Search Results (191)

In this study, using global liner shipping schedules, UNCTAD’s Port Liner Shipping Connectivity Index and Liner Shipping Bilateral Connectivity Index, together with bilateral trade-value data for 2022–2024, we construct a multilayer weighted port-to-port network that explicitly embeds port-level cargo-handling and service organisation capabilities, as well as demand-side routing pressure, into node and edge weights. Building on this network, we apply CONCOR-based structural-equivalence analysis to delineate functionally homogeneous port clusters, and adopt a structural role identification framework that combines multi-indicator connectivity metrics with Rank-Sum Ratio–entropy weighting and Probit-based binning to classify ports into high-efficiency core, bridge-control, and free-form bridge roles, thereby tracing the reconfiguration of cluster-level functional structures before and after the Red Sea crisis. Empirically, the clustering identifies four persistent communities—the Intertropical Maritime Hub Corridor (IMHC), Pacific Rim Mega-Port Agglomeration (PRMPA), Southern Commodity Export Gateway (SCEG), and Euro-Asian Intermodal Chokepoints (EAIC)—and reveals a marked spatial and functional reorganisation between 2022 and 2024. IMHC expands from 96 to 113 ports and SCEG from 33 to 56, whereas EAIC contracts from 27 to 10 nodes as gateway functions are reallocated across clusters, and the combined share of bridge-control and free-form bridge ports increases from 9.6% to 15.5% of all nodes, demonstrating a thicker functional backbone under rerouting pressures. Spatially, IMHC extends from a Mediterranean-centred configuration into tropical, trans-equatorial routes; PRMPA consolidates its role as the densest trans-Pacific belt; SCEG evolves from a commodity-based export gateway into a cross-regional Southern Hemisphere hub; and EAIC reorients from an Atlantic-dominated structure towards Eurasian corridors and emerging bypass routes. Functionally, Singapore, Rotterdam, and Shanghai remain dominant high-efficiency cores, while several Mediterranean and Red Sea ports (e.g., Jeddah, Alexandria) lose centrality as East and Southeast Asian nodes gain prominence; bridge-control functions are increasingly taken up by European and East Asian hubs (e.g., Antwerp, Hamburg, Busan, Kobe), acting as secondary transshipment buffers; and free-form bridge ports such as Manila, Haiphong, and Genoa strengthen their roles as elastic connectors that enhance intra-cluster cohesion and provide redundancy for inter-cluster rerouting. Overall, these patterns show that resilience under the Red Sea crisis is expressed through the cluster-level rebalancing of core–control–bridge roles, suggesting that port managers should prioritise parallel gateways, short-sea and coastal buffers, and sea–land intermodality within clusters when designing capacity expansion, hinterland access, and rerouting strategies. Full article

Wind-assisted ship propulsion (WASP) has gained considerable interest as a means of reducing fuel consumption and Greenhouse Gas (GHG) emissions, with further benefits when combined with weather-optimized routing. This study employs and extends a National Technical University of Athens (NTUA) weather-routing optimization tool to more realistically assess WASP performance through integrated modeling. The original tool minimized fuel consumption using forecasted weather data and a physics-based performance model. A previous extension to account for the WASP effect introduced a 1-Degree Of Freedom (DOF) model that accounted only for longitudinal hydrodynamic and aerodynamic forces, estimating the reduced main-engine power required to maintain speed in given conditions. The current study incorporates a 3-DOF model that includes side forces and yaw moments, capturing resulting drift and rudder deflection effects. A Kamsarmax bulk carrier equipped with suction sails served as the case study. Initial simulations across various operating and weather conditions compared the two models. The 1-DOF model predicted fuel-saving potential up to 26% for the tested apparent wind speed and the range of possible headings, whereas the 3-DOF model indicated that transverse effects reduce WASP benefits by 2–7%. Differences in Main Engine (ME) power estimates between the two models reached up to 7% Maximum Continuous Rating (MCR) depending on the speed of wind. The study then applied both models within a weather-routing optimization framework to assess whether the optimal routes produced by each model differ and to quantify performance losses. It was found that the revised optimal route derived from the 3-DOF model improved total Fuel Oil Consumption (FOC) savings by 1.25% compared with the route optimized using the 1-DOF model when both were evaluated with the 3-DOF model. Full article

