• Geotechnical Engineering
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• v.3 no.2
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• pp.55-70
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• 1987

An analytical solution procedure is described to estimate the developed passive lateral earth Pressures behind a vertical rigid retaintng wall rotating about its toe into a mass of cohesionless soil. Various stases of wall rotation, starting from an at-rest state to an initial Passive state to a full Passive state, are considered in the analysis. Condition of failure defined by a modified Mohr-coulomb criterion, together with equilibrium conditions, is used to obtain the necessary equations for the solution. Using methods of stress characteristics and numerical finite difference, a complete solution within and on the boundaries of the entire solution domain is made possible. The variations of the soil shear strength and the wall friction at various depths and stages of wall rotation are also taken into account in the analysis. The results predicted by the developed method of analysis are compared with those obtained from the experimental model tests on loose and dense sand. The comparisons show good agreements at various stages of retaining wall rotation Fin- ally, results of analytical parametric study are presented to demonstrate the effects of wall fric- tion on the resultant thrust and distribution of developed lateral earth pressures.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.3 s.94
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• pp.311-318
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• 2005

Periodically perforated slot structure in the upper wall of the parallel plate waveguide is analyzed with main interest focusing on the diffraction Properties. The Periodic slot array is of infinite extent in one direction and of finite extent in the other direction. Various numerical results for reflection from the slotted section and transmission beyond the slotted section, and the radiation through the slotted section into the upper half space are presented with the height of feeding parallel plate waveguide, single slot size, and the periodicity between slots as parameters. This study is thought to be helpful to the design of the ventilation hole in the TFT-LCD and PDP.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.2
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• pp.232-237
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• 2011

Recently, continuous research on cryogenic valves is being carried out with the rapid development of the cryogenic valve-related industry, and especially, high performance of cryogenic valves is being promoted due to the breakthrough development and demand of users, etc., of the mechanical, shipbuilding, semiconductor and display industry and the aerospace industry field, but it is the reality that technical development and research on cryogenic application equipment on vacuum insulation are insufficient. The present research focused on interception of heat exchange with the outside by keeping low pressure after installing a jacket pipe outside a stem and also considered heat transfer properties on changes in pressure of a vacuum part and radius of a jacket which can reduce heat exchange for effective heat transmission control by studying it in a three-dimensional numerical analysis method.

• Journal of the Korean Society for Railway
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• v.11 no.3
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• pp.300-310
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• 2008

Through this study, a conceptual design for the next generation high-speed EMU has been derived to meet the crash worthiness requirements of the Korean rollingstock safety regulation. The crashworthiness regulations require some performance requirements for two heavy collision accident scenarios; a train-to-train collision at the relative speed of 36 km/h, and a collision against a standard deformable obstacle of 15 ton at 110km/h. The complete train set will be composed of 2TC-6M with 13 ton axle load, which is different from KTX with the power car of 17 ton axle load. Using theoretical and numerical analyses, a crashworthy conceptual design was derived in terms of mean crush forces and energy absorptions for principal crushable structures and devices. The derived conceptual design was evaluated and improved using one dimensional dynamic simulations for the bar-spring-damper-mass model. It is shown from the simulation results that the suggested conceptual design can easily satisfy domestic crashworthiness requirements.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.3
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• pp.69-78
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• 2007

In this study, a time-dependent aspect of an embankment failure is considered to simulate a flood inundation map and calculate overtopping discharge induced by an embankment failure. A numerical model has been developed by solving the two dimensional nonlinear shallow water equations with a finite volume method on unstructured grids. To analyze a Riemann problem, the HLLC approximate Riemann solver and the Weighted Averaged Flux method are employed by using a TVD limiter and the source term treatment is also employed by using the operator splitting method. Firstly, the numerical model is applied to a dam break problem and a sloping seawall. Obtained numerical results show good agreements with experimental data. Secondly, the model is applied to a flow induced by an embankment failure by assuming that the width and elevation of embankment are varied with time-dependent functions. As a result of the comparison with each numerical overtopping discharge, established flood inundation discharges in the previous studies are overestimated than the result of the present numerical model.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.133-133
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• 2012

