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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Mathematical modelling of drug delivery to solid tumour

Zhan, Wenbo January 2014 (has links)
Effective delivery of therapeutic agents to tumour cells is essential to the success of most cancer treatment therapies except for surgery. The transport of drug in solid tumour involves multiple biophysical and biochemical processes which are strongly dependent on the physicochemical properties of the drug and biological properties of the tumour. Owing to the complexities involved, mathematical models are playing an increasingly important role in identifying the factors leading to inadequate drug delivery to tumours. In this study, a computational model is developed which incorporates real tumour geometry reconstructed from magnetic resonance images, drug transport through the tumour vasculature and interstitial space, as well as drug uptake by tumour cells. The effectiveness of anticancer therapy is evaluated based on the percentage of survival tumour cells by directly solving the corresponding pharmacodynamics equation using predicted intracellular drug concentration. Computational simulations have been performed for the delivery of doxorubicin through various delivery modes, including bolus injection and continuous infusion of doxorubicin in free form, and thermo-sensitive liposome mediated doxorubicin delivery activated by high intensity focused ultrasound. Predicted results show that continuous infusion is far more effective than bolus injection in maintaining high levels of intracellular drug concentration, thereby increasing drug uptake by tumour cells. Moreover, multiple-administration is found to be more effective in improving the cytotoxic effect of drug compared to a single administration. The effect of heterogeneous distribution of microvasculature on drug transport in a realistic model of liver tumour is investigated, and the results indicate that although tumour interstitial fluid pressure is almost uniform, drug concentration is sensitive to the heterogeneous distribution of microvasculature within a tumour. Results from three prostate tumours of different sizes suggest a nonlinear relationship between transvascular transport of anticancer drugs and tumour size. Numerical simulations of thermo-sensitive liposome-mediated drug delivery coupled with high intensity focused ultrasound heating demonstrate the potential advantage of this novel drug delivery system for localised treatment while minimising drug concentration in normal tissue.
22

Approximation methodologies for explicit model predictive control of complex systems

Lambert, Romain January 2014 (has links)
This thesis concerns the development of complexity reduction methodologies for the application of multi-parametric/explicit model predictive (mp-MPC) control to complex high fidelity models. The main advantage of mp-MPC is the offline relocation of the optimization task and the associated computational expense through the use of multi-parametric programming. This allows for the application of MPC to fast sampling systems or systems for which it is not possible to perform online optimization due to cycle time requirements. The application of mp-MPC to complex nonlinear systems is of critical importance and is the subject of the thesis. The first part is concerned with the adaptation and development of model order reduction (MOR) techniques for application in combination to mp-MPC algorithms. This first part includes the mp-MPC oriented use of existing MOR techniques as well as the development of new ones. The use of MOR for multi-parametric moving horizon estimation is also investigated. The second part of the thesis introduces a framework for the ‘equation free’ surrogate-model based design of explicit controllers as a possible alternative to multi-parametric based methods. The methodology relies upon the use of advanced data-classification approaches and surrogate modelling techniques, and is illustrated with different numerical examples.
23

On extending process monitoring and diagnosis to the electrical and mechanical utilities : an advanced signal analysis approach

Cecílio, Inês M. January 2014 (has links)
This thesis is concerned with extending process monitoring and diagnosis to electrical and mechanical utilities. The motivation is that the reliability, safety and energy efficiency of industrial processes increasingly depend on the condition of the electrical supply and the electrical and mechanical equipment in the process. To enable the integration of electrical and mechanical measurements in the analysis of process disturbances, this thesis develops four new signal analysis methods for transient disturbances, and for measurements with different sampling rates. Transient disturbances are considered because the electrical utility is mostly affected by events of a transient nature. Different sampling rates are considered because process measurements are commonly sampled at intervals in the order of seconds, while electrical and mechanical measurements are commonly sampled with millisecond intervals. Three of the methods detect transient disturbances. Each method progressively improves or extends the applicability of the previous method. Specifically, the first detection method does univariate analysis, the second method extends the analysis to a multivariate data set, and the third method extends the multivariate analysis to measurements with different sampling rates. The fourth method developed removes the transient disturbances from the time series of oscillatory measurements. The motivation is that the analysis of oscillatory disturbances can be affected by transient disturbances. The methods were developed and tested on experimental and industrial data sets obtained during industrial placements with ABB Corporate Research Center, Kraków, Poland and ABB Oil, Gas and Petrochemicals, Oslo, Norway. The concluding chapters of the thesis discuss the merits and limitations of each method, and present three directions for future research. The ideas should contribute further to the extension of process monitoring and diagnosis to the electrical and mechanical utilities. The ideas are exemplified on the case studies and shown to be promising directions for future research.
24

