J. Mar. Sci. Eng., Volume 12, Issue 3 (March 2024) – 162 articles

Precise surveys are indispensable in coastal engineering projects. The extensive presence of sand in the coastal area leads to significant attenuation of seismic waves within unsaturated loose sediments. As a result, it becomes challenging for seismic waves to penetrate the weathered zone and reach the desired depth with significant amount of energy. In this study, the application of three-dimensional (3D) cross-well elastic reverse time migration (RTM) imaging based on multi-wave and multi-component techniques in coastal engineering exploration is explored. Accurate decomposition of vector compressional (P) and shear (S) waves is achieved through two wavefield decoupling algorithms without any amplitude and phase distortion. Additionally, compressional wave pressure components are obtained, which facilitates subsequent independent imaging. This study discusses and analyzes the imaging results of four imaging strategies under cross-correlation imaging conditions in RTM imaging. The analysis leads to the conclusion that scalarizing vector wavefields imaging yields superior imaging of P- and S-waves. Furthermore, the imaging results obtained through this approach are of great physical significance. In order to validate the efficacy of this method in 3D geological structure imaging in coastal areas, RTM imaging experiments were performed on two representative models. The results indicate that the proposed 3D elastic wave imaging method effectively generates accurate 3D cross-well imaging of P- and S-waves. This method utilizes the multi-wave and multi-component elastic wave RTM imaging technique to effectively leverage the Earth’s elastic medium without increasing costs. It provides valuable information about the distribution of subsurface rock layers, interfaces, and other structures in coastal engineering projects. Importantly, this can be achieved without resorting to extensive excavation or drilling operations. This method addresses the limitations of current cross-well imaging techniques, thereby providing abundant and accurate geological and geophysical information for the analysis and interpretation of 3D geological structures in coastal engineering projects. It has important theoretical and practical significance in real-world production, as well as for the study of geological structures in coastal engineering. Full article

The decarbonization problem of maritime transport and new restrictions on CO₂ emissions (MARPOL Annex VI Chapter 4, COM (2021)562) have prompted the development and practical implementation of new decarbonization solutions. One of them, along with the use of renewable fuels, is the waste heat recovery of secondary heat sources from a ship’s main engine, whose energy potential reaches 45–55%. The organic Rankine cycle (ORC), which uses low-boiling organic working fluids, is considered one of the most promising and energy-efficient solutions for ship conditions. However, there remains uncertainty when choosing a rational cycle configuration, taking into account the energy consumption efficiency indicators of various low-temperature (cylinder cooling jacket and scavenging air cooling) and high-temperature (exhaust gas) secondary heat source combinations while the engine operates within the operational load range. It is also rational, especially at the initial stage, to evaluate possible constraints of ship technological systems for ORC implementation on the ship. The numerical investigation of these practical aspects of ORC applicability was conducted with widely used marine medium-speed diesel engines, such as the Wartsila 12V46F. Comprehensive waste heat recovery of all secondary heat sources in ORC provides a potential increase in the energy efficiency of the main engine by 13.5% to 21% in the engine load range of 100% to 25% of nominal power, while individual heat sources only achieve 3% to 8%. The average increase in energy efficiency over the operating cycle according to test cycles for the type approval engines ranges from 8% to 15% compared to 3% to 6.5%. From a practical implementation perspective, the most attractive potential for energy recovery is from the scavenging air cooling system, which, both separately (5% compared to 6.5% during the engine’s operating cycle) and in conjunction with other WHR sources, approaches the highest level of exhaust gas potential. The choice of a rational ORC structure for WHR composition allowed for achieving a waste heat recovery system energy efficiency coefficient of 15%. Based on the studied experimental and analytical relationships between the ORC (generated mechanical energy) energy performance ($P_{turb}$) and the technological constraints of shipboard systems ($G_w$), ranges for the use of secondary heat sources in diesel operational characteristic modes have been identified according to technological limits. Full article

