axiom of constraints
Fr.: axiome des contraintes
An axiom in → statics, stating that any → constrained body can be treated as a → free body detached from its → constraints, provided the latter are represented by their → reactions.
→ axiom; → constraint.
Fr.: gros grain
A type of → interstellar dust grains with a size ranging from 150 to 1000 Å. Big grains consist of graphite and silicates. They are in → thermal equilibrium with the radiation field and their emission can be described by a modified → blackbody radiation following from → Kirchhoff's law.
kânun-e Cassegrain (#)
Fr.: foyer Cassegrain
The main focus in → Cassegrain telescope.
→ Cassegrain telescope; → focus.
durbin Cassegrain, teleskop-e ~ (#)
Fr.: Télecope Cassegrain
A reflecting telescope whose primary mirror has a hole bored through the center to allow the reflected light from the convex secondary mirror be focused beyond the back end of the tube.
Cassegrain, named after the French priest and school teacher Laurent Cassegrain (1629-1693), who invented this system in 1672; → telescope.
pâvandidan, pâvand kardan
To confine forcibly, as by bonds; to force, compel, or oblige; to repress or restrain. → constrained body, → constrained system.
Fr.: corps lié
A → rigid body whose displacement is prevented because it is under → constraint or a body that can move only in certain directions. Contrasted with → free body.
Fr.: système contraint
Opposite of a → free system. See also → constraint.
1) General: Limitation or restriction.
M.E. constreinte, from M.F., from constreindre, from L. constringere "to bind together, tie tightly," from → com- "together" + stringere "to bind, draw tight."
Pâvand "fetter, shackle," from pâ "foot" (Mid.Pers. pâd, pây; Khotanese fad; Av. pad-; cf. Skt. pat-, Gk. pos, genitive podos; L. pes, genitive pedis; P.Gmc. *fot, E. foot, Ger. Fuss, Fr. pied; PIE *pod-/*ped-) + vand, variant band "tie, band," (Mod.-Mid./Pers. bastan/vastan "to bind, shut," Av./O.Pers. band- "to bind, fetter," banda- "band, tie," Skt. bandh- "to bind, tie, fasten," PIE *bhendh- "to bind," cf. Ger. binden, E. bind).
Fr.: pluie coronale
Material that condenses in the Sun's corona and appears to rain down into the chromosphere, as observed at the solar limb above strong sunspots.
Fr.: champ de Draine
A unit used to express the strength of → far ultraviolet (FUV) average → interstellar radiation field. It is equal to ~ 1.7 → Habing field.
Named after B. T. Draine, 1978, ApJS 36, 595.
dâne-ye qobâr (#)
Fr.: grains de poussière
A small, solid flake of → graphite and/or → silicates coated with water ice, found in the → interstellar medium or the → interplanetary medium. Dust grains are irregularly shaped with sizes from microns to Angstroms (→ very small grain; → big grain; → PAH). It is believed that the dust is mainly formed in the cool outer layers of → red giants and dispersed in the interstellar medium. In dense environments, such as → molecular clouds and around → protostars, dust grains grow due to collisions (→ grain growth). Therefore, dust grains in → protostellar disks should be larger than interstellar grains. Dust grains absorb and scatter optical and ultraviolet light and re-radiate in infrared (→ dust emission). Dust acts as a catalyst in the interstellar medium, because molecules form via reactions on the surface of dust grains.
fluffy dust grain
dâne-ye qobâr-e korkvâr
Fr.: grain de poussière duveteux
An aggregate of small particles loosely stuck together. Same as → porous dust grain.
1) A small, hard seed of plants, especially the seed of cereals.
M.E. grain, grein, from O.Fr. grein, from L. granum "seed;" akin to corn.
Dâné "grain, seed;" Mid.Pers. dân, dânag "seed, corn;" Av. dānô- in dānô.karš- "carrying grains; an ant;" cf. Skt. dhânâ- "corn, grain;" Tokharian B tāno "grain;" Lith. duona "corn, bread."
Fr.: coagulation des grains
Sticking together of micron- to centimetre-sized grains occurring in the interstellar and protoplanetary environments to form larger grain agglomerates.
→ grain; → coagulation.
Fr.: évaporation des grains
Conversion of dust grains into smaller grains due to high environmental temperatures.
→ grain; → evaporation.
Fr.: formation des grains
The process by which dust grains are assembled or produced.
ruyeš-e dâné (#)
Fr.: croissance des grains
The increase of dust grains to micron sizes in the interstellar environments due to various physical processes, for example mutual collisions and accumulation of ice mantles.
rupuš-e dâné (#)
Fr.: manteau de grain
A layer of icy molecules covering interstellar dust grains.
→ grain; mantle, from O.E. mentel "loose, sleeveless cloak," from L. mantellum "cloak," perhaps from a Celtic source.
Rupuš "overgarment, cloak," from ru "surface, face; aspect; appearance" (Mid.Pers. rôy, rôdh "face;" Av. raoδa- "growth," in plural form "appearance," from raod- "to grow, sprout, shoot;" cf. Skt. róha- "rising, height") + puš "covering, mantle," from pušidan "to cover; to put on" (Mid.Pers. pôšidan, pôš- "to cover; to wear;" cf. Mid.Pers. pôst; Mod.Pers. pust "skin, hide;" O.Pers. pavastā- "thin clay envelope used to protect unbaked clay tablets;" Skt. pavásta- "cover," Proto-Indo-Iranian *pauastā- "cloth").
Fr.: érosion des grains par pulvérisation
The ejection of atoms from interstellar dust grains due to impact by gas ions, which leads to grain destruction.
→ grain; sputtering, from sputter "to spit with explosive sounds," cognate with Du. sputteren.
Osparâni, verbal noun of osparândan, from os- "out of, outside," → ex- + parândan "to eject," transitive of paridan "to fly" (from Mid./Mod.Pers. par(r) "feather, wing," Av. parəna- "feather, wing;" cp. Skt. parna "feather," E. fern; PIE *porno- "feather").
interstellar dust grain
dâne-ye qobâr-e andaraxtari
Fr.: grain de poussière interstellaire
→ dust grain.
→ interstellar; → dust; → grain.