recession velocity tondâ-ye dur šodan Fr.: vitesse d'éloignement The velocity with which an object moves away from another object or a reference point. |
reciprocity theorem farbin-e dosuyegi Fr.: théorème de réciprocité 1) General: Any theorem that expresses various reciprocal relations for the
behavior of some physical systems, in which input and output can be
interchanged without altering the response of the system to a given
excitation. Reciprocity, from L. reciproc(us) "returning the same way, alternating" + → -ity; → theorem. Farbin, → theorem; dosuyegi, quality noun of dosuyé nuanced term of dosu "two-sided," from do, → two, + su "direction, side," from Mid.Pers. sôk "direction, side." |
relative velocity tondâ-ye bâzâni Fr.: vitesse relative For two objects A and B, the velocity which B, supposing itself at rest, assigns to A. |
relativistic velocity tondâ-ye bâzânigimand Fr.: vitesse relativiste The velocity of a body when it is a significant fraction of the → speed of light. → relativistic; → velocity. |
Rosseland mean opacity kederi-ye miyângin-e Rosseland Fr.: opacité moyenne de Rosseland The → opacity of a gas of given composition, temperature, and density averaged over the various wavelengths of the radiation being absorbed and scattered. The radiation is assumed to be in → thermal equilibrium with the gas, and hence have a → blackbody spectrum. Since → monochromatic opacity in stellar plasma has a complex frequency dependence, the Rosseland mean opacity facilitates the analysis. Denoted κ_{R}, it is defined by: 1/κ_{R} = (π/4σT^{3}) ∫(1/k_{ν}) (∂B/∂T)_{ν}dν, summed from 0 to ∞, where σ is the → Stefan-Boltzmann constant, T temperature, B(T,ν) the → Planck function, and k_{ν} monochromatic opacity (See Rogers, F.J., Iglesias, C. A. Radiative atomic Rosseland mean opacity tables, 1992, ApJS 79, 507). Named after Svein Rosseland (1894-1985), a Norwegian astrophysicist, who obtained the expression in 1924; → mean; → opacity. |
rotational velocity tondâ-ye catxeši Fr.: vitesse de rotation The velocity of a → rotational motion; same as → angular velocity. → rotational; → velocity. |
scientificity dânešigi Fr.: scientificité The quality of the practices and theories that aim at establishing reproducible regularities in phenomena by using experimental method and providing a clearly formulated description. → scientific + → -ity. |
solar metallicity felezigi-ye xoršidi Fr.: métallicité solaire The proportion of the solar matter made up of → chemical elements heavier than → helium. It is denoted by Z, which represents the sum of all elements heavier than → helium, in mass fraction. The most recent determination of the solar Z gives a value of 0.0134 (Asplund et al. 2009, ARAA 47, 481), corresponding to the present-day photospheric composition. → solar; → metallicity. |
solar velocity tondâ-ye xoršid, ~ xoršidi Fr.: vitesse solaire The rate of change of the Sun's position with respect to the local standard of rest toward the → solar apex. |
space velocity tondâ-ye fazây Fr.: vitesse spatiale The velocity of a star relative to the Sun. |
stellar metallicity felezigi-ye setâre-yi Fr.: métallicité stellaire The metallicity derived from observations of stars in galaxies. It is mainly based on spectral → absorption lines in → ultraviolet (UV) and optical ranges. Stellar metallicity is a direct measure of the amount of metals in a galaxy, since large part of heavy elements lies in its stars. → stellar; → metallicity. |
tangential velocity tondâ-ye sâyâni Fr.: vitesse tangentielle 1) The instantaneous linear velocity of a body moving in a circular path.
It is equal to the → angular velocity multiplied
by the radius: v_{t} = ωr. → tangential; → velocity. |
terminal velocity tondâ-ye pâyâni Fr.: vitesse terminale 1) The constant maximum velocity reached by a body falling under gravity through a
liquid or gas, especially the atmosphere. The body ceases
to accelerate downward because the force of gravity is equal
to the opposing force of resistance by the medium. |
thermoelectricity damâbarq (#) Fr.: thermo-éléctricité The electricity produced by heat or temperature difference in a conductor. → thermo- + → electricity. |
transverse velocity tondâ-ye tarâgozar Fr.: vitesse transverse Same as → tangential velocity. → transverse; → velocity. |
univocity yekvâzi Fr.: monosémie |
vector angular velocity bordâr-e tondâ-ye zâviye-yi Fr.: vecteur de vitesse angulaire Of a rotating body, a vector of magnitude ω (→ angular velocity) pointing in the direction of advance of a right-hand screw which is turned in the direction of rotation. |
velocity tondâ Fr.: vitesse The time rate of change of position in a given direction, measured as length per unit time. → speed. L. velocitatem (nominative velocitas) "swiftness, speed," from velox (genitive velocis) "swift." Tondâ, from tond "swift, rapid, brisk; fierce, severe" (Mid.Pers. tund "sharp, violent;" Sogdian tund "violent;" cf. Skt. tod- "to thrust, give a push," tudáti "he thrusts;" L. tundere "to thrust, to hit" (Fr. percer, E. pierce, ultimately from L. pertusus, from p.p. of pertundere "to thrust or bore through;" PIE base *(s)teud- "to thrust, to beat") + noun suffix -â. |
velocity curve xam-e tondâ Fr.: courbe de vitesse A plot of the radial velocity of an object against time, derived from the Doppler shift of spectral lines. |
velocity dispersion pâšeš-e tondâ Fr.: dispersion de vitesses The → standard deviation of a velocity → distribution. It indicates how objects of the sample move relative to one another. Objects with similar velocities have a small velocity dispersion, whereas objects with very different velocities have a large velocity dispersion. → velocity; → dispersion. |