• The Journal of the Korea Contents Association
• /
• v.15 no.8
• /
• pp.556-563
• /
• 2015

The purpose of this study was to analyzed body movement of the right and left directions relative to stance width. Seven college students(male, height $174.9{\pm}4.8cm$, weight $70.9{\pm}6.6kg$) participated in this study. For the purpose of this study, nine high-speed cameras and two force plates was utilized. Stance width was limited into small stance width(mean 42.9cm) and large stance width(mean 65cm). The results showed that (1) the small stance width took shorter time than the large stance during landing of the right feet to toe-off; (2) the small stance width was took longer movement of the right feet after split step comparing to the large stance; (3)there was no significant difference in the speed of center of gravity between toe-off and maximum speed; (4) the small stance width was greater angles to hip joint and knee joint during toe-off of the right feet comparing to the large stance; (5) the was no significant difference in values for force plates between the small stance and the large stance width during toe-off of the right feet.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.35 no.9
• /
• pp.799-804
• /
• 2007

The behavior of spray emanating from an injector to be employed in a liquid-propellant thrust chamber is investigated by optical measurement techniques. The injector has eight holes, each of which has 30 cant angle from the center-axis with the diameter of 0.406 mm. In order to examine an atomization process according to the spray-generation conditions and the evolution along spray downstream, variational features in the velocity and size of droplets obtained through Dual-mode Phase Doppler An 799emometry (DPDA) are delineated and discussed together with instantaneous plane images captured by using Nd:Yag laser sheet beam. A categorization of spray-flow regime representing the atomization and turbulent nature is made through evaluating the non-dimensional parameters, i.e., Reynolds number and Weber number based upon the theoretical injection velocity. These qualitative and quantitative data of spray breakup will be a firm basis for the design of brand-new thruster

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

• Journal of the Society of Naval Architects of Korea
• /
• v.39 no.3
• /
• pp.48-56
• /
• 2002

The flow characteristics around KRISO 3600TEU container ship model have been experimentally investigated in a circulating water channel. The instantaneous velocity vectors were measured using 2-frame PIV measurement system. The mean velocity fields and turbulent statistics including turbulent kinetic energy and vorticity were obtained by ensemble-averaging 400 instantaneous velocity fields. The free stream velocity was fixed at 0.6m/s and the corresponding Reynolds number was $9{\times}10^5$. The test sections were divided into two regions, three transverse sections of the wake region(Station -0.5767, -1, -3) and five longitudinal sections of the wake((Z/(B/2)=0, 0.1, 0.2, 0.4, 0.6). In the wake region, large-scale longitudinal vortices of nearly same strength are symmetric with respect to the wake centerline and a relatively weak secondary vortex is formed near the waterline. With going downstream, the strength of longitudinal vortex is decreased and the wake region expands.

• Proceedings of the KSR Conference
• /
• 2011.05a
• /
• pp.812-817
• /
• 2011

Rolling stocks are often subjected to the effects of natural cross wind or train wind pressure due to the crossing train. These wind pressure cause the falling-off in running stability and turnover problem. It is sometimes reported that trains are blown over by a gust of wind in overseas. So, many countries enact regulations to secure the safety for wind speed. In this study, we analyzed the difference between the regulation for turnover safety of train which was enacted by Ministry of Land. Transport and Maritime Affairs and that based on the multi-body model. In case of multi-body model, it is assumed that the degrees of freedom for carbody and bogie are assigned an independent values respectively. The results show that the latter approach based on multi-body model can access the safety of turnover and replace the computational method which is accessing with lateral force, derailment coefficient and decrement of wheel load.

• Korean Journal of Applied Biomechanics
• /
• v.12 no.2
• /
• pp.159-177
• /
• 2002

The purpose of this study was to investigate the relations between the segments of the body, the three dimensional anatomical angle and the angular velocity of the air born phase and understand the control mechanism of the high-bar movement, the somersault, the double somersault, the double somersault with full twist. For this study seven well trained university gymnastic volunteered, Zatsiorky and Seluyanov(1983, 1985)'s sixteen segment system anatomical model was used for this study. For the movement analysis three dimensional cinematographical method(Arial Performance Analysis System : APAS) was used and for the calculation of the kinematic variables a self developed program was used with the LabVIEW 5.1 graphical profromming(Johnson, 1999) program. By using Eular's equations the three dimensional anatomical Cardan angles of the joint and angular velocity were defined. As a result of this study 1. As the rotation of the body increased in the air born phase the projection angle of the CM of the total increased, this resulted the increased of the max hight of the CM. 2. In three dimensional angular velocity the Z axis(vertical direction) projection angular velocity increased as the rotation of the body increased in the airborn phase, but the Y axis and the X axis projection angular velocity did not show significant differences. 3. As the rotation of the body increased in the air born phase the angular movement of the shoulder and the hip showed significant change. These movement act as the starter in the preparation phase. 4. The somersault angle, the twist angle, the tilt angle of the upper body related to the global reference frame in the releas phase the average somersault angle of the three types of high-bar movement was $57.7^{\circ}$, $38.8^{\circ}$, $39.7^{\circ}$, the average tilt angle was $-1.5^{\circ}$, $-5.4^{\circ}$, $-8.4^{\circ}$, the average twist angle was $13.4^{\circ}$, $10.6^{\circ}$, $23.3^{\circ}$. This result showed that the somersault with full twist had the largest movement.