Macroporous hydrogels formed by high internal phase emulsion-templating and their applications in tissue engineering

Oh, Bernice January 2014 (has links)
This thesis reports and discusses the development of several multifunctional biopolymers to be used in a cleaner approach for producing high porosity macroporous polymers by high internal phase emulsion (HIPE) templating for application as tissue engineering scaffolds. The aim is to identify and create biocompatible polymers that can self-stabilize HIPEs, be self-crosslinkable and also act simultaneously as the matrix for the macroporous polymers after emulsification, solidification and removal of the templating phase and aqueous solvent for the polymers. Firstly, the design of a self-emulsifying biopolymer was carried out using a chitosan based biopolymer grafted with thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) and oligolysine (CSNLYS). Self-emulsification of HIPEs was found to be successful using this copolymer. The HIPEs could be solidified by raising the temperature above the lower critical solution temperature (LCST) of the PNIPAM component to 40°C. In addition, it was found that by changing the degree of polymerization of the grafted oligolysine, HIPEs with very different emulsion droplet sizes resulted, ranging from microemulsions with average droplet sizes of 0.13 μm, to macroemulsions with average droplet sizes of 10.5 μm. Polymerized (high internal phase macroemulsion) (polyHIPE) and polymerized (high internal phase 7 microemulsion) (polyHIPME) were formed by removing the liquid templating phases resulting in closed celled high porosity foams. Chitosan-graft-poly(N-isopropylacrylamide)-graft-oligoproline (CSN-PRO) and chitosan-graft-poly(N-isopropylacrylamide)-graft-oligo(glutamic acid) (CSN-GLU) were synthesized next to produce self-stabilized HIPE. CSN-PRO was found to be able to stabilize HIPE but not CSN-GLU, forming closed pores with pore sizes ranging from 32 μm to 71 μm. Upon addition of a low concentration of the surfactant PEG(20)sorbitan monolaurate, and varying the polymer concentration and internal phase volume ratio, different polyHIPEs with pore size of up to 143 μm, porosities of up to 99%, surface areas >300 m 2 /g and controlled pore interconnectivity can be formed. The CSN-PRO stabilized polyHIPEs are able to retain their thermoresponsiveness and remain intact when immersed into water at physiological temperature but dissolve below their LCST, which is useful in applications such as drug delivery and for tissue engineering scaffolds. Murine embryonic stem cells which are nonanchorage dependent were seeded to assess biocompatibility and were found to be able to survive and enter the pores of the poly(CSN-PRO)HIPE hydrogel. To produce scaffolds suitable for the attachment of anchorage dependent cells, a polypeptide, gelatin was used to create the self-emulsifying copolymer gelatin-graft-PNIPAM (GN). It was found GN does self-stabilize HIPEs. Upon solidification of the HIPEs and the removal of the templating oil phase and water from the aqueous phase highly porous and interconnected tissue 8 engineering scaffold resulted without the use of any additional surfactant. Poly(GN)HIPEs can be formed by two different solidification mechanisms as conferred by the components of GN, gelatin and PNIPAM. By inheriting the temperature sensitivity of these two components, GNHIPEs can be solidified at either 4°C due to the gelatin component or 40°C due to the PNIPAM component. The physical properties of the resultant self-stabilized poly(GN)HIPEs can be controlled by varying the aqueous phase, emulsion phase volume ratio and solidification temperature. Because of the inherent temperature sensitivity, poly(GN)HIPE hydrogels are able to response rapidly to changes in temperature during the initial cell culturing period. Fibroblast cells seeded into the scaffold were seen to thrive, spread and proliferate in a culture period of 10 days, with a maximum depth of penetration of 360 μm. The cell-laden poly(GN)HIPE scaffold was shown to be injectable through a syringe without harming the encapsulated cells. This system provides a new strategy for the easy fabrication of safe and injectable biocompatible scaffolds for tissue engineering.
25

