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The application of acoustic emission (AE) in concrete faces great challenges due to complex material parameters of concrete materials and the rapid attenuation characteristics of acoustic emission wave. In order to clarify the influence of concrete strength level on acoustic emission wave propagation characteristics and create conditions for evaluating concrete damage by acoustic emission technology, the acoustic emission technology was used to study the propagation behavior of acoustic emission waves in concrete with different strength levels through parameter analysis and fast Fourier transform. The results show that the attenuation coefficients of AE energy in C30, C40 and C50 concrete are 0.013 94, 0.010 67 and 0.005 68, respectively, and the higher the strength is, the smaller the attenuation is. The benchmark wave speeds are 3 966 m/s, 4 193 m/s and 4 411 m/s, respectively, and the higher the intensity, the faster the wave speed. The frequency distribution tends to shift from high frequency to low frequency with the increase of propagation distance, but the signal attenuation and frequency deviation of concrete with high strength are slower. The signal wave types received within 500 mm and outside 500 mm are different, which is not conducive to the acoustic emission monitoring. When monitoring the acoustic emission of concrete, the sensor spacing should be within 500 mm to ensure the monitoring accuracy. [ABSTRACT FROM AUTHOR]

A kind of community detection method based on the combination of modularity and community structure attributes was proposed.Firstly,updating the whole network after communities merging every time could result in the high time complexity,therefore,introducing propagation distance parameter and “merger going after label propagation” was utilized to reduce time complexity.Secondly,CDMM-LPA algorithm was proposed by combing label propagation with community structure.Finally,empirical analysis on data networks verified the validity of the approaches.The experimental results show that the CDMM-LPA algorithm has a high modularity value and a more stable community structure while reducing the time complexity.