• The Korean Journal of Rheology
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• v.5 no.2
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• pp.99-108
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• 1993

시멘트 페이스트의 비선형적 점탄성 거동을 연구하기 위해 동적인 전단 유동 시험 이 수행되었다. 전단응력과 전단변형 또는 전단변형율간의 관계를 보여주는 히스테리시스 곡선을 얻기 위하여 전단응력이 연속적으로 측정되었다. 이는 기존의 주파수 혹은 변형의 증가에 의한 실험(frequency or strain sweep experiment)과는 달리 저자에 의해 수정된 점 성계(HAAKE Model RV20/RC20/CV20N)의 조정프로그램을 이용하여 수행되었다. 동적 전 단유동시험에서 얻어진 히스테리시스곡선은 시멘트 페이스트가 전단변형을 받는 동안 선형 탄성, 입자간 연결고리의 파괴 및 점성유체 거동을 보여준다. 측정된 항복전단응력은 전단변 형율의 증가에 따라 파우어함수(Power low equation)에 의해 증가함을 보여준다.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.149.1-149.1
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• 2005

• Proceedings of the Korean Society of Rheology Conference
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• 2000.05a
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• pp.11-14
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• 2000

• Journal of the Earthquake Engineering Society of Korea
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• v.1 no.3
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• pp.45-58
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• 1997

An analysis algorithm and a computer program have been developed to clarify the geometrically nonlinear response characteristics of a suspension bridge subject to the support excitation. The Finite Element procedures are utilized for the application to a self-anchored suspension bridge or to a mono-duo cable suspension bridge. The propagation of earthquake wave is simulated by taking a record as the input at the left anchorage of the bridge, and addign appropriate time delay to the other inputs for the purpose of considering the multi-support effects. According to the application for a mono-duo self-anchored suspension bridge, it has been found that the effects of nonlinear behavior and multi-support excitation are notable for this relatively short-spanned suspension bridge.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.208-208
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• 2011

최근 유연기판 기술을 기반으로 대면적 roll to roll 공정기술 개발이 활발히 연구됨에 따라 이에 적용 가능한 대면적 플라즈마 소스의 중요성이 대두되고 있다. 대면적 플라즈마 처리 공정에 적용 가능한 소스 중 closed drift 타입의 선형 이온 소스는 제작 및 대면적화가 용이함에 따라 다양한 산업 분야에서 사용되고 있다. 선형 이온 소스를 다양한 표면처리 공정에 효과적으로 적용하기 위해서는 방전 특성에 대한 이해를 바탕으로 각 공정에 맞는 이온빔 전류 밀도, 방전 전압 등의 방전 인자 조절이 필수적이다. 본 연구에서는 표면 개질, 식각 및 박막 증착 등의 다양한 분야에 활용 가능한 선형 이온 소스를 개발하였으며, 선형 이온 소스를 통한 표면 식각 공정을 집중적으로 연구하였다. 전극 및 자기장 구조에 따른 선형 이온 소스 내 플라즈마 방전거동 분석을 위해 object oriented particle in cell(OOPIC) 전산모사를 수행하였으며, 이를 통해 식각 또는 증착 공정에 적합한 이온 소스의 구조 및 공정 조건을 예측하였다. 또한 OOPIC 전산모사를 통해 예측된 이온빔 인출 경향을 Faraday cup을 이용한 이온빔 전류 밀도 측정을 통해 확인하였다. 실리콘 기판 식각 공정의 경우, 이온 전류밀도 및 에너지에 따른 식각 거동 분석, 이온빔 입사각 변화에 따른 식각 특성 분석을 통해 최적 식각 공정 조건을 도출하였다. 특히, 이온빔 입사각 변화에 따른 식각률 변화는 일반적으로 알려진 입사각에 따른 스퍼터링율과 유사한 경향을 보였다. 이온빔 에너지 3 kV, Ar 압력 1.3 mTorr 조건에서 기판 정지 상태시 약 8.5 nm/s의 식각 속도를 얻었다.

