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1.
城镇体系等级结构的分形维数及其测算方法*   总被引：95，自引：10，他引：85  
文章探讨了城镇体系等级结构的分形研究方法。首先,讨论了区域城镇规模分布的Zipf模型,并通过分形退化分析将其应用范围加以拓广,从而与非分形研究接口;第二,引进了分形结构因子,以此开创了城镇体系等级结构的FSF分析;第三,提出了表征城镇体系等级差异的差异度概念和度量方法。文章给出实例说明了各种方法的应用,并比较了三种方法的异同。  相似文献   

2.
This paper discusses the self-affinity dimensions of landscape surfaces at a short-range scale and the link to morphotectonic features of the young orogenic belts of Taiwan. The variogram method is adopted to estimate such parameters as the fractal dimension (D), the ordinate-intercept (γ) and the range (R) from data subsets of the digital elevation model (DEM) in a moving-window operation. The fractal morphology expressed by D and γ is found to be useful in defining geomorphic provinces that are related to tectonic features. The mountainous terrain is characterized by high gamma values and low fractal dimensions in contrast to the coastal plains where low gamma values and high fractal dimensions are found. A zone, defined by the fractal parameters (2.4<D<2.6 and 0<γ<2.4), is found to coincide with the most tectonically active zone of Taiwan. Active faults often occur at the boundary between landscapes with contrasting fractal patterns. In the flat lowlands along the western coast, the fractal morphology displays a west-facing amphitheatric pattern, which may be related to the indentation of the pre-Miocene Peikang Basement High. The fractal morphology may reflect some subtle changes in surface textures of a landscape sculpted by surface processes, which in turn are influenced by tectonic activities. The surface roughening and diffusive smoothing may concur to shape the landscape surface at the short ranges we discuss in this study.  相似文献   

3.
The fractal dimension (D) was estimated for nine tidal channels depicted in thematic mapper (TM) Landsat-5 imagery to derive information about the degree of geomorphological control on a tidal channel network characteristic of the Bahía Blanca Estuary (Argentina). Two methods, box counting and contiguity, were used to estimate fractal dimensions for each tidal channel. All channels produced D values close to 1, meaning that they are self-affine fractal features. However, these fractal dimensions do not represent the meandering pattern complexity characteristic of the tidal channels analysed. Although both methods allowed for estimation of D, the contiguity method showed that three of the channels actually are not fractal but have sinusoidal characteristics, a condition that was not detected by the former method.  相似文献   

4.
长江三角洲地区城市用地增长的时空特征分析   总被引：45，自引：2，他引：43  
以Landsat MSS、TM、ETM 卫星影像为主要数据源,利用遥感和GIS 手段,提取了长江三角洲地区5 个时相(1979 年、1990 年、1995 年、2000 年、2005 年) 城市用地信息,分析了城市用地扩展速度、扩展强度、空间结构的变化特征,进而探讨了长江三角洲1979 年以来的城市空间生长过程。结果表明：① 1979 年以来,长江三角洲城市用地增长呈明显的加快趋势,城市用地总体扩展强度也表现为不断提高。不同行政等级城市用地的扩展强度表现为直 辖市> 地级市> 副省级市> 县(县级市)。② 长江三角洲城市用地空间结构的分维和稳定性特征具有一定的波动性。城市用地的空间结构特征与城市用地增长过程和发展阶段具有一定的联系。③ 长江三角洲城市生长表现出“一核二带”、“二核三带”、“四核四带”和“五核五带”的空间轨迹。  相似文献   

5.

