homogeneous linear differential equation
hamugeš-e degarsâne-yi-ye xatti hamgen
Fr.: équation différentielle linéaire homogène
A → linear differential equation if the right-hand member is zero, Q(x) = 0, on interval I.
if and only if (iff)
agar va ivâz agar, ~ ~ tanhâ ~
Fr.: si et seulement si
Logic, Math.: An → expression indicating that two → statements so connected are → necessary and sufficient conditions for one another. The corresponding logical symbols usually used are: ↔, ⇔, ≡, and iff.
linear differential equation
hamugeš-e degarsâne-yi-ye xatti
Fr.: équation différentielle linéaire
An equation in which the → dependent variable y
and all its differential coefficients occur only
in the first degree. A linear differential equation of → order
order n has the form:
linearized differential equation
hamugeš-e degarsâneyi-ye xatti
Fr.: équation différentielle linéarisée
A differential equation that has been derived from an original nonlinear equation.
Fr.: diffusion magnétique
The process whereby the magnetic field tends to diffuse across the plasma and to smooth out any local inhomogeneities under the influence of a finite resistance in the plasma. For a stationary plasma the → induction equation becomes a pure → diffusion equation: ∂B/∂t = Dm∇2B, where Dm = (μ0σ0)-1 is the → magnetic diffusivity.
Fr.: diffusivité magnétique
nonhomogeneous linear differential equation
hamugeš-e degarsâne-yi-ye xatti nâhamgen
Fr.: équation différentielle linéaire non homogène
A → linear differential equation if Q(x)≠ 0 on interval I.
ordinary differential equation
hamugeš-e degarsâneyi-ye šunik
Fr.: équation différentielle ordinaire
partial differential equation
hamugeš-e degarsâne-yi bâ vâxane-ye pâri
Fr.: 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.
Fr.: différence de phase
The difference of phase (usually expressed as a time or an angle) between two periodic quantities which vary sinusoidally and have the same frequency.
Fr.: différence de potentiel
Between two points, the work done in taking the unit test object from one point to the other. Potential is a scalar quantity.
Fr.: diffusion radiative
A process of → radiative transfer in which photons are repeatedly absorbed and re-emitted by matter particles.
Fr.: diffusion thermique
A physical process resulting from → temperature gradients in stellar interiors, whereby more highly charged and more massive chemical species are concentrated toward the hottest region of the star, its center. Therefore, thermal diffusion and → gravitational settling tend to make heavier species sink relative to the light ones.
Fr.: météorite indifférenciée
A type of meteorite in which the constituting materials (stone, glass, metal) are mixed together in a disorderly mass, in contrast to → differentiated meteorites.
→ un-; → differentiated meteorite.
parâš-e partow-e iks
Fr.: diffraction de rayons X
The diffraction of X-rays by the atoms or ions of a crystal. The wavelength of X-rays are comparable to the size of interatomic spacings in solids. Since the atoms in a crystal are arranged in a set of regular planes, crystals serve as three-dimensional diffraction gratings for X-rays. Planes of repetition within the atomic structure of the mineral diffract the X-rays. The pattern of diffraction thus obtained is therefore used to identify minerals by bombarding them with X-rays.