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108-428: The WP-3Ds are equipped with three weather radars , C band radar in the nose and on the lower fuselage, and an X-band radar in the aircraft's tail. They are also equipped with the ability to deploy dropsondes into storm systems, and have onboard temperature sensors, and other meteorological equipment. While the aircraft are not specially strengthened for flying into hurricanes, their decks were reinforced to withstand

216-470: A fractal surface, such as rocks or soil, and are used by navigation radars. A radar beam follows a linear path in vacuum but follows a somewhat curved path in atmosphere due to variation in the refractive index of air, which is called the radar horizon . Even when the beam is emitted parallel to the ground, the beam rises above the ground as the curvature of the Earth sinks below the horizon. Furthermore,

324-428: A numeronym . For example, "i18n" abbreviates " internationalization ", a computer-science term for adapting software for worldwide use; the "18" represents the 18 letters that come between the first and the last in "internationalization". Similarly, "localization" can be abbreviated "l10n"; " multilingualization " "m17n"; and " accessibility " "a11y". In addition to the use of a specific number replacing that many letters,

432-645: A single word ("television" or "transvestite", for instance), and is in general spelled without punctuation (except in the plural). Although "PS" stands for the single English word " postscript " or the Latin postscriptum , it is often spelled with periods ("P.S.") as if parsed as Latin post scriptum instead. The slash ('/', or solidus ) is sometimes used to separate the letters in an acronym, as in "N/A" ("not applicable, not available") and "c/o" ("care of"). Inconveniently long words used frequently in related contexts can be represented according to their letter count as

540-424: A transmitter that emits radio waves known as radar signals in predetermined directions. When these signals contact an object they are usually reflected or scattered in many directions, although some of them will be absorbed and penetrate into the target. Radar signals are reflected especially well by materials of considerable electrical conductivity —such as most metals, seawater , and wet ground. This makes

648-507: A 1940 translation of a novel by the German writer Lion Feuchtwanger . It is an unsettled question in English lexicography and style guides whether it is legitimate to use the word acronym to describe forms that use initials but are not pronounced as a word. While there is plenty of evidence that acronym is used widely in this way, some sources do not acknowledge this usage, reserving

756-482: A different dielectric constant or diamagnetic constant from the first, the waves will reflect or scatter from the boundary between the materials. This means that a solid object in air or in a vacuum , or a significant change in atomic density between the object and what is surrounding it, will usually scatter radar (radio) waves from its surface. This is particularly true for electrically conductive materials such as metal and carbon fibre, making radar well-suited to

864-625: A different meaning. Medical literature has been struggling to control the proliferation of acronyms, including efforts by the American Academy of Dermatology. Acronyms are often taught as mnemonic devices: for example the colors of the rainbow are ROY G. BIV (red, orange, yellow, green, blue, indigo, violet). They are also used as mental checklists: in aviation GUMPS stands for gas-undercarriage-mixture-propeller-seat belts. Other mnemonic acronyms include CAN SLIM in finance, PAVPANIC in English grammar, and PEMDAS in mathematics. It

972-540: A full radar system, that he called a telemobiloscope . It operated on a 50 cm wavelength and the pulsed radar signal was created via a spark-gap. His system already used the classic antenna setup of horn antenna with parabolic reflector and was presented to German military officials in practical tests in Cologne and Rotterdam harbour but was rejected. In 1915, Robert Watson-Watt used radio technology to provide advance warning of thunderstorms to airmen and during

1080-781: A medial decimal point . Particularly in British and Commonwealth English , all such punctuation marking acronyms and other capitalized abbreviations is now uncommon and considered either unnecessary or incorrect. The presence of all-capital letters is now thought sufficient to indicate the nature of the UK , the EU , and the UN . Forms such as the U.S.A. for "the United States of America " are now considered to indicate American or North American English . Even within those dialects, such punctuation

1188-407: A period when the letters are pronounced individually, as in " K.G.B. ", but not when pronounced as a word, as in " NATO ". The logic of this style is that the pronunciation is reflected graphically by the punctuation scheme. When a multiple-letter abbreviation is formed from a single word, periods are in general not used, although they may be common in informal usage. "TV", for example, may stand for

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1296-749: A physics instructor at the Imperial Russian Navy school in Kronstadt , developed an apparatus using a coherer tube for detecting distant lightning strikes. The next year, he added a spark-gap transmitter . In 1897, while testing this equipment for communicating between two ships in the Baltic Sea , he took note of an interference beat caused by the passage of a third vessel. In his report, Popov wrote that this phenomenon might be used for detecting objects, but he did nothing more with this observation. The German inventor Christian Hülsmeyer

1404-498: A proposal for further intensive research on radio-echo signals from moving targets to take place at NRL, where Taylor and Young were based at the time. Similarly, in the UK, L. S. Alder took out a secret provisional patent for Naval radar in 1928. W.A.S. Butement and P. E. Pollard developed a breadboard test unit, operating at 50 cm (600 MHz) and using pulsed modulation which gave successful laboratory results. In January 1931,

1512-732: A pulsed system, and the first such elementary apparatus was demonstrated in December 1934 by the American Robert M. Page , working at the Naval Research Laboratory . The following year, the United States Army successfully tested a primitive surface-to-surface radar to aim coastal battery searchlights at night. This design was followed by a pulsed system demonstrated in May 1935 by Rudolf Kühnhold and

