• 농업과학연구
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• 제38권3호
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• pp.493-504
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• 2011

This study was carried out to safety evaluation, the practical application and improvement of design method of the agricultural reservoir due to raising embankments. Also, it was to compare and analyze the pore water pressure (PWP), seepage (leakage) quantity and piping phenomenon according to high water table and rapid drawdown. The seepage analysis by finite element analysis was used for steady state and transient condition. The pore water pressure distribution for steady state and transient condition showed positive(+) PWP on the upstream slope, it was gradually changed negative(-) PWP on the downstream slope. The PWP in the core ranged from 100 ~ -33 kPa, the seepage line in the incline-type core suddenly decreased towards the lower levels from the higher levels. The PWP according to rapid drawdown is remained in the vicinity of the upstream slope, therefore, it is investigated to be in an unstable state by the slope stability analysis. The PWP after raising embankments showed smaller than in the before raising embankments. It was likely to be the piping phenomenon because the gradients in the before raising embankments showed largely at downstream slope, and the stability for piping in the after raising embankments increased stable state. The seepage quantity per 1 day and the leakage per 100m for the steady state and transient condition appeared to be safe against the piping. It reduced slightly regardless of the transient condition before the raising embankments and it decreased largely about 2.4 times in the early days after the raising embankments.

• Nuclear Engineering and Technology
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• 제27권6호
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• pp.853-858
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• 1995

노심 천 이 현상의 모사계산을 위해서는 노심상태 의 초기조건을 실제노심과 일치시켜야 하는데 특히, 제논동특성이 관심의 대상이 되는 천이현상에 있어서는 직접적인 추정이 불가능한 노심내 제논분포의 초기상태가 천이현상의 해석결과에 커다란 영향을 미치게 된다 초기상태의 노심이 정확히 제논 평형상태에 있지 않는 경우 노심의 시간에 따른 변화를 잘 예측하기 위해서는 비평형 제논분포를 모사하는 초기화가 필수적이다. 본 연구에서는 천이현상 이전에 관측된 비평형 제논진동을 등가 제논진동으로 모사하여 천이현상을 보다 정확히 예측할 수 있는 제논 초기화 기법을 개발하였으며 영광 3, 4호기 시운전 시험에서 입수된 실측자료를 통하여 그 적용성을 입증 하였다.

• 전기전자학회논문지
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• 제26권1호
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• pp.124-128
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• 2022

기존 LDO 레귤레이터 외부 커패시터는 오버슈트 및 언더슈트와 같은 과도 응답 특성을 줄일 수 있다. 그러나 본 연구에서 제안한 Capless LDO 레귤레이터는 과도 응답을 개선하고 우수한 전류 구동 능력을 제공하기 위해 패스 트랜지스터에 바디 기술을 적용하였다. 제안하는 LDO 레귤레이터의 동작 조건은 3.3V ~ 4.5V 범위의 입력 전압, 최대 부하 전류 200mA, 출력 전압 3V로 설정하였다. 측정 결과, 부하 전류가 100mA일 때 전압은 언더슈트 상태에서 95 mV, 오버슈트 상태에서 105 mV임을 확인 할 수 있었다.

• 전력전자학회논문지
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• 제27권4호
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• pp.339-347
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• 2022

This study proposes the mitigation method for overcurrent and oscillation motor current in an active short-circuit operation. This operation is attracting attention as the safe state of electric vehicle traction inverters. However, the active short-circuit operation generates oscillation and overcurrent of motor currents during a transient state. The proposed method uses two different safe states in PMSM, such as active short circuit and freewheeling. The active short circuit is used for safe state in a steady state. To reduce the overshoot and oscillation, a freewheeling state is injected between active short-circuit operation by comparing the motor phase current with an analytically calculated steady-state motor current. Freewheeling state is only used in a transient state. The performance is demonstrated through simulations and experimental results. The peak current of the motor was reduced from 52 A to 40 A, and oscillation time was reduced.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1999년도 전력전자학술대회 논문집
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• pp.139-142
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• 1999

Recently, the application of the linear machine for industrial field is remarkable increased, especially for the gantry machine and machine tool system. In these application, high precise position control performance is essentially required in steady/transient state. This paper presents the generalized PID position control algorithm which have rare sensitivity to mass and disturbance. Through the experimental results, it is shown that the proposed algorithm have good performance for the linear machine drives in the steady state and transient state in spite of the load mass varing.

