Based on the characteristics of urban-rural dual economic structure in China,we build a dynamic endogenous urban-rural dual economic model closely linked to China's reality,and carry out mathematical economics ana...Based on the characteristics of urban-rural dual economic structure in China,we build a dynamic endogenous urban-rural dual economic model closely linked to China's reality,and carry out mathematical economics analysis of optimized conditions for urban and rural sectors. The main results show that:(i) The labor growth rate of urban-rural sectors must be greater than the time discount rate,or else there would be a vicious cycle of diminishing returns in the sectors;(ii) The accumulation rate of physical capital and human capital of urban-rural sectors,and the rate of technological progress,need to be greater than the corresponding depreciation rate plus the time discount rate,otherwise there would be a vicious cycle of diminishing returns in the sectors;(iii) The low accumulation rate in the rural sector,and the occurrence of labor outflow,human capital loss and lack of investment,will expand income gap between urban and rural areas,which is a reason for solidification of urban-rural dual economic structure.展开更多
The urban and rural areas are regarded as two major components of the regional economic system. Only through joint balanced development of the two can we achieve overall economic optimization and social welfare maximi...The urban and rural areas are regarded as two major components of the regional economic system. Only through joint balanced development of the two can we achieve overall economic optimization and social welfare maximization. But the great social division of labor has separated urban areas from rural areas,which casts the shadow of city-oriented theory on cooperative relations between urban and rural areas. Mutual separation between urban and rural settlements and independent development trigger off a range of social problems. We must undertake guidance through rational development path of urban-rural integration,to eliminate the phenomenon of urban-rural dual structure,and promote the sustainable development of population,resources and environment in urban and rural areas as soon as possible.展开更多
The electrochemical carbon dioxide reduction reaction(CO_(2)RR)for highvalue-added products is a promising strategy to tackle excessive CO_(2) emissions.However,the activity of and selectivity for catalysts for CO_(2)...The electrochemical carbon dioxide reduction reaction(CO_(2)RR)for highvalue-added products is a promising strategy to tackle excessive CO_(2) emissions.However,the activity of and selectivity for catalysts for CO_(2)RR still need to be improved because of the competing reaction(hydrogen evolution reaction).In this study,for the first time,we have demonstrated dual atomic catalytic sites for CO_(2)RR from a core-shell hybrid of the covalent-organic framework and the metal-organic framework.Due to abundant dual atomic sites(with CoN_(4)O and ZnN_(4) of 2.47 and 11.05 wt.%,respectively)on hollow carbon,the catalyst promoted catalysis of CO_(2)RR,with the highest Faradic efficiency for CO of 92.6%at-0.8 V and a turnover frequency value of 1370.24 h^(-1) at-1.0 V.More importantly,the activity and selectivity of the catalyst were well retained for 30 h.The theoretical calculation further revealed that CoN_(4)O was the main site for CO_(2)RR,and the activity of and selectivity for Zn sites were also improved because of the synergetic roles.展开更多
Based on urban-rural contrast coefficient,this article designs the agriculture relative development index(ARDI) as indicators measuring the intensity of urban-rural dual structure which is comparable among the countri...Based on urban-rural contrast coefficient,this article designs the agriculture relative development index(ARDI) as indicators measuring the intensity of urban-rural dual structure which is comparable among the countries of the world.This article calculates ARDI of 40 countries from 1980 to 2004.The result shows that ARDI in the developed countries and most of the middle-income countries are rising and yet there are declines in most of the low-income countries.The result also showed that most countries' ARDI will see a decline at the earlier stage of industrialization,so their dual economic structure will also aggravate and urban-rural gap will widen.With the economic development,the tendency will change and ARDI presents a U-shape change overall.The turning point is when a country becomes a middle-income one.展开更多
Porphyrinoid metal-organic frameworks(MOFs)with dual effective uranium uptake sites were synthesized through combined insitu and post-synthetic method.The MOF10@5 demonstrates the uptake amount of uranium reaches 1476...Porphyrinoid metal-organic frameworks(MOFs)with dual effective uranium uptake sites were synthesized through combined insitu and post-synthetic method.The MOF10@5 demonstrates the uptake amount of uranium reaches 1476 mg/g under visiblelight irradiation.The PN-MOF10@5 with dual uranyl uptake sites yields the amount of extracting uranyl of 1590 mg/g under visible-light irradiation.The density functional theory(DFT)calculations reveal strong interaction between uranyl and dual uranyl effective active sites.These MOFs demonstrate a powerful synthesis strategy for uranium extraction materials with dual effective active sites.展开更多
The purification of low-grade coal-bed methane is extremely important,but challenging,due to the very similar physical properties of CH_(4)and N2.Herein,we proposed a dual polarization strategy by employing triazine a...The purification of low-grade coal-bed methane is extremely important,but challenging,due to the very similar physical properties of CH_(4)and N2.Herein,we proposed a dual polarization strategy by employing triazine and polyfluoride sites to construct polar pores in COF materials,achieving the efficient separa-tion of CH_(4)from N2.As expected,the dual polarized F-CTF-1 and F-CTF-2 exhibit higher CH_(4)adsorption capacity and CH_(4)/N_(2)selectivity than CTF-1 and CTF-2,respectively.Especially,the CH4 uptake capacity and CH_(4)/N_(2)selectivity of F-CTF-2 is 1.76 and 1.42 times than that of CTF-2.This work not only developed promising COF materials for CH4/N_(2)separation,but also provided important guidance for the separation of other adsorbates with similar properties.展开更多
基金Supported by Chongqing Social Science Planning Project(2010YBJJ13)the Fundamental Research Funds for the Central Universities(XDJK2010C103)+1 种基金Humanities and Social Sciences Youth Project,the Ministry of Education(10YJC630205)Chongqing Key Humanities and Social Sciences Project(SWU 0810026)
文摘Based on the characteristics of urban-rural dual economic structure in China,we build a dynamic endogenous urban-rural dual economic model closely linked to China's reality,and carry out mathematical economics analysis of optimized conditions for urban and rural sectors. The main results show that:(i) The labor growth rate of urban-rural sectors must be greater than the time discount rate,or else there would be a vicious cycle of diminishing returns in the sectors;(ii) The accumulation rate of physical capital and human capital of urban-rural sectors,and the rate of technological progress,need to be greater than the corresponding depreciation rate plus the time discount rate,otherwise there would be a vicious cycle of diminishing returns in the sectors;(iii) The low accumulation rate in the rural sector,and the occurrence of labor outflow,human capital loss and lack of investment,will expand income gap between urban and rural areas,which is a reason for solidification of urban-rural dual economic structure.
