• Korean Journal of Applied Biomechanics
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• v.22 no.1
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• pp.55-63
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• 2012

The purpose of this study was to investigate the balance differences between skilled players and less-skilled players during Hakdariseogi motion of Keumgang Poomsae in Taekwondo. To achieve the study goal, total of 10 Taekwondo athletes; 5 skilled players(S, body mass: $67.0{\pm}5.7$ kg, height: $174.0{\pm}4.8$ cm, age: $20.0{\pm}2.0$ yrs) and 5 less-skilled players(LS, body mass: $73.0{\pm}4.9$ kg, height: $176.4{\pm}6.1$ cm, age: $20.8{\pm}1.3$ yrs) participated in this study. A three-dimensional motion analysis with 8 infrared cameras and one force plate whose sampling frequency as 30 Hz and 300 Hz, respectively, were performed. Participants' motion were divided into three phases which were preparation phase(P1), performing phase(P2) and maintaining phase(P3). The range and velocities of COP, the range and RMS of ground reaction torque and displacement between COM and center of BOS of each phase were computed. In this study, at P1 and P3 which were double and single stance, respectively, the range and M-L velocities of COP revealed significantly higher in LS compared with those of S(p<.05). At P2 which was single stance, LS indicated significantly higher in range of COP and ground reaction torque, and M-L velocities of COP than those of S(p<.05). The significantly shorter displacement between COM and center of BOS, however, was found in LS compared with that of S(p<.05). The results from our study indicated that S revealed more stable performance and a better posture control ability during performing Hakdariseogi motion.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.8
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• pp.104-111
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• 2009

In this paper, the gear design program is presented. The profile of gears is created using classical mathematic formulations. In each gear, a kinematic joint is applied and one can define the 20 contact condition between gear pairs. Initial and boundary conditions such as force, torque, velocity, acceleration, etc. can be set. Thus, it is possible to analyze dynamic characteristics of gear pairs such as reaction moment and the variation of angular velocity. In order to find the optimal profile of gear pairs, two optimization methods based on design of experiments are inserted in the program; One is the Taguchi method and the other is the response surface analysis method. To verify the program, the rack & pinion gear is created and analyzed. Simulation results show that the developed program is useful and result data is reliable.

• Journal of Biosystems Engineering
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• v.2 no.1
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• pp.25-32
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• 1977

This experiment was conducted in order to find out the drawing performance of a two-wheel tractor under different levels of the soil moisture and hardness, so as to obtain some basic data for improving their drawing performance. With fairly homogeneous soil, 5 levels of soil moisture contents (8, 13, 17, 20 and 23%) and 3 levels of soil hardness (0 , 2 and 4kg/$cm^2$) were selected for this experiment.The summerized results are as follows ;1. The draft force, on the hard soil (hardness ; 4kg/$cm^2$), had a distinct tendency to decrease with the increasing soil moisture. On the medium soil (hardness ; 2 kg/$cm^2$), and the soft soil (hardness ; 0kg$cm^2$), the draft force showed the highest when the moisture contents were within the range of 16-19%.But the maximum draft force, on the soft soil, was higher than that on the medium soil by 10 %. 2. The driving axle torque increased with increasing soil by 10 %. 3.The values of horizontal distance between the soil reaction point and axle shaft were within the range of 0~10cm , and it had the tendency to increase with the increasing soil moisture. Also, it s value was the largest on the hard soil and the smallest on the soft soil. 4.The tractive efficiency decreased with the increasing soil moisture. On the hard soil, the average value of tractive efficiency was higher than that on the medium soil by 19.0% and that on the soft soil was lower than that on the medium soil. 5.The traction ratio were within the range of 30 ~45%, and their changing tendency with respect to the soil moisture was similar to that in the case of the draft force. 6. The travel resistance ratio tended to increased with increasing soil moisture, and the highest value was found on the soft soil, and the lowest on the hard soil.

