• Title/Summary/Keyword: Transients

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PKC-Independent Stimulation of Cardiac $Na^+/Ca^{2+}$ Exchanger by Staurosporine

  • Kang, Tong-Mook
    • The Korean Journal of Physiology and Pharmacology
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    • v.12 no.5
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    • pp.259-265
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    • 2008
  • $[Ca^{2+}]_i$ transients by reverse mode of cardiac $Na^+/Ca^{2+}$ exchanger (NCX1) were recorded in fura-2 loaded BHK cells with stable expression of NCX1. Repeated stimulation of reverse NCX1 produced a long-lasting decrease of $Ca^{2+}$ transients ('rundown'). Rundown of NCX1 was independent of membrane $PIP_2$ depletion. Although the activation of protein kinase C (PKC) was observed during the $Ca^{2+}$ transients, neither a selective PKC inhibitor (calphostin C) nor a PKC activator (PMA) changed the degrees of rundown. By comparison, a non-specific PKC inhibitor, staurosporine (STS), reversed rundown in a dose-dependent and reversible manner. The action of STS was unaffected by pretreatment of the cells with calphostin C, PMA, or forskolin. Taken together, the results suggest that the stimulation of reverse NCX1 by STS is independent of PKC and/or PKA inhibition.

Studies of Switching Transients and Power Quality Improvement in Microgrid PCC Switch (마이크로그리드 계통연계 스위치의 스위칭 과도상태 해석과 전력품질 향상을 위한 연구)

  • Jyung, Tae-Young;Baek, Young-Sik
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.11
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    • pp.2142-2148
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    • 2009
  • A microgrid is defined as two or more distributed generation or storage assets configured in a networks and capable of operation in parallel or independently form a larger electric gird, while providing continuous power to one or more end users. And when microgrid are separated from grid oprating protection devices by faults of the grid side, microsources should charge electrical power needs of loads in microgrid and operate maintaining power quality. The magnitude of the switching transients will vary based on voltage phase difference between microgrid and grid, when the microgrid is resynchronized to grid. In this paper, when microgrid is resynchronized to grid, we analyzed the existing problems for reducing switching transients of SS(Static Switch).

Dynamic Behavior of Oxide and Nitride LMR Cores during Unprotected Transients

  • Na, Byung-Chan;Dohee Hahn
    • Proceedings of the Korean Nuclear Society Conference
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    • 1997.05a
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    • pp.489-494
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    • 1997
  • A comparative transient analyses were performed for oxide and nitride cores or a large (3000 MWt), pool-type, liquid-metal-cooled reactor (LMR). The study was focused on three representative accident initiators with failure to scram : the unprotected loss-of-flow (ULOF), the unprotected transient overpower (UTOP), and the unprotected fast transient overpower (UFTOP). The margins to fuel melting and sodium boiling have been evaluated for these representative transients. The results show that there is an increase in safety margin with nitride core which maintains the physical dimensions of the oxide core.

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Time domain Reduction Method for Electromagnetic Transients Study: Equivalent Driving-Point Impedance Model using Prony Analysis (과도현상 해석을 위한 시간 영역에서의 등가축약법 :프로니 해석기법을 이용한 등가 구동점 임피던스 모델의 구성)

  • 홍준희;박종근
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.43 no.4
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    • pp.687-690
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    • 1994
  • This paper presents a method of obtaining transmission network equivalents from the network's response to the pulse excitation signal. Proposed method is base on Prony signal analysis and jtransfer function identification technique. As a result Thevenin-type of discrete-time filter model can be generated. It can reproduce the driving point impedance characteristic of the network.

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Study on the Shifting Transients by Interfacing ECU with Simulation Program (자동변속장치 ECU와 프로그램의 Interface에 의한 변속과도특성 연구)

  • 조한상;박영일
    • Journal of the Korean Society of Safety
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    • v.10 no.3
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    • pp.21-29
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    • 1995
  • The automotive transmission is the principal component of the power transmission system which converts the engine power into the adjustable power for the vehicle driving system. To the unskilled driver the automization of transmission is required for the safety and fuel economy. In this study, the dynamic model of the automotive power transmission system was presented and simulation program and interface board which interface IBM-PC with ECU was devloped. Through the traveling simulation by interfacing ECU with simulation program, the shifting transients are investigated. For verification of simulation experiment was carried out, the results of simulation was agreed well with those of simulation.

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Phenomenon of Power Interference and Screening Factor (전력유도 현상과 차폐계수)

  • 황종선;김영민;이경욱;김재준
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2001.11a
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    • pp.621-624
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    • 2001
  • A metal sheath provides a cable with electrostatic screening and a degree of magnetic screening. The presence of a screen on a cable also reduces the induction arising from the high-frequency components of transients caused by power-line switching and also induced transients from lightning strokes; such transient induced voltages are of increasing importance with the increasing use of miniaturized telecommunication equipment with very small thermal capacity. This paper describes electrostatic induction and electromagnetic induction caused by power interference. Also screening factors are proposed.

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Simulation of the Magnetic Pulse Compression Modulator using Electromagnetic Transients Program (자기압축회로의 EMTP 시뮬레이션)

  • Choi, Young-Wook
    • Proceedings of the KIEE Conference
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    • 2005.07c
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    • pp.2182-2183
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    • 2005
  • A pulse generator of one stage magnetic pulse compression modulator was simulated by electromagnetic transients program (EMTP). The pulse generator was expected to generate ${\sim}80kV$ peak voltage, ${\sim}140ns$ pulse width and about $70{\sim}75%$ energy delivery efficiency from initial charge capacitor $(0.2{\mu}F)$ to dummy load $(25{\Omega})$. From this simulation, the scheme of pulse circuit could be estimated as a practically reasonable design.

