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Astrangia poculata, the northern star coral, is a temperate stony coral, widely documented along the eastern coast of the United States. The coral can live with and without zooxanthellae (algal symbionts), making it an ideal model organism to study microbial community interactions associated with symbiotic state. Howev... | Coral | Wikipedia | 391 | 47700 | https://en.wikipedia.org/wiki/Coral | Biology and health sciences | Cnidarians | null | vital_articles |
A study published in 2018 revealed evidence of phylosymbiosis between corals and their tissue and skeleton microbiomes. The coral skeleton, which represents the most diverse of the three coral microbiomes, showed the strongest evidence of phylosymbiosis. Coral microbiome composition and richness were found to reflect c... | Coral | Wikipedia | 426 | 47700 | https://en.wikipedia.org/wiki/Coral | Biology and health sciences | Cnidarians | null | vital_articles |
At certain times in the geological past, corals were very abundant. Like modern corals, their ancestors built reefs, some of which ended as great structures in sedimentary rocks. Fossils of fellow reef-dwellers algae, sponges, and the remains of many echinoids, brachiopods, bivalves, gastropods, and trilobites appear a... | Coral | Wikipedia | 383 | 47700 | https://en.wikipedia.org/wiki/Coral | Biology and health sciences | Cnidarians | null | vital_articles |
Modern corals
The currently ubiquitous stony corals, Scleractinia, appeared in the Middle Triassic to fill the niche vacated by the extinct rugose and tabulate orders and is not closely related to the earlier forms. Unlike the corals prevalent before the Permian extinction, which formed skeletons of a form of calcium c... | Coral | Wikipedia | 442 | 47700 | https://en.wikipedia.org/wiki/Coral | Biology and health sciences | Cnidarians | null | vital_articles |
Submarine springs found along the coast of Mexico's Yucatán Peninsula produce water with a naturally low pH (relatively high acidity) providing conditions similar to those expected to become widespread as the oceans absorb carbon dioxide. Surveys discovered multiple species of live coral that appeared to tolerate the a... | Coral | Wikipedia | 475 | 47700 | https://en.wikipedia.org/wiki/Coral | Biology and health sciences | Cnidarians | null | vital_articles |
However, adaptation to climate change has been demonstrated in many cases, which is usually due to a shift in coral and zooxanthellae genotypes. These shifts in allele frequency have progressed toward more tolerant types of zooxanthellae. Scientists found that a certain scleractinian zooxanthella is becoming more commo... | Coral | Wikipedia | 392 | 47700 | https://en.wikipedia.org/wiki/Coral | Biology and health sciences | Cnidarians | null | vital_articles |
Oxygen isotope anomaly
The comparison of coral strontium/calcium minimums with sea surface temperature maximums, data recorded from NINO 3.4 SSTA, time can be correlated to coral strontium/calcium and δ18O variations. To confirm the accuracy of the annual relationship between Sr/Ca and δ18O variations, a perceptible as... | Coral | Wikipedia | 492 | 47700 | https://en.wikipedia.org/wiki/Coral | Biology and health sciences | Cnidarians | null | vital_articles |
Many governments now prohibit removal of coral from reefs, and inform coastal residents about reef protection and ecology. While local action such as habitat restoration and herbivore protection can reduce local damage, the longer-term threats of acidification, temperature change and sea-level rise remain a challenge.
... | Coral | Wikipedia | 464 | 47700 | https://en.wikipedia.org/wiki/Coral | Biology and health sciences | Cnidarians | null | vital_articles |
In medicine, chemical compounds from corals can potentially be used to treat cancer, neurological diseases, inflammation including arthritis, pain, bone loss, high blood pressure and for other therapeutic uses. Coral skeletons, e.g. Isididae are being researched for their potential near-future use for bone grafting in ... | Coral | Wikipedia | 469 | 47700 | https://en.wikipedia.org/wiki/Coral | Biology and health sciences | Cnidarians | null | vital_articles |
The most popular kind of coral kept is soft coral, especially zoanthids and mushroom corals, which are especially easy to grow and propagate in a wide variety of conditions, because they originate in enclosed parts of reefs where water conditions vary and lighting may be less reliable and direct. More serious fishkeepe... | Coral | Wikipedia | 262 | 47700 | https://en.wikipedia.org/wiki/Coral | Biology and health sciences | Cnidarians | null | vital_articles |
A cotton gin—meaning "cotton engine"—is a machine that quickly and easily separates cotton fibers from their seeds, enabling much greater productivity than manual cotton separation. The separated seeds may be used to grow more cotton or to produce cottonseed oil.
