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Sinha, Asish Kumar. "Melt flow and cleanliness in continuous casting tundishes /." The Ohio State University, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487686243820661.
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Gießler, Cornelia. "Theoretical investigations of electromagnetic control of glass melt flow." Ilmenau : Univ.-Verl. [u.a.], 2008. http://d-nb.info/992639689/34.
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Giessler, Cornelia. "Theoretical investigations of electromagnetic control of glass melt flow." Ilmenau Univ.-Verl, 2008. http://d-nb.info/990665887/04.
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Kho, Rowin Wisadi. "Heat flow in the melt and crucible for crystal growth." Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/29991.
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A magnetic field is imposed on the melt during Czochralski crystal growth to control fluid flow. The influence of an applied magnetic field on heat transfer in a germanium melt has been investigated in this work. In heat-transfer modelling of the Czochralski process, values of thermal conductivity of the crucible material, pyrolytic boron nitride, are required as a function of temperature. The thermal conductivity of a pyrolytic boron nitride crucible material has also been determined in this work. Both the investigation
of the influence of the applied magnetic field and the determination of the thermal conductivity have involved experimental temperature measurements and mathematical modelling of heat transfer.
The finite element equations for the two-dimensional heat-conduction equation have been derived using the Galerkin method of weighted residuals. They have been validated by comparing the finite element solutions with the corresponding analytical solutions. The finite element results are in excellent agreement with the analytical solutions.
A steady-state conduction-dominated mathematical model has been developed to analyze
the temperature measurements obtained within the germanium melt in a Czochralski
crystal growth configuration with and without an applied magnetic field of 0.099 tesla. The effect of the applied magnetic field on the heat transfer in the melt has been determined by fitting the model-calculated results to the measurements. The effective thermal conductivity of the melt has been found to decrease by a factor of seven due to the magnetic field.
The thermal conductivity across a pyrolytic boron nitride crucible plate (through crucible thickness) has been determined from measurements of temperature responses
in liquid gallium positioned on both sides of the plate, in conjunction with a transient mathematical model which simulates the thermal responses. By matching the simulated thermal responses with the measurements, the thermal conductivity of the pyrolytic boron nitride crucible plate has been obtained as a function of temperature.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
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Kolnaar, J. W. H. "A temperature window of reduced flow resistance in polyethylene with implications for melt flow rheology." Thesis, University of Bristol, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357887.
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Gießler, Cornelia [Verfasser]. "Theoretical investigations of electromagnetic control of glass melt flow / Cornelia Gießler." Ilmenau : Univ.-Verl, 2008. http://d-nb.info/992639689/34.
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He, Chunxia 1968. "Shear flow behavior and molecular structure of high melt strength polypropylenes." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84208.
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Linear shear flow behavior and molecular structure studies were carried out on linear polypropylenes produced using Ziegler-Natta catalysts and sets of branched polypropylenes produced from these linear precursors.A method combining dynamic and creep measurements was employed to obtain a complete picture of the linear viscoelastic behavior of these polypropylenes. It was found that all samples in a set of polypropylenes have the same linear viscoelastic behavior in the high-frequency range, but display dramatic differences at low frequencies. Increasing branching level results in a steep increase of the zero-shear viscosity, an increase of the steady-state compliance, and a broadening of the relaxation spectrum whose shape changes dramatically and peaks shift to longer times.
Molecular models were tested and applied to the linear polypropylenes to predict linear viscoelastic properties from the molecular weight distribution (MWD). The parameters obtained from the best fit of predicted and experimental data of linear polypropylenes were used to calculate a fictive relaxation spectrum for branched polymers from their MWDs as if they were linear. The comparison between this predicted result and the experimental spectrum showed the separate effects of polydispersity and branching on rheology.
To obtain detailed structural information, the branching process of polypropylenes was simulated using a Monte-Carlo approach, which provides detailed information such as MWD and branching distribution. The simulated MWD was adjusted to the measured GPC curve using a single parameter simply related to the branching density lambda (LCB/1000C). Relations between branching parameters and moments of the MWD were determined, which offer the possibility to calculate branching parameters directly from GPC results. The branching efficiency was estimated and correlations between engineering properties of polypropylenes and the structural information were obtained, which is of valuable industrial interest for polymer design.
A determination of the weight fractions of branches and segments between branch points from the relaxation spectrum is proposed. Due to the complexity of molecular relaxation mechanisms, only approximate correlations between molecular architecture and rheology were observed.*
*This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Microsoft Office.
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Holt, James. "Structure of polyethylene materials subject to shear flow in the melt." Thesis, University of Reading, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250650.
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Chakraborty, Sanjib. "Melt flow and heat transfer in continuous casting ladles and tundishes /." The Ohio State University, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487694389392267.
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Spiegelman, Marc Willard. "Melting and melt extraction : the physics of flow in deformable porous media." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315127.
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Walker, Gregory James. "Numerical studies of two phase flow and melt extraction in two dimensions." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624305.
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Sherratt, Jo. "The effect of thermoplastics melt flow behaviour on the dynamics of fire growth." Thesis, University of Edinburgh, 2001. http://hdl.handle.net/1842/4788.
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The UK Health & Safety Executive are responsible for advising on ways to ensure the safety of employees within the workplace. One of the main areas of concern is the potential problem of unwanted fire, and it has been identified that within the area of large-scale storage in warehouses, there is an uncertainty posed by large quantities of thermoplastic. Some forms of thermoplastic exhibit melt-flow behaviour when heated, and a large vertical array exposed to a fire may melt and ignite forming a pool fire in addition to a wall fire. This project is largely experimental, and aimed at quantifying the effect of a growing pool fire fuelled by a melting wall on overall fire growth rate. The pool fire has been found to increase melting and burning rates, producing a much faster growing fire. It has also been found that - 80% of flowing and burning material will enter a potential pool fire, with only 20 - 25% of total mass loss actually burning from the original array. During the project 400+ small-scale tests and several medium-scale experiments have been undertaken at both Edinburgh University and the HSE's Fire & Explosion Laboratory, Buxton. The experiments have confirmed the main parameters governing pool fire development are molecular weight degradation rate and mechanism, which control flow viscosity. There have also been investigations into other influences, the most significant of which was found to be flooring substrate. These parameters then form the basis of a simple 1-D model. A semi-infinite heat transfer approximation is used to determine temperature profile through a thermoplastic exposed to its own flame flux, with extrapolated temperature dependant material properties. The derived profile is then inserted into a gravity driven flow model, to produce estimates of flow rate and quantity for plastics undergoing either random or end chain scission thermal degradation processes. The model identifies property data which are required to permit its use as a hazard assessment tool.
