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
With the continuous development of political, economic,social, empty nesters and more problems, it is not a simple personal issues, has become urgent to break the social proposition.This paper intr~,duces the concepts...With the continuous development of political, economic,social, empty nesters and more problems, it is not a simple personal issues, has become urgent to break the social proposition.This paper intr~,duces the concepts at the same time,Further analysis of the current situation empty-nesters of the problem and sort out the history of urban-rural dual structure,Finally, find information put forward some countermeasures and suggestions.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
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
Dual-asymmetric poly（vinylidene fluoride） （PVDF） separators have been fabricated by thermally induced phase separation with dimethyl sulfone （DMSO2） and glycerol as mixed diluents. The separators have a porous b...Dual-asymmetric poly（vinylidene fluoride） （PVDF） separators have been fabricated by thermally induced phase separation with dimethyl sulfone （DMSO2） and glycerol as mixed diluents. The separators have a porous bulk with large interconnected pores （-1.0 μm） and two surfaces with small pores （-30 nm）. This dual-asymmetric porous structure endows the separators with higher electrolyte uptake amount and rapider uptake rate, as well as better electrolyte retention ability than the commercialized Celgard 2400. The separators even maintain their dimensional stability up to 160 ℃, at which temperature the surface pores close up, leading to a dramatic decrease of air permeability. The electrolyte filled separators also show high ion conductivity （1.72 mS.cm-1） at room temperature. Lithium iron phosphate （LiFePO4）/lithium （Li） cells using these separators display superior discharge capacity and better rate performance as compared with those from the commercialized ones. The results provide new insight into the design and development of separators for high-performance lithium ion batteries with enhanced safety.展开更多
The severe shuttle effect problem of soluble polysulfides greatly hinders the development of long-life lithium-sulfur(Li-S)batteries,which can be improved by separator modification.This study develops a bilayer separa...The severe shuttle effect problem of soluble polysulfides greatly hinders the development of long-life lithium-sulfur(Li-S)batteries,which can be improved by separator modification.This study develops a bilayer separator based on an effective surface and structure dual modification strategy.This bilayer separator(named as TCNFs/SPNFs)is constructed by the integration of a carbon-based nanofiber layer(surface modification layer)with a polymer-based nanofiber layer(structure modification layer)through a facile electrospinning process.The excellent electrolyte wettability of the nanofibers accelerates lithium-ion migration,while the good electronic conductivity of the carbon layer facilitates fast electron conduction.The TiO_(2)and SiO_(2)nanoparticles embedded in the separator provide abundant active sites for immobilizing the polysulfides.Owing to these synergistic effects,this multi-functional separator helps inhibit the shuttling problem and thus enhances the active sulfur utilization.The as-prepared battery with the TCNFs/SPNFs separator delivers significantly enhanced the electrochemical performances,producing a low capacity decay rate of 0.061%per cycle at 1 C over 1000 cycles and an admirable rate capacity of 886.7 mAh g^(-1)at 2 C.Even with a high sulfur loading of 4.8 mg cm^(-2),a remarkable areal capacity of 6.0 mAh cm^(-2)is attained.This work is believed to provide a promising strategy to develop novel separators for high-performance Li-S batteries.展开更多
Urban and rural dual structure in Western China is obvious.The economic development of the central cities is relatively quick while that of the rural areas is lagging behind.The speeding up of urbanization contributes...Urban and rural dual structure in Western China is obvious.The economic development of the central cities is relatively quick while that of the rural areas is lagging behind.The speeding up of urbanization contributes to the intensively uncoordinated development of urban and rural areas.Besides,the eco-fragile environment,shortage of available water resources,adverse geographic location,and relatively backward social economy restrict the development of urbanization in Western China.However,Western China also has the advantages of backwardness.This paper analyzes the present situation and development trend of urbanization in Western China.The results show that Western China has basically formed a development pattern with"industry promotes agriculture and urban leads to village".Therefore,combined with the present situation of Western China,this paper describes and analyzes the opportunities and challenges that may appear in the process of urbanization in Western China,puts forward the development pattern in which urban and rural areas can gain mutual support and co-development,and provides related recommendations.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.
