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1
Asghari, Amir Kasra. "Microstructural engineering of cakes." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7757/.
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The objective of this thesis is to advance the current understanding of some pertinent formulation and processing interactions informing final cake microstructures. A primary concern is to understand how certain ingredients, fundamental to cake batter formation interact, to develop new methods and models for optimising and characterising these microstructures. The motivation of this work stems from the empirical methods still prevalent within cake research. However, an approach based on fundamental understanding of formulation and processing functions is necessary for both future innovation and eradication of some current challenges facing the cake baking industry. A bottom-up approach begins by exploring the interactions of key structural components; starch and protein within wet-foam systems with an objective of maximising foaming capacity and stability through focus on formulation design. Consequently, the structure of the model system is further developed to resemble a foam based cake in which the influence of formulation is evaluated through novel characterisation methods novel to this field of research. The work ultimately combines microstructure design, development and characterisation to maximise air retention within model cake systems.
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John, Unyime Edet. "Chemical performance of cement stabilised contaminated clay." Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/1453/.
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Urban demand has increased the need to redevelop contaminated land. New legislation for land management has actively discouraged previously acceptable dig and dump practices. This has encouraged in-situ remediation approaches, for which stabilisation / solidification (S/S) is particularly suitable for treating metal contamination. However, concerns over long-term effectiveness and durability of S/S needs to addressed, because contamination is contained but not removed. This requires effective chemical assessments to inform design. This study aims to design a suitable method for assessing S/S effectiveness, using a holistic risk based approach, for use during performance based S/S design. The processes that induce containment were evaluated, by assessing the solubility controlling mechanisms, and undertaking geochemical speciation modelling, to determine solubility controlling minerals. These findings can be used at the design stage to engineer S/S application to particular sites, and ensure long-term performance with minimal risk. Evaluations for structural master species (Al, Si, and Ca) and contaminants (Zn\(^2\)\(^+\), Cr\(^3\)\(^+\)) in cement stabilised contaminated kaolin were undertaken. The influences of common soil components (Humic acid and sodium sulphate), and increasing hydration durations were also assessed, to inform containment effectiveness and chemical durability. Findings showed that the assessment method was suitable for chemical characterisation of stabilised matrices, as a tool for informing design and application.
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Chen, Jay-San. "Standardisation of flexure testing of engineering ceramics." Thesis, University of Warwick, 2000. http://wrap.warwick.ac.uk/67042/.
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With the increase in usage of engineering ceramics, a new industrial standard is required in order to evaluate its properties and to perform a fair and just trade. The thesis investigates the faults and omissions of existing work and judges today's requirements thereby constructing a framework with which today's and future standards in flexure testing can be based. The draft standard presented in this thesis covers the three major testing methods for determining the biaxial flexural strength (modulus of rupture) of engineering ceramics. The ring-on-ring, ball-on-ring, and 4-Ball test fixtures were all adopted as standard, since it is known that each of these systems is suited for a particular application and each has different advantages and disadvantages. The three major biaxial test methods prescribed in this draft standard have been devised so that more consistent and accurate test results can be obtained. However, the uncertainty of measurement in flexure testing always exists and needs to be estimated. The estimation of uncertainty in flexure testing in this study is based on the methodology provided in the ISO Guide to the expression of uncertainty in measurement. The results of the estimation showed that the uncertainty in measurement for the biaxial flexure test standard proposed in this thesis is very low compared to the inherent variability of the strength of ceramic materials. It was also found that the applied load, thickness of the disc plate, and random effects are the three major components contributing to the overall uncertainty. The total uncertainty of measurement in biaxial flexure testing can be significantly minimised by the reduction of the uncertainty contributed from these components, especially from random effects.
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Chitez, Adriana. "Coupled thermo-hygro-chemical modelling of self-healing processes in cementitious materials." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/70906/.
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This thesis presents details of a numerical programme of study on the themo-hygrochemical (THC) processes occurring during the self-healing of cementitious materials. A comprehensive THC model, which is mechanistic in nature, is proposed and implemented in the framework of the finite element method. The aim of this model is to develop a useful computational tool that is capable of realistically predicting damage recovery in terms of the crack filling observed under specific environmental conditions. The early age and long term behaviour of the cementitious materials is simulated by solving a boundary value problem which couples moisture-temperature-ion transport mechanisms by means of mass and enthalpy balance equations. The model assumes that all the transport processes occur at the capillary pore level and that the selfhealing is driven by ongoing hydration. In this context, attention is focused on developing an innovative microstructural model that can predict the quantitative evolution of the capillary porosity. The microstructural model is based on an existing colloidal classification of the water forms present in the clinker hydrates, on hydration kinetics principles and on the stoichiometry of the Portland cement. The effect of the aggregate absorption on the capillary porosity is also examined. Firstly, the adopted theoretical considerations regarding the transport of moisture and temperature in cement-based materials are validated by comparing the numerical findings of the TH component with the reported results of three different sets of drying experiments. Then the THC model is applied to the simulation of a crack recovery experiment undertaken at Cardiff University. In both cases the proposed model was found to capture the essential characteristics of the thermo-hygro-chemical behaviour of cementitious materials.
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Smith, Gregory K. "Simulations of chemical catalysis." Thesis, The University of New Mexico, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3612623.
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This dissertation contains simulations of chemical catalysis in both biological and heterogeneous contexts. A mixture of classical, quantum, and hybrid techniques are applied to explore the energy profiles and compare possible chemical mechanisms both within the context of human and bacterial enzymes, as well as exploring surface reactions on a metal catalyst. A brief summary of each project follows.
Project 1 - Bacterial Enzyme SpvC
The newly discovered SpvC effector protein from Salmonella typhimurium interferes with the host immune response by dephosphorylating mitogen-activated protein kinases (MAPKs) with a β-elimination mechanism. The dynamics of the enzyme substrate complex of the SpvC effector is investigated with a 3.2 ns molecular dynamics simulation, which reveals that the phosphorylated peptide substrate is tightly held in the active site by a hydrogen bond network and the lysine general base is positioned for the abstraction of the alpha hydrogen. The catalysis is further modeled with density functional theory (DFT) in a truncated active-site model at the B3LYP/6-31 G(d,p) level of theory. The truncated model suggested the reaction proceeds via a single transition state. After including the enzyme environment in ab initio QM/MM studies, it was found to proceed via an E1cB-like pathway, in which the carbanion intermediate is stabilized by an enzyme oxyanion hole provided by Lys104 and Tyr158 of SpvC.
Project 2 - Human Enzyme CDK2
Phosphorylation reactions catalyzed by kinases and phosphatases play an indispensable role in cellular signaling, and their malfunctioning is implicated in many diseases. Ab initio quantum mechanical/molecular mechanical studies are reported for the phosphoryl transfer reaction catalyzed by a cyclin-dependent kinase, CDK2. Our results suggest that an active-site Asp residue, rather than ATP as previously proposed, serves as the general base to activate the Ser nucleophile. The corresponding transition state features a dissociative, metaphosphate-like structure, stabilized by the Mg(II) ion and several hydrogen bonds. The calculated free-energy barrier is consistent with experimental values.
Project 3 - Bacterial Enzyme Anthrax Lethal Factor
In this dissertation, we report a hybrid quantum mechanical and molecular mechanical study of the catalysis of anthrax lethal factor, an important first step in designing inhibitors to help treat this powerful bacterial toxin. The calculations suggest that the zinc peptidase uses the same general base-general acid mechanism as in thermolysin and carboxypeptidase A, in which a zinc-bound water is activated by Glu687 to nucleophilically attack the scissile carbonyl carbon in the substrate. The catalysis is aided by an oxyanion hole formed by the zinc ion and the side chain of Tyr728, which provide stabilization for the fractionally charged carbonyl oxygen.
Project 4 - Methanol Steam Reforming on PdZn alloy
Recent experiments suggested that PdZn alloy on ZnO support is a very active and selective catalyst for methanol steam reforming (MSR). Plane-wave density functional theory calculations were carried out on the initial steps of MSR on both PdZn and ZnO surfaces. Our calculations indicate that the dissociation of both methanol and water is highly activated on flat surfaces of PdZn such as (111) and (100), while the dissociation barriers can be lowered significantly by surface defects, represented here by the (221), (110), and (321) faces of PdZn. The corresponding processes on the polar Zn-terminated ZnO(0001) surfaces are found to have low or null barriers. Implications of these results for both MSR and low temperature mechanisms are discussed.
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Masum, Shakil Al. "Modelling of reactive gas transport in unsaturated soil : a coupled thermo-hydro-chemical-mechanical approach." Thesis, Cardiff University, 2012. http://orca.cf.ac.uk/38159/.
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This thesis presents the development of a reactive gas transport equation under coupled framework of thermal, hydraulic, chemical and mechanical (THCM) behaviour of variably saturated soil. The capabilities of theoretical and numerical modelling of THCM processes have been advanced by the successful implementation of various aspects of the new addition. The previously developed THCM model at the Geoenvironmental Research Centre (GRC) has been extended to include the multicomponent gas transport modelling coupled with chemical/geochemical processes. The mechanisms of advection and diffusion have been considered to define the transport of multicomponent gas and chemicals in respective phases as well as exchange via dissolution and exsolution. The governing mass transfer process is subjected to homogeneous and heterogeneous geochemical reactions under equilibrium condition. Numerical solutions of the governing flow and deformation equations have been achieved by employing finite element method for spatial discretisation and finite difference method for temporal discretisation. Advanced geochemical features of gas-chemical interactions have been incorporated in the transport model, COMPASS by coupling with the geochemical model PHREEQC. A sequential non-iterative approach has been adopted to couple the transport processes and geochemical interactions. Verification of various aspects of the developed gas transfer equation has been commenced via a number of simulation exercises. Good agreement between the results have been achieved which suggests accurate and successful implementation of the theoretical and numerical formulation. The model has been implemented to investigate the gas transport processes in variably saturated compacted clay buffers via a number of conceptual simulation scenarios which are representative of high level nuclear waste disposal. Simulation of gas migration through saturated buffer has been intended to investigate the maximum pressure development as well as the dominant flow mechanisms. Demonstration of the modelling capability in context of reactive gas transport has been carried out considering long term isothermal flow of hydrogen through unsaturated clay buffer. The conclusions drawn from the discussions of simulation results has favoured the understanding of some of the key issues associated with gas generation and migration in compacted porous media, particularly, as a case of high level nuclear waste disposal.
