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Dissertations / Theses on the topic 'DIFFUSIVE THEORY'

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Published: 10 March 2023

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1

Mukherjee, Sayak. "Applications of Field Theory to Reaction Diffusion Models and Driven Diffusive Systems." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/39293.

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In this thesis, we focus on the steady state properties of two systems which are genuinely out of equilibrium. The first project is an application of dynamic field theory to a specific non equilibrium critical phenomenon, while the second project involves both simulations and analytical calculations. The methods of field theory are used on both these projects. In the first part of this thesis, we investigate a generalization of the well-known field theory for directed percolation (DP). The DP theory is known to describe an evolving population, near extinction. We have coupled this evolving population to an environment with its own nontrivial spatio-temporal dynamics. Here, we consider the special case where the environment follows a simple relaxational (model A) dynamics. We find two marginal couplings with upper critical dimension of four, which couple the two theories in a nontrivial way. While the Wilson-Fisher fixed point remains completely unaffected, a mismatch of time scales destabilizes the usual DP fixed point. Some open questions and future work remain. In the second project, we focus on a simple particle transport model far from equilibrium, namely, the totally asymmetric simple exclusion process (TASEP). While its stationary properties are well studied, many of its dynamic features remain unexplored. Here, we focus on the power spectrum of the total particle occupancy in the system. This quantity exhibits unexpected oscillations in the low density phase. Using standard Monte Carlo simulations and analytic calculations, we probe the dependence of these oscillations on boundary effects, the system size, and the overall particle density. Our simulations are fitted to the predictions of a linearized theory for the fluctuation of the particle density. Two of the fit parameters, namely the diffusion constant and the noise strength, deviate from their naive bare values [6]. In particular, the former increases significantly with the system size. Since this behavior can only be caused by nonlinear effects, we calculate the lowest order corrections in perturbation theory. Several open questions and future work are discussed.
Ph. D.

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2

Merino, Aceituno Sara. "Contributions in fractional diffusive limit and wave turbulence in kinetic theory." Thesis, University of Cambridge, 2015. https://www.repository.cam.ac.uk/handle/1810/256994.

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This thesis is split in two different topics. Firstly, we study anomalous transport from kinetic models. Secondly, we consider the equations coming from weak wave turbulence theory and we study them via mean-field limits of finite stochastic particle systems. $\textbf{Anomalous transport from kinetic models.}$ The goal is to understand how fractional diffusion arises from kinetic equations. We explain how fractional diffusion corresponds to anomalous transport and its relation to the classical diffusion equation. In previous works it has been seen that particles systems undergoing free transport and scattering with the media can give rise to fractional phenomena in two cases: firstly, if in the dynamics of the particles there is a heavy-tail equilibrium distribution; and secondly, if the scattering rate is degenerate for small velocities. We use these known results in the literature to study the emergence of fractional phenomena for some particular kinetic equations. Firstly, we study BGK-type equations conserving not only mass (as in previous results), but also momentum and energy. In the hydrodynamic limit we obtain a fractional diffusion equation for the temperature and density making use of the Boussinesq relation and we also demonstrate that with the same rescaling fractional diffusion cannot be derived additionally for the momentum. But considering the case of conservation of mass and momentum only, we do obtain the incompressible Stokes equation with fractional diffusion in the hydrodynamic limit for heavy-tailed equilibria. Secondly, we will study diffusion phenomena arising from transport of energy in an anharmonic chain. More precisely, we will consider the so-called FPU-$\beta$ chain, which is a very simple model for a one-dimensional crystal in which atoms are coupled to their nearest neighbours by a harmonic potential, weakly perturbed by a nonlinear quartic potential. The starting point of our mathematical analysis is a kinetic equation; lattice vibrations, responsible for heat transport, are modelled by an interacting gas of phonons whose evolution is described by the Boltzmann Phonon Equation. Our main result is the derivation of an anomalous diffusion equation for the temperature. $\textbf{Weak wave turbulence theory and mean-field limits for stochastic particle systems.}$ The isotropic 4-wave kinetic equation is considered in its weak formulation using model homogeneous kernels. Existence and uniqueness of solutions is proven in a particular setting. We also consider finite stochastic particle systems undergoing instantaneous coagulation-fragmentation phenomena and give conditions in which this system approximates the solution of the equation (mean-field limit).

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3

Traytak, Sergey D. "Diffusive interaction in the clusters of sinks: theory and some applications." Diffusion fundamentals 11 (2009) 4, S. 1-2, 2009. https://ul.qucosa.de/id/qucosa%3A13921.

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4

Yokoyama, T., Y. Tanaka, and A. A. Golubov. "Theory of the Josephson effect in unconventional superconducting junctions with diffusive barriers." American Physical Society, 2007. http://hdl.handle.net/2237/8821.

