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๐ Abstract Nonsense
In mathematics, abstract nonsense, general abstract nonsense, generalized abstract nonsense, and general nonsense are nonderogatory terms used by mathematicians to describe long, theoretical parts of a proof they skip over when readers are expected to be familiar with them. These terms are mainly used for abstract methods related to category theory and homological algebra. More generally, "abstract nonsense" may refer to a proof that relies on category-theoretic methods, or even to the study of category theory itself.
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- "Abstract Nonsense" | 2023-08-26 | 19 Upvotes 4 Comments
๐ Goro Shimura has died
Gorล Shimura (ๅฟๆ ไบ้, Shimura Gorล, 23 February 1930 โ 3 May 2019) was a Japanese mathematician and Michael Henry Strater Professor Emeritus of Mathematics at Princeton University who worked in number theory, automorphic forms, and arithmetic geometry. He was known for developing the theory of complex multiplication of abelian varieties and Shimura varieties, as well as posing the TaniyamaโShimura conjecture which ultimately led to the proof of Fermat's Last Theorem.
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- "Goro Shimura has died" | 2019-05-04 | 86 Upvotes 10 Comments
๐ Opposition to and problems with neckties
A necktie, or simply a tie, is a long piece of cloth, worn, usually by men, for decorative purposes around the neck, resting under the shirt collar and knotted at the throat.
Variants include the ascot, bow, bolo, zipper, cravat, and knit. The modern necktie, ascot, and bow tie are descended from the cravat. Neckties are generally unsized, but may be available in a longer size. In some cultures men and boys wear neckties as part of regular office attire or formal wear. Some women wear them as well but usually not as often as men. Neckties can also be worn as part of a uniform (e.g. military, school, waitstaff), whereas some choose to wear them as everyday clothing attire. Neckties are traditionally worn with the top shirt button fastened, and the tie knot resting between the collar points.
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- "Opposition to and problems with neckties" | 2009-06-01 | 13 Upvotes 31 Comments
๐ rwall Incident (1987)
Jordan K. Hubbard (born April 8, 1963) is an open source software developer, authoring software such as the Ardent Window Manager and various other open source tools and libraries before co-founding the FreeBSD project with Nate Williams and Rodney W. Grimes in 1993, for which he contributed the initial FreeBSD Ports collection, package management system and sysinstall. In July 2001 Hubbard joined Apple Computer in the role of manager of the BSD technology group. In 2005, his title was "Director of UNIX Technology" and in October 2007, Hubbard was promoted to "Director of Engineering of Unix Technologies" at Apple where he remained until June 2013.
On July 15, 2013, he became CTO of iXsystems where he also led the FreeNAS open source project.
On March 24, 2017, he announced his plan to depart from iXsystems and that he would be joining TwoPoreGuys, a Biotechnology company, as VP of Engineering. From January 2019 - April 2020 he was part of the Engineering Leadership team at Uber and, as of April 2020, is currently Sr. Director for GPU Compute SW at NVidia [1].
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- "rwall Incident (1987)" | 2020-11-20 | 21 Upvotes 13 Comments
๐ Radioactivity in Ramsar, Iran
Ramsar (Persian: ุฑุงู ุณุฑ, also Romanized as Rรกmsar and Rรกnsar; formerly, Sakht Sar) is the capital of Ramsar County, Mazandaran Province, Iran. In 2012 its population was 33,018, in 9,421 families.
Ramsar lies on the coast of the Caspian Sea. It was also known as Sakhtsar in the past. The climate of Ramsar is hot and humid in summer and mild in winter. The proximity of the forest and the sea in this city has given a special beauty to this city and this attracts tourists in all seasons. Ramsar has an airport. The city of Ramsar was a small village in western Mazandaran until the Qajar period, and during the first Pahlavi period, with the rule of Reza Shah and with the support of the government, it became a beautiful city with many tourist facilities.
Ramsar is the westernmost county and city in Mazandaran. It borders the Caspian Sea to the north, Gilan province to the west, Qazvin Province to the south, and Tonekabon to the east.
๐ KullbackโLeibler Divergence
In mathematical statistics, the KullbackโLeibler divergence (also called relative entropy and I-divergence), denoted , is a type of statistical distance: a measure of how one probability distribution P is different from a second, reference probability distribution Q. A simple interpretation of the KL divergence of P from Q is the expected excess surprise from using Q as a model when the actual distribution is P. While it is a distance, it is not a metric, the most familiar type of distance: it is not symmetric in the two distributions (in contrast to variation of information), and does not satisfy the triangle inequality. Instead, in terms of information geometry, it is a type of divergence, a generalization of squared distance, and for certain classes of distributions (notably an exponential family), it satisfies a generalized Pythagorean theorem (which applies to squared distances).
