• 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 Ocean Engineering and Technology
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• v.7 no.2
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• pp.150-161
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• 1993

원초변수를 이용한 Navier-Stokes 방정식의 수치계산기법을 개발하고, 이를 응용하여 backward facing step의 층류 유동을 계산하였다. 직교좌표계에서의 비압축성 Navier-Stokes방정식을 풀기위해 시간과 공간항을 2차 정도의 유한 차분을 사용하여 이산화하였고 비교차격자계를 사용하여 양해법으로 수치 계산하였다. 운동량방정식과 연속방정식으로 부터 유도된 압력방정식(pressure-poisson equation)을 이용하여 무발산 조건을 만족시켰ㄲ다. Backward facing step의 층류 유동을 100.$\leq$R$_e$$\leq$1000 범위에 대해서 수치 계산하였으며 실험결과와 잘 일치하는 결과를 구할 수 있었다. 특히 step뒤에서 생기는 박리구간의 길이는 다른 계산결과들보다 실험치에 가까운 값을 얻을 수 있었으며, Re가 600보다 클때는 위쪽 벽에 또 다른 박리 유동이 발생되는 현상이 예측되었다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.4
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• pp.1-9
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• 1988

In the previous paper, the discussion has been made about theoritical estimation of Load-Deformation Response for reinforced concrete torsional members in the over-all load region. It is the purpose of this investigation to introduce pure torsional testing method, to discuss experimentaly the effects that the change of the wall thickness and the reinforcement ratio contribute to the torsional strength and the crack characteristics of reinforced concrete members.

• Proceedings of the KAIS Fall Conference
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• 2009.05a
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• pp.821-824
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• 2009

고속도로를 주행 중인 차량에 강풍이 작용할 경우 차량의 주행안정성 저하와 운전자의 상황에 따른 치명적인 교통사고로 이어질 수 있다. 특히, 최근에 건설되거나 추진 중인 고속도로는 교량과 터널의 연속적인 조합으로 강풍발생위험에 노출되어 있어 적극적인 강풍저감 대책이 필요하다. 효과적인 방풍 시설 설치나 사전예고 시스템의 도입을 위해서는 차량의 동역학적 거동 분석, 주행 중인 차량의 위험도 판단기준 연구, 강풍위험지역의 정확한 풍속 추정기법 연구, 지능화된 방풍벽 개발, 방풍시설 설치판단 기준 제시, 합리적인 차량 속도 규제정책 등의 연구 개발이 수행되어야 한다. 본 연구에서는 강풍 발생 구간을 주행하는 차량의 동역학적 거동모델을 제시하고, 이를 기반으로 기존에 제안된 위험도 판단기준의 합리성을 제고하였으며, 운전자의 상황을 고려한 현실적인 차량주행위험도 판단기준 제시를 목표로 하였다.

• Geotechnical Engineering
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• v.8 no.4
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• pp.51-66
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• 1992

As the scale of public works get recently larger and diversified. the construction of retain- ing walls is required for the effective use of land. In the design of the retaining wall, the reliability and fitness of the retaining wall itself are regarded prudently although there is a tendency to ignore the importance of backfill. In this study, the experiments under various conditions such as repetition-continuity-load, roller-press load, and working space of backfill, are carried out using a model retaining wall similar to the real system. The experimental roes tilts are interpreted theoretically, Using a computer program, the experimental results are analyzed and compared with other theoretical wonts.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.542-546
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• 2004

Fully non-local Quasicontinuum method using sub-divided region with Hermite interpolation function is proposed for simulation of carbon nanotube. Tersoff-Brenner potential is adopted for interaction of bonded atoms and also van der Waals force for non-bonded interaction. Bending of single wall carbon nanotube with chirality (20,0) and 15nm length is simulated up to 90 degree. Bending of double wall carbon nanotube with chirality (20,0) and (12,0) is simulated up to 65 degree. Bending of four wall carbon nanotube is simulated up to 45 degree.

