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Car Park

Car park

Parking lot is the American English term that refers to a cleared area that is more or less level and is intended for parking vehicles. Usually, the term refers to a dedicated area that has been provided with a durable or semi-durable surface. In Great Britain and other Commonwealth countries, parking lots are known as car parks which is usually applied to a surface car park, as opposed to a multi-storey car park.

General information

multi-storey car park The usual parking lot in the United States is paved with asphalt. Some are paved with concrete. Many are gravel lots. A few of the newer lots are surfaced with permeable paving materials. Parking lots have their own special type of engineering. While parking lots have traditionally been an overlooked element of development projects by governmental oversight, the recent trend has been to provide regulations for the configuration and spacing of parking lots, their landscaping, and drainage and pollution abatement issues.

Environmental considerations

Runoff handling

Parking lots have certain characteristics that set them apart from roadways in terms of their engineering and operating requirements. The first is that they often cover large contiguous areas with impermeable paving surface. This means that virtually all of the rain (minus evaporation) that falls becomes runoff. The parking lot must be built to effectively channel and collect that runoff. Traditionally, the runoff has been shunted directly into storm sewers, streams, or even sanitary sewers. However, most larger municipalities now require retention basins to catch runoff to reduce the stress on sewer systems or streamways.

Water pollution

Parking lots also tend to be subject to contamination with concentrated spots of pollutants such as motor oil. While motor vehicles on roadways may drip oil, they do so over a large area. Oil drips on parking lots are concentrated enough that they can have a deleterious effect on the water quality of the runoff. Other pollutants, even brake-lining dust, rust particles, and other particulate materials that settle on the parking lot surface, can be a similar problem. Therefore, an important second function of the retention basin for parking lots is to act as a temporary storage impoundment to allow particulate materials to settle out and to slow or even prevent the release of other pollutants into waterways. In some places, the water is not channeled into retention basins, but into dry wells.

Alternative paving

An alternative solution today is to use permeable paving surfaces, such as brick, stone, special paving blocks, or tire-tread woven mats. The intent of these is to allow precipitation falling on the surface to soak into the ground through the spaces inherent in the parking lot surface. The ground then may become contaminated in the surface of the parking lot, but this tends to stay in a small area of ground, which effectively filters water before it seeps away.

Parking lot landscaping

Many areas today also require minimum landscaping in parking lots. This usually principally means the planting of trees to provide shade. Customers have long preferred shaded parking spaces in the summer, but parking lot providers have long been antagonistic to planting trees because of the extra cost of cleaning the parking lot. However, parking lots represent significant heat islands and, indeed, heat sinks in urban areas. The heat from paved areas in urban zones has been shown to even have the power to change the weather locally. By providing trees or other means of shading parking lots, the heat and glare resulting from them can be significantly reduced.

Parking standards

Many municipalities also have established minimum spacing standards for parking lots, the standards depending on whether the parking is parallel, pull-in, or diagonal, and depending on what types of vehicles are allowed to park in the lot or a particular section of it. Codes also usually specify that a given parking lot must have a certain minimum number of spaces, depending on the floor area in a store, or how many bedrooms in an apartment complex.

American English

American English (AmE) is the dialect of the English language used mostly in the United States of America. Crystal (1997) estimates that approximately two thirds of native speakers of English live in the United States. American English is also sometimes called United States English or U.S. English.

History

English was inherited from British colonization. The first wave of English-speaking immigrants was settled in North America in the 17th century. In that century, there were also speakers in North America of the Dutch, French, German, myriad Native American, Spanish, Swedish, Scots, Welsh, Irish, Scottish Gaelic and Finnish languages.

Phonology

In many ways, compared to British English, American English is conservative in its phonology. The conservatism of American English is largely the result of the fact that it represents a mixture of various dialects from the British Isles. Dialect in North America is most distinctive on the East Coast of the continent; this is largely because these areas were in contact with England, and imitated prestigious varieties of British English at a time when those varieties were undergoing changes. The interior of the country was settled by people who were no longer closely connected to England, as they had no access to the ocean during a time when journeys to Britain were always by sea. As such the inland speech is much more homogeneous than the East Coast speech, and did not imitate the changes in speech from England. East Coast-influenced non-rhotic pronunciations may be found among blacks throughout the country.]]Most North American speech is rhotic, as English was in most places in the 17th century. Rhoticity was further supported by Hiberno-English, Scottish English, and West Country English. In most varieties of North American English, the sound corresponding to the letter "R" is a retroflex semivowel rather than a trill or a tap. The loss of syllable-final r in North America is confined mostly to the accents of eastern New England, New York City and surrounding areas, South Philadelphia, and the coastal portions of the South. Dropping of syllable-final r sometimes happens in natively rhotic dialects if r is located in unaccented syllables or words and the next syllable or word begins in a consonant. In England, lost 'r' was often changed into (schwa), giving rise to a new class of falling diphthongs. Furthermore, the 'er' sound of (stressed) fur or (unstressed) butter, which is represented in IPA as stressed or unstressed is realized in American English as a monophthongal r-colored vowel. This does not happen in the non-rhotic varieties of North American speech. Some other British English changes in which most North American dialects do not participate:
- The shift of to (the so-called "broad A") before alone or preceded by . This is the difference between the British Received Pronunciation and American pronunciation of bath and dance. In the United States, only linguistically conservative eastern-New-England speakers took up this innovation.
- The shift of intervocalic to glottal stop , as in for bottle. This change is not universal for British English (and in fact is not considered to be part of Received Pronunciation), but it does not occur in most North American dialects. Newfoundland English and the dialect of New Britain, Connecticut are notable exceptions. On the other hand, North American English has undergone some sound changes not found in Britain, at least not in standard varieties. Many of these are instances of phonemic differentiation and include
- The merger of and , making father and bother rhyme. This change is nearly universal in North American English, occurring almost everywhere except for parts of eastern New England, like the Boston accent.
- The replacement of the lot vowel with the strut vowel in what, was, of, from, everybody, nobody, somebody, anybody, because, and in some dialects want.
- The merger of and . This is the so-called cot-caught merger, where cot and caught are homophones. This change has occurred in eastern New England, in Pittsburgh and surrounding areas, and from the Great Plains westward.
- Vowel merger before intervocalic . Which (if any) vowels are affected varies between dialects.
- The merger of and after palatals in some words, so that cure, pure, mature and sure rhyme with fir in some speech registers for some speakers.
- Dropping of after alveolar consonants so that new, duke, Tuesday, suit, resume, lute are pronounced , , , , , .
- Æ-tensing in environments that vary widely from accent to accent. In some accents, particularly those from Philadelphia to New York City, and can even contrast sometimes, as in Yes, I can vs. tin can .
- Laxing of , and to , and before , causing pronunciations like , and for pair, peer and pure.
- The flapping of intervocalic and to alveolar tap before reduced vowels. The words ladder and latter are mostly or entirely homophonous, possibly distinguished only by the length of preceding vowel. For some speakers, the merger is incomplete and 't' before a reduced vowel is sometimes not tapped following or when it represents underlying 't'; thus greater and grader, and unbitten and unbidden are distinguished. Even among those words where and are flapped, words that would otherwise be homophonous are, for some speakers, distinguished if the flapping is immediately preceded by the diphthongs or ; these speakers tend to pronounce writer with and rider with . This is called Canadian raising; it is general in Canadian English, and occurs in some northerly versions of American English as well (often just applying to the diphthong , but not to ).
- Both intervocalic and may be realized as or , making winter and winner homophones. This does not occur when the second syllable is stressed, as in entail.
- The pin-pen merger, by which is raised to before nasal consonants, making pairs like pen/pin homophonous. This merger originated in Southern American English but is now widespread in the Midwest and West as well. Some mergers found in most varieties of both American and British English include:
- The horse-hoarse merger of the vowels and before 'r', making pairs like horse/hoarse, corps/core, for/four, morning/mourning etc. homophones.
- The wine-whine merger making pairs like wine/whine, wet/whet, Wales/whales, wear/where etc. homophones. Many older varieties of southern and western American English still keep these distinct, but the merger appears to be spreading.

