• Journal of Environmental Science International
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• v.21 no.6
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• pp.725-738
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• 2012

Recently, a variety of GIS-based tools enabling to generate topographic parameters for hydrologic and hydraulic researches have been developed. However, most of GIS-based tools are usually insufficient to estimate and visualize river channel slopes especially along the river network, which can be possibly utilized for many hydraulic equations such as Manning's formula. Many existing GIS-based tools have simply averaged cell-based slopes for the other advanced level of hydrologic units as likely as the mean watershed slope, thus that the river channel slope from the simple approach resulted in the inaccurate channel slope particularly for the mountain region where the slope varies significantly along the downstream direction. The paper aims to provide several more advanced GIS-based methodologies to assess the river channel slopes along the given river network. The developed algorithms were integrated with a newly developed tool named RiverSlope, which adapted theoretical formulas of river hydraulics to calculate channel slopes. For the study area, Han stream in the Jeju island was selected, where the channel slopes have a tendency to rapidly change the upstream near the Halla mountain and sustain the mild slope adjacent to watershed outlet heading for the ocean. The paper compared the simple slope method from the Arc Hydro, with other more complicated methods. The results are discussed to decide better approaches based on the given conditions.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.11
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• pp.2944-2953
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• 1994

Active range finders using laser beam have been widely used for the factory automation and quality assurance, but they may be unreliable if the object' slope is steep or its surface is specular. The reliability of an active range finder was analyzed for the variation of the reflected laser beam intensity. First, the properties of the object's reflection were modeled by using the bidirectional reflectance-distribution function(BRDF), and then the variation of the laser beam brightness was formulated for the different configuratioin of the object and sensor. The experimental data of the laser beam reflection were obtained for two materials, mild steel and stainless steel. The parameters of the proposed model were obtained by fitting the data of the mild steel to the model and it was found that the results calculated from the proposed model were in good agreement with the experimental data.

• Corrosion Science and Technology
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• v.7 no.6
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• pp.319-323
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• 2008

The polarization resistance of mild steel in 0.5M hydrochloric acid has been evaluated by using impedance (Z) and linear polarization (LPR) techniques and compared to the noise resistance obtained from electrochemical noise data. The degree of localization of this general corrosion has also been discussed by evaluating localization index and power spectral density. Polarization resistance obtained by LPR technique ($28\Omega$) was higher than that obtained by impedance technique ($15\Omega$). Noise resistance ($11\Omega$) was much lower than polarization resistance measured by both of above techniques. Higher polarization resistance obtained by LPR technique is generally caused by passivation effect in the presence of scales or deposits which can introduce an increased resistance as can low conductivity electrolytes. The reason why noise resistance is lower than polarization resistance is the effect of background noise detected by using three platinum electrodes cell in 0.5M hydrochloric acid. Slope($-\beta$) of power spectral density (PSD) obtained from analysis of noise data ($-\beta$ = 3.3) was much higher than 2 which indicates mild steel corroded uniformly. Localization index (LI) calculated from statistical analysis (LI=0.08) is much lower than 1 which indicates that mild steel did not corroded locally. However, LI value is still higher than $1x10^{-3}$ and this indicates that mild steel corroded locally in microscopic point of view.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.04a
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• pp.179-186
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• 2004

Introduction of wave model, considered the effect of shoaling, refraction, diffraction, partial reflection, bottom friction, breaking at the coastal waters of complex bathymetry, is a very important factor for most coastal engineering design and disaster prevention problems. As waves move from deeper waters to shallow coastal waters, the fundamental wave parameters will change and the wave energy is redistributed along wave crests due to the depth variation, the presence of islands, coastal protection structures, irregularities of the enclosing shore boundaries, and other geological features. Moreover, waves undergo severe change inside the surf zone where wave breaking occurs and in the regions where reflected waves from coastline and structural boundaries interact with the incident waves. Therefore, the application of mild-slope equation model in this field would help for understanding of wave transformation mechanism where many other models could not deal with up to now. The purpose of this study is to form a extended mild-slope equation wave model and make comparison and analysis on variation of harbor responses in the vicinities of Pohang Old Harbor and Pohang New Port, etc. due to construction of New Port in Youngil Bay. This type of trial might be a milestone for port development in macroscale, where the induced impact analysis in the existing port due to the developemnt could be easily neglected.

