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Dissertations / Theses on the topic 'Modelling of filtration processes'

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Published: 4 June 2021
Last updated: 9 February 2022

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1

Jones, Franck Anderson. "Modelling of novel rotating membrane bioreactor processes." Thesis, Brunel University, 2017. http://bura.brunel.ac.uk/handle/2438/16345.

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Previous membrane researches undertaken over the years to develop general deadend filtration models made use of an approach that combined all three classical fouling mechanisms, namely, pore blocking, pore constriction and cake filtration. More recently researchers have modified and adapted this modelling approach for a cross flow side-stream membrane bioreactor (MBR) system. Literature also reveals that there have been numerous recent experimental studies conducted on rotating membrane bioreactor (RMBR) systems. Some of these studies have resulted in the creation of RMBR models of the membrane fouling process as well. However, simulation and modelling of the fouling in RMBRs is still a nascent topic to date due to poor understanding and great complexity of the system hydrodynamics involved. Even when models are developed, they are either too complex to be useful at operational level, or not comprehensive enough to express all possible operational scenarios. In many cases they are simply too difficult to calibrate and thus ending up being more suited as research tools rather than for direct process control. As such, further research is required in this area. The research reported in this thesis consists of the development and validation of a RMBR system fouling model that incorporates all three classical fouling mechanisms. This thesis work is divided into two main sections. On top of a literature review that thoroughly describes the background theory and general information on MBRs along with their state of the art, the first section of the thesis also explains the specific methodologies used to accomplish all the main tasks carried out in this research work. The first step of these methodologies involves the setting-up of a rotating MBR system process based upon the FUV-185-A15R Flexidisks membrane module that was developed by Avanti Membrane Technology (USA). This system was used to collect the majority of the data used in this thesis. Since some of these data outputs were compared against non-rotating MBR systems, a similar setting-up process for a bespoke static square MBR system was carried out as well. Using synthetic wastewater in conjunction with activated sludge, mixed liquor suspended solids in both MBR system bioreactors were increased in levels over time to desired levels (i.e. by periodic excess sludge wasting). Trans-membrane pressure (TMP)-stepping fouling data was then acquired from operations of these membrane ultrafiltration processes. This data was obtained by measuring the flux decline or TMP increase. Following data collection, a dynamic fouling model for this RMBR system was then created in Matlab (using the Genetic Algorithm function). To do this, hydrodynamic regimes such as air scouring and rotating shear effects along with all the three classical fouling mechanisms were included in the mathematical fouling model that was created from first principles. For the purpose of comparison, a similar fouling model was created without incorporating the rotational effects for the static square MBR system. This included modelling of the hydrodynamics as well. Finally, both these models were validated and calibrated using the data that were collected from both laboratory-based MBR systems. The second phase of the thesis explores the numerous outputted results produced via model simulations which were then discussed and analysed in great detail. Results from this research indicate that the mathematical models give a decent portrayal and description of the fouling mechanisms occurring within a rotating MBR system. It was found that the rotational mechanisms in terms of fouling prevention accounted for only twelve percent of cake removal with the rest being accomplished through the air scouring mechanism. However, it was found that although the slowly rotating spindle induced a weak crossflow shear, it was still able to even out cake build up across the membrane surface, thus reducing the likelihood of localised critical flux being exceeded, which would lead to dramatic loss of flux. Furthermore, when compared against the static MBR system, the study concluded that a rotating MBR system could increase the flux throughput by a significant amount. In conclusion, RMBR systems appear to represent alternative viable solutions when compared against the traditional static MBR systems that currently dominate the industrial and municipal marketplace. In future, RMBR systems may become the systems of first choice once there is a better understanding of the rotational processes, and once research and design into this sector broadens. Future study areas should thus focus on: whether the forces acting on an activated sludge particle during rotation have a significant effect on the fouling or the shear hydrodynamic regimes; whether activated sludge and benchmark models could be created for rotating MBRs whilst including the shear effects and hydrodynamic regimes; whether model predictive control using these developed RMBR models would enhance efficiency gains within an operational plant; and, whether the real measured soluble microbial products (SMP) concentrations could be used to create an even better SMP predictive model that accurately explains fouling behaviour.
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2

Campos, Luiza Cintra. "Modelling and simulation of the biological and physical processes of slow sand filtration." Thesis, University College London (University of London), 2002. http://discovery.ucl.ac.uk/43778/.

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Slow sand filtration (SSF) is the earliest form of engineered potable water treatment and remains one of the most efficient processes for improving the physical, biological and chemical quality of water. However, whilst widely used throughout the world, knowledge of the filtration mechanisms remains limited. This is important in understanding and managing the processes that are responsible for gradually blocking the filter reducing its operational life and filtration efficiency. The objective of this thesis was to develop a mechanistic simulation model of the fundamental physico-chemical and biological processes responsible for the filtration mechanisms operating in slow sand filters. The model solves a set of equations describing schmutzdecke development above the sand and microbial biomass growth within the sand. The model assumes that the schmutzdecke layer contributes to the water purification process and its growth is described as linear function in relation to time. The dynamic interactions between the principal groups of microorganisms including: algae, bacteria and protozoa, were modelled using Monod-type kinetic equations. The filtration performance of the filter media was defined in the model by the removal of particulate material from water and was represented by a combination of headloss and filtration coefficient functions. The model was calibrated and verified using data from full and pilot plant-scale SSF operated by Thames Water Utilities Ltd. Simulation results showed that interstitial biomass was the smallest part of the bulk specific deposit in both covered and uncovered filters. However, microbial dynamics played an important role in the filtration performance. Schmutzdecke development had a major influence on the operation of uncovered filters and was responsible for the significant increase of headloss observed during operation. The model provides a representation of the fundamental nature of SSF processes and could form the basis of an operational management system to optimise SSF.
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3

Wiese, Bernd Ulrich. "Spatially and temporally scaled inverse hydraulic modelling, multi tracer transport modelling and interaction with geochemical processes at a highly transient bank filtration site." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=983980969.

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4

Wiese, Bernd Ulrich. "Spatially and temporally scaled inverse hydraulic modelling, multi tracer transport modelling and interaction with geochemical processes at a highly transient bank filtration site." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, 2007. http://dx.doi.org/10.18452/15607.

