Wyniki wyszukiwania - BazTech

1

Stability of GPS and GLONASS onboard clocks on a monthly basis

Ziętala Michał

Zeszyty Naukowe. Transport / Politechnika Śląska

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2022

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z. 114

193--209

EN

This paper presents the stability of the GPS and GLONASS system clocks’ stability. It describes the construction of these two systems and calculated four different Allan variances (AVAR), based on the MGEX (the Multi-GNSS Experiment) clock products. Four used variances allowed making a better analysis of each GNSS system clock. The results are shown at different averaging times from 5 s as successive multiples to 655,360 s in a monthly period. The stability of GPS and GLONASS clocks is included in the range of 10-12~10-14 s. The results showed that GLONASS clocks are stable (10-12~10-14 s) and are affected with white frequency noise (WFM). The GPS clock stability models have more fluctuations for τ > 40,960 s and the mean stability is concluded between 10-12~10-13 s. Mean frequency accuracy for GPS clocks is related with WFM and Random Walk Frequency (RWF). The differences in clock stability are caused by several factors – block type, type of clock and the time of a satellite in orbit. These factors have an influence on stability results.

2

Czas kolejowy

Jerczyński Michał

Kwartalnik Historii Nauki i Techniki

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2021

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T. 66, nr 3

61--84

EN

The inventions of the electromagnetic telegraph and the railroads significantly accelerated communication in time and space. It greatly influenced the way time was expressed and forced a change of centuries-old patterns and habits. It became necessary to gradually move away from local times (the average solar times of individual places) to the uniform time in the scale of entire countries, and then to the zone time. This process began in the 1830s on the railway and a few years later in the telegraph service, developing in parallel and in conjunction with the railroads. Initially, individual railway authorities adopted the same railway time on their networks (usually the capital time of a given country or the directorate’s headquarters). From 1884 until the first decade of the 20th century, culminating in the early 1990s, they gradually switched to zone time. Its introduction improved the work of railways, increased traffic safety, and made it easier for passengers to find their way around train timetables. Almost in parallel, since the mid-1860s, the process of switching from a twelve-hour count to a 24-hour count of time on the railways took place. In the rich literature devoted to time in its various aspects, few studies focus on the issues of organizing the measurement and expression of time on railways, and there are virtually no studies relating to railways in the present-day Polish lands which at the time operated under three different state authorities. The work aims to collect and systematize the facts that contributed to the process of introducing the 24-hour zone time on Central European railways and to present this process in the context of the world railways.

3

How Coarse-grained Clock Impacts on Performance of NDN Rate-based Congestion Control with Explicit Rate Reporting

Kato Toshihiko, Enda Takumi, Yamamoto Ryo, Ohzahata Satoshi

Annals of Computer Science and Information Systems

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2020

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Vol. 21

479--488

EN

Named Data Networking (NDN) is a widely adopted future Internet architecture well-suited to large scale content retrieval. The congestion control is one of the research topics actively studied, and the rate-based congestion control method is considered to be fitted to NDN. From the viewpoint of implementation, however, the rate-based method has an issue that it requires the fine-grained clock management, which is hard to implement in off-the-shelf computers. Among the rate-based congestion control methods, an approach in which intermediate nodes report a maximum rate explicitly for a flow is considered to work well. In this paper, we pick up the Multipath-aware ICN Rate-based Congestion Control as an example of explicit rate reporting scheme, and examine how coarse-grained clock gives impacts to its performance. This paper provides the performance evaluation when consumers and NDN routers use the system clock with long time interval. This paper also proposes a method for smoothening Interest sending under a coarse-grained clock and evaluates the performance of proposed method.

