• Journal of the Korean earth science society
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• v.24 no.8
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• pp.704-710
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• 2003

A study for analysing the characteristics of the 'Tsunami Earthquake' and 'Tsunamigenic Earthquake' has been done in terms of stress drop and tectonic characteristics using previous studies on magnitude, moment, energy, and length of fault. The 'Tsunami Earthquake' seemed to occur mainly on the subduction environment with a very low stress drop of about 10 bars and a thrust dip angle comparing those of the 'Tsunamigenic Earthquake' or other earthquakes. Released energy to moment ratio of the 'Tsunami Earthquake' also seemed to be lower. Earthquakes which generated tsunami in the East Sea seemed to be 'Tsunamigenic Earthquake' with a stress drop of about 30${\sim}$50 bars, and an average energy to moment ratio. Hence, stress drop, energy to moment ratio, and thrust dip angle seem to be indicators of earthquakes that produce tsunamis.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.1
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• pp.19-25
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• 2022

Physical experiments were conducted to establish an empirical formula that predicts the wave force on the upside of the pavement behind crown wall of rubble mound seawall due to wave overtopping as well as the uplift force on the downside of the pavement. The experiments were performed by different conditions of the parapet, water depth, relative freeboard, and thickness of the armour layer. Then, the wave force on the upside and downside of the pavement behind the crown wall was analyzed. The parameters that affect the wave overtopping force and the uplift force were identified and empirical formulae were suggested for evaluating the forces on the pavement.

• Solar Energy
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• v.20 no.1
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• pp.21-29
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• 2000

In this research, the intensity of solar energy, which was injected to the different angle plane every hour day by day, was technically documented and quantitatively analyzed through actual observations. In order to group every days into days with similar intensity, graph was drawn with respect to time for every day and each area value under the curve was calculated. Then, the search for grouped days having similar intensity curve patterns was carried out. In order to maximize the efficiency of solar energy systems, the optimum incident angle of absorber plate was derived.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.1
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• pp.39-44
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• 2009

To improve the accuracy of numerical simulation of wave trans- formation across the surf zone, nonlinear shoaling effect based on Shuto's empirical formula and breaking mechanism are induced in the elliptic modified mild slope equation. The variations of shoaling coefficient with relative depth and deep water wave steepness are successfully reproduced and show good agreements with Shuto's formula. Breaking experiments show larger wave height distributions than linear model due to nonlinear shoaling but breaking mechanism shows a little bit larger damping in 1/20 beach slope experiment.

• Journal of the Korean Society for Marine Environment & Energy
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• v.12 no.3
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• pp.165-172
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• 2009

A set of equations for description of transformation of harmonic waves is proposed here. Velocity potential function and separation of variables are introduced for the derivation. The continuity equation is in a vertical plane is integrated through the water so that a horizontal one-dimensional wave equation is produced. The new equation composed of the complex velocity potential function, further be modified into. A set up of equations composed of the wave amplitude and wave phase gradient. The horizontally one-dimensional equations on the wave amplitude and wave phase gradient are the first and second-order ordinary differential equations. They are solved in a one-way marching manner starting from a side where boundary values are supplied, i.e. the wave amplitude, the wave amplitude gradient, and the wave phase gradient. Simple spatially-centered finite difference schemes are adopted for the present set of equations. The equations set is applied to three test cases, Booij's inclined plane slope profile, Massel's smooth bed profile, and Bragg's wavy bed profile. The present equations set is satisfactorily verified against existing theories including Massel's modified mild-slope equation, Berkhoff's mild-slope equation, and the full linear equation.

• Journal of Energy Engineering
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• v.18 no.1
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• pp.1-8
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• 2009

This paper reports the experimental study of natural convection heat transfer with $Al_2O_3$-water nanofluid. Experimental apparatus was a cylindrical enclosure with adjustable fluid layer thickness, and the aspect ratio was varied between 10.9 and 30.4. Heat transfer coefficients seemed to have reached a steady value within 30 minutes as the case with pure water. But, decrease in heat transfer coefficient continued for over $1{\sim}2$ hours for inclination angle of $0^{\circ}$, and oscillation in heat transfer was observed for certain inclination angles and aspect ratios for over 10 hours. Oscillation shape and period depended on the aspect ratio and inclination angle. For example, the oscillation period for $0^{\circ}$ was more than twice that for $60^{\circ}$. The maximum Nusselt number occurred at the inclination angle of $30^{\circ}$, and the minimum occurred at $60^{\circ}$ for Rayleigh number less than 1.E5. However the present results were obtained with aggregated nanofluid and would be devoid of generalities.

