To overcome the deficiencies of traditional ant colony optimization (ACO) in pheromone updating, local optima convergence, and path planning safety, this study proposes a global path planning algorithm based on improved ACO and turning-point refinement. The heuristic function is improved using the reciprocal of the Euclidean distance between current path nodes and the destination, along with balancing parameters for iteration number, search quality, and efficiency, thereby enhancing global and local search capabilities while avoiding local optima. An adaptive pheromone evaporation coefficient is designed by utilizing characteristics of cosine function to dynamically adjust the convergence of the proposed ant colony optimization in its early and late stages. Considering the complexity of maritime environments and practical navigation requirements, a grid-based navigation environment is constructed. An obstacle-adjacent node detection method and fixed-point approximation algorithm is proposed for turning point refinement to improve navigation safety and ensure optimized paths better conform to maritime practice. Simulation experiments demonstrate that, compared with traditional ACO and other improved algorithms, the proposed algorithm shortens the average path length by approximately 39% and reduces the average iteration number by 79%, significantly improving solution quality and convergence efficiency. It effectively alleviates issues of insufficient search directionality and susceptibility to local optima. These results verify the reliability of the proposed approach for global path planning of unmanned surface vehicles and its high efficiency in redundant waypoint optimization, thereby providing effective decision support in practical applications.

Ship motion modeling is crucial for developing intelligent control technology. Traditional modeling methods, however, have drawbacks such as a large number of parameters and insufficient precision. To address these issues, this paper focuses on the latest intelligent research and training ship "Xin-Hong-Zhuan" of Dalian Maritime University. A ship motion characteristic model is constructed using the characteristic modeling method. First, the study begins with Kalman filtering to preprocess real-ship test data. Next, the nonlinear innovation recursive least squares method with a forgetting factor is used to identify the model's parameters. Finally, turning circle tests and zigzag maneuver tests are conducted to verify the model's effectiveness and accuracy. The results show that the model has an agreement of 89.7%, fewer parameters, and higher precision than the traditional Nomoto model. This research offers a theoretical reference for applying characteristic models in navigation and is significant for improving the precision of ship motion control.

Suction pile can not only provide sufficient bearing capacity for deepwater oil and gas well construction, but also be used more and more widely in subsea production systems as the foundation of subsea structure. The stability of suction pile structure in offshore installation faces challenges due to its large span and harsh working environment and installation conditions. Taking a large suction pile with a diameter of 8 m and a total height of 19. 68 m applied to a gas field in the South China Sea as the research object, a 1∶1 finite element model was constructed. Based on the operating environment of the gas field in the South China Sea, the typical installation process of suction pile under transporting, lifting and installation during offshore construction is studied, and the worst conditions under each working condition are obtained through load calculation and analysis. The results show that the maximum stress under the transportation condition is negative transverse acceleration + vertical acceleration + Y negative wind load, and the high stress is concentrated at the fixed place between the suction pile and barge. In the lifting condition, the trapped water on the suction pile is considered for air and underwater lifting analysis. The high stress occurs at the welding point of the lifting point, which is the focus area of the field operation. The calculation of suction pile installation and inclination of manifold installation under the installation condition meets the standard requirements. Based on the above calculation, combined with the offshore installation practice, the whole offshore construction process of suction pile is safe and reliable, and the final installation precision is very high. The relevant research results can provide reference for the optimal design and offshore installation of deep-water suction piles.

Considering the rudder features of a twin-propeller and twin-rudder ship, a series of numerical simulations of rudder-force tests with different rudder sectional parameters are carried out by using the Computational Fluid Dynamics method, from which the normal force coefficients of the rudder are obtained and the effects of rudder aspect ratio and thickness ratio on the hydrodynamic performances of the rudder are analyzed. On this basis, the standard turning circle and zigzag maneuvering motions are numerically simulated with the established mathematical model of ship maneuvering motion with four degrees of freedom. The maneuvering parameters are obtained from numerical simulations and the effects of rudder aspect ratio and thickness ratio on the turning ability, course-keeping ability and yaw-checking ability of the twin-propeller and twin-rudder ship are discussed. The research findings provide reference significance for optimizing rudder geometric parameter design and improving ship maneuverability.

In order to solve the problems of low positioning accuracy, poor anti-interference performance and actuator wear due to the uncertainty of model parameters and unknown time-varying environmental interference in the control of Dynamic Positioning Vessel (DPV), an adaptive backstepping sliding mode control method based on a dynamic event triggering mechanism was proposed. Firstly, sliding mode control is combined with backstepping technology to ensure the robustness of the system to uncertainty and interference. At the same time, the adaptive law is used to estimate the unknown uncertainty term. Based on this, an adaptive backstepping sliding mode control controller is designed. Finally, a dynamic event-triggered mechanism is designed to reduce the frequency of actuator update, thereby reducing unnecessary wear and tear. In order to verify the effectiveness and stability of the proposed control method, the Lyapunov stability theory method is used to prove that all signals in the system are uniformly and ultimately bounded, and Zeno phenomenon can be effectively avoided. The simulation results further verify the superior performance and wide application prospect of the proposed control method in DPV control system.

