• Korean Journal of Applied Biomechanics
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• v.15 no.3
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• pp.71-78
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• 2005

The purpose of this research was to conduct an analysis on the factors that determine the distance at the time of target swing based on the use of late hitting of outstanding college golfers to verify the difference between late hitting and the distance that target increases in regular swing and the distance. Then, this research conducts an analysis on the correlation between club head velocity, ball velocity, launch angle, back spin, meet ratio and distance that become kinematics variables at the time of target swing. To attain the above mentioned purpose, 25 outstanding college players with average experience and handicap of 6 years and 5, respectively, were targeted Comparative analysis on two swing that target increase in regular and the distance was conducted by used driver. When it pertained to two types of swing. analysis system comprised of an analytical software called the Science Eye of the Bridgestone and peripheries was used to define the relationship between variables of club head velocity, ball velocity, launch angle, back spin, meet ratio that become kinematics variables. As for the method of processing data pertaining to the factors that determine the distance, differences of distance by the type of swing was verified by using independent T-test that leveraged SPSS 120 statistics program. Moreover, level of correlation between variables that contribute to the increase in distance through relation of correlation, and analysis of tendencies was conducted to analyze tendency of non-distance to increase in accordance to the increase of each variable. Key results produced through this experiment are as follows: 1. Artificial late hitting for increased non-distance that targets skilled players had effect on increased the distance(p<. 05). 2 The drive distance is correlated with each measured variable that is positive correlation to ball velocity, club head velocity, meet ratio and relation of back spin and launch angle are negative correlation. ball velocity and club head velocity are very high correlated with drive distance(p<.01), back spin and distance are negative correlation(p<.01). 3. Among each measured variable increasing the club velocity is the most contribution, and ball velocity and meet ratio and the increasing launch angle and back spin is negative effect for increasing distance.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.04b
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• pp.332-339
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• 2000

In this paper the characteristics of vibration induced by subway trains running on track is discussed. The quantitative prediction of the vibration level and the countermeasure for reduction of necessary, is of importance for the better environment. It was made the constructed Bundang line as first step with the modified Young-Dan type to basis on the Japanese Young-Dan type. In this paper it was measured and analyzed to two region (①Susuh-Bokjung, ②Chorim-Suhyun region) of this, at present operational Bundang line when averaging velocity of train is 60(㎞/h). As the response characteristics of frequency induced by subway operation, it was confirmed that frequency band of neighborhood of 30∼80Hz in generally dominant. Also to assess the quantitative vibration as response level to be measured for each point of two region in subway operation, the vibrational response level was measured at the state to be not subway operation. And the level was approximately 1/5∼1/10 level comparing to subway operation.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.391-396
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• 2008

A level set based topological shape optimization using extended B-spline basis functions is developed for steady state heat conduction problems. The only inside of complicated domain is identified by the level set functions and taken into account in computation. The solution of Hamilton-Jacobi equation leads to an optimal shape according to the normal velocity field determined from the sensitivity analysis, minimizing a thermal compliance while satisfying a volume constraint. To obtain exact shape sensitivity, the precise normal and curvature of geometry need to be determined using the level set and B-spline basis functions. The nucleation of holes is possible whenever and wherever necessary during the optimization using a topological derivative concept.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.113-118
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• 2001

We present a new interface tracking method for computing two-phase flow. This method is based on VOF method coupled with Level set method. The method is verified to calculate an interfacial curvature accurately as well as to achieve volume conservation during the whole computation period. We apply the present method to calculate a falling drop. The calculated shape and terminal velocity of the falling drop showed good agreement with the data reported in the literature. Also, the present method was proven to be applicable to drop-wall collision phenomenon.

• Journal of The Korean Society of Agricultural Engineers
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• v.55 no.2
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• pp.87-95
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• 2013

The aim of this study is to examine the behavior of reservoir fill dam with the water level raising by use of the centrifugal model test and the numerical simulation. In this study, LIQCA2D-SF based on the cyclic elasto-plastic constitutive model proposed by Oka et al. (1999) is applied for numerical simulation. In order to investigate the displacements and the pore water pressures in the fill dam due to the water level raising velocity, three model tests in centrifugal field of 50g for fill dams were conducted. A comparison between the test result and the simulation result has provided the influence on the displacement and the pore water pressure of the fill dam with increasing up of the water level.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.623-624
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• 2008

We present a level set method for numerical shape optimization of electromagnetic systems. The level set method does not only lead to efficient computational schemes, but also is able to handle topological changes such as merging, splitting and even disappearing of connected components. The velocity field on boundaries is obtained by a shape derivative of continuum sensitivity analysis using the material derivative concept and an adjoint variable technique. Two numerical results of dielectric optimization between electrodes showed that the level set method is feasible and effective in solving shape optimization problems of electromagnetic systems.