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.5
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• pp.617-623
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• 2012

In this paper, we propose a gait generation method for a quadruped robot to walk efficiently on the slope, which uses the waist joint of a quadruped robot. We derive the kinematic model of a quadruped robot with waist joint using the Denavit-Hartenberg representation method and the algebraic method. In addition, the gaits are generated based on the wave gait. In the proposed gait generation method, first in order to alleviate the mechanical restriction and the reduction of the stride, we determine the appropriate waist joint angle according to the slope degree, and then decide the location of the tiptoe of a quadruped robot by exploring the workspace. Finally, through computer simulations, we verify the effectiveness and applicability of the proposed method.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.137-137
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• 2017

우리나라는 산지가 64%를 차지하고 있기 때문에 토양침식 위험성이 큰 급경사지가 많다. 산지사면 토양은 대부분 사질토와 사양토로 이루어졌다. 급경사면에서의 토양침식이 많이 발생함에도 이에 대한 연구결과는 부족한 실정이다. 본 연구에서는 사양토로 구성된 나지사면에 대한 토양침식 특성을 파악하고자 강우모의 실험을 수행하였다. 강우모의 실험의 강우강도는 전국의 확률강우분포 3~200년 빈도의 30분 강우강도인 60mm/hr~130mm/hr의 범위였다. 사면경사는 급경사지 범위을 대표하는 $24^{\circ}$와 $28^{\circ}$에서 실험을 하였다. 실험은 발생하는 지표유출과 지표하유출를 수집하여 측정하였으며, 지표표면에 잉크를 뿌린 다음 실험을 동영상 촬영하여 속도를 측정하였다. 지표유출량을 건조로에 넣고 건조시켜 토양침식량을 측정하였다. 그리고 강우운동에너지는 광학디스트로메터(Pasivel)을 이용하여 측정하였다. 강우운동에너지를 측정한 결과 $800J/m^2{\sim}1700J/m^2$ 범위였다. 강우강도가 클수록 지표유출량과 토사유출량은 증가하였다. 경사가 증가함에 따라 지표유출량은 큰 변화가 없으나, 토양침식량은 크게 증가하였다. 지표하유출량은 강우강도와 경사가 증가하여도 큰 변화가 없었으며, 강우 발생이 멈추면 즉시 감소하였다. 사양토의 점토성분이 강우의 침투를 저해하고, 모래보다 많은 양의 물을 함유하는 있는 것으로 파악 되었다. 그러나 사질토보다 토양입자가 작은 사양토에서 상대적으로 많은 토양침식이 발생하였다. 강우에너지가 증가하면 유사농도는 감소하는 경향을 보였다. 이는 강우에너지가 증가함에 따라 지표유출량의 증가율에 비해 토양침식량의 증가율이 작기 때문인 것으로 판단된다.

• Solar Energy
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• v.18 no.2
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• pp.69-89
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• 1998

The measured solar radiation incident on tilted surfaces by all directions has been widely used as important solar radiation data in installing solar collectors, hot water systems, and photovoltaic modules, and in designing solar buildings and houses. To maximize the incident beam radiation, the slope, which is the angle between the plane of the surface in question and the horizontal, and the solar azimuth angles are needed for these solar applied systems. To respond to above needs, a theoretical study with actual measurements on moving route of the sun is carried out. This study focuses on the development of an solar expert system and on the selection of slopes for solar absorber plates in Korea.

• Journal of the Korean Solar Energy Society
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• v.38 no.3
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• pp.1-20
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• 2018

It is a very important and fundamental process to know accurately the intensity of the solar energy coming into the installed module considering the tilted angle. Europe and the US commonly use a program called PVsyst to convert the global horizontal irradiation to global irradiation on tilted plane. There are two types of models that PVsyst uses to convert to irradiation on tilted plane. In this paper, Perez model, which is a decomposition model and Perez model, which is a transposition model used in PVsyst, are applied based on global horizontal irradiation and global irradiation on tilted plane measured in a specific area. The comparison of the decomposition model shows the effect of the transpostion model on global irradiation on tilted plane conversion by comparing the ratio of the horizontal diffuse irradiation amount of the Watanabe model which are highly trusted in Asia and the Perez model. The comparison of transposition model confirm the error between the measured data and the calculated value which is applied Perez model to global horizontal irradiation decomposed by Perez model and Watanabe model. Based on the two comparisons, This paper propose a method to confirm the reliability of transposition model and reduce the error when PVsyst is used in Korea.