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RISS 인기검색어
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- 저자 : Zhijun Lai (검색결과 3 건)
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Qin Zhijun,Lai Yu 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.5
False data injection attack (FDIA) is a typical cyber-attack targeting on power system state estimation. By inserting bias into the power system meter measurements, FDIA can cause errors in state estimation and consequently mislead power system operation. Recently, the coordinated state-and-topology FDIA was developed to falsify both the meter measurements and the topology information to conceal a cyber or physical attack. Conventional machine-learning-based detection methods against FDIA depend on the complete observability of power system topology, therefore cannot detect the coordinated state-andtopology FDIA. To address this challenge, we propose a multi-modal learning model based on Graph Auto-Encoder (GAE) and Residual Neural Networks (ResNet) to detect this type of FDIA. First, GAE is used to learn the compact representation of power system topologies. Then, the obtained topological representation is fused with the measurement to obtain the multi-modal features. Third, ResNet is trained as a multi-label classifi er to accept the fused features and generate an array, which can detect attack scenarios and identify the falsifi ed measurements/topologies by coordinated attacks. Comprehensive case studies using IEEE 9-bus, IEEE 57-bus, and IEEE 118-bus systems are presented. The simulation results show that, as compared to single feature methods, the proposed method is more eff ective in detecting coordinated state-and-topology attacks, and more robust in case of FDIA under unseen topological changes in power system operation
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Form- finding analysis of suspension bridges using an explicit Iterative approach
Hongyou Cao,Yun-Lai Zhou,Zhijun Chen,Magd Abdel Wahab 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.62 No.1
This paper presents an explicit analytical iteration method for form-finding analysis of suspension bridges. By extending the conventional analytical form-finding method predicated on the elastic catenary theory, two nonlinear governing equations are derived for calculating the accurate unstrained lengths of the entire cable systems both the main cable and the hangers. And for the gradient-based iteration method, the derivation of explicit calculation for the Jacobian matrix while solving the nonlinear governing equation enhances the computational efficiency. The results from sensitivity analysis show well performance of the explicit Jacobian matrix compared with the traditional finite difference method. According to two numerical examples of long span suspension bridges studied, the proposed method is also compared with those reported approaches or the fundamental criterions in suspension bridge structural analysis, which eventually confirms the accuracy and efficiency of the proposed approach.
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Jieguang Song,Xueqing Yang,Ping Chen,Hao Xu,Deping Luo,Rongjin Liu,Zhijun Lai 한양대학교 세라믹연구소 2022 Journal of Ceramic Processing Research Vol.23 No.4
The prepared permeable bricks using electric porcelain waste as the main raw material are investigated, which improves theutilization rate of electric porcelain waste, and realizes the organic unity of recycling resource and ecological environmentprotection. The effects of different raw material ratios on the permeability coefficient, apparent porosity, compressive strength,volume shrinkage rate and microstructure properties of electric porcelain waste permeable bricks are investigated. The electricporcelain waste with a ratio of over 85 wt.% have greatly improved the utilization rate of electric porcelain waste. The resultsare shown that the water-to-material ratio or foaming agent content are increased, the porosity and water permeability of theelectric porcelain waste permeable brick are increased, but the compressive strength of the electric porcelain waste permeablebrick is decreased. The 90 wt.% electric porcelain waste, the 3 wt.% kaolin, the 5 wt.% sintering aid, and the 2 wt.% foamingagents are optimum raw materials ratios, the water-to-material ratio for 0.9 and the drying temperature at 40 oC, the sinteringtemperature at 1200 oC and holding time for 1 h are obtained the excellent performance electric porcelain waste permeablebricks. The permeability coefficient is 3.9×10−2 cm/s, the volume shrinkage rate is 37.88%, the compressive strength is 1.146MPa, and the porosity is 79.0%.
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