Quantitative structure-property and structure-activity relationships of the silicon carbide compounds necessitate expressions for the molecular topological features of these compounds. Topological indices are vital devices for investigating chemical compounds to comprehend the fundamental topology of chemical structures. Ev-degree and ve-degree based topological indices are two novel degrees based indices as of late defined in chemical graph theory. Ev-degree and ve-degree based topological indices have been defined as corresponding to their relating partners. In this article, we have computed degree based topological indices namely ev-degree Zagreb type index, ev-degree Randic index, ve-degree atom-bond connectivity index, ve-degree geometric-arithmetic index, ve-degree harmonic index, and ve degree sum-connectivity (ve-χ) based on ev-degree and ve-degree for silicon carbide Si₂C₃-II[p, q].

As a crucial tool for exploring and characterizing the structure properties of the molecular graphs, spectrum analysis and computation are flourishing in recent year. Let L_n be obtained from the transformation of the graph $L_n^{6,4},$ which obtained by attaching crossed four-membered rings to the terminal of crossed phenylenes. In this article, we first determine the (normalized) Laplacian spectra of L_n, then obtain its (multiplicative degree) Kirchhoff index and complexity corresponding to L_n. Finally, by comparing with its Wiener index and Gutman index, we are pleased to find that the (multiplicative degree) Kirchhoff index of L_n is nearly one quarter of its (Gutman) Wiener index. Graphical Abstract

Small- and medium-sized enterprises (SMEs) are considered to have potential innovation capabilities and can create new market opportunities. Venture capital can financially support entrepreneurial activities for economic growth and governs and nurtures the growth of the SMEs. The aim of this study is to investigate the influence mechanism of venture capital on the development of SMEs in agri-food industry. Based on the enterprise growth theory, this study constructed an evaluation model, consisting of technological innovation, profitability, development capability, and solvency, to examine the effect of venture capital on the growth of agricultural SMEs. Using data of 40 agricultural SEMs from the SME and ChiNext boards in China, the empirical analysis has been conducted with the multivariate regression analysis method. The results show that the venture capital can significantly improve the technology innovation, profitability, and growth ability of SMEs. For the solvency of SMEs, the promoting role of venture capital is not obvious. Finally, the practical implications of this study for venture capitalists, entrepreneurs, and regulators are discussed.

The original radial VRS super-efficiency model in DEA excludes the DMU under evaluation from the reference set. However, it must lead to the problem of infeasibility specifically when the DMU under consideration is at the extremity of the frontier. In this paper, a modified nonradial VRS super-efficiency model is established. The super-efficiency model in the presence of nonradial measurement still maintains some good properties, and the original radial VRS super-efficiency model infeasibility can also be detected through it. Our model with nonradial measurement can help decision makers allocate input resources and arrange production activities because it finds an efficient benchmark DMU, which is different from the reference DMU under radial measurement.

Based on index, using kernel density estimation, Markov chain transition probability matrix, and survival analysis method, this paper analyzes the dynamics of Chinese export comparative advantage from 2001 to 2020 and draws the following conclusions. Firstly, after 20 years of export trade development, although the comparative advantage of a few commodities of China has weakened and comparative disadvantage has increased, the comparative advantage of most commodities is improving, and the overall distribution of comparative advantage remained unchanged. Secondly, the stability of Chinese comparative advantage is higher than liquidity, and liquidity as a whole shows a good trend. In addition, the viability of Chinese commodities with comparative advantage has performed well in the past 20 years. Therefore, China should optimize export mode based on comparative advantage.

Considering the coexistence of cold chain agro-products and ordinary agro-products in the market, the research object is the cold chain logistics subsidy. It is designed that a supply chain system consisting of duopoly upstream agro-products suppliers and a downstream agro-products retailer for research. The mechanism of cold chain logistics subsidy is studied by analyzing the influence of cold chain subsidy on pricing behavior and cold chain decision-making of cold chain agro-products and ordinary agro-products. Based on the decentralized decision-making model without government subsidy, a differential pricing model for cold chain agro-products and ordinary agro-products with government subsidy is established in order to reduce the cost of cold chain agro-products. The optimal pricing strategy of two agro-products suppliers and their downstream retailer can be obtained by solving this problem. The research finds that differential pricing caused by government subsidy can achieve profit Pareto improvement of suppliers, retailer, and supply chain system of cold chain agro-products, but cannot achieve the optimal profit of the whole supply chain. Therefore, in view of the loss of supply chain efficiency caused by decentralized decision-making, the Shapley value method is used to make coordination, and the contract coordination mechanism is designed. Finally, the sensitivity of parameters is analyzed by a numerical example.