A fan is a powered machine used to create flow within a fluid a gas such as air. A fan consists of a rotating arrangement of blades which act on the air; the rotating assembly of blades and hub is known as a rotor, or a runner. It is contained within some form of housing or case; this may direct the increase safety by preventing objects from contacting the fan blades. Most fans are powered by electric motors, but other sources of power may be used, including hydraulic motors, internal combustion engines, solar power. Mechanically, a fan can be vanes used for producing currents of air. Fans produce air flows with high volume and low pressure, as opposed to compressors which produce high pressures at a comparatively low volume. A fan blade will rotate when exposed to an air fluid stream, devices that take advantage of this, such as anemometers and wind turbines have designs similar to that of a fan. Typical applications include climate control and personal thermal comfort, vehicle engine cooling systems, machinery cooling systems, fume extraction, removing dust, drying and to provide draft for a fire.
While fans are used to cool people, they do not cool air, but work by evaporative cooling of sweat and increased heat convection into the surrounding air due to the airflow from the fans. Thus, fans may become ineffective at cooling the body if the surrounding air is near body temperature and contains high humidity. During periods of high heat and humidity, governments advise against the use of fans; the punkah fan was used in India about 500 BCE. It was a handheld fan made from bamboo strips or other plant fibre, that could be rotated or fanned to move air. During British rule, the word came to be used by Anglo-Indians to mean a large swinging flat fan, fixed to the ceiling, pulled by a servant called the punkawallah. For purposes of air conditioning, the Han Dynasty craftsman and engineer Ding Huan invented a manually operated rotary fan with seven wheels that measured 3 m in diameter. In the 17th century, the experiments of scientists including Otto von Guericke, Robert Hooke and Robert Boyle, established the basic principles of vacuum and airflow.
The English architect Sir Christopher Wren applied an early ventilation system in the Houses of Parliament that used bellows to circulate air. Wren's design would be the catalyst for much improvement and innovation; the first rotary fan used in Europe was for mine ventilation during the 16th century, as illustrated by Georg Agricola. John Theophilus Desaguliers, a British engineer, demonstrated a successful use of a fan system to draw out stagnant air from coal mines in 1727 and soon afterwards he installed a similar apparatus in Parliament. Good ventilation was important in coal mines to reduce casualties from asphyxiation; the civil engineer John Smeaton, John Buddle installed reciprocating air pumps in the mines in the North of England. However, this arrangement was not ideal. With the advent of practical steam power, fans could be used for ventilation. In 1837 William Fourness of England installed a steam-driven fan at Leeds. In 1849 a 6 m radius steam driven fan, designed by William Brunton, was made operational in the Gelly Gaer Colliery of South Wales.
The model was exhibited at the Great Exhibition of 1851. In 1851 David Boswell Reid, a Scottish doctor, installed four steam powered fans in the ceiling of St George's Hospital in Liverpool, so that the pressure produced by the fans would force the incoming air upward and through vents in the ceiling. Improvements in the technology were made by James Nasmyth, Frenchman Theophile Guibal and J. R. Waddle. Between 1882 and 1886 Schuyler Wheeler invented a fan powered by electricity, it was commercially marketed by the American firm Curtis electric motor company. In 1882, Philip Diehl developed the world's first electric ceiling fan. During this intense period of innovation, fans powered by alcohol, oil, or kerosene were common around the turn of the 20th century. In 1909, KDK of Japan pioneered the invention of mass-produced electric fans for home use. In the 1920s, industrial advances allowed steel fans to be mass-produced in different shapes, bringing fan prices down and allowing more homeowners to afford them.