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5

Mohan, Aruna 1981. "Studies on the hydrodynamic equations based on the theory of diffusive volume transport." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29377.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, June 2004.
Includes bibliographical references (leaves 41-42).
A recently formulated continuum theory has postulated that the momentum per unit volume of fluid differs from the mass flux whenever there are density gradients in the fluid resulting from the molecular transport of heat or mass. In such cases, the Navier-Stokes equations are unable to correctly predict the continuum fields and observed flow phenomena. A new set of continuum equations has been postulated to take into account density inhomogeneities in the fluid, and the consequent difference between the fluid's momentum per unit mass and mass velocity. In this thesis, the modified set of continuum equations is used to solve problems related to fluid flow in the presence of heat and mass transport. Additionally, this thesis includes a comparison between the momentum per unit volume and the mass flux of a fluid calculated from the generalized kinetic equation of Klimontovich.
by Aruna Mohan.
S.M.

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6

Miao, Jiayuan. "Theory and Simulation of the Responses of Polymers to Electric Fields, Stress, Irradiation, and Diffusive Solvents." Case Western Reserve University School of Graduate Studies / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1481279886096515.

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7

Shamsalsadati, Sharmin. "Interferometry in diffusive systems: Theory, limitation to its practical application and its use in Bayesian estimation of material properties." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/50596.

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Interferometry in geosciences uses mathematical techniques to image subsurface properties. This method turns a receiver in to a virtual source through utilizing either random noises or engineered sources. The method in seismology has been discussed extensively. Electromagnetic interferometry at high frequencies with coupled electromagnetic fields was developed in the past. However, the problem was not addressed for diffusive electromagnetic fields where the quasi-static limit holds. One of the objectives of this dissertation was to theoretically derive the impulse response of the Earth for low-frequency electromagnetic fields. Applying the theory of interferometry in the regions where the wavefields are diffusive requires volumetrically distributed sources in an infinite domain. That precondition imposed by the theory is not practical in experiments. Hence, the aim of this study was to quantify the important areas and distribution of sources that makes it possible to apply the theory in practice through conducting numerical experiments. Results of the numerical analysis in double half-space models revealed that for surface-based exploration scenarios sources are required to reside in a region with higher diffusivity. In contrast, when the receivers straddle an interface, as in borehole experiments, there is no universal rule for which region is more important; it depends on the frequency, receiver separation and also diffusivity contrast between the layers and varies for different scenarios. Time-series analysis of the sources confirmed previous findings that the accuracy of the Green\'s function retrieval is a function of both source density and its width. Extending previous works in homogenous media into inhomogeneous models, it was found that sources must be distributed asymmetrically in the system, and extend deeper into the high diffusivity region in comparison to the low diffusivity area. The findings were applied in a three-layered example with a reservoir layer between two impermeable layers. Bayesian statistical inversion of the data obtained by interferometry was then used to estimate the fluid diffusivity (and permeability) along with associated uncertainties. The inversion results determined the estimated model parameters in the form of probability distributions. The output demonstrated that the algorithm converges closely to the true model.
Ph. D.

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8

Cheung, Sai-Kit. "The study of weak localization effects on wave dynamics in mesoscopic media in the diffusive regime and at the localization transition /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202006%20CHEUNG.

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9

Sawa, Y., T. Yokoyama, Y. Tanaka, and A. Golubov A. "Quasiclassical Green's function theory of the Josephson effect in chiral ρ-wave superconductor/diffusive normal metal/chiral ρ-wave superconductor junctions." American Physical Society, 2007. http://hdl.handle.net/2237/8824.

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10

Wilks, Theresa M. "Toroidal phasing of resonant magnetic perturbation effect on edge pedestal transport in the DIII-D tokamak." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47558.

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Resonant Magnetic Perturbation (RMP) fields produced by external control coils are considered a viable option for the suppression of Edge Localized Modes (ELMs) in present and future tokamaks. Repeated reversals of the toroidal phase of the I-coil magnetic field in RMP shot 147170 on DIII-D has generated uniquely different edge pedestal profiles, implying different edge transport phenomena. The causes, trends, and implications of RMP toroidal phase reversal on edge transport is analyzed by comparing various parameters at 0 and 60 degree toroidal phases, with an I-coil mode number of n=3. An analysis of diffusive and non-diffusive transport effects of these magnetic perturbations it the plasma edge pedestal for this RMP shot is characterized by interpreting the ion and electron heat diffusivities, angular momentum transport frequencies, ion diffusion coefficients, and pinch velocities for both phases.

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11

Nazarov, Andrei V., and Alexandr A. Mikheev. "Theory of diffusion under stress." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-195525.

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12

Nazarov, Andrei V., and Alexandr A. Mikheev. "Theory of diffusion under stress." Diffusion fundamentals 2 (2005) 32, S. 1-2, 2005. https://ul.qucosa.de/id/qucosa%3A13312.

