With the widespread application of photoelectric detection systems, light attenuation materials that affect imaging and detection performance have received increasing attention. As a novel type of light attenuation materials, biological extinction material has the advantages of low preparation cost, environmental protection, non-toxic, easy degradation, and broad extinction band. This paper mainly introduces the research status of biological extinction materials from two aspects: the extinction characteristics of biological materials and the deposition and diffusion of biological aerosols. In order to promote the research and application transformation of biological extinction materials, comprehensively understand the research status of wide band biological extinction materials, and further optimize the extinction performance of biological aerosols in ultraviolet (UV), visible, infrared (IR) and other bands, the research progress in the material preparation and optical constant measurement of biological extinction materials, modeling of biological particle aggregation structure, extinction performance calculation, deposition and diffusion calculation simulation and related experiments are summarized. In view of the challenges in the study of biological extinction materials, perspectives on future material modification optimization, extinction band expanding, and improving the aerodynamic characteristics are provided.
The prediction of infrared extinction performance is one of the indispensable factors for the research of smoke screen. So far, it is still short of an accurate numerical simulation for the infrared extinction performance after releasing smoke screen. We present a method for calculating the infrared extinction performance of smoke screen. The standard k − ε turbulence model and the concentration equation of smoke screen are combined to carry out numerical simulation research on the sedimentation and diffusion process of smoke screen in the field. The shape and mass concentration distribution of smoke screen are studied under different wind speeds and ground roughness. Lambert–Beer’s law is combined to calculate the infrared extinction area of the smoke screen under different conditions, and the influence law on the smoke screen extinction performance is analyzed under different conditions. The validity of the numerical simulation results is verified by the field test. It is a useful method for guiding the design of field experiments. This work is widely used in the evaluation of extinction performance and provided more information for use by decision makers.
With the development of extinction materials, various materials suitable for smoke are widely used. Smoke is essentially composed of solid aerosol. The extinction properties of aerosol are affected by diffusion characteristics. Aerodynamics is used to describe the motion of aerosol particles. Normal 𝑘 - 𝜀 model and DPM model are used to simulate aerosol diffusion process in outdoor environment. The diffusion law of aerosol under different wind speed is analyzed. Distribution characteristics of aerosol mass concentration is studied. Combined with Lambert-Beer law, the effective infrared extinction area of aerosol is calculated. The result shows that the wind speed play an important role in aerosol diffusion in the initial state. When the wind speed is near 1m/s, aerosol can diffuse steadily, and the extinction area will show a trend of rise. In addition, the area of effective concentration will not decrease too fast, but will show a trend of slow rise and begin to decline after 30s.
A multilayer structure of microbial cells can result in multiple attenuations of electromagnetic waves, making the biological particles have a strong extinction ability. However, the influence of various morphologies on infrared band optical extinction performance of biomaterials is unclear. The combination of shape, dimension, and structure parameters is proposed to evaluate and enhance the optical extinction properties of artificial bioparticles. Combined with the preliminary work of our research group, four artificial biological particles were selected to simulate and calculate their extinction performance with different parameters theoretically based on the discrete-dipole approximation method. The results show the extinction properties of bioparticles with different shapes and dimensions in the 3.0 to 5.0 μm and 8.0 to 14.0 μm wavebands. It was found that the chain-shaped particles with more constituent spheres and a bending angle of 60 deg as well as the ellipsoid-shaped particles with an axis ratio of 1:2 exhibit better extinction properties in the above two bands. Among them, the regulation of extinction efficiency can reach ∼13.92 % and 18.16%.
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