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bottom-up structure formation diseš-e sâxtâr az pâyin bé
bâlâ Fr.: formation des structures du bas vers le haut A → structure formation scenario in which small galaxies form first, and larger structures are then formed in due course. Contrary to → top-down structure formation. |
bound 1) bandidé; 2) karân Fr.: lié; lien 1) (adj.) Tied, confined by bonds. → bound cluster,
→ bound charge, → bound system. |
bound charge bâr-e bandidé Fr.: charge liée Any electric charge which is bound to an atom or molecule, in contrast to free charge, such as metallic conduction electrons, which is not. Also known as → polarization charge. |
bound cluster xuše-ye bandidé Fr.: amas lié A cluster of astronomical objects, such as stars or galaxies, held together by their mutual gravitational attraction. → bound system. |
bound occurrence roxdâd-e bandidé Fr.: occurrence liée Any → occurrence of a → variable x in an x-bound part of a → wff. → bound; → occurrence. |
bound orbit madâr-e bandidé Fr.: orbite liée The orbit described by an object around a central gravitational force in a system whose total energy is negative. An elliptical orbit. |
bound system râžmân-e bandidé Fr.: système lié A system composed of several material bodies the total energy of which (the sum of kinetic and potential energies) is negative, e.g. a → bound cluster. |
bound-bound transition gozareš-e bandidé-bandidé Fr.: transition liée-liée A transition between two energy levels of an electron bound to a nucleus. The electron remains tied to the nucleus before and after the transition. → bound-free transition; → free-free emission. Bound, p.p. of → bind; → transition. |
bound-free transition gozareš-e bandidé-âzâd Fr.: transition liée-libre A transition in which a bound electron is liberated. → free-bound emission; → free-free emission. |
boundary karân (#) Fr.: limite, bord 1) General:
Something that indicates a border or limit; the border or limit so indicated. From Fr., from O.Fr. bodne, from M.L. bodina, butina "boundary, boundary marker." Karân, karâné, kenâr from Mid.Pers. karânag, Av. karana- "boundary." |
boundary conditions butârhâ-ye karân, ~ karâni Fr.: conditions à la limite 1) Math: Restriction on the limits of applicability of an equation.
In a differential equation, conditions that allow to fix the constant
of integration and reach a unique solution. The number of boundary conditions
necessary to determine a solution matches the order of the equation. |
boundary effect oskar-e karân Fr.: effet de bords An effect that forbids or invalidate locally the use of an idealized model of a system in which one or several of its dimensions are supposed to be infinite. |
boundary layer lâye-ye karâni Fr.: couche limite A layer of fluid that is formed wherever a fluid flows past a solid surface and the effects of → viscosity are important. The boundary level forms because as the fluid moves past the object, the molecules which are in direct contact with the surface stick to the surface. The molecules just above the surface are slowed down in their collisions with the molecules sticking to the surface. These molecules in turn slow down the flow just above them, but less effectively. This creates a thin layer of fluid near the surface in which the velocity changes from zero at the surface to the free stream value away from the surface. The boundary layer may be either → laminar or → turbulent in character, depending on the value of the → Reynolds number. The concept of boundary level was first put forward by Ludwig Prandlt (1875-1953) in 1904. |
bounded karânmand (#), karândâr (#) Fr.: limité General: Having bounds or limits. Adj. from → bound. |
bounded function karyâ-ye karânmand, ~ karândâr Fr.: fonction bornée The function y = f(x) in a given range of the argument x if there exists a positive number M such that for all values of x in the range under consideration the inequality | f(x) | ≤ M will be fulfilled. → unbounded function. |
Boussinesq approximation nazdineš-e Boussinesq Fr.: approximation de Boussinesq A simplification in the equations of → hydrodynamics that treats the density as constant except in the → buoyancy term. This approximation is motivated by the fact that when pressure and temperature differences in a flow are small, then it follows from the thermodynamic → equation of state that a change in the density is also small. Named after Joseph Valentin Boussinesq (1842-1929), a French physicist who made significant contributions to the theory of hydrodynamics, vibration, light, and heat; → approximation. |
bow 1) kamân; 2) farâl Fr.: proue 1a) A bent, curved, or arched object. 1) M.E., from O.E. boga "archery bow, arch, rainbow" (cf.
O.Norse bogi, Du. boog, Ger. Bogen "bow");
PIE root *bheug- "to bend;" cf. Skt. bhujati "bends;"
O.H.G. boug, O.E. beag "a ring"). 1) Kamân "bow, arc," from Mid.Pers. kamân, related to xam "curve," cf. Breton kamm "curved, bent," Gk. kampe "a corner, a joint," L. campus "a field," Lith. kampus "corner," PIE *kamb- "to bend, crook." Farâl, from farâ "forward" (farâ raftan "to go forward, proceed," farâ rândan "to drive forward"), equivalent to → pro-, + relation suffix -âl, → -al. Compare farâl with prow "bow," Fr. la proue "prow, bow," from dialectal It. proa, prua, from L. prora "bow," from Gk. proira, related to pro "before, forward." |
bow shock farâl-toš farâl-šok Fr.: choc de proue A → shock wave created in front of an object moving through a medium with a velocity higher than that of the → sound waves in that medium. See, for example, → magnetosphere. |
bow wave farâl-mowj, mowj-e farâl Fr.: onde de proue The wave which appears in front of a speeding boat and goes out behind it in a distinctive "V". It is due to the fact that waves pile up on each other before they can move away. |
Bowen fluorescence mechanism sâzokâr-e fluoresti-ye Bowen Fr.: mécanisme de fluorescence de Bowen A mechanism, made possible by certain chance coincidences between → spectral lines of He II, O III and N III in some → planetary nebulae , that explains the presence with a high intensity of a selected group of O III and N III lines while all other lines of these elements are missing. After I. S. Bowen who first discovered this mechanism in 1935; → fluorescence; → mechanism. |
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