• 한국전자통신학회논문지
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• 제12권4호
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• pp.575-584
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• 2017

제어시스템의 시간응답을 해석하기 위해 전기회로망을 제안한다. 전달함수와 상태방정식을 이용해 시스템의 시간응답을 계산함으로써 고전제어와 현대제어의 연계성을 분석한다. 상태천이방정식의 복잡한 적분과정을 생략하고, 상태천이행렬과 전달함수의 조합만으로도 시간응답의 해석이 가능함을 제시한다. 단위계단함수와 정현파입력에 따른 전압­전류의 출력응답을 표현하기 위해 프로그램을 코딩하였다. 단위계단입력에서는 과도응답을 해석하였으며, 정현파입력에서는 전압과 전류의 위상차를 해석하였다. 제안된 내용을 과도응답이나 상태공간에 기술함으로써 제어공학의 이해도와 설계능력을 높인다.

• 한국생산제조학회지
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• 제19권2호
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• pp.211-215
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• 2010

Continuous contraction and expansion of disk brake can be due to friction and temperature difference at repeated sudden braking. As serious vibration at disk is produced, the braking force will be changed ununiformly and braking system can not be stabilized. Temperature and heat flux at disk brake are investigated by structural and thermal analysis in this study. The maximum equivalent stress and displacement are shown respectively at the ventilated hole and the lower part of disk plate. At thermal analysis of initial state, temperature on disk plate is distributed from $95.9^{\circ}C$ to $100^{\circ}C$. The maximum heat flux of $0.0168W/mm^2$ is shown at the inner friction part between disk plate and pad. At thermal analysis of transient state, temperature on disk plate is distributed from $95^{\circ}C$ to $96.5^{\circ}C$ after 100 second. The maximum heat flux of $0.0024W/mm^2$ is also shown at the inner friction part between disk plate and pad. By comparing with initial state, the temperature on disk plate is more uniformly distributed and heat flux is more decreased by 7 times at transient state.

• 한국태양에너지학회 논문집
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• 제26권2호
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• pp.61-67
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• 2006

The use of the wind energy resource is a rapidly growing area world-wide. The number of installed units is continuously increasing, and therefore, it is important to respect and to deal with the impact of wind power generation system. From the view of an electric grid utility, there is a major problem with the impact of the wind system on the voltage of the electric grid, to which a turbine is connected. In this paper, it is investigated the voltage impact and transient state analysis on distribution line, with which wind power generation system is connected. Connections of wind power system usually occur to voltage drop due to reactive power absorption and sometime result in higher than nominal voltage.

• Journal of Electrical Engineering and Technology
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• 제10권1호
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• pp.83-91
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• 2015

This paper presents preventive and emergency control measures for on line transient stability (security) enhancement. For insecure operating state, generation rescheduling based on a real power generation shift factor (RPGSF) is proposed as a preventive control measure to bring the system back to secure operating state. For emergency operating state, two emergency control strategies namely generator shedding and load shedding have been developed. The proposed emergency control strategies are based on voltage magnitudes and rotor trajectories data available through Phasor Measurement Units (PMUs) installed in the systems. The effectiveness of the proposed approach has been investigated on IEEE-39 bus test system under different contingency and fault conditions and application results are presented.

• 대한화학회지
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• 제11권3호
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• pp.105-110
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• 1967

액체구조의 천이상태이론을 아산화질소($N_2O$)와 사산화질소($N_2O_4$)에 적용하여 이 액체들의 상태합을 유도하였다. 이상태합들을 써서 각 액체의 몰부피, 증기압, 증발엔트로피, 임계점에서의 성질 등, 여러가지 열역학적양들을 계산한 결과 모두 실험치와 좋은 일치를 얻었다.