The naval sector holds paramount importance for the global economy, yet it entails significant environmental impacts throughout the entire life cycle of ships. This review explores the application of life-cycle assessment (LCA) in the naval sector, a methodology for evaluating the environmental impacts associated with all the life stages of a product or service. LCA analysis in the naval context is essential for identifying and mitigating environmental impacts, thus promoting more sustainable development of the sector. This work provides a comprehensive overview of current LCA applications in the naval sector, highlighting major environmental impacts, in particular focusing on greenhouse-gas emissions and climate change. Additionally, this study integrates an analysis of greenhouse-gas emissions using a normalization approach, which has enabled the comparison of various types of fuels and ships, thereby enhancing our understanding of their environmental impacts. Moreover, the limits and challenges to applying LCA in the naval sector are discussed, offering insights for future research and developments in the field. This review aims to raise awareness among policymakers, designers, and operators in the naval sector about the importance of adopting LCA for more sustainable and responsible management of naval activities, thereby contributing to the protection of the marine and global environment. Full article

The design strategies for flood risk reduction in coastal towns must be informed by the likelihood of flooding resulting from both precipitation and coastal storm surge. This paper discusses various bivariate extreme value methods to investigate the joint probability of the exceedance of thresholds in both precipitation and sea level and estimate their dependence structure. We present the results of the dependence structure obtained using the observational record at Bridgeport, CT, a station with long data records representative of coastal Connecticut. Furthermore, we evaluate the dependence structure after removing the effects of harmonics in the sea level data. Through this comprehensive analysis, our study seeks to contribute to the understanding of the joint occurrence of sea level and precipitation extremes, providing insights that are crucial for effective coastal management. Full article

In this study, laboratory experiments were conducted to investigate the influence of changes in storm wave height and water level on beach response in a medium-scale wave flume. A schematic storm was simulated (rising, apex, and waning phases). A non-intrusive photogrammetric method was used to collect high-resolution and synchronous data regarding the free surface water elevation and bed level, from which shoreline location, sandbar position, cross-shore sediment transport rates, and nonlinear wave parameters were derived. The cross-shore sediment transport was in agreement with previous laboratory measurements, including the monotonous exchange from foreshore erosion to shoaling zone accretion in most stages of the storm simulation. The surf zone was the main region supplying sediment for beach morphology modification and sandbar generation. The degree of storm erosion was not completely determined by the largest wave height and water level or the cumulative wave power of the apex phase. The largest gradients of the wave parameter sequence change occurred in the rising phase, and this was the main factor generating efficient beachface erosion. It induced an increase in sandbar size, accompanied by the cross-shore motion of maximum velocity amplitude, more violent disturbances of wave nonlinearity, and increased surf zone erosion, with these factors increasing beach instability and leading to more severe storm erosion. The large wave height and water level resulted in shoreline retreat, with a more significant swash zone erosion under a higher runup. The offshore sediment transport turned toward the onshore direction as the original large sandbar deteriorated under the decreasing wave parameter sequence in the waning phase. Full article

Understanding the factors that control carbonate systems is an important goal due to the complex interactions between the hydrophysical and chemical–biological conditions in coastal basins. The results of this paper present the state of the carbonate system in Penzhina Bay and its adjacent waters—the Shelikhov Gulf—in July 2023, during spring tides with 13 m height. The area we studied included the length of the largest river in the region, the Penzhina River, from the peak of its summer flood to its boundary with the Shelikhov Gulf (the Sea of Okhotsk). This unique dynamic basin, with a length of about 800 km, was studied over 17 days. During this period, the entire water column of Penzhina Bay, down to a depth of about 60 m, and the surface water layer of the Shelikhov Gulf were undersaturated in terms of CO₂, with low levels relative to those of the atmosphere. To explain this observation, the dissolved oxygen, nutrients in mineral and organic forms, humic substances, chlorophyll a, and photic zone thickness are presented for the entire basin under study, together with its hydrological data. The results of daily observations of the carbonate system at fixed anchorage stations characterize two contrasting regions of Penzhina Bay: one that was more exposed to continental runoff, which had salinity levels in the range of 8.0–21.3 psu during one tidal cycle; the second had smaller variations in salinity in the range of 31.6–32.9 psu during one tidal cycle. This study emphasizes the importance of biological processes and continental runoff on the variability of the carbonate system parameters and CO₂ fluxes at a water/atmosphere boundary with extreme tidal conditions in this ecosystem that is barely affected by human activities. Full article

