• 대한토목학회논문집
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• 제30권5D호
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• pp.477-483
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• 2010

기존 대중교통시스템은 한정된 수송용량, 포화상태인 도로 교통체계 등으로 인해 새로운 교통수단이 발전할 수 있는 단초를 제공하였으나, 교통당국에서는 기존의 도시철도의 규모를 축소시킨 경량 전철 위주로 신교통시스템의 도입을 추진하고 있다. 특히 각 도시별로 대중교통(버스 또는 도시철도)을 계획할 때 특별한 대중교통시스템 선정기준이 없어 해당 지자체별로 어려움을 겪고 있어, 대중교통축별로 어떠한 대중교통시스템이 적정한지를 판단할 수 있는 선정 기준이 필요하다는 목소리가 높아지고 있는 실정이다. 이에 따라 도시의 교통축별로 GIS Buffering 분석기법에 기반한 대중교통수요 예측모형을 개발하고, 대중교통시스템별 용량을 설정하여 교통축별 최적의 대중교통시스템을 선정하고자 하였으며, 대중교통이 운행하는 대중교통축별로 수요를 처리할 수 있는 적정 대중교통시스템을 선정하는 것이 가장 중요하므로, 선정 및 평가에 대해 필요조건과 충분조건으로 구분한 방법론을 제시하였다.

• 한국세라믹학회지
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• 제49권1호
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• pp.37-42
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• 2012

Mass transport near grain boundary in a magnetite bi-crystal has been estimated at 823 K by finite element method. Mass transport near grain boundary strongly depends on the diffusivities along grain boundary. If grain boundary diffusion has the same oxygen activity dependence as lattice diffusion, there is no mass transport between grains and grain boundary. On the other hand, mass transport between grains and grain boundary is observed in the case that grain boundary diffusion has different oxygen activity dependence.

• 한국항만학회지
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• 제6권2호
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• pp.25-31
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• 1992

Herein we investigate the mass transport velocity caused by the viscosity near the ocean structure such as circular pile and inclined breakwaters. The mass transport velocity which is represented by the sum of the Eulerian velocity and the stokes drift were derived by Carter, Liu and Mei(1973). The tangential components of the inviscid velocity field at the bottom needed in the calculation of the mass transport velocity is obtained by solving the scattering problem due to breakwaters. The matched asymptotic expansion technique is employed to obtain the inviscid flow fields scattered by inclined breakwaters. The numerical results show that heary sediments tends to be deposited near the center of breakwaters and that the narrowing of the entrance width results in reduction of the magnitude of mass transport.

• 한국재료학회지
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• 제8권5호
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• pp.419-423
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• 1998

매립형 InGaAnP/InP 레이저 다이오드 제작을 위한 질량 이동 현상의 최적화에 대한 연구를 수행하였다. Double heterostructure 레이저 다이오드 구조의 1차 성장은 액상 에피 성장 장치를 이용하였으며, 메사 에칭하였다. 활성층을 [110] 방향으로 선택적으로 에칭 한 후, 액상 에피 성장 장치를 이용하여 질량 이동 현상을 발생시켜 매립형 구조를 형성시켰다. 질량 이동 현상의 임계온도는 40분간 유지시켰을 때 $670^{\circ}C$로 나타났으며 재현성 있게 질량 이동 현상이 발생하였다. 질량 이동 현상에 의해 성장된 층의 폭은 온도증가에 따라 약간 증가하였다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 1988년도 제30회 수공학연구발표회논문초록집
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• pp.29-36
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• 1988

A general scheme is developed which determines the Lagrangian motions of water particles by the Eulerian velocity at their mean positions by use of Taylor's theorem. Utilizing the Stokes finite-amplitude wave theory, the mass transport velocity which includes the effects of higher-order wave components is determined. The fifth-order theory predicts the mass transport velocity less than that given by the existing second-order theory over the whole depth. Limited experimental data for changes in wave celerity in closed wave flumes are compared with the theoretical predictions.

