• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.318-321
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• 1991

For measuring the transient electromagnetic fields and related quantities created by disconnector operations in GIS, one needs the wide bandwidth sensors with simple transfer functions. This paper describes a new developed electric field sensor to measure the very fast transient electric fields and voltages, and the measuring principle, design and construction of planar electric field sensor are described. A calibration and/or correction technique of the sensor is investigated which enables an accurate determination of the sensor response to the time-changing electric fields. As a consequence, the low voltage calibrations certify that a rise time of 1.7 [ns] is achieved for the planar electric field sensor and a total bandwidth extending from several Hz to 200 MHz for the measuring system which presents the constant division ratio as a function of frequency.

• 한국자동차공학회논문집
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• 제11권3호
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• pp.20-27
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• 2003

In this paper, the fuel transport characteristics during transient condition was studied by using a Fast Response Flame Ionization Detector(FRFID). The quantitative measurement method for the inducted fuel mass into cylinder is studied. The inducted fuel mass into the cylinder was estimated by using calculated air-fuel ratio by hydrocarbon concentration of cylinder and air flow model. In order to estimate the transportation of injected fuel from the intake port into cylinder, the wall wetting fuel model was used. The two coefficient $\alpha$,$\beta$) of the wall-wetting fuel model was determined from the measured fuel mass that was inducted into the cylinder at the first cycle after injection cut-off To reduce an air/fuel ratio fluctuation during rapid throttle opening, the appropriate fuel injection rate was obtain from the wall wetting model with empirical coefficients. Result of air/fuel ratio control, air/fuel excursion was reduced.

• 전기학회논문지
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• 제64권7호
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• pp.971-977
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• 2015

The electric propulsion system requires more reliability and safety than the conventional propulsion system because any sudden changes of electric system would bring tremendous effects on the ship's safety and propulsion. So it is very important to consider the potential transient effects. This paper discusses one of the worst electric accident. That is, one or two of generators are out of service in normal seagoing condition. And the appropriate measures are simulated in order to prevent the frequency decline that can bring the other generator's tripping. In addition, the relation between the transient effects and the major factors(inertia of generator/motors, governor's drooping characteristic and response speed) are also identified using the ETAP software.

• 조명전기설비학회논문지
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• 제27권2호
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• pp.54-61
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• 2013

This paper presents transient response behavior and frequency-dependent ground impedance of a single carbon ground electrode. The ground impedance of the carbon ground electrode was measured as a function of frequency of injected currents and simulated by using the distributed parameter circuit model with due regard to the frequency-dependent soil parameters, and the transient response behavior of the carbon ground electrode against impulse currents were investigated. As a consequence, the frequency-dependent ground impedance of the carbon ground electrode showed the capacitive behavior, that is, the ground impedance decreases with increasing the frequency of injected currents and lowers at the fast front time of impulse current. It was found that the carbon ground electrode is effective in grounding system for lightning protection. The ground impedance simulated with due regard to the frequency-dependent soil parameters was in good agreement with the measured data. The adequacy of the simulation technique and the distributed parameter circuit model for the carbon ground electrode was verified. It is expected that the simulation methodology, which analyzes the frequency-dependent ground impedance of the carbon ground electrode proposed in this work, can be used in the design of a grounding system for protection against lightning.

• 한국자동차공학회논문집
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• 제6권2호
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• pp.212-219
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• 1998

Unburned hydrocarbon is a key contributor to both the fuel economy and emissions of automotive engine. Cyclic variation of HC emission is of importance, especially during throttle transients. The real time measurement of hydrocarbon is particularly important to obtain a better understanding of the mechanisms for combustion and emissions, especially during cold start and throttle transient condition. This paper reports the cycle resolved measurement technique of unburned hydrocarbons to quantify rapid changes of in-cylinder concentration in the vicinity of spark plug by using the Fast Response Flame Ionization Detector(FRFID). While this instrument actually measures fuel concentration, its results can be indicative of the AFR behaviour. In order to understand the rapid change of hydrocarbons with cylinder pressure, it is necessary to study the response time delay of the system, including the time associated with gas transportation to FID. And signal from FRFID is correlated with cylinder pressure data to relate changes in mixture preparation to the classic analysis, such as indicated mean effective(IMEF) and ignition delay, etc.

• Nuclear Engineering and Technology
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• 제47권3호
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• pp.227-239
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• 2015

The thermal, mechanical, and neutronic performance of the metal alloy fast reactor fuel design complements the safety advantages of the liquid metal cooling and the pool-type primary system. Together, these features provide large safety margins in both normal operating modes and for a wide range of postulated accidents. In particular, they maximize the measures of safety associated with inherent reactor response to unprotected, doublefault accidents, and to minimize risk to the public and plant investment. High thermal conductivity and high gap conductance play the most significant role in safety advantages of the metallic fuel, resulting in a flatter radial temperature profile within the pin and much lower normal operation and transient temperatures in comparison to oxide fuel. Despite the big difference in melting point, both oxide and metal fuels have a relatively similar margin to melting during postulated accidents. When the metal fuel cladding fails, it typically occurs below the coolant boiling point and the damaged fuel pins remain coolable. Metal fuel is compatible with sodium coolant, eliminating the potential of energetic fuel-coolant reactions and flow blockages. All these, and the low retained heat leading to a longer grace period for operator action, are significant contributing factors to the inherently benign response of metallic fuel to postulated accidents. This paper summarizes the past analytical and experimental results obtained in past sodium-cooled fast reactor safety programs in the United States, and presents an overview of fuel safety performance as observed in laboratory and in-pile tests.

