Blackboard

A blackboard (also known as a chalkboard) is a reusable writing surface on which text or drawings are made with sticks of calcium sulfate or calcium carbonate, known, when used for this purpose, as chalk. Blackboards were originally made of smooth, thin sheets of black or dark grey slate stone. Modern versions are often green because the colour is considered easier on the eyes.

Design

A blackboard can simply be a piece of board painted with matte dark paint (usually black or dark green). Black plastic sign material, using the trade name sintra is also used to create custom chalkboard art. Examples can be seen at Chalk It Up Signs. A more modern variation consists of a coiled sheet of plastic drawn across two parallel rollers, which can be scrolled to create additional writing space while saving what has been written. The highest grade blackboards are made of a rougher version porcelain enamelled steel (black, green, blue or sometimes other colours). Porcelain is very hard wearing and blackboards made of porcelain usually last 10–20 years in intensive use.

Blackboard system

A blackboard system is an artificial intelligence application based on the blackboard architectural model, where a common knowledge base, the "blackboard", is iteratively updated by a diverse group of specialist knowledge sources, starting with a problem specification and ending with a solution. Each knowledge source updates the blackboard with a partial solution when its internal constraints match the blackboard state. In this way, the specialists work together to solve the problem. The blackboard model was originally designed as a way to handle complex, ill-defined problems, where the solution is the sum of its parts.

Metaphor

The following scenario provides a simple metaphor that gives some insight into how a blackboard functions:

A group of specialists are seated in a room with a large blackboard. They work as a team to brainstorm a solution to a problem, using the blackboard as the workplace for cooperatively developing the solution.

The session begins when the problem specifications are written onto the blackboard. The specialists all watch the blackboard, looking for an opportunity to apply their expertise to the developing solution. When someone writes something on the blackboard that allows another specialist to apply their expertise, the second specialist records their contribution on the blackboard, hopefully enabling other specialists to then apply their expertise. This process of adding contributions to the blackboard continues until the problem has been solved.

Blackboard (design pattern)

In software engineering, the blackboard pattern provides a computational framework for the design and implementation of systems that used to integrate large and diverse specialized modules, and implement complex, non deterministic control strategies. Blackboard pattern comes under behavioral design patter.

This pattern has been identified by the members of the HEARSAY-II project and first applied for speech recognition.

Structure

the blackboard model defines three main components:

Implementation

First step is to design the solution space (i.e. various solutions) which leads to leads to the definition of blackboard structure. Then, knowledge source are to be identified. These two activities are very related.

The next step is to specify the control component which is generally in the form of a complex schedular that makes use of a set of domain-specific heuristic to rate the relevance of executable knowledge sources.

Holography

Holography is the science and practice of making holograms. Typically, a hologram is a photographic recording of a light field, rather than of an image formed by a lens, and it is used to display a fully three-dimensional image of the holographed subject, which is seen without the aid of special glasses or other intermediate optics. The hologram itself is not an image and it is usually unintelligible when viewed under diffuse ambient light. It is an encoding of the light field as an interference pattern of seemingly random variations in the opacity, density, or surface profile of the photographic medium. When suitably lit, the interference pattern diffracts the light into a reproduction of the original light field and the objects that were in it appear to still be there, exhibiting visual depth cues such as parallax and perspective that change realistically with any change in the relative position of the observer.

In its pure form, holography requires the use of laser light for illuminating the subject and for viewing the finished hologram. In a side-by-side comparison under optimal conditions, a holographic image is visually indistinguishable from the actual subject, if the hologram and the subject are lit just as they were at the time of recording. A microscopic level of detail throughout the recorded volume of space can be reproduced. In common practice, however, major image quality compromises are made to eliminate the need for laser illumination when viewing the hologram, and sometimes, to the extent possible, also when making it. Holographic portraiture often resorts to a non-holographic intermediate imaging procedure, to avoid the hazardous high-powered pulsed lasers otherwise needed to optically "freeze" living subjects as perfectly as the extremely motion-intolerant holographic recording process requires. Holograms can now also be entirely computer-generated and show objects or scenes that never existed.

This Is Us (Backstreet Boys album)

This Is Us is the seventh studio album, sixth in the United States, from American pop group Backstreet Boys. It is their second and last album as a quartet. It was released on September 30, 2009 in Japan through Sony Music Japan, October 5, 2009 in the UK through RCA, and October 6 in the U.S. as the final studio album through Jive Records.

On the album, the group has reunited with previous collaborator and producer Max Martin (responsible for the previous hit "I Want It That Way") to try and create their best record since their 1999 worldwide hit album Millennium. They worked with Ryan Tedder, Claude Kelly, Jim Jonsin, RedOne, Ne-Yo, Brian Kennedy, Alex James, Pitbull, Eddie Galan, Rami Yacoub, Kristian Lundin, and T-Pain amongst others for the album as well.

The album debuted at number 9 on the US Billboard 200 making them the first group since Sade to have their first seven albums reach top 10 on the chart.RedOne produced the album's lead single "Straight Through My Heart" which was released in August/September 2009 and reached number 1 in Taiwan, number 3 in Japan, number 5 in Spain, number 106 in Billboard Hot 100, 19 in Canada, 72 in the UK, and 18 on the US Hot Dance Club Songs chart. It was their final album under Jive and their last album as a quartet before original member Kevin Richardson rejoined the band in 2012.

Hologram (disambiguation)

A hologram is a three-dimensional image created by holography.

Hologram may also refer to:

See also