Bibliografie tematiche / Diffusion

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Letteratura scientifica selezionata sul tema "Diffusion"

Autore: Grafiati

Pubblicato: 4 giugno 2021

Ultima modifica: 9 novembre 2024

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Articoli di riviste sul tema "Diffusion"

Khair, Abul, Nilay Kumar Dey, Mohammad Harun-Ur-Rashid, Mohammad Abdul Alim, Newas Mohammad Bahadur, Sultan Mahamud e Syekat Ahmed. "Diffusimetry Renounces Graham’s Law, Achieves Diffusive Convection, Concentration Gradient Induced Diffusion, Heat and Mass Transfer". Defect and Diffusion Forum 407 (marzo 2021): 173–84. http://dx.doi.org/10.4028/www.scientific.net/ddf.407.173.

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Absolute diffusion rates of KMnO4 in vertical and flattened diffusimeters show the concentration gradient force as being stronger than the gravitational force. Hot water molecules move downward on self-diffusion against buoyancy. Diffusive convection (DC) in warm water and double-diffusive convection (DDC) in warm, saline water take place inside the diffusimeter with DDC transferring more heat than DC. In the diffusing medium the original reagents change or retain their compositions to give the diffusate molecules to diffuse. In water, the change is mostly hydration. The syngener BaCl2.2H2O separately with congeners 3CdSO4.8H2O, ZnSO4.7H2O, and ZnSO4.H2O presents two distinct pairs of overlapping concentration versus rate curves, first for having very close MWs of BaCl2 and CdSO4 and second for having ZnSO4.H2O as the common congener for both the zinc sulfates. Chlorides of Li, Na, and K diffusing at hindered rates in glucose solution show the least rate for LiCl inevitably on grounds of low mass and high Li+ hydration radius. Diffusion blocking occurs at higher glucose concentration. Diffusion of 0.6M AgNO3-0.6M NH4Cl standardizes this diffusimeter. Mass transfer of HCl, H2SO4, and H2C2O4 show oxalic acid diffusing as hydrate and 88 percentage transfer of sulfuric acid in 5 minutes. The Superdiffusive Anti Graham’s Law, Vd , is further consolidated by Ca (NO3)2-M2CO3(M = Na, K, NH4+) and Ca (NO3)2-Na2HPO4 diffusions. Odd and even diffusions are illustrated by AgNO3-NH4Cl and AgNO3-BaCl2 diffusions.

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Cheung, S. C. H. "Methods to measure apparent diffusion coefficients in compacted bentonite clays and data interpretation". Canadian Journal of Civil Engineering 16, n. 4 (1 agosto 1989): 434–43. http://dx.doi.org/10.1139/l89-073.

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The methods used to determine apparent diffusion coefficients and the appropriate parameters for modelling diffusion through compacted bentonite–water systems are assessed and discussed. The measured apparent diffusion coefficient can vary between methods. The discrepancies are shown to be due to heterogeneous diffusivities arising from the proximity of the surface of clay particles. Two different diffusivity pathways are identified and the diffusive flux is shown to be dictated by the charge of diffusing species, diffusion time, and soil fabric. Key words: apparent diffusion coefficient, methods, compacted bentonite, heterogeneous diffusion, parameters, pathways.

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Gadomski, Adam. "(Nano)Granules-Involving Aggregation at a Passage to the Nanoscale as Viewed in Terms of a Diffusive Heisenberg Relation". Entropy 26, n. 1 (17 gennaio 2024): 76. http://dx.doi.org/10.3390/e26010076.

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We are looking at an aggregation of matter into granules. Diffusion plays a pivotal role here. When going down to the nanometer scale (the so-called nanoscale quantum-size effect limit), quantum mechanics, and the Heisenberg uncertainty relation, may take over the role of classical diffusion, as viewed typically in the mesoscopic/stochastic limit. A d-dimensional entropy-production aggregation of the granules-involving matter in the granule-size space is considered in terms of a (sub)diffusive realization. It turns out that when taking a full d-dimensional pathway of the aggregation toward the nanoscale, one is capable of disclosing a Heisenberg-type (diffusional) relation, setting up an upper uncertainty bound for the (sub)diffusive, very slow granules-including environment that, within the granule-size analogy invoked, matches the quantum limit of h/2πμ (μ—average mass of a granule; h—the Planck’s constant) for the diffusion coefficient of the aggregation, first proposed by Fürth in 1933 and qualitatively foreseen by Schrödinger some years before, with both in the context of a diffusing particle. The classical quantum passage uncovered here, also termed insightfully as the quantum-size effect (as borrowed from the quantum dots’ parlance), works properly for the three-dimensional (d = 3) case, making use of a substantial physical fact that the (nano)granules interact readily via their surfaces with the also-granular surroundings in which they are immersed. This natural observation is embodied in the basic averaging construction of the diffusion coefficient of the entropy-productive (nano)aggregation of interest.