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Seit mehr als 100 Jahren wird Oberflächenwasser mit verschiedenen Verfahren versickert, wobei sich dessen Qualität stark verbessert. Sie finden zunehmend weltweit Anwendung, um eine zuverlässige Versorgung mit sauberem Trinkwasser zu gewährleisten. Solche Verfahren erfordern nur einen geringen technischen Aufwand. Während bei der Versicherung mit Schluckbrunnen und bei künstlichen Infiltrationsbecken das Wasser noch gepumpt und oft auch vorgereinigt werden muss, reduziert die Nutzung eines natürlichen Gewässers den Aufwand nochmals. Am Beispiel eines Untersuchungsgebiets am Tegeler See in Berlin werden die hydraulischen Prozesse modelliert. Die regionale, instationäre und 3-dimensionale Modellierung eines langen Zeitraums zeigt, dass die bisher verwendeten linearen Ansätze zur Beschreibung der Durchlässigkeit der Kolmationsschicht sowohl die infiltrierten Wassermengen als auch die Infiltrationsprozesse nur unzureichend wiedergeben. Grundwasserpiegelschwankungen werden stärker als bisher angenommen gedämpft. Als Folge dieser Wasserspiegelschwankungen wird die Bodenluft in der ungesättigten Bodenzone ausgetauscht und Sauerstoff eingetragen. Auf diese Weise erhöht sich die Durchlässigkeit der Kolmationsschicht um mindestens eine Größenordnung. Auf Grundlage dieser Ergebnisse wurden eine instationäre Wasserbilanz aufgestellt und die Uferfiltratanteile bestimmt. Die genaue lokale Lage eines Grundwasserstauers wird mit Hilfe eines neu entwickelten inversen Modellkonzeptes bestimmt. Er wird mit räumlich verteilten Pilot Points und Überparameterisierung unter Nebenbedingungen kalibriert. Die Zielgröße sind Piezometerhöhenschwankungen. Kreuzvalidierung bestätigt, dass die Lage des Grundwasserstauers präzise bestimmt wird. Diese hat einen entscheidenden Einfluss auf das räumliche Strömungsfeld und liefert neue Anhaltspunkte zur Genese des Tegeler Sees. Ein Transportmodell liefert lediglich mit den hydraulisch kalibrierten Parametern eine genaue Anpassung der Durchbruchskurven von Chlorid, 18O und Temperatur. Dies kann als Vorhersage angesehen werden und zeigt die Güte des Modells. Es konnte gezeigt werden, dass der Sauerstoffeintrag die Redoxprozesse in der Infiltrationszone dominiert. In Kombination mit der Lage des Grundwasserstauers können so auch zuvor widersprüchliche und lokale geochemische Verhältnisse schlüssig interpretiert werden. Es wird eine Theorie entwickelt, die erklärt, wie die vertikale Schichtung von oxidiertem und reduziertem Wasser zu starker Verockerung der Brunnen führt.
Several kinds of managed aquifer recharge techniques provide very good purification of surface water since more than 100 years. In order to maintain a reliable supply of clean water, they are becoming increasingly popular all over the world. These methods require low technical effort. At Aquifer Storage and Recovery and ponded infiltration the recharged amounts are technically controlled. The infiltration water has to be pumped and often pretreated. At bank filtration this is dispensable, the approach, of using existing surface water bodies is even more consequent. Exemplarily, at a test site at Lake Tegel, Berlin, Germany, the hydraulic processes are modelled. By means of 3D long term regional and transient hydraulic modelling it was detected that the existing approaches for determining the leakance induce large errors in the water balance and describe the infiltration zone insufficiently. The leakance could be identified to be triggered by the groundwater table, causing air exchange and intrusion of atmospheric oxygen, which reduces clogging by altered redox conditions by at least one order of magnitude. This causes that changes of the groundwater table are mitigated much more than previously assumed. Taking these findings into account, a transient water balance is determined and bank filtration ratios are quantified. A new inverse modelling concept has been developed and applied to a 3D short term local and transient hydraulic model. It comprises spatially distributed pilot points and overparameterisation constrained by regularisation and calibration to head differences. Significance of the results is demonstrated by cross validation. With this approach the spatial distribution of an aquitard have been identified with high precision. The highly transient and heterogeneous flow conditions are specified and a new viewpoint on the geologic formation of Lake Tegel is obtained. The good fit of modelled and observed breakthrough curves of 18O, chloride and temperature by just using transferred parameters obtained with the previous hydraulic methods, show the very good model performance and predictive capabilities. The intrusion of atmospheric oxygen into the unsaturated zone is identified to be the principal redox determining factor during infiltration. Previously inconsistent and also local geochemical conditions are identified to be determined by interaction of infiltration processes with the spatial extent of the aquitard. A theory for chemical clogging of abstraction wells is developed, identifying the strong vertical redox zoning as principal factor of influence.
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5

Sprenger, Christoph [Verfasser]. "Surface-groundwater interactions associated with river bank filtration in Delhi (India) : investigation and modelling of hydraulic and hydrochemical processes / Christoph Sprenger." Berlin : Freie Universität Berlin, 2011. http://d-nb.info/1026069564/34.

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6

Valentine, Mark Edward. "Fundamental flux enhancement modelling of membrane microfiltration." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:f1b0388e-25b9-4038-be04-360b1414d172.

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Membrane filtration is used in a variety of industries, including water treatment and the food industry. Membrane systems include microfiltration and reverse osmosis processes. Membranes used in reverse osmosis are nonporous or pores at 0.2-2 A. This work will focus on mechanical microfiltration. These filtration systems suffer from an accumulation of the rejected material near the membrane surface. This causes additional resistance to the flow through the membrane (flux), resulting in a decline in the performance of the system. Sparging gas bubbles into the mixture has been shown to improve performance. The flow field promotes the transport of material away from the membrane surface and into the bulk. The goal is to predict the sparging that will achieve the maximum flux. Existing flux prediction models often assume steady shear at the membrane surface but in bubbling regimes the shear stresses are unsteady. In this thesis a model is developed to calculate the flux based not solely on shear but on the behaviour and resistance of suspended particles in a gas-liquid flow field. The bubble shape and flow field is calculated using computation fluid dynamics (CFD). The flow around a bubble in gap between two parallel flat sheet membranes is investigated. The calculated bubble shape correlates well with the results seen in experiments. The bubble rise velocity with respect to gap width is shown to transition between that expected in the literature for extended flow for large gap widths and that for a two dimensional case for smaller gap widths. The transitional region however, does not behave as may be expected. The rise velocity does not monotonically decrease as the gap width is reduced. The particle concentration is found by the solution of the convection-diffusion equation, where the convection velocity terms are given by the results of the CFD calculation. The permeate flux is then calculated using a resistance model giving the enhancement due to the bubble. The model is also applied to single phase crossflow. As the shear stresses are steady in this single-phase flow regime, established membrane shear linked mass-transfer coefficient methods can be employed. Good agreement is found between the model and theory. The flux results obtained when the model is applied to the flow around the bubble show a peak in performance with respect to the gap between the membranes for a given bubble volume. The optimal flux enhancement is found to correlate well with the bubble size compared to the flow area. The results show a bubble width of around 60% of the flow width provides the best flux performance.
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7

