In the international shipping industry, digital intelligence transformation has become essential, with both governments and enterprises actively working to integrate diverse datasets. The domain of maritime and shippi...In the international shipping industry, digital intelligence transformation has become essential, with both governments and enterprises actively working to integrate diverse datasets. The domain of maritime and shipping is characterized by a vast array of document types, filled with complex, large-scale, and often chaotic knowledge and relationships. Effectively managing these documents is crucial for developing a Large Language Model (LLM) in the maritime domain, enabling practitioners to access and leverage valuable information. A Knowledge Graph (KG) offers a state-of-the-art solution for enhancing knowledge retrieval, providing more accurate responses and enabling context-aware reasoning. This paper presents a framework for utilizing maritime and shipping documents to construct a knowledge graph using GraphRAG, a hybrid tool combining graph-based retrieval and generation capabilities. The extraction of entities and relationships from these documents and the KG construction process are detailed. Furthermore, the KG is integrated with an LLM to develop a Q&A system, demonstrating that the system significantly improves answer accuracy compared to traditional LLMs. Additionally, the KG construction process is up to 50% faster than conventional LLM-based approaches, underscoring the efficiency of our method. This study provides a promising approach to digital intelligence in shipping, advancing knowledge accessibility and decision-making.展开更多
Deep-sea mineral resource transportation predominantly utilizes hydraulic pipeline methodology.Environmental factors induce vibrations in flexible pipelines,thereby affecting the internal flow characteristics.Therefor...Deep-sea mineral resource transportation predominantly utilizes hydraulic pipeline methodology.Environmental factors induce vibrations in flexible pipelines,thereby affecting the internal flow characteristics.Therefore,real-time monitoring of solid–liquid two-phase flow in pipelines is crucial for system maintenance.This study develops an autoencoder-based deep learning framework to reconstruct three-dimensional solid–liquid two-phase flow within flexible vibrating pipelines utilizing sparse wall information from sensors.Within this framework,separate X-model and F-model with distinct hidden-layer structures are established to reconstruct the coordinates and flow field information on the computational domain grid of the pipeline under traveling wave vibration.Following hyperparameter optimization,the models achieved high reconstruction accuracy,demonstrating R^(2)values of 0.990 and 0.945,respectively.The models’robustness is evaluated across three aspects:vibration parameters,physical fields,and vibration modes,demonstrating good reconstruction performance.Results concerning sensors show that 20 sensors(0.06%of total grids)achieve a balance between accuracy and cost,with superior accuracy obtained when arranged along the full length of the pipe compared to a dense arrangement at the front end.The models exhibited a signal-to-noise ratio tolerance of approximately 27 dB,with reconstruction accuracy being more affected by sensor failures at both ends of the pipeline.展开更多
We often hear statements like“the market raises expectations for central bank interest rate cuts,resulting in higher commodity prices”.Given the current situation,the People’s Bank of China might adopt a more accom...We often hear statements like“the market raises expectations for central bank interest rate cuts,resulting in higher commodity prices”.Given the current situation,the People’s Bank of China might adopt a more accommodative monetary policy to mitigate the impact of the China-U.S.trade friction.Will this further easing of the monetary environment lead to an increase in natural gas prices?展开更多
China and ASEAN(Association of Southeast Asian Nations)have concluded the negotiations for the China-ASEAN Free Trade Area 3.0.The recent ASEAN Summit also initiated“the ASEAN Community Vision 2045”,highlighting vas...China and ASEAN(Association of Southeast Asian Nations)have concluded the negotiations for the China-ASEAN Free Trade Area 3.0.The recent ASEAN Summit also initiated“the ASEAN Community Vision 2045”,highlighting vast cooperation potential and broad prospects for collaboration between the two sides in green and sustainable development.Under such background,this article issues new areas and opportunities for collaboration in climate-related fields for addressing the“Energy Trilemma”problems,based on the considerations of natural resource endowments and current cooperation status of both sides,in expectations of promoting inclusive and sustainable regional growth while achieving mutual benefits and win-win development for all parties involved.展开更多
The cost and strict input format requirements of GraphRAG make it less efficient for processing large documents. This paper proposes an alternative approach for constructing a knowledge graph (KG) from a PDF document ...The cost and strict input format requirements of GraphRAG make it less efficient for processing large documents. This paper proposes an alternative approach for constructing a knowledge graph (KG) from a PDF document with a focus on simplicity and cost-effectiveness. The process involves splitting the document into chunks, extracting concepts within each chunk using a large language model (LLM), and building relationships based on the proximity of concepts in the same chunk. Unlike traditional named entity recognition (NER), which identifies entities like “Shanghai”, the proposed method identifies concepts, such as “Convenient transportation in Shanghai” which is found to be more meaningful for KG construction. Each edge in the KG represents a relationship between concepts occurring in the same text chunk. The process is computationally inexpensive, leveraging locally set up tools like Mistral 7B openorca instruct and Ollama for model inference, ensuring the entire graph generation process is cost-free. A method of assigning weights to relationships, grouping similar pairs, and summarizing multiple relationships into a single edge with associated weight and relation details is introduced. Additionally, node degrees and communities are calculated for node sizing and coloring. This approach offers a scalable, cost-effective solution for generating meaningful knowledge graphs from large documents, achieving results comparable to GraphRAG while maintaining accessibility for personal machines.展开更多
