Fr.: point nodal
Any of the two points on the → axis of a → lens system, such that if the → incident ray passes through one, travelling in a given direction, the → emergent ray passes the other in a parallel direction.
Fr.: regression nodale
For a ring inclined to the planet's equator, the points at which the ring crosses the equator (nodes) slowly move around the planet (regress) in a direction opposite to that of the ring's orbital motion. (Ellis et al., 2007, Planetary Ring Systems, Springer).
1) A point of zero → amplitude in a system of
→ stationary waves. See also
From L. nodus "knot."
Gereh "knot," from Mid.Pers. grih "knot;" Sogdian γr'nš "knot, bond, joining;" Khotanese grantha- "knot;" cf. Skt. granthi- "knot."
mâh-e gerehi (#), ~ gowzahri (#)
Fr.: mois draconitique
The time interval between two successive passages of the Moon through its ascending node (27.212220 days, i.e., 27 days 5 hours 5 minutes 35.8 seconds). Nodical month is important for predicting eclipses. Also called → draconic month.
Fr.: théorème de Noether
A → symmetry in a physical system leads to a → conserved quantity. For example, symmetry under → translation corresponds to conservation of → momentum, symmetry under → rotation to conservation of → angular momentum, and symmetry in → time to conservation of → energy. The Noether symmetry theorem is a fundamental tool of modern theoretical physics and the calculus of variations, allowing to derive conserved quantities from the existence of variational symmetries.
Named in honor of the German-American woman mathematician Amalie Emmy Noether (1182-1935), who published the theorem in 1918 ("Invariante Variationsprobleme," Nachr. D. König. Gesellsch. D. Wiss. Zu Göttingen, Math-phys. Klasse 1918: 235-257).
1) The → random → fluctuations
that are always associated with a measurement that is repeated many times over.
Any unwanted disturbance, random or → systematic,
which contaminates the → signal from an object under study.
Noise, of obscure origin; it has been related to O.Fr. noise "uproar, brawl," apparently from L. nausea "disgust, annoyance," literally "seasickness." Alternatively the O.Fr. word is traced to L. noxia "hurting, injury, damage."
Nufé "noise," related to Mod.Pers. noyidan "to cry loud, lament," navidan, nâvidan "to lament," noyé, nôyah "plaint, mown," navâ "sound, song," (with prefix *uz-) zenudan, zenav-, zonudan "to wail," Ossetic niwyn/newun "to howl," O.Khotanese nuva- "to make a noise," Yaqnâvi nuyok "crying, howling," novva "sound," Shahmirzâdi nâv- "to cry; cf. Skt. nav- "to sound loudly, roar," náva- "show of joy or triumph;" L. nuntius "messenger," adnuntiare "to annoince;" Tocharian AB nu- "to roar, PIE *neu- "to shout".
Fr.: source de bruit
An electronic device designed to generate known amounts of radio noise in order to test and calibrate the receivers of radio telescopes.
Fr.: température de bruit
A means for specifying the noise generated as unwanted → electromagnetic radiation in a receiver system or one of its components. It is usually measured in terms of the equivalent temperature in a → Rayleigh-Jeans spectrum. Noise temperature is used mainly in radio astronomy.
Fr.: voltage de bruit
Fluctuations of electric potential in a physical system due to spontaneous disturbances in the system.
tavân-e ham-arz-e nufé
Fr.: puissance équivalente de bruit
A measure of the sensitivity of an electronic detector, defined as the power input to the detector that will create a signal to noise ratio of one for an integration time of half a second.
A set or system of names or terms assigned to objects or items in a particular science or art.
From Fr. nomenclature, from L. nomenclatura "calling of names," from nomenclator, variant of nomenculator "one who announces names, namer," from nomen, → name, + calator "caller," from calare "to call."
Nâmgozâri, from nâm, → name, + gozâri, verbal noun of gozâštan "to place, put; to allow, let," related to gozaštan "to pass, proceed, go over;" Mid.Pers. vitar- "to let pass, lead; to pass;" O.Pers. vitar- "to go across," viytarrayam "I put across;" Av. tar- "to cross over," vī-tərəta- "taken away, isolated;" ultimately Proto-Ir. *ui-tar-.
1) Of, pertaining to, or constituting a name or names, a noun or nouns.
From L. nominalis "pertaining to a name or names," from nomen "name," cognate with Pers. nâm, as below.
Nâmin, from nâm, → name, + adj. suffix -in.
nominal focal length
derâzâ-ye kânuni-ye nâmin
Fr.: distance focale nominale
An approximate value of the → focal length, used for the classification of lenses, mirrors, or cameras, as opposed to the measured one.
Fr.: valeur nominale
The assigned, specified, or intended value of a quantity.
A prefix meaning "not."
From O.Fr. non-, from L. non "not," from Old L. noenum "not one;" in some cases perhaps from M.E. non "not" (adj.), from O.E. nan.
Nâ- "no, not," variants na, ni, ma- (prohibitive) "not;" from Mid.Pers. nê, ma "no, not;" O.Pers. naiy, nai "not;" Av. nôit, naē "not;" cf. Skt. ná "not;" cf. L. ne-, in-, un-; Gk. ni; Lith. nè; O.C.S. ne "not;" PIE *ne-.
Fr.: fonction non algébrique
A → transcendental function. Examples are: exponential, logarithmic, and trigonometric functions.
non-baryonic dark matter
mâde-ye siyâh-e nâbâriyoni
Fr.: matière noire non-baryonique
mâdde-ye nâbâriyoni (#)
Fr.: matière non-baryonique
Matter that, unlike the ordinary matter, is not made of baryons (including the neutrons and protons). It is proposed as a possible constituent of dark matter.
tâbeš-e nâhamdus (#)
Fr.: rayonnement incohrént
Radiation having waves that are out of phase in space and/or time; radiation which is not → coherent.
Fr.: non contingent