During the process of establishing the analytical quaternion ship domain model, the impact of ship traffic conditions and navigator state was not taken into consideration. However, the significance of these factors in the ship domain cannot be ignored. To create a more realistic representation of changes in the ship domain in real navigation environments, this study further considers the influence of ship encounter course, waterway traffic intensity, relative ship velocity, and the navigator state based on the quaternion ship domain model. As a result, a new dynamic quaternion ship domain model is proposed. To assess the changes in the size and shape of the ship domain under various navigation environments, ship domain scaling and shape transformation functions are introduced. Specifically, this study focuses on analyzing the ship traffic near the Lao Tie Shan Waterway, simulating the size and shape changes of the ship domain during the navigation process in this area. The findings indicate that the size of the ship domain dynamically adjusts to the traffic conditions. Additionally, when the navigator state is excellent, the ship domain takes on an irregular diamond shape with the smallest area, whereas when the navigator state is poor, the shape approximates a rectangle with the largest area. Furthermore, the dynamic quaternion ship domain model proposed in this study is compared to the ship domain models put forth by Goodwin, Davis, and co-authors. The results demonstrate that the dynamic quaternion ship domain model is more compatible and suitable for open waters compared to the static quaternion ship domain model. Full article

This study utilizes a bidirectional fluid–structure interaction numerical method to investigate the hydrodynamic and energy harvesting characteristics of two tandem three rigidly connected cylinder oscillators with different inter-oscillator spacing ratios. The analysis considers inter-oscillator spacing ratios of 8, 12, and 16 within a reduced velocity range of U* = 2–13 (equivalent to flow velocities of 0.18–1.16 m/s). The research explores the hydrodynamic interference features, energy harvesting variations, and the efficiency and density of energy harvesting of both upstream and downstream three-cylinder oscillators. The findings indicate that with increasing reduced velocity and inter-oscillator spacing ratio, the mutual interference between upstream and downstream oscillators diminishes. Wake patterns observed in the two series-connected three-cylinder oscillators include 2P, 2S, and 2T patterns, with fragmented vortices and banded vortices at specific reduced velocities. The most significant disparity in energy harvesting efficiency between upstream and downstream oscillators is observed at U* = 9. Full article

Gongolaria barbata plays a crucial role as a habitat-forming Fucales species in the Mediterranean Sea, thriving in shallow, sheltered coastal regions, where it exhibits optimal growth in a temperature range of 10 to 25 °C. In the northern Adriatic Sea, a semi-enclosed part of the Mediterranean, there has been a remarkable increase in seawater temperatures in recent decades, often exceeding 28 °C in summer. These high temperatures pose a significant threat to the vulnerable early life stages of G. barbata. This study delves into the effects of four temperatures (15, 18, 24, and 28 °C) on the growth of G. barbata over its first 16 days, closely monitoring mortality, deformities, and overall survival. Our experiments reveal that higher temperatures can result in deformities and increased mortality of germlings. Notably, a temperature of 28 °C resulted in the death of all germlings within the first week, whereas those exposed to 24 °C survived until the second week, albeit with significant deformities prior to death. In contrast, germlings cultivated at 15 and 18 °C exhibited normal development with minimal deformities. These results highlight the susceptibility of the early life stages of G. barbata to temperature-induced stress and provide valuable insights into the potential consequences of rising seawater temperatures in the Mediterranean. Full article

Ship trajectory prediction is essential for ensuring safe route planning and to have advanced warning of the dangers at sea. With the development of deep learning, most of the current research has explored advanced prediction methods based on historical spatio-temporal Automatic Identification System (AIS) data. However, environmental factors such as sea wind and visibility also affect ship navigation in real-world maritime shipping. Therefore, developing reliable models utilizing multimodal data, such as AIS and environmental data, is challenging. In this research, we design an adaptive multimodal vessel trajectory data prediction model (termed AMD) based on satellite AIS and environmental data. The AMD model mainly consists of an AIS-based extraction network, an environmental-based extraction network, and a fusion block. In particular, this work considers multimodal data such as historical spatio-temporal information and environmental factors. Time stamps and distances are correlated with AIS and environmental data, and a multilayer perceptron and gated recurrent unit networks are used to design multimodal feature extraction networks. Finally, the fusion block realizes the fusion output of multimodal features to improve the reliability of the AMD model. Several quantitative and qualitative experiments are conducted using real-world AIS and multimodal environmental datasets. Numerous experimental results prove that prediction performance using multimodal data can ensure satisfactory accuracy and reliability while exhibiting a positive impact on improving maritime transport services. Full article

