Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 37 for “"Extensional Flow"”.
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Crystallization kinetics of polymer melts in extensional flow
A technique to study the kinetics of flow-induced crystallization of polymers in extensional flow has been developed which uses a 4-Roll Mill. The kinetics of a High Density Polyethylene were found to be well described by the Avrami treatment, indicated that the crystallization occurred by sporadic …
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The rheology and structure of thermotropic liquid crystalline polymers in extensional flow
The transient shear and elongational flow behavior of HPC EF, G, and HBA/HNA (Vectra A900) have been measured in order to determine the behavior of liquid crystalline polymer systems and to establish whether this behavior is different from that for isotropic flexible-chain polymer melts and …
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MOLECULAR DYNAMICS STUDY ON THE STRUCTURE, DYNAMICS AND STRESS RESPONSE OF DILUTE MICELLAR SYSTEMS IN UNIAXIAL EXTENSIONAL DEFORMATION
… of single micelles in solution to uniaxial extensional flow deformation. These knowledge gaps are possibly due to the inability of traditional experimental studies to investigate micellar properties at the time- and length-scale pertinent to self-assembly and micellar dynamics. To this end, …
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Flow History - Morphology - Property Interactions in Poly(vinylidene Fluoride)
A numerical and experimental analysis of the melt flow history of poly(vinylidene fluoride), PvF$\sb2$, in an extensional flow, film-processing geometry as well as morphological characterization and property measurements of the melt extruded films are presented.
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Mechanical algal disruption for efficient biodiesel extraction
… to an algal solution. The configuration studied flows the solution through a tube and insonifies a small section with a high-pressure ultrasound wave. Previous biomedical research has shown effective cell membrane damage on animal cells with similar methods, but the present research is the first …
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Viscoelastic Fluid Flow Past a Submerged Spheroidal Body (Birefringence, Free Energy)
… to study the problem of homogeneous axisymmetric flow of a third order fluid past a spheriodal body. The numerical solution was shown to agree well with existing analytical solutions for several limiting cases (such as flow past a sphere), and was used to investigate the effects of the (a) body …
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Single molecule studies of polymers and self-assembling materials: Effects of chain topology and entanglements
… and functional materials in nonequilibrium flow conditions is of key importance for controlling materials properties during processing, which often involves highly nonequilibrium states that cannot be understood in terms of equilibrium principles or thermodynamics. From this view, it is …
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High-rate deformation behavior and applications of fluid filled reticulated foams
… small and large amplitude oscillatory shear flow and also in transient extensional flow. Oscillatory experiments indicate that both the onset and magnitude of the shear thickening depends on the frequency and strain applied and show that rapid time-varying deformations result in maximum …
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Coupling molecular conformation to polymer chemistry and composition via flow
… behavior of polymers in the presence of fluid flow over the past century. There remain, however, fundamental questions about how flows couple to molecular degrees of freedom and vice versa. This pressing problem has profound implications in polymer processing in industry, both for traditional …
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The Computer Simulation of Dilute Solution Particle Dynamics
… solution is described. Equilibrium, shear and extensional flow fields are considered. The program tracks particles individually and is therefore capable of calculating statistical averages of a wide range of properties; particle inertia and Brownian motion are included in the simulation, …
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Controllability of Non-Newtonian fluids under homogeneous flows
… popular constitutive models under homogeneous extensional and shear flows via the Lie bracket method. The constitutive models are as follows: the Phan-Thien-Tanner model; the Johnson-Segalman model; and the Doi model. The effect of extensional flow on these models and the effect of shear flow …
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Structure Formation and Crystallization in Two-Phase Polymer Blend Flows (Fibers, Polyethylene, Polypropylene)
Flow induced crystallization of high density polyethylene and polypropylene has been studied in a two-phase flow system using linear low density polyethylene as the carrier phase. Extensional stresses were generated under slow flow conditions by either of two methods: one involving flow past a …
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Single polymer dynamics in semi-dilute solutions: linear and ring polymers
… intermolecular interactions in non-equilibrium flows. Over the past two decades, single molecule techniques have been established to investigate molecular-level dynamics, thereby allowing direct access to polymer chain relaxation mechanisms and polymer non-linear response under a variety of …
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Single stranded DNA: A new model system for single molecule polymer dynamics
… individual ssDNA molecules stretching in an extensional flow generated inside a microfluidic device. It is anticipated that the model polymer system presented here will serve to promote further investigations of flexible polymer dynamics at the molecular level.
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Contraction/expansion flow of dilute elastic solutions in microchannels
… experimental study is conducted on the nature of extensional flows of mobile dilute polymer solutions in microchannel. By observing such fluids on the microscale it is possible to generate large strain rates ([approximately] 50,000 s⁻¹) that are greater than values which have been observed in …
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Energy absorption of reticulated foams filled with shear-thickening silica suspensions
… small and large amplitude oscillatory shear flow and also in transient extensional flow. The viscosity of the polydisperse suspension is found to be much greater than the monodisperse one due to the difference in particles shape. Oscillatory experiments indicate that both the onset and …
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Single molecule studies of branched polymer dynamics in non-dilute solutions
… of semi-dilute unentangled linear polymers in extensional flow (Chapter 3). Comb polymer dynamics in semi-dilute solutions are compared to those in dilute solutions and also to linear polymers in semi-dilute solutions. Our results show that comb polymers in semi-dilute solutions exhibit complex …
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Conformation and Rheology of Semiflexible Macromolecules Using Non-Equilibrium Brownian Dynamics and Monte Carlo Simulations
… and polyelectrolytes undergoing shear and extensional flow. The mathematical model utilizes a discretized version of the Kratky-Porod wormlike (or persistent) chain as the building block, generalized to include flow. This discrete chain contains beads which interact through stretching and …
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Single molecule studies of flexible polymer systems
… imaged single ssDNA polymers stretching in fluid flows in microfluidic devices (Chapter 2). In addition, we have developed an automated flow-based method to isolate individual polymer chains for long periods of time in planar extensional flow (Chapter 3). By combining the tools we developed we …
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Image processing for in-situ feedback control of fiber spinning of carbon nanotubes
… focuses on an emerging technology that uses an extensional flow apparatus to produce continuous strands of CNTs from a suspension of CNT nanoparticles. The properties of the CNTs produced depend heavily on the configuration of flow rates of the CNT solution and the surrounding solvent. To …
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