• 조명전기설비학회논문지
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• 제17권3호
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• pp.127-137
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• 2003

논문에서는 대규모 계통의 미소신호안전도 평가 및 해석을 위해 고유치 감도/perturbation 이론에 근거한 상정사고 지표를 제안하였으며 이를 실제 계통에 적용한 결과를 기술하였다. 선로정수와 제어기점수에 대한 미소신호 안정도 상정사고 지표를 제시하였고 이로부터 심각한 저주파진동 문제를 발생할 수 있는 파라메타들을 선택하였다. 또한 각 발전기의 발전량 증감에 대한 고유치 변화로부터 미소신호안정도 상정사고를 일으킬 수 있는 발전기들을 선택하였다. 이 논문에서는 모든 결과들을 2000년 KEPCO 실계통의 시간영역해석과 비교 검증하여 제안한 미소신호안정도 상정사고 해석법이 정확함을 확인하였다.

• 동력기계공학회지
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• 제2권1호
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• pp.73-79
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• 1998

In practical fields, the sway of crane systems leads to extra stress to the crane structure during the transporting operation and it is in close connection with its life. Usually, when we operate the cranes with high speed and manual control, the sway motion is irreducible. In this paper, a new type of crane system is proposed to avoid the irreducible sway of the crane systems. The proposed system is composed of mechanical arm with function of anti-sway based on conventional line system. By the anti-sway arm, we can realize to prevent the sway of the container box but cannot avoid the oscillation for the overall body of the crane. So, a controller design method to solve the above stated problem must be considered. The problem is solved by adopting the velocity pattern control methods of trapezoidal and curve types and its effectiveness is proved through experimental results.

• 한국산업융합학회 논문집
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• 제24권4_2호
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• pp.481-490
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• 2021

In the ultrasonic welding machine, when the load fluctuates, the L and C of the piezo element in the oscillation part change. As a result, the resonant frequency is changed, so it is necessary to match the operating frequency of the ultrasonic welding machine to the new resonant frequency. That is, in order to maximize the output of the oscillation unit of the ultrasonic welding machine, it is inevitable to follow the resonance frequency. Accordingly, many methods for following the resonant frequency are being actively studied. In addition, in order to check the effect of external inductance on the operation of the ultrasonic welding machine, The equivalent circuit of the piezo element was analyzed by including the external inductance for resonance in the equivalent circuit of the piezo element, and the method of selecting an appropriate inductance was described. In this paper, we propose a new system that allows the switching frequency of the inverter to tracking the resonance frequency even if the resonance frequency is changed due to the load of the ultrasonic welding machine.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국제학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.42-47
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• 1993

Importance of separation of a nonlinear dynamical system into nonlinear static part and linear dynamical part was insisted in designing a controller for the nonlinear system. We further proposed compensation techniques for oscillation of controlled variables caused by system time delay and compensation of steady state errors caused by modelling errors of the systems. The proposed principle of designing procedure and the compensation methods were discussed by applying them for temperature and level control of an actual tanked water system.

• 한국전산유체공학회지
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• 제16권1호
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• pp.48-52
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• 2011

Aerodynamic analysis was done for a fuselage and wing configuration of a mid-sized aircraft using unsteady 3-dimensional Navier-Stokes solver. Various turbulent models including a transitional SST were used to observe a dynamic stall as well as cruise characteristics. Also, different mesh moving methods were evaluated. Flow hysteresis which causes dynamic stall was investigated through flow field investigations.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제45회 KOSCO SYMPOSIUM 초록집
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• pp.53-54
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• 2012

In an IGCC plant, one of the most important issues on fuel flexibility in the lean premixed combustor is combustion instabilities. They are characterized by large amplitude pressure oscillations which are caused by unsteady heat release from the flames. The relationship between the unsteady heat release and flow oscillation can be qualitatively and quantitatively explained by flame transfer function. This paper introduces combustion instability modeling methods based on the flame transfer function approach.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.37-39
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• 2010

Aerodynamic analysis was done for a fuselage and wing configuration of a mid-sized aircraft using 3-dimensional Navier-Stokes solver. Various turbulent models including a transitional SST were implemented to observe a dynamic stall as well as cruise characteristics. Also, different mesh moving methods were evaluated. Flow hysteresis which causes dynamic stall was investigated through flow field investigations.

• 한국광학회:학술대회논문집
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• 한국광학회 2001년도 제12회 정기총회 및 01년도 동계학술발표회
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• pp.222-223
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• 2001

Optical parametric oscillator(OPO) has been used to generate coherent and tunable laser source with birefringent phase-matching technique in various nonlinear materials. In birefringent phase-matching, the output wavelength is controlled with angle or temperature tuning of the refractive index. However these tuning methods have several limitations such as restriction of tuning wavelength due to reasonable angular and temperature tuning ranges, Poynting vector walk-off which limits the interaction length, and thermal stabilization time. (omitted)

• 대한기계학회논문집A
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• 제21권8호
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• pp.1218-1228
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• 1997

The move limit strategy is used to avoid the excessive approximation in the structural optimization. The size of move limit has been obtained by engineering experience. Recently, efforts based on analytic methods are performed by some researchers. These methods still have problems, such as prematurity or oscillation of the move limit size. The existing methods usually control the bound of design variables based on the magnitude. Thus, they can not properly handle the configuration variables based on the geometry in the configuration optimization. In this research, the size of move limit is calculated based on the accuracy of approximation. The method is coded and applied to the two-point reciprocal quadratic approximation method. The efficiency is evaluated through examples.

• 한국습지학회지
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• 제13권3호
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• pp.499-514
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• 2011

전통적 수문빈도분석의 기본가정은 기후와 수문사상이 정상성이라는 것으로 즉, 분포형의 매개변수들이 시간에 따라 불변이라는 것이다. 댐, 제방, 운하, 교량 등 수공 관련 기간시설물을 계획하고 설계할 때는 과거 상황을 이해하고 미래에도 그 상황이 유지될 것이라는 것을 근거로 한다. 그러나 현실은 기본가정과는 달리 수문자료들은 비정상성을 지니고 있으며 수자원관리자들에 의해 항상 기간시설물을 계획하고 설계 할 때 비정상성을 다루고자 끊임없이 노력해 왔다. 본 논문에서는 비정상성 수문빈도분석기법을 소개하고, 조건부 Generalized Extreme Value(GEV) 분포를 이용하여 비정상성 빈도분석을 실시하였다. 본 논문에서는 6개 기상관측소지점의 24시간 연최고치 강우량을 대상으로 비정상성 빈도분석을 실시하였으며 최우도법(Maximum Likelihood)을 사용하여 GEV 분포형의 매개변수를 추정하였다. 그 결과 비정상성 GEV 분포가 확률 강우량을 산정하는데 있어 적합함을 확인 할 수 있었다. 또한 ENSO(El Nino Southern Oscillation)를 나타내는 지수인 SOI(Southern Oscillation Index)를 이용하여 기후변동 고려한 비정상성 빈도분석을 실시하였다.