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Red for cross-section areas from 0.5 to 1 mm²
Blue for cross-section areas from 1.5 to 2.5 mm²
Yellow for cross-section areas over 4 to 6 mm²
Blade connectors
A blade connector is a type of single wire, plug-and-socket connection device using a flat conductive blade (plug) that is inserted into a receptacle. Wires ... | Electrical connector | Wikipedia | 234 | 152654 | https://en.wikipedia.org/wiki/Electrical%20connector | Technology | Components | null | vital_articles |
Loop quantum gravity (LQG) is a theory of quantum gravity that incorporates matter of the Standard Model into the framework established for the intrinsic quantum gravity case. It is an attempt to develop a quantum theory of gravity based directly on Albert Einstein's geometric formulation rather than the treatment of g... | Loop quantum gravity | Wikipedia | 448 | 152664 | https://en.wikipedia.org/wiki/Loop%20quantum%20gravity | Physical sciences | Quantum mechanics | Physics | vital_articles |
In 1994, Rovelli and Smolin showed that the quantum operators of the theory associated to area and volume have a discrete spectrum. That is, geometry is quantized. This result defines an explicit basis of states of quantum geometry, which turned out to be labelled by Roger Penrose's spin networks, which are graphs labe... | Loop quantum gravity | Wikipedia | 506 | 152664 | https://en.wikipedia.org/wiki/Loop%20quantum%20gravity | Physical sciences | Quantum mechanics | Physics | vital_articles |
Constraints and their Poisson bracket algebra
Dirac observables
The constraints define a constraint surface in the original phase space. The gauge motions of the constraints apply to all phase space but have the feature that they leave the constraint surface where it is, and thus the orbit of a point in the hypersurf... | Loop quantum gravity | Wikipedia | 414 | 152664 | https://en.wikipedia.org/wiki/Loop%20quantum%20gravity | Physical sciences | Quantum mechanics | Physics | vital_articles |
(where is the flat space metric, and the above equation expresses that , when written in terms of the basis , is locally flat). (Formulating general relativity with triads instead of metrics was not new.) The densitized triads are not unique, and in fact one can perform a local in space rotation with respect to the in... | Loop quantum gravity | Wikipedia | 485 | 152664 | https://en.wikipedia.org/wiki/Loop%20quantum%20gravity | Physical sciences | Quantum mechanics | Physics | vital_articles |
There are still problems in properly defining all these equations and solving them. For example, the Hamiltonian constraint Ashtekar worked with was the densitized version instead of the original Hamiltonian, that is, he worked with . There were serious difficulties in promoting this quantity to a quantum operator. Mor... | Loop quantum gravity | Wikipedia | 472 | 152664 | https://en.wikipedia.org/wiki/Loop%20quantum%20gravity | Physical sciences | Quantum mechanics | Physics | vital_articles |
LQG includes the concept of a holonomy. A holonomy is a measure of how much the initial and final values of a spinor or vector differ after parallel transport around a closed loop; it is denoted
.
Knowledge of the holonomies is equivalent to knowledge of the connection, up to gauge equivalence. Holonomies can also be... | Loop quantum gravity | Wikipedia | 458 | 152664 | https://en.wikipedia.org/wiki/Loop%20quantum%20gravity | Physical sciences | Quantum mechanics | Physics | vital_articles |
where means the operator but with the reverse factor ordering (remember from simple quantum mechanics where the product of operators is reversed under conjugation). The action of this operator on the Wilson loop is evaluated as a calculation in the connection representation and the result is rearranged purely as a ma... | Loop quantum gravity | Wikipedia | 488 | 152664 | https://en.wikipedia.org/wiki/Loop%20quantum%20gravity | Physical sciences | Quantum mechanics | Physics | vital_articles |
In the space spanned by and there is an infinitesimal parallelogram described by and . Using (where the indices and run from 1 to 2), yields the area of the surface given by
where and is the determinant of the metric induced on . The latter can be rewritten where the indices go from 1 to 2. This can be furth... | Loop quantum gravity | Wikipedia | 375 | 152664 | https://en.wikipedia.org/wiki/Loop%20quantum%20gravity | Physical sciences | Quantum mechanics | Physics | vital_articles |
where by we mean the loop traversed in the opposite direction and means the loop obtained by going around the loop and then along . See figure below. Given that the matrices are unitary one has that . Also given the cyclic property of the matrix traces (i.e. ) one has that . These identities can be combined with ea... | Loop quantum gravity | Wikipedia | 420 | 152664 | https://en.wikipedia.org/wiki/Loop%20quantum%20gravity | Physical sciences | Quantum mechanics | Physics | vital_articles |
An important aspect of the Hamiltonian operator is that it only acts at vertices (a consequence of this is that Thiemann's Hamiltonian operator, like Ashtekar's operator, annihilates non-intersecting loops except now it is not just formal and has rigorous mathematical meaning). More precisely, its action is non-zero on... | Loop quantum gravity | Wikipedia | 459 | 152664 | https://en.wikipedia.org/wiki/Loop%20quantum%20gravity | Physical sciences | Quantum mechanics | Physics | vital_articles |
In loop quantum gravity (LQG), a spin network represents a "quantum state" of the gravitational field on a 3-dimensional hypersurface. The set of all possible spin networks (or, more accurately, "s-knots" – that is, equivalence classes of spin networks under diffeomorphisms) is countable; it constitutes a basis of LQG ... | Loop quantum gravity | Wikipedia | 470 | 152664 | https://en.wikipedia.org/wiki/Loop%20quantum%20gravity | Physical sciences | Quantum mechanics | Physics | vital_articles |
There are however severe difficulties with this particular approach, for example the Hamiltonian operator is not self-adjoint, in fact it is not even a normal operator (i.e. the operator does not commute with its adjoint) and so the spectral theorem cannot be used to define the exponential in general. The most serious ... | Loop quantum gravity | Wikipedia | 486 | 152664 | https://en.wikipedia.org/wiki/Loop%20quantum%20gravity | Physical sciences | Quantum mechanics | Physics | vital_articles |
Another difficulty here is that spin foams are defined on a discretization of spacetime. While this presents no problems for a topological field theory as it has no local degrees of freedom, it presents problems for GR. This is known as the problem triangularization dependence.
