Discrete Particle Simulation of Gas-Solid Flow in Air-Blowing Seed Metering Device

In this paper,the gas and seed flow characters in the air-blowing seed metering device are investigated by using the coupled computational fluid dynamics and discrete element method(CFD-DEM)in three dimensions(3D).The method of establishing boundary model based on the computer-aided design(CAD)drawing,has been used to build the boundary model of seed metering device.The 3D laser scanning technique and multi-element method are adopted to establish the particle model.Through a combined numerical and experimental effort,using 3D CFD-DEM software,which is based on the in-house codes,the mechanisms governing the gas and solid dynamic behaviors in the seed metering device have been studied.The gas velocity field and the effect of different rotational speeds and air pressures on the seeding performance and particle velocity have been studied,similar agreements between numerical and experimental results are gained.This reveals that the 3D CFD-DEM model established is able to predict the performance of the air-blowing seed metering device.It can be used to design and optimize the air-blowing seed metering device and other similar agriculture devices.

Post-tuberculosis lung disease and chronic obstructive pulmonary disease

The burden of chronic airway diseases,including chronic obstructive pulmonary disease(COPD),continues to increase,especially in low-and middle-income countries.Post-tuberculosis lung disease(PTLD)is characterized by chronic lung changes after the"cure"of pulmonary tuberculosis(TB),which may be associated with the pathogenesis of COPD.However,data on its prevalence,clinical manifestations,computed tomography features,patterns of lung function impairment,and influencing factors are limited.The pathogenic mechanisms underlying PTLD remain to be elucidated.This review summarizes the recent advances in PTLD and TB-associated COPD.Research is urgently needed both for the prevention and management of PTLD.