• 한국항해학회지
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• 제14권1호
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• pp.39-55
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• 1990

Numerical model simulations are conducted for the evaluation of the water level variation in and out of the harbor due to the development and improvement of a harbor. The method used for the numerical analysis is the hybrid element method which includes energy dissipation due to imperfect reflection at the shore boundary and friction at the bottom. The model also includes the radiation condition on the open boundary by the analytic formulation and is applied to a real harbor, Guryongpo Harbor at the east coast of Korea. The result of experiment within the selected wave frequency band shows that the amplification factor out of the harbor is more than 2.0 at 32 sec period and strong responses near 20 sec, 25 sec, 54 sec periods in the harbor. Moreover, simulation results indicate that other longer wave periods affect to the variation of water level and horizontal water particle velocity exist. Thus, it seems to be necessary to modify the planform and the design of the harbor structures for the coming development.

• 한국전자파학회논문지
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• 제7권5호
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• pp.440-446
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• 1996

다중 ridge 원형 도파관을 퓨리에 급수 전개와 모드 정합법을 이용하여 정확하게 해석하였다. 경계 조건을 이용하여 두 급수식을 전개하고 이를 풀어 모드를 정확하게 구하였다. 다중 ridge 원형 도파관의 ridge의 수, 길이, 폭에 따른 차단 파수(cutoff wavenumber)의 변화를 살펴보았다. 구한 해는 정확하고 수렴성이 뛰어나며 dominant mode에 대해서는 간단한 근사식을 제시하였다.

• 디지털융복합연구
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• 제11권10호
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• pp.47-57
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• 2013

빅데이터 분석은 데이터의 양, 처리속도, 다양성 측면에서 데이터 마이닝과 달리 문제해결과 의사결정을 위해서는 새로운 도구를 필요로 한다. 많은 글로벌 IT기업들은 사용하기 쉽고 기능성이 우수한 모델링 능력을 가진 다양한 빅데이터 제품을 출시하고 있다. 빅데이터 패키지는 분석도구, 인프라, 플랫폼 형태로 하드웨어와 소프트웨어를 포함한 솔루션이다. 빅데이터의 수집, 저장, 분석, 시각화가 가능한 제품이다. 빅데이터 패키지는 업체별로 제품 종류가 많고 복잡한 기능을 가질 뿐만 아니라 선정에 있어서 전문 지식을 필요로 하며 일반적인 소프트웨어 패키지보다 그 중요성이 높기 때문에 의사결정 방법의 개발이 요구된다. 본 연구는 빅데이터 패키지 도입을 위한 의사결정지원방법을 제안하는 것이 목표이다. 문헌적 고찰을 통하여 빅데이터 패키지의 특징과 기능을 비교하고, 선정기준을 제안한다. 패키지 도입 타당성을 평가하기 위하여 비용과 혜택 각각을 목표노드로 하는 AHP 모델 및 선정기준을 목표노드로 하는 AHP 모델을 제안하고 이들을 결합하여 최적의 패키지를 선정하는 과정을 보인다.

• The Journal of the Acoustical Society of Korea
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• 제25권3E호
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• pp.131-136
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• 2006

The PML developed for the radio wave propagation is a powerful numerical domain truncation technique. We perform an analytic study on the reflection from the PML inserted in the ocean bottom. In the ocean bottom, we show the PML to have the improved performance but simultaneously the degeneration below the critical angle of the fast ocean bottom. The degeneration of the PML can be simply relaxed by stretching the thickness of the PML or putting the attenuation coefficient to the ocean bottom. As a better solution, we propose the improved truncation technique based on the PML and the non-local boundary condition. Finally, we apply the PML to the acoustic wave propagation using split-step Pade PE solver. For the problems of the ocean waveguide, the numerical efficiency of the PML is examined and the usefulness of the PML is confirmed.

• 터널과지하공간
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• 제4권1호
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• pp.1-16
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• 1994

The study on the flow characteristics and analysis of groundwater in discontinuous rock mass is very important, since the water inflow into the underground opening during excavation induces serious stability and environmental problems. To investigate the flow through single rock joint, the effect of various aperture distribution on the groundwater flow has been analyzed. Observed through the analysis is the "channel flow", the phenomenon that the flow is dominant along the path of large aperture for given joint. The equivalent hydraulic conductivity is estimated and verified through the application of the joint network analysis for 100 joint maps generated statistically. Both the analytic aproach based on isotropic continuum premise and the joint network analysis are tested and compared analyzing the gorundwater inflow for underground openings of different sizes and varying joint density. The joint network analysis is considered better to reflect the geometric properties of joint distribution in analyzing the groundwater flow.ater flow.

• 한국유체기계학회 논문집
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• 제10권4호
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• pp.55-60
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• 2007

This paper describes an evaluation method of pressure drop in a circular pipe of waste collection piping system. Accurate pressure drop in a piping system is very important to determine the capacity of turbo blower, which is one of the main elements in the system. Three-dimensional Navier-Stokes analysis is introduced to analyze the pressure drop in the piping system. Organic waste is selected and modeled using the result of site survey performed in an apartment area. Evaluation method of pressure drop used In the present numerical simulation is performed in the shortened pipe line prior to the calculation of the real system. Throughout the numerical simulation, pressure drop in a waste pipe is obtained and compared to the value determined by analytical method. The pressure drop obtained by numerical simulation has a good agreement with that of the analytic method. It is noted that present evaluation method is effective to determine a pressure drop in the piping system. Detailed flow characteristics inside the pipe line are also analyzed and discussed.

