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  • Dietz, Robert Sinclair (American geophysicist)

    Robert S. Dietz, American geophysicist and oceanographer who set forth a theory of seafloor spreading in 1961. Dietz was educated at the University of Illinois (B.S., 1937; M.S., 1939; Ph.D., 1941). After serving as an officer in the U.S. Army Air Corps during World War II, he became a civilian

  • Dieu (work by Hugo)

    Victor Hugo: Exile (1851–70): … (“The End of Satan”) and Dieu (“God”), both of them confrontations of the problem of evil. Written between 1854 and 1860, they were not published until after his death because his publisher preferred the little epics based on history and legend contained in the first installment (1859) of the gigantic…

  • Dieu du carnage, Le (play by Reza)

    Yasmina Reza: …Le Dieu du carnage (2006; God of Carnage), Reza focused on two couples who meet to discuss a fight between their young sons. The play made its London debut in 2008 and subsequently won a Laurence Olivier Award. The Broadway production of God of Carnage, which opened a year later,…

  • Dieudonné d’Artois, Henri-Charles-Ferdinand-Marie (French noble)

    Henri Dieudonné d’Artois, count de Chambord, last heir of the elder branch of the Bourbons and, as Henry V, pretender to the French throne from 1830. The posthumous son of the assassinated Charles-Ferdinand, Duke de Berry, and grandson of King Charles X, he was forced to flee France in 1830 when

  • Dieudonné, Jean (French mathematician)

    Jean Dieudonné, French mathematician and educator known for his writings on abstract algebra, functional analysis, topology, and his theory of Lie groups. Dieudonné was educated in Paris, receiving both his bachelor’s degree (1927) and his doctorate (1931) from the école Normale Supérieure. He was

  • Dieudonné, Jean-Alexandre-Eugène (French mathematician)

    Jean Dieudonné, French mathematician and educator known for his writings on abstract algebra, functional analysis, topology, and his theory of Lie groups. Dieudonné was educated in Paris, receiving both his bachelor’s degree (1927) and his doctorate (1931) from the école Normale Supérieure. He was

  • Dieulafoy, Marcel-Auguste (French archaeologist)

    Marcel-Auguste Dieulafoy, French archaeologist and civil engineer who excavated the palaces of the ancient Persian kings Darius I the Great and Artaxerxes II at Susa (modern Shūsh, Iran) in 1885 and gathered a large collection of archaeological fragments, which were placed in the Louvre.

  • Dieux ont soif, Les (work by France)

    French literature: The novel later in the century: …Les Dieux ont soif (1912; The Gods Are Athirst). For Anglophone readers right up to the end of World War II, he spoke for that Voltairean liberal humanism, reason, and justice of which France became the symbol in a Europe twice overrun by German imperial ambitions.

  • Dieva dēli (Baltic religion)

    Dievs: Dievs has two sons (Dieva dēli in Latvian; Dievo sūneliai in Lithuanian), who are known as the Heavenly Twins and the morning and evening stars. Like their Greek (Dioscuri) and Vedic (A?vins, or Nāsatyas) counterparts, Dieva dēli are skilled horsemen. They associate with Saules meita, the daughter of the…

  • Dievaitis (Baltic god)

    Mēness: …or “new,” moon, sometimes called Dievaitis (Lithuanian: “Little God,” or “Prince”), is especially receptive to human prayers and is honoured by farmers.

  • Dievas (Baltic god)

    Dievs, in Baltic religion, the sky god. Dievs and Laima, the goddess of human fate, determine human destiny and world order. Dievs is a wooer of Saule, the sun. As pictured by the pre-Christian Balts, he is an Iron Age Baltic king who lives on a farmstead in the sky. Wearing a silver gown,

  • Dievo sūneliai (Baltic religion)

    Dievs: Dievs has two sons (Dieva dēli in Latvian; Dievo sūneliai in Lithuanian), who are known as the Heavenly Twins and the morning and evening stars. Like their Greek (Dioscuri) and Vedic (A?vins, or Nāsatyas) counterparts, Dieva dēli are skilled horsemen. They associate with Saules meita, the daughter of the…

  • Dievs (Baltic god)