Catalytic and sorption measurements using flux response technology

Sasegbon, Ayodeji Oladipo January 2014 (has links)
Advancements in characterisation techniques in the field of heterogeneous catalysis have been explored, in particular the powerful in situ perturbation method, Flux Response Technology (FRT). The adaptation of FRT as a novel in situ perturbation technique in gas sorption measurements continues to yield consistent results with literature values. This is made possible because FRT measures miniscule changes in transient flows in the order of 10-2 μl/min for gaseous processes involving a change in volume (dV/dt). These changes are measured directly by a very sensitive differential pressure transducer (DPT) in a pneumatic system analogous to an electrical Wheatstone bridge assembly, whereby gas molecules replace electrons and capillaries function as resistors. By showing the successful incorporation of the measurements of adsorption capacities and diffusivity coefficients in the same experimental window, FRT's use as a bolt-on technology for the rapid screening of catalyst material has been highlighted. The technique possesses a distinct advantage in requiring no prior calibrations to the system, enabling the analysis of a broad spectrum of materials and gases. The FRT technique also features a unique ability in being able to act as a dual flowrate and composition detector through the use of carefully calculated delay lines to separate changes in flowrate caused by perturbations of concentration and changes in composition. The FRT technique provides a quick, simple, accurate, and inexpensive method of characterising material properties in situ in heterogeneous catalysis. Several studies into the dynamics of gas sorption processes utilising FRT measurements on adsorbents were undertaken in the completion of this PhD. The diffusivity parameters of propane in varying alumina/CeZrOx washcoats of Cordierite monoliths were investigated under isothermal conditions. A novel method of analysing FRT derived response profiles with the Zero Length Column (ZLC) model was established and reported on. The diffusion coefficients obtained were consistent with previously reported macroscopic data and compared well when evaluating the structural differences of the washcoats of each sample (Granato et al., 2010). The dynamics of ammonia sorption on commercially available zeolites with varying SiO2/Al2O3 ratios was analysed to investigate the total acidity of these zeolites. The dynamics of carbon dioxide sorption were also investigated to analyse the total basicity of the same zeolite samples. Process optimisations were conducted to obtain an ultra fast isotherm measurement technique for the analysis of nitrogen sorption on aluminium oxides with varying surface areas at 77 K. Finally, insights into the development of a dynamic parallel performance testing (DPPT) FRT setup were undertaken to directly compare the activities of catalytic material operating side by side.
26

