• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.205-210
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• 2001

In this work, virtual material characterization of 3D orthogonal woven composites is performed to predict the elastic properties by a full scale FEA. To model the complex geometry of 3D orthogonal woven composites, an accurate unit structure is first prepared. The unit structure includes warp yarns, filler yarns, stuffer yams and resin regions and reveals the geometrical characteristics. For this virtual experiments by using finite element analysis, parallel multifrontal solver is utilized and the computed elastic properties are compared to available experimental results and the other analytical results. It is founded that a good agreement between material properties obtained from virtual characterization and experimental results. Using the method of this virtual material characterization, the effects of inconsistent filler yarn distribution on the in-plane shear modulus and filler yarn waviness on the transverse Young's modulus are investigated. Especially, the stiffness knockdown of 3D woven composite structures is simulated by virtual characterization. Considering these results, the virtual material characterization of composite materials can be used for designing the 3D complex composite structures and may supplement the actual experiments.

• 패션비즈니스
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• 제17권1호
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• pp.30-41
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• 2013

Augmented reality techniques have been increasingly employed in the textile and fashion industry as well as computer graphics sectors. Three-dimensional virtual clothing CAD systems have also been widely used in the textile industries and academic institutes. Motion tracking techniques are grafted together in the 3D and augmented reality techniques in order to develop the virtual three-dimensional clothing and fitting systems in the fashion and textile industry sectors. In this study, three-dimensional virtual clothing sample has been prepared using a 3D virtual clothing CAD along with a 3D scanning and reconstruction system. Motion of the user has been captured through an RGB-D sensor system, and the virtual clothing fitted on the user's body is allowed to move along with the captured motion flow of the user. Acutal fabric specimens are selected for the material characterization. This study is a primary step toward building a comprehensive system for the user to experience interactively virtual clothing under real environment.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.911-914
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• 2005

Soft tissue characterization and modeling based on living tissues has been investigated in order to provide a more realistic behavior in a virtual reality based surgical simulation. In this paper, we characterize the nonlinear viscoelastic properties of intra-abdominal organs using the data from in vivo animal experiments and inverse FE parameter estimation algorithm. In the assumptions of quasi-linear-viscoelastic theory, we estimated the nonlinear material parameters to provide a physically based simulation of tissue deformations. To calibrate the parameters to the experimental results, we developed a three dimensional FE model to simulate the forces at the indenter and an optimization program that updates new parameters and runs the simulation iteratively. The comparison between simulation and experimental behavior of pig intra abdominal soft tissue are presented to provide a validness of the tissue model using our approach.

• 한국전기전자재료학회논문지
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• 제15권12호
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• pp.1054-1059
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• 2002

A great deal of research has been done in the field of characterization for piezoelectric thin films after the first report on the measurement for the piezoelectric coefficient of thin films in 1990. The main idea of this research is to provide a distinctive solution for the measurement and standardization of both the longitudinal and the transverse piezoelectric d-coefficients, d33 and d31, of ferroelectric thin films. In general, to get these two coefficients of thin films, two different measuring systems are required. Here, we propose the improved method for the evaluation of these two coefficients with single equipment and with the relatively convenient procedure. The two-step loading process of applying the both positive and the negative pressure has been introduced to acquire the piezoelectric coefficients. These results have been calibrated for both the longitudinal and 4he transverse piezoelectric d-coefficients, d33 and 431, of thin films by comparison with the virtual standard created from FEM. In this experiments, we have obtained d33 of 331pC/N and 031 of -92.2pC/N for the PZT thin films.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 춘계학술대회 논문집 전자세라믹스 센서 및 박막재료 반도체재료 일렉트렛트 및 응용기술
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• pp.47-51
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• 2000

A modified direct bonding technique employing a wet chemical deposition of $SiO_2$ film on a wafer surface to be bonded is proposed for the fabrication of Si-$SiO_2$-Si structures. Structural and electrical quality of the bonded wafers is studied. Satisfied insulating properties of interfacial $SiO_2$ layers are demonstrated. Elastic strain caused by surface morphology is investigated. The diminution of strain in the grooved structures is semi-quantitatively interpreted by a model considering the virtual defects distributed over the interfacial region.

