Development.

T-64.

The development of the T-72 was a direct result of the introduction of the T-64 tank. The T-64 (Object 432) was a very ambitious project to build a competitive well-armoured tank with a weight of not more than 36 tons. Under the direction of Alexander Morozov in Kharkiv a new design emerged with the hull reduced to the minimum size possible. To do this, the crew was reduced to three soldiers, removing the

Mobilization model.

Because of the time-consuming construction of the 5TDF engines, which took about twice as long as the contemporary V-45, the Malyshev Factory in Kharkiv could not provide a sufficient number of 5TDF engines for all Soviet tank factories. This led to efforts at Uralvagonzavod to design a version of the T-64 with the cheaper and much more reliable V-45 engine of 780 hp. This model was only to be serially produced in the event of a war, a so-called "mobilization model".  In 1967, the Uralvagonzavod formed "Section 520", which was to prepare the serial production of the T-64 for 1970. The team soon found out that the more powerful V-45 engine put a lot of stress on the T-64 hull, so that after

T-72.

Uralvagonzavod produced the first prototype with a 125-mm gun and V-45K engine in 1968 as "Object 172". After intensive comparative testing with the T-64A, Object 172 was re-engineered in 1970 to deal with some minor problems. However, being only a mobilization model, serial production of Object 172 was not possible in peacetime. In an unclear political process decree number 326-113 was issued, which allowed the production of Object 172 in the Soviet

Production history.

The 1st series production of T-72 Object 172M began in July at UKBM in Nizhny Tagil. However, due to difficulties in getting the factory organised for the change in production from T-64 to T-72, only 30 completed tanks were delivered in 1973. Troubles continued in 1974 where out of a state production quota of 440 only 220 were officially declared, with the actual number of completed tanks being close to 150. As a result, substantial investment in tooling was undertaken. Only after modernisation, could the factory begin full-scale production of the T-72. Nizhny Tagil produced the tank in various modifications until 1992.  The T-72 was the most common tank used by the Warsaw Pact from the 1970s until the collapse of the Soviet Union in 1991. It was also exported to other countries, such as Finland, India, Iran, Iraq, Syria and Yugoslavia, as well as being copied elsewhere, both with and without licenses.  Licensed versions of the T-72 were made in Poland and Czechoslovakia, for Warsaw Pact consumers. These tanks had better and more consistent quality of make but with inferior armour, lacking the resin-embedded ceramics layer inside the turret front and glacis armour, replaced with all steel. The Polish-made T-72G tanks also had thinner armour compared to Soviet Army standard (410 mm for turret). Before 1990, Soviet-made T-72 export versions were similarly downgraded for non-Warsaw Pact customers (mostly the Arab countries). Many parts and tools are not interchangeable between the Soviet, Polish and Czechoslovakian versions, which caused logistical problems.  Yugoslavia developed the T-72 into the more advanced M-84, and sold hundreds of them around the world during the 1980s. The Iraqis called their T-72 copies the "Lion of Babylon" ("Asad Babil"). These Iraqi tanks were assembled from kits sold to them by the Soviet Union as a means of evading the UN-imposed weapons embargo. More modern derivatives include the Polish PT-91 "Twardy". Several countries, including Russia and Ukraine, also offer modernization packages for older T-72s.  Various versions of the T-72 have been in production for decades, and the specifications for its armour have changed considerably. Original T-72 tanks had homogeneous cast steel armour incorporating spaced armour technology and were moderately well protected by the standards of the early 1970s. In 1979, the Soviets began building T-72 modification with composite armour similar to the T-64 composite armour, in the front of the turret and the front of the hull. Late in the 1980s, T-72 tanks in Soviet inventory (and many of those elsewhere in the world as well) were fitted with reactive armour tiles.  Laser rangefinders have appeared in T-72 tanks since 1978; earlier examples were equipped with parallax optical rangefinders, which could not be used for distances under. Some export versions of the T-72 lacked the laser rangefinder until 1985 or sometimes only the squadron and platoon commander tanks (version K) received them. After 1985, all newly made T-72s came with reactive armour as standard, the more powerful V-84 engine and an upgraded design main gun, which can fire guided anti-tank missiles from the barrel. With these developments, the T-72 eventually became almost as powerful as the more expensive T-80 tank, but few of these late variants reached the economically ailing Warsaw Pact allies and foreign customers before the Soviet bloc fell apart in 1990.  Since 2000, export vehicles have been offered with thermal imaging night-vision gear of French manufacture as well (though it may be more likely that they might simply use the locally manufactured 'Buran-Catherine' system, which incorporates a French thermal imager). Depleted uranium armour-piercing ammunition for the gun has been manufactured in Russia in the form of the BM-32 projectile since around 1978, though it has never been deployed, and is less penetrating than the later tungsten BM-42 and the newer BM-42M.

Design characteristics.

The T-72 shares many design features with other tank designs of Soviet origin. Some of these are viewed as deficiencies in a straight comparison to NATO tanks, but most are a product of the way these tanks were envisioned to be employed, based on the Soviets' practical experiences in World War II.

Weight.

The T-72 is extremely lightweight, at forty-one tonnes, and very small compared to Western main battle tanks. Some of the roads and bridges in former Warsaw Pact countries were designed such that T-72s can travel along in formation, but NATO tanks could not pass at all, or just one-by-one, significantly reducing their mobility. The basic T-72 is relatively underpowered, with a supercharged version of the basic V-12 diesel

Nuclear, biological, and chemical protection.

The T-72 has a nuclear, biological, and chemical (NBC) protection system. The inside of both hull and turret is lined with a synthetic fabric made of boron compound, meant to reduce the penetrating radiation from neutron bomb explosions. The crew is supplied

Interior.

Like all Soviet-legacy tanks, the T-72's design has traded off interior space in return for a very small silhouette and efficient use of armour, to the point of replacing the fourth crewman with a mechanical loader. The basic T-72 design has extremely small periscope viewports, even by the constrained standards of battle tanks and the driver's field of vision is significantly

Armour.

Armour protection of the T-72 was strengthened with each succeeding generation. The original T-72 "Ural" Object 172M's (from 1973) turret is made from conventional cast HHS steel armour with no laminate inserts. It is believed that the maximum thickness is and the nose is. The glacis of the new laminated armour is thick, comprising HHS steel, double layer of laminate and RHA steel, which when inclined gives about thickness along the line of sight. In 1977 the armour of the T-72 Object 172M was slightly changed. The turret now featured insert filled with ceramic sand bars "kwartz" rods and the glacis place composition was changed. It was now made up of HHA steel, glass Tekstolit laminate and RHA steel. This version was often known in Soviet circles as T-72 "Ural-1". The next armour update was introduced by the T-72A (Object 176), which was designed in 1976 and replaced the original on the production lines during 1979–1985. T-72 Object 1976 is also known as T-72A. With the introduction of the T-72B (Object 184) in 1985, the composite armour was again changed. According to retired major, James M. Warford, variants developed after the T-72 base model and T-72M/T-72G MBT, featured a cast steel turret that included a cavity filled with quartz or sand in a form similar to US "fused-silica" armour. Steven J. Zaloga mentions that the T-72 Model 1978 (Obiekt 172M sb-4), which entered production in 1977, featured a new turret with special armour composed of ceramic rods.  The T-72A featured a new turret with thicker, nearly vertical, frontal armour. Due to its appearance, it was unofficially nicknamed "Dolly Parton" armour by the US Army. This used the new ceramic-rod turret filler, incorporated improved glacis laminate armour, and mounted new anti-shaped-charge sideskirts.  The T-72M was identical to the base T-72 Ural model in terms of protection, retaining the monolithic steel turret. The modernized T-72M1 was closer to the T-72A in terms of protection. It featured an additional 16 mm (0.63 in) of high hardness steel appliqué armour on

Gun.

The T-72 is equipped with the 2A46 series main gun, a significantly larger (20-mm larger) calibre than the standard gun found in contemporary Western MBTs, and still slightly larger than the 120 mm/L44 found in many modern Western MBTs. As is typical of Soviet tanks, the gun is capable of firing anti-tank guided missiles, as well as standard main gun ammunition, including HEAT and APFSDS rounds.  The original T-72 Object 172M (1973) used 2A26M2 model gun first mounted on T-64. The barrel had a length of 6350mm or 50.8 calibers and had maximum rated chamber pressure of 450 MPa. The cannon had an

Autoloader.

Like the earlier domestic-use-only T-64, the T-72 is equipped with an automatic loading system, eliminating the need for a dedicated crewmember, decreasing the size and weight of the tank.  However, the autoloader is of a noticeably different design. Both the T-64 and T-72 carry their two-section 125 mm ammunition (shell and full propellant charge, or missile and reduced propellant charge) in separate loading trays positioned on top of each other; but firstly, in T-64, 28 of these were arranged vertically as a ring under the turret ring proper, and were rotated to put the correct tray into position under the hoist system in the turret rear. This had the disadvantage of cutting the turret off from the rest of the tank, most notably, the driver. Accessing the hull required partial removal of the trays. The T-72 uses a design that has lower width requirements and does not isolate the turret compartment: the trays are arranged in a circle at the very bottom of the fighting compartment; the trade-off is the reduction of the number of trays to 22.

Service.

The T-72 was never used in the Afghanistan War. The 40th Soviet Army that was deployed there had mainly T-55, T-62 and few T-64 tanks.  The Russian Federation has over 5,000 T-72 tanks in use, including around 2,000 in active service and 3,000 in reserve. The T-72 has been used by the Russian Army in the fighting during the First and Second Chechen Wars and the Russo-Georgian War. The T-72 has been used by over 40 countries worldwide.

Syria.

In the 1982 Lebanon War, Syrian T-72s are believed to have engaged Israeli tanks ( M60A1, Magach or probably Merkava tanks) in the south of Lebanon. The most reliable version of the facts is Syrian T-72 never met the Merkava in battle. On 9 June 1982, the Syrian General HQ ordered a brigade of the 1st Armored Division, recently equipped with T-72 tanks, to move straight ahead, cross the border, and hit the right flank of the Israeli units advancing along the eastern side of Beka'a valley. This attack is claimed by some sources to have destroyed some Israeli companies. After the

Iraq.

