1.
Pennsylvania
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Pennsylvania /ˌpɛnsᵻlˈveɪnjə/, officially the Commonwealth of Pennsylvania, is a state located in the northeastern and Mid-Atlantic regions of the United States. The Appalachian Mountains run through its middle, Pennsylvania is the 33rd largest, the 5th most populous, and the 9th most densely populated of the 50 United States. The states five most populous cities are Philadelphia, Pittsburgh, Allentown, Erie, the state capital, and its ninth-largest city, is Harrisburg. Pennsylvania has 140 miles of shoreline along Lake Erie and the Delaware Estuary. The state is one of the 13 original founding states of the United States, it came into being in 1681 as a result of a land grant to William Penn. Part of Pennsylvania, together with the present State of Delaware, had earlier been organized as the Colony of New Sweden and it was the second state to ratify the United States Constitution, on December 12,1787. Independence Hall, where the United States Declaration of Independence and United States Constitution were drafted, is located in the states largest city of Philadelphia, during the American Civil War, the Battle of Gettysburg, was fought in the south central region of the state. Valley Forge near Philadelphia was General Washingtons headquarters during the winter of 1777–78. Pennsylvania is 170 miles north to south and 283 miles east to west, of a total 46,055 square miles,44,817 square miles are land,490 square miles are inland waters, and 749 square miles are waters in Lake Erie. It is the 33rd largest state in the United States, Pennsylvania has 51 miles of coastline along Lake Erie and 57 miles of shoreline along the Delaware Estuary. Cities include Philadelphia, Reading, Lebanon and Lancaster in the southeast, Pittsburgh in the southwest, the tri-cities of Allentown, Bethlehem, the northeast includes the former anthracite coal mining communities of Scranton, Wilkes-Barre, Pittston City, and Hazleton. Erie is located in the northwest, the state has 5 regions, namely the Allegheny Plateau, Ridge and Valley, Atlantic Coastal Plain, Piedmont, and the Erie Plain. Straddling two major zones, the majority of the state, with the exception of the corner, has a humid continental climate. The largest city, Philadelphia, has characteristics of the humid subtropical climate that covers much of Delaware. Moving toward the interior of the state, the winter climate becomes colder, the number of cloudy days increase. Western areas of the state, particularly locations near Lake Erie, can receive over 100 inches of snowfall annually, the state may be subject to severe weather from spring through summer into fall. Tornadoes occur annually in the state, sometimes in large numbers, the Tuscarora Nation took up temporary residence in the central portion of Pennsylvania ca. Both the Dutch and the English claimed both sides of the Delaware River as part of their lands in America
2.
Ohio River
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The Ohio River, which streams westward from Pittsburgh, Pennsylvania, to Cairo, Illinois, is the largest tributary, by volume, of the Mississippi River in the United States. The 981-mile river flows through or along the border of six states, through its largest tributary, the Tennessee River, the basin includes many of the states of the southeastern U. S. It is the source of drinking water for three million people and it is named in Iroquoian or Seneca, Ohi, yó, lit. Good River or Shawnee, Pelewathiipi and Spelewathiipi, the river had great significance in the history of the Native Americans, as numerous civilizations formed along its valley. For thousands of years, Native Americans used the river as a major transportation, in 1669, René-Robert Cavelier, Sieur de La Salle led a French expedition to the Ohio River, becoming the first Europeans to see it. After European-American settlement, the served as a border between present-day Kentucky and Indian Territories. It was a transportation route for pioneers during the westward expansion of the early U. S. In his Notes on the State of Virginia published in 1781–82, Thomas Jefferson stated and its current gentle, waters clear, and bosom smooth and unbroken by rocks and rapids, a single instance only excepted. During the 19th century, the river was the boundary of the Northwest Territory. Where the river was narrow, it was the way to freedom for thousands of slaves escaping to the North, many helped by free blacks and whites of the Underground Railroad resistance movement. The Ohio River is a transition area, as its water runs along the periphery of the humid subtropical. It is inhabited by fauna and flora of both climates, in winter, it regularly freezes over at Pittsburgh but rarely further south toward Cincinnati and Louisville. At Paducah, Kentucky, in the south, near the Ohios confluence with the Mississippi, Paducah was founded there because it is the northernmost ice-free reach of the Ohio. The Ohio River is formed by the confluence of the Allegheny and Monongahela rivers at Point State Park in Pittsburgh, from there, it flows northwest through Allegheny and Beaver counties, before making an abrupt turn to the south-southwest at the West Virginia–Ohio–Pennsylvania triple-state line. From there, it forms the border between West Virginia and Ohio, upstream of Wheeling, West Virginia, the river then follows a roughly southwest and then west-northwest course until Cincinnati, before bending to a west-southwest course for most of its length. The course forms the borders of West Virginia and Kentucky. The Ohio drains parts of 15 states in four regions, northeast New York, a small area of the southern border along the headwaters of the Allegheny. Pennsylvania, a corridor from the corner to north central border
3.
