• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.4
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• pp.461-473
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• 2000

This paper deals with a numerical model for the time-dependent analysis of steel and concrete composite beams with partial shear connection. A linear partial interaction theory is adopted in formulation of structural slip behavior, and the effect of concrete creep and shrinkage are considered. The proposed model is effective in simulating the slip behavior, combined with concrete creep and shrinkage, of multi-span continuous composite beams. Finally, correlation studies and several parameter studies are conducted with the objective to establish the validity of the proposed model.

• Proceedings of the Korean Society of Computer Information Conference
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• 2017.07a
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• pp.384-385
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• 2017

과학 모델은 복잡한 자연현상을 단순화하고 패턴화한 것이다. 따라서 과학 모델은 특정한 알고리즘을 가지며, 과학 모델에 대한 이해는 모델이 갖는 특정한 알고리즘에 대한 이해와 직접적으로 관련되어있다. 본 연구에서는 많은 학생들이 대안 개념을 가지고 있는 산-염기를 주제로 하여, 이 모델이 가지는 알고리즘을 학습하기 위한 프로그램을 설계하고, 알고리즘을 학습 하였을 때 과학 학습에 미치는 효과를 확인하였다. 고등학생 3학년을 대상으로 4차시로 수업을 진행하였으며, 수업의 사전과 사후 검사를 실시하여, 학생들의 모델에 대한 이해를 분석하였다. 수업 결과, 학생들은 모델의 정의와 화학반응 및 화학평형의 정성적인 부분에서는 이해의 향상을 보였으나, 정량적인 부분에는 효과를 보이지 못하였다. 이는 화학이 많은 수의 입자를 고려해야 하는 독특한 과목의 특성에 기인하며, 이를 보완하기 위하여 추후 컴퓨터프로그램을 교육 도구로 사용하는 수업을 통해 후속연구를 진행하고자 한다.

• Journal of the Korean Ceramic Society
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• v.38 no.6
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• pp.545-550
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• 2001

본 연구에서는 분사연소합성(SCS)을 위한 기초단계로서 용액연소합성에 대한 거동을 살펴보고자 알루미나 합성을 모델로 하였으며 이를 위해 전구체에 대한 열분해거동, 그리고 각 온도에서의 평형종 분압 계산 및 합성과정을 조사하였다. 각각의 열중량 분석(TGA) 결과 산화제와 환원제(연료)의 열분해 이력이 서로 다르게 나타났으며, 열역학 응용 프로그램인 ChemSag에 의한 평형종 분압의 계산에서 연소속도를 저하시킬 수 있는 $CO_2$와 수증기 가스 분압이 상당부분 존재하였다. 산화제/환원제 혼합물의 열분석(DTA/TG) 결과 산화제와 환원제의 열분해 거동의 차이, 그리고 매우 작은 시료의 양으로 인해 263$^{\circ}C$에서 발열피크가 매우 작게 나타났다. 열분석 시료에 비해 발열 에너지를 높이기 위해 산화제와 환원제 혼합 전구체를 비이커에서 증기압을 조절하며 가열시켜 본 결과 27$0^{\circ}C$에서 $\alpha$-Al$_2$O$_3$생성물을 얻을 수 있었다. 따라서 분사연소합성 반응을 통해 세라믹 원료를 합성하기 위해서는 연소과정 중 열분해 거동과 평형종의 분압을 고려하여야 한다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.4
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• pp.459-467
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• 2004

This paper presents an efficient reanalysis algorithm, named PRAS (Partial Reanalysis algorithm using Adaptable Substructuring), for the partially changed structures. The algorithm recalculates directly any displacement or member force under consideration in real time without a full reanalysis in spite of local changes in member stiffness or connectivity_ The key procedures consists of 1) partitioning the whole structure into the changed part and the unchanged part, 2) condensing the internal degrees of freedom and forming the unchanged part substructure, 3) assembling and solving the new stiffness matrix from the unchanged part substructure and the changed members.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.3
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• pp.119-128
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• 1988

The purpose of this research is to quantify the effects of water content(0.3~1.255%) and temperature ($4{\sim}40^{\circ}C$) on the equilibrium distribution of toxic organic pollutant in unsaturated soil. The priority pollutants, Dichloromethane and 1, 1, 1-Trichloroethane were selected as toxic organic pollutants and the Korean decomposed granite soil as the experimental soil media. Two models were developed on the basis of shapes of soil water distribution in unsaturated soil and compared; complete surface coating(model I) vs. spot clustering (model II). From the experiment, a large decrease in the values of effective partition coefficient ($K_{eff}$) was observed as the water content increased. As the temperature increased, the $K_{eff}$ values decreased, and this effect was magnified at lower water contents. The values of $K_{eff}$ were correlated better with the estimated values using model II. Thus it was experimentally proved that the soil water tends to enclose the soil grain partly at lower water contents.

