Machine

A machine (or mechanical device) is a mechanical structure that uses power to apply forces and control movement to perform an intended action. Machines can be driven by animals and people, by natural forces such as wind and water, and by chemical, thermal, or electrical power, and include a system of mechanisms that shape the actuator input to achieve a specific application of output forces and movement. They can also include computers and sensors that monitor performance and plan movement, often called mechanical systems.

Renaissance natural philosophers identified six simple machines which were the elementary devices that put a load into motion, and calculated the ratio of output force to input force, known today as mechanical advantage.[1]

Modern machines are complex systems that consist of structural elements, mechanisms and control components and include interfaces for convenient use. Examples include a wide range of vehicles, such as automobiles, boats and airplanes, appliances in the home and office, including computers, building air handling and water handling systems, as well as farm machinery, machine tools and factory automation systems and robots.

Bonsack machine
James Albert Bonsack's cigarette rolling machine, invented in 1880 and patented in 1881

Etymology

The English word machine comes through Middle French from Latin machina,[2] which in turn derives from the Greek (Doric μαχανά makhana, Ionic μηχανή mekhane "contrivance, machine, engine",[3] a derivation from μῆχος mekhos "means, expedient, remedy"[4]).[5] The word mechanical (Greek: μηχανικός) comes from the same Greek roots. A wider meaning of "fabric, structure" is found in classical Latin, but not in Greek usage. This meaning is found in late medieval French, and is adopted from the French into English in the mid-16th century.

In the 17th century, the word could also mean a scheme or plot, a meaning now expressed by the derived machination. The modern meaning develops out of specialized application of the term to stage engines used in theater and to military siege engines, both in the late 16th and early 17th centuries. The OED traces the formal, modern meaning to John Harris' Lexicon Technicum (1704), which has:

Machine, or Engine, in Mechanicks, is whatsoever hath Force sufficient either to raise or stop the Motion of a Body... Simple Machines are commonly reckoned to be Six in Number, viz. the Ballance, Leaver, Pulley, Wheel, Wedge, and Screw... Compound Machines, or Engines, are innumerable.

The word engine used as a (near-)synonym both by Harris and in later language derives ultimately (via Old French) from Latin ingenium "ingenuity, an invention".

History

Flint hand axe
Flint hand axe found in Winchester

The hand axe, made by chipping flint to form a wedge, in the hands of a human transforms force and movement of the tool into a transverse splitting forces and movement of the workpiece.

The idea of a simple machine originated with the Greek philosopher Archimedes around the 3rd century BC, who studied the Archimedean simple machines: lever, pulley, and screw.[6][7] Archimedes discovered the principle of mechanical advantage in the lever.[8] Later Greek philosophers defined the classic five simple machines (excluding the inclined plane) and were able to roughly calculate their mechanical advantage.[1] Heron of Alexandria (ca. 10–75 AD) in his work Mechanics lists five mechanisms that can "set a load in motion"; lever, windlass, pulley, wedge, and screw,[7] and describes their fabrication and uses.[9] However, the Greeks' understanding was limited to statics (the balance of forces) and did not include dynamics (the tradeoff between force and distance) or the concept of work.

During the Renaissance the dynamics of the Mechanical Powers, as the simple machines were called, began to be studied from the standpoint of how much useful work they could perform, leading eventually to the new concept of mechanical work. In 1586 Flemish engineer Simon Stevin derived the mechanical advantage of the inclined plane, and it was included with the other simple machines. The complete dynamic theory of simple machines was worked out by Italian scientist Galileo Galilei in 1600 in Le Meccaniche ("On Mechanics").[10][11] He was the first to understand that simple machines do not create energy, they merely transform it.[10]

The classic rules of sliding friction in machines were discovered by Leonardo da Vinci (1452–1519), but remained unpublished in his notebooks. They were rediscovered by Guillaume Amontons (1699) and were further developed by Charles-Augustin de Coulomb (1785).[12]

James Watt patented his parallel motion linkage in 1782, which made the double acting steam engine practical.[13] The Boulton and Watt steam engine and later designs powered steam locomotives, steam ships, and factories.

The Industrial Revolution was a period from 1750 to 1850 where changes in agriculture, manufacturing, mining, transportation, and technology had a profound effect on the social, economic and cultural conditions of the times. It began in the United Kingdom, then subsequently spread throughout Western Europe, North America, Japan, and eventually the rest of the world.

Starting in the later part of the 18th century, there began a transition in parts of Great Britain's previously manual labour and draft-animal-based economy towards machine-based manufacturing. It started with the mechanisation of the textile industries, the development of iron-making techniques and the increased use of refined coal.[14]

Simple machines

Table of Mechanicks, Cyclopaedia, Volume 2
Table of simple mechanisms, from Chambers' Cyclopædia, 1728.[15] Simple machines provide a "vocabulary" for understanding more complex machines.

The idea that a machine can be decomposed into simple movable elements led Archimedes to define the lever, pulley and screw as simple machines. By the time of the Renaissance this list increased to include the wheel and axle, wedge and inclined plane. The modern approach to characterizing machines focusses on the components that allow movement, known as joints.

Wedge (hand axe): Perhaps the first example of a device designed to manage power is the hand axe, also called biface and Olorgesailie. A hand axe is made by chipping stone, generally flint, to form a bifacial edge, or wedge. A wedge is a simple machine that transforms lateral force and movement of the tool into a transverse splitting force and movement of the workpiece. The available power is limited by the effort of the person using the tool, but because power is the product of force and movement, the wedge amplifies the force by reducing the movement. This amplification, or mechanical advantage is the ratio of the input speed to output speed. For a wedge this is given by 1/tanα, where α is the tip angle. The faces of a wedge are modeled as straight lines to form a sliding or prismatic joint.

Lever: The lever is another important and simple device for managing power. This is a body that pivots on a fulcrum. Because the velocity of a point farther from the pivot is greater than the velocity of a point near the pivot, forces applied far from the pivot are amplified near the pivot by the associated decrease in speed. If a is the distance from the pivot to the point where the input force is applied and b is the distance to the point where the output force is applied, then a/b is the mechanical advantage of the lever. The fulcrum of a lever is modeled as a hinged or revolute joint.

Wheel: The wheel is clearly an important early machine, such as the chariot. A wheel uses the law of the lever to reduce the force needed to overcome friction when pulling a load. To see this notice that the friction associated with pulling a load on the ground is approximately the same as the friction in a simple bearing that supports the load on the axle of a wheel. However, the wheel forms a lever that magnifies the pulling force so that it overcomes the frictional resistance in the bearing.

Kinematics of Machinery - Figure 21
Illustration of a four-bar linkage from The Kinematics of Machinery, 1876

The classification of simple machines to provide a strategy for the design of new machines was developed by Franz Reuleaux, who collected and studied over 800 elementary machines.[16] He recognized that the classical simple machines can be separated into the lever, pulley and wheel and axle that are formed by a body rotating about a hinge, and the inclined plane, wedge and screw that are similarly a block sliding on a flat surface.[17]

Simple machines are elementary examples of kinematic chains or linkages that are used to model mechanical systems ranging from the steam engine to robot manipulators. The bearings that form the fulcrum of a lever and that allow the wheel and axle and pulleys to rotate are examples of a kinematic pair called a hinged joint. Similarly, the flat surface of an inclined plane and wedge are examples of the kinematic pair called a sliding joint. The screw is usually identified as its own kinematic pair called a helical joint.

This realization shows that it is the joints, or the connections that provide movement, that are the primary elements of a machine. Starting with four types of joints, the rotary joint, sliding joint, cam joint and gear joint, and related connections such as cables and belts, it is possible to understand a machine as an assembly of solid parts that connect these joints called a mechanism .[18]

Two levers, or cranks, are combined into a planar four-bar linkage by attaching a link that connects the output of one crank to the input of another. Additional links can be attached to form a six-bar linkage or in series to form a robot.[18]

Mechanical systems

SteamEngine Boulton&Watt 1784
The Boulton & Watt Steam Engine, 1784

A mechanical system manages power to accomplish a task that involves forces and movement. Modern machines are systems consisting of (i) a power source and actuators that generate forces and movement, (ii) a system of mechanisms that shape the actuator input to achieve a specific application of output forces and movement, (iii) a controller with sensors that compare the output to a performance goal and then directs the actuator input, and (iv) an interface to an operator consisting of levers, switches, and displays.

