• Journal of the Korean Society of Physical Medicine
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• v.14 no.3
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• pp.63-71
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• 2019

PURPOSE: This study was examined the effects of coordinative locomotor training (CLT) on the postural imbalance and gait in children. METHODS: Four children were sampled as subjects. A single subject study (A-B-A') was conducted by measuring the following: baseline five sessions;, intervention phase, 15 sessions;, and postline (A') five sessions. The research period was eight weeks. The CLT program consisted of warming-up exercise, main exercise, and finishing exercise, and it was performed for one hour per day. A oneleg standing test (OLST) was performed determine the static balance. A functional reach test (FRT) was performed determine the reactionary balance. To determine the dynamic balance, the time up and go test (TUG) was performed. A 10m walking test (10 MWT) was performed to determine the walking ability. A statistical test was performed through descriptive statistics to present the average and standard deviation, and the variation rate was compared using a visual analysis method with graphs. RESULTS: As a result of CLT application, all four subjects improved the OLST, FRT, TUG, and 10 MWT compared to the intervention period baseline, and postline period. CONCLUSION: CLT appeared to improve the posture imbalance and gait in children.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.10
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• pp.1159-1165
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• 2011

The recording density of HDD is increasing in ratio of 100% each year. Because the increasing of recording density requires the feature of high rotation, fixation and low-noise, fluid hydrodynamic bearing(FDB) has been paid attention to overcome a limitation in ball bearing. Most of researches related to improving performance of FDB have been studied in Japan which has 80% more market share of HDD spindle motor assembly. Main subject of studies are about for the design of the groove shape, manufacturing process of fluid dynamic bearing, performance evaluation and measurement. In HDD, non-repeatable runout(NRRO) is most important parameter which determines the performance of HDD spindle system because NRRO is unpredictable that cannot be compensated in head/slider servo system. In this study, performance evaluation system can measure dynamic behaviors were designed and methodology for calculating imbalance, RRO, and NRRO were proposed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.11
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• pp.861-871
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• 2020

Raising the speed of the momentum wheel in the CMG increases the unintended force and torque caused by mass imbalance. This unintended force and torque should be minimized to get the better quality of satellite SAR image because they lead to the vibration of the output image. This paper shows the works on compensating the static imbalance and couple mass imbalance in the CMG wheel. First, the force and torque at the center of mass generated by the mass imbalance were predicted through M&S analysis. Second, the force and torque were estimated similarly through the M&S analysis when the measurement point was moved from the rotation center. Third, the measurement configuration for the force and torque by the mass imbalance was described. Fourth, the change of the force and torque by adding the specified mass to the momentum wheel was observed after comparing the measurements with the results of the M&S. And finally, the effect of the compensation was analyzed by comparing the force and torque before and after the correction while 24Nm class CMG was running in the standby mode.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.491-492
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• 2009

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.495-496
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• 2010

• Progress in Superconductivity and Cryogenics
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• v.3 no.1
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• pp.50-55
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• 2001

A new type of flywheel energy storage system that has a horizontal axle with High $T_c$, superconductor bearings using Y123 single-domained crystals was developed.The dynamic Properties, stiffness and damping of the high $T_c$, superconductor radial bearings were experimentally estimated using a imbalance excitation method. The imbalance excitation method applied to this rotor- bearing system identified the identified stiffness and damping of the high temperature superconductor beatings to be 2.8 $3.3 {\times} 10^5 N/m and 775 204$ Nsec/m respectively.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.354-357
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• 2001

The developed method is proposed to identify rotor dynamic parameters. The method known imbalance vector, which renders over-determined linear system equation. The solution of the system equation can be obtained using least square method. The sensitivity analysis is performed to extract optimized solution, which is considered to be insensitive to inherent measurement errors. As an alternative approach to identify the parameters of bearings and rotor, adding a known imbalance to the rotor produces another equation set to make the system equations over-determined and linearly independent.

• Journal of Aerospace System Engineering
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• v.2 no.1
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• pp.13-16
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• 2008

The line of sight(LOS) is affected by the vibration of spacecraft. It is necessary to predict the effect of disturbance on LOS stability. Reaction wheel assembly is anticipated to be the largest disturbance source on spacecraft. The disturbance which is occurred mainly due to the mass imbalance is analyzed with harmonic numbers. The accuracy and stability are verified by probability density function with dynamic equation of the satellite motion.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.6
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• pp.8-14
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• 2001

We develop a method to analyze dynamic behavior off multi-stage gear train system. The example system consists of three shafts supported by ball bearings at the ends of them and two pairs of spur gear set. For exact analysis, the meshing tooth pair of gear set is modeled as spring and damper having time-dependent meshing stiffness and damping. The bearing is modeled as spring. The result of this analysis is compared to that of other model having mean mesh stiffness. The effect of the excitation force by the unbalance off rotor off motor is also analyzed. Finally, the change ova natural frequency of the whole system due to the change of an angle between three shafts is compared in each case, and from this analysis, the avoiding angle for design is advised.

• Journal of Advanced Technology Convergence
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• v.2 no.3
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• pp.59-66
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• 2023

The most important thing in digital transformation is SW technology. However, many companies are having difficulty securing SW technology and manpower. In particular, it is reported that the shortage of SW manpower will increase further. The government is carrying out manpower training policies and many support projects to resolve SW manpower supply and demand policies, but accurate predictions of demand and supply of the software industry are essential for these policies to be effectively established. Therefore, this study developed a simulation using a system dynamics methodology that can perform dynamic structural analysis to resolve the supply and demand imbalance in the software industry. System dynamics is appropriate to find the cause and policy alternatives from a dynamic perspective on the imbalance in manpower supply and demand in the software industry. In detail, the U.S. Bureau of Labor Statistics (BLS) methodology was used to develop a prediction model for manpower demand and supply in the software industry, and scenario analysis was performed to derive policy implications.