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dynamical age senn-e tavânik Fr.: âge dynamique Age based on dynamical properties of a system. For example, the time derived for a system to evolve from an initial state to its present state, based on velocity and dimension (size) measurements. |
dynamical disruption gosixt-e tavânik Fr.: rupture dynamique The process whereby a → bound system, such as a → binary system or a → globular cluster, is broken apart. → dynamical; → disruption. |
dynamical equilibrium tarâzmandi-ye tavânik Fr.: équilibre dynamique Of a physical system, a condition in which the parts of the system are in continuous motion, but they move in opposing directions at equal rates so that the system as a whole remains in equilibrium. → dynamical; → equilibrium. |
dynamical friction mâleš-e tavânik Fr.: frottement dynamique The gravitational interaction between a relatively massive body and a field of much less massive bodies through which the massive body travels. As a result, the moving body loses → momentum and → kinetic energy. An example of dynamical friction is the sinking of massive stars to the center of a → star cluster, a process called → mass segregation. Dynamical friction plays an important role in → stellar dynamics. It was first quantified by Chandrasekhar (1943). |
dynamical law qânun-e tavânik Fr.: loi dynamique A law that describes the motion of individual particles in a system, in contrast to → statistical laws. |
dynamical mass jerm-e tavânik Fr.: masse dynamique The mass of an object derived indirectly from theoretical formulae based on the laws governing the behavior of a → dynamical system. |
dynamical parallax didgašt-e tavânik Fr.: parallaxe dynamique A method for deriving the distance to a binary star. The angular diameter of the orbit of the stars around each other and their apparent brightness are observed. By applying Kepler's laws and the mass-luminosity relation, the distance of the binary star can be calculated. |
dynamical relaxation vâheleš-e tavânik Fr.: relaxation dynamique The evolution over time of a gravitationally → bound system consisting of N components because of encounters between the components, as studied in → stellar dynamics. Due to this process, in a → star cluster, → low-mass stars may acquire larger random velocities, and consequently occupy a larger volume than → high-mass stars. As a result, massive stars sink to the cluster centre on a time-scale that is inversely proportional to their mass. See also → mass segregation. → dynamical; → relaxation. |
dynamical system râžmân-e tavânik Fr.: système dynamique A system composed of one or more entities in which one state develops into another state over the course of time. |
dynamical time zamân-e tavânik Fr.: temps dynamique The independent variable in the theories which describe the motions of bodies in the solar system. The most widely used form of it, known as Terrestrial Time (TT) or Terrestrial Dynamical Time (TDT) uses a fundamental 86,400 Systeme Internationale seconds (one day) as its fundamental unit. → Terrestrial Time; → Terrestrial Dynamical Time; → Barycentric Dynamical Time. |
dynamical time scale marpel-e zamâni-ye tavânik Fr.: échelle de temps dynamique 1) The characteristic time it takes a protostellar cloud to collapse
if the pressure supporting it against gravity were suddenly removed;
also known as the → free-fall time. → dynamical; → time-scale. |
dynamical variable vartande-ye tavânik Fr.: variable dynamique Mechanics: One of the variables used to describe a system in classical mechanics, such as coordinates (of a particle), components of velocity, momentum, angular momentum, and functions of these quantities. |
dynamics tavânik Fr.: dynamique The branch of → mechanics that explains how particles and systems move under the influence of forces. |
dynamo tavânzâ (#) Fr.: dynamo An electric generator, i.e. a machine that converts mechanical energy into electrical energy by virtue of the → electromagnetic induction. From Ger. dynamoelektrischemaschine, coined (1867) by the German inventor Werner von Siemens (1816-1892), from Gk. dynamis "power," → dynamics. Tavânzâ, from tavân "power," → dynamics + -zâ "generator," from zâdan "to give birth," Mid.Pers. zâtan, Av. zan- "to bear, give birth to a child, be born," infinitive zazâite, zâta- "born," cf. Skt. janati "begets, bears," L. gignere "to beget," PIE base *gen- "to give birth, beget." |
dynamo effect oskar-e dinâmo Fr.: effet dynamo The generation of magnetic fields by movements within a → plasma, such as the → convective cores and → convective envelopes of stars. The magnetic field is intensified by the motion of the plasma in much the same way as in a dynamo. The generated magnetic field is not static, but evolves over time. |
dynamo model model-e tavânzâ Fr.: modèle dynamo A theory for the generation of a star's or planet's magnetic field by the circulation of conducting fluids inside it. → solar dynamo. |
dynamo theory negare-ye tavânzâ Fr.: théorie de la dynamo Branch of magnetohydrodynamics concerned with self-excitation of magnetic fields in any large rotating mass of conducting fluid in motion (usually turbulent). Self-exciting dynamo action is believed to account for magnetic fields at the planetary, stellar, and galactic scales. |
dynamometer tavânsanj (#) Fr.: dynamomètre A device for measuring mechanical force; specifically, one that measures the output or driving torque of a rotating machine. Dynamometer, from → dynamo + → -meter. Tavânsanj, from tavân "power," → dynamics + -sanj, → -meter. |
dyne din (#) Fr.: dyne The centimeter-gram-second (cgs) unit of force (symbol dyn) that imparts an acceleration of 1 cm s^{-2} to a mass of 1 gram. 1 dyn = 10^{-5} → newton. From Fr., from dynamis "power," → dynamics. |
dynode dinod (#) Fr.: dynode An electrode that performs electron multiplication by means of secondary emission. From dyn(a)- a combining form meaning "power," → dynamics + -ode a combining form meaning "way, road," used in the formation of compound words (anode; electrode), from Gk. hodos "way." As above. |
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