• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.6
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• pp.537-545
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• 2010

This study presents a method to evaluate overturning safety and derailment safety of korean tilting train using kinematic analysis of four-bar linkage tilting mechanism. The safety is evaluated considering tilting vehicle body CG displacement. The design sensitivity for stable and safe maximum speed is evaluated around current korean tilting train design data. The current design shows minimum center of gravity displacement. Higher speed can be achieved with larger center of gravity displacement.

• Journal of Korea Foundry Society
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• v.32 no.5
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• pp.231-240
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• 2012

In present study, the effect of heat treatment on the microstructure and mechanical properties of the gravity cast superchargers housing using A356 alloy were investigated. In order to identify the characteristics of superchagers housing casting with heat treatment, Vickers hardness test, electrical conductivity test, opical and scanning electron microscopy were performed. And also, to investigate their mechanical properties, the T6 treated superchagers housing casting in optimum heat treatment condition were carried out tensile test using UTM (Universal Testing Machine).

• Journal of Ocean Engineering and Technology
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• v.16 no.3
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• pp.34-39
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• 2002

본 논문에서는 수면파(Surface wave)와 수중파 (Internal wave)간의 동적 상관관계에 관하여 수행된 연구결과를 정리하였다. 표면파의 비선형 문제는 파의 경사매개변수를 2차원으로 가정하여 해석하였으며, Cauchy 문제는 불균일 조류상의 균일 수면중력파에 대하여 해석하였다. 또한, 파의 경사, 주기의 범위(Frequency range) 그리고 자유표면하의 조류의 분포들간의 조화에 대한 연구가 수행되었으며 해류 및 이동파와 연계되어 수중파의 최전 후방에 형성될 수 있는 정적 파형 (Steady wave pattern)이 수면파형에 포함되었다.

• 한국데이터정보과학회:학술대회논문집
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• 2004.04a
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• pp.51-60
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• 2004

K-means clustering is an iterative algorithm in which items are moved among sets of clusters until the desired set is reached. K-means clustering has been widely used in many applications, such as market research, pattern analysis or recognition, image processing, etc. It can identify dense and sparse regions among data attributes or object attributes. But k-means algorithm requires many hours to get k clusters that we want, because it is more primitive, explorative. In this paper we propose a new method of k-means clustering using a center of gravity for grid-based sample. It is more fast than any traditional clustering method and maintains its accuracy.

• Proceedings of the Korean Society of Computer Information Conference
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• 2014.01a
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• pp.303-304
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• 2014

본 논문에서는 연속적인 이미지 정보를 이용하여 스노보더의 무게 중심을 분석하는 시각화 도구를 설계한다. 스노보드는 무게중심 운동으로 최대한 자세 긴장도를 낮추는 것이 중요하다. 자세긴장도에 영향을 미치는 요소 중에 가장 중요한 것이 기저면과 무게중심인데 본 연구에서는 자세에 따른 무게 중심의 이동과 안정성을 추적하여 비교분석하기 위한 도구를 설계한다. 본 연구결과는 향후 스노보드 시각화 도구의 기초자료로 활용될 수 있을 것이다.

• Journal of Biosystems Engineering
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• v.42 no.3
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• pp.127-135
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• 2017

Purpose: Purpose: The usability of a mathematical model modified for analysis of the static stability of an asymmetric tractor-harvester system was investigated. Method: The modified asynchronous mathematical model was validated through empirical experiments, and the effects of movements of the center of gravity (CG) coordinates on the stability against lateral overturning were analyzed through simulations. Results: Changes in the lateral overturning angle of the system were investigated when the coordinates of the CG of the system were moved within the variable range. The errors between simulation results and empirical experiments were compared, and the results were -4.7% at the left side overturning and -0.1% at the right side overturning. The asymmetric system was characterized in such a way that the right side overturning had an increase in overturning angle in the (+) variable range, while it had a decrease in overturning angle in the (-) variable range. In addition, the left side overturning showed an opposite result to that of the right side. At the declination angle (296<${\gamma}$<76), the right side overturning had an increase in the maximum overturning angle of 3.6%, in the minimum overturning angle of 20.3%, and in the mean overturning angle of 15.9%. Furthermore, at the declination angle (284<${\gamma}$<64), the left side overturning had a decrease in the maximum overturning angle of 29.2%, in the minimum overturning angle of 44%, and in a mean overturning angle of 39.7%. Conclusion: The modified mathematical model was useful for predicting the overturning angle of the asymmetric tractor-harvester system, and verified that a movement of the CG coordinates had a critical effect on its stability. In particular, the left side overturning was the most vulnerable to stability, regardless of the direction of declination angle.

