• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 1993.07a
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• pp.146-151
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• 1993

쇄파대에서 발생되는 연안류의 분포는 완만한 곡선분포를 보이는데 단순파인 경우이의 해석은 확산계수의 도입으로만 가능하다는 점은 널리 알려진 사실이다. Harris(1967)는 현장관측과 수조실험으로 이 분야 초기연구로서 쇄파대 확산의 변이를 무시하고 평균확산계수치만을 고려하였다. 연안류해석의 확고한 이론적 기초를 마련한 Longuet-Higgins(1970)는 그의 이론식 도출고정에서 확산계수 도입의 필요성을 인식하였으며, 특성길이로서 연안선으로부터의 거리를 택하고 특성속도로서 파속을 택하였으며 쇄파대내에서 파속은 군속도와 같다고 가정하였다. (중략)

• Journal of the Society of Naval Architects of Korea
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• v.33 no.2
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• pp.127-138
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• 1996

The strip method, unified theory and 3-D panel method are commonly used methods for the seakeeping analysis of high-speed vessels. The strip method which is basically 2-dimensional method is known to give incorrect hydrodynamic coefficients and motion responses for the cases of high speed and low frequency region. And the unified theory which uses two dimensional approach in inner domain and slender body theory in outer domain is very complicate in computational modelling. Though the 3-D panel method requires comparatively long computation time, it is believed that the method gives good results without any limitation in ship speed and range of frequency for computation. In the 3-D panel method the source singularity representing translating and pulsating Green function is used and Hoff's method is adopted for the numerical calculation of the Green function. The computation time can be reduced by using the symmetry relationship with respect to longitudinal axis. In this paper the strip method and the 3-D panel method are compared for the seakeeping analysis of a high-speed catamaran. The Compared items are the hydrodynamic coefficients, wave exciting forces, frequency response functions and short-term responses in irregular waves.

• 한국공간정보시스템학회:학술대회논문집
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• 2000.06a
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• pp.181-186
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• 2000

