• Magazine of the Korea Concrete Institute
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• v.4 no.1
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• pp.81-87
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• 1992

In this thesis, the fatigue tests were performed on a series of SFRC(steel fiber reinforced concrete) to investigate the fatigue behavior of SFRC varying with the steel fiber contents and the steel fiber aspect ratios. The three point loading system is used in the fatigue tests. In tl1ese tests, relations between the repeated loading cycles and the mid-span deflections, number of repeated loadmg cycles when specimen was fractured were observed. On this basis, the mid-span deflections, the elastic strain energy and inelastic strain energy of SFRC were studied. A S - N curve \vas drawn to present the fatigue strength of SFRC beam. From che test results, by increasing the steel fiber content the energy lost on the permanent deformation decreases and the energy spent on crack growth increases. But in case of SFRC with the same steel fiber content the higher the steel fiber aspect ratio is, the less the elastic strain energy is. According to S - N curve drawn by the regression analysis on the fatugue test results, the fatigue strength with 2,000,000 repeated loading cycles in SFRC with the steel fiber content is 1.0% shows about 70% on the first crack static flexural strength.

• Proceedings of the KIEE Conference
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• 2006.10d
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• pp.28-30
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• 2006

본 논문에서는 대용량 동기발전기 회전자 권선의 다양한 단락사고 유형에 따라 발생하는 공극자속 파형의 변형정도에 대한 민감도해석을 수행하였다. 우선 정밀 전자장 수치해석도구를 이용하여 발전기 회전자 권선의 단락사고 유형에 대한 과도상태 해석을 수행하여 공극자속 파형에 대한 기본 데이터를 수집하였다. 이를 바탕으로 정상상태의 공극자속 파형을 기준으로 각 단락사고 유형별로 발생하는 공극자속 파형에 대한 최대 전압차에 다구찌법을 적용하여 Signal to Nose(SN) ratio 및 Percentage Contribution(PC) 등을 분석함으로써 단락사고 유형에 따른 공극자속 파형의 변형정도를 정량화하였다. 따라서 본 연구결과는 향후 대용량 발전기 회전자 단락사고 진단 및 감시 시스템 구축에 관련한 분야에 중요한 기초데이터로 활용될 것으로 사료된다.

• Proceedings of the KAIS Fall Conference
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• 2008.11a
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• pp.371-374
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• 2008

본 연구에서는 무도장 Weldless 평가금형을 이용하여 사출성형 공정조건에 따라 다양한 형태의 변형이 생기는 성형품을 CAE를 통하여 ABS와 PC의 사출조건 냉각시간, 보압의 유/무 등에 따라서 발생되는 문제점과 변형량을 예측하고, 실제 사출성형 되어진 성형품과의 비교 분석을 통하여 사출성형 CAE 해석을 실제 사출성형 공정에서의 활용방안에 대하여 검토하였다.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.4
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• pp.490-496
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• 2012

The main object of this research is to minimize the shock effects which frequently result in fatal damage in offshore wind turbine on impact of barge. The collision between offshore wind turbine and barge is generally a complex problem and it is often impractical to perform rigorous finite element analyses to include all effects and sequences during the collision. On applying the impact force of a barge to the offshore wind turbine, the maximum acceleration, internal energy, and plastic strain are calculated for each load case using the finite element method. A parametric study is conducted with the experimental data in terms of the velocity of barge, thickness of the offshore wind turbine, and thickness and Mooney-Rivlin coefficient of the rubber fender. Through the analysis proposed in this study, it is possible to determine the proper size and material properties of the rubber fender and the optimal moving conditions of barge.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2008.11a
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• pp.219-222
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• 2008

본 논문은 공간영역 상에서 다양하게 변형된 복제 영상과 원본 영상간의 통계적 특성을 이용하여 그 유사도를 측정하고 복제 여부를 판단하는 계층적 구조의 불법 비디오 감식 방법을 제안한다. 영상의 대표적 특성인 명암도에 따라 순위를 매김으로써 공간적 변형에 영향을 받지 않도록 하였으며, 데이터베이스에 저장된 방대한 양의 영상들에 대한 검색 시간과 계산량을 줄이기 위해 순위 표본 프레임을 이용하여 유사한 후보 영상군을 추출한다. 이러한 후보 영상군을 대상으로 일반적인 불법복제 비디오의 형태를 감안하여 각 프레임의 중앙 영역을 포함하여 통계 검정을 이용함으로써 복제 여부를 판단한다. 실험 결과 제안하는 방법은 기존 방법과 유사한 정확도를 보이며 동시에 선택된 순위 표본 프레임 수는 약 50% 가량 적게 추출되어 검색 시간과 계산량이 감소하였다. 또한 영상의 화질 열화, 대비 변형, 확대 및 축소, letterbox 등 다양한 공간적 변형에도 포괄적으로 복제 여부를 판단할 수 있음을 실험을 통해 확인하였다.

