49) LIST OF ENGINEERING TOPICS FOR LETTER "W"

Washington Accord
The Washington Accord is an international accreditation agreement for professional engineering academic degrees, between the bodies responsible for accreditation in its signatory countries. Established in 1989, the signatories as of 2007 are Australia, Canada, the Republic of Ireland, Hong Kong, Japan, New Zealand, Singapore, South Africa, South Korea, Taiwan, the United Kingdom and the United States.

The agreement recognizes that there is substantial equivalency of programs accredited by those signatories. Graduates of accredited programs in any of the signatory countries are recognized by the other signatory countries as having met the academic requirements for entry to the practice of engineering. It is important to note that recognition of accredited programs is not retroactive but takes effect only from the date of admission of the country to signatory status.


Waveguide
A waveguide is a structure which guides waves, such as electromagnetic waves or sound waves. There are different types of waveguide for each type of wave. Waveguides differ in their geometry which can confine light in one dimension such as in slab waveguides or two dimensions as in fiber or channel waveguides.

Wear
In materials science, wear is the erosion of material from a solid surface by the action of another surface. It is related to surface interactions and more specifically the removal of material from a surface as a result of mechanical action. The need for mechanical action, in the form of contact due to relative motion, is an important distinction between mechanical wear and other processes with similar outcomes.

The definition of wear does not include loss of dimension from plastic deformation, although wear has occurred despite no material removal. This definition also fails to include impact wear, where there is no sliding motion, cavitation, where the counterbody is a fluid, and corrosion, where the damage is due to chemical rather than mechanical action.

Wear can also be defined as a process in which interaction of the surfaces or bounding faces of a solid with its working environment results in dimensional loss of the solid, with or without loss of material. Aspects of the working environment which affect wear include loads (such as unidirectional sliding, reciprocating, rolling, and impact loads), speed, temperature, type of counterbody (solid, liquid, or gas), and type of contact (single phase or multiphase, in which the phases involved can be liquid plus solid particles plus gas bubbles).

Wind engineering
Wind engineering is a field of structural engineering devoted to the analysis of wind effects on the natural or built environment to protect it from possible damage. It includes strong winds which may cause discomfort as well as extreme winds such as tornadoes, hurricanes and storms which may cause widespread destruction.

Wind engineering draws upon meteorology, aerodynamics, Geographic Information System, Wind energy, Air Pollution and a number of specialist engineering disciplines. The tools used include climate models, atmospheric boundary layer wind tunnels and numerical models. It involves, among other topics, how wind impacting buildings must be accounted for in engineering.

Wind engineering may be considered closely related to earthquake engineering and explosion protection.

48) LIST OF ENGINEERING TOPICS FOR LETTER "V"

Validation
The word validation has several uses:

In common usage, validation is the process of checking if something satisfies a certain criterion. Examples would include checking if a statement is true (validity), if an appliance works as intended, if a computer system is secure, or if computer data are compliant with an open standard. Validation implies one is able to document that a solution or process is correct or is suited for its intended use.
In engineering or as part of a quality management system, validation confirms that the needs of an external customer or user of a product, service, or system are met. Verification is usually an internal quality process of determining compliance with a regulation, standard, or specification. An easy way of recalling the difference between validation and verification is that validation is ensuring "you built the right product" and verification is ensuring "you built the product right." Validation is confirming that it satisfies stakeholder's or user's needs.
Validation can mean to declare or make legally valid or to prove valid or confirm the validity of data, information, or processes:
Validation of foreign studies and degrees.
In computer terminology, validation refers to the process of data validation, controlling that data inserted into an application satisfies pre determined formats or complies with stated length and character requirements and other defined input criteria.
In computer security, validation also refers to the process of assuring or authorizing that a user or computer program is allowed to do something.
In computer security, programs such as Validate (McAfee) are used to check program and data checksum values.
In the computer architecture and hardware world, validation refers to the process of verifying that the operations of the piece of hardware or architecture meets the specification. In some cases, validation not only refers to finding bugs in the hardware but also proving absence of certain critical bugs which may not have workarounds and may lead to project cancellation or product recall.
In psychology and human communication, validation is the reciprocated communication of respect which communicates that the other's opinions are acknowledged, respected, heard, and (regardless whether or not the listener actually agrees with the content), they are being treated with genuine respect as a legitimate expression of their feelings, rather than marginalized or dismissed.
In research psychology, validation is part of developing a test or questionnaire. A validated test has been shown to measure what it purports to measure, for example, showing that people with high scores on a questionnaire about risk-taking actually do take more risks than people with low scores. Compare to reliability, which means that the different items on a test all get at the same thing.
In the medical device, pharmaceutical and biotechnology manufacturing industries, validation refers to establishing documented evidence that a process or system, when operated within established parameters, can perform effectively and reproducibly to produce a medicinal product meeting its pre-determined specifications and quality attributes (from European Union Good Manufacturing Practices Guide, Annex 15). Regulatory bodies in the U.S., European Union, and Japan (amongst many others) require validation, causing it to become its own sub-industry supporting the pharmaceutical, biotechnology, and medical device industries.
in finance, validation is a process part of the "trade life-cycle."
Validation is important because it disallows data that can not possibly be either true or real to be entered into a database or computer system.
Validation against an incomplete or insufficient set of criteria can lead to a state of "validated" where "validated" does not confer the confidence that the term intends. Thus validation of the validation criteria is an important aspect that is often overlooked. Establishing such validation criteria can be a very difficult task when evaluating complex systems such as Air Traffic Management systems. Establishing "fitness for purpose" is often a more useful concept to support evaluation of complex systems in that the approach focuses on involving stakeholders in establishing and reviewing the purpose that the system must satisfy as the system emerges from early design. This allows flexibility in the evaluation process as ideas turn into detailed designs. Such flexibility is essential in the early development phases in order to avoid engineering white elephants. [The European Operational Concept Validation Methodology E-OCVM provides an approach to validating complex Air Traffic Management systems by establishing fitness for purpose in a world of shifting and incomplete validation criteria].

