Period (geology)

A geologic period is one of several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place.

These periods form elements of a hierarchy of divisions into which geologists have split the Earth's history.

Eons and eras are larger subdivisions than periods while periods themselves may be divided into epochs and ages.

Structure

The twelve currently recognised periods of the present eon – the Phanerozoic – are defined by the International Commission on Stratigraphy (ICS) by reference to the stratigraphy at particular locations around the world.

In 2004 the Ediacaran Period of the latest Precambrian was defined in similar fashion (and was the first such newly designated period in 130 years) but earlier periods are simply defined by age.

A consequence of this approach to the Phanerozoic periods is that the ages of their beginnings and ends can change from time to time as the absolute age of the chosen rock sequences, which define them, is more precisely determined.

Ring of periods

In mathematics, a period is a number that can be expressed as an integral of an algebraic function over an algebraic domain. Sums and products of periods remain periods, so the periods form a ring.

Maxim Kontsevich and Don Zagier (2001) gave a survey of periods and introduced some conjectures about them.

Definition

A real number is called a period if it is the difference of volumes of regions of Euclidean space given by polynomial inequalities with rational coefficients. More generally a complex number is called a period if its real and imaginary parts are periods.

The values of absolutely convergent integrals of rational functions with algebraic coefficients, over domains in given by polynomial inequalities with algebraic coefficients are also periods, since integrals and irrational algebraic numbers are expressible in terms of areas of suitable domains.

Examples

Besides the algebraic numbers, the following numbers are known to be periods:

Power!

Power! (known as Critical Mass in Europe) is a computer game developed by Simon Francis in 1985 for the Amstrad CPC, Commodore 64 and ZX Spectrum.

Plot

The player operates a rocket-powered hovercraft whose mission is to destroy an enemy transfer beam that is protected not only by long-distance enemy raiders and mines, but also molecular disorientation that sucks the energy from the player's attack craft.

Gameplay

The player may control the hovercraft in either a normal joystick operational mode or with vectored movement. When the player pushes forward on the joystick, the hovercraft accelerates, and when pulling back on the joystick, speed decreases.

Reception

In 1988, Dragon reviewed Power!, and gave the game 4 out of 5 stars.

References

External links

PoweredUSB

PoweredUSB, also known as Retail USB, USB PlusPower, and USB +Power, is an addition to the Universal Serial Bus standard that allows for higher-power devices to obtain power through their USB host instead of requiring an independent power supply or external AC adapter. It is mostly used in point-of-sale equipment, such as receipt printers and barcode readers.

History

PoweredUSB, as a proprietary variant of USB, was developed and proposed by IBM, Berg (now FCI), NCR and Microsoft between 1998 and 1999, with the last revision (0.8g) issued in 2004. The specification is not endorsed by the USB Implementers Forum (USB-IF). IBM, who owns patents to PoweredUSB, charges a licensing fee for its use.

PoweredUSB was licensed by Hewlett-Packard, Cyberdata, Fujitsu, Wincor and others.

Implementation

PoweredUSB uses a more complex connector than standard USB, maintaining the standard USB 1.x/2.0 interface for data communications and adding a second connector for power. Physically, it is essentially two connectors stacked such that the bottom connector accepts a standard USB plug and the top connector takes a power plug.

Power (2014 Telugu film)

Power is a 2014 Telugu action comedy film written and directed by K. S. Ravindra and produced by Rockline Venkatesh under the banner Rockline Entertainments, both marking their debut in Telugu cinema. It features Ravi Teja playing a dual role with Hansika Motwani and Regina Cassandra playing the female lead roles. S. Thaman composed the music while Gautham Raju edited the film. Arthur A. Wilson and Jayanan Vincent handled the film's cinematography. The film revolves around two similar looking people, Baldev Sahay - a corrupt ACP in Kolkata and Tirupathi - a person aspiring to become a police officer in Hyderabad. The home minister of Kolkata recruits Tirupathi to play as Baldev to catch a gangster rescued by Baldev. Rest of the story is all about why Baldev became a corrupt cop and how Tirupathi executed the unfinished mission of Baldev.

Production began on 11 December 2013. The film's talkie part was shot in Hyderabad, Bangalore, Kolkata, Chennai and Bangkok while two songs were shot in Bulgaria marking it the first Telugu film to be shot there. Principal photography ended on 14 August 2014. The film released on 12 September 2014 to positive reviews from critics and was a commercial success.