• The Journal of Engineering Geology
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• v.23 no.1
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• pp.47-55
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• 2013

To analyze lateral displacement of excavation walls exposed during the construction of Subway Line 1 in the Daegu region, inclinometer measurement data for sites D4, D5, and Y6 are investigated from the perspective of engineering geology. The study area, in the Banyawol Formation, Hayang Group, Gyeongsang Supergroup, is in the lower part of bedrock of andesitic volcanics, calcareous shale, sandstone, hornfels, and felsite dykes that are unconformably overlain by soil. The rock mass around the D4 site is classified as RMR-V grade and the maximum lateral displacement of 101.39 mm, toward N34W, was measured at a bedding-parallel fault, at a depth of 12 m. The rock mass around the D5 site is classified as RMR-IV grade and the maximum lateral displacement of 55.17 mm, toward the south, was measured at a lithologic contact between shale and felsite, at a depth of 14 m. The rock mass around the Y6 site is classified as RMR-III grade and the maximum lateral displacement of 12.65 mm, toward S52W, was measured at an unconformity between the soil and underlying bedrocks, at a depth of 7 m. The directions of lateral displacement in the excavation walls are vector sums of the directions perpendicular to the excavation wall and horizontally parallel to the excavation wall. Lateral displacement graphs according to depth in the soil profile show curvilinear trajectories, whereas those in bedrock show straight and rapid-displacement trajectories.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.1
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• pp.85-92
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• 2015

This article presents the dynamic instability response of sigmoid functionally graded material plates on elastic foundation using the higher-order shear deformation theory. The higher-order shear deformation theory has ability to capture the quadratic variation of shear strain and consequently shear stress through the plate thickness. The governing equations are then written in the form of Mathieu-Hill equations and then Bolotin's method is employed to determine the instability regions. The boundaries of the instability regions are represented in the dynamic load and excitation frequency plane. The results of dynamic instability analysis of sigmoid functionally graded material plate are presented using the Navier's procedure to illustrate the effect of elastic foundation parameter on dynamic response. The relations between Winkler and Pasternak elastic foundation parameter are discussed by numerical results. Also, the effects of static load factor, power-law index and side-to-thickness ratio on dynamic instability analysis are investigated and discussed. In order to validate the present solutions, the reference solutions are used and discussed. The theoretical development as well as numerical solutions presented herein should serve as reference for the dynamic instability study of S-FGM plates.

• Journal of the Korean Society for Nondestructive Testing
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• v.18 no.5
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• pp.389-397
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• 1998

For an effective and efficient management of large amounts of preservice/inservice inspection(PSI/ISI) data in nuclear power plants, an intellegent Windows 95-based data management program was developed. This program enables the prompt extraction of previously conducted PSI/ISI conditions and results so that the time-consuming data management, painstaking data processing and analysis in the past are avoided. The program extracts, and the associated remedies. Furthermore, additional inspection data and comments can be easily added or deleted for subsequent PSI/ISI operation. Although the initial version of the program was applied to Kori nuclear power plant, this program can be equally applied to other nuclear power plant. And also this program can be used to offer the fundamental data for application of evaluation data related to fracture mechanics analysis(FMA), probabilistic reliability assessment(PRA) of PSI/ISI results, performance demonstration initiative(PDI) and risk-informed ISI based on probability of detection(POD) information of ultrasonic examination. Besides, the program can be further developed as a unique PSI/ISI data management expert system that can be apart of PSI/ISI data management expert system that can be a part of PSI/ISI Total Support System(TSS) for Korean nuclear power plants.

• Journal of Korea Water Resources Association
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• v.53 no.7
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• pp.545-555
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• 2020

A feasibility modeling for potential hydroelectric dam site selection was suggested using 1 sec ASTGTM (ASTER Global Digital Elevation Model) and Terra/Aqua MODIS (Moderate Resolution Imaging Spectroradiometer) derived land use (MCD12Q1) data. The modeling includes DEM pre-processing of peak, sink, and flat, river network generation, watershed delineation and segmentation, terrain analysis of stream cross section and reservoir storage, and estimation of submerged area for compensation. The modeling algorithms were developed using Python and as an open source GIS. When a user-defined stream point is selected, the model evaluates potential hydroelectric head, reservoir surface area and storage capacity curve, watershed time of concentration from DEM, and compensation area from land use data. The model was tested for 4 locations of already constructed Buhang, BohyunMountain, Sungdeok, and Yeongju dams. The modeling results obtained maximum possible heads of 37.0, 67.0, 73.0, 42.0 m, surface areas of 1.81, 2.4, 2.8, 8.8 ㎢, storages of 35.9, 68.0, 91.3, 168.3×10⁶ ㎥ respectively. BohyunMountain and Sungdeok show validity but in case of Buhang and Yeongju dams have maximum head errors. These errors came from the stream generation error due to ASTGTM. So, wrong dam watershed boundary limit the head. This study showed a possibility to estimate potential hydroelectric dam sites before field investigation especially for overseas project.

