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1
Kriel, Carmen Cornelia. "Gel-particles for ink-jet paper coating applications". Thesis, Stellenbosch : Stellenbosch University, 2004. http://hdl.handle.net/10019.1/49970.
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Thesis (MSc)--Stellenbosch University, 2004.ENGLISH ABSTRACT: An unsaturated, linear, aliphatic polyamide was synthesized from 1,6-hexanediamine and fumaric acid by means of a phosphorylation polycondensation reaction, and successfully crosslinked with a vinyl monomer during an inverse suspension polymerization reaction. The two vinyl monomers that were used were 2-hydroxyethyl methacrylate (HEMA) and 4-vinyl pyridine. The linear polyamide was characterized by means of nuclear magnetic resonance (NMR) and electrospray mass spectrometry (ESMS), while the crosslinked product was characterized by light scattering and scanning electron microscopy (SEM), as well as cryo-SEM. The average particle diameters of the crosslinked product were found to be in the range of 100 to 300 nm. One of the synthesized crosslinked products was used in coating formulations on starchcoated paper. The paper samples were evaluated and compared on the basis of printing quality, colour density and colour uniformity of a printed image, as well as the wet-rub resistance of the coating. A formulation containing 0,1% of the HEMA crosslinked polyamide product was found to give the best performance of the printed image in terms of printing quality, colour density and colour uniformity. Wet-rub resistance was found to improve with increasing concentration of the crosslinked polyamide product.
AFRIKAANSE OPSOMMING: 'n Onversadigde, lineêre, alifatiese poli-amied is berei vanaf die monomere 1,6- heksaandiamien en fumaarsuur deur middel van 'n fosforilasie-polikondensasie reaksie, waarna die produk suksesvol gekruisbind is tydens 'n inverse-suspensie polimerisasiereaksie. Twee vinielmonomere, naamlik 2-hidroksi-etiel-metakrilaat (HEMA) en 4- viniel-piridien, is gebruik. Die lineêre poli-amied is deur middel van kern magnetiese resonansie (KMR) en elektronsproei-massaspektrornetrie (ESMS) gekarakteriseer, en die kruisgebinde produk deur middel van ligverstrooing, skandeer-elektronrnikroskopie (SEM), en lae-temperatuur SEM. Daar is bevind dat die gemiddelde partikeldeursneë van die kruisgebinde produk tussen 100 en 300 nm was. Een van die bereide, kruisgebinde produkte (wat met HEMA kruisgebind is) is gebruik in bedekkingsformules op stysel-bedekte papier. Die papiermonsters is ge-evalueer en vergelyk ten opsigte van drukkwaliteit en die diepte en egaligheid van die kleur van 'n gedrukte beeld, asook die natskuurweerstand van die deklaag. Daar is bevind dat 'n formulering wat 0.1% van die kruisgebinde poli-amied produk bevat die beste vertoning lewer in terme van drukkwaliteit, kleur diepte en egaligheid van kleur. Daar is verder bevind dat die natskuurweerstand van die deklaag verbeter het wanneer die konsentrasie van die kruisgebinde poli-amied produk in die formulering verhoog is.
2
Laitinen, O. (Ossi). "Utilisation of tube flow fractionation in fibre and particle analysis". Doctoral thesis, Oulun yliopisto, 2011. http://urn.fi/urn:isbn:9789514294495.
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Abstract The tube flow fractionation method used in this thesis is one of the field flow separation processes, which can be used to fractionate particles over the entire size range of pulp particles (1–5000 µm) with high selectivity. The classification of particles in different size categories enables the fractional analysis of samples. According to this thesis, particle length is the most significant individual shape factor in particle classification for different size categories using tube flow fractionation. The fractional approach investigated in this thesis offers an interesting tool for investigating different pulp types more thoroughly than many other conventional laboratory methods such as the Bauer-McNett classification of pulp or the hyperwashing of DIP samples. The tube flow fractionator can be used to replace the Bauer-McNett device to determine the mass percentages of pulp sample fractions. Furthermore, pulp fractionation can be done quickly with the tube flow fractionation method and the results achieved are also comparable to the Bauer-McNett classification. The utilisation of recycled raw material in paper production is likely to continue to increase in the near future. This fact leads to even more heterogeneous raw material becoming one of the major challenges in deinked pulp production. Changes in the quality of raw material such as age or paper type have a notable effect on the deinkability of pulp. This creates a need to develop new methods for measuring DIP properties; in particular, information about the ink-releasing rate and ink particle size would be useful in controlling the deinking process. If DIP is fractionated with tube flow fractionation, it is possible to study the ink size distribution and ink content inside each fraction, thus obtaining fractional information on the ink release rate and ink particle size. A comparison of different DIP raw materials and process solutions can be performed with the fractional analysis presented in this thesis. It was noticed that aging had a negative effect on the slushing rate of LWC and SC raw material, but not on ONP. The ink detachment of LWC and SC was poorer when furnishes aged. However, the aging of LWC and SC did not result in a significant fragmentation of ink particles. In contrast, strong ink fragmentation is typical of aged ONP furnishes. The fractional approach gives new insight into deinking mechanisms, and could be essential for finding optimal deinking process conditions, for example in a pulping process or flotation environment. The method would also enable enhanced control of different DIP process stages and would contribute to creating a more efficient process with better waste management and improved final product qualityTiivistelmä Tässä työssä käytetyllä putkivirtausfraktioinnilla, joka on eräs kenttävirtausfraktioinnin sovellus, voidaan luokitella hyvin selektiivisesti erikokoisia (1–5000 µm) partikkeleita. Partikkeleiden luokittelu partikkelikooltaan erikokoisiin jakeisiin mahdollistaa näytteiden fraktionaalisen analyysin. Tässä työssä todettiin, että partikkelin pituus on tärkein yksittäinen muototekijä, joka vaikuttaa partikkelien fraktioitumiseen eri kokoluokkiin putkivirtausfraktioinnissa. Työssä tutkittu fraktionaalinen menetelmä mahdollistaa paljon syvällisemmän paperisulppujen analyysin kuin monet perinteiset laboratorioanalyysit, kuten Bauer McNett -luokittelu tai siistausmassojen hyperpesu. Putkivirtausfraktionaattorilla voidaan korvata Bauer McNett -luokittelu massasulppujen eri fraktioiden massaosuuksien määrityksessä. Lisäksi massojen fraktiointi putkivirtausfraktionaattorilla on nopea ja luotettava menetelmä, ja saadut tulokset ovat vertailukelpoisia Bauer McNett -luokittelulla saatujen tulosten kanssa. Kierrätyspaperiraaka-aineen kasvava hyödyntäminen paperin tuotannossa jatkunee lähivuosina. Tämä tarkoittaa, että siistausprosessissa hyödynnettävän raaka-aineen laatuvaihtelut aiheuttavat entistä suurempia haasteita. Muutokset raaka-aineen laadussa, kuten paperin ikä tai käytetty paperityyppi vaikuttavat huomattavasti massan siistattavuuteen. Näistä tekijöistä johtuen on tarvetta kehittää uusia mittausmenetelmiä määrittää siistausmassojen ominaisuuksia. Erityisesti musteen irtoaminen ja mustepartikkeleiden kokojen määritys voisi auttaa musteenpoistoprosessin ohjauksessa. Jos siistausmassa fraktioidaan putkivirtausfraktionaattorilla, on mahdollista tutkia mustekokojakaumia ja mustepitoisuuksia eri fraktioissa ja näin saadaan tietoa mustepartikkeleiden irtoamisesta ja mustepartikkelien koosta. Fraktionaalisella analyysilla on tässä työssä tutkittu eri siistausmassojen raaka-aineita ja prosessiratkaisuja. Työssä huomattiin, että LWC- ja SC-paperin ikääntymisellä on negatiivinen vaikutus paperin sulputtumisnopeuteen pulpperissa, mutta sanomalehtipaperilla vastaavaa ilmiötä ei huomattu. Musteen irtoaminen oli huonompaa LWC- ja SC-paperin ikääntyessä. Kuitenkaan ikääntyminen ei vaikuttanut LWC- ja SC-paperin mustepartikkeleiden pilkkoutumiseen merkittävästi. Sen sijaan sanomalehtipaperilla havaittiin voimakasta mustepartikkeleiden pilkkoutumista raaka-aineen ikääntyessä. Fraktionaalinen tutkiminen antaa uuden näkökulman musteenpoistomekanismeihin ja voisi olla hyödyllinen, kun etsitään optimaalisia musteenpoisto-olosuhteita esimerkiksi pulpperointiin tai flotaatioon. Menetelmä voisi mahdollistaa myös eri siistausprosessin osaprosessien säätämisen. Lisäsi menetelmän avulla voitaisiin saada tehostettua prosesseja ja parannettua laatua sekä saada prosesseista ympäristöystävällisempiä
3
Gläser, Kerstin. "Ink Jet Printing auf Wasseroberflächen und dessen Verwendung zur Stabilisierung von Mikrosieben". Doctoral thesis, Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-216849.
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In dieser Arbeit wird gezeigt, wie Mikrosiebe über das Float Casting Verfahren hergestellt und durch Ink Jet Druck stabilisiert werden. Dazu wurde ein Verfahren entwickelt, das es erlaubt Mikrosiebe großflächig auf einem Langmuirtrog herzustellen und noch schwimmend auf der Wasseroberfläche zu bedrucken, so dass stabilisierte Mikrosiebe von der Wasseroberfläche abgehoben werden können. Zur Herstellung der Mikrosiebe wird das Prinzip der Partikel-assistierten Benetzung verwendet, bei dem eine Dispersion aus Silikapartikeln, Monomer und Initiator auf einer Wasseroberfläche gespreitet wird. Die Partikel ordnen sich dabei von selbst in einer hexagonal dichtesten Packung an und dienen sowohl als Spreithilfe als auch als Porenbildner. Nach dem Entfernen der Partikel entsteht ein poröses Mikrosieb mit einheitlichen, dicht gepackten Poren. Durch das Aufdrucken einer Wabenstruktur als Stützstruktur wird eine ausreichende Stabilisierung erreicht, so dass die Siebe in Filtrationsversuchen eingesetzt werden können. Das entstehende Gefüge, bestehend aus einem Mikrosieb mit einer Dicke im Nanometerbereich wird von einer Stützstruktur, welche eine Dicke im Mikrometerbereich besitzt, stabilisiert.
Außerdem wird gezeigt, wie eine Wasseroberfläche Schritt für Schritt modifiziert wird, so dass es möglich ist grazile Strukturen auf eine Wasseroberfläche zu drucken. Diese Strukturen können anschließend von der Wasseroberfläche abgehoben werden und stehen nach dem Trocknen als freistehende Strukturen zur Verfügung.
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Gazzola, Daniele <1976>. "Control of the position of particles in open microfluidic systems". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/926/.
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Faenza, Andrea <1983>. "Microsystems for electronic positioning and monitoring of single cells and particles". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3629/.
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Grandi, Raffaele <1976>. "Coordination and Control of Autonomous Mobile Robots Swarms by using Particle Swarm Optimization Algorithm and Consensus Theory". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5904/.
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This thesis presents some different techniques designed to drive a swarm of robots in an a-priori unknown environment in order to move the group from a starting area to a final one avoiding obstacles. The presented techniques are based on two different theories used alone or in combination: Swarm Intelligence (SI) and Graph Theory. Both theories are based on the study of interactions between different entities (also called agents or units) in Multi- Agent Systems (MAS). The first one belongs to the Artificial Intelligence context and the second one to the Distributed Systems context. These theories, each one from its own point of view, exploit the emergent behaviour that comes from the interactive work of the entities, in order to achieve a common goal. The features of flexibility and adaptability of the swarm have been exploited with the aim to overcome and to minimize difficulties and problems that can affect one or more units of the group, having minimal impact to the whole group and to the common main target. Another aim of this work is to show the importance of the information shared between the units of the group, such as the communication topology, because it helps to maintain the environmental information, detected by each single agent, updated among the swarm. Swarm Intelligence has been applied to the presented technique, through the Particle Swarm Optimization algorithm (PSO), taking advantage of its features as a navigation system. The Graph Theory has been applied by
exploiting Consensus and the application of the agreement protocol with the aim to maintain the units in a desired and controlled formation. This approach has been followed in order to conserve the power of PSO and to control part of its random behaviour with a distributed control algorithm
like Consensus.
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McKeague, Thomas Anderson. "Holographic particle image velocimetry of ink jet streams". Thesis, Durham University, 2015. http://etheses.dur.ac.uk/10997/.