    Dievs, in Baltic religion, the sky god. Dievs and Laima, the goddess of human fate, determine human destiny and world order. Dievs is a wooer of Saule, the sun. As pictured by the pre-Christian Balts, he is an Iron Age Baltic king who lives on a farmstead in the sky. Wearing a silver gown,

  • Diexue shangxiong (film by Woo [1989])

    Chow Yun-Fat: …II ), Diexue shangxiong (1989; The Killer), Zongheng sihai (1991; Once a Thief), and Lat sau san taam (1992; Hard-Boiled). Chow also made several popular action films with director Ringo Lam, including Lung fu fong wan (1987; City on Fire), Ban wo chuang tian ya (1989; Wild Search), and Xia…

  • Diez, Friedrich Christian (German scholar)

    Friedrich Christian Diez, German-born language scholar who made the first major analysis of the Romance languages and thus founded an important branch of comparative linguistics. As a student Diez acquired a deep interest in Italian poetry, but a visit to the great German poet J.W. von Goethe in

  • Difang Hui (international religious group)

    The Local Church, international Evangelical Christian group founded in China in the 1930s and based on the belief that a city or town should have only one church. The Local Church grew out of the ministry of Watchman Nee (1903–72), a Chinese Christian who had been strongly influenced by the

  • Difaqane (African history)

    Mfecane, (Zulu: “The Crushing”) series of Zulu and other Nguni wars and forced migrations of the second and third decades of the 19th century that changed the demographic, social, and political configuration of southern and central Africa and parts of eastern Africa. The Mfecane was set in motion

  • Difda, Kaparusha Ahrah (American musician)

    Kalaparusha Maurice McIntyre, (Maurice Benford McIntyre; Kaparusha Ahrah Difda), American jazz musician (born March 24, 1936, Clarksville, Ark.—died Nov. 9, 2013, Bronx, N.Y.), played tenor saxophone with singular rhythmic poise and melodic flow and was a vital figure among 1960s free-jazz

  • Difesa di Dante (work by Gozzi)

    Gasparo, Count Gozzi: …known for verse satires and Difesa di Dante (1758; “Defense of Dante”), an attack on the critic Saviero Bettinelli for preferring Virgil to Dante as a model for Italian poets. More important was his publication and, in large part, his writing of two periodicals similar in style to those of…

  • différance (linguistics)

    Jacques Derrida: Life and work: …Saussure, Derrida coined the term différance, meaning both a difference and an act of deferring, to characterize the way in which linguistic meaning is created rather than given. For Derrida as for Saussure, the meaning of a word is a function of the distinctive contrasts it displays with other, related…

  • difference (heraldry)

    heraldry: Cadency: Cadency is the use of various devices designed to show a man’s position in a family, with the aforementioned basic aim of reserving the entire arms to the head of the family and to differentiate the arms of the rest, who are the cadets,…

  • Difference and Repetition (book by Deleuze)

    Gilles Deleuze: …vein, producing two major works, Difference and Repetition (1968) and The Logic of Sense (1969). In the former he argued against the devaluation of “difference” in Western metaphysics and tried to show that difference inheres in repetition itself.

  • Difference Between a Tribe and a Band

    Although many indigenous peoples, particularly those of Canada, have adopted the word nation in order to emphasize their sovereign political status, others continue to use the words tribe and band. Are all these terms interchangeable, or do they have specific meanings? To some extent, the answer to

  • Difference Engine (calculating machine)

    Difference Engine, an early calculating machine, verging on being the first computer, designed and partially built during the 1820s and ’30s by Charles Babbage. Babbage was an English mathematician and inventor; he invented the cowcatcher, reformed the British postal system, and was a pioneer in

  • Difference Engine No. 2 (mathematical device)

    Charles Babbage: In 1991 British scientists built Difference Engine No. 2—accurate to 31 digits—to Babbage’s specifications, and in 2000 the printer for the Difference Engine was also built.