1620-442: A rescue. For similar reasons, objects intended to avoid detection will not have inside corners or surfaces and edges perpendicular to likely detection directions, which leads to "odd" looking stealth aircraft . These precautions do not totally eliminate reflection because of diffraction , especially at longer wavelengths. Half wavelength long wires or strips of conducting material, such as chaff , are very reflective but do not direct

1728-436: A single word, such as NATO (as distinct from B-B-C )" but adds later "In everyday use, acronym is often applied to abbreviations that are technically initialisms, since they are pronounced as separate letters." The Chicago Manual of Style acknowledges the complexity ("Furthermore, an acronym and initialism are occasionally combined (JPEG), and the line between initialism and acronym is not always clear") but still defines

1836-677: A system might do, Wilkins recalled the earlier report about aircraft causing radio interference. This revelation led to the Daventry Experiment of 26 February 1935, using a powerful BBC shortwave transmitter as the source and their GPO receiver setup in a field while a bomber flew around the site. When the plane was clearly detected, Hugh Dowding , the Air Member for Supply and Research , was very impressed with their system's potential and funds were immediately provided for further operational development. Watson-Watt's team patented

1944-515: A twentieth-century phenomenon. Linguist David Wilton in Word Myths: Debunking Linguistic Urban Legends claims that "forming words from acronyms is a distinctly twentieth- (and now twenty-first-) century phenomenon. There is only one known pre-twentieth-century [English] word with an acronymic origin and it was in vogue for only a short time in 1886. The word is colinderies or colinda , an acronym for

2052-514: A wide region and direct fighter aircraft towards targets. Marine radars are used to measure the bearing and distance of ships to prevent collision with other ships, to navigate, and to fix their position at sea when within range of shore or other fixed references such as islands, buoys, and lightships. In port or in harbour, vessel traffic service radar systems are used to monitor and regulate ship movements in busy waters. Meteorologists use radar to monitor precipitation and wind. It has become

2160-471: A word, an abbreviation is not an acronym." In contrast, some style guides do support it, whether explicitly or implicitly. The 1994 edition of Merriam-Webster's Dictionary of English Usage defends the usage on the basis of a claim that dictionaries do not make a distinction. The BuzzFeed style guide describes CBS and PBS as "acronyms ending in S". Acronymy, like retronymy , is a linguistic process that has existed throughout history but for which there

2268-677: A word. American English dictionaries such as Merriam-Webster , Dictionary.com's Random House Webster's Unabridged Dictionary and the American Heritage Dictionary as well as the British Oxford English Dictionary and the Australian Macquarie Dictionary all include a sense in their entries for acronym equating it with initialism , although The American Heritage Dictionary criticizes it with

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2376-907: A writeup on the apparatus was entered in the Inventions Book maintained by the Royal Engineers. This is the first official record in Great Britain of the technology that was used in coastal defence and was incorporated into Chain Home as Chain Home (low) . Before the Second World War , researchers in the United Kingdom, France , Germany , Italy , Japan , the Netherlands , the Soviet Union , and

2484-572: Is a subset with a narrower definition: an initialism pronounced as a word rather than as a sequence of letters. In this sense, NASA / ˈ n æ s ə / is an acronym but USA / j uː ɛ s ˈ eɪ / is not. The broader sense of acronym , ignoring pronunciation, is its original meaning and in common use. Dictionary and style-guide editors dispute whether the term acronym can be legitimately applied to abbreviations which are not pronounced as words, and they do not agree on acronym spacing , casing , and punctuation . The phrase that

2592-488: Is a question about how to pluralize acronyms. Often a writer will add an 's' following an apostrophe, as in "PC's". However, Kate L. Turabian 's A Manual for Writers of Research Papers, Theses, and Dissertations , writing about style in academic writings, allows for an apostrophe to form plural acronyms "only when an abbreviation contains internal periods or both capital and lowercase letters". Turabian would therefore prefer "DVDs" and "URLs" but "Ph.D.'s". The style guides of

2700-452: Is a simplification for transmission in a vacuum without interference. The propagation factor accounts for the effects of multipath and shadowing and depends on the details of the environment. In a real-world situation, pathloss effects are also considered. Frequency shift is caused by motion that changes the number of wavelengths between the reflector and the radar. This can degrade or enhance radar performance depending upon how it affects

2808-436: 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 . A radar system consists of a transmitter producing electromagnetic waves in

2916-451: Is as follows, where F D {\displaystyle F_{D}} is Doppler frequency, F T {\displaystyle F_{T}} is transmit frequency, V R {\displaystyle V_{R}} is radial velocity, and C {\displaystyle C} is the speed of light: Passive radar is applicable to electronic countermeasures and radio astronomy as follows: Only

3024-721: Is becoming increasingly uncommon. Some style guides , such as that of the BBC , no longer require punctuation to show ellipsis ; some even proscribe it. Larry Trask , American author of The Penguin Guide to Punctuation , states categorically that, in British English , "this tiresome and unnecessary practice is now obsolete." Nevertheless, some influential style guides , many of them American , still require periods in certain instances. For example, The New York Times Manual of Style and Usage recommends following each segment with

3132-411: Is common for grammatical contractions (e.g. don't , y'all , and ain't ) and for contractions marking unusual pronunciations (e.g. a'ight , cap'n , and fo'c'sle for "all right", "captain", and "forecastle"). By the early twentieth century, it was standard to use a full stop/period/point , especially in the cases of initialisms and acronyms. Previously, especially for Latin abbreviations , this

