Dissertations / Theses on the topic 'Phase Behaviour'
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1
Shannon, Richard John. "Phase behaviour of glycerides." Thesis, Liverpool John Moores University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.237927.
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Dimitrova, Galya Tzvetanova. "Phase behaviour of nonionic surfactants." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244794.
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Naughton, John Robert. "Phase behaviour of copolymer mixtures." Thesis, University of Reading, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402201.
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Legrix, Anabelle. "Phase behaviour in polysulphide solutions." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.481816.
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Blešić, Marijana. "Phase behaviour of alternative solvents." Doctoral thesis, Universidade Nova de Lisboa, Instituto de Tecnologia Química e Biológica, 2008. http://hdl.handle.net/10362/5243.
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Dissertation presented to obtain the Ph.D. degree in Chemistry (Physical Chemistry) at the Instituto de Tecnologia Química e Biológica da Universidade Nova de LisboaThis Thesis is mainly focused on phase behaviour in macro and nano domains and thermodynamic properties of mixtures containing ionic liquids and water, fluorinated or organic solvents. A broad list of commercially available ionic liquids or specific and functionalised, synthesised and characterised by the author of the Thesis is included in this study. The used ionic liquids contained the following cations: 1-alkyl-3-methylimidazolium [Cnmim]+, 1-alkyl-3-methylpyridinium [Cnmpyr]+, 1- alkyl-1-methylpyrrolidinium [Cnmpyrr]+, 1-alkyl-1-methylpiperidinium [Cnmpip]+, and tetraalkylphosphonium [CxCyCzCwP]+ and some of the anions: chloride Cl-, Br-, hexafluorophosphate [PF6]-, bis{(trifluoromethyl)sulfonyl}amide [NTf2]-, alkylsulfonate [CmSO3]-, trifluoromethanesulfonate [OTf]-, dicyanamide [dca]- and acetate [Ac]-.(...)
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Simpkin, Neil John. "Solution behaviour and phase-phase diffusion of microbial lipases." Thesis, University of Nottingham, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387207.
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Gillott, Nicola C. "Capillary electrochromatography : retention behaviour of pharmaceuticals." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312243.
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Opps, Sheldon B. "Phase behaviour of model Langmuir monolayers." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ47405.pdf.
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Verberkmoes, Alain. "Tiling models: phase behaviour and scaling." [S.l : Amsterdam : s.n] ; Universiteit van Amsterdam [Host], 2003. http://dare.uva.nl/document/71144.
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Ouzzane, Djamel Eddine. "Phase behaviour in gas condensate reservoirs." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417922.
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Morley, Wayne Gerald. "The phase behaviour of food surfactants." Thesis, University of Salford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308204.
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Galloway, Linda A. "Phase behaviour of colloid-micelle mixtures." Thesis, University of Edinburgh, 2000. http://hdl.handle.net/1842/10916.
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We have studied the phase behaviour of both charged and uncharged hard colloidal particles in a solution of wormlike micelles of the nonionic surfactant C16E6. The behaviour found is similar to that in the case of colloid-polymer mixtures. The phase boundaries agree well with theoretical predictions of an adapted colloid-polymer depletion model that accounts for the concentration induced growth and the exponential size distribution of the micelles. In the case of uncharged colloids a stable one phase fluid region is found at low surfactant concentrations. As the concentration of C16E6 increases, phase separation into coexisting colloid-rich and colloid-poor phases is observed, as a result of the increase of the concentration and/or average length of the micelles. At higher concentrations a metastable gel is found. Similar behaviour is found in the case of charged colloid, both with and without added electrolyte to screen the coulombic repulsion between the particles. A more realistic, industrial type system with charged colloids in an aqueous solution of anionic micelles of sodium lauryl ether sulfate (SLES) and cocoamidopropylbetaine (CAPB) was also investigated. A ternary phase diagram of SLES/H2O/NaCl, where the salt is used to promote the formation of wormlike micelles, resembles that found in the C16E6 systems and agrees qualitatively with the theoretical predictions. At low surfactant/salt concentrations the mixture is a one phase fluid. As the concentration of surfactant and/or salt is increased first phase separation into coexisting colloid-rich and colloid-poor phases, then colloidal gels are observed. The collapse of these gels was studied by diffusive-wave spectroscopy and shows a qualitatively reproducible behaviour of the particle dynamics during the gel collapse.
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Magee, James. "Phase behaviour of core-softened particles." Thesis, University of Edinburgh, 2003. http://hdl.handle.net/1842/12542.
