• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.493-494
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• 2008

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.6A
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• pp.825-832
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• 2000

광섬유 통신 시스템이 고속화되고 장거리를 전송하게 될 수록 편광모드 분산의 중요성은 더욱 부각되어 있다. 따라서 본 논문에서는 복굴절 광섬유에서 비선형 광펄스의 전파특성을 편광 모드 분산의 영향을 고려하여 시뮬레이션하였으며 이러한 현상이 발생되는 것을 알 수 있었다. 그리고 광섬유 비션형성에 의해서 GVD(Group Velocity Dispersion)와 마찬가기로 PMD(Polarization Mode Dispersion)에서도 부분적인 보상 현상이 나타남을 수치 결과를 통해 알 수 있었다. 이러한 광 전송 시뮬레이션을 구현하기 위해서 기존의 단계분할 푸리에 방식 (SS-FM, Split-Step Fourier Method)보다 장거리 전송시 오차의 발생이 적은 단계 분할 유한 요소법)SS-FEM, Split-Step Finite Element Method)을 적용하였으며, 또한 그 단점인 수행 속도를 개선한 희귀 행렬 근사 단계 분할 유한 요소법을 제안하였다. 그 결과 제안된 방법이 기존의 푸리에 연산법이나 일반적인 유한 요소법과 비교하여 더 빠른 수행 속도를 나타내는 것을 알 수 있었다.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1439-1441
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• 2003

전기절연재의 구조재로 많이 사용되고 있는 FRP(fiber reinforced plastics)는 열경화성 수지를 접착성 결합제(binder)로 하고 고강도 섬유를 보강재로 한 복합재료로서 기계적, 화학적, 전기적 특성이 매우 우수하다. FRP의 기계적 강도는 유리섬유에 의존 하고 있으므로 유리섬유의 방향과 힘을 가하는 방향에 따라서 그 강도의 차이는 매우 크게 나타난다. 본 연구에서는 섬유의 배향에 따른 강도의 변화를 이해하기 위하여 시편을 제작하여 압축강도를 측정하고 압축강도와 응력의 분포를 유한요소법으로 시뮬레이션하였다. FRP rod에 압축응력이 가해졌을 때 섬유의 배향에 따른 파괴강도와 응력의 분포를 유한요소법을 이용하여 시뮬레이션하였고 모델링에는 3-D Shell과 3-D Brick 요소를 사용하였다. 제작된 시편의 강도특성과 시뮬레이션을 통한 응력의 분포를 서로 비교하여 시편의 파괴에 미치는 응력을 고찰하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.4
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• pp.385-391
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• 2014

A wheeled armored vehicle is a military vehicle that has been developed to enhance combat capabilities and mobility for the army. The wheeled armored vehicle has a high center of gravity, and it operates on unpaved and sloped roads. Therefore, this vehicle has a high risk of rollover crashes. To design the interior of the military vehicle, the crew's safety during rollover crashes is an important factor. However, actual vehicle tests for design are extremely expensive. In this paper, nonlinear dynamic analysis is performed to simulate the rollover crashes and the passenger injury is assessed for a wheeled armored vehicle. The scope of this research is the rollover condition, FE modeling of the wheeled armored vehicle and the dummy, arrangement of dummies, assessment of passenger injuries, and simulation model for rollover crashes.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.2
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• pp.76-82
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• 2018

In this present study, in order to update the finite element model considering the boundary conditions, a method has been proposed. The conventional finite element model updating method, updates the finite element model by using the dynamic characteristics (natural frequency, mode shape) which can be estimated from the ambient vibration test. Therefore, prediction of the static response of an actual structure is difficult. Furthermore, accurate estimation of the physical properties is relatively hard. A novel method has been proposed to overcome the limitations of conventional method. Initially, the proposed method estimates the rotational spring constant of a finite element model using the deflection of structure and the rotational displacement of support measurements. The final updated finite element model is constructed by estimating the material properties of the structure using the finite element model with updated rotational spring constant and the dynamic characteristics of the structure. The proposed finite element model updating method is validated through numerical simulation and compared with the conventional finite element model updating method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.3
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• pp.559-567
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• 1999

