1.
Deformation (mechanics)
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Deformation in continuum mechanics is the transformation of a body from a reference configuration to a current configuration. A configuration is a set containing the positions of all particles of the body, a deformation may be caused by external loads, body forces, or changes in temperature, moisture content, or chemical reactions, etc. Strain is a description of deformation in terms of displacement of particles in the body that excludes rigid-body motions. In a continuous body, a deformation field results from a field induced by applied forces or is due to changes in the temperature field inside the body. The relation between stresses and induced strains is expressed by constitutive equations, e. g. Hookes law for linear elastic materials, deformations which are recovered after the stress field has been removed are called elastic deformations. In this case, the continuum completely recovers its original configuration, on the other hand, irreversible deformations remain even after stresses have been removed. Another type of deformation is viscous deformation, which is the irreversible part of viscoelastic deformation. In the case of elastic deformations, the response function linking strain to the stress is the compliance tensor of the material. Strain is a measure of deformation representing the displacement between particles in the relative to a reference length. A general deformation of a body can be expressed in the form x = F where X is the position of material points in the body. Such a measure does not distinguish between rigid body motions and changes in shape of the body, a deformation has units of length. We could, for example, define strain to be ε ≐ ∂ ∂ X = F ′ − I, hence strains are dimensionless and are usually expressed as a decimal fraction, a percentage or in parts-per notation. Strains measure how much a given deformation differs locally from a rigid-body deformation, a strain is in general a tensor quantity. Physical insight into strains can be gained by observing that a given strain can be decomposed into normal and this could be applied by elongation, shortening, or volume changes, or angular distortion. However, it is sufficient to know the normal and shear components of strain on a set of three perpendicular directions. In this case, the undeformed and deformed configurations of the continuum are significantly different and this is commonly the case with elastomers, plastically-deforming materials and other fluids and biological soft tissue. Infinitesimal strain theory, also called small strain theory, small deformation theory, small displacement theory, in this case, the undeformed and deformed configurations of the body can be assumed identical. Large-displacement or large-rotation theory, which assumes small strains but large rotations, in each of these theories the strain is then defined differently
2.
Insulator (electricity)
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An electrical insulator is a material whose internal electric charges do not flow freely, very little electric current will flow through it under the influence of an electric field. This contrasts with other materials, semiconductors and conductors, which conduct electric current more easily, the property that distinguishes an insulator is its resistivity, insulators have higher resistivity than semiconductors or conductors. A perfect insulator does not exist, because even insulators contain small numbers of mobile charges which can carry current, in addition, all insulators become electrically conductive when a sufficiently large voltage is applied that the electric field tears electrons away from the atoms. This is known as the voltage of an insulator. Some materials such as glass, paper and Teflon, which have high resistivity, are good electrical insulators. Examples include rubber-like polymers and most plastics which can be thermoset or thermoplastic in nature, insulators are used in electrical equipment to support and separate electrical conductors without allowing current through themselves. An insulating material used in bulk to wrap electrical cables or other equipment is called insulation, the term insulator is also used more specifically to refer to insulating supports used to attach electric power distribution or transmission lines to utility poles and transmission towers. They support the weight of the suspended wires without allowing the current to flow through the tower to ground, electrical insulation is the absence of electrical conduction. Electronic band theory says that a charge flows if states are available into which electrons can be excited and this allows electrons to gain energy and thereby move through a conductor such as a metal. If no such states are available, the material is an insulator, most insulators have a large band gap. This occurs because the valence band containing the highest energy electrons is full, there is always some voltage that gives electrons enough energy to be excited into this band. Once this voltage is exceeded the material ceases being an insulator, however, it is usually accompanied by physical or chemical changes that permanently degrade the materials insulating properties. Materials that lack electron conduction are insulators if they lack other mobile charges as well, for example, if a liquid or gas contains ions, then the ions can be made to flow as an electric current, and the material is a conductor. Electrolytes and plasmas contain ions and act as conductors whether or not electron flow is involved, when subjected to a high enough voltage, insulators suffer from the phenomenon of electrical breakdown. These freed electrons and ions are in turn accelerated and strike other atoms, creating more charge carriers, rapidly the insulator becomes filled with mobile charge carriers, and its resistance drops to a low level. In a solid, the voltage is proportional to the band gap energy. The air in a region around a conductor can break down and ionise without a catastrophic increase in current. Even a vacuum can suffer a sort of breakdown, but in case the breakdown or vacuum arc involves charges ejected from the surface of metal electrodes rather than produced by the vacuum itself
3.
Cyanoacrylate
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Cyanoacrylates are a family of strong fast-acting adhesives with industrial, medical, and household uses. Cyanoacrylate adhesives have a shelf life if not used, about one year from manufacture if unopened. Cyanoacrylates include methyl 2-cyanoacrylate, ethyl-2-cyanoacrylate, n-butyl cyanoacrylate and 2-octyl cyanoacrylate, Octyl cyanoacrylate was developed to address toxicity concerns and to reduce skin irritation and allergic response. Cyanoacrylate adhesives are sometimes known generically as instant glues, power glues or superglues, the abbreviation CA is commonly used for industrial grades. The original patent for cyanoacrylate was filed in 1942 by Goodrich Company, as an outgrowth of a search for materials suitable for clear plastic gun sights for the war effort. In 1942, a team of scientists headed by Harry Coover Jr. stumbled upon a formulation that stuck to everything with which it came in contact. The team quickly rejected the substance for the application, but in 1951, while working as researchers for Eastman Kodak, Coover. The two realized the commercial potential, and a form of the adhesive was first sold in 1958 under the title Eastman #910. During the 1960s, Eastman Kodak sold cyanoacrylate to Loctite, which in turn repackaged and distributed it under a different brand name Loctite Quick Set 404, in 1971 Loctite developed its own manufacturing technology and introduced its own line of cyanoacrylate, called Super Bonder. Loctite quickly gained market share, and by the late 1970s it was believed to have exceeded Eastman Kodaks share in the North American industrial cyanoacrylate market, National Starch and Chemical Company purchased Eastman Kodak’s cyanoacrylate business and combined it with several acquisitions made throughout the 1970s forming Permabond. Other manufacturers of cyanoacrylate include LePage, the Permabond Division of National Starch and Chemical, together, Loctite, Eastman and Permabond accounted for approximately 75% of the industrial cyanoacrylate market. As of 2013 Permabond continued to manufacture the original 910 formula, in its liquid form, cyanoacrylate consists of monomers of cyanoacrylate molecules. Methyl-2-cyanoacrylate has a weight equal to 111.1, a flashpoint of 79 °C. Ethyl 2-cyanoacrylate has a weight equal to 125 and a flashpoint of >75 °C. To facilitate easy handling, an adhesive is frequently formulated with an ingredient such as fumed silica to make it more viscous or gel-like. More recently, formulations are available with additives to increase shear strength, such additives may include rubber, as in Loctites Ultra Gel, or others which are not specified. In general, cyanoacrylate is a resin that rapidly polymerises in the presence of water, forming long, strong chains. Because the presence of moisture causes the glue to set, exposure to normal levels of humidity in the air causes a thin skin to start to form within seconds, because of this cyanoacrylate is applied thinly, to ensure that the reaction proceeds rapidly for bonding
4.
Wheatstone bridge
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A Wheatstone bridge is an electrical circuit used to measure an unknown electrical resistance by balancing two legs of a bridge circuit, one leg of which includes the unknown component. The primary benefit of a bridge is its ability to provide extremely accurate measurements. Its operation is similar to the original potentiometer, the Wheatstone bridge was invented by Samuel Hunter Christie in 1833 and improved and popularized by Sir Charles Wheatstone in 1843. One of the Wheatstone bridges initial uses was for the purpose of soils analysis, in the figure, R x is the unknown resistance to be measured, R1, R2, and R3 are resistors of known resistance and the resistance of R2 is adjustable. If the bridge is unbalanced, the direction of the current indicates whether R2 is too high or too low, R2 is varied until there is no current through the galvanometer, which then reads zero. Detecting zero current with a galvanometer can be done to extremely high accuracy, therefore, if R1, R2, and R3 are known to high precision, then R x can be measured to high precision. Very small changes in R x disrupt the balance and are readily detected and this setup is frequently used in strain gauge and resistance thermometer measurements, as it is usually faster to read a voltage level off a meter than to adjust a resistance to zero the voltage. The equation for this is, V G = V s where VG is the voltage of node D relative to node B, the Wheatstone bridge illustrates the concept of a difference measurement, which can be extremely accurate. Variations on the Wheatstone bridge can be used to measure capacitance, inductance, impedance and other quantities, such as the amount of gases in a sample. The Kelvin bridge was adapted from the Wheatstone bridge for measuring very low resistances. The concept was extended to alternating current measurements by James Clerk Maxwell in 1865, the Wheatstone bridge is the fundamental bridge, but there are other modifications that can be made to measure various kinds of resistances when the fundamental Wheatstone bridge is not suitable. Some of the modifications are, Carey Foster bridge, for measuring small resistances Kelvin bridge, for measuring small four-terminal resistances Maxwell bridge, Wheatstone Bridge – Interactive Tutorial National High Magnetic Field Laboratory Test Set I-49
5.
Electrical resistance and conductance
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The electrical resistance of an electrical conductor is a measure of the difficulty to pass an electric current through that conductor. The inverse quantity is electrical conductance, and is the ease with which a current passes. Electrical resistance shares some parallels with the notion of mechanical friction. The SI unit of resistance is the ohm, while electrical conductance is measured in siemens. An object of uniform cross section has a proportional to its resistivity and length. All materials show some resistance, except for superconductors, which have a resistance of zero and this proportionality is called Ohms law, and materials that satisfy it are called ohmic materials. In other cases, such as a diode or battery, V and I are not directly proportional. The ratio V/I is sometimes useful, and is referred to as a chordal resistance or static resistance, since it corresponds to the inverse slope of a chord between the origin and an I–V curve. In other situations, the derivative d V d I may be most useful, in the hydraulic analogy, current flowing through a wire is like water flowing through a pipe, and the voltage drop across the wire is like the pressure drop that pushes water through the pipe. Conductance is proportional to how much flow occurs for a given pressure, the voltage drop, not the voltage itself, provides the driving force pushing current through a resistor. In hydraulics, it is similar, The pressure difference between two sides of a pipe, not the pressure itself, determines the flow through it, for example, there may be a large water pressure above the pipe, which tries to push water down through the pipe. But there may be a large water pressure below the pipe. If these pressures are equal, no water flows, in the same way, a long, thin copper wire has higher resistance than a short, thick copper wire. A pipe filled with hair restricts the flow of more than a clean pipe of the same shape. The difference between copper, steel, and rubber is related to their structure and electron configuration. In addition to geometry and material, there are other factors that influence resistance and conductance, such as temperature. Substances in which electricity can flow are called conductors, a piece of conducting material of a particular resistance meant for use in a circuit is called a resistor. Conductors are made of high-conductivity materials such as metals, in particular copper, Resistors, on the other hand, are made of a wide variety of materials depending on factors such as the desired resistance, amount of energy that it needs to dissipate, precision, and costs
6.