At the beginning of the Iran–Iraq War, an Iraqi tank battalion, equipped with T-72s, in a battle near the town of Qasr-e Shirin completely defeated an Iranian tank battalion which consisted of Chieftain tanks, without incurring losses. Iranian M47 Patton, M48 Patton, and M60 Patton tanks suffered losses during clashes with Iraqi T-72s. Iraqi T-72Ms and T-72M1s had great success in the battle for Basra and the last stages of the war. 105mm M68 tank guns and TOW missiles proved ineffective against the frontal armor of Iraqi T-72s. 60 T-72 tanks were lost during the eight years of war. According to Iranians and Iraqis, the T-72 was the most feared tank of the Iran–Iraq War.  During the invasion of Kuwait Iraq used 690 tanks, mainly T-55s, T-62s and T-72s. On the other hand, Kuwait had 281 tanks, including 6 T-72s, 165 Chieftains, 70 Vickers and 40 Centurions. On the morning of August 2, near the Mutla Pass, an armoured battle took place between the Vickers tanks of the 6th Kuwaiti Mechanized Brigade and the T-72s of the

Chechen wars.

During the First Chechen War (December 1994 to September 1996) fought between the Russian Federation and the self-proclaimed Chechen Republic of Ichkeria, led by Dzhokhar Dudayev, the Russian Federation deployed both T-72 and T-80 tanks. Russian AFV losses during the first three months fighting amounted to 62 tank (T72/T80) losses (44 T-72s of 141, 18 T-80s of 71 and 0 PT-76s of 9). Analysis of damage to non repairable vehicles showed that no T72 were lost to frontal penetration of the hull from man portable anti tank weapons.  Analysis of the causes of these losses indicated the majority were caused by Chechen 4-man anti-armour hunter-killer teams consisting of a gunner armed with a Russian RPG-7 or RPG-18 shoulder-fired antitank rocket launcher, and a machine gunner and a sniper, with five or

Russo-Georgian War.

During the war in South Ossetia in 2008 both sides deployed great numbers of T-72 tanks. Many of the Georgian tanks were destroyed, disabled or captured, including T-72Sim1s and T-72B1s. At the time of the conflict, the Georgian military fielded 191 T-72 tanks of which 120 were modified to T-72Sim1s. The Georgian army deployed a total of 75 of its T-72 tanks into South Ossetia. The majority of those and several other were captured by Russian forces in South Ossetia and Georgia proper during and after the Georgian retreat, while at least 10 were destroyed in

War in Donbass.

On 26 August 2014, International Institute for Strategic Studies claimed that it had identified a mixed column composed of at least 3 T-72B1s and a lone T-72BM in the War in Donbass. The significance of this sighting was that Russia attempted to maintain plausible deniability over the issue of supplying tanks and other arms to the separatists. Russia continuously claimed that any tanks operated by the separatists must have been captured

Further service.

In June 2013, Azerbaijan bought from Russia a $1 billion package of tanks, artillery, and rocket launchers starting on 18 June. Although the T-72 tanks Azerbaijan had were outdated, they were modified by Israel's Elbit Systems and Rafael. Together the two tweaked T-72A and T-72M1 tanks with improved sights, thermal imaging cameras, wind sensors, and NATO communication systems to name a few. Even with these upgrades, military

The T-72 is a family of Soviet main battle tanks that first entered production in 1971. About 20,000 T-72 tanks have been built, and refurbishment has enabled many to remain in service for decades. The T-72A version introduced in 1979 is considered a second-generation main battle tank. It was widely exported and saw service in 40 countries and in numerous conflicts. The T-72B3 version introduced in 2010 is considered a third-generation main battle tank.

T-72 je druhá generace sovětských hlavních bojových tanků. Jejich výroba začala v roce 1971 a dosud bylo vyrobeno okolo 20 tisíc kusů, čímž se tyto stroje staly po sériích T-54/55 druhými nejrozšířenějšími tanky poválečné produkce, protože byly určené převážně pro export do spřátelených zemí namísto kvalitnějších a dražších T-80. Vyvíjeny byly současně s dražším typem T-64, který ovšem rovněž nebyl určen k vývozu jako T-80. Vzniklo mnoho verzí, např. původní typy T-72 mají čelní pancíř silný 200 mm, zatímco typy T-72G a T-72M 350 až 400 mm. Později byl z typu T-72 vyvinut tank T-90.


Definition.

The term "skyscraper" was first applied to buildings of steel framed construction of at least 10 storeys in the late 19th century, a result of public amazement at the tall buildings being built in major American cities like Chicago, New York City, Philadelphia, Detroit, and St. Louis. The first steel-frame skyscraper was the Home Insurance Building (originally 10 storeys with a height of ) in Chicago, Illinois in 1885. Some point to Philadelphia's 10-storey Jayne Building (1849–50) as a proto-skyscraper, or to New York's seven-floor Equitable Life Building (New York City), built in 1870, for its innovative use of a kind of skeletal frame, but such designation depends largely on what factors are chosen. Even the scholars making the argument find it to be purely academic.  The structural definition of the word "skyscraper" was refined later by architectural historians, based on engineering developments of the 1880s that had enabled construction of tall multi-storey buildings. This definition was based on the steel skeleton—as opposed to constructions of load-bearing masonry, which passed their practical limit in 1891 with Chicago's Monadnock Building.  The Council on Tall Buildings and Urban Habitat defines skyscrapers as those buildings which reach or exceed in height. Others in the United States and Europe also draw the lower limit of a skyscraper at.  The Emporis Standards Committee defines a high-rise building as "a multi-storey structure between 35–100 metres tall, or a building of unknown height from 12–39 floors" and a skyscraper as "a multi-storey building whose architectural height is at least ". Some structural engineers define a highrise as any vertical construction for which wind is a more significant load factor than earthquake or weight. Note that this criterion fits not only high-rises but some other tall structures, such as towers.  The word "skyscraper" often carries a connotation of pride and achievement. The skyscraper, in name and social function, is a modern expression of the age-old symbol of the world center or "axis mundi": a pillar that connects earth to heaven and the four compass directions to one another.  The tallest building in ancient times was the Great Pyramid of Giza in ancient Egypt, built in the 26th century BC. It was not surpassed in height for thousands of years, the Lincoln Cathedral having exceeded it in 1311–1549, before its central spire collapsed. The latter in turn was not surpassed until the Washington Monument in 1884. However, being uninhabited, none of these structures actually comply with the modern definition of a skyscraper.  High-rise apartments flourished in classical antiquity. Ancient Roman insulae in imperial cities reached 10 and more storeys. Beginning with Augustus (r. 30 BC-14 AD), several emperors attempted to establish limits of 20–25 m for multi-storey buildings, but met with only limited success. Lower floors were typically occupied by shops or wealthy families, the upper rented to the lower classes. Surviving Oxyrhynchus Papyri indicate that seven-storey buildings existed in provincial towns such as in 3rd century AD Hermopolis in Roman Egypt.  The skylines of many important medieval cities had large numbers of high-rise urban towers, built by the wealthy for defense and status. The residential Towers of 12th century Bologna numbered between 80 and 100 at a time, the tallest of which is the high Asinelli Tower. A Florentine law of 1251 decreed that all urban buildings be immediately reduced to less than 26 m. Even medium-sized towns of the era are known to have proliferations of towers, such as the 72 up to 51 m height in San Gimignano.  The medieval Egyptian city of Fustat housed many high-rise residential buildings, which Al-Muqaddasi in the 10th century described as resembling minarets. Nasir Khusraw in the early 11th century described some of them rising up to 14 storeys, with roof gardens on the top floor complete with ox-drawn water wheels for irrigating them. Cairo in the 16th century had high-rise apartment buildings where the two lower floors were for commercial and storage purposes and the multiple storeys above them were rented out to tenants. An early example of a city consisting entirely of high-rise housing is the 16th-century city of Shibam in Yemen. Shibam was made up of over 500 tower houses, each one rising 5 to 11 storeys high, with each floor being an apartment occupied by a single family. The city was built in this way in order to protect it from Bedouin attacks. Shibam still has the tallest mudbrick buildings in the world, with many of them over high.  An early modern example of high-rise housing was in 17th-century Edinburgh, Scotland, where a defensive city wall defined the boundaries of the city. Due to the restricted land area available for development, the houses increased in height instead. Buildings of 11 storeys were common, and there are records of buildings as high as 14 storeys. Many of the stone-built structures can still be seen today in the old town of Edinburgh. The oldest iron framed building in the world, although only partially iron framed, is The Flaxmill (also locally known as the "Maltings"), in Shrewsbury, England. Built in 1797, it is seen as the "grandfather of skyscrapers", since its fireproof combination of cast iron columns and cast iron beams developed into the modern steel frame that made modern skyscrapers possible. In 2013 funding was confirmed to convert the derelict building into offices.

Design and construction.

The design and construction of skyscrapers involves creating safe, habitable spaces in very tall buildings. The buildings must support their weight, resist wind and earthquakes, and protect occupants from fire. Yet they must also be conveniently accessible, even on the upper floors, and provide utilities and a comfortable climate for the occupants. The problems posed in skyscraper design are considered among the most complex encountered given the balances required between economics, engineering, and construction management.  One common feature of skyscrapers is a steel framework from which curtain walls are suspended, rather than load-bearing walls of conventional construction. Most skyscrapers have a steel frame that enables them to be built taller than typical load-bearing walls of reinforced concrete. Skyscrapers usually have a particularly small surface area of what are conventionally thought of as walls. Because the walls are not load-bearing most skyscrapers are characterized by surface areas of windows made possible by the concept of steel frame and curtain wall. However, skyscrapers can also have curtain walls that mimic conventional walls and have a small surface area of windows.  The concept of a skyscraper is a product of the industrialized age, made possible by cheap fossil fuel derived energy and industrially refined raw materials such as steel and concrete. The construction of skyscrapers was enabled by steel frame construction that surpassed brick and mortar construction starting at the end of the 19th century and finally surpassing it in the 20th century together with reinforced concrete construction as the price of steel decreased and labour costs increased.  The steel frames become inefficient and uneconomic for supertall buildings as usable floor space is reduced for progressively larger supporting columns. Since about 1960, tubular designs have been used for high rises. This reduces the usage of material (more efficient in economic terms – Willis Tower uses a third less steel than the Empire State Building) yet allows greater height. It allows fewer interior columns, and so creates more usable floor space. It further enables buildings to take on various shapes.  Elevators are characteristic to skyscrapers. In 1852 Elisha Otis introduced the safety elevator, allowing convenient and safe passenger movement to upper floors. Another crucial development was the use of a steel frame instead of stone or brick, otherwise the walls on the lower floors on a tall building would be too thick to be practical. Today major manufacturers of elevators include Otis, ThyssenKrupp, Schindler, and KONE.  Advances in construction techniques have allowed skyscrapers to narrow in width, while increasing in height. Some of these new techniques include mass dampers to reduce vibrations and swaying, and gaps to allow air to pass through, reducing wind shear.

