• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.2A
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• pp.63-69
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• 2003

In this paper, the scattered field from a perfectly conducting fractal surface by Finite-Difference Time-Domain(FDTD) method was computed. A one-dimensional fractal surface was generated by using the fractional Brownian motion model. Back scattering coefficients are calculated with different values of the spectral parameter(S0), fractal dimension(D) which determine characteristics of the fractal surface. The number of surface realization for the computed field, the point number, and the width of surface realization are set to be 80, 1024, 16λ, respectively. In order to verify the computed results these results are compared with those of small perturbation methods, which show good agreement between them.

• Journal of Astronomy and Space Sciences
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• v.23 no.3
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• pp.227-236
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• 2006

The fractal dimension is a quantitative parameter describing the characteristics of irregular time series. In this study, we use this parameter to analyze the irregular aspects of solar activity and to predict the maximum sunspot number in the following solar cycle by examining time series of the sunspot number. For this, we considered the daily sunspot number since 1850 from SIDC (Solar Influences Data analysis Center) and then estimated cycle variation of the fractal dimension by using Higuchi's method. We examined the relationship between this fractal dimension and the maximum monthly sunspot number in each solar cycle. As a result, we found that there is a strong inverse relationship between the fractal dimension and the maximum monthly sunspot number. By using this relation we predicted the maximum sunspot number in the solar cycle from the fractal dimension of the sunspot numbers during the solar activity increasing phase. The successful prediction is proven by a good correlation (r=0.89) between the observed and predicted maximum sunspot numbers in the solar cycles.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.29-32
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• 2007

Tidal channel development is influenced by sediment type, grain size, composition and tidal current. Tidal channels are usually characterized by channel development, density and shape. Quantitative analysis of tidal channels using remotely sensed data have rarely been studied. The objective of this study is to quantify tidal channels in terms of fractal dimension and compare different inter-tidal channel patterns. For the fractal analysis, we used Box counting method which had been successfully applied to streams, coastlines and others linear features. For a study, the southern part of Ganghwado tidal flats was selected where is famous for high dynamics of tidal currents and vast tidal flats. This area has different widths and lengths of tidal channels. IKONOS and Komsat-2 MSC images were used for extracting tidal channels, and the Box counting method was applied to obtain fractal dimensions (D) for each tidal channel. Yeochari area possesses channels with linear pattern and less dense development and accordingly show low D values ranging from 1.037 to 1.038. On other hands, area (near Donggumdo and Yeongjongdo ) of dendrites channel pattern and dense development resulted in high D values from 1.2057 to 1.2667. Also, area possesses channels with linear pattern had low density about $18{\sim}24%$. Area of dendritic channel pattern had high density about $34{\sim}69%$. The difference of fractal dimensions about 0.2 according to channel development in tidal flats is relatively large enough to use as an index for tidal channel classification. Also, area where channels showed linear pattern had low density about $18{\sim}24%$. Area of dendritic channel pattern had high density about $34{\sim}69%$. Using fractal dimension and density, it would be possible to quantify the tidal channel development in association with surface characteristics.

• Journal of the Institute of Convergence Signal Processing
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• v.11 no.2
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• pp.157-162
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• 2010

In this paper we propose a fractal analysis based on the discrete wavelet transform. It is well known that Fourier Transform is widely used for frequency analysis of random signal. However, the frequency domain is not used for expressing the sudden signal change and non-stationary signal at the time-axis by this method. Maximum value in the wavelet modules can be expressed by the Lipschitz exponent, which is useful to represent the characteristics of signal or the edge of an image. It is possible to reconstruct the original image only by using the few maximum points. The v possible image It iusing oil was acquired to interpret the maximum value. ufter that, it was applied to the v possible image of a ship model. In addition, the fractal dimens by by the conlapse process of the sediment particle was examined. In this paper, the fractal dimens by has been obtained by the maximum value and the experiment obtained from the visualized image also acquired the same result as existing methods.

• Journal of the Korean Geotechnical Society
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• v.19 no.2
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• pp.199-206
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• 2003

Particle-size distribution in soils is one of the most fundamental physical properties of soils. One of the latest developments in the study of particle-size distributions has focused on the use of fractal theories. In this study, the fragmentation fractals were used for determining the characteristics of the particle-size distribution curve. It was shown that the mass-size distribution method was more practical than the cumulative number-size distribution method. From the co-relation between fractal dimensions($D_{tot}$) and the coefficient of uniformity($C_{u}$), there was a sharp increase in fractal dimensions for $C_{u}$<4, but fractal dimension converged the single value for $D_{u}$$\geq$6. Fractal dimensions were affected by small sized particles for $C_{c}$$\geq$3 and large sized particles for $C_{c}$/<3. As a result of the analysis of the influence of the effective size($D_{10}$), it was observed that the changes of $D_{tot}$/ were nominal beyond the effective size.

