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Reprocessing of nuclear fuel to achieve closed nuclear fuel cycle can effectively improve the utilization efficiency of nuclear fuel. At present, the nuclear fuel reprocessing process that has been realized engineering application is to separate different metal ions by using different partition coefficients of metal ions in extractants. Therefore, extraction equipment is the key core equipment in the field of nuclear fuel reprocessing. The centrifugal extractor has the advantages of high mass transfer efficiency and low hydraulic retention time, but the existing single-stage centrifugal extractor usually occupies a large area, which leads to expensive plant construction costs. In order to meet the throughput requirement of the reprocessing plant under the premise of minimizing the plant area, in this study, a high flux SDMS-350-8 multistage centrifugal extractor with a drum diameter of 350 mm and a total number of stages of 8 was designed and manufactured, which can realize multistage centrifugal extraction in a single device. Based on the engineering application conditions, the hydraulic performance experiments were carried out with HNO3 aqueous solution and 30% TBP-kerosene. The effects of the drum rotating speed, heavy phase weir plate semidiameter and mixing paddle size on the hydraulic performance of SDMS-350-8 multistage centrifugal extractor were studied. The results show that the suitable drum rotating speed range of SDMS-350-8 centrifugal extractor is 1 400-1 600 r/min, when it is lower than 1 400 r/min, it is difficult to establish a stable hydraulic operation state under the required flow ratio (200/800). With the increase of drum rotating speed, the two-phase entrainment will gradually increase. The effects of heavy phase weir plate semidiameter and flow ratio on the maximum treatment flux of SDMS-350-8 centrifugal extractor were studied. In addition, it is found that different aqueous phase weir plate semidiameters are suitable for different flow ratios. The aqueous phase weir plate with 113 mm semidiameter is suitable for the flow ratios of 1/5-1/3, the aqueous phase weir plate with 110 mm semidiameter is suitable for the flow ratios of 1/1-2.5/1, and the aqueous phase weir plate with 107.5 mm semidiameter is suitable for the flow ratio of 5/1. The size of the mixing paddle was also optimized. The results show that by increasing the size of mixing paddle from 118 mm to 122 mm, the maximum treatment flux increases to 1 600 L/h. The above results show that the SDMS-350-8 multistage centrifugal extractor has the advantages of large treatment flux, wide operation range and good hydraulic performance, and has the potential to be applied in nuclear engineering.

Timely and accurate tree species mapping is crucial for forest resource inventory, supporting management, conservation biology, and ecological restoration. This study utilized Sentinel-1 and Sentinel-2 data to classify five dominant tree species in Chengde and Beijing. To effectively capture the influence of multi-temporal data, data were acquired in March, June, September, and December 2020, extracting various features, including bands, spectral indices, texture features, and topographic variables. The optimal input variable combination was explored using 1519 field survey samples for training and testing datasets. Classification employed Random Forest, XGBoost, and deep learning models, with performance evaluated through out-of-bag estimation and cross-validation. The XGBoost model achieved the highest accuracy of 81.25% (kappa = 0.74) when using Sentinel-1 and Sentinel-2 bands, indices, texture features, and DEM data. Results demonstrate the effectiveness of using Sentinel data for tree species classification and emphasize the value of machine learning algorithms. This study underscores the potential of combining synthetic aperture radar (SAR) and optical data for large-scale tree species classification, with significant implications for forest monitoring and management. [ABSTRACT FROM AUTHOR]

The unique structure of ancient buildings poses a significant risk of fire hazards, so the assessment of potential fire risk is of great significance to fire safety management. This paper examines the fire risk associated with the building complex of the Palace Museum. Firstly, a fire risk assessment indicator system was constructed based on three dimensions: hazard factors, sensitivity of hazard-bearing bodies, and loss control factors. Secondly, the weight values for each index were calculated based on the entropy weight method. Finally, the monthly fire risk assessment levels in the year 2019 were visualized by using a geographic information system. Based on the fire risk assessment results, this study quantitatively reveals the fire risk driving mechanism of ancient buildings in the Palace Museum from the perspective of spatial stratified heterogeneity by using the geodetector model. The results show that there are differences between the main factors that affect the weight of fire risk assessment and the main factors that cause the spatial heterogeneity of fire risk. Factors such as the safety protective grade and staff number contribute to a stronger explanation of the spatial stratified heterogeneity for fire risk within the museum. The results can help us to understand the driving factors affecting the distribution patterns of fire risk for the Palace Museum and could provide support for the formulation of fire prevention and safety management measures. [ABSTRACT FROM AUTHOR]

Ecological vulnerability assessment is crucial for environment protection, ecological restoration and resource utilization. However, many former studies have limitations in the indicator system of the assessment, which were not comparable for different types of ecologically vulnerable areas. It is difficult to apply directly to the ecological vulnerability assessment of different types and in various regions. Aiming to solve these problems, the study proposed a well-established and comprehensive indicator system for ecological vulnerability assessment and conducted ecological vulnerability assessment application of five types of typical ecologically vulnerable areas of China based on remote sensing, meteorological, geographic and other data. The results show that the average EVIs value of Zhangbei County ranging from 0.525 to 0.559 are the highest among the five research areas during the four periods, followed by Zoige region and Xiamen bay. However, the region with the lowest average EVI value varies. In 2005 and 2015, it was Taihe County, while in 2010 and 2020, it was the Sanjiangyuan region. The variation of average EVIs in the five typical areas presents slight fluctuation and remains generally stable from 2005 to 2020. It indicates that the environmental protection measures and projects undertaken by the Chinese government in recent years have had a striking effect, curbing the trend of ecological environment deterioration. [ABSTRACT FROM AUTHOR]