  • difference equation

    Difference equation, mathematical equality involving the differences between successive values of a function of a discrete variable. A discrete variable is one that is defined or of interest only for values that differ by some finite amount, usually a constant and often 1; for example, the discrete

  • difference feminism (international relations)

    feminism: Dissension and debate: Finally, cultural or “difference” feminism, the last of the three currents, rejected the notion that men and women are intrinsically the same and advocated celebrating the qualities they associated with women, such as their greater concern for affective relationships and their nurturing preoccupation with others. Inherent…

  • Difference Machine No. 2 (mathematical device)

    Charles Babbage: In 1991 British scientists built Difference Engine No. 2—accurate to 31 digits—to Babbage’s specifications, and in 2000 the printer for the Difference Engine was also built.

  • difference principle (philosophy)

    political philosophy: Rawls: …first, known as the “difference principle,” requires that any unequal distribution of social or economic goods (e.g., wealth) must be such that the least-advantaged members of society would be better off under that distribution than they would be under any other distribution consistent with principle 1, including an equal…

  • difference quotient

    calculus: Calculating velocities and slopes: …gh/2 and is called the difference quotient of the function gt2/2. As h approaches 0, this formula approaches gt, which is interpreted as the instantaneous velocity of a falling body at time t.

  • difference set (mathematics)

    combinatorics: BIB (balanced incomplete block) designs: …said to form a perfect difference set mod υ, if among the k(k ? 1) differences di ? dj, i ≠ j, i, j = 0, 1, · · ·, k, reduced mod υ, each nonzero positive integer less than υ occurs exactly the same number of times λ. For…

  • difference tone (music)

    Giuseppe Tartini: … by his discovery of the difference tone, also called the Tartini tone, a third note heard when two notes are played steadily and with intensity. He also devised a theory of harmony based on affinities with algebra and geometry, set forth in his Trattato di musica (1754; “Treatise on Music”)…

  • différence, La (album by Keita)

    Salif Keita: …albinism in his 2009 release, La différence, a musical celebration of difference. Proceeds from the album were donated to his foundation.

  • difference-in-conditions insurance

    insurance: Miscellaneous insurance: …use of policies generally termed difference-in-conditions insurance (DIC). The DIC policy insures property and liability losses not covered by basic insurance contracts. It can be written to insure almost any peril, including earthquake and flood, subject to deductibles and stated exclusions. It is often written on an all-risk basis. An…

  • Différences (work by Berio)

    Luciano Berio: Différences (1958–59, revised 1967) contrasts live and prerecorded instruments. His Sequenza series (1958–2002) includes solo pieces for flute, harp, female voice (Sequenza III [1966] was written for performance by his former wife, soprano Cathy Berberian), piano, and

  • Differend: Phrases in Dispute, The (work by Lyotard)

    Jean-Fran?ois Lyotard: …his most important philosophical work, The Differend: Phrases in Dispute (1983), Lyotard compared discourses to “language games,” a notion developed in the later work of Ludwig Wittgenstein (1889–1951); like language games, discourses are discrete systems of rule-governed activity involving language. Because there is no common set of assumptions in terms…

  • Different Forms of Flowers on Plants of the Same Species, The (work by Darwin)

    Charles Darwin: The patriarch in his home laboratory: His next book, The Different Forms of Flowers on Plants of the Same Species (1877), was again the result of long-standing work into the way evolution in some species favoured different male and female forms of flowers to facilitate outbreeding. Darwin had long been sensitive to the effects…

  • Different from the Others (German documentary film [1919])

    Magnus Hirschfeld: …decriminalization and acceptance of homosexuality, Different from the Others (1919). The controversial film ignited much debate and was banned by German officials within a year. In 1928 Hirschfeld founded the World League for Sexual Reform (WLSR), which had its roots in an early conference that he had organized in 1921,…

  • Different Kind of Truth, A (album by Van Halen)

    Van Halen: A Different Kind of Truth, Van Halen’s first collection of new material in more than a decade, surfaced in 2012. The band’s second live album—and the first with Roth as frontman—was Tokyo Dome Live in Concert (2015).

  • Different Trains (work by Reich)

    Steve Reich: For Different Trains (1988), Reich integrated fragments of audio recordings pertaining to rail travel, including the reminiscences of Holocaust survivors, with a string quartet that mimicked both the rhythm of a train and the natural musicality of the voices on tape. The piece, as performed by…

  • Different World, A (American television program)

    The Cosby Show: It produced a spin-off program, A Different World (1987–93), set in a historically black college and initially focusing on Bonet’s Denise character.