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Doerpinghaus, Phillip J. Jr. "Flow Behavior of Sparsely Branched Metallocene-Catalyzed Polyethylenes." Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/28626.
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This work is concerned with a better understanding of the influences that sparse long-chain branching has on the rheological and processing behavior of commercial metallocene polyethylene (mPE) resins. In order to clarify these influences, a series of six commercial polyethylenes was investigated. Four of these resins are mPE resins having varying degrees of long-chain branching and narrow molecular weight distribution. The remaining two resins are deemed controls and include a highly branched low-density polyethylene and a linear low-density polyethylene. Together, the effects of long-chain branching are considered with respect to the shear and extensional rheological properties, the melt fracture behavior, and the ability to accurately predict the flow through an abrupt 4:1 contraction geometry.
The effects that sparse long-chain branching (Mbranch > Mc) has on the shear and extensional rheological properties are analyzed in two separate treatments. The first focuses on the shear rheological properties of linear, sparsely branched, and highly branched PE systems. By employing a time-molecular weight superposition principle, the effects of molecular weight on the shear rheological properties are factored out. The results show that as little as 0.6 LCB/104 carbons (<1 LCB/molecule) significantly increases the zero-shear viscosity, reduces the onset of shear-thinning behavior, and increases elasticity at low deformation rates when compared to linear materials of equivalent molecular weight. Conversely, a high degree of long-chain branching ultimately reduces the zero-shear viscosity. The second treatment focuses on the relationship between long-chain branching and extensional strain-hardening behavior. In this study, the McLeish-Larson molecular constitutive model is employed to relate long-chain
branching to rheological behavior. The results show that extensional strain hardening arises from the presence of LCB in polyethylene resins, and that the frequency of branching in sparsely branched metallocene polyethylenes dictates the degree of strain hardening. This observation for the metallocene polyethylenes agrees well with the proposed mechanism for polymerization.
The presence of long-chain branching profoundly alters the melt fracture behavior of commercial polyethylene resins. Results obtained from a sparsely branched metallocene polyethylene show that as few as one long-chain branch per two molecules was found to mitigate oscillatory slip-stick fracture often observed in linear polyethylenes. Furthermore, the presence and severity of gross melt fracture was found to increase with long-chain branching content. These indirect effects were correlated to an early onset of shear-thinning behavior and extensional strain hardening, respectively. Conversely, linear resins exhibiting a delayed onset of shear-thinning behavior and extensional strain softening were found to manifest pronounced slip-stick fracture and less severe gross melt fracture. The occurrence of surface melt fracture appeared to correlate best with the degree of shear thinning arising from both molecular weight distribution and long-chain branching.
The ability to predict the flow behavior of long-chain branched and linear polyethylene resins was also investigated. Using the benchmark 4:1 planar contraction geometry, pressure profile measurements and predictions were obtained for a linear and branched polyethylene. Two sets of finite element method (FEM) predictions were obtained using a viscoelastic Phan-Thien/Tanner (PTT) model and an inelastic Generalized Newtonian Fluid (GNF) model. The results show that the predicted profiles for the linear PE resin were consistently more accurate than those of the branched PE resin, all of which were within 15% of the measured vales. Furthermore, the differences in the predictions provided by the two constitutive models was found to vary by less than 5% over the range of numerical simulations obtained. In the case of the branched PE resin, this range was very narrow due to loss of convergence. It was determined that the small differences between the PTT and GNF predictions were the result of the small contraction ratio utilized and the long relaxation behavior of the branched PE resin, which obscured the influence of extensional strain hardening on the pressure predictions. Hence, it was expected that numerical simulations of the 4:1 planar contraction flow for the mildly strain hardening metallocene polyethylenes would not be fruitful.Ph. D.
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Damle, Chandrashekharr. "Melt flow, mixing and grade change studies in the continuous casting of steel /." The Ohio State University, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487859313344697.
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Faust, Karsten, André Bergmann, and Jens Sumpf. "Influence of the Melt Flow Rate on the Mechanical Properties of Polyoxymethylene (POM)." Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-231703.
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In this article the correlation between the average molar mass and the melt flow rate (MFR) is achieved. Based on the example of Polyoxymethylene (POM) it is shown that a high average molar mass is associated with a low MFR (high viscosity). On the basis of this dependency, the mechanical properties of static and dynamic tensile strength, elastic modulus, hardness and notched impact strength are investigated. It was found that the characteristic values of static tensile strength, elastic modulus and hard-ness increase with increasing MFR (decreasing viscosity). On the other hand the dynamic long-term properties and notched impact strengths decrease with increasing MFRIm Beitrag wird der Zusammenhang zwischen der mittleren molaren Masse und des Schmelzfließindex (MFR) hergestellt. Dabei wird am Beispiel von Polyoxymethylen (POM) ersichtlich, dass eine hohe mittlere molare Masse mit einem geringen MFR (hochviskos) einhergeht. Basierend auf dieser Abhängigkeit werden die mechanischen Eigenschaften statische und dynamische Zugfestigkeit, E-Modul, Härte sowie Kerbschlagzähigkeit untersucht. Dabei konnte festgestellt werden, dass die Kenngrößen statische Zugfestigkeit, E-Modul und Härte mit steigendem MFR (abnehmende Viskosität) zunehmen. Die dynamischen Langzeiteigenschaften und Kerbschlagzähigkeiten sinken hingegen mit zunehmendem MFR
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Soontaranun, Wit. "Effect of flow on the miscibility of partially miscible polymer blends." Thesis, Imperial College London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266261.
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Larsson, Katarina. "Utveckling av modell för kvalitetsstyrning av polyetenreaktor." Thesis, University West, Department of Technology, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-377.
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De'ath, Rosalyn M. "Numerical modelling of iceberg flow, melt and sedimentation in the Eurasian Arctic during deglaciation." Thesis, University of Bristol, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.573926.
