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This paper presents experimental and numerical investigations into the post-fire cross-section compressive behaviour and resistances of circular recycled aggregate concrete-filled stainless steel tube (RACFSST) stub columns. Twelve stub column specimens, fabricated from concretes with three recycled coarse aggregate replacement ratios (0%, 35% and 70%), were tested after exposure to the ISO-834 standard fire for 0 min (i.e. at ambient temperature), 15 min, 30 min and 45 min. The experimental investigation included heating and cooling of specimens, cylinder tests and post-fire tensile coupon tests and stub column tests. The test results, including load–end shortening curves, failure loads and failure modes, were fully reported and the initial compressive stiffnesses and confinement effect were discussed. The numerical investigation was subsequently conducted, where thermal and mechanical finite element models were developed and validated against the test results and then used to perform parametric studies to generate further numerical data. Given the absence of design codes for stainless steel–recycled aggregate concrete composite structures after exposure to fire, the relevant design rules for circular natural aggregate concrete-filled carbon steel tube stub columns at ambient temperature, as set out in the European code, Australia/New Zealand standard and American specification, were assessed, using post-fire material properties, for their applicability to circular RACFSST stub columns after exposure to fire, based on the test and numerical data. The assessment results generally revealed that the European code and the Australian/New Zealand standard led to an acceptable level of design accuracy and consistency, while the American specification resulted in rather conservative and scattered post-fire cross-section compression resistance predictions. • The compressive behaviour of circular RACFSST stub columns after exposure to fire is investigated. • Post-fire compression tests on twelve circular RACFSST stub column specimens are conducted. • The influences of heating durations and RCA replacement ratios are analysed. • Thermal and mechanical FE models are validated against test results and then used to conduct parametric studies. • The relevant design codes are assessed against the test and FE data. [ABSTRACT FROM AUTHOR]

Noble metals act as nanozymes that can generate reactive oxygen species (ROS) by catalysis to induce apoptosis of tumor cells for cancer therapy. But they are easy to aggregate, which will affect their further application. Carbon materials are often used as the carrier of noble metals to improve their catalytic performance. However, designing a composite structure to build an efficient carbon/noble metal hybrid nanozyme with high catalytic performance for tumor therapy is still a significant challenge. In this work, a core-in-shell structure nanozyme composed of gold nanoparticles (AuNPs) embedded in nitrogen-doped hollow carbon nanoshells (AuNPs@N-HCNs) were fabricated, which exhibited peroxidase-like (POD-like) and oxidase-like (OXD-like) activity. Compared with core-out-of-shell structure composite, the AuNPs@N-HCNs showed a better ability to generate ROS to kill tumor cells. Furthermore, AuNPs@N-HCNs also exhibited satisfactory photothermal conversion properties, which helped build a platform for photothermal therapy. Meanwhile, the enzyme activity produced by AuNPs@N-HCNs increased significantly under light irradiation. Comparing the size of AuNPs in carbon shell, 15 nm AuNPs were better than 2 nm in both enzyme-like activities and in vivo therapeutic effect. In vitro and in vivo studies demonstrated that under the synergistic effect of light-enhancing nanozyme catalysis and photothermal therapy, AuNPs@N-HCNs could induce cancer cell apoptosis and destroy tumors effectively, which provided evidence for the feasibility of tumor catalytic-photothermal treatment. [Display omitted] • AuNPs bedded in nitrogen-doped hollow carbon nanoshells nanozyme were fabricated. • 15 nm AuNPs in the carbon showed significant enzyme-like catalytic activity. • AuNPs@N-HCNs@TPGS(15) can inhibit CT26 cells in vitro and in vivo. • The photothermal-catalysis synergistic therapy has good antitumor effect. [ABSTRACT FROM AUTHOR]