With the continuous development of artificial intelligence and natural language processing technologies, traditional retrieval-augmented generation (RAG) techniques face numerous challenges in document answer precisio...With the continuous development of artificial intelligence and natural language processing technologies, traditional retrieval-augmented generation (RAG) techniques face numerous challenges in document answer precision and similarity measurement. This study, set against the backdrop of the shipping industry, combines top-down and bottom-up schema design strategies to achieve precise and flexible knowledge representation. The research adopts a semi-structured approach, innovatively constructing an adaptive schema generation mechanism based on reinforcement learning, which models the knowledge graph construction process as a Markov decision process. This method begins with general concepts, defining foundational industry concepts, and then delves into abstracting core concepts specific to the maritime domain through an adaptive pattern generation mechanism that dynamically adjusts the knowledge structure. Specifically, the study designs a four-layer knowledge construction framework, including the data layer, modeling layer, technology layer, and application layer. It draws on a mutual indexing strategy, integrating large language models and traditional information extraction techniques. By leveraging self-attention mechanisms and graph attention networks, it efficiently extracts semantic relationships. The introduction of logic-form-driven solvers and symbolic decomposition techniques for reasoning significantly enhances the model’s ability to understand complex semantic relationships. Additionally, the use of open information extraction and knowledge alignment techniques further improves the efficiency and accuracy of information retrieval. Experimental results demonstrate that the proposed method not only achieves significant performance improvements in knowledge graph retrieval within the shipping domain but also holds important theoretical innovation and practical application value.展开更多
Unmanned surface vehicles(USVs)play a crucial role in various fields,including ocean climate change monitoring,ma-rine resource exploitation,and ecological environment exploration.Out of the many types of USVs,unmanne...Unmanned surface vehicles(USVs)play a crucial role in various fields,including ocean climate change monitoring,ma-rine resource exploitation,and ecological environment exploration.Out of the many types of USVs,unmanned sailboats have gained considerable attention for their ability to conduct green,large-scale ocean observations.Building on this concept,this paper proposes an unmanned sailboat propelled by parallel dual-wing sails,which is designed to meet the demands of extensive and three-dimensional marine comprehensive observation and data collection.With a focus on the parallel dual-wing sails,this study particularly investi-gates the effects of variations in the airfoil’s angle of attack and the impact of the spacing ratio between the dual sails on propulsion performance.It further analyzes the influence of one sail’s angle of attack on the performance of the other sail,as well as the flow field between the two sails.For the air navigation and underwater states,the force characteristics of the dual sail under different inflow velocities were investigated.The research findings indicate that,under certain conditions,the thrust coefficient exhibits a trend of first increasing,then decreasing,and finally increasing again with alterations in the angle of attackα.Different single-sail angles of attack have varying impacts on the opposite sail and the flow field between the dual sails.Moreover,the generated forces are positively correlated with inflow velocity in the air navigation and underwater states.The findings reveal that it is possible to reduce drag,mitigate the adverse effects of sail interaction,and thereby enhance the propulsion performance and overall navigational stability of the sailboat by applying an optimal spacing ratio design and adjusting the angle of attack and inflow velocity.展开更多
With the development of marine resources,a dual-platform joint operation has been paid more attention.In this paper,the mooring layout space and relative motion limitation of the dual-platform berthing operation were ...With the development of marine resources,a dual-platform joint operation has been paid more attention.In this paper,the mooring layout space and relative motion limitation of the dual-platform berthing operation were fully considered.A new hybrid mooring system with“X+buoy”combination was designed based on the characteristics of catenary and tension mooring.The hydrodynamic characteristics of the new mooring system were analyzed by combining numerical simulation with model experiment.Under the regular and freak waves with different wave heights and periods,the time-domain full-coupling analysis method was used to study the hydrodynamic characteristics of the mooring system.It can be found that the arrangement of dual-platform under 0◦wave direction is optimal,and the“X+buoy”combined mooring system designed in this paper has a good follow-up between the two platforms under different regular and freak waves.The relative motion response between the two platforms can be effectively controlled,and finally the positioning of the dual-platform joint operation is realized.Research results of this paper provide a theoretical basis and technical support for the hydrodynamic performance analysis and safety assessment of deep-sea offshore platforms in China.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
