某水电站库区泥石流发育特征及其非线性特性研究

通过对某水电站库区内12条主要的泥石流沟从沟道数与流域面积,沟道数与主沟长,沟道数与沟谷坡降关系上研究了库区内泥石流沟发育的非线性特征,并通过其双对数曲线方程得到了各自的分维数,其意义是在对泥石流危险度评判中为各因素权重的求取提供一个定量的手段,并据此可利用非线性技术来解决泥石流灾害研究中的预测及防治等主要问题,为泥石流灾害防治提供新的思路。     

分形方法在南麂岛土地覆盖类型分析中的应用

借助分形理论对南麂列岛国家级海洋自然保护区内的主岛---南麂岛的地面覆盖及其状况进行分析,把各地类图斑的复杂性、破碎性和形状等定性概念,用分维值和形状因子进行定量描述和比较,分析其形成机制。结果表明,灌木林地和草地等自然性较强的地类分维值较大,而晒场和居民地等人为干预较多的地类分维值较小,庄稼地的分维值则介于它们之间。     

基于遥感技术的无锡市城镇形态分形研究

城镇形态研究不仅是城镇规划、城镇建设和城镇土地利用的重要依据 ,也是城镇社会经济发展的理论基础。对地理现象形态的关注和研究早已成为地理学者的一项工作。从地貌学者所关注的地形到城市地理学家所关注的城市形态分类 ,都有形态问题。从 2 0世纪 90年代以来 ,我国在城市形态研究领域 ,无论在理论方面还是在应用方面 ,都取得了许多成就 ,但大多数研究主要集中在空间结构变化的机制和城镇内部结构形态的变化这两方面 ,对城镇形态的自身特征及其变化研究不多 ,对城镇形态的空间信息如何客观、准确地提取则涉及得更少。据此 ,本文的研究重点首先是解决如何客观、有效地提取城镇形态信息和空间数据 ;其次是根据提取出的空间信息和数据 ,对无锡市城镇外部形态特征进行分形研究 ,以揭示出城镇形态的复杂性和稳定性。     

QPOG技术及其应用研究

研究了地震资料的现场处理技术－－QPOG（Quickly Predicting Oil and Gas），提出利用QPOG技术右以在地震勘探中快速有效地进行油气预测，并给出了有井区和无进区的两种预测方法；有井区以人工神经网络、模糊相似优先比等方法为主，无井区以分形、混沌、突变等理论方法为主，通过对具体研究区的实际预测，证明了方法的实用性。     

基于DEM的流域水系分维估算方法探讨

分形理论是现代数学的一个新的分支，是一种新世界观和方法论。分形理论与地学的结合，极大地推动了地理学的发展。介绍了分形理论在水文学研究中的应用和发展，介绍了利用Arc/Info，以DEM为数据源提取流域信息的方法。提供了一种将分形理论、GIS技术和流域地貌模型巧妙耦合，分别用基于覆盖法的分维估算方法和基于Horton定理的分维估算方法计算了马连河流域水系分形维数。这种方法与传统方法相比，具有易于操作、高效等优点。     

地震断裂系统的分形和在地震预报中的应用

本文基于地震断层具有自相似结构,从分形概念出发,依据地震资料提出了适合于前震和余震的分形模型,在此基础上讨论了前震和余震的b值特征,提出了地震矩不均衡度的概念。本文还探讨了利用分数维和地震矩不均衡度进行地震预报的可能性。研究发现,正常情况下,地震矩不均衡度呈现低值,大震发生前出现高值异常,震后降低;在空间上,震前2—4年其异常范围大,震前一年异常区逐渐缩小,大震发生在异常集中区内或其边缘。     

苏锡常地区地裂缝分形的初步研究

利用分形理论对苏锡常地区地裂缝的空间分布特征进行了初步探讨,计算出该区地裂缝的分维值在0987～0996之间。分析认为,该区地裂缝在地质作用过程中自组织程度一致性较强,并具局部与整体的自相似性,这种自相似性,对研究该区地裂缝的进一步发展可能有一定的预测意义     

Modeling aggregate size distribution of eroded sediment resulting from rain-splash and raindrop impacted flow processes

Soil susceptibility to detachment and transport sub-processes of erosion is generally controled by the aggregate breakdown mechanism. Measuring particle size and aggregation to the estimate erodibility potential of soils is important under erosive rainfall conditions. The Aggregate Size Distribution (ASD) is one of the most important determinants of soil structure along with soil organic matter content for describing the efficiency of applied, sustainable management strategies. This study aimed to compare the performances of three different aggregate size distribution models to predict the characteristic aggregate size parameter (median diameter, D50) for eroded sediment from interrill erosion processes of Rain- Splash Transport (RST) and Raindrop Impacted Flow Transport (RIFT). The ASDs of 1143 collected sediment samples from the RST and RIFT processes were measured and modeled by the Log-normal, Fractal, and Weibull approaches. The D50 value, as a characteristic parameter for aggregate size distributions, derived from the cumulative ASD curve was compared for soils from different land use types and different slope and rainfall intensity conditions. The performance of each model was evaluated using the Mean Square Error (MSE) and Coefficient of Determination (R^2). The Weibull approach was the most accurate model showing the best fit with the lowest MSE values (0.0002 ≤MSE≤ 0.0048) and having the greatest R2 values (0.936≤ R^2≤ 0.998) when compared with the Log-normal and Fractal models. Herewith, for semi-arid land use and soil, specific shape and scale parameters for the Weibull distribution, the respective ASDs were successfully re-generated for modeling the eroded sediment of the simulated RST and RIFT interill processes.     

典型地形SAR回波模拟与SAR图像仿真

SAR成像算法的验证需要相应的回波数据, 同时SAR图像目标识别算法的检验需要大量的SAR图像, 针对这一要求, 提出了一种典型地形SAR回波模拟与图像仿真的方法。首先分析了分形布朗曲面及其水平集的特征。在此基础上, 运用中点位移法生成了描述山脉地形的数字高程数据, 提出了生成海岸地形(“归零法”)及河流沟壑地形(“归零取反法”)的新方法。引入电磁散射模型, 计算了每个分辨单元的后向散射系数。给出了基于二维快速傅立叶变换的SAR回波模拟算法的推导过程及相应的仿真结果, 并对结果进行了分析和讨论, 证明了该方法的正确性。     

ULF geomagnetic anomalies of possible seismogenic origin observed at Teoloyucan station, México, in 1999–2001: Intermediate and short-time analysis

The analysis of ULF geomagnetic field measured at Teoloyucan station (Central Mexico, 11′35.735″ W, 19 44′45.100″ N, 2280 m height) is presented in an intermediate (± 15 days) and short time scale (the day of the EQ occurrence) in relation to 7 major earthquakes occurred in Mexico in 1999–2001. Local changes in the fractal dynamics of the magnetic field are found to be important: a pronounced fall of the fractal index is frequently observed prior to the main shock. The study of the ULF resonant structure recently discovered in the frequencies f_R1 = 10.2−11.1 mHz and f_R2 = 13.6−14.5 mHz reveals changes in their character probably related to the processes of the earthquakes preparation. The success of the observation of the mentioned anomalies (specially the fractal index decrease) strongly depends on how close is the station from the epicenter, and what is the magnitude of the earthquake.