The Liberty ship was a class of cargo ship built in the United States during World War II. Though British in conception, the design was adapted by the United States for its simple, mass-produced on an unprecedented scale, the now iconic Liberty ship came to symbolize U. S. wartime industrial output. The class was developed to meet British orders for transports to replace those torpedoed by German U-boats, the vessels were purchased both for the U. S. fleet and lend-lease deliveries of war materiel to Britain and the Soviet Union. Eighteen American shipyards built 2,710 Liberty ships between 1941 and 1945, easily the largest number of ships produced to a single design and their production mirrored on a much larger scale the manufacture of the Hog Islander and similar standardized ship types during World War I. Only three Liberty Ships are preserved, two as operational museum ships. S, the number was doubled in 1939 and again in 1940 to 200 ships a year. Ship types included two tankers and three types of merchant vessel, all to be powered by steam turbines, limited industrial capacity, especially for reduction gears, meant that relatively few of these ships were built.
In 1940 the British government ordered 60 Ocean-class freighters from American yards to replace war losses and these were simple but fairly large with a single 2,500 horsepower compound steam engine of obsolete but reliable design. Britain specified coal-fired plants, because it had extensive coal mines, the order specified an 18-inch increase in draft to boost displacement by 800 long tons to 10,100 long tons. The accommodation and main engine were located amidships, the first Ocean-class ship, SS Ocean Vanguard, was launched on 16 August 1941. The design was modified by the United States Maritime Commission, in part to increase conformity to American construction practices, but more importantly to make it even quicker and cheaper to build. The US version was designated EC2-S-C1, EC for Emergency Cargo,2 for a ship between 400 and 450 feet long, S for steam engines, and C1 for design C1. The new design replaced much riveting, which accounted for one-third of the costs, with welding. It was adopted as a Merchant Marine Act design, and production awarded to a conglomerate of West Coast engineering and construction companies headed by Henry J.
Kaiser known as the Six Companies. Liberty ships were designed to carry 10,000 long tons of cargo, usually one type per ship, during wartime, generally carried loads far exceeding this. On 27 March 1941, the number of ships was increased to 200 by the Defense Aid Supplemental Appropriations Act and increased again in April to 306. By 1941, the turbine was the preferred marine steam engine because of its greater efficiency compared to earlier reciprocating compound steam engines. Eighteen different companies built the engine. It had the advantage of ruggedness and simplicity
Carbon is a chemical element with symbol C and atomic number 6. It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds, three isotopes occur naturally, 12C and 13C being stable, while 14C is a radioactive isotope, decaying with a half-life of about 5,730 years. Carbon is one of the few elements known since antiquity, Carbon is the 15th most abundant element in the Earths crust, and the fourth most abundant element in the universe by mass after hydrogen and oxygen. It is the second most abundant element in the body by mass after oxygen. The atoms of carbon can bond together in different ways, termed allotropes of carbon, the best known are graphite and amorphous carbon. The physical properties of carbon vary widely with the allotropic form, for example, graphite is opaque and black while diamond is highly transparent. Graphite is soft enough to form a streak on paper, while diamond is the hardest naturally occurring material known, graphite is a good electrical conductor while diamond has a low electrical conductivity.
Under normal conditions, carbon nanotubes, and graphene have the highest thermal conductivities of all known materials, all carbon allotropes are solids under normal conditions, with graphite being the most thermodynamically stable form. They are chemically resistant and require high temperature to react even with oxygen, the most common oxidation state of carbon in inorganic compounds is +4, while +2 is found in carbon monoxide and transition metal carbonyl complexes. The largest sources of carbon are limestones and carbon dioxide, but significant quantities occur in organic deposits of coal, oil. For this reason, carbon has often referred to as the king of the elements. The allotropes of carbon graphite, one of the softest known substances, and diamond. It bonds readily with other small atoms including other carbon atoms, Carbon is known to form almost ten million different compounds, a large majority of all chemical compounds. Carbon has the highest sublimation point of all elements, although thermodynamically prone to oxidation, carbon resists oxidation more effectively than elements such as iron and copper that are weaker reducing agents at room temperature.
