An Etymological Dictionary of Astronomy and AstrophysicsEnglish-French-Persian

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

Homepage

Number of Results: 6 Search : variation
 annual variation   ورتش ِ سالانه   varteš-e sâlânéFr.: variation annuelle   Generally, the variation of a quantity over a year. In particular the yearly change in the right ascension or declination of a star, produced by the combined effects of the precession of the equinoxes and the proper motion of the star.→ annual; → variation. calculus of variations   افماریک ِ ورتش‌ها   afmârik-e vartešhâFr.: calcul des variations   The study of maximum and minimum properties of → definite integrals.→ calculus; → variation.Afmârik, → calculus; varteš→ variation. secular variation   ورتش ِ دیریاز   varteš-e diryâzFr.: variation séculaire   Same as → secular perturbation.→ secular; → variation. variation   ورتش   vartešFr.: variation   1) General: An instance of changing, or something that changes. 2) Astro.: The periodic inequality in the Moon's motion that results from the combined gravitational attraction of the Earth and the Sun. Its period is half the synodic month, that is 14.77 days, and the maximum longitude displacement is 39'29''.9. See also: → calculus of variations, → annual variation, → secular variation.M.E., from O.Fr. variation, from L. variationem (nominative variatio) "difference, change," from variatus, p.p. of variare "to change," → vary.Varteš, verbal noun from vartidan, → vary. variational   ورتشی   vartešiFr.: variationnel   Of or describing a → variation.→ variation; → -al. variational principle   پروز ِ ورتشی   parvaz-e vartešiFr.: principe variationnel   Any of the physical principles that indicate in what way the actual motion of a state of a mechanical system differs from all of its kinematically possible motions or states. Variational principles that express this difference for the motion or state of a system in each given instant of time are called → differential. These principles are equally applicable to both → holonomic and → nonholonomic systems. Variational principles that establish the difference between the actual motion of a system during a finite time interval and all of its kinematically possible motions are said to be → integral. Integral variational principles are valid only for holonomic systems. The main differential variational principles are: the → virtual work principle and → d'Alembert's principle.→ variational; → principle.