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🔗 Cognitive science 🔗 Robotics

A cognitive architecture refers to both a theory about the structure of the human mind and to a computational instantiation of such a theory used in the fields of artificial intelligence (AI) and computational cognitive science. One of the main goals of a cognitive architecture is to summarize the various results of cognitive psychology in a comprehensive computer model. However, the results need to be formalized so far as they can be the basis of a computer program. The formalized models can be used to further refine a comprehensive theory of cognition, and more immediately, as a commercially usable model. Successful cognitive architectures include ACT-R (Adaptive Control of Thought - Rational) and SOAR.

The Institute for Creative Technologies defines cognitive architecture as: "hypothesis about the fixed structures that provide a mind, whether in natural or artificial systems, and how they work together – in conjunction with knowledge and skills embodied within the architecture – to yield intelligent behavior in a diversity of complex environments."

🔗 Physics 🔗 Astronomy 🔗 Time 🔗 Holidays 🔗 Festivals

A solstice is an event occurring when the Sun appears to reach its most northerly or southerly excursion relative to the celestial equator on the celestial sphere. Two solstices occur annually, around June 21 and December 21. In many countries, the seasons of the year are determined by reference to the solstices and the equinoxes.

The term solstice can also be used in a broader sense, as the day when this occurs. The day of a solstice in either hemisphere has either the most sunlight of the year (summer solstice) or the least sunlight of the year (winter solstice) for any place other than the Equator. Alternative terms, with no ambiguity as to which hemisphere is the context, are "June solstice" and "December solstice", referring to the months in which they take place every year.

The word solstice is derived from the Latin sol ("sun") and sistere ("to stand still"), because at the solstices, the Sun's declination appears to "stand still"; that is, the seasonal movement of the Sun's daily path (as seen from Earth) pauses at a northern or southern limit before reversing direction.

Interactive EasyFlow was one of the first diagramming and flow charting software packages available for personal computers. This product was the flagship software produced by HavenTree Software Limited, of Kingston, Ontario Canada. HavenTree software, formed in 1981, offered predecessor non-interactive products "EasyFlow" (1983) and "EasyFlow-Plus" (1984). Interactive EasyFlow - so named to distinguish it from the preceding products - was offered from 1985 until the early 1990s, when the company dropped the "Interactive" adjective in favour of simply "HavenTree EasyFlow". It offered the software for sale until it filed for protection under Canada's Bankruptcy and Insolvency Act in April 1996. The assets of the company were purchased by SPSS Inc. in 1998.

🔗 Books 🔗 Business 🔗 Comics 🔗 Comics/Comic strips

The Dilbert principle is a concept in management developed by Scott Adams, creator of the comic strip Dilbert, which states that companies tend to systematically promote incompetent employees to management to get them out of the workflow. The Dilbert principle is inspired by the Peter principle, which holds that employees are promoted based on success in their current position until they reach their "level of incompetence" and are no longer promoted. Under the Dilbert principle, employees who were never competent are promoted to management to limit the damage they can do. Adams first explained the principle in a 1995 Wall Street Journal article, and expanded upon it in his 1996 business book The Dilbert Principle.

🔗 Mathematics 🔗 Percussion

To hear the shape of a drum is to infer information about the shape of the drumhead from the sound it makes, i.e., from the list of overtones, via the use of mathematical theory.

"Can One Hear the Shape of a Drum?" is the title of a 1966 article by Mark Kac in the American Mathematical Monthly which made the question famous, though this particular phrasing originates with Lipman Bers. Similar questions can be traced back all the way to Hermann Weyl . For his paper, Kac was given the Lester R. Ford Award in 1967 and the Chauvenet Prize in 1968.

The frequencies at which a drumhead can vibrate depend on its shape. The Helmholtz equation calculates the frequencies if the shape is known. These frequencies are the eigenvalues of the Laplacian in the space. A central question is whether the shape can be predicted if the frequencies are known; for example, whether a circle-shaped triangle can be recognized in this way. Kac admitted he did not know if it was possible for two different shapes to yield the same set of frequencies. The question of whether the frequencies determine the shape was finally answered in the negative in the early 1990s by Gordon, Webb and Wolpert.

