doc_id
int64 0
9.68k
| text
stringlengths 151
3.71k
| title
stringlengths 3
59
|
|---|---|---|
1,200 |
Unaspirated or tenuis consonants are occasionally marked with the modifier letter for unaspiration ⟨◌˭⟩, a superscript equal sign: ⟨t˭⟩. Usually, however, unaspirated consonants are left unmarked: ⟨t⟩.
|
Aspirated_consonant
|
1,201 |
Icelandic and Faroese have preaspirated [ʰp ʰt ʰk]; some scholars interpret these as consonant clusters as well. In Icelandic, preaspirated stops contrast with double stops and single stops:
|
Aspirated_consonant
|
1,202 |
Preaspirated stops also occur in most Sami languages; for example, in North Sami, the unvoiced stop and affricate phonemes /p/, /t/, /ts/, /tʃ/, /k/ are pronounced preaspirated ([ʰp], [ʰt] [ʰts], [ʰtʃ], [ʰk]) when they occur in medial or final position.
|
Aspirated_consonant
|
1,203 |
The term aspiration sometimes refers to the sound change of debuccalization, in which a consonant is lenited (weakened) to become a glottal stop or fricative [ʔ h ɦ].
|
Aspirated_consonant
|
1,204 |
Although most aspirated obstruents in the world's language are stops and affricates, aspirated fricatives such as [sʰ], [fʰ] or [ɕʰ] have been documented in Korean, in a few Tibeto-Burman languages, in some Oto-Manguean languages, and in the Siouan language Ofo. Some languages, such as Choni Tibetan, have up to four contrastive aspirated fricatives [sʰ] [ɕʰ], [ʂʰ] and [xʰ].
|
Aspirated_consonant
|
1,205 |
Phonetically in some languages, such as Navajo, aspiration of stops tends to be realised as voiceless velar airflow; aspiration of affricates is realised as an extended length of the frication.
|
Aspirated_consonant
|
1,206 |
Some linguists restrict the double-dot subscript ⟨◌̤⟩ to murmured sonorants, such as vowels and nasals, which are murmured throughout their duration, and use the superscript hook-aitch ⟨◌ʱ⟩ for the breathy-voiced release of obstruents.
|
Aspirated_consonant
|
1,207 |
Western Armenian has a two-way distinction between aspirated and voiced: /tʰ d/. Western Armenian aspirated /tʰ/ corresponds to Eastern Armenian aspirated /tʰ/ and voiced /d/, and Western voiced /d/ corresponds to Eastern voiceless /t/.
|
Aspirated_consonant
|
1,208 |
In some languages, such as English, aspiration is allophonic. Stops are distinguished primarily by voicing, and voiceless stops are sometimes aspirated, while voiced stops are usually unaspirated.
|
Aspirated_consonant
|
1,209 |
Hydrogen's rarer isotopes also each have specific applications. Deuterium (hydrogen-2) is used in nuclear fission applications as a moderator to slow neutrons, and in nuclear fusion reactions. Deuterium compounds have applications in chemistry and biology in studies of reaction isotope effects. Tritium (hydrogen-3), produced in nuclear reactors, is used in the production of hydrogen bombs, as an isotopic label in the biosciences, and as a radiation source in luminous paints.
|
Hydrogen
|
1,210 |
The universal emergence of atomic hydrogen first occurred during the recombination epoch. At standard temperature and pressure, hydrogen is a colorless, odorless, tasteless, non-toxic, nonmetallic, highly combustible diatomic gas with the molecular formula H2. Since hydrogen readily forms covalent compounds with most non-metallic elements, most of the hydrogen on Earth exists in molecular forms such as in the form of water or organic compounds. Hydrogen plays a particularly important role in acid–base reactions as many acid-base reactions involve the exchange of protons between soluble molecules. In ionic compounds, hydrogen can take the form of a negative charge (i.e., anion) when it is known as a hydride, or as a positively charged (i.e., cation) species denoted by the symbol H+. The hydrogen cation is written as though composed of a bare proton, but in reality, hydrogen cations in ionic compounds are always more complex species than that would suggest. As the only neutral atom for which the Schrödinger equation can be solved analytically, study of the energetics and bonding of the hydrogen atom has played a key role in the development of quantum mechanics.
|
Hydrogen
|
1,211 |
Hydrogen poses a number of hazards to human safety, from potential detonations and fires when mixed with air to being an asphyxiant in its pure, oxygen-free form. In addition, liquid hydrogen is a cryogen and presents dangers (such as frostbite) associated with very cold liquids. Hydrogen dissolves in many metals, and, in addition to leaking out, may have adverse effects on them, such as hydrogen embrittlement, leading to cracks and explosions. Hydrogen gas leaking into external air may spontaneously ignite. Moreover, hydrogen fire, while being extremely hot, is almost invisible, and thus can lead to accidental burns.
|
Hydrogen
|
1,212 |
Throughout the universe, hydrogen is mostly found in the atomic and plasma states whose properties are quite different from molecular hydrogen. As a plasma, hydrogen's electron and proton are not bound together, resulting in very high electrical conductivity and high emissivity (producing the light from the Sun and other stars). The charged particles are highly influenced by magnetic and electric fields. For example, in the solar wind they interact with the Earth's magnetosphere giving rise to Birkeland currents and the aurora. Hydrogen is found in the neutral atomic state in the interstellar medium. The large amount of neutral hydrogen found in the damped Lyman-alpha systems is thought to dominate the cosmological baryonic density of the Universe up to redshift z=4.
|
Hydrogen
|
1,213 |
From all the fault gases formed in power transformers, hydrogen is the most common and is generated under most fault conditions; thus, formation of hydrogen is an early indication of serious problems in the transformer's life cycle.
|
Hydrogen
|
1,214 |
Under anaerobic conditions, iron and steel alloys are slowly oxidized by the protons of water concomitantly reduced in molecular hydrogen (H
2). The anaerobic corrosion of iron leads first to the formation of ferrous hydroxide (green rust) and can be described by the following reaction:
|
Hydrogen
|
1,215 |
The energy levels of hydrogen can be calculated fairly accurately using the Bohr model of the atom, which conceptualizes the electron as "orbiting" the proton in analogy to the Earth's orbit of the Sun. However, the electromagnetic force attracts electrons and protons to one another, while planets and celestial objects are attracted to each other by gravity. Because of the discretization of angular momentum postulated in early quantum mechanics by Bohr, the electron in the Bohr model can only occupy certain allowed distances from the proton, and therefore only certain allowed energies.
