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🔗 Aviation 🔗 Military history 🔗 Military history/Military aviation 🔗 Military history/Military science, technology, and theory 🔗 Military history/Weaponry 🔗 Aviation/aircraft 🔗 Military history/World War II 🔗 Military history/European military history 🔗 Military history/British military history

A bouncing bomb is a bomb designed to bounce to a target across water in a calculated manner to avoid obstacles such as torpedo nets, and to allow both the bomb's speed on arrival at the target and the timing of its detonation to be pre-determined, in a similar fashion to a regular naval depth charge. The inventor of the first such bomb was the British engineer Barnes Wallis, whose "Upkeep" bouncing bomb was used in the RAF's Operation Chastise of May 1943 to bounce into German dams and explode underwater, with effect similar to the underground detonation of the Grand Slam and Tallboy earthquake bombs, both of which he also invented.

🔗 Mathematics 🔗 Physics 🔗 Statistics

In mathematical statistics, the Kullback–Leibler divergence (also called relative entropy and I-divergence), denoted ${\displaystyle D_{\text{KL}}(P\parallel Q)}$, 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.

🔗 Computer science 🔗 Mathematics 🔗 Systems

An L-system or Lindenmayer system is a parallel rewriting system and a type of formal grammar. An L-system consists of an alphabet of symbols that can be used to make strings, a collection of production rules that expand each symbol into some larger string of symbols, an initial "axiom" string from which to begin construction, and a mechanism for translating the generated strings into geometric structures. L-systems were introduced and developed in 1968 by Aristid Lindenmayer, a Hungarian theoretical biologist and botanist at the University of Utrecht. Lindenmayer used L-systems to describe the behaviour of plant cells and to model the growth processes of plant development. L-systems have also been used to model the morphology of a variety of organisms and can be used to generate self-similar fractals.

🔗 Germany 🔗 Skepticism 🔗 Paranormal

An April 1561 broadsheet by Hans Glaser described a mass sighting of celestial phenomena or unidentified flying objects (UFO) above Nuremberg (then a Free Imperial City of the Holy Roman Empire). Ufologists have speculated that these phenomena may have been extraterrestrial spacecraft. Skeptics assert that the phenomenon was likely to have been another atmospheric phenomenon, such as a sun dog, although the print doesn't fit the usual classic description of the phenomena.

🔗 Aviation 🔗 Aviation/aircraft 🔗 Florida

The Wingless Electromagnetic Air Vehicle (WEAV) is a heavier than air flight system developed at the University of Florida, funded by the Air Force Office of Scientific Research. The WEAV was invented in 2006 by Dr. Subrata Roy, plasma physicist, aerospace engineering professor at the University of Florida, and has been a subject of several patents. The WEAV employs no moving parts, and combines the aircraft structure, propulsion, energy production and storage, and control subsystems into one integrated system.

🔗 Soviet Union 🔗 Spaceflight 🔗 Solar System

The Vega program (Cyrillic: ВеГа) was a series of Venus missions that also took advantage of the appearance of comet 1P/Halley in 1986. Vega 1 and Vega 2 were uncrewed spacecraft launched in a cooperative effort among the Soviet Union (who also provided the spacecraft and launch vehicle) and Austria, Bulgaria, France, Hungary, the German Democratic Republic, Poland, Czechoslovakia, and the Federal Republic of Germany in December 1984. They had a two-part mission to investigate Venus and also flyby Halley's Comet.

The flyby of Halley's Comet had been a late mission change in the Venera program following on from the cancellation of the American Halley mission in 1981. A later Venera mission was canceled and the Venus part of the Vega 1 mission was reduced. Because of this, the craft was designated VeGa, a contraction of Venera and Gallei (Венера and Галлея respectively, the Russian words for "Venus" and "Halley"). The spacecraft design was based on the previous Venera 9 and Venera 10 missions.

