• The Journal of Korean Physical Therapy
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• v.28 no.1
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• pp.8-13
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• 2016

Purpose: The purpose of the present current study was to examine control of upper limb multi-joint movements with differential coordination stability. To achieve the goals of the study, torque analyses were utilized to answer questions about how torque components were differed among various elbow-wrist coordination patterns. Methods: Eight self-reported right-handed college students (3 males and 5 females, mean age=20.6 yr) were volunteered. The task required participants to rhythmically coordinate the flexion-extension motions of their elbow and wrist with coordination relationship of $0^{\circ}$, $90^{\circ}$, and $180^{\circ}$relative phases between the two joints. Mean relative phase and phase stability (standard deviation of relative phase) were computed to for analysisze of overall coordination performance. To determine the figure out characteristics of torque components in elbow and wrist joints, impulse values of muscle torque (MT) and interactive torque (IT) and MT as a percentage of cycle duration (MT-PCD) were analyzed. Results: Torque results showed that the proximal elbow joint generated motions with mainly muscle efforts regardless of coordination patterns, while the distal wrist joint adjusted the coordination patterns by changing amount of MT. Impulse analyses showed that the least stable $90^{\circ}$ pattern was performed by utilizing a similar coordination strategy of the most stable $0^{\circ}$ pattern. Conclusion: The present current study suggests that the roles of distal and proximal joints differ in order to achieve various multi-joint coordination movements. This study provides information for use in gives an idea to development of rehabilitation or training programs for to persons with an impaired upper limb motor ability.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.4
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• pp.1-11
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• 2020

In this study, study on the internal ballistic analysis method for single-chamber dual-thrust rocket motors meeting a dual-thrust profile requirement by tailoring the grain burning area is presented. The analysis method, which can acquire variables required for the performance prediction, considering gradual change of burning rate correction factor and specific impulse in the transition phase, is proposed. Improvements compared to the analysis method in the previous study, which do not consider change in the transition phase, are verified through comparison between the newly proposed method and the method in the previous study. Internal ballistic variables are obtained for four different ground firing test conditions using the proposed method, and the performance prediction for each condition is conducted using these variables. These prediction results and the ground test data are in good agreement, so it is confirmed that the performance prediction of dual-thrust motors with same design geometries based on the proposed analysis method is available.

• The Journal of the Korea Contents Association
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• v.8 no.8
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• pp.244-252
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• 2008

This research differentiate the technique of Jungkwon-jirugi, one of the basic movements of Taekwondo, into two movements stop-jirugi and push-jirugi and gives analysis of the impulse, acceleration and velocity in the point of motor control. For this, we tried graphic analysis using an acceleration sensor and high speed camera which was made from USA in 2005 and took pictures at 250 frames per second. We reached the following conclusions. First, the acceleration wave of push-jirugi was a period longer than stop-jirugi, meaning that the push-jirugi motion asserts force for a longer time. Second, the acceleration and velocity graph shows that the highest velocity occurs on the point when the acceleration begins to decrease right after reaching its maximum. Third, according to the image analysis using the high speed camera, we could find out that the shoulder is pushed a little even in the stop-jirugi motion.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.1
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• pp.17-24
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• 2011

TMED(Transmission Mounted Electric Device) parallel hybrid configuration can realize EV(Electric Vehicle) mode by disengaging the clutch between an engine and a transmission-mounted motor to improve efficiencies of low load driving and regenerative braking. In the EV mode, however, jerk can be induced since there are insufficient damping elements in the drive-train. Though the jerk gives demoralizing influence upon driving comport, adding a physical damper is not applicable due to constraints of the layout. This study suggests the jerk reduction control, composed of active damping method and torque profiling method, to suppress the jerk without hardware modification. The former method creates a virtual damper by generating absorbing torque in the opposite direction of the oscillation. The latter method reduces impulse on the mated gear teeth of the drive-train by limiting the gradient of traction torque when the direction of the torque is reversed. To validate the effectiveness of the suggested strategy, a series of vehicle tests are carried out and it is observed that the amplitude of the oscillation can be reduced by up to 83%.

