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: 13116 Search : far
diffuse interstellar medium
  مدیم ِ اندر‌اختری ِ پخشیده   
madim-e andaraxtari-ye paxšidé

Fr.: milieu interstellaire diffus   

The interstellar matter outside condensed molecular clouds. Diffuse interstellar medium consists of a hot intercloud medium, a warm intercloud medium, and a cold neutral medium with hydrogen atom densities nH ~ 0.003, ~ 0.25, and ~ 40 cm-3, and mean gas → kinetic temperatures Tk ~ 5 x 105, ~ 104, and 80 K, respectively.

diffuse; → interstellar; → medium.

diffuse molecular cloud
  ابر ِ مولکولی ِ پخشیده   
abr-e molekuli-ye paxšidé

Fr.: nuage moléculaire diffus   

A type of → molecular cloud in which the → interstellar radiation field is sufficiently attenuated, so that the local fraction of → molecular hydrogen (H2) becomes substantial (> 0.1). However, enough interstellar radiation is still present to → photoionize any atomic carbon, or to → photodissociate → carbon monoxide (CO) such that carbon is predominantly still in the form of C+ (> 0.5). In steady state, diffuse molecular clouds must necessarily be surrounded by diffuse atomic gas, in order to provide the → shielding of radiation. This means that most sightlines that cross a diffuse molecular cloud will also cross → diffuse atomic gas (Snow & McCall, 2006, ARA&A 44, 367).

diffuse; → molecular; → cloud.

diffuse nebula
  میغ ِ پخشیده   
miq-e paxšidé

Fr.: nébuleuse diffuse   

An irregularly shaped and low density interstellar cloud visible in the optical wavelengths.

diffuse; → nebula.

diffuse reflection
  بازتاب ِ پخشیده   
bâztâb-e paxšidé

Fr.: réflexion diffuse   

Reflection of light from a rough or granular surface, which takes place in all directions due to the microscopic irregularities of the interface; opposed to → specular reflection.

diffuse; → reflection.

diffuse transmission
  تراگسیل ِ پخشیده   
tarâgosil-e paxšidé

Fr.: transmission diffuse   

Transmission accompanied by diffusion or scatter to the extent that there is no regular or direct transmission.

diffuse; → transmission.

diffuser
  پخشنده، پخشگر   
paxšandé, paxšgar

Fr.: diffuseur   

A device used to scatter or disperse light emitted from a source.

From → diffuse + -er.

From paxš, present stem of paxšidan, → diffuse, + -andé or -gar (→ detector).

diffusion
  پخش   
paxš (#)

Fr.: diffusion   

1) Movement of a gas or liquid as a result of the random thermal motion of its atoms or molecules.
2) The random spreading out of a beam of radiation on reflection (→ diffuse reflection) or transmission through a translucent medium (such as amber, milk, or frosted glass).
3) In chemical thermodynamics, the process of attaining an equilibrium distribution of the → concentration within the phases. A result of diffusion at constant equilibrium is the equalization of the → chemical potentials.
Related terms: → diffraction; → dispersion; → distribution; → scatter; → scattering.

L. diffusionem, from stem of diffundere "scatter, pour out," from dif- "apart, in every direction," → dis-, + fundere "to melt, cast, pour out," from PIE *gheud-, from root *gheu- "to pour."

Paxš, verbal noun and stem of paxšidandiffuse.

diffusion coefficient
  همگر ِ پخش   
hamgar-e paxš

Fr.: coefficient de diffusion   

A factor of proportionality involved in the → diffusion equation. It may be defined as the amount of the quantity diffusing across a unit area through a unit concentration gradient in unit time. → magnetic diffusivity.

diffusion; → coefficient.

diffusion equation
  هموگش ِ پخش   
hamugeš-e paxš

Fr.: équation de diffusion   

An equation that expresses the time rate of change of a quantity in terms of the product of the diffusion coefficient and the → Laplacian operating on the quantity. For example the diffusion equation for temperature is: ∂T/∂t = D2T.

diffusion; → equation.

diffusion region
  ناحیه‌ی ِ پخش   
nâhiye-ye paxš

Fr.: région de diffusion   

A narrow boundary layer above the solar → photosphere, between two magnetic field lines, where the plasma becomes demagnetized or unfrozen. The presence of a localized magnetic region is necessary for → magnetic reconnection.

local; → -ize; → diffusion; → region.

diffusive
  پخشنده، پخشی   
paxšandé, paxši

Fr.: diffusif, de diffusion   

Tending to diffuse; characterized by → diffusion.

diffuse + → -ive.

diffusivity
  پخشندگی، همگر ِ پخش   
paxšandegi, hamgar-e paxš

Fr.: coefficient de diffusion   

1) The ability to permit or undergo diffusion.
2) → magnetic diffusivity.

diffusive; → -ity.

digit
  رقم   
raqam (#)

Fr.: chiffre   

A symbol, numeral, or graphic character that represents an integer.

From L. digitus "finger, toe."