Differences in British English and American English

Main article: American and British English differences American English has both spelling and grammatical differences from British English (or Commonwealth English), some of which were made as part of an attempt to rationalize the English spelling used by British English at the time. Unlike many 20th century language reforms (for example, Turkey's alphabet shift, Norway's spelling reform) the American spelling changes were not driven by government, but by textbook writers and dictionary makers. The first American dictionary was written by Noah Webster in 1828. At the time America was a relatively new country and Webster's particular contribution was to show that the region spoke a different dialect from Britain, and so he wrote a dictionary with many spellings differing from the standard. Many of these changes were initiated unilaterally by Webster. Webster also argued for many "simplifications" to the idiomatic spelling of the period. Somewhat ironically, many, although not all, of his simplifications fell into common usage alongside the original versions, resulting in a situation even more confused than before. Many words are shortened and differ from other versions of English. Spellings such as center are used instead of centre in other versions of English. Conversely, American English sometimes favors words that are morphologically more complex, whereas British English uses clipped forms, such as AmE transportation and BrE transport or where the British form is a back-formation, such as AmE burglarize and BrE burgle (from burglar).

English words that arose in the U.S.

A number of words that arose in the United States have become common, to varying degrees, in English as it is spoken internationally. Although its origin is disputed, the most famous word is probably OK, which is sometimes used in other languages as well. Other American introductions include "belittle," "gerrymander" (from Elbridge Gerry), "blizzard", "teenager", and many more.

English words obsolete outside the U.S.

A number of words that originated in the English of the British Isles are still in everyday use in North America, but are no longer used in most varieties of British English. The most conspicuous of these words are fall, the season; to quit, as in "to cease an activity" (as opposed to "to leave a location" as still used in most other Anglophone countries); and gotten as a past participle of get. Americans are more likely than Britons to name a stream whose breadth or volume is judged insufficient for it to be a river or a creek. The word diaper goes back at least to Shakespeare, and usage was maintained in the U.S. and Canada, but was replaced in the British Isles with nappy. Some of these words are still used in various dialects of the British Isles, but not in formal standard British English. Many of these older words have cognates in Lowland Scots. The subjunctive mood is livelier in North American English than it is in British English; it appears in some areas as a spoken usage, and is considered obligatory in more formal contexts in American English. British English has a strong tendency to replace subjunctives with auxiliary verb constructions.

Regional differences

Main article: American English regional differences Spoken American English is not homogeneous throughout the country, and various regional and ethnic variants exist. These differences affect both pronunciation and the lexicon, and can make one accent a little difficult for speakers of another accent to understand. General American is the name given to any American accent that is relatively free of noticeable regional influences. It enjoys high prestige among Americans, but is not a standard accent in the way that Received Pronunciation is in England.

References

External links

- [http://www.pbs.org/speak/ Do You Speak American]: PBS special
- [http://cfprod01.imt.uwm.edu/Dept/FLL/linguistics/dialect/ Dialect Survey] of the United States, by Bert Vaux et al., Harvard University. The answers to various questions about pronunciation, word use etc. can be seen in relationship to the regions where they are predominant.
- [http://www.ling.upenn.edu/phono_atlas/home.html Phonological Atlas of North America] at the University of Pennsylvania
- [http://students.csci.unt.edu/~kun Guide to Regional English Pronunciation] includes working versions of the Telsur Project maps from the Phonologial Atlas site
- [http://www.peak.org/~jeremy/dictionary/ The American•British British•American Dictionary]
- [http://classweb.gmu.edu/accent/ Speech Accent Archive]
- [http://www.world-english.org/ World English Organization]
- [http://www.esuus.org English Speaking Union of the United States]
- [http://canadianenglish1.narod.ru American Canadian British English Lexical Differences In One Table]
- [http://australianenglish1.narod.ru Australian American British English Lexical Differences In One Table And More]
- [http://www.englisch-hilfen.de/en/words_list/british_american.htm British, American, Australian English - Lists and Online Exercises]
- [http://www.globalenglishsalon.com/ Listen to spoken American English (midwest

British English

British English (BrE) is a term used to differentiate the form of the written English language in the United Kingdom from other forms of the English language. It is also used by some, particularly Americans, to describe the spoken versions of English used within England. The term is rarely heard within the United Kingdom. British people say that they speak English - but never British - and that others speak English with an accent, such as a 'South African accent'. When speaking, they will often drop the word "accent" and simply say Canadian, American, Jamaican and so on. A less ambiguous term is English English. Although British English can describe the formal written English used in the United Kingdom, the forms of spoken English used in the United Kingdom vary considerably more than in most other areas of the world where English is spoken. Dialects and accents vary not only within regions of the UK, for example in Scotland, Northern Ireland and Wales, but also within England. The written form of the language, as taught in schools, is universally Commonwealth English with a slight emphasis on a few words that might be more common in some areas than in others. For example, although the words "wee" and "small" are interchangeable, one is more likely to see "wee" written by a Scot than by a Londoner. For historical reasons dating back to the rise of London in the 9th century, the variety of language spoken in London and the East Midlands became the standard English within the Court and thus the form of language generally accepted for use in the law, government, literature and education of the British Isles. Like other forms of languages, the English used in Britain changes over time. Although British English is often used in the United States to denote the English spelling and lexicon used outside the US, the term Commonwealth English is more accurate for this purpose. The British spellings were most famously recorded in Samuel Johnson's A Dictionary of the English Language (1755). Historically, the widespread usage of English across the world is attributed to the power once held by the British Empire, and hence the most common form of English used by the British ruling class was the English used in south-east England (in the area around the capital city London, and the main English university towns of Oxford and Cambridge). This form of the language is associated with Received Pronunciation (RP), which is still regarded by many people outside the UK (especially in the United States) as "the British accent". From the second half of the 20th century to the present day, the preeminence of the English language has largely been linked to the economic, military and political dominance of the United States in world affairs, and American English is often regarded as the most prominent form of English in the world today, especially with the large amount of U.S. cultural products (such as films, books, and music) around the world, which is not matched in volume by those from other English-speaking nations. The form of English spoken and particularly written in the United Kingdom still has a major cultural influence on the English used in many Commonwealth countries, including Australia, South Africa, and India, as well as in the European Union. Although British English is taught and used in the former British colonies of Hong Kong, Singapore and Malaysia, American English is often taught in Chinese and Japanese schools, and in other schools throughout Asia.

-ise versus -ize

Words of the sort organize/organise and their derivatives can be spelt with either s or z in British English. The -ize forms are promoted by the Oxford English Dictionary. British English with -ize is sometimes known as OED spelling, and may be marked by the registered IANA language tag 'en-GB-oed'. It is the spelling used by the Encyclopaedia Britannica, by the United Nations, and by many international organizations and academic publications. The -ize forms were used by the London Times until the mid-1980s. The -ise forms are now generally used by the British government, by the European Union and mostly taught in the British school system. They are far more prevalent in common usage. Pam Peters (2004, -ize/-ise) relates that British National Corpus data indicates the ratio of popularity for -ise forms to -ize forms in Britain is 3:2.

Multi-storey car park

A multi-storey car park is a building (or part thereof) which is designed specifically to be for automobile parking and where there are a number of floors or levels (stories or storeys) on which parking takes place. It is essentially a stacked car park or parking lot.

