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A thyristor is a solid-state semiconductor device with four layers of alternating P- and N-type materials. It acts as a bistable switch, conducting when the gate receives a current trigger, continuing to conduct until the voltage across the device is reversed biased, or until the voltage is removed. There are two designs. In a three-lead thyristor, a small current on its Gate lead controls the larger current of the Anode to Cathode path. In a two-lead thyristor, conduction begins when the potential difference between the Anode and Cathode themselves is sufficiently large; some sources define silicon-controlled thyristor as synonymous. Other sources define thyristors as more ornately constructed devices that incorporate at least four layers of alternating N-type and P-type substrate; the first thyristor devices were released commercially in 1956. Because thyristors can control a large amount of power and voltage with a small device, they find wide application in control of electric power, ranging from light dimmers and electric motor speed control to high-voltage direct-current power transmission.

Thyristors may be used in power-switching circuits, relay-replacement circuits, inverter circuits, oscillator circuits, level-detector circuits, chopper circuits, light-dimming circuits, low-cost timer circuits, logic circuits, speed-control circuits, phase-control circuits, etc. Thyristors relied only on current reversal to turn them off, making them difficult to apply for direct current; the latter is known as a gate turn-off GTO thyristor. A thyristor is not a proportional device like a transistor. In other words, a thyristor can only be on or off, while a transistor can lie in between on and off states; this makes useful as a switch. The thyristor is a four-layered, three-terminal semiconductor device, with each layer consisting of alternately N-type or P-type material, for example P-N-P-N; the main terminals, labelled anode and cathode, are across all four layers. The control terminal, called the gate, is attached to p-type material near the cathode; the operation of a thyristor can be understood in terms of a pair of coupled bipolar junction transistors, arranged to cause a self-latching action: Thyristors have three states: Reverse blocking mode – Voltage is applied in the direction that would be blocked by a diode Forward blocking mode – Voltage is applied in the direction that would cause a diode to conduct, but the thyristor has not been triggered into conduction Forward conducting mode – The thyristor has been triggered into conduction and will remain conducting until the forward current drops below a threshold value known as the "holding current" The thyristor has three p-n junctions.

When the anode is at a positive potential VAK with respect to the cathode with no voltage applied at the gate, junctions J1 and J3 are forward biased, while junction J2 is reverse biased. As J2 is reverse biased, no conduction takes place. Now if VAK is increased beyond the breakdown voltage VBO of the thyristor, avalanche breakdown of J2 takes place and the thyristor starts conducting. If a positive potential VG is applied at the gate terminal with respect to the cathode, the breakdown of the junction J2 occurs at a lower value of VAK. By selecting an appropriate value of VG, the thyristor can be switched into the on state quickly. Once avalanche breakdown has occurred, the thyristor continues to conduct, irrespective of the gate voltage, until: the potential VAK is removed or the current through the device becomes less than the holding current specified by the manufacturer. Hence VG can be a voltage pulse, such as the voltage output from a UJT relaxation oscillator; the gate pulses are characterized in terms of gate trigger current.

Gate trigger current varies inversely with gate pulse width in such a way that it is evident that there is a minimum gate charge required to trigger the thyristor. In a conventional thyristor, once it has been switched on by the gate terminal, the device remains latched in the on-state, providing the anode current has exceeded the latching current; as long as the anode remains positively biased, it cannot be switched off until holding current. In normal working condition the latching current is always greater than holding current. In the above figure IL has to come above the IH on y-axis since IL>IH. A thyristor can be switched off if the external circuit causes the anode to become negatively biased. In some applications this is done by switching a second thyristor to discharge a capacitor into the cathode of the first thyristor; this method is called forced commutation. After the current in a thyristor has extinguished, a finite time delay must elapse before the anode can again be positively biased and retain the thyristor in the off-state.

This minimum delay is called the circuit commutated turn off time. Attempting to positively bias the anode within this time causes the thyristor to be self-triggered by the remaining charge carriers that have not yet recombined. For applications with frequencies higher than the domestic AC mains supply, thyristors with lower values of tQ are required; such fast thyristors can be made by diffusing heavy metal ions such as go

Clendenin District, Mason County, West Virginia

Clendenin Magisterial District is one of ten magisterial districts in Mason County, West Virginia. The district was established as a civil township in 1863, converted into a magisterial district in 1872. In 2010, Clendenin District was home to 3,715 people. Clendenin District is located along the Ohio River in the southern part of Mason County. To the north, it is bounded by the Ohio and Kanawha Rivers, by Lewis District. Across the river are Gallipolis and Clay Townships, in Gallia County and the village of Gallipolis. Clendenin District includes submerged land in the Ohio River to the low water mark on the Ohio shore reserved by the state of Virginia, when it ceded its claim to the Northwest Territory in 1784; as a result, the district includes Gallipolis Island, a quarter-mile long island two hundred feet from the Gallipolis shore. The district includes the Robert C. Byrd Locks and Dam, on the Ohio River just above Apple Grove. Excluded from Clendenin District is Raccoon Island, a former island, now a shoal in the Ohio River opposite the mouth of Crab Creek.

