Glossary of engineering: A–L

{{defn|defn=is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond. The simplest acyclic alkynes with only one triple bond and no other functional groups form a homologous series with the general chemical formula {{chem2|C_{n}H_{2n−2}|}}.}} {{defn|defn=In particle physics, annihilation is the process that occurs when a subatomic particle collides with its respective antiparticle to produce other particles, such as an electron colliding with a positron to produce two photons. The total energy and momentum of the initial pair are conserved in the process and distributed among a set of other particles in the final state. Antiparticles have exactly opposite additive quantum numbers from particles, so the sums of all quantum numbers of such an original pair are zero. Hence, any set of particles may be produced whose total quantum numbers are also zero as long as conservation of energy and conservation of momentum are obeyed. {{cite web ==B==

{{defn|defn=also called beta ray or beta radiation (symbol β), is a high-energy, high-speed electron or positron emitted by the radioactive decay of an atomic nucleus during the process of beta decay. There are two forms of beta decay, β− decay and β+ decay, which produce electrons and positrons respectively. and occurs in Planck's law of black-body radiation and in Boltzmann's entropy formula. It was introduced by Max Planck, but named after Ludwig Boltzmann. It is the gas constant divided by the Avogadro constant : : k=\frac{R}{N_\text{A}} ..}} {{defn|defn=In quantum mechanics, a boson (, is an infinite array (or a finite array, if we consider the edges, obviously) of discrete points generated by a set of discrete translation operations described in three dimensional space by: :\mathbf{R}=n_{1}\mathbf{a}_{1} + n_{2}\mathbf{a}_{2} + n_{3}\mathbf{a}_{3} where ni are any integers and ai are known as the primitive vectors which lie in different directions (not necessarily mutually perpendicular) and span the lattice. This discrete set of vectors must be closed under vector addition and subtraction. For any choice of position vector R, the lattice looks exactly the same.}} {{defn|defn=Brownian motion, or pedesis, is the random motion of particles suspended in a fluid (a liquid or a gas) resulting from their collision with the fast-moving molecules in the fluid. {{cite book ==C==

{{defn|defn=In cell biology, the centrosome is an organelle that serves as the main microtubule organizing center (MTOC) of the animal cell as well as a regulator of cell-cycle progression. The centrosome is thought to have evolved only in the metazoan lineage of eukaryotic cells. and Benoît Paul Émile Clapeyron, is a way of characterizing a discontinuous phase transition between two phases of matter of a single constituent. On a pressure–temperature (P–T) diagram, the line separating the two phases is known as the coexistence curve. The Clausius–Clapeyron relation gives the slope of the tangents to this curve. Mathematically, :\frac{\mathrm{d}P}{\mathrm{d}T}=\frac{L}{T\,\Delta v}=\frac{\Delta s}{\Delta v}, where \mathrm{d}P/\mathrm{d}T is the slope of the tangent to the coexistence curve at any point, L is the specific latent heat, T is the temperature, \Delta v is the specific volume change of the phase transition, and \Delta s is the specific entropy change of the phase transition.}} {{defn|defn=The Clausius theorem (1855) states that a system exchanging heat with external reservoirs and undergoing a cyclic process, is one that ultimately returns a system to its original state, :\oint \frac{\delta Q}{T_{surr}} \leq 0, where \delta Q is the infinitesimal amount of heat absorbed by the system from the reservoir and T_{surr} is the temperature of the external reservoir (surroundings) at a particular instant in time. In the special case of a reversible process, the equality holds. The reversible case is used to introduce the entropy state function. This is because in a cyclic process the variation of a state function is zero. In words, the Clausius statement states that it is impossible to construct a device whose sole effect is the transfer of heat from a cool reservoir to a hot reservoir. Equivalently, heat spontaneously flows from a hot body to a cooler one, not the other way around. The generalized "inequality of Clausius" :dS > \frac{\delta Q}{T_{surr}} for an infinitesimal change in entropy S applies not only to cyclic processes, but to any process that occurs in a closed system.}} {{defn|defn=Cosmic rays are high-energy radiation, mainly originating outside the Solar System. The new definition defines the elementary charge (the charge of the proton) as exactly coulombs. This would implicitly define the coulomb as elementary charges.}} {{defn|defn=''Coulomb's law, or Coulomb's inverse-square law'', is a law of physics for quantifying Coulomb's force, or electrostatic force. Electrostatic force is the amount of force with which stationary, electrically charged particles either repel, or attract each other. This force and the law for quantifying it, represent one of the most basic forms of force used in the physical sciences, and were an essential basis to the study and development of the theory and field of classical electromagnetism. The law was first published in 1785 by French physicist Charles-Augustin de Coulomb. In its scalar form, the law is: : F=k_e\frac{q_1 q_2}{r^2}, where k is the Coulomb constant (k ≈ ), q and q are the signed magnitudes of the charges, and the scalar r is the distance between the charges. The force of the interaction between the charges is attractive if the charges have opposite signs (i.e., F is negative) and repulsive if like-signed (i.e., F is positive). Being an inverse-square law, the law is analogous to Isaac Newton's inverse-square law of universal gravitation. Coulomb's law can be used to derive Gauss's law, and vice versa.}} {{defn|defn=A cyclotron is a type of particle accelerator invented by Ernest O. Lawrence in 1929–1930 at the University of California, Berkeley, and patented in 1932. A cyclotron accelerates charged particles outwards from the center along a spiral path.{{cite web ==D==

