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🔗 Computer science

In computer science, the shunting-yard algorithm is a method for parsing mathematical expressions specified in infix notation. It can produce either a postfix notation string, also known as Reverse Polish notation (RPN), or an abstract syntax tree (AST). The algorithm was invented by Edsger Dijkstra and named the "shunting yard" algorithm because its operation resembles that of a railroad shunting yard. Dijkstra first described the Shunting Yard Algorithm in the Mathematisch Centrum report MR 34/61.

Like the evaluation of RPN, the shunting yard algorithm is stack-based. Infix expressions are the form of mathematical notation most people are used to, for instance "3 + 4" or "3 + 4 × (2 − 1)". For the conversion there are two text variables (strings), the input and the output. There is also a stack that holds operators not yet added to the output queue. To convert, the program reads each symbol in order and does something based on that symbol. The result for the above examples would be (in Reverse Polish notation) "3 4 +" and "3 4 2 1 − × +", respectively.

The shunting-yard algorithm was later generalized into operator-precedence parsing.

🔗 Robotics

An eigenface () is the name given to a set of eigenvectors when used in the computer vision problem of human face recognition. The approach of using eigenfaces for recognition was developed by Sirovich and Kirby (1987) and used by Matthew Turk and Alex Pentland in face classification. The eigenvectors are derived from the covariance matrix of the probability distribution over the high-dimensional vector space of face images. The eigenfaces themselves form a basis set of all images used to construct the covariance matrix. This produces dimension reduction by allowing the smaller set of basis images to represent the original training images. Classification can be achieved by comparing how faces are represented by the basis set.

🔗 Physics 🔗 Philosophy 🔗 Philosophy/Philosophy of science 🔗 Philosophy/Contemporary philosophy

In theoretical physics, the problem of time is a conceptual conflict between general relativity and quantum mechanics in that quantum mechanics regards the flow of time as universal and absolute, whereas general relativity regards the flow of time as malleable and relative. This problem raises the question of what time really is in a physical sense and whether it is truly a real, distinct phenomenon. It also involves the related question of why time seems to flow in a single direction, despite the fact that no known physical laws seem to require a single direction.

🔗 Computing 🔗 Computing/Software

Sixel, short for "six pixels", is a bitmap graphics format supported by terminals and printers from DEC. It consists of a pattern six pixels high and one wide, resulting in 64 possible patterns. Each possible pattern is assigned an ASCII character, making the sixels easy to transmit on 7-bit serial links.

Sixel was first introduced as a way of sending bitmap graphics to DEC dot matrix printers like the LA50. After being put into "sixel mode" the following data was interpreted to directly control six of the pins in the nine-pin print head. A string of sixel characters encodes a single 6-pixel high row of the image.

The system was later re-used as a way to send bitmap data to the VT200 series and VT320 terminals when defining custom character sets. A series of sixels are used to transfer the bitmap for each character. This feature is known as soft character sets or dynamically redefinable character sets (DRCS). With the VT240, VT241, VT330, and VT340, the terminals could decode a complete sixel image to the screen, like those previously sent to printers.

🔗 Computing 🔗 Computing/Software

PAQ is a series of lossless data compression archivers that have gone through collaborative development to top rankings on several benchmarks measuring compression ratio (although at the expense of speed and memory usage). Specialized versions of PAQ have won the Hutter Prize and the Calgary Challenge. PAQ is free software distributed under the GNU General Public License.

🔗 Ancient Near East 🔗 Meteorology 🔗 Meteorology/droughts and fire events 🔗 Ancient Egypt

The 4.2-kiloyear BP aridification event was one of the most severe climatic events of the Holocene epoch. It defines the beginning of the current Meghalayan age in the Holocene epoch. Starting in about 2200 BC, it probably lasted the entire 22nd century BC. It has been hypothesised to have caused the collapse of the Old Kingdom in Egypt as well as the Akkadian Empire in Mesopotamia, and the Liangzhu culture in the lower Yangtze River area. The drought may also have initiated the collapse of the Indus Valley Civilisation, with some of its population moving southeastward to follow the movement of their desired habitat, as well as the migration of Indo-European-speaking people into India.

Some scientists disagree with this conclusion and point out that the event was neither a global drought nor did it happen in a clear timeline.

🔗 Film 🔗 Film/American cinema 🔗 Comedy 🔗 Chicago

Windy City Heat is a made-for-TV reality film produced by Comedy Central. It first aired on October 12, 2003.

🔗 United States 🔗 International relations 🔗 Disaster management 🔗 Medicine 🔗 Viruses 🔗 Death

The 2009 flu pandemic in the United States was a novel strain of the Influenza A/H1N1 virus, commonly referred to as "swine flu", that began in the spring of 2009. The virus had spread to the US from an outbreak in Mexico.

The U.S. Centers for Disease Control and Prevention (CDC) estimates that from April 12, 2009 to April 10, 2010, there were 60.8 million cases, 274,000 hospitalizations, and 12,469 deaths (0.02% infection fatality rate/Mortality rate) in the United States due to the virus.

🔗 Lists 🔗 Philosophy 🔗 Philosophy/Logic 🔗 Business 🔗 Psychology 🔗 Cognitive science

Cognitive biases are systematic patterns of deviation from norm or rationality in judgment, and are often studied in psychology and behavioral economics.

Although the reality of most of these biases is confirmed by reproducible research, there are often controversies about how to classify these biases or how to explain them. Some are effects of information-processing rules (i.e., mental shortcuts), called heuristics, that the brain uses to produce decisions or judgments. Biases have a variety of forms and appear as cognitive ("cold") bias, such as mental noise, or motivational ("hot") bias, such as when beliefs are distorted by wishful thinking. Both effects can be present at the same time.

There are also controversies over some of these biases as to whether they count as useless or irrational, or whether they result in useful attitudes or behavior. For example, when getting to know others, people tend to ask leading questions which seem biased towards confirming their assumptions about the person. However, this kind of confirmation bias has also been argued to be an example of social skill: a way to establish a connection with the other person.

Although this research overwhelmingly involves human subjects, some findings that demonstrate bias have been found in non-human animals as well. For example, loss aversion has been shown in monkeys and hyperbolic discounting has been observed in rats, pigeons, and monkeys.