Economic rationale.

Skyscrapers are usually situated in city centers where the price of land is high. Constructing a skyscraper becomes justified if the price of land is so high that it makes economic sense to build upward as to minimize the cost of the land per the total floor area of a building. Thus the construction of skyscrapers is dictated by economics and results in skyscrapers in a certain part of a large city unless a building code restricts the height of buildings.  Skyscrapers are rarely seen in small cities and they are characteristic

Environmental impact.

The amount of steel, concrete, and glass needed to construct a single skyscraper is large, and these materials represent a great deal of embodied energy. Skyscrapers are thus energy intensive buildings, but skyscrapers have a long lifespan, for example the Empire State Building in New York City, United States completed in 1931 and is still in active use.  Skyscrapers have considerable mass, which means that they must be built on a sturdier foundation than would be required for shorter, lighter buildings. Building materials must also be lifted to the top of a skyscraper during construction, requiring more energy than would be necessary at lower heights. Furthermore, a skyscraper consumes much electricity because potable and non-potable water have to be pumped to the highest occupied floors, skyscrapers are usually designed to be mechanically ventilated, elevators are generally used instead of stairs, and natural lighting cannot be utilized in rooms far from the windows and the windowless spaces such as elevators, bathrooms and stairwells.

History of the tallest skyscrapers.

At the beginning of the 20th century, New York City was a center for the Beaux-Arts architectural movement, attracting the talents of such great architects as Stanford White and Carrere and Hastings. As better construction and engineering technology became available as the century progressed, New York City and Chicago became the focal point of the competition for the tallest building in the world. Each city's striking skyline has been composed of numerous and varied skyscrapers, many of which are icons of 20th-century architecture:  Momentum in setting records passed from the United States to other nations with the opening of the Petronas Twin Towers in Kuala Lumpur, Malaysia, in 1998. The record for the world's tallest building has remained in Asia since the opening of Taipei 101 in Taipei, Taiwan, in 2004. A number of architectural records, including those of the world's tallest building and tallest free-standing

Future developments.

Proposals for such structures have been put forward, including the Burj Mubarak Al Kabir in Kuwait and Azerbaijan Tower in Baku. Kilometer-plus structures present architectural challenges that may eventually place them in a new architectural category. The first building under construction and planned to be over one kilometre tall is the Jeddah Tower.

Wooden skyscrapers.

Several wooden skyscraper designs have been designed and built. A 14-storey housing project in Bergen, Norway known as 'Treet' or 'The Tree' became the world's tallest wooden apartment block when it was completed in late 2015. The Tree's record was eclipsed by Brock Commons, an 18-storey wooden dormitory at the University of British Columbia in Canada, when it was completed in September 2016.  A 40-storey residential building 'Trätoppen' has been proposed by architect Anders Berensson to be built in Stockholm, Sweden. Trätoppen would be the tallest building in Stockholm, though there are no immediate plans

A skyscraper is a continuously habitable high-rise building that has over 40 floors and is taller than. Historically, the term first referred to buildings with 10 to 20 floors in the 1880s. The definition shifted with advancing construction technology during the 20th century. Skyscrapers may host offices, hotels, residential spaces, and retail spaces. For buildings above a height of, the term supertall skyscrapers can be used, while skyscrapers reaching beyond are classified as megatall skyscrapers.

Mrakodrap je souvisle obyvatelná výšková budova, která má přes 40 pater a je vyšší než přibližně 150 metrů. Za mrakodrapy se také někdy označují budovy, jejichž výška přesahuje 100 metrů. V historii termín nejdříve označoval budovy s 10 až 20 patry, a to koncem 19. století. Definice se posunula s pokrokem ve stavitelství v průběhu 20. století. V mrakodrapech mohou být kanceláře, hotely, byty a obchody. Za mrakodrap se naopak nepovažuje vyhlídková věž či vysílač. Anglická podoba výrazu ("skyscraper") vznikla ve Spojených státech amerických, kde byly také první mrakodrapy postaveny. Později se rozšířily do velkých měst celého světa.


Geography and geology.

These volcanic islands are located (Suva to Ahau) north of Fiji. Rotuma Island itself is long and wide, with a land area of approximately, making it the 12th largest island of Fiji. The island is bisected into a larger eastern part, and a western peninsula, by a low narrow isthmus only wide, the location of Motusa village (Itu'ti'u district). North of the isthmus is Maka Bay, and in the south Hapmafau Bay. There are a large population of coral reefs in these bays, through which there are boat passages.  Rotuma is a shield volcano made of alkali-olivine basalt and hawaiite, with many small cones, and reaches above sea level at Mount Suelhof near the center of the island. Satarua Peak, high, lies near the eastern end of the island. While very secluded from much of Fiji proper, the large reef and untouched beaches are renowned as some of the most beautiful in all of Fiji.  There are some islands located at a distance between and from the main island, but still within the fringing reef:  Additionally, there is a separate chain of islands between and northwest and west of the westernmost point of Rotuma Island. From northeast to southwest, are:  The geological features of this unique island contribute to its national significance as outlined in Fiji's Biodiversity Strategy and Action Plan.

Flora and fauna.

A area covering the main island and its small satellite islets is the Rotuma Important Bird Area. The Important Bird Area area covers the entire range of the vulnerable Rotuma myzomela, and the Rotuman subspecies of Polynesian starling and lesser shrikebill. Rotuma also supports isolated outlying populations of Crimson-crowned fruit dove and Polynesian triller. The offshore islets of Ha’atana, Hofliua and Hatawa have nationally significant seabird colonies.

History.

Linguistic evidence.

Linguistic evidence suggests an original settlement from Fiji. Linguists include the Rotuman language in a subgroup with the languages of western Fiji, but Rotuman also has a large number of Polynesian loanwords, indicating later contact with Samoa and Tonga.

Origins in oral history.

Rotuman oral history indicates that the islands' first inhabitants came from Samoa, whence they were led by a man named Raho. Shortly thereafter, further settlers arrived from Tonga. Later, additional settlers came from Tonga and Kiribati. In the 1850s and 1860s, Tongan Prince Ma'afu claimed Rotuma and sent subordinates to administer the main island and islets.  Ratzel wrote about a legend relating to the Samoans and Rotuma as follows:  "Thus the Samoans relate that one of their chiefs fished up Rotuma and planted coco-palm on it. But in a later migration the chief Tokaniua came that way with a canoe full of men and quarrelled with him about the prior right of possession."

European contact.

The first known European sighting of Rotuma was in 1791, when Captain Edward Edwards and the crew of HMS "Pandora" landed in search of sailors who had disappeared following the Mutiny on the Bounty. There has been some argument whether the island discovered by Quirós known as "Tuamaco" fits the description and location of Rotuma, but no claim has been fully substantiated.

Mid-19th century.

A favorite of whaling ships in need of reprovisioning, in the mid-nineteenth century Rotuma became a haven for runaway sailors, some of whom were escaped convicts. Some of these deserters married local women and contributed their genes to an already heterogeneous pool; others met violent ends, reportedly at one another's hands. The first recorded whaler to visit was the "Loper" in 1825. The last known whaling visit was by the "Charles W. Morgan" in 1894. Rotuma was visited as part of the United States Exploring Expedition in 1840.

Cession to Britain.

Wesleyan teachers from Tonga arrived on Rotuma in June 1841, followed by Catholic Marists in 1847. The Roman Catholic missionaries withdrew in 1853 but returned in 1868. Conflicts between the two groups, fuelled by previous political rivalries among the chiefs of Rotuma's seven districts, resulted in hostilities that led the local chiefs in 1879 to ask Britain to annex the island group. On 13 May 1881, Rotuma was officially ceded to the United Kingdom, seven years after Fiji became a colony. The event is annually celebrated as Rotuma Day.

Demographics.

Although the island has been politically part of Fiji since 1881, Rotuman culture more closely resembles that of the Polynesian islands to the east, most noticeably Tonga, Samoa, Futuna, and Uvea. Because of their Polynesian appearance and distinctive language, Rotumans now constitute a recognizable minority group within the Republic of Fiji. The great majority of Rotumans (9,984 according to the 2007 Fiji census) now live elsewhere in Fiji, with 1,953 Rotumans remaining on Rotuma. Rotumans are culturally conservative and maintain their customs in the face of changes brought about by increased contact with the outside world. As recently as 1985, some 85 percent of Rotumans voted against opening the island up to tourism, wary of the influence of Western tourists. P&O Cruises landed on the island twice in the 1980s.

Notable Rotumans and people of Rotuman descent.

Riamkau Sau, Last King of Rotuma  Tomoniko Vaurasi, Veterinary  - Dr Robin Everett Mitchell: President of Association of National Olympic Committees, President of Oceania National Olympic Committee, Olympic Solidarity.

Politics and society.

Rotuma was governed as an integral part of the Colony of Fiji after cession to the United Kingdom in 1881 when a group of Rotuman chiefs travelled to London to meet Queen Victoria. The Paramount chief was granted the name of Albert by the Queen in honour of her husband Prince Albert who had died twenty years earlier.  Following Fiji's independence in 1970 and the military coups of 1987, Rotuma remained with Fiji.

Social organization.

Rotuma is divided into seven autonomous districts, each with its own headman or chief (Gagaj 'es Itu'u), with villages:  The district chiefs and elected district representatives make up the Rotuma Island Council. The districts are divided into subgroupings of households (ho'aga) that function as work groups under the leadership of a subchief (gagaj 'es ho'aga). All district headmen and the majority of ho'aga headmen are titled. In addition, some men hold titles without headship (as tög), although they are expected to exercise leadership roles in support of the district headman. Titles, which are held for life, belong to specified house sites (fuạg ri). All the descendants of previous occupants of a fuạg ri have a right to participate in the selection of successors to titles.  On formal occasions titled men and dignitaries such as ministers and priests, government officials, and distinguished visitors occupy a place of honor. They are ceremonially served food from special baskets and kava. In the daily routine of Village life, however, they are not especially privileged. As yet no significant class distinctions based on wealth or control of resources have emerged, but investments in elaborate housing and motor vehicles by a few families have led to visible differences in standard of living.

Political organization.