Fabric and roughness of the pore-size distributions in organic-rich shales determine their fluid flow and storage capabilities. Accurate estimation of the pore-surface fractal dimension (D) provides valuable insight to these qualities in shales. Low-pressure gas adsorption isotherms are widely used for determining D, typically applying the Frenkel–Halsey–Hill (FHH) method. Other D estimation methods, proposed by Neimark (NM) and Wang and Li (WL), are theoretically consistent and mathematically related to the FHH model but yield distinctive D values for many shales. This study evaluates the mathematical relationships between the FHH, NM and WL fractal determination methods, and with the aid of twenty-six published adsorption isotherms from shales around the world, compares their similarities and differences. Uncertainties exist in establishing best-fit lines to curved data trends in the FHH and NM methods, and in fitting power curves to data trends in the NM and WL methods. The FHH and WL D values are found to be more consistent for whole isotherm and isotherm segment analysis than the NM D values, which are systematically higher. The reasons for this are explained in terms of their graphical relationships. This leads to a novel 10-step protocol for a more thorough determination of shale D values that incorporates all three methods and involves graphical analysis that clearly exposes the uncertainties associated with the values determined. Applying this protocol should derive reliable D values to compare with key shale properties such as surface area, surface volume, thermal maturity and organic richness in future research.

  相似文献   

6.
Variable complexity of the US Continental Divide trace   总被引：1，自引：0，他引：1  
Abstract

Map-view complexity of 65 contiguous segments of the conterminous US Continental Divide trace was evaluated by the divider method, with each segment’s geometry approximated by a fractal dimension (D) value, or two D values applying to fine and coarse scales of inspection. Results support a generalization that D values in the range 1.05–1.12 are typical for drainage divides viewed at regional to national scales. However about 20% of cases reviewed in this study are smoother (D = 1.01–1.04) or more complex (D = 1.13–1.18) traces. Complexities of these watershed boundary segments show no significant correlation with physiographic province or local relief. The primary influence of bedrock lithology and surface process is seen in zones of Quaternary volcanism, where uncommonly smooth and highly complex divide trace segments are more the rule than exception. Uncommonly smooth divide traces are also found descending mountain pediments in areas of parallel drainage, and some of the most tortuous traces are associated with drainage patterns disrupted by non-fluvial processes. Divide trace segments crossing terrain with uniform lithology show decreased complexity, but traces with the broadest range of complexity, including highest D values, occur in areas with moderate, not extreme, degrees of bedrock diversity.  相似文献   

7.
以多时相Landsat MSS、TM和ETM 卫星影像为数据源,提取宁波城市各组团(三江片、镇海片和北仑片) 多时相的用地信息,分析了港口城市用地扩展的时空特征及外部形态演变过程。结果表明: (1) 1979年以来,宁波城市用地面积扩展速度和扩展强度不断提高,但各个组团的表现有较大的差异。(2) 各组团城市用地空间结构分维数的波动与城市用地的空间扩展模式表现出明显的相关性。(3) 3个组团的城市用地扩展强度指数峰区相对城市质心有不断外移趋势,但扩展强度指数峰值的变化在各个片区有一定差异。(4) 3个组团城市用地外部形态演变在不同方向上的差异性与宁波港口迁移及港口经济的发展密切相关。(5) 随着宁波港口从内河港向河口港、海岸港的迁移,宁波城市外部形态演变经历块状单一集中型内河港城市、 "一城一镇"飞地式群组河口港城市、"一城二镇" 飞地式群组海港城市和"一城多镇"不连续带状群组海港城市发展阶段,最后将形成"T"型带状群组现代化国际港口城市。  相似文献   