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Hindley, Sarah. "Atomic layer deposition and metal organic chemical vapour deposition of materials for photovoltaic applications." Thesis, University of Liverpool, 2014. http://livrepository.liverpool.ac.uk/16313/.
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In this thesis, the development of thin films and nanostructures prepared with chemical vapour techniques are investigated for applications in photovoltaics. The deposition of both p-type and n-type oxides are investigated as a means of preparing all oxide p-n junctions. Both CVD and ALD precursors and processes have been developed. Zinc oxide nanowires are of interest as an n-type absorber layer with high surface area. In this thesis, the crystal structures of DEZn and DMZn were revisited and a new understanding of conventional zinc CVD precursors is presented. For DEZn a single structure was isolated and characterised with single crystal XRD. In the case of DMZn two temperature dependant structures were identified: namely α and β at 200K and 150K respectively. The DMZn precursor was subsequently exploited in a series of adduct-based precursors of the notation [DMZn.L] (where L = 1,2-dimethoxyethane, 1,4-dioxane and 1,4-thioxane). The crystal structures of these precursors were determined, and they were subsequently used to grow ZnO and sulphur doped ZnO across a range of CVD growth conditions. The microstructure and electronic properties of the nanowires have been characterised with electron microscopy, x-ray diffraction, Raman spectroscopy and photoluminescence. The II:VI ratio and substrate temperatures were both confirmed as playing a significant role in determining the microstructure of the nanowires. It has been demonstrated that the use of [DMZn.L] can avoid the pre-reaction between DMZn and oxygen. The studies with the thioxane adduct suggests the involvement of the ligand and hence sulphur incorporation in the nanowires. Two copper precursors were selected as the basis of p-type copper oxide film studies. The first Cu(hfac)(COD) has been used previously to deposit copper oxide by conventional CVD. In this thesis it is demonstrated for the first time that a pulsed LI-ALD approach can be exploited to deposit CuO with ozone as the co-reagent. An unexpected outcome of the research was the successful growth of electrically conductive copper metal films with a sheet resistance of 0.83Ω/□ when the precursor was thermally decomposed. The second copper precursor, namely CpCu(tBuNC) was used in atomic layer deposition to successfully deposit CuO or Cu2O with oxygen plasma and water respectively. Having identified that the β-diketonate compound yielded copper, the cyclopentadienyl based precursor was investigated as a route for the deposition of conductive copper metal films. Both thermal decomposition and a hydrogen plasma ALD process have been shown to deposit copper. With the plasma process, deposition of copper was demonstrated as low as 75˚C with a sheet resistance of only 0.55Ω/□. This thesis has demonstrated novel deposition routes for p- and n-type oxide materials which have potential future applications in thin film or nanostructured photovoltaic technology.
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Tang, Yiping. "A study of fluid behavior by a general analytical solution of the Ornstein-Zernike equation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq26141.pdf.
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Parrilla, Gutierrez Juan Manuel. "Investigating automated chemical evolution of oil-in-water droplets." Thesis, University of Glasgow, 2016. http://theses.gla.ac.uk/7744/.
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One of the main unresolved questions in science is how non-living matter became alive in a process known as abiognesis, which aims to explain how from a primordial soup scenario containing simple molecules, by following a ``bottom up'' approach, complex biomolecules emerged forming the first living system, known as a protocell. A protocell is defined by the interplay of three sub-systems which are considered requirements for life: information molecules, metabolism, and compartmentalization. This thesis investigates the role of compartmentalization during the emergence of life, and how simple membrane aggregates could evolve into entities that were able to develop ``life-like'' behaviours, and in particular how such evolution could happen without the presence of information molecules. Our ultimate objective is to create an autonomous evolvable system, and in order tp do so we will try to engineer life following a ``top-down'' approach, where an initial platform capable of evolving chemistry will be constructed, but the chemistry being dependent on the robotic adjunct, and how then this platform can be de-constructed in iterative operations until it is fully disconnected from the evolvable system, the system then being inherently autonomous. The first project of this thesis describes how the initial platform was designed and built. The platform was based on the model of a standard liquid handling robot, with the main difference with respect to other similar robots being that we used a 3D-printer in order to prototype the robot and build its main equipment, like a liquid dispensing system, tool movement mechanism, and washing procedures. The robot was able to mix different components and create populations of droplets in a Petri dish filled with aqueous phase. The Petri dish was then observed by a camera, which analysed the behaviours described by the droplets and fed this information back to the robot. Using this loop, the robot was then able to implement an evolutionary algorithm, where populations of droplets were evolved towards defined life-like behaviours. The second project of this thesis aimed to remove as many mechanical parts as possible from the robot while keeping the evolvable chemistry intact. In order to do so, we encapsulated the functionalities of the previous liquid handling robot into a single monolithic 3D-printed device. This device was able to mix different components, generate populations of droplets in an aqueous phase, and was also equipped with a camera in order to analyse the experiments. Moreover, because the full fabrication process of the devices happened in a 3D-printer, we were also able to alter its experimental arena by adding different obstacles where to evolve the droplets, enabling us to study how environmental changes can shape evolution. By doing so, we were able to embody evolutionary characteristics into our device, removing constraints from the physical platform, and taking one step forward to a possible autonomous evolvable system.
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Chippendale, Richard. "Modelling of the thermal chemical damage caused to carbon fibre composites." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/361708/.
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Previous investigations relating to lightning strike damage of Carbon Fibre Composites (CFC), have assumed that the energy input from a lightning strike is caused by the resistive (Joule) heating due to the current injection and the thermal heat ux from the plasma channel. Inherent within this statement, is the assumption that CFCs can be regarded as a perfect resistor. The validity of such an assumption has been experimentally investigated within this thesis. This experimental study has concluded that a typical quasi-isotropic CFC panel can be treated as a perfect resistor up to a frequency of at least 10kHz. By considering the frequency components within a lightning strike current impulse, it is evident that the current impulse leads predominately to Joule heating. This thesis has experimentally investigated the damage caused to samples of CFC, due to the different current impulse components, which make up a lightning strike. The results from this experiment have shown that the observed damage on the surface is different for each of the different types of current impulse. Furthermore, the damage caused to each sample indicates that, despite masking only the area of interest, the wandering arc on the surface stills plays an important role in distributing the energy input into the CFC and hence the observed damage. Regardless of the different surface damage caused by the different current impulses, the resultant damage from each component current impulse shows polymer degradation with fracturing and lifting up of the carbon fibres. This thesis has then attempted to numerically investigate the physical processes which lead to this lightning strike damage. Within the current state of the art knowledge there is no proposed method to numerically represent the lightning strike arc attachment and the subsequent arc wandering. Therefore, as arc wandering plays an important role in causing the observed damage, it is not possible to numerically model the lightning strike damage. An analogous damage mechanism is therefore needed so the lighting strike damage processes can be numerically investigated. This thesis has demonstrated that damage caused by laser ablation, represents a similar set of physical processes, to those which cause the lightning strike current impulse damage, albeit without any additional electrical processes. Within the numerical model, the CFC is numerically represented through a homogenisation approach and so the relevance and accuracy of a series of analytical methods for predicting the bulk thermal and electrical conductivity for use with CFCs have been investigated. This study has shown that the electrical conductivity is dominated by the percolation effects due to the fibre to fibre contacts. Due to the more comparable thermal conductivity between the polymer and the fibres, the bulk thermal conductivity is accurately predicted by an extension of the Eshelby Method. This extension allows the bulk conductivity of a composite system with more than two composite components to be calculated. Having developed a bespoke thermo-chemical degradation model, a series of validation studies have been conducted. First, the homogenisation approach is validated by numerically investigating the electrical conduction through a two layer panel of CFC. These numerical predictions showed initially unexpected current ow patterns. These predictions have been validated through an experimental study, which in turn validates the application of the homogenisation approach. The novelty within the proposed model is the inclusion of the transport of produced gasses through the decomposing material. The thermo-chemical degradation model predicts that the internal gas pressure inside the decomposing material can reach 3 orders of magnitude greater than that of atmospheric pressure. This explains the de-laminations and fibre cracking observed within the laser ablated damage samples. The numerical predictions show that the inclusion of thermal gas transport has minimal impact on the predicted thermal chemical damage. The numerical predictions have further been validated against the previously obtained laser ablation results. The predicted polymer degradation shows reasonable agreement with the experimentally observed ablation damage. This along with the previous discussions has validated the physical processes implemented within the thermo-chemical degradation model to investigate the thermal chemical lightning strike damage.
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Howell, Bill. "Physical and chemical aspects of the solvent extraction of uranium by a tertiary amine." Thesis, University of Ottawa (Canada), 1986. http://hdl.handle.net/10393/4574.
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LLoyd-Evans, Nellie. "Studies on the survival and chemical disinfection of human rotavirus (Wa) on inanimate surfaces." Thesis, University of Ottawa (Canada), 1986. http://hdl.handle.net/10393/4711.
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Moheb, Ahmad. "A general study of electrodialysis processes in a cell fitted with an organic membrane." Thesis, Imperial College London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266498.
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Hasan, Muhammad Sami. "Phosphate glass fibre reinforced composite for bone repair applications : investigation of interfacial integrity improvements via chemical treatments." Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/12777/.
