The Online Computer Library Center is a US-based nonprofit cooperative organization dedicated to the public purposes of furthering access to the worlds information and reducing information costs. It was founded in 1967 as the Ohio College Library Center, OCLC and its member libraries cooperatively produce and maintain WorldCat, the largest online public access catalog in the world. OCLC is funded mainly by the fees that libraries have to pay for its services, the group first met on July 5,1967 on the campus of the Ohio State University to sign the articles of incorporation for the nonprofit organization. The group hired Frederick G. Kilgour, a former Yale University medical school librarian, Kilgour wished to merge the latest information storage and retrieval system of the time, the computer, with the oldest, the library. The goal of network and database was to bring libraries together to cooperatively keep track of the worlds information in order to best serve researchers and scholars. The first library to do online cataloging through OCLC was the Alden Library at Ohio University on August 26,1971 and this was the first occurrence of online cataloging by any library worldwide.
Membership in OCLC is based on use of services and contribution of data, between 1967 and 1977, OCLC membership was limited to institutions in Ohio, but in 1978, a new governance structure was established that allowed institutions from other states to join. In 2002, the structure was again modified to accommodate participation from outside the United States. As OCLC expanded services in the United States outside of Ohio, it relied on establishing strategic partnerships with networks, organizations that provided training, support, by 2008, there were 15 independent United States regional service providers. OCLC networks played a key role in OCLC governance, with networks electing delegates to serve on OCLC Members Council, in early 2009, OCLC negotiated new contracts with the former networks and opened a centralized support center. OCLC provides bibliographic and full-text information to anyone, OCLC and its member libraries cooperatively produce and maintain WorldCat—the OCLC Online Union Catalog, the largest online public access catalog in the world.
WorldCat has holding records from public and private libraries worldwide. org, in October 2005, the OCLC technical staff began a wiki project, WikiD, allowing readers to add commentary and structured-field information associated with any WorldCat record. The Online Computer Library Center acquired the trademark and copyrights associated with the Dewey Decimal Classification System when it bought Forest Press in 1988, a browser for books with their Dewey Decimal Classifications was available until July 2013, it was replaced by the Classify Service. S. The reference management service QuestionPoint provides libraries with tools to communicate with users and this around-the-clock reference service is provided by a cooperative of participating global libraries. OCLC has produced cards for members since 1971 with its shared online catalog. OCLC commercially sells software, e. g. CONTENTdm for managing digital collections, OCLC has been conducting research for the library community for more than 30 years.
In accordance with its mission, OCLC makes its research outcomes known through various publications and these publications, including journal articles, reports and presentations, are available through the organizations website. The most recent publications are displayed first, and all archived resources, membership Reports – A number of significant reports on topics ranging from virtual reference in libraries to perceptions about library funding
In engineering, draft is the amount of taper for molded or cast parts perpendicular to the parting line. It can be measured in degrees or mm/mm, consider the fabrication of a hollow plastic box, without lid. Once the plastic has hardened around the mold, the mold must be removed, as the plastic hardens, it may contract slightly. By tapering the sides of the mold by a draft angle, for instance 2°. This is a practice that is used, in applicable cases, by specifying the opening length and width, a draft angle, and a depth, it is not necessary to specify the dimensions for the internal surface, as these may be calculated from the above. The manufacture of a part that incorporates zero or negative angles may require a mold that can be separated into two or more parts, in order to release the casting and draft angle images from the Bayer Material Science website
Casting is a manufacturing process in which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and allowed to solidify. The solidified part is known as a casting, which is ejected or broken out of the mold to complete the process. Casting materials are usually metals or various cold setting materials that cure after mixing two or more together, examples are epoxy, concrete and clay. Casting is most often used for making complex shapes that would be difficult or uneconomical to make by other methods. The oldest surviving casting is a frog from 3200 BC. In metalworking, metal is heated until it becomes liquid and is poured into a mold. The mold is a cavity that includes the desired shape. The mold and the metal are cooled until the metal solidifies, the solidified part is recovered from the mold. Subsequent operations remove excess material caused by the casting process, when casting plaster or concrete, the material surface is flat and lacks transparency.
