Starting JPom a low level China＇s rapid urOamzatlon ttas talcen on a targe scale over the past three decades. The urbanization of urban clusters has become a key driver of China＇s economic development. However, Chin...Starting JPom a low level China＇s rapid urOamzatlon ttas talcen on a targe scale over the past three decades. The urbanization of urban clusters has become a key driver of China＇s economic development. However, China＇s urbanization has been confronted with many issues, such as high resource and environmental costs, low level of citizenship for migrant workers, strong economic polarization and excessive dependence on land encroachment. In the near future, China＇s urbanization will enter a period of strategic transitioning, and the enhancement of the quality of urbanization will become a strategic priority. China＇s urbanization rate is projected to reach 60% by 2020 and 68% by 2030, eventually exceeding 80% by 2050. China＇s future urbanization must proceed from local realities, promote the balanced development of small, medium-sized and large cities and towns, optimize the spatial layout of urbanization, and follow a sensible pattern.展开更多
During the last 30 years, China has witnessed rapid economic growth and dramatic urbanization, with about 1.2 x 107 rural people migrating annually into urban areas. Meanwhile, especially since 1995, the rural populat...During the last 30 years, China has witnessed rapid economic growth and dramatic urbanization, with about 1.2 x 107 rural people migrating annually into urban areas. Meanwhile, especially since 1995, the rural population has been declining, which is closely linked to land circulation and the increase in farm size in many villages. Increasing scale of farming operations is often regarded as a key to avoiding the abandonment of farmland and to increasing the income of rural farmers. However, until now, there has been little research on the spatial and temporal variability of farm size at the national level in China. Using data from the national agricultural cen- sus and rural household surveys, this study examines the characteristics of land use circulation and the consequent changes in the area of farmland per household. The results show that： 1） 12.2% of rural households were involved in land circulation at the national level. The highest amounts of land circulation have occurred in those provinces where the farmland per capita is more than 0.2 ha or less than 0.1 ha; 2） over 80% of households operate less than 0.6 ha of farmland; 3） the proportion of mid-sized farms （between 0.2 ha and 0.6 ha per household） has decreased while the smallest and the largest farms have increased. This bears some similarity with the phenomenon known as the ＇disappearing middle＇, referring to the changes in farm size. This study establishes a framework for interpreting the factors affecting the changes in farm size in China, which include two promoting factors （urbanization and agriculture） and four hindering fac- tors （agricultual land system, household registration, stable clan system, and farmland loss）.展开更多
As a typical car-dependent city, Los Angeles （LA） is extensively used as an example in research to illustrate car influences on city form. Focusing on the features of LA＇s geologic conditions and civil circumstance...As a typical car-dependent city, Los Angeles （LA） is extensively used as an example in research to illustrate car influences on city form. Focusing on the features of LA＇s geologic conditions and civil circumstances, we argued that the relationship between LA＇s low-density pattern and car dependence is more involved than previously deemed simple causality. The low density should be primarily credited to the spacious requirement of the mining industry, frequent earthquakes and multiethnic population of the city. Off reserves in LA fueled its economic boom and fast urbanization that coincided with the start of mass production of cheap cars, and cars became medium-priced consumables for average families. Politicians preference for short constrnction-period projects enabled fast establishment of LA＇s highway infrastructure. The popularity of car use in return faciliatated further development of the low-density pattern of the city. The low-density urban form and car dependence created environmental and social problems for LA. Looking at P. R. China＇s motorization and urban development, we found that the trajectory of Beijing＇s motorization between 197g and 2003 coincides with that of the U.S. in the 1910s and 1920s. Lessons from LA＇s urban and transportation development should be suggestive to China＇s urban and transportation planning.展开更多
The Sichuan Basin is endowed with unique natural and cultural conditions, which provide good conditions for the creation of traditional ＂shan-shui dries＂. As an important constituent dement of ＂shan-hui cities＂M, ...The Sichuan Basin is endowed with unique natural and cultural conditions, which provide good conditions for the creation of traditional ＂shan-shui dries＂. As an important constituent dement of ＂shan-hui cities＂M, boundaries delimit cities and nature and determine the scope and scale of cities. This paper divides the boundaries into dty boundary, mountain boundary, water boundary and celestial horizon, which integrate with each other and embody the boundary feature of four in one.展开更多