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Ink jet technology is a rapidly growing and diverse field of research. Ink jets are used to deliver very precise and small (picolitre) volumes of fluid to a surface. Recent advances in ink jet technology demand a better understanding of the dynamics of the fluid during jetting. The aim of this project was to design a method capable of measuring the flow velocities inside ink jet streams. This objective has been achieved by the use of digital holographic particle image velocimetry. The difficulty with measuring flows inside tightly curved samples is that the refractive index change over the boundary leads to an optical distortion and therefore particles cannot be viewed or tracked reliably. Optical distortion is compensated for by taking advantage of the ability to replay a holographically recorded wave. The light scattered by particles is propagated numerically back through the sample’s surface, to form a three-dimensional image in which all refractions at the interface have been accounted for. Three dimensional particle fields are then analysed using custom particle detection and correlation code to extract the displacement of individual particles between exposures, which facilitates the construction of full flow profiles. Holograms were recorded with a simple off-axis holographic microscope, comprising two point sources of divergent light, formed from the same objective lens, acting as the source of illumination and reference light, respectively. Experiments were conducted on continuous ink jet streams of water issuing from a nozzle with 100 µm diameter. For a few millimetres after the nozzle exit, the jet is cylindrical, it then starts to form swells and necks; the swells continue to grow at the expense of the necks until the jet breaks up into a stream of droplets. Measurements of the stream wise component of velocity have been successful in the cylindrical parts of the jet, in swells and in necks greater than 20 µm in diameter. To my knowledge measurements of particle velocities on fluid jets at this scale have not been accomplished previously.
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Emerson, Zachery Ian. "Particle and bubble interactions in flotation systems". Auburn, Ala., 2007. http://repo.lib.auburn.edu/2007%20Spring%20Dissertations/EMERSON_ZACHERY_45.pdf.
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Infantino, Angelo <1985>. "Advanced aspects of radiation protection in the use of particle accelerators in the medical field". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amsdottorato.unibo.it/6807/.
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In this work, the well-known MC code FLUKA was used to simulate the GE PETrace cyclotron (16.5 MeV) installed at “S. Orsola-Malpighi” University Hospital (Bologna, IT) and routinely used in the production of positron emitting radionuclides. Simulations yielded estimates of various quantities of interest, including: the effective dose distribution around the equipment; the effective number of neutron produced per incident proton and their spectral distribution; the activation of the structure of the cyclotron and the vault walls; the activation of the ambient air, in particular the production of 41Ar, the assessment of the saturation yield of radionuclides used in nuclear medicine. The simulations were validated against experimental measurements in terms of physical and transport parameters to be used at the energy range of interest in the medical field.
The validated model was also extensively used in several practical applications uncluding the direct cyclotron production of non-standard radionuclides such as 99mTc, the production of medical radionuclides at TRIUMF (Vancouver, CA) TR13 cyclotron (13 MeV), the complete design of the new PET facility of “Sacro Cuore – Don Calabria” Hospital (Negrar, IT), including the ACSI TR19 (19 MeV) cyclotron, the dose field around the energy selection system (degrader) of a proton therapy cyclotron, the design of plug-doors for a new cyclotron facility, in which a 70 MeV cyclotron will be installed, and the partial decommissioning of a PET facility, including the replacement of a Scanditronix MC17 cyclotron with a new TR19 cyclotron.In questo lavoro, il codice Monte Carlo (MC) FLUKA è stato utilizzato per simulare il ciclotrone GE PETtrace (16.5 MeV) installato presso l’azienda ospedaliera “S. Orsola-Malpighi” (Bologna, IT), quotidianamente utilizzato per la produzione di radiofarmaci PET. Le simulazioni sono state effettuate per valutare diversi fenomeni e quantità d’interesse radiologico tra cui l’equivalente di dose ambientale nell’intorno dell’acceleratore, il numero di neutroni emessi per protone incidente e la loro distribuzione spettrale, l’attivazione dei componenti del ciclotrone e delle pareti del bunker, l’attivazione dell’aria interna al bunker ed in particolare la produzione di 41Ar, la resa a saturazione di radionuclidi d’interesse in medicina nucleare. Le simulazioni sono state validate, in termini di parametri fisici e di trasporto da utilizzare nel range energetico caratteristico delle applicazioni mediche, con una serie di misure sperimentali. Il modello MC validato è stato quindi applicato ad altri casi pratici quali lo studio di fattibilità della produzione diretta in ciclotrone di 99mTc, la produzione di radionuclidi ad uso medico con il ciclotrone TR13 (13 MeV) installato presso il centro di ricerca TRIUMF (Vancouver, CA), la progettazione completa del nuovo centro PET dell’ospedale “Sacro Cuore-Don Calabria” di Negrar (Verona, IT), incluso il ciclotrone ACSI TR19 (19 MeV), lo studio del campo di dose nell’intorno di un sistema di selezione dell’energia (degrader) di un ciclotrone per terapia, la progettazione di specifiche “porte a tappo” per un sito di produzione di radionuclidi ad uso medico, in cui verrà installato un ciclotrone da 70 MeV e sei diverse beam line, e per il parziale decommissioning di un centro PET e la sostituzione di un ciclotrone Scanditronix MC17 (17 MeV), attualmente installato, con una nuova unità TR19.
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Previti, Alberto <1985>. "Fast and accurate numerical solutions in some problems of particle and radiation transport: synthetic acceleration for the method of short characteristics, Doppler-broadened scattering kernel, remote sensing of the cryosphere". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6599/.
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The aim of this work is to present various aspects of numerical simulation of particle and radiation transport for industrial and environmental protection applications, to enable the analysis of complex physical processes in a fast, reliable, and efficient way.
In the first part we deal with speed-up of numerical simulation of neutron transport for nuclear reactor core analysis.
The convergence properties of the source iteration scheme of the Method of Characteristics applied to be heterogeneous structured geometries has been enhanced by means of Boundary Projection Acceleration, enabling the study of 2D and 3D geometries with transport theory without spatial homogenization.
The computational performances have been verified with the C5G7 2D and 3D benchmarks, showing a sensible reduction of iterations and CPU time.
The second part is devoted to the study of temperature-dependent elastic scattering of neutrons for heavy isotopes near to the thermal zone.
A numerical computation of the Doppler convolution of the elastic scattering kernel based on the gas model is presented, for a general energy dependent cross section and scattering law in the center of mass system.
The range of integration has been optimized employing a numerical cutoff, allowing a faster numerical evaluation of the convolution integral.
Legendre moments of the transfer kernel are subsequently obtained by direct quadrature and a numerical analysis of the convergence is presented.
In the third part we focus our attention to remote sensing applications of radiative transfer employed to investigate the Earth's cryosphere.
The photon transport equation is applied to simulate reflectivity of glaciers varying the age of the layer of snow or ice, its thickness, the presence or not other underlying layers, the degree of dust included in the snow, creating a framework able to decipher spectral signals collected by orbiting detectors.Questo lavoro si propone di presentare diversi aspetti della simulazione numerica del trasporto di particelle e di radiazione per applicazioni industriali e di protezione ambientale, per consentire l'analisi di processi fisici complessi in modo veloce, affidabile ed efficiente. Nella prima parte è trattata la velocizzazione della simulazione numerica del trasporto di neutroni per l'analisi del nocciolo di un reattore nucleare. Le proprietà di convergenza della source iteration del Metodo delle Caratteristiche applicate a geometrie strutturate eterogenee sono state migliorate per mezzo della Boundary Projection Acceleration, consentendo lo studio di geometrie 2D e 3D con la teoria del trasporto senza omogeneizzazione spaziale. Le prestazioni computazionali sono state verificate tramite il benchmark C5G7 2D e 3D, mostrando una sensibile riduzione del numero di iterazioni e del tempo di calcolo. La seconda parte è dedicata allo studio dello scattering elastico dei neutroni con isotopi pesanti in funzione della temperatura vicino alla zona termica. È presentato il calcolo numerico della convoluzione Doppler del kernel di scattering elastico col modello gas per una generale sezione d'urto dipendente dall'energia e per una generica legge di scattering nel sistema del centro di massa. L'intervallo di integrazione è stata ottimizzato utilizzando un cutoff numerico, consentendo una valutazione numerica più veloce dell'integrale. I momenti di Legendre del kernel di trasferimento sono successivamente ottenuti per quadratura diretta e validati tramite un'analisi numerica della convergenza. La terza parte è focalizzata alle applicazioni di telerilevamento del trasferimento radiativo per indagini sulla criosfera terrestre. L'equazione del trasporto per fotoni è applicata per simulare la riflettività dei ghiacciai a diverse età dello strato di neve o ghiaccio, al suo spessore, alla presenza o meno di altri strati sottostanti, al grado di polvere inclusa nella neve, creando un sistema in grado di decifrare segnali spettrali raccolti dai rivelatori orbitanti.
11
Mack, Stuart Anderson. "Experimental and computational study of the behaviour of free-cells in discharging silos". Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/experimental-and-computational-study-of-the-behaviour-of-freecells-in-discharging-silos(1f0b6130-7c2c-4a96-ad56-54ff71af2e98).html.
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This study aims to deduce an appropriate shape and density for an electronic free-cell that could be placed into a silo so that position and other desired physical parameters could be recorded. To determine how density and shape affects the trajectory and displacement of free cells, the trajectory and displacement of cylindrical, cuboid and triangular prism free-cells of equivalent volume was investigated in a discharging quasi 3D silo slice. The free-cells were placed at twelve different starting positions spread evenly over one half of the 3D slice. Tests were conducted using a monosized batch of spherical particles with a diameter of approximately 5 mm. Tests were also conducted in a binary mixture consisting of particles of different sizes (5 mm/4 mm) and the same density (1.28 g/cm3) and a binary mixture consisting of particles of different size (6 mm/5 mm) and different densities (1.16 g/cm3/1.28 g/cm3).The rotation of the free cells was also briefly discussed.Computer simulations were conducted using the Discrete Element Method (DEM). The simulation employed the spring-slider-dashpot contact model to represent the normal and tangential force components and the modified Euler integration scheme was applied to calculate the particle velocities and positions at each time step. One trial of each of the metal and plastic, cylindrical, cuboid and triangular prism free cells was compared with the average of three experimental trials. The trajectory and displacement of a representative particle positioned at the same starting position as the free cell was also obtained from DEM simulation and compared with the path and displacement of each of the free cells to determine which free cell followed the particle most closely and hence to determine a suitable free cell that would move with the rest of the grains. Spherical particles are idealised particles. Therefore tests were also conducted with a small number of polyhedral particles, to deduce their flow rate and the critical orifice width at which blockages were likely to form. Simulations were also conducted to test the feasibility of the DEM in modelling the behaviour of these polyhedral particles.Results indicate that for a free cell to move along the same trajectory and have the same displacement and velocity as an equivalent particle in the batch it should have a similar density to the majority of the other particles. A cylindrical free cell of similar density to the particles was found to follow the path of the representative particle more closely than the cuboid or triangular prism. Polyhedral particles were found to have a greater flow rate than spherical particles of equivalent volume.
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Ajjarapu, Kameswara Pavan Kumar. "Sintering Behavior of Ni/TiC Cermet Scaffolds Fabricated via Particle-Based Ink Extrusion 3D Printing". University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1563526881882643.
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Guzman, Francisco J. "Separation of Colloidal Particles in a Packed Column using Depletion Forces". Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/34831.
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Depletion forces were used to separate an equinumber density binary dispersion of 1.5 and 0.82 µm polystyrene sulfate (PS) particles. Experiments consisted of injecting a pulse of a binary dispersion of PS particles into the inlet of a packed bed of 0.5 mm silica collector beads. Prior to injection, a carrier fluid of either KCl and KOH electrolyte or a silica nanoparticle dispersion was flowing through the column at steady state. When the carrier fluid was a dispersion of silica nanoparticles, the ratio of PS particles in the column outlet would change from 1:1 big to small particles to slightly over 2:1. This implies that more of the smaller 0.82 µm particles were being trapped on the surface of the collector beads due to depletion forces. Experiments with a single particle type (either 1.5 or 0.82 µm PS particle) were also done and correlated with the binary dispersion measurements. Potential energy profiles between a PS particle and a flat silica plate were calculated. The secondary energy barrier for the 1.5 µm particles was two times greater than for the 0.82 µm particles. Hence, the 0.82 µm particles were more likely to overcome the energy barrier and get trapped on the surface of the collector beads. Although the potential energy profiles were calculated at equilibrium, they can be used as a tool in finding the optimal conditions for separation.Master of Science
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Charbonnier, Antoine. "Synthèse et caractérisation d'encres électrophorétiques pour la réalisation de papier électronique couleur". Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14660/document.
