• Nuclear Engineering and Technology
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• 제54권3호
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• pp.1109-1114
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• 2022

The SMART (System-integrated Modular Advanced ReacTor) is an integral-type small modular reactor developed by KAERI (Korea Atomic Energy Research Institute). This paper discusses the feasibility and applicability of a 3D-based equivalent model using dynamic condensation method for seismic analysis of a SMART control rod drive mechanism. The equivalent model is utilized for complicated seismic analysis during the design of the SMART. While the 1D-based beam-mass equivalent model is widely used in the nuclear industry for its calculation efficiency, the 3D-based equivalent model is suggested for the seismic analysis of SMART to enhance the analysis accuracy of the 1D-based equivalent model while maintaining its analysis efficiency. To verify the suggested model, acceleration response spectra from seismic analysis based on the 3D-based equivalent model are compared to those from the 1D-based beam-mass equivalent model and experiments. The accuracy and efficiency of the dynamic condensation method are investigated by comparison to analysis results based on the conventional modeling methodology used for seismic analysis.

• 한국공간구조학회논문집
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• 제6권2호
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• pp.131-136
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• 2006

It is important to evaluate energy absorption capacity of frames required during a design earthquake. An inelastic computer analysis based on mathematical modelling of energy absorbing frames and elements makes it possible to evaluate required energy absorption capacity. But such an analysis sometimes consumes much computation time particularly in case of complicated structural system. This paper presents a proposal to predict energy absorption of multi-bent steel frames by simple equivalent linear method.

• 한국소음진동공학회논문집
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• 제20권4호
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• pp.397-404
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• 2010

The use of equivalent circuit models of piezoelectric energy harvesters is inevitable when power circuitry including rectifying and smoothing circuit elements is connected to them for evaluating DC electrical outputs. This is because it is difficult to incorporate the electro-mechanical coupling resulting from the additional circuitry into the conventional finite element analysis. Motivated by this observation, we propose a method to accurately extract the equivalent circuit parameters by using commercially available FEM software such as ANSYS which provides three-dimensional AC piezoelectric analysis. Then the equivalent circuit can be analyzed by circuit simulators such as $SimPowerSystems^{TM}$ of MATLAB. While the previous works have estimated the circuit parameters by experimental measurements or by analytical solutions developed only for limited geometries and boundary conditions, the proposed method has no such limitation because piezoelectric energy harvesters of any shapes and boundary conditions can be treated in FEM software. For the verification of the proposed method, multi-modal AC electrical power output by using a corresponding equivalent circuit is compared with that by ANSYS. The proposed method is then shown to be very useful in the subsequent evaluation of DC electrical output which is obtained by attaching a bridge diode and a storage capacitor to a piezoelectric energy harvester.

• Nuclear Engineering and Technology
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• 제35권1호
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• pp.1-13
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• 2003

In this study, an effective method to estimate the fundamental frequencies of co-axial cylinders immersed in fluid is proposed. The proposed method makes use of the equivalent mass or density that is derived from the added mass matrix caused by the fluid-structure interaction (FSI) phenomenon. The equivalent mass is defined from the added mass matrix based on a 2-D potential flow theory. The theory on two co-axial cylinders extended to the case of three cylinders. To prove the validity of the proposed method, the eigenvalue analyses upon coaxial cylinders coupled with fluid gaps are peformed using the equivalent mass. The analyses results upon various fluid gap is conditions reveal that the present method could provide accurate frequencies and be suitable for expecting the fundamental frequencies of fluid coupled cylinders in beam mode vibration.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 봄 학술발표회 논문집
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• pp.19-26
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• 2003

In energy-based design, the structures are generally transformed into equivalent SDOF systems to obtain the input and the dissipated energy. In this study the energy demands in multi-story structures were compared with that of equivalent single degree of freedom systems to validate the transformation method. Three-, eight-, and twenty-story steel moment-resisting frames and buckling restrained braced frames are compared with those of equivalent single degree of freedom systems. Sixty earthquake ground motions recorded in different soil conditions were used to compute the input and hysteretic energy demands in model structures. According to the analysis results, in 3 and 8-story structures the hysteretic energy demands computed in the equivalent SDOF structures are compatible with those computed in the original MDOF structures, while in the 20-story structures the transformed equivalent structures underestimated the hysteretic energy demands.