Iron
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Iron is a chemical element with symbol Fe and atomic number 26. It is a metal in the first transition series and it is by mass the most common element on Earth, forming much of Earths outer and inner core. It is the fourth most common element in the Earths crust, like the other group 8 elements, ruthenium and osmium, iron exists in a wide range of oxidation states, −2 to +6, although +2 and +3 are the most common. Elemental iron occurs in meteoroids and other low oxygen environments, but is reactive to oxygen, fresh iron surfaces appear lustrous silvery-gray, but oxidize in normal air to give hydrated iron oxides, commonly known as rust. Unlike the metals that form passivating oxide layers, iron oxides occupy more volume than the metal and thus flake off, Iron metal has been used since ancient times, although copper alloys, which have lower melting temperatures, were used even earlier in human history. Pure iron is soft, but is unobtainable by smelting because it is significantly hardened and strengthened by impurities, in particular carbon. A certain proportion of carbon steel, which may be up to 1000 times harder than pure iron. Crude iron metal is produced in blast furnaces, where ore is reduced by coke to pig iron, further refinement with oxygen reduces the carbon content to the correct proportion to make steel. Steels and iron alloys formed with metals are by far the most common industrial metals because they have a great range of desirable properties. Iron chemical compounds have many uses, Iron oxide mixed with aluminium powder can be ignited to create a thermite reaction, used in welding and purifying ores. Iron forms binary compounds with the halogens and the chalcogens, among its organometallic compounds is ferrocene, the first sandwich compound discovered. Iron plays an important role in biology, forming complexes with oxygen in hemoglobin and myoglobin. Iron is also the metal at the site of many important redox enzymes dealing with cellular respiration and oxidation and reduction in plants. A human male of average height has about 4 grams of iron in his body and this iron is distributed throughout the body in hemoglobin, tissues, muscles, bone marrow, blood proteins, enzymes, ferritin, hemosiderin, and transport in plasma. The mechanical properties of iron and its alloys can be evaluated using a variety of tests, including the Brinell test, Rockwell test, the data on iron is so consistent that it is often used to calibrate measurements or to compare tests. An increase in the content will cause a significant increase in the hardness. Maximum hardness of 65 Rc is achieved with a 0. 6% carbon content, because of the softness of iron, it is much easier to work with than its heavier congeners ruthenium and osmium. Because of its significance for planetary cores, the properties of iron at high pressures and temperatures have also been studied extensively
4.