|
Hydrogen
|
1,216 |
Hydrogen is the only element that has different names for its isotopes in common use today. During the early study of radioactivity, various heavy radioactive isotopes were given their own names, but such names are no longer used, except for deuterium and tritium. The symbols D and T (instead of 2H and 3H) are sometimes used for deuterium and tritium, but the corresponding symbol for protium, P, is already in use for phosphorus and thus is not available for protium. In its nomenclatural guidelines, the International Union of Pure and Applied Chemistry allows any of D, T, 2H, and 3H to be used, although 2H and 3H are preferred.
|
Hydrogen
|
1,217 |
An alloy of aluminium and gallium in pellet form added to water can be used to generate hydrogen. The process also produces alumina, but the expensive gallium, which prevents the formation of an oxide skin on the pellets, can be re-used. This has important potential implications for a hydrogen economy, as hydrogen can be produced on-site and does not need to be transported.
|
Hydrogen
|
1,218 |
Although exotic on Earth, one of the most common ions in the universe is the H+
3 ion, known as protonated molecular hydrogen or the trihydrogen cation.
|
Hydrogen
|
1,219 |
This reaction is favored at low pressures but is nonetheless conducted at high pressures (2.0 MPa, 20 atm or 600 inHg). This is because high-pressure H
2 is the most marketable product and Pressure Swing Adsorption (PSA) purification systems work better at higher pressures. The product mixture is known as "synthesis gas" because it is often used directly for the production of methanol and related compounds. Hydrocarbons other than methane can be used to produce synthesis gas with varying product ratios. One of the many complications to this highly optimized technology is the formation of coke or carbon:
|
Hydrogen
|
1,220 |
H
2 is produced in chemistry and biology laboratories, often as a by-product of other reactions; in industry for the hydrogenation of unsaturated substrates; and in nature as a means of expelling reducing equivalents in biochemical reactions.
|
Hydrogen
|
1,221 |
Hydrogen gas (dihydrogen or molecular hydrogen) is highly flammable and will burn in air at a very wide range of concentrations between 4% and 75% by volume. The enthalpy of combustion for hydrogen is −286 kJ/mol:
|
Hydrogen
|
1,222 |
Hydrogen is not an energy resource, except in the hypothetical context of commercial nuclear fusion power plants using deuterium or tritium, a technology presently far from development. The Sun's energy comes from nuclear fusion of hydrogen, but this process is difficult to achieve controllably on Earth. Elemental hydrogen from solar, biological, or electrical sources require more energy to make it than is obtained by burning it, so in these cases hydrogen functions as an energy carrier, like a battery. Hydrogen may be obtained from fossil sources (such as methane), but these sources are unsustainable.
|
Hydrogen
|
1,223 |
Under ordinary conditions on Earth, elemental hydrogen exists as the diatomic gas, H2. However, hydrogen gas is very rare in the Earth's atmosphere (1 ppm by volume) because of its light weight, which enables it to escape from Earth's gravity more easily than heavier gases. However, hydrogen is the third most abundant element on the Earth's surface, mostly in the form of chemical compounds such as hydrocarbons and water. Hydrogen gas is produced by some bacteria and algae and is a natural component of flatus, as is methane, itself a hydrogen source of increasing importance.
|
Hydrogen
|
1,224 |
Even interpreting the hydrogen data (including safety data) is confounded by a number of phenomena. Many physical and chemical properties of hydrogen depend on the parahydrogen/orthohydrogen ratio (it often takes days or weeks at a given temperature to reach the equilibrium ratio, for which the data is usually given). Hydrogen detonation parameters, such as critical detonation pressure and temperature, strongly depend on the container geometry.
|
Hydrogen
|
1,225 |
Hydrogen forms a vast array of compounds with carbon called the hydrocarbons, and an even vaster array with heteroatoms that, because of their general association with living things, are called organic compounds. The study of their properties is known as organic chemistry and their study in the context of living organisms is known as biochemistry. By some definitions, "organic" compounds are only required to contain carbon. However, most of them also contain hydrogen, and because it is the carbon-hydrogen bond which gives this class of compounds most of its particular chemical characteristics, carbon-hydrogen bonds are required in some definitions of the word "organic" in chemistry. Millions of hydrocarbons are known, and they are usually formed by complicated synthetic pathways, which seldom involve elementary hydrogen.
|
Hydrogen
|
1,226 |
Large quantities of H
2 are needed in the petroleum and chemical industries. The largest application of H
2 is for the processing ("upgrading") of fossil fuels, and in the production of ammonia. The key consumers of H
2 in the petrochemical plant include hydrodealkylation, hydrodesulfurization, and hydrocracking. H
2 has several other important uses. H
2 is used as a hydrogenating agent, particularly in increasing the level of saturation of unsaturated fats and oils (found in items such as margarine), and in the production of methanol. It is similarly the source of hydrogen in the manufacture of hydrochloric acid. H
2 is also used as a reducing agent of metallic ores.
|
Hydrogen
|
1,227 |
In 1671, Robert Boyle discovered and described the reaction between iron filings and dilute acids, which results in the production of hydrogen gas. In 1766, Henry Cavendish was the first to recognize hydrogen gas as a discrete substance, by naming the gas from a metal-acid reaction "flammable air". He speculated that "flammable air" was in fact identical to the hypothetical substance called "phlogiston" and further finding in 1781 that the gas produces water when burned. He is usually given credit for its discovery as an element. In 1783, Antoine Lavoisier gave the element the name hydrogen (from the Greek ὑδρο- hydro meaning "water" and -γενής genes meaning "creator") when he and Laplace reproduced Cavendish's finding that water is produced when hydrogen is burned.