In the 1930s, the first art deco fan was designed. By the 1940s, Crompton Greaves of India became the world's largest manufacturer of electric ceiling fans for sale in India and the Middle East. By the 1950s, table and stand fans were manufactured in eye catching. Window and central air conditioning in the 1960s caused many companies to discontinue production of fans, but in the mid 1970s, with an increasing awareness of the cost of electricity and the amount of energy used to heat and cool homes, turn-of-the-century styled ceiling fans became immensely popular again as both decorative and energy efficient units. In 1998, Walter K. Boyd invented the HVLS ceiling fan. A lifelong inventor, Boyd was charged with developing a system to cool dairy cattle. Dairy cattle, when over
Singer Corporation is an American manufacturer of sewing machines, first established as I. M. Singer & Co. in 1851 by Isaac Merritt Singer with New York lawyer Edward Clark. Best known for its sewing machines, it was renamed Singer Manufacturing Company in 1865 The Singer Company in 1963, it is based in La Vergne, near Nashville. Its first large factory for mass production was built in Elizabeth, New Jersey, in 1863. Singer's original design, the first practical sewing machine for general domestic use, incorporated the basic eye-pointed needle and lock stitch developed by Elias Howe, who won a patent-infringement suit against Singer in 1854. Patent No. 8294, of August 12, 1851, introduced one of the most useful machines, one of the most remarkable men, that have figured in the development of the sewing machine. Isaac Merritt Singer, strolling player, theater manager and millionaire, brought into the business a new machine and novel methods of exploitation, which gave a powerful impulse to the youthful industry.
The Singer improvements met the demand of the tailoring, leather industries for a heavier and more powerful machine. Singer consolidated enough patents in the field to enable him to engage in mass production, by 1860, his company was the largest manufacturer of sewing machines in the world. In 1885, Singer produced its first "vibrating shuttle" sewing machine, an improvement over contemporary transverse shuttle designs. Singer began to market its machines internationally in 1855 and won first prize at the Paris World's Fair; the company demonstrated the first workable electric sewing machine at the Philadelphia electric exhibition in 1889 and began mass-producing domestic electric machines in 1910. Singer was a marketing innovator and was a pioneer in promoting the use of installment payment plans. By 1876, Singer was claiming cumulative sales of two million machines and displaying the two millionth in Philadelphia. In 1867, the Singer Company decided that the demand for their sewing machines in the UK was sufficiently high to open a local factory in Glasgow on John Street.
Glasgow was selected for its iron making industries, cheap labour and because at the time the General Manager of the US Singer Manufacturing Company was George McKenzie, of Scottish descent. Demand for sewing machines outstripped production at the new plant and by 1873, a new larger factory was completed on James Street, Bridgeton. By now, Singer employed over 2,000 people in Scotland, but they still could not produce enough machines. In 1882, George McKenzie, now President-elect of the Singer Manufacturing Company, undertook the ground breaking ceremony on 46 acres of farmland at Kilbowie, Clydebank. Two main buildings were constructed, each 800-foot long, 50-foot wide and three storeys high; these were connected by three wings. Built above the middle wing was a 200-foot tall clock tower with the "Singer" name displayed for all to see for miles around. A total of 2.75 miles of railway lines were laid throughout the factory to connect the different departments such as the boiler room, foundry and the lines to main railway stations.
Sir Robert McAlpine was the building contractor and the factory was designed to be fire proof with water sprinklers, making it the most modern factory in Europe at that time. With nearly a million square feet of space and 7,000 employees, it was possible to produce on average 13,000 machines a week, making it the largest sewing machine factory in the world; the Clydebank factory was so productive that in 1905, the US Singer Company set up the Singer Manufacturing Company Ltd. as a UK registered company. Demand continued to exceed production, so each building was extended upwards to 6 storeys high. In the First World War, sewing machine production gave way to munitions; the Singer Clydebank factory received over 5000 government contracts, made 303 million artillery shells, shell components and aeroplane parts, as well as grenades, rifle parts, 361,000 horseshoes. Its labour force of 14,000 was about 70% female at war's end. From its opening in 1884 until 1943, the Kilbowie factory produced 36,000,000 sewing machines.