Modern formulation of spin foams
Just a... | Loop quantum gravity | Wikipedia | 405 | 152664 | https://en.wikipedia.org/wiki/Loop%20quantum%20gravity | Physical sciences | Quantum mechanics | Physics | vital_articles |
Theorems establishing the uniqueness of the loop representation as defined by Ashtekar et al. (i.e. a certain concrete realization of a Hilbert space and associated operators reproducing the correct loop algebra) have been given by two groups (Lewandowski, Okołów, Sahlmann and Thiemann; and Christian Fleischhack). Befo... | Loop quantum gravity | Wikipedia | 157 | 152664 | https://en.wikipedia.org/wiki/Loop%20quantum%20gravity | Physical sciences | Quantum mechanics | Physics | vital_articles |
Difficulties and progress checking the semiclassical limit
There are a number of difficulties in trying to establish LQG gives Einstein's theory of general relativity in the semiclassical limit:
There is no operator corresponding to infinitesimal spatial diffeomorphisms (it is not surprising that the theory has no ge... | Loop quantum gravity | Wikipedia | 472 | 152664 | https://en.wikipedia.org/wiki/Loop%20quantum%20gravity | Physical sciences | Quantum mechanics | Physics | vital_articles |
Formulating observables for classical general relativity is a formidable problem because of its non-linear nature and spacetime diffeomorphism invariance. A systematic approximation scheme to calculate observables has been recently developed. | Loop quantum gravity | Wikipedia | 48 | 152664 | https://en.wikipedia.org/wiki/Loop%20quantum%20gravity | Physical sciences | Quantum mechanics | Physics | vital_articles |
Difficulties in trying to examine the semiclassical limit of the theory should not be confused with it having the wrong semiclassical limit.
Concerning issue number 2 above, consider so-called weave states. Ordinary measurements of geometric quantities are macroscopic, and Planckian discreteness is smoothed out. The f... | Loop quantum gravity | Wikipedia | 408 | 152664 | https://en.wikipedia.org/wiki/Loop%20quantum%20gravity | Physical sciences | Quantum mechanics | Physics | vital_articles |
The master constraint
Thiemann's Master Constraint Programme for Loop Quantum Gravity (LQG) was proposed as a classically equivalent way to impose the infinite number of Hamiltonian constraint equations in terms of a single master constraint , which involves the square of the constraints in question. An initial object... | Loop quantum gravity | Wikipedia | 502 | 152664 | https://en.wikipedia.org/wiki/Loop%20quantum%20gravity | Physical sciences | Quantum mechanics | Physics | vital_articles |
The spectrum of the master constraint may not contain zero due to normal or factor ordering effects which are finite but similar in nature to the infinite vacuum energies of background-dependent quantum field theories. In this case it turns out to be physically correct to replace with provided that the "normal orderi... | Loop quantum gravity | Wikipedia | 449 | 152664 | https://en.wikipedia.org/wiki/Loop%20quantum%20gravity | Physical sciences | Quantum mechanics | Physics | vital_articles |
The spin foam description then follows from the application of on a spin network resulting in a linear combination of new spin networks whose graph and labels have been modified. Obviously an approximation is made by truncating the value of to some finite integer. An advantage of the extended master constraint is tha... | Loop quantum gravity | Wikipedia | 494 | 152664 | https://en.wikipedia.org/wiki/Loop%20quantum%20gravity | Physical sciences | Quantum mechanics | Physics | vital_articles |
An oversight in the application of the no-hair theorem is the assumption that the relevant degrees of freedom accounting for the entropy of the black hole must be classical in nature; what if they were purely quantum mechanical instead and had non-zero entropy? This is what is realized in the LQG derivation of black ho... | Loop quantum gravity | Wikipedia | 469 | 152664 | https://en.wikipedia.org/wiki/Loop%20quantum%20gravity | Physical sciences | Quantum mechanics | Physics | vital_articles |
A detailed study of the quantum geometry of a black hole horizon has been made using loop quantum gravity. Loop-quantization does not reproduce the result for black hole entropy originally discovered by Bekenstein and Hawking, unless one chooses the value of the Immirzi parameter to cancel out another constant that ari... | Loop quantum gravity | Wikipedia | 496 | 152664 | https://en.wikipedia.org/wiki/Loop%20quantum%20gravity | Physical sciences | Quantum mechanics | Physics | vital_articles |
Loop quantum gravity phenomenology
Quantum gravity effects are difficult to measure because the Planck length is so small. However recently physicists, such as Jack Palmer, have started to consider the possibility of measuring quantum gravity effects mostly from astrophysical observations and gravitational wave detect... | Loop quantum gravity | Wikipedia | 481 | 152664 | https://en.wikipedia.org/wiki/Loop%20quantum%20gravity | Physical sciences | Quantum mechanics | Physics | vital_articles |
