Plywood is a material manufactured from thin layers or "plies" of wood veneer that are glued together with adjacent layers having their wood grain rotated up to 90 degrees to one another. It is an engineered wood from the family of manufactured boards which includes medium-density fibreboard and particle board. All plywoods bind wood fibre sheets to form a composite material; this alternation of the grain is called cross-graining and has several important benefits: it reduces the tendency of wood to split when nailed in at the edges. There is an odd number of plies, so that the sheet is balanced—this reduces warping; because plywood is bonded with grains running against one another and with an odd number of composite parts, it has high stiffness perpendicular to the grain direction of the surface ply. Smaller and lower-quality plywoods may only have their plies arranged at right angles to each other; some better-quality plywood products will by design have five plies in steps of 45 degrees, giving strength in multiple axes.
The word ply derives from the French verb plier, "to fold", from the Latin verb plico, from the ancient Greek verb πλέκω. In 1797 Samuel Bentham applied for patents covering several machines to produce veneers. In his patent applications, he described the concept of laminating several layers of veneer with glue to form a thicker piece – the first description of what we now call plywood. Bentham was a British naval engineer with many shipbuilding inventions to his credit. Veneers at the time of Bentham were rift sawn or quarter sawn. About fifty years Immanuel Nobel, father of Alfred Nobel, realized that several thinner layers of wood bonded together would be stronger than a single thick layer of wood. Understanding the industrial potential of laminated wood, he invented the rotary lathe. There is little record of the early implementation of the rotary lathe and the subsequent commercialization of plywood as we know it today, but in its 1870 edition, the French dictionary Robert describes the process of rotary lathe veneer manufacturing in its entry Déroulage.
One can thus presume that rotary lathe plywood manufacturer was an established process in France in the 1860s. Plywood was introduced into the United States in 1865 and industrial production started shortly after. In 1928, the first standard-sized 4 ft by 8 ft plywood sheets were introduced in the United States for use as a general building material. Artists use plywood as a support for easel paintings to replace traditional cardboard. Ready-made artist boards for oil painting in three-layered plywood were produced and sold in New York as early as 1880. In India Plywood is known as "Kitply" after the brand which pioneered the concept of "Branded Plyboards" in the early 70's. A typical plywood panel has face veneers of a higher grade than the core veneers; the principal function of the core layers is to increase the separation between the outer layers where the bending stresses are highest, thus increasing the panel's resistance to bending. As a result, thicker panels can span greater distances under the same loads.
In bending, the maximum stress occurs in the outermost layers, one in tension, the other in compression. Bending stress decreases from the maximum at the face layers to nearly zero at the central layer. Shear stress, by contrast, is higher in the center of the panel, at the outer fibres. Different varieties of plywood exist for different applications: Softwood plywood is made either of cedar, Douglas fir or spruce and fir or redwood and is used for construction and industrial purposes; the most common dimension is 1.2 by 2.4 metres or the larger imperial dimension of 4 feet × 8 feet. Plies vary in thickness from 1.4 mm to 4.3 mm. The number of plies --, always odd -- depends on the grade of the sheet. Roofing can use the thinner 5⁄8-inch plywood. Subfloors are at least 3⁄4 inch thick, the thickness depending on the distance between floor joists. Plywood for flooring applications is tongue and groove. T&G plywood is found in the 1⁄2-to-1-inch range. Hardwood plywood is used for demanding end uses.