This can be seen in Watt's steam engine (see the illustration) in which the power is provided by steam expanding to drive the piston. The walking beam, coupler and crank transform the linear movement of the piston into rotation of the output pulley. Finally, the pulley rotation drives the flyball governor which controls the valve for the steam input to the piston cylinder.

The adjective "mechanical" refers to skill in the practical application of an art or science, as well as relating to or caused by movement, physical forces, properties or agents such as is dealt with by mechanics.[19] Similarly Merriam-Webster Dictionary[20] defines "mechanical" as relating to machinery or tools.

Power flow through a machine provides a way to understand the performance of devices ranging from levers and gear trains to automobiles and robotic systems. The German mechanician Franz Reuleaux[21] wrote, "a machine is a combination of resistant bodies so arranged that by their means the mechanical forces of nature can be compelled to do work accompanied by certain determinate motion." Notice that forces and motion combine to define power.

More recently, Uicker et al.[18] stated that a machine is "a device for applying power or changing its direction." McCarthy and Soh[22] describe a machine as a system that "generally consists of a power source and a mechanism for the controlled use of this power."

Power sources

Model Engine Luc Viatour
Diesel engine, friction clutch and gear transmission of an automobile.
Generator-20071117
Early Ganz Electric Generator in Zwevegem, West Flanders, Belgium

Human and animal effort were the original power sources for early machines.

Waterwheel: Waterwheels appeared around the world around 300 BC to use flowing water to generate rotary motion, which was applied to milling grain, and powering lumber, machining and textile operations. Modern water turbines use water flowing through a dam to drive an electric generator.

Windmill: Early windmills captured wind power to generate rotary motion for milling operations. Modern wind turbines also drives a generator. This electricity in turn is used to drive motors forming the actuators of mechanical systems.

Engine: The word engine derives from "ingenuity" and originally referred to contrivances that may or may not be physical devices. See Merriam-Webster's definition of engine. A steam engine uses heat to boil water contained in a pressure vessel; the expanding steam drives a piston or a turbine. This principle can be seen in the aeolipile of Hero of Alexandria. This is called an external combustion engine.

An automobile engine is called an internal combustion engine because it burns fuel (an exothermic chemical reaction) inside a cylinder and uses the expanding gases to drive a piston. A jet engine uses a turbine to compress air which is burned with fuel so that it expands through a nozzle to provide thrust to an aircraft, and so is also an "internal combustion engine." [23]

Power plant: The heat from coal and natural gas combustion in a boiler generates steam that drives a steam turbine to rotate an electric generator. A nuclear power plant uses heat from a nuclear reactor to generate steam and electric power. This power is distributed through a network of transmission lines for industrial and individual use.

Motors: Electric motors use either AC or DC electric current to generate rotational movement. Electric servomotors are the actuators for mechanical systems ranging from robotic systems to modern aircraft.

Fluid Power: Hydraulic and pneumatic systems use electrically driven pumps to drive water or air respectively into cylinders to power linear movement.

Mechanisms

The mechanism of a mechanical system is assembled from components called machine elements. These elements provide structure for the system and control its movement.

The structural components are, generally, the frame members, bearings, splines, springs, seals, fasteners and covers. The shape, texture and color of covers provide a styling and operational interface between the mechanical system and its users.

The assemblies that control movement are also called "mechanisms."[21][24] Mechanisms are generally classified as gears and gear trains, which includes belt drives and chain drives, cam and follower mechanisms, and linkages, though there are other special mechanisms such as clamping linkages, indexing mechanisms, escapements and friction devices such as brakes and clutches.

The number of degrees of freedom of a mechanism, or its mobility, depends on the number of links and joints and the types of joints used to construct the mechanism. The general mobility of a mechanism is the difference between the unconstrained freedom of the links and the number of constraints imposed by the joints. It is described by the Chebychev-Grübler-Kutzbach criterion.

Gears and gear trains

NAMA Machine d'Anticythère 1
The Antikythera mechanism (main fragment)

The transmission of rotation between contacting toothed wheels can be traced back to the Antikythera mechanism of Greece and the south-pointing chariot of China. Illustrations by the renaissance scientist Georgius Agricola show gear trains with cylindrical teeth. The implementation of the involute tooth yielded a standard gear design that provides a constant speed ratio. Some important features of gears and gear trains are:

Cam and follower mechanisms

A cam and follower is formed by the direct contact of two specially shaped links. The driving link is called the cam (also see cam shaft) and the link that is driven through the direct contact of their surfaces is called the follower. The shape of the contacting surfaces of the cam and follower determines the movement of the mechanism.

Linkages

Landing gear schematic
Schematic of the actuator and four-bar linkage that position an aircraft landing gear.

A linkage is a collection of links connected by joints. Generally, the links are the structural elements and the joints allow movement. Perhaps the single most useful example is the planar four-bar linkage. However, there are many more special linkages:

  • Watt's linkage is a four-bar linkage that generates an approximate straight line. It was critical to the operation of his design for the steam engine. This linkage also appears in vehicle suspensions to prevent side-to-side movement of the body relative to the wheels. Also see the article Parallel motion.
  • The success of Watt's linkage lead to the design of similar approximate straight-line linkages, such as Hoeken's linkage and Chebyshev's linkage.
  • The Peaucellier linkage generates a true straight-line output from a rotary input.
  • The Sarrus linkage is a spatial linkage that generates straight-line movement from a rotary input. Select this link for an animation of the Sarrus linkage
  • The Klann linkage and the Jansen linkage are recent inventions that provide interesting walking movements. They are respectively a six-bar and an eight-bar linkage.

Planar mechanism

A planar mechanism is a mechanical system that is constrained so the trajectories of points in all the bodies of the system lie on planes parallel to a ground plane. The rotational axes of hinged joints that connect the bodies in the system are perpendicular to this ground plane.

Spherical mechanism

A spherical mechanism is a mechanical system in which the bodies move in a way that the trajectories of points in the system lie on concentric spheres. The rotational axes of hinged joints that connect the bodies in the system pass through the center of these circle.

Spatial mechanism

A spatial mechanism is a mechanical system that has at least one body that moves in a way that its point trajectories are general space curves. The rotational axes of hinged joints that connect the bodies in the system form lines in space that do not intersect and have distinct common normals.

Flexure mechanisms

A flexure mechanism consists of a series of rigid bodies connected by compliant elements (also known as flexure joints) that is designed to produce a geometrically well-defined motion upon application of a force.

Machine elements

The elementary mechanical components of a machine are termed machine elements. These elements consist of three basic types (i) structural components such as frame members, bearings, axles, splines, fasteners, seals, and lubricants, (ii) mechanisms that control movement in various ways such as gear trains, belt or chain drives, linkages, cam and follower systems, including brakes and clutches, and (iii) control components such as buttons, switches, indicators, sensors, actuators and computer controllers.[25] While generally not considered to be a machine element, the shape, texture and color of covers are an important part of a machine that provide a styling and operational interface between the mechanical components of a machine and its users.

Structural components

A number of machine elements provide important structural functions such as the frame, bearings, splines, spring and seals.