Varistor
A varistor is an electronic component with a significant non-ohmic current–voltage characteristic. The name is a portmanteau of variable resistor. Varistors are often used to protect circuits against excessive transient voltages by incorporating them into the circuit in such a way that, when triggered, they will shunt the current created by the high voltage away from the sensitive components. A varistor is also known as Voltage Dependent Resistor or VDR. A varistor’s function is to conduct significantly increased current when voltage is excessive.

*Note: only non-ohmic variable resistors are usually called varistors. Other, ohmic types of variable resistor include the potentiometer and the rheostat.


Euclidean vector
The magnitude of the vector is the length of the segment and the direction characterizes the displacement of B relative to A: how much one should move the point A to "carry" it to the point B. Many algebraic operations on real numbers such as addition, subtraction, multiplication, and negation have close analogues for vectors, operations which obey the familiar algebraic laws of commutativity, associativity, and distributivity. These operations and associated laws qualify Euclidean vectors as an example of the more generalized concept of a vector space.

Vectors play an important role in physics: velocity and acceleration of a moving object and forces acting on a body are all described by vectors. Many other physical quantities can be usefully thought of as vectors. The mathematical representation of a physical vector depends on the coordinate system used to describe it. Other vector-like objects that describe physical quantities and transform in a similar way under changes of the coordinate system include pseudovectors and tensors.


Vibration control
In earthquake engineering, vibration control is a set of technical means aimed to mitigate seismic impacts in building and non-building structures.

All seismic vibration control devices may be classified as passive, active or hybrid where:


Base isolator being tested at the UCSD Caltrans-SRMD facilitypassive control devices have no feedback capability between them, structural elements and the ground;
active control devices incorporate real-time recoding instrumentation on the ground integrated with earthquake input processing equipment and actuators within the structure;
hybrid control devices have combined features of active and passive control systems.
When ground seismic waves reach up and start to penetrate a base of a building, their energy flow density, due to reflections, reduces dramatically: usually, up to 90%. However, the remaining portions of the incident waves during a major earthquake still bear a huge devastating potential.

After the seismic waves enter a superstructure, there is a number of ways to control them in order to sooth their damaging effect and improve the building's seismic performance, for instance:

to dissipate the wave energy inside a superstructure with properly engineered dampers;
to disperse the wave energy between a wider range of frequencies;
to absorb the resonant portions of the whole wave frequencies band with the help of so called mass dampers

Volt
The volt (symbol: V) is the SI derived unit of electromotive force, commonly called "voltage (difference)". It is also the unit for the related but slightly different quantity electric potential difference (also called "electrostatic potential difference"). It is named in honor of the Lombard physicist Alessandro Volta (1745–1827), who invented the voltaic pile, possibly the first chemical battery (see Baghdad Battery).

47) LIST OF ENGINEERING TOPICS FOR LETTER "U"

Uncertainty principle
In quantum physics, the Heisenberg uncertainty principle states that certain pairs of physical properties, like position and momentum, cannot both be known to arbitrary precision. That is, the more precisely one property is known, the less precisely the other can be known. It is impossible to measure simultaneously both position and velocity of a microscopic particle with any degree of accuracy or certainty. This is not a statement about the limitations of a researcher's ability to measure particular quantities of a system, but rather about the nature of the system itself and hence it expresses a property of the universe.

In quantum mechanics, a particle is described by a wave. The position is where the wave is concentrated and the momentum is the wavelength. The position is uncertain to the degree that the wave is spread out, and the momentum is uncertain to the degree that the wavelength is ill-defined.

The only kind of wave with a definite position is concentrated at one point, and such a wave has an indefinite wavelength. Conversely, the only kind of wave with a definite wavelength is an infinite regular periodic oscillation over all space, which has no definite position. So in quantum mechanics, there are no states that describe a particle with both a definite position and a definite momentum. The more precise the position, the less precise the momentum.

The uncertainty principle can be restated in terms of measurements, which involves collapse of the wavefunction. When the position is measured, the wavefunction collapses to a narrow bump near the measured value, and the momentum wavefunction becomes spread out. The particle's momentum is left uncertain by an amount inversely proportional to the accuracy of the position measurement. The amount of left-over uncertainty can never be reduced below the limit set by the uncertainty principle, no matter what the measurement process.


Unreinforced masonry building
Unreinforced masonry building (or UMB) is a type of building where load bearing walls, non-load bearing walls, or other structures such as chimneys are made of brick, cinderblock, tiles, adobe, or other masonry material that is not braced by reinforcing beams. The term is used as a classification of certain structures for earthquake safety purposes, and is subject to some variation from place to place.

UMB structures are vulnerable to collapse in an earthquake. One problem is that most mortar used to hold bricks together is not strong enough.Additionally, masonry elements may "peel" from the building and fall onto occupants or passersby outside.

In California, construction of new unreinforced masonry buildings was prohibited in 1933, and state law enacted in 1986 required seismic retrofitting of existing structures. Retrofits are relatively expensive, and may include tying the building to its foundation, tying building elements (such as roof and walls) to each other so that the building moves as a single unit rather than creating internal shear during an earthquake, attaching walls more securely to underlying supports so that they do not buckle and collapse, and bracing or removing parapets and other unsecured decorative elements. Retrofits are generally intended to prevent injury and death to people, not to protect the building itself.