Hardwood plywood is characterized by its excellent strength and resistance to creep. It has a high planar shear strength and impact resistance, which make it suitable for heavy-duty floor and wall structures. Oriented plywood construction has a high wheel-carrying capacity. Hardwood plywood has excellent surface hardness, damage- and wear-resistance. Tropical plywood is made of mixed species of tropical timber. From the Asian region, it is now manufactured in African and South American countries. Tropical plywood is superior to softwood plywood due to its density, evenness of layers, high quality, it is sold at a premium in many markets if manufactured with high standards. Tropical plywood is used in the UK, United States, Korea and other countries worldwide, it is used for construction purposes in many regions due to its low cost. However, many countries’ forests have been over-harvested, including th
Recreational drug use
Recreational drug use is the use of a psychoactive drug to induce an altered state of consciousness for pleasure, by modifying the perceptions and emotions of the user. When a psychoactive drug enters the user's body, it induces an intoxicating effect. Recreational drugs are in three categories: depressants. Many people use prescribed and illegal opioids along with opiates and benzodiazepines. In popular practice, recreational drug use is a tolerated social behaviour, rather than perceived as the serious medical condition of self-medication. However, heavy use of some drugs is stigmatized. Recreational drugs include alcohol. What controlled substances are considered illegal drugs varies by country, but includes methamphetamines, cocaine, LSD, psilocybin mushrooms, MDMA and club drugs. In 2015, it was estimated that about 5% of people aged 15 to 65 had used illegal drugs at least once. Many researchers have explored the etiology of recreational drug use; some of the most common theories are: genetics, personality type, psychological problems, self-medication, age, instant gratification, basic human need, rebelliousness, a sense of belonging to a group and attachment issues, history of trauma, failure at school or work, socioeconomic stressors, peer pressure, juvenile delinquency, historical factors, or sociocultural influences.
There has not been agreement around any one single cause. Instead, experts tend to apply the biopsychosocial model. Any number of these factors are to influence an individual's drug use as they are not mutually exclusive. Regardless of genetics, mental health or traumatic experiences, social factors play a large role in exposure to and availability of certain types of drugs and patterns of drug use. According to addiction researcher Martin A. Plant, many people go through a period of self-redefinition before initiating recreational drug use, they tend to view using drugs as part of a general lifestyle that involves belonging to a subculture that they associate with heightened status and the challenging of social norms. Plant says, “From the user's point of view there are many positive reasons to become part of the milieu of drug taking; the reasons for drug use appear to have as much to do with needs for friendship and status as they do with unhappiness or poverty. Becoming a drug taker, to many people, is a positive affirmation rather than a negative experience.”
Anthropological research has suggested that humans "may have evolved to counter-exploit plant neurotoxins". The ability to use botanical chemicals to serve the function of endogenous neurotransmitters may have improved survival rates, conferring an evolutionary advantage. A restrictive prehistoric diet may have emphasised the apparent benefit of consuming psychoactive drugs, which had themselves evolved to imitate neurotransmitters. Chemical–ecological adaptations, the genetics of hepatic enzymes cytochrome P450, have led researchers to propose that "humans have shared a co-evolutionary relationship with psychotropic plant substances, millions of years old." Severity and type of risks that come with recreational drug use vary with the drug in question and the amount being used. There are many factors in the environment and within the user that interact with each drug differently. Overall, some studies suggest. However, studies which focus on a moderate level of alcohol consumption have concluded that there can be substantial health benefits from its use, such as decreased risk of cardiac disease and cognitive decline.
This claim has been disputed. Researcher David Nutt stated that these studies showing benefits for "moderate" alcohol consumption lacked control for the variable of what the subjects were drinking, beforehand. Experts in the UK have suggested that some drugs that may be causing less harm, to fewer users, include cannabis, psilocybin mushrooms, LSD, ecstasy; these drugs are not without their own particular risks. The concept of "responsible drug use" is that a person can use drugs recreationally or otherwise with reduced or eliminated risk of negatively affecting other aspects of one's life or other people's lives. Advocates of this philosophy point to the many well-known artists and intellectuals who have used drugs, experimentally or otherwise, with few detrimental effects on their lives. Responsible drug use becomes problematic only when the use of the substance interferes with the user's daily life. Responsible drug use advocates that users should not take drugs at the same time as activities such as driving, operating machinery, or other activities that are unsafe without a sober state.
Responsible drug use is emphasized as a primary prevention technique in harm-reduction drug policies. Harm-reduction policies were popularized in the late 1980s, although they began in the 1970s counter-culture, when cartoons explaining responsible drug use and the co
Jakarta the Special Capital Region of Jakarta, is the capital and largest city of Indonesia. Located on the northwest coast of the world's most populous island, Java, it is the centre of economics and politics of Indonesia, with a population of 10,075,310 as of 2014. Jakarta metropolitan area has an area of 6,392 square kilometers, known as Jabodetabek, it is the world's second largest urban agglomeration with a population of 30,214,303 as of 2010. Jakarta is predicted to reach 35.6 million people by 2030 to become the world's biggest megacity. Jakarta's business opportunities, as well as its potential to offer a higher standard of living, attract migrants from across the Indonesian archipelago, combining many communities and cultures. Established in the 4th century as Sunda Kelapa, the city became an important trading port for the Sunda Kingdom, it was the de facto capital of the Dutch East Indies. Jakarta is a province with special capital region status, but is referred to as a city; the Jakarta provincial government consists of five administrative cities and one administrative regency.
