Accurately predicting the State of Health(SOH)of lithium-ion batteries is a critical challenge to ensure their reliability and safety in energy storage systems,such as electric vehicles and renewable energy grids.The ...Accurately predicting the State of Health(SOH)of lithium-ion batteries is a critical challenge to ensure their reliability and safety in energy storage systems,such as electric vehicles and renewable energy grids.The intricate battery degradation process is influenced by evolving spatial and temporal interactions among health indicators.Existing methods often fail to capture the dynamic interactions between health indicators over time,resulting in limited predictive accuracy.To address these challenges,we propose a novel framework,Dynamic Graph Learning with Spatial-Temporal Fusion Attention(DGL-STFA),which transforms health indicator series time-data into time-evolving graph representations.The framework employs multi-scale convolutional neural networks to capture diverse temporal patterns,a self-attention mechanism to construct dynamic adjacency matrices that adapt over time,and a temporal attention mechanism to identify and prioritize key moments that influence battery degradation.This combination enables DGL-STFA to effectively model both dynamic spatial relationships and long-term temporal dependencies,enhancing SOH prediction accuracy.Extensive experiments were conducted on the NASA and CALCE battery datasets,comparing this framework with traditional time-series prediction methods and other graph-based prediction methods.The results demonstrate that our framework significantly improves prediction accuracy,with a mean absolute error more than 30%lower than other methods.Further analysis demonstrated the robustness of DGL-STFA across various battery life stages,including early,mid,and end-of-life phases.These results highlight the capability of DGL-STFA to accurately predict SOH,addressing critical challenges in advancing battery health monitoring for energy storage applications.展开更多
Unsupervised learning methods such as graph contrastive learning have been used for dynamic graph represen-tation learning to eliminate the dependence of labels.However,existing studies neglect positional information ...Unsupervised learning methods such as graph contrastive learning have been used for dynamic graph represen-tation learning to eliminate the dependence of labels.However,existing studies neglect positional information when learning discrete snapshots,resulting in insufficient network topology learning.At the same time,due to the lack of appropriate data augmentation methods,it is difficult to capture the evolving patterns of the network effectively.To address the above problems,a position-aware and subgraph enhanced dynamic graph contrastive learning method is proposed for discrete-time dynamic graphs.Firstly,the global snapshot is built based on the historical snapshots to express the stable pattern of the dynamic graph,and the random walk is used to obtain the position representation by learning the positional information of the nodes.Secondly,a new data augmentation method is carried out from the perspectives of short-term changes and long-term stable structures of dynamic graphs.Specifically,subgraph sampling based on snapshots and global snapshots is used to obtain two structural augmentation views,and node structures and evolving patterns are learned by combining graph neural network,gated recurrent unit,and attention mechanism.Finally,the quality of node representation is improved by combining the contrastive learning between different structural augmentation views and between the two representations of structure and position.Experimental results on four real datasets show that the performance of the proposed method is better than the existing unsupervised methods,and it is more competitive than the supervised learning method under a semi-supervised setting.展开更多
Dynamic graph fraud detection aims to distinguish fraudulent entities that deviate significantly from most benign entities within an ever-changing graph network.However,when dealing with different financial fraud scen...Dynamic graph fraud detection aims to distinguish fraudulent entities that deviate significantly from most benign entities within an ever-changing graph network.However,when dealing with different financial fraud scenarios,existing methods face challenges,resulting in difficulty in effectively ensuring financial security.In fraud scenarios,transaction data are generated in real time,in which a strong temporal relationship between multiple fraudulent transactions is observed.Traditional dynamic graph models struggle to effectively balance the temporal features of nodes and spatial structural features,failing to handle different types of nodes in the graph network.In this study,to extract the temporal and structural information,we proposed a dynamic heterogeneous transaction graph embedding(DyHDGE)network based on a dynamic heterogeneous transaction graph,considering both temporal and structural information while incorporating heterogeneous data.To separately extract temporal relationships between transactions and spatial structural relationships between nodes,we used a heterogeneous temporal graph representation learning module and a temporal graph structure information extraction module.Additionally,we designed two loss functions to optimize node feature representations.Extensive experiments demonstrated that the proposed DyHDGE significantly outperformed previous state-of-the-art methods on two simulated datasets of financial fraud scenarios.This capability contributes to enhancing security in financial consumption scenarios.展开更多
基金sponsored by the National Key Research and Development Program of China(No.2023YFB4606200)Key Program of Science and Technology of Yunnan Province,China (No.202302AB080020)Key Project of Shanghai Zhangjiang National Independent hnovation Demonstration Zone,China(No.ZJ2021-2D-006).