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In this thesis, we have made an extended study of a particular core-softened system in two dimensions (originally studied in Sadr-Lahijany et al. Physical Review Letters 81, p.4895 [1]). Whereas most studies have only examined single facets of the phase behaviour for a given model, we have systematically studied both liquid and solid state phase behaviour, using a combination of analytic and state of the art simulation methods. Our aim has been to gain a greater understanding of the key features behind the unusual phase behaviour associated with core softened systems. After an introduction, we review previous work on the phase behaviour of core-softened systems, in which we see that these apparently “simple” potentials can give rise to a range of unusual and exotic behaviours. We then briefly study the behaviour of a simple one-dimensional core softened model. This demonstrates liquid state anomalies and a zero temperature transition point, as well as illuminating the dangers of generalising between potentials and across dimensionality. We then move onto the two dimensional system. We study the solid state using a combination of the harmonic approximation, Lattice Switch Monte Carlo (a recently developed simulation technique which allows Monte Carlo moves between structures), and Gibbs-Duhem integration. We find two triangular lattice phases, separated by a region of stable square lattice phase at intermediate pressure; we also find evidence for an isostructural transition (with possible critical point) between the triangular phases at densities metastable with respect to the square lattice phase. To study the liquid state, we use Lennard-Jones Devonshire cell theory and extensive Monte Carlo simulation. We reevaluate the cell theory model, and find strong evidence that Lennard-Jones and Devonshire’s original results were misinterpreted, as were the cell theory results for the system at hand [1]. Our liquid state simulation results confirm the presence of reentrant melting and liquid-state anomalies in the system. We find that, contrary to previous suggestions, these anomalies do not originate from a liquid-liquid transition, but instead from a continuous or near-continuous melting transition, a phenomenon only possible in two dimensions.
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Pörtsch, Asja. "The phase behaviour, flow behaviour, and interfacial properties of protein-polysaccharide aqueous two-phase systems with sugar." Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3528/.
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The aim of this work is to better understand the structuring processes in low fat dairy emulsions. Model sodium caseinate-galactomannan aqueous two-phase systems (NaCAS-GM ATPS) differing in GM-type (locust bean gum (LBG), tara gum (TG), guar gum (GG), fenugreek gum (FG)) and added sugar (trehalose, sucrose, glucose and fructose) were studied by the phase-volume ratio method, rheooptics, and droplet retraction method on phase equilibria, flow behaviour and interfacial properties, respectively, at pH 5.8 and 20°C. The results revealed that the presence of sugar in concentrations 5-40 wt% resulted in an increase in cosolubility of the phases and a decrease in interfacial tension (σ). Sugar concentrations > 40 wt% decreased cosolubility. Based on the mannose:galactose ratio of GM and type of sugar (added in concentration 15 wt%) the best cosolubility and corresponding smallest σ was attributed to FG and trehalose, respectively. The flow of ATPS depended on quiescent microstructure, the shear and physical properties of the phases. In polysaccharide-continuous ATPS, the occurrence of a shear-induced phase inversion event was observed for 0- 20 wt% sugar. A further increase in sugar concentration >20 wt% was found to suppress this phenomenon due decreased viscosity ratio and formation of thread like structures in flow.
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Jackson, Andrew N. "Structural phase behaviour via Monte Carlo techniques." Thesis, University of Edinburgh, 2001. http://hdl.handle.net/1842/4850.
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There are few reliable computational techniques applicable to the problem of structural phase behaviour. This is starkly emphasised by the fact that there are still a number of unanswered questions concerning the solid state of some of the simplest models of matter. To determine the phase behaviour of a given system we invoke the machinery of statistical physics, which identifies the equilibrium phase as that which minimises the free-energy. This type of problem can only be dealt with fully via numerical simulation, as any less direct approach will involve making some uncontrolled approximation. In particular, a numerical simulation can be used to evaluate the free-energy difference between two phases if the simulation is free to visit them both. However, it has proven very difficult to find an algorithm which is capable of efficiently exploring two different phases, particularly when one or both of them is a crystalline solid. This thesis builds on previous work (Physical Review Letters 79 p.3002), exploring a new Monte Carlo approach to this class of problem. This new simulation technique uses a global coordinate transformation to switch between two different crystalline structures. Generally, this `lattice switch' is found to be extremely unlikely to succeed in a normal Monte Carlo simulation. To overcome this, extended-sampling techniques are used to encourage the simulation to visit `gateway' microstates where the switch will be successful. After compensating for this bias in the sampling, the free-energy difference between the two structures can be evaluated directly from their relative probabilities. As concrete examples on which to base the research, the lattice-switch Monte Carlo method is used to determine the free-energy difference between the face-centred cubic (fcc) and hexagonal close-packed (hcp) phases of two generic model systems --- the hard-sphere and Lennard-Jones potentials. The structural phase behaviour of the hard-sphere solid is determined at densities near melting and in the close-packed limit. The factors controlling the efficiency of the lattice-switch approach are explored, as is the character of the `gateway' microstates. The face-centred cubic structure is identified as the thermodynamically stable phase, and the free-energy difference between the two structures is determined with high precision. These results are shown to be in complete agreement with the results of other authors in the field (published during the course of this work), some of whom adopted the lattice-switch method for their calculations. Also, the results are favourably compared against the experimentally observed structural phase behaviour of sterically-stabilised colloidal dispersions, which are believed to behave like systems of hard spheres. The logical extension of the hard sphere work is to generalise the lattice-switch technique to deal with `softer' systems, such as the Lennard-Jones solid. The results in the literature for the structural phase behaviour of this relatively simple system are found to be completely inconsistent. A number of different approaches to this problem are explored, leading to the conclusion that these inconsistencies arise from the way in which the potential is truncated. Using results for the ground-state energies and from the harmonic approximation, we develop a new truncation scheme which allows this system to be simulated accurately and efficiently. Lattice-switch Monte Carlo is then used to determine the fcc-hcp phase boundary of the Lennard-Jones solid in its entirety. These results are compared against the experimental results for the Lennard-Jones potential's closest physical analogue, the rare-gas solids. While some of the published rare-gas observations are in approximate agreement with the lattice-switch results, these findings contradict the widely held belief that fcc is the equilibrium structure of the heavier rare-gas solids for all pressures and temperatures. The possible reasons for this disagreement are discussed. Finally, we examine the pros and cons of the lattice-switch technique, and explore ways in which it can be extended to cover an even wider range of structures and interactions.
