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1.
基于DEM的流域水系分维计算与结果分析 总被引：7，自引：0，他引：7
利用ArcGIS8.3和ArcVIEW3.2中的水文分析模块,根据不同最小河流长度,提取晋江流域河网信息,采用传统的网格法计算提取的不同河网的分维,研究以最小河流长度所提取的不同河网密度与分维的关系,确定晋江流域分维,分析流域地貌的演变。 相似文献
2.
XU Jianhua CHEN Yaning LI Weihong DONG Shan 《中国地理科学(英文版)》2008,18(1):77-84
Based on the time series data from the Aral hydrological station for the period of 1958-2005, the paper reveals the long-term trend and fractal of the annual runoff process in the mainstream of the Tarim River by using the wavelet analysis method and the fractal theory. The main conclusions are as follows： 1） From a large time scale point of view, i.e. the time scale of 16 （24） years, the annual runoff basically shows a slightly decreasing trend as a whole from 1958 to 2005. If the time scale is reduced to 8 （23） or 4 （22） years, the annual runoff still displays the basic trend as the large time scale, but it has fluctuated more obviously during the period. 2） The correlation dimension for the annual runoff process is 3.4307, non-integral, which indicates that the process has both fractal and chaotic characteristics. The correlation dimension is above 3, which means that at least four independent variables are needed to describe the dynamics of the annual runoff process. 3） The Hurst exponent for the first period （1958-1973） is 0.5036, which equals 0.5 approximately and indicates that the annual runoff process is in chaos. The Hurst exponents for the second （1974-1989） and third （1990-2005） periods are both greater than 0.50, which indicate that the annual runoff process showed a long-enduring characteristic in the two periods. The Hurst exponent for the period from 1990 to 2005 indicates that the annual runoff will show a slightly increasing trend in the 16 years after 2005. 相似文献
3.
水系分形维数的计算与分析,有助于深入理解其与地貌发育、流域径流和侵蚀产沙等过程之间的关系。从分形维数的计算原理,提出了一种在MATLAB环境下,能够同时计算水系计盒维数和信息维数的方法,改进了现有通过图像分析计算分形维数的不足。采用已知分形维数的规则分形集进行验证,结果表明:该方法单独对图像载体上的目标图形(关注区域)进行处理,不受其与整幅图像的比例的限制能够自动确定最佳的对目标图形进行网格分割覆盖的递减等分条件,计算精度高利用元胞数组实现了网格的自动分割,程序紧凑,可读性增强。最后以泾河、北洛河水系为例,说明了该方法的应用过程。本研究为水系分形维数的科学计算提供了新的思路。 相似文献
4.
本文汇总整理了2000-2014年中国发生的472起重特大煤矿事故,获得其空间分布状况;基于分形理论,利用网格法统计不同网格尺度下覆盖重特大煤矿事故的非空网格中的事故数量,计算煤矿事故的全国、三大自然地理区以及干湿分区的分维值,分析其空间分布分形特征;利用R/S方法研究15年来重特大煤矿事故发生的时间分形特征。研究表明,从全国范围来看,重特大煤矿事故具有较好的空间分形特性,但不同区域的重特大煤矿事故的分形特性却具有很大差别。15年来发生重特大事故数量及事故死亡人数逐年下降,由R/S分析得到的Hurst指数表明事故时间序列的分形特征客观存在,并且年发生事故数量及事故死亡人数量减少趋势。 相似文献
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6.
Wetland plant communities in the plateau lakes of Yunnan Province, China, have decreased significantly over the past decades. To better understand this degradation, we analyzed the processes and characteristics of changes in wetland plant communities in two of the largest lakes in Yunnan Province, Dianchi and Erhai lakes. We collected records of native and alien plant communities in the two lakes from literature published from the 1950s to current period. We calculated plant community types and their area in some historical periods when related data were reported, and analyzed the relationship between changes in plant communities and water pollution. In Dianchi Lake, 12 community types of native plant communities, covering over 80% of the surface in the 1950s and 1960s, were reduced to four types covering 2.4% by the late 2000s. Alien plant communities started to appear in the lake in the late 1970s, and have since come to cover 4.9% of the lake surface, thereby becoming dominant. In Erhai Lake, 16 community types of native plant communities, covering 47.1% of the lake surface in the late 1970s, declined to 10 community types, covering 9.3% of the surface, by the late 2000s. Alien plant communities appeared in the middle 1980s, and at present cover 0.7% of the surface area. It was indicated that changes in plant communities were significant related to water eutrophication. The area occupied by native and alien plant communities was, respectively, negatively and positively related to the content of nutrients in water. This showed lacustrine pollution played an important role in native plant loss and alien plant invasion in the two plateau lakes. 相似文献
7.