3240-631: Is especially important for paper media, where no search utility is available to find the first use.) It also gives students a convenient review list to memorize the important acronyms introduced in a textbook chapter. Expansion at first use and abbreviation keys originated in the print era, but they are equally useful for electronic text . While acronyms provide convenience and succinctness for specialists, they often degenerate into confusing jargon . This may be intentional, to exclude readers without domain-specific knowledge. New acronyms may also confuse when they coincide with an already existing acronym having

3348-464: Is generally said as two letters, but IPsec for Internet Protocol Security is usually pronounced as / ˌ aɪ ˈ p iː s ɛ k / or / ˈ ɪ p s ɛ k / , along with variant capitalization like "IPSEC" and "Ipsec". Pronunciation may even vary within a single speaker's vocabulary, depending on narrow contexts. As an example, the database programming language SQL is usually said as three letters, but in reference to Microsoft's implementation

Lockheed WP-3D Orion - Misplaced Pages Continue

3456-567: Is intended. Radar relies on its own transmissions rather than light from the Sun or the Moon, or from electromagnetic waves emitted by the target objects themselves, such as infrared radiation (heat). This process of directing artificial radio waves towards objects is called illumination , although radio waves are invisible to the human eye as well as optical cameras. If electromagnetic waves travelling through one material meet another material, having

3564-459: Is not uncommon for acronyms to be cited in a kind of false etymology , called a folk etymology , for a word. Such etymologies persist in popular culture but have no factual basis in historical linguistics , and are examples of language-related urban legends . For example, " cop " is commonly cited as being derived, it is presumed, from "constable on patrol", and " posh " from " port outward, starboard home ". With some of these specious expansions,

3672-417: Is the range. This yields: This shows that the received power declines as the fourth power of the range, which means that the received power from distant targets is relatively very small. Additional filtering and pulse integration modifies the radar equation slightly for pulse-Doppler radar performance , which can be used to increase detection range and reduce transmit power. The equation above with F = 1

3780-415: Is traditionally pronounced like the word sequel . In writing for a broad audience, the words of an acronym are typically written out in full at its first occurrence within a given text. Expansion At First Use (EAFU) benefits readers unfamiliar with the acronym. Another text aid is an abbreviation key which lists and expands all acronyms used, a reference for readers who skipped past the first use. (This

3888-516: The Colonial and Indian Exposition held in London in that year." However, although acronymic words seem not to have been employed in general vocabulary before the twentieth century (as Wilton points out), the concept of their formation is treated as effortlessly understood (and evidently not novel) in an Edgar Allan Poe story of the 1830s, " How to Write a Blackwood Article ", which includes

3996-574: The Gulfstream IV-SP , is named Gonzo ; they complement the fleet of WC-130 aircraft operated by the United States Air Force 53rd Weather Reconnaissance Squadron . As of 2014, the two Orions had each flown more than 10,000 hours and flown into more than 80 hurricanes. In 2024, NOAA announced plans to replace these two aircraft with modified C-130Js , and they are scheduled to be retired by 2030. Between 2015 and 2017,

4104-623: The Modern Language Association and American Psychological Association prohibit apostrophes from being used to pluralize acronyms regardless of periods (so "compact discs" would be "CDs" or "C.D.s"), whereas The New York Times Manual of Style and Usage requires an apostrophe when pluralizing all abbreviations regardless of periods (preferring "PC's, TV's and VCR's"). Possessive plurals that also include apostrophes for mere pluralization and periods appear especially complex: for example, "the C.D.'s' labels" (the labels of

4212-628: The Nyquist frequency , since the returned frequency otherwise cannot be distinguished from shifting of a harmonic frequency above or below, thus requiring: Or when substituting with F D {\displaystyle F_{D}} : As an example, a Doppler weather radar with a pulse rate of 2 kHz and transmit frequency of 1 GHz can reliably measure weather speed up to at most 150 m/s (340 mph), thus cannot reliably determine radial velocity of aircraft moving 1,000 m/s (2,200 mph). In all electromagnetic radiation ,

4320-717: The RAF's Pathfinder . The information provided by radar includes the bearing and range (and therefore position) of the object from the radar scanner. It is thus used in many different fields where the need for such positioning is crucial. The first use of radar was for military purposes: to locate air, ground and sea targets. This evolved in the civilian field into applications for aircraft, ships, and automobiles. In aviation , aircraft can be equipped with radar devices that warn of aircraft or other obstacles in or approaching their path, display weather information, and give accurate altitude readings. The first commercial device fitted to aircraft

4428-539: The Restoration witticism arranging the names of some members of Charles II 's Committee for Foreign Affairs to produce the "CABAL" ministry . OK , a term of disputed origin, dates back at least to the early nineteenth century and is now used around the world. Acronyms are used most often to abbreviate names of organizations and long or frequently referenced terms. The armed forces and government agencies frequently employ acronyms; some well-known examples from

Lockheed WP-3D Orion - Misplaced Pages Continue

4536-440: The electromagnetic spectrum . One example is lidar , which uses predominantly infrared light from lasers rather than radio waves. With the emergence of driverless vehicles, radar is expected to assist the automated platform to monitor its environment, thus preventing unwanted incidents. As early as 1886, German physicist Heinrich Hertz showed that radio waves could be reflected from solid objects. In 1895, Alexander Popov ,

4644-460: The radio or microwaves 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 information about the objects' locations and speeds. Radar was developed secretly for military use by several countries in

