It is a bottleneck of Apriori algorithm for mining association rules that the candidate set C ₂ is used to generate the frequent 2-item set L ₂. In the Direct Hashing and Pruning (DHP) algorithm, a generated Hash table H ₂ is used to delete the unused candidate item sets in C ₂ for improving the efficiency of generating L ₂. However,the traditional DHP is a serial algorithm, which cannot effectively deal with large scale data. In order to solve the problem, a DHP parallel algorithm, termed H_DHP algorithm, was proposed. First, the feasibility of parallel strategy in DHP was analyzed and proved theoretically. Then, the generation method for the Hash table H ₂ and frequent item sets L ₁, L ₃- L _k was developed in parallel based on Hadoop, and the association rules were generated by Hbase database. The simulation experimental results show that, compared with the DHP algorithm, the H_DHP algorithm has better performance in the processing efficiency of data, the size of the data set, the speedup and scalability.

In view of the contradiction between capability, invisibility and robustness of the existing information hiding algorithms, a preprocessing algorithm for digital image based on CL (Chui-Lian) multi-wavelet transform and Combination Bit Plane (CBP) was proposed. Then the digital image preprocessed by CL multi-wavelet and CBP was taken as the cover image to embed secret information for confidential communication and image sharing. CL multi-wavelet transform could divide the cover image into four lowest resolution sub-images with different energy level. And CBP method could analyze the above four sub-images into different bit planes as the final embedding regions. During the hiding procedure, robust information, secret information and fragile information could be embedded according to the energy and robustness characteristics of the embedding regions. The experimental results show that the robustness against several common attacks described in this paper has certain enhancement compared with other two methods when the embedding rate is 25%. The Peak Signal-to-Noise Ratio (PSNR) is increased by 37.16% and 20.00% respectively compared with Discrete Cosine Transform-Least Significant Bit (DCT-LSB) and Discrete Wavelet Transform -Least Significant Bit (DWT-LSB) algorithm.

Attribute reduction is one of the key problems in rough set theory, and determination of core attribute is the basis to solve the problem of attribute reduction. First, by using the tree structure knowledge expression in the decision table, an approach for computing positive and negative regions was introduced. Next, according to changes of positive and negative regions in tree structure decision table relative to the conditional attribute set, an algorithm for computing core attributes was developed. An efficiency of the proposed methods was illustrated by time and space complexities analysis and experimental result in a weather decision table.

Grid service provides a distributed computing service over heterogeneous network environment by taking the advantage of the Web Service. The relationship among grid system and network systems, especially the Web Service system, was examined in the perspective of computer network architecture. An emphasis has been given to clarification of Open Grid Service Architecture(OGSA), in which some of layers irrelevant to network functionality (outside of the scope of OSI/RM) were miss-represented in early documents.

Grid service provides a distributed computing service over heterogeneous network environment by taking the advantage of the Web Service. The relationship among grid system and network systems, especially the Web Service system, was examined in the perspective of computer network architecture. An emphasis has been given to clarification of Open Grid Service Architecture(OGSA), in which some of layers irrelevant to network functionality (outside of the scope of OSI/RM) were miss-represented in early documents.

Based on ExLF Log file format, the Session Tabel was defined, and the conception of user session graph was expounded in detail. A heuristic algorithm of creating graph of user sessions identification was presented. At last, an example illustrated the efficiency of this algorithm.