Carbon is the element, with a ground-state electron configuration of 1s22s22p2. Its first four ionisation energies,1086.5,2352.6,4620.5 and 6222.7 kJ/mol, are higher than those of the heavier group 14 elements. Carbons covalent radii are normally taken as 77.2 pm,66.7 pm and 60.3 pm, although these may vary depending on coordination number, in general, covalent radius decreases with lower coordination number and higher bond order. Carbon compounds form the basis of all life on Earth
In materials science, a dislocation is a crystallographic defect or irregularity within a crystal structure. The presence of dislocations strongly influences many of the properties of materials, some types of dislocations can be visualized as being caused by the termination of a plane of atoms in the middle of a crystal. In such a case, the planes are not straight. The two primary types of dislocations are edge dislocations and screw dislocations, mixed dislocations are intermediate between these. Mathematically, dislocations are a type of defect, sometimes called a soliton. Dislocations behave as stable particles, they can move around, two dislocations of opposite orientation can cancel when brought together, but a single dislocation typically cannot disappear on its own. Two main types of dislocations exist and screw, dislocations found in real materials are typically mixed, meaning that they have characteristics of both. A crystalline material consists of an array of atoms, arranged into lattice planes.
One approach is to begin by considering a 3D representation of a crystal lattice. The viewer may start to simplify the representation by visualising planes of atoms instead of the atoms themselves, an edge dislocation is a defect where an extra half-plane of atoms is introduced mid way through the crystal, distorting nearby planes of atoms. When enough force is applied from one side of the crystal structure, a simple schematic diagram of such atomic planes can be used to illustrate lattice defects such as dislocations. In an edge dislocation, the Burgers vector is perpendicular to the line direction, the stresses caused by an edge dislocation are complex due to its inherent asymmetry. A screw dislocation is much harder to visualize, imagine cutting a crystal along a plane and slipping one half across the other by a lattice vector, the halves fitting back together without leaving a defect. This is similar to the Riemann surface of the complex logarithm, if the cut only goes part way through the crystal, and slipped, the boundary of the cut is a screw dislocation.
It comprises a structure in which a path is traced around the linear defect by the atomic planes in the crystal lattice. Perhaps the closest analogy is a spiral-sliced ham, in pure screw dislocations, the Burgers vector is parallel to the line direction. Despite the difficulty in visualization, the caused by a screw dislocation are less complex than those of an edge dislocation. This equation suggests a long cylinder of stress radiating outward from the cylinder, please note, this simple model results in an infinite value for the core of the dislocation at r=0 and so it is only valid for stresses outside of the core of the dislocation
Extrusion is a process used to create objects of a fixed cross-sectional profile. A material is pushed through a die of the desired cross-section and it forms parts with an excellent surface finish. Drawing is a process, which uses the tensile strength of the material to pull it through the die. This limits the amount of change which can be performed in one step, so it is limited to simpler shapes, Drawing is the main way to produce wire. Metal bars and tubes are often drawn. Extrusion may be continuous or semi-continuous, the extrusion process can be done with the material hot or cold. Commonly extruded materials include metals, ceramics, play dough, the products of extrusion are generally called extrudates. Hollow cavities within extruded material cannot be produced using a simple flat extrusion die, the die assumes the shape of a block with depth, beginning first with a shape profile that supports the center section. The die shape internally changes along its length into the final shape, the material flows around the supports and fuses together to create the desired closed shape.
