• Title/Summary/Keyword: NTP

Search Result 101, Processing Time 0.159 seconds

High-Performance Synchronization for Circuit Emulation in an Ethernet MAN

  • Hadzic Ilija;Szurkowski Edward S.
    • Journal of Communications and Networks
    • /
    • v.7 no.1
    • /
    • pp.1-12
    • /
    • 2005
  • Ethernet is being deployed in metropolitan area networks (MANs) as a lower-cost alternative to SONET-based infrastructures. MANs are usually required to support common communication services, such as voice and frame relay, based on legacy synchronous TDM technology in addition to asynchronous packet data transport. This paper addresses the clock synchronization problem that arises when transporting synchronous services over an asynchronous packet infrastructure, such as Ethernet. A novel algorithm for clock synchronization is presented combining time-stamp methods used in the network time protocol (NTP) with signal processing techniques applied to measured packet interarrival times. The algorithm achieves the frequency accuracy, stability, low drift, holdover performance, and rapid convergence required for viable emulation of TDM circuit services over Ethernet.

Oxidation of Soot Particles with O Radicals Generated in a AC Streamer Corona Discharge (AC 스트리머 코로나 방전으로 생성된 O 라디칼과 매연 입자의 산화반응)

  • Kim, Pil-Seung;Lee, Kyo-Seung;Hwang, Jung-Ho
    • Journal of the Korean Society of Combustion
    • /
    • v.8 no.1
    • /
    • pp.9-16
    • /
    • 2003
  • Carbon soot emission from combustion processes, especially from diesel engines, is a subject of growing concern since soot is known to seriously affect human health. Efforts have been made to oxidize soot particles utilizing Non-Thermal Plasma(NTP) techniques. When oxygen is carried into a plasma device, electrons generated by the plasma dissociate the oxygen, resulting in the formation of oxygen atoms. These highly activated atoms, called O radicals, are known as strong oxidizing agent. This paper presents concentration variations of CO and $CO_2$ at the exit of the plasma device, resulting from the soot oxidation by O radicals, with variations of inlet oxygen concentration, gas temperature, and gas flow rate. Based on the data, Arrehenious rate constants of reactions between C(s)+O and C(s)+O+O were proposed.

  • PDF

Effects of propane substitution for safety improvement of hydrogen-air flame (수소-공기 화염의 안전성 향상을 위한 프로판 첨가 효과)

  • Kwon, Oh-Chae
    • Transactions of the Korean hydrogen and new energy society
    • /
    • v.15 no.1
    • /
    • pp.12-22
    • /
    • 2004
  • In order to evaluate the potential of partial hydrocarbon substitution to improve the safety of hydrogen use in general and the performance of internal combustion engines in particular, the outward propagation and development of surface cellular instability of spark-ignited spherical premixed flames of mixtures of hydrogen, hydrocarbon, and air were experimentally studied at NTP (normal temperature and pressure) condition in a constant-pressure combustion chamber. With propane being the substituent, the laminar burning velocities, the Markstein lengths, and the propensity of cell formation were experimentally determined, while the laminar burning velocities and the associated flame thicknesses were computed using a recent kinetic mechanism. Results show substantial reduction of laminar burning velocities with propane substitution, and support the potential of propane as a suppressant of both diffusional-thermal and hydrodynamic cellular instabilities in hydrogen-air flames.

Tin Doping Mechanism in Indium Oxide by MD Simulation

  • Utsuno, Futoshi;Yamada, Naoomi;Kamei, Masayuki;Yasui, Itaru
    • The Korean Journal of Ceramics
    • /
    • v.5 no.1
    • /
    • pp.40-43
    • /
    • 1999
  • In order to investigate Sn substitution sites and interstitial O atoms in tin-doped indium oxide, molecular dynamics (MD) simulations were carried out. There are two kinds of cation sites in $In_2O_3$, namely b-site and d-site. NTP-MD simulations under the condition of 300 K and 0 GPa were performed with two kinds of cells substituted by Sn atoms at each site. The excess oxygen atom accompanied with Sn doping was also taken into consideration. According to the calculations of Sn potential energies in each site, it was revealed that Sn atoms were substituted for b-sites rather than for d-sites. It was also revealed that the interstitial excess oxygen atoms tend to be connected with the Sn atoms substituted for the d-sites Sn rather than for the b-site. There MD simulation results well agreed with the experimental results.

  • PDF

A study on the performance evaluation of high speed interprocessor communication netowrk in a large capacity digital switching system (대용량 전자교환기의 고속 내부통신망 성능 평가에 관한 연구)

  • 최진규;박형준;정윤쾌;권보섭;이충근
    • Journal of the Korean Institute of Telematics and Electronics A
    • /
    • v.33A no.5
    • /
    • pp.55-64
    • /
    • 1996
  • This paper presents performance evaluation of a new high speed inter-processor communication(HIPC) network for large capacity and high performance digitral switching system. The HIPC structure implements the fast reservation and concurrent arbitration technique (modified round-robin arbitration). The performance evaluation of HIPC was performed by not only computer simulation but also numerical approximation method which was derived for a single server multi-queue system with nonexhaustive cyclic service. The approximation results are almost same with that of computer simulation. The TDX-10 basic callscenario was applied to the HIPC netowrk and analyzed. these results were compared with TDX-10 IPC and shows that the difference of th emean waiting time in the TX buffer of NTP node increases sharply according to the increase of the message arrival rate.