Electrical conductor
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In physics and electrical engineering, a conductor is an object or type of material that allows the flow of an electrical current in one or more directions. Materials made of metal are common electrical conductors, Electrical current is generated by the flow of negatively charged electrons, positively charged holes, and positive or negative ions in some cases. In order for current to flow, it is not necessary for one charged particle to travel from the producing the current to that consuming it. Instead, the particle simply needs to nudge its neighbor a finite amount who will nudge its neighbor and on and on until a particle is nudged into the consumer. Essentially what is occurring here is a chain of momentum transfer between mobile charge carriers, the Drude model of conduction describes this process more rigorously. Insulators are non-conducting materials with few mobile charges that support only insignificant electric currents, the resistance of a given conductor depends on the material it is made of, and on its dimensions. For a given material, the resistance is proportional to the cross-sectional area. For example, a copper wire has lower resistance than an otherwise-identical thin copper wire. Also, for a material, the resistance is proportional to the length, for example. The resistance R and conductance G of a conductor of uniform cross section, therefore, the resistivity and conductivity are proportionality constants, and therefore depend only on the material the wire is made of, not the geometry of the wire. Resistivity and conductivity are reciprocals, ρ =1 / σ, resistivity is a measure of the materials ability to oppose electric current. This formula is not exact, It assumes the current density is uniform in the conductor. However, this still provides a good approximation for long thin conductors such as wires. Another situation this formula is not exact for is with alternating current, then, the geometrical cross-section is different from the effective cross-section in which current actually flows, so the resistance is higher than expected. Similarly, if two conductors are each other carrying AC current, their resistances increase due to the proximity effect. Aside from the geometry of the wire, temperature also has a significant effect on the efficacy of conductors, temperature affects conductors in two main ways, the first is that materials may expand under the application of heat. The amount that the material will expand is governed by the expansion coefficient specific to the material. Such an expansion will change the geometry of the conductor and therefore its characteristic resistance, however, this effect is generally small, on the order of 10−6
7.
Elasticity (physics)
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In physics, elasticity is the ability of a body to resist a distorting influence or deforming force and to return to its original size and shape when that influence or force is removed. Solid objects will deform when adequate forces are applied on them, if the material is elastic, the object will return to its initial shape and size when these forces are removed. The physical reasons for elastic behavior can be different for different materials. In metals, the atomic lattice changes size and shape when forces are applied, when forces are removed, the lattice goes back to the original lower energy state. For rubbers and other polymers, elasticity is caused by the stretching of polymer chains when forces are applied, perfect elasticity is an approximation of the real world. The most elastic body in modern science found is Quartz fibre which is not even a perfect elastic body, so perfect elastic body is an ideal concept only. Most materials which possess elasticity in practice remain purely elastic only up to very small deformations. In engineering, the amount of elasticity of a material is determined by two types of material parameter, the first type of material parameter is called a modulus, which measures the amount of force per unit area needed to achieve a given amount of deformation. The SI unit of modulus is the pascal, a higher modulus typically indicates that the material is harder to deform. The second type of measures the elastic limit, the maximum stress that can arise in a material before the onset of permanent deformation. Its SI unit is also pascal, when describing the relative elasticities of two materials, both the modulus and the elastic limit have to be considered. Rubbers typically have a low modulus and tend to stretch a lot, of two rubber materials with the same elastic limit, the one with a lower modulus will appear to be more elastic, which is however not correct. When an elastic material is deformed due to a force, it experiences internal resistance to the deformation. The various moduli apply to different kinds of deformation, for instance, Youngs modulus applies to extension/compression of a body, whereas the shear modulus applies to its shear. The elasticity of materials is described by a curve, which shows the relation between stress and strain. The curve is nonlinear, but it can be approximated as linear for sufficiently small deformations. For even higher stresses, materials exhibit behavior, that is, they deform irreversibly. Elasticity is not exhibited only by solids, non-Newtonian fluids, such as viscoelastic fluids, in response to a small, rapidly applied and removed strain, these fluids may deform and then return to their original shape. Under larger strains, or strains applied for longer periods of time, because the elasticity of a material is described in terms of a stress-strain relation, it is essential that the terms stress and strain be defined without ambiguity
8.
Stress (physics)
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For example, when a solid vertical bar is supporting a weight, each particle in the bar pushes on the particles immediately below it. When a liquid is in a container under pressure, each particle gets pushed against by all the surrounding particles. The container walls and the pressure-inducing surface push against them in reaction and these macroscopic forces are actually the net result of a very large number of intermolecular forces and collisions between the particles in those molecules. Strain inside a material may arise by various mechanisms, such as stress as applied by external forces to the material or to its surface. Any strain of a material generates an internal elastic stress, analogous to the reaction force of a spring. In liquids and gases, only deformations that change the volume generate persistent elastic stress, however, if the deformation is gradually changing with time, even in fluids there will usually be some viscous stress, opposing that change. Elastic and viscous stresses are usually combined under the mechanical stress. Significant stress may exist even when deformation is negligible or non-existent, stress may exist in the absence of external forces, such built-in stress is important, for example, in prestressed concrete and tempered glass. Stress may also be imposed on a material without the application of net forces, for example by changes in temperature or chemical composition, stress that exceeds certain strength limits of the material will result in permanent deformation or even change its crystal structure and chemical composition. In some branches of engineering, the stress is occasionally used in a looser sense as a synonym of internal force. For example, in the analysis of trusses, it may refer to the total traction or compression force acting on a beam, since ancient times humans have been consciously aware of stress inside materials. Until the 17th century the understanding of stress was largely intuitive and empirical, with those tools, Augustin-Louis Cauchy was able to give the first rigorous and general mathematical model for stress in a homogeneous medium. Cauchy observed that the force across a surface was a linear function of its normal vector, and, moreover. The understanding of stress in liquids started with Newton, who provided a formula for friction forces in parallel laminar flow. Stress is defined as the force across a small boundary per unit area of that boundary, following the basic premises of continuum mechanics, stress is a macroscopic concept. In a fluid at rest the force is perpendicular to the surface, in a solid, or in a flow of viscous liquid, the force F may not be perpendicular to S, hence the stress across a surface must be regarded a vector quantity, not a scalar. Moreover, the direction and magnitude depend on the orientation of S. Thus the stress state of the material must be described by a tensor, called the stress tensor, with respect to any chosen coordinate system, the Cauchy stress tensor can be represented as a symmetric matrix of 3×3 real numbers
9.
Adhesive
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The use of adhesives offers many advantages over binding techniques such as sewing, mechanical fastening, thermal bonding, etc. Adhesives are typically organized by the method of adhesion and these are then organized into reactive and non-reactive adhesives, which refers to whether the adhesive chemically reacts in order to harden. Alternatively they can be organized by whether the raw stock is of natural or synthetic origin, Adhesives may be found naturally or produced synthetically. The earliest human use of substances was approximately 200,000 years ago. The first references to adhesives in literature first appeared in approximately 2000 BCE, the Greeks and Romans made great contributions to the development of adhesives. In Europe, glue was not widely used until the period 1500–1700 CE, from then until the 1900s increases in adhesive use and discovery were relatively gradual. Only since the last century has the development of synthetic adhesives accelerated rapidly, the earliest use of adhesives was discovered in central Italy when two stone flakes partially covered with birch-bark tar and a third uncovered stone from the Middle Pleistocene era were found. This is thought to be the oldest discovered human use of tar-hafted stones, the birch-bark-tar adhesive is a simple, one-component adhesive. Although sticky enough, plant-based adhesives are brittle and vulnerable to environmental conditions, the first use of compound adhesives was discovered in Sibudu, South Africa. The ability to produce stronger adhesives allowed middle stone age humans to attach stone segments to sticks in greater variations, more recent examples of adhesive use by prehistoric humans have been found at the burial sites of ancient tribes. Archaeologists studying the sites found that approximately 6,000 years ago the tribesmen had buried their dead together with food found in clay pots repaired with tree resins. The glue was analyzed as pitch, which requires the heating of tar during its production, the retrieval of this tar requires a transformation of birch bark by means of heat, in a process known as pyrolysis. The first references to adhesives in literature first appeared in approximately 2000 BCE, further historical records of adhesive use are found from the period spanning 1500–1000 BCE. Artifacts from this period include paintings depicting wood gluing operations and a made of wood. Other ancient Egyptian artifacts employ animal glue for bonding or lamination, such lamination of wood for bows and furniture is thought to have extended their life and was accomplished using casein -based glues. The ancient Egyptians also developed starch-based pastes for the bonding of papyrus to clothing, from 1 to 500 AD the Greeks and Romans made great contributions to the development of adhesives. Wood veneering and marquetry were developed, the production of animal and fish glues refined, egg-based pastes were used to bond gold leaves incorporated various natural ingredients such as blood, bone, hide, milk, cheese, vegetables, and grains. The Greeks began the use of slaked lime as mortar while the Romans furthered mortar development by mixing lime with volcanic ash and this material, known as pozzolanic cement, was used in the construction of the Roman Colosseum and Pantheon
10.