• Journal of the Korean Geotechnical Society
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• v.21 no.7
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• pp.91-105
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• 2005

In this study, the deformation behavior of Daegok dam during the construction was analyzed based on the measurement data and a comparative analysis with foreign CFRD measurements was performed. From measuring settlements of Daegok dam with depth, overall behavior was evaluated to be consistent with measured data of other CFRD dams. In addition, construction modulus, void ratio and shape factor were also evaluated to be major factors in predicting the settlement behavior during construction of CFRD-typed dam from measured data of 38 CFRD-typed dams, and the maximum internal settlement is proportional to the void ratio. From the relationship between the maximum internal settlement and the height of a dam, 26 dams were assessed to have its relative modulus ranging between 0.001 and 0.01. In case of general CFRD, the average modulus of maximum internal settlement to the height of a dam is estimated to be 0.005. In case of a low void ratio, the construction modulus was high with its shape factor below 4. On the other hand, in case of a high void ratio, the relative settlement rate was high with its shape factor more than 4.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.4
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• pp.223-231
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• 2022

Residual stress that can occur during the metal additive manufacturing process is an important factor that must be properly controlled for the precise production of metal parts through 3D printing. Therefore, in this study, the factors affecting these residual stresses were investigated using an experimental method. For the experiment, a specimen was manufactured through an additive manufacturing process, and the amount of deformation was measured by cutting it. By appropriately calibrating the measured data using methods such as curve fitting, it was possible to quantitatively analyze the effect of process parameters and metal powder reuse on deformation due to residual stress. From this result, it was confirmed that the factor that has the greatest influence on the magnitude of deformation due to residual stress in the metal additive manufacturing process is whether the metal powder is reused. In addition, it was confirmed that process parameters such as laser pattern and laser scan angle can also affect the deformation.

• Tunnel and Underground Space
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• v.31 no.1
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• pp.66-81
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• 2021

The effects of directional fracture tensor components and first invariant of fracture tensor on deformation moduli and shear moduli of fractured rock masses is analyzed based on regression analysis performed between 3-D fracture tensor parameters and deformability of DFN blocks. Using one or two deterministic joint sets, a total of 224 3-D discrete fracture network (DFN) cube blocks were generated with various configurations of deterministic density and probabilistic size distribution. The fracture tensor parameters were calculated for each generated DFN systems. Also, deformability moduli with respect to three perpendicular direction of the DFN cube blocks were estimated based on distinct element method. The larger the first invariant of fracture tensor, the smaller the values for the deformability moduli of the DFN blocks. These deformability properties present an asymptotic pattern above the certain threshold. It is found that power-law function describes the relationship between the directional deformability moduli and the corresponding fracture tensor components estimated in same direction.

• Journal of the Korean Geotechnical Society
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• v.15 no.1
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• pp.161-173
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• 1999

Settlement analysis based on oedometer test results with or without Skempton-Bjerrum's modification method ( widely used for practical purposes when estimating consolidation settlements of soft clay deposits) has shortcomings that it cannot simulate real stress states and deformation behaviors of soils in case that in-situ loading and deformation conditions are not 1-dimensional. In this study, the stress path method, reflecting various probable stress paths, was employed to normally - consolidated kaolinite samples by using automated triaxial testing device which can control stress paths automatically. From this experimental study, elastic, consolidation, secondary compression and pore pressure development - dissipation behaviors under various stress paths were analyzed and deformation characteristics of soft clays, which can be the basis of rational estimation of settlements, were studied. Also by comparing results of stress path tests with those of 1-dimensional consolidation tests, limitations and problems of conventional methods were clarified.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.867-874
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• 2003

섬유보강재를 이용한 성토제체의 설계에서 기존의 방법은 보강재의 변형을 무시하고 흙의 변형만을 중요시하고 있다. 보강재에 의해 보강된 성토제체의 파괴면에서 보강재와 흙의 거동은 초기응력단계에서는 일체거동현상을 나타내지만 응력의 증가에 따라 변형량에서 차이를 보인다. 이러한 문제는 토공구조물의 보강재를 설계하는데 있어서 중요한 요소로서 보강효과에 큰 영향을 미칠 수 있다. 본 연구에서는 연약지반 위에 PET Mat로 보강하여 축조한 성토제체에서 보강재와 흙의 응력 - 변형거동을 수치해석을 통하여 분석하였다. 연구결과, 파괴면에서 보강재의 변형은 보강재의 인장강도 크기에 따라 큰 차이를 보이고 있다. 외부하중에 의해 보강재에 발생하는 최대응력은 보강재의 항복인장강도를 초과하지 않으며, 보강재에 발생하는 응력이 성토체에서 발생하는 응력이상일 때 이상적인 것으로 나타났다. 또한 제체의 전단파괴에 대한 안전율은 보강재의 항복인장강도가 증가할수록 증가하는데 보강재와 흙의 변형이 일치되는 이후부터는 안전율의 증가율은 거의 미미한 것으로 나타났다.