• 한국컴퓨터정보학회논문지
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• 제8권4호
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• pp.126-131
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• 2003

다중 유니캐스트 전송기법보다 멀티캐스트 전송기법이 장점이 많은 것이 사실이지만 IP 멀티캐스트 프로토콜은 간편한 관리제어 목적으로 몇몇 네트워크 영역으로 국한된다. 영역간 멀티캐스트 배치는 기술적인 면과 관리적인 면으로 인하여 진척이 느려지고 있다. 이에 대안으로 최근에 오버레이 멀티캐스팅 기술이 제시되었고, 본 논문에서 우리는 종단 호스트 멀티캐스트 트리 프로토콜 (EMTP)를 제안한다. EMTP는 리프 노드에 도달할 때까지 한번에 트리의 두 레벨을 검색하면서 또 한편으로는 가입하고자 하는 노드와 트리상의 가장 가까운 노드를 찾아낸다. 비록 해당 위치의 노드가 허용 가능한 차수가 없을지라도 그 노드를 잠재적인 부모노드로 선택 가능하게 함으로써 차후에 스위칭 횟수를 줄여 트리의 안정성을 높이고 데이터 전송 시간의 감소를 가져온다.

• 설비공학논문집
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• 제25권3호
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• pp.168-172
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• 2013

A preliminary performance test of a 30RT 2-stage screw heat pump was carried out in order to develop a high performance large-scale unutilized energy source heat pump system, which will be used for district heating and cooling. In this study, two issues of the system operating control were investigated. The first issue is the mode switching control from 1-stage to 2-stage. A stable 2-stage heating operation is guaranteed, only if the load-side water inlet temperature is over a certain value, where the 1-stage heating operation should be done first from a cold start. The second issue is oil level control. An oil shortage problem in the low stage compressor, which depends on the degree of suction superheat, was solved by a proper oil level control scheme.

• 전력전자학회논문지
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• 제9권4호
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• pp.364-371
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• 2004

본 논문에서는 PWM 펄스를 랜덤하게 위치시킬 수 있는 새로운 3상 공간 벡터 RPWM(Random PWM) 기법을 제안한다. 기존의 RPWM 방식과 달리 3상 대칭 변조 기법에 의해 발생된 공간 전압 벡터 PWM(Space Vector PWM) 펄스를 랜덤하게 위치시키는 원리를 각 섹터마다 달리 적용하여 RPWM을 구현하는 기법을 제안한다. 제안 된 기법의 타당성 검증을 위하여, 제안된 RPWM 기법 알고리즘에 대해 MATLAB/SIMULINK를 이용한 시뮬레이션 및 DSP를 이용한 IGBT 인버터를 구성하여 실험을 수행한다. 특히 10,000 rpm 이상의 고속운전 시, 공간 전압 벡터 PWM 기법과 제안된 RPWM 기법에 의해 발생되는 인버터 출력 전류의 고조파 스펙트럼을 비교한다. 즉 전류 고조파 스펙트럼에서 스위칭 주파수 정수배에 해당하는 고조파의 크기를 비교하여 제안된 RPWM의 기법의 타당성을 검증하고자한다.

• 전력전자학회논문지
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• 제22권4호
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• pp.297-304
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• 2017

The purpose of this paper is to analyze losses because of switching devices and the secondary side circuit diodes of 500 W full bridge dc-dc converter by applying gallium nitride (GaN) field-effect transistor (FET), which is one of the wide band gap devices. For the detailed device analysis, we translate the specific resistance relation caused by the GaN FET material property into algebraic expression, and investigate the influence of the GaN FET structure and characteristic on efficiency and system specifications. In addition, we mathematically compare the diode rectifier circuit loss, which is a full bridge dc-dc converter secondary side circuit, with the synchronous rectifier circuit loss using silicon metal-oxide semiconductor (Si MOSFET) or GaN FET, which produce the full bridge dc-dc converter analytical value validity to derive the final efficiency and loss. We also design the heat sink based on the mathematically derived loss value, and suggest the heat sink size by purpose and the heat divergence degree through simulation.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.506-506
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• 2000

To improve control performance of a non-linear system, many other researches have used the sliding mode control algorithm. The sliding mode controller is known to be robust against nonlinear and unmodeled dynamic terms. However. this algorithm raises the inherent chattering caused by excessive switching inputs around the sliding surface. Therefore, in order to solve the chattering problem and improve control performance, this study has developed the sliding mode controller with a perturbation estimator using the observer-based fuzzy adaptive network generates the control input for compensating unmodeled dynamics terms and disturbance. And, the weighting parameters of the fuzzy adaptive network are updated on-line by adaptive law in order to force the estimation errors to converge to zero. Therefore, the combination of sliding mode control and fuzzy adaptive network gives rise to the robust and intelligent routine. For evaluating control performance of the proposed approach. tracking control simulation is carried out for the hydraulic motion simulator which is a 6-degree of freedom parallel manipulator.

