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In petrochemical plant, the in-operation repairing is usually a repairing strategy with pressured inoperation repairing for avoiding huge economic losses caused by unplanned shutdown when some slight local leakage happens in pipes. This paper studies the effects of repairing strategies on the failure probability of the pipe systems in process industries based on the time-average fault tree approach, especially the in-operation repairing strategies including pressured in-operation repairing activities. The fault tree model can predict the effect of different repairing plans on the pipe failure probability, which is significant to the optimization of the repairing plans. At first pipes are distinguished into four states in this model, i.e., successive state, flaw state, leakage state and failure state. Then the fault tree approach, which is usually applied in the studies of dynamic equipment, is adopted to model the pipe failure. Moreover, the effect of pressured in-operation repairing is also considered in the model. In addition, this paper proposes a series of time-average parameters of the fault tree model, all of which are used to calculate node parameters of the fault tree model. At last, a practical case is calculated based on the fault tree model in a repairing activity of pipe thinning. 相似文献
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混合式教学是一种将由学生控制的网络学习和由教师在教室中直接授课的面对面学习融合在一起的新兴教学模式,而以直播为特征的混合式教学,则是将教室面对面学习搬进线上直播课堂。基于传统教学存在的问题,文章构建了“线上学习—课堂教学—课后拓展提升”三位一体的面对面式和直播式混合教学,并提出了囊括线上、课堂及课后三个环节且考核评价要素丰富的多维考核评价方法。以工程制图及CAD课程为例,传统教学和混合式教学的教学实践表明,具有良好学习基础的学生在面对面式或直播式混合教学及合理的课程安排下,学习效果优于传统教学,学生的学习过程参与度得到了提高,学习积极性也被调动起来,知识水平和综合能力得到了极大提升。 相似文献
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