• Economic and Environmental Geology
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• v.36 no.3
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• pp.233-242
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• 2003

The southeasternmost coastal area of the Korean peninsula has been regarded as a seismologically stable area as neither Quaternary faults nor earthquake activity has been reported. To clarify whether the active tectonic movement has occurred or not, a digital marine terrace mapping and fracture mapping have been done in the coastal area. Bed rocks are composed of the Cretaceous volcanic and sedimentary rocks and the Paleogene granite. Wave-cut platform in the area is smaller and narrower relative to that of the northern coastal area. Most of the platforms in the area have little Quaternary sediment. The platforms except the Holocene terrace (1 st terrace) can be divided into three steps. The lowest platform (2nd terrace) has an altitude of 8-11 m. The broad middle one (3rd terrace) is 17 to 22 m high. The highest terrace (4th terrace) is a narrow and sporadic bench with an altitude of about 44 m high. The lowest terrace is correlated to the 2nd terrace of the northern area, which corresponds to the oxygen isotopic stage 5a. The uplift rate calculated from a graphic method is 0.19 m/ky. This low uplift is typical of an intra-plate, suggesting that the area is tectonically stable. The elevation of the platforms tends slightly lower from the north to the south in the survey area. The decreasing altitude of the platforms towards the south is interpreted to result from a local block tilting during the Latest Pleistocene. This also indicates that the eastern coast of the Korean peninsula has been suffering a subsidence to the south.

• Journal of the Korean Vacuum Society
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• v.15 no.1
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• pp.64-72
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• 2006

We demonstrated organic light-emitting devices (OLEDs) based on the organic thin-film materials such as tris-(8-hydroxyquinoline) aluminum $(Alq_3)$. The structure of OLEDs was vacuum deposited upon transparent and thin glass substrates pre-coated with a transparent, conducting indium tin oxide thin film. The luminance characteristics, current, capacitance, and dispersion factor for degraded OLEDs, which were made by various bias currents $(0.5mA\;{\leq}\;I_{Bias}\;{\leq}9mA)$, are studied. The current dependences of lifetime were divided at approximately 2mA, and they represented nearly linear behaviors but had different slopes in a logarithmic plot of lifetime versus bias current. With lighting OLEDs, the anomaly of capacitance, as shown in the CV curve, occurred because of two factors, polarization in the bulk of organic materials and the interface between the metal and organic layers. In decayed OLEDs that had lower bias currents of less than 2mA, it was found that the degradation of luminance was related to both the decrease of polarization and to the lowering of the injection barrier.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.880-884
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• 2009

여름철 강우시 저수지로 유입하는 고탁도의 하천수는 저수지 주변 수체에 비해 낮은 수온과 높은 부유물질 농도(SS)로 인해 상대적으로 높은 밀도를 가지며, 저수지 내에서 동일 밀도층을 따라 분포하며 밀도류를 형성하게 된다. 탁수는 대부분 장기간 저수지에 체류하며 수질과 수생태계에 큰 영향을 주게 된다. 따라서 저수지로 유입한 탁수의 밀도류 거동특성을 파악하는 것은 저수지 운영, 수질관리 및 수생태계 보호를 위한 관리대책 수립에 있어서 중요한 요소이다. 본 연구의 목적은 횡방향 평균 2차원 수치모델을 이용하여 초기수위별 다양한 유량규모에서 소양호로 유입하는 밀도류의 거동특성(유입경계지점 수심($h_0$), 침강점 수심($d_p$)과 거리($X_p$), 분리점 수심($d_s$), 중층류 관입두께($h_i$), 댐 축 도달시간($t_a$), 희석율(${\beta}$))을 분석하여 저수지 수질관리를 위한 의사결정지원 기초정보를 제공하는데 있다. 밀도류의 거동분석을 위해 사용된 유량조건은 그동안 소양호에서 발생한 홍수크기를 바탕으로 7개의 등급으로 나누었으며, 각각의 유량조건별 수문곡선은 2007년 수문사상 중 7월 30일부터 8월 30일까지의 수문사상을 바탕으로 수정가우시안 공식을 사용하여 산정하였다. 탁수 거동 특성의 모의는 서로 다른 초기 수위 및 유량조건하에서의 탁수거동을 나타냈고, SS농도 25 mg/L 이상을 기준으로 하여 탁수층의 $d_p$, $X_p$, $d_s$, $h_i$, $t_a$, ${\beta}$를 산정하였다. 일반적으로 유량규모가 커질수록 $d_p$와 $d_s$는 증가하였고, $X_p$는 댐 축으로부터 가까워짐이 확인되었으나, 동일 유량규모에 대해 초기 수위가 증가함에 따라 $X_p$는 대체로 댐으로부터 멀어졌다. $h_i$는 유량규모가 증가함에 따라 완만하게 증가하는 경향을 보였고, $t_a$는 초기수위가 EL. 165 m일 때 유량이 2,000 CMS 미만인 경우 댐 앞까지 도달하지 못하는 것으로 나타났으며, 나머지 수위조건에서는 유량이 3,000 CMS 미만인 경우 댐 앞까지 도달하지 못하는 것으로 나타났다. 유량 규모에 따라 $X_p$가 0 km인 지점과 19 km인 지점에서의 ${\beta}$ 값을 산정한 결과 일반적으로 유량규모가 커질수록 유입수의 희석효과는 작아지며 초기수위가 커질수록 증가하는 경향을 나타냈다. 연구 결과는 탁수 발생 초기 저수지 운영 실무자들이 유량규모 및 초기 수위조건에 따른 밀도류의 거동특성을 신속히 예측하는 목적으로 사용될 수 있다.

