Gas metal arc welding is a semi-automatic or automatic arc welding process in which a continuous and consumable wireelectrode and a shielding gas are fed through a welding gun. A constant voltage, direct current power source is most commonly used with GMAW, but constant current systems, as well as alternating current, can be used. There are four primary methods of metal transfer in GMAW, called globular, short-circuiting, spray, and pulsed-spray, each of which has distinct properties and corresponding advantages and limitations.
A gas explosion in a residential area of Rosario, the third-largest city in Argentina, occurred on August 6, 2013. It was caused by a large gas leak; a nearby building collapsed, and others were at high risk of structural failure. Twenty-two people died, and sixty were injured. Several organizations helped secure the area, search for survivors and aid people who lost their homes. Shortly after the explosion, the time needed for reconstruction was estimated at six months.
The provincial judiciary launched an investigation into the cause of the explosion. Primary suspects were Litoral Gas (the natural-gas provider for Rosario) and an employee who carried out maintenance work at the building that day. Several public figures sent condolences, and most of the candidates for the 2013 primary elections suspended their political campaigns.
Shielded metal arc welding (SMAW), also known as manual metal arc welding (MMA or MMAW), flux shielded arc welding informally as stick welding, is a manual arc welding process that uses a consumable electrode choveres with a flux to lay the weld.
Welding is a fabrication or sculpturalprocess that joins materials, usually metals or thermoplastics, by causing fusion, which is distinct from lower temperature metal-joining techniques such as brazing and soldering, which do not melt the base metal. In addition to melting the base metal, a filler material is often added to the joint to form a pool of molten material (the weld pool) that cools to form a joint that can be as strong, or even stronger, than the base material. Pressure may also be used in conjunction with heat, or by itself, to produce a weld.
A distributed element filter is an electronic filter in which capacitance, inductance and resistance (the elements of the circuit) are not localised in discrete capacitors, inductors and resistors as they are in conventional filters. Its purpose is to allow a range of signal frequencies to pass, but to block others. Conventional filters are constructed from inductors and capacitors, and the circuits so built are described by the lumped element model, which considers each element to be "lumped together" at one place. That model is conceptually simple, but it becomes increasingly unreliable as the frequency of the signal increases, or equivalently as the wavelength decreases. The distributed element model applies at all frequencies, and is used in transmission line theory; many distributed element components are made of short lengths of transmission line. In the distributed view of circuits, the elements are distributed along the length of conductors and are inextricably mixed together. The filter design is usually concerned only with inductance and capacitance, but because of this mixing of elements they cannot be treated as separate "lumped" capacitors and inductors. There is no precise frequency above which distributed element filters must be used but they are especially associated with the microwave band (wavelength less than one metre).
The history of draining and development of the Everglades dates back to the 19th century. During the Second Seminole War beginning in 1836, the United States military's mission was to seek out Seminole people in the Everglades and capture or kill them. Those missions gave the military the opportunity to map land that seemed to frustrate and confound them at every turn. A national push for expansion and progress toward the latter part of the 19th century stimulated interest in draining the Everglades for agricultural use. According to historians, "From the middle of the nineteenth century to the middle of the twentieth century, the United States went through a period in which wetland removal was not questioned. Indeed, it was considered the proper thing to do."
Grand Coulee Dam is a gravity dam on the Columbia River in the U.S. state of Washington, built to produce hydroelectric power and provide irrigation water. It was constructed between 1933 and 1942, originally with two power plants. A third power station was completed in 1974 to increase its energy production. It is the largest electric power-producing facility in the United States.
The proposal to build the dam was the focus of a bitter debate during the 1920s between two groups. One group wanted to irrigate the ancient Grand Coulee with a gravity canal, and the other supported a high dam and pumping scheme. Dam supporters won in 1933, but for fiscal reasons the initial design was for a "low dam" 290 feet (88 m) high which would generate electricity, but not support irrigation. The U.S. Bureau of Reclamation and a consortium of three companies called MWAK (Mason-Walsh-Atkinson Kier Company) began construction that year. After visiting the construction site in August 1934, President Franklin Delano Roosevelt began endorsing the "high dam" design which, at 550 ft (168 m) high, would provide enough electricity to pump water to irrigate the Columbia Basin. The high dam was approved by Congress in 1935 and completed in 1942; the first water over-topped its spillway on June 1 of that year.
A Halkett boat is a type of lightweight inflatable boat designed by Lt Peter Halkett (1820–1885) during the 1840s. Halkett had long been interested in the difficulties of travelling in the Canadian Arctic, and the problems involved in designing boats light enough to be carried over arduous terrain, but robust enough to be used in extreme weather conditions.