The California law left implementation, and standards, up to local jurisdictions. Compliance took many years. As of 2008 most but not all unreinforced masonry buildings have undergone some retrofitting.

46) LIST OF ENGINEERING TOPICS FOR LETTER "R"

Chemical kinetics
Chemical kinetics, also known as reaction kinetics, is the study of rates of chemical processes. Chemical kinetics includes investigations of how different experimental conditions can influence the speed of a chemical reaction and yield information about the reaction's mechanism and transition states, as well as the construction of mathematical models that can describe the characteristics of a chemical reaction. In 1864, Peter Waage and Cato Guldberg pioneered the development of chemical kinetics by formulating the law of mass action, which states that the speed of a chemical reaction is proportional to the quantity of the reacting substances.

Reliability engineering
Reliability engineering is an engineering field, that deals with the study of reliability: the ability of a system or component to perform its required functions under stated conditions for a specified period of time. It is often reported in terms of a probability.


Resistor
A resistor is a two-terminal electronic component that produces a voltage across its terminals that is proportional to the electric current through it in accordance with Ohm's law:

V = IR
Resistors are elements of electrical networks and electronic circuits and are ubiquitous in most electronic equipment. Practical resistors can be made of various compounds and films, as well as resistance wire (wire made of a high-resistivity alloy, such as nickel/chrome).

The primary characteristics of a resistor are the resistance, the tolerance and the power rating. Other characteristics include temperature coefficient, noise, and inductance. Less well-known is critical resistance, the value below which power dissipation limits the maximum permitted current flow, and above which the limit is applied voltage. Critical resistance depends upon the materials constituting the resistor as well as its physical dimensions; it's determined by design.

Resistors can be integrated into hybrid and printed circuits, as well as integrated circuits. Size, and position of leads (or terminals) are relevant to equipment designers; resistors must be physically large enough not to overheat when dissipating their power.

Resonator
A resonator is a device or system that exhibits resonance or resonant behavior, that is, it naturally oscillates at some frequencies, called its resonance frequencies, with greater amplitude than at others. Although its usage has broadened, the term usually refers to a physical object that oscillates at specific frequencies because its dimensions are an integral multiple of the wavelength at those frequencies. The oscillations or waves in a resonator can be either electromagnetic or mechanical (including acoustic). Resonators are used to either generate waves of specific frequencies or to select specific frequencies from a signal. Musical instruments use acoustic resonators that produce sound waves of specific tones.

A cavity resonator, usually used in reference to electromagnetic resonators, is one in which the waves exist in a hollow space inside the device. Acoustic cavity resonators, in which sound is produced by air vibrating in a cavity with one opening, are known as Helmholtz resonators.


Robot
A robot is a virtual or mechanical artificial agent. In practice, it is usually an electro-mechanical system which, by its appearance or movements, conveys a sense that it has intent or agency of its own. The word robot can refer to both physical robots and virtual software agents, but the latter are usually referred to as bots. There is no consensus on which machines qualify as robots, but there is general agreement among experts and the public that robots tend to do some or all of the following: move around, operate a mechanical limb, sense and manipulate their environment, and exhibit intelligent behavior, especially behavior which mimics humans or other animals.

45) LIST OF ENGINEERING TOPICS FOR LETTER "Q"

Quality (business)
Quality in business, engineering and manufacturing has a pragmatic interpretation as the non-inferiority or superiority of something. Quality is a perceptual, conditional and somewhat subjective attribute and may be understood differently by different people. Consumers may focus on the specification quality of a product/service, or how it compares to competitors in the marketplace. Producers might measure the conformance quality, or degree to which the product/service was produced correctly.

Numerous definitions and methodologies have been created to assist in managing the quality-affecting aspects of business operations. Many different techniques and concepts have evolved to improve product or service quality. There are two common quality-related functions within a business. One is quality assurance which is the prevention of defects, such as by the deployment of a quality management system and preventative activities like FMEA. The other is quality control which is the detection of defects, most commonly associated with testing which takes place within a quality management system typically referred to as verification and validation.


Quality control
In engineering and manufacturing, quality control and quality engineering are used in developing systems to ensure products or services are designed and produced to meet or exceed customer requirements. Refer to the definition by Merriam-Webster for further information. These systems are often developed in conjunction with other business and engineering disciplines using a cross-functional approach.

Quality control is the branch of engineering and manufacturing which deals with assurance and failure testing in design and production of products or services, to meet or exceed customer requirements.


Quantum hydrodynamics
Quantum hydrodynamics (QHD) is most generally the study of hydrodynamic systems which demonstrate behavior implicit in quantum subsystems (usually quantum tunneling). They arise in semiclassical mechanics in the study of semiconductor devices, in which case being derived from the Wigner-Boltzmann equation. In quantum chemistry they arise as solutions to chemical kinetic systems, in which case they are derived from the Schrodinger equation by way of Bohmian mechanics.

An important system of study in quantum hydrodynamics is that of superfluidity. Some other topics of interest in quantum hydrodynamics are quantum turbulence, quantized vortices, first, second and third sound, and quantum solvents. The quantum hydrodynamic equation is an equation in Bohmian mechanics, which, it turns out, has a mathematical relationship to classical fluid dynamics. This is a rich theoretical field.

Some common experimental applications of these studies are in liquid helium (He-3 and He-4), and of the interior of neutron stars and the quark-gluon plasma. Many famous scientists have worked in quantum hydrodynamics, including Richard Feynman, Lev Landau, and Pyotr L. Kapitsa.


