• Journal of the Earthquake Engineering Society of Korea
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• v.16 no.1
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• pp.1-12
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• 2012

In this paper, the reduction factors to calculate the site coefficients of an embedded foundation are estimated, considering the effect of a poor backfill for the seismic design of a building built on an embedded foundation. This is determined by utilizing in-house finite element software, P3DASS, which has the capability of horizontal pseudo 3D seismic analysis with nonlinear soil. The 30m thick soil on stiff rock was assumed to be homogeneous, elastic, viscous and isotropic, and equivalent circular rigid foundations with radii of 10-70m were assumed to be embedded 0, 10, 20, and 30 m in the soil. Seismic analyses were performed with 7 bedrock earthquake records de-convoluted from the outcrop records; the scaling of the peak ground accelerations were to 0.1 g. The study results show that the site coefficients of a poor-backfilled foundation are gradually reduced as the foundation embedment ratio increases, except in the case of a small foundation embedded deeply in the weak soft soil. In addition, it was found that the deviation of the site coefficients due to the foundation size was not significant. Therefore, the typical reduction factors of an embedded foundation with poor backfill are proposed in terms of the shear wave velocity and site class. This is in order to find the site coefficients of an embedded foundation by multiplying the reduction factor by a site coefficient of a surface foundation specified in the design code. They can then be interpolated to determine the intermediate shear wave velocity.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.182-187
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• 2010

In the various fields of Civil Engineering, shear modulus is very important input parameters to design many constructions and to analyze ground behaviors. In general, a shear wave velocity profile is decided by various experiments before constructing a structure and, analysis and design are carried out by using decided shear wave velocity profile of the site. However, if civil structures are started to construct, the shear wave velocity will be increased more than before constructions because of confining pressure increase by the load of structure. The evaluation of the change in shear wave velocity profile is used very importantly when maintaining, managing, reinforcing and regenerating existing structures. In this study, a non-destructively geotechnical investigation method by using the HWAW method is applied to an evaluation of change in properties of the site according to construction. Generally, the space for experiments is narrow when underground of existing or on-going structures is evaluate, so a prompt non-destructive experiment is required. This prompt non-destructive experiment would be performed by various in-situ seismic methods. However, most of in-situ seismic methods need more space for experiments, so it is difficult to be applied. The HWAW method using the Harmonic wavelet transforms, which is based on time-frequency analysis, determines shear wave velocity profile. It consists of a source as well as short receiver spacing that is 1~3m, and is able to determine a shear wave velocity profile from surface to deep depth by one test on a space. As the HWAW method uses only the signal portion of the maximum local signal/noise ratio to determine a profile, it provides reliability shear modulus profile such as under construction or noisy situation by minimizing effects of noise from diverse vibration on a construction site or urban area. To estimate the applicability of the proposed method, field tests were performed in the change of geotechnical properties according to constructing a minimized modeling bent. Through this study, the change of geotechnical properties of the site was effectively evaluated according to construction of a structure.

• Journal of Environmental Science International
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• v.17 no.9
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• pp.1053-1068
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• 2008

This study aims to produce fundamental database for Environment Impact Assessment by monitoring vertical structure of the atmosphere due to the mountain valley wind in spring season. For this, we observed surface and upper meteorological elements in Sangin-dong, Daegu using the rawinsonde and automatic weather system(AWS). In Sangin-dong, the weather condition was largely affected by mountains when compared to city center. The air temperature was low during the night time and day break, and similar to that of city center during the day time. Relative humidity also showed similar trend; high during the night time and day break and similar to that of city center during the day time. Solar radiation was higher than the city, and the daily maximum temperature was observed later than the city. The synoptic wind during the measurement period was west wind. But during the day time, the west wind was joined by the prevailing wind to become stronger than the night time. During the night time and daybreak, the impact of mountain wind lowered the overall temperature, showing strong geographical influence. The vertical structure of the atmosphere in Dalbi valley, Sangin-dong had a sharp change in air temperature, relative humidity, potential temperature and equivalent potential temperature when measured at the upper part of the mixing layer height. The mixing depth was formed at maximum 1896m above the ground, and in the night time, the inversion layer was formed by radiational cooling and cold mountain wind.

