analog-to-digital unit (ADU)
Fr.: unité analogue-numérique
A number that represents a → charge-coupled device (CCD)'s output and is proportional to the → electron charge created by the → photons, plus the constant → bias offset. The relationship between the ADUs generated and the number of electrons acquired on the CCD is defined by the → CCD gain. Intensities given in ADUs provide a convenient method for comparing images and data generated by different cameras. Also referred to as → count and digital number. In most cases, the analog signal is digitalized by an analog-to-digital (A/D) converter and fed into a computer where further manipulation and analysis are done on what the detector originally produced from the star's photons (Howell, S.B., Handbook of CCD Astronomy, Cambridge Univ. Press, 2000).
Angstrom unit (Å)
Fr.: unité d'Ångström
Unit of length used to describe wavelengths and interatomic distances. 1 Å = 10-10 m.
Named after Anders Jonas Ångström, Swedish physicist and astronomer who founded the science of spectroscopy and discovered by studying the solar spectrum that there is hydrogen in the Sun's atmosphere; → unit.
astronomical unit (au)
yekâ-ye axtaršenâsik, ~ axtaršenâxti (#)
Fr.: unité astronomique
1) A unit of length equal to 149 597 870 700 m exactly, with symbol "au"
(re-definition at the International Astronomical Union's 28th General
Assembly in Beijing, China, August 20-31). The astronomical unit equals
1.5813 × 10-5 → light-years and
4.8481 ×10-6 → parsecs.
atomic mass unit (amu)
yekâ-ye jerm-e atomi (#)
Fr.: unité de masse atomique
A unit of mass used for atoms and molecules, equal to 1/12 of the mass of an atom of carbon-12 (including orbital electrons). It is equal to 1.660 33 × 10-24 g.
central processing unit (CPU)
yekâ-ye âmâyeš-e markazi
Fr.: unité centrale de traitement
The primary component of a → computer that processes instructions. It runs the → operating system and → applications, constantly receiving input from the user or active → software programs. The CPU has two typical components: 1) Control Unit, which extracts instructions from memory and decodes and executes them. 2) Arithmetic Logic Unit (ALU), which handles arithmetic and logical operations.
yekâhâ-ye CGS (#)
Fr.: unités CGS
A member of a communistic community; an advocate of such a community.
A doctrine or system of social organization that upholds the importance of communities. It tends to lessen the focus on individual rights and increase the focus on communal responsibilities.
Of or relating to a community; communal.
1) hamdârgân; 2) hamdâri
1a) A social group whose members
share common characteristics or interests, such as values, identity, and often
a common location (e.g. a village, town, or neighborhood).
electrostatic unit (esu)
yekâ-ye barqistâ-ye bâr
Fr.: unité électrostatique de charge
The unit of electric charge in the → cgs system of units. Also called the → statcoulomb. The esu is defined such that if two objects, each carrying a charge of +1 esu, are 1 cm aparat, then they repel each other with a force of 1 → dyne. 1 esu = 3.3356 × 10-10 → coulombs.
Fr.: unité de flux
In radio astronomy, same as → jansky (symbol Jy), a unit of electromagnetic flux equivalent to 10-26 watts per square meter per Hertz.
International System of Units (SI)
râžmân-e jahâni-ye yekâhâ
Fr.: système international des unités
The metric system of units based on the → meter, → kilogram, → second, → ampere, → kelvin, and → candela. Also called MSKA system. Other SI units are → hertz, → radian, → newton, → joule, → watt, → coulomb, → volt, → ohm, → farad, → weber, and → tesla.
yekâ-ye metri (#)
Fr.: unité métrique
Fr.: unités MKS
Fr.: unités naturelles
Physical units of measurement defined in terms of universal physical constants in such a manner that some chosen physical constants (e.g. the speed of light, Planck's constant, Boltzmann's constant, etc.) are equal to unity. The use of natural units allows these constants to be omitted from mathematical equations, leading to simpler calculations.
1) An appropriate or favorable time or → occasion.
yekâhâ-ye Planck (#)
Fr.: unités de Planck
A set of → natural units in which the normalized units are: the gravitational constant, Planck's constant, the speed of light, the Coulomb constant, and Boltzmann's constant.
Fr.: unitarité quantique
A property in → quantum mechanics whereby in a quantum system the sum of all probabilities of all possible outcomes must be 1. Quantum unitarity makes the modulous of a → quantum state invariant with time.
Fr.: unité d'échantillonnage
One of the units into which an aggregate is divided for the purpose of sampling, each unit being regarded as individual and indivisible when the selection is made.