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Back-of-the-envelope Calculation
A back-of-the-envelope calculation is a rough calculation, typically jotted down on any available scrap of paper such as an envelope. It is more than a guess but less than an accurate calculation or mathematical proof. The defining characteristic of back-of-the-envelope calculations is the use of simplified assumptions. A similar phrase in the U.S. is "back of a napkin", also used in the business world to describe sketching out a quick, rough idea of a business or product. In British English, a similar idiom is "back of a cigarette pack, fag packet". History In the natural sciences, ''back-of-the-envelope calculation'' is often associated with physicist Enrico Fermi, who was well known for emphasizing ways that complex scientific equations could be approximated within an order of magnitude using simple calculations. He went on to develop a series of sample calculations, which are called "Fermi Questions" or "Back-of-the-Envelope Calculations" and used to solve Fermi problems. Fe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Envelope
An envelope is a common packaging item, usually made of thin, flat material. It is designed to contain a flat object, such as a letter (message), letter or Greeting card, card. Traditional envelopes are made from sheets of paper cut to one of three shapes: a rhombus, a short-arm cross or a Kite (geometry), kite. These shapes allow the envelope structure to be made by folding the sheet sides around a central rectangular area. In this manner, a rectangle-faced enclosure is formed with an arrangement of four flaps on the reverse side. Overview A folding sequence such that the last flap closed is on a short side is referred to in commercial envelope #Manufacture, manufacture as a pocket – a format frequently employed in the packaging of small quantities of seeds. Although in principle the flaps can be held in place by securing the topmost flap at a single point (for example with a wax seal), generally they are pasted or gummed together at the overlaps. They are most commonly u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radar
Radar is a system that uses radio waves to determine the distance ('' ranging''), direction ( azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track aircraft, ships, spacecraft, guided missiles, motor vehicles, map weather formations, and terrain. The term ''RADAR'' was coined in 1940 by the United States Navy as an acronym for "radio detection and ranging". The term ''radar'' has since entered English and other languages as an anacronym, a common noun, losing all capitalization. A radar system consists of a transmitter producing electromagnetic waves in the radio or microwave domain, a transmitting antenna, a receiving antenna (often the same antenna is used for transmitting and receiving) and a receiver and processor to determine properties of the objects. Radio waves (pulsed or continuous) from the transmitter reflect off the objects and return to the receiver, giving ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ken Thompson
Kenneth Lane Thompson (born February 4, 1943) is an American pioneer of computer science. Thompson worked at Bell Labs for most of his career where he designed and implemented the original Unix operating system. He also invented the B (programming language), B programming language, the direct predecessor to the C (programming language), C language, and was one of the creators and early developers of the Plan 9 from Bell Labs, Plan 9 operating system. Since 2006, Thompson has worked at Google, where he co-developed the Go (programming language), Go language. A recipient of the Turing award, he is considered one of the greatest computer programmers of all time. Other notable contributions included his work on regular expressions and early computer text editors QED (text editor), QED and ed (text editor), ed, the definition of the UTF-8 encoding, and his work on computer chess that included the creation of endgame tablebases and the chess machine Belle (chess machine), Belle. He won ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
World Wide Web
The World Wide Web (WWW or simply the Web) is an information system that enables Content (media), content sharing over the Internet through user-friendly ways meant to appeal to users beyond Information technology, IT specialists and hobbyists. It allows documents and other web resources to be accessed over the Internet according to specific rules of the HTTP, Hypertext Transfer Protocol (HTTP). The Web was invented by English computer scientist Tim Berners-Lee while at CERN in 1989 and opened to the public in 1993. It was conceived as a "universal linked information system". Documents and other media content are made available to the network through web servers and can be accessed by programs such as web browsers. Servers and resources on the World Wide Web are identified and located through character strings called uniform resource locators (URLs). The original and still very common document type is a web page formatted in Hypertext Markup Language (HTML). This markup lang ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
UTF-8
UTF-8 is a character encoding standard used for electronic communication. Defined by the Unicode Standard, the name is derived from ''Unicode Transformation Format 8-bit''. Almost every webpage is transmitted as UTF-8. UTF-8 supports all 1,112,064 valid Unicode code points using a variable-width encoding of one to four one- byte (8-bit) code units. Code points with lower numerical values, which tend to occur more frequently, are encoded using fewer bytes. It was designed for backward compatibility with ASCII: the first 128 characters of Unicode, which correspond one-to-one with ASCII, are encoded using a single byte with the same binary value as ASCII, so that a UTF-8-encoded file using only those characters is identical to an ASCII file. Most software designed for any extended ASCII can read and write UTF-8, and this results in fewer internationalization issues than any alternative text encoding. UTF-8 is dominant for all countries/languages on the internet, with 99% global ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Washington Post