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Bengtsson, Lisa, Sander Tijm, Filip Váňa e Gunilla Svensson. "Impact of Flow-Dependent Horizontal Diffusion on Resolved Convection in AROME". Journal of Applied Meteorology and Climatology 51, n. 1 (gennaio 2012): 54–67. http://dx.doi.org/10.1175/jamc-d-11-032.1.

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AbstractHorizontal diffusion in numerical weather prediction models is, in general, applied to reduce numerical noise at the smallest atmospheric scales. In convection-permitting models, with horizontal grid spacing on the order of 1–3 km, horizontal diffusion can improve the model skill of physical parameters such as convective precipitation. For instance, studies using the convection-permitting Applications of Research to Operations at Mesoscale model (AROME) have shown an improvement in forecasts of large precipitation amounts when horizontal diffusion is applied to falling hydrometeors. The nonphysical nature of such a procedure is undesirable, however. Within the current AROME, horizontal diffusion is imposed using linear spectral horizontal diffusion on dynamical model fields. This spectral diffusion is complemented by nonlinear, flow-dependent, horizontal diffusion applied on turbulent kinetic energy, cloud water, cloud ice, rain, snow, and graupel. In this study, nonlinear flow-dependent diffusion is applied to the dynamical model fields rather than diffusing the already predicted falling hydrometeors. In particular, the characteristics of deep convection are investigated. Results indicate that, for the same amount of diffusive damping, the maximum convective updrafts remain strong for both the current and proposed methods of horizontal diffusion. Diffusing the falling hydrometeors is necessary to see a reduction in rain intensity, but a more physically justified solution can be obtained by increasing the amount of damping on the smallest atmospheric scales using the nonlinear, flow-dependent, diffusion scheme. In doing so, a reduction in vertical velocity was found, resulting in a reduction in maximum rain intensity.

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Da Silva, Marly Terezinha Quadri Simões, e Wellington Mazer. "Diffusion coefficient and tortuosity: Brownian Motion". CONTRIBUCIONES A LAS CIENCIAS SOCIALES 16, n. 9 (28 settembre 2023): 18281–302. http://dx.doi.org/10.55905/revconv.16n.9-264.

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The objective of this research is to determine the chloride ion diffusion through Brownian motion using images. The research also aims at the search for diffusional physical tortuosity due to Brownian motion to understand the transport flow of the chloride ion. Through micro-CT scanned images of concrete samples, a 3D reconstruction is performed for the representative element and define its microscopic properties. The implementation of the Brownian motion of the chloride ion particles in the porous network of the representative element considered the initial diffusion coefficient defined by the Stokes-Einstein equation. The diffusion coefficient is an important parameter for predicting the depth of attack of the chloride ion and its displacement due to Brownian motion helps to define the tortuosity of this diffusive transport. The research used computational modeling with MATLAB® software. The results show diffusion due to Brownian motion and tortuousness.

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Khoulif, S., E. B. Hannech e N. Lamoudi. "Study of Reactive Diffusion in Cu/Zn Diffusion Couple". Indian Journal Of Science And Technology 15, n. 48 (27 dicembre 2022): 2740–47. http://dx.doi.org/10.17485/ijst/v15i48.13.

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Lens, Piet N. L., Rakel Gastesi, Frank Vergeldt, Adriaan C. van Aelst, Antonio G. Pisabarro e Henk Van As. "Diffusional Properties of Methanogenic Granular Sludge: 1H NMR Characterization". Applied and Environmental Microbiology 69, n. 11 (novembre 2003): 6644–49. http://dx.doi.org/10.1128/aem.69.11.6644-6649.2003.

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ABSTRACT The diffusive properties of anaerobic methanogenic and sulfidogenic aggregates present in wastewater treatment bioreactors were studied using diffusion analysis by relaxation time-separated pulsed-field gradient nuclear magnetic resonance (NMR) spectroscopy and NMR imaging. NMR spectroscopy measurements were performed at 22°C with 10 ml of granular sludge at a magnetic field strength of 0.5 T (20 MHz resonance frequency for protons). Self-diffusion coefficients of H2O in the investigated series of mesophilic aggregates were found to be 51 to 78% lower than the self-diffusion coefficient of free water. Interestingly, self-diffusion coefficients of H2O were independent of the aggregate size for the size fractions investigated. Diffusional transport occurred faster in aggregates growing under nutrient-rich conditions (e.g., the bottom of a reactor) or at high (55°C) temperatures than in aggregates cultivated in nutrient-poor conditions or at low (10°C) temperatures. Exposure of aggregates to 2.5% glutaraldehyde or heat (70 or 90°C for 30 min) modified the diffusional transport up to 20%. In contrast, deactivation of aggregates by HgCl2 did not affect the H2O self-diffusion coefficient in aggregates. Analysis of NMR images of a single aggregate shows that methanogenic aggregates possess a spin-spin relaxation time and self-diffusion coefficient distribution, which are due to both physical (porosity) and chemical (metal sulfide precipitates) factors.

