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Energy analysis of the deformation and failure process of sandstone and damage constitutive model
Tao Wen,Huiming Tang,Junwei Ma,Junwei Ma 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.2
The damage theory was introduced to clarify and simulate the strain softening property of rocks. On the basis of the theory, an energy method was utilized to portray the rock mechanical properties from microscopic perspective. Firstly, from the perspective of rock microstructure, damage variable (expressed as D) was redefined by dividing the rock into three portions: undamaged materials, damaged materials and micro-defects, and an impact factor was introduced as the connection between the damaged material and the micro-defects. Meanwhile, the method for determining the impact factor was presented. Secondly, the damage variable was redefined in light of energy dissipation, then damage evolution analysis was conducted based on triaxial tests. An improved rock damage constitutive model was further obtained in another expression to reflect the energy change law. Subsequently, the relationship between D and the deformation and failure process of rocks was analyzed on account of the damage evolution equation formularized by fitting to a logistic function, which can measure the influence of energy dissipation on the propagation of micro-defects. By comparing between experimental results and theoretical results of illustrative examples, the effectiveness of the improved model was validated, and the its application was also discussed.
An Efficient Provable Secure Public Auditing Scheme for Cloud Storage
( Chunxiang Xu ),( Yuan Zhang ),( Yong Yu ),( Xiaojun Zhang ),( Junwei Wen ) 한국인터넷정보학회 2014 KSII Transactions on Internet and Information Syst Vol.8 No.11
Cloud storage provides an easy, cost-effective and reliable way of data management for users without the burden of local data storage and maintenance. Whereas, this new paradigm poses many challenges on integrity and privacy of users` data, since users losing grip on their data after outsourcing the data to the cloud server. In order to address these problems, recently, Worku et al. have proposed an efficient privacy-preserving public auditing scheme for cloud storage. However, in this paper, we point out the security flaw existing in the scheme. An adversary, who is on-line and active, is capable of modifying the outsourced data arbitrarily and avoiding the detection by exploiting the security flaw. To fix this security flaw, we further propose a secure and efficient privacy-preserving public auditing scheme, which makes up the security flaw of Worku et al.`s scheme while retaining all the features. Finally, we give a formal security proof and the performance analysis, they show the proposed scheme has much more advantages over the Worku et al.`s scheme.
Changqing Ren,Fugui He,Xianzhi Gao,Dongsheng Wu,Wenli Yao,Jianzhang Tian,Huiping Guo,Yuanxin Huang,Li Wang,Han Feng,Junwei Li 한국지질과학협의회 2019 Geosciences Journal Vol.23 No.6
The Shulu Sag which is a rifted sag with NNE trend is located in the south of Jizhong Depression, Bohai Bay Basin, northern China. The gentle slope and three troughs are situated in the west and east of the sag, respectively. Both of the lower part of Shasan Member (Es3x) and the lower part of Shayi Member (Es1x) act as source rocks in this sag. Researches on the type, quantity, quality and thermal maturity of the respective organic matter have been conducted using Rock-Eval pyrolysis data. Type II is the dominant kerogen in Es1x of all troughs. However, Type II1 and III is the dominant kerogen in Es3x of Middle-Southern and Northern trough, respectively. TOC (total organic carbon) and pyrolysis S2 (hydrocarbon) values suggest that the Es1x source rocks in Middle-Southern and Northern trough are fair to good and poor to fair generative potential of hydrocarbon, separately. The Es3x source rocks in Middle-Southern and Northern trough possess fair to excellent and poor to fair generative potential of hydrocarbon, individually. Tmax (pyrolysis temperature at maximum S2) values indicate that most of Es3x samples are thermally mature, but all Es1x samples are thermally immature. Under large scale condition, the hydrocarbon secondary migration in the upper part of Shasan Member (Es3s), Shaer Member (Es2) and the upper part of Shayi Member (Es1s) have been simulated using fluid potential model with Arcgis 9.3 software. The simulation results reveal the direction of hydrocarbon secondary migration and the distribution of hydrocarbon migration-accumulation units (HMAUS), and also suggest that the hydrocarbon migration direction is obviously controlled by nose-like structure belts where most of hydrocarbons accumulate. That shows high reliability because they are consistent with the hydrocarbon exploration result in this area. On the basis of integrated analyses of source rocks and hydrocarbon migration direction, the following five areas in the gentle slope are identified to be the preferred hydrocarbon accumulation area: Taijiazhuang area, northern and southern Xicaogu area, as well as northern and southern Leijiazhuang area. It is considerably helpful to reduce the risk in hydrocarbon exploration of Shulu Sag.