• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.359-360
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• 2009

홈 네트워크 구축의 핵심 부품인 전력선 통신용 블로킹 필터를 제조하였으며, 신호 감쇄 특성을 측정하고 적용가능성을 평가 하였다. 전자장 모의 해석을 통하여 자심재료에 대한 포화자속밀도 특성을 분석 하였으며, 최소의 크기를 갖는 I 형상의 자심재료에 $3.2\Phi$의 나동선을 10.5턴 권선하여 대용량 인덕터를 제조하고, $4.3\;{\mu}H$의 인덕턴스를 구현하였다. 설계된 대용량 인덕터를 적용하여 30A급의 블로킹 필터를 제조하였고, 1.7 MHz ~ 30 MHz 대역에서의 -60 dB의 신호감쇄 특성을 얻었다.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.4
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• pp.10-19
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• 1998

With the advent of high-speed networks, the increasingly stringent performance requeirements are being placed on the underlying switching systems. Under these circumstances, simulation methods for evaluating the performace of such a switch requires vast computational cost and accordingly the importance of anlytical methods increases. In general, the performance analysis of a switch architecture is also a very difficult task in that the conventional queueing system such as switching systems, which consists of a large numbe of queues which interact with each other in a fiarly complicated manner. To overcome these difficulties, most of the past research results assumed that multiple queues become decoupled as the switch size grows unboundely large, which enables the conventional queueing theory to be applied. In this apepr, w analyze a non-blocking space-division ATM swtich with input queueing, and prove analytically the pheonomenon that virtual queues formed by the head-of-line cells become decoupled as the switch size grows unboundedly large. We also establish various properties of the limiting queue size processes so obtained and compute the maximum throughput associated with ATM switches with input queueing.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.05a
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• pp.288-292
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• 2002

We propose the new type of on-chip ESD protection method for RF applications. By using the properties of RF circuits, we can use the short-circuited stub as ESD protection device in front of the DC blocking capacitor Specially, we can use short-circuited stub as the portion of the matching circuit so to reduce the and various parameters of the transmission line. This new type ESD protection method is very different from the conventional ESD protection method. With the new type ESD protection method, we remove the parasitic capacitance of ESD protection device which degrade the performance of core circuit.

• Journal of Communications and Networks
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• v.15 no.6
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• pp.614-634
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• 2013

The proliferation of real-time multimedia services requires huge amounts of data transactions demanding strict quality-of-service (QoS) guarantees. Multicast transmission is a promising technique because of its efficient network resource utilization. However, high head-of-line (HOL) blocking probability and lack of service-specific QoS control should be addressed for practical implementations of multicast networks. In this paper, a topology aware fanout set division (TAFD) scheme is proposed to resolve these problems. The proposed scheme is composed of two techniques that reduce HOL blocking probability and expedite packet delivery for large-delay branches regarding multicast tree topology. Since management of global topology information is not necessary, scalability of the proposed scheme is guaranteed. Mathematical analysis investigates effects of the proposed scheme and derives optimal operational parameters. The evaluation results show that the TAFD scheme achieves significant delay reduction and satisfies required delay bounds on various multicast networks.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.8
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• pp.1508-1516
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• 2017

Multipath TCP (MPTCP) is a transport layer protocol that supports multipath transmission. If a bufferbloat occurs in one of the subflows of MPTCP, HoL blocking occurs at the receiver due to the difference in packet arrival time among paths. In MPTCP, HoL blocking degrades not only the performance of the path where bufferbloat occurs, but also the performance of other paths. In this paper, we propose a bandwidth measurement based scheduler to solve this problem. Bandwidth measurement based scheduler is designed to measure the bandwidth of each subflow and to perform packet scheduling based on it. In order to verify the proposed scheduler, we implemented the proposed scheduler in the Linux kernel and constructed a testbed in which bufferbloat occurs. Experimental results show that the proposed scheduler has better performance than the legacy MPTCP in bufferbloat environment.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.2 no.2
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• pp.3-10
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• 1991

The new structure method of GaAs microwave amplifiers using DC block function and impedance transforming property of DC block/transformer(non-symmetrical two - microstrip coupled line and interdigital three - microstrip coupled line), instead of chip capacitor, is presented. The newly structured microwave amplifier showed wideband characteristics(bandwidth, 3.5 GHz) and flat frequency response. Interdigital three - microstrip coupled line which is used for microwave amplifier can be used to match amplifiers as well as DC blocking.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.6
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• pp.1116-1122
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• 2009

