Portal:Technology/Selected articles

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Portal:Technology/Selected articles/1

Electrical engineering

Electrical engineering is a professional engineering discipline that deals with the study and application of electricity, electromagnetism and electronics. The field first became an identifiable occupation in the late nineteenth century with the commercialization of the electric telegraph and electrical power supply and now encompasses a range of sub-disciplines including power, control systems, electronics and telecommunications. Whilst these terms are often used to mean the same, electrical engineering is sometimes distinguished from electronics engineering. Where this distinction is made, electrical engineering is considered to deal with the problems associated with large-scale electrical systems such as power transmission and motor control whereas electronics engineering deals with the study of small-scale electronic systems including semiconductors and the design of integrated circuits. Advances during the 20th century in radio technologies, followed by the invention of early computers and integrated circuits, led to the development of the specialized field. Meanwhile, universities were developing formal programs of study, and today, the field's practitioners generally hold an academic degree in their discipline and may be certified by a professional body.

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mechanical filter

A mechanical filter is a signal processing filter usually used in place of an electronic filter at radio frequencies to allow a range of signal frequencies to pass, but to block others. The filter acts on mechanical vibrations. Transducers at the input and output of the filter convert the electrical signal into, and then back from, these mechanical vibrations. The mechanical elements obey mathematical functions which are identical to their corresponding electrical elements. Electrical theory has developed a large library of mathematical forms that produce useful filter frequency responses for use in the design of mechanical filters. Steel and nickeliron alloys are common materials for mechanical filter components. Resonators in the filter made from these materials need to be machined to precisely adjust their resonance frequency prior to final assembly. The high "quality factor", Q, that mechanical resonators can attain, far higher than that of an all-electrical LC circuit, made possible the construction of mechanical filters with excellent selectivity. Good selectivity, being important in radio receivers, made such filters highly attractive. Contemporary researchers are working on microelectromechanical filters, the mechanical devices corresponding to electronic integrated circuits.

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Microsoft is an international computer technology corporation with 2005 global sales of US$42.64 billion and more than 63,000 employees in 102 countries and regions that develop, manufacture, license, and support a wide range of software products for computing devices. Headquartered in Redmond, Washington, USA, its most popular products are the Microsoft Windows operating system and the Microsoft Office suite of productivity software, each of which has achieved near ubiquity in the desktop computer market. Microsoft possesses footholds in other markets, with assets such as the MSNBC cable television network, the MSN Internet portal, and the Microsoft Encarta multimedia encyclopedia. The company also markets both computer hardware products such as the Microsoft mouse, as well as home entertainment products such as the Xbox, the Xbox 360, and MSN TV.

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Illustration of a Song Dynasty junk, a type of ship

The technology of the Song Dynasty (960–1279 AD) was advanced, providing some of the most prolific technological advancements in Chinese history, much of which came from talented statesmen drafted by the government through imperial examinations. The ingenuity of mechanical engineering had a long tradition in China. The Song Dynasty engineer Su Song admitted that he and his contemporaries were building upon the achievements of the ancients such as Zhang Heng, 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 Dynasty to ward off its militant enemies until its collapse to the Mongol forces of Kublai Khan, in the late 13th century. Notable advancements in civil engineering, nautics, and metallurgy were made in Song China, as well as the introduction of the windmill to China during the 13th century. These advancements, along with the introduction of paper-printed money, helped revolutionize and sustain the economy of the Song Dynasty.

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A diagram of one shale oil extraction process

Shale oil extraction is an industrial process for unconventional oil production. This process converts kerogen in oil shale into shale oil by pyrolysis, hydrogenation, or thermal dissolution. The resultant shale oil is used as fuel oil or upgraded to meet refinery feedstock specifications by adding hydrogen and removing sulfur and nitrogen impurities. 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 earliest description of the process dates to the 10th century. The industry shrank in the mid-20th century following the discovery of large reserves of conventional oil, but high petroleum prices at the beginning of the 21st century have led to renewed interest. As of 2010, major long-standing extraction industries are operating in Estonia, Brazil, and China. Its economic viability varies with the ratio of local energy input costs to energy output value. National energy security issues have also played a role in its development. Critics of shale oil extraction pose questions about environmental management issues, such as waste disposal, extensive water use and waste water management, and air pollution.

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Sholes and Glidden typewriter

The Sholes and Glidden typewriter was the first commercially successful typewriter. Principally designed by Christopher L. Sholes, it was developed with the assistance of Samuel W. Soule and Carlos S. Glidden. 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, incorporating elements which became fundamental to typewriter design, such as a cylindrical platen and a four-rowed QWERTY keyboard. Several design deficiencies remained, however. The Sholes and Glidden could print only upper-case letters and the typist could not see what was being written as it was entered. Initially, the typewriter received an unenthusiastic reception from the public. Lack of an established market, high cost, and the need for trained operators slowed its adoption. The new communication technologies and expanding businesses of the late 19th century had created a need for expedient, legible correspondence, and so the Sholes and Glidden and its contemporaries soon became ubiquitous office fixtures.

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The reference image for Acid2

Acid2 is a test page published and promoted by the Web Standards Project to expose web page rendering flaws in web browsers and other applications that render HTML. It was developed in the spirit of Acid1, a relatively narrow test of compliance with the Cascading Style Sheets 1.0 (CSS1) standard, and was released on April 13, 2005. Like Acid1, an application passes the test if the way it displays the test page matches a reference image. Acid2 tests aspects of HTML markup, CSS 2.1 styling, PNG images, and data URIs. The Acid2 test page will be displayed correctly in any application that follows the World Wide Web Consortium and Internet Engineering Task Force specifications for these technologies. These specifications are known as web standards because they describe how technologies used on the web are expected to function. While at the time of Acid2's release no web browser passed the test, Acid2 was designed with Microsoft Internet Explorer particularly in mind. The creators of Acid2 were dismayed that Internet Explorer did not follow web standards and, consequently, Internet Explorer was prone to display web pages differently from other browsers. Acid2 represented a challenge to Microsoft to bring Internet Explorer in line with web standards, making it easier to design web pages that work as intended in any web browser.

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"O" logo used by Opera Software as the browser logo

Opera is a web browser and internet suite developed by the Opera Software company. Opera handles common Internet-related tasks such as displaying web sites, sending and receiving e-mail messages, managing contacts, IRC online chatting, downloading files via BitTorrent, and reading web feeds. Opera is offered free of charge for personal computers and mobile phones, but for other devices it must be paid for. Features of Opera include tabbed browsing, page zooming, mouse gestures, and an integrated download manager. Its security features include built-in phishing and malware protection, strong encryption when browsing secure web sites, and the ability to easily delete private data such as cookies and browsing history by simply clicking a button. Opera runs on a variety of personal computer operating systems, including Microsoft Windows, Mac OS X, Linux, FreeBSD, and Solaris. Though evaluations of Opera have been largely positive, Opera has captured only a fraction of the worldwide personal computer browser market. Opera has a stronger market share on mobile devices such as mobile phones, smartphones, and personal digital assistants. Editions of Opera are available for devices using the Symbian and Windows Mobile operating systems, as well as Java ME-enabled devices. Approximately 40 million mobile phones have shipped with Opera pre-installed.