• Journal of Navigation and Port Research
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• v.28 no.5
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• pp.421-428
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• 2004

Introduction of wave model, considered the effect of shoaling, refraction, diffraction, partial reflection, bottom friction, breaking at the coastal waters of complex bathymetry, is a very important factor for most coastal engineering design and disaster prevention problems. As waves move from deeper waters to shallow coastal waters, the fundamental wave parameters will change and the wave energy is redistributed along wave crests due to the depth variation, the presence of islands, coastal protection structures, irregularities of the enclosing shore boundaries, and other geological features. Moreover, waves undergo severe change inside the surf zone where wave breaking occurs and in the regions where reflected waves from coastline and structural boundaries interact with the incident waves. Therefore, the application of mild-slope equation model in this field would help for understanding of wave transformation mechanism where many other models could not deal with up to now. The purpose of this study is to form a extended mild-slope equation wave model and make comparison and analysis on variation of harbor responses in the vicinities of Pohang Old Harbor and Pohang New Port, etc. due to construction of New Port in Youngil Bay. This type of trial might be a milestone for port development in macroscale, where the induced impact analysis in the existing port due to the development could be easily neglected.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.532-537
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• 2005

The techniques of internally generating waves on a curve in a rectangular grid system are developed using the line source method. Numerical experiments are conducted using the extended mild-slope equations of Suh et al. (1997). For five different types of wave generation layout, numerical experiments are conducted in the cases of the propagation of waves on a flat bottom, and the refraction and shoaling of waves on a plane slope. The fifth type of wave generation, which consists of two parallel lines connected to a semicircle, shows the best solutions especially when the grid size is small enough.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.27 no.2
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• pp.173-182
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• 1994

A numerical experiment on the effective discharge of waste materials caused in recirculating aquaculture basins was performed. The numerical model used in this study was a 4-level hydrodynamic and advection-diffusion model. Flow structures and settling processes of ss in the various mathematical model basins are discussed. The calculated flow fields of the numerical basin corresponded well with the measured velocity in field basin. In the cases of steep bottom slopes in 4/30, the non-dimensional tractive force($U{\ast}/U{\ast}_c$) which is all important parameter for the deposition pattern of waste materials was stronger than with the mild slope one. The settling pattern of ss depended considerably on the degree of bottom slope of basin. To concentrate deposited waste materials into the center discharge pipe, it is useful to design a cylindrical basin with a steeply conical bottom. In addition, to prevent movement of the deposit area away from the center, it is necessary to locate the circulating ducts at diametrically opposed points on the basin sides.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.1 no.1
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• pp.1-7
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• 1989

Theoretical studies have been made to analyze combined refraction diffraction of the wind waves propagating on a large scale current in water of varying depth. The governing equation for monochromatic waves was derived through splitting a mild slope equation into two equations. A numerical model is developed using finite difference scheme which is computationally very efficient for modelling large area. Numerical examples concerning the interactions between waves and rip currents over a gentle slope are presented, in which the current effects on the wave diffraction in the caustic region are closely examined.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.3
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• pp.254-261
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• 2001

It is well known that when long waves propagate from deep ocean onto a continental shelf with a very steep continental slope, the waves reflected from the shore can not propagate offshore and are re-reflected from the continental slope so that large water level fluctuations are induced near the shore. Liu(1986) has analyzed this phenomenon by assuming a topography which has a depth discontinuity along a semicircular offshore boundary, but his solution is erroneous. In the present paper, we correct his analytical solutions for a straight shoreline and a rectangular harbor. The corrected solution is then compared with the numerical results of the Galerkin finite element model of Jeong et al.(1998), which is based on the extended mild-slope equation.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 1995.10a
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• pp.75-80
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• 1995

The model for the combined refraction and diffraction of water waves, the so-called mild-slope equation, was first developed by Berkhoff (1972) and has been studied by many coastal engineers because the model is able to consider the combined effect of refraction and diffraction of water waves and eliminate the problem of ray crossing which may happen in the previously developed ray theory. (omitted)