An optimization model and its solution algorithm for alternate traffic restriction(ATR) schemes were introduced in terms of both the restriction districts and the proportion of restricted automobiles. A bi-level progr...An optimization model and its solution algorithm for alternate traffic restriction(ATR) schemes were introduced in terms of both the restriction districts and the proportion of restricted automobiles. A bi-level programming model was proposed to model the ATR scheme optimization problem by aiming at consumer surplus maximization and overload flow minimization at the upper-level model. At the lower-level model, elastic demand, mode choice and multi-class user equilibrium assignment were synthetically optimized. A genetic algorithm involving prolonging codes was constructed, demonstrating high computing efficiency in that it dynamically includes newly-appearing overload links in the codes so as to reduce the subsequent searching range. Moreover,practical processing approaches were suggested, which may improve the operability of the model-based solutions.展开更多
Based on the land use change data obtained from the interpretation of remote sensing images in 1985, 1995, 2005 and 2008, the research applied principal component analysis, Markov chain and ESDA method, and took culti...Based on the land use change data obtained from the interpretation of remote sensing images in 1985, 1995, 2005 and 2008, the research applied principal component analysis, Markov chain and ESDA method, and took cultivated land patch as the basic unit of landscape. A comprehensive measure of the fragmentation of cultivated land was made in Jiangsu counties and its temporal and spatial evolution characteristics and driving process from the perspective of landscape ecology were discussed. The results are as follows:(1)The overall fragmentation of cultivated land in Jiangsu Province presents that the eastern coastal areas are low, the interior of the west is high, the fragmentation of northern and southern Jiangsu is high, while the fragmentation of mid-Jiangsu is low.(2)The degree of fragmentation of cultivated land in most area of southern Jiangsu and midJiangsu showed an upward trend, while the fragmentation of cultivated land in northern Jiangsu showed a downward trend from 1985 to 2008. The degree of agglomeration of cultivated land is weakened continuously, the area of high value agglomeration is decreasing and the trend of "polarization" is weakening.(3) Topographic condition is the decisive factor for the formation of the difference pattern. The change of rural residential land, cultivated land and the scale of urban land use plays a role on the cultivated land fragmentation index, among them, the change of rural residential land scale has the most significant effect on cultivated land fragmentation.展开更多
文摘Starting JPom a low level China＇s rapid urOamzatlon ttas talcen on a targe scale over the past three decades. The urbanization of urban clusters has become a key driver of China＇s economic development. However, China＇s urbanization has been confronted with many issues, such as high resource and environmental costs, low level of citizenship for migrant workers, strong economic polarization and excessive dependence on land encroachment. In the near future, China＇s urbanization will enter a period of strategic transitioning, and the enhancement of the quality of urbanization will become a strategic priority. China＇s urbanization rate is projected to reach 60% by 2020 and 68% by 2030, eventually exceeding 80% by 2050. China＇s future urbanization must proceed from local realities, promote the balanced development of small, medium-sized and large cities and towns, optimize the spatial layout of urbanization, and follow a sensible pattern.
基金Under the auspices of National Natural Science Foundation of China(No.4097111241161140352)Ministry of Environmental Protection of the People's Republic of China(No.STSN-09-04)
文摘During the last 30 years, China has witnessed rapid economic growth and dramatic urbanization, with about 1.2 x 107 rural people migrating annually into urban areas. Meanwhile, especially since 1995, the rural population has been declining, which is closely linked to land circulation and the increase in farm size in many villages. Increasing scale of farming operations is often regarded as a key to avoiding the abandonment of farmland and to increasing the income of rural farmers. However, until now, there has been little research on the spatial and temporal variability of farm size at the national level in China. Using data from the national agricultural cen- sus and rural household surveys, this study examines the characteristics of land use circulation and the consequent changes in the area of farmland per household. The results show that： 1） 12.2% of rural households were involved in land circulation at the national level. The highest amounts of land circulation have occurred in those provinces where the farmland per capita is more than 0.2 ha or less than 0.1 ha; 2） over 80% of households operate less than 0.6 ha of farmland; 3） the proportion of mid-sized farms （between 0.2 ha and 0.6 ha per household） has decreased while the smallest and the largest farms have increased. This bears some similarity with the phenomenon known as the ＇disappearing middle＇, referring to the changes in farm size. This study establishes a framework for interpreting the factors affecting the changes in farm size in China, which include two promoting factors （urbanization and agriculture） and four hindering fac- tors （agricultual land system, household registration, stable clan system, and farmland loss）.
