A prominent contradiction between supply and demand of water resources has restricted local development in social and economic aspects of Zhangye City,located in a typical arid region of China.Our study quantified the...A prominent contradiction between supply and demand of water resources has restricted local development in social and economic aspects of Zhangye City,located in a typical arid region of China.Our study quantified the Water Resource Stress Index(WRSI)from 2003 to 2017 and examined the factors of population,urbanization level,GDP per capita,Engel coefficient,and water consumption per unit of GDP by using the extended stochastic impact by regression on population,affluence and technology(STIRPAT)model to find the key factors that impact WRSI of Zhangye City to relieve the pressure on water resources.The ridge regression method is applied to improve this model to eliminate multicollinearity problems.The WRSI system was developed from the following three aspects:water resources utilization(WR),regional economic development water use(WU),and water environment stress(WE).Results show that the WRSI index has fallen from 0.81(2003)to 0.17(2017),with an average annual decreased rate of 9.8%.Moreover,the absolute values of normalized coefficients demonstrate that the Engel coefficient has the largest positive contribution to increase WRSI with an elastic coefficient of 0.2709,followed by water consumption per unit of GDP and population with elastic coefficients of 0.0971 and 0.0387,respectively.In contrast,the urbanization level and GDP per capita can decrease WRSI by−0.2449 and−0.089,respectively.The decline of WRSI was attributed to water-saving society construction which included the improvement of water saving technology and the adjustment of agricultural planting structures.Furthermore,this study demonstrated the feasibility of evaluating the driving forces affecting WRSI by using the STIRPAT model and ridge regression analysis.展开更多
Based on several typical domestic and foreign driving cycles, the energy usage efficiency of the EVs-XL 2000 type electric vehicle (EV) is analyzed. The energy usage efficiency of EVs and the evaluation index of elect...Based on several typical domestic and foreign driving cycles, the energy usage efficiency of the EVs-XL 2000 type electric vehicle (EV) is analyzed. The energy usage efficiency of EVs and the evaluation index of electromotor efficiency are studied. The concepts of "interval usage percentage of energy efficiency" and "exertion degree of energy efficiency" of electromotor are presented. The effects of driving cycles on the distribution of the running status of electromotor and the efficiency are investi-gated. The efficiency of electromotor and the trend of average driving force at different driving cycles are discussed. The exertion degree of energy efficiency and the total power train efficiency of the EVs-XL 2000 type electric vehicle at typical driving cycles are analyzed and calculated. The result indicates that the driving cycle engenders a big influence on the exertion degree of electromotor energy efficiency at different driving cycles. Dissimilar driving cycles result in different efficiency distributions of electromotor, the control system as well as the average driving force and driving range are variable.展开更多
基金the Natural Science Foundation of Gansu Province,China(Grant No.18JR3RA385)the National Natural Science Foundation of China(Grant No.41801079)The authors would like to thank the editors and anonymous reviewers for their detailed and constructive comments,which helped to significantly improve the manuscript.
文摘A prominent contradiction between supply and demand of water resources has restricted local development in social and economic aspects of Zhangye City,located in a typical arid region of China.Our study quantified the Water Resource Stress Index(WRSI)from 2003 to 2017 and examined the factors of population,urbanization level,GDP per capita,Engel coefficient,and water consumption per unit of GDP by using the extended stochastic impact by regression on population,affluence and technology(STIRPAT)model to find the key factors that impact WRSI of Zhangye City to relieve the pressure on water resources.The ridge regression method is applied to improve this model to eliminate multicollinearity problems.The WRSI system was developed from the following three aspects:water resources utilization(WR),regional economic development water use(WU),and water environment stress(WE).Results show that the WRSI index has fallen from 0.81(2003)to 0.17(2017),with an average annual decreased rate of 9.8%.Moreover,the absolute values of normalized coefficients demonstrate that the Engel coefficient has the largest positive contribution to increase WRSI with an elastic coefficient of 0.2709,followed by water consumption per unit of GDP and population with elastic coefficients of 0.0971 and 0.0387,respectively.In contrast,the urbanization level and GDP per capita can decrease WRSI by−0.2449 and−0.089,respectively.The decline of WRSI was attributed to water-saving society construction which included the improvement of water saving technology and the adjustment of agricultural planting structures.Furthermore,this study demonstrated the feasibility of evaluating the driving forces affecting WRSI by using the STIRPAT model and ridge regression analysis.
基金Supported by the National High Technology Research and Development Program of China ("863" Program) (Grant No. 2006AA11A112)the Leading Academic Discipline Project of Beijing Municipal Commission of Education
文摘Based on several typical domestic and foreign driving cycles, the energy usage efficiency of the EVs-XL 2000 type electric vehicle (EV) is analyzed. The energy usage efficiency of EVs and the evaluation index of electromotor efficiency are studied. The concepts of "interval usage percentage of energy efficiency" and "exertion degree of energy efficiency" of electromotor are presented. The effects of driving cycles on the distribution of the running status of electromotor and the efficiency are investi-gated. The efficiency of electromotor and the trend of average driving force at different driving cycles are discussed. The exertion degree of energy efficiency and the total power train efficiency of the EVs-XL 2000 type electric vehicle at typical driving cycles are analyzed and calculated. The result indicates that the driving cycle engenders a big influence on the exertion degree of electromotor energy efficiency at different driving cycles. Dissimilar driving cycles result in different efficiency distributions of electromotor, the control system as well as the average driving force and driving range are variable.