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Macintosh Classic

The Macintosh Classic is a personal computer that was manufactured by Apple Computer from October 15, 1990 to September 14, 1992. It was the first Apple Macintosh sold under US$1,000. Production of the Classic was prompted by the success of the Macintosh Plus and the SE. The Classic was very similar to its predecessors: due to limited technological advances, it used the same 9-inch (23 cm) monochrome CRT display, 512×342 pixel resolution, and its performance was hampered by the same 4 megabyte (MB) memory limit of the older Macintosh computers. Nevertheless, the Classic featured several improvements over the Macintosh Plus, which it replaced as Apple's low-end Mac computer. It was up to 25 percent faster than the Plus and included an Apple SuperDrive 3.5" floppy disk drive as standard. The Classic was an adaptation of Jerry Manock and Terry Oyama's Macintosh 128K industrial design, as was the earlier Macintosh SE. Apple released two versions that ranged in price from $1,000 to $1,500. Reviewers' reactions were mixed; most focused on the slow processor performance and lack of expansion slots. The consensus was that the Classic was only useful for word processing, spreadsheets and databases.

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Astrophysics Data System

The Astrophysics Data System is an online NASA database of over 7,000,000 astronomy and physics papers from both peer reviewed and non-peer reviewed sources. Abstracts are available free online for almost all articles, and full scanned articles are available in GIF and PDF format for older articles. New articles have links to electronic versions hosted at the journal's webpage, but these are typically available only by subscription (which most astronomy research facilities have). It is managed by the Harvard-Smithsonian Center for Astrophysics. ADS is an extremely powerful research tool, and has had a significant impact on the efficiency of astronomical research since it was launched in 1992. Literature searches which previously would have taken days or weeks can now be carried out in seconds via the sophisticated ADS search engine, which is custom-built for astronomical needs. Studies have found that the benefit to astronomy of the ADS is equivalent to several hundred million US dollars annually, and the system is estimated to have tripled the readership of astronomical journals. Use of ADS is almost universal among astronomers worldwide, and therefore ADS usage statistics can be used to analyze global trends in astronomical research.

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Caesar cipher

In cryptography, a Caesar cipher is one of the simplest and most well-known classical encryption techniques. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions further down the alphabet. For example, with a shift of 3, A would be replaced by D, B would become E, and so on. The method is named after Julius Caesar, who used it to communicate with his generals. The encryption step performed by a Caesar cipher is often incorporated as part of more complex schemes, such as the Vigenère cipher, and still has modern application in the ROT13 system. As for all single alphabet substitution ciphers, the Caesar cipher is easily broken and in practice offers no communication security.

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OpenBSD is a freely available Unix-like computer operating system descended from Berkeley Software Distribution (BSD), a Unix derivative created by the University of California, Berkeley. It was forked from NetBSD, a previous open source operating system based on BSD, by project leader Theo de Raadt in 1994, and is known among open source enthusiasts for the developers' insistence on open source and documentation, uncompromising position on software licensing, and focus on security and code correctness. OpenBSD includes a number of security features not found or optional in other operating systems and has a tradition of developers auditing the source code for software bugs and security problems, such as W^X and a malloc implementation similar to Electric Fence. The project maintains strict policies on licensing and prefers the open source BSD licence and its variants—in the past this has led to a comprehensive licence audit and moves to remove or replace code under licences found less acceptable.

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F-16 Fighting Falcon

The Lockheed Martin F-16 Fighting Falcon is a multirole jet fighter aircraft originally developed by General Dynamics for the United States Air Force. Designed as a lightweight fighter, it evolved into a successful multirole aircraft. The Falcon's versatility is a paramount reason it has proven a success on the export market, having been selected to serve in the air forces of 25 nations. The F-16 is the largest Western jet fighter program with over 4,400 aircraft built since production was approved in 1976. Though no longer being bought by the U.S. Air Force, advanced versions are still being built for export customers. In 1993, General Dynamics sold its aircraft manufacturing business to the Lockheed Corporation, which in turn became part of Lockheed Martin after a 1995 merger with Martin Marietta. The Fighting Falcon is a dogfighter with numerous innovations including a frameless, bubble canopy for better visibility, side-mounted control stick to ease control while under high g-forces, and reclined seat to reduce the effect of g-forces on the pilot. Weapons include a M61 Vulcan cannon and various missiles mounted on up to 11 hardpoints. It was also the first fighter aircraft deliberately built to sustain 9-g turns. It has a thrust-to-weight ratio greater than one, providing enough power to climb and accelerate vertically – if necessary. Although the F-16's official name is "Fighting Falcon", it is known to its pilots as the "Viper", due it resembling a cobra snake and after the Battlestar Galactica starfighter. It is used by the Thunderbirds air demonstration team.

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Parallel computing

Parallel computing is a form of computation in which many calculations are carried out simultaneously, operating on the principle that large problems can often be divided into smaller ones, which are then solved concurrently. There are several different forms of parallel computing: bit-level-, instruction-level-, data-, and task parallelism. As power consumption by computers has become a concern in recent years, parallel computing has become the dominant paradigm in computer architecture, mainly in the form of multicore processors. Parallel computers can be roughly classified according to the level at which the hardware supports parallelism—with multi-core and multi-processor computers having multiple processing elements within a single machine, while clusters, MPPs, and grids use multiple computers to work on the same task. Parallel computer programs are more difficult to write than sequential ones, because concurrency introduces several new classes of potential software bugs, of which race conditions are the most common. Communication and synchronization between the different subtasks are typically one of the greatest obstacles to getting good parallel program performance. The speed-up of a program as a result of parallelization is given by Amdahl's law.

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CFM International CFM56

The CFM International CFM56 series is a family of high-bypass turbofan aircraft engines made by CFM International with a thrust range of 18,500 to 34,000 pound-force (lbf) (80 to 150 kilonewtons (kN)). CFMI is a 50–50 joint-owned company of SNECMA and GE Aviation. Both companies are responsible for producing components and each has its own final assembly line. The CFM56 first ran in 1974 and, despite initial political problems, is now one of the most prolific jet engine types in the world: more than 20,000 have been built in four major variants. It is most widely used on the Boeing 737 airliner and under military designation F108 replaced the Pratt & Whitney JT3D engines on many KC-135 Stratotankers in the 1980s, creating the KC-135R variant of this aircraft. It is also one of two engines used to power the Airbus A340, the other being the Rolls-Royce Trent. The engine is also fitted to Airbus A320 series aircraft. Several fan blade failure incidents were experienced during the CFM56's early service, including one failure that was noted as a cause of the Kegworth air disaster, and some variants of the engine experienced problems caused by flight through rain and hail. However, both these issues were resolved with engine modifications.