Quantum mechanics
Quantum mechanics is a set of principles underlying the most fundamental known description of all physical systems at the submicroscopic scale (at the atomic level). Notable among these principles are both a dual wave-like and particle-like behavior of matter and radiation, and prediction of probabilities in situations where classical physics predicts certainties. Classical physics can be derived as a good approximation to quantum physics, typically in circumstances with large numbers of particles. Thus quantum phenomena are particularly relevant in systems whose dimensions are close to the atomic scale, such as molecules, atoms, electrons, protons and other subatomic particles. Exceptions exist for certain systems which exhibit quantum mechanical effects on macroscopic scale; superfluidity is one well-known example. Quantum theory provides accurate descriptions for many previously unexplained phenomena such as black body radiation and stable electron orbits. It has also given insight into the workings of many different biological systems, including smell receptors and protein structures.

44) LIST OF ENGINEERING TOPICS FOR LETTER "P"

Petroleum engineering

Petroleum engineering is an engineering discipline concerned with the subsurface activities related to the production of hydrocarbons, which can be either crude oil or natural gas. These activities are deemed to fall within the upstream sector of the oil and gas industry, which are the activities of finding and producing hydrocarbons. (Refining and distribution to a market are referred to as the downstream sector.) Exploration, by earth scientists, and petroleum engineering are the oil and gas industry's two main subsurface disciplines, which focus on maximizing economic recovery of hydrocarbons from subsurface reservoirs. Petroleum geology and geophysics focus on provision of a static description of the hydrocarbon reservoir rock, while petroleum engineering focuses on estimation of the recoverable volume of this resource using a detailed understanding of the physical behavior of oil, water and gas within porous rock at very high pressure.

The combined efforts of explorationists and petroleum engineers throughout the life of a hydrocarbon accumulation determine the way in which a reservoir is developed and depleted, and usually they have the highest impact on field economics. Petroleum engineering requires a good knowledge of many other related disciplines, such as geophysics, petroleum geology, formation evaluation (well logging), drilling, economics, reservoir simulation, well engineering, artificial lift systems, and oil & gas facilities engineering.


Phase angle
In the context of vectors and phasors, the term phase angle refers to the angular component of the polar coordinate representation. The notation for a vector with magnitude (or amplitude) A and phase angle ?, is called angle notation.

Physical compression
Physical compression is the result of the subjection of a material to compressive stress, resulting in reduction of volume. The opposite of compression is rarefraction tension.

PIN diode
A PiN diode is a diode with a wide, lightly doped 'near' intrinsic semiconductor region between a p-type semiconductor and an n-type semiconductor regions. The p-type and n-type regions are typically heavily doped because they are used for ohmic contacts.

The wide intrinsic region is in contrast to an ordinary PN diode. The wide intrinsic region makes the PIN diode an inferior rectifier (the normal function of a diode), but it makes the PIN diode suitable for attenuators, fast switches, photodetectors, and high voltage power electronics applications.


Plasticity (physics)
In physics and materials science, plasticity describes the deformation of a material undergoing non-reversible changes of shape in response to applied forces. For example, a solid piece of metal or plastic being bent or pounded into a new shape displays plasticity as permanent changes occur within the material itself. By contrast, a permanent crease in a sheet of paper or a re-shaping of wet clay is due to a rearrangement of separate fibers or particles. In engineering, the transition from elastic behavior to plastic behavior is called yield

Poisson's ratio
Poisson's ratio (?), named after Siméon Poisson, is the ratio, when the sample is stretched, of the contraction or transverse strain (normal to the applied load), to the extension or axial strain (in the direction of the applied load).

When a sample cube of a material is stretched in one direction, it tends to contract (or occasionally, expand) in the other two directions perpendicular to the direction of stretch. Conversely, when a sample of material is compressed in one direction, it tends to expand (or rarely, contract) in the other two directions. This phenomenon is called the Poisson effect. Poisson's ratio ? (nu) is a measure of the Poisson effect.


Positive feedback
Positive feedback, sometimes referred to as "cumulative causation", is a feedback loop system in which the system responds to perturbation in the same direction as the perturbation. In contrast, a system that responds to the perturbation in the opposite direction is called a negative feedback system. These concepts were first recognized as broadly applicable by Norbert Wiener in his 1948 work on cybernetics

Potential difference
In the physics of electrical circuits, the term potential difference or p.d. is sometimes used as an old-fashioned synonym for the modern quantity known as "the voltage (difference) between two positions in an electrical circuit". Following the discovery of the electron by J.J. Thomson in 1897, and later discoveries about electron behaviour and the role of electrons in the conduction of electricity in metals, it is now known that a "voltage difference" (as measured with a voltmeter) is not the same scientific quantity as the pre-atomic-era physical quantity "electric potential difference" (discussed, for example, by Maxwell in the 1891 edition of textbook. A treatise on electricity and magnetism (Vol. 1). Oxford: Clarendon. first printed 1891, reprinted 1998. ISBN 0-19-850373-3. In the context of electrical circuits, use of the term "potential difference" as a synonym for voltage (difference) is dropping out of use. This may be partly because science has no name (other than voltage) for the potential concerned, partly because of the possibility of confusion between the terms "potential difference" and "electric potential difference", which nowadays refer to different physical things. Use of the term "potential difference" as a synonym for voltage (difference) should be regarded as obsolescent/obsolete, and it is recommended that it should not be employed.

For further information on the science involved, see the articles on Voltage and Electric potential.

