• Journal of Korea Water Resources Association
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• v.51 no.3
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• pp.183-193
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• 2018

Channel-forming discharge for downstream section of Yeongju dam in Naesung stream was calculated to analyze stable channel geometry. Determined channel-forming discharge was applied to design stable channel slope, depth, and base width at Yonghyeol station. Used data for channel-forming discharge and stable channel analysis were collected in downstream section of Yeongju dam in Naesung stream before the dam construction. Specified recurrence interval discharge, effective discharge, and bankfull discharge were analyzed and compared to decide final channel-forming discharge which was $260m^3/s$ of bankfull discharge. Stable channel analysis and design program was applied to predict stable channel section of width, depth, and slope with various sediment transport equations of Ackers and White, Brownlie, Engelund and Hansen, and Yang's equations. As a result, all equations of sediment transport produced milder slopes compared to current bed slope of 0.00177 and Ackers and White equation presented the most similar flow depth of current section with the design constraint of current channel width.

• 한국지구물리탐사학회:학술대회논문집
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• 2004.06a
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• pp.232-237
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• 2004

Anatahan Volcano in the Commonwealth of the Northern Mariana Islands (CNMI) erupted for the first time in recorded history on 10 May 2003. The underwater acoustic records of earthquakes, explosions, and tremor produced during the eruption were recorded on a sound-channel hydrophone deployed in February 2003. Acoustic propagation models show the seismic to acoustic conversion at Anatahan is particularly efficient, aided by the slope of the seamount toward the hydrophone. The hydrophone records confirm the onset of earthquake activity at 01:53Z on 10 May, as well as the onset (at ${\~}$06:20Z) of continuous, low-frequency (5-40 Hz) acoustic energy that is likely volcanic tremor related to magma intrusion. The hydrophone recorded a total of 458 earthquakes associated with the eruption. To predict the character of acoustic signals generated from Anatahan, we developed a moment-tensor representation of a volcano-seismic source that is governed by the geometry of the source and the physical properties of the magma. A buried magmatic pipe model was adopted, and numerically modeling source parameters such as the pipe radius and magma viscosity enable us to grasp the inward nature of Anatahan Volcano.

• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.4
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• pp.94-102
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• 1998

This paper aims at developing the prediction technique of the deformation for the embankment such as sea dike and shore protection relevant to reclamation project along the southern coast of the Korean Peninsula. Generally total deformation of a sea dike over clayey foundation are composed of immediate settlement, plastic deformation and consolidation settlement. Plastic deformation occurs when the ultimate bearing capacity is less than overburden pressure containing the stress increment due to the construction of an embankment. The reliable prediction of total settlement is very important since deformed final geometry of sea dike is directly connected for analysing the safety of the long-term slope failure and piping. During this study, plastic deformation, major part of deformation was analysed using the program developed by authors, whereas immediate settlement and consolidation settlement were predicted by Mochinaka and Sena's method and Terzaghi's 1-dimensional theory of consolidation respectively. In order to validate the prediction technique for the deformation, a case study of Koheung Bay reclamation works was carried out. A good agreement was obtained between observation and prediction, which means the applicability of the technique.

• Journal of Korean Society of Forest Science
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• v.82 no.1
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• pp.34-43
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• 1993

In this paper, the characteristics of cable logging operations are discussed from a standpoint of mechanics. An example of standing skyline operations is used to illustrate the mechanical principles. Using force and moment boundary conditions, the maximum allowable payload was formulated as a function of slope profile, system geometry and operation options. This formulation includes fundamental equations for log drag and single segment mechanics. The catenary link model is the basic assumption in simulating cable segment stretches. In order to demonstrate the solution procedures of the formulation, a computer model was developed. The model uses Secant algorithm to determine the solution of the complex nonlinear equation set. Finally, the computer model was demonstrated using a hypothetical data set.

• The Journal of the Korea Contents Association
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• v.13 no.2
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• pp.505-511
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• 2013

A new boundary treatment technique which can be applied to axi-symmetric topography with inclined bottom was developed. Although the finite element method is good for complex geometry, there is no proper boundary treatment when a boundary is not a vertical section because the water depth at the coastline becomes zero. In this study, we developed a new boundary treatment for inclined bottom using the analytical solution for long wave. To develope a model, the mild-slope equation was used and then, a computational domain is divided into an analytical region and a numerical region. By combining a numerical and an analytical solutions, a complete solution was obtained. The developed solution was validated by comparing with a previous analytical solution.

