# 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 It might be outdated or ideologically biased.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 ?
STRONG DIAMETER 2 PROPERTY IS NEVER STABLE UNDER [l.sub.p]-SUMS
(4) Cranial transverse diameter: line/diameter linking the greater/major sciatic notch (Figure 4).
Acme Packet's Diameter signaling controller solution provides comprehensive Diameter mediation and interworking functions that allow BICS to accelerate service deployment.
* Tekelec estimates that more than 87,000 Diameter MPS traversed mobile networks globally in 2011.
Combining diameters and material types allows even more flexibility.
If you're familiar with the Remington Model 700-Series, then you know that the shaft used for the firing-pin assembly is made with different diameters and configurations.
At the age of 2 years, investigators administered the Bayley Scale of Infant Development, Second Edition, and found significant correlations between biparietal diameter during infancy and later scores on mental development index and performance developmental index.
The task was to send a tool through a 30-mile pipeline with a diameter of 24 inches except for a 4.5 mile-long 18-inch section located roughly in the middle of the line.
In experiments that used homogeneous aerosolized influenza virus suspensions (mean diameter 6 [micro]m), virus infectivity (assessed by in vitro culture) at a fixed relative humidity undergoes an exponential decay; this decay is characterized by very low death rate constants, provided that the relative humidity was in the low range of 15%40% (15,16).
The major diameter is the diameter at the crest of the thread and the minor diameter is the diameter at the root.
Friedman said he recently followed 24 very small lesions (2.3-5.7 mm in diameter) that, when removed after a period of observation, were found to be melanomas.
SDK has also started commercial production of the world's smallest 0.85-inch diameter HD media.

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