Singer sold more machines than all the other makers added together. In 1913, the factory shipped 1.3 million machines. The late 1950s and 1960s saw a period of significant change at the Clydebank factory. In 1958, Singer reduced production at their main American plant and transferred 40% of this production to the Clydebank factory in a bid to reduce costs. Between 1961 and 1964, the Clydebank factory underwent a £4 million modernization program which saw the Clydebank factory cease the production of cast iron machines and focus on the production of aluminium machines for western markets; as part of this modernisation programme, the famous Singer Clock was demolished in 1963. At the height of its productiveness in the mid 1960s, Singer employed over 16,000 workers but by the end of that decade, compulsory redundancies were taking place and 10 years the workforce was down to 5,000. Financial problems and lack of orders forced the world's largest sewing machine factory to close in June 1980, bringing to an end over 100 years of sewing machine production in Scotland.
The complex of buildings was demolished in 1998. Singer returned in developing sewing machines in 1946, they introduced its first sewing machine with zigzag function in the Slant-o-Matic. 2011 marked their 160th anniversary. They manufacture computerized, heavy duty, quilting and mechanical sewing machines. In 2017, they launched their new Singer Sewing Assistant App; the Singer sewing machine was the first complex standardized technology to be mass marketed
Philadelphia, sometimes known colloquially as Philly, is the largest city in the U. S. state and Commonwealth of Pennsylvania, the sixth-most populous U. S. city, with a 2017 census-estimated population of 1,580,863. Since 1854, the city has been coterminous with Philadelphia County, the most populous county in Pennsylvania and the urban core of the eighth-largest U. S. metropolitan statistical area, with over 6 million residents as of 2017. Philadelphia is the economic and cultural anchor of the greater Delaware Valley, located along the lower Delaware and Schuylkill Rivers, within the Northeast megalopolis; the Delaware Valley's population of 7.2 million ranks it as the eighth-largest combined statistical area in the United States. William Penn, an English Quaker, founded the city in 1682 to serve as capital of the Pennsylvania Colony. Philadelphia played an instrumental role in the American Revolution as a meeting place for the Founding Fathers of the United States, who signed the Declaration of Independence in 1776 at the Second Continental Congress, the Constitution at the Philadelphia Convention of 1787.
Several other key events occurred in Philadelphia during the Revolutionary War including the First Continental Congress, the preservation of the Liberty Bell, the Battle of Germantown, the Siege of Fort Mifflin. Philadelphia was one of the nation's capitals during the revolution, served as temporary U. S. capital while Washington, D. C. was under construction. In the 19th century, Philadelphia became a railroad hub; the city grew from an influx of European immigrants, most of whom came from Ireland and Germany—the three largest reported ancestry groups in the city as of 2015. In the early 20th century, Philadelphia became a prime destination for African Americans during the Great Migration after the Civil War, as well as Puerto Ricans; the city's population doubled from one million to two million people between 1890 and 1950. The Philadelphia area's many universities and colleges make it a top study destination, as the city has evolved into an educational and economic hub. According to the Bureau of Economic Analysis, the Philadelphia area had a gross domestic product of US$445 billion in 2017, the eighth-largest metropolitan economy in the United States.
Philadelphia is the center of economic activity in Pennsylvania and is home to five Fortune 1000 companies. The Philadelphia skyline is expanding, with a market of 81,900 commercial properties in 2016, including several nationally prominent skyscrapers. Philadelphia has more outdoor murals than any other American city. Fairmount Park, when combined with the adjacent Wissahickon Valley Park in the same watershed, is one of the largest contiguous urban park areas in the United States; the city is known for its arts, culture and colonial history, attracting 42 million domestic tourists in 2016 who spent US$6.8 billion, generating an estimated $11 billion in total economic impact in the city and surrounding four counties of Pennsylvania. Philadelphia has emerged as a biotechnology hub. Philadelphia is the birthplace of the United States Marine Corps, is the home of many U. S. firsts, including the first library, medical school, national capital, stock exchange and business school. Philadelphia contains 67 National Historic Landmarks and the World Heritage Site of Independence Hall.