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Rapid variations in climate through glacial periods have been associated with changes in ocean conditions. Modelling iceberg flow and melt is critical to evaluating their role in perturbing the state of oceans during glacial periods and subsequent deglaciation. This thesis aims to quantify the spatial and temporal history of icebergs flow, melt and sedimentation after release from the Eurasian Ice Sheet during the last deglaciation. The research structure required to meet this aim is in three steps. First, results from a numerical ice sheet model were processed in order to use them as input to an iceberg flow model. Other model inputs, such as topography and ocean and climate forcing fields, were also collated and input. Second, an iceberg model was compiled so that iceberg melt and sedimentation could be evaluated in the late glacial Nordic seas. Third, knowledge of the marine sedimentation record was built in order to compare with model results. This comparison allowed a number of literature-based hypotheses to be tested. This thesis has revealed the following results. The model showed that Eurasian icebergs may only be delivered to the North Atlantic under glacial ocean and atmospheric conditions. Under conditions similar to today, icebergs are restricted to the northern waters of the Nordic seas. The model also revealed that iceberg meltwater does not have a simple-distance-decay relationship. Instead, the pattern of meltwater release was found to be influenced by iceberg convergence zones; a consequence of the iceberg response to atmospheric and oceanic forcing. The model results also demonstrated that the locations of iceberg meltwater did not always coincide with modelled IRD. Consequently, the absence of IRD in the marine sedimentary record should not necessarily be interpreted as an indicator of absence of former icebergs. Models of the ice-ocean-atmosphere currently treat iceberg meltwater input in a simple way. The results presented here may be used in further numerical investigations of the processes responsible for rapid climate change in the last deglaciation.
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Forth, Shaun Anthony. "Morphological and hydrodynamic instabilities in undirectional alloy solidification." Thesis, University of Bristol, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292481.
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Xu, Han. "Melt flow singularity in linear polyethylene : influence of molar mass, molar mass distribution and carbon-based fillers." Thesis, Loughborough University, 2010. https://dspace.lboro.ac.uk/2134/7018.
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In the recent past it has been found that a considerable pressure drop occurred during the extrusion of linear polyethylene in the course of capillary flow. The pressure drop resides within a narrow temperature window of one to two degrees Celsius. In this research the hydrodynamic condition and molecular origin of the extrusion window of linear polymer were investigated further. The advantage of the extrusion window, viz. smooth extrudate with less die swell ratio attained at low extrusion pressure and temperature, has potential in industrial applications. However, the extrusion window, corresponding to linear polyethylene (PE) with relatively low polydispersity (<7), has a narrow window temperature interval, circa 1~2°C, thus it could not be applied to industrial scale processing at the industrial scale. To have a fundamental insight and make the process industrially viable, research in this thesis was devoted to broaden the extrusion window to tolerate the thermal fluctuations in conventional processing. To achieve this goal molecular weight dependence of window temperature and flow criticalities is revealed. The hydrodynamic conditions of the extrusion window observed in a rate-controlled rheometer and stick-slip flow studied in a stress-controlled rheometer could be traced back to the same origin, viz. slip flow arises due to the disentanglement of adsorbed chains on capillary wall from free chains in the bulk. Secondly, a dual window effect was uncovered in the course of capillary flow of a bimodal PE, which is consistent with the window temperature dependence on molecular weight. Moreover, it was found that flow induced orientation within the window effect is even less than that observed in steady state flow at a relatively low shear rate. This implies that in the window region only relaxed free chains are extruded through the capillary die and most of the adsorbed chains, which could be disengaged from the entangled melt, remain sticking to the inner capillary wall. This observation is consistent with the hydrodynamic origin of high-surface-energy-die slip flow. Finally, a unimodal linear PE with extremely broad molecular weight distribution, i.e. polydispersity (PDI) is 27, showed a broad window effect, circa 8°C, at an appropriate apparent shear rate. The molecular origin of such a broad window effect is due to its broad molecular weight distribution. These results have further implications for energy efficient processing.
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Hammond, William Charles. "Dynamics, flow and melt content of the Southern East Pacific Rise upper mantle from teleseismic tomography /." view abstract or download file of text, 2000. http://wwwlib.umi.com/cr/uoregon/fullcit?p9998033.
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Thesis (Ph. D.)--University of Oregon, 2000.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 139-151). Also available for download via the World Wide Web; free to University of Oregon users.
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Sierra-Irizarry, Eddie A. "Processing of polypropylene by melt transformation coextrusion process, study of flow birefringence, using an internally cooled die." Ohio : Ohio University, 1987. http://www.ohiolink.edu/etd/view.cgi?ohiou1183061054.
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Yang, Bing. "Non-isothermal flow of polymer melt and on-line computer control of profile extrusion using thermal method /." The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487323583623366.
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Singh, D. P. "Flow and mixing studies in a co-rotating intermeshing twin screw extruder." Thesis, Brunel University, 1988. http://bura.brunel.ac.uk/handle/2438/5548.
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The basic understanding of mixing in the process of polymer melt extrusion by twin screw extruder is limited by their geometrical complexity and the interactions of the process parameters. Mixing and flow in a 100mm diameter, trapezoidal channeled, intermeshing co-rotating twin-screw extruder have been characterised by determination of residence time distribution (RTD) and of the paths taken by tracers added to the melt. The axial mixing and the effects of varius parameters on it were established by studying RTD using tracer techniques. As the tail of the distribution is of paramount importance, the reproducibility of the RTD curve was extensively studied. Radioactive NnO2 was used as a tracer and detected by gamma ray spectroscopy giving more reproducible results than added barytes estimated gravimetrically after ashing. Shock cooling of the extruder and sectioning of the solidified compound in the screw channels was used to-study the flow mechanism. The maximum throughput achieved, polymer melting mechanism, filled volume and axial mixing Are interrelated, and are dependent on the configuration and position of segmented mixing discs present in the screw profile. In the upstream position these act as melting discs and their efficiency is increased in a closed configuration. Initial melting is achieved over a remarkably short distance along the screw profile. The screw speed affects the axial mixing which is shown to be related to the net relative pressure change at the screw tips. A flow model is proposed such that the overall material flow taking place in an anticlockwise direction along the screw channel comprises two separate flow regimes. The upper regime rotates anti-clockwise and is made up of main and small tetrahedron flow and calender flow. The lower flow regime rotates clockwise and is made up of main and small side leakage flows and a portion of the main tetrahedron flows together with a central flow. The flow studies show conclusively that the melt from a particular site ahead of the intermeshing zone occupies a predestined site after passing through the intermeshing zone.
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Xie, Wei. "Numerical analysis of corn flour melt flow in extruder die and extrusion of corn puffs with wheat starches /." free to MU campus, to others for purchase, 1999. http://wwwlib.umi.com/cr/mo/fullcit?p9946317.
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Clemeur, Nicolas. "Simulation, validation and application of a novel melt flow model for highly entangled linear and long chain branched polymers /." [St. Lucia, Q.], 2004. http://adt.library.uq.edu.au/public/adt-QU20050311.091736/index.html.