|
Hydrogen
|
1,228 |
Hydrogen is a chemical element with chemical symbol H and atomic number 1. With an atomic weight of 7000100794000000000♠1.00794 u, hydrogen is the lightest element on the periodic table. Its monatomic form (H) is the most abundant chemical substance in the Universe, constituting roughly 75% of all baryonic mass.[note 1] Non-remnant stars are mainly composed of hydrogen in its plasma state. The most common isotope of hydrogen, termed protium (name rarely used, symbol 1H), has one proton and no neutrons.
|
Hydrogen
|
1,229 |
Hydrogen gas forms explosive mixtures with air if it is 4–74% concentrated and with chlorine if it is 5–95% concentrated. The mixtures may be ignited by spark, heat or sunlight. The hydrogen autoignition temperature, the temperature of spontaneous ignition in air, is 500 °C (932 °F). Pure hydrogen-oxygen flames emit ultraviolet light and with high oxygen mix are nearly invisible to the naked eye, as illustrated by the faint plume of the Space Shuttle Main Engine compared to the highly visible plume of a Space Shuttle Solid Rocket Booster. The detection of a burning hydrogen leak may require a flame detector; such leaks can be very dangerous. Hydrogen flames in other conditions are blue, resembling blue natural gas flames. The destruction of the Hindenburg airship was an infamous example of hydrogen combustion; the cause is debated, but the visible orange flames were the result of a rich mixture of hydrogen to oxygen combined with carbon compounds from the airship skin.
|
Hydrogen
|
1,230 |
Water splitting, in which water is decomposed into its component protons, electrons, and oxygen, occurs in the light reactions in all photosynthetic organisms. Some such organisms, including the alga Chlamydomonas reinhardtii and cyanobacteria, have evolved a second step in the dark reactions in which protons and electrons are reduced to form H2 gas by specialized hydrogenases in the chloroplast. Efforts have been undertaken to genetically modify cyanobacterial hydrogenases to efficiently synthesize H2 gas even in the presence of oxygen. Efforts have also been undertaken with genetically modified alga in a bioreactor.
|
Hydrogen
|
1,231 |
American concerns that they had fallen behind the Soviet Union in the race to space led quickly to a push by legislators and educators for greater emphasis on mathematics and the physical sciences in American schools. The United States' National Defense Education Act of 1958 increased funding for these goals from childhood education through the post-graduate level.
|
Space_Race
|
1,232 |
The first landing was followed by another, precision landing on Apollo 12 in November 1969. NASA had achieved its first landing goal with enough Apollo spacecraft and Saturn V launchers left for eight follow-on lunar landings through Apollo 20, conducting extended-endurance missions and transporting the landing crews in Lunar Roving Vehicles on the last five. They also planned an Apollo Applications Program to develop a longer-duration Earth orbital workshop (later named Skylab) to be constructed in orbit from a spent S-IVB upper stage, using several launches of the smaller Saturn IB launch vehicle. But planners soon decided this could be done more efficiently by using the two live stages of a Saturn V to launch the workshop pre-fabricated from an S-IVB (which was also the Saturn V third stage), which immediately removed Apollo 20. Belt-tightening budget cuts soon led NASA to cut Apollo 18 and 19 as well, but keep three extended/Lunar Rover missions. Apollo 13 encountered an in-flight spacecraft failure and had to abort its lunar landing in April 1970, returning its crew safely but temporarily grounding the program again. It resumed with four successful landings on Apollo 14 (February 1971), Apollo 15 (July 1971), Apollo 16 (April 1972), and Apollo 17 (December 1972).
|
Space_Race
|
1,233 |
The German rocket center in Peenemünde was located in the eastern part of Germany, which became the Soviet zone of occupation. On Stalin's orders, the Soviet Union sent its best rocket engineers to this region to see what they could salvage for future weapons systems. The Soviet rocket engineers were led by Sergei Korolev. He had been involved in space clubs and early Soviet rocket design in the 1930s, but was arrested in 1938 during Joseph Stalin's Great Purge and imprisoned for six years in Siberia. After the war, he became the USSR's chief rocket and spacecraft engineer, essentially the Soviet counterpart to von Braun. His identity was kept a state secret throughout the Cold War, and he was identified publicly only as "the Chief Designer." In the West, his name was only officially revealed when he died in 1966.
|
Space_Race
|
1,234 |
The Soviet Union duplicated its dual-launch feat with Vostok 5 and Vostok 6 (June 16, 1963). This time they launched the first woman (also the first civilian), Valentina Tereshkova, into space on Vostok 6. Launching a woman was reportedly Korolev's idea, and it was accomplished purely for propaganda value. Tereshkova was one of a small corps of female cosmonauts who were amateur parachutists, but Tereshkova was the only one to fly. The USSR didn't again open its cosmonaut corps to women until 1980, two years after the United States opened its astronaut corps to women.
|
Space_Race
|
1,235 |
On January 31, 1958, nearly four months after the launch of Sputnik 1, von Braun and the United States successfully launched its first satellite on a four-stage Juno I rocket derived from the US Army's Redstone missile, at Cape Canaveral. The satellite Explorer 1 was 30.8 pounds (14.0 kg) in mass. It carried a micrometeorite gauge and a Geiger-Müller tube. It passed in and out of the Earth-encompassing radiation belt with its 194-by-1,368-nautical-mile (360 by 2,534 km) orbit, therefore saturating the tube's capacity and proving what Dr. James Van Allen, a space scientist at the University of Iowa, had theorized. The belt, named the Van Allen radiation belt, is a doughnut-shaped zone of high-level radiation intensity around the Earth above the magnetic equator. Van Allen was also the man who designed and built the satellite instrumentation of Explorer 1. The satellite actually measured three phenomena: cosmic ray and radiation levels, the temperature in the spacecraft, and the frequency of collisions with micrometeorites. The satellite had no memory for data storage, therefore it had to transmit continuously. Two months later in March 1958, a second satellite was sent into orbit with augmented cosmic ray instruments.