The city became a member of the Organization of World Heritage Cities in 2015, as the first World Heritage City in the United States. Although Philadelphia is undergoing gentrification, the city maintains mitigation strategies to minimize displacement of homeowners in gentrifying neighborhoods. Before Europeans arrived, the Philadelphia area was home to the Lenape Indians in the village of Shackamaxon; the Lenape are a Native American tribe and First Nations band government. They are called Delaware Indians, their historical territory was along the Delaware River watershed, western Long Island, the Lower Hudson Valley. Most Lenape were pushed out of their Delaware homeland during the 18th century by expanding European colonies, exacerbated by losses from intertribal conflicts. Lenape communities were weakened by newly introduced diseases smallpox, violent conflict with Europeans. Iroquois people fought the Lenape. Surviving Lenape moved west into the upper Ohio River basin; the American Revolutionary War and United States' independence pushed them further west.
In the 1860s, the United States government sent most Lenape remaining in the eastern United States to the Indian Territory under the Indian removal policy. In the 21st century, most Lenape reside in Oklahoma, with some communities living in Wisconsin, in their traditional homelands. Europeans came to the Delaware Valley in the early 17th century, with the first settlements founded by the Dutch, who in 1623 built Fort Nassau on the Delaware River opposite the Schuylkill River in what is now Brooklawn, New Jersey; the Dutch considered the entire Delaware River valley to be part of their New Netherland colony. In 1638, Swedish settlers led by renegade Dutch established the colony of New Sweden at Fort Christina and spread out in the valley. In 1644, New Sweden supported the Susquehannocks in their military defeat of the English colony of Maryland. In 1648, the Dutch built Fort Beversreede on the west bank of the Delaware, south of the Schuylkill near the present-day Eastwick neighborhood, to reassert their dominion over the area.
The Swedes responded by building Fort Nya Korsholm, or New Korsholm, named after a town in Finland with a Swedish majority. In 1655, a
The Franklin Institute is a science museum and the center of science education and research in Philadelphia, Pennsylvania. It is named after the American scientist and statesman, Benjamin Franklin, houses the Benjamin Franklin National Memorial. Founded in 1824, the Franklin Institute is one of the oldest centers of science education and development in the United States. On February 5, 1824, Samuel Vaughan Merrick and William H. Keating founded the Franklin Institute of the State of Pennsylvania for the Promotion of the Mechanic Arts. "…With a view further to develop the resources of the union, increase the national independence, call forth the ingenuity and industry of the people, thereby increase the comforts of the community at large. Franklin Institute, opening day 1924, Begun in 1825, the Institute was an important force in the professionalization of American science and technology through the nineteenth century, beginning with early investigations into steam engines and water power. In addition to conducting scientific inquiry it fostered research and education by running schools, publishing the influential Journal of The Franklin Institute, sponsoring exhibitions, recognizing scientific advancement and invention with medals and awards.
In the late twentieth century the Institute's research roles gave way to educating the general public through its museum. The Bartol Research Foundation of the Franklin Institute, founded in 1924 to conduct research in the physical sciences, is now part of the University of Delaware; the Franklin Institute Laboratories for Research and Development operated from the Second World War into the 1980s. Many scientists have demonstrated groundbreaking new technology at the Franklin Institute. From September 2 to October 11, 1884, it hosted the International Electrical Exhibition of 1884, the first great electrical exposition in the United States; the world's first public demonstration of an all-electronic television system was given by Philo Taylor Farnsworth on August 25, 1934. The first female member, Elizabeth Skinner, was elected to membership in 1833; the Franklin Institute was integrated in 1870, when Philadelphia teacher and activist Octavius Catto was admitted as a member. The Institute's original building at 15 South 7th Street, now the home of the Atwater Kent Museum proved too small for the Institute's research, educational programs, library.
