This may mean the mediator is offline or a network problem prevents connection.

这可能意味着中介已脱机或存在网络问题而不能连接。

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BP neural network model is designed to analyze and solve the problem, the relationship of operational life of concrete construction and environmental corrosion mediator.

设计了一个BP神经网络网络模型来分析解决这一问题，研究处于硫酸盐侵蚀下混凝土结构使用寿命与环境侵蚀介质间的关系。

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