Population aging and rural–urban migration have posed challenges to the elderly support system in developing countries that lack social safety net and services. Given that there is no consistent conclusion in the literature on whether adult children's internal migration can improve or impair their left-behind parents' health, little is known about the effect mechanisms. This paper investigates the comprehensive impact of adult children's migration on the health of their parents in rural China by analyzing the income effect and time allocation effect. The empirical analysis uses the rural sample of the China Health and Retirement Longitudinal Study (CHARLS) in 2013, 2015, and 2018. We found that adult children migration can improve parents' physical health, mainly thanks to the income effect. The analysis of the mechanism found that although the income effect has a positive effect on parents' health, the time allocation effect has a negative effect on parents' health because of the lack of care and increased working hours of parents. Our findings suggest that providing social care services and enhancing intergenerational communication can be practical strategies to mitigate the negative effect of children's migration to rural left-behind elderly parents.
In order to analysis the sulfate diffusion process in polypropylene fiber concrete, the influence of the introduction of polypropylene fiber on the porosity was calculated at first based on the spatial distribution features of polypropylene fiber in concrete, which was classified into three types, penetration type, half through type and embedded type. On the basis of Fick’s second law and reaction kinetics equation, the diffusion model of sulfate ions in polypropylene concrete was established. The numerical solution was achieved with the adoption of finite difference method and the concentration of sulfate ions at any position can be calculated. At last, the numerical solution was verified using the results of polypropylene fiber reinforced concrete sulfate attack test. The results show that the relative error between numerical calculation and the actual test results is less than 17.65 %, the accuracy of the model is relatively high.
Conservation tillage plays a crucial role in preventing soil erosion, improving soil quality, and encouraging sustainable agriculture. This study analyzes the effects of conservation tillage on farmers’ technical efficiency and its underlying mechanisms, using a sample of 853 households and 1706 land plots from China’s Jilin, Sichuan, Jiangsu, and Henan provinces. The results indicate that conservation tillage can enhance technical efficiency, resulting in an average increase of 0.022 units, The study further demonstrates that conservation tillage technology primarily enhances technical efficiency by increasing output and reducing production costs. This study proposes policy recommendations for promoting the use of conservation tillage technology to enhance farmers’ technical efficiency.
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