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Bone repair devices made from degradable polymers, such as poly lactic acid (PLA) have limitation in terms of matching the mechanical property requirements for bone repair, both initially and for the duration of repair. For this reason the use of totally degradable phosphate glass fibre (PGF) reinforced PLA composite has proved attractive. A crucial part of the success of such implants is maintenance of interfacial integrity between the polymer matrix and reinforcement phases of the composite. It is well known that most fibre reinforced composites loose 50% or more of their strength due to interfacial integrity loss. In this study candidate chemical treatments for PGF reinforced PLA composite are being investigated in terms of their reactability, biocompatibility, effect on interfacial mechanical properties and degradation behaviour of these composites. As a crucial part of this project, phosphate based glass (PBG) formulations were devised and assessed for structural, thermal, degradation and cytocompatibility variations with varying P2O5 or Fe2O3 content. Selected formulations were drawn into fibres and tested for single fibre tensile strength. Finally, a glass formulation (P45Ca16Mg24Na11Fe4, number indicates percentage molar concentration of oxides) was selected for surface modification and composite production. Chemical surface treatments were selected on the basis of potential to react with PBG and PLA. Mode of chemical interaction between PBG and surface treatments chemicals were analysed using surface analyses techniques (FTIR and XPS). It was found that aminopropyltriethoxy silane (APS), etidronic acid (EA) and hexamethylene diisocyanate (HDI) were linked through covalent bonds, other agents making hydrogen bonds with PBG. Chemical treatments were optimised and investigated for their effect on interfacial shear strength (IFSS) between polymer/glass, wettability and degradation behaviour. Chemically treated PBG was also assessed for cytocompatibility of elution products, short–term direct contact with MG63 osteosarcoma and long term direct contact with primary human osteoblasts. All selected surface treatment chemicals except amino phosphonic acid (APA) improved the interfacial bond between PBG and PLA. However, the covalently linked agents (HDI, APS and EA) saw up to 4–fold improvement in IFSS. SPLA also improved the IFSS significantly, which was attributed to the presence of several –OH groups. There was no significant effect on degradation rate of PBG. All agents demonstrated acceptable cytocompatibility for their elution products and in direct contact. Selected chemicals (APS, EA, SPLA and HDI) were investigated further in PGF reinforced PLA composite. PGF mats (UD or non–woven), treated with surface treatment chemical were sandwich–pressed between PLA sheets. Flexural mechanical properties with degradation, water–uptake, degradation rate and cytocompatibility were tested. It was found that surface chemical treatment improved the initial flexural properties (APS, SPLA) and/or delayed the mechanical integrity loss (HDI, APS), latter was attributed to the reduced water–uptake and maintenance of relatively strong interface. Human osteoblasts were found to perform normal functions when cultured on prepared composites.
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Panjapornpon, Chanin Soroush Masoud. "Model-based controller design for general nonlinear processes /." Philadelphia, Pa. : Drexel University, 2005. http://dspace.library.drexel.edu/handle/1860/611.
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Holavanhalli, Jayatirtha. "Growth and characterization of ZnSe on GaAs and Si substrates using organic chemical vapour deposition technique." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=55608.
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Elhag, Faisal Abdalla. "Density-damage relationships and chemical control of the Northern corn rootworm, Diabrotica barberi (Coleoptera : Chrysomelidae), in Quebec." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74045.
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Finstad, Casey Charles. "Gas phase surface preparation and activation of silicon using ultraviolet activated chemistries." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/280695.
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Microelectronic devices have been scaled down to the point where lateral dimensions are on the order of a hundred atoms and a film thicknesses might be less than ten atoms. This makes surface preparation an increasingly important part of the fabrication process. The atoms and molecules terminating surfaces between processing steps are now a relatively large fraction of the overall film thickness. These terminating monolayers have to function as passivation layers, diffusion barriers, and seed layers for subsequent thin film depositions. This work demonstrates that precise control of the atoms and molecules on a silicon surface can be achieved using gas phase processes. The Research Cluster Apparatus (RCA) was built with a reactor for oxide removal using hydrofluoric acid and water vapor (HF/vapor), and a reactor for the removal of metallic and organic contaminates using ultraviolet activated chlorine gas (UV-Cl₂). Both reactors were integrated via high vacuum with a surface analysis chamber so samples could be characterized without atmospheric exposure. The capabilities of the system were demonstrated by using an HF/vapor (100 Torr, 27°C, 200 s) and UV-Cl₂ (10 Torr Cl₂, 90°C, 15 min) sequence to remove a mixed oxide/fluorocarbon residue, characteristic of contamination generated by reactive ion etching (RIE). To demonstrate the metals removal capability, oxidized copper was cleaned from silicon. The UV-Cl₂ chemistry leaves the surface terminated with chlorine atoms, rather than hydrogen, promoting a deposition reaction with ammonia (1-1000 Torr, 75°C, 5-60 min) to produce a surface terminated with up to 0.3 monolayers of surface amine groups, as measured by XPS. The highly polar N-H bonds of surface amines can be used as a seed layer to promote nucleation of high-k dielectric films deposited on silicon using atomic layer deposition (ALD). To enhance the deposition of the amines, photolysis (λ < 217 nm) of gas phase ammonia (UV-NH₃) generated NH₂ photofragments that reacted with hydrogen terminated Si(100), saturating at up to 1.7 ML (10 Torr NH₃, 75°C, 35 mW/cm²). These processes help enable further miniaturization by adding another mechanism for atomic-level manipulation of surface properties to the nanotechnology toolbox.
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Zhang, Xiaohong. "Chemical mechanical polishing and grinding of silicon wafers." Diss., Manhattan, Kan. : Kansas State University, 2007. http://hdl.handle.net/2097/475.
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Ishola, A. "Advanced safety methodology for risk management of petroleum refinery operations." Thesis, Liverpool John Moores University, 2018. http://researchonline.ljmu.ac.uk/7984/.
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Petroleum refineries are important facilities for refining petroleum products that provide the primary source of energy for domestic and industrial consumption globally. Petroleum refinery operations provide significant contribution to global economic growth. Petroleum refineries are complex, multifaceted systems that perform multiple phase operations characterized by a high level of risk. Evidence based major accidents that have occurred within the last three decades in the petroleum refineries, around the world, indicates losses estimated in billions of US dollars. Many of these accidents are catastrophes, which have led to the disruption of petroleum refinery operations. These accidents have resulted in production loss, asset damage, environmental damage, fatalities and injuries. However, the foremost issue analysed in literatures in relation to major accidents in petroleum refineries, is the lack of robust risk assessment and resourceful risk management approaches to identify and assess major accident risks, in order to prevent or mitigate them from escalating to an accident. Thus, it is exceptionally critical to readdress the issue of petroleum refinery risk management with the development of a more dependable, adaptable and holistic risk modelling framework for major accident risks investigation. In this thesis, a proactive framework for advanced risk management to analyse and mitigate the disruption risks of petroleum refinery operations is presented. In this research, various risk elements and their attributes that can interact to cause the disruption of PRPU operations were identified and analysed, in order to determine their criticality levels. This thesis shows that the convergent effect of the interactions between the risk elements and their attributes can lead to the disruption of petroleum refinery operations. In the scheme of the study, Fuzzy Linguistic Preference Relation (FLPR), Fuzzy Evidential Reasoning (FER) and Fuzzy Bayesian Network (FBN) methodologies were proposed and implemented to evaluate the criticality of the risk elements and their attributes and to analyse the risk level of PRPU operations. Also, AHP-fuzzy VIKOR methodology was utilised for decision modelling to determine the optimal strategy for the risk management of the most significant risk elements’ attributes that can interact to cause the disruption of PRPU operations. The methodologies proposed and implemented in this research can be utilised in the petroleum refining industry, to analyse complex risk scenarios where there is incomplete information concerning risk events or where the probability of risk events is uncertain. The result of the analysis conducted in this research to determine the risk level of petroleum refinery operations can be utilised by risk assessors and decision makers as a threshold value for decision making in order to mitigate the disruption risk of PRPU operations. The decision strategies formulated in this thesis based on robust literature review and expert contributions, contributes to knowledge in terms of the risk management of petroleum refinery operations. The result of the evaluation and ranking of the risk elements and their attributes can provide salient risk information to duty holders and decision makers to improve their perceptions, in order to prioritise resources for risk management of the most critical attributes of the risk elements. Overall, the methodologies applied in this thesis, can be tailored to be utilised as a quantitative risk assessment tool, by risk managers and decision analysts in the petroleum refining industry for enhancement risk assessment processes where available information can sometimes be vague or incomplete for risk analysis.
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Glavan, Ana. "Chemical Approaches to the Surface Engineering of Paper and Cellulose-Based Materials for Microfluidics, Electronics and Low-Cost Diagnostics." Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:26718749.
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Paper (and other cellulose-based materials such as cotton thread and fabrics) are underexploited as materials for the construction of “high-tech” and “lab-on-a-chip” devices. One major drawback of paper is its tendency to absorb water from the environment and, with wetting, to change its mechanical properties; other challenges relate to control over the attachment of molecules (e.g. antibodies, DNA) and cells on its surface, and to the addition of electronic function. The goal of this thesis is to develop paper as a substrate for a range of applications— microfluidics, substrates for electronic systems and MEMS, low-cost diagnostics, cell biology, and optics. The approach involves chemically modifying the surface of the paper to provide new functions without altering any of its defining properties: mechanical flexibility, foldability, light weight, gas permeability, and low cost.
The first part of my thesis describes the modification of paper by silanization with organosilanes such as alkyl- and fluoroalkyl trichlorosilanes in the gas phase. Here, silanization is used to lower the surface free energy of the paper and to minimize the tendency of paper to absorb liquids and vapors, and especially water. Chapter 1 and Appendix 3 demonstrate that the combination of long fluoroalkyl chains of grafted siloxanes with the micro-scale roughness and porosity of paper yielded a material that is omniphobic (both hydrophobic and oleophobic), while preserving the properties of mechanical flexibility and low resistance to transport of gas of the untreated paper. Appendix 3 shows that features of omniphobic paper can be used to construct microtiter plates and liquid-filled gas sensors using standard paper folding techniques, while Appendix 4 shows that new type of microfluidic device fabricated by carving microchannels into the surface of omniphobic paper. The resulting devices have open, unobstructed channels (with dimensions as small as 45 μm) and thus exhibit fluid dynamics similar to conventional PDMS-based microfluidics, but are much lighter and have the potential to be much less expensive than PDMS-based devices.