Steel
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Steel is an alloy of iron and other elements, primarily carbon, that is widely used in construction and other applications because of its high tensile strength and low cost. Steels base metal is iron, which is able to take on two forms, body centered cubic and face centered cubic, depending on its temperature. It is the interaction of those allotropes with the elements, primarily carbon. In the body-centred cubic arrangement, there is an atom in the centre of each cube. Carbon, other elements, and inclusions within iron act as hardening agents that prevent the movement of dislocations that otherwise occur in the lattices of iron atoms. The carbon in steel alloys may contribute up to 2. 1% of its weight. Steels strength compared to pure iron is possible at the expense of irons ductility. With the invention of the Bessemer process in the mid-19th century and this was followed by Siemens-Martin process and then Gilchrist-Thomas process that refined the quality of steel. With their introductions, mild steel replaced wrought iron, further refinements in the process, such as basic oxygen steelmaking, largely replaced earlier methods by further lowering the cost of production and increasing the quality of the product. Today, steel is one of the most common materials in the world and it is a major component in buildings, infrastructure, tools, ships, automobiles, machines, appliances, and weapons. Modern steel is generally identified by various grades defined by assorted standards organizations, the noun steel originates from the Proto-Germanic adjective stakhlijan, which is related to stakhla. The carbon content of steel is between 0. 002% and 2. 1% by weight for plain iron–carbon alloys and these values vary depending on alloying elements such as manganese, chromium, nickel, iron, tungsten, carbon and so on. Basically, steel is an alloy that does not undergo eutectic reaction. In contrast, cast iron does undergo eutectic reaction, too little carbon content leaves iron quite soft, ductile, and weak. Carbon contents higher than those of steel make an alloy, commonly called pig iron, while iron alloyed with carbon is called carbon steel, alloy steel is steel to which other alloying elements have been intentionally added to modify the characteristics of steel. Common alloying elements include, manganese, nickel, chromium, molybdenum, boron, titanium, vanadium, tungsten, cobalt, and niobium. Additional elements are important in steel, phosphorus, sulfur, silicon, and traces of oxygen, nitrogen, and copper. Alloys with a higher than 2. 1% carbon content, depending on other element content, cast iron is not malleable even when hot, but it can be formed by casting as it has a lower melting point than steel and good castability properties
5.
Rail transport
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Rail transport is a means of conveyance of passengers and goods on wheeled vehicles running on rails, also known as tracks. It is also referred to as train transport. In contrast to road transport, where vehicles run on a flat surface. Tracks usually consist of rails, installed on ties and ballast, on which the rolling stock, usually fitted with metal wheels. Other variations are possible, such as slab track, where the rails are fastened to a concrete foundation resting on a prepared subsurface. Rolling stock in a transport system generally encounters lower frictional resistance than road vehicles, so passenger. The operation is carried out by a company, providing transport between train stations or freight customer facilities. Power is provided by locomotives which either draw electric power from a railway system or produce their own power. Most tracks are accompanied by a signalling system, Railways are a safe land transport system when compared to other forms of transport. The oldest, man-hauled railways date back to the 6th century BC, with Periander, one of the Seven Sages of Greece, Rail transport blossomed after the British development of the steam locomotive as a viable source of power in the 19th centuries. With steam engines, one could construct mainline railways, which were a key component of the Industrial Revolution, also, railways reduced the costs of shipping, and allowed for fewer lost goods, compared with water transport, which faced occasional sinking of ships. The change from canals to railways allowed for markets in which prices varied very little from city to city. In the 1880s, electrified trains were introduced, and also the first tramways, starting during the 1940s, the non-electrified railways in most countries had their steam locomotives replaced by diesel-electric locomotives, with the process being almost complete by 2000. During the 1960s, electrified high-speed railway systems were introduced in Japan, other forms of guided ground transport outside the traditional railway definitions, such as monorail or maglev, have been tried but have seen limited use. The history of the growth, decline and restoration to use of transport can be divided up into several discrete periods defined by the principal means of motive power used. The earliest evidence of a railway was a 6-kilometre Diolkos wagonway, trucks pushed by slaves ran in grooves in limestone, which provided the track element. The Diolkos operated for over 600 years, Railways began reappearing in Europe after the Dark Ages. The earliest known record of a railway in Europe from this period is a window in the Minster of Freiburg im Breisgau in Germany
6.
