Fr.: amortissement apériodique
A system in which the → damping is great enough to prevent oscillation.
Recurring at regular intervals of time.
Adjective of → period.
Fr.: comète périodique
A comet with a period of less than 200 years. Also called short-period comet.
Fr.: fonction périodique
A function f(x) if for all x, f(x + P) = f(x), where P is a positive constant. The least value of P > 0 is called the period of f(x).
Fr.: mouvement périodique
Any motion that recurs in identical forms at equal intervals of time.
Fr.: système périodique
jadval-e dowreyi (#)
Fr.: tableau périodique
An arrangement of the → chemical elements
in order of their → atomic numbers in such a way
as to demonstrate periodic similarities and trends in physical and chemical properties.
Elements with similar properties are arranged in the same column
(called a group), and elements with the same number of
→ valence electrons, or number of electrons in the outer shell,
are arranged in the same row (called a period).
Under the latest recommendations from IUPAC (the International Union of Pure
and Applied Chemistry), the groups are labelled 1 to 18 from left
to right (1988, Pure and Applied Chemistry 60, 431).
Also called Mendeleev's table.
Fr.: terme périodique
In perturbation theory used in celestial mechanics, a term that indicates a bounded disturbance which recurs regularly. → secular term.
Fr.: onde périodique
An oscillatory motion in which each point is repeatedly displaced at equal time intervals.
Same as → periodic.
periodically variable supergiant (PVSG)
abarqul-e vartande-ye dowreyi
Fr.: supergéante variable périodiquement
A variable → supergiant star with typical periods of the order of 10 to 100 days and amplitudes less than a few tenths of a magnitude. PVSGs are thought to be pulsating → g modes, caused by a density inversion, arising from an → opacity bump, most likely from Fe, H, and/or He.
A state or condition characterized by regular repetition in time or space.
Fr.: mouvement quasipériodique
In a dynamical system, a form of motion that is regular but never exactly repeating. Quasiperiodic motion appears when the system contains two or more incommensurate frequencies.