Dissertations / Theses on the topic 'Mesoscale'
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Shilling, Katharine Meghan. "Mesoscale Edge Characterization." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10471.
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In mesoscale manufacturing desired dimensional and surface characteristics are defined, but edge conditions are not specified in design. The final edge conditions that exist in mesoscale objects are created not only by the manufacturing process but, because of their size, also by part handling procedures. In these parts, the concern is not only with burrs, which can be formed by some mesoscale manufacturing processes, but also with the shape and size of the edge. These properties are critically important as the edge can constitute a large percentage of the smallest features of mesoscale objects. Undefined edge geometry can result in measurement, assembly, and operational difficulties.
Due to the potential problems caused by edge conditions, it is desirable to have the ability to measure and characterize the edge conditions of parts. This thesis considers mesoscale measurement tools to provide an edge measurement tool recommendation based on edge size and properties. A set of analysis techniques is developed to determine the size and shape of the measured edge, locate any local inconsistencies such as burrs or dents, and track trends in calculated parameters as a function of edge position. Additionally, a standard method for communicating design requirements is suggested in order to differentiate between acceptable and unacceptable edges.
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Douglass, Kyle. "Mesoscale Light-Matter Interactions." Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5933.
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Mesoscale optical phenomena occur when light interacts with a number of different types of materials, such as biological and chemical systems and fabricated nanostructures. As a framework, mesoscale optics unifies the interpretations of the interaction of light with complex media when the outcome depends significantly upon the scale of the interaction. Most importantly, it guides the process of designing an optical sensing technique by focusing on the nature and amount of information that can be extracted from a measurement.
Different aspects of mesoscale optics are addressed in this dissertation which led to the solution of a number of problems in complex media. Dynamical and structural information from complex fluids—such as colloidal suspensions and biological fluids—was obtained by controlling the size of the interaction volume with low coherence interferometry. With this information, material properties such as particle sizes, optical transport coefficients, and viscoelastic characteristics of polymer solutions and blood were determined in natural, realistic conditions that are inaccessible to conventional techniques.
The same framework also enabled the development of new, scale-dependent models for several important physical and biological systems. These models were then used to explain the results of some unique measurements. For example, the transport of light in disordered photonic lattices was interpreted as a scale-dependent, diffusive process to explain the anomalous behavior of photon path length distributions through these complex structures. In addition, it was demonstrated how specialized optical measurements and models at the mesoscale enable solutions to fundamental problems in cell biology. Specifically, it was found for the first time that the nature of cell motility changes markedly with the curvature of the substrate that the cells
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move on. This particular work addresses increasingly important questions concerning the nature of cellular responses to external forces and the mechanical properties of their local environment.
Besides sensing of properties and modeling behaviors of complex systems, mesoscale optics encompasses the control of material systems as a result of the light-matter interaction. Specific modifications to a material's structure can occur due to not only an exchange of energy between radiation and a material, but also due to a transfer of momentum. Based on the mechanical action of multiply scattered light on colloidal particles, an optically-controlled active medium that did not require specially tailored particles was demonstrated for the first time. The coupling between the particles and the random electromagnetic field affords new possibilities for controlling mesoscale systems and observing nonequilibrium thermodynamic phenomena.Ph.D.
Doctorate
Optics and Photonics
Optics and Photonics
Optics
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Seo, Hyodae. "Mesoscale coupled ocean-atmosphere interaction." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3263355.
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Thesis (Ph. D.)--University of California, San Diego, 2007.Title from first page of PDF file (viewed July 10, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 138-152).
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Varlioglu, Mesut. "Mesoscale constitutive behavior of ferroelectrics." [Ames, Iowa : Iowa State University], 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3369903.
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Fontenot, Sean, and Sean Fontenot. "Supramolecular Modification of Mesoscale Materials." Thesis, University of Oregon, 2012. http://hdl.handle.net/1794/12356.
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The process of surface modification allows us to combine the structural advantages of materials with the chemical functionality of organic compounds. Attachment of functional organic molecules to surfaces of high surface area substrates yields materials having dense chemical functionality. Materials with meso- and nanoscale features are often used as support substrates because their small-scale features provide very high surface area. Mesoporous silica is one of the most chemically accessible mesoscale materials, and the well-established chemistries of its production and modification lead to controlled pore structure and rapid kinetics. Such materials have seen use as sorbents for environmental remediation of contaminated water. For this application, their high degree of functionality and high-affinity surface chemistries permit a relatively small amount of material to effectively treat a large volume of water.
The many advantages of these highly engineered materials come at a relatively high economic cost. The high-affinity chemical functionalities that provide these materials with unprecedented efficiencies also make them correspondingly more difficult to recycle. One-time utilization of these materials makes the cost-per-use high which consequently limits their economically viable applications. The goal of this work has been to explore surface chemistries that will allow high performance, regenerable or recyclable sorbent materials. Shifting from a single-use material to a regenerable platform in which the mesoscale supports are recycled may lower the environmental and economic costs of the material while retaining the advantageous properties of the meso- and nanostructured materials.
We chose to approach this goal by developing non-covalent, supramolecular surface modification techniques as alternatives to current surface modification techniques which, almost without exception, are based on covalent modification motifs. Non-covalent attachment of organic molecules to surfaces allows us to avoid the necessity of optimizing the attachment for each class of organic molecule as well as avoid protection and de-protection procedures necessary to attach delicate or reactive functional groups to surfaces. In this way, supramolecular modification processes reduce the cost of material research and development in addition to the costs of material production and use.
The process of surface modification allows us to combine the structural advantages of materials with the chemical functionality of organic compounds. Attachment of functional organic molecules to surfaces of high surface area substrates yields materials having dense chemical functionality. Materials with meso- and nanoscale features are often used as support substrates because their small-scale features provide very high surface area. Mesoporous silica is one of the most chemically accessible mesoscale materials, and the well-established chemistries of its production and modification lead to controlled pore structure and rapid kinetics. Such materials have seen use as sorbents for environmental remediation of contaminated water. For this application, their high degree of functionality and high-affinity surface chemistries permit a relatively small amount of material to effectively treat a large volume of water.
The many advantages of these highly engineered materials come at a relatively high economic cost. The high-affinity chemical functionalities that provide these materials with unprecedented efficiencies also make them correspondingly more difficult to recycle. One-time utilization of these materials makes the cost-per-use high which consequently limits their economically viable applications. The goal of this work has been to explore surface chemistries that will allow high performance, regenerable or recyclable sorbent materials. Shifting from a single-use material to a regenerable platform in which the mesoscale supports are recycled may lower the environmental and economic costs of the material while retaining the advantageous properties of the meso- and nanostructured materials.
We chose to approach this goal by developing non-covalent, supramolecular surface modification techniques as alternatives to current surface modification techniques which, almost without exception, are based on covalent modification motifs. Non-covalent attachment of organic molecules to surfaces allows us to avoid the necessity of optimizing the attachment for each class of organic molecule as well as avoid protection and de-protection procedures necessary to attach delicate or reactive functional groups to surfaces. In this way, supramolecular modification processes reduce the cost of material research and development in addition to the costs of material production and use.
This dissertation contains previously published and unpublished co-authored material.
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Arif, Tansel. "Mesoscale modelling of steel processing." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/25738.