Global container shipping faces increasing pressure to reduce fuel consumption and greenhouse gas (GHG) emissions while still meeting strict port schedules under highly uncertain terminal operations and met-ocean conditions. However, most existing voyage-planning approaches either ignore real port operation variability or treat fuel optimization and just-in-time (JIT) arrival as separate problems, limiting their applicability in actual operations. This study presents a data-driven just-in-time voyage optimization framework that integrates port-side uncertainty and marine environmental dynamics into the routing process. A dwell-time prediction model based on Gradient Boosting was developed using port throughput and meteorological–oceanographic variables, achieving a validation accuracy of R² = 0.84 and providing a data-driven required time of arrival (RTA) estimate. A Transformer encoder model was constructed to forecast fuel consumption from multivariate navigation and environmental data, and the model achieved a segment-level predictive performance with an R² value of approximately 0.99. These predictive modules were embedded into a Deep Q-Network (DQN) routing model capable of optimizing headings and speed profiles under spatially varying ocean conditions. Experiments were conducted on three container-carrier routes in which the historical AIS trajectories served as operational benchmark routes. Compared with these AIS-based baselines, the optimized routes reduced fuel consumption and CO₂ emissions by approximately 26% to 69%, while driving the JIT arrival deviation close to zero. The proposed framework provides a unified approach that links port operations, fuel dynamics, and ocean-aware route planning, offering practical benefits for smart and autonomous ship navigation. Full article

This study presents a model experiment on the oblique maneuvering of a ship in a floating ice environment. A series of captive model tests was conducted in both open-water and synthetic ice fields at concentrations of 60%, 70%, and 80%. The model was tested in a conventional towing tank using non-refrigerated polypropylene ice floes to simulate a broken ice field. Surge force, sway force, and yaw moment on the hull were measured under various drift angles and three speeds. Results show that in oblique motion, ice floes around the hull experience significant overturning and piling up, especially on the drift side, leading to random collisions with the hull. These interactions markedly affect the hydrodynamic forces. As the drift angle increases, the surge, sway, and yaw forces on the hull increase nonlinearly. The comparison between open-water and ice conditions indicates that floating ice can significantly increase the resistance and maneuvering forces. Higher ice concentrations lead to more frequent and more extensive contact between the hull and the ice floes, thereby further amplifying all components of the hydrodynamic forces. This work provides experimental data for validating calculation methods of ship resistance and maneuvering in broken ice. It demonstrates a feasible experimental approach for studying ship maneuvers in a floating ice channel. Full article

With the increase in capacity of large ship electric power systems, medium-voltage electric power systems have gradually become an inevitable choice. Among China’s large ships, the neutral point of the power system is usually grounded by high resistance, and its grounding parameters need to be determined, taking the system’s capacitance to ground as a reference. Under different working conditions, the capacitance to the ground of the system will change, which requires online real-time measurement of the capacitance to the ground to provide a basis. However, the current flowing through the distributed capacitance and the capacitance itself cannot be directly measured by measuring instruments. Currently, the most commonly used method is the signal injection method, which can realize the secondary side measurement. This paper analyzed the traditional signal injection methods and found that all these methods are not suitable for real-time measurement of the capacitance to the ground of the medium-voltage electric power system of a ship. Among the current methods, this paper proposes combining the dual-frequency method and the high-frequency method. Through error analysis, for systems with different capacitances to ground, the frequency selection of the dual-frequency method will affect the measurement accuracy. To ensure the measurement accuracy, it is necessary to adopt the principle of “one low frequency + one high frequency”. Therefore, based on the dual-frequency method and the high-frequency method, the paper proposed an improved dual-frequency method, taking a combination method of high frequency and low frequency for capacitance measurement of medium-voltage power systems with high resistance grounding. Then the paper studied the high- and low-frequency selection scheme by simulation comparison and finally determined the frequency selection scheme of 5000/120 Hz. The paper also carried out simulation and experimental verification and finally proved that under the selected frequency selection scheme, the proposed method can accurately measure the capacitance to ground in a medium-voltage power grid with high resistance grounding. Full article