Jakarta is nicknamed the Big Durian, the thorny strongly-odored fruit native to the region, as the city is seen as the Indonesian equivalent of New York. Jakarta is an alpha world city and is the seat of the ASEAN secretariat, making it an important city for international diplomacy. Important financial institutions such as Bank of Indonesia, Indonesia Stock Exchange, corporate headquarters of numerous Indonesian companies and multinational corporations are located in the city; as of 2017, the city is home for two Fortune 500 and four Unicorn companies. In 2017, the city's GRP PPP was estimated at US$483.4 billion. Jakarta has grown more than Kuala Lumpur and Beijing. Jakarta's major challenges include rapid urban growth, ecological breakdown, gridlock traffic and congestion and inequality, potential crimes and flooding. Jakarta is sinking up to 17 cm per year, coupled with the rising of sea level, has made the city more prone to flooding. Jakarta has been home to multiple settlements: Sunda Kelapa, Batavia, Jakarta.
Its current name "Jakarta" derives from the word Jayakarta, derived from Sanskrit language. It was named after troops of Fatahillah defeated and drove away Portuguese invaders from the city in 1527. Before it was named "Jayakarta", the city was known as "Sunda Kelapa". In the colonial era, the city was known as Koningin van het Oosten in the 17th century for the urban beauty of downtown Batavia's canals and ordered city layout. After expanding to the south in the 19th century, this nickname came to be more associated with the suburbs, with their wide lanes, green spaces and villas. During Japanese occupation the city was renamed as Jakarta Tokubetsu Shi; the north coast area of western Java including Jakarta, was the location of prehistoric Buni culture that flourished from 400 BC to 100 AD. The area in and around modern Jakarta was part of the 4th century Sundanese kingdom of Tarumanagara, one of the oldest Hindu kingdoms in Indonesia; the area of North Jakarta around Tugu became a populated settlement at least in the early 5th century.
The Tugu inscription discovered in Batutumbuh hamlet, Tugu village, North Jakarta, mentions that King Purnawarman of Tarumanagara undertook hydraulic projects. Following the decline of Tarumanagara, its territories, including the Jakarta area, became part of the Hindu Kingdom of Sunda. From the 7th to the early 13th century, the port of Sunda was under the Srivijaya maritime empire. According to the Chinese source, Chu-fan-chi, written circa 1225, Chou Ju-kua reported in the early 13th century Srivijaya still ruled Sumatra, the Malay peninsula and western Java; the source reports the port of Sunda as strategic and thriving, mentioning pepper from Sunda as among the best in quality. The people worked in agriculture and their houses were built on wooden piles; the harbour area became known as Sunda Kelapa and by the 14th century, it was a major trading port for the Sunda kingdom. The first European fleet, four Portuguese ships from Malacca, arrived in 1513, while looking for a route for spices.
The Sunda Kingdom made an alliance treaty with the Portuguese by allowing them to build a port in 1522 to defend against the rising power of Demak Sultanate from central Java. In 1527, Fatahillah, a Javanese general from Demak attacked and conquered Sunda Kelapa, driving out the Portuguese. Sunda Kelapa was renamed Jayakarta, became a fiefdom of the Banten Sultanate, which became a major Southeast Asia trading centre. Through the relationship with Prince Jayawikarta of Banten Sultanate, Dutch ships arrived in 1596. In 1602, the English East India Company's first voyage, commanded by Sir James Lancaster, arrived in Aceh and sailed on to Banten where they were allowed to build a trading post; this site became the centre of English trade in Indonesia until 1682. Jayawikarta is thought to have made trading connections with
Plastic is material consisting of any of a wide range of synthetic or semi-synthetic organic compounds that are malleable and so can be molded into solid objects. Plasticity is the general property of all materials which can deform irreversibly without breaking but, in the class of moldable polymers, this occurs to such a degree that their actual name derives from this specific ability. Plastics are organic polymers of high molecular mass and contain other substances, they are synthetic, most derived from petrochemicals, however, an array of variants are made from renewable materials such as polylactic acid from corn or cellulosics from cotton linters. Due to their low cost, ease of manufacture and imperviousness to water, plastics are used in a multitude of products of different scale, including paper clips and spacecraft, they have prevailed over traditional materials, such as wood, stone and bone, metal and ceramic, in some products left to natural materials. In developed economies, about a third of plastic is used in packaging and the same in buildings in applications such as piping, plumbing or vinyl siding.
