angular power spectrum binâb-e tavâni-ye zâviye-yi Fr.: spectre de puissance angulaire Of the → cosmic microwave background radiation, a plot of how much the temperature varies from point to point on the sky versus the angular frequency. This spectrum answers fundamental questions about the nature of the Universe. → cosmic microwave background anisotropy; → dipole anisotropy. |
CMB angular power spectrum binâb-e tavâni-ye zâviye-yi-e CMB Fr.: spectre de puissance angulaire du CMB A plot displaying the amplitude of → cosmic microwave background anisotropy as a function of angular size or → multipole index. Same as → angular fluctuation spectrum. The plot, based the on WMAP and other data, shows a plateau at large angular or length scales (→ Sachs-Wolfe plateau), then a series of peaks at progressively smaller scales. These features arise from the gravity-driven acoustic oscillations of the coupled photon-baryon fluid in the early Universe (→ baryon acoustic oscillation). In particular, a strong peak is seen on an angular scale (at l ~220), corresponding to the physical length of the → sound horizon at the → recombination era. It depends on the curvature of space. If space is positively curved, then this sound horizon scale will appear larger on the sky than in a flat Universe (the first peak will move to the left). The second peak (l ~ 550), which is the first harmonic of the main peak, relates to the baryon/photon ratio. The third peak can be used to help constrain the total matter density. → angular; → fluctuation; → spectrum. |
dispersive power tâvân-e pâšeš Fr.: pouvoir dispersif A measure of the ability of a medium to separate different colors of light. It is defined by: (n_{2} - n_{1})/(n - 1), where n_{1} and n_{2} are refractive indices at two specified widely differing wavelengths, and n is the → index of refraction for the average of these wavelengths. → dispersive; → power. |
emissive power tavân-e gosili, ~ gosileši Fr.: pouvoir émissif The energy emitted from unit surface area of body per second. |
half-power beamwidth (HPBW) pahnâ-ye tâbé dar nim-tavân Fr.: largeur à mi-hauteur The angle between extreme points of the main lobe of an antenna pattern where the sensitivity of the antenna is half the value at the center of the lobe. This is the nominal resolving power of the antenna system. |
high-power laser leyzer-e por-tavân (#) Fr.: laser de puissance A laser beam with the output power in the range 10^{12}-10^{15} watts/cm^{2}, capable of depositing kilo-joule order energies during nano-second time intervals in small volumes (about 1 mm^{3}). High power lasers, which can produce temperatures of 10-50 million degrees and pressures of 10-100 million bars, are used to simulate astrophysical conditions in laboratories. leyzer, → laser; por "much, many, full," → full; tavân, → power. |
horsepower (hp) asb-e boxâr (#) Fr.: cheval-vapeur A unit that is used to measure the → power of engines and motors. Asb-e boxâr "vapor horse," translation of Fr. cheval-vapeur, from asb, → horse, + boxâr, → vapor. |
light-gathering power tavân-e gerdâvari-ye nur (#) Fr.: pouvoir collecteur de lumière The most important function of an astronomical telescope, which is directly related to the area (or to the square of the diameter) of the main mirror or lens. → light; gathering, from O.E. gadrian, gædrian "to gather, collect;" → power. Tavân, → power; gerdâvari, verbal noun of gerd âvardan, from gerd "round; around" (Mid.Pers. girt "round, all around," O.Iranian *gart- "to twist, to wreathe," cf. Skt. krt "to twist threads, spin, to wind, to surround," kata- "a twist of straw;" Pali kata- "ring, bracelet;" Gk. kartalos "a kind of basket," kyrtos "curved") + âvardan "to bring," Mid.Pers. âwurtan, âvaritan; Av. ābar- "to bring, to possess," from prefix ā- + Av./O.Pers. bar- "to bear, carry," bareθre "to bear (infinitive)," bareθri "a female that bears (children), a mother;" Mod.Pers. bordan "to carry;" Skt. bharati "he carries;" Gk. pherein; L. fero "to carry;" nur, → light. |
magnifying power tavân-e bozorgnemâyi (#) Fr.: grossissement The ratio between the focal lengths of the objective and ocular in a telescope. |
mechanical power tavân-e mekâniki (#) Fr.: puissance mécanique The → rate at which → work is done by a → force. In other words, → mechanical energy per unit time. Mechanical power is expressed in units of joules/sec (joules/s) or a watt (W) in the → mks system. → mechanical; → power. |
noise-equivalent power tavân-e ham-arz-e nufé Fr.: puissance équivalente de bruit A measure of the sensitivity of an electronic detector, defined as the power input to the detector that will create a signal to noise ratio of one for an integration time of half a second. → noise; → equivalent; → power. |
nuclear power tavân-e haste-yi Fr.: puissance nucléaire Electric or motive power whose primary source is nuclear energy. |
perfect power tavân-e farsâxt Fr.: puissance parfaite A → positive integer that can be expressed as an integer → power of another positive → integer. For example, n is a perfect power if there exist natural numbers m> 1, and k> 1 such that m^{k} = n. → perfect cube, → perfect square. |
power tavân (#) Fr.: puissance, pouvoir 1) Physics: The → rate of doing
→ work on transferring → energy, as
expressed in ergs/sec, watts, etc. Same as → mechanical power. M.E. pouer(e), poer(e), from O.Fr. povoir, noun use of the infinitive in O.Fr., "to be able," from V.L. *potere, from L. potis "powerful, able, capable;" cognate with Av. paiti- "lord, husband;" Mod.Pers. -bad (sepah-bad "general, commander of an army"); Skt. pái- "master, husband;" Gk. posis "husband;" Lith. patis "husband." Tavân "power, strength," tavânestan "to be powerful, able;" Mid.Pers. tuwan "power, might," from O.Pers./Av. base tav- "to have power, to be strong, to be able," Av. tavah- "power," təviši- "strength," Mod.Pers. tuš, tâb "power, ability," O.Pers. tauman- "power, strength," tunuvant- "powerful," Skt. tu- "to be strong, to have authority," tavas-, tavisa- "strong, energetic," tavisi- "power, strength." |
power function karyâ-ye tavâni Fr.: fonction de puissance A function of the form f(x) = x^{n}, where n is a → real number. |
power law qânun-e tavâni (#) Fr.: loi de puissance A mathematical relationship between two quantities expressed by a → power function. |
power series seri-ye tavâni (#) Fr.: série de puissance A series in which the terms contain regularly increasing powers of a variable. In general, a_{0} + a_{1}x + a_{2}x^{2} + ... + a_{n}x^{n}, where a_{0}, a_{1}, etc. are constants. |
power spectral density cagâli-ye binâbi-ye tavân Fr.: densité spectrale de puissance Same as → spectral density. |
power spectrum binâb-e tavâni (#) Fr.: spectre de puissance The plot that gives the portion of a signal's power falling within given frequency bins. The most common way of generating a power spectrum is by using a discrete Fourier transform. |
power-law distribution vâbâžeš bâ qânun-e tavâni Fr.: distribution en loi de puissance For a → random variable X, any → distribution which has the form: P(X ≥ x) = (k/x)^{α}, where x is a value in the range defined for X, k > 0 is a parameter termed location parameter, and α > 0 is the → slope parameter. → power; → law; → distribution. |