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π The Colditz Glider
The Colditz Cock was a glider built by British prisoners of war for an escape attempt from Oflag IV-C (Colditz Castle) in Germany.
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- "The Colditz Glider" | 2017-07-23 | 47 Upvotes 7 Comments
π Canadian Tire Money
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.
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- "Canadian Tire Money" | 2024-08-07 | 37 Upvotes 27 Comments
π Salyut 7 space station salvage mission
Docking and berthing of spacecraft is the joining of two space vehicles. This connection can be temporary, or partially permanent such as for space station modules.
Docking specifically refers to joining of two separate free-flying space vehicles. Berthing refers to mating operations where an inactive module/vehicle is placed into the mating interface of another space vehicle by using a robotic arm. Because the modern process of un-berthing needs more labor and is time-consuming, berthing operations are unsuited for rapid crew evacuations in the event of an emergency.
π Wringing
Gauge blocks (also known as gage blocks, Johansson gauges, slip gauges, or Jo blocks) are a system for producing precision lengths. The individual gauge block is a metal or ceramic block that has been precision ground and lapped to a specific thickness. Gauge blocks come in sets of blocks with a range of standard lengths. In use, the blocks are stacked to make up a desired length.
An important feature of gauge blocks is that they can be joined together with very little dimensional uncertainty. The blocks are joined by a sliding process called wringing, which causes their ultra-flat surfaces to cling together. A small number of gauge blocks can be used to create accurate lengths within a wide range. By using 3 blocks at a time taken from a set of 30 blocks, one may create any of the 1000 lengths from 3.000 to 3.999Β mm in 0.001Β mm steps (or .3000 to .3999 inches in 0.0001Β inch steps). Gauge blocks were invented in 1896 by Swedish machinist Carl Edvard Johansson. They are used as a reference for the calibration of measuring equipment used in machine shops, such as micrometers, sine bars, calipers, and dial indicators (when used in an inspection role). Gauge blocks are the main means of length standardization used by industry.
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- "Wringing" | 2019-07-05 | 356 Upvotes 77 Comments
π Soundex β a phonetic algorithm for indexing names by sound
Soundex is a phonetic algorithm for indexing names by sound, as pronounced in English. The goal is for homophones to be encoded to the same representation so that they can be matched despite minor differences in spelling. The algorithm mainly encodes consonants; a vowel will not be encoded unless it is the first letter. Soundex is the most widely known of all phonetic algorithms (in part because it is a standard feature of popular database software such as DB2, PostgreSQL, MySQL, SQLite, Ingres, MS SQL Server and Oracle.) Improvements to Soundex are the basis for many modern phonetic algorithms.
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- "Soundex β a phonetic algorithm for indexing names by sound" | 2019-10-20 | 106 Upvotes 41 Comments
- "Soundex" | 2018-05-25 | 95 Upvotes 26 Comments
π Uranium can be extracted from seawater in useful amounts
Uranium mining is the process of extraction of uranium ore from the ground. The worldwide production of uranium in 2019 amounted to 53,656Β tonnes. Kazakhstan, Canada, and Australia were the top three uranium producers, respectively, and together account for 68% of world production. Other countries producing more than 1,000 tonnes per year included Namibia, Niger, Russia, Uzbekistan, the United States, and China. Nearly all of the world's mined uranium is used to power nuclear power plants.
Uranium is mined by in-situ leaching (57% of world production) or by conventional underground or open-pit mining of ores (43% of production). During in-situ mining, a leaching solution is pumped down drill holes into the uranium ore deposit where it dissolves the ore minerals. The uranium-rich fluid is then pumped back to the surface and processed to extract the uranium compounds from solution. In conventional mining, ores are processed by grinding the ore materials to a uniform particle size and then treating the ore to extract the uranium by chemical leaching. The milling process commonly yields dry powder-form material consisting of natural uranium, "yellowcake," which is sold on the uranium market as U3O8.
