After careful and considered review of the content of this paper by a duly constituted expert committee, this paper has been found to be in violation of IEEE's Publication Principles.
We hereby retract the content of this paper. Reasonable effort should be made to remove all past references to this paper.
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New Event Detection is very important in emergency management. This paper introduced key technologies in NED and analyzed the advantages and disadvantages of these technologies. And future works have been proposed.