An Etymological Dictionary of Astronomy and AstrophysicsEnglish-French-Persian

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 24 Search : factor
 amplification factor   کروند ِ دامنه‌دهی   karvand-e dâmane-dahiFr.: facteur d'amplification   1) Electronics: The extent to which an → analogue → amplifier boosts the strength of a → signal. Also called → gain. 2) In → gravitational lensing, the ratio of the lensed brightness to unlensed brightness. This factor depends on the mass of the → lensing object and the closeness of the alignment between observer, lens, and source (→ impact parameter).→ amplification; → factor. attenuation factor   کروند ِ تنکش   karvand-e tonokešFr.: facteur d'atténuation   The ratio of the radiation intensity after traversing a layer of matter to its intensity before.→ attenuation; → factor. Boltzmann factor   کروند ِ بولتسمن   karvand-e BoltzmannnFr.: facteur de Boltzmann   The factor e-E/kT involved in the probability for atoms having an excitation energy E and temperature T, where k is Boltzmann's constant. clumping factor   کروند ِ گوده‌داری   karvand-e gudedâriFr.: facteur de grumelage   The ratio fcl = <ρ2> / <ρ >2, where ρ represents the → stellar wind density and the brackets mean values. Unclumped wind has fcl = 1 and → clumping becomes significant for fcl≅ 4.→ clumping; → factor. cofactor   همکروند   hamkarvandFr.: cofacteur   A number associated with an → element of a → determinant. If A is a square matrix [aij], the cofactor of the element aij is equal to (-1)i+j times the determinant of the matrix obtained by deleting the i-th row and j-th column of A.→ co-; → factor. compression factor   کروند ِ تنجش   karvand-e tanješFr.: facteur de compression   In thermodynamics, the quantity Z = pVm/RT, in which P is the gas pressure, Vm 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. conversion factor   کروند ِ هاگرد   karvand-e hâgardFr.: facteur de conversion   1) A numerical factor that, by multiplication or division, translates one unit or value into another. 2) In → molecular cloud studies, a factor used to convert the → carbon monoxide (CO) line intensity to → molecular hydrogen (H2) → column density; usually denoted XCO = I(CO) / N(H2). This useful factor relates the observed CO intensity to the cloud mass. A general method to derive XCO is to compare the → virial mass and the 12CO (J = 1-0) luminosity of a cloud. The basic assumptions are that the CO and H2 clouds are co-extensive, and molecular clouds obey the → virial theorem. However, if the molecular cloud is subject to ultraviolet radiation, selective → photodissociation may take place, which will change the situation. Moreover, molecular clouds may not be in → virial equilibrium. To be in virial equilibrium molecular clouds must have enough mass, greater than about 105 solar masses. The way → metallicity affects XCO is a matter of debate, and there is no clear correlation between XCO and metallicity. Although lower metallicity brings about higher ultraviolet fields than in the solar vicinity, other factors appear to be as important as metallicity for the determination of XCO. In the case of the → Magellanic Clouds, XCO(SMC) = 14 ± 3 × 1020 cm-2 (K km s-1)-1, which is larger than XCO (LMC) = 7 ± 2 × 1020 cm-2 (K km s-1)-1. An independent method to derive XCO is to make use of the gamma ray emission from a cloud. The flow of → cosmic ray protons interacts with interstellar low-energy hydrogen nuclei in clouds creating neutral → pions. These pions quickly decay into two gamma rays. It is therefore possible to estimate the number of hydrogen nuclei and hence the cloud mass from the gamma ray counts. Such a gamma-ray based conversion factor is estimated to be 2.0 × 1020 cm-2 (K km s-1)-1 for Galactic clouds, in good agreement with the result obtained from the virial method. However, the gamma ray flux is not well known in general, so this method is uncertain as well. See, e.g., Fukui & Kawamura, 2010 (ARAA 48, 547).→ conversion; → factor. cosmic scale factor   کروند ِ مرپل ِ کیهانی   karvand-e marpal-e keyhâniFr.: 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(t0)/R(t1), where t0 is the present time and t1 is the time at emission of the radiation. The quantity (1 + z) gives the factor by which the → Universe has expanded in size between t1 and t0. 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.→ cosmic; → scale; → factor. deuterium enrichment factor   کروند ِ پرداری ِ دوتریوم   karvand-e pordâri-ye doteriomFr.: facteur d'enrichissement en deutérium   The ratio between the D/H value in → water and in → molecular hydrogen, as expressed by: f = [(1/2)HDO/H2O]/[(1/2)HD/H2] = (D/H)H2O/(D/H)H2. When f> 1, there is → deuterium enrichment.