• 한국수자원학회논문집
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• 제38권6호
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• pp.461-469
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• 2005

본 연구에서는 지진해일에 의하여 동해안에 발생하는 처오름을 모의하기 위하여 2차 정확도의 풍상차분기법을 사용하였으며, 그 결과는 현장관측값과 1차 정확도의 풍상차분기법의 산정 결과와 비교하였다. 수치해석 모형에서는 지배방정식으로 원해에서는 선형 천수 방정식, 근해에서는 비선형 천수방정식을 사용하였다. 대상 지진해일은 1983년 지진해일과 1993년 지진해일이다. 수치해석 결과 동해안의 처오름높이를 잘 재현하는 것으로 확인되었다. 또한, 지진해일 처오름 모의 결과를 범람도 작성에 이용할 수 있을 것으로 판단된다.

• Journal of Electrical Engineering and Technology
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• 제8권2호
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• pp.262-270
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• 2013

A boundary protection method for power distribution line based on equivalent boundary effect is presented in this paper. In the proposed scheme, the equivalent resonance component with a certain central frequency is sleeve-mounted at the beginning of protected zone. The 'Line Boundary' is built by using boundary effect, which is created by introducing impedance in the primary-side of line. The 'Line Boundary' is significantly different from line wave impedance. Therefore, the boundary protection principle can be applied to power distribution line without line traps. To analyze the frequency characteristic corresponding to traveling-waves of introducing impedance in the primary-side of line, distributed parameters model of equivalent resonance component is established. The results of PSCAD/EMTDC simulation prove the obvious difference of voltage high frequency component between internal faults and external faults due to equivalent resonance component, and validate the scheme.

• Journal of Mechanical Science and Technology
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• 제17권8호
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• pp.1219-1225
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• 2003

Acoustic sounds generated by uniform flow around a two-dimensional circular cylinder at Re=150 are simulated by applying the finite difference lattice Boltzmann method. A third-order-accurate up-wind scheme is used for the spatial derivatives. A second-order-accurate Runge-Kutta scheme is also used for time marching. Very small acoustic pressure fluctuation, with same frequency as that of Karman vortex street, is compared with pressure fluctuation around a circular cylinder. The propagation velocity of acoustic sound shows that acoustic approaching the upstream, due to the Doppler effect in uniform flow, slowly propagates. For the downstream, on the other hand, it quickly propagates. It is also apparent that the size of sound pressure is proportional to the central distance ${\gamma}$$\^$-1/2/ of the circular cylinder.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2001년도 추계 학술대회논문집
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• pp.84-90
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• 2001

Secondary instability of flow past a circular cylinder is examined using direct numerical simulation at Reynolds number 220 and 250. The higher-order finite difference scheme is employed for the spatial distributions along with the second order Adams-Bashforth and the first order backward-Euler time integration. In x-y plane, the convection term is applied by the 5th order upwind scheme, and the pressure and viscosity terms are applied by the 4th order central difference. In spanwise, Navier-Stokes equation is distributed using Spectral Method. The critical Reynolds number for this instability is found to be about Re=190. The secondary instability leads re three-dimensionality with a spanwise wavelength about 4 cylinder diameters at onset (A-mode). Results of three-dimensional effect in wake of a circular cylinder are represented with spanwise and streamwise vorticity contours as Reynolds numbers.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.570-577
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• 2001

Three-dimensional time-dependent flow past a circular cylinder is numerically investigated using direct numerical simulation for Reynolds number 280 and 300. The higher-order finite difference scheme is employed for the spatial distributions along with the second order Adams-Bashforth and the first order backward-Euler time integration. In x-y plane, the convection term is applied by the 5th order upwind scheme and the pressure and viscosity terms are applied by the 4th order central difference. And in spanwise, Navier-Stokes equation is distributed using of Spectral Method. At Reynolds number 259 the two-dimensional wake becomes linearly unstable to a second branch of modes with wavelength about 1.0 diameters at onset (B-mode). Present results of three-dimensional effects of in wake of a circular cylinder is represented with spanwise and streamwise vorticity contours as Reynolds numbers.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 추계학술대회 논문집
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• pp.234-239
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• 2002