The Institute moved into its current home on the Benjamin Franklin Parkway, near the intersection with 20th Street, in 1934. The new facility was intended from the start to educate visitors through hand-on interactions with exhibits: "Visitors to this museum would be encouraged to touch and operate the exhibits in order to learn how things work." Funds to build the new Institute and Franklin Memorial came from the Poor Richard Club, the City Board of Trust, the Benjamin Franklin Memorial, Inc. and the Franklin Institute. John T. Windrim's original design was a square building surrounding the Benjamin Franklin Statue, which had yet to be built. Despite the effects of the Great Depression, the Benjamin Franklin Memorial, Inc. raised $5 million between December 1929 and June 1930. Only two of the four wings envisioned by Windrim were built. On March 31, 1940, press agent William Castellini issued a press release stating that the world would end the next day; the story was picked up by KYW, which reported, "Your worst fears that the world will end are confirmed by astronomers of Franklin Institute, Philadelphia.
Scientists predict. This is no April Fool joke. Confirmation can be obtained from Wagner Schlesinger, director of the Fels Planetarium of this city." This caused a panic in the city which only subsided when the Franklin Institute assured people it had made no such prediction. Castellini was dismissed shortly thereafter. On December 21, 2017, during a party hosted by the museum, a partygoer with his companions slipped into a closed-off exhibit of ten terracotta warriors on loan from China. After his companions left, the partygoer stole a thumb from one of the warriors. Law enforcement agents recovered the stolen thumb; the vandalized cavalryman is valued at 4.5 million USD, is considered a "priceless part of China's cultural heritage". The vandalism stoked outrage in Chinese media such as Xinhua; the Franklin Institute blamed its external security contractor, stated it has reviewed its security measures and procedures to prevent such situations from recurring. James Ronaldson Samuel V. Merrick John C.
Cresson William Sellers John Vaughan Merrick Coleman Sellers Robert Empie Rogers William Penn Tatham Joseph Miller Wilson Dr. Walton Clark Dr. W. Laurence LePage Dr. Athelstan F. Spilhaus Dr. Bowen C. Dees Dr. Joel N. Bloom Dr. James L. Powell Dr. Dennis M. Wint Larry Dubinski Donald Morel William J. Avery Marsha R. Perelman James A. Unruh In 2006, the Franklin Institute began fundraising activities for the Inspire Science! capital campaign, a $64.7 million campaign intended to fund the construction of a 53,000 square foot building addition, new exhibits, upgrades and renovations to the existing Institute building and exhibits. In 2011, the Franklin Institute received a $10 million gift from Athena and Nicholas Karabots towards the Inspire Science! capital campaign. This gift is the largest gift in the Institute's history, put the Franklin Institute within $6 million of the $64
The United States of America known as the United States or America, is a country composed of 50 states, a federal district, five major self-governing territories, various possessions. At 3.8 million square miles, the United States is the world's third or fourth largest country by total area and is smaller than the entire continent of Europe's 3.9 million square miles. With a population of over 327 million people, the U. S. is the third most populous country. The capital is Washington, D. C. and the largest city by population is New York City. Forty-eight states and the capital's federal district are contiguous in North America between Canada and Mexico; the State of Alaska is in the northwest corner of North America, bordered by Canada to the east and across the Bering Strait from Russia to the west. The State of Hawaii is an archipelago in the mid-Pacific Ocean; the U. S. territories are scattered about the Pacific Ocean and the Caribbean Sea, stretching across nine official time zones. The diverse geography and wildlife of the United States make it one of the world's 17 megadiverse countries.