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Analysis on the Effect of Filter to Mitigate Transient Overvoltage on the High Voltage Induction Motor Fed by Multi Level Inverter using EMTP (EMTP를 이용한 멀티레벨 인버터 구동 고압유도전동기에서 발생하는 과도과전압 저감필터의 효과분석)

  • Kwon, Young-Mok;Kim, Jae-Chul
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.20 no.10
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    • pp.82-93
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    • 2006
  • In this paper, filters are designed to reduce transients overvoltage in inverter fed high-voltage large-capacity induction motor drive system. Design issues for a LCR filter at the inverter output terminals to reduce the dv/dt of the inverter output pulse and a RC filter at the induction motor input terminals to match the characteristic impedance between cable and induction motor are examined in detail. These filters are modeled to be suitable to high-voltage large-capacity induction motor. The performance of the filter is evaluated through simulation using EMTP(ElectroMagnetic Transients Program). We presented filters that used high voltage large-capacity induction Motor on the basis of this. Effect of the filter is analyzed for variation of the cable length. Characteristics of filters are analyzed to reduce harmonic in voltage waveform of induction motor input terminal. The switching surge voltage became the major cause to occur the insulation failure by serious voltage stress in the stator winding of induction motor. Filter for to mitigate transients overvoltage presents a required component in drive system of high-voltage large-capacity induction motor. Also, proposed filters are proved through simulation using EMTP.

Effects of Chrysosplenol C on Intracellular $Ca^{2+}$ Transient in Isolated Rat Ventricular Myocytes (Chrysosplenol C가 분리한 백서 심실 근세포 $Ca^{2+}$ Transient에 미치는 효과)

  • Jung, Suk-Han;Huong, Do Thi Thu;Sung, Tran Van;Cuong, Nguyen Manh;Kim, Young-Ho;Woo, Sun-Hee
    • YAKHAK HOEJI
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    • v.55 no.2
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    • pp.168-171
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    • 2011
  • Chrysosplenol C [5,6-dihydroxy-2-(4-hydroxy-3-methoxyphenyl)-3,7-dimethoxychromen-4-one] is a flavonoid found in Miliusa balansae and Pterocaulon sphacelatum. We have recently shown that chrysosplenol C has positive inotropic effect in isolated rat ventricular myocytes. In the present study, we explored a possible mechanism for the positive inotropic effect of chrysosplenol C by examining intracellular $Ca^{2+}$ transients during action potentials. The intracellular $Ca^{2+}$ transients were measured by confocal $Ca^{2+}$ imaging in field-stimulated single rat ventricular myocytes. Chrysosplenol C (50 ${\mu}M$) significantly increased the magnitudes (${\Delta}F/F_0$) of $Ca^{2+}$ transients (control, $1.08{\pm}0.05$; chrysosplenol C, $1.25{\pm}0.03$; n=8, P<0.01). Half decay time of the action potential-induced $Ca^{2+}$ transient was not altered by chrysosplenol C (50 ${\mu}M$) (control, $154{\pm}6$ ms; chrysosplenol C, $167{\pm}11$ ms; n=21). The $Ca^{2+}$ content in the sarcoplasmic reticulum (SR), measured as caffeine (10 mM)-induced $Ca^{2+}$ transient, was significantly decreased by chrysosplenol C (50 ${\mu}M$). These results indicate that chrysosplenol C increases $Ca^{2+}$ transients without altering $Ca^{2+}$ removal kinetics in ventricular myocytes, providing a possible mechanism for its positive inotropic effect.

Artificial neural network for predicting nuclear power plant dynamic behaviors

  • El-Sefy, M.;Yosri, A.;El-Dakhakhni, W.;Nagasaki, S.;Wiebe, L.
    • Nuclear Engineering and Technology
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    • v.53 no.10
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    • pp.3275-3285
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    • 2021
  • A Nuclear Power Plant (NPP) is a complex dynamic system-of-systems with highly nonlinear behaviors. In order to control the plant operation under both normal and abnormal conditions, the different systems in NPPs (e.g., the reactor core components, primary and secondary coolant systems) are usually monitored continuously, resulting in very large amounts of data. This situation makes it possible to integrate relevant qualitative and quantitative knowledge with artificial intelligence techniques to provide faster and more accurate behavior predictions, leading to more rapid decisions, based on actual NPP operation data. Data-driven models (DDM) rely on artificial intelligence to learn autonomously based on patterns in data, and they represent alternatives to physics-based models that typically require significant computational resources and might not fully represent the actual operation conditions of an NPP. In this study, a feed-forward backpropagation artificial neural network (ANN) model was trained to simulate the interaction between the reactor core and the primary and secondary coolant systems in a pressurized water reactor. The transients used for model training included perturbations in reactivity, steam valve coefficient, reactor core inlet temperature, and steam generator inlet temperature. Uncertainties of the plant physical parameters and operating conditions were also incorporated in these transients. Eight training functions were adopted during the training stage to develop the most efficient network. The developed ANN model predictions were subsequently tested successfully considering different new transients. Overall, through prompt prediction of NPP behavior under different transients, the study aims at demonstrating the potential of artificial intelligence to empower rapid emergency response planning and risk mitigation strategies.