• 한국구조물진단유지관리공학회 논문집
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• 제11권2호
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• pp.164-174
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• 2007

댐에서 관로 시스템을 효과적으로 설계하기 위해서는 수격작용과 같은 과도수리현상을 해석해야 만 한다. 일반적으로 조압수조는 터빈의 부하변화에 의한 과도수리현상에 의해 발생되는 압력의 변화를 감소시키기 위해서 사용된다. 본 연구에서는 댐 안전관리를 위한 조압수조의 적정규모를 조사하였다. 지배방정식을 이용하여 조압수조 내 수위변동을 계산하였다. Thoma-Jaeger의 안정조건을 사용하여 홍수위, 상시만수위, 정격수위, 저수위인 경우에 정적안정조건과 동적안정조건을 검토하였다. 끝으로 조압수조의 수직갱과 수실의 적정 지름을 결정하였다.

• 한국전산구조공학회논문집
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• 제28권1호
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• pp.101-113
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• 2015

이 논문은 화재에 노출된 철근콘크리트 구조에 대한 수치해석 모델을 제시하고, 기존의 자료 및 설계 규준과의 비교를 통해 구조물의 설계 시 고려 사항에 대해 제안하고 있다. 수치해석은 비정상 열전달 해석과 비선형 구조해석의 두 단계로 수행되며, 비정상 열전달 해석을 통해서 얻어진 화재시간에 따른 단면 온도분포를 바탕으로 비선형 구조해석하여 부재의 상태에 대한 정보를 얻게 된다. 이때, 철근콘크리트의 재료모델을 화재진행상태(Under-Fire)와 화재종료 후 냉각상태(After-Cooling)로 나뉘어 해석수행하여 각각의 재료상태에 따른 거동의 변화를 살펴본다. 해석된 결과는 여러 구조물에 대해 기존의 실험결과와 비교하여 검증하고, 설계 규준과의 비교를 통해 화재 시 구조물의 안전성에 대해 고찰하였다.

• 한국초전도ㆍ저온공학회논문지
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• 제7권4호
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• pp.14-19
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• 2005

A transient numerical simulation was conducted to have variation of temperature on an element of resistive Superconducting Fault Current Limiter (SFCL) under quench condition. It is very important engineering information for an optimum design of cryogenic system for cooling of a resistive SFCL element. A bifilar coil for resistive SFCL for 10 MVA system was incorporated as a model in this numerical study. From the numerical simulation result, it was found that the averaged temperature on the shunt and Bi-2212 element at 500 kW, 100 ms was 711.1 K and 198.4 K respectively. The temperature variation with the change of the hot-spot size and time is also obtained. The maximum temperature was continuously increased in all cases until the hot-spot stops at 100ms and it was going down after then. Such as, the details of temperature distribution on the SFCL element obtained from this numerical study and it should be very valuable information on the decision of the cooling capacity of cryogenic system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
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• pp.631-632
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• 2006

This paper is written by research for the transient characteristics of the Single-phase Line-start permanent Magnet. The Single-phase Line-start permanent Magnet is most likely to substitute for Single-phase Induction Motor which is used about many appliance currently, because that has good points. For example, It has a Line-start of ability and a High-efficiency. And it need not power convergence device. The rotor of The Single-phase Line-start permanent Magnet has cage-bar with permanent magnet. This motor is started by cage-bar. When it entered synchronous condition, the rotor is rotated by the permanent magnet. But the design of the permanent magnet is very important, because the breaking torque of the permanent magnet interrupt to start a rotor. Finally, if Flux Barrier is not concerned, we do not get result of our object. Therefore this thesis is concerned about Flux Barrier.

• 한국전산유체공학회지
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• 제14권4호
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• pp.1-6
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• 2009

In the present study, numerical simulations were performed in a stirred solid/liquid system by using Eulerian multi-phase model. The transient flow field of liquid and distribution of solid particles were predicted in the stirred tank with pitched paddle impeller and baffles. The Frozen rotor method is adopted to consider the rotating motion of the impeller. The effects of number and width of baffles on the mixing time and the quality of solid suspension in the stirred tank are presented numerically. The result shows that the mixing time decreases as the width and number of baffles increase. The present numerical methodology can be applied to optimizing mixing condition of industrial mixer.