  • The recognition that the frame of a mechanism is an important machine element changed the name three-bar linkage into four-bar linkage. Frames are generally assembled from truss or beam elements.
  • Bearings are components designed to manage the interface between moving elements and are the source of friction in machines. In general, bearings are designed for pure rotation or straight line movement.
  • Splines and keys are two ways to reliably mount an axle to a wheel, pulley or gear so that torque can be transferred through the connection.
  • Springs provides forces that can either hold components of a machine in place or acts as a suspension to support part of a machine.
  • Seals are used between mating parts of a machine to ensure fluids, such as water, hot gases, or lubricant do not leak between the mating surfaces.
  • Fasteners such as screws, bolts, spring clips, and rivets are critical to the assembly of components of a machine. Fasteners are generally considered to be removable. In contrast, joining methods, such as welding, soldering, crimping and the application of adhesives, usually require cutting the parts to disassemble the components

Controllers

Controllers combine sensors, logic, and actuators to maintain the performance of components of a machine. Perhaps the best known is the flyball governor for a steam engine. Examples of these devices range from a thermostat that as temperature rises opens a valve to cooling water to speed controllers such as the cruise control system in an automobile. The programmable logic controller replaced relays and specialized control mechanisms with a programmable computer. Servomotors that accurately position a shaft in response to an electrical command are the actuators that make robotic systems possible.

Computing machines

Arithmometre, designed by Charles Xavier Thomas, c. 1820, for the four rules of arithmetic, manufactured 1866-1870 AD, TM10901 - Tekniska museet - Stockholm, Sweden - DSC01567
Arithmometre, designed by Charles Xavier Thomas, c. 1820, for the four rules of arithmetic, manufactured 1866-1870 AD. Exhibit in the Tekniska museet, Stockholm, Sweden.

Charles Babbage designed machines to tabulate logarithms and other functions in 1837. His Difference engine can be considered an advanced mechanical calculator and his Analytical Engine a forerunner of the modern computer, though none were built in Babbage's lifetime.

The Arithmometer and the Comptometer are mechanical computers that are precursors to modern digital computers. Models used to study modern computers are termed State machine and Turing machine.

Molecular machines

The biological molecule myosin reacts to ATP and ADP to alternately engage with an actin filament and change its shape in a way that exerts a force, and then disengage to reset its shape, or conformation. This acts as the molecular drive that causes muscle contraction. Similarly the biological molecule kinesin has two sections that alternately engage and disengage with microtubules causing the molecule to move along the microtubule and transport vesicles within the cell, and dynein, which moves cargo inside cells towards the nucleus and produces the axonemal beating of motile cilia and flagella. "[I]n effect, the [motile cilium] is a nanomachine composed of perhaps over 600 proteins in molecular complexes, many of which also function independently as nanomachines...Flexible linkers allow the mobile protein domains connected by them to recruit their binding partners and induce long-range allostery via protein domain dynamics. "[26] Other biological machines are responsible for energy production, for example ATP synthase which harnesses energy from proton gradients across membranes to drive a turbine-like motion used to synthesise ATP, the energy currency of a cell.[27] Still other machines are responsible for gene expression, including DNA polymerases for replicating DNA, RNA polymerases for producing mRNA, the spliceosome for removing introns, and the ribosome for synthesising proteins. These machines and their nanoscale dynamics are far more complex than any molecular machines that have yet been artificially constructed.[28] These molecules are increasingly considered to be nanomachines.

Researchers have used DNA to construct nano-dimensioned four-bar linkages.[29][30]

Impact

Mechanization and automation

Agricola1
A water-powered mine hoist used for raising ore. This woodblock is from De re metallica by Georg Bauer (Latinized name Georgius Agricola, ca. 1555), an early mining textbook that contains numerous drawings and descriptions of mining equipment.

Mechanization or mechanisation (BE) is providing human operators with machinery that assists them with the muscular requirements of work or displaces muscular work. In some fields, mechanization includes the use of hand tools. In modern usage, such as in engineering or economics, mechanization implies machinery more complex than hand tools and would not include simple devices such as an un-geared horse or donkey mill. Devices that cause speed changes or changes to or from reciprocating to rotary motion, using means such as gears, pulleys or sheaves and belts, shafts, cams and cranks, usually are considered machines. After electrification, when most small machinery was no longer hand powered, mechanization was synonymous with motorized machines.[31]

Automation is the use of control systems and information technologies to reduce the need for human work in the production of goods and services. In the scope of industrialization, automation is a step beyond mechanization. Whereas mechanization provides human operators with machinery to assist them with the muscular requirements of work, automation greatly decreases the need for human sensory and mental requirements as well. Automation plays an increasingly important role in the world economy and in daily experience.

Automata

An automaton (plural: automata or automatons) is a self-operating machine. The word is sometimes used to describe a robot, more specifically an autonomous robot. A Toy Automaton was patented in 1863.[32]

Mechanics

Usher[33] reports that Hero of Alexandria's treatise on Mechanics focussed on the study of lifting heavy weights. Today mechanics refers to the mathematical analysis of the forces and movement of a mechanical system, and consists of the study of the kinematics and dynamics of these systems.

Dynamics of machines

The dynamic analysis of machines begins with a rigid-body model to determine reactions at the bearings, at which point the elasticity effects are included. The rigid-body dynamics studies the movement of systems of interconnected bodies under the action of external forces. The assumption that the bodies are rigid, which means that they do not deform under the action of applied forces, simplifies the analysis by reducing the parameters that describe the configuration of the system to the translation and rotation of reference frames attached to each body.[34][35]

The dynamics of a rigid body system is defined by its equations of motion, which are derived using either Newtons laws of motion or Lagrangian mechanics. The solution of these equations of motion defines how the configuration of the system of rigid bodies changes as a function of time. The formulation and solution of rigid body dynamics is an important tool in the computer simulation of mechanical systems.

Kinematics of machines

The dynamic analysis of a machine requires the determination of the movement, or kinematics, of its component parts, known as kinematic analysis. The assumption that the system is an assembly of rigid components allows rotational and translational movement to be modeled mathematically as Euclidean, or rigid, transformations. This allows the position, velocity and acceleration of all points in a component to be determined from these properties for a reference point, and the angular position, angular velocity and angular acceleration of the component.

Machine design

Machine design refers to the procedures and techniques used to address the three phases of a machine's lifecycle:

  1. invention, which involves the identification of a need, development of requirements, concept generation, prototype development, manufacturing, and verification testing;
  2. performance engineering involves enhancing manufacturing efficiency, reducing service and maintenance demands, adding features and improving effectiveness, and validation testing;
  3. recycle is the decommissioning and disposal phase and includes recovery and reuse of materials and components.

