An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 285 Search : if
Fresnel diffraction
  پراش ِ فرنل   
parâš-e Fresnel (#)

Fr.: diffraction de Fresnel   

The diffraction effects obtained when either the source of light or observing screen, or both, are at a finite distance from diffracting aperture or obstacle. → Fraunhofer diffraction.

Named after Jean Augustin Fresnel (1788-1827), French physicist, a key figure in establishing the wave theory of light. His earlier work on interference was carried out in ignorance of that of Thomas Young (1773-1829), English physician and physicist, but later they corresponded and were allies; → diffraction.

fuzzification
  پرزوارش   
porzvâreš

Fr.: fuzzification   

The first step carried out in a → fuzzy logic system during which a → crisp set of → input data are gathered and converted to a → fuzzy set using fuzzy → linguistic variables, fuzzy linguistic terms, and → membership functions.

Verbal noun of → fuzzify; → -tion.

fuzzify
  پرزواریدن   
pozvâridan

Fr.: fuzzifier   

To convert a → crisp set to a → fuzzy set in a → fuzzy logic system.

fuzzy; → -fy.

gaseous diffusion
  پخش ِ گازی   
paxš-e gâzi

Fr.: diffusion gazeuse   

An → isotope separation process using the different diffusion speeds of → atoms or → molecules for separation. This process is used to divide → uranium hexafluoride (UF6) into two separate streams of U-235 and U-238. Before processing by gaseous diffusion, uranium is first converted from → uranium oxide (U3O8) to UF6. The UF6 is heated and converted from a solid to a gas. The gas is then forced through a series of compressors and converters that contain porous barriers. Because uranium-235 has a slightly lighter isotopic mass than uranium-238, UF6 molecules made with uranium-235 diffuse through the barriers at a slightly higher rate than the molecules containing uranium-238. At the end of the process, there are two UF6 streams, with one stream having a higher concentration of uranium-235 than the other (EVS, a Division of Argonne National Laboratory).

gaseous; → diffusion.

Goldschmidt classification
  رده‌بندی ِ گولدسمیت   
radebandi-ye Goldschmidt

Fr.: classification de Goldschmidt   

A → geochemical classification scheme in which → chemical elements on the → periodic table are divided into groups based on their → affinity to form various types of compounds: → lithophile, → chalcophile, → siderophile, and → atmophile. The classification takes into account the positions of the elements in the periodic table, the types of electronic structures of atoms and ions, the specifics of the appearance of an affinity for a particular → anion, and the position of a particular element on the → atomic volume curve.

Developed by Victor Goldschmidt (1888-1947); → classification.

grand unified theory (GUT)
  نگره‌ی ِ یگانش ِ بزرگ   
negare-ye yegâneš-e bozorg (#)

Fr.: théorie de la grande unification   

Any physical theory that unites the strong, electromagnetic, and weak interactions at high energy. It is hoped that GUTs can ultimately be extended to incorporate gravity. → theory of everything.

M.E. graunt, from O.Fr. grant, grand, from L. grandis "big, great," also "full-grown;" unified, p.p. of → unify; → theory.

Negâré, → theory; yegâneš, verbal noun of yegânestan, → unify; bozorggreat.

gravitational redshift
  سرخ‌کیب ِ گرانشی   
sorxkib-e gerâneši

Fr.: décalage vers le rouge gravitationnel   

The change in the wavelength or frequency of electromagnetic radiation in a gravitational field predicted by general relativity.

gravitational; → redshift.

Great Rift
  چاک ِ بزرگ   
câk-e bozorg

Fr.:   

An apparent fissure in the bright clouds of the Milky Way between → Cygnus and → Sagittarius caused by a series of large, dark, overlapping clouds.

great; → rift.

half-life
  نیم‌زیست   
nim-zist

Fr.: demi-vie   

The length of time required for half of a given quantity of → radioactive material to → decay.

half; → life.

Harvard classification
  رده‌بندی ِ هاروارد   
radebandi-ye Hârvârd (#)

Fr.: classification de Harvard   

A classification of stellar spectra published in the Henry Draper catalogue, which was prepared in the early twentieth century by E. C. Pickering and Miss Annie Canon. It is based on the characteristic lines and bands of the chemical elements. The most important classes in order of decreasing temperatures are as follows: O, B, A, F, G, K, M.

