• Journal of Korean Orthopaedic Sports Medicine
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• v.2 no.1
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• pp.62-70
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• 2003

Purpose: We examined the kinematics and kinetics of the shoulder in youth baseball pitchers in light of the mechanisms of development of little league shoulder and humeral retrotorsion. Materials and Methods: The joint kinematics and the net force and torque acting on the humerus were calculated in fourteen youth pitchers throwing in a simulated game. Results: The major force component acting on the humerus was a tensile force of 378$\pm$81 N that peaked just after ball release. The predominant torque on the humerus was an external rotation torque about the long axis of the humerus. This torque reached a peak value of 35.3$\pm$6.7 Nm about 73$\%$through the pitching motion. This torque is approximately 66$\%$ of the torque required to fracture of the adult humerus. Conclusions: The direction of the humeral torque was consistent with the development of increased humeral retrotorsion in the throwing arm. Shear stress arising from the high torque during the late cocking phase likely leads to deformation the relatively weak proximal humeral epiphysis. The external rotation torque applied to the humerus during the pitch also agrees with the proposed mechanism for development little league shoulder, which has been hypothesized to be due to rotational stresses acting on the epiphysis during the throwing motion.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.5
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• pp.671-683
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• 2005

Statement of problem: The most commonly reported problem associated with dental implant restoration is the loosening of the screws. Purpose: This study compared the efficacy of an implant system incorporating an anti-rotational locking sleeve(Anti-Rotating Inner Post Screw System(ARIPS-system)) with other, traditional implant systems as a means of minimizing vibration loosening. Materials and methods: Three implant systems were examined; the conventional external hex type, the ARIPS-system, and the internal taper type implant system 30 specimens(10 samples per group)were fabricated and each abutment screw was secured to the implant future with 32Ncm of torque force and loosening torque was measured using a Torque Gauge. The procedure was repeated 3 times, recording initial loosening torque each time. The re-tightened abutment screw was subjected to a cyclic load having a maximum forte of 200N and minimum of 20N at 2Hz over a period of 12,600 cycles. after which the loosening torque was measured. Measured values were calaulated for statistical analysis. Analysis of measured value was performed by 3 methods: (i) as a percentage average of the initial 3 loosening-torque values(initial loosening value) to the tightening torque of 32Ncm, (ii) as a percentage of the loosening torque value after a load of 200N(experimental value) to the initial loosening value, and (iii) as a percentage of the experimental value to the 32Ncm of tightening torque. The analyses shows the amount of initial loosening at the screw, loosening by repetitive load and the the final loosening value. Results: The results of this study were as follows (1) Percentage of initial loosening value to tightening-torque was increased in order of external hex, ARIPS-system and internal taper and all values between each groups showed statistical significance (p<0.05). (2) Percentage of experimental value to initial loosening value was increased in order of external hex, ARIPS-system and internal taper. Value of internal taper showed significant difference with those of external hex and ARIPS-system (p<0.05). (3) Percentage of experimental value to tightening torque was increased in order of external hex, ARIPS-system and internal taper and all values between each groups showed statistical significance (p<0.05). Conclusion: The results of the analysis of the final loosening level value, which are closely correlated to clinical use, show that the ARIPS-system can be a useful means of minimizing abutment screw loosening when compared to the external hex type system. Although further clinical studies need to be made, the ARIPS-system should be considered to maximize the long-term success of the implant prosthesis.

• Journal of the Korean Geotechnical Society
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• v.23 no.7
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• pp.57-64
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• 2007

This study proposes a method to estimate drilling torque during ground boring with an aid of electrical energy required for rotating a boring-auger. Ground boring is commonly used in geotechnical engineering such as preboring precast pile installation, soil-cement grouting, ground exploration and so forth. In order to understand the correlation between required electrical energy to rotate the boring auger and the drilling torque, a small laboratory apparatus was designed and a pilot study was performed. The apparatus rotates common drill bits of $D=5{\sim}25mm$ in CBR specimens. The velocity of a bit is 19 RPM and predefined using a reduction gear which connects a main rotation axis to a 25 Watts AC electrical motor shaft. In the middle of drilling the motor current increments and the drilling torque were measured and the correlation between the current and the torque was obtained through linear square fits. Based on the correlation the acquired motor current during drilling was applied to predict the drilling torque in consequent testing and the prediction results were compared to the measured torque. The comparison leads a conclusion that the motor current during drilling using electrical power may be a good indicator to estimate/determine strength characteristics of the ground.