Halkett's first design was a collapsible and inflatable boat made of rubber-impregnated cloth. When deflated, the hull of the boat could be worn as a cloak, the oar used as a walking stick, and the sail as an umbrella. This was followed by a two-man craft that was small enough to fit into a knapsack, and when deflated served as a waterproof blanket.
Although widely praised by Canadian explorers, Halkett's designs had a limited market, and he was unable to persuade the Royal Navy that they would serve any useful purpose in general naval service. Efforts to market them as platforms for fishing and duck shooting failed, and they were commercially unsuccessful. Only two Halkett boats, that of Orcadian explorer John Rae, and one held in the Hudson's Bay Company Museum Collection at the Manitoba Museum are known to survive today.
The Hanford Site is a mostly decommissioned nuclear production complex operated by the United States federal government on the Columbia River in the U.S. state of Washington. The site has been known by many names, including: Hanford Project, Hanford Works, Hanford Engineer Works and Hanford Nuclear Reservation. Established in 1943 as part of the Manhattan Project in Hanford, south-central Washington, the site was home to the B Reactor, the first full-scale plutonium production reactor in the world. Plutonium manufactured at the site was used in the first nuclear bomb, tested at the Trinity site, and in Fat Man, the bomb detonated over Nagasaki, Japan.
During the Cold War, the project expanded to include nine nuclear reactors and five large plutonium processing complexes, which produced plutonium for most of the more than 60,000 weapons in the U.S. nuclear arsenal. Nuclear technology developed rapidly during this period, and Hanford scientists produced major technological achievements. Many early safety procedures and waste disposal practices were inadequate, and government documents have confirmed that Hanford's operations released significant amounts of radioactive materials into the air and the Columbia River.
Since about 1900, the Black Canyon and nearby Boulder Canyon had been investigated for their potential to support a dam that would control floods, provide irrigation water and produce hydroelectric power. In 1928, Congress authorized the project. The winning bid to build the dam was submitted by a consortium called Six Companies, Inc., which began construction on the dam in early 1931. Such a large concrete structure had never been built before, and some of the techniques were unproven. The torrid summer weather and lack of facilities near the site also presented difficulties. Nevertheless, Six Companies turned over the dam to the federal government on March 1, 1936, more than two years ahead of schedule.
The Ancient Egyptians divided the day into two 12-hour periods, and used large obelisks to track the movement of the sun. They also developed water clocks, which were probably first used in the Precinct of Amun-Re, and later outside Egypt as well; they were employed frequently by the Ancient Greeks, who called them clepsydrae. The Zhou dynasty is believed to have used the outflow water clock around the same time, devices which were introduced from Mesopotamia as early as 2000 BCE.
Other ancient timekeeping devices include the candle clock, used in ancient China, ancient Japan, England and Mesopotamia; the timestick, widely used in India and Tibet, as well as some parts of Europe; and the hourglass, which functioned similarly to a water clock. The sundial, another early clock, relies on shadows to provide a good estimate of the hour on a sunny day. It is not so useful in cloudy weather or at night and requires recalibration as the seasons change (if the gnomon was not aligned with the Earth's axis).
A mechanical filter is a signal processing filter usually used in place of an electronic filter at radio frequencies. Its purpose is the same as that of a normal electronic filter: to pass a range of signal frequencies, but to block others. The filter acts on mechanical vibrations which are the analogue of the electrical signal. At the input and output of the filter, transducers convert the electrical signal into, and then back from, these mechanical vibrations.
The components of a mechanical filter are all directly analogous to the various elements found in electrical circuits. The mechanical elements obey mathematical functions which are identical to their corresponding electrical elements. This makes it possible to apply electrical network analysis and filter design methods to mechanical filters. Electrical theory has developed a large library of mathematical forms that produce useful filter frequency responses and the mechanical filter designer is able to make direct use of these. It is only necessary to set the mechanical components to appropriate values to produce a filter with an identical response to the electrical counterpart.
The resulting dam would have created a lake roughly the size of Lake Erie, making it the largest man-made reservoir in the world. The plan for the dam itself called for a concrete structure 530 feet (162 m) high with a top length of about 4,700 feet (1,430 m). The proposed power facilities would have consistently generated between 3.5 and 5 gigawatts of electricity, based on the flow of the river as it differs between winter and summer.
The production of renewable energy in Scotland is an issue that has come to the fore in technical, economic, and political terms during the opening years of the 21st century. The natural resource base for renewable energy is extraordinary by European, and even global standards, with the most important potential sources being wind, wave, and tide.
At the end of 2015, there was 7,723 megawatts (MW) of installed renewable electricity capacity in Scotland, an increase of 5.5% (or 406 MW) from the end of 2014. Renewable electricity generation in Scotland was 21,983 GWh in 2015, up 15.2% on 2014. 57.7 per cent of Scotland's electricity came from renewables in 2015. Scottish renewable generation makes up approximately 26.4% of total UK renewable generation (down from 32% in 2014). In 2014, Scotland exported over 24 per cent of generation.
