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Possible life
Life may be possible in the TRAPPIST-1 system, and some of the star's planets are considered promising targets for its detection. On the basis of atmospheric stability, TRAPPIST-1e is theoretically the planet most likely to harbour life; the probability that it does is considerably less than that of Eart... | TRAPPIST-1 | Wikipedia | 484 | 50402274 | https://en.wikipedia.org/wiki/TRAPPIST-1 | Physical sciences | Notable stars | Astronomy |
Intense flaring activity of the host star—that could alter nearby planets' atmospheres irreversibly and significantly—raised doubts of the habitability of the system.
Although initial water reservoirs could have been lost during the early life of the system due to the stellar activity, a potential subsequent water del... | TRAPPIST-1 | Wikipedia | 226 | 50402274 | https://en.wikipedia.org/wiki/TRAPPIST-1 | Physical sciences | Notable stars | Astronomy |
TRAPPIST-1 is well-suited to the search of technosignatures that would indicate the existence of past or present technology in the TRAPPIST-1 system. Searches in 2017 found only signals coming from Earth, others in 2024 found nothing although their sensitivity is low. In less than two millennia, Earth will be transitin... | TRAPPIST-1 | Wikipedia | 487 | 50402274 | https://en.wikipedia.org/wiki/TRAPPIST-1 | Physical sciences | Notable stars | Astronomy |
Scientific importance
TRAPPIST-1 has drawn intense scientific interest. Its planets are the most easily studied exoplanets within their star's habitable zone owing to their relative closeness, the small size of their host star, and because from Earth's perspective they frequently pass in front of their host star. Futu... | TRAPPIST-1 | Wikipedia | 500 | 50402274 | https://en.wikipedia.org/wiki/TRAPPIST-1 | Physical sciences | Notable stars | Astronomy |
In chemistry, congeners are chemical substances "related to each other by origin, structure, or function".
Common origin and structure
Any significant quantity of a polyhalogenated compound is by default a blend of multiple molecule types because each molecule forms independently, and chlorine and bromine do not stron... | Congener (chemistry) | Wikipedia | 488 | 38403118 | https://en.wikipedia.org/wiki/Congener%20%28chemistry%29 | Physical sciences | Substance | Chemistry |
Quantum contextuality is a feature of the phenomenology of quantum mechanics whereby measurements of quantum observables cannot simply be thought of as revealing pre-existing values. Any attempt to do so in a realistic hidden-variable theory leads to values that are dependent upon the choice of the other (compatible) o... | Quantum contextuality | Wikipedia | 425 | 38407148 | https://en.wikipedia.org/wiki/Quantum%20contextuality | Physical sciences | Quantum mechanics | Physics |
All quantum-mechanical observables may be simultaneously assigned definite values (this is the realism postulate, which is false in standard quantum mechanics, since there are observables that are indefinite in every given quantum state). These global value assignments may deterministically depend on some "hidden" clas... | Quantum contextuality | Wikipedia | 434 | 38407148 | https://en.wikipedia.org/wiki/Quantum%20contextuality | Physical sciences | Quantum mechanics | Physics |
This framework gives rise in a natural way to a qualitative hierarchy of contextuality:
(Probabilistic) contextuality may be witnessed in measurement statistics, e.g. by the violation of an inequality. A representative example is the KCBS proof of contextuality.
Logical contextuality may be witnessed in the "possibil... | Quantum contextuality | Wikipedia | 424 | 38407148 | https://en.wikipedia.org/wiki/Quantum%20contextuality | Physical sciences | Quantum mechanics | Physics |
Contextuality-by-default (CbD) framework
In the CbD approach, developed by Ehtibar Dzhafarov, Janne Kujala, and colleagues, (non)contextuality is treated as a property of any system of random variables, defined as a set in which each random variable is labeled by its content the property it measures, and its contex... | Quantum contextuality | Wikipedia | 258 | 38407148 | https://en.wikipedia.org/wiki/Quantum%20contextuality | Physical sciences | Quantum mechanics | Physics |
with the maximum taken over all whose product is . If and , measuring the same content in different context, are always identically distributed, the system is called consistently connected (satisfying "no-disturbance" or "no-signaling" principle). Except for certain logical issues, in this case CbD specializes to tra... | Quantum contextuality | Wikipedia | 450 | 38407148 | https://en.wikipedia.org/wiki/Quantum%20contextuality | Physical sciences | Quantum mechanics | Physics |
Spekkens' contextuality can be motivated using Leibniz's law of the identity of indiscernibles. The law applied to physical systems in this framework mirrors the entended definition of noncontextuality. This was further explored by Simmons et al, who demonstrated that other notions of contextuality could also be motiva... | Quantum contextuality | Wikipedia | 425 | 38407148 | https://en.wikipedia.org/wiki/Quantum%20contextuality | Physical sciences | Quantum mechanics | Physics |
The concepts of extravalence and extracontextuality are very useful to spell out the role of contextuality in quantum mechanics, that is not non-contextual (like classical physical would be), but not either fully contextual, since modalities belonging to incompatible (non-commuting) contexts may be connected with cert... | Quantum contextuality | Wikipedia | 460 | 38407148 | https://en.wikipedia.org/wiki/Quantum%20contextuality | Physical sciences | Quantum mechanics | Physics |
Contextual fraction
A number of methods exist for quantifying contextuality. One approach is by measuring the degree to which some particular noncontextuality inequality is violated, e.g. the KCBS inequality, the Yu–Oh inequality, or some Bell inequality. A more general measure of contextuality is the contextual fract... | Quantum contextuality | Wikipedia | 391 | 38407148 | https://en.wikipedia.org/wiki/Quantum%20contextuality | Physical sciences | Quantum mechanics | Physics |
Measures of (non)contextuality within the Contextuality-by-Default (CbD) framework
Several measures of the degree of contextuality in contextual systems were proposed within the CbD framework, but only one of them, denoted CNT2, has been shown to naturally extend into a measure of noncontextuality in noncontextual sys... | Quantum contextuality | Wikipedia | 391 | 38407148 | https://en.wikipedia.org/wiki/Quantum%20contextuality | Physical sciences | Quantum mechanics | Physics |
Magic state distillation
Magic state distillation is a scheme for quantum computing in which quantum circuits constructed only of Clifford operators, which by themselves are fault-tolerant but efficiently classically simulable, are injected with certain "magic" states that promote the computational power to universal ... | Quantum contextuality | Wikipedia | 482 | 38407148 | https://en.wikipedia.org/wiki/Quantum%20contextuality | Physical sciences | Quantum mechanics | Physics |
Raussendorf
In 2013, Robert Raussendorf showed more generally that access to strongly contextual measurement statistics is necessary and sufficient for an l2-MBQC to compute a non-linear function. He also showed that to compute non-linear Boolean functions with sufficiently high probability requires contextuality.