• Korean Journal of Applied Biomechanics
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• v.15 no.4
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• pp.143-151
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• 2005

This study was conducted to investigate the technical factors of Cuervo forward straight vaults with single twist, single and half twists, and double twists actually performed by three execellent male gymnasts participated in artistic gymnastics competition of 2003 summer Universiade in Daegu and the 85th National Sports Festival in Cheongju. To accomplish the research goals the Cuervo vaults of three gymnasts were filmed by using three digital camcorders set by 60 Hz, and data were collected through the DLT method of three dimensional cinematography. The kinematic and kinetic variables as each phasic time, CM displacement velocity, release angle inclination angle hip joint angle landing angle, average horse reaction force average moment arm average torque, whoe body's total remote local angular momentum were analyzed, so the following conclusions were reached. Generally to perform the better Cuervo vault, a gymnast should touch down on the board with the great horizontal velocity of the whole body through the fast run-up, and touch down on the horse by decreasing the horizontal displacement of the whole body during the preflight, so raise CM height gradually within a short horse contact time. He should increase the horse reaction force through checking the horizontal velocity of the whole body effectively and the inclination angular displacement of the handstand, if so he can have the large vertical velocity of the whole body. By using the acquired the velocity and the angular momentum of the whole body, he can vault himself higher and twist sufficiently, then he can get better if the body could be tilted by swinging both arms and perform the cat twist with a little flexions at hip joints. According to the above outcomes we can judge that the best athletes is LuBin, the better is YTY, and the next is JSM.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.6
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• pp.1967-1974
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• 1991

When the functional electrical stimulation is employed to recover mobility to the plegic, it is very important to understand functions of the selected muscles. I have investigated how a muscle acts to accelerate the body segments, since the body segements are connected by joints so that contraction of a muscle not only rotates the segments to which it is attached but also causes other segments to rotate by creation a reaction force at every joint, which is called the inertial coupling. I found that a single-joint muscle always acts to accelerate the spanned joint in the same direction as the joint torque produced by the muscle. However, a double-joint muscle can act to accelerate the spanned joint in the opposite direction to the joint torque produced by the muscle depending on (1) the body position, (2) the body-segmental parameters, and (3) the type of the movement. Investigating the condition number of the inertia matrix of the body-segmental model gave us some insights into how controllable the body-segmental system is for different values of the factors mentioned above. The results suggested that the upright position is the most undesirable position to independently control the three segments(trunk, thigh and shank) and that the controllability is the most sensitive to variation of the shank length and the trunk mass, which implies that accuracy is required particularly when we estimate these two body-segmental parameters before the paralyzed muscles are innervated by using electrical stimulation.

• The Journal of Korean Academy of Prosthodontics
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• v.48 no.4
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• pp.308-314
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• 2010

Purpose: The purpose of this study is to analyze the change in re-osseointegration over time and bone reaction at the interface between implant fixture and the surface of the bone, after destroying re-osseointegration by distorting the bone-implant interface artificially. Materials and methods: Experimental implant fixtures (cp titanium, ${\phi}3.75\;mm{\times}4\;mm$) which didn't have surface treatment were produced. Two or three fixtures were implanted on both tibias of twelve female rabbits (New Zealand white, more than 3.5 kg). Then after six weeks, removal torque (RT) was measured and the results were recorded as the first measurement values. The fixtures were submerged again to get reosseointegration between the bone and fixture. To identify the change in re-osseointegration of submerged fixtures over time, six groups had the healing time for four days (group I), one week (group II), two weeks (group III), three weeks (group IV), four weeks (group V) and five weeks (group VI), and then the secondary removal torque was measured for each group. To identify the bone formation under fluorescent light, tetracycline (15 mg/kg, IM) were treated on the rabbits of each group. After the second measurement, the rabbits were sacrificed, and 16 slides were made, two or three for each group. The slides were observed under the fluorescent light with light microscope. To find out the change in the secondary removal torque over the primary removal torque in progress of time, the averages of the increase rate of the primary and secondary torque removal force were calculated. Then, to find out if there were any critical differences between the primary removal torque and the secondary removal torque in each group and among the groups, the results were analyzed statistically by paired t- test, one-way ANOVA, and Duncan's Multiple Range Test. Results: In group I and II, secondary removal torque decreased, especially in group I. In group III, IV, V, and VI, secondary removal torque increased critically. Comparing the differences among the groups, the critical difference was shown between group I, II and group III, IV, V, VI. Mineralization at the interface between the bone and implant fixture was identified from the first week, and bone formation was shown more clearly from the second week. Conclusion: If the implant fixture remains unforced for a certain period of time after the fixture has had iatrogenic mobility, re-osseointegration occurs at the surface of the fixture, and for tibias of rabbits, higher re-osseointegration was obtained within two weeks.

