Underwater images often suffer from color casts, insufficient contrast, and blurred details due to wavelength-dependent absorption and scattering, which limits their use in marine observation and underwater target recognition. Therefore, it remains challenging to jointly improve color fidelity, contrast, and detail visibility under varying water types and illumination. To address these issues, this paper proposes an underwater image enhancement method that integrates RGB Space color-cast correction with Lab Space luminance-chrominance synergistic enhancement. First, channel compensation is performed in the RGB space according to color-cast types, together with a Gray-World white-balance strategy, to suppress severe color bias and recover more natural tones. Subsequently, synergistic enhancement is conducted in the Lab space as follows: an improved Auto-MSR is applied on the L channel for contrast restoration while suppressing noise amplification, and an edge-aware detail enhancement module is incorporated to reinforce structural textures. Finally, chrominance balancing is applied to A and B channels to further improve color consistency and rendition. Experiments on the UIEB and UIQS datasets demonstrate that the proposed method achieves the best performance among the methods considered on AG, EI, and CCF. Specifically, it attains AG = 10.716, EI = 107.197, and CCF = 46.935 on UIEB, as well as AG = 10.136, EI = 103.780, and CCF = 39.433 on UIQS. These results indicate clear advantages in image clarity, edge detail preservation, and color rendition. Future work will focus on extending the proposed method to real-time underwater video enhancement.
This paper presents an energy-optimized path planning approach for fully actuated autonomous underwater vehicles (AUVs) in three-dimensional ocean environments to enhance their operational range and endurance. A fully actuated AUV is characterized by its high degrees of freedom and precise controllability. Using real terrain data, we construct environmental models incorporating a Lamb vortex and random obstacles. We develop a mathematical model of the AUV’s total energy consumption, accounting for constraints imposed by its fully actuated design and extensive maneuverability. To minimize energy usage, we propose an energy-optimized path planning algorithm that combines energy-optimized particle swarm optimization (EOPSO) and sequential quadratic programming (SQP). The proposed method identifies the optimal path for energy consumption and the corresponding optimal surge speed. The efficacy of the algorithm in optimizing the total energy consumption of the AUV is demonstrated through the simulation of various scenarios. In comparison to other algorithms, paths planned by this algorithm are shown to have superior robustness and optimized energy consumption.
Sergej Jakovlev, Tomas Eglynas, Valdas Jankunas
et al.
The damage to shipping containers during port handling operations continues to pose a significant challenge that adversely affects operational efficiency, equipment integrity, and supply chain accountability. This study utilises real-world measurement data gathered through accelerometers to examine the occurrence and dynamics of physical impacts, particularly side and rear collisions, during the handling of containers at Klaipėda City Port. The research prioritises two critical scenarios: side impacts during stacking operations with reach stackers and rear impacts during trailer loading procedures. Impact events are meticulously recorded and analysed to ascertain the magnitudes of acceleration across multiple axes. This reveals that side impacts produce significantly greater forces, particularly in the lateral direction, than rear impacts. This study employs sensor-based monitoring, advanced data visualisation techniques, and structured scenario analysis to delineate the variability and intensity of mechanical interactions during these operations. The findings emphasise the structural stress that containers experience and underscore the importance of embedded monitoring technologies for real-time event detection and damage prevention. The results contribute to the expanding body of knowledge that supports the digital transformation of container terminals and furnish actionable insights for enhancing handling protocols, informing insurance assessments, and improving safety measures within both automated and conventional port environments.
