• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1998년도 추계학술대회
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• pp.92-93
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• 1998

In this study, we have established the technique to estimate the gradient waveforms distorted by the eddy current in MRI. After obtaining the eddy current effect transfer function using the finite element method, we have used the transfer function to estimate the output gradient waveforms at any points inside the imaging region. We also present experimental results to be compared with estimated ones.

• 한국유체기계학회 논문집
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• 제12권4호
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• pp.7-13
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• 2009

The purposes of present work are to analyze the convective heat transfer with three-dimensional Reynolds-averaged Navier-Stokes analysis, and to optimize shape of the mixing vane using the analysis results. Response surface method is employed as an optimization technique. The objective function is defined as a combination of inverse of heat transfer rate and friction loss. Two bend angles of mixing vane are selected as design variables. Thermal-hydraulic performances have been discussed and optimum shape has been obtained as a function of weighting factor in the objective function. The results show that the optimized geometry improves the heat transfer performance far downstream of the mixing vane.

• 전기학회논문지P
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• 제63권4호
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• pp.260-265
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• 2014

Recently, many active noise control (ANC) systems, which employ the adaptive filter controlling method, have been reported for eliminating unwanted noise. ANC systems based on the filtered-X least mean square (FXLMS) algorithm have a problem with compensating the acoustic feedback of secondary route. It is difficult to apply the real time, because transfer function of secondary route must be measured by off-line method to solve this problem. In this paper, we propose the ANC system that applies a correlation LMS(CLMS) algorithm for improving a problem of transfer function measurement. The proposed algorithm is based on input of road noise. The proposed ANC systems have an advantage of real-time process without degradation of performance, although there are many calculation compared with FXLMS algorithm.

• 한국전산유체공학회지
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• 제14권2호
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• pp.1-8
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• 2009

The purposes of present work are to analyze the convective heat transfer with three-dimensional Reynolds-averaged Navier-Stokes analysis, and to optimize shape of the mixing vane taken tolerance into consideration by using the analysis results. Response surface method is employed as an optimization technique. The objective function is defined as a combination of heat transfer rate and inverse of pressure drop. Two bend angles of mixing vane are selected as design variables. Thermal-hydraulic performances have been discussed and optimum shape has been obtained as a function of weighting factor in the objective function. The results show that the optimized geometry improves the heat transfer performance far downstream of the mixing vane.

• ETRI Journal
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• 제16권1호
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• pp.1-15
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• 1994

A computationally-efficient approach to the calculation of the transient field of an acoustic radiator was developed. With this approach, a planar or curved source, radiating either continuous or pulsed waves, is divided into a finite number of shifted and/or rotated versions of an incremental source such that the Fraunhofer approximation holds at each field point. The acoustic field from the incremental source is given by a 2-D spatial Fourier transform. The diffraction transfer function of the entire source can be expressed as a sum of Fraunhofer diffraction pattern of the incremental sources with the appropriate coordinate transformations for the particular geometry of the radiator. For a given spectrum of radiator velocity, the transient field can be computed directly in the frequency domain using the diffraction transfer function. To determine the accuracy of the proposed approach, the impulse response was derived using the inverse Fourier transform. The results obtained agree well with published data obtained using the impulse response approach. The computational efficiency of the proposed method compares favorably to those of the point source method and the impulse response approach.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.465-466
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• 2007

Available transfer capability(ATC) quantifies the viable increase in real power transfer from one point to another in a power system. ATC calculation has predominantly focussed on steady-state viability. In many power systems, point-to-point transfer is not restricted by steady-state limits, but by undesirable dynamic behavior following large disturbance. In this paper, an energy function method for transient stability ATC computation is proposed, which utilizes a between the potential energy and energy function.