With an area greater than eighty-three square miles, Clendenin is the largest of Mason County's ten magisterial districts. It is one of three districts south of the Kanawha River, together with Hannan; the soil in the Ohio River bottoms of the western part of the district feature a productive mixture of sand and clay. The soil in the hills making up the majority of the district contains red and white clay, mixed with black loam; the main streams of Clendenin District are Salt Creek, Twomile Creek, Crab Creek, Flatfoot Creek, Sixteenmile Creek, Eighteenmile Creek, all of which empty into the Ohio River, Arbuckle Creek, which flows into the Ohio above Henderson. Of these and Sixteenmile are sometimes referred to as the Ohio Twomile and Sixteenmile, to distinguish them from the Kanawha Twomile and Sixteenmile Creeks, which flow into the Kanawha River from Arbuckle District. There was once a Kanawha Eighteenmile in Mason County, but since 1848 it has been part of Putnam County. Crab Creek is the largest stream lying in Clendenin District.

Its middle fork begins in the hills three miles east of Gallipolis Ferry, near the northwest corner of Arbuckle District. It flows south and west for about three miles, until it meets its Right-hand Fork, which flows westward from the hills east of Fay, taking in Horse Lick coming from the north below Mohrtown. Crab Creek flows westward out of the hills, meeting the Sand Fork at the base of the hills; the Sand Fork of Crab Creek flows south and west out of the hills a mile east of Gallipolis Ferry, reaching the river bottom at Beale meandering through the floodplain south and east for a mile and a half before joining the main branch. Crab Creek flows along the base of the hills for a mile and a half before abruptly turning northwest, meeting Mud Run, flowing out of the hills behind Ben Lomond, a mile to the south; the combined stream meanders through the bottomland before discharging into the Ohio, just above the mouth of Raccoon Creek on the opposite shore. Flatfoot Creek flows southeast out of the hills behind Hogsett, reaching the floodplain above Apple Grove running along the base of the hills north to Hogsett.

Here the creek turned southward, meandered toward the Ohio, which it joined at the boundary of Clendenin and Hannan Districts. In the 1990s, part of the western portion of the floodplain along the Robert C. Byrd Locks and Dam was removed and flooded to build two auxiliary locks, Flatfoot Creek diverted to empty into the Ohio at Hogsett; the original lower course of the creek was used to create a series of ponds below the locks. The Ohio Sixteenmile drains much of the southern part of the district, its upper waters are in western Arbuckle District, along with its tributaries, the Wolfpen Branch and the Willow Branch, which join the main branch southeast of Arlee, along the district boundary. Sixteenmile curves around the base of Loggerhead Ridge, meeting the Loggerhead Fork, flows south for about three miles past Potts Hollow and Potts Chapel Ridge, meets the Righthand Fork flowing west from the hills near Sevenmile Ridge. From here, Sixteenmile flows west, meeting with Millstone Creek flowing from the north, turning southwest, meeting with Daves Run, crossing into Hannan District.

The creek makes a dogleg turn to the southeast, crosses back into Clendenin District, where it meets Jerrys Run, flowing westward continues southwest through Hannan District to the river. As it exits the hills, Sixteenmile is joined by Stonecoal Run, the upper waters of which are in Clendenin District; the main branch of Eighteenmile Creek only flows for a short distance through the southernmost part of Clendenin District, as it travels from western Putnam County to the Ohio River below Ashton in Hannan District. However, several of its tributaries flow out of Clendenin District, including the Spring Branch of Whitepine Creek, which joins Eighteenmile at the Putnam County line. Other streams of Clendenin District include a Willow Branch that flows into the Ohio below Henderson.