Other uses include automobiles and toys. In the developing world, the applications of plastic may differ—42% of India's consumption is used in packaging. Plastics have many uses in the medical field as well, with the introduction of polymer implants and other medical devices derived at least from plastic; the field of plastic surgery is not named for use of plastic materials, but rather the meaning of the word plasticity, with regard to the reshaping of flesh. The world's first synthetic plastic was bakelite, invented in New York in 1907 by Leo Baekeland who coined the term'plastics'. Many chemists have contributed to the materials science of plastics, including Nobel laureate Hermann Staudinger, called "the father of polymer chemistry" and Herman Mark, known as "the father of polymer physics"; the success and dominance of plastics starting in the early 20th century led to environmental concerns regarding its slow decomposition rate after being discarded as trash due to its composition of large molecules.
Toward the end of the century, one approach to this problem was met with wide efforts toward recycling. The word plastic derives from the Greek πλαστικός meaning "capable of being shaped or molded" and, in turn, from πλαστός meaning "molded"; the plasticity, or malleability, of the material during manufacture allows it to be cast, pressed, or extruded into a variety of shapes, such as: films, plates, bottles, amongst many others. The common noun plastic should not be confused with the technical adjective plastic; the adjective is applicable to any material which undergoes a plastic deformation, or permanent change of shape, when strained beyond a certain point. For example, aluminum, stamped or forged exhibits plasticity in this sense, but is not plastic in the common sense. By contrast, some plastics will, in their finished forms, break before deforming and therefore are not plastic in the technical sense. Most plastics contain organic polymers; the vast majority of these polymers are formed from chains of carbon atoms,'pure' or with the addition of: oxygen, nitrogen, or sulfur.
The chains comprise many repeat units, formed from monomers. Each polymer chain will have several thousand repeating units; the backbone is the part of the chain, on the "main path", linking together a large number of repeat units. To customize the properties of a plastic, different molecular groups "hang" from this backbone; these pendant units are "hung" on the monomers, before the monomers themselves are linked together to form the polymer chain. It is the structure of these side chains; the molecular structure of the repeating unit can be fine tuned to influence specific properties in the polymer. Plastics are classified by: the chemical structure of the polymer's backbone and side chains. Plastics can be classified by: the chemical process used in their synthesis, such as: condensation and cross-linking. Plastics can be classified by: their various physical properties, such as: hardness, tensile strength, resistance to heat and glass transition temperature, by their chemical properties, such as the organic chemistry of the polymer and its resistance and reaction to various chemical products and processes, such as: organic solvents and ionizing radiation.
In particular, most plastics will melt upon heating to a few hundred degrees celsius. Other classifications are based on qualities that are relevant for product design. Examples of such qualities and classes are: thermoplastics and thermosets, conductive polymers, biodegradable plastics and engineering plastics and other plastics with particular structures, such as elastomers. One important classification of plastics is by the permanence or impermanence of their form, or whether they are: thermoplastics or thermosetting polymers. Thermoplastics are the plastics that, when heated, do not undergo chemical change in their composition and so can be molded again and again. Examples include: polyethylene, polypropylene and polyvinyl chloride. Common thermoplastics range from 20,000 to 500,000 amu, while thermosets are assumed to have infinite molecular weight. Thermosets, or thermosetting polymers, can melt and take shape only once: after they have solidified, they stay solid. In the thermosetting process, a chemical reaction occurs, irreversible.
