An Etymological Dictionary of Astronomy and AstrophysicsEnglish-French-Persian

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 21 Search : coefficient
 absorption coefficient   همگر ِ درشم   hamgar-e daršamFr.: coefficient d'absorption   The fraction of normally incident light that is absorbed per unit path length or by a unit mass of absorbing medium. attenuation coefficient   همگر ِ تنکش   hamgar-e tonokešFr.: coefficient d'bsorption   The fraction of a beam of → X-rays or → gamma rays that is absorbed or scattered per unit thickness of the → absorber. The linear attenuation coefficient, denoted by the symbol μ, appears in the equation I(x) = I0e-μx, where I(x) is the intensity at depth of x cm and I0 is the original intensity. binomial coefficient   همگر ِ دونامین   hamgar-e donâminFr.: coefficient binomial   The factor multiplying the variable in a term of a → binomial expansion. For example, in (x + y)4 = x4 + 4x3y + 6x2y2 + 4xy3 + y4 the binomial coefficients are 1, 4, 6, 4, and 1. In general, the r-th binomial coefficient in the expression (x + y)n is: (n,r) = n!/[r!(n - r)!].→ binomial; → coefficient. coefficient   همگر   hamgar (#)Fr.: coefficient   1) Math.: A number or letter placed before an algebraic expression to indicate that the expression is to be multiplied by that factor, e.g. in the expression 2 x3, 2 is the coefficient of x3. In general, any factor of a product is called the coefficient of the product of the remaining factors. 2) Physics: Factor which measures some specified property of a given substance, and is constant for that substance under given conditions, such as the coefficient of friction. → factor.Hamgar, from ham- "together," → com- + -gar agent suffix, from kar-, kardan "to do, to make," Mid.Pers. kardan, O.Pers./Av. kar- "to do, make, build," Av. kərənaoiti "makes," cf. Skt. kr- "to do, to make," krnoti "makes," karma "act, deed;" PIE base kwer- "to do, to make." coefficient of viscosity   همگر ِ وشکسانی   hamgar-e vošksâniFr.: coefficient de viscosité   A quantity that indicates a property of fluids and is defined by the ratio of shearing → stress to the rate of change of shearing → strain. It is also simply called viscosity. The coefficient of viscosity is expressed by: μ = (F/A) / (dv/dy), where F is the force required to maintain a steady velocity difference dv between any two parallel layers of the fluid, A is the area of the layers, and dv/dy is the → velocity gradient between two points separated by a small distance measured at right angles to the direction of flow. The unit of viscosity is that of force times distance divided by area times velocity. Thus, in the cgs system, the unit is 1 dyne.cm/cm2.(cm/s), which reduces to 1 dyne.s/cm2. This unit is called 1 → poise.→ viscosity; → coefficient. correlation coefficient   همگر ِ هم‌باز‌آنش   hamgar-e hambâzânešFr.: coefficient de corrélation   A number between -1 and 1 which measures the degree to which two variables are linearly related. coupling coefficient   همگر ِ جفسری   hamgar-e jafsariFr.: coefficient de couplage   A parameter that indicates the strength of the interaction between two systems.→ coupling; → coefficient. diffusion coefficient   همگر ِ پخش   hamgar-e paxšFr.: coefficient de diffusion   A factor of proportionality involved in the → diffusion equation. It may be defined as the amount of the quantity diffusing across a unit area through a unit concentration gradient in unit time. → magnetic diffusivity.→ diffusion; → coefficient. dominant coefficient   همگر ِ چیرنده   hamgar-e cirandéFr.: coefficient dominant   Of a → non-zero polynomial, the coefficient of the → monomial which has the highest → degree.Dominant, adj. from → dominant; → coefficient. Einstein coefficient   همگر ِ اینشتین   hamgar-e EinsteinFr.: coefficient d'Einstein   A measure of the probability that a particular atomic transition leading to the formation of an atomic spectral line occurs. The coefficient of spontaneous emission is denoted by Aij, and the coefficient of stimulated emission by Bij, i representing the lower level and j is the upper level.Named after Albert Einstein (1879-1955) who introduced the coefficients in 1916; → coefficient. emission coefficient   همگر ِ گسیل   hamgar-e gosilFr.: coefficient d'émission   Electromagnetic flux emitted by a source per unit volume per unit time.→ emission; → coefficient. extinction coefficient   همگر ِ خاموشی   hamgar-e xâmušiFr.: coefficient d'extinction   Gradient of apparent magnitude with air mass. Fourier coefficient   همگر ِ فوریه   hamgar-e FourierFr.: coefficient de Fourier   One of the coefficients an or bn of cos (nx) and sin (nx) respectively in the → Fourier series representation of a function. They are expressed by: an = (1/π) ∫f(x) cos nx dx, for n≥ 0, summed over 0 to 2π bn = (1/π) ∫f(x) sin nx dx, for n≥ 1, summed over 0 to 2π.→ Fourier analysis; → series. gravity darkening coefficient   همگر ِ تاریکش ِ گرانشی   hamgar-e târikeš-e gerânešiFr.: coefficient de l'assombrissement gravitationnel   According to the → von Zeipel theorem, the emergent flux, F, of total radiation at any point over the surface of a rotationally or tidally distorted star in → hydrostatic equilibrium varies proportionally to the local gravity acceleration: F ∝ geffα, where geff is the → effective gravity and α is the gravity darkening coefficient. See also the → gravity darkening exponent.→ gravity; → darkening; → coefficient. mass absorption coefficient   همگر ِ درشم ِ جرمی   hamgar-e daršm-e jermiFr.: coefficient d'absorption de masse   A measure of the rate of absorption of radiation, expressed as the linear absorption coefficient divided by the density of the medium through which radiation is passing.→ mass; → absorption; → coefficient. recombination coefficient   همگر ِ بازمیازش   hamgar-e bâzmiyâzešFr.: coefficient de recombinaison   A measure of the specific rate at which oppositely charged ions join to form neutral particles. It is given by the rate at which those ions recombine, divided by the product of the densities of the two species involved. reddening coefficient   همگر ِ سرخش   hamgar-e sorxešFr.: coefficient de rougissement   A dimensionless quantity determined from the comparison of the observed → Balmer decrements with respect to the theoretical values for given physical conditions of electron temperature and density. The reddening coefficient at Hβ is defined as c(Hβ) = log (I(Hβ)/F(Hβ)), where I(Hβ) and F(Hβ) are → de-reddened and reddened Hβ fluxes respectively. Also called logarithmic extinction.→ reddening; → coefficient. reflection coefficient   همگر ِ بازتاب   hamgar-e bâztâb (#)Fr.: coefficient de réflexion   The ratio given by the → amplitude (or energy) of a reflected wave divided by the amplitude (or energy) of the incident wave. regression coefficient   همگر ِ وایازش   hamgar-e vâyâzeš (#)Fr.: coefficient de régression   The slope of the straight line that most closely relates two correlated variables. scattering coefficient   همگر ِ پراکنش   hamgar-e parâkanešFr.: coefficient de diffusion   The fraction of light scattered per unit distance in a medium.

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