• Journal of the Korean Geotechnical Society
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• v.36 no.12
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• pp.27-34
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• 2020

Use of axisymmetric shell element for the structure increases the efficiency and accuracy in finite element analysis of the interaction between the ground and the structure. This paper derived the force balance equation and the moment balance equation for an axisymmetric shell element based on Kirchhoff's theory. The governing equation for the axial deformation used the isoparametric shape function in the Galerkin formulation, and the governing equation for the shell bending used the higher-order shape function. The developed axisymmetric shell element was combined with Geo-COUS, a geotechnical finite element program for the coupled analysis with the ground. The accuracy of the developed element was confirmed through the example analyses of the circular plate and the liquid storage tank. And the energy balance equation for the axisymmetric shell element is presented.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 1997.10a
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• pp.86-89
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• 1997

해안의 자연지형은 흐름의 변화에 대해서 자신의 특성을 조절하는 능력을 가지고 있다. 흐름의 변화는 자연적 변화와 인위적 변화로 구분할 수 있다. 자연적 변화는 해일, 조류, 취송류 등에 의한 변화가 있다. 또한, 댐 방류량 조절 및 온배수 제트 등은 해안 흐름의 변화를 야기하며, 항만 등 수공구조물의 건설에 의해 흐름이 인위적으로 변화된다. 흐름이 변화하게 되면 이전의 동적 평형상태에 있던 해안은 수리학적 혹성, 유사특성의 변화를 초래하여 평형상태는 깨지게 된다. (중략)

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.244-245
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• 2017

본 논문은 병렬-입력 직렬-출력 구조의 모듈형 DAB (Dual active bridge) 컨버터의 출력 전압 평형 제어기법을 제안한다. 이를 위해, 먼저 모듈형 DAB 컨버터를 모델링하고 계층형 슬라이딩모드(Hierarchical SMC) 제어기를 설계한다. 제안된 기법을 시뮬레이션을 통해 검증한다.

• Journal of the Korean Geosynthetics Society
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• v.5 no.4
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• pp.11-18
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• 2006

Geotextile has been used for various types of containers, such as small hand-filled sandbags, 3-dimensional fabric forms for concrete paste, large soil and aggregate filled geotextile gabion, prefabricated hydraulically filled containers. They are hydraulically filled with dredged materials and have been applied in coastal protection and scour protection, dewatering method of slurry, temporary working platform for bridge construction, temporary embankment for spill way dam construction. Recently, geotextile tube technology is no longer alternative construction technique but suitable desired solution. The paper presents the stability behavior of geotextile tube composite structure by 2-D limit equilibrium and slope stability analysis. 2-D limit equilibrium analysis was performed to evaluate the stability of geotextile tube composite structure to the lateral earth pressure and also transient seepage and stability analysis were conducted to determine the pore pressure distribution by tide variation and slope stability. Based on the results of this paper, the three types of geotextile tube composite structure is stable and also slope stability of overall geotextile tube composite structures is stable with the variation of tidal conditions.

• Journal of Korea Soil Environment Society
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• v.4 no.3
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• pp.17-24
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• 1999

The effects of hydrophobic chain length and its structure of nonionic surfactants on surfactant adsorption and contaminated diesel removal were studied in kaolin soil. Hydrocarbon chain length and double bond in hydrophobic tail group of nonionic surfactants affected surfactant adsorption and diesel removal efficiency from kaolin soil. The degrees of surfactant adsorption and diesel removal were closely related each other. Among nonionic surfactants we studied, surfactants with shorter hydrophobic chain length and higher HLB value showed lower degree of adsorption and higher efficiency of diesel removal. The existence of unsaturated carbons in the structure of hydrophobic chain enhanced diesel removal by reducing surfactant adsorption to kaolin soil. The best diesel removal was obtained after adsorption saturation was reached. If surfactant concentration was higher than a critical value, diesel removal was reduced probably because of precipitation. liquid crystal formation, or coacervation of surfactants at high concentration.

