Papers by Keyword: Fractal Dimension

Abstract: The pore fractal dimensions of PVA/PAA-AM blend superabsorbent fiber were calculated by box-counting method. The results indicate that the pore structures of superabsorbent fiber have obvious fractal characteristics. In addition, we have also studied the relations of AM ratio with other parameters. Calculation shows that the addition of appropriate amount of AM can increase the porosity of superabsorbent fibers and improve its absorption ability.

Abstract: The pore structure of coal rock atYangquan Xinjing mine in Shanxi Province is analyzed with mercury intrusion porosimetry to obtain the specific pore volume data and calculate the fractal dimension of coal pore surface. The pores are divided into macropore, mesopore and micropore according to radius size considering the calculated fractal dimension. The distribution characteristics of pore radius size, specific surface area and specific pore volume of different types are effectively analyzed. The research results show that mesopore surface has significantly fractal characteristics, which features could be discussed quantitatively. The proposed method in this paper has reference significance for studying the sorption and desorption properties, the diffussion and permeation of coalbed methane.

Abstract: In MEMS parameter measure based on vision,the process of binarization is critical. In the situation of unbalancing illumination and noise background,the performance of traditional binarization method degrades. In this paper, a binarization method based on wavelet analysis and an optimal box counting (OBC) fractal dimension algorithm is proposed. At first,wavelet analysis is used to eliminate the effect of illumination distribution.Then the MEMS image binarization based on OBC reduces the effect of noise. Experiments show that, the method can get a considerable binarization result.

Abstract: The technology of image matching is very important in the field of image analysis. Studying on image correlation is the key to improve the accuracy of image matching, while the fractal self-similarity has the unique potential in making full use of image correlation. This paper put forwards a matching algorithm of the sub-pixel image matching based on fractal dimension. Firstly, by searching template subarea based on traverse in being matched image, and the sub-subareas are classified. Then, the fractal dimension of subareas and sub-subareas is calculated by using the optimal box counting method. The similarity maximum position can be found according to the statistical correlation. Finally, fractal interpolation method is used to improve the precision of image matching. Both theoretical analysis and experimental results show that this approach has good matching effect.

Abstract: In this work the microscopic morphology of titanium carbide thin films, obtained by pulsed laser ablation, are studied. A target of TiC has been ablated in vacuum with a laser Twinkle of Light Conversion Ltd. capable to furnish impulses of 250 fs, with a repetition frequency of 10 Hz at the wavelength of 527 nm. The ablated material has been deposited on (111) oriented silicon substrates, maintained at ambient temperature during the film deposition. Digital images of the films have been acquired through scanning electron microscopy. Numerical codes have been developed in Matlab environment, to obtain a three-dimensional reconstruction of the film surfaces starting from the bidimensional images. On such reconstruction a multi-scale analysis has been performed by hilbertian methods, for the characterization of the surface roughness and to study the distribution of the deposited nanoparticles. The results show that the free surface of the film has a characteristics scale invariance that allow the description by multi-fractal techniques. In particular the fractal dimension of the surface has been calculated in nanometric range. The investigation allows to identify some proper morphological indicators to characterize the film geometry and parameterize the tribological properties of the interface. These indicators, if opportunely employed together with classical methods of analysis, furnish a further tool for better understanding the complex nature of the deposits.

Abstract: For exploring the variation of the surface morphology of carbon fiber precursor which was obtained from different curing conditions,this paper used the fractal dimension measurement method to analyze morphological characters of carbon fiber precursor surface through the electronic scanning electron microscopy image recognition and computer fractal calculation system. The experimental results show:the surface fractal dimensions of carbon fiber precursor were between 2.480~2.622 by TPSAM method, and the surface fractal dimensions of carbon fiber precursor were between 2.555~2.633 by PCM method, both methods show that the carbon fiber precursor surface is smooth. And the CCM is 2.678~2.755, this method shows that the precursor surface is concave and convex. The fractal dimension value obtained by TPSAM method and PCM method is closer, while the CCM is different. But the trend is almost the same, which shows that using the fractal dimension method to desirable the surface structure of carbon fiber precursor is desirable.

Abstract: In this paper, a data-driven approach to localizing structural damage subjected to ground motion is proposed by using the fractal dimension of the time-frequency features of structural dynamic responses. The time-frequency feature is defined as the real part of wavelet coefficient and the fractal dimension adopts the box-counting method. It is shown that the proposed fractal dimensions at each story of linear system are identical, while the fractal dimension at the stories with nonlinearity is different from those at the stories with linearity. Therefore, the nonlinear behavior of structural damage caused by strong ground motions can be detected and localized through comparing the fractal dimensions of structural responses at different stories. Shaking table test on a uniform 16-story 3-bay steel frame with added friction dampers modelling interstory nonlinear behavior was conducted. The experiment results validate the effectiveness of the proposed method to localize single and multi seismic damage of structures.

Abstract: Bridging technology is one of the most effective methods to prevent the solid and liquid phases into the well fluid from invading the reservoir. And selecting the bridging agent which best matches with the reservoir pore size is the key of the successful implementation of bridging technology. Because of the lack of precise and quantitative degree of the preferred theory of bridging agent in field applications, temporary blocking fractal theory has been introduced. The reservoir pore size distribution and the fractal geometric distribution characteristics of bridging agent have been described. At the same time, the temporary blocking fractal theory and the fractal dimension calculation have been introduced. Conduct temporary blocking experiments on the core of Jilin Oilfield by this theory and the results proved to be perfect. As a result, the correctness of temporary blocking fractal theory has been verified.

Abstract: Though there are a lot of rules and models for metal material fracture, it makes lots of troubles for engineering application, because of the lacking of reasonable description of fracture principle and change law. This article discusses some basic problems of applying fractal geometry to fracture research, mainly including sectional fractal characteristics and measurement, the relationship of fractal dimension and fracture toughness, and some kinds of metal fractal models. At last, application of fractal theory in metal fracture is stated.

Abstract: To achieve rapid target detection by GPR (Ground Penetrating Radar),the article introduces fractal dimension as the characteristic to describe the complexity of the one-dimensional discrete signal and puts forward an algorithm for rapid target detection by GPR. First, calculate the fractal dimension of signals at different points in the direction of the survey line and depth direction after wavelet transform processing to obtain the curve of fractal dimension on two directions. Finally, determine the suspicious region in the curve of fractal dimension based on the judgment criterion to fulfill target detection. The measured data testify that the method can achieve the rapid detection on a specific target in a certain context.