The spatial distribution of sediments on the seafloor reflects the various dynamic processes involved in the marine realm. To analyze sediment transport patterns in the North Aegean Sea, 323 surficial samples were obtained and studied. The granulometry data revealed a diverse range of grain sizes of surficial sediments, ranging from purely sandy to clay. The predominant size classes were silt and muddy sand, followed by sandy silt and mud. However, there were very few samples that fell within the clay classes. The sorting coefficient ranged from 0.21 to 5.48, while skewness ranged from −1.09 to 1.29. The sediment transport patterns were analyzed based on the grain-size parameters (mean, sorting, and skewness). The results showed the variability of flow parameters involved in sediment distribution. River influx and longshore drift near the shoreline are the most significant factors affecting sediment transport. At the open sea, sediment distribution is mainly controlled by general water circulation patterns, especially by the outflow of low-salinity waters from the Black Sea through the Dardanelles and the Marmara Sea. The heterogeneity of sediment textural parameters across the study area suggests that seafloor sediments are further reworked in areas where water masses are highly energetic. It can be concluded that open sea water circulation controls sediment distribution patterns at the open shelf, while close to the coast, river discharge plays a key role. Full article

Addressing the automatic berthing task for vessels, this study introduces the Flow Matching Double Section Bezier Berth Method (FM-DSB) for handling downstream and upstream berthing instructions. By considering the orientation relationship between the direction of water flow and the berth, combined with berthing modes, the algorithm determines the vessel’s entry angle into the berth and plans the berthing path using double-section Bezier curves. Effective control of vessel speed post-path determination is essential. Therefore, based on the response of vessels to propeller inputs, this study introduces the Berthing Path Velocity Matching Method (BPVM). The BPVM ensures speed matching along the berthing path through analysis of vessel acceleration and deceleration capabilities. Subsequently, simulation experiments are conducted to validate the planning algorithm for both long-distance and short-distance berthing. Furthermore, the feasibility and effectiveness of the berthing path are verified using a dual-loop path tracker based on the planned results. Experimental outcomes illustrate the adaptability of the proposed algorithm in planning berthing paths that align with vessel motion characteristics, effectively guiding vessels into berths through the designed dual-loop control system. Full article

This paper examines hybrid threats to maritime transportation systems and their governance responses; focusing on the congested Straits of Malacca and Singapore (SOMS) as an illustrative case study. The methodology combines secondary sources with primary data from 42 expert interviews, a 28 respondent survey, and two maritime security roundtables. Key findings were that ships’ critical systems are increasingly interconnected, yet aging IT infrastructure and minimal cybersecurity awareness among crews heighten risks. Meanwhile, regional terrorist groups have previously targeted shipping and shown considerable skill in exploiting online tools, aligning with broader calls for jihadist violence. Furthermore, opportunistic piracy persists in the SOMS with the potential to disrupt shipping. Experts confirmed that maritime cybersecurity lags behind other critical infrastructure sectors and needs updated governance. Initial International Maritime Organization (IMO) guidelines lack specificity but revisions and updated IMO guidance are in process, while Port state implementation of maritime cybersecurity standards varies. Crucially, information sharing remains inadequate, even as recorded attacks increase. Findings underscore that although major hybrid incidents have not occurred, simulations and threat actors’ capabilities demonstrate potential for catastrophic collisions or cascading disruption in congested waterways. Mitigating factors like redundancy and crew training are deficient currently. Some alignment between SOMS states on maritime security cooperation exists, but not on cyber threats specifically. Key recommendations include an anonymous cyber attack reporting system, reinforced training and shipboard systems, and consolidated regional frameworks. Until these priorities are addressed, the analysis concludes that hybrid vulnerabilities in this vital global chokepoint remain a serious concern. Full article

The wave–current–seabed interaction problem is studied by using a coupled-mode system developed for modeling wave scattering by non-homogeneous, sheared currents in variable bathymetry regions. The model is based on a modal series expansion of wave velocity based on vertical eigenfunctions, dependent on local depth and flow parameters, including propagating and evanescent modes. The latter representation is able to accurately satisfy the wave flow continuity condition and the no-entrance boundary condition on the sloping parts of the seabed. A new derivation of a simplified nonlinear system is introduced using decomposition to a mean flow and a perturbative wave field. To force the system to consider incoming waves at the inlet, boundary knowledge of periodic, travelling nonlinear water waves over a flat bottom is required. For this purpose, specific solutions are derived using the semi-analytical method based on the stream function formulation, for cases of water waves propagating above linearly and exponentially sheared currents. Results obtained by the application of the CMS concerning the propagation of waves and currents—in particular, examples characterized by depth inhomogeneities—are presented and discussed, illustrating the applicability and performance of the method. Full article