Prézélus, Flavie. "Ecodesign of ultrafiltration membranes for drinking water production : an experimental and modelling approach." Thesis, Toulouse, INPT, 2019. http://www.theses.fr/2019INPT0088.

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Les procédés de traitement par ultrafiltration sont certes largement utilisés pour la production d’eau potable mais leurs performances environnementales restent néanmoins mal connues. Cetravail vise à une meilleure compréhension de l’empreinte environnementale des membranes, ainsi qu’à la proposition et mise en oeuvre de solutions innovantes et pertinentes afin de l’atténuer. Une approche multi-étapes d'écoconception est appliquée aux fibres creuses fabriquées par inversion de phase et utilisées en filtration frontale. Deux modèles paramétrés ontété développés pour évaluer les impacts environnementaux lors des étapes de fabrication et d'utilisation en fonction des conditions opératoires. L’analyse de cycle de vie a mis en évidenceque les conditions opératoires liées au glycérol étaient des leviers d’action intéressants pour l’étape de fabrication. La quasi-exclusivité des impacts environnementaux est toutefois liée à l’étape d’utilisation, pour laquelle la production d’électricité et la fabrication d’hypochlorite de sodium sont les deux principaux contributeurs. L'analyse montre également l'influence du flux de filtration. Des opportunités existent concernant l’utilisation de solvants biosourcés, d’où la stratégie d’amélioration qui consiste à remplacer les solvants d’origine pétrochimique lors de la fabrication membranaire. Un cadre méthodologique basé sur des indicateurs a été proposé afin de rationaliser la fabrication de membrane durable. Des membranes planes biosourcées ont ainsi été obtenues en utilisant le lactate de méthyle comme solvant. Les résultats environnementaux mitigés n'excluent pas pour autant le remplacement de solvant en tant que stratégied'amélioration. Les résultats soulignent la faisabilité et la pertinence de cette approche d'écoconception basée sur la modélisation de procédé et le travail expérimental, et posent lesbases des améliorations futures
Although ultrafiltration treatment processes are widely used for drinking water applications, their environmental performances remain poorly understood. The objectives of this work are to provide understanding of membrane environmental footprint, as well as to suggest and implement relevant innovative solutions for its mitigation. A multiphase ecodesign approach is applied to hollow fibres fabricated by phase inversion and operated in a dead-end mode. The two developed parameterized models evaluate environmental impacts during fabrication and operation as a function of operating conditions. The subsequent Life Cycle Assessment highlights glycerol-related operating conditions as interesting action levers for environmental mitigation of membrane fabrication. However, membrane operation accounts for nearly exclusively all environmental impacts, with electricity production and sodium hypochlorite fabrication as the two main contributors. The analysis also pinpoints the influence of filtration flux. Since opportunities for biosourced solvents exist, substitution of petrochemical solvents during membrane fabrication is chosen as an improvement strategy. A metrics-based methodological framework is suggested to rationalize sustainable membrane fabrication. Biosourced flat membranes using methyl lactate as a solvent have thus been prepared. The mixed environmental scores do not preclude solvent substitution as a relevant improvement strategy. Results highlight the feasibility and relevance of such an ecodesign approach based on process modelling and experimental work, and lay the foundations for further development
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8

Pumprlová, Němcová Miroslava. "Modelování biochemických pochodů ve filtračním prostředí kořenových čistíren." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227702.

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This master's thesis deals with the modeling of biochemical processes in saturated vertical filter (which is often part of constructed treatment wetland) using software HYDRUS 2D and the module Constructed Wetland CW2D. The introductory part of this thesis is the literature research of expertise that are introduce with the theme constructed treatment wetlands and should also provide a basic overview of the mathematical or numerical modeling issue. The last chapter describes the theoretical introduction of software HYDRUS 2D and CW2D module, it is the practical part used to create a numerical l model. The practical part is based on theoretical knowledge and demonstrates the creating process of mathematical model in program HYDRUS 2D, simulating the real biochemical processes on the vertical saturated filter. The model is created in the program HYDRUS 2D CW2D and based on real operated constructed wetland. The thesis describes the calibration and followed verification of this model. The final model can well simulate the real filter behavior and allows user to get information about the output concentrations of waste water emission, such as ammonia nitrogen (N-NH4+) and chemical oxygen demand (COD). The results should in the future contribute to create software intended to draft and layout constructed wetlands.
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Krupp, Armin Ulrich. "Mathematical modelling of membrane filtration." Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:ae6dd9e4-a862-4476-a8d9-35156848297f.

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In this thesis, we consider four different problems in membrane filtration, using a different mathematical approach in each instance. We account for the fluid-driven deformation of a filtercake using nonlinear poroelasticity in Chapter 2. By considering feeds with very high and very low particle concentrations, we introduce a quasi-static caking model that provides a suitable approximation to the full model for the physically realistic concentration regimes. We illustrate the agreements and differences between our model and the existing conventional cake-filtration law. In Chapter 3, we introduce a stochastic model for membrane filtration based on the quantised nature of the particles and show how it can be applied for feeds with different particle types and membranes with an interconnected pore structure. This allows us to understand the relation between the effects of clogging on the level of an individual pore and on the macroscopic level of the entire membrane. We conclude by explaining the transition between the discrete and continuous model based on the Fokker--Planck equation. In Chapter 4, we consider the inverse problem of determining the underlying filtration law from the spreading speed of a particle-laden gravity current. We first couple the theory of gravity currents with the stochastic model developed in Chapter~3 to determine a filtration law from a given set of experiments. We then generalise this idea for the porous medium equation, where we show that the position of the front follows a power law for the conventional filtration laws, which allows us to infer the clogging law in certain instances. We conclude the thesis by showing in Chapter 5 how we can combine experimental measurements for the clogging of a depth filter and simple fluid dynamics to accurately predict the pressure distribution in a multi-capsule depth filter during a filtration run.
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Kakutkina, NA, and MM Mbarawa. "Transition Processes in Filtration Gas Combustion." Plenum Publishing Corporation, 2004. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1001750.

