# An Etymological Dictionary of Astronomy and AstrophysicsEnglish-French-Persian

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 9 Search : partial
 first-order partial derivative   واخنه‌ی ِ پاری ِ رایه‌ی ِ نخست   vâxane-ye pâri-ye râye-ye naxostFr.: dérivée partielle du premier degré   For a → function with several → variables, the derivative, done only once, with respect to one of the variables. For example ∂u/∂x for u = u(x,y).→ first; → order; → partial; → derivative. partial   پاری، پارال   pâri (#), pârâlFr.: partiel   Being such in part only; not total or general; incomplete. See also: → partial derivative, → partial differential equation, → partial eclipse, → partial ionization zone, → partial lunar eclipse, → partial solar eclipse, → partial truth.M.E. parcial, from O.Fr. parcial, from M.L. partialis "pertaining to a part," from L. pars, → part; → -al.→ part; → -al. partial derivative   واخنه‌ی ِ پاری   vâxane-ye pâriFr.: dérivée partielle   The derivative of a function of two or more variables, e.g., z = f(x,y), with respect to one of the variables, the others being considered constants (denoted ∂z / ∂x).→ partial; → derivative. partial differential equation   هموگش ِ دگرسانه‌ای با واخنه‌ی ِ پاری   hamugeš-e degarsâne-yi bâ vâxane-ye pâriFr.: équation différentielle aux dérivées partielles   A type of differential equation involving an unknown function (or functions) of several independent variables and its (or their) partial derivatives with respect to those variables.→ partial; → differential; → equation. partial eclipse   گرفت ِ پاری   gereft-e pâriFr.: éclipse partielle   An eclipse that is not total. → partial lunar eclipse, → partial solar eclipse.→ partial; → eclipse. partial ionization zone   زنار ِ یونش ِ پاری   zonâr-e yoneš-e pâriFr.: zone d'ionisation partielle   One of several zones of the stellar interior where increased → opacity can provide the → kappa mechanism to drive → pulsations. See also → Kramers' law. In these zones where the gases are partially ionized, part of the energy released during a layer's compression can be used for further ionization, rather than raising the temperature of the gas. Partial ionization zones modulate the flow of energy through the layers of the star and are the direct cause of → stellar pulsation. The partial ionization zones were first identified by the Russian astronomer Sergei A. Zhevakin (1916-2001) in the 1950s. In most stars there are two main ionization zones. The hydrogen partial ionization zone where both the ionization of neutral hydrogen (H ↔ H+ + e-) and the first ionization of helium (He ↔ He+ + e-) occurs in layers with a characteristic temperature of 1.5 x 104 K. The second, deeper zone is called the He+ partial ionization zone, and involves the second ionization of helium (He+↔ He++ + e-), which occurs deeper at a characteristic temperature of 4 x 104 K. The location of these ionization zones within the star determines its pulsational properties. In fact if the → effective temperature of the star is ≥ 7500 K, the pulsation is not active, because the ionization zones will be located very near to the surface. In this region the density is quite low and there is not enough mass available to drive the oscillations. This explains the blue (hot) edge of the instability strip on the → H-R diagram. Otherwise if a star's surface temperature is too low, ≤ 5500 K, the onset of efficient convection in its outer layers may dampen the oscillations. The red (cool) edge of the instability strip is believed to be the result of the damping effect of convection. He+ ionization is the driving agent in → Cepheids. See also → gamma mechanism.→ partial; → ionization; → zone. partial lunar eclipse   مانگ‌گرفت ِ پاری   mânggereft-e pâriFr.: éclipse partielle de lune   A → lunar eclipse when the Earth's → umbra passes over only part of the Moon, causing only moderate darkening of the full Moon. See also → penumbral lunar eclipse.→ partial; → lunar; → eclipse. partial solar eclipse   خورگرفت ِ پاری   xorgereft-e pâriFr.: éclipse partielle de soleil   A → solar eclipse when only the → penumbra of the Moon touches the Earth. The → umbra passes either just above the North Pole or just below the South Pole, missing the Earth.→ partial; → solar; → eclipse. partial truth   راستینی ِ پاری، ~ پارال   râstini-ye pâri, ~ pârâlFr.: vérité partielle   A → truth value in → fuzzy logic where it can range between "completely true" and "completely false."→ partial; → truth.