• Steel and Composite Structures
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• v.6 no.2
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• pp.87-101
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• 2006

The deformation and dynamic behavior mechanism of submerged shell-like lattice structures with membranes are in principle of a non-conservative nature as circulatory system under hydrostatic pressure and disturbance forces of various types, existing in a marine environment. This paper deals with a characteristic analysis on quasi-periodic and chaotic behavior of a circular arch under follower forces with small disturbances. The stability region chart of the disturbed equilibrium in an excitation field was calculated numerically. Then, the periodic and chaotic behaviors of a circular arch were investigated by executing the time histories of motion, power spectrum, phase plane portraits and the Poincare section. According to the results of these studies, the state of a dynamic aspect scenario of a circular arch could be shifted from one of quasi-oscillatory motion to one of chaotic motion. Moreover, the correlation dimension of fractal dynamics was calculated corresponding to stochastic behaviors of a circular arch. This research indicates the possibility of making use of the correlation dimension as a stability index.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.15 no.2
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• pp.19-29
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• 2012

Numerous studies suggested that fish assemblage structure reflects the status of stream ecosystems. The status of streams integrity, including various trophic levels, water quality and habitat degradation, can be assessed by fish assemblages. In this study, we investigated the relationships between fish assemblages and streamline geometry of streams. Previous studies suggested that geomorphologic parameter can be a critical factor of permeability between adjacent two systems. From a landscape ecological perspective, edges may partially control the flow rate of energy between two adjacent systems. Thus, the Streamline geometry can be a geomorphologic parameter that exhibits the integrity of stream. We selected the Nakdong river for study areas, which is one of major rivers and the longest (525 km) River in South Korea. We used the revised IBI representing overall ecological characteristics of Korean fish assemblages and eight sub-assessment criteria of IBI, collected from 82 sampling sites in the Nakdong River. For calculating the Streamline geometry, we measured fractal dimension index that generally used in biology, ecology and landscape ecology. We used the digital land-use/land-cover map and generated a 1-km buffer for each sampling site and refined the shape of the Streamlines. Pearson correlation analyses were performed between Streamline geometry and IBI and sub-assessment criteria of IBI. The results show that IBI and eight sub-assessments of fish are significantly correlated with geometry of Streamline. The fractal dimension of Streamline geometry were related with IBI (r = 0.48) and six sub-assessments of IBI, including total number of native fish and native species, the number of riffle benthic species, sensitive species, tolerant species and native insectivore. Especially, the number of tolerant species(r = -0.52) and native insectivore(r = 0.52) show strong correlation with geometry of Streamline. These results indicate that lower Streamline geometry can result in poor fish assemblages, while higher geometry of Streamline can enhance fish assemblages by potentially supplying insects and better habitat conditions. We expect the results of our study to be useful for stream restoration and management. However, we see the necessity of study investigating the mechanisms how Streamline geometry affect fish assemblages.

• The Journal of Engineering Geology
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• v.24 no.2
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• pp.161-169
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• 2014

We present the results of an experimental physical weathering study that focuses on fresh and slightly weathered gneiss samples from the Wonju area of Korea. The study investigated changes in the physico-mechanical properties of these samples during accelerated laboratory-based weathering, including analyses of microfracture formation. The deteriorated samples used in the study were subjected to 100-150 freeze-thaw cycles, with index properties and microfracture geometries measured between each cycle. Each complete freeze-thaw cycle lasted 24 hours, and consisted of 2 hours of saturation in a vacuum chamber, 8 hours of freezing at $-21^{\circ}C{\pm}1^{\circ}C$, and 14 hours of thawing at room temperature. Specific gravity and seismic velocity values were negatively correlated with the number of freeze-thaw cycles, whereas absorption values tended to increase. The amount of deterioration of the rock samples was dependent on the degree of weathering of the rock prior to the start of the analysis. Absorption, specific gravity, and seismic velocity values can be used to infer the amount of physical weathering experienced by a gneiss in the study area. The sizes and density of microfracture in the rock specimens varied with the number of freeze-thaw cycles. We found that box fractal dimensions can be used to quantify the formation and propagation of microfracture in the samples. In addition, these box fractal dimensions can be used as a weathering index for the mid-and long-term prediction of rock weathering. The present results indicate that accelerated-weathering analysis can provide a detailed overview of the weathering characteristics of deteriorated rocks.