🔗 Mathematics 🔗 Ancient Egypt 🔗 British Museum

The Rhind Mathematical Papyrus (RMP; also designated as papyrus British Museum 10057 and pBM 10058) is one of the best known examples of ancient Egyptian mathematics. It is named after Alexander Henry Rhind, a Scottish antiquarian, who purchased the papyrus in 1858 in Luxor, Egypt; it was apparently found during illegal excavations in or near the Ramesseum. It dates to around 1550 BC. The British Museum, where the majority of the papyrus is now kept, acquired it in 1865 along with the Egyptian Mathematical Leather Roll, also owned by Henry Rhind. There are a few small fragments held by the Brooklyn Museum in New York City and an 18 cm (7.1 in) central section is missing. It is one of the two well-known Mathematical Papyri along with the Moscow Mathematical Papyrus. The Rhind Papyrus is larger than the Moscow Mathematical Papyrus, while the latter is older.

The Rhind Mathematical Papyrus dates to the Second Intermediate Period of Egypt. It was copied by the scribe Ahmes (i.e., Ahmose; Ahmes is an older transcription favoured by historians of mathematics), from a now-lost text from the reign of king Amenemhat III (12th dynasty). Written in the hieratic script, this Egyptian manuscript is 33 cm (13 in) tall and consists of multiple parts which in total make it over 5 m (16 ft) long. The papyrus began to be transliterated and mathematically translated in the late 19th century. The mathematical translation aspect remains incomplete in several respects. The document is dated to Year 33 of the Hyksos king Apophis and also contains a separate later historical note on its verso likely dating from the period ("Year 11") of his successor, Khamudi.

In the opening paragraphs of the papyrus, Ahmes presents the papyrus as giving "Accurate reckoning for inquiring into things, and the knowledge of all things, mysteries ... all secrets". He continues with:

This book was copied in regnal year 33, month 4 of Akhet, under the majesty of the King of Upper and Lower Egypt, Awserre, given life, from an ancient copy made in the time of the King of Upper and Lower Egypt Nimaatre. The scribe Ahmose writes this copy.

Several books and articles about the Rhind Mathematical Papyrus have been published, and a handful of these stand out. The Rhind Papyrus was published in 1923 by Peet and contains a discussion of the text that followed Griffith's Book I, II and III outline. Chace published a compendium in 1927–29 which included photographs of the text. A more recent overview of the Rhind Papyrus was published in 1987 by Robins and Shute.

In computer science and mathematics, a full employment theorem is a term used, often humorously, to refer to a theorem which states that no algorithm can optimally perform a particular task done by some class of professionals. The name arises because such a theorem ensures that there is endless scope to keep discovering new techniques to improve the way at least some specific task is done.

For example, the full employment theorem for compiler writers states that there is no such thing as a provably perfect size-optimizing compiler, as such a proof for the compiler would have to detect non-terminating computations and reduce them to a one-instruction infinite loop. Thus, the existence of a provably perfect size-optimizing compiler would imply a solution to the halting problem, which cannot exist. This also implies that there may always be a better compiler since the proof that one has the best compiler cannot exist. Therefore, compiler writers will always be able to speculate that they have something to improve. A similar example in practical computer science is the idea of no free lunch in search and optimization, which states that no efficient general-purpose solver can exist, and hence there will always be some particular problem whose best known solution might be improved.

Similarly, Gödel's incompleteness theorems have been called full employment theorems for mathematicians. In theoretical computer science this field of study is known as Kolmogorov complexity, or the smallest program which outputs a given string.

Tasks such as virus writing and detection, and spam filtering and filter-breaking are also subject to Rice's theorem.

🔗 Yugoslavia 🔗 Economics

Despite common origins, the economy of the Socialist Federal Republic of Yugoslavia (SFRY) was significantly different from the economies of the Soviet Union and other Eastern European socialist states, especially after the Yugoslav-Soviet break-up in 1948. The occupation and liberation struggle in World War II left Yugoslavia's infrastructure devastated. Even the most developed parts of the country were largely rural and the little industry of the country was largely damaged or destroyed.

🔗 Computing

Excess-3, 3-excess or 10-excess-3 binary code (often abbreviated as XS-3, 3XS or X3), shifted binary or Stibitz code (after George Stibitz, who built a relay-based adding machine in 1937) is a self-complementary binary-coded decimal (BCD) code and numeral system. It is a biased representation. Excess-3 code was used on some older computers as well as in cash registers and hand-held portable electronic calculators of the 1970s, among other uses.

🔗 Biography 🔗 India 🔗 India/Bihar

Dashrath Manjhi (1934 – 17 August 2007), also known as Mountain Man, was a laborer in Gehlaur village, near Gaya in Bihar, India, who carved a path 110 m long (360 ft), 9.1 m (30 ft) wide and 7.7 m (25 ft) deep through a ridge of hills using only a hammer and chisel. After 22 years of work, Dashrath shortened travel between the Atri and Wazirganj blocks of Gaya town from 55 km to 15 km.