Enhancing the production capacity of natural gas hydrates (NGHs) is critical for its commercial development. Complex structure wells may efficiently increase drainage areas while enhancing exploitation efficiency. Based on the field data of China’s first offshore NGH test production, the numerical method was used to analyze the production performance of different complex structure well types by continuous depressurization production for 360 days under the preconditions of fixed effective completion length of 300 m and a pressure difference of 6 MPa. Results indicated that the complex structure well types deployed at the three-phase layer demonstrated superior production performance within 240 days of production; the DLW2 and HW2 well types stood out, with an average gas production rate Q_g reaching 43,333 m³/d and a specific production index J of 24.1. After 360 days of production, benefiting from multi-layer combined production, the Cluster vertical well deployed at the multi-layer had the best production performance, with an average Q_g of 34,444 m³/d and a J-index of 19.1. The research results provided insights into the complex structure well-type selection strategy for NGH depressurization in this sea area. Full article

The article presents observations of near-inertial internal waves (NIWs) in the slope waters of the Black Sea in winter and summer. Rotary spectral analysis of a time series of sea current velocity measurements revealed the prevailing anticyclonic component of the motions near the local inertial frequency f. The clockwise rotation of the velocity vector with depth implies that the NIWs propagate downwards. The amplitude of NIWs usually was 0.1–0.2 m s⁻¹. NIWs were observed in the layer of the permanent pycnocline and the seasonal pycnocline, which attenuate below depths of 160 m and 80 m in winter and summer, respectively. The amplitude of the near-inertial kinetic energy (NIKE) showed a close relationship with vertical stratification. During winter, NIKE exhibited maximum values in the layer of the permanent pycnocline, whereas, in summer, it was primarily observed in the seasonal pycnocline layer. The near-inertial oscillations were generally more energetic in winter. Full article

Underwater object detection is crucial in marine exploration, presenting a challenging problem in computer vision due to factors like light attenuation, scattering, and background interference. Existing underwater object detection models face challenges such as low robustness, extensive computation of model parameters, and a high false detection rate. To address these challenges, this paper proposes a lightweight underwater object detection method integrating deep learning and image enhancement. Firstly, FUnIE-GAN is employed to perform data enhancement to restore the authentic colors of underwater images, and subsequently, the restored images are fed into an enhanced object detection network named YOLOv7-GN proposed in this paper. Secondly, a lightweight higher-order attention layer aggregation network (ACC3-ELAN) is designed to improve the fusion perception of higher-order features in the backbone network. Moreover, the head network is enhanced by leveraging the interaction of multi-scale higher-order information, additionally fusing higher-order semantic information from features at different scales. To further streamline the entire network, we also introduce the AC-ELAN-t module, which is derived from pruning based on ACC3-ELAN. Finally, the algorithm undergoes practical testing on a biomimetic sea flatworm underwater robot. The experimental results on the DUO dataset show that our proposed method improves the performance of object detection in underwater environments. It provides a valuable reference for realizing object detection in underwater embedded devices with great practical potential. Full article

Augmented reality (AR) technology has emerged as a promising solution that can potentially reduce head-down time and increase situational awareness during navigation operations. It is also useful for remote operation centers where video feeds from remote ships can be “augmented” with data and information. In this article, we introduce a user interface design concept that supports ship navigation by showing data about points of interest in AR. This approach enables users to view and interact with relevant data in the maritime environment by bridging the gap between digital information and real-world features. The proposed concept can provide operational data from various maritime systems, such as radar, GPS, AIS, or camera systems, empowering users with a wealth of information about their surroundings. Developed through an iterative user-centered design process, it was built as an extension to the OpenBridge design system, an open-source platform facilitating consistent design in maritime workplaces. Furthermore, we use this concept to propose a design framework that paves the way for establishing new standards for AR user interface design in the maritime domain. Full article