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Phillips, Jonathan William. "Phase behaviour of binary model platelet dispersions." Thesis, University of Bristol, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.535474.
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McDonald, J. A. "Phase behaviour and structure in microemulsion dispersions." Thesis, University of Kent, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375055.
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Turner, Simon C. "Architectural effects of block copolymer phase behaviour." Thesis, University of Sheffield, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340142.
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Grant, Stuart Alexander. "Phase transition behaviour in constraint satisfaction problems." Thesis, University of Leeds, 1997. http://etheses.whiterose.ac.uk/1273/.
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Many problems in artificial intelligence and computer science can be formulated as constraint satisfaction problems (CSPs). A CSP consists of a set of variables among which a set of constraints are imposed, with a solution corresponding to an assignment for every variable such that no constraints are violated. Most forms of CSP are NP-complete. Recent research has shown that the CSP exhibits a phase transition as a control parameter is varied. This transition lies between a region where most problems are easy and soluble, and a region where most problems are easy but insoluble. In the intervening phase transition region, the average problem difficulty is greatest. Phase transition behaviour can be exploited to create test beds of hard and easy problems for CSP algorithms. In this thesis, we study the phase transition of the binary CSP and examine various aspects of complete search algorithms for it. The phenomenon of exceptionally hard problems (`ehps') is examined in detail: these are rare searches on easy problems which become exceptionally expensive for a particular complete algorithm following a poor early search move. An explanation for the occurrence of ehps is proposed, and the relative susceptibility of certain algorithms to the phenomenon is explored. We then show that the phase transition paradigm can be applied to two tasks of polynomial cost complexity: attempting to establish arc and path consistency in a CSP. Phase transition behaviour analogous to that found when searching for a solution is demonstrated for these tasks, and the effectiveness and cost of establishing arc and path consistency is examined. The theme of establishing consistency in CSPs is extended by studying an algorithm which maintains arc consistency during search. Its performance is compared with that of an algorithm which maintains a lower level of consistency, and it is shown that the higher level of consistency reduces average search cost and ehp behaviour on many types of CSP. Finally, the subject of dynamically selecting the variable to instantiate at each stage in the search process is considered. We compare a number of heuristics which attempt to select the variable most likely to lead to failure, and show that the supposed principle behind these appears to be fundamentally flawed.
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Ashayer-Soltani, Roya. "Surfactant phase behaviour in relation to oil recovery." Thesis, Imperial College London, 1999. http://hdl.handle.net/10044/1/8736.
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Hussain, Arshad. "Phase behaviour of microemulsions for enhanced oil recovery." Thesis, Imperial College London, 1997. http://hdl.handle.net/10044/1/8492.
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Maddaford, Paul John. "Phase behaviour and structure of ternary surfactant systems." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318448.
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Zeb, Neelofar. "Synthesis and lyotropic phase behaviour of novel glycolipids." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336634.
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Huang, Zhi. "Structure and phase behaviour of phosphatidylcholine-amphiphile mixtures." Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283416.
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Boyd, Matthew. "The phase behaviour of xanthan based biopolymer mixtures." Thesis, University of Nottingham, 2006. http://eprints.nottingham.ac.uk/11588/.
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It was proposed that a phase separated system might be utilised to deliver a concentrated polysaccharide mucosal protective coating in gastro oesophageal reflux disease (GORD). In this context the phase behaviour of xanthan gum in combination with sodium alginate and other polymers was studied. Above a threshold concentration of alginate, aqueous mixtures of xanthan exhibited phase separation, resulting in loss of normal viscoelastic properties and the formation of a low viscosity system. The shape of the phase diagram showed behaviour typical of a segregative system, with the continuous phase composed exclusively of alginate and the disperse phase being rich in xanthan gum. Increasing alginate molecular weight reduced the threshold concentration for separation, as predicted by the Flory-Huggins theory, but changes in alginate mannuronate:guluronate ratio had no effect. Increasing ionic strength elevated the threshold concentration. Xanthan separation was elicited by other aqueous anionic polyelectrolytes, but not neutral water soluble polymers. Scleroglucan, another rigid-rod polysaccharide, was investigated as an alternative to xanthan but did not show similar separation behaviour, suggesting that the charge on the xanthan molecule is a necessary prerequisite. Reversal of phase separation by dilution across the phase boundary provided increases in viscosity. A 1% xanthan:2% alginate mixture doubled in viscosity whereas if diluted with simulated gastric fluid a seven-fold increase was seen, as a result of conversion to an alginic acid gel. This offers a mechanism for producing the desired viscosity barrier. Low viscosity polyelectrolytes, with concentrations close to the phase boundary yielded the greatest viscosity increases. In the phase separated system, the disperse phase exhibited an unusual strand-like morphology whose birefringence suggests a liquid crystalline structure. The variable size of the strands was explained in terms of kinetics of xanthan molecular aggregation in media of different viscosity.
