PGR

PGR may stand for:

Project Gotham Racing (series)

Project Gotham Racing (PGR) was a series of racing video games developed by Bizarre Creations and published by Microsoft Studios (Xbox and Xbox 360) and Sega (Dreamcast). This franchise is exclusive to the Dreamcast, Xbox and Xbox 360 consoles, and consists of Metropolis Street Racer (Dreamcast), Project Gotham Racing (Xbox), Project Gotham Racing 2 (Xbox), Project Gotham Racing 3 (Xbox 360), and Project Gotham Racing 4 (Xbox 360).

The PGR series have a system called Kudos points. These are given for performing stunts with the vehicle (such as power sliding, overtaking another driver, two wheels, etc.). The longer the stunt is maintained, the more points the player receives. Colliding with the guard rails and other surroundings will cause the Kudos points from that stunt to be lost.

PGR2, PGR3 and PGR4 support gameplay via Xbox Live, while the first installment in the series does not.

The cover of each game in the Project Gotham Racing franchise has featured a Ferrari car on it, going from the F50 (PGR) to the Enzo (PGR2), the F430 (PGR3), and the 599 GTB Fiorano (PGR4). The car manufacturer was even the main focus of a free mobile entry in the series, PGR: Ferrari Edition for the Zune HD, similar to that of Porsche in Need for Speed: Porsche Unleashed.

Cage

Cage may refer to:

Technology

Rolling-element bearing

A rolling-element bearing, also known as a rolling bearing, is a bearing which carries a load by placing rolling elements (such as balls or rollers) between two bearing rings called races. The relative motion of the races causes the rolling elements to roll with very little rolling resistance and with little sliding.

One of the earliest and best-known rolling-element bearings are sets of logs laid on the ground with a large stone block on top. As the stone is pulled, the logs roll along the ground with little sliding friction. As each log comes out the back, it is moved to the front where the block then rolls on to it. It is possible to imitate such a bearing by placing several pens or pencils on a table and placing an item on top of them. See "bearings" for more on the historical development of bearings.

A rolling element rotary bearing uses a shaft in a much larger hole, and cylinders called "rollers" tightly fill the space between the shaft and hole. As the shaft turns, each roller acts as the logs in the above example. However, since the bearing is round, the rollers never fall out from under the load.

Cage (graph theory)

In the mathematical area of graph theory, a cage is a regular graph that has as few vertices as possible for its girth.

Formally, an (r,g)-graph is defined to be a graph in which each vertex has exactly r neighbors, and in which the shortest cycle has length exactly g. It is known that an (r,g)-graph exists for any combination of r ≥ 2 and g ≥ 3. An (r,g)-cage is an (r,g)-graph with the fewest possible number of vertices, among all (r,g)-graphs.

If a Moore graph exists with degree r and girth g, it must be a cage. Moreover, the bounds on the sizes of Moore graphs generalize to cages: any cage with odd girth g must have at least

vertices, and any cage with even girth g must have at least

vertices. Any (r,g)-graph with exactly this many vertices is by definition a Moore graph and therefore automatically a cage.

There may exist multiple cages for a given combination of r and g. For instance there are three nonisomorphic (3,10)-cages, each with 70 vertices : the Balaban 10-cage, the Harries graph and the Harries–Wong graph. But there is only one (3,11)-cage : the Balaban 11-cage (with 112 vertices).