• Journal of Korean Society of Coastal and Ocean Engineers
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• v.3 no.3
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• pp.117-125
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• 1991

Two methods are presented to calculate the natural frequency of an elastic thin circular cylindrical shell vibrating in fluid. Both of them give the natural frequency in analytical expression One is in a simple form and suitable for higher deformation mode of the shell. Another seems to be exact and be used to a case of the shell partially immersed in fluid. When the shell is fully immersed in fluid results show： fur the lower deformation mode of the shell, the surrounding fluid has remarkable effect upon the natural frequency； for the higher mode, the fluid effect becomes small. When the shell is partially immersed in fluid. it does not occur always that the greatest effect take place at the lowest deformation mode.

• Journal of Korea Water Resources Association
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• v.31 no.6
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• pp.845-854
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• 1998

Following the approach of Ebersole (1985), water wave transformation is predicted using the eikonal equation and transport equation for wave energy which are reduced from the extended mild-slope equation of Massel (1993), and also the irrotationality of wave number vectors. The higher-order bottom effect terms, i.e., squared bottom slope and bottom curvature, are neglected in the study of Ebersole but are included in the present study. It was expected that, if these terms are included in this study, the approach would give more accurate solution in the case of rapidly varying topography. But, the expectation was frustrated. It is probably because, in the case of rapidly varying topography, the diffraction effect which is included in the eikonal equation does not work well and thus the solution is deteriorated.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.17 no.3
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• pp.257-264
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• 1999

The lens distortions were corrected directly using the high-order polynomial which was offered in camera calibration data for the forward transformation and the root of Newton-Raphson's $2\times{2}$ nonlinear system for the backward transformation. The 0.04~0.08 pixels increase in accuracy was indicated through the use of direct correction of lens distortions instead of least square methods of commercial software. The least square adjustment method of high-order polynomial requires many control points which has a same weight. But this suggested method which is unnecessary to determine control points was developed and applied. The algorithm showed improved efficacy.

• Korean Journal of Cognitive Science
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• v.30 no.4
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• pp.175-197
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• 2019

Writing is an activity known to enhance higher level thinking. It allows the writer to utilize, apply, and actively expand the acquired knowledge. One way to increase writing activity in classroom setting is to use peer assessment. In this study, we sought to increase the accuracy of peer assessment by having students discuss about the scoring rubric or by referring to an expert's assessment. One hundred and fifty college students participated in the experiment. In the group that referred to the expert's assessment, the accuracy of peer assessment increased when the same piece of writing was evaluated; however, no such increase was observed when another piece of writing was assessed. On the other hand, in the group that discussed about the scoring rubric, the accuracy of peer assessment remained the same when the same piece of writing was evaluated, but increased when another piece of writing was assessed. Also, in the discussion group, the accuracy increased in proportion to the number of comments during the discussion. The results suggest that active and voluntary participation of students increase the accuracy of peer assessment.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.5
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• pp.9-14
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• 2002

A higher order zig-zag plate theory is developed to accurately predict fully coupled mechanical, thermal, and electric behaviors. Both the in-plane displacement and temperature fields through the thickness are constructed by superimposing linear zig-zag field to the smooth globally cubic varying field. Smooth parabolic distribution through the thickness is assumed in the transverse deflection in order to consider transverse normal deformation. Linear zig-zag form is adopted in the electric field. The layer-dependent degrees of freedom of displacement and temperature fields are expressed in tern-is of reference primary degrees of freedom by applying interface continuity conditions as well as bounding surface conditions of transverse shear stresses and transverse heat flux. The numerical examples of coupled and uncoupled analysis demonstrate the accuracy and efficiency of the present theory. The present theory is suitable for the predictions of fully coupled behaviors of thick smart composite plate under mechanical, thermal, and electric loadings combined.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.3
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• pp.341-349
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• 1997

The characteristics of defect correction method are discussed in a sample heat conduction problem showing the numerical solution of the error correction equation can predict the error of the numerical solution of the original governing equation. A way of using defect correction method combined with the existing algorithm for the incompressible fluid flow, is proposed and subsequently tested for the driven square cavity problem. The error correction equations for the continuity equation and the momentum equations are considered to estimate the errors of the numerical solutions of the original governing equations. With this new approach, better velocity and pressure fields can be obtained by correcting the original numerical solutions using the estimated errors. These calculated errors also can be used to estimate the orders of magnitude of the errors of the original numerical solutions.

