昆明历史洪涝灾害时间序列分形特征研究

根据昆明1312～1911年的洪涝灾害史料,构建了洪涝灾害发生时间序列,并用Samalley法计算了昆明历史洪涝灾害时间序列的分维值。结果表明:昆明地区历史洪涝灾害的发生存在分形特征,分维值为0.689 6,洪涝灾害的发生有一定自组织程度,但自组织程度还不高。洪涝灾害的发生从初期的混沌状态发展到后期的具有较高程度的自组织状态,洪涝灾害发生的可能性大大提高。     

AM真菌对宿主植物三叶鬼针草根系形态的影响

[目的]为研究AM真菌影响植物抗逆性的机理提供理论依据。[方法]分别用AM真菌Glomus etunicatum和G.mosseae接种三叶鬼针草,用WinRHIZO图像分析系统和Fractal analysis system for Windows软件分析AM真菌对宿主植物根系形态的影响。[结果]接种AM真菌后,三叶鬼针草的生物量和根系总长度、根系体积、根系表面积和细根(d0.5 mm)所占比例均显著增加,而根系平均直径减小。分形分析结果表明,接种AM真菌后三叶鬼针草的根系分枝强度增加。[结论]AM真菌是通过影响宿主植物的根系形态促进宿主植物生长的,且不同AM真菌对宿主植物生长的促进作用不同。     

Spatial analysis of selected soil attributes across an alpine topographic/snow gradient

The impact of the topographic/snow gradient on soil processes in alpinetundra on Niwot Ridge of the Colorado Front Range (Rocky mts, USA) was assessedusinggeostatistical modeling and a fractal approach. The mean snow depth, whichmeasured between 1984 and 2000, exhibited a smooth spatial continuity acrossthestudy grid area (550 × 400 meter). Soil color variables showed a nestedstructure that was attributed to a confounded effect of various soil-formingfactors on catenary processes. The spatial structure of texture classesexhibited no spatial structure and was explained by data sparsity,cryoturbation, and biological processes that mask the expected long-distancevariations (i.e., 550-m) of the catenary processes. Organic C, pH, bulkdensity,and soil moisture content showed various degrees of spatial continuity, but allindicated that the topographic/snow gradient is not the only dominantsoil-forming factor in this alpine ecosystem. The estimated fractal dimensionDfor the grid landform and the mean snow depth varied between 1.2 and 1.4,indicating that they vary smoothly with long-range variation. The estimatedDofthe soil variables ranged between 1.6 and 1.8, showing a noisy appearance withshort-range variations. These results strongly suggest that most small andmicro-scale variations in the alpine soil environs resulted from the combinedeffect of cryoturbation, biological activity, parent-material and eoliandeposition, whereas the large-scale variations originated as a result of thetopographic/snow gradient.This revised version was published online in May 2005 with corrections to the Cover Date.     

基于分数布朗随机场与分形参数的原木漏节图像处理

本文提供了一种基于分形理论中分数布朗随机场模型和分形参数H值的X -射线原木漏节图像处理方法。分数布朗随机场模型是描述自然景物的有效方法 ,在图像区域的小范围内 ,灰度表面具有统计意义上的自相似性 ,但在不同图像区域的交界处 ,这种分形的规律性将会被破坏 ,在此求出的分形参数H值将会发生奇异 ,据此可以判断出该处为图像的边缘或交界处。从试验的结果可以看出这种方法对X -射线原木漏节图像非常有效 ,同时对计算机进行自动模式识别有重要意义     

基于混沌-分形理论的往复式活塞隔膜泵磨损故障分

针对往复式活塞隔膜泵磨损故障,采用混沌理论和分形技术,对隔膜泵不同连接处磨损时的系统非线性表现形式加以研究.通过对不同故障类型振动信号的分析,绘制了相应的庞加莱截面图,并计算了各种磨损故障的最大李雅普诺夫指数和关联维数.研究表明当没有磨损故障时,系统为准周期态;而隔膜泵的各种磨损故障信号呈现混沌性态,且不同故障状态的最大李雅普诺夫指数和关联维数有着较大的差别,可以用作其状态监测和故障诊断的特征参数.     

