Clustering Research on Fractal Parameter of GIS PD UHF Signals

2013 ◽  
Vol 380-384 ◽  
pp. 3818-3821 ◽  
Author(s):  
Yu Xin Yun
Keyword(s):  
Pattern Recognition ◽  
Noise Level ◽  
Fractal Theory ◽  
Box Dimension ◽  
Control Parameters ◽  
Wavelet Method ◽  
Filtering Algorithm ◽  
Fractal Parameter ◽  
Fractal Parameters ◽  
Signal Changes

The distribution of fractal parameters (box dimension and lacunarity) vary with noise level of GIS PD UHF signal is the main obstacle to the use of fractal theory in GIS PD pattern recognition. According to the characteristic of fractal parameters, box dimension and wavelet method have been used in control the noise level and gather the fractal parameters of each kind of GIS PD UHF signals. Simulations show that, the fuzzy control parameters filtering algorithm based on the box dimension will lead to the dispersive of lacunarity and the distribution of fractal parameters changes as the noise level of GIS PD UHF signal changes. However, the wavelet method has a good performance in gathering those two fractal parameters of different GIS PD UHF signals. And its a promising approach to expand the applicability of classifiers used in GIS PD pattern recognition.

Research of Coal Pores and Integrity Evaluation Method Based on Fractal Theory

2014 ◽  
Vol 670-671 ◽  
pp. 258-262 ◽  
Author(s):  
Ji Li ◽  
Xin Wu
Keyword(s):  
Fractal Dimension ◽  
Coal Sample ◽  
Evaluation Method ◽  
Structural Integrity ◽  
Gas Adsorption ◽  
Fractal Theory ◽  
Physical And Mechanical Properties ◽  
Box Dimension ◽  
Sem Images ◽  
Sem Image

Coal is a natural porous media, its porosity and structural integrity influenced the gas adsorption and desorption characteristics greatly, as well as physical and mechanical properties of coal. Scanning electron microscopy (SEM) is applied to acquire SEM image of four kinds of coal samples at different zoom levels, and the box dimension can be worked out based on the pore preprocessing of SEM images. Then, the numerical value of box dimension is used to describe the development degree of the four kinds of coal sample and four development degrees’ sequence. At last, the intrinsic relevance between fractal dimension and other parameters is analyzed through mathematic method. The results show as follows: coal sample has self-similarity characteristic; the fractal dimension is related to both the total number of pores and porosity degree; the data of the coal pore, analyzed through fractal dimension, are consistent with that through traditional method; what’s more, fractal dimension has more advantages in describing accuracy and simplicity.

scholarly journals Description of Fracture Network of Hydraulic Fracturing Vertical Wells in Unconventional Reservoirs

2021 ◽  
Vol 9 ◽  
Author(s):  
Jinghua Liu ◽  
Mingjing Lu ◽  
Guanglong Sheng
Keyword(s):  
Flow Rate ◽  
Early Stage ◽  
Fractal Theory ◽  
Fracture Network ◽  
Unconventional Reservoirs ◽  
Box Dimension ◽  
Vertical Wells ◽  
Reservoir Permeability ◽  
Fractal Index ◽  
Volume Fracturing

Based on the distribution of complex fractures after volume fracturing in unconventional reservoirs, the fractal theory is used to describe the distribution of volume fracture network in unconventional reservoirs. The method for calculating the fractal parameters of the fracture network is given. The box dimension method is used to analyze a fracturing core, and the fractal dimension is calculated. The fractal index of fracture network in fracturing vertical wells are also firstly calculated by introducing an analysis method. On this basis, the conventional dual-media model and the fractal dual-media model are compared, and the distribution of reservoir permeability and porosity are analyzed. The results show that the fractal porosity/permeability can be used to describe the reservoir physical properties more accurately. At the same time, the flow rate calculating by conventional dual-media model and the fractal dual-media model were calculated and compared. The comparative analysis found that the flow rate calculated by the conventional dual-media model was relatively high in the early stage, but the flow rate was not much different in the later stage. The research results provide certain guiding significance for the description of fracture network of volume fracturing vertical well in unconventional reservoirs.

