Land use and land cover change as the core of coupled human-environment systems has become a potential field of land change science （LCS） in the study of global environmental change. Based on remotely sensed data of...Land use and land cover change as the core of coupled human-environment systems has become a potential field of land change science （LCS） in the study of global environmental change. Based on remotely sensed data of land use change with a spatial resolution of 1 km × 1 km on national scale among every 5 years, this paper designed a new dynamic regionalization according to the comprehensive characteristics of land use change including regional differentiation, physical, economic, and macro-policy factors as well. Spatial pattern of land use change and its driving forces were investigated in China in the early 21 st century. To sum up, land use change pattern of this period was characterized by rapid changes in the whole country. Over the agricultural zones, e.g., Huang-Huai-Hai Plain, the southeast coastal areas and Sichuan Basin, a great proportion of fine arable land were engrossed owing to considerable expansion of the built-up and residential areas, resulting in decrease of paddy land area in southern China. The development of oasis agriculture in Northwest China and the reclamation in Northeast China led to a slight increase in arable land area in northern China. Due to the ＂Grain for Green＂ policy, forest area was significantly increased in the middle and western developing regions, where the vegetation coverage was substantially enlarged, likewise. This paper argued the main driving forces as the implementation of the strategy on land use and regional development, such as policies of ＂Western Development＂, ＂Revitalization of Northeast＂, coupled with rapidly economic development during this period.展开更多
The decision tree and the threshold methods have been adopted to delineate boundaries and features of water bodies from LANDSAT images. After a spatial overlay analysis and using a remote sensing technique and the wet...The decision tree and the threshold methods have been adopted to delineate boundaries and features of water bodies from LANDSAT images. After a spatial overlay analysis and using a remote sensing technique and the wetland inventory data in Beijing, the water bodies were visually classified into different types of urban wetlands, and data on the urban wetlands of Beijing in 1986, 1991, 1996, 2000, 2002, 2004 and 2007 were obtained. Thirteen driving factors that affect wetland change were selected, and gray correlation analysis was employed to calculate the correlation between each driving factor and the total area of urban wetlands. Then, six major driving factors were selected based on the correlation coefficient, and the contribution rates of these six driving factors to the area change of various urban wetlands were calculated based on canonical correlation analysis. After that, this research analyzed the relationship and mechanism between the main driving factors and various types of wetlands. Five conclusions can be drawn. （1） The total area of surface water bodies in Beijing increased from 1986 to 1996, and gradually decreased from 1996 to 2007. （2） The areas of the river wetlands, water storage areas and pool and culture areas gradually decreased, and its variation tendency is consistent with that of the total area of wetlands. The area of the mining water areas and wastewater treatment plants slightly increased. （3） The six factors of driving forces are the annual rainfall, the evaporation, the quantity of inflow water, the volume of groundwater available, the urbanization rate and the daily average discharge of wastewater are the main factors affecting changes in the wetland areas, and they correlate well with the total area of wetlands. （4） The hydrologic indicators of water resources such as the quantity of inflow water and the volume of groundwater are the most important and direct driving forces that affect the change of the wetland area. These factors have a combined contribution rate of 43.94%. （5） Climate factors such as rainfall and evaporation are external factors that affect the changes in wetland area, and they have a contribution rate of 36.54%. （6） Human activities such as the urbanization rate and the daily average quantity of wastewater are major artificial driving factors. They have an influence rate of 19.52%.展开更多
The pace and scale of China＇s contemporary urbanization are stunning. This paper reviews process and the underlying driving forces of China＇s urbanization between 1949-2015. Contemporary China＇s urbanization has ex...The pace and scale of China＇s contemporary urbanization are stunning. This paper reviews process and the underlying driving forces of China＇s urbanization between 1949-2015. Contemporary China＇s urbanization has experienced four stages, and each has had different driving forces： 1） economic re-construction and industrialization-led urbanization 0949-1977）; 2） economic reform and mar- ket-led urbanization （1978-1995）; 3） economic globalization and the global-local urbanization （1996-2010）; and 4） the land-economy- led urbanization （2010-）. These urbanization processes and driving forces will undoubtedly provide scientific reference and have sig- nificant implications for developing countries, especially African countries, to formulate their urbanization public policies.展开更多
Research into urban expansion patterns and their driving forces is of great significance for urban agglomeration development planning and decision-making.In this paper,we reveal the multi-dimensional characteristics o...Research into urban expansion patterns and their driving forces is of great significance for urban agglomeration development planning and decision-making.In this paper,we reveal the multi-dimensional characteristics of urban expansion patterns,based on the intensity index of the urban expansion,the differentiation index of the urban expansion,the fractal dimension index,the land urbanization rate,and the center of gravity model,by taking the Beijing-Tianjin-Hebei(Jing-Jin-Ji)urban agglomeration as an example.We then build the center of gravity-geographically and temporally weighted regression(GTWR)model by coupling the center of gravity model with the GTWR model.Through the analysis of the temporal and spatial patterns and by using the center of gravity-GTWR model,we analyze the driving forces of the urban land expansion and summarize the dominant development modes and core driving forces of the Jing-Jin-Ji urban agglomeration.The results show that:1)Between 1990 and 2015,the expansion intensity of the Jing-Jin-Ji urban agglomeration showed a down-up-down trend,and the peak period was in 2005-2010.Before 2005,high-speed development took place in Beijing,Tianjin,Baoding,and Langfang;after 2005,rapid development was seen in Xingtai and Handan.2)Although the barycenter of cities in the Jing-Jin-Ji urban agglomeration has shown a divergent trend,the local interaction between cities has been enhanced,and the driving forces of urban land expansion have shown a characteristic of spatial spillover.3)The spatial development mode of the Jing-Jin-Ji urban agglomeration has changed from a dual-core development mode to a multi-core development mode,which is made up of three functional cores:the transportation core in the northern part,the economic development core in the central part,and the investment core in the southern part.The synergistic development between each functional core has led to the multi-core development mode.4)The center of gravity-GTWR model combines the analysis of spatial and temporal nonstationarity with urban spatial interaction,and analyzes the urban land expansion as a space-time dynamic system.The results of this study show that the model is a feasible approach in the analysis of the driving forces of urban land expansion.展开更多
Karst rocky desertification is one of the major ecological and environmental problems that threaten the sustainable development of southwestern China. It is caused by irrational and intensive land-use patterns in kars...Karst rocky desertification is one of the major ecological and environmental problems that threaten the sustainable development of southwestern China. It is caused by irrational and intensive land-use patterns in karst geo-ecological environment. Therefore, it is vital to identify how human forces work on this degraded environment. Based on the soil erosion information in 2000 and remote sensing images of Guanling County collected in 2000 and 2007, four grades of karst rocky desertification data in 14 villages of Guanling County were extracted. Impacts of population, affluence, and other human forces on karst rocky desertification were analyzed using STIRPAT model. The results show that:1) Factors of population and affluence had strong influence on karst rocky desertification. In the STIRPAT model analysis, the population and affluence coefficients were positive, indicating that the increase in population and affluence would lead to more serious desertification. 2) Factors of farmer correlated with karst rocky desertification negatively, especially the way of viewing the relationship between people and nature, and the level of knowledge about rocky desertification. Government behavior was not a significant factor in this analysis. 3) The findings provide evidence that STIRPAT model can be used to analyze the relationship between human driving forces and rocky desertification.展开更多
