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
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
Ship emissions contribute considerably to air pollution and are expected to decline under domestic policies and international cooperation such as green shipping corridors(GSCs).However,evaluation of the emission reduc...Ship emissions contribute considerably to air pollution and are expected to decline under domestic policies and international cooperation such as green shipping corridors(GSCs).However,evaluation of the emission reduction potential by the Domestic Emission Control Area(DECA)policy and GSC cooperation is still lacking.Here,a series of multi-year high spatiotemporal ship emission inventories around Hainan,a representative island province of China,were developed with the state-of-the-art Shipping Emission Inventory Model.The improved origin-destination identification algorithm allowed emission allocation to port level.The emission reduction potential of the DECA policy and Hainan's joining GSCwas analyzed.In 2022,ship emission intensity in waters 12 Nm from Hainan(Hainan-12Nm)were 6.4%-7.4% of that in waters 12 Nm from China.From 2019 to 2022,Hainan-12Nm emissions dropped by 66.7%-77.8% for SO_(2) and PM2.5.Ideally,with adequate ultra-low-sulfur fuel,DECA can reduce SO_(2) and PM2.5 emissions by 16.6% and 22.4% yearly compared with no-DECA scenario.However,emission reduction would drop markedly if ultra-low-sulfur fuel is short in supply.Emissions of voyages passing through 200 Nm from Hainan took up 1%-4%of international shipping emissions,implying great emission reduction potential for Hainan's establishing GSCs,especially considering the flourishing South-South trade.This study provides a thorough assessment of the current state of shipping emissions around Hainan as well as offers excellent data support for Hainan to further advance the future upgrade of ship emission management policies.展开更多
Ships experience rolling motion under the action of sea waves and may even face the risk of capsizing.Anti-rolling devices are designed to reduce this motion and enhance vessel safety.This is especially critical for e...Ships experience rolling motion under the action of sea waves and may even face the risk of capsizing.Anti-rolling devices are designed to reduce this motion and enhance vessel safety.This is especially critical for engineering ships operating at sea under zero-speed conditions,where a stable posture is essential for efficient performance.Gyro stabilizers can suppress roll motion at zero speed;however,their high cost typically makes them unsuitable for large civilian vessels.Additionally,most existing anti-rolling devices rely on a certain water speed to function,which results in increased drag.In this study,an anti-rolling system incorporating swing control is proposed.Inspired by the human body's ability to maintain balance by swinging arms during walking or running,the system generates an antirolling moment by oscillating a water tank.This approach operates independently of water speed and does not generate additional drag.The mechanical design of the anti-rolling system is introduced,and a corresponding control system model is derived.The swing-tank mechanism provides phase lead compensation and reduces the system's sensitivity to wave disturbances.To enhance performance,robust control techniques are applied.Simulation results demonstrate that the proposed anti-rolling system delivers effective roll reduction for ships.展开更多
UAV shipboard landing poses significant challenges in terms of safety and efficiency,due to the oscillatory ship motion caused by wave interactions and wind gusts,especially in rough sea states.To solve this issue,a f...UAV shipboard landing poses significant challenges in terms of safety and efficiency,due to the oscillatory ship motion caused by wave interactions and wind gusts,especially in rough sea states.To solve this issue,a flight envelope constrained fixed-time control strategy is proposed to achieve a reliable UAV landing on a maneuvering ship.Firstly,a sliding data window autoregressive model is designed to predict the ship's roll and pitch motions,which are accordingly utilized to identify an appropriate quiescent period for safe landing.Subsequently,a barrier-function-based nonsingular terminal sliding mode controller is developed to eliminate the tracking errors within the identified quiescent period,while ensuring the errors remain bounded to satisfy flight envelope constraints.In particular,lumped disturbance components are estimated by integrating a fixed-time disturbance observer and compensated in the controller.The key advantage of the proposed approach is that it well balances the control requirements between precise landing position and safe landing attitude,guaranteeing both steady-state performance and transient behavior of the tracking error.Finally,comparative Gazebo simulations in different sea state scenarios are conducted to verify the satisfactory control performance.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
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