The second part of my thesis is focused on engineering the surface of paper to enable efficient immobilization of capture and target molecules for bioanalysis. In one approach, described in Appendix 5, we exploit the ease with which the surface chemistry of paper (i.e. the surface of the cellulose fibers making up the paper) can be modified, in order to enhance the immobilization of antibodies and antigens on the surface of the paper via hydrophobic interactions, while preventing the wicking of the fluids into the paper substrate. As an application in low-cost diagnostics, we describe a low-cost electrochemical device for ELISA intended for use in resource-limited settings. In a second approach, described in Chapter 2, we developed of an efficient procedure for assembling microarrays of ssDNA and proteins on paper, at the lowest practical cost. This method starts with the synthesis of DNA oligonucleotides covalently linked to paper, and proceeds to generate ssDNA arrays that, through hybridization with complementary strands of DNA, are capable of simultaneously capturing DNA, DNA-conjugated protein antigens, and DNA-conjugated antibodies.
The third part of my thesis describes the simple, inexpensive fabrication of electrodes for paper-based electrochemical systems. A first method describes, in Appendix 6, the development of inkjet printing as a method for high resolution printing of conductive patterns on omniphobic “RF” paper, both to extend its promise as a substrate for paper electronics, and to enable us to integrate it into our program in low-cost, paper based diagnostics. A second method, described in Chapter 3, circumvents the need for printing, and instead focuses on the fabrication and reconfiguration of simple, versatile, and inexpensive electroanalytical devices in which conventional stainless-steel pins—in unmodified form or after coating with a carbon paste—are used as electrodes.Chemistry and Chemical Biology
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Malik, Nur Hafizah. "Microstructural development of high solid food systems during freeze-drying." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8664/.
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Freeze-drying is an energy demanding operation involving dehydration through sublimation of ice crystals. It has important application in the production of high quality dried food such as instant coffee. Correlating the operating conditions with product attributes is essential to design processes that are energy efficient whilst producing product of desired characteristics. In this study, microstructure development and evaluation for gum arabic and coffee solutions during freeze-drying have been considered. Freeze-drying processes were carried by varying the material’s concentration (20-60% w/w) and properties as well as freezing and primary drying conditions. Microstructural evaluation and reconstitution behaviour of freeze-dried solids were assessed using scanning electron microscopy, X-ray computed tomography and high resolution camera. Initially, water crystallization was studied under temperature oscillation, slow, fast and unidirectional freezing where large crystal dendrites developed on fluctuating temperature and different freezing rates produced comparable crystal network. At reduced water content, smaller crystals developed and distinct orientation of crystal growth was visible. Meanwhile, at increasing primary drying temperature and concentration, the freeze- dried systems showed extensive structure expansion. The potential of aeration to assist freeze-drying of high solid solutions is demonstrated by improved structure uniformity and porosity. Reconstitution of the freeze-dried solids was influenced by the microstructure generated and physical mechanisms involved during dissolution. High porosity and presence of large pores enable rapid dissolution of the dried solids. Different dissolution mechanisms between gum arabic and coffee had strong impact on the kinetics of dissolution. The concept of process-microstructure-property relationship is thus very clear in this study.
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Sandells, Jamie Ian. "Mathematical modelling of planar solid oxide fuel cells." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/4908/.
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In this thesis we construct a series of mathematical models from first principles to examine the advection, diffusion and reactions of species within a planar Solid Oxide Fuel Cell (SOFC). We reduce the complexity of an SOFC to flow and reaction across a flat, impermeable plate and begin by establishing a simplistic model for the incompressible, isothermal flow and reaction of hydrogen. Throughout the thesis we seek to extend this initial model by adding appropriate levels of complexity such as alternative fuels, compressibility and thermal effects. In establishing solutions to these models we use a series of analytical techniques. We adopt the concept of boundary-layer flow and self similarity to simplify the model equations into a form where we can obtain analytical and efficient numerical solutions. We also utilise asymptotics to examine and validate the model around regions of singularities within the flow. Within each model we have examined the electrical performance of the cell and in some cases we have validated these results with existing experimental data.
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Liu, Li. "Computational fluid dynamics modelling of complex fluid flow in stirred vessels." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/4753/.
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Fluid mixing in stirred vessels is widely encountered in a number of industries. In this work, different experimental techniques and the CFD modelling approach are used to measure the mixing of a wide range of fluids in stirred vessels. As the detailed validation is essential for CFD modelling, CFD predictions are compared in detail with different experimental measurements. The capability of CFD modelling of the 3D spatial distribution of velocity and solid concentration within opaque concentrated solid-liquid suspensions with the mean solid concentration up to 40 wt% is assessed by comparing with the experimental data obtained from positron emission particle tracking (PEPT) measurements. Because the impeller configuration is of significant importance to the flow pattern, the performance of different impellers for single-phase mixing of Newtonian and non-Newtonian fluids in stirred vessels is compared. CFD predictions of flow fields generated from different impellers are compared with those measured by the well-established particle image velocimetry (PIV) technique. The capability of CFD modelling of different mixing features of non-Newtonian fluids in stirred vessels are verified by comparing with experimental data obtained from PIV, PEPT, and planar laser induced fluorescence (PLIF) measurements.
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Day, George. "The immobilisation of Caesium and Strontium from nuclear waste captured by IONSIV." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8206/.
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A previous study revealed Cs_2TiNb_6O_1_8 to be the major Cs-containing phase after hot isostatic pressing Cs-loaded IONSIV (a commercial exchanger) which demonstrated excellent wasteform properties. Both experimental and theoretical studies have been carried out in order to assess if Cs_2TiNb_6O_1_8 is able to retain ^1^3^7Ba^2^+, the transmutation product of ^1^3^7Cs^+. A series of samples with different charge compensation mechanisms have been synthesised including Cs_2_-_xBa_xTi^(^4^+^)_1_+_xNb^(^5^+^)_6_-_xO_1_8, Cs_2_-_xBa_xTi^(^3^+^)_xTi^(^4^+^)_1_-_xNb_6O_1_8 and Cs_2_-_xBa_xTiNb^(^4^+^)_xNb^(^5^+^)_6_-_xO_1_8. Analysis suggested that Ba incorporation was not successful because of the identification of Ba impurities in the X-ray diffraction patterns. A series of atomistic simulations have also been performed to support the experimental work, using the General Utility Lattice Program code which suggested that Ba incorporation is not energetically favourable. Sr-loaded IOSNIV has also been thermally converted via calcination (in air) and hot isostatic pressing. The removal and immobilisation of Sr is an important process on account of ^9^0Sr being one of the more problematic radionuclides produced from the fission process. Both thermal conversion methods produced crystalline phase assembles which were analysed by X-ray diffraction, X-ray fluorescence and microscopy studies. The HIPed materials performed well in aqueous durability tests, suggesting these wasteforms will be suitable for final disposal in a geological disposal facility.
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Chen, Ziyu. "The crystallization of poly(ethylene terephthalate) studied by thermal analysis and FTIR spectroscopy." Thesis, University of Birmingham, 2013. http://etheses.bham.ac.uk//id/eprint/4251/.
Full textAbstract:
This thesis concerns the thermal behaviour and properties, isothermal crystallization kinetics and seeded crystallization study of Poly (ethylene terephthalate) (PET) using thermal analysis Fourier transform infrared (TA-FTIR), two-dimensional infrared correlation spectroscopy (2D-FTIR) and differential scanning calorimetry (DSC). TA-FTIR has been used to characterize phase transitions by a change in the absorbance or peak position with temperature in thermal cycling. It assigns the phase transition temperature to an individual chain segment and observes two different types of thermal behaviours of the functional groups. FTIR finds out that the carbonyl stretching band has an amorphous band and a crystalline band following by analysis of 2D-FTIR. The isothermal crystallization kinetics of PET was measured from 230 to 240\(^o\)C by FTIR focusing on carbonyl ester group. The deconvolution of these two overlapping absorption bands analyzes the kinetics of both primary and secondary crystallization by Avrami equations. Melting behaviour study on DSC observes crystallinity, melting temperature and calculated lamellae thickness of PET increase with the extending time period of isothermal crystallization in secondary process. Seeded crystallization crystallizes polymers at higher temperatures to produce greater lamellae thicknesses and higher melting temperature and to discuss the effect of this morphology on their mechanical and physical properties.
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Liu, Yinzhe. "Low melting point alkali metal borohydride mixtures for hydrogen storage." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8447/.
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With relatively high gravimetric and volumetric hydrogen capacities and low hydrogen operating pressures, borohydrides are being investigated for their potential use as solid-state hydrogen storage media. This work focuses on investigating the hydrogen sorption mechanisms for \(LiBH_4\)-based low-melting-point borohydride mixtures (e.g. \(0.62LiBH_4\)-\(0.38NaBH_4\), \(0.75LiBH_4\)-\(0.25KBH_4\)), and their destabilized systems using selected additives. Solid solutions and bimetallic borohydride are found in the as-prepared \(0.62LiBH_4\)-\(0.38NaBH_4\) and \(0.75LiBH_4\)-\(0.25KBH\) mixtures, respectively. Under Ar, the \(0.62LiBH_4\)-\(0.38NaBH_4\) mixture releases 10.8 wt.% of hydrogen at 650 °C; whilst the \(0.75LiBH_4\)-\(0.25KBH_4\) mixture releases 8.9 wt.% of hydrogen at 700 °C. Their dehydrogenation peak temperatures are strongly affected by Na+ or K+ and therefore higher than \(LiBH_4\). These mixtures have poor cycling stabilities. Additives, such as micron-sized \(SiO_2\) and nano-sized Ni, cannot affect their melting points; but they cause lower dehydrogenation temperatures, decrease the hydrogen evolution, and facilitate the formation of metal dodecaborates. Besides, the addition of nano-sized Ni cannot significantly improve the cycling stability; however, it leads to partial reversible \(LiBH_4\). Therefore, a further compositional optimization with respect to the rehydrogenation conditions, in parallel with the use of nano-confinement of the mixture via an infiltration approach, is needed before practical use of a low-melting-point alkali metal borohydride mixture.