Offshore platforms are important infrastructures that often face severe environmental conditions, such as corrosion, throughout their lifetime. This can continuously decrease their structural robustness. Despite the availability of many anti-corrosion strategies, there is still a need for a sound management scheme that can systematically address the lifetime operation of offshore platforms under corrosion. To address this, the work here proposes a corrosion- and repair-based reliability framework for the lifetime operation of offshore platforms. A fixed offshore platform is designed based on current design codes for severe environmental conditions in a given return period, and the effect of corrosion on the structure’s serviceability is modeled. The results show that the extent of the corrosion depth and damage in different years highly affects the ability of a repair to restore a damaged element to its original design strength. The results also show that the residual reliability of the structural members under the splash zone becomes almost zero after the first 10 years of the operation period, implying that these members require quick repair strategies. This study establishes a management program for fixed offshore platforms subjected to long-term corrosion by performing reliability analyses on the components of the platforms and evaluating the maintenance of the components in the splash zone. In the absence of commonly accepted contemporary industry practice standards, this study proposes a corrosion growth model based on API-RP-2A, DNV, and NORSOK standards that can effectively evaluate code-based structural designs. The framework developed here can help offshore platform owners in their decision-making process for corrosion-based safety analysis. Full article

In response to the constant power negative impedance characteristics on the load side of a ship DC microgrid, leading to voltage oscillation issues in the DC bus, this paper proposes a control optimization method based on impedance reshaping using bus voltage feedback. First, a simplified small-signal diagram of a lithium battery energy storage system converter is analyzed. Combining active damping control technology, an impedance regulator is introduced, and its parameters are optimized to effectively reduce the output impedance magnitude on the power source side. Subsequently, a ship DC microgrid simulation model is constructed using MATLAB R2022a/Simulink for validation, and comparative analysis is conducted on the anti-interference ability of the DC bus voltage before and after impedance reshaping. Finally, a model is built on a semi-physical simulation platform to experimentally verify the proposed method. The research results indicate that the proposed control optimization method can effectively increase the system’s stability margin, suppress DC bus oscillations, and enhance the anti-interference ability of the ship DC microgrid’s bus voltage when facing significant power load variations. Full article

Predicting wind speed over the ocean is difficult due to the unequal distribution of buoy stations and the occasional fluctuations in the wind field. This study proposes a dynamic graph embedding-based graph neural network—long short-term memory joint framework (DGE-GAT-LSTM) to estimate wind speed at numerous stations by considering their spatio-temporal information properties. To begin, the buoys that are pertinent to the target station are chosen based on their geographic position. Then, the local graph structures connecting the stations are represented using cosine similarity at each time interval. Subsequently, the graph neural network captures intricate spatial characteristics, while the LSTM module acquires knowledge of temporal interdependence. The graph neural network and LSTM module are sequentially interconnected to collectively capture spatio-temporal correlations. Ultimately, the multi-step prediction outcomes are produced in a sequential way, where each step relies on the previous predictions. The empirical data are derived from direct measurements made by NDBC buoys. The results indicate that the suggested method achieves a mean absolute error reduction ranging from 1% to 36% when compared to other benchmark methods. This improvement in accuracy is statistically significant. This approach effectively addresses the challenges of inadequate information integration and the complexity of modeling temporal correlations in the forecast of ocean wind speed. It offers valuable insights for optimizing the selection of offshore wind farm locations and enhancing operational and management capabilities. Full article

Changes in the masses of icebergs due to deterioration processes affect the drift of icebergs and should be taken into account when assessing iceberg risks in the areas of offshore development. In 2022 and 2023, eight laboratory experiments were carried out in the wave tank of the University Centre in Svalbard to study the melting of icebergs in sea water under calm and rough conditions. In the experiments, the water temperatures varied from $0 ℃$ to $2.2 ℃$. Cylindrical iceberg models were made from columnar ice cores with a diameter of 24 cm. In one experiment, the iceberg model was protected on the sides with plastic fencing to investigate the iceberg’s protection from melting when towed to deliver fresh water. The iceberg masses, water temperatures, and ice temperatures were measured in the experiments. The water velocity near the iceberg models was measured with an acoustic Doppler velocimeter. During the experiments, time-lapse cameras were used to describe the shapes and measure the vertical dimensions of the icebergs. Using experimental data, we calculated the horizontal dimensions of icebergs, latent heat fluxes, conductive heat fluxes inside the iceberg models, and turbulent heat fluxes in water as a function of time. We discovered the influence of surface waves and water mixing on the melt rates and found a significant reduction in the melt rates due to the lateral protection of the iceberg model using a plastic barrier. Based on the experimental data obtained, the ratio of the rates of lateral and bottom melting of the icebergs and lateral melting of the icebergs under wave conditions was parametrized depending on the wave frequency. Full article

