• Korean Journal of Applied Biomechanics
• /
• v.21 no.1
• /
• pp.39-46
• /
• 2011

The purpose of this study was to examine differences between players who bend the left elbow and those who stretch it during the forward swing from BST to BC in a 2-handed backhand stroke among outstanding high school tennis players, and to assess the detailed 3D rotational kinematic characteristics of the shoulder and the hip. Statistically significant differences were observed between groups in the longitudinal axis rotation angle of the shoulder and the angle between the shoulder and the arm at BST, and in the side to side movement of the shoulder, the up and down movement of the hip, the side tilt angular velocity of the shoulder, the side tilt angular velocity of the hip, and the front tilt angular velocity of the hip at BC. The difference in the longitudinal axis rotation angle of the shoulder between the 2 groups suggests a difference in the flexibility of the joint in the shoulder arm racquet system. The longitudinal axis rotation angular velocity of the shoulder reached its peak at 75 % of the duration of the analyzed segment and then decreased little by little until BC. This time is considered the stage for increasing the angular velocity of the upper arm, the forearm, the hand and then the racquet, which are more distal segments than the shoulder.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2002.10a
• /
• pp.1066-1069
• /
• 2002

Dynamic postural control varies with the environmental context, specific task and intentions of the subject. In this paper, dynamic postural control against forward-backward perturbations of a platform was estimated using tri-axial accelerometers and a force plate. Ten young healthy volunteers stood upright in comfortable condition on the perturbation system which was controlled by an AC servo motor. With anterior-posterior perturbations, movements of ankle, knee and hip Joints were obtained by tri-axial accelerometers. and ground reaction forces with corresponding displacements of the center of pressure(CoP) by the force plate. The result showed that the ankle moved first and the trunk forward, which implies that the mechanism of the dynamic postural control in forward-backward perturbations, occurred in the procedure of the ankle, the knee and the hip. Knee flexion and hip extension in the period of acceleration, constant velocity and deceleration phase is very important fur the balance recovery. These responses depends on the magnitude and timing of the perturbation. From the present study the accelerometry-system appears to be a promising tool for understanding kinematic accelerative In response to a transient platform perturbation. A more through understanding of balance recovery mechanism may aid in designing methods for reducing falls and the resulting injuries.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.17 no.10
• /
• pp.958-966
• /
• 2007

This study presents full vehicle dynamics model for the dynamic characteristic analysis of chassis parts which are suspension and brake system. This vehicle dynamics model is appled to kinematics and quasi-static analysis for each chassis part. In order to develop the vehicle dynamics model, the parameters of each chassis element part which are bush, spring and damper are measured by experiment. Also the wheel forces and moments of 6 DOF are measured at each wheel center. These data are applied to input parameter for vehicle dynamics model. And the verification of the developed model is achieved to comparison with the experimental force data of spring, trailing arm and assist arm by using the load response by strain gauge. These experimental force data are acquired by road test at event surfaces of P/G which are belgian and chuck holes roads.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.2 no.3
• /
• pp.143-151
• /
• 1990

The sediment transport in shallow water regions has been studied in various ways and, accordingly, many formulas have been proposed. However, when these formulas are applied practically in the field, they are not sufficient to fully estimate the sediment transport rate yet. The primary reason is how to take into account the effect of irregularities of field waves : wave heights, periods and directions. Therefore, it is necessary to investigate stochastic and kinematic characteristics of waves in three dimensional random seas in order to more accurately estimate it. In particular, the asymmetrical properties of directional spectrum become significant and play an important role in various phenomena in a shallow water region. In this study, their effects of incident waves the joint distribution of wave heights, periods and directions are investigated through field measurements.

• Journal of Biosystems Engineering
• /
• v.13 no.2
• /
• pp.1-8
• /
• 1988

A scale model of power tiller-trailer system with the same kinematic characteristics was constructed one eighth of the actual size to validate the effectiveness of mathematical model of motion. The parameters for the scale model of power tiller-trailer system were measured by a series of laboratory experiments. Validation tests for the: scale model was conducted under several ground and operating conditions. The tests were performed on artificial ground surfaces with several kind, of slope and obstacle. The travel path of the scale model was photographed successively in three directions. The travel paths obtained from both the film analysis and the simulation model appeared to be consistent with each other. It was concluded that the simulation model could be used to predict the motion of actual power tiller-trailer system if the parameters for actual power tiller and trailer are provided.

• International Journal of Aeronautical and Space Sciences
• /
• v.9 no.1
• /
• pp.66-75
• /
• 2008

In this work, we explore the feasibility of roll-pitch-yaw integrated autopilots for high angle-of-attack missiles. An investigation of the aerodynamic characteristics of a surface-to-air missile is presented, which reveals the strong effects of cross coupling between the longitudinal and lateral dynamics. Robust control techniques based on $H_{\infty}$ synthesis are employed to design roll-pitch-yaw integrated autopilots. The performance of the proposed roll-pitch-yaw integrated controller is tested in high-fidelity nonlinear five-degree-of-freedom simulations accounting for kinematic cross-coupling effects between the lateral and longitudinal channels. Against nonlinearity and cross-coupling effects of the missile dynamics, the integrated controller demonstrates superior performance when compared with the controller designed in a decoupled manner.