• Journal of Astronomy and Space Sciences
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• v.11 no.2
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• pp.296-307
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• 1994

Using X-Window system (Motif Graphic User Interface), the AKM (Apogee Kick Motor) firing software for Koreasat which will be launched in 1995 has been developed to transfer the spacecraft from its transfer orbit, provided by the DeltaII launch vehicle, into a nearly geostationary drift orbit. The AKM firing software runs in one of two modes. In mission analysis mode, using a fixed magnitude impulsive velocity change, it provides the necessary data for planning the burn parameters. In insert mode, it uses the orbit propagator function to integrate the spacecraft state through the AKM burn. In this case, an AKM thrust profile and specific impulse are applied to the necessary data for planning the burn parameters to obtain the best possible drift orbit. The apogee burn planning simulation for orbital transfer of Koreasat has been performed using the AKM firing software. And the result of this simulation has been analyzed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.97-100
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• 2008

A hybrid sounding rocket carrying about 10kg payload reaching up to 15km altitude has been designed. The commercial seamless aluminium tube and liquid ${N_2}O$ without pressurization devices were chosen as rocket motor case and oxidizer supply system respectively. A hybrid rocket engine performing required propulsion impulse is designed with time dependent internal ballistic scheme. Engine performance, aerodynamic characteristics, and trajectory were predicted by a integral technique of internal ballistics and external ballistics. The design results were evaluated by comparison with previous experimental data, technical reports, and literatures.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.2
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• pp.8-14
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• 2008

Solid Rocket Motor(SRM) has advantages such as - high specific impulse, operational safety and simplicity in design and manufacturing process but thrust magnitude can't be controlled. For studying of pintle nozzle that can control the thrust magnitude of SRM, cold flow test and numerical analysis about needle type pintle shape were performed and results were presented in this paper. As the results of this study, pintle tip's shape and nozzle contour were important design parameters because thrust performance and variable thrust range of pintle nozzle depend on them. Especially, the thrust of needle typed pintle nozzle adopted in this test was predicted 13% higher than normal nozzle without pintle.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.1
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• pp.63-69
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• 2015

Recently, research and interests in pilotless and radio-controlled quadcopters have increased due to military, hobby, and air-photo applications. However, quadcopters are fragile and can very easily to break when they crash. Therefore, it is necessary to create a protective device such that these devices can protect the main board, motor, and propellers from outside impacts. In this paper, a protective device for a quadcopter is designed in the form of a circle to disperse shock. Also, a dropping and impact simulation was performed to verify that the quadcopter can be efficiently protected when using the proposed device, created with the commercial finite element software Solidworks.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.289-294
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• 2007

Solid Rocket Motor(SRM) has advantages such as - high specific impulse, operational safety and simplicity in design and manufacturing process, but thrust magnitude can't be controlled. For studying of pintle nozzle that can control the thrust magnitude of SRM, cold flow test and numerical analysis about needle type pintle shape were performed and results were presented in this paper. As the results of this study, pintle tip's shape and nozzle contour were important design parameters because thrust performance and variable thrust range of pintle nozzle depend on them. Especially, the thrust of needle typed pintle nozzle adopted in this test was predicted 13% higher than normal nozzle without pintle.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.3
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• pp.381-387
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• 1994

In this paper, we found the improved SPICE heat transfer modeling of impulsed magnetizing fixture system and investigated temperature characteristics using the proposed model. As the detailed thermal characteristics of magnetizing fixture can be obtained, the efficient design of the impulsed magnetizing fixture which produce desired magnet will be possible using our heat transfer modeling. The knowledge of the temperature of the magnetizing fixture is very important of forecast the characteristics of the magnetizing fixture which produce desired magnet will be possible using our heat transfer modeling. The knowledge of the temperature of the magnetizing fixture is very important to forecast the characteristics of the magnetizing circuits under different conditions. The capacitor voltage was not raised above 810[V] to protect the magnetizing fixture from excessive heating. The purpose of this work is to compute the temperature increasing for different magnetizing conditions. The method uses multi-lumped model with equivalent thermal resistance and thermal capacitance. The reliable results are obtained by using iron core fixture (stator magnet of air cleaner DC motor) coupled to a low-voltage magnetizer(charging voltage : 1000[V], capacitor : 3825[$\mu$F]. The modeling and experimental results are in close aggrement.