seconds. The duration of Group 2 is about 20 seconds. Events in beam 14 last 5 seconds, followed by 15 seconds of events in beam 15.

The two groups of candidates, even the other candidates which are verified be part of RFI, are very consistent with the two rules of ETI assumption. This result indicates that our data processing pipeline can pick out the signals that fit the assumption of ETI. Actually, this paper has presented the effectiveness of our method for RFI removal and candidate selection, which can certainly guarantee the successful implementation of observation for SETI with FAST.

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Note that the background does not represent the raw data but data after Nebula, because the raw data is too big to plot at the same time. \[fig:14\]

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The RFI environment of FAST {#sec:6.4}
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As the largest single-aperture telescope in the world, the electromagnetic environment of FAST is a very important consideration. Due to its extreme sensitivity, it is a big challenge for FAST to mitigate RFI. The solutions for RFI mitigation of FAST include the Electromagnetic Compatibility measures of the telescope and the maintenance of radio-quiet zones around the site [@8738491]. Besides, 