An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



<< < ari mea > >>

Number of Results: 36 Search : mean
mean profile
  فراپال ِ میانگین   
farâpâl-e miyângin

Fr.: profil moyen   

The shape of a pulsar's pulse as determined by averaging several pulses.

mean; → profile.

mean sidereal day
  روز ِ اختری ِ میانگین   
ruz-e axtari-ye miyângin

Fr.: jour sidéral moyen   

The average time interval between two successive → upper transits of the → mean equinox.

mean; → sidereal; → day.

mean sidereal time
  زمان ِ اختری ِ میانگین   
zamân-e axtari-ye miyângin (#)

Fr.: temps sidéral moyen   

The hour angle of the mean equinox for a given observer.

mean; → sidereal; → time.

mean solar day
  روز ِ خورشیدی ِ میانگین   
ruz-e xoršidi-ye miyângin (#)

Fr.: jour solaire moyen   

The average length of the apparent solar day. In other words, the interval between successive transits of the mean Sun for a given observer.

mean; → solar; → day.

mean solar time
  زمان ِ خورشیدی ِ میانگین   
zamân-e xoršidi-ye miyângin (#)

Fr.: temps solaire moyen   

The time since the mean Sun crossed the meridian with 12 hours added to make the day begin at midnight.

mean; → solar; → time.

mean spectrum
  بیناب ِ میانگین   
binâb-e miyângin

Fr.: spectre moyen   

A plot of the mass-to-charge ratio of elementary particles, sorted by their isotopic mass.

mean; → spectrum.

mean Sun
  خورشید ِ میانگین   
xoršid-e miyângin (#)

Fr.: Soleil moyen   

A hypothetical Sun that moves along the ecliptic at a uniform rate equal to the average motion of the real Sun.

mean; → sun.

mean term
  ترم ِ میانی   
tarm-e miyâni

Fr.: terme moyen   

In → syllogism, the term which is common to both → premises and is excluded from the → conclusion.

mean; → term.

mean value theorem
  فربین ِ ارزش ِ میانگین   
farbin-e arzeš-e miyângin

Fr.: théorème des accroissements finis   

1) If f(x) is a continuous function on the interval from a to b, then:
f(x) dx = f(c)(b - a) (summed from a to b) for at least one point in that interval.
2) More generally, If f(x) and g(x) are continuous functions on the interval from a to b and g(x)≥ 0, then:
f(x)g(x) dx = f(c) ∫ g(x) dx (both integrals summed from a to b).

mean; → value; → theorem.

cemâr (#)

Fr.: sens, signification   

The sense or significance of a word, sentence, symbol, etc. The study dealing with meanings is called → semantics. See also → semiotics.

M.E., from mean; O.E. mænan "to mean, intend, signify" (cf. O.Fris. mena "to signify," O.S. menian "to intend, signify," M.Du. menen, Du. meenen, Ger. meinen "think, suppose"), related to Pers. maneš "disposition, temperament," mênidan "to think, consider," → idea; + → -ing.

Cemâr, from cem or cim "meaning, signification;" Mid.Pers. cim "meaning, reason, cause;" ultimately from Proto-Ir. *cahmāt "wherefore?" cf. Skt. kasmāt "why, where from? whence?," kim "what? how? why?" + âr short form of âvar present stem of âvardan "to cause or produce; to bring," → production, as in bonâr, → cause, used also as a nuance suffix; see also the verb → mean.

period-mean density relation
  باز‌آنش ِ دوره-چگالی ِ میانگین   
bâzâneš-e dowré-cagâli-ye miyângin

Fr.: relation période-densité moyenne   

A relation that gives a rough estimate of the oscillation period of a → pulsating star as a function of its mean density. This relation is obtained by considering how long it would take a sound wave to travel across the diameter of a model star: Π ≅ (3π/2γGρ)1/2, where ρ is the mean density, γ the ratio of → specific heats (Cp/Cv), and G the → gravitational constant. This relation shows that the pulsation period of a star is inversely proportional to the square root of its mean density. And this is the reason why the pulsation periods decrease along the → instability strip from the luminous, very tenuous → supergiants to the faint, very dense → white dwarfs.

period; → mean; → density; → relation.

root mean square (rms)
  ریشه‌ی ِ چاروشی ِ میانگین، ~ ِ دوم ِ ~   
riše-ye câruši-ye miyângin, ~ dovom-e ~

Fr.: valeur quadratique moyenne   

The square root of the arithmetic mean of the squares of the numbers in a given set.

root; → mean; → square.

root-mean-square error
  ایرنگ ِ ریشه‌ی ِ چاروشی ِ میانگین، ~ ~ ِ دوم ِ ~   
irang-e riše-ye câruši-ye miyângin, ~ ~ dovom-e ~


The square root of the second moment corresponding to the frequency function of a random variable.

root; → mean; → square; → error.

root-mean-square value
  ارزش ِ ریشه‌ی ِ چاروشی ِ میانگین   
arzeš-e riše-ye câruši-ye miyângin

Fr.: écart quadratique moyen, écart type   

Statistics: The square root of the arithmetic mean of the squares of the deviation of observed values from their arithmetic mean.

root; → mean; → square; → deviation.

Rosseland mean opacity
  کدری ِ میانگین ِ روسلاند   
kederi-ye miyângin-e Rosseland

Fr.: opacité moyenne de Rosseland   

The → opacity of a gas of given composition, temperature, and density averaged over the various wavelengths of the radiation being absorbed and scattered. The radiation is assumed to be in → thermal equilibrium with the gas, and hence have a → blackbody spectrum. Since → monochromatic opacity in stellar plasma has a complex frequency dependence, the Rosseland mean opacity facilitates the analysis. Denoted κR, it is defined by: 1/κR = (π/4σT3) ∫(1/kν) (∂B/∂T)νdν, summed from 0 to ∞, where σ is the → Stefan-Boltzmann constant, T temperature, B(T,ν) the → Planck function, and kν monochromatic opacity (See Rogers, F.J., Iglesias, C. A. Radiative atomic Rosseland mean opacity tables, 1992, ApJS 79, 507).

Named after Svein Rosseland (1894-1985), a Norwegian astrophysicist, who obtained the expression in 1924; → mean; → opacity.

weighted mean
  میانگین ِ وزنی   
miyângin-e vazni (#)

Fr.: moyenne pondérée   

An mean which is obtained by combining different numbers according to the relative importance of each.

weight; → mean.

<< < ari mea > >>