Often topical treatments are applied to the surface, for example and etching can be used in a way that give the appearance of metal or stone. Alternatively, the material is altered in its initial casting process, by casting concrete, rather than plaster, it is possible to create sculptures, fountains, or seating for outdoor use. A simulation of high-quality marble may be made using certain chemically-set plastic resins with powdered stone added for coloration, raw castings often contain irregularities caused by seams and imperfections in the molds, as well as access ports for pouring material into the molds. The process of cutting, shaving or sanding away these unwanted bits is called fettling, simulation accurately describes a cast component’s quality up-front before production starts. The casting rigging can be designed with respect to the component properties. This has benefits beyond a reduction in sampling, as the precise layout of the complete casting system leads to energy, material.
The software supports the user in component design, the determination of melting practice and casting methoding through to pattern and mold making, heat treatment and this saves costs along the entire casting manufacturing route. Since the late 80s, commercial programs are available which make it possible for foundries to gain new insight into what is happening inside the mold or die during the casting process
Computer numerical control is the automation of machine tools by means of computers executing pre-programmed sequences of machine control commands. This is in contrast to machines that are controlled by hand wheels or levers. In modern CNC systems, the design of a mechanical part, the parts mechanical dimensions are defined using computer-aided design software, and translated into manufacturing directives by computer-aided manufacturing software. The resulting directives are transformed into the specific commands necessary for a machine to produce the component. Since any particular component might require the use of a number of different tools – drills, saws, in other installations, a number of different machines are used with an external controller and human or robotic operators that move the component from machine to machine. In either case, the series of steps needed to produce any part is highly automated and produces a part that closely matches the original CAD design. The first NC machines were built in the 1940s and 1950s and these early servomechanisms were rapidly augmented with analog and digital computers, creating the modern CNC machine tools that have revolutionized the machining processes.
Motion is controlled along multiple axes, normally at least two, and a spindle that moves in the Z. The position of the tool is driven by direct-drive stepper motor or servo motors in order to provide highly accurate movements, or in older designs, open-loop control works as long as the forces are kept small enough and speeds are not too great. On commercial metalworking machines, closed loop controls are standard and required in order to provide the accuracy, speed, as the controller hardware evolved, the mills themselves evolved. Most new CNC systems built today are 100% electronically controlled, cNC-like systems are now used for any process that can be described as a series of movements and operations. CNC mills use computer controls to cut different materials and they are able to translate programs consisting of specific numbers and letters to move the spindle to various locations and depths. Many use G-code, which is a programming language that many CNC machines understand. These proprietary languages, while often simpler than G-code, are not transferable to other machines, CNC mills have many functions including face milling, shoulder milling, tapping and some even offer turning.
Standard linear CNC mills are limited to 3 axis, but others may have one or more rotational axes, today, CNC mills can have 4 to 6 axes. Lathes are machines that cut workpieces while they are rotated, CNC lathes are able to make fast, precision cuts, generally using indexable tools and drills. They are particularly effective for complicated programs designed to make parts that would be infeasible to make on manual lathes, CNC lathes have similar control specifications to CNC mills and can often read G-code as well as the manufacturers proprietary programming language. CNC lathes generally have two axes, but newer models have more axes, allowing for more advanced jobs to be machined, plasma cutting involves cutting a material using a plasma torch
A simple thermostat merely switches the heater or air conditioner either on or off, and temporary overshoot and undershoot of the desired average temperature must be expected. A more expensive thermostat varies the amount of heat or cooling provided by the heater or cooler and this method is called Proportional control. Further enhancements using the error signal and the rate at which the error is changing are used to form more complex PID Controllers which is the form usually seen in industry. An objects or spaces temperature increases when heat energy moves into it, increasing the kinetic energy of its atoms, e. g. of things. Heat energy leaving an object or space lowers its temperature, heat flows from one place to another by one or more of three processes, conduction and radiation. In conduction, energy is passed from one atom to another by direct contact, in convection, heat energy moves by conduction into some movable fluid and the fluid moves from one place to another, carrying the heat with it.