The effect of sulfur on chemical looping combustion with iron oxides

Zhang, Zili January 2014 (has links)
Advancing climate change poses an increasing threat to humanity, together with the higher demand for energy around the world. New 'cleaner' technologies for the production of energy from solid fuels (coal or biomass) via thermo-chemically viable routes are required. Chemical looping combustion (CLC) is a process concept using metal oxide (oxygen carrier) for transportation of oxygen from air for electrical power generation and inherent production of a pure stream of CO2. CLC has been generally applied to gaseous fuel; however, by integrating chemical looping and gasification, the combined process shows great potential for producing H2 and power from solid fuels. Coal and biomass contain significant quantities of sulfur. Upon gasification, the sulfur is released in the form of H2S, which will be then be introduced into the iron-based chemical looping process, followed by further gasification. Iron oxides are known to form stable sulfides under reducing conditions. The performance of chemical looping using iron-based oxygen carrier could therefore be adversely affected by the introduction of H2S in a real system. The overarching aim of this thesis is to assess the effect of H2S on chemical looping combustion using iron (III) oxide in a laboratory scale spouted bed reactor. A closed-system spouted bed reactor has been designed and constructed to study the solid looping system with gaseous fuel. A model of the bed was developed, from which the bed could reasonably be assumed to be a well-mixed bubbling fluidised bed reactor at certain conditions. The reactor was used for the kinetic study of reduction of Fe2O3 to Fe3O4 with a CO/CO2 mixture under isothermal condition at the temperature range of 723K - 973K. The oxygen carrier before and after thermal cycling was characterised using SEM, mercury porosimetry, BET surface area analysis. Using a nominal particle size of Fe2O3, the rate of reduction was controlled mainly by intrinsic chemical reaction kinetics with a high effectiveness factor. The intrinsic rate constant was estimated with an activation energy of 73 kJ mol-1, which is comparable to values reported in the literature. The reactor was modified for use in the quartz internal, together with acid-washed, calcined sand (Quartz-T) to be able to significantly reduce interactions between sulfur and the inert material used in the construction of the reactor and the spouted bed. The fate of H2S in the chemical looping cycling was determined and the effect of H2S on reduction of Fe2O3 to Fe3O4 over multiple cycles was studied. There were two major mechanisms of reaction between H2S and Fe2O3 that were found to affect the rate of reduction of Fe2O3 and main sulfur product distribution: (1) production of SO2 as a main sulfur product, (2) production of FeS as a main sulfur product. The dominating mechanism was found to depend on the thermodynamic potential of S2, the thermodynamic potential of O2 (which depends on the extent of reduction), and the temperature. The effect of the H2S on the kinetics of reduction was found to be due to the structural change of Fe2O3 particles that is governed by the reaction between H2S and Fe2O3. A mathematical simulation based on a grain model under chemical reaction control was used to satisfactorily describe the relationship between rate of reduction and the extent of the reaction in the presence of sulfur.
27

Force field parameters from the SAFT equation of state for the molecular simulation of fused molecules

Yaroson, Omolara January 2014 (has links)
In this work, the analytical SAFT-γ Mie equation of state (EoS) is used in the efficient development of intermolecular force field parameters which can be used in direct molecular simulation for a range of fused dimer molecules. In its original formulation, the SAFT-γ Mie EoS only provides a direct link to the force field parameters for tangent models. A novel development here is to extend the application of the equation of state to obtain intermolecular potentials for fused models which more faithfully mimic realistic molecules. The proposed methodology consists of a two stage process: - An empirical mapping between the parameters of the theory and parameters used in simulation is first obtained by performing molecular dynamics simulations of the vapour-liquid equilibria for a wide range of homonuclear model dimer molecules with different bond lengths and Mie repulsive exponents. The simulation results are matched with those obtained using the theory for corresponding systems in order to determine the relationship between the parameters of the theory and the potential model. A methodology for obtaining unlike interaction parameters in heteronuclear dimer molecules is also developed and validated. - The mapping obtained is then used to translate the equation of state parameters of real molecules into a simulation force field with an explicit bond length. Force fields are obtained for a range of molecules with different levels of molecular resolution including atomistic models for molecular oxygen and nitrogen, united-atom models for ethane and perfluoroethane and more coarse-grained dimer models of propylbenzene and carbon dioxide. The properties obtained by simulation include vapour pressures, saturated liquid densities and interfacial tensions. This top-down methodology of obtaining force field parameters for computer simulation of fluids is much less computer and time intensive than the traditional methods. In the concluding chapter, a preliminary extension of the approach to trimers molecules is presented.
28

