scholarly journals Pulsar Astrometry and Improved Terrestrial Clocks

1996 ◽  
Vol 160 ◽  
pp. 113-114
Author(s):  
Demetrios N. Matsakis ◽  
Frederick J. Josties ◽  
Roger S. Foster
Keyword(s):  
Inverse Problem ◽  
Time Scales ◽  
Time Scale ◽  
World Wide ◽  
State Of The Art ◽  
Frequency Standards ◽  
A Value ◽  
The World ◽  
Averaging Time ◽  
Atomic Time

AbstractRecent improvements in cesium and hydrogen terrestrial frequency standards have brought the frequency precision of International Atomic Time (TAI) to a value of 2.5E-15 s/s over an averaging time of a month. In this paper we illustrate the improvement graphically, and discuss the state of the art for frame ties between the radio, dynamical, and optical frames. In a larger paper, available via the World Wide Web, we illustrate the measured accuracy curves of the frequency standards, show their effect on the ensemble time scales, explain the reasons for the confusing array of available time scales, and discuss the inverse problem of using pulsar data to correct the terrestrial time scale.

The long-term instability of the new generation hydrogen masers

2020 ◽  
pp. 35-38
Author(s):  
S.I. Donchenko ◽  
I.Y. Blinov ◽  
I.B. Norets ◽  
Y.F. Smirnov ◽  
A.A. Belyaev ◽  
...  
Keyword(s):  
Time Scale ◽  
Frequency Difference ◽  
Clock Frequency ◽  
Quantum Frequency ◽  
Frequency Standards ◽  
Quantum Frequency Standards ◽  
New Generation ◽  
Atomic Time

The latest changes in the algorithm for the formation of the international atomic time scale TAI are reported in terms of estimating the weights of the clocks involved in the formation of TAI. Studies of the characteristics of the long-term instability of new-generation hydrogen masers based on processing the results of the clock frequency difference with respect to TAI are performed. It has been confirmed that at present, new-generation hydrogen masers show significantly less long-term instability in comparison with quantum frequency standards ofsimilar and other types.

Infrastructure Support for Smart Organizations

2009 ◽  
pp. 897-918
Author(s):  
Peter Bertok ◽  
Xinjian Xu
Keyword(s):  
Web Services ◽  
World Wide ◽  
Value Added ◽  
The Internet ◽  
Service Component ◽  
New Approach ◽  
Competitive Edge ◽  
A Value ◽  
New Organizational Forms ◽  
The World

In a rapidly changing world, continuous adoption of new practices is crucial for survival; organizations embracing the latest technologies have a competitive edge. Smart organizations readily take on board new organizational forms and practices, those in particular that offer agility and responsiveness. The Internet and the World Wide Web offer a new way of collaboration via Web services, but heterogeneity of different service components make cooperation difficult. This chapter describes a new approach to combine Web services by employing a layered structure, in which composition of a value-added service can be built from individual components, and each service component can have semantically equivalent but syntactically different alternatives.

A Signal-Representation-Based Parser to Extract Text-Based Information from the Web

2010 ◽  
Vol 14 (5) ◽  
pp. 531-539
Author(s):  
Mu-Chun Su ◽  
◽  
Shao-Jui Wang ◽  
Chen-Ko Huang ◽  
Pa-ChunWang ◽  
...  
Keyword(s):  
Web Services ◽  
World Wide ◽  
Information Sources ◽  
State Of The Art ◽  
Value Added ◽  
Web Pages ◽  
Web Page ◽  
Web Information ◽  
The World ◽  
The Web

Most of the dramatically increased amount of information available on the World Wide Web is provided via HTML and formatted for human browsing rather than for software programs. This situation calls for a tool that automatically extracts information from semistructured Web information sources, increasing the usefulness of value-added Web services. We present a <u>si</u>gnal-<u>r</u>epresentation-b<u>a</u>sed <u>p</u>arser (SIRAP) that breaks Web pages up into logically coherent groups - groups of information related to an entity, for example. Templates for records with different tag structures are generated incrementally by a Histogram-Based Correlation Coefficient (HBCC) algorithm, then records on a Web page are detected efficiently using templates generated by matching. Hundreds of Web pages from 17 state-of-the-art search engines were used to demonstrate the feasibility of our approach.

