• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.389-391
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• 1994

This paper proposes an approach to control the current amplitude and phase simultaneously. To do this, variable structure control and adaptive parameter estimation arc applied to the current control of a single-phase PWM inverter with unknown R-L series load. The load parameters, R and L, are estimated by using the recursive least square method and these parameters are used to adjust the feedback gains of control input. The inverter system is modelled in a 2nd-order system by treating load current variation caused by inductive component as a disturbance. Simulation and experiment based on the 2nd -order model are done and the results show good dynamic response and low THD.

• 전기학회논문지
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• 제61권10호
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• pp.1477-1482
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• 2012

This paper deals with a new variable microwave power distributor and a connector between a deck plate and a input power waveguide for indoor microwave wireless power transmission. We design a new type connector built in the 3-stage coaxial line structure, and calculate the return loss of the connector at 2.45GHz. Newly designed connector shows the excellent return loss performance less than -30dB at the operating frequency of 2.45GHz. And we show a power distributor in which the dividing ratio of the power is controlled mechanically by three rotary fins. The distributor can control the dividing power from 4.5% to 58% with the variance of 5% output power. The experimentally tested results of the distributor are good agreement with the simulation within the return loss of 1%.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.360-363
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• 2000

A half bridge type double resonant high frequency resonant inverter using PFM is described. This proposed inverter can reduce distribution of the switching current because of using the current of the serial resonant circuit to the input current of the parallel one. In the case of variable capacitance of the DC voltage source separated capacitor the analysis of inverter circuit has generally described by using normalized parameter and operating characteristics has been evaluated in terms of switching frequency and parameters. Based on the characteristics value a method of the circuit design is proposed. The theoretical results are in good agreement with the experimental ones. In the future this proposed circuit is considerated to be useful for induction heating and discharge lamp.

• 전기학회논문지
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• 제67권1호
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• pp.46-51
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• 2018

Constant slip frequency control has been conventionally used in thrust control of the linear induction motor(LIM) for magnetically levitated train. However in this paper variable slip frequency control method is presented to increase LIM efficiency according to change of driving notch. Thrust, attractive force, input power to inverter, regenerative power of the LIM are analyzed by finite element method when the train runs according to the presented control method. As a result it is proved experimentally that the electrical energy to inverter is reduced than the conventional method.

• The Journal of the Acoustical Society of Korea
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• 제16권2E호
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• pp.14-20
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• 1997

The future teleconferencing systems will need an appropriate system which controls properly the acoustic echo for the convenient communication. The conventional acoustic echo cancellation algorithms involve large adaptive filters identifying the impulse response of the echo path. The use of adaptive IIR filters appears to be a reasonable way to reduce computational complexity. Effective cancellation of acoustic echo presented in teleconferencing system requires that adaptive filters have a rapid convergence speed. One of the main problems of acoustic echo cancellation techniques is that the convergence properties degrade for an highly correlated signal input such as speech signals. By the way, the introduction of linear prediction filers onto the structure of the acoustic echo cancellation represents one approach to decorrelate the speech signal. And variable step-size LMS algorithm improves the convergence speed through a little increasing of computational complexity. In this paper, we applied these two methods to the acoustic echo canceller(AEC) and showed that these methods have better performances than the conventional AEC.

• 응용통계연구
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• 제27권3호
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• pp.419-430
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• 2014

전력수급의 정확한 예측은 국민들의 일상적 생활 유지, 산업활동, 그리고 국가경영을 위하여 매우 중요하다. 본 연구에서는 시계열모형화에 의해 전력판매량을 예측한다. 실제 자료분석을 통하여 입력시계열로서 냉난방도일과 개입변수로 펄스함수를 사용한 전이함수모형이 다른 시계열모형에 비해서 제곱근평균제곱오차 및 평균절대오차의 의미에서 더 우수하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1994년도 Proceedings of the Korea Automatic Control Conference, 9th (KACC) ; Taejeon, Korea; 17-20 Oct. 1994
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• pp.177-182
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• 1994

In this paper, an output feedback adaptive variable structure control scheme is presented for stabilization of large scale power systems. An additional input signal which is called a power system stabilizer(PSS) is needed to improve the stability of a power system and to maintain the synchronization of generators. The proposed PSS scheme does not require a priori knowledge of uncertainty bounds. It is guaranteed that the closed-loop system is globally uniformly ultimately bounded by the Lyapunov stability theory. Simulation results for a multimachine power system are given to show the feasibility of the proposed scheme and the superiority of the proposed PSS in comparison with the conventional lead-lag PSS of PID-type.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.609-611
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• 1996

Zero-Cross Detector makes pilot signal to control the power to CEDM(Control Element Drive Mechanism). Existing Zero-Cross Detectors has had a problem which can cause unexpected reactor trip resulted from fluctuating frequency of input signal coming from M/G Set. The existing Zero-Cross Detector can't work properly when power frequency is varying because it was designed to work under stable M/G Set operation, and produces wrong pilot signal and output voltage. In this report the Zero-Cross Detector is improved to resolve voltage fluctuating problem by using new devices such as digital noise filtering circuit, variable cycle compensator and alarm circuit. And through the performance verification it shows that new circuit is better than old one. If suggested detector is applied to plant, it is possible to use it under House Load Operation because stable voltage can be generated by new Zero-Cross Detector.

• 대한전자공학회논문지
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• 제26권11호
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• pp.1839-1849
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• 1989

An optimal variable assignment algorithm is presented as a decomposition method of MVL functions. A given 3-valued combinational logic function is disintegrated into subfunction composed of the function dependant relation, then extracted implicant output elements from subfunctions are assigned to a T-gates. As a circuit implementation tool, a programmable integarated T-gate module is proposed, and the construction procedure of combinational MVL functions is systematized in each step. This method is expected to give properties of the systematic procedure, possibility of T-gate number reduction, unification of module, and flexibility of module composition. Specially variable decomposition method can be pointed out as an approach to solving the limitation problem of the input and output terminal number in VLSI implementations.

• 전자공학회논문지B
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• 제32B권1호
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• pp.103-109
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• 1995

In this paper, we propose a postprocessing method that neatly removes blocking effect but retains visually important image details and edges. The iterative thresholded lowpass filter is basically a low pass filter whose ouput depends on three variable elements. I.e. iteration number, threshold value and passband width. The threshold value restricts the difference between the output of the proposed filter and the original input independent of the iteration number. With this property, the iterative thresholded lowpass filter can retain most of the image details while smoothing the block boundaries. The other two variable elements, i.e. iteration number and passband width, can determine the convergence speed of the proposed filter. In this paper, we also propose several adaptive filtering techniques based on the iterative thresholded lowpass filter with their simulation results.