Molecular simulation of diffusive mass transport in porous materials

Frentrup, Hendrik January 2014 (has links)
Ever increasing control over the shape and form of a material's nanoscale features provokes the pursuit of a detailed understanding for the main factors influencing fluid transport. It is sought to facilitate the intelligent design of novel materials used in membrane separation processes. In addition to a strong dependence on molecular mobility, mass transport is heavily influenced by thermodynamic effects. Isolating thermodynamic and mobility effects is useful to understand the significant driving forces for mass transport through porous materials and their selective characteristics. However, experimental techniques are limited in probing this behaviour at the nanometre scale. In response to experimental challenges, the present study makes extensive use of the ability of molecular simulations to reflect the molecular character of nanoscale diffusion and identify equilibrium and transport properties individually. First, this work investigates diffusive mass transport inside a planar slit pore focusing on the influence of solid-fluid interactions, pore width, and fluid density. The influence of solid-fluid interactions, in particular, have often been neglected in studies of mass transport in porous solids. The vast variety of functionalised nano-materials is virtually endless and has spurred interest in this area. Equilibrium simulations were employed to determine self- and collective diffusivities and Grand Canonical insertions were used for the determination of thermodynamic factors. In addition, this work showcases the implementation of a highly efficient Non-Equilibrium Molecular Dynamics (NEMD) method through which effective transport was studied. The method was used to determine effective diffusivities which incorporate thermodynamic effects, the dominating contribution to transport for dense fluids. It is well suited to observe effective fluid transport in confined spaces as opposed to measuring self-diffusion, a measure for single-particle mobility only. The method is effective in studying mass transport in model systems as well as more realistic, complex geometries. As a second exemplary case, gas permeation through an atomistically detailed model of a high free-volume polymer was simulated explicitly with the NEMD approach. In addition to determining permeability and solubility directly from NEMD simulations, the results also shed light on the permeation mechanism of the penetrant gases, suggesting a departure from the expected pore-hopping mechanism due to the considerable accessibility of permeation paths.
29

Food industry supply chain planning with product quality indicators

Mehdizadeh, Ali January 2014 (has links)
Quantitative supply chain modelling has contributed substantially to a number of fields, such as the automotive industry, logistics and computer hardware. The inherent methods and optimisation techniques could also be explored in relation to the food industry in order to offer potential benefits. One of the major issues of the food industry is to overcome supply seasonality and on-shelf demand. On the shelf demand is the consumer's in store demand which could also be seasonal. Objective of this work is to add flexibility to seasonal products (i.e. soup) in order to meet the on-shelf demand. In order to achieve this, a preparation process is introduced and integrated into the manufacturing system. This process increases the shelf-life of raw materials before starting the production process. This process, however, affects the quality of fresh raw materials and requires energy. Therefore, a supply chain model is developed, which is based on the link between the quality of the raw material and the processing conditions, which have an effect on the process' energy consumption and on the overall product quality. It is challenging to quantify the quality by looking at the processing conditions (degrees of freedom) and by linking it with energy in order to control and optimise the quality and energy consumption for each product. The degrees of freedom are defined differently for each process and state. Therefore, the developed model could be applied to all states and processes in order to generate an optimum solution. Moreover, based on the developed model, we have determined key factors in the whole chain, which are most likely to affect the product quality and consequently overall demand. There are two main quality indicator classes to be optimised, which are both considered in the model: static and time dependent indicators. Also, this work considers three different preparation processes - the air-dry, freeze-dry and freezing process - in order to increase the shelf-life of fresh raw materials and to add flexibility to them. A model based on the interrelationship between the quality and the processing conditions has been developed. This new methodology simplifies and enables the model to find the optimum processing conditions in order to obtain optimum quality across all quality indicators, whilst ensuring minimum energy consumption. This model is later integrated into the supply chain system, where it generates optimum solutions, which are then fed into the supply chain model. The supply chain model optimises the quality in terms of customer satisfaction, energy consumption and wastage of the system linked to environmental issues, and cost, so that the final products are more economical. In this system, both the manufacturing and inventory systems are optimised. This model is later implemented with a real world industrial case study (provided by the industrial collaborator). Two case studies are considered (soya milk and soup) and interestingly enough only one of them (soup) corresponds with this model. The advantage of this model is that it compares the two systems and then establishes which system generates an optimum end product.
30

Development of coarse-grained force fields from a molecular based equation of state for thermodynamic and structural properties of complex fluids