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- "Uranium can be extracted from seawater in useful amounts" | 2022-01-22 | 14 Upvotes 1 Comments
π Kostroma Moose Farm
Kostroma Moose Farm (Russian: ΠΠΎΡΡΡΠΎΠΌΡΠΊΠ°ΜΡ Π»ΠΎΡΠ΅ΡΠ΅ΜΡΠΌΠ°) is an experimental farm in Kostroma Oblast, Russia, where a herd of moose is kept, primarily for milk production; the farm supplies moose's milk to a nearby sanitorium. It is located near the village of Sumarokovo in Krasnoselsky District of Kostroma Oblast, some 25Β km east of the city of Kostroma.
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- "Kostroma Moose Farm" | 2019-08-18 | 30 Upvotes 11 Comments
π Crinkle Crankle Wall
A crinkle crankle wall, also known as a crinkum crankum, serpentine, ribbon or wavy wall, is an unusual type of garden wall built in a serpentine pattern with alternating curves.
The crinkle crankle wall economizes on bricks, despite its sinuous configuration, because it can be made just one brick thin. If a wall this thin were to be made in a straight line, without buttresses, it would easily topple over. The alternate convex and concave curves in the wall provide stability and help it to resist lateral forces.
"Crinkle crankle" is an ablaut reduplication, defined as something with bends and turns, first attested in 1598 (though "crinkle" and "crankle" have somewhat longer histories). However, it was not until the 18th century that the term began to be applied to wavy walls. At that time these garden walls were usually aligned east-west, so that one side faced south to catch the warming sun and were historically used for growing fruit.
Many crinkle crankle walls are found in the East Anglia region of England where the marshes of The Fens were drained by Dutch engineers starting in the mid-1600s. The walls' construction is attributed to these engineers who called them slangenmuur, meaning snake wall.Β The county of Suffolk claims at least 50 examples, twice as many as in the whole of the rest of the country, and where crinkle crankle is said to derive from a local dialect. In the estate village of Easton the noted crinkle crankle wall running from the former manor house to All Saints' Church is supposed to be the longest existing example. In Lymington, Hampshire, there are at least two examples of crinkle crankle walls. The oldest is thought to have been constructed at the time of the Napoleonic Wars (1803β1815) by exiled Hanoverian soldiers living in the adjacent house.
As a minor part of a larger system of fortification, such a wall may have been used to force oncoming troops to break ranks from closed to open ranks, and further expose them to defensive assault.
Thomas Jefferson (1743β1826) incorporated so-called serpentine walls into the architecture of the University of Virginia, which he founded. Flanking both sides of its landmark rotunda and extending down the length of the lawn are ten pavilions, each with its own walled garden separated by crinkle crankle walls. Although some authorities claim Jefferson invented this design, he was merely adapting a well-established English style of construction. A university document in his own hand shows how he calculated the savings and combined aesthetics with utility.
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- "Crinkle Crankle Wall" | 2019-11-16 | 214 Upvotes 56 Comments
π OpenMusic: visual programming env for musical composition based on Common Lisp
OpenMusic (OM) is an object-oriented visual programming environment for musical composition based on Common Lisp.
It may also be used as an all-purpose visual interface to Lisp programming. At a more specialized level, a set of provided classes and libraries make it a very convenient environment for music composition.
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- "OpenMusic: visual programming env for musical composition based on Common Lisp" | 2019-07-17 | 29 Upvotes 4 Comments
π Kriegspiel
Kriegspiel is a chess variant invented by Henry Michael Temple in 1899 and based upon the original Kriegsspiel (German for war game) developed by Georg von Reiswitz in 1812. In this game each player can see their own pieces, but not those of their opponent. For this reason, it is necessary to have a third person (or computer) act as an umpire, with full information about the progress of the game. When it is a player's turn he or she will attempt a move, which the umpire will declare to be 'legal' or 'illegal'. If the move is illegal, the player tries again; if it is legal, that move stands. Each player is given information about checks and captures. They may also ask the umpire if there are any legal captures with a pawn. Since the position of the opponent's pieces is unknown, Kriegspiel is a game of imperfect information. The game is sometimes referred to as blind chess.
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- "Kriegspiel" | 2019-07-31 | 291 Upvotes 88 Comments