• KOMUNHWA
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• no.69
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• pp.63-89
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• 2007

The Archaeological sites of so called Round Clay Rim Pottery (Jeomtodaetogi : 점토대토기) culture in Kangwon region have been rarely excavated in proper form. Since most cases belong to those of ground surface gatherings, it is difficult to certify the nature and the association with other artifacts. Therefore, researches on that culture have been limited to simply set the chronological order in the Bronze Age in realtion with the Plain Pottery culture. However, a comparative study trying to explain the Round Clay Rim Pottery culture in both Yeongseo(영서) and Yeongdong(영동) has become possible thanks to recent excavation results from the sites of Chilgeon-dong(칠전동) in Chunchon City(춘천시) and Songrim-ri(송림리) in Kangneung City(강릉시), for example. Certain difference can be observed in form and amount of artifacts in between Yeongseo and Yeongdong. Such difference can be seen as individual localization in different places diffused from a common source, rather than showing different stages of unilineal developmental process of one culture. The Round Clay Rim Pottery culture seems to have been coexisted with the Rim-Perforated Pottery(공렬토기) and Dolmen(지석묘) culture. According to the radiocarbondatings, the upper time limit of the Round Clay Rim Pottery culture goes back considerably beyond the alleged upper limit of either the late fourth century or the second century B.C.. However, both cultures absorbed into the Iron Culture during the same period.

• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.1
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• pp.152-157
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• 2004

Physicochemical characteristics of rice milled by newly designed abrasive milling machine were studied. Crude protein and crude lipid contents were 7.81∼8.50% and 1.07∼0.95%, respectively, and they showed a tendency to decrease with milling times. However, they showed higher values than that of polished rice. Major fatty acids of crude lipid were palmitic acid, oleic acid, and linoleic acid. Whiteness of tested samples was higher than brown rice but lower than polished rice. The remain rate of rice germ of four pass-through and polished one time sample (FPS) was 39.33%, and it was higher than that of polished rice (4.00%). One thousand grain weight of samples over than three pass-through was significantly different from brown rice (p<0.05). FPS had smooth surface similar to polished rice and it showed some residual rice germ by scanning electron microscopy. Sensory evaluation showed that the taste of three pass-through rice, four pass-through rice, and FPS was not significantly different from polished rice, whereas their color, odor, texture, and overall acceptability had lower score than polished rice but higher than brown rice. Therefore, we estimate that rice ground over three pass-through by newly designed abrasive milling machine might be a good source having nutritive value.

• Journal of the Korean Geotechnical Society
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• v.31 no.8
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• pp.5-15
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• 2015

One-dimensional rainfall laboratory tests using gneissic weathered soil were conducted to investigate effect of antecedent rainfall on infiltration characteristics. Experimental results using samples from Chuncheon and Chungju sites showed that rainfall onto the ground surface decreased initial negative pore water pressure of unsaturated soils, which recovered gradually after the end of rainfall. Rainfall intensity increases water infiltration rate, and infiltration rate during main rainfall is faster than that of the preceding rainfall. It is considered that higher water saturation after antecedent rainfall increases water infiltration rate during main rainfall. In particular, Chungju sample with higher clay content had slower recovery of negative pore water pressure and infiltration rate. Numerical results using finite element slope stability analysis showed that reduction of initial negative pore pressure due to rainfall infiltration deteriorates slope stability, and diffusion of pore water pressure after the end of rainfall further reduces FS of the slope in the short term. Main rainfall after prior rainfall further reduced factor of safety of the unsaturated slope. Pattern of antecedent rainfall has a significant impact on the magnitude and distribution of initial pore water pressure in unsaturated soils which are controlling factor to assess factor of safety of unsaturated slope during rainfall.