국가지리정보체계사업을 시작으로 여러 응용분야에서 지리정보시스템을 구축하고 있으며, 특히 지자체에서는 도시정보화 차원에서 UIS(Urban Information System;도시정보시스템)를 구축하고 있다. 지자체의 업무들은 지자체의 상황에 따라 조금씩 차이를 보이지만 업무 단위로 따져 볼 때 공통적으로 수행되는 업무들이 많으며, 지리정보 관련 업무 또한 예외가 아니다. 지금까지 각 지자체의 도시정보시스템은 공통업무에 대하여 중복개발이 불가피 하였으며, 재사용성을 기대하기 어려웠다. 이런 비효율을 극복하는 방안으로 컴포넌트 기술이 대두되었으며, 컴포넌트 기술을 이용하여 업무변화에 유연하고 재활용을 극대화할 수 있는 업무 컴포넌트 개발이 필요한 시점이다. 본 논문은 지자체의 지리정보 관련 업무의 하나인 하수도 업무 중 하수배출용량 산정을 위한 하수도 관망해석 컴포넌트 설계를 제시하였다. 하수도 관망해석 컴포넌트는 하수배출용량을 산정하고, 하수 배출용량을 토대로 통수능이 부족한 하수관거를 추출하며, 통수능 부족 관거에 대하여 적정한 교체 관경 결정을 지원할 수 있도록 설계하였다 컴포넌트 설계과정은 표준업무를 지원할 수 있도록 업무분석을 수행하였으며, 이의 결과물로 하수도 관망해석 알고리즘을 도출하였으며, 알고리즘을 기반으로 하수도 관망해석 업무를 수행하는 하수도 관망해석 컴포넌트를 설계하고 설계 내용을 UML(Unified Modeling Language)로써 명세화 하였다. 현재 설계에 따라 하수도 관망해석 컴포넌트가 개발되고 있으며, 개발된 컴포넌트를 이용한 하수도 관망해석 시스템을 구축할 예정이다. 추후에는 하수도 관망해석 컴포넌트와 하수도 업무 컴포넌트와의 통합부분에 대한 연구가 진행되어야 할 것이다.7.0로 하고 표준(標準) EDTA 용액(溶液)을 소량(少量)넣고 8N-KOH로 pH $12{\sim}13$으로 하고 N-N 희석분말(稀釋粉末)을 지시약(指示藥) 으로써 표준(標準) EDTA 용액(溶液)으로 적정(滴定)하여 Ca 치(値)를 얻었다. Ca와 Mg의 합계결정치(合計決定値)와 Ca 적정치(滴定値) 차(差)로 Mg 치(値)를 얻었다. 음(陰) ion 구분(區分)으로부터 상법(常法)에 의하여 $MgNH_4PO_4$의 침전(沈澱)을 만들어서 HCl에 녹키고 일정량(一定量)의 표준(標準) EDTA 용액(溶液)을 넣어 pH 7.0로 한다음 완충액(緩衝液)으로 pH 10으로 하고 BT 지시약(指示藥)을 써서 표준(標準) Mg $SO_4$용액(溶液)으로 적정(滴定)하여 P 치(値)를 얻었다. 본법(本法)으로 Na-phytate를 분석(分析)한 결과(結果) Na-phytate의 분자식(分子式)을 $C_6H_6O_{24}P_6Mg_4CaNa_2{\cdot}5H_2O$라고 하였을 때의 이론치(理論値)에 비(比)하여 P가 98.9% Cark 97.1%, Mg가 99.1%이고 통계처리(統計處理)한 결과분석치(結果分析値)와 이론치(理論値)는 잘 일치(一致)된다. 그러나 종래법(從來法)에 의(依)한 분석치(分析値)는 이론치(理論値)에 비(比)하여 P가 92.40%, Cark 86.80%, Mg가 93.80%로서 이론치(理論値)와 일치(一致)하지 않는다. 3) Na-phytate를 전분(澱粉)과 일정(一定)한 비(比)로 혼합(混合)하고 본법(本法)으로 P,Ca 및 Mc를 정량(定量)한 결과(結果) 이들의 회수율(回收率)은 거의 100%이었다. 4) 본분석법

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.7
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• pp.72-80
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• 2018

With the ever increasing advances in computers and their computing power, computational fluid dynamics(CFD) has become an essential engineering tool in the design and analysis of engineering applications. Accordingly, many universities have developed and implemented a course on CFD for undergraduate students. On the other hand, many professors have used industrial examples supplied by computational analysis software companies as CFD examples. This makes many students think of CFD as difficult and confusing. This paper presents a simple CFD example used in the department of mechanical design engineering of Kangwon National University and shows its effectiveness. Most students answered that a simple CFD example is more comprehensive than an industrial example. Therefore, it is necessary to develop simple computational analysis problems in the engineering education field.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.2212-2218
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• 2015

In order to find out the load bearing behavior of sand and clay which sustain three types of shallow footing, finite element analyses were performed. Failure zone of sand which sustain strip footing was affected by relative density of sand whereas, failure zone of clay was not affected by soil strength and it was similar to the failure zone which is considered in theory. Considering the shape of load-settlement curves obtained by numerical analyses, punching shear failure can be seen in loose sand and ultimate bearing load can not be seen in dense sand whereas, yielding point can be seen in clay. Ultimate bearing loads for sand predicted by theory were greater than those obtained by numerical analyses and ultimate bearing loads for clay predicted by theory were similar to those of numerical analyses. Ultimate bearing loads determined by 1 inch settlement criteria were slightly less than those of numerical analyses.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.2
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• pp.1-10
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• 1992

