Etymology.

The name "Manchester" originates from the Latin name "Mamucium" or its variant "Mancunio" and the citizens are still referred to as Mancunians (). These names are generally thought to represent a Latinisation of an original Brittonic name. The generally accepted etymology of this name is that

History.

Early history.

The Brigantes were the major Celtic tribe in what is now known as Northern England; they had a stronghold in the locality at a sandstone outcrop on which Manchester Cathedral now stands, opposite the bank River Irwell. Their territory extended across the fertile lowland of what is now Salford and Stretford. Following the Roman conquest of Britain in the 1st century, General Agricola ordered the construction of a fort named Mamucium in the year 79 to ensure that Roman interests in Deva Victrix (Chester) and Eboracum (York) were protected from the Brigantes. Central Manchester has been permanently settled since

Industrial Revolution.

Manchester's history is concerned with textile manufacture during the Industrial Revolution. The great majority of cotton spinning took place in the towns of south Lancashire and north Cheshire, and Manchester was for a time the most productive centre of cotton processing.  Manchester became known as the world's largest marketplace for cotton goods and was dubbed "Cottonopolis" and "Warehouse City" during the Victorian era. In Australia, New Zealand and South Africa, the term "manchester" is still used for household linen: sheets, pillow cases, towels, etc. The industrial revolution brought about huge change in Manchester and was key to the increase in Manchester's population.  Manchester began expanding "at an astonishing rate" around the turn of the 19th century as people flocked to the city for work from Scotland, Wales, Ireland and other areas of England as part of

Blitz.

Like most of the UK, the Manchester area was mobilised extensively during the Second World War. For example, casting and machining expertise at Beyer, Peacock and Company's locomotive works in Gorton was switched to bomb making; Dunlop's rubber works in Chorlton-on-Medlock made barrage balloons; and just outside the city in Trafford Park, engineers Metropolitan-Vickers made Avro Manchester and Avro Lancaster bombers and Ford built the

Post-Second World War.

Cotton processing and trading continued to fall in peacetime, and the exchange closed in 1968. By 1963 the port of Manchester was the UK's third largest, and employed over 3,000 men, but the canal was unable to handle the increasingly large container ships. Traffic declined, and the port closed in 1982. Heavy industry suffered a downturn from the 1960s and was greatly reduced under the economic policies followed by Margaret Thatcher's government after 1979. Manchester lost 150,000 jobs in manufacturing between 1961 and 1983. Regeneration began in the late 1980s, with initiatives such as the Metrolink, the Bridgewater Concert Hall, the Manchester

Since 2000.

Spurred by the investment after the 1996 bomb and aided by the XVII Commonwealth Games, the city centre has undergone extensive regeneration. New and renovated complexes such as The Printworks and Corn Exchange have become popular shopping, eating and entertainment areas. Manchester Arndale is the UK's largest city-centre shopping centre.  Large city sections from the 1960s have been demolished, re-developed or modernised with the use of glass and steel. Old mills have been converted into apartments. Hulme has undergone extensive regeneration, with million-pound loft-house apartments being developed. The 47-storey, Beetham Tower was the tallest UK building outside London and the highest residential accommodation in Europe when completed in 2006. It was surpassed in 2018 by the

Government.

The City of Manchester is governed by the Manchester City Council. The Greater Manchester Combined Authority, with a directly elected mayor, has responsibilities for economic strategy and transport, amongst other areas, on a Greater Manchester-wide basis. Manchester has been a member of the English Core Cities Group since its inception in 1995.  The town of Manchester was granted a charter by Thomas Grelley in 1301, but lost its borough status in a court case of 1359. Until the 19th century local government was largely in the hands of manorial courts, the last of which was dissolved in 1846.  From a very early time, the township of Manchester lay within the historic or ceremonial county boundaries of Lancashire. Pevsner wrote "That [neighbouring] Stretford and Salford are not administratively one with Manchester is one of the most curious anomalies of England". A stroke of a Norman baron's pen is said to have divorced Manchester and Salford, though it was not Salford that became separated from Manchester, it was Manchester, with its humbler line of lords, that was separated from Salford. It was this separation

Geography.

At, northwest of London, Manchester lies in a bowl-shaped land area bordered to the north and east by the Pennines, an upland chain that runs the length of northern England, and to the south by the Cheshire Plain. Manchester is north-east of Liverpool and north-west of Sheffield, making the city the halfway point between the two. The city centre is on the east bank of the River Irwell, near its confluences with the Rivers Medlock and Irk, and is relatively low-lying, being between above sea level. The River Mersey flows through the south of Manchester. Much of the inner city, especially in the south, is flat, offering extensive views from many highrise buildings in the city of the foothills and moors of the Pennines, which can often be capped with snow in the winter months. Manchester's geographic features were highly influential in its early development as the world's first industrial city. These features are its climate, its proximity to a seaport at Liverpool, the availability of water power from its rivers, and its nearby coal reserves.  The name Manchester, though officially applied only to the metropolitan district within Greater Manchester, has been applied to other, wider divisions of land, particularly across much of the Greater Manchester county and urban area. The "Manchester City Zone", "Manchester post town" and the "Manchester Congestion Charge" are all examples of this.  For purposes of the Office for National Statistics, Manchester forms the most populous settlement within the Greater Manchester Urban Area, the United Kingdom's third-largest conurbation. There is a mix of high-density urban and suburban locations. The largest open space in the city, at around, is Heaton Park. Manchester is contiguous on all sides with several large settlements, except for a small section along its southern boundary with Cheshire. The M60 and M56 motorways pass through Northenden and Wythenshawe respectively in the south of Manchester. Heavy rail lines enter the city from all directions, the principal destination being Manchester Piccadilly station.

Climate.

Manchester experiences a temperate oceanic climate (Köppen: "Cfb"), like much of the British Isles, with warm summers and cool winters. Summer daytime temperatures regularly top 20 Celsius, quite often reaching 25 Celsius on sunny days during July and August in particular. In more recent years, temperatures have occasionally reached over 30 Celsius. There is regular but generally light precipitation throughout the year. The city's average annual rainfall is compared to a UK average of, and its mean

Green belt.

Manchester lies at the centre of a green belt region extending into the wider surrounding counties. This reduces urban sprawl, prevents towns in the conurbation from further convergence, protects the identity of outlying communities, and preserves nearby countryside. It is achieved by restricting inappropriate development within the designated areas and

Demographics.

Below are the 10 largest foreign nationalities of Manchester in 2011.  Historically the population of Manchester began to increase rapidly during the Victorian era, estimated at 354,930 for Manchester and 110,833 for Salford in 1865, and peaking at 766,311 in 1931. From then the population began to decrease rapidly, due to slum clearance and the increased building of social housing overspill estates by Manchester City Council after the Second World War such as Hattersley and Langley.  The 2012 mid-year estimate for the population of Manchester was 510,700. This was an increase of 7,900, or 1.6 per cent, since the 2011 estimate. Since 2001, the population has grown by 87,900, or 20.8 per cent, making Manchester the third fastest-growing area in the 2011 census. The city experienced the greatest percentage population growth outside London, with an increase of 19 per cent to over 500,000. Manchester's population is projected to reach 532,200 by 2021, an increase of 5.8 per cent from 2011. This represents a slower rate of growth than the previous decade.  The Greater Manchester Built-up Area in 2011 had an estimated population of 2,553,400. In 2012 an estimated 2,702,200 people lived in Greater Manchester. An 6,547,000 people were estimated in 2012 to live within of Manchester and 11,694,000 within.  Between the beginning of July 2011 and end of June 2012 (mid-year estimate date), births exceeded deaths by 4,800. Migration (internal and international) and other changes accounted for a net increase of 3,100 people between July 2011 and June 2012. Compared with Greater Manchester and with England, Manchester has a younger population, with a particularly large 20–35 age group.  There were 76,095 undergraduate and postgraduate students at Manchester Metropolitan

Economy.

The Office for National Statistics does not produce economic data for the City of Manchester alone, but includes four other metropolitan boroughs, Salford, Stockport, Tameside, Trafford, in an area named Greater Manchester South, which had a GVA of £34.8 billion. The economy grew relatively strongly between 2002 and 2012, when growth was 2.3 per cent above the national average. The wider metropolitan economy is the second largest in the United Kingdom. It is ranked as a beta world city by the Globalization and World Cities Research Network.  As the UK economy continues to recover from its 2008–2010 downturn, Manchester compares favourably according to recent figures. In 2012 it showed the strongest annual growth in business stock (5 per cent) of all core cities. The city had a relatively sharp increase in the number of business deaths, the largest increase in all the core cities, but this was offset by strong growth in new businesses, resulting in strong net growth.  Manchester's civic leadership has a reputation for business acumen. It owns two of the country's four busiest airports and uses its earnings to fund local projects. Meanwhile, KPMG's competitive alternative report found that in 2012 Manchester had the 9th lowest tax cost of any industrialised city in the world, and fiscal devolution has come earlier to Manchester than to any other British city: it can keep half the extra taxes it gets from transport

Landmarks.

