Under the background that economy and urbanization of China are gradually entering the stage of high-quality development,clarifying the influence of economic development on urban livability is of significant academic ...Under the background that economy and urbanization of China are gradually entering the stage of high-quality development,clarifying the influence of economic development on urban livability is of significant academic and practical value.In this paper,regarded as one“factor”,livability was introduced into the research framework of production function,and a theoretical model of the impact of economic development on urban livability was established.Based on the panel data of 40 cities in China from 2005 to 2019,the System GMM,panel threshold model and other methods were further adopted to carry out an empirical analysis.The results show that:(1)The livability level of large and medium-sized cities in China from 2005 to 2019 has been rising generally,but they present obvious characteristics of dimensional and spatial differentiation.(2)In general,economic development has an inhibiting effect on the improvement of urban livability,but this logical effect shows obvious heterogeneity in different time periods and diverse city scales.This inhibitory effect is more significant for the cities before entering the new normal phase of economy,and large-scale municipalities and economically-developed provincial capitals(namely Class-A cities).(3)There are significant threshold effects in the impact of economic development on urban livability,where the threshold variables are income level and economic development.With the increase of city dwellers’income,this effect presents an inverted N-shaped nonlinear feature.When the development of economy makes the average wage of employees between 60,000and 80,000 yuan,economic development can significantly improve urban livability.Also,there is a significant single threshold inhibitory effect when economic development is taken as a threshold variable.However,its negative impact shows a law of diminishing marginal efficiency.In addition,a similar threshold effect is found in smaller-scale Class-B cities.The findings of this research can provide some insights for urban planners and 展开更多
The control method for machining non-cylinder pin hole of piston was studied systematically. A new method was presented by embedding giant magnetostrictive material (GMM) into the tool bar proper position. The model i...The control method for machining non-cylinder pin hole of piston was studied systematically. A new method was presented by embedding giant magnetostrictive material (GMM) into the tool bar proper position. The model is established to characterize the relation between control current of coil and deformation of tool rod. A series of tests on deformation of giant magnetostrictive tool bar were done and the results validated the feasibility of the principle. The methods of measuring magne- tostrictive coefficient of rare earth GMM were analyzed. The measuring device with the bias field and prestress was designed. A series of experiments were done to test magnetostrictive coefficient. Experimental results supplied accurate characteristic pa- rameter for designing application device of GMM. The constitution of the developed control system made up of displacement detection and temperature detection for thermal deformation compensation was also introduced. The developed machine tool for boring the non-cylinder pin hole of piston has the micron order accuracy. This control method can be applied to other areas for machining precision or complex parts.展开更多
基金National Natural Science Foundation of China,No.41901205Natural Science Foundation of Jiangsu Province,No.BK20190482。
文摘Under the background that economy and urbanization of China are gradually entering the stage of high-quality development,clarifying the influence of economic development on urban livability is of significant academic and practical value.In this paper,regarded as one“factor”,livability was introduced into the research framework of production function,and a theoretical model of the impact of economic development on urban livability was established.Based on the panel data of 40 cities in China from 2005 to 2019,the System GMM,panel threshold model and other methods were further adopted to carry out an empirical analysis.The results show that:(1)The livability level of large and medium-sized cities in China from 2005 to 2019 has been rising generally,but they present obvious characteristics of dimensional and spatial differentiation.(2)In general,economic development has an inhibiting effect on the improvement of urban livability,but this logical effect shows obvious heterogeneity in different time periods and diverse city scales.This inhibitory effect is more significant for the cities before entering the new normal phase of economy,and large-scale municipalities and economically-developed provincial capitals(namely Class-A cities).(3)There are significant threshold effects in the impact of economic development on urban livability,where the threshold variables are income level and economic development.With the increase of city dwellers’income,this effect presents an inverted N-shaped nonlinear feature.When the development of economy makes the average wage of employees between 60,000and 80,000 yuan,economic development can significantly improve urban livability.Also,there is a significant single threshold inhibitory effect when economic development is taken as a threshold variable.However,its negative impact shows a law of diminishing marginal efficiency.In addition,a similar threshold effect is found in smaller-scale Class-B cities.The findings of this research can provide some insights for urban planners and
基金Project supported by the National Natural Science Foundation of China (No. 50575205) and the Natural Science Foundation of Zheji-ang Province (Nos. Y104243 and Y105686), China
文摘The control method for machining non-cylinder pin hole of piston was studied systematically. A new method was presented by embedding giant magnetostrictive material (GMM) into the tool bar proper position. The model is established to characterize the relation between control current of coil and deformation of tool rod. A series of tests on deformation of giant magnetostrictive tool bar were done and the results validated the feasibility of the principle. The methods of measuring magne- tostrictive coefficient of rare earth GMM were analyzed. The measuring device with the bias field and prestress was designed. A series of experiments were done to test magnetostrictive coefficient. Experimental results supplied accurate characteristic pa- rameter for designing application device of GMM. The constitution of the developed control system made up of displacement detection and temperature detection for thermal deformation compensation was also introduced. The developed machine tool for boring the non-cylinder pin hole of piston has the micron order accuracy. This control method can be applied to other areas for machining precision or complex parts.