기후변화에 관한 정부 간 패널 IPCC의 4차 보고서에 의하면 지난 100년간 지구 평균 기온의 선형추세선 기울기가 $0.74^{\circ}C$/년을 보이고 있으며 21세기말 지구의 평균기온은 최대 $6.3^{\circ}C$까지 더 상승할 것으로 전망하고 있다. 이러한 대기기온의 상승은 저수지 및 하천의 수온과 밀접한 관계를 지니는데, 저수지 표층 수온 및 유입 하천의 수온을 증가시켜 저수지 수온 성층형성시기를 앞당겨 성층화 기간을 증가시키고 또한 성층강도도 증가하게 된다. 이러한 수온성층기간 및 강도의 증가는 심수층의 용존산소 고갈과 이에 따른 퇴적층의 영양염류 용출량을 증가시켜 저수지 수질관리에 어려움을 야기할 것으로 전망되고 있다. 특히 온대기후대에 속하는 우리나라의 대부분의 대형 인공 저수지는 여름철 뚜렷한 수온성층구조가 확인되고 있어 대기기온 상승이 수온성층구조에 미치는 영향을 분석하는 것은 미래 기후변화에 대비한 저수지 수질관리 전략 수립을 위해 필요한 기초 연구라 판단되어진다. 본 연구에서는 2차원 횡방향 평균 수치모형(CE-QUAL-W2)을 활용하여 대기 온도 변화에 따른 충주호의 수온분포를 모의하고 수온 성층구조의 변동경향을 분석하였다. 지구 온난화 영향 모의에 앞서 2010년과 2008년의 충주호 수문조건에 모형을 적용하여 수온 성층구조의 재현성을 확인하였다. 미래 대기기온 자료는 국립기상연구소에서 제공하는 한반도 기후전망 모의자료(RCM) 중 충주댐 유역의 평균 기온자료를 수집하여 사용하였으며, 모의연도는 2011, 2040, 2070, 2100으로 하였다. 또한, 대기기온과 유입수온 자료를 제외한 모든 입력자료는 보정년도인 2010년과 동일하다고 가정하여 대기기온 변화의 영향만을 고려하였다. 2011년에 비해 2100년의 대기기온이 연평균 $2.44^{\circ}C$ 증가하였을 때 표층수온은 평균 $1.72^{\circ}C$, 최대 $4.31^{\circ}C$ 증가하는 것으로 나타났으며, 심층수온은 평균 $0.36^{\circ}C$, 최대 $1.33^{\circ}C$ 증가하는 것으로 나타났다. 성층구조 형성기간의 비교를 위해 표층과 심층의 수온이 $5^{\circ}C$ 이상의 차이를 보이는 기간을 조사한 결과 2011년에 비해 2100년에서 5일 일찍 시작되어 11일 더 지속되는 것으로 나타났다.

• Economic and Environmental Geology
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• v.52 no.4
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• pp.291-297
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• 2019

Fluid flow through rock fractures has been quantified using equations such as Stokes equations, Reynolds equation (or local cubic law), cubic law, etc. derived from the Navier-Stokes equations under the assumption that linear flow prevails. Therefore, these simplified equations are limited to linear flow regime, and cause errors in nonlinear flow regime. In this study, causal mechanism of nonlinear flow and critical Reynolds number were presented by carrying out fluid flow modeling with both the Navier-Stokes equations and the Stokes equations for a three-dimensional rough-walled rock fracture. This study showed that flow regimes changed from linear to nonlinear at the Reynolds number greater than 10. This is because the inertial forces, proportional to the square of the fluid velocity, increased enough to overwhelm the viscous forces. This tendency was also shown for the unmated (slightly sheared) rock fracture. It was found that nonlinear flow was caused by the rapid increase in the inertial forces with increasing fluid velocity, not by the growing eddies that have been ascribed to nonlinear flow.