Acoustic sounds generated by a uniform flow around a two-dimensional circular cylinder at Re=200 are simulated using finite difference lattice Boltzmann method. A third-order-accurate up-wind scheme is used for spartial derivatives, and a second-order-accurate Runge-Kutta scheme is used for time marching. The results show that in capturing very small acoustic pressure fluctuation with same frequency of Karman vortex street compared with the pressure fluctuation around a circular cylinder. The propagation velocity of acoustic sound is presented that acoustic which approaches tire upstream due to Doppler effect in the uniform flow slowly propagates, while that for the downstream quickly propagates. It is also apparent that the size of sound pressure is proportional for central distance $r^{-1/2}$ of the cylinder.

• 정보처리학회논문지B
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• 제14B권5호
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• pp.361-368
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• 2007

본 논문은 비디오 영상에서 블록기반 차영상을 이용한 연기검출 방법을 제시한다. 제안된 방법은 배경으로부터 변경된 영역 검출 단계, 배경영상 갱신단계, 검출된 영역이 연기인지를 판단하는 단계의 세 단계로 구성된다. 입력 비디오에서 각 프레임의 블록 평균영상을 계산하였으며, 변화영역을 검출하기 위하여 배경영상의 블록평균영상과 입력영상의 블록평균영상의 차이를 사용한다. 블록기반 차영상을 투영하여 변화된 사각영역을 검출한다. 차영상의 투영을 이용한 배경블록평균영상의 갱신방법을 제안한다. 변화영역의 중심위치 및 YUV 색상의 시간적 특징을 이용하여 연기영역을 판단한다.

• 지구물리와물리탐사
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• 제20권3호
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• pp.121-128
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• 2017

국내에서 시간영역 전자탐사(time-domain/transient electromagnetic, TEM) 자료의 해석은 1차원 알고리듬에 주로 의존하고 있는 실정이기 때문에 정밀한 해석을 위하여 3차원 모델링 및 역산 해석 프로그램의 개발이 필요한 상황이다. 이 연구에서는 엇갈린 격자를 이용한 시간영역 유한차분(staggered-grid finite-difference time-domain, FDTD)법에 기초하여 3차원 TEM 반응 모델링 알고리듬을 개발하였다. 시간영역 전자탐사의 모델링을 위해 맥스웰 방정식을 현시적 중앙점 FDTD법을 이용하여 이산화하였으며 수치 안정성을 높이기 위해 가상 변위전류항을 도입하였다. 일반적으로 많이 활용되는 소형 코일 송신원을 수치적으로 구현하여 균질 반무한 공간에서의 해석해와 비교 검증하고 3차원 이상체에 대한 반응을 분석하였다. 이 연구에서 개발된 모델링 프로그램은 향후 TEM 전자탐사 자료의 정밀 해석에 기초가 될 것으로 기대한다.

• Structural Engineering and Mechanics
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• 제11권2호
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• pp.185-197
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• 2001

This paper presents the effect of axial stretching on large amplitude free vibration of an extensible suspended cable supported at the same level. The model formulation developed in this study is based on the virtual work-energy functional of cables which involves strain energy due to axial stretching and work done by external forces. The difference in the Euler equations between equilibrium and motion states is considered. The resulting equations govern the horizontal and vertical motion of the cables, and are coupled and highly nonlinear. The solution for the nonlinear static equilibrium configuration is determined by the shooting method while the solution for the large amplitude free vibration is obtained by using the second-order central finite difference scheme with time integration. Numerical examples are given to demonstrate the vibration behaviour of extensible suspended cables.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권11호
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• pp.559-566
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• 2002

In this paper, we present an accurate and stable method for the solution of the transient electromagnetic response from the conducting wire structures using the time domain integral equation. By using an implicit scheme with the central finite difference approximation for the time domain electric field integral equation, we obtain the transient response from a wire scatterer illuminated by a plane wave and a conducting wire antenna with an impressed voltage source. Also, we consider a wire above a 3-dimensional conducting object. Numerical results are presented, which show the validity of the presented methodology, and compared with a conventional method using backward finite difference approximation.