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Preparation of slag-based foam concrete by chemical foaming for CO2 sequestration

Li Wei, Lyu Zhiwen, Liu Jian, Li Wei, Sun Ziqiang, Ma Yan, Cheng Weimin, Meng Xiangjun, Xin Lin, Sun Xikui

Environment Protection Engineering

2024

Vol. 50, nr 2

95--114

Carbon dioxide emissions are among the most influential causes of global warming, and the recovery, capture, and comprehensive utilization of CO2 are the keys to carbon emissions reduction. High-porosity foam concrete was prepared using CaO as the alkali activator, and H2O2 as the foaming agent. Based on a single-factor experiment and response surface analysis, the best preparation condi-tions for foam concrete were obtained (water-to-cement ratio 0.4, alkali excitation dosage 10.73%, foaming agent dosage 8.26%). The porous material prepared under the optimal process conditions can achieve a CO2. sequestration performance of 91.59 kg/m3, and the actual sequestration capacity is con-sistent with the theoretical prediction value of 90.89 kg/m3. Mechanistic analysis shows that the precarbonation hydration products of foam concrete are mainly C-S-H gel, Ca(OH)2, and hydrotalcite-like compounds, which bond the slag particles together to form a three-dimensional spatially firmly con-nected structure. This study provides a reference for the application of alkaline solid waste materials in the field of carbon sequestration.

Double-image encryption scheme based on the phase-truncated multiple-parameter Fresnel transform

Zhou Ling, Zhou Hang, Ma Yan, Zhou Nan-Run

Optica Applicata

2022

Vol. 52, nr 2

163--177

A double-image encryption algorithm is proposed with the phase-truncated multiple-parameter Fresnel transform. Firstly, the pixel positions of two plaintext images are scrambled and then the results are merged into one image with the scrambling operation. Subsequently, the resulting image is encrypted by phase truncation and phase reservation in the multiple-parameter Fresnel transform domain. The phase information is scrambled by the affine transform and then recombined with the amplitude information. The final encryption image is obtained with the pixel scrambling and diffusion methods to further enhance the security of the image encryption system, where the scrambling and diffusion operations are based on logistic map, logistic-sine system and 2D logistic-adjusted-sine map. The image encryption scheme is robust against the common attacks due to the nonlinear properties of diffusion and phase truncation. Numerical simulation results verify the performance and the security of the proposed double-image algorithm based on the phase-truncated multiple-parameter Fresnel transform.