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potentially hazardous asteroid (PHA) seyyârak-e tavandâné âpenâk Fr.: astéroïde potentiellement dangereux An asteroid that could make a threatening close approach to the Earth. In technical terms a PHA is defined as having an → absolute magnitude of 22 or brighter and an → Earth Minimum Orbit Intersection Distance (MOID) of less than 0.05 → astronomical unit or 7.5 million km. → potentially; → hazardous; → asteroid. |
potentiometer tavandsanj Fr.: potentiomètre An instrument for measuring electrical quantities by balancing an unknown potential difference against a known potential difference. |
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. |
power-law elliptical galaxy kahkešân-e beyzigun bâ qânun-e tavâni Fr.: galaxie elliptique en loi de puissance An → elliptical galaxy whose → surface brightness can be approximated by a single → power law at small radii (r ≤ 10-20''). More modern interpretations have emphasized that these profiles can be better understood as the inward continuation of the galaxy's overall → Sersic profile, usually modified by an additional, nuclear-scale stellar component (S. P. Rusli et al., 2013, AJ 146, 160). |
Poynting vector bordâr-e Poynting Fr.: vecteur de Poynting The amount of electromagnetic energy flowing through unit area, perpendicular to the direction of energy propagation, per unit time, given by (c/2 π)[E x H]. → Poynting's theorem. → Poynting's theorem; → vector. |
Poynting's theorem farbin-e Poynting Fr.: théorème de Poynting The space through which electromagnetic radiation passes is filled with electric and magnetic fields at right angles to each other and to the direction of propagation of the radiation. The rate of energy transfer is given by the Poynting vector. In honor of John Henry Poynting (1852-1914), English physicist; → theorem. |
Poynting-Robertson drag kerre-ye Poynting-Robertson Fr.: traînée de Poynting-Robertson A loss of → orbital angular momentum by tiny ring particles associated with their absorption and re-emission of → solar radiation. Also known as the → Poynting-Robertson effect (Ellis et al., 2007, Planetary Ring Systems, Springer). → Poynting-Robertson; → drag. |
Poynting-Robertson effect oskar-e Poynting-Robertson Fr.: effet Poynting-Robertson The effect of → solar radiation on a small (centimeter-sized) particle in → orbit around the Sun that causes it to lose velocity and fall gradually into the Sun. The particle → absorbs solar radiation and → radiates the energy → isotropically in its own frame. The particle thereby preferentially radiates (and loses → angular momentum) in the forward direction in the → inertial frame of the Sun (aberration effect). This leads to a decrease in the particle's angular momentum and causes it to spiral sunward. In contrast, the → Yarkovsky effect is anisotropic; the object may be accelerated or decelerated. → Poynting's theorem; Howard Percy Robertson (1903-1961), American physicist and mathematician; → effect. |
practicable varzpazir, varzidani Fr.: praticable That can be done or used or put into practice. |
practical varzâl Fr.: pratique Concerned with practice, as opposed to → theory. |
practice 1) varzidan (#); 2) varzé (#) Fr.: 1) pratiquer; 2) pratique 1a) To do habitually or regularly. M.E. practisen, practizen; O.Fr. practiser "to practice," from M.L. practicare "to do, perform," from L.L. practicus "practical," from Gk. praktikos "practical." 1) Varzidan "to practice, perform; to accustom oneself to; to labor; to sow a field;"
Mid.Pers. warz- "to work, do, practice;"
Av. varəz- "to work, do, perform, exercise;" cf.
Gk. ergon "work;" Arm. gorc "work;" Lith. verziu "tie, fasten, squeeze,"
vargas "need, distress;" Goth. waurkjan; O.E. wyrcan "work,"
wrecan "to drive, hunt, pursue;" E. work;
PIE base *werg- "to work." |
practicing varzandé Fr.: pratiquant Actively following a specified career or way of life. |
practitioner varzmand Fr.: praticien A professional man, especially in medicine and the law. |
Praesepe Perâysepé, Kandu, Âxor Fr.: la Crèche An → open cluster in the constellation → Cancer containing about 50 stars of 6th magnitude or fainter. It lies 577 light-years away. Also called NGC 2632, the Beehive Cluster, or the Manger. From L. praesepe "crib," from which cattle or horses are fed, manger; the neighboring brighter stars Gamma and Delta Cancri (Asellus Borealis and Asellus Australis) were pictured as asses which fed from a manger. Perâysepé, loan from L., as above. |
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