A... | Quantum contextuality | Wikipedia | 326 | 38407148 | https://en.wikipedia.org/wiki/Quantum%20contextuality | Physical sciences | Quantum mechanics | Physics |
A blockchain is a distributed ledger with growing lists of records (blocks) that are securely linked together via cryptographic hashes. Each block contains a cryptographic hash of the previous block, a timestamp, and transaction data (generally represented as a Merkle tree, where data nodes are represented by leaves). ... | Blockchain | Wikipedia | 475 | 44065971 | https://en.wikipedia.org/wiki/Blockchain | Technology | Computer security | null |
History
Cryptographer David Chaum first proposed a blockchain-like protocol in his 1982 dissertation "Computer Systems Established, Maintained, and Trusted by Mutually Suspicious Groups". Further work on a cryptographically secured chain of blocks was described in 1991 by Stuart Haber and W. Scott Stornetta. They want... | Blockchain | Wikipedia | 446 | 44065971 | https://en.wikipedia.org/wiki/Blockchain | Technology | Computer security | null |
In May 2018, Gartner found that only 1% of CIOs indicated any kind of blockchain adoption within their organisations, and only 8% of CIOs were in the short-term "planning or [looking at] active experimentation with blockchain". For the year 2019 Gartner reported 5% of CIOs believed blockchain technology was a 'game-cha... | Blockchain | Wikipedia | 462 | 44065971 | https://en.wikipedia.org/wiki/Blockchain | Technology | Computer security | null |
Sometimes separate blocks can be produced concurrently, creating a temporary fork. In addition to a secure hash-based history, any blockchain has a specified algorithm for scoring different versions of the history so that one with a higher score can be selected over others. Blocks not selected for inclusion in the chai... | Blockchain | Wikipedia | 472 | 44065971 | https://en.wikipedia.org/wiki/Blockchain | Technology | Computer security | null |
Blockchain security methods include the use of public-key cryptography. A public key (a long, random-looking string of numbers) is an address on the blockchain. Value tokens sent across the network are recorded as belonging to that address. A private key is like a password that gives its owner access to their digital a... | Blockchain | Wikipedia | 509 | 44065971 | https://en.wikipedia.org/wiki/Blockchain | Technology | Computer security | null |
Openness
Open blockchains are more user-friendly than some traditional ownership records, which, while open to the public, still require physical access to view. Because all early blockchains were permissionless, controversy has arisen over the blockchain definition. An issue in this ongoing debate is whether a privat... | Blockchain | Wikipedia | 478 | 44065971 | https://en.wikipedia.org/wiki/Blockchain | Technology | Computer security | null |
Permissioned blockchains use an access control layer to govern who has access to the network. It has been argued that permissioned blockchains can guarantee a certain level of decentralization, if carefully designed, as opposed to permissionless blockchains, which are often centralized in practice.
Disadvantages of pe... | Blockchain | Wikipedia | 300 | 44065971 | https://en.wikipedia.org/wiki/Blockchain | Technology | Computer security | null |
Blockchain analysis
The analysis of public blockchains has become increasingly important with the popularity of bitcoin, Ethereum, litecoin and other cryptocurrencies. A blockchain, if it is public, provides anyone who wants access to observe and analyse the chain data, given one has the know-how. The process of under... | Blockchain | Wikipedia | 472 | 44065971 | https://en.wikipedia.org/wiki/Blockchain | Technology | Computer security | null |
Centralized blockchain
Although most of blockchain implementation are decentralized and distributed, Oracle launched a centralized blockchain table feature in Oracle 21c database. The Blockchain Table in Oracle 21c database is a centralized blockchain which provide immutable feature. Compared to decentralized blockchai... | Blockchain | Wikipedia | 445 | 44065971 | https://en.wikipedia.org/wiki/Blockchain | Technology | Computer security | null |
Consortium blockchain
A consortium blockchain is a type of blockchain that combines elements of both public and private blockchains. In a consortium blockchain, a group of organizations come together to create and operate the blockchain, rather than a single entity. The consortium members jointly manage the blockchain ... | Blockchain | Wikipedia | 511 | 44065971 | https://en.wikipedia.org/wiki/Blockchain | Technology | Computer security | null |
In 2019, the BBC World Service radio and podcast series Fifty Things That Made the Modern Economy identified blockchain as a technology that would have far-reaching consequences for economics and society. The economist and Financial Times journalist and broadcaster Tim Harford discussed why the underlying technology mi... | Blockchain | Wikipedia | 500 | 44065971 | https://en.wikipedia.org/wiki/Blockchain | Technology | Computer security | null |
Banks are interested in this technology not least because it has the potential to speed up back office settlement systems. Moreover, as the blockchain industry has reached early maturity institutional appreciation has grown that it is, practically speaking, the infrastructure of a whole new financial industry, with all... | Blockchain | Wikipedia | 472 | 44065971 | https://en.wikipedia.org/wiki/Blockchain | Technology | Computer security | null |
The first known game to use blockchain technologies was CryptoKitties, launched in November 2017, where the player would purchase NFTs with Ethereum cryptocurrency, each NFT consisting of a virtual pet that the player could breed with others to create offspring with combined traits as new NFTs. The game made headlines ... | Blockchain | Wikipedia | 468 | 44065971 | https://en.wikipedia.org/wiki/Blockchain | Technology | Computer security | null |
There have been several different efforts to employ blockchains in supply chain management.
