• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.417-422
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• 2002

The main purpose of this paper is to determine the dynamic optimal shapes of tapered column with constant volume. The linear, parabolic and sinusoidal tapers with the regular polygon cross-section are considered, whose material volume and span length are always held constant. The ordinary differential equation including the effect of axial load is applied to calculate the natural frequencies. The Runge-Kutta method and Regula-Falsi methods are used to integrate the differential equation and compute the frequencies, respectively. Then the dynamic optimal shape whose lowest natural frequency is highest is determined by reading the critical value of the frequency versus section ratio curve plotted by the frequency data. In the numerical examples, the tapered columns are analysed and the numerical result of this study are shown in table and figures.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.819-823
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• 2003

The differential equations governing the shape of displacement for the shallow parabolic arch subjected to multiple dynamic point step loads were derived and solved numerically The Runge-Kutta method was used to perform the time integrations. Hinged-hinged end constraint was considered. Based on the Budiansky-Roth criterion, the dynamic critical point step loads were calculated and the dynamic stability regions for such loads were determined by using the data of critical loads obtained in this study.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.396-401
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• 2006

Dynamic behaviors of the impact damper are studied experimentally and numerically. In order to investigate wide range of excitation frequencies and amplitudes, a simple but high amplifying and bias-free experimental setup is designed. Experiments focused on the harsh operation condition demonstrate Accelerated mass loading which not only deteriorates the performance of the impact damper but also involves the structural resonance which should be avoided for the stability of the system. In the previous studies, instability or deterioration of the performance was reported for the off resonance frequency region. But this paper shows that the performance deterioration and structural resonances can be predicted. Using finite element modeling and analysis, accurate system parameters were derived and used for the numerical modeling employing the conservation of the momentum. Numerical study of the transient responses using 4th-order Runge-Kutta method demonstrates general performance of the system, and shows that accelerated mass loading phenomenon is deeply related with the vibration amplitudes and the mass of the auxiliary system.

• Korean Journal of Hydrosciences
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• v.8
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• pp.111-123
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• 1997

A one-dimensional eddy diffusion model and a mixed-layer model are developed and applied to simulate the vertical temperature profiles in lakes. Also the running result of each method are compared and analyzed. In an eddy diffusion model, molecular diffusivity is neglected and eddy diffusivity which does not need lake-specific fitting parameter and constant lake's level are applied. The heat exchanges at the water surface and the bottom are formulated by the energy balance and zero energy gradient, respectively. In a mixed-layer model, two layers approach which has a constant thickness is adopted. The application of these models which use explicit finite difference and Runge-Kutta methods respectively demonstrates that the models simulate water temperatures efficiently.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.2
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• pp.30-41
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• 1995

Gear rattle is a source of vibration and noise in automotive gearbox casing and generally occurs at or near system resonant frequencies. The neutral gear rattle of the gearbox. is affected by the stiffness and hysteresis torque in the clutch disk and drag torque determining balancing point of the clutch disk operating range. The experiment is carried out in the pre-damper type clutch and a manual transmission of a automobile equipped for inline four-sylinder four-cycle 1.5L MPI engine and the computer simulation is executed by 5th order Runge-Kutta method. The results of the simulation analysis and experimental studies show the dynamic behavior of clutch and a phenomenon of the neutral gear rattle with respect to drag torque and torsional characteristics of the clutch.

• Proceedings of the KIEE Conference
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• 1987.11a
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• pp.421-424
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• 1987

Recently, the problem associated with the achievement of desired trajectories for non-linear robotic manipulatory systems are researched. The control system which is designed for this robot manipulator, poses a number of severe problem. The methods proposed to deal with the problem fall loosely into three main classes : "direct" "adaptive", "anthropomorphic". Besides there is an approach which is described based upon the application of optimal control theory. In this paper, using the optimal theory, we choose error-coordinate, between the desired trajectories and the practical as the state values, and determine the control law U which minimize a corresponding performance criterion. Let's consider the robotic arm proposed by Freund and set up the deviations of it's trajectory as a measure of performance. To find the optimal control law $U^*$ and the next state value which need to obtain $U^*$ here, we should introduced the conjugate gradient algorithm and the Runge Kutta method.