Handheld roller gins had been used in the Indian subc... | Cotton gin | Wikipedia | 389 | 47710 | https://en.wikipedia.org/wiki/Cotton%20gin | Technology | Farm and garden machinery | null | vital_articles |
Whitney's gin is made with two rotating cylinders. The first cylinder has lines of teeth around the circumference, and angled against this cylinder is a metal plate with small holes, "ginning ribs", through which the teeth can fit with minimal gaps. The teeth grip the cotton fibers as the mechanism rotates, dragging th... | Cotton gin | Wikipedia | 496 | 47710 | https://en.wikipedia.org/wiki/Cotton%20gin | Technology | Farm and garden machinery | null | vital_articles |
The worm gear roller gin, which was invented in the Indian subcontinent during the early Delhi Sultanate era of the 13th to 14th centuries, came into use in the Mughal Empire sometime around the 16th century, and is still used in the Indian subcontinent through to the present day. Another innovation, the incorporation ... | Cotton gin | Wikipedia | 483 | 47710 | https://en.wikipedia.org/wiki/Cotton%20gin | Technology | Farm and garden machinery | null | vital_articles |
Whitney's cotton gin model was capable of cleaning of lint per day. The model consisted of a wooden cylinder covered by rows of slender wires which caught the fibers of the cotton bolls. Each row of wires then passed through the bars of a comb-like grid, pulling the cotton fibers through the grid as they did. The comb... | Cotton gin | Wikipedia | 257 | 47710 | https://en.wikipedia.org/wiki/Cotton%20gin | Technology | Farm and garden machinery | null | vital_articles |
McCarthy's gin
While Whitney's gin facilitated the cleaning of seeds from short-staple cotton, it damaged the fibers of extra-long staple cotton (Gossypium barbadense). In 1840 Fones McCarthy received a patent for a "Smooth Cylinder Cotton-gin", a roller gin. McCarthy's gin was marketed for use with both short-staple a... | Cotton gin | Wikipedia | 503 | 47710 | https://en.wikipedia.org/wiki/Cotton%20gin | Technology | Farm and garden machinery | null | vital_articles |
By the 1960s, many other advances had been made in ginning machinery, but the manner in which cotton flowed through the gin machinery continued to be the Munger system.
Economic Historian William H. Phillips referred to the development of system ginning as "The Munger Revolution" in cotton ginning. He wrote,
"The Mun... | Cotton gin | Wikipedia | 324 | 47710 | https://en.wikipedia.org/wiki/Cotton%20gin | Technology | Farm and garden machinery | null | vital_articles |
The invention of the cotton gin caused massive growth in the production of cotton in the United States, concentrated mostly in the South. Cotton production expanded from 750,000 bales in 1830 to 2.85 million bales in 1850. As a result, the region became even more dependent on plantations that used black slave labor, w... | Cotton gin | Wikipedia | 483 | 47710 | https://en.wikipedia.org/wiki/Cotton%20gin | Technology | Farm and garden machinery | null | vital_articles |
The cotton then enters a dryer, which removes excess moisture. The cylinder cleaner uses six or seven rotating, spiked cylinders to break up large clumps of cotton. Finer foreign material, such as soil and leaves, passes through rods or screens for removal. The stick machine uses centrifugal force to remove larger fo... | Cotton gin | Wikipedia | 313 | 47710 | https://en.wikipedia.org/wiki/Cotton%20gin | Technology | Farm and garden machinery | null | vital_articles |
Direct current (DC) is one-directional flow of electric charge. An electrochemical cell is a prime example of DC power. Direct current may flow through a conductor such as a wire, but can also flow through semiconductors, insulators, or even through a vacuum as in electron or ion beams. The electric current flows in a... | Direct current | Wikipedia | 409 | 47713 | https://en.wikipedia.org/wiki/Direct%20current | Physical sciences | Electrical circuits | null | vital_articles |
The late 1870s and early 1880s saw electricity starting to be generated at power stations. These were initially set up to power arc lighting (a popular type of street lighting) running on very high voltage (usually higher than 3,000 volts) direct current or alternating current. This was followed by the widespread use o... | Direct current | Wikipedia | 461 | 47713 | https://en.wikipedia.org/wiki/Direct%20current | Physical sciences | Electrical circuits | null | vital_articles |
Circuits
A direct current circuit is an electrical circuit that consists of any combination of constant voltage sources, constant current sources, and resistors. In this case, the circuit voltages and currents are independent of time. A particular circuit voltage or current does not depend on the past value of any circ... | Direct current | Wikipedia | 505 | 47713 | https://en.wikipedia.org/wiki/Direct%20current | Physical sciences | Electrical circuits | null | vital_articles |
Domestic DC installations usually have different types of sockets, connectors, switches, and fixtures from those suitable for alternating current. This is mostly due to the lower voltages used, resulting in higher currents to produce the same amount of power.
It is usually important with a DC appliance to observe pola... | Direct current | Wikipedia | 487 | 47713 | https://en.wikipedia.org/wiki/Direct%20current | Physical sciences | Electrical circuits | null | vital_articles |
High-voltage direct current (HVDC) electric power transmission systems use DC for the bulk transmission of electrical power, in contrast with the more common alternating current systems. For long-distance transmission, HVDC systems may be less expensive and suffer lower electrical losses.
Other
Applications using fuel... | Direct current | Wikipedia | 100 | 47713 | https://en.wikipedia.org/wiki/Direct%20current | Physical sciences | Electrical circuits | null | vital_articles |
A high-voltage direct current (HVDC) electric power transmission system uses direct current (DC) for electric power transmission, in contrast with the more common alternating current (AC) transmission systems. Most HVDC links use voltages between 100 kV and 800 kV.
