• 한국지반공학회지:지반
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• 제6권1호
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• pp.25-34
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• 1990

지하공동의 해석에 관한 유한요소법과 경계요소법의 해법은 많은 연구가 되어있다. 지하공동과 같은 구조물의 안정성해석시, 대상의 영역이 무한영역중의 극히 작은 일부분일 경우가 많다. 이 경우 무한영역은 비정의영역이므로 유한요소의 이산화가 불가능하며, 영향범위를가정하여 정의령 역으로 변환하면, 유한요소해석중에 강성매트릭스가 커지게되어 컴퓨터의 용량 및 계산시간상의 문제점을 일으키게 된다. 경계요소법을 적용하면, 무한영역을 고려할 수 있으나, 재료의 특성을 고려하기는 어려움이 많다. 본 논문은 특정부분의 변위 및 응력을 상세히 알 수 있으며,재료의 가음을 고려한 프로그램을 이용할 수 있는 유한요소법의 장점과 무한영역을 쉽게 고려할 수 있는 경계요소법의 장점을 갖는 유한요소와 경계요소를 결합한 해석법으로 무한탄성지반중의 지하공동안정해석에 대한 수치해석치와 이론치를 비교하여 효용성을 검토하였다. 그 결과 엄밀해에 가까운 경계요소법보다는 정도가 떨어지나 유한요소법보다는 정도가 개선되었다.

• Computers and Concrete
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• 제18권3호
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• pp.367-388
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• 2016

In this paper, a simple practical method is introduced in which a simple weight measurement of concrete and finite element numerical analysis are used to determine the moisture transfer coefficient of concrete with a satisfactory accuracy. Six concrete mixtures with different water-to-cementitious material (w/cm) ratios and two pozzolanic materials including silica fume and zeolite were examined to validate the proposed method. The comparison between the distribution of the moisture content obtained from the model and the one from the experimental data during both the wetting and drying process properly validated the performance of the method.With the proposed method, it was also shown that the concrete moisture transfer coefficient considerably depends on the pore water saturation degree. The use of pozzolanic materials and also lowering w/cm ratio increased the moisture transfer coefficient during the initial sorption, and then, it significantly decreased with an increase in the water saturation degree.

• 전기학회논문지
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• 제61권1호
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• pp.99-103
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• 2012

The electromagnetic topology and the BLT equation has been used as useful techniques to analyze coupling effects of huge devices. But in the case of systems including complex parts, applying the BLT equation can be difficult to manifest the complex parts with analytic solutions. To resolve this problem, a numerical method can be used to parts of the whole system in advance. In this paper, a microstrip line filter is analyzed using the BLT equation combined with numerical solutions. Consequently, achieved graphs from the BLT equation show good agreements with graphs obtained using a numerical method only.

• Computers and Concrete
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• 제30권5호
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• pp.369-375
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• 2022

Current exertion reports the numerical analysis of boundary layer slip flow of Casson Nano fluid along a permeable cylinder that is stretching in exponential manner. The modeled PDEs are changed into nonlinear ODEs through appropriate nonlinear transformations. Numerical results are attained using a renowned numerical scheme shooting method with Runge-Kutta procedure of 6^th-order. Influential role of relevant parameters like Reynolds, suction, Casson fluid and slip parameters on velocity profile is investigated. The effect of influence of slip parameter γ on temperature profile is seen through graph. To ensure the authenticity of numerical procedure, outcomes of some special cases of present work are compared with published work and strong agreement is noticed.

• 산업경영시스템학회지
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• 제29권2호
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• pp.58-66
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• 2006

This paper addresses the analysis of the travel distance and the number of storage location for storage location allocation methods in a warehouse system. The dedicated, randomized, combined and limited storage methods are considered. The combined and the limited storage methods are suggested here, which the combined storage method is to divide the storage locations into the dedicated storage area and the randomized storage area, and the limited storage method is to restrict the storage area of each product. Through a numerical example, the average travel distance between input/output point and the storage locations, and the number of storage location needed in the warehouse are compared between storage location allocation methods. The nearest randomized storage method is shown as the reasonable one in the travel distance and the number of storage location.

