• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권2호
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• pp.93-101
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• 2000

This paper presents a novel method for the transient of eddy currents in the dampers of a super-conducting synchronous generator(SCG). The method proposes a 2-D corrected model which takes into account the influence of leakage fluxes of the field winding ends by increasing the effective air gap in order to consider the high precision of the analysis for the conventional 2-D model. The electromagnetic fields for the corrected model are analyzed by the time-stepping finite element method, thus the eddy currents in the dampers and electro-motive forces(EMF) in the stator windings are calculated. As the results, it is proved the presented method is comparatively accurate by comparing measured phase EMF values and the simulation ones, where about 6.4% error at the maximum value of EMF is occurred between them.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 1995년도 춘계학술대회
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• pp.38-40
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• 1995

There have reports suggested that cerebral blood flow (CBF) has decreased in patients with both senile dementia of the Alzheimer's type and multi-infarct dementia, which are characterized by marked cognitive impairments. In addition, recent studies have demonstrated that decrease of CBF precedes the onset of multi-infarct dementia. These findings further suggest that chronic reduction of CBF may play an important role in the formation and progression of cerebral vascular dementia. Although transient cerebral ischemia, based upon vascular “reperfusion”, is apparently not paralleling the clinical condition, the transient cerebral ischemia model is one of the major methods investigated and the other is the cerebral embolism operation. Cognitive impairment and neuronal damages have been fully studied using these transient and/or embolic ischemia models. There are, however, few investigations focused the attention on the influence of chronic decrease of CBF on cognitive processes. In the present study, we have chosen a chronic ischemic model which is produced by permanent occlusion of bilateral common carotid arteries (2VO) in rats to investigate the neuronal damage and cognitive deficits through radial maze performance. We investigated furtherly the effects of tetramethylpyrazine (TMP), a constituent isolated from Ligusticum Chuanxiong on such a model.

• 대한전자공학회논문지
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• 제18권2호
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• pp.27-35
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• 1981

본 연구에서는 비정질 갈코게나이트박막의 스위칭과도 특성을 분석하기 위해 공체전하중를 모델에 의한 수식적 이론과 그 이론의 타부성에 따른 실험을 연하였다. 이론과 실험에 대한 분석적인 관찰을 실온에서 비정용 잘코게나이드박막에 전압펄스를 인가할 때 생기는 스위칭과도 특성에 대해 비교하였다. 결과로는 전자스위칭 특성에 대한 단순한 이론적 모델의 형태로 설명할 수 있다. 캐리어의 주입은 스위칭 특성을 유발시키기에 필요하며 주입된 캐리어들은 공간전하제한전류(SCLC)로서 전류 흐름에 기여한다. 그러므로 제안된 전하제어 스위칭 특성은 2중 주입 공간 전하중첩 모델로 해석할 수 있다.

• Nuclear Engineering and Technology
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• 제53권10호
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• pp.3196-3206
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• 2021

For the Korean design of the PCCS (passive containment cooling system) in an innovative PWR, the overall thermal resistance around a condenser tube is dominated by the heat transfer coefficient of steam condensation on the exterior surface. It has been reported, however, that the calculated heat transfer coefficients by thermal-hydraulic system codes were much lower than measured data in separate effect tests. In this study, a new empirical model of steam condensation in the presence of a noncondensable gas was implemented into the MARS-KS 1.4 code to replace the conventional Colburn-Hougen model. The selected correlation had been developed from condensation test data obtained at the JERICHO (JNU Experimental Rig for Investigation of Condensation Heat transfer On tube) facility, and considered the effect of the Grashof number for naturally circulating gas mixture and the curvature of the condenser tube. The modified MARS-KS code was applied to simulate the transient response of the containment equipped with the PCCS to the large-break loss-of-coolant accident. The heat removal performances of the PCCS and corresponding evolution of the containment pressure were compared to those calculated via the original model. Various thermal-hydraulic parameters associated with the natural circulation operation through the heat transport circuit were also investigated.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제45회 KOSCO SYMPOSIUM 초록집
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• pp.137-138
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• 2012

The two-equation soot model based on the transient laminar flamelet model is implemented for soot formation of laminar non-premixed $CH_4/Air$ flame with detailed chemical reaction mechanism and complex thermodynamic properties. The soot model represents nucleation, growth and oxidation with gas-phase chemistry. This represented unsteady flamelet soot model has been tested and compared using well verified reference calculation result obtained solving the Full Transport Equations method.

• Journal of Mechanical Science and Technology
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• 제14권7호
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• pp.796-806
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• 2000

To understand the transient behavior of droplets after impingement in a diesel engine, a numerical model for diesel sprays impinging on a flat wall is newly developed by the proposition of several mathematical formulae to determine the post-impingement characteristics of droplets. The new model consists of three representative regimes such as rebound, deposition and splash. The gas phase is modeled in terms of the Eulerian conservation equations, and the dispersed phase is calculated using a discrete droplet model. To validate the new model, the calculated results are compared with several experimental data. The results show that the new model is generally in good agreement with the experimental data. Therefore, it is thought that the new model is acceptable for the prediction of transient behavior of wall sprays.

• Advances in Energy Research
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• 제3권3호
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• pp.133-142
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• 2015

A large wind farm can be simplified by the aggregated wind farm models for load flow, steady and transient stability studies. When a fault (such as a short circuit) happens in a large wind farm, some of wind turbines trip while others do not. This paper is to design a controller to modify the aggregated wind farm model in the case of one or more unit removed or added from the complete model. This is without stopping the simulation process during performing the steady state and transient analysis of the whole system. This controller can modulate the status of the wind turbines in the aggregated model in a given farm according to any change in this farm. By this controller, we save effort and time to change the status of wind turbines in the aggregated model. The proposed wind farm is composed of some smaller farms of permanent magnet synchronous generators (PMSGs) and others of squirrel cage induction generators (SCIGs).

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 D
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• pp.1127-1129
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• 1997

In this paper, we developed to artificial neural network for load characteristic identification of power system. We can acquire active power and reactive power of individual load depending on the variation of voltage and frequency from the experimentation of a dynamic characteristic of load. The data of the experimental results were be used in learning of ANN. A proposed ANN model is applied to analyze the transient stability. To demonstrate the propriety of the power system transient stability with load model using ANN, the simulation of the two-machine five-bus system is carried out.

• Structural Engineering and Mechanics
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• 제26권5호
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• pp.545-556
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• 2007

In this paper, a hybrid boundary element technique is implemented to analyze nonlinear transient pile soil interaction in Gibson type nonhomeogenous soil. Inelastic modeling of soil media is presented by introducing a rational approximation to the continuum with nonlinear interface springs along the piles. Modified $\ddot{O}$zdemir's nonlinear model is implemented and systems of equations are coupled at interfaces for piles and pile groups. Linear beam column finite elements are used to model the piles and the resulting governing equations are solved using an implicit integration scheme. By enforcing displacement equilibrium conditions at each time step, a system of equations is generated which yields the solution. A numerical example is performed to investigate the effects of nonlinearity on the pile soil interaction.

• 한국추진공학회지
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• 제10권4호
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• pp.19-25
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• 2006

STS 304 발열선과 $Zr-KCIO_4$ 기폭화약을 사용한 전기식 착화기에 대한 열전이 특성을 시험하고 Fitted Wire Model로 분석한 결과, 약 $300^{\circ}C$ 부근에서 기폭화약과 관련된 열전이 특성 파라미터가 급격하게 변화되었다. 이 현상은 기폭화약에 사용된 $KCIO_4$의 상변화로 인한 흡열반응에 의해 발생된 것으로 판단된다.