• The Journal of the Korea Contents Association
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• v.13 no.3
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• pp.109-118
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• 2013

The purpose of this study was to determine the effects of line dance programme on the balance ability during walking to reveal the exercise intervention for fall prevention. A 12-week line dance programme was applied to 18 elderly females who aged more than 65 years in the community. Balance ability during walking was evaluated by the range of center of pressure(cop), the velocity of cop, and free torque that calculated on the basis of ground reaction force data. The range and velocity of cop in the anterio-posterior were significantly reduced after performing(p<.01, p<.05, respectively), but change in those of cop in the medio-lateral and free torque were not found. It was demonstrates that 12-week line dance programme allows more effective in anterio-posterior stability of walking. It was suggested that the effect of fall prevention exercise should be studied more associate with fall frequency as future study.

• International journal of advanced smart convergence
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• v.9 no.2
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• pp.38-48
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• 2020

The shaking-off the dust from balustrade of higher stories may cause the higher risk of falling accident rate. Main purpose of this study was to quantify an effect of balustrade heights and blanket types on possibility of falling accident relative to one's motor controllability during shaking-off the dust of the blanket from balcony. Female participants, who consisted of total 10 under condition of balustrade height of 3 kinds (90 cm, 110 cm, 130 cm) and blanket types (0.4 kg, 1.6 kg, 3 kg, 200^⁎230 cm), performed repetitively the task of shaking-off the dust of the blanket. Vertical position and velocity of center of mass due to increase of blanket weigh in case of balustrade height of 90 cm was increased, but vertical ground reaction force was decreased swiftly. That is, the higher balustrade height was, the less distance difference between center of mass and center of pressure was.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.4
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• pp.38-45
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• 2017

A finite element analysis-based approach which investigates the causes of the breakdown in the outer ring of the choke at hot rod rolling mill is presented. Two-dimensional drawings of the whole vertical-type mill stand are transformed into three-dimensional CAD models. Non-linear elasto-plastic deformation analysis of material at the roll gap is performed for computing roll force and torque of the work roll. Then, the reaction forces of the bearing rings together with a set of roller bearings that support the work roll are obtained by means of rigid body motion analysis. Finally, stress behaviors in the bearing rings together with a set of roller bearings that support the work roll are investigated by linear elastic analysis. Results reveal that stress at the contact area between the outer ring and roller bearing is extraordinary high when an internal gap between an external surface of the outer ring and the internal surface of the chock due to wear of the inside of the chock occurs.

• Journal of Power System Engineering
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• v.3 no.1
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• pp.16-22
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• 1999

The purpose of this study is to prevent the stick, scuffing, scratch between piston and cylinder, is to contribute the piston design such as piston profile, clearance by calculating reaction force by over-lap of piston skirt, as measuring the temperature distributions of cylinder wall. The experiment has been peformed to obtain data during actual engine operation. Temperature gradient in peripheral and axial distributions of cylinder wall according to torque and speed of engine were measured by use of an 800cc class gasoline engine. The results obtained are summarized as follows ; 1) The temperature of cylinder wall at TDC was about $50{\sim}75^{\circ}C$ higher than temperature of cooling water. 2) The rear side temperature of top dead center was $141^{\circ}C$(1/4 load) in axial distribution, whereas the rear side of midway position temperature was $98^{\circ}C$. 3) The temperature of cylinder wall increased in according to rising temperature of cooling water. 4) The thrust side temperature of cylinder wall was about $15^{\circ}C$ in all load test. 5) The rear side temperature of top dead center was $159^{\circ}C$ (1/2 load) in peripheral distribution, it was about $39^{\circ}C$ higher than thrust side temperature.