• Electrical & Electronic Materials
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• v.3 no.2
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• pp.90-98
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• 1990

Y-Bi-Ba-Cu-O계 초전도체를 보통의 ceramic방법과 screen printing과 소결법으로 원판형과 후막형으로 제작하였다. B $i_{2}$ $O_{3}$를 첨가하여 소결한 $Y_{1}$B $a_{2}$C $u_{3}$ $O_{7-y}$의 초전도 성질은 전기저항측정과 자석위에 부상 유무로 조사하였다. 또한 B $i_{2}$ $O_{3}$를 첨가함에 따라 소결된 시편의 미세구조에 어떠한 영향을 주었는지 알아보았다. 전기저항 측정시 Yttrium 대신에 Bi로 부분적으로 치환한 경우인 $Y_{0.85}$B $i_{0.15}$B $a_{2}$C $u_{3}$ $O_{7-y}$의 상온 저항치가 기본조성인 $Y_{1}$B $a_{2}$C $u_{3}$ $O_{7-y}$의 그것보다 향상된 미세구조로 인해 더 작은 값을 나타낸다. 반면 $Y_{1}$B $a_{2}$C $u_{3}$ $O_{7-y}$에다가 초과로 B $i_{2}$ $O_{3}$를 첨가한 경우 오히려 미세구조는 불량하고 상온저항치도 더 높다. 이러한 사실은 입계에 잔류하는 이차상은 전기적 성질에는 크게 영향을 주나 자기적 성질에는 거의 영향을 주지않는 것으로 보인다. 후막으로 Y-Bi-Ba-Cu-O를 제작시 기판에 의해 좌우되는데 단지 magnesia 기판에서 소결시 bulk시편과 유사한 성질을 나타냈다.질을 나타냈다.다.

• Journal of the Korea Convergence Society
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• v.8 no.3
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• pp.31-40
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• 2017

The rise of eco-friendly personal electric mobility is a worldwide trend and the first Korean-made IT convergence electric skateboard, Youth Board, is developed to lead the trend. Youth Board is remotely controllable using either Youth Wearable Controller or Youth App through Bluetooth v4.0 communication, can speed up to 25 km/hr, and operating time is approximately 1.5 hr. A LED display located in the front side of Youth Board deck shows three different states to a rider for user convenience: remaining battery SOC, current driving speed, and braking amount. Indoor EMC test results between Youth Board and Youth Wearable Controller and outdoor Youth Board driving test results are analyzed. In particular, driving test results show the maximum current output is about 15% lowered compared to the other competitor electric skateboard and it lessens the power burden of the motor ESC. These results show Youth Board's usefulness as a personal mobility in the sense of small, light, and inexpensive aspects.

• Journal of agricultural medicine and community health
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• v.45 no.2
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• pp.89-99
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• 2020

Objective: This study aimed to report the relationship between walking activity and perceived physical activity barriers after classifying the age group(≤64, 65-74, ≥75). Methods: The subjects were conducted on 1500 residents of two areas, and the walking activity was defined as five or more times a week, 10 minutes or more at a time, and 30 minutes or more per day. Perceived physical activity barriers were lack of time, lack of social support, lack of energy, lack of willpower, and fear of falling. Results: In the group under 64 year, the lack of time (exp(B)=0.819, p=0.002) and the lack of willpower (exp(B)=0.656, p<0.001) were significantly associated. In the 65-74 year old group, the lack of willpower (exp(B)=0.714, p<0.001) and fear of falling (exp(B)=0.787, p=0.003) were a significant association. In the group aged 75 years and over, lack ofwill power (exp(B)=0.734, p<0.001) and fear of falling (exp(B)=0.807, p=0.003) were significantly associated. Conclusion: In order to solve the lack of willpower and lack of time, a walking activity should be performed together at a certain time in the village, and the elderly in the late ages should reduce the fear of falling by performing a fall prevention exercise in parallel.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.1
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• pp.87-95
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• 2018

The high-precision magnetic levitation transport system is a transport device applying the principle of magnetic levitation. So it is preferable for manufactory process of semiconductor and display industries. In this system, the gap sensors are arranged discontinuously and turned on or off when the tray moves in the running direction. Therefore, precise gap data is important for precise control of the carrier. However, a slight error occurs in the process of installing the gap sensor. So, in this paper, we introduce the high-precision magnetic levitation transport system for OLED evaporation process. Also, we propose a strategy for stable flight control and an offset algorithm for tracking installation errors transport system. The performances of the proposed algorithm are validated through simulation.