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Dansereau, Véronique. "Ice shelf-ocean interactions in a general circulation model : melt-rate modulation due to mean flow and tidal currents." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78549.
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Thesis (S.M.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 121-123).
Interactions between the ocean circulation in sub-ice shelf cavities and the overlying ice shelf have received considerable attention in the context of observed changes in flow speeds of marine ice sheets around Antarctica. Modeling these interactions requires parameterizing the turbulent boundary layer processes to infer melt rates from the oceanic state at the ice-ocean interface. Here we explore two such parameterizations in the context of the MIT ocean general circulation model coupled to the z-coordinates ice shelf cavity model of Losch (2008). We investigate both idealized ice shelf cavity geometries as well as a realistic cavity under Pine Island Ice Shelf (PIIS), West Antarctica. Our starting point is a three-equation melt rate parameterization implemented by Losch (2008), which is based on the work of Hellmer and Olbers (1989). In this form, the transfer coefficients for calculating heat and freshwater fluxes are independent of frictional turbulence induced by the proximity of the moving ocean to the fixed ice interface. More recently, Holland and Jenkins (1999) have proposed a parameterization in which the transfer coefficients do depend on the ocean-induced turbulence and are directly coupled to the speed of currents in the ocean mixed layer underneath the ice shelf through a quadratic drag formulation and a bulk drag coefficient. The melt rate parameterization in the MITgcm is augmented to account for this velocity dependence. First, the effect of the augmented formulation is investigated in terms of its impact on melt rates as well as on its feedback on the wider sub-ice shelf circulation. We find that, over a wide range of drag coefficients, velocity-dependent melt rates are more strongly constrained by the distribution of mixed layer currents than by the temperature gradient between the shelf base and underlying ocean, as opposed to velocity-independent melt rates. This leads to large differences in melt rate patterns under PIIS when including versus not including the velocity dependence. In a second time, the modulating effects of tidal currents on melting at the base of PIIS are examined. We find that the temporal variability of velocity-dependent melt rates under tidal forcing is greater than that of velocity-independent melt rates. Our experiments suggest that because tidal currents under PIIS are weak and buoyancy fluxes are strong, tidal mixing is negligible and tidal rectification is restricted to very steep bathymetric features, such as the ice shelf front. Nonetheless, strong tidally-rectified currents at the ice shelf front significantly increase ablation rates there when the formulation of the transfer coefficients includes the velocity dependence. The enhanced melting then feedbacks positively on the rectified currents, which are susceptible to insulate the cavity interior from changes in open ocean conditions.
by Véronique Dansereau.
S.M.
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Pretelt, Caceres Juan Antonio. "Characterization of the viscoelastic and flow properties of High Density Polyethylene Resins for Pipes in the Solid and Melt State." Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/96454.
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The frequent use of high-density polyethylene pipes over the last decades has been possible because these pipes are lightweight, corrosion resistant, unlikely to have leaks, and are low cost. The chain structure of the polymer, the extrusion and cooling conditions, the resulting morphology and the ambient conditions all play an important role in the pipe's performance. A new generation of high density polyethylene resins has improved the performance of pipes, but brought new challenges to their testing and characterization. There is a need to understand the rheological behavior of the resins, their processing, and their associated properties in a finished pipe.
The rheological behavior of the resins was studied to characterize the effect of high molecular weight tails in a bimodal molecular weight distribution. The use of cone-and-plate and parallel-plate geometries in a rheometer provided simple flow that characterized the steady and dynamical response of the polymer melts. The rheological measurements detected differences in the resins: the resin with higher molecular weight tail showed increased zero shear-rate viscosity, a much slower relaxation of stresses and a resin that more readily deviates from linear viscoelastic behavior. The rheology of the resins allowed modeling their flow through different extrusion dies. The flow channels for pipe dies are thick, so velocities and shear rates are low. Using a different die had a larger impact in shear rates and stresses compared to using different resins. The resin with higher molecular weight shows much higher shear stresses for the same die and temperature, which makes processing harder.
The flow of a fluid through a pipe causes constant stress, which at long enough times is one the reasons for pipe failure. Tests that characterize the service lifetime of pipes take long times and are expensive. Dynamical mechanical analysis allows characterizing the viscoelastic properties of the pipe and creep testing confirms that shift factors work for viscoelastic properties measured inde-pendently. For the characterized pipes, one hour of testing at 80 °C is equivalent to a month of test-ing at 25 °C. This works characterizes pipes made from two resins and two different dies. The meas-urements showed that the pipes were statistically the same.Doctor of Philosophy
The use of high-density polyethylene pipes has thrived over the last decades. This has been possible because these pipes are lightweight, corrosion resistant, unlikely to have leaks, and are low cost. The structure of the polymer and the manufacturing process both affect the pipe's performance. A new generation of high density polyethylene resins has improved the performance of the pipes, but brought new challenges to their testing and characterization. There is a need to understand the flow characteristics of the resins and their properties as a finished pipe. The flow behavior of the polymers in simple geometries gave insights into the polymer's structure. A higher molecular weight resin showed increased resistance to flow and deviated from ideal behavior more readily. These flow characteristics let one model certain aspects of the manufac-turing process. Pipe manufacturing is a slow process because of the high resistance to flow of the polymer. Changing the processing equipment, and to a minor degree changing the resins, had an im-portant impact in the manufacturing process. The tests that characterize the service lifetime of pipes take long times and are expensive. When pipes have fluids flowing at high pressures, it takes decades for them to fail. There are viscoe-lastic tests that allow much quicker characterization of pipes and help predict their long term behav-ior. This works characterizes pipes made from two resins and two different dies. This works charac-terizes pipes made from two resins and two different dies. The measurements showed that the pipes were statistically the same.
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Zuanetti, Bryan. "Plate Impact Experiments for Studying the Dynamic Response of Commercial-Purity Aluminum at Temperatures Approaching Melt." Case Western Reserve University School of Graduate Studies / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1557132337419911.
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Wang, Xiujun. "Melt transformation coextrusion of polyethylene and polybutylene measurements of streamline flow and pressure effect on birefringence and interface visualization in the MTCE process." Ohio : Ohio University, 1989. http://www.ohiolink.edu/etd/view.cgi?ohiou1182182580.
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Strandberg, Marcus. "Determination and implementation of polymer parameters into simulations of the twin-screw extrusion process." Thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Maskinteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-27184.
