Research on Regional Structure and Spatial Fractal Characteristics of Urban Agglomerations at Northern Slope of Tianshan Mountains

Optimization of geographic spatial structure is an important aspect and main content of studying urban sustainable development.Mastering the rules of the form and changes in the city clusters will have significant meaning in promoting the urban agglomerations development.Through analyzing the geographic spatial structure including the hierarchical structure,the structure urban functional changes and the spatial-temporal feature of size,which is based on using the fractal theory and combining the cluster analysis,this paper discusses the development route of oasis urban agglomerations from 1990 to 2005 and the method of optimization of geographic spatial structure at the northern slope of the Tianshan Mountains in arid area.The research suggested that the rank-scale distribution and spatial interaction has fractal character.The hierarchical structure in urban agglomerations at the northern slope of the Tianshan Mountains has the characteristic such as loosing,primate city distribution,and the uneven population distribution and polarization trend.But from 1990 to 2005,the urban primacy index decreased and the structure of size-scale optimized.The trend of the agglomerations population is that the centre changed from single to multi-center.The functional division in urban agglomerations is not very distinct.The urban economic structure is similar: the leading sector is industry and sectors with superiority are transportation and business industry.In 1990,there was only single isolated relatively centre,so the impact of centralization was remarkable.In 2005,with the function of central cities developing,its centralization and pervasion was enhanced.The urban functional structure is developing and perfecting.Impacted on natural environment influence and restriction,the spatial distribution is linear,and the most cities lie on a geographic element as rivers,railway and national artery.The connectivity degree is relatively strong.The display of spatial organizational structure of cities is belt,integration of partial and whole,concentration of megalopolis and economic zone.