Precious commodities mining — Blockchain technology has been used for tracking the origins of gemstones and other precious commodities. In 2016, The Wall Street Journal reported that the blockchain technology company Everledger... | Blockchain | Wikipedia | 497 | 44065971 | https://en.wikipedia.org/wiki/Blockchain | Technology | Computer security | null |
Specific TLDs include ".eth", ".luxe", and ".kred", which are associated with the Ethereum blockchain through the Ethereum Name Service (ENS). The .kred TLD also acts as an alternative to conventional cryptocurrency wallet addresses as a convenience for transferring cryptocurrency.
Other uses
Blockchain technology c... | Blockchain | Wikipedia | 479 | 44065971 | https://en.wikipedia.org/wiki/Blockchain | Technology | Computer security | null |
Blockchain could be used in detecting counterfeits by associating unique identifiers to products, documents and shipments, and storing records associated with transactions that cannot be forged or altered. It is however argued that blockchain technology needs to be supplemented with technologies that provide a strong b... | Blockchain | Wikipedia | 454 | 44065971 | https://en.wikipedia.org/wiki/Blockchain | Technology | Computer security | null |
Early concern over the high energy consumption was a factor in later blockchains such as Cardano (2017), Solana (2020) and Polkadot (2020) adopting the less energy-intensive proof-of-stake model. Researchers have estimated that bitcoin consumes 100,000 times as much energy as proof-of-stake networks.
In 2021, a study ... | Blockchain | Wikipedia | 431 | 44065971 | https://en.wikipedia.org/wiki/Blockchain | Technology | Computer security | null |
In October 2014, the MIT Bitcoin Club, with funding from MIT alumni, provided undergraduate students at the Massachusetts Institute of Technology access to $100 of bitcoin. The adoption rates, as studied by Catalini and Tucker (2016), revealed that when people who typically adopt technologies early are given delayed ac... | Blockchain | Wikipedia | 472 | 44065971 | https://en.wikipedia.org/wiki/Blockchain | Technology | Computer security | null |
In September 2015, the first peer-reviewed academic journal dedicated to cryptocurrency and blockchain technology research, Ledger, was announced. The inaugural issue was published in December 2016. The journal covers aspects of mathematics, computer science, engineering, law, economics and philosophy that relate to cr... | Blockchain | Wikipedia | 121 | 44065971 | https://en.wikipedia.org/wiki/Blockchain | Technology | Computer security | null |
The fruit doves, also known as fruit pigeons, are a genus (Ptilinopus) of birds in the pigeon and dove family (Columbidae). These colourful, frugivorous doves are found in forests and woodlands in Southeast Asia and Oceania. It is a large genus with over 50 species, some threatened or already extinct.
