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Vibration signals of rolling element bearings faults are usually immersed in background noise, which makes it difficult to detect the faults. Wavelet-based methods being used commonly can reduce some types of noise, but there is still plenty of room for improvement due to the insufficient sparseness of vibration signals in wavelet domain. In this work, in order to eliminate noise and enhance the weak fault detection, a new kind of peak-based approach combined with multiscale decomposition and envelope demodulation is developed. First, to preserve effective middle-low frequency signals while making high frequency noise more significant, a peak-based piecewise recombination is utilized to convert middle frequency components into low frequency ones. The newly generated signal becomes so smoother that it will have a sparser representation in wavelet domain. Then a noise threshold is applied after wavelet multiscale decomposition, followed by inverse wavelet transform and backward peak-based piecewise transform. Finally, the amplitude of fault characteristic frequency is enhanced by means of envelope demodulation. The effectiveness of the proposed method is validated by rolling bearings faults experiments. Compared with traditional wavelet-based analysis, experimental results show that fault features can be enhanced significantly and detected easily by the proposed method.

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It is widely recognized that brownfield regeneration to green space is a sustainable form of urban development. However, it is essential to choose those brownfields that have the greatest potential to be integrated into urban green infrastructure (GI). This paper addresses how to quantitatively assess the ecological potential of coal mining brownfields at the city level, and looks at how these brownfields can be best adapted to enhance the GI system. Taking Xuzhou as an example, an ecological potential assessment method for brownfield regeneration to green space is established considering both its ecological importance and the capacity of maintaining GI connectivity. The results show that more than half of the coal mining brownfields have relatively higher ecological importance values, and only four patches play an important role in maintaining GI connectivity. The final ecological potential values of brownfield regeneration to green space are obtained by overlaying the values of ecological importance and the capacity values of maintaining GI connectivity. Then, all the brownfields are divided into five groups according to their ecological potential values, which are significantly different in each group. Around 51.35% of the brownfields have a high or very high potential for restoration to GI, which are distributed in the southeastern part of the western mining area and the central part of the eastern mining area. The presented method can assist reclamation scientists and urban planners in decision making based on quantitative analysis.