Raqam, from Ar.

digital
  رقمی   
raqami (#)

Fr.: numérique   

1) Of or pertaining to a digit.
2) Representing data as a series of numerical values. Often opposed to → analogue.

digit + → -al.

digital computer
  رایانگر ِ رقمی   
râyângar-e raqami (#)

Fr.: ordinateur numérique   

A computer that accepts and operates with → discrete data in the form of combinations of digits, letters, or other characters. In modern terminology, generally called computer.

digital + → computer.

digitize
  رقمیدن   
raqamidan (#)

Fr.: numériser   

To convert an → analogue signal to a → digital signal that represents the same information as the analogue signal.

digit + → -ize.

dihedral
  دودیمه‌ای   
dodime-yi

Fr.: dihédral   

1) Having formed by two half-planes which intersect.
2) Of or relating to a → dihedron.

dihedron; → -al.

dihedral angle
  زاویه‌ی ِ دودیمی   
zâviye-ye dodimi

Fr.: angle dièdre   

An angle formed by two planes meeting along a common line. Compare with → face angle.

angle; → dihedral.

dihedron
  دودیمه   
dodimé

Fr.: dièdre   

A figure formed by two intersecting planes.

di-; → -hedron.

dilate
  ۱) فراخاندن؛ ۲) فراخیدن   
1) farâxândan; 2) farâxidan (#)

Fr.: 1) dilater; 2) se dilater   

1) (v.tr.) To make wider or larger; cause to expand.
2) (v.intr.) To spread out; expand.

M.E. dilaten, from O.Fr. dilater, from L. dilatare "make wider, enlarge," from → dis- "apart" + latus "wide," → latitude.

Farâxândan, farâxidan, infinitive from farâx "broad, wide, spacious;" Mid.Pers. frâxv, fraxv "broad, wide," frâxvitan, frâxvênitan "to spread."

<< < -es -iv -ti 21 a p abe abs abs aca acc acc acr act ada adh Adr aer aga air Alf Alg alk Alp alt alu amm ana And ang ani ano ant ant Ap apo app app Aqu Arc arg arr asc ass ast ast asy atm ato att aur aut axi B-m bad Bal bar bar Bay Bed ber Bet bif bim bin bio bis bla ble blu Bod Bol bor bou Bra Bre bro bul C-t Cal Cam can car Car Cas cat cav cel cen cer Cha cha Cha che chl Cir cir cir Cla cli clo clu co- coc coh col col col Com com com com com com com com Com con 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 Dan dat Dav de- Deb dec dec dee def deg del Den den der det deu dew dic dif dif dil Dip dir dis dis dis dis dis diu dod Dop dou Dra dua dus dwa dyn DZ Ear ecc eco edi EHB Ein ela ele ele ele ele ell eme emp end Eng ent epi equ equ era ESP eth Eur evi exa exc exe exi exp exp ext ext ext fac fal far fec Fer fer fie fin fir fis fla Flo flu fog for for Fou fra fre fre Fro fun G s Gal gal gal Gar gau geg gen geo geo geo ger gla gly gra gra gra gra gra Gre gro GYR Had Hal hap Har HD hea hel hel Hen Her hex hig Hil hol Hoo hor hou Hub hum hyb hyd hyd hyp hys ide ign ima imp imp in- inc Ind ind ine inf inf inf ini ins ins ins int int int int Int int int int inv ion iri irr iso iso iso Jea Jor jum K c Kep Ker kin kno lab Lam Lan Lap las lat Le lef len lev lig lig lin lin lin liq Lit loc log lon lou LS lun lun Lym M s Mag mag mag mag mag mag maj man Mar mas mas mat May mea mec mel mer mes met met met mic mid mil Min Mir mix mod mod mol mon mor mov mul mur mys nan nat nav nec Nep neu New New NGC nob nom non non nor nos nuc nuc num nut obj obl obs occ oct off oli oni ope opp opt opt orb ord org orp osc out ove oxi P-w pal par par par par Pas pat pej per per per per per per pha Phe pho pho pho phy pin pla Pla pla pla pla plu poi pol pol Pol pol por pos pot Poy pre pre pre pre pri pri pri pro pro pro pro pro pro Psa pul pum Q i qua qua qua qua R A rad rad rad rad rad rad Ram Ran rat rea rea rec rec red red ref ref reg rei rel rel rem rep res res res ret rev Rho Rie ril riv rog Ros rot rul S A Sag sam sat sca sca Sch Sco Sec sec sec seg sel sem sen set Sha sha shi sho sid sig sim sin Sir ske sli Smo soc sof sol sol sol sol sou sou spa spe spe Spe spe sph spi Spi spr sta sta sta sta sta ste ste ste Sto str str sub sub sub suc sun sup sup sup sup sur swa syn syn tac tas tel tem ter tes the the the the thi thr tid til tip ton tor tou tra tra tra tra Tri tri tru tsu tur two Typ UHE ult unc uni uni uni upg ura uti val var vec Vel ver Ver vie Vir vis vis vol W-R war wav wav wea Wei wha wid win WN3 Wol wri xen yok zen zij > >>