|
Space_Race
|
1,236 |
The Space Race was a 20th-century competition between two Cold War rivals, the Soviet Union (USSR) and the United States (US), for supremacy in spaceflight capability. It had its origins in the missile-based nuclear arms race between the two nations that occurred following World War II, enabled by captured German rocket technology and personnel. The technological superiority required for such supremacy was seen as necessary for national security, and symbolic of ideological superiority. The Space Race spawned pioneering efforts to launch artificial satellites, unmanned space probes of the Moon, Venus, and Mars, and human spaceflight in low Earth orbit and to the Moon. The competition began on August 2, 1955, when the Soviet Union responded to the US announcement four days earlier of intent to launch artificial satellites for the International Geophysical Year, by declaring they would also launch a satellite "in the near future". The Soviet Union beat the US to this, with the October 4, 1957 orbiting of Sputnik 1, and later beat the US to the first human in space, Yuri Gagarin, on April 12, 1961. The Space Race peaked with the July 20, 1969 US landing of the first humans on the Moon with Apollo 11. The USSR tried but failed manned lunar missions, and eventually cancelled them and concentrated on Earth orbital space stations. A period of détente followed with the April 1972 agreement on a co-operative Apollo–Soyuz Test Project, resulting in the July 1975 rendezvous in Earth orbit of a US astronaut crew with a Soviet cosmonaut crew.
|
Space_Race
|
1,237 |
On May 10, 1962, Vice President Johnson addressed the Second National Conference on the Peaceful Uses of Space revealing that the United States and the USSR both supported a resolution passed by the Political Committee of the UN General Assembly on December 1962, which not only urged member nations to "extend the rules of international law to outer space," but to also cooperate in its exploration. Following the passing of this resolution, Kennedy commenced his communications proposing a cooperative American/Soviet space program.
|
Space_Race
|
1,238 |
Gagarin became a national hero of the Soviet Union and the Eastern Bloc, and a worldwide celebrity. Moscow and other cities in the USSR held mass demonstrations, the scale of which was second only to the World War II Victory Parade of 1945. April 12 was declared Cosmonautics Day in the USSR, and is celebrated today in Russia as one of the official "Commemorative Dates of Russia." In 2011, it was declared the International Day of Human Space Flight by the United Nations.
|
Space_Race
|
1,239 |
On April 2, 1958, President Eisenhower reacted to the Soviet space lead in launching the first satellite, by recommending to the US Congress that a civilian agency be established to direct nonmilitary space activities. Congress, led by Senate Majority Leader Lyndon B. Johnson, responded by passing the National Aeronautics and Space Act, which Eisenhower signed into law on July 29, 1958. This law turned the National Advisory Committee on Aeronautics into the National Aeronautics and Space Administration (NASA). It also created a Civilian-Military Liaison Committee, chaired by the President, responsible for coordinating the nation's civilian and military space programs.
|
Space_Race
|
1,240 |
The United States recovered from the Apollo 1 fire, fixing the fatal flaws in an improved version of the Block II command module. The US proceeded with unpiloted test launches of the Saturn V launch vehicle (Apollo 4 and Apollo 6) and the Lunar Module (Apollo 5) during the latter half of 1967 and early 1968. Apollo 1's mission to check out the Apollo Command/Service Module in Earth orbit was accomplished by Grissom's backup crew commanded by Walter Schirra on Apollo 7, launched on October 11, 1968. The eleven-day mission was a total success, as the spacecraft performed a virtually flawless mission, paving the way for the United States to continue with its lunar mission schedule.
|
Space_Race
|
1,241 |
On December 21, 1968, Frank Borman, James Lovell, and William Anders became the first humans to ride the Saturn V rocket into space on Apollo 8. They also became the first to leave low-Earth orbit and go to another celestial body, and entered lunar orbit on December 24. They made ten orbits in twenty hours, and transmitted one of the most watched TV broadcasts in history, with their Christmas Eve program from lunar orbit, that concluded with a reading from the biblical Book of Genesis. Two and a half hours after the broadcast, they fired their engine to perform the first trans-Earth injection to leave lunar orbit and return to the Earth. Apollo 8 safely landed in the Pacific ocean on December 27, in NASA's first dawn splashdown and recovery.
|
Space_Race
|
1,242 |
The trip to the Moon took just over three days. After achieving orbit, Armstrong and Aldrin transferred into the Lunar Module, named Eagle, and after a landing gear inspection by Collins remaining in the Command/Service Module Columbia, began their descent. After overcoming several computer overload alarms caused by an antenna switch left in the wrong position, and a slight downrange error, Armstrong took over manual flight control at about 180 meters (590 ft), and guided the Lunar Module to a safe landing spot at 20:18:04 UTC, July 20, 1969 (3:17:04 pm CDT). The first humans on the Moon would wait another six hours before they ventured out of their craft. At 02:56 UTC, July 21 (9:56 pm CDT July 20), Armstrong became the first human to set foot on the Moon.
|
Space_Race
|
1,243 |
On October 21, 1959, Eisenhower approved the transfer of the Army's remaining space-related activities to NASA. On July 1, 1960, the Redstone Arsenal became NASA's George C. Marshall Space Flight Center, with von Braun as its first director. Development of the Saturn rocket family, which when mature, would finally give the US parity with the Soviets in terms of lifting capability, was thus transferred to NASA.
|
Space_Race
|
1,244 |
The circumlunar program (Zond), created by Vladimir Chelomey's design bureau OKB-52, was to fly two cosmonauts in a stripped-down Soyuz 7K-L1, launched by Chelomey's Proton UR-500 rocket. The Zond sacrificed habitable cabin volume for equipment, by omitting the Soyuz orbital module. Chelomey gained favor with Khruschev by employing members of his family.
|
Space_Race
|
1,245 |
Meanwhile, the Soviet Union was having its own problems with Soyuz development. Engineers reported 200 design faults to party leaders, but their concerns "were overruled by political pressures for a series of space feats to mark the anniversary of Lenin's birthday."[citation needed] On April 24, 1967, the single pilot of Soyuz 1, Vladimir Komarov, became the first in-flight spaceflight fatality. The mission was planned to be a three-day test, to include the first Soviet docking with an unpiloted Soyuz 2, but the mission was plagued with problems. Early on, Komarov's craft lacked sufficient electrical power because only one of two solar panels had deployed. Then the automatic attitude control system began malfunctioning and eventually failed completely, resulting in the craft spinning wildly. Komarov was able to stop the spin with the manual system, which was only partially effective. The flight controllers aborted his mission after only one day. During the emergency re-entry, a fault in the landing parachute system caused the primary chute to fail, and the reserve chute became tangled with the drogue chute; Komarov was killed on impact. Fixing the spacecraft faults caused an eighteen-month delay before piloted Soyuz flights could resume.
