To study the ultimate load-carrying capacity of pipe-plate Vierendeel truss joints, the analyses of joint failure modes and parameter effects were undertaken using nonlinear finite element method and uniform design approach. The plate instability was included in the failure modes. Factors such as the pipe diameter, the pipe thickness, the plate width, the plate height, and the plate thickness were considered in the joint models. Three kind of loading conditions on the plate, the axial force, the moment, the composed loading of axial force and moment were analyzed. The relationships between the joint failure modes and the factors are achieved. The joint ultimate load-bearing capacity formulas are proposed by regression analysis. The effects of factors on the joint strength are illustrated.
This study expands the STIRPAT framework and utilizes mechanistic analysis and spatiotemporal heterogeneity analysis to examine the impact of market integration on carbon emission intensity and heterogeneity in East China. The findings reveal that market integrations play a significant role in reducing carbon emission intensity, and tax environment, urbanization, and consumption power prove to be important mechanism factors. The average treatment effect of industrial structure and energy structure also positively promotes emission reduction efforts. However, market integration coupling coordination degree, technology level, and the gap in high-quality development act as inhibiting factors on carbon emission intensity. Furthermore, the spatial and temporal heterogeneous evolution trend demonstrates distinct and evident agglomeration patterns among economic regions. To effectively leverage the unified large market mechanism to reduce carbon emission intensity, it is essential to consider the regional characteristics of different influencing factors and also focus on the role of important node cities in driving emission reduction efforts.
The leaching efficiency of copper smelter slag with high silicon is investigated in this study.The leaching test is carried out at normal pressure with H2SO4 and Na2SO4 in a ventilating air stirring reactor.The filtrate with a low content of silicon and iron is obtained by using Ca(OH)2 as a neutralizer.Parameters which influence the result of leaching are optimized,with the leaching efficiency of Co being 89.1%.
Abstract. Observations of atmospheric CO2 molar fraction and its 13C isotope composition (δ13C) in urban airsheds provide constraints on the roles of anthropogenic and natural sources in local and regional C cycles. In this study, we report observations of these quantities in Nanjing at hourly intervals from March 2013 to August 2015 using a laser-based optical instrument. Nanjing is the second largest city located in the highly industrialized Yangtze River Delta (YRD), Eastern China. The mean CO2 molar fraction and 13C were 439.7 ppm and −8.48 ‰ over this observational period. The peak monthly mean δ13C (−7.44 ‰, July 2013) was 1.03 ‰ higher than that observed at the Mauna Loa Observatory. The highly enriched 13C signal was attributed to the influence of cement production in the region. By applying the Keeling plot and the Miller–Tans method to midnight and midday observations, respectively, we showed that the 13C signal of C sources in the Nanjing Municipality was 0.48 ‰ lower than that in the YRD. Flux partitioning calculations revealed that natural ecosystems in the YRD were a negligibly small sink of atmospheric CO2, consistent with the Carbon Tracker inverse modeling result.
Purpose: The study was to evaluate the physical condition and mental health of Chinese college student COVID-19 survivors, and to perform severity clustering of physical symptoms. Participants: The study finally included 1912 Chinese college students. Methods: A total of 33 symptoms including general physical symptoms, cardiopulmonary system, digestive system, neurological system, mental health and other symptoms were investigated three months after recovery from COVID-19, and these symptoms are identified using latent class analysis. Results: Three clusters were identified through latent class analysis: 13.2% with severe impairment (cluster 1), 27.2% with mild physical symptoms (cluster 2), and 59.5% with no or mild symptoms (cluster 3). The students who smoked, drank alcohol, did not exercise, or had a history of underlying medical conditions were more likely to have moderate to severe symptoms. Conclusions: Young COVID-19 survivors with a history of underlying diseases and unhealthy habits are more likely to have moderate to severe COVID-19 sequelae. Varying degrees of symptoms should be treated with different rehabilitation plans.
Abstract Hydrocarbon (HC) contamination of soil occurs during oil extraction, transportation and treatment. To enhance the efficacy of HC-polluted soil restoration is an important challenge. In greenhouse and field experiments, two silicon (Si)-rich substances were tested for reduction of HC content in diesel + used motor oil contaminated soil. Over 3 months the HC content decreased from 3 to 2.8; 1.1 and 0.8% in control, calcium silicate slag- and amorphous Si dioxide-treated soils, respectively. Silicon-rich substances remarkably increased the catalase and dehydrogenase activities in the contaminated soil. Several mechanisms underlying the Si-mediated purification of HC-contaminated soil are suggested: a) changing soil physical properties; b) capsulation of HC molecules by polysilicic acid; c) adsorption of monosilicic acid by HCs leading to enhanced hydrophilicity; d) direct effect on soil microbial activity. Many types of Si-rich materials are cheap and available in large volumes (industrial by-products) that potentially could be used for the purification of HC-polluted environment after ecological expertise of the absence of inorganic pollutants.
Continuous-flow microwave heating stands out for its ability to rapidly and uniformly heat substances, making it widely applicable in chemical production. However, in practical applications, the permittivity of the heated liquid changes dramatically as the reaction progresses, affecting the efficiency and uniformity of continuous-flow heating. Herein, this work presents a novel microwave heating device based on a coaxial structure for high-performance heating. Our approach commenced with the development of a multiphysical field model, incorporating spiraled polytetrafluoroethylene (PTFE) as a water channel and the coaxial waveguide as a container. The analysis shows that the uniform distribution of the sectional electric field of electromagnetic waves in the TEM mode within the coaxial structure can enhance heating uniformity. Then, a continuous-flow microwave heating system for different liquid loads was established, and experimental measurements were conducted. The heating efficiency for all loads exceeded 90%, which basely matched the simulation results, validating the accuracy of the model. Finally, the heating efficiency and uniformity under different permittivity loads were analyzed, as well as the impact of channel radius on heating efficiency. The device exhibits high heating efficiency under different loads, with uniform radial electric field distribution and stable heating uniformity. This continuous-flow microwave device is suitable for chemical research and production because of its high adaptability to the large dynamic range of permittivity, contributing to the promotion of microwave energy applications in the chemical industry.
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