Soweto is a township of the City of Johannesburg Metropolitan Municipality in Gauteng, South Africa, bordering the city's mining belt in the south. Its name is an English syllabic abbreviation for South Western Townships. A separate municipality, it is now incorporated in the City of Johannesburg Metropolitan Municipality, Suburbs of Johannesburg. George Harrison and George Walker are today credited as the men who discovered an outcrop of the Main Reef of gold on the farm Langlaagte in February 1886; the fledgling town of Johannesburg was laid out on a triangular wedge of "uitvalgrond" named Randjeslaagte, situated between the farms Doornfontein to the east, Braamfontein to the west and Turffontein to the south. Within a decade of the discovery of gold in Johannesburg, 100,000 people flocked to this part of the Zuid-Afrikaansche Republic in search of riches, they were of all nationalities. In October 1887 the government of the South African Republic bought the south-eastern portion of the farm Braamfontein.
There were large quantities of clay, suitable for brickmaking, along the stream. The government decided that more money was to be made from issuing brick maker's licences at five shillings per month; the result was that many landless Dutch-speaking burghers of the ZAR settled on the property and started making bricks. They erected their shacks there. Soon the area was known either Veldschoendorp. Soon other working poor, Coloureds and Africans settled there; the government, who sought to differentiate the white working class from the black, laid out new suburbs for the Burghers, Coolies and Black Africans, but the whole area stayed multiracial. Soweto was created in the 1930s when the White government started separating Blacks from Whites, creating black "townships". Blacks were moved away from Johannesburg, to an area separated from White suburbs by a so-called cordon sanitaire this was a river, a railway track, an industrial area or a highway etc. they did this by using the infamous'Urban Areas Act' in 1923.
Soweto became the largest Black city in South Africa, but until 1976 its population could have status only as temporary residents, serving as a workforce for Johannesburg. It experienced civil unrest during the Apartheid regime. There were serious riots in 1976, sparked by a ruling that Afrikaans be used in African schools there. Reforms followed, but riots flared up again in 1985 and continued until the first multiracial elections were held in April 1994. In 2010, South Africa's oldest township hosted the FIFA Soccer World Cup final and the attention of more than a billion soccer spectators from all over the world was focused on Soweto. William Carr, chair of non-European affairs, initiated the naming of Soweto in 1959, he called for a competition to give a collective name to townships dotted around the South-west of Johannesburg. People responded to this competition with great enthusiasm. Among the names suggested to the City Council was KwaMpanza, meaning Mpanza's place, invoking the name of Mpanza and his role in bringing the plight of Orlando sub tenants to the attention of the City Council.
The City Council settled for the acronym SOWETO. The name Soweto was first used in 1963 and within a short period of time, following the 1976 uprising of students in the township, the name became internationally known. In April 1904 there was a bubonic plague scare in the shanty town area of Brickfields; the town council burn it down. Beforehand most of the Africans living there were moved far out of town to the farm Klipspruit, south-west of Johannesburg, where the council had erected iron barracks and a few triangular hutments; the rest of them had to build their own shacks. The fire brigade set the 1600 shacks and shops in Brickfields alight. Thereafter the area was redeveloped as Newtown. Pimville was next to Kliptown, the oldest Black residential district of Johannesburg and first laid out in 1891 on land which formed part of Klipspruit farm; the future Soweto was to be laid out on Klipspruit and the adjoining farm called Diepkloof. In the Zuid-Afrikaansche Republiek and the subsequent Transvaal Colony it was lawful for people of colour to own fixed property.
The township of Sophiatown was laid out in 1903 and Blacks were encouraged to buy property there. For the same reasons Alexandra, Gauteng was planned for Black ownership in 1912; the subsequent Natives Land Act of 1913 did not change the situation because it did not apply to land situated within municipal boundaries. In 1923 the Parliament of the Union of South Africa passed the Natives Act; the purpose of the Act was to provide for improved conditions of residence for natives in urban areas, to control their ingress into such areas and to restrict their access to intoxicating liquor. The Act required local authorities to provide accommodation for Natives lawfully employed and resident within the area of their jurisdiction. Pursuant to this Act the Johannesburg town council formed a Municipal Native Affairs Department in 1927, it bought 1 300 morgen of land on the farm Klipspruit No. 8 and the first houses in what was to become Orlando Location were built there in the latter half of 1930. The township was named after the chairman of Mr. Edwin Orlando Leake.