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Construction of the World Trade Center

The construction of the World Trade Center started as a post-World War II urban renewal project, spearheaded by David Rockefeller, to help revitalize Lower Manhattan. The project was developed by the Port Authority of New York and New Jersey, which hired architect Minoru Yamasaki who came up with the specific idea for twin towers. The towers were designed as framed tube structures, which provided tenants with open floor plans, uninterrupted by columns or walls. This was accomplished using numerous, closely-spaced perimeter columns to provide much of the strength to the structure, along with gravity load shared with the core columns. The elevator system, which made use of sky lobbies and a system of express and local elevators, allowed substantial floor space to be freed up for use as office space by making the structural core smaller. The design and construction of the World Trade Center twin towers involved many other innovative techniques, such as the slurry wall for digging the foundation, and wind tunnel experiments. Construction of the World Trade Center's North Tower began in August 1968, and the South Tower in 1969. Extensive use of prefabricated components helped to speed up the construction process. The first tenants moved into the North Tower in December 1970 and into the South Tower in January 1972. Four other, low-level buildings were constructed as part of the World Trade Center in the 1970s, and a seventh building was constructed in the mid-1980s.

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Gas tungsten arc welding

Gas tungsten arc welding is an arc welding process that uses a nonconsumable tungsten electrode to produce the weld. The weld area is protected from atmospheric contamination by a shielding gas (usually an inert gas such as argon), and a filler metal is normally used, though some welds, known as autogenous welds, do not require it. A constant-current welding power supply produces energy which is conducted across the arc through a column of highly ionized gas and metal vapors known as a plasma. GTAW is most commonly used to weld thin sections of stainless steel and light metals such as aluminum, magnesium, and copper alloys. The process grants the operator greater control over the weld than competing procedures such as shielded metal arc welding and gas metal arc welding, allowing for stronger, higher quality welds. However, GTAW is comparatively more complex and difficult to master, and furthermore, it is significantly slower than most other welding techniques. A related process, plasma arc welding, uses a slightly different welding torch to create a more focused welding arc and as a result is often automated.

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Harold and Inge Marcus Department of Industrial and Manufacturing Engineering

The Harold and Inge Marcus Department of Industrial and Manufacturing Engineering is the industrial engineering department at the Pennsylvania State University in State College, Pennsylvania. Founded in 1908, it is the oldest such department in the world. According to the most recent U.S. News & World Report university rankings, both the graduate and undergraduate programs ranked fourth in the United States. The department is currently headed by Richard J. Koubek and since 2000 has been based in the Leonhard Building, a $12 million structure containing the acclaimed FAME manufacturing lab. Named for alumnus Harold Marcus and his wife Inge, the department employs 25 faculty members, who in 2007 served 163 graduate and 345 undergraduate students. Among the department's alumni are Harold W. Gehman, a former NATO Supreme Allied Commander, Atlantic, and Gregory Lucier, the President and CEO of Invitrogen.

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Horseshoe Curve (Pennsylvania)

Horseshoe Curve is a 3,485-foot (1,062 m), triple-tracked railroad curve on Norfolk Southern Railway's Pittsburgh Line in Logan Township, Blair County, in the U.S. state of Pennsylvania. It is close to 1,300 feet (400 m) in diameter and has a grade of almost two percent. As a train travels west from Altoona, it ascends almost 60 feet (20 m) in the 0.66-mile (1.06 km) segment that makes up the curve and rotates 220 degrees. The curve was completed in 1854 by the Pennsylvania Railroad as a means of lessening the grade to the summit of the Allegheny Mountains by increasing the distance. It was built as alternative to the time-consuming Allegheny Portage Railroad, the only other method of traversing the mountains. It has formed an important part of the region's transportation infrastructure since its opening, and during World War II was targeted by Nazi Germany in 1942 as a part of Operation Pastorius. Horseshoe Curve was added to the National Register of Historic Places and designated a National Historic Landmark in 1966. It was also designated a National Historic Civil Engineering Landmark in 2004.

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Rolls-Royce Merlin

The Rolls-Royce Merlin is a British, liquid-cooled, 27-litre (1,650 cu in) capacity, V-12 piston aero engine, designed and built by Rolls-Royce Limited. Initially known as the PV-12, Rolls-Royce named the engine the Merlin following the company convention of naming its piston aero engines after birds of prey. The PV-12 first ran in 1933, and a series of rapidly applied developments brought about by wartime needs improved the engine's performance markedly. 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 any other aircraft; however, the engine is most closely associated with the Spitfire and powered its maiden flight in 1936. Considered a British icon, the Merlin was one of the most successful aircraft engines of the World War II era, and many variants were built by Rolls-Royce in Derby, Crewe and Glasgow, as well as by Ford of Britain in Trafford Park, Manchester. The Packard V-1650 was a version of the Merlin built in the United States. Production ceased in 1950 after a total of almost 150,000 engines had been delivered, the later variants being used for airliners and military transport aircraft. In military use the Merlin was superseded by its larger capacity stablemate, the Rolls-Royce Griffon. Merlin engines remain in Royal Air Force service today with the Battle of Britain Memorial Flight, and power many restored aircraft in private ownership worldwide.

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Hubble Space Telescope

The Hubble Space Telescope is a telescope located at the outer edges of Earth's atmosphere. The telescope was launched by Space Shuttle Discovery on April 24, 1990. This had been postponed from a 1986 launch date by the Space Shuttle Challenger explosion. It was later discovered that the main mirror had a defect, which was repaired in December 1993. Hubble's scientific successor, the James Webb Telescope is scheduled for launch in October 2018.

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Toronto Magnetic and Meteorological Observatory

The Toronto Magnetic and Meteorological Observatory is a small observatory located on the grounds of the University of Toronto. The original building was constructed in 1840 as part of a worldwide research project run by Edward Sabine to determine the cause of fluctuations in magnetic declination. Measurements from the Toronto site demonstrated that sunspots were responsible for this effect on Earth's magnetic field. When this project ended in 1853, the observatory was taken over by the Canadian government, greatly expanded in 1855, and operated as the primary meteorological station and official Canadian timekeeper for over fifty years. The Observatory is the country's oldest surviving scientific institution, and is considered the birthplace of Canadian astronomy.

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Rosetta@home is a distributed computing project for protein structure prediction on the Berkeley Open Infrastructure for Network Computing (BOINC) platform, run by the Baker laboratory at the University of Washington. Rosetta@home also aims to predict protein-protein docking and design new proteins with the help of over 86,000 volunteered computers processing over 68 teraFLOPS on average. Though much of the project is oriented towards basic research on improving the accuracy and robustness of the proteomics methods, Rosetta@home also does applied research on malaria, Alzheimer's disease and other pathologies. Like all BOINC projects, Rosetta@home uses idle computer processing resources from volunteers' computers to perform calculations on individual workunits. Completed results are sent to a central project server where they are validated and assimilated into project databases. The project is cross-platform, and runs on a wide variety of hardware configurations. Users can view the progress of their individual protein structure prediction on the Rosetta@home screensaver. Rosetta@home consistently ranks among the foremost docking predictors, and is one of the best tertiary structure predictors available.

