• Journal of the Korean GEO-environmental Society
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• v.5 no.2
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• pp.51-62
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• 2004

Granular compaction piles have the load bearing capacity of the soft ground increase and have the settlement of foundation built on the reinforced soil reduce. The granular compaction group piles also have the consolidation of the soft ground accelerate and have the liquefaction caused by earthquake prevent using the granular materials such as sand, gravel, stone etc. However, this method is one of unuseful methods in Korea. The Granular compaction piles are constructed by grouping it with a raft system. The confining pressure at the center of bulging failure depth is a major variable in relation to estimate for the ultimate bearing capacity of the granular compaction piles. Therefore, a share of loading is determined considering the effect of load concentration ratio between the granular compaction piles and surrounding soils, and varies the magnitude of the confining pressure. In this study, method for the determination of the ultimate bearing capacity is proposed to apply a change of the horizontal pressure considering bulging failure depth, surcharge and loaded area. Also, the ultimate bearing capacity of the granular compaction piles is evaluated on the basis of previous study on the estimation of the ultimate bearing capacity and compared with the results obtained from laboratory scale model tests. And using the result from laboratory model tests, it is studied increase effect of the bearing capacity on the granular compaction piles and variance of coefficient of consolidation for the ground.

• Management & Information Systems Review
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• v.34 no.1
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• pp.65-80
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• 2015

In previous studies concerning turnover, they argue individual stock's turnover must be identical to market portfolio's turnover under one condition where 2 funds separation theorem holds. In this kind of world, all market participants hold and trade the same portfolio and this should be only market portfolio. If one's trading portfolio's shape is different from market portfolio's, this would mean he or she has an advantage over others in information and this kind of information would be private. In accordance with this theory, we develop a metric which measures how far one's trading portfolio from market's and name it as Stock Selection by Investor(SSI). We apply this measurement to the various types of investor groups classified as individual, institutional and foreign who participate in Korea stock market. To test the validity of measure, we regress price ratio on this measurement using SUR method. As a result, individual investor group shows large number in SSI, but the coefficient in regression is not significant and economically meaningless. In case of institutional investor group, the coefficient proves to be significantly negative. We can infer from this fact that their trading is somehow far from informed trading. Stock selection activity by foreign investor groups proves to be informed trading by showing significantly positive coefficient and the magnitude of coefficient is economically meaningful, especially in sell activity.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.1
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• pp.94-100
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• 1999

Mercurous chloride($Hg_2Cl_2$) crystals hold promise for many acousto-optic and opto-electronic applications, which are prepared in closed ampoules by the physical vapor transport(PVT) growth methods. The thermal boundary conditions established by imposing different temperature on sidewalls of the enclosure cause simultaneous horizontal and vertical convectie flow in the PVT processes of$Hg_2Cl_2$ . It is found that for the ratios of horizontal to vertical thermal Rayleigh numbers$Ra_H/Ra{\ge}1.5$, the convective flow structure changes from multicellular to unicellular for the base parametric state of Ra=($2.79{\times}10^4$) , Pr=0.91, Le=1.01, Pe=4.60, Ar=0.2 and$C_V =1.01$. For the $\Delta T^{*}_H$ greater than 0.3, the $$\mid$U$\mid$_{max}$is increased with increasing $\Delta$ T^{*}_H$ and decreasing the aspect ratio. For the aspect ratios ranging from 0.1 to 1.0, there is a direct and linear relationship between $$\mid$U$\mid$_{max}$ and $\sqrt{{\Delta}T^_H\;^{\ast}}$.A decrease in the aspect ratio destabilizes the convective flow and results in an increase of the magnitude of convection in the crystal growth reactor. The vertical gradient tends to destabilize the convective flow which leads to oscillations, whereas the horizontal gradient stabilizes the convection.

• Journal of the Korean Society for Nondestructive Testing
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• v.17 no.2
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• pp.89-99
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• 1997

