• Korean Journal of Applied Biomechanics
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• v.21 no.4
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• pp.467-477
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• 2011

This study was performed to investigate the effects of tibial rotation while going up stair on muscle activity of vastus medialis oblique and vastus lateralis, and on patellar displacement. The subjects included 30 people (male: 15; female: 15) who were randomly assigned to the tibial internal-rotation, neutral-rotation, and external-rotation groups. The subjects went up the stair while performing the assigned rotations, and the rotation of the hip and the displacement of the patella were measured using a 3D motion analyzer. In addition, the maximum voluntary isometric contraction (MVIC) of the vastus medialis oblique and vastus lateralis were measured using surface electromyogram. On the tibial internal rotation, the hip rotation significantly appeared in the same direction and so did on the tibial neutral and external rotations(p<.001). Although the MVIC of the vastus medialis oblique and vastus lateralis did not significantly differ by tibial rotation during the stair ascent, the MVIC of the vastus medialis oblique was higher than that of the vastus lateralis during the internal and neutral rotations (p<.05). In addition, during the stair ascent, the displacement of the patella was more significant during the tibial external rotation than during the tibial internal and neutral rotations(p<.001). Thus, patients with patellofemoral pain are required to be considered the effects of tibial rotation for their rehabilitation.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.39 no.1
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• pp.60-66
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• 2002

In this paper, an efficient content-based rotation-invariant retrieval of the trademarks is proposed using the edge-direction histogram for a principal symmetry axis and the moment invariants. Rotation invariant retrieval of trademarks is difficult for the conventional retrieval systems because their feature vectors are not rotation-invariant. In this paper, to obtain rotation invariant feature vectors, in addition to invariant moments, the edge-direction histogram for a principal symmetry axis is introduced and is used to solve the bin shift problem of the histogram resulted from the rotated trademark. Performance evaluation has been carried out for a database of 300 kinds of trademarks including 20 kinds of typical trademarks which are reported to be difficult to retrieve when rotated, and the proposed scheme is proved to retrieve trademarks more efficiently, especially for the rotated trademarks, than the conventional methods.

• Korean Journal of Materials Research
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• v.27 no.6
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• pp.331-338
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• 2017

This study was carried out to investigate the optimum condition of a friction stir welding process for a joint of AA2219-T87 and AA2195-T8 dissimilar aluminum alloys. These alloys are known to have good cryogenic properties, and as such to be suitable for use in fuel tanks of space vehicles. The welding parameters include the travelling speed, rotation speed and rotation direction of the tool. The experiment was conducted under conditions in which the travelling speed of the tool was 120-300 mm/min and the rotation speed of the tool was 400-800 rpm. To investigate the effect of the rotation direction of the tool, the joining was performed by switching the positions of the two dissimilar alloys. After welding, the microstructure was observed and the micro-hardness were measured; non-destructive evaluation was carried out to perform tensile tests on defect-free specimens. The result was that the microstructure of the weld joint underwent dynamic recrystallization due to sufficient deformation and frictional heat. The travelling speed of the tool had little effect on the properties of the joint, but the properties of the joint varied with the rotation speed of the tool. The conditions for the best joining properties were 600 rpm and 180-240 mm/min when the AA2219-T8 alloy was on the retreating side(RS).

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.2
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• pp.206-214
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• 2003

Mean flow and turbulence properties of developing turbulent flows in a 90 degree square bend with spanwise rotation were measured by a hot-wire anemometer. A slanted wire is rotated into 6 orientations and the voltage outputs from them are combined to obtain the mean velocity and Reynolds stress components. The combinative effects of the centrifugal and Coriolis forces due to the curvature and the rotation of bend on the mean motion and turbulence structures are investigated experimentally. Results show that the two body forces can either enhance or counteract each other depending on the flow direction in the bend.

• Journal of Sensor Science and Technology
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• v.22 no.6
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• pp.393-399
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• 2013

We propose a method of sensing the rotation and distance of a camera by using a fisheye lens system as a vision sensor. We estimate the rotation angle of a camera with a modified correlation method by clipping similar regions to avoid symmetry problems and suppressing highlight areas. In order to eliminate the rectification process of the distorted points of a fisheye lens image, we introduce an offline process using the normalized focal length, which does not require the image sensor size. We also formulate an equation for calculating the distance of a camera movement by matching the feature points of the test image with those of the reference image.

• The korean journal of orthodontics
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• v.25 no.5 s.52
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• pp.543-555
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• 1995

In the orthopedic therapy, the biomechanical analysis of the appliance is necessary to get a desirable orthopedic effect. The purpose of this study was to investigate the desirable direction and application position of the protraction force. The protraction force of 500g was applied to the first premolar or to the first molar. The direction of force application was paralell or $20^{\circ}$ downward to the occlusal plane respectively. The stress distribution and the displacement within the maxilla was analyzed by a 3-dimensional finite element method. The findings obtained were as follows 1. Protraction forces caused a counterclockwise rotation of the maxilla. 2. The degree of maxillary rotation was less when the force was applied $20^{\circ}$ downward direction to the occlusal plane than when applied to the parallel direction. 3. The degree of rotation of maxilla was greater when the parallel force was applied to the 1st premolar than when applied to the first molar, whereas it was greater when force is applied $20^{\circ}$ downward than at the first premolar. In conclusion, the $20^{\circ}$ downward protraction from the first premolar induced the least counterclockwise rotation of the maxilla and was thought as the desirable direction and application position of the protraction force.

