Toughness and A{\alpha}-spectral radius in graphs

Let $\alpha\in[0,1)$, and let $G$ be a connected graph of order $n$ with $n\geq f(\alpha)$, where $f(\alpha)=6$ for $\alpha\in[0,\frac{2}{3}]$ and $f(\alpha)=\frac{4}{1-\alpha}$ for $\alpha\in(\frac{2}{3},1)$. A graph $G$ is said to be $t$-tough if $|S|\geq tc(G-S)$ for each subset $S$ of $V(G)$ with $c(G-S)\geq2$, where $c(G-S)$ is the number of connected components in $G-S$. The $A_{\alpha}$-spectral radius of $G$ is denoted by $\rho_{\alpha}(G)$. In this paper, it is verified that $G$ is a 1-tough graph unless $G=K_1\vee(K_{n-2}\cup K_1)$ if $\rho_{\alpha}(G)\geq\rho_{\alpha}(K_1\vee(K_{n-2}\cup K_1))$, where $\rho_{\alpha}(K_1\vee(K_{n-2}\cup K_1))$ equals the largest root of $x^{3}-((\alpha+1)n+\alpha-3)x^{2}+(\alpha n^{2}+(\alpha^{2}-\alpha-1)n-2\alpha+1)x-\alpha^{2}n^{2}+(3\alpha^{2}-\alpha+1)n-4\alpha^{2}+5\alpha-3=0$. Further, we present an $A_{\alpha}$-spectral radius condition for a graph to be a $t$-tough graph.Comment: 11 page

Environmental Finance:An Interdisciplinary Review

Environmental finance has gained considerable attention globally as an emerging interdisciplinary research area. This study uses bibliometric analysis to systematically review major studies on environmental finance-related areas published since the 1970s. Through a bibliometric analysis of 892 environmental finance-related articles sourced from the Web of Science database, we identified the main research streams and illustrated the trending research themes of environmental finance. We find that publications related to environmental finance have increased exponentially over the past decade. Current research streams include corporate and social re- sponsibility (CSR), climate negotiations, natural gas price volatility, national policy, and cost comparisons. Further analysis of the recent five years of literature shows that emerging research topics include climate finance, sustainable finance, firm value, climate risk, and green bonds. Finally, we conclude with a future research agenda for environmental finance

Adaptive CO2 emissions mitigation strategies of global oil refineries in all age groups

Continuous expansion of fossil fuel-based energy infrastructure can be one of the key obstacles in delivering the Paris Agreement goals. The oil refinery is the world's third-largest stationary emitter of greenhouse gases (GHGs), but the historical mapping of the regional-specific refining industry, their CO2 emission patterns, and mitigation potentials remain understudied. This study develops a plant-level, technical-specific, and time-series global refinery CO2 emission inventory, covering 1,056 refineries from 2000 to 2018. The CO2 emissions of the refinery industry were about 1.3 gigatonnes (Gt) in 2018, representing 4% of the total. If current technical specifications continue, the global refineries will cumulatively emit 16.5 Gt of CO2 during 2020–2030. The refineries vary in operation age, refining configuration structure, and geographical location, leading to the demand for specific mitigation strategies, such as improving refinery efficiency and upgrading heavy oil processing technologies, which could potentially reduce global cumulative emissions by 10% during 2020–2030

A Decision Model to Predict the Optimal Size of the Diversified Management Industry from the View of Profit Maximization and Coordination of Industrial Scale

To avoid the risk of single and homogeneous development, China’s coal enterprises have explored a diversified development model and are actively developing coal-based industries such as electric power, coal chemical, coal equipment manufacturing, logistics, and building materials. In previous studies of the diversification strategy, the focus has been placed on the motivation for diversification, the measurement of diversification, and the relationship between diversification and enterprise performance. From an enterprise strategic decision, we predicted the optimal size of each industry by considering the limited enterprise capital, human resources, the synergetic relationship among industrial clusters (mainly the scale coordination), and policy factors. The optimal decision model for diversified industrial management was constructed using linear programming methods. The decision target was to maximize the enterprise’s profit, but to also consider the social and environmental benefits. One of the largest listed coal enterprises in China, China Coal Energy (also a typical diversified enterprise), was selected as a case for analysis. Data were collected from surveys and annual reports from 2010 to 2014. The optimal scales of coal, electric power, chemical, and equipment manufacturing were predicted, and could be used as a reference for future enterprise production decisions. Furthermore, this decision model can be used as a reference for other diversified enterprises