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13

Rao, Sanjeev M., and Marc-Olivier Coppens. "Simplified theory to predict mixture diffusion in zeolites." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-183068.

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14

Pounders, Justin M. "Stochastically Generated Multigroup Diffusion Coefficients." Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14007.

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The generation of multigroup neutron cross sections is usually the first step in the solution of reactor physics problems. This typically includes generating condensed cross section sets, collapsing the scattering kernel, and within the context of diffusion theory, computing diffusion coefficients that capture transport effects as accurately possible. Although the calculation of multigroup parameters has historically been done via deterministic methods, it is natural to think of using the Monte Carlo method due to its geometric flexibility and robust computational capabilities such as continuous energy transport. For this reason, a stochastic cross section generation method has been implemented in the Mont Carlo code MCNP5 (Brown et al, 2003) that is capable of computing macroscopic material cross sections (including angular expansions of the scattering kernel) for transport or diffusion applications. This methodology includes the capability of tallying arbitrary-order Legendre expansions of the scattering kernel. Furthermore, several approximations of the diffusion coefficient have been developed and implemented. The accuracy of these stochastic diffusion coefficients within the multigroup framework is investigated by examining a series of simple reactor problems.

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15

Klages, Rainer. "Deterministic chaos and diffusion: from theory to experiments." Diffusion fundamentals 2 (2005) 24, S. 1-2, 2005. https://ul.qucosa.de/id/qucosa%3A14354.

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16

Li, Dan. "The diffusion study on Chinese outbound tourism —Based on “diffusion of innovations” theory." Thesis, Umeå universitet, Kulturgeografi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-105535.

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From 1983 in which year Chinese people started being allowed to travel to the first outbound destination to nowadays that more than 150 countries have signed the ADS (approved destination status) with Chinese government, Chinese outbound tourism had a great progress in 32 years. During these years, more and more Chinese tourists could be seen in different places in the world. In 2014, the number of Chinese outbound tourists firstly achieve to over 100 million. The numbers are predicted to continue by 2020. It is meaningful to put Chinese outbound tourism as an object and discover its future development. Therefore, the aim of this study is set as to analyse the future diffusion of Chinese outbound tourism. The available theoretical foundation is diffusion theory (Rogers, 2003). Its mature and practical theoretical system guides the research framework of this study. This theory is reliable for analysing and discussing the diffusion of Chinese outbound tourism from some aspects such as S-shaped curve, communication channels, adopter classification, etc. A questionnaire survey and some hypothetical indicators are designed in this study to fulfil the aim and research questions. Results are described from several aspects. The analysis of results prove that Chinese outbound tourism could be reckoned as an innovation. Finally, conclusions show that Chinese outbound tourism is currently going through the developing process between ‘innovators’ and ‘early adopters’. If the influencing factors which derived based on diffusion theory could be developed or solved positively, it is possible for Chinese outbound tourism to develop continually following the S-shaped curve in the future. The influencing factors has been studied out. They are the communication channels, the conscious gap between people who live in cities and people who live in towns and villages, the wealth gap between rich people and poor people. Not many related implementations are given out in this study, which needs future researches to explore.

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17

Deroo, Frederik. "Damage detection in concrete using diffuse ultrasound measurements and an effective medium theory for wave propagation in multi-phase materials." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31801.

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Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2010.
Committee Chair: Laurence J. Jacobs; Committee Member: Jianmin Qu; Committee Member: Jin-Yeon Kim. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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18

Monson, Peter A. "Dynamic mean field theory for fluids in mesoporous materials." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-184643.

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19

Yasseri, Saam. "Generalized spatial homogenization method in transport theory and high order diffusion theory energy recondensation methods." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/51727.