Parex Bank

Parex Bank was a Latvian bank founded in 1992 by Valērijs Kargins and Viktors Krasovickis as a owned full-service banking company in Riga, Latvia. Its services were marketed both locally and to international clients in both the Russia, its failure and state takeover was one of the major events of the 2008-2010 Latvian financial crisis crisis in Latvia. On April 3, 1991, Parex Bank received the first licence issued to a private company for currency exchange operations in the territory of the Soviet Union – issued by the second President of the Bank of Latvia, Paul Sakss. In May, Parex opened the first exchange office, visited by many clients from all over USSR. In August 1991, Valērijs Kargins, along with Viktors Krasovickis and his wife Nina Kondratyev, reorganized Parex and became the new bank AS PAREX's sole owners. Kargins owned half of the shares, while the remaining 50% were distributed in similar amounts between Viktors Krosovickis and his wife. In January 1992, Parex Bank was founded, with the owners Valērijs Kargins and Viktors Krasovickis having equal shares in the bank.

Krasovicki`s wife Nina did not participate in the bank`s future activities as they divorced that year. However, she continued to hold significant deposit in it. In 1993, about 30% of Parex Bank`s shares were bought by offshore company Europe Holdings Ltd and by the year 2001 its share reached 51%; the company remained in the list of owners until 2002, when Kargins and Krasovickis formally repurchased parts of Europe Holdings Ltd, again becoming the sole owners of the bank. However, by the end of 2007, around 14% of the Bank`s total paid-in share capital was in the hands of 59 small shareholders. By the beginning of 2008, Britain had nationalized Northern Rock to save it from bankruptcy. In the second half of 2008, a number of large and pre-eminent banks and financial institutions went bankrupt, such as Lehman Brothers in the United States and Carnegie in Sweden. In autumn of 2008, after the bankruptcy of several major banks and financial institutions, the global financial crisis began in earnest.

Several countries in the world had to seek international financial assistance, many countries provided support or took over state-controlled banks and other credit institutions. In October 2008, the European Commission agreed on a plan to allow governments to engage in bank rescue. On July 30, 2008, in a letter from Financial and Capital Market Commission to the Chairman of the Board of Parex Bank titled, "On the results of the risk assessment of the bank," it was stated that an inspection had been carried out for the period from 12 November, 2007 to 18 January, 2008 and that the test results indicated that "the bank's performance characterized by a moderate level of risk, the methods used by the institution to manage risk satisfactory, although improvements needed in some areas."From August 18 until October 3, 2008, the FCMC conducted an inspection with the aim of reviewing and evaluating Parex's lending process. The inspection revealed significant shortcomings in the lending process. On October 14, 2008, the FCMC authorized Parex to include audited profit for the first half of 2008 in Tier 1 capital and to include Parex Group's audited profit for the first half of 2008 in Tier 1 capital of Parex Consolidation Group.

This decision showed that Parex's capital adequacy position was stable in mid-October 2008. On October 20, 2008, as a result of the inspection, more accurate information was obtained about the current or current financial situation of Parex; the FCMC informed Parex of the deficiencies found during the inspection and invited Parex representatives to negotiate the improvements of deficiencies. After the initial refusal, a meeting between FCMC and Parex representatives took place only a week later. On October 22, 2008, Parex owners requested state support to maintain the bank's solvency by proposing a state treasury deposit to Parex Bank; the Ministry of Finance rejected this suggestion. The outflow of money from Parex continued. Finance Minister Atis Slakteris discussed the situation with the FCMC and the Bank of Latvia, on October 28 the Minister of Finance informed Prime Minister Ivars Godmanis; the authorities involved at the beginning of November concluded that Parex needs to be taken over by the state.

Several options were considered - the full takeover of Parex banka into state ownership, the transfer of 51% of Parex banka's shares to the Mortgage and Land Bank, as well as the refusal of assistance. In the latter case, the state would have to pay the bank's customers at least LVL 660 million as a state guarantee for deposits; the Cabinet of Ministers supported the takeover of the bank into state ownership. It was considered that there would be no security for the use of public funds if the bank remained in the hands of its shareholders. On October 27, 2008, withdrawals from Parex began to accelerate rapidly. Due to the risk of default of capital adequacy ratios and taking into account the promise of Parex's major shareholders to increase the capital base in case of necessity, FCMC requested Parex to submit by 29 October 2008 the Parex Capital Adequacy Recovery Plan. On this day along, around 29 million lats of capital left Parex. In early November 2008, it was clear that Parex's problems were so serious that it would involve the Cabinet of Ministers, that Parex's takeover could be one of the most effective options for stabilizing the Latvian financial system by providing support to Parex.

