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utility 1) hudemandi; 2) hudemand Fr.: 1) utilité; 2) utilitaire 1) The state or quality of being useful; usefulness. M.E. utilite, from O.Fr. utilite "usefulness," earlier utilitet, from L. utilitatem "usefulness, profit," from utilis "usable," from uti "to use." Hudemandi, from hudemand "utile," from hudé "use" (as in bihudé "useless, vain, absurd"), from Mid.Pers. hudâg "good, useful, beneficent;" Av. hūdā- "doing good, producing wealth," from hū-, hu-, → eu-, + Av./O.pers. dā- "to give, grant, put," dadāiti "he gives;" Mid.Pers./Mod.Pers. dâdan "to give, put" (cf. Skt. dadáti "he gives;" Gk. tithenai "to place, put, set," didomi "I give;" L. dare "to give, offer;" Rus. delat' "to do;" O.H.G. tuon, Ger. tun, O.E. don "to do;" PIE base *dhe- "to put, to do") + -mand(i) |
utility software narm-afzâr-e hudemand Fr.: logiciel utilitaire A part of the system software designed to support the operation of application software and is used to manage the computer files. Examples of utility software are disk diagnosis program, backup software, password generation software, and virus protection software. Also called utilities. |
validity pâymandi Fr.: validité Logic: Of an argument, whether or not the conclusion follows logically from the premises and the allowable syllogisms of the logical system being used. Quality noun from → valid. |
variability vartandegi Fr.: variabilité The quality, state, or degree of being variable or changeable. Quality noun from → variable. |
variability index dišan-e vartandegi Fr.: indice de variabilité A measure of variability of a star (such as Welch-Stetson variability index) which combines the information from two passbands assuming that changes in the star's luminosity occur nearly simultaneously at all optical wavelengths. → variability; → index. |
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. |
vector density cagâli-ye bordâr Fr.: densité de vecteur A → tensor density of → order 1. |
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. |
velocity gradient zine-ye tondâ Fr.: gradient de vitesse Fluid Mechanics: The rate at which the velocity changes with the distance across the flow. When a fluid flows past a stationary wall, the fluid right close to the wall does not move. However, away from the wall the flow speed is not zero. Therefore a velocity gradient exists, which is due to adhesive, cohesive, and frictional forces. The amount of the velocity gradient is characteristic of the fluid. |
velocity law qânun-e tondâ Fr.: loi de vitesse In the theory of → radiation-driven winds, an equation that describes the behavior of the → wind velocity of → hot stars as a function of distance from the star. This velocity β-law is given by the expression: v(r) = v_{∞}(1 - R_{*}/r)^{β}, where v_{∞} is the → terminal velocity, R_{*} is the stellar radius, and r the distance from the center. For → O-type stars, the exponent is estimated to be β = 0.8. |
velocity of light tondi-ye nur, tondâ-ye ~ Fr.: vitesse de la lumière A → physical constant which represents the ultimate speed limit for anything moving through space, according to the theory of → special relativity. It is the speed of propagation of → electromagnetic waves in a vacuum, equal to 299,792.458 km/s (nearly 3 x 10^{8} m/s). The velocity of light appears as the connecting link between mass and energy in the → mass-energy relation. Usually denoted by c, from L. celeritas "swiftness," from celer "swift," → acceleration. |
velocity pressure fešâr-e tavânik Fr.: pression dynamique |
velocity profile farâpâl-e tondâ Fr.: profil de vitesse A plot of the fluid velocity as a function of position. |
velocity space fazâ-ye tondâyi, ~ tondâhâ Fr.: espace de vitesses Of a dynamical system, a three-dimensional space which consists of the set of values that the velocity can take (v_{x}, v_{y}, v_{z}). → phase space. |
velocity-distance relation bâzâneš-e tondâ-durâ Fr.: relation vitesse-distance The linear relation wherein all galaxies are moving away from one another, with velocities that are greater with increasing distance of the galaxy. Same as → Hubble's law. |
Venus visibility padidâri-ye Nâhid Fr.: visibilité de Vénus The conditions under which Venus can be seen from Earth as
it travels in its orbit around the Sun.
The → synodic period of Venus, that is the time Venus takes to
be seen again from the
Earth in the same position with respect to the Sun, is 583,92 days
or just over 19 months. When Venus is between Earth and Sun
(→ inferior conjunction) or on the far side of the sun
(→ superior conjunction), it is invisible in the Sun's glare. Since its
→ greatest elongation
from the Sun is never more than 47°, Venus appears only as
"the morning star" and "the evening star."
So at its greatest → western elongation
Venus will rise about
three hours ahead of the Sun and at its greatest → eastern elongation
it will set about three hours after sunset.
Its entire cycle is as follows: → Venus; → visibility. |
verifiability principle parvaz-e râst-jost-paziri Fr.: principe de vérifiabilité In logical positivism philosophy, the claim that a statement is literally meaningful (it expresses a proposition) if and only if it either actually has been verified or could at least in principle be verified. Quality noun from → verifiable; → principle. |
viscosity vošksâni (#) Fr.: viscosité The property of a → fluid that resists the force tending to cause the fluid to flow. Viscosity may be thought of as the internal → friction of two fluid layers which flow parallel to each other at different speeds. The cause of viscosity is the transport of → momentum by the molecules from one layer to the other. Viscosity is given by η = φ.u.λ.ρ, where φ is a coefficient which depends on the nature of the interaction between the molecules, u is the average velocity of thermal motion of the molecules, λ is the → mean free path, and ρ the → density of the fluid. Also called → dynamic viscosity or → absolute viscosity. See also → kinematic viscosity. |
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