In this study, the 'Comb-structure' model which has been developed from truss analogy is modified in order to be applied to the shear analysis of partially prestressed concrete members. The proposed 'Comb-structure' model is modified so that the position, the slope of concrete compressive chord and the slope of concrete diagonal strut may change according to the magnitude of loads and prestress. For the proposed mechanical model, non-linear beam and truss elements are used. By modifying the 'Compression-Field' theory, the equation to determine the slope angle of concrete diagonal strut can be induced. The anaysis results by the proposed 'Comb-structure' model are compared with the experimental results and validity of model is examined. It shows that the the result of 'Comb-structure' analysis lies between that of the modified M$\ddot{o}$rsch theory and classical M$\ddot{o}$rsch theory, and close to the measured value after cracking. The deflection of the beam and the stress of stirrup show good agreement, so it can be concluded that the proposed 'Comb-structure' analysis model explains the shear behavior of partially prestressed concrte beams after crack initiation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.11
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• pp.983-989
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• 2007

The bird strike simulation is a problem characterized by a high degree of uncertainty. It deals with nonlinear dynamics, complicated models of bird materials and geometry, as well as a plenty of possible boundary and initial conditions. In this complex field, uncertainty management plays an important role. This paper aims to assess the effect of input uncertainty of bird strike analysis on the impact behavior of the leading edge of the WIG(Wing in Ground Effect) craft obtained with finite element analysis using LS-DYNA 3D. The uncertainties of the bird strike simulation arise due to imprecision or lack of information, due to variability or scatter, or as a consequence of model simplification. These uncertain parameters are represented by fuzzy numbers with their membership functions quantifying an initial guess for the actual value of the model parameter. Using the transformation method as a special implementation of fuzzy arithmetic, the model can be analyzed with the intention of determining the influence of each uncertain parameter on the overall bird strike behavior.

• Bulletin of the Society of Naval Architects of Korea
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• v.27 no.4
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• pp.51-57
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• 1990

There exist residual stresses and deformations in welded structures because of nonuniform temperature distribution. The thermal elasto-plastic analysis is necessary to describe the behavor of the structure during welding. In this paper, we calculated the residual stresses and deformations of the welded beam using the I-dimensional layered beam theory. In the previous 1-dimensional analyses, there were restrictions that the equilibrium conditions which were effective only on beams with infinite length were used, and the boundary conditions could not be considered adequately. But, the layered beam theory based on the incremental finite element method, can overcome these restrictions. On the other hand, in the 2-dimensional analysis, the computing time is large because of many degrees of freedom, and there was inaccuracy in the calculation of welding deformations. However, the layered beam theory can take into account the variation of properties along the depth, and can reduce the degrees of freedom considerably in comparision with the 2-dimensional analysis, and shows good agreement with the experiments.

• Computational Structural Engineering
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• v.10 no.4
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• pp.217-228
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• 1997

The high precision analysis by the p-version of the finite element method are fairly well established as highly efficient method for linear elastic problems, especially in the presence of stress singularity. It has been noted that the merits of the p-version are accuracy, modeling simplicity, robustness, and savings in user's and CPU time. However, little has been done to exploit their benefits in elasto-plastic analysis. In this paper, the p-version finite element model is proposed for the materially nonlinear analysis that is based on the incremental theory of plasticity using the constitutive equation for work-hardening materials, and the associated flow rule. To obtain the solution of nonlinear equation, the Newton-Raphson method and initial stiffness method, etc are used. Several numerical examples are tested with the help of the square plates with cutout, the thick-walled cylinder under internal pressure, and the circular plate with uniformly distributed load. Those results are compared with the theoretical solutions and the numerical solutions of ADINA

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.4
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• pp.297-303
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• 2014

Using the bond-based peridynamics and the parallel computation with binary decomposition, an adjoint shape design sensitivity analysis(DSA) method is developed for the dynamic crack propagation problems. The peridynamics includes the successive branching of cracks and employs the explicit scheme of time integration. The adjoint variable method is generally not suitable for path-dependent problems but employed since the path of response analysis is readily available. The accuracy of analytical design sensitivity is verified by comparing it with the finite difference one. The finite difference method is susceptible to the amount of design perturbations and could result in inaccurate design sensitivity for highly nonlinear peridynamics problems with respect to the design. It turns out that $C^1$-continuous volume fraction is necessary for the accurate evaluation of shape design sensitivity in peridynamic discretization.