[6] [6] ZHU Hongqing, WANG Haoran, LIU Jiuli, et al. Application of terahertz dielectric constant spectroscopy for discrimination of oxidized coal and unoxidized coal by machine learning algorithms[J]. Fuel, 2021(293):120470. doi:10.1016/j.fuel.2021.120470.

[7] [7] YANG Menghan,ZOU Bin,JIANG Chen,et al. Elucidation of elemental and structural changes in high-volatile bituminous coal during thermal treatment by X-ray diffraction and terahertz time-domain spectroscopy[J]. Fuel, 2021(293): 120410. doi:10.1016/j.fuel.2021.120410.

[10] [10] DENG Jingjing,ORNIK J,ZHAO Kai,et al. Recognition of coal from other minerals in powder form using terahertz spectroscopy[J].Optics Express, 2020,28(21):30943-30951. doi:10.1364/OE.405438.

[11] [11] WANG Xin,HU Kexiang,ZHANG Lei,et al. Characterization and classification of coals and rocks using Terahertz Time-Domain Spectroscopy[J]. Journal of Infrared Millimeter and Terahertz Waves, 2017,38(2):248-260. doi:10.1007/s10762-016-0317-2.

[12] [12] DORNEY T D,BARANIUK R G,MITTLEMAN D M. Material parameter estimation with Terahertz Time-Domain Spectroscopy[J].Journal of the Optical Society of America A: Optics, Image Science, and Vision, 2001, 18(7): 1562-1571. doi: 10.1364/JOSAA.18.001562.

[13] [13] DUVILLARET L, GARET F, COUTAZ J L. A reliable method for extraction of material parameters in Terahertz Time-Domain Spectroscopy[J]. IEEE Journal of Selected Topics in Quantum Electronics, 1996,2(3):739-746. doi:10.1109/2944.571775.

[14] [14] DUVILLARET L,GARET F,COUTAZ J L. Highly precise determination of optical constants and sample thickness in Terahertz Time-Domain Spectroscopy[J]. Applied Optics, 1999,38(2):409-415. doi:10.1364/AO.38.000409.