• Journal of Environmental Science International
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• v.22 no.5
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• pp.571-580
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• 2013

In this study, compared with the result of water surface elevation and water velocity on the establishment of river maintenance basic plan and result of HEC-GeoRAS based GIS, and after use the result of water surface elevation and velocity were observed in the Han stream on Jeju island, analysis 2 dimensional stream flow. the lateral hydraulic characteristics and curved channel of the stream were analyzed by applying SMS-RMA2 a 2 dimensional model. The results of the analysis using HEC-RAS model and HEC-GeoRAS model indicated that the distribution ranges of water surface elevation and water velocity were similar, but the water surface elevation by section showed a difference of 0.7~2.18 EL.m and 0.63~1.16 EL.m respectively, and water velocity also showed differences of maximum 1.58m/sec and 2.67m/sec. SMS-RMA2 analysis was done with the sphere of Muifa the typhoon as a boundary condition, and as a result, water velocity distribution was found to be 1.19 through 3.91 m/sec, and the difference of lateral water velocity in No. 97 through 99 the curved channel of the stream was analyzed to be 1.59 through 2.36 m/sec. In conclusion it is anticipated that the flow analysis of 2 dimension model of stream can reflect the hydraulic characteristics of the stream curved channel or width and shape, and can be applied effectively in the establishment of river maintenance basic plan or management and designing of stream.

• Journal of Korea Water Resources Association
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• v.48 no.4
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• pp.299-308
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• 2015

The aim of this study is that a theoretical formula for estimating the one-dimensional longitudinal dispersion coefficient is derived based on a transverse distribution equation for the depth averaged stream-wise velocity in open channel. In "Part I. Theoretical equation for stream-wise velocity" which is the former volume of this article, the velocity distribution equation is derived analytically based on the Shiono-Knight Method (SKM). And then incorporating the velocity distribution equation into a triple integral formula which was proposed by Fischer (1968), the one-dimensional longitudinal dispersion coefficient can be derived theoretically in "Part II. Longitudinal dispersion coefficient" which is the latter volume of this article. The proposed equations for the velocity distribution and the longitudinal dispersion coefficient are verified by using observed data set. As a result, the non-dimensional longitudinal dispersion coefficient is inversely proportional to square of the Manning's roughness coefficient and the non-dimensional transverse dispersion coefficient, and is directly proportional to square of the aspect ratio (channel width to depth).

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.986-990
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• 2005

The present study aims to illuminate the vertical velocity profile of outer region of open-channel flow. Two sets of experiments were performed with PIV and propeller velocimeter. The first set was conducted to investigate the effect of bed roughness on the velocity distribution. The second set of experiments was carried out to find the effect of the Froude number on the velocity profile under the same bed roughness. The results reveal that the wake-law fits well with the experimental data from the bottom to the depth of maximum velocity, but it deviates from the experimental data above the maximum velocity point due to velocity-dip phenomenon, and that the velocity profile of the outer region is more influenced by the Froude number than the roughness. It is also shown that both the velocity difference between maximum velocity and surface velocity and the ratio of the average velocity to surface velocity become larger as the Froude number increases.

• Journal of the Korean Society of Visualization
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• v.9 no.1
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• pp.29-35
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• 2011

In this paper, we applied various microfluidic chambers to visualize cell migration and measured the migration velocity in microchannels. Migration speed of B16 cell in a large channel was similar with that of wound healing experiment. However, the speed decreased gradually as the cell move inside of the channel. It is expected that this phenomenon is due to the shortage of oxygen or nutrition, whichare essential for cell growth. In the case of cell in the small channel whose size is smaller than the cell, its speed was slower than that in a larger channel.

• Journal of Korea Water Resources Association
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• v.30 no.1
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• pp.15-22
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• 1997

The flow in meandering channel has a great influence on curved bank revetment in river morphology. It is difficult to state generalized cirteria for channel improvement applicable to any paricular river. But it is very important to provide some principles and guidelines for design engineers. The objective of this experimental study in fixed bed model is to povide effective data that find out maximum velocity size by the mean velocity and the radius of curvature in curved channel, for the purpose of improving small stream without hydraulic modeling test each time.

• 한국가시화정보학회:학술대회논문집
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• 2004.12a
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• pp.157-168
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• 2004

The effects of pulsation in a pulsating flow through a rectangular channel have been investigated by Particle Image Velocimetry in both laminar and turbulent flow conditions. PIV results on a square channel (aspect ratio:1) have been reported on the cases of Reynolds number Re=80 in laminar and Re=8800 in turbulent region. For both in the laminar and turbulent regions, the influence of the pulsation onto the magnitude changes of the average velocity was negligible. In the turbulent region, the magnitude profiles of the stream-wise pulsating component obtained by the theoretical analysis based on the Stokes analogy were slightly different from the experimental ones due to the influence of the turbulent viscosities onto the pulsating flows.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.1
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• pp.74-80
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• 1990

The transconductance of short channel LDD MOSFETs in the saturation region (high Vd)has shown different characteristics from that of conventional device. The transconductance in saturation regime of short channel LDD MOSFETs is reduced from maximum value at higher gate voltage. This decline is analyzed as the velocity saturation effects of carrier at LDD region but accurate analytical expressions for the drain current Idsat and the transconductance Gmsat in the saturation regime are still not in existence. Recently the drain current dependence of parasitic source resistance Rs has been modeled from the velocity saturation of carriers in LDD region. In this study, we approximate that Rmsat that Rs is linearly dependent on the applied gate voltage. Analytical expressions for Idsat and Gmsat obtained from this approximation show the same general behavior as experimental results of short channel LDD NMOSFETs.

• JSTS:Journal of Semiconductor Technology and Science
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• v.9 no.1
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• pp.55-60
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• 2009

The channel backscattering coefficient and injection velocity have been extracted experimentally in 65nm MOSFETs. Thanks to an experimental extraction methodology taking into account multi-subband population, we demonstrate that the short channel ballistic efficiency is slightly greater than long channel ballistic efficiency.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2816-2821
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• 2008

This paper investigates the flow field and organism concentration in a UV disinfection channel in which vertical ultraviolet lamps are arranged in a staggered configuration. Turbulence is described by low Reynolds number ${\kappa}-{\varepsilon}$ turbulence model and standard ${\kappa}-{\varepsilon}$ turbulence model, respectively. P-1 method has been employed to solve the radiative transfer equation. The obtained incident radiation is used to compute the inactivation term in the species equation. The CFD results are in good agreement with the existing experimental data for the UV channel. For the flow field, the low-Reynolds number ${\kappa}-{\varepsilon}$ model is superior to the standard ${\kappa}-{\varepsilon}$ model. The approach velocity has a significant effect on the disinfection efficiency. The organism concentration at the outlet decreases fast to a low inlet velocity.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.29A no.7
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• pp.56-63
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• 1992

A measurement technique of the surface generation velocity S$_o$ using the BC(buried channel) MOS structure with shallow and low doped channel layer (BC MOS S$_o$ measurement technique) is presented and verified analytically and experimentally. Using this measurement technique, S$_o$ can be measured more accurately than that measured using the gate-controlled diode SS1oT measurement technique. When S$_o$ is measured for the two techniques from a BC MOS structure test patten with gate length of 171$\mu$m, the results are 0,66cm/sec and 0.28cm/sec for the former and the latter respectively.