absorption coefficient hamgar-e daršam Fr.: coefficient d'absorption The fraction of normally incident light that is absorbed per unit path length or by a unit mass of absorbing medium. → absorption; → coefficient. |
attenuation coefficient hamgar-e tonokeš Fr.: 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) = I_{0}e^{-μx}, where I(x) is the intensity at depth of x cm and I_{0} is the original intensity. → attenuation; → coefficient. |
binomial coefficient hamgar-e donâmin Fr.: coefficient binomial
The factor multiplying the variable in a term of a → binomial expansion. For example, in (x + y)^{4} = x^{4} + 4x^{3}y + 6x^{2}y^{2} + 4xy^{3} + y^{4} 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 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 x^{3},
2 is the coefficient of x^{3}. In general, any factor of
a product is called the coefficient of the product of the remaining
factors. 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 k^{w}er- "to do, to make." |
coefficient of viscosity hamgar-e vošksâni Fr.: 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/cm^{2}.(cm/s), which reduces to 1 dyne.s/cm^{2}. This unit is called 1 → poise. → viscosity; → coefficient. |
correlation coefficient hamgar-e hambâzâneš Fr.: coefficient de corrélation A number between -1 and 1 which measures the degree to which two variables are linearly related. → correlation; → coefficient. |
coupling coefficient hamgar-e jafsari Fr.: coefficient de couplage A parameter that indicates the strength of the interaction between two systems. → coupling; → coefficient. |
diffusion coefficient hamgar-e paxš Fr.: 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 hamgar-e cirandé Fr.: coefficient dominant Of a → non-zero polynomial, the coefficient of the → monomial which has the highest → degree. Dominant, adj. from → dominant; → coefficient. |
Einstein coefficient hamgar-e Einstein Fr.: 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 A_{ij}, and the coefficient of stimulated emission by B_{ij}, 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 hamgar-e gosil Fr.: coefficient d'émission Electromagnetic flux emitted by a source per unit volume per unit time. → emission; → coefficient. |
extinction coefficient hamgar-e xâmuši Fr.: coefficient d'extinction Gradient of apparent magnitude with air mass. → extinction; → coefficient. |
Fourier coefficient hamgar-e Fourier Fr.: coefficient de Fourier One of the coefficients a_{n} or b_{n} of cos (nx)
and sin (nx) respectively in the → Fourier series
representation of a function. They are expressed by: → Fourier analysis; → series. |
gravity darkening coefficient hamgar-e târikeš-e gerâneši Fr.: 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 ∝ g_{eff}^{α}, where g_{eff} is the → effective gravity and α is the gravity darkening coefficient. See also the → gravity darkening exponent. → gravity; → darkening; → coefficient. |
mass absorption coefficient hamgar-e daršm-e jermi Fr.: 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 hamgar-e bâzmiyâzeš Fr.: 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. → recombination; → coefficient. |
reddening coefficient hamgar-e sorxeš Fr.: 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 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. → reflection; → coefficient. |
regression coefficient hamgar-e vâyâzeš (#) Fr.: coefficient de régression The slope of the straight line that most closely relates two correlated variables. → regression, → coefficient. |
scattering coefficient hamgar-e parâkaneš Fr.: coefficient de diffusion The fraction of light scattered per unit distance in a medium. → scattering; → coefficient. |