• Journal of Electrical Engineering and Technology
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• 제6권4호
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• pp.474-483
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• 2011

Solid-state fault current limiters (SSFCL) in power systems are alternative devices to limit prospective short circuit currents from reaching lower levels. Fault current limiters (FCL) can be classified into two categories: R-type (resistive) FCLs and L-type (inductive) FCLs. L-type FCL uses an inductor to limit fault level and is more efficient in suppressing voltage drop during a fault. In contrast, R-type FCL is constructed with a resistance and is more effective in consuming the acceleration energy of generators during a fault. Both functions enhance the transient stability of the power system. In the present paper, a novel SSFCL is proposed to enhance power system transient stability and power quality. The proposed SSFCL uses both functions of an L-type and R-type FCL. SSFCL consists of four diodes, one self-turn-off IGCT, a current-limiting by-pass inductor (L), and a variable resistance parallel with an inductor for improvement of power system stability and prevention of over-voltage across SSFCL. The main advantages of the proposed SSFCL are the simplicity of its structure and control, low steady-state impedance, fast response, and the existence of R-type and Ltype impedances during the fault, all of which improve power system stability and power quality. Simulations are accomplished in PSCAD/EMTDC.

• The Korean Journal of Physiology and Pharmacology
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• 제9권6호
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• pp.347-352
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• 2005

The effects of nitric oxide (NO) on inhibitory neurotransmitter receptors and some types of inhibitory receptors in dissociated rod bipolar cell (RBC) were investigated. In the whole cell voltage-clamping mode, the gamma-aminobutyric acid (GABA) activated current showed both sustained and transient components. GABA activated transient current was fully blocked by bicuculine, a $GABA_A$ receptor antagonist. The cis-4-aminocrotonic acid (CACA), a $GABA_C$ receptor agonist, evoked the sustained current that was not blocked by bicuculline (BIC). Glycine activated the transient current. These results indicate that the RBCs possess $GABA_A$, $GABA_C$, and glycine inhibitory receptors. Sodium nitroprusside (SNP), a NO analogue, reduced the currents activated by $GABA_A$ receptor only, however, did not reduce the currents activated by either $GABA_C$ or glycine receptors. This study signifies further that only NO depresses the fast inhibitory response activated by $GABA_A$ receptor in RBC. We, therefore, postulate that NO might depress the light-on/off transient inhibitory responses in RBCs in the rat retina.

• 융합신호처리학회논문지
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• 제14권4호
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• pp.222-230
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• 2013

망막 쌍극세포는 광자극에 대하여 완만한 전위응답을 하며, 막전위에 의존하여 전달물질(glutamine 산)을 방출한다. 본 논문에서는 ON형 쌍극세포의 시냅스 앞단에서 전달물질 방출 기구에 관한 여러 가지의 생리학적 정보를 수식적 모델로 통합하였다. 전달물질 방출의 빠른 성분과 느린 성분의 공급원을 병렬로 배치한 본 모델은 전달물질 방출의 막전위 및 세포 내 $Ca^{2+}$ 농도 의존성을 충실하게 재현할 수가 있었다. 또한 전달물질의 빠른 방출 성분은 사다리꼴 모양의 막전위 의존성을 나타내는 데에 반하여, 느린 방출 성분은 종모양의 막전위 의존성을 나타내기 때문에 세포 내의 $Ca^{2+}$ 농도 상승을 $Ca^{2+}$ 완충제로 억제하여 느린 방출 성분이 감소되고, 전달 물질 방출의 막전위 의존성이 사다리꼴 모양의 특성이 되는 것을 확인하였다. 그리고 ON 형 쌍극세포의 광응답에서 일시적 성분과 지속적 성분에 의하여 발생하는 전달물질 방출을 시뮬레이션한 결과 광응답의 시작은 전달물질을 빠르게 방출하게 하였으며, 광응답의 일시적 성분과 초기의 지속적 성분은 전달물질을 느리게 방출하도록 하였다. 또한 광응답의 후기 지속적 성분은 저장 pool로부터 보충된 시냅스 소포에 의하여 지속적인 방출이 발생하기 때문이라는 것을 확인하였다.

• 한국정보통신학회논문지
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• 제7권5호
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• pp.879-886
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• 2003

주파수 도약 대역확산시스템에서의 광대역 주파수 도약을 위해 주파수 합성기가 널리 이용된다. 따라서 본 논문에서는 효과적인 무선 디지털 데이터 전송 성능을 얻기 위한 FH-FSK 통신에 미치는 주파수 합성기의 영향을 분석하였다. 이를 위해 PLL의 성능을 좌우하는 위상 변화, 스퓨리어스의 발생, PLL의 과도응답 특성에 의해 영향을 받는 주파수 도약율 등 여러 가지 파라미터들에 따른 성능을 분석하였다. 전형적인 PLL을 사용한 주파수 도약 시스템에서는 주파수 도약을 위한 반송파 신호를 국부 발진기에서 만들어낸다. 반송파 간격이 협대역인 협대역 무선 통신 시스템일 경우에는 빠른 주파수 도약을 위한 PLL의 구현이 어렵다. 본 논문에서는 이런 문제점을 해결하기 위해 디지털 주파수 합성기/CPM 변조기를 사용하여 빠른 주파수 도약을 위한 PLL 구현이 가능함을 Matlab tool를 사용한 시뮬레이션 결과를 통해 분석할 수 있었다.