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π Hacker's Delight
Hacker's Delight is a software algorithm book by Henry S. Warren, Jr. first published in 2002. It presents fast bit-level and low-level arithmetic algorithms for common tasks such as counting bits or improving speed of division by using multiplication.
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- "Hacker's Delight" | 2024-05-22 | 13 Upvotes 1 Comments
- "Hacker's Delight" | 2024-03-18 | 17 Upvotes 3 Comments
π An account of travel to the five Indian kingdoms β 723 CE
Wang ocheonchukguk jeon (Korean pronunciation:Β [waΛΕotΙΚ°ΚntΙΚ°ukkΝuktΙΝΚn]; pinyin: wΗng wΗ tiΔnzhΓΊ guΓ³ zhuΓ n; "An account of travel to the five Indian kingdoms") is a travelogue by Buddhist monk Hyecho, who traveled from Korea to India, in the years 723 - 727/728 CE.
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- "An account of travel to the five Indian kingdoms β 723 CE" | 2022-09-17 | 113 Upvotes 17 Comments
π Zamburak
Zamburak (Persian: Ψ²Ω Ψ¨ΩΨ±Ϊ©β), literally meaning wasp, was a specialized form of self-propelled artillery from the early modern period, featuring small cannons fired from swivel-mounts on camels. The operator of a zamburak is known as a zamburakchi. The weapon was used by the gunpowder empires, especially the Iranian empires of the Safavid dynasty, Timurid Empire and Afsharid dynasty, due to the ruggedness of the Iranian Plateau, which made typical transportation of heavy cannons problematic.
The zamburak became a deadly weapon in the 18th century. The Pashtuns used it to deadly effect in the Battle of Gulnabad, routing a numerically superior imperial Safavid army. The zamburak was also used successfully in Nader's Campaigns, when the shah and military genius Nader Shah utilized a zamburak corps in conjunction with a regular artillery corps of conventional cannon to devastating effect in numerous battles such as at the Battle of Damghan (1729), the Battle of YeghevΔrd, and the Battle of Karnal.
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- "Zamburak" | 2020-07-13 | 52 Upvotes 28 Comments
π Emirp Primes
An emirp (prime spelled backwards) is a prime number that results in a different prime when its decimal digits are reversed. This definition excludes the related palindromic primes. The term reversible prime is used to mean the same as emirp, but may also, ambiguously, include the palindromic primes.
The sequence of emirps begins 13, 17, 31, 37, 71, 73, 79, 97, 107, 113, 149, 157, 167, 179, 199, 311, 337, 347, 359, 389, 701, 709, 733, 739, 743, 751, 761, 769, 907, 937, 941, 953, 967, 971, 983, 991, ... (sequence A006567 in the OEIS).
All non-palindromic permutable primes are emirps.
As of NovemberΒ 2009, the largest known emirp is 1010006+941992101Γ104999+1, found by Jens Kruse Andersen in October 2007.
The term 'emirpimes' (singular) is used also in places to treat semiprimes in a similar way. That is, an emirpimes is a semiprime that is also a (distinct) semiprime upon reversing its digits.
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- "Emirp Primes" | 2019-05-02 | 27 Upvotes 14 Comments
π Free Speech Zone
Free speech zones (also known as First Amendment zones, free speech cages, and protest zones) are areas set aside in public places for the purpose of political protesting. The First Amendment to the United States Constitution states that "Congress shall make no law ... abridging ... the right of the people peaceably to assemble, and to petition the Government for a redress of grievances." The existence of free speech zones is based on U.S. court decisions stipulating that the government may reasonably regulate the time, place, and manner β but not content β of expression.
The Supreme Court has developed a four-part analysis to evaluate the constitutionality of time, place and manner (TPM) restrictions. To pass muster under the First Amendment, TPM restrictions must be neutral with respect to content, be narrowly drawn, serve a significant government interest, and leave open alternative channels of communication. Application of this four-part analysis varies with the circumstances of each case, and typically requires lower standards for the restriction of obscenity and fighting words.
Free speech zones have been used at a variety of political gatherings. The stated purpose of free speech zones is to protect the safety of those attending the political gathering, or for the safety of the protesters themselves. Critics, however, suggest that such zones are "Orwellian", and that authorities use them in a heavy-handed manner to censor protesters by putting them literally out of sight of the mass media, hence the public, as well as visiting dignitaries. Though authorities generally deny specifically targeting protesters, on a number of occasions, these denials have been contradicted by subsequent court testimony. The American Civil Liberties Union (ACLU) has filed, with various degrees of success and failure, a number of lawsuits on the issue.
Though free speech zones existed prior to the Presidency of George W. Bush, it was during Bush's presidency that their scope was greatly expanded. These zones continued through the presidency of Barack Obama; he signed a bill in 2012 that expanded the power of the Secret Service to restrict speech and make arrests.
Many colleges and universities earlier instituted free speech zone rules during the Vietnam-era protests of the 1960s and 1970s. In recent years, a number of them have revised or removed these restrictions following student protests and lawsuits.
