An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

A type of → algorithm that dynamically achieves high → resolution in localized regions of multidimensional → numerical simulations. AMR provides a higher → accuracy solution at lower costs, through an automatically → optimal distribution of → grid points for the computation region. It relies on locally refined mesh or mesh patches to increase the resolution of an underlying coarse mesh only where needed. It can alleviate some of the complexities of the generation of high quality grid and reduce the number of → iterations of "trial-and-error" between the grid generation and solution required for tailoring the grid to the specification of a problem. Thus, it can offer orders of magnitude saving in computational and storage costs over an equivalent uniformly refined mesh. AMR was originally developed for → inviscid, → compressible flow (Berger et al., 1984, Adaptive Mesh Refinement for Hyperbolic Partial Differential Equations. J. Comp. Phy., 53, 484). It has been extended to solve → Navier-Stokes equations, time dependent problems and more. Several AMR techniques have been developed and applied to compressible flow fields to capture characteristics at the strong gradient or discontinuous regions requiring higher space resolution, such as regions involving → shock waves, vortices (→ vortex), and → wakes (see, e.g., Qingluan Xue, "Development of Adaptive Mesh Refinement Scheme and Conjugate Heat Transfer Model for Engine Simulations" (2009), Iowa State Univ., Graduate Theses and Dissertations, Paper 10678).
See also → Smoothed Particle Hydrodynamics.

→ adaptive; → mesh; → refinement.

Math.: Of or pertaining to the geometry of → affine transformations. See also: → affine combination, → affine geometry, → affine set, → affinity.

From Fr., from L. affinis "bordering on; neighboring; related."

Karvan, literally "bordering on; possessing border (with); related," from (Bašgard) ker "border, boundary," (Fin Bandar Abbas) karaq "border, edge;" classical Pers. karân, kenâr "boundary, side, edge;" + -van suffix of possession, relation.

A linear combination of vectors in which all the vector coefficients add up to one.

→ affine; → combination.

The study of the properties which are → invariant under → affine transformations.

→ affine; → geometry.

A set → if and only if (iff) for any two points in the → set, the line through them is contained in the set. In other words, for any two points in the set, their → affine combinations are in the set itself.

→ affine; → set.

Any → transformation preserving → collinearity.

→ affine; → transformation.

To enclose within bounds; to restrict.

M.E., from M.Fr. confins, confines, from L. confinis "boundary, border," from con-, → com- "with" + finis "end."

Parbastan, parbast kardan, literally "close around," from par- "around," → circum-, + bast, bastan "to close," → closed.

Plasma in which magnetic field lines forming closed surfaces confine the plasma.

Confined, p;p. of → confine; → plasma.

General: The act of confining; the state of being confined. Physics: A property of quantum electrodynamics whereby quarks cannot exist as free particles, but are forever bound into protons, neutrons, etc.

Noun from → confine.

1) To state or set forth the meaning of (a word, concept, etc.).
2) To explain or identify the nature or essential qualities of.
3) To fix or mark the boundaries or extent of.

From O.Fr. définir "to end, determine," from L. definire "to limit, determine, explain," from → de- + finire "to bound, limit," from finis "boundary."

Hedâridan, infinitive from Semnâni hedâr "boundary (between pieces of lands)," Tabari hedâri "boundary, border," may be related to Av. haêtav- "dam, dike," Skt. setu- "a ridge of earth, bank, dike, dam, bridge."

1) Clearly characterized or fixed.
2) Showing clearly the outline or profile or boundary.
3) Computer science: A variable having received a value prior to a given point in a program.

P.p. of → define.

Very thin or slender. → fine structure, → fine-structure constant.

M.E. fin, from O.Fr. fin "perfected, of highest quality," from L. finis "end, limit."

Nâzok "thin, slender, subtle," from Mid.Pers. nâzuk "tender, gentle," variant nâzik, from nâz "joy, pride, glory" + → -ik.

Meteorology: An → inhomogeneous  → mixture of tiny, part → solid, part → liquid or → gaseous  → particles that are, in average, smaller than ten → microns. The constituents are soot, heavy metals, organic substances, and dioxins. The smaller these dust particles, the deeper they penetrate into the lung. Larger particles are intercepted by mucous membrane in nose, mouth, and throat but smaller particles can penetrate the smallest lung bronchioles and may cause severe damage (various respiratory disorders, lung cancer) → particulate matter.

→ fine; → dust.

Closely spaced components seen at high resolution in a → spectral line. The phenomenon is explained by the fact that instead of a single → energy level corresponding to a given value of the → quantum number  n, there are actually a number of energy levels lying close to one another. → fine-structure constant, → fine-structure line.

→ fine; → structure.

A measure of the strength of → interaction between a → charged particle and the → electromagnetic field. It is a → dimensionless number expressed (in → cgs units) by α = e²/ħc, where e is the → electron charge, ħ is the → reduced Planck's constant, and c is the → speed of light. It is approximately equal to 1/137 or 7.3 × 10^-3. The smallness of this number is of great importance since it determines the size of → atoms and the → stability of → matter. Same as → electromagnetic coupling constant.

→ fine structure; → constant.

A → spectral line whose → energy levels have a → fine structure. Examples are [C II] 157.7 μm (→ singly ionized carbon), [O III] 88 μm, and [Ne II] 12.8 μm.

→ fine; → structure; → line.

Extremely fine or thin, especially of a → spectral line split into two or more very thin components. → hyperfine structure; → hyperfine transition.

→ hyper-, → fine structure.

In spectroscopy, the → splitting of a spectral line into a number of very thin components. It results from a small perturbation in the energy levels of atoms or molecules due to the magnetic dipole-dipole interaction arising from the interaction of the nuclear → magnetic moment with the → spin of the electron. It can be observed only at high spectral dispersion. → fine structure.

→ hyperfine; → structure.

An → atomic transition involving a → hyperfine structure.

→ hyperfine; → transition.

The phenomenon wherein the → quarks are permanently bound together and can never be removed from the → hadrons they compose.

→ quark; → confinement.