An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



<< < acr non set > >>

Number of Results: 44 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. See also → radiative levitation, → element diffusion, → thermal diffusion.

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 ِ مانگ   
forušod-e mâng (#)

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 ِ مانگ   
lek-e forušod-e mâng

Fr.: retard du coucher de la lune   

The delay between → sunset and → moonset.

moonset; → lag.

<< < acr non set > >>