文摘Accurately predicting the State of Health(SOH)of lithium-ion batteries is a critical challenge to ensure their reliability and safety in energy storage systems,such as electric vehicles and renewable energy grids.The intricate battery degradation process is influenced by evolving spatial and temporal interactions among health indicators.Existing methods often fail to capture the dynamic interactions between health indicators over time,resulting in limited predictive accuracy.To address these challenges,we propose a novel framework,Dynamic Graph Learning with Spatial-Temporal Fusion Attention(DGL-STFA),which transforms health indicator series time-data into time-evolving graph representations.The framework employs multi-scale convolutional neural networks to capture diverse temporal patterns,a self-attention mechanism to construct dynamic adjacency matrices that adapt over time,and a temporal attention mechanism to identify and prioritize key moments that influence battery degradation.This combination enables DGL-STFA to effectively model both dynamic spatial relationships and long-term temporal dependencies,enhancing SOH prediction accuracy.Extensive experiments were conducted on the NASA and CALCE battery datasets,comparing this framework with traditional time-series prediction methods and other graph-based prediction methods.The results demonstrate that our framework significantly improves prediction accuracy,with a mean absolute error more than 30%lower than other methods.Further analysis demonstrated the robustness of DGL-STFA across various battery life stages,including early,mid,and end-of-life phases.These results highlight the capability of DGL-STFA to accurately predict SOH,addressing critical challenges in advancing battery health monitoring for energy storage applications.
文摘Unsupervised learning methods such as graph contrastive learning have been used for dynamic graph represen-tation learning to eliminate the dependence of labels.However,existing studies neglect positional information when learning discrete snapshots,resulting in insufficient network topology learning.At the same time,due to the lack of appropriate data augmentation methods,it is difficult to capture the evolving patterns of the network effectively.To address the above problems,a position-aware and subgraph enhanced dynamic graph contrastive learning method is proposed for discrete-time dynamic graphs.Firstly,the global snapshot is built based on the historical snapshots to express the stable pattern of the dynamic graph,and the random walk is used to obtain the position representation by learning the positional information of the nodes.Secondly,a new data augmentation method is carried out from the perspectives of short-term changes and long-term stable structures of dynamic graphs.Specifically,subgraph sampling based on snapshots and global snapshots is used to obtain two structural augmentation views,and node structures and evolving patterns are learned by combining graph neural network,gated recurrent unit,and attention mechanism.Finally,the quality of node representation is improved by combining the contrastive learning between different structural augmentation views and between the two representations of structure and position.Experimental results on four real datasets show that the performance of the proposed method is better than the existing unsupervised methods,and it is more competitive than the supervised learning method under a semi-supervised setting.
基金supported in part by the National Key Research and Development Program of China(2021YFC3300602)the National Natural Science Foundation of China(grant no.72204155)the Natural Science Foundation of Shanghai(grant no.23ZR1423100).
文摘Dynamic graph fraud detection aims to distinguish fraudulent entities that deviate significantly from most benign entities within an ever-changing graph network.However,when dealing with different financial fraud scenarios,existing methods face challenges,resulting in difficulty in effectively ensuring financial security.In fraud scenarios,transaction data are generated in real time,in which a strong temporal relationship between multiple fraudulent transactions is observed.Traditional dynamic graph models struggle to effectively balance the temporal features of nodes and spatial structural features,failing to handle different types of nodes in the graph network.In this study,to extract the temporal and structural information,we proposed a dynamic heterogeneous transaction graph embedding(DyHDGE)network based on a dynamic heterogeneous transaction graph,considering both temporal and structural information while incorporating heterogeneous data.To separately extract temporal relationships between transactions and spatial structural relationships between nodes,we used a heterogeneous temporal graph representation learning module and a temporal graph structure information extraction module.Additionally,we designed two loss functions to optimize node feature representations.Extensive experiments demonstrated that the proposed DyHDGE significantly outperformed previous state-of-the-art methods on two simulated datasets of financial fraud scenarios.This capability contributes to enhancing security in financial consumption scenarios.
