Screw

A screw is a type of fastener, sometimes similar to a bolt (see Differentiation between bolt and screw below), typically made of metal, and characterized by a helical ridge, known as a male thread (external thread) or just thread. A screw is an inclined plane wrapped around a nail. Some screw threads are designed to mate with a complementary thread, known as a female thread (internal thread), often in the form of a nut or an object that has the internal thread formed into it. Other screw threads are designed to cut a helical groove in a softer material as the screw is inserted. The most common uses of screws are to hold objects together and to position objects.

A screw will usually have a head on one end that contains a specially formed shape that allows it to be turned, or driven, with a tool. Common tools for driving screws include screwdrivers and wrenches. The head is usually larger than the body of the screw, which keeps the screw from being driven deeper than the length of the screw and to provide a bearing surface. There are exceptions; for instance, carriage bolts have a domed head that is not designed to be driven; set screws often have a head smaller than the outer diameter of the screw; J-bolts have a J-shaped head which is not designed to be driven, but rather is usually sunk into concrete allowing it to be used as an anchor bolt. The cylindrical portion of the screw from the underside of the head to the tip is known as the shank; it may be fully threaded or partially threaded. The distance between each thread is called the "pitch".

Screw (card game)

Screw, Moonshine, or Popcorn is a card game where the players try to be the first to lose all their cards. Like Palase, it is derived from the Finnish card game Paskahousu.

Rules

Screw (song)

"Screw" (stylized as SCREW) was 14th single by the J-pop singer, Kotoko, was released on December 16, 2009. The title track was used as the theme song for Mamoru Oshii's film Assault Girls.

The single comes in a limited CD+DVD edition (GNCV-0022) and a regular CD-only edition (GNCV-0023). The DVD contains the promotional video for "SCREW".

Track listing

Charts and sales

References

Duality

Duality may refer to:

Mathematics

Philosophy, logic, and psychology

Science

Electrical and mechanical

Duality (projective geometry)

In geometry a striking feature of projective planes is the symmetry of the roles played by points and lines in the definitions and theorems, and (plane) duality is the formalization of this concept. There are two approaches to the subject of duality, one through language (§ Principle of Duality) and the other a more functional approach through special mappings. These are completely equivalent and either treatment has as its starting point the axiomatic version of the geometries under consideration. In the functional approach there is a map between related geometries that is called a duality. Such a map can be constructed in many ways. The concept of plane duality readily extends to space duality and beyond that to duality in any finite-dimensional projective geometry.

Principle of Duality

A projective plane C may be defined axiomatically as an incidence structure, in terms of a set P of points, a set L of lines, and an incidence relation I that determines which points lie on which lines. These sets can be used to define a plane dual structure.

Duality (CoPs)

In the context of a Community of practice the notion of a duality is used to capture the idea of the tension between two opposing forces which become a driving force for change and creativity. Wenger (Wenger 1998) uses the concept of dualities to examine the forces that create and sustain a Community of Practice. He describes a duality thus: '... a single conceptual unit that is formed by two inseparable and mutually constitutive elements whose inherent tensions and complementarity give the concept richness and dynamism' (Wenger 1998, p. 66).

Some compare the concept of a duality to that of Yin and Yang, i.e. two mutually defining opposites.

The opposing entities in a duality need to be viewed from a perspective of balance rather than opposition. The term implies a dynamism, continual change and mutual adjustment as the tensions that are inherent in dualities can be both creative and constraining. (Wenger 1998) identifies four dualities that exist in Communities of Practice: participation-reification, designed-emergent, identification-negotiability and local-global.