8.
Surface-process models (SPMs) have the potential to become an important tool in predicting sediment flux to basins, but currently suffer from a lack of quantitative understanding of their controlling parameters, as well as difficulties in identifying landscape properties that can be used to test model predictions. We attempt to constrain the parameter values that enter a SPM by comparing predictions of landscape form (as expressed by hypsometric and fractal measures) and process rates obtained for different parameter sets with observations from the south-eastern Australian highlands, a rifted margin mountain belt that has remained tectonically stable during Cenozoic times. We map the hypsometry and fractal characteristics of south-eastern Australia and find that the roughness amplitude (G) correlates well with local relief, whereas the hypsometric integral (H ) correlates slightly better with elevation than with relief. The fractal dimension (D) does not correlate with any other morphometric measure and varies randomly throughout the region. Variograms generally show three kinds of scaling behaviour of topography with increasing wavelength, with topography only being truly self-affine at wavelengths between ～1 and 10 km. From a review of the available data on long-term denudation rates in south-eastern Australia, we infer that these have been 1–10 m Myr?1, and average escarpment retreat rates 0.2–1.0 km Myr?1, throughout the Cenozoic. Model predictions, using a SPM that includes hillslope diffusion and long-range fluvial transport, suggest that landscape form evolves with time; after an initial phase where D, G and relief increase, all morphometric measures decrease with increasing denudation. The behaviour of GandH in the models is qualitatively compatible with the observations; D, however, varies predictably in the models, in contrast with its random behaviour in the real world. The observed present-day morphology of SE Australia does not impose quantitative constraints on parameter values. The fractal analyses do impose general conditions of relative parameter values that have to be met in order to create ‘realistic’ topographies. They also suggest that there is no theoretical basis for including hillslope diffusion in SPMs with a spatial resolution coarser than 1 km. A comparison of the observed denudation and retreat rates with model predictions places order-of-magnitude constraints on parameter values. Thus, data pertaining to landscape evolution are much more valuable than static present-day topography data for calibrating SPMs.  相似文献   

9.
福建省城镇体系分形研究   总被引：13，自引：0，他引：13  
伍世代  王强 《地理科学》2007,27(4):493-498
应用分形理论对福建省城镇体系进行了规模和空间结构研究,验证了福建省城镇体系得规模分布和空间布局均符合局部的分形特征,同时得出以下结论:第一,福建省城镇体系规模分布还处于初级的首位型阶段,城镇体系规模等级发育不成熟;第二,福建省城镇体系在空间分布上存在区域、地方两个不协调的现象;第三,福建省地区城镇体系交通网络的通达性较高,城市间联系较为紧密,但也注意到区域城镇网络的均衡性还有待提高。最后,通过自然、社会及历史等原因对成因进行讨论,据此提出福建省城镇体系结构优化的建议。  相似文献   

10.
《自然地理学》2013,34(6):528-555
Stream channel response to urban land use has not been well documented for southeastern Coastal Plain streams. In this study, urban channel response was evaluated in small Inner Coastal Plain watersheds (<5 km2) in eastern North Carolina. Reaches were selected across a range of watershed total impervious area (0-67% TIA). Channel dimensions and sediment grain size data were collected along 20 urban (>10% TIA) and 20 rural reaches (<10% TIA), and at 10 stormwater outfall sites (180 cross-sections). Urban cross-sectional area, channel incision ratio, and channel grain size (gravel%, D50, and D84) were greater, relative to rural channels. Bankfull cross-sectional areas were approximately 1.78 times greater for urban watersheds than for rural watersheds. Channels in urban watersheds were incised and had median full-channel capacities approximately 3.4 times greater than channels draining rural watersheds. Watershed TIA explained 65-72% of channel capacity enlargement. Urban expansion in the region began in the 1960s, with major urbanization occurring over the last 25 years. Channels draining urban watersheds are still responding to this land use change by downcutting and widening. Urban channel incision has frequently cut off streams from their floodplains, reducing floodplain sediment retention and water quality functions.  相似文献   