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In this dissertation, three different methods for solving the Boltzmann neutron transport equation (and its low-order approximations) are developed in general geometry and implemented in 1D slab geometry. The first method is for solving the fine-group diffusion equation by estimating the in-scattering and fission source terms with consistent coarse-group diffusion solutions iteratively. This is achieved by extending the subgroup decomposition method initially developed in neutron transport theory to diffusion theory. Additionally, a new stabilizing scheme for on-the-fly cross section re-condensation based on local fixed source calculations is developed in the subgroup decomposition framework. The method is derived in general geometry and tested in 1D benchmark problems characteristic of Boiling Water Reactors (BWR) and Gas Cooled Reactor (GCR). It is shown that the method reproduces the standard fine-group results with 3-4 times faster computational speed in the BWR test problem and 1.5 to 6 times faster computational speed in the GCR core. The second method is a hybrid diffusion transport method for accelerating multi-group eigenvalue transport problems. This method extends the subgroup decomposition method to efficiently couple a coarse-group high-order diffusion method with a set of fixed-source transport decomposition sweeps to obtain the fine-group transport solution. The advantages of this new high-order diffusion theory are its consistent transport closure, straight forward implementation and numerical stability. The method is analyzed for 1D BWR and High Temperature Test Reactor (HTTR) benchmark problems. It is shown that the method reproduces the fine-group transport solution with high accuracy while increasing the computationally efficiency up to 16 times in the BWR core and up to 3.3 times in the HTTR core compared to direct fine-group transport calculations. The third method is a new spatial homogenization method in transport theory that reproduces the heterogeneous solution by using conventional flux weighted homogenized cross sections. By introducing an additional source term via an “auxiliary cross section” the resulting homogeneous transport equation becomes consistent with the heterogeneous equation, enabling easy implementation into existing solution methods/codes. This new method utilizes on-the-fly re-homogenization, performed at the assembly level, to correct for core environment effects on the homogenized cross sections. The method is derived in general geometry and continuous energy, and implemented and tested in fine-group 1D slab geometries typical of BWR and GCR cores. The test problems include two single assembly and 4 core configurations. It is believed that the coupling of the two new methods, namely the hybrid method for treating the energy variable and the new spatial homogenization method in transport theory set the stage, as future work, for the development of a robust and practical method for highly efficient and accurate whole core transport calculations.

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20

Martinez, Irene Suarez. "Theory of diffusion and plasticity in layered carbon materials." Thesis, University of Sussex, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439023.

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21

Esteban, Puyuelo Raquel. "A Study of Atomic Diffusion from First Principles Theory." Thesis, Uppsala universitet, Materialteori, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-298039.

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In this work Density Functional Theory and the Nudged Elastic Band method are used to calculate energy barriers to study atomic diffusion. Diffusion is one of the processes that leads to non ideal experimental conditions such as defects or not sharp enough interfaces. In collaboration with Seagate Technology, vacancy-driven diffusion across an Au/X interface is studied in the first part of this thesis. This is done in the pursuit of the best X material that provides hardness to the Au/X heterostructure under high temperatures and still has good plasmonic properties. Itis found that a layered heterostructure of 10 monolayers of Au and 6 monolayers of TiN is the best of the combinations tested and it is attributed to TiN high packaging compared to Au. It is also seen that the density of the X material is more relevant than a high melting temperature or a good lattice match with the Au lattice, as it was suggested before. In a second project, the diffusion of an adatom on a surface of the same material is investigated to find out the infuence of the magnetic phase of the surface on the diffusion barriers. With this aim, ferromagnetic and non magnetic (001) fcc Ni surfaces and bcc Fe are simulated. Additionally, a paramagnetic (001) Fe surface has been simulated with the distribution of moments determined by a Special Quasirandom Structure approach to the Disordered Local Moment method. It is found that energy barriers relevant for diffusion along the surface are lower for the magnetic phases but that the infuence of the magnetic phase on diffusion is not trivial.

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22

Glicksman, Martin Eden, Richard DiDomizio, and Afina Lupulescu. "Theory and simulation of Fick’s historical verification of the 2nd law." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-195125.

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23

Magalhães, Rosinda M. F. "Essays on skill-biased technology diffusion." Thesis, University of Warwick, 2011. http://wrap.warwick.ac.uk/49471/.

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My thesis is a collection of three essays that consider various aspects of a skillbiased technology diffusion as well as skill premium, human capital acumulation and redistributive policies. The first chapter, co-authored with Christian Hellström, investigates the effects of skill-bisead technology change (SBTC) on income inequality and skills supply in the last 30 years in the US. In spite of the intensive debate about the effects of SBTC, its general equilibrium effects on the accumulation of skills and labor supply have been neglected. Thus, we build a dynamic general equilibrium model, in which growth is driven by skill-biased technology diffusion. Households have forward-looking expectations, and differ in terms of innate and idiosyncratic acquisition of skills. Contrary to pure technology progress models, technology diffusion models provide an explanation for the slowdown of the skill premium in the 70s compatible with the slow productivity growth. We find that first, technology diffusion raises the demand for skills and, consequently, the supply of skills. Second, skill-biased technology diffusion explains both the slowdown and the sharp increase of the skill premium observed in the 70s and 80s, respectively. In spite of the slowdown of the skill premium in the 70s, households anticipate the speed up of the technology diffusion and raise their investment in education, even during the economic slowdown. Therefore, the skills supply has continually increased since the 70s. Through a calibration exercise, we replicate the US trends for the skill-premium, skills supply, unskilled wages, consumption inequality and labor supply. The second chapter is motivated by the finding that the skill-biased technology diffusion increases both the skill-premium and skills supply in the last 30 years in the US . This chapter analyzes the effectiveness of redistributive policies in periods of technology diffusion. We build a microfounded general equilibrium model with skill-biased technology diffusion, endogenous labor supply, schooling decisions and redistributive policies. We show that, under endogenous schooling decisions, lump-sum transfers are ineffective. This policy raises the skill premium, in particular during the economic boom and in the long run, and reduces the social welfare during almost all of the technology cycle. Yet education subsidies incentivize the investment in education, decreasing the skill premium, raising the skills supply and social welfare. The investment in education tends to be counter-cyclical. On the one hand, forward-looking individuals anticipate the increase of demand for skills during the economic boom, increasing their investment in education during the economic recession. On the other hand, they also anticipate the maturation of the technology diffusion, reducing their investment in education during the economic boom. Finally, we show that education subsidies are Pareto-effcient, increasing welfare of both high- and low-skilled individuals. The third chapter endogenizes the technology diffusion path assumed in the first chapter. This chapter presents a two-sector growth model that explains the adoption of a skill-biased technology. There are two types of technology: low-tech and high-tech, and the latter is more productive and skill-biased. Technology is not embodied. To adopt high-technology, users must pay an instantaneous adoption cost, which decreases over time due to technology progress. Firms are homogeneous and act strategically, maximizing their profits given their rivals' behavior, leading to a technology sequential adoption pattern due to stock effects. We found that the decrease of the adoption cost and the increase of the technology knowledge due to learning effects leads to an increasing technology diffusion over time. The former has an constant effect over time, but for the latter, although positive, the effect is not constant, changing the speed of the technology diffusion over time.