• The Journal of Engineering Geology
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• v.12 no.3
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• pp.333-344
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• 2002

To clarify the relationship between groundwater flow tate and statistical distribution of fractures in Youngchun waterway tunnel, the fracture characteristics and fractal dimensions of groundwater flow section were evaluated. The flow rate of 84,465m$^3$/day was identified in fault, accounting for about 70 percent of the total How rate. The flow rate of 36,525m$^3$/day was identified in joint, accounting for about 30 percent of the total flow rate. The flow late in the NATM section of sedimentary rocks increased with the fractal dimensions. The fractal dimensions determined in fault or fracture zones show more positive relation with the flow rate than those in joint developed zones.

• The Transactions of the Korea Information Processing Society
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• v.2 no.5
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• pp.691-700
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• 1995

Most fractal image codings using fractal concept require long encoding time because a large amount of computation is needed to find an optimal affine transformation point. Such a problem can be solved by designing a block classifier fitted to characteristics of image blocks. In general, it is possible to predict more precise and various types of blocks in frequency domain than in spatial domain. In this paper, we propose a block classifier to predict the block type using characteristics of DCT(Discrete Cosine Transform). This classifier has merits to enhance the quality of decoded images as well as to reduce the encoding time meeting fractal features. AC coefficient values in frequency domain make it possible to predict various types of blocks. As the results, the number of comparisons between a range block and the correspoding domain blocks to reach an optimal affine transformation point can be reduced. Specially, signs of DCT coefficients help to find the optimal affine transformation point with only two isometric transformations by eliminating unnecessary isometric transformations among eight isometric transformations used in traditional fractal codings.

• Environmental Engineering Research
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• v.17 no.3
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• pp.139-144
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• 2012

In this study, the effects of starvation on floc characteristics when treating saline wastewater using a sequencing batch reactor (SBR) were investigated. The effectiveness over 5 days of starvation for aerobic and non-aerobic strategies for maintaining the physical characteristics of floc-forming sludge and the recovery period needed to regain the initial pollutant removal efficiency were investigated. Experiment results revealed that the sludge volume index (SVI) increased and the floc size and fractal dimension decreased after starvation under both aerobic and non-aerobic conditions. Sludge settleability deteriorated faster under aerobic conditions compared to non-aerobic conditions. Under non-aerobic conditions, the SBR required less time to return to its initial pollutant removal efficiency and settleability. Floc size, fractal dimension, and SVI were observed to be fairly correlated with each other. The results demonstrated that it was better to maintain the sludge under non-aerobic rather than aerobic starvation, because it adapted to, resisted starvation and had a quicker re-start afterward.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.369-372
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• 2000

ZnO varistor is studied to sintering condition and mixing condition for the improvement to non linear of electrical characteristics. In this paper, ZnO varistor, ZnO-Bi$_2$O$_3$-Y$_2$O$_3$-MnO-Cr$_2$O$_3$-Sb$_2$O$_3$series, is fabricated with Sb$_2$O$_3$mol ratio(0.5~4[mol%]) and sintered at 1250[$^{\circ}C$] for 2 hours. The grain size to Sb$_2$O$_3$moi ratio was measured by fractal mathematics. The ZnO varistors that Sb$_2$O$_3$mot ratio is 1[mol%] were shown small grain size because of spinel phase. The fractal dimension were increased with increasing of Sb$_2$O$_3$mo ratios. The capacitance of ZnO varistors with increasing of Sb$_2$O$_3$additive in voltage-capacitance characteristics was decreased by small grain size.

• Korean Journal of Remote Sensing
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• v.23 no.6
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• pp.567-573
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• 2007

Tidal channel development is influenced by sediment type, grain size, composition and tidal current. Tidal channels are usually characterized by channel formation, density and shape. Quantitative analysis of tidal channels using remotely sensed data have rarely been studied. The objective of this study is to quantify tidal channels in terms of fractal dimension and compare different inter-tidal channel patterns and compare with DEM (Digital Elevation Model). For the fractal analysis, we used box counting method which had been successfully applied to streams, coastlines and others linear features. For a study, the southern part of Ganghwado tidal flats was selected which know for high dynamics of tidal currents and vast tidal flats. This area has different widths and lengths of tidal channels. IKONOS was used for extracting tidal channels, and the box counting method was applied to obtain fractal dimensions (D) for each tidal channel. Yeochari area where channels showed less dense development and low DEM had low fractal dimenwion near $1.00{\sim}1.20$. Area (near Donggumdo and Yeongjongdo) of dendritic channel pattern and high DEM resulted in high fractal dimension near $1.20{\sim}1.35$. The difference of fractal dimensions according to channel development in tidal flats is relatively large enough to use as an index for tidal channel classification. Therefore we could conclude that fractal dimension, channel development and DEM in tidal channel has high correlation. Using fractal dimension, channel development and DEM, it would be possible to quantify the tidal channel development in association with surface characteristics.