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Bayliss, Katie. "Colloid-microgel mixtures : phase behaviour and temperature response." Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.633101.
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Recently, interest has been shown in stimuli responsive microgel particles as depletants, capable of inducing entropy driven phase transitions in colloidal systems. Due to their temperature induced deswelling transition , which occurs above ~32 'c, poly(N-isopropylacrylamide) (pNIPAM) microgels present opportunities for the easy modulation of depletion interactions between colloids. The aim of the current project was to gain an understanding of the phase behaviour of colloidal particles mediated by pNIPAM microgels both below and above the volume phase transition temperature (VPTT) , for potential applications in formulation science. For this purpose, a simple model system comprising an aqueous suspension of polystyrene (PS) latex particles, stabilised with Synperonic PE/ Pl05 PEOPPO- PEO (Pl05) copolymer, and pNIPAM microgels was developed . The majority of experiments were conducted at a microgel/ colloid size ratio, q, close to 0.1 at room temperature. A phase diagram for the colloid-microgel mixture at room temperature was determined experimentally using differential interference contrast (DIC) microscopy. At sufficient microgel volume fraction, mixtures were found to separate into colloidal fluid and solid phases. At higher particle concentrations, gelation was observed. The phase diagram was compared to that for a colloid-linear polymer mixture at similar q. Similarities in the two systems were found in the position of the fluid- solid phase boundary; however , differences in the kinetics of phase separation were apparent in the earlier onset of gelation in the colloid-microgel phase diagram. This result may be due to the greater rigidity of the microgels. Interestingly, the colloidmicrogel gel line was found to coincide with the theoretical metastable fluid-fluid phase boundary calculated for binary hard sphere systems at q = O.l.
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Golightly, John Anthony. "NMR studies of phase behaviour in polyacrylonitrile solutions." Thesis, University of Nottingham, 1998. http://eprints.nottingham.ac.uk/13172/.
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The aim of the thesis was to study the phase behaviour of aqueous polyacrylonitrile/NaSCN solutions using a variety of nuclear magnetic resonance techniques. Polyacrylonitrile (PAN) is the basis of the acrylic fibre industry, as such fibres contain at least 85% PAN. Despite this industrial importance, the available literature describing the phase behaviour of PAN in solution is far from comprehensive. Bulk 1H NMR relaxation measurements were carried out over a wide range of concentrations and temperatures to probe the molecular dynamics of the PAN and water molecules. Both the T1 and T2 relaxation data was found to be bi-exponential decay for all samples, the relative amplitudes of which were shown to be equal to the ratio of PAN protons to water protons. Both species were found to be in the regime of rapid molecular motion. Bulk 1H NMR self diffusion measurements, using the PFGSTE technique, exhibited a bi-exponential decay of the echo amplitudes. By careful selection of the observation time, Δ, it was possible to independently probe the water and PAN translational diffusion. A background gradient, resulting from inhomogeneities of the magnetic field, complicated the analysis of the data and a novel polynomial least squares fitting procedure was devised to overcome this effect. The measured attenuation of the water diffusion coefficients (D~10-6-10-5 cm²s-1) with increasing PAN volume fraction was modelled according to various theories, including free volume and scaling laws. The study of the PAN diffusion coefficient (D~10-7-10-6 cm²s-1) was limited by the experimental constraints of the NMR spectrometer. A 1H NMR one-dimensional imaging technique was used to study the nonsolvent induced phase separation (coagulation) of a PAN solution. The time dependence of the measured profiles allowed observation of the coagulation process. A diffusion model was developed to fit the experimental data using a semi-infinite diffusion framework. The fitting parameters represented the diffusion coefficients of the water molecules in the solution/ coagulated PAN network, and in the bulk non-solvent/solvent. PAN films were cast at a range of temperatures in non-solvent baths. This was a scaling up of the dimensions of the fibre spinning process and was used to investigate the range of morphologies which can be formed in the wet-spinning of acrylic fibres. Before any drying processes, water molecules were confined in the porous structure of the saturated films, and their NMR relaxation and self diffusion behaviour was investigated. Parameters describing the pore size and the tortuosity were derived from these studies and scanning electron microscopy was used as a comparative technique. The pore sizes predicted from the NMR data span a smaller spatial range than those observed from SEM. This is explained by the fundamental differences between the two techniques.
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Tabatabaei-Nejad, Seyyed Ali Reza. "Phase behaviour modelling of petroleum wax and hydrates." Thesis, Heriot-Watt University, 1999. http://hdl.handle.net/10399/593.
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Katsikides, Andrew. "Phase behaviour structure and dynamics of microemulsion systems." Thesis, University of Kent, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329298.
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Richmond, T. D. "The phase behaviour of dimyristoyl phosphatidylcholine/water mixtures." Thesis, University of Leeds, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382045.
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Mesmari, H. R. A. "Strength and fatigue behaviour of dual phase steels." Thesis, University of Strathclyde, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382450.
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Madden, Andrea. "Phase behaviour of side-chain liquid-crystalline polymers." Thesis, University of Southampton, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241165.
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Sokolova, Maia. "Determination of phase behaviour in supercritical reaction mixtures." Thesis, University of Nottingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.537666.
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Wood, Jared Anthony. "Self-assembly and Phase Behaviour of Colloidal Nanorods." Thesis, The University of Sydney, 2021. https://hdl.handle.net/2123/25756.