At the time of arrival by Europeans there were three pan-Rotuman political positions: the fakpure, the sạu, and the mua. The fakpure acted as convener and presiding officer over the council of district headmen and was responsible for appointing the sạu and ensuring that he was cared for properly. The fakpure was headman of the District that headed the alliance that had won the last war. The sạu's role was to take part in the ritual cycle, oriented toward ensuring prosperity, as an object of veneration. Early European visitors referred to the sạu as "king," but he actually had no secular power. The position of sạu was supposed to rotate between districts, and a breach of this custom was considered to be incitement to war. The role of mua is more obscure, but like the sạu, he was an active participant in the ritual cycle. According to some accounts the mua acted as a kind of high priest.  Following Christianization in the 1860s, the offices of sạu and mua were terminated. Colonial administration involved the appointment by the governor of Fiji of a Resident Commissioner (after 1935, a District Officer) to Rotuma. He was advised by a council composed of the district chiefs. In 1940 the council was expanded to include an elected representative from each district and the Assistant Medical Practitioner. Following Fiji's independence in 1970, the council assumed responsibility for the internal governance of Rotuma, with the District Officer assigned to an advisory role. Up until the first coup, Rotuma was represented in the Fiji legislature by a single senator.  Administratively, Rotuma is fully incorporated into Fiji, but with local government so tailored as to give the island a measure of autonomy greater than that enjoyed by other political subdivisions of Fiji. Rotuma has the status of a Dependency, and its administrative capital is 'Ahạu in the district of Itu'ti'u, where the "tariạgsạu" (traditionally the name of the sạu's palace) meeting house for the Council of Rotuma is based.  At the national level, Fijian citizens of Rotuman descent elect one representative to the Fijian House of Representatives, and the Council of Rotuma nominates one representative to the Fijian Senate. Rotuma is also represented in the influential Great Council of Chiefs by three representatives chosen by the Council of Rotuma. For electoral purposes, Rotumans were formerly classified as Fijians, but when the Constitution was revised in 1997–1998, they were granted separate representation at their own request. (The majority of seats in Fiji's House of Representatives are allocated on a communal basis to Fiji's various ethnic groups) In addition, Rotuma forms part (along with Taveuni and the Lau Islands) of the Lau Taveuni Rotuma Open Constituency, one of 25 constituencies whose representatives are chosen by universal suffrage.

Social control.

The "ho'aga", a kinship community, was the basic residential unit in pre-contact Rotuma. The basis for social control is a strong socialization emphasis on social responsibility and a sensitivity to shaming. Gossip serves as a mechanism for sanctioning deviation, but the most powerful deterrent to antisocial behavior is an abiding belief in imminent justice, that supernatural forces (the 'atua or ghosts of ancestors) will punish wrongdoing. Rotumans are a rather gentle people; violence is extremely rare and serious crimes nearly nonexistent.

Conflict.

Prior to cession, warfare, though conducted on a modest scale, was endemic in Rotuma. During the colonial era political rivalries were muted, since power was concentrated in the offices of Resident Commissioner and District Officer. Following Fiji's independence, however, interdistrict rivalries were again given expression, now in the form of political contention. Following the second coup, when Fiji left the Commonwealth of Nations, a segment of the Rotuman population, known as the "Mölmahao Clan" of Noa’tau rejected the council's decision to remain with the newly declared republic. Arguing that Rotuma had been ceded to the United Kingdom and not to Fiji, these rebels declared in 1987 independence of Republic of Rotuma and were charged with sedition. It did not have any substantive support, majority opinion appears to favor remaining with Fiji, but rumblings of discontent remain.

Rotuma is a Fijian dependency, consisting of Rotuma Island and nearby islets. The island group is home to a large and unique indigenous ethnic group which constitutes a recognisable minority within the population of Fiji, known as "Rotumans". Its population at the 2017 census was 1,594, although many more Rotumans live on mainland Fijian islands, totaling 10,000.

Ostrov Rotuma je hlavním ostrovem fidžijského souostroví Rotuma. Ostrov je 13 km dlouhý a 4 km široký s rozlohou 43 km2. Je jediným trvale obydleným ostrovem souostroví Rotuma. Při sčítání v roce 1996 měl 2 810 obyvatel.


Design and development.

With the failure of the CIA's Project Rainbow to reduce the radar cross-section (RCS) of the U-2, preliminary work began inside Lockheed in late 1957 to develop a follow-on aircraft to overfly the Soviet Union. Designer Kelly Johnson said, "In April 1958 I recall having long discussions with [CIA Deputy Director for Plans] Richard Bissell over the subject of whether there should be a follow-on to the U-2 aircraft. We agreed... that there should be one more round before satellites would make aircraft reconnaissance obsolete for covert reconnaissance."  Under Project Gusto the designs were nicknamed "Archangel", after the U-2 program, which had been known as "Angel". As the aircraft designs evolved and configuration changes occurred, the internal Lockheed designation changed from Archangel-1 to Archangel-2, and so on. These names for the evolving designs soon simply became known as "A-1", "A-2", etc. The CIA program to develop the follow-on aircraft to the U-2 was code-named "Oxcart".  These designs had reached the A-11 stage when the program was reviewed. The A-11 was competing against a Convair proposal called Kingfish, of roughly similar performance. However, the Kingfish included a number of features that greatly reduced its RCS, which was seen as favorable to the board. Lockheed responded with a simple update of the A-11, adding twin canted fins instead of a single right-angle one, and adding a number of areas of non-metallic materials. This became the A-12 design. On 26 January 1960, the CIA ordered 12 A-12 aircraft.

New materials and production techniques.

Because the A-12 was well ahead of its time, many new technologies had to be invented specifically for the Oxcart project with some remaining in use in present day. One of the biggest problems that engineers faced at that time was working with titanium.  In his book "Skunk Works: A Personal Memoir of My Years at Lockheed", Ben Rich stated, "Our supplier, Titanium Metals Corporation, had only limited reserves of the precious alloy, so the CIA conducted a worldwide search and using third parties and dummy companies, managed to unobtrusively purchase the base metal from one of the world's leading exporters – the Soviet Union. The Russians never had an inkling of how they were actually contributing to the creation of the airplane being rushed into construction to spy on their homeland."  Before the A-12, titanium was used only in high-temperature exhaust fairings and other small parts directly related to supporting, cooling, or shaping high-temperature areas on aircraft like those subject to the greatest kinetic heating from the airstream, such as wing leading edges. The A-12, however, was constructed mainly of titanium. Titanium is quite rigid and difficult to machine, which made it difficult to form into curves given available techniques. This made the construction of the leading edges of the wing and similar surfaces difficult to form. The solution was found by machining only small "fillets" of the material with the required shape and then gluing them onto the underlying framework which was more linear. A good example is on the wing; the underlying framework of spars and stringers formed a grid, leaving triangular notches along the leading edge that were filled with fillets.  With the move to the A-12, another improvement in RCS was made by replacing the fillets with new radar-absorbing composite materials made from iron ferrite and silicon laminate, both combined with asbestos to absorb radar returns and make the aircraft more stealthy.

Flight testing.

After development and production at the Skunk Works, in Burbank, California, the first A-12 was transferred to Groom Lake test facility. On 25 April 1962 it was taken on its first (unofficial and unannounced) flight with Lockheed test pilot Louis Schalk at the controls. The first official flight later took place on 30 April and subsequent supersonic flight on 4 May 1962, reaching speeds of Mach 1.1 at.  The first five A-12s, in 1962, were initially flown with Pratt & Whitney J75 engines capable of thrust each, enabling the J75-equipped A-12s to obtain speeds of approximately Mach 2.0. On 5 October 1962, with the newly developed J58 engines, an A-12 flew with one J75 engine, and one J58 engine. By early 1963, the A-12 was flying with J58 engines, and during 1963 these J58-equipped A-12s obtained speeds of Mach 3.2. Also, in 1963, the program experienced its first loss when, on 24 May, "Article 123" piloted by Kenneth S. Collins crashed near Wendover, Utah.  Collins safely ejected and was wearing a standard flight suit, avoiding unwanted questions from the truck driver who picked him up. He called Area 51 from a highway patrol office. The reaction to the crash illustrated the secrecy and importance of the project. The CIA called the aircraft a Republic F-105 Thunderchief in news articles and official records; two nearby farmers were told that the aircraft was carrying atomic weapons to dissuade them from approaching the crash site; and local law enforcement and a passing family were strongly warned to keep quiet about the crash. Each was also paid $25,000 in cash to do so; the project often used such cash payments to avoid outside inquiries into its operations. The project received ample funding; contracted security guards were paid $1,000 monthly with free housing on base, and chefs from Las Vegas were available 24 hours a day for steak, Maine lobster, or other requests.  In June 1964, the last A-12 was delivered to Groom Lake, from where the fleet made a total of 2,850 test flights. A total of 18 aircraft were built through the program's production run. Of these, 13 were A-12s, three were prototype YF-12A interceptors for the U.S. Air Force (not funded under the OXCART program), and two were M-21 reconnaissance drone carriers. One of the 13 A-12s was a dedicated trainer aircraft with a second seat, located behind the pilot and raised to permit the Instructor Pilot to see forward. The A-12 trainer, known as "Titanium Goose", retained the J75 power plants for its entire service life.  Three more A-12s were lost in later testing. On 9 July 1964, "Article 133" crashed while making its final approach to the runway when a pitch-control servo device froze at an altitude of and airspeed of causing it to begin a smooth steady roll to the left. Lockheed test pilot Bill Parks could not overcome the roll. At about a 45-degree bank angle and altitude he ejected and was blown sideways out of the aircraft. Although he was not very high off the ground, his parachute did open and he landed safely.  On 28 December 1965, the third A-12 was lost when "Article 126" crashed 30 seconds after takeoff when a series of violent yawing and pitching actions was followed very rapidly with the aircraft becoming uncontrollable. Mele Vojvodich was scheduled to take aircraft number 126 on a performance check flight which included a rendezvous beacon test with a KC-135 tanker and managed to eject safely above the ground. A post-crash investigation revealed that the primary cause of the accident was a maintenance error in that the flight line technician was negligent in performing his duty when he connected the wiring harnesses for the yaw and pitch rate gyroscopes of the stability augmentation system in reverse. It was also found that a contributing cause was a design deficiency which made it possible to physically connect the wiring harnesses in reverse.  The first fatality of the Oxcart program occurred on 5 January 1967, when "Article 125" crashed, killing CIA pilot Walter Ray when the aircraft ran out of fuel while on its descent to the test site. No precise cause could be established for the loss and it was considered most probable that a fuel gauging error led to fuel starvation and engine flameout from the base. Ray ejected successfully but was unable to separate from the seat and was killed on impact.