→ deuterium; → enrichment; → factor. dilution factor   کروند ِ اوتالش   karvand-e owtâlešFr.: facteur de dilution   The energy density of a radiation field divided by the equilibrium value for the same color temperature.→ dilution; → factor. Eddington factor   کروند ِ ادینگتون   karvand-e EddingtonFr.: facteur d'Eddington   Same as → Eddington parameter. factor   کروند   karvandFr.: facteur   1) One that actively contributes to the production of a result. 2) Math.: Any of the numbers or symbols that when multiplied together form a → product.M.Fr. facteur "agent, representative," from L. factor "doer or maker," from facere "to do" (cf. Fr. faire, Sp. hacer); from PIE base *dhe- "to put, to do;" cf. Skt. dadhati "puts, places;" Av. dadaiti "he puts;" Hitt. dai- "to place;" Gk. tithenai "to put, set, place;" Lith. deti "to put;" Rus. det' "to hide," delat' "to do;" O.H.G. tuon; Ger. tun; O.S., O.E. don "to do."Karvand, from kar- root of Mod.Pers. verb kardan "to do, to make" (Mid.Pers. kardan; O.Pers./Av. kar- "to do, make, build;" Av. kərənaoiti "he makes;" cf. Skt. kr- "to do, to make," krnoti "he makes, he does," karoti "he makes, he does," karma "act, deed;" PIE base kwer- "to do, to make") + -vand a suffix forming adjectives and agent nouns. factor tree   درخت ِ کروند   deraxt-e karvandFr.: arbre des facteurs   A diagram representing a systematic way of determining all the prime factors of a number.→ factor; → tree. factorial   ۱) کرونده؛ ۲) کروندی   1) karvandeh; 2) karvandiFr.: factoriel   1) (n.) The product of all the positive integers from 1 to n, denoted by symbol n! 2) (adj.) of or pertaining to factors or factorials.→ factor + -ial, from L. -alis, → -al. factorize   کروندیدن، کروند گرفتن   karvandidan, karvand gereftanFr.: factoriser   The operation of resolving a quantity into factors.→ factor + → -ize. filling factor   کروند ِ پُری   karvand-e poriFr.: facteur de remplissage   Of a molecular cloud or a nebula, the ratio of the volumes filled with matter to the total volume of the cloud.Filling, from fill, from O.E. fyllan, from P.Gmc. *fullijan (cf. Du. vullen, Ger. füllen "to fill"), a derivative of adj. *fullaz→ full; → factor.Karvand, → factor; pori, from por, → full. Gaunt factor   کروند ِ گاؤنت   karvand-e GauntFr.: facteur de Gaunt   In the atomic theory of spectral line formation, a quantum mechanical correction factor applied to the absorption coefficient in the transition of an electron from a bound or free state to a free state.Gaunt, after John Arthur Gaunt (1904-1944), English physicist born in China, who significantly contributed to the calculation of continuous absorption using quantum mechanics; → factor integrating factor   کروند ِ درستالنده   karvand-e dorostâlandéFr.: facteur intégrant   A function that converts a → differential equation, which is not exact, into an → exact differential equation. This is done by multiplying all terms of the original equation by the integrating factor.→ integrate; → factor. ionization correction factor (ICF)   کروند ِ ارشایش ِ یونش   karvand-e aršâyeš-e yonešFr.: facteur de correction d'ionisation   A quantity used in studies of → emission nebulae to convert the → ionic abundance of a given chemical element to its total → elemental abundance. The elemental abundance of an element relative to hydrogen is given by the sum of abundances of all its ions. In practice, not all the ionization stages are observed. One must therefore correct for unobserved stages using ICFs. A common way to do this was to rely on → ionization potential considerations. However, → photoionization models show that such simple relations do not necessarily hold. Hence, ICFs based on grids of photoionization models are more reliable. Nevertheless here also care should be taken for several reasons: the atomic physics is not well known yet, the ionization structure of a nebula depends on the spectral energy distribution of the stellar radiation field, which differs from one model to another, and the density structure of real nebulae is more complicated than that of idealized models (see, e.g., Stasińska, 2002, astro-ph/0207500, and references therein).→ ionization; → correction; → factor. Landé factor   کروند ِ لانده   karvand-e LandéFr.: facteur de Landé   The constant of proportionality relating the separations of lines of successive pairs of adjacent components of the levels of a spectral multiplet to the larger of the two J-values for the respective pairs. The interval between two successive components J and J + 1 is proportional to J + 1.After Alfred Landé (1888-1976), a German-American physicist, known for his contributions to quantum theory; → facteur.

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