collisional cross section
sekanj-e oskarmand-e hamkubeši
Fr.: section efficace de collision
Same as → cross section.
calipâ (#), xâj (#)
(n.) 1a) The Southern Cross, → Crux.
1b) A figure or pattern formed by the intersection of two lines.
M.E. cros, from O.E., probably from Old Norse kross, from O.Ir. cros, from L. crux "stake, cross."
Calipâ, loanword from Aramaic. Xâj loanword from Arm.
hamvbâzâneš-e calipâyi, ~ xâji
Fr.: corrélation croisée
In radio astronomy, the process performed by a → cross correlator or the result of the process.
hambâzângar-e calipâyi, ~ xâji
In radio interferometry, a device that multiplies together the signals received by each pair of antennas in an array and performs several operations on the signal (filtering out the noise added to the signal by the receiver electronics, correcting for the Doppler shift and geometric delay due to the position and motion of the antennas). The correlated signal, corresponding to the spatial frequency given by the distance between the two antennas, is then combined with the other spatial frequency to reconstruct the map of the source.
pâšande-ye calipâyi, ~ xâji
A device producing cross dispersion.
pâšeš-e calipâyi, ~ xâji
Fr.: dispersion croisée
Dispersion of a light beam by using two dispersing elements (grating, grism), one for separating spectral orders, the other for resolving spectral features within an order.
Fr.: identification croisée
The identification of an object in a data base or catalog and matching it with the same object identified in another catalog.
→ cross; → identification.
Fr.: produit vectoriel
Same as → vector product.
bâzbord-e dosuyé (#), ~ candsuyé (#)
Fr.: référence croisée
Reference from one part or element of a book or data catalog to something in another for further information.
Fr.: 1) section plane; 2) section efficace
1) Math: The intersection of a plane with a geometric figure,
usually at right angles to an axis of symmetry.
In classical mechanics, the cross section for the collision of a point particle with a hard sphere is just be the surface of a section through the middle of the sphere. This explains the name "cross section." → cross; → section.
binâbnegâr bâ pâšeâš-e chalipaayi, ~ ~ ~ xâji
Fr.: spectrographe à dispersion croisée
A spectrograph that utilizes cross dispersion.
A system of two perpendicular fine threads of wire placed in the focus of the eyepiece of an optical instrument and used as a sighting reference.
Târbast, from târ + bast. The first component târ "thread, string, wire," cognate with tanidan, tan- "to spin, twist, weave," → tension; the second component bast "to bind; to arrange" (past stem of bastan, from Mid.Pers. bastan/vastan "to bind, shut," → band.
zamân-e gozar (#)
Fr.: temps de traversée
A concept used for checking the stability of a group of mass such as a cluster of galaxies or a stellar cluster. The crossing time is given by tc = R/V, where R is the average projected radial distance of group members from the center of mass and V the Gaussian dispersion in internal velocity.
Zamân, → time; gozar "crossing," infinitive gozaštan, Mid.Pers. vitartan "to pass," Sogdian wytr "to go," O.Pers./Av. vitar- "to put across," from prefix vi- "away, apart," + tar- "to cross over" (Skt. tr- "to cross over," tarati "crosses," cf. Av. taro, Skt. tirah "through, beyond," L. trans "beyond," Ger. durch, E. through; PIE base *tr- "through").
Fr.: croix d'Einstein
An image of a distant quasar (redshift 1.7) formed by a foreground spiral galaxy (redshift 0.039) through gravitational lensing. The image of the quasar is split into four point sources forming a cross at the center of the galaxy.
Fr.: conversion intersystème
A → radiationless relaxation process in which a molecule in some excited → electronic state converts to a state of different spin → multiplicity. Intersystem crossing is analogous to → internal conversion.
Fr.: croix de Mills
Named after the Australian engineer and astronomer Bernard Yarnton Mills (1920-2011; see R.H. Frater et al. 2013, arXiv:1306.6371); → cross.
Fr.: Croix du Nord
An arrangement of stars in the form of a cross in the constellation → Cygnus.
Fr.: section efficace nucléaire
Apparent cross-section possessed by an atomic nucleus when it undergoes a particular type of collision process.
Fr.: Croix du Sud
Popular name for the constellation → Crux. Its four brightest stars form a distinctive cross shape.
Thomson cross section
Fr.: section efficace de Thomson
The → cross section involved the → Thomson scattering of electromagnetic waves by a free electron. It is defined by: σT = 8πre2/3, where re is the classical → electron radius. Its value is 0.665 245 x 10-28 m2.