Manchester's buildings display a variety of architectural styles, ranging from Victorian to contemporary architecture. The widespread use of red brick characterises the city, much of the architecture of which harks back to its days as a global centre for the cotton trade. Just outside the immediate city centre are a large number of former cotton mills, some of which have been left virtually untouched since their closure, while many have been redeveloped as apartment buildings and office space. Manchester Town Hall, in Albert Square, was built in the Gothic revival style and is seen as one of the most important Victorian buildings in England.  Manchester also has a number of skyscrapers built in the 1960s and 1970s, the tallest being the CIS Tower near Manchester Victoria station until the Beetham Tower was completed in 2006. The latter exemplifies a new surge in high-rise building. It includes a Hilton hotel, a restaurant and apartments. The largest skyscraper is now Deansgate Square South Tower,

Transport.

Rail.

Manchester Liverpool Road was the world's first purpose-built passenger and goods railway station and served as the Manchester terminus on the Liverpool and Manchester Railway – the world's first inter-city passenger railway. It is still extant and its buildings form part of the Museum of Science and Industry.  Two of the city's four main line termini did not survive the 1960s: Manchester Central and Manchester Exchange each closed in 1969. In addition, Manchester Mayfield station closed to passenger services in 1960; its buildings and platforms are still extant, next to Piccadilly station, but are due to be redeveloped in the 2020s.  Today, the city is well served by its rail network although it is now working to capacity, and is at the centre of

Metrolink (tram).

Manchester became the first city in the UK to acquire a modern light rail tram system when the Manchester Metrolink opened in 1992. In 2016–2017, 37.8 million passenger journeys were made on the system.<ref name="16/17DfTstats"></ref> The present system

Bus.

The city has one of the most extensive bus networks outside London, with over 50 bus companies operating in the Greater Manchester region radiating from the city. In 2011, 80 per cent of public transport journeys in Greater Manchester were made by bus, amounting to 220 million passenger journeys each year. After deregulation in 1986, the bus system was

Air.

Manchester Airport serves Manchester, Northern England and North Wales. The airport is the third busiest in the United Kingdom and the largest outside the London region. Services cover many destinations in Europe, North America, the Caribbean, Africa, the Middle East, and Asia (with more destinations from Manchester than any other airport in Britain). A second runway was opened in 2001 and there have been continued terminal improvements. The airport has the highest rating available: ""Category 10"", encompassing an elite group of airports able to

Canal.

An extensive canal network, including the Manchester Ship Canal, was built to carry freight from the Industrial Revolution onward; the canals are still maintained,

Culture.

Music.

Bands that have emerged from the Manchester music scene include Van der Graaf Generator, Oasis, The Smiths, Joy Division and its successor group New Order, Buzzcocks, The Stone Roses, The Fall, The Durutti Column, 10cc, Godley & Creme, The Verve, Elbow, Doves, The Charlatans, M People, The 1975, Simply Red, Take That, Dutch Uncles, Everything Everything, Pale Waves and The Outfield. Manchester was credited as the main driving force behind British indie music of the 1980s led by The Smiths, later including The Stone Roses, Happy Mondays, Inspiral Carpets, and James. The later groups came from what became known as the "Madchester" scene that also centred on The Haçienda nightclub developed by the founder of Factory Records, Tony Wilson. Although from southern England, The Chemical Brothers subsequently formed in Manchester. Former Smiths frontman Morrissey, whose lyrics often refer to Manchester locations and culture, later found international success as a solo artist. Previously, notable Manchester acts of the 1960s include The Hollies, Herman's Hermits, and Davy Jones of the Monkees (famed in the

Performing arts.

Manchester has a thriving theatre, opera and dance scene, with a number of large performance venues, including Manchester Opera House, which feature large-scale touring shows and West End productions; the Palace Theatre; and the Royal Exchange Theatre in Manchester's former cotton exchange, which is the largest theatre in the round in the UK.  Smaller venues include the Contact Theatre and Z-arts in Hulme. The Dancehouse on Oxford Road is dedicated to dance productions. In 2014, HOME, a new custom-built arts complex

Museums and galleries.

Manchester's museums celebrate Manchester's Roman history, rich industrial heritage and its role in the Industrial Revolution, the textile industry, the Trade Union movement, women's suffrage and football. A reconstructed part of the Roman fort of Mamucium is open to the public in Castlefield. The Science and Industry Museum, housed in the former Liverpool Road railway station, has a large collection of steam locomotives, industrial machinery, aircraft and a replica of the world's first stored computer program (known as the Manchester Baby). The Museum of Transport displays a collection of historic buses and trams. Trafford Park in the neighbouring borough of Trafford is home to Imperial

Literature.

Manchester is a UNESCO City of Literature known for a "radical literary history". Manchester in the 19th century featured in works highlighting the changes that industrialisation had brought. They include Elizabeth Gaskell's novel "Mary Barton: A Tale of Manchester Life" (1848), and studies such as "The Condition of the Working Class in England in 1844" by Friedrich Engels, while living and working here. Manchester was the meeting place of Engels and Karl Marx. The two began writing "The Communist Manifesto" in Chetham's Library – founded in 1653 and claiming to be the oldest public library in the English-speaking world. Elsewhere in the city, the John Rylands Library holds an extensive collection of early printing. The Rylands Library Papyrus P52, believed to be the earliest extant New Testament text, is on permanent display there. Letitia Landon's poem "Manchester" in Fisher's Drawing Room Scrap Book, 1835, records the rapid growth of the city

Nightlife.

The night-time economy of Manchester has expanded significantly since about 1993, with investment from breweries in bars, public houses and clubs, along with active support from the local authorities. The more than 500 licensed premises in the city centre have a capacity to deal with more than visitors, with 110,000–130,000 people visiting on a typical weekend night, making Manchester the most popular city for events at 79 per thousand people. The night-time economy has a value of about £100 million. and supports 12,000 jobs.  The Madchester scene of the 1980s, from which groups including New Order, The Smiths, The Stone Roses, the Happy Mondays, Inspiral Carpets, 808 State, James

Gay Village.

Public houses in the Canal Street area have had an LGBTQ+ clientele since at least 1940, and now form the centre

Education.

There are three universities in the City of Manchester. The University of Manchester, Manchester Metropolitan University and Royal Northern College of Music. The University of Manchester is the largest full-time non-collegiate university in the United Kingdom, created in 2004 by the merger of Victoria University of Manchester, founded in 1904, and UMIST, founded in 1956 having developed from the Mechanics' Institute founded, as indicated in the university's logo, in 1824. The University of Manchester includes the Manchester Business School, which offered the first MBA course in the UK in 1965.  Manchester Metropolitan University was formed as Manchester Polytechnic on the merger of three colleges in 1970. It gained university status in 1992, and in the same year absorbed Crewe and Alsager College of Higher Education in South Cheshire. The University of Law, the largest provider of vocation legal training in Europe, has a campus in the city.  The three universities are grouped around Oxford Road on the southern side of the city centre, which forms Europe's largest urban higher-education precinct. Together they have a combined population of 76,025 students in higher education as of 2015, although

Sport.

Manchester is well known as a city of sport. Two decorated Premier League football clubs bear the city name – Manchester United and Manchester City. Manchester United play its home games at Old Trafford, in the Manchester suburb of Trafford, the largest club football ground in the United Kingdom. Manchester City's home ground is the City of Manchester Stadium (also known as the Etihad Stadium for sponsorship purposes); its former ground, Maine Road was demolished in 2003. The City of Manchester Stadium was initially built as the main athletics stadium for the 2002 Commonwealth Games and was then reconfigured into a football stadium before Manchester City's arrival. Manchester has hosted domestic, continental and international football competitions at Fallowfield Stadium, Maine Road, Old Trafford and the City of Manchester Stadium. Competitions hosted in city include the FIFA World Cup (1966), UEFA European Football Championship (1996), Olympic Football (2012), UEFA Champions League Final (2003), UEFA Cup Final (2008), four

Media.

The ITV franchise Granada Television is partly headquartered on the old Granada Studios site in Quay Street and partly at a new location at MediaCityUK as part of the initial phase of its migration to Salford Quays. It produces "Coronation Street," local news and programmes for North West England. Although its influence has waned, Granada had been described as "the best commercial television company in the world".  Manchester was one of the BBC's three main centres in England. Programmes including "Mastermind", and "Real Story", were made at New Broadcasting House. The "Cutting It" series set in the city's Northern Quarter and "The Street" were set in Manchester as was "Life on Mars". The first edition of "Top of the Pops" was broadcast from a studio in Rusholme on New Year's Day 1964. Manchester was the regional base for BBC One North West Region programmes before it relocated to MediaCityUK in nearby Salford Quays. The Manchester television channel, Channel M, owned by the Guardian Media Group operated from 2000, but closed in 2012. Manchester is also covered by two internet television channels: Quays News and Manchester.tv. The city had a new terrestrial channel from January 2014 when YourTV Manchester, which won the OFCOM licence bid in February 2013. It began its first broadcast, but in 2015, That's Manchester took over to air on 31 May and launched the freeview channel 8

International relations.