Air pollution is a serious problem brought by the rapid urbanization and economic development in China, imposing great challenges and threats to population health and the sustainability of the society. Based on the re...Air pollution is a serious problem brought by the rapid urbanization and economic development in China, imposing great challenges and threats to population health and the sustainability of the society. Based on the real-time air quality monitoring data obtained for each Chinese city from 2013 to 2014, the spatiotemporal characteristics of air pollution are analyzed using various exploratory spatial data analysis tools. With spatial econometric models, this paper further quantifies the influences of socioeconomic factors on air quality at both the national and regional scales. The results are as follows： （1） From 2013 to 2014, the percentage of days compliance of urban air quality increased but air pollution deteriorated and the worsening situation in regions with poor air quality became more obvious. （2） Changes of air quality show a clear temporal coupling with regional socioeconomic activities, basically ＂relatively poor at daytime and relatively good at night＂. （3） Urban air pollution shows a spatial pattern of ＂heavy in the east and light in the west, and heavy in the north and light in the south＂. （4） The overall extent and distribution of regional urban air pollution have clearly different characteristics. The formation and evolution of regional air pollution can be basically induced as ＂the pollution of key cities is aggravated--pollution of those cities spreads-- regional overall pollution is aggravated--the key cities lead in pollution governance--regional pollution joint prevention and control is implemented--regional overall pollution is reduced＂. （5） At the national level, energy consumption, industrialization and technological progress are the major factors in the worsening of urban air quality, economic development is a significant driver for the improvement of that quality. （6） Influenced by resources, environment and the development stage, the socioeconomic factors had strongly variable impacts on air quality, in both direction and intensity in different regions. Based on the conclusion, the regional differ- entiation and development idea of the relationship between economic development and en- vironmental changes in China are discussed.展开更多
Changes of cultivated land patterns caused by major water conservation projects are rarely reported. We selected the Three Gorges Reservoir area in China to study the change in area and landscape pattern of the cultiv...Changes of cultivated land patterns caused by major water conservation projects are rarely reported. We selected the Three Gorges Reservoir area in China to study the change in area and landscape pattern of the cultivated land in the head,central, and tail areas of the reservoir that took place between 1992 and 2015;we then studied the spatial distribution of the cultivated land in the three parts of the reservoir;finally, we studied the driving forces behind the changes in the cultivated land. The results derived are as follows.(1) During the construction of the Three Gorges Project(TGP, 1992–2015), the area of cultivated land around the reservoir decreased by30.23 million ha. This reduction occurred in phases:the most severe change in cultivated land occurred during the later stage of the project(2002–2010);only 0.62 million ha of cultivated land did not change between 1992 and 2015.(2) Spatial pattern analysis showed that the cultivated land in the three parts of the reservoir changed from a northern distribution to a southern distribution;thus, the area of cultivated land in the north decreased over the time period. The area of cultivated land in the head and tail areas decreased by varying degrees, while it increased in the central area over the 23 years, indicating that the change in cultivated land showed regional differences.(3) The TGP, the policy of reverting farmland to forest,and urbanization were the main driving factors for the change of cultivated land, but there were differences in their impacts at different stages.(4) According to the patch dynamics of the land cover change, the degree of change gradually intensified during the early and later stages of the project and then stabilized during the operational period. Our research provides scientific support for the protection of cultivated land resources and food security in the reservoir area and for the coordination of social and economic development, which is of great significance to sustainable development in the reservoir area.展开更多
This study applies ArcGIS to analyze the spatiotemporal distribution of cultural sites in the Ill River Valley in northwestern China. It explores relationships between the sites＇ spatiotemporal evolutionary character...This study applies ArcGIS to analyze the spatiotemporal distribution of cultural sites in the Ill River Valley in northwestern China. It explores relationships between the sites＇ spatiotemporal evolutionary characteristics, human history, and the natural environment. The results indicate that the numbers and proportions of the sites, and the frequency of their oc- currence, exhibited an inverted V-shaped change trend during six historical periods. The ＂high in the east and low in the west＂ spatial distribution pattern of the first three periods shifted to the one the ＂high in the west and low in the east＂ during the latter three periods, demonstrating a change in the spatial center of gravity of human activities. The sites were mainly distributed on slopes of grades 1-5, with their proportions increasing from 75% during the Spring and Autumn Period （770 BC-476 BC）-Qin Dynasty （221 BC-207 BC） to 93.75% during the Qing Dynasty-Modern period. The concentrated distribution of site elevations shifted from grades 4-8 during the Spring and Autumn Period-Qin Dynasty, and the Western Han （206 BC-8）-Southern and Northern Dynasties （420-589）, to grades 1-4 during the latter three periods. The number of sites showed a shifting trend from high-elevation mountains and hills to low-elevation plains, and from high slopes to low slopes. In particular, the sites exhibited a special ＂moist＂ evolutionary pattern of migration from middle and upstream areas to downstream areas, as opposed to the migration pattern of sites located in typical arid areas. The study also considered factors influencing the distribution and spatiotemporal evolution of cultural sites, notably, human factors and natural factors.展开更多
Based on the long-term serial NOAA/NDVI dataset during 1983-1999 and SPOT/VGT dataset in 2001, the land use/cover change information in the 13 provinces of northern China was extracted based on the analysis of the cul...Based on the long-term serial NOAA/NDVI dataset during 1983-1999 and SPOT/VGT dataset in 2001, the land use/cover change information in the 13 provinces of northern China was extracted based on the analysis of the cultivated landscape characteristics at first, then the effects of human activities on cultivated land process were explored by GIS and the driving forces of cultivated land change were investigated. The conclusions can be drawn as follows： （1） The constant increase of weak ecological function land as desert and cultivated land and the decrease of the ecological function land of forest and shrub were the main characteristics of the land use/cover change in the 13 provinces from 1983 to 1999, which showed the effects on the ecological adjustment fimction. However, such situations were changed to some extent in the 2000s because of the eco-construction policy of the government. （2） From 1983 to 2001, the Barycenter of cultivated land tended to move from northeast to southwest with the topography and transportation situations being the main influences on the cultivated land distribution. It is found that the cultivated land use intensity decreased noticably with the increase of distance from the main communication arteries. （3） The improvement of the people＇s living standard is closely related with the cultivated land change. The structural adjustment in the agricultural land caused by economic development and the improvement of the people＇s living standard ig an important factor affecting the cultivated land change in northern China from 1983 to 2001展开更多
