An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 12948 Search : far
self-induction
  خود-درهازش   
xod-darhâzeš

Fr.: auto-induction   

The generation of a voltage in a circuit due to self-inductance, the polarity of which tends to oppose the changing current in the circuit.

self-; → induction.

self-shadowed disk
  گرده‌ی ِ خود-پرده، دیسک ِ ~   
gerde-ye xod-pardé, disk-e ~

Fr.: disque auto-écranté   

A model of → accretion disk around a → pre-main sequence star or a → protostar in which the outer parts of the disk are geometrically flat, in contrast to a → flared disk. Inward of a certain radius (0.5-1 AU from the star) the dust in the disk evaporates. Because the dust is the main source of opacity and the gas in the disk is usually optically thin, the irradiation burns a hole in the disk. Moreover, the inner rim puffs up, similarly to the case of flared disks. The difference lies in the outer parts. The inner rim casts its shadow over the disk all the way out. Since the disk thickness is almost constant, no photons can reach the surface of the disk and the outer parts of the disk remain shadowed by the inner rim and the midplane temperatures decrease accordingly. This model explains the observed → spectral energy distribution of some pre-main sequence stars, such as HD 101412. It also accounts for the observed weak → far infraredexcess, weak or no → PAH emission, and weak or no [O I] emission.

self-; → shadow; → disk.

Gerdé, → disk; xod-, → self-; pardé, → screen.

self-shielding
  خود-سپرکرد   
xod-separkard

Fr.: auto-écrantage   

The phenomenon whereby the → photodissociation transitions of a molecule in interstellar clouds become → optically thick, so that the molecule in question is "shielded" by other molecules against dissociating stellar → far-ultraviolet (FUV) photons. In the case of → molecular hydrogen (H2), when the → column density exceeds 1014 cm-2, the UV absorption bands become optically thick, and H2 undergoes self-shielding. More specifically, all of the photons that could lead to UV photodissociation are absorbed by H2 in the outer layers of the cloud, hence protecting the H2 within the cloud. Self-shielding occurs in → diffuse interstellar clouds exposed to the interstellar → radiation field or in → molecular clouds in proximity to sources of UV photons. Dust can also absorb UV photons, further limiting the photodissociation, but it dominates only when the local UV radiation field is unusually intense relative to the density of the cloud.

self-; → shield; → -ing.

self-similar
  خودهمانند   
xod-hamânad

Fr.: auto-similaire   

1) Of a geometric figure, having a structure analogous or identical to its overall structure. → fractal.
2) The quality of a variable entity in which the shape does not change with time, such as a → self-similar process.

self-; → similar.

self-similar process
  فراروند ِ خودهمانند   
farâravand-e xod-hamânad

Fr.: processus auto-similaire   

A process that is invariant in distribution under scaling of time. Schematically, images taken of such a process at different time scales will look similar.

self-; → similar; → process.

self-similarity
  خودهمانندی   
xod-hamânadi

Fr.: auto-similarité   

The property of being → self-similar.

self-; → similarity.

Sellmeier's equation
  هموگش ِ زلمایر   
hamugeš-e Sellmeier

Fr.: équation de Sellmeier   

An empirical relation between the → refractive index of a medium and the wavelength of light passing through the medium: n2 - 1 = Σ (Aiλ2/(λ2 - λi2)), where n is the refractive index at wavelength λ, and Ai and λi are constants.

Named after Wolfgang Sellmeier who derived the equation in 1871; → equation.

semantic
  چماریک   
cemârik

Fr.: sémantique   

1) Of, pertaining to, or arising from the different meanings of words or other signs and symbols.
2) Of or pertaining to → semantics.

From Fr. sémantique, from Gk. semantikos "significant," from semainein "to show, signify, indicate by a sign," from sema "sign."

Cemârik, from cemâr, → meaning, + -ik, → -ic.

semantics
  چماریک   
cemârik

Fr.: sémantique   

The study of the → meaning of signs or symbols, as opposed to their formal relations (→ syntactics).

semantic; → -ics.

semen
  شسر   
šosar (#)

Fr.: sperme, semence   

Biology: The male reproductive fluid, containing spermatozoa in suspension. → inseminate, → insemination; → fecundate, → fecundation.

