Image Candleburning.jpg thumb right The common flame of a candle is a classic example of a diffusionflame. Its yellow color owing to the large amount of incandescent soot particles in the incomplete combustion reaction of the flame. File Fire breathing 2 Luc Viatour.jpg thumb 500px right In a diffusionflame , combustion takes place at the flame surface only, where the fuel meets oxygen in the flammability limit right concentration the interior of the flame contains unburnt fuel. This is opposite to combustion in a premixed flame . The fire breather s spurting of fuel likely kerosene , combined with strong convection flows due to intense heat gives a turbulent diffusionflame. In combustion , a diffusionflame is a flame in which the oxidizer combines with the fuel by diffusion . As a result, the flame speed is limited by the rate of diffusion. Diffusion flames tend to burn slower and to produce more soot than premixed flame s because there may not be sufficient oxidizer for the reaction ... in a diffusionflame becomes incandescent from the heat of the flame and lends the flame its readily identifiable orange yellow color. Diffusion flames tend to have a less localized flame front than premixed flames. The contexts for diffusion may vary somewhat. For instance, a candle uses the heat of the flame itself to vaporize its wax fuel and the oxidizer oxygen diffuses into the flame from the surrounding air, while a Gas lighting gaslight flame or the safety flame of a bunsen burner uses fuel ... flame front, such as in the candle seen here. This is a rare example of a diffusionflame which ... The common flame of a candle is a classic example of a diffusionflame. Its yellow color ... Image Australia Cairns Flame.jpg A nearly turbulent diffusionflame File Fire breathing 2 Luc Viatour.jpg A turbulent diffusionflame Image Candlespace.jpg A candle in a microgravity environment. This is a rare example of a diffusionflame which does not produce much soot and does not therefore ... more details
about the generic concept of the time dependent random process File Diffusion.svg thumb right A diffusion ... but diffusion will still continue to occur, just that there will be no net flux . Diffusion describes ... concentration. The time dependence of the statistical distribution in space is given by the diffusion equation . The concept of diffusion is tied to that of mass transfer driven by a concentration gradient, but diffusion can still occur when there is no concentration gradient but there will be no net flux . diffusion is invoked in the social sciences to describe the spread of ideas. Diffusion in physics In molecular diffusion , the moving entities are small molecules which are self propelled .... They move at random because they frequently collide. Diffusion is this thermal motion of all liquid and gas molecules at temperatures above absolute zero . Diffusion rate is a function of only temperature ... diffusion center.gif thumb 350px right The following image shows change in excess carriers being ... of an intrinsic semiconductor bar. Electrons have a higher diffusion constant than holes ... molecules is observable under a microscope, small molecule diffusion can only be probed in carefully controlled experimental conditions. Under normal conditions, molecular diffusion is relevant only ..., some often cited examples of diffusion are wrong If cologne is sprayed in one place, it will soon be smelled in the entire room, but a simple calculation shows that this cannot be due to diffusion ... evolution of the spatial distribution, which clearly indicates convection diffusion dominates only in perfect ... e.g. a metal spoon partly immersed in a hot liquid . This explains why the diffusion of heat was explained mathematically before the diffusion of mass. Other types of diffusion Anisotropic diffusion , also known as the Perona Malik equation, enhances high gradients Atomic diffusion , in solids. Eddy diffusion , in coarse grained description of turbulent flow Effusion of a gas through small holes ... more details
