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π Lojban
Lojban (pronounced [ΛloΚban] (listen)) is a constructed, syntactically unambiguous human language created by the Logical Language Group and succeeding the Loglan project.
The Logical Language Group (LLG) began developing Lojban in 1987. The LLG sought to realize Loglan's purposes, and further improve the language by making it more usable and freely available (as indicated by its official full English title, "Lojban: A Realization of Loglan"). After a long initial period of debating and testing, the baseline was completed in 1997, and published as The Complete Lojban Language. In an interview in 2010 with The New York Times, Arika Okrent, the author of In the Land of Invented Languages, stated: "The constructed language with the most complete grammar is probably Lojbanβa language created to reflect the principles of logic."
Lojban is proposed as a speakable language for communication between people of different language backgrounds, as a potential means of machine translation and to explore the intersection of human language and software.
π Sussman anomaly
The Sussman anomaly is a problem in artificial intelligence, first described by Gerald Sussman, that illustrates a weakness of noninterleaved planning algorithms, which were prominent in the early 1970s. In the problem, three blocks (labeled A, B, and C) rest on a table. The agent must stack the blocks such that A is atop B, which in turn is atop C. However, it may only move one block at a time. The problem starts with B on the table, C atop A, and A on the table:
However, noninterleaved planners typically separate the goal (stack A atop B atop C) into subgoals, such as:
- get A atop B
- get B atop C
Suppose the planner starts by pursuing Goal 1. The straightforward solution is to move C out of the way, then move A atop B. But while this sequence accomplishes Goal 1, the agent cannot now pursue Goal 2 without undoing Goal 1, since both A and B must be moved atop C:
If instead the planner starts with Goal 2, the most efficient solution is to move B. But again, the planner cannot pursue Goal 1 without undoing Goal 2:
The problem was first identified by Sussman as a part of his PhD research. Sussman (and his supervisor, Marvin Minsky) believed that intelligence requires a list of exceptions or tricks, and developed a modular planning system for "debugging" plans. Most modern planning systems can handle this anomaly, but it is still useful for explaining why planning is non-trivial.
Discussed on
- "Sussman anomaly" | 2018-01-15 | 151 Upvotes 41 Comments
π Har Gobind Khorana
Har Gobind Khorana (9 January 1922 β 9 November 2011) was an Indian-American biochemist. While on the faculty of the University of WisconsinβMadison, he shared the 1968 Nobel Prize for Physiology or Medicine with Marshall W. Nirenberg and Robert W. Holley for research that showed the order of nucleotides in nucleic acids, which carry the genetic code of the cell and control the cell's synthesis of proteins. Khorana and Nirenberg were also awarded the Louisa Gross Horwitz Prize from Columbia University in the same year.
Born in British India, Khorana served on the faculties of three universities in North America. He became a naturalized citizen of the United States in 1966, and received the National Medal of Science in 1987.
π Akaike information criterion
The Akaike information criterion (AIC) is an estimator of out-of-sample prediction error and thereby relative quality of statistical models for a given set of data. Given a collection of models for the data, AIC estimates the quality of each model, relative to each of the other models. Thus, AIC provides a means for model selection.
AIC is founded on information theory. When a statistical model is used to represent the process that generated the data, the representation will almost never be exact; so some information will be lost by using the model to represent the process. AIC estimates the relative amount of information lost by a given model: the less information a model loses, the higher the quality of that model.
In estimating the amount of information lost by a model, AIC deals with the trade-off between the goodness of fit of the model and the simplicity of the model. In other words, AIC deals with both the risk of overfitting and the risk of underfitting.
The Akaike information criterion is named after the Japanese statistician Hirotugu Akaike, who formulated it. It now forms the basis of a paradigm for the foundations of statistics; as well, it is widely used for statistical inference.
Discussed on
- "Akaike information criterion" | 2018-01-08 | 36 Upvotes 15 Comments
π ElitzurβVaidman bomb tester
The ElitzurβVaidman bomb-tester is a quantum mechanics thought experiment that uses interaction-free measurements to verify that a bomb is functional without having to detonate it. It was conceived in 1993 by Avshalom Elitzur and Lev Vaidman. Since their publication, real-world experiments have confirmed that their theoretical method works as predicted.
The bomb tester takes advantage of two characteristics of elementary particles, such as photons or electrons: nonlocality and wave-particle duality. By placing the particle in a quantum superposition, it is possible for the experiment to verify that the bomb works without triggering its detonation, although there is still a 50% chance that the bomb will detonate in the effort.
Discussed on
- "ElitzurβVaidman bomb tester" | 2018-01-06 | 55 Upvotes 6 Comments
- "The bomb-testing problem in quantum mechanics" | 2008-01-24 | 25 Upvotes 4 Comments
π Wang tile
Wang tiles (or Wang dominoes), first proposed by mathematician, logician, and philosopher Hao Wang in 1961, are a class of formal systems. They are modelled visually by square tiles with a color on each side. A set of such tiles is selected, and copies of the tiles are arranged side by side with matching colors, without rotating or reflecting them.
The basic question about a set of Wang tiles is whether it can tile the plane or not, i.e., whether an entire infinite plane can be filled this way. The next question is whether this can be done in a periodic pattern.