• Solar Energy
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• v.10 no.2
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• pp.44-58
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• 1990

Heat transfer characteristics of heat storing processes in paraffin-filled horizontal circular cylinder is studied. The unmelted solid paraffin is allowed to fall on the bottom wall under gravity. In the upper liquid phase, natural convection is considered to take place while in the lower liquid film between the solid paraffin and the wall conduction is thought to take place instead. Experimental analyses are also carried out. The amount of the latent heat stored is obtained by recording the time wisely changing side area of the solid paraffin photographically. The mass of paraffin melted in the upper section is obtained by substracting the amount of melted mass in the lower section from the total mass melted and therefrom variation of heat transfer rate in each section is studied.

• Journal of the Korean Geophysical Society
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• v.5 no.4
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• pp.293-303
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• 2002

Applying elastic plate model, we estimated elastic thickness and rigidity of the lithosphere in southern part of the Korean Peninsula($332km{\times}332km$ area of which center is $36.5^{\circ}N$ in latitude and $127.5^{\circ}E$ in longitude) by analysing terrain data and gravity data measured up to 2002. We tried to exclude the East Sea in choosing the study area because it has different tectonic environment. The mean Moho depth was estimated to be 30 km by power spectrum analysis of gravity data in the study area, Assuming one layer crust and applying elastic plate model, the loads with wavelengths of greater than 300 km are locally compensated, loads with wavelengths in the range 80-300km are partially supported by the strength of the lithosphere, and loads with wavelengths of less than 80km are almost completely supported by lithospheric strength. Assuming crustal model and rigidity, we calculated predicted coherence and compared it with observed coherence. As a result, we wert able to estimate the effective elastic thickness to be of 15 km(corresponding flexural rigidity is $3.0{\times}10^{22}Nm$). This indicates that the crust of the study area is relatively weaker than other old and stable continental regions but is similar to continental margins or oceanic area. The low rigidity could be explained by many tectonic and thermal activities such as orogenic activities, magmatic intrusions, volcanic activities, foldings, faultings, etc.

• Geotechnical Engineering
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• v.14 no.6
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• pp.33-44
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• 1998

Preliminary study has been conducted to analyse the co-relation between shallow landslides frequently occurring in rainy seasons and the water infiltration into the slope. The change of stress state due to partial saturation of a soil and hence the reduction of its shear strength have been reviewed. The variation of the safety factor of an infinite planar slope in accordance with various water infiltration scenarios has been estimated by limit equilibrium method to explain the mechanism of shallow slope failure. Numerical analysis under the same condition as those of some models dealt with in the previous method has been carried out by using FLAC, a finite difference program, and the results have been compared with the ones obtained by limit equilibrium method. Both results proved to be identical, which implies the ability of the numerical approach to the problems related to the stability analysis of unsaturated slope with the irregular geometry. Further improvement, however, should be made to apply the present analysis procedure to general slopes since it deals with a simple one.

• Nuclear Engineering and Technology
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• v.16 no.1
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• pp.1-10
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• 1984

General time-volume averaged conservation equations and jump conditions for two-phase flows are derived here. The time-averaged equations for a single phase region in two-phase flow are obtained from local instant balance equations by a technique often used for single phase turbulent flow equations. The results obtained by integrating the time averaged equations over a flow volume are spatially averaged twice; first, they are averaged over a single phase region of the k-th phase and then averaged over the total volume of the k-th phase, in a flow volume. The mass, momentum, and energy conservation equations are obtained from the general time-volume averaged equations. The advantages of the present model are explained by comparing it with Ishii's model (1) and Banerjee's model (2). Finally, the assumptions and approximate terms of the equations of the THERMIT-6S are clarified.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.2
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• pp.69-78
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• 2009

Cavitating flow simulation is of practical importance for many hydraulic engineering systems, such as pump, turbine, nozzle, injector, etc. In the present work, a solver for cavitating flow has been developed and applied to simulate the flows past axisymmetric cylinders. Governing equations are the two-phase Navier-Stokes equations, comprised of continuity equation of liquid and vapor phase. The momentum equation is in the mixture phase. The solver employed an implicit, dual time, preconditioned algorithm in curvilinear coordinates. Computations were carried out for three axisymmetric cylinders: hemispherical, ogive, and caliber-0 forebody shape. Then, the present calculations were compared with experiments and other numerical results to validate the present solver. Also, the code has shown its capability to accurately simulate the re-entrant jet phenomena and ventilated cavitation. Hence, it has been found that the present numerical code has successfully accounted for cavitating flows past axisymmetric cylinders.