HVDC lines are commonly used for long-distance power ... | High-voltage direct current | Wikipedia | 510 | 47716 | https://en.wikipedia.org/wiki/High-voltage%20direct%20current | Technology | Electricity transmission and distribution | null | vital_articles |
Practical conversion of current between AC and DC became possible with the development of power electronics devices such as mercury-arc valves and, starting in the 1970s, power semiconductor devices including thyristors, integrated gate-commutated thyristors (IGCTs), MOS-controlled thyristors (MCTs) and insulated-gate ... | High-voltage direct current | Wikipedia | 469 | 47716 | https://en.wikipedia.org/wiki/High-voltage%20direct%20current | Technology | Electricity transmission and distribution | null | vital_articles |
Mercury arc valves
First proposed in 1914, the grid controlled mercury-arc valve became available during the period 1920 to 1940 for the rectifier and inverter functions associated with DC transmission. Starting in 1932, General Electric tested mercury-vapor valves and a 12 kV DC transmission line, which also served to... | High-voltage direct current | Wikipedia | 485 | 47716 | https://en.wikipedia.org/wiki/High-voltage%20direct%20current | Technology | Electricity transmission and distribution | null | vital_articles |
On March 15, 1979, a 1920 MW thyristor based direct current connection between Cabora Bassa and Johannesburg () was energized. The conversion equipment was built in 1974 by Allgemeine Elektricitäts-Gesellschaft AG (AEG), and Brown, Boveri & Cie (BBC) and Siemens were partners in the project. Service interruptions of se... | High-voltage direct current | Wikipedia | 286 | 47716 | https://en.wikipedia.org/wiki/High-voltage%20direct%20current | Technology | Electricity transmission and distribution | null | vital_articles |
The development of higher rated insulated-gate bipolar transistors (IGBTs), gate turn-off thyristors (GTOs), and integrated gate-commutated thyristors (IGCTs), has made HVDC systems more economical and reliable. This is because modern IGBTs incorporate a short-circuit failure mode, wherein should an IGBT fail, it is me... | High-voltage direct current | Wikipedia | 462 | 47716 | https://en.wikipedia.org/wiki/High-voltage%20direct%20current | Technology | Electricity transmission and distribution | null | vital_articles |
Depending on voltage level and construction details, HVDC transmission losses are quoted at 3.5% per , about 50% less than AC (6.7%) lines at the same voltage. This is because direct current transfers only active power and thus causes lower losses than alternating current, which transfers both active and reactive power... | High-voltage direct current | Wikipedia | 472 | 47716 | https://en.wikipedia.org/wiki/High-voltage%20direct%20current | Technology | Electricity transmission and distribution | null | vital_articles |
Cable systems
Long undersea or underground high-voltage cables have a high electrical capacitance compared with overhead transmission lines since the live conductors within the cable are surrounded by a relatively thin layer of insulation (the dielectric), and a metal sheath. The geometry is that of a long coaxial cap... | High-voltage direct current | Wikipedia | 477 | 47716 | https://en.wikipedia.org/wiki/High-voltage%20direct%20current | Technology | Electricity transmission and distribution | null | vital_articles |
Finally, depending upon the environmental conditions and the performance of overhead line insulation operating with HVDC, it may be possible for a given transmission line to operate with a constant HVDC voltage that is approximately the same as the peak AC voltage for which it is designed and insulated. The power deliv... | High-voltage direct current | Wikipedia | 505 | 47716 | https://en.wikipedia.org/wiki/High-voltage%20direct%20current | Technology | Electricity transmission and distribution | null | vital_articles |
In contrast to AC systems, realizing multi-terminal systems is complex (especially with line commutated converters), as is expanding existing schemes to multi-terminal systems. Controlling power flow in a multi-terminal DC system requires good communication between all the terminals; power flow must be actively regulat... | High-voltage direct current | Wikipedia | 506 | 47716 | https://en.wikipedia.org/wiki/High-voltage%20direct%20current | Technology | Electricity transmission and distribution | null | vital_articles |
An April 2010 announcement for a 2,000 MW, line between Spain and France is estimated at €700 million. This includes the cost of a tunnel through the Pyrenees.
Conversion process
Converter
At the heart of an HVDC converter station, the equipment that performs the conversion between AC and DC is referred to as the ... | High-voltage direct current | Wikipedia | 502 | 47716 | https://en.wikipedia.org/wiki/High-voltage%20direct%20current | Technology | Electricity transmission and distribution | null | vital_articles |
With line commutated converters, the converter has only one degree of freedom the firing angle, which represents the time delay between the voltage across a valve becoming positive (at which point the valve would start to conduct if it were made from diodes) and the thyristors being turned on. The DC output voltage of ... | High-voltage direct current | Wikipedia | 387 | 47716 | https://en.wikipedia.org/wiki/High-voltage%20direct%20current | Technology | Electricity transmission and distribution | null | vital_articles |
Each thyristor valve will typically contain tens or hundreds of thyristor levels, each operating at a different (high) potential with respect to earth. The command information to turn on the thyristors therefore cannot simply be sent using a wire connection it needs to be isolated. The isolation method can be magnetic ... | High-voltage direct current | Wikipedia | 301 | 47716 | https://en.wikipedia.org/wiki/High-voltage%20direct%20current | Technology | Electricity transmission and distribution | null | vital_articles |
With some other types of semiconductor devices such as the insulated-gate bipolar transistor (IGBT), both turn-on and turn-off can be controlled, giving a second degree of freedom. As a result, they can be used to make self-commutated converters. In such converters, the electric polarity of DC voltage is usually fixed ... | High-voltage direct current | Wikipedia | 500 | 47716 | https://en.wikipedia.org/wiki/High-voltage%20direct%20current | Technology | Electricity transmission and distribution | null | vital_articles |
At the AC side of each converter, a bank of transformers, often three physically separated single-phase transformers, isolate the station from the AC supply, to provide a local earth, and to ensure the correct eventual DC voltage. The output of these transformers is then connected to the converter.