4752-407: The reflective surfaces . A corner reflector consists of three flat surfaces meeting like the inside corner of a cube. The structure will reflect waves entering its opening directly back to the source. They are commonly used as radar reflectors to make otherwise difficult-to-detect objects easier to detect. Corner reflectors on boats, for example, make them more detectable to avoid collision or during

4860-480: The "belief" that the etymology is acronymic has clearly been tongue-in-cheek among many citers, as with "gentlemen only, ladies forbidden" for " golf ", although many other (more credulous ) people have uncritically taken it for fact. Taboo words in particular commonly have such false etymologies: " shit " from "ship/store high in transit" or "special high-intensity training" and " fuck " from "for unlawful carnal knowledge", or "fornication under consent/command of

4968-534: The "new boy" Arnold Frederic Wilkins to conduct an extensive review of available shortwave units. Wilkins would select a General Post Office model after noting its manual's description of a "fading" effect (the common term for interference at the time) when aircraft flew overhead. By placing a transmitter and receiver on opposite sides of the Potomac River in 1922, U.S. Navy researchers A. Hoyt Taylor and Leo C. Young discovered that ships passing through

5076-463: The 160-character SMS limit, and to save time, acronyms such as "GF" ("girlfriend"), "LOL" ("laughing out loud"), and "DL" ("download" or "down low") have become popular. Some prescriptivists disdain texting acronyms and abbreviations as decreasing clarity, or as failure to use "pure" or "proper" English. Others point out that languages have always continually changed , and argue that acronyms should be embraced as inevitable, or as innovation that adapts

5184-461: The 18 letters between the initial "i" and the final "n"). Authors of expository writing will sometimes capitalize or otherwise distinctively format the initials of the expansion for pedagogical emphasis (for example, writing: "the onset of Congestive Heart Failure (CHF)" or "the onset of c ongestive h eart f ailure (CHF)"). Capitalization like this, however, conflicts with the convention of English orthography, which generally reserves capitals in

5292-413: The 1920s went on to lead the U.K. research establishment to make many advances using radio techniques, including the probing of the ionosphere and the detection of lightning at long distances. Through his lightning experiments, Watson-Watt became an expert on the use of radio direction finding before turning his inquiry to shortwave transmission. Requiring a suitable receiver for such studies, he told

5400-466: The British press may render it "Nato"), but uses lower case in " Unicef " (from "United Nations International Children's Emergency Fund") because it is more than four letters, and to style it in caps might look ungainly (flirting with the appearance of "shouting capitals"). While abbreviations typically exclude the initials of short function words (such as "and", "or", "of", or "to"), this is not always

5508-564: The U.S. Navy, is "COMCRUDESPAC", which stands for "commander, cruisers destroyers Pacific"; it is also seen as "ComCruDesPac". Inventors are encouraged to anticipate the formation of acronyms by making new terms "YABA-compatible" ("yet another bloody acronym"), meaning the term's acronym can be pronounced and is not an offensive word: "When choosing a new name, be sure it is 'YABA-compatible'." Acronym use has been further popularized by text messaging on mobile phones with short message service (SMS), and instant messenger (IM). To fit messages into

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5616-560: The United States are among the " alphabet agencies " (jokingly referred to as " alphabet soup ") created under the New Deal by Franklin D. Roosevelt (himself known as "FDR"). Business and industry also coin acronyms prolifically. The rapid advance of science and technology also drives the usage, as new inventions and concepts with multiword names create a demand for shorter, more pronounceable names. One representative example, from

5724-724: The United States, independently and in great secrecy, developed technologies that led to the modern version of radar. Australia, Canada, New Zealand, and South Africa followed prewar Great Britain's radar development, Hungary and Sweden generated its radar technology during the war. In France in 1934, following systematic studies on the split-anode magnetron , the research branch of the Compagnie générale de la télégraphie sans fil (CSF) headed by Maurice Ponte with Henri Gutton, Sylvain Berline and M. Hugon, began developing an obstacle-locating radio apparatus, aspects of which were installed on

5832-411: The acronym may use normal case rules, e.g. it would appear generally in lower case, but with an initial capital when starting a sentence or when in a title. Once knowledge of the words underlying such an acronym has faded from common recall, the acronym may be termed an anacronym . Examples of anacronyms are the words " scuba ", " radar ", and " laser ". The word "an acro nym" should not be confused with

5940-545: The acronym stands for is called its expansion . The meaning of an acronym includes both its expansion and the meaning of its expansion. The word acronym is formed from the Greek roots akro- , meaning 'height, summit, or tip', and -nym , 'name'. This neoclassical compound appears to have originated in German , with attestations for the German form Akronym appearing as early as 1921. Citations in English date to

6048-433: The additional equipment load. It has a barber's pole sampler (named for its red and white stripes) that protrude from the aircraft's front, a tail Doppler weather radar , and other unique-looking instruments hanging from the wing. NOAA currently operates two WP-3Ds nicknamed Miss Piggy and Kermit , and their logos feature the characters created by Jim Henson Productions . NOAA's other hurricane hunting aircraft,

6156-590: The adoption of acronyms was modern warfare, with its many highly technical terms. While there is no recorded use of military acronyms dating from the American Civil War (acronyms such as "ANV" for " Army of Northern Virginia " post-date the war itself), they became somewhat common in World War I , and by World War II they were widespread even in the slang of soldiers, who referred to themselves as G.I.s . The widespread, frequent use of acronyms across