|
Space_Race
|
1,246 |
Unknown to the Americans, the Soviet Moon program was in deep trouble. After two successive launch failures of the N1 rocket in 1969, Soviet plans for a piloted landing suffered delay. The launch pad explosion of the N-1 on July 3, 1969 was a significant setback. The rocket hit the pad after an engine shutdown, destroying itself and the launch facility. Without the N-1 rocket, the USSR could not send a large enough payload to the Moon to land a human and return him safely.
|
Space_Race
|
1,247 |
Most of the novice pilots on the early missions would command the later missions. In this way, Project Gemini built up spaceflight experience for the pool of astronauts who would be chosen to fly the Apollo lunar missions.
|
Space_Race
|
1,248 |
The first satellite, BeiDou-1A, was launched on October 31, 2000. The second satellite, BeiDou-1B, was successfully launched on December 21, 2000. The last operational satellite of the constellation, BeiDou-1C, was launched on May 25, 2003.
|
BeiDou_Navigation_Satellite_System
|
1,249 |
In 2015, the system began its transition towards global coverage with the first launch of a new-generation of satellites, and the 17th one within the new system.
|
BeiDou_Navigation_Satellite_System
|
1,250 |
In December 2011, the system went into operation on a trial basis. It has started providing navigation, positioning and timing data to China and the neighbouring area for free from 27 December. During this trial run, Compass will offer positioning accuracy to within 25 meters, but the precision will improve as more satellites are launched. Upon the system's official launch, it pledged to offer general users positioning information accurate to the nearest 10 m, measure speeds within 0.2 m per second, and provide signals for clock synchronisation accurate to 0.02 microseconds.
|
BeiDou_Navigation_Satellite_System
|
1,251 |
On 2 November 2006, China announced that from 2008 BeiDou would offer an open service with an accuracy of 10 meters, timing of 0.2 microseconds, and speed of 0.2 meters/second.[citation needed]
|
BeiDou_Navigation_Satellite_System
|
1,252 |
According to Sun Jiadong, the chief designer of the navigation system, "Many organizations have been using our system for a while, and they like it very much."
|
BeiDou_Navigation_Satellite_System
|
1,253 |
In 2007, the official Xinhua News Agency reported that the resolution of the BeiDou system was as high as 0.5 metres. With the existing user terminals it appears that the calibrated accuracy is 20m (100m, uncalibrated).
|
BeiDou_Navigation_Satellite_System
|
1,254 |
The first satellite, BeiDou-1A, was launched on 30 October 2000, followed by BeiDou-1B on 20 December 2000. The third satellite, BeiDou-1C (a backup satellite), was put into orbit on 25 May 2003. The successful launch of BeiDou-1C also meant the establishment of the BeiDou-1 navigation system.
|
BeiDou_Navigation_Satellite_System
|
1,255 |
Unlike the American GPS, Russian GLONASS, and European Galileo systems, which use medium Earth orbit satellites, BeiDou-1 uses satellites in geostationary orbit. This means that the system does not require a large constellation of satellites, but it also limits the coverage to areas on Earth where the satellites are visible. The area that can be serviced is from longitude 70°E to 140°E and from latitude 5°N to 55°N. A frequency of the system is 2491.75 MHz.
|
BeiDou_Navigation_Satellite_System
|
1,256 |
In February 2007, the fourth and last satellite of the BeiDou-1 system, BeiDou-1D (sometimes called BeiDou-2A, serving as a backup satellite), was sent up into space. It was reported that the satellite had suffered from a control system malfunction but was then fully restored.
|
BeiDou_Navigation_Satellite_System
|
1,257 |
The ranging signals are based on the CDMA principle and have complex structure typical of Galileo or modernized GPS. Similar to the other GNSS, there will be two levels of positioning service: open and restricted (military). The public service shall be available globally to general users. When all the currently planned GNSS systems are deployed, the users will benefit from the use of a total constellation of 75+ satellites, which will significantly improve all the aspects of positioning, especially availability of the signals in so-called urban canyons. The general designer of the COMPASS navigation system is Sun Jiadong, who is also the general designer of its predecessor, the original BeiDou navigation system.
|
BeiDou_Navigation_Satellite_System
|
1,258 |
The three latest satellites will jointly undergo testing of a new system of navigation signaling and inter-satellite links, and start providing navigation services when ready.
|
BeiDou_Navigation_Satellite_System
|
1,259 |
BeiDou-1 is an experimental regional navigation system, which consists of four satellites (three working satellites and one backup satellite). The satellites themselves were based on the Chinese DFH-3 geostationary communications satellite and had a launch weight of 1,000 kilograms (2,200 pounds) each.
|
BeiDou_Navigation_Satellite_System
|
1,260 |
Compass-M1 transmits in 3 bands: E2, E5B, and E6. In each frequency band two coherent sub-signals have been detected with a phase shift of 90 degrees (in quadrature). These signal components are further referred to as "I" and "Q". The "I" components have shorter codes and are likely to be intended for the open service. The "Q" components have much longer codes, are more interference resistive, and are probably intended for the restricted service. IQ modulation has been the method in both wired and wireless digital modulation since morsetting carrier signal 100 years ago.
|
BeiDou_Navigation_Satellite_System
|
1,261 |
Frequencies for COMPASS are allocated in four bands: E1, E2, E5B, and E6 and overlap with Galileo. The fact of overlapping could be convenient from the point of view of the receiver design, but on the other hand raises the issues of inter-system interference, especially within E1 and E2 bands, which are allocated for Galileo's publicly regulated service. However, under International Telecommunication Union (ITU) policies, the first nation to start broadcasting in a specific frequency will have priority to that frequency, and any subsequent users will be required to obtain permission prior to using that frequency, and otherwise ensure that their broadcasts do not interfere with the original nation's broadcasts. It now appears that Chinese COMPASS satellites will start transmitting in the E1, E2, E5B, and E6 bands before Europe's Galileo satellites and thus have primary rights to these frequency ranges.