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Numerical methods are utilised to reproduce the evolution of a system observed in natural phenomena. Within the area of materials science there is an increase of interest in modelling techniques that can accurately predict the microstructure of a material subject to various processing conditions. Recently, there is a requirement of techniques that have the ability to be applied to systems involving microstructural change in the presence of fluid flow. This presents a challenge since the forces governing these processes involve those predominately influenced by thermodynamics as well as those influenced by hydrodynamics. The phase-field method, a popular technique used in this area, has been shown to have the ability to cope with phase transformation dynamics such as solidification and solid-state phase transformations. However, its predictive capabilities mainly apply to a flow free environment where flow effects are minimal compared to other effects. Other techniques such as smoothed particle hydrodynamics exist that are more than capable of describing the mechanisms of flow demonstrating superiority in many complex flow problems. The thermodynamic quantities related to the evolution of a system to which this method is applied must then be consistent in order to be translated between models. This thesis develops the tools necessary to deal with phase growth and microstructural change within the presence of flow. This is done by developing phase-field models that can efficiently deal with displacive transformations in steels as well as diffusive, and SPH models with the ability to be coupled with thermodynamics. The phase-field models are developed to be applied to structure growth observed at relatively low temperatures within steels, namely martensite and bainite growth. The SPH method is analysed in order to assess and provide solutions for consistency when considered for coupling with models mainly dependent on thermodynamics.
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Kuypers, Michael A. "Understanding mesoscale error growth and predictability." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2000. http://handle.dtic.mil/100.2/ADA379536.
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Thesis (M.S. in Meteorology and Physical Oceanography)--Naval Postgraduate School, June 2000.Thesis advisor(s): Nuss, Wendell A. "June 2000." Includes bibliographical references (p. 101-102). Also available online.
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Liu, Shaohua, Jian Zhang, Renhao Dong, Pavlo Gordiichuk, Tao Zhang, Xiaodong Zhuang, Yiyong Mai, Feng Liu, Andreas Herrmann, and Xinliang Feng. "Two-Dimensional Mesoscale-Ordered Conducting Polymers." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-235473.
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Despite the availability of numerous two-dimensional (2D) materials with structural ordering at the atomic or molecular level, direct construction of mesoscale-ordered superstructures within a 2D monolayer remains an enormous challenge. Here, we report the synergic manipulation of two types of assemblies in different dimensions to achieve 2D conducting polymer nanosheets with structural ordering at the mesoscale. The supramolecular assemblies of amphipathic perfluorinated carboxylic acids and block co-polymers serve as 2D interfaces and meso-inducing moieties, respectively, which guide the polymerization of aniline into 2D, freestanding mesoporous conducting polymer nanosheets. Grazingincidence small-angle X-ray scattering combined with various microscopy demonstrates that the resulting mesoscale-ordered nanosheets have hexagonal lattice with d-spacing of about 30 nm, customizable pore sizes of 7–18 nm and thicknesses of 13–45 nm, and high surface area. Such template-directed assembly produces polyaniline nanosheets with enhanced π–π stacking interactions, thereby resulting in anisotropic and record-high electrical conductivity of approximately 41 S cm–1 for the pristine polyaniline nanosheet based film and approximately 188 S cm–1 for the hydrochloric acid-doped counterpart. Our moldable approach creates a new family of mesoscale-ordered structures as well as opens avenues to the programmed assembly of multifunctional materials.
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Porfyrakis, Kyriakos. "Mesoscale modelling of processing toughened polymers." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342634.
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Kikuchi, Norio. "A mesoscale model for polymer hydrodynamics." Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289276.
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Younger, Keri. "Assessing Mesoscale-Equivalent Temperature in Kentucky." TopSCHOLAR®, 2015. http://digitalcommons.wku.edu/theses/1459.
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The purpose of this research is to investigate mesoscale-equivalent temperatures (TE) in Kentucky and potential land cover influences. Kentucky presents a unique opportunity to perform a study of this kind because of the observational infrastructure provided by the Kentucky Mesonet (www.kymesonet.org). This network maintains 65 research-grade, in-situ weather and climate observing stations across the Commonwealth. Equivalent temperatures were calculated utilizing high-quality observations from 33 of these stations. In addition, the Kentucky Mesonet offers higher spatial and temporal resolution than previous research on this topic. As expected, the differences (TE-T) were greatest in summer (smallest in winter), with an average of 35 ºC (5 ºC). In general, the differences were found to be largest in the western climate division. This is attributed to poorly drained land and the mesonet stations’ adjacency to agricultural land. These differences are smaller during periods of drought, signifying less influence of moisture. Additionally, an inverse relationship between TE and pressure deviation on a daily timescale was found, suggesting a synoptic influence on near-surface heat content.
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Ioannidou, Evangelia. "A mesoscale view of frontal instability." Thesis, University of Reading, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295305.
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Ferris, P. D. "Frontal structure in a mesoscale model." Thesis, University of Reading, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234649.
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Pinna, Marco. "Mesoscale modelling of block copolymer systems." Thesis, University of Central Lancashire, 2009. http://clok.uclan.ac.uk/19729/.
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This thesis is dealing with a set of physical phenomena occurring in various block copolymer systems and trying to understand them by means of computer simulation. In the course of the work Cell Dynamics Simulation (CDS) was implemented as a computer program and further developed when necessary. The choice of CDS is due to the fact that it is a simplest minimal model of the Ginzburg-Landau type and its ability to describe complex physical situations was debated. The thesis clarifies this issue by a systematic study of diblock copolymers subjected to the external influences such as electric field, shear flow, confining surfaces and nanoparticles. The thesis results prove that CDS can describe such complex phenomena rather well and therefore, is a complementary method to other more elaborate techniques. The thesis provides a ground for a future development of a tandem simulation where a very fast CDS method can be used as a precursor to more elaborate but slow techniques as, for instance, Dynamics Self-Consistent Field Theory.
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Craven, Galen Thomas. "Minimalist theory for mesoscale reaction dynamics." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/54292.
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The prediction of an atomistic system's macroscopic observables from microscopic physical characteristics is often intractable, either by theory or computation, due to the intrinsic complexity of the underlying dynamical rules. This complexity can be simplified by identifying key mechanisms that drive behavior and considering the system in a reduced representation that captures these mechanisms. Through theory, this thesis examines complex relationships in structured assembly and reaction mechanisms that occur when effective interactions are applied to mesoscale structures. In the first part of this thesis, the structure and assembly of soft matter systems are characterized while varying the interpenetrability of the constituent particles. The nature of the underlying softness allows these systems to be packed at ever higher density, albeit with an increasing penalty in energy. Stochastic equations of motion are developed in which mesoscopic structures are mapped to single degrees of freedom through a coarse-graining procedure. The effective interactions between these coarse-grained sites are modeled using stochastic potentials that capture the spatial behavior observed in systems governed by deterministic bounded potentials. The second part of this thesis presents advancements in time-dependent transition state theory, focusing on chemical reactions that are induced by oscillatory external forces. The optimal dividing surface for a model driven reaction is constructed over a transition state trajectory. The stability of the transition state trajectory is found to directly dictate the reaction rate, and it is thus the fundamental and singular object needed to predict barrier-crossing rates in periodically driven chemical reactions. This thesis demonstrates that using minimalist models to examine these complex systems can provide valuable insight into the dynamical mechanisms that drive behavior.
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Blamey, Ross. "Mesoscale convective complexes over southern Africa." Doctoral thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/10167.
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Includes bibliographical references.A combination of numerous factors, including geographic position, regional orography and local sea surface temperatures, ensures that subtropical southern Africa experiences considerable spatial and temporal variability in rainfall and is prone to both frequent flooding and drought events.