{{defn|defn=In probability theory, the de Moivre–Laplace theorem, which is a special case of the central limit theorem, states that the normal distribution may be used as an approximation to the binomial distribution under certain conditions. In particular, the theorem shows that the probability mass function of the random number of "successes" observed in a series of n independent Bernoulli trials, each having probability p of success (a binomial distribution with n trials), converges to the probability density function of the normal distribution with mean np and standard deviation\sqrt{np(1-p)}, as n grows large, assuming p is not 0 or 1.}} {{defn|defn= The density, or more precisely, the volumetric mass density, of a substance is its mass per unit volume. The symbol most often used for density is ρ (the lower case Greek letter rho), although the Latin letter D can also be used. Mathematically, density is defined as mass divided by volume: : \rho=\frac{m}{V} where ρ is the density, m is the mass, and V is the volume. In some cases (for instance, in the United States oil and gas industry), density is loosely defined as its weight per unit volume, although this is scientifically inaccurate – this quantity is more specifically called specific weight.}} {{defn|defn=Direct integration is a structural analysis method for measuring internal shear, internal moment, rotation, and deflection of a beam. For a beam with an applied weight w(x) , taking downward to be positive, the internal shear force is given by taking the negative integral of the weight: : V(x)=-\int w(x)\, dx The internal moment M(x) is the integral of the internal shear: : M(x)=\int V(x)\, dx= -\int [\int w(x)\ \, dx] dx The angle of rotation from the horizontal, \theta, is the integral of the internal moment divided by the product of the Young's modulus and the area moment of inertia: : \theta (x)=\frac{1}{EI} \int M(x)\, dx Integrating the angle of rotation obtains the vertical displacement \nu : : \nu (x)=\int \theta (x) dx .}} {{defn|defn=In optics, dispersion is the phenomenon in which the phase velocity of a wave depends on its frequency. ==E==

{{defn|defn=is a flow of electric charge. In electric circuits this charge is often carried by moving electrons in a wire. It can also be carried by ions in an electrolyte, or by both ions and electrons such as in an ionised gas (plasma). ==F==

{{defn|defn=Denoted by the symbol and sometimes stylized as ℱ, is named after Michael Faraday. In physics and chemistry, this constant represents the magnitude of electric charge per mole of electrons. It has the value : This constant has a simple relation to two other physical constants: : F = eN_\text{A} where : : Both of these values have exact defined values, and hence F has a known exact value. NA is the Avogadro constant (the ratio of the number of particles, N, which is unitless, to the amount of substance, n, in units of moles), and e is the elementary charge or the magnitude of the charge of an electron. This relation holds because the amount of charge of a mole of electrons is equal to the amount of charge in one electron multiplied by the number of electrons in a mole.}} {{defn|defn=In optics, Fermat's principle, or the principle of least time, named after French mathematician Pierre de Fermat, is the principle that the path taken between two points by a ray of light is the path that can be traversed in the least time. This principle is sometimes taken as the definition of a ray of light. However, this version of the principle is not general; a more modern statement of the principle is that rays of light traverse the path of stationary optical length with respect to variations of the path. When a test fails to meet the thickness and other test requirements that are in place to ensure plane strain conditions, the fracture toughness value produced is given the designation K_\text{c}. Fracture toughness is a quantitative way of expressing a material's resistance to crack propagation and standard values for a given material are generally available.}} {{defn|defn=Is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction: • Dry friction is a force that opposes the relative lateral motion of two solid surfaces in contact. Dry friction is subdivided into static friction ("stiction") between non-moving surfaces, and kinetic friction between moving surfaces. With the exception of atomic or molecular friction, dry friction generally arises from the interaction of surface features, known as asperities (see Figure 1). • Fluid friction describes the friction between layers of a viscous fluid that are moving relative to each other.{{cite web ==G==