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Wong, Yuen Mei. "Optimising the plastic optical fibre evanescent field biofilm sensor." Thesis, Liverpool John Moores University, 2008. http://researchonline.ljmu.ac.uk/5906/.
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This thesis describes the development, characterisation and application of large diameter multimode plastic optical fibre (POF) sensors using evanescent field modulation. The exposed polymethylmethacrylate (PMMA) core of the POF fibre forms the sensor interface that detects refractive index changes of a measurand acting as the cladding. When a liquid measurand is used, the sensor can detect changes in refractive index, absorption and suspended particulates. It is this simple mechanism by which the evanescent field POF sensor operates. The evanescent field POF sensor has been characterised for refractive index of surrounding liquid from 1.33 to 1.49. The sensor demonstrated accuracy of ± 7x 10-3 refractive index units below 1.4 and ±2x 10-3 refractive index units above 1.4. Components have been selected and designed for this project to ruggedise the sensor, to make the sensor more self-contained and cheaper. The original design of the test conditions did not allow for optimum deployment of the sensor as it stripped out the very modes of light that were required for sensing purposes. The system was also operating under pressure, not reflecting the real conditions under which the sensor would be operating. The re-design of test conditions holds the sensor without straining the POF and operates under normal atmospheric pressure. The POF sensor was demonstrated reacting to a real measurand eg biofilm in which initial growth affects the optical properties at the core cladding interface by refractive index modulation. This sensor was capable of measuring biofouling and scaling at water interfaces. The sensor was trialled in a European Commission funded project (CLOOPT) to study biofouling and scaling in closed loop water systems such as heat exchangers in the cooling tower of an electric power plant, and as an interface sensor for water quality monitoring (AQUA-STEW) involving biofilm removal and surface cleansing with a new application for contact lens protein removal systems. Tapering multimode POF was a desirable goal as this increases the proportion of light coupled into the core available for sensing purposes, to achieve a more sensitive evanescent field POF sensor. Optically clear and consistent smooth tapering of ends and mid-lengths of POF fibre were achieved through chemical removal of material. The tapered POF sensor was characterised with a range of refractive indices, and it exhibited two distinct regions; the water/alcohol region below 1.4 refractive index units, and the oil region above 1.4 suggesting the sensor's use as an oil-in-water, or water-in-oil sensor. From 95% confidence limits, the accuracy of the POF was ±O.006 refractive index units (to 2 standard deviations) for fluids of refractive indices above 1.4. Tapered POF is sensitive to refractive index providing a cheap, easy to handle and rugged throwaway sensor for water and beverage process and quality monitoring.
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Waugh, William. "Development of a new manufacturing method of electrodes for solid oxide fuel cells." Thesis, Edinburgh Napier University, 2010. http://researchrepository.napier.ac.uk/Output/3750.
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It is well established that anodes for solid oxide fuel cells (SOFCs) can be manufactured by processes involving final sintering. This research investigated a novel alternative method which relies on the electroless co-deposition of yttria-stabilised zirconia (YSZ) or ceria-stabilised zirconia (CeSZ) and nickel onto a YSZ substrate. This process allows complex or simple shaped substrates to be coated, thereby replacing the high temperature sintering and reduction stages with a single plating operation, which is substantially more cost effective and greatly simplifies the manufacture of any cell design. The technique also eliminates the production of larger nickel grains (which occurs during sintering), thus improving cell performance. Through a series of multifactoral experiments, a successful method was established and optimised for the deposition of the metal-ceramic composite which was successfully used in Solid Oxide Fuel Cell stack. The typical process involves degreasing and chemical pre-treatment of the substrates, followed by electroless co-deposition of the cermet coating, using either proprietary based chemicals or standard analytical reagents which have been specially formulated. Through the metallurgical examination of the experimental samples it has been shown that the ratio of the metal to ceramic can be varied, thus catering to a potentially large customer base, and that a composition gradient can be achieved through the coating. Additional parameters such as porosity and electrical conductivity have also been evaluated and the results have been so encouraging that there has been significant commercial interest in the process. Further work is continuing as part of a Proof of Concept (POC) project, with funding generously provided by Scottish Enterprise. Intellectual Property has been secured initially through funding supplied by Edinburgh Napier University, then subsequently through the POC project, with the aim that on completion of the project a spin-out company from Edinburgh Napier University is established.
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Matthews, Samuel Aaron 1962. "High pressure biomass liquefaction in a short-residence time autoclave." Thesis, The University of Arizona, 1990. http://hdl.handle.net/10150/277800.
Full textAbstract:
The University of Arizona has developed an advanced extruder-feeder biomass liquefaction reactor system. This 11-year project successfully provided an alternative energy process for converting biomass to a crude oil, which can be hydrotreated and ultimately processed into liquid transportation fuels. In order to provide support studies for this process, a short-residence time autoclave capable of providing very brief heat-up and quenching periods in comparison to the time at reaction temperature has been designed and operated. Wood liquefaction in the presence of carbon monoxide, water, and sodium carbonate catalyst has been conducted at residence times of 1.75-60 minutes at temperatures of 340-400°C. Results indicate that the primary thermal decomposition reactions reach completion in less than 1.75 minutes. As a consequence, this research concentrated mostly on the effects of secondary reactions, and even shorter residence times are required to study the primary reactions.
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Mobed, Maryam. "In-vitro and in-vivo characterization of carboxymethylchitin-coated liposomes." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=42098.
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The survival of red blood cells in circulation has been correlated to a negative surface charge in the membrane due to the presence of N-acetyl neuraminic acid (NANA) residues. In this study, biodegradable NANA analogs such as the polyelectrolytes Carboxymethylchitin (CMC) and Carboxymethyl/Glycolchitin (CO) have been adsorbed by physical adsorption onto the surface of positive and neutral liposomes. The dye Alcian Blue has been used to standardize the initial polymer concentration between unequally substituted polymer batches of the same molecular weight. The amount of polymer adsorbed on the surface of the liposomes can be quantified using chitinase from Streptomyces griseus (EC 3.2.1.14), provided that the polymeric substrate is first desorbed from the surface of the liposomes. A Factorial Design is used to optimize the adsorption conditions of CMC and CO onto 0.22 $ mu$m diameter liposomes in phosphate buffer saline (PBS, $ kappa$ = 154 mM, pH = 7.4). The molecular weight of the polymer ranges from $5.00 times 10 sp4$ to $1.20 times 10 sp6.$ Increasing the liposome diameter from 0.22 to 0.45 $ mu$m reduces the extent of polymer-induced aggregation in PBS buffer. Polymer adsorption results in disaggregation of liposome suspensions for all polymer-coated suspensions in plasma and blood. The theoretical stability ratios (W) obtained using the classical DLVO theory show that the CMC-coated liposomes are more stable than the CO-coated and stealth (DSPC:CHOL:DSPE-PEG2000,5:4:1) liposomes. Meanwhile, experimental values of W prove that the lipid-grafted stealth is the most stable suspension. Results of simulations of liposome-macrophage interactions show that the polymer-coated liposomes are not prone to uptake by macrophages prior and after plasma incubation. Measurements of zeta potential, calorimetry and plasma protein adsorption on stealth, polymer-coated and (DSPC:CHOL:DMPG, 5:4:1) ( (-)) liposomes show that for the polymer-coated liposomes the change in zeta p
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Stavrinides, Alexander James. "Isothermal microwave biology : catalysis and fermentation." Thesis, Liverpool John Moores University, 2012. http://researchonline.ljmu.ac.uk/6110/.
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This thesis looks directly into the controversial subject of the microwave field effect by the production of a versatile prototype isothermal microwave reactor for the investigation of enzymatic and microbiological reactions. The observed results from the prototype reactor and experiments conducted conclude that there is a nonthermal, nonlinear response between the exposure microwave power and rate and yield of cellulose saccharification. The nature of the nonthermal response is controversial and may be dependent on the definition of "nonthermal,' leading to ambiguity of exact mechanism. Enzymatic and microbial conversion of cellulosic material to ethanol is a highly desirable industrial process. Whether the demand is for the mitigation of climate change, political obligations or energy independence, the use of arable land for energy crops limits the available glucose carbon sources for conversion to bioproducts. To prevent this limitation, cellulose (~-l,4-linked glucose polymers) are touted as the "silver bullet" to prevent carbon exhaustion or impinging on food crops. The technical constraint for the industrialization of cellulose based processing is the rate limitation in the cellulase enzymatic action on cellulose. The enzyme rate is limited by feedback cycles and limited mechanical freedom, therefore a relatively high enzyme concentration is required to speed up the process. To date, the associated enzyme production costs and infrastructure prevents bulk volume exploitation. Biomolecular advances (amino acid substitutions, recombination of expression vectors etc) have gone some way to increase either enzymatic rate or enzyme concentration. The work presented in this thesis differs by increasing the rate of the enzyme without molecular modification. Using a microwave field, the work presented shows that by separating the system into its base units, irradiation of the enzyme/substrate complex in an aqueous environment can increase both the initial enzyme rate and the saccharification yield without alteration of the temperature set point. This study shows that the rate increase is not proportional to the microwave field power. An optimal power in each study is either found or suggested. The results cited show that in the three systems (Endoglucanase and cellobiohydrolase with cellulose, endoglucanase and cellobiohydrolase and ~- glucosidase with cellulose, and ~-glucosidase with cellobiose) the initial rates can be increased by 201 %, 65.5% and 69% respectively. In the total hydrolytic process (endoglucanase and cellobiohydrolase and ~-glucosidase on a cellulose substrate) the final glucose yield was increased by 43% in comparison to the conventional thermal control reaction. This is shown in Figure 1. 10.000 1 9.000 1 8.000 j 7.000 6.000 o 20 40 60 80 100 120 140 160 180 I I 1 I U 5.000 r:: o u 4.000 3.000 2.000 j i t t , f 1.000 0.000 Time (hours) =->=OOOW Glucose' °012W Glucose ?p025W Glucose ~050W Glucose ·075W Glucose Figure 1. Microwave irradiated "cellulase" enzymes with cellulose substrate I For development into an industrial system and looking towards simultaneous saccharification and fermentation (SSF), the yeast Saccharomyces cerevisiae was subjected to irradiated microwave fermentations on a glucose substrate. Although inconclusive in terms of rate increase, cell density 1 was comparable across the power range showing that the irradiation does not have a derogatory effect. ! The natural evolution of the conclusions drawn would be development of the system into a SSF or SSCF configuration for bio-product formation is possible with irradiation up to SOW. ii The novelty of the experiments conducted is twofold. Firstly, the reactor has been designed to ensure that the microwave irradiation is independent of the bulk temperature therefore allowing the exploration of the microwave field effect independently to the thermal effect. Secondly, the microwave source is a continuous microwave irradiation (none pulse irradiation) ensuring that the reaction is subjected to the microwave field for the entire reaction.
