• 한국경영과학회지
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• 제32권3호
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• pp.1-15
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• 2007

In this paper, the return link of interactive GEO satellite network providing multimedia services is considered. First, we classify data by delay characteristics, and analyze the numbers of expected lost packets and expected delay packets for each data class of each terminal. Next we mathematically formulate optimal rate scheduling model to minimize the weighted sum of the numbers of expected lost packets and expected delay packets considering priority of each data class. We also suggest a dynamic rate scheduling scheme based on Lagrangean relaxation technique and subgradient technique to solve the proposed model in a fast time. Extensive experiments show that the proposed scheme provides encouraging results.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 통신소사이어티 추계학술대회논문집
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• pp.172-175
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• 2003

In this paper we propose a method fur the evaluation of the quality of service for VoIP services in NGN. Specifically, let us anatomize the elements of delay of a voice connection in the network in an end-to-end manner and investigate expected value at each point. We extract the delay time in each element in the network such as gateway, network node, and terminal equipment, and estimate an upper bound fur the tolerable delay in each element.

• 한국통신학회논문지
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• 제37B권12호
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• pp.1174-1185
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• 2012

본 논문은 무선메쉬네트워크 환경에서 패킷의 지연 보장을 위한 호 접속 제어 방안을 제안하였다. 각 노드에서 클래스별 가용 대역폭을 구하여 지연 성능을 예측하고 이를 기반으로 호 접속 허용 여부를 결정짓는다. 새로운 트래픽 증가로 인해 영향 받는 모든 노드들을 호 접속 제어에 반영하여 기존 트래픽의 지연 성능이 보전되도록 하였다. 그 과정에서 추가적인 메시지 교환 없이 간섭 노드들의 가용 대역폭을 효과적으로 관측하는 방안을 제시하였다. 클래스 간의 차별화된 지연 제어는 큐잉 정책으로 수용하여 MAC 동작을 간결하게 하였다. 컴퓨터 시뮬레이션을 이용하여 제안된 방식의 타당성을 확인하였다. 새로운 호 추가에 따르는 지연 예상이 적절하게 이루어짐을 확인하였고, 호 접속 제어 기능으로 지연 성능이 보장되는 것을 보였다.

• Journal of the Optical Society of Korea
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• 제7권4호
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• pp.224-229
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• 2003

We report a novel optical delay line that can be implemented using only optical fiber and fiber devices without the need for any bulk-optic devices such as lens, prism, and moving mirror. The dispersive property of a chirped fiber Bragg grating (CFBG) is exploited to get the delay. The proposed delay line constitutes two identical CFBGs cascaded in the reverse order with one of them being strained. Analysis reveals that the small displacement or the strain applied on the CFBG is effectively amplified in the delay line by the ratio of the minimum resonant wavelength and the reflection bandwidth of the CFBG. The dispersion properties of the CFBG with and without the strain are analyzed in detail. The theoretical performance of the proposed delay line is also discussed. Applications of the proposed delay line are expected in the field of high-speed optical coherence tomograpy.

• 한국통신학회논문지
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• 제21권9호
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• pp.2494-2504
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• 1996

This paper describes about the spread specturm radio wave propagation characteristics in urban microcells. The experiments are carried out with respect to the mean excess delay, the RMS delay spread, and the received maximum peak power in the two kinds of geogrphical areas, LOS area and N-LOS area, especially whose variations are observed while varying the transmission distance and tilting the transmitting antenna. The typical results obtained in pariticular urban sites in Seoul are 300-600 nsec of mean excess delay and about 75 nsec of averaged RMS delay spread for LOS area, and 270-280 nsec of mean excess delay and about 100 nsec for N-LOS area. With the transmitting antenna gilted, obsered in the experiments are increase in RMS delay spread as expected, but increase of the received power at N-LOS areas in particular.

• Industrial Engineering and Management Systems
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• 제9권3호
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• pp.262-274
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• 2010

This article investigates how to adaptively predict the time-varying metrology delay that could realistically occur in the semiconductor manufacturing practice. Metrology delays pose a great challenge for the existing run-to-run (R2R) controllers, driving the process output significantly away from target if not adequately predicted. First, the expected asymptotic double exponentially weighted moving average (DEWMA) control output, by using the EWMA and recursive least squares (RLS) prediction methods, is derived. It has been found that the relationships between the expected control output and target in both estimation methods are parallel, and six cases are addressed. Within the context of time-varying metrology delay, this paper presents a modified recursive least squares-linear trend (RLS-LT) controller, in combination with runs test. Simulated single input-single output (SISO) R2R processes subject to various time-varying metrology delay scenarios are used as a testbed to evaluate the proposed algorithms. The simulation results indicate that the modified RLS-LT controller can yield the process output more accurately on target with smaller mean squared error (MSE) than the original RLSLT controller that only deals with constant metrology delays.

• 한국항공운항학회지
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• 제13권4호
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• pp.1-10
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• 2005

According to the aviational definition, the fog is an obscuration phenomenon when prevailing visibility becomes less than 1,000m. Fog defined above causes so many aviation traffic problems like detour, flight delay and cancel. Therefore this study investigated quantitatively the fog effects on flight operation using flight delay and cancel statistic data during last four years from 1st Jul. 2001 to 30th Jun. 2005 at the Incheon Int'l Airport. The results of this study show that the hazardous meteorological condition is a important cause of flight delay and cancel, especially fog phenomenon. And it is expected that the results of this study give us the necessary and importance of fog prediction at the Incheon Int'l Airport.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2000년도 추계학술대회
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• pp.329-333
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• 2000

Delay time analysis is a pragmatic mathematical concept readily embraced by engineers which has been developed as a means to model maintenance decision problem. This paper considers an inspection period using delay time analysis for fishing vessel equipment. We assume that delay time distribution is Weibull and inspections are perfect. In this paper, we determine the optimal inspection period which minimize the expected downtime per unit time.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2015년도 춘계 학술논문 발표대회
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• pp.190-191
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• 2015

Construction delays occur frequently in outrigger framework of tall buildings due to the unexpected conditions and lack of experience. However, delay factors of the outrigger framework has not been managed efficiently. Therefore, the systematic management is needed by perceiving possible delay factors before constructing management system. In this study, the major delay factors of outrigger framework are conducted to derive by using the Importance Performance Analysis(IPA). It is expected that the results of this study are utilized for planning of systematic scheduling in outrigger framework of tall building.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2011년도 춘계 학술논문 발표대회 1부
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• pp.191-192
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• 2011

The construction projects contain a lot of variables and risk affecting productivity. The duration of the project must be recognized important as for quality, unit cost and safety. There is need for improving work efficiency by investigating relationship of works to prevent delay. This study focuses on analysing the delay factors of steel staircase system to suggest regression model that enables construction productivity estimation. The position of the observers and construction delay factors were expressed by the independent variable of the regression model and productivity was expressed by a dependent variable. This paper suggests quantitative productivity and it is expected that will be helpful estimating application in construction new technologies.