Coordinated Universal Time Research Articles

NUMERICAL AND GRAPHICAL RESULTS OF FINITE SYMMETRIC INVERSE (I_{n}) AND FULL (T_{n}) TRANSFORMATION SEMIGROUPS

Supposed is a finite set, then a function is called a finite partial transformation semigroup , which moves elements of from its domain to its co-domain by a distance of where . The total work done by the function is therefore the sum of these distances. It is a known fact that and . In this this research paper, we have mainly presented the numerical solutions of the total work done, the average work done by functions on the finite symmetric inverse semigroup of degree , and the finite full transformation semigroup of degree , as well as their respective powers for a given fixed time in space. We used an effective methodology and valid combinatorial results to generalize the total work done, the average work done and powers of each of the transformation semigroups. The generalized results were tested by substituting small values of and a specified fixed times in space. Graphs were plotted in each case to illustrate the nature of the total work done and the average work done. The results obtained in this research article have an important application in some branch of physics and theoretical computer science

Research on Time Comparison Based on Galileo PPP

Time comparison based on global navigation satellite system (GNSS) is one of the main techniques in Coordinated Universal Time (UTC) calculation. At present, there is a goal to promote the Galileo system to join the UTC calculation to provide high-precision services for users all over the world. In this paper, the Precision Point Positioning (PPP) time comparison based on Galileo is studied. The data used in this paper include the original data of pseudo-range and carrier phase from National Time Service Center of Chinese Academy of Sciences (NTSC) and Royal Observatory of Belgium (ROB), and the data of precision orbit and clock offset released by International GNSS Service (IGS) which includes the German Research Center for Geoscience (GFZ), Centre for Orbit Determination in Europe (CODE) and Shanghai Astronomical Observatory (SHAO). The results show that the pseudo-range multipath noise of E1 and E5a are all less than ±1 m. When the Galileo PPP is applied to the short baseline common clock time comparison, the time difference by using the precision products of three analysis centers are less than ±0.5 ns, and the standard deviation of the time difference are less than 0.2 ns. For long baseline of Asia Europe time comparison, based on the precision products of three IGS analysis centers, the time comparison between UTC(NTSC) and UTC(TP) by using Galileo PPP have the same trend as the GPS PPP, which is released by International Bureau of Weights and Measures (BIPM), the stability of Galileo PPP is the same with GPS PPP, and it can reach to E-15/ day. As a result, with the performance improvement of Galileo system, the high-precision time comparison based on Galileo will provide better services for users, and the experiment results indicate that the Galileo can also be used as one of the formal methods by BIPM for precision time comparison in the future.

Assessment of Normalized Water-Leaving Radiance Derived from GOCI Using AERONET-OC Data

The geostationary ocean color imager (GOCI), as the world’s first operational geostationary ocean color sensor, is aiming at monitoring short-term and small-scale changes of waters over the northwestern Pacific Ocean. Before assessing its capability of detecting subdiurnal changes of seawater properties, a fundamental understanding of the uncertainties of normalized water-leaving radiance (nLw) products introduced by atmospheric correction algorithms is necessarily required. This paper presents the uncertainties by accessing GOCI-derived nLw products generated by two commonly used operational atmospheric algorithms, the Korea Ocean Satellite Center (KOSC) standard atmospheric algorithm adopted in GOCI Data Processing System (GDPS) and the NASA standard atmospheric algorithm implemented in Sea-Viewing Wide Field-of-View Sensor Data Analysis System (SeaDAS/l2gen package), with Aerosol Robotic Network Ocean Color (AERONET-OC) provided nLw data. The nLw data acquired from the GOCI sensor based on two algorithms and four AERONET-OC sites of Ariake, Ieodo, Socheongcho, and Gageocho from October 2011 to March 2019 were obtained, matched, and analyzed. The GDPS-generated nLw data are slightly better than that with SeaDAS at visible bands; however, the mean percentage relative errors for both algorithms at blue bands are over 30%. The nLw data derived by GDPS is of better quality both in clear and turbid water, although underestimation is observed at near-infrared (NIR) band (865 nm) in turbid water. The nLw data derived by SeaDAS are underestimated in both clear and turbid water, and the underestimation worsens toward short visible bands. Moreover, both algorithms perform better at noon (02 and 03 Universal Time Coordinated (UTC)), and worse in the early morning and late afternoon. It is speculated that the uncertainties in nLw measurements arose from aerosol models, NIR water-leaving radiance correction method, and bidirectional reflectance distribution function (BRDF) correction method in corresponding atmospheric correction procedure.