Some quantum theories of gravity posit a spin-2 quantum field that is quantized, giving rise to gravitons. In string theory, one generally starts with quantized excitations on top of a classically fixed background. This theory is thus described as background dependent. Particles like photons as well as changes in the s... | Loop quantum gravity | Wikipedia | 488 | 152664 | https://en.wikipedia.org/wiki/Loop%20quantum%20gravity | Physical sciences | Quantum mechanics | Physics | vital_articles |
Since LQG has been formulated in 4 dimensions (with and without supersymmetry), and M-theory requires supersymmetry and 11 dimensions, a direct comparison between the two has not been possible. It is possible to extend mainstream LQG formalism to higher-dimensional supergravity, general relativity with supersymmetry an... | Loop quantum gravity | Wikipedia | 387 | 152664 | https://en.wikipedia.org/wiki/Loop%20quantum%20gravity | Physical sciences | Quantum mechanics | Physics | vital_articles |
Furthermore, LQG has drawn philosophical comparisons with causal dynamical triangulation and asymptotically safe gravity, and the spinfoam with group field theory and AdS/CFT correspondence. Smolin and Wen have suggested combining LQG with string-net liquid, tensors, and Smolin and Fotini Markopoulou-Kalamara quantum g... | Loop quantum gravity | Wikipedia | 454 | 152664 | https://en.wikipedia.org/wiki/Loop%20quantum%20gravity | Physical sciences | Quantum mechanics | Physics | vital_articles |
Presently, no semiclassical limit recovering general relativity has been shown to exist. This means it remains unproven that LQG's description of spacetime at the Planck scale has the right continuum limit (described by general relativity with possible quantum corrections). Specifically, the dynamics of the theory are ... | Loop quantum gravity | Wikipedia | 317 | 152664 | https://en.wikipedia.org/wiki/Loop%20quantum%20gravity | Physical sciences | Quantum mechanics | Physics | vital_articles |
The Z3 was a German electromechanical computer designed by Konrad Zuse in 1938, and completed in 1941. It was the world's first working programmable, fully automatic digital computer. The Z3 was built with 2,600 relays, implementing a 22-bit word length that operated at a clock frequency of about 5–10 Hz. Program code ... | Z3 (computer) | Wikipedia | 348 | 152671 | https://en.wikipedia.org/wiki/Z3%20%28computer%29 | Technology | Early computers | null | vital_articles |
Zuse designed the Z1 in 1935 to 1936 and built it from 1936 to 1938. The Z1 was wholly mechanical and only worked for a few minutes at a time at most. Helmut Schreyer advised Zuse to use a different technology. As a doctoral student at the Technische Hochschule in Charlottenburg (now Technische Universität Berlin) in 1... | Z3 (computer) | Wikipedia | 507 | 152671 | https://en.wikipedia.org/wiki/Z3%20%28computer%29 | Technology | Early computers | null | vital_articles |
The Z3 was completed in 1941 and was faster and far more reliable than the Z1 and Z2. The Z3 floating-point arithmetic was improved over that of the Z1 in that it implemented exception handling "using just a few relays", the exceptional values (plus infinity, minus infinity and undefined) could be generated and passed ... | Z3 (computer) | Wikipedia | 410 | 152671 | https://en.wikipedia.org/wiki/Z3%20%28computer%29 | Technology | Early computers | null | vital_articles |
Z3 as a universal Turing machine
It was possible to construct loops on the Z3, but there was no conditional branch instruction. Nevertheless, the Z3 was Turing-complete – how to implement a universal Turing machine on the Z3 was shown in 1998 by Raúl Rojas. He proposed that the tape program would have to be long enoug... | Z3 (computer) | Wikipedia | 487 | 152671 | https://en.wikipedia.org/wiki/Z3%20%28computer%29 | Technology | Early computers | null | vital_articles |
The ENIAC computer, completed after the war, used vacuum tubes to implement switches and used decimal representation for numbers. Until 1948 programming was, as with Colossus, by patch leads and switches.
The Manchester Baby of 1948 along with the Manchester Mark 1 and EDSAC both of 1949 were the world's earliest work... | Z3 (computer) | Wikipedia | 426 | 152671 | https://en.wikipedia.org/wiki/Z3%20%28computer%29 | Technology | Early computers | null | vital_articles |
A hovercraft (: hovercraft), also known as an air-cushion vehicle or ACV, is an amphibious craft capable of travelling over land, water, mud, ice, and various other surfaces.
Hovercraft use blowers to produce a large volume of air below the hull, or air cushion, that is slightly above atmospheric pressure. The pressur... | Hovercraft | Wikipedia | 478 | 152690 | https://en.wikipedia.org/wiki/Hovercraft | Technology | Maritime transport | null | vital_articles |
In 1915, the Austrian Dagobert Müller von Thomamühl (1880–1956) built the world's first "air cushion" boat (). Shaped like a section of a large aerofoil (this creates a low-pressure area above the wing much like an aircraft), the craft was propelled by four aero engines driving two submerged marine propellers, with a f... | Hovercraft | Wikipedia | 496 | 152690 | https://en.wikipedia.org/wiki/Hovercraft | Technology | Maritime transport | null | vital_articles |
During World War II, an American engineer, Charles Fletcher, invented a walled air cushion vehicle, the Glidemobile. Because the project was classified by the U.S. government, Fletcher could not file a patent.