of combustion to a flame. In a diffusionflame , oxygen and fuel diffuse into each other where they meet the flame occurs. In a premixed flame , the oxygen and fuel are premixed beforehand, which results in a different type of flame. Candle flames a diffusionflame operate through evaporation of the fuel ..., diffusionflame ref name temp cite book url http books.google.com ?id Q7Pb2wXV2woC&pg PA4 pages ... and Space Administration, April 2005. ref Experiments by NASA reveal that diffusionflame s in microgravity ... flame of a burning candle. A flame from Latin wikt en flamma Latin flamma is the visible light ... and temperature of a flame are dependent on the type of fuel involved in the combustion, as, for example ... flame. The high temperature of the flame causes the vaporized fuel molecules to Chemical decomposition .... Sufficient energy in the flame will excited state excite the electron s in some of the transient ... radical species produce which specific colors . As the combustion temperature of a flame increases if the flame contains small particles of soot unburnt carbon or other material , so does the average energy of the electromagnetic radiation given off by the flame see blackbody . Other oxidizers besides oxygen can be used to produce a flame. Hydrogen burning in chlorine produces a flame and in the process ... kinetics occurring in the flame are very complex and involves typically a large number of chemical .... Flame color File Spectrum of blue flame.png thumb Spectrum of the blue premixed, i.e., complete combustion flame from a butane torch showing molecular Radical chemistry radical band emission and Swan ... burner flame types .jpg thumb Different flame types of a Bunsen burner depend on oxygen supply. On the left a rich fuel with no premixed oxygen produces a yellow sooty diffusionflame on the right a lean fully oxygen premixed flame produces no soot and the flame color is produced by molecular ... Citation needed date March 2011 Flame color depends on several factors, the most important typically ... more details
The Flame could refer to The Flame Steve Lacy album The Flame Steve Lacy album , a 1982 album by American jazz saxophonist Steve Lacy The Flame Annabel Lamb album The Flame Annabel Lamb album , a 1984 album by British singer Annabel Lamb The Flame Arcadia song The Flame Arcadia song , a 1986 song by British band Arcadia The Flame Cheap Trick song The Flame Cheap Trick song , a 1988 song by American band Cheap Trick The Flame , a 1996 song by British band Fine Young Cannibals The Flame , the official song of the 2000 Sydney Summer Olympics performed by Tina Arena The Flame Dover Album The Flame , a 2003 Album by Spanish Band, Dover The Flame , a newspaper of the British National Front The Flame newspaper The Flame , a student newspaper of the University of Houston Victoria The Flame DHARMA Initiative , a fictional research project station featured in the American television series Lost Flame comics , a fictional superhero character The Flame wrestler , one of Professional wrestling professional wrestler Jody Hamilton ring name Texas Conference of Seventh day Adventists Publications The FLAME , a Seventh day Adventist magazine See also Flac ra disambiguation disambig ... more details
In Flame is a 2000 play by Charlotte Jones writer Charlotte Jones . Its premiere at the Bush Theatre transferring to the New Ambassadors Theatre was directed by Anna Mackmin and featured Marcia Warren , Kerry Fox , Rosie Cavaliero , Ivan Kaye , Jason Hughes actor Jason Hughes and Emma Dewhurst . It is set in 1908 and 2000 and centred around two men and three women. External links http www.curtainup.com inflame.html Review Category 2000 plays Category 1908 in fiction Category 2000 in fiction ... more details
Infobox album See Wikipedia WikiProject Albums Name Flame On Type studio Artist Machel Montano Cover FlameOn0001.jpg Released Flagicon TTO 16 January 2008 Recorded 2007 , 2008 Genre Soca music Soca Length 57 40 Label Ruf Rex Productions Ltd Producer Machel Montano Reviews TriniJungleJuice.com http www.trinijunglejuice.com cdreview flameon.html link Last album Book of Angels br 2007 This album Flame On br 2008 Next album Heavenly Drum br 2009 Misc Extra album cover Upper caption North American release Type studio Cover Wining season cover.jpg Lower caption Cover to the North American release Wining Season which included two additional tracks over the original release. Flame On is an album released by popular Soca music Soca artist Machel Montano from Trinidad and Tobago in 2008 ref http www.machelmontanohd.com index.php?page music Machel Montano Discography at Official Website ref . It was first launched at Trinidad s Club Zen on January 16, 2008 ref http www.trinijunglejuice.com machel album release zen 2008 Machel Montano HD Flame On Album Release ref . The album marks Machel Montano s second release after rebranding to Machel Montano HD in 2007 . A release in the United States has been reported to be upcoming on the Delicious Vinyl label with a different album name, Wining