• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.659-663
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• 1995

The fiber oriented conditied inside fiber reinforced composite material is a basic factor of mechanical properties of composite materials. It is very important to measure the fiber orientation angel for the determination of molding conditions, mechanical charactistics, and the design of composite materials. In the work, the fiber orientation distribution of simulation figure plotted by PC is measured using image processing in order to examine thr accuracy of intersection counting method. The fiber orientation function measured by intersection countingmethod using image processing is compared with the calculated fiber orientation function. The results show that the measured value of fiber orientation function using intersection counting method is lower than the calculated value, because the number of intersection between the secant line and the fiber with smaller fiber aspect ratio is counted less than with larger fiber aspect ratio.

• 전기학회논문지
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• 제62권8호
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• pp.1144-1150
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• 2013

The stabilizing controller design problem of time-delay singularly perturbed systems is considered. The proposed approach is based on the $H_{\infty}$ norm and the composite control method. A sufficient condition for the stability of the time-delay slow subsystem is presented. Using this condition, we can construct the composite control law for the time-delay singularly perturbed system and analysis the system by the matrix Lambert W function. Illustrated examples are presented to demonstrate the validity and applicability of the proposed method.

• KIEAE Journal
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• 제8권1호
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• pp.105-110
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• 2008

Most high rise buildings have been constructed with steel structure systems with metal deck floors and concrete topping. Since the mass of the metal deck floor system is relatively thinner than that of the concrete floor system and due to the larger span compared to other floor systems, vibration serviceability problems are frequently occurred. Most of vibration problems are induced by the movement of humans. A walking load function was proposed for the better estimation of composite deck floor vibration based on site measurements in this paper.

• 한국수학교육학회지시리즈A:수학교육
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• 제58권2호
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• pp.239-262
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• 2019

본 연구에서는 특정한 학생의 질문에서 시작된 고민을 다루고 있으며, 교과서 분석을 통하여 해당 질문이 충분히 제기 가능한 질문임을 확인하였다. 또한 면담을 거쳐 두 대응관계가 연결된 새로운 대응관계에서 학생들이 합성함수 여부 판정과 역함수 존재 여부 판정에서 정의역에 대한 고민이 학생들에게서 어떻게 의미 있는 수학 지식으로 재구성 되어가는 지에 대한 사례를 관찰하였다. 본 연구에서 제시된 사례들은 제한된 상황에서의 특정한 사례라는 한계가 있기 때문에 곧바로 교수학습 상황에 적용될 수는 없으나 다른 연구자들에게 함수 학습 관련 연구에 대하여 통찰의 기회를 제공할 수 있을 것으로 기대된다.

• Steel and Composite Structures
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• 제24권1호
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• pp.53-63
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• 2017

The paper presents the simplified matrix stiffness method for analysis of composite and prestressed beams. The method is based on the previously developed "exact" analysis method that uses the mathematical theory of linear integral operators to derive all relations without any mathematical simplifications besides inevitable idealizations related to the material rheological properties. However, the method is limited since the closed-form solution can be found only for specific forms of the concrete creep function. In this paper, the authors proposed the simplified analysis method by introducing the assumption that the unknown deformations change linearly with the concrete creep function. Adopting this assumption, the nonhomogeneous integral system of equations of the "exact" method simplifies to the system of algebraic equations that can be easily solved. Therefore, the proposed method is more suitable for practical applications. Its high level of accuracy in comparison to the "exact" method is preserved, which is illustrated on the numerical example. Also, it is more accurate than the well-known EM method.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 1999년도 추계학술발표대회 논문집
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• pp.63-67
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• 1999

This paper presents the optimization of CFRP laminated rectangular plates using fuzzy theory. In optimization, thickness of CFRP lamina and fiber angle are taken as design variables, and total thickness of the plates is minimized under Tsai-Hill failure criterion. The uncertainties are entered by introducing fuzzy material strengths and then the objective and constraints are represented by a membership function of their own according to the intersection method. Various design results are presented for the CFRP laminated composites plates.

• Steel and Composite Structures
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• 제20권6호
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• pp.1173-1182
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• 2016

The objective of this work was to evaluate the ductile cracked structures with bonded composite patch used in probabilistic elastic plastic fracture mechanics subjected to tensile load. The finite element method is used to analyze the stress intensity factors for elastic case, the effect of cracks and the thickness of the patch ($e_r$) are presented for calculating the stress intensity factors. For elastic-plastic the Monte Carlo method is used to predict the distribution function of the mechanical response. According to the obtained results, we note that the stress variations are important factors influencing on the distribution function of (J/Je).

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 봄 학술발표회 논문집
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• pp.407-414
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• 2002

The knowledge of interaction of electromagnetic waves in composite structures is important for designing the shielding structure for antenna such as radome. Recently, radomes are constructed in the form of foam core sandwich structures that have many mechanical advantages such as high strength, long fatigue life, low density and adaptability to the intended function of structure. However, the propagation of electromagnetic waves is affected by high anisotropic permeability and loss tangent of the composite skin. In this study, the analytical model to understand the propagation of electromagnetic waves in the anisotropic composites and foam core sandwich structures with composite skins was proposed. Numerical analyses of unidirectional composites and foam core sandwich structure as a function of incident angle were performed. From the results of analysis, the general tendencies of transmittance of electromagnetic wave through composites and foam core sandwich structure were obtained.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
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• pp.123-126
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• 2002

Acoustic vibration analysis has been performed using random vibration analysis module of MSC/NASTRAN to evaluate the safety of the composite satellite antenna structure under the acoustic pressure from the launch vehicle. It was found that maximum $3\sigma$ stress by acoustic excitation was less than allowable stress.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 1999년도 춘계학술발표대회 논문집
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• pp.53.1-56
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• 1999

The vibration behavior of glass-fabric reinforced plastic(GFRP) composite beams subjected to various transverse impacts has been investigated as a function of fiber orientation and void fraction. Theoretical results of resonant frequency damping coefficient and modal amplitude dispersion using the Euler-beam theory were obtained along with the finite element analysis which were compared with experimental ones Consequently it was shown that the transverse vibration characteristics were largely affected by fiber orientation and void fraction.