??????????κ??????R/S????????????????????????????M??4.5????1970??2010??????M??1.0?????з???????????????????????????????????????????????????????е?H???H=0.79????????????е?H?(H=0.87)???????????????????????????ν??? 相似文献
8.
Symmetrical relationships between humans and their environment have been referred to as an extension of symmetries in the human geographical system and have drawn great attention. This paper explored the symmetry between physical and human systems through fractal analysis of the road and drainage networks in Wuling mountainous area. We found that both the road and drainage networks reflect weak clustering distributions. The evolution of the road network shared a significant self-organizing composition, while the drainage network showed obvious double fraetal characteristics. The geometric fractal dimension of the road network was larger than that of the drainage network. In addition, when assigned a weight relating to hierarchy or length, neither the road network nor drainage network showed a fractal property. These findings indicated that the fractal evolution of the road network shared certain similarities with fractal distribution of the drainage network. The symmetry between the two systems resulted from an interactive process of destroying symmetry at the lower order and reconstructing symmetry at the higher order. The relationships between the fractal dimensions of the rural-urban road network, the drainage network andthe urban system indicated that the development of this area was to achieve the symmetrical isomorphism of physical-human geographical systems. 相似文献
9.
广东省公路交通网络分形空间特征研究 总被引：2，自引：0，他引：2
基于分形理论,以GIS技术为支撑,利用回转半径法测算了广东省全域及其所辖21个地级市公路交通网络半径维数DL、分枝维数Db和对应相关系数R2。依据广东省公路交通网络的特点,将其辖区分为四个子区域:珠三角、东部沿海、西部沿海和粤北地区,分析其半径维数和分枝维数的空间分布特征。研究表明,珠三角地区为广东省公路交通网络密度最大、结构最复杂、功能最完善、连通性最优的区域;以珠三角为中心,广东省公路交通网络分形半径维数和分枝维数随距离增大而衰减,沿海衰减程度微弱,粤北衰减程度较大。结果显示,半径维数和分枝维数结合能够更为合理系统地分析交通网络分形特征的时空差异特性。 相似文献
10.
岩石作为一种典型的多孔介质,其内部孔隙结构、形态特征极为复杂,运用常规线性系统内参数描述较为困难,因而采用非线性系统内分形维数这一参数来定量表征孔隙结构的非线性分布特征较为合适。岩石内部孔隙结构分布具有统计意义上的分形特征,因此分形维数的确定对于定量表征孔隙结构分布规律,以及揭示岩石各种力学行为与物理力学指标有着重要意义。将图像处理与阈值分割、分形理论和数理统计相结合,针对CT扫描切片图像,三维重建孔隙结构空间分布模型,计算Hausdorff测度空间下孔隙结构分布盒维数与集束维数。同时,针对孔隙结构空间分布复杂程度的定量表征,提出体素盒维数与圆柱体空间集束维数假想,并通过多种数理统计方法进行假设检验。最后,指出孔隙结构分布是一种多标度分形模型,仅仅单个维数无法描述其全部细节特征,需采用多重分形谱来更为全面表征孔隙分布的细观特征。研究结果表明,Hausdorff测度空间下的平面盒维数可较为全面表征平面孔隙分布特征,但对于针对灰度CT图像构建的体素盒维数可替代传统意义下定义的盒维数,在细观尺度下能更可靠、准确、全面地定量表征孔隙体积分布规律; 集束维数实质是用来定量表征孔隙位置分布规律,若等于欧氏维数,则表明孔隙位置分布具有随机性。 相似文献
11.
