• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.5
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• pp.837-844
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• 2019

In this paper, we propose the AMBM(: Adaptive Multi-channel Backoff Machisum) -Mac protocol to provide high throughput for non-safety applications in VANET(: Vehicular Ad Hoc Networks) environment. The proposed protocol guarantees the quality of service of non-safety packets by dynamically adjusting CW(: Channel Window) of WSA(: WAVE Service Advertisement) to maximize throughput between non-safety packets of different priority. It also shows that allocating a large amount of time for channel coordination and time slot reservation for SC and dynamically adjusting CW and CCI as nodes increase to reduces transmission delay than IEEE 1609.9, C-MAC(: Coordinated multi-channel MAC, and Q-VCI(: QoS Variable CCH Interval) protocols.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.05a
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• pp.38-41
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• 2005

IGBT를 이용한 형광등 백라이트 제어기를 설계 제작하여 특성 실험을 한 결과, 타 방식의 백라이트 제어기 비하여 고효율, 고역률, 고품질의 특성을 가지는 한편, 스위칭 시에 발생하는 피크 전류 및 노이즈로 인한 인접 전기전자기기에 영향을 미치지 않도록 함으로써 안정성이 뛰어나며, 또한 기존의 슬라이닥스를 이용한 전원장치를 대체하는 한편 원격제어를 손쉽게 구현할 수 있는 장점을 가지고 있다. 또한 본 제어기는 제로크로싱 동기를 채택하여 온 오프 시에 발생하는 피이크 전류를 방지함으로서 제품의 안전성을 극대화시킬 수 있는 장점을 가지고 있어 차후 산업용 전원 장치 및 각종 가변 전원을 필요로 하는 대상에도 광범위하게 응용될 수 있을 것이다.

• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.435-436
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• 2015

본 논문에서는 벅 컨버터와 플라이백 컨버터를 직렬로 결합한 회로를 바탕으로 하여 높은 입력전압의 범위를 갖는 새로운 SMPS 토폴로지 및 스위칭기법을 제안하였다. 제안한 고압용 SMPS에서 벅 컨버터는 감압을 위한 온-오프 제어를 행하고, 플라이백 컨버터는 출력전압 제어를 행한다. 제안한 회로는 기존에 특정 목적을 위해 구성된 SMPS의 한계를 극복하고, 다양한 입력전압에 대해 안정된 출력전압을 제어하기 위한 토폴로지이다. 제안된 회로는 PSIM 시뮬레이션을 통하여 그 타당성을 검증하였다.

• Proceedings of the KIEE Conference
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• 2005.10c
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• pp.205-207
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• 2005

플라이백 컨버터의 경계점 도통 모드 운전은 변압기의 자화인덕턴스 전류를 연속과 불연속의 경계에서 도통시킴으로써 기존의 고정주파수 컨버터에서 소프트 스위칭을 위하여 사용하였던 별도의 스위치나 보조회로를 추가하지 않으면서 전력소자의 소프트 스위칭을 가능하게 하는 장점을 가진다. 본 논문에서는 스위치의 온 오프시 변압기의 인덕턴스와 스위치의 기생 커패시터 성분이 일으키는 공진구간을 전체 스위칭 주기에 포함시킴으로써 경계점 도통 모드 운전에서 부하출력에 따른 스위칭 주파수의 변화를 보다 정확히 제시하고 이를 바탕으로한 정상상태모델링을 통하여 경계점 도통 모드 플라이백 컨버터의 여러 운전 특성을 분석하였다.

• Journal of Korea Multimedia Society
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• v.6 no.5
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• pp.849-860
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• 2003

As mobile device is becoming more popular, E-Commerce changes into M-Commerce. Especially, IMT-2000 (International Mobile Telecommunication 2000) service is prepared for M-Commerce and this has USIM (Universal Subscriber Identity Module) as a core of certification of individuality and transactions. As a result, the area of mobile service going to expand by USIM. But, mobile services using USIM leave much to be desired, and developed application don't variety. In this paper, for the efficient design of USIM, the structure of USIM and protocol is analyzed, and secure payment solution in USIM is proposed. Specially, offline payment system is proposed for the verification of proposed protocols including security, saving, and calculation of balance. finally, the simulation of proposed payment system on USIM is performed using Java Card.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.4
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• pp.351-361
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• 2014