6264-708: The aircraft received major overhauls, costing a total of $ 35 million. This work was performed by the United States Navy 's Fleet Readiness Center Southeast in Jacksonville Florida . The work included new wings and engines and upgraded radars and avionics. NOAA anticipates that these changes will allow the aircraft to fly until between 2032 and 2037. Data from Riders of the storms General characteristics Performance Related development Aircraft of comparable role, configuration, and era Related lists Radar Radar

6372-506: The apostrophe should be reserved for the possessive ("the TV's antenna"). In some languages, the convention of doubling the letters in the acronym is used to indicate plural words: for example, the Spanish EE.UU. , for Estados Unidos ('United States'). This old convention is still sometimes followed for a limited number of English abbreviations, such as SS. for Saints , pp. for

6480-537: The arrest of Oshchepkov and his subsequent gulag sentence. In total, only 607 Redut stations were produced during the war. The first Russian airborne radar, Gneiss-2 , entered into service in June 1943 on Pe-2 dive bombers. More than 230 Gneiss-2 stations were produced by the end of 1944. The French and Soviet systems, however, featured continuous-wave operation that did not provide the full performance ultimately synonymous with modern radar systems. Full radar evolved as

6588-479: The beam path caused the received signal to fade in and out. Taylor submitted a report, suggesting that this phenomenon might be used to detect the presence of ships in low visibility, but the Navy did not immediately continue the work. Eight years later, Lawrence A. Hyland at the Naval Research Laboratory (NRL) observed similar fading effects from passing aircraft; this revelation led to a patent application as well as

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6696-1163: The case. Sometimes function words are included to make a pronounceable acronym, such as CORE ( Congress of Racial Equality ). Sometimes the letters representing these words are written in lower case, such as in the cases of "TfL" (" Transport for London ") and LotR ( The Lord of the Rings ); this usually occurs when the acronym represents a multi-word proper noun. Numbers (both cardinal and ordinal ) in names are often represented by digits rather than initial letters, as in "4GL" (" fourth generation language ") or "G77" (" Group of 77 "). Large numbers may use metric prefixes , as with " Y2K " for "Year 2000". Exceptions using initials for numbers include " TLA " ("three-letter acronym/abbreviation") and "GoF" (" Gang of Four "). Abbreviations using numbers for other purposes include repetitions, such as " A2DP " ("Advanced Audio Distribution Profile"), " W3C " ("World Wide Web Consortium"), and T3 ( Trends, Tips & Tools for Everyday Living ); pronunciation, such as " B2B " ("business to business"); and numeronyms , such as "i18n" ("internationalization"; "18" represents

6804-413: The compact discs). In some instances, however, an apostrophe may increase clarity: for example, if the final letter of an abbreviation is "S", as in "SOS's" (although abbreviations ending with S can also take "-es", e.g. "SOSes"), or when pluralizing an abbreviation that has periods. A particularly rich source of options arises when the plural of an acronym would normally be indicated in a word other than

6912-564: The contrived acronym "P.R.E.T.T.Y.B.L.U.E.B.A.T.C.H." The use of Latin and Neo-Latin terms in vernaculars has been pan-European and pre-dates modern English. Some examples of acronyms in this class are: The earliest example of a word derived from an acronym listed by the OED is "abjud" (now " abjad "), formed from the original first four letters of the Arabic alphabet in the late eighteenth century. Some acrostics pre-date this, however, such as

7020-408: The detection of aircraft and ships. Radar absorbing material , containing resistive and sometimes magnetic substances, is used on military vehicles to reduce radar reflection . This is the radio equivalent of painting something a dark colour so that it cannot be seen by the eye at night. Radar waves scatter in a variety of ways depending on the size (wavelength) of the radio wave and the shape of

7128-476: The detection process. As an example, moving target indication can interact with Doppler to produce signal cancellation at certain radial velocities, which degrades performance. Sea-based radar systems, semi-active radar homing , active radar homing , weather radar , military aircraft, and radar astronomy rely on the Doppler effect to enhance performance. This produces information about target velocity during

7236-411: The detection process. This also allows small objects to be detected in an environment containing much larger nearby slow moving objects. Doppler shift depends upon whether the radar configuration is active or passive. Active radar transmits a signal that is reflected back to the receiver. Passive radar depends upon the object sending a signal to the receiver. The Doppler frequency shift for active radar

7344-626: The device in patent GB593017. Development of radar greatly expanded on 1 September 1936, when Watson-Watt became superintendent of a new establishment under the British Air Ministry , Bawdsey Research Station located in Bawdsey Manor , near Felixstowe, Suffolk. Work there resulted in the design and installation of aircraft detection and tracking stations called " Chain Home " along the East and South coasts of England in time for

7452-438: The dictionary entries and style guide recommendations regarding the term acronym through the twentieth century did not explicitly acknowledge or support the expansive sense. The Merriam–Webster's Dictionary of English Usage from 1994 is one of the earliest publications to advocate for the expansive sense, and all the major dictionary editions that include a sense of acronym equating it with initialism were first published in

7560-538: The electric field is perpendicular to the direction of propagation, and the electric field direction is the polarization of the wave. For a transmitted radar signal, the polarization can be controlled to yield different effects. Radars use horizontal, vertical, linear, and circular polarization to detect different types of reflections. For example, circular polarization is used to minimize the interference caused by rain. Linear polarization returns usually indicate metal surfaces. Random polarization returns usually indicate