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This thesis was conducted in cooperation with a Swedish company that develops and manufactures plastic compounds. An increasing need for identifying material properties is seen within the industry in order to predict the outcome of the extrusion process by using simulations. The purpose of this study was to expand a material database with the results obtained through various measurements of the material parameters in order to enable simulations. The numerical descriptions would be analyzed and validated in relation to the obtained results and conducted methods to enable implementation of the material data into the industry. In order to fulfill the purpose, scientific methods was applied by chosen literature studies, research approaches and experimental research. Machine tests were conducted to collect relevant output data that was compared with the results obtained during the simulation process where the experimentally determined material parameters were applied in a material database. Typical injection molding qualities of PET, POM, PC/ABS, SAN and PA66 has been investigated by conducting measurement methods described by standards of the melt flow rate, specific heats, viscosity, crystallinity and melt- and glass transition temperatures. With exception of the viscosity, the material parameters are considered to have high external validity and high reliability and can be implemented into the industry. The bulk- and melt density was determined by adapted methods that need further investigations. The external validity is reduced until these methods and measurements have been validated. The determined material parameters proved to be able to generate reliable simulation results that indicate of how the extrusion process will turn out based on the output values investigated. The data obtained through machine tests was compared with the results that were achieved through simulations and deviated at most 10.9% from the actual outcomes. The viscosity is considered to be the main factor that affects the differences of the output data between the machine tests and the simulation results.
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BAIG, MUHAMMAD SOHAIB. "IMPACTS OF CLIMATE CHANGE ON THE QUANTITY AND TIMING OF RIVER FLOW IN THE UPPER INDUS BASIN, KARAKORAM-HIMALAYA, PAKISTAN." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/265201.
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京都大学新制・課程博士
博士(工学)
甲第23429号
工博第4884号
新制||工||1763(附属図書館)
京都大学大学院工学研究科社会基盤工学専攻
(主査)教授 田中 茂信, 准教授 田中 賢治, 准教授 佐山 敬洋
学位規則第4条第1項該当
Doctor of Philosophy (Engineering)
Kyoto University
DFAM
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Dogan, Erkan. "Ter Blend Of Poly (ethylene Terephthalate), Polypropylene And Low Density Polyethylene." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/4/1045574/index.pdf.
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This study covers the recycling of waste poly(ethylene terephthalate) (PET) bottles through melt blending with low density polyethylene (LDPE) and polypropylene (PP). In general, polymer blends are known to be immiscible and incompatible with poor mechanical properties. This problem is due to the low intermolecular forces between the components of the immiscible blends. In order to enhance the interaction and compatibility between these matrices, some reactive or non-reactive copolymers were used. In this workPET was treated with silane coupling agent (SCA) (low molecular weight reactive additive) for compatilization of LDPE-PP-PET blends. LDPE-PP-PET blends were prepared in different compositions (by weight) with and without silane coupling agent at high temperatures by a single screw extrusion and injection molding. Mechanical properties of treated and non-treated blends were studied in terms of tensile strength, strain at break and impact strength. Melt flow properties of blends were investigated by melt flow index. The impact fractured surfaces and thermal behaviour of the blends were examined with Scanning Electron Microscope (SEM) and Differential Scanning Calorimeter (DSC), respectively. Through out the studies, good adhesion between PET and LDPE-PP matrix was successfully achieved by the surface treatment of PET particles. The adhesion was also observed in SEM studies. Also the variation in mechanical properties was found to be highly dependent on the number of extrusion.
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Druet, Pierre-Etienne. "Analysis of a coupled system of partial differential equations modeling the interaction between melt flow, global heat transfer and applied magnetic fields in crystal growth." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, 2009. http://dx.doi.org/10.18452/15893.
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Hauptthema der Dissertation ist die Analysis eines nichtlinearen, gekoppelten Systems partieller Differentialgleichungen (PDG), das in der Modellierung der Kristallzüchtung aus der Schmelze mit Magnetfeldern vorkommt. Die zu beschreibenden Phenomäne sind einerseits der im elektromagnetisch geheizten Schmelzofen erfolgende Wärmetransport (Wärmeleitung, -konvektion und -strahlung), und andererseits die Bewegung der Halbleiterschmelze unter dem Einfluss der thermischen Konvektion und der angewendeten elektromagnetischen Kräfte. Das Modell besteht aus den Navier-Stokeschen Gleichungen für eine inkompressible Newtonsche Flüssigkeit, aus der Wärmeleitungsgleichung und aus der elektrotechnischen Näherung des Maxwellschen Systems. Wir erörtern die schwache Formulierung dieses PDG Systems, und wir stellen ein Anfang-Randwertproblem auf, das die Komplexität der Anwendung widerspiegelt. Die Hauptfrage unserer Untersuchung ist die Wohlgestelltheit dieses Problems, sowohl im stationären als auch im zeitabhängigen Fall. Wir zeigen die Existenz schwacher Lösungen in geometrischen Situationen, in welchen unstetige Materialeigenschaften und nichtglatte Trennfläche auftreten dürfen, und für allgemeine Daten. In der Lösung zum zeitabhängigen Problem tritt ein Defektmaß auf, das ausser der Flüssigkeit im Rand der elektrisch leitenden Materialien konzentriert bleibt. Da eine globale Abschätzung der im Strahlungshohlraum ausgestrahlten Wärme auch fehlt, rührt ein Teil dieses Defektmaßes von der nichtlokalen Strahlung her. Die Eindeutigkeit der schwachen Lösung erhalten wir nur unter verstärkten Annahmen: die Kleinheit der gegebenen elektrischen Leistung im stationären Fall, und die Regularität der Lösung im zeitabhängigen Fall. Regularitätseigenschaften wie die Beschränktheit der Temperatur werden, wenn auch nur in vereinfachten Situationen, hergeleitet: glatte Materialtrennfläche und Temperaturunabhängige Koeffiziente im Fall einer stationären Analysis, und entkoppeltes, zeitharmonisches Maxwell für das transiente Problem.The present PhD thesis is devoted to the analysis of a coupled system of nonlinear partial differential equations (PDE), that arises in the modeling of crystal growth from the melt in magnetic fields. The phenomena described by the model are mainly the heat-transfer processes (by conduction, convection and radiation) taking place in a high-temperatures furnace heated electromagnetically, and the motion of a semiconducting melted material subject to buoyancy and applied electromagnetic forces. The model consists of the Navier-Stokes equations for a newtonian incompressible liquid, coupled to the heat equation and the low-frequency approximation of Maxwell''s equations. We propose a mathematical setting for this PDE system, we derive its weak formulation, and we formulate an (initial) boundary value problem that in the mean reflects the complexity of the real-life application. The well-posedness of this (initial) boundary value problem is the mainmatter of the investigation. We prove the existence of weak solutions allowing for general geometrical situations (discontinuous coefficients, nonsmooth material interfaces) and data, the most important requirement being only that the injected electrical power remains finite. For the time-dependent problem, a defect measure appears in the solution, which apart from the fluid remains concentrated in the boundary of the electrical conductors. In the absence of a global estimate on the radiation emitted in the cavity, a part of the defect measure is due to the nonlocal radiation effects. The uniqueness of the weak solution is obtained only under reinforced assumptions: smallness of the input power in the stationary case, and regularity of the solution in the time-dependent case. Regularity properties, such as the boundedness of temperature are also derived, but only in simplified settings: smooth interfaces and temperature-independent coefficients in the case of a stationary analysis, and, additionally for the transient problem, decoupled time-harmonic Maxwell.