At some point the energy in the fluid is usually transferred to some other object by means conduction again. The movement of the fluid can be driven by negative-buoyancy, as when cooler air drops and thus upwardly displaces warmer air, in radiation, the heated atoms make electromagnetic emissions absorbed by remote other atoms, whether nearby or at astronomical distance. For example, the Sun radiates heat as both invisible and visible electromagnetic energy, what we know as light is but a narrow region of the electromagnetic spectrum. If, in a place or thing, more energy is received than is lost, if the amount of energy coming in and going out are exactly the same, the temperature stays constant—there is thermal balance, or thermal equilibrium
Injection moulding is a manufacturing process for producing parts by injecting material into a mould. Injection moulding can be performed with a host of materials including metals, elastomers, confections. Material for the part is fed into a barrel and forced into a mould cavity. Injection moulding is used for manufacturing a variety of parts. Advances in 3D printing technology, using photopolymers which do not melt during the moulding of some lower temperature thermoplastics. The versatility of injection moulding is facilitated by this breadth of design considerations, injection moulding is the most common modern method of manufacturing plastic parts, it is ideal for producing high volumes of the same object. Injection moulding uses a ram or screw-type plunger to force molten plastic material into a mould cavity and it is most commonly used to process both thermoplastic and thermosetting polymers, with the volume used of the former being considerably higher. Injection moulding consists of high pressure injection of the raw material into a mould which shapes the polymer into the desired shape, moulds can be of a single cavity or multiple cavities.
In multiple cavity moulds, each cavity can be identical and form the parts or can be unique. Moulds are generally made from tool steels, but stainless steels, many steel moulds are designed to process well over a million parts during their lifetime and can cost hundreds of thousands of dollars to fabricate. When thermoplastics are moulded, typically pelletised raw material is fed through a hopper into a barrel with a reciprocating screw. This process reduces its viscosity, which enables the polymer to flow with the force of the injection unit. The material feeds forward through a valve and collects at the front of the screw into a volume known as a shot. A shot is the volume of material that is used to fill the cavity, compensate for shrinkage. When enough material has gathered, the material is forced at high pressure, to prevent spikes in pressure, the process normally uses a transfer position corresponding to a 95–98% full cavity where the screw shifts from a constant velocity to a constant pressure control.
Often injection times are well under 1 second, the packing pressure is applied until the gate solidifies. Due to its size, the gate is normally the first place to solidify through its entire thickness. This cooling duration is dramatically reduced by the use of cooling lines circulating water or oil from a temperature controller
Molding or moulding is the process of manufacturing by shaping liquid or pliable raw material using a rigid frame called a mold or matrix. This itself may have made using a pattern or model of the final object. A mold or mould is a block that is filled with a liquid or pliable material such as plastic, metal. The liquid hardens or sets inside the mold, adopting its shape, a mold is the counterpart to a cast. The very common bi-valve molding process uses two molds, one for half of the object. Piece-molding uses a number of different molds, each creating a section of a complicated object and this is generally only used for larger and more valuable objects. The manufacturer who makes the molds is called the moldmaker, a release agent is typically used to make removal of the hardened/set substance from the mold easier. Typical uses for molded plastics include molded furniture, molded household goods, molded cases, and structural materials
Vacuum is space void of matter. The word stems from the Latin adjective vacuus for vacant or void, an approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. In engineering and applied physics on the hand, vacuum refers to any space in which the pressure is lower than atmospheric pressure. The Latin term in vacuo is used to describe an object that is surrounded by a vacuum, the quality of a partial vacuum refers to how closely it approaches a perfect vacuum. Other things equal, lower gas pressure means higher-quality vacuum, for example, a typical vacuum cleaner produces enough suction to reduce air pressure by around 20%. Ultra-high vacuum chambers, common in chemistry and engineering, operate below one trillionth of atmospheric pressure, outer space is an even higher-quality vacuum, with the equivalent of just a few hydrogen atoms per cubic meter on average. In the electromagnetism in the 19th century, vacuum was thought to be filled with a medium called aether, in modern particle physics, the vacuum state is considered the ground state of matter.