  • differentia, definition by genus and

    Aristotelianism: Relationship to Neoplatonism: These were the concepts of genus, or kind (as animal is the genus, or kind, under which Socrates falls); species, or sort (Socrates is a man); differentia, or distinguishing characteristic (rationality distinguishes humans from other members of the genus animal); property (being capable of laughter was said to be a…

  • differentiable function (mathematics)

    mathematics: Making the calculus rigorous: …defined, the concepts of a differentiable function and an integrable function can be defined in terms of them. Unfortunately, neither of these concepts is easy to grasp, and the much-needed degree of precision they bring to mathematics has proved difficult to appreciate. Roughly speaking, a function is continuous at a…

  • differential (mathematics)

    Differential, in mathematics, an expression based on the derivative of a function, useful for approximating certain values of the function. The derivative of a function at the point x0, written as f′(x0), is defined as the limit as Δx approaches 0 of the quotient Δy/Δx, in which Δy is f(x0 + Δx) ?

  • differential analyzer (device)

    Differential analyzer, computing device for solving differential equations. Its principal components perform the mathematical operation of integration (see also integrator). The American electrical engineer Vannevar Bush and others at the Massachusetts Institute of Technology invented the first

  • Differential Aptitude Test (abilities test)

    aptitude test: The Differential Aptitude Test (DAT) measures specific abilities such as clerical speed and mechanical reasoning as well as general academic ability.

  • differential association (sociology)

    criminology: Sociological theories: …approaches include the theory of differential association, which claims that all criminal behaviour is learned and that the learning process is influenced by the extent of the individual’s contact with persons who commit crimes. The more an individual associates with such persons, the more likely it becomes that he will…

  • Differential Association-Reinforcement Theory of Criminal Behavior, A (work by Akers and Burgess)

    Ronald L. Akers: Burgess and published as “A Differential Association-Reinforcement Theory of Criminal Behavior” (1966), drew upon earlier work by the American criminologist Edwin Sutherland and the American psychologist B.F. Skinner. On the basis of Sutherland’s differential theory of crime (according to which criminal acts are most likely to occur in social…

  • differential blood count

    blood count: A differential blood count is the percentage of each type of white blood cell per 100 white cells counted; the white cells of a normal adult are about 55 percent neutrophils, 30 percent lymphocytes, and small percentages of eosinophils, basophils, and monocytes. A decrease in the…

  • differential calculus (mathematics)

    Differential calculus, Branch of mathematical analysis, devised by Isaac Newton and G.W. Leibniz, and concerned with the problem of finding the rate of change of a function with respect to the variable on which it depends. Thus it involves calculating derivatives and using them to solve problems

  • differential diagnosis (medicine)

    diagnosis: Formulating a diagnosis: …of the disorder, called the differential diagnosis. The clinician then decides what tests to order to help refine the list or identify the specific disease responsible for the patient’s complaints. During this process, some possible diseases will be discarded and new ones added as tests either confirm or deny the…

  • differential discriminator (physics)

    radiation measurement: Counting systems: Alternatively, a differential discriminator (also known as a single-channel analyzer) will select only those pulses whose amplitudes lie within a preset window between a given minimum and maximum value. In this way, the accepted pulses can be restricted to those in which the charge Q from the…

  • differential distillation (chemical process)

    chemical analysis: Distillation: …volatile components in the later fractions. The analyte typically goes through several vaporization-condensation steps prior to arriving at the condenser.

  • differential equation

    Differential equation, mathematical statement containing one or more derivatives—that is, terms representing the rates of change of continuously varying quantities. Differential equations are very common in science and engineering, as well as in many other fields of quantitative study, because what

  • differential gear

    Differential gear, in automotive mechanics, gear arrangement that permits power from the engine to be transmitted to a pair of driving wheels, dividing the force equally between them but permitting them to follow paths of different lengths, as when turning a corner or traversing an uneven road. On

  • differential geometry

    Differential geometry, branch of mathematics that studies the geometry of curves, surfaces, and manifolds (the higher-dimensional analogs of surfaces). The discipline owes its name to its use of ideas and techniques from differential calculus, though the modern subject often uses algebraic and