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Benga, Gheorghe, Octavian Popescu e Victor I. Pop. "Water exchange through erythrocyte membranes: p-choloromercuribenzene sulfonate inhibition of water diffusion in ghosts studied by a nuclear magnetic resonance technique". Bioscience Reports 5, n. 3 (1 marzo 1985): 223–28. http://dx.doi.org/10.1007/bf01119591.

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A comparison of water diffusion in human erythrocytes and ghosts revealed a longer relaxation time in ghosts, A comparison of water diffusion in human erythrocytes and ghosts revealed a longer relaxation time in ghosts, corresponding to a decreased exchange rate. However, the diffusional permeability of ghosts was not significantly different from that of erythrocytes. The changes in water diffusion following exposure to p-chloromercuribenzene sulfonate (PCMBS) have been studied on ghosts suspended in isotonic solutions. It was found that a significant inhibitory effect of PCMBS on water diffusion occurred only after several minutes of incubation at 37°C. No inhibition was noticed after short incubation at 0°C as previously used in some labelling experiments. This indicates the location in the membrane interior of the SH groups involved in water diffusion across human erythrocyte membranes. The nuclear magnetic resonance (n. m. r.) method appears as a useful tool for studying changes in water diffusiofl in erythrocyte ghosts with the aim of locating the water channel.

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Pinholt, Henrik D., Søren S. R. Bohr, Josephine F. Iversen, Wouter Boomsma e Nikos S. Hatzakis. "Single-particle diffusional fingerprinting: A machine-learning framework for quantitative analysis of heterogeneous diffusion". Proceedings of the National Academy of Sciences 118, n. 31 (28 luglio 2021): e2104624118. http://dx.doi.org/10.1073/pnas.2104624118.

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Single-particle tracking (SPT) is a key tool for quantitative analysis of dynamic biological processes and has provided unprecedented insights into a wide range of systems such as receptor localization, enzyme propulsion, bacteria motility, and drug nanocarrier delivery. The inherently complex diffusion in such biological systems can vary drastically both in time and across systems, consequently imposing considerable analytical challenges, and currently requires an a priori knowledge of the system. Here we introduce a method for SPT data analysis, processing, and classification, which we term “diffusional fingerprinting.” This method allows for dissecting the features that underlie diffusional behavior and establishing molecular identity, regardless of the underlying diffusion type. The method operates by isolating 17 descriptive features for each observed motion trajectory and generating a diffusional map of all features for each type of particle. Precise classification of the diffusing particle identity is then obtained by training a simple logistic regression model. A linear discriminant analysis generates a feature ranking that outputs the main differences among diffusional features, providing key mechanistic insights. Fingerprinting operates by both training on and predicting experimental data, without the need for pretraining on simulated data. We found this approach to work across a wide range of simulated and experimentally diverse systems, such as tracked lipases on fat substrates, transcription factors diffusing in cells, and nanoparticles diffusing in mucus. This flexibility ultimately supports diffusional fingerprinting’s utility as a universal paradigm for SPT diffusional analysis and prediction.

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Hutzenthaler, Martin, e Jesse Earl Taylor. "Time reversal of some stationary jump diffusion processes from population genetics". Advances in Applied Probability 42, n. 4 (dicembre 2010): 1147–71. http://dx.doi.org/10.1239/aap/1293113155.

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We describe the processes obtained by time reversal of a class of stationary jump diffusion processes that model the dynamics of genetic variation in populations subject to repeated bottlenecks. Assuming that only one lineage survives each bottleneck, the forward process is a diffusion on [0,1] that jumps to the boundary before diffusing back into the interior. We show that the behavior of the time-reversed process depends on whether the boundaries are accessible to the diffusive motion of the forward process. If a boundary point is inaccessible to the forward diffusion then time reversal leads to a jump diffusion that jumps immediately into the interior whenever it arrives at that point. If, instead, a boundary point is accessible then the jumps off of that point are governed by a weighted local time of the time-reversed process.