|
BeiDou_Navigation_Satellite_System
|
1,262 |
In April 2007, the first satellite of BeiDou-2, namely Compass-M1 (to validate frequencies for the BeiDou-2 constellation) was successfully put into its working orbit. The second BeiDou-2 constellation satellite Compass-G2 was launched on 15 April 2009. On 15 January 2010, the official website of the BeiDou Navigation Satellite System went online, and the system's third satellite (Compass-G1) was carried into its orbit by a Long March 3C rocket on 17 January 2010. On 2 June 2010, the fourth satellite was launched successfully into orbit. The fifth orbiter was launched into space from Xichang Satellite Launch Center by an LM-3I carrier rocket on 1 August 2010. Three months later, on 1 November 2010, the sixth satellite was sent into orbit by LM-3C. Another satellite, the Beidou-2/Compass IGSO-5 (fifth inclined geosynchonous orbit) satellite, was launched from the Xichang Satellite Launch Center by a Long March-3A on 1 December 2011 (UTC).
|
BeiDou_Navigation_Satellite_System
|
1,263 |
The BeiDou-2 system began offering services for the Asia-Pacific region in December 2012. At this time, the system could provide positioning data between longitude 55°E to 180°E and from latitude 55°S to 55°N.
|
BeiDou_Navigation_Satellite_System
|
1,264 |
According to China daily. Fifteen years after the satellite system was launched, it is now generating $31.5 billion for major companies such as China Aerospace Science and Industry Corp, AutoNavi Holdings Ltd, and China North Industries Group Corp.
|
BeiDou_Navigation_Satellite_System
|
1,265 |
In 2008, a BeiDou-1 ground terminal cost around CN¥20,000RMB (US$2,929), almost 10 times the price of a contemporary GPS terminal. The price of the terminals was explained as being due to the cost of imported microchips. At the China High-Tech Fair ELEXCON of November 2009 in Shenzhen, a BeiDou terminal priced at CN¥3,000RMB was presented.
|
BeiDou_Navigation_Satellite_System
|
1,266 |
The investigation of the transmitted signals started immediately after the launch of Compass -M1 on 14 April 2007. Soon after in June 2007, engineers at CNES reported the spectrum and structure of the signals. A month later, researchers from Stanford University reported the complete decoding of the “I” signals components. The knowledge of the codes allowed a group of engineers at Septentrio to build the COMPASS receiver and report tracking and multipath characteristics of the “I” signals on E2 and E5B.
|
BeiDou_Navigation_Satellite_System
|
1,267 |
The official English name of the system is BeiDou Navigation Satellite System. It is named after the Big Dipper constellation, which is known in Chinese as Běidǒu. The name literally means "Northern Dipper", the name given by ancient Chinese astronomers to the seven brightest stars of the Ursa Major constellation. Historically, this set of stars was used in navigation to locate the North Star Polaris. As such, the name BeiDou also serves as a metaphor for the purpose of the satellite navigation system.
|
BeiDou_Navigation_Satellite_System
|
1,268 |
The second generation of the system, officially called the BeiDou Navigation Satellite System (BDS) and also known as COMPASS or BeiDou-2, will be a global satellite navigation system consisting of 35 satellites, and is under construction as of January 2015[update]. It became operational in China in December 2011, with 10 satellites in use, and began offering services to customers in the Asia-Pacific region in December 2012. It is planned to begin serving global customers upon its completion in 2020.
|
BeiDou_Navigation_Satellite_System
|
1,269 |
In December 2011, Xinhua stated that "[t]he basic structure of the Beidou system has now been established, and engineers are now conducting comprehensive system test and evaluation. The system will provide test-run services of positioning, navigation and time for China and the neighboring areas before the end of this year, according to the authorities." The system became operational in the China region that same month. The global navigation system should be finished by 2020. As of December 2012, 16 satellites for BeiDou-2 have been launched, 14 of them are in service.
|
BeiDou_Navigation_Satellite_System
|
1,270 |
In September 2003, China intended to join the European Galileo positioning system project and was to invest €230 million (USD296 million, GBP160 million) in Galileo over the next few years. At the time, it was believed that China's "BeiDou" navigation system would then only be used by its armed forces. In October 2004, China officially joined the Galileo project by signing the Agreement on the Cooperation in the Galileo Program between the "Galileo Joint Undertaking" (GJU) and the "National Remote Sensing Centre of China" (NRSCC). Based on the Sino-European Cooperation Agreement on Galileo program, China Galileo Industries (CGI), the prime contractor of the China’s involvement in Galileo programs, was founded in December 2004. By April 2006, eleven cooperation projects within the Galileo framework had been signed between China and EU. However, the Hong Kong-based South China Morning Post reported in January 2008 that China was unsatisfied with its role in the Galileo project and was to compete with Galileo in the Asian market.
|
BeiDou_Navigation_Satellite_System
|
1,271 |
The first BeiDou system, officially called the BeiDou Satellite Navigation Experimental System (simplified Chinese: 北斗卫星导航试验系统; traditional Chinese: 北斗衛星導航試驗系統; pinyin: Běidǒu wèixīng dǎoháng shìyàn xìtǒng) and also known as BeiDou-1, consists of three satellites and offers limited coverage and applications. It has been offering navigation services, mainly for customers in China and neighboring regions, since 2000.
|
BeiDou_Navigation_Satellite_System
|
1,272 |
BeiDou-2 (formerly known as COMPASS) is not an extension to the older BeiDou-1, but rather supersedes it outright. The new system will be a constellation of 35 satellites, which include 5 geostationary orbit satellites for backward compatibility with BeiDou-1, and 30 non-geostationary satellites (27 in medium Earth orbit and 3 in inclined geosynchronous orbit), that will offer complete coverage of the globe.