It is quite common for physics undergraduates either to be taught (incorrectly) that "electric potential difference" and "voltage difference" mean the same thing, or for the issue of "what voltage really is" to be avoided (presumably, on the grounds that this is too complicated for them to understand). Some older textbooks are also incorrect or ambiguous, or do not discuss the issue. However, some advanced solid-state textbooks (e.g., Ashcroft and Merrin Solid State Physics. New York: Holt, Reinhart and Winston. 1976. - see section on Thermoelectric Power) do clearly acknowledge that in principle voltmeters do not measure electric potential difference.

Part of the problem with electricity is that real electric currents involve the flow of electrons in the opposite direction to conventional current; another part of the problem is that electrons are subject to "chemical" effects as well as "electrostatic" effects. This kind of difficulty does not arise in many other areas of physics (e.g., the theory of gravitation): in these areas, there is a unique definition of a related potential, and "potential difference" can be defined without ambiguity as the difference in the related potential.

43) LIST OF ENGINEERING TOPICS FOR LETTER "O"

Observability
Observability, in control theory, is a measure for how well internal states of a system can be inferred by knowledge of its external outputs. The observability and controllability of a system are mathematical duals.

Formally, a system is said to be observable if, for any possible sequence of state and control vectors, the current state can be determined in finite time using only the outputs (this definition is slanted towards the state space representation). Less formally, this means that from the system's outputs it is possible to determine the behaviour of the entire system. If a system is not observable, this means the current values of some of its states cannot be determined through output sensors: this implies that their value is unknown to the controller and, consequently, that it will be unable to fulfil the control specifications referred to these outputs.


Ohm's law
Ohm's law applies to electrical circuits; it states that the current through a conductor between two points is directly proportional to the potential difference or voltage across the two points, and inversely proportional to the resistance between them.

Operational amplifier
An operational amplifier, which is often called an op-amp, is a DC-coupled high-gain electronic voltage amplifier with differential inputs and, usually, a single output. Typically the output of the op-amp is controlled either by negative feedback, which largely determines the magnitude of its output voltage gain, or by positive feedback, which facilitates regenerative gain and oscillation. High input impedance at the input terminals (ideally infinite) and low output impedance (ideally zero) are important typical characteristics.

Op-amps are among the most widely used electronic devices today, being used in a vast array of consumer, industrial, and scientific devices. Many standard IC op-amps cost only a few cents in moderate production volume; however some integrated or hybrid operational amplifiers with special performance specifications may cost over $100 US in small quantities.

Modern designs are electronically more rugged than earlier implementations and some can sustain direct short circuits on their outputs without damage.

The op-amp is one type of differential amplifier. Other types of differential amplifier include the fully differential amplifier (similar to the op-amp, but with 2 outputs), the instrumentation amplifier (usually built from 3 op-amps), the isolation amplifier (similar to the instrumentation amplifier, but which works fine with common-mode voltages that would destroy an ordinary op-amp), and negative feedback amplifier (usually built from 1 or more op-amps and a resistive feedback network).

Optimal control
Optimal control theory, an extension of the calculus of variations, is a mathematical optimization method for deriving control policies. The method is largely due to the work of Lev Pontryagin and his collaborators in the Soviet Union and Richard Bellman in the United States.

42) LIST OF ENGINEERING TOPICS FOR LETTER "N"

Nanoengineering
Nanoengineering is the practice of engineering on the nanoscale. It derives its name from the nanometre, a unit of measurement equalling one billionth of a meter.

Nanoengineering is closely related to nanotechnology.

The first nanoengineering program in the world was started at the University of Toronto within the Engineering Science program as one of the Options of study in the final years. In 2005, the University of Waterloo established a unique program which offers a full degree in Nanotechnology Engineering. The University of California, San Diego followed shortly thereafter in 2007 with its own department of Nanoengineering.


Nanotechnology
Nanotechnology, shortened to "Nanotech", is the study of the control of matter on an atomic and molecular scale. Generally nanotechnology deals with structures of the size 100 nanometers or smaller, and involves developing materials or devices within that size. Nanotechnology is very diverse, ranging from novel extensions of conventional device physics, to completely new approaches based upon molecular self-assembly, to developing new materials with dimensions on the nanoscale, even to speculation on whether we can directly control matter on the atomic scale.

There has been much debate on the future of implications of nanotechnology. Nanotechnology has the potential to create many new materials and devices with wide-ranging applications, such as in medicine, electronics, and energy production. On the other hand, nanotechnology raises many of the same issues as with any introduction of new technology, including concerns about the toxicity and environmental impact of nanomaterials , and their potential effects on global economics, as well as speculation about various doomsday scenarios. These concerns have led to a debate among advocacy groups and governments on whether special regulation of nanotechnology is warranted.

Negative feedback
Negative feedback occurs when the output of a system acts to oppose changes to the input of the system; with the result that the changes are attenuated. If the overall feedback of the system is negative, then the system will tend to be stable.

Nonlinear control
Nonlinear control is the area of control engineering specifically involved with systems that are nonlinear, time-variant, or both. Many well-established analysis and design techniques exist for LTI systems (e.g., root-locus, Bode plot, Nyquist criterion, state-feedback, pole placement); however, one or both of the controller and the system under control in a general control system may not be an LTI system, and so these methods cannot necessarily be applied directly. Nonlinear control theory studies how to apply existing linear methods to these more general control systems. Additionally, it provides novel control methods that cannot be analyzed using LTI system theory. Even when LTI system theory can be used for the analysis and design of a controller, a nonlinear controller can have attractive characteristics (e.g., simplier implementation, increased speed, or decreased control energy); however, nonlinear control theory usually requires more rigorous mathematical analysis to justify its conclusions.

