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Several composites of modified graphitic carbon nitride (MCN) and Fe3O4 particles were obtained through pyrolysing MCN/iron acetylacetone (Fe(acac)3) at different temperatures to form electromagnetic wave (EWM) absorbers. By decreasing the nitrogen content of g-C3N4 and introducing Fe3O4 particles, the EMW absorption ability of the g-C3N4 derivatives (MCN/Fe3O4) improved remarkably. For MCN/Fe3O4-500 with 6 wt% filling, the minimum reflection loss (RLmin) reached −73.93 dB at a thickness of 3.4 mm and the effective absorption bandwidth (EAB) was as high as 5.44 GHz at a thickness of 1.9 mm. Additionally, the mass ratio of MCN and Fe3O4 and the EMW absorption mechanism of MCN/Fe3O4-500 were also discussed. This study provides a new approach for the preparation of high-efficiency EMW absorbers by modification of g-C3N4. [ABSTRACT FROM AUTHOR]

Varicella is a highly infectious contagious disease, and Chongqing is one of the high incidence areas in China. To understand the epidemic regularity and predict the epidemic trend of varicella is of great significance to the risk analysis and health resource allocation in the health sector. First, we used the 'STL' function to decompose the incidence of varicella to understand its trend and seasonality. Second, we established SARIMA model for linear fitting, and then took the residual of the SARIMA model as the sample to fit the LS-SVM model, to explain the non-linearity of the residuals. The monthly varicella incidence peaks in April to June and October to December. Mixed model was compared to SARIMA model, the prediction error of the hybrid model was smaller, and the RMSE and MAPE values of the hybrid model were 0.7525 and 0.0647, respectively, the mixed model had a better prediction effect. Based on the study, the incidence of varicella in Chongqing has an obvious seasonal trend, and a hybrid model can also predict the incidence of varicella well. Thus, hybrid model analysis is a feasible and simple method to predict varicella in Chongqing. [ABSTRACT FROM AUTHOR]

With the application of low frequency radar and the demand for stealth of high temperature resistant components, it is increasingly urgent to develop absorbing materials with both low frequency and high temperature resistant properties. Here, we successfully prepared various carbon/polyimide composites as low-frequency electromagnetic wave absorbing materials by simple blending method. The well-designed mesh lap structure introduces a large amount of free space, further optimizing the impedance matching of the material. At the same time, the multiple loss mechanism formed by the combination of carbon black dominated polarization and carbon nanotube dominated conductive loss enhances the loss of incident electromagnetic wave. The results showed that only 10 wt% filler loading of the CB/CNT@PI is achieved in the low frequency range (1-4 GHz) with a minimum RL strength of - 18.3 dB, which has obvious advantages compared with other works in recent years. This study provides a way for the design and preparation of resin-based absorbing materials., (© 2024 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved.)