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Kong Q.,CAS Institute of Automation | Mao W.,CAS Institute of Automation | Liu C.,CNCERT CC
Proceedings of 2016 4th IEEE International Conference on Cloud Computing and Intelligence Systems, CCIS 2016 | Year: 2016

The interactive behavior of Web users often makes some online contents more popular than others. Thus the popularity of online contents can help us understand public interest and attention behind user interactions. Modeling and predicting the popularity of online contents is an important research topic and can facilitate many practical applications in different domains. Previous work on popularity modeling and prediction usually treat each online content separately, and neglect the interaction information between online contents, represented as interaction relations. In this paper, we explore the interaction relations between online contents, specifically competition and cooperation relations, for popularity prediction. We first define the interaction relations between different online contents and propose a method for the calculation of interaction information. We then apply the non-negative matrix factorization (NMF) technique to get a low dimensional representation of interaction features for online contents, which are used by classifiers for popularity prediction. We finally evaluate the proposed approach using two datasets from SinaWeibo (i.e., original tweets and topic hashtags). The experimental results show that interaction features alone can yield relatively good performance, and by incorporating interaction features into traditional feature based methods, our method can further improve popularity prediction results. © 2016 IEEE.

Zhang X.,Harbin Institute of Technology | Tian Z.,CNCERT CC | Zhang L.,Harbin Institute of Technology
Proceedings - 2016 IEEE 1st International Conference on Data Science in Cyberspace, DSC 2016 | Year: 2016

Although Mainline DHT is not an official BitTorrent protocol so far, it's widely used in many BitTorrent clients such as Utorrent, Vuze, BitComet and Xunlei. Despite there are millions of Mainline DHT users, only little research focus on Mainline DHT. In this paper, we present two kinds of measurement results based on crawling Mainline DHT. Firstly, we develop an effective crawler and crawl Mainline DHT over 10 days. We collected 10,149,649 magnet links and received over 264,846,482 getpeers requests from 57,065,499 unique peers. Based on the measurement results, we found that: (1) Russian and China play dominant roles in Mainline DHT which contribute 35% peers in it, and there are 5% Internet users use Mainline in Europe; (2) UTorrent is the most popular clients so far, half of peers use it. (3) We found that most clients use randomly chosen port numbers, only 8.9% use constant port. (4) Zona is a popular Russia peer to peer client, nine in ten top popular magnet links are unique in Zone, and only one is BitTorrent magnet link. (5) The peers' size of torrent almost follows a Zipf distribution. 11% torrents take up 95% peers of the total. 46% torrents only get one peer during our experiment. Secondly, we study two ways to convert magnet link to torrent file: Converting by five popular torrent storage services and converting by Extension protocol. We compare the performance of them in terms of converting rate, converting time, advantages and disadvantages and discover that: (1) The converting rate of torrent storage services and Extension protocol are 46.9% and 22.7%. (2) The average successful converting time of Extension protocol is 75s, and if a magnet spends more than 150s to convert but still couldn't get good peers, it tends to convert unsuccessfully at present. The best scheme is stopping for a while, and waiting good peers on line. (3) NAT is the main reason caused the converting or downloading failure, there are 32.5% peers stay in NAT or firewall. The best solution of NAT user is the popularized of IPv6 or Tunneling. Understanding DHT in depth can improve the performance of current DHT system. © 2016 IEEE.

Liu L.,Peking University | Tu B.,CNCERT CC | Chen T.,Peking University | Liu Y.,Peking University | Wang D.,Peking University
Journal of Lightwave Technology | Year: 2014

To achieve rapid establishment of free-space optical (FSO) links, we previously proposed an ultrawide field-of-view (FOV) acquisition scheme, which combines the fisheye lens and Voigt anomalous dispersion optical filter. In this paper, we focus on the angle detection accuracy of this ultrawide FOV acquisition scheme, which is one of primary factors for rapid establishment of FSO links. The positioning process is composed of two parts. One is the spot location, which acquires the position of the imaging spot of the incident beam. The other is the mapping from spot location to incident angle, with which the position of imaging spot can be turned into the angles of the incident beam. For the first part, an improved centroid locating algorithm is present to realize the subpixel accuracy of spot location, and theory and simulation are carried out to demonstrate the improved accuracy of this algorithm. For the second part, we propose the fisheye lens calibration algorithm, which integrates the fisheye lens projection model and natural neighbor interpolation algorithm. In addition, by combining with the measured data, the angle detection accuracy of this method can be improved gradually with the increased number of the measured data. The simulation results indicate that this new method can provide high-precision positioning of the laser beams, and the maximum angle detection error of this ultrawide FOV acquisition scheme can be less than 0.054° (0.94 mrad). © 2014 IEEE.

Dong H.,Beihang University | Zhang T.,Petrochina | Hao Q.,Beihang University | Zhang B.,CNCERT CC
Parallel and Distributed Computing, Applications and Technologies, PDCAT Proceedings | Year: 2010

as a most prevalent topic in recent few years, the public has shown great interest on cloud computing----the brand new concept about service pattern for IT industry. However, the public view is now mainly focused on the technical development of such a framework that is practically available, yet little research has been taken from the aspect of the academic. This article is written with the intention for some discussion and exploration on relationships between virtualization and Cloud Computing. The article provides one way it provides an attempt to give out a formal definition of cloud computing from the viewpoint of virtualization and the set theory upon which the concept of virtualization is based. © 2010 IEEE.

