• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.10
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• pp.4733-4738
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• 2013

This paper proposes a method to obtain the dynamic equilibrium configuration of a constrained mechanical system by using multibody dynamic analysis. Dynamic equilibrium equations with independent coordinates are derived from the time-dependent constraint equations and dynamic equations of a multibody system. The Newton-Raphson method is used to find numerical solutions for nonlinear algebraic equations that are composed of the dynamic equilibrium and constraint equations. The proposed method is applied to obtain the dynamic equilibrium configuration of a speed governor, and the results are verified on the basis of the results from conventional dynamic analysis. Furthermore, vertical displacements at equilibrium configuration, which varied with the rotational velocity of the speed governor, are calculated, and design parameter analysis of the equilibrium configuration is presented.

• Journal of the Korean Applied Science and Technology
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• v.38 no.4
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• pp.1107-1116
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• 2021

The purpose of this study investigate the effects of 8 weeks plyometric training on power, dynamic balance and joint position sensory in Taekwoondo demmonstrators. Twenty healthy collegiate Taekwoondo demonstrators were randomly assigned to either an exercise group (Ex=10), and a control group (Con=10), Ex group completed the plyometric training in three times a week, 60 minute for 8 weeks. Testing before and after training include the Sargent jump, standing long jump, back muscle strength, Dynamic balance and joint position sensory. Sargent jump, standing long jump and back muscle strength were significantly development(p<.05). And dynamic balance were significantly exercise effect in posterolateral(p<.01) and posteromedial(p<.05). Not only but also, joint position sensroy were significantly exercise effect in left food 15°(p<.01) and 45°(p<.05). The results of the study showed that 8 weeks of plyometric training had a positive effect on the power, dynamic balance and joint position sensory in Taekwondo demonstrator.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.7 s.124
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• pp.579-586
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• 2007

Analytical method to analyze the effect of tolerance on the modal characteristic of multi-body systems in dynamic equilibrium position is suggested in this paper. Monte-Carlo method is conventionally employed to perform the tolerance analysis. However, Monte-Carlo method spends too much time for analysis and has a greater or less accuracy depending on sample condition. To resolve these problems, an analytical method is suggested in this paper. Sensitivity equations for damped natural frequencies and the transfer function are derived at the dynamic equilibrium position. By employing the sensitivity information of mass, damping and stiffness matrices, the sensitivities of damped natural frequencies and the transfer function can be calculated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.109-114
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• 2007

Analytical method to analyze the effect of tolerance on the modal characteristic of multi-body systems in dynamic equilibrium position is suggested in this paper. Monte-Carlo Method is conventionally employed to perform the tolerance analysis. However, Monte-Carlo Method spends too much time for analysis and has a greater or less accuracy depending on sample condition. To resolve these problems, an analytical method is suggested in this paper. By employing the sensitivity information of mass, damping and stiffness matrices, the sensitivities of damped natural frequencies and the transfer function can be calculated at the dynamic equilibrium position. The effect of tolerance on the modal characteristic can be analyzed from tolerance analysis method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.835-840
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• 2010

This study develops a variable structure controller using nonlinear surface instead of the fixed, which has been the robustness against parameter variations and extraneous disturbance during the reaching phase. reaching time of the system trajectory is faster than the fixed method. This proposed scheme has better performance than the conventional method in reaching time, parameter variation and extraneous disturbance. The effectiveness of the proposed control scheme is verified by simulation results.

• Journal of KSNVE
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• v.9 no.2
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• pp.355-362
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• 1999

Vibration reduction of an optical disk drive is achieved by an automatic ball balancer and dynamic behaviors of the drive are studied by theoretical approaches. Using Lagrange's equation, we derive nonlinear equations of motion for a non-autonomous system with respect to the rectangular coordinate. To investigate the dynamic stability of the system in the neighborhood of equilibrium positions, the Floquet theory is applied to the perturbed equations. On the other hand, time responses are computed by an explicit time integration method. We also investigate the effects of mass center and the position of the ABB on the dynamic behaviors of the system.

