modulation transfer function (MTF) karyâ-ye tarâvaž-e degarâhangeš Fr.: fonction de transfert de modulation A measure of the ability of an optical system to reproduce (transfer) various levels of detail from the object to the image, as shown by the degree of contrast (modulation) in the image. → optical transfer function. → modulation; → transfer; → function. |
nested function karyâ-ye tu-dar-tu Fr.: fonction imbriquée In computer programing, a function that is defined inside the definition of another function. |
non-algebraic function karyâ-ye nâjabri Fr.: fonction non algébrique A → transcendental function. Examples are: exponential, logarithmic, and trigonometric functions. |
optical transfer function (OTF) karyâ-ye tarâvaž-e nuri Fr.: fonction de transfert optique The function that provides a full description of the imaging quality of an optical system. A combination of the → modulation transfer function (MTF) and the → phase transfer function (PTF) , the OTF describes the spatial (angular) variation as a function of spatial (angular) frequency. |
orthogonal functions karyâhâ-ye ardâkonj Fr.: fonctions orthogonales A set of functions, any two of which, by analogy to orthogonal vectors, vanish if their product is summed by integration over a specified interval. → orthogonal; → function. |
partition function karâ-ye parkeš Fr.: fonction de partition See → integer partition. |
periodic function karyâ-ye dowreyi Fr.: fonction périodique A function f(x) if for all x, f(x + P) = f(x), where P is a positive constant. The least value of P > 0 is called the period of f(x). |
phase function karyâ-ye fâz Fr.: fonction de phase The variation in brightness of a target as the phase angle (the angle between Sun and observer as seen from the target) varies between 0° and 180°. The directional distribution of reflected (or scattered) radiation. The phase angle is the supplement of the scattering angle (the angle between the incident ray and the emerging ray); in other words, the sum of the phase angle and the scattering angle is always 180° (Ellis et al., 2007, Planetary Ring Systems, Springer). |
phase transfer function (PTF) karyâ-ye tarâvaž-e fâz Fr.: fonction de transfert de phase A measure of the relative phase in the image as function of frequency. It is the phase component of the → optical transfer function. A relative phase change of 180°, for example, results in an image with the black and white areas reversed. |
piecewise continuous function karyâ-ye peyvaste-ye tekke-yi Fr.: fonction continue par morceaux A function f(x) in an interval if :1) the interval can be divided into a finite number of pieces in each of which f(x) is continuous, and 2) the limits of f(x) as x approaches the boundary point of each piece are finite. In other words, a piecewise continuous function is one that is made up of a finite number of continuous pieces. → piecewise; → continuous; → function. |
Planck function karyâ-ye Planck Fr.: fonction de Planck Same as → Planck's blackbody formula. |
point spread function (PSF) karyâ-ye gostareš-e noqté, ~ ~ pandé Fr.: fonction d'étalement du point The two-dimensional intensity distribution about the image of a point source. |
power function karyâ-ye tavâni Fr.: fonction de puissance A function of the form f(x) = xn, where n is a → real number. |
present-day mass function (PDMF) karyâ-ye jerm-e konuni, ~ ~ emruzi Fr.: fonction de masse actuelle The present number of stars on the → main sequence per unit logarithmic mass interval per square parsec. The PDMF is the basis for deriving the → initial mass function (IMF). This mass function is not corrected for stellar evolution nor losses through stellar deaths. |
probability density function karyâ-ye cagâli-ye šavânâyi Fr.: fonction de densité de probabilité A mathematical function whose integral over any interval gives the probability that a continuous → random variable has values in this interval. Also known as → density function, frequency function, → probability function. → probability; → density; → function. |
probability function karyâ-ye šavânâyi Fr.: fonction de probabilité A function that represents a probability distribution in terms of integrals. Also called probability density function or density function. → probability; → function. |
reddening function karyâ-ye sorxeš Fr.: fonction de rougissement The normalized interstellar extinction at a given wavelength. It is defined by f(λ) = A(λ)/A(Hβ) - 1, where A(λ) is the extinction at the given wavelength and A(Hβ) the extinction at Hβ, with f(Hβ) = 0. It is used to → de-redden observed fluxes: I(λ)/I(Hβ) = F(λ)/F(Hβ).10c(Hβ).f(λ), where I represents the flux in the absence of extinction and F the observed flux affected by extinction, c(Hβ) being the → reddening coefficient. |
regression function karyâ-ye vâyâzeš Fr.: fonction de régression A mathematical function that describes the relationship between two or more variables in a set of data. → regression, → function. |
regular function karyâ-ye bâsâmân Fr.: fonction régulière A function of a complex variable which is single-valued in a domain and which has a finite derivative at every point. |
Salpeter function karyâ-ye Salpeter Fr.: équation de Salpeter The first mathematical description of the → initial mass function (IMF) of newly formed stars of solar to → intermediate-masses. It is proportional to M -2.35, where M is the stellar mass. → Salpeter slope. Named after the Austrian-Australian-American astrophysicist Edwin Ernest Salpeter (1924-2008); → function. |