An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 20 Search : rich
chemical enrichment
  پرداری ِ شیمیایی   
pordâri-ye šimiyâyi

Fr.: enrichissement chimique   

The → process by which the relative → abundance of a given → chemical element or → species in an → astrophysical object is increased. For example the the → increase of the → heavy element content of the → interstellar medium due to → stellar evolution.

chemical; → enrichment.

deuterium enrichment
  پرداری ِ دوتریوم   
pordâri-ye doteriom

Fr.: enrichissement de deutérium   

The → enrichment of deuterium (D) with respect to → hydrogen (H) in → Solar System molecules when compared with the D/H ratio in the → interstellar → solar nebula. H-bearing molecules in → comets, → planets, and → chondrite  → meteorites show a systematic D enrichment relative to the → molecular hydrogen of the solar nebula. Because there is no nuclear source for D in the Universe, the observed → isotopic enrichment must have its origin in chemical reactions having faster reaction rates for D than for H. In the Solar nebula the → isotopic fractionation of D between → water and H followed the reversible reaction:
H2O + HD ⇔ HDO + H2.
At low temperatures, this reaction favors the concentration of D in HDO. In the → interstellar medium grain chemistry plays a crucial role in D enrichment. See also → enrichment factor.
Apart from → deuterium fractionation, D could be enriched through another mechanism. Since molecular hydrogen (H2) is more → volatile than molecular deuterium (D2), D/H ratio could increase in certain planets that orbit near their star.

deuterium; → enrichment.

deuterium enrichment factor
  کروند ِ پرباری ِ دوتریوم   
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:
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.

Dirichlet condition
  بوتار ِ دیریکله   
butâr-e Dirichlet

Fr.: condition de Dirichlet   

One of the following conditions for a → Fourier series to converge:
1) The function f(x) is defined and single valued, except possibly at a finite number of points in the interval -π, +π.
2) f(x) has a period of 2π.
3) f(x) and f'(x) are → piecewise continuous functions on -π, +π.
Then, the Fourier series converges to:
(a) f(x) if x is a point of continuity.
(b) (f(x + 0) + f(x - 0))/2, if x is a point of discontinuity.

Named after Peter Gustav Lejeune Dirichlet (1805-1859), German mathematician who made valuable contributions to → number theory, → analysis, and → mechanics; → condition.

enrich
  پرداریدن، پردار کردن   
pordâridan, pordâr kardan

Fr.: enrichir   

To increase the → concentration or → abundance of a specified → component or → isotope in a material.

From en- a prefix forming verbs with a particular sense + → rich.

Pordâridan, pordâr kardan, infinitives from pordâr, → rich.

enriched
  پرداریده   
pordâridé

Fr.: enrichi   

Supplied with abundance of something. → enriched gas, → enriched uranium.

Past participle of → enrich.

enriched gas
  گاز ِ پرداریده   
gâz-e pordâridé

Fr.: gaz enrichi   

A gas, usually → interstellar, in which the → abundance of particular chemical or atomic species is higher than the expected values.

enriched; → gas.

enriched uranium
  اورانیوم ِ پرداریده   
urânium-e pordâridé

Fr.: uranium enrichi   

Uranium in which the → proportion of the → isotope U-235 has been increased (above the 0.7% value in natural uranium).

enriched; → uranium.

enrichment
  پردارش   
pordâreš

Fr.: enrichissement   

1) A process that changes the → isotopic ratio in a material. For example, for uranium the ratio of U-235 to U-238 may be increased by gaseous diffusion of uranium hexafluoride.
2) → chemical enrichment.

Verbal noun of → enrich.

gas-rich galaxy
  کهکشان ِ پرگاز   
kahkešân-e porgâz

Fr.: galaxie riche en gaz   

A galaxy, usually young, which has a relatively important gas content.

gas; → rich; → galaxy.

metal-rich environment
  پرگیر ِ پرفلز   
pargir-e porfelez

Fr.: environnement riche en métaux   

An environment (→ galaxy, → nebula) whose → metallicity is larger than that of the → Milky Way galaxy.

metal; → rich; → environment.

rich
  پر-، پردار   
por-, pordâr

Fr.: riche   

Having large amounts of something specified. → metal-rich environment, → rich cluster; → enrich, → enrichment, → richness, → poor.

