选拔算法是两级逻辑综合中求解最小化覆盖的经典方法之一，但在输出变量集合和质立方体集合规模较大的情况下，采用选拔法求最小化覆盖存在空间复杂度高、求解时间长等问题。

But as the output variables and the prime implicant grow up, both the long processing time and the resource requirement become the major problems to be resolved with the extraction method.

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全站设备的控制逻辑关系分为上下两级，下级为直接过程控制级，上级为集中监督控制级。

The control logic relation of all the station equipments can be divided into two stages. The bottom is a direct process control stage and the top is a compute supervisory control stage.

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