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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.


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Charles Babbage designed machines to tabulate logarithms and other functions in 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. 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.

Flexible linkers allow the mobile protein domains connected by them to recruit their binding partners and induce long-range allostery via protein domain dynamics. These machines and their nanoscale dynamics are far more complex than any molecular machines that have yet been artificially constructed. Researchers have used DNA to construct nano-dimensioned four-bar linkages. 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.

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. 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 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. 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.


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  7. 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.

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

    From Wikipedia, the free encyclopedia. This article is about devices designed to perform tasks. For other uses, see Machine disambiguation. Main article: Simple machine. Main articles: Mechanization and Automation. Main article: Automaton. Main articles: Outline of machines and Outline of industrial machinery. A History of Mechanical Inventions. Archived from the original on Houghton Mifflin Co. Inquiry into Physics. Retrieved Kluwer Academic publishers.

    Greenwood Publishing Group. Wheels, clocks, and rockets: a history of technology. USA: W. Control of machines with friction. USA: Springer. World History: Patterns of Interaction. Evanston, Illinois: McDougal Littell. Uicker, G. Pennock, and J. Oxford English Dictionary 3rd ed. Oxford University Press. September Subscription or UK public library membership required.

    McCarthy and G. This transfer happens in three different ways—by conduction within solids, by the flow of liquid or gas convection , and by radiation, which can travel across space. Even when a system is isolated such as Earth in space , energy is continually being transferred into and out of it by radiation.

    The processes underlying convection and conduction can be understood in terms of models of the possible motions of particles in matter. Radiation can be emitted or absorbed by matter. Uncontrolled systems always evolve toward more stable states—that is, toward more uniform energy distribution within the system or between the system and its environment e. Any object or system that can degrade with no added energy is unstable.

    Eventually it will change or fall apart, although in some cases it may remain in the unstable state for a long time before decaying e. Energy is present whenever there are moving objects, sound, light, or heat. When objects collide, energy can be transferred from one object to another, thereby changing their motion. In such collisions, some energy is typically also transferred to the surrounding air; as a result, the air gets heated and sound is produced. Light also transfers energy from place to place. For example, energy radiated from the sun is transferred to Earth by light.

    Energy can also be transferred from place to place by electric currents, which can then be used locally to produce motion, sound, heat, or light. The currents may have been produced to begin with by transforming the energy of motion into electrical energy e.

    When the motion energy of an object changes, there is inevitably some other change in energy at the same time. For example, the friction that causes a moving object to stop also results in an increase in the thermal energy in both surfaces; eventually heat energy is transferred to the surrounding environment as the surfaces cool. Similarly, to make an object start moving or to keep it moving when friction forces transfer energy away from it,. The amount of energy transfer needed to change the temperature of a matter sample by a given amount depends on the nature of the matter, the size of the sample, and the environment.

    Energy is transferred out of hotter regions or objects and into colder ones by the processes of conduction, convection, and radiation. Conservation of energy means that the total change of energy in any system is always equal to the total energy transferred into or out of the system. Mathematical expressions, which quantify how the stored energy in a system depends on its configuration e. The availability of energy limits what can occur in any system. Uncontrolled systems always evolve toward more stable states—that is, toward more uniform energy distribution e.

    Eventually it will do so, but if the energy releases throughout the transition are small, the process duration can be very long e. When two objects interact, each one exerts a force on the other. These forces can transfer energy between the objects. Forces between two objects at a distance are explained by force fields gravitational, electric, or magnetic between them.

    Contact forces between colliding objects can be modeled at the microscopic level as due to electromagnetic force fields between the surface particles. When two objects interacting via a force field change their relative position, the energy in the. For any such pair of objects the force on each object acts in the direction such that motion of that object in that direction would reduce the energy in the force field between the two objects. However, prior motion and other forces also affect the actual direction of motion.