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24

Monson, Peter A. "Dynamic mean field theory for fluids in mesoporous materials." Diffusion fundamentals 16 (2011) 13, S. 1-2, 2011. https://ul.qucosa.de/id/qucosa%3A13742.

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Franosch, Thomas, and Felix Höfling. "Cluster-resolved dynamic scaling theory and universal corrections for transport on percolating systems." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-190406.

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For a continuum percolation model, it has been shown recentlythat the crossover from pure subdiffusion to normal diffusion extends over five decades in time [1, 2]; in addition, the asymptotic behavior is slowly approached and the large corrections cannot simply be ignored. Thus, it is of general interest to develop a systematic description of universal corrections to scaling in percolating systems. For percolating systems, we propose a universal exponent relation connecting the leading corrections to scaling of the cluster size distribution with the dynamic corrections to the asymptotic transport behavior at criticality. Our derivation is based on a cluster-resolved scaling theory unifying the scaling of both the cluster size distribution and the dynamics of a random walker. We corroborate our theoretical approach by extensive simulations for a site percolating square lattice and numerically determine both the static and dynamic correction exponents [3].

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26

Jack, David Abram. "Incorporation of directionally dependent diffusion with polymer composite flow theory." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4579.

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Thesis (M.S.) University of Missouri-Columbia, 2006.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 23, 2007) Includes bibliographical references.

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Gilardi, Marco. "A framework for local terrain deformation based on diffusion theory." Thesis, University of Sussex, 2015. http://sro.sussex.ac.uk/id/eprint/57832/.

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Terrains have a key role in making outdoor virtual scenes believable and immersive as they form the support for every other natural element in the scene. Although important, terrains are often given limited interactivity in real-time applications. However, in nature, terrains are dynamic and interact with the rest of the environment changing shape on different levels, from tracks left by a person running on a gravel soil (micro-scale), to avalanches on the side of a mountain (macro-scale). The challenge in representing dynamic terrains correctly is that the soil that forms them is vastly heterogeneous and behaves differently depending on its composition. This heterogeneity introduces difficulties at different levels in dynamic terrains simulations, from modelling the large amount of different elements that compose the oil to simulating their dynamic behaviour. This work presents a novel framework to simulate multi-material dynamic terrains by taking into account the soil composition and its heterogeneity. In the proposed framework soil information is obtained from a material description map applied to the terrain mesh. This information is used to compute deformations in the area of interaction using a novel mathematical model based on diffusion theory. The deformations are applied to the terrain mesh in different ways depending on the distance of the area of interaction from the camera and the soil material. Deformations away from the camera are simulated by dynamically displacing normals. While deformations in a neighbourhood of the camera are represented by displacing the terrain mesh, which is locally tessellated to better fit the displacement. For gravel based soils the terrain details are added near the camera by reconstructing the meshes of the small rocks from the texture image, thus simulating both micro and macro-structure of the terrain. The outcome of the framework is a realistic interactive dynamic terrain animation in real-time.

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28

Islam, Mazharul M., and Thomas Bredow. "Li Diffusion in Various Polymorphs of LiTiS2: Insights from Theory." Diffusion fundamentals 21 (2014) 12, S.1, 2014. https://ul.qucosa.de/id/qucosa%3A32418.

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In the present contribution, the stoichiometric and defect properties in 1T, c and 3R polymorphs of lithium titanium disulphide (LixTiS2) are investigated theoretically with periodic quantum chemical methods.

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29

Mulzet, Alfred Kenric. "Exponential Stability for a Diffusion Equation in Polymer Kinetic Theory." Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/30473.