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Cette thèse s’intéresse principalement à la réalisation de nouvelles encres électrophorétiques pour les applications de type papier électronique couleur. Une méthode simple et peu contraignante basée sur la polymérisation en dispersion a été développée, permettant de réaliser de manière contrôlée et en milieu peu polaire des particules de polymère chargeables positivement ou négativement. Puis, grâce à ce nouvel outil, des particules électrophorétiques hybrides ont été synthétisées à partir de pigments inorganiques et caractérisées sous champ électrique. Enfin une nouvelle solution pour aller vers des dispositifs couleur a été proposée et la fabrication d’un démonstrateur test a été abordéeThe effective sharing of information is a key parameter in our actual society. Electronic paper based on the controlled motion of electrophoretic particles appears thus promising since it combines the advantages of the usual paper (flexibility, reflective display) and the capacity to refresh information on the same support like the more common LCD or OLED technologies. Electrophoretic inks are composed of coloured charged particles which migrate under an electrical field between two electrodes. Depending of the position of the particles on the front plane, the colour on the screen can be tuned. The design of electrophoretic particles based on pigment or dyed polymer and their integration in electronic devices were successfully achieved during the last decade but are still limited to a two colour-electrophoretic system. Up to date the majority of these particles were synthesized in aqueous media and the electrophoretic mobility was achieved by a ionic stabilizer or by a polyelectrolyte surfactant. Moreover the final electrophoretic particles incorporated in the electronic devices have to be dispersed in an organic media (paraffin oil) in order to achieve the desired stability of the display and thus leads to a large variety of problems during the phase exchange process.In this work our goals were to rationalize and improve the ink synthesis as well as to design electrophoretic inks with the full colour panel in order to realize the next generation of electrophoretic displays. We performed the particle synthesis by using an organic dispersion technique in aliphatic hydrocarbon solvents leading to chargeable electrophoretic particles with a good size control over a large range (from 75nm to 20µm) and a good stability. In order to obtain the full color panel, the encapsulation of several inorganic pigments was achieved by using the same technique and the electrophoretic behaviour of the resulting inks was characterized in a cell specially designed for electrophoretic measurements in organic media
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Joutsensaari, Jorma. "Aerosol synthesis of nanostructured, ultrafine fullerene particles /". Espoo [Finland] : Technical Research Centre of Finland, 1999. http://www.vtt.fi/inf/pdf/publications/1999/P400.pdf.
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Lyyränen, Jussi. "Particle formation, deposition, and particle induced corrosion in large-scale medium-speed diesel engines /". Espoo VTT, 2006. http://www.vtt.fi/inf/pdf/publications/2006/P598.pdf.
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Mirbel, Déborah. "Synthèse et formulation d'encres électrophorétiques pour le papier électronique". Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0375/document.
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Au cours de ces travaux de thèse, la synthèse et le comportement électrophorétiquede particules hybrides dispersées en présence d'un nouveau contrôleur de charge, latridodécylamine, en milieu électrophorétique (non-polaire), ont été étudiés pour des applicationsde type papier électronique. Dans le but de contrôler et comprendre les interactions présentesdans ce système, la tridodécylamine a tout d'abord été examinée seule dans le milieu souhaité.Il a été observé que ce tensioactif, solubilisé dans un milieu type huile paraffine, a uneconcentration micellaire critique approximative de 250 mM et apporte des charges dans lemilieu. Ensuite, la synthèse par polymérisation en dispersion ou par voie sol gel a permisd'obtenir des particules inorganiques, polymères ou hybrides type framboise, stables en milieunon-polaire. Leur comportement électrophorétique en présence du nouveau contrôleur decharge a été élucidé. En outre, il a été montré que des interactions acido-basiques avec lesgroupements hydroxyles des pigments inorganiques et le tensioactif donnent des particuleshybrides chargées négativement. Celles-ci ont par la suite été intégrées dans une encreélectrophorétique et testées dans un dispositif prototype innovant, le contrôle del'électrophorèse étant géré via un polymère ferroélectriqueIn this work, the synthesis and the electrophoretic behavior of hybrid particlesdispersed in apolar media, in the presence of a new charge control agent, the tridodecylamine,have been investigated for electronic paper applications. In order to control and to understandinteractions present in the system, the tridodecyamine was studied in the apolar medium. It hasbeen observed that this surfactant, solubilized in a non-polar medium, has a critical micelleconcentration of approximately 250mM and creates charges in the medium. Then, the synthesisby polymerisation in dispersion or by using a sol-gel process gave rise to the creation ofinorganic, polymeric or raspberry type hybrid particles, stable in non-polar media. Theirelectrophoretic behavior in the presence of tridodecylamine was elucidated. Acid-baseinteractions between hydroxyl groups from inorganic material surfaces and surfactant led to thecreation of negatively charged hybrid particles. These particles were integrated into anelectrophoretic ink and tested into an innovative electrophoretic device where theelectrophoresis is monitored via a ferroelectric polymer
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Blanco-Mantecon, Mireia. "Interactions, particle size and surface effects in magnetic nanoparticle systems". Thesis, Bangor University, 2000. https://research.bangor.ac.uk/portal/en/theses/interactions-particle-size-and-surface-effects-in-magnetic-nanoparticle-systems(2f7d3ef7-ef4c-43b0-b3ad-9e5c68f629e5).html.
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This work has involved the study of the magnetic behaviour of small magnetic nanoparticle systems. Due to the reduced size of magnetic nanoparticles they present distinctive properties, such as size and surface effects, that have been analysed in this work, as well as the effect of interactions in such systems. The samples chosen for the study were magnetite particles in the form of a ferrofluid and Co nanoclusters in a nonmagnetic matrix of Cu. Both systems present very narrow particle size distributions, which facilitates the interpretation of the data. The samples have been subjected to basic characterisation, which includes the determination of the distribution of magnetic particle sizes using the magnetisation curves at room temperatures, TEM microscopy and X-ray diffraction, in the case of the ferrofluid samples. For the nanoclusters, a time of flight spectrometer has been used to obtain the number of atoms per cluster. Many of the measurements have been performed at low temperatures, where thermal effects are minimised. For such measurements the samples have been frozen in a zero applied field, so that they have a random distribution of magnetic moments prior to the measurement. The energy barrier distributions have been calculated via the temperature decay of remanence (TDR). From this study, an effective anisotropy constant has been calculated. For the study of the interactions, surface and size effects, magnetisation, susceptibility (ZFC), remanence and delta-M curves, as well as the time dependence of magnetisation have been studied. The attempt frequency of the different particle size systems has been calculated using different techniques. The basic magnetic behaviour can be explained on the basis of the Neel blocking model. It has been found that the systems with the smaller particles have significant surface effects, which are enhanced at lower temperatures. Interactions, which are weak due to the low concentration of magnetic material in the samples (<10%), have been found to be overall demagnetising and the evolution of the magnetic properties with dilution has been explained. As is the case for the surface effects, interaction effects are stronger at low temperatures due the reduction of thermal effects. The experimental results have been compared with calculations from a Montecarlo model for fine particles, which includes the effects of concentration, anisotropy, particle size and temperature.
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Mikkanen, Pirita. "Fly ash particle formation in kraft recovery boilers /". Espoo [Finland] : Technical Research Centre of Finland, 2000. http://www.vtt.fi/inf/pdf/publications/2000/P421.pdf.
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Serment, Béatrice. "Synthèse et modification de pigments inorganiques pour affichage électrophorétique en couleurs". Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0453.
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Ces travaux de thèse portent sur la synthèse de particules hybrides à partir de pigments inorganiques pour la formulation d’encres électrophorétiques colorées. Les pigments doivent répondre à un cahier des charges spécifique à ce type d’application. Ils doivent avoir une taille sub-micronique, une faible densité et un haut indice de réfraction afin d’exalter les phénomènes de diffusion. Les pigments bleus et cyan de structure spinelle CoAl2O4 et NiAl2O4 ont été synthétisés par voie Pechini. Dans les deux cas, des phénomènes de démixtion influençant la couleur ont été observés. Cependant, de par la différence de rayon ionique entre le Co2+ et le Ni2+ (rCo2+ < rNi2+), les origines en sont différentes. Dans le premier cas il a fallu éliminer les ions Co3+ stabilisés en site [6] pour obtenir une phase pure où la majorité des ions cobalt occupent les sites [4]. Dans le second cas l’ajout d’ions Al3+ a été nécessaire pour stabiliser une phase spinelle pure en présence de lacunes cationiques et d’ions Ni2+ occupant partiellement les sites [4] et [6]. Ensuite, nous avons développé des pigments magenta et jaunes de structure olivine explorant la solution solide LiCoxNi1-xPO4. Dans ces composés, l’étude des transitions électroniques corrélées à la structure et à l’environnement des ions chromophores Ni2+ et Co2+ en site [6] a permis de montrer des champs cristallins proches et un effet néphélauxétique presque identique. Finalement l’analyse de l’état de valence du chrome dans les structures de type rutile SnxCr1-xO2 a permis de synthétiser des pigments violets. Dans un second temps, la surface des pigments a été modifiée avec des chaines silanes de type n-trimethoxysilane afin de favoriser la dispersion des pigments dans un milieu apolaire. Puis les pigments modifiés ont été polymérisés dans l’Isopar G par polymérisation radicalaire contrôlée par les nitroxydes avec du méthacrylate de méthyle afin de diminuer la densité globale des particules hybrides et ainsi obtenir des encres stables. L’étude de l’influence des conditions expérimentales a été effectuée sur chaque pigment afin de formuler des encres colorées et chargées sans ajout de contrôleur de charge. La réalisation d’un dispositif électrophorétique à deux couleurs bleu et blanc a finalement pu être développéThis work deals with the hybrid particles synthesis, using inorganic pigment for the coloured electrophoretic inks formulation. To comply with this type of application, pigments must have a sub-micrometer size, a low density and a high refractive index in order to exalt the diffusion phenomena. Blue and cyan spinel structure pigments CoAl2O4 and NiAl2O4 have been synthesized by Pechini process. In both these oxides, steric and electronic effects allowed stabilizing pure phases with enhanced colouring effects. In the case of CoAl2O4, we have to avoid the occurrence of Co3+ (LS) whereas for NiAl2O4, excess of Al3+ is necessary to get pure phases with nanosized crystallites. Then, magenta and yellow olivine structure pigments have been developed with the exploration of the solid solution LiCoxNi1-xPO4. In these compounds, the study of the electronic transitions combined with Ni2+ and Co2+ chromophores ions structure and environment in [6] site leads to comparable crystal field and so an almost similar nephelauxetic effect for both ions. Finally, the investigation of the valence state and the environment of chromium in rutile type structure Sn1-xCrxO2 allowed the synthesis of purple pigments. In a second part, the pigment surface has been modified with n-trimethoxysilane chains to improve the pigment dispersion in apolar media. Then, modified pigments have been polymerised in Isopar-G by nitroxyde mediated radical polymerisation with methyl methacrylate to decrease the hybrids density and to obtain stable inks. The impact of the experimental conditions has been studied on each pigments in order to formulate coloured and charged inks without any charge control agent. A two-colour electrophoretic device (blue/white) has been finally tested
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Nahid, Masrur Morshed. "In Quest of Printed Electrodes for Light-emitting Electrochemical Cells: A Comparative Study between Two Silver Inks". Thesis, Umeå universitet, Institutionen för fysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-62827.
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This thesis presents a comparative study between two silver nanoparticle inks that were deposited using a Drop-on-Demand (DoD) inkjet printer, aiming at finding a functional ink that can be used to print electrodes in Light-emitting Electrochemical Cells (LECs). To achieve this, a DoD inkjet printer was installed and an acquaintance with the printer was attained. Among the two inks, one was employed as received while the other was reformulated, and successful deposition of both the inks was observed. During the reformulation process, it was seen that the highly volatile tetrahydrofuran (THF) solvent can be used to improve the ink properties, in contrast to what is recommended. After that, the inks were deposited on UV-ozone treated glass substrates, sintered at an elevated temperature under ambient conditions, and their specific resistances and thicknesses were measured. Finally, the inks were used to print the anode in a structured sandwich-cell LEC. The performance comparison was conducted by observing the emitted light of the LECs. The results indicate that the reformulated ink performs better, probably due to the lower silver concentration that results in flatter surface, which in turn effectively alleviates shorts.
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Karlsson, Marie. "The translation of hedging, adjectives and non-finite ing-participles in Horses Talking by Margrit Coates". Thesis, Växjö University, School of Humanities, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:vxu:diva-784.