Nomenclature

The term "multi-storey car park" is used in the United Kingdom, Hong Kong, Singapore and many British Commonwealth countries. In most of North American English, the term parking garage is used (in contrast to a home, which just has a "garage"). In many places in North America, "parking garage" refers only to an indoor (often underground) structure – outdoor multi-level parking facilities being referred to by a number of regional terms, most often parking deck in eastern American English, or the uniquely Canadian English parkade (a portmanteau of "parking arcade"). Architects and civil engineers are likely to call it a parking structure instead, since their work is all about various structures, and that term is the vernacular in some of the western United States. The term parking ramp is used in the upper Midwest, especially Minnesota and Wisconsin, and has been sighted as far east as Toledo, Ohio and Buffalo, New York.

Design

Movement of vehicles between floors can be effected by:
- interior ramps, most often
- exterior ramps - which may take the form of a circular ramp ( a.k.a. a 'whirley-gig' )
- vehicle lifts or elevators, rarely In locations where the car park is built on sloping land, the car park may be split-level. Many car parks are independent buildings that are dedicated exclusively to that use. In recent times, car parks built to serve residential and some business properties are built as part of a larger building, and often are built underground as part of the basement. Car parks which serve shopping centres can sometimes be built adjacent to the shopping centre so as to effect easier access at each floor between shops and parking. One example would be the Mall of America in Minneapolis, Minnesota, USA, which has two large car parks attached to the building at the eastern and western ends of the mall. category: buildings and structures category: road transport

Concrete

In construction, concrete is a composite building material made from the combination of aggregate and cement binder. The most common form of concrete is Portland cement concrete, which consists of mineral aggregate (generally gravel and sand), Portland cement and water. It is commonly believed that concrete dries after mixing and placement. Actually, concrete does not solidify because water evaporates, but rather cement hydrates, gluing the other components together and eventually creating a stone-like material. When used in the generic sense, this is the material referred to by the term concrete. Concrete is used to make pavements, building structures, foundations, motorways/roads, overpasses, parking structures, bases for gates/fences/poles, and cement in brick or block walls. An old name for concrete is liquid stone.

History

The Assyrians and Babylonians used clay as cement in their concretes. The Egyptians used lime and gypsum cement. In the Roman Empire, cements made from pozzolanic ash/pozzolana and an aggregate made from pumice were used to make a concrete very similar to modern portland cement concrete. In 1756, British engineer John Smeaton pioneered the use of portland cement in concrete, using pebbles and powdered brick as aggregate. In the modern day, the use of recycled/reused materials as concrete ingredients is gaining popularity due to increasingly stringent environmental legislation. The most conspicuous of these is pulverized fuel ash, recycled from the ash by-products of coal power plants. This has a significant impact in reducing the amount of quarrying and the ever-attenuating landfill space.

Characteristics

During hydration and hardening, concrete needs to develop certain physical and chemical properties, among others, mechanical strength, low permeability to ingress of moisture, and chemical and volume stability. Concrete has relatively high compressive strength, but significantly lower tensile strength (about 10% of the compressive strength). As a result, concrete always fails from tensile stresses - even when loaded in compression. The practical implication of these facts is that concrete elements that are subjected to tensile stresses must be reinforced. Concrete is most often constructed with the addition of steel bar or fiber reinforcement. The reinforcement can be by bars (rebars), mesh, or fibres to produce reinforced concrete. Concrete can also be prestressed (reducing tensile stress) using steel cables, allowing for beams or slabs with a longer span than is practical with reinforced concrete. The ultimate strength of concrete is related to water/cement ratio, the proportion and type of cement to fillers, and the size, shape, and strength of the aggregate used. Concrete with lower water/cement ratio (down to 0.35) makes a stronger concrete than a higher ratio. Concrete made with smooth pebbles is weaker than that made with rough-surfaced broken rock pieces for example. Certain shapes are very strong in compression, such as arches and vaults, and are therefore preferred for concrete construction. Concrete is placed in a wet or plastic state, and therefore can be manipulated and molded as needed. Hydration and hardening of concrete may lead to tensile stresses at a time when it has not yet gained significant strength, resulting in shrinkage cracks. However, when concrete mix is placed in accordance with the best recommended practice, cracking may be minimal. vault

Additives

Additives are organic or non-organic materials in form of solids or fluids that are added to the concrete to give it certain characteristics. In normal use the additives make up less than 5% of the cement weight. The most used types of additives are:
- Accelerators: Speed up the hydration (strengthening) of the concete.
- Retarders: Slow the hydration of concrete.
- Air-entrainers: Add and distribute air to the concrete.
- Plasticizers: Increase the workability of concrete.

Workability

Workability is the ability of a fresh (plastic) concrete mix to fill the form/mould properly with the desired work (vibration) and without reducing the concrete's quality. Workability depends on water content, additives, aggregate (shape and size distribution) and age (level of hydration). Raising the water content or adding plasticizer will increase the workability. Too much water will lead to bleeding (loss of water) and/or segregation (concrete starts to get heterogeneous) and the resulting concrete will have reduced quality. Workability is normally tested by slump measurement. High flow concrete, like self compacting concrete, are normaly tested by one of several flow measuring methods. Concrete slump is a simplistic measure of fresh (plastic) concrete's workability. Slump is normally determined by the ASTM C 143 or EN 12350-2 slump test standards, using the Abrams cone, into which concrete is placed for testing. When the cone is carefully lifted off the enclosed material, it will slump a certain amount due to its water content. A relatively dry sample will slump very little, and be given a slump of one or two inches (25 or 50 mm), while a relatively wet concrete sample may slump as much as six or seven inches (150 to 175 mm). To increase the slump, the rule of thumb is:
- US units :Add 1 US gallon of water per cubic yard of concrete in the mixer truck to increase slump by 1 inch. Adding 27 US gallons to 9 cubic yards of batched concrete will therefore increase the slump by about 3 inches.
- Metric units (converted from US rule of thumb) :Add 2 litres of water per cubic metre of concrete in the mixer truck to increase slump by 1 cm. Adding 54 litres to 9 cubic metres of batched concrete will therefore increase the slump by about 3 cm. Slump can also be increased by adding a plasticizer, without changing the water/cement ratio.

Self compacting concretes

During the 1980s a number of countries including Japan, Sweden and France developed a range of concretes that were self-compacting. These 'SCC's are characterised by their extreme fluidity (using plasticizers), behaving more like water than the traditional viscous concrete. SCCs are characterized by
- extreme fluidity measured by flow or slump, typically measured between 700-750 mm.
- no need for vibrators to compact the concrete, which can be noisy
- no or little need for expensive concrete pumping equipment
- no bleed water (excess water draining out of the concrete) SCC can offer benefits of up to 50% in labour costs, due to it being poured up to 80% faster and having reduced wear and tear on formwork. As of 2005, self compacting concretes account for 10-15% of concrete sales in some European countries.

Shotcrete / sprayed concrete

Main article: Shotcrete

Shotcrete uses compressed air to shoot (cast) concrete to a frame or structure. Shotcrete is mostly used for rock support, especially in tunnelling. Today there are two application methods for shotcrete: the dry-mix and the wet-mix procedure. In Dry-mix the dry mixture of cement and aggregates is filled into the machine and conveyed with compressed air through the hoses. The water needed for the hydration is added at the nozzle. In Wet-mix the mixes are prepared with all necessary water for hydration. The mixes are pumped through the hoses. At the nozzle compressed air is added for spraying. For both methods additives such as plasticizers and accelerators may be used. Shotcrete is normally reinforced by fibers.

