• Korean Journal of Applied Biomechanics
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• v.23 no.1
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• pp.19-24
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• 2013

The aim of the study was a quantitative analysis of elite athlete's $540^{\circ}$ Dwihuryeochagi and effects of ground movements to the jumping height and kicking velocity. Eleven elite players(Taekwondo demonstration team) participated in this study. In order to get the kinetic and kinematic variables, ten Vicon cameras and a force plate were used. Foot segment velocity(FSV), vertical ground reaction force(GRF), impulse, ground time(GT) in phase 1, trunk angular velocity(TAV), vertical center of gravity(COG), flight time(FT) in phase 2 and kicking leg segment velocity(KSV) in phase 3 were measured and analyzed. Results indicated that there were similar patterns of variables among phases between subjects. Non-significant correlation(r=.145) between flight time(FT) and impulse was found. Also non-significant correlation(r=.119) between center of gravity(COG) and impulse was found. In conclusions, there were similar strategies in phase 1, phase 2, and phase 3 between subjects.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.10
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• pp.1006-1013
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• 2011

In this paper, we propose an optimal posture control law for an unmanned bicycle by deriving linear bicycle model from fully nonlinear differential equations. We calculate each equilibrium point of a bicycle under any given turning radius and angular speed of rear wheel. There is only one equilibrium point when a bicycle goes straight, while there are a lot of equilibrium points in case of turning. We present an optimal equilibrium point which makes the leaning input minimum when a bicycle is turning. As human riders give rolling torque by moving center of gravity of a body, many previous studies use a movable mass to move center of gravity like humans do. Instead we propose a propeller as a new leaning input which generates rolling torque. The propeller thrust input makes bicycle model simpler and removes input magnitude constraint unlike a movable mass. The proposed controller can hold optimal equilibrium points using both steering input and leaning input. The simulation results on linear control for circular motion are demonstrated to show the validity of the proposed approach.

• Plant Journal
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• v.13 no.3
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• pp.30-35
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• 2017

Module can be categorized as PAS(Pre-Assembled Steel structure), PAR(Pre-Assembled pipe Rack), PAU(Pre-Assembled Unit), VAU(Vendor Assembled Unit) and VPU(Vendor Package Unit). At the stage of design and fabrication of module, the condition of land and ocean transportation is considered and these conditions are reflected on the module division design. The control of the module's center of gravity is important to transport and install modules safely and the steel structure should have the strength enough to resist the sea acceleration force during the ocean transportation. The transportation condition and the installation method influence the size and weight of module. The size and weight of module are considered for the design of module division.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.635-636
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• 2006

In this study, the diffusion behaviors of C and Co in liquid phase sintering of WC-Co system were investigated whether these two components diffused in the same direction in case of having opposite gradient each other with not being $\eta$ phase. The green compacts with controlled compositions in not being of $\eta$ phase and gradient composition which one is WC-5Co-1.2%C, the other is WC-XCo-0.2%C (where X = 5, 10, 15, 20, 25) were sintered at $1350^{\circ}C$ and $1400^{\circ}C$ and then the diffusion behaviors of C and Co were investigated by analyses of compositional change, also determined for microstructure and microhardness. Also, same testing was carried out on the specimens with dual layers sintered in upright and reverse positions to evaluate the effect of gravity on the diffusion in liquid Co. From the results of this study, we can find the fact that the direction of diffusion for C and Co in WC-Co system during liquid phase sintering was different and the effect of gravity for the liquid was insignificant. Also other physical properties were changed on the diffusion of elements.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.17 no.4
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• pp.70-75
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• 2009

According to the aviation statistics, tail strike incidents and accidents are cyclic. Although many tail strikes occurred during takeoff, these are less than during landing cases. Many cases are related on human factors. In my opinion it is possible to analyze the causes of takeoff tail strikes to some extent. There are major casual factors of tail strike during takeoff such as; (1) Mis-trimmed horizontal stabilizer (2) premature rotation prior to $V_R$ (3) Excessive pitch up rate during rotation (4) Improper use of the flight director. Among these causes improper use of flight director is excluded in this paper because it is recommended that pilot should use flight director after airborne. So I analyzed the other three causes as following. Firstly, because mis-trimmed stabilizer is related to center of gravity(CG), the relationship between stabilizer and CG is reviewed. Secondly, concerned premature rotation prior to $V_R$ I reviewed the background of rotation speed($V_R$) establishment and analyzed theoretically what speed leads to tail strikes. Thirdly, concerning excessive pitch up rate during rotation I analyzed what excessive pitch up rate can decrease ground clearance while using FDR data.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.5
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• pp.717-724
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• 2010