M.E., from L. semen "seed;" akin to serere "to sow;" cf. O.C.S. seme, O.H.G. samo; E. sow.

From Mid.Pers. šusar "semen; liquid, fluid;" Av. xšudra- "semen; liquid, fluid;" related to Pers. šostan/šuy- "to → wash."

semi-
  نیم-، نیمه-   
nim- (#), nimé- (#)

Fr.: semi-, demi-   

A combining form meaning "half," freely prefixed to English words of any origin.

From L. semi- "half," from PIE *semi-; cf. Skt. sāmi "half," sāmi-krita- "half-done;" Gk. hemi- "half;" O.E. sam-; Goth. sami- "half."

Nim, nimé "half," from Mid.Pers. nêm, nêmag "half;" Av. naēma- "half;" cf. Skt. néma- "half."

semi-forbidden line
  خط ِ نیمه-بژکم   
xatt-e nime-bažkam

Fr.: raie semi-interdite   

A → spectral line for which the upper and lower → energy levels have different values of S, the total → spin angular momentum. These lines violate the quantum mechanical → selection rule under → LS coupling, ΔS = 0. For example, the Ca I λ6573 line results from transition between the upper → triplet state (3P1) with a total spin angular momentum S = 1 and the → ground state, a → singlet state (1S0, total spin angular momentum S = 0). A semi-forbidden line is marked by a right bracket following the atom name, i.e. Ca I], in the above-mentioned case. Same as → interconnection line and → intersystem line.

semi-; → forbidden; → line.

semi-forbidden transition
  گذرش ِ نیمه-بژکم   
gozareš-e nime-bažkam

Fr.: transition semi-interdite   

An → atomic transition whose probability is reduced by a factor of the order of 106 because of → selection rules. Same as → interconnection line.

semi-; → forbidden; → transition.

semi-major axis
  آسه‌ی ِ نیمه‌مهین   
âse-ye nimeh-mehin

Fr.: demi grand axe   

Half the length of the major axis of an ellipse; a standard element used to describe an elliptical orbit. see orbital elements

semi-; → major; → axis.

semiconductor
  نیم-هازا، نیمه-رسانا   
nim-hâzâ, nime-rasânâ

Fr.: semi-conducteur   

Any of various solid crystalline substances, such as germanium or silicon, which has conducting properties intermediate between metals and insulators.

semi-; → conductor.

semiconductor junction
  جوهه‌ی ِ نیم-هازا   
juhe-ye nim-hâzâ

Fr.: jonction semi-conducteur   

In a semiconductor device, a region of transition between semiconducting regions of different electrical properties.

semiconductor; → junction.

semiconvection
  نیم-همبز   
nim-hambaz

Fr.: semi-convection   

An instability occurring in the region just outside the → convective core of a → massive star. The instability occurs when a → superadiabatic layer is stabilized by a chemical gradient. In fact, semiconvection takes place if → Schwarzschild's criterion for convection is fulfilled but at the same time → Ledoux's criterion is not fulfilled. The time-scale of semiconvection is the thermal time-scale, which is short compared to the nuclear time-scale in → main sequence stars but long compared to the time-scale of convection. However, semiconvection has a profound influence on the → post-main sequence star evolution. It affects the convective mixing above the hydrogen shell source, determines the appearance and extent of → blue loops in the → Hertzsprung-Russell diagram during core → helium burning, and is essential for defining the extent of the convective cores during core helium burning (See, e.g., N. Langer, 2012, Ann. Rev. Astron. Astrophys. 50, 107).

semi-; → convection.

semidetached binary
  دُرین ِ نیم-جدا   
dorin-e nim-jodâ

Fr.: bianire semi-détachée   

A binary system whose secondary member fills its Roche lobe but whose primary member does not.

semi-; detached, p.p. of detach, from O.Fr. destachier (Fr. détacher), from des- "apart," + -tachier (as in atachier "to attach"); → binary.