A great ellipse route (GER), as one of the fundamental routes for ocean voyages, directly influences the actual voyage distance and the complexity of vessel maneuvering through the location and number of its waypoints. Against the backdrop of global warming, the melting of Arctic sea ice has accelerated the opening of the Arctic shipping route. This paper addresses the issue of how to reasonably segment and adopt rhumb line routes to approximate the GER in the special navigational environment of the Arctic. Using historical routes, recommended routes, and geospatial data that have passed through the Arctic shipping lane as constraints, this paper proposes a waypoint optimization model based on an adaptive hybrid particle swarm optimization-genetic algorithm (AHPSOGA). Additionally, by integrating Arctic remote sensing ice condition data and the Polar Operational Limit Assessment Risk Indexing System (POLARIS), a safety assessment model tailored for this route has been developed, enabling the quantification of sea ice risks and dynamic evaluation of segment safety. Experimental results indicate that the proposed waypoint optimization model reduces the number of waypoints and voyage distance compared to recommended routes and conventional shipping industry methods. Furthermore, the AHPSOGA algorithm achieves a 16.41% and 19.19% improvement in convergence speed compared to traditional GA and PSO algorithms, respectively. In terms of computational efficiency, the average runtime is improved by approximately 12.00% and 14.53%, respectively. The risk levels of each segment of the optimized route are comparable to those of the recommended Northeast Passage route. This study provides an effective theoretical foundation and technical support for intelligent planning and decision-making for Arctic shipping routes.
This study employs a one-way coupling method based on CFD and FEA to evaluate and compare the structural strength of a planing hull under calm water and wave navigation conditions. A high-speed planing hull is selected as the research object. The wave loads under different navigation states are computed using the CFD method, and the pressure distribution on the hull bottom is mapped to a finite element model for structural strength analysis. The study investigates the variations in hull bottom pressure and structural stress under three navigation states: displacement, semi-planing, and planing. Additionally, the stress characteristics under wave conditions, including hogging and sagging states, are simulated and evaluated. By comparing the results with those obtained from the conventional empirical formula method, the accuracy and advantages of CFD in wave load calculations are validated, and the localized stress concentration areas under calm planing conditions are identified. The results demonstrate that this method not only enhances the precision of wave load calculations but also provides an effective approach for structural strength evaluation in planing hull design, thereby improving the technical and economic performance of planing hulls.
Sarah Karoline Rodrigues, Wilson Thadeu Valle Machado, João Barreira
et al.
The environmental condition of surface sediments in Sepetiba Bay is influenced by trace metals derived from human activities. Four sediment cores were collected from both the inner (Coroa Grande and Enseada das Garças) and outer (Guaratiba and Marambaia) areas of the bay. Trace metals content varied considerably, with the highest values recorded at Enseada das Garças (e.g., Cd: 2.4 mg kg<sup>−1</sup>; Zn: 393 mg kg<sup>−1</sup>), and lowest at Marambaia Barrier Island (e.g., Cd: <0.001 mg kg<sup>−1</sup>; Zn: 3.35 mg kg<sup>−1</sup>). Mean annual metal fluxes have increased since the 1950s, especially for Cd (from 8 × 10<sup>−5</sup> to 0.4 g m<sup>−5</sup> y<sup>−1</sup>) and Zn (from 4.0 to 68.7 g m<sup>−2</sup> y<sup>−1</sup>). However, a decreasing trend has been observed since the 2000s. Pollution indexes indicated that Cd poses the highest contamination and ecological risk in recent layers of the inner bay, and moderate risk at the Marambaia Barrier Island (maximum values of Cd: 0.67 mg kg<sup>−1</sup> and Zn: 94.9 mg kg<sup>−1</sup>). Metal distribution patterns are influenced by mineral phases and sediment dynamics. Findings emphasize the need to monitor other metals like Cu and Pb, besides the historical heavy loadings of Cd and Zn, considering recent industrial and port expansions in the Sepetiba Bay region.
Jianhao Liang, Yaning Wang, Shangfeng Zhang
et al.