基金Funded by Key Project of the Natural Science Foundation of China under the grant No. 40635026.
文摘As a typical car-dependent city, Los Angeles （LA） is extensively used as an example in research to illustrate car influences on city form. Focusing on the features of LA＇s geologic conditions and civil circumstances, we argued that the relationship between LA＇s low-density pattern and car dependence is more involved than previously deemed simple causality. The low density should be primarily credited to the spacious requirement of the mining industry, frequent earthquakes and multiethnic population of the city. Off reserves in LA fueled its economic boom and fast urbanization that coincided with the start of mass production of cheap cars, and cars became medium-priced consumables for average families. Politicians preference for short constrnction-period projects enabled fast establishment of LA＇s highway infrastructure. The popularity of car use in return faciliatated further development of the low-density pattern of the city. The low-density urban form and car dependence created environmental and social problems for LA. Looking at P. R. China＇s motorization and urban development, we found that the trajectory of Beijing＇s motorization between 197g and 2003 coincides with that of the U.S. in the 1910s and 1920s. Lessons from LA＇s urban and transportation development should be suggestive to China＇s urban and transportation planning.
基金Sponsored by Fundamental Research Funds for the Central Universities(2682018CX57)
文摘The Sichuan Basin is endowed with unique natural and cultural conditions, which provide good conditions for the creation of traditional ＂shan-shui dries＂. As an important constituent dement of ＂shan-hui cities＂M, boundaries delimit cities and nature and determine the scope and scale of cities. This paper divides the boundaries into dty boundary, mountain boundary, water boundary and celestial horizon, which integrate with each other and embody the boundary feature of four in one.
基金Projects(71171200,51108465,71101155)supported by the National Natural Science Foundation of China
文摘An optimization model and its solution algorithm for alternate traffic restriction(ATR) schemes were introduced in terms of both the restriction districts and the proportion of restricted automobiles. A bi-level programming model was proposed to model the ATR scheme optimization problem by aiming at consumer surplus maximization and overload flow minimization at the upper-level model. At the lower-level model, elastic demand, mode choice and multi-class user equilibrium assignment were synthetically optimized. A genetic algorithm involving prolonging codes was constructed, demonstrating high computing efficiency in that it dynamically includes newly-appearing overload links in the codes so as to reduce the subsequent searching range. Moreover,practical processing approaches were suggested, which may improve the operability of the model-based solutions.
基金Supported by National Natural Science Foundation of China(41301651,41401629)a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘Based on the land use change data obtained from the interpretation of remote sensing images in 1985, 1995, 2005 and 2008, the research applied principal component analysis, Markov chain and ESDA method, and took cultivated land patch as the basic unit of landscape. A comprehensive measure of the fragmentation of cultivated land was made in Jiangsu counties and its temporal and spatial evolution characteristics and driving process from the perspective of landscape ecology were discussed. The results are as follows:(1)The overall fragmentation of cultivated land in Jiangsu Province presents that the eastern coastal areas are low, the interior of the west is high, the fragmentation of northern and southern Jiangsu is high, while the fragmentation of mid-Jiangsu is low.(2)The degree of fragmentation of cultivated land in most area of southern Jiangsu and midJiangsu showed an upward trend, while the fragmentation of cultivated land in northern Jiangsu showed a downward trend from 1985 to 2008. The degree of agglomeration of cultivated land is weakened continuously, the area of high value agglomeration is decreasing and the trend of "polarization" is weakening.(3) Topographic condition is the decisive factor for the formation of the difference pattern. The change of rural residential land, cultivated land and the scale of urban land use plays a role on the cultivated land fragmentation index, among them, the change of rural residential land scale has the most significant effect on cultivated land fragmentation.