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Lee, Yousub. "Simulation of Laser Additive Manufacturing and its Applications." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1440360229.
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Kanjilal, Suranita [Verfasser], Harro [Akademischer Betreuer] [Gutachter] Schmeling, and Doris [Gutachter] Breuer. "Theory and numerical modelling of two phase flow : melt percolation process through porosity dependent viscous matrix inside the Earth / Suranita Kanjilal ; Gutachter: Harro Schmeling, Doris Breuer ; Betreuer: Harro Schmeling." Frankfurt am Main : Universitätsbibliothek Johann Christian Senckenberg, 2016. http://d-nb.info/1117647943/34.
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Altintas, Bekir. "Electrical And Mechanical Properties Of Carbon Black Reinforced High Density Polyethylene/low Density Polyethylene Composites." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/2/12604976/index.pdf.
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In this study, the High Density Polyethylene (HDPE) and Low Density Polyethylene (LDPE) blends prepared by Plasticorder Brabender were strengthened by adding Carbon Black (CB).
Blends were prepared at 190 °C. Amounts of LDPE were changed to 30, 40, 50 and 60 percent by the volume and the percent amounts of CB were changed to 5, 10,15, 20 and 30 according to the total volume. Thermal and morphological properties were investigated by using Differential Scanning Calorimeter (DSC), Scanning Electron Microscope (SEM). Mechanical properties were investigated by tensile test and hardness measurements. Melt flow properties were studied by Melt Flow Index (MFI) measurements. Electrical conductivities were measured by four probe and two probe techniques. Temperature dependence of electrical conductivity was also studied. In general, it is observed that stress at break and MFI values decrease by the addition of CB
however, modulus and hardness increase. DSC results indicated that the crystallization of the polymer blend was decreased by the addition of CB. SEM results showed that the components were mixed homogenously. Increasing CB content increased electrical conductivity. Furthermore, by increasing the temperature, positive temperature coefficient behavior was observed which increases when CB content decreased.
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Subhedar, Amol [Verfasser], Fathollah [Gutachter] Varnik, and Ingo [Gutachter] Steinbach. "Phase-field modelling of solidification in the presence of melt flow : a Galilean invariant coupling scheme in the thin interface limit / Amol Subhedar ; Gutachter: Fathollah Varnik, Ingo Steinbach ; Fakultät für Maschinenbau." Bochum : Ruhr-Universität Bochum, 2018. http://d-nb.info/1167505395/34.
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Lucca, Eneida Aparecida de. "Modelagem e simulação de reatores industriais em fase liquida do tipo Loop para polimerização de propileno." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266238.
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Orientadores: Rubens Maciel Filho, Jose Carlos Costa da Silva Pinto, Priamo Albuquerque Melo JuniorDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
Made available in DSpace on 2018-08-10T00:03:32Z (GMT). No. of bitstreams: 1 Lucca_EneidaAparecidade_M.pdf: 1657459 bytes, checksum: 56b6b6c35a2802734e03ed28ceb76c67 (MD5) Previous issue date: 2007
Resumo: Reatores tubulares do tipo loop são amplamente empregados nas indústrias de poliolefinas. No caso da produção de polipropileno, compõem a tecnologia Spheripol. São constituídos de duas seções tubulares interconectadas por um ponto de alimentação e por uma bomba, que promove a recirculação da massa reacional. O simulador dinâmico desenvolvido nesse trabalho é capaz de estimar valores de diversas variáveis chave no monitoramento do processo; dentre elas, o XS e o MFI. As validações feitas mostraram que o simulador é capaz de representar de forma acurada os dados experimentais disponíveis em uma planta real de polimerização, inclusive para ¿N¿ reatores em série
Abstract: Tubular loop reactors are widely used in the polyolefins industries. In the particular case of polypropylene production, loop reactors are part of the Spheripol technology. Loop reactors are composed of two tubular reactors that are connected by a feed point and a pump that is responsible for promoting recirculation of the reaction mass. The dynamic simulator developed here is able to estimate values of several important variables used to monitor the industrial process, like the XS and the MFI. The model was validated with actual industrial data obtained for different reactor configurations, including ¿N¿ reactors in series
Mestrado
Engenharia de Processos
Mestre em Engenharia Química
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Dadzis, Kaspars. "Modeling of directional solidification of multicrystalline silicon in a traveling magnetic field." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2013. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-117492.
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Melt flow plays an important role in directional solidification of multicrystalline silicon influencing the temperature field and the crystallization interface as well as the transport of impurities. This work investigates the potential of a traveling magnetic field (TMF) for an active control of the melt flow. A system of 3D numerical models was developed and adapted based on open-source software for calculations of Lorentz force, melt flow, and related phenomena. Isothermal and non-isothermal model experiments with a square GaInSn melt were used to validate the numerical models by direct velocity measurements. Several new 3D flow structures of turbulent TMF flows were observed for different melt heights. Further numerical parameter studies carried out for silicon melts showed that already a weak TMF-induced Lorentz force can stir impurities near to the complete mixing limit. Simultaneously, the deformed temperature field leads to an increase of the deflection of crystallization interface, which may exhibit a distinct asymmetry. The numerical results of this work were implemented in a research-scale silicon crystallization furnace. Scaling laws for various phenomena were derived allowing a limited transfer of the results to the industrial scale.
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Handlíř, Tadeáš. "Vliv přídavku recyklátu na strukturu a vlastnosti vysokohustotního polyetylénu." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2021. http://www.nusl.cz/ntk/nusl-444213.
