• Title/Summary/Keyword: NTP

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An Imbedded System for Time Synchronization in Distributed Environment based on the Internet (인터넷 기반 분산 환경에서 시각 동기를 위한 임베디드 시스템)

  • Hwang So-Young;Yu Dong-Hui;Li Ki-Joune
    • Journal of KIISE:Computing Practices and Letters
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    • v.11 no.3
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    • pp.216-223
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    • 2005
  • A computer clock has limits in accuracy and precision affected by its inherent instability, the environment elements, the modification of users, and errors of the system. So the computer clock needs to be synchronized with a standard clock if the computer system requires the precise time processing. The purpose of synchronizing clocks is to provide a global time base throughout a distributed system. Once this time base exists, transactions among members of distributed system can be controlled based on time. This paper discusses the integrated approach to clock synchronization. An embedded system is considered for time synchronization based on the GPS(Global Positioning System) referenced time distribution model. The system uses GPS as standard reference time source and offers UTC(Universal Time Coordinated) through NTP(Network Time Protocol). A clock model is designed and adapted to keep stable time and to provide accurate standard time with precise resolution. Private MIB(Management Information Base) is defined for network management. Implementation results and performance analysis are also presented.

A Network Time Server using CPS (GPS를 이용한 네트워크 시각 서버)

  • 황소영;유동희
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.8 no.5
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    • pp.1004-1009
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    • 2004
  • Precise time synchronization is a main technology in high-speed communications, parallel and distributed processing systems, Internet information industry and electronic commerce. Synchronized clocks are useful for many leasers. Often a distributed system is designed to realize some synchronized behavior, especially in real-time processing in factories, aircraft, space vehicles, and military applications. Nowadays, time synchronization has been compulsory thing as distributed processing and network operations are generalized. A network time server obtains, keeps accurate and precise time by synchronizing its local clock to standard reference time source and distributes time information through standard time synchronization protocol. This paper describes design issues and implementation of a network time server for time synchronization especially based on a clock model. The system uses GPS (Global Positioning System) as a standard reference time source and offers UTC (universal Time coordinated) through NTP (Network Time protocol). Implementation result and performance analysis are also presented.

Effect of non-thermal plasma on the shear bond strength of resin cements to Polyetherketoneketone (PEKK)

  • Labriaga, Wilmart;Song, So-Yeon;Park, Jin-Hong;Ryu, Jae-Jun;Lee, Jeong-Yol;Shin, Sang-Wan
    • The Journal of Advanced Prosthodontics
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    • v.10 no.6
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    • pp.408-414
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    • 2018
  • PURPOSE. This study aimed to assess the effect of non-thermal plasma on the shear bond strength of resin cements to polyetherketoneketone (PEKK) in comparison to other surface treatment methods. MATERIALS AND METHODS. Eighty PEKK discs were subjected to different surface treatments: (1) Untreated (UT); (2) Non-thermal plasma (NTP); (3) Sandblasting with $50{\mu}m$ $Al_2O_3$ particles (SB); and (4) Sandblasting + Non-thermal plasma (SB+NTP). After each surface treatment, the contact angle was measured. Surface conditioning with Visio.Link was applied in all groups after pre-treatment. RelyX Unicem resin cement was bonded onto the PEKK specimens. After fabrication of the specimens, half of each group (n=10) was initially tested, while the other half was subjected to thermocycling ($5^{\circ}C$ to $55^{\circ}C$ at 10,000 cycles). Shear bond strength (SBS) testing was performed using a universal testing machine, and failure modes were assessed using stereomicroscopy. The SBS results were analyzed statistically using one-way ANOVA followed by Tukey's post hoc test. Independent t-test was used to examine the effect of thermocycling (P<.05). RESULTS. The highest SBS values with or without thermocycling were observed with PEKK specimens that were treated with SB+NTP followed by the SB group. The lowest SBS results were observed in the UT groups. CONCLUSION. The shear bond strength between PEKK and resin cements was improved using non-thermal plasma treatment in combination with sandblasting.

A CLINICAL STUDY OF THE NASAL MORPHOLOGIC CHANGES FOLLOWING LEFORT I OSTEOTOMY (상악골 수평골절단술 후 비외형 변화에 관한 임상적 연구)

