# 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: 77 Search : function
 Schechter function   کریای ِ ششتر   karyâ-ye SchechterFr.: fonction de Schechter   A mathematical expression that describes the → luminosity function of galaxies. The function correctly reflects the facts that the luminosity function decreases with increasing luminosity and that the decrease is particularly marked at high luminosities. It is expressed as: φ(L) = φ*(L/L*)α exp (-L/L*), which has two parts and three parameters: φ* is an empirically determined amplitude, α is an empirically derived exponent, and L* is a characteristic luminosity which separates the low and high luminosity parts. For small luminosities (L much smaller than L*) the Schechter function approaches a power law, while at high luminosities (L much larger than L*) the frequency of galaxies drops exponentially. φ*, L*, and the faint-end slope α depend on the observed wavelength range, on the → redshift, and on the environment where the galaxies are observed.Named after the American astronomer Paul Schechter (1948-), who proposed the function in 1976 (ApJ 203, 297); → function. source function   کریای ِ خن   karyâ-ye xanFr.: fonction source   For a radiating material, the ratio of emissivity to opacity.→ source; → function. spline function   کریای ِ اسپلین   karyâ-ye splinFr.: fonction spline   A function consisting of several segments, usually → polynomials, joined smoothly together at specific points with an explicitly stated degree of accuracy. Spline functions are used to approximate a given function on an interval.From East Anglian dialect, maybe related to O.E. splin and to modern splint. A spline was originally a slat or a thin strip of wood. A later meaning was "a long, thin, flexible strip used as a guide for drawing arcs of curves;" → function. stellar creation function   کریای ِ آفرینش ِ ستارگان   karyâ-ye âfarineš-e setâregânFr.: fonction de création stellaire   The number of stars born per unit area in the mass range log M to log M + d log M during the time interval t to t + dt. The integration of the creation function over time gives the → present-day mass function (Miller & Scalo, 1797, ApJSS 41, 513).→ stellar; → creation; → function. step function   کریای ِ پله‌ای   karyâ-ye pelle-yiFr.: fonction échelon   Math.: A function f of a real variable defined on an interval [a,b] so that [a,b] can be divided into a finite number of sub-intervals on each of which f is a constant. The graph of a step function is a series of line segments resembling a set of steps.Step, from M.E. steppen, O.E. steppan; cf. Du. stap, O.H.G. stapfo, Ger. stapfe "footprint;" → function.Karyâ, → function; pellé "stair, step;" Mid.Pers. pylg "step," pillagân "steps, staircase;" from *palak, from *padak, from pad-, → foot, + relation suffix -ak. total function   کریای ِ هماک   karyâ-ye hamâkFr.: fonction totale   A function whose value is defined for all possible input values.→ total; → function. transcendental function   کریای ِ ترا-فرازنده   karyâ-ye tarâfarâzandéFr.: fonction transcendante   A function which is not → algebraic. For example y = cosx, y = 10xx. transfer function   کریای ِ تراوژ   karyâ-ye tarâvažFr.: fonction de transfert   The mathematical relationship between the output of a control system and its input: for a linear system, it is the Laplace transform of the output divided by the Laplace transform of the input under conditions of zero initial-energy storage.→ transfer; → function. transition function   کریای ِ گذرش   karyâ-ye gozarešFr.: fonction de transition   The → probability of finding the → Universe in a → state labelled X2 at a time t2, if it was in a state X1 at an earlier time t1.→ transition; → function. trigonometric function   کریای ِ سه‌برسنجیک   karyâ-ye sebarsanjikFr.: fonction circulaire, ~ trigonomtérique   A function of an angle, one of six functions (sine, cosine, tangent, cotangent, secant, and cosecant) that represent ratios of sides of right triangles. Also called circular function. truth function   کریای ِ راستینی   karyâ-ye râstiniFr.: fonction de vérité   A → total function from → truth values to truth values (a sequence of truth values).→ truth; → function. unbounded function   کریای ِ بیکران   karyâ-ye bikarânFr.: fonction non bornée   The function y = f(x) in a given range of the argument x if there is no number M such that for all values of x in the range under consideration the inequality | f(x) | ≤ M will be fulfilled. → bounded function.→ unbound; → function. vector function   کریای ِ برداری   karyâ-ye bordâriFr.: fonction vectorielle   A function whose value at each point is n-dimensional, as compared to a scalar function, whose value is one-dimensional.→ vector; → function. visibility function   کریای ِ دیاری، ~ پدیداری   karyâ-ye diyâri, ~ padidâriFr.: fonction de visibilité   The → Fourier transform of a source's → brightness distribution, weighted by the characteristics of the → interferometer's antennas.→ visibility; → function. wave function   کریای ِ موج   karyâ-ye mowjFr.: fonction d'onde   In → quantum mechanics, the function of space and time that satisfies → Schrodinger equation. The square of the modulus of its amplitude at any point represents the probability of finding a particle there.→ wave; → function. window function   کریای ِ روزنه   karyâ-ye rowzanéFr.: fonction fenêtre   A function whose value is zero outside a given interval. Applications of window functions include signal filtering and spectral analysis. The various types of windw functions include: → rectangular window, cosine window, triangular window, Gaussian window, Hanning window, and so on.→ window; → function. work function   کریای ِ کار   karyâ-ye kârFr.: travail d'extraction   The least amount of energy required to remove an electron from the surface of a solid, to a point just outside the solid where the electron has zero kinetic energy. See also → photoelectric effect.→ work; → function.

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