to subalkaline basalt compositional field. Trace elements (e.g., (La/Sm)N = 0.49–0.79) show that the samples are N-MORBs. However, the primitive mantle-normalized trace element patterns showed that the studied samples were clearly enriched in Rb, U, Pb, and other fluid-mobile elements. Meanwhile, the trace element ratios, such as Nb/U and Ce/Pb, are also significantly different from the typical N-MORB. Combined with the Nd-Hf isotopic composition, we propose that these anomalies are not related to continental crust material, delaminated subcontinental lithospheric mantle (SCLM), recycled sediments, direct supply of mantle plume, nor are they the result of subduction directly affecting the mantle source, but are caused by the incorporation of mantle material modified by subduction. Full article
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14 pages, 8556 KiB  
Article
Similarity Study of Electromagnetic and Underwater Acoustic Scattering by Three-Dimensional Targets in Unbounded Space
by Jie Wang, Hai Lin, Huaihai Guo, Qi Zhang and Junxiang Ge
J. Mar. Sci. Eng. 2023, 11(2), 440; https://doi.org/10.3390/jmse11020440 - 17 Feb 2023
Viewed by 1391
Abstract
The characterization of targets by electromagnetic (EM) scattering and underwater acoustic scattering is an important object of research in these two related fields. However, there are some difficulties in the simulation and measurement of the scattering by large targets. Consequently, a similarity study [...] Read more.
The characterization of targets by electromagnetic (EM) scattering and underwater acoustic scattering is an important object of research in these two related fields. However, there are some difficulties in the simulation and measurement of the scattering by large targets. Consequently, a similarity study between acoustic and EM scattering may help to share results between one domain and the other and even provide a general reference method for the simulation of scattering characteristics in both fields. Based on the method of physical optics, the similarity between the EM scattering of conductors and the acoustic scattering of soft/hard targets and the similarity between the EM scattering of dielectrics and the acoustic scattering of elastics are studied. In particular, we derive how to transfer quantities from one domain into another so that similar scattering patterns arise. Then, according to these transfer rules, the EM scattering and acoustic scattering of three typical targets with different types of boundaries were simulated and measured, and the simulated EM scattering and acoustic scattering curves were found to be in perfect agreement, with correlation coefficients above 0.93. The correlation coefficients between the electromagnetic and acoustic scattering patterns were above 0.98, 0.91, and 0.65 for three typical targets. The simulated and measured scattering results verify the proposed similarity theory of EM and acoustic scattering, including the transfer from one domain into the other and the conditions of EM and acoustic scattering, and illustrate that the acoustic scattering characteristic of the target can be simulated using the EM scattering based on the derived conditions and vice versa. Full article
(This article belongs to the Section Physical Oceanography)
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22 pages, 24316 KiB  
Article
A Curved Plate-Flattening Method to Construct the Membrane Strain Distribution
by Lichun Chang, Yao Zhao, Hua Yuan and Zhenshuai Wei
J. Mar. Sci. Eng. 2023, 11(2), 439; https://doi.org/10.3390/jmse11020439 - 16 Feb 2023
Viewed by 1444
Abstract
The surface-flattening process has many applications in industries such as shipbuilding. Curved surfaces in the industry are usually formed from flat surfaces, so the target surface needs to be flattened to obtain its corresponding initial shape. In addition, the surface flattening process obtains [...] Read more.