• Corrosion Science and Technology
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• 제18권3호
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• pp.102-109
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• 2019

The hydrogen diffusion and trapping model with a numerical finite difference method (FDM) was modified and extended to accommodate $H_2S$ corrosion and scale forming processes of high-strength steel under tensile stress condition. The newly proposed diffusion model makes it possible to clearly understand combined effect of tensile stress and $H_2S$ corrosion process on hydrogen diffusion behaviors. The core concept of this theoretical approach is that overall diffusion behavior is separated into diffusion process through two respective layers: an outer sulfide scale and an inner steel matrix. Diffusion coefficient values determined by curve-fitting permeation data reported previously with the newly proposed diffusion model indicate that the application of tensile stress can contribute to continual increase in the diffusivity in the sulfide scale with a high density of defect. This suggests that the scale with a lower stability under the stress condition can be a key parameter to enhance hydrogen influx in the steel matrix. Consequently, resistance to hydrogen assisted cracking of the steel under tensile stress can be decreased significantly.

• 한국지반공학회논문집
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• 제30권3호
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• pp.59-72
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• 2014

모래지반 표면에 위치한 강체 원형기초를 대상으로 수치해석을 통하여 수직-모멘트 조합하중 조건에서의 지지력을 구하였다. 지반은 Mohr-Coulomb 소성모델을 이용하여 모델링하였으며 관련흐름법칙을 적용하였고, 거친 기초 바닥면 조건에 대하여 검토하였다. 적은 수의 해석으로 조합하중 상관도를 산출할 수 있는 swipe 재하 방법과 통상적인 재하실험에서 적용되는 probe 재하 방법을 적용하여 비교한 결과, 두 방법은 유사한 결과를 나타내었다. 모멘트하중을 고려하기 위하여 전통적으로 사용되는 유효폭 및 유효면적 개념을 사용한 결과와 편심계수($e_{\gamma}$)를 사용한 방법들을 비교하였으며, 기존의 제안식들과 수치모델링으로 구해진 본 연구의 결과를 비교하였다. 수직-모멘트 조합하중 지지력의 내부마찰각에 따른 변화는 미미한 것으로 나타났으며, 유효폭 개념은 편심계수의 형태로 변환하여 원형기초에도 그대로 적용이 가능한 것으로 나타났다. 본 연구의 수치모델링 결과는 기존의 실험에 기반한 결과들에 비해 다소 작은 값을 주는 것으로 나타났으며, 편심 및 모멘트하중이 증가할수록 그 차이는 증가하였다. 수치모델링과 실험 결과가 차이를 나타내는 요인과 향후 연구 방향에 대하여 고찰하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
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• pp.211-216
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• 2000

Numerical studies were carried out to develop the moment magnifier method for long-term behavior of flat plates, subjected to combined in-plane compressive and transverse loads. Nonlinear finite element analyses were performed for the numerical studies. Through the numerical studies, the long term behavior of the flat plate subjected to uniform or nonuniform floor load was investigated, and creep effects on the degradation of strength and stiffness of the slabs were examined. As the result, the creep factor was developed to epitomizes with creep effect on the flat plate. The moment magnifier method using the creep factor was developed for long-term behavior of flat plates. Also, the design examples are shown for verification of proposed design method.

• 대한기계학회논문집B
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• 제25권3호
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• pp.389-396
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• 2001

Direct numerical simulation of bubble growth and merger process on a single nucleation site during partial nucleate boiling is performed. The equations governing conservation of mass, momentum and energy are solved using a finite difference method combined with a level set method for capturing the vapor-liquid interface. The level set method is modified to include the effects of phase change at the interface and contact angle at the wall. Also, a simplified formulation for predicting the evaporative heat flux in a thin liquid micro-layer is developed and incorporated into the level set formulation. Based on the numerical results, the bubble growth and merger pattern and its effect on the heat transfer are discussed.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2004년도 봄 학술발표회 논문집
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• pp.341-348
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• 2004

This paper presents a modeling technique of cracks by combined extended and superposed finite element method (XSFEM) which is a combination of the extended finite element method (XFEM) and the mesh superposition method (sversion FEM). In the proposed method, the near-tip field is modeled by a superimposed patch consisting of quarter point elements and the rest of the discontinuity is treated by the XFEM. The actual crack opening in this method is measured by the sum of the crack openings of XFEM and SFEM in transition region. This method retains the strong point of the XFEM so it can avoid remeshing in crack evolution and trace the crack growth by translation or rotation of the overlaid mesh and the update of the nodes to be enriched by step functions. Moreover, the quadrature of the Galerkin weak form becomes simpler. Numerical experiments are provided to demonstrate the effectiveness and robustness of the proposed method.