    Patterns of motion, such as a weight bobbing on a spring or a swinging pendulum, can be understood in terms of forces at each instant or in terms of transformation of energy between the motion and one or more forms of stored energy. Elastic collisions between two objects can be modeled at the macroscopic scale using conservation of energy without having to examine the detailed microscopic forces. A bigger push or pull makes things go faster. Faster speeds during a collision can cause a bigger change in shape of the colliding objects. Magnets can exert forces on other magnets or on magnetizable materials, causing energy transfer between them e.

    When two objects interact, each one exerts a force on the other that can cause energy to be transferred to or from the object. For example, when energy is transferred to an Earth-object system as an object is raised, the gravitational field energy of the system increases. This energy is released as the object falls; the mechanism of this release is the gravitational force.

    Likewise, two magnetic and electrically charged objects interacting at a distance exert forces on each other that can transfer energy between the interacting objects. Force fields gravitational, electric, and magnetic contain energy and can transmit energy across space from one object to another. When two objects interacting through a force field change relative position, the energy stored in the force field is changed. Each force between the two interacting objects acts in the direction such that motion in that direction would reduce the energy in the force field between the objects.

    How do food and fuel provide energy? If energy is conserved, why do people say it is produced or used? This refers to the fact that energy in concentrated form is useful for generating electricity, moving or heating objects, and producing light, whereas diffuse energy in the environment is not readily captured for practical use. Therefore, to produce energy typically means to convert some stored energy into a desired form—for example, the stored energy of water behind a dam is released as the water flows downhill and drives a turbine generator to produce electricity, which is then delivered to users through distribution systems.

    Food, fuel, and batteries are especially convenient energy resources because they can be moved from place to place to provide processes that release energy where needed. A system does not destroy energy when carrying out any process. However, the process cannot occur without energy being available. The energy is also not destroyed by the end of the process. Most often some or all of it has been transferred to heat the surrounding environment; in the same sense that paper is not destroyed when it is written on, it still exists but is not readily available for further use.

    Naturally occurring food and fuel contain complex carbon-based molecules, chiefly derived from plant matter that has been formed by photosynthesis. The chemical reaction of these molecules with oxygen releases energy; such reactions provide energy for most animal life and for residential, commercial, and industrial activities. Electric power generation is based on fossil fuels i. Transportation today chiefly depends on fossil fuels, but the use of electric and alternative fuel e.

    Pendulum - Wikipedia

    All forms of electricity generation and transportation fuels have associated economic, social, and environmental costs and benefits, both short and long term. Technological advances and regulatory decisions can change the balance of those costs and benefits. Although energy cannot be destroyed, it can be converted to less useful forms. In designing a system for energy storage, for energy distribution, or to perform some practical task e.

    Improving efficiency reduces costs, waste materials, and many unintended environmental impacts. When two objects rub against each other, this interaction is called friction. Friction between two surfaces can warm of both of them e. There are ways to reduce the friction between two objects. Food and fuel also release energy when they are digested or burned. The energy released by burning fuel or digesting food was once energy from the sun that was captured by plants in the chemical process that forms plant matter from air and water. Boundary: The fact that plants capture energy from sunlight is introduced at this grade level, but details of photosynthesis are not.

    It is important to be able to concentrate energy so that it is available for use where and when it is needed. For example, batteries are physically transportable energy storage devices, whereas electricity generated by power plants is transferred from place to place through distribution systems. The chemical reaction by which plants produce complex food molecules sugars requires an energy input i. In this reaction, carbon dioxide and water combine to form carbon-based organic molecules and release oxygen.

    Boundary: Further details of the photosynthesis process are not taught at this grade level. Both the burning of fuel and cellular digestion in plants and animals involve chemical reactions with oxygen that release stored energy. In these processes, complex molecules containing carbon react with oxygen to produce carbon dioxide and other materials. Machines can be made more efficient, that is, require less fuel input to perform a given task, by reducing friction between their moving parts and through aerodynamic design.

    Friction increases energy transfer to the surrounding environment by heating the affected materials. Nuclear fusion processes in the center of the sun release the energy that ultimately reaches Earth as radiation. The main way in which that solar energy is captured and stored on Earth is through the complex chemical process known as photosynthesis. A variety of multistage physical and chemical processes in living organisms, particularly within their cells, account for the transport and transfer release or uptake of energy needed for life functions. Although energy cannot be destroyed, it can be converted to less useful forms—for example, to thermal energy in the surrounding environment.

