Long-span bridges are usually constructed over waterways that involve substantial ship traffic,resulting in a risk of collisions between the bridge girders and over-height ships.The consequences of this can be severe ...Long-span bridges are usually constructed over waterways that involve substantial ship traffic,resulting in a risk of collisions between the bridge girders and over-height ships.The consequences of this can be severe structural damage or even collapse.Accurate measurement of ship dimensions is an effective way to monitor approaching over-height ships and avoid collisions.However,the performance of current techniques for estimating the size of moving objects can be undermined by large sensor-to-object distance,limiting their applicability.In this study,we propose a digital twin-assisted ship size measurement framework that can overcome such limitations through a predictive model and virtual-to-real-world transfer learning.Specifically,a 3D synthetic environment is first established to generate a synthetic dataset,which includes ship images,positions,and dimensions.Then the pixel information and spatial coordinates of ships are adopted as regressors,and ship dimensions are selected as the output variables to pre-train deep learning models using the generated dataset.Coordinate system transformations are applied to address dataset bias between the simulated world and real-world,as well as improve the model’s generalization.The pre-trained models are compared using supervised virtual-to-real-world transfer learning to select the version with optimal real-world performance.The mean absolute percentage error is only 3.74%across varying camera-to-ship distances,which demonstrates that the proposed method is effective for over-limit ship monitoring.展开更多
Ship operations are crucial to global trade,and their decarbonization is essential to mitigate climate change.This study evaluates the economic viability of existing and emerging decarbonization technologies in mariti...Ship operations are crucial to global trade,and their decarbonization is essential to mitigate climate change.This study evaluates the economic viability of existing and emerging decarbonization technologies in maritime shipping using the levelized cost of energy methodology.It includes a detailed comparative analysis based on essential criteria and sensitivity assessments to highlight the economic impacts of technological advancements.Key factors influencing total costs include fuel costs,carbon pricing,and energy demands for carbon capture.The findings reveal that methanol is more cost-effective than heavy fuel oil(HFO)when priced below 3000 CNY/t,assuming HFO costs 4400 CNY/t.Additionally,methanol with post-combustion carbon capture is less expensive than pre-combustion carbon capture.When carbon prices rise above 480 CNY/t,carbon capture technologies prove more economical than purchasing carbon emission allowances for HFO and liquefied natural gas.Enhanc-ing the use of exhaust gas waste heat is recommended for cost savings.Post-combustion carbon capture also shows greater efficiency,requiring about 1.1 GJ/t less energy than pre-combustion methods,leading to lower overall costs.Future research should focus on market mechanisms to stabilize fuel prices and develop less energy-intensive carbon capture technologies.This study offers critical insights into effective decarbonization strategies for advancing global maritime trade in the present and future.展开更多
The issue of resistance reduction through hull ventilation is of particular interest in contemporary research.This paper presents multiphase computational fluid dynamics(CFD)simulations with 2-DOF motion of a planing ...The issue of resistance reduction through hull ventilation is of particular interest in contemporary research.This paper presents multiphase computational fluid dynamics(CFD)simulations with 2-DOF motion of a planing hull.The original hull was modified by introducing a step to allow air ventilation.Following an assessment of the hull performance,a simulation campaign in calm water was conducted to characterize the hull at various forward speeds and air insufflation rates for a defined single step geometry.Geometric analysis of the air layer thickness beneath the hull for each simulated condition was performed using a novel method for visualizing local air thickness.Additionally,two new parameters were introduced to understand the influence of spray rails on the air volume beneath the hull and to indicate the primary direction of ventilated air escape.A validation campaign and an assessment of uncertainty of the simulation has been conducted.The features offered by the CFD methodology include the evaluation of the air layer thickness as a function of hull velocity and injection flow rate and the air volume distribution beneath the hull.The air injection velocity can be adjusted across various operating conditions,thereby preventing performance or efficiency loss during navigation.Based on these findings,the study highlights the benefits of air insufflation in reducing hull resistance for high-speed planing vessels.This work lays a robust foundation for future research and new promising topics,as the exploration of air insufflation continues to be a topic of contemporary interest within naval architecture and hydrodynamics.展开更多
To address critical challenges in nighttime ship detection—high small-target missed detection(over 20%),insufficient lightweighting,and limited generalization due to scarce,low-quality datasets—this study proposes a...To address critical challenges in nighttime ship detection—high small-target missed detection(over 20%),insufficient lightweighting,and limited generalization due to scarce,low-quality datasets—this study proposes a systematic solution.First,a high-quality Night-Ships dataset is constructed via CycleGAN-based day-night transfer,combined with a dual-threshold cleaning strategy(Laplacian variance sharpness filtering and brightness-color deviation screening).Second,a Cross-stage Lightweight Fusion-You Only Look Once version 8(CLF-YOLOv8)is proposed with key improvements:the Neck network is reconstructed by replacing Cross Stage Partial(CSP)structure with the Cross Stage Partial Multi-Scale Convolutional Block(CSP-MSCB)and integrating Bidirectional Feature Pyramid Network(BiFPN)for weighted multi-scale fusion to enhance small-target detection;a Lightweight Shared Convolutional and Separated Batch Normalization Detection-Head(LSCSBD-Head)with shared convolutions and layer-wise Batch Normalization(BN)reduces parameters to 1.8M(42% fewer than YOLOv8n);and the FocalMinimum Point Distance Intersection over Union(Focal-MPDIoU)loss combines Minimum Point Distance Intersection over Union(MPDIoU)geometric constraints and Focal weighting to optimize low-overlap targets.Experiments show CLFYOLOv8 achieves 97.6%mAP@0.5(0.7% higher than YOLOv8n)with 1.8 M parameters,outperforming mainstream models in small-target detection,overlapping target discrimination,and adaptability to complex lighting.展开更多