An Architecture for Reliable Transportation of Delicate Goods.

Adequate conditions are critical to avoiding damage or degradation of products during transportation, especially in the case of delicate goods like food products, live animals, precision machinery or art items, among others. The damages are not always readily identified: sometimes they are only detected several days or weeks after the merchandise has been delivered. Moreover, it may be hard to assess if the problems resulted from the transport conditions, and it may be even harder to prove it, making it difficult to determine and assign responsibilities. Also, transport is a global business, typically involving different companies and means (truck, train, plane, ship, …). Usually, customers hire the service to a single commercial entity, but the service is performed by several companies, like transporters, stockists and dispatchers. To know whether the transport requirements are fulfilled or not is thus essential to assessing responsibilities and encouraging compliance by all the players in the process. In this paper, the authors propose an architecture that allows certifying, in an exempt manner, the conditions under which the transport of sensitive goods are carried out. In case of compliance, it protects the entities of the transport chain and ensures the customer that the merchandise has not been subject to conditions that may have affected its integrity or quality. If problems are detected, it allows to identify the non-compliant players and to assign responsibilities. The solution is based on ultra-low-power, low-cost devices (equipped with several sensors, a real-time clock, and Bluetooth Low Energy services), a mobile application and several cloud services (including a Coordinated Universal Time service).

Detection of the Ether Using the Global Positioning System

In this paper the latest evidence for the existence of a cosmic ether obtained using modern technology is reviewed. The synchronized clocks of the GPS are applied in the search for ether drift by direct measurement of light travel times in the East-West direction. This method reveals that light travels faster West than East and therefore indicates the existence of an Earth-bound ether which we identify as the Earth-centered Inertial (ECI) frame for light transmission. The GPS clocks are then applied in the search for ether drift by direct measurement of light travel times in a modified Michelson-Morley experiment. The East-West light speed difference enables the unambiguous detection of ether drift and the direct confirmation of the existence of a preferred frame. The range equation of the GPS that operates in the Earth-centered inertial (ECI) frame is employed to demonstrate ether drift for rotational motion and Time Transfer technology involving a geo-stationary GPS satellite provides further confirmation of ether drift resulting from the rotating Earth. Finally, using a model applicable in the sun-centered inertial (SCI) frame with Coordinated Universal Time, light speed variation arising from the Earth's orbital motion for light reflected from planets and spacecraft and received at the surface of the Earth is demonstrated. The evidence then is that modern technology has detected ether drift for rotational and orbital motion from the frame of the moving Earth.

The Performance Evaluation of BeiDou-3 System Time Based on CGGTTS

According to the Common GNSS Generic Time Transfer Standard Version2E (CGGTTS_V2E) developed by the GNSS (Global Navigation Satellite System) Working Group of the International Consultative Committee for Time and Frequency (CCTF), the data processing software is developed by using the pseudorange signal measured by the GNSS receiver, which is used to generate the CGGTTS files in the standard format, and its reliability is verified. The results show that, compared with the CGGTTS files generated by sbf2cggtts software, the offset between the GNSS system time and local time scale calculated by the same GPS and BDS satellite observations in the same epoch is identical, and the difference with the absolute value of the difference less than 0.5 ns accounts for 96% and 94% of the total, respectively. Taking Chinese standard time UTC(NTSC) (Coordinated Universal Time (National Time Service Center)) as the reference time scale, the data processing software is used to process the observations of the B1I and B3I dual-frequency ionospheric combination of BeiDou-2 and BeiDou-3 satellites, and generate the CGGTTS files in the standard format, and the performance of BeiDou system time is evaluated by analyzing the parameter of offset between the GNSS system time and local time scale. The results show that, compared with BeiDou-2, the internal precision of BeiDou-3 system time is increased by about 28%, and the frequency stability of medium and long-term is obviously better than BeiDou-2 after one day.

