A Tentative Theoretical Interpretation of the Fractal Dimension of Urban Form
本文尝试从理论上解释城市形态的平均分形维数，指出城市人口动态类似扩散限制聚集模型，交通网络类似介电击穿模型，发展中的城市兼具两者特征，平均维数接近1.71，并建议用分形维数指导城市规划。
A tentative interpretation of the mean fractal dimension values of real urban form is presented. Urban population dynamics has some property of diffusion-limited aggregation (DLA) model. The fractal dimension of DLA is about 1.67 in two-dimensional space. On the other hand, urban transport network has some character of di-electric breakdown model (DBM). The fractal dimension of DBM is near 1.75 in two-dimensional space when the control parameter η=1. A developing city always has features of both DLA and DBM models, so its dimension is close to 1.71 on the average. In practice, the mean value of fractal dimension of city form can be employed to guide urban planning or designs now that fractal structure is a kind of optimal structure in nature. Two indices based on fractal dimension are suggested for future urban planning as a quantitative criterion of urban form optimization.