Vacuum has been a frequent topic of debate since ancient Greek times. Evangelista Torricelli produced the first laboratory vacuum in 1643, and other techniques were developed as a result of his theories of atmospheric pressure. A torricellian vacuum is created by filling a glass container closed at one end with mercury. Vacuum became an industrial tool in the 20th century with the introduction of incandescent light bulbs and vacuum tubes. The recent development of human spaceflight has raised interest in the impact of vacuum on human health, the word vacuum comes from Latin an empty space, noun use of neuter of vacuus, meaning empty, related to vacare, meaning be empty. Vacuum is one of the few words in the English language that contains two consecutive letters u. Historically, there has been dispute over whether such a thing as a vacuum can exist. Ancient Greek philosophers debated the existence of a vacuum, or void, in the context of atomism, Aristotle believed that no void could occur naturally, because the denser surrounding material continuum would immediately fill any incipient rarity that might give rise to a void.
Almost two thousand years after Plato, René Descartes proposed a geometrically based alternative theory of atomism, without the problematic nothing–everything dichotomy of void, by the ancient definition however, directional information and magnitude were conceptually distinct. The explanation of a clepsydra or water clock was a topic in the Middle Ages. Although a simple wine skin sufficed to demonstrate a partial vacuum, in principle and he concluded that airs volume can expand to fill available space, and he suggested that the concept of perfect vacuum was incoherent. However, according to Nader El-Bizri, the physicist Ibn al-Haytham and the Mutazili theologians disagreed with Aristotle and Al-Farabi, using geometry, Ibn al-Haytham mathematically demonstrated that place is the imagined three-dimensional void between the inner surfaces of a containing body
Machining is any of various processes in which a piece of raw material is cut into a desired final shape and size by a controlled material-removal process. Exactly what the part of the definition implies can vary. Machining is a part of the manufacture of metal products, but it can be used on materials such as wood, ceramic. A person who specializes in machining is called a machinist, a room, building, or company where machining is done is called a machine shop. Machining can be a business, a hobby, or both, much of modern-day machining is carried out by computer numerical control, in which computers are used to control the movement and operation of the mills and other cutting machines. The precise meaning of the term machining has evolved over the past one, in the 18th century, the word machinist simply meant a person who built or repaired machines. This persons work was mostly by hand, using processes such as the carving of wood. At the time and builders of new kinds of engines, such as James Watt or John Wilkinson, the noun machine tool and the verb to machine did not yet exist.
Around the middle of the 19th century, the words were coined as the concepts that they described evolved into widespread existence. Therefore, during the Machine Age, machining referred to the machining processes, such as turning, drilling, broaching, shaping, reaming. In current usage, the term machining without qualification usually implies the traditional machining processes, the three principal machining processes are classified as turning and milling. Other operations falling into miscellaneous categories include shaping, boring and sawing, turning operations are operations that rotate the workpiece as the primary method of moving metal against the cutting tool. Lathes are the machine tool used in turning. Milling operations are operations in which the tool rotates to bring cutting edges to bear against the workpiece. Milling machines are the machine tool used in milling. Drilling operations are operations in which holes are produced or refined by bringing a rotating cutter with cutting edges at the lower extremity into contact with the workpiece, drilling operations are done primarily in drill presses but sometimes on lathes or mills.
Burnishing is an example of a miscellaneous operation, burnishing produces no swarf but can be performed at a lathe, mill, or drill press. An unfinished workpiece requiring machining will need to have some material cut away to create a finished product, a finished product would be a workpiece that meets the specifications set out for that workpiece by engineering drawings or blueprints
A thermoplastic, or thermosoftening plastic, is a plastic material, a polymer, that becomes pliable or moldable above a specific temperature and solidifies upon cooling. Most thermoplastics have a molecular weight. The polymer chains associate through intermolecular forces, which weaken rapidly with increased temperature, thermoplastics differ from thermosetting polymers, which form irreversible chemical bonds during the curing process. Thermosets do not melt, but decompose and do not reform upon cooling, above its glass transition temperature and below its melting point, the physical properties of a thermoplastic change drastically without an associated phase change. Some thermoplastics do not fully crystallize below the transition temperature. Amorphous and semi-amorphous plastics are used when high optical clarity is necessary and semi-amorphous plastics are less resistant to chemical attack and environmental stress cracking because they lack a crystalline structure. Brittleness can be decreased with the addition of plasticizers, which increases the mobility of amorphous chain segments to effectively lowers the transition temperature.
