To study the fatigue performance of bolted connections in timber-concrete composite structures(TCC), this paper adopts a combination of experimental research and theoretical analysis to design 15 push out specimens for static and fatigue tests. The changes in mechanical properties such as fatigue life, residual slip development, shear bearing capacity, and stiffness of bolted connections are obtained. On this basis, the fatigue failure mode is analyzed to provide reference for the fatigue design of TCC.
To analyze the source apportionment, potential ecological risk, and health risk of heavy metals in soils surrounding a manganese tailings pond in Chongqing, a positive matrix factorization （PMF） model, potential ecological risk index, and health risk assessment model were used. Further, all three models were combined to explore the risks of heavy metals in soils by different pollution sources to determine the priority control factors. The results showed that except for the Cr concentration, the average values of Mn, Cd, As, Pb, Cu, Zn, and Ni concentration were higher than their corresponding background values. Using the PMF model analysis, mining, natural, agricultural, and industrial sources were identified as the determinants for the accumulation of heavy metals in soils, with contribution rates of 23.9%, 30.2%, 18.8%, and 27.1%, respectively. Using potential ecological risk index analysis, the ecological risk was predominantly categorized as "strong" risk, with the rate of 77.8%. The health risk assessment model analysis revealed that, the carcinogenic risks of adults and children were tolerable, whereas the non-carcinogenic risks were acceptable. According to the analysis results of the relationship among heavy metals, pollution sources, potential ecological risk, and health risks showed that agricultural sources were identified as the priority control sources, with Cd as the primary control factor. Mining sources and industrial sources were identified as secondary control sources, with Mn and As as the secondary control factors.
In the monitoring of cable fire, it is of great significance to be able to conduct early fire warning, which requires that sensors have high sensitivity to the cable vapors at low temperatures. In this study, WO 3 thick films modified with Au, Pd, and Pt single or bimetallic nanoparticles were fabricated via magnetron sputtering. Gas sensors utilizing these materials exhibited significant response to the low-temperature vapor emitted by YJV22 and YJY23 cables. Among them, Pd/WO 3 -20 demonstrated a response value of 20 to the vapor of 81[Formula: see text]C YJV22 cables, marking a remarkable 6.3-fold increase compared to pure WO 3 , and the response time was 13 s. Similarly, Pt/WO 3 -10 exhibited a response value of 11.11 to the vapor of 104[Formula: see text]C YJY23 cables, representing a 6.9-fold enhancement over pure WO 3 with a response time of 12 s. The heating temperature of cables remains below their critical threshold, indicating that it is in the early stages of cable fires, the findings hold significant implications for early warning systems designed to detect cable fires promptly.
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