• Proceedings of the Korean Nuclear Society Conference
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• 1999.05a
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• pp.124-124
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• 1999

An ultrasonic method is developed for the measurement of the two-phase mixture level in the reactor vessel or steam generator. The ultrasonic method is selected among the several non¬nuelear two-phase mixture level measurement methods through two steps of selection procedure. A commercial ultrasonic level measurement method is modified for application into the high temperature, pressure, and other conditions. The calculation method of the ultrasonic velocity is modified to consider the medium as the homogeneous mixture of air and steam. and to be applied into the high temperature and pressure conditions. The cross-correlation technique is adopted as a detection method to reduce the effects of the attenuation and the dif.JUsed reflection caused by suface fluctuation. The waveguides are developed to reduce the loss of echo and to remove the effects of obstructs. The present experimental study shows that the developed ultrasonic method measures the two-phase mixture level more accurately than the conventional methods do.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.2
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• pp.50-61
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• 2019

The aspects of typhoon-induced surges were classified into three types at the Western coast, and their characteristics were examined. The typhoons OLGA (9907) and KOMPASU (1007) were the representative steep types. As they pass close to the coasts with fast translation velocity, the time of maximum surge is unrelated to tidal phase. However, typhoons PRAPIROON (0012) and BOLAVEN (1215) were the representative mild types, which pass at a long distance to the coasts with slow translation velocity, and were characterized by having maximum surge time is near low tide. Meanwhile, typhoons MUIFA (1109) and WINNIE (9713) can be classified into mild types, but they do not show the characteristics of the mild type. Thus they are classified into propagative type, which are propagated from the outside. Analyzing the annual highest high water level data, the highest water level ever had been recorded when the WINNIE (9713) had attacked. At that time, severe astronomical tide condition overlapped modest surge. Therefore, if severe astronomical tide encounter severe surge in the future, tremendous water level may be formed with very small probability. However, considering that most of the huge typhoons are mild type, time of maximum surge tends to occur at low tide. In case of estimating the extreme water level by a numerical simulation, it is necessary not only to apply various tide conditions and accompanying tide-modulated surge, but also to scrutinize typhoon parameters such as translation velocity and so on.

• Composites Research
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• v.13 no.6
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• pp.1-8
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• 2000

The fabrication Process of $Al_2O_{3p}$/AC8A composites by pressureless infiltration technique and the effects of additive Mg content and volume fraction of particulate reinforcement on mechanical and wear properties were investigated. It was found that the bending strength decreased with increasing volume fraction of $Al_2O_{3p}$ particles. Whereas hardness increased with volume fraction of $Al_2O_{3p}$ particles. The decrement of strength in case of high volume fraction of $Al_2O_{3p}$ particles was attributed to high porosity level. In terms of additive Mg content, $Al_2O_{3p}$/AC8A composites containing around 5~7wt% of additive Mg indicated the highest strength, and hardness values increased with additive Mg contents. Wear resistance of AC8A alloy were improved by reinforcement of $Al_2O_{3p}$ particles especially at high sliding velocity. Wear property of $Al_2O_{3p}$/AC8A composites and AC8A alloy exhibited different aspects. $Al_2O_{3p}$/AC8A composites indicated more wear loss than AC8A alloy at slow velocity region. However a transition point of wear loss was found at middle velocity region which shows the minimum wear loss and wear loss at high velocity region exhibited almost same value as at slow velocity region, whereas wear loss of AC8A alloy almost linearly increased with sliding velocity. It was found that $Al_2O_{3p}$/AC8A composites containing $Al_2O_{3p}$ volume fraction of 20% exhibited abrasive wear surface regardless of sliding velocity and $Al_2O_{3p}$/AC8A composites containing $Al_2O_{3p}$ volume fraction of 40% showed slightly adhesive wear surface at low sliding velocity, and it progressed to severe wear as increasing the sliding velocity.

• 한국해양학회지
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• v.29 no.2
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• pp.119-131
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• 1994

Vertical structures of wind-driven and tidal currents in a rectangular shaped uniform-depth basin of homogeneous water have been investigated using a mode-splitted, multi-level grid-box, hydrodynamic numerical model. The model was verified using analytical solutions for various vertical eddy viscosity profiles such as: a constant eddy viscosity, a linearly decreasing or increasing variation with depth, a quadratic variation with depth and an exponential variation with depth. Particular attention has been paid on the effects of "near-surface wall layer" on vertical shear of velocity. In numerical calculations, the whole water depth was divided into 13 levels with an unequal grid spacing. the model satisfactorily reproduces the velocity profile, but in case the eddy viscosity decreases rapidly with depth as in quadratical or exponential variation with depth, the vertical gradient of velocity near the bottom became very steep, and analytical solutions and numerical results showed some discrepancy. The vertical structures of horizontal velocity vary with both the depth-averaged value of eddy viscosity and its profiles. the velocity near the sea surface and near the bottom responded sensitively to the eddy viscosity of wall layer. For wind-driven current, the strong velocity shear was generated near the sea surface as eddy viscosity near the surface became small. For tidal current, the velocity above the sea bottom layer was almost constant regardless of the profiles of vertical eddy viscosity, but velocity in the sea bottom layer showed strong shear as eddy viscosity became small.