Manchester has formal twinning arrangements (or "friendship agreements") with several places. In addition, the British Council maintains a metropolitan centre in Manchester.  Manchester is home to the largest group of consuls in the UK outside London. The expansion of international trade links during the Industrial Revolution led to the introduction of the first consuls in the 1820s and since then over 800, from all parts of the world, have been based in Manchester. Manchester hosts consular services for most of the north of England.

Manchester () is a city and metropolitan borough in Greater Manchester, England. It is historically and traditionally a part of the county of Lancashire. It has a population of 547,627 as of 2018 (making it the fifth most populous English district). It lies within the United Kingdom's second-most populous urban area, with a population of 2.5 million and third most populous metropolitan area, with a population of 3.3 million. It is fringed by the Cheshire Plain to the south, the Pennines to the north and east, and an arc of towns with which it forms a continuous conurbation. The local authority for the city is Manchester City Council.

曼彻斯特(英语:Manchester),是英格兰西北区域大曼彻斯特郡的都市自治市。


Overview.

Pattern recognition is generally categorized according to the type of learning procedure used to generate the output value. "Supervised learning" assumes that a set of "training data" (the "training set") has been provided, consisting of a set of instances that have been properly labeled by hand with the correct output. A learning procedure then generates a "model" that attempts to meet two sometimes conflicting objectives: Perform as well as possible on the training data, and generalize as well as possible to new data (usually, this means being as simple as possible, for some technical definition of "simple", in accordance with Occam's Razor, discussed below). Unsupervised learning, on the other hand, assumes training data that has not been hand-labeled, and attempts to find inherent patterns in the data that can then be used to determine the correct output value for new data instances. A combination of the two that has recently been explored is semi-supervised learning, which uses a combination of labeled and unlabeled data (typically a small set of labeled data combined with a large amount of unlabeled data). Note that in cases of unsupervised learning, there may be no training data at all to speak of; in other words,and the data to be labeled "is" the training data.  Note that sometimes different terms are used to describe the corresponding supervised and unsupervised learning procedures for the same type of output. For example, the unsupervised equivalent of classification is normally known as "clustering", based on the common perception of the task as involving no training data to speak of, and of grouping the input data into "clusters" based on some inherent similarity measure (e.g. the distance between instances, considered as vectors in a multi-dimensional vector space), rather than assigning each input instance into one of a set of pre-defined classes. In some fields, the terminology is different: For example, in community ecology, the term "classification" is used to refer to what is commonly known as "clustering".  The piece of input data for which an output value is generated is formally termed an "instance". The instance is formally described by a vector of "features", which together constitute a description of all known characteristics of the instance. (These feature vectors can be seen as defining points in an appropriate multidimensional space, and methods for manipulating vectors in vector spaces can be correspondingly applied to them, such as computing the dot product or the angle between two vectors.) Typically, features are either categorical (also known as nominal, i.e., consisting of one of a set of unordered items, such as a gender of "male" or "female", or a blood type of "A", "B", "AB" or "O"), ordinal (consisting of one of a set of ordered items, e.g., "large", "medium" or "small"), integer-valued (e.g., a count of the number of occurrences of a particular word in an email) or real-valued (e.g., a measurement of blood pressure). Often, categorical and ordinal data are grouped together; likewise for integer-valued and real-valued data. Furthermore, many algorithms work only in terms of categorical data and require that real-valued or integer-valued data be "discretized" into groups (e.g., less than 5, between 5 and 10, or greater than 10).

Probabilistic classifiers.

Many common pattern recognition algorithms are "probabilistic" in nature, in that they use statistical inference to find the best label for a given instance. Unlike other algorithms, which simply output a "best" label, often probabilistic algorithms also output a probability of the instance being described by the given label. In addition, many probabilistic algorithms output a list of the "N"-best labels with associated probabilities, for some value of "N", instead of simply a single best label. When the number of possible labels is fairly small (e.g., in the case of classification), "N" may be set so that the probability of all possible labels is output. Probabilistic algorithms have many advantages over non-probabilistic algorithms:

Number of important feature variables.

Feature selection algorithms attempt to directly prune out redundant or irrelevant features. A general introduction to feature selection which summarizes approaches and challenges, has been given. The complexity of feature-selection is, because of its non-monotonous character, an optimization problem where given a total of formula_1 features the powerset consisting of all formula_2 subsets of features need to be explored. The Branch-and-Bound algorithm does reduce this complexity but is intractable for medium to large values of the number of available features formula_1. For a large-scale comparison of feature-selection algorithms see  Techniques to transform the raw feature vectors (feature extraction) are sometimes used prior to application of the pattern-matching algorithm. For example, feature extraction algorithms attempt to reduce a large-dimensionality feature vector into a smaller-dimensionality vector that is easier to work with and encodes less redundancy, using mathematical techniques such as principal components analysis (PCA). The distinction between feature selection and feature extraction is that the resulting features after feature extraction has taken place are of a different sort than the original features and may not easily be interpretable, while the features left after feature selection are simply a subset of the original features.

Problem statement (supervised version).

Formally, the problem of supervised pattern recognition can be stated as follows: Given an unknown function formula_4 (the "ground truth") that maps input instances formula_5 to output labels formula_6, along with training data formula_7 assumed to represent accurate examples of the mapping, produce a function formula_8 that approximates as closely as possible the correct mapping formula_9. (For example, if the problem is filtering spam, then formula_10 is some representation of an email and formula_11 is either "spam" or "non-spam"). In order for this to be a well-defined problem, "approximates as closely as possible" needs to be defined rigorously. In decision theory, this is defined by specifying a loss function or cost function that assigns a specific value to "loss" resulting from producing an incorrect label. The goal then is to minimize the expected loss, with the expectation taken over the probability distribution of formula_12. In practice, neither the distribution of formula_12 nor the ground truth function formula_4 are known exactly, but can be computed only empirically by collecting a large number of samples of formula_12 and hand-labeling them using the correct value of formula_16 (a time-consuming process, which is typically the limiting factor in the amount of data of this sort that can be collected). The particular loss function depends on the type of label being predicted. For example, in the case of classification, the simple zero-one loss function is often sufficient. This corresponds simply to assigning a loss of 1 to any incorrect labeling and implies that the optimal classifier minimizes the error rate on independent test data (i.e. counting up the fraction of instances that the learned function formula_8 labels wrongly, which is equivalent to maximizing the number of correctly classified instances). The goal of the learning procedure is then to minimize the error rate (maximize the correctness) on a "typical" test set.  For a probabilistic pattern recognizer, the problem is instead to estimate the probability of each possible output label given a particular input instance, i.e., to estimate a function of the form where the feature vector input is formula_19, and the function "f" is typically parameterized by some parameters formula_20. In a discriminative approach to the problem, "f" is estimated directly. In a generative approach, however, the inverse probability formula_21 is instead estimated and combined with the prior probability formula_22 using Bayes' rule, as follows:  When the labels are continuously distributed (e.g., in regression analysis), the denominator involves integration rather than summation:  The value of formula_25 is typically learned using maximum a posteriori (MAP) estimation. This finds the best value that simultaneously meets two conflicting objects: To perform as well as possible on the training data (smallest error-rate) and to find the simplest possible model. Essentially, this combines maximum likelihood estimation with a regularization procedure that favors simpler models over more complex models. In a Bayesian context, the regularization procedure can be viewed as placing a prior probability formula_26 on different values of formula_25. Mathematically:  where formula_29 is the value used for formula_25 in the subsequent evaluation procedure, and formula_31, the posterior probability of formula_25, is given by  In the Bayesian approach to this problem, instead of choosing a single parameter vector formula_34, the probability of a given label for a new instance formula_19 is computed by integrating over all possible values of formula_25, weighted according to the posterior probability:

Frequentist or Bayesian approach to pattern recognition.

The first pattern classifier – the linear discriminant presented by Fisher – was developed in the frequentist tradition. The frequentist approach entails that the model parameters are considered unknown, but objective. The parameters are then computed (estimated) from the collected data. For the linear discriminant, these parameters are precisely the mean vectors and the covariance matrix. Also the probability of each class formula_22 is estimated from the collected dataset. Note that the usage of 'Bayes rule' in a pattern classifier does not make the classification approach Bayesian.  Bayesian statistics has its origin in Greek philosophy where a distinction was already made between the 'a priori' and the 'a posteriori' knowledge. Later Kant defined his distinction between what is a priori known – before observation – and the empirical knowledge gained from observations. In a Bayesian pattern classifier, the class probabilities formula_22 can be chosen by the user, which are then a priori. Moreover, experience quantified as a priori parameter values can be weighted with empirical observations – using e.g., the Beta- (conjugate prior) and Dirichlet-distributions. The Bayesian approach facilitates a seamless intermixing between expert knowledge in the form of subjective probabilities, and objective observations.  Probabilistic pattern classifiers can be used according to a frequentist or a Bayesian approach.