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Più fonti

Tesi sul tema "Diffusion"

Imoto, Yu, e Takashi Odagaki. "Diffusion on diffusing particles". Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-193282.

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We investigate random walk of a particle constrained on cells, where cells behave as a lattice gas on a two dimensional square lattice. By Monte Carlo simulation, we obtain the mean first passage time of the particle as a function of the density and temperature of the lattice gas. We find that the transportation of the particle becomes anomalously slow in a certain range of parameters because of the cross over in dynamics between the low and high density regimes; for low densities the dynamics of cells plays the essential role, and for high densities, the dynamics of the particle plays the dominant role.

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Imoto, Yu, e Takashi Odagaki. "Diffusion on diffusing particles". Diffusion fundamentals 6 (2007) 11, S. 1-7, 2007. https://ul.qucosa.de/id/qucosa%3A14185.

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Bernhardt, Thomas. "Reflected diffusions and piecewise diffusion approximations of Levy processes". Thesis, London School of Economics and Political Science (University of London), 2017. http://etheses.lse.ac.uk/3659/.

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In the first part of the thesis, the solvability of stochastic differential equations with reflecting boundary conditions is studied. Such equations arise in singular stochastic control problems as a way for determining the optimal strategies. The stochastic differential equations represent homogeneous one-dimensional diffusions while the boundaries are given by c`adl`ag functions. Pathwise solutions are constructed under mild assumptions on the coefficients of the equations. In particular, the solutions are derived as the diffusions’ scale functions composed with appropriately time-changed reflected Brownian motions. Several probabilistic properties are addressed and analysed. In the second part of the thesis, piecewise diffusion approximations of Levy processes are studied. Such approximating processes have been called Itˆo semi-diffusions. While keeping the statistical fit to Levy processes, this class of processes has the analytical tractability of Ito diffusions. At a given time grid, their distribution is the same as the one of the underlying Levy processes. At times outside the grid, they evolve like homogeneous diffusions. The analysis identifies conditions under which Itˆo semi-diffusions can be used as an alternative to Levy processes for modelling financial asset prices. In particular, for a sequence of Itˆo semi-diffusions determined by a given Levy process, conditions for the convergence of their finite-dimensional distributions to the ones of the Levy process are established. Furthermore, for a single Ito semi-diffusion, conditions for the existence of pricing measures are established.

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Prehl, Janett Hoffmann Karl-Heinz. "Diffusion on fractals Diffusion auf Fraktalen /". [S.l. : s.n.], 2007.

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Rane, Swati. "Diffusion tensor imaging at long diffusion time". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29708.

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Thesis (Ph.D)--Biomedical Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Hu, Xiaoping; Committee Member: Brummer, Marijn; Committee Member: Duong, Tim; Committee Member: Keilholz, Shella; Committee Member: Schumacher, Eric. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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Coulon, Anne-Charline. "Propagation in reaction-diffusion equations with fractional diffusion". Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/277576.