Recently,ship detection technology has been applied extensively in the marine security monitoring field.However,achieving accurate marine ship detection still poses significant challenges due to factors such as varyin...Recently,ship detection technology has been applied extensively in the marine security monitoring field.However,achieving accurate marine ship detection still poses significant challenges due to factors such as varying scales,slightly occluded objects,uneven illumination,and sea clutter.To address these issues,we propose a novel ship detection approach,i.e.,the Twin Feature Pyramid Network and Data Augmentation(TFPN-DA),which mainly consists of three modules.First,to eliminate the negative effects of slightly occluded objects and uneven illumination,we propose the Spatial Attention within the Twin Feature Pyramid Network(SA-TFPN)method,which is based on spatial attention to reconstruct the feature pyramid.Second,the ROI Feature Module(ROIFM)is introduced into the SA-TFPN,which is used to enhance specific crucial details from multi-scale features for object regression and classification.Additionally,data augmentation strategies such as spatial affine transformation and noise processing,are developed to optimize the data sample distribution.A self-construct dataset is used to train the detection model,and the experiments conducted on the dataset demonstrate the effectiveness of our model.展开更多
Polar marine equipment plays an important role in Arctic engineering,especially in the development of polar ships and ice-class propellers.When polar ships navigate in brash ice channels,the brash ice not only increas...Polar marine equipment plays an important role in Arctic engineering,especially in the development of polar ships and ice-class propellers.When polar ships navigate in brash ice channels,the brash ice not only increases resistance but also has adverse effects on their propulsion performance.On the basis of coupled computational fluid dynamics(CFD)and the discrete element method(DEM),this paper aims to numerically investigate the resistance and propulsion performance of a polar in a brash ice channel while considering the rotation status of the propeller by both experimental and numerical methods.Both ship resistance and ice motion under Froude numbers of 0.0557,0.0696,0.0836,0.975,and 0.1114 are studied when the propeller does not rotate.The influences of the rotating propeller on the ice brash resistance and flow are discussed.The thrust due to the propeller and ice resistance in the equilibrium state are also predicted.The errors between the thrust and total resistance are approximately 1.0%,and the maximum error between the simulated and predicted total resistance is 3.7%,which validates the CFD-DEM coupling method quite well.This work could provide a theoretical basis for the initial design of polar ships with low ice class notation and assist in planning navigation for merchant polar ships in brash ice fields.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
Obtaining accurate ship positions and headings in remote sensing images plays a crucial role in various applications.However,current deep learning-based methods primarily focus on ship position detection,while the det...Obtaining accurate ship positions and headings in remote sensing images plays a crucial role in various applications.However,current deep learning-based methods primarily focus on ship position detection,while the detection of ship wakes relies on traditional non-deep learning approaches,which often underperform in complex marine environments.We proposed a novel,simple,and efficient method called Point-Vector Net.The proposed method leverages convolutional neural networks(CNN)for feature extraction and subsequently integrates multi-scale features to generate high-resolution feature maps.In the final stage,ship positions and headings are represented using a combination of points and vectors.Comparative experiments with results from automatic identification system(AIS)reports demonstrate that our method achieved impressive performance in two-class ship target detection,with an average precision of 96.4%,recall rate of 94.3%,and an F 1 score of 95.2%.Notably,the average heading error was 3.3°.The proposed model achieved a practical inference speed(FPS>30),and the average processing time for inferring a large-scale Sentinel-2 remote sensing image was 11.4 s.展开更多
To safeguard the ocean ecosystem,fuel cells are excellent candidates as the primary energy supply for marine vessels due to their high efficiency,low noise,and cleanliness.However,fuel cells in hybrid power systems ar...To safeguard the ocean ecosystem,fuel cells are excellent candidates as the primary energy supply for marine vessels due to their high efficiency,low noise,and cleanliness.However,fuel cells in hybrid power systems are highly susceptible to load transients,which can severely damage fuel cells and shorten their lifespan.Therefore,the formulation of energy management strategies accounting for power degradation is crucial and urgent.In this study,an improved strategy for equivalent consumption minimization strategy(ECMS)considering power degradation is proposed.The improved energy control strategy effectively controls the energy distribution of hydrogen fuel cells,lithium batteries,and supercapacitors in hybrid power ships.The proposed control strategy combines the ECMS with an adaptive filteringmethod.The main objective of the ECMS is to allocate power to the fuel cell systems and energy storage systems(ESS)to stabilize the power output of fuel cells,prolong their service life,and reduce the hydrogen consumption in fuel cells.The adaptive filteringmethod,by low-pass filtering of the energy in the energy storage system,is used to allocate power between lithium batteries and supercapacitors to minimize the effect of transient and peak energy output on the lifespan of lithium batteries.To verify the superiority of the control strategy,a mathematical model for the hybrid power system is developed.In comparison to traditional ECMS and traditional ECMS considering degradation,the improved ECMS considering power degradation shows better performance in the overall economy,the durability of fuel cells and batteries,and system dynamic performance.展开更多