Uses.

Within medical science, pattern recognition is the basis for computer-aided diagnosis (CAD) systems. CAD describes a procedure that supports the doctor's interpretations and findings. Other typical applications of pattern recognition techniques are automatic speech recognition, classification of text into several categories (e.g., spam/non-spam email messages), the automatic recognition of handwriting on postal envelopes, automatic recognition of images of human faces, or handwriting image extraction from medical forms. The last two examples form the subtopic image analysis of pattern recognition that deals with digital images as input to pattern recognition systems.  Optical character recognition is a classic example of the application of a pattern classifier, see OCR-example. The method of signing one's name was captured with stylus and overlay starting in 1990. The strokes, speed, relative min, relative max, acceleration and pressure is used to uniquely identify and confirm identity. Banks were first offered this technology, but were content to collect from the FDIC for any bank fraud and did not want to inconvenience customers.  Artificial neural networks (neural net classifiers) and deep learning have many real-world applications in image processing, a few examples:  For a discussion of the aforementioned applications of neural networks in image processing, see e.g.  In psychology, pattern recognition (making sense of and identifying objects) is closely related to perception, which explains how the sensory inputs humans receive are made meaningful. Pattern recognition can be thought of in two different ways: the first being template matching and the second being feature detection. A template is a pattern used to produce items of the same proportions. The template-matching hypothesis suggests that incoming stimuli are compared with templates in the long term memory. If there is a match, the stimulus is identified. Feature detection models, such as the Pandemonium system for classifying letters (Selfridge, 1959), suggest that the stimuli are broken down into their component parts for identification. For example, a capital E has three horizontal lines and one vertical line.

Algorithms.

Algorithms for pattern recognition depend on the type of label output, on whether learning is supervised or unsupervised, and on whether the algorithm is statistical or non-statistical in nature. Statistical algorithms can further be categorized as generative or discriminative.

Classification algorithms (supervised algorithms predicting categorical labels).

Parametric: Nonparametric:

Multilinear subspace learning algorithms (predicting labels of multidimensional data using tensor representations).

Unsupervised:

Real-valued sequence labeling algorithms (predicting sequences of real-valued labels).

Supervised (?):

Regression algorithms (predicting real-valued labels).

Supervised:  Unsupervised:

Sequence labeling algorithms (predicting sequences of categorical labels).

Supervised:  Unsupervised:

Pattern recognition is the automated recognition of patterns and regularities in data. It has applications in statistical data analysis, signal processing, image analysis, information retrieval, bioinformatics, data compression, computer graphics and machine learning. Pattern recognition has its origins in statistics and engineering; some modern approaches to pattern recognition include the use of machine learning, due to the increased availability of big data and a new abundance of processing power. However, these activities can be viewed as two facets of the same field of application, and together they have undergone substantial development over the past few decades. A modern definition of pattern recognition is: This article focuses on machine learning approaches to pattern recognition. Pattern recognition systems are in many cases trained from labeled "training" data (supervised learning), but when no labeled data are available other algorithms can be used to discover previously unknown patterns (unsupervised learning). Machine learning is strongly related to pattern recognition and originates from artificial intelligence. KDD and data mining have a larger focus on unsupervised methods and stronger connection to business use. Pattern recognition focuses more on the signal and also takes acquisition and Signal Processing into consideration. It originated in engineering, and the term is popular in the context of computer vision: a leading computer vision conference is named Conference on Computer Vision and Pattern Recognition. In pattern recognition, there may be a higher interest to formalize, explain and visualize the pattern, while machine learning traditionally focuses on maximizing the recognition rates. Yet, all of these domains have evolved substantially from their roots in artificial intelligence, engineering and statistics, and they've become increasingly similar by integrating developments and ideas from each other.

模式识别(英语:Pattern recognition),就是通过计算机用数学技术方法来研究模式的自动处理和判读。我们把环境与客体统称为“模式”。随着计算机技术的发展,人类有可能研究复杂的信息处理过程。信息处理过程的一个重要形式是生命体对环境及客体的识别。对人类来说,特别重要的是对光学信息(通过视觉器官来获得)和声学信息(通过听觉器官来获得)的识别。这是模式识别的两个重要方面。市场上可见到的代表性产品有光学字符识别、语音识别系统。


Terminology.

The word "engine" derives from Old French "engin", from the Latin "ingenium"–the root of the word "ingenious". Pre-industrial weapons of war, such as catapults, trebuchets and battering rams, were called "siege engines", and knowledge of how to construct them was often treated as a military secret. The word "gin", as in "cotton gin", is short for "engine". Most mechanical devices invented during the industrial revolution were described as engines—the steam engine being a notable example. However, the original steam engines, such as those by Thomas Savery, were not mechanical engines but pumps. In this manner, a fire engine in its original form was merely a water pump, with the engine being transported to the fire by horses.  In modern usage, the term "engine" typically describes devices, like steam engines and internal combustion engines, that burn or otherwise consume fuel to perform mechanical work by exerting a torque or linear force (usually in the form of thrust). Devices converting heat energy into motion are commonly referred to simply as "engines". Examples of engines which exert a torque include the familiar automobile gasoline and diesel engines, as well as turboshafts. Examples of engines which produce thrust include turbofans and rockets.  When the internal combustion engine was invented, the term "motor" was initially used to distinguish it from the steam engine—which was in wide use at the time, powering locomotives and other vehicles such as steam rollers. The term "motor" derives from the Latin verb "" which means to set in motion, or maintain motion. Thus a motor is a device that imparts motion.  "Motor" and "engine" are interchangeable in standard English. In some engineering jargons, the two words have different meanings, in which "engine" is a device that burns or otherwise consumes fuel, changing its chemical composition, and a motor is a device driven by electricity, air, or hydraulic pressure, which does not change the chemical composition of its energy source. However, rocketry uses the term rocket motor, even though they consume fuel.  A heat engine may also serve as a "prime mover"—a component that transforms the flow or changes in pressure of a fluid into mechanical energy. An automobile powered by an internal combustion engine may make use of various motors and pumps, but ultimately all such devices derive their power from the engine. Another way of looking at it is that a motor receives power from an external source, and then converts it into mechanical energy, while an engine creates power from pressure (derived directly from the explosive force of combustion or other chemical reaction, or secondarily from the action of some such force on other substances such as air, water, or steam).

History.

Antiquity.

Simple machines, such as the club and oar (examples of the lever), are prehistoric. More complex engines using human power, animal power, water power, wind power and even steam power date back to antiquity. Human power was focused by the use of simple engines, such as the capstan, windlass or treadmill, and with ropes, pulleys, and block and tackle arrangements; this power was transmitted usually with the forces multiplied and the speed reduced. These were used in cranes and aboard ships in Ancient Greece, as well as in mines, water pumps and siege engines in Ancient Rome. The writers of those times, including Vitruvius, Frontinus and Pliny the Elder, treat these engines as commonplace, so their invention may be more ancient. By the 1st century AD, cattle and horses were used in mills, driving machines similar to those powered by humans in earlier times.  According to Strabo, a water powered mill was built in Kaberia of the kingdom of Mithridates during the 1st century BC. Use of water wheels in mills spread throughout the Roman Empire over the next few centuries. Some were quite complex, with aqueducts, dams, and sluices to maintain and channel the water, along with systems of gears, or toothed-wheels made of wood and metal to regulate the speed of rotation. More sophisticated small devices, such as the Antikythera Mechanism used complex trains of gears and dials to act as calendars or predict astronomical events. In a poem by Ausonius in the 4th century AD, he mentions a stone-cutting saw powered by water. Hero of Alexandria is credited with many such wind and steam powered machines in the 1st century AD, including the Aeolipile and the vending machine, often these machines were associated with worship, such as animated altars and automated temple doors.

Medieval.

Medieval Muslim engineers employed gears in mills and water-raising machines, and used dams as a source of water power to provide additional power to watermills and water-raising machines. In the medieval Islamic world, such advances made it possible to mechanize many industrial tasks previously carried out by manual labour.  In 1206, al-Jazari employed a crank-conrod system for two of his water-raising machines. A rudimentary steam turbine device was described by Taqi al-Din in 1551 and by Giovanni Branca in 1629.  In the 13th century, the solid rocket motor was invented in China. Driven by gunpowder, this simplest form of internal combustion engine was unable to deliver sustained power, but was useful for propelling weaponry at high speeds towards enemies in battle and for fireworks. After invention, this innovation spread throughout Europe.

Industrial Revolution.

