• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.63-63
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• 2021

Bed shear stress is important variable in river flow analysis. The bed shear stress has an effects on bed erosion, sediment transport, and mean flow characteristics. Quadratic formula to estimate bed shear stress is widely used, 𝜏=𝜌c_fu|u| in which friction coefficient, c_f, needs to be assigned to numerical models. The aim of this study is to estimate Chezy coefficient using bathymetry data measured by ADCP. Bed form geometry variables will be estimated form bed profile, then Chezy coefficient will be determined using estimated bed form geometry variables in order to set friction coefficient to numerical model. From the probability density function obtained from the bathymetry data, Chezy coefficient will be randomly generated since Chezy coefficient is not uniform over the space and it does not depend on spatial variables such as water depth and distance from river bank. Numerical test will be performed to find to demonstrate randomly extracted Chezy coefficient is appropriate. The result of this study is valuable in that the friction coefficient is estimated in consideration of the bed profile, and as a result, uncertainty of the friction coefficient can be reduced.

• Journal of Korea Water Resources Association
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• v.31 no.1
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• pp.115-120
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• 1998

In this paper, a depth-averaged two-dimensional transport model is introduced, and its error bound is presented as the results of sensitivity analysis. The results show that the calculated SS concentration is highly dependant on Manning roughness coefficient, mixing coefficient. fall velocity. and critical shear stress. On the other hand, water level and dispersion coefficient are proved to be less significant in the variation of SS concentration.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.234-238
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• 2008

The energy conservation theory is introduced for investigating processes of runoff and soil erosion on the hillslope system changed vegetation condition by wildfire The rainfall energy, input energy consisted of kinetic and potential energy, is influenced by vegetation coverage and height. Output energy at the outlet of hillslope is decided as the kinetic energy of runoff and erosion soil, and mechanical work according to moving water and soil is influenced dominantly by the work rather than the kinetic energy. Relationship between output and input energy is possible to calculate the energy loss in the runoff and erosion process. The absolute value of the energy loss is controlled by the input energy size of rainfall because energy losses of runoff increase as many rainfall pass through the hillslope system. The energy coefficient which is dimensionless is defined as the ratio of input energy of rainfall to output energy of runoff water and erosion soil such as runoff coefficient. The energy coefficient and runoff coefficient showed the highest correlation coefficient with the vegetation coverage. Maximum energy coefficient is about 0.5 in the hillslope system. The energy theory for output energy of runoff and soil erosion is presented by the energy coefficient theory associated with vegetation factor. Also runoff and erosion soil resulting output energy have the relation of power function and the rates of these increase with rainfall.

• Journal of Korean Association for Spatial Structures
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• v.13 no.2
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• pp.67-73
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• 2013

This paper attempted to bridge this gap by identifying the number of flat-plate solar collectors. The characteristics of wind pressure coefficients acting on flat-plate solar collectors which are most widely used were investigated for various wind direction. Findings from this study found that the location where the maximum wind pressure coefficient occurred in the solar collector was the edge of the collector. Regarding the characteristics according to the number of collectors, the paper found that downward wind pressure coefficient of the lower edge of the collector was higher than the upward wind pressure coefficient of the upper edge of the collector in the basic module (1 piece). However, as the number of collectors increases, the upward wind pressure coefficient of the upper edge become higher than the downward wind pressure coefficient of the lower edge. Finally yet important, it was found that the location of the maximum wind pressure coefficient was changed according to the number of solar collectors.

• 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).

• Journal of the Korean Home Economics Association
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• v.11 no.1
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• pp.14-25
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• 1973

The measurements includings 22 items such as height, weight, body width were carried out for Korean male and female students, one hundred each, from 18 to 24 years old. The correlation coefficient was calculated for every two items. The values are basic for the Clothing construction and the Pattern grading. The results are as follows : 1) The measuring values are as shown in Table 1 and the index are as shown in Table 2. 2) The correlation coefficient of length to length is larger than that of length to girth and that of length to width. The correlation coefficient of girth to girth is larger than girth to length and that of girth to width. The correlation coefficient of width to width does not show remarkable difference from those of others. 3) The correlation coefficient values of weight to lengths, weight to lengths, weight to girths and weight to width are larger. Among these, the correlation coefficient of weight to girths is the largest. 4) The correlation coefficient in general shows almost positive values except a few exception showing negative values. 5) No meaning differences are found between males and females.