Converter transform... | High-voltage direct current | Wikipedia | 507 | 47716 | https://en.wikipedia.org/wiki/High-voltage%20direct%20current | Technology | Electricity transmission and distribution | null | vital_articles |
All power electronic converters generate some degree of harmonic distortion on the AC and DC systems to which they are connected, and HVDC converters are no exception.
With the recently developed modular multilevel converter (MMC), levels of harmonic distortion may be practically negligible, but with line-commutated c... | High-voltage direct current | Wikipedia | 422 | 47716 | https://en.wikipedia.org/wiki/High-voltage%20direct%20current | Technology | Electricity transmission and distribution | null | vital_articles |
The task of designing AC harmonic filters for HVDC converter stations is complex and computationally intensive, since in addition to ensuring that the converter does not produce an unacceptable level of voltage distortion on the AC system, it must be ensured that the harmonic filters do not resonate with some component... | High-voltage direct current | Wikipedia | 445 | 47716 | https://en.wikipedia.org/wiki/High-voltage%20direct%20current | Technology | Electricity transmission and distribution | null | vital_articles |
The electrodes are usually located some tens of kilometers from the stations and are connected to the stations via a medium-voltage electrode line. The design of the electrodes themselves depends on whether they are located on land, on the shore or at sea. For the monopolar configuration with earth return, the earth cu... | High-voltage direct current | Wikipedia | 479 | 47716 | https://en.wikipedia.org/wiki/High-voltage%20direct%20current | Technology | Electricity transmission and distribution | null | vital_articles |
In bipolar transmission a pair of conductors is used, each at a high potential with respect to ground, in opposite polarity. Since these conductors must be insulated for the full voltage, transmission line cost is higher than a monopole with a return conductor. However, there are a number of advantages to bipolar trans... | High-voltage direct current | Wikipedia | 512 | 47716 | https://en.wikipedia.org/wiki/High-voltage%20direct%20current | Technology | Electricity transmission and distribution | null | vital_articles |
Back to back
A back-to-back station (or B2B for short) is a plant in which both converters are in the same area, usually in the same building. The length of the direct current line is kept as short as possible. HVDC back-to-back stations are used for
coupling of electricity grids of different frequencies (as in Japan ... | High-voltage direct current | Wikipedia | 492 | 47716 | https://en.wikipedia.org/wiki/High-voltage%20direct%20current | Technology | Electricity transmission and distribution | null | vital_articles |
China is expanding its grid to keep up with increased power demand, while addressing environmental targets. China Southern Power Grid started a three terminals VSC HVDC pilot project in 2011. The project has designed ratings of ±160 kV/200 MW-100 MW-50 MW and will be used to bring wind power generated on Nanao island i... | High-voltage direct current | Wikipedia | 503 | 47716 | https://en.wikipedia.org/wiki/High-voltage%20direct%20current | Technology | Electricity transmission and distribution | null | vital_articles |
Corona discharge
Corona discharge is the creation of ions in a fluid (such as air) by the presence of a strong electric field. Electrons are torn from neutral air, and either the positive ions or the electrons are attracted to the conductor, while the charged particles drift. This effect can cause considerable power lo... | High-voltage direct current | Wikipedia | 486 | 47716 | https://en.wikipedia.org/wiki/High-voltage%20direct%20current | Technology | Electricity transmission and distribution | null | vital_articles |
AC network interconnectors
AC transmission lines can interconnect only synchronized AC networks with the same frequency with limits on the allowable phase difference between the two ends of the line. Many areas that wish to share power have unsynchronized networks. The power grids of the UK, Northern Europe and contine... | High-voltage direct current | Wikipedia | 411 | 47716 | https://en.wikipedia.org/wiki/High-voltage%20direct%20current | Technology | Electricity transmission and distribution | null | vital_articles |
A number of studies have highlighted the potential benefits of very wide area super grids based on HVDC since they can mitigate the effects of intermittency by averaging and smoothing the outputs of large numbers of geographically dispersed wind farms or solar farms. Czisch's study concludes that a grid covering the fr... | High-voltage direct current | Wikipedia | 492 | 47716 | https://en.wikipedia.org/wiki/High-voltage%20direct%20current | Technology | Electricity transmission and distribution | null | vital_articles |
In 2010, ABB Group built the world's first 800 kV UHVDC in China. The Zhundong–Wannan UHVDC line with 1100 kV, length and 12 GW capacity was completed in 2018. As of 2020, at least thirteen UHVDC transmission lines in China have been completed.