At Yangpu Port on the northwestern tip of Hainan Island,towering quay cranes are lined in neat rows, hoisting containers on and off cargo vessels in constant motion.“Today, half of the international ships we pilot ar...At Yangpu Port on the northwestern tip of Hainan Island,towering quay cranes are lined in neat rows, hoisting containers on and off cargo vessels in constant motion.“Today, half of the international ships we pilot are ultra-large vessels over 200meters in length,” said Lin Hongpin,head of the Yangpu branch of Hainan Provincial Ship Pilot Station. Since the launch of the island-wide special customs operations, port throughput has continued to climb, with pilotage services for such large ships rising by nearly 20 percent year on year.展开更多
The concept of hybrid ships has gained significant attention in recent years,as they offer an effective means of enhancing energy utilization and reducing environmental pollution.However,the navigational environments ...The concept of hybrid ships has gained significant attention in recent years,as they offer an effective means of enhancing energy utilization and reducing environmental pollution.However,the navigational environments of ships are often subject to changes,which in turn affect their energy efficiency in a complex manner.It is therefore evident that enhancing the energy efficiency of hybrid ships is a worthwhile goal.In this study,we take a diesel-electric hybrid ship navigating in inland waterways as the research object,and propose a hierarchical optimization method for ship energy efficiency.The upper-layer control establishes a predictive model for propulsion motor speed and fuel consumption through multivariate time series predictions,and employs the model predictive control(MPC)method to optimize the propulsion motor speed.The lower-layer control utilizes an equivalent fuel consumption minimization method,which is based on improving the equivalence factor.This involves combining the variation of the supercapacitor’s state of charge(SOC)with the propulsion motor speed obtained from the MPC optimization in the upper-layer control.Furthermore,a proportional integral(PI)controller is used to adjust the equivalence factor,in order to adapt the equivalent fuel consumption minimization method to the working conditions.Our results demonstrate that the proposed hierarchical optimization method can reduce the energy efficiency operating indicator(EEOI)by approximately 11.54%and the fuel consumption by approximately 9.47%in comparison to the pre-optimization scenario.展开更多
In 2024,global shipments of new short-staple spindles and open-end rotors decreased by 40%and 39%,respectively(year-on-year).Deliveries of long-staple spindles increased by 62%.The number of draw texturing spindles im...In 2024,global shipments of new short-staple spindles and open-end rotors decreased by 40%and 39%,respectively(year-on-year).Deliveries of long-staple spindles increased by 62%.The number of draw texturing spindles improved by 77%and shipped shuttleless looms grew by 32%.Shipments of large circular knitting machines deteriorated by 15%and shipped flat knitting machines registered a 16%increase.The sum of all deliveries in the fin-ishing segment slightlyrose by 6%.展开更多
The accelerated decline of Arctic sea ice since the 1980s has paradoxically amplified greenhouse gas(GHG)emissions through increased shipping activities in this ecologically vulnerable region.This study investigates h...The accelerated decline of Arctic sea ice since the 1980s has paradoxically amplified greenhouse gas(GHG)emissions through increased shipping activities in this ecologically vulnerable region.This study investigates how to reconcile the decarbonization of Arctic shipping with conflicting environmental,economic,and geopolitical interests.Through systematic literature review and interest-balancing analysis,our findings identify three systemic barriers:(1)inadequate adaptation of International Maritime Organization(IMO)regulations to Arctic-specific environmental risks,(2)fragmented enforcement mechanisms among Arctic and non-Arctic States,and(3)technological limitations in clean fuel adoption for ice-class vessels.To address these challenges,a tripartite governance framework is proposed.First,legally binding amendments to International Convention for the Prevention of Pollution from Ships(MARPOL)Annex VI introducing Arctic-specific Energy Efficiency eXisting ship Index(EEXI)standards and extending energy efficiency regulations to fishing vessels.Second,a phased fuel transition prioritizing liquefied natural gas(LNG)and methanol,followed by hydrogen-ammonia synthetics.Third,enhanced multilateral cooperation through an Arctic Climate Shipping Alliance to coordinate joint research and development in cold-adapted technologies and ice-route optimization.By integrating United Nations Convention on the Law of the Sea(UNCLOS)obligations with IMO Polar Code implementation,this study advances a dynamic interest-balancing framework for policymakers,offering actionable pathways to achieve Paris Agreement targets while safeguarding Arctic ecosystems.展开更多