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This thesis focuses on the long time behaviour of solutions to Fisher-KPP reaction-diffusion equations involving fractional diffusion. This type of equation arises, for example, in spatial propagation or spreading of biological species (rats, insects,...). In population dynamics, the quantity under study stands for the density of the population. It is well-known that, under some specific assumptions, the solution tends to a stable state of the evolution problem, as time goes to infinity. In other words, the population invades the medium, which corresponds to the survival of the species, and we want to understand at which speed this invasion takes place. To answer this question, we set up a new method to study the speed of propagation when fractional diffusion is at stake and apply it on three different problems. Part I of the thesis is devoted to an analysis of the asymptotic location of the level sets of the solution to two different problems : Fisher-KPP models in periodic media and cooperative systems, both including fractional diffusion. On the first model, we prove that, under some assumptions on the periodic medium, the solution spreads exponentially fast in time and we find the precise exponent that appears in this exponential speed of propagation. We also carry out numerical simulations to investigate the dependence of the speed of propagation on the initial condition. On the second model, we prove that the speed of propagation is once again exponential in time, with an exponent depending on the smallest index of the fractional Laplacians at stake and on the reaction term. Part II of the thesis deals with a two dimensional environment, where reproduction of Fisher-KPP type and usual diffusion occur, except on a line of the plane, on which fractional diffusion takes place. The plane is referred to as 'the field' and the line to 'the road', as a reference to the biological situations we have in mind. Indeed, it has long been known that fast diffusion on roads can have a driving effect on the spread of epidemics. We prove that the speed of propagation is exponential in time on the road, whereas it depends linearly on time in the field. Contrary to the precise asymptotics obtained in Part I, for this model, we are not able to give a sharp location of the level sets on the road and in the field. The expansion shape of the level sets in the field is investigated through numerical simulations.
Esta tesis se centra en el comportamiento en tiempos grandes de las soluciones de la ecuación de Fisher- KPP de reacción-difusión con difusión fraccionaria. Este tipo de ecuación surge, por ejemplo, en la propagación espacial o en la propagación de especies biológicas (ratas, insectos,...). En la dinámica de poblaciones, la cantidad que se estudia representa la densidad de la población. Es conocido que, bajo algunas hipótesis específicas, la solución tiende a un estado estable del problema de evolución, cuando el tiempo tiende a infinito. En otras palabras, la población invade el medio, lo que corresponde a la supervivencia de la especie, y nosotros queremos entender con qué velocidad se lleva a cabo esta invasión. Para responder a esta pregunta, hemos creado un nuevo método para estudiar la velocidad de propagación cuando se consideran difusiones fraccionarias, además hemos aplicado este método en tres problemas diferentes. La Parte I de la tesis está dedicada al análisis de la ubicación asintótica de los conjuntos de nivel de la solución de dos problemas diferentes: modelos de Fisher- KPP en medios periódicos y sistemas cooperativos, ambos consideran difusión fraccionaria. En el primer modelo, se prueba que, bajo ciertas hipótesis sobre el medio periódico, la solución se propaga exponencialmente rápido en el tiempo, además encontramos el exponente exacto que aparece en esta velocidad de propagación exponencial. También llevamos a cabo simulaciones numéricas para investigar la dependencia de la velocidad de propagación con la condición inicial. En el segundo modelo, se prueba que la velocidad de propagación es nuevamente exponencial en el tiempo, con un exponente que depende del índice más pequeño de los Laplacianos fraccionarios y también del término de reacción. La Parte II de la tesis ocurre en un entorno de dos dimensiones, donde se reproduce un tipo ecuación de Fisher- KPP con difusión estándar, excepto en una línea del plano, en el que la difusión fraccionada aparece. El plano será llamado "campo" y la línea "camino", como una referencia a las situaciones biológicas que tenemos en mente. De hecho, desde hace tiempo se sabe que la difusión rápida en los caminos puede causar un efecto en la propagación de epidemias. Probamos que la velocidad de propagación es exponencial en el tiempo en el camino, mientras que depende linealmente del tiempo en el campo. Contrariamente a los precisos exponentes obtenidos en la Parte I, para este modelo, no fuimos capaces de dar una localización exacta de los conjuntos de nivel en la carretera y en el campo. La forma de propagación de los conjuntos de nivel en el campo se investiga a través de simulaciones numéricas

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Benson, Debbie Lisa. "Reaction diffusion models with spatially inhomogeneous diffusion coefficients". Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239337.

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Prehl, Janett. "Diffusion on fractals and space-fractional diffusion equations". Doctoral thesis, Universitätsbibliothek Chemnitz, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-201001068.

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Ziel dieser Arbeit ist die Untersuchung der Sub- und Superdiffusion in fraktalen Strukturen. Der Fokus liegt auf zwei separaten Ansätzen, die entsprechend des Diffusionbereiches gewählt und variiert werden. Dadurch erhält man ein tieferes Verständnis und eine bessere Beschreibungsweise für beide Bereiche. Im ersten Teil betrachten wir subdiffusive Prozesse, die vor allem bei Transportvorgängen, z. B. in lebenden Geweben, eine grundlegende Rolle spielen. Hierbei modellieren wir den fraktalen Zustandsraum durch endliche Sierpinski Teppiche mit absorbierenden Randbedingungen und lösen dann die Mastergleichung zur Berechnung der Zeitentwicklung der Wahrscheinlichkeitsverteilung. Zur Charakterisierung der Diffusion auf regelmäßigen und zufälligen Teppichen bestimmen wir die Abfallzeit der Wahrscheinlichkeitsverteilung, die mittlere Austrittszeit und die Random Walk Dimension. Somit können wir den Einfluss zufälliger Strukturen auf die Diffusion aufzeigen. Superdiffusive Prozesse werden im zweiten Teil der Arbeit mit Hilfe der Diffusionsgleichung untersucht. Deren zweite Ableitung im Ort erweitern wir auf nichtganzzahlige Ordnungen, um die fraktalen Eigenschaften der Umgebung darzustellen. Die resultierende raum-fraktionale Diffusionsgleichung spannt ein Übergangsregime von der irreversiblen Diffusionsgleichung zur reversiblen Wellengleichung auf. Deren Lösungen untersuchen wir mittels verschiedener Entropien, wie Shannon, Tsallis oder Rényi Entropien, und deren Entropieproduktionsraten, welche natürliche Maße für die Irreversibilität sind. Das dabei gefundene Entropieproduktions-Paradoxon, d. h. ein unerwarteter Anstieg der Entropieproduktionsrate bei sinkender Irreversibilität des Prozesses, können wir nach geeigneter Reskalierung der Entropien auflösen
The aim of this thesis is the examination of sub- and superdiffusive processes in fractal structures. The focus of the work concentrates on two separate approaches that are chosen and varied according to the corresponding regime. Thus, we obtain new insights about the underlying mechanisms and a more appropriate way of description for both regimes. In the first part subdiffusion is considered, which plays a crucial role for transport processes, as in living tissues. First, we model the fractal state space via finite Sierpinski carpets with absorbing boundary conditions and we solve the master equation to compute the time development of the probability distribution. To characterize the diffusion on regular as well as random carpets we determine the longest decay time of the probability distribution, the mean exit time and the Random walk dimension. Thus, we can verify the influence of random structures on the diffusive dynamics. In the second part of this thesis superdiffusive processes are studied by means of the diffusion equation. Its second order space derivative is extended to fractional order, which represents the fractal properties of the surrounding media. The resulting space-fractional diffusion equations span a linking regime from the irreversible diffusion equation to the reversible (half) wave equation. The corresponding solutions are analyzed by different entropies, as the Shannon, Tsallis or Rényi entropies and their entropy production rates, which are natural measures of irreversibility. We find an entropy production paradox, i. e. an unexpected increase of the entropy production rate by decreasing irreversibility of the processes. Due to an appropriate rescaling of the entropy we are able to resolve the paradox