    Machines are judged as efficient or inefficient based on the amount of energy input needed to perform a particular useful task. Inefficient machines are those that produce more waste heat while performing a task and thus require more energy input. It is therefore important to design for high efficiency so as to reduce costs, waste materials, and many environmental impacts. Waves are a repeating pattern of motion that transfers energy from place to place without overall displacement of matter.

    Light and sound are wavelike phenomena. By understanding wave properties and the interactions of electromagnetic radiation with matter, scientists and engineers can design systems for transferring information across long distances, storing information, and investigating nature on many scales—some of them far beyond direct human perception. Whether a wave in water, a sound wave, or a light wave, all waves have some features in common. A simple wave has a repeating pattern of specific wavelength, frequency, and amplitude. The wavelength and frequency of a wave are related to one another by the speed of travel of the wave, which, for each type of wave, depends on the medium in which the wave is traveling.

    Waves can be combined with other waves of the same type to produce complex information-containing patterns that can be decoded at the receiving end. Waves, which transfer energy and any encoded information without the bulk motion of matter, can travel unchanged over long distances, pass through other waves undisturbed, and be detected and decoded far from where they were produced. Information can be digitized converted into a numerical representation , sent over long distances as a series of wave pulses, and reliably stored in computer memory.

    Sound is a pressure wave in air or any other material medium. The human ear and brain working together are very good at detecting and decoding patterns of information in sound e. Resonance is a phenomenon in which waves add up in phase i. Structures have particular frequencies at which they resonate when some time-varying force acting on them transfers energy to them.

    This phenomenon e. When a wave passes an object that is small compared with its wavelength, the wave is not much affected; for this reason, some things are too small to see with visible light, which is a wave phenomenon with a limited range of wavelengths. When a wave meets the surface between two different materials or conditions e.

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    The change of speed of the wave when passing from one medium to another can cause the wave to change direction or refract. These wave properties are used in many applications e. Waves, which are regular patterns of motion, can be made in water by disturbing the surface. When waves move across the surface of deep water, the water goes up and down in place; it does not move in the direction of the wave—observe, for example, a bobbing cork or seabird—except when the water meets the beach.


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    Sound can make matter vibrate, and vibrating matter can make sound. Waves of the same type can differ in amplitude height of the wave and wavelength spacing between wave peaks.

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    Waves can add or cancel one another as they cross, depending on their relative phase i. Boundary: The discussion at this grade level is qualitative only; it can be based on the fact that two different sounds can pass a location in different directions without getting mixed up. A simple wave has a repeating pattern with a specific wavelength, frequency, and amplitude. A sound wave needs a medium through which it is transmitted.

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    Geologists use seismic waves and their reflection at interfaces between layers to probe structures deep in the planet. The wavelength and frequency of a wave are related to one another by the speed of travel of the wave, which depends on the type of wave and the medium through which it is passing. The reflection, refraction, and transmission of waves at an interface between two media can be modeled on the basis of these properties. Combining waves of different frequencies can make a wide variety of patterns and thereby encode and transmit information. Information can be digitized.

    Resonance is a phenomenon in which waves add up in phase in a structure, growing in amplitude due to energy input near the natural vibration frequency.

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    Structures have particular frequencies at which they resonate. What is light? How can one explain the varied effects that involve light? What other forms of electromagnetic radiation are there? Electromagnetic radiation e. Each model is useful for understanding aspects of the phenomenon and its inter-actions with matter, and quantum theory relates the two models. Many modern technologies are based on the manipulation of electromagnetic waves. All electromagnetic radiation travels through a vacuum at the same speed, called the speed of light.

    Its speed in any given medium depends on its wavelength and the properties of that medium. At the surface between two media, like any wave, light can be reflected, refracted its path bent , or absorbed. What occurs depends on properties of the surface and the wavelength of the light. When shorter wavelength electromagnetic radiation ultraviolet, X-rays, gamma rays is absorbed in matter, it can ionize atoms and cause damage to living cells.