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Colloidal nanorods are a fascinating and useful material. Their small size and anisotropic shape give them unique optical, electronic and mechanical properties. However, to make full use of these properties they need to be assembled into an ordered structure.
To assemble the rods, it is important to control the conditions, otherwise disordered aggregates or misaligned micro-domains may be form, removing the anisotropy. Consequently, understanding these assemblies and what affects their structure is vital.
This thesis aims to characterise the self-assembly behaviour of nanorods and their ordered assemblies. We look at the structure of the assemblies that form, focusing on the number of layers and how it affects the structure.
We also investigate the nucleation pathway by which a disordered set of rods transforms into an ordered crystalline assembly, again looking at the structure of the cluster, identifying monolayers as the preferred nucleus and characterising the free energy changes of the pathway.
We then characterise the types of assemblies that can be formed by Janus nanorods which are attractive on one part of the rod and repulsive on the other, noting the formation of trapped disordered monolayers and no thermodynamically independent micelle phase.
Finally, we look at the phenomena of chiral twisted platelets, seen in viral capsid assemblies and identify the driving forces causing the platelet's edges to twist, despite being achiral.
We used Monte Carlo and molecular dynamics for these simulations, and several different models for our system: an explicit polymer model, where the polymer is modelled as self-penetrating spheres, implicit models, where a pair potential represents the polymer and a square-well bead model where the rod is represented by a set of interacting spheres.
We also use biased sampling techniques such as umbrella sampling, to properly characterise nucleation pathways, multi-body effects and the impact of assembly structure on the free energy.
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Chalmers, Christopher. "Modelling evaporation and phase behaviour of particle suspensions." Thesis, Loughborough University, 2017. https://dspace.lboro.ac.uk/2134/33719.
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We present two statistical mechanics based methods for simulating the evaporation of droplets of nanoparticle suspensions from upon a heterogeneous surface. These are based on a generalised lattice-gas model. Properties such as wettability and the dynamic contact angle, are determined by the attraction strength parameters between particles and from the dynamic mobility coefficients. Both models incorporate the effects of surface roughness and slip at the surface. The two approaches used are Monte Carlo (MC) computer simulations and Dynamical Density Functional Theory (DDFT). We calculate the bulk fluid phase behaviour including the influence of the suspended nanoparticles, comparing results from the two approaches. We also calculate thermodynamic quantities such as the surface tensions. Our results show that the presence of steps in the surface can be crucial in controlling dewetting from heterogeneous surfaces. We also observe that coffee ring stains can be formed via the coupling of evaporation to phase separation and that the advective hydrodynamics within the droplets in not required for ring stains to form.
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Schechter, David S. "Immiscible flow behaviour in porous media." Thesis, University of Bristol, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234777.
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Götze, Ingo O. "Coarse graining dendritic macromolecules: from conformations to phase behaviour." [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975646478.
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Agbenorhevi, Jacob Kwaku. "Phase behaviour of oat β-glucan/sodium caseinate mixtures." Thesis, University of Huddersfield, 2011. http://eprints.hud.ac.uk/id/eprint/17475/.
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Oat β-glucan is a water soluble polysaccharide which has been approved as a functional bioactive ingredient. In this thesis, β-glucan was successfully isolated from oat flour and samples of different molecular weights were produced. The structural features and molecular weights(Mw) were characterized by 13C–NMR spectroscopy and high performance size-exclusion chromatography, respectively. The rheological properties and microstructure of aqueous oat β-glucan solutions were investigated by rheometry and atomic force microscopy (AFM),respectively. The samples with β-glucan content between 78-86 % on a dry weight basis had Mw, intrinsic viscosity ([η]) and critical coil overlap concentration (c*) in the range of 142 - 2800 x 103 g/mol, 1.7 - 7.2 dL/g and 0.25 - 1.10 g/dL, respectively. The flow and viscoelasticvbehaviour was highly dependent on Mw and on the concentration of the β-glucan solutions. AFM images revealed the formation of cluster or aggregates linked via individual polymer chains scattered heterogeneously throughout the system. The aggregate size was also dependent on molecular weight of the samples and influences the rheological behaviour of β-glucan solutions. The isothermal phase behaviour at 5 oC of β-glucan/sodium caseinate mixtures were investigated by means of phase diagram construction, rheometry, electrophoresis and fluorescence microscopy. Phase diagrams indicated that the compatibility of the β-glucan/sodium caseinate system increases as β-glucan Mw decreases. Images of the mixtures taken at various biopolymer concentrations revealed phase separation with the presence of β-glucan aggregates,whose size depends on Mw and concentration. At the same protein concentration in the mixtures, the viscosity increases with increasing Mw and concentration of β-glucan. However, the results also revealed that in the state of thermodynamic equilibrium with comparable polymer concentrations in mixture, the lower Mw samples yielded similar or higher viscosity. At equivalent hydrodynamic volume of β-glucan component in the mixture, all the samples exhibited similar viscosity/flow behaviour. A deviation dependent on the protein concentration was observed for the high Mw sample in the concentrated regime due to the size of the β-glucan aggregates formed. Results demonstrate that by controlling the structural features of β-glucan in mixture with sodium caseinate, informed manipulation of rheological properties in these systems can be achieved.
