Fatigue Defect of Layer Steel Fiber Reinforced Concrete

An experimental study is carried out on fatigue defect of layer steel fiber reinforced concrete (LSFRC). Based on experimental data,the various relation curves are given corresponding to different stress levels 0.9, 0.85, and 0.8. Furthermore, the fatigue defect degree is defined, and the strain cycle ratio equations and defect cycle ratio equations with the correlation coefficients very close to 1, are regressed in terms of the cubic polynomial,of which the fittings are preferable.In addition,the results show that the fatigue defect of LSFRC presents three phase development regularity too.And in comparison with the plain concrete,the third phase of the fatigue defect of LSFRC is longer, therefore the fatigue failure of LSFRC is more ductile.The mechanism of the fatigue defect is discussed too.

A Polyimide-Based Photocatalyst for Continuous Hydrogen Peroxide Production Using Air and Water under Solar Light

Hydrogen peroxide(H_(2)O_(2))is a clean disinfectant,bleaching agent,and value-added fuel in various systems and is industrially produced through multistep energy-intensive hydrogenation/oxidation using H_(2)and O_(2).The exploitation of metal-free catalysts for alternative H_(2)O_(2)photoconversion is limited by their limited activity and selectivity,especially for the continuous H_(2)O_(2)production using only air,water,and solar light.Now,a cheap and robust polymer,poly(4,4′,4″-(1,3,5-triazine-2,4,6-triyl)triphenyl pyromellitimide)(PTTPI)was rationally synthesized by thermal structure-defect control under relatively low temperature(80-190℃),and the resulting metal-free material with a concisely refined band structure functioned as an efficient and ultra-stable photocatalyst for H_(2)O_(2)production over a wide pH range.The PTTPI photocatalyst with an optimized defective degree(0.51)and moderate bandgap(2.3 eV)exhibited a H_(2)O_(2)production yield rate of 16.6μg h^(−1) mg_(cat)^(−1) and a high apparent quantumefficiency of 16.2%.By merging the well-designed PTTPI catalyst with the water transport path of natural cotton,a zero-emission and sunlightonly input system is constructed for continuous H_(2)O_(2)production from air and water in the natural environment.The design of the polyimide-based catalyst reveals a sustainable future toward efficient H_(2)O_(2)synthesis with sunlight-only energy input,enabling its implementation in other photocatalytic systems and on-site processing communities.