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To quantitatively test the migration distance of water in coal, this paper develops the resistivity measurement technology and discusses its feasibility. The results show that the water transport distance measured by layered electrode arrangement method and color indicator method increase with the increase of time. With the increase of migration time, the change of coal sample resistivity can be divided into three change processes, which are sudden change process, rapid change process and gradual change process. The migration distance measured by resistivity method and color indicator method are basically the same, and the relative error is between -4.2% and 5.8%. The methods of arranging comb electrodes, arranging layered electrodes and arranging test electrodes with vertical holes at one end can be used to test the migration distance of unloaded confining pressure cylindrical samples, loaded axial pressure/surrounding constrained samples and loaded axial pressure/confining pressure samples, respectively.

To investigate the extraction process and physicochemical properties of the pectin from coffee peel, the Yunnan arabica coffee peel was used as the raw material. Based on single factor experiments, response surface design was employed to optimize the ultrasound-assisted enzymatic extraction of pectin. Fourier transform infrared spectroscopy (FT-IR) was used to identify the functional groups of the pectin. Crude pectin was purified through decolorization and deproteinization by the AB-8 macroporous resin and Sevage method. The physicochemical properties of the pectins before and after purification were compared. The results showed that the optimal extraction conditions were as follows: cellulase addition, 1.49%; enzymolysis time, 45.78 min; ultrasonic time, 19.30 min. The resulting extraction yield was 16.42%. FT-IR results Abstract: To investigate the extraction process and physicochemical properties of the pectin from coffee peel, the Yunnan arabica coffee peel was used as the raw material. Based on single factor experiments, response surface design was employed to optimize the ultrasound-assisted enzymatic extraction of pectin. Fourier transform infrared spectroscopy (FT-IR) was used to identify the functional groups of the pectin. Crude pectin was purified through decolorization and deproteinization by the AB-8 macroporous resin and Sevage method. The physicochemical properties of the pectins before and after purification were compared. The results showed that the optimal extraction conditions were as follows: cellulase addition, 1.49%; enzymolysis time, 45.78 min; ultrasonic time, 19.30 min. The resulting extraction yield was 16.42%. FT-IR results [ABSTRACT FROM AUTHOR]