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Liu Z.,Nankai University | Luo D.,Chengdu University of Technology | Luo D.,Key Laboratory of Geomathematics of Sichuan Province | Li J.,Guangzhou University | And 2 more authors.
International Journal of Computer Mathematics

Compared with traditional online social networks (OSNs), mobile OSNs (mOSNs) take a step further in that they provide the location-based services, and location-sharing is a fundamental component of mOSN. However, without privacy protection, users may be hesitant to share their locations. In this paper, we present a new privacy-preserving location-sharing system for mOSN, which is flexible to support a variety of location-based applications, in that it enables location-sharing between both trusted social relations and untrusted strangers. It allows user to dynamically change his sharing decryption key when to add or revoke a friend. We further propose a security improved system, which can be secure against neighborhood attacks. In our proposed systems, threat models are further analysed and users’ location privacy is proved secure. Implementation and evaluation show that they are efficient and practical. © 2014 Taylor & Francis. Source

Chen H.,Chengdu University of Technology | Chen H.,Key Laboratory of Geomathematics of Sichuan Province | Chen H.,MOE Key Laboratory of Earth Exploration and Information Techniques | He Y.-S.,China National Petroleum Corporation | And 5 more authors.
Xinan Shiyou Daxue Xuebao/Journal of Southwest Petroleum University

Wave equation prestack depth migration is an effective way to deal with imaging in complex geological structure. Final imaging result is obtained by prestack depth migration, but the migration velocity analysis and AVA / AVO analysis are completed by common imaging point gathers. Common imaging gathers are sensitive to migration velocity which has an effect on the feasibility and the number of iterative convergence of migration velocity analysis. Based on this, the method of extraction of common imaging point gathers during wave field extrapolation by using double square root preserved-amplitude migration operator is presented in the paper. It ensures the energy characteristics of amplitude and is better for AVA/AVO analysis. The sensitivity of common imaging point gathers in offset domain and ray parameter domain to migration velocity can meet the needs and enhance the accuracy of migration velocity analysis. Source

Zhan Z.-D.,Chengdu University of Technology | Zhan Z.-D.,Key Laboratory of Geomathematics of Sichuan Province | Zhan Z.-D.,Sinopec | Guo K.,Key Laboratory of Geomathematics of Sichuan Province | And 3 more authors.
Journal of Chengdu University of Technology (Science and Technology Edition)

This paper explores the method and means of quantitative analysis about correlation of small layers to compensate the lack of the conventional and artificial correlation of small layers and make sure of the validity of the structure modelling. This paper researches the correlation of small layer by taking it as a grey system, simulates the human brain and creative thinking, applies the mathematical methods to conduct grey relational analysis, and uses the association degree as the quantitative analysis standard to establish the corresponding relation between mathematical operators and geological interpretation. The result shows that this method can realize the automatic connection of small layers quantitatively and prepare for the structure modelling better, and can detect the results of the division and correlation of small layers by hand and exclude abnormal small layers division. Source

Zhou Z.-L.,Chengdu University of Technology | Zhou Z.-L.,Key Laboratory of Geomathematics of Sichuan Province | Gong H.,Key Laboratory of Geomathematics of Sichuan Province
Wutan Huatan Jisuan Jishu

The paper, on the basis of the characteristics of the sedimentary environment and facies the Chang 6 formation of Baoziwan, synthetically analyzes the reservoir formation model in the work area. Stochastic theory and mediodology are then applied to the establishment of the spatial model reflecting the 3D distribution of the reservoir sand body in Baoziwan Chang 6. Finally 3D simulation of the sand body distribution is fulfilled by adopting character-point stochastic simulation technology. The error analysis shows that the 3D distribution is of good quality and precision when compared with the practical situation in reservoir engineering. Source

Huang W.-T.,Key Laboratory of Geomathematics of Sichuan Province | Lu H.,Key Laboratory of Geomathematics of Sichuan Province | Guo K.,Key Laboratory of Geomathematics of Sichuan Province
Wutan Huatan Jisuan Jishu

Evidence theory is widely used in data fusion systems. However, it is never used in seismic attributes analysis. A new application of D-S evidence theory in seismic attribute is presented. The process of the D-S information fusion method contains the following steps: firstly, using the complex seismic trace analysis to extract three instantaneous attributes (instantaneous amplitude, instantaneous phase and instantaneous frequency); then, utilizing the modified D-S algorithm on the combination of three instantaneous attributes and getting the final result of the data fusion system; finally, effectively combination of the useful information of the three seismic attributes which reflects more clear local changes of seismic signals than single attribute. The actual example shows D-S information fusion method brings better reflections on changes of seismic properties, geological phenomenon and geological deposition. Source

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