• Water Engineering Research
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• 제4권2호
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• pp.99-109
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• 2003

Since bed elevation changes are mainly dependent on the flow velocity and corresponding shear stress, it is possible to predict bed elevation numerically using velocity components. For the scour analysis due to channel contraction, a bed load transport model is developed and applied to estimate scour depth around coffer dam in the Mississippi River. During Phase I of the Lock & Dam No. 26 replacement project, a coffer dam was constructed to reduce the flow area approximately by 50%. Flow velocity increases due to the flow area reduction yields significant lowering (erosion) of the channel bed elevation. The proposed numerical model solves the sediment continuity equation using the finite element method to evaluate scour process in the vicinity of the coffer dam

• Bulletin of the Korean Chemical Society
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• 제34권10호
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• pp.2931-2936
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• 2013

This paper presents results for the calculation of transport properties of noble gases (He, Ne, Ar, Kr, and Xe) at 273.15 K and 1.00 atm using equilibrium molecular dynamics (EMD) simulations through a Lennard-Jones (LJ) intermolecular potential. We have utilized the revised Green-Kubo formulas for the stress (SAC) and the heat-flux auto-correlation (HFAC) functions to estimate the viscosities (${\eta}$) and thermal conductivities (${\lambda}$) of noble gases. The original Green-Kubo formula was employed for diffusion coefficients (D). The results for transport properties (D, ${\eta}$, and ${\lambda}$) of noble gases at 273.15 and 1.00 atm obtained from our EMD simulations are in a good agreement with the rigorous results of the kinetic theory and the experimental data. The radial distribution functions, mean square displacements, and velocity auto-correlation functions of noble gases are remarkably different from those of liquid argon at 94.4 K and 1.374 $g/cm^3$.

• 대한약학회:학술대회논문집
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• 대한약학회 2003년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2-2
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• pp.69.2-69.2
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• 2003

The purpose of this study is to examine whether the efflux system for taurine from brain to blood is present on the blood-brain barrier (BBB) using the brain efflux index (BEl) method and taurine transport system is regulated by CNS cell damage with oxidative stress agent such as diethyl maleate (DEM) or tumor necrosis factor-${\alpha}$ (TNF-${\alpha}$) in vivo. ［$^3$H]Taurine was microinjected into parietal cortex area 2 (Par2) of the rat brain, and was eliminated from the brain with efflux transport rate of 1.22 10$\^$-2//min, and the process is saturable with a $K_{m}$ of 43.5 ${\mu}$M. (omitted)

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2002년도 학술발표회 논문집(I)
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• pp.3-16
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• 2002

This article describes some of the recent and on-going research developments of the author at Colorado State University. Advances in the field of sedimentation and river mechanics include basic research and computer modeling on several topics. Only a few selected topics are considered here: (1) analytical determination of velocity profiles, shear stress and sediment concentration profiles in smooth open channels; (2) experiments on bedload particle velocity in smooth and rough channels; (3) field measurements of sediment transport by size fractions in curved flumes. In terms of computer modeling, significant advances have been achieved in: (1) flashflood simulation with raster-based GIOS and radar precipitation data; and (2) physically-based computer modeling of sediment transport at the watershed scale with CASC2D-SED. Field applications, measurements and analysis of hydraulic geometry and sediment transport has been applied to: (1) gravel-bed transport measurements in a cobble-bed stream at Little Granite Creek, Wyoming; (2) sand and gravel transport by size fraction in the sharp meander bends of Fall River, Colorado; (3) changes in sand dune geometry and resistance to flow during major floods of the Rhine River in the Netherlands; (4) changes in hydraulic geometry of the Rio Grande downstream of Cochiti Dam, New Mexico; and (5) analysis of the influence of water temperature and the Coriolis force on flow velocity and sediment transport of the Lower Mississippi River in Louisiana. Recent developments also include two textbooks on "Erosion and Sedimentation" and "River Mechanics" by the author and state-of-the-art papers in the ASCE Journal of Hydraulic Engineering.

