The Blemish Identify in Ultrasonic Testing of Friction Welded Joints Based on Fractal Theory

2015 ◽  
Vol 799-800 ◽  
pp. 942-946
Author(s):  
Yuan Peng Liu ◽  
Xin Yin ◽  
Min Wang
Keyword(s):  
Fractal Dimension ◽  
Welded Joints ◽  
Ultrasonic Testing ◽  
Fractal Theory ◽  
Metal Alloys ◽  
Box Dimension ◽  
Box Counting ◽  
Signal Characteristics ◽  
Box Counting Dimension ◽  
Dimension Number

The friction welded joints made by GH4169 heat metal alloys are detected by U1traPAC system of the ultrasonic wave explore instrument. Aimed at the blemish signal characteristics, a method is put forward to identify the blemish signal in ultrasonic testing of friction welded joints based on fractal theory., A new kind of fractal dimension number calculation method—normalized scale box-counting dimension method is used to calculate the box-dimension of the blemish signal, and statistic and analysis the scopes of the box-dimension of the blemish signal and the square differ of the result. The preliminary experimental results show that the blemish signal and have each fractal dimension zones, and don’t hand over to fold. So it can use to judge whether the blemish exist or not. The method is identified to have better covariance characteristics about the blemish identify of the friction welded joints.

Box-Counting Dimension of Fractal Urban Form

2012 ◽  
Vol 3 (3) ◽  
pp. 41-63 ◽  
Author(s):  
Shiguo Jiang ◽  
Desheng Liu
Keyword(s):  
Fractal Dimension ◽  
Urban Form ◽  
Fractal Dimensions ◽  
Reliable Estimate ◽  
Box Dimension ◽  
Beijing City ◽  
Box Counting ◽  
Window Method ◽  
Box Counting Dimension ◽  
Data Points

The difficulty to obtain a stable estimate of fractal dimension for stochastic fractal (e.g., urban form) is an unsolved issue in fractal analysis. The widely used box-counting method has three main issues: 1) ambiguities in setting up a proper box cover of the object of interest; 2) problems of limited data points for box sizes; 3) difficulty in determining the scaling range. These issues lead to unreliable estimates of fractal dimensions for urban forms, and thus cast doubt on further analysis. This paper presents a detailed discussion of these issues in the case of Beijing City. The authors propose corresponding improved techniques with modified measurement design to address these issues: 1) rectangular grids and boxes setting up a proper box cover of the object; 2) pseudo-geometric sequence of box sizes providing adequate data points to study the properties of the dimension profile; 3) generalized sliding window method helping to determine the scaling range. The authors’ method is tested on a fractal image (the Vicsek prefractal) with known fractal dimension and then applied to real city data. The results show that a reliable estimate of box dimension for urban form can be obtained using their method.

scholarly journals Fractal Dimension Analysis of the Julia Sets of Controlled Brusselator Model

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Yuqian Deng ◽  
Xiuxiong Liu ◽  
Yongping Zhang
Keyword(s):  
Fractal Dimension ◽  
Control Method ◽  
Fractal Theory ◽  
Julia Set ◽  
Reaction Diffusion ◽  
Reaction Diffusion Equations ◽  
Brusselator Model ◽  
Box Counting ◽  
Box Counting Dimension ◽  
Feedback Control Method

Fractal theory is a branch of nonlinear scientific research, and its research object is the irregular geometric form in nature. On account of the complexity of the fractal set, the traditional Euclidean dimension is no longer applicable and the measurement method of fractal dimension is required. In the numerous fractal dimension definitions, box-counting dimension is taken to characterize the complexity of Julia set since the calculation of box-counting dimension is relatively achievable. In this paper, the Julia set of Brusselator model which is a class of reaction diffusion equations from the viewpoint of fractal dynamics is discussed, and the control of the Julia set is researched by feedback control method, optimal control method, and gradient control method, respectively. Meanwhile, we calculate the box-counting dimension of the Julia set of controlled Brusselator model in each control method, which is used to describe the complexity of the controlled Julia set and the system. Ultimately we demonstrate the effectiveness of each control method.