Season . ref http mustardseedmedia.blogspot.com 2008 03 rounds machel montano to release new.html Mustard Seed Media Blog ref ref http www.dancehallareaz.com news 25824 machel montano new york.html Dhaz Street Journal ref The album features several solo and collaborative tracks, with popular artists such as Cuban American Pitbull rapper Pitbull , United States American Lil Jon , Jamaican s Shaggy artist Shaggy & Buju Banton , Trinidadian s Patrice Roberts , The Mighty Sparrow and David Rudder . The song Blazin D Trail on the album placed third in the 2008 Road March Competition for Trinidad and Tobago ... Flame On Category Machel Montano albums Category Soca albums Category 2008 albums ... more details
Wiktionarypar diffusionDiffusion most often refers to a time dependent random process causing a spread in space, see diffusion . In the physical sciences Molecular diffusion also commonly without additional ... Conduction of heat Diffusion of heat Momentum diffusionDiffusion of momentum Diffusion equation ... gradient Heat equation Eddy diffusion In physical sciences, more specific or modified meanings Diffusion MRI Diffusion acoustics Acoustic diffusion of sound waves Atomic diffusion Brownian motion , for example of a single particle in a solvent Collective diffusion , the diffusion of a large number of possibly interacting particles Facilitated diffusion Effusion of a gas through small holes Gaseous diffusion It diffusion Knudsen diffusion of particles from very small containers Osmosis Photon diffusion , an optical effect Diffuse reflection , the reflection of light from an uneven or granular surface Reverse diffusion Rotational diffusion Self diffusion Surface diffusion Thermodiffusion In the social sciences such as sociology , geography , or cultural anthropology Diffusion of innovations within a society or a culture or between them Lexical diffusion within a culture Trans cultural diffusion of culture items between cultures Spatial diffusion of an innovation, an artifact, or populations ... from an uneven or granular surface Diffusion cryptography , the spreading of influence of bits in a cipher Error diffusion in image processing In other areas Diffusion business , the process by which a new idea or new product is accepted by the market Diffusion process , in probability theory the solution to a stochastic differential equation Diffusion of responsibility Society for the Diffusion of Useful Knowledge The Diffusion Science Radio Show , a science radio show and podcast on 2SER in Sydney Diffusion Records , an independent record label Diffusion 7for4 album Diffusion 7for4 album , a music album by 7for4 See also Migration disambiguation Diffuse nebula disambig de Diffusion Begriffskl rung ... more details
Thermal diffusion may refer to Uranium enrichment Thermal diffusion Thermal diffusion , an obsolete method of uranium enrichment Brownian motion at a constant non zero absolute temperature . Diffusion in a temperature gradient thermophoresis , also called thermodiffusion . See also Molecular diffusion Heat conduction i.e., diffusion of heat disambig ... more details
, lifted jet diffusion flames journal Combustion and Flame volume 144 issue 3 pages 494 512 year 2006 .... title Experimental analysis of local flame extinction in a turbulent jet diffusionflame by high ... and or viruses. See also Turbulence Atmospheric dispersion modeling Diffusionflame Fick s laws of diffusion ... crf article.php?id 144 Turbulent DiffusionFlame Research http www.shodor.org master environmental ...Orphan date April 2010 Turbulent diffusion is the transport of mass, heat, or momentum within a system ..., density gradients, and high velocities. It occurs much more rapidly than molecular diffusion and is therefore ... diffusion acts as an excellent process for quickly reducing the concentrations of a species in a fluid ... and fully functional model that can be applied to the diffusion of a species in all turbulent ... Roberts02 cite book author Roberts, P.J.W., & Webster, D.R. chapter Turbulent Diffusion editor Shen ... Atmospheric diffusion and pollutants Atmospheric dispersion, or diffusion, studies how pollutants ... both been used to simulate atmospheric diffusion, and are important for a proper understanding of how ... vertical and horizontal wind, but additionally integrate Fickian diffusion theory to account for turbulence ... in time, it is difficult to better calculate the effects of turbulent diffusion on pollutants. Fickian diffusion theory and further advancements in research on atmospheric diffusion can be applied ... ref Turbulent diffusion flames Using planar laser induced fluorescence PLIF and particle image velocimetry PIV processes, there has been on going research on the effects of turbulent diffusion in flames ... reactions in jet diffusion flames involving methane CH sub 4 sub , hydrogen H sub 2 sub and nitrogen ... to turbulent diffusion focuses on an infinitesimal volume at a specific space and time in a fixed ... ref name Csanady73 cite book author Csanady, G.T. title Turbulent diffusion in the environment publisher ... of an element or species is balanced by its diffusion, generation by reaction, and addition from other ... more details