• 한국공작기계학회논문집
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• 제17권1호
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• pp.71-76
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• 2008

Nonlinear dynamic system under random excitation was analyzed by using stochastic method. A linearization method was used in order to linearize non-linear structural characteristics but the parametric excitation was used as it was given. An equivalent energy method which equalizes the expectation value of energy of the original nonlinear system and that of quasi-linearized system was proposed. Ito's differential rule was applied to obtain steady state moments. Quasi-linearization coefficients can be obtained the iterative calculation of linearization scheme and steady state moments. Monte Carlo simulation was used to verify the results of the proposed method. Nonlinear vibration of a slender beam was analyzed in this research. The analysis results were compared with Monte Carlo simulation result and showed good agreement. As the spectral density of the given excitation increased, the analysis results showed the better agreement with Monte Carlo simulation.

• KEPCO Journal on Electric Power and Energy
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• 제2권4호
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• pp.569-575
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• 2016

In this paper, we propose a method to develop a static equivalent model of an inverter-based distributed energy resource (DER), where the model is used for a steady-state fault analysis of a power grid. First, we introduce the characteristics of an inverter-based DER as well as its general configuration. Then, we derive the equivalent model of the DER on the basis of the characteristics. Last, the performance of the proposed method is proven by the results of computer simulations.

• 한국전산구조공학회논문집
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• 제34권1호
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• pp.1-8
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• 2021

플랜트 증기운 폭발은 TNT 폭발물에 의한 폭발과는 다른 특징이 있으며 압력파 양상과 비슷하다. 대표적인 유형의 폭압 산정법은 TNT 등가량 환산법과 멀티에너지법이 있다. TNT 등가량 환산법은 폭굉과 같은 충격파를 전제로 하며, 멀티에너지법은 폭연과 같은 압력파를 전제로 한다. 본 연구는 세 가지 플랜트 폭발 사례를 적용하여 플랜트 증기운 폭발의 적절한 폭압을 도출하기 위한 연구를 수행하였다. 폭발 사례에 대하여 피해를 입은 부재를 선정한 후, 단자유도 해석과 비선형 동적 해석을 수행하여 변형과 손상 정도를 비교분석하였다. 구조물의 피해 정도는 TNT 등가량 환산법보다는 멀티에너지법에 의한 폭압을 사용한 경우가 실제 상황에 더욱 근접한 것으로 나타났다. 또한, 멀티에너지법의 폭발강도계수를 7 또는 8로 가정할 경우 증기운 폭발의 폭압 모델을 비교적 정확하게 산정할 수 있을 것으로 판단된다.

• 한국광물학회지
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• 제3권2호
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• pp.89-97
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• 1990

To examine how London energy controls the c-dimensions of phyllosilicates, London energy, as well as Coulomb and Pauli repulstion energy was calculated as a function of d(001) for 1M and d(002) for 2M 1 phyllosilicates. London and Pauli repulstion energy calcualtion use a direct interaction calculation method and Coulomb energy calculation adopts Fourier synthesis method. The energy calculations show that Coulmb and Pauli repulsion energy dominantly control the c-dimensions of phyllosilicates having the interlayer cationss, i.e., the layer charges. On the other hand, if phyllosilicates have no interlayer cations, London energy is solely responsible for holding the layers and maintain the c-dimensions. The significance of London energy in determining the c-dimensions of phyllosislicates de-creases as the layer charge increases. When the layer charge is lower than one equivalent on the basis of Oη(OH)2 formula, London energy plays an important role in determing the c-dimensions. however, if the layer charge is higher than one equivalent, London energy becomes insignifi-cant in determining the c-dimension.

• 화약ㆍ발파
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• 제33권3호
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• pp.1-13
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• 2015

국내외에서 가스폭발 사고가 빈번하게 발생하고 있으며 가스 폭발의 평가와 분석을 위해 TNT 등가량 산정법이 사용되고 있다. 본 연구에서는 TNT 폭발 시 화학반응식의 선택과 반응 생성 물질들의 엔탈피의 선택에 따른 폭발에너지, 폭발압력, 폭굉속도 및 온도의 차이를 계산하였다. 화학반응식의 선택에 따라 계산되는 폭굉압은 최고값이 최저값에 비해 2배까지 나타났다. 밀폐된 공간에서의 메탄가스 폭발을 가정하고 TNT 등가량을 산정하였으며 이를 통해 폭발지점에서의 거리에 따른 최대압력과 임펄스 변화를 추정할 수 있었다.