The Watt steam engine was the first type of steam engine to make use of steam at a pressure just above atmospheric to drive the piston helped by a partial vacuum. Improving on the design of the 1712 Newcomen steam engine, the Watt steam engine, developed sporadically from 1763 to 1775, was a great step in the development of the steam engine. Offering a dramatic increase in fuel efficiency, James Watt's design became synonymous with steam engines, due in no small part to his business partner, Matthew Boulton. It enabled rapid development of efficient semi-automated factories on a previously unimaginable scale in places where waterpower was not available. Later development led to steam locomotives and great expansion of railway transportation.  As for internal combustion piston engines, these were tested in France in 1807 by de Rivaz and independently, by the Niépce brothers. They were theoretically advanced by Carnot in 1824. In 1853–57 Eugenio Barsanti and Felice Matteucci invented and patented an engine using the free-piston principle that was possibly the first 4-cycle engine.  The invention of an internal combustion engine which was later commercially successful was made during 1860 by Etienne Lenoir.  In 1877 the Otto cycle was capable of giving a far higher power to weight ratio than steam engines and worked much better for many transportation applications such as cars and aircraft.

Automobiles.

The first commercially successful automobile, created by Karl Benz, added to the interest in light and powerful engines. The lightweight gasoline internal combustion engine, operating on a four-stroke Otto cycle, has been the most successful for light automobiles, while the more efficient Diesel engine is used for trucks and buses. However, in recent years, turbo Diesel engines have become increasingly popular, especially outside of the United States, even for quite small cars.

Horizontally opposed pistons.

In 1896, Karl Benz was granted a patent for his design of the first engine with horizontally opposed pistons. His design created an engine in which the corresponding pistons move in horizontal cylinders and reach top dead center simultaneously, thus automatically balancing each other with respect to their individual momentum. Engines of this design are often referred to as flat engines because of their shape and lower profile. They were used in the Volkswagen Beetle, the Citroën 2CV, some Porsche and Subaru cars, many BMW and Honda motorcycles, and propeller aircraft engines.

Advancement.

Continuance of the use of the internal combustion engine for automobiles is partly due to the improvement of engine control systems (onboard computers providing engine management processes, and electronically controlled fuel injection). Forced air induction by turbocharging and supercharging have increased power outputs and engine efficiencies. Similar changes have been applied to smaller diesel engines giving them almost the same power characteristics as gasoline engines. This is especially evident with the popularity of smaller diesel engine propelled cars in Europe. Larger diesel engines are still often used in trucks and heavy machinery, although they require special machining not available in most factories. Diesel engines produce lower hydrocarbon and emissions, but greater particulate and pollution, than gasoline engines. Diesel engines are also 40% more fuel efficient than comparable gasoline engines.

Increasing power.

In the first half of the 20th century, a trend of increasing engine power occurred, particularly in the U.S models. Design changes incorporated all known methods of increasing engine capacity, including increasing the pressure in the cylinders to improve efficiency, increasing the size of the engine, and increasing the rate at which the engine produces work. The higher forces and pressures created by these changes created engine vibration and size problems that led to stiffer, more compact engines with V and opposed cylinder layouts replacing longer straight-line arrangements.

Combustion efficiency.

The design principles favoured in Europe, because of economic and other restraints such as smaller and twistier roads, leant toward smaller cars and corresponding to the design principles that concentrated on increasing the combustion efficiency of smaller engines. This produced more economical engines with earlier four-cylinder designs rated at 40 horsepower (30 kW) and six-cylinder designs rated as low as 80 horsepower (60 kW), compared with the large volume V-8 American engines with power ratings in the range from 250 to 350 hp, some even over 400 hp (190 to 260 kW).

Engine configuration.

Earlier automobile engine development produced a much larger range of engines than is in common use today. Engines have ranged from 1- to 16-cylinder designs with corresponding differences in overall size, weight, engine displacement, and cylinder bores. Four cylinders and power ratings from 19 to 120 hp (14 to 90 kW) were followed in a majority of the models. Several three-cylinder, two-stroke-cycle models were built while most engines had straight or in-line cylinders. There were several V-type models and horizontally opposed two- and four-cylinder makes too. Overhead camshafts were frequently employed. The smaller engines were commonly air-cooled and located at the rear of the vehicle; compression ratios were relatively low. The 1970s and 1980s saw an increased interest in improved fuel economy, which caused a return to smaller V-6 and four-cylinder layouts, with as many as five valves per cylinder to improve efficiency. The Bugatti Veyron 16.4 operates with a W16 engine, meaning that two V8 cylinder layouts are positioned next to each other to create the W shape sharing the same crankshaft.  The largest internal combustion engine ever built is the Wärtsilä-Sulzer RTA96-C, a 14-cylinder, 2-stroke turbocharged diesel engine that was designed to power the "Emma Mærsk", the largest container ship in the world when launched in 2006. This engine has a mass of 2,300 tonnes, and when running at 102 RPM (1.7 Hz) produces over 80 MW, and can use up to 250 tonnes of fuel per day.

Types.

An engine can be put into a category according to two criteria: the form of energy it accepts in order to create motion, and the type of motion it outputs.

Heat engine.

Combustion engine.

Combustion engines are heat engines driven by the heat of a combustion process.

Internal combustion engine.

The "internal combustion engine" is an engine in which the combustion of a fuel (generally, fossil fuel) occurs with an oxidizer (usually air) in a combustion chamber. In an internal combustion engine the expansion of the high temperature and high pressure gases, which are produced by the combustion, directly applies force to components of the engine, such as the pistons or turbine blades or a nozzle, and by moving it over a distance, generates mechanical work.

External combustion engine.

An "external combustion engine" (EC engine) is a heat engine where an internal working fluid is heated by combustion of an external source, through the engine wall or a heat exchanger. The fluid then, by expanding and acting on the mechanism of the engine produces motion and usable work. The fluid is then cooled, compressed and reused (closed cycle), or (less commonly) dumped, and cool fluid pulled in (open cycle air engine).  "Combustion" refers to burning fuel with an oxidizer, to supply the heat. Engines of similar (or even identical) configuration and operation may use a supply of heat from other sources such as nuclear, solar, geothermal or exothermic reactions not involving combustion; but are not then strictly classed as external combustion engines, but as external thermal engines.  The working fluid can be a gas as in a Stirling engine, or steam as in a steam engine or an organic liquid such as n-pentane in an Organic Rankine cycle. The fluid can be of any composition; gas is by far the most common, although even single-phase liquid is sometimes used. In the case of the steam engine, the fluid changes phases between liquid and gas.

Air-breathing combustion engines.

"Air-breathing combustion engines" are combustion engines that use the oxygen in atmospheric air to oxidise ('burn') the fuel, rather than carrying an oxidiser, as in a rocket. Theoretically, this should result in a better specific impulse than for rocket engines.  A continuous stream of air flows through the air-breathing engine. This air is compressed, mixed with fuel, ignited and expelled as the exhaust gas.  Typical air-breathing engines include:

Environmental effects.

The operation of engines typically has a negative impact upon air quality and ambient sound levels. There has been a growing emphasis on the pollution producing features of automotive power systems. This has created new interest in alternate power sources and internal-combustion engine refinements. Though a few limited-production battery-powered electric vehicles have appeared, they have not proved competitive owing to costs and operating characteristics. In the 21st century the diesel engine has been increasing in popularity with automobile owners. However, the gasoline engine and the Diesel engine, with their new emission-control devices to improve emission performance, have not yet been significantly challenged. A number of manufacturers have introduced hybrid engines, mainly involving a small gasoline engine coupled with an electric motor and with a large battery bank, but these too have yet to make much of an inroad into the market shares of gasoline and Diesel engines.

Air quality.

Exhaust gas from a spark ignition engine consists of the following: nitrogen 70 to 75% (by volume), water vapor 10 to 12%, carbon dioxide 10 to 13.5%, hydrogen 0.5 to 2%, oxygen 0.2 to 2%, carbon monoxide: 0.1 to 6%, unburnt hydrocarbons and partial oxidation products (e.g. aldehydes) 0.5 to 1%, nitrogen monoxide 0.01 to 0.4%, nitrous oxide <100 ppm, sulfur dioxide 15 to 60 ppm, traces of other compounds such as fuel additives and lubricants, also halogen and metallic compounds, and other particles. Carbon monoxide is highly toxic, and can cause carbon monoxide poisoning, so it is important to avoid any build-up of the gas in a confined space. Catalytic converters can reduce toxic emissions, but not completely eliminate them. Also, resulting greenhouse gas emissions, chiefly carbon dioxide, from the widespread use of engines in the modern industrialized world is contributing to the global greenhouse effect – a primary concern regarding global warming.

Non-combusting heat engines.

Some engines convert heat from noncombustive processes into mechanical work, for example a nuclear power plant uses the heat from the nuclear reaction to produce steam and drive a steam engine, or a gas turbine in a rocket engine may be driven by decomposing hydrogen peroxide. Apart from the different energy source, the engine is often engineered much the same as an internal or external combustion engine. Another group of noncombustive engines includes thermoacoustic heat engines (sometimes called "TA engines") which are thermoacoustic devices which use high-amplitude sound waves to pump heat from one place to another, or conversely use a heat difference to induce high-amplitude sound waves. In general, thermoacoustic engines can be divided into standing wave and travelling wave devices.