Electric ships have been developed in recent years to reduce greenhouse gas emissions. In this system, inverters are the key equipment for the permanent-magnet synchronous motor (PMSM) drive system. The cascaded insulated-gated bipolar transistor (IGBT)-based H-bridge inverter is one of the most attractive multilevel topologies for modern electric ship applications. Usually, the fault-tolerant control strategy is designed to keep the ship in operation for a certain period. However, the fault-tolerant control strategy with hardware redundancy is expensive and slow in response. In addition, after fault-tolerant control, the ship’s PMSM may experience shock and overheating, and IGBT life is reduced due to uneven switching frequency distribution. Therefore, a stratified reconfiguration carrier disposition Sinusoidal Pulse Width Modulation (SPWM) fault-tolerant control strategy is proposed. The proposed strategy can achieve fault tolerance without any extra hardware. A reconfiguration carrier is applied to improve the fundamental amplitude of inverter output voltage to maintain the operation of the ship’s PMSM. In addition, the available states of faulty H-bridge are fully used to contribute to the output. These can improve the life of IGBTs by reducing and balancing the power loss of each H-bridge. The principles of the proposed strategy are described in detail in this study. Taking a cascaded H-bridge seven-level inverter as an example, simulation and experimental results verify that the proposed strategy, in general, has a potential future application on electric ships. Full article

Wind is a significant factor influencing the stability of breakwater armor stones. However, few existing studies have considered the effects of wind on these structures. In this study, two-dimensional laboratory experiments were conducted to examine the effect of wind on the stability of breakwater armor stones. The stability factor ($K_D$) of the armor stone, fluid velocity, runup, and rundown were observed under the action of waves and winds. A wind turbine was installed in front of the physical model of the breakwater to generate extreme wind conditions of 5.5 and 12 m/s. The results showed that $K_D$ decreased by 42.18% at 5.5 m/s and 57.82% at 12 m/s compared with that without wind. The maximum runup and rundown heights increased with wind velocity, following a Rayleigh distribution. The fluid velocity distribution conformed to a normal distribution, with the mean velocity directed offshore. Many studies have suggested that runup, rundown, and fluid velocity are the main factors affecting the stability of breakwater armor stones. The analysis revealed that wind affects these factors and lowers the stability coefficient. These wind-induced hydrodynamic changes suggest the need for a detailed hydrodynamic review of wind-wave conditions. Full article

Tidal stream turbines (TSTs) harness the kinetic energy of tides to generate electricity by rotating the rotor. Biofouling will lead to an imbalance between the blades, resulting in imbalanced torque and voltage across the windings, ultimately polluting the grid. Therefore, rotor condition monitoring is of great significance for the stable operation of the system. Image-based attachment detection algorithms provide the advantage of visually displaying the location and area of faults. However, due to the limited availability of data from multiple machine types and environments, it is difficult to ensure the generalization of the network. Additionally, TST images degrade, resulting in reduced image gradients and making it challenging to extract edge and other features. In order to address the issue of limited data, a novel non-data-driven edge detection algorithm, indexed resemble-normal-line guidance detector (IRNLGD), is proposed for TST rotor attachment fault detection. Aiming to solve the problem of edge features being suppressed, IRNLGD introduces the concept of “indexed resemble-normal-line direction” and integrates multi-directional gradient information for edge determination. Real-image experiments demonstrate IRNLGD’s effectiveness in detecting TST rotor edges and faults. Evaluation on public datasets shows the superior performance of our method in detecting fine edges in low-light images. Full article

This paper focuses on optimizing the deployment plan for standby points of professional rescue vessels based on the data of maritime incidents in the Beihai area of China. The primary objective is to achieve multi-level and multiple coverage of the jurisdictional waters of the Beihai Rescue Bureau. Models including the coverage quality of the jurisdictional waters, the coverage quality in high-risk areas, the maximum coverage of jurisdictional areas, and the maximum coverage of high-risk areas are constructed and solved using 0–1 integer programming. The optimal plan for eight standby points and their corresponding deployment plans for rescue vessels are obtained. A comparison with the current site selection plan of the Beihai Rescue Bureau validates the superiority of the proposed deployment plan for rescue vessel standby points in this paper. Full article

