The population analysis unit(PAU)is the basic unit employed in studies of urban populations.The commonly used PAUs are mostly administrative divisions,regular geographic grids.However,these units are different from ur...The population analysis unit(PAU)is the basic unit employed in studies of urban populations.The commonly used PAUs are mostly administrative divisions,regular geographic grids.However,these units are different from urban forms,and cannot be used to consider the characteristics of population distributions and flow changes.In this study,we proposed a method for constructing a fine population analysis zone(FPAZ)based on the population aggregation pattern and urban form elements.First,considering the spatial structure of a city and the fine-grained demands of population analysis,the basic analysis unit was divided according to the functional heterogeneity of the population activity region at the micro-scale by combining urban form elements.Next,a population aggregation preference model was established by considering the spatial distribution characteristics of the local aggregation of the urban population flow and long-term stability characteristics depending on the dynamic changes in entrances and exits.Finally,we divided the FPAZ combined with the microstructural elements.Experimental results showed that compared with other types of PAUs,the FPAZ was more consistent with the urban morphology and was an appropriate and general spatial unit for expressing the accurate characteristics of population distributions and changes at the micro-scale.展开更多
The aggregation behavior of submicron-sized particles of praseodymium-doped zirconium silicate, a ceramic pigment, in aqueous suspension was predicted by a modified population balance model, In the model, the collisio...The aggregation behavior of submicron-sized particles of praseodymium-doped zirconium silicate, a ceramic pigment, in aqueous suspension was predicted by a modified population balance model, In the model, the collision frequencies were selected to describe evolution of the particle size distribution of the suspension. The collision efficiency was estimated as a function of interaction potential between particles based on Derjaguin-Landau-Verwey-Overbeek theory. The population balance model was modified to predict the stable state of the aggregation by introducing the volume mean size of aggregate to stability ratio. In addition, aggregation of the particles in aqueous suspension in the presence of sodium dodecyl benzene sulfonate or potassium chloride was experimentally investigated. The predicted data (i.e., the final aggregate size, aggregation rate, and particle size distribution) were similar to the experimentalresults.展开更多
This paper calculated spatial accessibility of all counties (city,urban district) in China with cost weighted distance method. Region divisions of county accessibility were conducted,and relation of traffic accessib...This paper calculated spatial accessibility of all counties (city,urban district) in China with cost weighted distance method. Region divisions of county accessibility were conducted,and relation of traffic accessibility and population aggregation was discussed in this paper. The results indicated that county accessibility in China had mainly low values and a distribution structure of circle layer and reverse-to-natural gradient. There was an obvious correlation between county accessibility and population density in China. With these analyses,inner mechanisms of population migration in different traffic conditions and region types were revealed,and can provide useful proposals to regional planning,traffic planning and smart distribution of people in China.展开更多
Under the background of population aggregation in megacities,some adjustments are made to the urbanization strategy,whose focus is shifted to the development of megacities and megacity clusters.Meanwhile,the housing p...Under the background of population aggregation in megacities,some adjustments are made to the urbanization strategy,whose focus is shifted to the development of megacities and megacity clusters.Meanwhile,the housing price differentiation among cities tends to become increasingly serious.This paper,from the perspective of population mobility,takes provincial capitals and municipalities with independent planning status(PCs&MIPSs)as research samples to evaluate the level of housing price differentiation within provincial-level administrative divisions of China,and analyze from the perspective of demand side how the metropolitanization effects regarding the population formed due to population aggregation in megacities affect the housing prices of megacities and the housing price difference between megacities and other cities.The research found that:1)The increasing net inflow of population boosts the housing prices and accelerate the housing price differentiation;2)The impact of the increasing net inflow of population on housing price increases and housing price differentiation has regional heterogeneity and city size heterogeneity;3)The income gap strengthens the effect of population inflow upon the housing price differentiation.展开更多
The compositional distribution within aggregates of a given size is essential to the functionality of com- posite aggregates that are usually enlarged by rapid Brownian coagulation, There is no analytical solution for...The compositional distribution within aggregates of a given size is essential to the functionality of com- posite aggregates that are usually enlarged by rapid Brownian coagulation, There is no analytical solution for the process of such two-component systems, Monte Carlo method is an effective numerical approach for two-component coagulation, In this paper, the differentially weighted Monte Carlo method is used to investigate two-component Brownian coagulation, respectively, in the continuum regime, the free-molecular regime and the transition regime. It is found that (1) for Brownian coagulation in the continuum regime and in the free-molecular regime, the mono-variate compositional distribution, i.e., the number density distribution function of one component amount (in the form of volume of the component in aggregates) satisfies self-preserving form the same as particle size distribution in mono-component Brownian coagulation; (2) however, for Brownian coagulation in the transition regime the mono-variate compositional distribution cannot reach self-similarity; and (3) the bivariate compositional distribution, i.e., the combined number density distribution function of two component amounts in the three regimes satisfies a semi self-preserving form. Moreover, other new features inherent to aggregative mixing are also demonstrated; e.g., the degree of mixing between components, which is largely controlled by the initial compositional mass fraction, improves as aggregate size increases.展开更多
基金supported by the National Natural Science Foundation of China(U20A2091,41771426).
