Convolutional Neural Networks(CNNs)have recently attracted much attention in the ship detection from Synthetic Aperture Radar(SAR)images.However,compared with optical images,SAR ones are hard to understand.Moreover,du...Convolutional Neural Networks(CNNs)have recently attracted much attention in the ship detection from Synthetic Aperture Radar(SAR)images.However,compared with optical images,SAR ones are hard to understand.Moreover,due to the high similarity between the man-made targets near shore and inshore ships,the classical methods are unable to achieve effective detection of inshore ships.To mitigate the influence of onshore ship-like objects,this paper proposes an inshore ship detection method in SAR images by using hybrid features.Firstly,the sea-land segmentation is applied in the pre-processing to exclude obvious land regions from SAR images.Then,a CNN model is designed to extract deep features for identifying potential ship targets in both inshore and offshore water.On this basis,the high-energy point number of amplitude spectrum is further introduced as an important and delicate feature to suppress false alarms left.Finally,to verify the effectiveness of the proposed method,numerical and comparative studies are carried out in experiments on Sentinel-1 SAR images.展开更多
In this work,we constructed a neural network proxy model(NNPM)to estimate the hydrodynamic resistance in the ship hull structure design process,which is based on the hydrodynamic load data obtained from both the poten...In this work,we constructed a neural network proxy model(NNPM)to estimate the hydrodynamic resistance in the ship hull structure design process,which is based on the hydrodynamic load data obtained from both the potential flow method(PFM)and the viscous flow method(VFM).Here the PFM dataset is applied for the tuning,pre-training,and the VFM dataset is applied for the fine-training.By adopting the PFM and VFM datasets simultaneously,we aim to construct an NNPM to achieve the high-accuracy prediction on hydrodynamic load on ship hull structures exerted from the viscous flow,while ensuring a moderate data-acquiring workload.The high accuracy prediction on hydrodynamic loads and the relatively low dataset establishment cost of the NNPM developed demonstrated the effectiveness and feasibility of hybrid dataset based NNPM achieving a high precision prediction of hydrodynamic loads on ship hull structures.The successful construction of the high precision hydrodynamic prediction NNPM advances the artificial intelligence-assisted design(AIAD)technology for various marine structures.展开更多
针对燃料电池船舶复合供能系统中的燃料电池功率波动问题和储能单元电池荷电状态(State of Charge, SOC)极端分化问题,依据系统拓扑结构,提出基于负载功率频率分解与模糊逻辑控制法相结合的复合供能系统控制策略设计。采用实例仿真验证...针对燃料电池船舶复合供能系统中的燃料电池功率波动问题和储能单元电池荷电状态(State of Charge, SOC)极端分化问题,依据系统拓扑结构,提出基于负载功率频率分解与模糊逻辑控制法相结合的复合供能系统控制策略设计。采用实例仿真验证该设计的优势。结果表明,该设计可有效保持燃料电池输出功率平滑,对储能单元SOC具有良好的均衡控制效果。展开更多
锂离子电池系统成本高昂是阻碍其在电动设备中广泛使用的最大挑战之一。对某船采用的电池混合储能系统(Hybrid Energy Storage System,HESS)进行研究,分析电池混合对成本、系统效率和电池重量等3个关键指标的影响。该HESS的使用寿命设计...锂离子电池系统成本高昂是阻碍其在电动设备中广泛使用的最大挑战之一。对某船采用的电池混合储能系统(Hybrid Energy Storage System,HESS)进行研究,分析电池混合对成本、系统效率和电池重量等3个关键指标的影响。该HESS的使用寿命设计为10 a,采用镍钴锰酸锂和钛酸锂作为高能(High-Energy,HE)和高功率(High-Power,HP)电池单体。研究表明,与采用HP电池和HE电池的单一型电池储能系统相比,HESS的效率没有下降,成本能分别下降约28%和14%,总重量能减少30%以上。展开更多
As the maneuverability of a ship navigating close to a bank is influenced by the sidewall, the assessment of ship maneuvering stability is important. The hydrodynamic derivatives measured by the planar motion mechani...As the maneuverability of a ship navigating close to a bank is influenced by the sidewall, the assessment of ship maneuvering stability is important. The hydrodynamic derivatives measured by the planar motion mechanism （PMM） test provide a way to predict the change of ship maneuverability. This paper presents a numerical simulation of PMM model tests with variant distances to a vertical bank by using unsteady RANS equations. A hybrid dynamic mesh technique is developed to realize the mesh configuration and remeshing of dynamic PMM tests when the ship is close to the bank. The proposed method is validated by comparing numerical results with results of PMM tests in a circulating water channel. The first-order hydrodynamic derivatives of the ship are analyzed from the time history of lateral force and yaw moment according to the multiple-run simulating procedure and the variations of hydrodynamic derivatives with the ship-sidewall distance are given. The straight line stability and directional stability are also discussed and stable or unstable zone of proportional-derivative （PD） controller parameters for directional stability is shown, which can be a reference for course keeping operation when sailing near a bank.展开更多