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Methane
Summary The behavior of gas filtration combustion waves in the low-velocity regime has been studied experimentally with variation in the parameters of the gas flow and porous medium. It is shown that in transition processes there may be quenching or formation of a stable combustion-wave structure that does not correspond to the initial or final conditions. A nontrivial type of transition process accompanied by spatial transfer of the combustion zone is found.
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Vengadasalam, Kirijen. "Computational modelling of coalescence filtration process." Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/17323/.

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The low water-diesel interfacial tensions arising in biodiesels pose a problem for fuel filters designed to separate water contamination from diesel fuel. Such filters operate by passing the fuel through a fibrous non-woven material with the aim of capturing small water droplets on the fibres and holding them while further droplets coalesce with the captured droplets until the droplets are large enough to be carried away from the fibres and subsequently settle out of the fuel by gravity. The coalescence process is however less effective at lower interfacial tensions. The main purpose of this research is to explore the mechanisms at work in a coalescence filter by developing and applying computer simulations of the process, and to understand the effects of fibre properties such as wettability, size and separation on the filtration performance. Following a detailed review of the relevant literature, a macroscopic simulation of the flow within a filter housing is first presented, using finite element analysis via COMSOL Multiphysics to establish the main flow patterns through the filter system. The filter medium itself in this model is treated as a continuous porous medium. The flow at the pore/fibre scale is then analysed by means of a multiphase lattice Boltzmann method based on the multicomponent Shan-Chen model. The wettability of the fibres is incorporated through specification of a fluid density at the solid surfaces, allowing easy control of the local contact angle. The code developed is tested against previously published and validated finite volume/volume-of-fluid simulations of free droplet coalescence, with good agreement seen in the predicted dynamics. The interactions between individual water droplets and fibres is explored, in particular to establish critical conditions (flow speed, fibre contact angle, droplet/fibre size, droplet-fibre separation, fuel viscosity etc.) under which droplets carried by the flow can be captured by fibres, and the conditions under which droplets are released from fibres. The results confirm the difficulties in achieving rapid and effective coalescence when the interfacial tension is low, and reveal the sensitivity of the droplet-fibre dynamics to the contact angle on the fibres and the relative size of the droplets and fibres. In particular larger fibres are not effective for small droplets, so small fibres are essential in the filtration process. Also investigated are the dynamics of multiple droplets with arrays of fibres representing the filtration media. It is found that higher contact angles ( > 120°) lead to lower capture efficiency compared to lower contact angle, while contact angles less than 106° tend to produce a small variation in capture efficiency and capture most of the droplets at a filter porosity of 0.87. It is concluded that the inlet layer of the filter should have fibres with 78° contact angle and the exit layer fibres with contact angle 106°.
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Bao, Sarina. "Filtration of Aluminium-Experiments, Wetting,and Modelling." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-15147.

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The present work deals with the inclusion removal mechanism in aluminium filtration and the use of alternative filter materials. Four routes are investigated. First, an overview of previous research on filtration knowledge is summarized. The filtration mechanism comprises two parts: transport of inclusions to the filter wall and attachment of inclusions on the wall. We have mainly investigated collision by interception and the wetting (surface tension) of inclusion-Al and Al-filter in this work. Second, the wetting behaviour of inclusion-Al and Al-filter is measured in the laboratory. In filtration it is important that particles to be removed contact, or come close to the filter walls. Therefore the metal carrying the inclusions must come into close contact,i.e. wet the filter material. A systematic and comprehensive investigation of the wetting behaviour in the molten aluminium-filter system is presented. In aluminium filtration,alumina is the most common filter material, even though alumina is not wetted by aluminium. Therefore we have investigated the use of alternative filter materials withimproved wetting. In the laboratory, SiC and graphite demonstrate good wetting bymolten aluminium. Problems with these materials exist, as SiC is easily oxidized to SiO2 and both react with aluminium to give Al4C3. However, SiO2 and SiC react slowly with aluminium, but this does not seem to influence the wetting. The wettability of the inclusion-Al may play a key role in aluminium filtration. Particlesto be removed should ideally have poor wetting with aluminium and filter should hasgood wetting with aluminium. A challenge is that SiC and Al4C3 inclusions show betterwetting with aluminium than alumina. Third, plant scale filtration experiments were carried out with Al2O3 and SiC industrial filters. Metal composition was not changed by the industrial filters. Improved wetting of aluminium on filter materials is an advantage in getting molten metal to infiltrate filtersand thus to improve the filtration efficiency. A SiC filter gives better filtration efficiency. Filtration efficiency increases with particle size. SiC reacts with aluminium so slowly that no carbide inclusions were produced in the industrial SiC filter with approximately 60% of SiC. SiC filters have better wetting than Al2O3 filters with aluminium. Thus SiC could be a good alternative filter material. Fourth, a theoretical model is developed regarding the interceptional and gravitational collision considering the filter as a collection of branches (cylinders). A filtration efficiency equation is derived based on particle diameter, branch diameter, porosity,filter thickness, filter specific surface area, and Reynolds number. The filtration efficiency decreases with the flow rate until it reaches a minimum, and then increases. Gravitational collision must be taken into account at the lower flowrates. The greater the velocity the less time particles have to settle. Thus gravitationalcollision efficiency decays with increasing flow rate. The interceptional collision efficiency increases with the velocity since then more liquid and particles come into contact with the collector. The interceptional collision efficiency that dominates at high velocities is the main topic of the model
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Tupas, Ronald-Ray Tiñana. "Artificial neural network modelling of filtration performance." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0011/MQ59890.pdf.

