Fr.: système exoplanétaire
Fr.: système extrasolaire
federated database system (FDBS)
râžmân-e pâygâh-e dâdehâ-ye hiyâvidé
Fr.: système de base de données fédéré
A composition of different databases which work in an integrated manner while preserving their autonomy.
Fr.: système à cinq couleurs
A photometric system which uses five filters, from ultraviolet to the red part of the visual spectrum: U, B, V, R and I.
Fr.: système de forces
Any set of forces acting on a → rigid body.
râžmân-e diseyi, ~ disevar
Fr.: système formel
In logic and mathematics, a system in which statements can be constructed and manipulated with logical rules.
Fr.: système libre
fuzzy inference system
râžmân-e darbord-e porzvâr
A way of → mapping an → input space to an → output space using → fuzzy logic. FIS uses a collection of fuzzy → membership functions and rules, instead of Boolean logic, to reason about data. Also called → fuzzy logic system.
fuzzy logic system
râžmân-e guyik-e porzvâr
Fr.: système de logic flou
An engineering system which uses → fuzzy logic. It generally consists of four main components: → fuzzification interface (fuzzifier), → fuzzy rule base, → fuzzy inferencing unit, and → defuzzification interface (difuzzifier). Also called → fuzzy inference system.
Fr.: système galactique
Same as → galactic coordinates.
geocentric coordinate system
râžmân-e hamârâhâ-ye zamin-markazi
Fr.: système de coordonnées géocentriques
A coordinate system which has as its origin the center of the Earth.
Fr.: système géocentrique
An ancient model of the Universe whereby all the celestial bodies travel around the Earth in circular orbits. Eudoxus of Cnidus (c. 390- c. 337 BC), one of Plato's pupils, maintained that all objects in the sky are attached to moving crystalline spheres, with the Earth at the centre. This model is often named → Ptolemaic system after its most famous supporter, the Greco-Roman astronomer Ptolemy.
geographic coordinate system
râžmân-e hamârâhâ-ye zaminnegârik
Fr.: système de coordonnées géographiques
Global Positioning System (GPS)
râžmân-e nehešdâd-e jahâni
Fr.: système de positionnement par satellites
A coordinate positioning tool, using a combination of satellites that can rapidly and accurately determine the → latitude, → longitude, and the → altitude of a point on or above the Earth's surface. The GPS is based on a constellation of 24 Earth-orbiting satellites at an altitude of about 26,000 km. The system is a direct application of the thories of → special relativity and → general relativity.
Greek numeral system
râžmân-e adadhâ-ye Yunâni
Fr.: numération grecque
A → numeral system in which letters represent numbers. In an earlier system, called acrophonic, the symbols for numerals came from the first letter of the number name. Subsequently, the numerals were based on giving values to the letters of alphabet. For example α, β, γ, and δ represented 1, 2, 3, and 4; while ι, κ, λ, and μ stood for 10, 20, 30, and 40, and ρ, σ, τ, and υ for 100, 200, 300, and 400. The Greek also used the additive principle. For example 11, 12, 13, 14, and 374 were written ια, ιβ, ιγ, ιδ, and τοδ. The numbers between 1000 and 9000 were expressed by adding a subscript or superscript ι (iota) to the symbols for 1 to 9. For example ιA and ιΘ for 1000 and 9000. Numbers greater than 9999 were expressed using M, which was the myriad, 10,000. Therefore, since 123 was represented by ρκγ, 123,000 was written as Mρκγ.
Fr.: système héliocentrique
A system in which the Sun is assumed to lie at its central point while the Earth and other bodies revolve around it.
Henry Draper system
râžmân-e Henry Draper
Fr.: système de Henry Draper
A catalog of stars in which every star is classified by its stellar spectrum. This system is named for the astronomer Henry Draper, but was cataloged by Annie J. Cannon (225,300 stars), and later extended by Margaret W. Mayall.
Henry Draper (1837-1882), an American pioneer of astronomical spectroscopy who established the observing techniques and program for the work that would bear his name when published, seven years after his early death; → system.
hierarchical multiple system
râžmân-e bastâyi-ye pâygâni
Fr.: système multiple hiérarchique
A → multiple star system in which the stars can be divided into two groups, each of which traverses a larger orbit around the system's center of mass. Each of these smaller groups must also be hierarchical, which means that they must be divided into smaller subgroups which themselves are hierarchical, and so on. Hierarchical multiple systems have long-term dynamical stability.
hierarchical triple system
râžmân-e bastâyi-ye nâpâygâni
Fr.: système multiple non hiérarchique
A triple star system in which the (inner) binary is orbited by a third body in a much wider orbit. → hierarchical multiple system.
High Energy Stereoscopic System (H.E.S.S.)
râžmân-e estereyo-ye meh kâruž (H.E.S.S.)
Fr.: Système stéréoscopique de haute énergie (H.E.S.S.)
An array of → IACT telescopes for studying cosmic → gamma rays in the 100 GeV to 100 TeV energy range. The HESS observatory is located in Namibia, southern Africa, at an altitude of 1800 m, and the project is an international collaboration of more than 100 scientists from nine countries. In its Phase I, HESS used four telescopes each consisting of a light collector with a diameter of 13 m and a focal length of 15 m placed at the corners of a square 120 m apart. Each telescope is segmented into 380 round mirror facets of 60 cm diameter and uses a camera consisting of 960 closely packed → photomultiplier tubes. The first of the telescopes went into operation in Summer 2002. Phase II includes a fifth telescope, called Large Cherenkov Telescope (LCT), of 27 m diameter, located in the centre of the initial array. This upgrade lowers the triggering threshold of the HESS array to about 20 GeV, thus broadening the energy window in which gamma-ray astronomy can be done, opening up more opportunities in astrophysical research (see, e.g., Bernlöhr et al. 2003, Astroparticle Physics 20, 111).
H.E.S.S., short for High Energy Stereoscopic System, is also intended to pay homage to Victor F. Hess (1883-1964), an Austrian-American physicist who received the Nobel Prize in Physics in 1936 for his discovery of → cosmic rays.