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This paper reports an experimental and numerical study on the spherical indentation behavior of three-dimensional (3D) warp-knitted mesh fabrics. A full-size finite element (FE) model of a typical 3D mesh fabric is established at the yarn level based on the realistic monofilament architecture from micro-computed tomography (μCT) scanning and verified with experiments. The structural change of the fabric in the spherical indentation process is quantitatively analyzed in terms of fabric global deformation, local deformation, mesh deformation, and spacer monofilament deformation from the FE simulation. The numerical results show that the fabric shrinks walewise and expands coursewise from the spherical indentation of the continuous intermeshed monofilament architecture, showing counterintuitive partial auxeticity. The coursewise symmetry and walewise asymmetry of the 3D mesh fabric produce relatively symmetrical coursewise deformation and asymmetrical walewise deformation under spherical indentation. The symmetrical coursewise deformation includes even widening, good fitting of the indenter, and almost identical mesh sizes in the coursewise direction. Walewise asymmetry leads to uneven shortening, inferior fitting of the indenter, and considerably varied mesh sizes in the walewise direction. Spacer monofilaments in different positions relative to the spherical indenter have different deformations. The closer to the indenter, the greater bending and twisting of the spacer monofilament. The spacer monofilament knitted earlier of the tested fabric has smaller deformation than that knitted later due to the walewise asymmetry. The coursewise symmetry and walewise asymmetry of the inhomogeneous 3D mesh fabric structure result in a highly nonlinear spherical indentation behavior. [ABSTRACT FROM AUTHOR]

Weft-knitted spacer fabrics, a kind of three-dimensional fabric structure, are potential substitutes for typical rubber sponges and polyurethane foams for the protection of human body from exposure to vibrations. To explore the capability and the designability of weft-knitted spacer fabrics as the functional material of personal protective equipment against vibration, such as anti-vibration gloves and car cushions, the vibration behavior and physical properties of weft-knitted spacer fabrics manufactured using flat knitting technology were studied. In the first part of the article, the vibration behavior of top-loaded weft-knitted spacer fabric under harmonic base excitation was analyzed. The effects of monofilament diameter, linking distance and excitation acceleration level on the transmissibility curve of the mass-spacer fabric were evaluated. It was shown that to broaden the frequency range for vibration isolation, spacer fabrics with smaller monofilament diameter and longer linking distance were preferred. In the second part of the article, the effects of monofilament type, monofilament diameter, and spacer structure on the physical properties of spacer fabric including fabric shrinkage coefficient, fabric thickness, fabric stitch densities, and fabric areal mass were analyzed. It was found that fabric thickness was increased by employing spacer structures with longer linking distance and lower filling density of spacer monofilament. In addition, in order to obtain an optimized high fabric thickness, nylon monofilament was preferred to polyester monofilament. On the other hand, monofilament diameter has a significant influence on stitch densities and fabric areal mass. Larger monofilament diameter resulted in lower stitch densities and heavier areal mass for spacer fabric. [ABSTRACT FROM AUTHOR]

As a key policy tool for China' s achievement of the goals of reaching peak carbon emissions and carbon neutrality, the carbon emissions trading mechanism has attracted widespread attention for its effect on reducing pollution and carbon emissions. This study incorporated carbon dioxide reduction and environmental pollution control into the same research framework. Based on the panel data of 30 provinces in China from 2010 to 2019, it took the carbon emissions trading mechanism as the policy background and used the improved entropy weight TOPSIS model to calculate the environmental pollution index to measure the local environmental quality and environmental pollution degree. The intersection term of carbon emissions and environmental pollution index was used to characterize the level of pollution reduction and carbon reduction. The difference-in-differences model and the synthetic control method were used to empirically test the pollution and carbon emission reduction effects of the carbon emissions trading mechanism. The results showed that: (1) From the perspective of the average treatment effect of the policy, the carbon emissions trading mechanism reduced the emissions of carbon dioxide and environmental pollutants in the pilot provinces compared with non-pilot provinces. After adding relevant control variables, the level of pollution and carbon reduction in the pilot provinces increased by 16%. From the perspective of the policy effects of pilot individuals, Beijing, Shanghai, Tianjin, and Chongqing performed better; that is, their carbon emissions showed a significant downward trend, followed by Guangdong, while Hubei performed worse. (2) The influential mechanisms and heterogeneity test revealed that the carbon emissions trading system achieved an increase in the synergistic governance level of pollution and carbon reduction through energy consumption restructuring and technological innovation. (3) Meanwhile, the pollution and carbon reduction levels showed regional heterogeneity, with the eastern and western regions performing best and the central region performing poorly. Furthermore, a grey correlation model was used to investigate the relationship between the pollution and carbon reduction levels and the potential for synergistic emission reduction in each province. The results found that the average correlation degree of Shanghai, Guangdong, Guangxi, Guizhou, and Xinjiang was greater than other provinces, showing a higher level and potential. Therefore, it is necessary to accelerate and improve the construction of the national carbon emissions trading market; give full play to the synergistic emissions reduction effects of market-based carbon emissions trading policies on carbon dioxide emissions and environmental pollutants; and accelerate the synergy of carbon emissions trading policies by increasing investment in technological innovation and the transformation and upgrading of energy consumption structures and formulating regionally differentiated carbon emission reduction policies. [ABSTRACT FROM AUTHOR]