# diameter

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## diameter

a. a straight line connecting the centre of a geometric figure, esp a circle or sphere, with two points on the perimeter or surface
b. the length of such a line
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

## Diameter

The diameter of a circle is the chord that passes through the center of the circle. Moreover, the diameter of a circle is the length of this chord, equal to two radii.

In analytic geometry the diameter of a conic section (or of a curve of the second order) is understood to mean the straight line that passes through the midpoints of a set of parallel chords. For central curves of the second order (circles, ellipses, hyperbolas) this is the straight line passing through the center of the curve. In the case of the parabola, all diameters are parallel to its axis.

The concept of the diameter of a circle as the length of a segment is applied to other geometric figures and to sets of a more general nature. The diameter of a figure (or a set in metric space) is precisely the upper bound of the distances between all possible pairs of points of this figure. In this sense, the diameter of an ellipse is equal to the length of the semimajor axis, and the diameter of a square is equal to the length of its diagonal.

## diameter

[dī′am·əd·ər]
(mathematics)
A line segment which passes through the center of a circle, and whose end points lie on the circle.
The length of such a line.
For a conic, any straight line that passes through the midpoints of all the chords of the conic that are parallel to a given chord.
For a set, the smallest number that is greater than or equal to the distance between every pair of points of the set.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

## diameter

The diameter of a graph is the maximum value of the minimum distance between any two nodes.

## Diameter

An authentication, authorization and accounting (AAA) protocol that replaces RADIUS (Diameter is a play on the word RADIUS). Like RADIUS, Diameter uses a challenge/response method; however, unlike RADIUS, Diameter uses the reliable TCP and SCTP protocols rather than the unreliable UDP for transport. Diameter also supports error reporting and is better at scaling than RADIUS. See RADIUS, network access server and challenge/response.
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References in periodicals archive ?
A la fin des annees soixante-dix, Ducati a leve le voile sur une nouvelle version appelee S D Sportplus performante equipee de carburateurs de 40 mm de diametre et de silencieux Conti.
Inside a battery-operated, circuit-sensing board transmits the rock's location as it falls from the six-inch diametre borehole in-to the ore chambers.
An SNGPL spokesman said on Tuesday that main gas pipelines of 12' and 8' diametre on GT Road near Jinnah Park would to be re-routed.
Il est ainsi procede au changement des canalisations par la pose de nouvelles conduites de 315 ml de diametre, a precise Said Ben-Alioua.
Valued at Dh30 million, the new project includes the planning and laying of new water pipe distribution networks ranging in size from 100-450mm in diametre, and over a total length of 30 kilometres.
Le pot, de plus de deux metres de diametre et 1,60 m de hauteur, a ete presente devant plus de 10.000 personnes dans la station de ski de Tochal, sur les hauteurs de la capitale, selon la societe.
Surveille de pres par l'agence spatiale americaine, un asteroide de 45 metres de diametre a frole la Terre vendredi sans faire de degats, contrairement a une meteorite tombee le meme jour en Russie qui a explose et blesse un millier de personnes.
For example, we are currently studying the use of bigger nets with holes having bigger diametre so that baby fishes are spared and only bigger ones are caught," he added.
The project will involve processing of one billion standard cubic feet per day of high pressure gas and transporting it from the Abu Dhabi Marine Operating Company's (Adma-Opco) offshore Umm Shaif field via a new 46 inch diametre pipeline to Adgas's integrated gas development facility on Das Island.

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