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Previous literatures have focused on the impact of sectorial urban specialization on energy efficiency. As a future trend of urban specialization, the importance of functional urban specialization (FUS) in improving industrial energy efficiency is ignored. To fill this gap, this study explores the impact of FUS on industrial energy efficiency. Utilizing prefecture-level city data from 2005 to 2017, this paper adopts an extended stochastic frontier analysis (SFA) model to measure industrial energy efficiency. Hierarchical linear model (HLM) is used for the estimation of the nested data with cluster-level and city-level, which reduces the bias by nested estimation. The results show that 1) city-level industrial energy efficiency has increased from 0.4133 in 2005 to 0.4461 in 2017, mainly driven by peripheral cities rather than core cities; 2) FUS has a significantly positive impact on industrial energy efficiency in full sample and peripheral cities; 3) FUS reduces the negative effects of city scale and the positive effects of investment and enhances the positive effects of transportation. In addition, the positive effects of FUS on industrial energy efficiency is significant only at low levels of FUS. Practicable policies to improve industrial energy efficiency in China are suggested and applicable to other emerging economies. • City-level industrial energy efficiency is measured by an extended SFA model. • We demonstrate the mechanism of FUS affecting industrial energy efficiency. • HLM is used to estimate nested data with cluster-level and city-level. • FUS has positive impacts on energy efficiency in full sample and peripheral cities. • Findings are generalizable to other emerging economies. [ABSTRACT FROM AUTHOR]

Coal is the primary fossil fuel in China's energy sector. As the amount of mining continues to increase, the high concentration of dust generated poses a severe threat to equipment and frontline workers. The coupling influence of HCl and temperature on the structure and wettability of coal were conducted by experiments. The phenomenon indicates that the contact angle between coal treated with HCl of different temperatures and water is reduced, the settling distance in an aqueous solution is longer, and the effect is significant with the increase of temperature, demonstrating the acid-thermal coupling solution improves the wettability of coal. Secondly, detailed analysis of coal functional groups and surface element, shows that the percentage of hydrophilic groups increased, such as OH⋯O, free –OH, and hydrophobic groups were destroyed, such as the asymmetric deformation vibration of adjacent H. The L, 'C' , and DOC show an increasing trend, while I first increase and then decrease by analyzing the trends of IR indices of coal. The conclusions prove that the degree of coal deterioration changed after treatment with acid-thermal coupling conditions. The influence mechanism of acid-thermal coupling solution on coal was explored to provide ideas for improving the wettability of coal from the source. • The effect of acid-thermal coupling on the wettability of coal was studied. • The influence of acid-thermal coupling on functional groups in coal was analyzed. • Acid-thermal coupling has an impact on the degree of coal metamorphism. • As The temperature increases, the acid-thermal coupling effect is significant. [ABSTRACT FROM AUTHOR]