Paleo-Indians migrated from Siberia to the North American mainland at least 12,000 years ago. European colonization began in the 16th century; the United States emerged from the thirteen British colonies established along the East Coast. Numerous disputes between Great Britain and the colonies following the French and Indian War led to the American Revolution, which began in 1775, the subsequent Declaration of Independence in 1776; the war ended in 1783 with the United States becoming the first country to gain independence from a European power. The current constitution was adopted in 1788, with the first ten amendments, collectively named the Bill of Rights, being ratified in 1791 to guarantee many fundamental civil liberties; the United States embarked on a vigorous expansion across North America throughout the 19th century, acquiring new territories, displacing Native American tribes, admitting new states until it spanned the continent by 1848. During the second half of the 19th century, the Civil War led to the abolition of slavery.
By the end of the century, the United States had extended into the Pacific Ocean, its economy, driven in large part by the Industrial Revolution, began to soar. The Spanish–American War and World War I confirmed the country's status as a global military power; the United States emerged from World War II as a global superpower, the first country to develop nuclear weapons, the only country to use them in warfare, a permanent member of the United Nations Security Council. Sweeping civil rights legislation, notably the Civil Rights Act of 1964, the Voting Rights Act of 1965 and the Fair Housing Act of 1968, outlawed discrimination based on race or color. During the Cold War, the United States and the Soviet Union competed in the Space Race, culminating with the 1969 U. S. Moon landing; the end of the Cold War and the collapse of the Soviet Union in 1991 left the United States as the world's sole superpower. The United States is the world's oldest surviving federation, it is a representative democracy.
The United States is a founding member of the United Nations, World Bank, International Monetary Fund, Organization of American States, other international organizations. The United States is a developed country, with the world's largest economy by nominal GDP and second-largest economy by PPP, accounting for a quarter of global GDP; the U. S. economy is post-industrial, characterized by the dominance of services and knowledge-based activities, although the manufacturing sector remains the second-largest in the world. The United States is the world's largest importer and the second largest exporter of goods, by value. Although its population is only 4.3% of the world total, the U. S. holds 31% of the total wealth in the world, the largest share of global wealth concentrated in a single country. Despite wide income and wealth disparities, the United States continues to rank high in measures of socioeconomic performance, including average wage, human development, per capita GDP, worker productivity.
The United States is the foremost military power in the world, making up a third of global military spending, is a leading political and scientific force internationally. In 1507, the German cartographer Martin Waldseemüller produced a world map on which he named the lands of the Western Hemisphere America in honor of the Italian explorer and cartographer Amerigo Vespucci; the first documentary evidence of the phrase "United States of America" is from a letter dated January 2, 1776, written by Stephen Moylan, Esq. to George Washington's aide-de-camp and Muster-Master General of the Continental Army, Lt. Col. Joseph Reed. Moylan expressed his wish to go "with full and ample powers from the United States of America to Spain" to seek assistance in the revolutionary war effort; the first known publication of the phrase "United States of America" was in an anonymous essay in The Virginia Gazette newspaper in Williamsburg, Virginia, on April 6, 1776. The second draft of the Articles of Confederation, prepared by John Dickinson and completed by June 17, 1776, at the latest, declared "The name of this Confederation shall be the'United States of America'".
The final version of the Articles sent to the states for ratification in late 1777 contains the sentence "The Stile of this Confederacy shall be'The United States of America'". In June 1776, Thomas Jefferson wrote the phrase "UNITED STATES OF AMERICA" in all capitalized letters in the headline of his "original Rough draught" of the Declaration of Independence; this draft of the document did not surface unti
Engineers, as practitioners of engineering, are professionals who invent, analyze and test machines, systems and materials to fulfill objectives and requirements while considering the limitations imposed by practicality, regulation and cost. The word engineer is derived from the Latin words ingenium; the foundational qualifications of an engineer include a four-year bachelor's degree in an engineering discipline, or in some jurisdictions, a master's degree in an engineering discipline plus four to six years of peer-reviewed professional practice and passage of engineering board examinations. The work of engineers forms the link between scientific discoveries and their subsequent applications to human and business needs and quality of life. In 1961, the Conference of Engineering Societies of Western Europe and the United States of America defined "professional engineer" as follows: A professional engineer is competent by virtue of his/her fundamental education and training to apply the scientific method and outlook to the analysis and solution of engineering problems.
