Coal petrography extraction approach based on multiscale mixed-attention-based residual U-net

Coal petrography extraction is crucial for the accurate analysis of coal reaction characteristics in coal gasification, coal coking, and metal smelting. Nevertheless, automatic extraction remains a challenging task because of the grayscale overlap between exinite and background regions in coal photomicrographs. Inspired by the excellent performance of neural networks in the image segmentation field, this study proposes a reliable coal petrography extraction method that achieves precise segmentation of coal petrography from the background regions. This method uses a novel semantic segmentation model based on Unet, referred to as M2AR-Unet. To improve the efficiency of network learning, the proposed M2AR-Unet framework takes Unet as a baseline and further optimizes the network structure in four ways, namely, an improved residual block composed of four units, a mixed attention module containing multiple attention mechanisms, an edge feature enhancement strategy, and a multiscale feature extraction module composed of a feature pyramid and atrous spatial pyramid pooling module. Compared to current state-of-the-art segmentation network models, the proposed M2AR-Unet offers improved coal petrography extraction integrity and edge extraction.