• 정보처리학회논문지C
• /
• 제11C권2호
• /
• pp.263-268
• /
• 2004

멀티미디어 응용 서비스에서는 특정 시간 내에 데이터 전송이 이루어져야 하는 시간 의존성이 있다. 이러한 실시간 특성은 네트웍의 QoS 보장을 위한 중요한 요소이다. 네트웍 사용자의 증가와 응용 프로그램의 데이터 전송율의 증가로 네트웍 자원을 효율적으로 사용하기 위한 연구는 계속 진행되고 있다. 종단간(End-to-End) 지연시간 제한 조건을 만족하면서 최소 비용을 갖는(Delay Constrained Least Cost, DCLC) 경로를 찾는 문제는 이미 NP-hard 문제로 알려져 있다. 최소 지연시간 경로의 비용은 최소 비용 경로의 비용보다 상대적으로 높은 경로 비용을 갖으며, 역으로 최소 비용 경로의 지연시간은 최소 지연시간 경로의 지연 시간보다 상대적으로 높은 지연시간을 갖는다. 본 논문에서는 이러한 단점을 극복하여 DCLC문제에 접근하기 위해 링크비용과 지연시간을 확률적으로 조합한 인자를 사용한 새로운 알고리즘을 연구하였다. 최근 Salama에 의해 제안된 DCUR 알고리즘은 최적에 가까운 알고리즘이나, 제안한 알고리즘은 DCUR 알고리즘과 비교하여 종합적인 컴퓨터 시뮬레이션 결과에 의하면 노드 수 200에서 38% 이상의 효과를 보았다. 본 알고리즘의 특징은 선택의 요소로서 새로운 인자를 만들었고, 링크를 순차적으로 선택하지 않고 동적으로 선택하는 방법을 구현하였다는 것이다.

• 한국항행학회논문지
• /
• 제25권5호
• /
• pp.320-326
• /
• 2021

항공사에서 정시성(on-time performance, OTP)이란, 항공사의 신뢰성의 척도이며, 타 항공사와 비교할 때 중요한 지표로 활용된다. 본 연구는 코로나로 인해 항공 편수가 급격히 줄어든 2020년 3월을 기준으로 전후 1년간의 국내 K항공사 자료를 분석하여 지연 요인들이 항공사의 정시성에 미치는 영향 및 강도를 분석하였다. 또한, 계절에 따른 기상 영향으로 발생되는 지연을 분석하였으며, 코로나 상황으로 급감한 승객이 지연요인에 어떠한 영향을 주는지 연구하였다. 지연 요인(delay factor)은 IATA의 지연 코드(delay code)에 자체 코드를 추가한 K 항공사의 지연 코드를 적용하였다. 본 연구의 분석을 바탕으로 항공사의 정시성에 영향을 주는 지연 요인을 최소화하는 방안을 제안하고자 한다.

• 한국군사과학기술학회지
• /
• 제16권2호
• /
• pp.191-198
• /
• 2013

Geo-pointing is a function that maintains LOS(Line of Sight) to a stationary ground target by controlling azimuth and elevation angles of a EOS(Electro-Optical System) which are calculated from aircraft navigation data and target coordinates. In design and implementation of the geo-pointing, a transmission time delay between GPS/INS and EOS is a major degradation factor of the geo-pointing performance when the aircraft is rapidly maneuvered especially. In this paper, a kalman filter is designed to compensate the transmission time delay of aircraft navigation data. Simulation and test results show that the geo-pointing performance is enhanced by the proposed compensation technique.

• 한국암반공학회:학술대회논문집
• /
• 한국암반공학회 2009년도 학술발표회 논문집
• /
• pp.73-82
• /
• 2009

터널외곽에 적용하는 지발뇌관의 시차 정밀도 차이가 터널의 여굴 형성에 어떠한 영향을 미치는가를 알아보기 위하여 Particle Flow Code 2D (PFC2D)라는 개별요소법을 기반으로 하여 개발된 상용프로그램(Itasca CG, 2004)을 사용하여 분석하였다. 그 결과 시차 정밀도가 정확하면 정확하지 않은 것보다 모암의 손상 및 여굴이 감소하는 것으로 나타났다.

• 전자공학회논문지A
• /
• 제33A권2호
• /
• pp.50-58
• /
• 1996

This paper proposes the channel-access protocol suitable to a very high speed photonic WDM network with star configuration, which can provide a high channel utilization and insensitivity to the propagation delay. The proposed protocol employs a control channel and a simple status table to deal with the propagation delay which has been a major limiting factor in the performance of the very high speed optical communication networks. The control channel transmits control information in order to reserve access on data channels, and each node constitutes a status table after the reception of control pckets which holds information about the availbility of destination node and data channel. The proposed protocol is insensitive to the propagation delay time by removing necessity of the retransmission and by allowing parallel transmission of control packet and data packets. It is proved in analysis and discrete event simulation that the proposed protocol is superior in throughput and mean delay, especially at the high load conditions compared to the existing high speed channel-access protocols.

• 반도체디스플레이기술학회지
• /
• 제10권3호
• /
• pp.21-28
• /
• 2011

In recent years, owing to the development of the image processing technology, the research to build control system using a vision sensor is stimulated. However, a random time delay must be considered, because it works of a various time to get a result of an image processing in the system. It can be seen as an obstacle factor to a control of visual tracking in real system. In this paper, implementing two vision controllers each, first one is made up PID controller and the second one is consisted of a Smith Predictor, the possibility was shown to overcome a problem of a random time delay in a visual tracking system. A number of simulations and experiments were done to show the validity of this study.

