• ETRI Journal
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• 제33권2호
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• pp.279-282
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• 2011

Coexistence analysis is extremely important in examining the possibility for spectrum sharing between orthogonal frequency-division multiplexing (OFDM)-based international mobile telecommunications (IMT)-Advanced and other wireless services. In this letter, a new closed form method is derived based on power spectral density analysis in order to analyze the coexistence of OFDM-based IMT-Advanced systems and broadcasting frequency modulation (FM) systems. The proposed method evaluates more exact interference power of IMT-Advanced systems in FM broadcasting systems than the advanced minimum coupling loss (A-MCL) method. Numerical results show that the interference power is 1.3 dB and 3 dB less than that obtained using the A-MCL method at cochannel and adjacent channel, respectively. This reduces the minimum separation distance between the two systems, which eventually saves spectrum resources.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2009년도 학술발표회 초록집
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• pp.516-523
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• 2009

The artificial compressibility (AC) method for the incompressible Navier-Stokes equations in the generalized curvilinear coordinates using the primitive form is implemented. The main advantage of the AC approach is that the resulting system of equations resembles the system of compressible N-S equations and can thus be integrated in time using standard, well-established time-marching methods. The errors, which are the odd-even oscillation, for pressure field in using the artificial compressibility can be eliminated by using the $4^{th}$ order artificial dissipation term which is explicitly included. Even though this paper focuses exclusively on 2D laminar flows to validate and assess the performance of this solver, this numerical method is general enough so that it can be readily extended to carry out 3D URANS simulation of engineering flows. This algorithm yields practically identical velocity profiles and primary vortex and secondary vortices that are in excellent overall agreement with the results of the vorticity-stream function formulation (Ghia et al., 1982). However, the grid resolution have to be required to be large enough to express the various vortices.

• 한국컴퓨터정보학회논문지
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• 제8권2호
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• pp.88-96
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• 2003

마이크로스트립 라인은 마이크로웨이브와 밀리미터웨이브 집적회로에 있어서 가장 필수적인 소자 중의 하나이다. 그동안 여러 가지 주파수 영역 해석법에 의해 이러한 마이크로스트립 라인의 주파수 종속특성이 해석되었다. 하지만 본 논문에서 제시된 3차원 TLM법은 마이크로스트립 라인의 주파수 영역 해를 얻기 위한 또 다른 독립적인 해석법이다. 이러한 TLM 알고리즘을 이용하여 해석된 구조는 스텝 불연속 마이크로스트립 라인이며 대칭압축노드가 사용되었다. 수치해석 과정을 거쳐 시간 영역 데이터를 퓨리어 변환함으로써 스텝 불연속 마이크로스트립 라인의 주파수 종속 산란 파라메터가 계산되었다. 시간 영역 TLM 해석 결과로부터 이와 같은 수치해석법이 스텝 불연속 마이크로스트립 라인과 같이 복잡한 구조를 모델링하는데 있어 효율적인 방법임을 보였다.

• 한국터널지하공간학회 논문집
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• 제7권4호
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• pp.335-341
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• 2005

대단변 NATM터널에서 지반자체로 막장의 안정을 유지하기 위해 분할굴착공법을 사용한다. 분할굴착을 해야 한다면 더 나은 응력 상태를 유지할 수 있는 분할굴착공법을 강구해야할 것이다. 따라서 본 연구에서는 터널의 단면분할 굴착공법 중 CD굴착 (중벽분할굴착)공법에서 굴착순서에 따른 응력분포를 수치해석적인 방법을 이용하여 검토하고, 막장주변의 응력집중을 최소로 하는 최적의 막장 이격거리와 굴착순서를 도출하였다. 해석에 사용한 프로그램은 국내에서 상용화되고 있는 3차원 연속체 해석 프로그램인 FLAC-3D Ver 2.1을 사용하였고, 암반등급 3과 5에 대해 막장거리 2m, 4m, 6m, ${\cdots}$, 20m, 40m를 적용하여 안정성 검토를 행하였다.