Although discontinuously reinforced metal matrix composite(MMC) is one of the most promising materials for applications of aerospace, automotive industries, the thermal residual stresses developed in the MMC due to the mismatch in coefficients of thermal expansion between the matrix and the fiber under a temperature change has been pointed out as one of the serious problem in practical applications. There are very limited nondestructive techniques to measure the residual stress of composite materials. However, many difficulties have been reported in their applications. Therefore it is important to establish analytical model to evaluate the thermal residual stress of MMC for practical engineering application. In this study, an elastic model is developed to predict the average thermal residual stresses in the matrix and fiber of a misoriented short fiber composite. The thermal residual stresses are induced by the mismatch in the coefficient of the thermal expansion of the matrix and fiber when the composite is subjected to a uniform temperature change. The model considers two-dimensional in-plane fiber misorientation. The analytical formulation of the model is based on Eshelby's equivalent inclusion method and is unique in that it is able to account for interactions among fibers. This model is more general than past models to investigate the effect of parameters which might influence thermal residual stress in composites. The present model is to investigate the effects of fiber volume fraction, distribution type, distribution cut-off angle, and aspect ratio on thermal residual stress for in-plane fiber misorientation. Fiber volume fraction, aspect ratio, and distribution cut-off angle are shown to have more significant effects on the magnitude of the thermal residual stresses than fiber distribution type for in-plane misorientation.

• Journal of the Korean Geographical Society
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• v.36 no.2
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• pp.126-140
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• 2001

The influence of small urban parks(green ratio is 100%) on the temperature pattern over the urban and its surrounding area was examined by analyzing the case of in and around Changkyeong palace, Changdeok plalace and Jongmyo, Jongro-gu, Seoul. The pattern of temperature over urban parks and their surrounding built-up area was analyzed from September to November 2000, measuring maximum and minimum temperatures with fixed sensors(maximum and minimum thermometer)and real-time temperature depends largely on both the land-use type and the distance from the park border. In the case of maximum temperature, the lowest value appeared on the green area within parks and the highest value on the built-up area far from the green area. The maximum temperature difference between parks and built-up areas was up to $7.3^{\circ}C$. In the built-up area, the maximum temperature of commercial areas was higher than residential areas. In the night time, not only land-use type but also topography is important for the spatial distributlon of temperature because of the cold airflow from adjacet hills. The horizontal temperature profile by mobile measurement is also related to land-use type and to the distance from the park borders. There is a magnitude of $1^{\circ}C$ temperture difference over a distance of 200m and $3~4^{\circ}C$ over a distance of 400m from the park borders.

• Journal of the Korean Society for Railway
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• v.13 no.2
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• pp.186-193
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• 2010

Track system and periodic live load are characteristics of railway bridges. In the design and construction of railway bridge, periodic live load increases the importance of dynamic behavior. And It is well known that behavior of railway bridge may be affected by track system in real bridge. Through experimental study, static and dynamic behaviors were investigated. Deflection and stress due to bending moment were measured, the location of neutral axis of each section, natural frequency, damping ratio were analyzed for each three track systems - girder only, installed ballast track system and installed concrete slab track system. According to measured values for the each type of track system, concrete track system increases the stiffness of bridge by 50%, and ballast system does by 7%, dynamic responses of structure change linearly with the magnitude of load and location of neutral axis of each sections varies with each track system. Damping ratio is almost equal without and with track. Therefore, the effects of track system on the integral behaviors of railway bridge can not be ignored in the design of bridge, especially in the case of concrete slab track system. So study of the quantitative analysis method for effects of track system must be performed.

• Journal of Astronomy and Space Sciences
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• v.28 no.1
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• pp.27-36
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• 2011

The present study examines the morning-afternoon asymmetry of the geosynchronous magnetic field strength on the dayside (magnetic local time [MLT] = 06:00~18:00) using observations by the Geostationary Operational Environmental Satellites (GOES) over a period of 9 years from February 1998 to January 2007. During geomagnetically quiet time (Kp < 3), we observed that a peak of the magnetic field strength is skewed toward the earlier local times (11:07~11:37 MLT) with respect to local noon and that the geosynchronous field strength is larger in the morning sector than in the afternoon sector. That is, there is the morning-afternoon asymmetry of the geosynchronous magnetic field strength. Using solar wind data, it is confirmed that the morning-afternoon asymmetry is not associated with the aberration effect due to the orbital motion of the Earth about the Sun. We found that the peak location of the magnetic field strength is shifted toward the earlier local times as the ratio of the magnetic field strength at MLT = 18 (B-dusk) to the magnetic field strength at MLT = 06 (B-dawn) is decreasing. It is also found that the dawn-dusk magnetic field median ratio, B-dusk/B-dawn, is decreasing as the solar wind dynamic pressure is increasing. The morning-afternoon asymmetry of the magnetic field strength appears in Tsyganenko geomagnetic field model (TS-04 model) when the partial ring current is included in TS-04 model. Unlike our observations, however, TS-04 model shows that the peak location of the magnetic field strength is shifted toward local noon as the solar wind dynamic pressure grows in magnitude. This may be due to that the symmetric magnetic field associated with the magnetopause current, strongly affected by the solar wind dynamic pressure, increases. However, the partial ring current is not affected as much as the magnetopause current by the solar wind dynamic pressure in TS-04 model. Thus, our observations suggest that the contribution of the partial ring current at geosynchronous orbit is much larger than that expected from TS-04 model as the solar wind dynamic pressure increases.