Beam (structure)
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A beam is a structural element that primarily resists loads applied laterally to the beams axis. Its mode of deflection is primarily by bending, the loads applied to the beam result in reaction forces at the beams support points. The total effect of all the acting on the beam is to produce shear forces and bending moments within the beam. Beams are characterized by their manner of support, profile, length, historically beams were squared timbers but are also metal, stone, or combinations of wood and metal such as a flitch beam. Beams generally carry vertical gravitational forces but can also be used to carry horizontal loads, the loads carried by a beam are transferred to columns, walls, or girders, which then transfer the force to adjacent structural compression members. In light frame construction joists may rest on beams, in carpentry a beam is called a plate as in a sill plate or wall plate, beam as in a summer beam or dragon beam. In engineering, beams are of types, Simply supported - a beam supported on the ends which are free to rotate and have no moment resistance. Fixed - a beam supported on both ends and restrained from rotation, over hanging - a simple beam extending beyond its support on one end. Double overhanging - a simple beam with both ends extending beyond its supports on both ends, continuous - a beam extending over more than two supports. Cantilever - a projecting beam fixed only at one end, trussed - a beam strengthened by adding a cable or rod to form a truss. In the beam equation I is used to represent the moment of area. It is commonly known as the moment of inertia, and is the sum, about the axis, of dA*r^2, where r is the distance from the neutral axis. Therefore, it not just how much area the beam section has overall. The greater I is, the stiffer the beam in bending, internally, beams experience compressive, tensile and shear stresses as a result of the loads applied to them. Above the supports, the beam is exposed to shear stress, there are some reinforced concrete beams in which the concrete is entirely in compression with tensile forces taken by steel tendons. These beams are known as prestressed concrete beams, and are fabricated to produce a more than the expected tension under loading conditions. High strength steel tendons are stretched while the beam is cast over them, then, when the concrete has cured, the tendons are slowly released and the beam is immediately under eccentric axial loads. This eccentric loading creates a moment, and, in turn
11.
Pressure sensor
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These types of sensors are also known as a pressure switch. Pressure sensors can be classified in terms of pressure ranges they measure, temperature ranges of operation, Pressure sensors are variously named according to their purpose, but the same technology may be used under different names. Absolute pressure sensor This sensor measures the relative to perfect vacuum. Gauge pressure sensor This sensor measures the relative to atmospheric pressure. A tire pressure gauge is an example of pressure measurement. Vacuum pressure sensor This term can cause confusion, differential pressure sensor This sensor measures the difference between two pressures, one connected to each side of the sensor. Differential pressure sensors are used to measure many properties, such as pressure drops across oil filters or air filters, sealed pressure sensor This sensor is similar to a gauge pressure sensor except that it measures pressure relative to some fixed pressure rather than the ambient atmospheric pressure. Piezoresistive strain gauge Uses the piezoresistive effect of bonded or formed strain gauges to detect due to applied pressure. Common technology types are Silicon, Polysilicon Thin Film, Bonded Metal Foil, Thick Film, generally, the strain gauges are connected to form a Wheatstone bridge circuit to maximize the output of the sensor and to reduce sensitivity to errors. This is the most commonly employed sensing technology for general purpose pressure measurement, capacitive Uses a diaphragm and pressure cavity to create a variable capacitor to detect strain due to applied pressure, capacitance decreasing as pressure deforms the diaphragm. Common technologies use metal, ceramic, and silicon diaphragms, electromagnetic Measures the displacement of a diaphragm by means of changes in inductance, LVDT, Hall Effect, or by eddy current principle. Piezoelectric Uses the piezoelectric effect in materials such as quartz to measure the strain upon the sensing mechanism due to pressure. This technology is employed for the measurement of highly dynamic pressures. Optical Techniques include the use of the change of an optical fiber to detect strain due to applied pressure. A common example of this type utilizes Fiber Bragg Gratings, another analogous technique utilizes an elastic film constructed in layers that can change reflected wavelengths according to the applied pressure. Potentiometric Uses the motion of a wiper along a resistive mechanism to detect the strain caused by applied pressure, other types These types of electronic pressure sensors use other properties to infer pressure of a gas, or liquid. Resonant Uses the changes in resonant frequency in a mechanism to measure stress, or changes in gas density. This technology may be used in conjunction with a force collector, alternatively, resonant technology may be employed by exposing the resonating element itself to the media, whereby the resonant frequency is dependent upon the density of the media
12.
Murphy's law
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Murphys law is an adage or epigram that is typically stated as, Anything that can go wrong, will go wrong. The perceived perversity of the universe has long been a subject of comment, the concept may be as old as humanity. Recent significant research in this area has been conducted by members of the American Dialect Society, Society member Stephen Goranson has found a version of the law, not yet generalized or bearing that name, in a report by Alfred Holt at an 1877 meeting of an engineering society. It is found that anything that can go wrong at sea generally does go wrong sooner or later, sufficient stress can hardly be laid on the advantages of simplicity. The human factor cannot be neglected in planning machinery. If attention is to be obtained, the engine must be such that the engineer will be disposed to attend to it, in later publications whatever can happen will happen occasionally is termed Murphys law, which raises the possibility—if something went wrong—that Murphy is De Morgan misremembered. American Dialect Society member Bill Mullins has found a slightly broader version of the aphorism in reference to stage magic. Whether we must attribute this to the malignity of matter or to the depravity of inanimate things, whether the exciting cause is hurry, worry, or what not. Anne Roes papers are in the American Philosophical Society archives in Philadelphia, robertsons papers are at the Caltech archives, there, in a letter Robertson offers Roe an interview within the first three months of 1949. The Robertson interview apparently predated the Muroc scenario said by Nick Spark to have occurred in or after June,1949, the name Murphys law was not immediately secure. Atomic Energy Commission Chairman Lewis Strauss was quoted in the Chicago Daily Tribune on February 12,1955 and it could be stated about like this, If anything bad can happen, it probably will. An excerpt from the reads, The laws namesake was Capt. Ed Murphy, a development engineer from Wright Field Aircraft Lab, I assigned Murphys law to the statement and the associated variations. Dawkins points out that a class of events may occur all the time. He gives as an example aircraft noise interfering with filming, Aircraft are in the sky all the time, but are only taken note of when they cause a problem. This is a form of confirmation bias whereby the investigator seeks out evidence to confirm his already formed ideas, selection bias will ensure that those ones are remembered and the many times Murphys law was not true are forgotten. There have been persistent references to Murphys law associating it with the laws of thermodynamics from early on, in particular, Murphys law is often cited as a form of the second law of thermodynamics because both are predicting a tendency to a more disorganised state. Atanu Chatterjee investigated this idea by formally stating Murphys law in mathematical terms, Chatterjee found that Murphys law so stated could be disproved using the principle of least action
13.
Kelvin connection
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Four-terminal sensing is used in some ohmmeters and impedance analyzers, and in wiring for strain gauges and resistance thermometers. Four-point probes are used to measure sheet resistance of thin films. Separation of current and voltage electrodes eliminates the lead and contact resistance from the measurement and this is an advantage for precise measurement of low resistance values. For example, an LCR bridge instruction manual recommends the four-terminal technique for accurate measurement of resistance below 100 ohms. Four-terminal sensing is also known as Kelvin sensing, after William Thomson, Lord Kelvin, each two-wire connection can be called a Kelvin connection. A pair of contacts that is designed to connect a pair to a single terminal or lead simultaneously is called a Kelvin contact. A clip, often a crocodile clip, that connects a force-and-sense pair is called a Kelvin clip, when a Kelvin connection is used, current is supplied via a pair of source connections. These generate a voltage drop across the impedance to be measured according to Ohms law V=IR, a pair of sense connections are made immediately adjacent to the target impedance, so that they do not include the voltage drop in the force leads or contacts. Since almost no current flows to the instrument, the voltage drop in the sense leads is negligible. It is usual to arrange the sense wires as the inside pair, if the force and sense connections are exchanged, accuracy can be affected, because more of the lead resistance is included in the measurement. The force wires may have to carry a current when measuring very small resistances, and must be of adequate gauge. The technique is used in low-voltage power supplies, where it is called remote sensing. It is common to provide 4-wire connections to current-sensing shunt resistors of low resistance operating at high current, a variant uses three wires, with separate load and sense leads at one end, and a common wire on the other. Voltage drop in the wire is compensated for by assuming that it is the same as in the load wire, of the same gauge. This technique is used in resistance thermometers, also known as resistance temperature detectors or RTDs. Another example is in the ATX power supply standard, which includes a sense wire connected to the 3.3 V supply line at connector pin 13. Electrode array DC Metering Circuits chapter from Lessons In Electric Circuits Vol 1 DC free ebook,4 wire resistance measurement tutorial video Four-Point Techniques for Measuring Electrical Conductivity and Resistivity
14.
Non-Intrusive Stress Measurement System
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Non-Intrusive Stress Measurement is a method for determining dynamic blade stresses in rotating turbomachinery. NSMS is also known by the names Blade Tip Timing, Arrival Time Analysis, Blade Vibration Monitoring Beruehrungslose Schaufel Schwingungsmessung, NSMS uses externally mounted sensors to determine the passing times of turbomachinery blades. The passing times after conversion to deflections, can be used to measure each blade’s vibratory response characteristics such as amplitude/stress, phase, frequency, since every blade is measured, stage effects such as flutter, blade mistuning, and nodal diameter can also be characterized. The measurement method has been used successfully in all stages of the gas turbine engine, the ability to apply the technology to a given situation is dependent upon a sensor type that can meet the environmental requirements. A set of sensors is used to measure the times of rotating blades. These arrival times, in comparison to a baseline, are used to determine blade deflections, the blade deflections over a number of revolutions and/or across a number of sensors can be used to determine vibratory characteristics. This information, in conjunction with a Finite Element Model, can then be used to determine the stresses in a rotating part. Any sensor or probe that can provide an indication of a blade’s passing can be used in an NSMS System. Commonly optical probes using fiber optics are used to obtain a level of spatial resolution. A light source, typically a laser, and fiber optics are used to direct a constant beam of light into the path of a rotating blade. As a blade passes the probe, light is reflected and captured by fiber optic, field type sensors such as Eddy Current, Capacitive, and Microwave sensors are useful in harsh environments and for long duration testing. NSMS technology was patented as early as 1949, with improvements patented since that date. Some recent US practitioners believe that NSMS was first developed in 1980 and it may be envisioned as a replacement technology to rotating strain gauges, however it is currently used as an essential complement to strain gauges. The technology is used for turbo-machinery development and high cycle fatigue troubleshooting. Due to the direct observation, external mounting and inherent serviceability of the sensors. More recently, multiple practitioners are becoming active in this application of the technology
15.