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Water fluoridation

Water fluoridation is the controlled addition of fluoride to a public water supply to reduce tooth decay. Fluoridated water has fluoride at a level that is effective for preventing cavities; this can occur naturally or by adding fluoride. Fluoridated water operates on tooth surfaces: in the mouth it creates low levels of fluoride in saliva, which reduces the rate at which tooth enamel demineralizes and increases the rate at which it remineralizes in the early stages of cavities. Typically a fluoridated compound is added to drinking water, a process that in the U.S. costs an average of about $1.04 per person-year. Defluoridation is needed when the naturally occurring fluoride level exceeds recommended limits. A 1994 World Health Organization expert committee suggested a level of fluoride from 0.5 to 1.0 mg/L (milligrams per liter), depending on climate. Dental cavities remain a major public health concern in most industrialized countries, affecting 60–90% of schoolchildren and the vast majority of adults, and costing society more to treat than any other disease. Water fluoridation prevents cavities in both children and adults, with studies estimating an 18–40% reduction in cavities when water fluoridation is used by children who already have access to toothpaste and other sources of fluoride. There is no clear evidence of adverse effects other than dental fluorosis. It is controversial, and opposition to it has been based on ethical, legal, safety, and efficacy grounds.

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Folding@home is a distributed computing project for disease research that simulates protein folding, computational drug design, and other types of molecular dynamics. The project is powered by the idle processing resources of thousands of personal computers owned by volunteers who have installed the software on their systems. Its primary purpose is to determine the mechanisms of protein folding, which is the process by which proteins reach their final three-dimensional structure, and to examine the causes of protein misfolding. This is of significant academic interest with major implications for medical research into Alzheimer's disease, Huntington's disease, and many forms of cancer, among other diseases. Folding@home is developed and operated by the Pande laboratory at Stanford University, under the direction of Vijay Pande. It is shared by various scientific institutions and research laboratories across the world. The project has pioneered the use of GPUs, PlayStation 3s, and Message Passing Interface for distributed computing and scientific research. Folding@home is one of the world's fastest computing systems. Since its launch in 2000, it has assisted over 100 scientific research papers.

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Hydro-Québec's electricity transmission system

Hydro-Québec's electricity transmission system is an expansive, international power transmission system located in Quebec, Canada with extensions into the Northeastern United States. Major expansion of the network began with the commissioning of the alternating current 735 kV power line in November 1965, as there was a need for electricity transmission over vast distances from hydroelectric power stations in northwestern Quebec and Labrador to southern Quebec. The transmission system, containing over 32,000 kilometres (20,000 mi) of power lines, is managed by Hydro-Québec TransÉnergie, a division of the crown corporation Hydro-Québec. One unique feature of the power system is its alternating current (AC) centers of Montreal and Quebec City to the distant hydroelectric dams and power stations of the James Bay Project and Churchill Falls. The 735 kV power lines serve as the main backbone of the entire transmission system, and thus much of Quebec's population is powered by a handful of 735 kV power lines. This contributed to the severity of the blackout that ensued after the Ice Storm of 1998. The extent and duration of this blackout has generated criticism of the transmission system, and there is controversy concerning the use of hydroelectric dams. Hydro-Québec's electric system is part of the Northeast Power Coordinating Council, even though it technically is its own interconnection, and its own system is minimally connected with other NPCC member utilities.

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DNA nanotechnology

DNA nanotechnology is the design and manufacture of artificial nucleic acid structures for technological uses. In this field, nucleic acids such as DNA are used as non-biological engineering materials for nanotechnology rather than as the carriers of genetic information in living cells. Researchers in the field have created static structures such as crystal lattices, nanotubes, polyhedra, and arbitrarily shaped DNA origami; as well as functional structures including molecular machines and DNA computers. The conceptual foundation for DNA nanotechnology was first laid out in the early 1980s, and the field began to attract widespread interest in the mid-2000s. The field is beginning to be used as a tool to solve basic science problems in structural biology and biophysics, such as protein structure determination, and potential real-world applications in nanomedicine and molecular scale electronics are under development.

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Buro Happold

Buro Happold is a professional services firm providing engineering consultancy, design, planning, project management and consulting services for all aspects of buildings, infrastructure and the environment, with its head office in Bath, Somerset. It was founded in 1976, by Sir Edmund Happold in Bath in the southwest of England when he left Ove Arup and Partners to take up a post at the University of Bath as Professor of Architecture and Engineering Design. Originally working mainly on projects in the Middle East, the firm now operates worldwide and in almost all areas of engineering for the built environment, with offices in seven countries. The parent company owns the subsidiary companies Happold Consulting, Happold Media and Happold Safe and Secure. The firm includes a number of specialist engineering consultancy groups, including fire engineering and lighting consultancy.

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Synthetic diamond

Synthetic diamond is diamond produced in a technological process, as opposed to natural diamond which is created in geological processes. Numerous claims of diamond synthesis were documented between 1879 and 1928; every attempt has been carefully analyzed and none has been confirmed. In the 1940s, systematic research began in the United States, Sweden and the Soviet Union to grow diamond using chemical vapor deposition (CVD) and high-pressure high-temperature synthesis (HPHT) processes. The first reproducible synthesis was reported around 1953. Those two processes still dominate the production of synthetic diamond. The properties of synthetic diamond depend on the details of the manufacturing processes, and can be inferior or superior to those of natural diamond; the hardness, thermal conductivity and electron mobility are superior in some synthetic diamonds. Consequently, synthetic diamond is widely used in abrasives, cutting and polishing tools and in heat sinks. Electronic applications of synthetic diamond are being developed, including high-power switches at power stations, high-frequency field-effect transistors and light-emitting diodes. Both CVD and HPHT diamonds can be cut into gems and various colors can be produced: clear white, yellow, brown, blue, green and orange.

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Apollo 8

Apollo 8 was the second manned mission of the Apollo space program. Commander Frank Borman, Command Module Pilot James Lovell and Lunar Module Pilot William Anders became the first humans to travel beyond Earth orbit and into an orbit around the Moon. It was also the first manned launch of the Saturn V rocket. NASA prepared for the mission in only four months. The hardware involved had only been used a few times—the Saturn V had only launched twice before, and the Apollo spacecraft had only just finished its first manned mission, Apollo 7. However the success of the mission paved the way for the successful completion of John F. Kennedy's goal of landing on the Moon before the end of the decade. After launching on December 21, 1968, the crew took three days to travel to the Moon, which they orbited for twenty hours. While in lunar orbit they made a Christmas Eve television broadcast that is thought to be one of the most watched of all time.

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Shuttle-Mir Program

The Shuttle-Mir Program was a collaborative space program between Russia and the United States, which involved American Space Shuttles visiting the Russian space station Mir, Russian cosmonauts flying on the shuttle and American astronauts engaging in long-duration expeditions aboard Mir. The program, under the code name 'Phase One', was intended to allow the United States to learn from Russian experience into long-duration spaceflight and to foster a spirit of cooperation between the two nations and their respective space agencies, NASA and RKA, in preparation for further cooperative space ventures. Announced in 1993 with the first mission occurring in 1994, the program continued until its scheduled completion in 1998, and consisted of eleven shuttle missions, a joint Soyuz flight and almost 1000 days in space for American astronauts over seven expeditions. The program was, however, marred by various concerns, notably the safety of Mir following a fire and collision on board the station, financial issues with the cash-strapped Russian Space Program and worries from astronauts about the attitudes of the program administrators. Nevertheless, a large amount of science, expertise in space station construction and knowledge in working in a cooperative space venture was gained from the combined operations, allowing 'Phase Two' of the joint project, the construction of the International Space Station, to proceed much more smoothly than otherwise possible.