In order to analyze the ice-going ship’s performance under the pack ice conditions, synthetic ice was introduced into a towing tank. A barrier using floating cylinder in the towing tank was designed to carry out the ...In order to analyze the ice-going ship’s performance under the pack ice conditions, synthetic ice was introduced into a towing tank. A barrier using floating cylinder in the towing tank was designed to carry out the resistance experiment. The test results indicated that the encountering frequency between the ship model and the pack ice shifts towards a high-velocity point as the concentration of the pack ice increases, and this encountering frequency creates an unstable region of the resistance, and the unstable region shifts to the higher speed with the increasing concentration. The results also showed that for the same speed points, the ratio of the pack ice resistance to the open water resistance increases with the increasing concentration, and for the same concentrations, this ratio decreases as the speed increases. Motion characteristics showed that the mean value of the heave motion increases as the speed increases, and the pitch motion tends to increase with the increasing speed. In addition, the total resistance of the fullscale was predicted.展开更多
Global strength is a significant item for floating production storage and offloading(FPSO) design, and steel weight plays an important role in the building costs of FPSO. It is the main task to consider and combine th...Global strength is a significant item for floating production storage and offloading(FPSO) design, and steel weight plays an important role in the building costs of FPSO. It is the main task to consider and combine these two aspects by optimizing hull dimensions. There are many optional methods for the global strength analysis. A common method is to use the ABS FPSO Eagle software to analyze the global strength including the rule check and direct strength analysis. And the same method can be adopted for the FPSO hull optimization by changing the depth. After calculation and optimization, the results are compared and analyzed. The results can be used as a reference for the future design or quotation purpose.展开更多
The stiffened cylindrical shell is commonly used for the pressure hull of submersibles and the legs of offshore platforms. There are various failure modes because of uncertainty with the structural size and material p...The stiffened cylindrical shell is commonly used for the pressure hull of submersibles and the legs of offshore platforms. There are various failure modes because of uncertainty with the structural size and material properties, uncertainty of the calculation model and machining errors. Correlations among failure modes must be considered with the structural reliability of stiffened cylindrical shells. However, the traditional method cannot consider the correlations effectively. The aim of this study is to present a method of reliability analysis for stiffened cylindrical shells which considers the correlations among failure modes. Firstly, the joint failure probability calculation formula of two related failure modes is derived through use of the 2D joint probability density function. Secondly, the full probability formula of the tandem structural system is given with consideration to the correlations among failure modes. At last, the accuracy of the system reliability calculation is verified through use of the Monte Carlo simulation. Result of the analysis shows the failure probability of stiffened cylindrical shells can be gained through adding the failure probability of each mode.展开更多
The crashworthiness of the cargo containment systems （CCSs） of a floating liquid natural gas （FLNG） and the side structures in side-by-side offioading operations scenario are studied in this paper. An FLNG vessel ...The crashworthiness of the cargo containment systems （CCSs） of a floating liquid natural gas （FLNG） and the side structures in side-by-side offioading operations scenario are studied in this paper. An FLNG vessel is exposed to potential threats from collisions with a liquid natural gas carrier （LNGC） during the offioading operations, which has been confirmed by a model test of FLNG-LNGC side-by-side offioading operations. A nonlinear finite element code LS-DYNA is used to simulate the collision scenarios during the offioading operations. Finite element models of an FLNG vessel and an LNGC are established for the purpose of this study, including a detailed LNG cargo containment system in the FLNG side model. Based on the parameters obtained from the model test and potential dangerous accidents, typical collision scenarios are defined to conduct a comprehensive study. To evaluate the safety of the FLNG vessel, a limit state is proposed based on the structural responses of the LNG CCS. The different characteristics of the structural responses for the primary structural components, energy dissipation and collision forces are obtained for various scenarios. Deformation of the inner hull is found to have a great effect on the responses of the LNG CCS, with approximately 160 mm deformation corresponding to the limit state. Densely arranged web frames can absorb over 35% of the collision energy and be proved to greatly enhance the crashwo- rthiness of the FLNG side structures.展开更多
