• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.10
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• pp.2060-2066
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• 2002

The closed-loop state and input observer is a pole-placement type observer and estimates unknown state and input variables simultaneously. Pole-placement type observers may have poor transient performance with respect to ill-conditioning factors such as unknown initial estimates, round-off error, etc. For the robust transient performance, the effects of these ill-conditioning factors must be minimized in designing observers. In this paper, the transient performance of the closed-loop state and input observer is investigated quantitatively by considering the error bounds due to ill-conditioning factors. The performance indices are selected from these error bounds and are related to the observer robustness with respect to the ill -conditioning factors. The closed-loop state and input observer with small performance indices is considered as a well-conditioned observer from the transient perspective.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05a
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• pp.88-93
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• 1996

The initial condition should be consistent with real reactor core state for the simulation of the core transient. The initial xenon distribution, which cad not be measured in the core, has a significant effect on the transient with xenon dynamics of PWR. In the simulation of the transient stating from non-equilibrium xenon state, the accurate initialization of the non-equilibrium xenon distribution is essential to predict the core transient behavior. In this study, the xenon initialization method to predict the core transient more accurately was developed through the first-order perturbation theory of the relationship between simulated power and measured power distribution and verified by the application of the simulation for a startup test of Yonggwang Unit 3.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05b
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• pp.526-531
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• 1997

기존의 발전소 피로수명 평가 프로그램들은 On-Line Fatigue Analysis애 중점을 두고 개발되어 운전 초기부터 Transient모니터링 프로그램이 설치되는 시점까지의 Transient 데이터가 확보되지 않은 오래된 발전소의 경우 전 수명기간 동안의 피로수명 계산에 어려움이 많다. 따라서 본 연구에서는 특별한 경우를 제외하고는 Off-Line 계산을 하는 것이 경제적이고 피로수명 평가에 문제가 되지 않는다고 판단하여 Transient 모니터링을 용해 Transient 종류를 파악하고 이를 데이터베이스화 한뒤 충분한 시간을 가지고 Transient 이력 과 응력데이타를 조합하여 CUF를 계산하는 등 프로그램 기능의 모듈화를 시도하여 필요한 기능을 지속적으로 보완 개발해 나갈 수 있도록 하였다. 본 Software는 국내 원전이 Transient Counting이나 피로분석의 전산화와 관련한 경험이 부족하고 또 외국 프로그램을 도입하여 사용하기에는 과거 데이터가 부족하여 활용에 어려움이 많을 것을 고려하여 기존의 수작업에 의한 Fatigue Evaluation 의 불편함을 보완하고 On-Line Analysis의 필요성과 Off-Line Analysis외 경제성을 적절히 조합하여 현재 발전소 환경에서 가장 적절히 사용할 수 있도록 개발 을 추진하였고 향후 필요한 기능은 지속적으로 보완함으로써 발전소 수명관리에 유용하게 사용될 것이다.

• Korean Journal of Optics and Photonics
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• v.2 no.4
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• pp.209-213
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• 1991

Recently, the developments in generating and amplifying ultrashort optical pulses $(ps=10^{-12}s or fs=10^{-15}s)$ have imposed on great advances in the time-resolved laser spectroscopy. Especially, the transient absorption spectroscopy has a wide application range and the main idea of this technique is pump & probe method. After the pump pulse makes the material an excited or a transient states, the probe pulse is sent through the material to measure the absorbance change due to the transient states. Here, if the absorbance change was measured by the time delay between pump & probe pulses, the dynamic information of the excited or the transient states (the transient abnsorption changes by time & wavelength) can be obtained. At our laboratory, the ultrashort optic1 pulse (

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.4
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• pp.495-507
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• 1998

The transient characteristics of a 4.0㎾ inverter driven heat pump was investigated by theoretical and experimental studies. The heat pump used in this study consists of a high side scroll compressor and $\Phi$7 compact heat exchangers with two capillary tubes. A series of tests was peformed to examine the transient characteristics of heat pump in heating and cooling mode when the operating speed was varied from 30Hz to 102Hz. One of the major issues that has not been addressed so far is transient characteristics during speed modulation. A cycle simulation model has been developed to predict the cycle performance under frequency rise-up conditions, and the results of theoretical study were compared with the results of experimental study. The theoretical model was driven from mass conservation and energy conservation equations to predict the operation points of refrigerant cycle and the performances at various operating speeds. For transient conditions, the simulated results are in good agreement with the experimental results within 10%. The transient cycle migration of the liquid state refrigerant causes a significant dynamic change in system. Thus, the migration of refrigerant is the most important factor whenever An experimental analysis is performed or A simulation model is developed.