Fractal and Convolutional Analysis for Deep Atmospheric Turbulence Using Machine Learning

2021 ◽  
Author(s):  
Nicholas Dudu ◽  
Arturo Rodriguez ◽  
Gael Moran ◽  
Jose Terrazas ◽  
Richard Adansi ◽  
...  
Keyword(s):  
Fractal Dimension ◽  
Atmospheric Turbulence ◽  
Isotropic Turbulence ◽  
Passive Scalar ◽  
Counting Method ◽  
Data Set ◽  
Box Counting ◽  
Box Counting Dimension ◽  
Self Similar ◽  
Box Counting Method

Abstract Atmospheric turbulence studies indicate the presence of self-similar scaling structures over a range of scales from the inertial outer scale to the dissipative inner scale. A measure of this self-similar structure has been obtained by computing the fractal dimension of images visualizing the turbulence using the widely used box-counting method. If applied blindly, the box-counting method can lead to misleading results in which the edges of the scaling range, corresponding to the upper and lower length scales referred to above are incorporated in an incorrect way. Furthermore, certain structures arising in turbulent flows that are not self-similar can deliver spurious contributions to the box-counting dimension. An appropriately trained Convolutional Neural Network can take account of both the above features in an appropriate way, using as inputs more detailed information than just the number of boxes covering the putative fractal set. To give a particular example, how the shape of clusters of covering boxes covering the object changes with box size could be analyzed. We will create a data set of decaying isotropic turbulence scenarios for atmospheric turbulence using Large-Eddy Simulations (LES) and analyze characteristic structures arising from these. These could include contours of velocity magnitude, as well as of levels of a passive scalar introduced into the simulated flows. We will then identify features of the structures that can be used to train the networks to obtain the most appropriate fractal dimension describing the scaling range, even when this range is of limited extent, down to a minimum of one order of magnitude.

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.

ON THE MENDÈS FRANCE FRACTAL DIMENSION OF STRANGE ATTRACTORS: THE HÉNON CASE

2002 ◽  
Vol 12 (07) ◽  
pp. 1549-1563 ◽  
Author(s):  
M. PIACQUADIO ◽  
R. HANSEN ◽  
F. PONTA
Keyword(s):  
Fractal Dimension ◽  
Hausdorff Dimension ◽  
Strange Attractors ◽  
Planar Curves ◽  
Box Counting ◽  
Box Counting Dimension

We consider the Hénon attractor ℋ as a curve limit of continuous planar curves H(n), as n → ∞. We describe a set of tools for studying the Hausdorff dimension dim H of a certain family of such curves, and we adapt these tools to the particular case of the Hénon attractor, estimating its Hausdorff dimension dim H (ℋ) to be about 1.258, a number smaller than the usual estimates for the box-counting dimension of the attractor. We interpret this discrepancy.

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.

DIMENSION ANALYSIS OF CONTINUOUS FUNCTIONS WITH UNBOUNDED VARIATION

Fractals ◽  
2017 ◽  
Vol 25 (01) ◽  
pp. 1730001 ◽  
Author(s):  
JUN WANG ◽  
KUI YAO
Keyword(s):  
Hausdorff Dimension ◽  
Fractal Dimensions ◽  
Continuous Functions ◽  
Packing Dimension ◽  
Box Dimension ◽  
Box Counting ◽  
Dimension Analysis ◽  
Box Counting Dimension ◽  
Self Similar

In this paper, we mainly discuss fractal dimensions of continuous functions with unbounded variation. First, we prove that Hausdorff dimension, Packing dimension and Modified Box-counting dimension of continuous functions containing one UV point are [Formula: see text]. The above conclusion still holds for continuous functions containing finite UV points. More generally, we show the result that Hausdorff dimension of continuous functions containing countable UV points is [Formula: see text] also. Finally, Box dimension of continuous functions containing countable UV points has been proved to be [Formula: see text] when [Formula: see text] is self-similar.

scholarly journals An Analysis of COVID-19 in Europe Based on Fractal Dimension and Meteorological Data