Taxonomy
The gen... | Fruit dove | Wikipedia | 452 | 47197916 | https://en.wikipedia.org/wiki/Fruit%20dove | Biology and health sciences | Columbimorphae | Animals |
The genus contains 57 species:
Banded fruit dove, Ptilinopus cinctus (Temminck, 1809)
Black-banded fruit dove, Ptilinopus alligator Collett, 1898 – split from banded fruit dove
Red-naped fruit dove, Ptilinopus dohertyi Rothschild, 1896
Pink-headed fruit dove, Ptilinopus porphyreus (Temminck, 1822)
Flame-breasted f... | Fruit dove | Wikipedia | 491 | 47197916 | https://en.wikipedia.org/wiki/Fruit%20dove | Biology and health sciences | Columbimorphae | Animals |
Kosrae fruit dove, Ptilinopus hernsheimi Finsch, 1880 – split from crimson-crowned fruit dove
Palau fruit dove, Ptilinopus pelewensis Hartlaub & Finsch, 1868
Lilac-crowned fruit dove, Ptilinopus rarotongensis Hartlaub & Finsch, 1871
Mariana fruit dove, Ptilinopus roseicapilla (Lesson, RP, 1831) | Fruit dove | Wikipedia | 90 | 47197916 | https://en.wikipedia.org/wiki/Fruit%20dove | Biology and health sciences | Columbimorphae | Animals |
Rose-crowned fruit dove, Ptilinopus regina Swainson, 1825
Silver-capped fruit dove, Ptilinopus richardsii Ramsay, EP, 1882
Geelvink fruit dove, Ptilinopus speciosus Schlegel, 1871 – split from yellow-bibbed fruit dove
Grey-green fruit dove, Ptilinopus purpuratus (Gmelin, JF, 1789)
Raiatea fruit dove, Ptilinopus chry... | Fruit dove | Wikipedia | 411 | 47197916 | https://en.wikipedia.org/wiki/Fruit%20dove | Biology and health sciences | Columbimorphae | Animals |
Orange-bellied fruit dove, Ptilinopus iozonus Gray, GR, 1858
Knob-billed fruit dove, Ptilinopus insolitus Schlegel, 1863
Grey-headed fruit dove, Ptilinopus hyogastrus (Temminck, 1824)
Carunculated fruit dove, Ptilinopus granulifrons Hartert, EJO, 1898
Black-naped fruit dove, Ptilinopus melanospilus (Salvadori, 1875... | Fruit dove | Wikipedia | 388 | 47197916 | https://en.wikipedia.org/wiki/Fruit%20dove | Biology and health sciences | Columbimorphae | Animals |
Fruit doves, as their name implies, eat fruit. Ficus is especially important. They live in various kinds of forest or woodland. Some species are restricted to primary forest, such as lowland rainforest, montane forest, or monsoon forest, while others prefer secondary forest or disturbed areas. Some species specialize ... | Fruit dove | Wikipedia | 204 | 47197916 | https://en.wikipedia.org/wiki/Fruit%20dove | Biology and health sciences | Columbimorphae | Animals |
Slack is a cloud-based team communication platform developed by Slack Technologies, which has been owned by Salesforce since 2020. Slack uses a freemium model. Slack is primarily offered as a business-to-business service, with its userbase being predominantly team-based businesses while its functionalities are focused ... | Slack (software) | Wikipedia | 454 | 41202764 | https://en.wikipedia.org/wiki/Slack%20%28software%29 | Technology | Social network and blogging | null |
On December 5, 2022, Salesforce announced that Butterfield was leaving Slack and would be succeeded by Lidiane Jones, an executive vice president at Salesforce. On November 13, 2023, Salesforce executive Denise Dresser was appointed to replace Jones, who was in turn replacing Whitney Wolfe Herd as Bumble CEO.
In Augus... | Slack (software) | Wikipedia | 480 | 41202764 | https://en.wikipedia.org/wiki/Slack%20%28software%29 | Technology | Social network and blogging | null |
Slack integrates with many third-party services and supports community-built integrations, including Google Drive, Trello, Dropbox, Box, Heroku, IBM Bluemix, Crashlytics, GitHub, Runscope, Zendesk, and Zapier. In July 2015, Slack launched an integration with Google Calendar. Later, in December of the same year, a searc... | Slack (software) | Wikipedia | 423 | 41202764 | https://en.wikipedia.org/wiki/Slack%20%28software%29 | Technology | Social network and blogging | null |
Business model
Slack is a freemium product whose main paid features are the ability to search more than 90 days' archived messages and add unlimited apps and integrations. They also claim support for an unlimited number of users. When freeCodeCamp attempted to switch its community of over 8,000 users to Slack in 2015, ... | Slack (software) | Wikipedia | 421 | 41202764 | https://en.wikipedia.org/wiki/Slack%20%28software%29 | Technology | Social network and blogging | null |
The digital rights group Electronic Frontier Foundation (EFF) has cautioned that "Slack stores and is able to read all of your communications, as well as identifying information for everyone in your workspace." They commended the company for following several best practices in standing up for users concerning governmen... | Slack (software) | Wikipedia | 272 | 41202764 | https://en.wikipedia.org/wiki/Slack%20%28software%29 | Technology | Social network and blogging | null |
The Tapanuli orangutan (Pongo tapanuliensis) is a species of orangutan restricted to South Tapanuli in the island of Sumatra in Indonesia. It is one of three known species of orangutan, alongside the Sumatran orangutan (P. abelii), found farther northwest on the island, and the Bornean orangutan (P. pygmaeus). It was d... | Tapanuli orangutan | Wikipedia | 372 | 55694751 | https://en.wikipedia.org/wiki/Tapanuli%20orangutan | Biology and health sciences | Apes | Animals |
Phylogeny
Genetic comparisons show that Tapanuli orangutans diverged from Sumatran orangutans about 3.4 million years ago, and became more isolated after the Lake Toba eruption that occurred about 75,000 years ago. They had continued sporadic contact that stopped between 10,000 and 20,000 years ago. Tapanuli orangutan... | Tapanuli orangutan | Wikipedia | 454 | 55694751 | https://en.wikipedia.org/wiki/Tapanuli%20orangutan | Biology and health sciences | Apes | Animals |
Behavior
The loud, long-distance call or 'long call' of male Tapanuli orangutans has a higher maximum frequency than that of Sumatran orangutans, and lasts much longer and has more pulses than that of Bornean orangutans. Their diet is also unique, containing unusual items like caterpillars and conifer cones. Tapanuli ... | Tapanuli orangutan | Wikipedia | 465 | 55694751 | https://en.wikipedia.org/wiki/Tapanuli%20orangutan | Biology and health sciences | Apes | Animals |
Cosmic voids (also known as dark space) are vast spaces between filaments (the largest-scale structures in the universe), which contain very few or no galaxies. In spite of their size, most galaxies are not located in voids. This is because most galaxies are gravitationally bound together, creating huge cosmic structur... | Void (astronomy) | Wikipedia | 445 | 42644968 | https://en.wikipedia.org/wiki/Void%20%28astronomy%29 | Physical sciences | Basics_3 | null |
The structure of the Universe can be broken down into components that can help describe the characteristics of individual regions of the cosmos. These are the main structural components of the cosmic web:
Voids – vast, largely spherical regions with very low cosmic mean densities, up to 100 megaparsecs (Mpc) in diamet... | Void (astronomy) | Wikipedia | 347 | 42644968 | https://en.wikipedia.org/wiki/Void%20%28astronomy%29 | Physical sciences | Basics_3 | null |
Timeline
A summarized timeline of important events in the field of cosmic voids from its beginning to recent times is as follows:
1961 – Large-scale structural features such as "second-order clusters", a specific type of supercluster, were brought to the astronomical community's attention.
