Arnett's rule razan-e Arnett Fr.: règle d'Arnett The → peak luminosity of a → Type Ia supernova is proportional to the rate of → radioactive decay and hence directly proportional to the mass of ^{56}Ni. Arnett, W. D. 1982, ApJ, 253, 785; → rule. |
chondrule kondrul Fr.: chondrule Millimeter-sized grains of → silicate sometimes found in large numbers in → chondrite meteorites. They are essentially glassy beads made by a violent but brief heating event that caused dust grains to form melt droplets. However, the cause of the heating remains unknown. From Gk. chondr-, from chondros "grain," + diminutive suffix → -ule. |
commutation rules razanhâ-ye hammuteš Fr.: règles de commutation The specification of commutators of operators that in quantum physics correspond to the coordinates and momenta of a system. → commutation; → rule. |
Fleming's rules razanhâ-ye Fleming Fr.: règles de Fleming Two rules used to assist in remembering the relative directions of the magnetic field, current, and motion in electrical machines, using one's fingers. The right hand refers to generators, the left hand to motors. The three directions are represented by the thumb (for force or motion), forefinger (for field), and second finger (for current), all held at right angles to each other. Devised by the British physicist and electrical engineer John Ambrose Fleming (1849-1945). |
fuzzy rule base pâygâh-e razan-e porzvâr Fr.: A rule base in a → fuzzy logic system constructed to control the → output variable. A fuzzy rule is a simple if-then rule with a condition and a conclusion. |
Hund's rule razan-e Hund Fr.: règle de Hund An empirical rule stating that all orbitals of a given sublevel must be occupied by single electrons before pairing begins. After the German physicist Friedrich Hund (1896-1997), known for his work on atoms and molecules. → rule. |
leap year rule razan-e sâl-e andarheli Fr.: régle des années bissextiles The three criteria that identify → leap years in the → Gregorian calendar: 1) The year must be evenly divisible by 4; 2) If the year can be evenly divided by 100, it is not a leap year, unless; 3) The year is also evenly divisible by 400. This means that in the Gregorian calendar, the years 1600, 2000, and 2400 are leap years, while 1700, 1800, 1900, 2100, 2200, 2300 and 2500 are not leap years. |
left-hand rule razan-e dast-e cap Fr.: règle de la main gauche See → Fleming's rules. |
Maxwell's rule razan-e Maxwell Fr.: règle de Maxwell Every part of a deformable electric circuit tends to move in such a direction as to enclose the maximum magnetic flux. |
right-hand rule razan-e dast-e râst Fr.: règle de la main droite See → Fleming's rules. |
right-hand screw rule razan-e pic-e rast-gard Fr.: règle de la vis droite A rule that gives the direction of the resultant vector in a → vector product: A x B = C. It is the direction of advance of a right-hand screw whose axis, held perpendicular to the plane of A and B, is rotated in the same sense that rotates the first-named vector (A) into the second-named vector B through the smaller angle. |
rigorous selection rule razan-e gozineš-e farsaxt Fr.: règle de sélection rigoureuse A → selection rule obeyed by → discrete transitions. Among them are: rigorous selection rules for → electric dipole transitions (→ permitted) requiring: 1) ΔJ must be 0 or ± 1 with J = 0 ↔ 0 forbidden. 2) ΔM_{J} = 0, ± 1. 3) → Parity change, i.e. even ↔ odd. |
rule razan Fr.: règle 1) A law or regulation that governs behaviors, actions, or operations.
→ Arnett's rule, → commutation rule,
→ Fleming's rule, → Hund's rule,
→ left-hand rule, → Maxwell's rule,
→ right-hand rule, → rigorous selection rule,
→ selection rule, and
→ Trouton's rule. M.E. riule, reule, from O.Fr. riule, from L. regula "straight stick, bar, ruler," related to regere "to rule, straighten, guide;" cognate with Pers. râst "right, straight," razan "rule," as below. Razan from Av. razan "rule, order," from rāz- "to direct, put in line, set," rasman- "the lines or files of the army;" O.Pers. rāsta- "straight, true," rās- "to be right, straight, true;" Mid.Pers. râst "true, straight, direct;" Soghdian rəšt "right," rây-, râyênitan "to arrange;" Mod.Pers. râst "right, true; just, upright, straight;" raj "line, row," variants raž, rak, râk, rezg (Lori), radé, râdé "line, rule, row," rasté, râsté "row, a market with regular ranges of shops;" ris, risé "straight;" cf. Skt. raj- "to direct, stretch," rjuyant- "walking straight;" Gk. orektos "stretched out;" L. regere "to lead straight, guide, rule," p.p. rectus "right, straight;" PIE base *reg- "move in a straight line," hence, "to direct, rule." |
rule of decision razan-e vâsun Fr.: régle de décision Same as → significance testing and → test of significance. |
rule of three razan-e sé Fr.: règle de trois Te method of finding the fourth term in a proportion when three terms are given. |
ruled grating turi-ye šiyârdâr Fr.: réseau à traits A → diffraction grating with a series of grooves that have been ruled on a reflective surface with a diamond tool mounted on a ruling machine. Ruled gratings may have triangular or trapezoidal groove profiles, whereas → holographic gratings usually have sinusoidal groove profiles. Turi, → grating; šiyârdâr "having grooves," from šiyâr, → groove, + -dâr "having, possessor," → property. |
ruled surface ruye-ye xatt sâxté Fr.: surface réglée A surface, such as a cylinder or cone, that can be generated by moving a straight line. Ruled, p.p. of rule; → surface. Ruyé, → surface; xatt sâxté "built, formed by a line," from xatt→ line; sâxté, p.p. of sâxtan "to build, make, fashion; to adapt, adjust, be fit" (from Mid.Pers. sâxtan, sâz-, Manichean Parthian s'c'dn "to prepare, to form;" Av. sak- "to understand, to mark," sâcaya- (causative) "to teach"). |
selection rule razan-e gozineš Fr.: règle de sélection Any of a set of rules specifying the relationships between the → quantum numbers that characterize the initial and final states of a quantum-mechanical system in a → discrete transition. Transitions that do not agree with the selection rules are called → forbidden and have considerably lower probability. There are several types of selection rules (→ rigorous selection rule, → LS coupling, etc.) for → electric dipole transition (→ permitted), → magnetic dipole (forbidden), electric → quadrupole (forbidden), etc. |
spherule guyel Fr.: sphérule Any of many vitrified droplets of rock formed by the solidification of molten meteoritic material that flows off a meteorite during its passage through the Earth's atmosphere. Sizes range typically from 10 to 200 microns. "Small sphere," from → sphere + diminutive suffix → -ule. Guyel "small globe," from guy "ball, sphere" (variants golulé, gullé, goruk, gulu, gudé; cf. Skt. guda- "ball, mouthful, lump, tumour," Pali gula- "ball," Gk. gloutos "rump," L. glomus "ball," globus "globe," Ger. Kugel, E. clot; PIE *gel- "to make into a ball") + -el diminutive suffix, → -ule. |
Trouton's rule razan-e Trouton Fr.: règle de Trouton The ratio of the → molar heat of vaporization of any liquid to its → boiling point is a constant, about 88 joules per mole per Kelvin. The rule is equivalent to the statement that the → entropy of vaporization is constant. It is not always followed, especially by liquids such as water in which hydrogen bonding occurs between the molecules. Named after Frederick Thomas Trouton (1863-1922), an Irish physicist; → rule. |