Nuclear engineering
Nuclear engineering is the application of the breakdown of atomic nuclei and/or other sub-atomic physics, based on the principles of nuclear physics. It includes, but is not limited to, the interaction and maintenance of nuclear fission systems and components— specifically, nuclear reactors, nuclear power plants, and/or nuclear weapons. The field may also include the study of nuclear fusion, medical and other applications of (generally ionizing) radiation, nuclear safety, heat/thermodynamics transport, nuclear fuel and/or other related (e.g., waste disposal) technology, nuclear proliferation, and the effect of radioactive waste or radioactivity in the environment.

41) LIST OF ENGINEERING TOPICS FOR LETTER "M"

Machine
A machine is any device that uses energy to perform some activity. In common usage, the meaning is that of a device having parts that perform or assist in performing any type of work. A simple machine is a device that transforms the direction or magnitude of a force without consuming any energy. The word "machine" is derived from the Latin machina.

Magnetic circuit
The concept of a 'magnetic circuit' exploits a one to one correspondence between the equations of the magnetic field in a non-hysteretic material to that of an electrical circuit. Using this concept the magnetic fields of complex devices such as transformers can be quickly solved using the methods and techniques developed for electrical circuits.

A magnetic circuit is made up of one or more closed paths containing a magnetic flux. It generally contains magnetic elements such as permanent magnets, ferromagnetic materials, and electromagnets, but may also contain air gaps and other materials.

Some examples of magnetic circuits are:

horseshoe magnet with iron keeper (low-reluctance circuit)
horseshoe magnet with no keeper (high-reluctance circuit)
electric motor (variable-reluctance circuit)

Magnetic flux
Magnetic flux, represented by the Greek letter F (phi), is a measure of quantity of magnetism, taking into account the strength and the extent of a magnetic field. The SI unit of magnetic flux is the weber (in derived units: volt-seconds), and the unit of magnetic field is the weber per square meter, or tesla.



Magnetic moment
The magnetic moment of a system is a measurement of the magnetic strength and direction used in physics, astronomy, chemistry, and electrical engineering. More technically, the term magnetic moment of a system (such as a loop of electric current, a bar magnet, an electron, a molecule, or a planet) usually refers to its magnetic dipole moment, and quantifies the contribution of the system's internal magnetism to the external dipolar magnetic field produced by the system (that is, the component of the external magnetic field that drops off with distance as the inverse cube). Any dipolar magnetic field pattern is symmetric with respect to rotations around a particular axis, therefore it is customary to describe the magnetic dipole moment that creates such a field as a vector with a direction along that axis. For quadrupolar, octupolar, and higher-order multipole magnetic moments, see Multipole expansion.

Magnetostatics
Magnetostatics is the study of static magnetic fields. In electrostatics, the charges are stationary, whereas here, the currents are stationary or dc(direct current). As it turns out magnetostatics is a good approximation even when the currents are not static as long as the currents do not alternate rapidly.

Mass transfer
Mass transfer is the transfer of mass from high concentration to low concentration. The phrase is commonly used in engineering for physical processes that involve molecular and convective transport of atoms and molecules within physical systems. Mass transfer includes both fluid flow and separation unit operations.


Material
Material is synonymous with Substance, and is anything made of matter - hydrogen, air and water are all examples of materials. Sometimes the term Material is used more narrowly to refer to substances or components with certain physical properties which are used as inputs to production or manufacturing. In this sense, materials are the pieces required to make something else, from buildings and art to stars and computers.

A material can be anything: a finished product in its own right or an unprocessed raw material. Raw materials are first extracted or harvested from the earth and divided into a form that can be easily transported and stored, then processed to produce semi-finished materials. These can be input into a new cycle of production and finishing processes to create finished materials, ready for distribution, construction, and consumption.

An example of a raw material is cotton, which is harvested from plants, and can then be processed into thread (also considered a raw material), which can then be woven into cloth, a semi-finished material. Cutting and sewing the fabric turns it into a garment, which is a finished material. Steelmaking is another example—raw materials in the form of ore are mined, refined and processed into steel, a semi-finished material. Steel is then used as an input in many other industries to make finished products.

Maxwell's equations
In electromagnetism, Maxwell's equations are a set of four partial differential equations that describe the properties of the electric and magnetic fields and relate them to their sources, charge density and current density. These equations are used to show that light is an electromagnetic wave. Individually, the equations are known as Gauss's law, Gauss's law for magnetism, Faraday's law of induction, and Ampère's law with Maxwell's correction.

These four equations, together with the Lorentz force law are the complete set of laws of classical electromagnetism. The Lorentz force law itself was actually derived by Maxwell under the name of "Equation for Electromotive Force" and was one of an earlier set of eight Maxwell's equations.

Measurement
Measurement is the process of assigning a number to an attribute (or phenomenon) according to a rule or set of rules. The term can also be used to refer to the result obtained after performing the process.

Mechanics
Mechanics (Greek ???a????) is the branch of physics concerned with the behaviour of physical bodies when subjected to forces or displacements, and the subsequent effect of the bodies on their environment. The discipline has its roots in several ancient civilizations (see History of classical mechanics and Timeline of classical mechanics). During the early modern period, scientists such as Galileo, Kepler, and especially Newton, laid the foundation for what is now known as classical mechanics.

Mechatronics
Mechatronics (or Mechanical and Electronics Engineering) is the synergistic combination of mechanical engineering, electronic engineering, control engineering, systems design engineering, and computer engineering to create useful products. The purpose of this interdisciplinary engineering field is the study of automata from an engineering perspective and serves the purposes of controlling advanced hybrid systems. The word itself is a combination of 'Mechanics' and 'Electronics'.