After several modifications, the first production variants of the PV-12 were completed in 1936. The first operational aircraft to enter service using the Merlin were the Fairey Battle, Hawker Hurricane and Supermarine Spitfire. More Merlins were made for the four-engined Avro Lancaster heavy bomber than for any other aircraft; however, the engine is most closely associated with the Spitfire, starting with the Spitfire's maiden flight in 1936. A series of rapidly applied developments, brought about by wartime needs, markedly improved the engine's performance and durability.
The Rolls-Royce R was a British aero engine designed and built specifically for air racing purposes by Rolls-Royce Limited. Nineteen R engines were assembled in a limited production run between 1929 and 1931. Developed from the Rolls-Royce Buzzard, it was a 37-litre (2,240 cu in) capacity, superchargedV-12 capable of producing just under 2,800 horsepower (2,090 kW), and weighed 1,640 pounds (770 kg). Intensive factory testing revealed mechanical failures which were remedied by redesigning the components, greatly improving reliability.
The R was used with great success in the Schneider Trophyseaplane competitions held in England in 1929 and 1931. Shortly after the 1931 competition, an R engine using a special fuel blend powered the winning Supermarine S.6B aircraft to a new airspeed record of over 400 miles per hour (640 km/h). Continuing through the 1930s, both new and used R engines were used to achieve various land and water speed records by such racing personalities as Sir Henry Segrave, Sir Malcolm Campbell and his son Donald, the last record being set in 1939. A final R-powered water speed record attempt by Donald Campbell in 1951 was unsuccessful.
A protest group was formed to resist the proposed construction, and attracted support from the botanist and environmental campaigner David Bellamy. Despite the opposition, planning permission was granted in 2005 and construction began in 2007. Although work on the project was hampered by harsh weather, difficult terrain, and previous mining activity, the wind farm was officially opened on 25 September 2008 after "years of controversy", at a cost of £50 million.
Shale oil extraction is usually performed above ground (ex situ processing) by mining the oil shale and then treating it in processing facilities. Other modern technologies perform the processing underground (on-site or in situ processing) by applying heat and extracting the oil via oil wells.
The Sholes and Glidden typewriter (also known as the Remington No. 1) was the first commercially successful typewriter. Principally designed by the AmericaninventorChristopher Latham Sholes, it was developed with the assistance of fellow printer Samuel W. Soule and amateur mechanic Carlos S. Glidden. Work began in 1867, but Soule left the enterprise shortly thereafter, replaced by James Densmore, who provided financial backing and the driving force behind the machine's continued development. After several short-lived attempts to manufacture the device, the machine was acquired by E. Remington and Sons in early 1873. An arms manufacturer seeking to diversify, Remington further refined the typewriter before finally placing it on the market on July 1, 1874.
During its development, the typewriter evolved from a crude curiosity into a practical device, the basic form of which became the industry standard. The machine incorporated elements which became fundamental to typewriter design, including a cylindrical platen and a four-rowed QWERTY keyboard. Several design deficiencies remained, however. The Sholes and Glidden could print only upper-case letters—an issue remedied in its successor, the Remington No. 2—and was a "blind writer", meaning the typist could not see what was being written as it was entered.
The Shuttle–Mir Program was a collaborative space program between Russia and the United States, which involved American Space Shuttles visiting the Russian space stationMir, Russian cosmonauts flying on the shuttle, and an American astronaut flying aboard a Soyuz spacecraft to engage in long-duration expeditions aboard Mir.
The project, sometimes called "Phase One", was intended to allow the United States to learn from Russian experience with long-duration spaceflight and to foster a spirit of cooperation between the two nations and their space agencies, the US National Aeronautics and Space Administration (NASA) and the Russian Federal Space Agency (Roskosmos). The project helped to prepare the way for further cooperative space ventures; specifically, "Phase Two" of the joint project, the construction of the International Space Station (ISS). The program was announced in 1993, the first mission started in 1994 and the project continued until its scheduled completion in 1998. Eleven Space Shuttle missions, a joint Soyuz flight and almost 1000 cumulative days in space for American astronauts occurred over the course of seven long-duration expeditions.
The ingenuity of advanced mechanical engineering had a long tradition in China. The Song engineer Su Song admitted that he and his contemporaries were building upon the achievements of the ancients such as Zhang Heng (78–139), an astronomer, inventor, and early master of mechanical gears. The application of movable type printing advanced the already widespread use of woodblock printing to educate and amuse Confucian students and the masses. The application of new weapons employing the use of gunpowder enabled the Song to ward off its militant enemies—the Liao, Western Xia, and Jin with weapons such as cannons—until its collapse to the Mongol forces of Kublai Khan in the late 13th century.