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Hagemann, Kilian. "Mesoscale wind atlas of South Africa." Doctoral thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/5287.
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This thesis explores the utility of the MM5 regional climate model iii product big a detailed wind climatology for South Africa in the context of wind power applications. Given the background of limited available computational resources a sophisticated temporal subsetting algorithm is developed and applied. The goal here is to allow a high resolution 18 by 18km simulation to be carried out over only 365 days of historical records (20 March 1996 until 19 March 1997), yet ensure that it is possible to construct a reasonably accurate climatology from such a short time period because it represents the most typical year available. Throughout the research the modelâs sensitivity towards different boundary layer and cwnulus parametrisations as well as observational and grid nudging is investigated in depth. New error metrics are specifically designed and applied based on 17 reliable lOni weather stations around the country with the specific purpose of evaluating model skill with respect to the wind patterns that are important for wind turbines. An optimal model configuration is established by using the Pleim Xiu land surface scheme coupled with the Atmospheric Convective Model for the planetary boundary layer, in addition to the Kain Fiitsch II cumulus parametrisation and observational wind nudging. The model is then integrated at 18km for the entire country and the results validated in detail. It is found that average wind speeds are within 0.2 + 0.7ms (68% confidence interval) and that the daily cycle, which constitutes the largest part of the observed variance, is predicted to within 18% + 20% of amplitude and lii of timing at coastal sites.
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Gruen, Karen Davis. "Mesoscale temperature estimates for Western Virginia." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-09292009-020343/.
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Beattie, Jodi C. "A numerical investigation of mesoscale predictability." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Mar%5FBeattie.pdf.
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Thesis (M.S. in Meteorology and Physical Oceanography)--Naval Postgraduate School, March 2003.Thesis advisor(s): Wendell A. Nuss, David S. Brown. Includes bibliographical references (p. 77-78). Also available online.
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White, Bethan Alice. "Modelling of elevated mesoscale convective systems." Thesis, University of Leeds, 2012. http://etheses.whiterose.ac.uk/3151/.
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Elevated convection occurs when convection originates from above the boundary layer. The interaction of an elevated storm with the stable layer beneath it often generates features such as waves and bores that maintain the convection. The Convective Storm Initiation Project (CSIP) took place in the UK in 2005. Only one case of elevated convection was observed during CSIP, in which several mesoscale convective systems (MCSs) formed. One MCS remained elevated and wave-lifted throughout the observation period. Another elevated MCS observed during IOP 3 was associated with Kelvin-Helmholtz billows. The billows and the elevated convection appeared to interact. The aim of this thesis is to use high-resolution numerical models to investigate the processes occurring in the elevated MCSs observed during CSIP. The thesis is presented in two parts. In the first part a simulation is performed using the Weather Research and Forecasting (WRF) model. The model reproduces the wave-lifted elevated convection in the early stages of the simulation but, unlike the observations, the simulated convection becomes surface-based and gravity current-lifted. The sensitivity of the simulated MCS to surface heat fluxes and diabatic cooling processes is explored. Surface heating and advection are shown to increase the buoyancy of the boundary layer air and enhance the transition to surface-based convection. Diabatic cooling processes are shown to maintain the simulated MCS in two ways: they strengthen the descent of the rear-inflow jet, generating a wave, and they also strengthen the undercurrent via cold outflow from the north of the storm. In the second part of this thesis the Met Office Large Eddy Model is used to investigate the interaction between Kelvin-Helmholtz billows and elevated convection. It is shown that there is a strong coupling between the updraughts and downdraughts in the billows and convective clouds.
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Robichaud, Raymond M. "An analysis of the synoptic and mesoscale forcing of the 08/09 March 1992 STORMFEST mesoscale convective system." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA306103.
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Correia, James. "Observations and simulations of mesoscale convective systems." [Ames, Iowa : Iowa State University], 2007.
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Blaskovic, Miriam. "Mesoscale study of a squall line system." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63308.
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Cai, Wei 1977. "Atomistic and mesoscale modeling of dislocation mobility." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/8682.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2001.Vita.
Includes bibliographical references (p. 297-320).
Dislocation is a line defect in crystalline materials, and a microscopic carrier of plastic deformation. Because dislocation has both a localized core and a long-range stress field, linking atomistic and meso scales is often the most challenging step in studying its dynamics. This Thesis presents theories and simulations of dislocations in Si and BCC transition metals, with emphasis on the atomistic-mesoscale coupling. Contributions are made in both methods development and mechanistic understanding of dislocation mobility. For atomistic studies of defects embedded in a mesoscale surrounding, we have given rigorous treatments of two types of boundary effects. A method is derived for quantifying artificial image energies in dislocation simulations with a periodic cell, in which a longstanding conditional convergence problem in lattice summation is resolved. We have also developed a systematic approach based on the linear response theory, which minimizes boundary wave reflections in molecular dynamics simulations without artificial damping. When predictive models are confronted with experiments at the level of mesoscale kinetics, the challenge is to properly incorporate atomistic details into a coarse-grained simulation.
(cont.) We have investigated dislocation core and kink mechanisms and obtained deeper understandings on the shuffle-glide controversy in Si and edge versus screw dislocations in BCC Mo, with some of these breakthroughs related to a better control of artificial boundary effects. The atomistic-mesoscale coupling is then manifested in our formulation of a kinetic Monte Carlo description of dislocation glide in Si at the mesoscale, based on kink mechanisms. As a result, the nature of "weak obstacles" to kink propagation, a long-standing postulate for interpreting low stress dislocation mobility data, is clarified. This model is then generalized to incorporate cross slip for modeling screw dislocation motion in a BCC lattice. Lastly, a physically-motivated procedure is derived for removing the stress singularity in mesoscale dislocation dynamics simulations.
by Wei Cai.
Ph.D.
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Chandramoorthy, Nisha. "Molecular dynamics-based approaches for mesoscale lubrication." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/107059.
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Thesis: S.M., Massachusetts Institute of Technology, Computation for Design and Optimization Program, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 101-109).
Classical lubrication theory is unable to describe nanoscale flows due to the failure of two of its constitutive components: a) the Newtonian stress-strain rate relationship and b) the no-slip boundary condition. In this thesis, we present a methodology for deriving a modified Reynolds equation (referred to as the Molecular Dynamics-based Equation for Lubrication, or the MODEL) which overcomes these limitations by introducing a Molecular Dynamics-based constitutive relationship for the flow rate through the lubrication gap, that is valid beyond the range of validity of the Navier-Stokes constitutive models. We demonstrate the proposed methodology for the flow of a simple lubricant, n-hexadecane, between smooth Iron walls and show that the MODEL is able to predict flow rates with good accuracy even in nanochannels that are only a few atomic layers wide. The MODEL constitutive relationship for the flow rate used in this work is a slip-corrected Poiseuille model with the slip length and viscosity derived from Molecular Dynamics (MD) simulations of pressure-driven flow in nanochannels sufficiently large that the Navier-Stokes description is valid. Although more general expressions for the flow rate can certainly be used, for the lubricant-solid system modeled here, the slip-corrected Poiseuille flow was surprisingly found to be sufficient. We validate the MODEL by comparing MD results for the pressure distribution in a barrel-drop lubrication configuration with the analytical solution for the pressure obtained by solving the MODEL. The excellent agreement obtained between the dynamic pressure in the fluid measured from these MD simulations and the MODEL results suggests that it is possible to extend pde-based hydrodynamic modelling of lubrication problems even to nanoscale films beyond the validity of the Navier-Stokes description. In other words, once the flow rate constitutive relation is obtained, lubrication problems in nanoscale films can be solved without resorting to expensive particle methods like MD. We demonstrate that slip cannot be neglected in the boundary lubrication regime by considering various lubrication problems of practical interest. Using a simple barrel-drop lubrication model for the top two rings in an internal combustion engine, we show that for lubrication gaps with a minimum thickness that is ten times the size of the slip length, the normal force and the frictional force are overestimated by a factor of 1.5 when assuming no-slip. By modifying the Twin Land Oil Control Ring (TLOCR)-liner interface model to include slip, we find significant reduction in the hydrodynamic pressure and the friction when compared to the original model; the oil flow rate does not change appreciably. Finally, we chalk out a procedure for the inclusion of slip in the methodology for developing correlations for the pressure, friction and the flow rate in the TLOCR-liner system.
by Nisha Chandramoorthy.