• Journal of the Korean association of regional geographers
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• v.9 no.4
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• pp.481-492
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• 2003

This study aims to analyze quantitatively changes of forest and cropland landscape due to cropland increase toward higher mountain slope during 9 years from 1993 to 2002, using Landsat images and field survey in the vicinity of Manpo and Gangae cities, Jagang Province, Northwest Korea, During 9 years, cropland has increased as 49.9%, forest area decreased as 16%. The spatial characteristics of cropland changes present that average elevation of cropland are increased from 381m of 1993 year to 412m of 2002 year, and average gradient increased from $10^{\circ}$ to $13^{\circ}$. In increased area of cropland during 9 years, the average elevation is 455m, and average gradient is $15^{\circ}$ with maximum gradient $70^{\circ}$. Analysis of the patch phenomena by fragmentation of vegetation landscape show that number of patch increased from 394 to 1,241 and also values of shape index, and fractal dimension of vegetation are increased slightly, during 9 years. Croplands have developed mainly in mountain slopes of elevation between 450 to 750m. For improvement of agricultural productivity, it should be required political and social stabilization, international and South Korea's assistance, and restoration of mountain forest.

• Economic and Environmental Geology
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• v.42 no.3
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• pp.261-272
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• 2009

An experimental study of the accelerated weathering was performed to investigate the variations of physicomechanical properties of deteriorated rocks due to freeze-thaw weathering for the Jurassic granite specimens from Wonju, Gangwon-do. Each complete cycle of freeze and thaw was lasted 24 hours, comprising 2 hours saturating in vacuum chamber, 8 hours freezing at -20$\pm1^{\circ}C$ and 14 hours thawing at room temperature. Freeze-thaw cycles were implemented with measuring the index physical properties as well as geometries of microfractures. The seismic velocity was found to decrease with increasing freeze-thaw cycles. On the other hand, absorption tends to increase with freeze-thaw cycles. In the end, it was concluded that variations of the index properties of deteriorated specimen depend on its initial properties and flaws in rock. The size and density of the traces of the microfracture on slab specimen were changed continuously with increasing freeze-thaw weathering. The results obtained in this study show that the box fractal dimension($D_B$) has the strong capability of quantifying the combined effect of size and density of the microfractures.

• Tunnel and Underground Space
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• v.19 no.2
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• pp.146-157
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• 2009

An experimental study of accelerated weathering on mudstone sample specimens from Haman, Gyeongnam was performed to investigate the variations of physico-mechanical properties of deteriorated rocks due to freeze-thaw weathering. Each complete cycle of freeze and thaw lasted 24 hours, comprising 2 hours of saturating in vacuum chamber, 8 hours of freezing at $-16{\pm}1^{\circ}C$ and 14 hours of thawing at room temperature. Total of 55 cycles of freeze-thaw were completed with measuring the index properties as well as geometries of microfractures. The measured specific gravity and P-wave velocity found to decrease with increasing freeze-thaw cycles. On the other hand, absorption ratio and effective porosity were continuously increased with increasing freeze-thaw cycles. It was found that the index properties of deteriorated sample specimen depend on its initial properties and flaws in rock. The size and density of the traces of the microfracture on slab specimen exhibited abrupt changes after 30 cycles of freeze-thaw weathering. The results obtained in this study show that the box fractal dimension($D_B$) given in this paper has the strong capability of quantifying the size and density of the microfracture.

• Annals of Clinical Neurophysiology
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• v.3 no.1
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• pp.31-36
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• 2001

Background & Objectives : Fractal Dimension(FD) could be an index of correlation between variable parameters in non-linear chaotic signals. We tried to demonstrate that EEG wave is compatible with chaotic waves by measuring the Lyapunov exponent index and compared the difference of FD between variable age groups(teens, 30's, 50's) Methods : We estimated the Lyapunov exponent index and the FD from digital EEG data among five persons in each normal age groups by using the software which is programmed in our laboratory. Statistical analysis was done with SPSS win 8.0. The statistical differences of Lyapunov exponent index and FD between each electrodes and each age groups were done with ANOVA and paired sample t-test. Result : The Lyapunov exponent indexes were larger than 1 in each electrode and age group. There is no statistical difference in FD between each electrodes and each age groups. Except in 30th age group. In this group the FD of right hemisphere is larger than that of left hemisphere. Conclusion : The result of Lyapunov exponent index means EEG wave is a non-linear chaotic signal. And the results of FD suggest that chaotic parameters of right hemisphere is larger than those of left hemisphere at rest at least in younger people. We think that chaotic parameters can be a useful tool in investigating the variable diseases or brain states.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.34 no.1
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• pp.52-61
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• 1998

