Kai Chen

East China JiaoTong University, Jiangxi, Gansu Sheng, China

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Publications (38)1.46 Total impact

  • Pei Shen, Yi Zhou, Kai Chen
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    ABSTRACT: Microblogging has become a popular means of communication and information diffusion. Due to the huge amount of microblogs generated daily, the communication and computing costs required for real hot event detection is a big challenge. Choosing a small subnet of nodes to detect events has received increasing research interests in recent years. But the previous methods manage to select nodes to cover all the events including less popular events in sample datasets under the limited subnet size, which cause a big difference of event detection ratio between sample events and online real events in microblogs. In this paper we propose a new subnet nodes selection scheme based on the event detection ratio and nodes' events participation probabilities. Under the requirement of average event detection ratio, we prefer to choose the nodes who are active in propagating hot events than the nodes who participate in the less popular events. And we take dynamic programming to accelerate the computing. The experimental results show that our proposed method has a better performance.
    Proceedings of the 2013 IEEE/ACM International Conference on Advances in Social Networks Analysis and Mining; 08/2013
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    ABSTRACT: Spamming has been a widespread problem for social networks. In recent years there is an increasing interest in the analysis of anti-spamming for microblogs, such as Twitter. In this paper we present a systematic research on the analysis of spamming in Sina Weibo platform, which is currently a dominant microblogging service provider in China. Our research objectives are to understand the specific spamming behaviors in Sina Weibo and find approaches to identify and block spammers in Sina Weibo based on spamming behavior classifiers. To start with the analysis of spamming behaviors we devise several effective methods to collect a large set of spammer samples, including uses of proactive honeypots and crawlers, keywords based searching and buying spammer samples directly from online merchants. We processed the database associated with these spammer samples and interestingly we found three representative spamming behaviors: aggressive advertising, repeated duplicate reposting and aggressive following. We extract various features and compare the behaviors of spammers and legitimate users with regard to these features. It is found that spamming behaviors and normal behaviors have distinct characteristics. Based on these findings we design an automatic online spammer identification system. Through tests with real data it is demonstrated that the system can effectively detect the spamming behaviors and identify spammers in Sina Weibo.
    Proceedings of the 7th Workshop on Social Network Mining and Analysis; 08/2013
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    ABSTRACT: We propose a cost-effective hot event detection system over Sina Weibo platform, currently the dominant microblogging service provider in China. The problem of finding a proper subset of microbloggers under resource constraints is formulated as a mixed-integer problem for which heuristic algorithms are developed to compute approximate solution. Preliminary results show that by tracking about 500 out of 1.6 million candidate microbloggers and processing 15,000 microposts daily, 62% of the hot events can be detected five hours on average earlier than they are published by Weibo.
    Proceedings of the 22nd international conference on World Wide Web companion; 05/2013
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    ABSTRACT: This paper researches on Matthew Effect in Sina Weibo microblogger. We choose the microblogs in the ranking list of Hot Microblog App in Sina Weibo microblogger as target of our study. The differences of repost number of microblogs in the ranking list between before and after the time when it enter the ranking list of Hot Microblog app are analyzed. And we compare the spread features of the microblogs in the ranking list with those hot microblogs not in the list and those ordinary microblogs of users who have some microblog in the ranking list before. Our study proves the existence of Matthew Effect in social network.
    Big Data, 2013 IEEE International Conference on; 01/2013
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    ABSTRACT: Edges are of significant importance in visual resolution perception. In this paper, we propose a novel image super-resolution method by enhancing the edges in the low resolution image. We first define a new edge sharpness feature: gradient profile sharpness (GPS), which considers both the absolute magnitude and the spatial scattering of edge gradient profile. Then we learn the relationship between GPSs in high resolution images and low resolution images, and we formulate a linear GPS transform to provide gradient prior for image reconstruction. Our GPS can represent edge sharpness perceptually well. And our super-resolution method can output harmonious and faithful images with better reconstruction quality.
    Pattern Recognition (ICPR), 2012 21st International Conference on; 01/2012