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The purpose of this study was to translate a number of selected pages from the book Horses Talking by Margrit Coates into Swedish. An analysis of the source text and the translation was carried out with the focus on three aspects: hedging, adjectives and non-finite ing-participles. The subject of the translated text lies within the broad field of animal behaviour, parapsychology and telepathy, and focuses exclusively on communication between humans and horses. Given the nature of the text, which contains cautious advice and qualified recommendations to the reader, hedging has an important function to fill. Furthermore, there are many adjectives, which give the text a certain character, and they are essential to the message of the book: how to create a good relationship between humans and horses. Theories within the translation shift approach were applied to the study. In particular, Catford’s model and terminology were looked at. Hedging at word and phrase level primarily proved to be realised by the use of modal auxiliary verbs as hedges in the source text; this application was also primarily transferred into the target text. The most common translation strategy used was literal translation. A compound noun or noun (class shift) and a prepositional phrase (unit shift) were the most common translation methods for the attributive adjectives in the analysis. The predicative adjectives were primarily translated with a verb (class shift) or a verb phrase (unit shift) and with a prepositional phrase (unit shift). For the non-finite ing-participles, a variety of methods were applied, among which the most important were the att-infinitive (grammatical shift) and a relative clause (unit shift).
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Bordes, Nicole. "Etude du dosage d'éléments traces dans InP par activation avec des particules chargées, comparaison avec d'autres méthodes de caractérisation". Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb375961583.
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BORDES, NICOLE. "Etude du dosage d'elements traces dans inp par activation avec des particules chargees; comparaison avec d'autres methodes de caracterisation". Toulouse, INSA, 1986. http://www.theses.fr/1986ISAT0035.
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Le phosphure d'indium (inp) est un materiau semiconducteur interessant pour ses proprietes electriques dans le domaine de la microelectronique et de l'optoelectronique. Dans le but de maitriser son elaboration et de mieux comprendre ses proprietes, il est necessaire de determiner la concentration des elements traces ou des dopants presents dans le materiau. Les methodes nucleaires d'activation par particules chargees sont actuellement parmi les plus sensibles pour l'analyse d'impuretes dans les materiaux, et surtout elles sont quantitatives. Les possibilites analytiques offertes par des protons de haute energie (superieure a 20 mev) ont ete etudiees et appliquees au dosage du chrome, cuivre, zinc et fer dans inp et in. Les sensibilites obtenues sont comprises entre 10**(13) et 8. 10**(13) a nontcm**(3). La presence de quelques impuretes legeres a egalement ete recherchee dans inp. Oxygene et carbone ont ete doses a l'aide de tritons de 6 mev et de deutons de 8 mev respectivement, avec une sensibilite de 4. 10**(13) a nontcm**(3) et 2. 10**(14) a nontcm**(3). Les protons de 13 mev ont permis le dosage du soufre dans l'indium avec une limite de detection de 2. 10**(15) a nontcm**(3). Le silicium a ete dose au moyen de tritons de 3 mev : une limite de quelques 10**(16) a nontcm**(3) a ete obtenue. Des comparaisons avec d'autres methodes de caracterisation telles que sims, ssms ont ete faites. Nous avons ensuite etudie d'une part la repartition de ces impuretes dans des lingots prepares par la methode czochralski sous encapsulant liquide (lec) et d'autre part suivi le transfert de ces impuretes au cours de la cristallogenese. Nous presentons enfin les caracteristiques electriques et cristallines des lingots d'inp etudies et nous avons essaye de les relier a la presence de ces elements
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Rantamäki, Karin. "Particle-in-cell simulations of the near-field of a lower hybrid grill /". Espoo : Technical Research Centre of Finland, 2003. http://www.vtt.fi/inf/pdf/publications/2003/P493.pdf.
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Sharp, David Keith. "Trends in single-particle energies in N=51 nuclei". Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/trends-in-singleparticle-energies-in-n51-nuclei(fe5f71e3-c0ab-4ace-98ae-af674f923b44).html.
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A systematic study of the neutron single-particle states in N=51 isotones has been performed. Final states in 89Sr, 91Zr and 93Mo have been populated using the (d,p) and (alpha,3He) single-neutron adding reactions. The Yale tandem provided beams of 15-MeV deuterons and 50-MeV alpha particles with the outgoing ejectiles momentum analysed using an Enge split-pole spectrometer. A supplementary measurement of the d(86Kr,p)87Kr reaction, at a beam energy of 10 MeV/u, was made in inverse kinematics using the HELIOS spectrometer. Outgoing protons execute a helical orbit in a uniform field before detection, before they return to axis, using a position-sensitive silicon array. Absolute cross sections were measured for states up to 4 MeV in excitation. The transferred angular momentum was identified through a comparison of angular distributions and the ratio of cross section between reactions. Relative spectroscopic factors were extracted through a DWBA analysis.The measured centroids for the single-particle energies of the s1/2, d3/2, d5/2, g7/2 and h11/2 orbitals were compared to calculations using a Gaussian central potential with and without the addition of a tensor interaction. Through this comparison it was deduced that the inclusion of a tensor interaction is required to explain the observed shifts in the single-particle energies of the d3/2 and g7/2 orbitals. This system provided an observation of a switch in behaviour, from repulsive to attractive and vice versa, of the effect of the tensor interaction. This occurs due to a change from j> to j< proton occupancy at Z=40.
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Young, Gillian. "Understanding the nucleation of ice particles in polar clouds". Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/understanding-the-nucleation-of-ice-particles-in-polar-clouds(4f80f81b-ed06-480a-944b-6e3594ba8471).html.
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Arctic clouds are poorly represented in numerical models due to the complex, small-scale interactions which occur within them. Modelled cloud fractions are often significantly less than observed in this region; therefore, the radiative budget is not accurately simulated and forecasts of the melting cryosphere are fraught with uncertainty. Our ability to accurately model Arctic clouds can be improved through observational studies. Recent in situ airborne measurements from the springtime Aerosol-Cloud Coupling and Climate Interactions in the Arctic (ACCACIA) campaign are presented in this thesis to improve our understanding of the cloud microphysical interactions unique to this region. Aerosol-cloud interactions - where aerosol particles act as ice nucleating particles (INPs) or cloud condensation nuclei (CCN) - are integral to the understanding of clouds on a global scale. In the Arctic, uncertainties caused by our poor understanding of these interactions are enhanced by strong feedbacks between clouds, the boundary layer, and the sea ice. In the Arctic spring, aerosol-cloud interactions are affected by the Arctic haze, where a stable boundary layer allows aerosol particles to remain in the atmosphere for long periods of time. This leads to a heightened state of mixing in the aerosol population, which affects the ability of particles to act as INPs or CCN. Aerosol particle compositional data are presented to indicate which particles are present during the ACCACIA campaign, and infer how they may participate in aerosol-cloud interactions. Mineral dusts (known INPs) are identified in all flights considered, and the dominating particle classes in each case vary with changing air mass history. Mixed particles, and an enhanced aerosol loading, are identified in the final case. Evidence is presented which suggests these characteristics may be attributed to biomass burning activities in Siberia and Scandinavia. Additionally, in situ airborne observations are presented to investigate the relationship between the Arctic atmosphere and the mixed-phase clouds - containing both liquid cloud droplets and ice crystals - common to this region. Cloud microphysical structure responds strongly to changing surface conditions, as strong heat and moisture fluxes from the comparatively-warm ocean promote more turbulent motion in the boundary layer than the minimal heat fluxes from the frozen sea ice. Observations over the transition from sea ice to ocean show that the cloud liquid water content increases four-fold, whilst ice crystal number concentrations, N_ice, remain consistent at ~0.5/L. Following from this study, large eddy simulations are used to illustrate the sensitivity of cloud structure, evolution, and lifetime to N_ice. To accurately model mixed-phase conditions over sea ice, marginal ice, and ocean, ice nucleation must occur under water-saturated conditions. Ocean-based clouds are found to be particularly sensitive to N_ice, as small decreases in N_ice allow glaciating clouds to be sustained, with mixed-phase conditions, for longer. Modelled N_ice also influences precipitation development over the ocean, with either snow or rain depleting the liquid phase of the simulated cloud.
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Sajih, Mustafa. "Identification and characterization of radioactive particles in the environment". Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/identification-and-characterization-of-radioactive-particles-in-the-environment(91448929-a753-458b-8c4f-cd84f9ebadde).html.
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Radioactive particles have been released into the environment from different sources (e.g. nuclear weapon tests, nuclear accidents, nuclear reprocessing plants, and use of depleted uranium (DU) munitions). Nuclear fuel particles have been released from authorised discharges of low-level radioactive effluent into the Irish Sea sediments from the nuclear fuel reprocessing plant at Sellafield, UK. Following the use of depleted uranium munitions in the Gulf wars and the Balkan conflicts, the environmental impact of depleted uranium and its behaviour in the environment have been of great concern. In this thesis, nuclear fuel particles released from Sellafield and retained in the intertidal Irish Sea salt marsh sediments, and DU particles arising from testing of DU munitions against hard targets and corrosion of DU metal buried in soil at Eskmeals firing range, UK, were investigated using a range of microanalytical, analytical and radiometric techniques. The particles were characterised in terms of size and morphology, elemental and radionuclide compositions, isotopic composition of associated radionuclides and, crystalline structure of uranium forms. The results demonstrate the usefulness of the applied techniques in characterising environmental radioactive particles, and lead to better understanding of the origin, behaviour and fate of these particles in the environment. The nuclear fuel particles were 1-20 µm in size, composed mainly of uranium and irradiated in the reactor as the transuranium elements (Np, Pu, Am and Cm) can be identified. The isotopic composition of uranium and plutonium suggest that these particles are derived from reprocessing of spent fuel. The results demonstrated the persistence for some decades of irradiated fuel particles in estuarine marine environment.DU particles from firing impacts were oxidized uranium forms (UO2 and U3O8) and composed mainly of uranium with few molten particles composed of a mixture of uranium and iron. DU particles from corrosion processes were mainly sand grains coated with metaschoepite corrosion product. The results showed the diversity of particles which can be produced through the use of DU munitions and the potential for these to persist in the environment for many years.
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Hill, Thomas. "Evolution of second phase particles with deformation in aluminium alloys". Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/evolution-of-second-phase-particles-with-deformation-in-aluminium-alloys(e87af2eb-bf04-46d5-9b51-d44d4584c579).html.
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The effect of high temperature, high strain rate deformation on the evolution of second phase particles in commercial aluminium alloys has been investigated. Three model alloys provided by Novelis have been examined, and the evolution of particles during deformation has been examined for the alloy that most closely resembles the composition of alloys used in commercial applications. The effect of deformation mechanisms was expected to be an enhancement of diffusion controlled processes; therefore the first part of the work was to develop a heat treatment that would produce a fine distribution of dispersoid particles. This heat treatment was then used to prepare material for torsion testing, at strain rates similar to those found during the hot rolling stage of commercial production. Testing was performed at both the end of heat treatment temperature, to remove thermal effects, and at a lower temperature which more closely represents the temperature during commercial rolling. Material was examined by optical microscopy, FEGSEM and TEM and the particle populations were characterised by backscattered FEGSEM imaging and image analysis. This demonstrated that the disperoid particle population develops in multiple ways. Along with the enhancement of coarsening there is a significant shape change to the dispersoid particles, suggesting a change in the character of their interface. It has also been demonstrated that there is nucleation of new particles, despite a long prior hold time, in material deformed at the same temperature as the heat treatment. Material deformed at lower temperatures also demonstrated a larger increase in the volume fraction of dispersoid than material with the same thermal history. A constitutive model for diffusion enhancement and a model for particle evolution have been combined to simulate the effects of thermomechanical processing on the particle population.
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Butterworth, Sean. "Shape and chemical anisotropic particles in low dielectric constant media". Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/shape-and-chemical-anisotropic-particles-in-low-dielectric-constant-media(d8ace7a1-8993-4a6b-a50d-2a2ea71c10f8).html.
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Electrophoretic displays (EDPs) are an attractive low power technology for small to large area displays. Such display technology has seen a surge of research interest with the launch of successful e-readers in the market place, owing to their lower power consumption and paper-like quality. This work aims to look at the influence of shape on the electrophoretic mobility of particles for such devices. Crosslinked poly(methyl methacrylate) (PMMA) precursor particles with a narrow size distribution were produced by non aqueous dispersion polymerisation utilising a pump-feed method. To produce shape anisotropic particles an adapted version of the dynamic swelling method for polar media was chosen. Suitable monomers were screened by the use of Hansen solubility theory to find monomers which interact with PMMA but not the solvent. It was found that 2- hydroxyethyl methacrylate (HEMA) and N-hydroxyethyl acrylamide (HEAm) were two such suitable monomers, methyl methacrylate (MMA) was also used as a control series.It was found that cluster-like particle morphologies could be produced by the MMA system by the inclusion of small quantities of crosslinking monomer. This was due to precipitation of higher molecular weight polymer segments to the seed particle surface. The cluster-like morphology could be enhanced by use of a polar crosslinking monomer and by sequential reactions. For the polar system, it was found that the reactions with pure monomer were unclean, due to the solubility mismatch of the monomer and the solvent system. This was overcome by a copolymerisation with MMA. The system showed different particle morphologies could be produced by varying the polar monomer content. In one case a sample of pure dumbbell-like particles could be produced. These dumbbell-like particles are thought to be chemical as well as shape anisotropic owing to monomer composition. EPD evaluation for the particles was undertaken and showed that all particles can become highly charged in low dielectric constant media, but that the shape anisotropic particles are prone to adsorption to the cell walls and electrodes.The work outlined in this thesis shows the first reporting of shape anisotropic polymeric particles produced in low dielectric constant solvents system.