Non-thermal chemically powered motor.

Non-thermal motors usually are powered by a chemical reaction, but are not heat engines. Examples include:

Electric motor.

An "electric motor" uses electrical energy to produce mechanical energy, usually through the interaction of magnetic fields and current-carrying conductors. The reverse process, producing electrical energy from mechanical energy, is accomplished by a generator or dynamo. Traction motors used on vehicles often perform both tasks. Electric motors can be run as generators and vice versa, although this is not always practical. Electric motors are ubiquitous, being found in applications as diverse as industrial fans, blowers and pumps, machine tools, household appliances, power tools, and disk drives. They may be powered by direct current (for example a battery powered portable device or motor vehicle), or by alternating current from a central electrical distribution grid. The smallest motors may be found in electric wristwatches. Medium-size motors of highly standardized dimensions and characteristics provide convenient mechanical power for industrial uses. The very largest electric motors are used for propulsion of large ships, and for such purposes as pipeline compressors, with ratings in the thousands of kilowatts. Electric motors may be classified by the source of electric power, by their internal construction, and by their application.  The physical principle of production of mechanical force by the interactions of an electric current and a magnetic field was known as early as 1821. Electric motors of increasing efficiency were constructed throughout the 19th century, but commercial exploitation of electric motors on a large scale required efficient electrical generators and electrical distribution networks.  To reduce the electric energy consumption from motors and their associated carbon footprints, various regulatory authorities in many countries have introduced and implemented legislation to encourage the manufacture and use of higher efficiency electric motors. A well-designed motor can convert over 90% of its input energy into useful power for decades. When the efficiency of a motor is raised by even a few percentage points, the savings, in kilowatt hours (and therefore in cost), are enormous. The electrical energy efficiency of a typical industrial induction motor can be improved by: 1) reducing the electrical losses in the stator windings (e.g., by increasing the cross-sectional area of the conductor, improving the winding technique, and using materials with higher electrical conductivities, such as copper), 2) reducing the electrical losses in the rotor coil or casting (e.g., by using materials with higher electrical conductivities, such as copper), 3) reducing magnetic losses by using better quality magnetic steel, 4) improving the aerodynamics of motors to reduce mechanical windage losses, 5) improving bearings to reduce friction losses, and 6) minimizing manufacturing tolerances. "For further discussion on this subject, see Premium efficiency.)"  By convention, "electric engine" refers to a railroad electric locomotive, rather than an electric motor.

Physically powered motor.

Some motors are powered by potential or kinetic energy, for example some funiculars, gravity plane and ropeway conveyors have used the energy from moving water or rocks, and some clocks have a weight that falls under gravity. Other forms of potential energy include compressed gases (such as pneumatic motors), springs (clockwork motors) and elastic bands.  Historic military siege engines included large catapults, trebuchets, and (to some extent) battering rams were powered by potential energy.

Pneumatic motor.

A "pneumatic motor" is a machine that converts potential energy in the form of compressed air into mechanical work. Pneumatic motors generally convert the compressed air to mechanical work through either linear or rotary motion. Linear motion can come from either a diaphragm or piston actuator, while rotary motion is supplied by either a vane type air motor or piston air motor. Pneumatic motors have found widespread success in the hand-held tool industry and continual attempts are being made to expand their use to the transportation industry. However, pneumatic motors must overcome efficiency deficiencies before being seen as a viable option in the transportation industry.

Hydraulic motor.

A "hydraulic motor" is one that derives its power from a pressurized fluid. This type of engine can be used to move heavy loads or produce motion.

Performance.

Engine speeds.

Given that the majority of engines for which a speed is defined rotate, engine speed is measured in revolutions per minute (RPM). Engines may be classified as low-speed, medium-speed or high-speed, but these terms are always relative and depend on the type of engine being described. Generally, diesel engines operate at lower speeds (~1500–4000 RPM for an automotive diesel) compared to gasoline engines (~2200–6000 RPM for an automotive gasoline engine). Electric motors and turboshafts are capable of very high speeds (~10,000 RPM or more), generally constrained only by the bulk modulus and intended service life of the parts constituting the rotor, which must bear the brunt of the centrifugal force.

Thrust.

Thrust is the force arising from the interaction between two masses which exert equal but opposite forces on each other due to their speed. The force can be measured either in newtons (N, SI units) or more rarely in pounds-thrust (lb, imperial units).

Torque.

Torque is the force being exerted on a theoretical lever connected to the output shaft of an engine. This is expressed by the formula: where is the length of the lever, is the force applied on it, and is the vector cross product. Torque is typically measured in newton-metres (N·m, SI units) and a few countries use the older foot-pounds (ft·lb, imperial units).

Power.

Power is the amount of work being done, or energy being produced, per unit of time. This is expressed by the formula:  With a quick demonstration, it can be shown that:  This formula with linear forces and speeds can be used equally well for both engines outputting thrust and engines exerting torque.  When considering propulsive engines, typically only the raw force of the core mass flow is considered, leading to such engines having their 'power' rated in any of the units discussed above for forces.  If the engine in question outputs its power on a shaft, then:  This is the reason why any engine outputting its power on a rotating shaft is usually quoted, along with its rated power, the rotational speed at which that rated power is developed.

Efficiency.

Depending on the type of engine employed, different rates of efficiency are attained.  For heat engines, efficiency cannot be greater than the Carnot efficiency.

Sound levels.

In the case of sound levels, engine operation is of greatest impact with respect to mobile sources such as automobiles and trucks. Engine noise is a particularly large component of mobile source noise for vehicles operating at lower speeds, where aerodynamic and tire noise is less significant. Generally speaking, gasoline and diesel engines emit less noise than turboshafts of equivalent power output; electric motors very often emit less noise than their fossil fuel-powered equivalents. Thrust-outputting engines, such as turbofans, turbojets and rockets emit the greatest amount of noise because their method of producing thrust is directly related to the production of sound. Various methods have been devised to reduce noise. Gasoline and diesel engines are fitted with mufflers (silencers); newer turbofans often have outsized fans (the so-called high-bypass technology) in order to reduce the proportion of noisy, hot exhaust from the integrated turboshaft in the exhaust stream, and hushkits exist for older, low-bypass turbofans. No known methods exist for reducing the noise output of rockets without a corresponding reduction in thrust.

Engines by use.

Particularly notable kinds of engines include:

An engine or motor is a machine designed to convert one form of energy into mechanical energy. Heat engines, like the internal combustion engine, burn a fuel to create heat which is then used to do work. Electric motors convert electrical energy into mechanical motion, pneumatic motors use compressed air, and clockwork motors in wind-up toys use elastic energy. In biological systems, molecular motors, like myosins in muscles, use chemical energy to create forces and ultimately motion.

发动机,或称动力机、引擎(Engine)、马达(Motor),是将任何形式的能量转化为机械能的装置,亦可以机一字来简称(如:热机);将电能、流体动能、压缩空气的内能转化为机械能的装置称为电动机或马达,也称发-{}-动机。。常见的引擎有把热能转成动能的热引擎(热机),与把电能转成动能的电动机,本条目着重于前者。


Origins.

"Mir" was authorised by a 17 February 1976 decree, to design an improved model of the Salyut DOS-17K space stations. Four Salyut space stations had been launched since 1971, with three more being launched during "Mir"'s development. It was planned that the station's core module (DOS-7 and the backup DOS-8) would be equipped with a total of four docking ports; two at either end of the station as with the Salyut stations, and an additional two ports on either side of a docking sphere at the front of the station to enable further modules to expand the station's capabilities. By August 1978, this had evolved to the final configuration of one aft port and five ports in a spherical compartment at the forward end of the station.  It was originally planned that the ports would connect to modules derived from the Soyuz spacecraft. These modules would have used a Soyuz propulsion module, as in Soyuz and Progress, and the descent and orbital modules would have been replaced with a long laboratory module. Following a February 1979 governmental resolution, the programme was consolidated with Vladimir Chelomei's manned Almaz military space station

Station structure.

Assembly.

The orbital assembly of "Mir" began on 19 February 1986 with the launch of the "Proton-K" rocket. Four of the six modules which were later added ("Kvant"-2 in 1989, "Kristall" in 1990, "Spektr" in 1995 and "Priroda" in 1996) followed the same sequence to be added to the main "Mir" complex. Firstly, the module would be launched independently on its own Proton-K and chase the station automatically. It would then dock to the forward docking port on the core module's docking node, then extend its Lyappa arm to mate with a fixture on the node's exterior. The arm would then lift the module away from the forward docking port and rotate it on to the radial port where it was to mate, before lowering it to dock. The node was equipped with only two "Konus" drogues, which were required for dockings. This meant that, prior to the arrival of each new module, the node would have to be depressurised to allow spacewalking cosmonauts to manually relocate the drogue to the next port to be occupied.  The other two

Pressurised modules.