Numerical simulations of evolution characteristics of slug flow across a 90°pipe bend have been carried out to study the fluid−structure interaction response induced by internal slug flow.The two-phase flow patte...Numerical simulations of evolution characteristics of slug flow across a 90°pipe bend have been carried out to study the fluid−structure interaction response induced by internal slug flow.The two-phase flow patterns and turbulence were modelled by using the volume of fluid(VOF)model and the Realizable k−εturbulence model respectively.Firstly,validation of the CFD model was carried out and the desirable results were obtained.The different flow patterns and the time-average mean void fraction was coincident with the reported experimental data.Simulations of different cases of slug flow have been carried out to show the effects of superficial gas and liquid velocity on the evolution characteristics of slug flow.Then,a one-way coupled fluid-structure interaction framework was established to investigate the slug flow interaction with a 90°pipe bend under various superficial liquid and gas velocities.It was found that the maximum total deformation and equivalent stress increased with the increasing superficial gas velocity,while decreased with the increasing superficial liquid velocity.In addition,the total deformation and equivalent stress has obvious periodic fluctuation.Furthermore,the distribution position of maximum deformation and stress was related to the evolution of slug flow.With the increasing superficial gas velocity,the maximum total deformation was mainly located at the 90°pipe bend.But as the superficial liquid velocity increases,the maximum total deformation was mainly located in the horizontal pipe section.Consequently,the slug flow with higher superficial gas velocity will induce more serious cyclical impact on the 90°pipe bend.展开更多
The roll motions are influenced by significant viscous effects such as the flow separation.The 3D simulations of free decay roll motions for the ship model DTMB 5512 are carried out by Reynold averaged NavierStokes(RA...The roll motions are influenced by significant viscous effects such as the flow separation.The 3D simulations of free decay roll motions for the ship model DTMB 5512 are carried out by Reynold averaged NavierStokes(RANS) method based on the dynamic mesh technique.A new moving mesh technique is adopted and discussed in details for the present simulations.The purpose of the research is to obtain accurate numerical prediction for roll motions with their respective numerical/modeling errors and uncertainties.Errors and uncertainties are estimated by performing the modern verification and validation(V&V) procedures.Simulation results for the free-floating surface combatant are used to calculate the linear,nonlinear damping coefficients and resonant frequencies including a wide range of forward speed.The present work can provide a useful reference to calculate roll damping by computational fluid dynamics(CFD) method and simulate a general ship motions in waves.展开更多
The scale effect leads to large discrepancies between the wake fields of model-scale and actual ships, and causes differences in cavitation performance and exciting forces tests in predicting the performance of actual...The scale effect leads to large discrepancies between the wake fields of model-scale and actual ships, and causes differences in cavitation performance and exciting forces tests in predicting the performance of actual ships. Therefore, when test data from ship models are directly applied to predict the performance of actual ships, test results must be subjected to empirical corrections. This study proposes a method for the reverse design of the hull model. Compared to a geometrically similar hull model, the wake field generated by the modified model is closer to that of an actual ship. A non-geometrically similar model of a Korean Research Institute of Ship and Ocean Engineering （KRISO）’s container ship （KCS） was designed. Numerical simulations were performed using this model, and its results were compared with full-scale calculation results. The deformation method of getting the wake field of full-scale ships by the non-geometrically similar model is applied to the KCS successfully.展开更多
The ice resistance on a ship hull affects the safety of the hull structure and the ship maneuvering performance in icecovered regions.In this paper,the discrete element method(DEM)is adopted to simulate the interactio...The ice resistance on a ship hull affects the safety of the hull structure and the ship maneuvering performance in icecovered regions.In this paper,the discrete element method(DEM)is adopted to simulate the interaction between level ice and ship hull.The level ice is modeled with 3D bonded spherical elements considering the buoyancy and drag force of the water.The parallel bonding approach and the de-bonding criterion are adopted to model the freezing and breakage of level ice.The ship hull is constructed with rigid triangle elements.To improve computational efficiency,the GPU-based parallel computational algorithm was developed for the DEM simulations.During the interaction between the ship hull and level ice,the ice cover is broken into small blocks when the interparticle stress approaches the bonding strength.The global ice resistance on the hull is calculated through the contacts between ice elements and hull elements during the navigation process.The influences of the ice thickness and navigation speed on the dynamic ice force are analyzed considering the breakage mechanism of ice cover.The Lindqvist and Riska formulas for the determination of ice resistance on ship hull are employed to validate the DEM simulation.The comparison of results of DEM,Lindqvist,and Riska formula show that the DEM result is between those the Lindqvist formula and Riska formula.Therefore the proposed DEM is an effective approach to determine the ice resistance on the ship hull.This work can be aided in the hull structure design and the navigation operation in ice-covered fields.展开更多