• 한국연소학회:학술대회논문집
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• 2007.05a
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• pp.191-196
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• 2007

The enhancement of flame stability in coflow jets has been investigated experimentally by observing the liftoff behaviors of nonpremixed propane and methane flames in the electric fields. The liftoff or blowoff velocities has been measured in terms of the applied AC voltages and frequency. The experimental results showed that the liftoff velocity could be extended significantly just by applying the high voltage to the central fuel nozzle both for propane and methane. As increasing the applied voltage, the liftoff velocity increases almost linearly with the applied voltage and have its maximum value at certain applied voltage. After that, the liftoff velocity showed decrease with the applied voltage. Through the experimental observation, we found that the liftoff velocity could be correlated well with the applied voltage and frequency in the linearly increasing regime. And after having maximum in the liftoff velocity, it was observed that the liftoff velocity decreases with the applied voltage irrespective of AC frequencies. To visualize the change of flame structure with electric fields, planar laser induced fluorescence technique was adopted, and the enhancement of flame stability has been explained based on the flame structural change in electric fields.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.12
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• pp.689-697
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• 2005

In this paper, an application of a decentralized $H_{\infty}$ controller(DHC) to multiple controlled-permanent magnet(CMAG) magnetic levitation(Maglev) systems is presented. The designed DHC using two Riccati equations iteratively has simpler structure and needs less computational loads than conventional centralized $H_{\infty}$ controller. A target plant is a hybrid-type CMAG system with permanent magnet and coil, and its mathematical model is firstly derived to design the DHC. To implement the designed algorithm, a real Maglev vehicle system including digital controller, chopper, sensor, etc., is manufactured. To compare the performances of the DHC method with an observer-based state feedback control(OSFC), the input tracking and disturbance rejection characteristics are experimentally tested. As performance indices(PI), integral of squared error(ISE), integral of absolute error(IAE), integral of time multiplied by absolute error(ITAE) and integral of time multiplied by squared error(ITSE) are used. From the experimental results, it can be seen that the input tracking and disturbance rejection performances of the DHC are better than those of the conventional controller.

• Composites Research
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• v.31 no.5
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• pp.192-201
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• 2018

The use of 3D printing for rapid tooling and manufacturing has promised to produce components with complex geometries according to computer designs and it is emerging as the next generation key of manufacturing. Due to the intrinsically limited mechanical/electrical properties and functionalities of printed pure polymer parts, there is a critical need to develop 3D printable polymer composites with high performance. This article gives a review on 3D printing techniques of polymer composite materials and the properties and performance of 3D printed composite parts as well as their potential applications in the various fields.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.638-641
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• 1997

This paper describes the electrical design, characteristic and test results of both VVVF Inverter system and a auxiliary power supply system for UTM-01. As the propulsion system for SLIMs, GTO type VVVF inverter is used. IGBT 3 level inverter is adopt in Auxiliary Power Supply system. The control of two systems is fully digitalized by DSP TMS320C31. So a performance of two systems is more improved.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.616-618
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• 2008

This paper propose nonlinear electromagnet suspension system model and defines electromagnet design specification of Maglev vehicle for transport system of semiconductor manufacturing line. The bandwidth of the acceleration sensor is defined and manufactured using i-mems technique acceleration sensor from this Nonlinear electromagnet suspension model. Through the simulation of non-linear model it was possible to compare the gain with the experiment to confirm the accuracy of the nonlinear suspension system. Till now mainly linear model has been used in many electromagnet suspension system, which results different gains in simulation and experiments. This more accurate non-linear model can be applied in many ways in designing electromagnet suspension systems.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1877-1878
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• 2008

고품질, 고 신뢰도를 지향하는 미래 지능형 전력시스템에 대한 기대와 함께 전력 기기 및 설비의 디지털화에 관심이 집중되면서, 전력시장에서는 전력정보의 양방향 교환 표준을 위한 공통정보모델(CIM : Common Information Model)의 개발 및 활용이 새로운 화두로 부상하였다. CIM은 차세대 전력시스템과 미래형 부가서비스 등의 전반적인 운영측면에서 혁신을 이루는데 사용할 수 있도록 표준화된 데이터교환 모델이다. 이는 전력시스템 내 모든 다양한 객체(변전소, 송전선, 변압기, 차단기, 설비자산, 작업지시, 작업원 등)들이 어떻게 상호 연결되는지를 표현하는 방식이다. 최근 CIM/GID(GID : Generic Interface Definition)에 대한 관심이 고조되면서 CIM/GID를 어떻게 도입하고 활용할 것인가에 대한 논의가 활발하다. 그 활용 방안의 일환으로 개발된 시스템에 대한 상호 운용성 테스트를 수행함으로써 제품 또는 시스템의 표준화 준수 여부와 활용성에 대한 검증이 가능하다. CIM/GID 상호운용성 테스트는 UCA International Users Group에서 가입 회원들을 대상으로 지속적으로 진행되고 있다. 본 논문에서는 미국 클리블랜드에서 2003년 11월 18일$\sim$20일 사이에 진행되었던 5차 CIM/GID 상호운용성 테스트 결과를 토대로 CIM/GID와 CIM XML의 상호 운용성 테스트 방안을 소개하고자 한다.