While the majority of recent UHVDC technology deployment is in China, it ... | High-voltage direct current | Wikipedia | 249 | 47716 | https://en.wikipedia.org/wiki/High-voltage%20direct%20current | Technology | Electricity transmission and distribution | null | vital_articles |
The coulomb (symbol: C) is the unit of electric charge in the International System of Units (SI). It is defined to be equal to the electric charge delivered by a 1 ampere current in 1 second. It is used to define the elementary charge e.
Definition
The SI defines the coulomb as "the quantity of electricity carried in... | Coulomb | Wikipedia | 463 | 47719 | https://en.wikipedia.org/wiki/Coulomb | Physical sciences | Electromagnetism | null | vital_articles |
By 1878, the British Association for the Advancement of Science had defined the volt, ohm, and farad, but not the coulomb. In 1881, the International Electrical Congress, now the International Electrotechnical Commission (IEC), approved the volt as the unit for electromotive force, the ampere as the unit for electric ... | Coulomb | Wikipedia | 222 | 47719 | https://en.wikipedia.org/wiki/Coulomb | Physical sciences | Electromagnetism | null | vital_articles |
The Brooklyn Bridge is a hybrid cable-stayed/suspension bridge in New York City, spanning the East River between the boroughs of Manhattan and Brooklyn. Opened on May 24, 1883, the Brooklyn Bridge was the first fixed crossing of the East River. It was also the longest suspension bridge in the world at the time of its o... | Brooklyn Bridge | Wikipedia | 503 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
To provide sufficient clearance for shipping in the East River, the Brooklyn Bridge incorporates long approach viaducts on either end to raise it from low ground on both shores. Including approaches, the Brooklyn Bridge is a total of long when measured between the curbs at Park Row in Manhattan and Sands Street in Bro... | Brooklyn Bridge | Wikipedia | 436 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
An elevated pedestrian-only promenade runs in between the two roadways and above them. It typically runs below the level of the crossbeams, except at the areas surrounding each tower. Here, the promenade rises to just above the level of the crossbeams, connecting to a balcony that slightly overhangs the two roadways.... | Brooklyn Bridge | Wikipedia | 382 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
The Brooklyn Bridge contains four main cables, which descend from the tops of the suspension towers and help support the deck. Two are located to the outside of the bridge's roadways, while two are in the median of the roadways. Each main cable measures in diameter and contains 5,282 parallel, galvanized steel wires w... | Brooklyn Bridge | Wikipedia | 412 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
The anchorages also contain numerous passageways and compartments. Starting in 1876, in order to fund the bridge's maintenance, the New York City government made the large vaults under the bridge's Manhattan anchorage available for rent, and they were in constant use during the early 20th century. The vaults were used ... | Brooklyn Bridge | Wikipedia | 390 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
Caissons
The towers rest on underwater caissons made of southern yellow pine and filled with cement. Inside both caissons were spaces for construction workers. The Manhattan side's caisson is slightly larger, measuring and located below high water, while the Brooklyn side's caisson measures and is located below hig... | Brooklyn Bridge | Wikipedia | 364 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
Proposals for a bridge between the then-separate cities of Brooklyn and New York had been suggested as early as 1800. At the time, the only travel between the two cities was by a number of ferry lines. Engineers presented various designs, such as chain or link bridges, though these were never built because of the diffi... | Brooklyn Bridge | Wikipedia | 370 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
Roebling was subsequently named the chief engineer of the work and, by September 1867, had presented a master plan. According to the plan, the bridge would be longer and taller than any suspension bridge previously built. It would incorporate roadways and elevated rail tracks, whose tolls and fares would provide the me... | Brooklyn Bridge | Wikipedia | 432 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
Construction of the Brooklyn Bridge began on January 2, 1870. The first work entailed the construction of two caissons, upon which the suspension towers would be built. The Brooklyn side's caisson was built at the Webb & Bell shipyard in Greenpoint, Brooklyn, and was launched into the river on March 19, 1870. Compresse... | Brooklyn Bridge | Wikipedia | 373 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
The Manhattan side's caisson was the next structure to be built. To ensure that it would not catch fire like its counterpart had, the Manhattan caisson was lined with fireproof plate iron. It was launched from Webb & Bell's shipyard on May 11, 1871, and maneuvered into place that September. Due to the extreme underwate... | Brooklyn Bridge | Wikipedia | 415 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
After the caissons were completed, piers were constructed on top of each of them upon which masonry towers would be built. The towers' construction was a complex process that took four years. Since the masonry blocks were heavy, the builders transported them to the base of the towers using a pulley system with a contin... | Brooklyn Bridge | Wikipedia | 488 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
Cables
The first temporary wire was stretched between the towers on August 15, 1876, using chrome steel provided by the Chrome Steel Company of Brooklyn. The wire was then stretched back across the river, and the two ends were spliced to form a traveler, a lengthy loop of wire connecting the towers, which was driven by... | Brooklyn Bridge | Wikipedia | 370 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
The spinning of the wires required the manufacture of large coils of it which were galvanized but not oiled when they left the factory. The coils were delivered to a yard near the Brooklyn anchorage. There they were dipped in linseed oil, hoisted to the top of the anchorage, dried out and spliced into a single wire, an... | Brooklyn Bridge | Wikipedia | 382 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
A subsequent investigation discovered that Haigh had substituted inferior quality wire in the cables. Of eighty rings of wire that were tested, only five met standards, and it was estimated that Haigh had earned $300,000 from the deception. At this point, it was too late to replace the cables that had already been cons... | Brooklyn Bridge | Wikipedia | 444 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
Further complicating the situation, Washington Roebling had failed to appear at the trustees' meeting in June 1882, since he had gone to Newport, Rhode Island. After the news media discovered this, most of the newspapers called for Roebling to be fired as chief engineer, except for the Daily State Gazette of Trenton, N... | Brooklyn Bridge | Wikipedia | 432 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
The New York and Brooklyn Bridge was opened for use on May 24, 1883. Thousands of people attended the opening ceremony, and many ships were present in the East River for the occasion. Officially, Emily Warren Roebling was the first to cross the bridge. The bridge opening was also attended by U.S. president Chester A. A... | Brooklyn Bridge | Wikipedia | 334 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
At the time of opening, the Brooklyn Bridge was not complete; the proposed public transit across the bridge was still being tested, while the Brooklyn approach was being completed. On May 30, 1883, six days after the opening, a woman falling down a stairway at the Brooklyn approach caused a stampede which resulted in a... | Brooklyn Bridge | Wikipedia | 430 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
Concerns about the Brooklyn Bridge's safety were raised during the turn of the century. In 1898, traffic backups due to a dead horse caused one of the truss cords to buckle. There were more significant worries after twelve suspender cables snapped in 1901, though a thorough investigation found no other defects. After t... | Brooklyn Bridge | Wikipedia | 386 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
Ostensibly in an attempt to reduce traffic on nearby city streets, Grover Whalen, the commissioner of Plant and Structures, banned motor vehicles from the Brooklyn Bridge on July 6, 1922. The real reason for the ban was an incident the same year where two cables slipped due to high traffic loads. Both Whalen and Roebli... | Brooklyn Bridge | Wikipedia | 403 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
The widened south roadway was completed in May 1951, followed by the north roadway in October 1953. The restoration was finished in May 1954 with the completion of the reconstructed elevated promenade. While the rebuilding of the span was ongoing, a fallout shelter was constructed beneath the Manhattan approach in anti... | Brooklyn Bridge | Wikipedia | 484 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
The Brooklyn Bridge gradually deteriorated due to age and neglect. While it had 200 full-time dedicated maintenance workers before World War II, that number dropped to five by the late 20th century, and the city as a whole only had 160 bridge maintenance workers. In 1974, heavy vehicles such as vans and buses were bann... | Brooklyn Bridge | Wikipedia | 355 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
Additional problems persisted, and in 1993, high levels of lead were discovered near the bridge's towers. Further emergency repairs were undertaken in mid-1999 after small concrete shards began falling from the bridge into the East River. The concrete deck had been installed during the 1950s renovations and had a lifes... | Brooklyn Bridge | Wikipedia | 391 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
In August 2016, the NYCDOT announced that it would conduct a seven-month, $370,000 study to verify if the bridge could support a heavier upper deck that consisted of an expanded bicycle and pedestrian path. By then, about 10,000 pedestrians and 3,500 cyclists used the pathway on an average weekday. Work on the pedestri... | Brooklyn Bridge | Wikipedia | 454 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
A plan for congestion pricing in New York City was approved in mid-2023, allowing the Metropolitan Transportation Authority to toll drivers who enter Manhattan south of 60th Street. Congestion pricing was implemented in January 2025. Most traffic to and from FDR Drive is exempt from the toll, but all other Manhattan-bo... | Brooklyn Bridge | Wikipedia | 483 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
The New York and Brooklyn Bridge Railway, a cable car service, began operating on September 25, 1883; it ran on the inner lanes of the bridge, between terminals at the Manhattan and Brooklyn ends. Since Washington Roebling believed that steam locomotives would put excessive loads upon the structure of the Brooklyn Brid... | Brooklyn Bridge | Wikipedia | 483 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
The BRT did not run any elevated train through services from 1899 to 1901. Due to increased patronage after the opening of the Interborough Rapid Transit Company (IRT)'s first subway line, the Park Row station was rebuilt in 1906. In the early 20th century, there were plans for Brooklyn Bridge elevated trains to run un... | Brooklyn Bridge | Wikipedia | 430 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