大菱鲆选育家系体重性状的分形特征

分析了2007～2010年度18月龄体重性状的信息维数和关联维数。分析结果显示,2007～2010年度所构建的大菱鲆选育家系群体18月龄体重性状的信息维数介于0．9422～0．9586之间,不同年度之间的信息雏数变异不显著,这说明不同年度各选育家系群体18月龄体重性状的信息维数均为较大值,所统计群体的遗传变异都十分丰富,统计性状的变异范围也较大,显示出良好的育种潜力。相应数据的关联维数分析结果表明,除2008年度小尺度范围的关联维数是0．4284外,其余各小尺度范围的关联维数均高于0．73,这表明,从分析结果的总体来看,大菱鲆各选育家系群体内个体间的遗传结构的相关性较高;信息维数和关联维数作为研究分形特征的指标,从两个角度阐明了选育性状遗传结构的分形特征,在实际的良种选育过程中,应考虑这两方面的因素,确定适当的留种率。     

Loess erosion in relation to land-use changes in the ganspoel catchment,central Belgium

This paper examines the changes of land uses and landscape patterns in the Ganspoel Catchment, central Belgium, using aerial photography interpretation (photographs taken in 1947, 1969 and 1986). The comparison of land cover areal changes and a transition matrix were used to assess land-use changes in time and space. The size, fractal dimension and elongation index of patches were quantified for landscape pattern analysis. Grassland increased and farmland decreased in the study area from the 1940s to the 1980s. Forest increased from 1947 to 1969 and decreased from 1969 to 1986. About 49 per cent of the study area experienced changes of land use between 1947 and 1969, and about 36 per cent between 1969 and 1986. The landscape of the study area is more fragmented than it was in the 1940s. Patches have generally increased in number and decreased in size, although the landscape was most fragmented in 1969; fractal dimension of patches are lower, indicating less complex shapes. From 1969 to 1986, 59 per cent of the area of change was on 0–3 degree slopes, and from 1969 to 1986 6.7 per cent was on >8 degree slopes. Changing land uses and landscape patterns may have important ecological implications.     

基于分形维数的玉米和杂草图像识

提出了利用分形维数来识别玉米和杂草的方法.将田间采集到的原始图像转化到HSI空间,利用H分量的不变特性进行图像变换,以消除光照的影响,有利于图像的分割处理.为了识别出玉米和杂草,比较了3种分形维数的计算公式和计算方法,利用Matlab编写的分形软件得到了玉米和杂草的平均分形维数,试验结果表明:Bouligand-Minkowski方法最佳,其中玉米和杂草的平均分形维数分别为1.204和1.079.利用SVM方法进行识别,正确率可以达到80%.     

分形多孔介质孔道网络模型的构

采用压汞试验获得实际多孔介质的微观结构参数.以冻干马铃薯为例计算了孔隙分形维数,结果表明冻干马铃薯结构具有显著的分形特性.运用位似变换理论、分形理论、Voronoi图以及马铃薯的特征参数等,构建出与马铃薯结构参数相对应的二维分形孔道网络模型.构建的网络模型考虑了影响多孔介质干燥的孔道微细结构特征,模型参数能够很好地反映多孔物料的微观结构.且获得了合理的分形维数.     

7种草坪草的根系生长量及分形特征比较研究

以王朝早熟禾、凤凰高羊茅、普通脱壳狗牙根、艾森特黑麦草、三叶草、百脉根、弯叶画眉草为供试材料,研究不同种类草坪草的根系生长能力及分形特征。研究结果表明:凤凰高羊茅、普通脱壳狗牙根、弯叶画眉草的冠部生长茂盛,根系发达,根系生长能力较强。