共查询到20条相似文献，搜索用时 861 毫秒
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I "trod notionNatural lines, such as coastlines, mountain outlines, or boundaries between forest types, usuallyhave spatial dimensions, called "f racial dimensions,"that are greater than one. The excess over one indicates the amount of convolution within a line. Similarly, the dimensions of natural surfsces exceed two.Natural lines are hybrids betWeen ideal lines andsurfaces, just as classical surfaces and volumesserve as the ideal extremes of actual surfsces.Tree crown is a truly fractal obj… 相似文献
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The changes of fractal dimension ofPicea koraiensis seedlings under different light intensities in natural secondary forests was studied. The results showed that with the change
of light environment, crown characters ofPicea koraiensis seedlings exhibited a greater plastic in lateral number, lateral increment, lateral dry weight, and specific leaf area. The
range of calculated fractal dimensions of seedling crowns was confined between 2.5728 and 2.1036, but maximum of fractal dimension
achieved in term moderate shading and in extreme low light conditions fractal dimension was least.
Foundation item: This paper was supported by the National Natural Science Foundation of China (No.39670152) and Chinese Academy of Sciences.
Biography: ZHOU Yong-bin (1970-), female, Ph. Doctor, lecture in Shenyang Agricultural University, Shenyang 110161, P.R. China
Responsible editor: Song Funan 相似文献
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木材干缩的分形分析 总被引：12，自引：2，他引：10
本文通过一个木材干缩实验 ,展示了木材多孔性的分形特征。用银杏 (GinkgobilobaL .)和板栗(Castaneamollissima)木材作试材 ,用逐渐升高温度的方式处理试样 ,同时称重和量取尺寸 ,可以获得不同温度之间的重量和体积变化值 ,由变化值和立方体边长的对数值得直线斜率。直线斜率反映了木材中空隙体积的分形维数。这种方法可以通过不同树种、不同温度状态下木材水分逸出过程空隙空间分形维数的变化 ,分析木材的干缩规律。建议分形理论可成为木材多孔性研究的有效途径 相似文献
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The rough extent of leaf surface may be described by protruding of waxes which like as wart and of stomatal aperture and of
width of the cuticular ledge around guard cells. Because the morphology of the leaf surface has obviously similar itself,
so one can use the theory of the fractal dimension to deal with the problems of leaf surface rough. The paper studied the
rough extent and the result showed: with the leaf growing up, the waxes accumulate more and more, the leaf surface is more
rough and the dimension is larger. The dimension D
w
p
which indicates the rough extent of warts protruding is about 2.10–2.20 on the above epidermis; On the beneath epidermis
the dimension D
s
p
of stomatal opening protruding is about 2.00–2.24; Maximum widthL of cuticular ledge is about 1.0–7.4μm.
The project supported by Natural Science Foundation of China 相似文献
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The gloss of wood is a unique texture compared to that of other materials. To express it quantitatively, two digital-image analyses were performed. One method was multiresolutional contrast analysis, which was the new method developed in this study. The other method was fractal image analysis. Twenty-four specimens, including solid woods, wood-plastic composites (WPCs), printed grains, and granites, were prepared. Digital images of specimens were obtained in five sizes and in two illuminant directions (perpendicular and parallel to the grain). The multiresolutional contrast values of perpendicular illuminated images were calculated and compared among specimens. The result of this quantitative analysis was that the gloss of wood was characterized by bright spots in a relatively small area. Using fractal analysis, the fractal dimension of a digital image was used as an index of brightness changes, not for expressing the self-similarity. These indices showed results similar to those of the multiresolutional contrast analysis.Part of this paper was presented at the 47th annual meeting of the Japan Wood Research Society in Kochi, April 1997 相似文献