The decrease of total cultivated area and the lower per capita available arable land resource are now serious problems in Shandong Province, a major agricultural province in China. These problems will become more seri...The decrease of total cultivated area and the lower per capita available arable land resource are now serious problems in Shandong Province, a major agricultural province in China. These problems will become more serious along with the further development of economy. In this paper, based on the statistical information at provincial and county levels, the changes of arable land in Shandong Province and their driving forces during the last 50 years are analyzed. The general changing trends of arable land and per capita available arable land are reducing, and the trends of decrease will continue when the economy is developing. The result of GIS spatial analysis shows that the change of the arable land use in Shandong Province has a regional difference. Eight variables having influences on cultivated land change are analyzed by principal component analysis. The results show that the dynamic development of economy, pressure of social system and progress of scientific techniques in agriculture are the main causes for cultivated land reduction. The principal factors which can be considered as driving forces for arable land change include per capita net living space, total population and per ha grain yield. By using regressive equation, along with analysis on population growth and economic development, cultivated areas in Shandong Province in 2005 and 2010 are predicted respectively. The predicted cultivated areas in Shandong will be 6435.47 thousand hain 2005 and 6336.23 thousand ha in 2010 respectively.展开更多
The Ecological Footprint(EF) equation provides useful accounting to analyze the relationship between human activities and the environment.Knowledge of the specific forces driving EF is not fully understood but the STI...The Ecological Footprint(EF) equation provides useful accounting to analyze the relationship between human activities and the environment.Knowledge of the specific forces driving EF is not fully understood but the STIRPAT model provides a simple framework for decomposing the impact of human activities on environment.We applied the EF model in Sichuan Province,China to assess the impact of human activities.The per capita EF increased by 2 fold in the 14 years between 1995 and 2008,but ecological capacity decreased in the same period,suggesting that the biologically productive area of Sichuan Province is inadequate to sustain human activities.According to the refined STIRPAT model,the hypothesized driving forces of EF include population size(P),GDP per capita(A1),quadratic term of GDP per capita(A2),percentage of GDP from industry(T1) and urbanization rate(T2).However,the multi-collinearity among these drivers could be a substantial problem which may reveal negative effect in the final results.Application of the Ridge Regression(RR) method to fit the STIRPAT model had the advantage of being able to avoid the collinearity among independent variables.The results showed that population is the principal driving force of EF variation in Sichuan Province and that urbanization and industrialization also have a positive association with the EF.Analysis of affluence elasticity(EEA) showed that the relationship betweenEF and economic growth was not curvilinear,suggesting that variation of EF does not follow an Environmental Kuznets Curve relative to economic growth in Sichuan Province.展开更多
By establishing the interpreting elements, and applying supervised classification, the sandy desertific- ation was interpreted and the desertified land areas of the counties in the western Jilin Province in 1986 and i...By establishing the interpreting elements, and applying supervised classification, the sandy desertific- ation was interpreted and the desertified land areas of the counties in the western Jilin Province in 1986 and in 2000 were obtained. Taking Tongyu and Qian’an as examples, the natural driving forces and man-made driving forces were analyzed. The paper comes the conclusions that the material sources and the warming and dry climate are the internal causes of potential land desertification; the irrational human activities, such as destroying forest and reclaiming the grassland, are the external causes of potential land desertification; while more rational human activities, such as planting trees and restoring grassland can reverse the land desertification. Furthermore, the countermeasures and suggestions for the development of agriculture and animal husbandry in the western Jilin Province are put forward.展开更多
Urbanization has both direct and indirect impacts on land use change, and analyzing spatio-temporal characteristics of land use change is essential for understanding these impacts. By comparing Landsat TM images, this...Urbanization has both direct and indirect impacts on land use change, and analyzing spatio-temporal characteristics of land use change is essential for understanding these impacts. By comparing Landsat TM images, this paper examines the changes of land use structure and landscape patterns in Shanghai from 1990 to 2015. It finds that the city doubled in size, with the growth of isolated construction land being most significant among eight land use types. A land use change matrix was established and landscape indices were selected to evaluate the change of spatial structure in Shanghai. In order to identify the main driving forces of city expansion in Shanghai, this research ran partial least square regression models to assess the impact of 10 social-economic factors on land use change of Shanghai from 1990 to 2015. It then conducted bivariate correlation analysis to explore the drivers of change of various land use types: urban settlement, rural settlement and isolated construction land. Besides quantitative analysis, this paper analyzes the influence of policy-dimensional factors in land use change. It concludes with future potential research topics on land use change in a rapidly urbanizing context.展开更多
The land use patterns in Guyuan City,Ningxia Hui Autonomous Region of China,have changed greatly over the years,due to population growth and farming and stock raising development.This study,using 50-year statis-tical ...The land use patterns in Guyuan City,Ningxia Hui Autonomous Region of China,have changed greatly over the years,due to population growth and farming and stock raising development.This study,using 50-year statis-tical data of cultivated land and 14-year spatial data of land use pattern,analyzed the developmental stages,the char-acter,and the spatial variance of farmland in the city,and discussed the driving forces of cultivated land changes based on empirical and conceptual statistical models.First,the change of cultivated land area went through different stages of rapid increase,fluctuating change,decrease and rapid decrease from 1949 to 2004,additionally,social and economic policies in different stages had an important impact on farmland variance.Second,from 1986 to 2000,the quantity of cultivated land increased,but its quality decreased.Third,social and economic factors are determinant factors in culti-vated land transition.Five constructed paths explain cultivated land transition.Factors that have direct or indirect ef-fects on farmland include the economy(Xeco),the population(Xpop),agricultural output(Xagr),and scientific input(Xsci).The sequence of impact was Xeco>Xpop>Xsci>Xagr.Among all these impacts,Xeco was the major positive one,and Xpop was the major negative one.It is urgent to take measures or adopt a policy to stop the vicious cycle in eco-environment and agriculture production.Otherwise,negative patterns of farmland use will increase,and high-quality cultivated land will continue to decline.展开更多
Maqu County is located in the northeast Qinghai-Tibetan Plateau, and it is the main watershed for the Yellow River. The ecosystem there is extremely vulnerable and sensitive to climate change and human activities, whi...Maqu County is located in the northeast Qinghai-Tibetan Plateau, and it is the main watershed for the Yellow River. The ecosystem there is extremely vulnerable and sensitive to climate change and human activities, which have caused significant deterioration of the eco-environment in this region. In order to restore the ecological environment, a government project to restore the grazing areas to grassland was implemented in Maqu County in early 2004. This study evaluates the effects of that restoration project on land use and land cover change （LUCC）, and explores the driving forces of LUCC in Maqu County. In the study we used Landsat images obtained in 1989, 2004, 2009, and 2014 to establish databases of land use and land cover. Then we derived LUCC information by overlaying these layers using GIS software. Finally, we analyzed the main forces responsible for LUCC. The results showed that forests, high-coverage grasslands, and marshes experienced the most significant decreases during 1989–2004, by 882.8 ha, 35,250.4 ha, and 2,753.4 ha, respectively. However, moderate- and low-coverage grasslands and sand lands showed the opposite trend, increasing by 12,529.7 ha, 25,491.0 ha, and 577.5 ha, respectively. LUCC in 2004–2009 showed that ecological degradation slowed compared with 1989？2004. During 2009–2014, high- and moderate-coverage grasslands increased obviously, but low-coverage grasslands, marshes, unused lands, sand lands, and water areas showed the opposite trend. These results suggested that the degradation of the eco-environment was obvious before 2009, showing a decrease in the forests, grasslands, and water areas, and an increase in unused lands. The ecological degradation was reversed after 2009, as was mainly evidenced by increases in high- and mod-erate-coverage grasslands, and the shrinkage rate of marshes decreased obviously. These results showed that the project of restoring grazing lands to grassland had a positive effect on the LUCC. Other major factors that influence the LUCC include increasing temperature, variation in the seasonal frozen soil environment, seasonal overgrazing, and pest and rodent damage.展开更多