The two spacecraft were launched on 15 and 21 December 1984, respectively. With their redesignated dual missions, the Vega probes became part of the Halley Armada, a group of space probes that studied Halley's Comet during its 1985/1986 perihelion.

🔗 United States 🔗 Law

Hedges v. Obama was a lawsuit filed in January 2012 against the Obama administration and members of the U.S. Congress by a group including former New York Times reporter Christopher Hedges, challenging the National Defense Authorization Act for Fiscal Year 2012 (NDAA). The legislation permitted the U.S. government to indefinitely detain people "who are part of or substantially support Al Qaeda, the Taliban or associated forces engaged in hostilities against the United States". The plaintiffs contended that Section 1021(b)(2) of the law allows for detention of citizens and permanent residents taken into custody in the U.S. on "suspicion of providing substantial support" to groups engaged in hostilities against the U.S. such as al-Qaeda and the Taliban respectively that the NDAA arms the U.S. military with the ability to imprison indefinitely journalists, activists and human-rights workers based on vague allegations.

A federal court in New York issued a permanent injunction blocking the indefinite detention powers of the NDAA but the injunction was stayed by the Second Circuit Court of Appeals pending appeal by the Obama Administration. On July 17, 2013, the Second Circuit Court of Appeals overturned the district court's permanent injunction blocking the indefinite detention powers of the NDAA because the plaintiffs lacked legal standing to challenge the indefinite detention powers of the NDAA. The Supreme Court declined to hear the case on April 28, 2014, leaving the Second Circuit decision intact.

🔗 Military history 🔗 Military history/Early Modern warfare 🔗 Military history/American Revolutionary War 🔗 Military history/Maritime warfare 🔗 Ships 🔗 Connecticut

Turtle (also called American Turtle) was the world's first submersible vessel with a documented record of use in combat. It was built in 1775 by American David Bushnell as a means of attaching explosive charges to ships in a harbor, for use against Royal Navy vessels occupying North American harbors during the American Revolutionary War. Connecticut Governor Jonathan Trumbull recommended the invention to George Washington, who provided funds and support for the development and testing of the machine.

Several attempts were made using Turtle to affix explosives to the undersides of British warships in New York Harbor in 1776. All failed, and her transport ship was sunk later that year by the British with the submarine aboard. Bushnell claimed eventually to have recovered the machine, but its final fate is unknown. Modern replicas of Turtle have been constructed and are on display in the Connecticut River Museum, the U.S. Navy's Submarine Force Library and Museum, the Royal Navy Submarine Museum, and the Oceanographic Museum (Monaco).

🔗 Canada 🔗 Finance & Investment 🔗 Marketing & Advertising 🔗 Numismatics 🔗 Automobiles 🔗 Retailing

Canadian Tire money, officially Canadian Tire 'money' or CTM, is a loyalty program operated by the Canadian retail chain Canadian Tire Corporation (CTC). It consists of both paper coupons introduced in 1958 and used in Canadian Tire stores as scrip, and since 2012 in a digital form introduced as Canadian Tire Money Advantage, rebranded in 2018 as Triangle Rewards. Both forms of the loyalty program remain current as of December 2022. Canadian Tire Money has been noted as the most successful loyalty program in Canadian retail history.

Canadian Tire Money is denominated in Canadian dollars. It is earned based on the pre-tax amount of a purchase, excluding labour and shop supplies costs. The initial rate earned was 5% of the eligible purchase price, but it was lowered to 3%, then to 1.4% and now is 0.4%.

When used to pay for merchandise, CTM is considered to be a cash equivalent and may be used to pay for any part of a purchase, including sales taxes. CTM cannot be exchanged for real Canadian currency.

🔗 Computing 🔗 Computing/Software

"You aren't gonna need it" (YAGNI) is a principle of extreme programming (XP) that states a programmer should not add functionality until deemed necessary. XP co-founder Ron Jeffries has written: "Always implement things when you actually need them, never when you just foresee that you need them." Other forms of the phrase include "You aren't going to need it" and "You ain't gonna need it".