The initial trajectory of a spheroid configuration bobbin for precision guidance has been investigated by analyzing its aerodynamic load and six-degree-of-freedom motion. The effects of changes in the spheroidal head configuration, flow angle and lateral center-of-gravity offset are numerically studied using the commercial software "FLUENT". A wind tunnel test is also conducted to validate the numerical scheme and to examine effect of the Reynolds number on the flow around the bobbin. It is shown that the size of the separation bubble formed on the surface decreases significantly when the Reynolds number is varied between 110,000 and 140,000. At a zero flow angle, an oblate spheroidal head shows relatively moderate rotation while a prolate spheroidal head shows rapid rotation. The bobbin with a spherical head shape has little effect on the flow direction; however, the oblate bobbin is sensitive to the flow angle. The roll motion of the bobbin is greatly influenced by the lateral center-of-gravity offset and maximum dispersion is observed at half of the radius.

• Journal of the Korean Institute of Intelligent Systems
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• v.19 no.5
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• pp.603-608
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• 2009

In this paper, a similarity measure between interval-valued vague sets is proposed. In the interval-valued vague sets representation, the upper bound and the lower bound of a vague set are represented as intervals of interval-valued fuzzy set respectively. Proposed method combines the concept of geometric distance and the center-of-gravity point of interval-valued vague set to evaluate the degree of similarity between interval-valued vague sets. We also prove three properties of the proposed similarity measure. It provides a useful way to measure the degree of similarity between interval-valued vague sets.

• Journal of Aerospace System Engineering
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• v.9 no.3
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• pp.23-30
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• 2015

In this study, a transient structural load analysis system was constructed to calculate the applied load on the suspension equipment corresponding to the aircraft flight conditions based on military specifications. Aircraft flight data (altitude, velocity, acceleration, angle of attack and etc. at aircraft center of gravity) were used as input parameters and the calculated load of the suspension equipment at wings on the left and right side was printed out for the structural load analysis. As a calculation procedure, first of all, load analysis was carried out at the center of gravity of the external store, Secondly, a trial reaction force analysis was conducted on hook and swaybrace of suspension equipment. All procedure of calculations was programed to analyze the structural load automatically. To verify the numerical results, structural load analysis using the experimental flight data was performed.

• Archives of Craniofacial Surgery
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• v.20 no.1
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• pp.3-9
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• 2019

Facial nerve palsy has an effect on a person's well-being functionally and psychologically. Therefore, comprehensive patient management is essential. One of the most common uncomfortable and potentially debilitating features is associated with the incapacity for eye closure. Restoration of eye closure is a key consideration during the surgical management of facial palsy. In this article, we introduce simple surgical methods-which are relatively easy to learn and involve the upper and lower eyelids-for achieving eye closure. Correcting upper eyelid function involves facilitating the component of eye closure that is in the same direction as gravity and is, therefore, less complicated and favorable outcomes than correction of lower lid. Aesthetic aspects should be considered to correct the asymmetry caused by facial palsy. Lower eyelid function involves a force that opposes gravity for eye closure, which makes correction of lower eyelid ectropion more challenging than surgery for the upper eyelid, particularly in terms of effecting a sustained correction. Initially, proper ophthalmic evaluation is required, including identifying the chronicity and severity of ectropion. Also, it is important to determine whether or not lateral canthoplasty is necessary. The lateral tarsal strip procedure is commonly used for lower lid correction. However, effective lower lid correction can be achieved with better cosmesis when extensive supporting techniques are applied, including those involving cheek tissue.

• Physical Therapy Rehabilitation Science
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• v.12 no.2
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• pp.161-166
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• 2023

Objective: The purpose of the study was to investigate the effect of shoe sole deformation on the muscle activity and balance of the lower extremities when standing on one foot. Design: Crossed-control group study Methods: A total of 18 healthy adults participated in this study. 9 participants with normal shoe and 9 participants with deformed in shoe out-soles (wear shoes) were included. Muscle activity of the tibialis anterior, fibularis longus and gluteus medius during one leg standing was measured using a electromyography. A balance board was used to evaluate balance ability when standing on one leg. The balance ability when standing on one leg was measured by the sway speed and distance of the center of gravity. Results: Muscle activity of the tibialis anterior, fibularis longus and gluteus medius was no significant difference between groups (P > 0.05). Balance ability when standing on one leg was significantly different from the group wearing normal shoes in all variables related to the sway distance and sway speed of the center of gravity. Conclusions: Through this study, the wear of the outer sole of the shoe indirectly confirmed the effect on the wearer's lower extremity muscle activity and balance ability when standing on one foot. These results of this study are expected to be used as basic data for future studies on shoe wear, lower extremity muscle activity and balance ability.