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Kuchel, Philip W., e Guilhem Pages. "NMR diffusion diffraction and diffusion interference from cells". Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-194150.

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Pulsed field gradient spin-echo (PGSE) NMR spectroscopy is the definitive means for measuring translational motion of molecules in free solution and in heterogeneous systems. A unique ‘twist’ on the method is that in some systems in which diffusion is restricted the PGSE experiment yields information on the geometrical properties of the confining boundaries. When applied to red blood cells (RBCs) in suspensions, using intense magnetic field gradients (around 10 T m-1), the graph of normalized NMR-signal intensity versus the magnitude of the field gradients has the form of the diffraction and interference patterns that are seen in physical optics. We review here the nature of these so called q-space plots and discuss a data-processing method that adds objectivity to estimates of the mean RBC diameter. Convection potentially interferes with the veracity of these measurements so an experiment is reported in which a cell-free sample was deliberately made to flow. The very simple analysis of flow diffraction yielded estimates of flow that were in remarkable agreement with gravimetric measurements. Finally, in a theoretical study using a model of uniformly arrayed octagonal prisms that were ‘morphed’ in a systematic way, the dependence of the form of q-space plots on prism shape and packing density was obtained. This showed that elaborately shaped q-space plots can be obtained from simple periodic arrays of ‘cells’. The uniqueness or otherwise of shapes of q-space plots, and the prospect of generally solving the inverse problem whereby q-space analysis yields detailed information on packing arrangements is poised for further detailed investigations.

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Kuchel, Philip W., e Guilhem Pages. "NMR diffusion diffraction and diffusion interference from cells". Diffusion fundamentals 6 (2007) 74, S. 1-16, 2007. https://ul.qucosa.de/id/qucosa%3A14254.

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Più fonti

Libri sul tema "Diffusion"

Chakraverty, S., e Sukanta Nayak. Neutron Diffusion. Boca Raton : CRC Press, 2017.: CRC Press, 2017. http://dx.doi.org/10.1201/b22222.

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Vogl, Gero. Adventure Diffusion. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-04681-1.

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Ghez, Richard. Diffusion Phenomena. Boston, MA: Springer US, 2001. http://dx.doi.org/10.1007/978-1-4757-3361-7.

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Tringides, M. C., a cura di. Surface Diffusion. Boston, MA: Springer US, 1997. http://dx.doi.org/10.1007/978-1-4899-0262-7.

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L, Gaile Gary, e Thrall Grant Ian, a cura di. Spatial diffusion. Newbury Park: Sage Publications, 1988.

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Seizō, Itō. Diffusion equations. Providence, R.I: American Mathematical Society, 1992.

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Stock, James H. Diffusion indexes. Cambridge, MA: National Bureau of Economic Research, 1998.

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Jovanovic, Boyan. Competitive diffusion. Cambridge, MA: National Bureau of Economic Research, 1993.

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NATO Advanced Study Institute on Diffusion in Materials (1989 Aussois, France). Diffusion in materials. Dordrecht: Kluwer Academic Publishers, 1990.