• 대한조선학회논문집
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• 제36권2호
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• pp.50-60
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• 1999

안전하고 경제적인 쌍동선형을 설계하기 위해서는 횡갑판(cross deck)에 작용하는 파랑 동하중의 정확한 추정이 필요하다. 본 논문에서는 Lee 등[3]이 제시한 2차원 스트립 방법을 6자유도 운동을 갖는 3차원의 경우로 확장하여 임의 입사파에서 파랑하중(수직 및 수평 전단력, 굽힘모멘트 및 비틀림모멘트)을 추정하였고, 발표된 계산 결과(스트립 방법 및 3차원 패널법) 및 Wahab 등[2]의 실험 결과와 비교하였다. 일반적으로 2차원 결과보다 3차원 방법이 실험 결과와 잘 일치하였으나, 같은 이론을 사용한 3차원 방법에 있어서도 몇몇 경우에 계산값의 차이가 있었다. 파랑하중 추정의 정도를 향상시키기 위해서 점성항의 고려 및 엄밀한 속도항의 고려가 필요하다고 생각된다.

• 한국CDE학회논문집
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• 제21권4호
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• pp.409-416
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• 2016

This study aims to investigate dynamic interaction characteristics between Maglev train and 3 span continuous guideway. The integrated model including a 3D full vehicle model based on multibody dynamics, flexible guideway by a modal superposition method, and levitation electromagnets with the feedback controller is proposed. The proposed model was applied to the Incheon Airport Maglev Railway to analyze the dynamic response of the vehicle and guideway from the numerical simulation. Using field test data of air gap and guideway deflections, obtained from the Incheon Airport Maglev Railway, the analysis method is verified. From the results, it is confirmed that Maglev railway system are designed and constructed safely according to the design criteria.

• Structural Engineering and Mechanics
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• 제11권2호
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• pp.211-219
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• 2001

This paper presents the tangent stiffness method for 3-D geometrically nonlinear folding analysis of a reversal arch. Experimental tests are conducted to verify the numerical analysis. The tangent stiffness method can accurately evaluate the geometrical nonlinearity due to the element translating as a rigid body, and the method can exactly handle the large rotation of the element in space. The arch in the experiment is made from a thin flat bar, and it is found that the folding process of the arch may be captured exactly by the numerical analysis with a model consisting of only 18 elements with the same properties.

• Journal of Advanced Marine Engineering and Technology
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• 제27권3호
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• pp.365-372
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• 2003

The Flow patterns around two cylinders in various arrangements were studied by a discrete vortex method. The flow for the surface of each cylinder was represented by arranging bound vortices at adequate intervals. The viscous diffusion of fluid was represented by the random walk method. The vortex distributions. streaklines. timelines and velocity vectors around two cylinders were calculated for centre-to-centre pitch ratios of P/D=1.5 and 2.5, attack ang1es of $a=0^{circ}, 30^{circ}, 60^{circ} and 90^{\circ}$. and Reynolds number of Re= 1200. The results of simulation correspond to the photographs by flow visualization and the flow intereference between two cylinders in various arrangements were clearly visualized by a numerical simulation.

• Structural Engineering and Mechanics
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• 제3권1호
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• pp.25-34
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• 1995

General free vibration characteristics of cantilevered circular cylindrical tanks are analyzed using the integral equations technique with the cubic spline functions. For computations, the partial differential equations for thin shallow shells as given by Flugge's have been employed after the addition of the inertia forces. The application of the method is illustrated with a numerical examples of tanks which are free at the top edge and fixed at the bottom. The results obtained by this method have been compared with the available results and a good agreement was found.

• 소성∙가공
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• 제20권6호
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• pp.439-449
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• 2011

The temperature distribution and subsequent permanent deformation of SS400 carbon steel plate subjected to an induction-based line heating process were studied by a numerical method involving coupled 3-D electromagnetic-thermal-structural analysis. The numerical study revealed that the amount of permanent deformation is strongly related to the Joule loss caused by such process conditions as input power and moving speed of the heat source. To validate the numerical analysis results, line heating experiments were carried out with a high frequency(HF) induction heating(IH) equipment capable of bending thick plate with the moving accuracy of ${\pm}0.1mm$ in heating coil position. The amount of permanent deformation increased with decreasing moving speed and increasing input power.