  • Bae, Jun-Soo;You, Jun-Young;Lyoo, Jong-Ho;Kim, Yong-Kwan
    • Journal of the Korean Association of Oral and Maxillofacial Surgeons
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    • v.25 no.4
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    • pp.324-329
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    • 1999
  • The facial esthetics are much affected by nasal changes due to especially its central position in relation to facial outline and so appropriately evaluated should be the functional and esthetic aspects of the nose associated with the facial appearance. Generally, a maxillary surgical movement is known to induce the changes of nasolabial morphology secondary to the skeletal repositioning accompanied by muscular retraction. These changes can be desirable or undesirable to individuals according to the direction and amount of maxillary repositioning. We investigated the surgical changes of bony maxilla and its effects to nasal morphology through the analysis of the lateral cephalogram in the Le Fort I osteotomy. Subjects were 10 patients(male 2, female 8, mean age 22.3 years) and cephalograms were obtained 2 weeks before surgery(T1) and 6 months after surgery(T2). The surgical maxillary movement was identified through the horizontal and vertical repositioning of point A. Soft-tissue analysis of the nasal profile was performed employing two angles: nasal tip projection(NTP), columellar angle(CA). Also, alar base width(ABW) was assessed directly on the patients with a slide gauge. The results were as follows; 1. Both anterior and superior movement above 2mm of maxilla rotated up nasal tip above 1mm. Either anterior or superior movement above 2mm of maxilla made prediction of the amount & direction of NTP changes difficult. Especially, a correlation between horizontal movement of maxilla and NTP rotated-up was P<0.01. 2. Both much highly anterior and superior movement of maxilla is accompanied by more CA increase than either highly. Especially, the correlation between horizontal movement of maxilla and CA change was P<0.05. 3. Anterior and/or superior movement of maxilla was accompanied by the unpredictable ABW widening. 4. The amount of changes of NTP, CA, and ABW is not in direct proportion to amout of anterior and/or superior movement of maxilla. 5. Nasal morphologic changes following Le Fort I osteotomy are affacted by not merely bony repositioning but other multiple factors.

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A CDMA Network-based Wireless System for Measuring Lap Time on a Ski Slope (CDMA 망에 기반한 스키장 슬로프의 무선 구간 기록 측정 시스템)

  • Lee, Hyung-Bong;Park, Lae-Jeong;Moon, Jung-Ho;Chung, Tae-Yun
    • The KIPS Transactions:PartD
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    • v.16D no.1
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    • pp.133-138
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    • 2009
  • This paper introduces a pilot CDMA network-based wireless lap time measurement system set up on a ski slope of Yongpyong Ski Resort. The wireless lap time measurement system is one output of U-Sports Project of Gangwon Province, which is intendended for promoting local strategic business and preparation for hosting 2018 Winter Olympic Games at Pyeongchang. A pair of laser sensors is installed at the entry and exit points of a section requiring lap time measurement on a ski slope. Each laser sensor is connected to a sensor node via wire so that the sensor node can detect the time when a skier enters or exits the section. Also each sensor node is connected to a CDMA network via a modem and receives a standard time from a NTP server. Each node executes the NTP algorithm to synchronize its local time to the received server time. As a result of the time synchronization, the sensor nodes maintain its local time within a resolution of at least 10 miliseconds and transmit the time of detection to a central control center. While the wireless lap time measurement system introduced in the paper does not need expensive measurement equipment, the system allows the central control center to provide lap time records in a more convenient manner compared to conventional manual lap time measuremnt methods.

A Study on Classification and Management System for arcinogens (발암물질 분류 및 관리 체계 고찰)

  • Choi, Sang-Jun;Lim, Kyong-Che
    • Journal of the Korea Safety Management & Science
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    • v.12 no.3
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    • pp.107-119
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    • 2010
  • The aim of this study was to compare the carcinogen classification systems of developed countries or global organizations with domestic system under Industrial Safety and Health Act (ISHA). We selected the representative institutions which had carcinogen classification system such as International Agency for Research on Cancer (IARC), National Toxicological Program (NTP), Environmental Protection Agency (US-EPA), American Conference of Governmental Industrial Hygienists (ACGIH), and European Union (EU). We collected the carcinogen lists issued by 5 institutions, and merged by CAS number of each chemical with Microsoft Access 7.0. We found that confirmed human carcinogens, probable human carcinogens and possible human carcinogens were 34, 179, and 252, respectively. All of the institutions classified chemicals as 2 (NTP), 3 (EU) or 5 (IARC, ACGIH, US-EPA) categories based on the weight of scientific evidences for carcinogenicity and periodically updated the carcinogen list by regular procedure. However, a total of 90 chemicals could be classified as carcinogen under ISHA in Korea. There was no procedure or system which periodically update the carcinogen lists. In addition, the status of carcinogen classification according to regulation was confused. In conclusion, these findings suggest that the carcinogen classification and management system should be amended by consideration of systems of advanced institutions and the domestic regulation system.