See also

References

  1. ^ a b Usher, Abbott Payson (1988). A History of Mechanical Inventions. USA: Courier Dover Publications. p. 98. ISBN 978-0-486-25593-4. Archived from the original on 2016-08-18.
  2. ^ The American Heritage Dictionary, Second College Edition. Houghton Mifflin Co., 1985.
  3. ^ "μηχανή" Archived 2011-06-29 at the Wayback Machine, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus project
  4. ^ "μῆχος" Archived 2011-06-29 at the Wayback Machine, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus project
  5. ^ Oxford Dictionaries, machine
  6. ^ Asimov, Isaac (1988), Understanding Physics, New York, New York, USA: Barnes & Noble, p. 88, ISBN 978-0-88029-251-1, archived from the original on 2016-08-18.
  7. ^ a b Chiu, Y. C. (2010), An introduction to the History of Project Management, Delft: Eburon Academic Publishers, p. 42, ISBN 978-90-5972-437-2, archived from the original on 2016-08-18
  8. ^ Ostdiek, Vern; Bord, Donald (2005). Inquiry into Physics. Thompson Brooks/Cole. p. 123. ISBN 978-0-534-49168-0. Archived from the original on 2013-05-28. Retrieved 2008-05-22.
  9. ^ Strizhak, Viktor; Igor Penkov; Toivo Pappel (2004). "Evolution of design, use, and strength calculations of screw threads and threaded joints". HMM2004 International Symposium on History of Machines and Mechanisms. Kluwer Academic publishers. p. 245. ISBN 1-4020-2203-4. Archived from the original on 2013-06-07. Retrieved 2008-05-21.
  10. ^ a b Krebs, Robert E. (2004). Groundbreaking Experiments, Inventions, and Discoveries of the Middle Ages. Greenwood Publishing Group. p. 163. ISBN 978-0-313-32433-8. Archived from the original on 2013-05-28. Retrieved 2008-05-21.
  11. ^ Stephen, Donald; Lowell Cardwell (2001). Wheels, clocks, and rockets: a history of technology. USA: W. W. Norton & Company. pp. 85–87. ISBN 978-0-393-32175-3. Archived from the original on 2016-08-18.
  12. ^ Armstrong-Hélouvry, Brian (1991). Control of machines with friction. USA: Springer. p. 10. ISBN 978-0-7923-9133-3. Archived from the original on 2016-08-18.
  13. ^ Pennock, G. R., James Watt (1736-1819), Distinguished Figures in Mechanism and Machine Science, ed. M. Ceccarelli, Springer, 2007, ISBN 978-1-4020-6365-7 (Print) 978-1-4020-6366-4 (Online).
  14. ^ Beck B., Roger (1999). World History: Patterns of Interaction. Evanston, Illinois: McDougal Littell.
  15. ^ Chambers, Ephraim (1728), "Table of Mechanicks", Cyclopaedia, A Useful Dictionary of Arts and Sciences, London, England, Volume 2, p. 528, Plate 11.
  16. ^ Moon, F. C., The Reuleaux Collection of Kinematic Mechanisms at Cornell University, 1999 Archived 2015-05-18 at the Wayback Machine
  17. ^ Hartenberg, R.S. & J. Denavit (1964) Kinematic synthesis of linkages Archived 2011-05-19 at the Wayback Machine, New York: McGraw-Hill, online link from Cornell University.
  18. ^ a b c J. J. Uicker, G. R. Pennock, and J. E. Shigley, 2003, Theory of Machines and Mechanisms, Oxford University Press, New York.
  19. ^ "mechanical". Oxford English Dictionary (3rd ed.). Oxford University Press. September 2005. (Subscription or UK public library membership required.)
  20. ^ Merriam-Webster Dictionary Definition of mechanical Archived 2011-10-20 at the Wayback Machine
  21. ^ a b Reuleaux, F., 1876 The Kinematics of Machinery Archived 2013-06-02 at the Wayback Machine (trans. and annotated by A. B. W. Kennedy), reprinted by Dover, New York (1963)
  22. ^ J. M. McCarthy and G. S. Soh, 2010, Geometric Design of Linkages, Archived 2016-08-19 at the Wayback Machine Springer, New York.
  23. ^ "Internal combustion engine", Concise Encyclopedia of Science and Technology, Third Edition, Sybil P. Parker, ed. McGraw-Hill, Inc., 1994, p. 998 .
  24. ^ J. J. Uicker, G. R. Pennock, and J. E. Shigley, 2003, Theory of Machines and Mechanisms, Oxford University Press, New York.
  25. ^ Robert L. Norton, Machine Design, (4th Edition), Prentice-Hall, 2010
  26. ^ Satir, Peter; Søren T. Christensen (2008-03-26). "Structure and function of mammalian cilia". Histochemistry and Cell Biology. 129 (6): 687–93. doi:10.1007/s00418-008-0416-9. PMC 2386530. PMID 18365235. 1432-119X.
  27. ^ Kinbara, Kazushi; Aida, Takuzo (2005-04-01). "Toward Intelligent Molecular Machines: Directed Motions of Biological and Artificial Molecules and Assemblies". Chemical Reviews. 105 (4): 1377–1400. doi:10.1021/cr030071r. ISSN 0009-2665. PMID 15826015.
  28. ^ Bu Z, Callaway DJ (2011). Proteins MOVE! Protein dynamics and long-range allostery in cell signaling. Advances in Protein Chemistry and Structural Biology. 83. pp. 163–221. doi:10.1016/B978-0-12-381262-9.00005-7. ISBN 9780123812629. PMID 21570668.
  29. ^ Marras, A., Zhou, L., Su, H., and Castro, C.E. Programmable motion of DNA origami mechanisms, Proceedings of the National Academy of Sciences, 2015 Archived 2017-08-04 at the Wayback Machine
  30. ^ McCarthy, C, DNA Origami Mechanisms and Machines | Mechanical Design 101, 2014 Archived 2017-09-18 at the Wayback Machine
  31. ^ Jerome (1934) gives the industry classification of machine tools as being "other than hand power". Beginning with the 1900 U.S. census, power use was part of the definition of a factory, distinguishing it from a workshop.
  32. ^ "U.S. Patent and Trademark Office, Patent# 40891, Toy Automaton". Google Patents. Retrieved 2007-01-07.
  33. ^ A. P. Usher, 1929, A History of Mechanical Inventions Archived 2013-06-02 at the Wayback Machine, Harvard University Press (reprinted by Dover Publications 1968).
  34. ^ B. Paul, Kinematics and Dynamics of Planar Machinery, Prentice-Hall, NJ, 1979
  35. ^ L. W. Tsai, Robot Analysis: The mechanics of serial and parallel manipulators, John-Wiley, NY, 1999.

Further reading

  • Oberg, Erik; Franklin D. Jones; Holbrook L. Horton; Henry H. Ryffel (2000). Christopher J. McCauley; Riccardo Heald; Muhammed Iqbal Hussain (eds.). Machinery's Handbook (26th ed.). New York: Industrial Press Inc. ISBN 978-0-8311-2635-3.
  • Reuleaux, Franz (1876). The Kinematics of Machinery. Trans. and annotated by A. B. W. Kennedy. New York: reprinted by Dover (1963).
  • Uicker, J. J.; G. R. Pennock; J. E. Shigley (2003). Theory of Machines and Mechanisms. New York: Oxford University Press.
  • Oberg, Erik; Franklin D. Jones; Holbrook L. Horton; Henry H. Ryffel (2000). Christopher J. McCauley; Riccardo Heald; Muhammed Iqbal Hussain (eds.). Machinery's Handbook (30th ed.). New York: Industrial Press Inc. ISBN 9780831130992.

External links

AK-47

The AK-47, officially known as the Avtomat Kalashnikova (Russian: Автома́т Кала́шникова, tr. Avtomát Kaláshnikova, lit. automatic device Kalashnikov; also known as the Kalashnikov and AK), is a gas-operated, 7.62×39mm assault rifle, developed in the Soviet Union by Mikhail Kalashnikov. It is the originating firearm of the Kalashnikov rifle (or "AK") family.

Design work on the AK-47 began in 1945. In 1946, the AK-47 was presented for official military trials, and in 1948, the fixed-stock version was introduced into active service with selected units of the Soviet Army. An early development of the design was the AKS (S—Skladnoy or "folding"), which was equipped with an underfolding metal shoulder stock. In early 1949, the AK-47 was officially accepted by the Soviet Armed Forces and used by the majority of the member states of the Warsaw Pact.

Even after almost seven decades, the model and its variants remain the most popular and widely used assault rifles in the world because of its reliability under harsh conditions, low production costs compared to contemporary Western weapons, availability in virtually every geographic region, and ease of use. The AK-47 has been manufactured in many countries and has seen service with armed forces as well as irregular forces and insurgencies worldwide, and was the basis for developing many other types of individual, crew-served and specialised firearms. As of 2004, "Of the estimated 500 million firearms worldwide, approximately 100 million belong to the Kalashnikov family, three-quarters of which are AK-47s".

Artificial intelligence

In computer science, artificial intelligence (AI), sometimes called machine intelligence, is intelligence demonstrated by machines, in contrast to the natural intelligence displayed by humans. Colloquially, the term "artificial intelligence" is used to describe machines/computers that mimic "cognitive" functions that humans associate with other human minds, such as "learning" and "problem solving".As machines become increasingly capable, tasks considered to require "intelligence" are often removed from the definition of AI, a phenomenon known as the AI effect. A quip in Tesler's Theorem says "AI is whatever hasn't been done yet." For instance, optical character recognition is frequently excluded from things considered to be AI, having become a routine technology. Modern machine capabilities generally classified as AI include successfully understanding human speech, competing at the highest level in strategic game systems (such as chess and Go), autonomously operating cars, intelligent routing in content delivery networks, and military simulations.