A stress sensitivity model for the permeability of porous media based on bi-dispersed fractal theory

2018 ◽  
Vol 29 (02) ◽  
pp. 1850019 ◽  
Author(s):  
X.-H. Tan ◽  
C.-Y. Liu ◽  
X.-P. Li ◽  
H.-Q. Wang ◽  
H. Deng
Keyword(s):  
Porous Media ◽  
Fractal Dimension ◽  
Fractal Theory ◽  
Stress Sensitivity ◽  
Maximum Diameter ◽  
Proposed Model ◽  
Fractal Parameters ◽  
Stress Changes ◽  
Capillary Bundle ◽  
Definition Of

A stress sensitivity model for the permeability of porous media based on bidispersed fractal theory is established, considering the change of the flow path, the fractal geometry approach and the mechanics of porous media. It is noted that the two fractal parameters of the porous media construction perform differently when the stress changes. The tortuosity fractal dimension of solid cluster [Formula: see text] become bigger with an increase of stress. However, the pore fractal dimension of solid cluster [Formula: see text] and capillary bundle [Formula: see text] remains the same with an increase of stress. The definition of normalized permeability is introduced for the analyzation of the impacts of stress sensitivity on permeability. The normalized permeability is related to solid cluster tortuosity dimension, pore fractal dimension, solid cluster maximum diameter, Young’s modulus and Poisson’s ratio. Every parameter has clear physical meaning without the use of empirical constants. Predictions of permeability of the model is accordant with the obtained experimental data. Thus, the proposed model can precisely depict the flow of fluid in porous media under stress.

Coupling fractal model for fretting wear on rough contact surfaces

2020 ◽  
pp. 1-32
Author(s):  
Yi Wang ◽  
Gang Liang ◽  
Shuo LIU ◽  
Yi Cui
Keyword(s):  
Contact Surface ◽  
Fractal Theory ◽  
Three Dimensional ◽  
Parameter Analysis ◽  
Fretting Wear ◽  
Wear Depth ◽  
Contact Parameter ◽  
Wear Process ◽  
Actual Surface ◽  
Fractal Parameters

Abstract In this paper, a fretting damage model based on fractal theory is proposed. The Weierstrass-Mandelbrot function of fractal theory is used to represent the rough contact surface, and a corresponding contact parameter analysis method is also established. Based on neural network algorithm, the values of fractal parameters are fitted, and the fitting accuracy has been greatly improved compared with traditional methods. According to the fractal parameters of the actual surface, the fretting wear process of the rough contact surface is analyzed based on theory of adhesive and three body abrasive wear. A generic program for the analysis of three-dimensional fretting wear problems is also proposed. Compared with material tests, the prediction error of fretting wear simulation model is 13.4% for wear depth and 16.7% and 3.9% for width and length of wear scar in stable wear stage. The prediction results show that the model can be applied to the prediction of the actual three-dimensional fretting wear model.

Study on Fractal Characteristics of Acoustic Emission in Circular Double-Layer Stirrup Confined Concrete

2014 ◽  
Vol 578-579 ◽  
pp. 359-368 ◽  
Author(s):  
Peng Fei Geng ◽  
Lin Zhu Sun ◽  
Fang Yang ◽  
Wei Li
Keyword(s):  
Acoustic Emission ◽  
Fractal Dimension ◽  
Double Layer ◽  
Fractal Theory ◽  
Equivalent Stress ◽  
Concrete Columns ◽  
Confined Concrete ◽  
Box Dimension ◽  
Emission Parameter ◽  
Fractal Characteristics

Vertical bearing capacity experiments were conducted with circular double-layer stirrup confined concrete columns as study objects, data acquisition was carried out using acoustic emission (AE) equipment and the AE parameters and graphs acquired during the experiments were analyzed to obtain the damage evolution of steel reinforced concrete columns under compression. The correlation between fractal dimension of AE graphs and curve was studied using the fractal theory, and the results show that the AE parameter graphs have fractal characteristics and the box dimension of each AE parameter graph constantly increases with the increase in stress, with a positive correlation exhibited between the fractal dimension and stress level. The loss variable expressed with fractal dimension was defined to establish actual equivalent stresses and the equivalent stress curves and experimental curves were compared; the results show that the fractal dimension of acoustic emission parameter graph can characterize the damage laws of the concrete member.