• Journal of Veterinary Clinics
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• v.26 no.1
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• pp.23-28
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• 2009

Peritoneal dialysis (PD) is a clinical technique that therapeutically removes toxic solutes from body fluids and normalizes endogenous solutes whose aberrant concentrations disrupt normal physiology. This study retrospectively evaluated clinical outcomes and complications of PD in 20 dogs with renal failure. Blood works (total count of red blood cells (RBC), packed cell volume (PCV), the serum biochemical, and electrolyte values related to renal insufficiency) and complications associated with peritoneal dialysis, and clinical outcomes were recorded before and after PD. Additionally, creatinine reduction ratio (CRR) and urea nitrogen reduction ratio (URR) were calculated for evaluating the efficacy of PD. PD resulted in a significant (p < 0.05) reduction in blood urea nitrogen (BUN) concentration in 19 dogs, while a significant (p < 0.05) reduction in creatinine concentration in 17 dogs. The complications of PD were hypoalbuminemia (12/20, 60%), anemia (10/20, 50%), subcutaneous dialysate leakage (9/20, 45%), bacterial peritonitis (6/20, 30%), dialysate retention (5/20, 25%) and limb edema (4/20, 20%). This study demonstrated that PD was effective in reducing the magnitude of azotemia in dogs with renal failure especially in acute phase, although the complication rate was high but manageable.

• Journal of Korea Water Resources Association
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• v.53 no.4
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• pp.293-301
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• 2020

This study determined appropriate threshold level (cumulative period and percentage) of precipitation for drought management in dam basin. The 5 dam basins were selected, the daily dam storage level and daily precipitation data were collected. MAP (Mean Areal Precipitation was calculated by using Thiessen polygon method, and MAP were converted to accumulated values for 6 cumulative periods (30-, 60-, 90-, 180-, 270-, and 360-day). The correlation coefficient and ratio of variation coefficient between storage level and MAP for 6 cumulative periods were used to determine the appropriate cumulative period. Correlation of cumulative precipitation below 90-day was low, and that of 270-day was high. Correlation was high when the past precipitation during the flood period was included within the cumulative period. The ratio of variation coefficient was higher for the shorter cumulative period and lower for the longer in all dam, and that of 270-day precipitation was closed to 1.0 in every month. ROC (Receiver Operating Characteristics) analysis with TLWSA (Threshold Line of Water Supply Adjustment) was used to determine the percentage of precipitation shortages. It is showed that the percentage of 270-day cumulative precipitation on Boryung dam and other 4-dam were less than 90% and 80% as threshold level respectively, when the storage was below the attention level. The relationship between storage and percentage of dam outflow and precipitation were analyzed to evaluate the impact of artificial dam operations on drought analysis, and the magnitude of dam outflow caused uncertainty in the analysis between precipitation and storage data. It is concluded that threshold level should be considered for dam drought analysis using based on precipitation.

• Journal of the Korean earth science society
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• v.37 no.1
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• pp.40-51
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• 2016

The problem has been pointed out that the domestic design response spectrum does not reflect site amplification, particularly in the high frequency bands, including the fact that site specific response spectrum from the observed ground motions appears relatively higher than design response spectrum. Among various methods, this study applied H/V spectral ratio of ground motion for estimating site amplification. This method, originated from S waves and Rayleigh waves, recently has been extended to Coda waves and background noise for estimating site amplification. For limited time of periods, 4 electric substation sites had operated seismic stations at two separate locations (bedrock and borehole) within each substation site. H/V spectral ratio of S wave, Coda wave, and background noise, was applied to 36 accelerations of 3 macro earthquakes (Odaesan, Jeju and Gongju earthquakes), larger than magnitude 3.4. observed simultaneously at each bedrock location within 4 electric substation sites. Site amplifications at the bedrock location of 4 sites were compared among S wave, Coda wave energy, and background noise, and then compared to the previous results from the borehole location data. The site classification was also tried using resonancy frequency information at each site and location. The results suggested that all the electric substation sites showed similar site amplification patterns among S wave, Coda wave, and background noise. Each station showed its own characteristics of site amplification property in low, high and specific resonance frequency ranges. Comparison of this study to other results using different method can give us much more information about dynamic amplification of domestic sites characteristics and site classification.