This paper deeply explores the autonomous collision avoidance algorithm for intelligent ships,aiming to enhance the intelligence level and safety of ship collision avoidance by integrating navigation experience.An aut...This paper deeply explores the autonomous collision avoidance algorithm for intelligent ships,aiming to enhance the intelligence level and safety of ship collision avoidance by integrating navigation experience.An autonomous collision avoidance algorithm based on navigation experience is designed,a collision avoidance experience database is constructed,a quantitative model is established,and specific algorithm steps are implemented.The algorithm is verified and analyzed through simulation tests.The results show that the algorithm can effectively achieve autonomous ship collision avoidance in different scenarios,providing new ideas and methods for the development of intelligent ship collision avoidance technology.展开更多
The global shipping industry,like many others,is under growing pressure to be more sustainable.Regulation,renewable energy advances and customer demand have created a golden opportunity to make shipping more environme...The global shipping industry,like many others,is under growing pressure to be more sustainable.Regulation,renewable energy advances and customer demand have created a golden opportunity to make shipping more environmentally sustainable,which,however,entails significant funding.Traditional ship financing has been done largely on a secured basis,with relatively few considerations around sustainability and environmental protection.This approach is ripe for innovation,given the industry’s significant environmental footprint.Evidence from other industries suggests that borrowers could benefit in pricing and structure from sustainable borrowing mechanisms,such as green bonds(where proceeds are dedicated to environmental and social investment).The trend is also increasing for sustainable loans,which can help to meet the growing demand for retrofit financing within existing vessels to meet CO_(2)emission targets.This paper aims to explore the attitudes of shipping industry participants,through the use of a survey,to green financing,that is,issuing unsecured and covered green,social,and sustainable bonds and other related financing instruments.These could effectively advance the environmental and social agenda in the industry,strengthening environmental,social,and governance(ESG)structures at the same time.Preliminary results suggest that there is considerable scope for improving knowledge and awareness among marine professionals to bridge the sustainability gap.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
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.
基金supported by the National Natural Science Foundation of China(No.42325505)the National Key R&D Program of China(No.2022YFC3704200)the Tsinghua University Initiative Scientific Research Program.
文摘Ship emissions contribute considerably to air pollution and are expected to decline under domestic policies and international cooperation such as green shipping corridors(GSCs).However,evaluation of the emission reduction potential by the Domestic Emission Control Area(DECA)policy and GSC cooperation is still lacking.Here,a series of multi-year high spatiotemporal ship emission inventories around Hainan,a representative island province of China,were developed with the state-of-the-art Shipping Emission Inventory Model.The improved origin-destination identification algorithm allowed emission allocation to port level.The emission reduction potential of the DECA policy and Hainan's joining GSCwas analyzed.In 2022,ship emission intensity in waters 12 Nm from Hainan(Hainan-12Nm)were 6.4%-7.4% of that in waters 12 Nm from China.From 2019 to 2022,Hainan-12Nm emissions dropped by 66.7%-77.8% for SO_(2) and PM2.5.Ideally,with adequate ultra-low-sulfur fuel,DECA can reduce SO_(2) and PM2.5 emissions by 16.6% and 22.4% yearly compared with no-DECA scenario.However,emission reduction would drop markedly if ultra-low-sulfur fuel is short in supply.Emissions of voyages passing through 200 Nm from Hainan took up 1%-4%of international shipping emissions,implying great emission reduction potential for Hainan's establishing GSCs,especially considering the flourishing South-South trade.This study provides a thorough assessment of the current state of shipping emissions around Hainan as well as offers excellent data support for Hainan to further advance the future upgrade of ship emission management policies.