An investigation of the 27 July 2018 bolide and meteorite fall over Benenitra, southwestern Madagascar

Several dozen stones of an ordinary chondrite meteorite fell in and around the town of Benenitra in southwestern Madagascar during the early evening of 27 July 2018, minutes after a widely observed meteor fireball (bolide) transit and detonation. The event was confirmed by low-frequency infrasound recordings received at ~17h15 UTC (Coordinated Universal Time; 19h15 local time) at the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO) infrasound station I33MG near Antananarivo, 542 km north-northeast of Benenitra. An energy release equivalent to 2.038 kt of TNT was calculated from the infrasound signals. Seismograph readings at the SKRH station 77 km north-northwest of Benenitra recorded a twostage signal consistent with the arrivals of an initial air-coupled ground wave at 16h48:08 UTC and a stronger pulse at 16h49:22 UTC linked directly to the atmospheric pressure wave. The infrasound and seismic signal arrival times suggest that the bolide entry and detonation occurred at approximately 18h46 local time (16h46 UTC), entry was from the northwest, and the detonation hypocentre was located within ~20 km of Benenitra. Despite meteorite debris being found among buildings within Benenitra, there was no damage to structures or injuries reported. Eyewitness accounts and photographic records indicate that approximately 75 mostly intact stones were collected; however, the remoteness of the area, the rugged nature of the terrain and sales of fragments to meteorite collectors have limited scientific analysis of the fall and the extent of the strewn field. The total mass of recovered stones is estimated at between 20 kg and 30 kg, with one fragment of 11.2 kg and several of ~1 kg. Petrographic and mineral chemical analyses indicate that the stones belong to the L6 class of ordinary chondrites. Cosmogenic radionuclide analysis confirms that the fall is linked to the bolide event. The name Benenitra has been officially accepted by the Meteoritical Bulletin Database.Significance:
 
 Eyewitness reports, CTBTO infrasound records, seismograph records and cosmogenic radionuclide analysis confirm a meteorite fall over Benenitra on 27 July 2018.
 Petrographic and geochemical analyses confirm that the meteorite is an L6 ordinary chondrite.
 Recovery of meteorite falls is rare; this is Madagascar’s second known meteorite fall and the first that can be linked to a bolide.
 Regional and global science monitoring networks can be interrogated to improve the understanding of bolide events.
 Interaction of scientists with local communities is important to dispel misunderstandings around scientific phenomena, and can improve collection of data.

Traceability of network time service to UTC(NIM): online calibration

Network time service provided by Network Time Protocol (NTP) servers is widely used to synchronize the clocks of computers and other networked equipment. With the rapid development of smart devices and their applications, more NTP servers as time sources need to be calibrated to a legal time reference. This work proposes using a low-cost and convenient calibration method to investigate the time service capability of ten NTP servers located at different cities in China. The uncertainties (k = 2) of the time offsets between Coordinated Universal Time (National Institute of Metrology) and network time from NTP servers for a single measurement are generally less than 150 ms, and the uncertainties (k = 2) of the mean time offsets for 24 h are less than 85 ms. Calibration results were found at the same level when applying the two time references, which were maintained a time offset less than 10 ns and located more than 1000 km apart.

