Resource constraints and firm innovation:When less is more?

This paper explores the relationship between resource constraints and innovation of new firms.Drawing upon the relevant literature,we incorporate resource constraints as the antecedent to the bricolage-innovation link.Compared to prior studies that treated resource constraints as a one-dimensional variable,we operationalize it along two dimensions:knowledge constraints and financial constraints.Our argument posits that knowledge constraints and financial constraints act as catalysts for innovation in new firms,with bricolage serving as a mediating role.To test our hypotheses,we conducted a survey involving 183 entrepreneurs in the United States.The data analysis demonstrates that bricolage fully mediates the relationship between knowledge con‐straints and innovation and partially mediates the relationship between financial constraints and innovation.Theoretical and practical implications are discussed.

Digital economy,industrial structure,and carbon emissions:An empirical study based on a provincial panel data set from China

This paper uses the mediation effect and a spatial panel model using panel data from 30 provinces in China from 2011 to 2019 to study the relationship between the digital economy,industrial structure,and carbon emission.The research results show that the development of digital economy can effectively promote the reduction of carbon emissions.The development of the digital economy has a significant role in promoting the rationalization of the industrial structure.The digital economy not only directly suppresses carbon emissions,but also indirectly has a significant inhibitory effect on carbon emissions by promoting the rationalization and improvement of the industrial structure.The development of the digital economy suppresses the optimization of the industrial structure.The improvement of industrialization has hindered the industrialization process.It is necessary to strengthen research and development into digital technology and enhance the capacity of the digital economy to promote carbon emissions reduction.

Educational divergence among urban residents and migrant workers: Evidence from China

While the Harris-Todaro model is a traditional approach used in researching the urban-rural dichotomy,it fails to explain families’goals to maximize their current utility in terms of intertemporal decision-making con‐ditions.To fill this gap,in this paper,an urban-rural dichotomy model involving labor migration and educa‐tion is established,in which it is assumed that family utility derives from consumption and children’s educa‐tional achievement.The steady-state path derived through the Bellman equation suggests that increasing edu‐cational investment and family education intensity leads to a significant urban-rural difference in children’s educational achievement.Compared with the traditional Harris-Todaro model,the transversality condition is loosened in this model,while the unavailability of loans constrains migrant families.Four hypotheses are made and tested using an empirical study.An ordinary least squares regression was used in the analysis,but due to the endogeneity caused by missing variables,the instrumental variable method and two-stage least squares regression were used.The results demonstrate that the household registration system can explain 44.5%of the educational achievement difference,and the initial difference is inflated 4.73 times after nine years of compulsory education.This divergence could increase the differences caused by household registra‐tion status,resulting in larger income gaps and intergenerational heredity of identities.

Forecasting China's primary energy demand based on an improved AI model

An improved energy demand forecasting model is built based on the autoregressive distributed lag(ARDL) bounds testing approach and an adaptive genetic algorithm(AGA) to obtain credible energy demand forecasting results. The ARDL bounds analysis is first employed to select the appropriate input variables of the energy demand model. After the existence of a cointegration relationship in the model is confirmed, the AGA is then employed to optimize the coefficients of both linear and quadratic forms with gross domestic product, economic structure, urbanization,and technological progress as the input variables. On the basis of historical annual data from1985 to 2015, the simulation results indicate that the proposed model has greater accuracy and reliability than conventional optimization methods. The predicted results of the proposed model also demonstrate that China will demand approximately 4.9, 5.6, and 6.1 billion standard tons of coal equivalent in 2020, 2025, and 2030, respectively.

Piston Problems of Two-Dimensional Chaplygin Gas

In this paper,the authors study the piston problem for the unsteady two-dimensional Euler system for a Chaplygin gas.The angle of the piston is allowed to vary in a wide range.The piston can be pushed forward into the static gas,or pulled back from the gas.The global existence of solution to the piston problem with any initial speed is established,and the structures of the global solutions are clearly described.The authors find that for the proceeding piston problem the front shock can be detached,attached or even adhere to the surface of the piston depending on the parameters of the flow and the piston;while for the receding problem the front rarefaction wave is always detached and the concentration will never occur.

High Speed Flight and Partial Differential Equations

Aircraft comes out at the beginning of the last century. Accompanied by the progress of high speed flight the theory of partial differential equations has been greatly developed. This paper gives a brief review on the history of applications of partial differential equations to the study of supersonic flows arising in high speed flight.

Generalized Tricomi Problem for a Quasilinear Mixed Type Equation

In this paper,the Tricomi problem and the generalized Tricomi problem for a quasilinear mixed type equation are studied.The coefficients of the mixed type equation are discontinuous on the line,where the equation changes its type.The existence of solution to these problems is proved.The method developed in this paper can be used to study more difficult problems for nonlinear mixed type equations arising in gas dynamics.