An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 1965 Search : ion
radiative collision
  همکوبش ِ تابشی   
hamkubeš-e tâbeši

Fr.: collision radiative   

A collision between charged particles in which part of the kinetic energy is converted into electromagnetic radiation.

radiative; → collision.

radiative diffusion
  پخش ِ تابشی   
paxš-e tâbeši

Fr.: diffusion radiative   

A process of → radiative transfer in which photons are repeatedly absorbed and re-emitted by matter particles.

radiative; → diffusion.

radiative levitation
  بالاشد ِ تابشی   
bâlâšod tâbeši

Fr.: lévitation radiative   

A physical process occurring in → stellar atmospheres whereby → radiation pressure selectively pushes certain → chemical elements outward, leading to an atmospheric overabundance of such elements. See also → gravitational settling.

radiative; → levitation.

radiative recombination
  بازمیازش ِ تابشی   
bâzmiyâzeš-e tâbeši

Fr.: recombinaison radiative   

The process by which an ionized atom binds a free electron in a → plasma to produce a new atomic state with the subsequent radiation of photons.

radiative; → recombination.

radiative transfer equation
  هموگش ِ تراوَژ ِ تابش   
hamugeš-e tarâvaž-e tâbeš

Fr.: équation de transfer radiatif, ~ ~ de rayonnement   

The equation that describes the → radiative transfer. It states that the → specific intensity of radiation Iσ during its propagation in a medium is subject to losses due to → extinction and to → gains due to → emission: dIσ/dx = - μσ . Iσ + ρ . jσ, where x is the coordinate along the → optical path, μσ is the → extinction coefficient, ρ is the mass → density, and jσ is the → emission coefficient per unit mass.

radiative; → transfer; → equation.

radiative transition
  گذرش ِ تابشی   
gozareš-e tâbeši

Fr.: transition radiative   

A transition between two states of an atomic or molecular entity, the energy difference being emitted or absorbed as photons.

radiative; → transition.

radio continuum emission
  گسیل ِ پیوستار ِ رادیویی   
gosil-e peyvastâr-e râdio-yi

Fr.: émission de continuum radio   

A → continuum emission with frequencies in the radio range of the electromagnetic spectrum.

radio; → continuum; → emission.

radio emission
  گسیل ِ رادیویی   
gosil-e râdio-yi

Fr.: émission radio   

Electromagnetic radiation carried by → radio waves.

radio; → emission.

radio recombination line
  خط ِ بازمیازش ِ رادیویی   
xatt-e bâzmiyâzeš-e râdioyi

Fr.: raie de recombinaison radio   

A → recombination line whose wavelength lies in the radio range of the electromagnetic spectrum. Radio recombination lines are the result of electronic transitions between high energy levels (n > 50) in an atom or ion.

radio; → recombination line.


Fr.: radionucléide   

A radioactive → nuclide.

radio + → nuclide.

radius of gyration
  شعاع ِ لرش   
šo'â'-e lereš

Fr.: gyrorayon   

Same as → Larmor radius.

radius; → gyration.

random thermal motion
  جنبش ِ گرمایی ِ کاتوره   
jonbeš-e garmâyi-ye kâturé

Fr.: mouvement thermique aléatoire   

The agitated motion of molecular, atomic, or → subatomic particles in all possible directions at any temperature, except at → absolute zero, where → thermal motion would cease.

random; → thermal; → motion.

kâtureš (#)

Fr.: aléation   

Arrangement of data in such a way as to simulate chance occurrence.

Verbal noun of → randomize.

Rankine-Hugoniot conditions
  بوتارهای ِ رانکین-هوگونیو   
butârhâ-ye Rankine-Hugoniot

Fr.: conditions de Rankine-Hugoniot   

Hydrodynamics → conservation laws (which can be extended to → magnetohydrodynamics, MHD) which describe the physical conditions of material across a → shock front. A fluid is completely described by its velocity, density, pressure, specific heat ratio, and magnetic field (in the MHD case). Mass, momentum, and energy fluxes are conserved in the shock, leading to the Rankine-Hugoniot relations. Also called Rankine-Hugoniot jump conditions. See also → jump condition.

Named after William John Rankine, → Rankine scale, and Pierre Henri Hugoniot, → Hugoniot curve; → condition.


Fr.: raréfaction   

The state of being rarefied, less dense.
An instantaneous reduction in density of a gas resulting from passage a sound wave; opposite of → compression.

M.E. rarefien, from M.Fr. rarefier, from L. rarefacere "make rare," from rarus "loose, wide apart, thin, infrequent."

Verbal noun from âlar present stem of âlaridanrarefy + , a suffix.

rarefaction wave
  موج ِ آلرش   
mowj-e âlareš

Fr.: onde de raréfaction   

A pressure wave in a fluid generated by rarefaction. It travels in the opposite direction to that of a shock wave in the medium.

rarefaction; → wave.

  ۱) راینی، راینوار؛ ۲) خردانه، خردمندانه؛ ۳) وابری   
1) râyani, râyanvâr; 2) xeradâné, xeradmandâné; 3) vâbari

Fr.: rationnel   

1) Having or exercising the ability to → reason.
2) Consistent with or based on reason; logical; in accordance with sound reasoning.
3) Math.: Capable of being expressed as a quotient of integers.

M.E. racional, from O.Fr. racionel, from L. rationalis "of or belonging to reason, reasonable," from ratio (genitive rationis) "reckoning, calculation, reason," from rat-, pp. stem of reri "to reckon, calculate; consider, think."

1) Râyani, of or pertaining to râyan, → reason.
2) Xeradâné, xeradmandâné, of or pertaining to xerad "understanding, judgement, intellect, wisdom;" Mid.Pers. xrad "reason, intellect, intelligence, wisdom, understanding;" O.Pers. xraθu- "wisdom;" Av. xratu- "intelligence, undestanding, wisdom; will, purpose, council;" cf. Skt. krátu- "power, will-power;" Gk. kratos "power, strength."
3) vâbari, of or pertaining to vâbar, → ratio.

rational number
  عدد ِ وابری   
'adad-e vâbari

Fr.: nombre rationnel   

Any number that can be expressed as a ratio of two integers, providing the second number is not zero.

rational; → number.


Fr.: raisonnement, exposé raisonné   

1) The fundamental reason or reasons serving to account for something.
2) A statement of reasons.
3) A reasoned exposition of principles (

L. neuter of rationalis.

Râyanâl, from râyan, → reason, + -âl, → -al.

  راین‌باوری، خردباوری   
râyan-bâvari, xerad-bâvari

Fr.: rationalisme   

A philosophical doctrine that holds that → reason alone, unaided by experience, can arrive at basic truth regarding the world.

From → rational + -ism a Gk. suffix used in the formation of nouns denoting action or practice, state or condition, principles, doctrines, and so forth.

Râyan, → reason; xerad, → rational; bâvari, from bâvar "belief" (Mid.Pers. wâbar "beleif;" Proto-Iranian *uar- "to choose; to convince; to believe;" cf. Av. var- "to choose; to convince" varəna-, varana- "conviction, faith;" O.Pers. v(a)r- "to choose; to convince;" Skt. vr- "to choose," vara- "choosing").

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