Fig. 1. Structure diagram of pre-treatment mold

Fig. 2. Schematic diagram of terahertz time-domain spectroscopy system

Fig. 3. Schematic diagram of terahertz spectroscopic measurement of liquid water

Fig. 4. Terahertz spectral measurement process for HMX with various moisture contents

Fig. 5. Terahertz refractive indices and absorption spectra of HMX particles and liquid water. (a) HMX particles; (b) liquid water

Fig. 6. Terahertz refractive index spectra and absorption spectra of HMX with various moisture contents. (a) Refractive index spectra; (b) absorption spectra

Fig. 7. Modeling results of refractive index and absorption coefficient based on support vector machine (SVR). (a) Internal validation; (b) external validation

Fig. 8. Modeling results of fusion of mass and refractive index based on SVR. (a) Direct mass fusion; (b) mass proportional fusion

Fig. 9. External validation results of mass proportional fusion based on SVR

Fig. 10. Modeling and prediction results of two optimization algorithms. (a) GA modeling results; (b) PSO modeling results; (c) GA prediction result; (d) PSO prediction result