• Nuclear Engineering and Technology
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• 제53권7호
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• pp.2221-2228
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• 2021

One-dimensional oxygen transport relation is indispensable to study the oxygen distribution in the LBE-cooled system with an oxygen control device. In this paper, a numerical research is carried out to study the oxygen transport characteristics in a gas-phase oxygen control device, including the static case and dynamic case. The model of static oxygen control is based on the two-phase VOF model and the results agree well with the theoretical expectation. The model of dynamic oxygen control is simplified and the gas-liquid interface is treated as a free surface boundary with a constant oxygen concentration. The influences of the inlet and interface oxygen concentration, mass flow rate, temperature, and the inlet pipe location on the mass transfer characteristics are discussed. Based on the results, an oxygen mass transport relation considering the temperature dependence and velocity dependence separately is obtained. The relation can be used in a one-dimensional system analysis code to predict the oxygen provided by the oxygen control device, which is an important part of the integral oxygen mass transfer models.

• 한국환경과학회지
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• 제3권1호
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• pp.11-16
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• 1994

Generally, it is difficult to predict water quality in a tidal river, because tidal flows make the transport phenomena more complicated. The purpose of this study is to clarify long-term mass transport in a tidal river through suggestion of simulation model. A simulation model based on a Lagrangian coordinate system, which has the advantage reducing numerical dispersion, was used to calculate changes in concentration of chlorides. Several field surveys were conducted to verify calculated results. Concludingly, long-term behavior of mas transport in a tidal river can be represented using the model.

• 한국세라믹학회지
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• 제56권3호
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• pp.325-330
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• 2019

Band convergence is known to be effective in improving thermoelectric performance by increasing the Seebeck coefficient without significantly reducing electrical conductivity. Decoupling of the Seebeck coefficient and electrical conductivity in converged bands is the key requirement. Yet, the degree of decoupling depends on the band parameters of the converging bands. Herein, we report theoretical transport properties of two valence bands as their energy difference changes from 0.25 eV to 0 eV. In order to demonstrate the effect of band parameters in transport, we first conducted calculations for the case where the two bands have the same parameters. Then, we conducted the same calculation by doubling the density-of-states effective mass of one valence band. Given that there are two bands, each band's effective mass was doubled one at a time while the other band's effective mass remained constant. We found that the decoupling was strongest when the bands participating in convergence had the same band parameters.

• Computers and Concrete
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• 제8권2호
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• pp.177-192
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• 2011

This research paper aims at computer based modeling of carbonation induced corrosion under extreme conditions and its experimental verification by incorporating enhanced electrochemical and mass balance equations based on thermo-hygro physics with strong coupling of mass transport and equilibrium in micro-pore structure of carbonated concrete for which the previous research data is limited. In this paper the carbonation induced electrochemical corrosion model is developed and coupled with carbon dioxide transport computational model by the use of a concrete durability computer based model DuCOM developed by our research group at concrete laboratory in the University of Tokyo and its reliability is checked in the light of experiment results of carbonation induced corrosion mass loss obtained in this research. The comparison of model analysis and experiment results shows a fair agreement. The carbonation induced corrosion model computation reasonably predicts the quantitative behavior of corrosion rate for normal air dry relative humidity conditions. The computational model developed also shows fair qualitative corrosion rate simulation and analysis for various pH levels and coupled environmental actions of chloride and carbonation. Detailed verification of the model for the quantitative carbonation induced corrosion rate computation under varying relative conditions, different pH levels and combined effects of carbonation and chloride attack remain as scope for future research.

• 한국전산구조공학회논문집
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• 제23권6호
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• pp.651-657
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• 2010

Solute transport through a groove is affected by its vortices. Our laboratory and numerical experiments of dye transport through a single axisymmetric groove reveal evidence of enhanced spreading and mixing by the vortex, i.e., a new kind of dispersion called here the vortex dispersion. The uptake and release of contaminants by vortices in porous media is affected by the flow Reynolds number. The larger the flow Reynolds number, the larger is the vortex dispersion, and the larger is the mass-transfer rate between the mobile zone and the vortex. The long known dependence of the mass-transfer rate between the mobile and "immobile" zones in porous media on flow velocity can be explained by the presence of vortices in the "immobile" zone and their uptake and release of contaminants.