Several muhicast key management schemes such as those proposed by Wallner et al and Wong et al are based on a multilevel, logical hierarchy （or tree） of key-encrypting keys. When used in conjunction with a reliahle ...Several muhicast key management schemes such as those proposed by Wallner et al and Wong et al are based on a multilevel, logical hierarchy （or tree） of key-encrypting keys. When used in conjunction with a reliahle muhicast infrastructure, this approach results in a highly efficient key update mechanism in which the number of muhicast messages transmitted upon a membership update is proportional to the depth of the tree, which is logarithmic to the size of the secure muhicast group. But this is based on the hypothesis that the tree is maintained in a balanced manner. This paper proposes a scalable rekeying scheme---link-tree structure for implementing secure group communication. Theoretical calculation and experimentation show that this scheme has better performance than the tree structure and the star structure, and at the same time still keep the link-tree structure balanced.展开更多
Objective For computer-aided Chinese medical diagnosis and aiming at the problem of insufficient segmentation,a novel multi-level method based on the multi-scale fusion residual neural network(MF2ResU-Net)model is pro...Objective For computer-aided Chinese medical diagnosis and aiming at the problem of insufficient segmentation,a novel multi-level method based on the multi-scale fusion residual neural network(MF2ResU-Net)model is proposed.Methods To obtain refined features of retinal blood vessels,three cascade connected UNet networks are employed.To deal with the problem of difference between the parts of encoder and decoder,in MF2ResU-Net,shortcut connections are used to combine the encoder and decoder layers in the blocks.To refine the feature of segmentation,atrous spatial pyramid pooling(ASPP)is embedded to achieve multi-scale features for the final segmentation networks.Results The MF2ResU-Net was superior to the existing methods on the criteria of sensitivity(Sen),specificity(Spe),accuracy(ACC),and area under curve(AUC),the values of which are 0.8013 and 0.8102,0.9842 and 0.9809,0.9700 and 0.9776,and 0.9797 and 0.9837,respectively for DRIVE and CHASE DB1.The results of experiments demonstrated the effectiveness and robustness of the model in the segmentation of complex curvature and small blood vessels.Conclusion Based on residual connections and multi-feature fusion,the proposed method can obtain accurate segmentation of retinal blood vessels by refining the segmentation features,which can provide another diagnosis method for computer-aided Chinese medical diagnosis.展开更多
The special characteristics of the mobile environment, such as limited bandwidth, dynamic topology, heterogeneity of peers, and limited power, pose additional challenges on mobile peer-to-peer （MP2P） networks. Trust...The special characteristics of the mobile environment, such as limited bandwidth, dynamic topology, heterogeneity of peers, and limited power, pose additional challenges on mobile peer-to-peer （MP2P） networks. Trust management becomes an essential component of MP2P networks to promote peer transactions. However, in an MP2P network, peers frequently join and leave the network, which dynamically changes the network topology. Thus, it is difficult to establish long-term and effective trust relationships among peers. In this paper, we propose a dynamic grouping based trust model （DGTM） to classify peers. A group is formed according to the peers＇ interests. Within a group, mobile peers share resources and tend to keep stable trust relationships. We propose three peer roles （super peers, relay peers, and ordinary peers） and two novel trust metrics （intragroup trust and intergroup trust）. The two metrics are used to accurately measure the trust between two peers from the same group or from different groups. Simulations illustrate that our proposed DGTM always achieves the highest successful transaction rate and the best communication overhead under different circumstances.展开更多
基金Sponsored by the National Natural Science Foundation of China (Grant No.60203012) and Shanghai Rising-Star Program in Science and Technology (Grant No.02QD14027).
文摘Several muhicast key management schemes such as those proposed by Wallner et al and Wong et al are based on a multilevel, logical hierarchy （or tree） of key-encrypting keys. When used in conjunction with a reliahle muhicast infrastructure, this approach results in a highly efficient key update mechanism in which the number of muhicast messages transmitted upon a membership update is proportional to the depth of the tree, which is logarithmic to the size of the secure muhicast group. But this is based on the hypothesis that the tree is maintained in a balanced manner. This paper proposes a scalable rekeying scheme---link-tree structure for implementing secure group communication. Theoretical calculation and experimentation show that this scheme has better performance than the tree structure and the star structure, and at the same time still keep the link-tree structure balanced.
基金Key R&D Projects in Hebei Province(22370301D)Scientific Research Foundation of Hebei University for Distinguished Young Scholars(521100221081)Scientific Research Foundation of Colleges and Universities in Hebei Province(QN2022107)。
文摘Objective For computer-aided Chinese medical diagnosis and aiming at the problem of insufficient segmentation,a novel multi-level method based on the multi-scale fusion residual neural network(MF2ResU-Net)model is proposed.Methods To obtain refined features of retinal blood vessels,three cascade connected UNet networks are employed.To deal with the problem of difference between the parts of encoder and decoder,in MF2ResU-Net,shortcut connections are used to combine the encoder and decoder layers in the blocks.To refine the feature of segmentation,atrous spatial pyramid pooling(ASPP)is embedded to achieve multi-scale features for the final segmentation networks.Results The MF2ResU-Net was superior to the existing methods on the criteria of sensitivity(Sen),specificity(Spe),accuracy(ACC),and area under curve(AUC),the values of which are 0.8013 and 0.8102,0.9842 and 0.9809,0.9700 and 0.9776,and 0.9797 and 0.9837,respectively for DRIVE and CHASE DB1.The results of experiments demonstrated the effectiveness and robustness of the model in the segmentation of complex curvature and small blood vessels.Conclusion Based on residual connections and multi-feature fusion,the proposed method can obtain accurate segmentation of retinal blood vessels by refining the segmentation features,which can provide another diagnosis method for computer-aided Chinese medical diagnosis.
基金Project supported by the National Natural Science Foundation of China （Nos. 61502118, 61370212, and 61402127） and the Nat- ural Science Foundation of Heilongjiang Province, China （Nos. F2015029 and QC2015070）
文摘The special characteristics of the mobile environment, such as limited bandwidth, dynamic topology, heterogeneity of peers, and limited power, pose additional challenges on mobile peer-to-peer （MP2P） networks. Trust management becomes an essential component of MP2P networks to promote peer transactions. However, in an MP2P network, peers frequently join and leave the network, which dynamically changes the network topology. Thus, it is difficult to establish long-term and effective trust relationships among peers. In this paper, we propose a dynamic grouping based trust model （DGTM） to classify peers. A group is formed according to the peers＇ interests. Within a group, mobile peers share resources and tend to keep stable trust relationships. We propose three peer roles （super peers, relay peers, and ordinary peers） and two novel trust metrics （intragroup trust and intergroup trust）. The two metrics are used to accurately measure the trust between two peers from the same group or from different groups. Simulations illustrate that our proposed DGTM always achieves the highest successful transaction rate and the best communication overhead under different circumstances.
