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. → homogeneous; → linear; → differential; → equation. |
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: → linear; → differential; → equation. |
linearized differential equation hamugeš-e degarsâneyi-ye xatti Fr.: équation différentielle linéarisée A differential equation that has been derived from an original nonlinear equation. Linearized, p.p. of → linearize; → differential; → equation. |
magnetic diffusion paxš-e meqnâtisi 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 = D_{m}∇^{2}B, where D_{m} = (μ_{0}σ_{0})^{-1} is the → magnetic diffusivity. |
magnetic diffusivity paxšandegi-ye meqnâtisi Fr.: diffusivité magnétique The → diffusion coefficient for a magnetic field. It is expressed as: η = 1/(μ_{0}σ), where μ_{0} is the → magnetic permeability and σ the → conductivity. → magnetic; → diffusivity. |
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. → nonhomogeneous; → linear; → differential; → equation. |
ordinary differential equation hamugeš-e degarsâneyi-ye šunik Fr.: équation différentielle ordinaire A → differential equation in which the unknown function depends on only one → independent variable, as contrasted with a → partial differential equation. → ordinary; → differential; → equation. |
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. → partial; → differential; → equation. |
phase difference degarsâni-ye fâz 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. → phase; → difference. |
potential difference degarsâni-ye tavand 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. → potential; → difference. |
radiative diffusion paxš-e tâbeši Fr.: diffusion radiative A process of → radiative transfer in which photons are repeatedly absorbed and re-emitted by matter particles. |
thermal diffusion paxš-e garmâyi 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. |
undifferentiated meteorite šahâbsang-e nâdegarsânidé 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. |
X-ray diffraction 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. → X-ray; → diffraction. |