Yu J.,National University of Defense Technology | Xiao P.,Beihang University | Li Z.,Beihang University | Zhou Y.,CNCERT CC
IEEE Communications Letters | Year: 2011

DHTs have been widely used in designing various applications, especially P2P file sharing systems. It is crucial but difficult to get an accurate snapshot of a DHT network, since such network is serverless and peers join and depart dynamically. In this letter, we analyze and empirically verify that neither breadth-first search nor depth-first search is optimal for DHT snapshot crawling, due to uneven ID distribution of contacts in the routing table of each DHT peer. We then propose a hybrid search strategy which could both start up quickly and slow down slowly. The experiment performed on Mainline shows that this approach significantly outperforms breadth-first or depth-first search strategy. © 2011 IEEE.

Wang Y.,Chinese Academy of Sciences | Yun X.,CNCERT CC | Wang S.,Chinese Academy of Sciences | Wang X.,Chinese Academy of Sciences
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2016

Membership query of dynamic sets is essential for applications which generate or process a continuous stream of data items. These applications often require to cache items dynamically and answer membership queries for duplicate detection on unbounded data streams. Three key challenges for the caching mechanism are the limited memory space, high precision requirement and different priority-levels related with items. In this paper, we propose a compact in-memory index, Bloom Filter Ring (BFR), which is more suitable for dynamic caching of items on unbounded data streams. We demonstrate the time complexity and precision of BFR in finite memory space, and theoretically prove that BFR has higher expectation of average capacity than Aging Bloom Filter, the current state of art. Furthermore, we propose Priority-aware BFR (PBFR) to support membership query scheme which takes into account priority levels of items. Experimental results show that our algorithms gain better performance in term of cache hit ratio and false negative rate. © Springer International Publishing Switzerland 2016.

Zheng X.,University of Science and Technology of China | Si J.,Changan Communication Technology Co. | Dai S.,CNCERT CC
ACM International Conference Proceeding Series | Year: 2016

Inspired by the constant density constraints in position-based fluids (PBF), we propose a novel blue noise sampling algorithm. We formulate and solve a set of sampling points' positional constraints to enforce constant density, which is similar to the PBF. Points converge to distribute evenly and stochastically in space. Fourier spectral analysis of the converged points' distribution shows that it has great blue noise spectrum. By adjusting a single parameter, our method can generate blue noise samplings from Capacity Constrained Voronoi Tebellations (CCVT) to Lloyd's relaxation, and it can also trade off the noise and aliasing of samplings. We utilize the grid-based signed distance field to represent sampling regions, which makes our method fit for general dimensions. Varying the gird size can adjust the number of points. We put points at sampling boundary to solve the points deficiency. Adaptive sampling is achieved with a sampling density function. Experimental results show our method is efficient, stable and controllable in both twodimensional (2D) plane sampling, and adaptive sampling. Moreover, it is suitable for image stippling. © 2016 ACM.

Pervasive and Mobile Computing | Year: 2014

In a mobile ad hoc network (MANET), the lack of a trusted infrastructure makes secure and reliable packet forwarding very challenging, especially for providing QoS guarantee for multimedia applications. In this paper, we firstly introduce the concept of trust and QoS metric estimation into establishing a trust-based QoS model. In this model, we estimate the trust degree between nodes from direct trust computation of direct observation and indirect trust computation by neighbors' recommendations. On the other hand, due to the NP-completeness of the multi-QoS constraints problem, we only take into account link delay as the QoS constraint requirement. Then, we design a trust-based QoS routing algorithm (called TQR) from the trade-off between trust degree and link delay. At last, by using NS2 we implement this algorithm based on AODV (Ad hoc On-demand Distance Vector). We compare its performance with AODV, Watchdog-DSR and QAODV. The simulation results show that TQR scheme can prevent attacks from malicious nodes and improve the security performance of the whole network, especially in terms of packet delivery ratio, average end-to-end delay, routing packet overhead and detection ratio of malicious nodes. Crown Copyright © 2013 Published by Elsevier B.V. All rights reserved.

Proceedings of 2014 IEEE International Conference on Behavioral, Economic, Socio-Cultural Computing, BESC 2014 | Year: 2014

In this paper, we investigate the relationship among trading volume, volatility and jump based on Hu-Shen300 index high frequency data. We measure volatility using realized volatility proposed by Andersen and Bollerslev (1998) and decompose it into upside and downside parts by the asymptotic properties of realized upside and downside power variation defined in Bi, Zhang and Wu(2013). To measure jump component, we use a novel jump measure called signed jump proposed by Patton and Sheppard(2011). Our empirical analysis show that trading volume are positively related with realized volatility, RUPV and RDPV. We also find that trading volume is negatively related with signed jump. © 2014 IEEE.

Tongxin Xuebao/Journal on Communications | Year: 2013

Due to the absence of enough physical protection, dynamic topology, distributed collaboration, the limited bandwidth and computing ability in ad hoc network, traditional routing security mechanism cannot adapt to the design of routing protocols. Recently, opportunistic routing is one of the research hotspots, which can cope with the unreliable transmissions to improve throughput of the whole network by exploiting the broadcast nature of the wireless medium and spatial diversity of multi-hop wireless network. The concept of trust-based similarity in opportunistic routing for ad hoc network was incorporated, and a novel trusted opportunistic forwarding model based on trust degree of node and least cost of opportunistic routing were also built. Then a trusted minimum cost routing algorithm (MCOR) was proposed and the correctness and effectiveness of this algorithm from theoretical analysis were proved. Finally, MCOR algorithm was verified by simulation and was compared with the classic protocols: ExOR, TAODV and Watchdog-DSR. The simulation results show that MCOR scheme can detect and mitigate node misbehaviors. Furthermore, MCOR scheme outperforms the other protocols in terms of throughput, delay, expected ETX and cost of routing.

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