Entity

Time filter

Source Type


Liao G.,Jiangxi University of Finance and Economics | Liao G.,Jiangxi Province Key Laboratory of Data and Knowledge Engineering | Li J.,Jiangxi University of Finance and Economics
Jisuanji Yanjiu yu Fazhan/Computer Research and Development | Year: 2010

Recently, RFID technologies have been widely used in many fields, such as real-time monitoring, object identification and item tracing, so it is very important to detect abnormal states of tagged objects in time. However, due to various environmental factors and unreliability of wireless communication technology, the data collected by the RFID readers are often noisy. According to the characteristics of distributed RFID data stream, such as huge-volume, variability, unreliability and distribution, the authors propose a distance-based local stream outlier detection algorithm (LSOD) and an approximate estimate-based global stream outlier detection algorithm (GSOD). LSOD need maintain a data stream structure, CSL, to identify the safe inlier. With the help of the characteristics of safe inliers, LSOD not only can reduce the memory space of stream data, but also can save the query time on stream objects. Under the distance-based outlier definition, it is a fact that global outlier on center node is a subset of the union of local outliers on every distributed node. Thus, GSOD uses a sample-based method to estimate approximately the global outliers for reducing the communication volume and calculate load of the centre node. Finally, several experiments have been accomplished, confirming that the proposed algorithms have the characteristics such as short running time, small memory space and high accuracy. Source


Liao G.,Jiangxi University of Finance and Economics | Liao G.,Jiangxi Province Key Laboratory of Data and Knowledge Engineering | Xiong A.,Jiangxi University of Finance and Economics | Di G.,Jiangxi University of Finance and Economics | And 3 more authors.
Jisuanji Yanjiu yu Fazhan/Computer Research and Development | Year: 2014

Considering the features of mobile Ad Hoc networks such as lack of center nodes, multi-hops routing and limited resources, a hybrid checkpointing strategy combining synchronous checkpointing and asynchronous checkpointing is suggested for clustering-based Ad Hoc networks. Namely, the checkpoints in the same cluster must keep synchronous, while the checkpoints in different clusters are independent. Firstly, a hybrid checkpointing model and its correctness criteria are discussed. Then, the elimination rules of different kinds of checkpoints are suggested based on the intra-cluster and inter-cluster checkpoint dependency graphs. Finally, the algorithms of checkpointing and rollback recovery are given, and the correctness of recovery is proved. The proposed strategy can not only avoid resource waste due to cascading rollback among the processes in the same clusters, but also avoid too much message transmission among the processes in different clusters, to reduce the wireless communication delay largely. Experiment results show that, comparing with the pure synchronous and pure asynchronous checkpointing methods, the proposed hybrid checkpointing strategy is a flexible and good trade-off scheme taking all kinds of resource constraints of Ad Hoc networks into account, and has the advantages such as short recovery time, less dependence on cluster heads. Source


Liu X.,Jiangxi University of Finance and Economics | Liu X.,Jiangxi Province Key Laboratory of Data and Knowledge Engineering | Wan C.,Jiangxi University of Finance and Economics | Wan C.,Jiangxi Province Key Laboratory of Data and Knowledge Engineering | And 2 more authors.
Jisuanji Yanjiu yu Fazhan/Computer Research and Development | Year: 2010

XML documents involve both contents and structures, and can be retrieved by means of not only content-only (CO) but also content-and-structure (CAS) queries. In this paper, a novel approach for CAS retrieval is proposed. The approach proceeds in three steps: it first decomposes a CAS query into a set of query fragments, and then processes each query fragment. Finally, it combines results on each query fragments. By this approach, on the one hand, the adverse effects of structural vagueness on answer nodes selection can be removed; on the other hand, the effect of structural constraints on scoring is incorporated properly. The features of this approach make it applicable in versatile homogeneous and heterogeneous data environments. To measure the relevance query results to a given CAS query, a novel scoring scheme is presented. In accordance with the query processing approach, the scoring method first computes the scores of a query result with respect to each query fragment, and then combines these partial scores to arrive at an overall score. The proposed scoring method considers the relevance of both contents and structures in the retrieval results, and thus reflects the user's query intention and conforms to query semantics. Comprehensive experimental studies demonstrate the effectiveness of the proposed methods. Source

Discover hidden collaborations