• 정보과학회지
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• 제5권2호
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• pp.94-98
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• 1987

本 論文에서는 多値論理回路를 實現함에 있어서 發生하는 Hazard를 2가 지, 卽 Function Hazard와 Logic Hazard로 分類하였고 이의 解決方案으로 入力 信號가 Switching하여 最終 安定 level에 到達했을 때 Switching函數를 決定하고 이 函數로써 Switching函數의 Unate性을 試圖하였다. 그리고 內部回路에서 信號 가 遷移될 때 內部回路의 遲延 遲延時間으로 말미암아 發生되는 Hazard狀態를 Redundant回路를 實現하였다. 또 이 論理回路를 基本으로한 N値 Flip-flop N과 Shift Register, Counter等의 順序論理回路를 構成하였다.

• 한국위성정보통신학회논문지
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• 제9권3호
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• pp.86-90
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• 2014

DC-DC 컨버터는 인덕터 전류의 동작에 따라 연속전류모드와 불연속전류모드, 임계모드로 나눌 수 있다. 임계모드는 연속전류모드와 불연속전류모드의 경계에서 동작한다. DC-DC 컨버터를 임계모드에서 동작하도록 설계하면 인덕터 크기를 줄일 수 있으며 ZCS(Zero Current Switching) 동작을 하여 스위치와 다이오드의 전력 손실을 줄일 수 있다. 본 논문에서는 임계모드로 동작하는 부스트형 컨버터를 인공위성 용 태양전력 조절기에 적용한다. 임계모드 동작 시 DC-DC 컨버터의 입출력 조건에 따라 DC-DC 컨버터의 스위칭 주파수가 변한다. 최대 스위칭 주파수 제한을 위해 스위칭 주파수 제한 로직을 적용하였다. 한편, 임계모드 부스트형 태양전력 조절기는 소신호 전달함수가 간단하여 제어기 설계가 용이하다. 임계모드 부스트형 태양전력 조절기의 소신호 전달함수를 유도하고 이를 바탕으로 전압제어기를 설계하였다. 최종적으로 모의실험을 통해 임계모드로 동작하는 태양전력 조절기를 검증하였다.

• Journal of the Korean Data and Information Science Society
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• 제28권2호
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• pp.451-459
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• 2017

There are many researches showing that when a process change has occurred, variable sampling intervals (VSI) control chart is better than the fixed sampling interval (FSI) control chart in terms of reducing the required time to signal. When the process engineers use VSI control procedure, frequent switching between different sampling intervals can be a complicating factor. However, average number of samples to signal (ANSS), which is the amount of required samples to signal, and average time to signal (ATS) do not provide any control statistics about switching performances of VSI charts. In this study, we evaluate numerical switching performances of multivariate VSI EWMA chart including average number of switches to signal (ANSW) and average switching rate (ASWR). In addition, numerical study has been carried out to examine how to improve the performance of considered chart with accumulate-combine approach under several different smoothing constant and sample size. In conclusion, process engineers, who want to manage the correlation coefficients of related quality variables, are recommended to make sample size as large and smoothing constant as small as possible under permission of process conditions.

• 한국항공우주학회지
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• 제36권6호
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• pp.574-580
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• 2008

이 논문에서는 최근에 개발한 무충돌 전환 구현 알고리즘을 사용하여 전비행영역 제어를 위한 제어기 교체법을 제시한다. 이 교체법은 비행기의 속도와 고도에 따라 제어기를 교체하는 일반적인 방법과 제어기 교체 기준으로 충돌 현상에 관계된 가격함수를 사용하는 최적화 방법을 적절한 규칙에 의해 결합한 것이다. 제안된 제어기 교체법의 성능을 확인하기 위해 시험표준 문제로 고성능 비행체에 적용하여 넓은 비행영역에서 모의실험을 수행하고 제어성능이 향상됨을 예시한다.