基金Supported by Key Research Base Foundation of Research Center for Information Industry Development of Shaanxi ProvinceProject of Shaanxi Provincial Department of Education ( 11JK0053)
文摘The urban and rural areas are regarded as two major components of the regional economic system. Only through joint balanced development of the two can we achieve overall economic optimization and social welfare maximization. But the great social division of labor has separated urban areas from rural areas,which casts the shadow of city-oriented theory on cooperative relations between urban and rural areas. Mutual separation between urban and rural settlements and independent development trigger off a range of social problems. We must undertake guidance through rational development path of urban-rural integration,to eliminate the phenomenon of urban-rural dual structure,and promote the sustainable development of population,resources and environment in urban and rural areas as soon as possible.
基金Q.Xu acknowledges financial support from the Natural Science Foundation of Shanghai(20ZR1464000)G.Zeng is grateful for the support from the National Natural Science Foundation of China(21878322,22075309)the Science and Technology Commission of Shanghai(19ZR1479200).The authors also thank the Shanghai Synchrotron Radiation Facility for XAFS measurements at Beamline BL14w1.
文摘The electrochemical carbon dioxide reduction reaction(CO_(2)RR)for highvalue-added products is a promising strategy to tackle excessive CO_(2) emissions.However,the activity of and selectivity for catalysts for CO_(2)RR still need to be improved because of the competing reaction(hydrogen evolution reaction).In this study,for the first time,we have demonstrated dual atomic catalytic sites for CO_(2)RR from a core-shell hybrid of the covalent-organic framework and the metal-organic framework.Due to abundant dual atomic sites(with CoN_(4)O and ZnN_(4) of 2.47 and 11.05 wt.%,respectively)on hollow carbon,the catalyst promoted catalysis of CO_(2)RR,with the highest Faradic efficiency for CO of 92.6%at-0.8 V and a turnover frequency value of 1370.24 h^(-1) at-1.0 V.More importantly,the activity and selectivity of the catalyst were well retained for 30 h.The theoretical calculation further revealed that CoN_(4)O was the main site for CO_(2)RR,and the activity of and selectivity for Zn sites were also improved because of the synergetic roles.
基金Under the auspices of the Key Project of National Natural Science Foundation of China (Grant no. 40635029)
文摘Based on urban-rural contrast coefficient,this article designs the agriculture relative development index(ARDI) as indicators measuring the intensity of urban-rural dual structure which is comparable among the countries of the world.This article calculates ARDI of 40 countries from 1980 to 2004.The result shows that ARDI in the developed countries and most of the middle-income countries are rising and yet there are declines in most of the low-income countries.The result also showed that most countries' ARDI will see a decline at the earlier stage of industrialization,so their dual economic structure will also aggravate and urban-rural gap will widen.With the economic development,the tendency will change and ARDI presents a U-shape change overall.The turning point is when a country becomes a middle-income one.
基金supported by the National Natural Science Foundation of China(No.22301108)the Project Startup Foundation for Distinguished Scholars of Jiangsu University(No.4111310026).
文摘Porphyrinoid metal-organic frameworks(MOFs)with dual effective uranium uptake sites were synthesized through combined insitu and post-synthetic method.The MOF10@5 demonstrates the uptake amount of uranium reaches 1476 mg/g under visiblelight irradiation.The PN-MOF10@5 with dual uranyl uptake sites yields the amount of extracting uranyl of 1590 mg/g under visible-light irradiation.The density functional theory(DFT)calculations reveal strong interaction between uranyl and dual uranyl effective active sites.These MOFs demonstrate a powerful synthesis strategy for uranium extraction materials with dual effective active sites.
基金supported by National Key R&D Program of China(No.2022YFA1503300)National Natural Science Foundation of China(Nos.21978138,22035003)+1 种基金the Fundamental Research Funds for the Central Universities(Nankai University)the Haihe Laboratory of Sustainable Chemical Transformations(No.YYJC202101).
文摘The purification of low-grade coal-bed methane is extremely important,but challenging,due to the very similar physical properties of CH_(4)and N2.Herein,we proposed a dual polarization strategy by employing triazine and polyfluoride sites to construct polar pores in COF materials,achieving the efficient separa-tion of CH_(4)from N2.As expected,the dual polarized F-CTF-1 and F-CTF-2 exhibit higher CH_(4)adsorption capacity and CH_(4)/N_(2)selectivity than CTF-1 and CTF-2,respectively.Especially,the CH4 uptake capacity and CH_(4)/N_(2)selectivity of F-CTF-2 is 1.76 and 1.42 times than that of CTF-2.This work not only developed promising COF materials for CH4/N_(2)separation,but also provided important guidance for the separation of other adsorbates with similar properties.