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An Experiment on a Bird in the Air Pump

An Experiment on a Bird in the Air Pump is a 1768 oil-on-canvas painting by Joseph Wright of Derby, part of a series of candlelit scenes that Wright painted during the 1760s. The Air Pump departed from previous painting conventions by depicting a scientific subject in the reverential manner formerly reserved for scenes of historical and religious significance. Wright was intimately involved in depicting the Industrial Revolution and the scientific advances of the Enlightenment, but while his paintings were recognized as something out of the ordinary by his contemporaries, his provincial status and choice of subjects meant the style was never widely imitated. The picture has been owned by the National Gallery since 1863 and is still regarded as a masterpiece of British art. The painting depicts a natural philosopher, a forerunner of the modern scientist, recreating one of Robert Boyle's air pump experiments, in which a bird is deprived of oxygen, before a varied group of onlookers. The group exhibit different reactions, but for most scientific curiosity overcomes concern for the bird. The central figure looks out of the picture as if inviting the viewer's participation in the outcome.

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Discovery Expedition

The Discovery Expedition of 1901–1904 was the first official British exploration of the Antarctic regions since James Clark Ross's voyage sixty years earlier. Organised on a large scale under a joint committee of the Royal Society and the Royal Geographical Society, the new expedition aimed to carry out scientific research and geographical exploration in what was then largely an untouched continent. It launched the Antarctic careers of many who would become leading figures in the Heroic Age of Antarctic exploration including Robert Falcon Scott who led the expedition, Ernest Shackleton, Edward Wilson, Frank Wild, Tom Crean and William Lashly. Its scientific results covered extensive ground in biology, zoology, geology, meteorology and magnetism. There were important geological and zoological discoveries, including those of the snow-free McMurdo Dry Valleys and the Cape Crozier Emperor Penguin colony. In the field of geographical exploration, achievements included the discoveries of King Edward VII Land, and the Polar Plateau via the western mountains route. The expedition did not, however, make a serious attempt on the South Pole, its principal southern journey reaching a Furthest South at 82°17'S. As a trailbreaker for later ventures, the Discovery Expedition was a landmark in British Antarctic exploration history.

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Hanford Site

The Hanford Site is a decommissioned nuclear production complex on the Columbia River in south-central Washington operated by the United States government. Established in 1943 as part of the Manhattan Project, it was home to the B-Reactor, the first full-scale plutonium production reactor in the world. During the Cold War, the project was expanded to include nine nuclear reactors and five massive plutonium processing complexes, which produced plutonium for most of the 60,000 weapons in the U.S. nuclear arsenal. Nuclear technology developed rapidly during this period, and Hanford scientists produced many notable technological achievements. However, many of the early safety procedures and waste disposal practices were inadequate. Government documents have since confirmed that Hanford's operations released significant amounts of radioactive materials to the air and to the Columbia River, threatening the health of residents and ecosystems. Today, Hanford is the most contaminated nuclear site in the United States and is the focus of the nation's largest environmental cleanup effort. While most of the current activity at the site is related to the cleanup project, Hanford also hosts a commercial nuclear power plant, the Columbia Generating Station, and various centers for scientific research and development.

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history of biology

The history of biology traces the study of the living world from ancient to modern times. Although the concept of biology as a single coherent field arose in the 19th century, the biological sciences emerged from traditions of medicine and natural history reaching back to ancient Egyptian medicine and the works of Aristotle and Galen in the ancient Greco-Roman world, which were then further developed in the Middle Ages by Muslim physicians and scholars such as Avicenna. During the European Renaissance and early modern period, biological thought was revolutionized in Europe by a renewed interest in empiricism and the discovery of many novel organisms. Prominent in this movement were Vesalius and Harvey, who used experimentation and careful observation in physiology, and naturalists such as Linnaeus and Buffon who began to classify the diversity of life and the fossil record, as well as the development and behavior of organisms. Over the 18th and 19th centuries, biological sciences such as botany and zoology became increasingly professional scientific disciplines. Naturalists began to reject essentialism and reconsider the importance of extinction and the mutability of species. Cell theory provided a new perspective on the fundamental basis of life. These developments, as well as the results were synthesized in Charles Darwin's theory of evolution by natural selection.

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A battleship firing her main battery

A battleship is a large, heavily armored warship with a main battery consisting of the largest calibre of guns. Battleships were larger, better armed, and better armored than cruisers and destroyers. Battleship design continually evolved to incorporate and adapt technological advances to maintain an edge. The word battleship was coined around 1794 and is a shortened form of line-of-battle ship, the dominant wooden warship during the Age of Sail. The term came into formal use in the late 1880s to describe a type of ironclad warship, now referred to as pre-dreadnought battleships. In 1906, the launch of HMS Dreadnought heralded a revolution in battleship design. Following battleship designs that were influenced by the HMS Dreadnought were referred to as "dreadnoughts". Battleships were a potent symbol of naval dominance and national might, and for decades the battleship was a major factor in both diplomacy and military strategy. The global arms race in battleship construction in the early 20th century was one of the causes of World War I, which saw a clash of huge battle fleets at the Battle of Jutland. The Naval Treaties of the 1920s and 1930s limited the number of battleships but did not end the evolution of design. Both the Allies and the Axis Powers deployed battleships of old construction and new during World War II.

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Science and technology of the Han Dynasty

The Han dynasty (206 BCE – 220 CE) of ancient China, divided between the eras of Western Han (206 BCE – 9 CE, when the capital was at Chang'an), Xin dynasty of Wang Mang (r. 9–23 CE), and Eastern Han (25–220 CE, when the capital was at Luoyang, and after 196 CE at Xuchang), witnessed some of the most significant advancements in premodern Chinese science and technology. There were great innovations in metallurgy. In addition to Zhou-dynasty China's (c. 1050 BCE – 256 BCE) previous inventions of the blast furnace and cupola furnace to make pig iron and cast iron, respectively, the Han period saw the development of steel and wrought iron by use of the finery forge and puddling process. With the drilling of deep boreholes into the earth, the Chinese used not only derricks to lift brine up to the surface to be boiled into salt, but also set up bamboo-crafted pipeline transport systems which brought natural gas as fuel to the furnaces. Smelting techniques were enhanced with inventions such as the waterwheel-powered bellows; the resulting widespread distribution of iron tools facilitated the growth of agriculture. For tilling the soil and planting straight rows of crops, the improved heavy-moldboard plough with three iron plowshares and sturdy multiple-tube iron seed drill were invented in the Han, which greatly enhanced production yields and thus sustained population growth. The method of supplying irrigation ditches with water was improved with the invention of the mechanical chain pump powered by the rotation of a waterwheel or draft animals, which could transport irrigation water up elevated terrains. The waterwheel was also used for operating trip hammers in pounding grain and in rotating the metal rings of the mechanical-driven astronomical armillary sphere representing the celestial sphere around the Earth.