In observation of efficiently utilizing the boil off gas(BOG)from onboard liquefied natural gas(LNG),storage by adsorption is employed to construct an auxiliary system for fuel storage.A typical LNG powered ship was s...In observation of efficiently utilizing the boil off gas(BOG)from onboard liquefied natural gas(LNG),storage by adsorption is employed to construct an auxiliary system for fuel storage.A typical LNG powered ship was selected,and the storage by adsorption system was designed as per the amount of BOG released during the process of charging and that from daily evaporation on the LNG storage tank.Researches were conducted experimentally and numerically on a 1 L conformable vessel typically designed for adsorbing BOG.Verification of the accuracy of the results from simulations was performed by comparing the data recorded during the charging and discharging process of methane on the vessel packed with one kind of commercially available activated carbon SAC-01(S_(BET)=1507 m^(2)·g^(-1)).Simulations were conducted further to evaluate the performance of the vessel respectively filled with activated carbon AX-21,HKUST-1,MIL-101(Cr),MOF-5.It shows that the mean relative error between the data from simulations and the experimental data is less than 5%.Results also reveal that,within the flow rates range in correspondence with the fuel consumed by the model ship's power unit under its typical working conditions,the mean temperature fluctuation within the vessel is the weakest while packing HKUST-1,which results in the largest accumulated amount of discharge.It suggests that HKUST-1 is a suitable adsorbent for storage by adsorption of BOG from on board LNG.展开更多
Researchers have achieved notable advancements over the years in exploring ship damage and stability resulting from underwater explosions(UNDEX).However,numerous challenges and open questions remain in this field.In t...Researchers have achieved notable advancements over the years in exploring ship damage and stability resulting from underwater explosions(UNDEX).However,numerous challenges and open questions remain in this field.In this study,the research progress of UNDEX load is first reviewed,which covers the explosion load during the shock wave and bubble pulsation stages.Subsequently,the research progress of ship damage caused by UNDEX is reviewed from two aspects:contact explosion and noncontact explosion.Finally,the research progress of ship navigation stability caused by UNDEX is reviewed from three aspects:natural factors,ship’s internal factors,and explosion factors.Analysis reveals that most existing research has focused on the damage to displacement ships caused by UNDEX.Meanwhile,less attention has been paid to the damage and stability of non-displacement ships caused by UNDEX,which are worthy of discussion.展开更多
In designing modern vessels, calculating the propulsion performance of ships in ice is important, including propeller effective thrust, number of revolutions, consumed power, and ship speed. Such calculations allow fo...In designing modern vessels, calculating the propulsion performance of ships in ice is important, including propeller effective thrust, number of revolutions, consumed power, and ship speed. Such calculations allow for more accurate prediction of the ice performance of a designed ship and provide inputs for designers of ship power and automation systems. Preliminary calculations of ship propulsion and thrust characteristics in ice can enable predictions of full-scale ice resistance without measuring the propeller thrust during sea trials. Measuring propeller revolutions,ship speed, and the power delivered to propellers could be sufficient to determine the propeller thrust of the vessel. At present, significant difficulties arise in determining the thrust of icebreakers and ice-class ships in ice conditions. These challenges are related to the fact that the traditional system of propeller/hull interaction coefficients does not function correctly in ice conditions. The wake fraction becomes negative and tends to minus infinity starting from a certain value of the propeller advance coefficient. This issue prevents accurate determination of the performance characteristics, thrust, and rotational speed of the propulsors. In this study, an alternative system of propeller/hull interaction coefficients for ice is proposed. It enables the calculation of all propulsion parameters in ice based on standard hydrodynamic tests with selfpropulsion models. An experimental method is developed to determine alternative propeller/hull interaction coefficients. A prediction method is suggested to determine propulsion performance in ice based on the alternative interaction coefficient system. A case study applying the propulsion prediction method for ice conditions is provided. This study also discusses the following issues of ship operation in ice: the scale effect of icebreaker propellers and the prospects for introducing an ice interaction coefficient.展开更多
Ship outfitting is a key process in shipbuilding.Efficient and high-quality ship outfitting is a top priority for modern shipyards.These activities are conducted at different stations of shipyards.The outfitting plan ...Ship outfitting is a key process in shipbuilding.Efficient and high-quality ship outfitting is a top priority for modern shipyards.These activities are conducted at different stations of shipyards.The outfitting plan is one of the crucial issues in shipbuilding.In this paper,production scheduling and material ordering with endogenous uncertainty of the outfitting process are investigated.The uncertain factors in outfitting equipment production are usually decision-related,which leads to difficulties in addressing uncertainties in the outfitting production workshops before production is conducted according to plan.This uncertainty is regarded as endogenous uncertainty and can be treated as non-anticipativity constraints in the model.To address this problem,a stochastic two-stage programming model with endogenous uncertainty is established to optimize the outfitting job scheduling and raw material ordering process.A practical case of the shipyard of China Merchants Heavy Industry Co.,Ltd.is used to evaluate the performance of the proposed method.Satisfactory results are achieved at the lowest expected total cost as the complete kit rate of outfitting equipment is improved and emergency replenishment is reduced.展开更多