• 실천공학교육논문지
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• 제14권3호
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• pp.479-489
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• 2022

본 연구는 K대학교 온라인평생교육원의 가상훈련 콘텐츠 활용을 높이는 방안을 파악하기 위해 운영기관 사례를 중심으로 활용경험, 콘텐츠 인식, 현장실습 대체, 요구사항 등을 살펴보았다. 이를 위해 2020년 K대학교 온라인평생교육원이 보급한 가상훈련 콘텐츠를 운영한 12개 기관을 선정하여 심층인터뷰를 실시하고, 최종 인터뷰한 11개 기관의 인터뷰 내용을 질적 분석하였다. 분석 결과, 첫째, 가상훈련 운영기관의 콘텐츠 활용경험은 교육환경의 변화, 이론학습의 보완, 실무감각의 향상이 목적이었다. 둘째, 가상훈련 콘텐츠 인식을 조사한 결과, 콘텐츠의 중요도와 활용도가 높다고 인식한 경우에는 구비가 어려운 시설과 장비의 경험, 흥미유발 및 주의집중에 도움, 안전교육에 유용, 비대면 수업시 현장실습에 대체 가능한다고 응답했다. 셋째, 현장실습에 대체에 대한 인식은 다수의 경우, 현장실습의 사전 교육자료로 활용하기에는 무리가 없지만 현장실습을 대체하기에는 어렵다고 응답했다. 넷째, 콘텐츠 질 개선사항으로 콘텐츠 질 제고, 콘텐츠 접근 및 조작 개선, 전용 기기 개발, 교수자 대상 연수실시, 교육과정 체계화로 요약할 수 있다. 다섯째, 기관의 요구사항으로 가상훈련 콘텐츠 자체의 질 제고, 장비지원, 교육과정 체계화 및 특성화, 체계적인 교육과정 및 세부 콘텐츠 목적 공유 등이며, 홍보방안으로 교수자 대상으로 연수 진행하며 가상 훈련 콘텐츠 활용에 대한 자세한 안내, 가상훈련 콘텐츠 활용과 타 사업 연계, 콘텐츠 활용방법 소개 및 활용 강사모집 등이었다. 본 연구는 가상훈련 콘텐츠 운영기관의 인식을 바탕으로 가상훈련 콘텐츠 활용도 제고를 위한 방안을 모색했다는데 의의가 있다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 추계학술발표대회 논문집
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• pp.170-174
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• 2002

In this study, the material characterization and the dynamic behavior of 3D orthogonal woven composite materials has been studied under transverse central low-velocity impact condition by means of the micromechanical model using finite elements. To build up the micromechanical model considering tow spacing and waviness, an accurate unit structure is stacked in x-y-z direction repeatedly. First, the mechanical properties of 3D orthogonal woven composites are obtained by means of virtual experiment using full scale Finite Element Analysis based on the DNS concepts, and the computed elastic properties are validated by comparison to available experimental results[9]. Second, using the implementation of this validated micromechanical model, 3D transient finite-element analysis is performed considering contact and impact, and the impact behavior of 3D orthogonal woven composite is investigated. A comparison study will be carried out in terms of energy absorption capabilities.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 추계학술발표대회 논문집
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• pp.53-56
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• 2005

In this study, the material characterization and the dynamic behavior of 3D orthogonal woven composite materials has been studied under transverse central low-velocity impact condition by means of the micromechanical model using finite elements. To build up the micromechanical model considering tow spacing and waviness, an accurate unit structure is stacked in x-y-z direction repeatedly. First, the mechanical properties of 3D orthogonal woven composites arc obtained by means of virtual experiment using full scale Finite Element Analysis based on the DNS concepts, and the computed elastic properties arc validated by comparison to available experimental results. Second, using the implementation of this validated micromechanical model, 3D transient finite-clement analysis is performed considering contact and impact, and the impact behavior of 3D orthogonal woven composite is investigated. A comparison study with the homogenized model will be carried out in terms of global and local behaviors.

• Composites Research
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• 제21권4호
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• pp.7-14
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• 2008

접착제 이용 결합 조인트의 하중지지 능력 예측 기법은 점착제를 이용한 접합 조인트 설계에 있어서 가장 중요한 기술이다. 본 연구 계면 파괴역학을 이용하여 복합재료/금속 접착 조인트의 하중지시 능력을 예측하는 기법을 소개한다. 구체적으로 복합재료/탄소강 결합의 접착 강도를 계면 균열의 에너지 방출률과 계면 파괴인성치 개념을 사용하여 평가하는 방법을 제시 검증하였다. 계면 균열의 에너지 방출률은 유한요소해선 결과를 이용한 가상 균열 닫음 기법 (VCCT)을 사용하여 계산하였으며, 게면 파괴인성치는 이종재료 ENF (end-notched flexure) 시편을 고안하여 측정하였다. 고안된 이종 재료 ENF 시편을 사용하여 시편의 두께에 상관없이 일관된 Mode II 계면 파괴인성치를 측정할 수 있음과 양면 겹치기 접합 조인트의 특성 에너지 방출률이 측정된 계면 파괴인성치와 일치함을 확인하였다. 따라서 에너지 방출률에 근거한 계면 균열 진전 기준은 접착 조인트의 하중지지 능력을 신뢰성 있게 예측하는 실제적인 설계 도구로서 활용될 수 있다.