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In this paper we present an exponential stability result for a diffusion equation arising from dumbbell models for polymer flow. Using the methods of semigroup theory, we show that the semigroup U(t) associated with the diffusion equation is well defined and that all solutions converge exponentially to an equilibrium solution. Both finitely and infinitely extensible dumbbell models are considered. The main tool in establishing stability is the proof of compactness of the semigroup.
Ph. D.

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30

Chakraborty, Sumit. "Multicomponent cation diffusion in aluminosilicate garnets: Theory, experiments and applications." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185214.

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Results from experiments in this work have been combined with existing data to yield tracer diffusivities of divalent cations in natural multicomponent garnets at 10-40 kb, 1100 - 1475°C. For the garnet compositions studied in this work, the activation energy for tracer diffusion of Mn < Fe ≃ Mg, while activation volumes increase in the order Mg < Fe < Mn. These data may be used with theoretical models to calculate the full multicomponent diffusion coefficient matrix as a function of pressure, temperature, composition and oxygen fugacity. An analytical model has been developed to describe the relaxation of compositional zoning in metapelitic garnets during metamorphism. It is found that a significant amount of relaxation occurs during heating and the composition at the core of a garnet crystal is disturbed very early in the process. The extent of relaxation depends on a number of factors which include the grain size, the initial shape of the compositional profile, details of the thermal history and the textural mode of occurrence of the garnet. Complications such as oscillations in a compositional profile may be explained by the mathematical form of the equations describing the process. Graphical representation of the results of this model have been provided that allow quick and easy determination of the extent of relaxation or time scale of metamorphic processes. Calculations using the diffusion data indicate that Fe-Mg exchange geothennometry and Sm-Nd geochronology involving garnets may not yield the peak metamorphic conditions for certain geologically realistic situations. Model calculations on natural assemblages suggest that the diffusion data may be used to yield infonnation on metamorphic processes ranging from time scales to crystal growth rates during metamorphism. Veracity of P-T paths calculated from garnet zoning may also be checked using the diffusion data. Illustrative examples of such calculations have been provided.

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Shaw, Paul Edward. "Measurements of exciton diffusion in conjugated polymers /." St Andrews, 2009. http://hdl.handle.net/10023/831.

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32

Freitas, Pedro S. C. de. "Some problems in nonlocal reaction-diffusion equations." Thesis, Heriot-Watt University, 1994. http://hdl.handle.net/10399/1401.

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33

Zhao, Qi, Shaji Chempath, and Randall Q. Snurr. "Determining binary diffusion coefficients for mixtures in zeolites from PFG NMR, MD simulation, and theory." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-195699.

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34

Glicksman, Martin Eden, Richard DiDomizio, and Afina Lupulescu. "Theory and simulation of Fick’s historical verification of the 2nd law." Diffusion fundamentals 2 (2005) 3, S. 1-2, 2005. https://ul.qucosa.de/id/qucosa%3A14332.

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35

Penev, Evgeni Stefanov. "On the theory of surface diffusion in InAs/GaAs(001) heteroepitaxy." [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=963921266.

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36

Yang, Yuanjie. "Reaction-diffusion equations with time delay, theory, application, and numerical simulation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq23095.pdf.

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37

Dooley, Phillip. "The Effective implementation of GIS in local government using diffusion theory /." Connect to thesis, 2001. http://eprints.unimelb.edu.au/archive/00001047.

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38

McKinley, Michael Scott. "Higher-order boundary condition perturbation methods in transport and diffusion theory." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/16034.

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39

Liang, Y. "Investigation into gradient diffusion coefficients of colloidal dispersions : experiment and theory." Thesis, Swansea University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637906.

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Gradient diffusion coefficients of BSA were systematically determined up to much higher concentration than had been reported previously, which were found to be in accordance with the theoretical predictions based on the calculations of thermodynamic and hydrodynamic coefficients via different approaches. Dynamic light scattering experiments were also conducted with the commercially significantly protein, recombinant human lactoferrin, on which no gradient diffusion coefficients had been reported before. With the experimental results, a further development of the predictive method was made via applying the Watzlawek and Nägele's equation as well as the Zick and Homsy's data to the calculations of hydrodynamic coefficients. The refined model gives the greatly improved calculations of the gradient diffusion coefficients of lactoferrin. Experiments were extended from bio-colloids to inorganic colloids to more extensively test the model. Silica was chosen to carry out the measurements. Dilute limit calculations of gradient diffusion coefficients agreed well with the experiments. However, further work is required for the gradient diffusion model over a wide range of concentration studied. A theoretical analysis depending upon the calculations of thermodynamic and hydrodynamic coefficients has been applied. The thermodynamic coefficient was determined via (i) dilute limit calculations, (ii) solution of the Ornstein-Zernike equation or (iii) cell model calculations. Furthermore, the hydrodynamic coefficient was computed via (i) dilute limit calculations or (ii) a combination of perturbation theory and the results of an exact numerical solution for an ordered system. These coefficients were then combined, according to the generalized Stokes-Einstein equation, to allow comparison between theory and experiment.

