Hard (surname)

Hard is a surname. Notable people with the surname include:

Hardcourt

A hardcourt (or hard court) is a surface or floor on which a sport is played, most usually in reference to tennis courts. They are typically made of rigid materials such as asphalt or concrete, and covered with acrylic material to seal the surface and mark the playing lines, while providing some cushioning. Historically, hardwood surfaces were also in use in indoor settings, similar to an indoor basketball court, but these are now rare.

Tennis

Tennis hard courts are made of synthetic/acrylic layers on top of a concrete or asphalt foundation and can vary in color. These courts tend to play medium-fast to fast because there is little energy absorption by the court, like in grass courts. The ball tends to bounce high and players are able to apply many types of spin during play. Flat balls are favored on hard courts because of the extremely quick play style. Speed of rebound after tennis balls bounce on hard courts is determined by how much sand is in the synthetic/acrylic layer placed on top of the asphalt foundation. More sand will result in a slower bounce due to more friction.

Complete (complexity)

In computational complexity theory, a computational problem is complete for a complexity class if it is, in a technical sense, among the "hardest" (or "most expressive") problems in the complexity class.

More formally, a problem p is called hard for a complexity class C under a given type of reduction, if there exists a reduction (of the given type) from any problem in C to p. If a problem is both hard for the class and a member of the class, it is complete for that class (for that type of reduction).

A problem that is complete for a class C is said to be C-complete, and the class of all problems complete for C is denoted C-complete. The first complete class to be defined and the most well-known is NP-complete, a class that contains many difficult-to-solve problems that arise in practice. Similarly, a problem hard for a class C is called C-hard, e.g. NP-hard.

Normally it is assumed that the reduction in question does not have higher computational complexity than the class itself. Therefore it may be said that if a C-complete problem has a "computationally easy" solution, then all problems in "C" have an "easy" solution.

Cave

A cave or cavern is a hollow place in the ground, especially a natural underground space large enough for a human to enter. Caves form naturally by the weathering of rock and often extend deep underground. The word cave can also refer to much smaller openings such as sea caves, rock shelters, and grottos.

Speleology is the science of exploration and study of all aspects of caves and the cave environment. Visiting or exploring caves for recreation may be called caving, potholing, or spelunking.

Types and formation

The formation and development of caves is known as speleogenesis. Caves are formed by various geologic processes and can be variable sizes. These may involve a combination of chemical processes, erosion from water, tectonic forces, microorganisms, pressure, and atmospheric influences.

It is estimated that the maximum depth of a cave cannot be more than 3,000 metres (9,800 ft) due to the pressure of overlying rocks. For karst caves the maximum depth is determined on the basis of the lower limit of karst forming processes, coinciding with the base of the soluble carbonate rocks.

Cave, Lazio

Cave is a town and comune in the Latium region of Italy, 42 kilometres (26 mi) southeast of Rome. As of 2011 its population was of 10,421.

History

The town was mentioned first in 998 AD, and was later a fief of the Colonna family. In 1482 it was besieged by Pope Sixtus IV and obliged to surrender. It is especially known for the Treaty of Cave, signed on 12 September 1557 by plenipotentiaries of Pope Paul IV and Fernando Álvarez de Toledo, the Spanish viceroy of Naples.

Geography

Cave borders with Castel San Pietro Romano, Genazzano, Palestrina, Rocca di Cave, and Valmontone. It counts the hamlets (frazioni) of Collepalme and San Bartolomeo.

References

External links

Media related to Cave at Wikimedia Commons

Cave (song)

"Cave" is the second single by English alternative rock band Muse, and the second to be released from their debut album, Showbiz. It was released on 7" vinyl—backed with an instrumental remix of the song—and double CD—backed with a remix of the song alongside "Twin," "Host," and "Coma";—on 6 September 1999 and reached #52 in the UK Singles Chart—an improvement of 21 positions on "Uno". In the United States a five-track extended play was also released by Maverick Records. "Cave" also appears on the soundtrack for the film Little Nicky.

Background

Bellamy has given two statements about what Cave is about. Once he said it was about "an old friend of mine" in a strangely warbled voice before a live performance of the song and on a different occasion he stated "The idea for Cave came from that rubbish American book, Men Are From Mars, Women Are From Venus. There's this bit about how men go into a cave when they get stressed and I think that's probably true, although, personally, I tend to let it out. I did have a bit of a tantrum in my hotel bathroom last night - but I managed to repair the toilet, so that's OK."