  • differential interference contrast (optics)

    microscope: Interference microscopes: Meanwhile, differential interference contrast (DIC) was developed by Polish-born French physicist Georges Nomarski in 1952. A beam-splitting Wollaston prism emits two beams of polarized light that are plane-polarized at right angles to each other and that slightly diverge. The rays are focused in the back plane…

  • differential navigation

    GPS: Augmentation: Differential navigation employs a stationary “base station” that sits at a known position on the ground and continuously monitors the signals being broadcast by GPS satellites in its view. It then computes and broadcasts real-time navigation corrections to nearby roving receivers. Each roving receiver, in…

  • differential operator (mathematics)

    Differential operator, In mathematics, any combination of derivatives applied to a function. It takes the form of a polynomial of derivatives, such as D2xx ? D2xy · D2yx, where D2 is a second derivative and the subscripts indicate partial derivatives. Special differential operators include the

  • differential psychology

    Differential psychology, branch of psychology that deals with individual and group differences in behaviour. Charles Darwin’s studies of the survival capabilities of different species and Sir Francis Galton’s researches on individual visual and auditory skills, as well as more recent experiments,

  • differential pulse voltammetry (chemistry)

    chemical analysis: Pulse and differential pulse voltammetry: Differential pulse voltammetry adds a periodically applied potential pulse (temporary increase in potential) to the voltage ramp used for LSV. The current is measured just prior to application of the pulse and at the end of the applied pulse. The difference between…

  • differential rent (economics)

    rent: The classical economic view: …return to them was called differential rent. It was also observed, however, that rent emerged not only as cultivation was pushed to the “extensive margin” (to less fertile acreage) but also as it was pushed to the “intensive margin” through more intensive use of the more fertile land. As long…

  • differential suicide (sociology)

    individualism: …are Durkheim’s classic account of differential suicide rates in terms of degrees of social integration and the account of the incidence of protest movements in terms of the structure of political opportunities. Ontological individualism contrasts with various ways of seeing institutions and collectivities as “real”—e.g., the view of corporations or…

  • differential thermal analysis (chemistry)

    Differential thermal analysis (DTA), in analytical chemistry, a technique for identifying and quantitatively analyzing the chemical composition of substances by observing the thermal behaviour of a sample as it is heated. The technique is based on the fact that as a substance is heated, it

  • differential-algebraic system (mathematics)

    numerical analysis: Applications: …of these mixed systems, called differential-algebraic systems, is quite difficult but necessary in order to model moving mechanical systems. Building simulators for cars, planes, and other vehicles requires solving differential-algebraic systems in real time.

  • differentiation (mathematics)

    Differentiation, in mathematics, process of finding the derivative, or rate of change, of a function. In contrast to the abstract nature of the theory behind it, the practical technique of differentiation can be carried out by purely algebraic manipulations, using three basic derivatives, four

  • differentiation (biology)

    cell: Cell differentiation: Adult organisms are composed of a number of distinct cell types. Cells are organized into tissues, each of which typically contains a small number of cell types and is devoted to a specific physiological function. For example, the epithelial tissue lining the small intestine…

  • differentiation (geology)

    Earth: Planetary differentiation: Once hot, Earth’s interior could begin its chemical evolution. For example, outgassing of a fraction of volatile substances that had been trapped in small amounts within the accreting planet probably formed the earliest atmosphere. Outgassing of water to Earth’s surface began before 4.3 billion…

  • differentiator (device)

    Differentiator, a device or set of components for performing the mathematical operation of differentiation—i.e., supplying an output proportional to the derivative of the input with respect to one or more variables. The many common examples of mechanical differentiators in which a displacement is

  • Difficile liberté (work by Lévinas)

    Emmanuel Lévinas: …1963 as Difficile liberté (Difficult Freedom). In his interpretations of the Talmud, he seemed to be searching for what he called “a wisdom older than the patent presence of a meaning…[a] wisdom without which the message buried deep within the enigma of the text cannot be grasped.”