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history of Mars observation

The recorded history of Mars observation dates back to the era of the ancient Egyptian astronomers in the 2nd millennium BCE. Detailed observations of the position of Mars were made by Babylonian astronomers, and ancient Greek philosophers and Hellenistic astronomers developed a geocentric model to explain the planet's motions. Indian and Muslim astronomers estimated its size and distance from Earth. The first telescopic observation of Mars was by Galileo Galilei in 1610. The first crude map of Mars was published in 1840. When astronomers mistakenly thought they had detected the spectroscopic signature of water in the Martian atmosphere, the idea of life on Mars became popular. During the 1920s, the range of Martian surface temperature was measured; it ranged from −85 °C (−121 °F) to 7 °C (45 °F). The planetary atmosphere was found to be arid with only trace amounts of oxygen and water. Since the 1960s, multiple robotic spacecraft have been sent to explore Mars. The planet has remained under observation by ground and space-based instruments and the discovery of meteorites on Earth that originated on Mars has allowed laboratory examination of the chemical conditions on the planet.

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history of timekeeping devices

The history of timekeeping devices begins thousands of years ago with the invention of the sexagesimal system of time measurement in approximately 2000 BC, in Sumer. 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. Other ancient timekeeping devices include the candle clock, used in China, Japan, England, and Iraq; the timestick, used in India and Tibet, as well as some parts of Europe; and the hourglass, which functioned similarly to a water clock. The first clock with an escapement, which transferred rotational energy into discrete motions, appeared in China in the 8th century, and Muslim engineers invented weight-driven clocks in the 11th century. Mechanical clocks were introduced to Europe at the turn of the 14th century, and became the standard timekeeping device until the 20th century. During the 20th century, quartz oscillators were invented, followed by atomic clocks. Atomic clocks are far more accurate than any previous timekeeping device, and are used to calibrate other clocks and to calculate the proper time on Earth; a standardized civil system, Coordinated Universal Time, is based on atomic time.

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Manhattan Project

The Manhattan Project was a research and development program by the United States with the United Kingdom and Canada that produced the first atomic bomb during World War II. From 1942 to 1946, the project was under the direction of Major General Leslie Groves of the US Army Corps of Engineers. The Army component of the project was designated the Manhattan District; "Manhattan" gradually superseded the official codename, "Development of Substitute Materials", for the entire project. Along the way, the Manhattan Project absorbed its earlier British counterpart, Tube Alloys. Reactors were constructed at Hanford, Washington, in which uranium was irradiated and transmuted into plutonium. The plutonium was then chemically separated from the uranium. The gun-type design proved impractical to use with plutonium so a more complex implosion-type weapon was developed in a concerted design and construction effort at the project's weapons research and design laboratory in Los Alamos, New Mexico. The first nuclear device ever detonated was an implosion-type bomb at the Trinity test, conducted at New Mexico's Alamogordo Bombing and Gunnery Range on 16 July 1945. Little Boy, a gun-type weapon, and the implosion-type Fat Man were used in the atomic bombings of Hiroshima and Nagasaki, respectively.

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Voltage doubler

A voltage doubler is an electronic circuit which charges capacitors from the input voltage and switches these charges in such a way that, in the ideal case, exactly twice the voltage is produced at the output as at its input. The simplest of these circuits are a form of rectifier which take an AC voltage as input and output a doubled DC voltage. The switching elements are simple diodes and they are driven to switch state merely by the alternating voltage of the input. DC to DC voltage doublers cannot switch in this way and require a driving circuit to control the switching. They frequently also require a switching element that can be controlled directly, such as a transistor, rather than relying on the voltage across the switch as in the simple AC to DC case. Voltage doublers are a variety of voltage multiplier circuit. Many (but not all) voltage doubler circuits can be viewed as a single stage of a higher order multiplier: cascading identical stages together achieves a greater voltage multiplication.

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OS X (/ˌ ɛs ˈtɛn/), previously Mac OS X, is a series of Unix-based graphical interface operating systems developed, marketed, and sold by Apple Inc. It is designed to run exclusively on Mac computers, having been pre-loaded on all Macs since 2002. It was the successor to Mac OS 9, released in 1999, the final release of the "classic" Mac OS, which had been Apple's primary operating system since 1984. The first version released was Mac OS X Server 1.0 in 1999, and a desktop version, Mac OS X v10.0 "Cheetah" followed on March 24, 2001. Releases of OS X are named after big cats: for example, OS X v10.8 is referred to as "Mountain Lion". OS X, whose X is the Roman numeral for 10 and is a prominent part of its brand identity, is built on technologies developed at NeXT between the second half of the 1980s and Apple's purchase of the company in late 1996. The 'X' is also used to emphasize the relatedness between OS X and UNIX. Versions 10.5 "Leopard" running on Intel processors, 10.6 "Snow Leopard", and 10.8 "Mountain Lion" have obtained UNIX 03 certification. iOS, which runs on the iPhone, iPod Touch, iPad, and the 2nd and 3rd generation Apple TV, shares the Darwin core and many frameworks with OS X. An unnamed variant of v10.4 powered the first generation Apple TV.

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YouTube headquarters in San Bruno

YouTube is a video sharing website where users can upload, view and share video clips. YouTube was created in mid-February 2005 by three former PayPal employees. The San Bruno-based service uses Adobe Flash technology to display a wide variety of video content, including movie clips, TV clips and music videos, as well as amateur content such as videoblogging and short original videos. In October 2006, Google Inc. announced that it had reached a deal to acquire the company for US$1.65 billion in Google stock. The deal closed on November 13, 2006. Unregistered users can watch most videos on the site, while registered users are permitted to upload an unlimited number of videos. Some videos are available only to users of age 18 or older (e.g. videos containing potentially offensive content). The uploading of pornography or videos containing nudity is prohibited. Related videos, determined by title and tags, appear onscreen to the right of a given video. In YouTube's second year, functions were added to enhance user ability to post video 'responses' and subscribe to content feeds. Few statistics are publicly available regarding the number of videos on YouTube. However, in July 2006 the company revealed that more than 100 million videos were being watched every day, and 2.5 billion videos were watched in June 2006.

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Google Inc. is an American multinational corporation that provides Internet-related products and services, including internet search, cloud computing, software and advertising technologies. Advertising revenues from AdWords generate almost all of the company's profits. The company was founded by Larry Page and Sergey Brin while both attended Stanford University. Together, Brin and Page own about 16 percent of the company's stake. Google was first incorporated as a privately held company on September 4, 1998, and its initial public offering followed on August 19, 2004. The company's mission statement from the outset was "to organize the world's information and make it universally accessible and useful" and the company's unofficial slogan is "Don't be evil". In 2006, the company moved to its current headquarters in Mountain View, California.