The extrusion process in metals may increase the strength of the material. In 1797, Joseph Bramah patented the first extrusion process for making out of soft metals. It involved preheating the metal and forcing it through a die via a hand-driven plunger, in 1820 Thomas Burr implemented that process for lead pipe, with a hydraulic press. At that time the process was called squirting, in 1894, Alexander Dick expanded the extrusion process to copper and brass alloys. The process begins by heating the stock material and it is loaded into the container in the press. A dummy block is placed behind it where the ram presses on the material to push it out of the die, afterward the extrusion is stretched in order to straighten it. If better properties are required it may be treated or cold worked. The extrusion ratio is defined as the starting cross-sectional area divided by the area of the final extrusion. One of the advantages of the extrusion process is that this ratio can be very large while still producing quality parts
Gold is a chemical element with symbol Au and atomic number 79. In its purest form, it is a bright, slightly yellow, soft, malleable. Chemically, gold is a metal and a group 11 element. It is one of the least reactive chemical elements and is solid under standard conditions, Gold often occurs in free elemental form, as nuggets or grains, in rocks, in veins, and in alluvial deposits. It occurs in a solid solution series with the element silver and naturally alloyed with copper. Less commonly, it occurs in minerals as gold compounds, often with tellurium, golds atomic number of 79 makes it one of the higher numbered, naturally occurring elements. It is thought to have produced in supernova nucleosynthesis, from the collision of neutron stars. Because the Earth was molten when it was formed, almost all of the present in the early Earth probably sank into the planetary core. Gold is resistant to most acids, though it does dissolve in aqua regia, a mixture of acid and hydrochloric acid. Gold dissolves in solutions of cyanide, which are used in mining and electroplating.
Gold dissolves in mercury, forming amalgam alloys, but this is not a chemical reaction, as a precious metal, gold has been used for coinage and other arts throughout recorded history. A total of 186,700 tonnes of gold is in existence above ground, the world consumption of new gold produced is about 50% in jewelry, 40% in investments, and 10% in industry. Gold is used in infrared shielding, colored-glass production, gold leafing, certain gold salts are still used as anti-inflammatories in medicine. As of 2014, the worlds largest gold producer by far was China with 450 tonnes, Gold is cognate with similar words in many Germanic languages, deriving via Proto-Germanic *gulþą from Proto-Indo-European *ǵʰelh₃-. The symbol Au is from the Latin, the Latin word for gold, the Proto-Indo-European ancestor of aurum was *h₂é-h₂us-o-, meaning glow. This word is derived from the root as *h₂éu̯sōs, the ancestor of the Latin word Aurora. This etymological relationship is presumably behind the frequent claim in scientific publications that aurum meant shining dawn, Gold is the most malleable of all metals, a single gram can be beaten into a sheet of 1 square meter, and an avoirdupois ounce into 300 square feet.
Gold leaf can be thin enough to become semi-transparent
Zamak is a family of alloys with a base metal of zinc and alloying elements of aluminium and copper. Zamak alloys are part of the aluminium alloy family, they are distinguished from the other ZA alloys because of their constant 5% aluminium composition. The name zamak is an acronym of the German names for the metals of which the alloys are composed, Aluminium, the New Jersey Zinc Company developed zamak alloys in 1929. Zinc alloys are referred to as pot metal or white metal. While zamak is held to higher standards, it is still considered a pot metal. The most common zamak alloy is zamak 3, besides that, zamak 2, zamak 5 and zamak 7 are commercially used. These alloys are most commonly die cast, zamak alloys are frequently used in the spin casting industry. A large problem with early zinc die casting materials was zinc pest, zamak avoided this by the use of 99. 99% pure zinc metal, produced by New Jersey Zincs use of a refluxer as part of the smelting process. Zamak can be electroplated, wet painted, and chromate conversion coated well, in the early 1930s Morris Ashby in Britain had licensed the New Jersey zamak alloy.
The high-purity refluxer zinc was not available in Britain and so acquired the right to manufacture the alloy using a locally available electrolytically refined zinc of 99. 95% purity. This was given the name Mazak, partly to distinguish it from zamak, in 1933, National Smelting licensed the refluxer patent with the intent of using it to produce 99. 99% zinc in their plant at Avonmouth. Zamak 2 has the greatest strength out of all the zamak alloys, over time it retains its strength and hardness better than the other alloys, however, it becomes more brittle and less elastic. Zamak 2 is known as Kirksite when gravity cast for use as a die and it was originally designed for low volume sheet metal dies. It gained popularity for making short run injection molding dies and it is less commonly used for non-sparking tools and mandrels for metal spinning. The KS alloy was developed for spin casting decorative parts and it has the same composition as zamak 2, except with more magnesium in order to produce finer grains and reduce the orange peel effect.