|
BeiDou_Navigation_Satellite_System
|
1,273 |
The institutions and practices of canon law paralleled the legal development of much of Europe, and consequently both modern civil law and common law (legal system) bear the influences of canon law. Edson Luiz Sampel, a Brazilian expert in canon law, says that canon law is contained in the genesis of various institutes of civil law, such as the law in continental Europe and Latin American countries. Sampel explains that canon law has significant influence in contemporary society.
|
Canon_law
|
1,274 |
The canon law of the Eastern Catholic Churches, which had developed some different disciplines and practices, underwent its own process of codification, resulting in the Code of Canons of the Eastern Churches promulgated in 1990 by Pope John Paul II.
|
Canon_law
|
1,275 |
The Apostolic Canons or Ecclesiastical Canons of the Same Holy Apostles is a collection of ancient ecclesiastical decrees (eighty-five in the Eastern, fifty in the Western Church) concerning the government and discipline of the Early Christian Church, incorporated with the Apostolic Constitutions which are part of the Ante-Nicene Fathers In the fourth century the First Council of Nicaea (325) calls canons the disciplinary measures of the Church: the term canon, κανὠν, means in Greek, a rule. There is a very early distinction between the rules enacted by the Church and the legislative measures taken by the State called leges, Latin for laws.
|
Canon_law
|
1,276 |
Other churches in the Anglican Communion around the world (e.g., the Episcopal Church in the United States, and the Anglican Church of Canada) still function under their own private systems of canon law.
|
Canon_law
|
1,277 |
The law of the Eastern Catholic Churches in full union with Rome was in much the same state as that of the Latin or Western Church before 1917; much more diversity in legislation existed in the various Eastern Catholic Churches. Each had its own special law, in which custom still played an important part. In 1929 Pius XI informed the Eastern Churches of his intention to work out a Code for the whole of the Eastern Church. The publication of these Codes for the Eastern Churches regarding the law of persons was made between 1949 through 1958 but finalized nearly 30 years later.
|
Canon_law
|
1,278 |
Currently, (2004), there are principles of canon law common to the churches within the Anglican Communion; their existence can be factually established; each province or church contributes through its own legal system to the principles of canon law common within the Communion; these principles have a strong persuasive authority and are fundamental to the self-understanding of each of the churches of the Communion; these principles have a living force, and contain in themselves the possibility of further development; and the existence of these principles both demonstrates unity and promotes unity within the Anglican Communion.
|
Canon_law
|
1,279 |
In the Church of England, the ecclesiastical courts that formerly decided many matters such as disputes relating to marriage, divorce, wills, and defamation, still have jurisdiction of certain church-related matters (e.g. discipline of clergy, alteration of church property, and issues related to churchyards). Their separate status dates back to the 12th century when the Normans split them off from the mixed secular/religious county and local courts used by the Saxons. In contrast to the other courts of England the law used in ecclesiastical matters is at least partially a civil law system, not common law, although heavily governed by parliamentary statutes. Since the Reformation, ecclesiastical courts in England have been royal courts. The teaching of canon law at the Universities of Oxford and Cambridge was abrogated by Henry VIII; thereafter practitioners in the ecclesiastical courts were trained in civil law, receiving a Doctor of Civil Law (D.C.L.) degree from Oxford, or a Doctor of Laws (LL.D.) degree from Cambridge. Such lawyers (called "doctors" and "civilians") were centered at "Doctors Commons", a few streets south of St Paul's Cathedral in London, where they monopolized probate, matrimonial, and admiralty cases until their jurisdiction was removed to the common law courts in the mid-19th century.
|
Canon_law
|
1,280 |
The first Code of Canon Law, 1917, was mostly for the Roman Rite, with limited application to the Eastern Churches. After the Second Vatican Council, (1962 - 1965), another edition was published specifically for the Roman Rite in 1983. Most recently, 1990, the Vatican produced the Code of Canons of the Eastern Churches which became the 1st code of Eastern Catholic Canon Law.
|
Canon_law
|
1,281 |
In Presbyterian and Reformed churches, canon law is known as "practice and procedure" or "church order", and includes the church's laws respecting its government, discipline, legal practice and worship.
|
Canon_law
|
1,282 |
The Catholic Church has what is claimed to be the oldest continuously functioning internal legal system in Western Europe, much later than Roman law but predating the evolution of modern European civil law traditions. What began with rules ("canons") adopted by the Apostles at the Council of Jerusalem in the first century has developed into a highly complex legal system encapsulating not just norms of the New Testament, but some elements of the Hebrew (Old Testament), Roman, Visigothic, Saxon, and Celtic legal traditions.
|
Canon_law
|
1,283 |
In the Catholic Church, canon law is the system of laws and legal principles made and enforced by the Church's hierarchical authorities to regulate its external organization and government and to order and direct the activities of Catholics toward the mission of the Church.
|
Canon_law
|
1,284 |
In the Roman Church, universal positive ecclesiastical laws, based upon either immutable divine and natural law, or changeable circumstantial and merely positive law, derive formal authority and promulgation from the office of pope, who as Supreme Pontiff possesses the totality of legislative, executive, and judicial power in his person. The actual subject material of the canons is not just doctrinal or moral in nature, but all-encompassing of the human condition.
|
Canon_law
|
1,285 |
Much of the legislative style was adapted from the Roman Law Code of Justinian. As a result, Roman ecclesiastical courts tend to follow the Roman Law style of continental Europe with some variation, featuring collegiate panels of judges and an investigative form of proceeding, called "inquisitorial", from the Latin "inquirere", to enquire. This is in contrast to the adversarial form of proceeding found in the common law system of English and U.S. law, which features such things as juries and single judges.
|
Canon_law
|
1,286 |
The Greek-speaking Orthodox have collected canons and commentaries upon them in a work known as the Pēdálion (Greek: Πηδάλιον, "Rudder"), so named because it is meant to "steer" the Church. The Orthodox Christian tradition in general treats its canons more as guidelines than as laws, the bishops adjusting them to cultural and other local circumstances. Some Orthodox canon scholars point out that, had the Ecumenical Councils (which deliberated in Greek) meant for the canons to be used as laws, they would have called them nómoi/νόμοι (laws) rather than kanónes/κανόνες (rules), but almost all Orthodox conform to them. The dogmatic decisions of the Councils, though, are to be obeyed rather than to be treated as guidelines, since they are essential for the Church's unity.