11.
Cellular automata (CA) models are used to analyze and simulate the global phenomenon of urban growth. However, these models are characterized by ignoring spatially heterogeneous transition rules and asynchronous evolving rates, which make it difficult to improve urban growth simulations. In this paper, a partitioned and asynchronous cellular automata (PACA) model was developed by implementing the spatial heterogeneity of both transition rules and evolving rates in urban growth simulations. After dividing the study area into several subregions by k-means and knn-cluster algorithms, a C5.0 decision tree algorithm was employed to identify the transition rules in each subregion. The evolving rates for cells in each regularly divided grid were calculated by the rate of changed cells. The proposed PACA model was implemented to simulate urban growth in Wuhan, a large city in central China. The results showed that PACA performed better than traditional CA models in both a cell-to-cell accuracy assessment and a shape dimension accuracy assessment. Figure of merit of PACA is 0.368 in this research, which is significantly higher than that of partitioned CA (0.327) and traditional CA (0.247). As for the shape dimension accuracy, PACA has a fractal dimension of 1.542, which is the closest to that of the actual land use (1.535). However, fractal dimension of traditional CA (1.548) is closer to that of the actual land use than that of partitioned CA (1.285). It indicates that partitioned transition rules play an important role in the cell-to-cell accuracy of CA models, whereas the combination of partitioned transition rules and asynchronous evolving rates results in improved cell-to-cell accuracy and shape dimension accuracy. Thus, implementing partitioned transition rules and asynchronous evolving rates yields better CA model performance in urban growth simulations due to its accordance with actual urban growth processes.  相似文献   

12.
杭州城市形态和土地利用结构的时空演化   总被引：53，自引：3，他引：50  
冯健 《地理学报》2003,58(3):343-353
根据分形理论研究杭州1949~1996年间城市形态和土地利用结构的演化特征,发现杭州城市具有明确的自相似规律。研究表明,杭州城市形态和土地利用结构的分形性态逐渐变好,这与国外学者“演化的城市分形”观相互印证。各类土地形态的维数都小于整个城市形态的维数,从而证实了国内学者“城市化地区的分维大于各职能类土地空间分布维数”的理论推断。从时空变化来看,杭州城市形态的分维呈上升趋势,1996年接近Batty等提出的理论预期维数D = 1.71;居住用地、工业用地和对外交通用地的分维近20年来趋于增大,而教育用地和绿化用地的分维则有所减小。杭州市的分形演化和分维变化总体上揭示了城市自组织演化的特征,但工业用地维数的大幅度上升和绿化用地维数的下降显然暗示该城市在进化过程中的局部退化倾向。  相似文献   

13.

The legal city and the urbanized area fail to depict accurately the physical area of urban development and therefore prevent an accurate calculation of population densities. When underbounding occurs, densities tend to be unrealistically high and with overbounding they are low. Delimitations made by air photo interpretation demonstrate that the physical city, measured on a 21/2 acre scale of generalization, provides a more accurate basis for calculating population densities of urban areas than either the legal city or urbanized area because the bounding problems are eliminated.  相似文献   

14.
土地利用与土地覆被变化的分形分析--以郑汴间沙岗地为例   总被引：16，自引：2，他引：14  
文章应用盒子计数法计算了郑汴之间沙岗土地各种土地覆被类型空间分布的分维值,讨论了土地利用与土地覆被变化(LUCC)的分形性质.结果表明,土地利用与土地覆被是一种分形事物.分维是综合表征LUCC空间分布状况的一个特征参数,其值域为0＜D＜2.分维值越大,表明土地覆被空间分布愈不规则、愈复杂;分维值的变化可以反映出土地利用与土地覆被类型的空间结构在时间维上的变化.  相似文献   

15.
Taken fractal dimension, compact ratio, urban centroid and urban principal axis as the urban spatial characteristic indices, Tianjin city’s urban area is investigated in the last 26 years in a quantitative perspective, and its traits and changes during different periods are also analyzed. It is clear that these indices can not only scientifically and explicitly assess the urban morphology, urban direction and its changes and trends, but also uncover long-term effects of economy and urban planning on urban morphology.  相似文献   

16.
Zipf维数和城市规模分布的分维值的关系探讨   总被引：28，自引：4，他引：24  
谈明洪  范存会 《地理研究》2004,23(2):243-248
城市位序 规模理论和分形理论是研究城市系统的重要基础。前者可以较好地刻画城市的规模分布 ,后者可用来深入地解释城市规模的分布规律。其中 ,城市规模分布的分维值和Zipf维数是这两个基础理论中的重要参数。在研究我国城市规模的分布规律时 ,理论上可认为分维值和Zipf维数的乘积等于 1。但本文认为这种理论上的关系并不能直接套用到统计分析中去 ,如果城市规模分布的分维值和Zipf维数是利用对于样本的OLS (最小二乘法 )估计所得 ,两者的乘积应等于判定系数 (R2 )。最后我们对此结果进行了推导和证明 ,并对其所具有的理论意义和实践价值进行了简要阐述。  相似文献   