S.M.
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Mohd, Rasdi Fatimah Rubaizah Binti. "Continuous screening using mesoscale oscillatory baffled reactors." Thesis, University of Newcastle upon Tyne, 2010. http://hdl.handle.net/10443/2552.
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A mesoscale Oscillatory Baffled Reactor (“mesoscale-OBR”) is a laboratory-scale reactor (5mm inner diameter) with a total volume of approximately 5.5mL containing equally spaced baffles. Due to its small volume, it is suitable as a platform technology for process screening or investigating reaction kinetics. Traditionally, these are conducted in batch; however, continous screening can be performed in the mesoscale-OBR, with flexible adjustment of the input and reduced reagent usage. In this project, continuous dynamic and “steady state” screening was demonstrated in the mesoscale-OBR. These techniques can be used to rapidly and logically obtain process data and kinetics of any liquid-liquid reactions. Exothermic reactions of several aldehydes (benzaldehyde, o-tolualdehyde, m-tolualdehyde and p-tolualdehyde) with n-butylamine to form imines were chosen as the case studies to demonstrate the ability of the mesoscale-OBR. Online FTIR was used to monitor reactions. The mesoscale-OBR exhibited a high degree of consistency in experimental results: the uncertainty in the rate constant for benzaldehyde and n-butylamine imination was three times lower than in a conventional batch beaker method. MATLAB was used to model reaction kinetics and validated using experimental data. Both experiments and modelling demonstrated that the rate constant for 1-butanamine, N-(phenylmethylene)-synthesis was 2.1 x 10-1mol-0.9L0.9s-1 with total reaction order of 1.9 (1.7 for benzaldehyde and 0.22 for n-butylamine). The process development time when using “dynamic screening” (i.e continuous variation of one of the input parameters) was reduced by 50% compared to batch screening using beakers. A higher area to volume ratio of the mesoscale-OBR (than the beaker) allowed exothermic reactions to be screened safely and quickly e.g. temperature for solvent free imination was at ~40oC in a jacketed mesoscale-OBR, whereas ~90oC (above the boiling point of n-butylamine) for a jacketed beaker. To passively improve the temperature distribution along the length of the reactor, the centrally baffled mesoscale-OBR was constructed inside a thermosyphon: the temperature difference along the reactor length at residence times of 60s and 90s was reduced to 2oC, rendering the reaction safer and more amenable to determination of exothermic reaction kinetic parameters.
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Forryan, Alexander. "Shear enhanced nutrient supply at the Mesoscale." Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/195037/.
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Phytoplankton live almost exclusively in the sunlit waters of the euphotic zone. However, in addition to sunlight, phytoplankton require a regular supply of nutrients to grow. In the open ocean such nutrients are abundant in the dark waters below the euphotic zone. Hence, to a large extent it is the physical mechanisms driving the transfer of nutrient rich water into the euphotic zone which dictate patterns of phytoplankton growth. Using a combination of observation and high resolution computer modelling this thesis investigates whether shear associated with mesoscale features leads to locally enhanced turbulent mixing and a shear-enhanced nutrient supply. Measurements of turbulent diffusivity and nutrient concentrations have been made in a region containing an eddy dipole, a strong mesoscale feature, consisting of a cyclonic eddy and an anti-cyclonically rotating mode-water eddy. The effect of this strong mesoscale feature on vertical turbulent mixing is assessed by investigating whether variations in vertical shear associated with the mesoscale feature enhance the observed vertical turbulent mixing. Using these observations of turbulent diffusivity, augmented by further measurements from two other ocean regions, a new parametrization of shear-enhanced vertical turbulent mixing is developed. The new shear-enhanced mixing parametrization is implemented in a high-resolution computer model of a mode-water eddy. This model is then used to examine the effect of interactions between the eddy and the wind on vertical nutrient fluxes. The shear enhancement to nutrient supply by mesoscale circulation is found to be potentially of much greater significance than has previously been considered. Modelling suggests that when forced by high variability winds mode-water eddies appear to be capable of locally enhancing the vertical turbulent nutrient flux by up to an order of magnitude. The work in this thesis suggests that vertical turbulent flux may well be underestimated as a stimulus to new production.
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Kozyniak, Kathleen. "Integrated mesoscale-hydrometeorological modelling for flood forecasting." Thesis, University of Bristol, 2001. http://hdl.handle.net/1983/f54ba862-fc88-4ae1-9f6a-fe955dc5e581.
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In an effort to improve upon rainfall forecasts produced by simple storm advection methods (nowcasts) and to broach the gap between them and the forecasts of complex Numerical Weather Prediction (NWP) models, in terms of the spatial detail and length of lead-time each provides, the research presented explores the possibility of combining elements of each into a physically-based algorithm for rainfall forecasting. It is an algorithm that uses as its foundation the rainfall prediction model of Mark French and Witold Krajewski, developed in 1994. Their model was designed to take advantage of the high resolution rainfall observations and tracking abilities provided by weather radar and to achieve a rainfall forecast by augmenting extrapolation techniques with a representation of storm dynamics in the form of "rising parcel" theory. The new algorithm/model retains those features but incorporates NWP data to assist with forecasting, using it as a means to enable an informed choice of algorithm pathways and, more specifically, to identify the ingredients of precipitation, namely ascending air of high moisture content. A case study application of the new rainfall forecasting model to storms in Northern England shows its performance, at a lead-time of one hour, compares favourably with respect to extrapolation and persistence techniques and also NWP forecasts, and that it is able to provide more assured forecasts than persistence and nowcasts at longer lead-times. The robustness of the model is tested and confirmed by way of another case study, this time using Mediterranean storms and with predictions made in the context of urban hydrology. The case studies help to identify aspects of the model that need improvement, with representation of orographic forcing being a key one. Both the model's encouraging performance and its pinpointed weaknesses provide impetus for further research in the area of integrated mesoscale-hydrometeorological modelling for flood forecasting.
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Odins, Andrew Michael. "Mesoscale predictability of an extreme warm-season precipitation event." Texas A&M University, 2004. http://hdl.handle.net/1969.1/1423.
Full textAbstract:
During the period of June 29 through July 6, 2002, an extreme precipitation event occurred over Texas, resulting in catastrophic flooding. Operational forecasts performed poorly, neither predicting the copious amounts of rain nor its longevity. The Penn State University/NCAR Mesoscale Model version 5 (MM5) was used to conduct predictability experiments, which follow closely to the research conducted by Zhang et al. A control simulation initialized at 00Z 1 July is established over a 30-km grid. First, practical predictability experiments are performed by exploring the impacts due to different lead-times, resolution dependence, and different physics parameterizations. Second, intrinsic predictability is investigated by inducing a random temperature perturbation in the initial conditions, followed by numerous simulations with various perturbed initializations. Similar results to those found by Zhang et al. were discovered here: the prominent initial error growth is associated with moist processes leading to convection. Eventually these errors grow from the convective scale to sub-synoptic scale, essentially below 1000 kilometers. This indicates that as the forecast time extends further beyond initialization, the resulting errors will impact forecasts of larger-scale features such as differences in the
positioning and intensity of positive PV anomalies and distribution of precipitation from the control simulation.