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Jirakittidul, Kittimon. "Structure-property relationships in polyurethane-carbon particle nanocomposites". Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/structureproperty-relationships-in-polyurethanecarbon-particle-nanocomposites(01f05095-9aa2-4d88-999b-73ea88ed9bca).html.
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In this research work, the relationships between structure and properties in micro-composites and nano-composites of polyurethane (PU) and conductive carbon particles have been studied. PU is a class of block copolymers containing the urethane linkage (-NHCO-O-) within its structure. Most PU block copolymers consist of alternating ‘soft’ and ‘hard’ segments. The hard segment used in this study was based on 4,4’-methylenebisphenylisocyanate (MDI) and 2-methyl 1,3 propanediol (MP-Diol) which produced a stiff aromatic polyurethane. Two soft segments; poly(tetrahydofuran) (PTHF) and poly(propylene oxide) based polyol end-capped with ethylene oxide (PPO-EO) were used to study the effects of soft segment structure on PU properties. DMTA, DSC and modulated-DSC indicated that PU-PTHF had higher microphase separation due to greater immiscibility between PTHF and the MDI/MP-Diol hard segments. In order to improve the electrical and mechanical properties of PU, conductive carbon particles were incorporated. The critical factor was the dispersion of these conductive fillers in the PU matrix to obtain optimum properties. The first carbon filler studied was carbon black (CB). PU composites prepared by the adding of MP-Diol plus ultrasonication (MU) gave the best dispersion of CB aggregates resulting in higher thermal decomposition temperature and good conductivity. However, the mechanical toughness was reduced. In subsequent studies, PU composites incorporating three different treated multiwalled carbon nanotubes (MWCNT) were investigated. MWCNT were disentangled and shortened by ultrasonication and acid cutting treatments. The ultrasonicated MWCNT (MWCNT_U) had longer length than the acid-cut MWCNT (MWCNT_AC). Ultrasonication was the best technique for dispersing MWCNT since the storage modulus was increased by ~200% at low MWCNT_U loading and the toughness remained the same as unfilled PU. PU/MWCNT_AC nanocomposites at 1 – 3 wt% of MWCNT_AC exhibited similar electrical conductivities to unfilled PU at an order of 10-8 S/cm, implying that the acid cutting treatment might disturb the inherent conductivity in MWCNT. The conductive percolation thresholds of composites were determined following the percolation theory. It was found that the percolation thresholds for MWCNT-filled composites were significantly lower than that of CB-filled composites. The lowest percolation threshold was observed in MWCNT_U-filled composite at 0.31 wt%.
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Tan, Jun. "Mechanical properties characterisation of silicon carbide layers in simulated coated particles". Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/mechanical-properties-characterisation-of-silicon-carbide-layers-in-simulated-coated-particles(ef03dbb5-f61a-44f3-a4d9-57e3fb042e16).html.
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In the TRISO (tristructural isotropic) coated fuel particle used in the High Temperature Reactor, the most important layer is a silicon carbide layer which acts as a pressure vessel. In this study, we have focused our study on the investigation of the Young’s modulus, hardness, residual stress, and fracture toughness of the SiC layer. Moreover, microstructures and impurities in silicon carbide were characterised and then related to both Young’s modulus and hardness of the SiC layer. Both nanoindentation and micro-indentation were used to determine Young’s modulus and hardness of the SiC. Raman spectroscopy, X-ray diffraction, and scanning electron microscopy techniques were used to examine impurities, phases and microstructure of silicon carbide layers, respectively. Young’s modulus was measured at different positions of a polished surface of the SiC with different CVD growth and crystal orientations. With help from the finite element modelling, it has been found that Young’s modulus of the SiC is dependent on the grain orientation of the SiC. Mechanical properties of silicon carbide are affected by the presence of excess silicon, excess carbon, stacking faults, texture, grain size, property of grain boundary. The effect of these factors on Young’s modulus and hardness, are investigated with the orthogonal analysis. The analysis concludes that the most important factor on Young’s modulus is texture while the most significant factor on hardness is grain boundary. Grain size is secondarily important factor to affect hardness. Stacking faults and impurities almost have no influence on Young’s modulus and hardness. The residual stress in the silicon carbide layer was measured based on the peak shift in Raman spectra of the SiC and is in a range of 150-300 MPa. Fracture resistance in the radial direction of the SiC layer is larger than those in the circumferential direction. The difference is controlled by the layer-like structure of the SiC coating.
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Oh, Ji Young. "Unusual particle motions in the liquid crystal phases". Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/unusual-particle-motions-in-the-liquid-crystal-phases(59978a53-5523-4066-8a84-98cd5e7a6e16).html.
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The motions of particles dispersed in liquid crystals can be influenced by the application of an electric field, the effect depending on the field frequency and field amplitude. Sandwich cells under the application of electric field are widely used as the tool in order to investigate the fundamental research relating to electro-optic display technology. Therefore, the aim of this experimental work is to find and investigate novel motion of the particles dispersed in the liquid crystal phases, held within a sandwich cell. For the liquid crystal–particle systems in the sandwich cells in this thesis, the particle shapes, temperature and cell geometry are all shown to have an influence on the regime of the particle’s motions, with different phenomena observed using three different phases of liquid crystals. The experiments are designed to find and investigate the novel motion of the micron sized silica particles in the liquid crystal phases. In the chiral nematic phase, spherical particles are shown to exhibit linear motion, which is related to the electrophoretic mobility. Such spherical particles are also observed to show circular motion which is found to have a field dependency that can be related to Quincke rotation. A maximum frequency for motion occurs which is found to possibly be related to the effect of the ion diffusion in the liquid crystal-particle composite system. The direction of the circular motion is found to be independent of the handedness of the chiral nematic material. In the isotropic phase of a chiral nematic liquid crystal, the spherical particles do not exhibit any linear motion, which shows the system does not follow the traditional electrophoresis observed in normal isotropic liquids. The circular motion of the spherical particle that is observed in the isotropic phase is analysed in terms of the Quincke rotation and again shows the Maxwell relaxation time. The electric-field induced motion of elongated particles in four different nematic systems is examined. In this case of planar aligned systems, linear motion is observed, in which the velocity shows a minimum for particles of the same length as the cell gap. A novel field-induced defect texture appears in the homeotropic device containing a nematic liquid crystal of negative dielectric anisotropy. Interestingly, the motion of the particle is found to be strongly coupled with the defects formed.
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Howard, Alan Michael. "Trends in neutron single-particle energies below N=82". Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/trends-in-neutron-singleparticle-energies-below-n82(fa34e3a5-98a4-45a3-b71d-47f8cd18e267).html.
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Two separate investigations are described, linked by their common interest in single-particle structure around the N=82 shell closure. A systematic study of single-particle strength below the N=82 shell closure is reported. States in 137Ba, 139Ce, 141Nd and 143Sm were populated using the single-neutron removal reactions (p,d) and (3He,α) at beam energies of 23 MeV and 34 MeV, respectively. Absolute cross sections are presented for all observed states. Relative spectroscopic factors have been determined through a dwba analysis. The observed g 7/2 strength is consistently lower than that of h11/2 across all four isotones. It is postulated that as much as 50% of the g7/2 strength is fragmented into unresolved states which form part of the reaction background below 3.5 MeV. A speculative analysis based upon the observed strength reveals a relative behaviour of the g7/2 and h11/2 centroid energies that is in qualitative agreement with the predicted action of the tensor force.Details are presented also from an exploratory study of the 132Sn region using the 136Xe + 238U reaction at 926 MeV. The time-of-flight spectrometer prisma was used to identify the beam-like reaction products, and a mass resolution > 1/200 and Z-resolution of ~ 1/60 is reported. The total production yields at the focal plane are compared to calculations using the multi-nucleon transfer code grazing and rather poor agreement found for transfer of more then a few nucleons. The prospects for future studies in the region, particularly lifetime measurements, are discussed.
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Tipton, Denver Leonard John. "Electron correlations in quantum dots". Thesis, King's College London (University of London), 2001. https://kclpure.kcl.ac.uk/portal/en/theses/electron-correlations-in-quantum-dots(b6e1a547-fbb8-41f7-9d2b-f235b68b85be).html.
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Bari, Klaudio. "Assessing the feasibility of encapsulating spent fuel particles (TRISO) and ion exchange resins in borosilicate glass". Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/assessing-the-feasibility-of-encapsulating-spent-fuel-particles-triso-and-ion-exchange-resins-in-borosilicate-glass(98ff8368-041f-43b0-b349-1f8277ed04d9).html.
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A safe treatment and disposal of spent Tri-Structural Isotropic (TRISO) coated fuel particles is one of the most important issues for developing the next generation of nuclear reactors, such as a Very High Temperature Reactor (VHTR). The project investigates the encapsulation of surrogated TRISO particles in Glass-Graphite Composite (GGC) and in Alumina Borosilicate Glass (ALBG) and compares their geological performance in the repository. The study deals with the assessment and performance of both matrices in a geological repository's conditions, measuring their chemical durability for 28 days at temperatures ranging 25-90°C and using American Standard for Testing Material (ASTM-C1220-98). The leach test revealed that only sintered ALBG with TRISO particles doped in cesium oxide could provide a safe Engineering Barrier System (EBS). The thermal property of the matrices was examined by measuring their thermal diffusivities. The thermal diffusivity of ALBG bearing various proportions of TRISO particles was measured experimentally using Laser Flash Analysis (LFA). The experimental results validated through a numerical method using Image Based Modelling (IBM). The effect of the porosity in decreasing the thermal diffusivity of TRISO particles was also discussed. In addition, the study deals with the immobilisation of ion exchange resins (doped with radioactive and non-radioactive cesium and cobalt) in borosilicate glass. The thermal analysis revealed that a successful immobilisation could be achieved once the sulfur functional group in the resin was decomposed and evaporated in a form of SO2/SO. The minimum required temperature of the heat treatment was 500°C under air environment as a pre-conditioning stage before immobilisation.
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Stanier, Adam. "Magnetic reconnection and particle acceleration in semi-collisional plasmas". Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/magnetic-reconnection-and-particle-acceleration-in-semicollisional-plasmas(26c3b17d-87ca-4d98-b5b5-3a3d78e0dd03).html.
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Magnetic reconnection is an important mechanism for the restructuring of magnetic fields, and the conversion of magnetic energy into plasma heating and non-thermal particle kinetic energy in a wide range of laboratory and astrophysical plasmas. In this thesis, reconnection is studied in two semi-collisional plasma environments: flares in the solar corona, and the start-up phase of the Mega-Ampere Spherical Tokamak (MAST) magnetic confinement device. Numerical simulations are presented using two different plasma descriptions; the test-particle approach combined with analytical magnetohydrodynamic fields is used to model populations of high-energy particles, and a two-fluid approach is used to model the bulk properties of a semi-collisional plasma. With the first approach, a three-dimensional magnetic null-point is examined as a possible particle acceleration site in the solar corona. The efficiency of acceleration, both within the external drift region and in the resistive current sheet, is studied for electrons and protons using two reconnection models. Of the two models, it is found that the fan-reconnection scenario is the most efficient, and can accelerate bulk populations of protons due to fast and non-uniform electric drifts close to the fan current-sheet. Also, the increasing background field within the fan-current sheet is shown to stabilise particle orbits, so that the energy gain is not limited by ejection. With the second approach, the effects of two-fluid physics on merging flux-ropes is examined, finding fast two-fluid tearing-type instabilities when the strength of dissipation is weak. The model is then extended to the tight-aspect ratio toroidal-axisymmetric geometry of the MAST device, where the final state after merging is a MAST-like spherical tokamak with nested flux-surfaces and a monotonically increasing q-profile. It is also shown that the evolution of simulated 1D radial density profiles closely resembles the Thomson scattering electron density measurements in MAST. An intuitive explanation for the origin of the measured density structures is proposed, based upon the results of the toroidal Hall-MHD simulations.