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Stroock, Daniel W. Multidimensional diffusion processes. 2^a ed. Berlin: Springer, 1997.

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Capitoli di libri sul tema "Diffusion"

Ahmed, Hesham M., Christopher T. Aquina, Vicente H. Gracias, J. Javier Provencio, Mariano Alberto Pennisi, Giuseppe Bello, Massimo Antonelli et al. "Diffusion". In Encyclopedia of Intensive Care Medicine, 718. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-00418-6_3085.

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Annesini, Maria Cristina, Luigi Marrelli, Vincenzo Piemonte e Luca Turchetti. "Diffusion". In Artificial Organ Engineering, 3–22. London: Springer London, 2016. http://dx.doi.org/10.1007/978-1-4471-6443-2_1.

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Salsa, Sandro. "Diffusion". In UNITEXT, 17–114. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-15093-2_2.

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Cooper, Jeffery. "Diffusion". In Introduction to Partial Differential Equations with MATLAB, 73–110. Boston, MA: Birkhäuser Boston, 1998. http://dx.doi.org/10.1007/978-1-4612-1754-1_3.

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Durand-Charre, Madeleine. "Diffusion". In Microstructure of Steels and Cast Irons, 163–77. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-662-08729-9_8.

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Savva, Michalakis. "Diffusion". In Pharmaceutical Calculations, 181–208. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-20335-1_8.

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Porter, D. A., e K. E. Easterling. "Diffusion". In Phase Transformations in Metals and Alloys, 60–109. Boston, MA: Springer US, 1992. http://dx.doi.org/10.1007/978-1-4899-3051-4_2.

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Scherer, Philipp O. J. "Diffusion". In Graduate Texts in Physics, 479–91. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-61088-7_21.

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Liang, Yan. "Diffusion". In Encyclopedia of Earth Sciences Series, 1–13. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-39193-9_336-1.

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Liang, Yan. "Diffusion". In Encyclopedia of Earth Sciences Series, 363–75. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-39312-4_336.

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Atti di convegni sul tema "Diffusion"

Yang, Yijun, Ruiyuan Gao, Xiaosen Wang, Tsung-Yi Ho, Nan Xu e Qiang xu. "MMA-Diffusion: MultiModal Attack on Diffusion Models". In 2024 IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR), 7737–46. IEEE, 2024. http://dx.doi.org/10.1109/cvpr52733.2024.00739.

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Zhang, Biao, e Peter Wonka. "Functional Diffusion". In 2024 IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR), 4723–32. IEEE, 2024. http://dx.doi.org/10.1109/cvpr52733.2024.00452.

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Guo, Jiayi, Xingqian Xu, Yifan Pu, Zanlin Ni, Chaofei Wang, Manushree Vasu, Shiji Song, Gao Huang e Humphrey Shi. "Smooth Diffusion: Crafting Smooth Latent Spaces in Diffusion Models". In 2024 IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR), 7548–58. IEEE, 2024. http://dx.doi.org/10.1109/cvpr52733.2024.00721.

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Chen, Xiyi, Marko Mihajlovic, Shaofei Wang, Sergey Prokudin e Siyu Tang. "Morphable Diffusion: 3D-Consistent Diffusion for Single-image Avatar Creation". In 2024 IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR), 10359–70. IEEE, 2024. http://dx.doi.org/10.1109/cvpr52733.2024.00986.

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Huang, Ziyang, Pengfei Cao, Jun Zhao e Kang Liu. "DiffusionSL: Sequence Labeling via Tag Diffusion Process". In Findings of the Association for Computational Linguistics: EMNLP 2023. Stroudsburg, PA, USA: Association for Computational Linguistics, 2023. http://dx.doi.org/10.18653/v1/2023.findings-emnlp.860.

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Li, Xiuyu, Yijiang Liu, Long Lian, Huanrui Yang, Zhen Dong, Daniel Kang, Shanghang Zhang e Kurt Keutzer. "Q-Diffusion: Quantizing Diffusion Models". In 2023 IEEE/CVF International Conference on Computer Vision (ICCV). IEEE, 2023. http://dx.doi.org/10.1109/iccv51070.2023.01608.

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Choi, Saemi, Yusuke Matsui e Kiyoharu Aizawa. "Diffusion". In SA'14: SIGGRAPH Asia 2014. New York, NY, USA: ACM, 2014. http://dx.doi.org/10.1145/2668975.2668987.

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Chen, Yunmei, e Stacey Chastain. "Anisotropic diffusion driven by diffusion tensors". In International Symposium on Optical Science and Technology, a cura di David C. Wilson, Hemant D. Tagare, Fred L. Bookstein, Francoise J. Preteux e Edward R. Dougherty. SPIE, 2000. http://dx.doi.org/10.1117/12.402435.