From time frames to temperature bias in temperature series

The article offers an overview of the time frames used in instrumental series and how to transform them into modern units. In the early instrumental period, time was measured with sundials or mechanical clocks regulated every day with the culmination at noon, making reference to the apparent solar time (AST) and the local meridian. Every day had a slightly different duration, start, and end for the apparent changes of speed of the Sun. When canonical hours were used, hours were computed starting from twilight. In the late eighteenth century, the start was established at midnight. In the mid-nineteenth century, when precise clocks were available, it was possible to adopt an average time, with all days having the same duration, but related to the local meridian. A further step was to unify the time of all cities of a country adopting the time of the capital. Finally, the interregional rails, the telegraph, the telephone, and the international contacts required to unify the different time frames. This lead to the creation of the Coordinated Universal Time (UTC) and the time zones (TZ). The change from AST to UTC introduced two important time differences: one related to the variability of the apparent solar motion and one related to the longitude of the site. Instrumental records, especially the longest ones, are affected by changes in time frames that may cause bias. In this paper, the time changes of 92 selected European cities when they passed from AST to Western European Time, Central Europe Time, or Eastern Europe Time, are considered, and the departures during the calendar year are calculated. Moreover, the bias in temperature derived from the time frame change has also been evaluated in ten case studies over Europe. This paper will assist historians and climatologists to recognize and correct the time departures that affect meteorological series concerning temperature, barometric pressure, and other variables with daily cycles. This correction is crucial to assess climate changes. Specific aims are as follows: to make a friendly explanation of the methodology to pass from old time frames to UTC; to provide transformation equations to remove the bias for the time difference; to pass from time difference to temperature bias to homogenize early records with modern ones.

Endpoint-based optimal fractal interpolation for predicting BDS-3 system time offsets

In order to improve the interoperability within the Global Navigation Satellite System (GNSS), the International Committee on Global Navigation Satellite Systems published a joint statement in December 2019 that stated that all GNSS providers agree to monitor and broadcast the time offsets between each system timescale and the Universal Time Coordinated (UTC) or the rapid realization of UTC (UTCr). This commitment requires the study of precise prediction models for system time offsets. The prediction model of system time offsets is different from that of the atomic clock because of the control of the system timescale. The offsets between the system time of the Beidou Satellite Navigation System-3 (BDS-3) and the National Time Service Center (NTSC), called [UTC(NTSC)-BDT], have two main periods of 12 h and 24 h, according to the Fast Fourier Transform analysis. The rescaled range (R/S) analysis demonstrates that it has long memory, making it a fractal time series with a memory period of about 10.4 h. While using the fractal interpolation method to predict the [UTC(NTSC)-BDT] series, we found that the prediction error reaches its minimum value if adding disturbance on the estimated endpoint of the forecasted interval. After verifying the correlation between the estimated endpoints with the minimal interpolation error and minimal prediction error and proving the existence and uniqueness of the estimated endpoint with the minimal interpolation error, we established the endpoint-based optimal fractal interpolation prediction method. The experimental results indicate that the average prediction accuracy of the proposed prediction model is improved by 57.90% and 39.26% compared to that of a quadratic model and standard fractal prediction model, respectively. The accuracy analysis results of numerical tests indicate that the proposed prediction model can restrain the divergence of prediction error. Finally, we transform the [UTC(NTSC)-BDT] into [UTCr -BDT] using the [UTCr-UTC(NTSC)] published by the Bureau International des Poids et Mesures (BIPM) to meet the requirement of GNSS interoperability. The prediction accuracies of daily [UTCr-BDT] using the proposed prediction model are no more than 1.5 ns with uncertainty about 6 ns.

Sub-nanosecond one-way real-time time service system based on UTC

Coordinated Universal Time (UTC) is the worldwide standard of time, and UTC (k) is its physical implementation by any participating laboratory k. We describe a one-way real-time time service system that relies on GNSS to provide a realization UTC (NTSC) of China’s National Time Service Center, to a precision of sub-nanosecond. The system is inexpensive, easy to implement, and has been tested.