• Journal of Auto-vehicle Safety Association
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• v.5 no.2
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• pp.17-23
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• 2013

This paper describes an algorithm for Advanced Emergency Braking(AEB) with tire-road friction coefficient estimation. The AEB is a system to avoid a collision or mitigate a collision impact by decelerating the car automatically when forward collision is imminent. Typical AEB system is operated by Time-to-collision(TTC), which considers only relative velocity and clearance from control vehicle to preceding vehicle. AEB operation by TTC has a limit that tire-road friction coefficient is not considered. In this paper, Tire-road friction coefficient is also considered to achieve more safe operation of AEB. Interacting Multiple Model method(IMM) is used for Tire-road friction coefficient estimation. The AEB algorithm consists of friction coefficient estimator and upper level controller and lower level controller. The numerical simulation has been conducted to demonstrate the control performance of the proposed AEB algorithm. The simulation study has been conducted with a closed-loop driver-controller-vehicle system using using MATLAB-Simulink software and CarSim Vehicle model.

• Journal of the Korean Home Economics Association
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• v.23 no.3
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• pp.9-16
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• 1985

There are two standards for evaluation of fabric aesthetics, the feeling of fabric and the fabric sense of sight. Its drapalility with lustre is one of factors to decide the fabric sense of sight. This study was carried out to investigate the drape property property of fabrics. The fabric characteristics and the physisical properties of fabrics were tested. And the effect of the laundering on the drape properties was examined. RESULTS : 1. The drape coefficients of sampled fabrics were increasd as the thickness of fabrics were increased, excluding the fabric consisting of 60% polyester$\times$40% wool. 2. The drape coefficient of sampled fabrics were decreased as the cover faders of fabrics were increased, excluding the summer clothes and the fabrics of 100% wool. 3. The drape coefficients of fabrics other than sumer clothes were increased as the weight of fabrics were in creased. 4. Positive correlation was observed between the stiffness and the drape coefficient. 5. Negative correlation was observed between the fabric shrinkage and the drape coefficient. 6. The drape coefficient was decreased to a certain limit by laundering.But as the laundering was repeated up to certain number, the drape coefficient and the node number, a significant correlation was observed between the drape coefficient and the node shape.

• Journal of the Korean housing association
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• v.12 no.3
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• pp.133-140
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• 2001

This study investigated the heat transmission coefficient through the experiment that the skylight, slope window of 60 degree and 30 degree consisted of pair glass and the double window of external window and internal window paper were suitable for heat insulation. As the result of experiment, the heat transmission coefficient of slope window was 1.06 times in the 60 degree, 1.18 times in the 30 degree and 1.31 times in the skylight as a standard lateral window. The heat transmission coefficient in the double window of external window and internal window paper was 3.017$\textrm{㎉}$/$\textrm{m}^2$.hr.$^{\cire}C$. The slope window was not suitable for the prescription by the increase of the heat transmission coefficient, so the user must pay attention to the treatment. This study investigated only the slope window of 12mm and 16mm pair glass and the double window of external window and internal window paper, study on the various pattern of window must be achived in a future.

• Proceedings of the Korea Contents Association Conference
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• 2008.05a
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• pp.780-783
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• 2008

This study developed a model that could calculate roughness using Manning's and Chezy coefficient for Yangjae-stream. The estimated roughness by model developed was used for roughness coefficient in the stream without water level-discharge data. Roughness coefficient was estimated using assumed and calculated water level about each discharge scale by unsteady flow analysis. As a result, error of water surface level by model was shown 1.29m, it was shown that the flow resistance tends to increase with the desity of vegetation.