• Journal of the Korean Magnetics Society
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• v.24 no.5
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• pp.152-159
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• 2014

Magnetic gear can transmit torque without any mechanical contact among rotational parts in rotating mechanical systems. Especially, magnetic gear using rare-earth PMs can be used in variety of industry application because of their great power efficiency. Thus, recent trend shows that magnetic gear can be replaced with common mechanical gear. This paper deals with comparison and torque analysis for magnetic gears with parallel and Halbach magnetization according to various design parameters. Using a two dimensional (2D) finite element (FE) analysis, suitable gear ratio is selected. We performed analysis for magnetically connected inner and outer torque with respect to various design parameters including thickness of inner and outer PM, steel pole angle, segments of Halbach array and magnetization pattern of inner and outer PMs. Finally, we can obtain improved design model having parallel and Halbach magnetization with larger torque, compared with an initial design model.

• Journal of the Korean Institute of Intelligent Systems
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• v.27 no.2
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• pp.89-98
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• 2017

The control moment gyroscope(CMG) can be used for essential balancing control of a one-wheeled mobile robot. A single-gimbal CMG has a simple structure and can supply strong restoring torque against external disturbances. However, the CMG generates unwanted directional torque also besides the restoring torque; the unwanted directional torque causes instability in the one-wheeled robot control system that has high rotational degrees of freedom. This study proposes a control system for a one-wheeled mobile robot by using a CMG scissored pair to eliminate the unwanted directional torque. The well-known LQR control algorithm is designed for robustness against modeling error in the dynamic motion equations of a one-wheeled robot. Computer simulations for 3D nonlinear dynamic equations are carried out to verify the proposed control system with the CMG scissored pair and the LQR control algorithms.

• Korean Journal of Agricultural Science
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• v.51 no.2
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• pp.133-146
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• 2024

Selection of gear reduction ratio is essential for machine design to ensure suitable power and speed during agricultural operations. The goal of the study was to evaluate the gear reduction ratio for a 1.6 kW four-wheel-drive (4WD) multi-purpose agricultural electric vehicle platform using workload data under different off-road conditions. A data acquisition system was fabricated to collect workload (torque) of the vehicle acting on the gear shaft. Field tests were performed under three driving surfaces (asphalt, concrete, and grassland), payload operations (981, 2,942, and 4,903 N), and slope conditions (0 - 4°, 4 - 8°, and 8 - 12°), respectively. Commercial speed reduction gear phases were attached to the input shaft of the vehicle powertrain. The maximum required torque was recorded as 37.5 Nm at a 4,903 N load with 8 - 12° slope levels, and the minimum torque was 12.32 Nm at 0 - 4° slope levels with a 981 Nm load for a 4 km/h speed on asphalt, concrete, and grassland roads. Based on the operating load condition and motor torque and rotational speed (TN) curve, the minimum and maximum gear reduction ratios were chosen as 1 : 50 and 1 : 64, respectively. The selected motor satisfied power requirements by meeting all working torque criteria with the gear reduction ratios. The chosen motor with a gear reduction ratio of 1 : 50 was suitable to fit with the motor T-N curve, and produced the maximum speeds and loads needed for driving and off-road activities. The findings of the study would assist in choosing a suitable gear reduction ratio for electric vehicle multi-purpose field operations.

• Korean Journal of Applied Biomechanics
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• v.16 no.1
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• pp.81-88
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• 2006

Present study is to know the relation with throwing speed according to the uniform torque by the shoulder joint, over 20 persons of professional baseball, and were measured the uniform torque by the shoulder joint accordance with throwing speed between (A-low speed) and (B-high speed) of each group. In the present study, three components were measured, and analyzed with having an approximated output value appearing by changing angular velocity, and in $30^{\circ}/sec$, the maximum strength of muscles was measured, and in$210^{\circ}/sec$, the points of endurance strength of muscles were measured and analyzed, and the following result could be obtained. 1. In muscles strength (peak torque)of inner rotation, and outer rotation for respect to each speed of shoulder joint, though there did not appear outstanding difference between A group and B group in the $30^{\circ}/sec$, it showed that group B has priority in a little. Also in outer rotation by shoulder joint, though there appeared the same difference between A group and B group, B group is tended to be prior to A group in a little. 2 In the view of muscles strength (peak torque)of inner rotation, and outer rotation for respect to each speed of shoulder joint, though there did not appear outstanding difference between A group and B group in the $30^{\circ}/sec$, it showed that group B has priority in a little. Also in outer rotation by shoulder joint, though there appeared the same difference between A group and B group, B group is tended to be prior to A group in a little. 3. In the view of muscles strength(peak torque)of inner rotation, and outer rotation for respect to each speed of shoulder joint, though there did not appear outstanding difference between A group and B group in the $30^{\circ}/sec$, it showed that B group has priority in a little. Also in outer rotation by shoulder joint, though there appeared the same difference between A group and B group, B group is tended to be prior to A group in a little. 4. In the view of peak torque for respect to the weight accordance with each velocity of shoulder joint, there did not appear outstanding difference between A group and B group. In outer rotation by the shoulder joint, there was not appeared clear difference between A group and B group. 5. In the concern of the peak torque for respect to the weight accordance with each velocity of shoulder joint, there did not appear outstanding difference between A group and B group in $30^{\circ}/sec$. In outer rotation by the shoulder joint, there was not appeared clear difference between A group and B group. 6. In the concern of the peak torque for respect to the weight accordance with each velocity of shoulder joint, there did not appear outstanding difference between A group and B group in $210^{\circ}/sec$. In outer rotation by the shoulder joint, there was not appeared clear difference between A group and B group. As conclusion, there did not appear a correlation of uniform torque by shoulder joint versus the speed throwing by a pitcher of professional base ball.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.70.4-70.4
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• 2019