Artificial intelligence can be classified into three different types of systems: analytical, human-inspired, and humanized artificial intelligence. Analytical AI has only characteristics consistent with cognitive intelligence; generating cognitive representation of the world and using learning based on past experience to inform future decisions. Human-inspired AI has elements from cognitive and emotional intelligence; understanding human emotions, in addition to cognitive elements, and considering them in their decision making. Humanized AI shows characteristics of all types of competencies (i.e., cognitive, emotional, and social intelligence), is able to be self-conscious and is self-aware in interactions with others.

Artificial intelligence was founded as an academic discipline in 1956, and in the years since has experienced several waves of optimism, followed by disappointment and the loss of funding (known as an "AI winter"), followed by new approaches, success and renewed funding. For most of its history, AI research has been divided into subfields that often fail to communicate with each other. These sub-fields are based on technical considerations, such as particular goals (e.g. "robotics" or "machine learning"), the use of particular tools ("logic" or artificial neural networks), or deep philosophical differences. Subfields have also been based on social factors (particular institutions or the work of particular researchers).The traditional problems (or goals) of AI research include reasoning, knowledge representation, planning, learning, natural language processing, perception and the ability to move and manipulate objects. General intelligence is among the field's long-term goals. Approaches include statistical methods, computational intelligence, and traditional symbolic AI. Many tools are used in AI, including versions of search and mathematical optimization, artificial neural networks, and methods based on statistics, probability and economics. The AI field draws upon computer science, information engineering, mathematics, psychology, linguistics, philosophy, and many other fields.

The field was founded on the claim that human intelligence "can be so precisely described that a machine can be made to simulate it". This raises philosophical arguments about the nature of the mind and the ethics of creating artificial beings endowed with human-like intelligence which are issues that have been explored by myth, fiction and philosophy since antiquity. Some people also consider AI to be a danger to humanity if it progresses unabated. Others believe that AI, unlike previous technological revolutions, will create a risk of mass unemployment.In the twenty-first century, AI techniques have experienced a resurgence following concurrent advances in computer power, large amounts of data, and theoretical understanding; and AI techniques have become an essential part of the technology industry, helping to solve many challenging problems in computer science, software engineering and operations research.

Computer

A computer is a machine that can be instructed to carry out sequences of arithmetic or logical operations automatically via computer programming. Modern computers have the ability to follow generalized sets of operations, called programs. These programs enable computers to perform an extremely wide range of tasks. A "complete" computer including the hardware, the operating system (main software), and peripheral equipment required and used for "full" operation can be referred to as a computer system. This term may as well be used for a group of computers that are connected and work together, in particular a computer network or computer cluster.

Computers are used as control systems for a wide variety of industrial and consumer devices. This includes simple special purpose devices like microwave ovens and remote controls, factory devices such as industrial robots and computer-aided design, and also general purpose devices like personal computers and mobile devices such as smartphones. The Internet is run on computers and it connects hundreds of millions of other computers and their users.

Early computers were only conceived as calculating devices. Since ancient times, simple manual devices like the abacus aided people in doing calculations. Early in the Industrial Revolution, some mechanical devices were built to automate long tedious tasks, such as guiding patterns for looms. More sophisticated electrical machines did specialized analog calculations in the early 20th century. The first digital electronic calculating machines were developed during World War II. The speed, power, and versatility of computers have been increasing dramatically ever since then.

Conventionally, a modern computer consists of at least one processing element, typically a central processing unit (CPU), and some form of memory. The processing element carries out arithmetic and logical operations, and a sequencing and control unit can change the order of operations in response to stored information. Peripheral devices include input devices (keyboards, mice, joystick, etc.), output devices (monitor screens, printers, etc.), and input/output devices that perform both functions (e.g., the 2000s-era touchscreen). Peripheral devices allow information to be retrieved from an external source and they enable the result of operations to be saved and retrieved.

Denmark

Denmark (Danish: Danmark, pronounced [ˈtænmak] (listen)), officially the Kingdom of Denmark, is a Nordic country and the southernmost of the Scandinavian nations. Denmark lies southwest of Sweden and south of Norway, and is bordered to the south by Germany. The Kingdom of Denmark also comprises two autonomous constituent countries in the North Atlantic Ocean: the Faroe Islands and Greenland. Denmark proper consists of a peninsula, Jutland, and an archipelago of 443 named islands, with the largest being Zealand, Funen and the North Jutlandic Island. The islands are characterised by flat, arable land and sandy coasts, low elevation and a temperate climate. Denmark has a total area of 42,924 km2 (16,573 sq mi), land area of 42,394 km2 (16,368 sq mi), and the total area including Greenland and the Faroe Islands is 2,210,579 km2 (853,509 sq mi), and a population of 5.8 million (as of 2018).The unified kingdom of Denmark emerged in the 10th century as a proficient seafaring nation in the struggle for control of the Baltic Sea. Denmark, Sweden, and Norway were ruled together under one sovereign ruler in the Kalmar Union, established in 1397 and ending with Swedish secession in 1523. The areas of Denmark and Norway remained under the same monarch until 1814, Denmark–Norway. Beginning in the 17th century, there were several devastating wars with the Swedish Empire, ending with large cessions of territory to Sweden. After the Napoleonic Wars, Norway was ceded to Sweden, while Denmark kept the Faroe Islands, Greenland, and Iceland. In the 19th century there was a surge of nationalist movements, which were defeated in the 1864 Second Schleswig War. Denmark remained neutral during World War I. In April 1940, a German invasion saw brief military skirmishes while the Danish resistance movement was active from 1943 until the German surrender in May 1945. An industrialised exporter of agricultural produce in the second half of the 19th century, Denmark introduced social and labour-market reforms in the early 20th century that created the basis for the present welfare state model with a highly developed mixed economy.

The Constitution of Denmark was signed on 5 June 1849, ending the absolute monarchy, which had begun in 1660. It establishes a constitutional monarchy organised as a parliamentary democracy. The government and national parliament are seated in Copenhagen, the nation's capital, largest city, and main commercial centre. Denmark exercises hegemonic influence in the Danish Realm, devolving powers to handle internal affairs. Home rule was established in the Faroe Islands

in 1948; in Greenland home rule was established in 1979 and further autonomy in 2009. Denmark became a member of the European Economic Community (now the EU) in 1973, but negotiated certain opt-outs; it retains its own currency, the krone. It is among the founding members of NATO, the Nordic Council, the OECD, OSCE, and the United Nations; it is also part of the Schengen Area.

Denmark is considered to be one of the most economically and socially developed countries in the world. Danes enjoy a high standard of living and the country ranks highly in some metrics of national performance, including education, health care, protection of civil liberties, democratic governance, prosperity, and human development. The country ranks as having the world's highest social mobility, a high level of income equality, has the lowest perceived level of corruption in the world, the eleventh-most developed in the world, has one of the world's highest per capita incomes, and one of the world's highest personal income tax rates.

Florence and the Machine

Florence and the Machine (stylised as Florence + the Machine) are an English indie rock band that formed in London in 2007, consisting of vocalist Florence Welch, keyboardist Isabella Summers, and a collaboration of other musicians. The band's music received praise across the media, especially from the BBC, which played a large part in their rise to prominence by promoting Florence and the Machine as part of BBC Introducing. At the 2009 Brit Awards they received the Brit Awards "Critics' Choice" award. The band's music is renowned for its dramatic and eccentric production and also Welch's powerful vocal performances.