External link

- [http://inventors.about.com/library/inventors/blconcrete.htm History of Concrete] Category:Concrete Category:Civil engineering Category:Materials Category:Construction Category:Pavements Category:Heterogeneous mixtures ms:Konkrit ja:コンクリート simple:Concrete

Gravel

] Gravel is rock that is of a certain size range. In geology, gravel is any loose rock that is at least two millimeters in its largest dimension (about 1/12 of an inch), and no more than 75 millimeters (about 3 inches). Sometimes gravel is restricted to rock in the 2-4 millimeter range, with pebble being reserved for rock 4-75 millimeters (some say 64 millimeters). The next smaller size class in geology is sand, which is 0.02 mm to 2 mm in size. The next larger size is cobble, which is 75 (64) millimeters to 256 millimeters (about ten inches). Gravel is an important commercial product, used in many applications. Some important types of gravel include:
- Crushed stone: This is generally limestone or dolomite that has been crushed and graded by screens to certain size classes. It is widely used in concrete and as a surfacing for roads and driveways, sometimes with tar applied over it. Crushed stone may also be made from granite and other rocks. A special type of limestone crushed stone is dense grade aggregate, or DGA, also known as crusher run. This is a mixed grade of mostly small crushed stone in a matrix of crushed limestone powder.
- Creek rock: This is generally rounded stones, potentially of a wide range of types, that are dredged or scooped from river beds and creek beds. It is also often used as concrete aggregate and less often as a paving surface. In Britain, gravel always refers to smooth, rounded, river-worn material, never to angular stones or crushed rock. British gravel ranges in size from 4 mm to about 30 mm, the smaller sizes up to 8 mm are usually called 'pea gravel'. Many roadways are surfaced with gravel, especially in rural areas where there is little traffic. Globally, far more roads are surfaced with gravel than with concrete or tarmac; Russia alone has over 400,000 km of gravel-surfaced roads. Large gravel deposits are a common geological feature, being formed as a result of the weathering and erosion of rocks. The action of rivers and waves tends to pile up gravel in large concentrations. This can sometimes result in gravel becoming compacted and concreted into the sedimentary rock called conglomerate. Where natural gravel deposits are insufficient for human purposes, gravel is often produced by quarrying and crushing hard-wearing rocks, such as sandstone, limestone, or basalt. Quarries where gravel is extracted are known as gravel pits. Southern England possesses particularly large concentrations of them due to the widespread deposition of gravel in the region during the Ice Ages. The word comes from the French gravelle, meaning "coarse sand".

Types of gravel

French]] Multiple types of gravel have been recognised by geologists. They include:
- Bank gravel: gravel intermixed with sand or clay.
- Bench gravel: a bed of gravel located on the side of a valley above the present stream bottom, indicating the former location of the stream bed when it was at a higher level.
- Fine gravel: gravel consisting of particles with a diameter of 1 to 2 mm.
- Lag gravel: a surface accumulation of coarse gravel produced by the removal of finer particles.
- Pay gravel: also known as "pay dirt"; a nickname for gravel with a high concentration of gold and other precious metals. The metals are recovered through gold panning.
- Piedmont gravel: a coarse gravel carried down from high places by mountain streams and deposited on relatively flat ground, where the water runs more slowly.
- Plateau gravel: a layer of gravel on a plateau or other region above the height at which stream-terrace gravel is usually found.
- River run gravel: naturally deposited gravel found in and next to rivers and streams.

Permeable paving

Permeable paving, also called pervious paving or "porous pavement", is a term used to describe paving methods for roads, parking lots and walkways that allow the movement of water and air through the paving material. Although some porous paving materials appear nearly indistinguishable from nonporous materials, their environmental effects are qualitatively different. Their effects are important because pavements are two-thirds of the potentially impervious surface cover in urban areas. Porous pavements have been called “the holy grail of environmental site design” and “potentially the most important development in urban watersheds since the invention of the automobile”. To date, porous pavements constitute only a minute fraction of the paving done each year in the United States. But their rate of growth, on a percentage basis, is very high, primarily because of public concern about and legal requirements for stormwater management. In new suburban growth, porous pavements protect pristine watersheds. In old town centers, redevelopment and reconstruction are opportunities for environmental rehabilitation simultaneously with urban renewal.

Advantages of permeable paving

Permeable paving surfaces are highly desirable because of the problems associated with water runoff from paved surfaces (see Wikipedia article on Impervious Surfaces). Part of the problem is creating an unnatural volume of runoff from precipitation, which causes serious erosion and siltation in streams and other bodies of waters. Part of the problem is also the washing off of vehicular pollutants into water bodies. Permeable paving surfaces keep the pollutants in place in the soil or other material underlying the roadway, and allow water seepage to recharge groundwater while preventing the stream erosion problems. They capture the heavy metals that fall on them, preventing them from washing downstream and accumulating inadvertently in the environment. In the void spaces, naturally occurring micro-organisms digest car oils, leaving little but carbon dioxide and water; the oil ceases to exist as a pollutant. Rainwater infiltration through the pavement into the underlying soil reduces stormwater volume and restores natural subsurface flow paths. The cost of porous pavement, with its built-in stormwater management, is usually less that that of an impervious pavement with a separate stormwater management facility somewhere downstream. Porous pavements give urban trees the rooting space they need to grow to full size. A “structural-soil” pavement base combines structural aggregate with soil; a porous surface admits vital air and water to the rooting zone. This integrates healthy ecology and thriving cities, with the living tree canopy above, the city’s traffic on the ground, and living tree roots below.

Types of permeable paving surfaces

Installation of porous pavements is not more difficult than that of dense pavements, but it is different, and its different specifications and procedures must be strictly adhered to. Nine different families of porous paving materials present distinctive advantages and disadvantages for specific applications. Here are examples: "Porous asphalt" is mixed at conventional asphalt plants, but fine (small) aggregate is omitted from the mixture. The remaining large, single-sized aggregate particles leave open voids that give the material its porosity and permeability. Under the porous asphalt surface is a base course of further single-sized aggregate. Porous asphalt surfaces are being used on highways to improve driving safety by removing water from the surface. "Porous concrete", like porous asphalt, can bear frequent traffic, and is universally accessible. It depends for its quality on a qualified installer. "Single-sized aggregate" without any binder is the most permeable paving material in existence — and the least expensive. Although it can be used only in very low-traffic settings such as seldom-used parking stalls, its potential cumulative area is great. "Porous turf", if properly constructed, can be used for occasional parking like that at churches and stadiums. Living turf transpires water, actively counteracting the “heat island” with what appears to be a green open lawn. "Open-jointed blocks" are concrete or stone units with open, permeable spaces between the units. They given an architectural appearance, and can bear surprisingly heavy traffic.

Reference

Ferguson, Bruce K., 2005, Porous Pavements, Boca Raton: CRC Press.

Outside links

- [http://www.pavingexpert.com/permabl1.html McCormock & Son's pavingexpert site]
- [http://www.greenbuilder.com/sourcebook/PerviousMaterials.html Sustainable Building Sourcebook]
- [http://www.lid-stormwater.net/permeable_pavers/permtrans_home.htm Low-Impact Development Center, Inc.]
- [http://www.concretenetwork.com/concrete/porous_concrete_pavers/ Concrete Network]
- [http://www.advancedpavement.com/system.htm Advanced Pavement Technology]
- [http://www.stormwatercenter.net/ Stormwater Manager’s Resource Center]
- [http://www.biopaver.com/problems.html Biopaver] Category:Pavements É

Landscaping

A landscape is the character of an expanse of land.
- Landscape architecture is the planning and design of the land, including not just gardens and parks, but also industrial installations. This practice is known as landscaping.
- Landscape painting is the depiction of a landscape, with the emphasis on large-scale, distant features rather than foreground objects.
- Landscaping refers to building a model landscape, e.g. for model train layouts.
- Landscaping of the male body is heretofore referred to as manscaping.
- Landscape was also a British 1980's synthpop band.