• Journal of Korean Society of Steel Construction
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• v.11 no.2 s.39
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• pp.153-165
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• 1999

In order to trace the lateral-torsional post-bucking behaviors of thin-walled space frames with non-symmetric cross sections, a geometrically non-linear finite element formulation is presented by applying incremental equilibrium equations based on the updated Lagrangian formulation and introducing Vlasov's assumption. The improved displacement field for non-symmetric thin-walled cross sections is introduced based on inclusion of second order terms of finite rotations, and the potential energy corresponding to the semitangential rotations and moments is consistently derived. For finite element analysis, tangent stiffness matrices of thin-walled space frame element are derived by using the Hermition polynomials as shape functions. A co-rotational formulation in order to evaluate the unbalanced loads is presented by separating the rigid body rotations and pure deformations from incremental displacements and evaluating the updated direction cosines and incremental member forces.

• Computational Structural Engineering
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• v.6 no.1
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• pp.39-43
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• 1993

본문에 열거한 빙하중의 산정방법을 비교해 볼 때, 구조물의 규모가 크고 다년생 얼음이 설계하중으로 작용하는 경우 에너지 평형 방법 중 소성 극한이론을 근거로 한 Korzhavin식을 이용하는 것이 타당하리라 판단된다. 극한 응력에 의한 방법은 구조물의 직경이 작은 경우에 완전 관입이 되는 것을 가정하기 때문에 직경이 큰 구조물에서는 빙하중의 크기가 과대 평가될 가능성이 크며, 극한 하중에 의한 방법은 Ridge Building Force의 부정확성 때문에 쉽게 적용하기 곤란하여 이에 대한 통계적 자료가 크게 요구된다. 지반과 구조물의 유연성을 고려한 동적 모델에 의한 방법은 참고문헌을 소개하는 것으로 대신한다.

• Proceedings of the Korea Society for Simulation Conference
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• 2003.06a
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• pp.85-88
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• 2003

본 논문에서는 다중 프로세서 시스템에서 부하를 재분배할 때 소요되는 통신비용을 줄이기 위한 알고리즘을 제안한다. 또한 시뮬레이션을 이용하여 제안된 알고리즘의 성능을 기존의 알고리즘과 비교한다. 제안하는 알고리즘에서는 되도록 많은 수의 링크가 부하 평형에 참여 할 수 있도록 한다. 이를 위하여 부하 이동량 계산시에 각 프로세서는 자신과 연결된 모든 링크를 이용하여 부하 평형을 시도한다. 그리고 한 번의 링크를 통해 이동되는 부하 량을 단위 량으로 제한시키는 대신에 반복적인 방법으로 부하 이동량을 계산한다. 시뮬레이션은 8$\times$8, 10$\times$10, 12$\times$12, 14$\times$14, 16$\times$16개의 프로세서를 갖는 메쉬 구조에서 실시하였다. 시뮬레이션 결과 기존의 알고리즘에 비하여 전체 부하 이동량은 약 30%, 부하 이동 시간은 약 70% 감소함을 보였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.9
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• pp.912-918
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• 2011

In this paper, a composite right-/left-handed(CRLH) rectangular waveguide satisfying a balanced condition above the cut-off frequency is presented. The proposed structure consists of one shorted stub and two twisted H-plane irises which produce an effectively negative permeability and permittivity, respectively. The CRLH structure can independently control the series and shunt resonance frequencies of a CRLH transmission line which determine the left-handed(LH) and right-handed(RH) bands due to a minimized coupling between a shorted stub and twisted H-plane irises. Thus, the design of the CRLH waveguide satisfying a balanced condition is possible. To analyze the CRLH structure, a crossly connected equivalent circuit is derived. The simulated and measured results confirm that the proposed CRLH waveguide has a transmission property without a band gap among the LH and RH bands.

• Journal of Korean Society of Steel Construction
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• v.21 no.6
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• pp.563-574
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• 2009

This paper briefly describes the fundamental strategies--path-tracing, pin-pointing, and path-switching--in the computational elastic bifurcation theory of geometrically non-linear single-load-parameter conservative elastic spatial structures. The stability points in the non-linear elasticity may be classified into limit points and bifurcation points. For the limit points, the path tracing scheme that successively computes the regular equilibrium points on the equilibrium path, and the pinpointing scheme that precisely locates the singular equilibrium points were sufficient for the computational stability analysis. For the bifurcation points, however, a specific procedure for path-switching was also necessary to detect the branching paths to be traced in the post-buckling region. After the introduction, a general theory of elastic stability based on the energy concept was given. Then path tracing, an indirect method of detecting multiple bifurcation points, and path switching strategies were described. Next, some numerical examples of bifurcation analysis were carried out for a trussed stardome, and a pin-supported plane circular arch was described. Finally, concluding remarks were given.