Zamak 3 is the de facto standard for the series of zinc alloys. Zamak 3 has the composition for the zamak alloys. It has excellent castability and long term dimensional stability, more than 70% of all North American zinc die castings are made from zamak 3
Metalworking is the process of working with metals to create individual parts, assemblies, or large-scale structures. The term covers a range of work from large ships and bridges to precise engine parts. It therefore includes a wide range of skills, processes. Metalworking is a science, hobby and trade and its historical roots span cultures and millennia. Metalworking has evolved from the discovery of smelting various ores, producing malleable and ductile metal useful for tools, modern metalworking processes, though diverse and specialized, can be categorized as forming, cutting, or joining processes. Todays machine shop includes a number of machine tools capable of creating a precise, the oldest archaeological evidence of copper mining and working was the discovery of a copper pendant in northern Iraq from 8,700 BCE. The earliest substantiated and dated evidence of metalworking in the Americas was the processing of copper in Wisconsin, Copper was hammered until brittle heated so it could be worked some more.
This technology is dated to about 4000-5000 BCE, the oldest gold artifacts in the world come from the Bulgarian Varna Necropolis and date from 4450 BCE. Not all metal required fire to obtain it or work it, isaac Asimov speculated that gold was the first metal. His reasoning is that by its chemistry it is found in nature as nuggets of pure gold, in other words, gold, as rare as it is, is sometimes found in nature as the metal that it is. There are a few metals that sometimes occur natively. Almost all other metals are found in ores, a mineral-bearing rock, another feature of gold is that it is workable as it is found, meaning that no technology beyond a stone hammer and anvil to work the metal is needed. This is a result of properties of malleability and ductility. The earliest tools were stone, bone and sinew, at some unknown point the connection between heat and the liberation of metals from rock became clear, rocks rich in copper and lead came into demand. These ores were mined wherever they were recognized, remnants of such ancient mines have been found all over Southwestern Asia.
Metalworking was being carried out by the South Asian inhabitants of Mehrgarh between 7000–3300 BCE, the end of the beginning of metalworking occurs sometime around 6000 BCE when copper smelting became common in Southwestern Asia. Ancient civilisations knew of seven metals. Here they are arranged in order of their potential, Iron +0.44 V
In chemistry and atomic physics, an electron shell, or a principal energy level, may be thought of as an orbit followed by electrons around an atoms nucleus. The closest shell to the nucleus is called the 1 shell, followed by the 2 shell, the 3 shell, the shells correspond with the principal quantum numbers or are labeled alphabetically with letters used in the X-ray notation. Each shell can contain only a number of electrons, The first shell can hold up to two electrons, the second shell can hold up to eight electrons, the third shell can hold up to 18. The general formula is that the nth shell can in principle hold up to 2 electrons, since electrons are electrically attracted to the nucleus, an atoms electrons will generally occupy outer shells only if the more inner shells have already been completely filled by other electrons. However, this is not a requirement, atoms may have two or even three incomplete outer shells. For an explanation of why electrons exist in these shells see electron configuration, the electrons in the outermost occupied shell determine the chemical properties of the atom, it is called the valence shell.
Each shell consists of one or more subshells, and each consists of one or more atomic orbitals. The shell terminology comes from Arnold Sommerfelds modification of the Bohr model, sommerfeld retained Bohrs planetary model, but added mildly elliptical orbits to explain the fine spectroscopic structure of some elements. The multiple electrons with the principal quantum number had close orbits that formed a shell of positive thickness instead of the infinitely thin circular orbit of Bohrs model. The existence of electron shells was first observed experimentally in Charles Barklas, barkla labeled them with the letters K, L, M, N, O, P, and Q. The origin of this terminology was alphabetic, a J series was suspected, though experiments indicated that the K absorption lines are produced by the innermost electrons. These letters were found to correspond to the n values 1,2,3. They are used in the spectroscopic Siegbahn notation, the physical chemist Gilbert Lewis was responsible for much of the early development of the theory of the participation of valence shell electrons in chemical bonding.