• The Journal of Korean Society for Radiation Therapy
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• v.29 no.2
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• pp.53-64
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• 2017

Purpose: To evaluate the usefulness of the $HexaPOD^{TM}$ evo RT system(6DoF couch) and the tendency of dose difference according to size of rotational direction error for volumetric rotational modulated radiotherapy(V-MAT) in patients with long target lengths. Therefore, it is suggested to recommend the need for rotational error correction. Materials and Methods: Ten patients with Esophagus cancer or Breast cancer including SCL treated with HexaPOD 6DoF(Six-Degree of Freedom) couch were included in this study. 6DoF couch was used to measure the difference in dose according to the rotation error in the directions of Rx(pitch), Ry(roll), and Rz(yaw). Each rotation error was applied. Positioning variation on x, y and z axis was verified and random variations were made by 6DoF couch with positioning variation. Modified DQA is conducted and point dose and gamma value are analyzed and compared. In addition, after applying the rotation error every $1^{\circ}$ to treatment plans of each target with a diameter of 3 cm, 5, 10, 15, and 20 cm respectively, gamma passing rate is being monitored by its aspect of change according to types and sizes of the target length and rotation error. Results: Mean error of the point dose and Gamma passing rate when the position variation was applied were $2.50{\pm}1.11%$ and $84.1{\pm}7.39%$ in the Rx direction, $2.36{\pm}1.16%$, and $81.0{\pm}8.49%$ in the Ry, $2.35{\pm}1.10%$ and $84.4{\pm}6.99%$ in the Rz direction, respectively. As a result of analysis on gamma passing rate according to types and sizes of the target length and rotation error, the gamma passing rate tended to decrease with increasing rotation error in the Rx and Rz directions except Ry direction. In particular, the lowest gamma passing rate (74.2 %) was in the case of $2.5^{\circ}$ rotation error in Rz direction of the target of 10 cm. Conclusion: The correction of the rotational error is needed for volumetric modulated radiotherapy of the treatment area with a long target length, and the use of 6DoF couch will improve the reproducibility of the patient position and the quality of the treatment.

• Korean Journal of Applied Biomechanics
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• v.27 no.2
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• pp.91-97
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• 2017

Objective: To investigate rotation movement of segment for performing each position and its effect on knee/hip angulation, COM inclination, and edging angle changes. Method: Twelve Alpine skiers (age: $25.8{\pm}4.8years$, height: $173.8{\pm}5.9cm$, weight: $71.4{\pm}7.4kg$, length of career: $9.9{\pm}4.6years$) participated in this study. Each skier was asked to perform counter-rotation, neutral, and rotation positions. Results: Shank and thigh were less rotated in the counter-rotation position than in other positions, whereas the trunk and pelvis were more counter-rotated (p<.05). Hip angulation, COM inclination, and edging angle were significantly greater in the counter-rotation position than in other positions (p<.05). Conclusion: Our finding proved that the counter-rotation position increases hip angulation, COM inclination, and edging angle. Consequently, we suggest that skiers should perform counter-rotation of the trunk and pelvis relative to the ski direction in the vertical axis for the counter-rotation position. Further analysis will continue to investigate the effects of the counter-rotation position in real ski slope with kinetic analysis.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.4
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• pp.77-82
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• 2013

In this paper, the design of experiment with two-way factorial design was adopted and from that, optimum values of welding variables including the welding speed and rotation speed were found to improve the strength of AZ31 magnesium alloy sheets joined by the friction stir technique. Tool with shoulder diameter of 12 mm and pin diameter of 3.5 mm was used. Also the welding direction was aligned with the material rolling direction, and dimensions of the AZ31 magnesium alloy sheets were $100{\times}100{\times}2mm$. Conditions of rotation speed were 1000, 1100 and 1200 rpm and those of welding speed were 200, 300 and 400 mm/min. As far as this work is concerned, the optimal conditions for friction stir joint were predicted as the rotation speed of 1200 rpm and welding speed of 200 mm/min.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1438-1441
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• 2005

To establish of standard technique of nano-length measurement in 2D plane, new AFM system has been designed. In this system, measurement uncertainty is dominantly affected by the Abbe error of XY scanning stage. No linear stage is perfectly straight; in other words, every scanning stage is subject to tilting, pitch and yaw motion. In this paper, an AFM system with minimum offset of XY sensing is designed. And XY scanning stage is designed to minimize rotation angle because Abbe errors occur through the multiply of offset and rotation angle. To minimize the rotation angle optimal design has performed by maximizing the stiffness ratio of motion direction to the parasitic motion direction of each stage. This paper describes the design scheme of full AFM system, especially about XY stage. Full range of fabricated XY scanner is $100um\times{100um}$. And tilting, pitch and yaw motion are measured by autocollimator to evaluate the performance of XY stage. Using this AFM system, 3um pitch specimen was measured. As a result, the uncertainty of total system has been evaluated.