1978 – The first two paper... | Void (astronomy) | Wikipedia | 510 | 42644968 | https://en.wikipedia.org/wiki/Void%20%28astronomy%29 | Physical sciences | Basics_3 | null |
VoidFinder algorithm
This first-class method uses each galaxy in a catalog as its target and then uses the Nearest Neighbor Approximation to calculate the cosmic density in the region contained in a spherical radius determined by the distance to the third-closest galaxy. El Ad & Piran introduced this method in 1997 t... | Void (astronomy) | Wikipedia | 478 | 42644968 | https://en.wikipedia.org/wiki/Void%20%28astronomy%29 | Physical sciences | Basics_3 | null |
This third-class method is drastically different from the previous two algorithms listed. The most striking aspect is that it requires a different definition of what it means to be a void. Instead of the general notion that a void is a region of space with a low cosmic mean density; a hole in the distribution of galaxi... | Void (astronomy) | Wikipedia | 371 | 42644968 | https://en.wikipedia.org/wiki/Void%20%28astronomy%29 | Physical sciences | Basics_3 | null |
The simultaneous existence of the largest-known voids and galaxy clusters requires about 70% dark energy in the universe today, consistent with the latest data from the cosmic microwave background. Voids act as bubbles in the universe that are sensitive to background cosmological changes. This means that the evolution ... | Void (astronomy) | Wikipedia | 436 | 42644968 | https://en.wikipedia.org/wiki/Void%20%28astronomy%29 | Physical sciences | Basics_3 | null |
Voids offer opportunities to study the strength of intergalactic magnetic fields. For example, a 2015 study concluded, based on the deflection of blazar gamma-ray emissions that travel through voids, that intergalactic space contains a magnetic field of strength at least 10 G. The specific large-scale magnetic structur... | Void (astronomy) | Wikipedia | 373 | 42644968 | https://en.wikipedia.org/wiki/Void%20%28astronomy%29 | Physical sciences | Basics_3 | null |
The insides of voids often seem to adhere to cosmological parameters which differ from those of the known universe. It is because of this unique feature that cosmic voids are useful laboratories to study the effects that gravitational clustering and growth rates have on local galaxies and structure when the cosmologica... | Void (astronomy) | Wikipedia | 163 | 42644968 | https://en.wikipedia.org/wiki/Void%20%28astronomy%29 | Physical sciences | Basics_3 | null |
The field-effect transistor (FET) is a type of transistor that uses an electric field to control the current through a semiconductor. It comes in two types: junction FET (JFET) and metal-oxide-semiconductor FET (MOSFET). FETs have three terminals: source, gate, and drain. FETs control the current by the application of... | Field-effect transistor | Wikipedia | 415 | 41228216 | https://en.wikipedia.org/wiki/Field-effect%20transistor | Technology | Semiconductors | null |
The first FET device to be successfully built was the junction field-effect transistor (JFET). A JFET was first patented by Heinrich Welker in 1945. The static induction transistor (SIT), a type of JFET with a short channel, was invented by Japanese engineers Jun-ichi Nishizawa and Y. Watanabe in 1950. Following Shockl... | Field-effect transistor | Wikipedia | 259 | 41228216 | https://en.wikipedia.org/wiki/Field-effect%20transistor | Technology | Semiconductors | null |
The foundations of MOSFET technology were laid down by the work of William Shockley, John Bardeen and Walter Brattain. Shockley independently envisioned the FET concept in 1945, but he was unable to build a working device. The next year Bardeen explained his failure in terms of surface states. Bardeen applied the theor... | Field-effect transistor | Wikipedia | 494 | 41228216 | https://en.wikipedia.org/wiki/Field-effect%20transistor | Technology | Semiconductors | null |
By the end of the first half of the 1950s, following theoretical and experimental work of Bardeen, Brattain, Kingston, Morrison and others, it became more clear that there were two types of surface states. Fast surface states were found to be associated with the bulk and a semiconductor/oxide interface. Slow surface st... | Field-effect transistor | Wikipedia | 505 | 41228216 | https://en.wikipedia.org/wiki/Field-effect%20transistor | Technology | Semiconductors | null |
Metal-oxide-semiconductor FET (MOSFET)
In 1955, Carl Frosch and Lincoln Derrick accidentally grew a layer of silicon dioxide over the silicon wafer, for which they observed surface passivation effects. By 1957 Frosch and Derrick, using masking and predeposition, were able to manufacture silicon dioxide transistors and... | Field-effect transistor | Wikipedia | 373 | 41228216 | https://en.wikipedia.org/wiki/Field-effect%20transistor | Technology | Semiconductors | null |
In 1948, Bardeen and Brattain patented the progenitor of MOSFET, an insulated-gate FET (IGFET) with an inversion layer. Their patent and the concept of an inversion layer, forms the basis of CMOS technology today. CMOS (complementary MOS), a semiconductor device fabrication process for MOSFETs, was developed by Chih-Ta... | Field-effect transistor | Wikipedia | 444 | 41228216 | https://en.wikipedia.org/wiki/Field-effect%20transistor | Technology | Semiconductors | null |
All FETs have source, drain, and gate terminals that correspond roughly to the emitter, collector, and base of BJTs. Most FETs have a fourth terminal called the body, base, bulk, or substrate. This fourth terminal serves to bias the transistor into operation; it is rare to make non-trivial use of the body terminal in c... | Field-effect transistor | Wikipedia | 440 | 41228216 | https://en.wikipedia.org/wiki/Field-effect%20transistor | Technology | Semiconductors | null |
The FET controls the flow of electrons (or electron holes) from the source to drain by affecting the size and shape of a "conductive channel" created and influenced by voltage (or lack of voltage) applied across the gate and source terminals. (For simplicity, this discussion assumes that the body and source are connect... | Field-effect transistor | Wikipedia | 503 | 41228216 | https://en.wikipedia.org/wiki/Field-effect%20transistor | Technology | Semiconductors | null |
Effect of drain-to-source voltage on channel
For either enhancement- or depletion-mode devices, at drain-to-source voltages much less than gate-to-source voltages, changing the gate voltage will alter the channel resistance, and drain current will be proportional to drain voltage (referenced to source voltage). In this... | Field-effect transistor | Wikipedia | 273 | 41228216 | https://en.wikipedia.org/wiki/Field-effect%20transistor | Technology | Semiconductors | null |
Even though the conductive channel formed by gate-to-source voltage no longer connects source to drain during saturation mode, carriers are not blocked from flowing. Considering again an n-channel enhancement-mode device, a depletion region exists in the p-type body, surrounding the conductive channel and drain and sou... | Field-effect transistor | Wikipedia | 480 | 41228216 | https://en.wikipedia.org/wiki/Field-effect%20transistor | Technology | Semiconductors | null |
The channel of a FET is doped to produce either an n-type semiconductor or a p-type semiconductor. The drain and source may be doped of opposite type to the channel, in the case of enhancement mode FETs, or doped of similar type to the channel as in depletion mode FETs. Field-effect transistors are also distinguished b... | Field-effect transistor | Wikipedia | 91 | 41228216 | https://en.wikipedia.org/wiki/Field-effect%20transistor | Technology | Semiconductors | null |
The MOSFET (metal–oxide–semiconductor field-effect transistor) utilizes an insulator (typically SiO2) between the gate and the body. This is by far the most common type of FET.
The DGMOSFET (dual-gate MOSFET) or DGMOS, a MOSFET with two insulated gates.
The IGBT (insulated-gate bipolar transistor) is a device for power... | Field-effect transistor | Wikipedia | 505 | 41228216 | https://en.wikipedia.org/wiki/Field-effect%20transistor | Technology | Semiconductors | null |
The JFET (junction field-effect transistor) uses a reverse biased p–n junction to separate the gate from the body.
The static induction transistor (SIT) is a type of JFET with a short channel.
The DEPFET is a FET formed in a fully depleted substrate and acts as a sensor, amplifier and memory node at the same time. It c... | Field-effect transistor | Wikipedia | 512 | 41228216 | https://en.wikipedia.org/wiki/Field-effect%20transistor | Technology | Semiconductors | null |
The CNTFET (carbon nanotube field-effect transistor).
The OFET (organic field-effect transistor) uses an organic semiconductor in its channel.
The QFET (quantum field effect transistor) takes advantage of quantum tunneling to greatly increase the speed of transistor operation by eliminating the traditional transistor's... | Field-effect transistor | Wikipedia | 269 | 41228216 | https://en.wikipedia.org/wiki/Field-effect%20transistor | Technology | Semiconductors | null |
Advantages
Field-effect transistors have high gate-to-drain current resistance, of the order of 100 MΩ or more, providing a high degree of isolation between control and flow. Because base current noise will increase with shaping time, a FET typically produces less noise than a bipolar junction transistor (BJT), and is ... | Field-effect transistor | Wikipedia | 444 | 41228216 | https://en.wikipedia.org/wiki/Field-effect%20transistor | Technology | Semiconductors | null |
Failure modes
Field-effect transistors are relatively robust, especially when operated within the temperature and electrical limitations defined by the manufacturer (proper derating). However, modern FET devices can often incorporate a body diode. If the characteristics of the body diode are not taken into consideratio... | Field-effect transistor | Wikipedia | 362 | 41228216 | https://en.wikipedia.org/wiki/Field-effect%20transistor | Technology | Semiconductors | null |
An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combustion engine, the expansion of the high-temperature and high-pressure gases pr... | Internal combustion engine | Wikipedia | 483 | 41228673 | https://en.wikipedia.org/wiki/Internal%20combustion%20engine | Technology | Tools and machinery | null |
Various scientists and engineers contributed to the development of internal combustion engines. In 1791, John Barber developed the gas turbine. In 1794 Thomas Mead patented a gas engine. Also in 1794, Robert Street patented an internal combustion engine, which was also the first to use liquid fuel, and built an engine ... | Internal combustion engine | Wikipedia | 484 | 41228673 | https://en.wikipedia.org/wiki/Internal%20combustion%20engine | Technology | Tools and machinery | null |
Etymology
At one time, the word engine (via Old French, from Latin , "ability") meant any piece of machinery—a sense that persists in expressions such as siege engine. A "motor" (from Latin , "mover") is any machine that produces mechanical power. Traditionally, electric motors are not referred to as "engines"; howeve... | Internal combustion engine | Wikipedia | 503 | 41228673 | https://en.wikipedia.org/wiki/Internal%20combustion%20engine | Technology | Tools and machinery | null |
Classification
There are several possible ways to classify internal combustion engines.