• Journal of Advanced Marine Engineering and Technology
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• 제32권1호
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• pp.110-118
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• 2008

It is essential for the valid design of a marine flow-control valve to exactly know its flow characteristics. The present study has numerically investigated the flow characteristics inside a marine throttle-type globe valve using a kind of commercial CFD code, CFX10.0, with an adoption of the SST (Shear-Stress Transport) turbulence model. To validate the numerical approach, the flow coefficients are compared with the experimental ones. Results show that the globe valve is effective in the control of flow rate according to the opening ratio in case of the forward-direction flow, whereas it is effective in the flow shutoff in case of the reverse-direction flow. Around the inlet of the valve, a recirculation region is formed due to the blunt body shape, the turbulence intensity becomes strengthened and then an abrupt pressure loss occurs.

• 대한토목학회논문집
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• 제10권2호
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• pp.129-135
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• 1990

아산만(牙山灣)의 조석(潮汐)과 관련수리현상(關聯水理現象)을 조사(調査)하기 위한 2차원(次元) 비선형조석모형(非線型潮汐模型)을 수립(樹立)하였다. 첫 단계로서 주태음반일주조(主太陰半日週潮)의 조석체계(潮汐體系)를 산정(算定)하였으며 해저최대마찰응력(海底最大摩擦應力)과 토사이동포텐셜을 산정하여 토사이동과의 관련성을 초기추정하였다.

• 한국초전도ㆍ저온공학회논문지
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• 제6권4호
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• pp.22-26
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• 2004

For practical applications, the evaluation of reliability or endurance of HTS conductors is necessary. The mechanical properties and the critical current, Ie, of multifilamentary Bi-2223 superconducting tapes, externally reinforced with stainless steel foils, subjected to high cycle fatigue loading in the longitudinal direction were investigated at 77K. The S-N curves were obtained and its transport property was evaluated with the increase of repeated cycles at different stress amplitudes. The effect of the stress ratio, R, on the Ie degradation behavior under fatigue loading was also examined considering the practical application situation of HTS tapes. Microstructure observation was conducted in order to understand the Ie degradation mechanism in fatigued Bi-2223 tapes.

• 한국수자원학회논문집
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• 제31권1호
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• pp.115-120
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• 1998

본 논문에서는 수심적분 2차원 모형을 하나 소개하고, 이 모형이 가질 수 있는 오차의 한계를 민감도분석을 통해 제시하였다. 민감도 분석 결과, Manning 조도계수, 혼합계수, 침강속도, 한계전단력 등이 부유사농도에 대해 모형에 미치는 영향은 매우 크게 나타났으며, 조위와 확산계수의 영향은 거의 없는 것으로 나타났다.

• Computers and Concrete
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• 제15권2호
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• pp.183-198
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• 2015

Chloride ingress implies a complex interaction between physical and chemical process, in which heat, moisture and chloride ions transport through concrete cover. Meanwhile, reinforced concrete structure itself undergoes evolution due to variation in temperature, relative humidity and creep effects, which can potentially change the deformation and trigger some micro-cracks in concrete. In addition, all of these process show time-dependent performance with complex interaction between structures and environments. In the present work, a time-dependent behavior of chloride transport in reinforced concrete beam subjected to flexural load is proposed based on the well-known section fiber model. The strain state varies because of stress redistribution caused by the interaction between environment and structure, mainly dominated by thermal stresses and shrinkage stress and creep. Finally, in order to clear the influence of strain state on the chloride diffusivity, experiment test were carried out and a power function used to describe this influence is proposed.

• 한국수산과학회지
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• 제26권6호
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• pp.538-548
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• 1993

한국 동해 연안역 해수순환 및 수온분포에 대한 바람응력의 효과에 관하여 검토하였다. 동해상의 바람응력은 국립수산진흥원 정선관측 바람자료 및 일본기상청 Buoy No. 6에서의 10년간($1978{\sim}1987$)의 약 5,100개의 바람 관측자료를 사용하여 계산하였다. 여름과 겨울의 계절풍의 전환에 따른 에크만 수송의 변화가 대한해협에서의 대마난류 수송량에 미치는 영향을 정량적으로 평가하였다. 특히 동해에서의 평균적인 바람응력의 회전성(wind stress curl) 값이 음이 되는 사실에서 울릉도 근해의 난수층의 형성에 부분적으로 도움이 됨을 알았다. 한편, 동해 난수층의 분포를 단순화된 3층 경계면모델을 적용하여 설명하였다.