• Geotechnical Engineering
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• v.9 no.2
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• pp.41-54
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• 1993

This paper presents the two and three -dimensional stability analysis of nonhom- ogeneous, c-o soil slopes. Potential failure surface is assumed as a logspiral curve refracted in boundaries of layers. In 3-D analysis, rotational soil mass is assumed with a cylindroid central part terminated with plane ends. Seismic force is considered by sesmic intensity. The program developed in this study is compared with the program PCSTABLS. The ratio of three-dimensional minimum factor of safety to two-dimensional case is examined and factor of safety changes are showed for the ratio of cylindroid length to slope height and numbers of slice. On such bases the following conclusions may by made : (1) The program developed in this program is less conservative than the program PCSTABLS. (2) The value of F2 of this study shows the larger differences than that of PCSTABLS with increasing friction angle (3) Factors of safety computed for 3-D geometry differ considerablely from ordinary 2-D factors of safety. Since Fb/F2 exceeds unity, three -dimensional effects tend to increase the factor of safety. (4) As the ratio of three - dimensional failure width of slope height, b/H increase, the value of Fb/Ff decreases and approaches 1.0 when bye is 14. (5) In calculating the factor of safety using the developed program the number of slices is suitable with the ranges of 30-40

• Journal of Korea Multimedia Society
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• v.11 no.5
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• pp.610-622
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• 2008

Moving object segmentation is an essential technique for various video surveillance applications. The result of moving object segmentation often contains shadow regions caused by the color difference of shadow pixels. Hence, moving object segmentation is usually followed by a shadow elimination process to remove the false detection results. The common assumption adopted in previous works is that, under the illumination variation, the value of chromaticity components are preserved while the value of intensity component is changed. Hence, color transforms which separates luminance component and chromaticity component are usually utilized to remove shadow pixels. In this paper, various color spaces (YCbCr, HSI, normalized rgb, Yxy, Lab, c1c2c3) are examined to find the most appropriate color space for shadow elimination. So far, there have been some research efforts to compare the influence of various color spaces for shadow elimination. However, previous efforts are somewhat insufficient to compare the color distortions under illumination change in diverse color spaces, since they used a specific shadow elimination scheme or different thresholds for different color spaces. In this paper, to relieve the limitations of previous works, (1) the amount of gradients in shadow boundaries drawn to uniform colored regions are examined only for chromaticity components to compare the color distortion under illumination change and (2) the accuracy of background subtraction are analyzed via RoC curves to compare different color spaces without the problem of threshold level selection. Through experiments on real video sequences, YCbCr and normalized rgb color spaces showed good results for shadow elimination among various color spaces used for the experiments.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.5
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• pp.84-95
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• 2011

In this paper, we present a deblocking algorithm that removes grid and staircase noises, which are called "blocking artifacts", occurred in the compressed satellite images. Particularly, the given satellite images are compressed with equal quantization coefficients in row according to region complexity, and more complicated regions are compressed more. However, this approach has a problem that relatively less complicated regions within the same row of complicated regions have blocking artifacts. Removing these artifacts with a general deblocking algorithm can blur complex and undesired regions as well. Additionally, the general filter lacks in preserving the curved edges. Therefore, the proposed algorithm presents an adaptive filtering scheme for removing blocking artifacts while preserving the image details including curved edges using the given quantization step size and content analysis. Particularly, WLFPCA (weighted lowpass filter using principle component analysis) is employed to reduce the artifacts around edges. Experimental results showed that the proposed method outperforms SA-DCT in terms of subjective image quality.