• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.7
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• pp.548-554
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• 2003

This study alms to investigate the dynamic properties of express buses in the very low frequencies which cause motion sickness Incidence. Since passengers often use express buses for long distance traveling. it is a critical point whether the ride give rise to motion sickness or not. In the study accelerations at the three Points on the floor of the six test vehicles were measured during the driving at constant speeds. By applying the frequency weighting corves suggested in ISO 26.31-1, the Physical quantity of accelerations were changed into the perceptual amount used to judge quantitatively the incidence of motion sickness. Motion sickness dose values were calculated from the frequency weighted time history of acceleration signals, and compared between the vehicles, driving conditions. and the seat positions in the bus. During the 50 minutes' driving on the public road and high ways. the vomiting incidence ratios were seen to range from 0.4 to 0.8 ％. which is equivalent to 2.4 to 4.8 ％ for 5 hours' driving. Unlike the very smooth road conditions considered in this work, motion sickness dose values encountered in real situations are expected to increase.

• Korean Journal of Applied Biomechanics
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• v.13 no.3
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• pp.217-229
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• 2003

The purpose of this study was to present the basic data on improving the skills for 3 junior high school national badminton players in clear and drop motion through the 3-dimensional image analysis. Therefore, the results of this study are as follows: 1. In the duration times per phase, subject C relatively showed a similar time between clear and drop motion. Accordingly, C took a more effective motion than A and B. 2. In the velocities of racket head, subject A and C showed similar changes relatively. However, in case of subject B, the velocity was decreased before back swing(E2) and increased until impact(E3). 3. Regardless of clear and drop motion, the changing phases of joint angle for wrist and elbow showed similar changes comparatively. 4. In the angles of upper body, clear motion was average 85.0 degree and drop one was average 80.7 degree during the impact(E3). Hence, it showed that drop motion hit the ball bowing the upper body more than clear one. 5. In the angles of racket head, clear motion was average 87.7 degree and drop one was average 85.6 degree during the impact(E3). Consequently, drop motion was impacted forward more than clear one.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2002.05a
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• pp.190-194
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• 2002

Human uses sight, tactile sense to evaluate Total Hand Value(FUUAI) of textile fabrics. Tactile sense is important factor which decided the Total Hand Value of a textile fabric. When human feels the FUUAI, physical and physiological phenomena are occurred in finger. We first found out physical variable that is happened in fingertip when human is feeling the FUUAI. Such physical variable means characteristic of action tactual motion of finger such as moving range, tactile time, moved distance, speed of finger and applied force by finger. We study the relationship between action tactual motion and the ability in which the human distinguishes the textile fabric. As a result, we could know the characteristics of the tactual motion of fingertip to get high distinguishable ability. The characteristics were different in men and women respectively. In the case of man, touched time and moving range influenced to distinguish, and moving range, and the moving speed of finger influenced, in woman's case.

• Korean Journal of Applied Biomechanics
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• v.18 no.4
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• pp.99-107
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• 2008

The aim of this study was to provide fundamental data in training to improve athletes' competitiveness through the comparative analysis of kinematic variables according to the types of stance. For this study, the subjects selected 4 Junior Weight lifters. Subjects performed two type(8-type and 11-type) Dead-lift and their performance was sampled at 60frame/sec. using four high-speed digital video cameras. After digitizing images from four cameras, the two-dimensional coordinates were used to produce three-dimensional coordinates of the 15 body segments(20 joint makers and 2 bar makers). And the results were as follows. 1. As for the time required for stances, 8-type motion was faster than 11-type motion. 2. As for the body-center shift in stances, 8-type motion was bigger than 11-type motion in back and forth motion shift, and 11-type motion was bigger than 8-type motion in right and left, up and down motion shift. 3. As for the speed of a body-center and a babel, 8-type motion was faster than 11-type motion. 4. As for the motion-trace of a babel in stances, 8-type motion was bigger than 11-type in back and forth, right and left motion and 11-type motion was bigger than 8-type in up and down motion. 5. As for the body-angles in stances, 8-type motion was bigger than 11-type in the stance angle, and 11-type motion is bigger than 8-type in the angles of a coxa, a knee and an ankle. As a result of the comparative analysis between 8-type and 11-type stance of Junior Weight lifters dead-lift, both were generally similar in variables, but 8-type motion was more stable than 11-type in aspects of time, speed, center shift, angle change.

• Korean Journal of Applied Biomechanics
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• v.29 no.2
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• pp.121-128
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• 2019