Twice-painting technique was adopted to prepare heavy-duty anticorrosive coating films formed by aqueous latexes of copolymers of vinylidene chloride（VDC） with an acrylate, namely methyl acrylate（MA）, ethyl acryl...Twice-painting technique was adopted to prepare heavy-duty anticorrosive coating films formed by aqueous latexes of copolymers of vinylidene chloride（VDC） with an acrylate, namely methyl acrylate（MA）, ethyl acrylate（EA）, butyl acrylate（BA） or 2-ethylhexyl acrylate（EHA）. Harsh salt-spray corrosion tests demonstrated that the optimized twicepainting technique was that the acidic latex solution was adjusted to p H 5-6 for the first painting, while it was utilized directly for the second painting. The test of 600 h of harsh salt-spray corrosion showed that MA-VDC85 coating could protect the steel excellently, whereas the other acrylate-VDC coatings with 75%-90% VDC content could not protect the steel so effectively. Further corrosion test showed that（1） MA-VDC85 coating protected steel from loss of metallic luster for at least 1000 h of salt-spray corrosion;（2） adhesion of MA-VDC85 coating to steel was excellent for at least 800 h of saltspray corrosion, but became very poor after 1000 h. Differential scanning calorimetry, thermogravimetric analysis, X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy were used to evaluate the corroded MA-VDC85 film.展开更多
文摘In the international shipping industry, digital intelligence transformation has become essential, with both governments and enterprises actively working to integrate diverse datasets. The domain of maritime and shipping is characterized by a vast array of document types, filled with complex, large-scale, and often chaotic knowledge and relationships. Effectively managing these documents is crucial for developing a Large Language Model (LLM) in the maritime domain, enabling practitioners to access and leverage valuable information. A Knowledge Graph (KG) offers a state-of-the-art solution for enhancing knowledge retrieval, providing more accurate responses and enabling context-aware reasoning. This paper presents a framework for utilizing maritime and shipping documents to construct a knowledge graph using GraphRAG, a hybrid tool combining graph-based retrieval and generation capabilities. The extraction of entities and relationships from these documents and the KG construction process are detailed. Furthermore, the KG is integrated with an LLM to develop a Q&A system, demonstrating that the system significantly improves answer accuracy compared to traditional LLMs. Additionally, the KG construction process is up to 50% faster than conventional LLM-based approaches, underscoring the efficiency of our method. This study provides a promising approach to digital intelligence in shipping, advancing knowledge accessibility and decision-making.
基金financial support by the National Natural Science Foundation of China (Nos.52471293 and 12372270)the National Youth Science Foundation of China (Nos.52101322 and 52108375)+3 种基金the Program for Intergovernmental International S&T Cooperation Projects of Shanghai Municipality, China (Nos.24510711100 and 22160710200)The Oceanic Interdisciplinary Program of Shanghai Jiao Tong University (No.SL2022PT101)funded by the Open Fund of the State Key Laboratory of Coastal and Offshore Engineering of Dalian University of Technology (No.LP2415)National Key R&D Program of China (No.2023YFC2811600)
文摘Deep-sea mineral resource transportation predominantly utilizes hydraulic pipeline methodology.Environmental factors induce vibrations in flexible pipelines,thereby affecting the internal flow characteristics.Therefore,real-time monitoring of solid–liquid two-phase flow in pipelines is crucial for system maintenance.This study develops an autoencoder-based deep learning framework to reconstruct three-dimensional solid–liquid two-phase flow within flexible vibrating pipelines utilizing sparse wall information from sensors.Within this framework,separate X-model and F-model with distinct hidden-layer structures are established to reconstruct the coordinates and flow field information on the computational domain grid of the pipeline under traveling wave vibration.Following hyperparameter optimization,the models achieved high reconstruction accuracy,demonstrating R^(2)values of 0.990 and 0.945,respectively.The models’robustness is evaluated across three aspects:vibration parameters,physical fields,and vibration modes,demonstrating good reconstruction performance.Results concerning sensors show that 20 sensors(0.06%of total grids)achieve a balance between accuracy and cost,with superior accuracy obtained when arranged along the full length of the pipe compared to a dense arrangement at the front end.The models exhibited a signal-to-noise ratio tolerance of approximately 27 dB,with reconstruction accuracy being more affected by sensor failures at both ends of the pipeline.
文摘We often hear statements like“the market raises expectations for central bank interest rate cuts,resulting in higher commodity prices”.Given the current situation,the People’s Bank of China might adopt a more accommodative monetary policy to mitigate the impact of the China-U.S.trade friction.Will this further easing of the monetary environment lead to an increase in natural gas prices?
文摘China and ASEAN(Association of Southeast Asian Nations)have concluded the negotiations for the China-ASEAN Free Trade Area 3.0.The recent ASEAN Summit also initiated“the ASEAN Community Vision 2045”,highlighting vast cooperation potential and broad prospects for collaboration between the two sides in green and sustainable development.Under such background,this article issues new areas and opportunities for collaboration in climate-related fields for addressing the“Energy Trilemma”problems,based on the considerations of natural resource endowments and current cooperation status of both sides,in expectations of promoting inclusive and sustainable regional growth while achieving mutual benefits and win-win development for all parties involved.
