• Design & Manufacturing
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• 제13권1호
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• pp.5-12
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• 2019

In this paper, we studied the micro tool deflection, micro cutting with low temperature, and deformation of micro ribs caused by cutting forces. First, we performed an integrated machining error compensation method based on captured images of tool deflection shapes in micro cutting process. In micro cutting process, micro tool deflection generates very serious problems in contrast to macro tool deflection. To get the real images of micro tool deflection, it is possible to estimate tool deflection in cutting conditions modeled and to compensate for machining errors using an iterative algorithm correcting tool path. Second, in macro cutting fields, the cryogenic cutting process has been applied to cut the refractory metal but, the serious problem may be generated in micro cutting fields by the cryogenic environment. However, if the proper low temperature is applied to micro cutting area, the cooling effect of cutting heat is expected. Such effect can make the reduction of tool wear and burr formation. For verifying this passibility, the micro cutting experiment at low temperature was performed and SEM images were analyzed. Third, the micro pattern was deformed by the cutting forces and the shape error occurred in the sidewall multi-step cutting process were minimized. As the results, the relationship between the cutting conditions and the deformation of micro-structure during micro cutting process was investigated.

• 대한토목학회논문집
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• 제30권4A호
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• pp.383-389
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• 2010

현재 우리나라의 콘크리트구조설계기준은 강도설계법에 근간하고 있다. 강도설계법에 의해 휨부재를 설계할 경우, 콘크리트 응력-변형률 관계는 사용하중 상태에서 선형으로 가정하지만 이후 극한한계 상태까지에 대해서는 규정되어 있지 않다. 이로 인해 콘크리트구조설계기준에서는 처짐 및 균열폭 등의 산정에 대해 개별적인 규정을 두고 있다. 그러나 한계상태설계법에 근거한 EC에서는 재료에 대한 응력-변형률 관계를 규정하고 있다. 따라서 재료의 응력-변형률 관계로부터 휨강도 및 처짐 등을 직접 계산할 수 있다. 본 연구에서는 휨부재에 대하여 주어진 재료 모델을 바탕으로 평형방정식과 적합조건식을 적용하여 휨모멘트-곡률 관계를 계산하였다. 이로부터 휨강도 및 처짐을 산정하여 현행 콘크리트구조설계기준에 의한 값과 비교하였다. 해석 결과 재료 모델로부터 휨모멘트-곡률 관계를 통해 산정된 처짐은 실험 결과와도 비교적 잘 일치하고, 항복 이후의 처짐 계산도 가능한 것으로 나타났다.

• Journal of Advanced Marine Engineering and Technology
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• 제30권2호
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• pp.190-198
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• 2006

• 대한조선학회논문집
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• 제31권3호
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• pp.119-128
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• 1994

기관실 상갑판 특히 거주구 외부의 상갑판 판부재는 외적인 수직하중이 거의 작용하지 않음에도 불구하고 건조중인 대형선박에서 갑판에 널리 대처짐 현상이 발생할 때가 있는 반면에 수직하중이 작용하는 거주구 내부의 기관실 상갑판은 처짐발생 크기 및 분포정도가 미미한, 규명하기 어려운 현상들이 나타나고 있다. 따라서, 본 연구에서는 3차원 구조해석으로부터 얻은 거주구 및 자중에 의한 정적하중의 영향, 손상보고에 따라 계측된 처짐량 자료 및 분포상황, 초기처짐의 크기 및 형상, 용접잔류응력, 면내하중 성분들을 대상으로 비선형 시리즈 해석을 수행하고, 이로부터 판부재에 발생하는 최대처짐 추정식을 제시하였다. 또한, 본 연구를 통하여 개발된 추정식을 이용하여 기존 손상선박의 처짐원인 분석, 거주구 탑재 및 진수 전후의 기관실 상갑판의 처짐거동 그리고 기존의 선각품질관리기준이 기관실 상갑판의 처짐에 미치는 영향을 살펴보았고, 마지막으로 건조예정에 있는 기관실의 처짐현상을 예측하여 보았다.

• 한국전기화학회:학술대회논문집
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• 한국전기화학회 2000년도 춘계총회 및 학술발표회
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• pp.29-29
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• 2000

• Restorative Dentistry and Endodontics
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• 제30권6호
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• pp.442-449
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• 2005