Dorin, → binary; nim-jodâ, from nim-semi- + jodâ "separate," from Mid.Pers. yut "separate, different;" Av. yuta- "separate, apart."

semidetached system
  راژمان ِ نیم-جدا   
râšmân-e nim-jodâ

Fr.: système semi-détaché   

Same as → semidetached binary.

semi-; detached, p.p. of detach, from O.Fr. destachier (Fr. détacher), from des- "apart," + -tachier (as in atachier "to attach"); → system.

Râžmân, → system; nim-jodâ, from nim-semi- + jodâ "separate," from Mid.Pers. yut "separate, different;" Av. yuta- "separate, apart."

semidiameter
  نیم-ترامون   
nim-tarâmun

Fr.: demi-diamètre   

The angle at the observer subtended by the equatorial radius of the Sun, Moon, or a planet.

semi-; → diameter.

<< < -es -iv -ti 21- A r abe abs abs acc acc acc act act ada adi adu aff age alc Alf ali all alp alt ama amp ana ang ang ann ano ant ant ape apo app aps arc Arg ari art ass ast ast ast atm ato att aur aut axi B r bac Bal Bar Bar Bay bec Ber Bet Bie bij bin bio bis bla bla blu blu bol Bor bou Bra bre bro Bug C-s cal Cam can car Car Cas cat cav cel cen cer Cha cha cha che cho cir cir cir cla clo clo clu coa coe coh col col col com com com com com com com com com con con con con con con con con con con con coo cor cor cor cos cos cos Cou cou Cra Cre cri cro cub cur cyc cyl dar dat daw de- Deb dec dec dee def deg del Den dep der det deu dew dic dif dif dil dip dir dis dis dis dis dis div dog Dop dou dra dua dus dwa dyn e-m ear ecl eco eff ein Ein elb ele ele ele ele Els emi emp ene enr env epi equ equ Eri est Euc eva evo exc exc exh exo exp exp ext ext f-n Fah fam fau fee Fer fib fil fin fir fix fle flu foc for for for fra fre fre fri fun fuz gal gal gal Gan gau GCN gen geo geo geo geo Gl glo gra gra gra gra gra gre gro GW1 hab hal han HAR haz hea hel hel Hen Her heu Hig Hil hol hop hor hou Hub Hum Hyd hyd hyd hyp hys ide ign ima imp imp inc inc ind ine inf inf inf inh INP ins ins int int int int Int int int int inv ion iri irr iso iso iso Jea Jos Jun K2 Kep key kin Kol lag lam Lan lar las lav lea leg len lev lig lim lin lin lin lis lob loc log lor low lum lun lun Lym Mac mag mag mag mag mag mai Mal mar mas mas mat max mea mea mee Men mer met met met mic mid Mil min Mir mix mod mod mol mon Mor mou mul muo mys nan nat nav nec Nep neu New New NGC nob nom non non nor not nuc nuc num Nyq obj obs obs oce oen OH omn opa ope opt opt opt orb ord Ori ort osc out ove oxy pal pan par Par par par pas pea Pen per per per per per pet pha pho pho pho phy pie Pit Pla pla pla pla ple Poi pol pol pol pol pop pos pos pow pre pre pre Pre pri pri pri pro pro pro pro pro pro Pro pub pul pyr qua qua qua qua Qui rad rad rad rad rad rad ram ran rat rea rec rec rec red ref ref reg reg rel rel rem rep res res res ret rev rho Rie rim riv rol Ros rot rul S a Sah san Sat sca Sch Sch scr sec sec sec sei sel sem sep set sha she sho sid sig sil sim sin sit sky slu sno sof sol sol sol sol sou sou spa spa spe spe spe sph spi spl spr sta sta sta sta sta ste ste sti sto str str sub sub sub sug sun sup sup sup sup sur syl syn sys tal Tay tel ten ter tex the the the thi tho thu tid tim tod top tot tra tra tra tra tri tri tro tru tur twi Typ UFO ult unc uni uni uni upg ura uti val var vec vel ver ver vig vir vis voc von wak Was wav wax wea wei whi Wie win WN6 wom X-r yel you zer zod > >>