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Zabari, Nir, Aharon Azulay, Alexey Gorkor, Tavi Halperin e Ohad Fried. "Diffusing Colors: Image Colorization with Text Guided Diffusion". In SA '23: SIGGRAPH Asia 2023. New York, NY, USA: ACM, 2023. http://dx.doi.org/10.1145/3610548.3618180.

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Odiachi, Judah, Felipe Cruz e Ali Tinni. "Diffusional and Electrical Tortuosity in Unconventional Shale Reservoirs". In SPE Annual Technical Conference and Exhibition. SPE, 2022. http://dx.doi.org/10.2118/210164-ms.

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Abstract (sommario):

Abstract Tortuosity is a porous medium property which measures the interconnectedness and sinuosity of the pore space. It is important in order to understand advective, diffusive transport and electric current flow in low porosity low permeability reservoirs such as unconventional shale reservoirs. However, experimental values of diffusional and electrical tortuosity of shales are scarce in the literature. To improve the understanding of diffusive transport and electrical flow in unconventional shale reservoirs, we have conducted the independent measurements of diffusional and electrical tortuosities of 12 shale samples from Utica, Bakken, Wolfcamp and Eagle Ford formations and 3 sandstones as control samples. For the purpose of this study, the samples were characterized by measurements of total organic carbon (TOC), mineralogy, and total porosity. Diffusional tortuosity was measured by immersing brine saturated samples into D2O to allow the diffusion of D2O into the samples. The rates at which D2O diffused into the samples were measured with 12 MHz NMR measurements. The combination of the effective diffusion coefficient of D2O and the bulk diffusion coefficient of D2O were used to compute the diffusional tortuosity. To measure electrical tortuosity, the samples were resaturated with 2.5% KCl brine prior to immersion into 6% KCl brine. The measurements of the samples’ resistivities as function of time after the immersion into the 6% KCl brine were used to compute ionic diffusion coefficients. Electrical tortuosity was calculated using the bulk ionic diffusion coefficient and the ionic diffusion coefficients of the samples. The results show that diffusional and electrical tortuosity have similar values. These tortuosities vary between 1.7 and 5.8 for shale samples while they have values between 1.4 and 3.9 for sandstones. We also observed that TOC exerts a primary control on the tortuosity of shales.

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Rapporti di organizzazioni sul tema "Diffusion"

Lin, Jeong-long, e William Taylor. Thermodynamics of Thermal Diffusion: Thermal Diffusion in Liquids and Thermal Diffusion in Gasses. Office of Scientific and Technical Information (OSTI), dicembre 1988. http://dx.doi.org/10.2172/967180.

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Cooper, Michael William Donald, K. A. Gamble, Christopher Matthews e Anders David Ragnar Andersson. Irradiation enhanced diffusion and diffusional creep in U₃Si₂. Office of Scientific and Technical Information (OSTI), giugno 2020. http://dx.doi.org/10.2172/1633555.

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Glynn, Peter W. Diffusion Approximations. Fort Belvoir, VA: Defense Technical Information Center, luglio 1989. http://dx.doi.org/10.21236/ada212581.

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Stock, James, e Mark Watson. Diffusion Indexes. Cambridge, MA: National Bureau of Economic Research, agosto 1998. http://dx.doi.org/10.3386/w6702.

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Stokey, Nancy. Technology Diffusion. Cambridge, MA: National Bureau of Economic Research, luglio 2020. http://dx.doi.org/10.3386/w27466.

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Jovanovic, Boyan, e Glenn MacDonald. Competitive Diffusion. Cambridge, MA: National Bureau of Economic Research, settembre 1993. http://dx.doi.org/10.3386/w4463.

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Burgess Jr, Donald R. Self-Diffusion and Binary-Diffusion Coefficients in Gases. Gaithersburg, MD: National Institute of Standards and Technology, 2023. http://dx.doi.org/10.6028/nist.tn.2279.

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Yang, T. Diffusion of Zonal Variables Using Node-Centered Diffusion Solver. Office of Scientific and Technical Information (OSTI), agosto 2007. http://dx.doi.org/10.2172/924607.

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Dayananda, M. A., e R. Venkatasubramanian. Diffusion path representation for two-phase ternary diffusion couples. Office of Scientific and Technical Information (OSTI), gennaio 1986. http://dx.doi.org/10.2172/5851361.

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Trowbridge, L. Isotopic selectivity of surface diffusion: An activated diffusion model. Office of Scientific and Technical Information (OSTI), novembre 1989. http://dx.doi.org/10.2172/5462238.

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