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Schreckenberg, Jens Manfred Alois. "Modelling the effect of electrolytes on fluid phase behaviour." Thesis, Imperial College London, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.544287.
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Ragupathy, Lakshminarayanan. "Phase behaviour of polymer blends : experimental and theoretical predictions." Thesis, Heriot-Watt University, 2006. http://hdl.handle.net/10399/156.
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Fasolo, Moreno. "Polydispersity effects in the phase behaviour of colloidal systems." Thesis, King's College London (University of London), 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414981.
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Wang, Ge. "Phase switching behaviour in lead-free Na0.5Bi0.5TiO3-based ceramics." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/phase-switching-behaviour-in-leadfree-na05bi05tio3based-ceramics(267b315d-3757-4865-9f88-5eeed76d61c4).html.
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This PhD project is focused on three lead-free ferroelectric solid solutions, which are specifically Na0.5Bi0.5TiO3-KNbO3(NBT-KN), Na0.5Bi0.5TiO3-NaNbO3(NBT-NN) and Na0.5Bi0.5TiO3-BaTiO3(NBT-BT), to evaluate the effects of composition, electric field and temperature on structural and electrical properties. Novel observations of both reversible and irreversible electric field-induced phase switching were made in both NBT-KN and NBT-NN ceramics. The NBT-KN solid solution is the primary focus of this thesis. All compositions were observed to be cubic in the as-sintered, unpoled state. However, a well-defined ferroelectric hysteresis P-E loop was obtained for compositions with low KN contents, indicating that an irreversible phase transition from a weak-polar relaxor ferroelectric (RF) to a long-range ordered metastable ferroelectric (FE) state had occurred during the measurement procedure. Both the unpoled and poled ceramic powders were examined using high resolution synchrotron XRD. For the poled state, a rhombohedral R3c structure was identified for compositions with low KN content, confirming the occurrence of the irreversible electric field-induced structural transformation from cubic to rhombohedral. In contrast, a cubic structure was retained for high KN contents, giving rise to reversible phase switching evidenced by constricted P-E hysteresis loops. Similar behaviour was observed for NBT-NN system. An 'in-situ' electric field poling experiment was conducted using high energy synchrotron XRD. In certain NBT-KN compositions the structural transformation, from cubic to mixed phase cubic+rhombohedral and finally single phase rhombohedral, occurred progressively with increasing cycles of a bipolar electric field. Similar behaviour was observed for NBT-NN compositions having low NN contents. Furthermore, the distributions of domain orientation and lattice strain over a range of orientations relative to the poling direction were determined for NBT-KN, NBT-NN and NBT-BT ceramics exhibiting the rhombohedral phase. By combining the structural information with the results of dielectric and ferroelectric measurements, a phase diagram was constructed to illustrate the influence of temperature and composition on the stability of the metastable ferroelectric and relaxor ferroelectric states for the NBT-KN system. Furthermore, the phase transition temperatures obtained from dielectric measurements were correlated with the ferroelectric and thermal depolarisation characteristics for each of the NBT-KN, NBT-NN and NBT-BT systems.
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Kruszewski, Andrew Peter. "The behaviour of stirred, two and three phase systems." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/38075.
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Mutombo, Pierre Abraham Mulamba. "Two-phase behaviour in a sequence of random variables." Thesis, Stellenbosch : Stellenbosch University, 2007. http://hdl.handle.net/10019.1/19645.
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Thesis (MSc)--University of Stellenbosch, 2007.ENGLISH ABSTRACT: Buying and selling in financial markets are driven by demand. The demand can be quantified by the imbalance in the number of shares QB and QS transacted by buyers and sellers respectively over a given time interval t. The demand in an interval t is given by (t) = QB − QS. The local noise intensity is given by = h|aiqi − haiqii|i where i = 1, . . . ,N labels the transactions in t, qi is the number of shares traded in transaction i, ai = ±1 denotes buyer- initiated and seller- initiated trades respectively and h· · · i is the local expectation value computed from all the transactions during the interval t. In a paper [1] based on data from the New York Stock Exchange Trade and Quote database during the period 1995-1996, Plerou, Gopikrishnan and Stanley [1] reported that the analysis of the probability distribution P( | ) of demand conditioned on the local noise intensity revealed the surprising existence of a critical threshold c. For < c, the most probable value of demand is roughly zero; they interpreted this as an equilibrium phase in which neither buying nor selling predominates. For > c two most probable values emerge that are symmetrical around zero demand, corresponding to excess demand and excess supply; they interpreted this as an out-of-equilibrium phase in which the market behaviour is buying for half of the time, and selling for the other half. It was suggested [1] that the two-phase behaviour indicates a link between the dynamics of a financial market with many interacting participants and the phenomenon of phase transitions that occurs in physical systems with many interacting units. This thesis reproduces the two-phase behaviour by means of experiments using sequences of random variables. We reproduce the two-phase behaviour based on correlated and uncorrelatd data. We use a Markov modulated Bernoulli process to model the transactions and investigate a simple interpretation of the two-phase behaviour. We sample data from heavy-tailed distributions and reproduce the two-phase behaviour. Our experiments show that the results presented in [1] do not provide evidence for the presence of complex phenomena in a trading market; the results are a consequence of the sampling method employed.