• Korean Journal of Optics and Photonics
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• v.6 no.4
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• pp.282-287
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• 1995

We have studied the characteristics of a cw Ti:sapphire laser pumped by an Ar-ion laser. Ti:sapphire is one of the most attractive materials for the generation of ultra-short pulses because of its very broad gain bandwidth. We used a 4.1 mm thick, 0.15 wt. % $Ti^{3+}$ -doped, Brewster-angled Ti:sapphire crystal and made a folded cavity to create a strong focusing mode. The folding angle of the cavity was adjusted to $15.4^{\circ}$ to compensate for the astigmatism from the Brewster-angled Ti:sapphire crystal. 5 WAr-ion laser was used as a pumping source. We observed that the Ti:sapphire cw output power was sensitively changed with respect to the condition of the folded cavity. The threshold pumping power was 2 Wand the slope efficiency was 16% when an output coupler of 10% transmission was used. The maximum output power was more than 450 mW at 5 W pumping. mping.

• Journal of the Korean Society of Combustion
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• v.5 no.2
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• pp.51-62
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• 2000

The relationship among the flame radiation, NOx emissions, residence time, and global strain rate are examined for turbulent non-premixed jet flames with wide variations in coaxial air conditions. Measurements of NOx emission, flame geometry and flame radiation were made to explain the NOx emission scaling based on global parameters such as flame residence time, global strain rate, and radiant fraction. The overall 1/2-power scaling is observed in coaxial air flames, irrespective of coaxial air conditions, but the degree of deviation from the 1/2-slope curve in each case differs from one another. From the comparison between the results of pure hydrogen flames and those of helium diluted hydrogen flames, it is observed that flame radiation plays a significant role in pure hydrogen flames with coaxial air and the deviation from 1/2-power scaling may be explained in two reasons: the difference in the flame radiation and the difference in jet similarity in coaxial air flames. From the radiation measurements, more detailed explanations on these deviations were suggested.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.186-195
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• 2001

The purpose of this study is to develop the time-dependent, one-dimensional numerical model on the interaction between irregular waves and two-layer permeable coastal structures, by extending and modifying the numerical model PBREAK(Wurjanto and Kobayashi, 1992) which is applicable only to one-layer permeable coastal structures. The two-layer permeable coastal structure consists of two permeable underlayers with different permeable media resting on an impermeable slope and an armor layer covering the permeable underlayer. The numerical model of this study simulates the wave over rough permeable underlayer of arbitrary geometry as well as the waves inside two-permeable underlayers of arbitrary thickness for specified normally-incident irregular waves. The utility of the numerical model is founded from comparing with PBREAK and the four hydraulic model tests under irregular waves. The sensitivities of computed results according to typical parameters(porosity, stone diameter, horizontal width of the permeable underlayer) and major factors(friction factor of primary armor layer etc.) discussed.

• Geomechanics and Engineering
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• v.10 no.5
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• pp.657-676
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• 2016

In this paper, the active lateral earth pressure is evaluated using the stress characteristics or slip line method. The lateral earth pressure is expressed as the lateral earth pressure coefficients due to the surcharge, the unit weight and cohesion of the backfill soil. Seismic horizontal and vertical pseudo-static coefficients are used to consider the seismic effects. The equilibrium equations along the characteristics lines are solved by the finite difference method. The slope of the ground surface, the wall angle and the adhesion and friction angle of the soil-wall interface are also considered in the analysis. A computer code is provided for the analysis. The code is capable of solving the characteristics network, determining active lateral earth pressure distribution and calculating active lateral earth pressure coefficients. Closed-form solutions are provided for the lateral earth pressure coefficients due to the surcharge and cohesion. The results of this study have a good agreement with other reported results. The effects of the geometry of the retaining wall, the soil and soil-wall interface parameters are evaluated. Non-dimensional graphs are presented for the active lateral earth pressure coefficients.

• Journal of Korea Water Resources Association
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• v.40 no.11
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• pp.899-908
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• 2007

In this study, wave reflection due to depression of seabed is calculated by using eigenfunction expansion method. The proper numbers of steps and evanescent modes needed for analysis are suggested by applying the eigenfunction expansion method to bottom topography of which slope or curvature varies. While satisfying shallow or intermediate water depth condition, the optimal figure of depression of seabed is obtained by calculating reflection coefficient for various depressions of seabed. The reflection coefficient with distance between the depression of seabeds is then calculated after arraying the optimal geometry in two and three rows.