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    ABSTRACT: In this poster we report our study on the microblog spammers with samples attracted by 50 honeyspots from two popular Chinese microblogging networks: Sina Weibo (weibo.com), and Ten cent Weibo (t.QQ.com) in seven months. We studied their features such as social information, activity, account age and spamming strategy. Several distinguishing characteristics of spammers on these two social network communities are observed, which can be helpful to the further study on automatic detection of microblog spammers. To our best knowledge our work is the first of its kind on the analysis of features of Chinese micloblog spammers.
    Advances in Social Networks Analysis and Mining (ASONAM), 2012 IEEE/ACM International Conference on; 01/2012
  • Source
    12/2011; 6:2341-2349. DOI:10.4304/jsw.6.12.2341-2349
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    ABSTRACT: In this paper we investigate rate adaptation algorithm SampleRate, which spends a fixed time on bit-rates other than the currently measured best bit-rate. A simple but effective analytic model is proposed to study the steady-state behavior of the algorithm. Impacts of link condition, channel congestion and multi-rate retry on the algorithm performance are modeled. Simulations validate the model. It is also observed there is still a large performance gap between SampleRate and optimal scheme in case of high frame collision probability.
    IEEE Communications Letters 05/2011; 15(5):524-526. DOI:10.1109/LCOMM.2011.031411.102497 · 1.46 Impact Factor
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    ABSTRACT: Dynamic Binary Translation (DBT) is widely used, but it suffers from substantial overhead. Several methods are taken to improve its performance, such as linking/chaining, building super block according to profiling and/or tracing. Reorganizing code layout of software cache can also improve performance on the ground that the execution stream will be more approximate to its control flow. Once the target code in software cache is reframed properly, hot code will be gathered together and well organized. Because of exact prediction and improved locality, the execution stream will concentrate on a small area with less control transfer. In this paper, we designed a new approach using dynamic-static combined framework to reorganize code layout of software cache. Then we compare it with another two conventional types of code layout in detail. Experimental result shows that our method can significantly cut down the overhead. The overall run time reduced by about 30% on average. Finally, we analyze the reason why reorganizing code layout can improve the performance of dynamic binary translator from several different perspectives.
    Parallel Architectures, Algorithms and Programming (PAAP), 2010 Third International Symposium on; 01/2011
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    ABSTRACT: System virtualization, which provides good isolation, is now widely used in server consolidation. Meanwhile, one of the hot topics in this field is to extend virtualization for embedded systems. However, current popular virtualization platforms do not support real-time operating systems such as embedded Linux well because the platform is not real-time ware, which will bring low-performance I/O and high scheduling latency. The goal of this paper is to optimize the Xen virtualization platform to be real-time operating system friendly. We improve two aspects of the Xen virtualization platform. First, we improve the xen scheduler to manage the scheduling latency and response time of the real-time operating system. Second, we import multiple real-time operating systems balancing method. Our experiment demonstrates that our enhancement to the Xen virtualization platform support real-time operating system well and the improvement to the real-time performance is about 20%.
    Embedded and Ubiquitous Computing (EUC), 2010 IEEE/IFIP 8th International Conference on; 01/2011
  • Source
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    ABSTRACT: In Recent years embedded world has been undergoing a shift from traditional single-core processors to processors with multiple cores. However, this shift poses a challenge of adapting legacy uniprocessor-oriented real-time operating system (RTOS) to exploit the capability of multi-core processor. In addition, some embedded systems are inevitably going towards the direction of integrating real-time with off-the-shelf time-sharing system, as the combination of the two has the potential to provide not only timely and deterministic response but also a large application base. Virtualization technology, which ensures strong isolation between virtual machines, is therefore a promising solution to above mentioned issues. However, there remains a concern regarding the responsiveness of the RTOS running on top of a virtual machine. In this paper we propose an embedded real-time virtualization architecture based on Kernel-Based Virtual Machine (KVM), in which VxWorks and Linux are combined together. We then analyze and evaluate how KVM influences the interrupt-response times of VxWorks as a guest operating system. By applying several real-time performance tuning methods on the host Linux, we will show that sub-millisecond interrupt response latency can be achieved on the guest VxWorks.
    Computer Sciences and Convergence Information Technology (ICCIT), 2010 5th International Conference on; 01/2011