scholarly journals Evaluation of CMORPH Precipitation Products at Fine Space–Time Scales

2009 ◽  
Vol 10 (1) ◽  
pp. 300-307 ◽  
Author(s):  
Dawit A. Zeweldi ◽  
Mekonnen Gebremichael
Keyword(s):  
High Resolution ◽  
Time Scales ◽  
Spatial Patterns ◽  
Time Scale ◽  
Statistical Techniques ◽  
Spatial Fields ◽  
Satellite Rainfall ◽  
Performance Statistics ◽  
Averaging Time ◽  
Temporally Correlated

Abstract In this study, a comparison of the spatial patterns of high-resolution precipitation products obtained from the Climate Prediction Center’s morphing technique (CMORPH), which is a satellite-only product, and gauge-adjusted Next Generation Weather Radar (NEXRAD) rainfall observations is performed using a variety of statistical techniques for the Little Washita watershed region in Oklahoma for a 3-yr period. Results show that 1) the performance statistics of CMORPH show tremendous variability from one hour to the next, suggesting that the performance statistics are dynamic in time, and therefore each satellite rainfall product should be accompanied by an error product to make it more meaningful; 2) CMORPH is positively biased in summer and negatively biased in winter, consistent with the findings of previous studies; 3) CMORPH spatial fields tend to be smoother than NEXRAD output; 4) the errors are temporally correlated, in particular within the range from 1 to 6 accumulation hours, implying that averaging CMORPH products over these time scales does not reduce the errors significantly; and 5) the errors become less correlated in time as the averaging time scale increases to the range from 6 to 24 h.

scholarly journals Impact of new frequency standards on the international time scales

2009 ◽  
Vol 5 (H15) ◽  
pp. 223-224
Author(s):  
E. Felicitas Arias ◽  
Gianna Panfilo
Keyword(s):  
Time Scales ◽  
World Wide ◽  
Clock Frequency ◽  
Time Transfer ◽  
Reference Time ◽  
Weights And Measures ◽  
International Bureau ◽  
Frequency Standards ◽  
Remote Sites ◽  
Primary Frequency

AbstractThe reference time scales maintained at the International Bureau of Weights and Measures (BIPM) are constructed with data from industrial clocks and primary frequency standards operated in national metrology laboratories and observatories world-wide distributed. Clocks are compared making use of techniques of time transfer between remote sites. The algorithm of calculation relies on clock weighting and clock frequency prediction. We briefly present hereafter the influence of some clocks on the scales, as well as the possibilities for improvement.

scholarly journals Annual Wave in the world-wide F-Region Ionization

MAUSAM ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 69-72
Author(s):  
B. N. BHARGAVA
Keyword(s):  
Linear Relationship ◽  
World Wide ◽  
F Region ◽  
A Value ◽  
The World ◽  
Latitude Variation ◽  
Order Of Magnitude ◽  
Annual Component ◽  
Relationship Of ◽  
Made In

An analysis of squares of noon median F2 layer critical frequencies for a 3-year period has been made in order to derive the latitude variation of the annual effect in the electron densities and its relation to average F21ayer ionization. The results indicate that the annual component varies with the latitude in a manner very nearly similar to that of the steady ionization R0 and that for a given value of Ro for any latitude. R1 which can be derived approximately from a linear relationship of the type Rl = 0.3 Ro-4.5. A similar analysis of 9-year data, for precise phase and amplitude of the annual component for a pair of stations yields a value of Rl which is of the same order of magnitude as Ro and which attains a maximum around the epoch of minimum sun-earth distance.