Linus Pauling generalized and extended the theory while applying insights from quantum mechanics. The electron shells are labeled K, L, M, N, O, P, and Q, or 1,2,3,4,5,6, and 7, going from innermost shell outwards. Electrons in outer shells have higher energy and travel farther from the nucleus than those in inner shells. This makes them important in determining how the atom reacts chemically and behaves as a conductor, because the pull of the atoms nucleus upon them is weaker. In this way, a given elements reactivity is highly dependent upon its electronic configuration, each shell is composed of one or more subshells, which are themselves composed of atomic orbitals
Play-Doh is a modeling compound used by young children for art and craft projects at home and in school. Composed of flour, salt, boric acid, and mineral oil, the product was reworked and marketed to Cincinnati schools in the mid-1950s. Play-Doh was demonstrated at a convention in 1956 and prominent department stores opened retail accounts. Advertisements promoting Play-Doh on influential childrens television shows in 1957 furthered the products sales, since its launch on the toy market in the mid-1950s, Play-Doh has generated a considerable amount of ancillary merchandise such as The Fun Factory. In 2003, the Toy Industry Association named Play-Doh in its Century of Toys List and it was devised at the request of Kroger Grocery, which wanted a product that could clean coal residue from wallpaper. McVickers nephew, Joe McVicker, joined Kutol with the remit to save the company from bankruptcy, Joe McVicker was the brother-in-law of nursery school teacher Kay Zufall, and Zufall had seen a newspaper article about making art projects with the wallpaper cleaning putty.
Her students enjoyed it, and she persuaded Bill Rhodenbaugh and Joe McVicker to manufacture it as a child’s toy and her husband came up with the name Play-Doh, Joe McVicker and Rhodenbaugh had wanted to call it Rainbow Modeling Compound. Joe McVicker took Play-Doh to a convention for manufacturers of school supplies, and Woodward & Lothrop. In 1956, the McVickers formed the Rainbow Crafts Company to make, in 1956, a three-pack of 7-ounce cans was added to the product line, after in-store demonstrations, Macys of New York and Marshall Fields of Chicago opened retail accounts. In 1957, chemist Dr. Tien Liu reduced Play Dohs salt content, and Play-Doh ads were telecast on Captain Kangaroo, Ding Dong School, in 1958, Play-Dohs sales reached nearly $3 million. In 1964, Play-Doh was exported to Britain, France, in the 1980s, its cardboard can was scuttled for a more cost effective plastic container. By 1965, Rainbow Crafts was issued a patent for Play-Doh, in 1965, General Mills purchased Rainbow Crafts and all rights to Play-Doh for $3 million, placing the compound with its Kenner Products subsidiary.
In 1971, Rainbow Crafts and Kenner Products merged, and, in 1987, in 1991, Hasbro became Play-Dohs owner, and continues to manufacture the product today through its preschool division. In 1996, gold and silver were added to Play-Dohs palette to celebrate its 40th anniversary, Play-Doh packaging was briefly illustrated with children in the mid-1950s, but replaced by an elf mascot which, in 1960, was superseded by Play-Doh Pete, a smock and beret-wearing cartoonish boy. In 2002, Play-Doh Petes beret was replaced with a baseball cap, since 2011, living Play-Doh cans named the Doh-Dohs have been seen in adverts. A petroleum additive gives the compound a smooth feel, and borax prevents mold from developing, many home-made recipes will include salt, flour or corn starch, a vegetable oil and cream of tartar. In 1960, the Play-Doh Fun Factory was invented by Bob Boggild, the Play-Doh Fuzzy Pumper Barber & Beauty Shop of 1977 featured a figurine whose extruded hair could be styled. Making its debut in 1996 for computer-savvy young modelers was an educational software CD-ROM game, Play-Doh Creations, and, in 2003, in 2012, Play-Doh Plus was created
Lead is a chemical element with atomic number 82 and symbol Pb. When freshly cut, it is bluish-white, it tarnishes to a dull gray upon exposure to air and it is a soft and heavy metal with a density exceeding that of most common materials. Lead has the second-highest atomic number of the stable elements. Lead is a relatively unreactive post-transition metal and its weak metallic character is illustrated by its amphoteric nature and tendency to form covalent bonds. Compounds of lead are found in the +2 oxidation state. Exceptions are mostly limited to organolead compounds, like the lighter members of the group, lead exhibits a tendency to bond to itself, it can form chains and polyhedral structures. Lead is easily extracted from its ores and was known to people in Western Asia. A principal ore of lead, often bears silver, Lead production declined after the fall of Rome and did not reach comparable levels again until the Industrial Revolution. Nowadays, global production of lead is about ten million tonnes annually, Lead has several properties that make it useful, high density, low melting point and relative inertness to oxidation.
