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convocation hamvac Fr.: convocation The act of convoking. The state of being convoked. Verbal noun of → convoke. |
convoke hamvacidan Fr.: convoquer To call together; summon to meet or assemble (Dictionary.com). M.E., from M.Fr. convoquer, from L. convocare "to call together," from → con- "together," + vocare "to call," from vox, → voice. Hamvacidan, from ham-, → com-, + vac "word," → voice, + -idan infinitive suffix. |
convolution hamâgiš Fr.: convolution 1) A mathematical combination of two functions which involves multiplying
the value of one function at a given point with the value of another
function, the weighting function, for a displacement from that point
and then integrating over all such displacements. The process is
repeated for every point of the function. Convolution expresses how the shape of
a function is altered by the other. In mathematical terms, the convolution of two functions
f(x) and g(x) is defined by:
f*g = ∫f(u)g(x - u) du, integral from -∞ to +∞. Verbal noun of → convolve. |
convolution theorem farbin-e hamâgiš Fr.: théorème de convolution A theorem stating that the → Fourier transform of the convolution of f(x) and g(x) is equal to the product of the Fourier transform of f(x) and g(x): F{f*g} = F{f}.F{g}. → convolution; → theorem. |
convolve hamâgišidan Fr.: convoluer 1) To roll or wind together. From L. convolvere "to roll together," from → com- "together" + volvere "to roll, turn," PIE base *wel- "to turn, revolve;" cf. Skt. valati "he turns," ulba- "womb, vulva," Gk. eilyein "to roll, wrap, fold." Hamâgiš, from ham- "together", → com-, + âgišidan "to entwine, to twist" (Dehxodâ), from Mid.Pers. gyš- "to bind, tie," hangyš- "to fasten to;" cf. Sogd. patigyš- "to imprison, confine;" Proto-Ir. *kaš- "to imprison" (Cheung 2007). |
cookie cookie Fr.: cookie An identifier file that a website automatically places in the user's computer hard drive. The cookie is used by the website to identify that a user has been on the website previously. Users concerned about privacy may disable cookies in their browser's setting. From Du. koekje "little cake," diminutive of koek "cake," from M.Du. koke, akin to cake, M.E., from O.N. kaka (O.H.G. kuocho "cake"), any relation with Pers. kâk "biscuit; dry bread"? (loaned in Ar. ka'k). |
cool sard (#) Fr.: froid Moderately cold. M.E., from O.E. col, PIE base *gel- "cold, to freeze." Sard "cold, cool," from Mid.Pers. sart, Av. sarəta- "cold," Skt. śiśira- "cold," Ossetian sald "cold," L. calidus "warm," Lith. šaltas "cold," Welsh clyd "warm," PIE *keltos- "cool". |
cool hypergiant hiperqul-e sard Fr.: hypergéante froide A highly unstable, → very massive star lying just below the empirical upper luminosity boundary in the → H-R diagram (→ Humphreys-Davidson limit) with spectral types ranging from late A to M. Cool hypergiants very likely represent a very short-lived evolutionary stage, and are distinguished by their high → mass loss rates. Many of them also show photometric and spectroscopic variability, and some have large → infrared excesses and extensive circumstellar ejecta. The evolutionary state of most of these stars is not known but they are all → post-main-sequence stars (Humphreys, 2008, IAUS 250). → cool; → hypergiant. |
coolant sardgar Fr.: refroidissant An agent of → cooling process. → cooling. |
cooling 1) sardeš; 2) sardkonandé, sardgar Fr.: 1) refroidissement; 2) refroidissant 1) The process of losing heat; a falling temperature. |
cooling flow tacân-e sardeš Fr.: flot de refroidissement A phenomenon observed in a → cluster of galaxies, whereby the cluster core loses energy via X-ray radiation because of the collisions between the gas particles. The radiation rate is proportional to the square of the density, and the → cooling time, which remains in the outer parts too large, becomes smaller than the → Hubble time in the core. As a result, the central regions of clusters of galaxies cool down; and since in the center of a cluster gas pressure and gravitational attraction are in equilibrium, the gas density has to rise to maintain the pressure necessary for supporting the outer layers of gas. To cause its density to rise, the cooled gas has to flow inward. As the densest gas, which cools quickest, is already concentrated in the center of the cluster, the inward flow will start at the center, soon followed by the outer layers. This flow of gas is called the cooling flow. Cooling flows are moderated through feedback due to the → supermassive black hole in the nucleus of the central galaxy. The gas inflow to the center fuels the → active galactic nucleus (AGN). The latter then heats again the gas through its → radio jets. |
