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first quarter cârak-e naxost Fr.: premier quartier A → lunar phase that occurs in the middle of the interval between the → new Moon and the → full Moon, when half of the Moon's disk is illuminated. At first quarter, the Moon is situated at 90° east of the Sun. |
first star naxostin setâré Fr.: première étoile A member of the → Population III → massive stars that formed some 500 Myr after the → Big Bang. First stars had a simple chemical composition consisting only of H, He, and traces of ^{7}Li and were very short-lived. They are the most likely sources of → reionization of the Universe, which put an end to the → Cosmic Dark Age. |
first-order differential equation hamugeš-e degarsâne-yi-ye râye-ye naxost Fr.: équation différentielle du premier ordre A → differential equation containing only the first → derivative. For example, dy/dx = 3x and 2y(dy/dx) + 3x = 5. → first; → order; → differential; → equation. |
first-order logic (FOL) guyik-e farâsani-ye râye-ye naxost, ~ farâsanhâ-ye ~ ~ Fr.: logique des prédicats du premier ordre A system of → formal logic that is an extension of → propositional logic. It is also known as → first-order predicate calculus and → predicate logic. FOL eliminates deficiencies of propositional logic by: representing → objects (their properties, relations and statements about them), introducing → variables, and introducing → quantifiers. |
first-order partial derivative vâxane-ye pâri-ye râye-ye naxost Fr.: dérivée partielle du premier degré For a → function with several → variables, the derivative, done only once, with respect to one of the variables. For example ∂u/∂x for u = u(x,y). → first; → order; → partial; → derivative. |
first-order predicate calculus afmârik-e farâsani-ye râye-ye naxost Fr.: cacul des prédicats du premier ordre Same as → first-order logic. |
first-order spectrum binâb-e râye-ye naxost Fr.: spectre du premier ordre An optical spectrum, produced by a diffraction grating, in which the difference in path length of light from adjacent slits is one wavelength. |
fish mâhi (#) Fr.: poisson A limbless cold-blooded vertebrate animal with gills and fins living wholly in water (OxfordDictionaries.com). M.E. fis(c)h, fyssh, O.E. fisc; cognate with Du. vis, Ger. Fisch, O.Norse fiskr, Goth. fisks; akin to L. piscis; PIE root *pisk- "a fish." Mâhi "fish," from Mid.Pers. mâhik; Av. masya-; cf. Skt. matsya-, Pali maccha-. |
fissile šekâftpazir (#), šekâftani (#) Fr.: fissile Any material that is capable of undergoing → nuclear fission by → thermal neutrons. The three primary fissile materials are uranium-233, uranium-235, and plutonium-239. Although sometimes used as a synonym for → fissionable material, this term has acquired a more restricted meaning. From L. fissilis, from fiss(us), + -illis a suffix of adjectives expressing capability, susceptibility, liability, aptitude, etc. Šekâftani, from šekâft, → fission + -i a suffix expressing capability, aptitude, etc. |
fissile isotope izotop-e šektpazir Fr.: isotope fissile An isotope that is capable of undergoing nuclear fission after capturing either fast neutron or thermal neutron. Typical fissionable isotopes: ^{238}U, ^{240}Pu, but also ^{235}U, ^{233}U, ^{239}Pu, ^{241}Pu |
fission šekâft (#) Fr.: fission 1) The act or process of splitting or breaking into parts. Fission, from L. fissionem "a breaking up, cleaving," from root of findere "to split." Šekâft, stem of šekâftan "to split, break, tear," akin to kaftan, kâftan "to split; to dig," Parthian Mid.Pers. q'f- "to split;" Sogdian kβ "to split;" Chorasmian kf- "to split, be split;" Proto-Iranian *kap-, *kaf- "to split." |
fission products farâvardehâ-ye šekâft (#) Fr.: produits de fission Nuclides generated by the fission of higher mass elements or by subsequent radioactive decay of nuclides directly generated by fission. |
fissionable šekâftpazir (#) Fr.: fissile The material that can be fissioned by fast neutrons, such as uranium-238. Commonly used as a synonym for → fissile material. |
fit 1) saz kardan; 2) saz Fr.: 1) ajuster; 2) ajustement 1) (v.) To pass a mathematical line or curve through data points. From M.E. fitten; akin to M.Du. vitten "to befit." Saz, from sazidan "to suit, fit, be worthy," sazâ "suitable, agreeing with, congruous, deserving of," Mid.Pers. sacitan/sazidan "to fit," sazešn "fitness," sazâg "fitting, worth;" Av. ^{1}sak- "to understand or know a thing; to mark;" cf. Skt. śak- "to be able, powerful" śakta- "able, competent," śakti- "ability, power;" alternatively from Av. ^{2}sak- "to go by, pass, pass away; to be up or over (of time)." |
fitting saz-kard, saz Fr.: ajustement The process or instance of adapting a mathematical curve to data points. Verbal form of → fit. |
fitting error irang-e saz-kard, ~ saz Fr.: erreur d'ajustement The discrepancy between the mathematical curve and data points. → fit. |
five panj (#) Fr.: cinq A cardinal number whose symbol is 5, V, or Five, from O.E. fif, from P.Gmc. *fimfe (cf. O.S. fif, O.H.G. funf), from PIE *penk^{w}e "five;" cognate with Pers. panj, as below. Panj, from Mid.Pers. panj; Av. panca; cf. Skt. páñca; Gk. pente; L. quinque; E. five, as above. |
five-color system râžmân-e panj-rangé Fr.: système à cinq couleurs A photometric system which uses five filters, from ultraviolet to the red part of the visual spectrum: U, B, V, R and I. |
Five-hundred-meter Aperture Spherical radio Telescope (FAST) FAST Fr.: FAST The 500 m diameter → radio telescope which is the largest → single-dish antenna in the world. It is an Arecibo type telescope nestled within a natural basin in China's remote and mountainous Dawodang, Kedu Town, in southeastern China's Guizhou Province. The → reflector consists of 4,450 triangular panels, each with a side length of 11 m. More than 2,000 → actuators are used, according to the feedback from the measuring system, to deform the whole reflector surface and directly correct for → spherical aberration. Several detectors are used to cover a frequency range of 70 MHz to 3 GHz. → five; → hundred; → meter; → aperture; → spherical; → radio; → telescope. |
fix barjâyidan Fr.: fixer 1) To make fast, firm, or stable. M.E. fixen, probably from O.Fr. fixe "fixed," from L. fixus "fixed, fast, established, settled," p.p. of figere "to fix, fasten." Infinitive, from barjâ, → fixed. |
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