Unreferenced stub auto yes date December 2009 Orphan date December 2009 Reverse diffusion refers to a situation where the transport of particles atom s or molecule s in a medium occurs towards regions of lower concentration gradients, opposite to that observed during diffusion . This phenomenon occurs during phase matter phase separation and is described by the Cahn Hilliard equation . Reverse diffusion also refers to when water is forced from an region of lower concentration to high. DEFAULTSORT Reverse Diffusion Category Diffusion Physics stub cs Reverzn osm za ... more details
According to IUPAC definition, ref http goldbook.iupac.org S05582.html IUPAC Compendium of Chemical Terminology, 2nd edition ref self diffusion coefficient is the diffusion coefficient math D i math of species math i math when the chemical potential gradient equals zero. It is linked to the diffusion coefficient math D i math by the equation math D i D i frac partial ln c i partial ln a i . math Here, math a i math is the activity chemistry activity of the species math i math in the solution and math c i math is the concentration of math i math . This term is commonly assumed to be equal to the tracer diffusion determined by watching the movement of an Isotopic labeling isotope in the material of interest. See also Diffusion Molecular diffusion References reflist DEFAULTSORT Self Diffusion Category Diffusion physics stub pt Autodifus o ... more details
Jump diffusion is a stochastic process that involves jumps and diffusion. It has important applications in condensed matter physics and in option pricing . In physics In crystals, atomic diffusion typically consists of jumps between vacant lattice sites. On time and length scales that average over many single jumps, the net motion of the jumping atoms can be described as regular diffusion . Jump diffusion can be studied on a microscopic scale by inelastic neutron scattering and by M bauer spectroscopy . Closed expression for the self correlation function have been derived for several jump diffusion models Singwi, Sj lander 1960 alternation between oscillatory motion and directed motion Chudley, Elliot 1961 jumps on a lattice Sears 1966, 1967 jump diffusion of rotational degrees of freedom Hall, Ross 1981 jump diffusion within a restricted volume In economy In option pricing , a jump diffusion model is a form of mixture model , mixing a jump process and a diffusion process . Jump diffusion models have been introduced by Robert C. Merton as an extension of jump model s. Derivatives market Volatility Category Stochastic processes Category Options economics stub physics stub ... more details
Atomic diffusion is a diffusion process whereby the random thermally activated movement of atom s in a solid ... and the concentration gradient. In crystals Image Chemical surface diffusion slow.gif thumb 288px right Interstitial Atomic diffusion across a 4 coordinated lattice. Note that the atoms often block each other from moving to adjacent sites. As per Fick s law of diffusion Fick s law , the net ... . In the crystal solid state, diffusion within the crystal lattice occurs by either Interstitial defect interstitial or substitutional mechanisms and is referred to as lattice diffusion coefficient lattice diffusion ref P. Heitjans, J. Karger, Ed, Diffusion in condensed matter Methods, Materials, Models, 2nd edition, Birkhauser, 2005, pp. 1 965. ref . In interstitial lattice diffusion, a diffusant .... In substitutional lattice diffusion self diffusion for example , the atom can only move by substituting place with another atom. Substitutional lattice diffusion is often contingent upon the availability ... diffusion . Since the prevalence of point vacancies increases in accordance with the Arrhenius equation , the rate of crystal solid state diffusion increases with temperature. For a single atom in a defect ... of math Tt