In April 1958, Ford engineers demonstrated the Glide-air, a model of a wheel-less vehicle that speeds on a t... | Hovercraft | Wikipedia | 320 | 152690 | https://en.wikipedia.org/wiki/Hovercraft | Technology | Maritime transport | null | vital_articles |
Cockerell came across the key concept in his design when studying the ring of airflow when high-pressure air was blown into the annular area between two concentric tin cans (one coffee and the other from cat food) and a hairdryer. This produced a ring of airflow, as expected, but he noticed an unexpected benefit as wel... | Hovercraft | Wikipedia | 436 | 152690 | https://en.wikipedia.org/wiki/Hovercraft | Technology | Maritime transport | null | vital_articles |
The SR.N1 was powered by a 450 hp Alvis Leonides engine powering a vertical fan in the middle of the craft. In addition to providing the lift air, a portion of the airflow was bled off into two channels on either side of the craft, which could be directed to provide thrust. In normal operation this extra airflow was di... | Hovercraft | Wikipedia | 491 | 152690 | https://en.wikipedia.org/wiki/Hovercraft | Technology | Maritime transport | null | vital_articles |
Latimer-Needham and Cockerell devised a high skirt design, which was fitted to the SR.N1 to produce the Mk V, displaying hugely improved performance, with the ability to climb over obstacles almost as high as the skirt. In October 1961, Latimer-Needham sold his skirt patents to Westland, who had recently taken over Sa... | Hovercraft | Wikipedia | 485 | 152690 | https://en.wikipedia.org/wiki/Hovercraft | Technology | Maritime transport | null | vital_articles |
Another major pioneering effort of the early hovercraft era was carried out by Jean Bertin's firm in France. Bertin was an advocate of the "multi-skirt" approach, which used a number of smaller cylindrical skirts instead of one large one in order to avoid the problems noted above. During the early 1960s he developed a ... | Hovercraft | Wikipedia | 466 | 152690 | https://en.wikipedia.org/wiki/Hovercraft | Technology | Maritime transport | null | vital_articles |
Hovercraft can be powered by one or more engines. Smaller craft, such as the SR.N6, usually have one engine with the drive split through a gearbox. On vehicles with several engines, one usually drives the fan (or impeller), which is responsible for lifting the vehicle by forcing high pressure air under the craft. The a... | Hovercraft | Wikipedia | 457 | 152690 | https://en.wikipedia.org/wiki/Hovercraft | Technology | Maritime transport | null | vital_articles |
The first passenger-carrying hovercraft to enter service was the Vickers VA-3, which, in the summer of 1962, carried passengers regularly along the north Wales coast from Moreton, Merseyside, to Rhyl. It was powered by two turboprop aero-engines and driven by propellers.
During the 1960s, Saunders-Roe developed severa... | Hovercraft | Wikipedia | 386 | 152690 | https://en.wikipedia.org/wiki/Hovercraft | Technology | Maritime transport | null | vital_articles |
As well as Saunders-Roe and Vickers (which combined in 1966 to form the British Hovercraft Corporation (BHC)), other commercial craft were developed during the 1960s in the UK by Cushioncraft (part of the Britten-Norman Group) and Hovermarine based at Woolston (the latter being sidewall hovercraft, where the sides of t... | Hovercraft | Wikipedia | 424 | 152690 | https://en.wikipedia.org/wiki/Hovercraft | Technology | Maritime transport | null | vital_articles |
The commercial success of hovercraft suffered from rapid rises in fuel prices during the late 1960s and 1970s, following conflict in the Middle East. Alternative over-water vehicles, such as wave-piercing catamarans (marketed as the SeaCat in the UK until 2005), use less fuel and can perform most of the hovercraft's ma... | Hovercraft | Wikipedia | 477 | 152690 | https://en.wikipedia.org/wiki/Hovercraft | Technology | Maritime transport | null | vital_articles |
The Scandinavian airline SAS used to charter an AP1-88 hovercraft for regular passengers between Copenhagen Airport, Denmark, and the SAS Hovercraft Terminal in Malmö, Sweden.
In 1998, the US Postal Service began using the British built Hoverwork AP1-88 to haul mail, freight, and passengers from Bethel, Alaska, to and... | Hovercraft | Wikipedia | 389 | 152690 | https://en.wikipedia.org/wiki/Hovercraft | Technology | Maritime transport | null | vital_articles |
From the 1960s, several commercial lines were operated in Japan, without much success. In Japan the last commercial line had linked Ōita Airport and central Ōita but was shut down in October 2009. However, the commercial line between Ōita Airport and central Ōita is scheduled to reopen in 2024.
Hovercraft are still m... | Hovercraft | Wikipedia | 413 | 152690 | https://en.wikipedia.org/wiki/Hovercraft | Technology | Maritime transport | null | vital_articles |
The first application of the hovercraft for military use was by the British Armed Forces, using hovercraft built by Saunders-Roe. In 1961, the United Kingdom set up the Interservice Hovercraft Trials Unit (IHTU) based at RNAS Lee-on-Solent (HMS Daedalus), now the site of the Hovercraft Museum, near Portsmouth. This uni... | Hovercraft | Wikipedia | 315 | 152690 | https://en.wikipedia.org/wiki/Hovercraft | Technology | Maritime transport | null | vital_articles |
During the 1960s, Bell licensed and sold the Saunders-Roe SR.N5 as the Bell SK-5. They were deployed on trial to the Vietnam War by the United States Navy as PACV patrol craft in the Mekong Delta where their mobility and speed was unique. This was used in both the UK SR.N5 curved deck configuration and later with modif... | Hovercraft | Wikipedia | 447 | 152690 | https://en.wikipedia.org/wiki/Hovercraft | Technology | Maritime transport | null | vital_articles |
The World Hovercraft Championships are run under the auspices of the World Hovercraft Federation. So far the World Hovercraft Championships had been hosted by France: 1993 in Verneuil, 1997 in Lucon, 2006 at the Lac de Tolerme; Germany: 1987 in Bad Karlshafen, 2004 in Berlin, 2012 and 2018 in Saalburg; Portugal: 1995 i... | Hovercraft | Wikipedia | 502 | 152690 | https://en.wikipedia.org/wiki/Hovercraft | Technology | Maritime transport | null | vital_articles |
Mackace (Mackley Air Cushion Equipment), now known as Hovertrans, produced a number of successful Hoverbarges, such as the 250 ton payload "Sea Pearl", which operated in Abu Dhabi, and the twin 160 ton payload "Yukon Princesses", which ferried trucks across the Yukon River to aid the pipeline build. Hoverbarges are sti... | Hovercraft | Wikipedia | 393 | 152690 | https://en.wikipedia.org/wiki/Hovercraft | Technology | Maritime transport | null | vital_articles |
A test track for a tracked hovercraft system was built at Earith near Cambridge, England. It ran southwest from Sutton Gault, sandwiched between the Old Bedford River and the smaller Counter Drain to the west. Careful examination of the site will still reveal traces of the concrete piers used to support the structure. ... | Hovercraft | Wikipedia | 374 | 152690 | https://en.wikipedia.org/wiki/Hovercraft | Technology | Maritime transport | null | vital_articles |
In the late 1960s and early 1970s, the U.S. Department of Transport's Urban Mass Transit Administration (UMTA) funded several hovertrain projects, which were known as Tracked Air Cushion Vehicles or TACVs. They were also known as Aerotrains since one of the builders had a licence from Bertin's Aerotrain company. Three ... | Hovercraft | Wikipedia | 433 | 152690 | https://en.wikipedia.org/wiki/Hovercraft | Technology | Maritime transport | null | vital_articles |
Non-transportation
The Hoover Constellation was a spherical canister-type vacuum cleaner notable for its lack of wheels. Floating on a cushion of air, it was a domestic hovercraft. They were not especially good as vacuum cleaners as the air escaping from under the cushion blew uncollected dust in all directions, nor as... | Hovercraft | Wikipedia | 428 | 152690 | https://en.wikipedia.org/wiki/Hovercraft | Technology | Maritime transport | null | vital_articles |
World's largest civil hovercraft – The BHC SR.N4 Mk.III, at 56.4 m (185 ft) length and 310 metric tons (305 long tons) weight, can accommodate 418 passengers and 60 cars.
World's largest military hovercraft – The Russian Zubr class LCAC at 57.6 metres (188 feet) length and a maximum displacement of 535 tons. This hove... | Hovercraft | Wikipedia | 320 | 152690 | https://en.wikipedia.org/wiki/Hovercraft | Technology | Maritime transport | null | vital_articles |
A tractor is an engineering vehicle specifically designed to deliver a high tractive effort (or torque) at slow speeds, for the purposes of hauling a trailer or machinery such as that used in agriculture, mining or construction. Most commonly, the term is used to describe a farm vehicle that provides the power and tra... | Tractor | Wikipedia | 448 | 152692 | https://en.wikipedia.org/wiki/Tractor | Technology | Other | null | vital_articles |
In parallel with the early portable engine development, many engineers attempted to make them self-propelled – the fore-runners of the traction engine. In most cases this was achieved by fitting a sprocket on the end of the crankshaft, and running a chain from this to a larger sprocket on the rear axle. These experimen... | Tractor | Wikipedia | 432 | 152692 | https://en.wikipedia.org/wiki/Tractor | Technology | Other | null | vital_articles |
Richard Hornsby & Sons are credited with producing and selling the first oil-engined tractor in Britain, invented by Herbert Akroyd Stuart. The Hornsby-Akroyd Patent Safety Oil Traction Engine was made in 1896 with a engine. In 1897, it was bought by Mr. Locke-King, the first recorded British tractor sale. That year, ... | Tractor | Wikipedia | 447 | 152692 | https://en.wikipedia.org/wiki/Tractor | Technology | Other | null | vital_articles |
In 1908, the Saunderson Tractor and Implement Co. of Bedford introduced a four-wheel design, and became the largest tractor manufacturer in Britain at the time. While the earlier, heavier tractors were initially very successful, it became increasingly apparent at this time that the weight of a large supporting frame wa... | Tractor | Wikipedia | 495 | 152692 | https://en.wikipedia.org/wiki/Tractor | Technology | Other | null | vital_articles |
Configuration
Tractors can be generally classified by number of axles or wheels, with main categories of two-wheel tractors (single-axle tractors) and four-wheel tractors (two-axle tractors); more axles are possible but uncommon. Among four-wheel tractors (two-axle tractors), most are two-wheel drive (usually at the r... | Tractor | Wikipedia | 483 | 152692 | https://en.wikipedia.org/wiki/Tractor | Technology | Other | null | vital_articles |
Gasoline and kerosene
Since the turn of the 20th century, internal combustion engines have been the power source of choice. Between 1900 and 1960, gasoline was the predominant fuel, with kerosene (the Rumely Oil Pull was the most notable of this kind)being a common alternative. Generally, one engine could burn any of ... | Tractor | Wikipedia | 499 | 152692 | https://en.wikipedia.org/wiki/Tractor | Technology | Other | null | vital_articles |
Slow, controllable speeds are necessary for most of the operations performed with a tractor. They help give the farmer a larger degree of control in certain situations, such as field work. When travelling on public roads, the slow operating speeds can cause problems, such as long queues or tailbacks, which can delay or... | Tractor | Wikipedia | 354 | 152692 | https://en.wikipedia.org/wiki/Tractor | Technology | Other | null | vital_articles |
In newer designs, unsynchronized transmission designs were replaced with synchronization or with continuously variable transmissions (CVTs). Either a synchronized manual transmission with enough available gear ratios (often achieved with dual ranges, high and low) or a CVT allow the engine speed to be matched to the de... | Tractor | Wikipedia | 420 | 152692 | https://en.wikipedia.org/wiki/Tractor | Technology | Other | null | vital_articles |
The drawbar system necessitated the implement having its own running gear (usually wheels) and in the case of a plow, chisel cultivator or harrow, some sort of lift mechanism to raise it out of the ground at turns or for transport. Drawbars necessarily posed a rollover risk depending on how the tractive torque was app... | Tractor | Wikipedia | 418 | 152692 | https://en.wikipedia.org/wiki/Tractor | Technology | Other | null | vital_articles |
Three-point and quick
The drawbar system was virtually the exclusive method of attaching implements (other than direct attachment to the tractor) before Harry Ferguson developed the three-point hitch. Equipment attached to the three-point hitch can be raised or lowered hydraulically with a control lever. The equip... | Tractor | Wikipedia | 505 | 152692 | https://en.wikipedia.org/wiki/Tractor | Technology | Other | null | vital_articles |
Early tractors used belts or cables wrapped around the flywheel or a separate belt pulley to power stationary equipment, such as a threshing machine, buzz saw, silage blower, or stationary baler. In most cases, it was impractical for the tractor and equipment to move with a flexible belt or cable between them, so this ... | Tractor | Wikipedia | 475 | 152692 | https://en.wikipedia.org/wiki/Tractor | Technology | Other | null | vital_articles |
Some modern tractors also have (or offer as optional equipment) a button on the gear stick for controlling the clutch, in addition to the standard pedal, allowing for gear changes and the tractor to be brought to a stop without using the foot pedal to engage the clutch. Others have a button for temporarily increasing ... | Tractor | Wikipedia | 495 | 152692 | https://en.wikipedia.org/wiki/Tractor | Technology | Other | null | vital_articles |
Levers and switches
Many functions once controlled with levers have been replaced with some model of electrical switch with the rise of indirect computer controlling of functions in modern tractors.
Until the late of the 1950s, tractors had a single register of gears, hence one gear stick, often with three to five fo... | Tractor | Wikipedia | 446 | 152692 | https://en.wikipedia.org/wiki/Tractor | Technology | Other | null | vital_articles |
These structures were first required by legislation in Sweden in 1959. Before they were required, some farmers died when their tractors rolled on top of them. Row-crop tractors, before ROPS, were particularly dangerous because of their 'tricycle' design with the two front wheels spaced close together and angled inward... | Tractor | Wikipedia | 408 | 152692 | https://en.wikipedia.org/wiki/Tractor | Technology | Other | null | vital_articles |
A variety of specialty farm tractors have been developed for particular uses. These include "row crop" tractors with adjustable tread width to allow the tractor to pass down rows of cereals, maize, tomatoes or other crops without crushing the plants, "wheatland" or "standard" tractors with fixed wheels and a lower cen... | Tractor | Wikipedia | 471 | 152692 | https://en.wikipedia.org/wiki/Tractor | Technology | Other | null | vital_articles |
A bulldozer is a track-type tractor with a blade attached in the front and a rope-winch behind. Bulldozers are very powerful tractors and have excellent ground-hold, as their main tasks are to push or drag.
Bulldozers have been further modified over time to evolve into new machines which are capable of working in way... | Tractor | Wikipedia | 508 | 152692 | https://en.wikipedia.org/wiki/Tractor | Technology | Other | null | vital_articles |
Their relatively small frames and precise controls make backhoe-loaders very useful and common in urban engineering projects, such as construction and repairs in areas too small for larger equipment. Their versatility and compact size make them one of the most popular urban construction vehicles.
In the UK and Ireland... | Tractor | Wikipedia | 444 | 152692 | https://en.wikipedia.org/wiki/Tractor | Technology | Other | null | vital_articles |
Compact utility tractors require special, smaller implements than full-sized agricultural tractors. Very common implements include the box blade, the grader blade, the landscape rake, the post hole digger (or post hole auger), the rotary cutter (slasher or a brush hog), a mid- or rear-mount finish mower, a broadcast s... | Tractor | Wikipedia | 490 | 152692 | https://en.wikipedia.org/wiki/Tractor | Technology | Other | null | vital_articles |
A general-purpose or row-crop tractor is tailored specifically to the growing of crops grown in rows, and most especially to cultivating these crops. These tractors are universal machines, capable of both primary tillage and cultivation of a crop.
The row-crop tractor category evolved rather than appearing overnight,... | Tractor | Wikipedia | 437 | 152692 | https://en.wikipedia.org/wiki/Tractor | Technology | Other | null | vital_articles |
Many early row-crop tractors had a tricycle design with two closely spaced front tires, and some even had a single front tire. This made it dangerous to operate on the side of a steep hill; as a result, many farmers died from tractor rollovers. Also, early row-crop tractors had no rollover protection system (ROPS), mea... | Tractor | Wikipedia | 495 | 152692 | https://en.wikipedia.org/wiki/Tractor | Technology | Other | null | vital_articles |
Visually, the distinction between a garden tractor and a lawn tractor is often hard to make – generally, garden tractors are more sturdily built, with stronger frames, 12-inch or larger wheels mounted with multiple lugs (most lawn tractors have a single bolt or clip on the hub), heavier transaxles, and ability to accom... | Tractor | Wikipedia | 395 | 152692 | https://en.wikipedia.org/wiki/Tractor | Technology | Other | null | vital_articles |
The ingenuity of farm mechanics, coupled in some cases with OEM or aftermarket assistance, has often resulted in the conversion of automobiles for use as farm tractors. In the United States, this trend was especially strong from the 1910s through 1950s. It began early in the development of vehicles powered by internal ... | Tractor | Wikipedia | 488 | 152692 | https://en.wikipedia.org/wiki/Tractor | Technology | Other | null | vital_articles |
The German occupation of Italy during World resulted in a severe shortage of mechanized farm equipment. The destruction of tractors was a sort of scorched-earth strategy used to reduce the independence of the conquered. The shortage of tractors in that area of Europe was the origin of Lamborghini. The war was also ... | Tractor | Wikipedia | 412 | 152692 | https://en.wikipedia.org/wiki/Tractor | Technology | Other | null | vital_articles |
Nomenclature
The term "tractor" (US and Canada) or "tractor unit" (UK) is also applied to:
Road tractors, tractor units or traction heads, familiar as the front end of an articulated lorry / semi-trailer truck. They are heavy-duty vehicles with large engines and several axles.
The majority of these tractors are desi... | Tractor | Wikipedia | 474 | 152692 | https://en.wikipedia.org/wiki/Tractor | Technology | Other | null | vital_articles |
Sculptor is a faint constellation in the southern sky. It represents a sculptor. It was introduced by Nicolas Louis de Lacaille in the 18th century. He originally named it Apparatus Sculptoris (the sculptor's studio), but the name was later shortened.
History
The region to the south of Cetus and Aquarius had been nam... | Sculptor (constellation) | Wikipedia | 511 | 152710 | https://en.wikipedia.org/wiki/Sculptor%20%28constellation%29 | Physical sciences | Other | Astronomy | vital_articles |
Eta Sculptoris is a red giant of spectral type M4III that varies between magnitudes 4.8 and 4.9, pulsating with multiple periods of 22.7, 23.5, 24.6, 47.3, 128.7 and 158.7 days. Estimated to be around 1,082 times as luminous as the Sun, it is 460 ± 20 light-years distant from Earth.
R Sculptoris is a red giant that ha... | Sculptor (constellation) | Wikipedia | 376 | 152710 | https://en.wikipedia.org/wiki/Sculptor%20%28constellation%29 | Physical sciences | Other | Astronomy | vital_articles |
Intensive agriculture, also known as intensive farming (as opposed to extensive farming), conventional, or industrial agriculture, is a type of agriculture, both of crop plants and of animals, with higher levels of input and output per unit of agricultural land area. It is characterized by a low fallow ratio, higher us... | Intensive farming | Wikipedia | 497 | 152772 | https://en.wikipedia.org/wiki/Intensive%20farming | Technology | Forms | null | vital_articles |
The first phase involved a continuing process of mechanization. Horse-drawn machinery such as the McCormick reaper revolutionized harvesting, while inventions such as the cotton gin reduced the cost of processing. During this same period, farmers began to use steam-powered threshers and tractors. In 1892, the first gas... | Intensive farming | Wikipedia | 416 | 152772 | https://en.wikipedia.org/wiki/Intensive%20farming | Technology | Forms | null | vital_articles |
Pasture intensification is the improvement of pasture soils and grasses to increase the food production potential of livestock systems. It is commonly used to reverse pasture degradation, a process characterized by loss of forage and decreased animal carrying capacity which results from overgrazing, poor nutrient manag... | Intensive farming | Wikipedia | 428 | 152772 | https://en.wikipedia.org/wiki/Intensive%20farming | Technology | Forms | null | vital_articles |
Rotational grazing is a variety of foraging in which herds or flocks are regularly and systematically moved to fresh, rested grazing areas (sometimes called paddocks) to maximize the quality and quantity of forage growth. It can be used with cattle, sheep, goats, pigs, chickens, turkeys, ducks, and other animals. The h... | Intensive farming | Wikipedia | 452 | 152772 | https://en.wikipedia.org/wiki/Intensive%20farming | Technology | Forms | null | vital_articles |
The CAFO designation resulted from the 1972 U.S. Federal Clean Water Act, which was enacted to protect and restore lakes and rivers to a "fishable, swimmable" quality. The United States Environmental Protection Agency identified certain animal feeding operations, along with many other types of industry, as "point sourc... | Intensive farming | Wikipedia | 420 | 152772 | https://en.wikipedia.org/wiki/Intensive%20farming | Technology | Forms | null | vital_articles |
With the availability of molecular genetics in Arabidopsis and rice the mutant genes responsible (reduced height (rht), gibberellin insensitive (gai1) and slender rice (slr1)) have been cloned and identified as cellular signalling components of gibberellic acid, a phytohormone involved in regulating stem growth via its... | Intensive farming | Wikipedia | 452 | 152772 | https://en.wikipedia.org/wiki/Intensive%20farming | Technology | Forms | null | vital_articles |
Water catchment management measures include recharge pits, which capture rainwater and runoff and use it to recharge groundwater supplies. This helps in the replenishment of groundwater wells and eventually reduces soil erosion. Dammed rivers creating reservoirs store water for irrigation and other uses over large area... | Intensive farming | Wikipedia | 346 | 152772 | https://en.wikipedia.org/wiki/Intensive%20farming | Technology | Forms | null | vital_articles |
A paddy field is a flooded parcel of arable land used for growing rice and other semiaquatic crops. Paddy fields are a typical feature of rice-growing countries of east and southeast Asia, including Malaysia, China, Sri Lanka, Myanmar, Thailand, Korea, Japan, Vietnam, Taiwan, Indonesia, India, and the Philippines. They... | Intensive farming | Wikipedia | 489 | 152772 | https://en.wikipedia.org/wiki/Intensive%20farming | Technology | Forms | null | vital_articles |
Intercropping can increase yields or reduce inputs and thus represents (potentially sustainable) agricultural intensification. However, while total yield per unit land area is often increased, yields of any single crop often decrease. There are also challenges to farmers who rely on farming equipment optimized for mono... | Intensive farming | Wikipedia | 488 | 152772 | https://en.wikipedia.org/wiki/Intensive%20farming | Technology | Forms | null | vital_articles |