Reciprocating
By number of strokes:
Two-stroke engine
Clerk cycle
Day cycle
Four-stroke engine (Otto cycle)
Six-stroke engine
By type of ignition:
Compression-ignition engine
Spark-ignition engine (commonly found as gasol... | Internal combustion engine | Wikipedia | 504 | 41228673 | https://en.wikipedia.org/wiki/Internal%20combustion%20engine | Technology | Tools and machinery | null |
The pistons are short cylindrical parts which seal one end of the cylinder from the high pressure of the compressed air and combustion products and slide continuously within it while the engine is in operation. In smaller engines, the pistons are made of aluminum; while in larger applications, they are typically made o... | Internal combustion engine | Wikipedia | 277 | 41228673 | https://en.wikipedia.org/wiki/Internal%20combustion%20engine | Technology | Tools and machinery | null |
The cylinder head is attached to the engine block by numerous bolts or studs. It has several functions. The cylinder head seals the cylinders on the side opposite to the pistons; it contains short ducts (the ports) for intake and exhaust and the associated intake valves that open to let the cylinder be filled with fres... | Internal combustion engine | Wikipedia | 301 | 41228673 | https://en.wikipedia.org/wiki/Internal%20combustion%20engine | Technology | Tools and machinery | null |
The crankcase is sealed at the bottom with a sump that collects the falling oil during normal operation to be cycled again. The cavity created between the cylinder block and the sump houses a crankshaft that converts the reciprocating motion of the pistons to rotational motion. The crankshaft is held in place relative ... | Internal combustion engine | Wikipedia | 489 | 41228673 | https://en.wikipedia.org/wiki/Internal%20combustion%20engine | Technology | Tools and machinery | null |
Intake, induction or suction: The intake valves are open as a result of the cam lobe pressing down on the valve stem. The piston moves downward increasing the volume of the combustion chamber and allowing air to enter in the case of a CI engine or an air-fuel mix in the case of SI engines that do not use direct injecti... | Internal combustion engine | Wikipedia | 435 | 41228673 | https://en.wikipedia.org/wiki/Internal%20combustion%20engine | Technology | Tools and machinery | null |
The defining characteristic of this kind of engine is that each piston completes a cycle every crankshaft revolution. The 4 processes of intake, compression, power and exhaust take place in only 2 strokes so that it is not possible to dedicate a stroke exclusively for each of them. Starting at TDC the cycle consists of... | Internal combustion engine | Wikipedia | 408 | 41228673 | https://en.wikipedia.org/wiki/Internal%20combustion%20engine | Technology | Tools and machinery | null |
Some SI engines are crankcase scavenged and do not use poppet valves. Instead, the crankcase and the part of the cylinder below the piston is used as a pump. The intake port is connected to the crankcase through a reed valve or a rotary disk valve driven by the engine. For each cylinder, a transfer port connects in one... | Internal combustion engine | Wikipedia | 467 | 41228673 | https://en.wikipedia.org/wiki/Internal%20combustion%20engine | Technology | Tools and machinery | null |
The main advantage of 2-stroke engines of this type is mechanical simplicity and a higher power-to-weight ratio than their 4-stroke counterparts. Despite having twice as many power strokes per cycle, less than twice the power of a comparable 4-stroke engine is attainable in practice.
In the US, 2-stroke engines were b... | Internal combustion engine | Wikipedia | 461 | 41228673 | https://en.wikipedia.org/wiki/Internal%20combustion%20engine | Technology | Tools and machinery | null |
An example of this type of engine is the Wärtsilä-Sulzer RTA96-C turbocharged 2-stroke diesel, used in large container ships. It is the most efficient and powerful reciprocating internal combustion engine in the world with a thermal efficiency over 50%. For comparison, the most efficient small four-stroke engines are a... | Internal combustion engine | Wikipedia | 477 | 41228673 | https://en.wikipedia.org/wiki/Internal%20combustion%20engine | Technology | Tools and machinery | null |
Because there is no obstruction in the cylinder of the fuel to move directly out of the exhaust port prior to the piston rising far enough to close the port, early engines used a high domed piston to slow down the flow of fuel. Later the fuel was "resonated" back into the cylinder using an expansion chamber design. Whe... | Internal combustion engine | Wikipedia | 485 | 41228673 | https://en.wikipedia.org/wiki/Internal%20combustion%20engine | Technology | Tools and machinery | null |
Some systems disable alternator field (rotor) power during wide-open throttle conditions. Disabling the field reduces alternator pulley mechanical loading to nearly zero, maximizing crankshaft power. In this case, the battery supplies all primary electrical power.