math math r sim sqrt Tt . math Diffusion in polycrystalline materials can involve short circuit diffusion mechanisms. For example, along the grain boundaries and certain crystalline defects such as dislocations there is more open space, thereby allowing for a lower activation energy for diffusion. Atomic diffusion in polycrystalline materials is therefore often modeled using an effective diffusion coefficient , which is a combination of lattice, and grain boundary diffusion coefficient s. In general, surface diffusion occurs much faster than grain boundary diffusion, and grain boundary diffusion occurs much faster than lattice diffusion. See also Kirkendall effect Mass diffusivity References reflist refbegin refend External links http dragon.unideb.hu zerdelyi Diffusion on the nanoscale ... more details
Unreferenced stub auto yes date December 2009 A diffusion filter is a translucent filter photography photographic filter used for a special effect . When used in front of the photographic lens camera lens , a photon diffusiondiffusion filter softens subjects and generates a dreamy haze . This can also be improvise d by smearing petroleum jelly on a UV filter or shooting through a nylon stocking . Diffusion filters may be uniform or may have a clear center area to create a vignetting vignette of diffused area around the clear center subject. Diffusion filters are also used in stage lighting and likewise in photography setups , where they may also be called diffusion gel , or just diffusion . This is a reference to color gel , which is another type of lighting gel . Diffusion gels soften the light in order to reduce or diffuse shadow s or glare . Silk sheets can also be used in this manner, and in fact were until the invention of translucent plastic s. Opal is a common translucent or opalescent diffusion. See also Diffuser optics Soft focus DEFAULTSORT Diffusion Filter Category Photography equipment Category Optical filters Category Photographic lighting Category Stage lighting Photography stub ... more details
for the marketing term Diffusion of innovations In probability theory , a branch of mathematics , a diffusion process is a solution to a stochastic differential equation . It is a continuous time Markov process with continuous function continuous sample paths. A sample path of a diffusion process mimics the trajectory of a molecule, which is embedded in a flowing fluid and at the same time subjected to random displacements due to collisions with other molecules, i.e. Brownian motion . The position of this molecule is then random its probability density function is governed by an advection equation advection diffusion equation . See also Sample continuous process It diffusion Category Stochastic processes math stub date May 2009 gl Teor a da difusi n ... more details
Image GearDiagram.jpg thumb Schematic cutaway view of a diffusion hardened metal gear inline date September 2010 Diffusion hardening is a process used in manufacturing that increases the hardness of steels. In diffusion hardening, diffusion occurs between a steel with a low carbon content and a carbon rich environment to increase the carbon content of the steel and ultimately harden the workpiece. Diffusion ... may be performed on a diffusion hardened part to increase the hardness of the core as desired, but in most cases in which diffusion hardening is performed, it is desirable to have parts with a hard ... amounts of wear, such as gears, the non uniform properties acquired through diffusion hardening are desired ... and more impact resistant core. Process Diffusion hardening is performed by completely surrounding ... on the type of diffusion process being performed. The concentration of the diffusing element surrounding the part must be higher than the concentration of the element inside the part, or diffusion ... high for diffusion to occur. In the case of pack carburizing, the temperature must be 900 C and the part must be allowed to sit for 12 to 72 hours for the correct amount of diffusion to occur. Types Diffusion hardening can be done in many different ways to achieve different hardnesses and different surface finishes on metal parts. Some of the different diffusion hardening operations include Carburizing , Nitriding , Carbonitriding , Nitrocarburizing , Boriding , Titanium carbon diffusion , and Toyota diffusion . While diffusion hardening is performed mainly on steel parts and carbon is mainly the element used for diffusion, diffusion hardening can also be performed with other diffusion ... and diffusion elements used, diffusion hardening processes differ in the temperature required for diffusion, the phase of the diffusion element, and additional treatments such as quenching and tempering ... is inefficient. All these things must come into consideration when choosing a diffusion hardening ... more details