ZHUXiao-hua CAIYun-long 《中国地理科学(英文版)》2004,14(1):9-14
MANDELBROT enunciated the uncertainty of the length of a coastline in his paper “How long is the coastline of Britain?” published in Science in 1967. The fractal concept was presented for the first time in that paper and has been applied to many fields ever since. Although fractal dimensions of lots of phenomena were calculated by the box-counting method, the quantitative influence of series of square grids on them is ignored. The issue is systematically discussed as a case study of the mountains of China‘s Mainland in this paper. And some significant conclusions are drawn as follows: 1) Although the fractal character objectively exists in the mountains of China‘s Mainland, and it does not vary with the changes of series of square grids, the fractal dimensions of the mountains of China‘s Mainland are different with these changes. 2) The fractal dimensions of the mountains of China‘s Mainlandvary with the average lengths of sides of series of square grids. The fractal dimension of the mountains of China‘s Mainland is the function of the average length of side of square grid. They conform to the formula D=f(r) (where D is the fractal dimension, and r is the average length of side of square grid). 3) Different dots of data collection can affect the fractal dimension of the mountains of China‘s Mainland. 4) The same range of length of side of square grid and dots of data collection can ensure the comparison of fractal dimensions of the mountains of China‘ s Mainland. The research is helpful to get the more understanding of fractal and fractal dimension, and ensure that the fractal studies would be scientific. 相似文献
12.
淮河流域洪涝变化混沌演化特征研究 总被引：6，自引：0，他引：6
本文在淮河流域洪涝变化分形特征、吸引子维数研究的基础上,以相空间重构为理论,通过Lyaponov指数论证了淮河流域洪涝变化的混沌性和耗散性,分析了洪涝变化的混沌演化特征. 相似文献
13.
14.
The Aral Sea was one of the largest lakes in the world before it started to shrink in the 1960s due to water withdrawal for agricultural irrigation.Precipitation decreased from 9.4 km3 in 1960 to 3.2 km3 in 2009,and annual river inflow into the Aral Sea decreased from 31.5 km3 in 1998 to 5.2 km3 in 2009.Comparison on the hydrological data of the Aral Sea between 1960 and 2009 showed the evaporation,water surface area,and water volume decreased by 90%,80%,and 88%,respectively.This study employs the observed values of water volume,precipitation,runoff,evaporation,and salinity to estimate water volume and salinity from 1960 to 2009,and the efficiency coefficients for predicted water volume and salinity are 0.975 and 0.974,respectively.Regression equations calculated from the observed data are used to predict precipitation,runoff,evaporation,and salinity from 2010 to 2021,and the results are then applied in the estimation of water volume and salinity.Our estimates suggest that salinity will increase to around 200 g/L and water volume will decrease to around 83 km3 in 2021. 相似文献
15.
Floodplains are important and distinctive ecosystems around the world, and the recruitment of ichthyoplankton from river to floodplain lakes is crucial to maintain this unique ecosystem. However,this process has not been well documented. In this study, ichthyoplankton were sampled to investigate the details of ichthyoplankton recruitment from the Changjiang(Yangtze) River to the Dongting Lake via a floodway channel, the Songzi River, from May to July in 2013 and 2014. During the study period, 41 species of eggs and larvae were sampled. Among the samples, 16 were river-lake migratory species(RL), representing23.5% of the species in the Dongting Lake. In 2013, an estimated 130 million eggs and 3 180 million larvae drifted through the sampling section, and in 2014, an estimated 1 060 million eggs and 1 040 million larvae drifted through the sampling section. The amount of eggs and larvae of RL reached 3 210 million in 2013 and 1 850 million in 2014, respectively. These results demonstrated the importance of ichthyoplankton recruitment from the river to the lake, as species diversity will decrease sharply without this recruitment.Canonical correspondence analysis(CCA) showed that water temperature and water flow are the two most important factors influencing the spawning activities of fish. To maintain the high fish diversity in the Changjiang floodplain, we suggest to irrigate the channel to increase water discharge and increase the transport of ichthyoplankton from the Changjiang mainstream into the Dongting Lake. 相似文献
16.
Variation in intermediate water salinity in the South China Sea (SCS) between the 1960s and 1980s was studied using historical hydrographic data. The results demonstrate that the water was significantly fresher in the 1980s than in the 1960s, indicating that vertical mixing at intermediate water depth was reduced in the 1980s. This was partially because of the change of the SCS meridional overturning circulation (MOC) connecting local intermediate water with deep water. Data assimilation showed a 0.5Sv (1 Sv=10 6m 3/s) reduction in the strength of the MOC, which is about one third of the mean SCS MOC. Because the SCS MOC is linked to the Pacific Ocean, such an interdecadal variation in the intermediate water SCS may reflect anthropogenic climate change in the world ocean. 相似文献
17.
