An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



Number of Results: 8 Search : ideal
Eley-Rideal mechanism
  ساز-و-کار ایلی-ردیل   
sâzokâr-e Eley-Rideal

Fr.: mécanisme de Eley-Rideal   

A → chemical reaction on solid surfaces in which one atom or molecule is → adsorbed on the catalyst surface, and another reacts directly from the gas phase. This type of mechanism may occur preferentially on very small → dust grains, where transient heating events prevent weakly bound species from remaining and in larger grains at high temperatures. Compare with the → Langmuir-Hinshelwood mechanism.

Proposed in 1938 by D. D. Eley (1914-2015), a British chemist and Professor of Physical Chemistry and E. K. Rideal (1890-1974), an English physical chemist.

  ۱) آرمان، مینه‌وار؛ ۲) آرمانی، مینه‌ای، مینه‌وار   
1) (n.) ârmân (#), minevâr; 2) (adj.) ârmâni (#), mineyi, minevâr

Fr.: idéal   

1) (n.) A standard of perfection, beauty, or excellence.
Math.: A subset of a ring that is closed under addition and multiplication by any element of the ring.
2) (adj.) Existing only in the imagination; not real or actual.
Conforming exactly to an ideal, law, or standard; perfect. → ideal gas.

M.E. ydeall, from L.L. idealis "existing in idea," from L. → idea.

Ârmân "ideal" in Mod.Pers., traditionally "desire; hope; grief," variants armân, urmân, prefixed from mân, "thought, mind," → idea. The first element may be related to Av. armaē- "in peace, still; quietly;" PIE base *er[ə]- "to be still" (cf. Skt. īrmā (adv.) "quiet, still, being in the same place;" Gk. erôé "calm, peace;" O.H.G. rouwa "rest"), as in Av. armaē.šad- "sitting quietly," armaē.štā- "standing still, stagnant." Therefore, Pers. ârmân may be related to Av. *armaē.manah- (PIE *ermen-) "thought in peace, quiet mind."
Mineyi, minevâr, adj. from miné, → idea.

ideal fluid
  شاره‌ی ِ آرمانی، ~ مینه‌وار   
šâre-ye ârmâni, ~ minevâr

Fr.: fluide idéal   

An fluid which has no internal friction or → viscosity, and no → resistivity as well if the fluid is a plasma.

ideal; → fluid.

ideal gas
  گاز ِ آرمانی، ~ ِ مینه‌وار   
gâz-e ârmâni, ~-e minevâr

Fr.: gaz idéal   

Theoretical gas assumed to consist of perfectly elastic molecules of negligible volume and mutual attraction force. Also called → perfect gas.

ideal; → gas.

ideal gas law
  قانون ِ گاز ِ آرمانی، ~ ~ مینه‌وار   
qânun-e gâz-e ârmâni, ~ ~ minevâr

Fr.: loi des gaz parfaits   

An → equation of state that relates pressure (P), temperature (T), and volume (V) of an ideal or → perfect gas: PV = nRT, where n is the number of → moles of gas present and R is the → universal gas constant. Equivalently: PV = NkT, where N is the number of atoms of gas present and k is → Boltzmann's constant.

ideal; → gas; → law.

ideal magnetohydrodynamics (MHD)
  مغنات-و-هیدروتوانیک ِ آرمانی، ~ مینه‌وار   
meqnâtohidrotavânik-e ârmâni, ~ minevâr

Fr.: magnétohydrodynamique idéale   

Magnetohydrodynamics of a → plasma with very large (infinite) → conductivity. In this condition, → Ohm's law reduces to E = -v × B, where E represents → electric field, B → magnetic field, and v the → fluid velocity. Ideal MHD is the simplest model to describe the dynamics of plasmas immersed in a magnetic field. It is concerned with → one-fluid magnetohydrodynamics and neglects → resistivity. This theory treats the plasma composed of many charged particles with locally neutral charge as a continuous single → fluid. Ideal MHD does not provide information on the velocity distribution and neglects the physics relating to wave-particle interactions, as does the two-fluid theory as well. It does have the advantage that the macroscopic dynamics of the → magnetized plasma can be analyzed in realistic three-dimensional geometries (K. Nishikawa & M. Wakatani, 2000, Plasma Physics, Springer). See also → non-ideal magnetohydrodynamics.

ideal; → magnetohydrodynamics.


Fr.: idéalisme   

Any one of a variety of systems of philosophical thought, which would make the ultimate reality of the Universe expressible or intangible only in terms of idea in mind, rather than in terms of matter in space.

From → ideal, see also → idea, + → -ism.

non-ideal magnetohydrodynamics (MHD)
  مغنات-و-هیدروتوانیک ِ نا-آرمانی، ~ نا-مینه‌وار   
meqnâtohidrotavânik-e nâ-ârmâni, ~ nâ-minevâr

Fr.: magnétohydrodynamique non idéale   

A → magnetohydrodynamics approach dealing with → plasmas which is an improvement with respect to → ideal magnetohydrodynamics. Non-ideal magnetohydrodynamics allows for a drift between particles, redistributing the → magnetic flux and acting on both the → angular momentum and magnetic flux conservation issues.

non-ideal; → magnetohydrodynamics.