Atlas

An atlas is a collection of maps; it is typically a map of Earth or a region of Earth, but there are atlases of the other planets (and their satellites) in the Solar System. Furthermore, atlases of anatomy exist, mapping out the human body or other organisms. Atlases have traditionally been bound into book form, but today many atlases are in multimedia formats. In addition to presenting geographic features and political boundaries, many atlases often feature geopolitical, social, religious and economic statistics. They also have information about the map and places in it.

Etymology

The word atlas dates from 1636, first in reference to the English translation of Atlas, sive cosmographicae meditationes de fabrica mundi (1585) by Flemish geographer Gerhardus Mercator, who might have been the first to use this word in this way. A picture of the Titan Atlas holding up the world appeared on the frontispiece of this and other early map collections.

History

The first work that contained systematically arranged woodcut maps of uniform size, intended to be published in a book, thus representing the first modern atlas, was De Summa totius Orbis (1524–26) by the 16th-century Italian cartographer Pietro Coppo. Nonetheless, this distinction is conventionally awarded to the Flemish cartographer Abraham Ortelius who in 1570 published the collection of maps Theatrum Orbis Terrarum.

Atlas (computer)

The Atlas Computer was a joint development between the University of Manchester, Ferranti, and Plessey. The first Atlas, installed at Manchester University and officially commissioned in 1962, was one of the world's first supercomputers, considered to be the most powerful computer in the world at that time. It was said that whenever Atlas went offline half of the United Kingdom's computer capacity was lost. It was a second-generation machine, using discrete germanium transistors. Two other Atlas machines were built: one for British Petroleum and the University of London, and one for the Atlas Computer Laboratory at Chilton near Oxford.

A derivative system was built by Ferranti for Cambridge University. Called the Titan, or Atlas 2, it had a different memory organisation and ran a time-sharing operating system developed by Cambridge University Computer Laboratory. Two further Atlas 2s were delivered: one to the CAD Centre in Cambridge (later called CADCentre, then AVEVA), and the other to the Atomic Weapons Research Establishment (AWRE), Aldermaston.

Atlas (topology)

In mathematics, particularly topology, one describes a manifold using an atlas. An atlas consists of individual charts that, roughly speaking, describe individual regions of the manifold. If the manifold is the surface of the Earth, then an atlas has its more common meaning. In general, the notion of atlas underlies the formal definition of a manifold and related structures such as vector bundles and other fibre bundles.

Charts

The definition of an atlas depends on the notion of a chart. A chart for a topological space M (also called a coordinate chart, coordinate patch, coordinate map, or local frame) is a homeomorphism from an open subset U of M to an open subset of Euclidean space. The chart is traditionally recorded as the ordered pair .

Formal definition of atlas

An atlas for a topological space M is a collection of charts on M such that . If the codomain of each chart is the n-dimensional Euclidean space and the atlas is connected, then M is said to be an n-dimensional manifold.

Par

Par or PAR may refer to:

Golf

Media

Computing

Culture

Geography

Parè

Parè is a comune (municipality) in the Province of Como in the Italian region Lombardy, located about 40 kilometres (25 mi) northwest of Milan and about 6 kilometres (4 mi) west of Como, on the border with Switzerland. As of 31 December 2007, it had a population of 1,784 and an area of 2.2 square kilometres (0.85 sq mi).

Parè borders the following municipalities: Cavallasca, Chiasso (Switzerland), Drezzo, Faloppio, Gironico, Olgiate Comasco.

History

In the Napoleonic era the municipality of Parè was suppressed and united to Gironico (also municipalities of Drezzo and Montano were aggregated to it). The union lasted until 1816 when the previous municipalities were restored.

In 1928 the municipalities of Parè, Drezzo and Cavallasca were united into a single municipality called Lieto Colle (name inspired by Margherita Sarfatti, the lover of Benito Mussolini who had a palace in Cavallasca). The town hall was in Parè. After the end of Fascism, the discontent against the union grew, but only in 1956 the municipality of Lieto Colle was suppressed and the three municipalities of Parè, Drezzo and Cavallasca restored.

Parchive

Parchive (a portmanteau of parity archive, and formally known as Parity Volume Set Specification) is an erasure code system that produces par files for checksum verification of data integrity, with the capability to perform data recovery operations that can repair or regenerate corrupted or missing data. Parchive was originally written to solve the problem of reliable file sharing on Usenet, but it is now commonly used for protecting any kind of data from data corruption, bit rot, and accidental or malicious damage. Despite the name, Parchive uses more advanced techniques that do not utilize simplistic parity methods of error detection and correction.

The original SourceForge Parchive project has been inactive since November 9, 2010. As of 2014, Par1 is obsolete, Par2 is mature for widespread use, and Par3 is an experimental version being developed by MultiPar author Yutaka Sawada.

History

Parchive was intended to increase the reliability of transferring files via Usenet newsgroups. Usenet was originally designed for informal conversations, and the underlying protocol, NNTP was not designed to transmit arbitrary binary data. Another limitation, which was acceptable for conversations but not for files, was that messages were normally fairly short in length and limited to 7-bit ASCII text.