• 한국통신학회논문지
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• 제25권10B호
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• pp.1707-1713
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• 2000

We have proposed a tunable optical ADM using a fiber-optic transversal filter which is composed of fiber couplers and metal-film coated fiber-optic tapped delay-lines with a flat spectral response in abroad range of wavelength. Simulation results show that the optical loss at the DROP and PASS wavelengths of the OADM is negligible and the wavelength tunability is 0.78${\mu}{\textrm}{m}$/ps for the unit time delay of 2 ps. In order to investigate the effects of wavelength drift of the imput optical signal on the OADM the loss at the DROP port and the crosstalks to the other ports have been calculated. The maximum bit rates have been calculated at 46.26 Gb/s for the input Gaussian pulse width of 10 ps.

• 대한안전경영과학회지
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• 제12권3호
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• pp.163-168
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• 2010

Recently, there are many problems of service qualities such as regular-rapid-safe -comfortable transport, that was traditionally advantages in urban railway transportations. These problems cause train delays that affects consecutive schedule, capacity, operation plans, and it is hard to prevent the propagation of delay and find the recovery solution. Because the urban transport demands is continuously increased and the railway service is also expanded, the railway operation company makes efforts to improve operation performance and efficiency for passengers. In this paper, we analyse the issues and problems existing in the major operation line of high-density urban railways, and suggest the development direction of intelligent operation technology to improve the urban railway service by minimizing the occurrence and propagation of delay. And the result of numerical case study is also presented.

• Journal of Communications and Networks
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• 제15권6호
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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.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.673-678
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• 2008

In crushed service areas of Metro railway lines, there are problems such as the buildup discontent, the irregular operation time and rotation of rolling stocks, caused by frequently occurred train delay. Train delay is affected by operation conditions or infrastructure capacities such as train schedule, line capacity, car rotation plan, shunting movements at origin and destination, and also by transport demand characteristics. Furthermore, a delay produce another delays and spread over the following trains. So it is not easy to build up a protection and recovery plan. In this research, we conduct experimental analysis study based on the real metro data, and as a result, present the relation between the traffic demand and the dwell time. And finally, propose future research themes for improving the operation efficiency of metro railways.

• 전기학회논문지
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• 제65권6호
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• pp.955-961
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• 2016

Fault location estimation is an important element for rapid recovery of power system when fault occur in transmission line. In order to calculate line impedance, most of fault location algorithm uses by measuring relaying waveform using DFT. So if there is a calculation error due to the influence of phasor by DC offset component, due to large vibration by line impedance computation, abnormal and non-operation of fault locator can be issue. It is very important to implement the robust fault location algorithm that is not affected by DC offset component. This paper describes an enhanced fault location algorithm based on the DC offset elimination filter to minimize the effects of DC offset on a long transmission line. The proposed DC offset elimination filter has not need any erstwhile information. The phase angle delay of the proposed DC offset filter did not occurred and the gain error was not found. The enhanced fault location algorithm uses DFT filter as well as the proposed DC offset filter. The behavior of the proposed fault location algorithm using off-line simulation has been verified by data about several fault conditions generated by the ATP simulation program.

• 한국통신학회논문지
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• 제32권3A호
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• pp.261-270
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• 2007

실시간과 비실시간 서비스 클래스의 각 QoS요구 사항을 만족하면서 전체 시스템 용량을 최대화하기 위하여 DTPQ스케줄링 알고리즘이 제안된 바 있다. 기존 DTPQ방식은 개별 서비스 클래스의 QoS를 만족하면서 전체 시스템의 평균 수율을 극대화하기 위해 실시간 서비스의 HOL 패킷의 지연 시간이 정해진 임계값을 넘는 경우에만 서비스하는 접근으로서, 이를 구현하기 위해서는 주어진 환경에서 적절한 지연 임계값을 설정할 수 있어야 한다. 본 논문에서는 실시간 사용자의 채널 상태와 지연 시간에 따라 지연 임계값을 적응적으로 적용하는 A-DTPQ 기반의 스케줄링 기법을 제안한다. 이는 기존의 DTPQ알고리즘과 달리 트래픽 부하 및 채널 특성 등에 따라 지연 임계값을 적응적으로 결정하는 방식이다. 시스템 레벨 시뮬레이션을 통해 제안 방식의 고정된 최적 임계값을 가지는 DTPQ방식보다 성능이 향상시킬 수 있음을 확인하였으며, 향후 연구에서는 다양한 서비스 클래스에 대해 이와 같은 개념을 일반화할 수 있을 것이다.