Objective: The aim of this study was to examine the relation between swing phase and airborne phase of Tkatchev motion which was successfully performed with following motion by excellent middle and high school athletes in horizontal bar. Method: The subjects for this study were 8 male middle and high school top athletes. After their Tkatchev motions were filmed by two digital highspeed camcorders setting in 90 frames/sec at the 44th National Gymnastics against Cities and Provinces, the % lapse time lapse time of each instant, inferred maximum force acting on horizontal bar, and other kinematical variables were calculated through DLT method. After the relations among the % lapse times of each instants of downswing-start, downswing-finish, whipswing-finish, release, peak-height, and lapse time of regrasp, the relation among maximum force acting on bar, % lapse time, peak height, and the relation between % lapse time and release height were examined, the biomechanical timing characteristics of Tkatchev motion were as follows. Results: Firstly, it was revealed that the whole lapse time was $1.62{\pm}.06s$ and the correlation between the % lapse time of downswing-start and % lapse time of release was .819. Secondly, it was revealed that the pattern of COG path was shifted forwardly and tilted 11 clockwise from origin. Thirdly, it was revealed that maximum force acting on bar was inferred in $2,283{\pm}425N$ ($4.7{\pm}.6BW$) and the correlation between maximum force and peak height was r = .893. Lastly, it was revealed that the horizontal and vertical component of body COG velocity was $-2.14{\pm}.29m/s$, $2.70{\pm}.43m/s$ respectively, release height was $.49{\pm}.12m$, and shoulder angle was $139{\pm}5deg$, and that the later the % lapse time of release, the higher the release height (r = .935). Conclusion: It is desired that the gymnastic athletes should delay the downswing-start near the horizontal plane on $2^{nd}$ quadrant because the later the % lapse time of downswing, the higher the release height. After all the higher release height could ensure the athletes to regrasp the bar safely, the athletes should exercise to make downswing-start delay.

• Journal of the Korean Society of Safety
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• v.17 no.2
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• pp.58-62
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• 2002

Longitudinal wave tests with finite elastic medium were performed to investigate the difference between measured values and theoretical values of propagation velocity and elasticity modulus. Each accelerometer was attached on finite elastic medium with same phase and different positions to check the particle motion. The results show that measured values of elasticity moduli from both time domain and frequency domain were similiar to theoretical value. Polarity of signal depends entirely on the phase of accelerometer. It proved that the propagation velocity and the particle motion are in the same direction when a compressive stress is applied. And also the propagation velocity and the particle motion depend on the intensity of the stress and material properties respectively.

• Earthquakes and Structures
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• v.8 no.1
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• pp.185-204
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• 2015

This study investigates the impact of the earthquake incident angle on the structural demand and the influence of ground motion selection and scaling methods on seismic directionality effects. The structural demand produced by Non-Linear Time-History Analyses (NLTHA) varies with the seismic input incidence angle. The seismic directionality effects are evaluated by subjecting four three-dimensional reinforced concrete structures to different scaled and un-scaled records oriented along nine incidence angles, whose values range between 0 and 180 degrees, with an increment of 22.5 degrees. The results show that NLTHAs performed applying the ground motion records along the principal axes underestimate the structural demand prediction, especially when plan-irregular structures are analyzed. The ground motion records generate the highest demand when applied along the lowest strength structural direction and a high energy content of the records increases the structural demand corresponding to this direction. The seismic directionality impact on structural demand is particularly important for irregular buildings subjected to un-scaled accelerograms. However, the orientation effects are much lower if spectrum-compatible combinations of scaled records are used. In both cases, irregular structures should be analyzed first with pushover analyses in order to identify the weaker structural directions and then with NLTHAs for different incidence angles.

• Journal of Electrical Engineering and Technology
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• v.7 no.6
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• pp.926-931
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• 2012

Since robot industry growing, the machine that could move with multi-DOF has been studied in many industrial fields. Spherical motor is one of the multi-DOF machine that doesn't need gear for multi-DOF motion. Unlike conventional motor, spherical motor can not only rotate on the shaft axis (rotating motion), but tilt the shaft with 2-DOF motion (positioning motion). In the typical type of spherical motor, one coil took part in positioning motion and rotating motion at the same time. As the result, the control algorithm was complex. To solve this problem, this study proposed a novel type of coil on the stator. The coils were separated for positioning motion and rotating motion. Thus the linkage flux of rotating coil didn't be affected the positioning angle. In this paper, comparing the back-EMF of typical and novel type was conducted and the driving experiment was carried out as the positioning angle. From the experiment result, the performance of proposed spherical motor could be verified.

• IEMEK Journal of Embedded Systems and Applications
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• v.13 no.6
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• pp.297-303
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• 2018

Recently, the tasks assigned to surface ship are becoming diverse and important. In this trend, shipboard directional pedestals are widely used for surveillance and electronic warfare because ships are always under angular motion such as rolling, pitching and yawing. To estimate the performance of pedestal, the motion responses of vessel as well as mechanical characteristics of pedestal should be considered. In this study, both the motion responses of vessel which the pedestal will be mounted and the behavior of 3-axis pedestal are considered. Numerical analysis based on potential theory is used to obtained motion characteristics of vessel and then 6-DOF motions of vessel are simulated under operational condition. 1st-order time delay model and LQR control algorithm are used for modeling of pedestal drive model and control model, respectively. By using coordinate transform, the angular motions which the pedestal should compensate are calculated from the vessel's angular motion. Through these M&S methodologies, time history of pedestal behavior and maximum angular error of each pedestal axis are obtained. Overall M&S results show that 3-axis pedestal compensate the angular motion induced by vessel, efficiently.

• The Korean Journal of Applied Statistics
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• v.11 no.2
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• pp.317-333
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• 1998

In this study, I employed the autoregressive model and the geometric Brownian motion model to analyze the recent stock prices of Korea. For all 7 series of stock prices(or index) the geometric Brownian motion model gives better predicted values compared with the autoregressive model when we use smaller number of observations.