Due to the unique geographical location and historical background of Central Asia,the region’s geo-relation networks are complex and changeable.A social network analysis was conducted in this study to visualize the 2...Due to the unique geographical location and historical background of Central Asia,the region’s geo-relation networks are complex and changeable.A social network analysis was conducted in this study to visualize the 20-year evolutionary process of bilateral(diplomatic relations)and multilateral(intergovernmental organization(IGO)connections)networks in Central Asia since 1993.Additionally,a further empirical study determined the significant driving forces of the construction of the geo-relation networks.The results showed that since the independence of the five Central Asian countries,their degree centrality(C,D(ni))values have been increasing,with the index values being the highest for Kazakhstan,followed by Uzbekistan,while the other three countries had relatively low values.The Central Asian countries maintain bilateral relations with post-Soviet nations,neighboring countries,and Western powers,and have gradually deepened and expanded their diplomatic networks.From each state’s perspective,the geostrategic approaches adopted by the five countries were different.Kazakhstan has focused on expanding its bilateral and multilateral relations,while the other Central Asian countries have attempted to increase their influence by joining influential IGOs.Various driving forces,including economic,political,cultural,and geographical factors,have played significant roles in the construction of geo-relation networks in Central Asia.The importance of these factors has changed over time,from political and cultural factors(before 1995)to relations with neighboring countries(1996-2001),and finally to economic power and cultural and religious proximity(after 2002).展开更多
Improving comprehensive agricultural productivity is an important measure to realize agricultural modernization.Based on the data from Jilin Statistical Yearbook,this study analyzed the spatial and temporal characteri...Improving comprehensive agricultural productivity is an important measure to realize agricultural modernization.Based on the data from Jilin Statistical Yearbook,this study analyzed the spatial and temporal characteristics of comprehensive agricultural productivity discrepancy in the main agricultural production areas of Jilin Province,China.The comprehensive agricultural productivity of 25 county-level administrative units were evaluated by a comprehensive index system based on five aspects which included 20 indicators from 2004 to 2017.The pattern of the discrepancy was analyzed by the spatial differentiation indices and spatial convergence theory.The results were as follows:1) the overall comprehensive agricultural productivity was in a ’W-type’ rising trend;2) the discrepancy was in’inverted W-type’ trend;3) the spatial distribution characteristics were mainly discrete plaque and ’inverted V-type’;4) the formation of differences was forced by a combination of internal and external driving forces.Our study demonstrates the effectiveness of rising agricultural productivity and the level of economic and social developments in different counties in Jilin Province.展开更多
This paper presents an integrated study of urban spatial expansion in the Hexi Corridor, Gansu Province, China based on TM, ETM remote sensing data in 1987, 1990, 1995, 2000, 2006 and 2011. The study explores the char...This paper presents an integrated study of urban spatial expansion in the Hexi Corridor, Gansu Province, China based on TM, ETM remote sensing data in 1987, 1990, 1995, 2000, 2006 and 2011. The study explores the characteristics of urban spatial expansion and dynamic mechanism by using expansion speed index, expansion intensity index, compact index, fractal dimension, and extended flexibility index. We built the index system of influencing factors of urban spatial expansion by using the grey incidence model. The results showed that urban spatial expansion rate in the Hexi Corridor has been on the upward trend since 1987. Expansion intensity showed an obvious upward trend, however, the upward trend varied in different urban areas. In addition, the urban structure was loose relatively, but the urban compactness was more obvious. The urban spatial form tended to be simple, and the urban land use tended to become more intensive. Urban spatial expansion experienced several stages: padding internally, external expansion and padding internally. The main driving factors of urban spatial expansion are not the urban water resources and the oasis scale, but one or several factors such as economy, traffic, population, resource and national policy.展开更多
Self-assembly of metal halide perovskite nanocrystals(NCs)into superlattices can exhibit unique collective properties,which have significant application values in the display,detector,and solar cell field.This review ...Self-assembly of metal halide perovskite nanocrystals(NCs)into superlattices can exhibit unique collective properties,which have significant application values in the display,detector,and solar cell field.This review discusses the driving forces behind the self-assembly process of perovskite NCs,and the commonly used self-assembly methods and different self-assembly structures are detailed.Subsequently,we summarize the collective optoelectronic properties and application areas of perovskite superlattice structures.Finally,we conclude with an outlook on the potential issues and future challenges in developing perovskite NCs.展开更多
Climate change is a long-term and important challenge facing the whole world. Mitigation of CO2 emissions is one of important measures responding to climate change. The task of responding to climate change facing each...Climate change is a long-term and important challenge facing the whole world. Mitigation of CO2 emissions is one of important measures responding to climate change. The task of responding to climate change facing each city is very urgent. The total amount of Tianjin City＆#39;s CO2 emissions from energy use and industrial processes is large and the amount of CO2 emissions per capita from fossil fuel combustion is quite high. Mitigation of CO2 emission in Tianjin City encounters many difficulties such as increasing population, rapidly growing economy, heavy industrial structure, backward tertiary industry, low level of energy efficiency and product technologies, and energy structure relying mainly on coal. This paper analyzes Tianjin City＆#39;s general situation of economic and social developments, estimates Tianjin City＆#39;s status of CO2 emissions using 2006 IPCC Guidelines for National Greenhouse Gas Inventories, analyzes Tianjin City＆#39;s driving forces of CO2 emissions by methodology to analyze the driving forces of energy-related CO2 emissions, and puts forward countermeasures mitigating CO2 emissions in Tianjin City, such as strictly controlling increasing population, expediting industrial structure adjustment, insisting on strategy of energy conserving, vigorously enhancing energy efficiency, exploiting and using clean and renewable energy, advancing energy structure adjustments, and actively developing carbon capture and storage （CCS） technologies.展开更多
基金National Basic Research Program of China, No.2009CB421105National Key Technology R&D Program, No.2006BAC08B00Knowledge Innovation Program of the CAS, No.KSCX1-YW-09-01
文摘Land use and land cover change as the core of coupled human-environment systems has become a potential field of land change science （LCS） in the study of global environmental change. Based on remotely sensed data of land use change with a spatial resolution of 1 km × 1 km on national scale among every 5 years, this paper designed a new dynamic regionalization according to the comprehensive characteristics of land use change including regional differentiation, physical, economic, and macro-policy factors as well. Spatial pattern of land use change and its driving forces were investigated in China in the early 21 st century. To sum up, land use change pattern of this period was characterized by rapid changes in the whole country. Over the agricultural zones, e.g., Huang-Huai-Hai Plain, the southeast coastal areas and Sichuan Basin, a great proportion of fine arable land were engrossed owing to considerable expansion of the built-up and residential areas, resulting in decrease of paddy land area in southern China. The development of oasis agriculture in Northwest China and the reclamation in Northeast China led to a slight increase in arable land area in northern China. Due to the ＂Grain for Green＂ policy, forest area was significantly increased in the middle and western developing regions, where the vegetation coverage was substantially enlarged, likewise. This paper argued the main driving forces as the implementation of the strategy on land use and regional development, such as policies of ＂Western Development＂, ＂Revitalization of Northeast＂, coupled with rapidly economic development during this period.