Knudsen diffusion is a means of diffusion that occurs in a long pore with a narrow diameter 2 50nm because molecules frequently collide with the pore wall. ref cite web url http sinnott.mse.ufl.edu Backgrounds theo02 diff.html title Transport in Small Pores accessdate 2009 10 20 ref Knudsen self diffusion In the Knudsen diffusion regime, the molecules do not interact with one another, so that they move in straight lines between points on the pore channel surface. Self diffusivity is a measure of the translational mobility of individual molecules. Under conditions of thermodynamic equilibrium, a molecule is tagged and its trajectory followed over a long time. If the motion is diffusive, and in a medium without long range correlations, the squared displacement of the molecule from its original position will eventually grow linearly with time Einstein s equation . To reduce statistical errors in simulations, the self diffusivity, Ds , of a species is defined from ensemble averaging Einstein s equation over a large enough number of molecules,N ref cite web first Knudsen Self and Fickian Diffusion in Rough Nanoporous Media url http www.uni leipzig.de diffusion pdf MalekCoppens JCP 031.pdf ref See also Knudsen Flow Knudsen number Diffusion References reflist Category Diffusion physics stub de Knudsen Diffusion pl Dyfuzja Knudsena pt Difus o de Knudsen ru ... more details
Anomalous diffusion is a term used to describe a diffusion process with a non linear relationship to time, in contrast to a typical diffusion process, in which the mean squared displacement msd of a particle is a linear function of time. Diffusion is often described by a power law, msd t Dt sup sup , where D is the diffusion coefficient and t is the elapsed time. In a typical diffusion process, 1. If 1, the phenomenon is called super diffusion. Super diffusion can be the result of active cellular transport processes. If 1, the particle undergoes sub diffusion . Sub diffusion has been proposed as a measure of macromolecular crowding in the cytoplasm . References Avi Caspi, Rony Granek, and Michael Elbaum. http link.aps.org doi 10.1103 PhysRevE.66.011916 Diffusion and directed motion in cellular transport . Physical Review E 66, 011916 2002 . Matthias Weiss, Markus Elsner, Fredrik Kartberg, and Tommy Nilsson. http www.cell.com biophysj abstract S0006 3495 04 73816 3 Anomalous Subdiffusion Is a Measure for Cytoplasmic Crowding in Living Cells . Biophysical Journal 87 3518 3524 2004 Jean Philippe Bouchaud. http dx.doi.org 10.1016 0370 1573 90 90099 N Anomalous diffusion in disordered media . Physics Reports 195 4 5 127 293 1990 . A. von Kameke et al. , http pre.aps.org abstract PRE v81 i6 e066211 Propagation of a chemical wave front in a quasi two dimensional superdiffusive flow , Phys. Rev. E 81 6 2010 . reflist External links http dragon.unideb.hu zerdelyi Diffusion on the nanoscale node4.html Boltzmann s transformation, Parabolic law animation http dragon.unideb.hu zerdelyi Diffusion on the nanoscale node13.html Anomalous interface shift kinetics Computer simulations and Experiments Category Physical chemistry chem stub phys stub pt Difus o an mala ... more details
Eddy diffusion , eddy dispersion , or turbulence turbulent diffusion is any diffusion process by which substances are mixed in the atmosphere or in any fluid system due to eddy motion . ref IUPAC Compendium of Chemical Terminology 2nd Edition 1997 Gold Book http www.iupac.org goldbook E01889.pdf Link ref ref Science world, wolframe ref In another definition ref Glossary of Meteorology http amsglossary.allenpress.com glossary browse?s e&p 9 Link ref it is mixing that is caused by eddy fluid dynamics eddies that can vary in size from the small Kolmogorov microscales to subtropical gyre s. Because the microscopic processes responsible for atmospheric mixing are too complex to model in detail, atmospheric modelers generally treat atmospheric mixing as a macroscopic eddy diffusion process. In this approach, the diffusion rate at each pressure level is parameterized by a quantity known as the eddy diffusion coefficient , K ref Chamberlain and Hunten 1987, pp. 75 and 90 ref also sometimes called eddy diffusivity . References Reflist Category diffusion de Eddy Diffusion nl Eddy diffusie pt Difus o turbulenta ... more details
