• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.5
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• pp.461-466
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• 2015

Atomic force microscopy (AFM) is powerful tool for determining properties of samples based on interactions between the sample surface and an approaching probe tip. In this study, we modeled the interactions between the sample and the tip of the AFM microcantilever as a single nonlinear spring with an equivalent stiffness element and simulated the dynamic behaviors of the AFM microcantilevers using the finite element method (FEM) and ANSYS software. With the simulation results, we analyzed the complex dynamic responses of the AFM cantilever using proper orthogonal decomposition (POD). In addition, we compared the simulation and experimental results using the same method. Consequently, we suggest an effective method to express the interaction between the tip and sample, and we confirm that the influence of the higher order model due to the interaction between the tip and sample is increased.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.190-190
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• 2011

사회 다변화 및 급속한 경제성장과 도시밀집화로 인하여, 화재의 발생으로 인하여 막대한 인명피해 및 대규모의 재산상의 피해가 지속적으로 발생하고 있다. 이러한 화재의 피해를 예측하기 위해서는 실제 규모의 화재실험이 매우 유용하지만, 막대한 비용과 현실적 제약조건으로 인하여 실제 실험에는 많은 어려움이 따른다. 따라서 막대한 예산이 소요되는 실제규모의 화재실험의 대체방법으로 실제를 모사하는 축소모형 화재모의실험 및 컴퓨터를 이용한 화재 시뮬레이션 기법이 널리 이용되고 있다. 본 논문에서는 범용 컴퓨터를 이용한 화재 시뮬레이션 기법(CFAST)을 이용하여 수직 공간 구성을 가지는 단독주택의 화재 성상을 검토하였다. 시뮬레이션 모델로는 단독주택을 대상건물로 하여 2층으로 수직 공간을 가지는 단독주택 건물에 대한 모의 화재 시뮬레이션을 수행 하였다. 화재 시뮬레이션 결과는 각 구획실별 온도, 일산화탄소량, 공기 중 산소량 등을 도출하여 기존 이론에 의한 화재성장 그래프와 시뮬레이션 데이터를 비교하여 정확도를 검토하였다. 본 논문에서는 두가지의 시나리오를 작성하여 화재 시뮬레이션 프로그램의 결과 값을 분석하였다. (1) 시나리오 1 : 화재시뮬레이션 대상건물 1층 거실(2번방)에서 스프링클러 미 설치시 화재가 발생한 경우를 가정하여 수평방향인 3번방과 수직방향인 7번방의 화재 확산 피해정도를 살펴보고, 화재 그래프의 이론값과 실험값의 차이를 비교하여 그 정합성을 검토하였다. 발화물질은 Curtain, TV set, Sofa, Table으로 하며 시간은 60초 간격으로 총 3600초(1시간)를 분석 하였고, 발화지점의 온도, 일산화탄소, 공기중 산소 농도를 분석하였다. (2) 시나리오 2 : 시나리오 1과 동일한 화재발현 조건으로 스프링클러가 설치되어 있을 때 화재 발생 했을 경우, 수평방향인 3번방과 수직방향인 7번방의 화재 확산 피해를 시나리오 1과 비교 검토 하였다. 기존 이론에 의한 화재 성장 그래프와 이번 시뮬레이션 결과값을 토대로 만든 그래프 형태를 비교해보면 두 그래프의 형태가 비슷한 형태를 나타내어 Flash Over 현상과 Back Draft 현상이 이론값과 같은 경향을 나타내고 있음을 확인 할 수 있었다. 따라서, 본 논문에서 수행한 화재 시뮬레이션 기법으로 건축물의 실제 화재시의 피해정도를 예측하는 데 유용하게 활용될 것으로 판단된다.

• The Journal of the Korea Contents Association
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• v.9 no.2
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• pp.133-141
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• 2009

This paper propose an expanded ASP exclusive development framework method. We applied a module to the suggested method which suit to develope ASP. Proposed method is a kind of module, which manages MVC develope methodology and treats Query and ASP information as a XML. It has flexibility which meets the client's request quickly. Using inherited base model which previously exist in template source, developer only concerned with development methodology so that they can reduce development time and reinforce a integrity of system. We proposed these improvements as a framework. Experimental results validate our scheme, showing a fewer number of files and a better flexibility than other development method, and also about 29% of program code has been reduced.