基于混沌时间序列的地下水位多步预测模型 总被引：3，自引：0，他引：3
利用相空间重构技术,并借助G-P算法、C-C方法和Wolf方法从宁陵地区地下水位一维时间序列中提取Lyapunov指数,结果表明此时间序列具有混沌特征。计算了宁陵地区地下水位时间序列的关联维数、时间延迟和最大Lyapunov指数,将局域加权一阶多步预测模型应用于地下水位预测。预测表明,此模型可有效应用于地下水位时间序列的多步预测。 相似文献
18.
Based on the data from gauging stations,the changes in water discharge and sediment load of the Huanghe (Yellow)River were analyzed by using the empirical mode decomposition(EMD)method.The results show that the periodic oscillation of water discharge and sediment load of the Huanghe River occurs at the interannual,decadal,and multi-decadal scales,caused by the periodic oscillations of precipitation,and El Nio/Southern Oscillation(ENSO)affects water discharge by influencing precipitation distribution and contributes to periodic varations in precipitation and water discharge at interannual timescale.The water discharge and sediment load of the Huanghe River have decreased since the 1960s under the influence of precipitation and huamn activities,and human activities attribute more than precipitation to the reduction in the water discharge and sediment load,furthermore,water abstraction and water-soil conservation practices are the main causes of the decrease in water discharge and sediment load,respectively.The reduction in sediment load has directly impacted on the lower reaches of the Huanghe River and the river delta, causing considerable erosion of the river channel in the lower reaches since the 1970s along with River Delta changing siltation into erosion around 2000. 相似文献
19.
A riverhead is the demarcation point of continuous water channel and seasonal channel, which is characterized by a critical flow that can support a continuous water body. In this study, the critical support discharge(CSD) is defined as the critical steady flows required to form the origin of a stream. The CSD is used as the criterion to determine the beginning of the riverhead, which can be controlled by hydro-climate factors(e.g., annual precipitation, annual evaporation, or minimum stream flow in arid season). The CSD has a close correlation with the critical support/source area(CSA) that largely affects the density of the river network and the division of sub-watersheds. In general, river density may vary with regional meteorological and hydrological conditions that have to be considered in the analysis. In this paper, a new model referring to the relationship of CSA and CSD is proposed, which is based on the physical mechanism for the origin of riverheads. The feasibility of the model was verified using two watersheds(Duilongqu Basin of the Lhasa River and Beishuiqu Basin of the Nyangqu River) in Tibet Autonomous Region to calculate the CSA and extract river networks. A series of CSAs based on different CSDs in derived equation were tested by comparing the extracted river networks with the reference network obtained from a digitized map of river network at large scales. Comparison results of river networks derived from digital elevation model with real ones indicate that the CSD(equal to criterion of flow quantity(Q_c)) are 0.0028 m~3/s in Duilongqu and 0.0085 m~3/s in Beishuiqu. Results show that the Q_c can vary with hydro-climate conditions. The Q_c is high in humid region and low in arid region, and the optimal Q_c of 0.0085 m~3/s in Beishuiqu Basin(humid region) is higher than 0.0028 m~3/s in Duilongqu Basin(semi-arid region). The suggested method provides a new application approach that can be used to determine the Q_c of a riverhead in complex geographical regions, which can also reflect the effect of hydro-climate change on rivers supply in different regions. 相似文献
20.
IMPACT OF URBANIZATION ON STRUCTURE AND FUNCTION OF RIVER SYSTEM——Case Study of Shanghai, China 总被引：3，自引：1，他引：2
YUAN Wen Philip JAMES YANG Kai 《中国地理科学(英文版)》2006,16(2):102-108
1INTRODUCTION Since the 1750s, promoted by Industry Revolution and the rapid development of science and technology, large-scale urbanization swept over the world. So far, it isestimatedthatmorethan60%oftheriversin the world have been experienced high levels of human modifica- tion (ALLAN, 1995). River systems have now become oneofthemostdeeplyhuman-affectedecosystemsinthe earth. To approach the impact ofhuman activitieson riv- ersystem as a multidiscipline topic has been a focus of res… 相似文献