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line profile variability (LPV) vartandegi-ye farâpâl-e xatt Fr.: variabilité du profil de raie The change in the shape of a → spectral line over time. For instance, in → Wolf-Rayet stars the line profile varying on time-scales of minutes to hours is attributed to → microturbulence. → line; → profile; → variability. |
line spectrum binâb-e xatti (#) Fr.: spectre de raies Spectrum consisting of discrete lines (emission or absorption), each corresponding to a particular wavelength, as opposed to a continuous spectrum. |
line strength zur-e xatt Fr.: intensité de raie Same as → line intensity. |
line wing xatbâl, bâl-e xatt Fr.: aile de raie Part of the line profile between the continuum level and the half value of the emission or absorption peak. The wings are due to matter traveling at much greater speeds than that providing the main peak. → red wing; → blue wing. |
line-blanketed model model-e patumand Fr.: A stellar atmosphere model which includes metals or uses methods to reproduce their effects, → line blanketing. |
line-driven wind bâd-e xattzâd Fr.: vent induit par raie Same as → radiation-driven wind. |
linea xaš Fr.: ligne Any of a countless number of dark streaks visible on → Europa's surface that crisscross the whole → Galilean satellite. They are up to 1,000 km long, 20 km wide, and 1 km deep, but only hundred of meters high. In many cases, the ridges are double, often with dark outer edges and a central band. Images show that on each side of the lines, the edges have moved relative to each other. According to the most likely hypothesis, lineae result from eruptions of warm water, in a scenario similar to the present day mid- oceanic ridges on Earth. From L. linea, → line. Xaš, → streak. |
linear xatti (#) Fr.: linéaire Confined to first-degree algebraic terms in the relevant variables. Adj. of → line. |
linear acceleration šetâb-e xatti Fr.: accélération linéaire The rate of change of the → linear velocity with time. It is defined by the expression Δv/Δt and is equal to the → first derivative of the → linear velocity. → linear; → acceleration. |
linear approximation nazdineš-e xatti Fr.: approximation linéaire Taking the first term in the Taylor series as an approximation to a mathematical function at a given point. → first approximation. → linear; → approximation. |
linear astrolabe ostorlâb-e xatti Fr.: astrolabe linéaire A version of → planispheric astrolabe in which the → celestial sphere and the various circles of altitude and declination are projected on to a line represented by a staff. The staff is equivalent to the meridian line and contains markings to indicate the centers of these circles and their intersections with the meridian. By attaching three ropes to the appropriate points on the staff to act as radii, the circles and their intersections can be reconstructed. One of the ropes was attached to a plumb line. A scale giving chord lengths in the meridian circle extended the linear astrolabe's range of applications. It was invented by the Iranian mathematician and astronomer Sharafeddin Tusi (c1135-1213), but no early example has survived. Same as → Sharafeddin's staff and Tusi's staff. |
linear correlation hambâzâneš-e xatti Fr.: corrélation linéaire A measure of how well data points fit a straight line. When all the points fall on the line it is called a perfect correlation. When the points are scattered all over the graph there is no correlation. → linear; → correlation. |
linear diameter tarâmun-e xatti Fr.: diamètre linéaire The real physical diameter, as opposed to angular diameter. |
linear differential equation hamugeš-e degarsâne-yi-ye xatti Fr.: équation différentielle linéaire An equation in which the → dependent variable y
and all its differential coefficients occur only
in the first degree. A linear differential equation of → order
order n has the form: → linear; → differential; → equation. |
linear electric quadrupole cahârqotbe-ye barqi-ye xatti Fr.: quadrupôle électrique linéaire A system of three charges +q, -2q, and +q, arranged along a line to form an axial quadrupole. The → electric potential V due to a linear quadrupole varies as 1/r^{3}, whereas the → electric intensity E varies as 1/r^{4}. → linear; → electric; → quadrupole. |
linear equation hamugeš-e xatti Fr.: équation linéaire An equation composed of first degree variables and representing a straight line. |
linear function karyâ-ye xatti Fr.: fonction linéaire A function expressed by a → first degree equation that can be graphically represented in the → Cartesian coordinate plane by a → straight line. |
linear instability nâpâydâri-ye xatti (#) Fr.: instabilité linéaire An instability that can be described (to first-order accuracy) by linear (or tangent linear) equations. → linear; → instability. |
linear momentum jonbâak-e xatti Fr.: quantité de mouvement linéaire The product of an object's → mass and → velocity. It is a → vector and points in the same direction as the velocity vector. Linear momentum is distinguished from → angular momentum. When there is no opportunity for confusion, usually the term momentum is used instead of linear momentum. |
linear perturbation theory negare-ye partureš-e xatti Fr.: théorie de perturbation linéaire Assumption that the variations in the plasma parameters, due to the presence of waves, are small (to the first order) as compared to the undisturbed parameters. This makes it possible to linearize equations by dropping out second order (and higher) nonlinear terms. → linear; → perturbation; → theory. |
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