• Journal of Advanced Navigation Technology
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• v.13 no.3
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• pp.412-418
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• 2009

This study aims to develop a system that enables 20 to 25 wafers to be automatically aligned at the position of the corresponding serial number and facilitates the checkout of wafer processing by sensing them before and after semiconductor processing. It also suggests compensation algorithm and stepper motor control algorithm that carefully align notches. This study minimizes the rate of occurrence by adopting materials of which the surface has proper coefficient of friction when wafers are rotating and that do not rarely produce particles. This study completed the development of a slip resistance apparatus and carried out performance tests through mathematical verification. This system is expected to improve semiconductor yield due to anti-pollution technology in semiconductor processing and can be selectively applied to a large size wafer over 450mm in the future.

• 전기의세계
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• v.13 no.4
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• pp.1-9
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• 1964

수차발전기에서 이상진동이 발생하였을 경우 일반적인 진동판별법을 서술하기로 한다. 실제로 부디치는 진동문제를 취급하여 보면 단순한 원인에 의한 것 뿐만아니라 여러가지 원인이 중첩되어 복잡한 비선형적인 현상이 나타날 경우가 많다. 원동기측 및 피동기측의 회전자급 고정자의 각각에 진동을 발생하는 다수의 요인이 있고 또 각각의 진동원인들의 상호간의 영향력이 작용하여 복잡한 진동현상을 가지고 있어서 그 원인을 판별하기가 용이한 일이 아니다. 이러한 진동원인중 주 되는 몇가지 원인을 찾아내기 위하여는 진동특성에 관한 충분한 이해와 적절한 측정장치를 선택할 필요가 있다.

• Clinics in Shoulder and Elbow
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• v.12 no.2
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• pp.180-188
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• 2009

Purpose: We evaluate the short-term clinical outcome of arthroscopic rotator cuff tendon repair with suture-bridge technique in patients with full thickness rotator cuff tear. Materials and Methods: 29 (male:17, female:12) consecutive shoulders treated with this index procedure and early rehabilitation were enrolled. Mean age was 56.4 years (range, 34~73 years) and mean follow-up period was 13 months (range, 12-15 months). Clinical outcomes were evaluated by using the University of California Los Angeles (UCLA) score, the Korean Shoulder Scoring System (KSS) and Visual Analogue Scale (VAS). Postoperative cuff integrity was evaluated through magnetic resonance imaging (MRI) and categorized by Sugaya classification. Results: Postoperative UCLA scores improved from 16.4 to 31.6 (p< 0.05) and KSS scores showed 88 at 6 months and 92 at last follow up. Preoperative VAS score was 8.6, which was decreased to 2.1 at 3 months and 1.4 at 6 months postoperatively. 28 patients (96.5%) had increase in range of motion. The follow up MRI was taken in 15 shoulders and the cuff integrity was type I in 6 cases, type II in 7, type III in 1 and type V in 1 by Sugaya classification. Conclusion: Arthroscopic suture-bridge technique resulted in good or excellent clinical outcome in 96.5% of the cases, so we think this technique is one of the reliable procedure for full-thicknes rotator cuff tear.

• The Journal of the Korea Contents Association
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• v.10 no.11
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• pp.446-451
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• 2010

To investigate the vortex induced vibrations the 2-d.o.f. spring mounted circular cylinder was tested in the wind tunnel. The circular cylinder was designed to have the translational and the rotational mode uncoupled to each other. During the wind tunnel tests the resonance behaviors of the translational and the rotational modes by the locking-on phenomena were observed. From the locking-on phenomena observed it is shown that the vortex shedding is correlated with the responses of the structures. And the forces generated by the vortex shedding are influenced by the amplitudes and the frequencies of the cylinders.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.5
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• pp.165-172
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• 2013

Convergence is increasingly prevalent in the IT world which generally refers to the combination of two or more different technologies in a single device. Especially, the spectrum scarcity is becoming a big issue because there are exponential growth of broadcasting and communication systems in the spectrum demand. Cognitive radio (CR) is a convergence technology that is envisaged to solve the problems in wireless networks resulting from the limited available spectrum and the inefficiency in the spectrum usage by exploiting the existing wireless spectrum opportunistically. However, the very process of convergence is likely to expose significant security issues due to the merging of what have been separate services and technologies and also as a result of the introduction of new technologies. The main purpose of this research is focused on devising an adaptive security framework based on carousel for CR networks as a distinct telecommunication convergence application, which are still at the stage of being developed and standardized with the lack of security concerns. The framework uses a secure credential, named as carousel, initialized with the location related information from objects position, which is used to design security mechanisms for supporting privacy and various securities based on it. The proposed adaptive security framework could be used as a security building block for the CR network standards and various convergence applications.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.5
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• pp.459-466
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• 2000