• Journal of Power Electronics
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• 제15권2호
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• pp.479-486
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• 2015

The application of soft-switching techniques is increasing in the DC/DC converter area. It is important to design soft-switching parameters to ensure the converter operates properly and efficiently. An optimized design method is presented in this paper. The objective function is the total power loss of a converter, while the variables are soft-switching parameters and the constraints are the electrical requirements for soft-switching. Firstly, a response surface methodology (RSM) model with a high precision is built, and the rough optimized parameters can be obtained with the help of a genetic algorithm (GA) in the solution space determined by the constraints. Secondly, a re-optimization is conducted with a SPICE model and a GA, and accurate optimized parameters can be obtained. Simulation and experiment results show that the proposed method performs well in terms of a wide adaptability, efficiency, and global optimization.

• Journal of Power Electronics
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• 제19권6호
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• pp.1458-1466
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• 2019

Multilevel inverters have appeared as a successful and utilitarian solution in many power applications. The prime objective of an inverter is to keep the fundamental component of the output voltage of a multilevel inverter at a preferred value. Equally important is the need to keep the harmonic components in the output voltage within stated harmonic limits. Therefore, the basis of this research is to develop a harmonic minimization function that optimizes the switching angles of cascaded H-bridge multilevel inverter. Due to benefits of the Cuckoo Search (CS) algorithm, it is applied to determine the switching angles, which are further used to generate the switching pattern for firing the H-bridges of multilevel inverter. Simulation results are compared with SPWM based firing scheme. The switching frequency for SPWM firing scheme is taken as 200 Hz since the switching losses are increased when switching frequency is high. To validate the ability of Cuckoo Search optimized firing scheme in minimization of harmonics, experimental results obtained from hardware prototype of Five Level Cascaded H-Bridge Multilevel Inverter equipped with a FPGA controller are presented to verify the simulation results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 추계학술대회 논문집 학회본부
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• pp.382-385
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• 1991

In order to stabilize linear time-invariant systems with the unknown system matrix, a piecewise constant linear state feedback control law including switching logic is developed. A number of feedback gain matrices are first precomputed by solving the Algebraic Riccati Equation with prescribed degree of stability, and then are switched over in a direction to increase degree of stability. Switching stops when a Lyapunov function shows the decreasing property, and hence switching times are finite.

• 대한전자공학회논문지
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• 제17권3호
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• pp.45-51
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• 1980

본 논문에서는 Galois 스윗칭함수를 구성하기 위한 하나의 방법을 제시하였다. 먼저 단일변수에 대한 Lagrange 보계법을 다항식 형태로 전개시켜서 Galois 스윗칭함수를 구성한 다음 2변수에 대한 구성이론을 밝혔다. 이를 바탕으로 하여 다변수에 대한 Galois스윗칭함수를 구성하였다. 구성이론을 뒷받침하기 위한 예제를 타논문에서 인용하였으며 그 결과가 기존논문의 결과와 동일함을 보였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.236-241
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• 2001

This paper presents a novel prototype of active voltage-clamping capacitor-assisted edge resonant soft switching PWM inverter operating at a constant frequency variable power (VPCF) regulation scheme, which is suitable for consumer high-power induction-heating cooking appliances. New generation IGBT with a trench gate is particularly improved in order to reduce conduction loss due to its lowered saturation voltage characteristics. The soft switching load resonant and quasi-resonant inverter designed distinctively using the latest IGBTs is evaluated from an experimental point of view.

• 한국세라믹학회지
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• 제36권10호
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• pp.1035-1039
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• 1999

Ferroelectric properties and reliability characteristics of(111) and (100) preferentially oriented tetragonal Pb(Zr0.2Ti0.8)O3 (PZT) thin film capacitors have been investigated as a function of the top electrode thickness. The (111) preferentially oriented film exhibits 180$^{\circ}$domain switching process with better squareness of hysterisis loop and abrupt change of small singal capacitance-voltage comparing to the (100) preferentially oriented film having 90$^{\circ}$ domain switching process. The domain swithcing process of tetragonal phase PZT is different from that of rhobohedral phase. The film with thinner top electrode shows less initial switching polarization due to less compressive stress but it exhibits better endurance characteristics due to enhancing partial switching region.