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compound fraction barxe-ye candsâxt Fr.: fraction composée Same as → complex fraction. |
compression factor karvand-e tanješ Fr.: facteur de compression In thermodynamics, the quantity Z = pV_{m}/RT, in which P is the gas pressure, V_{m} the molar volume, R the gas constant, and T the temperature. The compression factor is a measure of the deviation of a real gas from an ideal gas. For an ideal gas the compression factor is equal to 1. → compression; → facteur. |
conformal compactification hampakâneš-e hamdi Fr.: compactification conforme A mapping of an infinite → space-time onto a finite one that may make the far away parts of the former accessible to study. The technique invented by Penrose defines an equivalence class of → metrics, g_{ab} being equivalent to ĝ_{ab} = Ω^{2}g_{ab}, where Ω is a positive scalar function of the space-time that modifies the distance scale making the asymptotics of the physical metric accessible to study. → conformal; → compactification. |
contact 1) parmâs (#); 2) parmâsidan (#) Fr.: 1) contact; 2) contacter, toucher 1a) The act or state of touching or being in immediate proximity, as in a
→ contact binary. From L. contactus "a touching," p.p. of contingere "to touch," from → com- "together" + tangere "to touch." Parmâs "contact, touching," stem of parmâsidan "to touch, feel," from *pari-mars-, from Indo-Iranian *pari- "around" (O.Pers. pariy "around, about," Av. pairi "around, over," Skt. pari) + *mars- "to touch; to wipe, rub," Mid.Pers. marz "contact, touching," marzitan "to touch," Mod.Pers. mâlidan "to rub," Av. marəz- "to rub, wipe," marəza- "border, district," Skt. mrś- "to touch," mrśáti; L. mulceo "to caress," margo "edge" (Fr. marge "margin"); P.Gmc. *marko; Ger. Mark; E. mark, margin. |
contact binary dorin-e parmâsi Fr.: binaire de contact A binary system in which the two components are so close that they exchange gases in a complex manner. Their overlapping gravitational fields form a "peanut" shaped equipotential surface. |
continued fraction barxe-ye peydâšté Fr.: fraction continue In mathematics, a fraction whose numerator is an integer and whose denominator is an integer plus a fraction whose numerator is an integer and whose denominator is an integer plus a fraction and so on. |
contract terengidan Fr.: se contracter, contracter 1) To become smaller, shorter, tighter, as a metal when cooled. From M.E., from O.F., from L. contractus, p.p. of contrahere "to draw together," from → com- "together" + trahere "to draw." Terengidan, variant taranjidan [Dehxodâ] "to contract, become rough and hard, to be squeezed, compressed," Borujerdi terengessa "cramped, tightly dressed," Malâyeri terengidan "to be tightly dressed, cramped in a garment," related to tarang "horse girth, a strap for fastening a load," Proto-Iranian *trng- "to pull tight, squeeze, compress;" PIE base *strenk- "to pull tight, twist; tight, narrow" (cf. L. stringere "to bind or draw tight;" Gk. strangein "to twist;" Lith. stregti "to congeal;" O.E. streccian "to stretch," streng "string;" Ger. stramm, Du. stram "stiff"). |
contraction terengeš Fr.: contraction An act or instance of contracting; the quality or state of being contracted. Verbal noun of → contract. |
conversion factor karvand-e hâgard Fr.: facteur de conversion 1) A numerical factor that, by multiplication or division, translates one
unit or value into another. → conversion; → factor. |
corotating interaction region (CIR) nâhiye-ye andaržireš-e hamcarxandé Fr.: région d'interaction en corotation A spiral-shaped density enhancement formed around a star when fast stellar winds collide with slower material. This large-scale wind structure can extend from the stellar surface to possibly several tens of stellar radii. The CIRs can be produced by intensity irregularities at the stellar surface, such as dark and bright spots, magnetic loops and fields, or non-radial pulsations. The surface intensity variations alter the radiative wind acceleration locally, which creates streams of faster and slower wind material. CIRs are responsible for the → discrete absorption components seen in some ultraviolet → resonance lines of → hot stars (S. R. Cranmer & S. P. Owocki, 1996, ApJ 462, 469). → corotate; → interaction; → region. |