• Journal of the Korean Geotechnical Society
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• v.27 no.5
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• pp.33-43
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• 2011

In this study, simplified analysis (discrete analysis of column and pile) of pile bent structures was performed on the basis of the equivalent base spring model. And the minimum reinforcement ratio in pile bent structures was evaluated by taking into account various factors. To obtain the detailed information, simplified analysis was performed for column-pile interactions and the behavior of a column-pile was estimated and highlighted. Based on this study, it is shown that previous design method based on virtual fixed point theory cannot adequately predict the physical behavior of pile bent structures. It is found that the maximum bending moment is located within craking moment of the pile when material non-linearity is considered. It is also found that the minimum reinforcement ratio (=0.4%) is appropriately applicable for the optimal design of pile bent structure under ultimate lateral loading.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.1
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• pp.57-69
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• 1990

The static nonlinear analysis of offshore pipeline is carried out by the finite element method. The governing equilibrium equation are derived by the principle of minimum potential energy and the modified Newton-Raphson procedure is used to solve the system of nonlinear algebraic equation. Geometrically nonlinear beam elements and spring elements are utilized to model the pipeline, stinger, pipe supports and seabed simultaneously. The beam element developed can be used to model redundant structures. It provides for both the torsional deformation and elongation of pipeline, and permits the use of different physical properties in each principal direction. The validity of this method is investigated by comparing the results with these obtained by other methods.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.7
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• pp.837-842
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• 2010

The wiper system of a vehicle is important because it wipes the windshield, thereby enabling drivers to see through the windshield even under conditions of rain and snow. The blade is the key component of the wiper system because it wipes the windshield. When wiper-arm spring causes the blade to be pressed on the windshield optimum performance of wiping can be achieved when appropriate contact pressure is maintained. In this study, a dynamic analysis of the wiper system is carried out. A three-dimensional finite-element model of the wiper system is generated using SAMCEF, a commercial structural dynamic analysis program. The distribution of the contact pressure of the blade in its dynamic state is calculated. The simulation result is compared to the experiment result. Using the results of this study, the contact pressure of the blade can be estimated.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.4
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• pp.376-387
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• 2012

Based on the nonlinear spring model coupled with perturbation method, 2nd harmonic waves generated by oblique incident ultrasound on nonlinear crack interface were calculated and investigated. Reflected and transmitted waves from the interface were determined and analyzed at various angle of incidence for the cracks with different interfacial stiffness in order to estimate the 2nd harmonic generation of incident ultrasound. It was shown in computer simulation that the 2nd harmonic components changed much with the increase of incidence angle in both reflected and transmitted wave, but became very small when the incident angle approached toward 90 degree. It can be concluded that the 2nd harmonic component of reflected wave has a meaningful amplitude as much as the transmitted 2nd harmonic wave from partly closed crack.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.1
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• pp.13-30
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• 2016

This paper concerns the development of an optimized TBM segmental lining design system for a subsea tunnel. The subsea tunnel is normally laid down under the sea water and submarine ground which consists of soil or rock. The design system is the series of process which can predict segmental lining member forces by ANN (artificial neural network system), analyze suitable section for the designated ground, construction and tunnel conditions. Finally, this lining design system aims to be connected with a BIM system for designing the subsea tunnel automatically. The lining member forces are predicted based on the ANN which was calculated by a FEM (finite element analysis) and it helps designers determine its segmental lining dimension easily without any further FE calculations.

• Transactions of Materials Processing
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• v.29 no.5
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• pp.241-250
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• 2020

In this study, the methodology of the springback prediction of automotive parts applied 3rd generation AHSS was investigated using the response surface model analysis based on a regression model, and the meta model analysis based on a Kriging model. To design the learning data set for constructing the springback prediction models, and the experimental design was conducted at three levels for each processing variable using the definitive screening designs method. The hat-shaped member, which is the basic shape of the member parts, was selected and the springback values were measured for each processing type and processing variable using the finite element analysis. When the nonlinearity of the variables is small during the hat-shaped member forming, the response surface model and the meta model can provide the same processing parameter. However, the accuracy of the springback prediction of the meta model is better than the response surface model. Even in the case of the simple shape parts forming, the springback prediction accuracy of the meta model is better than that of the response surface model, when more variables are considered and the nonlinearity effect of the variables is large. The efficient global optimization algorithm-based Kriging is appropriate in resolving the high computational complexity optimization problems such as developing automotive parts.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.3
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• pp.303-311
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• 2013

This research deals with the analysis and design of a driving mechanism for an automatic pneumatic drug injector, which can precisely control the injection volume using a relatively simple friction-driven mechanism, without any complicated control system. Through a dynamic analysis, the effects of the design parameters of the driving mechanism associated with the geometry, spring stiffness, and fiction are analyzed, and the results are reflected in a proto-type drug injector design, which is under development for mass production. A test is performed to assess the durability of the mechanism for up to one million operations, and comparison of its displacement after one million operations, verifies the mechanism's durability.