Journal of China Universities of Posts and Telecommunications最新文献

Collaborative filtering algorithms have become one of the most used approaches to provide personalized services for users to deal with abundance of information. The traditional algorithms just use the explicit user-item rating matrix to find similar users or items. To improve the accuracy of the ratings predicted by the collaborative filtering algorithms, social information is widely incorporated into the traditional ones. Different with the existed works focus on directly connected neighbors, we consider the community between the users. We design the algorithms in two aspects: one is that the members in the same community have similar tastes and preferences, the other is that the member's taste is affected by the other members. We simplify these two factors as community similarity and community affection. Community similarity is incorporated into modifying the model-based collaborative filtering algorithm as the social community-based regularization (SCR), which improves 6.2% in mean absolute error (MAE) and 6.1% in root mean square error (RMSE) compared to the existed social recommendation algorithm. Community affection is incorporated into modifying the neighborhood-based collaborative filtering algorithm as the neighbor-based collaborative filtering based on community detection (NCFC) which improve 14.8% in MAE and 8.1% in RMSE compared to user-based collaborative filtering (UCF).

We put forward an algorithm on friend-recommendation of social networking sites based on SimRank and ant colony optimization, which broadens the appliance of the algorithm in this academic question. The algorithm focuses on the existing relationships between the members as the initial measurement and constructs artificial ants’ completed routing graph. Finally, an ordered and limited list of personalized recommendations through recursive optimization is produced. In the end, we verify the algorithm's rationality and validity through simulation and the result shows that it can improve the precision of friend-recommendation.

Network address hopping (NAH) proposed a mechanism to enhance data protection in communications across untrusted networks. It spread the data stream of a communication session across multiple channels, which tried to obstruct information interception in the first place by obscuring the fact that communication takes place between certain end-points. However, the time-stamped packets between two peers would provide a hint for correlating the intercepted packets in case the encryption of the counter got compromised. Furthermore, due to synchronization, the Internet Protocol version 6 (IPv6) addresses pair of the channel ends would appear and disappear strictly, which would perform time-relevance character. A Network-based hopping communication mechanism (NetHop) is proposed in this paper. The address hopping function is deployed on the network side instead of endpoint, which can support secure hopping communication function for universal endpoints without any restriction of Operating System or hardware. By using IPv6 to IPv6 network address translation (NAT), NetHop fully exploits the superiority of IPv6 huge address space. The hopping addresses are generated by hash function and the hopping addresses pair can be chosen randomly. Consequently, NetHop performs better on randomness and concealment than channel-rule NAH.

A combined feature extraction and recognition method is proposed based on higher-order spectrum, cyclic spectrum and time-frequency characteristics. In the application of this method, α-dimensional features, quadratic spectral characteristics and Fourier transform spectral characteristics of the signal are used to extract three characteristic values including the envelope means (EM) of α plane, the recursive normalized frequency component detection value (RNFCDV) and the quadratic spectrum normalized frequency component detection value (QSNFCDV), which have the merits of less identification parameters, insensitive to noise, less computation, high recognition rate, and multi-species identification. With this method, simulation results show that the recognition rate is more the 98% with the signal to noise rate (SNR) not less than 6 dB. And the performance of this method is better than the common recognition algorithms. There are eight types of signal, such as amplitude modulation (AM), phase modulation (PM), amplitude shift keying (ASK), frequency shift keying (FSK), phase shift keying (PSK), minimum shift keying (MSK), quadrature amplitude modulation (QAM) and direct sequence spread spectrum (DSSS), have been used to validate the feasibility of the method.

Dissipative solitons in the passively mode-locked fiber lasers based on the gain medium of erbium-doped (Er-doped) fiber have attracted a lot of interest in recent years. In this paper, we study the influences of finite gain bandwidth on dissipative solitons in passively mode-locked Er-doped fiber laser. We investigate the influences of the finite gain bandwidth on pulse duration, pulse peak power and single pulse energy of dissipative solitons. The results show that gain bandwidth of the gain medium has influence on dissipative soliton characteristics in passively mode-locked Er-doped fiber laser. The research in this paper has important theoretical and practical significance.

Login authentication security is indispensable to applications of client/server (C/S) structure. Although some security technology in login authentication is relatively mature after years of development, it cannot meet high security requirements for the system in the case of limited resources. To deal with it, this paper proposes a new login authentication solution and applies it in electricity operation information system (EOIS), an application aiming at electrical equipment overhaul and report. The authors firstly discuss the reason why combined public key (CPK) is adopted as the key technology instead of the common one public key infrastructure (PKI). Secondly, they expatiate on CPK generation mechanism and the realizing process of login authentication, including local authentication using CPK-based digital signature and remote authentication using web service. Then, some results from three encryption methods (message-digest algorithm 5(MD5), secure hash algorithm (SHA-1) and CPK-based digital signature) to test EOIS are given, which show that the new solution builds its security on Hash function chosen and protection of combined private key. Finally, the security analysis reveals that CPK-based login authentication is safer to ensure the certainty of user identity, the integrality and non-repudiation of messages, and the confidentiality of transmission.

Real-time collaborative editing systems are important groupware tools in the computer supported cooperative work (CSCW) field. They support geographically dispersed users to edit shared files, graphics, etc. simultaneously. Currently popular real-time collaborative editing systems mostly use plain text data for edit and synchronization, and the corresponding operations are deleting, adding or modifying characters. The data acquisition system's metadata in this article is the module, such as deleting, adding or modifying a certain question. On the basis of differential synchronization algorithms and generic operation transformation (GOT) algorithm, this paper proposes a new concurrency control algorithm differential synchronization and generic operation transformation control algorithm (DSGOT).

This paper is devoted to research the characteristics of the dissipative solitons formed in a passively mode-locked Yb-doped fiber (YDF) laser under limitation of the gain saturation energy. The parabolic shape dissipative solitons with linear chirps are observed in the fiber laser. The influences of the gain saturation energy on pulse duration, peak power and single pulse energy of the dissipative solitons are investigated in-depth.

In Internet of Things (IoT), the similar functional services are evolving in different quality of services (QoS) due to the widespread deployment of spatially distributed things on dynamic networks through the web. Therefore, the user involvement in service selection systems becomes a vital role to enhance the system performance by taking into account of subjective factors. This paper proposes a flexible QoS-based service selection algorithm (FQSA) which mainly targets to the users to be able to give their subjective preferences in an easy and friendly manner. The FQSA algorithm selects the services based on subjective information provided by the service consumers and objective information supported by the service providers. It adopts artificial neural network backpropagation algorithm to find the objective factors and applies similarity aggregation method to evaluate the creditability of the user subjective factors which have already been evaluated by ontological reasoning with the help of proposed QoS ontology. The comparative study and experimental results show that our FQSA algorithm is superior to other service selection approaches.

Optical soliton communication is the frontier research topic of optical fiber communication. In this paper, we study optical solitons generated by passively mode-locked Erbium-doped (Er-doped) fiber (EDF) laser. We analyze the variation of nonlinear equilibrium point parameter N of the passively mode-locked EDF laser in the role of group-velocity dispersion (GVD) and small-signal gain, and adjusting system parameter N is as close as to possible to 1. The ground state first-order optical soliton which generated through system parameter optimization of the passively mode-locked EDF laser will improve the efficiency and stability of optical soliton communication system. The research of this paper will have provided the theoretical foundation of parameter optimization in a passively mode-locked EDF laser. And it will be possible for the passively mode-locked fiber laser in optical fiber communication system to be applied from the laboratory stage to the practical application.