ATS(Automatic Train Stop) system makes train stop when it runs over the speed limit and ensure the safe operation of train. Seoul Metro line 2 in Korea, which started its passenger service in 1982, has adopted ATS system for its signaling system. The ATS system has only a train stop function at the time of emergency, and Seoul Metro is planning to replaced them with ATC(Automatic Train Control)/ATO(Automatic Train Operation) system which can provide the dedicated speed control for headway reduction and automatic operation of train. Until all the ATS system is replaced with the new ATC system, both systems are to operate simultaneously at the same metro line. In this situation, ATS system sometimes reveals improper operation: train stops suddenly without any obstacles in front of it. These emergency stops cause interruption of passenger service, and abnormal abrasion of wheels and rail. This paper makes it clear that these interruptions are caused by EMI phenomena between ATS on-board device and ATC wayside device : Signal current flowing in AF track circuit of ATC is turn out to be a EMI source that prevent normal operation of the ATS on-board device. Although the two systems have different frequency-ranges (ATS system has frequency range between $78{\sim}130$[kHz] and ATC system has frequency range between $9.5{\sim}16.5$[kHz]), it turned out that EMI phenomena appears between the both systems. This is investigated by measuring the output signal from ATS on-board device passing over ATC wayside device. The FFT(Fast Fourier Transform) analysis of the signal reveals that AF track circuit signal is transmitted to the ATS on-board device and induce noise causing improper operation. The countermeasures to the EMI phenomena are examined in three ways; blocking EMI transmission, enforcement of EMS (Electromagnetic Susceptibility) of ATS on-board device, and blocking the EMI source. It is suggested that the practical solution be blocking EMI source temporarily, that is breaking AF track circuit signal when the trains with ATS on-board device pass over it. To this purpose, TODS(Train Occupation Detection System) is developed, and has made a success in preventing the EMI problem of Seoul Metro line 2.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.3
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• pp.432-438
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• 2001

In this paper, after applying Defected Ground Structure(DGS) to DC block, changes of gap and length of λ/4 coupled line are investigated by EM simulation and fabrication. As a result, on condition of the same output with the case using typical DC block, the gap between λ/4 coupled line is widen from 0.1 mm to 0.46 mm by 0.36 mm and the length of λ/4 coupled line gets shorter from 17.7 mm to 13.2 mm by 4.5 mm. Also three type power amplifiers using blocking capacitor, typical DC block and DGS DC block are fabricated and investigated. At first, when S parameter characteristics of each amplifier are considered at frequency band of 3.2 +-0.O5 GHz, every amplifier has similar characteristics of gain and S parameter. Second when the output power of amplifiers is 25 dBm after putting CW signal of 3.2 GHz into three type amplifiers, the difference of dominant signal and 2nd harmonic signal using blocking capacitor, typical DC block and DGS DC block is each -44.83 dBc, -66.84 dBc and -64.33 dBc. Therefore harmonic characteristics of amplifiers using typical DC block and DGS DC block is almost same.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.1247-1252
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• 2004

ATC(Automatic Train Control) system employed in Bundang urban transit is operated in accordance with automatic blocking equipment. Using AF(Audio Frequency) track circuits installed at a block section, the block signal is automatically controlled and the safety of train operation is supported. In this paper, we investigate the operation mode of bundang urban transit and analyze the operation algorithm of ATC on-board system.

• Proceedings of the Korea Society for Simulation Conference
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• 2002.05a
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• pp.133-138
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• 2002

생산라인에서 시스템의 생산율을 높이기 위해서는 각 Stage에 새로운 기계를 추가하거나, 버퍼를 설치할 수 있다. 새로운 기계를 추가하게 되면, 그 Stage의 생산속도를 증가시켜 전체 시스템의 생산율을 높일 수 있고, 버퍼를 설치하게 되면 Starvation과 Blocking을 줄여 생산율을 높일 수 있다. 본 연구에서는 각 Stage에서 고장과 수리가 확률적으로 발생하는 여러 대의 기계가 있고, 유한한 용량의 버퍼가 있을 때, 전체 시스템의 생산율을 구하는 방법을 제안한다.