In summer maize growth period,the water supply and demand ratio is regarded as the evaluation index of drought and waterlogging for the summer maize in Liaocheng City. Using GIS,statistics,agrometeorology and other me...In summer maize growth period,the water supply and demand ratio is regarded as the evaluation index of drought and waterlogging for the summer maize in Liaocheng City. Using GIS,statistics,agrometeorology and other methods,we analyze the precipitation during the summer maize growth period in Luxi Plains from 1961 to 2011. Through the calculation of drought and waterlogging index,it indicates that the disasters of drought and waterlogging frequently occur during the summer maize growth period,mainly affected by the drought; the frequency of occurrence of drought accounts for 80. 4%,that is,it is very prone to serious drought phenomenon,seriously affecting the normal growth and development of summer maize during the seedling period. With global warming,the industrial and domestic water demand is increasing year by year,so it is extremely difficult to increase the water diversion to solve the problem of water shortage for the growth of summer maize. Finally we put forth the following recommendations:( i) Selecting drought-resistant varieties,and improving the water resource use efficiency;( ii)Promoting the water and fertilizer coupling,sprinkler irrigation,drip irrigation,micro-irrigation and other water-saving irrigation technologies,and improving the water use efficiency;( iii) Promoting the ditch,ridge and laminating cultivation technology,reducing the field evapotranspiration,keeping warming and conserving moisture,and saving water resources;( iv) Strengthening the construction of water conservancy facilities,so that it can be irrigated during drought and drained during waterlogging;( v) During dry season,timely organizing artificial rainfall operation,and increasing precipitation in arid areas to ease drought;( vi) Rationally exploiting the groundwater,and improving the underground water use efficiency.展开更多
Organic carbon, total nitrogen, amino acids, sugars, and chlorophyll were determined in < 1 mm fractions of the samples collected by successive large aperture time-series sediment traps (Honjo-Mark Ⅵ ) in northern...Organic carbon, total nitrogen, amino acids, sugars, and chlorophyll were determined in < 1 mm fractions of the samples collected by successive large aperture time-series sediment traps (Honjo-Mark Ⅵ ) in northern China China Sea during September 1987 to October1988. The ratio of C/N and the relative abundance of amino acids and sugars show that organicmatter in the settling particles from northem South China Sea is derived mainly from marineplantkon (especially phytoplankton). The organic carbon fluxes in our sediment traps are lowerthan those in other sediment traps. But the relative contents of Corg/total particulate matter aregenerally similar to those in the Panama Basin, Arabian Sea and Subarctic Pacific. It is suggested that monsoon-caused changes of physical and chemical conditions in the upper euphoticlayer would contro the fluxes of organic matter as well as its composition and transport innorthern South China Sea.展开更多
We apply the CIP(Cubic Interpolated Profile)scheme to the numerical sim-ulation of the acoustic wave propagation based on characteristic equations.The CIP scheme is based on a concept that both the wavefield and its s...We apply the CIP(Cubic Interpolated Profile)scheme to the numerical sim-ulation of the acoustic wave propagation based on characteristic equations.The CIP scheme is based on a concept that both the wavefield and its spatial deriv ative propa-gate along the same characteristic curves derived from a hyperbolic differential equa-tion.We describe the derivation of the characteristic equations for the acoustic waves from the basic equations by means of the directional splitting and the diagonaliza-tion of the coffcient matrix,and establish geophysical boundary conditions.Since the CIP scheme calculates both the wavefield and its spatial derivatives,it is easy to realize the boundary conditions theretically.We also show some numerical simula-tion examples and the CIP can simulate acoustic w ave propagation with high stability and less numerical dispersion.The method of characteristics with the CIP scheme is a very powerful technique to deal w ith the wave propagation in complex geophysical problems.展开更多
Studies on the renovation and governance of urban villages have become the interest of human geography since the 1990s.However up to now,there is little literature focusing on the development patterns and dynamic mech...Studies on the renovation and governance of urban villages have become the interest of human geography since the 1990s.However up to now,there is little literature focusing on the development patterns and dynamic mechanism of the spatial evolution of urban villages based on the theoretical system of urban spatial structure,and there are few scholars doing analyses on the relationship between urban villages and general urban areas in terms of spatial development.In this paper,Shenzhen,the most representative city of China in terms of urban village development,is taken as a case for exploring the characteristics and modes of the spatial evolution of urban villages.With census data of urban village construction in 1999 and 2004 in terms of built-up area,floor area,and construction intensity,the spatial and temporal evolution of the 91 administrative urban villages in the original Shenzhen Special Economic Zone have been analyzed in comparison with that of Shenzhen's general urban areas.It is indicated that the spatial evolution of urban villages matches with the general rules of the spatial development of general urban areas in three aspects.First,land expansion is the most remarkable mode of spatial evolution in the early stage of development;second,in the period of rapid development,there is the obvious tendency of "distance-decay" in terms of construction intensity accompanied by some anomalous fluctuations at certain points;third,renewal and redevelopment are carried out gradually in the mature stage of development.However,because of historical and institutional restrictions,the spatial evolution of urban villages shows its unique characteristics in the aspects of original spatial distribution and spatial expansion mode in the period of rapid development,etc.The outcomes of this study would help not only enrich the theoretical study on the evolution mode of urban spatial structure,but also strengthen the administration over urban villages,in particular with the suggestions that the spatial evolution of urban villages as a type of urban space should not be the same as that of general urban areas and its unique characteristics should not be ignored;specific rules should be set up to guide the rational spatial evolution of urban villages according to the economic development of the city,as well as the housing demands of various kinds of residents.展开更多