2021 ◽  
Author(s):  
Cristina Maria Pacurar ◽  
Victor Dan Păcurar ◽  
Marius Paun
Keyword(s):  
Fractal Dimension ◽  
Meteorological Parameters ◽  
Prediction Models ◽  
Meteorological Data ◽  
Global Radiation ◽  
Reproduction Rate ◽  
Box Counting ◽  
Box Counting Dimension ◽  
First Choice ◽  
Research Efficiency

The present paper proposes a fractal analysis of the Covid-19 dynamics in 45 European countries. We introduce a new idea of using the box-counting dimension of the epidemiologic curves as a means of classifying the Covid-19 pandemic in the countries taken into consideration. The classification can be a useful tool in deciding upon the quality and accuracy of the data available. We also investigated the reproduction rate, which proves to have significant fractal features, thus enabling another perspective on this epidemic characteristic. Moreover, we studied the correlation between two meteorological parameters: global radiation and daily mean temperature and two Covid-19 indicators: daily new cases and reproduction rate. The fractal dimension differences between the analysed time series graphs could represent a preliminary analysis criterion, increasing research efficiency. Daily global radiation was found to be stronger linked with Covid-19 new cases than air temperature (with a greater correlation coefficient -0.386, as compared with -0.318), and consequently it is recommended as the first-choice meteorological variable for prediction models.

scholarly journals The linkage between box-counting and geomorphic fractal dimensions in the fractal structure of river networks: the junction angle

2020 ◽  
Vol 51 (6) ◽  
pp. 1397-1408
Author(s):  
Xianmeng Meng ◽  
Pengju Zhang ◽  
Jing Li ◽  
Chuanming Ma ◽  
Dengfeng Liu
Keyword(s):  
Fractal Dimension ◽  
Fractal Structure ◽  
Fractal Dimensions ◽  
River Networks ◽  
Stream Length ◽  
Box Counting ◽  
Linear Relationships ◽  
Box Counting Dimension ◽  
Junction Angle

Abstract In the past, a great deal of research has been conducted to determine the fractal properties of river networks, and there are many kinds of methods calculating their fractal dimensions. In this paper, we compare two most common methods: one is geomorphic fractal dimension obtained from the bifurcation ratio and the stream length ratio, and the other is box-counting method. Firstly, synthetic fractal trees are used to explain the role of the junction angle on the relation between two kinds of fractal dimensions. The obtained relationship curves indicate that box-counting dimension is decreasing with the increase of the junction angle when geomorphic fractal dimension keeps constant. This relationship presents continuous and smooth convex curves with junction angle from 60° to 120° and concave curves from 30° to 45°. Then 70 river networks in China are investigated in terms of their two kinds of fractal dimensions. The results confirm the fractal structure of river networks. Geomorphic fractal dimensions of river networks are larger than box-counting dimensions and there is no obvious relationship between these two kinds of fractal dimensions. Relatively good non-linear relationships between geomorphic fractal dimensions and box-counting dimensions are obtained by considering the role of the junction angle.

scholarly journals Fractal Characteristic of Rock Cutting Load Time Series

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Hongxiang Jiang ◽  
Changlong Du ◽  
Songyong Liu ◽  
Kuidong Gao
Keyword(s):  
Time Series ◽  
Size Distribution ◽  
Fragment Size ◽  
Fractal Theory ◽  
Rock Cutting ◽  
Water Jet ◽  
Fragment Size Distribution ◽  
Fractal Characteristic ◽  
Box Counting ◽  
Box Counting Dimension

A test-bed was developed to perform the rock cutting experiments under different cutting conditions. The fractal theory was adopted to investigate the fractal characteristic of cutting load time series and fragment size distribution in rock cutting. The box-counting dimension for the cutting load time series was consistent with the fractal dimension of the corresponding fragment size distribution, which indicated that there were inherent relations between the rock fragmentation and the cutting load. Furthermore, the box-counting dimension was used to describe the fractal characteristic of cutting load time series under different conditions. The results show that the rock compressive strength, cutting depth, cutting angle, and assisted water-jet types all have no significant effect on the fractal characteristic of cutting load. The box-counting dimension can be an evaluation index to assess the extent of rock crushing or cutting. Rock fracture mechanism would not be changed due to water-jet in front of or behind the cutter, but it would be changed when the water-jet was in cutter.

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