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Roberts, Joseph. "Synthesis and characterisation of nanoscale oxides for energy applications." Thesis, University of Liverpool, 2014. http://livrepository.liverpool.ac.uk/2005979/.
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The motivation for this research is the synthesis and characterisation of nanostructured oxide materials for potential applications in renewable energy generation or storage. In particular, the research in this thesis addresses the development of nanostructured oxide materials which could be exploited as photovoltaics and transparent conductive oxides. The exploitation of anodised aluminium oxide (AAO) to fabricate nanostructured semiconductor pn-junctions as the basis photovoltaic devices is investigated. Various microstructures are modelled with the aim of identifying ones with high interface area and consequently high energy conversion efficiencies. Experiments reveal that AAO prepared using an oxalic acid electrolyte could be achieved with a growth rate of 5.7μm/h. The uniformity and size of the hexagonal cross-section pores is influenced by the first-step anodisation time. Atomic layer deposition (ALD) was used to coat commercially available AAO, to synthesise conformal nanotubes or wires. It was observed that the uniformity of the nanostructures breaks down towards the bulk of the AAO, without high exposures, due to the lack of precursor penetration. However, the proposed geometric mass-gain model to understand the process is supported by experimental mass gain measurements and how deposition occurs within the templates. A second materials system based on copper / copper oxide is also explored as a method of synthesising and controlling the formation of nanostructured oxide materials. The surface preparation of the starting copper sheet material was investigated and it was found to be pivotal in the nanoscale morphology achievable with subsequent heat treatment to grow nanowires and porous layers. Thermal growth of CuO and Cu2O on pre- treated copper foils at 500°C exhibited growth of high aspect ratio CuO nanowires. Further studies on the growth process disproved the vapour-liquid-solid and vapour-solid growth mechanisms for the nanowires and showed that tensile strain within the Cu substrate was the driving force behind the nanowire growth. The use of nanometre-scale ALD alumina barrier layers was employed to suppress spallation and preserve the nanowire surfaces. It was found that for samples with alumina layers between ~3 and 15nm the oxide spallation was significantly reduced and that for samples with ~20nm of alumina the diffusion of Cu atoms to the surface was hindered. Photovoltaic measurements were made on electrolytically synthesised Cu2O surfaces coated with ALD TiO2, ZnO and Ga-doped ZnO to form pn-junctions. The samples showed only weakly rectifying behaviour which was attributed to short-circuits between the n-type layers and the back contact. Several of the samples did show some difference in electrical response when under illumination indicating that, at least in some parts of the device, the pn-junction had formed. Lastly the growth and characterisation of ALD Ga-doped ZnO was investigated to determine the optimal doping levels for the growth of highly conductive and transparent oxides, to be used as a front contact for photovoltaic devices. It was found that Ga doping at around 1at% in ZnO produced film with the lowest resistivity. CdTe films were then grown onto substrates coated in 1at% Ga-doped ZnO and subjected to AM1.5 photovoltaic IV testing, yielding photovoltaic cells with conversion efficiencies ~10.8% and fill-factors of ~65%.
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de, Sá Ribeiro Albina Maria. "Studies of gas-liquid flow in bends." Thesis, University of Birmingham, 1994. http://etheses.bham.ac.uk//id/eprint/5069/.
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The present investigation is concerned primarily with air-water flow in a horizontal 0.032 m ID tube, and the influence of a 90° horizontal bend on the flow characteristics. Visualisation studies using high speed still photography and cine film, and entrainment and drop size measurements were conducted before and after the bend. Entrained mass fluxes were determined from film flow measurements carried out using the film removal technique, while the drop size distributions were measured with a laser diffraction technique. During these measurements the pressure in the test section was held between 1.0-1.4 bar, and at ambient temperature. Prior to the horizontal flow study, drop size and film flow rates were measured for vertical air-water flow in a 0.01026 m ID tube. This extended the work of Jepson (1992) who reported the effect of gas density and surface tension on film flow rate, drop size and deposition mass transfer coefficient. Modifications to the equipment described by Jepson (1992) allowed an extension of the measurements to higher flow conditions. The visualisation study was taken across flow conditions that include stratified, annular and pseudo-slug flow regimes. Still photographs show the presence of air bubbles entrained in the liquid film, and the creation of liquid drops at the crest of roll waves. Drops were seen to be entrained from the liquid film by both bag break-up and ligament break-up mechanisms. At the bend, the phenomenon of film inversion was seen to occur. Also, a secondary flow existing in the gas phase at the bend can be responsible for a swirl movement observed in the liquid film, in which at the upper part of the tube the liquid was pulled from the outer wall of the bend to the top of the tube in an anti-clockwise, cork screwing fashion. In the lower half, the liquid film was drawn from the outer wall towards the bottom of the tube in a clockwise motion. From the cine films, information on drop velocity was also extracted. This showed the axial drop velocity to be constant over the time frame of analysis. No significant correlation was found between the drop size and the axial drop velocity. The entrainment results in the horizontal tube showed that for stratified/annular conditions the entrained liquid mass flux increases with liquid flow rate (for a fixed gas flow rate), and in some instances plateau conditions were reached. However, for the pseudo-slug regime the level of entrainment falls considerably. For the whole range of flow conditions studied, the entrained liquid mass flux increases with superficial gas velocity, except for GL = 10 kg/m 2 s where the amount of entrainment is constant. The reduction in entrained liquid mass flux after the bend above certain flow conditions, is caused by drops depositing on the outside wall of the bend. For the flow conditions under study, the Sauter mean diameter varies between 60-110 um. Gas velocity has a strong influence on drop size, ie, the higher the gas velocity the smaller the drop size. The effect of liquid flow rate is somewhat more complex. At the lower liquid flow rates, drop size seems to be controlled by the entrainment mechanisms, while at the higher liquid flows drop coalescence has a dominant effect. The influence of the 90° bend on the drop size distribution was to increase the diameter of the drops. Both the entrained liquid mass flux and drop size were found to be lower for horizontal annular flow than in vertical flow, for the same flow conditions and tube diameter. The measurements carried out for air-water flow in the vertical 0.01026 m ID tube, showed the entrained mass flux to increase with both gas and liquid flow rates. For the flow conditions analysed, the Sauter mean diameter varies between 26-45 um. Drop size was seen to be influenced by gas and liquid flow rates, following similar trends to those observed during the horizontal study.
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Zhang, Yuning. "Analysis of radial oscillations of gas bubbles in Newtonian or viscoelastic mediums under acoustic excitation." Thesis, University of Warwick, 2012. http://wrap.warwick.ac.uk/55427/.
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Acoustic cavitation plays an important role in a broad range of biomedical, chemical and oceanic engineering problems. For example, kidney stone can be crushed into the powder (being discharged naturally) by the acoustic cavitation generated by carefully controlled focused ultrasonic beams. Therefore, the prediction of generation of acoustic cavitation is essential to the aforementioned emerging non-invasive technique for kidney stone crushing. The objective of this PhD program is to study the generation of acoustic cavitation (e.g. through rectified mass diffusion across bubble interface) theoretically in the Newtonian fluids (e.g. water) or viscoelastic mediums (e.g. human soft tissue) under acoustic excitation of single or dual frequency. The compressibility and the viscosity of the liquid, heat and mass transfer across bubble-medium interface are all considered in this study. During this PhD program, the established works in the literature on the above topic have been re-examined. More physically general formulas of natural frequency and damping of gas bubble oscillations in Newtonian or viscoelastic mediums has been derived and further employed for solving the problem of bubble growth under acoustic field (i.e. rectified mass diffusion). For rectified mass diffusion of gas bubbles in Newtonian liquids, the predictions have been improved for high-frequency region of megahertz and above. Effects of medium viscoelasticity and dual-frequency acoustic excitation on rectified mass diffusion have also been studied. To facilitate the fast growth of bubble under acoustic field, dynamic-frequency and dual-frequency techniques have been proposed and demonstrated.
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Curnick, Oliver J. "Ionomer-stabilised Pt and Pt-Ti bimetallic electrocatalysts for the proton exchange membrane fuel cell." Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3732/.