Semiconductor
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Semiconductors are crystalline or amorphous solids with distinct electrical characteristics. They are of high electrical resistance — higher than typical resistance materials and their resistance decreases as their temperature increases, which is behavior opposite to that of a metal. The behavior of charge carriers which include electrons, ions and electron holes at these junctions is the basis of diodes, transistors and all modern electronics. Semiconductor devices can display a range of properties such as passing current more easily in one direction than the other, showing variable resistance. The modern understanding of the properties of a semiconductor relies on quantum physics to explain the movement of carriers in a crystal lattice. Doping greatly increases the number of carriers within the crystal. When a doped semiconductor contains mostly free holes it is called p-type, the semiconductor materials used in electronic devices are doped under precise conditions to control the concentration and regions of p- and n-type dopants. A single semiconductor crystal can have many p- and n-type regions, although some pure elements and many compounds display semiconductor properties, silicon, germanium, and compounds of gallium are the most widely used in electronic devices. Elements near the so-called metalloid staircase, where the metalloids are located on the table, are usually used as semiconductors. Some of the properties of materials were observed throughout the mid 19th. The first practical application of semiconductors in electronics was the 1904 development of the Cats-whisker detector, developments in quantum physics in turn allowed the development of the transistor in 1947 and the integrated circuit in 1958. There are several developed techniques that allow semiconducting materials to behave like conducting materials and these modifications have two outcomes, n-type and p-type. These refer to the excess or shortage of electrons, respectively, an unbalanced number of electrons would cause a current to flow through the material. Heterojunctions Heterojunctions occur when two differently doped semiconducting materials are joined together, for example, a configuration could consist of p-doped and n-doped germanium. This results in an exchange of electrons and holes between the differently doped semiconducting materials, the n-doped germanium would have an excess of electrons, and the p-doped germanium would have an excess of holes. The transfer occurs until equilibrium is reached by a process called recombination, a product of this process is charged ions, which result in an electric field. Excited Electrons A difference in electric potential on a material would cause it to leave thermal equilibrium. This introduces electrons and holes to the system, which interact via a process called ambipolar diffusion, whenever thermal equilibrium is disturbed in a semiconducting material, the amount of holes and electrons changes
16.
Piezoresistive effect
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The piezoresistive effect is a change in the electrical resistivity of a semiconductor or metal when mechanical strain is applied. In contrast to the effect, the piezoresistive effect causes a change only in electrical resistance. The change of resistance in metal devices due to an applied mechanical load was first discovered in 1856 by Lord Kelvin. With single crystal silicon becoming the material of choice for the design of analog and digital circuits, in conducting and semi-conducting materials, changes in inter-atomic spacing resulting from strain affect the bandgaps, making it easier for electrons to be raised into the conduction band. This results in a change in resistivity of the material, within a certain range of strain this relationship is linear, so that the piezoresistive coefficient ρ σ = ε where ∂ρ = Change in resistivity ρ = Original resistivity ε = Strain is constant. Usually the resistance change in metals is due to the change of geometry resulting from applied mechanical stress. However, even though the effect is small in those cases it is often not negligible. Pure nickels piezoresistivity is -13 times larger, completely dwarfing and even reversing the sign of the resistance change. Hence, semiconductor strain gauges with a high coefficient of sensitivity can be built. For precision measurements they are difficult to handle than metal strain gauges. For silicon, gauge factors can be two orders of magnitudes larger than observed in most metals. The resistance of n-conducting silicon mainly changes due to a shift of the three different conducting valley pairs, the shifting causes a redistribution of the carriers between valleys with different mobilities. This results in varying mobilities dependent on the direction of current flow, a minor effect is due to the effective mass change related to changing shapes of the valleys. In p-conducting silicon the phenomena are more complex and also result in mass changes, since silicon is today the material of choice for integrated digital and analog circuits the use of piezoresistive silicon devices has been of great interest. It enables the integration of stress sensors with Bipolar and CMOS circuits. This has enabled a range of products using the piezoresistive effect. Many commercial devices such as sensors and acceleration sensors employ the piezoresistive effect in silicon. But due to its magnitude the piezoresistive effect in silicon has also attracted the attention of research, Semiconductor Hall sensors, for example, were capable of achieving their current precision only after employing methods which eliminate signal contributions due the applied mechanical stress
17.
Colloidal gold
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Colloidal gold is a sol or colloidal suspension of nanoparticles of gold in a fluid, usually water. The liquid is usually either a red colour or blue/purple. The properties of gold nanoparticles, and thus their applications, depend strongly upon their size. For example, rodlike particles have both transverse and longitudinal absorption peak, and anisotropy of the shape affects their self-assembly. Known, or at least used since ancient times, the synthesis of gold was crucial to the 4th-century Lycurgus Cup. Later it was used as a method of staining glass, during the Middle Ages, soluble gold, a solution containing gold salt, had a reputation for its curative property for various diseases. In 1618, Francis Anthony, a philosopher and member of the profession, published a book called Panacea Aurea. The book introduces information on the formation of gold and its medical uses. About half a century later, English botanist Nicholas Culpepper published book in 1656, Treatise of Aurum Potabile, in 1676, Johann Kunckel, a German chemist, published a book on the manufacture of stained glass. In 1842, John Herschel invented a process called chrysotype that used colloidal gold to record images on paper. Modern scientific evaluation of colloidal gold did not begin until Michael Faradays work in the 1850s, in 1856, in a basement laboratory of Royal Institution, Faraday accidentally created a ruby red solution while mounting pieces of gold leaf onto microscope slides. Since he was interested in the properties of light and matter. He prepared the first pure sample of gold, which he called activated gold. He used phosphorus to reduce a solution of gold chloride, the colloidal gold Faraday made 150 years ago is still optically active. For a long time, the composition of the gold was unclear. Several chemists suspected it to be a tin compound, due to its preparation. Faraday recognized that the color was due to the miniature size of the gold particles. He noted the light scattering properties of suspended gold microparticles, which is now called Faraday-Tyndall effect, in 1898, Richard Adolf Zsigmondy prepared the first colloidal gold in diluted solution
18.
Carbon black
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Carbon black is a material produced by the incomplete combustion of heavy petroleum products such as FCC tar, coal tar, ethylene cracking tar, and a small amount from vegetable oil. Carbon black is a form of carbon that has a high surface-area-to-volume ratio. It is dissimilar to soot in its much higher surface-area-to-volume ratio, however, carbon black is widely used as a model compound for diesel soot for diesel oxidation experiments. Carbon black is used as a reinforcing filler in tires. In plastics, paints, and inks carbon black is used as a color pigment, the current International Agency for Research on Cancer evaluation is that, Carbon black is possibly carcinogenic to humans. Short-term exposure to concentrations of carbon black dust may produce discomfort to the upper respiratory tract. Total production was around 8,100,000 metric tons in 2006, the most common use of carbon black is as a pigment and reinforcing phase in automobile tires. Carbon black also helps conduct heat away from the tread and belt area of the tire, reducing thermal damage, the high tinting strength and stability of carbon black has also provided use in coloring of resins and films. About 20% of world production goes into belts, hoses, the balance is mainly used as a pigment in inks, coatings and plastics. For example, it is added to polypropylene because it absorbs ultraviolet radiation, Carbon black from vegetable origin is used as a food coloring, in Europe known as additive E153. It is approved for use as additive 153 in Australia and New Zealand but has been banned in the US, Carbon black has been used in various applications for electronics. As a good conductor of electricity, carbon black is used as a mixed in plastics, elastomer, films, adhesives. Application of carbon black as an agent has provided uses as an additive for fuel caps. Additionally, the color pigment carbon black has been used in food. It is used in multi-layer UHT milk bottles in the US, parts of Europe and Asia, and South Africa, the Canadian Government’s assessment in 2011 concluded that carbon black should continue to be used in products – including food packaging for consumers – in Canada. The highest volume use of black is as a reinforcing filler in rubber products. It is used often in the Aerospace industry in elastomers for aircraft vibration control components such as engine mounts, practically all rubber products where tensile and abrasion wear properties are crucial use carbon black, so they are black in color. Traditionally silica fillers had worse abrasion wear properties, but the technology has improved to a point where they can match carbon black abrasion performance
19.
Hemodynamics
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Hemodynamics or hæmodynamics is the dynamics of blood flow. The circulatory system is controlled by mechanisms, much as hydraulic circuits are controlled by control systems. Hemodynamic response continuously monitors and adjusts to conditions in the body, thus hemodynamics explains the physical laws that govern the flow of blood in the blood vessels. Blood is a fluid, best studied using rheology rather than hydrodynamics. Blood vessels are not rigid tubes, so classic hydrodynamics and fluids mechanics based on the use of classical viscometers are not capable of explaining hemodynamics, Blood is composed of plasma and formed elements. The plasma contains 91. 5% water, 7% proteins and 1. 5% other solutes, normal blood plasma behaves like a Newtonian fluid at physiological rates of shear. Typical values for the viscosity of human plasma at 37 °C is 1.4 mN·s/m2. The osmotic pressure of solution is determined by the number of particles present, for example, a 1 molar solution of a substance contains 7023602200000000000♠6. 022×1023 molecules per liter of that substance and at 0 °C it has an osmotic pressure of 2.27 MPa. The osmotic pressure of the plasma affects the mechanics of the circulation in several ways, an alteration of the osmotic pressure difference across the membrane of a blood cell causes a shift of water and a change of cell volume. The changes in shape and flexibility affect the properties of whole blood. This in turn affects the mechanics of the whole blood, the red blood cell is highly flexible and biconcave in shape. Its membrane has a Youngs modulus in the region of 106 Pa, deformation in red blood cells is induced by shear stress. When a suspension is sheared, the red blood cells deform and spin because of the velocity gradient, with the rate of deformation and spin depending on the shear-rate and this can influence the mechanics of the circulation and may complicate the measurement of blood viscosity. From the above equation we can see that the velocity of the particle depends on the square of the radius. If the particle is released from rest in the fluid, its sedimentation velocity Us increases until it attains the value called the terminal velocity. We have looked at blood flow and blood composition, before we look at the main issue, hemodilution, let us take a brief history into the use of blood. Its therapeutic use is not a modern phenomenon, egyptian writings dates back at least 2000 years suggest oral ingestion of blood as a ‘sovereign remedy’ for leprosy. However, the use of blood comes with significant risks
20.