• Journal of the Korean Society of Visualization
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• v.22 no.2
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• pp.82-89
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• 2024

In this study, experiments were conducted to visualize and analyze the dynamic characteristics of splash and residual liquid film formation during and after the injection of water droplets onto vertically situated solid substrates with varying surface wettability, elasticity, and microtexture. As wettability decreased (higher contact angle), more splash droplets formed, and the residual liquid film decreased. Low contact angles resulted in thin residual films and less splash. Surface elasticity absorbed the impact forces of droplets, thereby decreasing splash phenomena and significantly reducing the formation of residual liquid films due to surface vibration. Surfaces with microtextures demonstrated control over droplet splash direction, guiding the liquid along desired pathways. High-speed imaging provided detailed insights, showing that surface properties critically influence splash dynamics and residual liquid film formation.

• Journal of the Korea Organic Resources Recycling Association
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• v.16 no.3
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• pp.29-37
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• 2008

The objective of this research is to evaluate the optimum treatment methods for disposal sludge cake at different temperatures and periods of time. The disposal dehydrated sewage cake used in this study was obtained from N wastewater treatment plant in the P City. This system consists of continuous conveyer thermal dryer and pyrolysis. The continual conveyer thermal dryer was operated to evaluate the optimum conditions with temperature settings, ranges from 130 to $180^{\circ}C$, loading rates of 650~750 kg/hr and operating times of 110~120 minutes. The continual pyrolysis was also operated to evaluate the optimum conditions with temperature settings, ranges from 650 to $750^{\circ}C$, loading rates of 100~158 kg/hr and operating times of 20~40 minutes. The sewage sludge cake has a moisture content of 78~80% (wt) which decreased up to 1~3%(wt) resulted in breaking of cell wall after operating the continuous conveyer thermal dryer and pyrolysis. Important parameters which were operating times, moisture contents, loading rates, conveyer velocities and rotary velocities effects on the thermal kinetics and dynamics were investigated to evaluate the optimum conditions for the continual thermal dryer and pyrolysis.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.3
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• pp.833-840
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• 2014

This study presents numerical simulation of turbulent flows in a rectangular open-channel that has a width-to-depth ratio of 2 using the source code provided by OpenFOAM. Large eddy simulations are carried out by solving the filtered continuity and momentum equations numerically. For the non-isotropic residual stress term, Smagorinsky's (1963) model is used. The flow in the open-channel whose width-to-depth ratio is 2, from experiment of Tominaga et al. (1989), is simulated numerically. Simulation results are compared with measured data by Tominga et al. (1989) and Nezu and Rodi (1985) and with LES data by Shi et al. (1999). Comparisons revealed that the model simulates the mean flow and turbulence statistics well. Specifically, the model reproduced the inner secondary currents located at the corner of sidewall and free surface successfully. In addition, the vortical component of turbulence intensity shows bulged contours towards the bottom edge.

• Composites Research
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• v.37 no.2
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• pp.132-138
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• 2024

In this study, a molecular dynamics simulation study was performed to investigate the size-dependent electroelastic properties of single-walled boron nitride nanotubes(BNNT). To describe the elasticity and polarization of BNNT under mechanical loading, the Tersoff potential model and rigid ion approximation were adopted. For the prediction of piezoelectric constants and Young's modulus of BNNTs, piezoelectric constitutive equations based on the Maxwell's equation were used to calculate the strain-electric displacement and strain-stress relationships. It was found that the piezoelectric constants of BNNTs gradually decreases as the radius of the tubes increases showing a nonnegligible size effect. On the other hand, the elastic constants of the BNNTs showed opposites trends according to the equivalent geometrical assumption of the tubular structures. To establish the structure-property relationships, localized configurational change of the primarily bonded B-N bonded topology was investigated in detail to elucidate the BNNT curvature dependent elasticity.