Operation Sigma Sigma

The Sigma is an experimental glider developed in Britain from 1966 by a team led by Nicholas Goodhart. After disappointing performance during flight testing the Sigma was passed on to a Canadian group which carried out modifications, making the Sigma more competitive.

Design and development

Designed to compete in the 1970 World Championships, the team aimed to develop a wing that would climb well through a high lift coefficient and a large wing area, but equally had the "maximum possible reduction of area for cruise at low lift coefficients". At the same time for the minimum possible drag they aimed for "extensive" laminar flow. To achieve this they employed flaps that would alter both wing area and wing camber. Based on analysis of the nature of thermals encountered in cross-country flying, they reasoned that by having a slow turning circle, their sailplane could stay close to the central (and strongest) part of the thermal and gain maximum benefit.

Its unusual feature is its ability to vary its wing area using Fowler flaps. It had been tried before by the Hannover Akaflieg in 1938 with their AFH-4, the South African Beatty-Johl BJ-2 Assegai and the SZD Zefir gliders.

Sigma (cosmology)

Sigma in cosmology was a property of galaxies used when trying to work out the mystery of galaxies and their supermassive black holes.

History

In the late 1990s the NUKER experts had made observations with a spectroscope of two galaxies, one of an active galaxy with an active galactic nucleus called NGC10-68 and a dormant galaxy next door to us named Andromeda.

The observations are shown. The light from the centre in Andromeda galaxy was distorted proving the existence of super-massive black holes.

Other observations proved most galaxies had a similar centre whether it be active or dormant.

They then realised that the black holes must have something to do with a galaxy's formation, so they turned to something they thought was useless: the speed of the stars around the edge of the galaxy. This was Sigma, the speed of the stars at the edge of the galaxy supposedly unaffected by the mass of the black hole at the centre.

Usage In Cosmology

The NUKER team calculated the sigma of several stars in different galaxies and the mass of the black hole at the (nucleus) centre. They expected no correlation what so ever. But when plotting their results on a Scatter diagram and drawing a line of best fit they ended up with a positive correlation. It appeared that the heavier the black hole at the centre was the faster the stars within the galaxy travelled.

Sigma (duo)

Sigma is an English drum and bass duo consisting of Cameron Edwards and Joe Lenzie. They met at Leeds University at drum and bass nights. Their 2010 collaboration with DJ Fresh, "Lassitude", peaked at number 98 on the UK Singles Chart. Their single "Nobody to Love" topped the UK Singles Chart, becoming their first UK number one. Follow-up single "Changing", featuring Paloma Faith, also got to number one.

Career

Formation

Lenzie and Edwards met in 2006 at Leeds University; Cameron was working in local record store Tribe Records and with Echo Location's Obi running local night Event Horizon, while Lenzie was DJing hip-hop and warming up Event Horizon for such acts as Rahzel and Grandmaster Flash. Once they had finished in Leeds, they relocated to London and became a three-piece with Edwards' school friend Ben Mauerhoff, being signed under DJ Fresh's Breakbeat Kaos. After a while, long distances took their toll – Edwards and Mauerhoff were based in Surrey, whereas Lenzie was based in Harpenden, Hertfordshire and they couldn't get three people into the Harpenden studio – and Mauerhoff left. In December 2008 they formed their own record label, Life Recordings (so called because, according to Lenzie, the industry demanded that it be their life). Its inaugural release was a VIP mix of their early Bingo Beats single "El Presidente".

Wear

Wear is related to interactions between surfaces and specifically the removal and deformation of material on a surface as a result of mechanical action of the opposite surface.

In materials science, wear is erosion or sideways displacement of material from its "derivative" and original position on a solid surface performed by the action of another surface.

Wear of metals occurs by the plastic displacement of surface and near-surface material and by the detachment of particles that form wear debris. This process may occur by contact with other metals, nonmetallic solids, flowing liquids, or solid particles or liquid droplets entrained in flowing gasses.

Wear can also be defined as a process where interaction between two surfaces or bounding faces of solids within the working environment results in dimensional loss of one solid, with or without any actual decoupling and loss of material. Aspects of the working environment which affect wear include loads and features such as unidirectional sliding, reciprocating, rolling, and impact loads, speed, temperature, but also different types of counter-bodies such as solid, liquid or gas and type of contact ranging between single phase or multiphase, in which the last multiphase may combine liquid with solid particles and gas bubbles.

Jibe

A jibe (US) or gybe (Britain) is a sailing maneuver whereby a sailing vessel reaching downwind turns its stern through the wind, such that the wind direction changes from one side of the boat to the other. For square-rigged ships, this maneuver is called wearing ship.

In this maneuver, the mainsail will cross the center of the boat while the jib is pulled to the other side of the boat. If the spinnaker is up, the pole will have to be manually moved to the other side, to remain opposite the mainsail. In a dinghy, raising the centerboard can increase the risk of capsizing during what can be a somewhat violent maneuver, although the opposite is true of a dinghy with a flat, planing hull profile: raising the centerboard reduces heeling moment during the manouevre and so reduces the risk of capsize.

The other way to change the side of the boat that faces the wind is turning the bow of the boat into, and then through, the direction of the wind. This operation is known as tacking or coming about. Tacking more than 180° to avoid a jibe is sometimes referred to as a 'chicken jibe'.

Wear (surname)

Wear is a surname, and may refer to: