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A-Z of AVIONICS
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A-Z of AVIONICS
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Re: A-Z of AVIONICS
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Reply #700 on:
17/04/2007 21:02:31 »
V
acuum Tubes,
electronic devices, consisting of a glass or steel vacuum envelope and two or more electrodes between which electrons can move freely. The vacuum-tube diode was first developed by the English physicist John Ambrose Fleming. It contains two electrodes: the cathode, a heated filament or a small, heated, metal tube that emits electrons through thermionic emission; and the anode, or plate, which is the electron-collecting element. In diodes, the electrons emitted by the cathode are attracted to the plate only when the latter is positive with respect to the cathode. When the plate is negatively charged, no current flows through the tube. If an alternating potential is applied to the plate, the tube passes current only during the positive halves of the cycle and thus acts as a rectifier. Diodes are used extensively in the rectification of alternating current.
The introduction of a third electrode, called a grid, interposed between the cathode and the anode, forms the triode, which for many years was the basic tube used for amplifying current. (The triode was invented in 1906 by the American engineer Lee De Forest.) The function of the grid is to control the current flow. At a certain negative potential, the grid, because it repels electrons, can impede the flow of electrons between the cathode and the anode. At lower negative potentials, the electron flow depends on the grid potential. The grid usually consists of a network of fine wire surrounding the cathode. The capacity of the triode to amplify depends on the small changes in the voltage between the grid and the cathode causing large changes in the number of electrons reaching the anode.
Through the years more complex tubes with additional grids have been developed to provide greater amplification and to perform specialized functions. Tetrodes have an additional grid, closer to the anode, that forms an electrostatic shield between the anode and the grid to prevent feedback to the grid in high-frequency applications. The pentode has three grids between the cathode and the anode; the third grid, close to the anode, reflects electrons that are emitted by the anode as it is heated by electron impact when the electron current in the tube is high. Tubes with even more grids, called hexodes, heptodes, and octodes, find applications as frequency converters and mixers in radio receivers.
Vacuum tubes have now been almost entirely replaced by transistors, which are cheaper, smaller, and more reliable. Tubes still play an important role in certain applications, however, such as in power stages in radio and television transmitters, and in military equipment that must resist the voltage pulse (which destroys transistors) induced by an atmospheric nuclear explosion.
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Re: A-Z of AVIONICS
«
Reply #701 on:
19/04/2007 21:54:23 »
W
est Nile virus
http://www.west-nile-virus-prevention.com/
«
Last Edit: 19/04/2007 21:58:07 by iko
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Re: A-Z of AVIONICS
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Reply #702 on:
20/04/2007 15:17:00 »
X
enarthra
The superorder Xenarthra is a group of placental mammals (infraclass Eutheria), extant today only in the Americas. The origins of the order can be traced back as far as the early Tertiary (about 60 million years ago, or only a short time after the end of the dinosaur era). The presence of these animals in North America is explained by the Great American Interchange.
It includes the anteaters, sloths, and armadillos. In the past, these families were classified together with the pangolins and Aardvark as the order Edentata (meaning toothless, because the members do not have front incisor teeth or molars, or have poorly-developed molars). It was subsequently realized that Edentata was polyphyletic—that it contained unrelated families and was thus invalid by cladistic standards. Aardvarks and pangolins are now placed in individual orders, and the new order Xenarthra was erected to group the remaining families (which are all related). The name Xenarthra means "strange joints", and was chosen because their vertebral joints are unlike those of any other mammals. Because they lack characteristics believed to be present in the common ancestor of other known Eutherian mammals, morphological evidence suggests that the Xenarthra are outside the Epitheria, which contains all other known Eutherians today.
The morphology of Xenarthrans generally suggests that the anteaters and sloths are closest together within Xenarthra. The order Xenarthra is more and more often divided into two orders: Pilosa, containing the Vermilingua and Folivora (previously Tardigrada), and the separate order Cingulata. Xenarthra now has the rank of cohort or super-order. The Xenarthra are part of the super-cohort Atlantogenata.
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Re: A-Z of AVIONICS
«
Reply #703 on:
20/04/2007 16:42:47 »
Y
angtze river
http://cache.eb.com/eb/image?id=96642&rendTypeId=4
Chinese (Pinyin) Chang Jiang or (Wade-Giles romanization) Ch'ang Chiang
longest river in both China and Asia
and the
third longest river in the world
, with a length of 3,915 miles (
6,300
kilometres). Its basin, extending for some 2,000 miles (3,200 km) from west to east and for more than 600 miles (1,000 km) from north to south, drains an area of 698,265 square miles (1,808,500 square km). From its source on the Plateau of Tibet to its mouth on the East China Sea, the river traverses or serves as the border…
more from:
http://www.britannica.com/eb/article-9110538/Yangtze-River
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Re: A-Z of AVIONICS
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Reply #704 on:
20/04/2007 16:52:09 »
Z
ambales Mountains
, mountain range in the north-western Philippines, on western Luzon Island. Lying north to south, the Zambales extend 160 km (100 mi) from Lingayen Gulf and Pangasinan Province in the north, through Zambales Province, and end in Bataan Province in the south. The Zambales are home to Mount Pinatubo, which erupted, causing severe damage, in 1991 and 1992. The mountains reach their highest point at High Peak (2,037 m/6,683 ft) in the north-central part of the range.
The range is a southern extension of the Cordillera Central, that was shifted west of the main range by faulting. Extensions of the Cordillera Central also appear to the south on Mindoro and Palawan islands. The range is a highly tilted block with a high eastern edge facing the Central Plain, a prime sugar- and rice-growing region. Much of the range was formed by the volcanic activity of the Quaternary Period (from 2.5 million years ago to the present). The Zambales include many kinds of volcanic rocks, such as andesites, diorites, and gabbros, all of which are exposed. Many minerals are also found in the range, the most important of which is chromite.
A number of short, rapidly flowing streams, including the Pamatawan, Santo Tomas, Anonang, Jalakak, and Bucao, drain the western slopes and empty into the South China Sea. The slopes of the Zambales are forested with tall hardwood trees and, at higher elevations, pines.
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Re: A-Z of AVIONICS
«
Reply #705 on:
20/04/2007 22:07:38 »
A
-
Z of
A
nything/
A
nyone
A
ssociated with
A
nything Science
...Don't we need a list of the previous terms to avoid repeats?
and who should be in charge of this accessing/excelling business? [
] [
] [
]
Ikon't [
)]
apart from the 'oldies' like me and KarenW and Neilepus...yes! SuperSeany!!!
He's as fast as a rocket and will do it in a second!
So pleeeaaaase ShiningSeany help this dummies and let their silly game continue for another few months... [
]
«
Last Edit: 20/04/2007 22:19:57 by iko
»
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Re: A-Z of AVIONICS
«
Reply #706 on:
21/04/2007 00:43:41 »
That picture of the Yangtze River is absolutely mesmerising Iko..I've saved it on my pc..I luff it !!
Previous terms ?.who is volunteering to go back 29 pages of ABC stuff ?..not me !!...Karen ?
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Re: A-Z of AVIONICS
«
Reply #707 on:
24/04/2007 21:24:36 »
B
aade,
(Wilhelm Heinrich) Walter (1893-1960), German-born American astronomer:
Educated at the University of Göttingen, whose studies of stars in the Andromeda galaxy led him, in the 1950s, to double the common estimate of the size and age of the universe. Begun at Mount Wilson Observatory in 1931, these studies established two major types of stars: the younger, hotter, Population I type and the older, cooler, Population II (see Milky Way). In his career in Germany prior to 1931, Baade discovered the asteroids Icarus and Hidalgo.
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Re: A-Z of AVIONICS
«
Reply #708 on:
24/04/2007 21:42:28 »
Cherenkov radiation
...(also spelled Cerenkov, scientific transliteration: Čerenkov) is electromagnetic radiation emitted when a charged particle passes through an insulator at a speed greater than the speed of light in that medium. The characteristic "blue glow" of nuclear reactors is due to Cherenkov radiation. It is named after Soviet scientist Pavel Alekseyevich Cherenkov, the 1958 Nobel Prize winner who was the first to rigorously characterize it.
«
Last Edit: 24/04/2007 21:44:55 by Batroost
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Re: A-Z of AVIONICS
«
Reply #709 on:
24/04/2007 21:59:06 »
D
igital-to-Analogue Converter or DAC,
Device for converting digital data into current or voltage analogues. DACs are now widely used in compact disc (CD) players, in digital audiotape and videotape players, in digital signal processing audio and video equipment, and in digital radio and television receivers. In their simplest form, DACs use some form of resistor network . Digital data is applied to the resistors in groups of bits. The resistances vary in definite ratios; the current flow in each one relates directly to the binary value of the bit received. In the practical form, a more complicated network involving current switching into a net of different resistance networks is used. The brief successive currents occur end to end in time, so giving a continuously varying current that when converted into a voltage reconstructs the original analogue signal voltage that had been converted into digital form. This voltage still has minute quantized steps in it, but these are simply removed by a low-pass frequency filter.
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Re: A-Z of AVIONICS
«
Reply #710 on:
25/04/2007 18:35:34 »
E
nterobius vermicularis
..."The" human parasite: over 2x10E8 people carry it around!
(
from ikopedia
)
http://www.stanford.edu/class/humbio103/ParaSites2006/Enterobius/life%20cycle_clip_image002_0001.jpg
http://www.medicine.mcgill.ca/tropmed/imagesplaty/mapworm.jpg
http://www.smittskyddsinstitutet.se/upload/Analyser/Bild20-MLa.jpg
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Last Edit: 29/04/2007 10:58:51 by iko
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Re: A-Z of AVIONICS
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Reply #711 on:
26/04/2007 00:25:07 »
F
ahrenheit, Gabriel Daniel (1686-1736)
German physicist, born in Danzig (now Gdańsk, Poland). He settled in the Netherlands and engaged in the manufacture of meteorological instruments. In 1714 he constructed the first thermometer employing mercury instead of alcohol. Using this thermometer, he devised the temperature scale now known by his name. Fahrenheit also invented a hygrometer of improved design. He discovered that other liquids besides water have a fixed boiling point and that these boiling points vary with changes in atmospheric pressure.
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Re: A-Z of AVIONICS
«
Reply #712 on:
26/04/2007 00:26:10 »
Frankenstein
A
VERY
scary monster. [
]
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Re: A-Z of AVIONICS
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Reply #713 on:
26/04/2007 01:45:13 »
G
adolinium,
symbol Gd, silvery-white metallic element with an atomic number of 64. Gadolinium is one of the rare earth elements in the lanthanide series of the periodic table. It is named after the Finnish chemist John Gadolin.
Gadolinium occurs with other rare earth elements in many minerals, such as samarskite, gadolinite, monazite, and some varieties of Norwegian ytterspar. It is the 41st element in order of abundance in the crust of the Earth. Gadolinium melts at about 1313° C (about 2395° F), boils at about 3273° C (about 5923° F), and has a relative density of 7.9. The atomic weight of the element is 157.25.
Gadolinium oxide was first separated from other rare earth elements by the Swiss chemist Jean de Marignac in 1880. The oxide and many salts of gadolinium have been prepared. Gadolinium oxide is white and the salts are colourless.
Because gadolinium has the largest known cross section, or stopping power, for neutrons of any element, it is used as a component of control rods in nuclear reactors (see Nuclear Energy). Like the other rare earth elements, it is used in electronic apparatus such as capacitors and masers; in metal alloys; in high-temperature furnaces; and in apparatus for magnetic cooling.
