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line of action xatt-e žireš, ~ koneš Fr.: ligne d'action Of a force, the straight line along which the force → vector is directed. The action of a force on a → rigid body does not change when its point of application is displaced along the line of action. Hence, forces applied to a rigid body can be regarded as non-localized, or sliding, vectors. |
line of apsides xatt-e habâkhâ Fr.: ligne des apsides Of an elliptical orbit, the straight line drawn from the → perigee to the → apogee. |
line of equinoxes xatt-e hamugânhâ Fr.: ligne des équinoxes The intersection of the planes of ecliptic and celestial equator. |
line of flow xatt-e tacân Fr.: ligne d'écoulement Same as → streamline. |
line of force khatt-e niru (#) Fr.: ligne de force One of many → imaginary lines whose direction at all → points along its length is that of the electric or → magnetic field at those points. In → electric fields the lines of force are directed toward → negative charges and point away from → positive charges. In magnetic fields the lines of force are directed from the → north pole to the → south pole. |
line of induction xatt-e darhâzeš Fr.: ligne d'induction Same as → line of force in a magnetic field. |
line of nodes xatt-e gerehhâ (#) Fr.: lignes des nœuds The line created by the intersection of the equatorial plane and the orbital plane. |
line of sight xatt-e did, didxatt (#) Fr.: ligne de visée The imaginary straight line connecting the object and the objective lens of the viewing device. |
line profile farâpâl-e xatt Fr.: profil de raie The representation of a spectral line as produced by an observing instrument. |
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. |
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