Manufacturing
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Manufacturing is the value added to production of merchandise for use or sale using labour and machines, tools, chemical and biological processing, or formulation. Manufacturing engineering or manufacturing process are the steps through which raw materials are transformed into a final product, the manufacturing process begins with the product design, and materials specification from which the product is made. These materials are modified through manufacturing processes to become the required part. Manufacturing takes turns under all types of economic systems, in a free market economy, manufacturing is usually directed toward the mass production of products for sale to consumers at a profit. In a collectivist economy, manufacturing is more directed by the state to supply a centrally planned economy. In mixed market economies, manufacturing occurs under some degree of government regulation, modern manufacturing includes all intermediate processes required the production and integration of a products components. Some industries, such as semiconductor and steel manufacturers use the term fabrication instead, the manufacturing sector is closely connected with engineering and industrial design. Examples of major manufacturers in North America include General Motors Corporation, General Electric, Procter & Gamble, General Dynamics, Boeing, Pfizer, examples in Europe include Volkswagen Group, Siemens, and Michelin. Examples in Asia include Sony, Huawei, Lenovo, Toyota, Samsung, in its earliest form, manufacturing was usually carried out by a single skilled artisan with assistants. In much of the world, the guild system protected the privileges. Before the Industrial Revolution, most manufacturing occurred in rural areas, entrepreneurs organized a number of manufacturing households into a single enterprise through the putting-out system. Toll manufacturing is an arrangement whereby a first firm with specialized equipment processes raw materials or semi-finished goods for a second firm, manufacturing provides important material support for national infrastructure and for national defense. On the other hand, most manufacturing may involve significant social and environmental costs, the clean-up costs of hazardous waste, for example, may outweigh the benefits of a product that creates it. Hazardous materials may expose workers to health risks and these costs are now well known and there is effort to address them by improving efficiency, reducing waste, using industrial symbiosis, and eliminating harmful chemicals. The negative costs of manufacturing can also be addressed legally, developed countries regulate manufacturing activity with labor laws and environmental laws. Across the globe, manufacturers can be subject to regulations and pollution taxes to offset the costs of manufacturing activities. Labor unions and craft guilds have played a role in the negotiation of worker rights. Environment laws and labor protections that are available in developed nations may not be available in the third world, tort law and product liability impose additional costs on manufacturing
7.
Locomotive
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A locomotive or engine is a rail transport vehicle that provides the motive power for a train. A locomotive has no payload capacity of its own, and its purpose is to move the train along the tracks. In contrast, some trains have self-propelled payload-carrying vehicles and these are not normally considered locomotives, and may be referred to as multiple units, motor coaches or railcars. The use of these vehicles is increasingly common for passenger trains. Traditionally, locomotives pulled trains from the front, however, push-pull operation has become common, where the train may have a locomotive at the front, at the rear, or at each end. Prior to locomotives, the force for railroads had been generated by various lower-technology methods such as human power, horse power. The first successful locomotives were built by Cornish inventor Richard Trevithick, in 1804 his unnamed steam locomotive hauled a train along the tramway of the Penydarren ironworks, near Merthyr Tydfil in Wales. Although the locomotive hauled a train of 10 long tons of iron and 70 passengers in five wagons over nine miles, the locomotive only ran three trips before it was abandoned. Trevithick built a series of locomotives after the Penydarren experiment, including one which ran at a colliery in Tyneside in northern England, the first commercially successful steam locomotive was Matthew Murrays rack locomotive, Salamanca, built for the narrow gauge Middleton Railway in 1812. This was followed in 1813 by the Puffing Billy built by Christopher Blackett and William Hedley for the Wylam Colliery Railway, Puffing Billy is now on display in the Science Museum in London, the oldest locomotive in existence. In 1814 George Stephenson, inspired by the locomotives of Trevithick. He built the Blücher, one of the first successful flanged-wheel adhesion locomotives, Stephenson played a pivotal role in the development and widespread adoption of steam locomotives. His designs improved on the work of the pioneers, in 1825 he built the Locomotion for the Stockton and Darlington Railway, north east England, which became the first public steam railway. In 1829 he built The Rocket which was entered in and won the Rainhill Trials and this success led to Stephenson establishing his company as the pre-eminent builder of steam locomotives used on railways in the United Kingdom, the United States and much of Europe. The first inter city passenger railway, Liverpool and Manchester Railway, opened in 1830, there are a few basic reasons to isolate locomotive train power, as compared to self-propelled vehicles. Maximum utilization of power cars Separate locomotives facilitate movement of costly motive power assets as needed, flexibility Large locomotives can substitute for small locomotives when more power is required, for example, where grades are steeper. As needed, a locomotive can be used for freight duties. Obsolescence cycles Separating motive power from payload-hauling cars enables replacement without affecting the other, to illustrate, locomotives might become obsolete when their associated cars did not, and vice versa
8.