cosmic scale factor karvand-e marpal-e keyhâni Fr.: facteur d'échelle cosmologique A quantity, denoted a(t), which describes how the distances between any two galaxies change with time. The physical distance d(t) between two points in the Universe can be expressed as d(t) = R(t).x, where R(t) is the → scale factor and x the → comoving distance between the points. The cosmic scale factor is related to the → redshift, z, by: 1 + z = R(t_{0})/R(t_{1}), where t_{0} is the present time and t_{1} is the time at emission of the radiation. The quantity (1 + z) gives the factor by which the → Universe has expanded in size between t_{1} and t_{0}. It is also related to the → Hubble parameter by H(t) = R^{.}(t)/R(t), where R^{.}(t) is the time → derivative of the scale factor. In an → expanding Universe the scale factor increases with time. See also the → Friedmann equation. |
Coulomb interaction andaržireš-e Coulomb Fr.: interaction de Coulomb The reciprocal force between two or more → charged particles according to → Coulomb's law. → coulomb; → interaction. |
deactivate foružirândan Fr.: désactiver To cause to be → inactive; remove the → effectiveness of (Dictionary.com). |
decimal fraction barxe-ye dahdahi Fr.: fraction décimale A fraction expressed by using → decimal representation, as opposed to a vulgar fraction. For example, 2/5 is a vulgar fraction; 0.40 is a decimal fraction. |
deuterium enrichment factor karvand-e pordâri-ye doteriom Fr.: facteur d'enrichissement en deutérium The ratio between the D/H value in → water
and in → molecular hydrogen, as expressed by: → deuterium; → enrichment; → factor. |
deuterium fractionation barxâneš-e doteriom Fr.: fractionnement de deutérium The difference between the deuterium (D)/hydrogen (H) → abundance → ratio in an object with respect to that representing a standard or mean value for that type of objects. Same as → isotope fractionation of deuterium. In the gas phase chemistry many of the D fractionation reactions produce an excess of D atoms relative to → hydrogen atoms. Deuterium fractionation in → interstellar cloud cores, → protostars, and → Solar System bodies is frequently used to infer important aspects of their physical and chemical histories. For example, the → deuterium enhancement in the Earth's sea water, with respect to the cosmic abundance, has been interpreted as being due to → enrichment by → comet-like → planetesimals colliding with the young Earth. → deuterium; → fractionation. |
differential refraction šekast-e dagarsâneyi Fr.: refraction différentielle A problem encountered in astronomical spectroscopy, which consists of a loss of light from some wavelengths due to → atmospheric dispersion. In simple terms, differential refraction means that at nonzero → zenith distances an object cannot be simultaneously placed at the same position within a → slit at all wavelengths. This problem becomes more important for increasing → airmass, larger → spectral range, and smaller → slitwidths. To remedy this drawback, the slit should always be oriented along a direction perpendicular to the horizon, since differential refraction occurs in that direction. → differential; → refraction. |
diffract parâšidan (#) Fr.: diffracter Verbal form of → diffraction. → diffraction. |
diffraction parâš (#) Fr.: diffraction A wave property of light which allows it to curl around obstacles whose size is
about that of the wavelength of the light. As a → wavefront
of light passes by an opaque edge or through an opening, secondary weaker wavefronts
are generated, apparently originating at that edge. These secondary wavefronts will interfere
with the primary wavefront as well as with each other to form a
→ diffraction pattern. From Fr. diffraction, from Mod.L. diffractionem, from L. diffrac-, stem of diffringere "break in pieces," from → dis- "apart" + frangere "to break." Parâš "dispersion, scattering," variant of pâš, pâšidan, → dispersion. |
diffraction grating turi-ye parâš (#) Fr.: réseau de diffraction An optical device containing thousands of very fine parallel grooves which produce interference patterns in a way which separates out all the components of the light into a spectrum. → diffraction; → grating. |
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