• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.122-122
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• 2010

A Static Induction Thyristor (SI-Thyristor) has a great potential as power semiconductor switch for pulsed power or high voltage applications with fast turn-on switching time and high switching stress endurance (di/dt, dV/dt). However, due to direct commutation between gate driver and SI-Thyristor, it is difficult to design optimal gate driver at the aspect of impedance matching for fast gate current driving into internal SI-Thyristor. Thus, to penetrate fast positive gate current into steady off state of the SI-Thyristor, it is proposed and proceeded the internal impedance calculation of the SI-Thyristor at steady off state with the gate driver while switching conditions that are indicated applied gate voltage, $V_{GK}$ and applied high voltage across anode and cathode, $V_{AK}$.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1997년도 추계학술발표회논문집(1)
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• pp.772-777
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• 1997

Previous MELCOR and SCDAP/RELAP5 nodalizations for simulating the counter-current, natural circulation behavior of vapor flow within the RCS hot legs and SG U-tubes when core damage progress can not be applied to the steady state and water-filled conditions during the initial period of accident progression because of the artificially high loss coefficients in the hot legs and SG U-tubes which were chosen from results of COMMIX calculation and the Westinghouse natural circulation experiments in a 1/7-scale facility for simulating steam natural circulation behavior in the vessel and in the hot leg and SG during the TMLB' scenrio. The objective of this study is to develop a natural circulation modeling which can be used both for the liquid flow condition at steady state and for the vapor flow condition at the later period of in-vessel core damage. For this, the drag forces resulting from the momentum exchange effects between the two vapor streams in the hot leg was modeled as a pressure drop by pump model. This hot leg natural circulation modeling of MELCOR was able to reproduce similar mass flow rates with those predicted by previous models.

• International Journal of Automotive Technology
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• 제7권3호
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• pp.369-375
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• 2006

This paper describes a simple proportional and integral control algorithm for a swirl motor controller and its application. The control algorithm may be complicated in order to have desired performance, such as low steady state errors, fast response time, and relatively low overshoot. At the same time, it should be compact so that it can be easily implemented on a low cost microcontroller, which has no floating-point calculation capability and low computing speed. These conflicting requirements are fulfilled by the proposed control algorithm which consists of a gain scheduling proportional controller and an anti-windup integral controller. The mechanical friction, which is caused by gears and a return spring, varies very nonlinearly according to the angular position of the system. This nonlinear static friction is overcome by the proportional controller, which has a two-dimensional look up gain table. It has error axis and angular position axis. The integral controller is designed not only to minimize the steady state error but also to avoid the windup effect, which may be caused by the saturation of a motor driver. The proposed control algorithm is verified by use of a commercial product to prove the feasibility of the algorithm.

• Advances in materials Research
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• 제9권1호
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• pp.15-32
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• 2020

In this article, an analytical solution is presented for the steady-state axisymmetric thermal stress distributions in a composite hollow cylinder. The cylinder is composed of two isotropic and anisotropic materials which is subjected to the thermal boundary conditions of convective as well as radiative heating and cooling on the inner and outer surfaces, respectively. The solution of the temperature is obtained by means of Bessel functions and the thermal stresses are developed using Potential functions of displacement. Numerical results are derived for a cylinder which is similar to a gas turbine combustor and showed that the maximum temperature and thermal stresses (radial, hoop, axial) occurred in the middle point of cylinder and the values of thermal stresses in anisotropic cylinder are more than the isotropic cylinder. It is worthy to note that the values of the thermal conditions which estimated in this research, not to be presented in any other papers but these values are very accurate in calculation.

• 한국인터넷방송통신학회논문지
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• 제21권1호
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• pp.115-120
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• 2021

본 논문에서는 비례공진 전류제어기 기반의 단상 영구자석 동기전동기의 운전 알고리즘을 제안하였다. 일반적으로 단상 영구자석 동기전동기의 경우 회전자의 형상에 따른 비대칭 공극이 발생할 수 있으며, 이는 고속 운전시 소음과 진동의 원인이 된다. 따라서 본 논문에서는 제어 안정성이 뛰어난 비례공진 전류제어기를 적용한 단상 영구자석 동기전동기의 운전 알고리즘을 제안하였다. 비례공진 전류제어기법은 정상상태 오차가 없고 왜란에 대해 비교적 강인한 특성을 가지고 있으며, 복잡한 연산과정 없이 교류입력의 정상상태를 제거할 수 있다. 제안한 알고리즘의 유효성과 타당성을 실험을 통해 검증하였다.