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Meng, Zhiyong. "Tests of an ensemble Kalman filter for mesoscale and regional-scale data assimilation." Texas A&M University, 2003. http://hdl.handle.net/1969.1/5870.
Full textAbstract:
This dissertation examines the performance of an ensemble Kalman filter (EnKF)
implemented in a mesoscale model in increasingly realistic contexts from under a perfect
model assumption and in the presence of significant model error with synthetic
observations to real-world data assimilation in comparison to the three-dimensional
variational (3DVar) method via both case study and month-long experiments. The EnKF
is shown to be promising for future application in operational data assimilation practice.
The EnKF with synthetic observations, which is implemented in the mesoscale
model MM5, is very effective in keeping the analysis close to the truth under the perfect
model assumption. The EnKF is most effective in reducing larger-scale errors but less
effective in reducing errors at smaller, marginally resolvable scales. In the presence of
significant model errors from physical parameterization schemes, the EnKF performs
reasonably well though sometimes it can be significantly degraded compared to its
performance under the perfect model assumption. Using a combination of different
physical parameterization schemes in the ensemble (the so-called âÂÂmulti-schemeâ ensemble) can significantly improve filter performance due to the resulting better
background error covariance and a smaller ensemble bias. The EnKF performs
differently for different flow regimes possibly due to scale- and flow-dependent error
growth dynamics and predictability.
Real-data (including soundings, profilers and surface observations) are assimilated
by directly comparing the EnKF and 3DVar and both are implemented in the Weather
Research and Forecasting model. A case study and month-long experiments show that
the EnKF is efficient in tracking observations in terms of both prior forecast and
posterior analysis. The EnKF performs consistently better than 3DVar for the time
period of interest due to the benefit of the EnKF from both using ensemble mean for
state estimation and using a flow-dependent background error covariance. Proper
covariance inflation and using a multi-scheme ensemble can significantly improve the
EnKF performance. Using a multi-scheme ensemble results in larger improvement in
thermodynamic variables than in other variables. The 3DVar system can benefit
substantially from using a short-term ensemble mean for state estimate. Noticeable
improvement is also achieved in 3DVar by including some flow dependence in its
background error covariance.
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Nohut, Serkan. "Reliability of advanced ceramics macro- and mesoscale investigations." Göttingen Cuvillier, 2009. http://d-nb.info/999016105/04.
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Lane, Timothy Glenn. "ERICA IOP 5A : mesoscale structure and frontal evolution /." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1996. http://handle.dtic.mil/100.2/ADA322564.
Full textAbstract:
Thesis (M.S. in Meteorology and Physical Oceanography) Naval Postgraduate School, September 1996.Thesis advisor(s): Carlyle H. Wash, Paul A. Hirschberg. "Seotember 1996." Includes bibliographical references (p. 77-79). Also available online.
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Sampson, R. Mark. "Three dimensional visualization of a coastal mesoscale model." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA278576.
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Comstock, Kimberly K. "Mesoscale variability and drizzle in southeast Pacific stratocumulus /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/10013.
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Mohr, Matthias. "Mesoscale Simulations of Atmospheric Flow in Complex Terrain." Doctoral thesis, Uppsala University, Department of Earth Sciences, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3461.
Full textAbstract:
The MIUU mesoscale model was further developed, in order to include information on large-scale atmospheric fields from global or regional atmospheric climate- and weather-prediction models. For this purpose, a new lateral boundary condition was developed and implemented into the model. The new lateral boundary condition is a combination of two existing conditions, namely the flow relaxation scheme and the tendency modification scheme.
Tests indicated that an optimum lateral boundary configuration would be obtained with moderate to strong flow relaxation at higher levels, small flow relaxation at lower levels (within the atmospheric boundary layer), upstream advection at the outermost 4 grid points, and 6% horizontal grid stretching starting at a substantial distance from the lateral boundaries. The flow relaxation coefficients should be specified carefully, in order to minimize the reflection of all kinds of waves at the lateral boundaries.
The summer thermal low in the mean-sea-level pressure field over North America is traditionally analyzed over the northern end of the Gulf of California. The position of this low is influenced by the application of the so-called plateau correction in obtaining mean-sea-level pressure values from highly elevated stations in North America. A model study indicated that the low should be located approximately 450 km to the north and somewhat to the east of the above location.
A statistical comparison of model results from two mesoscale models against upper-air and surface measurements from several sites was carried out. Statistical methods, however, give only an insufficient picture of overall model performance. A comparison between predicted and measured tracer concentrations could be used to better evaluate the overall performance of different models.
Sound propagation in the atmosphere was predicted in a mountain valley using a mesoscale atmospheric model together with a sound propagation model. This suggests that forecasts of sound propagation should be possible in future.
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Aksoy, Altug. "Mesoscale ensemble-based data assimilation and parameter estimation." Texas A&M University, 2005. http://hdl.handle.net/1969.1/2523.
Full textAbstract:
The performance of the ensemble Kalman filter (EnKF) in forced, dissipative
flow under imperfect model conditions is investigated through simultaneous state and
parameter estimation where the source of model error is the uncertainty in the model
parameters. Two numerical models with increasing complexity are used with simulated
observations.
For lower complexity, a two-dimensional, nonlinear, hydrostatic, non-rotating,
and incompressible sea breeze model is developed with buoyancy and vorticity as the
prognostic variables. Model resolution is 4 km horizontally and 50 m vertically. The
ensemble size is set at 40. Forcing is maintained through an explicit heating function
with additive stochastic noise. Simulated buoyancy observations on land surface with
40-km spacing are assimilated every 3 hours. Up to six model parameters are
successfully subjected to estimation attempts in various experiments. The overall EnKF
performance in terms of the error statistics is found to be superior to the worst-case scenario (when there is parameter error but no parameter estimation is performed) with
an average error reduction in buoyancy and vorticity of 40% and 46%, respectively, for
the simultaneous estimation of six parameters.
The model chosen to represent the complexity of operational weather forecasting
is the Pennsylvania State University-National Center for Atmospheric Research MM5
model with a 36-km horizontal resolution and 43 vertical layers. The ensemble size for
all experiments is chosen as 40 and a 41st member is generated as the truth with the
same ensemble statistics. Assimilations are performed with a 12-hour interval with
simulated sounding and surface observations of horizontal winds and temperature. Only
single-parameter experiments are performed focusing on a constant inserted into the
code as the multiplier of the vertical eddy mixing coefficient. Estimation experiments
produce very encouraging results and the mean estimated parameter value nicely
converges to the true value exhibiting a satisfactory level of variability.
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Chambers, Christopher R. S. "High resolution mesoscale modeling of Kauai wintertime weather." Thesis, University of Hawaii at Manoa, 2003. http://hdl.handle.net/10125/7025.