• Nuclear Engineering and Technology
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• 제33권3호
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• pp.339-348
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• 2001

NSSS Control Systems automatically mitigate transient conditions and leads to a stable plant condition without operator actions when a transient occurs during normal power operation. In this paper, the function and performance of NSSS control systems were examined and evaluated by comparing the predicted results with the measured data for the selected events. Loss of a Main Feedwater Pump and Load Rejection to House Load Operation events were selected for the evaluation among the transient tests peformed during the Power Ascension Test (PAT) of UCN unit 4. The overall schematic control actions of NSSS control systems can be evaluated easily through the observation of these two typical events. The selected events were analyzed by the KISPAC computer code[l] which had been used in developing the control logic and determining the control setpoints during the plant design. Additionally, the performance of FWCS during low power operation was evaluated. The result of evaluation showed that the NSSS control systems were designed properly and the performance of the NSSS control systems was excellent and also the computer code had a good prediction capability.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 C
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• pp.1056-1058
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• 1998

Voltage dips caused by transmission system faults are usually of a short duration. High speed relaying and breaker operation will typically limit the disturbance to 0.1 seconds. Most motor controllers obtain their control power directly from the bus by means of a control transformer. Under this condition, a voltage dip can cause the contactor to drop out. disconnecting the motor from the line. The rapid re-energizing of the controller is in effect a fast reclosure which may result in motor damage. The time delay re-energizing of controller will result in a greater loss of speed and possibly loss of stability. Other means of controller can be used to prevent the motor from being disconnected from line during the fault. This can be accomplished by DC power controller or mechanically latched controller. This paper demonstrates that DC power controller or mechanically latched type controller to prevent the motor from being disconnected from line during the fault is, the most effective in minimizing speed reduction, transient motor current, transient motor torque and transient shaft torque by EMTP calculation.

• Nuclear Engineering and Technology
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• 제35권2호
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• pp.144-153
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• 2003

The object of this paper is the probabilistic failure analysis on the cladding performance of WPF(Whole Pin Furnace) test fuel pins under transient conditions, and analysis of the KALIMER fuel pin using the preceding analysis. The cumulative damage estimation and Weibull probability estimation of WPF test are performed. The probabilistic method was adapted for these analyses to determine the effective thickness thinning due to eutectic penetration depth. In the results, it is difficult to assume that a brittle layer depth made by eutectic reaction is all of the thickness reduction due to cladding thinning. About 93% cladding thinning of the eutectic penetration depth is favorable as an effective thickness of cladding. And the unreliability of the KALIMER driver fuel pin under the same WPF test condition is lower than that of the WPF pin because of the higher plenum-fuel volume ratio and lower cladding inner radius vs. thickness ratio. KALIMER fuel pin developed from conceptual design has a more stable transient performance for a failure mechanism due to fission gas buildup than the WPF pin.

• Nuclear Engineering and Technology
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• 제51권1호
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• pp.116-124
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• 2019

$M^2LFR-1000$ is a medium-power modular lead-cooled fast reactor, developed by University of Science and Technology of China (USTC), aiming at achieving a reactor design fulfilling the Gen IV nuclear system requirements and meanwhile emphasizing the optimum safety and economics. In order to evaluate the safety performance of $M^2LFR-1000$ reactor core, three typical transients are selected from initiating events, which are unprotected transient overpower (UTOP), unprotected loss of offsite power (ULOHS+ULOF) and increase of feedwater flowrate with primary pumps trip (IFW+PLOF). These three transients presented and discussed in this paper are performed with the code Analysis of THermal-hydraulics of LEaks and Transients (ATHLET), which is developed by Gesellschaft $f{\ddot{u}}r$ Anlagen-und Reaktorsicherheit gGmbH (GRS). The results indicate that the $M^2LFR$ is safe enough under these three transients due to the good inherent safety features of the reactor, without human intervention, the reactor will reach a new steady state under UTOP condition.

• Journal of Welding and Joining
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• 제10권2호
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• pp.32-42
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• 1992

A method of optimization of process parameters in Arc Welding has been discussed in this paper. The method of investigation is based on the numerical calculation of weld bead by a finite element method and non-linear optimization technique is applied to estimated the optimization process parameters from the numerical calculation. The common package program(ANSYS 4.4A) was used to obtain the process parameters for a thin plate arc welding (TIG, CO$_{2}$). The results on some test are satisfactory and the used method of this paper is a useful guide to the optimum welding condition.