Melting
Melting (sometimes called fusion) is a physical process that results in the phase change of a substance from a solid to a liquid. The internal energy of a solid substance is increased, typically by the application of heat or pressure, resulting in a rise of its temperature to the melting point, at which the rigid ordering of molecular entities in the solid breaks down to a less-ordered state and the solid liquefies. An object that has melted completely is molten.

Metallography
Metallography is the study of the physical structure and components of metals, typically using microscopy.

Ceramic and polymeric materials may also be prepared using metallographic techniques, hence the terms ceramography, plastography and, collectively, materialography.


Microcontroller
A microcontroller (also microcontroller unit, MCU or µC) is a small computer on a single integrated circuit consisting of a relatively simple CPU combined with support functions such as a crystal oscillator, timers, watchdog, serial and analog I/O etc. Program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a, typically small, read/write memory.

Microprocessor
A microprocessor incorporates most or all of the functions of a central processing unit (CPU) on a single integrated circuit (IC). The first microprocessors emerged in the early 1970s and were used for electronic calculators, using binary-coded decimal (BCD) arithmetic on 4-bit words. Other embedded uses of 4- and 8-bit microprocessors, such as terminals, printers, various kinds of automation etc, followed rather quickly. Affordable 8-bit microprocessors with 16-bit addressing also led to the first general purpose microcomputers in the mid-1970s. The recent development of fast microprocessors is also linked to the growing popularity of fourth generation programming languages.

Elastic modulus
An elastic modulus, or modulus of elasticity, is the mathematical description of an object or substance's tendency to be deformed elastically (i.e., non-permanently) when a force is applied to it. The elastic modulus of an object is defined as the slope of its stress-strain curve in the elastic deformation region:

Moment (physics)
In physics, the term "moment" can refer to many different concepts:

Moment of force (often just moment) is a synonym for torque, an important basic concept in physics, civil engineering, and mechanical engineering. In the context of mechanical engineering, the terms are not necessarily interchangeable, but one or the other may be preferred in a specific context. For example, "torque" is usually used to describe a rotational force of a shaft, for example a turning screw-driver, while "moment" is more often used to describe a bending force on a beam.
Moment arm is a quantity used when calculating torque. See the article torque.
The Principle of moments is a theorem concerning torques. See the article torque.

40) LIST OF ENGINEERING TOPICS FOR LETTER "L"

Laser diode
A laser diode is a laser where the active medium is a semiconductor similar to that found in a light-emitting diode. The most common and practical type of laser diode is formed from a p-n junction and powered by injected electric current. These devices are sometimes referred to as injection laser diodes to distinguish them from (optically) pumped laser diodes, which are more easily produced in the laboratory.

Newton's law of universal gravitation
Newton's law of universal gravitation is an empirical physical law describing the gravitational attraction between bodies with mass. It is a part of classical mechanics and was first formulated in Newton's work Philosophiae Naturalis Principia Mathematica, first published on 5 July 1687. In modern language it states the following:

Every point mass attracts every other point mass by a force pointing along the line intersecting both points. The force is directly proportional to the product of the two masses and inversely proportional to the square of the distance between the point masses:


Light-emitting diode
A light-emitting diode (LED) (pronounced /??li?'di?/, or just /l?d/), is an electronic light source. The LED was first invented in Russia in the 1920s, and introduced in America as a practical electronic component in 1962. Oleg Vladimirovich Losev was a radio technician who noticed that diodes used in radio receivers emitted light when current was passed through them. In 1927, he published details in a Russian journal of the first ever LED.

All early devices emitted low-intensity red light, but modern LEDs are available across the visible, ultraviolet and infra red wavelengths, with very high brightness.

LEDs are based on the semiconductor diode. When the diode is forward biased (switched on), electrons are able to recombine with holes and energy is released in the form of light. This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor. The LED is usually small in area (less than 1 mm2) with integrated optical components to shape its radiation pattern and assist in reflection.

LEDs present many advantages over traditional light sources including lower energy consumption, longer lifetime, improved robustness, smaller size and faster switching. However, they are relatively expensive and require more precise current and heat management than traditional light sources.

Applications of LEDs are diverse. They are used as low-energy indicators but also for replacements for traditional light sources in general lighting and automotive lighting. The compact size of LEDs has allowed new text and video displays and sensors to be developed, while their high switching rates are useful in communications technology.


Lorentz force
In physics, the Lorentz force is the force on a point charge due to electromagnetic fields. It is given by the following equation in terms of the electric and magnetic fields:


where

F is the force (in newtons)
E is the electric field (in volts per metre)
B is the magnetic field (in teslas)
q is the electric charge of the particle (in coulombs)
v is the instantaneous velocity of the particle (in metres per second)
× is the vector cross product
? and ? × are gradient and curl, respectively
or equivalently the following equation in terms of the vector potential and scalar potential:

39) LIST OF ENGINEERING TOPICS FOR LETTER "K"

Kelvin
The kelvin (symbol: K) is a unit increment of temperature and is one of the seven SI base units. The Kelvin scale is a thermodynamic (absolute) temperature scale where absolute zero, the theoretical absence of all thermal energy, is zero (0 K). The Kelvin scale and the kelvin are named after the British physicist and engineer William Thomson, 1st Baron Kelvin (1824–1907), who wrote of the need for an "absolute thermometric scale". Unlike the degree Fahrenheit and degree Celsius, the kelvin is not referred to as a "degree", nor is it typeset with a degree symbol; that is, it is written K and not °K.

