Comparison of aerosol properties derived from sampling and near-horizontal lidar measurements using Mie scattering theory

Exploration for adequate non-diffractive beam generation in dense scattering media

The propagation methods of a non-diffractive beam (NDB) for optical sensing in scattering media have been extensively studied. However, those methods can realize the high resolution and long depth of focus in the viewpoint of microscopic imaging. In this study, we focus on macroscopic sensing in living tissues with a depth of a few tens centimeters. An experimental approach for generating adequate NDB in dense scattering media based on the linear relationship between propagation distance and transport mean free path is reported. For annular beams with different diameters, the same changes of the center intensity ratio of NDB are obtained from the experiment results. They are discussed with theoretical analysis. As a result, the maximum center intensity ratio of the adequate generated NDB can be estimated at arbitrary propagation distance in the dense scattering media.

The experimental and simulation investigation of the dynamic characteristic of submicron-scale aerosol in high-voltage electric field by a visualization method

The high-voltage electric field can effectively capture charged aerosols and has the effect of killing microbial aerosols simultaneously. In this article, an innovative visualization method for investigating the dynamic characteristic of submicron-scale aerosol particles in the high-voltage electric field is developed. Based on reasonable working principles and reliable experimental schemes, the movement of submicron-scale aerosol particles is observed and visualization images in different working conditions are photographed. Besides, with the aid of numerical method and solution of related equations, simulation researches on flow field distribution, electrostatic field characteristics, particle charging and motion behavior characteristics are also carried out. Visualization results prove the linear motion law of aerosol particles in an electric field of 0-3 kV/cm unit. As for 1 µm diameter particle, its migration velocity in 1 kV/cm electric field is measured as 0.016 m/s and 0.019 m/s after positive and negative charging of 1.5 kV voltage, respectively. A reliable calculation formula (η=(V_jq_pL_j)/(3πμD²u_xd_p)) for predicting collection efficiency is derived and established based on actual particle migration velocity. The researches on the migration and capture law of submicron-scale aerosol in the high voltage electric field gives a key reference for the development and design of efficient removal of microbial aerosol and air purification equipment.