• 한국해양학회지
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• 제28권2호
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• pp.86-100
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• 1993

ADI(Alternating Direction Implicit) 유한차분법을 사용하여 3차원 경합 해수유 동 모델 BACHOM-3을 개발하였다. 본 모델을 장방형 내만에서 하나의 결점을 갖는 정상 파에 적용하여 해석해와 비교하였으며, 그 결과 해석해와 잘 일치하였다. 모델의 현지 적용성과 수영만의 해수유동을 조사하기 위해 모델을 수영만에 적용하여 대조기 평수 시 현지관측결과와 비교하였으며, 그 결과 현지 관측결과와 비교적 잘 일치하였다. 만 중앙부의 제 1층(수심 0∼2 m)과 제 2층(수심 2∼5 m)에서 조석잔차류는 시계방향으로 회전하는 순환류가 나타났으며, 또한 낙조류가 창조류보다 강하게 나타났다. 계산된 유속분포에 의하면, 표층과 저층 사이에 유속의 위상차가 나타나며, 표층으로 갈수록 위상의 지연이 나타났다. 그리고, 본 모델을 홍수시와 바람 효과를 고려한 흐름 장의 계산에도 적용하였다. 해양에서 육지로 바람이 불 때 표층에서는 풍향에 대응하는 유 속분포를 나타냈으나, 저층의 육지경계부근에서는 풍향과 반대방향의 흐름이 나타났 다.

• 대한기계학회논문집B
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• 제25권3호
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• pp.305-314
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• 2001

A modified model is proposed for calculation of transitional boundary layer flows. In order to develop the eddy viscosity model for the problem, the flow is divided into three regions; namely, pre-transition region, transition region and fully turbulent region. The pre-transition eddy-viscosity is formulated by extending the mixing length concept. In the transition region, the eddy-viscosity model employs two length scales, i.e., pre-transition length scale and turbulent length scale pertaining to the regions upstream and the downstream, respectively, and a universal model of stream-wise intermittency variation is used as a function bridging the pre-transition region and the fully turbulent region. The proposed model is applied to calculate three benchmark cases of the transitional boundary layer flows with different free-stream turbulent intensity (1%∼6%) under zero-pressure gradient. It was found that the profiles of mean velocity and turbulent intensity, local maximum of velocity fluctuations, their locations as well as the stream-wise variation of integral properties such as skin friction, shape factor and maximum velocity fluctuations are very satisfactorily predicted throughout the flow regions.

• 한국도로학회논문집
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• 제10권3호
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• pp.209-220
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• 2008

본 논문은 지반위에 놓인 콘크리트 슬래브가 환경하중에 의해 컬링 할 때의 거동을 해석할 경우에 하부층의 모델링 방법에 따른 해석 결과의 차이를 분석한 내용을 기술하였다. 지반위에 놓인 슬래브 시스템을 전체 3차원 모델, 3차원 슬래브와 하부층을 스프링으로 구성한 모델, 그리고 2차윈 슬래브와 하부층을 스프링으로 구성한 모델 등으로 개발하여 해석을 수행하였다. 먼저 하부층이 단일 층으로 구성되어 있을 경우에 하부층 모델링 방법에 따른 컬링 거동의 차이를 분석하였다. 그리고 하부층이 서로 다른 재료와 두께로 구성되어 있는 복층일 경우에 하부층 모델링에 따른 컬링 거동의 특성을 비교 분석하였다. 연구결과 하부층을 무인장 스프링으로 모델링 하면 하부층이 단층일 경우에는 일반적으로는 상당히 정확한 해석결과를 얻을 수 있으나, 하부층이 복층일 경우에는 상위하부층의 탄성계수가 클 때, 하위하부층의 탄성계수가 작을 때, 그리고 상위하부층과 하위하부층의 두께가 두꺼울 때는 컬링 시에 슬래브의 수직변위 차이를 과대평가하게 되며 최대응력은 과소평가하게 된다.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.204-209
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• 2000

It is the first step to establish the exact vibration model of the structure when constructing the smart structure with desired vibration scheme. In this paper, vibration model of beam with piezoelectric element boned on the surface is presented by considering the thickness effect of the bond layer. In contrast to the previous papers which neglect the effect of bond layer, the presented vibration model considers the effect of bond layer assuming the prefect bond condition. The perfect bond condition is tested by comparing the controllability of beams with three types of bond layer. An optimal vibration control of the beam can be performed when there exists perfect-bond condition between the piezoelectric element and the main structure.

• 한국도로학회논문집
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• 제14권5호
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• pp.1-9
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• 2012

PURPOSES: A viscoelastic axisymmetric finite element analysis code has been developed for stress analysis of asphalt pavement structures. METHODS: Generalized Maxwell Model (GMM) and 4-node isoparametric element were employed for finite element formulation. The code was developed using $C^{+}^{+}$ computer program language and named as KICTPAVE. For the verification of the developed code, a structural model of a pavement system was constructed. The structural model was composed of three layers: asphalt layer, crushed stone layer, and soil subgrade. Two types of analysis were considered for the verification: (1)elastic static analysis, (2)viscoelastic time-dependent analysis. For the elastic static analysis, linear elastic material model was assigned to all the layers, and a static load was applied to the structural model. For the viscoelastic time-dependent analysis, GMM and linear elastic material model were assigned to the asphalt layer and all the other layers respectively, and a cyclic loading condition was applied to the structural model. RESULTS: The stresses and deformations from KICTPAVE were compared with those from ABAQUS. The analysis results obtained from the two codes showed good agreement in time-dependent response of the element under the loading area as well as the surface deformation of asphalt layer, and horizontal and vertical stresses along the axisymmetric axis. CONCLUSIONS: The validity of KICTPAVE was confirmed by showing the agreement of the analysis results from the two codes.