In the end some 10,311 houses were built there by the municipality. In addition it built 4,045 temporary single-room shelters. In about 1934 James Sofasonke Mpanza
Brasília is the federal capital of Brazil and seat of government of the Federal District. The city is located atop the Brazilian highlands in the country's center-western region, it was founded on April 1960, to serve as the new national capital. Brasília is estimated to be Brazil's 3rd most populous city. Among major Latin American cities, Brasília has the highest GDP per capita. Brasília was planned and developed by Lúcio Costa, Oscar Niemeyer and Joaquim Cardozo in 1956 to move the capital from Rio de Janeiro to a more central location; the landscape architect was Roberto Burle Marx. The city's design divides it into numbered blocks as well as sectors for specified activities, such as the Hotel Sector, the Banking Sector and the Embassy Sector. Brasília was chosen as a UNESCO World Heritage Site due to its modernist architecture and uniquely artistic urban planning, it has been named "City of Design" by UNESCO in October 2017 and has been part of the Creative Cities Network since then. All three branches of Brazil's federal government are centered in the city: executive and judiciary.
Brasília hosts 124 foreign embassies. The city's international airport connects it to all other major Brazilian cities and many international destinations, is the third busiest airport in Brazil. Brasília is the most populous Portuguese-speaking capital city, it was one of the main host cities of the 2014 FIFA World Cup and hosted some of the football matches during the 2016 Summer Olympic Games. The city has a unique status in Brazil, as it is an administrative division rather than a legal municipality like other cities in Brazil. Although Brasília is used as a synonym for the Federal District through synecdoche, the Federal District is composed of 31 administrative regions, only one of, the area of the planned city called Plano Piloto; the rest of the Federal District is considered by IBGE to make up Brasília's metro area. From 1763 until 1960, Rio de Janeiro was Brazil's capital. At this time, resources tended to be centered in Brazil's southeast region near Rio de Janeiro and most of its population was concentrated near to the Atlantic Coast.
Brasília's geographically central location fostered a more regionally neutral federal capital. An article of the country's first republican constitution dating back to 1891 stated the capital should be moved from Rio de Janeiro to a place close to the country's center; the plan was conceived in 1827 by José Bonifácio, an advisor to Emperor Pedro I. He presented a plan to the General Assembly of Brazil for a new city called Brasília, with the idea of moving the capital westward from the populated southeastern corridor; the bill was not enacted because Pedro I dissolved the Assembly. According to legend, Italian saint Don Bosco in 1883 had a dream in which he described a futuristic city that fitted Brasília's location. In Brasília today, many references of Bosco, who founded the Salesian order, are found throughout the city and one church parish in the city bears his name. In 1955 Juscelino Kubitschek was elected president of Brazil. Upon taking office in January, 1956, in response to his campaign pledge, he initiated the planning and construction of the new capital.
In 1957 an international jury selected Lúcio Costa's plan to guide the construction of Brazil’s new capital, Brasília. Costa's plan was not as detailed as some of the plans presented by other architects and city planners, it did not include land use schedules, population charts or mechanical drawings, however, it was chosen by five out of six jurors because it had the features required to align the growth of a capital city Even though the initial plan was transformed over time, his plan oriented much of the construction and most of its features survived. Brasília's accession as the new capital and its designation for the development of an extensive interior region inspired the symbolism of the plan. Costa used a cross-axial design indicating the possession and conquest of this new place with a cross described by some as a dragonfly, an airplane or a bird. Costa's plan included the Monumental Axis and the Residential Axis; the Monumental Axis was assigned political and administrative activities and is considered the body of the city with the style and simplicity of its buildings, oversized scales, broad vistas and heights, producing the idea of Monumentality.