''The Washington Post'', locally known as ''The'' ''Post'' and, informally, ''WaPo'' or ''WP'', is an American daily newspaper published in Washington, D.C., the national capital. It is the most widely circulated newspaper in the Washington metropolitan area and has a national audience. As of 2023, the ''Post'' had 130,000 print subscribers and 2.5 million digital subscribers, both of which were the List of newspapers in the United States, third-largest among U.S. newspapers after ''The New York Times'' and ''The Wall Street Journal''. The ''Post'' was founded in 1877. In its early years, it went through several owners and struggled both financially and editorially. In 1933, financier Eugene Meyer (financier), Eugene Meyer purchased it out of bankruptcy and revived its health and reputation; this work was continued by his successors Katharine Graham, Katharine and Phil Graham, Meyer's daughter and son-in-law, respectively, who bought out several rival publications. The ''Post ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Border Gateway Protocol
Border Gateway Protocol (BGP) is a standardized exterior gateway protocol designed to exchange routing and reachability information among autonomous systems (AS) on the Internet. BGP is classified as a path-vector routing protocol, and it makes routing decisions based on paths, network policies, or rule-sets configured by a network administrator. BGP used for routing within an autonomous system is called Interior Border Gateway Protocol (iBGP). In contrast, the Internet application of the protocol is called Exterior Border Gateway Protocol (EBGP). History The genesis of BGP was in 1989 when Kirk Lougheed, Len Bosack and Yakov Rekhter were sharing a meal at an IETF conference. They famously sketched the outline of their new routing protocol on the back of some napkins, hence often referenced to as the “Two Napkin Protocol”. It was first described in 1989 in RFC 1105, and has been in use on the Internet since 1994. IPv6 BGP was first defined in in 1994, and it wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Super Bowl
The Super Bowl is the annual History of the NFL championship, league championship game of the National Football League (NFL) of the United States. It has served as the final game of every NFL season since 1966 NFL season, 1966 (with the exception of the Pro Bowl between the 1967 and 2009 seasons), superseding the History of the National Football League championship, NFL Championship Game. Since Super Bowl LVI, 2022, the game has been played on the second Sunday in February. Prior Super Bowls were played on Sundays in early to mid-January from 1967 to 1978, late January from 1979 to 2003, and the first Sunday of February from 2004 to 2021. Winning teams are awarded the Vince Lombardi Trophy, named after the legendary Vince Lombardi, Packers coach who won the first two Super Bowls. Because the NFL restricts the use of its "Super Bowl" trademark, it is frequently referred to as the "big game" or other generic terms by non-sponsoring corporations. The day the game is held is common ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vince Lombardi Trophy
The Vince Lombardi Trophy, also known simply as the Lombardi Trophy or just the Lombardi, is the trophy awarded each year to the winning team of the National Football League's championship game, the Super Bowl. The trophy is named in honor of NFL coach Vince Lombardi, who led the Green Bay Packers to victories in the first two Super Bowl games. During lunch with NFL commissioner Pete Rozelle in 1966, Tiffany & Co. vice president Oscar Riedner made a sketch on a cocktail napkin of what would become the Vince Lombardi Trophy: a football in a kicking position on a three concave sided stand. The original trophy was produced by Tiffany & Co. in Newark, New Jersey. Others have since been handcrafted by the company in Parsippany, New Jersey. As of 2017, the trophy is produced at the Tiffany & Co. Forest Hill manufacturing facility in Cumberland, Rhode Island. The first trophy, inscribed with the words "World Professional Football Championship," was awarded to the Green Bay Packe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tiffany & Co
Tiffany & Co. (colloquially known as Tiffany's) is an American luxury goods, luxury jewelry and specialty design house headquartered on Fifth Avenue in Manhattan. Tiffany is known for its luxury goods, particularly its sterling silver and diamond jewelry. These goods are sold at Tiffany stores, online, and through corporate merchandising. Its name and branding are licensed to Coty Inc., Coty for fragrances and to Luxottica for eyewear. Tiffany & Co. was founded in 1837 by the jeweler Charles Lewis Tiffany and became famous in the early 20th century under the artistic direction of his son Louis Comfort Tiffany. In 2018, net sales totaled US$4.44 billion. , Tiffany operated over 300 stores globally, in many countries including the United States, Japan, and Canada, as well as Europe, Latin America, and the collective Asia-Pacific region, and is exploring opportunities in Africa. The company's product line features fine jewelry, sterling silver, watches, porcelain, crystal, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pete Rozelle
Alvin Ray "Pete" Rozelle (; March 1, 1926 – December 6, 1996) was an American professional football executive. Rozelle served as the commissioner of the National Football League (NFL) for nearly thirty years, from January 1960 until his retirement in November 1989. He became the youngest commissioner in NFL history at the age of just 33. He is credited with making the NFL into one of the most successful sports leagues in the world. During his tenure, Rozelle saw the NFL grow from 12 teams to 28, oversaw the creation of large television-rights deals and the creation of '' Monday Night Football'' in 1970, oversaw the 1970 AFL–NFL merger and the creation of the Super Bowl, and helped the NFL move from a twelve-game schedule to a sixteen-game schedule. By the time of his retirement, many people considered him the most powerful commissioner in sports. He was inducted into the Pro Football Hall of Fame in 1985. Early life Born in South Gate, California, Rozelle grew up in neighbo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Charles Townes
Charles Hard Townes (July 28, 1915 – January 27, 2015) was an American physicist. Townes worked on the theory and application of the maser, for which he obtained the fundamental patent, and other work in quantum electronics associated with both maser and laser devices. He shared the 1964 Nobel Prize in Physics with Nikolay Basov and Alexander Prokhorov. Townes was an adviser to the United States Government, meeting every US president from Harry S. Truman (1945) to Bill Clinton (1999). He directed the US government's Science and Technology Advisory Committee for the Apollo lunar landing program. After becoming a professor of the University of California, Berkeley in 1967, he began an astrophysical program that produced several important discoveries, for example, the black hole at the center of the Milky Way galaxy. Townes was religious and believed that science and religion are converging to provide a greater understanding of the nature and purpose of the universe. Ear ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