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"Free speech flag" protesting suppression of the HD-DVD encryption key

The AACS encryption key controversy, also known as the AACS cryptographic key controversy, arose in April 2007 when the Motion Picture Association of America and the Advanced Access Content System Licensing Administrator, LLC (AACS LA) began issuing demand letters to websites publishing a 128-bit number, represented in hexadecimal as 09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0 (commonly referred to as 09 F9), which is one of the cryptographic keys for HD DVDs and Blu-ray Discs. The letters demanded the immediate removal of the key and any links to it, citing the anti-circumvention provisions of the U.S. Digital Millennium Copyright Act (DMCA). In response to widespread internet postings of the key, the AACS LA issued various press statements, praising those websites that complied with their requests as acting in a "responsible manner", warning that "legal and technical tools" were adapting to the situation. The controversy was further escalated in early May 2007, when aggregate news site Digg received a DMCA cease and desist notice and then removed numerous articles on the matter and banned users reposting the information. This sparked what some describe as a digital revolt, or "cyber-riot", in which users posted and spread the key throughout the internet en masse. The AACS LA described this situation as an "interesting new twist".

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Wikimania, annual conference for users of Wikipedia and other Wikimedia projects

Wikipedia is a multilingual, open content, free encyclopedia project operated by the non-profit Wikimedia Foundation. Its name is a portmanteau of the words wiki (a type of collaborative website) and encyclopedia. Launched in 2001, it is the largest, fastest growing and most popular general reference work currently available on the Internet. As of December 2007, Wikipedia had approximately 9 ¼ million articles in 253 languages, comprising a combined total of over 1.41 billion words for all Wikipedias. The English Wikipedia edition passed the 2,000,000 article mark on September 9, 2007. Wikipedia's articles have been written collaboratively by volunteers around the world and the vast majority of them can be edited by anyone with access to the Internet. Critics have questioned Wikipedia's reliability and accuracy, citing its open nature. The criticism is centered on its susceptibility to vandalism, such as the insertion of profanities or random letters into articles, and the addition of spurious or unverified information; uneven quality, systemic bias and inconsistencies; and for favoring consensus over credentials in its editorial process. Scholarly work suggests that vandalism is generally short-lived. When Time Magazine recognized "You" as their Person of the Year 2006, Wikipedia was the first particular "Web 2.0" service mentioned, followed by YouTube and MySpace.

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Talbot effect

The Talbot effect is a near-field diffraction effect first observed in 1836 by Henry Fox Talbot. When a plane wave is incident upon a periodic diffraction grating, the image of the grating is repeated at regular distances away from the grating plane. The regular distance is called the Talbot length, and the repeated images are called self images or Talbot images. Furthermore, at half the Talbot length, a self image also occurs, but phase-shifted by half a period (the physical meaning of this is that it is laterally shifted by half the width of the grating period). At smaller regular fractions of the Talbot length, sub-images can also be observed. At one quarter of the Talbot length, the self image is halved in size, and appears with half the period of the grating (thus twice as many images are seen). At one eighth of the Talbot length, the period and size of the images is halved again, and so forth creating a fractal pattern of sub images with ever decreasing size, often referred to as a Talbot carpet.

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The iLoo (short for Internet loo) was a cancelled Microsoft project to develop a Wi-Fi Internet-enabled portable toilet. The iLoo, which was to debut at British summer festivals, was described as being a portable toilet with wireless broadband Internet, an adjustable plasma screen, a membrane wireless keyboard, a six-channel speaker system, and toilet paper embossed with popular web site addresses. The iLoo was also to have an extra screen and keyboard on the outside, and was to be guarded. It was intended as the next in a series of successful initiatives by MSN UK which sought to introduce the internet in unusual locations, including MSN Street, MSN Park Bench and MSN Deckchair.

The project was announced by MSN UK on April 30, 2003, and was widely ridiculed before being declared a hoax by Microsoft on May 12. On May 13, another Microsoft press release stated that although the project had not been a hoax, it had been cancelled because it would do little to promote the MSN brand. There has since been speculation as to whether the project was cancelled for fear of being sued by Andrew Cubitt, who had invented the similarly named product "i-Loo". The iLoo was described as a public relations "debacle" by Online Journalism Review.

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Injection molding

Injection molding (British English: moulding) is a manufacturing process for producing parts by injecting material into a mold. Injection molding can be performed with a host of materials, including metals, glasses, elastomers, confections, and most commonly thermoplastic and thermosetting polymers. Material for the part is fed into a heated barrel, mixed, and forced into a mold cavity where it cools and hardens to the configuration of the cavity. After a product is designed, usually by an industrial designer or an engineer, molds are made by a moldmaker (or toolmaker) from metal, usually either steel or aluminum, and precision-machined to form the features of the desired part. Injection molding is widely used for manufacturing a variety of parts, from the smallest component to entire body panels of cars. Parts to be injection molded must be very carefully designed to facilitate the molding process; the material used for the part, the desired shape and features of the part, the material of the mold, and the properties of the molding machine must all be taken into account. The versatility of injection molding is facilitated by this breadth of design considerations and possibilities.

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The Huolongjing (traditional Chinese: 火龍經; simplified Chinese: 火龙经; pinyin: Huǒ Lóng Jīng; Wade-Giles: Huo Lung Ching; rendered by its translator into English as Fire Drake Manual; in modern English, Fire Dragon Manual) is a 14th century military treatise that was compiled and edited by Jiao Yu and Liu Bowen of the early Ming Dynasty (1368–1644 AD) in China. It outlined the use of various 'fire–weapons' involving the use of gunpowder. The Huolongjing provided information for various gunpowder compositions, including 'magic gunpowder', 'poison gunpowder', or 'blinding and burning gunpowder'. It had descriptions of the Chinese hollow cast iron grenade bomb, shrapnel bombs, and bombs with poisonous concoctions. The book had descriptions of the 10th century Chinese fire arrow, a simple wooden arrow with a spherical soft casing attached to the arrow and filled with gunpowder, ignited by a fuse so that it was propelled forward (and provided a light explosion upon impact). However, the book explained how this simple 'fire arrow' evolved into the metal-tube launched rocket. The book provided descriptions of various rocket launchers that launched tons of rockets at a time, the advent of the two stage rocket having a booster rocket igniting a swarm of smaller ones that were shot from the mouth of a missile shaped like a dragon, and even fin–mounted winged rockets. The book described the use of explosive land mines and descriptions of explosive naval mines at sea and on the river; this incorporated the use of a complex trigger mechanism of falling weights, pins, and a steel wheel lock to ignite the train of fuses. The book described various proto–guns including the fire lance (a short-burst flame-thrower that emitted a charge of shrapnel), multiple metal barrel handguns (with up to ten barrels), and descriptions of handguns with possible serpentine locks, used as components in matchlock firearms. The book provided descriptions of the early bombard and cannon, including the use of hollow gunpowder–packed exploding cannonballs, cannon barrels filled with metal balls containing poisonous gunpowder solutions, and cannons that were mounted on wheeled carriages so that they could be rotated in all directions.