4

GNSS-based sound card synchronization

Carôt Alexander, Mahmood Hasan, Hoene Christian

Annals of Computer Science and Information Systems

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2019

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Vol. 18

309-–312

EN

Audio communication on the public Internet suffers from not synchronized word clocks of the involved audio devices. The resulting clock drift leads to audio dropouts, which is typically compensated by a sample rate conversion (SRC) in standard telecommunication systems. This, however, does not fulfill the requirements of a high-quality audio system, in which all devices share one and the same word clock. Professional IP based network audio systems such as DANTE or AVB with their respective clock synchronization techniques have so been limited to LAN usage, where network jitter and loss have negligible importance regarding the required accuracy in the dimension of several nanoseconds. In a WAN, however, jitter in the millisecond dimension would lead to unacceptable measurement errors for the intended clock synchronization. As a consequence, we decided to investigate alternative clock synchronization techniques for WAN-distributed devices and developed a GNSS-based approach, which leads to precise clock synchronization.

5

Implementation of quasi real time estimation of BDS clock

Ning Wei, Wang Jian-Bo, Tang Long-Jiang

Acta Geophysica

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2019

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Vol. 67, no. 4

1131--1138

EN

To obtain high reliability and accuracy of the zenith tropospheric delay more quickly, this study describes a parameter estimation method that uses an epoch-differenced and undifferenced function model to estimate the clock of the BeiDou navigation satellite system (BDS)/global positioning system (GPS) satellites using a quasi-real-time process. Forty-five MGEX tracking stations distributed globally were selected for study. The initial orbit information of the clock estimation used the ultra-rapid orbit products released by the German Research Center for Geosciences and post-products as reference values. The experimental results showed that the accuracy of the GPS satellite clock was better than 0.06 ns. The precision of clock for three kinds of BDS satellites was between 0.04 and 0.08 ns, slightly worse than the GPS. The estimated BDS clock appears to meet the demands for computing the quasi-real-time zenith tropospheric delay.

6

Application of ASIP in Embedded Design with Optimized Clock Management

Venkanna M., Rao R., Sekhar P. Ch.

Annals of Computer Science and Information Systems

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2018

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Vol. 14

159--163

EN

As the demand for high performance computing increases, new approaches have to be found to automate the design of embedded processors. Simultaneously, new tools have to be developed to short the execution time consumption, and simpler design resulting in time to market. These are to be applied for the system architecture to achieve rapid exploration in on power consumption, chip area, and performance constraints. This enables interest in Application Specific Instruction Processors (ASIPs) design and application considerably. It has higher flexibility as compared to dedicated hardware. The current case study focuses on an ASIP design methodology considering the classical parameters computational performance and area as well as energy consumption simultaneously. In this paper, the clock gating is analyzed and designed. Further it is optimized using Fast genetic algorithm (FastGA). The optimization result is shown for ICORE (ISS-core) ASIP for DVB-T acquisition and tracking algorithms. Observation shows a potential of about one order of magnitude in savings of energy for optimization.

7

Mechanika precyzyjna jak w zegarku

Pojda A.

Stal, Metale & Nowe Technologie

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2014

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nr 5-6

149

PL

Tarnowska firma „Zegar” jest obecnie największym polskim producentem karniszy ze stali nierdzewnej i z mosiądzu, z imponującym asortymentem rozwiązań nagradzanych na wielu branżowych targach. To jednak nie jedyna forma działalności firmy – od początku istnienia zajmowała się mechaniką precyzyjną, a od niedawna te usługi wykonuje na wyjątkowo nowoczesnych maszynach.

8

Sztuka odmierzania czasu

Bielski M. W.

Nowa Elektrotechnika

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2005

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nr 1 (5)

1

9

O czasie i zegarach. Część II

Dobrogowski A.

Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

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2000

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nr 4

271-277

PL

Jest to druga część artykułu, w której opisano poglądy na początek Wszechświata, przywołano ważne daty jego historii i wskazano warianty jego możliwej przyszłości. Rozważano problematykę rachuby czasu za pomocą kalendarzy i zegarów. Przedstawiono astronomiczną i atomową skalę czasu.

EN

This is the second part of the paper, which some ideas for the origin of the Universe, the important events from its history and some variants its possible future arę discussed in. Time count using calendars and clocks is considered. Astronomical and atomie time scales arę addressed.