• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
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• pp.548-555
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• 2005

Since soil-structure interactions are one of the most important subjects in the structural/foundation engineering, much study concerning the soil-structure interactions had been carried out. One of typical structures related to the soil-structure interactions is the strip foundation which is basically defined as the beam or strip rested on or supported by the soils. At the present time, lack of studies on dynamic problems related to the strip foundations is still found in the literature. From these viewpoint, this paper aims to theoretically investigate dynamics of the elliptic strip foundations and also to present the practical engineering data for the design purpose. Differential equations governing the free, out-of-plane vibrations of such sap foundations we derived, in which effects of the rotatory and torsional inertias and also shear deformation are included although the warping of the cross-section is excluded. Governing differential equations subjected to the boundary conditions of free-free end constraints are numerically solved for obtaining the natural frequencies and mode shapes by using the numerical integration technique and the numerical method of non-linear equation.

• 한국재료학회지
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• 제9권4호
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• pp.341-344
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• 1999

We reported compositional separation(CS) into Co-enriched and Cri-enriched components inside the grains of Co-Cr based thin films prepared by rf sputtering. CS strongly depends on the sputtering conditions of substrate temperature and target composition. Tuning the microstructure of the Co-Cr films is important in order to employ the CS for high-density magnetic recording. We investigated the origin of CS from thermodynamic viewpoint. We employ a spinodal decomposition-like model to describe the origin of the CS in Co-Cr films. We consider the total free energy of the Co-Cr films as the sum of several free energies of; 1) thermodynamic mixing entropy of a binary solid solution, 2) magnetic ordering interaction(MOI) energy below the Curie temperature, and 3) excess interaction energy(XS) caused by the sputtering process as a function of temperature and composition. Those energies distorted the total free energy like the spinodal decomposition and caused the compositionally separated fine microstructure inside the grains. If the second derivative of the total free energy with respect to Cr composition becomes negative at a given substrate temperature, we may observe a metastable compositional separation inside the Co-Cr alloy films. We expect to exploit the microstructure of CS for ultra-high density magnetic recording.

• IEIE Transactions on Smart Processing and Computing
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• 제5권3호
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• pp.178-184
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• 2016

This paper proposes a new path-finding scheme using viewpoint-invariant landmarks. The scheme introduces the concept of landmark detection in images captured with a vision sensor attached to a mobile robot, and provides landmark clues to determine a path. Experiment results show that the scheme efficiently detects landmarks with changes in scenes due to the robot's movement. The scheme accurately detects landmarks and reduces the overall landmark computation cost. The robot moves in the room to capture different images. It can efficiently detect landmarks in the room from different viewpoints of each scene. The outcome of the proposed scheme results in accurate and obstacle-free path estimation.

• Journal of Mechanical Science and Technology
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• 제18권8호
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• pp.1271-1287
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• 2004

In this article, vapor bubble nucleation in liquid and the evaporation process of a liquid droplet at its superheat limit were discussed from the viewpoint of molecular clustering (molecular cluster model for bubble nucleation). For the vapor bubble formation, the energy barrier against bubble nucleation was estimated by the molecular interaction due to the London dispersion force. Bubble nucleation by quantum tunneling in liquid helium under negative pressure near the absolute zero temperature and bubble nucleation on cavity free micro heaters were also presented as the homogenous nucleation processes.

• Bulletin of the Korean Chemical Society
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• 제20권12호
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• pp.1479-1482
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• 1999

We have studied the behavior of interdiffusion between partially miscible polymer pair from a theoretical viewpoint by applying the reptation model for collective interdiffusion and spinodal decomposition in polymer mixtures with different molecular weights. We find that our predictions agree well with the experiments of Klein and co-workers, where the exponent α of the initial increase of interfacial width with time in $t^{\alpha}$ is significantly lower than 0.5 for free diffusion.

• 대한토목학회논문집
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• 제36권6호
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• pp.1069-1073
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• 2016

현행 지하철 무임승차제도는 1980년 도입된 이후 지금까지 시행되고 있지만 고령화 인구가 지속적으로 증가함에 따라 무임승차 대상자 역시 증가하고 있다. 이러한 상황은 결국 도시철도 재정지원 부담으로 작용하고 있다. 또한 지하철과 버스 간 원활한 환승서비스 구축이 미흡함에 따라 무임수송제도는 반쪽짜리 복지라는 평가를 받기도 한다. 이에 본 연구에서는 무임승차대상자의 카드자료를 분석하여 경제학적인 측면에서의 영향을 파악한다. 또한 통행패턴에 따른 대중교통수단간 환승패턴을 분석하고, 국외사례와 비교하여 이에 대한 문제점을 제시하였다. 현행 무임승차제도를 개선할 수 있는 방안을 마련하고, 이를 지원할 수 있는 대안을 제시하였다. 이를 통하여 현행 도시철도 운영기관의 운영적자 해소방안 및 향후 고령인구 증가에 따른 대중교통측면의 복지서비스 제공 등 무임승차제도 관련 교통정책의 발전방안을 제시하였다.

• 대한화학회지
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• 제35권6호
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• pp.730-736
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• 1991

Flory의 상태방정식 이론의 관점에서, 고분자용액 및 그 혼합물에서 나타날 수 있는 부분혼합도의 각 경우에 대한 일반화된 조건을 제시하였고, 혼합 Gibbs Energy ${\Delta}G_{mix}$에서 나타나는 에너지항과 free volume항들의 온도에 따른 변화를 조사하여 부분혼합도에 미치는 그것들의 영향을 일반화시켰으며, 그 밖의 매개변수들의 영향도 일반화시켰다.

• 전력전자학회논문지
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• 제5권2호
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• pp.163-169
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• 2000

전력변환시스템의 경제적인 설계를 위해서는 전력용 반도체소자의 전류정격을 모든 동작조건에서 최대한 이용하는 것이 매우 중요하다. 따라서 본 논문에서는 제안전압 한계의 변화, 연산지연시간, 시스템의 불확실성에 대해서도 오버슈트 없는 고속 전류제어 응답을 얻는 실용적인 디지털 전류제어기의 설계방법을 제안한다. 제안한 전류제어기는 수정된 시간지연보상기와 조건부 적분기를 갖는 고이득 PI제어기로 구성되어 있다. 제시된 시뮬레이션 및 실험 결과는 제안한 방법의 유효성을 보여준다.

• 대한조선학회논문집
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• 제45권3호
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• pp.337-343
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• 2008

There are various hull types on the mid-size superyachts around $30\;{\sim}\;45m$. In any case, it is important to design the proper hull shape in viewpoint of the reduction of wave resistance, because small vessels such as superyachts are running at relatively higher Froude Number than other merchant ships. FLUENT with a VOF option was employed to investigate the flow fields around the superyachts having three-typical hull types: U-, V-types and catamaran. Overall performances including free surface flow were compared to figure out hydrodynamic characteristics of superyachy by numerical simulation.

• Industrial Engineering and Management Systems
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• 제9권2호
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• pp.165-177
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• 2010

This paper discusses a method for pricing the storage of inbound containers in a container yard. The pricing structure is characterized by a free-time-limit and a storage price for the storage time that extends beyond the free-time-limit. A cost model is developed from the viewpoint of a public terminal operator as well as a private terminal operator. Unlike a previous study on this issue, this study assumes that the retrieval times follow a discrete probability distribution, which is more realistic than the previous study. A solution procedure is suggested and illustrated by using numerical examples.