基金National Natural Science Foundation of China, No.41171318 No.41001160+6 种基金 The Fundamental Research Funds for the Central Universities, the Beijing Plan Program of Science and Technology, No.D08040600580801 International Program for Cooperation in Science and Technology, No.2009DFA 91710 Beijing Forestry Survey and Design Institute provided the data and report of the wetland inventory. We would like to express our sincere appreciation for their suggestions, support and help. They are Prof. Ji Wei of University of Missouri-Kansas City Xue Li, Jianrui Zheng and Lingmei Huang of the Beijing Normal University Shiwu Gao, Gongying Yuan, Zhihua Yang and Zailan Yang of the Beijing Landscape Administration Liyuan Cui of the Chinese Academy of Forestry Jinzeng Wang of the Beijing Forestry Survey and Design Institute and Wenji Zhao, Lin Zhn and Zhaoning Gong of the Capital Normal University.
文摘The decision tree and the threshold methods have been adopted to delineate boundaries and features of water bodies from LANDSAT images. After a spatial overlay analysis and using a remote sensing technique and the wetland inventory data in Beijing, the water bodies were visually classified into different types of urban wetlands, and data on the urban wetlands of Beijing in 1986, 1991, 1996, 2000, 2002, 2004 and 2007 were obtained. Thirteen driving factors that affect wetland change were selected, and gray correlation analysis was employed to calculate the correlation between each driving factor and the total area of urban wetlands. Then, six major driving factors were selected based on the correlation coefficient, and the contribution rates of these six driving factors to the area change of various urban wetlands were calculated based on canonical correlation analysis. After that, this research analyzed the relationship and mechanism between the main driving factors and various types of wetlands. Five conclusions can be drawn. （1） The total area of surface water bodies in Beijing increased from 1986 to 1996, and gradually decreased from 1996 to 2007. （2） The areas of the river wetlands, water storage areas and pool and culture areas gradually decreased, and its variation tendency is consistent with that of the total area of wetlands. The area of the mining water areas and wastewater treatment plants slightly increased. （3） The six factors of driving forces are the annual rainfall, the evaporation, the quantity of inflow water, the volume of groundwater available, the urbanization rate and the daily average discharge of wastewater are the main factors affecting changes in the wetland areas, and they correlate well with the total area of wetlands. （4） The hydrologic indicators of water resources such as the quantity of inflow water and the volume of groundwater are the most important and direct driving forces that affect the change of the wetland area. These factors have a combined contribution rate of 43.94%. （5） Climate factors such as rainfall and evaporation are external factors that affect the changes in wetland area, and they have a contribution rate of 36.54%. （6） Human activities such as the urbanization rate and the daily average quantity of wastewater are major artificial driving factors. They have an influence rate of 19.52%.
基金Under the auspices of the National Natural Science Foundation of China(No.41590844)the Independent Research Program of Tsinghai University(No.2015THZ01)
文摘The pace and scale of China＇s contemporary urbanization are stunning. This paper reviews process and the underlying driving forces of China＇s urbanization between 1949-2015. Contemporary China＇s urbanization has experienced four stages, and each has had different driving forces： 1） economic re-construction and industrialization-led urbanization 0949-1977）; 2） economic reform and mar- ket-led urbanization （1978-1995）; 3） economic globalization and the global-local urbanization （1996-2010）; and 4） the land-economy- led urbanization （2010-）. These urbanization processes and driving forces will undoubtedly provide scientific reference and have sig- nificant implications for developing countries, especially African countries, to formulate their urbanization public policies.
基金National Natural Science Foundation of China,No.41571384Land Resources Survey and Evaluation Project of Ministry of Land and Resources of China,No.DCPJ161207-01+2 种基金Fund for Fostering Talents in Basic Science of National Natural Science Foundation of China,No.J1103409Key Program of National Natural Science Foundation of China,No.71433008Programme of Excellent Young Scientists of the Institute of Geographic Sciences and Natural Resources Research,CAS。
文摘Research into urban expansion patterns and their driving forces is of great significance for urban agglomeration development planning and decision-making.In this paper,we reveal the multi-dimensional characteristics of urban expansion patterns,based on the intensity index of the urban expansion,the differentiation index of the urban expansion,the fractal dimension index,the land urbanization rate,and the center of gravity model,by taking the Beijing-Tianjin-Hebei(Jing-Jin-Ji)urban agglomeration as an example.We then build the center of gravity-geographically and temporally weighted regression(GTWR)model by coupling the center of gravity model with the GTWR model.Through the analysis of the temporal and spatial patterns and by using the center of gravity-GTWR model,we analyze the driving forces of the urban land expansion and summarize the dominant development modes and core driving forces of the Jing-Jin-Ji urban agglomeration.The results show that:1)Between 1990 and 2015,the expansion intensity of the Jing-Jin-Ji urban agglomeration showed a down-up-down trend,and the peak period was in 2005-2010.Before 2005,high-speed development took place in Beijing,Tianjin,Baoding,and Langfang;after 2005,rapid development was seen in Xingtai and Handan.2)Although the barycenter of cities in the Jing-Jin-Ji urban agglomeration has shown a divergent trend,the local interaction between cities has been enhanced,and the driving forces of urban land expansion have shown a characteristic of spatial spillover.3)The spatial development mode of the Jing-Jin-Ji urban agglomeration has changed from a dual-core development mode to a multi-core development mode,which is made up of three functional cores:the transportation core in the northern part,the economic development core in the central part,and the investment core in the southern part.The synergistic development between each functional core has led to the multi-core development mode.4)The center of gravity-GTWR model combines the analysis of spatial and temporal nonstationarity with urban spatial interaction,and analyzes the urban land expansion as a space-time dynamic system.The results of this study show that the model is a feasible approach in the analysis of the driving forces of urban land expansion.
