A novel approach based on the passive acoustic emission (AE) monitoring technique has been established for analyzing particle–wall collision and friction separately in the present work. Using power spectrum density analysis, the main frequency of AE signal caused from particle–wall collision is found to be higher than that generated by particle–wall friction. Besides, a method for quantitatively extracting the information on particle–wall collision and friction has been set up by wavelet transform analysis. On the basis of these analyses, a theoretical approach has been established for relating the AE signals and solids loading ratio in a vertical pneumatic conveying pipe. The model predictions are verified using experimental data and are in good agreement. Particle mass flow rates obtained using this model give errors less than 6.62%. Conclusions can be drawn that the AE technique has great potential in the measurement of hydrodynamics in pneumatic conveying as well as similar particulate processes.

in Wiley Online Library (wileyonlinelibrary.com) Acoustic emission technique in conjunction with multiscale processing method has been utilized to investigate the flow behavior of the dense-phase pneumatic conveying system at high pressure. A clearly defined classification of microscale, mesoscale, and macroscale signals has been put forward with the aid of wavelet transform and V statistics analysis. The detailed signals d 1 -d 4 , d 5 -d 7 , d 8 -d 10 were recomposed into the microscale, mesoscale, and macroscale signals, respectively, which represent microscale particle-wall interactions, mesoscale interaction between gas phase and solid phase (such as bubbles, plugs, dunes), and macroscale flow-induced pipe vibration. Further analysis shows that as the mass flow rate of pulverized coal increases, the energy fraction (energy of detailed signal divided by the energy of original signal) of microscale signals decreases while that of mesoscale signals increases, which indicates that particles are more likely to move as particle aggregates than individual particles when mass flow rate increases.

Compared with ordinary uniform lenses, the length and refractive index distribution of gradient refractive index (GRIN) lenses can effectively correct aberration and chromatic aberration. This advantage makes the miniaturization, integration, and lens lightweight possible. Although the visible GRIN lenses based on silicate glass are widely used, the infrared GRIN lenses based on chalcogenide glass are still elusive. This paper introduces a new method for preparing this kind of lens by hot pressing sintering diffusion of chalcogenide glasses. A series of chalcogenide glasses Ge10As22Se68-xSx (x = 4, 7, 10, 14, 24, 28, 34 mol%) with refractive index range from 2.37 to 2.57 (n@8 µm) and similar glass transition temperature (ΔTg < 10℃) were prepared by melt quenching. The relationship between Raman peaks and the refractive index of glasses was studied. Furthermore, the refractive index profile formed by elemental diffusion was characterized by Raman signals. The results show that the diffusion length reaches more than 290 µm, and larger diffusion distances can be achieved by stacking multiple layers. The obtained GRIN glass maintains good transmittance in the whole atmospheric window of 2 ∼ 12 µm.