Fr.: facteur d'amplification
1) Electronics: The extent to which an
→ analogue → amplifier
boosts the strength of a → signal. Also called
→ amplification; → factor.
Fr.: facteur d'atténuation
The ratio of the radiation intensity after traversing a layer of matter to its intensity before.
→ attenuation; → factor.
Fr.: 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.
→ Boltzmann's constant; → factor.
Fr.: 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.
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.
Fr.: 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.
Fr.: facteur de conversion
1) A numerical factor that, by multiplication or division, translates one
unit or value into another.
→ conversion; → factor.
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(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.
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.
Fr.: facteur de dilution
The energy density of a radiation field divided by the equilibrium value for the same color temperature.
Fr.: facteur d'Eddington
Same as → Eddington parameter.
→ Eddington limit; → factor.
1) One that actively contributes to the production of a result.
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.
Fr.: arbre des facteurs
A diagram representing a systematic way of determining all the prime factors of a number.
1) karvandeh; 2) karvandi
1) (n.) The product of all the positive integers from 1 to n, denoted by
karvandidan, karvand gereftan
The operation of resolving a quantity into factors.
Fr.: 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.
Fr.: 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
Fr.: 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.
ionization correction factor (ICF)
karvand-e aršâyeš-e yoneš
Fr.: 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.
Fr.: 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.