A piezoelectric flextentional sonar transducer has been simulated using a coupled FE-BEM. The dynamics of the sonar transducer is modelled in three dimensions and is analyzed with external electrical excitation conditions. Different results are available such as steady-state displacement modes, underwater directivity patterns, resonant frequencies, bandwidths, quality factors, output acoustic powers and transmitting voltage responses. It is shown that the present barrel-stave sonar transducer of the piezoelectric material produces flextentional displacements which could be related with higher output power, lower quality factor and more omnidirectional beam pattern than other types of sonar transducers. The results of the present sonar transducer modelling are also compared with those of a commercial package such as ATILA.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.11
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• pp.114-123
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• 1996

The major objective of the present paper is to estabilish analytical technique in order to closely understand and analyze the actual shearing process. First of all, isothermal and non-isothermal FE-simulation of the shearing process are carried out using finite element software DEFORM. Based on preliminary simulation using DEFORM, the finite element program to analyze two dimensional shearing process is developed. The ductile fracture criterion and the element kill method are also used to estimate if and where a fracture will occur and to investigate the features of the sheared surface in shearing process. It can be seen that the developed program combined with the ductile fracture criterion and element kill method has enabled the achievement of FE-simulation from initial stage to final stage of shearing process. The effects of punch-die clearance on shearing process are also investigated. In order to verify the effectiveness of the proposed technique the simulation results are compared with the known expermental data. It is found that the results of the present work are in close agreement with the published experimental results.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.3
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• pp.373-384
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• 2000

To assess the safety of nonlinear steel frame structures subjected to short duration dynamic loadings, especially seismic loading, a nonlinear time domain reliability analysis procedure is proposed in the context of the stochastic finite element concept. In the proposed algorithm, the finite element formulation is combined with concepts of the response surface method, the first order reliability method, and the iterative linear interpolation scheme. This leads to the stochastic finite element concept. Actual earthquake loading time-histories are used to excite structures, enabling a realistic representation of the loading conditions. The assumed stress-based finite element formulation is used to increase its efficiency. The algorithm also has the potential to evaluate the risk associated with any linear or nonlinear structure that can be represented by a finite element algorithm subjected to seismic loading or any short duration dynamic loading. The algorithm is explained with help of an example and verified using the Monte Carlo simulation technique.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.6
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• pp.685-690
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• 2011

This paper describes a seismic analysis of chemical pump using automated mesh generation system. The use of an automated analysis system, involving FE codes together with CAD systems and FE pre- and post-processors, has provided an important step towards shortening the design process and structural optimization. The FE model, which is a FE mesh accompanied with the analysis condition, is automatically converted from the analysis model. The FE models are then automatically analyzed using the FE analysis code. This integrated FE simulation system is applied to an analysis of three-dimensional complex solid structures such as a chemical pump.

• Proceeding of EDISON Challenge
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• 2017.03a
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• pp.653-655
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• 2017

심근섬유증은 심장에서 전도 장애를 일으키며 심부전증상을 발생시킨다. 심근섬유증으로 인한 심장박동현상의 변화를 확인하기 위해 시뮬레이션 연구를 진행하였다. 심실의 유한요소 모델을 설계하고 무작위로 전도 블록을 생성하여 심근섬유증을 적용하고 그 비율을 조절하였다. 심근섬유증의 비율에 따라 전기생리학적 시뮬레이션을 진행하고 그 결과를 바탕으로 기계 수축 시뮬레이션을 진행하여 심실의 수축 변화를 확인하였다. 심근섬유증의 비율이 증가할수록 좌심실의 압력이 감소하고 박출되는 혈액량과 박출계수, 심장박동의 효율이 감소하였다.