He/she is able to assume personal responsibility for the development and application of engineering science and knowledge, notably in research, construction, superintending, managing and in the education of the engineer. His/her work is predominantly intellectual and varied and not of a routine mental or physical character, it requires the exercise of original thought and judgement and the ability to supervise the technical and administrative work of others. His/her education will have been such as to make him/her capable of and continuously following progress in his/her branch of engineering science by consulting newly published works on a worldwide basis, assimilating such information and applying it independently. He/she is thus placed in a position to make contributions to the development of engineering science or its applications. His/her education and training will have been such that he/she will have acquired a broad and general appreciation of the engineering sciences as well as thorough insight into the special features of his/her own branch.
In due time he/she will be able to give authoritative technical advice and to assume responsibility for the direction of important tasks in his/her branch. Engineers develop new technological solutions. During the engineering design process, the responsibilities of the engineer may include defining problems and narrowing research, analyzing criteria and analyzing solutions, making decisions. Much of an engineer's time is spent on researching, locating and transferring information. Indeed, research suggests engineers spend 56% of their time engaged in various information behaviours, including 14% searching for information. Engineers must weigh different design choices on their merits and choose the solution that best matches the requirements and needs, their crucial and unique task is to identify and interpret the constraints on a design in order to produce a successful result. Engineers apply techniques of engineering analysis in production, or maintenance. Analytical engineers may supervise production in factories and elsewhere, determine the causes of a process failure, test output to maintain quality.
They estimate the time and cost required to complete projects. Supervisory engineers are responsible for entire projects. Engineering analysis involves the application of scientific analytic principles and processes to reveal the properties and state of the system, device or mechanism under study. Engineering analysis proceeds by separating the engineering design into the mechanisms of operation or failure, analyzing or estimating each component of the operation or failure mechanism in isolation, recombining the components, they may analyze risk. Many engineers use computers to produce and analyze designs, to simulate and test how a machine, structure, or system operates, to generate specifications for parts, to monitor the quality of products, to control the efficiency of processes. Most engineers specialize in one or more engineering disciplines. Numerous specialties are recognized by professional societies, each of the major branches of engineering has numerous subdivisions. Civil engineering, for example, includes structural and transportation engineering and materials engineering include ceramic and polymer engineering.
Mechanical engineering cuts across just about every discipline since its core essence is applied physics. Engineers may specialize in one industry, such as motor vehicles, or in one type of technology, such as turbines or semiconductor materials. Several recent studies have investigated. Research suggests that there are several key themes present in engineers' work: technical work, social work, computer-based work and information behaviours. Among other more detailed findings, a recent work sampling study found that engineers spend 62.92% of their time engaged in technical work, 40.37% in social work, 49.66% in computer-based work. Furthermore, there was considerable overlap between these different types of work, with engineers spending 24.96% of their time engaged in technical and social work, 37.97% in technical and non-social, 15.42% in non-technical and social, 21.66% in non-technical and non-social. Engineering is an information-intensive field, with research finding that engineers spend 55
An electric light is a device that produces visible light from electric current. It is the most common form of artificial lighting and is essential to modern society, providing interior lighting for buildings and exterior light for evening and nighttime activities. In technical usage, a replaceable component that produces light from electricity is called a lamp. Lamps are called light bulbs. Lamps have a base made of ceramic, glass or plastic, which secures the lamp in the socket of a light fixture; the electrical connection to the socket may be made with a screw-thread base, two metal pins, two metal caps or a bayonet cap. The three main categories of electric lights are incandescent lamps, which produce light by a filament heated white-hot by electric current, gas-discharge lamps, which produce light by means of an electric arc through a gas, LED lamps, which produce light by a flow of electrons across a band gap in a semiconductor. Before electric lighting became common in the early 20th century, people used candles, gas lights, oil lamps, fires.