7668-473: The entire area in front of it, and then used one of Watson-Watt's own radio direction finders to determine the direction of the returned echoes. This fact meant CH transmitters had to be much more powerful and have better antennas than competing systems but allowed its rapid introduction using existing technologies. A key development was the cavity magnetron in the UK, which allowed the creation of relatively small systems with sub-meter resolution. Britain shared

7776-664: The exclusive sense for acronym and its earliest citation was from 1943. In early December 2010, Duke University researcher Stephen Goranson published a citation for acronym to the American Dialect Society e-mail discussion list which refers to PGN being pronounced "pee-gee-enn", antedating English language usage of the word to 1940. Linguist Ben Zimmer then mentioned this citation in his December 16, 2010 " On Language " column about acronyms in The New York Times Magazine . By 2011,

7884-763: The final word if spelled out in full. A classic example is "Member of Parliament", which in plural is "Members of Parliament". It is possible then to abbreviate this as "M's P", which was fairly common in mid-twentieth-century Australian news writing (or similar ), and used by former Australian Prime Minister Ben Chifley . This usage is less common than forms with "s" at the end, such as "MPs", and may appear dated or pedantic. In common usage, therefore, "weapons of mass destruction" becomes "WMDs", "prisoners of war" becomes "POWs", and "runs batted in" becomes "RBIs". Abbreviations that come from single, rather than multiple, words – such as "TV" ("television") – are usually pluralized without apostrophes ("two TVs"); most writers feel that

7992-466: The firm GEMA  [ de ] in Germany and then another in June 1935 by an Air Ministry team led by Robert Watson-Watt in Great Britain. In 1935, Watson-Watt was asked to judge recent reports of a German radio-based death ray and turned the request over to Wilkins. Wilkins returned a set of calculations demonstrating the system was basically impossible. When Watson-Watt then asked what such

8100-464: The first letter of acronyms, reserving all-caps styling for initialisms, writing the pronounced acronyms "Nato" and "Aids" in mixed case, but the initialisms "USA" and "FBI" in all caps. For example, this is the style used in The Guardian , and BBC News typically edits to this style (though its official style guide, dating from 2003, still recommends all-caps ). The logic of this style is that

8208-435: The king". In English, abbreviations have previously been marked by a wide variety of punctuation . Obsolete forms include using an overbar or colon to show the ellipsis of letters following the initial part. The forward slash is still common in many dialects for some fixed expressions—such as in w/ for "with" or A/C for " air conditioning "—while only infrequently being used to abbreviate new terms. The apostrophe

8316-500: The label "usage problem". However, many English language dictionaries, such as the Collins COBUILD Advanced Dictionary , Cambridge Advanced Learner's Dictionary , Macmillan Dictionary , Longman Dictionary of Contemporary English , New Oxford American Dictionary , Webster's New World Dictionary , and Lexico from Oxford University Press do not acknowledge such a sense. Most of

8424-836: The language to changing circumstances. In this view, the modern practice is just the "proper" English of the current generation of speakers, much like the earlier abbreviation of corporation names on ticker tape or newspapers. Exact pronunciation of "word acronyms" (those pronounced as words rather than sounded out as individual letters) often vary by speaker population. These may be regional, occupational, or generational differences, or simply personal preference. For instance, there have been decades of online debate about how to pronounce GIF ( / ɡ ɪ f / or / dʒ ɪ f / ) and BIOS ( / ˈ b aɪ oʊ s / , / ˈ b aɪ oʊ z / , or / ˈ b aɪ ɒ s / ). Similarly, some letter-by-letter initialisms may become word acronyms over time, especially in combining forms: IP for Internet Protocol

8532-418: The more general "x" can be used to replace an unspecified number of letters. Examples include "Crxn" for "crystallization" and the series familiar to physicians for history , diagnosis , and treatment ("hx", "dx", "tx"). Terms relating to a command structure may also sometimes use this formatting, for example gold, silver, and bronze levels of command in UK policing being referred to as Gx, Sx, and Bx. There

8640-508: The ocean liner Normandie in 1935. During the same period, Soviet military engineer P.K. Oshchepkov , in collaboration with the Leningrad Electrotechnical Institute , produced an experimental apparatus, RAPID, capable of detecting an aircraft within 3 km of a receiver. The Soviets produced their first mass production radars RUS-1 and RUS-2 Redut in 1939 but further development was slowed following

8748-531: The outbreak of World War II in 1939. This system provided the vital advance information that helped the Royal Air Force win the Battle of Britain ; without it, significant numbers of fighter aircraft, which Great Britain did not have available, would always have needed to be in the air to respond quickly. The radar formed part of the " Dowding system " for collecting reports of enemy aircraft and coordinating

8856-1302: The period before and during World War II . A key development was the cavity magnetron in the United Kingdom , which allowed the creation of relatively small systems with sub-meter resolution. 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 . The modern uses of radar are highly diverse, including air and terrestrial traffic control, radar astronomy , air-defense systems , anti-missile systems , marine radars to locate landmarks and other ships, aircraft anti-collision systems, ocean surveillance systems, outer space surveillance and rendezvous systems, meteorological precipitation monitoring, radar remote sensing , altimetry and flight control systems , guided missile target locating systems, self-driving cars , and ground-penetrating radar for geological observations. Modern high tech radar systems use digital signal processing and machine learning and are capable of extracting useful information from very high noise levels. Other systems which are similar to radar make use of other parts of