Storm sewer

A storm drain, storm sewer, stormwater drain (Australia) or surface water (UK) system is designed to drain excess rain and ground water from an area. Storm drains vary in design from small residential dry wells to large municipal systems. They are present on most motorways, freeways and other busy roads, as well as towns in areas which experience heavy rainfall, flooding and coastal towns which experience regular storms. Ideally, storm drains should be separate from sanitary sewers, though in some places the runoff from storm drains is subjected to sewage treatment when there is sufficient capacity to spare. In these systems a sudden large rainfall that exceeds sewage treatment capacity will be allowed to overflow directly from the storm drains into watersheds via structures called combined sewer overflows. Building codes vary greatly on the handling of storm drain runoff. New developments might be required to construct their own storm drain processing capacity for returning the runoff to the water table and bioswales may be required in sensitive ecological areas to protect the watershed. An international subculture has grown up around the exploration of stormwater drains. Societies such as the Cave Clan regularly explore the drains underneath cities. This is commonly known as 'urban exploration', but is also known as 'draining' when in specific relation to storm drains. Category:Sewerage Category:Subterranea Category:Water streams Category:Physical infrastructure

Sanitary sewer

A sanitary sewer (also called, especially in the UK, a foul sewer) is a type of underground carriage system for transporting sewage from houses or industry to treatment or disposal. In some areas, sanitary sewers are separate sewer systems specifically for the carrying of domestic and industrial wastewater, and are operated separately and independently of storm drains, which carry the runoff of rain and other water which wash into city streets. Category:Sewerage

Brake

:For the band, see Brakes (band). ---- A brake is a device for slowing or stopping the motion of a machine, and to keep it from starting to move. The kinetic energy lost by the moving part is usually translated to heat by friction. Alternatively, in regenerative braking, the energy is recovered and stored in a flywheel, capacitor or other device for later use. Note that kinetic energy increases with the square of the velocity (E = ½m·v² relationship). This means that if the speed of a vehicle doubles, it has four times as much energy. The brakes must therefore dissipate four times as much energy to stop it and consequently the braking distance is four times longer. Brakes of some description are fitted to most wheeled vehicles, including automobiles of all kinds, trucks, trains, motorcycles, and bicycles. Baggage and shopping carts may have them for use on a moving ramp. Some aeroplanes are fitted with wheel brakes on the undercarriage. Some aircraft also feature air brakes designed to slow them down in flight. Notable examples include gliders and some WWII-era fighter aircraft which allow the aircraft to maintain a safe speed in a steep descent. Most modern cars have vacuum assisted servo brakes. Deceleration and avoiding acceleration when going downhill, is also achieved by using a low gear, see engine braking. Friction brakes on cars store the heat in the rotating part (drum or disc) during the brake application and release it to the air gradually.

Types of brake

- Air brake (aircraft)
- Air brake (rail)
- Disc brake
- Drum brake
- Electromagnetic brake
- Hydraulic brake
- Vacuum brake

Rust

:This article is about a type of chemical corrosion. For the fungus, see rust (fungus). For the person, see Mathias Rust. For the town in Austria, see Rust, Austria. Rust, Austria Rust, Austria Rust, Austria Rust, Austria Rust is the substance formed when iron compounds corrode in the presence of water and oxygen. It is a mixture of iron oxides and hydroxides. Rusting is a common term for corrosion, and usually corrosion of steel. Iron is found naturally in the ore hematite as iron oxide, and metallic iron tends to return to a similar state when exposed to air, (hydrogen, oxygen, nitrogen, etc) and water. This corrosion is due to the oxidation reaction when iron metal returns to an energetically favourable state. Energy is given off when rust forms. The process of rusting can be summarized as three basic stages: The formation of iron(II) ions from the metal; the formation of hydroxide ions; and their reaction together, with the addition of oxygen, to create rust. Iron is the main component of steel and the corrosion of steel is observed more frequently, since iron is rarely used without alloying in the present day. When steel contacts water, an electrochemical process starts. On the surface of the metal, iron is oxidised to iron(II): :Fe → Fe²⁺ + 2e^- The electrons released travel to the edges of the water droplet, where there is plenty of dissolved oxygen. They reduce the oxygen and water to hydroxide ions: :4e^- + O₂ + 2H₂O → 4OH^- The hydroxide ions react with the iron(II) ions and more dissolved oxygen to form iron oxide. The hydration is variable, however in its most general form: :Fe²⁺ + 2OH^- → Fe(OH)₂ :4Fe(OH)₂ + O₂ → 2(Fe₂O₃.xH₂O) + 2H₂O Hence, rust is hydrated iron(III) oxide. Corrosion tends to progress faster in seawater than fresh water due to higher concentration of sodium chloride ions, making the solution more conductive. Rusting is also accelerated in the presence of acids, but inhibited by alkalis. Rust can often be removed through electrolysis, however the base metal object can not be restored through this method. Hydrated iron oxide is permeable to air and water, meaning that the metal continues to corrode after rust has formed. The iron mass eventually converts entirely to rust, and disintegrates. There are several methods available to control corrosion and prevent the formation of rust. Cathodic protection is a method to control corrosion and the formation of rust using electrochemical techniques. Galvanizing consists of coating metal with a thin layer of another metal, such as zinc. The electrochemical potential of zinc is more negative than steel (or iron) and will provide cathodic protection to the underlying steel. Typically, zinc is applied by either hot-dip galvanizing or electrogalvanizing. A good thing about galvanising is that a scratch on a galvanised piece of iron will not lead to rust at the scratch. The zinc layer acts as a galvanic anode. Corrosion control can be done using a coating to isolate the metal from the environment. Covering steel with concrete provides protection to steel by the high pH environment at the steel-concrete interface. However, if concrete covered steel does corrode, the rust formed can cause the concrete to spall and fall apart. This creates structural problems. Corrosion of aluminum is different from steel or iron, in that aluminum oxide formed on the surface of aluminum metal forms a protective, corrosion resistant coating, a process known as passivation. This is also true of magnesium, copper and other metals. Category:Corrosion ja:錆

Dry well

Dry well refers to an underground storage facility for water, typically storm water runoff. Simple dry wells consist of a pit full of riprap or other debris. More complex dry wells may be made of plastic or concrete. They have holes in the sides and bottom to let stored water percolate out to surrounding soil, and are sometimes used at the end of a French Drain to store runoff.

Permeable paving

Advantages of permeable paving

Types of permeable paving surfaces

Reference

Ferguson, Bruce K., 2005, Porous Pavements, Boca Raton: CRC Press.

Outside links

Brick

This page is about bricks used for construction. For other types of brick please see Brick (disambiguation). Brick (disambiguation) A brick is a ceramic block made of kiln-fired material, usually clay or ground shale. Clay bricks are formed in a mould (the soft mud method), or more frequently in commercial mass production by extruding clay through a die and then wire-cutting them to the proper size (the stiff mud process). Brick made from dampened clay must be formed in molds with a great deal of pressure, usually applied by a hydraulic press. These bricks are known as hydraulic-pressed bricks, and have a dense surface which makes them highly resistant to weathering, and thus suitable for facing work. The shaped clay is then dried and fired to achieve the final, desired strength. In modern brickworks, this is usually done in a continuously fired kiln, in which the bricks move slowly through the kiln on conveyors, rails, or kiln cars to achieve consistent physical characteristics for all bricks. Bricks are also known in the building trades as compressed earth blocks or CEBs.

History

clay In the Near East and India, bricks have been in use for more than five thousand years. The Tigris-Euphrates plain lacks rocks and trees. Sumerian structures were thus built of plano-convex mudbricks, not fixed with mortar or with cement. As plano-convex bricks (being rounded) are somewhat unstable in behaviour, Sumerian bricklayers would lay a row of bricks perpendicular to the rest every few rows. They would fill the gaps with bitumen, straw, marsh reeds, and weeds. The Ancient Egyptians and the Indus Valley Civilization also used mudbrick extensively, as can be seen in the ruins of Buhen, Mohenjo-daro and Harappa, for example. The Romans made use of fired bricks, and the Roman legions, which operated mobile kilns, introduced bricks to many parts of the empire. Roman bricks are often stamped with the mark of the legion that supervised its production. The use of bricks in Southern and Western Germany, for example, can be traced back to traditions already described by the Roman architect Vitruvius. In the 12th century, bricks from Northern Italy were re-introduced to Northern Germany, where an independent tradition evolved. It culminated in the so-called brick Gothic, a reduced style of Gothic architecture that flourished in Northern Europe, especially in the regions around the Baltic Sea which are without natural rock resources. Brick Gothic buildings, which are built almost exclusively of bricks, are to be found in Denmark, Germany, Poland and Russia. However, bricks were long considered an inferior substitute for natural rock. During the Renaissance and the Baroque, visible brick walls were unpopular and the brickwork was often covered with plaster. It was only during the mid-18th century that visible brick walls regained some degree of popularity, as illustrated by the Dutch Quarter of Potsdam, for example.

