Considering the impact of the number of potential new coronavirus infections in each city, this paper explores the relationship between temperature and cumulative confirmed cases of COVID-19 in mainland China through the non-parametric method. In this paper, the floating population of each city in Wuhan is taken as a proxy variable for the number of potential new coronavirus infections. Firstly, to use the non-parametric method correctly, the symmetric Gauss kernel and asymmetric Gamma kernel are applied to estimate the density of cumulative confirmed cases of COVID-19 in China. The result confirms that the Gamma kernel provides a more reasonable density estimation of bounded data than the Gauss kernel. Then, through the non-parametric method based on the Gamma kernel estimation, this paper finds a positive relationship between Wuhan’s mobile population and cumulative confirmed cases, while the relationship between temperature and cumulative confirmed cases is inconclusive in China when the impact of the number of potential new coronavirus infections in each city is considered. Compared with the weather, the potentially infected population plays a more critical role in spreading the virus. Therefore, the role of prevention and control measures is more important than weather factors. Even in summer, we should also pay attention to the prevention and control of the epidemic.
To fill the gap in the research on the convergence trend of air pollutants since 2013 in China and overcome the Galton fallacy caused by the parametric regression method, this study examines the convergence trend of the annual average concentration of fine particulate matter 2.5 (PM2.5) in China's prefecture-level cities after 2013 using a distribution dynamic approach. The winter PM2.5 pollution in Chinese cities is severe. Hence, the convergence of the average winter PM2.5 concentration of prefecturelevel cities is also explored in this study. The results show that during 2015-2019, the annual average PM2.5 concentration level improved significantly. However, the average PM2.5 winter concentration level in 2015-2018 did not significantly decrease, with some cities showing severe pollution levels. The annual average PM2.5 of China's prefecture-level cities exhibit club convergence, while the PM2.5 concentration in winter exhibits 'unikurtosis'. In the long run, the annual average PM2.5 clusters around two levels, at approximately 35 lg/m 3 and 60 lg/m 3 , while the average PM2.5 in winter is concentrated at 100 lg/m 3 . In the long run, in the central region, PM2.5 pollution is more severe than in northern and southern areas, regardless of the annual or winter average PM2.5 concentration.
We developed two models in this study: one to show the distribution of heat for pans of different shapes, and the other to select the best type of pan to maximize the number of pans that can fit in the oven and to maximize even heat distribution in the pans. We constructed a model of heat distribution. The uneven distribution of heat is mainly caused by heat conduction. We established a differential equation for heat conduction according to Fourier’s law. The finite-difference method and Gauss-Seidel iteration were used to solve the equation, and MATLAB was used to draw the corresponding heat-distribution chart. We built a quantitative model of the shape optimization with an evaluation equation. Using the permutation and combination method, we calculated the maximum number of pans and the utilization rate of area. Finally, we determined that the optimal pan type is a round square, which achieved the best state.
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