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Re: A-Z of AVIONICS
«
Reply #714 on:
26/04/2007 02:08:51 »
Hadron
Hahn, Otto
Half life
Hamilton, William Rowan
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Re: A-Z of AVIONICS
«
Reply #715 on:
26/04/2007 22:06:46 »
I
nstrument Landing System (ILS)
http://sprott.physics.wisc.edu/fractals/collect/1998/ils-runway.jpg
historical notes:
http://www.airwaysmuseum.com/DC3%20ILS%20calibration.htm
«
Last Edit: 29/04/2007 10:57:44 by iko
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Re: A-Z of AVIONICS
«
Reply #716 on:
30/04/2007 06:44:44 »
Joe-pye weed
[The name of an Indian Doctor said to have used the plant as medicine] any of a number of periniel American plants (genus Eupatorium) of the composite family, with whorled leaves and clusters of rayless, pinkish or purple flower heads.
(New World Dictionary of the American Language, second college edition)
«
Last Edit: 30/04/2007 06:53:35 by Karen W.
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Re: A-Z of AVIONICS
«
Reply #717 on:
01/05/2007 02:54:53 »
K
lingon
A humanoid being with ... oh .......
Kaolinite
A type of clay mineral that is the chief component of fine china. It is also used for most pottery when it isn't found in a relative impure clay (lots of other clay mineral in the mix.)
[Assumes refined British accent] It is of the latter that you Brown Betty is made, as well as all and sundry other pottery (Sneers)
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Re: A-Z of AVIONICS
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Reply #718 on:
01/05/2007 13:41:37 »
L
apislazzuli
http://i7.ebayimg.com/03/i/07/75/2d/ed_1_sbl.JPG
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Re: A-Z of AVIONICS
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Reply #719 on:
01/05/2007 18:31:02 »
M
cDonnell Douglas
McDonnell Douglas was a major American aerospace manufacturer, producing a number of famous commercial and military aircraft. It merged with Boeing in 1997 to form The Boeing Company.
The company was founded from the firms of James Smith McDonnell and Donald Wills Douglas. Both men were of Scottish ancestry, graduates of MIT and had worked for the aircraft manufacturer Glenn L. Martin Company. Douglas had been chief engineer at Martin before leaving to establish Davis-Douglas Company in early 1920 in Los Angeles. He bought out his backer and renamed the firm the Douglas Aircraft Company in 1921.
McDonnell founded J.S. McDonnell & Associates in Milwaukee, Wisconsin in 1928. His idea was to produce a personal aircraft for family use. The economic depression from 1929 ruined his ideas and the company collapsed. He went to work for Glenn L. Martin. He left in 1938 to try again with his own firm, McDonnell Aircraft Corporation, this time based near St. Louis, Missouri.
World War II was a major earner for Douglas. The company produced almost 30,000 aircraft from 1942 to 1945 and the workforce swelled to 160,000. Both companies suffered at the end of hostilities, facing an end of government orders and a surplus of aircraft. Both heavily cut their work forces.
After the war, Douglas continued to develop new aircraft, including the DC-6 (1946) and the DC-7 (1953). The company moved into jet propulsion, producing their first for the military - the conventional F3D Skyknight in 1948 and then the more 'jet age' F4D Skyray in 1951. Douglas also made commercial jets, producing the DC-8 in 1958 to compete with the Boeing 707. McDonnell was also developing jets, but being smaller they were prepared to be more radical, building on their successful FH-1 Phantom to become a major supplier to the Navy with the F2H Banshee, F3H Demon, and the F-101 Voodoo. The advent of the Korean War helped push McDonnell into a major military fighter supply role, especially with the noted F-4 Phantom II (1958).
Both companies were eager to enter the new missile business, Douglas moving from producing air-to-air rockets and missiles to entire missile systems under the 1956 Nike program and becoming the main contractor of the Skybolt ALBM program and the Thor ballistic missile program. McDonnell made a number of missiles, including the unusual ADM-20 Quail, as well as experimenting with hypersonic flight, research that enabled them to gain a substantial share of the NASA projects Mercury and Gemini. Douglas also gained contracts from NASA, notably for part of the enormous Saturn V rocket. Both companies were now major employers, but both were having problems.
Douglas was strained by the cost of the DC-8 and DC-9, and the companies began to sound each other out about a merger. Inquiries began in 1963; Douglas offered bid invitations from December 1966 and accepted that of McDonnell. The two firms were officially merged on April 28, 1967 as the McDonnell Douglas Corporation (MDC).
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