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This work aims to address the need for more durable electrocatalysts with lower precious metal content for proton exchange membrane fuel cells (PEMFCs), through the development of novel electrocatalyst materials and preparation routes. In this work, 'Nafion-Pt/C' electrocatalysts have been derived from ionomer-stabilised Pt nanoparticles synthesised via a novel, wet-chemical route that offers unprecedented control over the formation of the Pt-ionomer interface, with a view towards maximising the utilisation of the electrocatalyst. Nafion-Pt/C electrocatalysts have been characterised using ex-situ electrochemical techniques, and single-cell PEMFC testing to determine their activity and selectivity towards the oxygen reduction reaction (ORR), and to compare their utilisation and durability with commercially-available electrocatalysts. Nafion-Pt/C catalysts with agglomerated Pt particles exhibited a twofold improvement in durability vs. commercial catalysts, whilst offering similar ORR activities. Their enhanced durability was attributed to inhibition of Pt particle growth mechanisms by a passivating layer of Nafion introduced during the synthesis of Nafion-stabilised colloidal Pt. The second part of this work investigated methods for the synthesis of bimetallic nanoparticles consisting of an early transition-metal core (Ti) enclosed in a Pt shell, expected to offer higher intrinsic activity towards oxygen reduction than Pt alone, whilst being less prone to degradation than other alloys of Pt such as Pt-Ni, Pt-Co and Pt-Fe.
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Heidari, Ali. "Numerical simulation of deflagration to detonation transition in hydrogen explosion." Thesis, Kingston University, 2012. http://eprints.kingston.ac.uk/23725/.
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The issue of deflagration to detonation transition (DDT) is one of the key factors influencing safety standards, risk assessment and risk managements in the petrochemical industries. It is also one of the most outstanding problems in combustion theory. Despite the efforts from a number of scientists around the world, numerical predictions of DDT is still an un-resolved problem due to the high level of complexities involved. Although there have been relatively more experimental efforts, a comprehensive database to assist model validation and development is still lacking. The present thesis includes numerical analysis of a wide range of combustion regimes to establish the critical conditions under which transition from deflagration to detonation occurs. In order to facilitate the study, new correlations for hydrogen burning velocity are derived from curve-fitting to experimental data from literature and implemented in the code for simulation of initial stages of flame acceleration and deflagration propagation. DetoFOAM, a code for solving transient and fully compressible Euler equations, has been developed within the framework of the OpenFOAM toolbox for numerical simulations of gaseous detonation. The detonation solver uses the total variation diminishing (TVD) numerical schemes which are suitable for shock capturing. A one step reaction mechanism has been developed following first principle and tuned for both small and large scale simulations. Since the numerical solver for DDT simulations must be capable of handling both deflagration and detonation as well as the transition, a new solver, DDTFOAM, which is based on solving fully compressible and transient Navier-Stokes equations has also been developed. DDTFOAM also uses the TVD numerical schemes for shock capturing and uses the Implicit Large Eddy Simulation (ILES) approach as a compromise for accuracy and computational efficiency [131]. Implementing an adequate chemical reaction mechanism in the DDTFOAM has been challenging to ensure that the right amount of chemical energy release is supplied in the right place and at the right time. Incorrect models for chemical energy release can significantly modify the flow behaviour. The available reactions in the literature are very limited and valid for limited range of conditions, e.g. for laminar flames only. A single step Arrhenius type reaction has been designed, tuned and implemented in DDTFOAM. The reaction mechanism has been carefully designed to reproduce flame properties e.g. laminar flame speed and thickness as well as detonation properties such as detonation thickness, propagation velocity, etc. The main difference between DetoFOAM and DDTFOAM that the former is designed for supersonic combustions (detonations) only; therefore it neglects the diffusive effects and solves reactive Euler Equations, whereas in DDTFOAM full Navier Stokes Equations are solved. The detonation solver is mainly designed for large scale detonation simulations therefore the derived reaction mechanism for this solver is obtained trough slightly different procedure compared to the DDT solver. Obtaining the reaction mechanism for DDTFOAM is more challenging as it has to reproduce properties of deflagrations as well as detonations correctly. The computational power which is required to carry out the simulations is extremely high. Different techniques have been employed to reduce the computational cost without compromising accuracy. These include using the ILES approach in cooperation with adaptive mesh refinement and multiple meshes. Numerical predictions have been conducted for different combustion regimes including laminar flames, turbulent flames and detonations as well as the actually DDT processes. The predictions of deflagrations waves are found to be In reasonably good agreement with some published experiment data. In case of detonations, detailed studies have been conducted on the detonation front structure, cellular structures as well as large industrial scenarios. This work involved contributions to Buncefield explosion investigations [109-110]. Finally, numerical simulations of some standard DDT tests have been carried out. The predictions have again achieved reasonable agreement with published experimental data and previous simulations. Successful simulations of large scale detonation in the present work represent the capability of the present study to address the increasing demands from the industries to study real scale accidental scenarios. Furthermore the obtained results for DDT simulations compare well with the medium scale experimental works and provide a step forward towards large scale and unconfined DDT studies.
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Malik, Shoaib Ahmad. "Damage detection using self-sensing composites." Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/1750/.
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The primary aim of this research programme was to enable damage detection in glass fibre reinforced composites using the reinforcing fibres as the sensing element. In other words, E-glass fibres were used as light guides to detect the fracture of individual fibres, when loaded in tension. This was achieved by monitoring the transmitted light intensity through the reinforcing glass fibres. Two types of glass fibres and matrices were evaluated. In the case of glass fibres, E-glass and custom-made small-diameter (12 µm) optical fibre (SDOF) were used. Three types of low refractive index resin systems with specified failure strains were also used. The basic technology involved illuminating one end of the fibre bundle or composite with a white light or laser source and the opposite end was imaged using a high-speed CCD camera. Acoustic emission monitoring of fibre bundles revealed that there were two types of failures occurring in a bundle, a lower amplitude of the acoustic emission signal (AES) related to the inter-fibre friction and a high amplitude of the AES to fibre fractures. This characteristic was also confirmed by a Weibull statistical analysis where it was demonstrated that a two parameter distribution was present corresponding to two different flaw distributions. In the case of self-sensing composites, it was found that the specific failure modes in the composites (matrix failure, fibre fracture, debonding) generate their characteristic amplitudes of the AES and frequencies. These failure modes were recorded and correlated to the tensile test data. It was demonstrated that the attenuation of transmitted light can be related to the fracture of fibres in the bundle or a composite test specimen. It was found that the image analysis routines were capable of identifying and tracking the survival or fracture of each fibre in the bundle or composite. The results obtained from mechanical loading, acoustic emission and images analysis were cross-correlated.
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Witte, Christian. "Micromanipulation in microfluidics using optoelectronic and acoustic tweezing." Thesis, University of Glasgow, 2015. http://theses.gla.ac.uk/6391/.
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The thesis introduces a concept for a unified platform that enables the use of acoustic and electric fields for particle manipulations in microfluidic environments. In particular, optoelectronic tweezing (OET), also known as light induced dielectrophoresis is fused with acoustic tweezing, also known as acoustophoresis, on a versatile system. The system can be divided into two individual physical units. The first one represents the OET unit which integrates light induced electric fields into a robust microfluidic chip. The OET chip not only operates as a device for electric field generation but also as a transverse resonator to confine acoustic fields. These fields are the result of travelling surface acoustic waves excited by a piezoelectric transducer which defines the second unit. The developed platform is applied to a range of applications such as particle trapping, transporting, focussing, sorting as well particle alterations in form of cell lysis and microbubble insonation.
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Trimeloni, Thomas. "Accelerating Finite State Projection through General Purpose Graphics Processing." VCU Scholars Compass, 2011. http://scholarscompass.vcu.edu/etd/175.
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The finite state projection algorithm provides modelers a new way of directly solving the chemical master equation. The algorithm utilizes the matrix exponential function, and so the algorithm’s performance suffers when it is applied to large problems. Other work has been done to reduce the size of the exponentiation through mathematical simplifications, but efficiently exponentiating a large matrix has not been explored. This work explores implementing the finite state projection algorithm on several different high-performance computing platforms as a means of efficiently calculating the matrix exponential function for large systems. This work finds that general purpose graphics processing can accelerate the finite state projection algorithm by several orders of magnitude. Specific biological models and modeling techniques are discussed as a demonstration of the algorithm implemented on a general purpose graphics processor. The results of this work show that general purpose graphics processing will be a key factor in modeling more complex biological systems.
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Marigo, Michele. "Discrete element method modelling of complex granular motion in mixing vessels : evaluation and validation." Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3402/.
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In recent years, it has been recognised that a better understanding of processes involving particulate material is necessary to improve manufacturing capabilities and product quality. The use of Discrete Element Modeling (DEM) for more complicated particulate systems has increased concordantly with hardware and code developments, making this tool more accessible to industry. The principal aim of this project was to study DEM capabilities and limitations with the final goal of applying the technique to relevant Johnson Matthey operations. This work challenged the DEM numerical technique by modelling a mixer with a complex motion, the Turbula mixer. The simulations revealed an unexpected trend for rate of mixing with speed, initially decreasing between 23 rpm and 46 rpm, then increasing between 46 rpm and 69 rpm. The DEM results were qualitatively validated with measurements from Positron Emission Particle Tracking (PEPT), which revealed a similar pattern regarding the mixing behaviour for a similar system. The effect of particle size and speed on segregation were also shown, confirming comparable results observed in the literature. Overall, the findings illustrated that DEM could be an effective tool for modelling and improving processes related to particulate material.
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Aldarmaki, Naeema Ibrahim Karam Al-Darmaki. "Extraction and enrichment of minor lipid components of palm fatty acid distillate using supercritical carbon dioxide." Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3621/.