Railroad car
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A railroad car or railcar, railway wagon or railway carriage, also called a train car or train wagon, is a vehicle used for the carrying of cargo or passengers on a rail transport system. Such cars, when coupled together and hauled by one or more locomotives, alternatively, some passenger cars are self-propelled in which case they may be either single railcars or make up multiple units. The term car is used by itself in American English when a rail context is implicit. Indian English sometimes uses bogie in the manner, though the term has other meanings in other variants of English. In American English, railcar is a term for a railway vehicle, in other countries railcar refers specifically to a self-propelled, powered. Tables may be provided between seats facing one another, alternatively, seats facing in the same direction may have access to a fold-down ledge on the back of the seat in front. If the aisle is located between seats, seat rows may face the direction, or be grouped, with twin rows facing each other. In some vehicles intended for services, seats are positioned with their backs to the side walls. This gives a wide accessway and allows room for standing passengers at peak times, if the aisle is at the side, the car is usually divided into small compartments. These usually contain six seats, although sometimes in second class they contain eight, modern cars usually have either air-conditioning or windows that can be opened, or sometimes both. Various types of onboard train toilet facilities may also be provided, other types of passenger car exist, especially for long journeys, such as the dining car, parlor car, disco car, and in rare cases theater and movie theater car. In some cases another type of car is converted to one of these for an event. Observation cars were built for the rear of many trains to allow the passengers to view the scenery. Sleeping cars outfitted with small bedrooms allow passengers to sleep through their night-time trips, long-distance trains often require baggage cars for the passengers luggage. In European practice it used to be common for day coaches to be formed of compartments seating 6 or 8 passengers, in the UK, Corridor coaches fell into disfavor in the 1960s and 1970s partially because open coaches are considered more secure by women traveling alone. Another distinction is between single- and double deck train cars, an example of a double decker is the Amtrak superliner. A trainset is a semi-permanently arranged formation of cars, rather than one created ad hoc out of cars are available. These are only broken up and reshuffled on shed, trains are then built of one or more of these sets coupled together as needed for the capacity of that train
9.
Spring (device)
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A spring is an elastic object used to store mechanical energy. Springs are usually out of spring steel. There are a number of spring designs, in everyday usage the term often refers to coil springs. When a spring is compressed or stretched from its resting position, the rate or spring constant of a spring is the change in the force it exerts, divided by the change in deflection of the spring. That is, it is the gradient of the force versus deflection curve, an extension or compression springs rate is expressed in units of force divided by distance, for example lbf/in or N/m. A torsion spring is a spring that works by twisting, when it is twisted about its axis by an angle, a torsion springs rate is in units of torque divided by angle, such as N·m/rad or ft·lbf/degree. The inverse of spring rate is compliance, that is, if a spring has a rate of 10 N/mm, the stiffness of springs in parallel is additive, as is the compliance of springs in series. Springs are made from a variety of materials, the most common being spring steel. Small springs can be wound from pre-hardened stock, while larger ones are made from annealed steel, some non-ferrous metals are also used including phosphor bronze and titanium for parts requiring corrosion resistance and beryllium copper for springs carrying electrical current. Simple non-coiled springs were used throughout history, e. g. the bow. In the Bronze Age more sophisticated spring devices were used, as shown by the spread of tweezers in many cultures, coiled springs appeared early in the 15th century, in door locks. The first spring powered-clocks appeared in that century and evolved into the first large watches by the 16th century, in 1676 British physicist Robert Hooke discovered Hookes law which states that the force a spring exerts is proportional to its extension. Compression spring – is designed to operate with a compression load, flat spring – this type is made of a flat spring steel. Machined spring – this type of spring is manufactured by machining bar stock with a lathe and/or milling operation rather than a coiling operation, since it is machined, the spring may incorporate features in addition to the elastic element. Machined springs can be made in the load cases of compression/extension, torsion. Serpentine spring - a zig-zag of thick wire - often used in modern upholstery/furniture, the most common types of spring are, Cantilever spring – a spring which is fixed only at one end. Coil spring or helical spring – a spring is of two types, Tension or extension springs are designed to become longer under load and their turns are normally touching in the unloaded position, and they have a hook, eye or some other means of attachment at each end. Compression springs are designed to become shorter when loaded and their turns are not touching in the unloaded position, and they need no attachment points
10.