On November 8

Clinton Hill (artist)

Clinton Hill was an American abstract artist who created abstract color compositions on canvas, constructions made from wood and canvas and plastic relief sculptures, woodblock prints and unique assemblages of handmade paper. Born in Payette and raised on a working ranch, Clinton Hill served in the navy during World War II as commander of a minesweeper in the Pacific. Upon his return from service, Hill attended the University of Oregon from which he graduated in 1947, he moved to New York City, where Hill attended the Brooklyn Museum Art School from 1949 to 1951."The work of Clinton Hill is characterized by a lyrical abstraction, derived from the painterly tradition of the New York School" In 1951 he left for Paris where he furthered his art studies on the GI Bill at the Academie de la Grande Chaumiere and on to Florence, Italy where Hill studied painting at the Instituto d'Art Statale."Clinton's Hill's first important works were made in the period after 1950s." Upon returning to NY, Hill prepared for his first solo exhibition at the Zabriskie Gallery.

His friend Mark Rothko suggested the name of the show "Windows. Over a 55-year period Clinton Hill has been included in close to 100 exhibitions."Hill would expand his interest in physically assertive surfaces and outline into outright sculptural relief" In 1958 Hill traveled to India on a Fulbright scholarship."Since the late eighties he produced pieces with a linear element running through the handmade paper, sculptural forms utilizing wood and oil, sometimes attached to canvas and sometimes freestanding pieces, using similar color balances" For over 20 years he was Professor of Painting at Queens College of the City University of New York. Clinton Hill/Allen Tran Foundation, Clinton Hill: A 50 Year Survey. Melissa Morgan Gallery, Palm Desert and Jordan Schnitzer Museum, University of Oregon, Eugene, 2009–2010 Una Johnson. American Printmakers. Jules Heller. Papermaking. Harriet Janis & Rudi Blesh. Collage. Amy Winter. Clinton Hill, 1980-2002; the Godwin-Tembach Museum, Queens College, CUNY David Acton.

A Spectrum of Innovation: Color in American Printmaking, 1890-1960. Worcester Art Museum 1990. Stephan Westfall, Clinton Hill. Marilyn Pearl Gallery, New York, 1988 Martica Sawin. Clinton HIll. Paintings and Paperworks. Montclair Art Museum, 1981 Charlotta Kotik. With Paper, About Paper. Buffalo Fine Arts Academy, 1980 Jane M. Farmer. Paper as a Medium. Smithsonian Institution, 1978 Official website

Boeing 737

The Boeing 737 is a narrow-body aircraft produced by Boeing Commercial Airplanes at its Renton Factory in Washington. Developed to supplement the 727 on short and thin routes, the twinjet retains the 707 fuselage cross-section and nose with two underwing turbofans. Envisioned in 1964, the initial 737-100 made its first flight in April 1967 and entered service in February 1968 with Lufthansa; the lengthened 737-200 entered service in April 1968. It evolved through four generations; the -100/200 original variants were powered by Pratt & Whitney JT8D low-bypass engines and offered seating for 85 to 130 passengers. Launched in 1980 and introduced in 1984, the 737 Classic -300/400/500 variants were re-engined with CFM56-3 turbofans and offered 110 to 168 seats. Introduced in 1997, the 737 Next Generation -600/700/800/900 variants have updated CFM56-7s, a larger wing and an upgraded glass cockpit, seat 108 to 215 passengers; the latest generation, the 737 MAX -7/8/9/10, powered by improved CFM LEAP high bypass turbofans and accommodating 138 to 204 people, entered service in 2017.

Boeing Business Jet versions are produced since the 737NG, as well as military models. As of December 2019, 15,156 Boeing 737s have been 10,571 delivered. Actual backlog stands at 4,398 when including "additional criteria for recognizing contracted backlog with customers beyond the existence of a firm contract", it was the highest-selling commercial jetliner until being surpassed in total orders by the competing Airbus A320 family in October 2019. Before, it competed with the McDonnell Douglas DC-9 its MD-80/MD-90 derivatives. In March 2019, the Boeing 737 MAX was grounded worldwide following two fatal crashes. Boeing had been studying short-haul jet aircraft designs, wanted to produce another aircraft to supplement the 727 on short and thin routes. Preliminary design work began on May 11, 1964, Boeing's intense market research yielded plans for a 50- to 60-passenger airliner for routes 50 to 1,000 mi long; the initial concept featured podded engines on the aft fuselage and a T-tail like the 727, five-abreast seating, but engineer Joe Sutter instead placed the engines under the wings to lighten the structure, enabling fuselage widening for six-abreast seating.

