A lens used in the optical testing of an aspheric surface. It converts a spherical wavefront into one that precisely matches the surface under test. When the wavefront is reflected from that surface, it reverses its path and, if the surface is perfect, results in a perfect emerging spherical wavefront, which is easily evaluated.
Fr.: matrice nulle
An m × n matrix whose elements are all zeros. Also known as zero matrix.
Fr.: méthode de zéro
A method of comparing, or measuring, forces, electric currents, etc., by so opposing them that the pointer of an indicating apparatus remains at, or is brought to, zero, as contrasted with methods in which the deflection is observed directly. Same as zero method.
A device using the → nulling interferometry technique.
Agent noun of the verb → null.
nulling fraction (NF)
Fr.: fraction de phase d'arrêt
Fr.: interférométrie annulante
A technique for blocking the light of a bright source in order to reveal a faint source near it. This technique uses destructive → interference between two or more → coherent beams from a number of telescopes to make the bright center dark. Nulling interferometry can be used to search the region immediately around a star for → extrasolar planets and → circumstellar dust clouds by suppressing the star's glare.
Fr.: pulsar à phase d'arrêt
1) adad (#), šomâré (#); 2) šomâr (#)
Fr.: 1) nombre, numéro; 2) numéro
1) Any real or complex numeral quantity.
From M.E. nombre, from O.Fr. nombre, from L. numerus "a number, quantity," from PIE base *nem- "to divide, distribute, allot."
Adad, loan from Ar.
Fr.: densité nmérique
Number of a particular type of object found in each unit volume.
Fr.: nombre e
The → base of the → natural logarithm. It is defined as: e = lim (1 + 1/n)n when n→ ∞. For n = 1, e = 2 and for n = 10, e = 2.5937424601, etc. The number e is → irrational (Euler, 1737) and → transcendental (Hermite, 1873).
adad-e pi (π)
Fr.: nombre pi (π)
Symbol, π, for the ratio of the circumference of a circle to its diameter in Euclidean geometry; a fundamental mathematical constant, equal to 3.14159... π is an → irrational number (Lambert, 1761) and also a → transcendental number (von Lindemann, 1882). The most accurate determination of π prior to the Scientific Revolution belongs to the Iranian mathematician Jamshid Kashani, who gave 16 correct decimal places in A.D. 1424. With the advent of → calculus and more recently the invention of powerful computers, the decimal representation of π has now been computed to more than 1012 digits.
The π notation, representing the first letter of the Gk. word περιμετρον → perimeter, was first used by the British mathematician William Jones (1675-1749) in 1706. Its use was generalized after its adoption by the Swiss mathematician Leonard Euler (1707-1783) in 1737; → number.
râžmân-e adadhâ, ~ adadi
Fr.: système de numération
Same as → numeral system.
number system conversion
hâgard-e râžmân-e adadi
Fr.: conversion de système de numération
The conversion of a → number system
with a given → base to another system with a
different base; such as the conversion of a → decimal number
(base 10) to a → binary number system
In order to convert a number into its representation in a different
number base, we have to express the number in terms of powers of the other base.
For example, to convert the decimal number 100 to base 3, we must figure out how to
express 100 as the sum of powers of 3. We proceed as follows:
Fr.: théories des nombres
The branch of mathematics that studies the relationship between integers and their generalization.
1) šomârâl; 2) šomâre-yi (#), adadi (#)
Fr.: 1) numéral; 2) numéral, numérique
1) A symbol, group of symbols, or word used to express a number.
For any number there is an infinite number of numeral expressions.
For example, the number two can be written as 2, II, binary 10, 4/2, 18/8, etc.
râžmân-e adadi, é adadhâ
Fr.: système de numération
The quantity x in a fraction x/y). The quantity y is the → denominator.
L.L. numerator "a counter, numberer," from L. numera(re) "to number," → number + -tor a suffix forming personal agent nouns from verbs and, less commonly, from nouns.
Šomârân, agent noun of šomârdan, → number.
Relating to or expressed in numbers.
Adj. of → number.
Fr.: analyse numérique
The study of methods for approximation of solutions of various classes of mathematical problems including error analysis.
modelsâzi-ye adadi (#), tarzâlsâzi-ye ~
Fr.: modélisation numérique
The prediction of the evolution of a system via numerical construction of approximate solutions to the governing equations.