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Research on reliability analytical method of complex system based on CBN model
Yuantao Sun,Kaige Chen,Chao Liu,Qing Zhang,Xian-rong Qin 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.1
Considering that there are often many variables correlated to each other in complex system, copula functions are introduced into reliability analysis. While with the increase of variables, the dimension of copula function will be high. For the above problems, Bayesian network (BN) is introduced into reliability analysis and a copula Bayesian network (CBN) model is proposed. Taking driving system of new rail mounted container gantry (NRMG) as an example, Gaussian copula and t-copula are used and compared in the process of generating correlation data. Additionally, in order to construct local copula function between parent and descendent nodes, Gumbel and Clayton copulas are compared based on Akaike information criterion. Finally, the reliability inference based on CBN model is performed. Compared with BN model, the rationality of CBN model is verified, and the results show that the reliability calculated by CBN model is smaller, which will put forward higher requirements for the driving system.
Yuantao Sun,Zengzeng Zhang,Qing Zhang,Xian-rong Qin,Lifu Luo 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.10
The fatigue failure of crack structure is influenced by fracture failure and static strength failure in the process of its growth. And the correlation characteristics between them change with the crack growth, which brings difficulties to safety assessment. To solve this problem, we propose a reliability model of failure crack propagation (FCP) based on time-varying copula. Meanwhile, a dynamic parameter estimation is put forward to build the time-varying copula. First, a flexible mixed copula model was constructed, by means of linear weighted model, to describe the nonlinear dependence among failure modes. Then the time-varying correlation parameters of copula were obtained by maximum likelihood estimation and least square polynomial fitting. Therefore, the dynamic parameter estimation of copula was realized, and then we used the built time-varying copula model to solve the reliability of joint failure. Finally, a numerical example was provided to illustrate the feasibility and application of the built time-varying copula model.
Zhang Jia,Sun Yuantao 서울대학교 교육연구소 2018 Asia Pacific Education Review Vol.19 No.4
This mixed-method study developed a conceptual model for understanding the characteristics of professional learning communities (PLCs) in Chinese context. Exploratory qualitative interviews were first conducted to examine the characteristics of PLCs in several schools in Shanghai, China, through which an initial conceptual model was resulted. Based on the qualitative findings, a questionnaire was developed and then administered in 31 schools in Shanghai to adjust the conceptual model. Results show that rooted in the Chinese institutional (i.e., the accountability system and the Teaching Research System) and cultural (i.e., the collective and harmonious culture) context, PLCs in China could be operationalized in terms of eight characteristics at two levels, including collective inquiry and sharing, shared purpose and responsibility, informal collaborative learning, supportive leadership, organizational structure, collaborative relationship, institutional barriers, and cultural barriers. Practical implications and suggestions for future research are put forward.