  • PDF

Strain-specific mammary tumor development following life-time oral administration of Ochratoxin A in DA and Lewis rats

  • Son, Woo-Chan;Lee, Yong-Soon;Kang, Kyung-Sun
    • Proceedings of the Korean Society of Toxicology Conference
    • /
    • /
    • pp.39-40
    • /
    • 2003
  • Ochratoxin A (OA), a potent nephrotoxin in several species, is knownto be a renal carcinogen in animals and is implicated in the etiology of Balkan endemic nephropathy (BEN). The NTP (National Toxicology Program) classified Ochratoxin A as having clear evidence of carcinogenic activity, based on uncommon tubular adenomas and tubular cell carcinomas of the kidney and multiple fibroadenomas of the mammary gland, seen in the rat.(omitted)

  • PDF

A Study on Time Synchronization Method for IED Using IEC 61850 (IEC 61850용 IED의 시각 동기 방안 연구)

  • An, Yong-Ho;Kim, Byeong-Heon;Jang, Byung-Tae;Song, In-Jun;Kim, Young-Don;Jang, Su-Hyeong;Kim, Kyung-Ho
    • Proceedings of the KIEE Conference
    • /
    • /
    • pp.277-279
    • /
    • 2008
  • 현재 많은 전력계통용 보호제어 벤더들은 변전소 자동화 국제표준 프로토콜인 IEC 61850을 적용한 전력 장비들을 개발하여 변전소에 적용하고 있다. 이러한 많은 장비들은 표준화된 IEC 61850 프로토콜을 적용하여 상호 호환성을 유지하였으며, 기존에 적용되고 있는 표준화된 기술들을 채택하고 있다. 변전소 장비들은 정밀한 시간 동기를 위해서 표준화된 시각 동기 프로토콜인 SNTP(Simple Network Time Protocol)나 NTP(Network Time Protocol)를 사용하고 있다. 본 연구에서는 IEC 61850 프로토콜을 적용한 IED가 시각 동기 장치로부터 시간 동기화되는 방안에 대해 연구하였다.

  • PDF

A Study on Clock Synchronization at IEC61850 Process Level (IEC61850 프로세서 레벨에서의 시간 동기화에 관한 연구)

  • Kim, Gwan-Su;Nguyen Dinh Nhat;Lee, Hong-Hee
    • Proceedings of the KIPE Conference
    • /
    • /
    • pp.316-318
    • /
    • 2006
  • 현재 변전소 자동화의 국제표준으로 대두되고 있는 IEC61850은 스테이션 버스뿐만 아니라 프로세서 버스까지도 표준화된 통신 기술을 채용하였고, 자동화에 필요한 모델을 제시하고 있다. 본 연구에서는 IEC61850 프로세서 레벨에서 정밀한 시간동기화를 구현하기 위해 필요한 동기화 기술을 고찰하였다. 이와 더불어 전통적인 시간동기화 프로토콜인 NTP 및 최근 새롭게 개발된 시간동기화 프로토콜인 IEEE1588 프로토콜을 분석하고 실제로 이더넷 기반의 IEC61850 프로세서 레벨에서의 시간 동기화를 수행하였다.

  • PDF

Statistical Analysis of Bivariate Current Status Data with Informative Censoring Using Frailty Effects

  • Kim, Yang-Jin
    • The Korean Journal of Applied Statistics
    • /
    • v.25 no.1
    • /
    • pp.115-123
    • /
    • 2012
  • In animal tumorigenicity data, tumor onsets occur at several sites and onset times cannot be exactly observed. Instead, the existence of tumors is examined only at death time or sacrifice time of the animal. Such an incomplete data structure makes it difficult to investigate the effect of treatment on tumor onset times; in addition, such dependence should be considered when censoring due to death is related with tumor onset. A bivariate frailty effect is incorporated to model bivariate tumor onsets and to connect death with tumor. For the inference of parameters, EM algorithm is applied and a real NTP(National Toxicology Program) dataset is analyzed as an illustrative example.

Synchronization System for Time of Mission and Flight Computers over UAV Network

  • Lee, Won-Seok;Jang, Jun-Yong;Song, Hyoung-Kyu
    • Journal of Positioning, Navigation, and Timing
    • /
    • v.10 no.4
    • /
    • pp.387-393
    • /
    • 2021
  • This paper proposes a system to synchronize the time of computers over an unmanned aerial vehicle (UAV) network. With the proposed system, the UAVs can perform missions that require precise relative time. Also, data collected by UAVs can be fused precisely with synchronized time. In the system, to synchronize the time of all computers over the UAV network, two-step synchronization is performed. In the first step, the mission computers of the UAVs are synchronized through the server of the system. After the first step, the mission computers measure time offset between the time of the mission computers and the flight computers. The offset values are delivered to the server. In the second step, virtual time is determined by the server from the collected time offset. The measured offset is compensated by moving the synchronized time of mission computers to the reasonable virtual time. Since only the time of mission computers are controlled, any flight computers that use micro air vehicle link (MAVLink) protocol can be synchronized in the proposed system.