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.
Biomaterials are composed of biological particles, which are aggregated particle systems with complex spatial and fractal structures formed by smaller unit particles due to electrostatic forces, collisions, and adhesion. In this paper, the optical properties of aggregated particles were calculated based on optimized Ballistic Cluster-Cluster Aggregation (BCCA) model. The effect of different porosity and monomer numbers of aggregates on the absorption and scattering properties is investigated. The properties were found to be enhanced with decreasing porosity and increasing number of particle monomers. And it is also found that the error due to the randomness of the structure of the aggregated particles under the same conditions enables the above conclusion to be completely satisfied when the particle number difference is greater than or equal to 6.
The detection of biological spore activity is the basis for effective prevention and control of plant and animal diseases. However, the reduction of its activity level during storage is one of the major problems affecting the application. A rapid and accurate method to detect the activity of biological spores is of great value for exploration and research. In this paper, UV-Vis spectroscopy combined with a one-dimensional convolutional neural network (1D-CNN) is used for the discrimination of dead and viable biological spore. The spectrum of three biological spores were collected and preprocessed by the standard normal variate transformation (SNV). Unsupervised clustering of the sample set was performed using principal component analysis (PCA). The activity discrimination model of biological spores is constructed based on 1D-CNN. The experimental results show that the model has a discriminative accuracy of 100%, which has the potential to replace the traditional methods of determining the dead and viable biological spore.
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.
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