The band's debut studio album, Lungs, was released on 6 July 2009, and held the number-two position for its first five weeks on the UK Albums Chart. On 17 January 2010, the album reached the top position, after being on the chart for twenty-eight consecutive weeks. As of October 2010, the album had been in the top forty in the United Kingdom for sixty-five consecutive weeks, making it one of the best-selling albums of 2009 and 2010. The group's second studio album, Ceremonials, released in October 2011, entered the charts at number one in the UK and number six in the US. The band's third album, How Big, How Blue, How Beautiful, was released on 2 June 2015. It topped the UK charts, and debuted at number one on the US Billboard 200, their first to do so. The album reached number one in a total of eight countries and the top ten of twenty. Also in 2015, the band was the headlining act at Glastonbury Festival, making Florence Welch the first British female headliner this century.Florence and the Machine's sound has been described as a combination of various genres, including rock and soul. Lungs won the Brit Award for Best British Album in 2010. Florence and the Machine have been nominated for six Grammy Awards including Best New Artist and Best Pop Vocal Album. Additionally, the band performed at the 2010 MTV Video Music Awards and the 2010 Nobel Peace Prize Concert.

Gloria Estefan

Gloria Estefan (Spanish: [ˈɡloɾja esˈtefan]; born Gloria María Milagrosa Fajardo on September 1, 1957) is a Cuban-American singer, songwriter, actress, and businesswoman. A contralto, she started her career as the lead singer in the group "Miami Latin Boys", which later became known as Miami Sound Machine.

Estefan experienced worldwide success with "Conga" in 1985. The song became Estefan's signature song and led to the Miami Sound Machine winning the grand prix in the 15th annual Tokyo Music Festival in 1986. In the middle of 1988, she and the band got their first number-one hit for the song "Anything for You."

In March 1990, Estefan had a severe accident in her tour bus. She made her comeback in March 1991 with a new world tour and album called Into The Light. Her 1993 Spanish-language album, Mi Tierra, won the first of her three Grammy Awards for Best Tropical Latin Album. It was the first number-one album on the Billboard Top Latin Albums chart, established when it was released. It was also the first Diamond album in Spain. Many of her songs, such as "Rhythm Is Gonna Get You," "1-2-3," "Get On Your Feet," "Here We Are," "Coming Out of the Dark," "Bad Boy," "Oye!," "Party Time" and a remake of "Turn the Beat Around" became international chart-topping hits. Estefan has sold an estimated 115 million records worldwide including 31.5 million in the United States alone.

She has won three Grammy Awards and received a star on the Hollywood Walk of Fame and Las Vegas Walk of Fame. In 2015, she received the Presidential Medal of Freedom for her contributions to American music and received the Kennedy Center Honors in December 2017 for her contributions to American Culture Life. Estefan also won an MTV Video Music Award, she was honored with the American Music Award for Lifetime Achievement, as well as being named BMI Songwriter of the Year. She was inducted into the Songwriters Hall of Fame and has received multiple Billboard Awards. She is also on the list of VH1 top 100 Greatest Artists of All Time, and in Billboard's Top 100 Greatest Artists of All Time.

Google Translate

Google Translate is a free multilingual machine translation service developed by Google, to translate text. It offers a website interface, mobile apps for Android and iOS, and an API that helps developers build browser extensions and software applications. Google Translate supports over 100 languages at various levels and as of May 2017, serves over 500 million people daily.

Launched in April 2006 as a statistical machine translation service, it used United Nations and European Parliament transcripts to gather linguistic data. Rather than translating languages directly, it first translates text to English and then to the target language. During a translation, it looks for patterns in millions of documents to help decide on the best translation. Its accuracy has been criticized and ridiculed on several occasions. In November 2016, Google announced that Google Translate would switch to a neural machine translation engine - Google Neural Machine Translation (GNMT) - which translates "whole sentences at a time, rather than just piece by piece. It uses this broader context to help it figure out the most relevant translation, which it then rearranges and adjusts to be more like a human speaking with proper grammar". Originally only enabled for a few languages in 2016, GNMT is gradually being used for more languages.

Internet

The Internet (portmanteau of interconnected network) is the global system of interconnected computer networks that use the Internet protocol suite (TCP/IP) to link devices worldwide. It is a network of networks that consists of private, public, academic, business, and government networks of local to global scope, linked by a broad array of electronic, wireless, and optical networking technologies. The Internet carries a vast range of information resources and services, such as the inter-linked hypertext documents and applications of the World Wide Web (WWW), electronic mail, telephony, and file sharing.

The origins of the Internet date back to research commissioned by the federal government of the United States in the 1960s to build robust, fault-tolerant communication with computer networks. The primary precursor network, the ARPANET, initially served as a backbone for interconnection of regional academic and military networks in the 1980s. The funding of the National Science Foundation Network as a new backbone in the 1980s, as well as private funding for other commercial extensions, led to worldwide participation in the development of new networking technologies, and the merger of many networks. The linking of commercial networks and enterprises by the early 1990s marked the beginning of the transition to the modern Internet, and generated a sustained exponential growth as generations of institutional, personal, and mobile computers were connected to the network. Although the Internet was widely used by academia since the 1980s, commercialization incorporated its services and technologies into virtually every aspect of modern life.

Most traditional communication media, including telephony, radio, television, paper mail and newspapers are reshaped, redefined, or even bypassed by the Internet, giving birth to new services such as email, Internet telephony, Internet television, online music, digital newspapers, and video streaming websites. Newspaper, book, and other print publishing are adapting to website technology, or are reshaped into blogging, web feeds and online news aggregators. The Internet has enabled and accelerated new forms of personal interactions through instant messaging, Internet forums, and social networking. Online shopping has grown exponentially both for major retailers and small businesses and entrepreneurs, as it enables firms to extend their "brick and mortar" presence to serve a larger market or even sell goods and services entirely online. Business-to-business and financial services on the Internet affect supply chains across entire industries.

The Internet has no single centralized governance in either technological implementation or policies for access and usage; each constituent network sets its own policies. The overreaching definitions of the two principal name spaces in the Internet, the Internet Protocol address (IP address) space and the Domain Name System (DNS), are directed by a maintainer organization, the Internet Corporation for Assigned Names and Numbers (ICANN). The technical underpinning and standardization of the core protocols is an activity of the Internet Engineering Task Force (IETF), a non-profit organization of loosely affiliated international participants that anyone may associate with by contributing technical expertise. In November 2006, the Internet was included on USA Today's list of New Seven Wonders.

J. K. Rowling

Joanne Rowling , ( "rolling"; born 31 July 1965), writing under the pen names J. K. Rowling and Robert Galbraith, is a British novelist, philanthropist, film producer, television producer and screenwriter, best known for writing the Harry Potter fantasy series. The books have won multiple awards, and sold more than 500 million copies, becoming the best-selling book series in history. They have also been the basis for a film series, over which Rowling had overall approval on the scripts and was a producer on the final films in the series.Born in Yate, Gloucestershire, England, Rowling was working as a researcher and bilingual secretary for Amnesty International when she conceived the idea for the Harry Potter series while on a delayed train from Manchester to London in 1990. The seven-year period that followed saw the death of her mother, birth of her first child, divorce from her first husband and relative poverty until the first novel in the series, Harry Potter and the Philosopher's Stone, was published in 1997. There were six sequels, of which the last, Harry Potter and the Deathly Hallows, was released in 2007. Since then, Rowling has written five books for adult readers: The Casual Vacancy (2012) and—under the pseudonym Robert Galbraith—the crime fiction novels The Cuckoo's Calling (2013), The Silkworm (2014), Career of Evil (2015), and Lethal White (2018).Rowling has lived a "rags to riches" life story, in which she progressed from living on state benefits to being the world's first billionaire author. She lost her billionaire status after giving away much of her earnings to charity, but remains one of the wealthiest people in the world. She is the United Kingdom's bestselling living author, with sales in excess of £238M. The 2016 Sunday Times Rich List estimated Rowling's fortune at £600 million, ranking her as the joint 197th richest person in the UK. Time named her a runner-up for its 2007 Person of the Year, noting the social, moral, and political inspiration she has given her fans. In October 2010, Rowling was named the "Most Influential Woman in Britain" by leading magazine editors. She has supported charities, including Comic Relief, One Parent Families and Multiple Sclerosis Society of Great Britain, and launched her own charity which is named Lumos.

