• Korean Journal of Applied Biomechanics
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• v.25 no.2
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• pp.199-206
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• 2015

Objective : The purpose of this study was to conduct a biomechanical analysis of a one-legged jump in a traditional Korean dance (Wae Bal Ddwigi) according to breathing method. Method : Participants for this study were 10 dancers with experience for at least 10 years in traditional Korean dance. Independent variables for this test were two different types of breathing methods. Dependent variables were ground reaction force and lower extremity kinematic variables. The jumping movement was divided into three separate stages, take off, flight, and landing. The subjects were asked a questionnaire regarding the degree of impact force and stability of landing posture after the experiment. The Kistler Force Plate (9281B, Switzerland) was used to measure ground reaction force. A digital camera was used to look into angles of each joint of the lower part of body. SPSS was used for statistical analysis via the dependent t-test(p<.05). Results : There were significant differences in jumping according to breathing method. The inhalation & exhalation method yielded significantly longer flight times combined with greater ground reaction force. The breath-holding method required more core flexion during landing, increasing movement at the hips and shoulders. Conclusion : Consequently, there was more flexion at the knee to compensate for this movement. As a result, landing time was significantly higher for breath-holding.

• Journal of the Korean Society of Physical Medicine
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• v.8 no.1
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• pp.49-58
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• 2013

PURPOSE: The purpose of this study was to determine if auditory cues velocity has a greater effect on the gait pattern of patients with Parkinson's disease (PD) than the cues applied individually. METHODS: The subjects were 15 elderly patients diagnosed with PD, 15 healthy elderly persons. Patients were measured of three conditions performed in random order: slow, general, fast. The auditory cue velocity consisted of a metronome beat ${\pm}20%$ than the subject's general gait speed. Using a motion analysis and a force platform measurement system, changes in spatiotemporal variables, kinetic and kinematic variables were compared to gait analysis. RESULTS: Comparison between the auditory cues velocity, there was a significant difference in the spatiotemporal variables with regard to the cadence, stride length, support time, step length, double support time (p<.05). Comparison between the auditory cues velocity, there was a significant increase general and fast velocity gait than slow velocity gait in the maximum flexion in swing phase of knee joint (p<.05). There appears to be the aspect of an increasing ground reaction force (GRF) on the first peak in the vertical axis (p<.05). CONCLUSION: Auditory cues velocity improved of spatio-temporal factors, kinematic and kinetic factors depending on the velocity of the faster. Therefore at the rehabilitation training of PD patients auditory cues velocity would be used for recovery and gait reeducation, may arise through the patients functional ability.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.170.2-170
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• 2001

In this paper, the dynamic system modeling and the state sensitivity analysis of the spin-coater system for the reduction of the vibration are proposed. In the respect of modeling, the spin-coater system is composed of components of servomotor, belt, spindle, and a supported base. Each component is defined and combined modeling is derived to 3dimensional equations. Verification of modeling is verified by experimental values of actual system in the frequency domain. By direct differentiation the constraint equations with respect to kinematic design variables, such as eccentricity of spindle, moment of inertia, torsional stiffness and damping of supported base, sensitivity equations are derived to the verified state equations. Sensitivity of design variables could be used for vibration reduction and natural frequency shift in the frequency domain. Finally, dominant design variables ...

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.9
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• pp.2339-2348
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• 1994

The objective of this paper is to develop a solution method for the differential-algebraic equation(DAE) derived from constrained muti-body dynamic systems. Mechanical systems are often modeled as bodies and joints. Differential equations of motion are formulated for bodies. Since the bodies are connected by joint, the differential variables must satisfy the kinematic constraint equations that come from the joints. Difficulties are arised due to drift of the differential variables off the constraint equations. An optimization method is adopted to correct the drift of the differential variables. To demonstrate the efficiency of the proposed method a slider-crank mechanism is analyzed dynamically. Identical results are obtained as these from the commercial program DADS. Dynamic analysis of a High Mobility Multi-purpose Wheeled. Vehicle(HMMWV) is carried out to show the practicalism of the proposed method.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.2
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• pp.209-217
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• 2003

In this paper, the dynamic system modeling and the state sensitivity analysis of the spin-coater system are proposed for the reduction of the vibration. In the respect of modeling, the spin-coater system is considered to be composed of servomotor, spindle, supporting base and so on. Each component of model is combined and derived to 3 dimensional equations. The combined model is verified by experimental values of actual system in the frequency domain. By direct differentiation of the constraint equations with respect to kinematic design variables, such as eccentricity of spindle, moment of inertia, rotational stiffness and damping of supported base, sensitivity equations are derived to the verified state equations. Sensitivity of design variables could be used for vibration reduction and natural frequency shift in the frequency domain. Finally, dominant design variables are selected from the sensitivity analysis.