Optical fiber
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An optical fiber or optical fibre is a flexible, transparent fiber made by drawing glass or plastic to a diameter slightly thicker than that of a human hair. Fibers are also used for illumination, and are wrapped in bundles so that they may be used to carry images, thus allowing viewing in confined spaces, as in the case of a fiberscope. Specially designed fibers are used for a variety of other applications, some of them being fiber optic sensors. Optical fibers typically include a transparent core surrounded by a transparent cladding material with an index of refraction. Light is kept in the core by the phenomenon of internal reflection which causes the fiber to act as a waveguide. Fibers that support many propagation paths or transverse modes are called multi-mode fibers, multi-mode fibers generally have a wider core diameter and are used for short-distance communication links and for applications where high power must be transmitted. Single-mode fibers are used for most communication links longer than 1,000 meters, being able to join optical fibers with low loss is important in fiber optic communication. This is more complex than joining electrical wire or cable and involves careful cleaving of the fibers, precise alignment of the cores. For applications that demand a permanent connection a fusion splice is common, in this technique, an electric arc is used to melt the ends of the fibers together. Another common technique is a splice, where the ends of the fibers are held in contact by mechanical force. Temporary or semi-permanent connections are made by means of specialized optical fiber connectors, the field of applied science and engineering concerned with the design and application of optical fibers is known as fiber optics. The term was coined by Indian physicist Narinder Singh Kapany who is acknowledged as the father of fiber optics. Guiding of light by refraction, the principle that makes fiber optics possible, was first demonstrated by Daniel Colladon, John Tyndall included a demonstration of it in his public lectures in London,12 years later. When the ray passes from water to air it is bent from the perpendicular. If the angle which the ray in water encloses with the perpendicular to the surface be greater than 48 degrees, the angle which marks the limit where total reflection begins is called the limiting angle of the medium. For water this angle is 48°27′, for flint glass it is 38°41′, unpigmented human hairs have also been shown to act as an optical fiber. Practical applications, such as close internal illumination during dentistry, appeared early in the twentieth century, image transmission through tubes was demonstrated independently by the radio experimenter Clarence Hansell and the television pioneer John Logie Baird in the 1920s. The principle was first used for medical examinations by Heinrich Lamm in the following decade
21.
America's Cup
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The Americas Cup, affectionately known as the Auld Mug, is a trophy awarded to the winner of the Americas Cup match races between two sailing yachts. The timing of each match is determined by an agreement between the defender and the challenger, the Americas Cup is the oldest international sporting trophy. The ewer was originally awarded in 1851 by the Royal Yacht Squadron for a race around the Isle of Wight in England, any yacht club that meets the requirements specified in the deed of gift has the right to challenge the yacht club that holds the cup. If the challenging club wins the match, it gains stewardship of the cup, the history and prestige associated with the Americas Cup attracts not only the worlds top sailors and yacht designers but also the involvement of wealthy entrepreneurs and sponsors. It is a test not only of sailing skill and boat and sail design, from the first defense of the cup in 1870 through the twentieth defense in 1967, there was always only one challenger. Since 1983, Louis Vuitton has sponsored the Louis Vuitton Cup as a prize for the winner of the challenger selection series, early matches for the cup were raced between yachts 65–90 ft on the waterline owned by wealthy sportsmen. This culminated with the J-Class regattas of the 1930s, after a long legal battle, the 2010 Americas Cup was raced in 90 ft lwl multihull yachts in a best of three deed of gift match in Valencia, Spain. The victorious Golden Gate Yacht Club then elected to race the 34th Americas Cup in AC72 foiling, Golden Gate Yacht Club successfully defended the cup. The 35th Americas Cup match was announced to be sailed in 50 ft foiling catamarans, the history of the Americas Cup has included legal battles and disputes over rule changes including most recently over the rule changes for the 2017 Americas Cup. It was originally known as the R. Y. S, £100 Cup, standing for a cup of a hundred GB Pounds or sovereigns in value. The cup was subsequently mistakenly engraved as the 100 Guinea Cup by the America syndicate, today, the trophy is officially known as the Americas Cup after the 1851 winning yacht, and is affectionately called the Auld Mug by the sailing community. It is inscribed with names of the yachts that competed for it, the syndicate contracted with pilot boat designer George Steers for a 101 ft schooner, which was christened America and launched on 3 May 1851. On 22 August 1851, America raced against 15 yachts of the Royal Yacht Squadron in the Clubs annual 53-nautical-mile regatta around the Isle of Wight, America won, finishing 8 minutes ahead of the closest rival. Apocryphally, Queen Victoria, who was watching at the line, was reported to have asked who was second. No challenge to race for the Cup was issued until British railway tycoon James Lloyd Ashburys topsail schooner Cambria beat the Yankee schooner Sappho in the Solent in 1868. This success encouraged the Royal Thames Yacht Club in believing that the cup could be back home. Ashbury entered Cambria in the NYYC Queens Cup race in New York City on 8 August against a fleet of seventeen schooners, the Cambria only placed eighth, behind the aging America in fourth place and Franklin Osgoods Magic in the fleets lead. Trying again, Ashbury offered a match race challenge for October 1871
22.
Alinghi 5
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Alinghi 5 is a 90 ft,90 ft beam sloop-rigged catamaran built by Alinghi for the 33rd Americas Cup. She was launched on 8 July 2009 when she was lifted from the shed in Villeneuve, Vaud by a Mil Mi-26 helicopter. She was subsequently carried to Genoa, Italy, at the end of September 2009, the boat was shipped to Ras al Khaimah, the venue selected by the defender for the 33rd Americas Cup. At the end of October 2009, the New York Supreme Court ruled that the venue of Ras al Khaimah was not compliant with the Deed of Gift, after various discussions, Société Nautique de Genève agreed that the venue would be Valencia, Spain. An appeal by SNG regarding the venue was rejected and Alinghi 5 was shipped at the end of December 2009 from Ras al Khaimah to Valencia, where she arrived on 5 January 2010. Designed by Rolf Vrolijk and an Alinghi design team headed by Grant Simmer, Alinghi 5 was built in Villeneuve, Switzerland, by Alinghi-Décision, the mast is approximately 62 metres tall. An engine installed at the back of the boat provides power for the winches, when sailing upwind, the boat can sail at less than 20 degrees off the apparent wind. During a training run, Alinghi 5 covered 20 nautical miles to windward and back in 2.5 hours in 8–9-knot winds, so her velocity made good was 16 knots. An explanation of this phenomenon can be found in the article on sailing faster than the wind, the design of the yacht was influenced by that of racing catamarans developed for regattas on Lake Geneva. The first race of the 2010 Americas Cup took place on 12 February 2010, Alinghi 5 lost the race to the challenger, USA17. Alinghi 5 was ahead by 1,27 at the start and her official finish time was 15,28 behind the winner because Alinghi 5 had to perform a penalty turn, having failed to stay clear at the start. Alinghi 5 reached the mark in 1h32, so her velocity made good was about 13 knots. Alinghi 5 took 69 1⁄2 minutes to reach the mark, so her velocity made good downwind was about 17 knots. Alinghi 5 was behind by 0,24 at the start, by 0,28 at the mark, by 2,44 at the gybe mark. Her official finish time was 5,26 behind the winner because Alinghi 5 had to perform a penalty turn, Alinghi 5 reached the windward mark in 59 minutes, so her velocity made good was about 13.2 knots, or about 1.8 times wind speed. The course was a triangle, so the velocity made good downwind was only 11.1 knots, Alinghi 5 averaged 25.2 knots, or about 3.4 times the wind speed, on the faster first triangular leg. Most observers stated that USA 17s rigid wing sail had given her a decisive advantage and she could be seen on Google Maps while trialing on Lake Geneva, but disappeared with the imagery update of 2011. Using the Measurement tool in Google Maps renders her 110 feet LOA and 75 feet beam
23.
Microelectromechanical systems
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Microelectromechanical systems is the technology of microscopic devices, particularly those with moving parts. It merges at the nano-scale into nanoelectromechanical systems and nanotechnology, MEMS are also referred to as micromachines in Japan, or micro systems technology in Europe. They usually consist of a unit that processes data and several components that interact with the surroundings such as microsensors. MEMS technology is distinguished from molecular nanotechnology or molecular electronics in that the latter must also consider surface chemistry, the potential of very small machines was appreciated before the technology existed that could make them. MEMS became practical once they could be fabricated using modified semiconductor device fabrication technologies and these include molding and plating, wet etching and dry etching, electro discharge machining, and other technologies capable of manufacturing small devices. An early example of a MEMS device is the resonistor – an electromechanical monolithic resonator, silicon is the material used to create most integrated circuits used in consumer electronics in the modern industry. The economies of scale, ready availability of inexpensive high-quality materials, silicon also has significant advantages engendered through its material properties. In single crystal form, silicon is an almost perfect Hookean material, meaning that when it is flexed there is virtually no hysteresis and hence almost no energy dissipation. Even though the industry provides an economy of scale for the silicon industry, crystalline silicon is still a complex. Polymers on the hand can be produced in huge volumes. Metals can also be used to create MEMS elements, while metals do not have some of the advantages displayed by silicon in terms of mechanical properties, when used within their limitations, metals can exhibit very high degrees of reliability. Metals can be deposited by electroplating, evaporation, and sputtering processes, commonly used metals include gold, nickel, aluminium, copper, chromium, titanium, tungsten, platinum, and silver. The nitrides of silicon, aluminium and titanium as well as silicon carbide, alN crystallizes in the wurtzite structure and thus shows pyroelectric and piezoelectric properties enabling sensors, for instance, with sensitivity to normal and shear forces. TiN, on the hand, exhibits a high electrical conductivity. Moreover, the resistance of TiN against biocorrosion qualifies the material for applications in biogenic environments. One of the building blocks in MEMS processing is the ability to deposit thin films of material with a thickness anywhere between a few nanometres to about 100 micrometres. There are two types of processes, as follows. Physical vapor deposition consists of a process in which a material is removed from a target, chemical deposition techniques include chemical vapor deposition, in which a stream of source gas reacts on the substrate to grow the material desired
24.
