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196 results on '"Cao, Guang-Zhong"'

69. Dynamic Data Injection Attack Detection of Cyber-Physical Power Systems with Uncertainties

Author

Wang, Huaizhi, Ruan, Jiaqi, Zhou, Bin, Li, Canbing, Wu, Qiuwei, Raza, Muhammad Qamar, Cao, Guang-Zhong, Wang, Huaizhi, Ruan, Jiaqi, Zhou, Bin, Li, Canbing, Wu, Qiuwei, Raza, Muhammad Qamar, and Cao, Guang-Zhong

Abstract

Understanding potential behaviors of attackers is of paramount importance for improving the cyber-security of power systems. However, the attack behaviors in existing studies are often modeled statically on a single snapshot, which neglects the reality of a dynamically time-evolving power system. Accordingly, a dynamic cyber-attack model with local network information is proposed to characterize the typical data injection attack with the integration of potential dynamic behaviors of an attacker. The proposed model collaboratively alters the meter measurement in a stealthy way to illegally contaminate the system state, thus posing severe threats to cyber-physical power systems. We then develop a novel anomaly detection countermeasure from the perspective of state estimation to effectively recognize the dynamic injection attack. In this countermeasure, an interval state forecasting method is proposed to approximate the possible largest variation bounds of each state variable based on a worst-case analysis considering the forecasting uncertainties of renewable energy sources, electric loads, and network parameter perturbations. In addition, the kernel quantile regression is introduced and implemented to formulate the uncertainties in renewable energy and electric load forecast as a series of confidence intervals. When any state variable falls outside its pre-forecasted intervals, the proposed countermeasure detects the anomaly and sets an alarm condition indicating the possibility of data contamination. Finally, the results from our extensive studies on several IEEE standard test systems have been presented to demonstrate the feasibility of the dynamic attack and the effectiveness of the detection countermeasure.

Published
2019

70. Modeling of the rapid lifetime assessment system with multiple stresses for LED devices using adaptive genetic algorithm

Author

Cao Minggao, Liu Yan, Zhou Lin, Cao Guang-zhong, Jing Gang, Xiao Wenpeng, HU YiMin, Liu Huaiyuan, Wu Hailin, and Huang Sudan

Subjects
Imagination, Engineering, Chemical substance, Computer Networks and Communications, business.industry, media_common.quotation_subject, Accelerated life testing, law.invention, Reliability engineering, Vibration, Search engine, Control and Systems Engineering, law, Operating time, business, Simulation, media_common, Light-emitting diode, Diode
Abstract

The light-emitting diode (LED) is a promising candidate for the lighting, instrument reading, etc., due to its features of high efficiency, long lifetime, small size, fast response, anti vibration, low-voltage operation, and environmental protection, which is an emerging cold light source. This paper proposes a novel model of the rapid lifetime assessment system with multiple stresses for LED devices, to solve the problems of the complex environmental stresses imposed on the lifetime of LED devices, the model of accelerated life testing without consideration of multiple stresses, and the low-precision lifetime assessment model. This model is suitable for all types of LED devices. Taking the operating time to 30% of lumen depreciation as the lifetime of LED devices, the environmental temperature and humidity, and input current are the inputs of this model, and the lifetime of the LED device is the output of this model. The parameters of this model are determinated by using the designed adaptive genetic algorithm. A several number of sample data is first obtained through accelerated life testing under the condition of high temperature, humidity, and current. The parameters of this model are then identified with the obtained sample data. This model is further built by applying the identified parameters. Additionally, the lifetime evaluation is carried out via this model under the condition of normal temperature, humidity, and current. Research results demonstrate that the proposed model can evaluate the lifetime of LED devices fast with a comparatively high accuracy; the evaluated lifetime of the proposed model is close to the realizable life expectancy of the LED industry under the condition of normal temperature, humidity, and current; the practicability of the proposed model for lifetime reliability evaluation of LED devices is verified; the proposed model can be further developed with much more stresses.

Published
2016
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98. Surface instability of elastic half spaces with hydrostatic loading on their surfaces

Author

Cao Guang-zhong and Xu Zhi-hong

Subjects
Surface (mathematics), Materials science, Applied Mathematics, Mechanical Engineering, Hydrostatic pressure, Harmonic (mathematics), Mechanics, Instability, law.invention, Buckling, Mechanics of Materials, law, Compressibility, Hydrostatic equilibrium, Plane stress
Abstract

In this paper, the plane-strain buckling of compressible and incompressible elastic half-spaces, whose surfaces are loaded by constant hydrostatic pressures, is studied by using a small-deformation-superposed-on-large-deformation analysis, and the buckling condition for each case is obtained. For Blatz-Ko and harmonic compressible materials as well as Mooney incompressible material, the influence of the surface hydrostatic pressure on the critical buckling condition is discussed in detail.

Published
1992
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