Lobanova, Olga January 2014 (has links)
In spite of the vast array of modelling techniques and force fields available, the study of the phase behaviour, structure, microstructure, and dynamics of mixtures remains a challenging task. A systematic coarse-graining (CG) methodology is employed in this thesis involving the parameterisation of force fields using a top-down approach, by effectively describing a large number of target macroscopic thermodynamic states with a rigorous molecular-based equation of state. A recent incarnation of the Statistical Associating Fluid Theory (SAFT-gamma) is used. The underlying force field is based on the Mie intermolecular potential, which is a generalised form of the Lennard-Jones potential with a variable and versatile form of the repulsive and attractive interactions. The coarse-grained force fields developed in this manner are used directly in Molecular Dynamics simulations in order to explore the dynamical, structural, and interfacial properties, which can not be directly accessed by the equation of state (unless a suitable treatment of the inhomogenous properties of the system is made). The goal of any coarse-graining procedure is to derive simple, but accurate, robust, and transferable force fields. By aiming for the simplicity, the coarse-grained models developed in our work are typically based on the three-to-one mapping, i.e., one bead containing approximately three heavy atoms, or one-to-one mapping for the small spherical molecules, with the polar, directional, and long-ranged interactions between the beads treated implicitly using the effective spherically-symmetric Mie potentials. The SAFT-gamma Mie coarse-graining methodology is exemplified for a number of fluid systems of different complexities, including pure component systems, such as: the homologous series of n-alkanes, n-perfluoroalkanes, semifluorinated alkanes, ethers and water; binary and ternary mixtures, comprising the carbon dioxide, n-alkanes, and water; and finally the aqueous mixtures of alkyl polyoxyethylene glycol non-ionic surfactants. An accurate representation of the vapour-liquid properties with both, the equation of state and molecular simulation, is obtained for the molecules of different size and chemical nature. Describing the properties of water is, however, a much more difficult task. The CG model suffers from issues associated with the transferability and representability of the various properties for different thermodynamic conditions, as a consequence of the aggressive averaging of the strongly directional and polar forces into an effective spherically symmetrical potential. It has been shown that an isotropic single-site CG model based on a spherically symmetrical potential cannot capture all of the thermodynamic properties of water simultaneously (the issue of representability). Two different CG models of water are proposed: the first is designed to accurately reproduce the saturation liquid density and vapour pressure, and the second to capture the saturation liquid density and surface tension with high precision. Both models benefit from an accurate parameterisation of temperature dependence following the target properties over the entire temperature range of the fluid. An additional model is developed based on the two-to-one mapping, enabling more efficient large scale simulations in, for example, biomolecular systems. The models of the binary mixtures are developed by using the corresponding pure component models with an additional adjustable parameter to account for the unlike interactions; the latter are obtained by considering appropriate properties of the mixtures such as the fluid-phase equilibria or the thermodynamic properties of mixing. The unlike interactions are shown to be transferable for a quantitative description of the phase behaviour over a wide range of conditions and for the systems of related components. We are able to obtain an accurate prediction of the azeotropic point, critical loci, tree phase line, global density, and the shape of phase envelopes for studied mixtures. The quality of predictions is found comparable to the results from the atomistic models and other equations of state. The aqueous mixtures of alkyl polyoxyethylene glycol non-ionic surfactants are a key final goal of the research presented in this thesis. The CG models of the surfactants are developed within the SAFT-gamma group-contribution framework, where each functional group is derived from an accurate representation of the corresponding chemical moiety. By capturing a delicate interplay of the repulsive and attractive intermolecular interactions and obtaining the right balance between energetic and entropic effects, the various phase morphologies at ambient conditions can be reproduced in agreement with the experimental findings over the entire concentration range. The force fields developed in the current work allow for a prediction of key structural and interfacial properties. The Molecular Dynamics simulations reveal the spontaneous formation of micelles at low surfactant concentrations and a self-assembly into a bilayer at high surfactant concentrations. The aggregation numbers, the critical micelle concentration, area per molecule, the surface excess properties, and bilayer thickness are found in very good agreement with experimental data. This is very encouraging considering that only macroscopic thermophysical properties are used to develop the underlying force fields that describe the fine interactions between the molecules in the system. Despite the simplicity, coarse-grained force fields are shown to be robust and transferable; they can be applied to predict the properties which were not used in the original parameterisation procedure, with an accuracy comparable to the more sophisticated and computationally demanding models.

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