Optical ring resonators
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An optical ring resonator is a set of waveguides in which at least one is a closed loop coupled to some sort of light input and output. Because only a few wavelengths will be at resonance within the loop. Additionally, as implied earlier, two or more ring waveguides can be coupled to other to form an add/drop optical filter. Optical ring resonators work on the principles behind total internal reflection, constructive interference, the light travelling through the waveguides in an optical ring resonator remain within the waveguides due to the ray optics phenomenon known as total internal reflection. TIR is a phenomenon that occurs when a ray of light strikes the boundary of a medium. For an optical ring resonator to work well, total internal reflection conditions must be met, interference is the process by which two waves superimpose to form a resultant wave of greater or less amplitude. Interference usually refers to the interaction of waves that are correlated or coherent with each other, in constructive interference, the two waves are of the same phase interfere in a way such that the resultant amplitude will be equal to the sum of the individual amplitudes. As the light in a ring resonator completes multiple circuits around the ring component. Critical to understanding how an optical ring resonator works, is the concept of how the linear waveguides are coupled to the ring waveguide. When a beam of light passes through a guide as shown in the graph on the right. The reason for this phenomenon to happen is because the property of the light, or if we consider it in ray optics. In other words, if the ring and the waveguide are close enough, there are three aspects that affect the optical coupling, the distance, the coupling length and the refractive indices between the waveguide and the optical ring resonator. In order to optimize the coupling, it is usually the case to narrow the distance between the ring resonator and the waveguide, the closer the distance, the easier the optical coupling happens. In addition, the coupling length affects the coupling as well, the coupling length represents the effective curve length of the ring resonator for the coupling phenomenon to happen with the waveguide. It has been studied that as the coupling length increases. Furthermore, the index of the waveguide material, the ring resonator material. The medium material is usually the important one been studied since it has an effect on the transmission of the light wave. The refractive index of the medium can be large or small according to various applications
25.
Micro-Opto-Electro-Mechanical Systems
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MOEMS includes a wide variety of devices including optical switch, optical cross-connect, tunable VCSEL, microbolometers amongst others. These devices are fabricated using micro-optics and standard micromachining technologies using materials like silicon, silicon dioxide, silicon nitride. MOEMS includes two major technologies, MEMS and Micro-optics, both these two technologies independently involve in batch processing similar to integrated circuits, and micromachining similar to fabrication of microsensor. DARPA assigned a program manager for field and significantly soon MEMS is promoted to be the king of the technology. Several high tech journals that were originated were attached to MEMS by supporting miniaturization, many private companies which did not have sufficient knowledge about MEMS also started jumping on the bandwagon. Parallel with MEMS developments and even earlier, sensor technology advanced to microsensors, development of microsensors and microactuators were also due to a mother technology of micromachining. Micromachining is the root of everything we have today in high technology and this technology was never credited in history as it deserved. It was commercially used during the 1960s in Switzerland, for micromachining quartz orders of magnitudes harder than micromachining silicon, MEMS acronym was so powerful during the 1980s, that with no choice microsensors and microactuators that included micromachining, all joined MEMS by a soft landing. As a result, the MEMS acronym was more attractive for publicity, during the MEMS era, and before that time frame, Rockwell International was involved in commercial MEMS development under government contracts. During early 1980s Rockwell successfully built the first CMOS MEMS high performance, the wafer was processed inside Rockwell VLSI lab in Anaheim, CA. This was a breakthrough in MEMS technology, but it did not appear in literature until 1988, Rockwell Science Center also developed refractive microlens technology, including gray scale photolithography. This profile approximates the ideal kinoform lens surface, a special staircase process, called binary optics, is used to fabricate diffractive components. This was behind the acronym of MOEMS, when both MEMS and Micro-optics were merged in one single IC processing lab, MOEMS is a promising multi technology for miniaturization of critical optical systems. The acronym is defined of three high tech fields of micro-optics, micromechanics, and microelectronics, MOEMS indirectly could merge in micromachining, microsensors and microactuators if their processes are compatible with integrated circuits. All technologies of MOEMS have the potential of batch processing and embossed replication which, again, makes them highly attractive, MOEMS is an enabling technology for applications that cannot be addressed, using micro-optics alone and is currently playing a significant role in numerous optical applications. In this talk Dr. Motamedi introduced the figure below, for showing that MOEMS is the interaction of three major microtechnologies, namely Micro-optics, Micromechanics, and Microelectronics, digital micromirror device Microfabrication Microscanner P. Rai-Choudhury, MEMS and MOEMS. Technology and applications, SPIE Press, Washington,2000, micro-electro-mechanical systems Optical MEMS, From micromirrors to complex systems, IEEE Journal of Microelectromechanical Systems Nanoelectromechanical systems
26.
Variable capacitor
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A variable capacitor is a capacitor whose capacitance may be intentionally and repeatedly changed mechanically or electronically. Variable capacitors are used in L/C circuits to set the resonance frequency, e. g. to tune a radio, or as a variable reactance. In mechanically controlled variable capacitors, the distance between the plates, or the amount of surface area which overlaps, can be changed. Air or plastic foils can be used as dielectric material, by choosing the shape of the rotary plates, various functions of capacitance vs. angle can be created, e. g. to obtain a linear frequency scale. Various forms of reduction gear mechanisms are used to achieve finer tuning control, i. e. to spread the variation of capacity over a larger angle. Measurement of the capacitance of a rotary capacitor A vacuum variable capacitor uses a set of made from concentric cylinders that can be slid in or out of an opposing set of cylinders. These plates are sealed inside of a non-conductive envelope such as glass or ceramic. The movable part is mounted on a flexible membrane that seals. A screw shaft is attached to the plunger, when the shaft is turned the plunger moves in or out of the sleeve, the vacuum not only increases the working voltage and current handling capacity of the capacitor it also greatly reduces the chance of arcing across the plates. The most common usage for vacuum variables are in high powered transmitters such as used for broadcasting, military. Very cheap variable capacitors are constructed from layered aluminium and plastic foils that are pressed together using a screw. These so-called squeezers can’t provide a stable and reproducible capacitance, however, a variant of this structure that allows for linear movement of one set of plates to change the plate overlap area is also used and might be called a slider. This has practical advantages for makeshift or home construction and may be found in resonant loop antennas or crystal radios, small variable capacitors operated by screwdriver are called trimmer capacitors. In addition to air and plastic, trimmers can also be using a ceramic dielectric. Capacitors with multiple sections often include trimmer capacitors in parallel to the variable sections, since the peak RF current normally flows from one stator to the other without going through wiper contacts, butterfly capacitors can handle large resonance RF currents, e. g. in magnetic loop antennas. The closely related split stator variable capacitor does not have the limitation of 90° angle since it uses two separate packs of rotor electrodes arranged axially behind one another. Unlike in a capacitor with several sections, the plates in a split stator capacitor are mounted on opposite sides of the rotor axis. Differential variable capacitors can therefore be used in capacitive potentiometric circuits, the variable capacitor with air dielectric was invented by the Hungarian engineer Dezső Korda
27.
Civil engineering
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Civil engineering is traditionally broken into a number of sub-disciplines. It is the second-oldest engineering discipline after military engineering, and it is defined to distinguish non-military engineering from military engineering, Civil engineering takes place in the public sector from municipal through to national governments, and in the private sector from individual homeowners through to international companies. Engineering has been an aspect of life since the beginnings of human existence, during this time, transportation became increasingly important leading to the development of the wheel and sailing. The construction of pyramids in Egypt were some of the first instances of large structure constructions, the Romans developed civil structures throughout their empire, including especially aqueducts, insulae, harbors, bridges, dams and roads. In the 18th century, the civil engineering was coined to incorporate all things civilian as opposed to military engineering. The first self-proclaimed civil engineer was John Smeaton, who constructed the Eddystone Lighthouse, in 1771 Smeaton and some of his colleagues formed the Smeatonian Society of Civil Engineers, a group of leaders of the profession who met informally over dinner. Though there was evidence of some meetings, it was little more than a social society. In 1818 the Institution of Civil Engineers was founded in London, the institution received a Royal Charter in 1828, formally recognising civil engineering as a profession. The first private college to teach engineering in the United States was Norwich University. The first degree in engineering in the United States was awarded by Rensselaer Polytechnic Institute in 1835. The first such degree to be awarded to a woman was granted by Cornell University to Nora Stanton Blatch in 1905, throughout ancient and medieval history most architectural design and construction was carried out by artisans, such as stonemasons and carpenters, rising to the role of master builder. Knowledge was retained in guilds and seldom supplanted by advances, structures, roads and infrastructure that existed were repetitive, and increases in scale were incremental. Brahmagupta, an Indian mathematician, used arithmetic in the 7th century AD, based on Hindu-Arabic numerals, Civil engineers typically possess an academic degree in civil engineering. The length of study is three to five years, and the degree is designated as a bachelor of engineering. The curriculum generally includes classes in physics, mathematics, project management, design, after taking basic courses in most sub-disciplines of civil engineering, they move onto specialize in one or more sub-disciplines at advanced levels. In most countries, a degree in engineering represents the first step towards professional certification. After completing a degree program, the engineer must satisfy a range of requirements before being certified. Once certified, the engineer is designated as a engineer, a chartered engineer
28.
Indicator (distance amplifying instrument)
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The name comes from the concept of indicating to the user that which their naked eye cannot discern, such as the presence, or exact quantity, of some small distance. Many indicators have a display, in which a needle points to graduations in a circular array around the dial. Such indicators, of which there are types, are often called dial indicators. Other types of indicator include mechanical devices with cantilevered pointers and electronic devices with digital displays, Dial indicators typically measure ranges from 0.25 mm to 300 mm, with graduations of 0.001 mm to 0.01 mm or 0. 00005in to 0. 001in. There are several variables in dial indicators, Analog versus digital/electronic readout Dial size, indicators inherently provide relative measure only. But given that suitable references are used, they allow a practical equivalent of absolute measure. However, the user must know how to use them properly and understand how in some situations, to check for run-out when fitting a new disc to an automotive disc brake. Run-out can rapidly ruin the disc if it exceeds the specified tolerance, in a quality environment to check for consistency and accuracy in the manufacturing process. On the workshop floor to set up or calibrate a machine. By toolmakers in the process of manufacturing precision tooling, in metal engineering workshops, where a typical application is the centering of a lathes workpiece in a four jaw chuck. The DTI is used to indicate the run out of the workpiece, in areas other than manufacturing where accurate measurements need to be recorded. The dial has fine gradations for precise measurement, the spring-loaded probe moves perpendicularly to the object being tested by either retracting or extending from the indicators body. There may also be a lever arm available that allow the indicators probe to be retracted easily. Mounting the indicator may be several ways. Many indicators have a mounting lug with a hole for a bolt as part of the back plate, common outside diameters for the stem are 3/8 inch and 8 mm, though there are other diameters made. Another option that a few manufacturers include is dovetail mounts compatible with those on dial test indicators, a dial test indicator, also known as a lever arm test indicator or finger indicator, has a smaller measuring range than a standard dial indicator. A test indicator measures the deflection of the arm, the probe does not retract, the lever may be interchanged for length or ball diameter, and permits measurements to be taken in narrow grooves and small bores where the body of a probe type may not reach. The model shown is bidirectional, some types may have to be switched via a lever to be able to measure in the opposite direction
29.