Compared to a terrestrial communication, the high BER(Bit Error Ratio) and low channel bandwidth are the major factor of throughput degradation due to characteristics of underwater channel. Therefore, a MAC protocol must be designed to solve this problem in UWASNs(Underwater Acoustic Sensor Networks). MAC protocols for UWASNs can be classified into two major types according to the contention scheme(Contention-free scheme and Contention-based scheme). In large scale of sensor networks, a Contention-based scheme is commonly used due to time-synchronize problem of Contention-free scheme. In the contention-based scheme, Each node contends with neighbor nodes to access network channel by using Back-off algorithm. But a Slot-Time of Back-off algorithm has long delay times which are cause of decrease network throughput. In this paper, we propose a new scheme to solve this problem. The proposed scheme uses variable Slot-Time instead of fixed Slot-Time. Each node measures propagation delay from neighbors which are used by Slot-time. Therefore, Slot-Times of each node are optimized by considering node deployment. Consequently, the wasted-time for Back-off is reduced and network throughput is improved. A new mac protocol performance in throughput and delay is assessed through NS3 and compared with existing MAC protocol(MACA-U). Finally, it was proved that the MAC protocol using the proposed scheme has better performance than existing MAC protocol as a result of comparison.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.8
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• pp.9-18
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• 2004

The IEEE 802.11 Distributed Coordination Function(DCF) protocol provides a contention-based distribution channel access mechanism for stations to share the wireless medium. However, the performance of the DCF drops dramatically in terms of throughput, delay and delay jitter as the number of active stations becomes large. In this paper, we propose a simple and effective scheme, called DCF/VG(Distributed Coordination Function with Virtual Group), for improving the performance of the IEEE 802.11 DCF mechanism. In this scheme, each station independently decides the virtual group cycle using the information provided by the carrier sensing mechanism. The virtual group cycle consists of one or more virtual groups and a virtual group includes an idle period and a busy period. Each station operates in only one out of several virtual groups of the virtual group cycle and does not operate in the others. In other words, each station decreases its backoff counter and tries to transmit a packet only in its virtual group like the IEEE 802.11 DCF. Performance of the proposed scheme is investigated by numerical analysis and simulation. Numerical and simulation results show that the proposed scheme is very effective and has high throughput and low delay and jitter under a wide range of contention level.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.184-185
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• 2011

본 논문에서 coupled inductor를 이용한 새로운 고승압비 컨버터를 제안한다. 제안하는 컨버터는 스위치 전압 스트레스를 낮게 가져갈 수 있고 출력 다이오드 전압 스트레스도 출력 전압으로 제한된다. 추가적으로 공진 탱크의 최적 설계를 통해 스위치 턴 오프 손실을 저감시킬 수 있다. 기본적인 동작원리 및 특성을 좀더 자세하게 다루고, 실험 결과를 통해 제안하는 컨버터의 효용성을 보인다.

• Proceedings of the Korea Contents Association Conference
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• 2004.05a
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• pp.439-442
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• 2004

CBD 개발 방법론의 발전으로 많은 컴포넌트가 개발되면서 소프트웨어의 빠른 기술변화는 시스템 개발 생명주기가 갈수록 짧아지고 있으며, 최근 들어 시스템 개발에 있어서 오프라인보다 온라인으로 시스템 개발이 늘고 있다. 때문에 실시간으로 컴포넌트 형상관리의 필요성이 나타나고 있으며, 보다 향상된 기술의 개발방법이 요구되고 있다. 본 연구에서는 이를 위한 하나의 해결방법인 형상관리(Configuration Management)를 제안하고, 실시간 컴포넌트 형상관리 작업에 필요한 요구사항에 대해 기술하였다.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.37 no.5
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• pp.11-116
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• 2000

A topology decreased switching loss and voltage stress by zero voltage switching is presented in this paper. Generally, Switching mode converting productes voltage stress and power losses due to excessive voltage and current. which affect to performance of power supply and reduce overall efficiency of equipments. Virtually, In flyback converter, transient peak voltage and current at switcher are generated by parasitic elements. To solve these problems, present ZVS flyback converter topology applied a auxiliary circuit. Incorporation of auxiliary circuit into a conventional flyback topology serves to reduce power losses and to minimize switching voltage stress. Snubber capacitor in auxiliary circuit serves ZVS state by control voltage variable time at turn on and off of main switch, then reduces voltage stress and power losses. The proposed converter has lossless switching in variable load condition with wide range. A detailed analysis of the circuit is presented and the operation procedure is illustrated. A (50W 100kHz prototype) ZVS flyback converter using a auxiliary circuit is built which shows an efficiency improvement as compared to a conventional hard switching flyback converter.