Optimization of a Star Pattern Recognition Algorithm for Attitude Determination Using a Multi-Objective Genetic Algorithm

2005 ◽  
Author(s):  
Ebenezer Seisie-Amoasi ◽  
Brian G. Williams ◽  
Marco P. Schoen
Keyword(s):  
Genetic Algorithm ◽  
Pattern Recognition ◽  
Attitude Determination ◽  
Recognition Algorithm ◽  
Control Parameters ◽  
Pattern Recognition Algorithm ◽  
Multi Objective ◽  
Star Pattern ◽  
Multi Objective Genetic Algorithm ◽  
Star Pattern Recognition

Attitude determination for unmanned spacecrafts usually employs star trackers. The specifications for these devices dictate fast, reliable, robust, and autonomous algorithms to satisfy various mission constraints. This results into simple algorithms for reduced power consumption and reduced overall weight. Optimizing a Star Pattern Recognition Algorithm (SPRA), using an imbedded star map, requires the optimization of the genetic operators that constitute the SPRA and the control parameters within the SPRA. Simultaneous optimization of the control parameters of the SPRA results into a multi-objective and multi-parameter constrained optimization problem. The optimizing of genetic algorithms is often time consuming and rather tedious by nature. In this work, a Multi-Objective Genetic Algorithm (MOGA) acting as a meta-level GA is applied together with a double objective transition selection scheme to achieve the optimization. This approach results in significantly expediting the cost assignment process. By evolving a pareto set, an optimization population element rule is determined to exist between the control parameters of the SPRA. The existence of this rule ensures effective balance between population exploitation and exploration in the algorithm estimation process. This leads to effective solutions for finding the optimum with multiple concurrent objectives while taking the constraints into consideration. Simulation results using the optimized parameters for the SPRA indicate an improvement of the recognition accuracy from less than 60% to 100% as well as a reduction of the processing time of over 2000 generations to under 250 generations at 99% precision.

scholarly journals Modeling and Analysis of Nonlinear Axial Force Generated by Automotive Drive-shaft Systems Based on Fractal Theory

2021 ◽  
Author(s):  
Huayuan Feng ◽  
Wen-Bin Shangguan
Keyword(s):  
Fractal Theory ◽  
Surface Characteristics ◽  
Correction Method ◽  
Fractal Model ◽  
Drive Shaft ◽  
Correction Coefficient ◽  
Modeling And Analysis ◽  
Shaft System ◽  
Fractal Parameters ◽  
Micro Level

Abstract The nonlinear generated axial force (NGAF) of an automotive drive-shaft system is mainly induced by the tripod joint in the drive-shaft system, which will lead to vibration and noise of a vehicle. On the basis of fractal theory, this paper conducts modeling and analysis of the NGAF from the micro level to study the NGAF more effectively. In order to describe the micro contact and friction states between rollers and tracks inside the tripod joint more accurately, a correction method for correcting the distribution function of asperities between rollers and tracks is proposed. Based on the proposed correction method and a calculation model of the NGAF, a fractal model of the NGAF considering rough surface characteristics is established. The fractal model is mainly related to the fractal parameters, the material parameters, the operating conditions and the correction coefficient of the distribution function of asperities. Using Sobol' global sensitivity analysis method, the first order and overall global sensitivities of the fractal model of the NGAF are subsequently analyzed to determine the influence of the factors on the NGAF. The effectiveness of the fractal model and the analytical method for the NGAF is verified by the experiment and calculation examples. The results show that modeling and analysis of the NGAF considering rough surface characteristics are essential to reveal the relationships between the NGAF and the fractal parameters, the material parameters and the correction coefficient from the micro level, which is helpful for the design and analysis of the NGAF of the drive-shaft system.

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