In its completed configuration, the space station consisted of seven different modules,

Unpressurised elements.

In addition to the pressurised modules, "Mir" featured several external components. The largest component was the "Sofora" girder, a large scaffolding-like structure consisting of 20 segments which, when assembled, projected 14 metres from its mount on "Kvant"-1. A self-contained thruster block, the VDU, was mounted on the end of "Sofora" and was used to augment the roll-control thrusters on the core module. The VDU's increased distance from "Mir"'s axis allowed an 85% decrease in fuel consumption, reducing the amount of propellant required to orient the station. A second girder, "Rapana", was mounted aft of "Sofora" on "Kvant"-1. This girder, a small prototype of a structure intended to be used on "Mir"-2 to hold large parabolic dishes away from the main station structure, was 5 metres long and used as a mounting point for externally mounted exposure experiments.  To assist in moving objects around the exterior of the station during EVAs, "Mir" featured two "Strela" cargo cranes mounted to the sides of the

Power supply.

Photovoltaic (PV) arrays powered "Mir". The station used a 28 volt DC supply which provided 5-, 10-, 20- and 50-amp taps. When the station was illuminated by sunlight, several solar arrays mounted on the pressurised modules provided power to "Mir"'s systems and charged the nickel-cadmium storage batteries installed throughout the station. The arrays rotated in only one degree of freedom over a 180° arc, and tracked the sun using sun sensors and motors installed in the array mounts. The station itself also had to be oriented to ensure optimum illumination of the arrays. When the station's all-sky sensor detected that "Mir" had entered Earth's shadow, the arrays were rotated to the optimum angle predicted for reacquiring the sun once the station passed out of the shadow. The batteries, each of 60 Ah capacity, were then used to power the station until the arrays recovered their maximum output on the day side of Earth.  The solar arrays themselves were launched and installed over a period of eleven years, more slowly than originally planned, with the station continually suffering from a shortage of power as a result. The

Orbit control.

"Mir" was maintained in a near circular orbit with an average perigee of and an average apogee of, travelling at an average speed of 27,700 km/h (17,200 mph) and completing 15.7 orbits per day. As the station constantly lost altitude because of slight atmospheric drag, it needed to be boosted to a higher altitude several times each year. This boost was generally performed by Progress resupply vessels, although during the Shuttle-"Mir" programme the task was performed by US Space Shuttles, and, prior to the arrival of Kvant-1, the engines on the core module could also accomplish the task.  Attitude control was maintained by a combination of two mechanisms; in order to hold a set attitude, a system

Communications.

Radio communications provided telemetry and scientific data links between "Mir" and the RKA Mission Control Centre (TsUP). Radio links were also used during rendezvous and docking procedures and for audio and video communication between crew members, flight controllers and family members. As a result, "Mir" was equipped with several communication systems used for different purposes. The station communicated directly with the ground via the

Microgravity.

At "Mir"'s orbital altitude, the force of Earth's gravity was 88% of sea level gravity. While the constant free fall of the station offered

Life support.

"Mir"<nowiki>'</nowiki>s environmental control and life support system (ECLSS) provided or controlled atmospheric pressure, fire detection, oxygen levels, waste management and water supply. The highest priority for the ECLSS was the station's atmosphere, but the system also collected, processed, and stored waste and water produced and used by the crew—a process that recycles fluid from the sink, toilet, and condensation from the air. The "Elektron" system generated oxygen. Bottled oxygen and solid fuel

International cooperation.

Interkosmos.

Interkosmos () was a Soviet Union space exploration programme which allowed members from the military forces of allied Warsaw Pact countries to participate in manned and unmanned space

European involvement.

Various European astronauts visited

Shuttle–"Mir" program.

In the early 1980s, NASA planned to launch a modular space station called "Freedom" as a counterpart to "Mir", while the Soviets were planning to construct "Mir"-2 in the 1990s as a replacement for the station. Because of budget and design constraints, "Freedom" never progressed past mock-ups and minor component tests and, with the fall of the Soviet Union and the end of the Space Race, the project was nearly cancelled entirely by the United States House of Representatives. The post-Soviet economic chaos in Russia also led to the cancellation of "Mir"-2, though only after its base block, DOS-8, had been constructed. Similar budgetary difficulties were faced by other nations with space station projects, which prompted the US government to negotiate with European states, Russia, Japan, and Canada in the early 1990s to begin a collaborative project. In June 1992, American president George H. W. Bush and Russian president Boris Yeltsin agreed to cooperate on space

Life on board.

Inside, the "Mir" resembled a cramped labyrinth, crowded with hoses, cables and scientific instruments—as well as articles of everyday life, such as photos, children's drawings, books and a guitar. It commonly housed three crew members, but was capable of supporting as many as six for up to a month. The station was designed to remain in orbit for around five years; it remained in orbit for fifteen. As a result, NASA astronaut John Blaha reported that, with the exception of "Priroda" and "Spektr", which were added late in the station's life, "Mir" did look used, which is to be expected given it had been lived in for ten to eleven years without being brought home and cleaned.

Crew schedule.

The time zone used on board "Mir" was Moscow Time (). The windows were covered during night hours to give the impression of darkness because the station experienced 16 sunrises and sunsets a day. A typical day for the crew began with a wake-up at 08:00, followed by two hours of personal hygiene and breakfast. Work was conducted from 10:00 until 13:00, followed by an hour of exercise and an hour's lunch break. Three more hours of work and another hour of exercise followed lunch, and the crews began preparing for their evening meal at about 19:00. The cosmonauts were free to do as they wished in the evening, and largely worked to their own pace during the day.  In their spare time, crews were able to catch up with work, observe the Earth below, respond to letters, drawings and other items brought from Earth (and give them an official stamp to show they had been aboard "Mir"), or make use of the station's ham radio. Two amateur radio call signs, U1MIR and U2MIR, were assigned to "Mir" in the late 1980s, allowing

Exercise.

The most significant adverse effects of long-term weightlessness are muscle atrophy and deterioration of the skeleton, or spaceflight osteopenia. Other significant effects include fluid redistribution, a slowing of the cardiovascular system, decreased production of red blood cells, balance disorders, and a weakening of the immune system. Lesser symptoms include loss of body mass, nasal congestion, sleep disturbance, excess flatulence,

Hygiene.

There were two space toilets (ASUs) on "Mir", located in the core module and "Kvant"-2. They used a fan-driven suction system similar to the Space Shuttle Waste Collection System. The user is first fastened to the toilet seat, which was equipped with spring-loaded restraining bars to ensure a good seal. A lever operated a powerful fan and a suction hole slid open: the air stream carried the waste away. Solid waste was collected in individual bags which were stored in an aluminium container. Full containers were transferred to Progress spacecraft for disposal. Liquid waste was evacuated by a hose connected to the front of the toilet, with anatomically appropriate "urine funnel adapters" attached to the tube so both men and

Sleeping in space.

The station provided two permanent crew quarters, the "Kayutkas", phonebox-sized booths set towards the rear of the core module, each featuring a tethered sleeping bag, a fold-out desk, a porthole, and storage for personal effects. Visiting crews had no allocated sleep module,

Food and drink.

Most of the food eaten by station crews was frozen, refrigerated or canned. Meals were prepared by the cosmonauts, with the help of a dietitian, before their flight to the station. The diet was designed to provide around 100 g of protein, 130 g of fat and 330

Microbiological environmental hazards.

In the 1990s samples of extremophile moulds were taken from "Mir". Ninety species of micro-organisms were found in 1990, four years after the station's launch. By the time of its decommission in 2001, the number of known different micro-organisms had grown to 140. As space stations get older, the problems with contamination get worse. Moulds that develop aboard space stations can produce acids that degrade metal, glass and

Station operations.

Expeditions.

"Mir" was visited by a total of 28 long-duration or "principal" crews, each of which was given a sequential expedition number formatted as EO-X. Expeditions varied in length (from the 72-day flight of the crew of EO-28 to the 437-day flight of Valeri Polyakov), but generally lasted around six months. Principal expedition crews consisted of two or three crew members, who often launched as part of one expedition but returned with another (Polyakov launched with EO-14 and landed with EO-17). The principal expeditions were often supplemented with visiting crews who remained on the station during the week-long handover period between one crew and the next before returning with the departing crew, the station's life support system being able to support a crew of up to six for short periods. The station was occupied for a total of four distinct periods; 12 March–16 July 1986 (EO-1), 5 February 1987 – 27 April 1989 (EO-2–EO-4), the record-breaking run from 5 September 1989 – 28 August 1999 (EO-5–EO-27), and 4 April–16 June 2000 (EO-28). By the end, it had been visited by 104 different people from twelve different nations, making it the most visited spacecraft in history (a record later surpassed by the ISS).