Distributing time by fibre

Precise time underpins critical infrastructure in modern society, including telecommunications, computer networks, electrical power grids and broadcasting. At present, Global Navigation Satellite Systems (GNSS) provide the timing signals that are used by these applications; however, time signals delivered over fibre links can offer higher performance. The high accuracy time transfer achievable by fibre is important for synchronising clocks in high-end scientific research projects such as particle accelerators and radio telescope arrays. In addition, distributing time over an optical fibre directly from a timing institute can provide resiliency, accuracy and traceability to the international time scale Coordinated Universal Time (UTC). These are key requirements for timing in industry and commerce, and in applications such as the timestamping of financial trades, fibre distribution offers a secure alternative to time from GNSS. This article will present techniques for distributing time by fibre that are commercially available and widely used for applications in industry, science and metrology.

ВЛИЯНИЕ РОТАЦИОННОГО ПОСТЭФФЕКТА НА РАЗРЯДКУ В КОРОВОМ СЛОЕ

This work represents experiments which have been performed in an attempt to establish a correla-tion between the constantly changing rotational regime of the planet and the discharge in the crustal layer. From the displacement of the TAI, UTC, and UT1 time scales taken from the site of the Interna-tional Earth Rotation Service (IERS), the average annual and monthly angular rotation rates were cal-culated for the period from 1962 to 2018, and a catalog of earthquakes with 1962 to 2018. The com-piled algorithm and the written program found partial derivatives of the total deforming potential and the distribution of annual number of earthquakes over the Earth's surface per one square kilometer. The article presents the results of analytical analysis and calculations for further investigation of the rotational regime of the Earth and other planets.

Timing it right: Tips for planning remote meetings across time zones

Timing it right: Tips for planning remote meetings across time zones

A History of #BCSM and Insights for Patient-Centered Online Interaction and Engagement.

Participation in cancer support groups can provide a sense of community and may better prepare patients for interactions with their health care team. Online interactions may overcome some barriers to in-person support group participation. #BCSM (breast cancer social media), the first cancer support community established on Twitter, was founded in 2011 by two breast cancer survivors. The aims of this study are to describe the growth and changes in this community and to discuss future directions and lessons that may apply to other online support communities. Symplur Signals was used to obtain all #BCSM Twitter data from January 1, 2011, to January 1, 2020 (00:00:00 Coordinated Universal Time for both). Hashtag use by selected stakeholder groups, user locations, weekly tweet chat activity, and topics were determined. From year 1 (2011) to year 9 (2019), tweets using the #BCSM hashtag increased by 424%. Tweets by patient advocates increased by 226%, with a peak in 2016. Impressions, a measure of potential tweet views, by patient advocates increased by 517%. Tweets by doctors and nonphysician health care professionals increased by 693%. Weekly #BCSM tweet chat activity peaked in 2013, increasing by 58.1% from 2011. Chat topics have included survivorship, metastatic breast cancer, death and dying, advocacy, and highlights from national breast cancer meetings. #BCSM has experienced tremendous growth since 2011, although there are challenges to community sustainability. The weekly chats, as well as discussions utilizing the hashtag but occurring outside of scheduled chat times, serve as an important resource for patients and offer physicians an opportunity to both support and learn from patients.

Generating a real-time time scale making full use of the available frequency standards

We propose a time-scale algorithm for the automated generation of a real-time time scale, making full use of the frequency standards available in a typical time laboratory. The time-scale algorithm is made by a pre-processing stage, a steering algorithm, and a post-processing stage. In particular, in this work we propose a set of three different steering algorithms, running in parallel and eventually producing a unique steering correction to be applied to a master clock. Each algorithm is based on a different steering reference, namely, a primary frequency standard, an ensemble clock, and the Coordinated Universal Time (UTC), or its rapid version, UTCr. Pre- and post-processing stages help to provide robustness and to cope with data gaps. The proposed algorithms have been extensively and successfully tested offline, on real data from the time laboratory of the Italian National Institute of Metrological Research (INRiM), where an online test has also been performed in the period May-October 2019. Then, since the middle of January 2020, the time-scale algorithm has been applied for the generation of the Italian legal time scale, UTC(IT). We show here the results of the offline tests and of the 5-month online test. The proposed strategy can be used wherever a stable, accurate, and robust time reference is needed, e.g. for a local realization of UTC in a laboratory k, UTC(k), or for generating the reference time of a global navigation satellite system (GNSS).