To study the rolling motion of a ship in the presence of water on its deck,a linear-plus-quadratic damping term was incorporated into its equation of motion.Ship model tests indicates that the key dynamics of the phys...To study the rolling motion of a ship in the presence of water on its deck,a linear-plus-quadratic damping term was incorporated into its equation of motion.Ship model tests indicates that the key dynamics of the physical system are preserved in the ship rolling equation with the linear-plus-quadratic type damping term.To take into account the presence of randomness in the excitation and the response,a new method was developed and a Melnikov criterion was obtained to provide an upper bound on the domain of the potential chaotic rolling motion(erratic rocking).Additionally,the Melnikov criterion proposed in this study was verified by the utilization of phase plane diagrams and Poincare maps.Furthermore,this research has made the initial endeavor to systematically modify the system parameters in the rolling equation of motion for ship stability analysis.展开更多
Ice-going ships play a crucial role in polar transportation and resource extraction.Different from the existing modeling approach which assumes that ships remain stationary,dynamic overset grid technology and DFBI(Dyn...Ice-going ships play a crucial role in polar transportation and resource extraction.Different from the existing modeling approach which assumes that ships remain stationary,dynamic overset grid technology and DFBI(Dynamic Fluid-Body Interaction)method are employed in this paper to enable the free-running motion of the ship in modeling.A numerical model capable of simulating a ship navigating through pack ice area is proposed,which uses Computational Fluid Dynamics(CFD)method to solve the flow field and applies the Discrete Element Method(DEM)to simulate ship-ice and ice-ice interactions.Besides,the proposed high-precision method for generating pack ice area can be used in conjunction with the proposed numerical model.By comparing the numerical results with the available model test data and experimental observations,the effectiveness of the numerical model is validated,demonstrating its strong capability of predicting resistance and simulating ship navigation in pack ice,as well as its significant potential and applicability for further studies.展开更多
In order to accurately forecast the main engine fuel consumption and reduce the Energy Efficiency Operational Indicator(EEOI)of merchant ships in polar ice areas,the energy transfer relationship between ship-machine-p...In order to accurately forecast the main engine fuel consumption and reduce the Energy Efficiency Operational Indicator(EEOI)of merchant ships in polar ice areas,the energy transfer relationship between ship-machine-propeller is studied by analyzing the complex force situation during ship navigation and building a MATLAB/Simulink simulation platform based on multi-environmental resistance,propeller efficiency,main engine power,fuel consumption,fuel consumption rate and EEOI calculation module.Considering the environmental factors of wind,wave and ice,the route is divided into sections,the calculation of main engine power,main engine fuel consumption and EEOI for each section is completed,and the speed design is optimized based on the simulation model for each section.Under the requirements of the voyage plan,the optimization results show that the energy efficiency operation index of the whole route is reduced by 3.114%and the fuel consumption is reduced by 9.17 t.展开更多
World’s First Ammonia-Fueled Vessel Sets Sail The world's first pure ammonia-powered demonstration vessel,the Anhui,successfully completed its maiden voyage in Hefei,east China's Anhui Province,on June 28,mar...World’s First Ammonia-Fueled Vessel Sets Sail The world's first pure ammonia-powered demonstration vessel,the Anhui,successfully completed its maiden voyage in Hefei,east China's Anhui Province,on June 28,marking a major step forward for green shipping.Ammonia,a major chemical industry feedstock,has a high energy density and due to its carbon-free nature,produces only water and nitrogen when fully combusted.This makes it a highly promising fuel for decarbonizing shipping.展开更多
The Titanic sunk 113 years ago on April 14-15,after hitting an iceberg,with human error likely causing the ship to wander into those dangerous waters.Today,autonomous systems built on AI can help ships avoid such acci...The Titanic sunk 113 years ago on April 14-15,after hitting an iceberg,with human error likely causing the ship to wander into those dangerous waters.Today,autonomous systems built on AI can help ships avoid such accidents.But could such a system explain to the captain why it was controlling the ship in a certain way?展开更多
Semisubmersible naval ships are versatile military crafts that combine the advantageous features of high-speed planing crafts and submarines.At-surface,these ships are designed to provide sufficient speed and maneuver...Semisubmersible naval ships are versatile military crafts that combine the advantageous features of high-speed planing crafts and submarines.At-surface,these ships are designed to provide sufficient speed and maneuverability.Additionally,they can perform shallow dives,offering low visual and acoustic detectability.Therefore,the hydrodynamic design of a semisubmersible naval ship should address at-surface and submerged conditions.In this study,Numerical analyses were performed using a semisubmersible hull form to analyze its hydrodynamic features,including resistance,powering,and maneuvering.The simulations were conducted with Star CCM+version 2302,a commercial package program that solves URANS equations using the SST k-ωturbulence model.The flow analysis was divided into two parts:at-surface simulations and shallowly submerged simulations.At-surface simulations cover the resistance,powering,trim,and sinkage at transition and planing regimes,with corresponding Froude numbers ranging from 0.42 to 1.69.Shallowly submerged simulations were performed at seven different submergence depths,ranging from D/LOA=0.0635 to D/LOA=0.635,and at two different speeds with Froude numbers of 0.21 and 0.33.The behaviors of the hydrodynamic forces and pitching moment for different operation depths were comprehensively analyzed.The results of the numerical analyses provide valuable insights into the hydrodynamic performance of semisubmersible naval ships,highlighting the critical factors influencing their resistance,powering,and maneuvering capabilities in both at-surface and submerged conditions.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52338011 and 52108274)the Start-up Research Fund of Southeast University(No.RF1028624058),Chinasupport from the SEU Innovation Capability Enhancement Plan for Doctoral Students(No.CXJH_SEU 26112),China.