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Taha, Taha. "CFD modelling of slug flow enhanced membrane filtration." Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403424.

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Brignoni, Jimmy. "Modelling transfer processes /." [S.l.] : [s.n.], 2009. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.

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Mullins, Benjamin James, and n/a. "Study of Capture, Fibre Wetting and Flow Processes in Wet Filtration and Liquid Aerosol Filtration." Griffith University. School of Environmental Engineering, 2004. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20040919.124658.

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This thesis examines the particle capture, fibre wetting and droplet flow processes within wet filters collecting solid and liquid aerosols and within filters collecting only liquid aerosols. The processes involved in this type of filtration were examined through a series of experiments and models developed to describe the behaviour of fibre/liquid systems. This work can be summarized in 4 categories: (1) The bounce and immediate re-entrainment of liquid and solid monodisperse aerosols under a stable filtration regime (pre cake formation) by wet and dry fibrous filters. In this work it was found that the solid particles generally exhibited a lower fractional filtration efficiency than liquid particles (of the same size), although this difference decreased in the smaller size fractions. However, for the wet filtration regime (each fibre of the filter was coated by a film of water), no significant difference in filtration efficiency was detectable between solid and liquid aerosols. Either the bounce effect of the particles is inhibited by the liquid film, or the filtration conditions in the wet filter are so different that the aerosol properties are less significant with respect to capture. (2) A microscopic study of the effect of fibre orientation on the fibre wetting process and flow of liquid droplets along filter fibres when subjected to airflow and gravity forces was conducted. The flow of the liquid collected by the fibres was observed and measured using a specially developed micro-cell, detailed in the thesis. The experimental results were compared to a theoretical model developed to describe the flow of droplets on fibres. The theory and experimental results showed a good agreement. A sensitivity analysis of the model was performed which showed the droplet radius to be the most significant parameter. The model has the potential to improve filter self-cleaning and minimise water use. (3) An experimental study of the capture of solid and liquid (oil) aerosols on fibrous filters wetted with water. Variable quantities of liquid irrigation were used, and the possibility for subsequent fibre regeneration after clogging or drying was also studied. It was found that self-cleaning (removal of solid aerosols by water) occurred even under heavily dust-laden conditions, and post evaporation of water. With the collection of oil aerosols on fibres wetted with water, a predominance of the barrel shaped droplet on the fibre was observed, with oil droplets displacing water droplets (if the oil and fibre combination created a barrel shaped droplet), creating various compound droplets of oil and water not previously reported in literature. (4) An extensive experimental investigation of the wetting processes of fibre/liquid systems during air filtration (when drag and gravitational forces are acting) has shown many important features, including droplet extension, oscillatory motion, and detachment from fibres as airflow velocity increases. The droplet oscillation is believed to be induced by the onset of the transition from laminar to turbulent flow as droplet size increases. To model such oscillation it was necessary to create a new conceptual model to account for the forces both inducing and preventing such oscillation. The agreement between the model and experimental results is satisfactory for both the radial and transverse oscillations.
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Stanghelle, Daniel. "High temperature filtration of biomass combustion and gasification processes." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2008. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-5273.

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Risnes, Håvar. "High Temperature Filtration in Biomass Combustion and Gasification Processes." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Engineering Science and Technology, 2002. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1485.

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High temperature filtration in combustion and gasification processes is a highly interdisciplinary field. Thus, particle technology in general has to be supported by elements of physics, chemistry, thermodynamics and heat and mass transfer processes. This topic can be addressed in many ways, phenomenological, based on the up stream processes (i.e. dust/aerosol formation and characterisation) or apparatus oriented.

The efficiency of the thermochemical conversion process and the subsequent emission control are major important areas in the development of environmentally sound and sustainable technology. Both are highly important for combustion and gasification plant design, operation and economy.

This thesis is divided into four parts:

I. High temperature cleaning in combustion processes.

II. Design evaluations of the Panel Bed Filter technology.

III. Biomass gasification

IV. High temperature cleaning of biomass gasification product gas

The first part validates the filter performance through field experiments on a full scale filter element employed to a biomass combustion process and relates the results to state of the art within comparable technologies (i.e. based on surface filtration). The derived field experience led to new incentives in the search for a simplified design featuring increased capacity. Thus, enabling both high efficiency and simplified production and maintenance. A thorough examination of design fundamentals leading to the development of a new filter geometry is presented.

It is evident that the up-stream process has significant influence upon the operation conditions of a filter unit. This has lead to a detailed investigation of some selected aspects related to the thermochemical conversion. Furthermore, the influence of fuel characteristics upon conversion and product gas quality is discussed.

The last part discusses the quality of biomass gasification product gas and requirements put upon the utilisation of this gas in turbines, diesel engines or other high temperature applications. Filtration experiments conducted on product gas derived from wood gasification are reported and discussed.

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19

Dutton, Richard John. "Modelling transient storage processes." Thesis, University of Sheffield, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419618.

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Greenwood, Robert Mark. "Modelling processes with constraints." Thesis, University of Southampton, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261508.

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Alpay, Laurence Lea. "Modelling medical diagnostic processes." Thesis, Open University, 1990. http://oro.open.ac.uk/56449/.

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The thesis investigates the development of medical reasoning processes and how student modelling of such processes can be achieved in intelligent tutoring systems. The domain of orthopaedics was chosen for the research. Literature has shown that medical reasoning has been modelled mainly from an expert point of view. The research problem addressed is to model explicitly various levels of medical expertise in terms of reasoning strategies. The thesis reports on a system, DEMEREST (DEvelopment of MEdical REasoning STrategies), a developmental user model component which describes successive stages of medical reasoning and which could ultimately be part of a medical tutor. The system diagnoses physicians' reasoning strategies, determines the level of expertise and produces a plan corresponding to the application of these strategies. As a basis of doing so, a set of seven reasoning strategies was identified in the medical problem solving literature. These strategies are based on generalisation, specialisation, confirmation, elimination, problem refinement, hypothesis generation and anatomy. An empirical study was carried out to examine the development of these strategies. Protocols of ten physicians at various levels of expertise were collected and analysed. A number of interactions of strategies at different levels of expertise was identified in half of these protocols and this information was used to construct a model of changes of strategies over time. Planning in· artificial intelligence was used as a means of decomposing medical problem solving into a set of goals; the goals being associated with the reasoning strategies. By taking this approach, medical reasoning is viewed as a planning process. The remaining protocols from the empirical study were used to evaluate DEMEREST. The system was tested for its ability to determine a level of expertise for each protocol, model the reasoning strategies applied and their interactions, and generate a plan for each protocol. The assessment of the overall performance of the system showed that it was successful. This assessment also helped to identify conceptual as well as implementation constraints of the prototype system. The main result of the research undertaken in this thesis is that the design of the system DEMEREST demonstrates the feasibility of modelling the development of medical reasoning strategies and its usefulness for student modelling.
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22

Jones, Oliver Peter. "Modelling headland sandbank processes." Thesis, University College London (University of London), 2007. http://discovery.ucl.ac.uk/1446077/.