• Journal of the Korean GEO-environmental Society
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• v.2 no.3
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• pp.81-88
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• 2001

The behavior of porous medium is modeled by linear thermoporoelastic behavior, linear poroviscoelastic behavior, poroplastic behavior, and poroviscoplastic behavior, etc. The behavior has, in general, a complicated aspect which makes a mechanical description of the problem with time. Constitutive modeling for deformation behavior of porous medium with coupling effects is needed since there is interaction between the constituents in pores with a relative velocity to each other. In this work, it is explained 3-dimensional behavior depending on degree of saturation for porous medium composed of homogeneous, isotropic materials. It is obtained the governing equations based on continuum porous mechanics. In addition, it is developed constitutive model which can be understood of behavior for porous medium which can be understood, analysed behavior of porous medium. It can be accomplished exact analysis and prediction of behavior in porous medium. The behavior for porous medium is analysed exactly, and the prediction of deformation behavior is accomplished. Consequently, it will be basis to analyze 3-dimensional behavior in municipal solid waste landfill, and the practical using of porous medium ground which are composed of nonhomogeneous, anisotropic materials can be done widely.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.2
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• pp.103-112
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• 1990

This study examines the characteristics of soil behavior which includes many uncertainties in seismic design, evaluates the dynamic soil properties and studies the soil-structure interaction to generalize the applicability and economy of the available sites. An example analysis is performed for soil-structure system response assuming a containment structure built on site which includes soil layers using both elastic halfspace analysis and FEM analysis against the seismic loads from the actual design. This exercise is performed as a part of the safety analysis and economic assessment of the nuclear power plant built on soils. It includes the preparation of computer program capable of incorporating large nonlinearity in the analysis, resonable evaluation procedures to determine input soil data. Nonlinear FEM analysis of Seed and Idriss model is found suitable for the accurate analysis of dynamic response of soils. Linear FEM analysis using dynamic soil properties at strain level obtained by one-dimensional seismic response, and elastic half-space analysis using dynamic soil properties at strain level under static loads are recommended to evaluate the dynamic soil properties.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.1 s.71
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• pp.73-83
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• 2006

The failure mechanism of a hollow bridge deck which is made of fiber reinforced polymer (FRP) to improve its durability and life time significantly is investigated using both experiments and analyses. While the Load-displacement behavior of the deck in the longitudinal direction is almost linear just before the failure, the behavior in the transverse direction shows a strong nonlinearity even in its initial response with relatively small magnitude of loads. We found that the nonlinearity is due to the imperfection of the connection between the flange and the web; a plastic deformation can t라e place in the connection. The argument is demonstrated using a simple structural model in which a rigid plastic hinge is introduced to the connection. We also checked the contribution of the delamination mechanism to the failure. But the delamination is not the main mechanism which initiates and causes the failure of the bridge deck. In order to improved the structural behavior of the deck in the transverse direction, we suggested that the empty space of the bridge deck is filled with a foam and confirmed the improved behavior by a numerical analysis.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.6 s.40
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• pp.73-80
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• 2004

A nonlinear time-domain system identification algorithm using measured acceleration data is developed for structural damage assessment. To take account of nonlinear behavior of structural systems, an output error between measured and computed acceleration increments has been defined and a constrained nonlinear optimization problem is solved for optimal structural parameters. The algorithm estimates time-varying properties of stiffness and damping parameters. Nonlinear response of restoring force of a structural system is recovered by using the estimated time-varying structural properties and computed displacement by Newmark-$\beta$ method. In the recovery, no pre-defined model for inelastic behavior has been assumed. In developing the algorithm, noise and incomplete measurement in space and state have been considered. To examine the developed algorithm, numerical simulation and laboratory experimental studies on a three-story shear building have been carried out.

• Magazine of the Korea Concrete Institute
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• v.10 no.3
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• pp.219-226
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• 1998

본 연구에서는 경량콘크리트보의 거동을 연구하는데 적용될 수 있는 비선형해석이 나타나있다. 콘크리트에 대한 2축 실험 자료를 사용하여 경량콘크리트의 구성모델을 만들었다. 구성모델에서 콘크리트의 비선형성은 주응력비에 따른 강도증감계수와 탄성계수의 변화에 따른 비선형저감계수를 사용하여 나타내었다. 유한요소 모델해석에서 콘크리트는 8절점을 가진 사각형요소로 하고 철근은 1차원 선형요소로 가정하여 해석하였다. 유한요소해석으로부터 얻어진 수치해석결과와 실험실에서 행한 실험결과를 비교하였다.