Harvard, named for John Harvard (1607-1638), the English colonist, principal benefactor of Harvard College, now Harvard University. → classification

high redshift object
  بر‌آخت ِ مه-سرخ‌کیب   
barâxt-e meh-sorxkib

Fr.: objet à grand décalage vers le rouge   

A galaxy or quasar having a → redshift larger than about 0.8, corresponding to a → look-back time half the present age of the Universe. The qualifier "high" is, however, relative and depends on context and authors' assessment.

high; → redshift; → object.

homogeneous linear differential equation
  هموگش ِ دگرسانه‌ای ِ خطی همگن   
hamugeš-e degarsâne-yi-ye xatti hamgen

Fr.: équation différentielle linéaire homogène   

A → linear differential equation if the right-hand member is zero, Q(x) = 0, on interval I.

homogeneous; → linear; → differential; → equation.

Hubble classification
  رده‌بندی ِ هابل   
radebandi-ye Hubble (#)

Fr.: classification de Hubble   

The classification of galaxies according to their visual appearance into four basic types suggested by E. Hubble: → ellipticals (E), → spirals (S), → barred spirals (SB), and → irregulars (Ir). Later on a separate class of → lenticulars (S0) was appended as an intermediate type between ellipticals and spirals. The sequence starts with round elliptical galaxies (E0). Flatter galaxies are arranged following a number which is calculated from the ratio (a - b)/a, where a and b are the major and minor axes as measured on the sky. Ellipticals are divided into eight categories (E0, E1, ..., E7). Beyond E7 a clear disk is apparent in the lenticular (S0) galaxies. The sequence then splits into two parallel branches of disk galaxies showing spiral structure: ordinary spirals, S, and barred spirals, SB. The spiral and barred types are subdivided into Sa, Sb, Sc, and SBa, SBb, SBc, respectively. Along the sequence from Sa to Sc, the central bulge becomes smaller, while the spiral arms become more and more paramount. The original, erroneous idea that such arrangement of the galaxies might represent an evolutionary sequence led to the ellipticals being referred to as early-type galaxies, and the spirals and Irr I irregulars as late-type galaxies. See also → dwarf galaxy, → dwarf elliptical galaxy, → dwarf spheroidal galaxy.

Hubble; → classification.

Hubble-Sandage classification
  رده‌بندی ِ هابل-سندیج   
radebandi-ye Hubble-Sandage

Fr.: classification de Hubble-Sandage   

Same as the → Hubble classification.

Hubble; → Hubble-Sandage variable; → sequence.

identification
  ایدانش   
idâneš

Fr.: identification   

1) An act or instance of identifying; the state of being identified.
2) Psychology: The process of associating the self closely with other persons and assuming their characteristics or views unconsciously or partially so.
3) In psychological theories, a phase of recognition, the way in which the child's personality is formed by modeling it on a chosen parent.

Verbal noun of → identify.

Idâneš, verbal noun of idânidanidentify.

identification of lines
  ایدانش ِ خطها   
idâneš-e xatthâ

Fr.: identification de raies   

Recognizing the lines in the spectrum of a star, nebula, galaxy, etc. using a calibration template.

identification; → line.

identifier
  ایدانگر   
idângar

Fr.: identifiant   

Computers: 1) One or more characters used to identify, name, or characterize the nature, properties, or contents of a set of data elements.
2) A string of bits or characters that names an entity, such as a program, device, or system, in order that other entities can call that entity.
3) In programming languages, a lexical unit that names a language object, such as a variable, array, record, label, or procedure.

Agent noun of → identify.

identify
  ایدانیدن   
idânidan

Fr.: identifier   

To recognize or establish as being a particular person or thing; e.g. → identification of lines.

Identify, from Fr. identifier, from identité, → identity.

Idânidan, infinitive from idâni, → identity.

if
  اگر   
agar (#)

Fr.: si   

(Conjunction) in case that; granting or supposing that; on condition that. → if and only if.

M.E., from O.E. gif; akin to O.H.G. ibu "if."

Agar "if," from Mid.Pers. agar, hakar "if;" O.Pers. ha-karam "once;" from ha- "one," variant ham-, → com- (cf. Av. ha-; Skt. sa-; Gk. ha-; L. sem-; PIE *sem- "one"), + karam- "a time," maybe from kar- "to do; doing," → work; cf. Av. hakərət "once;" Skt. sakrt "once;" Gk. hapaks "once;" L. semel "once."

if and only if (iff)
  اگر و ایواز اگر، ~ ~ تنها ~   
agar va ivâz agar, ~ ~ tanhâ ~

Fr.: si et seulement si   

Logic, Math.: An → expression indicating that two → statements so connected are → necessary and sufficient conditions for one another. The corresponding logical symbols usually used are: ↔, ⇔, ≡, and iff.

if; → and; → only.

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