• 복식문화연구
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• 제20권3호
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• pp.378-391
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• 2012

Loyalty programs are used by many fashion firms as marketing tools for reducing customer switching and increasing customer loyalty in keen market competition conditions. The purpose of this study is to explore and propose an effective implementation of a loyalty program for a targeted fashion firm's customers by grasping their perceived value of and satisfaction with the loyalty program. Questionnaires were administered to 329 college students in Gwangju. For data analysis, factor analysis, Chronbach's ${\alpha}$, correlation analysis, and a Structural Equation Model using the LISREL 8.30 program were applied. The results were as follows. First, the degree of perceived value of the loyalty program was classified according to cash value, convenience of use, aspirational value, and suitability of use. The aspirational value and cash value significantly affected the students' satisfaction with the loyalty program, but the convenience of use and suitability of use were not significant. Second, higher satisfaction with the loyalty program was related to higher overall customer satisfaction but did not affect customer trust and loyalty. Finally, higher overall satisfaction was related to customer trust but did not affect customer loyalty, and higher trust affected customer loyalty.

• Journal of Power Electronics
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• 제9권1호
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• pp.51-60
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• 2009

Hybrid Electric Vehicles (HEVs) utilize electric power as well as a mechanical engine for propulsion; therefore the performance of HEV s can be directly influenced by the characteristics of the Energy Storage System (ESS). The ESS for HEVs generally requires high power performance, long cycle life and reliability, as well as cost effectiveness. So the Hybrid Energy Storage System (HESS), which combines different kinds of storage devices, has been considered to fulfill both performance and cost requirements. To improve operating efficiency, cycle life, and cold cranking of the HESS, an advanced dynamic control regime with which pertinent storage devices in the HESS can be selectively operated based on their status was presented. Verification tests were performed to confirm the degree of improvement in energy efficiency. In this paper, an advanced HESS with improved an Battery Management System (BMS), which has optimal switching control function based on the estimated State of Charge (SOC), has been developed and verified.

• 조명전기설비학회논문지
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• 제29권2호
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• pp.82-90
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• 2015

This paper proposes an efficient bi-directional DC/DC converter topology using multi-phase interleaved method for power storage system. The proposed converter topology is used for a power storage system using a vanadium redox flow battery(VRFB) and is configured to enable bidirectional power flow for charging and discharging of VRFB. Proposed DC/DC converter of the 4 leg method is reduced to 1/4 times the rating of the reactor and the power semiconductor device so can be reduce the system size. Also, proposed topology is obtained the effect of four times the switching frequency as compared to the conventional converter in each leg with a 90 degree phase shift 4 leg method. This can suppress the reduction of the life of the secondary battery because it is possible to reduce the current ripple in accordance with the charging and discharging of VRFB and may increase the efficiency of the entire system. In this paper, it proposed bidirectional high-efficiency DC/DC converter topology Using multi-phase interleaved method and proved the validity through simulations and experiments.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2006년도 춘계종합학술대회
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• pp.685-688
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• 2006

본 논문에서는 초전도에너지저장 시스템에 적합한 간략한 회로 구성과 높은 신뢰성을 가지는 단상 무정전 전원공급장치를 제안한다. 제안된 시스템은 공통암 방식을 적용하여 스위칭 소자수를 저감한다. Normal, Stored-energy, Bypass의 세 가지 동작 모드에 대하여 상세히 설명한다. 사용되는 스위칭 소자수를 저감시키거나 수동소자로 대체시킬 경우 제어가 복잡해지고 자유도를 감소키는 문제점이 있지만 고성능의 디지털 제어기를 통해 추가적인 부담 없이 해결할 수 있다. 제안된 시스템의 타당성 검증을 위해 시뮬레이션 결과를 제시한다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2014년도 전력전자학술대회 논문집
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• pp.191-192
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• 2014

Multiple output converters (MOCs) are widely used for applications which require various levels of the output voltages due to their benefits in cost, volume, and efficiency. However, most of the MOCs developed so far can regulate only one output tightly and require as many secondary windings in the transformer as the number of the outputs. In this paper, a novel Time Division Multiple Control (TDMC) method to regulate all the outputs in high precision is proposed and applied for the multiple output battery charger based on the phase shift full bridge topology to charge a multiple number of batteries at one time. The proposed converter can charge three different kinds of batteries or same kind of batteries in different state of charges (SOCs) by using constant current/constant voltage (CC/CV) charge mode independently. At the same time it can provide an even degree of tight regulation for each output to satisfy the strict ripple requirement of the battery. The validity and feasibility of the proposed method are verified through the experiments.