• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.4_1
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• pp.43-52
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• 1992

The shore attachment of jet in a cross flow is analysed by experiments and dimensional analysis. The jet flow is discharged with the same depth as that of the cross flow through a side channel perpendicular to the cross flow through a side channel perpendicular to the cross flow. For a momentum jet, nondimensional attachment length and height are dependent on nondimensional characteristic length $I_m/W$. For a buoyant jet, nondimensional attachment length is affected by $I_b/I_md$ and nondimensional temperature distribution is a function of $x/I_b$ and they all can be predicted as power laws. The shore attachment condition can be specified by velocity ratio R.

• The Science & Technology
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• no.2 s.405
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• pp.60-63
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• 2003

GM작물과 중국의 잣대/ 벤터, 인공 지놈 이용한 자기복제 생물 개발 첫발/ 일본, 올해 과학예산 103억 달러로 증액/ 이탈리아 연구예산 대폭 삭감/ 프랑스 과학예산도 삭감/ 올 과학시장 기상도 'IT'와 '가전시장' 호황 기대

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.5
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• pp.587-594
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• 2019

This study experimentally investigated the effects of high and low densities of vegetation patches on the flow characteristics in a stream-scale outdoor experimental channel with rooted willows. Stream-scale experiments on vegetated flows were carried out for an emergent condition of vegetation. Vegetation patches were arranged by alternate bar formation and the flows in vegetated and non-vegetated sections were compared. Three-dimensional flow structure was measured by ADV (Acoustic Doppler Velocimeter) and the vertical distributions of longitudinal velocity were mainly analyzed from the measurements at various points. Flow velocities show different patterns depending on the density of vegetation patches. The difference in flow velocity between in the vegetated and non-vegetated sections appear to large in the dense patches and the flow becomes complicated at the downstream edge of the patch. Despite the upstream flow disturbed by the first patch, the flows over the second patch show the similar pattern.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.3
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• pp.23-27
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• 2008

The new conjunctive surface-subsurface flow model at a large scale was developed by using a 1-D Diffusion Wave (DW) model for surface flow interacting with the 3-D Volume Averaged Soil-moisture Transport (VAST) model for subsurface flow for the comprehensive terrestrial water and energy predictions in Land Surface Models (LSMs). A selection of numerical implementation schemes is employed for each flow component. The 3-D VAST model is implemented using a time splitting scheme applying an explicit method for lateral flow after a fully implicit method for vertical flow. The 1-D DW model is then solved by MacCormack finite difference scheme. This new conjunctive flow model is substituted for the existing 1-D hydrologic scheme in Common Land Model (CLM), one of the state-of-the-art LSMs. The new conjunctive flow model coupled to CLM is tested for a study domain around the Ohio Valley. The simulation results show that the interaction between surface flow and subsurface flow associated with the flow routing scheme matches the runoff prediction with the observations more closely in the new coupled CLM simulations. This improved terrestrial hydrologic module will be coupled to the Climate extension of the next-generation Weather Research and Forecasting (CWRF) model for advanced regional, continental, and global hydroclimatological studies and the prevention of disasters caused by climate changes.

• 한국해양학회지
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• v.30 no.1
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• pp.13-26
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• 1995

In this paper three turbulence models including two-equation model by Blumberg and Mellor (1987), one-equation model with mixing length formula of Blackadar's (1962), and zero-equation model of Prandtl's (1925) were compared in homogeneous, unstratified channel flows. Steady flows which a steep-sided trapezoidal trench with uniform discharge, tidal flow and steady wind-driven flow in finite channels are considered in detail. Steady flows in a trench and tidal flows in a finite channel were reproduced fairly accurately and there was virtually no difference among results of three turbulence models. However, In case of steady wind-driven flow only two-equation model reproduced the important features of experimental data. the other two models underestimated the surface velocity. In tidal and wind-driven flows with negligibly small adjective and diffusive effects, the two-equation model gives rise to parabolic profile of eddy viscosity with maximum at the mid0depth, and the one and zero equation model based on Blackadar formula linear profile with maximum at the surface.

• Journal of Sensor Science and Technology
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• v.7 no.5
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• pp.319-326
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• 1998

Anodic half-reaction in the $Na^+$ ionic sensors using $Na_2CO_3$ and $MCO_3$ ($M=Cs_2,K_2,Li_2,Ca$) as a sensitive membrane is derived in continuous flow system to explain $CO_2$ sensing characteristics. For various gas-sensitive membranes, a well known overall reaction, $MCO_3\;=\;MO\;+\;CO_2$, cannot be applied for the EMF behaviors of these kinds of sensors. So, the anodic reaction is found to involve $Na_2CO_3$ and $M^{++}$-containing oxide phases by employing the ion exchange reaction at the interface of solid electrolyte and the sensitive membrane to maintain ionic balance in the whole cell. Based on the electrode reaction derived in flow system, differences of cell potentials between continuous and discontinuous flow systems were also discussed. These EMF differences were considerably caused by the partial pressures of oxygen and $CO_2$ as well as irreversible chemical reactions between electrode materials and $CO_2$ atmosphere.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.1
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• pp.11-22
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• 1987

