• 한국전자파학회논문지
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• 제19권5호
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• pp.501-505
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• 2008

이 논문에서는 휴대 장치의 지상파 DMB용 안테나로 다중 권선 loop 안테나를 제안한다. 제안된 안테나는 크기가 작으면서도 지상파 DMB 대역에서 충분한 수신 전력을 확보하도록 권수는 80회, 그리고 직경은 4 mm로 하였으며, 또한 높은 전달 함수 특성을 갖도록 품질 계수를 1로 하였다. 제작된 안테나는 길이가 30 mm로 소형이며, 이득은 약 -15 dBd로 길이 190 mm의 상용 지상파 DMB 모노폴 안테나와 비슷한 수신 능력을 가짐을 측정을 통해 확인하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 전기.전자공학 학술대회 논문집(II)
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• pp.854-858
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• 1987

This paper considers impulsive noise which produce burst error in high speed(approx.160Kbps) data transmission like ISDN(Integrated Servise Digital Network) using PSTN(Public Switching Telephone Network). To begin with, we obtains the transfer function of subscriber line to calculate the variation of bandwidth when the gain of receiver is fixed and channel capacity of non-gaussian channel in upper-and lower bound, and evaluates the transmission capability. In this paper compares channel capacity bounds which obtains when probability density function of impulsive noise is Laplacian distribution function with impulsive noise generated by waveform synthesier.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제48권3호
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• pp.131-138
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• 1999

Generally, the digital controller has many advantages such as high precision, robustness to electrical noise, capability of flexible programming and fast response to the load variation. In this study, we have established proper mathematical equivalent model of Brushless DC (BLDC) motor and estimated the motor parameter by means of the back-emf measurement as being the step input to the controlled target BLDC motor. And the validity of proposed estimation method is confirmed by the test result of step response. As well, we have designed the reasonable digital controller as a consequence of the root locus method which is obtained from the open-loop transfer function of BLDC motor with hall sensor, and the determination of control gain for variable speed control. Here, revised Ziegler-Nichols tuning method is applied for the proper digital gain establishment, and the system stability is verified by the frequency domain analysis with Bode-plot and experimentation.

• 한국의학물리학회지:의학물리
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• 제27권2호
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• pp.55-63
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• 2016

본 연구에서는 방사선치료기용 CBCT의 영상과 같이 해상도가 낮은 경우에 적용할 수 있는 MTF (modulation transfer function) 평가 방법을 고안하였다. 본 연구에서는 두꺼운 알루미늄 판의 영상을 이용하여 중복 표본(oversampling) 방법과 두께 보정 방법을 적용하여 MTF를 결정하였다. 다양한 알루미늄 판의 두께(0.3~1.2 mm)에 대해 MTF를 분석하였으며 경사 영상과 평행 영상의 경우에 대해서도 비교하였다. 연구 결과 치료계획용 CT인 경우에 알루미늄의 두께가 0.8 mm 이하 일 경우 MTF 측정이 가능한 것으로 나타났다. 따라서 두꺼운 알루미늄 판과 두께 보정을 이용한 MTF 측정이 CT 영상에서 가능하였다.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 1999년도 학술대회논문집-국제 전기방전 및 플라즈마 심포지엄 Proceedings of 1999 KIIEE Annual Conference-International Symposium of Electrical Discharge and Plasma
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• pp.114-118
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• 1999

This paper shows a structure for an electronic ballast of HID lamps. An electronic ballast for HID lamps usually employs a high-frequency resonant inverter and voltage-to-frequency converter to control the output. A half-bridge and series resonant circuit are chosen for the ballast. The inverter with V/F converter is modeled with a transfer function and a self-feedback controller is proposed. This structure is analyzed and the feedback gain is determined by using the inverter model. Experimental system is built with a commercial 250W high pressure sodium lamp and the results show a validity of the proposed ballast.