Resistance thermometer
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Resistance thermometers, also called resistance temperature detectors, are sensors used to measure temperature. Many RTD elements consist of a length of wire wrapped around a ceramic or glass core. The RTD wire is a material, typically platinum, nickel. The material has an accurate resistance/temperature relationship which is used to provide an indication of temperature, as RTD elements are fragile, they are often housed in protective probes. RTDs, which have higher accuracy and repeatability, are slowly replacing thermocouples in industrial applications below 600 °C, common RTD sensing elements constructed of platinum, copper or nickel have a repeatable resistance versus temperature relationship and operating temperature range. The R vs T relationship is defined as the amount of change of the sensor per degree of temperature change. The relative change in resistance varies only slightly over the range of the sensor. Nickel elements have a temperature range because the amount of change in resistance per degree of change in temperature becomes very non-linear at temperatures over 572 °F. Copper has a very linear resistance–temperature relationship, however, copper oxidizes at moderate temperatures, Platinum is the best metal for RTDs due to its very linear resistance–temperature relationship, highly repeatable over a wide temperature range. The unique properties of platinum make it the material of choice for temperature standards over the range of −272.5 °C to 961.78 °C and it is used in the sensors that define the International Temperature Standard, ITS-90. Platinum is chosen also because of its chemical inertness, the significant characteristic of metals used as resistive elements is the linear approximation of the resistance versus temperature relationship between 0 and 100 °C. Pure platinum has α =0.003925 Ω/ in the 0 to 100 °C range and is used in the construction of laboratory-grade RTDs, conversely, two widely recognized standards for industrial RTDs IEC60751 and ASTM E-1137 specify α =0.00385 Ω/. Before these standards were adopted, several different α values were used. It is still possible to find older probes that are made with platinum that have α =0.003916 Ω/ and 0.003902 Ω/ and these different α values for platinum are achieved by doping, basically, carefully introducing impurities into the platinum. The impurities introduced during doping become embedded in the structure of the platinum and result in a different R vs. T curve. To characterize the R vs T relationship of any RTD over a range that represents the planned range of use. This is necessary to meet calibration requirements, although RTDs are considered to be linear in operation, it must be proven that they are accurate with regard to the temperatures with which they will actually be used. Two common calibration methods are the fixed-point method and the comparison method, fixed point calibration is used for the highest-accuracy calibrations by national metrology laboratories
30.
International Standard Book Number
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The International Standard Book Number is a unique numeric commercial book identifier. An ISBN is assigned to each edition and variation of a book, for example, an e-book, a paperback and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, the method of assigning an ISBN is nation-based and varies from country to country, often depending on how large the publishing industry is within a country. The initial ISBN configuration of recognition was generated in 1967 based upon the 9-digit Standard Book Numbering created in 1966, the 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108. Occasionally, a book may appear without a printed ISBN if it is printed privately or the author does not follow the usual ISBN procedure, however, this can be rectified later. Another identifier, the International Standard Serial Number, identifies periodical publications such as magazines, the ISBN configuration of recognition was generated in 1967 in the United Kingdom by David Whitaker and in 1968 in the US by Emery Koltay. The 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108, the United Kingdom continued to use the 9-digit SBN code until 1974. The ISO on-line facility only refers back to 1978, an SBN may be converted to an ISBN by prefixing the digit 0. For example, the edition of Mr. J. G. Reeder Returns, published by Hodder in 1965, has SBN340013818 -340 indicating the publisher,01381 their serial number. This can be converted to ISBN 0-340-01381-8, the check digit does not need to be re-calculated, since 1 January 2007, ISBNs have contained 13 digits, a format that is compatible with Bookland European Article Number EAN-13s. An ISBN is assigned to each edition and variation of a book, for example, an ebook, a paperback, and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, a 13-digit ISBN can be separated into its parts, and when this is done it is customary to separate the parts with hyphens or spaces. Separating the parts of a 10-digit ISBN is also done with either hyphens or spaces, figuring out how to correctly separate a given ISBN number is complicated, because most of the parts do not use a fixed number of digits. ISBN issuance is country-specific, in that ISBNs are issued by the ISBN registration agency that is responsible for country or territory regardless of the publication language. Some ISBN registration agencies are based in national libraries or within ministries of culture, in other cases, the ISBN registration service is provided by organisations such as bibliographic data providers that are not government funded. In Canada, ISBNs are issued at no cost with the purpose of encouraging Canadian culture. In the United Kingdom, United States, and some countries, where the service is provided by non-government-funded organisations. Australia, ISBNs are issued by the library services agency Thorpe-Bowker
31.
Sensor
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A sensor is always used with other electronics, whether as simple as a light or as complex as a computer. Moreover, analog sensors such as potentiometers and force-sensing resistors are still widely used, applications include manufacturing and machinery, airplanes and aerospace, cars, medicine, robotics and many other aspects of our day-to-day life. A sensors sensitivity indicates how much the output changes when the input quantity being measured changes. For instance, if the mercury in a thermometer moves 1 cm when the changes by 1 °C. Some sensors can also affect what they measure, for instance, Sensors are usually designed to have a small effect on what is measured, making the sensor smaller often improves this and may introduce other advantages. Technological progress allows more and more sensors to be manufactured on a scale as microsensors using MEMS technology. In most cases, a microsensor reaches a higher speed. Most sensors have a transfer function. The sensitivity is defined as the ratio between the output signal and measured property. For example, if a sensor measures temperature and has a voltage output, the sensitivity is the slope of the transfer function. Converting the sensors electrical output to the measured units requires dividing the output by the slope. In addition, an offset is added or subtracted. For example -40 must be added to the output if 0 V output corresponds to -40 C input, for an analog sensor signal to be processed, or used in digital equipment, it needs to be converted to a digital signal, using an analog-to-digital converter. The full scale range defines the maximum and minimum values of the measured property, the sensitivity may in practice differ from the value specified. This is called a sensitivity error and this is an error in the slope of a linear transfer function. If the output differs from the correct value by a constant. This is an error in the y-intercept of a transfer function. Nonlinearity is deviation of a transfer function from a straight line transfer function
32.
Geophone
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A geophone is a device that converts ground movement into voltage, which may be recorded at a recording station. The deviation of this voltage from the base line is called the seismic response and is analyzed for structure of the earth. The term geophone derives from the Greek word γῆ meaning earth, geophones have historically been passive analog devices and typically comprise a spring-mounted magnetic mass moving within a wire coil to generate an electrical signal. The response of a geophone is proportional to ground velocity. MEMS have a higher noise level than geophones and can only be used in strong motion or active seismic applications. The frequency response of a geophone is that of an oscillator, fully determined by corner frequency. Since the corner frequency is proportional to the root of the moving mass. It is possible to lower the corner electronically, at the price of higher noise. Although waves passing through the earth have a nature, geophones are normally constrained to respond to single dimension - usually the vertical. However, some require the full wave to be used. In analog devices, three moving coil elements are mounted in an arrangement within a single case. The majority of geophones are used in seismology to record the energy waves reflected by the subsurface geology. In this case the primary interest is in the motion of the Earths surface. However, not all the waves are upwards travelling, a strong, horizontally transmitted wave known as ground-roll also generates vertical motion that can obliterate the weaker vertical signals. By using large areal arrays tuned to the wavelength of the ground-roll the dominant noise signals can be attenuated, analog geophones are very sensitive devices which can respond to very distant tremors. These small signals can be drowned by larger signals from local sources and it is possible though to recover the small signals caused by large but distant events by correlating signals from several geophones deployed in an array. Signals which are registered only at one or few geophones can be attributed to unwanted, local events and it can be assumed that small signals that register uniformly at all geophones in an array can be attributed to a distant and therefore significant event. The sensitivity of passive geophones is typically 30 Volts/, so they are in general not a replacement for broadband seismometers, conversely, some applications of geophones are interested only in very local events
33.
Hydrophone
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A hydrophone is a microphone designed to be used underwater for recording or listening to underwater sound. Most hydrophones are based on a piezoelectric transducer that generates electricity when subjected to a pressure change, such piezoelectric materials, or transducers, can convert a sound signal into an electrical signal since sound is a pressure wave. Some transducers can also serve as a projector, but not all have this capability, a hydrophone can listen to sound in air but will be less sensitive due to its design as having a good acoustic impedance match to water, which is a denser fluid than air. The earliest widely used design was the Fessenden oscillator, an electrodynamically driven clamped-edge circular plate transducer operating at 500,1000, ernest Rutherford, in England, led pioneer research in hydrophones using piezoelectric devices, and his only patent was for a hydrophone device. The acoustic impedance of piezoelectric materials facilitated their use as underwater transducers, the piezoelectric hydrophone was used late in World War I, by convoy escorts detecting U-boats, greatly impacting the effectiveness of submarines. From late in World War I until the introduction of active sonar, hydrophones were the method for submarines to detect targets while submerged. A small single cylindrical ceramic transducer can achieve near perfect omnidirectional reception and this type of hydrophone can be produced from a low-cost omnidirectional type, but must be used while stationary, as the reflector impedes its movement through water. A new way to direct is to use a body around the hydrophone. The array may be steered using a beamformer, most commonly, hydrophones are arranged in a line array but may be in two- or three-dimensional arrangements. These are capable of clearly recording extremely low frequency infrasound, including many unexplained ocean sounds, communication with submarines Underwater acoustics Sonar Reflection seismology Pike, John. How to build & use low-cost hydrophones, dOSITS—Hydrophone introduction at Discovery of Sound in the Sea orcasound. High Quality Hydrophones— High quality manufacturer of Hydrophones
34.