• Economic and Environmental Geology
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• v.56 no.4
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• pp.435-445
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• 2023

A delta is a depositional landform that is formed when sediment transported by a river is deposited in a relatively low-energy environment, such as a lake, sea, or a main channel. Among these, a delta formed at the confluence of rivers has a great importance in river management and research because it has a significant impact on the hydraulic and sedimentological characteristics of the river. Recently, the equilibrium state of the confluence area has been disrupted by large-scale dredging and construction of levees in the Nakdong River. However, due to the natural recovery of the river, the confluence area is returning to its pre-dredging natural state through ongoing sedimentation. The time-series data show that the confluence delta has been steadily growing since the dredging, but once it reaches a certain size, it repeats growth and retreat, and the overall size does not change significantly. In this study, we developed a model to explain the sedimentation-erosion processes in the confluence area based on the assumption that the confluence delta reaches a dynamic equilibrium. The model is based on two fundamental principles: sedimentation due to supply from the tributary and erosion due to the main channel. The erosion coefficient that represents the Nakdong River confluence areas, was obtained using data from the tributaries of the Nakdong River. Sensitivity analyses were conducted using the developed model to understand how the confluence delta responds to changes in the sediment and water discharges of the tributary and the main channel, respectively. We then used annual average discharge of the Nakdong River's tributaries to predict the dynamic equilibrium positions of the confluence deltas. Finally, we conducted a simulation experiment on the development of the Gamcheon-Nakdong River delta using recorded daily discharge. The results showed that even though it is a simple model, it accurately predicted the dynamic equilibrium positions of the confluence deltas in the Nakdong River, including the areas where the delta had not formed, and those where the delta had already formed and predicted the trend of the response of the Gamcheon-Nakdong River delta. However, the actual retreat in the Gamcheon-Nakdong River delta was not captured fully due to errors and limitations in the simplification process. The insights through this study provide basic information on the sediment supply of the Nakdong River through the confluence areas, which can be implemented as a basic model for river maintenance and management.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.266-271
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• 1997

본 연구는 믹서기의 다지기칼날(Mincing Knife)이 구조적으로 가지고 있는 모멘트불평형(Couple Unbalance) 문제를 해결하기 위한 밸런싱방법을 제시한다. 유한요소법에 의하여 칼날에 작용하는 원심력, 정적 불평형량(Static Unbalance) 및 불평형각위치(Unbalance Angle)를 계산하고, 이를 바탕으로 반고리(Semiannular) 형상의 질량을 설계하여 모멘트 밸런싱을 수행하였다. 밸런싱을 수행한 후의 다지기칼날은 분해칼날(Cutting Knife)과 거의 비슷한 동적거동을 가지게 됨을 확인하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.95-100
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• 2006

Tolerance analysis method for natural frequencies of multi-body systems having a equilibrium position is suggested in this paper. To perform the tolerance analysis, the Monte-Carlo Method is conventionally employed. However, the Monte-Carlo Method has some weakness; spending too much time for analysis and having a low accuracy and hard to converge in the numerical unstable area. To resolve these problems, a tolerance analysis method is suggested in this paper. Sensitivity equations of natural frequencies are derived at the equilibrium position. By employing the sensitivity information of mass, damping and stiffness matrices, the sensitivity of natural frequencies can be calculated.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.1 s.118
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• pp.65-71
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• 2007

Tolerance analysis method for natural frequencies of multi-body systems having a equilibrium position is suggested in this paper. To perform the tolerance analysis, the Monte-Carlo Method is conventionally employed. However, the Monte-Carlo Method has some weakness; spending too much time for analysis and having a low accuracy and hard to converge in the dynamical unstable area. To resolve these problems, a tolerance analysis method is suggested in this paper. Sensitivity equations of natural frequencies are derived at the equilibrium position. By employing the sensitivity information of mass, damping and stiffness matrices, the sensitivity of natural frequencies can be calculated.