• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.808-810
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• 2002

Higher current-rating and improved thermal performance are being sought for existing medium-voltage vacuum circuit breakers(VCB) in order to meet market needs which require to be compact and downsized. In this paper, thermal performance of medium voltage vacuum circuit breaker was investigated through experiments and numerical analysis. We changed several major parameters of current-rating and heat sink affecting on thermal behaviors in the breaker and observed the results. To predict the temperature distribution in complex three-dimensional (3-D) VCB components and gas, the commercial package was used to simulate conjugate heat transfer. Although some assumptions and simplifications were introduced to simulate the model, results from the computational model were in good agreement with actual temperature rise measurements obtained from experiments.

• Journal of Korea Multimedia Society
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• v.19 no.2
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• pp.317-324
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• 2016

This paper proposes a message transfer application using smartphone with NFC(Near Field Communication) and GCM(Goolge Cloud Messaging) technology for prevention of personal information leakage. In implementing for the proposed system, we design a NFC-based vehicle status alerts service which make it possible to communicate with smartpone message without phone-number between a car driver and an unspecified person. The application provides message communication mechanism without exposing the real phone number, using the NFC tag written with the driver's smartphone device ID and GCM push messages. Through the evaluation result of the actual implemented application, the proposed system can be efficient technology in protection for leakage of personal information such as personal phone- number in daily life.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.233-233
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• 2009

Piezoelectric Transformer (PT) was emerged in device and material industry. PT has some advantages such as low profile and mechanical energy transfer with little electromagnetic interface (EMI). But, It is known that the maximum PT efficiency can be obtained when it operates near the resonant frequency of the PT. Also PT's resonant frequency moves according to the load conditions Therefore, As the operating frequency moves further from the resonant frequency, the PT efficiency decreases dramatically due to the increase of the circulating current. This paper proposes analyzes modeling of PT convert and propose a guide-line to adaptive control

• International Journal of Control, Automation, and Systems
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• v.1 no.1
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• pp.1-10
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• 2003

This paper presents a high-precision magnetically levitated (maglev) stage to meet demanding motion specifications in the next-generation precision manufacturing and nanotechnology. Characterization of dynamic behaviors of such a motion stage is a crucial task. In this paper, we address the issues related to the stochastic modeling of the stage including transfer function identification, and noise/disturbance analysis and prediction. Provided are test results on precision dynamics, such as fine settling, effect of optical table oscillation, and position ripple. To deal with the dynamic coupling in the platen, we designed and implemented a multivariable linear quadratic regulator, and performed time-optimal control. We demonstrated how the performance of the current maglev stage can be improved with these analyses and experimental results. The maglev stage operates with positioning noise of 5 nm rms in $\chi$ and y, acceleration capabilities in excess of 2g(20 $m/s^2$), and closed-loop crossover frequency of 100 Hz.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.245-248
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• 2004

In the simple application programs, when the Bluetooth system is used, main packet, which is transmitted or many overheads, which depend on processing between every level, lead to superfluous outlay of resource area. It is shown in this paper, that all layers of bluetooth system are not used. And, it uses up to HCI layer which it is supported to make a connection between bluetooth and host device(ex. PC, PDA, etc$\ldots$), should be used levels up to HCI layer. Therefore, it is able to transfer every part of data what should be transmitted.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.257-260
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• 2004

This paper describes the software download framework for SDR(Software Defined Radio). SDR is expected to solve the compatibility problem among various mobile communication standards so that people can use the same device for different wireless network. We integrated the SDR software download process into Jini architecture, and modified Jini's several functions. We implemented this proposed framework on a Linux and windows operating systems with Java programming language. With Java platform, we can easily transfer this framework into hand-held devices.

• IEMEK Journal of Embedded Systems and Applications
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• v.15 no.1
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• pp.17-23
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• 2020

We propose a system time synchronization method between embedded Linux-based distributed control devices by using Transmission Control Protocol (TCP) communication and General Purpose Input Output (GPIO) device. The GPIO signal is used as the trigger signal for synchronization and the TCP communication is used to transfer the system time of master Linux, which serves as the reference clock, to slave Linux. Precise synchronization performance is achieved by measuring and compensating for the propagation delay of GPIO signal and the acquisition and setting latency of Linux system time. We build an experimental setup consisting of two embedded Linux systems, and perform extensive experiments to verify the performance of the proposed synchronization method.

• Journal of Industrial Technology
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• v.21 no.B
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• pp.125-132
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• 2001

Heat dissipation technology using flow resonant phenomenon is a kind of new concept in heat transfer area. A vibration exciter is needed to generate air turbulence which has the natural shedding frequency of heat system. A mechanical vibrating device for the air flow oscillation is introduced, which is driven by a moving coil actuator. An analytical dynamic model for this mechanical vibration exciter is presented and its' validity is verified by the comparison with experimental data. Values of some unknown system parameters in the analytic model are estimated through the system identification approach. Based on this mathematical model, the vibration exciter using strain displacement estimator is developed. And in the experiment, the feedback control is used. During the experimental verification phase, it turns out the high modal resonant characteristics of vibrating plate are the major barrier against obtaining a high bandwidth vibration exciter.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.6
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• pp.717-725
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• 2004

A power generation systems are proposed to convert ambient mechanical vibration into electrical energy using cantilever-type piezoelectric materials. The vibration-based power device can be used for self-powered systems without batteries. This paper presents the theoretical analysis for the coupled equations of piezoelectric and structural motions and investigates the dynamic characteristics of the self-power system using transfer function method. The theoretical model is verified by the finite element analysis of the resonance frequency, the dynamic response of the structure and the sensor sensibility. Experimental results measured using a prototype system agree with the theoretical predictions. The system is shown to produce 34.5 ㎼ in average. Finally, we perform the optimal design for system variables to maximize output power.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.05a
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• pp.57-60
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• 2001

The characterization of organic Metal/Insulator/Metal(MIM) devices were investigated from LB films. The physicochemical properties of the LB films were by UV absorption spectrum and AFM. We give pressure stimulation into organic thin films and then manufacture a device under the accumulation condition that the state surface pressure is 2, 10, 30[mN/ml The stable images are probably due to a strong interaction between the monolayer film and glass substrate. We are unable to obtain molecule resolution in images of the films but did see a marked contrast between images of the bare substrate and those with the network structure film deposited onto it.