文摘Long-span bridges are usually constructed over waterways that involve substantial ship traffic,resulting in a risk of collisions between the bridge girders and over-height ships.The consequences of this can be severe structural damage or even collapse.Accurate measurement of ship dimensions is an effective way to monitor approaching over-height ships and avoid collisions.However,the performance of current techniques for estimating the size of moving objects can be undermined by large sensor-to-object distance,limiting their applicability.In this study,we propose a digital twin-assisted ship size measurement framework that can overcome such limitations through a predictive model and virtual-to-real-world transfer learning.Specifically,a 3D synthetic environment is first established to generate a synthetic dataset,which includes ship images,positions,and dimensions.Then the pixel information and spatial coordinates of ships are adopted as regressors,and ship dimensions are selected as the output variables to pre-train deep learning models using the generated dataset.Coordinate system transformations are applied to address dataset bias between the simulated world and real-world,as well as improve the model’s generalization.The pre-trained models are compared using supervised virtual-to-real-world transfer learning to select the version with optimal real-world performance.The mean absolute percentage error is only 3.74%across varying camera-to-ship distances,which demonstrates that the proposed method is effective for over-limit ship monitoring.
基金supported by the National Key R&D Program of China(No.2022YFC3701500)the Key R&D Plan Projects of Zhejiang Province(No.2024SSYS0072)Zhejiang Provincial Natural Science Foundation(No.LDT23E0601).
文摘Ship operations are crucial to global trade,and their decarbonization is essential to mitigate climate change.This study evaluates the economic viability of existing and emerging decarbonization technologies in maritime shipping using the levelized cost of energy methodology.It includes a detailed comparative analysis based on essential criteria and sensitivity assessments to highlight the economic impacts of technological advancements.Key factors influencing total costs include fuel costs,carbon pricing,and energy demands for carbon capture.The findings reveal that methanol is more cost-effective than heavy fuel oil(HFO)when priced below 3000 CNY/t,assuming HFO costs 4400 CNY/t.Additionally,methanol with post-combustion carbon capture is less expensive than pre-combustion carbon capture.When carbon prices rise above 480 CNY/t,carbon capture technologies prove more economical than purchasing carbon emission allowances for HFO and liquefied natural gas.Enhanc-ing the use of exhaust gas waste heat is recommended for cost savings.Post-combustion carbon capture also shows greater efficiency,requiring about 1.1 GJ/t less energy than pre-combustion methods,leading to lower overall costs.Future research should focus on market mechanisms to stabilize fuel prices and develop less energy-intensive carbon capture technologies.This study offers critical insights into effective decarbonization strategies for advancing global maritime trade in the present and future.
基金supported by European Union funding(PON“Ricerca e Innovazione”2014‒2020).
文摘The issue of resistance reduction through hull ventilation is of particular interest in contemporary research.This paper presents multiphase computational fluid dynamics(CFD)simulations with 2-DOF motion of a planing hull.The original hull was modified by introducing a step to allow air ventilation.Following an assessment of the hull performance,a simulation campaign in calm water was conducted to characterize the hull at various forward speeds and air insufflation rates for a defined single step geometry.Geometric analysis of the air layer thickness beneath the hull for each simulated condition was performed using a novel method for visualizing local air thickness.Additionally,two new parameters were introduced to understand the influence of spray rails on the air volume beneath the hull and to indicate the primary direction of ventilated air escape.A validation campaign and an assessment of uncertainty of the simulation has been conducted.The features offered by the CFD methodology include the evaluation of the air layer thickness as a function of hull velocity and injection flow rate and the air volume distribution beneath the hull.The air injection velocity can be adjusted across various operating conditions,thereby preventing performance or efficiency loss during navigation.Based on these findings,the study highlights the benefits of air insufflation in reducing hull resistance for high-speed planing vessels.This work lays a robust foundation for future research and new promising topics,as the exploration of air insufflation continues to be a topic of contemporary interest within naval architecture and hydrodynamics.
基金the Shandong Provincial Key Research and Development Program(Grant No.2024SFGC0201).