To investigate the air layer drag reduction and the related flow field characteristics of ships, the gas–liquid two-phase numerical model using the VOF solver in STAR-CCM+ has been established, considering the effects of free surface and surface tension. The numerical model is first validated through experimental results for the drag reduction by air-injection on a simplified ship model. Then, the numerical simulations for the KVLCC2 at varying speeds and air-injection rates are conducted, considering different ship attitudes and air-injection surface configurations. The impacts of flow velocity, air-injection rates, ship attitude and air-injection configurations on air layer drag reduction are analyzed. The distributions of air and pressure around the ship and their influence mechanisms on drag reduction are discussed. The simulation results show that the drag reduction exhibits a positive correlation with air-injection rate until it reaches an optimal peak value. The combined action of the incoming flow and injection velocities causes the vortex recirculation of the air layer under the ship, leading to its disruption and the subsequent formation of air-free zones on the hull bottom. High air-injection rates and the stern trim induce air layer lateral spillage, increasing frictional resistance on the hull side surfaces. An air layer on the stern surface will reduce the viscous pressure resistance by changing the flow separation near the ship stern. Air-layer coverage area is closely correlated with inflow velocity and injection surface configurations. The reasonable configurations of the air-injection surfaces can significantly improve the drag reduction. Full article

Flexible polyurethane foam (FPUF) is widely used in ship cabins yet poses significant fire hazards due to its flammability and tendency to melt and drip during combustion. While previous studies have primarily focused on dripping behavior under static conditions, the effect of oscillatory motion, typical in maritime environments, remains poorly understood. This study investigated the dripping behavior of FPUF under both static and oscillating conditions using a custom-made experimental platform simulating ship motions. The results reveal that under static conditions, side ignition leads to a higher dripping frequency than central ignition. Under oscillation, central ignition produces a greater number of drips and higher dripping frequency compared to static conditions. Although oscillation promotes the formation of smaller droplets and reduces the proportion of large-size flaming drips, the absolute number of such flaming drips increases, elevating fire spread risk. Furthermore, while oscillation frequency and amplitude have limited effects on dripping frequency, they significantly expand the dripping spread range, which increased by over 300% at 30° and 0.1 Hz compared to static conditions. These findings provide insights for improving fire risk assessment and safety design of polymeric materials in dynamic operational environments such as ships. Full article

This study aims to provide a detailed analysis of the design choices and economic sustainability aspects associated with the implementation of shore-to-ship electrification, commonly known as “cold ironing”, in port docks, pertaining to the Italian context. This innovative technological solution aims to reduce the environmental impact of port operations by allowing docked ships to turn off their engines and connect directly to the shore-side power supply. A detailed analysis of present standards and applicable legislation is presented and implemented. Therefore, the objective of this work is to determine the conditions that make shore-side power supply economically sustainable and to study the most plausible future scenarios of greatest interest through the definition of possible management models integrated into the national and EU fiscal system. This enables a quantitative and reliable assessment of the current cold ironing incentive policies in promoting this technology, with some guidelines provided for the future promotion of this sector. Full article

This paper tackles a core challenge in reverse engineering: high-fidelity reconstruction of continuous B-spline surfaces from discrete point clouds, where optimal knot placement remains pivotal yet not fully resolved. We propose a new fitting method based on the Hungry Predation Algorithm (HPA) to improve efficiency, accuracy, and robustness. This method introduces a hybrid knot-guidance strategy that combines geometry-aware preselection with a complexity-driven probabilistic distribution to address knot placement. On the optimization side, HPA simulates starvation-driven predator–prey dynamics to enhance global search capability, maintain population diversity, and accelerate convergence. We also develop an adaptive parameter adjustment framework that automatically tunes key settings according to surface complexity and accuracy thresholds. Comparative experiments against classical approaches, six state-of-the-art optimizers, and the commercial CAD system CATIA demonstrate HPA’s superiority in control-point reduction, fitting accuracy, and computational efficiency. This method shows high applicability to engineering-scale tasks (e.g., ship hull design), where the point-to-surface RMSE (e.g., <10⁻³ L_max) achieved satisfies stringent requirements for downstream hydrodynamic performance analysis and manufacturing. Full article

