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Gusein-zade SM 《Journal of regional science》1993,33(4):547-558
ABSTRACT. The paper is devoted to modeling the relationship between the density of service centers and the density of population (or on the density of demand). Several models lead to an exponential function with the exponent equal to ⅔. For a number of real systems of centers, the power is considerably different from ⅔ (more often it is nearer to 1). I describe a series of models that explain this difference. 相似文献
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Revegetated Sand Mining Areas,Swamp Wallabies and Remote Sensing: North Stradbroke Island,Queensland
Mining of mineral sands has taken place on North Stradbroke Island for over 40 years. Revegetation of mined areas creates a mosaic of seral classes. For a mine site in the northwest of the island, Landsat Thematic Mapper data were used successfully to map the distribution of seven seral classes resulting from mining rehabilitation. Faecal pellet counts were used to assess usage of these areas and surrounding natural forest by swamp wallabies, Wallabia bicolor. Results indicated that revegetated sites from 2 to 4 years in age were heavily used by wallabies. Older revegetated sites, dominated by senile Acacia cunninghamii, and offering little or no forage, were avoided. Swamp wallabies used revegetated sites for night-time feeding sessions and rested, during the day, in surrounding eucalypt forest. 相似文献
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S.M. TURTON 《Geographical Research》1993,31(2):155-176
There is now widespread consensus among researchers that treefall gaps play a key role in the structure and function of closed-canopy forests, such as rain forests, with virtually all canopy tree species requiring growth in a gap to reach maturity. Until recently many believed that latitude and the size of treefall gaps were the main factors determining the availability of solar radiation in gaps and associated microclimates and vegetation dynamics. However, if solar radiation availability is the main limiting resource in such forests, then studies of gap dynamics need to take into account the other factors affecting the penetration and distribution of direct and diffuse irradiance within gaps. As a consequence, this is the first attempt to develop a universal model for the estimation of ‘effective gap’ solar radiation regimes that, along with latitude and gap size, incorporates factors such as slope angle, slope aspect, height of surrounding vegetation, sky conditions and daily and seasonal variation in the position of the sun. Results of three computer simulations are presented to demonstrate how latitude, topography and sky conditions affect solar radiation availability beneath circular canopy gaps of various configurations. Finally, the implications of these simulations for forest regeneration, reforestation and forest management are discussed. 相似文献
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Lee KS 《Journal of regional science》1984,24(4):509-517
A two-sector dynamic general equilibrium model is developed "to investigate the direction of migration in response to differing demographic and consumption demand behavior, as well as variations in production conditions." The model, which involves a rural sector and an urban sector, incorporates "returns to scale and the natural rate of sectoral population growth as important determinants of the direction of migration, in addition to price and income elasticities, and the sectoral technical change rate with which...previous studies dealt." 相似文献
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