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Mitchell, Alan John. "Investigating high-j single-particle energies in Z = 51 nuclei". Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/investigating-highj-singleparticle-energies-in-z--51-nuclei(42930c32-33e6-4607-855b-0f319d72d4bd).html.
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The work of this thesis consists of a systematic study of low-lying, proton single-particle states in Z = 51 isotopes. States in 113−125Sb were populated via (α,t) and (3He,d) single-proton adding reactions, performed on stable even tin isotopes. The Yale tandem accelerator delivered beams of 37.5-MeV α particles and 25-MeV 3He nuclei for the reactions. Outgoing tritons and deuterons were momentum analysed using an Enge split-pole spectrometer. To obtain absolute cross sections, the product of target thickness and spectrometer aperture size was calibrated for each target, using sub-Coulomb α- particle elastic scattering. States were observed up to ∼4 MeV excitation energy. Angular momentum transfer assignments were made through comparison of angular distributions and ratios of cross sections between different reactions. Relative spectroscopic factors ex- tracted through a DWBA analysis allowed energy centroids of the observed single-particle strength to be reconstructed.These measurements build upon the results of a previous (α,t) study, which was per- formed on the same targets. The previous measurements estimated that ∼ 90% of the πg7/2 and πh11/2 strength was held in the lowest-lying 7/2+ and 11/2− states, respectively. The difference in energy of these states increased with increasing neutron excess, and al- though they were in agreement with theoretical calculations that included contributions of the tensor interaction, poor statistics limited the information obtained regarding the weak fragments of high-j single-particle strength. Careful examination of these fragments, with the use of greater statistics, has been performed in this work. The (3He,d) measurements aid in making l transfer assignments and provide complementary information regarding the low-j states.Binding energies of the πg7/2 and πh11/2 orbitals measured in this work were compared to the energies of the lowest-lying 7/2+ and 11/2− states and theoretical calculations that include the tensor interaction. Though shifted higher in energy due to the fragmentation, trends in the centroids appear to be consistent with the lowest-lying states. The trend of the πg7/2–πh11/2 energy difference is in quantitative agreement with the predicted effects of the tensor interaction, with increasing neutron excess.
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Montgomerie, Roger. "The structural and elemental composition of inhaled particles in ancient Egyptian mummified lungs". Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/the-structural-and-elemental-composition-of-inhaled-particles-in-ancient-egyptian-mummified-lungs(e7d2dd35-e783-416d-bb46-5859173ed932).html.
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Since the first modern investigations into Egyptian mummies in the 1970s, anthracosis and silicosis have regularly been found in mummified lungs (Tapp, 1975; Walker et al, 1987). Anthracosis, lung irritation caused by carbon particles, is well researched in modern populations but very little is known about the disease in ancient times. Similarly, little is known about the prevalence of silicosis, caused by the inhalation of particles of silicon, in ancient times. It has been assumed that carbon was inhaled through the combustion of fuel for cooking and illumination whilst silicon came from the desert environment.This study aims to test these assumptions by characterising the shape, size and elemental composition of the organic and inorganic particles contained within ancient lung tissue. When these particles are compared against surrogate carbon and silicon particles, it may be possible to identify them and reveal their aetiology.Surrogate carbon particles were produced through controlled combustion of fuels the ancient Egyptians are likely to have used. The modern silica containing sand was collected from various archaeological sites in Egypt. A sonication method was used to extract particles from ancient tissue. After extraction, individual ancient particles were isolated and examined for size and shape analysis using light microscopy. The surrogate particles were examined in the same manner. The particles were then imaged using environmental scanning electron microscopy (ESEM) and elemental profiles determined by energy dispersive X-ray analysis (EDAX). Bulk analysis by mass spectrometry was then employed to qualitatively and quantitatively analyse the elements contained within ancient lung particles and the modern surrogates. Electron probe micro-analysis (EPMA) was used to map the deposition and elemental composition of inorganic compounds in sections of ancient lung. Further information on the bonds and chain length of soots were obtained through FTIR and Raman spectroscopy.Results have shown the presence of anthracosis and birefringent particles in all ancient lung tissues examined by this study. Both organic and inorganic ancient particles have been found to be respirable (ie, less than 10 microns in diameter) and were present in the lung pre-mortem. EDX and ICP-MS results show the inorganic particles to consist of aluminium silicates (sand) and calcium carbonate (limestone). FTIR and Raman spectroscopy were not accurate enough to detect the ancient or surrogate soot bonds and were not suited to this study.
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Day, Hugo Alistair. "Measurements and simulations of impedance reduction techniques in particle accelerators". Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/measurements-and-simulations-of-impedance-reduction-techniques-in-particle-accelerators(35666138-5941-4c8b-95b3-7beeb3bdfb24).html.
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Wakefields and the corresponding frequency-domain phenomenon beam coupling impedance have been well studied for a number of years as a source of beam instabilities within particle accelerators. With the development of the Large Hadron Collider (LHC) and the large beam currents stored in the LHC during fills for physics production, wakefield driven instabilities and strong beam induced heating have become a limiting factors in luminosity production due to both instantaneous luminousity and the available time for collisions.In this thesis is presented an in depth study of the beam coupling impedance of two important (from an impedance and operational point of view) devices in the LHC; the collimation system and the injection kicker magnets (MKIs). These systems have both been sources of concern for the beam impedance of the LHC, the collimators due to their large transverse impedance and the MKIs due to the strong heating observed during the increased of beam current during operation in 2011 and 2012. The source of the heating for the MKIs is studied in depth, found to be power lost by the beam to wakefields in the MKIs. Simulations and measurements are used to characterise the impedance and localise the areas responsible for the high impedance, here the beam screen and ferrite yoke of the magnet; improvements are proposed to better screen the ferrite yoke and verified. A new RF damping system using ferrite for the collimation system is studied and compared to the existing RF damping system, focusing on the heating of the damping system. Highlights include a new method for measuring the quadrupolar and constant transverse impedances of an asymmetric structure using a coaxial wire technique is proposed and verified using computational simulations, and a study of the heat loss in a ferrite damped cavity, focusing on the location of the power loss for cavities being damped to varying degrees.
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Webber, Adam Dane. "Radiation damage studies in the LHCb VELO detector and measurement of the flavour-specific asymmetry in semileptonic B-decays". Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/radiation-damage-studies-in-the-lhcb-velo-detector-and-measurement-of-the-flavourspecific-asymmetry-in-semileptonic-bdecays(6a41db51-8d4e-4b43-914b-80a1c73d5271).html.
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This thesis presents several studies of data collected at the LHCb detector during its first two years of operation. A detector upgrade study is first presented, using simulated events at an increased luminosity. A second study involves radiation damage to the silicon sensors of the LHCb Vertex Locator. During 2010 and 2011the silicon sensors were exposed to a range of fluences, with sensors in the mostactive regions exposed to fluences of up to approximately 45x10^12 1MeV neutron equivalent (1MeV neq). The first observation of n+-on-n sensor type inversion at the Large Hadron Collider is reported, occurring at a fluence of around (10-15)x10^12 of 1MeV neq. The effective depletion voltages of the only n+-on-p sensors in use at the Large Hadron Collider have also been studied, with decreases of around 25V observed after initial irradiation. Following this, the effective depletion voltage inn+-on-p type sensors is observed to increase at a comparable rate to type inverted n+-on-n type sensors. A reduction in the charge collection efficiency due to an unexpected effect involving the sensor readout lines is also observed. A third study relates to CP violation in neutral B-meson mixing, by the measurement of the flavour-specific asymmetry. In the Standard Model, CP violation from this source is expected to be of order 10^-4. Any measured enhancement of this would be a strong indication of new physics. The DØ collaboration has measured the flavour specific asymmetry from B0 and B0s mixing, and found it to be inconsistent with the Standard Model at a confidence level of 3.9 standard deviations, thus motivating an independent measurement from the LHCb experiment. Using the full 2011 LHCb dataset, corresponding to 1.0 fb^-1 of recorded luminosity, the B0s-meson component of the flavour-specific asymmetry is measured to be afs_s = (-0.12 +/- 0.48 +/- 0.34)%, where the first uncertainty is statistical and the second is systematic. This is the single most accurate measurement of afs_s, and is consistent with both the DØ measurement and the Standard Model prediction.
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Chen, Tao, Rainer Jordan e Stefan Zauscher. "Polymer brush patterning using self-assembled microsphere monolayers as microcontact printing stamps". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-138826.
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Self-assembled microsphere monolayers (SMMs) hold significant promise for micro- and nanopatterning. Here we exploit, for the first time, SMMs as stamps for microcontact printing (μCP) and demonstrate this to fabricate patterned initiator templates that can subsequently be amplified into polymer brushes by surface initiated atom transfer radical polymerization (SI-ATRP). SMM stamps avoid the need for expensive and sophisticated instrumentation in pattern generation, and provide a broad range of accessible surface chemistries and pitch size control.
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Geng, Xin. "Migration of metallic fission products through SiC or ZrC coating in TRISO coated fuel particles". Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/migration-of-metallic-fission-products-through-sic-or-zrc-coating-in-triso-coated-fuel-particles(c4ff06cb-1adf-4748-87ff-247d29916ba2).html.
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Release of metallic fission products from fully intact tri-structural isotropic (TRISO) fuel particles raises serious concern on the safety of high temperature gas-cooled reactors (HTGRs). In TRISO particles, SiC and/or ZrC coating is considered as the major barrier for the migration of the fission products. This thesis focuses on the migration mechanism study of Ag in SiC and Pd in ZrC.The mechanism of the migration of Ag in SiC is a long-lasting mystery. None of the currently existing models could satisfactorily explain the reported experimental facts. In this work, a new mechanism, termed as the “reaction-recrystallization” model, is proposed to explain the Ag migration behavior through SiC. Designed SiC/Ag diffusion couple experiments were carried out, and the results indicate that Ag migrates in SiC by the following three steps. First, Ag reacts with SiC to form an Ag-Si alloy (reaction). Second, carbon precipitates as a second phase and subsequently reacts with the Ag-Si alloy to form new β-SiC (recrystallization). Third, the Ag-Si alloy penetrates through the SiC layer by wetting its grain boundaries (migration). The validity of the proposed model was supported by thermodynamic calculations. (Chapter 3) The finding that SiC could be recrystallized in the presence of Ag inspires the idea of Ag-assisted crack healing in SiC. Cracks were intentionally generated by indenting the bulk SiC by a Vickers indenter. After vacuum annealing with Ag powder, the indent impressions were healed by newly-formed β-SiC grains with a recovery ratio of~ 60%. Median cracks were fully healed by both newly formed SiC and Ag-Si nodules. TEM observation reveals that the newly formed β-SiC layer is presented between the Ag-Si nodule and pristine SiC crack surface and smooths the tortuous crack surface. The above result is in potential to solve the problem of brittleness of SiC as a structural material. (Chapter 4)ZrC is considered as a candidate to replace SiC in TRISO fuel particles. The migration behavior of Pd in ZrC was investigated by designed Pd/ZrC diffusion couple experiments. It is found that ZrC reacts with Pd at temperatures higher than 600 °C to form Pd3Zr and amorphous carbon. The reaction kinetics parameters, i.e., the activation energy and the reaction order, along with the inter-diffusion coefficients of Zr and Pd, were calculated based on established models. These results provide preliminary explanation to the Pd migration in ZrC (Chapter 5).
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Zhang, Huixing. "Mechanical and microstructural study of silicon carbide and pyrolytic carbon coatings in TRISO fuel particles". Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/mechanical-and-microstructural-study-of-silicon-carbide-and-pyrolytic-carbon-coatings-in-triso-fuel-particles(64767ded-eafd-4ef6-a43f-8afbe0a07947).html.
