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🔗 Astronomy 🔗 Weather 🔗 Astronomy/Solar System 🔗 Weather/Weather 🔗 Weather/Space weather

Saturn's hexagon is a persistent approximately hexagonal cloud pattern around the north pole of the planet Saturn, located at about 78°N. The sides of the hexagon are about 14,500 km (9,000 mi) long, which is about 2,000 km (1,200 mi) longer than the diameter of Earth. The hexagon may be a bit more than 29,000 km (18,000 mi) wide, may be 300 km (190 mi) high, and may be a jet stream made of atmospheric gases moving at 320 km/h (200 mph). It rotates with a period of 10h 39m 24s, the same period as Saturn's radio emissions from its interior. The hexagon does not shift in longitude like other clouds in the visible atmosphere.

Saturn's hexagon was discovered during the Voyager mission in 1981, and was later revisited by Cassini-Huygens in 2006. During the Cassini mission, the hexagon changed from a mostly blue color to more of a golden color. Saturn's south pole does not have a hexagon, as verified by Hubble observations. It does, however, have a vortex, and there is also a vortex inside the northern hexagon. Multiple hypotheses for the hexagonal cloud pattern have been developed.

🔗 Linguistics 🔗 Antarctica 🔗 Languages 🔗 English Language

Antarctic English is a variety of the English language spoken by people living on the continent of Antarctica and within the subantarctic islands.^: vii Spoken primarily by scientists and workers in the Antarctic tourism industry, it consists of various unique words and is spoken with a unique accent. During the 19th and 20th centuries, Antarctic English was influenced by Spanish-speaking South Americans and Northern European explorers who introduced new words that continue to be used today.

🔗 Computer science

Boids is an artificial life program, developed by Craig Reynolds in 1986, which simulates the flocking behaviour of birds. His paper on this topic was published in 1987 in the proceedings of the ACM SIGGRAPH conference. The name "boid" corresponds to a shortened version of "bird-oid object", which refers to a bird-like object. Incidentally, "boid" is also a New York Metropolitan dialect pronunciation for "bird".

As with most artificial life simulations, Boids is an example of emergent behavior; that is, the complexity of Boids arises from the interaction of individual agents (the boids, in this case) adhering to a set of simple rules. The rules applied in the simplest Boids world are as follows:

• separation: steer to avoid crowding local flockmates
• alignment: steer towards the average heading of local flockmates
• cohesion: steer to move towards the average position (center of mass) of local flockmates

More complex rules can be added, such as obstacle avoidance and goal seeking.

The basic model has been extended in several different ways since Reynolds proposed it. For instance, Delgado-Mata et al. extended the basic model to incorporate the effects of fear. Olfaction was used to transmit emotion between animals, through pheromones modelled as particles in a free expansion gas. Hartman and Benes introduced a complementary force to the alignment that they call the change of leadership. This steer defines the chance of the boid to become a leader and try to escape.

The movement of Boids can be characterized as either chaotic (splitting groups and wild behaviour) or orderly. Unexpected behaviours, such as splitting flocks and reuniting after avoiding obstacles, can be considered emergent.

The boids framework is often used in computer graphics, providing realistic-looking representations of flocks of birds and other creatures, such as schools of fish or herds of animals. It was for instance used in the 1998 video game Half-Life for the flying bird-like creatures seen at the end of the game on Xen, named "boid" in the game files.

The Boids model can be used for direct control and stabilization of teams of simple Unmanned Ground Vehicles (UGV) or Micro Aerial Vehicles (MAV) in swarm robotics. For stabilization of heterogeneous UAV-UGV teams, the model was adapted for using onboard relative localization by Saska et al.

At the time of proposal, Reynolds' approach represented a giant step forward compared to the traditional techniques used in computer animation for motion pictures. The first animation created with the model was Stanley and Stella in: Breaking the Ice (1987), followed by a feature film debut in Tim Burton's film Batman Returns (1992) with computer generated bat swarms and armies of penguins marching through the streets of Gotham City.

The boids model has been used for other interesting applications. It has been applied to automatically program Internet multi-channel radio stations. It has also been used for visualizing information and for optimization tasks.