Microphone
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A microphone, colloquially nicknamed mic or mike, is a transducer that converts sound into an electrical signal. Several different types of microphone are in use, which employ different methods to convert the air pressure variations of a wave to an electrical signal. Microphones typically need to be connected to a preamplifier before the signal can be recorded or reproduced, in order to speak to larger groups of people, a need arose to increase the volume of the human voice. The earliest devices used to achieve this were acoustic megaphones, some of the first examples, from fifth century BC Greece, were theater masks with horn-shaped mouth openings that acoustically amplified the voice of actors in amphitheatres. In 1665, the English physicist Robert Hooke was the first to experiment with an other than air with the invention of the lovers telephone made of stretched wire with a cup attached at each end. German inventor Johann Philipp Reis designed an early sound transmitter that used a strip attached to a vibrating membrane that would produce intermittent current. Better results were achieved with the transmitter design in Scottish-American Alexander Graham Bells telephone of 1876 – the diaphragm was attached to a conductive rod in an acid solution. These systems, however, gave a poor sound quality. The first microphone that enabled proper voice telephony was the carbon microphone and this was independently developed by David Edward Hughes in England and Emile Berliner and Thomas Edison in the US. Although Edison was awarded the first patent in mid-1877, Hughes had demonstrated his working device in front of many witnesses some years earlier, the carbon microphone is the direct prototype of todays microphones and was critical in the development of telephony, broadcasting and the recording industries. Thomas Edison refined the carbon microphone into his carbon-button transmitter of 1886 and this microphone was employed at the first ever radio broadcast, a performance at the New York Metropolitan Opera House in 1910. In 1916, E. C. Wente of Western Electric developed the next breakthrough with the first condenser microphone, in 1923, the first practical moving coil microphone was built. The Marconi Skykes or magnetophon, developed by Captain H. J. Round, was the standard for BBC studios in London and this was improved in 1930 by Alan Blumlein and Herbert Holman who released the HB1A and was the best standard of the day. Also in 1923, the microphone was introduced, another electromagnetic type, believed to have been developed by Harry F. Olson. Over the years these microphones were developed by companies, most notably RCA that made large advancements in pattern control. With television and film technology booming there was demand for high fidelity microphones, electro-Voice responded with their Academy Award-winning shotgun microphone in 1963. During the second half of 20th century development advanced quickly with the Shure Brothers bringing out the SM58, digital was pioneered by Milab in 1999 with the DM-1001. The latest research developments include the use of optics, lasers and interferometers
35.
Seismometer
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Seismometers are instruments that measure motion of the ground, including those of seismic waves generated by earthquakes, volcanic eruptions, and other seismic sources. Records of seismic waves allow seismologists to map the interior of the Earth, the seismometer was invented by the Chinese polymath Zhang Heng in AD132 during the Han dynasty. The first Western description of a comes from the French physicist and priest Jean de Hautefeuille in 1703. The modern seismometer was developed in the 19th century by John Milne, James Alfred Ewing, seismograph is another Greek term from seismós and γράφω, gráphō, to draw. The concerning technical discipline is called seismometry, a branch of seismology, a simple seismometer that is sensitive to up-down motions of the earth can be understood by visualizing a weight hanging on a spring. The spring and weight are suspended from a frame that moves along with the earthʼs surface, as the earth moves, the relative motion between the weight and the earth provides a measure of the vertical ground motion. Any movement of the moves the frame. The mass tends not to move because of its inertia, early seismometers used optical levers or mechanical linkages to amplify the small motions involved, recording on soot-covered paper or photographic paper. In some systems, the mass is held nearly motionless relative to the frame by a negative feedback loop. The motion of the relative to the frame is measured. The voltage needed to produce this force is the output of the seismometer, in other systems the weight is allowed to move, and its motion produces a voltage in a coil attached to the mass and moving through the magnetic field of a magnet attached to the frame. This design is used in the geophones used in seismic surveys for oil. Professional seismic observatories usually have instruments measuring three axes, north-south, east-west, and the vertical, if only one axis is measured, this is usually the vertical because it is less noisy and gives better records of some seismic waves. The foundation of a station is critical. A professional station is mounted on bedrock. The best mountings may be in deep boreholes, which avoid thermal effects, ground noise and tilting from weather, other instruments are often mounted in insulated enclosures on small buried piers of unreinforced concrete. Reinforcing rods and aggregates would distort the pier as the temperature changes, a site is always surveyed for ground noise with a temporary installation before pouring the pier and laying conduit. Originally, European seismographs were placed in an area after a destructive earthquake
36.
Blind spot monitor
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The blind spot monitor is a vehicle-based sensor device that detects other vehicles located to the driver’s side and rear. Warnings can be visual, audible, vibrating, or tactile, however, blind spot monitors are an option that may do more than monitor the sides and rear of the vehicle. They may also include Cross Traffic Alert, which alerts drivers backing out of a parking space when traffic is approaching from the sides, if side view mirrors are properly adjusted on a car, there is no blind spot on the sides. Platzer received a patent for his blind spot monitor, and it has incorporated into various products associated with Ford Motor Company. The blind zone mirror has been touted as an elegant and relatively inexpensive solution to this recognized problem, Volvo BLIS is an acronym for Blind Spot Information System, a system of protection developed by Volvo. Volvos previous parent, Ford Motor Company, has adapted the system to its Ford, Lincoln. Mazda Mazda was the first Japanese automaker to offer a blind spot monitor and it was initially introduced on the 2008 Mazda CX-9 Grand Touring and remained limited to only that highest trim level through the 2012 model year. For 2013, BSM was standard on both the CX-9 Touring and Grand Touring models, Mazda also added BSM to the redesigned 2009 Mazda 6. Blind spot monitoring was standard equipment on the 6i and 6s Grand Touring trim levels, and was an available option on some lower trim levels. Mazda has since expanded the availability of BSM, having added it to the feature list of the Mazda3, CX-5, MX-5 Miata, Ford Ford uses the acronym BLIS for its blind spot detection. The system is both in drive and neutral transmission gears, and is turned off when in reverse or park gears. On Ford products, the system was first introduced in the spring of 2009, on the 2010 Ford Fusion and Fusion Hybrid,2010 Mercury Milan and Milan Hybrid, Mitsubishi Mitsubishi offers a Blind Spot Warning on the Pajero Sport launched in 2016. Toyota Toyota Motors Safety Sense package, which includes Blind Spot Monitoring, among other features, is standard equipment in multiple models sold in the U. S, in 2010, the Nissan Fuga/Infiniti M for the first time offered counter steering capabilities to keep the vehicle from colliding. Those capabilities have been adopted by competitors, such as Toyota, youTube Ford How-to video, BLIS with Cross-Traffic Alert Google patent search of Blind spot monitoring system The danger of blind zones The area behind your vehicle can be a killing zone
37.
Crankshaft position sensor
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A crank sensor is an electronic device used in an internal combustion engine, both petrol and diesel, to monitor the position or rotational speed of the crankshaft. This information is used by engine management systems to control the fuel injection or the ignition system timing, before electronic crank sensors were available, the distributor would have to be manually adjusted to a timing mark on petrol engines. This method is used to synchronise a four stroke engine upon starting, allowing the management system to know when to inject the fuel. It is also used as the primary source for the measurement of engine speed in revolutions per minute. Common mounting locations include the main crank pulley, the flywheel and this sensor is the 2nd most important sensor in modern-day engines after the camshaft position sensor. When it fails, there is a probability the engine will not start, there are three main types of sensor commonly in use. The Hall Effect sensor, Optical sensor or the Inductive sensor, some engines, such as GMs Premium V family, use crank position sensors which read a reluctor ring integral to the harmonic balancer. This is a more accurate method of determining the position of the crankshaft. The functional objective for the position sensor is to determine the position and/or rotational speed of the crank. Engine Control Units use the information transmitted by the sensor to control such as ignition timing. In a diesel the sensor will control the fuel injection, the sensor output may also be related to other sensor data including the cam position to derive the current combustion cycle, this is very important for the starting of a four stroke engine. Sometimes, the sensor may become burnt or worn out - or just die of old age at high mileage, one likely cause of crankshaft position sensor failure is exposure to extreme heat. Others are vibration causing a wire to fracture or corrosion on the pins of harness connectors, many modern crankshaft sensors are sealed units and therefore will not be damaged by water or other fluids. When it goes wrong, it stops transmitting the signal contains the vital data for the ignition. A bad crank position sensor can worsen the way the engine idles, if the engine is revved up with a bad or faulty sensor, it may cause misfiring, motor vibration or backfires. Acceleration might be hesitant, and abnormal shaking during engine idle might occur, in the worst case the car may not start. The first sign of crankshaft failure, usually, is the refusal of the engine to start when hot. Another type of sensor is used on bicycles to monitor the position of the crankset
38.
Curb feeler
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Curb feelers or curb finders are springs or wires installed on a vehicle which act as whiskers to alert drivers when they are at the right distance from the curb while parking. The devices are fitted low on the body, close to the wheels, as the vehicle approaches the curb, the protruding feelers scrape against the curb, making a noise and alerting the driver in time to avoid damaging the wheels or hubcaps. The feelers are manufactured to be flexible and do not easily break, curb feelers are still used on some hot rods when a 1950s look is wanted. They are especially popular for cars with tires, which easily lose their white coating when scraped against the curb. Sometimes curb feelers are found only on the side of the car. Sometimes they are added next to the front wheels. Some curb feelers have a wire or spring, while others have two to increase the area that can be protected. Any particular car may have just one curb feeler installed or more if attached near the front and rear, as well as on both sides of the vehicle. Buses are sometimes fitted with curb feelers, which can assist the driver in ensuring that the bus is close enough to the curb to allow passengers to step to and from the curb easily. This will give a warning nudge to anyone in the danger area, the belting is stiff enough to hold its shape but flexible enough to give if it runs into a miner or vice versa. The flexibility also allows this curb feeler to drag against the rib or be smacked by a car with little or no damage. A little spray from a can of paint will make the belt a visual warning device as well. One or two on each corner will help or put as many as you want, curb feelers based on optical technology are designed to function the same way but work in the proximity of an obstruction rather than having to come into physical contact with it. As described by one United States patent, An electronic curb feeler system uses two pairs of optical sensor units to detect an object located near the front end of a vehicle during parking. Devices such as this, and simpler electronic devices similar to the original wire curb feelers used on cars, are used in the design of various mobile robotic devices, one robotics company that does work for the United States Department of Defense uses laser-assisted curb feeler technology