• Journal of Power Electronics
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• 제16권3호
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• pp.1076-1086
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• 2016

PI controllers are one of the most widely used controllers in industrial control systems due to their simple algorithms and stability. The parameters K_p and K_i determine the performance of the system response. The response is expected to improve by increasing the gain of the PI controller. However, too large a gain will accelerate the speed response and cause vibrations, which is not what is expected. This paper proposes a way to suppress vibrations by detecting the vibration frequency and extracting the vibration signal as a compensation to the speed feedback. Additionally, in order to improve its disturbance rejection ability, a low-order disturbance observer is proposed. This paper also explains the operation principle of the proposed method by analyzing the transfer function and it describes the design of the controller parameters in detail. Simulation and experimental results are provided to verify the merits of the proposed method. These results also show the good performance of the proposed method. It has a rapid response and suppresses vibrations.

• 한국통신학회논문지
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• 제13권4호
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• pp.322-331
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• 1988

본 논문에서는 고차 inverse Chebyshev 함수를 이용하여 능동 RC필터로 설계할 때 최대 동적범위를 갖고, 감도가 낮은 종속연결법으로 실현하는 방법을 제시하였다. 이때, 최대 동적범위를 만족시키도록 평탄행렬에 의한 최적 극점-영점 결합과 종속 연결순서 및 이득 분배에 대한 알고리즘을 제시하였으며, 능동 RC 회로의 단점인 감도 문제를 향상시키기 위하여 부 궤환을 갖는 2차 블록과 1차 블록을 설계하였다. 제시된 설계 방법을 이용하여 규준화된 7차 inverse Chebyshev함수의 능동 RC저역통과 필터를 설계한 결과 주어진 설계 명세조건과 일치함을 보였다.

• Journal of Power Electronics
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• 제16권3호
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• pp.849-860
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• 2016

The high-switching-frequency operation of power converters can achieve high power density through size reduction of passive components, such as capacitors, inductors, and transformers. However, a small-output capacitor that has small capacitance and low effective series resistance changes the small-signal model of the converter power stage. Such a capacitor can make the converter unstable by increasing the crossover frequency in the transfer function of the small-signal model. In this paper, the design and implementation of a high-frequency LLC resonant converter are presented to verify the power density enhancement achieved by decreasing the size of passive components. The effect of small output capacitance is analyzed for stability by using a proper small-signal model of the LLC resonant converter. Finally, proper design methods of a feedback compensator are proposed to obtain a sufficient phase margin in the Bode plot of the loop gain of the converter for stable operation at 500 kHz switching frequency. A theoretical approach using MATLAB, a simulation approach using PSIM, and experimental results are presented to show the validity of the proposed analysis and design methods with 100 and 500 kHz prototype converters.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 춘계학술대회 논문집
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• pp.543-550
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• 2002

This work is concerned with the estimation of output derivatives and their use for the design of robust controller for linear systems with systems uncertainties due to modeling errors and disturbance. It is assumed that a nominal transfer function model and Quantitative bounds for system uncertainties are known. The developed control schemes are shown to achieve regulation of the system output and ensures boundedness of the system states without imposing any structural conditions on system uncertainties and disturbances. Output derivative estimation is first conducted trough restructuring of the plant in a specific parameterization. They are utilized for constructing robust nonlinear high-gain feedback controller of a SMC(Sliding Mode Controller) Type. The performances of the developed controller are evaluated and shown to be effective and useful through simulation study.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.253-258
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• 2002

This work is concerned with the estimation of output derivatives and their use for the design of robust controller for linear systems with systems uncertainties due to modeling errors and disturbance. It is assumed that a nominal transfer function model and quantitative bounds for system uncertainties are known The developed control schemes are shown to achieve regulation of the system output and ensures boundedness of the system states without imposing any structural conditions on system uncertainties and disturbances. Output derivative estimation is first conducted trough restructuring of the plant in a specific parameterization. They are utilized for constructing robust nonlinear high-gain feedback controller of a SMC(Sliding Mode Controller)Type. The performances of the developed controller are evaluated and shown to be effective and useful through simulation study.