• Journal of the Korean Society for Nondestructive Testing
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• v.15 no.2
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• pp.378-385
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• 1995

The ultrasonic non-destructive testing uses the directivity of the ultrasonic pulse wave which propagates in one direction. The directivity is expressed as the relationship between the propagate direction and its sound pressure. The directivity of ultrasonic wave is closely related to determination of probe arrangement, testing sensitivity, scanning pitch and defect location and characterization. The paper measured the directivity of shear wave, which reflected from artificial defect located in weld metal zone in butt welded joint similar model made of pyrex glass by using visualization method. 2 MHz and 4 MHz angle probes were used to measure the directivity of reflection wave at the artificial defect. The directivity of shear waves reflected from the defect was different according to the probe position and the shape of butt welded joint. The difference of directivity of reflection wave was existed between 2 MHz and 4 MHz angle probes. The angle of reflection wave became equal to angle of incidence as increase of the height of excess metal.

• Journal of Korean Foot and Ankle Society
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• v.9 no.2
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• pp.188-192
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• 2005

Purpose: It is to analyze the clinical utility of radiograhpic measurements for the insertional Achilles tendinitis patients who have Haglund's deformity and to evaluate the radiographic values related to Haglund's deformity in normal Korean population. Materials and Methods: We used the angle of Fowler and Philip, parallel pitch lines (PPL) and Chauveaux-Liet (CL) angle as radiographic measurements. We examined 50 cases of insertional Achilles tendinits patients and another 50 cases of normal foot as a control. Results: In normal feet, the mean value of angle of Fowler and Philip was $53.22^{\circ}$, CL angle was $-33.14^{\circ}$ and the PPL showed positive in 48%. In case of insertional Achilles tendinitis, the mean values were $55.39^{\circ}$, $-33.63^{\circ}$, positive in 56% respectively. There were not statistically significant differences (p>0.05). Conclusion: The radiographic values for Haglund's deformity between insertional Achilles tendinitis feet and the normal feet did not show significant difference. Therefore, it seems that the clinical utility of radiographic measurements for the insertional Achilles tendinitis with Haglund's deformity is not useful and the development of new diagnostic methods as MRI and ultrasonography is required.

• Journal of Korean Foot and Ankle Society
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• v.15 no.1
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• pp.1-6
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• 2011

Purpose: The purpose of this study was to compare the clinical and radiological results of single and double fusions in the transverse tarsal joint. Materials and Methods: Between December 2000 and April 2009, 16 patients (16 feet) who had been treated by fusion of transverse tarsal joint were included in this study. In 8 patients, only talonavicular joint was fused and in the other 8 patients, both talonavicular and calcaneocuboid joints were fused simultaneously. We have measured talo-first metatarsal angle, calcaneal pitch angle, talonavicular coverage angle and presence of adjacent joint arthritis for radiological assessment at both preoperative and last visit. Furthermore, we have evaluated Visual Analogue Scale (VAS), American Orthopaedic Foot and Ankle Society (AOFAS) score and patient's satisfaction. Results: In a single fusion group, VAS was improved from $6.4{\pm}1.4$ to $0.8{\pm}1.0$ (p=0.0011) and AOFAS score was improved from $63.8{\pm}6.2$ to $89.4{\pm}9.8$ (p=0.0012). In a double fusion group, VAS was improved from $8.0{\pm}0.75$ to $2.0{\pm}1.8$ (p=0.0011) and AOFAS score was improved from $60.5{\pm}11.2$ to $89.5{\pm}6.0$ (p=0.0012). In the difference of talo-first metatarsal angle between two groups, a single fused group was more improved than a double fused group (p=0.04). Conclusion: Both single and double fusions are useful and attractive treatment for the transverse tarsal joint arthritis. Furthermore, a single fusion has advantages of less invasiveness and preserving some degree of hindfoot motion and could be an effective alternative to a double fusion if patient meets appropriate criteria through careful preoperative evaluation.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.9 no.2
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• pp.137-144
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• 2015

In this paper, we present an inertial sensor-based gait analysis system to measure and analyze lower-limb movements. We developed an integral AHRS(Attitude Heading Reference System) using a combination of rate gyroscope, accelerometer and magnetometer sensor signals. Several AHRS modules mounted on segments of the patient's body provide the quaternions representing the patient segments's orientation in space. And a method is also proposed for calculating three-dimensional inter-segment joint angle which is an important bio-mechanical measure for a variety of applications related to rehabilitation. To evaluate the performance of our AHRS module, the Vicon motion capture system, which offers millimeter resolution of 3D spatial displacements and orientations, is used as a reference. The evaluation resulted in a RMSE(Root Mean Square Error) of 1.08 and 1.72 degree in yaw and pitch angle. In order to evaluate the performance of our the gait analysis system, we compared the joint angle for the hip, knee and ankle with those provided by Vicon system. The result shows that our system will provide an in-depth insight into the effectiveness, appropriate level of care, and feedback of the rehabilitation process by performing real-time limb or gait analysis during the post-stroke recovery.

