cluster


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Related to cluster: Cluster analysis, Cluster Headaches

cluster,

in astronomy: see star clusterstar cluster,
a group of stars near each other in space and resembling each other in certain characteristics that suggest a common origin for the group. Stars in the same cluster move at the same rate and in the same direction.
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; galaxygalaxy,
large aggregation of stars, gas, and dust, typically containing billions of stars. Recognition that galaxies are independent star systems outside the Milky Way came from a study of the Andromeda Galaxy (1926–29) by Edwin P.
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.

cluster

A group of stars whose members are sufficiently close to each other to be physically associated. Clusters range from dense congregations of many thousands of stars to loose groups of only a few stars. Current theories of stellar evolution suggest that stars form in associations, whose densest groupings remain bound as clusters while the other stars disperse; this view is supported by the relatively well-defined Hertzsprung–Russell diagrams of clusters, which indicate that cluster members are of essentially the same composition and age (see also turnoff point). Because the stars in a cluster are all at approximately the same distance, the observed differences in appearance are believed to be due mainly to differences in mass. An estimate of distance is obtained from the technique of main-sequence fitting. See globular cluster; open cluster.

Cluster

An ESA mission to study in three dimensions the shape and dynamic behavior of small-scale structures in the Earth's plasma environment. In effect, Cluster is examining ‘space weather’ – that is, the interaction between the particles of the solar wind and the Earth's magnetosphere. The mission consists of four identical 500-kg satellites, carrying the same 10 instruments. The satellites were carried into space in two pairs by Russian-made Soyuz rockets during the summer of 2000. The first pair, nicknamed Salsa and Samba, were launched July 16, followed by the second pair, Rumba and Tango, launched Aug. 9. The Cluster craft were scheduled to operate until 2005. The mission, which was designated Cluster II, was the replacement for an earlier failed mission. The original Cluster satellites were to have been sent into space together in June 1996, on an Ariane-5 rocket, but were destroyed when the rocket unexpectedly tilted and broke up soon after liftoff.

Cluster

Any configuration of elements that are grouped or gathered closely together.

cluster

[′kləs·tər]
(astronomy)
(computer science)
In a clustered file, one of the classes into which records with similar sets of content identifiers are grouped.
A grouping of hardware devices in a distributed processing system.
A group of disk sectors that is treated as a single entity by the operating system
(engineering)
A pyrotechnic signal consisting of a group of stars or fireballs.
A grouping of rocket motors fastened together.
(ordnance)
A collection of small bombs held together by an adapter for dropping.

cluster

i. Several bomblets forming part of a bomb as in cluster bomb. Once a bomb is released from the aircraft, individual bomblets are dispensed by the bomb.
ii. Two or more parachutes linked to support a single load.
iii. Several engines controlled by a single throttle.

cluster

1. Astronomy an aggregation of stars or galaxies moving together through space
2. Chem
a. a chemical compound or molecule containing groups of metal atoms joined by metal-to-metal bonds
b. the group of linked metal atoms present

cluster

(architecture)
Multiple servers providing the same service. The term may imply resilience to failure and/or some kind of load balancing between the servers. Compare RAIS.

cluster

(file system)
An elementary unit of allocation of a disk made up of one or more physical blocks.

A file is made up of a whole number of possibly non-contiguous clusters. The cluster size is a tradeoff between space efficiency (the bigger is the cluster, the bigger is on the average the wasted space at the end of each file) and the length of the FAT.

cluster

(1) Two or more systems working together. See clustering.

(2) Also called an "allocation unit" or "file allocation unit," it is a number of disk sectors treated as a unit. A cluster is the smallest unit of storage the operating system's file system can manage. That means if a 1KB file is stored in a system with a 32KB cluster (see table below), the 1KB file takes up 32KB of disk space.

Following are the cluster sizes for the FAT file systems for hard drives. When FAT32 came out, drive sizes were minuscule by today's standards, and the reduction of cluster size from 16KB and 32KB to 4KB** saved a lot of disk space for small files. See FAT, FAT32 and lost cluster.

                      Cluster Size                      FAT16   FAT32   Drive Size         (1984)  (1996)

        0-128MB         2KB
      128-256MB         4KB
      256-512MB         8KB
    512MB-1GB          16KB    4KB**
        1-2GB          32KB    4KB**
        1-8GB                  4KB**
        8-16GB                 8KB
       16-32GB                16KB
          32GB +              32KB
References in classic literature ?
Then, on the slight turn of the Lower Hope Reach, clusters of factory chimneys come distinctly into view, tall and slender above the squat ranges of cement works in Grays and Greenhithe.
But these and many other unpleasant additions to the view were unseen by the delighted Elizabeth, who, as the horses moved down the side of the mountain, saw only in gross the cluster of houses that lay like a map at her feet; the fifty smokes that were curling from the valley to the clouds; the frozen lake as it lay imbedded in mountains of evergreen, with the long shadows of the pines on its white surface, lengthening in the setting sun; the dark ribbon of water that gushed from the outlet and was winding its way toward the distant Chesapeake—the altered, though still remembered, scenes of her child hood.
Crawford; and Edmund, Fanny, and Miss Crawford remained in a cluster together.
OWYHEE, or Hawaii, as it is written by more exact orthographers, is the largest of the cluster, ten in number, of the Sandwich Islands.
Then she climbs to safe foothold and hangs, while other gorged bees hang on to her in a cluster.
It was a fruitless search, however, in so far as antelope is concerned; but one night as I lay courting sleep at the edge of a little cluster of date-palms that surround an ancient well in the midst of the arid, shifting sands, I suddenly became conscious of a strange sound coming apparently from the earth beneath my head.
It must have been close to three o'clock in the morning that Anderssen brought the boat's nose to the shore before a clearing where could be dimly seen in the waning moonlight a cluster of native huts encircled by a thorn boma.
At the fall of darkness they swung the dogs into a cluster of spruce trees on the edge of the waterway and made a camp.
After a moment he opened the door, and, on the landing, the sightless woman of marble appeared, draped to the chin, thrusting blindly at them a cluster of lights.
He had ornamented his hat with a cluster of peacock's feathers, but they were limp and broken, and now trailed negligently down his back.
Everything told of life and animation, but one dark cluster of objects in the centre of all--the black stage, the cross-beam, the rope, and all the hideous apparatus of death.
Occasionally they came upon a cluster of poor cottages, some with a chair or low board put across the open door to keep the scrambling children from the road, others shut up close while all the family were working in the fields.