The community structure in complex networks can help people recognize basic structure and functions of network. Aiming at the problems of low accuracy and high complexity of most community division algorithms, a community division algorithm based on similarity of common neighbor nodes was proposed. Firstly, a similarity model was proposed in order to calculate the similarity between nodes. In the model, the accuracy of similarity measurement was improved by calculating the tested node pairs and their neighbor nodes together. Secondly, local influence values of nodes were calculated, objectively showing the importances of nodes in the network. Thirdly, the nodes were hierarchically clustered according to the similarity and local influence values of nodes, and preliminary division of network community structure was completed. Finally, the preliminary divided sub-communities were clustered until the optimal modularity value was obtained. The simulation results show that compared with the new Community Detection Algorithm based on Local Similarity (CDALS), the proposed algorithm has the accuuracy improved by 14%, which proves that the proposed algorithm can divide the community structure of complex networks accurately and effectively.
By analyzing the security of a certificateless signature scheme without bilinear pairing proposed by Wang Y, et al. (WANG Y, DU W. Security analysis and improvement of certificateless signature scheme without bilinear pairing. Journal of Computer Applications, 2013, 33(8): 2250-2252), the result that the scheme can not resist forgery attack was pointed out and an improved scheme was proposed. The improved scheme enhanced the relationship of parameters in signature algorithm to resist forgery attack. The results of security analysis show that the improved scheme is proved to be existentially unforgeable against adaptive chosen message and identity attacks in random oracle model. The improved scheme is more efficient than the existing schemes for avoiding bilinear pairings and inverse operation.
In order to further improve the precision of navigation signal, band efficiency and the reliability performance for navigation systems, a new signal system adopted Minimum Shift Keying (MSK) with Binary Offset Carrier (BOC) based on Low Density Party Check (LDPC) codes was presented, which was called LDPC-MSK-BOC signal system. The navigation performances of the BOC and MSK-BOC were evaluated based on the parameters of Compass and GPS typical signals, which were scaled with power spectral density, code tracking error, multipath error envelope, bit error rate, anti-narrowband jamming merit factor and anti-matched spectrum jamming merit factor for demodulation processing, anti-narrowband jamming merit factor and anti-matched spectrum jamming merit factor for code tracking processing, and spectral separation coefficient. The theoretical analysis and simulation show that the proposed system has better performance in the field of code tracking precision and anti-multipath compared with BOC signal system under the limited spectrum resource condition. Meanwhile, the signal structure can further improve system reliability and band efficiency.
Atmospheric measurement not only impacts marine, land, and air transportation and resident trip, but also is a leading indicator of air quality. The existing visibility estimators based on image processing have problems such as constant computational formulae, poor stability and stringent requirement of application environment. Visibility measurement with supervised learning extracted features related to image edge in spatial domain and features of energy distribution in frequency domain to constitute the high-dimensional feature vector directly from observed scene images, and needed no manual object installing and modeling of the observed scene. It trained Support Vector Regression (SVR) model on the samples that were similar to test image and chosen by k-Nearest Neighbor (kNN), dynamically established the learning model between image features and visibility, and hid various impact factors of visibility in the model. The experimental results of natural scene show that the accuracy of the method can be as high as 96.29%, and moreover, it has good stability and real-time and simplicity of operation so that it is propitious for generalization in large scale.
The performance of DiffServ in wireless ad hoc networks was evaluated by simulation. The simulation results show that bandwidths obtained by high and low priority traffics were not consistent with their WRR(Weighted Round Robin) weight ratios. Combined with simulation trace, this phenomenon is caused by MAC mechanism. We conclude that it is impossible to proportionally distribute resource only using DiffServ at network layer in wireless ad hoc networks.