In some sectors certain operating conditions (such as the petroleum sector, pipeline), not allowed to use the path contraction of the valve.

在某些部门的某些工作条件下(如石油部门的输油管线)，不允许采用通径收缩的阀门。

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This aspect is to reduce the pipeline pressure loss, the other is to avoid the path contraction obstacle to the mechanical cleaning pipelines.

这一方面是为了减小管线的阻力损失，另一方面是为了避免通径收缩后给机械清扫管线造成障碍。

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In this paper we discuss the distribution of vertices of degree 5 on the longest path and cycle and thus give a characterization of contraction critical 5-connected graph in a certain aspect.

讨论收缩临界5 -连通图最长路和最长圈上5度点的分布情况，刻画收缩临界5 -连通图的结构。

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Recognizing the need to pursue growth-oriented policies that support demand and recovery, the United States will calibrate the pace of its fiscal consolidation by ensuring that its public finances are placed on a sustainable long-run path so that a sharp fiscal contraction in 2013 is avoided.

WHITEHOUSE: The Los Cabos Growth and Jobs Action Plan