  • U- and E-Service, Science and Technology - International Conference, UNESST 2011, Held as Part of the Future Generation Information Technology Conference, FGIT 2011, in Conjunction with GDC 2011, Jeju Island, Korea, December 8-10, 2011. Proceedings; 01/2011
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    ABSTRACT: Debugging could be a threat to system security when adopted by malicious attackers. The major challenges of software-only anti-debugging are compromised strategy and lack of self-protection. Leveraging hardware virtualization, we proposes a strategy of software protection through anti-debugging which imperceptibly monitors the debug event on a higher privilege level than the conventional kernel space. Our prototype can effectively prohibit the debugging behavior from selected popular debuggers in the replication experiment.
    Proceedings of the 2011 ACM Symposium on Applied Computing (SAC), TaiChung, Taiwan, March 21 - 24, 2011; 01/2011
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    ABSTRACT: Recently underwater sensor networks (UWSN) at- tracted large research interests. Medium access control (MAC) is one of the major challenges faced by UWSN due to the large propagation delay and narrow channel bandwidth of acoustic communications used for UWSN. Widely used slotted aloha (S-Aloha) protocol suffers large performance loss in UWSNs, which can only achieve performance close to pure aloha (P- Aloha). In this paper we theoretically model the performances of S-Aloha and P-Aloha protocols and analyze the adverse impact of propagation delay. According to the observation on the performances of S-Aloha protocol we propose two enhanced S-Aloha protocols in order to minimize the adverse impact of propagation delay on S-Aloha protocol. The first enhancement is a synchronized arrival S-Aloha (SA-Aloha) protocol, in which frames are transmitted at carefully calculated time to align the frame arrival time with the start of time slots. Propagation delay is taken into consideration in the calculation of transmit time. As estimation error on propagation delay may exist and can affect network performance, an improved SA-Aloha (denoted by ISA- Aloha) is proposed, which adjusts the slot size according to the range of delay estimation errors. Simulation results show that both SA-Aloha and ISA-Aloha perform remarkably better than S-Aloha and P-Aloha for UWSN, and ISA-Aloha is more robust even when the propagation delay estimation error is large.
    Proceedings of the 73rd IEEE Vehicular Technology Conference, VTC Spring 2011, 15-18 May 2011, Budapest, Hungary; 01/2011
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    ABSTRACT: It is crucial to minimize virtualization overhead for virtual machine deployment. The conventional ×86 CPU is incapable of classical trap-and-emulate virtualization, leading that paravirtualization was the optimal virtualization strategy formerly. Since architectural extensions are introduced to support classical virtualization, hardware assisted virtualization becomes a competitive alternative method. Hardware assisted virtualization is superior in CPU and memory virtualization, yet paravirtualization is still valuable in some aspects as it is capable of shortening the disposal path of I/O virtualization. Thus we propose the hybrid virtualization which runs the paravirtualized guest in the hardware assisted virtual machine container to take advantage of both. Experiment results indicate that our hybrid solution outweighs origin paravirtualization by nearly 30% in memory intensive test and 50% in microbenchmarks. Meanwhile, compared with the origin hardware assisted virtual machine, hybrid guest owns over 16% improvement in I/O intensive workloads.
    Proceedings of the 2011 ACM Symposium on Applied Computing (SAC), TaiChung, Taiwan, March 21 - 24, 2011; 01/2011
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    ABSTRACT: as the popularity of social networking sites increase, so does their attractiveness for criminals. In this work, we show how an adversary can build artificial identities using semantic information in social network. Our method make the identities look more like real people, therefore can be used to support many kinds of attacks, such as ASE (1), profile cloning (2). A prototype of this method is implemented, includes following stages: Firstly, categories of virtual identity are predefined, and each category has multiple properties, such as geographical region, hobby, education, age, interested topic/keywords, etc. Secondly, based on category information, each identity will foster its own "life" semantically, such as edit profile and update status, find hot related news/topic from Google then post to wall, find related groups/networks then request to add in, and find/like/create/comment pages/posts, etc. Thirdly, artificial identity will evolve to multiple stages according to its status (for example, number of friends of real people), single identity with different evolutionary stages is linked together to a group that will help to ensure the number of attack edges (3).
    International Conference on Advances in Social Networks Analysis and Mining, ASONAM 2011, Kaohsiung, Taiwan, 25-27 July 2011; 01/2011