Intensive farming creates conditions for parasite growth and transmission that are vastly different from what parasites encounter in natural host populations, potentially altering selection on a variety of traits such as life-history traits and virulence. Some recent epidemic outbreaks have highlighted the association ... | Intensive farming | Wikipedia | 234 | 152772 | https://en.wikipedia.org/wiki/Intensive%20farming | Technology | Forms | null | vital_articles |
In a multicellular organism, an organ is a collection of tissues joined in a structural unit to serve a common function. In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to act together in a function. Tissues of different types combine to form an organ ... | Organ (biology) | Wikipedia | 344 | 152776 | https://en.wikipedia.org/wiki/Organ%20%28biology%29 | Biology and health sciences | Basics_2 | null | vital_articles |
Except for placozoans, multicellular animals including humans have a variety of organ systems. These specific systems are widely studied in human anatomy. The functions of these organ systems often share significant overlap. For instance, the nervous and endocrine system both operate via a shared organ, the hypothalamu... | Organ (biology) | Wikipedia | 486 | 152776 | https://en.wikipedia.org/wiki/Organ%20%28biology%29 | Biology and health sciences | Basics_2 | null | vital_articles |
In the study of anatomy, viscera (: viscus) refers to the internal organs of the abdominal, thoracic, and pelvic cavities. The abdominal organs may be classified as solid organs or hollow organs. The solid organs are the liver, pancreas, spleen, kidneys, and adrenal glands. The hollow organs of the abdomen are the stom... | Organ (biology) | Wikipedia | 456 | 152776 | https://en.wikipedia.org/wiki/Organ%20%28biology%29 | Biology and health sciences | Basics_2 | null | vital_articles |
The study of plant organs is covered in plant morphology. Organs of plants can be divided into vegetative and reproductive. Vegetative plant organs include roots, stems, and leaves. The reproductive organs are variable. In flowering plants, they are represented by the flower, seed and fruit. In conifers, the organ that... | Organ (biology) | Wikipedia | 447 | 152776 | https://en.wikipedia.org/wiki/Organ%20%28biology%29 | Biology and health sciences | Basics_2 | null | vital_articles |
The English word "organ" dates back to the twelfth century and refers to any musical instrument. By the late 14th century, the musical term's meaning had narrowed to refer specifically to the keyboard-based instrument. At the same time, a second meaning arose, in reference to a "body part adapted to a certain function"... | Organ (biology) | Wikipedia | 485 | 152776 | https://en.wikipedia.org/wiki/Organ%20%28biology%29 | Biology and health sciences | Basics_2 | null | vital_articles |
The Portuguese war (Physalia physalis), also known as the man-of-war or bluebottle, is a marine hydrozoan found in the Atlantic Ocean and the Indian Ocean. It is considered to be the same species as the Pacific man o' war or bluebottle, which is found mainly in the Pacific Ocean. The Portuguese man o' war is the only ... | Portuguese man o' war | Wikipedia | 380 | 152952 | https://en.wikipedia.org/wiki/Portuguese%20man%20o%27%20war | Biology and health sciences | Cnidarians | Animals | vital_articles |
Coloniality
The man o' war is described as a colonial organism because the individual zooids in a colony are evolutionarily derived from either polyps or medusae, i.e. the two basic body plans of cnidarians. Both of these body plans comprise entire individuals in non-colonial cnidarians (for example, a jellyfish is a m... | Portuguese man o' war | Wikipedia | 504 | 152952 | https://en.wikipedia.org/wiki/Portuguese%20man%20o%27%20war | Biology and health sciences | Cnidarians | Animals | vital_articles |
The pneumatophore or bladder is the most conspicuous part of the man o' war. This large, gas-filled, translucent structure is pink, purple or blue in color; it is long and rises as much as above the water. The pneumatophore functions as both a flotation device and a sail, allowing the animal to move with the prevaili... | Portuguese man o' war | Wikipedia | 502 | 152952 | https://en.wikipedia.org/wiki/Portuguese%20man%20o%27%20war | Biology and health sciences | Cnidarians | Animals | vital_articles |
Man o' war individuals are dioecious, meaning each colony is either male or female. Gonophores producing either sperm or eggs (depending on the sex of the colony) sit on a tree-like structure called a gonodendron, which is believed to drop off from the colony during reproduction. Mating takes place primarily in the aut... | Portuguese man o' war | Wikipedia | 422 | 152952 | https://en.wikipedia.org/wiki/Portuguese%20man%20o%27%20war | Biology and health sciences | Cnidarians | Animals | vital_articles |
The man-of-war fish, Nomeus gronovii, is a driftfish native to the Atlantic, Pacific and Indian Oceans. It is notable for its ability to live within the deadly tentacles of the Portuguese man o' war, upon whose tentacles and gonads it feeds. Rather than using mucus to prevent nematocysts from firing, as is seen in some... | Portuguese man o' war | Wikipedia | 430 | 152952 | https://en.wikipedia.org/wiki/Portuguese%20man%20o%27%20war | Biology and health sciences | Cnidarians | Animals | vital_articles |
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