基金Under the auspices of National Natural Science Foundation of China(No.40801039,40801066,41001183)
文摘Karst rocky desertification is one of the major ecological and environmental problems that threaten the sustainable development of southwestern China. It is caused by irrational and intensive land-use patterns in karst geo-ecological environment. Therefore, it is vital to identify how human forces work on this degraded environment. Based on the soil erosion information in 2000 and remote sensing images of Guanling County collected in 2000 and 2007, four grades of karst rocky desertification data in 14 villages of Guanling County were extracted. Impacts of population, affluence, and other human forces on karst rocky desertification were analyzed using STIRPAT model. The results show that:1) Factors of population and affluence had strong influence on karst rocky desertification. In the STIRPAT model analysis, the population and affluence coefficients were positive, indicating that the increase in population and affluence would lead to more serious desertification. 2) Factors of farmer correlated with karst rocky desertification negatively, especially the way of viewing the relationship between people and nature, and the level of knowledge about rocky desertification. Government behavior was not a significant factor in this analysis. 3) The findings provide evidence that STIRPAT model can be used to analyze the relationship between human driving forces and rocky desertification.
基金Key Program of National Natural Science Foundation of China,No.41430636Youth Program of the Humanities and Social Science Research of Ministry of Education,No.16YJC790056
文摘Air pollution is a serious problem brought by the rapid urbanization and economic development in China, imposing great challenges and threats to population health and the sustainability of the society. Based on the real-time air quality monitoring data obtained for each Chinese city from 2013 to 2014, the spatiotemporal characteristics of air pollution are analyzed using various exploratory spatial data analysis tools. With spatial econometric models, this paper further quantifies the influences of socioeconomic factors on air quality at both the national and regional scales. The results are as follows： （1） From 2013 to 2014, the percentage of days compliance of urban air quality increased but air pollution deteriorated and the worsening situation in regions with poor air quality became more obvious. （2） Changes of air quality show a clear temporal coupling with regional socioeconomic activities, basically ＂relatively poor at daytime and relatively good at night＂. （3） Urban air pollution shows a spatial pattern of ＂heavy in the east and light in the west, and heavy in the north and light in the south＂. （4） The overall extent and distribution of regional urban air pollution have clearly different characteristics. The formation and evolution of regional air pollution can be basically induced as ＂the pollution of key cities is aggravated--pollution of those cities spreads-- regional overall pollution is aggravated--the key cities lead in pollution governance--regional pollution joint prevention and control is implemented--regional overall pollution is reduced＂. （5） At the national level, energy consumption, industrialization and technological progress are the major factors in the worsening of urban air quality, economic development is a significant driver for the improvement of that quality. （6） Influenced by resources, environment and the development stage, the socioeconomic factors had strongly variable impacts on air quality, in both direction and intensity in different regions. Based on the conclusion, the regional differ- entiation and development idea of the relationship between economic development and en- vironmental changes in China are discussed.
基金funded by the 135 Strategic Program of the Institute of Mountain Hazards and Environment, CAS (Grant No. SDS135-1703)Coupled relationship and regulation mechanism between rural livelihoods and ecosystem services in the Three Gorges Reservoir Area (No.41371539)
文摘Changes of cultivated land patterns caused by major water conservation projects are rarely reported. We selected the Three Gorges Reservoir area in China to study the change in area and landscape pattern of the cultivated land in the head,central, and tail areas of the reservoir that took place between 1992 and 2015;we then studied the spatial distribution of the cultivated land in the three parts of the reservoir;finally, we studied the driving forces behind the changes in the cultivated land. The results derived are as follows.(1) During the construction of the Three Gorges Project(TGP, 1992–2015), the area of cultivated land around the reservoir decreased by30.23 million ha. This reduction occurred in phases:the most severe change in cultivated land occurred during the later stage of the project(2002–2010);only 0.62 million ha of cultivated land did not change between 1992 and 2015.(2) Spatial pattern analysis showed that the cultivated land in the three parts of the reservoir changed from a northern distribution to a southern distribution;thus, the area of cultivated land in the north decreased over the time period. The area of cultivated land in the head and tail areas decreased by varying degrees, while it increased in the central area over the 23 years, indicating that the change in cultivated land showed regional differences.(3) The TGP, the policy of reverting farmland to forest,and urbanization were the main driving factors for the change of cultivated land, but there were differences in their impacts at different stages.(4) According to the patch dynamics of the land cover change, the degree of change gradually intensified during the early and later stages of the project and then stabilized during the operational period. Our research provides scientific support for the protection of cultivated land resources and food security in the reservoir area and for the coordination of social and economic development, which is of great significance to sustainable development in the reservoir area.
基金National Science and Technology Pillar Program, No.2012BAH48F01 Chinese Academy of Sciences Visiting Professorship for Senior International Scientists, No.2013T2Z0004+1 种基金 National Natural Science Foundation of China, No.41171165 No.41301204
文摘This study applies ArcGIS to analyze the spatiotemporal distribution of cultural sites in the Ill River Valley in northwestern China. It explores relationships between the sites＇ spatiotemporal evolutionary characteristics, human history, and the natural environment. The results indicate that the numbers and proportions of the sites, and the frequency of their oc- currence, exhibited an inverted V-shaped change trend during six historical periods. The ＂high in the east and low in the west＂ spatial distribution pattern of the first three periods shifted to the one the ＂high in the west and low in the east＂ during the latter three periods, demonstrating a change in the spatial center of gravity of human activities. The sites were mainly distributed on slopes of grades 1-5, with their proportions increasing from 75% during the Spring and Autumn Period （770 BC-476 BC）-Qin Dynasty （221 BC-207 BC） to 93.75% during the Qing Dynasty-Modern period. The concentrated distribution of site elevations shifted from grades 4-8 during the Spring and Autumn Period-Qin Dynasty, and the Western Han （206 BC-8）-Southern and Northern Dynasties （420-589）, to grades 1-4 during the latter three periods. The number of sites showed a shifting trend from high-elevation mountains and hills to low-elevation plains, and from high slopes to low slopes. In particular, the sites exhibited a special ＂moist＂ evolutionary pattern of migration from middle and upstream areas to downstream areas, as opposed to the migration pattern of sites located in typical arid areas. The study also considered factors influencing the distribution and spatiotemporal evolution of cultural sites, notably, human factors and natural factors.
