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regression curve xam-e vâyâzeš Fr.: courbe de régression A curve representing a non-linear relationship between two or more → variables. → regression, → curve. |
regression equation hamugeš-e vâyâzeš Fr.: équation de régression A mathematical expression that describes the relationship between two or more variables. It indicates the nature of the relationship and, in particular, the extent to which one can predict some variables by knowing others. → regression, → equation. |
regression function karyâ-ye vâyâzeš Fr.: fonction de régression A mathematical function that describes the relationship between two or more variables in a set of data. → regression, → function. |
regression line xatt-e vâyâzeš Fr.: droite de régression The curve representing a → linear regression. It is a line drawn through a set of data that summarizes the relationship between the → variables being studied. → regression, → line. |
regression of the nodes pasraft-e gerehhâ , ~ gowzahrhâ Fr.: régression des noeuds The slow motion of the → nodes of the Moon's orbit in the opposite direction to the Moon's movement. This westward motion, caused by perturbations of other bodies, mainly the Earth and Sun, has a rate of 19.35 degrees per year, making one rotation in 18.6 years. → regression; → node. |
regular function karyâ-ye bâsâmân Fr.: fonction régulière A function of a complex variable which is single-valued in a domain and which has a finite derivative at every point. |
regular reflection bâztâb-e bâsâmân Fr.: réflexion régulière The reflection of light when the reflecting surface is very smooth and the reflected rays bounce off parallel to each other. Opposite of → diffuse reflection; same as → specular reflection. → regular; → reflection. |
regulation razaneš Fr.: régulation 1) The act of regulating; the state of being regulated. Verbal noun of → regulate. |
Regulus (α Leonis) Širdel Fr.: Régulus The brightest star in the constellation → Leo (V = 1.35). Regulus is approximately 77.5 light-years from Earth. It is a triple star system composed of a hot, bluish-white star with a pair of small, faint companions. The main star (Regulus A) is a main sequence of type B7, with a luminosity 140 times brighter than the Sun. Its equatorial rotation speed being 317 kilometers per second, the fast rotation distorts Regulus into an oblate spheroid with an equatorial diameter about 30 percent larger than the polar diameter. As a result, the poles, with a temperature of 15,400 Kelvin, are much hotter than the equator, which glows at 10,200 Kelvin. L., literally "little king," diminutive of rex "king," related to regere "to keep straight, guide, lead, rule," from PIE base *reg- "to rule, to lead straight, to put right;" akin to Pers. râst "right, straight, correct," → right. Širdel, literally "the Lion's heart,"
on the model of Ar. Qalb al-Asad ( |
reionization bâzyoneš Fr.: reionisation 1) The act or process of reionizing a gas; an instance of this action. |
reionization epoch zime-ye bâzyoneš Fr.: époque de réionisation An early epoch in the → Universe's history, but after the → recombination epoch, when the → first stars formed and their → ultraviolet light began to ionize the → neutral hydrogen gas that filled the Universe. The epoch of reionization is estimated to last between → redshifts of 12 to 6 (or when the Universe had between 2 and 5% of its age). Reionization marks the end of the → Dark Age in cosmic history. → reionization; → epoch. |
reionize bâzyonidan Fr.: reioniser |
relation bâzâneš Fr.: relation General: A connection or association between two or more things. Verbal noun of → relate. |
relation symbol nemâd-e bâzâneš Fr.: symbole de relation Same as → predicate symbol. |
relational bâzâneši Fr.: relationnel Of or pertaining to relations. |
relational data structure sâxtâr-e dâdehâ-ye bâzâneši Fr.: structure de données relationnelle A type of data structure in which data are represented as tables in which no entry contains more than one value. → relational; → data; → structure. |
relational system râžmân-e bâzâneši Fr.: système relationnel A database management system in which a relational data structure is used. → relational; → system. |
relativistic aberration birâheš-e bâzânigimand Fr.: aberration relativiste The aberration of light for an object moving with
→ relativistic speed. In contrast to the classical case,
the → Lorentz transformation between the
→ rest frame of the observer and that of the object
must be used. Relativistic aberration is expressed by the equation:
cos φ' = (cos φ - → relativistic; → aberration. |
relativistic precession pišâyân-e bâzânigimand Fr.: précession relativiste A → general relativistic phenomenon in which the line joining the → apsides of an orbit gradually rotates in a → prograde direction. Also called the → orbital precession and → perihelion precession. Although the general relativistic precession of Mercury's orbit is extremely small, the similar precession observed in the orbit of the → binary pulsar PSR B1913+16 amounts to 4.23 degrees per year, i.e. 36,000 times greater than the → advance of perihelion of Mercury. → relativistic; → precession. |
relativistic spin precession pišâyân-e âse-ye carxeš-e bâzânigi-mand Fr.: précession de l'axe de rotation relativiste The change in the direction of the → rotation axis of a → pulsar in a → binary pulsar. In such a system, → geodetic precession leads to a relativistic → spin-orbit coupling, analogous of → spin-orbit coupling in atomic physics. In consequence, the pulsar spin precesses about the total → angular momentum, changing the relative → orientation of the pulsar toward Earth (Damour & Ruffini, 1974). As a result, the angle between the pulsar → rotation axis and our → line of sight changes with time, so that different portions of the emission beam can be observed leading to changes in the measured pulse profile. In extreme cases, the precession may even move the beam out of our line of sight and the pulsar may disappear as predicted for PSR 1913+16 for the year 2025. → relativistic; → spin; → precession. |
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