  • Difficult Classic (work by Bian Qiao)

    traditional Chinese medicine: Bian Qiao: Bian Qiao wrote the popular Nanjing (Difficult Classic), from which information on diagnostic methods was later incorporated into the Huangdi neijing. He also included the measurements and weights of various organs taken from cadavers. One of Bian Qiao’s major struggles was against superstition. He endeavoured to instruct medical men and…

  • difficult crossings problem

    number game: Kinds of problems: …for example, so-called decanting and difficult crossings problems. A typical example of the former is how to measure out one quart of a liquid if only an eight-, a five-, and a three-quart measure are available. Difficult crossings problems are exemplified by the dilemma of three couples trying to cross…

  • Difficult Freedom (work by Lévinas)

    Emmanuel Lévinas: …1963 as Difficile liberté (Difficult Freedom). In his interpretations of the Talmud, he seemed to be searching for what he called “a wisdom older than the patent presence of a meaning…[a] wisdom without which the message buried deep within the enigma of the text cannot be grasped.”

  • Diffie, Whitfield (American mathematician)

    cryptology: Public-key cryptography: , computer engineer Whitfield Diffie and Stanford University electrical engineer Martin Hellman realized that the key distribution problem could be almost completely solved if a cryptosystem, T (and perhaps an inverse system, T′), could be devised that used two keys and satisfied the following conditions:

  • diffraction (physics)

    Diffraction, the spreading of waves around obstacles. Diffraction takes place with sound; with electromagnetic radiation, such as light, X-rays, and gamma rays; and with very small moving particles such as atoms, neutrons, and electrons, which show wavelike properties. One consequence of

  • diffraction grating (optics)

    Diffraction grating, component of optical devices consisting of a surface ruled with close, equidistant, and parallel lines for the purpose of resolving light into spectra. A grating is said to be a transmission or reflection grating according to whether it is transparent or mirrored—that is,

  • diffraction pattern (physics)

    electron diffraction: …can be read from the patterns that are formed when various portions of the diffracted electron beam cross each other and by interference make a regular arrangement of impact positions, some where many electrons reach and some where few or no electrons reach. Some advanced analytical techniques, such as LEEDX…

  • diffraction, order of (physics)

    spectroscopy: X-ray optics: … is an integer called the order of diffraction, many weak reflections can add constructively to produce nearly 100 percent reflection. The Bragg condition for the reflection of X-rays is similar to the condition for optical reflection from a diffraction grating. Constructive interference occurs when the path difference between successive crystal…

  • diffuse ionized gas (astronomy)

    Diffuse ionized gas, dilute interstellar material that makes up about 90 percent of the ionized gas in the Milky Way Galaxy. It produces a faint emission-line spectrum that is seen in every direction. It was first detected from a thin haze of electrons that affect radio radiation passing through

  • diffuse nebula (astronomy)

    H II region, interstellar matter consisting of ionized hydrogen atoms. The energy that is responsible for ionizing and heating the hydrogen in an emission nebula comes from a central star that has a surface temperature in excess of 20,000 K. The density of these clouds normally ranges from 10 to

  • diffuse nervous system (physiology)

    nervous system: Diffuse nervous systems: The diffuse nervous system is the most primitive nervous system. In diffuse systems nerve cells are distributed throughout the organism, usually beneath the outer epidermal layer. Large concentrations of nerve cells—as in the brain—are not found in these systems, though there may…

  • diffuse radiation (atmospheric science)

    atmosphere: Radiation: Diffuse radiation, in contrast, reaches the surface after first being scattered from its line of propagation. On an overcast day, for example, the Sun’s disk is not visible, and all of the shortwave radiation is diffuse.

  • diffuse reciprocity (international relations)

    multilateralism: Diffuse reciprocity: Along with, and related to, the principle of indivisibility of interests, multilateralism is considered to give rise to expectations of diffuse reciprocity among participants. In situations characterized by diffuse reciprocity, there is an expectation that there will not be an equivalence of obligations…

  • diffuse root system (plant anatomy)

    root: Types of roots and root systems: …single seed leaf) have a fibrous root system, characterized by a mass of roots of about equal diameter. This network of roots does not arise as branches of the primary root but consists of many branching roots that emerge from the base of the stem.