• Journal of the Korean earth science society
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• v.32 no.4
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• pp.360-372
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• 2011

In order to clarify the advection and dispersion characteristics of volcanic tephra to be emitted from the Mt. Baekdu, several numerical experiments were carried out using three-dimensional atmospheric dynamic model, Weather and Research Forecast (WRF) and Laglangian particles dispersion model FLEXPART. Four different temporally averaged meteorological values including wind speed and direction were used, and their averaged intervals of meteorological values are 1 month, 10 days, and 3days, respectively. Real time simulation without temporal averaging is also established in this study. As averaging time of meteorological elements is longer, wind along the principle direction is stronger. On the other hands, the tangential direction wind tends to be clearer when the time become shorten. Similar tendency was shown in the distribution of volcanic tephra because the dispersion of particles floating in the atmosphere is strongly associated with wind pattern. Wind transporting the volcanic tephra is divided clearly into upper and lower region and almost ash arriving the Korean Peninsula is released under 2 km high above the ground. Since setting up the temporal averaging of meteorological values is one of the critical factors to determine the density of tephra in the air and their surface deposition, reasonable time for averaging meteorological values should be established before the numerical dispersion assessment of volcanic tephra.

• Journal of Korea Game Society
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• v.15 no.5
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• pp.143-152
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• 2015

Unlike simulating general 'particle-based fluid explosion', simulating fluid with elasticity requires various experimental methods in order to show the realistic deformation of the matter. The existing studies on particle-based viscoelastic fluid only focused on matters' plastic deformation which can be found in mud or paint, based on the maximum distortion energy theory and maximum shear stress theory. However, these former researches could not simulate the brittle deformation which can be seen from silicon or highly elastic rubber when great external forces above limits are applied. This study suggests a brittle simulation method based on the Coulomb-Mohr theory, the idea that a yield occurs when maximum stress on a matter reaches to its rupture stress. This theory has a significant difference from the existing particle-based simulations which measures the forces on a matter by length or volume. Using a strong-elastic semifluid which Coulomb-Mohr theory is applied, realistic deformation process of a matter was observed as its forced surface reached to the rupture stress. When semifluid hit the ground, the impact of deformation can be explained by using Coulomb-Mohr theory.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.9
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• pp.794-806
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• 2017

It is essential to protect the national space assets and space environment safely as a space development country from the continuously increasing space debris. And Active Debris Removal(ADR) is the most active way to solve this problem. In this paper, we studied the Artificial Neural Network(ANN) for a stable recognition model of vision-based space debris tracking system. We obtained the simulated image of the space environment by the KARICAT which is the ground-based space debris clearing satellite testbed developed by the Korea Aerospace Research Institute, and created the vector which encodes structure and color-based features of each object after image segmentation by depth discontinuity. The Feature Vector consists of 3D surface area, principle vector of point cloud, 2D shape and color information. We designed artificial neural network model based on the separated Feature Vector. In order to improve the performance of the artificial neural network, the model is divided according to the categories of the input feature vectors, and the ensemble technique is applied to each model. As a result, we confirmed the performance improvement of recognition model by ensemble technique.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.2B
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• pp.155-163
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• 2011

In this study, a soil moisture estimation model was developed using a decision tree model, an artificial neural networks (ANN) model, remotely sensed data, and ground network data of daily precipitation, soil moisture and surface temperature. Soil moisture data of the Yongdam dam basin (5 sites) were used for model validation. Satellite remote sensing data and geographical data and meteorological data were used in the classification and regression tree (CART) model for data classification and the ANNs model was applied for clustered data to estimate soil moisture. Soil moisture data of Jucheon, Bugui, Sangjeon, Ahncheon sites were used for training and the correlation coefficient between soil moisture estimates and observations was between 0.92 to 0.96, root mean square error was between 1.00 to 1.88%, and mean absolute error was between 0.75 to 1.45%. Cheoncheon2 site was used for validation. Test statistics showed that the correlation coefficient, the root mean square error, the mean absolute error were 0.91, 3.19%, and 2.72% respectively. Results demonstrated that the developed soil moisture model using CART and ANN was able to apply for the estimation of soil moisture distribution.