• 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.

• Korean Journal of Agricultural and Forest Meteorology
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• v.9 no.2
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• pp.140-148
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• 2007

The remote sensing observations of land surface properties are inevitably influenced by the landscape heterogeneity. In this paper, we introduce a geostatistical technique to provide a quantitative interpretation of landscape heterogeneity in terms of key land surface parameters. The study areas consist of the two KoFlux sites: (1) the Gwangneung site, covered with temperate mixed forests on a complex terrain, and (2) the Haenam site with mixed croplands on a relatively flat terrain. The semivariogram and fractal analyses were performed for both sites to characterize the spatial heterogeneity of two radiation parameters, i.e., land surface temperature (LST) and albedo. These parameters are the main factors affecting the reflected longwave and shortwave radiation components from the two study sites. We derived them from the high-resolution Landsat ETM+ satellite images collected on 23 Sep. 2001 and 14 Feb. 2002. The results of our analysis show that the characteristic scales of albedo was >1 km at the Gwangneung site and approximately 0.3 km at the Haenam site. For LST, the scale of heterogeneity was also >1 km at the Gwangneung site and >0.6 to 1.0 km at the Haenam site. At both sites, there was little change in the characteristic scales of the two parameters between the two different seasons.

• Clinical and Experimental Pediatrics
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• v.45 no.9
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• pp.1114-1119
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• 2002

Purpose : The purposes of this study were to determine short- and long-term fractal correlation behavior of heart rates during daily activity in patients with neurocardiogenic syncope. Methods : Twenty five patients with histories of neurocardiogenic syncope episodes were included. Their analogue 24h ambulatory Holter electrocardiograms were analyzed. The tape was digitized and the digitized electrocardiograms were partioned into sections of one hour. Then their RR intervals were measured and 20,000 points of RRI were used. To quantify the fractal correlation behavior, we employed the detrended fluctuation analysis, and short-term($n{\leq}16$, ${\alpha}_1$) and long-term(n>16, ${\alpha}_2$) fractal scaling exponents were calculated. Results : When compared to control, 24-hour average values of ${\alpha}_1$ and all ${\alpha}_1$ values at quarters of each day were significantly higher in patients with syncope. On the contrary, their 24-hour average value of ${\alpha}_2$ and all ${\alpha}_2$ values at quarters of each day were lower in patients with syncope. However, statistical significances were found in 24-hour average value of ${\alpha}_2$ and in ${\alpha}_2$ value at MN-6AM. Conclusion : In the syncope patients with neurocardiogenic syncope, short-term fractal scaling exponents of RR interval was significantly high throughout the day. Therefore, their RR intervals were smoother in the short term scale and had a tendency to continue in the same direction of increase or decrease, which may contribute to persistent decrease in heart rate during a syncopal attack.