The strip structure filling mining technology is suggested in response to the environmental issues such as surface subsidence and landslides brought on by the mining of 11,071 working faces in a mine in Guizhou. The mining technology system is studied through indoor testing, numerical simulation, and engineering monitoring. According to theoretical study, the filling strip can be steadily loaded and its value doesn't exceed 10 m when the width of the filling strip and the width of the filling interval are set to be equal. According to laboratory testing, fly ash can replace some of the cement in the cement mixture as a binder to maintain strength while cutting costs. The degree of crystallization gradually distributed into the network in the filling paste of various ages corresponds to its strength when combined with the findings of scanning electron microscopy; The numerical simulation results show that the maximum subsidence of the immediate roof is reduced from 340 to 3 mm from the filling rate of 0 to 100%, the filling effect is remarkable, and the shape of the settlement curve is changed from 'U' to 'basin', then to 'W'; during the local filling mining, the settlement curve of the immediate roof presents a 'wave' shape, and the stress curve of the immediate roof in the middle of the stope is also changed. The peak tension of the coal wall falls synchronously with filling spacing on both sides of the stope. The overall vertical stress below the mountain is larger, and the vertical stress at the top of the filling body eventually shifts from a "saddle" shape to a "inverted U" shape without zero support stress. In conjunction with the plastic zone, it is discovered that the stable bearing of the "filling strip-direct roof" composite structure increases with decreasing tensile and shear damage range of the hollow roof area and both sides of the top of the "filling 3 m interval 3 m" scheme; engineering measurement also reveals that the higher the position of the survey line is, the smaller the displacement is. However, the overall displacement of the strata directly above is negligible, and the greatest displacement is only 10.9 mm, which is consistent with the numerical simulation. At the same time, the displacement beneath the mountain area is too great. [ABSTRACT FROM AUTHOR]

The strip structure filling mining technology is suggested in response to the environmental issues such as surface subsidence and landslides brought on by the mining of 11,071 working faces in a mine in Guizhou. The mining technology system is studied through indoor testing, numerical simulation, and engineering monitoring. According to theoretical study, the filling strip can be steadily loaded and its value doesn't exceed 10 m when the width of the filling strip and the width of the filling interval are set to be equal. According to laboratory testing, fly ash can replace some of the cement in the cement mixture as a binder to maintain strength while cutting costs. The degree of crystallization gradually distributed into the network in the filling paste of various ages corresponds to its strength when combined with the findings of scanning electron microscopy; The numerical simulation results show that the maximum subsidence of the immediate roof is reduced from 340 to 3 mm from the filling rate of 0 to 100%, the filling effect is remarkable, and the shape of the settlement curve is changed from 'U' to 'basin', then to 'W'; during the local filling mining, the settlement curve of the immediate roof presents a 'wave' shape, and the stress curve of the immediate roof in the middle of the stope is also changed. The peak tension of the coal wall falls synchronously with filling spacing on both sides of the stope. The overall vertical stress below the mountain is larger, and the vertical stress at the top of the filling body eventually shifts from a "saddle" shape to a "inverted U" shape without zero support stress. In conjunction with the plastic zone, it is discovered that the stable bearing of the "filling strip-direct roof" composite structure increases with decreasing tensile and shear damage range of the hollow roof area and both sides of the top of the "filling 3 m interval 3 m" scheme; engineering measurement also reveals that the higher the position of the survey line is, the smaller the displacement is. However, the overall displacement of the strata directly above is negligible, and the greatest displacement is only 10.9 mm, which is consistent with the numerical simulation. At the same time, the displacement beneath the mountain area is too great. [ABSTRACT FROM AUTHOR]

Since high voltage insulation equipment fault and aging are always accompanied with insulation gas decomposition, it is critical to monitor and scavenge SF 6 decomposition gases. In this paper, based on density functional theory, Rh and Rh 2 doped C 3 N are utilized to detect SF 6 decomposition species (H 2 S, SO 2 , SOF 2 , and SO 2 F 2). The ideal binding energy of the most stable structures are −2.769 eV (Rh-C 3 N) and −3.482 eV (Rh 2 -C 3 N), respectively. The Rh n -C 3 N composite structure considerably increases the adsorption behaviors and electrical properties of SF 6 decomposition species. After gas molecules adsorption, changes of differential charge density, density of state, work function, and theoretical recovery time further support the sensing characteristic of composite structures. For various target gases, the results reveal that Rh-C 3 N and Rh 2 -C 3 N exhibit distinct adsorption types. SO 2 and H 2 S adsorption belongs to physical adsorption, while the type of SOF 2 and SO 2 F 2 adsorbed system is chemical adsorption. Even at high temperatures, the good recovery time (30.32 s and 21.77 s) for H 2 S adsorption systems can be acquired. The results demonstrate that Rh n -C 3 N (n = 1,2) is a novel carbon-based SF 6 gas sensing material that can be used to diagnose SF 6 decomposition in SF 6 electrical equipment insulation faults. [Display omitted] • Rh and Rh 2 nanoparticles decoration behavior on MoSe 2 has a significant doping effect. • Rh-MoSe 2 and Rh 2 -MoSe 2 exhibit ideal adsorption and scavenging properties for H 2 S, SO 2 F 2 , SOF 2 and SO 2. • Rh-MoSe 2 and Rh 2 -MoSe 2 can promote development of chemical resistive sensors in high voltage insulation faults monitoring. [ABSTRACT FROM AUTHOR]