This paper proposes an enhanced cooling method for multi-chip power modules (e.g., in MMC inverters) with uneven power loss in all-electric propulsion ships based on sintered heat pipe parameter optimization and special-shaped design. First, five key parameters of straight sintered heat pipes were optimized: placement directly under hotspot chips, 10 mm in diameter, quantity matching the number of hotspot chips, length equal to the heatsink side length, and direction perpendicular to heatsink fins. Then, a C-shaped heat pipe was designed using the parallel thermal resistance principle, which forms two parallel low-thermal-resistance paths and outperforms conventional U-shaped ones. Finite element simulations showed that the hotspot temperature of the conventional heatsink was 91.26 °C, while it dropped to 87.35 °C with optimized straight heat pipes and further to 80.85 °C with C-shaped ones. Experiments verified an 11.65% temperature reduction (from 86.7 °C of conventional heatsinks to 76.6 °C of C-shaped heat pipe heatsinks). This method effectively lowers hotspot temperatures, reduces device failure rates, improves the thermal reliability of power modules, and provides a generalized design methodology for heatsinks of various power electronic converters. Full article

Shore power systems, also known as cold ironing or shore-to-ship (STS) connections, are increasingly recognized as a viable solution to reduce emissions and noise from ships during berthing operations. This paper provides a comprehensive overview of shore power technology, with a focus on typical onboard energy consumption profiles across different types of ship, the main electrical architectures used in shore-side systems, and the compatibility challenges related to frequency, voltage, and control integration. The paper reviews international standards, particularly the ISO/IEC/IEEE 80005 series, that define technical requirements for interoperability and safety. A detailed analysis of recent patents highlights technological innovations in mobility, conversion topologies, and high-voltage integration. In addition, commercially available shore power solutions from major manufacturers are surveyed, with comparative data on power ratings, voltage levels, and converter topologies. Finally, the study discusses current limitations and outlines development directions for Onshore Power Supply systems, including regulatory developments, digital integration, and grid support functionalities. The insights presented aim to support the design, standardization, and deployment of efficient and scalable STS systems in line with global maritime decarbonization goals. Full article

Studies of microbial degradation of historic woods are essential to help protect and preserve these important cultural properties. The USS Cairo is a historic Civil War gunboat and one of the first steam-powered and ironclad ships used in the American Civil War. Built in 1861, the ship sank in the Yazoo River of Mississippi in 1862 after a mine detonated and tore a hole in the port bow. The ship remained on the river bottom and was gradually buried with sediments for over 98 years. After recovery of the ship, it remained exposed to the environment before the first roofed structure was completed in 1980, and it has been displayed under a tensile fabric canopy with open sides at the Vicksburg National Military Park in Vicksburg, Mississippi. Concerns over the long-term preservation of the ship initiated this investigation to document the current condition of the wooden timbers, identify the fungi that may be present, and determine the elemental composition resulting from past wood-preservative treatments. Micromorphological characteristics observed using scanning electron microscopy showed that many of the timbers were in advanced stages of degradation. Eroded secondary cell walls leaving a weak framework of middle lamella were commonly observed. Soft rot attack was prevalent, and evidence of white and brown rot degradation was found in some wood. DNA extraction and sequencing of the ITS region led to the identification of a large group of diverse fungi that were isolated from ship timbers. Soft rot fungi, including Alternaria, Chaetomium, Cladosporium, Curvularia, Xylaria and others, and white rot fungi, including Bjerkandera, Odontoefibula, Phanerodontia, Phlebiopsis, Trametes and others, were found. No brown rot fungi were isolated. Elemental analyses using induced coupled plasma spectroscopy revealed elevated levels of all elements as compared to sound modern types of wood. High concentrations of boron, copper, iron, lead, zinc and other elements were found, and viable fungi were isolated from this wood. Biodegradation issues are discussed to help long-term conservation efforts to preserve the historic ship for future generations. Full article