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40

Grindley, Peter Conrad. "A strategic analysis of the diffusion of innovations : theory and evidence." Thesis, London School of Economics and Political Science (University of London), 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308388.

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41

Watson, Sterling (Sterling Marina). "Experimental characterization of a coupled deformation-diffusion theory for elastomeric materials." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98753.

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Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (page 45).
Certain cross-liked polymer networks can absorb solvents and swell far beyond their initial volume, a useful property which may be exploited in a variety of applications. In this thesis, polydimethylsiloxane (PDMS) samples were swollen in pentane in order to experimentally characterize the transient and steady-state swelling behavior of this system, and to extract material properties in order to fully characterize a coupled deformation-diffusion theory. Free swelling experiments, transient swelling force measurements, and an analysis of the swollen geometry of a PDMS bilayer strip were performed, and compared to numerical simulations. The experimental results and numerical simulations were shown to be in good agreement.
by Sterling Watson.
S.B.

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42

Lewis, Gayle Arnn. "Leadership Products As Innovations In The Context Of Rogers' Diffusion Theory." Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/29839.

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In this study, two implementable leadership products were analogous to innovations, when framed in the context of Rogers’ diffusion-of-innovation theory. Thus, the products’ respective dissemination patterns were compared and contrasted-- quantitatively through purchase numbers, and qualitatively through opinions and events recollected by early users. The case-study approach was central to the investigation, and the results supported the Rogers model with regard to most constructs. The results pertaining to the S-shaped (sigmoidal) prototypical distribution curve, however, were enigmatic. The inverse conformity of sales figures with the S-shaped distribution curve implied that the dissemination process began during the field-testing stage rather than the purchasing stage. The organizational structure of the user institutions (targeted social system construct) conformed to Rogers’ theory that autonomy and teamwork characterized management climates where innovation tended to flourish. Field-testers and other early users were opinion leaders as construed by Rogers. The fact that twice as many field tests were conducted for the Case Studies as for the Simulation was likely a factor in the disparate 6:1 ratio of units of Cases sold to units of the Simulation sold for three consecutive years. Other factors possibly accounting for the disparate sales came from the attributes-of-innovation template which framed five generic attributes--compatibility, relative advantage, complexity, trialability, and observability. Both products conformed to the attributes as conceptualized by Rogers. The main difference that influenced the disparate sales was the greater complexity of the Simulation than of the Cases, although cost may have been a compatibility/relative advantage contributory factor. Finally, the study’s results indicated that dissemination parameters may have been narrowed by (a) the absence of mass media communication channels as part of the dissemination strategy at the awareness stage, and (b) lack of market research to focus the naming and packaging of the products for optimum compatibility and relative advantage. Researchers and change agencies can use these findings to improve future dissemination strategies and product designs.
Ph. D.

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43

Toyoura, Kazuaki. "Lithium diffusion in graphite intercalation compounds based on transition state theory." 京都大学 (Kyoto University), 2008. http://hdl.handle.net/2433/136279.

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44

Gomes, Rafael, and Sema Seyfi Osman. "Managing Organizational Adoption of IoT : Revisiting Rogers' Diffusion of Innovation Theory." Thesis, Uppsala universitet, Industriell teknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-398123.

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As a disruptive innovation, IoT has been creating a high impact over organizations’ current strategies and business models. This continuous process of change will have an increasing influence on how organizations and industries as a whole conduct their businesses, and is set to have an active role towards the development of entirely new business models and markets. With the development of IoT technologies, and its predicted exponential spread across all sectors of society, one can conclude that the future holds many opportunities for organizations looking to explore new ways of capturing and creating value, but at the same time there are also plenty of challenges to be addressed. While the diffusion and adoption process of IoT has been an ongoing phenomenon over the past decade, there is still not much certitude as to how organizations ought to adjust in order to successfully integrate IoT technologies in their structure and operations. In parallel fashion, there have also been many difficulties in ensuring that different smart, connected devices and ecosystems are able to effectively communicate between each other, as achieving interoperability has become one of the major concerns associated with IoT. The main focus of this study is to analyze the process of how organizations are currently integrating IoT within their businesses, while also investigating causes that hinder interoperability, and evaluating the future potential deployment of the Open IoT ecosystems in companies. For our research we have followed a case-study approach where we conducted semi-structured interviews with managers and project leaders from two organizations conducting pilot studies on Green IoT and Open IoT, and where one has been adopting IoT technologies in its business. Theoretically, we draw on a framework by combining Rogers’ Diffusion of Innovations theory and Christensen’s theory of Disruptive Innovations in order to analyze the integration of IoT into businesses’ core structure. The research goes through a functional framework that outlines the process of IoT adoption while also presenting the present challenges that are faced by the actors in the industry and the key enablers for successful IoT integration.