17.
上海大都市交通网络分形的时空特征演变研究   总被引：18，自引：4，他引：14  
刘妙龙  黄蓓佩 《地理科学》2004,24(2):144-149
分形理论的城市形态发生学研究应用,首先是从交通网络的应用开始的。国内外学者进行的大量案例研究表明,分形分维有可能是表征城市交通网络特征、解释城市交通网络发展,演化的一种较为理想的测度指标。以上海这一国际性大都市的交通网络为研究主体,通过测算上海市不同行政区域交通网络的分维值,研究分形特征的空间变化;利用不同时代上海市全域及典型行政区交通网络的分维,研究分形特征的时间演化。研究结果表明,在上海与一些发展相当成熟的大、中城市与城市化地区,交通网络形态1.7左右的分形分维值具有普适性,有可能是判断网络形态与功能、结构完善度的一个较为合宜的测度指标;分维的变化,表现在空间域上,上海城市交通网络的分形特征内域明显复杂于外域,在城市发展主轴方向表现为由内向外分维测度值的有序降低;而在时间域,近期的交通网络分形复杂度明显高于早期,网络的构型不断得到优化;这一总体趋势,与城市形态开发、经济发展的历程相一致。可以相信,分形测度与分维的演化将成为描述城市形态发生学过程的一个最有用的指标。  相似文献   

18.
Least squares linear regression (LSLR) analysis is often used for estimating fractal dimension from the slope of scatterplots produced by fractal analysis. Coefficients of determination close to unity are commonly accepted as sufficient evidence of linearity, and hence statistical self-similarity (or affinity). In this study, high R 2 values derived from linear regression analyses are shown to increase the likelihood of detecting significant curvature in a relation. While this curvature is unlikely to hinder the use of LSLR in predicting y from x, it is demonstrated that large variations in the slope coefficient, and hence in estimates of fractal dimension, can exist in the presence of R 2 values close to unity. Therefore, coefficients of determination close to unity should not be used as evidence of linearity. In light of this finding, it is strongly suggested that even in the presence of high coefficients of determination, residual analysis and/or other tests for linearity always be conducted when linear regression is employed in fractal analysis. [Key words: coefficient of determination, statistical self-similarity, fractal dimension.]  相似文献   