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The presented diploma thesis deals with the evaluation of the influence of the addition of 30, 60 and 90 % of recycled material on the structure and mechanical properties of high-density polyethylene (HDPE), where recycled material represents both HDPE from a several years old part and material multiple reprocessed by extrusion. The changes of supramolecular structure were examined by calorimetric measurement, which did not indicate degradation of the material due to multiple extrusion. Mechanical properties were investigated by tensile tests and dynamic-mechanical analysis. Both measurements showed the same trend, where the first and second pass of the material through the extruder led to improved mechanical properties, e.g. to increase stiffness, while the influence of the third and fourth passes through the extruder had not a significant effect on the mechanical properties. In terms of the structure and mechanical properties, a positive effect of the combination of material after the second extrusion passing (30%) with virgin material was recorded.
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Sirisinha, Chakrit. "Mechanisms of extrudate swell and melt fracture in SBR compounds." Thesis, Loughborough University, 1996. https://dspace.lboro.ac.uk/2134/13770.
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The purpose of this study is to identify and quantify factors governing extrudate swell and melt fracture. In the first part, the factors which control the extrudate swell of carbon black (N330) filled styrene-butadiene rubber (SBR) compounds at various states-of-mix were investigated. State-of-mix is quantified by effective filler volume fraction (EFVF), based on an estimate of the amount of rubber immobilised in the carbon black agglomerates. Extrudate swell was found to be dominated by recoverable strain and relaxation time, which are controlled by EFVF. In contrast, shear rate and the rubber-carbon black tridimensional transient network were not found to influence extrudate swell significantly. In the second part, melt fracture of the rubber compounds was investigated in terms of surface texture wavelength. The longer the wavelength, the greater the severity of the surface disruption. It was found that wavelength was controlled strongly by state-of mix (or by EFVF). In addition, a mechanism for melt fracture of the compounds studied has been proposed, based on average energy at the extrudate surface (t.E). Lastly, the influences of additives; paraffinic processing oil, stearic acid or a mixture of predominantly calcium fatty acid soaps on extrudate swell and melt fracture were investigated. For the rubber compounds with paraffinic processing oil or stearic acid, EFVF was found to play an important role in extrudate swell. The mixture of fatty acid soaps was shown to reduce significantly extrudate swell due to the presence of wall slip. The influence of the fatty acid soaps on extrudate swell is more noticeable for extrudates obtained from long dies, in which flow is dominated by shear. The major factors shown to exert a significant influence on melt fracture for the compounds with paraffinic processing oil or stearic acid are EFVF and green strength of the extrudate. Wall slip, promoted by a mixture of fatty acid soaps, was also found to decrease the melt fracture severity, particularly for long dies in which shear stresses are dominant.
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Soulages, Johannes Matthieu. "Flow birefringence and velocity measurements for polymer melts in a cross-slot flow channel /." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17180.
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Івіцький, Ігор Ігорович. "Пристінні ефекти в процесах течії полімерів у каналах переробного обладнання." Thesis, НТУУ "КПІ", 2016. https://ela.kpi.ua/handle/123456789/16117.
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Дисертаційна робота присвячена дослідженню наявності, характеру та
величини пристінних ефектів, що виникають при течії розплаву полімерних
матеріалах у каналах переробного обладнання.
Розроблено метод визначення наявності пристінних ефектів у полімерному
матеріалі та природи цих ефектів. В залежності від природи пристінних ефектів
розроблено методики визначення величини цих ефектів у матеріалі. Математичну
модель течії полімерних матеріалів доповнено врахуванням пристінних ефектів в
залежності від їх природи та матеріалу, що дозволило створити універсальний
підхід до визначення параметрів процесу течії під час числового моделювання.
Проведено числові дослідження впливу геометричних параметрів каналу на
розбіжності перепаду тиску між умовами відсутності швидкості на стінці та
врахування пристінних ефектів. На основі проведених досліджень виведено
емпіричні рівняння, що дозволяють враховувати пристінні ефекти при проектуванні
переробного обладнання без додаткового проведення числових досліджень.The dissertation is devoted to research presence, the nature and value of wall effects arising from the melt flow channels in polymer materials processing equipment. The method of determining the presence of wall effects polymeric material and the nature of these effects. Depending of the nature of wall effects developed methodology for determining the value of these effects in the material. Mathematical model of current polymer materials supplemented into account the effects of wall, depending on their nature and the material allowed us to create a universal approach to determining process parameters during the current numerical modeling. It was examine a numerical study of the influence of geometrical parameters of channel differences pressure between the absence of speed on the wall and consideration of wall effects. On the basis of empirical studies deduce equations to take into account when designing shelving effects without additional processing equipment of numerical studies.
Диссертация посвящена исследованию наличия, характера и величины пристенных эффектов, возникающих при течении расплава полимерных материалов в каналах перерабатывающего оборудования. Проведенный аналитический анализ современного состояния исследований течения полимера показал, что ранее рассматриваются отдельные вопросы пристенных эффектов при течении расплава полимера, однако они имеют ряд недостатков: не учитывают природу и характер возникновения пристенных эффектов в различных материалах, позволяют определить величину эффекта не во всем диапазоне сечений каналов, не позволяют использовать полученные данные для численного расчета с использованием систем автоматизированного проектирования. Разработан метод определения наличия пристенных эффектов в полимерном материале и природы этих эффектов. В зависимости от природы пристенных эффектов разработаны методики определения величины этих эффектов в материале, которые учитывают неньютоновские свойства материалов. Разработана методика проведения экспериментальных исследований на базе созданной экспериментальной установки для исследования пристенных эффектов. Проведены экспериментальные исследования с использованием трех типов полимерных материалов: полиэтилен низкого давления, полистирол, севилен. Также проведены эксперименты с использованием смазывающего агента для определения величины его влияния на пристенные эффекты. Установлены зависимости напряжения сдвига от скорости расплава материала на стенке, что позволило получить исходные данные для задания граничных условий при численном моделировании процесса Математическая модель течения полимерных материалов дополнена учетом пристенных эффектов в зависимости от их природы и материала, что позволило создать универсальный подход к определению параметров процесса течения при численном моделировании. Адекватность математической модели и граничных условий подтверждается сопоставлением результатов численного моделирования и экспериментальных данных, а также сопоставлением с существующими результатами исследований. Адекватность изотермического предположения проверялась числовым расчетом для изотермического режима и с учетом диссипации при постоянной температуре стенок. Адекватность экстраполяции результатов, полученных в экспериментальных исследованиях с цилиндрическими каналами на другие типы каналов, подтверждается проведением дополнительного опыта с капилляром прямоугольной формы, гидравлический диаметр которого совпадал с одним из исследуемых капилляров.