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: 25 Search : tropic
-tropic
   -گرد   
-gard (#)

Fr.: -trope   

A suffix denoting "turned toward" that specified by the initial element; → barotropic, → isotropic, → polytropic.

From Gk. -tropos "a turn, way, manner," from tropein "to turn," from PIE base *trep- "to turn" (cf. L. trepit "he turns").

Gard "turning, changing," from gardidan "to turn, to change," Mid.Pers. vartitan, Av. varət- "to turn, revolve," Skt. vartati, L. vertere, O.H.G. werden "to become;" PIE *werto, *wer-.

anisotropic
  نا-ایزوگرد   
nâ-izogard

Fr.: anisotrope   

Describing a medium in which certain physical properties are different in different directions.

anisotropy; → -ic.

anisotropic homogeneous cosmological model
  مدل ِ کیهانشناختی ِ همگن و نا-ایزوگرد   
model-e keyhânšenâxti-ye hamgen o nâ-izogard

Fr.: modèle cosmiologique homogène mais anisotrope   

A solution to Einstein's theory of → general relativity that is spatially homogeneous but allows for rotation and/or shear. See also → Bianchi cosmological model.

anisotropic; → homogeneous; → cosmological; → model.

barotropic
  فشارگرد   
fešârgard

Fr.: barotrope   

In a fluid, conditions where surfaces of constant pressure are parallel to surfaces of constant temperature. This state is equivalent to zero → baroclinicity.

baro-; → -tropic.

barotropic gas
  گاز ِ فشارگرد   
gâz-e fešârgard

Fr.: gaz barotrope   

A gas whose density is a function solely of pressure.

barotropic; → gas.

barotropic instability
  ناپایداری ِ فشارگرد   
nâpâydâri-ye fešârgard

Fr.: instabilité barotrope   

A hydrodynamical instability that arises when the horizontal → shear gradient becomes very large. Barotropic instabilities grow by extracting kinetic energy from the mean flow field.

barotropic; → instability.

Cancer, Tropic of
  هورگردِ خرچنگ   
Hurgard-e Xarcang

Fr.: Tropique du Cancer   

Tropic of Cancer.

Capricorn, Tropic of
  هورگردِ وهیگ   
hurgard-e vahig

Fr.: Tropique du Capricorne   

Tropic of Capricorn.

Capricornus.

hylotropic
  ماده‌گرد   
mâdegard

Fr.: hylotropique   

Physical chemistry: Describing a substance that is capable of undergoing a change in phase (as from a liquid to a gas), with no change in chemical composition. If the substance is hylotropic over a limited range of pressure and temperatures, it is a pure chemical substance. If it is hylotropic over all pressure and temperatures except the most extreme ones, it is a → chemical element. See also → hylotrope.

First suggested by Wilhelm Ostwald (1904, in Annalen der Naturphilosophie 3, 355), from Gk. hylo-, combining form of hyle "matter; wood," because of the dependence on the composition, + → -tropic.

Mâdegard, from mâdé, → matter, + gard, → -tropic.

isentropic
  ایزودرگاشت   
izodargâšt

Fr.: isentrope   

Having a constant entropy.

iso- + → entropy + → -ic.

isentropic flow
  تچان ِ ایزودرگاشت   
tacân-e izodargâšt

Fr.: écoulement isentrope   

A → reversible flow in which the value of → entropy remains → constant; i.e. no energy is added to the flow, and no energy losses occur due to friction or dissipative effects.

isentropic; → flow.

isentropic process
  فراروند ِ ایزودرگاشت   
farâravand-e izodargâšt

Fr.: process isentrope   

A → thermodynamic process for which there is no → heat transfer with the surroundings, and no change in → entropy.

isentropic; → process.

isotropic
  ایزوگرد، همسان‌گرد   
izogard, hamsângard (#)

Fr.: isotrope   

Having physical properties that do not vary with direction.

iso- + → -tropic.

isotropic Universe
  گیتی ِ ایزوگرد، ~ ِ همسان‌گرد   
giti-ye izogard, ~ hamsângard (#)

Fr.: Univers isotrope   

A Universe having observed properties that appear identical in every direction.

isotropic; → universe.

polytropic
  بُلگشتی   
bolgašti

Fr.: polytropique   

1) Math.: Describing a function which has different values for one variable.
2) Thermodynamics: Pertaining to pressure and volume change that maintains specific heat. → polytropic process.

poly- + → -tropic.

polytropic change
  دگرشد ِ بُلگشتی، دگرش ِ ~   
degaršod-e bolgašti, degareš-e ~

Fr.: changement polytropique   

A change in the → pressure or → volume of a → gas in a → polytropic process.

polytropic; → change.

polytropic gas
  گاز ِ بُلگشتی   
gâz-e bolgašti

Fr.: gaz polytropique   

A gas capable of undergoing a → polytropic process.

polytropic; → gas.

polytropic index
  دیشن ِ بُلگشت   
dišan-e bolgašt

Fr.: index polytropique   

A number appearing in the equation describing a → polytropic process.

polytropic; → index.

polytropic process
  فراروند ِ بُلگشتی   
farâravand-e bolgašti

Fr.: processus polytropique   

A thermodynamic process that obeys the relation: PVn = C, where P is pressure, V is volume, n is any real number, called the → polytropic index, and C is a constant.
If n = 0, then P = C and it is an → isobaric process.
If n = 1, then for an → ideal gas PV = NkT = C and it is an → isothermal process.
If n = γ, → adiabatic index, then for an ideal gas it is an → adiabatic process.

polytropic; → process.

tropic
  هورگرد   
hurgard

Fr.: tropique   

Either of the two parallels of latitude on Earth at which the Sun appears overhead at the → summer and → winter solstices each year: → Tropic of Cancer, → Tropic of Capricorn . The tropics lie at latitudes 23°26', north and south, an angle defined by the Earth's → axial inclination.

M.E., from L. tropicus, from Gk. tropikos "of or pertaining to a turn or change; of or pertaining to to the turn of the Sun's apparent motion at solstice," from trope "a turning."

Hurgard, literally "Sun's turning," from hur, → Sun, + gard "turning, changing," from gardidan "to turn, to change;" Mid.Pers. vartitan; Av. varət- "to turn, revolve;" Skt. vrt- "to turn, roll," vartate "it turns round, rolls;" L. vertere "to turn;" O.H.G. werden "to become;" PIE base *wer- "to turn, bend."

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