Operational history.

Although originally designed to succeed the U-2 in overflights over the Soviet Union and Cuba, the A-12 was never used for either role. After a U-2 was shot down in May 1960, the Soviet Union was considered too dangerous to overfly except in an emergency (and overflights were no longer necessary, thanks to reconnaissance satellites) and, although crews trained for flights over Cuba, U-2s continued to be adequate there.  The Director of the CIA decided to deploy some A-12s to Asia. The first A-12 arrived at Kadena Air Base on Okinawa on 22 May 1967. With the arrival of two more aircraft on 24 May, and 27 May this unit was declared to be operational on 30 May, and it began Operation Black Shield on 31 May. Mel Vojvodich flew the first Black Shield operation, over North Vietnam, photographing surface-to-air missile (SAM) sites, flying at, and at about Mach 3.1. During 1967 from the Kadena Air Base, the A-12s carried out 22 sorties in support of the Vietnam War. During 1968 further Black Shield operations were conducted in Vietnam. Additional sorties were also carried out during the Pueblo Crisis with North Korea.

Mission profile.

Operations and maintenance at Kadena AB began with the receipt of alert notification. Both a primary aircraft and pilot and a back-up aircraft and pilot were selected. The aircraft were given thorough inspection and servicing, all systems were checked, and the cameras equipped. Pilots received a detailed route briefing in the early evening prior to the day of flight. On the morning of the flight a final briefing occurred, at which time the condition of the aircraft and its systems was reported, last-minute weather forecasts reviewed, and other relevant intelligence communicated, together with any amendments or changes in the flight plan. Two hours prior to take-off the primary pilot had a medical examination, got into his suit, and was taken to the aircraft. If any malfunctions developed on the primary aircraft, the back-up could execute the mission one hour later.  A typical route profile for a mission over North Vietnam included a refueling shortly after take-off, south of Okinawa, the planned photographic pass or passes, withdrawal to a second aerial refueling in the Thailand area, and return to Kadena. Its turning radius of was such, however, that on some mission profiles it might intrude into Chinese airspace during the turn.  Once landed, the camera film was removed from the aircraft, boxed, and sent by special aircraft to the processing facilities. Film from earlier missions was developed at the Eastman Kodak plant in Rochester, New York. Later an Air Force Center in Japan carried out the processing in order to place the photointelligence in the hands of American commanders in Vietnam within 24 hours of completion of a mission.

SAM evasion over North Vietnam.

There were a number of reasons leading to the retirement of the A-12, but one major concern was the growing sophistication of Soviet-supplied surface-to-air missile (SAM) sites that it had to contend with over mission routes. In 1967, the vehicle was tracked with acquisition radar over North Vietnam, but the SAM site was unsuccessful with the Fan Song guidance radar used to home the missile to the target. On 28 October, a North Vietnamese SAM site launched a single, albeit unsuccessful, missile. Photography from this mission documented the event with photographs of missile smoke above the SAM firing site, and with pictures of the missile and of its contrail. Electronic countermeasures equipment appeared to perform well against the missile firing.  During a flight on 30 October 1967, pilot Dennis Sullivan detected radar tracking on his first pass over North Vietnam. Two sites prepared to launch missiles but neither did. During the second pass, at least six missiles were fired, each confirmed by missile vapor trails on mission photography. Looking through his rear-view periscope, Sullivan saw six missile contrails climb to about before converging on his aircraft. He noted the approach of four missiles, and although they all detonated behind him, one came within of his aircraft. Post-flight inspection revealed that a piece of metal had penetrated the lower right wing fillet area and lodged against the support structure of the wing tank. The fragment was not a warhead pellet but may have been a part of the debris from one of the missile detonations observed by the pilot.  The SA-2 'Guideline' was an early missile design intended to counter lower-flying and slower aircraft such as the B-52 and B-58. In response to faster, higher-flying designs like the B-70, the Soviets had begun development of greatly improved missile systems, notably the SA-5 'Gammon'. The Soviet Air Defence Forces ("Protivo-Vozdushnaya Oborona", PVO) cleared the SA-5 for service in 1967; if deployed to Vietnam, it would have provided an additional risk to the A-12.  The final Black Shield mission over North Vietnam and the Demilitarized Zone (DMZ) was flown on 8 March 1968. Good quality photography was obtained of Khe Sanh and the Laos, Cambodia, and South Vietnamese border areas. No usable photography was obtained of North Vietnam due to adverse weather conditions. There was no indication of a hostile weapons reaction and no ECM systems were activated.

Final missions over North Korea.

In 1968, three missions were flown over North Korea. The first mission occurred during a very tense period following seizure of the Navy intelligence ship "Pueblo" on 23 January. The aim was to discover whether the North Koreans were preparing any large scale hostile move following this incident and to actually find where the "Pueblo" was hidden. The ship was found anchored in an inlet in Wonsan Bay attended by two North Korean patrol boats and guarded by three Komars. Chinese tracking of the flight was apparent, but no missiles were fired at the Oxcart.  The second mission on 19 February 1968, was also the first two-pass mission over North Korea. The Oxcart vehicle photographed 84 primary targets plus 89 bonus targets. Scattered clouds covered 20 percent of the area, concealing the area in which the USS "Pueblo" was photographed on the previous mission. One new SA-2 site was identified near Wonsan.

Retirement.

Even before the A-12 became operational, its intended purpose of replacing the U-2 in overflights of the Soviet Union had become less likely. Soviet radar systems increased their blip-to-scan ratios, which rendered the A-12 vulnerable. In any event, President Kennedy had stated publicly that the United States would not resume such missions. By 1965, moreover, the photoreconnaissance satellite programs had progressed to the point that manned flights over the Soviet Union were unnecessary to collect strategic intelligence.  The A-12 program was ended on 28 December 1966 – even before Black Shield began in 1967 – due to budget concerns and because of the SR-71, which began to arrive at Kadena in March 1968. The twin-seat SR-71 was heavier and flew slightly lower and slower than the A-12.  Ronald L. Layton flew the 29th and final A-12 mission on 8 May 1968, over North Korea. On 4 June 1968, just 21⁄2 weeks before the fleet's retirement, an A-12 from Kadena, piloted by Jack Weeks, was lost over the Pacific Ocean near the Philippines while conducting a functional check flight after the replacement of one of its engines. Frank Murray made the final A-12 flight on 21 June 1968, to Palmdale, California, storage facility.  On 26 June 1968, Vice Admiral Rufus L. Taylor, the Deputy Director of Central Intelligence, presented the CIA Intelligence Star for valor to Weeks' widow and pilots Collins, Layton, Murray, Vojvodich, and Dennis B. Sullivan for participation in Black Shield.  The deployed A-12s and the eight non-deployed aircraft were placed in storage at Palmdale. All surviving aircraft remained there for nearly 20 years before being sent to museums around the U.S. On 20 January 2007, despite protests by Minnesota's legislature and volunteers who had maintained it in display condition, the A-12 preserved in Minneapolis, Minnesota, was sent to CIA headquarters to be displayed there.

Timeline.

Major events in the development and operation of the A-12 and its successor, the SR-71, include:  See SR-71 timeline for later SR-71 events.

Variants.

Training variant.

The A-12 training variant (60-6927 "Titanium Goose") was a two-seat model with two cockpits in tandem with the rear cockpit raised and slightly offset. In case of emergency, the variant was designed to allow the flight instructor to take control.

YF-12A.

The YF-12 program was a limited production variant of the A-12. Lockheed convinced the U.S. Air Force that an aircraft based on the A-12 would provide a less costly alternative to the recently canceled North American Aviation XF-108, since much of the design and development work on the YF-12 had already been done and paid for. Thus, in 1960 the Air Force agreed to take the seventh to ninth slots on the A-12 production line and have them completed in the YF-12A interceptor configuration.

M-21.

The "M-21", a two-seat variant, carried and launched the Lockheed D-21, an unmanned, faster and higher-flying reconnaissance drone. The M-21 had a pylon on its back for mounting the drone and a second cockpit for a Launch Control Operator/Officer (LCO) in the place of the A-12's Q bay. The D-21 was autonomous; after launch, it would fly over the target, travel to a predetermined rendezvous point, eject its data package, and self-destruct. A C-130 Hercules would catch the package in midair.  The M-21 program was canceled in 1966 after a drone collided with the mother ship at launch. The crew safely ejected, but LCO Ray Torick drowned when his flight suit filled with water after landing in the ocean.  The D-21 lived on in the form of a B-model launched from a pylon under the wing of the B-52 bomber. The D-21B performed operational missions over China from 1969 to 1971, but was not particularly successful.

Accidents and incidents.

Six of the 15 A-12s were lost in accidents, with the loss of two pilots and an engineer:  "Note":

The Lockheed A-12 was a high-altitude, Mach 3+ reconnaissance aircraft built for the United States Central Intelligence Agency (CIA) by Lockheed's Skunk Works, based on the designs of Clarence "Kelly" Johnson. The aircraft was designated A-12, the 12th in a series of internal design efforts for "Archangel", the aircraft's internal code name. In 1959, it was selected over Convair's FISH and Kingfish designs as the winner of Project GUSTO, and was developed and operated under Project Oxcart.

Lockheed A-12 bylo nejvýkonnější průzkumné letadlo dvacátého století. Bylo vyrobeno jako nástupce slavného výškového průzkumného letounu Lockheed U-2 a používáno výhradně CIA. Mnohem známější armádní verze nesla označení SR-71.


Etymology.

Old Norse literally means "ash tree" but the etymology of "embla" is uncertain, and two possibilities of the meaning of "embla" are generally proposed. The first meaning, "elm tree", is problematic, and is reached by deriving "*Elm-la" from "*Almilōn" and subsequently to ("elm"). The second suggestion is "vine", which is reached through "*Ambilō", which may be related to the Greek term (), itself meaning "vine, liana". The latter etymology has resulted in a number of theories.  According to Benjamin Thorpe "Grimm says the word embla, emla, signifies a busy woman, from amr, ambr, aml, ambl, assiduous labour; the same relation as Meshia and Meshiane, the ancient Persian names of the first man and woman, who were also formed from trees."

Attestations.