About spontaneous dispersion of mass a more generic treatment of diffusionDiffusion File DiffusionMicroMacro.gif thumb 250px Diffusion from a microscopic and macroscopic point of view. Initially, there are solution ... to low concentration areas, following Fick s laws. Molecular diffusion , often called simply diffusion ..., but is not a function of concentration. Diffusion explains the net flux of molecules from a region of higher concentration to one of lower concentration, but it is important to note that diffusion also occurs when there is no concentration gradient. The result of diffusion is a gradual ... on the particles, the diffusion process will eventually result in complete mixing. Diffusion equilibrium is reached when the concentration s of the Diffusion diffusing substance in the two compartments ... if food coloring is put in system A, eventually it would be of equal color to system B. Molecular diffusion is typically described mathematically using Fick s laws of diffusion . Applications Diffusion ... applications of diffusion Sintering to produce solid materials powder metallurgy , production of ceramic ... of semiconductor s. Significance File Diffusion 1 .png thumb 280px Schematic representation of mixing of two substances by diffusionDiffusion is part of the transport phenomena . Of mass transport mechanisms, molecular diffusion is known as a slower one. In biology In cell biology , diffusion is a main ... Upper Saddle River, New Jersey pages 66 67 url doi id isbn ref Diffusion of water H sub 2 sub O through ... respiration rely in part upon diffusion in addition to bulk or active processes. For example, in the pulmonary ... contain a large surface area to facilitate this gas exchange process. Tracer and chemical diffusion File Diffusion self1.svg thumb 340px Self diffusion, exemplified with an isotopic tracer of radioactive ... diffusion of sodium chloride in water Fundamentally, two types of diffusion are distinguished Tracer diffusion , which is a spontaneous mixing of molecules taking place in the absence of concentration ... more details
Expert subject Physics date May 2009 Unreferenced date May 2009 Diffusion current is a electric current current in a semiconductor caused by the diffusion of charge carriers holes and or electrons . Diffusion current can be in the same or opposite direction of a drift current , that is formed due to the electric field in the semiconductor. At equilibrium in a p n junction , the forward diffusion current in the depletion region is balanced with a reverse drift current, so that the net current is zero. The diffusion constant for a doped material can be determined with the Haynes Shockley experiment . References reflist Ben G. Streetman, Santay Kumar Banerjee Solid State Electronic Devices 6th Edition , Pearson International Edition pp. 126 135. Uncategorized date January 2011 physics stub ... more details
Unreferenced stub auto yes date December 2009 Photon diffusion is a situation where photon s travel through a material without being absorbed, but rather undergoing repeated scattering events which change the direction of their path. The path of any given photon is then effectively a random walk . A large statistical ensemble ensemble of such photons can be said to exhibit diffusion in the material, and can be described with a diffusion equation . Astrophysics In astrophysics , photon diffusion occurs inside a stellar atmosphere . To describe this phenomenon, one should develop the transfer equation in moments and use the Eddington approximation to radiative transfer i.e. the diffusion approximation . In 3D the results are two equations for the photon energy flux math vec F frac c 12 pi sigma vec nabla U, math math vec nabla cdot vec F 0, math where math sigma math is the opacity. By substituting the first equation into the second, one obtains the diffusion equation for the photon energy density math nabla 2 U frac 1 sigma vec nabla U cdot vec nabla sigma 0. math Medical science In medicine , the diffusion of photons can be used to create images of the body mainly brain and breast and has been contributing a lot to the advance of certain fields of research, such as neuroscience. This technique is known as diffuse optical imaging . See also Global dimming Radiative transfer equation and diffusion theory for photon transport in biological tissue Diffusion damping Diffuse reflection DEFAULTSORT Photon Diffusion Category Diffusion Category Photonics Physics stub ... more details