• Korean Journal of Applied Biomechanics
• /
• v.23 no.1
• /
• pp.1-9
• /
• 2013

The purpose of this study was to provide information on athletes' characteristics and advantages and disadvantages by analyzing the kinematic factors having a decisive influence on competitive abilities such as release conditions in the delivery phase on major Korean javelin athletes. Two supported javelin throwers of the Korean national team participated in this study. The total average time required of the delivery phase was 0.31(${\pm}0.016$). The athletes' release angle was 33.2 to 41.7 degrees. The attack angle varied widely from -3.5 to 5.9 degrees. The Javelin heights of Subject A and B were 95.9 and 89.2%Ht. The average stride length were 180.6 and 176.7cm. The center of mass velocity of LFD and REL was relatively low in all the subjects. The average deceleration rates of center of mass velocity of Subject A and B were 57.2 and 48.9%lose. The left knee angles of Subject A and B were 160.1 and 155.5 degrees in LFD, 153.0 and 164.0 degrees in REL. The joint velocity of upper limb segments was relatively low in all the subjects. The maximum average wrist velocity of Subject A and B was 18.2 and 16.3 m/s in REL.

• The Journal of Korea Robotics Society
• /
• v.6 no.3
• /
• pp.220-229
• /
• 2011

This paper focuses on a development of an anthropomorphic robot hand. Human hand is able to dexterously grasp and manipulate various objects with not accurate and sufficient, but inaccurate and scarce information of target objects. In order to realize the ability of human hand, we develop a robot hand and introduce a control scheme for stable grasping by using only kinematic information. The developed anthropomorphic robot hand, KITECH Hand, has one thumb and three fingers. Each of them has 4 DOF and a soft hemispherical finger tip for flexible opposition and rolling on object surfaces. In addition to a thumb and finger, it has a palm module composed the non-slip pad to prevent slip phenomena between the object and palm. The introduced control scheme is a quitely simple based on the principle of virtual work, which consists of transposed Jacobian, joint angular position, and velocity obtained by joint angle measurements. During interaction between the robot hand and an object, the developed robot hand shows compliant grasping motions by the back-drivable characteristics of equipped actuator modules. To validate the feasibility of the developed robot hand and introduced control scheme, collective experiments are carried out with the developed robot hand, KITECH Hand.

• Journal of Biomedical Engineering Research
• /
• v.18 no.1
• /
• pp.71-78
• /
• 1997

Kinematic and kinetic studies were performed to investigate the walking characteristics on a treadmill with various slopes at the same speed of 1.25m/sec. Six different slopes of the treadmill were selected . -4%(-$2.3^{\circ}$), 0%($0^{\circ}$), 5%($2.9^{\circ}$), 10%($5.7^{\circ}$), 15%($8.6^{\circ}$), and 20%($11.3^{\circ}$). With increased slopes of the treadmill, both hip and knee flexion angles significantly increased at initial contact, and the maximum hip flexion during swing phase and the maximum knee flexion during stance phase also significantly increased Ankle dorsiflexion angle at initial contact and the maximum dorsiflexion increased with increased slopes. However, the maximum plantarflexion in early swing was slightly reduced with increased slopes. Hip extension in late stance and the maximum knee flexion in early swing was not changed sigilificantly with increased slopes. As for the vertical ground reaction force, compared to the yond level walking, both the first and the second peak forces increased, but the mid-support force decreased.

• Journal of Astronomy and Space Sciences
• /
• v.35 no.1
• /
• pp.7-18
• /
• 2018

We have investigated the intensities and full width at half maximum (FWHM) of the high dispersion spectroscopic N III emission lines of AG Peg, observed with the Hamilton Echelle Spectrograph (HES) in three different epochs at Mt. Hamilton's Lick Observatory. The earlier theoretical Bowen line study assumed the continuum fluorescence effect, presenting a large discrepancy with the present data. Hence, we analyzed the observed N III lines assuming line fluorescence as the only suitable source: (1) The O III and N III resonance line profiles near ${\lambda}$ 374 were decomposed, using the Gaussian function, and the contributions from various O III line components were determined. (2) Based on the theoretical resonant N III intensities, the expected N III Bowen intensities were obtained to fit the observed values. Our study shows that the incoming line photon number ratio must be considered to balance at each N III Bowen line level in the ultraviolet radiation according to the observed lines in the optical zone. We also found that the average FWHM of the N III Bowen lines was about $5km{\cdot}s^{-1}$ greater than that of the O III Bowen lines, perhaps due to the inherently different kinematic characteristics of their emission zones.