19.
Quantitative regional assessments of streambed sedimentation and its likely causes are hampered because field investigations typically lack the requisite sample size, measurements, or precision for sound geomorphic and statistical interpretation. We adapted an index of relative bed stability (RBS) for data calculated from a national stream survey field protocol to enable general evaluation of bed stability and anthropogenic sedimentation in synoptic ecological surveys. RBS is the ratio of bed surface geometric mean particle diameter (Dgm) divided by estimated critical diameter (Dcbf) at bankfull flow, based on a modified Shield's criterion for incipient motion. Application of RBS to adequately depict bed stability in complex natural streams, however, has been limited because typical calculations of RBS do not explicitly account for reductions in bed shear stress that result from channel form roughness. We modified the index (RBS) to incorporate the reduction in bed shear stress available for sediment transport that results from the hydraulic resistance of large wood and longitudinal irregularities in channel dimensions (“form roughness”). Based on dimensional analysis, we derived an adjustment to bankfull shear stress by multiplying the bankfull hydraulic radius (Rbf) by the one-third power of the ratio of particle-derived resistance to total hydraulic resistance (Cp/Ct)1/3, where both resistances are empirically based calculations. We computed Cp using a Keulegan equation relating resistance to relative submergence of bed particles. We then derived an empirical equation to predict reach-scale hydraulic resistance Ct from thalweg mean depth, thalweg mean residual depth, and large wood volume based on field dye transit studies, in which total hydraulic resistance Ct was measured over a wide range of natural stream channel complexity, including manipulation of large wood volumes. We tested our estimates of Ct and RBS by applying them to data from a summer low flow probability sample of 104 wadeable stream reaches in the Coastal Ecoregion of Oregon and Washington, USA. Stream discharges calculated using these Ct estimates compared favorably with velocity–area measurements of discharge during summer low flow, and with the range of 1 to 2-year recurrence floods (scaled by drainage area) at U.S.Geological Survey gauged sites in the same region. Log [RBS] ranged from − 4.2 to + 0.98 in the survey region. Dgm ranged from silt to boulders, while estimated bankfull critical diameter, Dcbf, ranged from very fine gravel to large boulders. The median value of Dcbf (adjusted for form roughness influences) averaged 40% (inter quartile range 28 to 59%) of the unadjusted estimate Dcbf. Log[RBS] was consistently negatively related to human disturbances likely to produce excess sediment inputs or hydrologic alteration. Log [RBS] ranged from − 1.9 to + 0.5 in the streams within the lower quartile of human disturbance in their basin and riparian areas and was substantially lower (− 4.2 to − 1.1) in streams within the upper quartile of human disturbance. The synoptic survey methods and designs we used appear adequate to evaluate regional patterns in bed stability and sedimentation and their general relationship to human disturbances. Although the RBS concept also shows promise for evaluating sediment and bed stability in individual streams, our approach is relatively coarse, so site-specific assessments using these rapid field methods might prudently be confined to identifying severe cases of sedimentation or channel alteration. Greater confidence to discern subtle differences in site-specific assessments could be gained by calculating RBS using more precise field measurements of channel slope, bed particle size and bankfull dimensions, and by refining our adjustments for energy loss from channel form roughness.  相似文献   

20.
In the present study, spatio-temporal urban sprawl and land consumption patterns were analysed in seven capital cities located in the Himalayan region during 1972, 1991 and 2015 using multi-temporal satellite images. The study exhibits that capital Himalayan cities experienced rapid growth (830.92%) with high population increase (333.45%) during the observation period (1972–2015). The significant urban growth was observed in the cities of western and middle Himalayan region viz., Srinagar (9.36 km2–142.19 km2), Kathmandu (11.38 km2–92.58 km2) and Dehradun (4.1 km2–50.09 km2) in the higher altitudes due to remarkable increase in the population (0.5–1 million persons) during 1972–2015. On the contrary, Itanagar (7.19 km2), Gangtok (7.09 km2), Shimla (3.04 km2) and Thimphu (2.93 km2) observed less urban growth with moderate to low population growth (i.e., 0.05 to 0.15 million persons). The Shannon entropy based study exhibits that the cities viz., Kathmandu, Gangtok and Itanagar observed comparatively more dispersed urban growth during later period (1991–2015) as compared to the previous period (1972–1991) whereas, the remaining cities observed comparatively less dispersed urban growth during later period. The temporal land consumption pattern exhibits low density urban growth in Srinagar, Dehradun and Kathmandu, as observed with decrease in population density and increasing land consumption during 1972–2015 as compared to other cities, wherein urban densification was evident with increase in population density and decrease in land consumption. The cities in central and western Himalayan region observed high urban growth as compared to cities in eastern Himalayan region. The result shows that the capital cities contributes insignificant proportion (0.5%; 314 km2) of urban area in Himalayan region and accommodating large (ca. 4 million) population during 2015. The study indicates unplanned and haphazard growth in all capital Himalayan cities, leading towards urban densification as well as dispersion in the periphery with varied pattern and intensity. The specific trends and patterns of urban and population growth are governed by geographical as well as socio-economic-political factors at local to regional scale. The high population pressure induced higher risk to the urban residents as well as constrained urban growth over higher vulnerable zones. The study necessitates implementation of suitable urban planning methods considering socio-economic and physico-cultural characteristics of the region.  相似文献   

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