In the late 19th century, lead was recognized as poisonous, Lead is a neurotoxin that accumulates in soft tissues and bones, damaging the nervous system and causing brain disorders and, in mammals, blood disorders. A lead atom has 82 electrons, arranged in a configuration of 4f145d106s26p2. The combined first and second ionization energies—the total energy required to remove the two 6p electrons—is close to that of tin, leads upper neighbor in group 14. This is unusual since ionization energies generally fall going down a group as an elements outer electrons become more distant from the nucleus, the similarity is caused by the lanthanide contraction—the decrease in element radii from lanthanum to lutetium, and the relatively small radii of the elements after hafnium. The contraction is due to shielding of the nucleus by the lanthanide 4f electrons. The combined first four ionization energies of lead exceed those of tin, for this reason lead, unlike tin, mostly forms compounds in which it has an oxidation state of +2, rather than +4.
Relativistic effects, which become particularly prominent at the bottom of the periodic table, as a result, the 6s electrons of lead become reluctant to participate in bonding, a phenomenon called the inert pair effect. A related outcome is that the distance between nearest atoms in crystalline lead is unusually long, the lighter group 14 elements form stable or metastable allotropes having the tetrahedrally coordinated and covalently bonded diamond cubic structure. The energy levels of their outer s- and p-orbitals are close enough to allow mixing into four hybrid sp3 orbitals
A hammer is a tool or device that delivers a blow to an object. Most hammers are hand tools used to drive nails, fit parts, forge metal, hammers vary in shape and structure, depending on their purposes. Hammers are basic tools in many trades, the usual features are a head and a handle. Although most hammers are hand tools, powered versions exist, they are known as powered hammers, types of power hammer include steam hammers and trip hammers, often for heavier uses, such as forging. Some hammers have other names, such as sledgehammer, the term hammer applies to devices that deliver blows, such as the hammer of a firearm or the hammer of a piano or the hammer ice scraper. The use of simple hammers dates to about 2,600,000 BCE when various shaped stones were used to strike wood, bone, or other stones to break them apart and shape them. Stones attached to sticks with strips of leather or animal sinew were being used as hammers with handles by about 30,000 BCE during the middle of the Paleolithic Stone Age.
The hammers archeological record shows that it may be the oldest tool for which evidence exists of its early existence. A traditional hand-held hammer consists of a head and a handle, fastened together by means of a special wedge made for the purpose, or by glue. This two-piece design is used, to combine a dense metallic striking head with a non-metallic mechanical-shock-absorbing handle. If wood is used for the handle, it is often hickory or ash, rigid fiberglass resin may be used for the handle, this material does not absorb water or decay, but does not dissipate shock as well as wood. A loose hammer head is hazardous because it can fly off the handle when in use. Wooden handles can often be replaced when worn or damaged, specialized kits are available covering a range of sizes and designs. Some hammers are one-piece designs made primarily of a single material, a one-piece metallic hammer may optionally have its handle coated or wrapped in a resilient material such as rubber, for improved grip and reduced user fatigue.
The hammer head may be surfaced with a variety of materials, including brass, wood, rubber, some hammers have interchangeable striking surfaces, which can be selected as needed or replaced when worn out. A large hammer-like tool is a maul, a wood- or rubber-headed hammer is a mallet, the essential part of a hammer is the head, a compact solid mass that is able to deliver a blow to the intended target without itself deforming. The impacting surface of the tool is usually flat or slightly rounded, some upholstery hammers have a magnetized face, to pick up tacks. In the hatchet, the hammer head may be secondary to the cutting edge of the tool