An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 42 Search : set
acronical setting
  فروشد ِ شامگاهی   
forušod-e šâmgâhi

Fr.: coucher acronyque   

The setting of a star at nightfall. → heliacal setting.

acronical; → setting.

affine set
  هنگرد ِ کروَن   
hangard-e karvan

Fr.: ensemble affine   

A set → if and only if (iff) for any two points in the → set, the line through them is contained in the set. In other words, for any two points in the set, their → affine combinations are in the set itself.

affine; → set.

alpha offset
  اپنه ِ آلفا   
apneh-e Âlfâ

Fr.: offset en ascension droite   

A short distance from the target, in right ascension, where the telescope is pointed for various purposes.

alpha; → offset.

apparent setting
  فروشد ِ پدیدار   
forušod-e padidâr

Fr.: coucher apparent   

The instant of time when the object is in the West and the geometric → zenith distance is equal to 90° plus the → horizontal refraction plus the semidiameter minus the → parallax.

apparent; → setting.

bias offset
  اپنه ِ ورک   
apneh-e varak

Fr.: biais   

In → CCD detectors, same as → bias and → offset.

bias; → offset.

complete set
  هنگرد ِ اسپر   
hangard-e ospor

Fr.: ensemble complet   

Quantum mechanics: A set of states such that any state can be represented as a superposition of them.

complete; → set.

crisp set
  هنگرد ِ توج   
hangard-e tuj

Fr.: ensemble net   

A classical set that allows only full membership or no membership at all for its elements, as contrasted with a → fuzzy set. Crisp set can be viewed as a restricted case of the more general fuzzy set concept.

delta offset
  اپنه ِ دلتا   
apneh-e deltâ

Fr.: offset en déclinaison   

A short distance from the target, in → declination, where the → telescope is pointed for various purposes.

delta; → offset.

disk settling
  نیاشش ِ گرده، ~ دیسک   
niyâšeš-e gerdé, ~ disk

Fr.: stabilisation de disque   

The process whereby a → galaxy evolves from a disturbed to an ordered system, as it develops into a → rotation dominated → settled disk.

disk; → settling.

dust settling
  نیاشش ِ غبار   
niyâšeš-e qobâr

Fr.: dépose de poussières   

A process occurring in → protoplanetary disks whereby relatively large → dust grains settle to the disk midplane. These grains, with sizes from → micron to → millimeter, grow from smaller dust grains and will eventually give rise to a planetary system.

dust; → settling.

empty set
  هنگرد ِ تهی   
hangard-e tohi

Fr.: ensemble vide   

A set containing no → elements.

empty; → set.

family of sets
  خانواده‌ی ِ هنگردها   
xânevâde-ye hangardhâ

Fr.: famille de comètes   

A → collection of → subsets of a set.

family; → set.

finite set
  هنگرد ِ کرانمند   
hangard-e karânmand

Fr.: ensemble fini   

A → set whose elements can be numbered from 1 to n, for some positive integer n.

finite; → set.

fuzzy set
  هنگرد ِ پرزوار   
hangard-e porzvâr

Fr.: ensemble flou   

A set of → truth values in → fuzzy logic that does not have sharp boundaries. Instead, set members have degrees of membership. If the value of 1 is assigned to objects entirely within the set and a 0 is assigned to objects outside of the set, then any object partially in the set will have a value between 0 and 1. This contrast with → crisp sets in → classical logic where members assume a precise value of 1 or 0. Fuzzy sets were first introduced by Lotfi A. Zadeh (1965) and defined as follows. Let X be a space of points, with a generic element of X denoted by x. Thus X = {x}. A fuzzy set A in X is characterized by a → membership function  fA(x) which associates with each point in X a real number in the interval [0,1], with the values of fA(x) at x representing the "grade of membership" of x in A. Thus, the nearer the value of fA(x) to unity, the higher the grade of membership of x in A. Generally, the intersection operations of fuzzy sets are the expansion of that operation on → nonfuzzy sets. In other words, operations on nonfuzzy sets are a particular case of operations on fuzzy sets.

fuzzy; → set.

gravitational settling
  نیاشش ِ گرانشی   
niyâšeš-e gerâneši

Fr.: décantation par gravité   

A physical process occurring in stellar atmospheres whereby in a very stable atmosphere → heavy elements are gravitationally pulled down preferentially. If such an atmosphere is stable for long periods of time, the absorption lines of heavy elements may therefore become very weak. Observationally, the star seems to contain only hydrogen and helium. Gravitational settling takes place in the Sun at the bottom of the outer → convective zone where helium is dragged down, leading to a surface He abundant smaller than the cosmic value. It occurs also in the atmospheres of → brown dwarfs and → planets.

gravitational; → settling.

heliacal setting
  فروشد ِ هورانه   
forušod-e hurâné

Fr.: coucher héliaque   

The last visible setting of a star below the western horizon just after sunset entering into a conjunction with the Sun.

heliacal; → setting.

infinite set
  هنگرد ِ بیکران   
hangard-e bikarân

Fr.: ensemble infini   

A set which can be put in a one-to-one correspondence with part of itself.

infinite; → set.

Mandelbrot set
  هنگرد ِ ماندلبروت   
hangard-e Mandelbrot

Fr.: ensemble de Mandelbrot   

A set of points in the complex plane, the boundary of which forms a fractal with varying shapes at different magnifications. Mathematically, it is the set of all C values for which the iteration zn+1 = zn2 + C, starting from z0 = 0, does not diverge to infinity.

Discovered by Benoît Mandelbrot (1924-) a Polish-born French mathematician, best known as the "father of fractal geometry;" → set.

  فروشد ِ ماه   
forušod-e mâh (#)

Fr.: coucher de la lune   

The crossing of the visible horizon by the upper limb of the descending Moon.

moon; → set.

moonset lag
  لک ِ فروشد ِ ماه   
lek-e forušod-e mâh

Fr.: retard du coucher de la lune   

The delay between → sunset and → moonset.

moonset; → lag.

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