Vitreous enamel
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Vitreous enamel, also called porcelain enamel, is a material made by fusing powdered glass to a substrate by firing, usually between 750 and 850 °C. The powder melts, flows, and then hardens to a smooth, durable vitreous coating on metal, so in technical terms fired enamelware is an integrated layered composite of glass and metal. Enamelling is an old and widely adopted technology, for most of its history mainly used in jewelry, enamelled and enamelling are the preferred spellings in British English, while enameled and enameling are preferred in American English. The term enamel is most often restricted to work on metal, enamelled glass is also called painted, and overglaze decoration to pottery is often called enamelling. The word enamel comes from the Old High German word smelzan via the Old French esmail, or from a Latin word smaltum, used as a noun, an enamel is usually a small decorative object coated with enamel. Since the 19th century the term also to industrial materials and many metal consumer objects, such as some cooking vessels, dishwashers, laundry machines, sinks. The ancient Egyptians applied enamels to stone objects, pottery, and sometimes jewellery, the ancient Greeks, Celts, Georgians, and Chinese also used enamel on metal objects. Enamel powder could be produced in two ways, either by powdering coloured glass, or by mixing colourless glass powder with pigments such as a metallic oxide, designs were either painted freehand or over the top of outline incisions, and the technique probably originated in metalworking. Once painted, enamelled glass vessels needed to be fired at a high enough to melt the applied powder. Ancient Persians used this method for colouring and ornamenting the surface of metals by fusing over it brilliant colours that are decorated in an intricate design and called it Meenakari. Gold has been used traditionally for Meenakari Jewellery as it holds the enamel better, lasts longer, initially, the work of Meenakari often went unnoticed as this art was traditionally used as a backing for the famous kundan or stone-studded jewellery. This also allowed the wearer to reverse the jewellery as also promised a special joy in the secret of the hidden design, the Byzantine enamel style was widely adopted by the barbarian peoples of Migration Period northern Europe. The Byzantines then began to use cloisonné more freely to create images, the champlevé technique was considerably easier and very widely practiced in the Romanesque period. In Gothic art the finest work is in basse-taille and ronde-bosse techniques, from either Byzantium or the Islamic world, the cloisonné technique reached China in the 13-14th centuries. The first written reference to cloisonné is in a book from 1388, cloisonné remained very popular in China until the 19th century and is still produced today. Starting from the century, the Japanese also produced large quantities of very high technical quality. A resurgence in enamel-based art took place near the end of the 20th century in the Soviet Union, led by artists like Alexei Maximov, in Australia, abstract artist Bernard Hesling brought the style into prominence with his variously sized steel plates. Enamel was first applied commercially to sheet iron and steel in Austria, industrialization increased as the purity of raw materials increased and costs decreased
11.