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    ABSTRACT: As a key part of reverse engineering, decompilation plays a very important role in software security and maintenance. Unfortunately, most existing decompilation tools suffer from the low accuracy in identifying variables, functions and composite structures, which results in poor readability. To address these limitations, we present a practical decompiler called C-Decompiler for Windows C programs that (1) uses a shadow stack to perform refined data flow analysis, and (2) adopts inter-basic-block register propagation to reduce redundant variables. Our experimental results illustrate that on average C-Decompiler has the highest total percentage reduction of 55.91%, lowest variable expansion rate of 55.79% in the three tools, and the same Cyclomatic Complexity as the original source code for each test application. Furthermore, in our experiment, C-Decompiler is able to recognize functions with lower false positive and false negative rate. In the studies, we show that C-Decompiler is a practical tool to produce highly readable C code.
    Reverse Engineering (WCRE), 2010 17th Working Conference on; 11/2010
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    ABSTRACT: Although dynamic binary translators (DBT) are gaining popularity in the modern virtual execution environments (VEE), the requirement of DBTs' processing and memory resources has seriously hampered the performance of host platform. In this paper, we propose a distributed DBT system--DistriBit for resource-limited thin clients to overcome these challenges. Since thin client always has small memory and cannot cache all translated code, we divide its unified cache into a 2-level cache and design a dual locality cache management scheme to help thin client manage its translated code. Meanwhile, to improve the execution efficiency of thin client and reduce the overhead of network transmission, we not only optimize translated code on the server but also predict those thin client required code with a prediction scheme. Experimental results show that our DistriBit system could effectively improve a thin client's performance of SPECint2000 by 2%~26% relative to a monolithic thin client, and our dual locality cache management scheme that results in miss reduction of about 1.41%~20.6% for a thin client with a 2-level cache over a thin client with a unified cache.
    Proceedings of the 19th ACM International Symposium on High Performance Distributed Computing, HPDC 2010, Chicago, Illinois, USA, June 21-25, 2010; 01/2010
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    ABSTRACT: Hot trace building plays an important role in enhancing the performance of dynamic binary translators, since in most cases 10% of code takes 90% of execution time of the whole program. Hot traces can promote the code position to make better the locality of the code, therefore programs can achieve a better performance. Thus how to build qualified and long hot traces is the key point. Considering the situation when one single basic block is needed by more than two hot traces, code replication can help build hot traces with cost of expansion of code size. In this paper, a code replication method to help with building hot traces as well as code positioning is presented, and experiments have been done to evaluate the details of changes that code replication brings to the system, like trace fragment length, memory size expansion, etc. With this method, a performance promotion by 0.5%-3.5% against the original trace building method has been achieved.
    GCC 2010, The Ninth International Conference on Grid and Cloud Computing, Nanjing, Jiangsu, China, 1-5 November 2010; 01/2010
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    ABSTRACT: GPUs are many-core processors with tremendous computational power. However, as automatic parallelization has not been realized yet, developing high-performance parallel code for GPUs is still very challenging. The paper presents a novel translation framework designed for virtual execution environment based on CPU/GPU architecture. It addresses two major challenges of taking advantage of general purpose computation on graphics processing units (GPGPU) to improve performance: no rewriting the existing source code and resolving binary compatibility issues between different GPUs. The translation framework uses semi-automatic parallelization technology to port existing code to explicitly parallel programming models. It not only offers a mapping strategy from X86 platform to CUDA programming model, but also synchronizes the execution between the CPU and the GPUs. The input to our translation framework is parallelizable part of the program within binary code. With an additional information related to the parallelizable part, the translation framework transforms the sequential code into PTX code and execute it on GPUs. Experimental results on several programs from CUDA SDK Code Samples and Parboil Benchmark Suite show that our translation framework could achieve very high performance, even up to several tens of times speedup over the X86 native version.

Publication Stats

112 Citations
1.46 Total Impact Points

Institutions

  • 2009–2013
    • East China JiaoTong University
      Jiangxi, Gansu Sheng, China
  • 2008–2013
    • Shanghai University
      Shanghai, Shanghai Shi, China
  • 2009–2012
    • Shanghai Jiao Tong University
      • • Department of Electronic Engineering
      • • School of Software
      • • School of Information Security Engineering
      Shanghai, Shanghai Shi, China