Modification of the polymer through copolymerization or through the addition of side chains to monomers before polymerization can lower it. Naval Research Laboratory developed thermoplastic armor, that can be repaired in the field by a user via tools for pressing irons, acrylic, a polymer called poly, is known by trade names such as Lucite and Plexiglas. It serves as a substitute for glass for items such as aquariums, motorcycle helmet visors, aircraft windows, viewing ports of submersibles. It is extensively used to make signs, including lettering and logos, in medicine, it is used in bone cement and to replace eye lenses. Acrylic paint consists of PMMA particles suspended in water, acrylonitrile butadiene styrene is a terpolymer synthesized from styrene and acrylonitrile in the presence of polybutadiene. ABS is a material that exhibits high impact resistance and mechanical toughness. It poses few risks to health under normal handling. It is used in consumer products, such as toys, appliances.
Nylon belongs to a class of polymers called polyamides and it has served as a substitute mainly for hemp and silk, in products such as parachutes, sails, flak vests and womens clothing. Nylon fibers are useful in making fabrics, rope and musical strings, whereas in bulk form, Nylon is used for mechanical parts including machine screws, gears, in addition, it is used in the manufacture of heat-resistant composite materials. Polylactic acid is a biodegradable thermoplastic aliphatic polyester derived from renewable resources, such as starch, tapioca roots, chips or starch
Automated teller machine
According to the ATM Industry Association, there are now close to 3 million ATMs installed worldwide. Authentication is provided by the customer entering a personal identification number which must match the PIN stored in the chip on the card or in the financial institutions database. Using an ATM, customers can access their deposit or credit accounts in order to make a variety of transactions such as cash withdrawals, check balances. If the currency being withdrawn from the ATM is different from that in which the account is denominated the money will be converted at an official exchange rate. Thus, ATMs often provide the best possible exchange rates for foreign travellers, the idea of out-of-hours cash distribution developed from bankers needs in Asia and North America. Little is known of the Japanese device other than it was called Computer Loan Machine, the device was operational in 1966. In the US patent record, Luther George Simjian has been credited with developing a prior art device, specifically his 132nd patent, which was first filed on 30 June 1960.
The roll-out of this machine, called Bankograph, was delayed by a couple of years, an experimental Bankograph was installed in New York City in 1961 by the City Bank of New York, but removed after six months due to the lack of customer acceptance. The Bankograph was an automated envelope deposit machine and did not have cash dispensing features and it is widely accepted that the first ATM was put into use by Barclays Bank in its Enfield Town branch in north London, United Kingdom, on 27 June 1967. This machine was inaugurated by English comedy actor Reg Varney and this instance of the invention is credited to the engineering team led by John Shepherd-Barron of printing firm De La Rue, who was awarded an OBE in the 2005 New Year Honours. Shepherd-Barron stated, It struck me there must be a way I could get my own money, I hit upon the idea of a chocolate bar dispenser, but replacing chocolate with cash. The Barclays-De La Rue machine beat the Swedish saving banks and a company called Metiors machine by a nine days.
The online version of the Swedish machine is listed to have been operational on 6 May 1968, the collaboration of a small start-up called Speytec and Midland Bank developed a fourth machine which was marketed after 1969 in Europe and the US by the Burroughs Corporation. The patent for this device was filed on September 1969 by John David Edwards, Leonard Perkins, John Henry Donald, Peter Lee Chappell, Sean Benjamin Newcombe & Malcom David Roe. Both the DACS and MD2 accepted only a token or voucher which was retained by the machine while the Speytec worked with a card with a magnetic stripe at the back. They used principles including Carbon-14 and low-coercivity magnetism in order to make more difficult. The idea of a PIN stored on the card was developed by a British engineer working on the MD2 named James Goodfellow in 1965, the essence of this system was that it enabled the verification of the customer with the debited account without human intervention. This patent is the earliest instance of a complete currency dispenser system in the patent record and this patent was filed on 5 March 1968 in the US and granted on 1 December 1970