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Background With the improvement of economic level and changes in lifestyle of residents, the obesity among children and adolescents has become increasingly severe, threatening the healthy growth of children and adolescents. BMI was used as an evaluation index of obesity in most previous studies, which may underestimate the prevalence of central obesity. Therefore, it is urgent to evaluate the waist circumference (WC) and trend of the prevalence of central obesity among children and adolescents in Putuo District, in order to provide scientific basis for targeted proposed intervention. Objective To analyze WC and the trend in the prevalence of central obesity among children and adolescents aged 7-18 years in Putuo District, Shanghai, from 2018 to 2023. Methods Data on medical examinations of primary and secondary school students in Putuo District in 2018 and 2020 to 2023 were used to analyze the WC, the prevalence of central obesity and the trends. The 90th percentile (P90) age-specific children and adolescents of different genders was used as the cut-off point of high WC, and WC exceeding the P90 value was defined as central obesity. SPSS 22.0 and SAS 13.1 were used for statistical analysis and Excel 2021 was used for graphic plotting. Results A total of 280 648 primary and secondary school students participated in the medical examination in Putuo District, Shanghai, from 2018 to 2023, of which 146 334 (52.1%) were male students and 134 314 (47.9%) were female students, with an median age of 10.5 (8.7, 12.6) years. WC of male and female students from 2018 to 2023 showed fluctuating downward trends with a statistically significant difference (Hmale=209.785, Hfemale=373.076; P

Geosynthetic clay liners (GCLs) are commonly used in engineering to prevent seepage. These liners' surface fabric often suffers damage, especially in toxic environments and under high pressure. To mechanically strengthen the GCLs, this study proposes reinforcement by using needle bonding and glass geogrid to establish glass-geogrid-reinforced GCLs (i.e., GGCLs), consisting of glass geogrid, bentonite layer, and 0.3 mm thick melt-blown nonwoven fabric. Tensile durability of GGCLs was determined by exposing them to thermal oxidation and UV degradation. Hydraulic conductivity and heavy metal ions adsorption of GGCLs was explored to simulate the damage caused by garbage leachate. Tensile strengths of polyamide (PA)- and polyethylene terephthalate (PET)-contained GGCLs retained greater than 73% and 90%, respectively, even after 20 h thermal oxidation at 100°C and 60 h UV degradation. Improvement of hydraulic conductivity after 2 h adsorptions of Cu2+, Ni2+, and Pb2+ reached 51.09, 51.04, and 45.56%. The absorptions of Cu2+ and Ni2+ conformed to the quasi-secondary dynamics model, but that of Pb2+ followed both the quasi-first-order and quasi-secondary dynamics models. The mechanical properties and impermeability of the resulting GGCLs declined under the simulated conditions. This study provides a basic theory to predict the durability and adsorption of heavy metal ion of landfill GGCLs under natural and severe weather conditions. [ABSTRACT FROM AUTHOR]

This study proposes flexible multifunctional sandwich-structured composites that are reinforced by using aramid staple fibers and a needle-punching process and measures their cushion performance using a self-made drop-tower machine with a realistic depth sensor. The Mechanical properties of the laminated nonwoven composites are evaluated to examine the influence of the content of aramid staple fibers. Moreover, the puncture resistance rises linearly with the increasing aramid content. When the aramid content is 15%, the laminated nonwoven composites can bear 60.34% of dynamic impact force and have the maximum burst load of 1798.5 N, the maximum puncture resistance of 320.1 N, the maximum stab resistance of 191.9 N, the maximum sound absorption coefficient of 0.99, and NRC of 0.41. Therefore, aramid staple fibers are good candidate to be used as improvement in cushioning, stab resistant, and sound-absorbent properties of security walls. [ABSTRACT FROM AUTHOR]

In this study, the thicknesswise fibers of the low-melting polyethylene terephthalate (LPET) nonwoven fabrics are needle punched and intertwined with the intra-laminar basalt fibers (BF) of basalt plain woven fabric in order to strengthen the stab-resistant property of LPET/BF sandwich composites as well as to fabricate armor that is composed of less lamination layers. Two LPET nonwoven fabrics and a BF plain woven fabric as an interlayer are laminated and combined using a needle-punch reinforcing method. The response surface analysis based on the Box–Behnken design is used to examine the influences of structure parameters of low-melting PET nonwoven fabrics including areal density (AD) and manufacture parameters including needle punching density (ND), and depth of needle punch (DP) on the spike stab resistance, knife stab resistance, bursting resistance, and tensile property. An empirical regression model of AD, ND, and DP is thereby established. The test results show that the bursting strength and quasi-static stab resistance of sandwich composites are highly dependent on AD and ND. Likewise, DP has a significant influence on the knife stab resistance and bursting strength, while the tensile strength is solely dependent on ND. According to the empirical regress model, the acquired optimal needle punching parameters of sandwich composites are an AD of 400 g/m2, ND of 143.77 needles/cm2, and DP of 6.41 mm. The 95% confidence interval yielded by the empirical regression model is in conformity with the test results. The empirical regression model of the stab resistance is proven to provide effective prediction of the number of lamination layers required by armor in the future. [ABSTRACT FROM AUTHOR]

In this paper, the shear-thickening fluids(STFs) are prepared by 0.5 µm and 12 nm silica particles. The STFs rheological properties and the performance of stab resistance are studied. SiO2 particles with two sizes (12 nm and 0.5 µm) are mixed at different weight ratios to form shear thickening fluids and its rheological behaviors are tested. Next, the quasi-static spike and knife stab resistances, dynamic impact strength, and yarn pull-out of shear thickening fluid-impregnated Kevlar fabrics are tested. The investigation showed that the micro- and nano-sized particles of silica are present in the compound shear thickening fluid, and the rheological behavior was positively improved. Regardless of whether shear thickening fluid is composed of mono-sized or binary particle-sized SiO2 particles, the presence of shear thickening fluids can significantly strengthen Kevlar fabrics in terms of the quasi-static spike and knife stab resistances, dynamic impact strength, and promote the friction force of inter-yarn. In particular, shear thickening fluid-impregnated Kevlar fabrics have better performances when being composed of 12 nm and 0.5 µm SiO2 particles at ratios of 2:1, 1:1, and 1:2 than when being made of only micro-sized or nano-sized particles. [ABSTRACT FROM AUTHOR]

The area of forests continues decreasing while the water/soil loss becomes worse. In these complicated environments, mechanical properties, stability, high modulus and low elongation of geotextiles are required. On a premise of the acquisition of good mechanical properties and the improvement in the deformation and puncture resistance of nonwoven fabric, woven/nonwoven hybrid geotextiles are designed and made with needle punch processing technology in this study. The test results indicate that the mechanical properties of hybrid geotextiles are improved significantly when the areal density of nylon fabrics is increased. In particular, with the areal density of 400 g/m2, hybrid geotextiles exhibit the maximal mechanical properties and puncture resistance. Moreover, the pore fraction of hybrid geotextiles decreases as a result of a rise in the areal density of nylon top/bottom layers. The use of a 3 D mesh fabric as the interlayer provides the needle punched composite geotextiles with the highest tensile resistance, puncture resistance. The composite geotextiles are treated with acid and alkali to simulate the corrosion under natural conditions of stabilized soil. The resultant geotextile has good mechanical properties and acid/alkali degradation resistance. This allows the hybrid geotextiles to stabilize water and soil conservation in complicated conditions. [ABSTRACT FROM AUTHOR]