文摘To address critical challenges in nighttime ship detection—high small-target missed detection(over 20%),insufficient lightweighting,and limited generalization due to scarce,low-quality datasets—this study proposes a systematic solution.First,a high-quality Night-Ships dataset is constructed via CycleGAN-based day-night transfer,combined with a dual-threshold cleaning strategy(Laplacian variance sharpness filtering and brightness-color deviation screening).Second,a Cross-stage Lightweight Fusion-You Only Look Once version 8(CLF-YOLOv8)is proposed with key improvements:the Neck network is reconstructed by replacing Cross Stage Partial(CSP)structure with the Cross Stage Partial Multi-Scale Convolutional Block(CSP-MSCB)and integrating Bidirectional Feature Pyramid Network(BiFPN)for weighted multi-scale fusion to enhance small-target detection;a Lightweight Shared Convolutional and Separated Batch Normalization Detection-Head(LSCSBD-Head)with shared convolutions and layer-wise Batch Normalization(BN)reduces parameters to 1.8M(42% fewer than YOLOv8n);and the FocalMinimum Point Distance Intersection over Union(Focal-MPDIoU)loss combines Minimum Point Distance Intersection over Union(MPDIoU)geometric constraints and Focal weighting to optimize low-overlap targets.Experiments show CLFYOLOv8 achieves 97.6%mAP@0.5(0.7% higher than YOLOv8n)with 1.8 M parameters,outperforming mainstream models in small-target detection,overlapping target discrimination,and adaptability to complex lighting.
文摘At Yangpu Port on the northwestern tip of Hainan Island,towering quay cranes are lined in neat rows, hoisting containers on and off cargo vessels in constant motion.“Today, half of the international ships we pilot are ultra-large vessels over 200meters in length,” said Lin Hongpin,head of the Yangpu branch of Hainan Provincial Ship Pilot Station. Since the launch of the island-wide special customs operations, port throughput has continued to climb, with pilotage services for such large ships rising by nearly 20 percent year on year.
基金supported by the National Natural Science Foundation of China(No.52571367)and the Commissions Project of China(No.CBG4N21).
文摘The concept of hybrid ships has gained significant attention in recent years,as they offer an effective means of enhancing energy utilization and reducing environmental pollution.However,the navigational environments of ships are often subject to changes,which in turn affect their energy efficiency in a complex manner.It is therefore evident that enhancing the energy efficiency of hybrid ships is a worthwhile goal.In this study,we take a diesel-electric hybrid ship navigating in inland waterways as the research object,and propose a hierarchical optimization method for ship energy efficiency.The upper-layer control establishes a predictive model for propulsion motor speed and fuel consumption through multivariate time series predictions,and employs the model predictive control(MPC)method to optimize the propulsion motor speed.The lower-layer control utilizes an equivalent fuel consumption minimization method,which is based on improving the equivalence factor.This involves combining the variation of the supercapacitor’s state of charge(SOC)with the propulsion motor speed obtained from the MPC optimization in the upper-layer control.Furthermore,a proportional integral(PI)controller is used to adjust the equivalence factor,in order to adapt the equivalent fuel consumption minimization method to the working conditions.Our results demonstrate that the proposed hierarchical optimization method can reduce the energy efficiency operating indicator(EEOI)by approximately 11.54%and the fuel consumption by approximately 9.47%in comparison to the pre-optimization scenario.
文摘In 2024,global shipments of new short-staple spindles and open-end rotors decreased by 40%and 39%,respectively(year-on-year).Deliveries of long-staple spindles increased by 62%.The number of draw texturing spindles improved by 77%and shipped shuttleless looms grew by 32%.Shipments of large circular knitting machines deteriorated by 15%and shipped flat knitting machines registered a 16%increase.The sum of all deliveries in the fin-ishing segment slightlyrose by 6%.
基金supported by the Major Research Projects of the National Social Science Fund of China(NSFC,Grant no.23VHQ015).
文摘The accelerated decline of Arctic sea ice since the 1980s has paradoxically amplified greenhouse gas(GHG)emissions through increased shipping activities in this ecologically vulnerable region.This study investigates how to reconcile the decarbonization of Arctic shipping with conflicting environmental,economic,and geopolitical interests.Through systematic literature review and interest-balancing analysis,our findings identify three systemic barriers:(1)inadequate adaptation of International Maritime Organization(IMO)regulations to Arctic-specific environmental risks,(2)fragmented enforcement mechanisms among Arctic and non-Arctic States,and(3)technological limitations in clean fuel adoption for ice-class vessels.To address these challenges,a tripartite governance framework is proposed.First,legally binding amendments to International Convention for the Prevention of Pollution from Ships(MARPOL)Annex VI introducing Arctic-specific Energy Efficiency eXisting ship Index(EEXI)standards and extending energy efficiency regulations to fishing vessels.Second,a phased fuel transition prioritizing liquefied natural gas(LNG)and methanol,followed by hydrogen-ammonia synthetics.Third,enhanced multilateral cooperation through an Arctic Climate Shipping Alliance to coordinate joint research and development in cold-adapted technologies and ice-route optimization.By integrating United Nations Convention on the Law of the Sea(UNCLOS)obligations with IMO Polar Code implementation,this study advances a dynamic interest-balancing framework for policymakers,offering actionable pathways to achieve Paris Agreement targets while safeguarding Arctic ecosystems.
