angular differential imaging (ADI) tasvigari-ye degarsâne-yi-ye zâviye-yi Fr.: imagerie différentielle angulaire A high-contrast imaging technique that reduces minute temporal and spatial → seeing fluctuations and facilitates the detection of faint point sources, in close separation from their stars. It consists of the acquisition of a sequence of images with an → altazimuth mounting telescope while the instrument field derotator is switched off. This keeps the instrument and telescope optics aligned and allows the field of view to rotate with respect to the instrument. For each image, a reference → point spread function (PSF) is constructed from other appropriately selected images of the same sequence and subtracted to remove quasistatic PSF structure (Marois et al. 2006, ApJ 641, 556). → angular; → differential; → imaging. |
binomial differential degarsâne-ye donâmin Fr.: binôme différentiel An expression of the form x^{m}(a + bx^{n})^{p}dx, where m, n, p, a, and b are constants. → binomial; → differential. |
calculus of finite differences afmârik-e degarsânihâ-ye karânmand Fr.: calcul des différences finies A → claculus based on the properties of the successive values of → variable quantities and their → differences or → increments. → calculus, → finite, → difference. Afmârik, → calculus, degarsânihâ, plural of degarsân, → difference, karânmand, → finite. |
differ degarsân budan (#) Fr.: différer, être différent To be unlike, dissimilar, or distinct in nature or qualities. From O.Fr. différer, from L. differre "to set apart, differ," from → dis- "away from" + ferre "to carry, bear" (cf. Av. baraiti "carries," O.Pers. barantiy "they carry," Mod.Pers. barad "carries," Skt. bharati "carries," Arm. berem "I carry," Gk. pherein "to carry," O.E., O.H.G. beran, Rus. brat' "to take," bremya "a burden"). Degarsân "different," from degar "another, other" (Mid.Pers. dit, ditikar "the other, the second," O.Pers. duvitiya- "second," Av. daibitya-, bitya- "second," Skt. dvitiya- "second," PIE *duitiio- "second") + sân "manner, semblance" (variant sun, Mid.Pers. sân "manner, kind," Sogdian šôné "career") + budan "to be" (Mid.Pers. budan, from O.Pers./Av. bav- "to be; become, take place," Av. buta- perf. ptcpl. pass., bavaiti "becomes," Skt. bhavati "becomes, happens," bhavah "becoming; condition, state," PIE *bheu- "to be, come into being, become;" cf. Gk. phu- "become," phuein "to bring forth, make grow," L. fui "I was" (perf. tense of esse), futurus "that is to be, future," Ger. present first and second person sing. bin, bist, E. to be, O.Ir. bi'u "I am," Lith. bu'ti "to be," Rus. byt' "to be"). |
difference degarsâni (#) Fr.: différence The quality or condition of being different. Noun form of → differ. |
different degarsân (#) Fr.: différent Not alike in character or quality; differing; dissimilar. Adj. of → difference. |
differentiability degarsânipaziri Fr.: différentiabilité Of a mathematical function, the quality of being → differentiable. Noun from → differentiable. |
differentiable degarsânipazir, degarsânidani Fr.: différentiable Capable of being → differentiated. → differentiable function. From → differentiate + → -able. |
differentiable function karyâ-ye degarsânipazir, ~ degarsânidani Fr.: différentiable Property of a mathematical function if it has a → derivative at a given point. From → differentiable; → function. |
differential 1) degarsâné; 2) degarsâneyi Fr.: différentiel 1) Noun. From M.L. differentialis, from differenti(a), → difference, + → -al. Degarsâné, from degarsân, → different + noun suffix -é. |
differential and integral calculus afmârik-e degarsâne-yi va dorostâli Fr.: calcul différentiel et intégral The two branches of mathematics that make up the → calculus. → differential calculus; → integral calculus. → differential; → integral; → calculus. |
differential calculus afmârik-e degarsâneyi, ~ degarsânehâ Fr.: calcul différentiel A branch of calculus which is concerned with the instantaneous rate of change of quantities with respect to other quantities, or more precisely, the local behavior of functions. → integral calculus. → differential; → calculus. |
differential equation hamugeš-e degarsâneyi Fr.: équation différentielle An equation expressing a relationship between an → independent variable, x, an unknown → function, y = f(x), and its → derivatives. The general form of a differential equation is: F(x, y, y', y'', ..., y^{(n)}) = 0, or F(x,y, dy/dx, d^{2}y/dx^{2}, ..., d^{n}y/dx^{n}) = 0. See also: → ordinary differential equation; → partial differential equation; → linear differential equation; → exact differential equation; → first-order differential equation; → homogeneous linear differential equation; → nonhomogeneous linear differential equation; → differential equation with separated variables; → differential equation with separable variables. → differential; → equation. |
differential equation with separable variables hamugeš-e degarsâne-yi bâ vartandehhâ-ye jodâyi-pazir Fr.: équation différentielle à variables séparables A → differential equation of the form: M_{1}(x) N_{1}(y) dx + M_{2}(x) N_{2}(y) dy = 0, which can be reduced to a → differential equation with separated variables. → differential; → equation; → separate; → variable. |
differential equation with separated variables hamugeš-e degarsâne-yi bâ vartandehhâ-ye jodâ Fr.: équation différentielle à variables séparées A → differentail equation that can be transformed into the form: M(x)dx + N(x)dy = 0. → differential; → equation; → separate; → variable. |
differential geometry hendese-ye degarsâneyi Fr.: géométrie différentielle The study of curved spaces using differential calculus. → differential; → geometry. |
differential image motion monitor (DIMM) pahregar-e jonbeš-e degarsâneyi-ye vine, ~ ~ ~ tasvir Fr.: moniteur de mouvements d'images différentiels,
moniteur seeing A device that is commonly used to measure the → seeing at optical astronomical sites. The DIMM delivers an estimate of the → Fried parameter based on measuring the variance of the differential image motion in two small apertures, usually cut out in a single larger telescope pupil by a mask. The DIMM concept was introduced by Stock & Keller (1960, in Stars and Stellar Systems, Vol. 1, ed. G. P. Kuiper & B. M. Middlehurst, p. 138), whereas its modern implementation was first described by Sarazin & Roddier (1990, A&A 227, 294). → differential; → image; → motion; → monitor. |
differential refraction šekast-e dagarsâneyi Fr.: refraction différentielle A problem encountered in astronomical spectroscopy, which consists of a loss of light from some wavelengths due to → atmospheric dispersion. In simple terms, differential refraction means that at nonzero → zenith distances an object cannot be simultaneously placed at the same position within a → slit at all wavelengths. This problem becomes more important for increasing → airmass, larger → spectral range, and smaller → slitwidths. To remedy this drawback, the slit should always be oriented along a direction perpendicular to the horizon, since differential refraction occurs in that direction. → differential; → refraction. |
differential rotation carxeš-e degarsâneyi Fr.: rotation différentielle 1) Of a single body (such as a star or a gaseous planet), the axial rotation of
equatorial latitudes faster than polar latitudes. → differential; → rotation. |
differentially rotating system râžmân-e degarsâné carxân Fr.: système en rotation différentielle A system characterized by → differential rotation. In such a system the → angular velocity decreases as the distance from the rotation center increases. → differential; → rotating; → system. |