Historically, the Mediterranean Sea has been an area of cultural exchange and maritime commerce. One out of many submerged archaeological sites is the Roman shipwreck that was discovered in 2006 off the coast of Santo Stefano al Mare, in the Ligurian Sea, Italy. The wreck was dated to the 1st century B.C. and consists of a well-preserved cargo ship of Roman amphorae that were likely used for transporting wine. In this study, we present the results of the first underwater survey of the wreck using an Autonomous Underwater Vehicle (AUV) industrialized by Graal Tech. The AUV was equipped with a NORBIT WBMS multibeam sonar, a 450 kHz side-scan sonar, and inertial navigation systems. The AUV conducted multiple high-resolution surveys on the wreck site and the collected data were processed using geospatial analysis methods to highlight local anomalies directly related to the presence of the Roman shipwreck. The main feature was an accumulation of amphorae, covering an area of approximately 10 × 7 m with a maximum height of 1 m above the seabed. The results of this interdisciplinary work demonstrated the effectiveness of integrating AUV technologies with spatial analysis techniques for underwater archaeological applications. Furthermore, the success of this mission highlighted the potential for broader applications of AUVs in the study of the seafloor, such as monitoring seabed movements related to offshore underground energy storage or the identification of objects lying on the seabed, such as cables or pipelines. Full article

As free-flooding ships are a type of vessel with openings on their hull surfaces, accurately calculating and analyzing their roll hydrodynamic coefficients is of great significance for ship motion prediction. Based on the STAR CCM+ platform that employs the computational fluid dynamics (CFD) method, this paper first conducts numerical simulations of the forced roll motion of a damaged DTMB-5415 ship model. The applicability of this method to side-opening ship types is verified by comparing with experimental results. Subsequently, this numerical method is applied to simulate the forced roll of a free-flooding aquaculture ship under different working conditions, and the roll hydrodynamic coefficients of its hull and internal compartments are calculated and analyzed. The roll hydrodynamic coefficients of the intact ship and the free-flooding ship are compared. The results indicate the characteristics of roll hydrodynamic coefficients of free-flooding ships, and this research will facilitate the prediction of roll motion for this ship type. Full article

The article addresses the issue of liquefied natural gas (LNG) distribution as a marine fuel, analyzing both ecological and economic aspects in the context of the Baltic Sea basin. The authors emphasize that LNG plays an increasingly significant role in the global energy balance, and its application in maritime transport is crucial for implementing sustainable development policies and advancing the energy transition. From an ecological perspective, LNG offers a substantial reduction in harmful emissions compared with conventional marine fuels such as marine diesel oil (MDO) and heavy fuel oil (HFO). In particular, the use of LNG results in lower emissions of carbon dioxide (CO₂), sulfur oxides (SO_x), nitrogen oxides (NO_x), and particulate matter (PM). The reduction in these pollutants is essential not only for improving air quality in port and coastal areas but also for mitigating global environmental impacts, including climate change. On the economic side, the article focuses on the cost structure of LNG distribution, highlighting that its price dynamics are subject to significant fluctuations. These variations are driven by geopolitical developments, crude oil price volatility, environmental regulations, and the expansion of bunkering infrastructure. From an economic perspective, LNG prices show significant volatility depending on the year and market conditions. Between 2018 and 2023, LNG prices ranged from approximately 450 to 530 USD/ton, at times exceeding the cost of HFO (400–550 USD/ton) but in some years remaining cheaper. In comparison, MDO prices were consistently the highest, increasing over the analyzed period from 600 USD/ton to over 720 USD/ton. This variability results from geopolitical factors, supply and demand dynamics, and environmental regulations, which highlight the strategic importance of LNG as a transitional fuel in shipping. The purpose of this study is to examine the role of LNG as an alternative fuel for shipping in the Baltic Sea, with particular emphasis on the scale of vessel emissions and the key factors influencing its distribution costs. Full article