• Korean Journal of Applied Biomechanics
• /
• v.19 no.4
• /
• pp.739-748
• /
• 2009

The purpose of this study was to compare successful and failed trials of the dean and jerk exercise performed by an 2008 Beijing Olympic gold medalist. One successful and one failed trial of an Olympic gold medalist (2008 Beijing Olympic 77 kg event) were investigated for this study. A three-dimensional motion analysis was performed, using three digital camcorders (SF: 6Hz). The events were recorded during the 89th Korean National Athletic Games. After analyzing the jerk motion, the following results were found. The successful trial revealed a shorter performance time at Phase 1 and a longer one at Phase 3 and Phase 4 as compared to the failed trial. The vertical displacement of the knee in failed trial was lower than that m the successful one. The differences in the vertical velocity of barbell and knee between the trials were seen at Phase 3 and Phase 4. A faster COM inferior velocity was seen in the successful trial at Phase 3. A more flexed knee angle was seen in the failed trial as compared to the successful trial at E3.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.25 no.1
• /
• pp.70-80
• /
• 2001

A cycloid reducer is one of the rotational velocity reduction equipments of machinery. It has advantages of the higher reduction ratio, the higher accuracy, the easier adjustment of transmission ratio and the smaller workspace than other kinds of reducer. A cycloidal plate gear is a main part of the cycloid reducer. Its tooth shape is peculiar because of gearing with the roller gear that has the several rollers on the circular line. And then it can be designed to contact all teeth to rollers. So, the cycloid reducer has the good characteristics in the dynamic properties and the zero-backlash in the contact motion. It can be used in robots, high-precision machines and high capacity machinery. This paper proposes a new approach for the shape design of the cycloidal plate gear and presents a Computer-Aided-Design program developed by the proposed method. The first part of this paper defines the two types of the cycloid reducers and explains their mechanisms. The second part defines the instant velocity centers for each type of the cycloid reducers and calculates the contact angles and the contact points by using te geometric relationships and the kinematical properties of the reducers. The third part generates the full shape of the cycloidal plate gear by the coordinate transformation technique. Finally, this paper presents two examples for the shape design of the cycloidal plate gear in order to prove the theory of the proposed method in this paper and the accuracy of the \"CycloGear Designer\".

• Journal of Advanced Marine Engineering and Technology
• /
• v.37 no.2
• /
• pp.156-162
• /
• 2013

The characteristics of the unsteady flowfield of a square prism having a detached splitter plate at the wake side were investigated by advanced vortex method. The instantaneous and average velocity field and pressure field around a square prism without and having splitter plate were calculated by forcing the gap ratio having the maximum drag reduction rate, at Reynolds number $Re=1.0{\times}10^4$ and the width ratio H/B=1.0 of splitter to the prism width. The drag and lift coefficients on the square prism were also obtained. The calculated results agree with the measured drag coefficients and pressure distributions on the square prism. The vortices of the opposite direction at upside and down side of the splitter plate were generated by installing of the plate. And the drag on the square prism was decreased by increasing of the pressure of back face of the prism with the vortices.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.31 no.8
• /
• pp.8-18
• /
• 2003

An experimental study is carried out to investigate the Reynolds number effects on the near-wake of an airfoil oscillating in pitch. An NACA 4412 airfoil is sinusoidally pitched about the quarter chord point between the angle of attack -6$^{\circ}$ and +6$^{\circ}$. A hot-wire anemometer is used to measure the turbulent intensity in the near-wake region of an NACA 4412 airfoil. The freestream velocities of present work are 3.4, 12.4, 26.2 m/s, and the corresponding Reynolds numbers are $5.3{\times}10^4,\;1.9{\times}10^5,\;4.1{\times}10^5$ and the reduced frequency is 0.1. Axial turbulent intensity profiles are presented to show the Reynolds number effects on the near-wake region behind an airfoil oscillating in pitch. All the cases in these measurements show that the turbulent intensities by the change of the Reynolds number are very large at the lowest Reynolds number $R_N=5.3{\times}10^4$; and are small at the other Reynolds number $(R_N=1.9{\times}10^5\;and\;4.1{\times}10^5)$ in the near-wake region. The significant difference of turbulent intensity between $R_N=5.3{\times}10^4,\;and\;1.9{\times}l0^5$ is observed. A critical value of the Reynolds number in the near-wake of an oscillating NACA 4412 airfoil which indicates laminar separation, no separation or turbulent separation exists in the range between $R_N=5.3{\times}10^4\;and\;1.9{\times}10^5$.