• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.4
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• pp.659-665
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• 2016

The limit equilibrium method (LEM) is commonly used for slope design and stability analysis because it is easy to simulate slope and requires short calculating time. However, LEM cannot adequately simulate ploughing failure in a footwall slope with a joint set dipping parallel with slope, e.g. bedding joint set. This study performed parametric study to analyze the influence factors on ploughing failure using UDEC which is a commercial two-dimensional DEM (Distinct Element Method)-based numerical program. The influence of joint structure and properties on stability of a footwall slope against ploughing failure was investigated, and the factor of safety was estimated using the shear strength reduction method. It was found that the stability of footwall slope against ploughing failure strongly relies on dip angle of conjugate joint, and the critical bedding joint spacing and the critical length of slab triggering ploughing failure are also affected by dip angle of conjugate joint. The results obtained from this study can be used for effective slope design and construction including reinforcement.

• Journal of Energy Engineering
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• v.13 no.4
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• pp.267-274
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• 2004

Theoretical analysis for predicting the heat transport limitations of screen mesh wick and sintered wick heat pipes was performed. The heat pipe diameter was 8mm and water was used for working fluid. For the 250 mesh, each capillary pressures and heat transport limitations, thermal resistances were analyzed according to the operating temperatures, wick thicknesses and inclination angles, based on the effective capillary radius (r$\_$c/), porosity ($\varepsilon$) and permeability (K). The wick capillary limitation was increased as the operating temperature and the wick thickness were increased, and generally the sintered wick showed higher heat transport limitations than that of the screen wick. The thermal resistance of the screen wick was higher than that of the sintered wick and both thermal resistances were linearly increased as the wick thickness was increased.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.9
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• pp.97-103
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• 2005

In this paper, effects on the heat transport limitation of heat pipe by the wick structural factors were theoretically analyzed for the sintered-copper wick heat pipe. Uniformity of particle size and sintering process were acted as dominant factors on the pore distribution and wick porosity, and small deviations of the wick thickness and the pore size greatly affected the heat transport limitations of the heat pipe. Especially, slight variations of the wick thickness, mean particle radius and capillary radius along the vapor temperatures and inclination angles remarkably changed the capillary limitation of the heat pipe.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.4
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• pp.2428-2435
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• 2014

Numerical analysis with ALE (Arbitrary Lagrangian Eulerian) Adaptive Meshing technique was performed to evaluate the pullout capacity of the embedded suction anchors (ESA) in uniform clay. The numerical method was verified by the previous study, analytical results based on limit-equilibrium theory and centrifuge tests. The pullout capacity of the ESA under horizontal, vertical, and inclined loading were evaluated, and the effect of initial rotation of the ESA on pullout capacity was also investigated. The analysis results showed that the maximum horizontal capacity was obtained at the mid-point, and the each vertical capacity gave the similar value regardless of the loading points. Furthermore, the inclined capacity was decreased as the load inclination angle increased at the mid-point of the anchor, and almost the same pullout capacity was obtained when the initial rotation angles were below 30 degrees.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.12
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• pp.1023-1030
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• 2002

This paper is to research the heat transfer characteristic performance of the copper-water heat pipe with the screen wicks. Recently, the semiconductor capacity of an electronic unit has been larger, on the contrary, its size has been much smaller. As a result, a high-performance cooling system is needed. Experimental variables are inclination angles, temperatures of cooling water and the mesh number of screen wicks. The distilled water was used for the working fluid. At the inclination angle $6^{\circ}$ in top heat mode, the two layers of the 100-mesh screen wick showed the best heat transfer performance. The thermal resistance of the two layers with the 100-mesh screen was 0.7~$0.8^{\circ}C$/W.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.130-130
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• 2017

각 수계의 다기능보는 흐름 통제 단면으로서의 중요한 기능인 정밀한 유량 산정이 가능한 수리구조물이므로 다기능보를 각 유역의 표준유량을 산정할 수 있는 국가 유량기준점으로 활용할 수 있는 방안을 강구하는 것이 바람직하다. 현재 보의 방류량 산정 방법은 보의 설계 당시 수리모형실험과 1차원 수치모의 등의 방법에 의해 산정된 결과를 활용한 것으로 보의 상류 수위만을 고려하여 보의 방류량을 산정하는 방법으로 배수위 영향을 반영할 수 없을 뿐만 아니라 유량 측정시설로서의 보의 수리적 장점을 활용하지 못하는 한계가 존재한다. 이에 본 연구에서는 현행 방류량 산정 방법과 기존 연구의 한계점을 검토하여 보 상하류 수위와 보의 수리적 유량측정 기능을 상호 보완적으로 활용하여 방류량 추정량을 개선시킬 수 있는 수정 경사-면적법을 새롭게 제안하였으며, 금강의 백제보, 영산강의 승촌보, 죽산보를 대상으로 적용하고, 연구 결과의 적정성을 검토하였다. 적용 결과, 기존 방법은 하류 수위에 관계없이 보 상류의 수위가 상승하게 되면 증가하고, 반대로 하강하게 되면 방류량이 감소하는 등 상류 수위의 패턴을 그대로 따라가는 것을 알 수 있었으며, 수정 경사-면적법을 활용하여 추정한 결과, 상시적으로 변하는 상하류 수위차에 따라 방류량이 변동하여 보다 물리적인 현상을 더 잘 반영하는 것으로 판단된다.