Pediatrics electronic pages http://www.pediatrics.org

PEDIATRICS ◽  
1996 ◽  
Vol 98 (6) ◽  
pp. 1193-1194
Author(s):  
JEFFREY D. HORBAR ◽  
JOHN SACK
Keyword(s):  
Health Professionals ◽  
World Wide ◽  
State Of The Art ◽  
Scientific Communication ◽  
Printing Press ◽  
The Internet ◽  
Electronic Information ◽  
American Academy Of Pediatrics ◽  
The World ◽  
On Line

Pediatrics electronic pages, the official on-line journal of the American Academy of Pediatrics, will appear on the World Wide Web beginning in January 1997. This Internet publication represents a commitment by the Academy to provide its members and other health professionals with access to a state-of-the-art electronic information tool in the field of pediatrics. In partnership with HighWire Press of Stanford University, the Academy will strive to develop this new medium of scientific communication to meet the needs of both clinicians and scientists. The Internet has the potential to transform scientific communication; its impact may be as profound as the invention of the printing press.

scholarly journals Time scale bias in erosion rates of glaciated landscapes

2016 ◽  
Vol 2 (10) ◽  
pp. e1600204 ◽  
Author(s):  
Vamsi Ganti ◽  
Christoph von Hagke ◽  
Dirk Scherler ◽  
Michael P. Lamb ◽  
Woodward W. Fischer ◽  
...  
Keyword(s):  
Time Scales ◽  
Time Scale ◽  
Erosion Rate ◽  
Earth Science ◽  
Geologic Time ◽  
Erosion Rates ◽  
River Incision ◽  
Tightly Coupled ◽  
Heavy Tailed ◽  
Averaging Time

Deciphering erosion rates over geologic time is fundamental for understanding the interplay between climate, tectonic, and erosional processes. Existing techniques integrate erosion over different time scales, and direct comparison of such rates is routinely done in earth science. On the basis of a global compilation, we show that erosion rate estimates in glaciated landscapes may be affected by a systematic averaging bias that produces higher estimated erosion rates toward the present, which do not reflect straightforward changes in erosion rates through time. This trend can result from a heavy-tailed distribution of erosional hiatuses (that is, time periods where no or relatively slow erosion occurs). We argue that such a distribution can result from the intermittency of erosional processes in glaciated landscapes that are tightly coupled to climate variability from decadal to millennial time scales. In contrast, we find no evidence for a time scale bias in spatially averaged erosion rates of landscapes dominated by river incision. We discuss the implications of our findings in the context of the proposed coupling between climate and tectonics, and interpreting erosion rate estimates with different averaging time scales through geologic time.

Infrastructure Support for Smart Organizations

2011 ◽  
pp. 257-288
Author(s):  
Peter Bertok ◽  
Xinjian Xu
Keyword(s):  
Web Services ◽  
World Wide ◽  
Value Added ◽  
The Internet ◽  
Service Component ◽  
New Approach ◽  
Competitive Edge ◽  
A Value ◽  
New Organizational Forms ◽  
The World

In a rapidly changing world, continuous adoption of new practices is crucial for survival; organizations embracing the latest technologies have a competitive edge. Smart organizations readily take on board new organizational forms and practices, those in particular that offer agility and responsiveness. The Internet and the World Wide Web offer a new way of collaboration via Web services, but heterogeneity of different service components make cooperation difficult. This chapter describes a new approach to combine Web services by employing a layered structure, in which composition of a value-added service can be built from individual components, and each service component can have semantically equivalent but syntactically different alternatives.

scholarly journals Long term stability of atomic time scales

2012 ◽  
Vol 10 (H16) ◽  
pp. 209-210
Author(s):  
G. Petit ◽  
F. Arias
Keyword(s):  
Time Scales ◽  
Time Scale ◽  
Time Transfer ◽  
Long Term Stability ◽  
Relative Value ◽  
The Stability ◽  
Primary Standards ◽  
Stability And Accuracy ◽  
Atomic Time

AbstractWe review the stability and accuracy achieved by the reference atomic time scales TAI and TT(BIPM). We show that they presently are in the low 10−16 in relative value, based on the performance of primary standards, of the ensemble time scale and of the time transfer techniques. We consider how the 1 × 10−16 value could be reached or superseded and which are the present limitations to attain this goal.

Sign in / Sign up

Export Citation Format

Share Document