文摘With the continuous development of political, economic,social, empty nesters and more problems, it is not a simple personal issues, has become urgent to break the social proposition.This paper intr~,duces the concepts at the same time,Further analysis of the current situation empty-nesters of the problem and sort out the history of urban-rural dual structure,Finally, find information put forward some countermeasures and suggestions.
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financially supported by the National Natural Science Foundation of China(Nos.21174124 and 21534009)
文摘Dual-asymmetric poly（vinylidene fluoride） （PVDF） separators have been fabricated by thermally induced phase separation with dimethyl sulfone （DMSO2） and glycerol as mixed diluents. The separators have a porous bulk with large interconnected pores （-1.0 μm） and two surfaces with small pores （-30 nm）. This dual-asymmetric porous structure endows the separators with higher electrolyte uptake amount and rapider uptake rate, as well as better electrolyte retention ability than the commercialized Celgard 2400. The separators even maintain their dimensional stability up to 160 ℃, at which temperature the surface pores close up, leading to a dramatic decrease of air permeability. The electrolyte filled separators also show high ion conductivity （1.72 mS.cm-1） at room temperature. Lithium iron phosphate （LiFePO4）/lithium （Li） cells using these separators display superior discharge capacity and better rate performance as compared with those from the commercialized ones. The results provide new insight into the design and development of separators for high-performance lithium ion batteries with enhanced safety.
基金supported by the National Natural Science Foundation of China(Grant Nos.51975218 and U22A20193)the Natural Science Foundation of Guangdong Province(Grant No.2021A1515010642)+3 种基金Guangdong-Hong Kong Joint Innovation Project of Guangdong Province(Grant No.2021A0505110002)Guangdong-Foshan Joint Foundation(Grant No.2021B1515120031)the Innovation Group Project of Foshan(Grant No.2120001010816)the S&T Innovation Projects of Zhuhai City(Grant No.ZH01110405180034PWC)。
文摘The severe shuttle effect problem of soluble polysulfides greatly hinders the development of long-life lithium-sulfur(Li-S)batteries,which can be improved by separator modification.This study develops a bilayer separator based on an effective surface and structure dual modification strategy.This bilayer separator(named as TCNFs/SPNFs)is constructed by the integration of a carbon-based nanofiber layer(surface modification layer)with a polymer-based nanofiber layer(structure modification layer)through a facile electrospinning process.The excellent electrolyte wettability of the nanofibers accelerates lithium-ion migration,while the good electronic conductivity of the carbon layer facilitates fast electron conduction.The TiO_(2)and SiO_(2)nanoparticles embedded in the separator provide abundant active sites for immobilizing the polysulfides.Owing to these synergistic effects,this multi-functional separator helps inhibit the shuttling problem and thus enhances the active sulfur utilization.The as-prepared battery with the TCNFs/SPNFs separator delivers significantly enhanced the electrochemical performances,producing a low capacity decay rate of 0.061%per cycle at 1 C over 1000 cycles and an admirable rate capacity of 886.7 mAh g^(-1)at 2 C.Even with a high sulfur loading of 4.8 mg cm^(-2),a remarkable areal capacity of 6.0 mAh cm^(-2)is attained.This work is believed to provide a promising strategy to develop novel separators for high-performance Li-S batteries.
基金financially supported by the"Strategy and Policies on Environment and Development in Western China" project of "China Council for International Cooperation on Environment and Development(CCICED)"
文摘Urban and rural dual structure in Western China is obvious.The economic development of the central cities is relatively quick while that of the rural areas is lagging behind.The speeding up of urbanization contributes to the intensively uncoordinated development of urban and rural areas.Besides,the eco-fragile environment,shortage of available water resources,adverse geographic location,and relatively backward social economy restrict the development of urbanization in Western China.However,Western China also has the advantages of backwardness.This paper analyzes the present situation and development trend of urbanization in Western China.The results show that Western China has basically formed a development pattern with"industry promotes agriculture and urban leads to village".Therefore,combined with the present situation of Western China,this paper describes and analyzes the opportunities and challenges that may appear in the process of urbanization in Western China,puts forward the development pattern in which urban and rural areas can gain mutual support and co-development,and provides related recommendations.