🔗 Typography

An ink trap is a feature of certain typefaces designed for printing in small sizes. At an ink trap, the corners or details are removed from the letterforms. When the type is printed, ink naturally spreads into the removed area. Without ink traps, the excess ink would soak outwards and ruin the crisp edge.

Ink traps are only needed for small point sizes and are usually only found on typefaces designed for printing on newsprint. Fonts of this kind are applicable for classifieds or telephone books. Typefaces with ink traps may be offered in versions without them for display on screen or at larger sizes.

Typefaces featuring ink traps include Retina, Bell Centennial, and Tang.

🔗 Computing 🔗 Computing/Software 🔗 Computing/Free and open-source software 🔗 Linux

The Linux Router Project (LRP) is a now defunct networking-centric micro Linux distribution. The released versions of LRP were small enough to fit on a single 1.44MB floppy disk, and made building and maintaining routers, access servers, thin servers, thin clients, network appliances, and typically embedded systems next to trivial.

🔗 India 🔗 Numismatics 🔗 India/Indian politics workgroup

A zero-rupee note is a banknote imitation issued in India as a means of helping to fight systemic political corruption. The notes are "paid" in protest by angry citizens to government functionaries who solicit bribes in return for services which are supposed to be free. Zero-rupee notes, which are made to resemble the old 50-rupee banknote of India, are the creation of a non-governmental organization known as 5th Pillar which has, since their inception in 2007, distributed over 2.5 million notes as of August 2014. The notes remain in current use and thousands of notes are distributed every month.

🔗 Politics 🔗 Psychology 🔗 Sociology

A collective action problem or social dilemma is a situation in which all individuals would be better off cooperating but fail to do so because of conflicting interests between individuals that discourage joint action. The collective action problem has been addressed in political philosophy for centuries, but was most clearly established in 1965 in Mancur Olson's The Logic of Collective Action.

Problems arise when too many group members choose to pursue individual profit and immediate satisfaction rather than behave in the group's best long-term interests. Social dilemmas can take many forms and are studied across disciplines such as psychology, economics, and political science. Examples of phenomena that can be explained using social dilemmas include resource depletion and low voter turnout. The collective action problem can be understood through the analysis of game theory and the free-rider problem, which results from the provision of public goods. Additionally, the collective problem can be applied to numerous public policy concerns that countries across the world currently face.

🔗 Disability

The curb cut effect is the phenomenon of disability-friendly features being used and appreciated by a larger group than the people they were designed for. For example, many hearing people use closed captioning. The phenomenon is named for curb cuts – miniature ramps comprising parts of sidewalk – which were first made for wheelchair access in particular places, but are now universal and no longer widely recognized as a disability-accessibility feature.

The curb cut effect is a subset of universal design, which is the purposeful design of an environment so that it is accessible to all people regardless of ability or disability. The curb cut effect differs slightly from universal design as the curb cut phenomenon is often unintentional rather than purposeful, but results in a similar outcome.

🔗 Computer science 🔗 Mathematics

In combinatory logic for computer science, a fixed-point combinator (or fixpoint combinator),^: p.26 is a higher-order function (i.e. a function which takes a function as argument) that returns some fixed point (a value that is mapped to itself) of its argument function, if one exists.

Formally, if ${\displaystyle {\textsf {fix}}}$ is a fixed-point combinator and the function ${\displaystyle f}$ has one or more fixed points, then ${\displaystyle {\textsf {fix}}\ f}$ is one of these fixed points, i.e.

${\displaystyle f\ ({\textsf {fix}}\ f)={\textsf {fix}}\ f\ .}$

Fixed-point combinators can be defined in the lambda calculus and in functional programming languages and provide a means to allow for recursive definitions.

🔗 Computer science

Tacit programming, also called point-free style, is a programming paradigm in which function definitions do not identify the arguments (or "points") on which they operate. Instead the definitions merely compose other functions, among which are combinators that manipulate the arguments. Tacit programming is of theoretical interest, because the strict use of composition results in programs that are well adapted for equational reasoning. It is also the natural style of certain programming languages, including APL and its derivatives, and concatenative languages such as Forth. The lack of argument naming gives point-free style a reputation of being unnecessarily obscure, hence the epithet "pointless style".

Unix scripting uses the paradigm with pipes.