文摘The cost and strict input format requirements of GraphRAG make it less efficient for processing large documents. This paper proposes an alternative approach for constructing a knowledge graph (KG) from a PDF document with a focus on simplicity and cost-effectiveness. The process involves splitting the document into chunks, extracting concepts within each chunk using a large language model (LLM), and building relationships based on the proximity of concepts in the same chunk. Unlike traditional named entity recognition (NER), which identifies entities like “Shanghai”, the proposed method identifies concepts, such as “Convenient transportation in Shanghai” which is found to be more meaningful for KG construction. Each edge in the KG represents a relationship between concepts occurring in the same text chunk. The process is computationally inexpensive, leveraging locally set up tools like Mistral 7B openorca instruct and Ollama for model inference, ensuring the entire graph generation process is cost-free. A method of assigning weights to relationships, grouping similar pairs, and summarizing multiple relationships into a single edge with associated weight and relation details is introduced. Additionally, node degrees and communities are calculated for node sizing and coloring. This approach offers a scalable, cost-effective solution for generating meaningful knowledge graphs from large documents, achieving results comparable to GraphRAG while maintaining accessibility for personal machines.
文摘With the continuous development of artificial intelligence and natural language processing technologies, traditional retrieval-augmented generation (RAG) techniques face numerous challenges in document answer precision and similarity measurement. This study, set against the backdrop of the shipping industry, combines top-down and bottom-up schema design strategies to achieve precise and flexible knowledge representation. The research adopts a semi-structured approach, innovatively constructing an adaptive schema generation mechanism based on reinforcement learning, which models the knowledge graph construction process as a Markov decision process. This method begins with general concepts, defining foundational industry concepts, and then delves into abstracting core concepts specific to the maritime domain through an adaptive pattern generation mechanism that dynamically adjusts the knowledge structure. Specifically, the study designs a four-layer knowledge construction framework, including the data layer, modeling layer, technology layer, and application layer. It draws on a mutual indexing strategy, integrating large language models and traditional information extraction techniques. By leveraging self-attention mechanisms and graph attention networks, it efficiently extracts semantic relationships. The introduction of logic-form-driven solvers and symbolic decomposition techniques for reasoning significantly enhances the model’s ability to understand complex semantic relationships. Additionally, the use of open information extraction and knowledge alignment techniques further improves the efficiency and accuracy of information retrieval. Experimental results demonstrate that the proposed method not only achieves significant performance improvements in knowledge graph retrieval within the shipping domain but also holds important theoretical innovation and practical application value.
基金supported from the Shandong Provincial Natural Science Foundation(No.ZR2022ME147)the National Natural Science Foundation of China(No.52088102).
文摘Unmanned surface vehicles(USVs)play a crucial role in various fields,including ocean climate change monitoring,ma-rine resource exploitation,and ecological environment exploration.Out of the many types of USVs,unmanned sailboats have gained considerable attention for their ability to conduct green,large-scale ocean observations.Building on this concept,this paper proposes an unmanned sailboat propelled by parallel dual-wing sails,which is designed to meet the demands of extensive and three-dimensional marine comprehensive observation and data collection.With a focus on the parallel dual-wing sails,this study particularly investi-gates the effects of variations in the airfoil’s angle of attack and the impact of the spacing ratio between the dual sails on propulsion performance.It further analyzes the influence of one sail’s angle of attack on the performance of the other sail,as well as the flow field between the two sails.For the air navigation and underwater states,the force characteristics of the dual sail under different inflow velocities were investigated.The research findings indicate that,under certain conditions,the thrust coefficient exhibits a trend of first increasing,then decreasing,and finally increasing again with alterations in the angle of attackα.Different single-sail angles of attack have varying impacts on the opposite sail and the flow field between the dual sails.Moreover,the generated forces are positively correlated with inflow velocity in the air navigation and underwater states.The findings reveal that it is possible to reduce drag,mitigate the adverse effects of sail interaction,and thereby enhance the propulsion performance and overall navigational stability of the sailboat by applying an optimal spacing ratio design and adjusting the angle of attack and inflow velocity.
基金the National Natural Science Foundation of China(No.52071161)。
文摘With the development of marine resources,a dual-platform joint operation has been paid more attention.In this paper,the mooring layout space and relative motion limitation of the dual-platform berthing operation were fully considered.A new hybrid mooring system with“X+buoy”combination was designed based on the characteristics of catenary and tension mooring.The hydrodynamic characteristics of the new mooring system were analyzed by combining numerical simulation with model experiment.Under the regular and freak waves with different wave heights and periods,the time-domain full-coupling analysis method was used to study the hydrodynamic characteristics of the mooring system.It can be found that the arrangement of dual-platform under 0◦wave direction is optimal,and the“X+buoy”combined mooring system designed in this paper has a good follow-up between the two platforms under different regular and freak waves.The relative motion response between the two platforms can be effectively controlled,and finally the positioning of the dual-platform joint operation is realized.Research results of this paper provide a theoretical basis and technical support for the hydrodynamic performance analysis and safety assessment of deep-sea offshore platforms in China.