Численное моделирование проводилось на каналах цилиндрической, конической и прямоугольной геометрии, а также на геометрии формующей головки экструдера. Граничными условиями на стенке каналов послужили данные, полученные в результате проведения экспериментальных исследований. Проведены численные исследования влияния геометрических параметров каналов на разность перепадов давления между условиями отсутствия скорости на стенке и учетом пристенных эффектов, а также влияния смазывающего агента. Установлено, что характер влияния геометрических параметров на разность перепадов давления имеет, в основном, нелинейный характер. Исследования показали, что при численном моделировании течения полимерного материала по геометрии формующей головки пренебрежение пристенными эффектами приводит к погрешности в полученных результатах от 11% до 22% в зависимости от материала. Для определения степени влияния параметров и создания регресивной модели процесса был проведен полный факторный эксперимент, который позволил вывести эмпирические уравнения, позволяющие учитывать пристенные эффекты при проектировании перерабатывающего оборудования без дополнительного проведения численных исследований. Разработаны конструкции экструзионных головок, позволяющих компенсировать влияние пульсаций расплава, которые возникают в результате действия пристенных эффектов, а также конструкция червяка экструдера, которая позволяет обеспечить поглощение пульсаций давления, возникающих в результате действия пристенных эффектов.Проведены численные исследования влияния геометрических параметров каналов на разность перепадов давления между условиями отсутствия скорости на стенке и учетом пристенных эффектов, а также влияния смазывающего агента. Установлено, что характер влияния геометрических параметров на разность перепадов давления имеет, в основном, нелинейный характер. Исследования показали, что при численном моделировании течения полимерного материала по геометрии формующей головки пренебрежение пристенными эффектами приводит к погрешности в полученных результатах от 11% до 22% в зависимости от материала. Для определения степени влияния параметров и создания регресивной модели процесса был проведен полный факторный эксперимент, который позволил вывести эмпирические уравнения, позволяющие учитывать пристенные эффекты при проектировании перерабатывающего оборудования без дополнительного проведения численных исследований. Разработаны конструкции экструзионных головок, позволяющих компенсировать влияние пульсаций расплава, которые возникают в результате действия пристенных эффектов, а также конструкция червяка экструдера, которая позволяет обеспечить поглощение пульсаций давления, возникающих в результате действия пристенных эффектов.Проведены численные исследования влияния геометрических параметров каналов на разность перепадов давления между условиями отсутствия скорости на стенке и учетом пристенных эффектов, а также влияния смазывающего агента. Установлено, что характер влияния геометрических параметров на разность перепадов давления имеет, в основном, нелинейный характер. Исследования показали, что при численном моделировании течения полимерного материала по геометрии формующей головки пренебрежение пристенными эффектами приводит к погрешности в полученных результатах от 11% до 22% в зависимости от материала. Для определения степени влияния параметров и создания регресивной модели процесса был проведен полный факторный эксперимент, который позволил вывести эмпирические уравнения, позволяющие учитывать пристенные эффекты при проектировании перерабатывающего оборудования без дополнительного проведения численных исследований. Разработаны конструкции экструзионных головок, позволяющих компенсировать влияние пульсаций расплава, которые возникают в результате действия пристенных эффектов, а также конструкция червяка экструдера, которая позволяет обеспечить поглощение пульсаций давления, возникающих в результате действия пристенных эффектов.
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Ranganathan, Meera. "The transient flow rheology and instabilities of polyethylene melts." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621585.
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Mead, David Wayne. "Modelling polydisperse polymer melts with single integral constitutive equations." Thesis, University of Cambridge, 1988. https://www.repository.cam.ac.uk/handle/1810/250917.
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Corscadden, Stephen Paul. "Die entry flow of fibre reinforced thermoplastics." Thesis, University of Liverpool, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.257143.
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Descher, Stefan [Verfasser]. "Modeling and simulation of crystallization processes in polymer melt flows / Stefan Descher." Kassel : kassel university press c/o Universität Kassel - Universitätsbibliothek, 2021. http://d-nb.info/1231385715/34.
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Scelsi, Lino. "Experimental observation and numerical prediction of flow-induced crystallisation for polymer melts within complex flow geometries." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611551.
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Satpathi, Hirak. "Novel phosphorus containing poly(arylene ethers) as flame retardant additives and as reactant in organic synthesis." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-176136.
Full textAbstract:
Due to their outstanding properties, poly(arylene ethers) are useful as toughness modifiers in epoxy resins (EP). Furthermore, these polymers show rather low intrinsic fire risks. According to recent research it has been incorporated that poly(arylene ether phosphine oxides) [PAEPO’s] can further improve the fire behavior. Increasing phosphorous content of the PAEPO can influence the fire behavior too. Fire retardants containing phosphorus – regardless of whether an additive or reactive approach is used – show different mechanisms in the condensed and gas phase. In the present study PSU Control (BPA based polysulfone) with four different PAEPO’s and their corresponding blends with an EP were investigated.
All poly(arylene ether phosphine oxides) were synthesized by nucleophilic aromatic polycondensation. The polymers obtained covered a wide range of weight average molar masses (6,000 – 150,000 g/mol) as determined by size exclusion chromatography with multi-angle light scattering detection (MALLS). FTIR, NMR spectroscopy and MALDI-TOF revealed formation of the desired polymer structure of the linear poly(arylene ethers). All polymers were easily soluble in common organic solvents, thus enabling processing from solution.The pyrolysis and the fire retardancy mechanisms of the polymers and blends with epoxy resin (EP) were tackled by means of a comprehensive thermal analysis (thermogravimetry (TG), TG-evolved gas analysis) and fire tests [PCFC, limiting oxygen index (LOI), UL-94, cone calorimeter].
The Mitsunobu reaction of Dimethyl-5-hydroxyisophthalate and a long chain semifluorinated alcohol requires triphenyl phosphine as a reactant. Identical, in some case higher yield was obtained in the usual conditions, with triphenyl phosphine and with trivalent phosphorus containing polymers, which was prepared in solvent free bulk (melt) polymerization technique from trivalent phosphorus monomer and a silylated diphenol in presence of CsF. Purification and the recovery of the final product which is always a big challenge in case of Mitsunobu reaction, was far more easier using polymer compared to triphenyl phosphine. During polymerization there was a possibility to have polymer having repeating unit containing both trivalent phosphorus and phosphine oxide. The trivalent phosphorus content of the polymer can be varied using different molar concentration of CsF.