• Journal of Advanced Navigation Technology
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• v.9 no.1
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• pp.28-33
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• 2005

In this paper, we developed the algorithm to control longitudinal and lateral motion of UAV(Unmanned Aerial Vehicle) with Infrared heat sensors and GPS(Global Positioning System) receiver. UAV was controlled to be flown horizontally and also turned coordinately maintaining the constant altitude. Accomplishing the flight test of UAV sevral times, we were able to develope low price controller to control bank angle for lateral motion, and also pitch angle and altitude for longitudinal motion simultaneously.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.4
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• pp.336-341
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• 2015

This paper proposes a balancing and driving control system for a Mecanum wheel ball robot which has a two axis structure and four motors. The inverted pendulum control method is adopted to maintain the balance of the ball robot while it is driving. For the balancing control, an anon-model-based controller has been designed to control the device simply without the need of a complex formula. All the gains of the controller are heuristically adjusted during the experiments. The tilt angle is measured by IMU sensors, which is used to generate the control input of the roll and pitch controller to make the tilt angle zero. For the driving control, the PID control algorithm has been adopted with angles of the wheels and the encoder data. The performance of the designed control system has been verified through the real experiments with the suggested ball robot.

• Journal of Korean Foot and Ankle Society
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• v.11 no.1
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• pp.8-12
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• 2007

Purpose: The purpose of this study was to investigate the differences in simple radiographic parameters and results of 3-D scan among normal and patient groups. Materials and Methods: Seventy subjects in each group were studied. Control group consisted of subjects without plantar foot pain (normal group), and two patient groups were one with plantar forefoot pain (metatarsalgia group), the other with plantar heel pain (heel pain group). Simple radiographic parameters were obtained and 3-D scan was done with foot scanner (Nexscan, K&I, Korea) and The height and volumn of the space under the medial longitudinal arch was analyzed (Enfoot, K&I, Korea). These parameters were compared and correlation between radiological parameters and results of the 3-D scan were studied. Results: The results of all parameters istributed normally. There was no signigicant differences among the groups in radiological parameters (talo-first metatarsal angle, calcaneal pitch angle and height of the talar head in standing lateral radiograph) and arch height and arch volumn on 3-D scan. There were statistically significant correlations between radiological and 3-D scan results. Conclusion: This study revealed that there is no significant differences in medial longitudinal arch height and volumn among normal and different patient groups and there are variety of arch height in patients with similar symptoms.

• Journal of the Korean Society for Precision Engineering
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• v.2 no.2
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• pp.69-75
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• 1985

The object of this study is to discuss the effect of cutting fluid on the mechanism of chip formation in orthogonal cutting. Rehbinder effect has been known as a phenomenon, the reduction of mechanical strength, when the metal is exposed in a polar organic environment or the surface of metal is coated with some polar organic substances. About the cause of Rehbinder effect there have been many different ideas by Rehbinder, Merchant, Shaw, Sakakida and etc. In this report, the effects of surface active medium (magic ink) upon the mechanism of chip formation on the orthogonal cutting of copper and the mechanical properties of the work material are experimentally discussed with constant rake angle. Under the condition of polar organic environment the experimental results are as follows; 1) The chip thickness becomes thinner and slip line pitch on the free surface of chip becomes smaller than that of dried cutting area. 2) The order of alternation of cutting ratio was changed. 3) The friction angle on the tool face is not affected by the depth of cut. 4) The cutting force and shear strain on the shear plane decrease remarkably, therefore the work material must be embrittled under polar organic environment.

• Journal of Ocean Engineering and Technology
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• v.30 no.3
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• pp.221-226
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• 2016

An attitude controller for a 6-DOF hovering autonomous underwater vehicle (HAUV) is implemented. We add a vertical thruster, an underwater camera, a wireless communication device, and a DVL to the HAUV that was developed a year ago. The HAUV is composed of 5 thrusters, 2 servo-motors, and 4 apparatus parts. Two rotating thrusters control the surge, heave, and roll of the vehicle. The vertical thruster controls the pitch, and two horizontal thrusters control the sway and yaw of the vehicle. The HAUV’s movement in each direction is controlled by 6 PID controllers. Each PID controller controls the propulsive force and angle of a thruster. In a horizontal and vertical movement experiment, we showed the feasibility of the proposed controller by maintaining a given depth and heading angle of the HAUV.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.10
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• pp.1395-1400
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• 2018

EO TGP(Electro-Optical Targeting Pod) is an optical tracking system which has various functions such as target tracking and image stabilization and LOS(Line of Sight) change. Especially, it is very important to move the LOS into a interest point for joystick command. When pilot move joystick in order to observe different scene, EO TGP gimbals should be operated properly. Generally, most EOTS just operate corresponding gimbal for joystick command. For example, if pilot input horizontal command in order to observe right hand screen, it just drive azimuth gimbal at any position. But in the screen, the image dosen't move in a horizontal direction because gimbal structure is Euler angle. And image rotation is occurred by elevation gimbal angle. So we need to move Pitch gimbal. So in the paper, we designed LOS moving algorithm which convert LOS command to gimbal velocity command to move LOS properly. We modeled a differential kinematic equation and then change the joystick command into velocity command of gimbals. This algorithm generate velocity command of each gimbal for same horizontal direction command. Finally, we verified performance through MATLAB/Simulink.