• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.229-231
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• 2006

The paper presents a sensorless speed control of interior permanent magnet synchronous motors using an adaptive integral binary observer in view of composition with a main loop regulator and an auxiliary loop regulator. The binary observer has a property of the chattering alleviation in the constant boundary layer; however, the steady state estimation accuracy and robustness are dependent upon with width of the constant boundary. In order to improve the steady state performance of the binary observer, the binary observer is formed by adding extra integral dynamic to the switching hyperplane equation.

• Journal of Welding and Joining
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• 제18권4호
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• pp.104-110
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• 2000

An integral equation representation of cracks was presented, which differs from well-known "dislocation layer" representation. In this new representation, an integral equation representation of cracks was developed and coupled to the direct boundary-element method for treatment of cracks in plane finite bodies. The method was developed for in-plane (modes I and II) loadings only. In this paper, the method is formulated and applied to mode III problems involving smooth or kinked cracks in finite region. The results are compared to exact solutions where available and the method is shown to be very accurate despite of its simplicity.implicity.

• International Journal of Naval Architecture and Ocean Engineering
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• 제2권3호
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• pp.127-131
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• 2010

A two-layer fluid with free surface is simulated in the time domain by a two-dimensional potential-based Numerical Wave Tank (NWT). The developed NWT is based on the boundary element method and a leap-frog time integration scheme. A whole domain scheme including interaction terms between two layers is applied to solve the boundary integral equation. The time histories of surface elevations on both fluid layers in the respective wave modes are verified with analytic results. The amplitude ratios of upper to lower elevation for various density ratios and water depths are also compared.

• 대한기계학회논문집A
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• 제30권8호
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• pp.949-956
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• 2006

The method of Greenwood and Williamson is extended to obtain a solution to the coupled non-linear problem of steady-state electrical and thermal conduction across a crack in a conductive layer, for which the electrical resistivity and thermal conductivity are functions of temperature. The problem can be decomposed into the solution of a pair of non-linear algebraic equations involving boundary values and material properties. The new mixed-boundary value problem given from the thermal and electrical boundary conditions for the crack in the conductive layer is reduced in order to solve a singular integral equation of the first kind, the solution of which can be expressed in terms of the product of a series of the Chebyshev polynomials and their weight function. The non-existence of the solution for an infinite conductor in electrical and thermal conduction is shown. Numerical results are given showing the temperature field around the crack.

• 수산해양기술연구
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• 제27권2호
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• pp.120-124
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• 1991

이상의 결과를 정리하면 다음과 같이 요약할 수 있다. (1)Karman의 적분 방정식에 미소 거칠기 영향을 고려함으로서 디퓨져 닥트 표면의 경계층 계산에 응용한 결과 모멘트 적분법 및 실험치와의 비교에서 개선된 결과임이 확인되었다. (2) 국소 거칠기의 효과를 주는 방법으로는 Cole의 벽 및 와 법칙에 Clauser의 거칠기 함수와, 압력 기울기를 고려한 부가 형상계수 값으로 적분 방정식에 응용할 수 있다. (3) 국소 거칠기 분포에 의하여 경계층 특성을 교란시켜 표면 마찰력 계수를 줄일 수 있어 마찰력 손실을 줄일 수 있는 방안이 제시되었다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1997년도 봄 학술발표회 논문집
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• pp.35-42
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• 1997

The two-state or mutual M-integral which is derived from tile M-integral and is applicable for two elastic states, is applied for computing all intensity of a singular near-tip field around the vertex of a class of wedge, encountered in adhesive lap joints under mechanical loading. Numerically we verify that a simple auxiliary field associated with every eigenfunction for the composite wedge under consideration exists in the form of the conjugate solution in the sense of tile M-integral. The auxiliary field is then employed for superposition with the elastic field under consideration, and the associated two-state M-integral is computed via the domain integral technique. This enables us to extract the intensity for a singular field information for a singular elastic boundary layer is extracted form the domain integral representation without resort to singular finite element for the wedge vertex.

• 한국추진공학회지
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• 제9권1호
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• pp.9-16
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• 2005

제트베인은 로켓추진기관의 발사초기 자세제어와 조정 안정성의 확보를 위해 로켓노즐 출구부에 장착되어지며, 발사 수초 후까지 연소가스와의 접촉으로 인해 구동부를 가열시키고, 그 자체도 화학적 혹은 기계적으로 삭마된다. 본 연구는 제트베인의 열해석을 위한 기초연구로서 균일 초음속 유동장내에 위치한 단일 제트베인으로의 열전달 특성 해석을 수행하여 보았다. 경계층 적분법과 유한차분법의 연립해석이 이루어 졌으며, 벽근방에서 도출된 경계조건을 바탕으로 베인 내부의 비정상 열전도 해석도 수행되었다.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제53권3호
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• pp.152-163
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• 2004

This paper presents a sensorless speed control of cylindrical permanent magnet synchronous motors(PMSM) using an adaptive integral binary observer In view of composition with a main loop regulator and an auxiliary loop regulator, the binary observer has a property of the chattering alleviation in the constant boundary layer. However, the steady state estimation accuracy and robustness are dependent upon the width of the constant boundary. In order to improve the steady state performance of the binary observer, the binary observer is formed by adding extra integral dynamics to the switching hyperplane equation. With the help of integral characteristic, the rotor speed can be finely estimated and utilized for a sensorless speed controller for PMSM. Since the Parameters of the dynamic equations such as machine inertia or a viscosity friction coefficient are lot well known, there are many restrictions in the actual implementation. The proposed adaptive integral binary observer applies an adaptive scheme so that observer may overcome the problem caused by using the dynamic equations and the rotor speed is constructed by using the Lyapunov function. The observer structure and its design method are described. The experimental results of the proposed algorithm are presented to demonstrate the effectiveness of the approach.

• 한국전자파학회지:전자파기술
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• 제2권3호
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• pp.26-31
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• 1991

The scattering property of TMz illuminated a elliptic dielectric cylinders with arbitrary cross section are analyzed by the boundary element techniques. The boundary element equations are for- mulated via Maxwell's equations, weighted residual of Green's theorem, and the boundary conditions. The unknown surface fields on the boundaries are then calculated by the boundary element integral equations. Once the surface fields are found, the scattered fields in far-zone and scattering widths (SW) are readily determined. To show the validity and usefulness of this formulation, computations are compared with those obtained using analytical method and one layer circular cylinder. As exten- sion to arbitrary cross-sectioned cylinders, plane wave scattering from a elliptic dielectric cylinders are numerically analyzed. A general computer program has been developed using the quadratic ele- ments(Higher order borndary elements) and the Gaussian quadrature.

• 한국해양공학회지
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• 제23권4호
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• pp.6-11
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• 2009

In this study, the internal waves in two-density layered fluids were analyzed using the Numerical Wave Tank (NWT) technique in the frequency domain. The NWT is based on a two-domain Boundary Element Method with the potential fluids using the whole-domain matrix scheme. From the mathematical solution of the two-domain boundary integral equation, two different wave modes could be classified: a surface wave mode and an internal wave mode, and each mode were shown to have a wave number determined by a respective dispersion relation. The magnitudes of the internal waves against surface waves were investigated for various fluid densities and water depths. The calculated results are compared with available theoretical data.