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Currently the extraction of valuable components from oils is of growing interest. Palm fatty acid distillate is a by-product from palm oil refining process which contains valuable minor components. The scope of the present work was to investigate the enrichment of high value low concentration components of palm fatty acid distillate namely squalene (1.8-2.3 wt.% squalene) using supercritical carbon dioxide as solvent with counter-current packed column kept under isothermal and longitudinal thermal gradient. The overall objective of this work was to explore the effect of extraction process parameters such as pressure, temperature, and solvent to feed ratio to optimize the conditions that lead to high separation efficiency. This work has been centred on the study of the solubility of the main lipid components in supercritical carbon dioxide, isothermal counter-current extraction, longitudinal thermal gradient fractionation and the effect of feed concentration. Solubility studies have been conducted for binary, ternary and quaternary systems as function of state of conditions through the application of a dynamic method. Binary systems of CO2/squalene, CO2/oleic acid, CO2/\( \alpha \)-tocopherol, and CO2/pseudo-component palm olein were measured at temperatures of 313, 333 and 353 K, and at a pressure range of 10 to 30 MPa. A ternary system of CO2/squalene/palm olein and a quaternary system of CO2/squalene/ palm olein/ oleic acid were also investigated at 313 K and pressures of 10 to 25 MPa. Comparison of the ternary system with the binary system showed a decrease in the solubility of squalene, with a corresponding rise in the solubility of palm olein. In the quaternary system, the presence of oleic acid decreased the selectivity of squalene. Extraction of squalene has been carried out on a counter-current glass beads packed column with the dimensions of 11.45 mm internal diameter and 1.5 m of effective height. The pressure and temperature were the operating conditions investigated and they varied from 10 – 20 MPa and 313 – 353K, respectively. Experimentation has demonstrated that squalene high fraction is achievable, however, squalene recovery has been found to be highly dependent on the extraction pressure and temperature. Squalene and free fatty acids content in the extract increased, and triglycerides content decreased during most of the fractionation runs. Longitudinal thermal gradient profiles along the column were investigated for further recovery of squalene, results showed the highest squalene recovery of more than 95% was reached and concentration of squalene was increased from 2wt% in the feed to 16wt% in the top product.
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Parihar, Arun K. "Greenhouse gas emissions and strategies for mitigation : opportunities in agriculture and energy sector." Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/2066.
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Fang, Haitao. "Low Temperature and High Salt Concentration Effects on General CO2 Corrosion for Carbon Steel." Ohio : Ohio University, 2006. http://www.ohiolink.edu/etd/view.cgi?ohiou1163794555.
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Mee, Stephen J. "The synthesis, characterisation and properties of self- assembled hollow and low density microspheres." Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/3116/.
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Hollow low density microspheres were prepared by adsorbing kaolin nanoparticles onto a polystyrene (PS) template. A cationic polyelectrolyte, poly(diallydimethylammonium chloride), was initially adsorbed on the PS to render the surface cationic enabling the kaolin nanoparticles to form a shell structure due to electrostatic attraction forces. An increase in ionic strength by the addition of 0.1 M NaCl increased the amount of polyelectrolyte adsorbed at the PS surface. Solvent relaxation NMR experiments indicated that solvent molecules were bound at the PS surface suggesting attached polymer chains. Zeta potential experiments indicated a change in the surface potential at the PS interface due to the addition of a polyelectrolyte, as little as 0.1 g m-2 of polyelectrolyte was required to change the PS surface potential. Surface saturation of the PS resulted in a zeta potential of 63.5 \(\pm\)2.6 mV, at pH 6.6 \(\pm\)0.2. Kaolin adsorption was determined by reduced sediment volume experiments and observed by the use of scanning electron microscopy (SEM). The influence of an increase in the kaolin ratio and the calcination process on the microsphere structure was investigated. When calcined at 1000 ºC for 60 min the microsphere properties exhibited a particle size (d50) of 11.2 \(\pm\)0.4 \(\mu\)m and a bulk density of 0.13 \(\pm\)0.01 g/cm3. The internal structure of the calcined microspheres were characterised by the use of SEM and focused ion beam (FIB) instruments. The characteristic properties of the calcined kaolin microspheres were determined by thermogravimetric analysis (TGA), X-ray diffraction (XRD), X-ray fluorescence (XRF), and X-ray photoelectron spectroscopy (XPS).
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Ghahari, Seyed Majid. "In situ synchrotron x-ray characterisation and modelling of pitting corrosion of stainless steel." Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3269/.
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Pit propagation in stainless steels under electrochemical control was investigated using in situ synchrotron X-ray microtomography, which was used to confirm that the lacy covers commonly found for pits in stainless steels grow through perforation of the metal surface by upward growth of rapidly dissolving lobes from the main pit. In situ synchrotron X-ray radiography has been used to observe the evolution of 2D pits growing at the edge of stainless steel foils under electrochemical control in chloride solutions. Pit growth shape, kinetics and stability under current and potential control at various bulk chloride concentrations have been studied. It was found that the pit depth tends to grow under diffusion control, whereas lateral development is influenced by solution conductivity. The impact of the perforated cover on the pit growth and stability was examined and its formation was found to be similar to the observations from 3D by X-ray microtomography. A method for extracting the key dissolution kinetic parameters from radiographs has been developed. The local anodic current density along the boundary of a pit was directly measured from the rate of advance of the pit into the metal. Then the local metal ion concentration and potential drop inside the pit cavity was back-calculated using transport equations and the requirement to maintain charge neutrality, establishing the relationship between local current density, interfacial potential and metal ion concentration in the solution. The predictive model for pit propagation in stainless steel developed by Laycock and co-workers was examined, its sensitivity to key growth parameters was evaluated, and a modified version of the model was developed based on the kinetic parameters extracted from the radiographic measurements.
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Cao, Chundi. "In situ infared [i.e. infrared] studies of catalytic partial oxidation." Diss., Manhattan, Kan. : Kansas State University, 2008. http://hdl.handle.net/2097/887.
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Bourquin, Yannyk Parulian Julian. "Shaping surface waves for diagnostics." Thesis, University of Glasgow, 2012. http://theses.gla.ac.uk/4167/.
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Infectious diseases continue to kill millions of people every year and are a significant burden on the socio-economic development of developing countries. After many years of international policy aimed at containing diseases, it has recently become an explicit aim to move towards elimination of infectious diseases. However, if this is to occur, it will be necessary to have highly eficacious diagnostic tools to ensure infected individuals are identified and treated. However, the diagnosis of infectious diseases in the developed and developing world requires the full integration of complex assays in easy-to-use platforms with robust analytical performances at low cost. Many relevant bioanalytical technologies have been developed for use in laboratories and clinics, including the current gold standard for the diagnosis of tuberculosis and malaria. The miniaturization and integration of complex functions into lab-on-a-chip (LOC)technologies using microfluidics have only had limited success in translating diagnosis assays out of a centralized laboratory to point-of-care (POC) settings, because they still remain constrained due to chip interconnection and they are either not likely to go out of research laboratories or are not appropriate for low resource settings. In this thesis, a new microfluidic platform was developed that reduced the dependency of the diagnostic procedure on large laboratory instruments providing simplicity of use, enabling the patient sample to be processed and diagnosed on a low cost, disposable biochip. Surface acoustic wave (SAW) devices, which are commonly used in mobile phone technologies, were adapted to provide controlled microfluidic functions by shaping the SAW using particular designs of electrodes and phononic structures. The control of lateral positioning of the SAW was demonstrated using a slanted finger interdigitated transducer (IDT) in a frequency tuneable manner allowing microfluidic functions such as mixing, moving and merging, sequentially performed using a single IDT both on the substrate and on a disposable chip. Alternatively, phononic bandgaps were designed to break the symmetry of the SAW in a tuneable manner and gradient index phononic crystals (GRIN-PC) lenses were designed to focus the SAW and successfully increased the amplitude of the wave by a factor 3 while the focal position could be tuned with the frequency. The potential of these techniques was demonstrated by controlling the amplitude and direction of water jet towers by the use of a phononic horn structure that allowed the enhancement of energy at defined positions and by propelling and directing a macrometer scale object in water using a slanted IDT. As proof of concepts of diagnostic devices for the developing world, an immunoassay for tuberculosis using only mobile phone technologies (SAW, light-emitting diode(LED) and complementary metaloxidesemiconductor (CMOS) camera) was demonstrated with a limit of detection of 1 pM, which is the limit required in an interferon-release assay. This limit of detection was only achievable because of the ability of SAW to increase the mixing and to reduce the non-specific binding. Furthermore, a method to enrich malaria infected cells, based on SAW and isopycnic gradient, was also demonstrated and showed an enrichment up to 100x in the equivalent of a fingerprick of blood in 3 seconds. This technique will allow to reduce the limit of detection of the current gold standard. This platform not only opens a clear road toward POC diagnostics due to its size, cost, versatility and ease in integration, but has also the potential to provide useful tools in laboratory settings for large scale, high throughput technologies.
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Cruz, Jimenez Juan Carlos. "Hydrolases on fumed silica : conformational stability studies to enable biocatalysis in organic solvents." Diss., Manhattan, Kan. : Kansas State University, 2010. http://hdl.handle.net/2097/3648.
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Callaghan, Fergal James. "Co-digestion of agricultural and industrial wastes." Thesis, University of Birmingham, 1998. http://etheses.bham.ac.uk//id/eprint/3601/.
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Anaerobic digestion technology has not gained widespread acceptance on UK farms due mainly to the long return on investment periods involved. It has been suggested that co-digestion of agricultural and industrial wastes may enhance the economic viability of such installations. Batch and continuous digestion of cattle slurry and organic industrial wastes was carried out in specially constructed pilot plant digesters, to determine optimum mixtures of waste and digester loading rates. A total of 10 different wastes were tested, on a batch digestion basis, for their potential to co-digest with cattle slurry. Of these, 3 were chosen for continuous pilot plant trials, due to either a need to provide a disposal route for the waste, or positive effects of the waste on methane productivity. Chicken manure was found to slightly enhance methane productivity, but ammonia inhibition of methanogenic bacteria was noted over time. The organic fraction of municipal household waste (OFMSW) significantly enhanced digester methane productivity, while fish offal (FO) slightly enhanced methane productivity when added to the digester in small quantities, but quickly caused digester failure when added in larger amounts. An economic model of a digestion facility was developed and used to show the financial benefits of co-digestion.