energy generation equation
hamugeš-e âzâneš-e kâruž
Fr.: équation de génération d'énergie
energy generation rate
nerx-e âzâneš-e kâruž
Fr.: taux de génération d'énergie
Of a stellar → nuclear fusion, the energy produced per unit mass per unit time, usually denoted ε (erg g-1s-1). The general form of the energy generation equation is: ε = ε0ρλTν, where ε0, ρ, and λ are constants over some efficiently restricted range of → temperature T, → density ρ, and → chemical composition. The temperature exponent ν is about 4, 15, and 40 for → proton-proton chain, → CNO cycle, and → triple alpha process, respectively.
Fr.: niveau d'énergie
Any of the several discrete states of energy which a particle, atom, or molecule can adopt under conditions where the possible values are restricted by quantum mechanical laws.
Fr.: spectre d'énergie
Of cosmic rays, the plot representing the number of particles as a function of their energy.
Fr.: état d'énergie
Same as → energy level.
Fr.: transfert d'énergie
Fr.: tenseur énergie-quantité de mouvement
equipartition of energy
Fr.: équipartition de l'énergie
1) General: Equal sharing of the → total energy among all
→ components of a → system.
From Gk. ergon "work," from PIE base *werg- "to work" (cf. Av. varəz- "to work, do, perform, exercise;" Mod.Pers. varz-, varzidan "to labor, exercise, practise;" Arm. gorc "work;" Lith. verziu "tie, fasten, squeeze," vargas "need, distress;" Goth. waurkjan; O.E. wyrcan "work," wrecan "to drive, hunt, pursue").
The property of a dynamical system such that in an interval of sufficient duration, it will return to states that are closely similar to previous ones.
The study of the relationship between people and their working environment, in particular its effect on a person's efficiency. Ergonomics is applied in designing equipment and office systems to maximize productivity by reducing discomfort and fatigue of people in their workplace.
The region between the → event horizon and the → stationary limit of a rotating → Kerr black hole. It is possible for a particle falling inside the ergosphere to break into two parts, one of which will fall into the black hole and the other will come out.
Fr.: énergie d'excitation
Fr.: énergie de Fermi
The energy of the highest occupied quantum state in a system of fermions at absolute zero temperature. See also → Fermi sea.
Gibbs free energy
kâruž-e âzâd-e Gibbs
Fr.: énergie libre de Gibbs
The total energy needed to create a thermodynamic system minus the energy provided the environment. It is defined by G = U + PV -TS, where U is the → internal energy, T the → absolute temperature, S the → entropy, P the → pressure, and V is the final → volume. Same as the → Gibbs function and → thermodynamic potential.
Fr.: énergie gravitationnelle
Same as → gravitational potential energy.
gravitational potential energy
kâruž-e tavand-e gerâneši
Fr.: énergie potentielle gravitationnelle
1) The energy that an object possesses because of its position in a
→ gravitational field, especially an object near the
surface of the Earth where the → gravitational acceleration
can be assumed to be constant, at about 9.8 m s-2.
Heisenberg uncertainty principle
parvaz-e nâtâštigi-ye Heisenberg
Fr.: principe d'incertitude de Heisenberg
The uncertainty in the measurement of the position and momentum of an elementary particle. The more precisely one quantity is known, the less certain the precision of the other. A similarly linked pair of quantities is the time and energy content in a volume of space.
Named after Werner Heisenberg (1901-1976), the German physicist who in 1927 derived the uncertainty principle. In 1932 he was awarded the Nobel Prize in Physics; uncertainty, from → un- "not" + → certainty; → principle.
Helmholtz free energy
kâruž-e âzâd-e Helmholtz
Fr.: énergie libre de Helmholtz
Of a system, the quantity whose decrease gives the maximum amount of external work which is performed when any physical or chemical process is carried out reversibly at constant temperature. It is defined by F = U - TS, where U is the → internal energy, T the → absolute temperature, and S the final → entropy.
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.