Projecting future carbon emissions from cement production in developing countries

Achieving low-carbon development of the cement industry in the developing countries is fundamental to global emissions abatement, considering the local construction industry’s rapid growth. However, there is currently a lack of systematic and accurate accounting and projection of cement emissions in developing countries, which are characterized with lower basic economic country condition. Here, we provide bottom-up quantifications of emissions from global cement production and reveal a regional shift in the main contributors to global cement CO2 emissions. The study further explores cement emissions over 2020-2050 that correspond to different housing and infrastructure conditions and emissions mitigation options for all developing countries except China. We find that cement emissions in developing countries except China will reach 1.4-3.8 Gt in 2050 (depending on different industrialization trajectories), compared to their annual emissions of 0.7 Gt in 2018. The optimal combination of low-carbon measures could contribute to reducing annual emissions by around 65% in 2050 and cumulative emissions by around 48% over 2020-2050. The efficient technological paths towards a low carbon future of cement industry vary among the countries and infrastructure scenarios. Our results are essential to understanding future emissions patterns of the cement industry in the developing countries and can inform policies in the cement sector that contribute to meeting the climate targets set out in the Paris Agreement

Projecting future carbon emissions from cement production in developing countries

Achieving low-carbon development of the cement industry in the developing countries is fundamental to global emissions abatement, considering the local construction industry’s rapid growth. However, there is currently a lack of systematic and accurate accounting and projection of cement emissions in developing countries, which are characterized with lower basic economic country condition. Here, we provide bottom-up quantifications of emissions from global cement production and reveal a regional shift in the main contributors to global cement CO2 emissions. The study further explores cement emissions over 2020-2050 that correspond to different housing and infrastructure conditions and emissions mitigation options for all developing countries except China. We find that cement emissions in developing countries except China will reach 1.4-3.8 Gt in 2050 (depending on different industrialization trajectories), compared to their annual emissions of 0.7 Gt in 2018. The optimal combination of low-carbon measures could contribute to reducing annual emissions by around 65% in 2050 and cumulative emissions by around 48% over 2020-2050. The efficient technological paths towards a low carbon future of cement industry vary among the countries and infrastructure scenarios. Our results are essential to understanding future emissions patterns of the cement industry in the developing countries and can inform policies in the cement sector that contribute to meeting the climate targets set out in the Paris Agreement

Does diversification help improve the performance of coal companies? Evidence from China’s listed coal companies

As an important component of the natural resources and energy market, China's coal market has experienced a continuous downturn in recent years. Many coal enterprises have been diversifying their businesses in an effort to enhance their corporate performance. Although many studies have examined the relationship between diversification and performance, researchers have not reached a consensus regarding the nature of this relationship. Additionally, to our knowledge, no study has specifically examined this relationship in coal enterprises. In view of China's coal industry characteristics, such as natural resource dependence and state ownership, other industries’ diversified development could not provide good consults for it. In this study, we investigate the relationship between diversification and corporate performance by analyzing the business data of all of China's listed coal enterprises. After determining 35 listed coal enterprises’ main business and the proportion of their profit from the coal business, we choose 10 enterprises as representatives. Correlation and regression analyses including the time-series data analysis and panel data analysis are conducted to examine the relationship between diversification and performance. The results indicate that this relationship varies across firms; we observe nonlinear, positive linear, negative linear, and nonexistent relationships in the sample. Therefore, diversified development is not the “panacea” for the decline of coal enterprise. Enterprise performance is determined by integrated internal and external factors beyond diversification, including the market environment, the industry environment, and policy. Coal enterprises that aim to develop diversification strategy should be cautious. In addition, this study can serve as a reference for other energy enterprises that are planning to diversify their business to improve performance