基金supported by National Natural Science Foundation of China(51979121)Natural Science Foundation of Fujian Province(2024J01713,2023J01905)+1 种基金Xiamen Municipal Bureau of Sciences&Technology(3502Z20226011)Educational scientific research project for young and middle-aged teachers in Fujian Province(JAT210300).
文摘In observation of efficiently utilizing the boil off gas(BOG)from onboard liquefied natural gas(LNG),storage by adsorption is employed to construct an auxiliary system for fuel storage.A typical LNG powered ship was selected,and the storage by adsorption system was designed as per the amount of BOG released during the process of charging and that from daily evaporation on the LNG storage tank.Researches were conducted experimentally and numerically on a 1 L conformable vessel typically designed for adsorbing BOG.Verification of the accuracy of the results from simulations was performed by comparing the data recorded during the charging and discharging process of methane on the vessel packed with one kind of commercially available activated carbon SAC-01(S_(BET)=1507 m^(2)·g^(-1)).Simulations were conducted further to evaluate the performance of the vessel respectively filled with activated carbon AX-21,HKUST-1,MIL-101(Cr),MOF-5.It shows that the mean relative error between the data from simulations and the experimental data is less than 5%.Results also reveal that,within the flow rates range in correspondence with the fuel consumed by the model ship's power unit under its typical working conditions,the mean temperature fluctuation within the vessel is the weakest while packing HKUST-1,which results in the largest accumulated amount of discharge.It suggests that HKUST-1 is a suitable adsorbent for storage by adsorption of BOG from on board LNG.
基金Supported by the Key R&D Program of Heilongjiang Province(Grant No.JD22A024)the Science Fund for Excellent Youth Foundation of Heilongjiang Province of China(Grant No.YQ2021E010).
文摘Researchers have achieved notable advancements over the years in exploring ship damage and stability resulting from underwater explosions(UNDEX).However,numerous challenges and open questions remain in this field.In this study,the research progress of UNDEX load is first reviewed,which covers the explosion load during the shock wave and bubble pulsation stages.Subsequently,the research progress of ship damage caused by UNDEX is reviewed from two aspects:contact explosion and noncontact explosion.Finally,the research progress of ship navigation stability caused by UNDEX is reviewed from three aspects:natural factors,ship’s internal factors,and explosion factors.Analysis reveals that most existing research has focused on the damage to displacement ships caused by UNDEX.Meanwhile,less attention has been paid to the damage and stability of non-displacement ships caused by UNDEX,which are worthy of discussion.
基金supported by a grant No. 23-19-00039 of Russian Research Fund “Theoretical basis and application tools for developing a system of intellectual fleet planning and support of decisions on Arctic navigation”。
文摘In designing modern vessels, calculating the propulsion performance of ships in ice is important, including propeller effective thrust, number of revolutions, consumed power, and ship speed. Such calculations allow for more accurate prediction of the ice performance of a designed ship and provide inputs for designers of ship power and automation systems. Preliminary calculations of ship propulsion and thrust characteristics in ice can enable predictions of full-scale ice resistance without measuring the propeller thrust during sea trials. Measuring propeller revolutions,ship speed, and the power delivered to propellers could be sufficient to determine the propeller thrust of the vessel. At present, significant difficulties arise in determining the thrust of icebreakers and ice-class ships in ice conditions. These challenges are related to the fact that the traditional system of propeller/hull interaction coefficients does not function correctly in ice conditions. The wake fraction becomes negative and tends to minus infinity starting from a certain value of the propeller advance coefficient. This issue prevents accurate determination of the performance characteristics, thrust, and rotational speed of the propulsors. In this study, an alternative system of propeller/hull interaction coefficients for ice is proposed. It enables the calculation of all propulsion parameters in ice based on standard hydrodynamic tests with selfpropulsion models. An experimental method is developed to determine alternative propeller/hull interaction coefficients. A prediction method is suggested to determine propulsion performance in ice based on the alternative interaction coefficient system. A case study applying the propulsion prediction method for ice conditions is provided. This study also discusses the following issues of ship operation in ice: the scale effect of icebreaker propellers and the prospects for introducing an ice interaction coefficient.
基金supported in part by the High-tech ship scientific research project of the Ministry of Industry and Information Technology of the People’s Republic of China,and the National Nature Science Foundation of China(Grant No.71671113)the Science and Technology Department of Shaanxi Province(No.2020GY-219)the Ministry of Education Collaborative Project of Production,Learning and Research(No.201901024016).