• Proceedings of the KIEE Conference
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• 2001.11b
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• pp.88-91
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• 2001

본 연구에서는 전력계동의 다이나믹스를 정확하게 표현할 수 있는 기계적 시스템인 등가역학 모델(Equivalent Mechanical Model: EMM)을 제안하고, 이를 기초로 확고한 수학적 해석을 통해 에너지 함수의 유도 방법을 체계화 하고 물리적 의미를 파악함으로써 에너지 함수를 이용한 시스템 해석에 대한 이론적 배경을 마련한다. 또한 시영역 모의법을 이용한 과도안정도 해석의 간접법에서 SI법중 Trapezoidal법에서의 오차를 줄일수 있는 알고리즘을 제시한다. 먼저 수학적 이론을 바탕으로 전력계통에 적용하여 상태변수를 업데이트 시킴으로써 Trapezoidal법에서보다 더 정확한 데이터를 얻고자 한다. 본 연구에서는 명확한 수학적 이론의 적용을 위해 1기 무한대 모선을 모델로 시뮬레이션 하였으며 결과의 비교분석을 위해 Runge-Kutta법에 의한 시영역 모의와 비교하였다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.2
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• pp.121-127
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• 2008

This paper investigates the effects of outdoor pressure fluctuations on natural ventilation through an opening on a building envelope. The ventilation airflow rate depends on the magnitude and the period of the pressure fluctuations, the size of the opening relative to the space volume, and the resistance characteristics of the opening. Non-dimensional parameters have been derived, which determine indoor pressure responses due to outdoor pressure fluctuations. The flow regions are categorized into (1) synchronized region, (2) opening resistance region, and (3) transition region depending on the non-dimensional parameter derived. Pressure fluctuations and flow characteristics are investigated numerically using the 4th order Runge-Kutta method.

• Journal of Biomedical Engineering Research
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• v.13 no.3
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• pp.235-244
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• 1992

In this paper, fluttering behavior of mechanical monoleaflet tilting disc heart valve prostheses during the opening phase was analyzed taking into consideration the impact between the occluder and the guiding strut at the fully open position. The motion of the valve occluder was modeled as a rotating system, and equations were derived by employing the moment equilibrium principle. Forces due to lift, drag, gravity and buoyancy were considered as external forces acting on the occluder. The 4th order Runge-Kutta method was used to solve the governing equations. The results iimonstrated that the occludes reaches steady equilibrium position only after damped vibration. Fluttering frequency varies as a function of time after opening and is in the range of 8-84 Hz. Valve opening appears to be affected by the orientation of the valve relative to gravitational force. The opening velocities are in the range of 0.65-1.42m/sec and the dynamic loads by impact of the occludes and the strut are in the range of 90-190 N.

• Journal of Biomedical Engineering Research
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• v.12 no.3
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• pp.149-156
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• 1991

In this paper, fluttering behavior of mechanical bileaflet heart valve prosthesis was analyzed taking into consideration of the impact between valve plate and stopper Vibration system of the valve was modeled as a rotating system, and equations are induced by moment equilibrium equations. Lift force, drag force, gravity and buoyancy were considered as external forces acting on the valve plate/ The 4th order Runge-Kutta method was used to solve the equations. Valve plate does not come to the static equilibrium position at a stretch, but come to that position after under damping vibration. Damping ratio increases as the cardiac optput increases, and the mean damping ratio is in the range of 0.16~40.25. Fluttering frequency does not have any specific value, but varies as a function of time. It is in the range of 10~40Hz. Valve opening appears to be affected by the orientation of the of the valve relative to gravitational forces.