Discussed on
- "Wang tile" | 2018-01-05 | 145 Upvotes 24 Comments
π Whistled language
Whistled languages use whistling to emulate speech and facilitate communication. A whistled language is a system of whistled communication which allows fluent whistlers to transmit and comprehend a potentially unlimited number of messages over long distances. Whistled languages are different in this respect from the restricted codes sometimes used by herders or animal trainers to transmit simple messages or instructions. Generally, whistled languages emulate the tones or vowel formants of a natural spoken language, as well as aspects of its intonation and prosody, so that trained listeners who speak that language can understand the encoded message.
Whistled language is rare compared to spoken language, but it is found in cultures around the world. It is especially common in tone languages where the whistled tones transmit the tones of the syllables (tone melodies of the words). This might be because in tone languages the tone melody carries more of the functional load of communication while non-tonal phonology carries proportionally less. The genesis of a whistled language has never been recorded in either case and has not yet received much productive study.
Discussed on
- "Whistled language" | 2017-12-30 | 37 Upvotes 8 Comments
π Modelica
Modelica is an object-oriented, declarative, multi-domain modeling language for component-oriented modeling of complex systems, e.g., systems containing mechanical, electrical, electronic, hydraulic, thermal, control, electric power or process-oriented subcomponents. The free Modelica language is developed by the non-profit Modelica Association. The Modelica Association also develops the free Modelica Standard Library that contains about 1360 generic model components and 1280 functions in various domains, as of version 3.2.1.
Discussed on
- "Modelica" | 2017-12-27 | 57 Upvotes 12 Comments
π Jewish Exodus from Arab and Muslim Countries
The Jewish exodus from Arab and Muslim countries, or Jewish exodus from Arab countries, was the departure, flight, expulsion, evacuation and migration of 850,000 Jews, primarily of Sephardi and Mizrahi background, from Arab countries and the Muslim world, mainly from 1948 to the early 1970s. The last major migration wave took place from Iran in 1979β80, as a consequence of the Iranian Revolution.
A number of small-scale Jewish exoduses began in many Middle Eastern countries early in the 20th century with the only substantial aliyah (immigration to the area today known as Israel) coming from Yemen and Syria. Very few Jews from Muslim countries immigrated during the period of Mandatory Palestine. Prior to the creation of Israel in 1948, approximately 800,000 Jews were living in lands that now make up the Arab world. Of these, just under two-thirds lived in the French and Italian-controlled North Africa, 15β20% in the Kingdom of Iraq, approximately 10% in the Kingdom of Egypt and approximately 7% in the Kingdom of Yemen. A further 200,000 lived in Pahlavi Iran and the Republic of Turkey.
The first large-scale exoduses took place in the late 1940s and early 1950s, primarily from Iraq, Yemen and Libya. In these cases over 90% of the Jewish population left, despite the necessity of leaving their property behind. Two hundred and sixty thousand Jews from Arab countries immigrated to Israel between 1948 and 1951, accounting for 56% of the total immigration to the newly founded state; this was the product of a policy change in favour of mass immigration focused on Jews from Arab and Muslim countries. The Israeli government's policy to accommodate 600,000 immigrants over four years, doubling the existing Jewish population, encountered mixed reactions in the Knesset; there were those within the Jewish Agency and government who opposed promoting a large-scale emigration movement among Jews whose lives were not in danger.
Later waves peaked at different times in different regions over the subsequent decades. The peak of the exodus from Egypt occurred in 1956 following the Suez Crisis. The exodus from the other North African Arab countries peaked in the 1960s. Lebanon was the only Arab country to see a temporary increase in its Jewish population during this period, due to an influx of Jews from other Arab countries, although by the mid-1970s the Jewish community of Lebanon had also dwindled. Six hundred thousand Jews from Arab and Muslim countries had reached Israel by 1972. In total, of the 900,000 Jews who left Arab and other Muslim countries, 600,000 settled in the new state of Israel, and 300,000 migrated to France and the United States. The descendants of the Jewish immigrants from the region, known as Mizrahi Jews ("Eastern Jews") and Sephardic Jews ("Spanish Jews"), currently constitute more than half of the total population of Israel, partially as a result of their higher fertility rate. In 2009, only 26,000 Jews remained in Arab countries and Iran. and 26,000 in Turkey.
The reasons for the exoduses are manifold, including push factors, such as persecution, antisemitism, political instability, poverty and expulsion, together with pull factors, such as the desire to fulfill Zionist yearnings or find a better economic status and a secure home in Europe or the Americas. The history of the exodus has been politicized, given its proposed relevance to the historical narrative of the ArabβIsraeli conflict. When presenting the history, those who view the Jewish exodus as analogous to the 1948 Palestinian exodus generally emphasize the push factors and consider those who left as refugees, while those who do not, emphasize the pull factors and consider them willing immigrants.
π RIP Bob Givens, Looney Tunes and Tom and Jerry Artist
Robert Herman "Bob" Givens (March 2, 1918Β β December 14, 2017) was an American animator, character designer, and layout artist. He worked for numerous animation studios during his career, including Walt Disney Animation Studios, Warner Bros. Cartoons, Hanna-Barbera, and DePatieβFreleng Enterprises, beginning his career during the late 1930s and continuing until the early 2000s. He was a frequent collaborator with director Chuck Jones, working with Jones both at Warner Bros. and Jones' own production company.
Discussed on
- "RIP Bob Givens, Looney Tunes and Tom and Jerry Artist" | 2017-12-26 | 44 Upvotes 3 Comments