This axis includes the various ministries, national congress, presidential palace, supreme court building and the television and radio tower. The Residential Axis was intended to contain areas with intimate character and is considered the most important achievement of the plan; the urban design of the communal apartment blocks was based on Le Corbusier's Ville Radieuse of 1935 and the superblocks on the North American Radburn layout from 1929. Visually, the blocks were intended to appear absorbed by the landscape because they were isolated by a belt of tall trees and lower vegetation. Costa attempted to introduce a Brazil, more equitable, he designed housing for the working classes, separated from the upper and middle-class housing and was visually different, with the intention of avoiding slums (f
A suburb is a mixed-use or residential area, existing either as part of a city or urban area or as a separate residential community within commuting distance of a city. In most English-speaking countries, suburban areas are defined in contrast to central or inner-city areas, but in Australian English and South African English, suburb has become synonymous with what is called a "neighborhood" in other countries and the term extends to inner-city areas. In some areas, such as Australia, China, New Zealand, the United Kingdom, a few U. S. states, new suburbs are annexed by adjacent cities. In others, such as Saudi Arabia, Canada and much of the United States, many suburbs remain separate municipalities or are governed as part of a larger local government area such as a county. Suburbs first emerged on a large scale in the 19th and 20th centuries as a result of improved rail and road transport, which led to an increase in commuting. In general, they have lower population densities than inner city neighborhoods within a metropolitan area, most residents commute to central cities or other business districts.
Suburbs tend to proliferate around cities that have an abundance of adjacent flat land. The English word is derived from the Old French subburbe, in turn derived from the Latin suburbium, formed from sub and urbs; the first recorded usage of the term in English, was made by John Wycliffe in 1380, where the form subarbis was used, according to the Oxford English Dictionary. In Australia and New Zealand, suburbs have become formalised as geographic subdivisions of a city and are used by postal services in addressing. In rural areas in both countries, their equivalents are called localities; the terms inner suburb and outer suburb are used to differentiate between the higher-density areas in proximity to the city center, the lower-density suburbs on the outskirts of the urban area. The term'middle suburbs' is used. Inner suburbs, such as Te Aro in Wellington, Eden Terrace in Auckland, Prahran in Melbourne and Ultimo in Sydney, are characterised by higher density apartment housing and greater integration between commercial and residential areas.
In New Zealand, most suburbs are not defined which can lead to confusion as to where they may begin and end. Although there is a geospatial file defining suburbs for use by emergency services developed and maintained by Fire and Emergency New Zealand, in collaboration with other government agencies, to date this file has not been released publicly. New Zealand company Koordinates Limited requested access to the geospatial file under the Official Information Act 1982 but this request was rejected by the New Zealand Fire Service on the basis that it would prejudice the health & safety of, or cause material loss, to the public. In September 2014 a decision was made by the Ombudsman of New Zealand ruling that the New Zealand Fire Service refusal to release the geospatial file without agreeing to terms which included, among other restrictions, a prohibition on redistribution of the geospatial file, was reasonable. In the United Kingdom and in Ireland, suburb refers to a residential area outside the city centre, regardless of administrative boundaries.
Suburbs, in this sense, can range from areas that seem more like residential areas of a city proper to areas separated by open countryside from the city centre. In large cities such as London and Leeds, suburbs include separate towns and villages that have been absorbed during a city's growth and expansion, such as Ealing and Guiseley. In the United States and Canada, suburb can refer either to an outlying residential area of a city or town or to a separate municipality or unincorporated area outside a town or city; the earliest appearance of suburbs coincided with the spread of the first urban settlements. Large walled towns tended to be the focus around which smaller villages grew up in a symbiotic relationship with the market town; the word'suburbani' was first used by the Roman statesman Cicero in reference to the large villas and estates built by the wealthy patricians of Rome on the city's outskirts. Towards the end of the Eastern Han Dynasty, the capital, was occupied by the emperor and important officials.
As populations grew during the Early Modern Period in Europe, urban towns swelled with a steady influx of people from the countryside. In some places, nearby settlements were swallowed up as the main city expanded; the peripheral areas on the outskirts of the city were inhabited by the poorest. Due to the rapid migration of the rural poor to the industrialising cities of England in the late 18th century, a trend in the opposite direction began to develop; this trend accelerated through the 19th century in cities like London and Manchester that were growing and the first suburban districts sprung up around the city centres to accommodate those who wanted to escape the squalid conditions of the industrial towns. Toward the end of the century, with the development of public transit systems such as the underground railways and buses, it became possible for the majority of the city's population to reside outside the city and to commute into the