8964-729: The plural of 'pages', or mss. for manuscripts . The most common capitalization scheme seen with acronyms is all-uppercase ( all caps ). Small caps are sometimes used to make the run of capital letters seem less jarring to the reader. For example, the style of some American publications, including the Atlantic Monthly and USA Today , is to use small caps for acronyms longer than three letters; thus "U.S." and " FDR " in normal caps, but " nato " in small caps. The acronyms " AD " and " BC " are often smallcapped as well, as in: "From 4004 bc to ad 525 ". Where an acronym has linguistically taken on an identity as regular word,

9072-706: The primary tool for short-term weather forecasting and watching for severe weather such as thunderstorms , tornadoes , winter storms , precipitation types, etc. Geologists use specialized ground-penetrating radars to map the composition of Earth's crust . Police forces use radar guns to monitor vehicle speeds on the roads. Automotive radars are used for adaptive cruise control and emergency breaking on vehicles by ignoring stationary roadside objects that could cause incorrect brake application and instead measuring moving objects to prevent collision with other vehicles. As part of Intelligent Transport Systems , fixed-position stopped vehicle detection (SVD) radars are mounted on

9180-483: The pronunciation is reflected graphically by the capitalization scheme. However, it conflicts with conventional English usage of first-letter upper-casing as a marker of proper names in many cases; e.g. AIDS stands for acquired immuno-deficiency syndrome which is not a proper name, while Aids is in the style of one. Some style manuals also base the letters' case on their number. The New York Times , for example, keeps "NATO" in all capitals (while several guides in

9288-685: The publication of the 3rd edition of the Oxford English Dictionary added the expansive sense to its entry for acronym and included the 1940 citation. As the Oxford English Dictionary structures the senses in order of chronological development, it now gives the "initialism" sense first. English language usage and style guides which have entries for acronym generally criticize the usage that refers to forms that are not pronounceable words. Fowler's Dictionary of Modern English Usage says that acronym "denotes abbreviations formed from initial letters of other words and pronounced as

9396-432: The radial component of the velocity is relevant. When the reflector is moving at right angle to the radar beam, it has no relative velocity. Objects moving parallel to the radar beam produce the maximum Doppler frequency shift. When the transmit frequency ( F T {\displaystyle F_{T}} ) is pulsed, using a pulse repeat frequency of F R {\displaystyle F_{R}} ,

9504-414: The response. Given all required funding and development support, the team produced working radar systems in 1935 and began deployment. By 1936, the first five Chain Home (CH) systems were operational and by 1940 stretched across the entire UK including Northern Ireland. Even by standards of the era, CH was crude; instead of broadcasting and receiving from an aimed antenna, CH broadcast a signal floodlighting

9612-410: The resulting frequency spectrum will contain harmonic frequencies above and below F T {\displaystyle F_{T}} with a distance of F R {\displaystyle F_{R}} . As a result, the Doppler measurement is only non-ambiguous if the Doppler frequency shift is less than half of F R {\displaystyle F_{R}} , called

9720-427: The roadside to detect stranded vehicles, obstructions and debris by inverting the automotive radar approach and ignoring moving objects. Smaller radar systems are used to detect human movement . Examples are breathing pattern detection for sleep monitoring and hand and finger gesture detection for computer interaction. Automatic door opening, light activation and intruder sensing are also common. A radar system has

9828-407: The scattered energy back toward the source. The extent to which an object reflects or scatters radio waves is called its radar cross-section . The power P r returning to the receiving antenna is given by the equation: where In the common case where the transmitter and the receiver are at the same location, R t = R r and the term R t ² R r ² can be replaced by R , where R

9936-470: The sides of railroad cars (e.g., "Richmond, Fredericksburg and Potomac Railroad" → "RF&P"); on the sides of barrels and crates; and on ticker tape and newspaper stock listings (e.g. American Telephone and Telegraph Company → AT&T). Some well-known commercial examples dating from the 1890s through 1920s include " Nabisco " ("National Biscuit Company"), " Esso " (from "S.O.", from " Standard Oil "), and " Sunoco " ("Sun Oil Company"). Another field for

10044-554: The signal is attenuated by the medium the beam crosses, and the beam disperses. The maximum range of conventional radar can be limited by a number of factors: anacronym An acronym is a type of abbreviation consisting of a phrase whose only pronounced elements are the initial letters or initial sounds of words inside that phrase. Acronyms are often spelled with the initial letter of each word in all caps with no punctuation . For some, an initialism or alphabetism , connotes this general meaning, and an acronym

10152-491: The target. If the wavelength is much shorter than the target's size, the wave will bounce off in a way similar to the way light is reflected by a mirror . If the wavelength is much longer than the size of the target, the target may not be visible because of poor reflection. Low-frequency radar technology is dependent on resonances for detection, but not identification, of targets. This is described by Rayleigh scattering , an effect that creates Earth's blue sky and red sunsets. When

10260-475: The technology with the U.S. during the 1940 Tizard Mission . In April 1940, Popular Science showed an example of a radar unit using the Watson-Watt patent in an article on air defence. Also, in late 1941 Popular Mechanics had an article in which a U.S. scientist speculated about the British early warning system on the English east coast and came close to what it was and how it worked. Watson-Watt