This study has determined the period of sedimentation of the Lingshui Formation as the Oligocene (Rupelian-Chattian) through biostratigraphic data, including planktonic foraminifera zonation. The astronomical timescale framework for the Lingshui Formation was accurately constructed by integrating geophysical logging data and employing a multidisciplinary approach that includes time series analysis, cyclostratigraphy, astronomical dating, and Power Ratio Accumulation (PRA) methods. Sensitivity analysis of PRA has shown that natural gamma (GR) is the optimal paleoclimatic proxy, laying the foundation for subsequent analyses. The optimal sedimentation rate for the Lingshui Formation, determined by combining the coefficient of correlation (COCO) method with PRA analysis, is 5–5.4 cm/kyr. The duration of the Lingshui Formation was established at 5.02 Ma (28.52 Ma–23.5 Ma) based on time series analysis and astronomical tuning. The sediment noise model has revealed that the ~1.2 Myr obliquity modulation period has a significant impact on sea-level changes, further confirming the stratigraphic control of astronomical forcing on the sedimentation rate of the Lingshui Formation. This study establishes a high-precision astronomical timescale framework for the Lingshui Formation and provides a robust methodology, offering scientific basis for the research in astronomical chronostratigraphy and cycle stratigraphy, which has significant potential implications.
Maritime UAV path planning is a key link in realizing the intelligence of maritime emergency transportation, providing key support for fast and flexible maritime accident disposal and emergency material supply. However, most of the current UAV path planning methods are designed for land environments and lack the ability to cope with complex marine environments. In order to achieve effective path planning for UAV in marine environments, this paper proposes a Directional Drive-Rotation Invariant Quadratic Interpolation White Shark Optimization algorithm (DD-RQIWSO). First, the directional guidance of speed is realized through a directional update strategy based on the fitness value ordering, which improves the speed of individuals approaching the optimal solution. Second, a rotation-invariant update mechanism based on hyperspheres is added to overcome the tracking pause phenomenon in WSO. In addition, the quadratic interpolation strategy is added to enhance the utilization of local information by the algorithm. Then, a wind simulation environment based on the Lamb–Oseen vortex model was constructed to better simulate the real scenario. Finally, DD-RQIWSO was subjected to a series of tests in 2D and 3D scenarios, respectively. The results show that DD-RQIWSO is able to realize path planning under wind environments more accurately and stably.
The trans-medium water entry process of vehicles is often accompanied by multiphase flow, cavitation, phase change, and turbulence instability, which not only heighten the complexity of the flow field, but also render the forces highly unsteady and nonlinear. A numerical model for the water entry process of vehicles was developed. The volume of fluid(VOF) model was employed to capture the gas-liquid interface, and the Schnerr-Sauer model was utilized to describe the cavitation that occurred during the trans-medium process. The simulation of the water entry process of the trans-medium vehicle under different ventilation flows and deflection angles of the cavitator was carried out to investigate the flow field and cavity evolution laws during the trans-medium process. In addition, the fluid dynamics characteristics, as well as the kinematic characteristics of the vehicle during trans-medium process were analyzed. The simulation results show that the vehicle will present two different attitude change modes with the change of the ventilation flow during the water entry process: the increasing angular velocity leveling mode and the periodical pitching-type leveling mode. The water entry leveling process of the vehicle in different modes will show different motion characteristics. Moreover, an increase in the deflection angle of the cavitator and a decrease in the ventilation flow can improve the attitude change rate of the vehicle during the trans-medium water entry process.
Bays are extensively impacted by human activities, and an accurate assessment of ecological quality is crucial for the environmental management and protection of bays. Most studies indicate that evaluating the ecological quality of bays using a single index presents challenges. In our study, we used five benthic biotic indices and a composite index to assess the ecological quality of three bays in South Korea. Our results revealed disparities in the ecological quality status assessment using five benthic biotic indices. The composite index performed better than the other benthic biotic indices in a principal coordinate analysis. Significant differences were observed between the values classifying stations as having an acceptable or unacceptable final ecological quality in terms of species indices (except for the Pielou’s evenness index) and the abundance of opportunist species (<i>p</i> < 0.05). Consequently, we advocate for using a composite index to assess the ecological quality of the bays of the West Sea of South Korea. Furthermore, our study provides valuable information for marine ecological management and policy formulation in Korea and offers recommendations for using the composite index in future research.