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This thesis describes an investigation into near-shore headland-associated sandbanks that used process-based modelling techniques. The modelling experiments involved tidal, wave, sediment transport and morphological modules. The motivation came from a need to understand the dynamics of near-shore headland sandbanks which are valuable resources of raw material, ecology and coastal protection. An idealised model of a coastal headland was first used in which the physical system was simplified in order to quantify the influence of individual variables on sandbank initiation and growth. This approach provided a number of useful insights into headland sandbank dynamics. Firstly, the relative impact of the Coriolis force was shown to be minor in comparison with parameters including the seabed slope, headland geometry and tidal forcing. It was shown that a causal relationship between sandbank initiation and headland eddies does not exist. For certain headland geometries, however, the model suggested that the eddies become important in the long term maintenance of the associated headland sandbanks. The initiation and potential growth mechanisms of a real near-shore sandbank in the central Bristol Channel have also been investigated. The results confirmed many of the ideas obtained from the idealised investigation and provided a number of new insights into the complex physical system in which the bank exists. The presence of a wave- induced mechanism was detected, capable of replenishing sandy material in the large coastal embayments and supplying the headland sandbanks of the central Bristol Channel. The work also suggested that the sandbank itself was initiated, and its position controlled, by large gradients in the tidal currents produced by the headland. Its further maintenance and development was shown to be the result of a self- sustaining feedback mechanism, detected in the surrounding flow field.
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23

Marda, Saurabh. "Effect of Ozonation and BAC Filtration Processes on Monochloramine Demand." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/10577.

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Although the kinetics and mechanism of monochloramine decay in organic-free waters are relatively well understood, those in natural waters are not, due to exceedingly complex and poorly defined interactions of monochloramine with natural organic matter (NOM) and particles. Ozonation followed by a biologically activated carbon (BAC) filtration is a commonly practiced process option that affects the characteristics of both dissolved and particulate constituents in the water. However, how these changes in water constituents affect stability of the residual disinfectant, or monochloramine in particular, are currently unknown. Kinetics of monochloramine decay in water samples obtained before and after ozonation and BAC treatments were performed under varying operating conditions were determined by bench-scale batch experiments. Stability of monochloramine in the BAC filter effluent samples obtained at different times after backwashing was determined. It was found that in most cases monochloramine stability was greatly decreased after BAC filtration. Further filtering the BAC effluents with 1.2 and #61549;m polycarbonate membrane resulted in a substantial increase in monochloramine stability. A further increase was observed after filtering the samples using a 0.4 m membrane. This finding suggested that particulate matter generated from the filters could be the major cause of monochloramine instability. The fines from the activated carbon, possible components of the particulate matter eluting from the BAC filters, were found to exert an insignificant monochloramine demand both in the presence and absence of NOM, which is contrary to previous speculation in the literature about their demand for monochloramine. While there appears to exist a relationship between chloramine demand and HPC count of the filter effluent, more research will be needed to determine the effect of nature and type of microorganisms and their byproducts have on chloramine demand. Effect of ozonation on monochloramine stability is also under investigation using both the water sampled from full-scale plant and the synthetic water prepared with Suwannee River NOM.
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24

Ahmad, A. L. "Electrophoretic pulse filter cake release in dead-end filtration processes." Thesis, Swansea University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.635852.

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The application of pulsed electric field for filter cake release is used in dead-end filtration processes to remove materials deposited on the membrane surface by means of an electrophoretic effect. The released materials are swept out of the filtration module immediately at the end of each cleaning interval. An automatic test rig was developed to carry out the experiments and the process was tested for microfiltration and ultrafiltration processes using inorganic and biological materials as the process feeds. The effect of the process variables of pulse interval, pulse duration, pH, ionic strength, feed concentration and voltage applied were studied in detail. The experimental data collected, for all parameters, show that the use of pulsed electric fields and filter cake release is an effective means of collecting filter cakes from the membrane surface at enhanced filtration rates. A force balance model was developed to predict the average filtration rate at the end of cleaning process, taking both electrophoretic and electroosmosis effects into account. This model shows reasonable quantitative agreement with the experimental values in many cases. The process developed is most likely to find application in the clarification of process streams of low solute content.
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25

Zhao, Qihong. "Modelling removal efficiency for polydisperse suspensions in deep bed filtration." Thesis, University of Dundee, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265204.

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26

Qin, Yong. "Dynamic modelling of combustion processes." Thesis, Cardiff University, 2007. http://orca.cf.ac.uk/55453/.

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Neural aided combustion oscillator models (NACO) have been developed for time domain prediction of low frequency oscillations. The NACO method consists of two stages, one is the design of a core-stimulation (CS) model based on the co.
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27

Peng, B. "Molecular modelling of petroleum processes." Thesis, University of Manchester, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.515182.

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28

Curcin, Vasa`. "Workflow modelling for scientific processes." Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504975.

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Botten, Aleksandra Joanna. "Modelling single screw extrusion processes." Thesis, University of Birmingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396429.

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Szymanski, Marek Artur. "Modelling of silicon oxidation processes." Thesis, University College London (University of London), 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395532.

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31

Bai, Chengxin. "Modelling of spray impingement processes." Thesis, Online version, 1996. http://ethos.bl.uk/OrderDetails.do?did=1&uin=uk.bl.ethos.299814.

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32

Merchant, Tushar Praful. "Modelling of rapid thermal processes." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11784.

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33

Stockwell, Deianeira Zoe Zita. "Modelling some tropospheric cloud processes." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627185.

