摘要
城市化过程在宏观意义上是一种Logistic过程,可以采用S形曲线描述。Northam注意到城市人口比重变化的Logistic曲线特征,并且将其分为三个演化阶段。Northam曲线在国内城市地理学研究中具有较大的影响,但其划分结果不尽准确,前因后果也未澄清。借助系统论的有关思想,从城市—乡村人口的异速生长关系出发,导出城市化水平的Logistic方程,揭示城市化过程的理论基础;进而运用导数原理、Logistic曲线的内禀特征尺度以及城市化水平与经济发展水平的关系模型修正并且改进了Northam曲线,得到一个四阶段的划分结果,最后对重新分段的结果进行了地理空间解释。
A new pattern of Logistic process of urbanization is illustrated using mathematical transform and exponential laws in this paper. Urbanization course can be described by Logistic curve, which was divided into three stages by Northam （1979）： initial stage, acceleration stage, and terminal stage. However, the Northam＇s is just a phenomenological theory with several defects, e.g. no theoretical basis, no critical scale, etc. The authors demonstrate that the Logistic process falls into four phases. Taking the 50% of urbanization ratio as a tipping point named ＂urban half＂, the Logistic curve is divided into two stages： acceleration stage （urban majority） and deceleration stage （urban minority）. The tipping point is determined by differential coefficient of Logistic equation through mathematical transform. Then the two stages are respectively divided into two sub- stages by means of the exponential laws with a parameter as characteristic length. The first exponential law coming from Karmeshu＇ s urban - rural population replacement model, which is in fact an equivalent of the Logistic function of urbanization level and can be expressed with an inverse function i.e. X（t） = Cexp（kt）, where X（t） represents urban- rural population ratio, C and k are parameters 1/k is just the characteristic length of urbanization time t, which can be turn into an internal scale reflecting the local properties of urbanization course. In order to find an external scale reflecting the whole property of world urbanization in the sense of average, Zhou＇s model on the relationships between urbanization and economic development level is used as another exponential law, i.e. y = yoexp（Z/Z0 ） = 85. 6357exp（Z/19.0404）, where y denotes the economic development level of a region, and the parameter Z0 = 19.0404 is just the characteristic length of world urbanization that can act as an external scale. Taking Z0/100 = 19,0404% as one dividing point, the acceleration stage is compartmentalized into two sub- s
出处
《经济地理》
CSSCI
北大核心
2005年第6期817-822,共6页
Economic Geography
基金
国家自然科学基金重点项目(编号:40335051)
美国课题(theSpring2003NewFacultyAward)联合资助