Gasoline engines take in a mixture of air and gasoline... | Internal combustion engine | Wikipedia | 426 | 41228673 | https://en.wikipedia.org/wiki/Internal%20combustion%20engine | Technology | Tools and machinery | null |
Capacitor discharge ignition was developed. It produces a rising voltage that is sent to the spark plug. CD system voltages can reach 60,000 volts. CD ignitions use step-up transformers. The step-up transformer uses energy stored in a capacitance to generate electric spark. With either system, a mechanical or electrica... | Internal combustion engine | Wikipedia | 248 | 41228673 | https://en.wikipedia.org/wiki/Internal%20combustion%20engine | Technology | Tools and machinery | null |
For ignition, diesel, PPC and HCCI engines rely solely on the high temperature and pressure created by the engine in its compression process. The compression level that occurs is usually twice or more than a gasoline engine. Diesel engines take in air only, and shortly before peak compression, spray a small quantity of... | Internal combustion engine | Wikipedia | 484 | 41228673 | https://en.wikipedia.org/wiki/Internal%20combustion%20engine | Technology | Tools and machinery | null |
In a splash lubrication system no oil pump is used. Instead the crankshaft dips into the oil in the sump and due to its high speed, it splashes the crankshaft, connecting rods and bottom of the pistons. The connecting rod big end caps may have an attached scoop to enhance this effect. The valve train may also be sealed... | Internal combustion engine | Wikipedia | 476 | 41228673 | https://en.wikipedia.org/wiki/Internal%20combustion%20engine | Technology | Tools and machinery | null |
Other systems are also used to lubricate the cylinder and piston. The connecting rod may have a nozzle to throw an oil jet to the cylinder and bottom of the piston. That nozzle is in movement relative to the cylinder it lubricates, but always pointed towards it or the corresponding piston.
Typically forced lubrication... | Internal combustion engine | Wikipedia | 409 | 41228673 | https://en.wikipedia.org/wiki/Internal%20combustion%20engine | Technology | Tools and machinery | null |
Multiple crankshaft configurations do not necessarily need a cylinder head at all because they can instead have a piston at each end of the cylinder called an opposed piston design. Because fuel inlets and outlets are positioned at opposed ends of the cylinder, one can achieve uniflow scavenging, which, as in the four-... | Internal combustion engine | Wikipedia | 433 | 41228673 | https://en.wikipedia.org/wiki/Internal%20combustion%20engine | Technology | Tools and machinery | null |
Six-stroke engine
The six-stroke engine was invented in 1883. Four kinds of six-stroke engines use a regular piston in a regular cylinder (Griffin six-stroke, Bajulaz six-stroke, Velozeta six-stroke and Crower six-stroke), firing every three crankshaft revolutions. These systems capture the waste heat of the four-stro... | Internal combustion engine | Wikipedia | 455 | 41228673 | https://en.wikipedia.org/wiki/Internal%20combustion%20engine | Technology | Tools and machinery | null |
Jet engines use a number of rows of fan blades to compress air which then enters a combustor where it is mixed with fuel (typically JP fuel) and then ignited. The burning of the fuel raises the temperature of the air which is then exhausted out of the engine creating thrust. A modern turbofan engine can operate at as h... | Internal combustion engine | Wikipedia | 447 | 41228673 | https://en.wikipedia.org/wiki/Internal%20combustion%20engine | Technology | Tools and machinery | null |
The Wankel engine (rotary engine) does not have piston strokes. It operates with the same separation of phases as the four-stroke engine with the phases taking place in separate locations in the engine. In thermodynamic terms it follows the Otto engine cycle, so may be thought of as a "four-phase" engine. While it is t... | Internal combustion engine | Wikipedia | 448 | 41228673 | https://en.wikipedia.org/wiki/Internal%20combustion%20engine | Technology | Tools and machinery | null |
Fuels
The most common modern fuels are made up of hydrocarbons and are derived mostly from fossil fuels (petroleum). Fossil fuels include diesel fuel, gasoline and petroleum gas, and the rarer use of propane. Except for the fuel delivery components, most internal combustion engines that are designed for gasoline use c... | Internal combustion engine | Wikipedia | 479 | 41228673 | https://en.wikipedia.org/wiki/Internal%20combustion%20engine | Technology | Tools and machinery | null |
Diesel engines are generally heavier, noisier, and more powerful at lower speeds than gasoline engines. They are also more fuel-efficient in most circumstances and are used in heavy road vehicles, some automobiles (increasingly so for their increased fuel efficiency over gasoline engines), ships, railway locomotives, a... | Internal combustion engine | Wikipedia | 384 | 41228673 | https://en.wikipedia.org/wiki/Internal%20combustion%20engine | Technology | Tools and machinery | null |
Since air is plentiful at the surface of the earth, the oxidizer is typically atmospheric oxygen, which has the advantage of not being stored within the vehicle. This increases the power-to-weight and power-to-volume ratios. Other materials are used for special purposes, often to increase power output or to allow opera... | Internal combustion engine | Wikipedia | 447 | 41228673 | https://en.wikipedia.org/wiki/Internal%20combustion%20engine | Technology | Tools and machinery | null |
Internal combustion engines must have their cycles started. In reciprocating engines this is accomplished by turning the crankshaft (Wankel Rotor Shaft) which induces the cycles of intake, compression, combustion, and exhaust. The first engines were started with a turn of their flywheels, while the first vehicle (the ... | Internal combustion engine | Wikipedia | 483 | 41228673 | https://en.wikipedia.org/wiki/Internal%20combustion%20engine | Technology | Tools and machinery | null |
Once the available energy has been removed, the remaining hot gases are vented (often by opening a valve or exposing the exhaust outlet) and this allows the piston to return to its previous position (top dead center, or TDC). The piston can then proceed to the next phase of its cycle, which varies between engines. Any ... | Internal combustion engine | Wikipedia | 496 | 41228673 | https://en.wikipedia.org/wiki/Internal%20combustion%20engine | Technology | Tools and machinery | null |
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