    However, because X-rays can travel through soft body matter for some distance but are more rapidly absorbed by denser matter, particularly bone, they are useful for medical imaging. Photovoltaic materials emit electrons when they absorb light of a high-enough frequency. It is best explained using a particle model of light. Any object emits a spectrum of electromagnetic radiation that depends on its temperature.

    In addition, atoms of each element emit and preferentially absorb characteristic frequencies of light. These spectral lines allow identification of the presence of the element, even in microscopic quantities or for remote objects, such as a star. Nuclear transitions that emit or absorb gamma radiation also have distinctive gamma ray wavelengths, a phenomenon that can be used to identify and trace specific radioactive isotopes.

    Objects can be seen only when light is available to illuminate them. Very hot objects give off light e. Some materials allow light to pass through them, others allow only some light through, and others block all the light and create a dark shadow on any. Mirrors and prisms can be used to redirect a light beam. Boundary: The idea that light travels from place to place is developed through experiences with light sources, mirrors, and shadows, but no attempt is made to discuss the speed of light.

    A great deal of light travels through space to Earth from the sun and from distant stars.

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    An object can be seen when light reflected from its surface enters the eyes; the color people see depends on the color of the available light sources as well as the properties of the surface. Boundary: This phenomenon is observed, but no attempt is made to discuss what confers the color reflection and absorption properties on a surface. The stress is on understanding that light traveling from the object to the eye determines what is seen.

    Because lenses bend light beams, they can be used, singly or in combination, to provide magnified images of objects too small or too far away to be seen with the naked eye. The path that light travels can be traced as straight lines, except at surfaces between different transparent materials e. Lenses and prisms are applications of this effect.

    A wave model of light is useful for explaining brightness, color, and the frequency-dependent bending of light at a surface between media prisms. However, because light can travel through space, it cannot be a matter wave, like sound or water waves. The wave model is useful for explaining many features of electromagnetic radiation, and the particle model explains other features. Quantum theory relates the two models.

    Boundary: Quantum theory is not explained further at this grade level. Because a wave is not much disturbed by objects that are small compared with its wavelength, visible light cannot be used to see such objects as individual. Its speed in any other given medium depends on its wavelength and the properties of that medium.

    When light or longer wavelength electromagnetic radiation is absorbed in matter, it is generally converted into thermal energy heat. Shorter wavelength electromagnetic radiation ultraviolet, X-rays, gamma rays can ionize atoms and cause damage to living cells. Atoms of each element emit and absorb characteristic frequencies of light, and nuclear transitions have distinctive gamma ray wavelengths.

    These characteristics allow identification of the presence of an element, even in microscopic quantities. How are instruments that transmit and detect waves used to extend human senses? Understanding of waves and their interactions with matter has been used to design technologies and instruments that greatly extend the range of phenomena that can be investigated by science e.

    Light waves, radio waves, microwaves, and infrared waves are applied to communications systems, many of which use digitized signals i. Signals that humans cannot sense directly can be detected by appropriately designed devices e. When in digitized form, information can be recorded, stored for future recovery, and transmitted over long distances without significant degradation.

    Medical imaging devices collect and interpret signals from waves that can travel through the body and are affected by, and thus gather information about, structures and motion within it e. Sonar based on sound pulses can be used to measure the depth of the sea, and a system based on laser pulses can measure the distance to objects in space, because it is. Les married his wife Ann in They have a daughter, Stephanie, and a son, Adrian.

    His previous books are listed below. Metal fatigue. Oxford: Clarendon Press, ISBN 0 19 8. Reprinted with minor corrections. ISBN Pook L P. The role of crack growth in metal fatigue. London: Metals Society, ISBN 0 63 5. Linear elastic fracture mechanics for engineers. Theory and applications.

    Southampton: WIT Press, ISBN 1 Flexagons inside out. Cambridge: Cambridge University Press,