Lumber
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Lumber, or timber is wood that has been processed into beams and planks, a stage in the process of wood production. Lumber may also refer to currently un-needed furniture, as in Lumber room, or an awkward gait, ultimately derived from the look of unfashionable, Lumber may be supplied either rough-sawn, or surfaced on one or more of its faces. Besides pulpwood, rough lumber is the raw material for furniture-making and it is available in many species, usually hardwoods, but it is also readily available in softwoods, such as white pine and red pine, because of their low cost. Lumber is mainly used for structural purposes but has other uses as well. It is classified more commonly as a softwood than as a hardwood, in Australia, Ireland, New Zealand and Britain, the term timber describes sawn wood products, such as floor boards. In the United States and Canada, generally timber describes standing or felled trees, before they are milled into boards, Timber there also describes sawn lumber not less than 5 inches in its smallest dimension. The latter includes the often partly finished lumber used in timber-frame construction, remanufactured lumber is the result of secondary or tertiary processing/cutting of previously milled lumber. Specifically, it is cut for industrial or wood-packaging use. Lumber is cut by ripsaw or resaw to create dimensions that are not usually processed by a primary sawmill, resawing is the splitting of 1-inch through 12-inch hardwood or softwood lumber into two or more thinner pieces of full-length boards. For example, splitting a ten-foot 2×4 into two ten-foot 1×4s is considered resawing, structural lumber may also be produced from recycled plastic and new plastic stock. Its introduction has been opposed by the forestry industry. Blending fiberglass in plastic lumber enhances its strength, durability, logs are converted into timber by being sawn, hewn, or split. Sawing with a rip saw is the most common method, because sawing allows logs of lower quality, with grain and large knots. There are various types of sawing, Plain sawn —A log sawn through without adjusting the position of the log, quarter sawn and rift sawn—These terms have been confused in history but generally mean lumber sawn so the annual rings are reasonably perpendicular to the sides of the lumber. Boxed heart—The pith remains within the piece with some allowance for exposure, heart center—the center core of a log. Free of heart center —A side-cut timber without any pith, free of knots —No knots are present. Dimensional lumber is lumber that is cut to standardized width and depth, carpenters extensively use dimensional lumber in framing wooden buildings. Common sizes include 2×4, 2×6, and 4×4, the length of a board is usually specified separately from the width and depth
12.
Plaster
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Plaster is a building material used for the protective and/or decorative coating of walls and ceilings and for moulding and casting decorative elements. In English plaster usually means a material used for the interiors of buildings, another imprecise term used for the material is stucco, which is also often used for plasterwork that is worked in some way to produce relief decoration, rather than flat surfaces. The most common types of plaster mainly contain either gypsum, lime, or cement, the plaster is manufactured as a dry powder and is mixed with water to form a stiff but workable paste immediately before it is applied to the surface. The reaction with water liberates heat through crystallization and the hydrated plaster then hardens, plaster can be relatively easily worked with metal tools or even sandpaper, and can be moulded, either on site or to make pre-formed sections in advance, which are put in place with adhesive. Plaster is not a material, it is suitable for finishing, rather than load-bearing. Forms of plaster have several other uses, in medicine plaster orthopedic casts are still often used for supporting set broken bones. In dentistry plaster is used to make dental models, various types of models and moulds are made with plaster. In art, lime plaster is the matrix for fresco painting. Gypsum plaster, or plaster of Paris, is produced by heating gypsum to about 300 °F, when the dry plaster powder is mixed with water, it re-forms into gypsum. The setting of unmodified plaster starts about 10 minutes after mixing and is complete in about 45 minutes, if plaster or gypsum is heated above 266 °F, hemihydrate is formed, which will also re-form as gypsum if mixed with water. On heating to 180 °C, the nearly water-free form, called γ-anhydrite is produced, γ-Anhydrite reacts slowly with water to return to the dihydrate state, a property exploited in some commercial desiccants. On heating above 250 °C, the anhydrous form called β-anhydrite or dead burned plaster is formed. A large gypsum deposit at Montmartre in Paris led calcined gypsum to be known as plaster of Paris. Plasterers often use gypsum to simulate the appearance of surfaces of wood, stone, or metal, on movie, nowadays, theatrical plasterers often use expanded polystyrene, although the job title remains unchanged. Plaster of Paris can be used to impregnate gauze bandages to make a material called plaster bandages. It is used similarly to clay, as it is shaped when wet, yet sets into a resilient. This is the material that was used to make classic plaster orthopedic casts to protect limbs with broken bones, set Modroc is an early example of a composite material. The hydration of plaster of Paris relies on the reaction of water with the dehydrated or partially hydrated calcium sulfate present in the plaster, lime plaster is a mixture of calcium hydroxide and sand
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