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34

Andrade, Pacheco R. "Gaussian processes for spatiotemporal modelling." Thesis, University of Sheffield, 2015. http://etheses.whiterose.ac.uk/11173/.

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A statistical framework for spatiotemporal modelling should ideally be able to assimilate different types of data from different of sources. Gaussian processes are commonly used tool for interpolating values across time and space domains. In this thesis we work on extending the Gaussian processes framework to deal with diverse noise model assumptions. We present a model based on a hybrid approach that combines some of the features of the discriminative and generative perspectives, allowing continuous dimensionality reduction of hybrid discrete-continuous data, discriminative classification with missing inputs and manifold learning informed by class labels. We present an application of malaria density modelling across Uganda using administrative records. This disease represents a threat for approximately 3.3 billion people around the globe. The analysis of malaria based on the records available faces two main complications: noise induced by a highly variable rate of reporting health facilities; and lack of comparability across time, due to changes in districts delimitation. We define a Gaussian process model able to assimilate this features in the data and provide an insight on the generating process behind the records. Finally, a method to monitor malaria case-counts is proposed. We use vector-valued covariance kernels to analyze the time series components individually. The short term variations of the infection are divided into four cyclical phases. The graphical tool provided can help quick response planning and resources allocation.
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35

Kick, Marco. "Coalgebraic modelling of timed processes." Thesis, University of Edinburgh, 2004. http://hdl.handle.net/1842/24771.

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This thesis presents an abstract mathematical account of timed processes and their operational semantics, where time is modelled by a special kind of monoids, so-called time domains, and (the operational behaviour of) timed processes is represented by special labelled transition systems, so-called timed transition systems (TTSs), together with time bisimulation as an appropriate notion of equivalence of such processes. The importance of monoid-related notions for describing timed phenomena is then illustrated by showing that TTSs are the same as the (partial) actions of the monoid of time; moreover, total monoid actions are also shown to arise naturally in this approach in the form of delay operators. The two kinds of monoid actions are suitably combined in a new motion of biaction which captures the interplay of two very important features of timed processes: letting time pass and delaying. The TTSs are then characterised as coalgebras of a novel evolution comonad, which is inspired by well-known categorical descriptions of total monoid actions; in doing so, a coalgebraic description of time bisimulation is also provided. Additionally, biactions are characterised as bialgebras of a distributive law of a monad (for total monoid actions) over a comonad (the evolution comonad for partial monoid actions). Building on these results, it is possible to obtain an abstract categorical treatment of operational rules for timed processes. The approach taken here is based on the frame-work by Turi and Plotkin, using distributive laws and bialgebras (similar to the treatment of biactions), and which, subsequently, is extended to accommodate behaviour comonads, as required for the coalgebraic description of TTSs. These abstract rules then form the basis for the development of several new syntactic rule formats for timed processes which describe classes of particularly ‘well-behaved’ languages for specifying timed processes.
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36

Abdullah, Zia. "Mathematical modelling of casting processes." Thesis, University of Ottawa (Canada), 1988. http://hdl.handle.net/10393/21048.

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37

Price, Robert. "A study of hybrid clarification-filtration processes for potable water treatment." Thesis, University of Nottingham, 2005. http://eprints.nottingham.ac.uk/12410/.

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This research investigates the removal of natural organic matter (NOM) from low turbidity waters by optimising an integrated coagulation and membrane filtration process. In conjunction with a regional water utility, the feasibility and operability of pre-coagulation with ultrafiltration membrane units, is investigated at both the fundamental and applied levels. The pH of coagulation greatly affects the growth of flocs. Although flocs are produced over the range of pH values, there is a significant improvement in performance at the optimum pH. The results show that for ferric sulphate, the optimum pH value for coagulation was 4.8; for ferric chloride the optimum pH value was 5.0; and for alum the optimum pH value was 6. Manipulation of the mixing regime during orthokinetic flocculation allows control of the final floe size. A high shear rate (447 s-1) induces greater particle collision and micro-floc formation, allowing an increased rate of growth during slow mixing. A mixing regime of 60 seconds rapid mixing (shear rate G= 447 s­-1) followed by 3 minutes slow mixing (shear rate G= 20 s-1) is required for flocculation of the NOM and adequate enmeshment and removal of excess iron. Experiments conducted with the optimised coagulation regime and a Norit hollow fibre ultrafiltration membrane, operated in dead-end mode, leads to significant fouling. The results for the submerged Zenon ultrafiltration membrane also indicated membrane fouling, when the coagulation regime was optimised for NOM reduction and iron removal. Changing the coagulation regime altered the level of membrane fouling. It can be concluded that the optimum coagulation conditions in conventional water treatment are not always the optimum conditions for coagulation with ultrafiltration treatment and the unconventional coagulation conditions can be much more effective, than the conventional ones, in the context of membrane filtration, depending on the raw water characteristics.
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38

Sanches, Sandra. "Integration of Membrane Filtration and Photolysis Processes for Drinking Water Treatment." Doctoral thesis, Universidade Nova de Lisboa. Instituto de Tecnologia Química e Biológica, 2013. http://hdl.handle.net/10362/12031.

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Dissertation presented to obtain the Ph.D degree in Engineering and Technology Sciences, Chemical Engineering.
Water is a fundamental resource for life. The presence of hazardous micropollutants such as pesticides and hormones in drinking water sources as well as the evidence of their presence in several treated waters raised concerns regarding the quality of the water intended for human consumption. The development of new technologies which are able to cope with these micropollutants and ensure the fulfillment of future more stringent regulations is therefore needed. Low pressure ultraviolet direct and indirect photolysis (using hydrogen peroxide and titanium dioxide) and nanofiltration are extremely promising technologies to effectively remove organic micropollutants from water.(...)
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39

Headey, Jonathan Mark. "Modelling of river corridors : modelling urban particulate transport processes." Thesis, University of Birmingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289714.

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40

Sidborn, Magnus. "Modelling Some Biochemically Processes in Rocks." Licentiate thesis, KTH, Chemical Engineering and Technology, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1679.