AFRIKAANSE OPSOMMING: Aankope en verkope in finansi¨ele markte word deur aanvraag gedryf. Aanvraag kan gekwantifiseer word in terme van die ongebalanseerdheid in die getal aandele QB en QB soos onderskeidelik verhandel deur kopers en verkopers in ’n gegewe tyd-interval t. Die aanvraag in ’n interval t word gegee deur (t) = QB −QS. Die lokale geraasintensiteit word gegee deur = h|aiqi − haiqii|i waar i = 1, . . . ,N die transaksies in t benoem, qi die getal aandele verhandel in transaksies verwys, en h· · · i op die lokale verwagte waarde dui, bereken van al die tansaksies tydens die interval t. In ’n referaat [1] wat op data van die New York Effektebeurs se Trade and Quote databasis in die periode tussen 1995 en 1996 geskoei was, het Plerou, Gopikrishnan en Stanley [1] gerapporteer dat ’n analise van die waarskynlikheidsverspreiding P( | ) van aanvraag gekondisioneer op die lokale geraasintensiteit , die verrassende bestaan van ’n kritieke drempelwaarde c na vore bring. Vir < c is die mees waarskynlike aanvraagwaarde nagenoeg nul; hulle het dit ge¨ınterpreteer as ’n ekwilibriumfase waartydens n`og aankope n`og verkope die oormag het. Vir > c is die twee mees waarskynlike aanvraagwaardes wat te voorskyn kom simmetries rondom nul aanvraag, wat oorenstem met ’n oormaat aanvraag en ’n oormaat aanbod; hulle het dit geinterpreteer as ’n buite-ewewigfase waartydens die markgedrag die helfte van die tyd koop en die anderhelfte verkoop. Daar is voorgestel [1] dat die tweefase gedrag op ’n verband tussen die dinamiek van ’n finansiele mark met baie deelnemende partye, en die verskynsel van fase-oorgange wat in fisieke sisteme met baie wisselwerkende eenhede voorkom, dui. Hierdie tesis reproduseer die tweefase gedrag deur middel van eksperimente wat gebruik maak van reekse van lukrake veranderlikes. Ons reproduseer die tweefase gedrag gebaseer op gekorreleerde en ongekorreleerde data. Ons gebruik ’n Markov-gemoduleerde Bernoulli proses om die transaksies te moduleer en ondersoek ’n eenvoudige interpretasie van die tweefase gedrag. Ons seem steekproefdata van “heavy-tailed” verspreidings en reproduseer die tweefase gedrag. Ons ekperimente wys dat die resultate in [1] voorgested is nie bewys lewer vir die teenwoordigheid van komplekse verskynsel in’n handelsmark nie; die resultate is as gevolg van die metode wat gebruik is vir die generering van die steekproefdata.
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Sintyureva, Marina. "Engineering the phase behaviour of high performance inkjet colorants." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/engineering-the-phase-behaviour-of-high-performance-inkjet-colorants(0617f94f-7744-4576-9c05-69f659c52545).html.
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Dyes for inkjet printing are typically of the chromonic type. Chromonic mesophases have gained considerable attention as a well-defined group of lyotropic mesogens with different properties from conventional amphiphiles. While extensive research has been dedicated to the field of surfactant liquid crystals, structural and aggregation studies of chromonics have only emerged as a topic of interest within the last few years. The liquid crystalline structures in aqueous solutions of commercial Cu - phthalocyanine and black dyes have been examined using a combination of optical microscopy, UV-vis spectroscopy, nuclear magnetic resonance, wide- and small-angle X-ray diffraction and electronic paramagnetic resonance with a view to examining the phase behaviour of the chromonic mesophases formed over a broad range of concentrations and temperatures. These studies were performed in order to resolve outstanding problems concerning structural properties of these systems. Optical microscopy allowed us to identify the liquid crystalline phases and to construct the phase diagram. The observations show that both of these dyes form nematic mesophase above 15% wt / wt% dye. The small-angle diffraction data confirmed that the nematic phase for the black dye is maintained throughout the 16-25% composition range. A further increase in concentration leads to the formation of the hexagonal phase. The Cu – phthalocyanine dye also formed a nematic phase at low concentrations, with the aggregates undergoing a phase transition to an orientationally ordered chromonic liquid crystal phase at high dye concentration. These studies showed that this ordered phase possessed hexagonal symmetry. The wide-angle X-ray results demonstrated that aggregation involved π-π stacking of the molecules into columns. An additional reflection at ca. 6.8Å was observed for the black dye, which is believed to arise from “head – to – tail” packing of the molecules within the aggregates (a similar phenomenon observed in other azo dyes, e.g. Edicol Sunset Yellow).The densities of both dyes were measured over the studied range of concentrations. This enabled us to calculate the parameters of the aggregates within the hexagonal mesophase. A comparison between the area of the molecule and the cross-section of the aggregates showed that the aggregates of both dyes were the unimolecular stacks.
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Zeiner, Tim [Verfasser]. "Phase- and Interfacial Behaviour of Hyperbranched Polymer Solutions / Tim Zeiner." München : Verlag Dr. Hut, 2011. http://d-nb.info/1010446754/34.
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Shalliker, Ross Andrew, and mikewood@deakin edu au. "Studies on the behaviour of polystyrene in reversed phase chromatography." Deakin University. School of Sciences, 1992. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20051125.112118.
