• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2000.11a
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• pp.463-466
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• 2000

SAR imaging 시스템 전파환경에서 목표물의 정보를 성공적으로 추출해 내기 위해서는 반사된 신호를 수신할 때 Coherent detection이 필수적이다. 수신시 Incoherent detection은 복소 위상오차 형태로 나타나서 실제 목표물의 영상에 심각한 Degradation을 야기시켜 치명적인 결과를 초래하게된다. 본 논문에서는 하나의 목표물에서 수신되는 신호를 파동방정식으로부터 모델링하고 모델링된 신호의 각 주파수대의 조합에 의해 전체 수신신호로부터 위상오차의 기울기를 유도한다. 더욱더 정확한 위상오차를 추정하기 위해 추정된 위상오차로부터 수신신호에 포함된 오차를 제거하고, 오차가 제거된 신호의 대역폭을 추정한다. 추정된 대역폭에 맞도록 알고리즘에 재 적용시켜 교정되지 못한 오차를 추정해 나간다. 이때 반복적인 위상오차 제거기법을 적용하고 Iteration의 종료를 자동으로 결정하기 위해 지능형 대역폭 추정 기법을 제시한다. 컴퓨터의 모의 실험에서, 위상오차를 포함한 수신 신호로부터 알고리즘을 적용하여 오차를 제거하고,, Wavefront Reconstruction 기법에 적용시켜 알고리즘의 성능을 영상으로 확인한다.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.4 no.1
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• pp.45-49
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• 2004

A method for obtaining the power energy with high quality is to keep the power factor for a load as close to unity as feasible. In this paper, we present a new method to improve the power factor for a load. The proposed method uses fuzzy control techniques in order to determine how many parallel capacitors are to be connected to the load for the correction of the power factor.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.20 no.4
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• pp.39-44
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• 2012

This paper propose a transmission method for "Transportation system" that can decide precise position under wide area road traffic environment. For precise position detecting, central station collect multiple receiver station's satellite navigation data and generate correction information. In this process, we need efficient real time transmission method for satellite navigation message that has variable data size. We propose real time data transmission method. This real time transmission method offer efficient processing structure for multiple receiver station's satellite navigation message. This paper explains proposed real time transmission method and proofs this transmission method.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.529-534
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• 2000

Diode rectifier has been widely used as he preregulator of inverter arc welding machine(IAW). As it is linked to power utility a disorder of other instruments can be burst out. The adoption of voltage source PWM converters can be considered and which must catch the compromise of between performance and cost. So in this paper voltage source PWM converters which have single (i.e. PWM converter) control switch respectively are analyzed and evaluated through digital simulation and experiment. In addition the improved input characteristics of IAW are shown and compare to those of conventional one.

• Journal of Power Electronics
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• v.8 no.1
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• pp.51-59
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• 2008

This paper addresses several issues concerning the analysis, design, modeling, simulation and development of single-phase, single-switch, power factor corrected AC-DC high frequency switching converter topologies with transformer isolation. A detailed analysis and design is presented for single-switch topologies, namely forward buck, flyback, Cuk, Sepic and Zeta buck-boost converters, with high frequency isolation for discontinuous conduction modes (DCM) of operation. With an awareness of modem design trends towards improved performance, these switching converters are designed for low power rating and low output voltage, typically 20.25W with 13.5V in DCM operation. Laboratory prototypes of the proposed single-switch converters in DCM operation are developed and test results are presented to validate the proposed design and developed model of the system.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.65 no.4
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• pp.303-308
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• 2016

A light-emitting diode (LED) has been increasingly applied to various industrial fields and general lightings because of its high efficiency, low power consumption, environment-friendly characteristic and long lifetime. To drive this LED lighting, various types of power converters have been applied. Also, power factor correction (PFC) techniques play an important role in the power supply technology. In this paper, design and control of a DCM interleaved boost PFC converter is discussed. The proposed converter can reduce current ripples at input and output side by cancelling an each phase of inductor currents. Since the IC does not require the auxiliary winding of inductor for current detection, simple PFC circuit is achieved. Therefore, it contributes to increase efficiency and downsize the whole system volume, cost. Also, the performance of the proposed system is demonstrated through experiments.

• Journal of Biomedical Engineering Research
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• v.13 no.4
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• pp.331-338
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• 1992

In this study, Fuzzy control algorithm to generate a change of rocomotion condition according to an outer environment is introduced on a motorized wheelchair control. An optimal control rule for conquesting the less of safety and system Inefficiency in the past are given to this motorized wheelchair. And dynamic analysis Is also adopted to it. Using those rules, a proportional control was possible when the vehicle changed Its moving direction. The proposed method which considers the relationship between a moving velocity and the command from the joystick shows better performance in the change of moving direction.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.4
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• pp.574-579
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• 2012

In this paper, the battery charger developed which is satisfy by the characteristics of the rapid control and reduce the cost of the charger. analog-digital mixed mode controller developed with dedicated IC for PWM control and low-performance micro-processor is using for the operation control of charger. The low-cost NEV charger developed to verify the performance and usability is verified with charging battery experiment by of using developed charger.

• Journal of the Korean Graphic Arts Communication Society
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• v.14 no.1
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• pp.115-131
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• 1996

The PVT(pressure-volume-temperature) relation of main-chain dimer liquid crystals having structures such as $\alpha$,$\omega$-bis[(4,4`-cyanobiphenyl) oxy] alkane(CBA-n with=9, 10) were studied. these dimer liquid crystals are known to form an enantiotropic nematic mesophase. In this work, we have determined the volume change as a function of temperature and pressure by using a GNOMIX PVT apparatus. In the V-Tcurves obtaind from isobaris mearements on various pressures, volume changes were observed at the nematic-isotropiz and nematic-crystal phase transitions. The volume changes at the transition exhibit slight odd-even effect with respect to the number of methylene unit n. The values of the (S)v obtained at the NI transition for CBA-9 and -10 were 6.9 and 12.6J/mol k. The valuesof (S)v for the CN transition were estimated on the basis of DSC(differential scanning calorimetry) data: 58.8(CBA-9) and 65.3J/mol k (CBA-10). For both transition, it was found that the correction about the volume change is significant, ranging from 40% to 60% of the total transition entropy observed under constant pressure.

• Communications of the Korean Mathematical Society
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• v.33 no.3
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• pp.871-888
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• 2018

We study the nonrelativistic limit of the Chern-Simons-Dirac system on ${\mathbb{R}}^{1+2}$. As the light speed c goes to infinity, we first prove that there exists an uniform existence interval [0, T] for the family of solutions ${\psi}^c$ corresponding to the initial data for the Dirac spinor ${\psi}_0^c$ which is bounded in $H^s$ for ${\frac{1}{2}}$ < s < 1. Next we show that if the initial data ${\psi}_0^c$ converges to a spinor with one of upper or lower component zero in $H^s$, then the Dirac spinor field converges, modulo a phase correction, to a solution of a linear $Schr{\ddot{o}}dinger$ equation in C([0, T]; $H^{s^{\prime}}$) for s' < s.