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Based on the theme of sports risk prevention and control in colleges and universities, the connotation and classification of sports risk in colleges and universities are recognized and screened, the theoretical basis of sports risk prevention and control in colleges and universities is interpreted, and the needs of sports risk prevention and control in colleges and universities are analyzed. On the basis of questionnaire and expert interview, the analytic method is used to construct the evaluation index system of sports risk prevention and control in colleges and universities, including 5 first-level indexes, 9 second-level indexes, and 27 third-level indexes in colleges and universities, teachers, students, parents, and communities, in order to find out the characteristics and occurrence rules of sports risk in colleges and universities in Changsha, Zhuzhou and Xiangtan, Hunan Province. We find out the loopholes and shortcomings in the risk management of sports in colleges and universities and provide theoretical reference for reducing the risk of sports in colleges and universities in the region and improving students' physical quality. [ABSTRACT FROM AUTHOR]

Under the background of the promotion of the Olympic effect of the 2022 Beijing Winter Olympics and the in-depth implementation of the national ice and snow industry's strategy of "expanding from the south to the west and expanding from the east," China's ice and snow industry has ushered in a new period of development. By applying literature and logical analysis, etc., with in-depth analysis of various subjective and objective supplies for the integration of China's ice-snow industry and ecocultural tourism in Hunan Province, it is considered to be driven by the bidding and preparation effect of Beijing Winter Olympic Games in 2022. The supply capacity of ice-snow industry venues, professional facilities, and public services are gradually strengthened, and the soft power of construction of the ice-snow industry needs to be coordinated and improved. The problem of safety is prominent and it is urgent to build a safety prevention and emergency management of ice-snow tourism.The integration of ice-snow sports and ecotourism industry has gradually became a prototype, but the integration point, line, and surface still need to be further strengthened and expanded. Accordingly, this paper puts forward a method to realize the transformation and upgrading of the commercial operation mode of the integration of ice-snow industry and ecological culture tourism, comprehensively to improve the ecological innovation ability of ice-snow tourism public service, to create multi-industry ice-snow industry cluster area, and to construct the basic framework system of risk prevention and control and management with multisubject participation and other relevant strategies. [ABSTRACT FROM AUTHOR]

Frequency conversion exchanger control is the critical technology of solar water heaters. It can integrate solar thermal technology and heat pump technology and makes solar thermal energy conversion efficiency higher. Based on this research background, the paper first discusses the principle of the technology. Then, it optimizes the system control strategy based on maximizing the utilization of heat energy and the highest efficiency ratio. Finally, the article established a deep learning model of solar radiation based on different time-sharing. The experimental simulation confirmed that the thermal energy control optimization algorithm model proposed in this paper could effectively predict thermal energy exchange. [ABSTRACT FROM AUTHOR]

A Cu-catalyzed asymmetric detrifluoroacetylative aldol addition reaction of 2-fluoro-1,3-diketones/hydrates to aldehydes in the presence of base and chiral bidentate ligand was developed. The reaction was carried out under convenient conditions and tolerated awide range of substrates,resulting in fluorinated quaternary stereogenic α-fluoro-β-hydroxy ketone products with good chemical yields,diastereo-and enantioselectivities. This catalytic asymmetric detrifluoroacetylative aldol addition reaction provides anew approach for the preparation of biologically relevant products containing C-F quaternary stereogenic centers. [ABSTRACT FROM AUTHOR]

A Cu-catalyzed asymmetric detrifluoroacetylative aldol addition reaction of 2-fluoro-1,3-diketones/hydrates to aldehydes in the presence of base and chiral bidentate ligand was developed. The reaction was carried out under convenient conditions and tolerated a wide range of substrates, resulting in fluorinated quaternary stereogenic a-fluoro-β-hydroxy ketone products with good chemical yields, diastereo- and enantioselectivities. This catalytic asymmetric detrifluoroacetylative aldol addition reaction provides a new approach for the preparation of biologically relevant products containing C-F quaternary stereogenic centers. [ABSTRACT FROM AUTHOR]

Herein is reported a study of asymmetric decarboxylative Mannich addition reactions between (Ss)-N-t-butylsulfinyl-3,3,3-trifluoroacetaldimine and Schiff bases derived from various aldehydes and lithium 2,2-diphenylglycinate. These reactions proceed with excellent diastereoselectivities and good chemical yields, providing a practical method for preparation of trifluoromethyl-containing vicinal diamines. The procedures can be conducted under convenient conditions, rendering this approach of high synthetic value. [ABSTRACT FROM AUTHOR]

We have demonstrated that 3,3,3-trifluoroacetaldimine (S)-1 easily reacts with indole derivatives under Friedel-Crafts reactions to provide reliable and generalized access to biologically interesting compounds containing the CF3CH(NH2)-pharmacophoric group. The reactions proceed with high rates and generally excellent yields (>90%) and stereochemical outcomes (99:1 dr). [ABSTRACT FROM AUTHOR]

Here we describe the first attempts to scale up five addition reactions between (SS)-N-tert-butanesulfinyl-(3,3,3)-trifluoroacetaldimine 6 with C-nucleophiles derived from ketones (two examples), glycine Schiff base and heterocycles (two examples). In all cases studied, the observed stereochemical outcome of the scaled up (5.0-25.0 mmol) reactions was lower as compared with the original 0.5 mmol scale. However, the observed worsening of yields and diastereoselectivity was not identical and depended on the reaction conditions and reaction mechanisms. In general, scaling up of the reactions conducted at ambient temperatures presented no problems while the low-temperature (-78 °C) processes would require special equipment to provide strict maintenance of the reaction temperature to obtain the desirable outcome. Importantly, using procedures described here, series of biologically relevant compounds containing 2,2,2-trifluoro-1-(amino)ethyl [CF3CH(NH2)-] pharmacophore unit can be prepared in enantiomerically pure form on up to 5 g scale, allowing their systematic biological studies. [ABSTRACT FROM AUTHOR]