Effective timing synchronization methods for femtocell (펨토 기지국의 효과적인 타이밍 동기방안)

  • Shin, Jun-Hyo;Kim, Jung-Hun;Jeong, Seok-Jong
    • 한국정보통신설비학회:학술대회논문집
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    • 2008.08a
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    • pp.237-241
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    • 2008
  • Femtocells are cellular access points that connect to a mobile operator's network using residential DSL or cable broadband connections. They have been developed to work with a range of different cellular standards including CDMA, GSM and UMTS. Like legacy base station, the frequency accuracy and phase alignment is necessary for ensuring the quality of service (QoS) for applications such as voice, real-time video, wireless hand-off, and data over a converged access medium at the femtocell. But, the GPS has some problem to be used at the femtocell, because it is difficult to set-up, depends on the satellite condition, and very expensive. So, some techniques are discussed to alternate with the legacy GPS system. NTP, PTP, Synchronous Ethernet use the ethernet to synchronize distributed clocks in packet networks. AGPS support reliable position information than the legacy GPS in poor signal conditions. But, These method also have some problems. So, hybrid timing method like A-GPS+PTP and TV+GPS was developed to make up the weak point of GPS. This paper introduces the each method and compare each other and y propose much better solution for timing synchronization at the Femtocell

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Characterisation of multiple substrate-specific (d)ITP/(d)XTPase and modelling of deaminated purine nucleotide metabolism

  • Davies, Oluwafemi;Mendes, Pedro;Smallbone, Kieran;Malys, Naglis
    • BMB Reports
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    • v.45 no.4
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    • pp.259-264
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    • 2012
  • Accumulation of modified nucleotides is defective to various cellular processes, especially those involving DNA and RNA. To be viable, organisms possess a number of (deoxy)nucleotide phosphohydrolases, which hydrolyze these nucleotides removing them from the active NTP and dNTP pools. Deamination of purine bases can result in accumulation of such nucleotides as ITP, dITP, XTP and dXTP. E. coli RdgB has been characterised as a deoxyribonucleoside triphosphate pyrophosphohydrolase that can act on these nucleotides. S. cerevisiae homologue encoded by YJR069C was purified and its (d)NTPase activity was assayed using fifteen nucleotide substrates. ITP, dITP, and XTP were identified as major substrates and kinetic parameters measured. Inhibition by ATP, dATP and GTP were established. On the basis of experimental and published data, modelling and simulation of ITP, dITP, XTP and dXTP metabolism was performed. (d)ITP/(d)XTPase is a new example of enzyme with multiple substrate-specificity demonstrating that multispecificity is not a rare phenomenon

A Study of Time Synchronization Methods for IoT Network Nodes

  • Yoo, Sung Geun;Park, Sangil;Lee, Won-Young
    • International journal of advanced smart convergence
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    • v.9 no.1
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    • pp.109-112
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    • 2020
  • Many devices are connected on the internet to give functionalities for interconnected services. In 2020', The number of devices connected to the internet will be reached 5.8 billion. Moreover, many connected service provider such as Google and Amazon, suggests edge computing and mesh networks to cope with this situation which the many devices completely connected on their networks. This paper introduces the current state of the introduction of the wireless mesh network and edge cloud in order to efficiently manage a large number of nodes in the exploding Internet of Things (IoT) network and introduces the existing Network Time Protocol (NTP). On the basis of this, we propose a relatively accurate time synchronization method, especially in heterogeneous mesh networks. Using this NTP, multiple time coordinators can be placed in a mesh network to find the delay error using the average delay time and the delay time of the time coordinator. Therefore, accurate time can be synchronized when implementing IoT, remote metering, and real-time media streaming using IoT mesh network.

랫드의 간질성 폐염

  • Hyeon, Gang-Bu
    • Proceedings of the Korean Society of Veterinary Pathology Conference
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    • 2002.11a
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    • pp.12-20
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    • 2002
  • 1. 질병명 : Interstitial pneumonia 2. 본질명의 개요 역사 및 역학 Michael R Elwell, Joel F Mahler, G N Rao: “ Have You Seen This\ulcorner" ; Inflammatory Lesions in the Lungs of Rats. Toxicologic Pathology, 25: 529-531, 1997. Male and female F344 rats, approximately 19 weeks old, from prechronic toxicity studies performed for NTP/NIEHS over a period of several years at different laboraories located throughout the US. The rats were supplied by 2 different production colonies located in the eastern and western areas of the US. Gross findings ㆍ In some rats the lesions were noted as pale or tan foci in the lungs Microscopic findings ㆍ A prominent increase in perivascular lymphocytes ㆍ A variable increase in the amount of peribronchiolar lymphoid tissues ㆍ Frequently an inflammatory cell exudate within the alveolar spaces ㆍ Focal hyperplasia of alveolar type 2 cells Similar lung lesions were not observed in B6C3F1 mice concurrently on study with affected rats. Similar lung lesions were not observed in F344 rats at the end of 2-year NTP studies. Virus, mycoplasma, bacterial serology, bacterial culture, protozoal identification: negative EM: ㆍ No virus particles were identified. ㆍ Rod shaped bacteria were observed in the alveolar spaces. ㆍ Bacteria were not observed in the bronchi/ bronchioles of rats with alveolar organism. (omitted)

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