Construction and types

Potsdam Hard-burned brick should be used for face work exposed to the weather, and soft brick for filling, foundations, and the like. The mainstay standard US brick measures approximately 8 x 4 x 2.25 inches (203 x 102 x 57 millimeters), and has a crushing strength of between 1000 and 3000 lbf/in² (7 to 21 megapascals) depending on quality. The standard UK brick size is 215 x 102.5 x 65 millimetres. A highly impervious and ornamental surface may be laid on brick either by salt glazing, in which salt is added during the burning process, or by the use of a "slip," which is a glaze material into which the bricks are dipped. Subsequent reheating in the kiln fuses the slip into a glazed surface integral with the brick base.

Proportions

Regardless of size, bricks are usually manufactured with the depth equal to half the length (assuming that the brick is laid horizontally). This allows for several convenient layouts which must necessarily interweave the bricks in any structure, often both at the corners and within the wall depth in order to ensure the greatest possible durability of the structure.

Use

salt glazing) on the west side of Lake Lily in Maitland, Florida. It was built in 1915 or 1916, paved over at some point, and restored in 1999.]] Bricks are typically for building. In the USA at one time, it was popular to pave roads with bricks, but they were found incapable of withstanding heavy traffic. Brick paving is again coming back into use as a method of traffic calming or as a decorative surface in pedestrian precincts. Bricks are also used in the metallurgy and glass industries for lining furnaces. They have various uses, especially refractory bricks such as silica, magnesia and neutral (chromomagnesite) refractory bricks. This type of brick must have a series of properties such as good thermal shock resistance, refractoriness under load, high melting point, satisfactory porosity (which can influence several other properties), all of which are high-temperature properties. There is a large refractory brick industry, especially in the United Kingdom, Japan and the U.S.A.

Tire

A tire (U.S. spelling) or tyre (UK spelling) is a roughly toroidal piece of material placed on the circumference of a wheel, either for the purpose of cushioning or to protect the wheel from wear and tear.

Pneumatic tires

Air-filled tires are known as pneumatic tires, and these are the type in almost universal use today. Pneumatic tires are made of a flexible elastomer material such as rubber with reinforcing threads/wires inside the elastomer material. The air compresses as the wheel goes over a bump and acts as a shock absorber. Tires are inflated through a Schrader valve. Attempts have been made to make various types of solid tire but none has so far met with much success. The "steering feel" of such tires is different from that of pneumatic tires, as their solidity does not allow the amount of torsion that exists in the carcass of a pneumatic tire under steering forces, and the resultant sensory feedback through the steering apparatus. The common motor vehicle tire is mounted around a steel rim at service stations or repair shops for vehicles using a special tire mounting apparatus while the wheel is off the vehicle. After mounting, the tire is inflated (pressurized) with air through the valve stem to manufacturer's specified pressure, which is more than atmospheric pressure. The rim with the tire mounted onto it comprises the removable wheel, which is then attached to the vehicle through a number of holes in the rim using lug nuts. Because tires are often not made with perfectly even mass all around the tire, a special tire-balancing apparatus at a repair shop spins the wheel with the tire to determine where small weights should be attached to the outer edge of the rim to balance out the wheel. Such tire balancing with these kind of weights avoids vibration when the vehicle is driven at higher speeds. The same device used to mount a tire onto a rim is also used to remove a tire from the rim, again when the wheel is off the vehicle. On the wheels of many vehicles, hubcaps are often snapped in place over the part of the rim facing outside and the tightened lug nuts for decoration and, to some extent, for protection from the elements to reduce rusting of the rim and lug nuts. Some rims are already decoratively made and plated with chrome, so hubcaps are not used over them. The hubcap must be removed to take off the tire, and after the tire is replaced, the hubcap is put back on. The outer perimeter of the tire, often called the crown, has various designs of jagged shaped grooves in it. These grooves are especially useful during weather with rain (or snow). The water from the rain would be compressed into the grooves by the vehicle's weight, providing better traction in the tire to road contact. Without such grooves, a layer or film of water would form between the wet roads and the tire surface, which would substantially reduce the traction making the tire contact with the road very slippery. Traction is especially important for good braking. The depth of these grooves essentially constitutes the tread depth at any time during the lifetime of the car. When the tread on the outer perimeter of the tire inevitably wears away from use, reducing the tread depth, the tire should be replaced. The sidewalls are the sections of the tire which are between the crown and the inner circular edges of the tire contacting the rim. To avoid tearing at these inner edges, particularly when the tire is being mounted, there are a number of concentric steel wires buried inside the rubber at both inner edges of the tire. Some air-filled tires, especially those used with spoked wheels such as on bicycles, or on vehicles travelling on rough roads, have an inner tube; this was also formerly the case of automobile tires. This is a fully sealed rubber tube with a valve to control flow of air in and out. Others, including modern radial tires, use a seal between the metal wheel and the tire to maintain the internal air pressure (tubeless tire). This method, however, tends to fail desperately if the vehicle is used on rough roads (for example Kenyan roads) as a small bend on the rim (metal wheel) will result in deflation. The inner tubes are usually made of halobutyl rubber, because of its suitable mechanical properties and excellent impermeability for air. Pneumatic tires generally have reinforcing threads in them; based on the orientation of the threads, they are classified as bias-ply/cross ply or radial. Tires with radial yarns (known as radial tires) are standard for almost all modern automobiles.

History

automobiles For most of history wheels had very little in the way of shock absorption and journeys were very bumpy and uncomfortable. The modern tire came about in stages in the 19th century. In 1844, Charles Goodyear invented vulcanized rubber, the material that would later be used to produce tires. John Boyd Dunlop, a veterinary surgeon living in Belfast Ireland, is widely recognized as the father of the modern tire, although he was not the first to come up with the idea. In 1845 the first pneumatic (inflatable) tire was patented by Scottish engineer Robert William Thomson as the Aerial Wheel. This invention consisted of a canvas inner tube surrounded by a leather outer tire. The tire gave a good ride, but there were so many manufacturing and fitting problems that the idea had to be abandoned. John Dunlop re-invented the tire for his ten year old son's tricycle in 1887 and was awarded a patent for his tire in 1888 (rescinded 1890). Dunlop's tire had a modified leather hosepipe as an inner tube and rubber treads. It wasn't long before rubber inner tubes were invented. Carbon black was added to tires to improve durability and provide damage resistance, particularly from ultraviolet light from the sun. In recent years less of it is being used in order to improve gas mileage, and the resulting reduction in electrical conductivity makes static electricity more likely to build up and arc between a person and the metal part of the door when getting out of a car. [http://www.cartalk.com/content/columns/Archive/1994/November/11.html] Because neither bicycles nor automobiles had been invented when Thomson produced his tire, that tire was only applied to horse drawn carriages. By Dunlop's time, the bicycle had been fully developed (see Rover) and it proved a far more suitable application for pneumatic tires. Dunlop partnered with William Harvey du Cros to form a company which later became the Dunlop Rubber Company to produce his invention. The invention quickly caught on for bicycles and was later adapted for use on cars. Dunlop's company has since merged with the Goodyear company. The radial tire was invented by Michelin, a French company, in 1946, but did not see wide use in the United States, the largest market at that time, until the 1970s. This type of tire uses parallel carcass belts for the sidewalls and crossed belts for the crown of the tire. All modern car tires are now radial. In 2005, Michelin was reported to be attempting to develop a tire and wheel combination, the Tweel, which does not use air. External link: [http://www.mearns.org.uk/stonehaven/thomson.htm Robert William Thomson]

Etymology

According to the Oxford English Dictionary, quoted in Fowler's Modern English Usage, the word is a shortening of attire, and the British spelling tyre is a recent divergence from historical tradition. Fowler also notes that the altered spelling tyre originally met with resistance from conservative British institutions such as The Times newspaper.

