• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2004년도 추계 학술대회논문집
• /
• pp.207-213
• /
• 2004

A kinetic theory analysis is used to study the ultra-thin gas flow field in a gas slider bering, The Boltzmann equation simplified by a collision model is solved by means of a finite difference approximation with the discrete ordinate method. Calculations are made for a flow in a micro-channel between an inclined slider and a moving disk drive platter. The results are compared well with those from the DSMC method. The present method does not suffer from statistical noise which is common in particle based methods and requires much less computational effort.

• 한국전산유체공학회지
• /
• 제14권1호
• /
• pp.86-95
• /
• 2009

A kinetic theory analysis is used to study the ultra-thin gas flow field in gas bearings. The Boltzmann equation simplified by a collision model is solved by means of a finite difference approximation with the discrete ordinate method. Calculations are made for flows inside micro-channels of backward-facing step, forward-facing step, and slider bearings. The results are compared well with those from the DSMC method. The present method does not suffer from statistical noise which is common in particle based methods and requires less computational effort.

• Journal of Electrical Engineering and information Science
• /
• 제3권3호
• /
• pp.306-315
• /
• 1998

In this paper, a unified approach to the H\ulcorner controller design is proposed under the $\delta$-form for both continuous and discrete systems. Most of important basic concepts of H\ulcorner control, such as inner, co-inner, GCARE and GFARE, are reformulated by the unified form. The NLCF(Normalized left Comprime Factor) plant description has been reviewed in the $\delta$-form, and some corresponding results are proposed. And the unified H\ulcorner controller is designed which is based on the McFarlane and Glover{1]. The state-space parameterization for all suboptimal controllers is given under the NLCF model which may not be strictly proper, and the central controller is derived by using the solution to Hankel norm approximation problem[2]. The unified controller is applied to the industrial boiler control problem to exemplify the performance of the controller.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2013년도 전력전자학술대회 논문집
• /
• pp.449-450
• /
• 2013

본 논문에서는 이산 웨이블릿 변환(DWT;discrete wavelet transform)을 이용한 에너지 저장시스템(ESS;energy storage system)의 고장 검출 방법을 제안한다. ESS에 순간적인 고장 발생시 전압의 급격한 변화가 발생할 수 있으며 이는 다해상도 분석(MRA;multi-resolution analysis)을 이용한 시간-주파수 분석을 통해 분해된 저주파 전압 성분(approximation;$A_n$)과 고주파 전압 성분(detail;$D_n$)중 현저한 성분의 변화가 관찰되는 고주파 전압 성분을 선택한다. 이를 검증하기 위하여 모든 고주파 전압 성분의 절대값을 적용한 뒤 최대값 정보를 추출한다. 이 때, 추출된 각 성분의 최대값과 최대값의 평균을 비교하되 여러 사전실험을 통해 정해진 특정 임계값 대비 큰 값을 나타낼 때 고장이 발생하였음을 판단한다.

• 전자공학회논문지S
• /
• 제34S권3호
• /
• pp.24-32
• /
• 1997

This paper is on a discrete controller order reduction with the closed-loop stability and performance guaranteed. to achieve this, after finding the solutionsof two lyapunov inequalities and balancing the full order controller system, we find the reudced order controlers using the balanced truncation (BT) and the balanced singular perturbation approximation (BSPA). When the solutions of the two lyapunov inequalities exist, it is shown that the resulting controllers guarantee the closed-loop stability, and .inf.-norm error bounds are derived for the closed-loop performance region for the BT and in low frequency region for the BSPA. Finally, a numerical example is given to illustrate the validity of the proposed method.

• Journal of Ship and Ocean Technology
• /
• 제7권3호
• /
• pp.34-55
• /
• 2003

Explicit Kutta condition approximation, proved useful in existing time-domain solver of the unsteady propeller problem, requires a specified functional behavior of the vorticity in space near the trailing edge. In this paper, the strength of the discrete vortices is controlled to have a specified behavior in space in the frequency domain approach. A new formulation is introduced and is implemented for analysis of a lifting surface of a rectangular planform. Sample computations carried out according to the new formulation compares well with that of existing unsteady lifting problem in the time domain.

• 한국자동차공학회논문집
• /
• 제15권1호
• /
• pp.146-153
• /
• 2007

Weight reduction for automobile components has been sought to achieve fuel efficiency and energy conservation. There are two approaches in reducing their weights. One is by using material lighter than steel, and the other is by redesigning their structures. The latter has been performed by adopting hydroforming, tailor weled blank, optimization, etc. In this research, the kriging approximation method and simulated annealing algorithm are applied to the design of a front door made by TWB (Tailor Welded Blank) technology. The design variables are set up as the thicknesses of parts and the positions of parting lines. A thickness set considered as a design variable of each part is not arbitrarily determined but selected from standard products, so it is a discrete set. This research presents the discrete and continuous structural optimization method for an automotive door design.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2014년도 전력전자학술대회 논문집
• /
• pp.152-153
• /
• 2014

본 논문에서는 이차전지의 특성비교/분석을 위해 이산 웨이블릿 변환(DWT;discrete wavelet transform)과 웨이블릿 패킷 변환(WPT;wavelet packet transform)을 적용한 연구를 소개한다. 다해상도 분석(MRA; multi resolution analysis)의 시간-주파수 분석을 통해 저주파 성분(approximation;$A_n$)과 고주파 성분(detail;$D_n$)로 분해되는 것은 두 방법 동일하다. 하지만, 이산 웨이블릿 변환이 단순히 저대역 부분만 계속 분해하는 것과 달리 웨이블릿 패킷 변환은 저대역과 고대역을 모두 분해하여 높은 분해성능을 가지는 웨이블릿의 일반화이다. 웨이블릿 패킷 변환을 자세히 소개하고 이를 이차전지에 적용하여 이산 웨이블릿 변환과의 상관성을 정리하였다.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2014년도 전력전자학술대회 논문집
• /
• pp.150-151
• /
• 2014

높은 SOC(state-of-charge) 추정알고리즘의 성능을 위해서는 측정된 배터리 단자전압의 정확도가 요구된다. 그렇지만, 예기치 않은 에러로 인해 단자전압에 노이즈 성분이 추가될 경우 SOC 추정성능의 저하를 피할 수 없다. 그러므로, 본 논문에서는 이산 웨이블릿 변환(DWT;discrete wavelet transform)의 다해상도 분석(MRA;multi resolution analysis)의 디노이징(denoising)기법을 적용한 이차전지의 SOC 추정방법을 소개한다. MRA의 시간-주파수 분석을 통해 분해(decomposition)된 저주파 성분(approximation;$A_n$)과 고주파 성분(detail;$D_n$)중 노이즈에 관계된 $D_n$의 고주파 상세 계수(detail coefficient) $d_{j,k}$를 새로이 조정하고 이를 합성(synthesis)하여 디노이징을 마무리 한다. 확장 칼만필터(EKF;extended Kalman filter)의 비교 분석을 통해 제안된 방법의 타당성을 검증한다.

• 공학논문집
• /
• 제1권1호
• /
• pp.31-40
• /
• 1997

ATM망의 모델링에서 발생되어지는 D-BMAP/Geo/1/K queue의 departure 프로세스를 k-state MMBP로 특성화하는 근사화방법을 제시하고, 그 근사화방법과 decomposition algorithm을 이용하여 셀손실을 갖는 tandem 구조의 한정용량 대기 네트워크를 분석하였다.