Time And Frequency Theory And Fundamentals

The document is a tutorial Monograph describing various aspects of time and frequency (T/F). Included are chapters relating to elemental concepts of precise time and frequency; basic principles of quartz oscillators and atomic frequency standards; historical review, recent progress, and current status of atomic frequency standards; promising areas for developing future primary frequency standards; relevance of frequency standards to other areas of metrology including a unified standard concept; statistics of T/F data analysis coupled with the theory and construction of the NBS atomic time scale; an overview of T/F dissemination techniques; and the standards of T/F in the USA. The Monograph addresses both the specialist in the field as well as those desiring basic information about time and frequency. The authors trace the development and scope of T/F technology, its improvement over periods of decades, its status today, and its possible use, applications, and development in days to come.

The object of this NATO Advanced Study Institute was to pre sent a tutorial 'introduction both to the basic physics of recent spectacular advances achieved in the field of metrology and to the determination of fundamental physical constants. When humans began to qualify their description of natural phenomena, metrology, the science of measurement, developed along side geometry and mathematics. However, flam antiquity to modern times, the role of metrology was mostly restricted to the need of commercial, social or scientific transactions of local or at most national scope. Beginning with the Renaissance, and particularly in western Europe during the last century, metrology rapidly developed an international character as a result of growing needs for more accurate measurements and common standards in the emerging indus trial society. Although the concerns of metrology are deeply rooted to fundamental sciences, it was, until recently, perceived by much of the scientific community as mostly custodial in character.

Artificial Intelligence and Object-Oriented Technologies to Searching: An Algorithmic Tour

Periodical phenomena or, more precisely, quasiperiodical phenomena, occupy a central position in physics. For a long time, their most important parameter has been their period. However, nowadays, we are much more interested in their frequency, and the many reasons for this are discussed in this book. Throughout history, evaluations of time have been based on periodical phenomena such as the apparent motion of the Sun. Indeed, the oldest unit of time is the day. The apparent motion of the Moon and of the celestial sphere, including changes in the appearance of the former, provided longer units, namely, week, month and year. All these periodical phenomen- the natural clocks - were obviously well suited to the observation and prediction of the evolution of nature with its seasonal rhythm. The gnomon and the clepsydra gave reasonably precise subdivisions of the day that could be used in timing human activities, so long as they were mostly agricultural. The invention of the pendulum and of balance wheel clocks marked the dawn of industrial civilisation, which soon de manded measurements of time with ever increasing precision over shorter and shorter periods.

IAU C196 coincided with the 8 June 2004 transit of Venus, producing the exciting, eclectic mix that can be found in these proceedings: the amazing history of the English North-country astronomers of the seventeenth century; the AU at a precision of 1.4 m; the explanation for the infamous black drop effect; a possible Mayan observation of a transit of Venus in the thirteenth century; the vexed question of leap seconds and time scales; history, distances, parallaxes, the solar system at exquisite precision and future space missions that will revolutionise astronomy.