The Brooklyn Bridge has an elevated promenade open to pedestrians in the center of the bridge, located above the automobile lanes. The promenade is usually located below the height of the girders, except at the approach ramps leading to each tower's balcony. The path is generally wide, though this is constrained by ... | Brooklyn Bridge | Wikipedia | 429 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
During the 2003 blackouts, many crossing the bridge reported a swaying motion. The higher-than-usual pedestrian load caused this swaying, which was amplified by the tendency of pedestrians to synchronize their footfalls with a sway. Several engineers expressed concern about how this would affect the bridge, although ot... | Brooklyn Bridge | Wikipedia | 448 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
On March 1, 1994, Lebanese-born Rashid Baz opened fire on a van carrying members of the Chabad-Lubavitch Orthodox Jewish Movement, striking 16-year-old student Ari Halberstam and three others traveling on the bridge. Halberstam died five days later from his wounds, and Baz was later convicted of murder. He was apparent... | Brooklyn Bridge | Wikipedia | 475 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
On October 1, 2011, more than 700 protesters with the Occupy Wall Street movement were arrested while attempting to march across the bridge on the roadway. Protesters disputed the police account of the events and claimed that the arrests were the result of being trapped on the bridge by the NYPD. The majority of the ar... | Brooklyn Bridge | Wikipedia | 448 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
Impact
At the time of construction, contemporaries marveled at what technology was capable of, and the bridge became a symbol of the era's optimism. John Perry Barlow wrote in the late 20th century of the "literal and genuinely religious leap of faith" embodied in the bridge's construction, saying that the "Brooklyn B... | Brooklyn Bridge | Wikipedia | 479 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
To highlight the Brooklyn Bridge's cultural status, the city proposed building a Brooklyn Bridge museum near the bridge's Brooklyn end in the 1970s. Though the museum was ultimately not constructed, as many as 10,000 drawings and documents relating to it were found in a carpenter shop in Williamsburg in 1976. These doc... | Brooklyn Bridge | Wikipedia | 467 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
The construction of the Brooklyn Bridge is detailed in numerous media sources, including David McCullough's 1972 book The Great Bridge and Ken Burns's 1981 documentary Brooklyn Bridge. It is also described in Seven Wonders of the Industrial World, a BBC docudrama series with an accompanying book, as well as Chief Engin... | Brooklyn Bridge | Wikipedia | 82 | 47742 | https://en.wikipedia.org/wiki/Brooklyn%20Bridge | Technology | Transport infrastructure | null | vital_articles |
Transistor–transistor logic (TTL) is a logic family built from bipolar junction transistors. Its name signifies that transistors perform both the logic function (the first "transistor") and the amplifying function (the second "transistor"), as opposed to earlier resistor–transistor logic (RTL) and diode–transistor logi... | Transistor–transistor logic | Wikipedia | 454 | 47769 | https://en.wikipedia.org/wiki/Transistor%E2%80%93transistor%20logic | Technology | Semiconductors | null | vital_articles |
The Texas Instruments 7400 family became an industry standard. Compatible parts were made by Motorola, AMD, Fairchild, Intel, Intersil, Signetics, Mullard, Siemens, SGS-Thomson, Rifa, National Semiconductor, and many other companies, even in the Eastern Bloc (Soviet Union, GDR, Poland, Czechoslovakia, Hungary, Romania ... | Transistor–transistor logic | Wikipedia | 459 | 47769 | https://en.wikipedia.org/wiki/Transistor%E2%80%93transistor%20logic | Technology | Semiconductors | null | vital_articles |
TTL inputs are the emitters of bipolar transistors. In the case of NAND inputs, the inputs are the emitters of multiple-emitter transistors, functionally equivalent to multiple transistors where the bases and collectors are tied together. The output is buffered by a common emitter amplifier.
Inputs both logical ones. ... | Transistor–transistor logic | Wikipedia | 510 | 47769 | https://en.wikipedia.org/wiki/Transistor%E2%80%93transistor%20logic | Technology | Semiconductors | null | vital_articles |
A common variation omits the collector resistor of the output transistor, making an open-collector output. This allows the designer to fabricate wired logic by connecting the open-collector outputs of several logic gates together and providing a single external pull-up resistor. If any of the logic gates becomes logic ... | Transistor–transistor logic | Wikipedia | 501 | 47769 | https://en.wikipedia.org/wiki/Transistor%E2%80%93transistor%20logic | Technology | Semiconductors | null | vital_articles |
The main advantage of TTL with a "totem-pole" output stage is the low output resistance at output logical "1". It is determined by the upper output transistor V3 operating in active region as an emitter follower. The resistor R3 does not increase the output resistance since it is connected in the V3 collector and its i... | Transistor–transistor logic | Wikipedia | 272 | 47769 | https://en.wikipedia.org/wiki/Transistor%E2%80%93transistor%20logic | Technology | Semiconductors | null | vital_articles |
Standard TTL circuits operate with a 5-volt power supply. A TTL input signal is defined as "low" when between 0 V and 0.8 V with respect to the ground terminal, and "high" when between 2 V and VCC (5 V), and if a voltage signal ranging between 0.8 V and 2.0 V is sent into the input of a TTL gate, there is no certain r... | Transistor–transistor logic | Wikipedia | 443 | 47769 | https://en.wikipedia.org/wiki/Transistor%E2%80%93transistor%20logic | Technology | Semiconductors | null | vital_articles |
Packaging
