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United States National Radio Quiet Zone

United States United States Public Policy Virginia United States/West Virginia

The National Radio Quiet Zone (NRQZ) is a large area of land in the United States designated as a radio quiet zone, in which radio transmissions are heavily restricted by law to facilitate scientific research and the gathering of military intelligence. Roughly half of the zone is located in the Blue Ridge Mountains of west-central Virginia while the other half is the Allegheny Mountains of east-central West Virginia; a small part of the zone is in the southernmost tip of the Maryland panhandle.

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Jackson structured programming

Computer science Systems Systems/Scientific modeling

Jackson structured programming (JSP) is a method for structured programming developed by British software consultant Michael A. Jackson and described in his 1975 book Principles of Program Design. The technique of JSP is to analyze the data structures of the files that a program must read as input and produce as output, and then produce a program design based on those data structures, so that the program control structure handles those data structures in a natural and intuitive way.

JSP describes structures (of both data and programs) using three basic structures – sequence, iteration, and selection (or alternatives). These structures are diagrammed as (in effect) a visual representation of a regular expression.

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The turboencabulator or turbo-encabulator (and its later incarnations, the retroencabulator or retro-encabulator and Micro Encabulator) is a fictional machine whose alleged existence became an in-joke and subject of professional humor among engineers. The explanation of the supposed product makes extensive use of technobabble.

The gag was popular for many years. The following quote is from the original Students' Quarterly Journal article written by J. H. Quick in 1944. The citation in the later Time article misspells several of the technical terms. General Electric, Chrysler and Rockwell Automation use many of the same words.

The original machine had a base plate of prefabulated amulite, surmounted by a malleable logarithmic casing in such a way that the two main spurving bearings were in a direct line with the panametric fan. The latter consisted simply of six hydrocoptic marzlevanes, so fitted to the ambifacient lunar waneshaft that side fumbling was effectively prevented. The main winding was of the normal lotus-o-deltoid type placed in panendermic semi-boloid slots in the stator, every seventh conductor being connected by a nonreversible tremmie pipe to the differential girdlespring on the "up" end of the grammeters.

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Before Present

Time Geology

Before Present (BP) years is a time scale used mainly in archaeology, geology and other scientific disciplines to specify when events occurred in the past. Because the "present" time changes, standard practice is to use 1 January 1950 as the commencement date (epoch) of the age scale, reflecting the origin of practical radiocarbon dating in the 1950s. The abbreviation "BP" has been interpreted retrospectively as "Before Physics"; that refers to the time before nuclear weapons testing artificially altered the proportion of the carbon isotopes in the atmosphere, making dating after that time likely to be unreliable.

In a convention that is not always observed, many sources restrict the use of BP dates to those produced with radiocarbon dating; the alternative notation RCYBP is explicitly Radio Carbon Years Before Present.

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Smoothening complex polygons - Ramer–Douglas–Peucker algorithm

The Ramer–Douglas–Peucker algorithm, also known as the Douglas–Peucker algorithm and iterative end-point fit algorithm, is an algorithm that decimates a curve composed of line segments to a similar curve with fewer points.

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Great Man-Made River

Africa Water Rivers Africa/Libya

The Great Man-Made River (GMMR, النهر الصناعي العظيم) is a network of pipes that supplies fresh water obtained from the Nubian Sandstone Aquifer System fossil aquifer across Libya. It is the world's largest irrigation project. The project utilizes a pipeline system that pumps water from the Nubian Sandstone Aquifer System from down south in Libya to cities in the populous Libyan northern Mediterranean coast including Tripoli and Benghazi. The water covers a distance of up to 1,600 kilometers and provides 70% of all freshwater used in Libya.

According to its website, it is the largest underground network of pipes (2,820 kilometres (1,750 mi)) and aqueducts in the world. It consists of more than 1,300 wells, most more than 500 m deep, and supplies 6,500,000 m3 of fresh water per day to the cities of Tripoli, Benghazi, Sirte and elsewhere. The late Libyan Leader Muammar Gaddafi described it as the "Eighth Wonder of the World".

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Philosophy Skepticism Philosophy/Logic Philosophy/Social and political philosophy Philosophy/Philosophy of science Sociology Science

Scientism is the promotion of science as the best or only objective means by which society should determine normative and epistemological values. The term scientism is generally used critically, implying a cosmetic application of science in unwarranted situations considered not amenable to application of the scientific method or similar scientific standards.

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In mathematics, tetration (or hyper-4) is an operation based on iterated, or repeated, exponentiation. It is the next hyperoperation after exponentiation, but before pentation. The word was coined by Reuben Louis Goodstein from tetra- (four) and iteration.

Under the definition as repeated exponentiation, the notation n a {\displaystyle {^{n}a}} means a a a {\displaystyle {a^{a^{\cdot ^{\cdot ^{a}}}}}} , where n copies of a are iterated via exponentiation, right-to-left, I.e. the application of exponentiation n 1 {\displaystyle n-1} times. n is called the "height" of the function, while a is called the "base," analogous to exponentiation. It would be read as "the nth tetration of a".

Tetration is also defined recursively as

n a := { 1 if  n = 0 a ( ( n 1 ) a ) if  n > 0 {\displaystyle {^{n}a}:={\begin{cases}1&{\text{if }}n=0\\a^{\left(^{(n-1)}a\right)}&{\text{if }}n>0\end{cases}}} ,

allowing for attempts to extend tetration to non-natural numbers such as real and complex numbers.

The two inverses of tetration are called the super-root and the super-logarithm, analogous to the nth root and the logarithmic functions. None of the three functions are elementary.

Tetration is used for the notation of very large numbers.

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Luhn Algorithm for validating credit cards

Computing Mathematics

The Luhn algorithm or Luhn formula, also known as the "modulus 10" or "mod 10" algorithm, named after its creator, IBM scientist Hans Peter Luhn, is a simple checksum formula used to validate a variety of identification numbers, such as credit card numbers, IMEI numbers, National Provider Identifier numbers in the United States, Canadian Social Insurance Numbers, Israel ID Numbers, South African ID Numbers, Greek Social Security Numbers (ΑΜΚΑ), and survey codes appearing on McDonald's, Taco Bell, and Tractor Supply Co. receipts. It is described in U.S. Patent No. 2,950,048, filed on January 6, 1954, and granted on August 23, 1960.

The algorithm is in the public domain and is in wide use today. It is specified in ISO/IEC 7812-1. It is not intended to be a cryptographically secure hash function; it was designed to protect against accidental errors, not malicious attacks. Most credit cards and many government identification numbers use the algorithm as a simple method of distinguishing valid numbers from mistyped or otherwise incorrect numbers.

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