文摘Based on the long-term serial NOAA/NDVI dataset during 1983-1999 and SPOT/VGT dataset in 2001, the land use/cover change information in the 13 provinces of northern China was extracted based on the analysis of the cultivated landscape characteristics at first, then the effects of human activities on cultivated land process were explored by GIS and the driving forces of cultivated land change were investigated. The conclusions can be drawn as follows： （1） The constant increase of weak ecological function land as desert and cultivated land and the decrease of the ecological function land of forest and shrub were the main characteristics of the land use/cover change in the 13 provinces from 1983 to 1999, which showed the effects on the ecological adjustment fimction. However, such situations were changed to some extent in the 2000s because of the eco-construction policy of the government. （2） From 1983 to 2001, the Barycenter of cultivated land tended to move from northeast to southwest with the topography and transportation situations being the main influences on the cultivated land distribution. It is found that the cultivated land use intensity decreased noticably with the increase of distance from the main communication arteries. （3） The improvement of the people＇s living standard is closely related with the cultivated land change. The structural adjustment in the agricultural land caused by economic development and the improvement of the people＇s living standard ig an important factor affecting the cultivated land change in northern China from 1983 to 2001
基金The National Natural Science Foundation of China, No.49971004
文摘The decrease of total cultivated area and the lower per capita available arable land resource are now serious problems in Shandong Province, a major agricultural province in China. These problems will become more serious along with the further development of economy. In this paper, based on the statistical information at provincial and county levels, the changes of arable land in Shandong Province and their driving forces during the last 50 years are analyzed. The general changing trends of arable land and per capita available arable land are reducing, and the trends of decrease will continue when the economy is developing. The result of GIS spatial analysis shows that the change of the arable land use in Shandong Province has a regional difference. Eight variables having influences on cultivated land change are analyzed by principal component analysis. The results show that the dynamic development of economy, pressure of social system and progress of scientific techniques in agriculture are the main causes for cultivated land reduction. The principal factors which can be considered as driving forces for arable land change include per capita net living space, total population and per ha grain yield. By using regressive equation, along with analysis on population growth and economic development, cultivated areas in Shandong Province in 2005 and 2010 are predicted respectively. The predicted cultivated areas in Shandong will be 6435.47 thousand hain 2005 and 6336.23 thousand ha in 2010 respectively.
基金funded by the Knowledge Innovation Project of the Chinese Academy of Sciences(Grant No.KZCX2-YW-333)the National Natural Science Foundation of China(Grant No.40901299)
文摘The Ecological Footprint(EF) equation provides useful accounting to analyze the relationship between human activities and the environment.Knowledge of the specific forces driving EF is not fully understood but the STIRPAT model provides a simple framework for decomposing the impact of human activities on environment.We applied the EF model in Sichuan Province,China to assess the impact of human activities.The per capita EF increased by 2 fold in the 14 years between 1995 and 2008,but ecological capacity decreased in the same period,suggesting that the biologically productive area of Sichuan Province is inadequate to sustain human activities.According to the refined STIRPAT model,the hypothesized driving forces of EF include population size(P),GDP per capita(A1),quadratic term of GDP per capita(A2),percentage of GDP from industry(T1) and urbanization rate(T2).However,the multi-collinearity among these drivers could be a substantial problem which may reveal negative effect in the final results.Application of the Ridge Regression(RR) method to fit the STIRPAT model had the advantage of being able to avoid the collinearity among independent variables.The results showed that population is the principal driving force of EF variation in Sichuan Province and that urbanization and industrialization also have a positive association with the EF.Analysis of affluence elasticity(EEA) showed that the relationship betweenEF and economic growth was not curvilinear,suggesting that variation of EF does not follow an Environmental Kuznets Curve relative to economic growth in Sichuan Province.
基金The Key Project of Chinese Academy of Sciences(No.KZCX1-SW-19)
文摘By establishing the interpreting elements, and applying supervised classification, the sandy desertific- ation was interpreted and the desertified land areas of the counties in the western Jilin Province in 1986 and in 2000 were obtained. Taking Tongyu and Qian’an as examples, the natural driving forces and man-made driving forces were analyzed. The paper comes the conclusions that the material sources and the warming and dry climate are the internal causes of potential land desertification; the irrational human activities, such as destroying forest and reclaiming the grassland, are the external causes of potential land desertification; while more rational human activities, such as planting trees and restoring grassland can reverse the land desertification. Furthermore, the countermeasures and suggestions for the development of agriculture and animal husbandry in the western Jilin Province are put forward.
基金Under the auspices of National Natural Science Foundation of China(No.41590844)
文摘Urbanization has both direct and indirect impacts on land use change, and analyzing spatio-temporal characteristics of land use change is essential for understanding these impacts. By comparing Landsat TM images, this paper examines the changes of land use structure and landscape patterns in Shanghai from 1990 to 2015. It finds that the city doubled in size, with the growth of isolated construction land being most significant among eight land use types. A land use change matrix was established and landscape indices were selected to evaluate the change of spatial structure in Shanghai. In order to identify the main driving forces of city expansion in Shanghai, this research ran partial least square regression models to assess the impact of 10 social-economic factors on land use change of Shanghai from 1990 to 2015. It then conducted bivariate correlation analysis to explore the drivers of change of various land use types: urban settlement, rural settlement and isolated construction land. Besides quantitative analysis, this paper analyzes the influence of policy-dimensional factors in land use change. It concludes with future potential research topics on land use change in a rapidly urbanizing context.
基金Under the auspices of Major State Basic Research Development Program of China (No. 2002CB111506)National Natural Science Foundation of China (No. 30670374)Sixth Framework Programme of European Union (Priority 1.1.6.3) (No. 003874-2)
文摘The land use patterns in Guyuan City,Ningxia Hui Autonomous Region of China,have changed greatly over the years,due to population growth and farming and stock raising development.This study,using 50-year statis-tical data of cultivated land and 14-year spatial data of land use pattern,analyzed the developmental stages,the char-acter,and the spatial variance of farmland in the city,and discussed the driving forces of cultivated land changes based on empirical and conceptual statistical models.First,the change of cultivated land area went through different stages of rapid increase,fluctuating change,decrease and rapid decrease from 1949 to 2004,additionally,social and economic policies in different stages had an important impact on farmland variance.Second,from 1986 to 2000,the quantity of cultivated land increased,but its quality decreased.Third,social and economic factors are determinant factors in culti-vated land transition.Five constructed paths explain cultivated land transition.Factors that have direct or indirect ef-fects on farmland include the economy(Xeco),the population(Xpop),agricultural output(Xagr),and scientific input(Xsci).The sequence of impact was Xeco>Xpop>Xsci>Xagr.Among all these impacts,Xeco was the major positive one,and Xpop was the major negative one.It is urgent to take measures or adopt a policy to stop the vicious cycle in eco-environment and agriculture production.Otherwise,negative patterns of farmland use will increase,and high-quality cultivated land will continue to decline.