• Journal of computational fluids engineering
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• v.13 no.3
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• pp.69-78
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• 2008

The high-order numerical method based on the adaptive mesh refinement(AMR) on the quadrilateral unstructured grids has been developed in this paper. This adaptive-grid method, originally developed with MUSCL-TVD scheme, is now extended to the WENO (weighted essentially no-oscillatory) scheme with the Runge-Kutta time integration of fifth order in spatial and temporal accuracy. The multidimensional interpolation was studied in the preliminary research, which allows us to maintain the same order of accuracy for the computation of numerical flux between two adjacent cells of different levels. Some standard benchmark tests are done to validate this method for checking the overall capacity and efficiency of the present adaptive-grid technique.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.2
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• pp.33-47
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• 2001

성능에 기초한 내진설계에서는 구조물이 보유하고 있는 능력을 효과적으로 파악하기 위해서 비선형 정적 해석이 적용되고 있다. 그러나 비선형 정적해석은 고차모드에 대한 효과를 고려하지 못함으로써 고층구조물이나 비정형 구조물과 같은 경우에는 정확한 비선형 지진응답의 산정과 내진성능을 평가하는데 문제점을 가지고 있다. 본 연구에서는 건축구조물의 선형 및 비선형 지진응답 평가를 위하여 응답 스펙트럼해석을 통하여 얻어지는 층전단력으로부터 층하중을 산정하는 유사동적해석법이 적용되었다. 제안된 방법을 비선형 정적 해석에 적용하여 구조물의 비선형 자동응답을 비선형 시간이력해석의 결과와 비교하였다. 기존의 층분포하중에 의한 비선형 지진응답과 비교하였으며, 제안된 방법에 의한 지진 응답이 구조물의 비선형 거동특성을 가장 정확하게 표현하였다. 그러므로 본 연구에서 제안된 방법을 사용하여 비선형 정적 해석을 수행한다면 비교적 명확한 건축물의 비선형 거동특성과 내진성능을 평가할 수 있을 것으로 판단된다.

• 한국전산유체공학회:학술대회논문집
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• 2007.04a
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• pp.30-40
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• 2007

The implicit discontinuous Galerkin method for the two-dimensional Euler equations was developed on unstructured triangular meshes, which can achieve higher-order accuracy by wing hierachical basis functions based on Legendre polynomials. Numerical tests were conducted to estimate the convergence order of numerical solutions to the Ringleb flow and the supersonic vortex flow for which analytic solutions are available. And, the flows around a circle and a NACA0012 airfoil was also numerically simulated. Numerical results show that the implicit discontinuous Galerkin methods with higher-order representation of curved solid boundaries can be an efficient higher-order method to obtain very accurate numerical solutions on unstructured meshes.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.213-217
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• 2010

댐붕괴파 (dam-break flow)나 지진해일에 의해 발생하는 undular bore와 충격파 (shock) 현상을 동수압 및 분산효과를 고려하여 수치모의를 수행하였다. 완전비선형 Boussinesq-type equations 모형을 이용하여, 동수압 및 분산 효과를 고려하였다. 방정식은 4차 정확도의 유한체적법을 이용하여 해석하였고, 시간적으로도 4차정확도의 기법을 이용하여 고차미분항에 대한 수치분산을 억제하였다. 다양한 경우의 1차원과 2차원 공간에서의 수치모의를 수행하고 검증을 수행하였다. 그 결과, 완전비선형 Boussinesq-type equations 모형은 천수방정식 (shallow water equations) 기반의 모형에서 재현이 불가능한 undular bore 등을 재현 하는 등, 전반적으로 천수방정식 기반의 모형 보다 물리적으로도 타당하고 정량적으로도 실험결과와 잘 일치하는 경향을 보였다. 즉, 댐붕괴파나 지진해일 등에 의한 범람 모의에 있어 동수압과 분산 효과의 중요성이 공학적으로도 매우 중요한 고려사항 임이 나타났다.