• 한국컴퓨터정보학회논문지
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• 제11권2호
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• pp.7-13
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• 2006

시멘틱 웹의 대두로 인해 웹 상에서 데이터를 접근 할 수 있는 방법도 다양화 되었다. 이에 현재 진행되고 있는 웹 온톨로지 뿐만 아니라 기존에 구축된 지식베이스 시스템에 접근하여 데이터를 핸들링 할 수 있는 모델이 필요하다. 웹 온톨로지를 표현하기 위한 언어로 RDF(Resource Description Framework), DAML-OIL, OWL(Web Ontology Language)등이 사용되고 있다. 본 논문은 웹 온톨로지와 기존의 구축된 지식 베이스의 데이터를 접근, 표현 및 처리할 수 있는 온톨로지 객체 모델의 생성과 그 방법에 관한 것이다. 웹 온톨로지에 대한 접근 방법으로 각각의 언어에 맞는 파서(Parser)를 이용하여 메모리 상에 모델을 생성하여 접근하게 되어 있는 기존의 방법과는 다르게 본 논문에서는 웹 온톨로지를 표현하기 위한 모델을 계층별로 구별하여 프레임 기반의 상위 온톨로지(frame-based ontology layer), 다른 도메인에서도 사용이 가능한 공통된 어휘(vocabulary)를 표현한 핵심 온톨로지(generic ontology layer)와 각각의 온톨로지 언어에 의존적인 어휘를 표현한 기능 온톨로지(functional ontology layer)로 구성한다. 이는 표현의 중복을 없애고 재 사용성을 높이기 위한 모델을 제공함으로써, 외부 어플리케이션(온톨로지 추론, 온톨로지 병합, 온톨로지 저작 도구 등)에서의 온톨로지에 대한 쉬운 지식 표현과 접근 및 핸들링을 제공할 수 있다.

• 한국재료학회지
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• 제16권2호
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• pp.85-91
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• 2006

The fraction of $\varepsilon\;and\;\gamma$'-iron nitride in compound layer is predicted by x-ray diffraction using direct comparison method. The validity of formulation models was checked by comparing calculated results with metallographic analysis of iron nitride compound layer grown on steel S45C by gas nitriding. The fraction of $\varepsilon$ calculated by the three phase model, porous-$Fe_3N$/ dense-$Fe_3N$/ mixed layer with $Fe_3N\;and\;Fe_4N$, is 80 percent of that analyzed by etching technique. The $\varepsilon$ fraction predicted by mixed layer model is 122 percent of that measured by microscope.

• Structural Engineering and Mechanics
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• 제65권4호
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• pp.369-380
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• 2018

In this paper, a multi-layered finite element model for laminated glass plates is introduced. A layer-wise theory is applied to the analysis of laminated glass due to the combination of stiff and soft layers; the independent layers are connected via Lagrange multipliers. The von $K{\acute{a}}rm{\acute{a}}n$ large deflection plate theory and the constant Poisson ratio for constitutive equations are assumed to capture the possible effects of geometric nonlinearity and the time/temperature-dependent response of the plastic foil. The linear viscoelastic behavior of a polymer foil is included by the generalized Maxwell model. The proposed layer-wise model was implemented into the MATLAB code and verified against detailed three-dimensional models in ADINA solver using different hexahedral finite elements. The effects of temperature, load duration, and creep/relaxation are demonstrated by examples.

• 전기학회논문지
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• 제64권10호
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• pp.1469-1478
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• 2015

In this paper, The methodology of Type-2 fuzzy set-based Radial Basis Function Neural Network(T2RBFNN) is proposed for Sewage Treatment Process and the simulator is developed for application to the real-world sewage treatment plant by using the proposed model. The proposed model has robust characteristic than conventional RBFNN. architecture of network consist of three layers such as input layer, hidden layer and output layer of RBFNN, and Type-2 fuzzy set is applied to receptive field in contrast with conventional radial basis function. In addition, the connection weights of the proposed model are defined as linear polynomial function, and then are learned through Back-Propagation(BP). Type reduction is carried out by using Karnik and Mendel(KM) algorithm between hidden layer and output layer. Sewage treatment data obtained from real-world sewage treatment plant is employed to evaluate performance of the proposed model, and their results are analyzed as well as compared with those of conventional RBFNN.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 학술대회
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• pp.297-301
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• 2008

The flight vehicles have cavities such as wheel wells and bomb bays. The flow around a cavity is characterized as unsteady flow because of the formation and dissipation of vortices due to the interaction between the freestream shear layer and cavity internal flow, the generation of shock and expansion waves. Resonance phenomena can damage the structures around the cavity and negatively affect aerodynamic performance and stability. The flow field is observed to oscillate in the "shear layer mode" with low aspect ratio. In the present study, numerical analysis was performed for cavity flows by the unsteady compressible three dimensional Reynolds-Averaged Navier-Stokes (RANS) equations with Wilcox's $\kappa$-$\omega$ turbulence model. The flow field is observed to oscillate in the shear layer mode" with large aspect ratio. Based on the SPL(Sound Pressure Level) analysis of the pressure variation at the cavity trailing edge, the dominant frequency was analyzed and compared with the results of Rossiter's formul. The aero-acoustic wave analyzed with CPD(Correlation of Pressure Distribution).