• Journal of information and communication convergence engineering
• /
• 제5권4호
• /
• pp.295-299
• /
• 2007

This paper presents the ASF(Additional Secondary Factor) modeling of DGPS beacon signal. In addition to DGPS's original purpose, the feasibility to utilize DGPS system for timing and navigation has been studied. For timing and navigation, the positioning system must know the accurate time delay of signal traveling from the transmitter to receiver. Then the delay can be used to compute the user position. The DGPS beacon signal transmits the data using medium frequency, which travels through the surface and cause the additional delay rather than the speed of light according to conductivities and elevations of the irregular terrain. We introduce the modeling of additional delay(ASF) and present the results of implementation. The similar approach is Locan-C. Loran-C has been widely used as the maritime location system and was enhanced to E-Loran(Enhanced Loran). E-Loran system uses the ASF estimation method and is able to provide the more precise location service. However there was rarely research on this area in Korea. Hence, we introduce the ASF and its estimation model. With the comparison of the same condition and data from the original Monteath model and ASF estimation data of Loran system respectively, we guarantee that the implementation is absolutely perfect. For further works, we're going to apply the ASF estimation model to Korean DGPS beacon system with the Korean terrain data.

• Journal of Positioning, Navigation, and Timing
• /
• 제11권1호
• /
• pp.23-28
• /
• 2022

The eLoran system is a high-power terrestrial navigation system that is recognized as the most appropriate alternative to complement the GNSS's vulnerability to radio frequency interference. Accordingly, Korea has conducted eLoran technology development projects since 2016. The eLoran system developed in Korea provides 20 m positioning accuracy to maritime user in Incheon and Pyeongtaek harbor. To accurately calculate the position with the eLoran signal, it is necessary to apply a compensation method that mitigates the propagation delay. In this paper, we develop the compensation method to mitigate the eLoran signal propagation delay and evaluate the positioning performance in Incheon harbor. The propagation delay due to the terrain characteristics is pre-surveyed and stored in the user receiver. Real-time fluctuations in propagation delay compared to the pre-stored data are mitigated by the temporal correction generated at a nearby differential Loran station. Finally, two performance evaluation tests were performed to verify the positioning accuracy of the Korean eLoran system. The first test took place in December 2020 and the second in April 2021. As a result, the Korean eLoran service has been confirmed to provide 20 m location accuracy without GPS.

• 대한전자공학회논문지
• /
• 제11권6호
• /
• pp.1-15
• /
• 1974

본 연구는 탄성파 지연선에 이용되는 탄성표면파중에서 SH표면파 모우드에 대하여 이론적 해석을 하였으며 그 결과 전기-기계적 결합계수가 크며 또한 여전 매질내 깊이 방향으로 아주 작은 감쇠률을 갖고 표면을 따라 전파됨을 알았단. 예로서 PZT-4인 경우 에너지의 80%가 감쇠되는 깊이는 190파장이 된다. 또한 탄성표면파 지연선을 하나의 계단자강으로서 취급하여 삽입손실를 구하였으며 특히 SH표면파 모우드와 같이 전기-기계론 결합계수가 큰 경우는 인터디지탈 트랜스듀셔의 전극폭과 윤극간 간격 사이의 비에 따라 중심 주파수가 현저히 달라진다. 그리고 탄성파 지연선의 온도계수를 벌크파인 종파, 횡파에 대하여 구하였으며 LiTaO2 Z축방향 전파의 횡파는 지연시간의 온도계수가 5.4X10-6/℃로 아주 작아짐을 알았다. 또한 LiNbO3의 130°, 64° 로테이트 Y캇트, X전파의 탄성표면파의 온도계수가 이론치와 잘 일치함을 실험적으로 확인하였다.

• Asian Pacific Journal of Cancer Prevention
• /
• 제15권10호
• /
• pp.4339-4347
• /
• 2014

Purpose: This study aimed at exploring treatment delay (TD) among cancer patients in China with an attempt to develop a practical methodology facilitating frontline Chinese clinicians in promoting earlier cancer diagnosis and treatment. Materials and Methods: The study comprised framework development, qualitative interviews and paired factor rating. Framework development utilized systematic literature review, soft systems thinking and consensus groups. Qualitative interviews employed a checklist of open questions soliciting information about all the domains included the framework from cancer patients drawn via stratified randomized sampling of inpatients at 10 hospitals in Hefei, China. Paired factor rating used a self-developed computer aid and the interviewed patients as referring cases to weigh the relative importance of the factors listed in the framework in terms of their contributions to specific components of total delay (TD). Results: a) A conceptual framework was proposed consisting of a 6-step path to TD and 36 category determinants. b) A total of 227 patients were interviewed; their TD was 267.3 mean or 108 median days ranging from 0 to 2475 days; average appraisal, illness, behavioral, preparation and treatment delay accounted for 52.1%, 9.4%, 0.30%, 8.8% and 29.4% of the TD respectively. Individual side factors were rated substantially more important than environmental side factors (60% vs. 40%); most influential TD factors included cancer symptoms, overall health, family relations and knowledge about cancer and health. Conclusions: The framework proposed together with the interviewing and rating approaches used provide a potential new methodology for understanding cancer patients' TD and promoting earlier cancer treatment.