In the simple case, a relative entropy of 0 indicates that the two distributions in question have identical quantities of information. Relative entropy is a nonnegative function of two distributions or measures. It has diverse applications, both theoretical, such as characterizing the relative (Shannon) entropy in information systems, randomness in continuous time-series, and information gain when comparing statistical models of inference; and practical, such as applied statistics, fluid mechanics, neuroscience and bioinformatics.
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- "KullbackโLeibler Divergence" | 2023-08-21 | 177 Upvotes 74 Comments
๐ Shavarsh Karapetyan
Shavarsh Vladimiri (Vladimirovich) Karapetyan (Armenian: ีีกีพีกึีท ิฟีกึีกีบีฅีฟีตีกีถ; born May 19, 1953) is a retired former Soviet finswimmer, best known for saving the lives of 20 people in a 1976 incident in Yerevan.
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- "Shavarsh Karapetyan" | 2025-01-10 | 204 Upvotes 24 Comments
๐ Digital Mobile Radio
Digital mobile radio (DMR) is a limited open digital mobile radio standard defined in the European Telecommunications Standards Institute (ETSI) Standard TS 102 361 parts 1โ4 and used in commercial products around the world. DMR, along with P25 phase II and NXDN are the main competitor technologies in achieving 6.25ย kHz equivalent bandwidth using the proprietary AMBE+2 vocoder. DMR and P25 II both use two-slot TDMA in a 12.5ย kHz channel, while NXDN uses discrete 6.25ย kHz channels using frequency division and TETRA uses a four-slot TDMA in a 25 kHz channel.
DMR was designed with three tiers. DMR tiers I and II (conventional) were first published in 2005, and DMR III (Trunked version) was published in 2012, with manufacturers producing products within a few years of each publication.
The primary goal of the standard is to specify a digital system with low complexity, low cost and interoperability across brands, so radio communications purchasers are not locked into a proprietary solution. In practice, given the current limited scope of the DMR standard, many vendors have introduced proprietary features that make their product offerings non-interoperable with other brands.
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- "Digital Mobile Radio" | 2022-12-04 | 36 Upvotes 9 Comments
๐ Weather Underground Organization
The Weather Underground Organization (WUO), commonly known as the Weather Underground, was a radical left militant organization active in the late 1960s and 1970s, founded on the Ann Arbor campus of the University of Michigan. It was originally called the Weathermen. The WUO organized in 1969 as a faction of Students for a Democratic Society (SDS) largely composed of the national office leadership of SDS and their supporters. Beginning in 1974, the organization's express political goal was to create a revolutionary party to overthrow American imperialism.
The FBI described the WUO as a domestic terrorist group, with revolutionary positions characterized by black power and opposition to the Vietnam War. The WUO took part in domestic attacks such as the jailbreak of Timothy Leary in 1970. The "Days of Rage" was the WUO's first riot in October 1969 in Chicago, timed to coincide with the trial of the Chicago Seven. In 1970, the group issued a "Declaration of a State of War" against the United States government under the name "Weather Underground Organization".
In the 1970s, the WUO conducted a bombing campaign targeting government buildings and several banks. Some attacks were preceded by evacuation warnings, along with threats identifying the particular matter that the attack was intended to protest. Three members of the group were killed in an accidental Greenwich Village townhouse explosion, but none were killed in any of the bombings. The WUO communiquรฉ issued in connection with the bombing of the United States Capitol on March 1, 1971 indicated that it was "in protest of the U.S. invasion of Laos". The WUO asserted that its May 19, 1972 bombing of the Pentagon was "in retaliation for the U.S. bombing raid in Hanoi". The WUO announced that its January 29, 1975 bombing of the United States Department of State building was "in response to the escalation in Vietnam".
The WUO began to disintegrate after the United States reached a peace accord in Vietnam in 1973, and it was defunct by 1977.
The group took its name from Bob Dylan's lyric, "You don't need a weatherman to know which way the wind blows", from the song "Subterranean Homesick Blues" (1965). That Dylan line was also the title of a position paper distributed at an SDS convention in Chicago on June 18, 1969. This founding document called for a "White fighting force" to be allied with the "Black Liberation Movement" and other radical movements to achieve "the destruction of U.S. imperialism and form a classless communist world".
๐ Desiderata
"Desiderata" (Latin: "things desired") is an early 1920s prose poem by the American writer Max Ehrmann. Although he copyrighted it in 1927, he distributed copies of it without a required copyright notice during 1933 and c.โ1942, thereby forfeiting his US copyright. Largely unknown in the author's lifetime, its use in devotional and spoken word recordings in 1960 and 1971 called it to the attention of the world.
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- "Desiderata by Max Ehrmann" | 2022-08-19 | 60 Upvotes 36 Comments
- "Desiderata" | 2013-02-06 | 148 Upvotes 39 Comments