Wagon tires

The earliest tires were hoops of metal placed around wagon wheels. The tire was heated in a forge, placed on the wheel and quenched, causing the metal to contract and imparting stiffness to the wheel. This work was done by a wheelwright, a craftsman who specialized in making wagon wheels.

Maintenance

Friction from moving contact with the road causing the tread on the outer perimeter of the tire to eventually wear away. When the tire tread becomes too shallow, the tire is worn out and should be replaced. The same tire rims can usually be used throughout the lifetime of the car. Uneven or accelerated tire wear can be caused by bad wheel alignment. More wear on a tire facing the outside or the inside of a car is often a sign of bad wheel alignment. When the tread is worn away completely and especially when the wear on the outer rubber exposes the reinforcing threads inside them, the tire is said to be bald. A bald tire should be replaced as soon as possible. Sometimes tires with worn tread are recapped, i. e. a new layer of rubber with grooves is bonded onto the outer perimeter of a worn tire. Because this bonding may occasionally come loose on the tire, new tires are superior to recapped tires. Sometimes a pneumatic tire gets a hole or a leak through which the air inside leaks out resulting in a flat tire, a condition which must be fixed before the car can be driven further safely. A leak may be slow in a few cases, such as is sometimes observed when the seal between the rim and tire edge is not perfect. Many leaks in flat tires, though, are caused by nails, screws, caltrops, broken glass or other sharp objects puncturing the rubber tire wall. If the hole is small and not elongated, the tire can often be repaired by using plugs from a tire repair kit. A leak in a tire can often be found by submerging the tire, pressurized with air, under water to see where air bubbles come out. If submerging a tire underwater is not possible, the leak can be searched for by covering the pressurized tire surface with a soapy solution to see where leaking air forms soap bubbles. A puncturing object, such as a nail or a screw, can be pulled out using pliers. Then a plug coated with a semi-liquid form of rubber can be inserted into the hole with a special tool. The rubber covering the plug solidifies rather quickly, after which the protruding ends of the plug can be cut off, the tire can be refilled with air to the appropriate pressure, and the repaired wheel replaced on the vehicle. Patches covering a hole have been glued or rubber-cemented to the interior surface of a tire also, particularly if a hole is too elongated for a simple plug. tire repair with such patches requires the tire to be taken off the rim and then remounted after the patch is applied. Sometimes a more serious rupture of the tire material occurs resulting in a blowout. The damaged tire typically must be replaced after that. A leaking valve stem may occasionally be the cause of a leak, necessitating valve stem replacement. This replacement means the tire will have to be taken off the rim and remounted after the valve replacement. Occasionally, other types of damage require replacement of a tire. Vehicles typically carry a spare tire, already mounted on a rim, to be used in case a flat tire or blowout occurs. These days, most spare tires for cars are smaller than normal tires (to save on trunk space, gas mileage, and cost) and should not be driven very far before replacement with a full-size tire. Years ago, full-size or conventional spare tires were used. A few modern vehicle models may use conventional spare tires also. Jacks and tire irons for emergency replacement of a flat tire with a spare tire are included when buying a new car. Not included, but sometimes available separately, are hand or foot pumps for filling a tire with air by the vehicle owner. Cans of pressurized "gas" can sometimes be bought separately for convenient emergency refill of a tire. Front tires, especially on front wheel drive vehicles, have a tendency to wear out more quickly than rear tires. Routine maintenance including tire rotation, exchanging the front and rear tires with each other, is often done periodically to even out tire wear. There are simple hand-held tire-pressure gauges which can be temporarily attached to the valve stem to check a tire's interior air pressure. Because of slow leaks or changes in weather or other conditions, tire pressure may occasionally have to be adjusted, usually by refilling through the valve stem with some pressurized air which is often available at service stations.

Automobile tires

tire-pressure gauge]] Automobile tires have numerous rating systems. The size of a tire is measured with a single code, in the form AAA/BBRCC for radial tires. This code is often a source of confusion, as its format is an obscure mix of inches, millimeters, and percentages. In this form, AAA is the width of the tire, measured in millimeters. 200 is a common figure, but the range can be quite wide. The 2000 Honda Insight uses 165 mm wide tires, while the rear tires of the 2000 Dodge Viper fit 335 mm tires. BB is the "profile", i.e. the height of the sidewall (the distance from the edge of the wheel to the edge of the tire), measured as a percentage of AAA, the tire width. A 200/50 tire would have a 100 mm high sidewall. If the number BB is missing (e.g. 145/R12) then the height is 80% of the width. CC is the diameter of the wheel the tire is designed to fit on in inches. With all three of these numbers you can calculate the total diameter of the tire. New automotive tires now also have ratings for traction, treadwear, and temperature resistance (collectively known as [http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=48 UTQG] ratings); as well as speed and load [http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=35 ratings]. Some tread designs are unidirectional and the tire has a rotation direction. Tire rotation moves tires between the different wheels of the vehicle as front and back axles carry different loads and thus the tires wear differently. Tire tread gauges are small rulers designed to be inserted into tire treads to measure the remaining tread depth. Local legislation may specify minimum tread depths, typically between 1/8" (3.2 mm) and 1/32" (0.8 mm). Wearbars may be designed into the tire tread to indicate when it is time to replace the tire. Essentially, part of the tire tread is shallower than the rest and will show when the tire is worn down to that level. There is currently an attempt to reinforce the tire with nanomaterial. This is likely to increase the tire life, but may turn out to be a bad idea if the worn out part of nanocarbon deposited on the roads is washed off and end up in the food chain.

Types of automobile tires

- Performance tires
- Performance tires tend to be designed for use at higher speeds. They often have a softer rubber compound for improved traction, especially on high speed cornering.
- Performance tires are often called summer tires, because they sacrifice wet weather handling, by having shallower water channels, and tire life from softer rubber compounds, for dry weather performance. The ultimate variant of performance tires has no tread pattern at all and is called slick tire.
- Winter tires
- Winter tires are designed to remain pliable in subzero temperatures. They often have fine grooves and siping in the tread patterns that are designed to bite into the ice and snow on the road. Winter tires are usually removed for storage in the spring, because the rubber compound becomes too soft in warm weather resulting in a reduced tire life.
- Many winter tires are designed to be studded for additional traction on icy roads.
- All-season tires
- Most automobile tires are all season tires. These tires are an attempt to satisfy the needs of most road conditions, they have the deeper water channels that are found in winter tires, but often have harder rubber compound for greater tire life in warm weather.
- All-season tires attempt to strike a balance between performance, wet weather and comfort.
- All-terrain tires
- All-terrain tires are typically used on SUVs and light trucks. These tires often have stiffer sidewalls for greater resistance against puncture when traveling off-road, the tread pattern offers wider spacing than all-season tires to evacuate mud from the tread.
- Within the all-terrain category, many of the tires available are designed primarily for on-road use, particularly all-terrain tires that are originally sold with the vehicle.
- Mud tires
- Mud terrain tires are characterized by large, chunky tread patterns designed to bite into muddy surfaces and provide grip. The large open design also allows mud to clear more quickly from between the lugs.
- Mud terrain tires also tend to be wider than other tires, to spread the weight of the vehicle over a greater contact patch to prevent the vehicle from sinking too deep into the mud.
- Depending on the composition and tread pattern, many mud terrain tires are not well suited to on-road use. They can be noisy at highway speeds, and due to the open tread design, they have less of a contact area with the road, limiting traction. The large lugs on mud tires tend to tear and chip on roads, because they are made from hard rubber compounds that do not bend easily.