• Proceedings of the KAIS Fall Conference
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• 2007.05a
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• pp.99-103
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• 2007

정확하고 신뢰성 높은 유량 자료는 수자원의 정량적인 계획과 관리에 필수적이다. 이를 위하여 Chiu는 기존의 결정론적인 흐름 방향 유속분포식의 한계를 극복할 수 있는 방법으로 확률통계에서 사용되는 엔트로피 개념을 이용한 3차원 유속분포 식을 제안하였고, 이를 실험실 데이터와 자연하천에 적용하여 신뢰성과 정확성을 지속적으로 증명하여 마침내 이에 대한 활용성이 매우 크게 대두되어 Chiu의 유속공식을 적극적으로 사용하고 있는 실정이다. 그러나 지금까지 이론적인 유속 분포식을 검증하기 위하여 단면 형상이 일정한 직사각형이나 사다리꼴 동의 실험수로에서부터 불규칙한 단면 형상을 갖는 자연 하천에 대한 적용을 거의 이루고 있는 실정이나, 하상경사가 변하는 경우에도 엔트로피 파라미터(M)가 이에 대응하여 평형상태에 도달하려고 하는지에 대한 연구는 전무하다. 본 연구에서는 하상경사를 임의로 변경 가능한 실험수로를 선택하여 정밀법에 의한 유속측정을 실시하였다. 같은 지점의 같은 단면에서 하상경사(${\Theta}$)가 0.000935부터 0.025794까지 28번의 경사변화를 주고 각 경사마다 유량을 측정하여 28개의 유량측정 데이터를, Chiu의 엔트로피 유속공식에 적용하여, 평균유속과 최대유속 사이의 관계가 선형관계, 즉 하상경사가 변하는 경우에도 엔트로피 파라미터(M)가 이에 대응하여 평형상태에 도달함을 증명하였다.

• Proceedings of the KAIS Fall Conference
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• 2007.11a
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• pp.116-119
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• 2007

정확하고 신뢰성 높은 유량 자료는 수자원의 정량적인 계획과 관리에 필수적이다. 이를 위하여 Chiu는 기존의 결정론적인 흐름 방향 유속분포식의 한계를 극복할 수 있는 방법으로 확률통계에서 사용되는 엔트로피 개념을 이용한 3차원 유속분포 식을 제안하였고, 이를 실험실 테이터와 자연하천에 적용하여 신뢰성과 정확성을 지속적으로 증명하여, 마침내 이에 대한 활용성이 매우 크게 대두되어 Chiu의 유속공식을 적극적으로 사용하고 있는 실정이다. 그러나 지금까지 이론적인 유속 분포식을 검증하기위하여 단면 형상이 일정한 직사각형이나 사다리꼴 등의 실험수로에서부터 불규칙한 단면 형상을 갖는 자연 하천에 대한 적용을 거의 이루고 있는 실정이나, 하상경사가 변하는 경우에도 엔트로피 파라미터(M)가 이에 대응하여 평형상태에 도달하려고 하는지에 대한 연구는 전무하다. 본 연구에서는 하상경사를 임의로 변경 가능한 실험수로를 선택하여 정밀법에 의한 유속측정을 실시하였다. 같은 지점의 같은 단면에서 하상경사($\theta$)가 0.00069부터 0.019034까지 28번의 경사변화를 주고 각 경사마다 유량을 측정하여 28개의 유량측정 데이타를, Chiu의 엔트로피 유속공식에 적용하여, 평균유속과 최대유속 사이의 관계가 선형관계, 즉 하상경사가 변하는 경우에도 엔트로피 파라미터(M)가 이에 대응하여 평형상태에 도달함을 증명하였다.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.285-298
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• 2003

Shear properies of geosynthetic/geosynthetic and geosynthetic/soil interfaces which are widely met in landfill sites were evaluated from the inclined board tests. The inclined board testing apparatus is known to reproduce the shear behavior on the low normal stress most accurately. In this study, the friction angle of each interface was estimated and the tensile force mobilized at the geosynthetic was measured as well. The test results showed that the friction angle of each interface and the tensile force of the geosynthetics depended on the amount of normal stress, the type of the geosynthetics used, and the combinations of geosynthetics and soils. In addition, the sand/geotextile/geomembrane interface system was simulated in this study, and it was observed that the tensile force developed at the geomembrane decreased due to the protection effect of the geotextile located above the geomembrane. The test results of this research was compared with those of direct shear tests published, too. Finally, by comparing the measured tensile force of the geosynthetics when the initial displacement of the box occurs, when the slope is called as the critical slope, with suggested analytic solution, the accuracy of analytic solution and the applicability to design were identified.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.4
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• pp.16-25
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• 2004

Theoretical analysis for predicting the heat transport limitation of a copper powder sintered wick heat pipe was performed. The heat pipe diameter was 8mm and water was used for working fluid. The particle diameter was classified by 5 different meshes, and each capillary pressures and heat transport limitations. thermal resistances were analyzed according to the operating temperatures, wick thicknesses and inclination angles, based on the effective capillary radius($r_c$), porosity($\varepsilon$), Permeability (K). The wick capillary limitation was increased according as the particle diameter and the wick thickness and the operating temperature were increased. As the porosity and the capillary radius were larger. then the heat transport limitation was higher. The thermal resistance was greatly increased according as the wick thickness was increased.