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This paper employs a multidimensional fixed effects model and examines the impact of the digital economy on the performance of firms in traditional industries. We have identified a pattern similar to the "IT productivity paradox" observed in the United States during the 1980s. Using data from A-share listed Chinese firms from 2011–2019, we find that the digital economy significantly reduces the short-term performance of firms by intensifying market competition and increasing adjustment costs. On the contrary, the digital economy improves firms' long-term performance through accumulation of human capital and greater innovation capability. Competitive strategies strengthen the effect of the digital economy on the long-term performance of firms. Additionally, our research demonstrates that technology-intensive firms and small firms experience more pronounced negative effects in the short term but firms with high-tech titles suffer smaller shocks than other technology-intensive firms. These findings presents novel perspectives on the influence of the digital economy on firm performance, offering valuable insights for managers, investors, and policymakers involved in economic decision-making. [ABSTRACT FROM AUTHOR]

In recent years, heat storage technology has attracted wide attention in the fields of renewable energy storage for its relatively high melting point, high heat storage capacity and economy, Na2CO3 and eutectic salt mixtures containing Na2CO3 are promising candidates in the field of solar energy storage. In this paper, a molecular dynamics (MD) simulation of Na2CO3 was conducted with the Born–Mayer potential function. The simulated solid–liquid phase change temperature is 1200 K, and the error is 5.4%. The heat capacity at constant pressure (Cp) is higher in liquid than in solid, the average Cp of solid is 1.45 J/g and that of liquid is 1.79 J/g, and the minimum error is 2.8%. The simulation results revealed the change rules of density and thermal expansion coefficient of Na2CO3 in the process of heating up, and these changes were analyzed by radial distribution functions (RDF) and angular distribution functions (ADF). Moreover, the RDF and ADF results show that the atomic spacing of Na2CO3 increases, the coordination number decreases, and the angle distribution between atoms becomes wider as the temperature rises. Finally, this paper examined the microscopic changes of ions during the phase transition of Na2CO3 from solid to liquid. It is concluded that the angle change of CO 3 2 − in the liquid state is more sharply. This study improves the understanding of the thermodynamic properties and local structure of Na2CO3 and provides theoretical support for Na2CO3 heat storage materials. [ABSTRACT FROM AUTHOR]

This paper presents a new fuzzy time series forecasting model based on technical analysis, affinity propagation (AP) clustering, and a support vector regression (SVR) model. Technical analysis indicators are divided into three categories to construct multivariate fuzzy logical relationships. AP clustering without specifying the number of clusters is used to obtain a suitable partition for the universe of discourse, and the representative exemplars are generated as defuzzied values. The SVR model is employed to explore the unrecognized relationships and modify the forecasts. In addition, the error‐based evaluation criteria are applied to evaluate the methods. The performance of the method is evaluated using the Taiwan Capitalization Weighted Stock Index (TAIEX), Standard & Poor's 500 Index (S&P500), and Dow Jones Industrial Average (DJIA) dataset, and the experimental results demonstrate that the proposed method outperforms some classic models. [ABSTRACT FROM AUTHOR]