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The Huang-Huai-Hai Plain is an important commercial grain production base in China. Understanding the temporal and spatial variations in precipitation can help prevent drought and flood disasters and ensure food security. Based on the precipitation data for the Huang-Huai-Hai Plain from 1960 to 2019, this study analysed the spatiotemporal distribution of total precipitation at different time scales using the Mann–Kendall test, the wavelet analysis, the empirical orthogonal function (EOF), and the centre-of-gravity model. The results were as follows: (1) The winter precipitation showed a significant upward trend on the Huang-Huai-Hai Plain, while other seasonal trends were not significant. (2) The precipitation on the Huang-Huai-Hai Plain shows a zonal decreasing distribution from southeast to northwest. (3) The application of the EOF method revealed the temporal and spatial distribution characteristics of the precipitation field. The cumulative variance contribution rate of the first two eigenvectors reached 51.5%, revealing two typical distribution fields, namely a ‘global pattern’ and a ‘north-south pattern’. The ‘global pattern’ is the decisive mode, indicating that precipitation on the Huang-Huai-Hai Plain is affected by large-scale weather systems. (4) The annual precipitation barycentres on the Huang-Huai-Hai Plain were located in Jining city and Taian city, Shandong Province, and the spatial distribution pattern was north-south. The annual precipitation barycentres tended to move southwest, but the trend was not obvious. The annual precipitation barycentre is expected to continue to shift to the north in 2020.

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A precipitation barycenter reflects the overall spatial distribution and long-term evolution of regional precipitation. Understanding the changes in precipitation barycenter has significant implications for drought management, flood control, and water resource management. This paper analyzed the distribution and transfer of monthly, interannual, and interdecadal precipitation barycenter on the Huang-Huai-Hai Plain (‘3H’ Plain). We also discussed the influence of the station network spatial distribution on the changes in precipitation barycenter. The results were as follows: (1) The trajectory of the monthly precipitation barycenter on the ‘3H’ Plain was generally ‘8’-shaped. The rainy and dry season precipitation barycenters were located in the upper and lower parts of the ‘8’-shaped, respectively. (2) In the past 60 years, the interannual precipitation barycenter had a trend of moving southwest, but the trend was not apparent. (3) Station network density and uniformity dominated the changes in precipitation barycenter, showing positive correlations. When the station network density was large and exceeded a certain range, the influence of station network density on the changes in precipitation barycenter decreased.

The accuracy of flowmeter of the first circuit coolant sampling system in nuclear power plant affects the measurement of the Boron meter. If the fault treatment cannot be completed in time, the reactor state needs to be withdrawn, which will affect nuclear safety and cause great economic losses. In this paper, a feasible improvement scheme is proposed by analyzing the causes of instrument failure, researching the optimization direction, and adopting measures such as seismic analysis, prototype verification, split design, and interference suppression, which effectively improves the reliability of nuclear sampling flow measurement in nuclear power plants.