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🔗 Computing 🔗 Systems 🔗 Computing/Software 🔗 Systems/Systems engineering

Greenspun's tenth rule of programming is an aphorism in computer programming and especially programming language circles that states:

Any sufficiently complicated C or Fortran program contains an ad hoc, informally-specified, bug-ridden, slow implementation of half of Common Lisp.

🔗 Philosophy 🔗 Philosophy/Logic

Abductive logic programming (ALP) is a high-level knowledge-representation framework that can be used to solve problems declaratively based on abductive reasoning. It extends normal logic programming by allowing some predicates to be incompletely defined, declared as abducible predicates. Problem solving is effected by deriving hypotheses on these abducible predicates (abductive hypotheses) as solutions of problems to be solved. These problems can be either observations that need to be explained (as in classical abduction) or goals to be achieved (as in normal logic programming). It can be used to solve problems in diagnosis, planning, natural language and machine learning. It has also been used to interpret negation as failure as a form of abductive reasoning.

🔗 Computing

Koomey's law describes a trend in the history of computing hardware: for about a half-century, the number of computations per joule of energy dissipated doubled about every 1.57 years. Professor Jonathan Koomey described the trend in a 2010 paper in which he wrote that "at a fixed computing load, the amount of battery you need will fall by a factor of two every year and a half."

This trend had been remarkably stable since the 1950s (R² of over 98%). But in 2011, Koomey re-examined this data and found that after 2000, the doubling slowed to about once every 2.6 years. This is related to the slowing of Moore's Law, the ability to build smaller transistors; and the end around 2005 of Dennard scaling, the ability to build smaller transistors with constant power density.

"The difference between these two growth rates is substantial. A doubling every year and a half results in a 100-fold increase in efficiency every decade. A doubling every two and a half years yields just a 16-fold increase", Koomey wrote.

🔗 Technology 🔗 Aviation 🔗 Computing 🔗 Military history 🔗 Military history/Military aviation 🔗 Military history/North American military history 🔗 Military history/United States military history 🔗 Military history/Military science, technology, and theory 🔗 Aviation/aircraft 🔗 Military history/World War II

The Norden Mk. XV, known as the Norden M series in U.S. Army service, is a bombsight that was used by the United States Army Air Forces (USAAF) and the United States Navy during World War II, and the United States Air Force in the Korean and the Vietnam Wars. It was an early tachometric design that directly measured the aircraft's ground speed and direction, which older bombsights could only estimate with lengthy manual procedures. The Norden improved on older designs by using an analog computer that continuously recalculated the bomb's impact point based on changing flight conditions, and an autopilot that reacted quickly and accurately to changes in the wind or other effects.

Together, these features promised unprecedented accuracy for daytime bombing from high altitudes. During prewar testing the Norden demonstrated a circular error probable (CEP) of 75 feet (23 m), an astonishing performance for that period. This accuracy would enable direct attacks on ships, factories, and other point targets. Both the Navy and the USAAF saw it as a means to conduct successful high-altitude bombing. For example, an invasion fleet could be destroyed long before it could reach U.S. shores. To protect these advantages, the Norden was granted the utmost secrecy well into the war, and was part of a production effort on a similar scale as the Manhattan Project. Carl L. Norden, Inc. ranked 46th among United States corporations in the value of World War II military production contracts.

Under combat conditions the Norden did not achieve its expected accuracy, yielding an average CEP in 1943 of 1,200 feet (370 m), similar to other Allied and German results. Both the Navy and Air Forces had to give up using pinpoint attacks. The Navy turned to dive bombing and skip bombing to attack ships, while the Air Forces developed the lead bomber procedure to improve accuracy, and adopted area bombing techniques for ever larger groups of aircraft. Nevertheless, the Norden's reputation as a pin-point device endured, due in no small part to Norden's own advertising of the device after secrecy was reduced late in the war.

The Norden's secrecy had already been compromised by espionage before the United States entered the war. As early as January 1941, the Germans introduced a lightened derivative of the Norden called the Carl Zeiss Lotfernrohr 7 as the primary bombsight for most Luftwaffe level bombers and the first of its bombsights to have gyroscopic stabilization.

The Norden saw reduced use in the post-World War II period after radar-based targeting was introduced, but the need for accurate daytime attacks kept it in service, especially during the Korean War. The last combat use of the Norden was in the U.S. Navy's VO-67 squadron, which used them to drop sensors onto the Ho Chi Minh Trail as late as 1967. The Norden remains one of the best-known bombsights ever invented.

🔗 Biography

Daniel D. McCracken (July 23, 1930 – July 30, 2011) was a computer scientist in the United States. He was a Professor of Computer Sciences at the City College of New York, and the author of over two dozen textbooks on computer programming, with an emphasis on guides to programming in widely used languages such as Fortran and COBOL. His A Guide to Fortran Programming (Wiley, 1961) and its successors were the standard textbooks on that language for over two decades. His books have been translated into fourteen languages.

🔗 Holidays

System Administrator Appreciation Day, also known as Sysadmin Day, SysAdminDay, is an annual event created by system administrator Ted Kekatos. The event exists to show appreciation for the work of sysadmins and other IT workers. It is celebrated on the last Friday in July.

🔗 Business 🔗 Game theory

A Keynesian beauty contest is a concept developed by John Maynard Keynes and introduced in Chapter 12 of his work, The General Theory of Employment, Interest and Money (1936), to explain price fluctuations in equity markets.

🔗 Biography 🔗 France 🔗 Architecture 🔗 Biography/arts and entertainment 🔗 Craft

Ferdinand Cheval (19 April 1836 – 19 August 1924) was a French postman who spent thirty-three years of his life building Le Palais idéal (the "Ideal Palace") in Hauterives. The Palace is regarded as an extraordinary example of naïve art architecture.

🔗 Biography 🔗 Biography/science and academia 🔗 Astronomy 🔗 Middle Ages 🔗 Middle Ages/History

Ala al-Dīn Ali ibn Muhammed (1403 – 16 December 1474), known as Ali Qushji (Ottoman Turkish/Persian language: علی قوشچی, kuşçu – falconer in Turkish; Latin: Ali Kushgii) was an astronomer, mathematician and physicist originally from Samarkand, who settled in the Ottoman Empire some time before 1472. As a disciple of Ulugh Beg, he is best known for the development of astronomical physics independent from natural philosophy, and for providing empirical evidence for the Earth's rotation in his treatise, Concerning the Supposed Dependence of Astronomy upon Philosophy. In addition to his contributions to Ulugh Beg's famous work Zij-i-Sultani and to the founding of Sahn-ı Seman Medrese, one of the first centers for the study of various traditional Islamic sciences in the Ottoman caliphate, Ali Kuşçu was also the author of several scientific works and textbooks on astronomy.