During the last 50 years, the increase in the efforts of the longline fleet in the Eastern Pacific Ocean (EPO) resulted in an increase in the capture of the swordfish Xiphias gladius. We analyzed a historical database of swordfish catches (1980–2020) reported by the industrial longline fleet to the Inter-American Tuna Tropical Commission (IATTC), which contains catch and effort data aggregated in monthly quadrants of 5° × 5° in the EPO. The swordfish catch reported by the international longline fleets was analyzed to evaluate the spatiotemporal variation of the catch and the different phases through which this important fishery has gone through. Different statistical models such as the Generalized Additive Mixed Model (GAMM) and the breaks for additive season and trend BFAST algorithm were used for the decomposition of the time series. Results indicated that the effort directed towards the swordfish increased in recent years and that the highest catches occurred by Peru. The adjusted GAMM explained 80% of the total temporal variation of the swordfish catch per unit effort CPUE and had a 90% prediction efficiency. The BFAST algorithm found three break points in the time series of the standardized CPUE, points associated with abrupt changes, thus defining four distinct periods, all of them statistically significant. According to the BFAST model, the current trend of swordfish CPUE is upward. It is recommended to take this finding with caution to obtain the sustainable exploitation of the swordfish fishery resource. Full article

Hyperspectral technology has been playing a leading role in monitoring oil spills in marine environments, which is an issue of international concern. In the case of monitoring oil spills in local areas, hyperspectral technology of small dimensions is the ideal solution. This research explores the use of encoded hyperspectral signatures to develop automated classifiers capable of discriminating between polluted and clean water and distinguishing between various types of oil. The overall objective is to leverage these classifiers to be able to improve the performance of conventional systems that rely solely on hyperspectral imagery. The acquisition of the hyperspectral signatures of water and hydrocarbons was carried out with a spectroradiometer. The range of the spectroradiometer used in this study covers the ranges between [350–1000] (visible near-infrared) and [1000–2500] (short-wavelength infrared). This gives detailed information regarding the targets of interest. Different neural autoencoders (AEs) have been developed to reduce inputs into different dimensions, from 1 to 15. Each of these encoded sets was used to train decision tree (DT) classifiers. The results are very promising, as they show that the AE models encoded data with correlation coefficients above 0.95. The classifiers trained with the different sets provide accuracies close to 1. Full article

To enhance the safety of the in-water sinking operation for an integrated system, including a bucket foundation (BF), tower, and rotor nacelle assembly (RNA), in complex marine environmental conditions, a model test of in-water sinking for an offshore wind turbine and bucket foundation (OWT–BF) is conducted. The motion behavior of the OWT–BF and the sling tensions during the in-water sinking process are investigated, and the numerical method is validated through test results. The results demonstrate a positive correlation between the wave height and motion response of the OWT–BF. The most critical stage of the in-water sinking operation occurs when the top cover of the bucket is fully submerged, resulting from the substantial cross-sectional difference between the bucket base and the transition section. Furthermore, the closer the OWT–BF is to the seabed, the less it is affected by waves in terms of motion response. It is advisable to conduct the in-water sinking operation of the OWT–BF in sea states with wave heights below 1.5 m. Simultaneously, slings can efficiently control the motion response of the OWT–BF, thereby enhancing the safety of the sinking operation. Full article

In recent years, advanced methods and smart solutions have been investigated for the safe, secure, and environmentally friendly operation of ships. Since data acquisition capabilities have improved, data processing has become of great importance for ship operators. In this study, we introduce a novel approach to ship machinery monitoring, employing generative adversarial networks (GANs) augmented with failure mode and effect analysis (FMEA), to address a spectrum of failure modes in diesel generators. GANs are emerging unsupervised deep learning models known for their ability to generate realistic samples that are used to amplify a number of failures within training datasets. Our model specifically targets critical failure modes, such as mechanical wear and tear on turbochargers and fuel injection system failures, which can have environmental effects, providing a comprehensive framework for anomaly detection. By integrating FMEA into our GAN model, we do not stop at detecting these failures; we also enable timely interventions and improvements in operational efficiency in the maritime industry. This methodology not only boosts the reliability of diesel generators, but also sets a precedent for prescriptive maintenance approaches in the maritime industry. The model was demonstrated with real-time data, including 33 features, gathered from a diesel generator installed on a 310,000 DWT oil tanker. The developed algorithm provides high-accuracy results, achieving 83.13% accuracy. The final model demonstrates a precision score of 36.91%, a recall score of 83.47%, and an F1 score of 51.18%. The model strikes a balance between precision and recall in order to eliminate operational drift and enables potential early action in identified positive cases. This study contributes to managing operational excellence in tanker ship fleets. Furthermore, this study could be expanded to enhance the current functionalities of engine health management software products. Full article