10368-476: The term acronym only for forms pronounced as a word, and using initialism or abbreviation for those that are not. Some sources acknowledge the usage, but vary in whether they criticize or forbid it, allow it without comment, or explicitly advocate it. Some mainstream English dictionaries from across the English-speaking world affirm a sense of acronym which does not require being pronounced as

10476-502: The terms as mutually exclusive. Other guides outright deny any legitimacy to the usage: Bryson's Dictionary of Troublesome Words says "Abbreviations that are not pronounced as words (IBM, ABC, NFL) are not acronyms; they are just abbreviations." Garner's Modern American Usage says "An acronym is made from the first letters or parts of a compound term. It's read or spoken as a single word, not letter by letter." The New York Times Manual of Style and Usage says "Unless pronounced as

10584-879: The transmitter. The reflected radar signals captured by the receiving antenna are usually very weak. They can be strengthened by electronic amplifiers . More sophisticated methods of signal processing are also used in order to recover useful radar signals. The weak absorption of radio waves by the medium through which they pass is what enables radar sets to detect objects at relatively long ranges—ranges at which other electromagnetic wavelengths, such as visible light , infrared light , and ultraviolet light , are too strongly attenuated. Weather phenomena, such as fog, clouds, rain, falling snow, and sleet, that block visible light are usually transparent to radio waves. Certain radio frequencies that are absorbed or scattered by water vapour, raindrops, or atmospheric gases (especially oxygen) are avoided when designing radars, except when their detection

10692-570: The twenty-first century. The trend among dictionary editors appears to be towards including a sense defining acronym as initialism : the Merriam-Webster's Collegiate Dictionary added such a sense in its 11th edition in 2003, and both the Oxford English Dictionary and The American Heritage Dictionary added such senses in their 2011 editions. The 1989 edition of the Oxford English Dictionary only included

10800-487: The two length scales are comparable, there may be resonances . Early radars used very long wavelengths that were larger than the targets and thus received a vague signal, whereas many modern systems use shorter wavelengths (a few centimetres or less) that can image objects as small as a loaf of bread. Short radio waves reflect from curves and corners in a way similar to glint from a rounded piece of glass. The most reflective targets for short wavelengths have 90° angles between

10908-472: The use of radar altimeters possible in certain cases. The radar signals that are reflected back towards the radar receiver are the desirable ones that make radar detection work. If the object is moving either toward or away from the transmitter, there will be a slight change in the frequency of the radio waves due to the Doppler effect . Radar receivers are usually, but not always, in the same location as

11016-536: The whole range of linguistic registers is relatively new in most languages, becoming increasingly evident since the mid-twentieth century. As literacy spread and technology produced a constant stream of new and complex terms, abbreviations became increasingly convenient. The Oxford English Dictionary ( OED ) records the first printed use of the word initialism as occurring in 1899, but it did not come into general use until 1965, well after acronym had become common. In English, acronyms pronounced as words may be

11124-425: The word " an achro nym ", which is a type of misnomer. Words derived from an acronym by affixing are typically expressed in mixed case, so the root acronym is clear. For example, "pre-WWII politics", "post-NATO world", " DNase ". In some cases a derived acronym may also be expressed in mixed case. For example, " messenger RNA " and " transfer RNA " become "mRNA" and "tRNA". Some publications choose to capitalize only

11232-608: Was a 1938 Bell Lab unit on some United Air Lines aircraft. Aircraft can land in fog at airports equipped with radar-assisted ground-controlled approach systems in which the plane's position is observed on precision approach radar screens by operators who thereby give radio landing instructions to the pilot, maintaining the aircraft on a defined approach path to the runway. Military fighter aircraft are usually fitted with air-to-air targeting radars, to detect and target enemy aircraft. In addition, larger specialized military aircraft carry powerful airborne radars to observe air traffic over

11340-511: Was done with a full space between every full word (e.g. A. D. , i. e. , and e. g. for " Anno Domini ", " id est ", and " exempli gratia "). This even included punctuation after both Roman and Arabic numerals to indicate their use in place of the full names of each number (e.g. LII. or 52. in place of "fifty-two" and "1/4." or "1./4." to indicate "one-fourth"). Both conventions have fallen out of common use in all dialects of English, except in places where an Arabic decimal includes

11448-449: Was little to no naming , conscious attention, or systematic analysis until relatively recent times. Like retronymy, it became much more common in the twentieth century than it had formerly been. Ancient examples of acronymy (before the term "acronym" was invented) include the following: During the mid- to late nineteenth century, acronyms became a trend among American and European businessmen: abbreviating corporation names, such as on

11556-748: Was sent to the U.S. in 1941 to advise on air defense after Japan's attack on Pearl Harbor . Alfred Lee Loomis organized the secret MIT Radiation Laboratory at Massachusetts Institute of Technology , Cambridge, Massachusetts which developed microwave radar technology in the years 1941–45. Later, in 1943, Page greatly improved radar with the monopulse technique that was used for many years in most radar applications. The war precipitated research to find better resolution, more portability, and more features for radar, including small, lightweight sets to equip night fighters ( aircraft interception radar ) and maritime patrol aircraft ( air-to-surface-vessel radar ), and complementary navigation systems like Oboe used by

11664-463: Was the first to use radio waves to detect "the presence of distant metallic objects". In 1904, he demonstrated the feasibility of detecting a ship in dense fog, but not its distance from the transmitter. He obtained a patent for his detection device in April 1904 and later a patent for a related amendment for estimating the distance to the ship. He also obtained a British patent on 23 September 1904 for

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