• Communications for Statistical Applications and Methods
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• 제29권1호
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• pp.127-150
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• 2022

We discuss multiple change-point estimation as edge detection in piecewise smooth functions with finitely many jump discontinuities. In this paper we propose change-point estimators using concentration kernels with Fourier coefficients. The change-points can be located via the signal based on Fourier transformation system. This method yields location and amplitude of the change-points with refinement via concentration kernels. We prove that, in an appropriate asymptotic framework, this method provides consistent estimators of change-points with an almost optimal rate. In a simulation study the proposed change-point estimators are compared and discussed. Applications of the proposed methods are provided with Nile flow data and daily won-dollar exchange rate data.

• Tribology and Lubricants
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• 제17권5호
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• pp.391-398
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• 2001

Two dimensional slow viscous flow around two counter-rotating equal cylinders is investigated based on Stokes'approximation. An exact formal expression of the stream function is obtained by using the bipolar cylinder coordinates and Fourier series expansion. From the stream function obtained, the streamline patterns around the cylinders are shown and the pressure distribution in the flow field is determined. By integrating the stress distributions on the cylinder, the force and the moment exerted on the cylinder are calculated. The flow rate through the gap between the two cylinders is also determined as the distance between two cylinders varies. Special attention is directed to the case of very small distance between two cylinders concerned with the lubrication theory and the minimum pressure is calculated to explain a possible cavitation.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제31회 춘계학술대회
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• pp.142-149
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• 2000

Two dimensional slow viscous flow around two counter-rotating equal cylinders is Investigated based on Stokes' approximation. An exact formal expression of the stream function is obtained by using the bipolar cylinder coordinates and Fourier series expansion. From the stream function obtained, the streamline patterns around the cylinders are shown and the pressure distribution In the flow field is determined. By Integrating the stress distribution on the cylinder, the force and the moment exerted on the cylinder are calculated. The flow rate through the gap between the two cylinders is determined as the distance between two cylinders vary. It Is also revealed that the velocity at the far field has finite non-zero value. Special attention is directed to the case of very small distances between two cylinders by way of the lubrication theory.

• Tribology and Lubricants
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• 제18권6호
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• pp.411-417
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• 2002

Two dimensional slow viscous flow between a rotating cylinder and a translating plate is investigated using Stokes' approximation. An exact formal expression of the stream function is obtained by using the bipolar cylinder coordinates and Fourier series expansion. From the stream function obtained, the streamline patterns are shown and the pressure distribution in the flow field is determined. By integrating the stress distributions on the cylinder, the farce and the moment exerted on the cylinder are calculated. The flow rate through the gap between the cylinder and the plate is also determined as a function of the distance between the cylinder and the plate. Special attention is directed to the case of very small distance between the cylinder and the plate concerned with the lubrication theory and the minimum pressure is calculated to explain a possible cavitation.

• Structural Engineering and Mechanics
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• 제21권2호
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• pp.169-184
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• 2005

This study deals with the free vibration of a circular plate in contact with a fluid; submerged in fluid, beneath fluid or on fluid. An analytical method based on the finite Fourier-Bessel series expansion and Rayleigh-Ritz method is suggested. The proposed method is verified by the finite element analysis using commercial program with a good accuracy. The normalized natural frequencies are obtained in order to estimate the relative added mass effect of fluid on each vibration mode of the plate. Also, the location of plate coupled with fluid and the cases of free and bounded fluid surface are studied for the effect on the vibration characteristics.