• The Bulletin of The Korean Astronomical Society
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• v.30 no.2
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• pp.42.1-42.1
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• 2005

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.10
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• pp.941-946
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• 2013

In this paper, an enhanced method for attitude determination is proposed for systems using an IMU (Inertial Measurement Unit). In attitude determination with IMU, it is generally assumed that the IMU can be located in the center of gravity on the vehicle. If the IMU is not located in the center of gravity, the accelerometers of the IMU are disturbed from additive accelerations such as centripetal acceleration and tangential acceleration. Additive accelerations are derived from the lever arm which is the distance between the center of gravity and the position of the IMU. The performance of estimation errors can be maintained in system with a non-zero lever arm, if the lever arm is estimated to remove the additive accelerations from the accelerometer's measurements. In this paper, an estimation using Kalman filter is proposed to include the lever arm in the state variables of the state space equation. For the Kalman filter, the process model and the measurement model for attitude determination are made up by using quaternion. In order to evaluate the proposed algorithm, both of the simulations and the experiments are performed for the simplified scenario of motion.

• Korean Journal of Applied Biomechanics
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• v.13 no.3
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• pp.293-309
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• 2003

The purpose of this study was to analyze the kinematic variables of the right-straight punch(RSP) in boxing with three-dimensional analysis technical methods. The subjects are boxers who have been playing in national boxing representative team and the RSP is their special favorite technique, The right-straight punches were filmed on 16mm video cameras(30frames/sec.) The kinematic variables were temporal, postural and center of gravity(COG). The mean and the standard deviation of variables have been obtained and used as basic factors for examining characteristics of the RSP by out-boxers. From the data analysis and discussion, the following conclusions have been drawn. 1) Temporal variables It is a significant characteristic that LDJ and KDM s' the amount of elapsed time(EF) needed for both an attack and a defense were similar : ET for stretch-out of attack-arm was $0.52{\pm}0.04\;sec$. and return was $0.54{\pm}0.01\;sec$. Therefore, a defense motion is as important as an attack motion. 2) Posture variables When the subjects performed a RSP, the significant characteristic of the ankle angle was that it wasn't completely returned to the original position after stretching-out. Therefore it is necessary to do supplementary exercises, such as side steps, to move the center of gravity more effectively. The hee angle was not fully stretched either. In regard to the hip angle, it should be rotated with all strength to harmonize with the direction of movement. 3) Center of Gravity(COG) variables When both LDJ and KDM performed a RSP, a significant characteristic was the transformation of sagittal view rather than transverse or frontal views.

• Journal of International Academy of Physical Therapy Research
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• v.7 no.2
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• pp.1046-1050
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• 2016

The purpose of this study was to investigate the effects of strengthening and stretching exercises on forward head angle and static dynamic balance ability. 21 adults with the forward head posture were participated in this study. Subjects were randomly assigned to strengthening exercise group I(n=11) and stretching exercise group II (n=10) respectively. Each group were underwent six intervention over the period of 2 weeks, each session lasting 30 minutes. During a preliminary examination, forward head angle and static dynamic balance were measured, and a post examination was conducted that involved same procedure as preliminary examination. There were significant differences in forward head angle after exercise in both groups. In the strengthening group, center of gravity total sway distances was significantly changed under all conditions. In the stretching group, center of gravity total sway distances was significantly changed when subjects had their eyes open while standing on an foam surface. There were significant changes in center of gravity sway velocities in the strengthening group under all conditions, and the same was true in the stretching group only when the subjects had their eyes open while standing on an foam surface. In the comparison between groups, eyes closed while standing on a firm surface was significantly different. There was a significant difference in dynamic balance of the stretching group when the subjects tilted their bodies forward, and there was a statistically significant difference between groups under the same condition. The results of this study suggest that forward head posture can be corrected through therapeutic exercise, and muscle strengthening exercise more effective in improving static balance of forward head posture more than stretching exercise.