• Journal of the Korean Society of Mineral and Energy Resources Engineers
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• v.55 no.6
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• pp.596-603
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• 2018

The traffic congestion is frequently occurring due to increasing demand for vehicles and development of subcenter in roads of domestic-downtown. The design of a Great depth underground double-deck tunnel planned for construction as a solution however it's mainly for a compact-car. Its low height and small section cause causalities when fire occurs. From this study, the delay system for fire smoke diffusion is developed to minimize the occurrence of casualties when fire occurs in the Great depth underground double-deck tunnel and the CFD(Computational Fluid Dynamics) is used to find the optimal installation interval and the blockage ratio to maximize the system effects. The study analyzed the shorter the installation interval of the system, the higher the smoke delay effect but the efficiency-change tends to be slight above a certain distance and the larger the blockage ratio, the higher the effect but the efficiency-difference is slight according to installation interval.

• Journal of Korean Society of Disaster and Security
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• v.11 no.2
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• pp.83-89
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• 2018

The significant sedimentation at the estuary in the eastern coast of Korea frequently causes river mouth occlusion where disconnection between the river and sea is observed. River mouth occlusion causing watershed retention raises the environmental risk of the area as it impairs water quality and threatens the area's safety in the event of floods. This study proposes a plan to maintain stability of river channel and flow of flood discharge at the estuary with loss of its function for disaster prevention. To this end, the study tries to change the location and width of stream path, focusing on the center line of stream near the sand bar of river mouth. This allows to identify a shape of stream path that leads the most stable flow. To review the result, this study uses the SRH-2D, a model for two-dimensional hydraulic analysis, and conduct numeric simulation. The simulation result showed that the most effective plan for maintaining the stable flow of running water without having the area sensitive to changes in hydraulic characteristics is to lower the overall river bed height of the sand bar near the center line of stream to a equal level.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.04a
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• pp.243-246
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• 2010

최근 정보량의 급격한 증가로 데이터센터는 점차 대형화되고 있으며, 통합적으로 관리/운영되기 위해서는 전산실내 적절한 온도와 습도의 유지가 필수적이므로, 전산실내 에너지의 사용 효율을 극대화하기 위한 연구가 꾸준히 이루어지고 있다. 이 연구에서는 국내 공공부문의 대형 전산실을 모델로 선정하여 전산실 내 서버의 위치, 용량 그리고 냉각시스템 등을 고려하여 전산실내 열/유동특성을 수치적으로 규명함으로써, 에너지 효율 극대화를 추구하고 전력을 절감하여 저탄소 녹색성장과 그린IT 환경을 구축 하고자 한다. 이를 위하여 실제 측정한 환경 데이터를 바탕으로 전산유체역학(CFD)을 이용하여 3차원 비압축성, 정상상태의 열/유동특성을 예측한다. 또한 기존 및 개선된 전산실에 대한 비교결과를 바탕으로 새로운 열/유동조건을 도출하며, 이를 통하여 전산실 운영에 필요한 에너지 효율향상 방안을 제안하고자 한다. 연구 결과, 전산실 천장의 냉기유입부분과 열기배출부분으로 나뉘어 냉복도와 온복도를 형성하며, 내부 서버와 기타 각종 장비들의 발열 등으로 부분적인 열섬(Thermal island)현상이 나타났다. 이러한 열섬현상을 줄이고, 전산실내 환경을 최적화하기 위하여 찬공기 유입부분의 속도, 배출구의 유량, 그리고 냉/온 복도의 역할 변경 등 여러 가지 가능한 매개변수에 대한 연구가 필수적이다. 또한, 서버에서 발생한 고온의 공기를 배출하는 것이 전산실 내 적절한 온도구현에 효과적이며, 열섬현상을 방지하기 위해서는 이 부분에 차가운 공기의 유입이 필요하다는 것을 알 수 있었다.