• KIEAE Journal
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• 제16권6호
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• pp.159-166
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• 2016

Purpose: The architectural structures in the engineering field include more than one material, and the heat transfer through these multiple materials becomes complicated. More or less, the analytic solutions obtained by the hand calculation can provide the limited information of heat transfer phenomena. However, the engineers have generally been forced to obtain reliable results than those of the hand calculation. The numerical calculation such as a finite volume methods with the unstructured grid system is only the suitable means of the analysis for the complex and arbitrary domains that consists of multiple materials. In this study, a new numerical code is developed to provide temperature distributions in the multiple material domains, and the results of this code are compared with the validation cases in ISO10211. Method: Finite volume methods with an unstructured grid is employed. In terms of numerical methods, the heat transfer conduction coefficient is not defined on the surface of the cell between different material cells. The heat transfer coefficient is properly defined to accurately mimic the heat transfer through the surface. The boundary conditions of heat flux considering radiation or heat convection are also developed. Result: The comparison between numerical results and ISO 10211 cases. We are confirmed that the numerical method provides the proper temperature distributions, and the heat transfer equation and its boundary conditions are developed properly.

• Steel and Composite Structures
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• 제47권2호
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• pp.217-238
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• 2023

In this study, a parametric study was performed considering material properties of concrete, material properties of steel, the number of longitudinal reinforcement (reinforcement ratio), CFRP ply orientations, a number of layers as variables by using ABAQUS. Firstly, the parameters used in the Hashin failure criteria were verified using four coupon tests of CFRP. Secondly, the numerical models of the beams strengthened by CFRP were verified using five experimental data. Finally, eighty numerical models and eighty analytic calculations were developed to investigate the effects of the aforementioned variables. The results revealed that in the case of using fibrous polymer to prevent shear failure, the variables related to reinforced concrete significantly affected the behavior of specimens, whereas the variables related to CFRP composite have a slight effect on the behavior of the specimens. As a result of numerical analysis, while the increase in the longitudinal tensile and compression reinforcement, load bearing capacity increases between 23.6%-70.7% and 5.6%-12.2%, respectively. Increase in compressive strength (29 MPa to 35 MPa) leads to a slight increase in the load-carrying capacity of the specimens between 4.6% and 7.2%. However, the decrease in the compressive strength (29 MPa to 20 MPa) significantly affected (between 6.4% and 8.1% decrease observed) the behavior of the specimens. As the yield strength increases or decreases, the capacity of specimens increase approximately 27.1% or decrease 12.1%. The effects of CFRP ply orientation results have been obtained as a negligible well approximately 3.7% difference. An increasing number of CFRP layers leads to almost no effect (approximately 2.8%) on the behavior of the specimen. Finally, according to the numerical analysis, the ductility values obtained between 4.0 and 6.9 indicate that the beams have sufficient ductility capacity.

• 대한전기학회논문지
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• 제38권9호
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• pp.733-739
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• 1989

유한요소법과 반복법을 적용하여 Grad-Shafranov식을 풀어 축대칭 토로이달 플라즈마의 고정경계 MHD평형을 해석하였다. 토로이달 전류항은 플라즈마 압력과 토로이달 자장함수로 표현하였고 해의 타당성 검증을 위하여 수치해석 결과를 해석적 평형과 비교하였다. 서울대의 SUNT-79장치에 적용하여 압력과 자장함수 변화에 따른 자기면 형상과 전류분포를 고찰하였고 안전인자와 ${\beta}$값도 함께 산출하였다.

• 한국강구조학회 논문집
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• 제10권3호통권36호
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• pp.509-523
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• 1998

본 연구에서는 이축 대칭단면을 갖는 박벽 원형아치의 안정성해석을 수행할 수 있는 유한요소 이론 및 엄밀해를 제시하기 위하여, 가상일의 원리를 이용한 3차원 연속체의 운동방정식을 제시한다. 박벽단면의 구속된 비틂(restrained warping)효과를 고려하는 박벽 곡선보의 변위장을 도입하고 이를 연속체의 운동방정식에 대입하여 단면에 대해 적분함으로써 박벽 곡선보의 운동방정식을 유도한다. 단순지지되고 이축 대칭단면을 갖는 박벽 곡선보의 면외좌굴에 대한 엄밀해를 제시하고 박벽 곡선보를 유한요소로 분할하여 요소의 변위장을 요소 변위벡터에 관한 3차의 Hermitian 다항식으로 나타내어 운동방정식에 대입함으로써 탄성 강도행렬과 기하학적 강도행렬을 유도한다. 또한 본 연구에서 얻어진 엄밀해와 박벽 곡선보요소를 이용한 유한요소해석결과를 다른 연구자들의 결과 및 직선 박벽보 요소를 이용한 해석결과와 비교 검토를 함으로써 분 연구의 타당성을 입증한다.