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45

Sabbir, Md Mainul Hasan. "Accuracy of semi-infinite diffusion theory to estimate tissue hemodynamics in layered slab models." Miami University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=miami1627383040154061.

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46

Gourlay, Adrian R. "The diffusion of process innovation in the UK financial sector : an empirical analysis of automated teller machine (ATM) diffusion." Thesis, Loughborough University, 1999. https://dspace.lboro.ac.uk/2134/7082.

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Recent policy initiatives have identified that the diffusion of innovation constitutes an important component in technical change and progress and is the impetus behind changes in firm productivity. To date, however, the main emphasis of economists has been on the diffusion of process innovations in the industrial sector with diffusion in the financial sector either ignored or, at best, summarised by a number of stylised facts relating to the spread of information. The objective of this thesis is to explore the inter-firm determinants of ATM adoption and diffusion in the UK financial sector and identify firm-specific and market factors in the diffusion process. The empirical analysis draws on duration analysis which represents the current state-of-art modelling approach to inter-firm diffusion. This approach conceptualises inter-firm diffusion as a cross-section of durations of nonadoption from which, most importantly, hypothesised factors (or `covariates') can be examined by their significance or otherwise on the conditional probability of adoption. The main findings of this thesis support the stylised fact often made in the diffusion literature that the inter-firm diffusion curve is sigmoid and characterised by a nonmonotonic hazard function. Furthermore the empirical analysis supports the hypothesis that firm-specific characteristics and expectations have played a crucial role in the interfirm diffusion of ATMs. In addition, the results indicate that the diffusion of ATMs in the UK has been characterised by the existence of positive network externalities. The results are also shown to be robust across a number of model specifications and assumptions concerning the time-path of covariates.

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47

Ilas, Danut. "Coarse mesh transport theory model for heterogeneous systems." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/16089.

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48

Borneman, Troy W., David G. Cory, and Martin D. Hürlimann. "Signal optimization in inhomogeneous fields: application of quantum optimal control theory troy." Diffusion fundamentals 10 (2009) 12, S. 1-3, 2009. https://ul.qucosa.de/id/qucosa%3A14103.

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We demonstrate that pulses derived using Optimal Control Theory (OCT) techniques can be used to significantly enhance the robustness of the Carr-Purcell-Meiboom-Gill sequence (CPMG) [1,2] to inhomogeneities in the static BB0 field. By numerically inverting the Liouville - von Neumann equation, OCT pulses were derived that can be used directly in place of hard pulses in the CPMG sequence to greatly improve the bandwidth of refocusing. To retain the echo stability achieved by the Meiboom-Gill correction to the Carr-Purcell sequence, the refocusing pulses were designed to perform a unitary π-rotation as opposed to just a state inversion transfer. To illustrate this approach we present an example of optimized pulses that show an improved CPMG-like behavior with complete excitation and multiple refocusing over a bandwidth of +/- 2.6 γB1,max B with a pulse duration limited to 10 t180.

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49

Floyd, John-Patrick II. "A numerical investigation of extending diffusion theory codes to solve the generalized diffusion equation in the edge pedestal." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39607.

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The presence of a large pinch velocity in the edge pedestal of high confinement (H-mode) tokamak plasmas implies that particle transport in the plasma edge must be treated by a pinch-diffusion theory, rather than a pure diffusion theory. Momentum balance also requires the inclusion of a pinch term in descriptions of edge particle transport. A numerical investigation of solving generalized pinch-diffusion theory using methods extended from the numerical solution methodology of pure diffusion theory has been carried out. The generalized diffusion equation has been numerically integrated using the central finite-difference approximation for the diffusion term and three finite difference approximations of the pinch term, and then solved using Gauss reduction. The pinch-diffusion relation for the radial particle flux was solved directly and used as a benchmark for the finite-difference algorithm solutions to the generalized diffusion equation. Both equations are solved using several mesh spacings, and it is found that a finer mesh spacing will be required in the edge pedestal, where the inward pinch velocity is large in H-mode plasmas, than is necessary for similar accuracy further inward where the pinch velocity diminishes. An expression for the numerical error of various finite-differencing algorithms is presented.

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50

Zhao, Qi, Shaji Chempath, and Randall Q. Snurr. "Determining binary diffusion coefficients for mixtures in zeolites from PFG NMR, MD simulation, and theory: Determining binary diffusion coefficients for mixtures in zeolitesfrom PFG NMR, MD simulation, and theory." Diffusion fundamentals 2 (2005) 41, S. 1-2, 2005. https://ul.qucosa.de/id/qucosa%3A14371.

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