基金supported by the Jiangxi University of Water Resources and Electric Power Doctoral Research Initiation Fund(Grant No.2024kyqd030)。
文摘Ships experience rolling motion under the action of sea waves and may even face the risk of capsizing.Anti-rolling devices are designed to reduce this motion and enhance vessel safety.This is especially critical for engineering ships operating at sea under zero-speed conditions,where a stable posture is essential for efficient performance.Gyro stabilizers can suppress roll motion at zero speed;however,their high cost typically makes them unsuitable for large civilian vessels.Additionally,most existing anti-rolling devices rely on a certain water speed to function,which results in increased drag.In this study,an anti-rolling system incorporating swing control is proposed.Inspired by the human body's ability to maintain balance by swinging arms during walking or running,the system generates an antirolling moment by oscillating a water tank.This approach operates independently of water speed and does not generate additional drag.The mechanical design of the anti-rolling system is introduced,and a corresponding control system model is derived.The swing-tank mechanism provides phase lead compensation and reduces the system's sensitivity to wave disturbances.To enhance performance,robust control techniques are applied.Simulation results demonstrate that the proposed anti-rolling system delivers effective roll reduction for ships.
文摘UAV shipboard landing poses significant challenges in terms of safety and efficiency,due to the oscillatory ship motion caused by wave interactions and wind gusts,especially in rough sea states.To solve this issue,a flight envelope constrained fixed-time control strategy is proposed to achieve a reliable UAV landing on a maneuvering ship.Firstly,a sliding data window autoregressive model is designed to predict the ship's roll and pitch motions,which are accordingly utilized to identify an appropriate quiescent period for safe landing.Subsequently,a barrier-function-based nonsingular terminal sliding mode controller is developed to eliminate the tracking errors within the identified quiescent period,while ensuring the errors remain bounded to satisfy flight envelope constraints.In particular,lumped disturbance components are estimated by integrating a fixed-time disturbance observer and compensated in the controller.The key advantage of the proposed approach is that it well balances the control requirements between precise landing position and safe landing attitude,guaranteeing both steady-state performance and transient behavior of the tracking error.Finally,comparative Gazebo simulations in different sea state scenarios are conducted to verify the satisfactory control performance.
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 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Recently,ship detection technology has been applied extensively in the marine security monitoring field.However,achieving accurate marine ship detection still poses significant challenges due to factors such as varying scales,slightly occluded objects,uneven illumination,and sea clutter.To address these issues,we propose a novel ship detection approach,i.e.,the Twin Feature Pyramid Network and Data Augmentation(TFPN-DA),which mainly consists of three modules.First,to eliminate the negative effects of slightly occluded objects and uneven illumination,we propose the Spatial Attention within the Twin Feature Pyramid Network(SA-TFPN)method,which is based on spatial attention to reconstruct the feature pyramid.Second,the ROI Feature Module(ROIFM)is introduced into the SA-TFPN,which is used to enhance specific crucial details from multi-scale features for object regression and classification.Additionally,data augmentation strategies such as spatial affine transformation and noise processing,are developed to optimize the data sample distribution.A self-construct dataset is used to train the detection model,and the experiments conducted on the dataset demonstrate the effectiveness of our model.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFE0107000)the Fundamental Research Funds for the Central Universities(Grant No.HYGJXM202319).
文摘Polar marine equipment plays an important role in Arctic engineering,especially in the development of polar ships and ice-class propellers.When polar ships navigate in brash ice channels,the brash ice not only increases resistance but also has adverse effects on their propulsion performance.On the basis of coupled computational fluid dynamics(CFD)and the discrete element method(DEM),this paper aims to numerically investigate the resistance and propulsion performance of a polar in a brash ice channel while considering the rotation status of the propeller by both experimental and numerical methods.Both ship resistance and ice motion under Froude numbers of 0.0557,0.0696,0.0836,0.975,and 0.1114 are studied when the propeller does not rotate.The influences of the rotating propeller on the ice brash resistance and flow are discussed.The thrust due to the propeller and ice resistance in the equilibrium state are also predicted.The errors between the thrust and total resistance are approximately 1.0%,and the maximum error between the simulated and predicted total resistance is 3.7%,which validates the CFD-DEM coupling method quite well.This work could provide a theoretical basis for the initial design of polar ships with low ice class notation and assist in planning navigation for merchant polar ships in brash ice fields.