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Minneapolis wireless internet network

The city of Minneapolis, Minnesota is covered by a citywide broadband wireless internet network, sometimes called Wireless Minneapolis. The network was first proposed in 2003, at which point only a few other cities nationwide had such systems in place. Local firm US Internet beat out EarthLink to build and operate the network, with a guaranteed ten-year, multi-million-dollar contract from the city itself as the network's anchor tenant. Construction began on the project in 2006, but encountered several delays. Most of the city was covered by the network by 2010, and USI Wireless, the subsidiary of US Internet responsible for the system, set up numerous free internet access points at public locations around Minneapolis. The network, which offers speeds of one to six megabits per second at a rate of about $20 per month, has about 20,000 residential subscribers and is on track to reach 30,000 subscribers by 2013. Municipally, the network is used by city inspectors and employees, with plans in place for the police and fire departments to use it in the future. In 2007, when the I-35W Mississippi River bridge collapsed, the wireless system helped coordinate rescuers and emergency services. The city and USI Wireless have won praise for the network, which has been singled out for being one of the few successful municipal wireless ventures nationwide among a number of stalled or failed projects.

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The National Aeronautics and Space Administration (NASA) is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research. Since February 2006, NASA's mission statement has been to "pioneer the future in space exploration, scientific discovery and aeronautics research." President Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, replacing its predecessor, the National Advisory Committee for Aeronautics (NACA). The agency became operational on October 1, 1958. Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency's astronauts farther into space than ever before and provide the cornerstone for future human space exploration efforts by the U.S. NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate's Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories and associated programs. NASA shares data with various national and international organizations such as from the Greenhouse Gases Observing Satellite.

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2009 North Korean nuclear test

The 2009 North Korean nuclear test was the underground detonation of a nuclear device conducted on 25 May 2009 by the Democratic People's Republic of Korea. This was its second nuclear test, the first test having taken place in October 2006. Following the nuclear test, Pyongyang also conducted several missile tests. The test was nearly universally condemned by the international community. Following the test, the United Nations Security Council passed Resolution 1874 condemning the test and tightening sanctions on the country. It is widely believed that the test was conducted as a result of a succession crisis in the country. After Kim Jong-Il suffered a stroke in the summer of 2008, arrangements were made for his third son, Kim Jong-un, to take power upon his death. It is believed the North Koreans conducted the nuclear test to show that, even in a time of possible weakness, it did not intend to give up its nuclear weapons program.

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Air well (condenser)

An air well or aerial well is a structure or device that collects water by promoting the condensation of moisture from air.[1] Designs for air wells are many and varied, but the simplest designs are completely passive, require no external energy source and have few, if any, moving parts. Three principal designs are used for air wells: high mass, radiative and active. High-mass air wells were used in the early 20th century, but the approach failed.[2] From the late 20th century onwards, low-mass, radiative collectors proved to be much more successful.[2] Active collectors collect water in the same way as a dehumidifier; although the designs work well, they require an energy source, making them uneconomical except in special circumstances.

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Avro Canada VZ-9 Avrocar

The Avro Canada VZ-9 Avrocar was a VTOL aircraft developed by Avro Aircraft Ltd. (Canada) as part of a secret U.S. military project carried out in the early years of the Cold War. The Avrocar intended to exploit the Coandă effect to provide lift and thrust from a single "turborotor" blowing exhaust out the rim of the disk-shaped aircraft to provide anticipated VTOL-like performance. In the air, it would have resembled a flying saucer. Originally designed as a fighter-like aircraft capable of very high speeds and altitudes, the project was repeatedly scaled back over time and the U.S. Air Force eventually abandoned it. Development was then taken up by the U.S. Army for a tactical combat aircraft requirement, a sort of high-performance helicopter. In flight testing, the Avrocar proved to have unresolved thrust and stability problems that limited it to a degraded, low-performance flight envelope; subsequently, the project was cancelled in September 1961. Through the history of the program, the project was referred to by a number of different names. Avro referred to the efforts as Project Y, with individual vehicles known as Spade and Omega. Project Y-2 was later funded by the U.S. Air Force, who referred to it as WS-606A, Project 1794 and Project Silver Bug. When the U.S. Army joined the efforts it took on its final name "Avrocar", and the designation "VZ-9", part of the U.S. Army's VTOL projects in the VZ series.

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Fabyan Windmill

The Fabyan Windmill is an authentic, working Dutch windmill dating from the 1850s located in Kane County, Illinois, just north of Batavia, Illinois, off Illinois Route 25. The five-story wooden smock mill with a stage, which stands 68 feet (21 m) tall, sits upon the onetime estate of Colonel George Fabyan, but is now part of the Kane County Forest Preserve District. In 1979, the windmill was listed on the National Register of Historic Places. The following year, the windmill was selected to be on a U.S. postage stamp, as part of a series of five windmills in a stamp booklet called "Windmills USA." It originally operated as a custom grinding mill.

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The iconic Flatiron Building, New York, shortly after its construction in 1903

The early skyscrapers were a range of tall, commercial buildings built between 1884 and 1939, predominantly in the American cities of New York City and Chicago. Cities in the United States were traditionally made up of low-rise buildings, but significant economic growth after the Civil War and increasingly intensive use of urban land encouraged the development of taller buildings beginning in the 1870s. Technological improvements enabled the construction of fireproofed iron-framed structures with deep foundations, equipped with new inventions such as the elevator and electric lighting. These made it both technically and commercially viable to build a new class of taller buildings, the first of which, Chicago's 138-foot (42 m) tall Home Insurance Building, opened in 1884. Their numbers grew rapidly and by 1888 they were being labelled skyscrapers. Chicago initially led the way in skyscraper design, with many constructed in the center of the financial district during the late 1880s and early 1890s. Sometimes termed the products of the Chicago school of architecture, these skyscrapers attempted to balance aesthetic concerns with practical commercial design, producing large, square palazzo-styled buildings hosting shops and restaurants on the ground level and containing rentable offices on the upper floors. In contrast, New York's skyscrapers were frequently narrower towers which, more eclectic in style, were often criticised for their lack of elegance. In 1892, Chicago banned the construction of new skyscrapers taller than 150 feet (46 m), leaving the development of taller buildings to New York. The first decade of the 20th century saw a new wave of skyscraper construction. The demand for new office space to hold America's expanding workforce of white-collar staff continued to grow. Engineering developments made it easier to build and live in yet taller buildings. Chicago built new skyscrapers in its existing style, while New York experimented further with tower design. Iconic buildings such as the Flatiron were followed by the 612-foot (187 m) tall Singer Tower, the 700-foot (210 m) Metropolitan Life Insurance Company Tower and the 792-foot (241 m) Woolworth Building. Though these skyscrapers were commercial successes, criticism mounted as they broke up the ordered city skyline and plunged neighboring streets and buildings into perpetual shadow. Combined with an economic downturn, this led to the introduction of zoning restraints in New York in 1916.

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Adding articles

  1. ^ Popular Science 1933.
  2. ^ a b Beysens et al. 2006.