• Journal of Mechanical Science and Technology
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• 제17권9호
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• pp.1297-1315
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• 2003

This study deals with the free vibration of two identical circular plates coupled with a bounded or unbounded fluid. An analytical method based on the finite Fourier-Bessel series expansion and Rayleigh-Ritz method is suggested. The proposed method is verified by the finite element analysis using commercial program with a good accuracy The case of bounded or unbounded fluid is studied for the effect on the vibration characteristics of two circular plates. Also, the effect of gap between the plates on the fluid-coupled natural frequencies is investigated.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.389.1-389
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• 2002

An analytical study is presented on the hydroelastic vibration of two rectangular identical plates coupled with a bounded fluid by using the finite Fourier series expansion method. It is observed that the two contrastive modes, the so called the out-of-phase and in-phase modes. All natural frequency of the in-phase modes can be predicted well by the combination of the beam modes in the air, but the natural frequency of the out-of-phase mode cannot be estimated precisely. (omitted)

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.80-82
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• 2004

The single phase switched reluctance motor(SRM) is more simpler and robust in the structure than poly phase SRM. It has the merits that it reduces the switching elements and the energy density per volume is very high. Recently, it has been researched and developed in various types and starting method due to the technique of power electronics and the computer added design. This paper presents a analytical representation of the phase inductance of a single phase SRM, as function of position and current, taking into account the non-linearity of the magnetic circuit. the method is based on Fourier series expansion. Analytical expressions for the calculation of instantaneous phase inductance, flux linkage, coenergy and electromagnetic torque as a function of rotor position and winding currents are derived.

• 지구물리와물리탐사
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• 제13권4호
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• pp.315-322
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• 2010

위상막 구조보정과 split-step Fourier 구조보정은 주파수-파수, 주파수-공간 영역에서 단방향 파동방정식을 이용하여 빠른 계산 속도로 수평적 속도변화를 고려할 수 있는 구조보정이다. 일반화된-막(generalized-screen) 구조보정은 주파수-파수영역에서 수직전파를 가정하는 위의 두 구조보정과는 달리 수직전파를 가정하지 않고, 지수함수의 무한급수 전개를 이용한다. 또한 수직느리기항의 테일러 급수전개를 일반화하여 고차항을 추가함으로써 급격한 속도변화를 갖는 지하구조에서 넓은 각으로 전파하는 파동장에 대한 정확도를 향상시켰다. 이 논문은 다양한 경사와 급격한 속도변화를 포함하는 복잡한 지하구조를 효율적으로 보다 정확하게 영상화하기 위하여 2차원 일반화된-막 구조보정에 대하여 연구하였다. 일정한 미소변량(constant perturbation)을 갖는 매질과 SEG/EAGE 암염돔을 모사한 모델에 대하여 일반화된-막 전파자와 위상막 전파자의 전파된 파동장을 비교한 결과, 일반화된-막 전파자가 파동장의 넓은각 전파에 대해 위상막 전파자보다 높은 정확도를 보였다. 또한 일반화된-막 전파자의 차수를 증가시킬수록 넓은 각으로 전파하는 파동장의 정확도가 향상되었다. 큰 수평적 속도변화와 급경사를 갖는 모델과 SEG/EAGE 암염돔 합성 탄성파탐사 자료에 대하여 일반화된-막 구조보정과 위상막 구조보정을 적용한 결과, 일반화된-막 구조보정이 속도변화가 크고 급격한 경사를 갖는 반사면을 보다 정확한 위치에 뚜렷하게 영상화하였다.

• Journal of applied mathematics & informatics
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• 제9권2호
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• pp.657-666
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• 2002

ThE Gibbs' phenomenon in the classical Fourier series is well-known. It is closely related with the kernel of the partial sum of the series. In fact, the Dirichlet kernel of the courier series is not positive. The poisson kernel of Cesaro summability is positive. As the consequence of the positiveness, the partial sum of Cesaro summability does not exhibit the Gibbs' phenomenon. Most kernels associated with wavelet expansions are not positive. So wavelet series is not free from the Gibbs' phenomenon. Because of the excessive oscillation of wavelets, we can not follow the techniques of the courier series to get rid of the unwanted quirk. Here we make a positive kernel For Meyer wavelets and as the result the associated summability method does not exhibit Gibbs' phenomenon for the corresponding series .