基金the funding received from the Natural Science Foundation of China (41301003, 41371026, and 31470480)the Technology of the People's Republic of China (No. 2013CB956000)
文摘Maqu County is located in the northeast Qinghai-Tibetan Plateau, and it is the main watershed for the Yellow River. The ecosystem there is extremely vulnerable and sensitive to climate change and human activities, which have caused significant deterioration of the eco-environment in this region. In order to restore the ecological environment, a government project to restore the grazing areas to grassland was implemented in Maqu County in early 2004. This study evaluates the effects of that restoration project on land use and land cover change （LUCC）, and explores the driving forces of LUCC in Maqu County. In the study we used Landsat images obtained in 1989, 2004, 2009, and 2014 to establish databases of land use and land cover. Then we derived LUCC information by overlaying these layers using GIS software. Finally, we analyzed the main forces responsible for LUCC. The results showed that forests, high-coverage grasslands, and marshes experienced the most significant decreases during 1989–2004, by 882.8 ha, 35,250.4 ha, and 2,753.4 ha, respectively. However, moderate- and low-coverage grasslands and sand lands showed the opposite trend, increasing by 12,529.7 ha, 25,491.0 ha, and 577.5 ha, respectively. LUCC in 2004–2009 showed that ecological degradation slowed compared with 1989？2004. During 2009–2014, high- and moderate-coverage grasslands increased obviously, but low-coverage grasslands, marshes, unused lands, sand lands, and water areas showed the opposite trend. These results suggested that the degradation of the eco-environment was obvious before 2009, showing a decrease in the forests, grasslands, and water areas, and an increase in unused lands. The ecological degradation was reversed after 2009, as was mainly evidenced by increases in high- and mod-erate-coverage grasslands, and the shrinkage rate of marshes decreased obviously. These results showed that the project of restoring grazing lands to grassland had a positive effect on the LUCC. Other major factors that influence the LUCC include increasing temperature, variation in the seasonal frozen soil environment, seasonal overgrazing, and pest and rodent damage.
基金The Strategic Priority Research of the CAS,No.XDA20040400National Natural Science Foundation of China,No.41871118。
文摘Due to the unique geographical location and historical background of Central Asia,the region’s geo-relation networks are complex and changeable.A social network analysis was conducted in this study to visualize the 20-year evolutionary process of bilateral(diplomatic relations)and multilateral(intergovernmental organization(IGO)connections)networks in Central Asia since 1993.Additionally,a further empirical study determined the significant driving forces of the construction of the geo-relation networks.The results showed that since the independence of the five Central Asian countries,their degree centrality(C,D(ni))values have been increasing,with the index values being the highest for Kazakhstan,followed by Uzbekistan,while the other three countries had relatively low values.The Central Asian countries maintain bilateral relations with post-Soviet nations,neighboring countries,and Western powers,and have gradually deepened and expanded their diplomatic networks.From each state’s perspective,the geostrategic approaches adopted by the five countries were different.Kazakhstan has focused on expanding its bilateral and multilateral relations,while the other Central Asian countries have attempted to increase their influence by joining influential IGOs.Various driving forces,including economic,political,cultural,and geographical factors,have played significant roles in the construction of geo-relation networks in Central Asia.The importance of these factors has changed over time,from political and cultural factors(before 1995)to relations with neighboring countries(1996-2001),and finally to economic power and cultural and religious proximity(after 2002).
基金Under the auspices of the National Natural Science Foundation of China(No.41771138)。
文摘Improving comprehensive agricultural productivity is an important measure to realize agricultural modernization.Based on the data from Jilin Statistical Yearbook,this study analyzed the spatial and temporal characteristics of comprehensive agricultural productivity discrepancy in the main agricultural production areas of Jilin Province,China.The comprehensive agricultural productivity of 25 county-level administrative units were evaluated by a comprehensive index system based on five aspects which included 20 indicators from 2004 to 2017.The pattern of the discrepancy was analyzed by the spatial differentiation indices and spatial convergence theory.The results were as follows:1) the overall comprehensive agricultural productivity was in a ’W-type’ rising trend;2) the discrepancy was in’inverted W-type’ trend;3) the spatial distribution characteristics were mainly discrete plaque and ’inverted V-type’;4) the formation of differences was forced by a combination of internal and external driving forces.Our study demonstrates the effectiveness of rising agricultural productivity and the level of economic and social developments in different counties in Jilin Province.
基金Under the auspices of National Natural Science Foundation of China(No.41271133,41261104)National Social Science Foundation of China(No.12CTJ001)
文摘This paper presents an integrated study of urban spatial expansion in the Hexi Corridor, Gansu Province, China based on TM, ETM remote sensing data in 1987, 1990, 1995, 2000, 2006 and 2011. The study explores the characteristics of urban spatial expansion and dynamic mechanism by using expansion speed index, expansion intensity index, compact index, fractal dimension, and extended flexibility index. We built the index system of influencing factors of urban spatial expansion by using the grey incidence model. The results showed that urban spatial expansion rate in the Hexi Corridor has been on the upward trend since 1987. Expansion intensity showed an obvious upward trend, however, the upward trend varied in different urban areas. In addition, the urban structure was loose relatively, but the urban compactness was more obvious. The urban spatial form tended to be simple, and the urban land use tended to become more intensive. Urban spatial expansion experienced several stages: padding internally, external expansion and padding internally. The main driving factors of urban spatial expansion are not the urban water resources and the oasis scale, but one or several factors such as economy, traffic, population, resource and national policy.
基金financially supported by the National Key Research and Development Program of China (2021YFB3600403)the Fundamental Research Funds for the Central Universities (000-0903069032)。
文摘Self-assembly of metal halide perovskite nanocrystals(NCs)into superlattices can exhibit unique collective properties,which have significant application values in the display,detector,and solar cell field.This review discusses the driving forces behind the self-assembly process of perovskite NCs,and the commonly used self-assembly methods and different self-assembly structures are detailed.Subsequently,we summarize the collective optoelectronic properties and application areas of perovskite superlattice structures.Finally,we conclude with an outlook on the potential issues and future challenges in developing perovskite NCs.
基金supported by National Key Project of Scientific and Technical Supporting Programs Funded by Ministry of Science and Technology of China in the 11th Five Year Plan (Grant No. 2007BAC03A12)
文摘Climate change is a long-term and important challenge facing the whole world. Mitigation of CO2 emissions is one of important measures responding to climate change. The task of responding to climate change facing each city is very urgent. The total amount of Tianjin City＆#39;s CO2 emissions from energy use and industrial processes is large and the amount of CO2 emissions per capita from fossil fuel combustion is quite high. Mitigation of CO2 emission in Tianjin City encounters many difficulties such as increasing population, rapidly growing economy, heavy industrial structure, backward tertiary industry, low level of energy efficiency and product technologies, and energy structure relying mainly on coal. This paper analyzes Tianjin City＆#39;s general situation of economic and social developments, estimates Tianjin City＆#39;s status of CO2 emissions using 2006 IPCC Guidelines for National Greenhouse Gas Inventories, analyzes Tianjin City＆#39;s driving forces of CO2 emissions by methodology to analyze the driving forces of energy-related CO2 emissions, and puts forward countermeasures mitigating CO2 emissions in Tianjin City, such as strictly controlling increasing population, expediting industrial structure adjustment, insisting on strategy of energy conserving, vigorously enhancing energy efficiency, exploiting and using clean and renewable energy, advancing energy structure adjustments, and actively developing carbon capture and storage （CCS） technologies.