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financially supported by the National Natural Science Foundation of China(Grant No.51639004)
文摘In order to analyze the ice-going ship’s performance under the pack ice conditions, synthetic ice was introduced into a towing tank. A barrier using floating cylinder in the towing tank was designed to carry out the resistance experiment. The test results indicated that the encountering frequency between the ship model and the pack ice shifts towards a high-velocity point as the concentration of the pack ice increases, and this encountering frequency creates an unstable region of the resistance, and the unstable region shifts to the higher speed with the increasing concentration. The results also showed that for the same speed points, the ratio of the pack ice resistance to the open water resistance increases with the increasing concentration, and for the same concentrations, this ratio decreases as the speed increases. Motion characteristics showed that the mean value of the heave motion increases as the speed increases, and the pitch motion tends to increase with the increasing speed. In addition, the total resistance of the fullscale was predicted.
基金the sponsors of this project: American Bureau of Shipping
文摘Global strength is a significant item for floating production storage and offloading(FPSO) design, and steel weight plays an important role in the building costs of FPSO. It is the main task to consider and combine these two aspects by optimizing hull dimensions. There are many optional methods for the global strength analysis. A common method is to use the ABS FPSO Eagle software to analyze the global strength including the rule check and direct strength analysis. And the same method can be adopted for the FPSO hull optimization by changing the depth. After calculation and optimization, the results are compared and analyzed. The results can be used as a reference for the future design or quotation purpose.
基金The Defence Advance Research Program of Science and Technology of Ship Industry(Grant No.11J1.3.1)
文摘The stiffened cylindrical shell is commonly used for the pressure hull of submersibles and the legs of offshore platforms. There are various failure modes because of uncertainty with the structural size and material properties, uncertainty of the calculation model and machining errors. Correlations among failure modes must be considered with the structural reliability of stiffened cylindrical shells. However, the traditional method cannot consider the correlations effectively. The aim of this study is to present a method of reliability analysis for stiffened cylindrical shells which considers the correlations among failure modes. Firstly, the joint failure probability calculation formula of two related failure modes is derived through use of the 2D joint probability density function. Secondly, the full probability formula of the tandem structural system is given with consideration to the correlations among failure modes. At last, the accuracy of the system reliability calculation is verified through use of the Monte Carlo simulation. Result of the analysis shows the failure probability of stiffened cylindrical shells can be gained through adding the failure probability of each mode.
基金financially supported by the State Key Laboratory of Hydraulic Engineering Simulation and Safety,Tianjin University(Grant No.HESS-1404)the National Natural Science Foundation of China(Grant No.51239007)
文摘The crashworthiness of the cargo containment systems （CCSs） of a floating liquid natural gas （FLNG） and the side structures in side-by-side offioading operations scenario are studied in this paper. An FLNG vessel is exposed to potential threats from collisions with a liquid natural gas carrier （LNGC） during the offioading operations, which has been confirmed by a model test of FLNG-LNGC side-by-side offioading operations. A nonlinear finite element code LS-DYNA is used to simulate the collision scenarios during the offioading operations. Finite element models of an FLNG vessel and an LNGC are established for the purpose of this study, including a detailed LNG cargo containment system in the FLNG side model. Based on the parameters obtained from the model test and potential dangerous accidents, typical collision scenarios are defined to conduct a comprehensive study. To evaluate the safety of the FLNG vessel, a limit state is proposed based on the structural responses of the LNG CCS. The different characteristics of the structural responses for the primary structural components, energy dissipation and collision forces are obtained for various scenarios. Deformation of the inner hull is found to have a great effect on the responses of the LNG CCS, with approximately 160 mm deformation corresponding to the limit state. Densely arranged web frames can absorb over 35% of the collision energy and be proved to greatly enhance the crashwo- rthiness of the FLNG side structures.
基金sponsored by the National Natural Science Foundation of China(Grant No.51779143)the Oceanic Interdisciplinary Program of Shanghai Jiao Tong University(Grant No.SL2020ZD101)the Cultivation of Scientific Research Ability of Young Talents of Shanghai Jiao Tong University(Grant No.19X100040072).
文摘Numerical simulations of evolution characteristics of slug flow across a 90°pipe bend have been carried out to study the fluid−structure interaction response induced by internal slug flow.The two-phase flow patterns and turbulence were modelled by using the volume of fluid(VOF)model and the Realizable k−εturbulence model respectively.Firstly,validation of the CFD model was carried out and the desirable results were obtained.The different flow patterns and the time-average mean void fraction was coincident with the reported experimental data.Simulations of different cases of slug flow have been carried out to show the effects of superficial gas and liquid velocity on the evolution characteristics of slug flow.Then,a one-way coupled fluid-structure interaction framework was established to investigate the slug flow interaction with a 90°pipe bend under various superficial liquid and gas velocities.It was found that the maximum total deformation and equivalent stress increased with the increasing superficial gas velocity,while decreased with the increasing superficial liquid velocity.In addition,the total deformation and equivalent stress has obvious periodic fluctuation.Furthermore,the distribution position of maximum deformation and stress was related to the evolution of slug flow.With the increasing superficial gas velocity,the maximum total deformation was mainly located at the 90°pipe bend.But as the superficial liquid velocity increases,the maximum total deformation was mainly located in the horizontal pipe section.Consequently,the slug flow with higher superficial gas velocity will induce more serious cyclical impact on the 90°pipe bend.