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- "Free Speech Zone" | 2013-06-29 | 70 Upvotes 22 Comments
π LOOP (programming language)
LOOP is a programming language designed by Uwe SchΓΆning, along with GOTO and WHILE. The only operations supported in the language are assignment, addition and looping.
The key property of the LOOP language is that the functions it can compute are exactly the primitive recursive functions.
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- "LOOP (programming language)" | 2018-12-25 | 36 Upvotes 7 Comments
π Bioluminescence
Bioluminescence is the production and emission of light by living organisms. It is a form of chemiluminescence. Bioluminescence occurs widely in marine vertebrates and invertebrates, as well as in some fungi, microorganisms including some bioluminescent bacteria, and terrestrial arthropods such as fireflies. In some animals, the light is bacteriogenic, produced by symbiotic bacteria such as those from the genus Vibrio; in others, it is autogenic, produced by the animals themselves.
In a general sense, the principal chemical reaction in bioluminescence involves a light-emitting molecule and an enzyme, generally called luciferin and luciferase, respectively. Because these are generic names, luciferins and luciferases are often distinguished by the species or group, e.g. firefly luciferin. In all characterized cases, the enzyme catalyzes the oxidation of the luciferin.
In some species, the luciferase requires other cofactors, such as calcium or magnesium ions, and sometimes also the energy-carrying molecule adenosine triphosphate (ATP). In evolution, luciferins vary little: one in particular, coelenterazine, is found in 11 different animal phyla, though in some of these, the animals obtain it through their diet. Conversely, luciferases vary widely between different species, which is evidence that bioluminescence has arisen over 40 times in evolutionary history.
Both Aristotle and Pliny the Elder mentioned that damp wood sometimes gives off a glow. Many centuries later Robert Boyle showed that oxygen was involved in the process, in both wood and glowworms. It was not until the late nineteenth century that bioluminescence was properly investigated. The phenomenon is widely distributed among animal groups, especially in marine environments. On land it occurs in fungi, bacteria and some groups of invertebrates, including insects.
The uses of bioluminescence by animals include counterillumination camouflage, mimicry of other animals, for example to lure prey, and signaling to other individuals of the same species, such as to attract mates. In the laboratory, luciferase-based systems are used in genetic engineering and biomedical research. Researchers are also investigating the possibility of using bioluminescent systems for street and decorative lighting, and a bioluminescent plant has been created.
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- "Bioluminescence" | 2022-06-12 | 13 Upvotes 8 Comments
π Iloveyou
ILOVEYOU, sometimes referred to as Love Bug or Love Letter for you, is a computer worm that infected over ten million Windows personal computers on and after 4 May 2000 when it started spreading as an email message with the subject line "ILOVEYOU" and the attachment "LOVE-LETTER-FOR-YOU.txt.vbs". The latter file extension ('vbs', a type of interpreted file) was most often hidden by default on Windows computers of the time (as it is an extension for a file type that is known by Windows), leading unwitting users to think it was a normal text file. Opening the attachment activates the Visual Basic script. The worm inflicts damage on the local machine, overwriting random types of files (including Office files, image files, and audio files; however after overwriting MP3 files the virus hides the file), and sends a copy of itself to all addresses in the Windows Address Book used by Microsoft Outlook. This made it spread much faster than any other previous email worm.
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- "Iloveyou" | 2020-05-05 | 51 Upvotes 14 Comments
π Pitch Drop Experiment
The pitch drop experiment is a long-term experiment which measures the flow of a piece of pitch over many years. 'Pitch' is the name for any of a number of highly viscous liquids which appear solid; most commonly bitumen. At room temperature, tar pitch flows at a very low rate, taking several years to form a single drop.
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- "Pitch Drop Experiment" | 2024-01-29 | 82 Upvotes 32 Comments
- "Pitch Drop Experiment" | 2020-02-06 | 97 Upvotes 30 Comments
π A Canticle for Leibowitz
A Canticle for Leibowitz is a post-apocalyptic science fiction novel by American writer Walter M. Miller Jr., first published in 1959. Set in a Catholic monastery in the desert of the southwestern United States after a devastating nuclear war, the book spans thousands of years as civilization rebuilds itself. The monks of the Albertian Order of Leibowitz preserve the surviving remnants of man's scientific knowledge until the world is again ready for it.
The novel is a fixup of three short stories Miller published in The Magazine of Fantasy & Science Fiction that were inspired by the author's participation in the bombing of the monastery at the Battle of Monte Cassino during World War II. The book is considered one of the classics of science fiction and has never been out of print. Appealing to mainstream and genre critics and readers alike, it won the 1961 Hugo Award for best science fiction novel, and its themes of religion, recurrence, and church versus state have generated a significant body of scholarly research. A sequel, Saint Leibowitz and the Wild Horse Woman, was published posthumously in 1997.
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- "A Canticle for Leibowitz" | 2024-03-02 | 59 Upvotes 16 Comments
- "A Canticle for Leibowitz" | 2020-06-20 | 12 Upvotes 3 Comments