• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.26-31
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• 2002

본 연구는 초고속 지능형 라인센터 개발에 관한 것으로서 1 차 년도 볼 스크류 방식의 시험모델에 대한 종합 검토 결과를 바탕으로 2 차 연도에는 리니어 모터를 채택한 라인센터의 시제품 설계에 있어서 고속화를 위한 방안을 모색하고 컴팩트한 경량의 구조를 지향하는 라인 센터 구조물을 설계하였고, 3 차 년도에는 라인센터의 제작 및 종합적인 시험 평가를 통하여 상품화 모델을 정립하고자 하였다.

• 세라미스트
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• 제22권4호
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• pp.350-356
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• 2019

Recently, transition metal dichalcogenide (TMDC) monolayers have been the subject of research exploring the physical phenomenon generated by low dimensionality and high symmetry. One of the keys to understanding new physical observations is the electronic band structure of 2D TMDCs. Angle-resolved photoelectron spectroscopy (ARPES) is, to this point, the best technique for obtaining information on the electronic structure of 2D TMDCs. However, through ARPES research, obtaining the long-range well-ordered single crystal samples always proves a challenging and obstacle presenting issue, which has been limiting towards measuring the electronic band structures of samples. This is particularly true in general 2D TMDCs cases. Here, we introduce the approach, with a mathematical framework, to overcome such ARPES limitations by employing the high level of symmetry of 2D TMDCs. Their high symmetry enables measurement of the clear and sharp electronic band dispersion, which is dominated by the band dispersion of single-crystal TMDCs along the two high symmetry directions Γ-K and Γ-M. In addition, we present two important studies and observations for the direct measuring of the exciton binding energy and charge transfer of 2D TMDCs, both being established by the above novel approach.

• Wind and Structures
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• 제5권1호
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• pp.61-80
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• 2002

Wind tunnel aeroelastic model tests of the Commonwealth Advisory Aeronautical Research Council (CAARC) standard tall building were conducted using a three-degree-of-freedom base hinged aeroelastic(BHA) model. Experimental investigation into the effects of coupled translational-torsional motion, cross-wind/torsional frequency ratio and eccentricity between centre of mass and centre of stiffness on the wind-induced response characteristics and wind excitation mechanisms was carried out. The wind tunnel test results highlight the significant effects of coupled translational-torsional motion, and eccentricity between centre of mass and centre of stiffness, on both the normalised along-wind and cross-wind acceleration responses for reduced wind velocities ranging from 4 to 20. Coupled translational-torsional motion and eccentricity between centre of mass and centre of stiffness also have significant impacts on the amplitude-dependent effect caused by the vortex resonant process, and the transfer of vibrational energy between the along-wind and cross-wind directions. These resulted in either an increase or decrease of each response component, in particular at reduced wind velocities close to a critical value of 10. In addition, the contribution of vibrational energy from the torsional motion to the cross-wind response of the building model can be greatly amplified by the effect of resonance between the vortex shedding frequency and the torsional natural frequency of the building model.

• Structural Engineering and Mechanics
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• 제58권5호
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• pp.799-823
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• 2016

A finite element model for the non-linear dynamic analysis of a reinforced concrete (RC) containment shell of a nuclear power plant subjected to extreme loads such as impact and earthquake is presented in this work. The impact is modeled by using an uncoupled approach in which a load function is applied at the impact zone. The earthquake load is modeled by prescribing ground accelerations at the base of the structure. The nuclear containment is discretized spatially by using 20-node brick finite elements. The concrete in compression is modeled by using a modified $Dr{\ddot{u}}cker$-Prager elasto-plastic constitutive law where strain rate effects are considered. Cracking of concrete is modeled by using a smeared cracking approach where the tension-stiffening effect is included via a strain-softening rule. A model based on fracture mechanics, using the concept of constant fracture energy release, is used to relate the strain softening effect to the element size in order to guaranty mesh independency in the numerical prediction. The reinforcing bars are represented by incorporated membrane elements with a von Mises elasto-plastic law. Two benchmarks are used to verify the numerical implementation of the present model. Results are presented graphically in terms of displacement histories and cracking patterns. Finally, the influence of the shear transfer model used for cracked concrete as well as the effect due to a base slab incorporation in the numerical modeling are analyzed.

• Bulletin of the Korean Chemical Society
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• 제31권1호
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• pp.59-63
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• 2010

Calculations are presented for the $\gamma$-aminobutyric acid-$(H_2O)_n$ (n = 0-5) clusters in both canonical and zwitterionic forms. We examine the effects of microsolvation on the structures and transformation between the canonical and zwitterionic forms. The canonical forms are predicted to be more stable for n = 0-4. With five microsolvating water molecules, the two forms of $\gamma$-aminobutyric acid become quasidegenerate, with the energies of zwitterionic forms slightly (by 1 - 3 kcal/mol) higher. The lowest energy zwitterionic conformer of $\gamma$-aminobutyric acid-$(H_2O)_5$ cluster is calculated to isomerize to canonical form through a barrier-less proton transfer process and is thus predicted to be kinetically unstable. Therefore, we predict that the canonical conformers of $\gamma$-aminobutyric acid should be observed predominantly in the gas phase at low temperature in presence of up to five water molecules.