Realization of a free-running timescale based on a CsF1 cesium fountain clock and multiple active hydrogen masers

It is important to realize a stand-alone timescale with high-quality stability in short- and long-terms that can function accurately without any external inputs. A free-running timescale (FreeAT) was calculated as a weighted average of five active hydrogen masers and has operated freely for more than 400 d in the Beijing Satellite Navigation Center (BSNC). In the weighted average algorithm, a cesium fountain clock (CsF1) with a typical Type-A uncertainty of 4.50 × 10−16 for averaging times of 30 d was used as the frequency reference to estimate the frequency drifts of hydrogen masers. Additionally, the time difference between the rapid realization of Coordinated Universal Time (UTCr) and FreeAT was obtained indirectly by utilizing the timescale signal comparison between the BSNC and National Institute of Metrology via an optical fiber link. The overlapping Allan deviation of FreeAT with respect to UTCr is 8.69 × 10−16 for averaging times of 15 d, and its frequency difference and drift relative to UTCr are −1.20 × 10−16 and −2.08E-18/day, respectively. Therefore, the combination of a fountain and maser ensemble can generate a high-performance time scale.

A generalizable formalism for computing uncertainties in UTC

Algorithms to compute the statistical and systematic uncertainties in the difference between Coordinated Universal Time (UTC) and individual laboratory UTC realizations were published in several different, but equivalent, forms the early twenty-first century, at a time when the UTC algorithm was based on a minimal network. In this paper we extend the theory to compute the uncertainties in a manner entirely consistent with the earlier work, but which enables application to UTC computations employing redundant links, and correlated calibrations.

Smart Grid State Estimation with PMUs Time Synchronization Errors

State Estimation (SE) is one of the essential tasks to monitor and control the smart power grid. This paper presents a method to estimate the state variables combining the measurement of power demand at each bus with the data collected from a limited number of Phasor Measurement Units (PMUs). Although PMU data are usually assumed to be perfectly synchronized with the Coordinated Universal Time (UTC), this work explicitly considers the presence of time-synchronization errors due, for instance, to the actual performance of GPS receivers and the limited stability of the internal oscillator. The proposed algorithm is a recursive Kalman filter which not only estimates the state variables of the power system, but also the frequency deviations causing clock offsets which eventually affect the timestamps of the measures returned by different PMUs. The proposed solution was tested and compared with alternative approaches using both synthetic data applied to the IEEE 123 bus distribution feeder and real-field data collected from a small-size medium-voltage (MV) distribution system located inside the EPFL campus in Lausanne. Results show the validity of the proposed method in terms of state estimation accuracy. In particular, when some synchronization errors are present, the proposed algorithm can estimate and compensate for them.

On the possibility of getting traceable time and frequency measurements via GNSS receivers

The realization of Coordinated Universal Time, one of the tasks of the International Bureau of Weights and Measures, relies on a network of international time links which currently is organized in a star-like scheme that links all contributing laboratories. GPS signal reception is the technique most widely employed by the laboratories. The PTB currently plays a unique role in the process due to its function as the central pivot in the time transfer between the participating laboratories. We discuss how the PTB meets its obligations to the international timekeeping community as well as to its users in Germany. In its role as an National Metrology Institute (NMI), PTB is entrusted with the realization and dissemination of legal time in Germany. The services were offered to the public support measurements and timing applications traceable to the national and international standards to be made in calibration laboratories and in many industrial sectors. We thus discuss the meaning and definition of traceability, how different GNSS systems can be used to establish traceability and their performance in doing so.