In stanza 17 of the "Poetic Edda" poem "Völuspá", the seeress reciting the poem states that Hœnir, Lóðurr and Odin once found Ask and Embla on land. The seeress says that the two were capable of very little, lacking in "ørlög" and says that they were given three gifts by the three gods:  The meaning of these gifts has been a matter of scholarly disagreement and translations therefore vary.  According to chapter 9 of the "Prose Edda" book "Gylfaginning", the three brothers Vili, Vé, and Odin, are the creators of the first man and woman. The brothers were once walking along a beach and found two trees there. They took the wood and from it created the first human beings; Ask and Embla. One of the three gave them the breath of life, the second gave them movement and intelligence, and the third gave them shape, speech, hearing and sight. Further, the three gods gave them clothing and names. Ask and Embla go on to become the progenitors of all humanity and were given a home within the walls of Midgard.

Theories.

Indo-European origins.

A Proto-Indo-European basis has been theorized for the duo based on the etymology of "embla" meaning "vine." In Indo-European societies, an analogy is derived from the drilling of fire and sexual intercourse. Vines were used as a flammable wood, where they were placed beneath a drill made of harder wood, resulting in fire. Further evidence of ritual making of fire in Scandinavia has been theorized from a depiction on a stone plate on a Bronze Age grave in Kivik, Scania, Sweden.  Jaan Puhvel comments that "ancient myths teem with trite 'first couples' of the type of Adam and his by-product Eve. In Indo-European tradition, these range from the Vedic Yama and Yamī and the Iranian Mašya and Mašyānag to the Icelandic Askr and Embla, with trees or rocks as preferred raw material, and dragon's teeth or other bony substance occasionally thrown in for good measure".  In his study of the comparative evidence for an origin of mankind from trees in Indo-European society, Anders Hultgård observes that "myths of the origin of mankind from trees or wood seem to be particularly connected with ancient Europe and Indo-Europe and Indo-European-speaking peoples of Asia Minor and Iran. By contrast the cultures of the Near East show almost exclusively the type of anthropogonic stories that derive man's origin from clay, earth or blood by means of a divine creation act".

Other potential Germanic analogues.

Two wooden figures—the Braak Bog Figures—of "more than human height" were unearthed from a peat bog at Braak in Schleswig, Germany. The figures depict a nude male and a nude female. Hilda Ellis Davidson comments that these figures may represent a "Lord and Lady" of the Vanir, a group of Norse gods, and that "another memory of [these wooden deities] may survive in the tradition of the creation of Ask and Embla, the man and woman who founded the human race, created by the gods from trees on the seashore".  A figure named Æsc (Old English "ash tree") appears as the son of Hengest in the Anglo-Saxon genealogy for the kings of Kent. This has resulted in a number of theories that the figures may have had an earlier basis in pre-Norse Germanic mythology.  Connections have been proposed between Ask and Embla and the Vandal kings Assi and Ambri, attested in Paul the Deacon's 7th century AD work "Origo Gentis Langobardorum". There, the two ask the god Godan (Odin) for victory. The name "Ambri", like Embla, likely derives from "*Ambilō".

Catalog of dwarfs.

A stanza preceding the account of the creation of Ask and Embla in "Völuspá" provides a catalog of dwarfs, and stanza 10 has been considered as describing the creation of human forms from the earth. This may potentially mean that dwarfs formed humans, and that the three gods gave them life. Carolyne Larrington theorizes that humans are metaphorically designated as trees in Old Norse works (examples include "trees of jewellery" for women and "trees of battle" for men) due to the origin of humankind stemming from trees; Ask and Embla.

Modern influence.

Ask and Embla have been the subject of a number of references and artistic depictions. A sculpture depicting the two stands in the southern Swedish city of Sölvesborg, created in 1948 by Stig Blomberg. Ask and Embla are depicted on two of the sixteen wooden panels found on the Oslo City Hall in Oslo, Norway, by Dagfin Werenskiold.

In Norse mythology, Ask and Embla (from )—male and female respectively—were the first two humans, created by the gods. The pair are attested in both the "Poetic Edda", compiled in the 13th century from earlier traditional sources, and the "Prose Edda", written in the 13th century by Snorri Sturluson. In both sources, three gods, one of whom is Odin, find Ask and Embla and bestow upon them various corporeal and spiritual gifts. A number of theories have been proposed to explain the two figures, and there are occasional references to them in popular culture.

Ask a Embla byli v severské mytologii první muž a žena, podobně jako Adam a Eva v Genesis. Když bůh Ódin a jeho bratři Vili a Vé stvořili svět, procházeli se po mořském břehu a našli dva kmeny. Ódin jim dal život a dech, Vili rozum a Vé podobu, řeč, zrak a sluch. K životu jim byl dán Midgard a Ask („jasan“) a Embla („jilm“) se stali předchůdci všech lidí.


History.

Acoustics, the science of sound, starts as far back as Pythagoras in the 6th century BC, who wrote on the mathematical properties of stringed instruments. Echolocation in bats was discovered by Lazzaro Spallanzani in 1794, when he demonstrated that bats hunted and navigated by inaudible sound, not vision. Francis Galton in 1893 invented the Galton whistle, an adjustable whistle that produced ultrasound, which he used to measure the hearing range of humans and other animals, demonstrating that many animals could hear sounds above the hearing range of humans. The first technological application of ultrasound was an attempt to detect submarines by Paul Langevin in 1917. The piezoelectric effect, discovered by Jacques and Pierre Curie in 1880, was useful in transducers to generate and detect ultrasonic waves in air and water.

Definition.

Ultrasound is defined by the American National Standards Institute as "sound at frequencies greater than 20 kHz". In air at atmospheric pressure, ultrasonic waves have wavelengths of 1.9 cm or less.

Perception.

Humans.

The upper frequency limit in humans (approximately 20 kHz) is due to limitations of the middle ear. Auditory sensation can occur if high‐intensity ultrasound is fed directly into the human skull and reaches the cochlea through bone conduction, without passing through the middle ear.  Children can hear some high-pitched sounds that older adults cannot hear, because in humans the upper limit pitch of hearing tends to decrease with age. An American cell phone company has used this to create ring signals that supposedly are only audible to younger humans, but many older people can hear the signals, which may be because of the considerable variation of age-related deterioration in the upper hearing threshold. The Mosquito is an electronic device that uses a high pitched frequency to deter loitering by young people.

Animals.

Bats use a variety of ultrasonic ranging (echolocation) techniques to detect their prey. They can detect frequencies beyond 100 kHz, possibly up to 200 kHz.  Many insects have good ultrasonic hearing, and most of these are nocturnal insects listening for echolocating bats. These include many groups of moths, beetles, praying mantids and lacewings. Upon hearing a bat, some insects will make evasive manoeuvres to escape being caught. Ultrasonic frequencies trigger a reflex action in the noctuid moth that causes it to drop slightly in its flight to evade attack. Tiger moths also emit clicks which may disturb bats' echolocation, and in other cases may advertise the fact that they are poisonous by emitting sound.  Dogs and cats' hearing range extends into the ultrasound; the top end of a dog's hearing range is about 45 kHz, while a cat's is 64 kHz. The wild ancestors of cats and dogs evolved this higher hearing range to hear high-frequency sounds made by their preferred prey, small rodents. A dog whistle is a whistle that emits ultrasound, used for training and calling dogs. The frequency of most dog whistles is within the range of 23 to 54 kHz.  Toothed whales, including dolphins, can hear ultrasound and use such sounds in their navigational system (biosonar) to orient and to capture prey. Porpoises have the highest known upper hearing limit at around 160 kHz. Several types of fish can detect ultrasound. In the order Clupeiformes, members of the subfamily Alosinae (shad) have been shown to be able to detect sounds up to 180 kHz, while the other subfamilies (e.g. herrings) can hear only up to 4 kHz.  Ultrasound generator/speaker systems are sold as electronic pest control devices, which are claimed to frighten away rodents and insects, but there is no scientific evidence that the devices work.

Detection and ranging.

Non-contact sensor.

An ultrasonic level or sensing system requires no contact with the target. For many processes in the medical, pharmaceutical, military and general industries this is an advantage over inline sensors that may contaminate the liquids inside a vessel or tube or that may be clogged by the product.  Both continuous wave and pulsed systems are used. The principle behind a pulsed-ultrasonic technology is that the transmit signal consists of short bursts of ultrasonic energy. After each burst, the electronics looks for a return signal within a small window of time corresponding to the time it takes for the energy to pass through the vessel. Only a signal received during this window will qualify for additional signal processing.  A popular consumer application of ultrasonic ranging was the Polaroid SX-70 camera, which included a lightweight transducer system to focus the camera automatically. Polaroid later licensed this ultrasound technology and it became the basis of a variety of ultrasonic products.

Motion sensors and flow measurement.

A common ultrasound application is an automatic door opener, where an ultrasonic sensor detects a person's approach and opens the door. Ultrasonic sensors are also used to detect intruders; the ultrasound can cover a wide area from a single point. The flow in pipes or open channels can be measured by ultrasonic flowmeters, which measure the average velocity of flowing liquid. In rheology, an acoustic rheometer relies on the principle of ultrasound. In fluid mechanics, fluid flow can be measured using an ultrasonic flow meter.

Nondestructive testing.

Ultrasonic testing is a type of nondestructive testing commonly used to find flaws in materials and to measure the thickness of objects. Frequencies of 2 to 10 MHz are common, but for special purposes other frequencies are used. Inspection may be manual or automated and is an essential part of modern manufacturing processes. Most metals can be inspected as well as plastics and aerospace composites. Lower frequency ultrasound (50–500 kHz) can also be used to inspect less dense materials such as wood, concrete and cement.  Ultrasound inspection of welded joints has been an alternative to radiography for nondestructive testing since the 1960s. Ultrasonic inspection eliminates the use of ionizing radiation, with safety and cost benefits. Ultrasound can also provide additional information such as the depth of flaws in a welded joint. Ultrasonic inspection has progressed from manual methods to computerized systems that automate much of the process. An ultrasonic test of a joint can identify the existence of flaws, measure their size, and identify their location. Not all welded materials are equally amenable to ultrasonic inspection; some materials have a large grain size that produces a high level of background noise in measurements. Ultrasonic thickness measurement is one technique used to monitor quality of welds.

Ultrasonic range finding.