基金Soft Science Foundation of Liaocheng Municipal Bureau of Science and Technology(20082057)
文摘In summer maize growth period,the water supply and demand ratio is regarded as the evaluation index of drought and waterlogging for the summer maize in Liaocheng City. Using GIS,statistics,agrometeorology and other methods,we analyze the precipitation during the summer maize growth period in Luxi Plains from 1961 to 2011. Through the calculation of drought and waterlogging index,it indicates that the disasters of drought and waterlogging frequently occur during the summer maize growth period,mainly affected by the drought; the frequency of occurrence of drought accounts for 80. 4%,that is,it is very prone to serious drought phenomenon,seriously affecting the normal growth and development of summer maize during the seedling period. With global warming,the industrial and domestic water demand is increasing year by year,so it is extremely difficult to increase the water diversion to solve the problem of water shortage for the growth of summer maize. Finally we put forth the following recommendations:( i) Selecting drought-resistant varieties,and improving the water resource use efficiency;( ii)Promoting the water and fertilizer coupling,sprinkler irrigation,drip irrigation,micro-irrigation and other water-saving irrigation technologies,and improving the water use efficiency;( iii) Promoting the ditch,ridge and laminating cultivation technology,reducing the field evapotranspiration,keeping warming and conserving moisture,and saving water resources;( iv) Strengthening the construction of water conservancy facilities,so that it can be irrigated during drought and drained during waterlogging;( v) During dry season,timely organizing artificial rainfall operation,and increasing precipitation in arid areas to ease drought;( vi) Rationally exploiting the groundwater,and improving the underground water use efficiency.
文摘Organic carbon, total nitrogen, amino acids, sugars, and chlorophyll were determined in < 1 mm fractions of the samples collected by successive large aperture time-series sediment traps (Honjo-Mark Ⅵ ) in northern China China Sea during September 1987 to October1988. The ratio of C/N and the relative abundance of amino acids and sugars show that organicmatter in the settling particles from northem South China Sea is derived mainly from marineplantkon (especially phytoplankton). The organic carbon fluxes in our sediment traps are lowerthan those in other sediment traps. But the relative contents of Corg/total particulate matter aregenerally similar to those in the Panama Basin, Arabian Sea and Subarctic Pacific. It is suggested that monsoon-caused changes of physical and chemical conditions in the upper euphoticlayer would contro the fluxes of organic matter as well as its composition and transport innorthern South China Sea.
文摘We apply the CIP(Cubic Interpolated Profile)scheme to the numerical sim-ulation of the acoustic wave propagation based on characteristic equations.The CIP scheme is based on a concept that both the wavefield and its spatial deriv ative propa-gate along the same characteristic curves derived from a hyperbolic differential equa-tion.We describe the derivation of the characteristic equations for the acoustic waves from the basic equations by means of the directional splitting and the diagonaliza-tion of the coffcient matrix,and establish geophysical boundary conditions.Since the CIP scheme calculates both the wavefield and its spatial derivatives,it is easy to realize the boundary conditions theretically.We also show some numerical simula-tion examples and the CIP can simulate acoustic w ave propagation with high stability and less numerical dispersion.The method of characteristics with the CIP scheme is a very powerful technique to deal w ith the wave propagation in complex geophysical problems.
基金sponsored by the National Natural Science Foundation for Distinguished Young Scholars(40901080)the Postdoc Science Foundation of China(200804400237)the Social Science Project of Shenzhen in the11th Five-year Plan(105C020)
文摘Studies on the renovation and governance of urban villages have become the interest of human geography since the 1990s.However up to now,there is little literature focusing on the development patterns and dynamic mechanism of the spatial evolution of urban villages based on the theoretical system of urban spatial structure,and there are few scholars doing analyses on the relationship between urban villages and general urban areas in terms of spatial development.In this paper,Shenzhen,the most representative city of China in terms of urban village development,is taken as a case for exploring the characteristics and modes of the spatial evolution of urban villages.With census data of urban village construction in 1999 and 2004 in terms of built-up area,floor area,and construction intensity,the spatial and temporal evolution of the 91 administrative urban villages in the original Shenzhen Special Economic Zone have been analyzed in comparison with that of Shenzhen's general urban areas.It is indicated that the spatial evolution of urban villages matches with the general rules of the spatial development of general urban areas in three aspects.First,land expansion is the most remarkable mode of spatial evolution in the early stage of development;second,in the period of rapid development,there is the obvious tendency of "distance-decay" in terms of construction intensity accompanied by some anomalous fluctuations at certain points;third,renewal and redevelopment are carried out gradually in the mature stage of development.However,because of historical and institutional restrictions,the spatial evolution of urban villages shows its unique characteristics in the aspects of original spatial distribution and spatial expansion mode in the period of rapid development,etc.The outcomes of this study would help not only enrich the theoretical study on the evolution mode of urban spatial structure,but also strengthen the administration over urban villages,in particular with the suggestions that the spatial evolution of urban villages as a type of urban space should not be the same as that of general urban areas and its unique characteristics should not be ignored;specific rules should be set up to guide the rational spatial evolution of urban villages according to the economic development of the city,as well as the housing demands of various kinds of residents.