基金the National Natural Science Foundation of China(No.51579147)
文摘The roll motions are influenced by significant viscous effects such as the flow separation.The 3D simulations of free decay roll motions for the ship model DTMB 5512 are carried out by Reynold averaged NavierStokes(RANS) method based on the dynamic mesh technique.A new moving mesh technique is adopted and discussed in details for the present simulations.The purpose of the research is to obtain accurate numerical prediction for roll motions with their respective numerical/modeling errors and uncertainties.Errors and uncertainties are estimated by performing the modern verification and validation(V&V) procedures.Simulation results for the free-floating surface combatant are used to calculate the linear,nonlinear damping coefficients and resonant frequencies including a wide range of forward speed.The present work can provide a useful reference to calculate roll damping by computational fluid dynamics(CFD) method and simulate a general ship motions in waves.
基金the National Natural Science Foundation of China，the Fundamental Research Funds for the Central Universities，the Specialized Research Fund for the Doctoral Program of Higher Education
文摘The scale effect leads to large discrepancies between the wake fields of model-scale and actual ships, and causes differences in cavitation performance and exciting forces tests in predicting the performance of actual ships. Therefore, when test data from ship models are directly applied to predict the performance of actual ships, test results must be subjected to empirical corrections. This study proposes a method for the reverse design of the hull model. Compared to a geometrically similar hull model, the wake field generated by the modified model is closer to that of an actual ship. A non-geometrically similar model of a Korean Research Institute of Ship and Ocean Engineering （KRISO）’s container ship （KCS） was designed. Numerical simulations were performed using this model, and its results were compared with full-scale calculation results. The deformation method of getting the wake field of full-scale ships by the non-geometrically similar model is applied to the KCS successfully.
基金This study is financially supported by the National Key Research and Development Program of China(Grant Nos.2017YFE0111400 and 2016YCF1401505)the National Natural Science Foundation of China(Grant Nos.41576179 and 51639004)the China Postdoctoral Science Foundation(Grant No.2020M670746).
文摘The ice resistance on a ship hull affects the safety of the hull structure and the ship maneuvering performance in icecovered regions.In this paper,the discrete element method(DEM)is adopted to simulate the interaction between level ice and ship hull.The level ice is modeled with 3D bonded spherical elements considering the buoyancy and drag force of the water.The parallel bonding approach and the de-bonding criterion are adopted to model the freezing and breakage of level ice.The ship hull is constructed with rigid triangle elements.To improve computational efficiency,the GPU-based parallel computational algorithm was developed for the DEM simulations.During the interaction between the ship hull and level ice,the ice cover is broken into small blocks when the interparticle stress approaches the bonding strength.The global ice resistance on the hull is calculated through the contacts between ice elements and hull elements during the navigation process.The influences of the ice thickness and navigation speed on the dynamic ice force are analyzed considering the breakage mechanism of ice cover.The Lindqvist and Riska formulas for the determination of ice resistance on ship hull are employed to validate the DEM simulation.The comparison of results of DEM,Lindqvist,and Riska formula show that the DEM result is between those the Lindqvist formula and Riska formula.Therefore the proposed DEM is an effective approach to determine the ice resistance on the ship hull.This work can be aided in the hull structure design and the navigation operation in ice-covered fields.
基金financially supported by the Program for New Century Excellent Talents in Universitiesthe National Natural Science Foundation of China(No.21074088)
文摘Twice-painting technique was adopted to prepare heavy-duty anticorrosive coating films formed by aqueous latexes of copolymers of vinylidene chloride（VDC） with an acrylate, namely methyl acrylate（MA）, ethyl acrylate（EA）, butyl acrylate（BA） or 2-ethylhexyl acrylate（EHA）. Harsh salt-spray corrosion tests demonstrated that the optimized twicepainting technique was that the acidic latex solution was adjusted to p H 5-6 for the first painting, while it was utilized directly for the second painting. The test of 600 h of harsh salt-spray corrosion showed that MA-VDC85 coating could protect the steel excellently, whereas the other acrylate-VDC coatings with 75%-90% VDC content could not protect the steel so effectively. Further corrosion test showed that（1） MA-VDC85 coating protected steel from loss of metallic luster for at least 1000 h of salt-spray corrosion;（2） adhesion of MA-VDC85 coating to steel was excellent for at least 800 h of saltspray corrosion, but became very poor after 1000 h. Differential scanning calorimetry, thermogravimetric analysis, X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy were used to evaluate the corroded MA-VDC85 film.