  • diffuse thalamic projection system (physiology)

    attention: Physiological changes: …cortex via the thalamus, the diffuse thalamic projection system, appears concerned with moment-to-moment fluctuations in the focus of attention. Collectively, the primary sensory pathways, associated areas of the cerebral cortex, and the more diffuse projection systems cooperate in the process of registering the incoming sensory signal, evaluating its contents, and…

  • diffuse-porous wood

    tree: Growth ring formation: …be divided into ring-porous and diffuse-porous trees. In ring-porous trees the vessels laid down at the beginning of the growing season are much larger than subsequent vessels laid down at the end of the season (or ring). Diffuse-porous trees form vessels of roughly the same radial diameter throughout the growing…

  • diffuser (optics)

    enlarger: Another type is the diffuser, which scatters the light from the bulb so that it falls evenly across the film. Light sources and optical systems are chosen depending on the type of film being used and the characteristics desired on the enlarged print. Condensers are used for prints with…

  • diffuser pump

    pump: Kinetic pumps.: …flow centrifugal pump is the diffuser pump, in which, after the fluid has left the impeller, it is passed through a ring of fixed vanes that diffuse the liquid, providing a more controlled flow and a more efficient conversion of velocity head into pressure head.

  • diffusion (physics)

    Diffusion, process resulting from random motion of molecules by which there is a net flow of matter from a region of high concentration to a region of low concentration. A familiar example is the perfume of a flower that quickly permeates the still air of a room. Heat conduction in fluids involves

  • diffusion bonding (metallurgy)

    welding: Diffusion bonding: This type of bonding relies on the effect of applied pressure at an elevated temperature for an appreciable period of time. Generally, the pressure applied must be less than that necessary to cause 5 percent deformation so that the process can be applied…

  • diffusion chamber (device)

    Diffusion chamber, simple form of cloud chamber, a device used for radiation detection (see cloud

  • diffusion coefficient (physics)

    gas: Diffusion: …components and is called the diffusion coefficient, D12, for that gas pair. This relationship between the flow rate and the concentration difference is called Fick’s law of diffusion. The SI units for the diffusion coefficient are square metres per second (m2/s). Diffusion, even in gases, is an extremely slow process,…

  • diffusion equation (mathematics)

    fluid mechanics: Boundary layers and separation: This is a diffusion equation. It indicates that, if the plate oscillates to and fro with frequency f, then the so-called boundary layer within which Ω3 is nonzero has a thickness δ given by

  • diffusion flame (chemistry)

    combustion: Diffusion flames: Diffusion flames, smoothly flowing (laminar) or turbulent, belong to the class of flames whose ingredients are not mixed prior to entering the burning zone. Molecular or turbulent diffusion is responsible for the mixing of the gases in such flames. The distribution of the…

  • diffusion index (economics)

    economic forecasting: Selection of turning points: …use sets of statistics called diffusion indexes to calculate economic turning points. A diffusion index is a method of summarizing the common tendency of a group of statistical series. If a greater number of the series are rising than are declining, the index will be above 50; if fewer are…

  • diffusion layer (electronics)

    integrated circuit: Implantation: …annealing is therefore called a diffusion layer.

  • diffusion of innovations (sociology)

    Diffusion of innovations, model that attempts to describe how novel products, practices, or ideas are adopted by members of a social system. The theory of diffusion of innovations originated in the first half of the 20th century and was later popularized by American sociologist Everett M. Rogers in

  • diffusion process (physics)

    probability theory: Brownian motion process: …class of stochastic processes, called diffusion processes, of which Brownian motion is the most prominent member. Especially notable contributions to the mathematical theory of Brownian motion and diffusion processes were made by Paul Lévy and William Feller during the years 1930–60.

  • diffusion pump

    vacuum technology: Vapour diffusion pump: This pump is mainly used on equipment for the study of clean surfaces and in radio-frequency sputtering. Capacities are available up to 190,000 cu ft per minute with an operating pressure range of 10-2 to less than 10-9 torr when water-cooled baffles…

  • diffusion thermoeffect (physics)

    gas: Thermal diffusion: …of thermal diffusion, called the diffusion thermoeffect, in which an imposed concentration difference causes a temperature difference to develop. That is, a diffusing gas mixture develops small temperature differences, on the order of 1° C, which die out as the composition approaches uniformity. The transport coefficient describing the diffusion thermoeffect…

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