• 한국광학회지
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• 제6권4호
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• pp.302-309
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• 1995

상온에서 $1.55{\mu}m$ 를 발진하는 격자 정합된 InGaAs/InGaAsP 양자우물 레이저를 설계하여 주입 운반자 밀도와 온도의 함수로 이득 곡선을 계산하였다. 밴드 구조와 운동량 행력 요소의 계산에는 블록대각화된 8*8 이차 k.p 해밀토니안에 근거한 변환행렬법을 사용하였다. 이 격자정합된 양자우물은 TE 모우드로 발진하였다. 온도가 증가함에 따라 발진파장이 길어졌고, 투명 운반자 밀도는 증가하였으며 미분이득은 감소하였다. 이득 곡선의 온도의존도는 밴드 구조의 온도의존성과 페르미 함수의 온도의존성에 기인하는데 이중 후자의 효과가 주도적인 것이었다.

• Corrosion Science and Technology
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• 제14권5호
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• pp.232-238
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• 2015

Corrosion is of greatest concern for metallic materials exposed to corrosive seawater or aggressive marine atmospheres. Marine structures and components made of metallic materials incur an initial cost and additional large costs for corrosion control and maintenance. There have been worldwide efforts to minimize marine corrosion and extend service life of the materials. It is believed that various factors are associated with corrosion of marine grade metallic materials, particularly the temperature of the solution affecting the corrosion rate by changing dissolved oxygen solubility and concentrations of chloride. In the present study, the electrochemical characteristics of S355ML steel are investigated to identify corrosion acceleration tendencies with changes in solution temperature under marine environments. It was found that increasing seawater temperature, promoted not only activation of chloride ion transfer, but also the formation of porous $Fe(OH)_3$ or $Fe_2O_3$, leading to the acceleration of corrosion.

• 한국응용과학기술학회지
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• 제12권1호
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• pp.93-99
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• 1995

미셀반응, 유화중합, 상간이동촉매반응 등에 이용되는 계면활성제가 갖고 있는 문제점을 해결하기 위하여 반응 후 분해되는 분해성 계면활성제를 합성하였다. 케탈이나 아세탈반응에 의하여 이루워진 1,3-디옥솔란 고리가 산수용액 중에서 불안정해 쉽게 가수분해로 계면활성을 띠지 않는 분해성 계면활성제를 합성하였다. 합성된 화합물은 백색결정상태로 얻었으며 수율은 90% 이상이었다. 그리고 이 화합물과 중간생성물은 얇은막 크로마토그래피와 컬럼 크로마토그래피로 분리하여 적외선과 수소핵자기공명 및 원소분석 스텍트라로 그 화합물들의 구조를 확인하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
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• pp.435-438
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• 2005

The use of new hybrid systems that combine the advantages of steel and reinforced concrete structures has gained popularity. One of these new mixed systems consists of steel beams and reinforced concrete shear wall, which represents a cost- and time-effective type of construction. A number of previous studies have focused on examining the seismic response of steel coupling beams in a hybrid wall system. However, the shear transfer of steel coupling beam-wall connections with panel shear failure has not been thoroughly investigated. The objective of this research was to investigate the seismic performance of steel coupling beamwall connections governed by panel shear failure. To evaluate the contribution of each mechanism, depending upon connection details, an experimental study was carried out The test variables included the reinforcement details that confer a ductile behaviour on the steel coupling beam-wall connection, i.e., the face bearing plates and the horizontal ties in the panel region of steel coupling beam-wall connections. It investigates the seismic behaviour of the steel coupling beams-wall connections in terms of the deformation characteristics. The results and discussion presented in this paper provide background for a companion paper that includes a design model for calculating panel shear strength of the steel coupling beam-wall connections.

• Journal of Periodontal and Implant Science
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• 제45권1호
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• pp.8-13
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• 2015

Purpose: The aim of this study was to evaluate the transfer of different occlusal forces in various skeletal malocclusions using finite element analysis (FEA). Methods: Three representative human cone-beam computed tomography (CBCT) images of three skeletal malocclusions were obtained from the Department of Orthodontics, Yonsei University Dental Hospital, Seoul, South Korea. The CBCT scans were read into the visualization software after separating bones and muscles by uploading the CBCT images into Mimics (Materialise). Two separate three-dimensional (3D) files were exported to visualize the solid morphology of skeletal outlines without considering the inner structures. Individual dental impressions were taken and stone models were scanned with a 3D scanner. These images were integrated and occlusal motions were simulated. Displacement and Von Mises stress were measured at the nodes of the FEA models. The displacement and stress distribution were analyzed. FEA was performed to obtain the 3D deformation of the mandibles under loads of 100, 150, 200, and 225 kg. Results: The distortion in all three skeletal malocclusions was comparable. Greater forces resulted in observing more distortion in FEA. Conclusions: Further studies are warranted to fully evaluate the impact of skeletal malocclusion on masticatory performance using information on muscle attachment and 3D temporomandibular joint movements.