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A model for studying oxygen depletion in subsurfacefractured rock have been developed. It is based on currentknowledge in several different reasearch disciplines such asgeology, microbiology and hydrology. The model may be a usefultool for predicting oxygen penetration in rock fractures. Thisis important for example in the safety assessment of a deeprock nuclear waste repository. In such a repositroy a reducingenvironment is desirable. Several potential oxygen consumingprocesses, both parallel and serial, were identified, each ofwhich may considerably contribute to the depletion of oxygen.Abiotic as well as microbially mediated oxidation of rockminerals coupled with transport processes, both in thefractures and the rock matrix, were included. The model wasdivided into a number of case studies in which only one or afew processes were studied at a time. The different cases werethen compared so that the relative importance of each processcould be evaluated at different conditions. Even if it would bepossible to model all the processes simultaneously, thisapproach was chosen from result transparency and numericalefficiency reasons. The results show that in a relatively shorttime perspective, when oxidizable minerals are available in thefracture, reaction kinetics are important. In a long timeperspective, however, minerals in and adjacent to the fracturebecome oxidized and matrix diffusion is rate limiting.

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41

Ramkhelawan, Pratima. "Modelling and estimation of polycondensation processes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0020/MQ49725.pdf.

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42

Terrill, E. L. "Mathematical modelling of some spinning processes." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280001.

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43

Patterson, Michael Dickson. "Shallow water modelling of nearshore processes." Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393947.

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Siebler, Frank. "Connectionist modelling of social judgement processes." Thesis, University of Kent, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369679.

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Ou, Xiaoling. "Batch process modelling with Gaussian processes." Thesis, University of Newcastle Upon Tyne, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.440591.

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Marrocu, Emanuela. "Modelling identification and forecasting nonlinear processes." Thesis, University of Warwick, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340086.

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47

Pinney, Huw David. "Modelling chromatic processes in human vision." Thesis, City University London, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332774.

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48

Balla, Tobias. "Modelling of microelectronic processes and materials." Thesis, University of Southampton, 2011. https://eprints.soton.ac.uk/348865/.

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Organic electronics promises the creation of electronic components on flexible materials at low temperatures, by fast techniques and more environmentally friendly processes. The research followed two directions. The first part focused on the manufacturing technique nanoimprint lithography (NIL). A comprehensive review was undertaken and process capabilities were compared for trends. It was seen that small feature sizes (< 50 nm) have not been replicated over areas greater than 4 mm2, while aspect ratios greater than 10 have not been achieved. A questionnaire addressing market opportunities suggested NIL is likely to compete for the production of devices that currently use electron beam lithography and laser writing processes that are seeking to change their business strategy from a differentiation base to a cost reduction. NIL must also prove to customers that it is an economical investment. However, improvements in stamp creation, analysis techniques and overlay alignment need to be addressed for a larger share of the microfabrication market. It was apparent that physical limits exist to which imprints can be produced and an analytical model could predict these. A model was created to describe the de-embossing step and to explore how the various material properties and process variables interact. It showed a very strong dependence on the achievable aspect ratio on the pattern area ratio and the interfacial shear stress; that de-embossing using fluorinated coatings and current standard polymers is unlikely to fail for post radii on the order of 100 nm due to adhesion and that large area ratios and aspect ratios are more easily achieved by maintaining the polymer/stamp Young’s moduli ratio (RE) in the range 0.003 to 5. The second part of the research looked at the formation of crescent singularities in thin sheet materials, which affects the production of polymer electronic based devices produced by the sponsoring company. The author compared an analytical model by Cerda and Mahadevan for the formation of developable cones (d-cones) to a finite element (FE) model and showed that explicit elements could mimic the formation of a d-cone. Different elements were analysed for their suitability and the Belytschko-Lin-Tsay (BT) element was chosen based on its speed, robustness and similarity to the analytical results. An adapted three-point bend test set-up was conceived that would enable specific attributes to be independently varied, to understand their effect on d-cone formation in thin sheets. Digital image correlation (DIC) was used to calculate the displacements and strains. The same set-up was modelled using an FE model with the chosen BT element. The DIC results showed a variation in strain with plunger displacement before the visual appearance of a developable cone and that it occurred between 0.1 and 0.4 % in-plane strain. The FE data showed a similar trend to the DIC results, showing a change in strain once a d-cone began to form. Improvements and suggestions were then made advising how to make the DIC and FE models more accurate.
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Leonhardt, Kelly. "Modelling of electrochemical processes at microelectrodes." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/344287/.

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In this work, the finite element modelling of 2D and 3D scanning electrochemical microsopy (SECM) systems is presented. The main focus has been on the influence of tip geometry and the presence of defects on the limiting current of the SECM tip. The geometry of the electrode of particular interest is conical with conical insulation, as this is the shape of AFM-SECM probes fabricated by our coworkers. This thesis presents an extensive study of the electrochemical response of conical electrodes both in the bulk solution and close to a surface. Key equations were derived for conical electrodes and a thorough quantitative analysis of the influence of the tip geometry, be it the parameters describing it or the presence of defects, is reported. A novel equation was derived to calculate the current in the bulk at a conical electrode with conical insulation and an extensive study of possible defects was conducted to allow users to adjust the expression and obtain a more accurate estimation of the limiting current. The spatial resolution defined as the ability of an electroactive probe to detect a conducting region of a given size- and the lateral resolution -the distance necessary to fully resolve a conducting region form an inert region- were both investigated for a range of geometries as well as for a selection of defects. This enables us to draw conclusions on the ideal tip, and how sensitive it would be to features of the substrate. A set of equations was derived to describe positive and negative feedback approach curves for cones, and steps were defined for users to determine the shape of the electrode from experimental approach curves. Simulated curves are also provided to help with the extraction of kinetics at the substrate surface from the experimental approach curves. Finally, the influence of a ring disc tip geometry was evaluated by monitoring the collection efficiency as a function of tip-substrate distance for different disc-ring separations.
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Jidling, Carl. "Strain Field Modelling using Gaussian Processes." Thesis, Uppsala universitet, Avdelningen för systemteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-315254.

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This report deals with reconstruction of strain fields within deformed materials. The method relies upon data generated from Bragg edge measurements, in which information is gained from neutron beams that are sent through the sample. The reconstruction has been made by modelling the strain field as a Gaussian process, assigned a covariance structure customized by incorporation of the so-called equilibrium constraints. By making use of an approximation scheme well suited for the problem, the complexity of the computations has been significantly reduced. The results from numerical simulations indicates a better performance as compared to previous work in this area.
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