• 한국전자파학회논문지
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• 제17권8호
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• pp.739-745
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• 2006

본 논문은 공진 회로를 이용하여 군지연 시간을 조정할 수 있는 방법을 제안하였다. 군지연 시간을 조정할 수 있는 군지연 시간 조정기(GDTA)는 가변 캐패시터와 가변 등가 인덕터로 구성되어 있다. 가변 캐패시터와 가변 등가 인덕터는 병렬로 연결되어 있으며 각각 다른 바이어스에 의해 조절된다. 가변 등가 인덕터는 높은 임피던스를 갖는 전송 선로에 가변 캐패시터를 연결하여 구현했다. 군지연 시간은 병렬로 구성된 회로의 캐패시턴스와 인덕턴스의 변화에 의해 조정되어진다. 이 때, 공진 주파수는 고정되어지도록 해야 한다. 제안된 GDTA는 RFID 주파수 대역$(908.5{\sim}914 MHz)$에 맞추어 제작되었고, 군지연 시간의 조정범위는 약 3ns였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 V
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• pp.2851-2854
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• 2003

The purpose of this paper was to find out the stabilized and effective value of RC-parameter by using PSpice simulation, considering that gate signal voltage can be distorted by RC-delay of signal line. the results of this study were as follows: TFT-LCD with high quality resolution increased the number of gate signal line and this made TFT on-time shorter over-width of signal line to improve the performance of TFT made the electrostatic capacity increase and the time constant higher, making problems and errors. and owing to the decrease of the aperture ratio, an electro optic character of LCD, we must consider the capacity and the condition of production process in deciding the width and the thickness of the gate signal line.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.518-523
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• 2000

As the delay of the Kyungbu High Speed Railroad, HST should use conventional line through Daegoo to Pusan until the new railroad build. High speed railroad noise is one of the main causes of environmental impact. Whenever HST on conventional railroad line is planned or a housing project near an existing railroad is proposed, an estimate of the relevant noise levels is usually required. For this, it is necessary to Quantify those parameters that affect the railroad noise. This paper deals with an estimation of high speed railroad noise on conventional line.

• 한국광학회지
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• 제17권1호
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• pp.7-17
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• 2006

본 논문에서는 FBG 프리즘을 이용한 파장 의존형 광 실시간 지연선로(wavelength-dependent optical true time-delay; WDOTTD) 와 2${\times}$2 광 스위치의 크로스 포트에 각기 다른 길이의 광섬유 지연선로를 연결한 광섬유 지연선로 행렬인 파장 비의존형 광 실시간 지연선로(wavelength-independent optical true time-delay; WIOTTD)로 구성된 평면 위상 배열 안테나용 OTTD 구조를 제안하였다. 최대 시간 지연 차이가 810 ps인 WDOTTD와 $\pm$50 ps인 WIOTTD를 직렬 연결하여 10-GHz, 2비트${\times}$4비트 2차원 OTTD를 제작하였고, 모든 주사각에 대해서 시간지연과 삽입손실을 측정하였다. 광섬유 지연선로 행렬을 이용한 4-비트 WIOTTD의 시간 지연 측정오차는 $\pm$1 ps이하로 나타났다. 또한, 제안된 광 TTD의 성능을 분석하기 위하여, 8${\times}$8 마이크로스트립 안테나 소자들로 구성된 10-GHz 평면 PAA의 방사 패턴을 시뮬레이션으로 측정하고 분석하였다.