The 737 design was presented in October 1964 at the Air Transport Association maintenance and engineering conference by chief project engineer Jack Steiner, where its elaborate high-lift devices raised concerns about maintenance costs and dispatch reliability. It was decided to mount the nacelles directly to the underside of the wings to reduce the landing gear length and kept the engines low to the ground for easy ramp inspection and servicing. Many thickness variations for the engine attachment strut were tested in the wind tunnel and the most desirable shape for high speed was found to be one, thick, filling the narrow channels formed between the wing and the top of the nacelle on the outboard side; the span arrangement of the airfoil sections of the 737 wing was planned to be similar to that of the 707 and 727, but somewhat thicker. A substantial improvement in drag at high Mach numbers was achieved by altering these sections near the nacelle; the engine chosen was the Pratt & Whitney JT8D-1 low-bypass ratio turbofan engine, delivering 14,500 lbf thrust.

With the wing-mounted engines, Boeing decided to mount the horizontal stabilizer on the fuselage rather than the T-tail style of the Boeing 727. The launch decision for the $150 million development was made by the board on February 1, 1965. Lufthansa became the launch customer on February 19, 1965, with an order for 21 aircraft, worth $67 million in 1965, after the airline received assurances from Boeing that the 737 project would not be canceled. Consultation with Lufthansa over the previous winter resulted in an increase in capacity to 100 seats; this was renamed the 737-100. It competed with the McDonnell Douglas DC-9 its MD-80/MD-90 derivatives. On April 5, 1965, Boeing announced an order by United Airlines for 40 737s. United wanted a larger airplane than the original 737, so Boeing stretched the fuselage 36 in ahead of, 40 in behind the wing; the longer version was designated 737-200, with the original short-body aircraft becoming the 737-100. Detailed design work continued on both variants at the same time.

Boeing was far behind its competitors. To expedite development, Boeing used 60% of the structure and systems of the existing 727, the most notable being the fuselage cross-section; this fuselage permitted six-abreast seating compared to the rival BAC-111 and DC-9's five-abreast layout. The initial assembly of the Boeing 737 was adjacent to Boeing Field because the factory in Renton was filled to capacity with the production of the 707 and 727. After 271 of the Boeing 737 aircraft were built, production was moved to Renton in late 1970, it was the highest-selling commercial jetliner until being surpassed in total orders by the competing Airbus A320 family in October 2019. A significant portion of fuselage assembly—previously done by Boeing in Wichita, Kansas—is now performed by Spirit AeroSystems, which purchased some of Boeing's assets in Wichita. Key to increasing production efficiencies, the entire fuselage is shipped since the 737 Next Generation while it was sent in two pieces before; the fuselage is joined with the wings and landing gear and moves down the assembly line for the engines and interiors.

After rolling out the aircraft, Boeing tests the systems and engines befor

Ignatz von Popiel

Ignatz von Popiel was a Polish-Ukrainian chess player. Born into a noble family in Drohobych, Galicia, he began study law at the University of Graz. Started his chess career in Vienna, where he took 10th in 1886, took 2nd in 1887, took 2nd in 1888. In the period between 1889 and 1892, he studied law at the Jagiellonian University in Cracow. In 1889, he tied for 5th-6th at Breslau. In 1892, he took 7th in Dresden. In 1895, he won in the Lvov Chess Club championship. In 1896, he tied for 2nd-3rd in Eisenach, took 13th in Budapest, won in Lviv. In 1897, he won in Berlin. In 1898, he tied for 10th-11th in Cologne. In 1899-1900, he took 9th in Vienna. In 1900, he tied for 11th-12th in Munich. In 1902, he took 16th in Monte Carlo, took 18th in Hannover. In 1904, he took 3rd in the Lvov City championship, 3rd in Lvov. In 1905, he drew a match with Oskar Piotrowski, he took 5th at Lvov 1912, took 2nd, behind Piotrowski, in the Lvov City championship in 1914. During World War I, in 1915, he took 6th at Vienna.

After the war, Popiel was one of the strongest chess players in Poland. He participated several times in the Lvov City championship. Playing in a pre-Olympic tournament at Lodz 1935 took 13th place. In 1937 he left Lvov for Bochnia, tied for 5-7th in the Cracow City championship, he died on 2 May 1941 in Poland. He was the uncle of a Ukrainian chess master. Emanuel Lasker vs Ignatz von Popiel, Breslau 1889, Vienna Game, Mieses Variation, C26, 0-1 Ignatz von Popiel vs Dawid Janowski, Cologne 1898, DSB 11th Kongress, Sicilian Defense, Pin Variation, B40, 1-0 Ignatz von Popiel vs Georg Marco, Monte Carlo 1902, Philidor Defense, C41, 1-0