A plane buoyant jet discharged vertically upward into a crossflow is analyzed by numerical solution of the governing equations of continuity, momentum and constituent transport. The turbulent transport is modelled by the Prandtl's mixing length theory. In the numerical solution procedure, the governing equations are transformed by stream function and vorticity transport, non-dimensionalyzed by discharge velocity, slot width, and parameters representing flow characteristics, and solved by Gauss-Seidel iteration method with successive underrelaxation. The numerical experiments were performed for the region of established flow of buoyant jet in the range of discharge densimetric Froude number of 4 to 32 and in the range of velocity ratio of 8 to 15, which is the ratio of discharge velocity to crossflow velocity. Variations of velocities and temperatures, flow patterns and vorticity patterns of receiving water due to buoyant jet were investigated. Also investigated are the effects of velocity ratio and discharge densimetric Froude number on the trajectories of buoyant jet. Computed are velocities, temperatures and local densimetric Froude numbers along the trajectory of the buoyant jet. Spreading rate and dispersion ratio were analyzed in terms of discharge densimetric Froude number, local densimetric Froude number and distance from the source along the jet trajectory. It was noted that the similarity law holds in both the profiles of velocity and temperatures across the jet trajectory and the integral type analysis of Gaussian distribution is applicable.

• Korean Business Review
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• v.11
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• pp.241-253
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• 1998

One form of the anomalies of stock price changes as reaction to earnings information is believed to be caused by the so-called earnings fixation, which is the overreaction of stock prices to earnings. According to the Sloan (1996) study, stock price changes are positively associated with earnings at the time of earnings releases, but the association becomes negative after that, as the early overreaction is corrected. However, the problem in his study is to use cash flows computed by adjusting earnings with appropriate income statement and balance sheet items. As Bahnson et al. (1996) show, these cash flows substantially deviate from SFAS No. 95 cash flows and the sample used in this study is found to be subject to this substantial measurement error. Therefore, the result of Sloan might be driven by this error and the reexamination of earnings fixation is warranted. The results are generally consistent with those in Sloan. First, earnings is positively associated with stock price changes at the time of earnings releases, but the association becomes negative after that. Second, cash flows show a weak association with stock price changes at the time of earnings releases, but the association become stronger thereafter. Third, when seperated from cash flows, accruals have an incremental explanation about stock price changes beyond that of cash flows, accruals have a negative association later on. This finding is consistent with stock price overreaction to accruals, even when more cleaner cash flow data are used.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.367-371
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• 2005

본 논문에서는 수리실험을 통해 개수로의 바닥 조건에 따른 평균흐름 및 난류구조, 그리고 고유구조의 특성을 연구하였다. 레이저 도플러 유속계를 이용하여 2차원 순간속도를 측정하였다. 측정된 평균유속, 레이놀즈응력, 난류강도, 와점성계수, 혼합 길이 등의 난류량을 기존에 제시된 경험식과 비교하였으며 기존 연구 결과와 유사함을 확인하였다. 사분면 기법을 이용하여 개수로 흐름의 고유구조를 살펴본 결과, 분출 및 쓸기 현상의 발생 확률이 다른 상호작용에 비해 지배적임을 확인하였다. 고속 푸리에 변환을 통한 스펙트럼 분석을 통하여 에너지 폭포 현상 및 난류 와의 미시 및 거시 특성크기를 파악하였다.

• The Korean Journal of Financial Management
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• v.14 no.2
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• pp.21-55
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• 1997

본 연구는 기업규모, 장부가치/시장가치 비율, 순이익/주가 비율, 현금흐름/주가 비율, 레버리지 등 기본적 변수를 사용하여 주식수익률에 유의적인 변수를 확인하고, 또한 Fama and French(1993) 등에 의해서 제시된 다요인모형(multi-factor model)이 한국주식시장에서 적용가능한 지를 살펴보았다. 이를 위하여 본 연구에서는 Fama and MacBeth(1973)의 횡단면회귀모형과 Black, Jensen, and Scholes (1972)의 시계열모형을 사용하였으며, 실증분석결과를 요약하면 다음과 같다. 먼저 횡단면분석결과에 의하면, 장부가치/시장가치 비율(BE/ME), 현금흐름/주가 비율(C/P) 등이 주식수익률의 횡단면적 차이를 설명할 수 있는 유의적인 변수로 나타났다. 그리고 통계적 의미에서는 1월효과가 존재한다고 보기 어려우나, 경제적 의미에서 1월효과가 존재하는 것으로 생각된다. 시계열분석결과에 의하면, 시장요인, 기업규모요인, 장부가치/시장가치요인(또는 현금흐름/주가요인) 등의 3요인에 의해서 국내 주식수익률의 공통적 변동을 잘 설명할 수 있다. 즉 국내 증권시장에서도 Fama and French(1993)의 3요인모형이 성립될 수 있는 것으로 판단된다.