• Smart Structures and Systems
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• 제23권1호
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• pp.71-79
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• 2019

In general, it may be advantageous to measure the pressure pulsation near a valve to detect a valve defect in a linear compressor. However, the acceleration signals are more advantageous for rapid classification in a mass-production line. This paper deals with the performance improvement of fault classification using only the compressor-shell acceleration signal based on the relation between the refrigerant pressure pulsation and the shell acceleration of the compressor. A transfer function was estimated experimentally to take into account the signal noise ratio between the pressure pulsation of the refrigerant in the suction pipe and the shell acceleration. The shell acceleration signal of the compressor was modified using this transfer function to improve the defect classification performance. The defect classification of the modified signal was evaluated in the acceleration signal in the frequency domain using Fisher's discriminant ratio (FDR). The defect classification method was validated by experimental data. By using the method presented, the classification of valve defects can be performed rapidly and efficiently during mass production.

• 한국음향학회지
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• 제33권1호
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• pp.54-59
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• 2014

본 논문은 비정상 (nonstationary)특성을 가지는 잡음환경에서 마이크간 전달함수 비 (RTF, Relative Transfer Function) 추정 알고리즘을 제안한다. 음성을 이용한 다양한 기기에 다중 마이크를 이용한 잡음제거 기술은 널리 사용되며, 이때 각 마이크간의 입력 신호 사이의 관계는 필수적으로 추정되어야 한다. 본 논문에서는 기존의 OM-LSA(Optimally-Modified Log-Spectral Amplitude)기반의 추정 방식에 CASA (Computational Auditory Scene Analysis)를 접목시킨 방식을 제안한다. 제안한 방법의 성능 검증을 위하여 비정상 백색 잡음 (nonstationary white Gaussian noise) 환경에서 10명 화자 발음을 이용한 마이크간 전달함수 비 추정 성능 평가 실험을 수행하였다. 잡음 신호가 초당 8dB 증감하는 환경에서 SBF (Signal Blocking Factor)가 평균 2.65dB 개선됨을 확인하였다.

• Journal of KIEE
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• 제11권1호
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• pp.14-20
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• 2001

To design a controller based on the pole placement method, it is necessary to obtain either a target transfer function or a desired characteristic equation which results in the closed-loop response. Specially, a step response in which no overshoot occurs in highly desirable in many applications. In this paper, we present two new present two new prototypes of Type I target transfer functions whose step responses have an overshoot of less than 0.1%. One prototype is obtained by Taylor's approximation of a Gaussian function. It is, however, observed that the response delays increase with increasing order, while the rise times are nearly constant. The other prototype is a modification of the first prototype, so that their transfer function coefficients have particular values in terms of specific parameters ${\gamma}$i and $\tau$ (see section 2). The second prototype gives very useful properties in which step responses are almost the same shape, irrespective of the order. It, also, has no overshoot. Some other properties of the prototypes and an application example are given.

• 한국정보처리학회논문지
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• 제7권1호
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• pp.99-114
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• 2000

안전한 DNS(Domain Name System)는 기존 DNS에 비해 관리해야 할 존(Zone)의 정보가 크게 늘었고 이들 사이의 종속 관계도 매우 복잡하게 되어, 효율적으로 존 정보를 관리할 수 있는 메커니즘이 필요하게 되었다. 또한 안전한 DNS를 다른 인터넷 응용 서비스와 효율적으로 접속할 수 있도록 하려면 일관성 있는 인터페이스가 필요하다. 이에 따라 본 논문에서는 DNS의 존 정보를 동적으로 추가하고 삭제하는 동적 갱신과, 갱신된 존 정보를 DNS 서버간에 효율적으로 전송할 수 있는 존 전송의 기능을 추가한 확장된 안전한 DNS를 설계하고 구현하였다. 그리고 서버간에 효율적으로 전송할 수 있는 존 전송의 기능을 추가한 확장된 안전한 DNS를 설계하고 구현하였다. 그리고 효율적인 존 전송을 위해 전체 존 전송과 점진적 존 전송의 두 가지 존 전송을 통합하는 방법과 함께 존 전송 메시지의 압축 방법을 제시하였고, 존 전송과 동적 갱신을 동시에 제공하기 위해 델타파일이라는 새로운 자료구조를 제시하였다.