The surface-flattening process has many applications in industries such as shipbuilding. Curved surfaces in the industry are usually formed from flat surfaces, so the target surface needs to be flattened to obtain its corresponding initial shape. In addition, the surface flattening process obtains the inherent strain distribution required in forming. Different forming methods in the plate forming process will produce different membrane deformations, such as shrinkage in the line heating and tensile in the roller forming. Therefore, different surface-flattening methods should be used to obtain the inherent strain distribution suitable for different forming methods. This paper proposes a method to perform the surface flattening using the finite element method and constrain the membrane strain generated in the flattening deformation by modifying the material constitutive relationship. Using a dual modulus material constitutive model in membrane deformation makes the surface more inclined to deform at locations with less stiffness during the flattening process. This method yields predominantly tensile or compressive membrane strain without changing the bending strain. By modifying the material model, this method can control the compressive strain region and the principal strain direction. The results of the proposed method applying to different surface shapes and its application in the surface-forming process are given in this paper. Full article
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14 pages, 2069 KiB  
Article
Citizen Science and Expert Judgement: A Cost-Efficient Combination to Monitor and Assess the Invasiveness of Non-Indigenous Fish Escapees
by Paola Parretti, João Gama Monteiro, Francesca Gizzi, Roi Martínez-Escauriaza, Filipe Alves, Sahar Chebaane, Silvia Almeida, Miguel Pessanha Pais, Frederico Almada, Marc Fernandez, Natacha Nogueira, Carlos Andrade and João Canning-Clode
J. Mar. Sci. Eng. 2023, 11(2), 438; https://doi.org/10.3390/jmse11020438 - 16 Feb 2023
Cited by 2 | Viewed by 1453
Abstract
Mapping the distribution and evaluating the impacts of marine non-indigenous species (NIS) are two fundamental tasks for management purposes, yet they are often time consuming and expensive. This case study focuses on the NIS gilthead seabream Sparus aurata escaped from offshore farms in [...] Read more.
Mapping the distribution and evaluating the impacts of marine non-indigenous species (NIS) are two fundamental tasks for management purposes, yet they are often time consuming and expensive. This case study focuses on the NIS gilthead seabream Sparus aurata escaped from offshore farms in Madeira Island in order to test an innovative, cost-efficient combined approach to risk assessment and georeferenced dispersal data collection. Species invasiveness was screened using the Aquatic Species Invasiveness Screening Kit (AS-ISK), and revealed a high invasion risk. Occurrences of S. aurata were assessed involving citizens in GIS participatory mapping and data from recreational fishing contests. A probability map showed that S. aurata is well dispersed around Madeira Island. This assessment proved to be a cost-efficient early warning method for detecting NIS dispersal, highlighting the urgent need for additional surveys that should search for sexually mature individuals and assess the direct and indirect impacts in the native ecosystem. Full article
(This article belongs to the Special Issue Marine Biological Invasions: Experimental Approaches)
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17 pages, 4992 KiB  
Article
Hydroelastic Response to the Effect of Current Loads on Floating Flexible Offshore Platform
by Pouria Amouzadrad, Sarat Chandra Mohapatra and Carlos Guedes Soares
J. Mar. Sci. Eng. 2023, 11(2), 437; https://doi.org/10.3390/jmse11020437 - 16 Feb 2023
Cited by 3 | Viewed by 1490
Abstract
An analytical model of a current load’s interaction with a moored floating flexible structure based on the Timoshenko–Mindlin beam theory is developed under the assumption of small-amplitude wave theory and the structural response. Theoretical solutions on the displacement of the structure, reflection, and [...] Read more.
An analytical model of a current load’s interaction with a moored floating flexible structure based on the Timoshenko–Mindlin beam theory is developed under the assumption of small-amplitude wave theory and the structural response. Theoretical solutions on the displacement of the structure, reflection, and transmission coefficients are obtained by applying the matching technique along with the orthogonal model coupling relation. The results of the transmission coefficient and displacement amplitude are compared with the other calculations and experimental datasets available in the literature. The structural deflection and transmission coefficients are investigated via the hydroelastic response for wave–current loads along with design parameters. The comparison results showed that the present model result is supported by the numerical model’s results. This present analysis can provide further information for marine engineers to design floating flexible platforms in the marine environment. Full article
(This article belongs to the Special Issue Hydroelastic Behaviour of Floating Offshore Structures)
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17 pages, 3099 KiB  
Article
Discerning Discretization for Unmanned Underwater Vehicles DC Motor Control
by Jovan Menezes and Timothy Sands
J. Mar. Sci. Eng. 2023, 11(2), 436; https://doi.org/10.3390/jmse11020436 - 16 Feb 2023
Cited by 7 | Viewed by 2211
Abstract
Discretization is the process of converting a continuous function or model or equation into discrete steps. In this work, learning and adaptive techniques are implemented to control DC motors that are used for actuating control surfaces of unmanned underwater vehicles. Adaptive control is [...] Read more.