• New & Renewable Energy
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• v.4 no.4
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• pp.72-79
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• 2008

A numerical and experimental studies are carried out to investigate the transient heat transfer characteristics of 5kWth dish type solar air receiver. Measured solar radiation and temperatures at several different locations are used as boundary conditions for numerical a. Many parameters' effects (reflectivity of the reflector, the thermal conductivity of the receiver body, transmissivity of the quartz window, etc.) on the thermal performance are investigated. Discrete Transfer Method is used to calculate the radiation heat exchange in the receiver. A transient heat transfer model is developed and the rate of radiation, convection and conduction heat transfer are calculated. Comparing of the experimental and the numerical results, results of both are in good agreement. Using the numerical model, the transient heat transfer characteristics of volumetric air receiver for dish type solar thermal systems are known and the transient thermal performance of the receiver can be estimated.

• Journal of IKEEE
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• v.24 no.2
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• pp.598-603
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• 2020

In this paper present a Low Drop-Out(LDO) regulator that improves load transient characteristics due to the push-pull pass transistor structure is proposed. Improved load over the existing LDO regulator by improving the overshoot and undershoot entering the voltage line by adding the proposed push-pull circuit between the output stage of the error amplifier inside the LDO regulator and the gate stage of the pass transistor and the push-pull circuit at the output stage. It has a delta voltage value of transient characteristics. The proposed LDO structure was analyzed in Samsung 0.13um process using Cadence's Virtuoso, Spectre simulator.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.8
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• pp.998-1004
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• 2007

Connecting a synchronous generator to a power system is a dynamic process, requiring the coordinated operation of many components and systems. The goal is to connect the oncoming generator to the system smoothly i.e without causing any significant bumps, surges, or power swings, by closing the ACB when the oncoming generator matches the power system in voltage magnitude, phase angle, and frequency. If oncoming generator voltage is not matched to the power system voltage, reactive power will flow either into or out of the system at the instant of ACB closure. If this voltage difference is too great, the reactive power flow may result in high transient stresses that could damage the windings of the generator. Also, if oncoming generator frequency is not matched to the power system frequency, transient power will flow between generator and power system. If the frequency difference is too great, the transient power flow is reflected into the prime mover shaft, and this may result in excessive shaft or coupling stress. This paper tries to prove the necessity of correct synchronization for ship generators through a transient phenomenon analysis.

• Journal of Aerospace System Engineering
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• v.9 no.1
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• pp.12-18
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• 2015

The inter-conversion between different control laws in flight has a lot of risk. The SWM(Switching Mechanism) including logic and stand-by mode is designed to analyze the transient response of aircraft during inter-conversion between different control laws, based on the in-house software for non-real-time and real-time simulation. The SWM applies the fader logic of TFS(Transient Free Switch) to minimize the transient response of an aircraft during the inter-conversion, and applies the reset '0' type of the stand-by mode to prevent surface saturation due to integrator effect in the disengaged flight control law. The transition time is also important to minimize the objectionable transient response in the inter-conversion, as well as the transition control law design. This paper addresses the results of non-real-time simulation for the characteristics of transient response to different transition time to select the adequate transient time, and the real-time pilot evaluation, using SSWM(Software Switching Mechanism) and HSWM(Hardware Switching Mechanism), which is met for Level 1 flying qualities and assures safety of flight.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.6
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• pp.731-736
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• 2013

Most of faults occurring in transmission lines are transient faults. For such faults, automatic reclosing is economic and effective method to improve the reliability and transient stability of power system. Many countries apply various reclosing schemes considering issues of their own systems such as transient stability, rate of success. Currently, different reclosing schemes are applied in Korean transmission systems according to a rated voltage. In this paper, we conduct an evaluation of reclosing schemes in Korean transmission systems considering transient stability. Computer simulations are performed by using ElectroMagnetic Transient Program (EMTP) and transmission system is modeled based on actual data of Korea.