To address global climate change and achieve the greenhouse gas reduction targets set by the International Maritime Organization (IMO), the global fleet faces complex challenges in balancing emission reduction effectiveness and economic feasibility during energy transition and fuel pathway selection, necessitating more systematic assessment and optimization of fleet-level emission reduction pathways. Existing research still lacks comprehensive comparative analysis of multi-fuel pathways, particularly systematic comparisons that balance carbon reduction effects and cost-effectiveness, making it difficult to support scientific decision-making for fleet decarbonization routes. To address these issues, a technology-economic assessment method for evaluating and optimizing shipping greenhouse gas reduction pathways is proposed. First, taking the global fleet as the research object, quantitative modeling and feature extraction of carbon reduction amounts and costs are conducted for each of the 18 preset fuel pathways. Second, a comprehensive evaluation index is established to account for both carbon reduction effects and economic feasibility, enabling coupled comparisons of multiple fuel pathways in terms of emission reduction potential and cost constraints. Combined with scenario analysis and pathway optimization mechanisms, a complete technical assessment framework is formed. The results indicate that pathways primarily based on methanol have the lowest carbon reduction costs, followed by ammonia pathways, while green methanol pathways outperform Liquefied Natural Gas （LNG)-based pathways. Green methanol and ammonia fuel pathways demonstrate the best carbon reduction performance. Considering medium-to long-term perspectives, green methanol and green ammonia can serve as optimal fuel choices, providing a feasible technical pathway for global fleet greenhouse gas reduction route planning and fuel transition decision-making.

Under the Carbon Intensity Indicator (CⅡ) rules of the International Maritime Organization (IMO), most theoretical studies manage ship carbon intensity primarily by reducing carbon emissions. However, reducing carbon emissions at the expense of ship transport work no longer aligns with the goal of carbon peaking intensity. Therefore, considering sulfur emission limits, a model was developed to determine whether fuel switching or scrubber retrofitting should be adopted. Combining with carbon intensity management, a decision model for the ship deployment and scheduling problem is proposed, subject to the constraints on sailing speed, fleet deployment, and carbon intensity compliance. To solve the proposed mixed-integer nonlinear programming model, a hybrid algorithm combining linearization and CPLEX is designed. The model is validated using five routes operated by COSCO Shipping. The results show that, compared with the genetic algorithm, the proposed hybrid algorithm increases the solution time slightly by 7.6%, while reducing the operating cost significantly by 33.4%, and all solutions satisfy the engineering constraints. Without carbon intensity management, the carbon intensity of some routes deteriorates to a non-compliant level, which confirms that carbon intensity management can effectively reduce the risk of ship downgrade and service suspension. Based on the above results, two managerial insights are obtained. First, to reduce fleet fuel consumption, liner companies should reduce ship deadweight while still meeting cargo demand, and lower sailing speed within the allowable range. To reduce fleet carbon intensity, besides lowering speed within the allowable range, liner companies should also increase cargo demand to increase ship deadweight. Second, a higher reduction factor imposes stricter carbon intensity requirement. Limited by the minimum and maximum sailing speeds, carbon intensity management requires the deployment of ships with larger deadweight. To avoid carbon intensity non-compliance and excessively low ship loading rate, liner companies should focus on improving transport work by increasing cargo demand.

This paper reviews the historical development, research progress, and major challenges of nuclear-powered civilian vessels, and further explores their developmental trends and potential application pathways. First, it outlines the historical evolution of three typical applications, namely nuclear-powered merchant ships, nuclear-powered icebreakers, and offshore floating nuclear power plants, and summarizes the current status of relevant standards, regulations, and regulatory frameworks. Secondly, this study systematically reviews the current international research progress on various technical routes such as pressurized water reactors, fast reactors, molten salt reactors, small modular reactors, and micro modular reactors, and analyzes their potential advantages in civilian ship applications, as well as their limitations in terms of safety, economy, and regulation. Finally, the paper forecasts trends towards miniaturization, modularization, and inherent safety, and suggests steady progress through land-based testing, demonstration operations on fixed routes, segmented push-tug shipping modes, focused application scenarios, with the goal of improving economic efficiency and regulatory framework refinement.

To address the difficulty in quantitatively measuring and recognizing the similarity of multi-ship encounter scenarios, a similarity-based recognition method for multi-ship encounter scenarios based on topological graph sequences is proposed. First, multi-ship encounter scenarios are extracted from Automatic Identification System (AIS) data and represented using a topological graph sequence-based model that characterizes ship interaction relationships. Then, a two-stage similarity recognition algorithm is designed to calculate the similarity between graph sequences and identify similar encounter scenarios. Taking the waters of Ningbo-Zhoushan Port as a case study, 2, 898 multi-ship encounter scenarios are extracted from one month of AIS data, and two typical scenario types with higher proportions are selected for experimental validation. The recognition results are comparatively analyzed based on encounter feature parameters. Experimental results show that the identified similar scenarios exhibit dynamic evolution characteristics highly consistent with those of the original scenarios, and the proposed method can effectively recognize multi-ship encounter scenarios with similar encounter relationships. This demonstrates the feasibility and effectiveness of the proposed method for similarity measurement of multi-ship encounter scenarios. The findings can provide a reference for collision avoidance decision-making and encounter risk analysis in multi-ship encounter scenarios.

The Shipborne Helicopter Landing Platform (SHLP) provides an effective solution for ensuring the safe landing of shipborne helicopters by compensating for ship motions induced by wind, waves, and currents. To address the stabilization control problem of the SHLP subject to compound disturbances caused by ship motions, dynamic uncertainties, and load perturbations, a preset-time robust adaptive stabilization control method is proposed. First, a novel barrier Lyapunov function is designed, which allows the convergence time for regulating the supporting surface of the SHLP to the desired horizontal position to be preset in advance. Then, an adaptive compound disturbance estimator is constructed to achieve online estimation of the compound disturbances acting on the SHLP. Finally, by integrating the backstepping design approach with a projection algorithm, a preset-time robust adaptive stabilization control law for the SHLP is developed. Numerical simulation results demonstrate the effectiveness and robustness of the proposed control method under compound disturbance conditions.