{{defn|defn=In mathematics, the geometric mean is a mean or average, which indicates the central tendency or typical value of a set of numbers by using the product of their values (as opposed to the arithmetic mean which uses their sum). The geometric mean is defined as the th root of the product of numbers, i.e., for a set of numbers , the geometric mean is defined as :\left(\prod_{i=1}^n x_i\right)^\frac{1}{n}=\sqrt[n]{x_1 x_2 \cdots x_n}}} {{defn|defn=''Graham's law of effusion (also called Graham's law of diffusion'') was formulated by Scottish physical chemist Thomas Graham in 1848. Graham found experimentally that the rate of effusion of a gas is inversely proportional to the square root of the mass of its particles. Close to the Earth's surface, the gravitational field is approximately constant, and the gravitational potential energy of an object reduces to :U=mgh where m is the object's mass, g=GM_E/R_E^2 is the gravity of Earth, and h is the height of the object's center of mass above a chosen reference level. Thus, a gravitational field is used to explain gravitational phenomena, and is measured in newtons per kilogram (N/kg). In its original concept, gravity was a force between point masses. Following Isaac Newton, Pierre-Simon Laplace attempted to model gravity as some kind of radiation field or fluid, and since the 19th century, explanations for gravity have usually been taught in terms of a field model, rather than a point attraction. In a field model, rather than two particles attracting each other, the particles distort spacetime via their mass, and this distortion is what is perceived and measured as a "force". In such a model one states that matter moves in certain ways in response to the curvature of spacetime, and that there is either no gravitational force, or that gravity is a fictitious force. ==H==

{{defn|defn=In mathematics, the harmonic mean (sometimes called the subcontrary mean) is one of several kinds of average, and in particular, one of the Pythagorean means. Typically, it is appropriate for situations when the average of rates is desired. The harmonic mean can be expressed as the reciprocal of the arithmetic mean of the reciprocals of the given set of observations. As a simple example, the harmonic mean of 1, 4, and 4 is : \left(\frac{1^{-1} + 4^{-1} + 4^{-1}}{3}\right)^{-1}=\frac{3}{\frac{1}{1} + \frac{1}{4} + \frac{1}{4}}=\frac{3}{1.5}=2\,.}} {{defn|defn=In chemistry and biochemistry, the Henderson–Hasselbalch equation :\ce{pH}=\ce{p}K_\ce{a} + \log_{10} \left( \frac{[\ce{Base}]}{[\ce{Acid}]} \right) can be used to estimate the pH of a buffer solution. The numerical value of the acid dissociation constant, Ka, of the acid is known or assumed. The pH is calculated for given values of the concentrations of the acid, HA and of a salt, MA, of its conjugate base, A−; for example, the solution may contain acetic acid and sodium acetate.}} ==I==

{{defn|defn=Also called the general gas equation, is the equation of state of a hypothetical ideal gas. It is a good approximation of the behavior of many gases under many conditions, although it has several limitations. It was first stated by Benoît Paul Émile Clapeyron in 1834 as a combination of the empirical Boyle's law, Charles's law, Avogadro's law, and Gay-Lussac's law. and Rudolf Clausius in 1857. {{cite journal {{defn|defn=Also known as a ramp, is a flat supporting surface tilted at an angle, with one end higher than the other, used as an aid for raising or lowering a load.{{cite book ==J==

{{defn|defn=The ' (J/psi) meson or psion' is a subatomic particle, a flavor-neutral meson consisting of a charm quark and a charm antiquark. Mesons formed by a bound state of a charm quark and a charm anti-quark are generally known as "charmonium". The is the most common form of charmonium, due to its spin of 1 and its low rest mass. The has a rest mass of , just above that of the (), and a mean lifetime of . This lifetime was about a thousand times longer than expected. {{cite press release ==K==

{{defn|defn=In fluid dynamics, laminar flow is characterized by fluid particles following smooth paths in layers, with each layer moving smoothly past the adjacent layers with little or no mixing. At low velocities, the fluid tends to flow without lateral mixing, and adjacent layers slide past one another like playing cards. There are no cross-currents perpendicular to the direction of flow, nor eddies or swirls of fluids. In laminar flow, the motion of the particles of the fluid is very orderly with particles close to a solid surface moving in straight lines parallel to that surface. {{defn|defn=In mathematics, more specifically calculus, L'Hôpital's rule or L'Hospital's rule (, , ) provides a technique to evaluate limits of indeterminate forms. Application (or repeated application) of the rule often converts an indeterminate form to an expression that can be easily evaluated by substitution. The rule is named after the 17th-century French mathematician Guillaume de l'Hôpital. Although the rule is often attributed to L'Hôpital, the theorem was first introduced to him in 1694 by the Swiss mathematician Johann Bernoulli. L'Hôpital's rule states that for functions and which are differentiable on an open interval except possibly at a point contained in , if \lim_{x\to c}f(x)=\lim_{x\to c}g(x)=0 \text{ or} \pm\infty, and g'(x)\ne 0 for all in with , and \lim_{x\to c}\frac{f'(x)}{g'(x)} exists, then :\lim_{x\to c}\frac{f(x)}{g(x)}=\lim_{x\to c}\frac{f'(x)}{g'(x)}. The differentiation of the numerator and denominator often simplifies the quotient or converts it to a limit that can be evaluated directly.}} ==M–Z==