John Mayer

John Clayton Mayer (; born October 16, 1977) is an American singer-songwriter, guitarist, and record producer. Born in Bridgeport, Connecticut, Mayer attended Berklee College of Music in Boston, but disenrolled and moved to Atlanta in 1997 with Clay Cook. Together, they formed a short-lived two-man band called Lo-Fi Masters. After their split, Mayer continued to play local clubs, refining his skills and gaining a following. After his appearance at the 2001 South by Southwest Festival, he was signed to Aware Records, and then Columbia Records, which released his first EP, Inside Wants Out. His following two full-length albums—Room for Squares (2001) and Heavier Things (2003)—did well commercially, achieving multi-platinum status. In 2003, he won the Grammy Award for Best Male Pop Vocal Performance for the single "Your Body Is a Wonderland".

By 2005, Mayer had moved away from the acoustic music that characterized his early records, and begun performing the blues and rock music that had originally influenced him as a musician. He collaborated with blues artists such as B. B. King, Buddy Guy, and Eric Clapton. Forming the John Mayer Trio, he released a live album in 2005 called Try!, and his third studio album Continuum in 2006. Both albums received critical acclaim, and Continuum earned Mayer a 2007 Grammy Award for Best Pop Vocal Album. He also won Best Male Pop Vocal Performance for "Waiting on the World to Change". That album was followed by Battle Studies in 2009, a return to pop, with a Battle Studies World Tour.

After having several controversial incidents with the media, Mayer withdrew from public life in 2010 and began work on his fifth studio album, Born and Raised, which drew inspiration from the 1970s pop music of Laurel Canyon. However, the discovery of a granuloma on his vocal cords delayed the release of the album until May 2012, and forced him to cancel the planned tour. The album received a generally favorable reception, though was less commercially successful than his previous work. Mayer began performing as a singer again in January 2013, and that year released his sixth studio album, Paradise Valley, which incorporates country music influences. By 2014, he had sold a total of over 20 million albums worldwide. After developing an interest in the Grateful Dead and connecting with Bob Weir, Mayer formed Dead & Company with three former Grateful Dead musicians. The band's performances have been well-received, with tours in 2015, 2016, 2017, and 2018.

Mayer's secondary career pursuits extend to television hosting, comedy, and writing; he has authored columns for magazines such as Esquire. He supports various causes and has performed at charity benefits. He is a watch aficionado (with a collection he values in the "tens of millions" of dollars), contributing to the watch site Hodinkee, and has been on the jury at the Grand Prix d'Horlogerie de Genève.

Lockheed Martin F-22 Raptor

The Lockheed Martin F-22 Raptor is a fifth-generation, single-seat, twin-engine, all-weather stealth tactical fighter aircraft developed for the United States Air Force (USAF). The result of the USAF's Advanced Tactical Fighter (ATF) program, the aircraft was designed primarily as an air superiority fighter, but also has ground attack, electronic warfare, and signal intelligence capabilities. The prime contractor, Lockheed Martin, built most of the F-22's airframe and weapons systems and conducted final assembly, while Boeing provided the wings, aft fuselage, avionics integration, and training systems.

The aircraft was variously designated F-22 and F/A-22 before it formally entered service in December 2005 as the F-22A. Despite its protracted development and various operational issues, USAF officials consider the F-22 a critical component of the service's tactical air power. Its combination of stealth, aerodynamic performance, and situational awareness enable unprecedented air combat capabilities.Service officials had originally planned to buy a total of 750 ATFs. In 2009, the program was cut to 187 operational production aircraft due to high costs, a lack of clear air-to-air missions due to delays in Russian and Chinese fighter programs, a ban on exports, and development of the more versatile F-35. The last F-22 was delivered in 2012.

M2 Browning

The M2 Machine Gun or Browning .50 Caliber Machine Gun is a heavy machine gun designed toward the end of World War I by John Browning. Its design is similar to Browning's earlier M1919 Browning machine gun, which was chambered for the .30-06 cartridge. The M2 uses the much larger and much more powerful .50 BMG cartridge, which was developed alongside and takes its name from the gun itself (BMG standing for Browning Machine Gun). It has been referred to as "Ma Deuce", in reference to its M2 nomenclature. The design has had many specific designations; the official US military designation for the current infantry type is Browning Machine Gun, Cal. .50, M2, HB, Flexible. It is effective against infantry, unarmored or lightly armored vehicles and boats, light fortifications and low-flying aircraft.

The Browning .50 caliber machine gun has been used extensively as a vehicle weapon and for aircraft armament by the United States from the 1930s to the present. It was heavily used during World War II, the Korean War, the Vietnam War, the Falklands War, the Soviet–Afghan War, the Gulf War, the Iraq War and the War in Afghanistan in the 2000s and 2010s. It is the primary heavy machine gun of NATO countries, and has been used by many other countries as well. The M2 has been in use longer than any other firearm in U.S. inventory except the .45 ACP M1911 pistol, also designed by John Browning.

The current M2HB is manufactured in the U.S. by General Dynamics and U.S. Ordnance for use by the U.S. government, and for allies via Foreign Military Sales, as well as foreign manufacturers such as FN Herstal.

Machine learning

Machine learning (ML) is the scientific study of algorithms and statistical models that computer systems use in order to perform a specific task effectively without using explicit instructions, relying on patterns and inference instead. It is seen as a subset of artificial intelligence. Machine learning algorithms build a mathematical model based on sample data, known as "training data", in order to make predictions or decisions without being explicitly programmed to perform the task. Machine learning algorithms are used in a wide variety of applications, such as email filtering, and computer vision, where it is infeasible to develop an algorithm of specific instructions for performing the task. Machine learning is closely related to computational statistics, which focuses on making predictions using computers. The study of mathematical optimization delivers methods, theory and application domains to the field of machine learning. Data mining is a field of study within machine learning, and focuses on exploratory data analysis through unsupervised learning. In its application across business problems, machine learning is also referred to as predictive analytics.

Mechanical engineering

Mechanical engineering is the discipline that applies engineering, physics, engineering mathematics, and materials science principles to design, analyze, manufacture, and maintain mechanical systems. It is one of the oldest and broadest of the engineering disciplines.

The mechanical engineering field requires an understanding of core areas including mechanics, dynamics, thermodynamics, materials science, structural analysis, and electricity. In addition to these core principles, mechanical engineers use tools such as computer-aided design (CAD), computer-aided manufacturing (CAM), and product life cycle management to design and analyze manufacturing plants, industrial equipment and machinery, heating and cooling systems, transport systems, aircraft, watercraft, robotics, medical devices, weapons, and others. It is the branch of engineering that involves the design, production, and operation of machinery.Mechanical engineering emerged as a field during the Industrial Revolution in Europe in the 18th century; however, its development can be traced back several thousand years around the world. In the 19th century, developments in physics led to the development of mechanical engineering science. The field has continually evolved to incorporate advancements; today mechanical engineers are pursuing developments in such areas as composites, mechatronics, and nanotechnology. It also overlaps with aerospace engineering, metallurgical engineering, civil engineering, electrical engineering, manufacturing engineering, chemical engineering, industrial engineering, and other engineering disciplines to varying amounts. Mechanical engineers may also work in the field of biomedical engineering, specifically with biomechanics, transport phenomena, biomechatronics, bionanotechnology, and modelling of biological systems.