cooling line xatt-e sardkonandé, ~ sardgar Fr.: raie de refroidissement The spectral → emission line through which the → colling process takes place. |
cooling process farâravand-e sardeš Fr.: processus de refroidissement The process of → radiative cooling in which the → temperature of an astrophysical system decreases due to the radiation of a major → emission line. For example, → molecular → emission at → millimeter wavelengths and → submillimeter wavelengths results in decreasing the temperature in molecular clouds. At temperatures less than 300 K, the main → coolant is the → carbon monoxide (CO) molecule which contains most of the carbon. Similarly, the → [C II] line is a major coolant in → photodissociation regions. See also → line cooling, → cooling time. |
cooling time zamân-e sardeš Fr.: temps de refroidissement 1) The time in which a → white dwarf cools to half its
temperature. It depends on the composition, the mass, and the actual luminosity
at some point in time. Cooling time is given by the relation:
t = 8.8 × 10^{6} (12/A) (M)^{5/7} (μ/2)^{-2/7}
(L)^{-5/7} in years, where M and L are mass and luminosity in
solar units, A the mean → atomic mass, and μ the
→ mean molecular weight (Iben & Tutukov, 1984, ApJ 282, 615).
See also → Mestel theory;
→ white dwarf crystallization. |
coordinate 1) hamârâ (#); 2) hamârâstan Fr.: 1) coordonnée; 2) coordonner 1) Any of a series of numbers which, in relation to a given
→ frame of reference, locate a point in space. See also:
→ astronomical coordinates→ canonical coordinates→ Cartesian coordinates→ celestial coordinates→ cylindrical coordinates→ equatorial coordinates→ Galactic coordinates→ generalized coordinates→ polar coordinates→ spherical coordinates→ precessed coordinates→ topocentric coordinates. From L. co- "together," → com- + orinatus, p.p. of ordinare "to put in order, arrange," from ordo "order." Hamârâ, from ham- "together," → com- + ârâ stem of ârâstan "to arrange, to set in order, adorn," Mid.Pers. ârây-, ârâstan "to arrange, adorn," O.Pers. râs- "to be right, straight, true," râsta- "straight, true" (Mod.Pers. râst "straight, true"), râd- "to prepare," Av. râz- "to direct, put in line, set," Av. razan- "order," Gk. oregein "to stretch out," L. regere "to lead straight, guide, rule," p.p. rectus "right, straight," Skt. rji- "to make straight or right, arrange, decorate," PIE base *reg- "move in a straight line." |
coordinate system râžmân-e hamârâ Fr.: système de coordonnées Math: A system for locating each point in space by a set of numbers. → coordinate; → system. |
coordinate time zamân-e hamârâ Fr.: temps-coordonnée In relativity, the proper time in the specified reference frame. Because of time dilation, this may differ from the time experienced by any participant in the events being considered. It is the time basis (or coordinate) to be used in the theory of motions referred to this system. → coordinate; → time. |
Coordinated Universal Time (UTC) zamân-e jahâni-ye hamrârâsté Fr.: temps universel coordonné An international high-precision time standard based on the Greenwich Mean Time and adjusted to compensate for divergence from atomic time. It is based on the non-uniform rotation of the Earth (UT1) and the perfectly uniform international atomic time (TAI). UTC differs from TAI by the total number of → leap seconds, so that UT1-UTC stays smaller than 0.9 sec in absolute value. → coordinate; → universal; → time. |
coordination hamârâyeš Fr.: coordination The act or state of coordinating or of being coordinated. Verbal noun of → coordinate. |
coordination compound candsâxt-e hamârâyeš Fr.: composé de coordination A chemical compound in which a group of atoms or ions are attached by a coordination bond to a usually metallic central atom or ion. → coordination; → compound. |
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