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 the National Key R&D Program of China(No.2022YFB3902400)the China High Resolution Earth Observation System Program(No.41-Y30F07-9001-20/22)。
文摘Obtaining accurate ship positions and headings in remote sensing images plays a crucial role in various applications.However,current deep learning-based methods primarily focus on ship position detection,while the detection of ship wakes relies on traditional non-deep learning approaches,which often underperform in complex marine environments.We proposed a novel,simple,and efficient method called Point-Vector Net.The proposed method leverages convolutional neural networks(CNN)for feature extraction and subsequently integrates multi-scale features to generate high-resolution feature maps.In the final stage,ship positions and headings are represented using a combination of points and vectors.Comparative experiments with results from automatic identification system(AIS)reports demonstrate that our method achieved impressive performance in two-class ship target detection,with an average precision of 96.4%,recall rate of 94.3%,and an F 1 score of 95.2%.Notably,the average heading error was 3.3°.The proposed model achieved a practical inference speed(FPS>30),and the average processing time for inferring a large-scale Sentinel-2 remote sensing image was 11.4 s.
基金The study was founded by the National Key R&D Program of China(2022YFB4301403).
文摘To safeguard the ocean ecosystem,fuel cells are excellent candidates as the primary energy supply for marine vessels due to their high efficiency,low noise,and cleanliness.However,fuel cells in hybrid power systems are highly susceptible to load transients,which can severely damage fuel cells and shorten their lifespan.Therefore,the formulation of energy management strategies accounting for power degradation is crucial and urgent.In this study,an improved strategy for equivalent consumption minimization strategy(ECMS)considering power degradation is proposed.The improved energy control strategy effectively controls the energy distribution of hydrogen fuel cells,lithium batteries,and supercapacitors in hybrid power ships.The proposed control strategy combines the ECMS with an adaptive filteringmethod.The main objective of the ECMS is to allocate power to the fuel cell systems and energy storage systems(ESS)to stabilize the power output of fuel cells,prolong their service life,and reduce the hydrogen consumption in fuel cells.The adaptive filteringmethod,by low-pass filtering of the energy in the energy storage system,is used to allocate power between lithium batteries and supercapacitors to minimize the effect of transient and peak energy output on the lifespan of lithium batteries.To verify the superiority of the control strategy,a mathematical model for the hybrid power system is developed.In comparison to traditional ECMS and traditional ECMS considering degradation,the improved ECMS considering power degradation shows better performance in the overall economy,the durability of fuel cells and batteries,and system dynamic performance.
基金Research and Development of Unmanned Vessel System Based on Intelligent Ship-Shore Collaborative Technology,Hainan University of Science and Technology Science Research(HKKY2024-79)。
文摘This paper deeply explores the autonomous collision avoidance algorithm for intelligent ships,aiming to enhance the intelligence level and safety of ship collision avoidance by integrating navigation experience.An autonomous collision avoidance algorithm based on navigation experience is designed,a collision avoidance experience database is constructed,a quantitative model is established,and specific algorithm steps are implemented.The algorithm is verified and analyzed through simulation tests.The results show that the algorithm can effectively achieve autonomous ship collision avoidance in different scenarios,providing new ideas and methods for the development of intelligent ship collision avoidance technology.
文摘The global shipping industry,like many others,is under growing pressure to be more sustainable.Regulation,renewable energy advances and customer demand have created a golden opportunity to make shipping more environmentally sustainable,which,however,entails significant funding.Traditional ship financing has been done largely on a secured basis,with relatively few considerations around sustainability and environmental protection.This approach is ripe for innovation,given the industry’s significant environmental footprint.Evidence from other industries suggests that borrowers could benefit in pricing and structure from sustainable borrowing mechanisms,such as green bonds(where proceeds are dedicated to environmental and social investment).The trend is also increasing for sustainable loans,which can help to meet the growing demand for retrofit financing within existing vessels to meet CO_(2)emission targets.This paper aims to explore the attitudes of shipping industry participants,through the use of a survey,to green financing,that is,issuing unsecured and covered green,social,and sustainable bonds and other related financing instruments.These could effectively advance the environmental and social agenda in the industry,strengthening environmental,social,and governance(ESG)structures at the same time.Preliminary results suggest that there is considerable scope for improving knowledge and awareness among marine professionals to bridge the sustainability gap.
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.