A common use of ultrasound is in underwater range finding; this use is also called Sonar. An ultrasonic pulse is generated in a particular direction. If there is an object in the path of this pulse, part or all of the pulse will be reflected back to the transmitter as an echo and can be detected through the receiver path. By measuring the difference in time between the pulse being transmitted and the echo being received, it is possible to determine the distance.  The measured travel time of Sonar pulses in water is strongly dependent on the temperature and the salinity of the water. Ultrasonic ranging is also applied for measurement in air and for short distances. For example, hand-held ultrasonic measuring tools can rapidly measure the layout of rooms.  Although range finding underwater is performed at both sub-audible and audible frequencies for great distances (1 to several kilometers), ultrasonic range finding is used when distances are shorter and the accuracy of the distance measurement is desired to be finer. Ultrasonic measurements may be limited through barrier layers with large salinity, temperature or vortex differentials. Ranging in water varies from about hundreds to thousands of meters, but can be performed with centimeters to meters accuracy

Ultrasound Identification (USID).

Ultrasound Identification (USID) is a Real Time Locating System (RTLS) or Indoor Positioning System (IPS) technology used to automatically track and identify the location of objects in real time using simple, inexpensive nodes (badges/tags) attached to or embedded in objects and devices, which then transmit an ultrasound signal to communicate their location to microphone sensors.

Imaging.

The potential for ultrasonic imaging of objects, with a 3 GHz sound wave producing resolution comparable to an optical image, was recognized by Sokolov in 1939, but techniques of the time produced relatively low-contrast images with poor sensitivity. Ultrasonic imaging uses frequencies of 2 megahertz and higher; the shorter wavelength allows resolution of small internal details in structures and tissues. The power density is generally less than 1 watt per square centimetre to avoid heating and cavitation effects in the object under examination. High and ultra high ultrasound waves are used in acoustic microscopy, with frequencies up to 4 gigahertz. Ultrasonic imaging applications include industrial nondestructive testing, quality control and medical uses.

Acoustic microscopy.

Acoustic microscopy is the technique of using sound waves to visualize structures too small to be resolved by the human eye. Frequencies up to several gigahertz are used in acoustic microscopes. The reflection and diffraction of sound waves from microscopic structures can yield information not available with light.

Human medicine.

Medical ultrasound is an ultrasound-based diagnostic medical imaging technique used to visualize muscles, tendons, and many internal organs to capture their size, structure and any pathological lesions with real time tomographic images. Ultrasound has been used by radiologists and sonographers to image the human body for at least 50 years and has become a widely used diagnostic tool. The technology is relatively inexpensive and portable, especially when compared with other techniques, such as magnetic resonance imaging (MRI) and computed tomography (CT). Ultrasound is also used to visualize fetuses during routine and emergency prenatal care. Such diagnostic applications used during pregnancy are referred to as obstetric sonography. As currently applied in the medical field, properly performed ultrasound poses no known risks to the patient. Sonography does not use ionizing radiation, and the power levels used for imaging are too low to cause adverse heating or pressure effects in tissue. Although the long-term effects due to ultrasound exposure at diagnostic intensity are still unknown, currently most doctors feel that the benefits to patients outweigh the risks. The ALARA (As Low As Reasonably Achievable) principle has been advocated for an ultrasound examination that is, keeping the scanning time and power settings as low as possible but consistent with diagnostic imaging and that by that principle nonmedical uses, which by definition are not necessary, are actively discouraged.  Ultrasound is also increasingly being used in trauma and first aid cases, with emergency ultrasound becoming a staple of most EMT response teams. Furthermore, ultrasound is used in remote diagnosis cases where teleconsultation is required, such as scientific experiments in space or mobile sports team diagnosis.  According to RadiologyInfo, ultrasounds are useful in the detection of pelvic abnormalities and can involve techniques known as abdominal (transabdominal) ultrasound, vaginal (transvaginal or endovaginal) ultrasound in women, and also rectal (transrectal) ultrasound in men.

Veterinary medicine.

Diagnostic ultrasound is used externally in horses for evaluation of soft tissue and tendon injuries, and internally in particular for reproductive work evaluation of the reproductive tract of the mare and pregnancy detection. It may also be used in an external manner in stallions for evaluation of testicular condition and diameter as well as internally for reproductive evaluation (deferent duct etc.).  Starting at the turn of the century, ultrasound technology began to be used by the beef cattle industry to improve animal health and the yield of cattle operations. Ultrasound is used to evaluate fat thickness, rib eye area, and intramuscular fat in living animals. It is also used to evaluate the health and characteristics of unborn calves.  Ultrasound technology provides a means for cattle producers to obtain information that can be used to improve the breeding and husbandry of cattle. The technology can be expensive, and it requires a substantial time commitment for continuous data collection and operator training. Nevertheless, this technology has proven useful in managing and running a cattle breeding operation.

Processing and power.

High-power applications of ultrasound often use frequencies between 20 kHz and a few hundred kHz. Intensities can be very high; above 10 watts per square centimeter, cavitation can be inducted in liquid media, and some applications use up to 1000 watts per square centimeter. Such high intensities can induce chemical changes or produce significant effects by direct mechanical action, and can inactivate harmful microorganisms.

Physical therapy.

Ultrasound has been used since the 1940s by physical and occupational therapists for treating connective tissue: ligaments, tendons, and fascia (and also scar tissue). Conditions for which ultrasound may be used for treatment include the follow examples: ligament sprains, muscle strains, tendonitis, joint inflammation, plantar fasciitis, metatarsalgia, facet irritation, impingement syndrome, bursitis, rheumatoid arthritis, osteoarthritis, and scar tissue adhesion.

Biomedical applications.

Ultrasound also has therapeutic applications, which can be highly beneficial when used with dosage precautions. Relatively high power ultrasound can break up stony deposits or tissue, accelerate the effect of drugs in a targeted area, assist in the measurement of the elastic properties of tissue, and can be used to sort cells or small particles for research.

Ultrasonic impact treatment.

Ultrasonic impact treatment (UIT) uses ultrasound to enhance the mechanical and physical properties of metals. It is a metallurgical processing technique in which ultrasonic energy is applied to a metal object. Ultrasonic treatment can result in controlled residual compressive stress, grain refinement and grain size reduction. Low and high cycle fatigue are enhanced and have been documented to provide increases up to ten times greater than non-UIT specimens. Additionally, UIT has proven effective in addressing stress corrosion cracking, corrosion fatigue and related issues.  When the UIT tool, made up of the ultrasonic transducer, pins and other components, comes into contact with the work piece it acoustically couples with the work piece, creating harmonic resonance. This harmonic resonance is performed at a carefully calibrated frequency, to which metals respond very favorably.  Depending on the desired effects of treatment a combination of different frequencies and displacement amplitude is applied. These frequencies range between 25 and 55 kHz, with the displacement amplitude of the resonant body of between 22 and 50 μm (0.00087 and 0.0020 in).  UIT devices rely on magnetostrictive transducers.

Processing.

Ultrasonication offers great potential in the processing of liquids and slurries, by improving the mixing and chemical reactions in various applications and industries. Ultrasonication generates alternating low-pressure and high-pressure waves in liquids, leading to the formation and violent collapse of small vacuum bubbles. This phenomenon is termed cavitation and causes high speed impinging liquid jets and strong hydrodynamic shear-forces. These effects are used for the deagglomeration and milling of micrometre and nanometre-size materials as well as for the disintegration of cells or the mixing of reactants. In this aspect, ultrasonication is an alternative to high-speed mixers and agitator bead mills. Ultrasonic foils under the moving wire in a paper machine will use the shock waves from the imploding bubbles to distribute the cellulose fibres more uniformly in the produced paper web, which will make a stronger paper with more even surfaces. Furthermore, chemical reactions benefit from the free radicals created by the cavitation as well as from the energy input and the material transfer through boundary layers. For many processes, this sonochemical (see sonochemistry) effect leads to a substantial reduction in the reaction time, like in the transesterification of oil into biodiesel. Substantial ultrasonic intensity and high ultrasonic vibration amplitudes are required for many processing applications, such as nano-crystallization, nano-emulsification, deagglomeration, extraction, cell disruption, as well as many others. Commonly, a process is first tested on a laboratory scale to prove feasibility and establish some of the required ultrasonic exposure parameters. After this phase is complete, the process is transferred to a pilot (bench) scale for flow-through pre-production optimization and then to an industrial scale for continuous production. During these scale-up steps, it is essential to make sure that all local exposure conditions (ultrasonic amplitude, cavitation intensity, time spent in the active cavitation zone, etc.) stay the same. If this condition is met, the quality of the final product remains at the optimized level, while the productivity is increased by a predictable "scale-up factor". The productivity increase results from the fact that laboratory, bench and industrial-scale ultrasonic processor systems incorporate progressively larger ultrasonic horns, able to generate progressively larger high-intensity cavitation zones and, therefore, to process more material per unit of time. This is called "direct scalability". It is important to point out that increasing the power of the ultrasonic processor alone does "not" result in direct scalability, since it may be (and frequently is) accompanied by a reduction in the ultrasonic amplitude and cavitation intensity. During direct scale-up, all processing conditions must be maintained, while the power rating of the equipment is increased in order to enable the operation of a larger ultrasonic horn.

Ultrasonic manipulation and characterization of particles.

A researcher at the Industrial Materials Research Institute, Alessandro Malutta, devised an experiment that demonstrated the trapping action of ultrasonic standing waves on wood pulp fibers diluted in water and their parallel orienting into the equidistant pressure planes. The time to orient the fibers in equidistant planes is measured with a laser and an electro-optical sensor. This could provide the paper industry a quick on-line fiber size measurement system. A somewhat different implementation was demonstrated at Pennsylvania State University using a microchip which generated a pair of perpendicular standing surface acoustic waves allowing to position particles equidistant to each other on a grid. This experiment, called acoustic tweezers, can be used for applications in material sciences, biology, physics, chemistry and nanotechnology.

Ultrasonic cleaning.

Ultrasonic cleaners, sometimes mistakenly called "supersonic cleaners", are used at frequencies from 20 to 40 kHz for jewellery, lenses and other optical parts, watches, dental instruments, surgical instruments, diving regulators and industrial parts. An ultrasonic cleaner works mostly by energy released from the collapse of millions of microscopic cavitations near the dirty surface. The bubbles made by cavitation collapse forming tiny jets directed at the surface.

Ultrasonic disintegration.

Similar to ultrasonic cleaning, biological cells including bacteria can be disintegrated. High power ultrasound produces cavitation that facilitates particle disintegration or reactions. This has uses in biological science for analytical or chemical purposes (sonication and sonoporation) and in killing bacteria in sewage. High power ultrasound can disintegrate corn slurry and enhance liquefaction and saccharification for higher ethanol yield in dry corn milling plants.