We studied behaviour pattern of anchovy (Engraulis japonicus) shoal by a method of shoal echo integration and tested species identification by a method of artificial neural network using the acoustic data collected in the East China Sea in March 1994 and in the southern coastal waters of the East Sea of Korea in March 1995. Between areas, frequency distribution of 10 shoal descriptors was different, which showed characteristics of shoal behaviour in size, bathymetric position and acoustic strength. The range and mean of shoal size distribution in length and height was wider and bigger in the southern coastal waters of the East Sea than in the East China Sea. Relative shoal size of China Sea. Fractal dimension of shoal was almost same in both areas. Mean volume reverbration index of shoal was 3 dB higher in the southern coastal waters of the East Sea than in the East China Sea. The depth layer of shoal distribution was related to bottom depth in the southern coastal waters of the East Sea, while it was between near surface and central layer in the East China Sea. Principal component analysis of shoal descriptors showed the correlation between shoal size and acoustic strength which was higher in the southern coastal waters of the East Sea, than in the East China Sea. Correlation was also found among the bathymetric positions of shoal to some degree higher in the southern coastal waters of the East Sea than in the East China Sea. The anchovy shoal of two areas was identified by artificial neural network. The contribution factor index (Cio) of the shoal descriptors between two areas were almost identical feature. The shoal volume reverberation index (Rv) was showed the highest contribution to the species identification, while shoal length and shoal height showed relatively high negative contribution to the species identification.

• Geomechanics and Engineering
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• v.30 no.5
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• pp.401-411
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• 2022

To obtain the dynamic mechanical properties, fracture modes, energy and brittleness characteristics of Furong Baijiao coal rock, the dynamic impact compression tests under 0, 4, 8 and 12 MPa confining pressure were carried out using the split Hopkinson pressure bar. The results show that failure mode of coal rock in uniaxial state is axial splitting failure, while it is mainly compression-shear failure with tensile failure in triaxial state. With strain rate and confining pressure increasing, compressive strength and peak strain increase, average fragmentation increases and fractal dimension decreases. Based on energy dissipation theory, the dissipated energy density of coal rock increases gradually with growing confining pressure, but it has little correlation with strain rate. Considering progressive destruction process of coal rock, damage variable was defined as the ratio of dissipated energy density to total absorbed energy density. The maximum damage rate was obtained by deriving damage variable to reflect its maximum failure severity, then a brittleness index BD was established based on the maximum damage rate. BD value declined gradually as confining pressure and strain rate increase, indicating the decrease of brittleness and destruction degree. When confining pressure rises to 12 MPa, brittleness index and average fragmentation gradually stabilize, which shows confining pressure growing cannot cause continuous damage. Finally, integrating dynamic deformation and destruction process of coal rock and according to its final failure characteristics under different confining pressures, BD value is used to classify the brittleness into four grades.

• Tunnel and Underground Space
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• v.12 no.4
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• pp.268-276
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• 2002

In this study, a 3D coordinate measurement system equipped with a laser displacement meter for digitizing rock joint surface was established and the digitized data were used to calculate several roughness parameters. The parameters used in this study were micro avenge inclination $angle(i_{ave})$, average slope of joint $asperity(SL_{ ave})$, root mean square of $i-angle(i_{rms})$, standard deviation of height(SDH), standard deviation of $i-angle(SD_i)$, roughness profile $index(R_P)$, and fractal dimension(D). The relationships between the roughness parameters based on the digitzation of the surface profile were analyzed. Since the measured value varied according to the degree of reflection and the variation of colors at the measuring point, rock joint surface was painted in white to minimize the influence of the surface conditions. The comparison of the measured values and roughness parameters before and after painting revealed the better consequence from measurement on the painted surfaces. Also, effect of measuring interval was studied. As measured interval was increased, roughness parameters were exponentially decreased. The incremental sequence of degree of decrease was $SDH\; i_{ave},\; i_{rms},\; SD_i,\;and\; R_ p-1$. As a result of comparison of parameters from pin-type measurement system and laser type measurement system, all value of parameters were higher when laser-type measurement system was used, except SDH.