文摘Ship outfitting is a key process in shipbuilding.Efficient and high-quality ship outfitting is a top priority for modern shipyards.These activities are conducted at different stations of shipyards.The outfitting plan is one of the crucial issues in shipbuilding.In this paper,production scheduling and material ordering with endogenous uncertainty of the outfitting process are investigated.The uncertain factors in outfitting equipment production are usually decision-related,which leads to difficulties in addressing uncertainties in the outfitting production workshops before production is conducted according to plan.This uncertainty is regarded as endogenous uncertainty and can be treated as non-anticipativity constraints in the model.To address this problem,a stochastic two-stage programming model with endogenous uncertainty is established to optimize the outfitting job scheduling and raw material ordering process.A practical case of the shipyard of China Merchants Heavy Industry Co.,Ltd.is used to evaluate the performance of the proposed method.Satisfactory results are achieved at the lowest expected total cost as the complete kit rate of outfitting equipment is improved and emergency replenishment is reduced.
文摘To study the rolling motion of a ship in the presence of water on its deck,a linear-plus-quadratic damping term was incorporated into its equation of motion.Ship model tests indicates that the key dynamics of the physical system are preserved in the ship rolling equation with the linear-plus-quadratic type damping term.To take into account the presence of randomness in the excitation and the response,a new method was developed and a Melnikov criterion was obtained to provide an upper bound on the domain of the potential chaotic rolling motion(erratic rocking).Additionally,the Melnikov criterion proposed in this study was verified by the utilization of phase plane diagrams and Poincare maps.Furthermore,this research has made the initial endeavor to systematically modify the system parameters in the rolling equation of motion for ship stability analysis.
文摘Ice-going ships play a crucial role in polar transportation and resource extraction.Different from the existing modeling approach which assumes that ships remain stationary,dynamic overset grid technology and DFBI(Dynamic Fluid-Body Interaction)method are employed in this paper to enable the free-running motion of the ship in modeling.A numerical model capable of simulating a ship navigating through pack ice area is proposed,which uses Computational Fluid Dynamics(CFD)method to solve the flow field and applies the Discrete Element Method(DEM)to simulate ship-ice and ice-ice interactions.Besides,the proposed high-precision method for generating pack ice area can be used in conjunction with the proposed numerical model.By comparing the numerical results with the available model test data and experimental observations,the effectiveness of the numerical model is validated,demonstrating its strong capability of predicting resistance and simulating ship navigation in pack ice,as well as its significant potential and applicability for further studies.
文摘In order to accurately forecast the main engine fuel consumption and reduce the Energy Efficiency Operational Indicator(EEOI)of merchant ships in polar ice areas,the energy transfer relationship between ship-machine-propeller is studied by analyzing the complex force situation during ship navigation and building a MATLAB/Simulink simulation platform based on multi-environmental resistance,propeller efficiency,main engine power,fuel consumption,fuel consumption rate and EEOI calculation module.Considering the environmental factors of wind,wave and ice,the route is divided into sections,the calculation of main engine power,main engine fuel consumption and EEOI for each section is completed,and the speed design is optimized based on the simulation model for each section.Under the requirements of the voyage plan,the optimization results show that the energy efficiency operation index of the whole route is reduced by 3.114%and the fuel consumption is reduced by 9.17 t.
文摘World’s First Ammonia-Fueled Vessel Sets Sail The world's first pure ammonia-powered demonstration vessel,the Anhui,successfully completed its maiden voyage in Hefei,east China's Anhui Province,on June 28,marking a major step forward for green shipping.Ammonia,a major chemical industry feedstock,has a high energy density and due to its carbon-free nature,produces only water and nitrogen when fully combusted.This makes it a highly promising fuel for decarbonizing shipping.
文摘The Titanic sunk 113 years ago on April 14-15,after hitting an iceberg,with human error likely causing the ship to wander into those dangerous waters.Today,autonomous systems built on AI can help ships avoid such accidents.But could such a system explain to the captain why it was controlling the ship in a certain way?
文摘Semisubmersible naval ships are versatile military crafts that combine the advantageous features of high-speed planing crafts and submarines.At-surface,these ships are designed to provide sufficient speed and maneuverability.Additionally,they can perform shallow dives,offering low visual and acoustic detectability.Therefore,the hydrodynamic design of a semisubmersible naval ship should address at-surface and submerged conditions.In this study,Numerical analyses were performed using a semisubmersible hull form to analyze its hydrodynamic features,including resistance,powering,and maneuvering.The simulations were conducted with Star CCM+version 2302,a commercial package program that solves URANS equations using the SST k-ωturbulence model.The flow analysis was divided into two parts:at-surface simulations and shallowly submerged simulations.At-surface simulations cover the resistance,powering,trim,and sinkage at transition and planing regimes,with corresponding Froude numbers ranging from 0.42 to 1.69.Shallowly submerged simulations were performed at seven different submergence depths,ranging from D/LOA=0.0635 to D/LOA=0.635,and at two different speeds with Froude numbers of 0.21 and 0.33.The behaviors of the hydrodynamic forces and pitching moment for different operation depths were comprehensively analyzed.The results of the numerical analyses provide valuable insights into the hydrodynamic performance of semisubmersible naval ships,highlighting the critical factors influencing their resistance,powering,and maneuvering capabilities in both at-surface and submerged conditions.
