Papers by Keyword: Fractal Dimension

Abstract: Based on the land use data observed over the Tailan River Basin (TRB) during the years 1990, 2000, 2005 and 2008, fractal theory is adopted and applied to expound spatial distribution characteristics and variation law of land use change in the arid inland TRB, Xinjiang, China. The results demonstrate spatial fractal characteristics in all land use types. The analysis indicate that the fractal dimensions of different land use types in the TRB are in the order of waters > industrial, mining and residential areas > farmlands > grasslands > unused lands > woodlands in 1990, and in the order of waters > industrial, mining and residential areas > grasslands > farmlands > woodlands > unused lands in 2000, and in the order of waters > industrial, mining and residential areas > grasslands > woodlands > farmlands >unused lands in 2005, and in the order of waters > industrial, mining and residential areas > grasslands > unused lands > woodlands > farmlands in 2008. The fractal dimension values of land use in the TRB in 1990, 2000, 2005 and 2008 are calculated as 1.5993, 1.5986, 1.6079 and 1.6348 respectively. Fractal dimension of land use in the basin is decreased at first then increased, the spatial structure of land used exhibit complex trend, while the land use types show an increase trend. The stability indexes of spatial structure of land use in the TRB in 1990, 2000, 2005 and 2008 are 0.1720, 0.1563, 0.1435 and 0.1428 respectively. These values suggest that the stability of the spatial structure of land use in the basin is gradually decreased.

Abstract: By virtue of uniaxial cyclic loading and unloading tests on cemented backfill, the studies were carried out, which are mainly on the micro crack evolution characteristics and the AE fractal characteristics in various stage of micro crack evolution. The results show the value of AE energy and fractal dimension are high in the micro holes compaction stage. By contrast, the AE energy and the fractal dimension are at the lowest level in the micro cracks compression phase. In the micro crack stable development stage, the AE events become active, and the fractal dimension keeps a steady growth trend. Finally, with stress further increasing, the AE will take on a quiet period in which the AE energy is high and the AE fractal dimension drops continuously to the lowest value till the stress reaches at peak value of the cemented backfill.

Abstract: As a result of the presence of noise in the measured vibration signal has a great influence on the results of calculation of fractal dimension, Therefore the empirical mode decomposition method for noise reduction of gear vibration signal is used, calculation fractal dimension, extraction fault feature of Gear in different conditions. The measured results show that: Different fault states have different fractal dimension, we can judge the fault type of gear effectively by the fractal dimension.

Abstract: Corrosion morphology image is one of the most important features for the evaluation of the corrosion damage of materials. By using white light confocal profiler, the corrosion morphologies of AA2524 aluminum alloy specimen are obtained after full immersion to experimental 3.5% salt solution for different time. Through digital image processing, typical corrosion morphology characteristics are extracted, such as the fractal dimension, the depth of pit, the area of pit. By extended 3D box-dimension method, the fractal dimensions of the corrosion surface under immersing time of 24 and 120 hours are determined. The statistical analyses show that the corrosion areas and the characterization parameters ab/2c² obey Gumma distribution, and the corrosion depth obeys Gumbel, normal, Weibul and log-normal distributions.

Abstract: It is possible to successfully propose the physical-metallurgical and structural conditions for the equilibrium between steel strength and toughness by designing structural parameters which have a positive effect on the relation between local and macroscopic fracture processes. In carbon steels and microalloyed steels for a wide range of technical uses, whose structure after heat treatment consists of a basic matrix of tempered lower bainite with precipitated carbides and sometimes other types of inclusions, toughness is dependent primarily on the size distribution of second phase particles, their volume ratio, and also the strength of the matrix/particle phase boundary and the mechanical properties of structural phases. By modelling and simulating the process of main crack formation during high-energy ductile fracture, it is possible to propose optimum physical-metallurgical and geometric parameters of steel structure in order to achieve the required relation between strength characteristics and toughness. This paper presents an analysis of results achieved in several tasks carried out to predict mechanical properties in ductile fracture, and it outlines potential future developments. The aims are to determine the limit characteristics of mechanical behaviour of structural steels which can be achieved with a view to the current structural situation and technological possibilities, and furthermore to propose future methods for determining relations between microstructure and toughness.

Abstract: Edge detection plays an important role in computer vision and image processing. Fractal and Fuzzy theory show significant effect in the edge detection and have attracted much attention. Compared with traditional edge detection methods, this paper proposes a Fuzzy Box-counting Dimension Method (FBDM). This algorithm introduces the pre-judging mechanism to improve the speed of image segmentation, and the self-adaptive dimension threshold and the voting mechanism under multi-windows to improve the accuracy of the determination of edge points. Finally, closest principle is used to clear edge and reduce noise. Experimental results show FBDM can improve the precision of image edge detection effectively without pretreatment, and it has a very superior de-noising performance.

Abstract: The hydrological processes are becoming more and more complex. Fractal dimension is one of the important measurements of complexity. This paper utilizes wavelets transform technique to calculate the fractal dimension of rainfall in July for eight stations (Yushu, Xichang, Pingshan, Lijiang, Kunming, Huili, Deqin, Lnage ) in the Jinsha River Basin. The results show: the rainfall series in the Jinsha River Basin is fractal; the approach for estimating the fractal dimension by using wavelet transform coefficients is feasible and effective; the fractal dimension of rainfall reflect the influence of factors on the rainfall.

Abstract: This paper presents an introduction to the approach to calculation of fractal dimension of SiO₂/UPR granular composites. The porosity of quartz mixture, the density, the optimum amount of unsaturated polyester resin (UPR) and the mechanical properties of the SiO₂/UPR granular composites were tested. The relationship between the four factors and the fractal dimension was analyzed and the relation expressions were obtained by fitting. For the SiO₂/UPR granular composites, fractal theory is not only used for the design of gradation and the optimum amount of UPR, but also for calculating and evaluating the mechanical properties. Research shows that the fractal dimension plays a role of linking the microstructure and the macroscopic properties of the SiO₂/UPR granular composites.

Abstract: Surface morphology of thin films can be efficiently characterized using power spectral density method. Spectral based parameters from surface models can then be linked to electrical conductivity of thin films used for fabricating organic photovoltaic devices. In this study, the surface morphologies of the organic thin films phthalocyanine tetrasulfonic acid tetrasodium (TsNiPc) are investigated using atomic force microscopy. The thin film samples are imaged at 40-minutes and 120-minutes after the solvent treatment. The spectral exponent β is determined from the slope of PSD log-log plot and the fractal dimension D of each film is calculated based on fractal relation β = 8 2D. The relationship between surface roughness and fractal dimension with respect to electrical properties of thin film is discussed.

Abstract: Pulverizing problem, low mechanical strength and poor wear resistance of desulfurization sorbent limit the further development and industrialization of hot coal gas desulfurization technology. The present paper highlighted on the recent progress of hot gas desulfurization researches and gave a fully detailed introduction on physical parameters that reflect the texture of desulfurizer: specific surface area, pore volume, pore size and its distribution, porosity, fractal dimension and so on. Different from the traditional physical parameters, fractal dimension, as a comprehensive physical parameter describing a fractal structure, reflects the regularity degree of a porous structure. With the increase of sorbent fractal dimension, the complexity of pore spatial geometrical features increases, and the porosity and average diameter for pore decrease. The specific surface area also increased consequentially with the increase of micro-pore. Besides, this paper also investigated the proper texture of desulfurization sorbent that is favorable for desulfurization process on the basis of desulfurization mechanism for fuel gas.