Rage Against the Machine

Rage Against the Machine is an American rock band from Los Angeles, California. Formed in 1991, the group consists of vocalist Zack de la Rocha, bassist and backing vocalist Tim Commerford, guitarist Tom Morello, and drummer Brad Wilk. Their songs express revolutionary political views. As of 2010, they had sold over 16 million records worldwide.Rage Against the Machine released its eponymous debut album in 1992 to commercial and critical success, leading to a slot in the 1993 Lollapalooza festival. In 2003, the album was ranked number 368 on Rolling Stone's list of the 500 greatest albums of all time. Their second album, Evil Empire, was released in 1996. Their third, The Battle of Los Angeles, followed in 1999, and in 2003, it was ranked number 426 on the same list. During their initial nine-year run, they became one of the most popular and influential bands in music history. They were also ranked No. 33 on VH1's 100 Greatest Artists of Hard Rock. The band had a large influence on the nu metal genre which came to prominence during the second half of the 1990s.

In 2000, Rage Against the Machine released the cover album Renegades and disbanded after growing creative differences led to de la Rocha's departure. De la Rocha started a low-key solo career, while the rest of the band formed the rock supergroup Audioslave with Chris Cornell, the former frontman of Soundgarden; Audioslave recorded three albums before disbanding in 2007. The same year, Rage Against the Machine announced a reunion and performed together for the first time in seven years at the Coachella Valley Music and Arts Festival in April 2007. Until 2011, the band continued to perform at more live venues and festivals around the world. In 2016, Morello, Commerford and Wilk formed a new band, Prophets of Rage, with B-Real, Chuck D, and DJ Lord. In 2017, Rage Against the Machine were nominated for induction into the Rock & Roll Hall of Fame in their first year of eligibility and again for the 2018 class. Both bids failed.

Slot machine

A slot machine (American English), known variously as a fruit machine (British English, except Scotland), puggy (Scottish English), the slots (Canadian and American English), poker machine/pokies (Australian English and New Zealand English), or simply slot (British English and American English), is a casino gambling machine that creates a game of chance for its customers.

Its standard layout is a display with three or more reels which rotate when a lever is pulled or button pushed. Slot machines are also known as one-armed bandits because they were originally operated by pulling upon a large mechanical lever on the side of the machine (as distinct from the modern button on the front panel), and because of their ability to empty a player's pockets and wallet as a thief would. Many modern machines are still equipped with a legacy lever in addition to the button.

Slot machines include one or more currency detectors that validate the form of payment, whether coin, cash, or token. The machine pays off according to patterns of symbols appearing on its display when it stops. Slot machines are the most popular gambling method in casinos and constitute about 70 percent of the average US casino's income.Digital technology has resulted in variations on the original slot machine concept. Since the player is essentially playing a video game, manufacturers are able to offer more interactive elements, such as advanced bonus rounds and more varied video graphics.

Software

Computer software, or simply software, is a collection of data or computer instructions that tell the computer how to work. This is in contrast to physical hardware, from which the system is built and actually performs the work. In computer science and software engineering, computer software is all information processed by computer systems, programs and data. Computer software includes computer programs, libraries and related non-executable data, such as online documentation or digital media. Computer hardware and software require each other and neither can be realistically used on its own.

At the lowest programming level, executable code consists of machine language instructions supported by an individual processor—typically a central processing unit (CPU) or a graphics processing unit (GPU). A machine language consists of groups of binary values signifying processor instructions that change the state of the computer from its preceding state. For example, an instruction may change the value stored in a particular storage location in the computer—an effect that is not directly observable to the user. An instruction may also invoke one of many input or output operations, for example displaying some text on a computer screen; causing state changes which should be visible to the user. The processor executes the instructions in the order they are provided, unless it is instructed to "jump" to a different instruction, or is interrupted by the operating system. As of 2015, most personal computers, smartphone devices and servers have processors with multiple execution units or multiple processors performing computation together, and computing has become a much more concurrent activity than in the past.

The majority of software is written in high-level programming languages. They are easier and more efficient for programmers because they are closer to natural languages than machine languages. High-level languages are translated into machine language using a compiler or an interpreter or a combination of the two. Software may also be written in a low-level assembly language, which has strong correspondence to the computer's machine language instructions and is translated into machine language using an assembler.

Switzerland

Switzerland, officially the Swiss Confederation, is a sovereign state situated in the confluence of western, central, and southern Europe. It is a federal republic composed of 26 cantons, with federal authorities seated in Bern. Switzerland is a landlocked country bordered by Italy to the south, France to the west, Germany to the north, and Austria and Liechtenstein to the east. It is geographically divided between the Alps, the Swiss Plateau and the Jura, spanning a total area of 41,285 km2 (15,940 sq mi). While the Alps occupy the greater part of the territory, the Swiss population of approximately 8.5 million is concentrated mostly on the plateau, where the largest cities are located, among them the two global cities and economic centres of Zürich and Geneva.

The establishment of the Old Swiss Confederacy dates to the late medieval period, resulting from a series of military successes against Austria and Burgundy. Swiss independence from the Holy Roman Empire was formally recognized in the Peace of Westphalia in 1648. Since the Reformation of the 16th century, Switzerland has maintained a strong policy of armed neutrality; it has not fought an international war since 1815 and did not join the United Nations until 2002. Nevertheless, it pursues an active foreign policy and is frequently involved in peace-building processes around the world. Switzerland is the birthplace of the Red Cross, one of the world's oldest and best known humanitarian organisations, and is home to numerous international organisations, including the second largest UN office. It is a founding member of the European Free Trade Association, but notably not part of the European Union, the European Economic Area or the Eurozone. However, it participates in the Schengen Area and the European Single Market through bilateral treaties.

Switzerland occupies the crossroads of Germanic and Romance Europe, as reflected in its four main linguistic and cultural regions: German, French, Italian and Romansh. Although the majority of the population are German-speaking, Swiss national identity is rooted in a common historical background, shared values such as federalism and direct democracy, and Alpine symbolism. Due to its linguistic diversity, Switzerland is known by a variety of native names: Schweiz [ˈʃvaɪts] (German); Suisse [sɥis(ə)] (French); Svizzera [ˈzvittsera] (Italian); and Svizra [ˈʒviːtsrɐ, ˈʒviːtsʁɐ] (Romansh). On coins and stamps, the Latin name – frequently shortened to "Helvetia" – is used instead of the four national languages.

Switzerland is one of the most developed countries in the world, with the highest nominal wealth per adult and the eighth-highest per capita gross domestic product. It ranks at or near the top in several international metrics, including economic competitiveness and human development. Zürich, Geneva and Basel have been ranked among the top ten cities in the world in terms of quality of life, with the first ranked second globally.

Transgender

Transgender people have a gender identity or gender expression that differs from their assigned sex. Some transgender people who desire medical assistance to transition from one sex to another identify as transsexual. Transgender – often shortened as trans – is also an umbrella term: in addition to including people whose gender identity is the opposite of their assigned sex (trans men and trans women), it may include people who are not exclusively masculine or feminine (people who are non-binary or genderqueer, including bigender, pangender, genderfluid, or agender). Other definitions of transgender also include people who belong to a third gender, or else conceptualize transgender people as a third gender. Infrequently, the term transgender is defined very broadly to include cross-dressers, regardless of their gender identity.

Being transgender is independent of sexual orientation: transgender people may identify as heterosexual, homosexual, bisexual, asexual, or may decline to label their sexual orientation. The term transgender is also distinguished from intersex, a term that describes people born with physical sex characteristics "that do not fit typical binary notions of male or female bodies". The opposite of transgender is cisgender, which describes persons whose gender identity or expression matches their assigned sex.The degree to which individuals feel genuine, authentic, and comfortable within their external appearance and accept their genuine identity has been called transgender congruence. Many transgender people experience gender dysphoria, and some seek medical treatments such as hormone replacement therapy, sex reassignment surgery, or psychotherapy. Not all transgender people desire these treatments, and some cannot undergo them for financial or medical reasons.Many transgender people face discrimination in the workplace and in accessing public accommodations, and healthcare. In many places they are not legally protected from discrimination.

Wayback Machine

The Wayback Machine is a digital archive of the World Wide Web and other information on the Internet. It was launched in 2001 by the Internet Archive, a nonprofit organization based in San Francisco, California, United States.

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