• Korean Journal of Applied Biomechanics
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• v.12 no.2
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• pp.381-392
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• 2002

This study attempted to indentify changeability of the factorial structure of kinematic analysis in bowling. Subjects of group composed of three groups : Higher bowers who are national representative bowers with 200 average point and one pro-bowler. Middle bowlers who are three common persons with 170 average points. Lower bowler who are three common persons with 150 average points. Motion analysis on throw motion in three groups respectively has been made through three-dimension cinematography using DLT method. Two high-speed video camera at operating 180 and 60 frame per secondary. T-test factorial structure analysis has been used to define variable relations. It was concluded that : 1. The difference of x1, x2, x4, x8, x9, x11, x12, x13 where significant between two group. 2. The difference of number of spin and angle of the back-hand where statistically significant between two group(p<.001, p<.05) 3. The correlation over r=.5 between the kinematic data x1, x2, x3, x9, x10, x11. In the rotation loading matrix Factor 1 was x1, x2, x9, x10 and Factor 2 relates to x3, x11. 4. In order to obtain the factor score as follow as ; Factor 1 = (0.248)X1 + (0.265)X2 + (-0.074)X3 + (0.259)X9 + (0.259)X10 + (-0.025)X11 Factor 2=(-0.016)X1 + (-0.055)X2 + (0.84)X3 + (-0.013)X9 + (-0.007)X10 + (0.553)X11.

• Korean Journal of Applied Biomechanics
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• v.18 no.4
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• pp.67-76
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• 2008

The purpose of this study was to analyze differences in kinematic variables for mogul short turn motion between superior and inferior group, so that it can explore more effective mogul short turn motions. To meet the goals, this study selected total 10 ski players who would participate in mogul short turn event of the National Technical Ski Championship 2007, so that it could analyze kinematic variables by way of 3D motion analysis using DLT method. As a result, this study came to the following conclusions; For total and phase-specific duration, it was found that superior group took shorter time than inferior group. Superior group's Center of Mass was stands for more high value in up-down movement skill than inferior group. However right-left movement scale was less than them. In this reason, superior group was made a straight descent at the same time made a fast front-rear velocity. In the part of up-down movement velocity show that move slowly in the drop-in phase while increased in the bump-up phase. It is show that superior group was less tinny than inferior group include joint angle and knee joint angle. However leaning angle of trunk and the body inclination angle were more high figured than inferior group. Leaning angle of lower limbs also showed high figure at the center mogul. Lastly, In the part of body torsion angle show that superior group was high figure direction of right turn in the drop-in phase while in bump-up phase, made a high figure direction of left turn.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.306-311
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• 2017

This paper deals with the design optimization of the kinematic characteristics of an automotive suspension system. The kinematic characteristics of the suspension determine the attitude of the wheels, such as the toe and camber, which not only relates to tire wear during driving, but also greatly affects the control of the vehicle and its stability, which corresponds to the motion performance of the vehicle. Therefore, it is very important to determine the characteristics of the suspension mechanism at the initial stage of the design. In this study, a displacement analysis is performed to determine the kinematic properties of the suspension for the McPherson strut suspension. For this purpose, a set of constraint equations for the joints constituting the suspension mechanism was established and a program was developed to solve them. We also used ADS, a design optimization program, to obtain the desired kinematic characteristics of the suspension. As the design variables for optimization, we used the coordinates of the hard points, which are the points of attachment of the suspension to the vehicle body, and are defined as the summation of the toe-in for the up and down movement of the wheel as the objective function. As the constraint functions, the maximum camber angle and minimum roll center height, which are design requirements, are considered. As a result of this study, it was possible to determine the optimal locations of the hard points that satisfy both constraint functions and minimize the change of the toe-in.

