Congestion road condition is an important factor that must be considered in urban traffic path planning, while most path planning algorithms only consider the distance factor, which is not suitable for the current complex urban traffic congestion road condition. In order to solve the above problems, this paper proposes a dynamic path planning method based on improved ant colony algorithm in congested traffic. The method quantifies the main attributes of urban road length, number of lanes, incoming and outgoing traffic flow, and introduces the road factor used for replacing the distance parameters of particle swarm optimization and ant colony algorithm. In the method, the particle swarm algorithm can effectively optimize the parameters of the ant colony algorithm, and significantly improve the efficiency of ant colony algorithm, such that it is more applicable for dynamic path planning application to greatly reduce the congestion rate of path planning. In addition, this paper selects some intersections in the Beijing area to carry out the dynamic path planning experiment based on the improved ant colony algorithm under congested road conditions. The experimental results show that, compared with the ant colony algorithm based on distance parameter, the proposed dynamic path planning method can effectively reduce the average congestion rate ranging from 9.73% to 13.63%.

Flooding is widely used in unstructured Peer to Peer (P2P) systems, such as Gnutella. Although it is effective in content search, flooding among peers or super-peers causes large volume of unnecessary traffic. To address this problem, we propose an efficient and adaptive search mechanism, Adaptive Flooding Routing Algorithm (AFRA). AFRA provides the flexibility to adaptively adjust the number of relay neighbors and TTL value to meet different performance requirements. The effectiveness of AFRA is demonstrated through simulation studies. Primary experimental results show that our new AFRA solution reduces about 65% of the flooding messages while maintaining the acceptable high searching quality.I.

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P2P systems are currently the popular file-sharing platforms. The cooperation mechanism of P2P system can't offer fair exchange function. Because P2P system is a decentralized system, using a dedicated TTP server to support fair exchange is not suitable. A fair exchange protocol in P2P system without dedicated TTP is proposed, which is called P2PFair. P2PFair offers the fairness and secret guarantee. The fairness is provided by Dis_TTP which is composed of n random peers. P2PFair uses IBE to guarantee the secret of items exchanged. In order to eliminate collusion, Dis_TTP using threshold mechanism to manage the shadows of master key which is generated by distributed key generation algorithm. The threshold mechanism accommodates the fault-tolerant capacity at the same time. According to the probability analysis, the collusion probability is negligible. The protocol analysis shows that P2PFair is an effective solution of fair exchange in P2P sharing systems.

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