• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전력기술부문
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• pp.210-213
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• 2001

This study presents an effective variable forgetting factor method based on fuzzy logic to suppress frequency droop in extended integral load frequency control. The performance of the extended integral control is greatly dependent on the decaying factor. For an optimal or near optimal performance, it is necessary that the decaying factor as well as the feedback gains should be changed very quickly in response to changes in the system dynamics. However, because of its time-varing characteristic, the optimal decaying factor is difficult to be selected analytically. By adopting fuzzy set theory, the decaying factor can be determined quickly to respond to the variation of the feedback signals. This study builds a fuzzy rule base with use of the change of frequency and its rate as inputs. The computer simulation has been conducted for the single machine system. The simulation results show that the proposed fuzzy 1o81c based controller yields more improved control performance than the conventional PI controller.

• 복식문화연구
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• 제28권1호
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• pp.1-14
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• 2020

This study is based on a representative body shape drawn from previous studies that classify adult male torso shapes. In this study, a design method is proposed by developing a tight-fit pattern that can be easily developed into various items and designs using the body surface development figure. This is obtained by converting the 3D body shape of the model representing the representative body shape. The specific design method was conducted as follows. Actual measurement values were used for waist back length, waist-to-hip length, shoulder length. The scye depth was determined as C/4-1.7 cm, and the front and back Interscye was set at (1/2 × actual measurements)-0.2 cm. The front-back neck breadth was set to (1/5 × base neck circumference)-1.3 cm and (1/5 × base neck circumference) cm. The front-back neck depth was set to (1/5 × base neck circumference)-1.2 cm and 3.5 cm. Front chest circumference was C/4-1 (front-back difference)cm; (1/4 × back chest circumference) was C/4 + 1 (front-back difference) + 0.3 (dart amount) cm. Front waist circumference was W/4-0.2 (front-back difference) + 2.2 (dart amount) cm; back waist circumference was W/4 + 0.2 (front-back difference) + 2.5 (dartamount) cm; front hip circumference was H/4 + 0.2 (ease) + 0.2 (front-back difference) cm; and back hip circumference was H/4 + 0.2 (ease)-0.2 (front-back difference) cm; Front droop was 1.6 cm. The newly developed tight-fit pattern is expected to be of great use as a basis for garment construction.

• 한국통신학회논문지
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• 제28권5C호
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• pp.514-522
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• 2003

본 논문에서는 다수의 특징과 이진 분류 트리를 이용하여 장면 전환점(shot change)을 검출하는 향상된 방식을 제안한다. 기존의 장면 전환점 검출 방식에서는 인접한 프레임간에 단일 특징과 고정된 임계값을 주로 사용하였다. 하지만, 비디오 시퀀스 내의 장면 전환점에서는 인접한 프레임간의 내용(content)인 컬러, 모양, 배경 혹은 질감 등이 동시에 변화한다. 따라서 본 논문에서는 단일 특징보다는 상호 보완 관계를 갖는 다수의 특징을 이용하여 장면 전환점을 효율적으로 검출한다. 그리고 장면 전환점의 분류를 위해서는 이진 분류 트리(binary classification tree)를 이용한다. 이 분류 결과에 따라 장면 전환점 검출에 사용될 중요한 특징들을 선별하고, 각 특징들의 최적 임계값을 구한다. 또한, 분류 성능을 확인하기 위해 교차검증(cross-validation)과 드롭 케이스(drop-case)를 수행하였다. 실험 결과, 제안된 기법이 단일 특징들만을 사용한 기존의 방법들 보다 El(Evaluated Index, 성능평가지수)에서 평균 2%의 성능이 향상됨을 알 수 있었다.

• Journal of Power Electronics
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• 제18권5호
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• pp.1595-1607
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• 2018

In this paper, a hierarchical control strategy is introduced to control a new three-port multidirectional DC-DC converter for integrating an energy storage system (ESS) to a bipolar DC microgrid (BPDCMG). The proposed converter provides a voltage-balancing function for the BPDCMG and adjusts the states of charge (SoC) of the ESS. Previous studies tend to balance the voltage of the BPDCMG buses with active sources or by transferring power from one bus to another. Furthermore, the batteries available in BPDCMGs were charged equally by both buses. However, this power sharing method does not guarantee efficient operation of the whole system. In order to achieve a higher efficiency and lower energy losses, a triple-layer hierarchical control strategy, including a primary droop controller, a secondary voltage restoration controller and a tertiary optimization controller are proposed. Thanks to the multi-functional operation of the proposed converter, its conversion stages are reduced. Furthermore, the efficiency and weight of the system are both improved. Therefore, this converter has a significant capability to be used in portable BPDCMGs such as electric DC ships. The converter modes are analyzed and small-signal models of the converter are extracted. Comprehensive simulation studies are carried out and a BPDCMG laboratory setup is implemented in order to validate the effectiveness of the proposed converter and its hierarchical control strategy. Simulation and experimental results show that using the proposed converter mitigates voltage imbalances. As a result, the system efficiency is improved by using the hierarchical optimal power flow control.

• 한국전자파학회지:전자파기술
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• 제10권3호
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• pp.2-17
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• 1999

본 논문에서는 software radio 시스템의 핵심 부 분의 하나인 digital channelizer라고 불리우는 일종 의 programmable downconverter(PDC)를 간단하게 구현하는 방법을 제안한다. 제안하는 방법은 cas-caded integrator-comb(CIC) 여파기에 기초한 POC 를 효과적으로 설계하기 위해 새로운 보간된 2차 다항식 (Interpolated Second Order Polynomial. ISO OP)을 사용하는 것에 근간을 두고 있다. 이러한 ISOP는 매우 간단하면서도 미미하게 aliasing reR jection이 떨어지는 대신 통과대역 dr$\infty$p을 효과적 으로 감소시킨다는 장점을 가지고 있다. 뿐만 아니라 보통 CIC 여파기 다음에 위치 하는 halfband 여 파기를 효과적으로 간단히 만들 수 있도록 하여준 다 본 논문에서는 이러한 ISOP의 장점들을 이용 하여 ISOP여파기 이외에 기존의 halfband 여파기 를 대체할 수 있는 간단한 변형된 halfband 여파기(modified halfband filter. MHBF) 를 제 안한다. 결 국 PDC를 위해 제 안된 decimation 여 파기 는 CIC 여파기, ISOP, MHBF, 프로그램 가능한 FIR (prog grammable FIR. PFIR) 여파기들의 직렬 연결 구 조가 된다. 또한 본 논문에서는 이러한 직렬 연결 된 여러 가지 여파기들을 통시에 최적화하는 기법 을 제안한다. 설계 예제활 통하여 실제로 기존 방 법들보다 본 논문에서 제안하는 방법이 효과적임 을 보인다.