Like most integrated circuits of the period 1963–1990, commercial TTL devices are usually packaged in dual in-line packages (DIPs), usually with 14 to 24 pins, for through-hole or socket mounting. Epoxy plastic (PDIP) packages were often used for commercial temperature range components, while ceramic packages... | Transistor–transistor logic | Wikipedia | 464 | 47769 | https://en.wikipedia.org/wiki/Transistor%E2%80%93transistor%20logic | Technology | Semiconductors | null | vital_articles |
The TTL "totem-pole" output structure often has a momentary overlap when both the upper and lower transistors are conducting, resulting in a substantial pulse of current drawn from the power supply. These pulses can couple in unexpected ways between multiple integrated circuit packages, resulting in reduced noise marg... | Transistor–transistor logic | Wikipedia | 289 | 47769 | https://en.wikipedia.org/wiki/Transistor%E2%80%93transistor%20logic | Technology | Semiconductors | null | vital_articles |
Low-power TTL (L), which traded switching speed (33ns) for a reduction in power consumption (1 mW) (now essentially replaced by CMOS logic)
High-speed TTL (H), with faster switching than standard TTL (6ns) but significantly higher power dissipation (22 mW)
Schottky TTL (S), introduced in 1969, which used Schottky dio... | Transistor–transistor logic | Wikipedia | 403 | 47769 | https://en.wikipedia.org/wiki/Transistor%E2%80%93transistor%20logic | Technology | Semiconductors | null | vital_articles |
Applications
Before the advent of VLSI devices, TTL integrated circuits were a standard method of construction for the processors of minicomputer and midrange mainframe computers, such as the DEC VAX and Data General Eclipse; however some computer families were based on proprietary components (e.g. Fairchild CTL) while... | Transistor–transistor logic | Wikipedia | 390 | 47769 | https://en.wikipedia.org/wiki/Transistor%E2%80%93transistor%20logic | Technology | Semiconductors | null | vital_articles |
Serial signaling
TTL serial refers to single-ended serial communication using raw transistor voltage levels: "low" for 0 and "high" for 1. UART over TTL serial is a common debug interface for embedded devices. Handheld devices such as graphing calculators and GPS receivers and fishfinders also commonly use UART with ... | Transistor–transistor logic | Wikipedia | 173 | 47769 | https://en.wikipedia.org/wiki/Transistor%E2%80%93transistor%20logic | Technology | Semiconductors | null | vital_articles |
In computer science, an instruction set architecture (ISA) is an abstract model that generally defines how software controls the CPU in a computer or a family of computers. A device or program that executes instructions described by that ISA, such as a central processing unit (CPU), is called an implementation of that ... | Instruction set architecture | Wikipedia | 501 | 47772 | https://en.wikipedia.org/wiki/Instruction%20set%20architecture | Technology | Computer architecture concepts | null | vital_articles |
The concept of an architecture, distinct from the design of a specific machine, was developed by Fred Brooks at IBM during the design phase of System/360.
Some virtual machines that support bytecode as their ISA such as Smalltalk, the Java virtual machine, and Microsoft's Common Language Runtime, implement this by tr... | Instruction set architecture | Wikipedia | 428 | 47772 | https://en.wikipedia.org/wiki/Instruction%20set%20architecture | Technology | Computer architecture concepts | null | vital_articles |
Data handling and memory operations
Set a register to a fixed constant value.
Copy data from a memory location or a register to a memory location or a register (a machine instruction is often called move; however, the term is misleading). They are used to store the contents of a register, the contents of another memory... | Instruction set architecture | Wikipedia | 509 | 47772 | https://en.wikipedia.org/wiki/Instruction%20set%20architecture | Technology | Computer architecture concepts | null | vital_articles |
Complex instructions are more common in CISC instruction sets than in RISC instruction sets, but RISC instruction sets may include them as well. RISC instruction sets generally do not include ALU operations with memory operands, or instructions to move large blocks of memory, but most RISC instruction sets include SIMD... | Instruction set architecture | Wikipedia | 392 | 47772 | https://en.wikipedia.org/wiki/Instruction%20set%20architecture | Technology | Computer architecture concepts | null | vital_articles |
Conditional instructions often have a predicate field—a few bits that encode the specific condition to cause an operation to be performed rather than not performed. For example, a conditional branch instruction will transfer control if the condition is true, so that execution proceeds to a different part of the program... | Instruction set architecture | Wikipedia | 218 | 47772 | https://en.wikipedia.org/wiki/Instruction%20set%20architecture | Technology | Computer architecture concepts | null | vital_articles |
0-operand (zero-address machines), so called stack machines: All arithmetic operations take place using the top one or two positions on the stack: push a, push b, add, pop c.
C = A+B needs four instructions. For stack machines, the terms "0-operand" and "zero-address" apply to arithmetic instructions, but not to all in... | Instruction set architecture | Wikipedia | 505 | 47772 | https://en.wikipedia.org/wiki/Instruction%20set%20architecture | Technology | Computer architecture concepts | null | vital_articles |
C = A+B needs four instructions.
Unlike 2-operand or 1-operand, this leaves all three values a, b, and c in registers available for further reuse.
more operands—some CISC machines permit a variety of addressing modes that allow more than 3 operands (registers or memory accesses), such as the VAX "POLY" polynomial evalu... | Instruction set architecture | Wikipedia | 80 | 47772 | https://en.wikipedia.org/wiki/Instruction%20set%20architecture | Technology | Computer architecture concepts | null | vital_articles |
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