Disk (mathematics)

In geometry, a disk (also spelled disc) is the region in a plane bounded by a circle. A disk is said to be closed or open according to whether it contains the circle that constitutes its boundary.

Formulas

In Cartesian coordinates, the open disk of center and radius R is given by the formula

while the closed disk of the same center and radius is given by

The area of a closed or open disk of radius R is πR² (see area of a disk).

Properties

The disk has circular symmetry.

The open disk and the closed disk are not topologically equivalent (that is, they are not homeomorphic), as they have different topological properties from each other. For instance, every closed disk is compact whereas every open disk is not compact. However from the viewpoint of algebraic topology they share many properties: both of them are contractible and so are homotopy equivalent to a single point. This implies that their fundamental groups are trivial, and all homology groups are trivial except the 0th one, which is isomorphic to Z. The Euler characteristic of a point (and therefore also that of a closed or open disk) is 1.

Floppy disk

A floppy disk, also called a diskette or just disk, is a type of disk storage composed of a disk of thin and flexible magnetic storage medium, sealed in a rectangular plastic carrier lined with fabric that removes dust particles. Floppy disks are read and written by a floppy disk drive (FDD).

Floppy disks, initially as 8-inch (200 mm) media and later in 5¼-inch (133 mm) and 3½-inch (90 mm) sizes, were a ubiquitous form of data storage and exchange from the mid-1970s well into the 2000s.

By 2010, computer motherboards are rarely manufactured with floppy drive support; 3½-inch floppy disks can be used with an external USB floppy disk drive, but USB drives for 5¼-inch, 8-inch, and non-standard diskettes are rare to non-existent. These formats are usually handled by older equipment.

While floppy disk drives still have some limited uses, especially with legacy industrial computer equipment, they have been superseded by data storage methods with much greater capacity, such as USB flash sticks, flash storage cards, portable external hard disk drives, optical discs, and computer networks.

Sim

Sim or SIM may refer to:

Computing and technology

Organizations

Sim (Korean surname)

Sim or Shim is a Korean surname. There are six Shim clans in Korea based in the regions ofCheongsong, Pungsan, Samcheok, Buyu, Uiryeong, and Jeonju. The biggest Sim clan is Cheongsong; they comprise about 85% of the all those with the surname Shim. Fourteen percent of all Korean Shims are members of the Pungsan and Samcheok clans. As of 2000, there were 252,255 people with this surname in South Korea, less than 1% of the population.

List of famous people

Similitude (Star Trek: Enterprise)

"Similitude" is the tenth episode from the third season of the television series Star Trek: Enterprise. It first aired on November 19, 2003 and was the sixty-second episode of the series.

Plot

Commander Tucker, while endeavoring to increase to stable speed of Enterprise to Warp 5, becomes comatose when the engines destabilize and explode. Doctor Phlox suggests a radical and controversial procedure to save him - growing a mimetic symbiote as a neurological donor. Archer, concerned with the overarching goal of their mission, gives the order to do so. The symbiote, with a natural life-span of two weeks, is then injected with Tucker's blood and is soon born. Phlox names him "Sim", and as he develops rapidly, Tucker's memories and personality begin to express themselves (including an interest in engineering, and a romantic attraction to Sub-Commander T'Pol).

The window of time approaches when Phlox must perform the transplant, which, according to him, will unfortunately now be fatal to Sim-Trip. Sim, having now 'met' himself in sickbay, reveals knowledge of an experimental procedure that might allow for an extension (presumably by decades) of his lifespan. Archer learns that Phlox was aware of this procedure, but concealed his knowledge of it due to its highly experimental and poorly researched nature. Sim then expresses a strong desire to live —Tucker's own life notwithstanding—through the rest of his natural life. Later, a tired-looking Archer, angered at finding Sim in Trip's quarters, states he would rather Sim voluntarily submit to the fatal procedure than be forced to do so.