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城市系统的内部—外部复杂性及其演化的Stommel图 被引量:1
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作者 陈彦光 刘继生 《经济地理》 CSSCI 北大核心 2007年第1期26-29,21,共5页
城市地理系统可以采用一组标度定律刻画其空间复杂性特征。标度律既可以表示为一组幂律形式,通常也可以等价地分解为一组指数模型。指数律与幂律的逻辑转化揭示了简单性与复杂性的内在数理关系。从指数律出发,将城市系统空间复杂性分为... 城市地理系统可以采用一组标度定律刻画其空间复杂性特征。标度律既可以表示为一组幂律形式,通常也可以等价地分解为一组指数模型。指数律与幂律的逻辑转化揭示了简单性与复杂性的内在数理关系。从指数律出发,将城市系统空间复杂性分为内部复杂性和外部复杂性;从幂律出发,引导出城市化过程Stommel图的表示方法,据此反映城市地理系统演化的时空结构特征。 展开更多
关键词 指数律 幂律 标度律 分形 空间复杂性 stommel
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An exponential expanding meshes sequence and finite difference method adopted for two-dimensional elliptic equations
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作者 Navnit Jha Neelesh Kumar 《International Journal of Modeling, Simulation, and Scientific Computing》 EI 2016年第2期109-125,共17页
We demonstrate a new nonuniform mesh finite difference method to obtain accurate solutions for the elliptic partial differential equations in two dimensions with nonlinear first-order partial derivative terms.The meth... We demonstrate a new nonuniform mesh finite difference method to obtain accurate solutions for the elliptic partial differential equations in two dimensions with nonlinear first-order partial derivative terms.The method will be based on a geometric grid network area and included among the most stable differencing scheme in which the nine-point spatial finite differences are implemented,thus arriving at a compact formulation.In general,a third order of accuracy has been achieved and a fourth-order truncation error in the solution values will follow as a particular case.The efficiency of using geometric mesh ratio parameter has been shown with the help of illustrations.The convergence of the scheme has been established using the matrix analysis,and irreducibility is proved with the help of strongly connected characteristics of the iteration matrix.The difference scheme has been applied to test convection diffusion equation,steady state Burger’s equation,ocean model and a semi-linear elliptic equation.The computational results confirm the theoretical order and accuracy of the method. 展开更多
关键词 Geometric mesh finite difference compact method elliptic partial differential equations convection diffusion equation stommel ocean model
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