Full textAbstract:
Across the island of Kauai there are enormous gradients of rainfall, and in the center of the island Mt Waialeale is considered one of the wettest spots on Earth. Five high resolution MM5 case studies under different wintertime synoptic flow regimes have been performed to investigate the processes that lead to the observed rainfall distributions across the island. There is good agreement between the mOdeled rainfall and 3 day rain gauge totals for 4 out of the 5 case studies presented. This suggests that rainfall distributions and gradients across the island are to some extent realistically simulated. Analysis of the easterly wind case reveals significant structural changes to the trade wind layer as it passes over the island. On approach to the central mountains, there is a general deepening of the moist layer and a corresponding deepening of clouds associated with flow over, rather than around, the island. On the lee side downward moving air mixes dry air from above the inversion with the moist air below, leading to a drying of the moist layer over leeward areas. Trajectory analysis suggests that, aided by latent heat release, air from low levels under partially cloudy (i.e. trade cumulus) easterly wind conditions can lift up the windward slopes and flow over the top of Waialeale. Persistent heavy rainfall out of the consequent deep orographic clouds is triggered as upward motion shifts to downward motion over the summit. Wind flow changes over the summit crest are in turn likely to be largely dependent on the characteristics of the trade wind inversion. Other case studies under different synoptic flow also produce a maximum in rainfall over Waialeale. Results suggest, but do not prove, general intuitions about the conditions that favor the production of orographic rain. A deeper moist layer allows the development of deeper clouds leading to greater rainfall. Latent heat aided uplift within orographic clouds supports the flow of air over the mountains. Model testing of sensitivity to vegetation specification reveals that changing the vegetation type in the model leads to different total rainfall patterns across the island. These differences result as (either) a local island consequence of the altered surface fluxes associated with the vegetation changes made, and (or) the simulations producing different cloud and rain distributions generated by a separate forecast.x, 104 leaves
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Thomson, Keith Alec. "On the geographic variability of oceanic mesoscale motions." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/27209.
Full textAbstract:
Quasi-synoptic expendable bathythermograph data were acquired, from the Canadian Armed Forces, the United States Navy and the United States National Oceanographic Data Center, for the Pacific and Atlantic Oceans. On the basis of these data and the results of previous studies using climatological data, six geographic regions were defined: the high-energy regions of the Northwest Atlantic and Northwest Pacific, and the low-energy regions of the Northeast Atlantic, Northeast Pacific, South Atlantic and South Pacific. Spatial series of two variables, representative of the upper layer (400 m) mesoscale variability, were obtained for each section - the mid- thermocline temperature and the geopotential anomaly (0 - 4000 kPa).
The central moments and the wavenumber spectra of each variable were estimated for the six geographic regions, the combined high-energy areas and the combined low-energy areas. In the high-energy regions and the Northeast Atlantic, it was found that the temperature between 350 and 400 m is representative of the temperature variability due to the baroclinic eddy field, whereas, the temperature between 150 and 200 m is more representative of the eddy variability in most of the low-energy regions. The standard deviations of temperature, in the high- and low-energy regions, are 1.40 and 0.54°C, respectively. The standard deviations of the geopotential anomaly are 0.67 and 0.26 m²/s², respectively. The high-energy regions have dominant spectral wavelengths in the geopotential anomaly fields of 300 and 155 km, with corresponding baroclinic surface velocity scales of 9.6 and 17.5 cm/s. The low-energy regions have dominant wavelengths of 300 and 170 km with velocity scales of 4.5 and 5.5 cm/s, respectively. In general, the high-energy regions have a greater portion of their spectral variance concentrated in the higher wavenumbers (i.e. 280 to 100 km wavelengths), than the low-energy regions. The eddy kinetic energies per unit mass for the high- and low-energy regions were estimated at 250 and 36 cm²/s², respectively.
The geographic variability of the governing dynamics was inferred by evaluating the quasigeostrophic scaling parameters (i.e. the Rossby number (Ro), the Burger number (B) and the sphericity parameter (β*)) and the Rossby wave steepness parameter (M). Also, the properties of free linear dispersive Rossby waves were calculated with the observed wavelengths and the spectral power-laws of the temperature spectra were compared with several models of nonlinear geophysical turbulence. It was found that Ro<<1, B = 0(1) and β*<<1, which is consistent with the scaling for quasigeostrophy. The dynamics inferred from these analyses exhibit a distinct geographic variability. Motions with wavelengths greater than 200 km in all regions are consistent with linear/nonlinear Rossby wave theory. Mesoscale perturbations in the
high-energy regions are, of course, more nonlinear than the corresponding length scales in the low-energy regions. Motions, with wavelengths less than 200 km in the high-energy regions, are consistent with quasigeostrophic turbulence theory, more specifically, with Charney's (1971) model of three-dimensional quasigeostrophic turbulence. Motions with wavelengths less than 200 km in the low-energy regions have dynamics that are intermediate between linear/nonlinear Rossby wave theory, and quasigeostrophic turbulence theory.Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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Meunier, Véronique Marcelle. "Development of a mesoscale radiometer for weather research." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=116071.
Full textAbstract:
A new microwave radiometer, the Mesoradiometer, was constructed and the meteorological information contained in its data were examined. This instrument is designed to measure the distribution of water vapor and liquid water in the atmosphere.The Mesoradiometer uses 32 channels located on both sides of the 22.235 GHz water vapor absorption peak, as well as a narrow beam width antenna, and a pedestal giving the instrument the capacity to scan the atmosphere in order to detect water vapor. During the characterization of the instrument, a problem in maintaining the stability of the instrument's temperature was detected.
Even with this problem, the Mesoradiometer successfully measured atmospheric water vapor and liquid water. The instrument was capable of tracking the movements of clouds. This is possible thanks to its rapid scanning strategy, such tracking being impossible with traditional radiometers.
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Andrade, Amaya Carlos Alberto. "Mesoscale variability of the Caribbean Sea from GEOSAT." Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/28353.
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Gardner, Elizabeth B. "Mesoscale vertical structure of an explosive oceanic cyclone." Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/28354.
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Gutierrez-Camacho, Jorge Arturo. "Vorticity production in flows associated with mesoscale mountains." Thesis, University of Reading, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360754.
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Chin, Jonathan. "Mesoscale fluid simulation with the lattice Boltzmann method." Thesis, Queen Mary, University of London, 2005. http://qmro.qmul.ac.uk/xmlui/handle/123456789/1776.
Full textAbstract:
This thesis describes investigations of several complex fluid effects., including hydrodynamic spinodal decomposition, viscous instability. and self-assembly of a cubic surfactant phase, by simulating them with a lattice Boltzmann computational model. The introduction describes what is meant by the term "complex fluid", and why such fluids are both important and difficult to understand. A key feature of complex fluids is that their behaviour spans length and time scales. The lattice Boltzmann method is presented as a modelling technique which sits at a "mesoscale" level intermediate between coarse-grained and fine-grained detail, and which is therefore ideal for modelling certain classes of complex fluids. The following chapters describe simulations which have been performed using this technique, in two and three dimensions. Chapter 2 presents an investigation into the separation of a mixture of two fluids. This process is found to involve several physical mechanisms at different stages. The simulated behaviour is found to be in good agreement with existing theory, and a curious effect, due to multiple competing mechanisms, is observed, in agreement with experiments and other simulations. Chapter 3 describes an improvement to lattice Boltzmann models of Hele-Shaw flow, along with simulations which quantitatively demonstrate improvements in both accuracy and numerical stability. The Saffman-Taylor hydrodynamic instability is demonstrated using this model. Chapter 4 contains the details and results of the TeraGyroid experiment, which involved extremely large-scale simulations to investigate the dynamical behaviour of a self-assembling structure. The first finite- size-effect- free dynamical simulations of such a system are presented. It is found that several different mechanisms are responsible for the assembly; the existence of chiral domains is demonstrated, along with an examination of domain growth during self-assembly. Appendix A describes some aspects of the implementation of the lattice Boltzmann codes used in this thesis; appendix B describes some of the Grid computing techniques which were necessary for the simulations of chapter 4. Chapter 5 summarises the work, and makes suggestions for further research and improvement.