Complex organic molecules (COMs) are increasingly observed in the environs of young stellar objects (YSOs), including hot cores/corinos around high-mass/low-mass protostars and protoplanetary disks. It is widely believed that COMs are first formed in the ice mantle of dust grains and subsequently released to the gas by thermal sublimation at high temperatures (T>100 K) in strong stellar radiation fields. In this paper, we report a new mechanism that can desorb COMs from icy grain mantles at low temperatures (T<100K), which is termed rotational desorption. The rotational desorption process of COMs comprises two stages: (1) ice mantles on suprathermally rotating grains spun-up by radiative torques (RATs) are first disrupted into small fragments by centrifugal stress, and (2) COMs and water ice then evaporate rapidly from the tiny fragments (i.e., radius a <1nm) due to thermal spikes or enhanced thermal sublimation due to increased grain temperature for larger fragments (a>1 nm). We discuss the implications of rotational desorption for releasing COMs and water ice in the inner region of protostellar envelopes (hot cores and corinos), photodissociation regions, and protoplanetary disks (PPDs). In shocked regions of stellar outflows, we find that nanoparticles can be spun-up to suprathermal rotation due to supersonic drift of neutral gas, such that centrifugal force can be sufficient to directly eject some molecules from the grain surface, provided that nanoparticles are made of strong material. Finally, we find that large aggregates (a~ 1-100 micron) exposed to strong stellar radiations can be disrupted into individual icy grains via RAdiative Torque Disruption (RATD) mechanism, which is followed by rotational desorption of ice mantles and evaporation of COMs. In the RATD picture, we expect some correlation between the enhancement of COMs and the depletion of large dust grains in not very dense regions of YSOs.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.1
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• pp.53-59
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• 2009

The purpose of this study was to clarify the clinical efficiency of tungsten carbide/carbon coating on obtaining optimal preload of abutment screw compared with non-coated screw in external-hex implant system. In the present work, rotational value and the compressive force between abutment and fixture of abutment screws without coating and with coating tightened to 30Ncm were measured. Mean compressive force of coated screw was 504.6N. Then uncoated screw was tightened to clamping the abutment and the implant to 504.6N, and the tightening torque value and the rotational value was recorded. The following conclusions were drawn within the limitation of this study. Compressive force of coated screw was higher than that of uncoated screw after tightening at 30Ncm. The tightening torque that was nedeed to clamping the uncoated screw equal to coated screw tightened to 30Ncm was 55.6Ncm. In case of equal compressive force, there was no significant difference in rotation value between coated and uncoated screw.

• Journal of the Korean Society of Physical Medicine
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• v.12 no.3
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• pp.111-117
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• 2017

PURPOSE: To determine the effect of weight ball throw training as a preparatory exercise before golf practice for 8 weeks on back muscle strength, weight shifting of lower body, head speed of club, and driving distance of amateur golfers. METHODS: A total of 18 subjects were randomly assigned to the experimental group (n=9) and the control group (n=9), respectively. For the experimental group, Weight ball throw training was provided to the height of waist and shoulder similar to golf swing with the following schedule: 3 kg weight ball throw training from the first week to the 4th week; 5 kg weight ball throw training from the 5th week to the 8th week. Before and after 8 weeks of training, back muscle strength, weight shifting of lower body, head speed of club, and driving distance of subjects in the two groups were measured. RESULTS: The experimental group showed significant differences in rotational back extension torque, weight shifting of lower body, head speed of club, and driving distance during golf swing (p<.05). However, the control group only showed significant difference in driving distance during golf swing (p<.05). Back extension torque, weight shifting of lower body, and head speed of club showed significant differences between the two groups during golf swing (p<.05). CONCLUSION: Weight ball throw training can positively change rotational back muscle strength, weight shifting of lower body, head speed of club, and driving distance of amateur golfers. Therefore, it might be used as an effective warming up exercise for amateur golfers.