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TRISO fuel particles have been developed as nuclear fuels used for a generation IV nuclear reactor: high temperature reactor. Such particle consists of a fuel kernel, pyrolytic carbon (PyC) and silicon carbide (SiC) coatings. This study has been carried out to establish a relationship between mechanical properties and microstructures of SiC coating and PyC coatings produced by fluidized bed chemical vapour deposition. Indentations were used to measure hardness, Young’s modulus and fracture behaviour of SiC and PyC coatings. Fracture strength of SiC coatings was measured by crush test. Microstructure of SiC and PyC was mainly characterised by transmission/scanning electron microscopy and Raman spectroscopy. For SiC coatings produced at 1300 ºC, Young’s modulus is an exponential function of relative density. Hardness of SiC coatings is higher than the bulk SiC produced by CVD, and it is attributed to the high density of dislocations and their interactions. The deformation mechanism of SiC coatings under indentation is explained by presence of defects, such as grain boundaries and nano-pores. The fracture of these coatings beneath the Vickers indentation is the Palmqvist cracks, and indentation fracture toughness was in the range of 3.5-4.9 MPa m1/2. The stress-induced micro-cracks are assumed to be the mechanism for the high indentation fracture toughness. Different hardness and fracture toughness in these SiC coatings are attributed to influences of defects and grain morphology.Measurement of fracture strength was carried out on SiC coatings deposited at 1300-1500 ºC. Weibull modulus and fracture strength of the full shell are dominated by the ratio of radius to thickness of coatings, and decrease linearly with the increase of this ratio. The influence of SiC/PyC interfacial roughness on fracture strength of the SiC was quantified by self-affine theory. The fracture strength decreases linearly with the increase of the roughness ratio, which is the long-wavelength roughness characteristic. After thermal treatment at 2000 ºC, fracture strength decreased in SiC coatings due to the formation of pores, which are results of diffusion of native defects in as-deposited SiC coatings, and the change of Weibull modulus is related to the size and distribution of pores.For low density PyC coatings, Young’s modulus and the mean pressure increase with the increase of the density; however, for high density PyC coatings, they are determined by interstitial defects. The hysteresis deformation behaviour under nano-indenation has been found be affected by density variation and thermal treatment, which is proposed to be due to the disorder structure in PyC coatings.
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Closas, Gómez Pau. "Bayesian signal processing techniques for GNSS receivers: from multipath mitigation to positioning". Doctoral thesis, Universitat Politècnica de Catalunya, 2009. http://hdl.handle.net/10803/6942.
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Aquesta tesi gira al voltant del disseny de receptors per a sistemes globals de navegació per satèl·lit (Global Navigation Satellite Systems, GNSS). El terme GNSS fa referència a tots aquells sistemes de navegació basats en una constel·lació de satèl·lits que emeten senyals de navegació útils per a posicionament. El més popular és l'americà GPS, emprat globalment. Els esforços d'Europa per a tenir un sistema similar veuran el seu fruit en un futur proper, el sistema s'anomena Galileo. Altres sistemes globals i regionals existeixen dissenyats per al mateix objectiu: calcular la posició dels receptors. Inicialment la tesi presenta l'estat de l'art en GNSS, a nivell de l'estructura dels actuals senyals de navegació i pel que fa a l'arquitectura dels receptors.El disseny d'un receptor per a GNSS consta d'un seguit de blocs funcionals. Començant per l'antena receptora fins al càlcul final de la posició del receptor, el disseny proporciona una gran motivació per a la recerca en diversos àmbits. Tot i que la cadena de Radiofreqüència del receptor també és comentada a la tesis, l'objectiu principal de la recerca realitzada recau en els algorismes de processament de senyal emprats un cop realitzada la digitalització del senyal rebut. En un receptor per a GNSS, aquests algorismes es poden dividir en dues classes: els de sincronisme i els de posicionament. Aquesta classificació correspon als dos grans processos que típicament realitza el receptor. Primer, s'estima la distancia relativa entre el receptor i el conjunt de satèl·lits visibles. Aquestes distancies es calculen estimant el retard patit pel senyal des de que és emès pel corresponent satèl·lit fins que és rebut pel receptor. De l'estimació i seguiment del retard se n'encarrega l'algorisme de sincronisme. Un cop calculades la distancies relatives als satèl·lits, multiplicant per la velocitat de la llum el retards estimats, l'algorisme de posicionament pot operar. El posicionament es realitza típicament pel procés de trilateralització: intersecció del conjunt d'esferes centrades als satèl·lits visibles i de radi les distancies estimades relatives al receptor GNSS. Així doncs, sincronització i posicionament es realitzen de forma seqüencial i ininterrompudament. La tesi fa contribucions a ambdues parts, com explicita el subtítol del document.
Per una banda, la tesi investiga l'ús del filtrat Bayesià en el seguiment dels paràmetres de sincronisme (retards, desviaments Doppler i phases de portadora) del senyal rebut. Una de les fonts de degradació de la precisió en receptors GNSS és la presència de repliques del senyal directe, degudes a rebots en obstacles propers. És per això que els algorismes proposats en aquesta part de la tesi tenen com a objectiu la mitigació de l'efecte multicamí. La dissertació realitza una introducció dels fonaments teòrics del filtrat Bayesià, incloent un recull dels algorismes més populars. En particular, el Filtrat de Partícules (Particle Filter, PF) s'estudia com una de les alternatives més interessants actualment per a enfrontar-se a sistemes no-lineals i/o no-Gaussians. Els PF són mètodes basats en el mètode de Monte Carlo que realitzen una caracterització discreta de la funció de probabilitat a posteriori del sistema. Al contrari d'altres mètodes basats en simulacions, els PF tenen resultats de convergència que els fan especialment atractius en casos on la solució òptima no es pot trobar. En aquest sentit es proposa un PF que incorpora un seguit de característiques que el fan assolir millors prestacions i robustesa que altres algorismes, amb un nombre de partícules reduït. Per una banda, es fa un seguiment dels estats lineals del sistema mitjançant un Filtre de Kalman (KF), procediment conegut com a Rao-Blackwellization. Aquest fet provoca que la variància de les partícules decreixi i que un menor nombre d'elles siguin necessàries per a assolir una certa precisió en l'estimació de la distribució a posteriori. D'altra banda, un dels punts crítics en el disseny de PF és el disseny d'una funció d'importància (emprada per a generar les partícules) similar a l'òptima, que resulta ésser el posterior. Aquesta funció òptima no està disponible en general. En aquesta tesi, es proposa una aproximació de la funció d'importància òptima basada en el mètode de Laplace. Paral·lelament es proposen algorismes com l'Extended Kalman Filter (EKF) i l'Unscented Kalman Filter (UKF), comparant-los amb el PF proposat mitjançant simulacions numèriques.
Per altra banda, la presentació d'un nou enfocament al problema del posicionament és una de les aportacions originals de la tesi. Si habitualment els receptors operen en dos passos (sincronització i posicionament), la proposta de la tesi rau en l'Estimació Directa de la Posició (Direct Position Estimation, DPE) a partir del senyal digital. Tenint en compte la novetat del mètode, es proporcionen motivacions qualitatives i quantitatives per a l'ús de DPE enfront al mètode convencional de posicionament. Se n'ha estudiat l'estimador de màxima versemblança (Maximum Likelihood, ML) i un algorisme per a la seva implementació pràctica basat en l'algorisme Accelerated Random Search (ARS). Els resultats de les simulacions numèriques mostren la robustesa de DPE a escenaris on el mètode convencional es veu degradat, com per exemple el cas d'escenaris rics en multicamí. Una de les reflexions fruit dels resultats és que l'ús conjunt dels senyals provinents dels satèl·lits visibles proporciona millores en l'estimació de la posició, doncs cada senyal està afectada per un canal de propagació independent. La tesi també presenta l'extensió de DPE dins el marc Bayesià: Bayesian DPE (BDPE). BDPE manté la filosofia de DPE, tot incloent-hi possibles fonts d'informació a priori referents al moviment del receptor. Es comenten algunes de les opcions com l'ús de sistemes de navegació inercials o la inclusió d'informació atmosfèrica. Tot i així, cal tenir en compte que la llista només està limitada per la imaginació i l'aplicació concreta on el marc BDPE s'implementi.
Finalment, la tesi els límits teòrics en la precisió dels receptors GNSS. Alguns d'aquests límits teòrics eren ja coneguts, d'altres veuen ara la llum. El límit de Cramér-Rao (Cramér-Rao Bound, CRB) ens prediu la mínima variància que es pot obtenir en estimar un paràmetre mitjançant un estimador no esbiaixat. La tesi recorda el CRB dels paràmetres de sincronisme, resultat ja conegut. Una de les aportacions és la derivació del CRB de l'estimador de la posició pel cas convencional i seguint la metodologia DPE. Aquests resultats proporcionen una comparativa asimptòtica dels dos procediments pel posicionament de receptors GNSS. D'aquesta manera, el CRB de sincronisme pel cas Bayesià (Posterior Cramér-Rao Bound, PCRB) es presenta, com a límit teòric dels filtres Bayesians proposats en la tesi.
This dissertation deals with the design of satellite-based navigation receivers. The term Global Navigation Satellite Systems (GNSS) refers to those navigation systems based on a constellation of satellites, which emit ranging signals useful for positioning. Although the american GPS is probably the most popular, the european contribution (Galileo) will be operative soon. Other global and regional systems exist, all with the same objective: aid user's positioning. Initially, the thesis provides the state-of-the-art in GNSS: navigation signals structure and receiver architecture. The design of a GNSS receiver consists of a number of functional blocks. From the antenna to the final position calculation, the design poses challenges in many research areas. Although the Radio Frequency chain of the receiver is commented in the thesis, the main objective of the dissertation is on the signal processing algorithms applied after signal digitation. These algorithms can be divided into two: synchronization and positioning. This classification corresponds to the two main processes typically performed by a GNSS receiver. First, the relative distance between the receiver and the set of visible satellites is estimated. These distances are calculated after estimating the delay suffered by the signal traveling from its emission at the corresponding satellite to its reception at the receiver's antenna. Estimation and tracking of these parameters is performed by the synchronization algorithm. After the relative distances to the satellites are estimated, the positioning algorithm starts its operation. Positioning is typically performed by a process referred to as trilateration: intersection of a set of spheres centered at the visible satellites and with radii the corresponding relative distances. Therefore, synchronization and positioning are processes performed sequentially and in parallel. The thesis contributes to both topics, as expressed by the subtitle of the dissertation.
On the one hand, the thesis delves into the use of Bayesian filtering for the tracking of synchronization parameters (time-delays, Doppler-shifts and carrier-phases) of the received signal. One of the main sources of error in high precision GNSS receivers is the presence of multipath replicas apart from the line-of-sight signal (LOSS). Wherefore the algorithms proposed in this part of the thesis aim at mitigating the multipath effect on synchronization estimates. The dissertation provides an introduction to the basics of Bayesian filtering, including a compendium of the most popular algorithms. Particularly, Particle Filters (PF) are studied as one of the promising alternatives to deal with nonlinear/nonGaussian systems. PF are a set of simulation-based algorithms, based on Monte-Carlo methods. PF provide a discrete characterization of the posterior distribution of the system. Conversely to other simulation-based methods, PF are supported by convergence results which make them attractive in cases where the optimal solution cannot be analytically found. In that vein, a PF that incorporates a set of features to enhance its performance and robustness with a reduced number of particles is proposed. First, the linear part of the system is optimally handled by a Kalman Filter (KF), procedure referred to as Rao-Blackwellization. The latter causes a reduction on the variance of the particles and, thus, a reduction on the number of required particles to attain a given accuracy when characterizing the posterior distribution. A second feature is the design of an importance density function (from which particles are generated) close to the optimal, not available in general. The selection of this function is typically a key issue in PF designs. The dissertation proposes an approximation of the optimal importance function using Laplace's method. In parallel, Extended Kalman Filter (EKF) and Unscented Kalman Filter (UKF) algorithms are considered, comparing these algorithms with the proposed PF by computer simulations.
On the other hand, a novel point of view in the positioning problem constitutes one of the original contributions of the thesis. Whereas conventional receivers operate in a two-steps procedure (synchronization and positioning), the proposal of the thesis is a Direct Position Estimation (DPE) from the digitized signal. Considering the novelty of the approach, the dissertation provides both qualitative and quantitative motivations for the use of DPE instead of the conventional two-steps approach. DPE is studied following the Maximum Likelihood (ML) principle and an algorithm based on the Accelerated Random Search (ARS) is considered for a practical implementation of the derived estimator. Computer simulation results carried show the robustness of DPE in scenarios where the conventional approach fails, for instance in multipath-rich scenarios. One of the conclusions of the thesis is that joint processing of satellite's signals provides enhance positioning performances, due to the independent propagation channels between satellite links. The dissertation also presents the extension of DPE to the Bayesian framework: Bayesian DPE (BDPE). BDPE maintains DPE's philosophy, including the possibility of accounting for sources of side/prior information. Some examples are given, such as the use of Inertial Measurement Systems and atmospheric models. Nevertheless, we have to keep in mind that the list is only limited by imagination and the particular applications were BDPE is implemented. Finally, the dissertation studied the theoretical lower bounds of accuracy of GNSS receivers. Some of those limits were already known, others see the light as a result of the research reported in the dissertation. The Cramér-Rao Bound (CRB) is the theoretical lower bound of accuracy of any unbiased estimator of a parameter. The dissertation recalls the CRB of synchronization parameters, result already known. A novel contribution of
the thesis is the derivation of the CRB of the position estimator for either conventional and DPE approaches. These results provide an asymptotical comparison of both GNSS positioning approaches. Similarly, the CRB of synchronization parameters for the Bayesian case (Posterior Cramér-Rao Bound, PCRB) is given, used as a fundamental limit of the Bayesian filters proposed in the thesis.
