• 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.

• The Journal of the Korea Contents Association
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• v.10 no.3
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• pp.373-380
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• 2010

The purpose of this study was to evaluate the effects of recreational exercise on cognition, depression, dynamic balance and leg strength in elderly women. This study was nonequivalent control group pre-post test design. Subjects were divided into two group(exercise group=14, control group=13). Experimental group conducted recreational exercise program for eight-week. Cognition was assessed by K-WAIS(object assembly & digit symbol) and depression were assessed by questionnaire. Dynamic balance(DB) and leg strength(LS) were assessed by 244cm up & go and sit to stand respectively. The collected data analyzed by Wilcoxon singed rank test and Mann-Whitney U test. The exercise group significantly improved cognition(object assembly) and DB, but control group significantly reduced DB. DB in exercise group were significantly greater than in control group after eight-week. The program was effective on cognition and dynamic balance in elderly women.

• Explosives and Blasting
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• v.37 no.1
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• pp.14-23
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• 2019

It has been an always issue for the blasting or the impact analysis to consider the strength characteristics of the rock materials associate with loading rate dependency. Due to the nature of transient loading, the dynamic rock test requires a careful technique to achieve the stress equilibrium state of the specimen. In this study, to investigate the relationship between the rock dynamic strength and the stress equilibrium state, a series of dynamic uniaxial compression tests for Pocheon granite were performed. As a result, the unbalanced stress state on the specimen can lead to the premature failure on the specimen and the less estimation of dynamic strength characteristic as well as the overestimation of strain rate. Consequently, a careful consideration of rock fracture process to achieve the dynamic force balance on the specimen should be required to make an reasonable evaluation of rock dynamic strength.

• The Journal of the Acoustical Society of Korea
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• v.10 no.4
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• pp.48-55
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• 1991

In this study, the unbalanced rigid rotor mounted on two pedestals is balanced u. ng the dynamic balancing procedure, and the compensating masses are estimated by the seven run method. Also, the reductions of vibration level are examined, before and after balancing procedures. In the experimental results, it is shown that the vibration amplitudes measured at the two pedestals are proportional to the unbalanced mass. The seven run method which requires measurement of vibration amplitudes only and not vibration phase angle is proved markedly useful in consideration of the dynamic balancing procedure.

• Journal of the Korean Chemical Society
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• v.67 no.4
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• pp.241-252
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• 2023

This study aims to increase students' understanding of equilibrium, one of the many concepts in chemistry that students find difficult. Dynamic equilibrium must be dealt with at the sub-microscopic level where the real and the representation overlap in order to microscopically understand the constant motion and interaction of particles and to understand the macroscopic characteristics expressed through this. However, as a result of analyzing 9 Chemistry I textbooks, the expression approach for equilibrium had some limitations. As a strategy to understand equilibrium at a sub-microscopic approach, the classes using scratch were consisted of a total of 4 hours, and it was implemented with 56 students. The classes were composed of 6 steps, and it was designed to understand equilibrium step by step. As a result of comparing the pretest and post- test, the number of students who got both the microscopic and macroscopic explanations of chemical equilibrium correct increased largely. Through this, it was possible to get a glimpse of the applicability of classes using scratch as the approach strategy of the sub-microscopic representation.

• 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.

• Journal of the Korean Applied Science and Technology
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• v.37 no.6
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• pp.1669-1677
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• 2020

The purpose of this study was to evaluate the effects of a 14-week proprioceptive resistance exercise on muscle endurance strength, dynamic balance and gait ability of elderly women in a social welfare facility. Thirty community dwelling elderly subjects (mean age 70.84±3.33) divided into experimental (n=15) and control (n=15) groups. The participants performed the muscle endurance strength(30sec hair stand), dynamic balance (3m up and go) and low extremity performance (10m walking, 400m walking) pre and after the training program. The exercise groups were submitted to 14 weeks proprioceptive training with a Swiss ball three times a week. As a results were as follow. Significantly improvements were observed in low extremity strength and dynamic balance. And there have significantly improvements in 10m walking, 400m walking. Conclusionly, the improvement of dynamic balance and gait ability by proprioceptive resistance training will reduce the possibility in female elderly people.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.1
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• pp.45-49
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• 2011

The aim of study intends to investigate effect of weight of fire-protective clothing for physical balance and agility after maximum physical activity and to provide the base data for the safety of firefighter. For evaluation of static and dynamic-balance, the closed-eyes foot balance and the beam-walking were performed respectively. For evaluation of static and dynamic-agility, the whole body reaction and the side-step were carried out. This study demonstrates that after maximum physical activity, the weight of fire-protective clothing effects on physical static-balance and dynamic-agility and suggests that it could be useful for actual safety field studies of firefighters.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.5 s.176
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• pp.1093-1102
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• 2000

Dynamic behaviors are analyzed for an automatic ball balancer with double races which is a device to reduce eccentricity of rotors. Equations of motion are derived by using the polar coordinate sys tem instead of the rectangular coordinate system which is used in other previous researches. To analyze the stability around equilibrium positions, the perturbation method is used. On the other hand, the time responses are computed from the nonlinear equations of motion by using a time integration method.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.1 no.1
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• pp.87-92
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• 1989

In this study, the nonlinear dynamic model of the systems which include the offshore structure, the surrounding sea water in terms of the added mass, the foundation in terms of frequency independent springs, dashpots, and the floating ice feature with its hydrodynamic added mass, are proposed for the problem of the large ice floes impact. Dynamic Analysis is performed on two site conditions, sand site and silt site, and on two seasons, winter and summer, for various ice floe velocities. As a result of study, Ice floes from energy balenced method is lower than that from dynamic modeling on sand site, and higher than the on silt site.