Discretization is the process of converting a continuous function or model or equation into discrete steps. In this work, learning and adaptive techniques are implemented to control DC motors that are used for actuating control surfaces of unmanned underwater vehicles. Adaptive control is a strategy wherein the controller is designed to adapt the system with parameters that vary or are uncertain. Parameter estimation is the process of computing the parameters of a system using a model and measured data. Adaptive methods have been used in conjunction with different parameter estimation techniques. As opposed to the ubiquitous stochastic artificial intelligence approaches, very recently proposed deterministic artificial intelligence, a learning-based approach that uses the physics-defined process dynamics, is also applied to control the output of the DC motor to track a specified trajectory. This work goes further to evaluate the performance of the adaptive and learning techniques based on different discretization methods. The results are evaluated based on the absolute error mean between the output and the reference trajectory and the standard deviation of the error. The first-order hold method of discretization and surprisingly large sample time of seven-tenths of a second yields greater than sixty percent improvement over the results presented in the prequel literature. Full article
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23 pages, 7297 KiB  
Article
An Integrated Complete Ensemble Empirical Mode Decomposition with Adaptive Noise to Optimize LSTM for Significant Wave Height Forecasting
by Lingxiao Zhao, Zhiyang Li, Junsheng Zhang and Bin Teng
J. Mar. Sci. Eng. 2023, 11(2), 435; https://doi.org/10.3390/jmse11020435 - 16 Feb 2023
Cited by 6 | Viewed by 1643
Abstract
In recent years, wave energy has gained attention for its sustainability and cleanliness. As one of the most important parameters of wave energy, significant wave height (SWH) is difficult to accurately predict due to complex ocean conditions and the ubiquitous chaotic phenomena in [...] Read more.
In recent years, wave energy has gained attention for its sustainability and cleanliness. As one of the most important parameters of wave energy, significant wave height (SWH) is difficult to accurately predict due to complex ocean conditions and the ubiquitous chaotic phenomena in nature. Therefore, this paper proposes an integrated CEEMDAN-LSTM joint model. Traditional computational fluid dynamics (CFD) has a long calculation period and high capital consumption, but artificial intelligence methods have the advantage of high accuracy and fast convergence. CEEMDAN is a commonly used method for digital signal processing in mechanical engineering, but has not yet been used for SWH prediction. It has better performance than the EMD and EEMD and is more suitable for LSTM prediction. In addition, this paper also proposes a novel filter formulation for SWH outliers based on the improved violin-box plot. The final empirical results show that CEEMDAN-LSTM significantly outperforms LSTM for each forecast duration, significantly improving the prediction accuracy. In particular, for a forecast duration of 1 h, CEEMDAN-LSTM has the most significant improvement over LSTM, with 71.91% of RMSE, 68.46% of MAE and 6.80% of NSE, respectively. In summary, our model can improve the real-time scheduling capability for marine engineering maintenance and operations. Full article
(This article belongs to the Section Physical Oceanography)
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16 pages, 2762 KiB  
Article
Reducing Ship’s Energy Consumption through Accommodation and Cargo Spaces Lights Automation
by Dilyan Dimitranov and Blagovest Belev
J. Mar. Sci. Eng. 2023, 11(2), 434; https://doi.org/10.3390/jmse11020434 - 16 Feb 2023
Viewed by 1786
Abstract
The effective use of energy proposes using less energy to achieve the same goal. The International Maritime Organization started using criteria for ship’s energy efficiency in 2013, when the new International Convention for the Prevention of Pollution from Ships, Annex VI, was adopted. [...] Read more.