• Korean Journal of Applied Biomechanics
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• v.27 no.3
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• pp.197-203
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• 2017

Objective: The purpose of this study was to determine how exercise intensity affects muscle activity and kinematic variables during squat. Method: Fifteen trainers with >5 years of experience were recruited. For the electromyography (EMG) measurements, four surface electrodes were attached to both sides of the lower extremity to monitor the rectus femoris (RF) and biceps femoris. Three digital camcorders were used to obtain three-dimensional kinematics of the body. Each subject performed a squat in different conditions (40% one-repetition maximum [40%1RM], 60%1RM, and 80%1RM). For each trial being analyzed, three critical instants and two phases were identified from the video recording. For each dependent variable, one-way analysis of variance with repeated measures was used to determine whether there were significant differences among the three different conditions (p<.05). When a significant difference was found, post hoc analyses were performed using the contrast procedure. Results: The results showed that the average integrated EMG values of the RF were significantly greater in 80%1RM than in 40%1RM during the extension phase. The temporal parameter was significantly longer in 80%1RM than in 40%1RM and 60%1RM during the extension phase. The joint angle of the knee was significantly greater in 80%1RM than in 40%1RM at flexion. The range of motion of the knee was significantly less in 80%1RM than in 40%1RM and 60%1RM during the flexion phase and the extension phase. The angular velocity was significantly less in 80%1RM than in 40%1RM and 60%1RM during the extension phase. Conclusion: Generally, the increase of muscle strength decreases the pace of motion based on the relation between the strength and speed of muscle. In this study, we also found that the increase of exercise intensity may contribute to the increase of the muscle activity of the RF and the running time in the extension phase during squat motion. We observed that increased exercise intensity may hinder the regulation of the range of motion and joint angle. It is suitable to perform consistent movements while controlling the proper range of motion to maximize the benefit of resistance training.

• Korean Journal of Applied Biomechanics
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• v.16 no.3
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• pp.1-7
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• 2006

The Primary type of swinging motion in human movement is that which is characteristic of a pendulum. The two types of pendulums are identified as simple and compound. A simple pendulum consist of a small body suspended by a relatively long cord. Its total mass is contained within the bob. The cord is not considered to have mass. A compound pendulum, on the other hand, is any pendulum such as the human body swinging by hands from a horizontal bar. Therefore a compound pendulum depicts important motions that are harmonic, periodic, and oscillatory. In this paper one discusses and compares two algorithms of Newton's method(F = m a) and Euler's method (M = $I{\times}{\alpha}$) in compound pendulum. Through exercise model such as human body with weight(m = 50 kg), body length(L = 1.5m), and center of gravity ($L_c$ = 0.4119L) from proximal end swinging by hands from a horizontal bar, one finds kinematic variables(angle displacement / velocity / acceleration), and simulates kinematic variables by changing body lengths and body mass. BSP by Clauser et al.(1969) & Chandler et al.(1975) is used to find moment of inertia of the compound pendulum. The radius of gyration about center of gravity (CoG) is $k_c\;=\;K_c{\times}L$ (단, k= radius of gyration, K= radius of gyration /segment length), and then moment of inertia about center of gravity(CoG) becomes $I_c\;=\;m\;k_c^2$. Finally, moment of inertia about Z-axis by parallel theorem becomes $I_o\;=\;I_c\;+\;m\;k^2$. The two-order ordinary differential equations of models are solved by ND function of numeric analysis method in Mathematica5.1. The results are as follows; First, The complexity of Newton's method is much more complex than that of Euler's method Second, one could be find kinematic variables according to changing body lengths(L = 1.3 / 1.7 m) and periods are increased by body length increment(L = 1.3 / 1.5 / 1.7 m). Third, one could be find that periods are not changing by means of changing mass(m = 50 / 55 / 60 kg). Conclusively, one is intended to meditate the possibility of applying a compound pendulum to sports(balling, golf, gymnastics and so on) necessary swinging motions. Further improvements to the study could be to apply Euler's method to real motions and one would be able to develop the simulator.