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Bister, Marja Helena. "Development of tropical cyclones from mesoscale convective systems." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/57851.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1996.Includes bibliographical references (p. 109-112).
by Marja Helena Bister.
Ph.D.
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Zhao, Pengyang. "Mesoscale modeling of mechanical deformation of metallic glasses." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1417961426.
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Mapes, Brian. "The Australian monsoon and its mesoscale convective systems /." Thesis, Connect to this title online; UW restricted, 1992. http://hdl.handle.net/1773/10068.
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Richardson, Robin Archibald. "A mesoscale model for coarse-grained protein dynamics." Thesis, University of Leeds, 2014. http://etheses.whiterose.ac.uk/8099/.
Full textAbstract:
Proteins are the essential units of biological processes, but modelling their dynamics is a very computationally expensive task. A wide variety of simulation techniques exist, a popular example being Molecular Dynamics. However, such models typically involve detailed simulation of the protein's structure at or near the atomic level and as such are unsuitable for modelling biological systems composed of large or multiply interacting proteins. This research takes a coarse-graining approach, called Fluctuating Finite Element Analysis, in which large, globular proteins are approximated by viscoelastic continua subject to thermal noise. Each protein is discretised into a tetrahedral mesh, parameterised locally by its bulk continuum properties. The forces are then calculated using Finite Element Analysis. A parallel implementation of the FFEA algorithm has been developed for use on high performance computing facilities. The scalability of the algorithm with respect to number of cores and system size, and its stability with respect to integration time step has been investigated. A pipeline for fully automated FFEA system creation from atomistic (X-ray crystallography and NMR) or low resolution data (cryo-EM and SAXS) has also been developed. In order to tackle multiprotein systems, the FFEA model has been extended to include van derWaals interactions and electrostatics. FFEA has been applied to a number of diverse biological systems. The van der Waals scheme was tested through simulation of myoglobins interacting with a polystyrene substrate. The major modes of motion of V- and A- type rotary ATPases were extracted using Principal Component Analysis, and compared with the normal modes obtained from the Elastic Network Model. Finally, the effect of axonemal dynein c's interaction with the microtubule track on its step length and exploration of binding sites was investigated. A mapping was developed to allow in-simulation conformational switching of the dynein motor.
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van, Lidth de Jeude Jeroen Allard. "Analysing mesoscale structures in economic and financial networks." Thesis, IMT Alti Studi Lucca, 2019. http://e-theses.imtlucca.it/266/1/DeJeude_phdthesis.pdf.
Full textAbstract:
Modelling, characterising and detecting the structure of complex
networks is of primary importance to understand the
dynamics of the systems considered. This is especially true
for economic and financial networks, whose structural organisation
deeply affects their resilience to shock propagation.
Many real world networks are characterised by the presence
of mesoscale structures: while a lot of attention has been focused
on the community structure, many real-world networks
are characterised by core-periphery, bow-tie and bipartite structures,
especially so economic and financial networks. In this
thesis we present new methods to model and detect these
mesoscale structures. We apply these methods to characterise
the structure of real-world economic and financial networks.
Using maximum entropy networks encoding different levels
of information, we model the structure of the international
trade network and of national interbank exposures networks.
We find that constraining local information is enough to reconstruct
the mesoscale structure of these networks: hence,
we introduce a new method to detect statistically significant
bimodular structures, based on the connectivity within and
between network modules. We also apply our method to multiplex
networks. In particular, to unravel different types of
corporate networks, we construct a new multilayer dataset
of company interactions: we find that the disaggregate network
describes a small corporate world, but that these different
company interactions are characterised by vastly different
topological properties.
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AVUGADDA, SAHITYA KUMAR. "MESOSCALE ASSEMBLIES OF INORGANIC NANOPARTICLES FOR THERANOSTIC APPLICATIONS." Doctoral thesis, Università degli studi di Genova, 2020. http://hdl.handle.net/11567/1000709.
Full textAbstract:
During the three years of my Ph.D, Ph.D cycle XXXII (2016-2019), at the Fondazione Istituto Italiano di Tecnologia, under the supervision of Dr.Teresa Pellegrino and the co-supervision of Prof.Orietta Monticelli (University of Genova), my focus was mainly on developing colloidally stable nanoclusters assembled at well-defined geometries produced from benchmark iron oxide nanocubes. These nanoclusters were designed, exploited and characterized for their potential use in theranostic applications comprising their exploitation in Magnetic Hyperthermia, Magnetic Resonance Imaging (MRI) and Magnetic Nanoparticles Imaging.
As the first aim, my focus was on building a two-dimensional nanoplatform based on highly efficient iron oxide nanocubes enwrapped with a bacteria extracted, biodegradable and biocompatible polyhydroxyalkanoate copolymer. Moreover, these magnetic polymeric clusters exhibit the unique feature to disassemble upon exposure to an intracellular rich lytic enzyme solution thus providing a gradual change in the cluster configuration accompanied by a gradual increase of magnetic heat performances in comparison to the initial 2D-clusters and to the individual iron oxide nanocubes used as building blocks for the cluster preparation. Indeed, comparing magnetic heat properties of the 2D assemblies with three dimensional centro-symmetrical assemblies (3D-MNBs) or single iron oxide nanocubes from same batch of cubes, emphasize how the initial 2D-assembly of iron oxide nanocubes s (2D-MNBs) dispersed in water are more advanced than the 3D-assemblies, but worse with respect to individual nanocubes. In addition, the heat abilities of these 2D clusters progressively increased when incubated in presence of esterase enzyme under physiological temperature, after 3 hours of incubation the specific absorption rate values, a measure of the heat-ability of the nanoparticles under a radio frequency were almost double than that of single cubes. Such an increase corresponds to disassembling of 2D-MNBs into short chain-like clusters of few nanocubes. Remarkably, our 2D-MNBs did not exhibit any variations in heat performance even after inducing an intentional aggregation. This is not the case for individual nanocubes. Magnetophoresis measurements suggest a faster response of 3D and 2D clusters to external magnets (0.3T) than that of individual nanocubes. This feature is desirable for the physical accumulation of magnetic materials under external magnetic field gradients. To the best of our knowledge, this is the first example of a nanoplatform, which combined enzymatic cleavable properties to a clear enhancement of the magnetic heat losses. In addition to this cluster study, I have also contributed to characterize other chain-like assemblies, named Dimer/Trimer obtained by assembling low interacting core-shell of wustite/magnetite iron oxide nanocubes into an amphiphilic copolymer, poly(styrene-co-maleic anhydride) cumene-terminated. Interestingly, by modulating the amount of polymer to nanoparticle surface ratio, the geometry of the same clusters could be modulated from a single structure to Dimer/Trimer to centrosymmetric structures. The short chains of nanocubes exhibit even in this case an enhanced specific absorption rate value with respect to single cubes and centrosymmetric clusters. Overall these studies reveal the significance of particle arrangement as a means to improve magnetic heating performances of the same building blocks, the nanocubes in our case.