Ultrasonic humidifier.

The ultrasonic humidifier, one type of nebulizer (a device that creates a very fine spray), is a popular type of humidifier. It works by vibrating a metal plate at ultrasonic frequencies to nebulize (sometimes incorrectly called "atomize") the water. Because the water is not heated for evaporation, it produces a cool mist. The ultrasonic pressure waves nebulize not only the water but also materials in the water including calcium, other minerals, viruses, fungi, bacteria, and other impurities. Illness caused by impurities that reside in a humidifier's reservoir fall under the heading of "Humidifier Fever".  Ultrasonic humidifiers are frequently used in aeroponics, where they are generally referred to as foggers.

Ultrasonic welding.

In ultrasonic welding of plastics, high frequency (15 kHz to 40 kHz ) low amplitude vibration is used to create heat by way of friction between the materials to be joined. The interface of the two parts is specially designed to concentrate the energy for maximum weld strength.

Sonochemistry.

Power ultrasound in the 20–100 kHz range is used in chemistry. The ultrasound does not interact directly with molecules to induce the chemical change, as its typical wavelength (in the millimeter range) is too long compared to the molecules. Instead, the energy causes cavitation which generates extremes of temperature and pressure in the liquid where the reaction happens. Ultrasound also breaks up solids and removes passivating layers of inert material to give a larger surface area for the reaction to occur over. Both of these effects make the reaction faster. In 2008, Atul Kumar reported synthesis of Hantzsch esters and polyhydroquinoline derivatives via multi-component reaction protocol in aqueous micelles using ultrasound.  Ultrasound is used in extraction, using different frequencies.

Weapons.

Ultrasound has been studied as a basis for sonic weapons, for applications such as riot control, disorientation of attackers, up to lethal levels of sound.

Wireless communication.

In July 2015, The Economist reported that researchers at the University of California, Berkeley have conducted ultrasound studies using graphene diaphragms. The thinness and low weight of graphene combined with its strength make it an effective material to use in ultrasound communications. One suggested application of the technology would be underwater communications, where radio waves typically do not travel well.  Ultrasonic signals have been used in "audio beacons" for cross-device tracking of Internet users.

Other uses.

Ultrasound when applied in specific configurations can produce short bursts of light in an exotic phenomenon known as sonoluminescence. This phenomenon is being investigated partly because of the possibility of bubble fusion (a nuclear fusion reaction hypothesized to occur during sonoluminescence).  Ultrasound is used when characterizing particulates through the technique of ultrasound attenuation spectroscopy or by observing electroacoustic phenomena or by transcranial pulsed ultrasound.  Audio can be propagated by modulated ultrasound.  A formerly popular consumer application of ultrasound was in television remote controls for adjusting volume and changing channels. Introduced by Zenith in the late 1950s, the system used a hand-held remote control containing short rod resonators struck by small hammers, and a microphone on the set. Filters and detectors discriminated between the various operations. The principal advantages were that no battery was needed in the hand-held control box and, unlike radio waves, the ultrasound was unlikely to affect neighboring sets. Ultrasound remained in use until displaced by infrared systems starting in the late 1980s.

Safety.

Occupational exposure to ultrasound in excess of 120 dB may lead to hearing loss. Exposure in excess of 155 dB may produce heating effects that are harmful to the human body, and it has been calculated that exposures above 180 dB may lead to death. The UK's independent Advisory Group on Non-ionising Radiation (AGNIR) produced a report in 2010, which was published by the UK Health Protection Agency (HPA). This report recommended an exposure limit for the general public to airborne ultrasound sound pressure levels (SPL) of 70 dB (at 20 kHz), and 100 dB (at 25 kHz and above).

Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hear it. This limit varies from person to person and is approximately 20 kilohertz (20,000 hertz) in healthy young adults. Ultrasound devices operate with frequencies from 20 kHz up to several gigahertz.

Ultrazvuk (UZ) je akustické vlnění, jehož frekvence leží nad hranicí slyšitelnosti lidského ucha, slyšitelného zvuku, která je cca 20 kHz. Někteří živočichové část ultrazvukového spektra vnímají, případně i vydávají (delfíni, psi, netopýři) a využívají jej jak k běžné komunikaci, tak zejména k echolokaci.


Etymology.

The etymological origin of the name Cherusci is not known with certainty. According to the dominant opinion in scholarship, the name may derive from the ancient Germanic word "*herut" (Modern English "hart", i. e. "deer"). The tribe may have been named after the deer because it had a totemistic significance in Germanic symbolism. A different hypothesis, proposed in the 19th century by Jacob Grimm and others, derives the name from "*heru-", a word for "sword" (cf. Gothic "hairus", Old English "heoru"). Hans Kuhn has argued that the derivational suffix "-sk-", involved in both explanations, is otherwise not common in Germanic. He suggested that the name may therefore be a compound of ultimately non-Germanic origin, connected to the hypothesized "Nordwestblock".

History.

The first historical mention of the Cherusci occurs in Book 6.10 of Julius Caesar's "De Bello Gallico", which recounts events of 53 BC. Caesar relates that he crossed the Rhine again to punish the Suebi for sending reinforcements to the Treveri. He mentions that the Bacenis forest (a relatively impenetrable beech forest, possibly the Harz) separated the territory of the Cherusci from that of the Suebi. In 12 BC, the Cherusci and other Germanic tribes were subjugated by the Romans. They appear to have been living in the same homeland when Tacitus wrote, 150 years later, describing them as living east of the Chauci and Chatti. This is generally interpreted to be an area between the rivers Weser and Elbe.  As Rome tried to expand in northern Europe beyond the Rhine, it exploited divisions within the Cherusci, and for some time the tribe was considered a Roman ally. At this time, the tribe was split between Arminius (known in modern German as "Hermann der Cherusker", although his actual Germanic name was more likely Erminaz) and Segestes. Arminius advocated breaking allegiance to Rome and declaring independence, while Segestes wanted to remain loyal. By about 8 AD, Arminius had gained the upper hand and began planning rebellion. Segestes repeatedly warned Publius Quinctilius Varus, the governor of Gaul, that rebellion was being planned, but Varus declined to act until the rebellion had broken out.  In 9 AD, in the Battle of the Teutoburg Forest, an army of allied Germanic tribes under the command of Arminius (the Cherusci, Bructeri, Marsi, Sicambri, Chauci, and Chatti) annihilated three Roman legions commanded by Varus. The legions' eagle standards, of great symbolic importance to the Romans, were lost. The numbers of these three legions, Legio XVII, Legio XVIII, and Legio XIX, were never used again.  After the mutinies of the German legions in 14 AD, Germanicus decided, at the urging of his men, to march into Germany to restore their lost honor. In 15 AD, after a quick raid on the Chatti, they invaded the lands of the Marsi in 14 AD with 12,000 legionnaires, 26 cohorts of auxiliaries, and eight cavalry squadrons. According to Tacitus (Annals 1, 51), an area of 50 Roman miles wide was laid to waste with fire and sword: "No sex, no age found pity." A legion eagle from Varus's defeat, either from the XVII or XVIII, was recovered. Then, he began a campaign against the Cherusci. He received an appeal to rescue Segestes, who was besieged by Arminius. Segestes was rescued, along with a group of relatives and dependents, including Thusnelda, Segestes' daughter and the wife of Arminius. Germanicus spared them and gave them land in Gaul. He then found the site of the Battle of Teutoburg Forest. His men buried the dead and built a funeral mound.  A series of battles followed. After major casualties on the Romans, Tiberius forbid further campaigns. This effectively led to the withdrawal of the Roman troops until the collapse of the Roman Empire.  After Arminius' death, the Romans left the Cherusci more or less to their own devices. In 47 AD, the Cherusci asked Rome to send Italicus, the nephew of Arminius, to become king, as civil war had destroyed their nobility. He was initially well liked, but since he was raised in Rome as a Roman citizen, he soon fell out of favor. Tacitus writes of the Cherusci of his time (about 100 AD):Dwelling on one side of the Chauci and Chatti, the Cherusci long cherished, unassailed, an excessive and enervating love of peace. This was more pleasant than safe, for to be peaceful is self-deception among lawless and powerful neighbours. Where the strong hand decides, moderation and justice are terms applied only to the more powerful; and so the Cherusci, ever reputed good and just, are now called cowards and fools, while in the case of the victorious Chatti success has been identified with prudence. The downfall of the Cherusci brought with it also that of the Fosi, a neighbouring tribe, which shared equally in their disasters, though they had been inferior to them in prosperous days.  Claudius Ptolemy in his "Geography", describes the Χαιρουσκοὶ and Καμαυοὶ (Cherusci and Chamavi) as living near each other and also near to "Mount Melibocus" (probably the Harz Mountains) and to the Calucones, who lived on both banks of the Elbe.  The later history of the Cherusci is mostly unknown. In the fourth century AD, they perhaps contributed to the formation of the Saxon people.

The Cherusci were an early Germanic people that inhabited parts of the plains and forests of northwestern Germany, in the area possibly near present-day Hanover, during the first centuries BC and AD. Ethnically, Pliny the Elder groups them with their neighbours, the Suebi and Chatti, as well as the Hermunduri, as Hermiones, one of the Germanic groupings said to descend from an ancestor named Mannus. They led an important war against the Roman Empire. Subsequently, they were probably absorbed into the late classical Germanic tribal groups such as the Saxons, Thuringians, Franks, Bavarians and Allemanni.

Cheruskové byli jedním z germánských kmenů obývající údolí řeky Rýn, roviny a lesy v severozápadním Německu (mezi dnešními městy Osnabrück a Hannover) během 1. století př. n. l. a 1. století. Byli to první spojenci a nepřátelé Římské říše. Nejvíce se proslavili bitvou v Teutoburském lese, kdy spojené germánské kmeny (Cheruskové, Marsové, Chattové a Brukteři) pod vedením cheruského bojovníka Arminia zničily 3 římské legie, které vedl Publius Quinctilius Varus. Tato zdrcující porážka zastavila Římany v postupu a přinutila říši stáhnout se ještě na několik dalších let za Rýn, Dunaj a za hranice ("limes Germanicus"), které byly zbudovány jako důsledek ztrát v bitvě a uzavřely prostor mezi oběma řekami. Dle záznamů kmen patrně později splynul s jiným, jako byly například Frankové či Alamani.