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null lens adasi-ye nul Fr.: 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. |
null matrix mâtris-e nul Fr.: matrice nulle An m × n matrix whose elements are all zeros. Also known as zero matrix. |
null method raveš-e nul 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. |
nuller nulgar Fr.: A device using the → nulling interferometry technique. Agent noun of the verb → null. |
nulling fraction (NF) barxe-ye nuleš Fr.: fraction de phase d'arrêt The fraction of time that a → pulsar undergoes → pulse nulling. For most → nulling pulsars this fraction can range from zero (for the → Vela pulsar) to more than 50%. |
nulling interferometry andarzanešsanj-ye nuli 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. Nulling, from → null; → interferometry. |
nulling pulsar pulsâr-e nulandé Fr.: pulsar à phase d'arrêt A → pulsar that undergoes → pulse nulling. |
number 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. |
number density cagâli-ye adadi Fr.: densité nmérique Number of a particular type of object found in each unit volume. |
number e 'adad-e e 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). → number; |
number pi 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 10^{12} 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. |
number system 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
(base 2).
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: → number; → system; → conversion. |
number theory negare-ye adadhâ Fr.: théories des nombres The branch of mathematics that studies the relationship between integers and their generalization. |
numeral 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. From L.L. numeralis "of, or belonging to number," → number + → -al |
numeral system râžmân-e adadi, é adadhâ Fr.: système de numération A set of → symbols and → rules for representing → numbers. Same as → number system. See also: → Greek numeral system, → Roman numeral system, → Indian numeral system. |
numerator šomârân (#) Fr.: numérateur 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. |
numerical adadi (#) Fr.: numérique Relating to or expressed in numbers. Adj. of → number. |
numerical analysis ânâlas-e adadi Fr.: analyse numérique The study of methods for approximation of solutions of various classes of mathematical problems including error analysis. |
numerical modeling 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. |
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