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Rohbeck, Nadia. "The high temperature mechanical properties of silicon carbide in TRISO particle fuel". Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/the-high-temperature-mechanical-properties-of-silicon-carbide-in-triso-particle-fuel(275b2e07-8a5e-4b22-b575-3ded9c6b9008).html.
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The high temperature reactor (HTR) requires a completely new fuel design as it operates at around 1000°C in normal conditions and can reach up to 1600°C in case of an accident. The fuel and its cladding consist fully of ceramic materials, which precludes the possibility of a core meltdown and thus ensures inherent safety. The integral part of all HTR core designs is the tristructural-isotropic (TRISO) particle, which encapsulates the fissionable materials in succeeding coatings of pyrolytic carbon and silicon carbide (SiC). An exceptional mechanical integrity of the silicon carbide layer in all conditions is required to ensure full fission product retention. Within this work simulated TRISO fuel has been fabricated by fluidized bed chemical vapour deposition and was annealed in protective atmosphere up to 2200°C for short durations. Subsequent mechanical tests showed only minor reductions in the fracture strength of the SiC up to 2000°C. Substantial weight loss and crystal growth were observed after annealing at 2100°C and above. Raman spectroscopy identified the formation of a multi-layered graphene film covering the SiC grains after annealing and scanning electron microscopy revealed significant porosity formation within the coating from 1800°C onwards. These observations were attributed towards an evaporation-precipitation mechanism of SiC at very elevated temperatures that only slightly diminishes the hardness, elastic modulus or fracture strength, but might still be problematic in respect to fission product retention of the SiC layer. The new technique of high temperature nanoindentation was applied to measure the elastic modulus and hardness of SiC in-situ up to 500°C in argon atmosphere. The elastic modulus was found to be only slightly reduced over the measurement range, while the hardness showed a significant drop. Investigations of the deformation zone beneath the indenter tip executed by transmission electron microscopy showed slip and deformation twinning. On specimens that had been subject to neutron irradiation an irradiation hardening effect was noted. The elastic modulus showed only a minor increase compared with the non-irradiated samples. Oxidation experiments were carried out in air up to 1500°C. Analysis of the oxidation layer showed the formation of amorphous silica and cristobalite for the highest temperatures.
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Nichman, Leonid. "Optical measurements of the microphysical properties of aerosol and small cloud particles in the CLOUD project". Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/optical-measurements-of-the-microphysical-properties-of-aerosol-and-small-cloud-particles-in-the-cloud-project(ad792d0c-90d1-4704-b666-b75d284b40fe).html.
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Clouds play an important role in precipitation, solar radiation budget and electrification of Earth's atmosphere. The presence of small ice crystals in clouds and their morphology can complicate parametrisation and climate modelling, consequently leading to a net cooling feedback on climate. In situ airborne measurements provide single particle characterisation with high temporal and spatial resolution allowing better understanding of atmosphericprocesses of ice nucleation and growth. Simulations of the preindustrial clouds and accurate characterisation and comparison of the instruments require a well-controlled and often pristine environment. The experimental chamber setup allows simulations of these and other conditions. The microphysical features of the micrometric ice particles in clouds were examined in a laboratory setup, at numerous sub-zero temperatures [-10 to -50 ⁰C]. The following instruments were sampling the content of the CLOUD chamber air volume: Cloud and Aerosol Spectrometer with Polarisation (CASPOL), Particle Phase Discriminator mark 2 (PPD-2K, Karlsruhe edition), 3-View Cloud Particle Imager (3V-CPI), and the Scattering-Intensity-Measurements-for-the-Optical-detectioN-of-icE (SIMONE-Junior). Cluster analysis was applied to the data collected with CASPOL and compared with results from the other probes. We were able to discriminate and map the aerosol and cloud particles in the pristine chamber environment using polarisation ratios (Dpol/Backscatter and Dpol/Forwardscatter) of the scattered light. We demonstrate the sensitivity of the instruments in detecting secondary organic aerosol (SOA) phase transitions. Then, we show the ability of the viscous SOA to nucleate ice in a series of SPectrometer for Ice Nuclei (SPIN) measurements. The detected viscous SOA ice nucleation efficiency may affect global modelling and estimations of ice water content in the atmosphere. Subsequently, the analysis and discrimination technique used in the CLOUD chamber was applied to airborne measurements to test its efficiency and to retrieve the composition of clouds. Data from four flight campaigns on board of the FAAM BAe-146 were analysed: Aerosol-Cloud Coupling and Climate Interactions in the Arctic (ACCACIA), COnvective-Precipitation-Experiment (COPE) in south England, CIRrus Coupled Cloud-Radiation EXperiment (CIRCCREX), and PIKNMIX in Scotland. In these and other flights, we were able to identify unique clusters such as salts, minerals, organics, volcanic ash, water and ice, confirming some of the offline laboratory elemental analysis results, and providing complementary information. Single particle polarisation measurements were compared with bulk depolarisation, diffraction patterns, and imaging. Most of the optical instruments still suffer from ambiguity in phase derivation (i.e. water/ice) of optically spherical small shapes. We discuss some of the limitations of optical cloud particle discrimination in different ambient conditions and offer possible solutions to reduce the uncertainty, e.g., surface complexity derivation from scatteringpatterns. Our findings will help to develop better instruments and improve the models which are used for weather forecasts and climate change predictions.
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Johnson, Christopher Gurney. "Granular shocks, particle size segregation and levee formation in avalanches and debris flows". Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/granular-shocks-particle-size-segregation-and-levee-formation-in-avalanches-and-debris-flows(a90bcaa3-a056-4691-bc8d-de7b484e2590).html.
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Debris flows, avalanches and other geophysical mass flows pose a significant hazard to settlements in or near mountainous regions. Understanding the physical processes that govern these flows is an essential part of hazard assessment and mitigation strategies. This thesis addresses two aspects of geophysical mass flows: flow self-channelisation due to the formation of lateral levees, and granular shocks, which occur when a rapidly-moving debris flow or avalanche collides with an obstacle. We present the results of large-scale debris flow experiments in which the flow is channelised by coarse-particle levees that form at the flow margins. The flow surface velocities are measured with high speed overhead photography, and the deposits both sampled to obtain the grain size distribution and excavated to recover the deposited locations of tracer pebbles that were introduced in to the flow. We propose a model, supported by evidence from the large-scale experiments, that describes in detail the size segregation and kinematic transport processes responsible for the deposition of lateral levees. The second problem addressed in the thesis concerns granular shocks, or jumps, which are rapid changes in the depth and velocity of granular avalanches. We investigate these through experiments in which a falling jet of granular material impacts on an inclined plane, generating a steady granular jump, which is either teardrop-shaped or 'blunted'. Numerical solutions of a depth-averaged flow model agree quantitatively with many of the observed flow features. We use this model show that the transition between the teardrop-shaped and blunted jump regimes corresponds to a transition between two shock reflection structures, known as a regular and a Mach shock reflection. On planes inclined at a shallow angle, we demonstrate a wide variety of unsteady and channelised flows, which occur due to the complex interaction between flowing and stationary regions of granular material.
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Omidvar, Pourya. "Wave loading on bodies in the free surface using smoothed particle hydrodynamics (SPH)". Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/wave-loading-on-bodies-in-the-free-surface-using-smoothed-particle-hydrodynamics-sph(9d744522-6ecf-4496-a784-4ab08292e344).html.
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This thesis investigates wave loading on bodies in the free surface using smoothed particle hydrodynamics (SPH). This includes wave loading on fixed bodies, waves generated by heaving bodies in still water and the heave response of a body in waves, representing a wave energy device. SPH is a flexible Lagrangian technique for CFD simulations, which in principle applies to steep and breaking waves without special treatment allowing us to simulate highly nonlinear and potentially violent flows encountered in a real sea. However few detailed tests have been undertaken even with small amplitude waves.This research uses the open-source SPH code SPHysics. First two forms of SPH formulation, standard SPH with artificial viscosity and SPH-Arbitrary Lagrange Euler (ALE) with a Riemann solver, are used to simulate progressive waves in a 2-D tank. The SPH-ALE formulation with a symplectic time integration scheme and cubic spline kernel is found to model progressive waves with negligible dissipation whereas with the standard SPH formulation waves decay markedly along the tank. We then consider two well-defined test cases in two dimensions: progressive waves interacting with a fixed cylinder and waves generated by a heaving semi-immersed cylinder. To reduce computer time in a simple manner a variable particle mass distribution is tested with fine resolution near the body and coarse resolution further away, while maintaining a uniform kernel size. A mass ratio of 1:4 proved effective but increasing to 1:16 caused particle clumping and instability. For wave loading on a half-submerged cylinder the agreement with the experimental data of Dixon et al. (1979) for the root mean square force is within 2%. For more submerged cases, the results show some discrepancy, but this was also found with other modelling approaches. For the heaving cylinder, SPH results for the far field wave amplitude and vertical force on the cylinder show good agreement with the data of Yu and Ursell (1961). The variable mass distribution leads to a computer run time speedup of nearly 200% in these cases on a single CPU. The results of the vertical force and wave amplitude are shown to be quite sensitive to the value of the slope limiter in the Riemann solver for the 2-D heaving cylinder problem. A heaving 2-D wedge or 3-D cone whose oscillatory vertical motion is prescribed as the elevation of a focused wave group is a precise test case for numerical free-surface schemes. We consider two forms of repulsive boundary condition (Monaghan & Kos, 1999, and Rogers et al., 2008) and particle boundary force (Kajtar and Monaghan, 2009) for the 2-D wedge case, comparing the result with the experimental data of Drake et al. (2009). The repulsive boundary condition was more effective than the particle boundary force method. Variable particle mass with different kernel sizes was then tested for 2-D problems for mass ratios of 1:4, 1:16 and 1:4:16 with satisfactory results without particle clumping and instability. For the 3-D cone case, SPH reproduces the experimental results very closely for the lower frequency tested where there is no separation from the bottom surface of the body but for the higher frequencies the magnitudes of force minima were underestimated. The mass ratios of 1:8 and 1:8:27 in two and three nested regions are tested for the 3-D cone problem where a computer run time speedup of nearly 500% is achieved on 16 processors for the mass ratio of 1:8.Finally, the floating body of a heaving wave energy device known as the Manchester Bobber is modelled in extreme waves without power take-off. The results for a single float are in approximate agreement with the experiment.
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Hughes, Jonathan Mark. "Development of polyhipe chromatography and lanthanide-doped latex particles for use in the analysis of engineered nanoparticles". Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/development-of-polyhipe-chromatography-and-lanthanidedoped-latex-particles-for-use-in-the-analysis-of-engineered-nanoparticles(8688874b-cd1e-4209-81da-0739f1ac8e6c).html.
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The aims of this thesis were two-fold: A) To use high internal phase emulsion (HIPE) templated materials to produce a chromatographic stationary phase for the size separation of engendered nanoparticles (NPs). B) To produce well characterised lanthanide doped polymer NPs with a potential use as analytical standards. Initially, silica materials were prepared from oil-in-water HIPEs by a two stage acid/base catalysed sol gel process. As well as presenting the expected macroporosity typical of HIPE templated materials, it was also found that micro- and meso-porosity could be influenced by surfactant choice and reaction with iron (III) chloride or copper (I) chloride which had been included in the HIPE. However, the resulting silica materials were deemed inappropriate for the desired chromatography. Monolithic columns were prepared from HIPE templated polymers (polyHIPEs) and incorporated into a HPLC system. Poly(styrene-co-divinylbenzene) and poly(ethylene glycol dimethacrylate) polyHIPE columns were able to separate sub-micron polystyrene latexes, detected by UV absorption, and dysprosium doped polystyrene latex particles and gold nanoparticles detected by inductively coupled plasma mass spectrometry (ICP-MS).Dysprosium, gadolinium and neodymium doped polystyrene NPs were prepared by micro-emulsion polymerisation. Particle size was controlled (over a 40 – 160 nm range) by tailoring of surfactant and initiator concentrations. Particles were characterised by dynamic light scattering, differential centrifugal sedimentation, transition electron microscopy and hydrodynamic chromatography (HDC)-ICP-MS. Also, particle surface change, lanthanide content and solids content were analysed. The latter two appear related to particle size. As far as the author is aware there are no cases of the use of polyHIPE columns size separation in the literature. Nor are there any cases of encapsulation of metals within polymer nanoparticles by micro-emulsion polymerisation reported.