M.E., from O.E. rice "wealthy, powerful" (cf. Du. rijk, Ger. reich "rich"), from PIE base *reg- "move in a straight line," hence, "to direct, rule" (cf. Mod.Pers./Mid.Pers. râst "right, straight;" O.Pers. rāsta- "straight, true," rās- "to be right, straight, true;" Av. rāz- "to direct, put in line, set," razan- "order;" Skt. raj- "to direct, stretch," rjuyant- "walking straight;" Gk. orektos "stretched out;" L. regere "to lead straight, guide, rule," p.p. rectus "right, straight;" Ger. recht; E. right).

Por "full, much, very, too much" (Mid.Pers. purr "full;" O.Pers. paru- "much, many;" Av. parav-, pauru-, pouru-, from par- "to fill;" PIE base *pelu- "full," from *pel- "to be full;" cf. Skt. puru- "much, abundant;" Gk. polus "many," plethos "great number, multitude;" O.E. full); pordâr, literally "having much possession," from por + dâr "having, possessor," from dâštan "to have, to possess," → property.

rich cluster
  خوشه‌ی ِ پُردار   
xuše-ye pordâr

Fr.: amas riche   

A → galaxy cluster with a particularly large number of galaxies.

rich; → cluster.

Richardson cascade
  پی‌شار ِ ریچاردسون   
peyšâr-e Richardson

Fr.: cascade de Richarson   

Same as → energy cascade

Named after L. F. Richardson (1922), Weather Prediction by Numerical Process (Cambridge Univ. Press); → cascade.

Richardson criterion
  سنجیدار ِ ریچاردسون   
sanjidâr-e Richardson

Fr.: critère de Richardson   

A condition for the onset of → instability in multilayer fluids which compares the balance between the restoring force of → buoyancy and the destabilizing effect of the → shear.

Named after the British meteorologist Lewis Fry Richardson (1881-1953), who first arrived in 1920 to the dimensionless ratio now called → Richardson number. The first formal proof of the criterion, however, came four decades later for → incompressible flows (Miles, J. W. 1961, J. Fluid Mech., 10, 496; Howard, L. N., 1961, J. Fluid Mech., 10, 509). Its extension to → compressible flows was demonstrated subsequently (Chimonas 1970, J. Fluid Mech., 43, 833); → criterion.

Richardson number
  عدد ِ ریچاردسون   
adad-e Richardson

Fr.: nombre de Richardson   

A dimensionless number which is used according to the → Richardson criterion to describe the condition for the → stability of a flow in the presence of vertical density stratification. If the → shear flow is characterized by linear variation of velocity and density, with velocities and densities ranging from U1 to U2 and ρ1 to ρ2 (ρ2>ρ1), respectively, over a depth H, then the Richardson number is expressed as: Ri = (ρ2 - ρ1) gH / ρ0 (U1 - U2)2. If Ri < 0.25, somewhere in the flow turbulence is likely to occur. For Ri > 0.25 the flow is stable.

Richardson criterion; → number.

richness
  پرداری   
pordâri

Fr.: richesse   

The property of being very abundant.

rich; → -ness.

richness class
  رده‌ی ِ پرداری   
rade-ye pordâri

Fr.: classe de richesse   

A classification of → galaxy clusters into six groups (0 to 5), as in the → Abell catalog. It depends on the number of galaxies in a given cluster that lie within a → magnitude range m3 to m3+2, where m3 is the magnitude of the 3rd brightest member of the cluster. The first group contains 30-49 galaxies and the last group more than 299 galaxies.

richness; → group.

trichroism
  سه‌فامی   
sefâmi

Fr.: trichroïsme   

The property of some crystals of exhibiting three different colors when viewed from three different directions under white lights. → dichroism.

From Gk. tri- "three" + chroic, from chroma "color" + -ism.

Sefâmi, from se, → three, + fâm "color," + -i noun suffix.

uranium enrichment
  پُردارش ِ اورانیوم   
pordâreš-e urâniyom

Fr.: enrichissement de l'uranium   

The process by which the percentage of → fissile uranium in a sample is increased. Uranium obtained from mining contains several → isotopes of uranium in different compositions, such as U-238 (~99%), U-235 (~0.7%), and U-234 (~0.02%). Among them, U-235 is the only one that is fissile, i.e. can be used in a → nuclear reactor to produce heat (and consequently electricity) in a controlled manner. As such, the concentration of U-235 as a fuel used in a reactor needs to be increased, which is done using several techniques, such as → gaseous diffusion.

uranium; → enrichment.