According to our second aim, the above nanoclusters (developed for magnetic hyperthermia mentioned) were investigated as magnetic tracers, to unveil their diagnostic features for, recently emerging magnetic nanoparticles imaging (MPI) and for Magnetic resonance imaging (MRI). The multimodal imaging models with combined MPI and MRI properties could assist in real-time mapping of tissues that expected to improve the diagnostic accuracy. We found that the 2D-MNBs based on high interacting Iron oxide nanocubes exhibit poor MPI signal than that of standard Resovist. However, this signal of 2D-MNBs underwent a progressive increase upon incubation with esterase enzyme under physiological temperature (almost doubled) starting from their initial state, which attributes to the splitting of 2D beads into a small chain-like configuration. These results show a similar trend to the enzymatic triggered increase in heat performance, as mentioned above. Moreover, the 2D-MNBs possess a remarkable transverse relaxation rate (r2), indicating an efficient negative contrast of 2D-MNBs as agents for MRI. This value reduced by half upon exposure to lytic enzyme providing a significant T2-signal change upon to a stimulus triggered change (the enzymatic degradation). On the other side, among the nanoclusters based on core-shell iron oxide nanocubes; single structure, Dimer/Trimer to centrosymmetric structures, Dimer/Trimer exhibit a very remarkable MPI signal in comparison to the nanocube assemblies and to the individual nanoparticles and with respect to Resovist the most accepted FDA approved standard. Complementing the signal dominance in short chains of 2D-MNBs, the increase of MPI signal in Dimer/Trimer can also corresponds to their short uniaxial configuration. In addition, they have given a very significant transverse relaxation rate (r2) than many other superparamagnetic iron oxide nanoparticles. This kind of nanovectors with multifunctional theranostic features of MRI, MPI and magnetic hyperthermia are beneficial to improve thermo-therapy treatment of cancerous tissues while offering at the same time a potential readable and changing signal for image mapping.
Finally, as reported in chapter 3, we aim to develop an assembled nanoplatform made of magnetic iron oxide nanocube-based clusters and gadolinium-based nanoparticles that make the assembly responsive to the tumor microenvironment. This will enable to track tumor accumulation and disassembly of the nanoplatform for efficient thermotherapy based on T1 gadolinium-changing signal. For this purpose, we synthesize multicomponent nanostructures starting from iron oxide nanocubes embedded in a polymeric bead (MNBs) with a surface negative charge and decorated with Sodium gadolinium fluoride nanoparticles (NaGdF4 NPs), placed in between enzyme-degradable polymer spacers. Our hybrid structure achieved desired heating abilities under an alternative magnetic field of biological relevance. In addition to prominent T2 properties coming from MNBs, we demonstrated disassembling and detaching of polymer and NaGdF4 NPs from the surface of the MNBs upon exposure to enzymes that in turn improved water accessibility to NaGdF4 NP surface with a corresponding increase of T1 signal. In this way, we tracked the morphological changes of the systems at different time points of incubation in the presence of an enzyme, by MRI changing signal. This data was also confirmed by observing structural changes using TEM imaging. The integration of diagnostic tools to benchmark therapeutic probes could be a smart approach that enables to track the nanoparticle accumulation through artifact-free diagnosis and improve the heat efficiency of the magnetic hyperthermia treatment at the tumor.
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Xotta, Giovanna. "Mesoscale modelling of concrete as a multiphase material." Doctoral thesis, Università degli studi di Padova, 2012. http://hdl.handle.net/11577/3422951.
Full textAbstract:
In recent years, thanks to upgraded computational resources, concrete has started being modeled as porous medium at 3D meso level, distinguishing in the multiphase system the role of aggregates, cement paste and interfacial transition zone (ITZ). A deep knowledge on the behaviour of concrete materials at the mesoscale level requires, as a fundamental aspect, to characterize aggregates and specifically, their thermal properties if fire hazards (e.g. spalling) are accounted for. The assessment of aggregates performance (and, correspondingly, concrete materials made of aggregates, cement paste and ITZ) is crucial for defining a realistic structural response as well as damage scenarios.
A meso-scale approach has been here followed to study concrete behaviour under normal and high temperatures via the 3D fully coupled thermo-hydro-mechanical model developed at Padua University, called NEWCON3D. Particularly, it is assumed that concrete creep and damage are associated to cement paste and ITZ only and that creep of concrete obeys to the B3 model proposed by Bažant and Baweja, instead damage obeys to the Mazars’ damage law with non-local correction.
Therefore several numerical analyses at the mesolevel have been carried out: firstly the role of the ITZ and of the aggregates on the hygro-thermal response of concrete have been investigated, highlighting the barrier effect covered by aggregates towards the flux of humidity; subsequently the visco-damaged behaviour of concrete at the meso level is investigated, to understand the influence of ITZ and aggregates on the overall mechanical behaviour at medium temperatures. Indeed, these two components are crucial for defining a realistic structural response as well as damage scenarios allowing to define an appropriate concrete mixture to withstand spalling. Finally, the study of concrete under high temperature conditions, to catch the “shape effect”, comparing columns of different section at the macro level, and the crucial role of the aggregates and the ITZ on the real evolution of cracking, have been performed.Negli ultimi anni, grazie alle attuali risorse di calcolo, si è iniziato a modellare il calcestruzzo come un mezzo poroso al meso livello, distinguendo nel sistema multifase il ruolo degli aggregati, della pasta di cemento e dell’interfacial transition zone (ITZ). Una profonda conoscenza del comportamento del calcestruzzo al mesoscala richiede, come aspetto fondamentale, la caratterizzazione degli aggregati ed, in particolare, delle loro proprietà termiche, nel caso in cui vi siano rischi di incendio (e quindi di spalling). La valutazione delle prestazioni degli aggregati (e conseguentemente, di calcestruzzi come composti da inerti, pasta di cemento ed ITZ) è cruciale per la definizione sia di una risposta realistica strutturale, sia degli scenari di danno. In questo lavoro si è quindi seguito un approccio al mesoscala per studiare il comportamento del calcestruzzo, in condizioni di temperatura normale ed elevata, tramite un modello tridimensionale igro-termo-meccanico totalmente accoppiato sviluppato presso l’Università di Padova, chiamato NEWCON3D. Nello specifico, si è assunto che i fenomeni di viscosità e di danno fossero associati solo alla pasta di cemento e all’ITZ (per gli aggregati si assume un comportamento elastico) e che il creep obbedisse al modello B3 proposto da Bažant e Baweja, invece il danno alla legge di Mazars con la correzione non locale. Si sono pertanto condotte numerose analisi numeriche al meso livello: in primo luogo si è esaminato il ruolo dell’ITZ e degli aggregati sulla risposta igro-termica del calcestruzzo, mettendo in evidenza l'effetto barriera esercitato dagli aggregati sui flussi di umidità; successivamente si è indagato il comportamento visco-danneggiato del calcestruzzo al mesoscala, al fine di comprendere l'influenza dell’ITZ e degli aggregati sulla risposta meccanica globale a temperature medie. In realtà, come già detto precedentemente, queste due componenti sono molto importanti per ottenere una risposta realistica strutturale e per l’individuazione dei possibili scenari di danno, permettendo quindi di definire una miscela di calcestruzzo appropriata, in grado di resistere allo spalling. Infine, vi è uno studio del calcestruzzo in condizioni di temperatura elevata, al fine di catturare l '"effetto forma", confrontando due colonne di sezione differente al macro scala, ed il ruolo cruciale degli aggregati e dell’ITZ sull'evoluzione reale del danno.