An improved star-shaped honeycomb (ISSH) is a kind of honeycomb structure with excellent performance. The main objective of this study was to provide some ideas for the optimization of the ISSH structure in ships. As a result, 2D-ISSH specimens were fabricated using 3D printing technology, and a quasistatic compression test was carried out to investigate the deformation mode and mechanical properties. The experimental results showed that the 2D-ISSH structure exhibited “V”-shaped and “-”-shaped deformation patterns with a double-platform stress stage. To further utilize the excellent performance of the structure and obtain a better negative Poisson’s ratio effect and broader application, based on the properties of the 2D-ISSH specimen, a 3D-ISSH structure was proposed and a finite element simulation was carried out. The simulation results of the 3D-ISSH structure showed different deformation patterns, including “X”- shaped and “-”-shaped patterns. According to the deformation mechanism of typical cells, the stress formula for the 3D-ISSH double platform was derived, and the theoretical results agreed well with the numerical results. The effects of the structural design, materials, and dimensions on the mechanical properties, such as the energy absorption and negative Poisson’s ratio, of the ISSH and similar structures were explored. The combined performance of various honeycombs was evaluated from multiple perspectives.
The purpose of this paper is to investigate and evaluate the ship engine room fire spreading characteristics based on the effect of firefighting interventions. The large eddy simulation (LES) and theoretical models are employed to simulate a fire scene in the engine room. The fire spreading characteristics and the mechanism of the use of a fine water mist are obtained by varying the ventilation conditions and parameters of the water sprinkler. The results show that the reason why a pool fire can be more easily extinguished as the spray speed increases is because the water mist with a higher spray speed has a larger spray area. Meanwhile, the temperature in the engine room would drop more rapidly with the increasing spray area due to the higher evaporation rate. Furthermore, the arrangement of the ventilation conditions had an obvious effect on the fire spreading characteristics, as the depletion of the combustion medium affects the combustion situation.
The paper examines the sampling effectiveness of seabin devices and the composition of floating marine litter in port areas. Sampling was carried out from May to September 2021 in Port of Cristo and Port of Colonia de Sant Jordi on Mallorca Island, Spain. This is the first study of the composition of floating marine litter in the ports of Mallorca collected by seabin devices. During the study, 15,899 items and 336 kg of litter were collected and analyzed. The results indicate that seabin effectively collects floating litter from sea surfaces different in size (2 mm to 40 cm). Microplastics (60.8%) were the most commonly found litter, followed by soft plastic items > 5 mm (11.6%) and unidentified hard plastic items > 5 mm (9.6%). Significantly more marine litter was collected in the Port of Cristo (78.6%), compared to the collection of one device in the Port of Colonia de Sant Jordi (21.4%). Time series analysis showed that the average seasonal component was highest in May (68% above baseline). The linear time trend with an R2 of 52.25% indicated the acceptable significance of the model.
The double-row and double-chamfered aquaculture tank is a special tank structure of the aquaculture ship. The tank sloshing of this structure is coupled with the hull motion, which has an important impact on the safety of the hull motion. In the present study, research on the tank sloshing and hull motion response of aquaculture ships was conducted based on the model seakeeping and tank sloshing tests in regular waves. The test results were compared with the numerical simulation results of solid loading without sloshing. The results showed that the numerical simulation of the pitch motion was consistent with the amplitude-frequency response curve of the experimental results. Under certain transverse wave conditions, a large discrepancy existed between the amplitude-frequency response curve of the heave motion by the numerical simulation and the test results, and the roll motion differed most from the experimental result. Severe roll resonance occurred when the wave length-ship length ratio was 0.6. The roll motion amplitude was increased by 183.2%. Therefore, compared with aquaculture ships without sloshing, the sloshing of the tank has little effect on the pitch but has a great impact on the roll and heave motions, with the most significant effect on the roll motion.