Automobile tire codes

An automobile tire can be described with the following information:
- Width of the tire
- Relation of the flank hight to the total width of the tire in percent
- Construction of the tire (diagonal- or radial fabric)
- Diameter of the rim in inch
- Load index
- Speed rating
- Additional marks All this information can be found on the side of tires. Example 185/65 R 15 85 H: :185 the tread width is 185 mm :65 is the relation of flank height to width, here the height is 120 mm (=65% of 185 mm). :R radial fabric construction :15 necessary rim diameter in inches. :85 load index, here 515 kg. :H speed index, this means the maximum permitted speed, here 210 km/h.

Speed rating codes

The codes is made up of one or two letter from A to W (one letters) describing the maximum speed of the tire. Note: Driving 30 km/h over the speed index limit for more than 30 min will lead to irreparable damage or even burst of the tire. The code "ZR" are means a speed limit of the tire of more than 240 km/h. In this case there can be often found an extra code, example: 225/45 ZR 17 Y. On winter tires, at the end of the above mentioned codes the following abbreviation can be found: M&S for Mud and Snow. On spike tires there is an additional E after the S. Additional marks ;E4: Tire approved according ECE-regulations, 4 = Country of approval ;030908: Approval number of the tire ;DOT-Nummer: Production date; DOT = Department of Transportation; example: DOT 3204 = 32nd week in 2004; before 2000 there was a 3 number code with triangle-symbol used, Example: 122? = 12th week of 1992; prior this the following code was used: 065 = 6th week of 1985 ;Tubeless or TL ;Tubetype or TT, tire with a tube ;Made in: Country of production ;C (commercial): Tires for light lorries (Example: 185 R14 C) ;B: Belt tires for motorcycles (Example: 150/70 B 17 69 H) ;SFI: abbr. for "side facing inwards" = inside of asymmetrically tires ;SFO: abbr. for "side facing outwards" = outside of asymmetrically tires ;TWI: Tire wear index, an indicator in the main tire profile which shows when the tire is worn down and needs to be replaced ;XL (extra load): Tire for heavy loads ;rf: Reinforced tires

Train tires

Department of Transportation The steel wheels of trains are fitted with tires which are themselves usually made of steel. (Some trains, mostly certain types of metros and people movers, have rubber tires, including some lines of the Paris Métro, the Mexico City Metro and the Montreal Metro). Efficient though the rolling of steel wheel on steel rail is, wear still takes place - on acceleration, on braking, and on cornering. As well as the simple wearing away of the wheel surface, a wheel that wears begins to deviate from the correct profile. The shape of a train wheel is designed and specified precisely for the best possible riding and cornering characteristics, and too much wear can alter that. Wear can also take place unevenly if wheels lock up under heavy braking, causing flat spots. Another, different form of damage to a train's wheels takes place if violent wheelslip occurs. The friction so caused can heat the wheel (and rail) enough to cause permanent heat damage. Replacing a whole wheel because of a worn contact surface proves expensive, so the concept of fitting steel tires to train wheels came about. The tire is a hoop of steel that is fitted around the steel or iron wheel. No obvious form of fastening is generally used to attach it. As with wagon wheels, the tire is held by an interference fit - it is made slightly smaller than the wheel on which it is supposed to fit. To fit a tire, it is heated up until it is glowing hot. Railroad workshops generally have special equipment to do so. As the tire heats, it expands, making it big enough to fit around the wheel. After placing it on the wheel, the tire is cooled, and it shrink fits onto the wheel. When cold, friction between the tire and the wheel is such that the tire will not budge even under quite extreme forces. Removing a tire is done in reverse - the tire is heated while on the wheel until it loosens. Tires are reasonably thick, up to about an inch thick or more, giving plenty of room to wear. If a tire wears out of shape, or gets flat-spotted, but has a reasonable amount of metal left, it can be turned on a wheel lathe to refinish it, reshaping it to the correct profile.

Some tire manufacturing companies include:

- Bridgestone
- Firestone
- Continental
- Cooper
- Dunlop
- Goodyear
- Michelin
- B.F. Goodrich
- Pirelli
- Toyo tires
- Yokohama

Heat sink

:This article is about heat sinks as cooling devices. For alternative meanings see Heat sink (disambiguation) Heat sink (disambiguation) A heat sink is an environment or object capable of absorbing heat from another object with which it is in thermal contact (either direct contact or radiational "contact"). In common use, it is a device made of metal brought into contact with the hot surface of a component (in most cases, some kind of thermal interface material is put between the heat sink and the heat source to increase thermal throughput), such as a microprocessor chip or other power handling semiconductor in order to stablise its temperature through increased thermal mass and heat dissipation (primarily by conduction and convection and to a lesser extent by radiation). Heat sinks are widely used in electronics, and have become almost essential to modern central processing units. A heat sink usually consists of a metal structure with one or more flat surfaces to ensure good thermal contact with the components to be cooled, and an array of comb or fin like protrusions to increase the surface contact with the air, and thus the rate of heat dissipation. A heat sink is often used in conjunction with a fan in order to increase the rate of airflow over the heat sink, thus maintaining a larger temperature gradient by replacing warmed air faster than would be by convection, this is known as a forced air system. gradient Heat sinks are commonly made of a good thermal conductor such as copper or aluminum. Copper is significantly more expensive than aluminum but is also a better thermal conductor. The contact surface of a heat sink must be highly polished in order to ensure the best thermal contact with the object to be cooled. Sometimes a thermally conductive grease is employed to ensure the best thermal contact, such greases often contain colloidal silver (an even better thermal conductor than copper.) It is claimed that some brands of thermal grease that are advertised as containing silver or silver oxide actually contain neither, most notably that of CompUSA. Due to recent technological developments and public interest, the market for commercial heat sink cooling for CPUs has reached an all time high; many companies now compete to make the best heat sink for PC overclocking enthusiasts. Some of the more prominent heat sink makers include: Thermalright, Thermaltake, Aero Cool, Cooler Master, Zalman, and Swiftech. A good heat sink is vital to overclocked computer systems because the cooler a microprocessor is, the faster it can be made to run without instability. Temporary heat sinks are sometimes used in soldering circuit boards in order to prevent the heat from damaging sensitive nearby electronics - in the simplest case, this means gripping part of a component to be soldered with a crocodile clip or similar.

Car park

General information

Environmental considerations

Runoff handling

Water pollution

Alternative paving

Parking lot landscaping

Parking standards

See also

American English

History

Phonology

Differences in British English and American English

English words that arose in the U.S.

English words obsolete outside the U.S.

Regional differences

See also

Further reading

References

External links

British English

-ise versus -ize

See also

Multi-storey car park

Nomenclature

Design

Concrete

History

Characteristics

Additives

Workability

Self compacting concretes

Shotcrete / sprayed concrete

See also

External link

Gravel

Types of gravel

See also

Permeable paving

Advantages of permeable paving

Types of permeable paving surfaces

Reference

Outside links

Landscaping

Storm sewer

Sanitary sewer

Brake

Types of brake

See also

Rust

Dry well

See also

Permeable paving

Advantages of permeable paving

Types of permeable paving surfaces

Reference

Outside links

Brick

History

Construction and types

Proportions

Use

See also

Tire

Pneumatic tires

History

Etymology

Wagon tires

Maintenance

Automobile tires

Types of automobile tires

Automobile tire codes

Speed rating codes

Train tires

See also

Some tire manufacturing companies include:

Other external links

Heat sink

See also

Parking