• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.159-162
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• 2001

A combined finite element and experimental study based on the characteristic length method is performed to investigate the strength and behavior of the pin joint in composite control rod. The failure is estimated by the Yamada-Sun and Tsai-Wu criteria on the characteristic curve. The gap elements are used to simulate the contact between the pin and the composite fitting with hole. The accuracy and applicability of the method are validated by the joint tests. All the specimens were failed in the bearing mode in the test and finite element analysis, and good agreement was found between the predicted and test results on the joint strength of composite control rod.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.17-21
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• 2002

A finite element method based on the two-dimensional progressive failure analysis is presented for characterizing the strength and failure of the unidirectional-fabric hybrid laminated composite joints under pin loading. The 8-node laminated shell element is incorporated in the updated Lagrangian formulation. Various failure criteria including the maximum stress, Tsai-Wu, Yamada-Sun, and combinations of them are used in conjunction with the complete unloading stiffness degradation method. For the verification, joint tests are conducted for the specimens with various geometries. Although there are some differences depending on the geometry, the finite element model using the Yamada-Sun or the combined Yamada-Sun and Tsai-Wu criterion predicts the failure strength best.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.9-12
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• 2002

A parametric study has been conducted to investigate the effect of the geometry on the strength of an unidirectional and fabric hybrid laminated composite joint. Tests are conducted for the specimens with nine different edge-to-hole diameter or width-to-hole diameter ratios. For the finite element analysis, the characteristic length method is used, and the tests for determining the characteristic length are performed additionally. Nonlinear contact problem between the pin and laminate is modeled by the gap element in MSC/NASTRAN. Tsai-Wu failure criteria is applied to the stress on the characteristic curve. The finite element and experimental results shows good agreement in strength of composite joint. Results of the parametric study shows the effect of the geometry is remarkable in the specimens with width-to-hole diameter ratio less than 2.8 and edge-to-hole diameter ratio less than 1.4.

• Proceedings of the KWS Conference
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• v.43
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• pp.246-248
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• 2004

Effects of the post treatment on the fatigue strength of a bead-on-plate weldment were investigated in order to improve fatigue strength of the weldment. The post treatment applied were the grinding of weld toe and hammer peening at the weld toe. The fatigue strength of the weldment after post treatment increases. It is attributed to the decrease of the residual stress and the maximum stress at the weld toe by the post treatments. Based on the result, the principal factor controlling the fatigue strength of the weldment was identified as the toe shape of the bead-on-plate weldment.

• Proceedings of the KIEE Conference
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• 2007.10c
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• pp.256-257
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• 2007

본 논문에서는 연료전지용 PCS 설계 및 시뮬레이션 시 연료전지의 비선형 전원 특성에 의한 영향을 확인하기 위하여 고분자 전해질 연료전지 (PEMFC) 스택을 전기화학 방정식을 기반으로 모델링한다. 모델링된 연료전지 전원을 부스트 컨버터의 입력으로 활용하여 시뮬레이션을 수행한다.

• Proceedings of the KIEE Conference
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• 2007.10c
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• pp.264-265
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• 2007

본 논문에서는 하이브리드 전기 자동차(Hybrid Electric Vehicle, HEV)의 실제 주행패턴 데이터를 기준으로 하이브리드 전력 시스템용 양방향 DC-DC 컨버터를 설계하고, 시뮬레이터를 구성한다. HEV의 주행패턴 데이터 중 가 감속 구간 일부를 선택하여 전기적 부하 변화로 모델링하고, 이를 통해 양방향 DC-DC 컨버터의 모드별 동작을 시뮬레이션 한다.

• Proceedings of the KAIS Fall Conference
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• 2012.05a
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• pp.389-392
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• 2012

주식시장은 자본주의 경제에 있어서 기업에게는 자본조달의 창구라는 기능을, 일반 투자자에게는 투자기회를 제공하고 국민경제적 입장에서는 자산과 부의 재분배 기능을 수행하는 등 매우 중요한 역할을 수행하고 있다. 따라서 국민경제를 이루는 거시경제학적 변수와 관계가 있을 것으로 보고 일부 연구자들은 거시 경제변수가 주가에 어떤 영향을 주는 지를 분석하고자 했다. 한편 주식시장에 있어서 인구통계학적 변수 역시 의미있는 변수이다. 특히 주식시장에 투자자로 직접 참여하는 투자자수는 더욱 중요하다. 본 연구는 단지 일부 거시경제학적 변수만의 효과를 다루었던 연구와 달리 인구통계학적 변수까지 종합적으로 고려하여 이들 변수가 주가에 미치는 영향을 분석할 수 있는 이론적인 토대를 정리하고 모형 도출을 위한 선행연구이다.

• Microbiology and Biotechnology Letters
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• v.23 no.5
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• pp.499-505
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• 1995

Immobilization of anchorage-dependent animal cells was investigated using macroporous gelatin microcarriers developed in our laboratory. For the observation of the distribution of cells in macroporous beads, Vero-6 cells and CHO cells were cuttured and their distribution in macroporous beads was observed using a confocal microscope. In results, the final concentration of Vero-6 cells and CHO cells on macroporous beads was 2-3 times higher than that on commercial solid microcarriers (Cytodex-3). Also, macroporous microcarriers could hold cells in their macropores. Consequently, the pores protected cells against hydrodynamic shear. Based on Kolmogorov eddy length scale, the smaller eddies (80 $\mu $m) showed the detrimental effect on cells in macroporous beads as compared with 160 $\mu $m of eddies in conventional solid microcarriers.

• Proceedings of the KWS Conference
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• 2006.10a
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• pp.23-25
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• 2006

The purpose of this study is to optimize the plate thickness of the main frame of a construction equipment. For this, the load history at the joints of the main frame was evaluated using mechanism and finite element analysis. With the load data, the stress and the stiffness at the main frame was evaluated and the fatigue life at each weld joint of the main frame was assessed with the change of the plate thickness. Based on the results of this study, the proper plate thicknesses of the frame of the construction equipment were proposed.

• Proceedings of the KWS Conference
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• 2008.05a
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• pp.30-30
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• 2008