ObjectivesThe vibration-isolation thrust bearing is a new device for the longitudinal vibration control of propulsion shafts. Experimental results show that the dynamic transmission characteristics of the propulsion shaft are quite different from those of theoretical calculation predictions. Analysis shows that there is serious vibration energy leakage from the vibration-isolation thrust bearing. For better understanding the cause of poor acoustical property of the system, a study is conducted with the focus upon the flexible assemblies of the thrust bearing to determine directions for optimization improvement design. MethodsThe dynamic characteristic analysis is conducted concentrated on the coil spring and coil spring cylinder which are key vibration isolation components of the thrust bearing to research the vibration energy leakage. Then, the dynamic model of the coil spring cylinder is established based on both vibration isolation theory and experiment analysis. Moreover, the dynamic characteristic test bench in vertical state is also built up. ResultsThe experimental analysis results show that the vibration resonance peak of the coil spring is sharp and smooth, while that of the coil spring cylinder is flat with more harmonic components induced by contact friction. When there is contact friction, there will be additional stiffness and damping, which significantly change the dynamic characteristics of the coil spring cylinder. ConclusionThe dynamic model of the coil spring cylinder is verified by experiments. The dynamic transmission characteristics of the coil spring can be used as an evaluation standard for design improvement. The results of this study can provide theoretical support for the design optimization and improvement of the vibration-isolation thrust bearing, which can have great significance for practical engineering.
In this study, an investigation on the hull roughness measurement of a new ship, a 160m class car ferry, was performed. The hull roughness measurement was conducted in the ferry’s pre-coated state before launching. For measurement, the TQC manual and ITTC recommendations were considered, and measurements were made in a total of 230 zones below waterline of the ship. Accordingly, the average hull roughness of the car ferry was 81μm, which is relatively low compared to 150μm, the hull roughness of a new ship proposed by the ITTC. In addition, the measurement uncertainty was calculated using the ISO guidelines, and the effect of the number of zones on the hull roughness measurement was examined. Using the measured average hull roughness, we estimated the resistance performance at the design speed of the ship. Accordingly, it was confirmed that the total resistance of the new ship was reduced by approximately 2% owing to a decrease in its frictional resistance increase.
The occurrence of contaminated materials encountered during harbour dredging is becoming increasingly problematic for harbour and port authorities. The risks to human health, wildlife and port infrastructure of exposure to such contaminants necessitates the removal or containment of such risks. As with contaminated terrestrial sites the solidification and stabilization (S/S) of this material has been proven to be an effective alternative to disposing of contaminants off-site, typically via dumping at sea or in a landfill. Research, to date, on S/S has been focused on heavily contaminated sediments in large industrial ports. However, with tightening environmental regulations, the limits of acceptable contamination are generally decreasing. This means the number of port dredging projects requiring contaminant remediation is increasing. There is now a need to examine the effectiveness of S/S on harbour sites that are mildly contaminated from both an environmental and project feasibility viewpoint. To that end, this study examines the effectiveness of various S/S mix percentages of ordinary Portland cement (OPC) and ground granulated blast furnace slag (GGBS) in retarding the leaching of contaminants from a mildly contaminated harbour site.
Cherednichenko Oleksandr, Serbin Serhiy, Dzida Marek
In this paper, we consider the issue of thermo-chemical heat recovery of waste heat from gas turbine engines for the steam conversion of associated gas for offshore vessels. Current trends in the development of offshore infrastructure are identified, and the composition of power plants for mobile offshore drilling units and FPSO vessels is analyzed. We present the results of a comparison of power-to-volume ratio, power-to-weight ratio and efficiency for diesel and gas turbine power modules of various capacities. Mathematical modeling methods are used to analyze the parameters of an alternative gas turbine unit based on steam conversion of the associated gas, and the estimated efficiency of the energy module is shown to be 50%. In the modeling of the burning processes, the UGT 25000 serial low emission combustor is considered, and a detailed analysis of the processes in the combustor is presented, based on the application of a 35-reaction chemical mechanism. We confirm the possibility of efficient combustion of associated gas steam conversion products with different compositions, and establish that stable operation of the gas turbine combustor is possible when using fuels with low calorific values in the range 7–8 MJ/kg. It is found that the emissions of NOx and CO during operation of a gas turbine engine on the associated gas conversion products are within acceptable limits.