이 논문의 목적은 복합레진과 컴포머에서, 중합수축의 양과 이로 인하여 야기되는 교두변위와의 상관관계를 알아보기 위함이다. 수복재료로서 Dyract AP, Compoglass F, Z100, Surefil, Pyramid, Synergy Compact, Heliomolar와 Heliomolar HB가 사용되었으며, 접착제로서는 SE Bond 가 사용되었다. 수복재료의 중합수축의 양을 측정하기 위하여, 자체 제작한 linometer를 사용하여, 60초간 일어나는 선수축량을 측정하였다. 한 수복재료 당 10회 측정하였으며, one way ANOVA와 사후검정방법으로 Tukey Test를 이용하여 $95\%$ 신뢰수준에서 각 수복재료의 중합수축량의 차이를 비교하였다. 치아에서 일어나는 교두변위의 양을 측정하기 위하여 사람의 상악소구치에 표준화된 MOD 와동을 형성하고(깊이 3mm, 넓이 3.5mm), 접착제를 도포한 후 광조사 시킨 후, 수복재료로 충전하였다 치아를 자체 제작한 교두변위 측정장치에 위치시키고, 광조사 시키고, 이 때 발생하는 교두의 변위를 10분간 측정하였다. 한 수복재료 당 15회를 측정하였으며 one way ANOVA와 사후검정방법으로 Tykey Test를 이용하여 $95\%$ 신뢰수준에서 각 수복재료의 교두변위 량의 차이를 비교하였다. 중합수축의 양과 교두변위의 양의 상관관계를 회귀분석법을 이용하여 분석하였다. 중합수축의 양은 Heliomolar, Surefil < Heliomolar HB < Z100, Synergy Compact < Dyract AP, Pyramid, Compoglass F (p < 0.05), 교두변위의 양은 Heliomolar, Surefil, Z100, Heliomolar HB, Synergycompact < Compoglass F < Pyramid, Dyract AP (p < 0.05) 였다. 중합수축의 양과 교두변위는 높은 상관관계를 나타내었다 (p < 0.001).

• Steel and Composite Structures
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• 제43권2호
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• pp.229-240
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• 2022

The main objective of this work is presenting a mathematical model for the concrete slab with fiber reinforced polymer (FRP) layer under the impact load. Impacts are assumed to occur normally over the top slab and the interaction between the impactor and the structure is simulated using a new equivalent three-degree-of-freedom (TDOF) spring-mass-damper (SMD) model. The structure is assumed viscoelastic based on Kelvin-Voigt model. Based on the sinusoidal shear deformation theory (SSDT), energy method and Hamilton's principle, the motion equations are derived. Applying DQM, the dynamic deflection and contact force of the structure is calculated numerically so that the effects of mass, velocity and height of impactor, boundary conditions, FRP layer, structural damping and geometrical parameters of structure are shown on the dynamic deflection and contact force of system. Results show that considering structural damping leads to lower dynamic deflection and contact force. In addition, increasing the impact velocity of impactor yields to increases in the maximum contact force and deflection while the contact duration is decreased. The result shows that the contact force and the central deflection of the structure decreases and the contact time decreases with assuming FRP layer.

• 한국기계가공학회지
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• 제16권4호
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• pp.89-96
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• 2017

A cable tray is a structure made of metal or a non-combustible material that supports cables in the electrical wiring of buildings. Cable trays should be developed to meet the various requirements of the construction site. In this study, a design system was developed to calculate the maximum support load and the maximum deflection according to the cross-sectional shape of the cable tray. The cross-sections of cable trays were modeled by combining linear and arc elements, and cross-sectional characteristics such as the 2nd moment of area were calculated. The distributed load and the concentrated load were applied to the cable tray using the Euler beam theory, and then the deflection profiles and maximum stress were calculated. To verify the developed system, deflection distributions and maximum stresses for two types of cable trays were calculated and compared. The maximum deflection and maximum stress errors calculated from the developed system were found to be less than 4% compared with numerical analysis results.

• Restorative Dentistry and Endodontics
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• 제29권4호
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• pp.346-352
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• 2004

The purpose of present study was to evaluate the polymerization shrinkage stress and cuspal deflection in maxillary premolars resulting from polymerization shrinkage of composites and compomers. Composites and compomers which were used in this study were as follows: Dyract AP, Z100, Surefil. Pyramid, Synergy Compact, Heliomolar, Heliomolar HB, and Compoglass F. For measuring of polymerization shrinkage stress, Stress measuring machine (R&B, Daejon, Korea) was used. One-way ANOVA analysis with Duncan's multiple comparison test were used to determine significant differences between the materials. For measuring of cuspal deflection of tooth, MOD cavities were prepared in 10 extracted maxillary premolars. And reduction of intercuspal distance was measured by strain measuring machine (R&B, Daejon, Korea) One-way ANOVA analysis with Turkey test were used to determine significant differences between the materials. Polymerization shrinkage stress is $\mathbb{\ulcorner}$Heliomolar, Z100, Pyramid < Synergy Compact Compoglass F < Dyract AP < Heliomolr HB, surefil$\mathbb{\lrcorner}$ (P < 0.05). And cuspal delfelction is $\mathbb{\ulcorner}$Z100, Heliomolar, Heliomolar HB, Synergy Compact Surefil. < Compoglass F < Pyramid, Dyract AP$\mathbb{\lrcorner}$ (P < 0.05). Measurements of ploymerization shrinkage stress and those of cuspal deflection of the teeth was different. There is no correlation between polymerization shrinkage stress and cuspal deflection of the teeth(p > 0.05).

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 봄 학술논문 발표대회
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• pp.159-160
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• 2020

Flat plate structures are designed in the form of long span due to the development of construction materials and the improvement of construction technology. However, a high-rise structure of a flat plate of 50 less floors is constructed without detailed review of the inequality shortening, long-term deflection of the slab, and cracks. Therefore, it is possible to examine the case of defects in the structure due to deformation and damage of non-structures such as crack and leak, deflection of the door frame, and deformation of equipment ducts. In this study, it is a high-rise structure, and the inequality shortening and long-term deflection of the slab of the flat plate structure were evaluated through finite element analysis, and it was confirmed that prior precision analysis and correction during construction is necessary.