English chemist Humphry Davy developed the first incandescent light in 1802, followed by the first practical electric arc light in 1806. By the 1870s, Davy's arc lamp had been commercialized, was used to light many public spaces. Efforts by Swan and Edison led to commercial incandescent light bulbs becoming available in the 1880s, by the early twentieth century these had replaced arc lamps; the energy efficiency of electric lighting has increased radically since the first demonstration of arc lamps and the incandescent light bulb of the 19th century. Modern electric light sources come in a profusion of types and sizes adapted to many applications. Most modern electric lighting is powered by centrally generated electric power, but lighting may be powered by mobile or standby electric generators or battery systems. Battery-powered light is reserved for when and where stationary lights fail in the form of flashlights, electric lanterns, in vehicles. Types of electric lighting include: Incandescent light bulb, a heated filament inside a glass envelope Halogen lamps are incandescent lamps that use a fused quartz envelope filled with halogen gas LED lamp, a solid-state lamp that uses light-emitting diodes as the source of light Arc lamp Xenon arc lamp Mercury-xenon arc lamp Ultra-high-performance lamp, an ultra-high-pressure mercury-vapor arc lamp for use in movie projectors Metal-halide lamp Gas-discharge lamp, a light source that generates light by sending an electric discharge through an ionized gas Fluorescent lamp Compact fluorescent lamp, a fluorescent lamp designed to replace an incandescent lamp Neon lamp Mercury-vapor lamp Sodium-vapor lamp Sulfur lamp Electrodeless lamp, a gas discharge lamp in which the power is transferred from outside the bulb to inside via electromagnetic fieldsDifferent types of lights have vastly differing efficacies and color of light.
*Color temperature is defined as the temperature of a black body emitting a similar spectrum. The most efficient source of electric light is the low-pressure sodium lamp, it produces, for all practical purposes, a monochromatic orange-yellow light, which gives a monochromatic perception of any illuminated scene. For this reason, it is reserved for outdoor public lighting applications. Low-pressure sodium lights are favoured for public lighting by astronomers, since the light pollution that they generate can be filtered, contrary to broadband or continuous spectra; the modern incandescent light bulb, with a coiled filament of tungsten, commercialized in the 1920s, developed from the carbon filament lamp introduced about 1880. As well as bulbs for normal illumination, there is a wide range, including low voltage, low-power types used as components in equipment, but now displaced by LEDs Incandescent bulbs are being phased out in many countries due to their low energy efficiency. Less than 3% of the input energy is converted into usable light.
Nearly all of the input energy ends up as heat that, in warm climates, must be removed from the building by ventilation or air conditioning resulting in more energy consumption. In colder climates where heating and lighting is required during the cold and dark winter months, the heat byproduct has at least some value. Halogen lamps are much smaller than standard incandescent lamps, because for successful operation a bulb temperature over 200 °C is necessary. For this reason, most have a bulb of fused aluminosilicate glass; this is sealed inside an additional layer of glass. The outer glass is a safety precaution, to reduce ultraviolet emission and to contain hot glass shards should the inner envelope explode during operation. Oily residue from fingerprints may cause a hot quartz envelope to shatter due to excessive heat buildup at the contamination site; the risk of burns or fire is greater with bare bulbs, leading to their prohibition in some places, unless enclosed by the luminaire. Those designed for 12- or 24-volt operation have compact filaments, useful for good optical control.
They have higher efficacies and better lives than non-halogen types. The light output remains constant throughout their life. Fluorescent lamps consist of a glass tube that contains argon under low pressure. Electricity flowing through the tube causes the gases to give off ultraviolet energy; the inside of the tubes are coated with phosphors that give off visible light when struck by ultraviolet photons. They have much higher efficiency than incandescent lamps. For the same amount of light generated, they typic