In large‐scale factories or power plants metal tube clogging sometimes leads to serious accidents. However, metal tube testing for the detection of foreign objects requires a long testing time and considerable effort. Therefore, we proposed an original inspection method of a single metallic tube using electromagnetic wave reflection in the tube. However, for branched tubes, it is difficult to estimate the position of the clog by electromagnetic wave reflection. To evaluate the position of clog in the branched tubes, we proposed a new detection method using the group delay time in electromagnetic waves. The group delay time in electromagnetic waves is slightly affected by the bifurcation area. To verify the new method, the group delay time characteristics were measured in the branched tubes. The position of clog could be easily detected by the proposed method.

中文翻译：

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利用电磁波群时延特性的金属管堵塞检测方法

在大型工厂或发电厂中，金属管堵塞有时会导致严重事故。然而，用于检测异物的金属管测试需要较长的测试时间和相当大的努力。因此，我们提出了一种利用管中的电磁波反射来对单个金属管进行检查的原始方法。但是，对于分支管，难以通过电磁波反射来估计堵塞的位置。为了评估堵塞物在分支管中的位置，我们提出了一种利用电磁波中的群延迟时间的新检测方法。电磁波的群延迟时间受分叉面积的影响很小。为了验证新方法，在分支管中测量了群延迟时间特性。