• Nuclear Engineering and Technology
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• 제53권7호
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• pp.2312-2322
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• 2021

In recent studies, the creep rate of Zircaloy-4, one of the basic property parameters of the nuclear fuel code, has been commonly used with the axial creep model proposed by Rosinger et al. However, in order to calculate the circumferential deformation of the fuel cladding, there is a limitation that a difference occurs depending on the anisotropic coefficients used in deriving the circumferential creep equation by using the axial creep equation. Therefore, in this study, the existing axial creep law and the derived circumferential creep results were analyzed through a circumferential creep test by the internal pressurization method in the isothermal conditions. The circumferential creep deformation was measured through the optical image analysis method, and the results of the experiment were investigated through constructed IDECA (In-situ DEformation Calculation Algorithm based on creep) code. First, preliminary tests were performed in the isotropic β-phase. Subsequently in the anisotropic α-phase, the correlations obtained from a series of circumferential creep tests were compared with the axial creep equation, and optimized anisotropic coefficients were proposed based on the performed circumferential creep results. Finally, the IDECA prediction results using optimized anisotropic coefficients based on creep tests were validated through tube burst tests in transient conditions.

• 조명전기설비학회논문지
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• 제22권2호
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• pp.94-100
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• 2008

가용송전용량(ATC)은 계통내의 한 지역에서 다른 지역까지 실제 전력을 증가시키는 것이다. 지금까지 ATC 계산은 대부분 정상상태에서 실행가능성을 주로 고려하여 계산되어 왔다. 하지만 ATC 평가시 과도안정도로 제약된 ATC 계산은 매우 중요한 부분이다. ATC 평가시에는 제약조건으로 열적용량, 전압 및 과도안정도로 제약된 상정사고(n-1)시 안전도 평가가 요구된다. 본 논문은 자코비안 행렬의 고유치를 이용하여 상정사고 우선순위를 선정하였고, 에너지 함수법을 이용하여 선로의 열적용량, 전압안정도 및 과도안정도를 고려한 ATC를 계산하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3300-3305
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• 2007

Ignition delay of second injection of HSDI diesel engine was usually much shorter than that of first injection. It is due to the interaction between radicals generated during the combustion process, and mixed gas of second injection. In this paper, To analyze combustion phenomena of multiple injection mode in HSDI diesel engine effectively, two-dimensional flamelet combustion model was modified. To reduce calculation time, two-dimensional flamelet equations were only applied near stoichiometric region. If this region was ignited, species and temperature of other region were changed to the steady-state solutions of one dimensional flamelet equations. By this method calculation time for solving flamelet equations was reduced to 20 percents, thought the results were almost same. Modified flamelet combustion model was coupled to commercial CFD code interactively using user subroutine.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(2)
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• pp.271-276
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• 1996

Coolant flow distribution to the assemblies and core coolant/component temperatures should be determined in LMR core steady state thermal-hydraulic performance analysis. Sodium flow is distributed to core assemblies with the overall goal of equalizing the peak cladding midwall temperatures for the peak temperature pin of each pin bundle, thus pin cladding damage accrual and pin reliability. The flow orificing analysis for conceptual design will be performed with Excel spreadsheet program ORFCE which was set up and tested, using the calibration factors based on available analyses data. For the verification of this program, flow orificing calculation for the MDP 840MWth core was performed. The calculational results are satisfactory compared to those of CRIEPI calculation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.446-447
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• 2008

In this paper, a calculation method of the short-time emergency by considering a initial load level and overload time is presented. short-time emergency analyze transient thermal rating and Long-time emergency analyze steady-state thermal rating. Using the suggested method in the paper, increasing the short-term allowable current.