Unreferenced date November 2006 Orphan date November 2009 Streamline diffusion , given an advection equation advection diffusion equation , refers to all diffusion going on along the advection direction. Explanation If we take an advection equation, for simplicity of writing we have assumed math nabla cdot mathbf F 0 math , and math bold u 1 math math frac partial psi partial t bold u cdot nabla psi 0. math we may add a diffusion term, again for simplicty, we assume the diffusion to be constant over the entire field. math D nabla 2 psi math , Giving us an equation on the form math frac partial psi partial t bold u cdot nabla psi D nabla 2 psi 0 math We may now rewrite the equation on the following form math frac partial psi partial t bold u cdot nabla psi bold u bold u cdot D nabla 2 psi D nabla 2 psi bold u bold u cdot D nabla 2 psi 0 math The term below is called streamline diffusion. math bold u bold u cdot D nabla 2 psi math Crosswind diffusion Any diffusion orthogonal to the streamline diffusion is called crosswind diffusion, for us this becomes the term math D nabla 2 psi bold u bold u cdot D nabla 2 psi math Category Fluid dynamics Category Diffusion Category Partial differential equations Math stub ... more details
Orphan date September 2008 Diffusion networks are continuous time, continuous state recurrent neural network neural networks with a stochastic component. They are neural networks and stochastic diffusion processes, thus their name. Diffusion networks are related to a wide range of popular algorithms in the neural network and machine learning literature. For example Boltzmann machine Boltzmann machines are binary state versions of diffusion networks. Kalman filter Kalman filters are linear versions of diffusion networks. Diffusion networks can be trained using a variety of approaches, including Minimum Velocity, Contrastive Divergence, and standard Maximum Likelihood estimation ref Movellan2008 . The goal of learning in general is to learn entire probability distributions. One of the main advantages of this approach, when compared to other generative approaches, is that once a distribution has been learned, optimal inference is trivial. All it takes is to clamp the observable units and let the unobservable units settle to stochastic equilibrium. References note Movellan2008 1 Movellan J. R. Contrastive Divergence in Gaussian Diffusion Processes http mplab.ucsd.edu Neural Computation. In Press. Category Computational neuroscience ... more details
refimprove date March 2010 Image Scheme facilitated diffusion in cell membrane en.svg thumb 300px right Facilitated diffusion in cell membrane, showing ion channel s and carrier proteins Not to be confused with diffusion . Facilitated diffusion is not a type of diffusion thermal motion but a type of transport process. Facilitated diffusion also known as facilitated transport or passive mediated transport is a process of passive transport , facilitated by integral proteins. Facilitated diffusion is the spontaneous passage of molecules or ions across a biological membrane passing through specific transmembrane integral proteins. The facilitated diffusion may occur either across biological membrane s or through aqueous compartments of an organism. ref name isbn0 471 41759 9 cite book author Pratt, Charlotte Amerley Voet, Donald Voet, Judith G. title Fundamentals of biochemistry upgrade publisher Wiley location New York year 2002 pages 264 266 isbn 0 471 41759 9 oclc doi accessdate ref Polar molecules and charged ions are dissolved in water but they can not diffuse freely across the plasma membrane due to the hydrophobe hydrophobic nature of the fatty acid tails of phospholipid s that make up the lipid bilayer s. Only small nonpolar molecules, such as oxygen can diffuse easily across the membrane. All polar molecules are transported across cell membrane membranes by proteins that form transmembrane channels. These channels are gated so they can open and close, thus regulating the flow of ions or small polar molecules. Larger molecules are transported by transmembrane carrier proteins ... is required for facilitated diffusion. Only permease changes its shape in order to transport ... highered.mcgraw hill.com sites 0072495855 student view0 chapter2 animation how facilitated diffusion works.html McGraw Hill Facilitated Diffusion Animation Membrane transport DEFAULTSORT Facilitated Diffusion Category Diffusion Category Transport proteins ca Difusi facilitada fr Diffusion facilit e ... more details
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