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Aviation unsafe events often lead to major casualties and property losses. Aviation safety risk intelligent early warning is an important means to ensure the safe and reliable operation of aircraft. Therefore, an intelligent early warning model is urgently needed to quickly predict the risk level and identify potential risks to take targeted measures to realize the active management of safety. To realize the above process, the text mining method is used to extract key risk information from unsafe event reports and input it into the intelligent early warning model to predict its risk level, further constructing the priority processing index to achieve a rapid decision, and finally realize the intelligent safety management process of features extraction to early warning levels identification and then to priority processing. First, domain dictionary and Chinese stop word list are constructed to process the massive text data in the unsafe event's report. Further, TF-IDF and TextRank are fused to extract key risk information and convert it into feature vectors. Second, the IHT algorithm is used to alleviate the sample class imbalance problem. After that, input the balanced risk information into an improved stacking multi-model fusion algorithm to accurately identify the early warning level and improve the level of active management and control via priority processing index ranking. The effectiveness and feasibility of the proposed method are demonstrated by testing the unsafe event text data of some aircraft maintenance companies and airlines, which promotes the practical application value of text mining technology in the aviation field. [ABSTRACT FROM AUTHOR]

A symmetry relation of the integral operators in a layered medium proved by the reciprocal theory can be applied to improve the accuracy of the magnetic-field integral equation (MFIE). Based on the symmetric layered medium Green’s function, the normal vector can be transferred into the inner integral to keep the field integral as the inner integral of the elements in the impedance matrix. When discretized by the divergence-conforming function, this field-extracted scheme shows better performance than the classic expression in accuracy. Meanwhile, this form of expression can be applied in the combined-field integral equation (CFIE). Several numerical results are provided to validate the formulation of the symmetry relations from the layered medium Green’s function to the impedance matrices and to reveal its advantages in enhancing the accuracy of the field-extracted form of MFIE. [ABSTRACT FROM AUTHOR]