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980 results on '"Yang, Yunxia"'

18. Study on the Influencing Factors of the Competitive Network Pattern of Cobalt Industry Chain Trade in the Context of Big Data Analysis

Author

Yang Yunxia and Wang Ruibing

Subjects
cobalt industry chain, trade competition network pattern, time series model, influence factors, 62-07, Mathematics, QA1-939
Abstract

The article proposes a time series model to explore the influencing factors of the cobalt industry chain trade competition network pattern. By analyzing the current situation of the evolution of the cobalt industry chain trade network, the relevant variables are selected. The data are described based on the overview of the relevant algorithmic research of the time series model. Finally, the model based on the time series data is empirically tested. The unit root is verified to be in an unsteady state by first-order differencing, and the p-values all have a probability of accepting the original hypothesis greater than 0. After the second-order differencing ADF test, all the series are smooth and all of them are second-order monotonic. After the cointegration test, it was found that the residual series is smooth at the 5% critical level, and there is a cointegration relationship.

Published
2024
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19. Study on the factors influencing the evolution mechanism of cobalt trade network from the perspective of national competition

Author

Yang Yunxia and Guo Yaoqi

Subjects
national competitiveness, cobalt trade, trade network, network evolution mechanism, qap regression model, 62j05, Mathematics, QA1-939
Abstract

In order to enhance national competitiveness while ensuring the rational operation of world trade activities, the highly internationalized development of cobalt trade is promoted. This paper analyzes the current situation of world cobalt trade through the collection and collation of trade network data. That is, each node on the network represents an activity subject, and the relationship between nodes and nodes exists in terms of commodity demand and supply, reflecting the network Spatio-temporal divergence characteristics of global commodity trade. By measuring the topological network indicators such as density, point degree, intermediary centrality, and proximity to the center, the influence of a country in the trade network and whether it occupies the central position can be more clearly defined, effectively capturing the strength of the relationship between the nodes in the world trade network and facilitating the understanding of the evolution mechanism of the world trade network, and using the QAP regression model to calculate the relationship and trade volume between two countries that affect the trade connection. The results of the study show that China’s cobalt production in 2021 is 2,105 tons, down 8.5% year-on-year. With the passage of time, the overall scale of the international trade network of bauxite is growing, the number of countries involved in the trade is increasing, the trade volume is growing, and the trade relationship between countries is gradually increasing, which reflects the good development trend of global bauxite trade.

Published
2024
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38. Fabrication of two multifunctional phosphorus–nitrogen flame retardants toward improving the fire safety of epoxy resin

Author

Yang Yunxia and Xiao Dan

Subjects
epoxy resin, flame retardancy, trapping effect, diluting action, transparency, Polymers and polymer manufacture, TP1080-1185
Abstract

To improve the fire safety of epoxy resin (EP), two novel phosphorus–nitrogen flame retardants, which named as diphenyl allylphosphoramidate (DPCA) and N-allyl-P, P-diphenylphosphinic amide (DCA), were synthesized by acyl chloride reaction and introduced into EP for fabricating EP composites. The combustion tests showed that incorporation of 5 wt% DPCA or 5 wt% DCA into EP led to the exceptional limited oxygen index (LOI) value (27.1% or 31.6%). Besides, the peak of heat release rate of EP-5 wt% DPCA and EP-5 wt% DCA was reduced by 40.69% and 36.69%, respectively, compared to pure EP. The enhanced fire resistance of EP was ascribed to the trapping effect of fillers in the gas phase and the charring effect in the condensed phase. Furthermore, ultraviolet-visible spectra revealed that both EP-5 wt% DPCA and EP-5 wt% DCA have considerable transparency. This study is expected to broaden the application of EP in the industrial area.

Published
2022
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