The effective use of energy proposes using less energy to achieve the same goal. The International Maritime Organization started using criteria for ship’s energy efficiency in 2013, when the new International Convention for the Prevention of Pollution from Ships, Annex VI, was adopted. The purpose of the Annex is to improve the ships’ energy efficiency through the use of new technologies such as improved hull design, and new propulsion systems, including innovations in energy management. One of the topics for improving the car carriers’ energy efficiency is the constantly working lights in the superstructure and on the car decks. Lights’ energy consumption may be negligible on most ships, but on car carriers, the consumption is of greater magnitude. This article presents a survey of the improvement of energy consumption on board a car carrier during regular voyages as well as the cost-effectiveness of introducing light control automation. The authors of this article review an example of light automation set up to control the lights in a ship’s superstructure and on the car decks. The implementation of such a system and the different types of automation are also reviewed. This research is towards new regulations, established by Maritime Environment Protection Committee and implemented in shipping since 1 November 2022. Conclusions for practical use are extracted. Full article
(This article belongs to the Section Ocean Engineering)
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21 pages, 3299 KiB  
Article
Life-Cycle Cost Assessment Using the Power Spectral Density Function in a Coastal Concrete Bridge
by Mehrdad Hadizadeh-Bazaz, Ignacio J. Navarro and Víctor Yepes
J. Mar. Sci. Eng. 2023, 11(2), 433; https://doi.org/10.3390/jmse11020433 - 16 Feb 2023
Cited by 2 | Viewed by 1507
Abstract
Recently, the repair and maintenance of structures has been necessary to prevent these structures’ sudden collapse and to prevent human and financial damage. A natural factor in marine environments that destroys structures and reduces their life is the presence of chloride ions. So [...] Read more.
Recently, the repair and maintenance of structures has been necessary to prevent these structures’ sudden collapse and to prevent human and financial damage. A natural factor in marine environments that destroys structures and reduces their life is the presence of chloride ions. So regular health monitoring of concrete coastal buildings for on-time repair is essential. This study investigates the performance of the power spectral density (PSD) method as a non-destructive damage-detection method to monitor the location and amount of damage caused by chloride ions during a structure’s life using different approaches according to life-cycle assessment (LCA) and life-cycle cost assessment (LCCA). In this regard, chloride corrosion damage dependent on zone distance from seawater was first calculated to obtain the service life of each part of a coastal concrete bridge according to the conventional method. Based on rebar corrosion each year, the next stage forecasted the bridge’s concrete deterioration. The PSD method monitored the annual loss of reinforcement cross-sectional area, changes in dynamic characteristics such as stiffness and mass, and the bridge structure’s life using sensitivity equations and the linear-least-squares algorithm. Finally, according to the location and quality of damage in each year of bridge life until the end of life, LCC and maintenance and repair costs of the PSD method were compared with the conventional method. The results showed that this strategy was very effective at lowering and optimizing the costs of maintenance and repair caused by chloride corrosion. Full article
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17 pages, 5473 KiB  
Article
A Lightweight Network Model Based on an Attention Mechanism for Ship-Radiated Noise Classification
by Shuang Yang, Lingzhi Xue, Xi Hong and Xiangyang Zeng
J. Mar. Sci. Eng. 2023, 11(2), 432; https://doi.org/10.3390/jmse11020432 - 16 Feb 2023
Cited by 9 | Viewed by 1505
Abstract
Recently, deep learning has been widely used in ship-radiated noise classification. To improve classification efficiency, avoiding high computational costs is an important research direction in ship-radiated noise classification. We propose a lightweight squeeze and excitation residual network 10 (LW-SEResNet10). In ablation experiments of [...] Read more.
Recently, deep learning has been widely used in ship-radiated noise classification. To improve classification efficiency, avoiding high computational costs is an important research direction in ship-radiated noise classification. We propose a lightweight squeeze and excitation residual network 10 (LW-SEResNet10). In ablation experiments of LW-SEResNet10, the use of ResNet10 instead of ResNet18 reduced 56.1% of parameters, while the accuracy is equivalent to ResNet18. The improved accuracy indicates that the ReLU6 enhanced the model stability, and an attention mechanism captured the channel dependence. The ReLU6 activation function does not introduce additional parameters, and the number of parameters introduced by the attention mechanism accounts for 0.2‰ of the model parameters. The 3D dynamic MFCC feature performs better than MFCC, Mel-spectrogram, 3D dynamic Mel-spectrogram, and CQT. Moreover, the LW-SEResNet10 model is also compared with ResNet and two classic lightweight models. The experimental results show that the proposed model achieves higher classification accuracy and is lightweight in terms of not only the model parameters, but also the time consumption. LW-SEResNet10 also outperforms the state-of-the-art model CRNN-9 by 3.1% and ResNet by 3.4% and has the same accuracy as AudioSet pretrained STM, which achieves the trade-off between accuracy and model efficiency. Full article
(This article belongs to the Special Issue Application of Sensing and Machine Learning to Underwater Acoustic)
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