|
Canon_law
|
1,287 |
Canonical jurisprudential theory generally follows the principles of Aristotelian-Thomistic legal philosophy. While the term "law" is never explicitly defined in the Code, the Catechism of the Catholic Church cites Aquinas in defining law as "...an ordinance of reason for the common good, promulgated by the one who is in charge of the community" and reformulates it as "...a rule of conduct enacted by competent authority for the sake of the common good."
|
Canon_law
|
1,288 |
It is a fully developed legal system, with all the necessary elements: courts, lawyers, judges, a fully articulated legal code principles of legal interpretation, and coercive penalties, though it lacks civilly-binding force in most secular jurisdictions. The academic degrees in canon law are the J.C.B. (Juris Canonici Baccalaureatus, Bachelor of Canon Law, normally taken as a graduate degree), J.C.L. (Juris Canonici Licentiatus, Licentiate of Canon Law) and the J.C.D. (Juris Canonici Doctor, Doctor of Canon Law). Because of its specialized nature, advanced degrees in civil law or theology are normal prerequisites for the study of canon law.
|
Canon_law
|
1,289 |
The Roman Catholic Church canon law also includes the main five rites (groups) of churches which are in full union with the Roman Catholic Church and the Supreme Pontiff:
|
Canon_law
|
1,290 |
The Somali Telecommunication Association (STA), a watchdog organization that oversees the policy development and regulatory framework of Somalia's ICT sector, reported in 2006 that there were over half a million users of internet services within the territory. There were also 22 established ISPs and 234 cyber cafes, with an annual growth rate of 15.6%.
|
Communications_in_Somalia
|
1,291 |
After the start of the civil war, various new telecommunications companies began to spring up in the country and competed to provide missing infrastructure. Somalia now offers some of the most technologically advanced and competitively priced telecommunications and internet services in the world. Funded by Somali entrepreneurs and backed by expertise from China, Korea and Europe, these nascent telecommunications firms offer affordable mobile phone and internet services that are not available in many other parts of the continent. Customers can conduct money transfers (such as through the popular Dahabshiil) and other banking activities via mobile phones, as well as easily gain wireless Internet access.
|
Communications_in_Somalia
|
1,292 |
The Mogadishu-based Somali National Television is the principal national public service broadcaster. On March 18, 2011, the Ministry of Information of the Transitional Federal Government began experimental broadcasts of the new TV channel. After a 20-year hiatus, the station was shortly thereafter officially re-launched on April 4, 2011. SNTV broadcasts 24 hours a day, and can be viewed both within Somalia and abroad via terrestrial and satellite platforms.
|
Communications_in_Somalia
|
1,293 |
Communications in Somalia encompasses the communications services and capacity of Somalia. Telecommunications, internet, radio, print, television and postal services in the nation are largely concentrated in the private sector. Several of the telecom firms have begun expanding their activities abroad. The Federal government operates two official radio and television networks, which exist alongside a number of private and foreign stations. Print media in the country is also progressively giving way to news radio stations and online portals, as internet connectivity and access increases. Additionally, the national postal service is slated to be officially relaunched in 2013 after a long absence. In 2012, a National Communications Act was also approved by Cabinet members, which lays the foundation for the establishment of a National Communications regulator in the broadcasting and telecommunications sectors.
|
Communications_in_Somalia
|
1,294 |
Additionally, Somalia has several private television networks, including Horn Cable Television and Universal TV. Two such TV stations re-broadcast Al-Jazeera and CNN. Eastern Television Network and SBC TV air from Bosaso, the commercial capital of Puntland. The Puntland and Somaliland regions also each have one government-run TV channel, Puntland TV and Radio and Somaliland National TV, respectively.
|
Communications_in_Somalia
|
1,295 |
On March 22, 2012, the Somali Cabinet unanimously approved the National Communications Act, which paves the way for the establishment of a National Communications regulator in the broadcasting and telecommunications sectors. The bill was passed following consultations between government representatives and communications, academic and civil society stakeholders. According to the Ministry of Information, Posts and Telecommunication, the Act is expected to create an environment conducive to investment and the certainty it provides will encourage further infrastructural development, resulting in more efficient service delivery.
|
Communications_in_Somalia
|
1,296 |
According to the Centre for Law and Democracy (CLD) and the African Union/United Nations Information Support Team (IST), Somalia did not have systemic internet blocking or filtering as of December 2012. The application of content standards online was also unclear.
|
Communications_in_Somalia
|
1,297 |
After forming partnerships with multinational corporations such as Sprint, ITT and Telenor, these firms now offer the cheapest and clearest phone calls in Africa. These Somali telecommunication companies also provide services to every city, town and hamlet in Somalia. There are presently around 25 mainlines per 1,000 persons, and the local availability of telephone lines (tele-density) is higher than in neighboring countries; three times greater than in adjacent Ethiopia. Prominent Somali telecommunications companies include Somtel Network, Golis Telecom Group, Hormuud Telecom, Somafone, Nationlink, Netco, Telcom and Somali Telecom Group. Hormuud Telecom alone grosses about $40 million a year. Despite their rivalry, several of these companies signed an interconnectivity deal in 2005 that allows them to set prices, maintain and expand their networks, and ensure that competition does not get out of control.
|
Communications_in_Somalia
|
1,298 |
The northeastern Puntland region has around six private radio stations, including Radio Garowe, Radio Daljir, Radio Codka-Nabbada and Radio Codka-Mudug. Radio Gaalkacyo, formerly known as Radio Free Somalia, operates from Galkayo in the north-central Mudug province. Additionally, the Somaliland region in the northwest has one government-operated radio station.
|
Communications_in_Somalia
|
1,299 |
On 1 November 2013, international postal services for Somalia officially resumed. The Universal Postal Union is now assisting the Somali Postal Service to develop its capacity, including providing technical assistance and basic mail processing equipment.
|
Communications_in_Somalia
|
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.