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Polystyrene behaviour in reversed phase high performance liquid chromatography was influenced mainly by the solvent system, but secondary affects were observed depending on the stationary phase. A variety of reversed phase columns were investigated using mobile phase combinations of dichlorom ethane-methanol, dichloromethane-acetonitrile, ethyl acetate-methanol and ethyl acetate-acetonitrile. Several different modes of behaviour were observed depending on the polymer solubility in the solvent system.
In the dichloromethane-methanol solvent system, polymer-stationary phase interactions only occurred when the molecules had pore access. Retention of excluded polystyrene depended on the kinetics of precipitation and redissolution of the polymer. Peak splitting and band broadening occurred when the kinetics were slow and molecular weight separations were limited !o oligomers and polystyrenes lower than 5-10(4) dalton.
Excellent molecular weight separations of polystyrenes were obtained using gradient elution reversed phase chromatography with a dichloromethane-acetonitrile mobile phase on C18 columns. The retention was based on polymer-stationary phase interactions regardless of the column pore size. Separations were obtained on large diameter pellicular adsorbents that were almost as good as those obtained on porous adsorbents, showing that pore access was not essential for the retention of high molecular weight polystyrenes. In the best example, the separation ranged from the monomer to 10(6) dalton in a single analysis. Very little adsorption of excluded polymers was observed on C8 or phenyl columns.
Polystyrene molecular weight separations to 7-10(5) dalton were obtained in an ethyl acetate-acetonitrile solvent system on C18 columns. Adsorption was responsible for retention. When an ethyl acetate-methanol solvent system was used, no molecular weight separations were obtained because of complex peak splitting.
Reversed phase chromatography was compared to size exclusion chromatography for the analysis of polydisperse polystyrenes. Similar results were obtained using both methods. However, the reversed phase method was less sensitive to concentration effects and gave better resolution.
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Turcott, Rios Eduardo Enrique. "Experimental study of the compressional behaviour of two-phase media." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=70342.
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This thesis is concerned with the experimental evaluation of the volumetric deformation of a two-phase medium at the microscopic level. The basic definitions of the significant parameters involved in the mechanical response behaviour of the structured medium are based on the concepts of Probabilistic Micromechanics. A simple phenomenological model and the leading structural parameter $ theta sb{s}$ (Solid phase volume fraction) are discussed briefly. The experimental work makes use of a series of macroscopic tests to attain different states of deformation so that the evolution of the internal microstructural changes can be analyzed. The combined use of ultramicrotomy techniques and the Scanning Electron Microscopy operating in the Backscattered Electron mode allowed the quantification of the microstructural changes at large magnifications. The concepts of practical Stereology were adopted for the quantification of a large number of observation areas representative of the complete phenomenon to determine the leading structural parameter $ theta sb{s}.$ A semi-automatic system was developed for the determination of $ theta sb{s}$ corresponding to each observation area. A fully-automatic image analyzer also was used for the evaluation of the first state of deformation. The experimental procedure employed in this investigation is described in detail and its application is illustrated by the evaluation of $ theta sb{s}$ and its evolution at the microscopic level. The evaluations of the distributions of this parameter also are shown. In the conclusion of this thesis, the obtained results for the Al-Quetol are discussed and general remarks concerning the experimental technique and its application to other structured media are indicated.
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Clark, Gary Neil Ian. "Molecular modelling of the phase behaviour of water-soluble polymers." Thesis, Imperial College London, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.444146.
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Mohammadi, Amir Hossein. "Phase behaviour modelling of systems containing gas hydrates and asphaltenes." Thesis, Heriot-Watt University, 2006. http://hdl.handle.net/10399/138.
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Gas hydrates are crystalline compounds formed from a combination of water molecules with suitably sized non-polar or slightly polar molecules under certain conditions of temperature and pressure. They are well known for their role in the blockage of subsea pipelines and oil and gas production / processing facilities, which is a major concern for the petroleum industry. On the other hand, asphaltenes are the toluene / benzene soluble fractions that precipitate from petroleum when an excess (25 to 40 times) of n-heptane / n-pentane is mixed with petroleum and waiting at least four hours before filtering. Asphaltene precipitation causes fouling in the reservoir, in the well, in the pipeline and in the oil production and processing facilities. In this study, predictive methods and thermodynamic models to predict the hydrate and asphalt free zone of hydrocarbon fluids were developed for field applications. The topics studied included estimation of water content of natural gases in equilibrium with the liquid water, ice and gas hydrates, prediction of hydrate inhibition effects of mixed salt and organic inhibitor and finally modelling asphaltene precipitation conditions. The results showed that the existing predictive methods show large deviations for predicting the water content of natural gases at low temperature conditions and therefore, new predictive tools were developed. Furthermore, the application of a thermodynamic model was extended to mixed salt and chemical inhibitor commonly used in petroleum production and transportation. This will provide a basis for the design of production and transportation facilities, particularly for deepwater applications. A new correlation for predicting the hydrate inhibition effect of single and mixed thermodynamicin hibitors was also developed. A theoretical study was conducted to investigate asphaltene precipitation from petroleum fluids during petroleum production and transportation. The results showed that it is possible to use a polymer model namely the Scott-Magat theory combined with an equation of state to predict asphaltene precipitation from reservoir fluids. b