• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.11
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• pp.2749-2761
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• 2000

Densification, grain growth, and phase transformation of nanocrystalline ceramic powder were investigated under pressureless sintering, sinter forging, and hot pressing. A constitutive model for densification of nanocrystalline ceramic powder was proposed and implemented into a finite element program (ABAQUS). A grain growth model was also proposed by including the effect of applied stress on grain growth when phase transformation occurs. Finite element results by using the proposed models well predicted densification behavior, deformation, and grain growth of nanocrystalline titania powder during pressureless sintering, sinter forging, and hot pressing. Finite element results by using the proposed model also well predicted experimental data in the literature for densification behavior of nanocrystalline zirconia powder during pressureless sintering and sinter forging.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1174-1177
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• 2003

In this study, to achieve the optimal conditions for mechanical hyper-fine pattern fabrication process, deformation behavior of the materials during indentation was studied with numerical method by ABAQUS S/W. Polymer (PMMA) and brittle materials (Si, Pyrex glass) were used as specimens, and forming conditions to reduce the elastic recover and pile-up was proposed. The indenter was modeled a 3D rigid surface. Minimum mesh sizes of specimens are 1-10nm. Comparison between the experimental data and numerical result demonstrated that the finite element approach is capable of reproducing the loading-unloading behavior of a nanoindentation test. The result of the investigation will be applied to the fabrication of the hyper-fine pattern.

• 한국공간정보시스템학회:학술대회논문집
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• 2004.05a
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• pp.113-122
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• 2004

Cable domes deform very largely because of the characteristics of flexible hybrid system and pre-tension, and include geometrical non-linearity in those structural behavior. Especially wind load is more dominant than seismic load, because cable domes are flexible structures whose bending stiffness is very small and self-weight is very light. Therefore, in this paper, the Modified Stiffly Stable Method is applied to analyze the nonlinear dynamic behavior of cable domes and compared these results with ones of the $Newmark-{\beta}$ Method which is generally used. The Seoul Olympic Gymnastic Arena is taken as an numerical example and three kinds of models with giving each different intensity of pre-tension are selected. And dynamic nonlinear behavior of cable domes are analyzed by artificial spectrum of wind velocity wave which is similar to actual wind loads.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.894-899
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• 2004

In this paper, the track pull-in behavior analyses in an optical disk drive (ODD) using plane phase is treated and the parameters affecting it are discussed. Track pull-in is the track capture procedure to do track following control and it is key factor to increase data transfer rate. Simulation method, Runge-Kutta method to solve nonlinear equation, is used to evaluate the track pull-in conditions, and the real servo loop parameters are applied in this process to get the more real condition. Finally, the comments for the acquired results are discussed briefly.

• Journal of Industrial Technology
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• v.32 no.A
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• pp.79-86
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• 2012

In this paper, centrifuge model tests and numerical analysis on the breakwater structure were performed to investigate the stability and behavior of breakwater in field. In centrifuge model tests, construction sequence of breakwater structure such as preparation of weathered rock and sand deposit, construction of D.C.M, rubble mound with crushed stones and installment of breakwater structure was reconstructed like field condition and the behavior of ground settlement and breakwater displacement during stage of construction was observed during tests. For the final stage of simulating the horizontal movement of breakwater due to wave force, horizontal load was applied by horizontal loading apparatus being specially designed so that horizontal displacement of structure could be observed. Numerical analysis were also carried out and its results were compared with test results to assess the property of centrifuge model tests with respect to the behavior of structure as well as ground.

• Journal of Information Technology Applications and Management
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• v.13 no.1
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• pp.1-16
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• 2006

This paper empirically analyzed consumer price search behavior using Web log data of a Korean web site for price comparison. Consumer click-stream data of the site was used to test the effects of price level, product category, third party certification, reputation of retailers on click behavior. According to the descriptive statistics, 67.4% of shopbot users clicked the offer which was the lowest price returned in a search. We found that third party certification and reputation of retailers were significant determinants of clicking the lowest priced offer from legit analysis. We also applied Tobit regression analysis to estimate the price premium of the two determinants, but only reputation of retailers was found to have price premium of 4.9%.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.6
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• pp.645-652
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• 2016

The basic equation of body and mind that can be represented as body and mind based on love model of Romeo and Juliet is presented in this paper. In order verify validity for physical idea of unification for body and mind when the external force is applied in the basic equation. We display the time series and phase portrait for nonlinear behavior, and this paper confirms the point of difference between body-mind neutral monism and body-mind dualism.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.57-60
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• 2008

The studies for internal void closure have been conducted experimentally and numerically for open die forging. The FEM analysis is performed to investigate the deformation behavior of some internal voids in cast ingots during two upsetting stages. The calculated results of void closure behavior are compared with the measured results before and after upsetting. The shapes and sizes of each internal void are scanned by the X-ray scanner. From this result, the criteria for deformation amounts effect on the void closure can be investigated by the types of void. Closed voids could be compressed and eliminated after forging when the applied deformation amounts were larger than the critical effective strains. On the other hand, open voids could not be compressed and removed.

• Journal of the Korea Concrete Institute
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• v.13 no.1
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• pp.77-85
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• 2001

Concrete filled steel tubular (CFT) columns are becoming popular in structural applications. The increased popularity comes from their excellent structural properties such as high strength, high ductility, and large energy absorption capacity. However, the disadvantage feature of CFT column is the difficulty in predicting its time dependant characteristic (i.e., creep and shrinkage) of inner concrete. The time dependent behavior of CFT column can cause serious serviceability problems. Therefore, it is necessary to investigate the long term behavior of CFT column. This paper presents analytical and experimental studies on long-term behavior of CFT-column under a central axial loading. Two loading cases are considered in the research; (1) the load applied only at the inner core concrete of CFT-column and (2) the load applied simultaneously on both concrete and steel tube. Analysis method using the bond strength model is proposed and conclusions on long-term properties of CFT-column can be derived from the results.

• Steel and Composite Structures
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• v.12 no.3
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• pp.207-230
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• 2012

Nowadays CFRP (Carbon Fiber Reinforced Polymer) became widely used materials for the strengthening and retrofitting of structures. Many experimental and analytical studies are encountered at literature about strengthening beams by using this kind of materials against static loads and cyclic loads such as earthquake or wind loading for investigating their behavior. But authors did not found any study about strengthening of RC beams by using CFRP against low velocity impact and investigating their behavior. For these reasons an experimental study is conducted on totally ten strengthened RC beams. Impact loading is applied on to specimens by using an impact loading system that is designed by authors. Investigated parameters were concrete compression strength and drop height. Two different sets of specimens with different concrete compression strength tested under the impact loading that are applied by dropping constant weight hammer from five different heights. The acceleration arises from the impact loading is measured against time. The change of velocity, displacement and energy are calculated for all specimens. The failure modes of the specimens with normal and high concrete compression strength are observed under the loading of constant weight impact hammer that are dropped from different heights. Impact behaviors of beams are positively affected from the strengthening with CFRP. Measured accelerations, the number of drops up to failure and dissipated energy are increased. Finite element analysis that are made by using ABAQUS software is used for the simulation of experiments, and model gave compatible results with experiments.