A new control method for precision robust speed control of a PMSM(Permanent Magnet Synchronous Motor) using load torque observer is presented. Using this system, we can more precisely evacuate of vestibular function. Until now a rotating chair system, so called 2D-stimulator, which has vertical rotate axis is used to make dizziness. However, an inclined rotating chair system witch is called 3D-stimulator is needed to obtain the precise dizziness data. This 3D-stimulator include unbalanced load caused by unbalanced center of mass. In this case, new compensation method is considered to obtain robust speed control using load torque observer. To reduce the effect of this disturbance, we can use dead-beat observer that has high gain. The application of the load to torque observer is published in for position control. However, there is a problem of using speed information such as amplifying effect of noise. Therefore, we can reduce a noise effect by moving average process. The experimental results are depicted in this paper to show the effect of this proposed algorithm.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.8
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• pp.573-581
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• 2022

This paper deals with the development of CanSat system, which ejects two maple seed-type autorotating science payloads and collects weather information. The CanSat consists of two autorotating science payloads and a container. The container is equipped with devices for launching science payloads and communication with the ground station, and launches science payloads one by one at different designated altitudes. The science payload consists of a space for loading and a large wing, and rotates to generate lift for slowing down the fall speed. Specifically, after being ejected, it descends at a speed of 20 m/s or less, measures the rotation rate, atmospheric pressure, and temperature, and transmits the measured value to the container at a rate of once per second. The communication system is a master-slave structure, and the science payload transmits all data to the master container, which aggregates both the received data and its own data, and transmits it to the ground station. All telemetry can be checked in real time using the ground station software developed in-house. A simulation was performed in the simulation environment, and the performance of the CanSat system that satisfies the mission requirements was confirmed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.4
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• pp.511-519
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• 2013

Switching controllers for active magnetic bearings are claimed to minimize the copper losses because they do not use bias currents. In this study, we compare the performances of the switching controller with those of the widely used proportional-derivative (PD) controller. The PD controller is combined with a synchronous notch filter to reduce the effect of the unbalance disturbance. For a fair and objective comparison, the PD controller is designed systematically. The switching controller is designed so that the dynamics of the two controllers are almost identical. A system model is developed. This model includes the flexible modes of the rotor and the dynamics of the sensors and amplifiers. The simulation results show that the switching controller indeed reduces the copper loss at lower speeds. However, it fails to operate around the speed close to the bending mode of the rotor.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.1
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• pp.261-268
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• 2013

In this paper, we propose the algorithm that improves the linearity of the walking assistant robot on lateral slopes. The walking assistant robot goes out of the course due to the rotational moment which is caused by the weight of the robot and the slope. To compensate this, we give the weight to each driving axle after comparing the real rotational angular velocity with the target rotational angular velocity which is entered by an user. The results of applying the algorithm to the real walking assistant robot show that the yaw axis deviation of the robot without the algorithm diverges, but the yaw axis deviation of the robot with the algorithm lies within 20cm, which can be recognized as stable. In addition, the changing rate of the course deviation is stabilized and shows no more course deviation, after moving 300cm.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.11
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• pp.1277-1284
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• 2015

In this paper, 1-axis tracking mechanism of solar-cell panel, which is able to rotate from -90 degree to +90 degree for maintaining always perpendicular between solar-cell panel and sun, was analyzed. This paper propose the non-linear shaped guidance and analyze mathematical formulation of non-linear shape. This analysis shows that it is able to identify the non-linear shaped guidance. Especially, even though the length of rotating link have changed, the non-linear shaped guidance could be confirm with proper size. As effectiveness of this result, 10% efficiency rising is estimated compared to the conventional 1-axis tracking mechanism and also optimal non-linear shaped guidance can be suggested for various size of solar-cell panel. Therefore the flexible mass-production is possible for various size of non-linear shaped guidance.