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Lü Ning 《中国林学(英文版)》2003,5(1):39-43
Internal wood surfaces can be treated as fractals, which are between Euclidean geometry and complete randomness. The fractal dimension Dfs is very informative in investigating the roughness of the internal surfaces of wood. In this study, the water sorption isotherms, including adsorption and desorption isotherm, of untreated, benzene-alcohol extracted and delignified (after benzene-alcohol extracted) spruce (Cuninghamia lanceolata) were measured at 30℃. On the basis of these isotherms, the Dfs values were calculated by FHH equation, which is based on multimolecular sorption. The results showed that both groups of Dfs values (respectively calculated from adsorption and desorption isotherms) of untreated, benzene-alcohol extracted and delignified wood have same order, that is, untreated > benzene-alcohol extracted - delignified. Therefore, the conclusion can be made that the benzene-alcohol extractives have significant contribution to the fractal geometry of internal wood surfaces. Lignin also has influ 相似文献
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基于分形理论的木材纹理特征研究 总被引：9，自引：0，他引：9
介绍了一种利用自相关函数来估算图像分形维数的方法，并将其应用到木材的纹理分类检测中。实验表明，分形维数值直接反映了木材纹理的粗糙程度，可定性地作为描述木材纹理粗糙度的一种度量。 相似文献
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Fractal dimension of wood surfaces from sorption isotherms 总被引：4，自引：0，他引：4
Summary In this paper the method of fractal dimension is applied to characterize the wood surface by using water-sorption data. Three different methods are implemented to determine the fractal dimension. These methods are based on polymolecular sorption and capillary condensation and are found to estimate the fractal dimension in the range of 2.5–2.8. This implies that the estimation of the surface area of wood by determining the number of molecules of water corresponding to monolayer formation is not true. The surface in fact is far from two dimensional as being closer to a three dimensional one. 相似文献
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沂蒙山林区不同植物群落下土壤颗粒分形特征 总被引：2，自引：0，他引：2
运用土壤物理学和分形学原理与方法,研究了沂蒙山林区7种植物群落下的土壤颗粒组成与分形特征。结果表明:1)研究区土壤颗粒组成具有石质山地典型粗骨土的结构特征,各种植物群落的土壤中以粗砂粒含量最高,细砂粒含量次之,而石砾含量和粉黏粒含量较低;2)防护林群落具有显著地改善土壤颗粒组成和提高土壤颗粒分形维数的作用,其作用程度为针阔叶(赤松+麻栎)混交林依次高于阔叶林(刺槐纯林、麻栎纯林)和针叶林(赤松纯林);3)土壤颗粒分形维数与土壤中粉黏粒(粉粒及黏粒)含量呈极显著正相关,与细砂粒和粗砂粒含量呈显著的负相关,而与石砾含量的相关性不显著。研究成果可为沂蒙山区水土保持植被类型的合理选择与配置提供参考。 相似文献
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分数几何在林学和生态学上的应用 总被引：3，自引：1，他引：3
本文综述了分数几何(Fractal geometry)在林学和生态学上的应用:包括对林木冠层结构特征的描述;对群落格局、同质性的判定;对景观格局和过程的分析;对森林生长、演替等动态过程的分析等,并指出分数几何作为新兴的基础理论将成为林学和生态学研究中的有效手段之一。 相似文献
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基于分形维数特征的原木漏节图像的研究 总被引：1，自引：0，他引：1
采用X射线法透射木材,根据检测透射物体后射线的强度差异,建立木材X射线的分形模型。采用计算盒子维数的方法对原木漏节X射线图像进行有效的边缘检测,用分形维数D的大小来定量描述原木漏节图像的不规则程度,以确定缺陷所在。研究表明背景部分与边缘部分的分形维数存在一定程度的差别,正常部分分维数值大约在2.007 3左右,漏节边缘分维数值大约在1.400 0~1.900 0之间。 相似文献
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基于分数布朗随机场与分形参数的原木漏节图像处理 总被引：5，自引：0，他引：5
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 相似文献
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分形理论在木材科学与工艺学中的应用 总被引：12，自引：1，他引：12
分莆是一种新兴的基础理论,将在成为木材科学研究的有效手段之一,本文阐述了分形理论的基本概念、原理和应用,着重介绍分形在木材解剖学、木材物理力学和加工过程中的应用前景。 相似文献
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将分形的有关理论与削片机机械故障诊断联系起来,论述了分形维数的基本概念,并给出了相关算法.研究结果表明:基于分形的机械故障诊断对削片机机械系统的故障极为敏感. 相似文献