Early existence.

Due to the pressure to launch the station on schedule, mission planners were left without Soyuz spacecraft or modules to launch to the station at first. It was decided to launch Soyuz T-15 on a dual mission to both "Mir" and Salyut 7.  Leonid Kizim and Vladimir Solovyov first docked with "Mir" on 15 March 1986. During their nearly 51-day stay on "Mir", they brought the station online and checked its systems. They unloaded two Progress spacecraft launched after their arrival, Progress 25 and Progress 26.  On 5 May 1986, they undocked from "Mir" for a day-long journey to Salyut 7. They spent 51 days there and gathered 400 kg of scientific material from Salyut 7 for return to "Mir". While Soyuz T-15 was at Salyut 7, the unmanned Soyuz TM-1 arrived at the unoccupied "Mir" and remained for 9 days, testing the new Soyuz TM model. Soyuz T-15 redocked with "Mir" on 26 June and delivered the experiments and 20 instruments, including a multichannel spectrometer. The EO-1 crew spent their last 20 days on

Third start.

The launch of Soyuz TM-8 on 5 September 1989 marked the beginning of the longest human presence in space, until 23 October 2010, when this record was surpassed by the ISS. It also marked the beginning of "Mir's" second expansion. The Kvant-2 and "Kristall" modules were now ready for launch. Alexander Viktorenko and Aleksandr Serebrov docked with "Mir" and brought the station out of its five-month hibernation. On 29 September the cosmonauts installed equipment in the docking system in preparation for the arrival

Post-Soviet period.

The EO-10 crew, launched aboard Soyuz TM-13 on 2 October 1991, was the last crew to launch from the USSR and continued the occupation of "Mir" during the fall of the Soviet Union. The crew launched as Soviet citizens and returned to Earth on 25 March 1992 as Russians. The newly formed Russian Federal Space Agency (Roskosmos) was unable to finance the unlaunched "Spektr" and "Priroda" modules, instead putting them into storage and ending "Mir's" second expansion.  The first manned mission flown from an independent Kazakhstan was Soyuz TM-14, launched on 17 March 1992, which carried the EO-11 crew to "Mir", docking on 19 March before the departure of Soyuz TM-13. On 17 June, Russian President

Shuttle–"Mir".

The 3 February launch of, flying STS-63, opened operations on "Mir" for 1995. Referred to as the "near-"Mir"" mission, the mission saw the first rendezvous of a space shuttle with "Mir" as the orbiter approached within of the station as a dress rehearsal for later docking missions and for equipment testing. Five weeks after "Discovery" departure, the EO-18 crew, including the first US cosmonaut Norman Thagard, arrived in Soyuz TM-21. The EO-17 crew left a few days later, with Polyakov completing his record-breaking 437-day spaceflight. During EO-18, the "Spektr" science module (which served as living and working space for American astronauts) was launched aboard a Proton rocket and docked to the station, carrying research equipment from America and other nations. The expedition's crew returned to Earth aboard following the first Shuttle–"Mir" docking mission, STS-71. "Atlantis", launched on 27

Final days and deorbit.

Following the 8 June 1998 departure of "Discovery", the EO-25 crew of Budarin and Musabayev remained on "Mir", completing materials experiments and compiling a station inventory. On 2 July, Roskosmos director Yuri Koptev announced that, due to a lack of funding to keep "Mir" active, the station would be deorbited in June 1999. The EO-26 crew of Gennady Padalka and Sergei Avdeyev arrived on 15 August in Soyuz TM-28, alongside physicist Yuri Baturin, who departed with the EO-25 crew on 25 August in Soyuz TM-27. The crew carried out two spacewalks, one inside "Spektr" to reseat some power cables and another outside to set up experiments delivered by Progress M-40, which also carried a large amount of propellant to begin alterations to "Mir"s orbit in preparation for the station's decommissioning. 20 November 1998 saw the launch of "Zarya", the first module of the ISS, but delays to the new station's service module "Zvezda" had led to calls for "Mir" to be kept in orbit past 1999. Roscosmos confirmed that it would not fund "Mir" past the set deorbit date.  The crew of EO-27, Viktor Afanasyev and Jean-Pierre Haigneré, arrived in Soyuz TM-29 on 22 February 1999 alongside Ivan Bella, who returned to Earth with Padalka in Soyuz TM-28. The crew carried out three EVAs to retrieve experiments and deploy a prototype communications antenna on "Sofora". On 1 June it was announced that the deorbit of the station would be delayed by six months

Visiting spacecraft.

"Mir" was primarily supported by the Russian Soyuz and Progress spacecraft and had two ports available for docking them. Initially, the fore and aft ports of the core module could be used for dockings, but following the permanent berthing of "Kvant"-1 to the aft port in 1987, the rear port of the new module took on this role from the core module's aft port. Each port was equipped with the plumbing required for Progress cargo ferries to replace the station's fluids and also the guidance systems needed to guide the spacecraft for docking. Two such systems were used on "Mir"; the rear ports of both the core module and "Kvant"-1 were equipped with both the Igla and Kurs systems, whilst the core module's forward port featured only the newer Kurs.  Soyuz spacecraft provided manned access to and from the station allowing for crew rotations and cargo return, and also functioned as a lifeboat for the station, allowing for a relatively quick return to Earth in the event of an emergency. Two models of Soyuz flew to "Mir"; Soyuz T-15 was the only Igla-equipped Soyuz-T to visit the station, whilst all other flights used the newer, Kurs-equipped Soyuz-TM. A total of 31 (30 manned, 1 unmanned) Soyuz spacecraft flew to the station over a fourteen-year period.  The unmanned Progress cargo vehicles were only used to resupply the station, carrying a variety of cargoes including water, fuel, food and experimental equipment. The spacecraft were not equipped with reentry shielding and so, unlike their Soyuz counterparts, were incapable of surviving reentry. As a result, when its cargo had been unloaded, each Progress was

Mission control centre.

"Mir" and its resupply missions were controlled from the Russian mission control centre () in Korolyov, near the RKK Energia plant. Referred to by its acronym ЦУП ("TsUP"), or simply as 'Moscow', the facility could process data from up to ten spacecraft in three separate control

Unused equipment.

Three command and control modules were constructed for the "Mir" program. One was used in space; one remained in a Moscow warehouse as a source of repair parts if

Safety aspects.

Ageing systems and atmosphere.

In the later years of the programme, particularly during the Shuttle-"Mir" programme, "Mir" suffered from various systems failures. It had been designed for five years of use, but eventually flew for fifteen, and in the 1990s was showing its age, with frequent computer crashes, loss of power, uncontrolled tumbles through space and leaking pipes. Jerry Linenger in his book about his time on the facility says that the cooling system had developed tiny leaks too small

Accidents.

Several accidents occurred which threatened the station's safety, such as the glancing collision between "Kristall" and Soyuz TM-17 during proximity operations in January 1994. The three most alarming incidents occurred during EO-23. The first was on 23 February 1997 during the handover period from EO-22 to EO-23, when a malfunction occurred in the backup "Vika" system, a chemical oxygen generator later known as solid-fuel oxygen generator (SFOG). The "Vika" malfunction led to a fire which burned for around 90 seconds (according to official sources at the TsUP; astronaut Jerry Linenger insists the fire burned for around 14 minutes), and produced large amounts of toxic smoke that filled the station for

Radiation and orbital debris.

Without the protection of the Earth's atmosphere, cosmonauts were exposed to higher levels of radiation from a steady flux of cosmic rays and trapped protons from the South Atlantic Anomaly. The station's crews were exposed to an absorbed dose of about 5.2 cGy over the course of a 115-day expedition, producing an equivalent dose of 14.75 cSv, or 1133 μSv per day. This daily dose is approximately that received from natural background radiation on Earth in two years. The radiation environment of the station was not uniform; closer proximity to the station's hull led to an increased radiation dose, and the strength of radiation shielding varied between modules; "Kvant"-2's being better than the core module, for instance.  The increased radiation levels pose a higher risk of crews developing cancer, and can cause damage to the chromosomes of

Mir (, ; lit. "peace" or "world") was a space station that operated in low Earth orbit from 1986 to 2001, operated by the Soviet Union and later by Russia. "Mir" was the first modular space station and was assembled in orbit from 1986 to 1996. It had a greater mass than any previous spacecraft. At the time it was the largest artificial satellite in orbit, succeeded by the International Space Station (ISS) after "Mir"'s orbit decayed. The station served as a microgravity research laboratory in which crews conducted experiments in biology, human biology, physics, astronomy, meteorology, and spacecraft systems with a goal of developing technologies required for permanent occupation of space.

和平号空间站(俄语:,英语:Mir,兼有“和平”与“世界”之意)是前苏联建造的一个模组轨道空间站,苏联解体后归属俄罗斯。和平号经过数年由多个模块在轨道上组装而成。它是人类首个可长期居住的空间研究中心,同时也是首个第三代空间站。