基金Aeronautical Science Foundation of China(No.2018ZC51022)。
文摘Convolutional Neural Networks(CNNs)have recently attracted much attention in the ship detection from Synthetic Aperture Radar(SAR)images.However,compared with optical images,SAR ones are hard to understand.Moreover,due to the high similarity between the man-made targets near shore and inshore ships,the classical methods are unable to achieve effective detection of inshore ships.To mitigate the influence of onshore ship-like objects,this paper proposes an inshore ship detection method in SAR images by using hybrid features.Firstly,the sea-land segmentation is applied in the pre-processing to exclude obvious land regions from SAR images.Then,a CNN model is designed to extract deep features for identifying potential ship targets in both inshore and offshore water.On this basis,the high-energy point number of amplitude spectrum is further introduced as an important and delicate feature to suppress false alarms left.Finally,to verify the effectiveness of the proposed method,numerical and comparative studies are carried out in experiments on Sentinel-1 SAR images.
基金supported by a fellowship from China Scholar Council(No.201806680134).
文摘In this work,we constructed a neural network proxy model(NNPM)to estimate the hydrodynamic resistance in the ship hull structure design process,which is based on the hydrodynamic load data obtained from both the potential flow method(PFM)and the viscous flow method(VFM).Here the PFM dataset is applied for the tuning,pre-training,and the VFM dataset is applied for the fine-training.By adopting the PFM and VFM datasets simultaneously,we aim to construct an NNPM to achieve the high-accuracy prediction on hydrodynamic load on ship hull structures exerted from the viscous flow,while ensuring a moderate data-acquiring workload.The high accuracy prediction on hydrodynamic loads and the relatively low dataset establishment cost of the NNPM developed demonstrated the effectiveness and feasibility of hybrid dataset based NNPM achieving a high precision prediction of hydrodynamic loads on ship hull structures.The successful construction of the high precision hydrodynamic prediction NNPM advances the artificial intelligence-assisted design(AIAD)technology for various marine structures.
文摘针对燃料电池船舶复合供能系统中的燃料电池功率波动问题和储能单元电池荷电状态(State of Charge, SOC)极端分化问题,依据系统拓扑结构,提出基于负载功率频率分解与模糊逻辑控制法相结合的复合供能系统控制策略设计。采用实例仿真验证该设计的优势。结果表明,该设计可有效保持燃料电池输出功率平滑,对储能单元SOC具有良好的均衡控制效果。
文摘锂离子电池系统成本高昂是阻碍其在电动设备中广泛使用的最大挑战之一。对某船采用的电池混合储能系统(Hybrid Energy Storage System,HESS)进行研究,分析电池混合对成本、系统效率和电池重量等3个关键指标的影响。该HESS的使用寿命设计为10 a,采用镍钴锰酸锂和钛酸锂作为高能(High-Energy,HE)和高功率(High-Power,HP)电池单体。研究表明,与采用HP电池和HE电池的单一型电池储能系统相比,HESS的效率没有下降,成本能分别下降约28%和14%,总重量能减少30%以上。
基金supported by the National Key Basic Research Program of China(Grant No.2014CB046804)
文摘As the maneuverability of a ship navigating close to a bank is influenced by the sidewall, the assessment of ship maneuvering stability is important. The hydrodynamic derivatives measured by the planar motion mechanism （PMM） test provide a way to predict the change of ship maneuverability. This paper presents a numerical simulation of PMM model tests with variant distances to a vertical bank by using unsteady RANS equations. A hybrid dynamic mesh technique is developed to realize the mesh configuration and remeshing of dynamic PMM tests when the ship is close to the bank. The proposed method is validated by comparing numerical results with results of PMM tests in a circulating water channel. The first-order hydrodynamic derivatives of the ship are analyzed from the time history of lateral force and yaw moment according to the multiple-run simulating procedure and the variations of hydrodynamic derivatives with the ship-sidewall distance are given. The straight line stability and directional stability are also discussed and stable or unstable zone of proportional-derivative （PD） controller parameters for directional stability is shown, which can be a reference for course keeping operation when sailing near a bank.