文摘The population analysis unit(PAU)is the basic unit employed in studies of urban populations.The commonly used PAUs are mostly administrative divisions,regular geographic grids.However,these units are different from urban forms,and cannot be used to consider the characteristics of population distributions and flow changes.In this study,we proposed a method for constructing a fine population analysis zone(FPAZ)based on the population aggregation pattern and urban form elements.First,considering the spatial structure of a city and the fine-grained demands of population analysis,the basic analysis unit was divided according to the functional heterogeneity of the population activity region at the micro-scale by combining urban form elements.Next,a population aggregation preference model was established by considering the spatial distribution characteristics of the local aggregation of the urban population flow and long-term stability characteristics depending on the dynamic changes in entrances and exits.Finally,we divided the FPAZ combined with the microstructural elements.Experimental results showed that compared with other types of PAUs,the FPAZ was more consistent with the urban morphology and was an appropriate and general spatial unit for expressing the accurate characteristics of population distributions and changes at the micro-scale.
文摘The aggregation behavior of submicron-sized particles of praseodymium-doped zirconium silicate, a ceramic pigment, in aqueous suspension was predicted by a modified population balance model, In the model, the collision frequencies were selected to describe evolution of the particle size distribution of the suspension. The collision efficiency was estimated as a function of interaction potential between particles based on Derjaguin-Landau-Verwey-Overbeek theory. The population balance model was modified to predict the stable state of the aggregation by introducing the volume mean size of aggregate to stability ratio. In addition, aggregation of the particles in aqueous suspension in the presence of sodium dodecyl benzene sulfonate or potassium chloride was experimentally investigated. The predicted data (i.e., the final aggregate size, aggregation rate, and particle size distribution) were similar to the experimentalresults.
基金Foundation: National Natural Science Foundation of China, No.40871261 No.40971101 The Mega-project of Science and Technology Research for the 11th Five-Year Plan of China, No.2006BAJ05A06
文摘This paper calculated spatial accessibility of all counties (city,urban district) in China with cost weighted distance method. Region divisions of county accessibility were conducted,and relation of traffic accessibility and population aggregation was discussed in this paper. The results indicated that county accessibility in China had mainly low values and a distribution structure of circle layer and reverse-to-natural gradient. There was an obvious correlation between county accessibility and population density in China. With these analyses,inner mechanisms of population migration in different traffic conditions and region types were revealed,and can provide useful proposals to regional planning,traffic planning and smart distribution of people in China.
文摘Under the background of population aggregation in megacities,some adjustments are made to the urbanization strategy,whose focus is shifted to the development of megacities and megacity clusters.Meanwhile,the housing price differentiation among cities tends to become increasingly serious.This paper,from the perspective of population mobility,takes provincial capitals and municipalities with independent planning status(PCs&MIPSs)as research samples to evaluate the level of housing price differentiation within provincial-level administrative divisions of China,and analyze from the perspective of demand side how the metropolitanization effects regarding the population formed due to population aggregation in megacities affect the housing prices of megacities and the housing price difference between megacities and other cities.The research found that:1)The increasing net inflow of population boosts the housing prices and accelerate the housing price differentiation;2)The impact of the increasing net inflow of population on housing price increases and housing price differentiation has regional heterogeneity and city size heterogeneity;3)The income gap strengthens the effect of population inflow upon the housing price differentiation.
基金H.Zhao was supported by funds from"The National Natural Science Foundation of China"(50876037 and 50721005)"Program for New Century Excellent Talents in University"(NCET-10-0395)"National Key Basic Research and Development Program"(2010CB227004)
文摘The compositional distribution within aggregates of a given size is essential to the functionality of com- posite aggregates that are usually enlarged by rapid Brownian coagulation, There is no analytical solution for the process of such two-component systems, Monte Carlo method is an effective numerical approach for two-component coagulation, In this paper, the differentially weighted Monte Carlo method is used to investigate two-component Brownian coagulation, respectively, in the continuum regime, the free-molecular regime and the transition regime. It is found that (1) for Brownian coagulation in the continuum regime and in the free-molecular regime, the mono-variate compositional distribution, i.e., the number density distribution function of one component amount (in the form of volume of the component in aggregates) satisfies self-preserving form the same as particle size distribution in mono-component Brownian coagulation; (2) however, for Brownian coagulation in the transition regime the mono-variate compositional distribution cannot reach self-similarity; and (3) the bivariate compositional distribution, i.e., the combined number density distribution function of two component amounts in the three regimes satisfies a semi self-preserving form. Moreover, other new features inherent to aggregative mixing are also demonstrated; e.g., the degree of mixing between components, which is largely controlled by the initial compositional mass fraction, improves as aggregate size increases.