Kilogram-force
The unit kilogram-force (kgf or just kg) or kilopond (kp) is defined as the magnitude of the force exerted on one kilogram of mass by a 9.80665 m/s2 gravitational field (standard gravity, a conventional value approximating the average magnitude of gravity on Earth). So one kilogram-force is by definition equal to 9.80665 newtons.[1][2] Similarly a gram-force is 9.80665 millinewtons (or 0.00980665 newtons), and a milligram-force is 9.80665 micronewtons (or 9.80665×10-6 newtons).

The kilogram-force has never been a part of the International System of Units (SI), which was introduced in 1960. The SI unit of force is the newton.

Prior to this, the unit was widely used in much of the world; it is still in use for some purposes. The thrust of a rocket engine, for example, was measured in kilograms-force in 1940s Germany, in the Soviet Union (where it remained the primary unit for thrust in the Russian space program until at least the late 1980s), and it is still used today in China and sometimes by the European Space Agency.

It is also used for tension of bicycle spokes, for torque measured in "meter-kilograms", for pressure in kilograms per square centimeter, for the draw weight of bows in archery, and to define the "metric horsepower" (PS) as 75 metre-kiloponds per second.

The gram-force and kilogram-force were never well-defined units until the CGPM adopted a standard acceleration of gravity of 980.665 cm/s² for this purpose in 1901, though they had been used in low-precision measurements of force before that time.

A tonne-force, metric ton-force, megagram-force, or megapond (Mp) is 1000 kilograms-force.

The decanewton or dekanewton (daN) is used in some fields as an approximation to the kilogram-force, being exactly rather than approximately 10 newtons.


Kinematics
Kinematics (from Greek ???e??, kinein, to move) is the branch of classical mechanics that describes the motion of objects without consideration of the causes leading to the motion.

“ It is natural to begin this discussion by considering the various possible types of motion in themselves, leaving out of account for a time the causes to which the initiation of motion may be ascribed; this preliminary enquiry constitutes the science of Kinematics. — ET Whittaker ”

Kinematics is not to be confused with another branch of classical mechanics: analytical dynamics (the study of the relationship between the motion of objects and its causes), sometimes subdivided into kinetics (the study of the relation between external forces and motion) and statics (the study of the relations in a system at equilibrium). Kinematics also differs from dynamics as used in modern-day physics to describe time-evolution of a system.

The term kinematics is less common today than in the past, but still has a role in physics. (See analytical dynamics for more detail on usage). The term "kinematics" also finds use in biomechanics and animal locomotion.

The simplest application of kinematics is for particle motion, translational or rotational. The next level of complexity is introduced by the introduction of rigid bodies, which are collections of particles having time invariant distances amongst themselves. Rigid bodies might undergo translation and rotation or a combination of both. A more complicated case is the kinematics of a system of rigid bodies, possibly linked together by mechanical joints.

The kinematic description of fluid flow is even more complicated, and not generally thought of in the context of kinematics.

Kirchhoff's circuit laws
Kirchhoff's circuit laws are two equalities that deal with the conservation of charge and energy in electrical circuits, and were first described in 1845 by Gustav Kirchhoff. Widely used in electrical engineering, they are also called Kirchhoff's rules or simply Kirchhoff's laws (see also Kirchhoff's laws for other meanings of that term).

Both circuit rules can be directly derived from Maxwell's equations, but Kirchhoff preceded Maxwell and instead generalized work by Georg Ohm.



Knurling
Knurling is a manufacturing process, typically conducted on a lathe, whereby a visually-attractive diamond-shaped (criss-cross) pattern is cut or rolled into metal. This pattern allows hands or fingers to get a better grip on the knurled object than would be provided by the originally-smooth metal surface. Occasionally, the knurled pattern is a series of straight ridges or a helix of "straight" ridges rather than the more-usual criss-cross pattern.

Knurling may also be used as a repair method: because a rolled-in knurled surface has raised-up areas surrounding the depressed areas, these raised areas can make up for wear on the part. In the days when labor was cheap and parts expensive, this repair method was feasible on pistons of internal combustion engines, where the skirt of a worn piston was expanded back to the nominal size using a knurling process. As auto parts have become less expensive, knurling has become less prevalent than it once was, and is specifically recommended against by performance engine builders.

Knurling can also be used when a high precision component will be assembled into a low precision component, for example a metal pin into a plastic molding. The outer surface of the metal pin is knurled so that the raised detail 'bites' into the plastic irrespective of whether the size of the hole in the plastic closely matches the diameter of the pin.

On the lathe, knurl cutting is usually accomplished using the same automatic-feed mechanisms that are used to cut screw threads; knurling can be thought of as simply a series of threads cut at extremely coarse pitch and in both the left-hand and right-hand directions.

More common than knurl cutting, knurl rolling is usually accomplished using one or more very hard rollers that contain the reverse of the pattern to be imposed. It is possible for a "straight" knurl (not criss-crossed) to be pressed with a single roller, however the material needs to be supported adequately to avoid deformation. A criss-cross pattern can be accomplished using any of:

A single roller that contains the reverse of the complete desired pattern. These are available to form either "male" or "female" patterns,
A left-handed straight roller followed by a right-handed straight roller (or vice-versa), or
One or more left-handed rollers used simultaneously with one or more right-handed rollers.
Rolled knurls are somewhat more complicated to design than cut knurls because the outer diameter of the work piece must be chosen to allow the roller to roll an integral number of patterns around the workpiece. By comparison, for cut knurls, the spacing of the cuts is not preset and can be adjusted to allow an integral number of patterns around the workpiece no matter what the diameter of the workpiece.

Hand knurling tools are available. These resemble pipecutters but contain knurling wheels rather than cutting wheels. Usually, three wheels are carried by the tool: two left-handed wheels and one right-handed wheel or vice-versa.